Microscale modelling and simulation of the removal of water from diesel fuel using hydrophobic separator meshes
S. Antonyuk, Technische Universität Kaiserslautern; O. Elsayed*, R. Kirsch, S. Osterroth, Fraunhofer Institute for Industrial Mathematics (ITWM), Germany
Liquid-liquid separation systems are vital for many applications: power generators, automotive, hydraulic lines, etc. In the special case of diesel fuel, the trend towards sustainable fuel production and reduction of hazardous emissions lead to the increasing usage of ultra-low-sulfur diesel and bio-diesel. Such fuels exhibit a significantly reduced the surface tension between the diesel and the inevitable water content, rendering the removal of the water more difficult. Consequently, the design of separators in diesel fuel filters meeting today’s performance requirements imposes a challenge to the developing engineer and suitable simulation techniques. Hence, in order to improve and further optimize the current separator systems, a better understanding of the influence of material parameters such as wettability and geometric properties of the mesh on the separation performance would be very useful.
The challenge in modeling and simulation of such systems is the fact that phenomena on different length scales influence each other:
On the microscale, individual droplets are considered. In the free flow region, they are much smaller than the hydrodynamic length scale and their motion is mainly due to the flow. After coalescence at the hydrophobic separator screen, gravitational forces are more and more dominant and separation by drainage occurs. Both coalescence and drainage influence how much of the mesh surface is open. On the macroscopic scale, this affects the over-all differential pressure and the distribution of the local flow speed near the mesh, which in turn changes the transport of the water droplets towards the mesh.
The present work is devoted to the modeling and simulation of the interaction between the water droplets and the separator screen taking into account the gravity forces in the microscale. It is seen that...
Membrane science and functional materials
Prof. Dr. Liang-Yin Chu, Sichuan University, China
Functional membranes are playing paramount roles for sustainable development in myriad aspects such as energy, environments, resources and human health. However, the unalterable pore size and surface property of traditional porous membranes restrict their efficient applications. The performances of traditional functional membranes will be weakened upon the unavoidable membrane fouling, and they cannot be applied to the cases where self-regulated permeability and selectivity are required. Inspired by the natural cell membranes with stimuli-responsive channels, artificial stimuli-responsive smart functional membranes are developed by chemically/physically incorporating stimuli-responsive materials as functional gates into traditional porous functional membranes to provide advanced functions and enhanced performances for breaking the bottlenecks of traditional membrane technology. The smart functional membranes, integrating the advantages of traditional porous membrane substrates and smart functional gates, can self-regulate their permeability and selectivity via flexible adjustment of pore sizes and surface properties based on the “open/close” switch of the smart gates in response to environmental stimuli.[1-4] This presentation will introduce the recent development of stimuli-responsive smart functional membranes, including the design strategies and the fabrication strategies that based on introduction of the stimuli-responsive gates after or during membrane formation, the responsive models of versatile stimuli-responsive smart functional membranes, as well as the advanced applications of smart functional membranes for separating chemical/biological substances based on size or affinity, regulating substance concentration in reactors, and controlling release rate of drugs. With the self-regulated membrane performances, smart functional membranes show great power for global sustainable development...
The role of structural and surface properties of depth filter media designed for selected separation processes
Prof. Dr.-Ing. Andrzej Krasinski, Warsaw University, Poland
The presentation covers examples on the enhancement of filtration performance by modification of fibrous media tailored for specific processes. The topic will include an optimization of depth filter for solid filtration and coalescence (both gas-liquid and liquid-liquid), methods for modification of filter structure by deposition or synthesis of particles on the fibers to obtain expected wettability as well as fabrication and testing of antibacterial filters. The latter application will be addressed for filtration of water biofuels, where the formation of biofilm can lead to a rapid clogging of filter due to bacteria growth and bacteria reemission to the outlet. Other prospective features like photocatalytic effects of the composite filters for organics decomposition will also be presented...
Simulation of solid-liquid separation processes: Challenges in modeling and experimental validation
Prof. Dr.-Ing. Sergiy Antonyuk,Technische Universität Kaiserslautern, Germany
With the rapid increase in computing power, numerical simulation is becoming increasingly important for the prediction and description of solid-liquid separation processes. Numerical studies can improve knowledge of complex separation mechanisms and support the model-based optimization of existing and the development of novel separation processes.
The approaches used for the modeling and simulation of solid-liquid flow processes differ in the resolution of the flow and boundary layer, consideration of physical effects, microprocesses and interactions as well as the computational effort. This contribution gives an overview of the different approaches and demonstrates their suitability and challenges for the description of the transport and separation of fine particles by comparing simulations with measurements.
The focus is on the detailed description of the separation of particles from suspensions in complex nonwoven structures or in a filter cake by taking into account micromechanisms and real filter medium microstructure. The particle-particle, particle-fibre and particle-fluid interactions, formation and breakage of aggregates, clogging of pores and the compressibility of particles in the filter cake can show a major influence on the filtration process. For the description of these microprocesses, the particle separation can be simulated with the coupled Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD). The contacts between particles and fibres are calculated numerically by DEM with force and angular momentum balances, where contact deformation and adhesion as well as drag and viscous forces due to flow obtained with CFD are considered. The kinematics and dynamics of each individual particle and the entire particle collective in the suspension can be obtained. In contrast to other methods, DEM is able to consider such effects as particle size distribution and irregular shape, plastic deformation, friction, rotation, sticking of particles and breakage of agglomerates. The real microstructure of the filter medium can be obtained by computed microtomography and implemented in a 3D model for simulation of particle deposition.
The recent applications of DEM-CFD methods in the field of filtration are presented. The measurement methods for the parameter estimation (mechanical particle properties, friction, restitution coefficient, adhesion) and validation of the DEM-CFD model will be explained with examples of experiments...
Test membrane filtration and sustainable development
Prof. Dr. Pierre-Yves Pontalier, ENSIACET LCA Laboratoire de Chimie Agro-industrielle / France
Membrane processes are used in a very large number of industrial fields such as the food industry, the chemistry, the pharmaceuticals or the environment. Membrane processes contribute to the protection of the environment as they allow the depollution of industrial and urban effluents. They may also help to limit environmental degradation by integrating new cleaner processes, particularly those related to the biorefinery concept. This concept, which aims at the multivalorization of plant and animal resources, is a perfect example of the integration of membrane processes in this approach. For example, in the context of the valorization of lignocellulosic biomasses, the purification of hemicelluloses and lignins is carried out through a membrane filtration stage. Similarly, the valorization of proteins contained in wheat bran or rapeseed cake passes through an ultrafiltration stage. Another pathway that is developing is the fractionation of microalgae, called algo-refining, in which membrane processes are involved in the purification of polysaccharides and proteins.
In the case of drinking water production or industrial effluent treatment, very large membrane surfaces are used, with a lifetime of a few years. Thus, membrane processes become a very important source of pollution. The life cycle analysis of membrane processes thus shows that their impact is not negligible. Two types of impacts are generally highlighted, those related to the production of the membranes (e.g., the use of petro-sourced materials) and those related to the operation of the processes (e.g., the energy used and the chemicals during the cleaning phase). One environmental impact that is neglected is the end-of-life impact of the membranes, the fate of which poses problems. Studies are beginning to appear to evaluate methods of reusing used membranes in order to increase their lifespan, but this does not solve the problem of the end-of-life of the materials. Within the framework of sustainable development, it would be desirable to produce membranes from bio-sourced molecules and above all to facilitate their destruction...
Roaring twenties in air filtration - driving for a cleaner world
Dr. Martin Lehmann*, MANN+HUMMEL GmbH, Germany
In medias res: Air filtration is omnipresent for delivering clean air: protecting engine and equipment known as engine filtration, enabling processes and technology known as industrial filtration, providing comfort and indoor air quality known as HVAC filtration. Adding gas adsorption, the domain of cabin air filtration shows up. However, in this talk the focus will be on particle filtration.
Tempora mutantur et nos mutamur in illis. A bit more than twenty years ago, the digital revolution in air filtration started. First realistic simulations of particle collection on single fibers. First time visualization of the 3D microstructure of a fibrous filter. CFD and FEA have become a key tool for designing air intake systems. Nowadays, we are starting to use AI-based simulation tools for designing air filter elements. In addition, in the past twenty years the design of the filter elements changed significantly. There is no longer a set of just rectangular or round filter elements. With evolving production technology, we are now thinking and designing in flexible design shapes with concave curvature, oval shape or variable pleat heights. Customers have become used to filter elements fitting just right into their complex 3D design space.
Quo vadis air filtration? Our decade of the 2020s is a quite prosperous time for air filtration. The production of new internal combustion cars is still growing (until the end of 2020s), the vehicle in operations will further grow, and filtration for heavy duty and industrial equipment will continue to be in demand. But it is also a time to redefine air filtration: New air filtration products will be needed, even for e-mobility. Focusing on reducing emissions adds the need for innovative filtration solutions, such as brake dust filtration, but also demands some kind of an altruistic, community-centered approach: With my frond-end air filter, I contribute to lower fine dust emissions while driving!
The plenary lecture will be a personal collection of examples illustrating the evolution of air filtration in the approximately last twenty years as well as an outlook into the roaring 2020s in air filtration....
Impact on particle penetration in filter media due to variations in the physical properties of paraffin oil
M. Hu; G. Patel*, ATI - Air Techniques International, USA
The EN13274-7:2019 standard defines the method to test respiratory protective devices for, among other things, particle penetration. The particle penetration level is used to determine the class to which the mask meets and will be sold as, for example are they FFP1, FFP2 or FFP3? The EN13274-7 standard defines that the penetration test shall be done by two methods, one with a sodium chloride challenge and the other with paraffin oil. The standard specifies a CAS# (8012-95-1) for the Paraffin oil, but within the CAS# there is a broad acceptable range of oil characteristics (density and viscosity) that may lead to paraffin oil aerosols with different particle size distribution, which can significantly affect penetration test results of respiratory protective devices and their classification. This presentation will focus on the paraffin oil test, and specifically investigate how paraffin oils with the same CAS# but different physical properties can affect particle penetration results. ..
Nonwovens for hygiene and medical applications: Optical quality control can manage the increasing requirements for functional membranes
M. Klein, Dr. Schenk GmbH, Germany
Triggered by the intensive need for medical respirators, surgical masks and face masks (personal protective equipment) since the beginning of 2020, the production of high-end filter material was increased dramatically. However, not only the volume was boosted, but also the requirements on the quality of the mask material were tightened to fight the Covid 19 pandemic.
Defects in functional membranes, e.g. for medical respirators, may result in more airborne particles, e.g. droplets containing bacteria and viruses, passing through. The number of particles passing through is one of the main factors determining the protection class of a medical respirator:
Harmful dusts, smoke, aerosols and infectious agents.
Toxic and harmful dusts, smoke, aerosols and infectious agents.
Filtration of particles
As high filtration rates are essential according to the requirements given above, meltblown material is the favorite for MPE and PPE applications. However, local defects (such as micro-holes, dirt, drops and many more) can impair the function of the filter medium. Detecting these problems inline during production of the base material is a safeguard against delivery of defective products. Inline optical inspection in the subsequent converting process will provide the required attention and care to quality aspects.
In parallel, monitoring of more general material properties is necessary. Optical quality control systems can also help..
Differentiating membranes and filter materials by capillary flow porometry and electro-kinetic properties
Tba*, M. Kalmutzki, Anton Paar Germany GmbH, Germany
Mechanical filters or membranes are devices that use porous media, such as paper, foams, synthetic fibers, cotton, or spun fiberglass, to remove solid particles and other contaminants in applications requiring clean streams of gases or liquids.
We present technical solutions that can measure and analyze (1) the pore characteristics of materials used in different filtering applications from contaminant removal to medical devices and electronic fabrication; and (2) the net surface charge by means of the zeta potential, which is a powerful tool for additional analysis of the efficiency of surface functionalization, modification, and aging processes.
This presentation compares and contrasts the results for different filter types or modification types. On the one hand, two similar looking filters used for contaminants removal from an in-house air source are compared. On the other hand, a ceramic filter for water treatment and bacteria removal is investigated. Targeted surface modifications are focused on an extension for virus removal...
Round-Robin Study on ISO 16889
A. Gadhave*, R. Bharadwaj, A. Burnett, D. Avery, Lydall Performance Materials, Inc, USA
Hydraulic filtration is one of the biggest sectors in the filtration industry. A lot of efforts go towards making filtration media and filters more economical with longer life and higher dirt holding capacity. There are test standards that help in comparing the relative performance of filter media/filters to select the most appropriate ones, however, different test labs get different results for the same filter media and that makes round-robin testing between two test labs or two different test stands very difficult to compare.
Calibration of individual testing equipment such as particle counters and pressure gauges are always helpful. However, after installing these pieces of equipment in the system, it is hard to predict how they would behave over a period of time which may lead to inaccurate results. Deviation in test results from different test labs is very common, and more work needs to be done in this area including a detailed analysis of standard test equipment.
In this work, a standard media was tested using statistical process control tools on two different multipass test equipment at Lydall and at a third-party test lab. Test conditions in all three instances were the same, and the results were compared. A process capability analysis was conducted to understand our current state, and then a correlation was established to reduce the deviation among the three different systems’ results and to monitor our gage’s repeatability and reproducibility.
This study not only helped to compare the different testing systems from different labs, but it also helped Lydall to calibrate our multipass equipment and reduce possible variation...
Melt blown nonwoven -innovative approach in filter media production for micro-ultra filtration
N. Batta*, Dutch Fiber Netherlands, Netherlands
The paper will highlight the Innovative technology which provide MB NW high performance filter media products through Simulation based smart production in using a typical melt blown double beam line as an example. Due to its current relevance in Health sector of filter media in a pandemic, the not only got off to a quick start, but the implementation and results should also be implemented faster.
We show our expert domain through strong background to make this smart manufacturing "Melt blown productive” for Filtration market.
It gives opportunity to many attendees in the conference to learn about melt blown European supply chain. The production of many mass products has often been outsourced for importation in the past decades. However we show through our Presentation Melt blown nonwovens manufacturers remaining in Germany & Europe tend to focus more on high-quality technical textiles.
The paper explains commercial market requirements of melt blown & highlight the medium and longer-term perspective to boost the supply gaps in fiber grade sustainable synthetic & Bio Polymer application in filter media nonwoven. Research of of Dutch fiber Netherlands share sustainable supply chain of essential value engineerial material with in the EU & boost each country sustainable production model on their supplies and when production capacities which is expanded by new plants. One lesson to be learned from the crisis will also be to reduce the dependence on Importation, especially as a precautionary measure for crisis scenarios.
Air filter testing using bacteriophages as virus surrogate
B. Führer*, H. Elsayed, C. Hartl, M. Kaiser, G. Ettenberger,OFI Technology & Innovation Ltd, Austria ; U. Häfner, Freudenberg Filtration Technologies SE & Co. KG, Germany
Infectious particles such as viruses or bacteria are ubiquitous and most occurring transmission is from human to human. Virus-laden particles originating from the respiratory tract produced during sneezing or coughing is typically 5 µm or less in diameter. Particles that are smaller than 5 µm can remain airborne for hours and can be inhaled by a person. Indoor air filters or face masks can play a significant role within reduction or inactivation of infectious particles in respiratory aerosols, especially during pandemics such as COVID-19. Currently, air filters are mostly tested with well-defined mineral particles or plasticizer aerosols such as ISO 12103-1 A2 fine dust or DEHS. These standardized test dusts represent the particle size of bioaerosols, but are often not representative for the physicochemical properties of bioaerosols.
As biological particles such as viruses have a different behaviour and show detectable infectious potential compared to non-biological particles it is important for filter design and testing to investigate the interactions between bioaerosols and (biofunctional) filters. The aim was to develop a standardized method for testing filter media and modules with defined bioaerosol containing MS2 bacteriophages, serving as virus surrogate, via a special designed filter test rig. The focus lay on comparison of biological separation efficiency with the separation efficiency of common non-biological aerosols as it is important to know about the biological risk of the particles exposed to the filter and to humans and not only number and size.
A method to test filter media and whole filter modules directly with bioaerosols was developed on a filter test rig. Test aerosol consisting of a defined amount of MS2 bacteriophages was applied in order to determine viral filtration efficiency of filters. A stable method was established for different air flow rates depending on the field of application. Results demonstrate that...
Efficient filter media and membrane testing (cut-off) by number-based size distribution of nano- and microparticles (SPLS-Technology®)
E. Wollik, H. Woehlecke, H. Lichtenfeld, Dr. Lerche KG; M. Hussels, Physikalisch-Technische Bundesanstalt (PTB); D. Lerche, LUM GmbH, Germany
Quality and safety of filter media and separation membranes is important in design process and processing of liquid-based products. Testing of the cut-off and retention capacity for particulate components is therefore obligatory. These tests rely on efficient and accurate determination of a particle size distribution, particle number (concentration). This becomes especially challenging for filtermedia application in nanotechnology, where the cut-of for particles in the nano- and submicrometer range has to be quantifyed in terms of particle numbers in the filtrat and, on the other hand, the detection of very small subfractions of larger particles in the range of only hundreds per mL is important.
We describe for the first time the application of a newly developed advanced single particle light scattering technology quantifying number-based particle size distribution and its concentration of nano- and microparticles in the filtrat with high resolution and a dynamic range from...
Foaming adhesives – More joy or pain for industrial filtration?
F. Steegmanns*, Stockmeier Urethanes GmbH & Co.KG, Germany
In the industrial filtration industry, compact adhesives and potting systems been used for several years for the production of cartridges and filter elements. Here we will only consider the application of polyurethane systems. Obvious, the advantage for this is no other material offers such a comparable performance spectrum. From very soft to high-strength, as compact material or foam, with very good temperature and/or chemical resistance and a broad adhesion spectrum on a wide variety of substrates, almost all requirements can be met in the formulation of polyurethane.
When companies forced with the decision to reduce costs, they first have the possibility to change the material or the supplier. This brings smaller savings, but can also lead to disadvantages in quality and/or other disadvantages. The laws of business also apply here: Good chemistry costs money!
With the used adhesive and potting systems, a gap between the filter paper and the frame or end caps is usually filled and the filter stabilized. What could be more obvious than the idea of foaming exactly this system and thus quickly saving half or more of the adhesive and potting system used. In addition, you gain another decisive advantage: The weight of the filters is reduced by the amount of material saved also. So much for the theory.
The otherwise standardized and good-natured adhesive and potting systems used as a compact material cannot be replaced just so easily by foaming systems. Nearly every application needs to be considered in a separate project and requires a more or less individual solution as our many years of experience show us.
Advantages and disadvantages have to be weighed up against each other and the possible additional investments have to be compared with the expected savings. In lots cases the development of a new filter generation, including frames or endcaps, is necessary because the previous design does not allow the use of foaming products so easily.
A common, comprehensive and close cooperation is necessary in such a project from the very beginning.
Laser precision drilling for future applications against viral diseases
T. Barthels*, M. Reininghaus, Fraunhofer Institute for Laser Technology ILT, Germany
In the field of micro and nano laser structuring, ultrashort pulse (USP) laser material processing is attracting increasing attention due to its ability to generate precise hole pattern with high throughput and quality requirements. The multibeamscanner (MBS) enables laser processing with strong parallelization of more than 200 beams in order to achieve even higher throughputs while maintaining the same drilling quality.
The aim is transferring latest research results and years of process development for laser-based multibeam machining of tool inserts in consumer electronics to new and technologically demanding markets such as the filter industry. On the basis of the existing process knowledge the process of effectively drilling holes with micro- and sub-micrometer diameters is content of further investigations. The use of USP lasers offer the potential to produce filters made of stainless steel foil with < 1 µm sized holes. The MBS production technology is suitable for manufacturing micro and nano filters for industrial applications in the fields of biotechnology, pharmacy and medical technology. The use of the manufactured filters is also conceivable for special applications such as an atomizer module in inhalation devices for a targeted dosing of antiviral medication. Latest USP laser machines...
Sustainable weaving: Modular weaving machine concepts for the production of high-performance filter fabrics
L. Öller*, Lindauer DORNIER GmbH, Germany
The modern weaver faces many challenges: Digitisation is weaving its way deep into the production chain, sustainability requirements are increasing, and there is a shortage of young people and skilled workers. Flexibility in production is increasingly becoming an existential question. DORNIER's weaving machine system family offers answers to this – in the form of the very latest weaving machines and weaving solutions.
Under the motto "The Green Machine", the family-owned company from Lake Constance, which manufactures its machines exclusively in Germany, presents comprehensive solutions for sustainable technologies.
With this guiding principle DORNIER is not just hinting at the well-known green varnish of the weaving machines but, above all, at the "green effect" of the fabrics they produce.
These fabrics are of crucial importance for many "green technologies" in almost all industrial sectors. Whether finest filters for cleaning water or air, fabrics as carriers for catalysts or exhausts, in all these sectors DORNIER "Green Machines" are indispensable for the production of precision fabrics. Especially in these areas, where the highest demands are placed on the fabric, DORNIER weaving machines unfold their unique performance. This results from the quality of production, the imagination of the developers and engineers and the consequent exchange of ideas with customers.
Even more flexible, faster and more efficient: This is what the P2 rapier weaving machine in three versions stands for. In addition to the standard version, the P2V is also supplied as a reinforced version with a reed impact force of up to 37 kN and the P2S heavy fabric weaving machine with a maximum reed impact force of 50 kN for particularly heavy and dense technical fabrics. Like all DORNIER weaving machines, the P2 in all versions features the unrivalled DORNIER SyncroDrive® drive concept and the powerful interface for easy integration into the IT and tool environments of the weaving mills.
Further developments of the machines are always carried out under sustainability aspects and the company motto "Quality creates value". The DisCoS® (DCS) colour selector and feed system, which allows up to 16 colours to be processed particularly easily, and the DoPPIO® double-weft rapier heads with free colour feed and parallel weft insertion provide an additional increase in productivity.
Machines and plants with a service life of several decades, and worldwide support even for “green machines” that have been in production for over 30 years are not uncommon. With trained technicians working close to the customer, we guarantee a worldwide mechanical, electronic and weaving technological service...
ROTH Pleating machinery
M. Großkreutz*, Roth Composite Machinery GmbH, Germany
Based on a market experience of more than 30 years, Roth Composite Machinery offers pleating machines for the filter industry. The machines are characterized by a solid and simple technology as well as very high flexibility. We are using modular designs enabling our customers to add new modules and thus extend their machines at any time.
Besides the pleating machines being driven mechanically or by servo motor technology, the product program of Roth also includes all relevant add-on modules. This ranges from single or multiple unwinding units to slitting systems, perforation devices and splicing equipment as well as complex add-on modules, such as minipleat systems and semi or fully automated cross-cutters. Furthermore, the Roth program offers complex filter production lines based on the rotary pleating technology. These systems enable our customers to purchase all items from one provider and have one contact person in case of questions and additional technical challenges.
Roth machines cover all common parameters - and special solutions additionally. Thus, we can offer knife pleating machines for pleat heights from 2 mm to 500 mm. Working widths from 300 mm to 3,000 mm can be realized without any problem.
Rotary pleating machines can be offered with working widths from 100 mm to 1,300 mm as well as for velocities of up to 3,000 pleats/min.
Depending on the requested order volume, Roth also offers all additional aggregates for the rotary pleating lines, such as pre- and post-heating ovens or afterburning systems.
A proof of the flexibility of Roth Composite Machinery is the completion of a machine for the manufacture of rectangular inserts for respirator masks. For that, we designed a knife pleating machine having a width of 300 mm only, a hotmelt bead application system and an automatic cross-cutter. The rectangular filter elements being stabilized by the hotmelt beads are taken by a customer’s robot from a defined position and are glued in the frame.
The machine is able to manufacture elements having widths of 31 mm, 57 mm and 68 mm.
Naturally, all our machines are equipped with a remote service access allowing the realization of changes or modifications within a short period. We permanently enhance our products to make them even more effective and economic for our customers. On this occasion, we would like to present two of our latest innovations: A swivelling slitting system and an automated device for changing the pleating knives...
Inorganic membranes made of sintered clay for the treatment of biologically modified water
J. Bentama*, Sidi Mohamed Ben Abdellah University, Morocco
It is now commonly believed that membrane crossflow filtration processes can be considered as high performance separation techniques, not only in laboratory experiments but also for many industrial applications. The present work aims to describe and characterize inorganic membranes at low cost and to study their performance through a fermentation–crossflow microfiltration (MF) coupling process. New mineral membranes were created from sintered clay in which a certain quantity of coal was added to the mixture before the sintering operation in order to increase and control the membrane porosity.
Previous works have shown that these low-cost membranes can be used as MF membranes for surface water clarification. Crossflow MF of a biological fluid model was performed in a membrane bioreactor. In this technique the cell culture was continuous. This allowed us to control the environment of cells and to obtain very high active concentrations by the recycling of the microorganisms. The biological fluid model used in different operations of MF was a suspension of yeast. Periodic back-flushing coupled with chemical cleaning was done without isolating the membrane from the filtration module. Experiments of characterization of the fouling state of the membrane after a certain time of operation were started using an acoustic technique. The results are promising...
Ceramic membrane technology for efficient separation of chemical degraded lignosulfonates and target products
F. Boruta*, O. Schmitz, M. Ebrahimi, P. Czermak, University of Applied Sciences Mittelhessen, Germany
The ongoing discussion about a necessary reduction of CO2-emissions and depleted reservoirs of crude oil worldwide lead to an increasing interest in sustainable, renewable and alternative sources for aromatic molecules. In this context, lignin-containing process streams are in focus of several research programs as lignin is the most abundant renewable source of aromatic molecules on earth. The pulp and paper industry e.g. produces ca. 50 million tons of lignin per year, but only 2% are used for production of industrial products, the rest is incinerated for internal energy supply. This under-utilization of lignin is a result of its strong recalcitrance towards degradation and the problem of numerous degradation products and their purification.
In this work, a membrane based separation process for chemically degraded lignosulfonates is investigated. For the separation of desired products from partly degraded lignosulfonates (PDL) several ceramic ultrafiltration membranes were examined. The influence of relevant process parameters on separation efficiency, permeate flux and fouling effects strategies is part of this research work...
Production of nanofibers for filtration applications via solution electrospinning: Approaches of industrial scale production
T. Schneiders*, T. Gries, RWTH Aachen University, Germany
Nanofibers and submicronfibers, as a textile structure in the form of a nonwoven fabric, show excellent properties for applications such as tissue engineering, drug delivery in medical products, filtration, catalysis but also technical textiles and protective clothing. These properties include a high specific surface area, interconnected pores and adjustable pore sizes on the nanoscale. Several technologies are used and developed to produce fibers with a diameter below one micrometer. Most processes have either a high investment and operating cost and are limited to few polymers or material combinations like phase separation and melt blowing or produce wide spread and non-uniform fiber diameters like flash spinning.1,2 Solution electrospinning is considered a viable method to produce nanoscale fibers due to its simplicity, cost efficiency and material compatibility.
As solution electrospinning so far was used for small scale production and applications, a major challenge for the use in filtration and industrial scale production is the upscaling of nanofiber production while staying competitive to other technologies. Within solution electrospinning there are several approaches that demonstrate the possibility for upscaling or first results in industrial production. Needle based and open surface technologies pursue different innovations and ways to reach a higher output of nanofiber materials. A short overview of different solution electrospinning technologies and their challenges facing upscaling as well as the benefit for the filtration market will be given in this presentation...
Study of nanoscale structures for application in the filtering layer coupled with micro-scale materials for FFP2 masks
V. Pais*, C. Mota, J. Bessa, R. Fangueiro, Fibrenamics - University of Minho; J.G. Dias, Poleva – Termoconformados, S.A, Portugal
The ongoing COVID-19 disease has been declared a pandemic by the World Health Organisation (WHO) . This disease has different types of transmission routes,but respiratory droplet and airborne one are the most prevalent method of contamination. Therefore, the development of efficient protection systems is vital, either for application in the current pandemic or in other contexts that require it .
SARS-CoV-2 (the virus that is responsible for COVID-19 disease) has a size ranging from 60 to 140 nm . So, filters with small diameter fibers, like the ones produced by electrospinning, are an important solution to retain this specific type of virus, since the virus has very small dimensions.
In this study, polyamide (PA) nanofibers production appears has a solution with the potential to promote SARS-CoV-2 retention. The nanofibers were produced by electrospinning technique and variables such as polymers’ concentration, flow rate and needle’s diameter were optimized to obtain fibers with very low diameters. Fibers with diameters at nanoscale allow the presence of numerous tinny pores, which increases the filtration efficiency of nanoparticles....
Filter screen from permeable matrix of pressed metal wire and its properties
I.S. Pyatov, L.V. Vorobeva, A.N. Korchagin, I.V. Kirpichev, K.N. Petrunina*, REAM-RTI, LLC; V.N. Ivanovsky, A.V. Bulat, Gubkin National University of Oil and Gas, Russia
REAM-RTI, LLC introduce an innovative permeable matrix of pressed metal wire (PM), products from which are patented and used for filtration of liquids and gases. The manufacturing technology complies with modern ISO: 9001 standards and allows the manufacture of filter elements with a filtration rating up 5 to 500 microns with various geometry and sizes. The material is a wire structure that, as a result of cold pressing, forms an openly porous and elastic system permeable in all directions.
- The elastic system of filter allows:
- providing multiple regeneration (at least 50 times) with an efficiency of up to 90% recovery of initial properties without dismantling the equipment;
- change in filtration rating by axial compression, which allows it to be adaptive to changes in filtration fineness requirements;
- provides durability and high impact resistance of the filtering system;
- resistance to destruction in a hydrogen sulfide and hydrogen environment (SSK).
2. Low hydraulic resistance due to the use of round wire provides:
- high erosion resistance;
- high ratio of the area of the slots channels passing the filtered medium to the total area of the filter surface.
3. The possibility of manufacturing a filtering screen from various materials allows....
PlasmaMAXTM a versatile tool for high-functional coatings on filtration media and technical textiles
J. Jolibois*, H. Weiss, AGC Interpane Demonstration and Research Center, Germany; G. Arnoult, J. Schotsaert, H. Wiame, AGC Plasma Technology Solutions, Belgium; C. Gottlieb, AGC Business Development, USA
Conventional repellent coatings for filtration media are mainly based on long perfluoroalkyl chemicals (PFAS), deposited through wet coating or padding process. However, PFAS are subjected to restriction by REACH and in case of PFOS (i.e. C8) banned for use. In addition, wet processes require huge inputs of energy, water, and chemicals. The growing environmental and energy-saving concerns are incentives for the well-established surface finishing industry to gradually substitute many traditional wet chemical-based textile processing by dry-finishing processes such as plasma. Until now, plasma technologies have not yet proven to be really suitable for textile applications. Problems related to current plasma sources are the difficulty to scale up them for substrate widths beyond hundred centimeters resulting in poor uniformity and low durability of the deposited functionalities, and high OPEX.
PlasmaMAXTM developed by AGC Plasma is a cutting-edge technology designed to address different problems related to wet processes and overcome weaknesses of commercially available plasma systems. Technology core of PlasmaMAXTM is hollow cathode (HC) plasma source. This source can achieve high deposition rate with high uniformity (± 1% across 1-m web width) and allows functional coating without damaging the web. Functional coatings are deposited via plasma-enhanced chemical vapour deposition (PECVD) at low pressure. HC-PECVD is achieved by introducing reactive precursor gas in the vicinity of plasma area (see Figure 1). Chemical reactions are initiated by plasma-precursor interaction inducing the growth of functional thin-film (e.g. water repellent finish) on web surface.
In the present work, durable water repellent (DWR) and oil repellent coatings made by HC-PECVD on different types of substrate (e.g. PE woven) are shown. Then, we will discuss on how plasma parameters (i.e. pressure, power, precursor, etc.) modify the coating properties such as wettability, adhesion and so on. Finally, we will present two examples of HC-PECVD coatings, a DWR halogen-free finish and then oil repellent surface...
Biopolymers in filtration technology: Effects of PLA on pleating characteristics of synthetic filter media
G. Müller*, D. Weidt, F. Bauer, Sandler AG, Germany
In HVAC filtration and other sectors, such as automotive filtration, the trend for decreasing installation spaces requires smaller filters without compromising their performance and durability. Hence, the demand for pleatable filter media, which provide largest possible filtration surface in limited spaces, is continuing to grow.
Today, the pleatable filter market is dominated by glass fibre paper treated with chemical binders or adhesives. However, even small amounts of water or moisture can result in a reduced fold stability leading to the final collapse of the folds and, thus, of filter performance. Moreover, glass fibre filters may easily get damaged during production, assembling or due to in-service impact events causing fibrous airborne matter. Such fibre shedding poses health risks to skin, eyes and to the respiratory tract.
Self-supporting synthetic filter media compensate these drawbacks. When compared to traditional glass fibre, the high resilience and mechanical stability of such synthetic media leads to an extended lifetime and an excellent price-performance-ratio. Moreover, fibre shedding is not present. However, they possess also disadvantages. Synthetic filter media are (a) usually based on petrochemical raw materials such as PP (polypropylene) or PET (polyethylene terephthalate) and (b) show difficulties during pleating. The latter is visible in the lack of contour precision and pleat stability, which is most dominant for rotative pleating systems.
As the sustainable use of resources and the impact of products on the environment are shifted towards the centre of public attention, many efforts are made to exchange petrochemical by bio-based materials. Polymers such as polylactide (PLA) offer promising means for such applications due to their specific deformability, stiffness, electrical chargeability and sustainability.
To our knowledge this is the first study that describes the effect of incorporation of bio-based polymers into the meltblown on pleat characteristics. The work addresses the use of biopolymers from the perspective of processability and pleatability. The medium can either be based on the incorporation of renewable resources as component in a polymer blend, a meltblown monolayer or as a single layer within a composite. It is believed that material such as polylactide acid leads to a significant improvement in pleat performance.
The investigations covered the classical scale-up production process from laboratory to semi- and industrial scale. Two critical technical parameters were selected to quantify the pleatability of a medium: CRA (Crease Recovery Angle) and ∆ CRA (angle variation). Scanning electron microscopy (SEM) was used to study the morphology of the nonwovens. To investigate the thermal behaviour and the influence of crystallinity on CRA differential scanning calorimetry (DSC) was used. In addition, industrial conversion tests on a rotary mini pleat machine were performed.
Our investigations show that...
Melt electrospinning towards industrial scale nanofiber production: Challenges, solution approaches and applications
K. König*, G. Seide, Aachen-Maastricht Institute for Biobased Materials, Netherlands
Nanofiber webs offer the advantageous properties of an enormous specific surface area combined with a high flexibility. Melt-electrospinning is a process for the production of these nanofiber webs with a large surface-to-volume ratio, and porosity with both micro- and nanopores. Laboratory research and industrial production use these advantages of submicron fibers in a wide variety of applications such as energy and electronics, environment, filtration and separation, and textiles.
A key challenge for industry is the ability to upscale the nanofiber production within the melt-electrospinning process. Recent device developments such as multiple needle and needleless configurations have demonstrated a roadmap to increase the fiber productivity of melt electrospinning.
Melt-electrospinning upscaling beyond state of the art technologies has successfully been performed at the Aachen-Maastricht Institue for Biobased Materials (AMIBM) in cooperation with Fourné Maschinenbau GmbH (Alfter-Impekoven, Germany), Pötter-Klima Gesellschaft für Nanoheiztechnik mbH (Georgsmarienhütte, Germany) and Schnick Systemtechnik GmbH & Co KG (Heiligenhaus, Germany). The lecture addresses the challenges and solution approaches for the development of a multifilament melt-electrospinning plant with 600 nozzles and the implementation of a continuous melt-electrospinning process. The research work focuses on the material polypropylene and the process transferability to the biobased polymer polylactide acid (PLA)...
Stainless steel nanofibers a breakthrough for metallic filtration media
J. De Baerdemaeker*, A. Goux, Bekaert Fiber Technologies, Belgium
Bekaert has been using different technologies for over 3 decades to produce metal fibers from different alloys. The common range of these fibers has been from 80 down to 1,5 micron in diameter.
The use of metal fibers in the nanometer diameter range enables however, the development of filtration media and membranes with unpreceded filtration properties for high-end gas and liquid filtration applications.
In this presentation, we will highlight recent developments in Fiber and Filtration media processing that enables the manufacturing and use of stainless steel nanofibers. A new product offering including these nanofibers will be presented showcasing the huge impact of this breakthrough technology in various filtration applications...
New developments in woven wire filtration media: 3D high performance filter cloth – woven wire mesh combinations in solid-liquid separation
F. Edelmeier*, F. Meyer, Haver & Boecker OHG, Germany
Previous filter cloths with small pore sizes lead to reduced flow rates and significant pressure loss in the production process. The cloth structure of a newly developed three-dimensional weave increases the number of pores and thus the open surface over the same area. For a given pore size, the flow rate is more than doubled compared to conventional Dutch Weaves. The pore size within a batch can be calibrated as desired from 5 µm to 40 µm. Conventional woven wire filter cloths can cause turbulences that affect the filtration process at high flow rates. Turbulences with the 3D-filter cloth is effectively avoided. Its pore size can be calculated precisely in advance and adapted to the respective requirements. The mathematical formulae for determining permeability were developed in cooperation with the University of Stuttgart within the scope of AVIF projects A224 and A251, and experimentally validated by glass bead tests and air flow-through measurements. These predictable pore sizes can achieve extremely high cut-points and dimensional stability. The depth structure of the new woven wire filter cloth facilitates high separation efficiency without rapid blinding. This leads to longer filtration processes between cleaning intervals and longer service life for greater production reliability. The 3D metal filter cloth is woven from standard diameter wires. Moreover, it is possible to weave special materials such as Alloy 310 S, Hastelloy C 22, Inconel 600 or titanium even in the small pore range. Thus, for the first time, filter cloth with pore sizes below 40 µm can be manufactured in corrosion- and temperature-resistant alloys.
The effect of different gradient structures on the load-dependent fractional separation efficiency and its dirt hold capacity have been subject of design considerations in single and multi-layered woven wire mesh combinations in solid-liquid and solid-gaseous separation. In cooperation with the Institute of Mechanical Process Engineering in Stuttgart (IMVT) different gradient structures of wire mesh filtration media were investigated as to their influence on the load-dependent fractional separation efficiency (FAG) as well as their dirt holding capacity. In addition, different offline measurement techniques and particle systems and their influence on the result of the FAG and the dirt hold capacity were investigated and evaluated....
Influence of the layer structure on the filtration performance of fiber fleece-woven wire mesh-composite cloths
M. Müller*, Spörl KG, Germany
At the conference of the last Filtech in 2019 the different methods to increase the areas of application as well as the filtration performance of metal woven wire meshes were presented by the author . With their narrow pore size distribution metal woven wire cloths guarantee an excellent separation and classification accuracy. Due to their high chemical, thermal and mechanical resistance, wire meshes as metallic filter media can be used in demanding operating conditions, for instance in the form of high process pressures and temperatures or if sharp-edged particles have to be deposited. Depending on the combination of the warp wires and the weft wires during the weaving process, the production of different types of weave with different aperture sizes and filtration behaviors is possible.
One of the clarified methods to increase the filtration performance is the coordinated combination of a metal wire mesh with a metal fiber fleece on the upstream side. In the so-called Compomesh-media the fiber fleece as a depth filter medium ensures a high dirt holding capacity and prevents the metal wire mesh as surface filter in the second layer to be blocked. Due to its narrow pore size distribution the wire cloth acts as a control filter and guarantees a certain purity of the filtrate in every loading state. To prevent the discharge of nonwoven fibers to the filtrate side, in the Compomesh the individual filter layers are sintered together.
By combining metal fiber nonwovens with different properties, such as fiber diameter, specific weight or porosity, with metal wire cloths of different weaving type and aperture size, the filtration performance of the composite cloth Compomesh can be adapted to the requirements of the filtration process....
Development and evaluation of precision woven wire cloth for sieves and filters, an ultrafine woven wire cloth with a square opening size of 13 µm and mesh counts of 977 wires per linear inch
S. Nojima*, N. Hirajo, S. Shimokomaki, T. Matsumoto, Y. Mizuguchi, ASADA MESH Co. Ltd., Japan
With narrow square opening size distribution woven wire cloth guarantees an excellent separation and classifying accuracy. Stainless-steel is a common material for woven wire cloth, and due to the thermal and mechanical strength of stainless-steel and its high chemical stability, it can be used in demanding conditions, such as at high temperatures and high pressures. Therefore, the woven stainless-steel wire cloth has a wide range of applications as sieves and filters. We are an ultrafine woven wire cloth manufacturer and were the first in the world to successfully produce a precision woven stainless-steel wire cloth with a square opening size of 13 µm (0.0005 inch) and 977 wires per linear inch (product name Sieve SV13/13, hereafter called #977). Furthermore, a technique was also developed for weaving #977 with a width of 1220 mm. This abstract gives an overview of the evaluation of #977's square opening sizes.
Until now, ASTM E-11 designates nominal opening sizes of industrial woven wire cloth for sieving down to 20 µm (0.0008 inch) with 635 wires per linear inch. Our product list includes a woven stainless-steel wire cloth with a square opening size of less than 20 µm with a square opening size of 16 µm (0.0006 inch) and 795 wires per linear inch (product name Sieve SV16/16, hereafter called #795). However, no industrial standards for measuring the square opening size of #977 and #795 have been defined. In this study, the square opening size of #977 was measured using an image analyzer, PoreSizerTM (Whitehouse Scientific Ltd). The square opening size of #977 ranged from 11.0-15.7 µm, with a mode diameter of 13.0 µm and σ = 0.667. These results confirm that #977 is a high-precision woven wire cloth...
Topology optimization of filters using an adjoint solver
N. Jüngling*, D. Hoch, J. Niessner, Heilbronn University of Applied Sciences, Germany
Conventional filters consist of one or more filter layers, which are either woven or composed of tangled fibers. The quality of the separation results almost only from fiber density. Due to the manufacturing process, compromises between separation and pressure loss that are in the opposite relationship to each other are inevitable.
The development of additive manufacturing has made great progresses in recent years. The resolution of 3D printers now extends into the nano range. Using this technology, filter manufacturing is no longer restricted to conventional methods. At this point, the adjoint topology optimization of filters is a promising alternative opportunity of filter development. The idea behind this is to use the adjoint solver to generate geometries that have been optimized with regard to pressure loss and the filtration efficiency. The fluid region with the CAD model of the initial geometry is divided into volume cells. The cells at the fibers are then varied by mesh deformation until an optimum is found. The often bionic-looking optimized structures can be realized using additive manufacturing. In a further process step the structure can be coated.
The key to topology-optimized "bionic" filters is to find suitable cost function(s) controlling the optimization. These cost functions have...
Virtual production of filter media using simulation driven design
A. Schmeißer*, S. Gramsch, W. Arne, R. Wegener, Fraunhofer Institute for Industrial Mathematics (ITWM); F. J. Hahn, T. Gose, A. Koronai-Bauer, K. Riedinger, F. Keller, MANN+HUMMEL GmbH, Germany
The emission of fine dust from industrial processes and traffic as well as contamination-sensitive manufacturing technology and clean rooms call for the provision of clean indoor air and therefore requires highly efficient air filter media. Considering the rise in energy cost and the necessity of worldwide CO2 reduction the energy consumption of air filters becomes increasingly relevant. Developing filter media featuring both highest levels of filtration efficiency and lowest possible pressure drop poses an optimization challenge, as both design goals are conflicting.
The increased demand for high performance filters gives rise to challenging engineering tasks to develop efficient filters for different applications. An important aspect in the research and development of new filter media is virtual production with software simulation. A common approach for this models filters as fibrous media with given statistical properties. Using a simulation loop, these properties can be designed to yield optimal performance. However, this does not yet account for how a filter medium with the designed properties can be produced in an actual production process. Thus, the realization of virtually predicted optimal filter media prototypes requires extensive validation in trial runs and may sometimes not be achievable.
We aim to address this issue by means of a novel, holistic approach to the virtual media development. Within the scope of a publicly funded research project, we develop a simulation chain for the simulation-driven design of new filter media demonstrated exemplary using the spunblown process.
Our coupled approach uses a complex chain for the complete simulation from the production process to the final product and its filtration properties, along with a validation of results using experiments on the corresponding real filter media. Instead of the conventional parametric material model of the resulting filter media, we use a fully physical model of the production process starting from the spinning of filaments at the spinneret, down to the stretching in turbulent airflow and web forming of the nonwoven material. The visco-elastic material models used can...
Filter modeling and simulation with GeoDict
M. Azimian, A. Weber, A. Wiegmann, Math2Market GmbH, Germany
Several key parameters are essential as input data to precisely simulate the filtration characteristics of a filter element at macro scale, e.g. simulating the particles filtration through a whole filter with housing, as shown in Fig. 1. Flow conditions, simulation stop criterion, the fluid and particles characteristics, as well as input parameters related to the micro-structure of the media, should be defined. The main input parameters for the macro-scale simulation, which are related to the micro-structure of the media, are: permeability of the media, maximum particle packing density and maximum flow resistivity for both the depth filtration regime and cake filtration regime (four parameters), and also the fractional filtration efficiencies. These parameters are routinely obtained by flat sheet experiments through the filter media. However, the GeoDict software, a pioneer modeling and simulation tool can be applied to obtain these input parameters, thus reducing the need for the time-consuming and costly experimental tests.
The study of the micro-structure of the filter media is the starting point to understand, analyze, and optimize a filter. The first simulation step on the media scale (here woven media) consists of modeling the micro-structure of the woven media using WeaveGeo module of GeoDict...
Simulating the microstructure of nonwovens to predict their elastic-plastic behavior in 3D
K.M. Hoess*, F. Keller, MANN+HUMMEL GmbH; S.Schmauder, University Stuttgart, Germany
The performance level of flat filter media is measured using the three filtration quality parameters: Dust holding capacity, filtration efficiency and pressure drop . They directly correlate to the microstructural properties of the filter media. Hence, new multi-layered filter media with gradual fiber densities across the thickness and increased filtration performances are developed based on filtration simulations and parameter optimizations.
In order to gain the necessary volumetric flow rate, it is often necessary to pleat the filter media to achieve the needed filter media area in the given design space. The highly anisotropic elastic-plastic material behavior of these nonwovens is challenging. At this point of the microstructural design process, the effective mechanical properties of the new filter media are unknown. The ability to predict these anisotropic mechanical properties of a microstructural design is crucial to assess the viability of the new microstructural design for further processing in the manufacturing process. Hence, a virtual lab to test the microstructural designs for tension, compression and shear in all three spatial directions is needed.
In this presentation, a microstructural simulation model to predict the three-dimensional elastic-plastic behavior of nonwovens will be introduced...
Flow-induced deformation of filter media – Part 1: Experimental characterization and 3D simulation of the mechanical properties of filter media during perfusion
V. Puderbach*, S. Antonyuk, Technische Universität Kaiserslautern; R. Kirsch, R. Deshpande, Fraunhofer Institute for Industrial Mathematics (ITWM), Germany
Filter media made of nonwoven fibers are commonly used in multiple filtration applications especially oil and fuel filtrations. The filter medium in each case causes a specific pressure drop and the flow process applies forces on the medium. Those forces have an effect on the fibers and also the fiber bonds. Nonwoven filter media achieve their stability through the resulting fiber bonds, which can also be added by binders or additives (Petterson 1959; Backer und Petterson 1960; Ridruejo et al. 2010). Fibers and fiber bonds describe the planar structure of the material. However, not only the planar shape of the medium is relevant in the use case. Nonwovens are often used in a pleated form. So the fold causes a structural change that influences the pressure drop of the process (Grosjean et al. 2015) (Bourrous et al. 2016; Traut 2017).
This work is meant to investigate the mechanical properties of relevant liquid filter media and to use that information for the design of 3D simulations in order to make further investigations on the in-use behavior of the filter media...
Flow-induced deformation of filter media - part 2: modeling and simulation
R. Kirsch*, O. Lykhachova, Fraunhofer Institute for Industrial Mathematics (ITWM); S. Antonyuk, V. Puderbach, Technische Universität Kaiserslautern, R. Deshpande, Ruhr-Universität Bochum, Germany
The majority of simulation models for filter elements assume that the filter media are “rigid bodies”. In reality however, it is observed that the fluid flow causes deformations which can lead to well-known (and undesired) effects like pleat collapse, pleat crowding etc.
Several works were devoted to the development of models and methods to take into account this Fluid-Porous-Structure Interaction (FPSI) in order to obtain more realistic simulation results. By nature, the earlier studies focused on liquid filtration applications, of which only few are mentioned here: In , an effective permeability approach was used for an improved prediction of the relationship between pressure drop and flow rate in pleated cartridges. A coupling of flow and structural mechanics simulation based on Stokes-Brinkman equations and hyperelastic porous materials in three dimensions in space was presented in . Taber’s model for poroelastic plates was the starting point for the numerical simulation (two-dimensional in space) and experimental validation of small flow-induced deformations in . Deformations of filter media are observed in air filtration, too. In , a coupled simulation (two-dimensional in space) of the deformation of pleats in cabin air filters was studied.
The aim of the present work is to extend the applicability of the coupled simulations for liquid filtration at constant flow rates in a way that the simulations will be done in 3D, include faster flow regimes (Navier-Stokes-Brinkman) and allow for larger deformations and non-linear elasticity...
smartMELAMINE® - the first melamine meltblown nonwoven
C. Löning*, N. Zorko, SmartMELAMINE d.o.o., Slovenia
smartMELAMINE® belongs to the class of high-performance materials, it does not burn, does not shrink and does not melt, remains stable even at higher temperatures up to 240°C of constant exposure and is UV-resistant. smartMELAMINE® is an excellent thermal and acoustic insulator and is also well suited for filtration due to the fine fibers and its chemical resistance.
As a result of the global COVID-19 pandemic of 2020, a filter product, complying with different standards for protective face masks has been developed. From raw material to the end product the smartMELAMINE® nonwoven is produced in the EU.
With the meltblown technology, the nonwoven could be produced with very fine fibers, at around 1 - 2µm fiber diameter or even below, reaching a range of filter classes, applicable for HVAC filtration.
Aramid type filters and other traditional filters in hot-gas filtration generally have much coarser fibers compared to smartMELAMINE®. The addition of smartMELAMINE® with much finer fibers increased the fractional collection efficiency of up to 10x.
smartMELAMINE® nonwoven can also be cut into short-cut fibers, which can then be quite easily dispersed in water and used in a wet laid process for the production of paper like filters. Due to its high temperature and chemical resistance it can be an adequate synthetic substitute to glass fibers.
In addition, there are different potential applications in the fields of thermal and acoustic insulation or filtration for the use in: automobiles, trains, buses, trucks and aircrafts; protective workwear; filtration; construction and various industrial applications...
New plasma nanocoatings to boost performance of filtration media and their relevance to the fight against COVID-19
F. Legein*, Europlasma NV, Belgium
Plasma is a unique technology to deposit ultra-thin coatings on all exposed surfaces of a material or product. It is increasingly used in manufacturing of filtration media and elements to achieve functionalities such as hydrophilic, hydrophobic or oleophobic. Improvements in process and machine design allow to deposit the coatings in a very cost effective way, with a process that is completely dry and clean. The technology is giving an increasing number of producers of technical nonwovens, membranes, mesh or nanofibers a clear competitive edge. The presentation will introduce a new generation of plasma nanocoatings specifically designed to boost performance of electret filter media and discuss their relevance to the fight against COVID-19.
The presentation will start with a short introduction of plasma technology.
Then it will review industrial concepts for both batch and roll-to-roll treatment. It will also compare industrial equipment for atmospheric and low pressure plasma deposition. An overview will be given of typical coating chemistries used for such coatings.
Subsequently advances will be discussed using real industrial case studies.
One case study will discuss the use of hydrophilic nanocoatings for culture growth media. Another case study will review the use of similar nanocoatings for blood filter media.
One of the key areas of interest is the nanocoating of electrets used in HEPA filters. A new generation of plasma nanocoatings (Nanofics E) specifically designed for electrets will be discussed. Advances in process chemistry allow to deposit coatings which boost and maintain filter efficiency over time, while not affecting the pressure drop.
Also advances in durable water repellent coating of membranes for use in sporting and outdoor jackets will be discussed.
The presentation will conclude with an overview of the societal and environmental benefits of plasma technology, with a special focus on the importance of nanocoated electrets in the fight against COVID-19.
Precoating for dust filters challenged with metallic nanoparticles
N. Khirouni*, D. Bemer, Institut National de Recherche et de Sécurité (INRS); A. Charvet, D. Thomas, Lorraine University, France
The regeneration of fibrous filters challenged with metallic nanoparticles, emitted from metallurgical processes, is currently problematic. In a previous work, results revealed that the pulse-jet cleaning is a patchy inefficient cleaning that does not exceed 30% and that the filter cake has a high adhesion force. Furthermore, a rapid increase of the pressure drop during particle loading was registered, indicating that the nanostructured filter cake has a high resistance to the airflow. Ensuring an efficient cleaning of the filter elements after loading is of great importance for filtration systems as it allows using them for a longer period of time. Failing to remove the dust deposit implies that a recurrent replacement of the filters is required, which can be very expensive. In this work, the precoating, which consists of protecting the filter surface with a layer of micron-sized particles, is considered as a solution to overcome the cleaning difficulties caused by the metallic nanoparticles. This technique is often viewed as a low cost and a practical solution to enhance filtration performances of industrial filtration systems.
The objective of this study is to verify the application of precoating as a viable solution to overcome cleaning difficulties caused by metallic nanoparticles...
Investigation of the pm emission behavior of individual filter bags via local & simultaneous measurement applying low-cost PM-sensors in a pilot plant scale baghouse filter
P. Bächler*, J. Meyer, A. Dittler, Karlsruhe Institute of Technology (KIT), Germany
Baghouse filters are used in a variety of gas cleaning applications, as low dust emissions are required to meet statutory limits in order to protect the environment (e.g. waste incineration plants). In other applications like the cement industry, surface filters are used for product recovery, or downstream unit operations (e.g. catalysts) may rely on particle free air. Thus, the dust emission of pulse-jet cleaned filters is a key parameter for plant operators. The origins of the dust emission in baghouse filters are well known. In the case of “ideal” filter operation, particles can penetrate the filter medium after jet pulse cleaning and the removal of the dust cake, where the pulse is triggered after exceeding a maximum differential pressure or a specified time. This causes a PM emission peak until a sufficient dust cake is formed. In real baghouses, other factors like leaks of the filter bag or the plenum plate, damaged filter media and the seams of the filter medium, or incorrectly installed filter bags contribute to the overall dust emission. The location of these PM emission hotspots remains unknown, as in most cases only the global dust emission of the entire facility is monitored at the end of the pipe (e.g. in the stack), if at all. An easy online method for the identification of leaks and spatial PM levels on the clean gas side could greatly help plant operators. In previous publications, the capabilities of optical low-cost PM-sensors to characterize the PM-emission behavior of surface filters was shown in a filter test rig and a pilot plant scale baghouse filter with nine filter bags. Each bag was equipped with a low-cost sensor to enable spatial and simultaneous PM monitoring. The main particle emission of individual cleaning events was detected by the low-cost sensor installed at the corresponding filter bag only. This study expands upon the results. In order to evaluate spatial PM differences, one filter bag with sealed seams was exchanged with a filter bag with open seams for multiple bag mounting positions on the clean gas side for several test runs...
CFD modelling of a bag filter plant for flue gas cleaning under consideration of flow shift and particle deposition relocations
U. Heck*, M. Becker, DHCAE Tools GmbH, Germany
Bag filter systems for exhaust gas purification are characterized by a large number of bag filters (usually over 1000), which are loaded with dust particles and cleaned at regular intervals with a pressurized medium. In plant operation, malfunctions often occur due to uneven loading of the filters, which leads to reduced service life with typically high repair costs and plant downtime.
In the problem at hand, a bag filter system for flue gas cleaning in a power plant operation showed several failures within one year, in which cracks occurred in the filter fabric of individual bags. As a result, the specifications for air pollution control could no longer be met. The plant had to be shut down frequently and defective filters had to be replaced.
In general, CFD analyses have proven their potential for optimizing various processes, especially in plant construction industries considering the relatively high investment and operating costs of the plants, but also to avoid plant failures. But the size of the bag filtration plant with the high amount of filters to be considered as well as the dynamic interactions between the continuous particle deposition on filters, the local increase in flow resistance at the filter and the associated flow and deposition displacement make it difficult to optimize the plants with typical flow simulation tools. Since common CFD tools cannot take these interactions between deposition, resistance increase and displacement into account, adapted calculation tools are required especially for these problems.
The CFD modelling was done using the filter modelling tool from DHCAE Tools based on the CFD toolbox OpenFOAM  . The modelling extension uses an Euler-Lagrangian approach whereby the interactions between filter loading, displacement of the continuous flow due to the increase in resistance and subsequent particle deposition are considered in an iterative process. This enabled the filters in the plant to be identified which receive a permanently increased particle load. As a result, these filters showed...
Natural vortex length and its effects on the performance of a sampling cyclone
D. Misiulia*, S. Antonyuk, Technische Universität Kaiserslautern, Germany; G. Lidén, Stockholm University, Sweden
Personal cyclone samplers have been widely used to measure the respirable mass of particles in occupational and ambient environments. In respirable dust sampling, it is essential that the cyclone cut-off characteristics be known and constant, and that each cyclone be operated at a flow rate which produces the desired cut-off.
The aim of this work is to investigate the ﬂow pattern and performance of a sampling cyclone at different flow rates and reveal the effects of the natural vortex length on pressure losses and particle penetration using Computational Fluid Dynamics (CFD)...
A CFD study on gas flow and liquid spray atomization using a spiral nozzle in a wet scrubber
O.j Kristof, P. Bulejko*, T. Sverak, J. Kalivoda, Brno University of Technology, Czech Republic
This work is a first attempt to simulate liquid spray atomization using a spiral nozzle in a spray. Spiral nozzle has a special non-axisymmetric geometry able to create a spray pattern in the form of three concentric hollow cone liquid sheets. This geometry leads to a mass transfer intensification among pollutant gas and the absorption liquid as well as a better capturing efficiency of PM. Thus, only one nozzle can be used instead of a system of several nozzles in the spray column. First, we simulated the gas phase distribution inside the scrubber chamber using a Reynolds stress model with the coupled solving scheme. This model is suitable for description of extremely turbulent flow. Second, we used a two-phase VOF model to investigate basic parameters of liquid flow escaping the spiral nozzle (refer to figure below). Both simulations can then be used to study liquid shower in the scrubber in a counter-flow with the entering polluted gas using a DPM model of the sprayed liquid. The DPM model provides us with information about distribution of liquid fragments and individual droplets to estimate the interface area necessary for adequate mass transfer rate. Result of this study can help to better optimize gas scrubbers in terms of capturing efficiency, size, usage/regeneration of absorption liquids and energy demands, which is tightly related to acquisition and operating costs...
Simulating filter quality of nanofiber filter: Effects of slip-flow and implications for filter design
Y.T. Chen, T.C. Hsiao, C.W. Lin, S.H. Huang, C.C. Chen*, National Taiwan University; Y.M. Kuo, Chung Hwa University of Medical Technology, Taiwan
This work presents simulated results of filter quality factors (FQ), also referred to as Figure of Merit (FOM), of nanofiber/microfiber mixed filters in order to produce the filter with the highest FQ. The computational scheme is based on the theory of single-fiber efficiency and the semi-empirical equation of pressure drop proposed by Davies (1953) and Bian et al. (2018). The equation cited here has considered the air molecule “slip-effect” on particle collection efficiencies and the pressure drop across the filter. We assumed here that filter with micro-size (1 μm) and that with nano-size (50 nm) contribute independently to the particle collections and air resistances. The results of pressure drop predictions, both with and without considering the effects of gas-slip on nanofiber were...
Simulation of particulate matter detachment and transport in wall flow filters using lattice Boltzmann methods
N. Hafen*, A. Dittler, M.J. Krause, Karlsruhe Institute of Technology (KIT), Germany
Wall-flow particulate filters are used for particulate matter (PM) removal from exhaust gas in a variety of aftertreatment systems of combustion engines. Here, they significantly reduce PM emissions. Inside these filters, the gas flow is forced through a porous wall between oppositely arranged inlet and outlet channels.
During this process, porous PM layers, which consist of both reactive and inert components, are formed inside the filter channels, resulting in an increase of the filter back pressure. This leads to the necessity of regenerating the filter by oxidizing the reactive components continuously or in reoccurring intervals and breaking up the continuous PM layer into individual layer fractions. When reactive-inert particulate matter structures re-arrange during the regeneration process, remaining inert material can be observed in different deposition patterns, impacting operational filter performance. The objective of this work is a deeper understanding of wall flow filter operational behaviour beyond sole engine applications.
Due to its massive parallelization capability, the Lattice Boltzmann Method has been shown...
Conceptional design for fractional filtration efficiency testing of gasoline particle filters (GPF)
D. Göhler*, C. Rupf, S. Große, C. Peters, A. Rudolph, Topas GmbH, Germany
Gasoline particle filters (GPFs) are gaining an increasing importance since regulations for engine particle emissions become more and more strict not only for diesel engines (Joshi & Johnson 2018). Thus, high effort was spent in the recent years on the development of GPFs (Lambert et al. 2017). But the current state of the art regarding production control related to particle removal efficiency is claimed to be not satisfying (e.g.: test time, GPF loading).
To fill this gap, a comprehensive testing program was performed by means of an approved production control test system (AFC 132 QC HEPA, Topas GmbH, Germany) that permits a complete particle separation efficiency testing in 30 s. On the basis of several GPF specimens with quite different separation efficiencies, a comprehensive testing program was performed using quasi-monodisperse and polydisperse, metastable reference aerosols composed either of liquid or solid (see Fig. 1) particles. Separation efficiencies were characterised by contemporaneous analyses of upstream and downstream aerosol. For this purpose, different aerosol-analytical instruments/methods like condensation particle counters, optical particle counters or optical particle size spectrometers were operated. Moreover, separation efficiencies of quasi-monodisperse aerosols were cross-checked with fractional separation efficiencies based on polydisperse test aerosols and differential electrical mobility analysis.
Received data are promising and allow a deduction of recommendations for suitable test setup configurations. This includes also meaningful process and test parameters for the determination of (fractional) separation efficiencies of GPFs for research and development in laboratories or quality assurance tests at production lines. The presentation will give detailed information on the performed analyses and process relevant test parameters as well as on testing requirements (e.g.: face velocity, residence time, inert test substances), which are different to standard air filter efficiency testing due to the special GPF particle filtration mechanisms...
Characterization of oil structures on thin, porous fibre media through µ-CT imaging
C. Straube*, J. Meyer, A. Dittler, Karlsruhe Institute of Technology (KIT), Germany
Fibrous coalescence filters are widely applied in gas cleaning processes to separate liquid droplets from a gas flow (e.g. oil mist). When separated on the fibres of the filter medium, the oil droplets can take many shapes dependent on the wettability, roughness and diameter of the fibres, droplet volume and fibre arrangement (e.g. axisymmetric barrel-shaped droplets and axially asymmetric clamshell-shaped droplets). The overall morphology of the deposited droplets on the filter fibres is well known from optical microscopy, however, no studies exist regarding the impact of these separated droplets within the filter matrix on the separation efficiency. To investigate a change in the filtration efficiency the exact morphology of oil structures on and between adjacent filter fibres has to be characterised. Thus, the spatial deposition of the droplets on the fibres (upstream, downstream or partially upstream and downstream side) as well as...
Coupling micro-scale and macro-scale CFD models for liquid aerosol filtration
D. Hoch*, A. Baumann, J. Niessner, Heilbronn University of Applied Sciences, Germany
Liquid aerosol filtration is a multi-scale process making modeling and CFD simulation extremely challenging. On the micro-scale, fibers and droplets are resolved and filtration efficiency can be predicted. However, these micro-scale simulations are restricted to small sections of the filter medium. In order to calculate the pressure loss of the whole filter over the filter life time, a macro-scale simulation is needed. Therefore, averaged parameters (porosity, permeability) and constitutive relationships (relative permeability – and capillary pressure – saturation relationship) need to be obtained from the micro-scale . Since on the macro-scale, droplets and fibers are not resolved, the deposition is modeled by a source term, which is the focus of this work.
In order to obtain this source term locally as a function of air velocity, liquid saturation, and droplet size spectrum of each macro-scale cell, the micro-scale simulation is carried through on the real fibrous structure of the filter medium obtained from µCT scans. This micro-scale model has been validated by comparison to an empirical solution . The filtration efficiency was calculated using different velocity and saturation levels as well as different droplet sizes, matching the maximum value range occurring in the macro-scale simulation. The saturation difference is realized using different geometries, treating the liquid phase as solid phase. In between the data points considered in the micro-scale simulations, linear splines are used. Using this filtration efficiency, it is possible to...
Comparing mesh-based and voxel-based CFD models for aerosol deposition in complex fibrous filters
D. Hoch, A. Baumann, J. Behringer, J. Niessner, Heilbronn University of Applied Sciences; M. Azimian, Math2Market GmbH, Germany
Today, liquid aerosols are generated in many industrial processes like machining, manufacturing of catalysts or in pneumatic compressors. Liquid aerosols may be harmful since small droplet may enter the respiratory system and cause lung cancer, allergies, or other diseases. Also, due to the recent COVID-19 outbreak, aerosols containing viruses are classified as dangerous. We present results of micro-scale simulations of mist deposition on fibrous structures and validate them by comparison to single fiber efficiency (SFE) theory and to experimental data...
Influence of the interaction between water droplets and soluble filter cakes on the fractional separation efficiency of surface filters in gas cleaning applications
A. Schwarz*, J. Meyer, A. Dittler, Karlsruhe Institute of Technology (KIT), Germany
The presence of water droplets in a filtration system in gas cleaning applications (e.g. gas turbines exposed to ambient air) due to fog, spray rain or condensation (caused by slight differences in temperature within the system) has an impact on the filters’ operational performance. The differential pressure between the raw and the clean gas side of the filter and the fractional separation efficiency are key parameters considering the operational performance of the filter.
This study presents experimental investigations, which show the influence of the interaction between water droplets and soluble filter cakes on the fractional efficiency of surface filters during operation in a modular filter test rig manufactured by Palas®.
When a particle-laden surface filter is exposed to water droplets, the structure of the filter cake changes. Dendrite structures may collapse, or crusts may form depending on the composition of the cake (e.g. ratio of soluble salt particles and insoluble dust). These structural changes in turn cause a change in the pressure drop and the fractional separation efficiency of the filter. During the experimental procedure, surface filters are loaded...
Dosing of hygroscopic salt particles for influencing the operating behavior of surface filters for dust separation
D. Horst*, Q. Zhang, E. Schmidt, University of Wuppertal, Germany
When separating dusts with surface filters, the structure of the dust cake that forms in the process is of great importance, as it has a decisive influence on the operating behavior of the filter. With regard to the cyclic regeneration of the filter, the mechanical strength of the dust cake is particularly relevant, which in turn can be influenced by so-called raw gas conditioning. The adhesive forces of the particle contacts have a considerable influence on the mechanical strength of the dust cake. An increased mechanical strength in turn improves the cyclic regeneration of the filter, resulting in sufficient removal of the dust cake from the filter medium with less energy input.
In any dust cake of non-hygroscopic particles, the metered addition of a fraction of hygroscopic salt particles offers a possibility to influence the operating behavior of surface filters. For this purpose, a temporary change in gas humidity induces the deliquescence and efflorescence of the added salt particles. In this case, the deliquescence and efflorescence properties of hygroscopic salt particles are used to subsequently change the adhesive forces of the particle contacts as well as the structure of the dust cake formed on the filter medium and thus influence the operating behavior of the filter.
In the present paper experimental investigations on the influence of the concept on the operating behavior of test filters, especially with regard to the regeneration of the filter, are presented...
Precoating: influence of moisture and thickness on collection efficiency
B.K.S.A. Andrade*, M.L. Aguiar, Federal University of São Carlos; R. Sartim, ArcelorMittal Global R&D, Brazil
Precoating consists of covering filter media with particulate material forming an initial powder layer which is responsible for reaching the clogging point. The particulate matter accumulates in the fibers and in the particles already captured, forming the dendrites, and then the cake. Consequently, it increases the efficiency of dust collection at the beginning of filtration, guarantees the passage of air flow freely through the bag, promoting better detachment of the cake while extending its life span. In order to analyze the influence of moisture and precoating layer thickness on the collection efficiency for micrometric particles, were performed filtrations following the VDI 3926 Standard. Initially, the characterization of the particulate material was carried out to obtain the aerodynamic diameter, the average volumetric diameter, the chemistry composition and images in a Scanning Electron Microscope (SEM). Then, the filter medium was characterized to obtain the fiber diameter, porosity and permeability. Then, an experimental design was made, varying the conditions of humidity (5, 10 and 15%) and thickness according to the limit pressure drop (50, 100, 150, 200, 300 e 400 Pa). Precoating was carried out to the desired thickness by feeding the particulate material with the specified humidity. Then, primary sintering powder was fed to evaluate the collection efficiency...
Influence of stitching holes in the clogging point and filtration efficiency of a filter medium
C.R. de Lacerda*, B.J. Chiaramonte de Castro, B. Râmela de Melo, M.L. Aguiar, Federal University of Sao Carlos; R. Sartim, Brazil
Seams are commonly used during the manufacturing of filter bags to ensure the cylindrical design. However, the seam may influence the filtration performance due to the presence of stitching holes. In the initial moments of filtration, more specifically in the first filtration cycle, the filter pores are filled with particles, however at that moment the stitching holes can cause preferential paths to the flow and thus, changing the clogging point behavior. . The issue of seam has been discussed in the literature from the perspective of emissions but there are few works concerning the influence of seam in the dust cake formation. The aims of this work were to investigate the influence of stitching holes in the clogging point behavior of particles from the sinter plant process and to evaluate the filtration performance of microparticles using a mixture of aromatic polyimide (PI) and polytetrafluorethylene (PTFE) filter material....
Correlation between clogging point and precoat to obtain high collection efficiency in bag filters
B. Râmela de Melo, C.R. de Lacerda*, B.J. Chiaramonte de Castro, M.L. Aguiar, Federal University of Sao Carlos, R. Sartim, ArcelorMittal Global R&D, Brazil
Mostly virgin filter media have low collection efficiency, which requires superficial treatments to obtain a better performance. One of these treatments is coating filters with PTFE membrane. However, surface treatment increases the pressure drop and its cost, and consequently also increases the cost of equipment maintenance and operation. Another alternative commonly used in the industry is precoating, which is less expensive and has good performance in terms of filtration efficiency, but there are few studies on this subject. Other advantages of precoating are the lower initial filter media pressure drop, the possibility of increasing the useful life of the filter bag, and can also contributes to the chemisorption of pollutants present in the gas, such as HCl and SO2. For the efficient use of this technique, it is necessary to know the ideal mass of precoat material that guarantees high filtration efficiency. In the present work we evaluated the necessary mass of precoating material to be used and its correlation with the clogging point.
The grade collection efficiencies for micro and nanoparticles were analyzed for different masses of limestone precoat deposited on the polyester filter medium (PE), in which, one of them was the mass obtained by the clogging point. Also a polyester filter medium with PTFE membrane (PE/PTFE) was used to compare the results. The clogging point, obtained by...
Performance of a bench-scale hybrid filter in the collection of nanoparticles
B.J. Chiaramonte de Castro, C.R. de Lacerda a, B. Râmela de Melo, M.L. Aguiar*, Federal University of São Carlos; Rafael Sartim, ArcelorMittal Global R&D, Brazil
Polytetrafluorethylene (PTFE) membranes are commonly used in the coating of fibrous filter media to ensure the efficient collection of fine particles, reduce particle penetration, facilitate the bag cleaning and extend the service life of the bags. However, the cost of a filter medium with membrane is around seven times higher than the cost of a bag of the same fibrous material without membrane. Since an industrial bag filter commonly have hundreds of bags that need to be periodically replaced, an important question must be answered for each specific application: is the choice of an expensive filter medium, such as a filter with PTFE membrane, really worthwhile? In this context, this work aimed to assess the collection efficiency of fine particles from the sintering process of a steel industry using a polyacrylonitrile (PAN) filter with and without PTFE membrane, at two filtration velocities: 1.0 and 2.0 m min-...
Production of microfibers by electrospinning for applications in air filtration
D.P.F. Bonfim*, V. Guerra, M.L. Aguiar, Federal University of São Carlos, Brazil
The high concentration of particulate matter in atmospheric air is now a worldwide pollution problem, which makes removing particulate matter from air flows a major challenge. For this reason the use and development of fibrous filter media has been extensively studied. The electrospinning process is the most used for the production of fibers and is different from other production processes due to the versatility of processing different polymers, the capacity to control the diameter, morphology, orientation and structure of the fiber, where it is possible to achieve high efficiency of particle collection with low pressure drop. Therefore, the objective of this work was to produce filtering media by electrospinning for use in nanoparticle filtration operations from polymeric solutions in different concentrations...
Techniques evaluating the resistance to moisture of electrospun pva nanofibers for air filtration
A.E. de Oliveira, M.L. Aguiar, V.G. Guerra, Federal University of São Carlos, Brazil
Poly (Vinyl Alcohol) (PVA) has been used to produce nanofibers with electrospinning for several applications related to the non-toxicity of the material, including wound dressing and tissue engineering. The application in air filtration has been developed, however, the high hydrophilicity of the material requires the crosslinking of PVA with additives, as glutaraldehyde, or even different organic acids, as citric acid. Different methodologies are employed in the literature to verify the resistance of the polymers nanofibers and films to water and to prove the efficiency of the crosslinking, which includes the evaluation of the loss mass after immersion in water and the measurement of the water contact angle, which are not suitable for air filtration applications. The present work studied different techniques to verify the resistance of PVA nanofibers made of aqueous solutions (~10 wt.%) manufactured with electrospinning and crosslinked with citric acid (0.5 wt.%). The surfactant Triton X-100 was...
Nanoparticle filtration from table 3D printers using hollow-fiber membranes
P. Bulejko*, K. Mayerová, O. Krištof, A. Zatočilová, Brno University of Technology, Czech Republic
This work is a first attempt to simulate liquid spray atomization using a spiral nozzle in a spray. Spiral nozzle has a special non-axisymmetric geometry able to create a spray pattern in the form of three concentric hollow cone liquid sheets. This geometry leads to a mass transfer intensification among pollutant gas and the absorption liquid as well as a better capturing efficiency of PM. Thus, only one nozzle can be used instead of a system of several nozzles in the spray column. First, we simulated the gas phase distribution inside the scrubber chamber using a Reynolds stress model with the coupled solving scheme. This model is suitable for description of extremely turbulent flow. Second, we used a two-phase VOF model to investigate basic parameters of liquid flow escaping the spiral nozzle (refer to figure below). Both simulations can then be used to study liquid shower in the scrubber in a counter-flow with the entering polluted gas using a DPM model of the sprayed liquid. The DPM model provides us with information about distribution of liquid fragments and individual droplets to estimate the interface area necessary for adequate mass transfer rate. Result of this study can help to better optimize gas scrubbers in terms of capturing efficiency, size, usage/regeneration of absorption liquids and energy demands, which is tightly related to acquisition and operating costs...
Influence of pulse jet cleaning interval on the effective filtration area of a pleated filter in the plug-in type dust collector
K. Fukui*, T. Narita, K. Furumoto, T. Fukasawa, T. Ishigami, Hiroshima University, Japan
Pulse-jet plug-in type compact dust collectors remove dust from the gases generated in factories. A pleated filter is widely used in this device because the filter media is folded in a pleated shape to increase the filtration area. In order to operate this device continuously, the dust particles deposited on the filter should be removed from the filter. However, since some dust particles accumulate inside the filter and form a thin layer (the primary adhesion layer) which cannot be removed, the performance of the dust collector changes with operation time.
Therefore, in this study, the effect of the pulse jet cleaning interval on the deposition state of the dust particles on the filter was analyzed and it was also aimed to develop the evaluation method for the dust collection performance...
Removal of nanoparticles by electrostatic precipitation: evaluation of the collection efficiency behavior with the electric field and air velocity
F. A. Lima*, V.G. Guerra, Federal University of São Carlos, Brazil
The development and optimization of equipment aimed at removing nanoparticles from atmospheric air has been gaining importance in the current scenario. The adverse effects of these ultrafine particles on human health and the environment motivate the development of techniques for their removal, both for the processes’ sustainability and the mitigation of pollutants. Among the commonly used equipment, electrostatic precipitators stand out for their versatility and, for certain configurations, efficiencies are up to 99.9% in a wide size range. The present study aims to evaluate the influence of the electric field and spacing between wires in the collection of polydispersed NaCl nanoparticles....
Study on flow patterns in gas-liquid cylindrical cyclone based on signal processing and similarity analysis
Y.A. Wang*, J.-Y. Chen, Y.H. Zhou, Y.J. Huang, China University of Petroleum, China
Gas-Liquid Cylindrical Cyclone (GLCC) is a compact and efficient oil-gas separation equipment used in subsea production system. The flow pattern of liquid film in the upper cylinder of GLCC significantly affects its separation performance. In the past, the definition and classification of flow patterns of liquid film in GLCC were too subjective, and the study on its flow pattern transformation was very rare. In this paper, the liquid film thickness in the upper cylinder of GLCC was measured by using conductance sensor. Its transient signals were analyzed by using frequency spectrum and cumulative probability density function (CPDF). It was found that the different flow patterns have different characteristics, and these characteristics were then used to identify the flow patterns so as to obtain the flow pattern map in the upper cylinder of GLCC objectively. On this basis, the idea of similarity theory was applied to the study of GLCC’s flow pattern transformation, and the similarity analysis method was used to obtain the pivotal similar principle numbers. Furthermore, by introducing the dimensionless characteristic gas and liquid velocity parameters, a GLCC’s flow pattern transition prediction formula was proposed. The predictive formula has high...
Structural optimization and performance research of new cyclone separator with high efficiency and low resistance
H. Cui *, J.-Y. Chen, L. Kong, M. Cao, China University of Petroleum, China
Improvement of efficiency and reduction of pressure drop are the main optimization directions of cyclone separator. however, efficiency improving often accompanies pressure drop improving, and this is the difficulty of optimization. Herein, on the basis of the PV cyclone separator, the structure of the entrance, exhaust pipe, cylinder and ash hopper of the separator were optimized respectively, and a new type of cyclone separator was designed; subsequently, the separation performance of the new cyclone separator was compared with that of the PV cyclone separator by experimental method; furthermore, the internal flow fields of separators were studied by the method of numerical simulation, and the reason for the excellent performance of the new cyclone separator were analyzed; finally, the theoretical calculation methods of pressure drop and efficiency of new cyclone separator were put forward. The results showed that...
Formation and rearrangement behaviour of ash particles in diesel particulate filters
M. Kaul*, E. Schmidt, University of Wuppertal, Germany
Diesel particulate filter (DPF) are used for exhaust aftertreatment in passenger cars and commercial vehicles. The particles to be separated are primarily carbon-based components formed in the engine compartment due to incomplete combustion. The aftertreatment converts those components into ash particles.
The particle-formation inside the DPF has an impact on the filtration device´s operating performance, e.g. the separation and the backpressure behaviour. Three different kinds of particle formation can be differentiated as shown in figure: The layer formation, the filling at the end of the channel, and a blocking at the front side of the channel.
At the Institute of Particle Technology of the University of Wuppertal, a wind tunnel with a DPF unit brick has been built to study the storage and rearrangement processes inside the channels...
Modeling and simulation of catalytic converters for exhaust gas after-treatment with GeoDict
A. Weber*, M. Azimian, Math2Market GmbH, Germany
Since many years, the software GeoDict is used to simulate filtration processes and modeling of filtration media. This includes simulation of the air flow inside the filter as well as tracking particles and simulation of their interaction on the filter surface.
In our newest version - GeoDict 2021 - we have adapted these functionalities for the simulation of Diesel Particulate Filters and Catalyst Monoliths. For example, new ways of modeling monolithic structures, detailed diffusive movement statistics, and 1st order reaction simulation are now available. These improvements aim to model and optimize air flow, soot filtering, and noxious gas reduction in exhaust gas systems.
Exhaust gas treatment bears many challenging problems at different scales. From the larger scale, where macroscopic flow through the monolith channels is of interest, down to the diffusive movement between and even inside the highly porous ceramic grains. Surely, completely different effects take place at each scale. Nevertheless, GeoDict simulates all those effects through different modeling and simulation modules.
At different scales and using various modules, we present some examples on how:
- The flow passes through a plugged or un-plugged monolith
- The molecules interact with the washcoat layer and the catalytic centers within
- The catalytic reaction is simulated in the micro scale
In essence, we show how GeoDict helps optimizing the catalytic and filtration efficiency....
Optimization of the setup of a mist filter based on CFD simulation and a DoE-based response surface
A. Baumann*, D. Hoch, J. Niessner, Heilbronn University of Applied Sciences, Germany
Similar to fine dust, liquid aerosols (mist) represent a risk to human health since small droplets may enter the respiratory system and cause lung cancer, intoxication, allergies, or severe diseases, such as COVID-19. Oil mist emissions from production processes are reduced by filters (production halls) and by air dryer cartridges while virus-like aerosols are removed by face-masks and respirators. The challenging goal for filters are to obtain a high filtration efficiency at a low pressure loss. In order to predictively design a filter setup fulfilling these conditions an optimization process based on modeling and simulation of two-phase flow in this work is presented.
In order to optimize the quality characteristics pressure loss and separation efficiency of a filter, an optimization analysis is performed with the help of ANSYS DesignXplorer. The pressure loss and the ratio of oil mass flow by drainage to oil mass flow across the inlet are used as target values. In order to develop a filter that is as efficient in energy and separation as possible, a low pressure drop and high discharge ratio is desirable. To determine the structure of the filter, the filter is set up with three layers which all have the same thickness. In these layers, the variables entry pressure and permeability serve as design variables for optimization. Using a DoE approach based on the Latin Hypercube method within certain, defined limits, the two-phase flow processes in more than 100 different filters are simulated and both filtration efficiency and pressure loss are determined. These samples then serve as the basis for a response surface with the genetic aggregation technique to determine the optimum filter with respect to the target variables. To minimize possible inaccuracies, the determined optimum is used as a starting point for a second optimization run with narrower limits. The optimum from the second optimization run is used as a basis for the filter properties inlet pressure and permeability to produce a prototype of the filter. The results...
Numerical investigation of coalescence filtration: Multiphase flow through fibrous structures
J. Chaudhuri*, K. Boettcher, P. Ehrhard, Technical University Dortmund, Germany
Coalescence filtration is a mechanical filtration process, which is used for the removal of dispersed aerosol particles in a gas stream. It is widely employed in industrial applications, for example in the removal of oil particles present in compressed gases. The performance of such a filter, is quantified, based mainly on its capture efficiency and flow resistance and estimating these parameters, using numerical methods, is a cost-effective and time-saving alternative to experimental studies.
For this purpose, multi-phase flow simulation using an Euler-Euler formulation is performed with the help of the commercial CFD software ANSYS CFX to model the macro scale filtration process. The model is scaled with the filter thickness and a perfect wetting of the fibers is assumed. To model the capture of the dispersed phase, the penetration approach for single fiber capture-efficiency is extrapolated to multiple fibers resulting in an exponentially decaying interpolation scheme. To model the flow of air through the filter, an empirical pressure-drop correlation is developed based on fibre-scale flow simulations for various flow parameters using the design of experiments (DOE) methodology. For the fibre-scale simulations, 3D fibers are generated with random position, thickness and orientation using algorithms developed in house, ensuring that all fibers remain in the filter bed and that the fibers do not intersect. Simulations are performed using...
Simulation of slip flow for nanofiber filters
L. Cheng*, S. Linden, A. Wiegmann, Math2Market GmbH, Germany
When the air in motion contacts with a solid surface, usually the air is thought to be approaching to a complete stop at the surface, and the velocity is zero relative to the solid surface. However, when the solid is so small that when the air passes the solid, only a fraction of the air molecules contact the surface. As the result, only those molecules have their velocities changed. The remaining air molecules remain their bulk flow motion. When we still consider the air as a continuum, the air velocity near the solid surface is not zero. That is the phenomenon called as slip flow.
The slip flow effect explains the low pressure drop for nanofiber filters because fewer air molecules exchange momentum with the fiber, there is less air drag on the fiber leading to less energy loss. Also because of the slip flow, the flow streamline is closer to the fiber surface and the single fiber efficiency of small particles is increased on nanofiber . Therefore, the slip flow is a very important factor for nanofiber filtration. It must be considered when simulating the nanofiber filtration.
The slip flow was studied historically either with empirical equations or for very simple 1D or 2D structures, which cannot provide detailed information for a complicated 3D fibrous material structure. Cheng et al.  presented the approach to implement slip flow for 3D voxelized structures. In this approach, the expression of the slip velocity, which assumes the slip velocity proportional to the shear stress at the surface, is reformulated for a locally quadratic velocity profile instead of the standard linear profile, and reimplemented in our flow solver. The direct simulation of the slip flow is then possible, and it can be validated with analytic solutions.
The simulation results are compared to the newly obtained measurement data for nanofiber filters. The influence of slip flow in nanofiber structures then is studied and the results of flow and filtration simulations are presented...
Morphology of deposits on single fibres build by deposition of aerosol particles in the diffusion and interception regime
J. Zoller*, J. Meyer, A. Dittler, Karlsruhe Institute of Technology (KIT), Germany
The morphology of particulate structures build on single filter fibres due to exposure to aerosol is not reported experimentally for particles smaller 360 nm in literature, although common particles from exhaust gases are in this size range.
This study investigates the morphology of deposits build on a 40 μm single fibre exposed to propane soot (157 – 238 nm count median diameter) or aerosol generated by spark discharge between carbon electrodes (68 – 134 nm count median diameter). The fibre was positioned perpendicular to the flow and the flow range was 6 – 57 cm/s. The figure shows...
Particle structure detachment from a single elastic fiber during multiple stretching cycles
L. Poggemann*, J. Meyer, A. Dittler, Karlsruhe Institute of Technology (KIT), Germany
Depth filtration is commonly used for particulate matter removal in several fields of applications like air-conditioning, cleanroom technology and cabin air filters. The primary factors to characterize the operational behavior of depth filters are the separations efficiency, the pressure drop and the loading capacity. Normally the pressure drop across a filter system is increasing with the deposited particulate mass in the filter medium (Payatakes und Gradoń 1980; Kanaoka und Hiragi 1990; Brown 1993). In conventional depth filter systems, operating flow velocities are way below 1 m/s. At these velocities the particle deposit at the fiber. At velocities well above 1 m/s particles are likely to bounce off or being blown off from the fiber. To detach particles of 10 µm from filter fibers, high flow velocities above 1 m/s are needed (Löffler 1972). All the findings of Löffler are valid for stiff fibers. "But how do behave inert particles on stretchable fiber when the single fiber is stretched and exposed to an airflow at low velocity?” Currently little knowledge is available on this new fundamental question about the above-mentioned processes, especially about the re-arrangement and detachment mechanism of particulate matter on a stretchable single fiber. To obtain insights, experiments on a single fiber are examined.
A compact particle structure was deposited on a stretchable single fiber. Using a new fiber mounting device the fiber is stretched in multiple cycles or in a stepwise procedure to sound out the limits of the dynamic element. While stretching the fiber is exposed to flow at low velocity. Particle structures re-arrange and detach during the stretching procedure. In addition, the fiber rotates on its own axis while stretching the fiber. The size analysis of those detaching particle structures and the analysis of the rotation is examined by image analysis. For validation of the particle structure size, first experiments with a laser-sheet measurement technique are executed...
Hot gas filtration for the recovery of heavy metal-reduced ashes from sewage sludge incineration
L.F. Köhl*, U. Petasch, J. Adler, M. Lincke, B. Faßauer and A. Michaelis, Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Germany
Ashes from sewage sludge incineration contain phosphorus which is a vital and irreplaceable nutrient and is used as a fertiliser in agriculture. Due to the chemical composition of the phosphorus compounds and the excessive content of heavy metals, sewage sludge ashes do not fulfil the requirements for direct use as fertiliser in agriculture. To be able to use the ashes, they must be reduced of heavy metals. In recent years various chemical and thermal processes have been developed. Thermochemical processes are used for phosphorus recovery from sewage sludge ashes in which the desired substance conversions can be achieved by reacting the ashes with special additives. This technique is exclusively carried out in downstream process steps that are completely decoupled from the actual sewage sludge incineration but uses reaction temperatures of 800 – 1000 °C, which are in the range of the of the temperatures of the incineration process. Energetically advantageous would be processes which directly utilise the thermal energy in the incineration process to modify the ashes and, by fractionating the reaction products via hot gas filtration, enable the production of ash fractions suitable for use as fertiliser. However, the combination of hot gas filtration and thermochemical conversion is not yet a sufficiently researched process and can lead to considerable stress on the filter material.
In this work, the novel procedure with its technological challenges will be introduced and the advantages and disadvantages will be presented. Special focus will be placed on the hot gas filter, which are exposed to particularly high loads due to the new process...
Experimental investigations into electrostatically assisted wet precipitation inside a wind tunnel
M. Zillgitt *, E. Schmidt, University of Wuppertal, Germany
During the processing of bulk materials and the subsequent transport and storage, large dust emissions occur, which have to be reduced to protect human health. In this context water dispersion systems are often used. Airborne particles are bound to water droplets and thus settle more quickly afterwards. The precipitation of particles of small size, which are often classified under the so-called Particulate Matter (PM) fractions, is a particularly considerable challenge. Due to their low mass, the effect of inertia becomes less important with decreasing particle size. Therefore, a new approach is required to increase the probability of collision between particles and droplets in order to ensure effective air pollution control.
Based on the use of two-fluid nozzles, in which small amounts of water are atomized by a high use of compressed air, this approach is achieved by implementing an electric field within the nozzle. The generated water spray mist is thereby electrostatically charged. By increasing the individual droplet charge, electrical forces cause...
Improvement of dust release functions on the basis of single particle investigations
N. Schwindt, G. Reznik*, M. Kaul, E.Schmidt, University of Wuppertal; D. Schulz, H. Kruggel-Emden, Technical University Berlin, Germany
Dust emissions result from the handling of bulk solids in production processes. These emissions can lead to environmental pollution, long-term diseases or cause explosive atmospheres. In order to reduce all this kind of possible hazards for the environment and humans prediction methods of dust emissions determining the dust mass reliable during a process step have to be developed.
In order to improve the dust release functions gained in a previous project collaboration between the Institute of Particle Technology (University of Wuppertal) and the Department of Mechanical Process Engineering and Solids Processing (Technische Universität Berlin) further investigations on an experimental and numerical level are carried out. Here, the first parts of the experimental studies are presented which are achieved by the Institute of Particle Technology. In contrast to previous investigations now experiments with single particles, which derive from a so-called Rerefence Test Bulk Material (RTBM), are performed. The RTBM is a blend of spheres and a well-defined powder in which the powder represents the fine material and the spheres act as the coarse material. The aim of the focus on single particles is to gain more detailed information about the impact factors of the release of fine particles (powder) from a surface (spheres) in dependency of physical parameters...
Comparative life cycle assessment between a novel loose-fill packaging material and maize starch packing peanuts
J. Lunewski*, E. Schmidt, University of Wuppertal, Germany
In addition to digitalization, the actual SARS-CoV-2 pandemic is increasing online trading, leading to rising parcel demand. In general, a parcel consists of packaging and support material. The group of support material may include sealing, identification and securing material, as well as filling and padding material. In the context of filling and padding matter, foam peanuts and bubble wrap most commonly used.
As part of the research, the goal is to investigate the environmental impact of the so-called “ExpandOS” as a novel loose-fill packaging material made of kraft paper compared with state-of-the-art maize starch packing peanuts. The “ExpandOS” representing small triangular prisms, where the edges feature a sawtooth structure. The “ExpandOS” main advantage is to avoid the movement of heavy products inside parcels, due to their surface geometry, with a tendency of forming a strong compound in bulk.
Life cycle assessment (LCA) represents a tool for quantifying and evaluating the environmental impacts like greenhouse gas emissions of a product over its entire life cycle. In application to the chosen loose-fill packaging materials, the bulk volume represents the functional unit. Furthermore, the system boundary has been set from cradle to grave. This approach includes the modelling of all production steps out of the resources, the utilization phase and the subsequent disposal of both systems. In this context, the open-source software “openLCA” was used as a modelling environment in combination with “ReCiPe 2016” as a possible impact assessment method...
Filter testing according to ISO 29461 - Air intake filter systems for rotary machinery
M. Neukirch, C. Kappelt, A. Rudolph, C. Peters, S. Große*, Topas GmbH, Germany
For the application of rotary machinery the air filter systems are an essential component of the complete turbine/compressor system. The machines have become more complex over the last few years and therefore the protection of the machines is becoming more and more important. Particulate contamination with salt or other corrosive particles can significantly impair a turbine power system through erosion, fouling or hot corrosion. Another challenge is the different climatic conditions from desert, offshore, rain forest to arctic conditions.
Due to the different requirements for the filters, the ISO 29461 standard is divided into 7 parts. It should be noted, that part 1 is the only part which is already approved by the ISO committee, the parts 2 to 7 are still under development.
Topas has developed a test system that covers the parts 1, 5 and 7 of the ISO 29461 series of standards respectively of the drafts of the ISO 29461 standard. The presentation will show the latest state of the test procedure as well as the test system and focuses on the description of the fully automated filter test system with flame photometer and optical particle counters. Furthermore, important key components for filter performance testing like humidifier, water spray system and aerosol generators (DEHS, NaCl and ISO A2 fine dust) will be presented. As well as the evaluation of the obtained measurement data such as differential pressure, particle separation efficiency, water separation efficiency, dust loading, salt and water deluge challenge. The creation of a summary report, which includes all determined and recorded parameters for a direct interpretation of the test results, is also a part of the presentation...
PALAS - EN149 Penetration test – Uncertainties and physical background of the measurement technology
M. Schmidt*, PALAS GmbH, Germany
Face masks are currently and in future one of our major weapons to protect people from infections by airborne particles as viruses or bacteria.
As the perfect function of the mask is the basis for the safety of the user, these masks need to be tested concerning their performance in particle removal.
Standards as EN 149 in Europe, GB 2626 in China and 42 CFR 84 in United States must ensure a clear comparability of test results for the protection degree of the mask. Below is an extract of the main test parameters for the evaluation of face mask efficiency:
Comparable penetration test results in respiratory filter testing – From the QC-lab to the production line
J. Spielvogel*, S. Percot, TSI GmbH, Germany; T. Johnson, J. Koczak, TSI Incorporated, USA
Filtration products need to be regularly tested in order to assess the correct protection level against harmful airborne matter. It is also important, that equipment that is used for testing the filtration products gives consistent results. Usually test equipment can be verified by tracing the results to a standard. For respiratory filter testing commonly used standards are EN 143/149, 42CFR part 84, and GB2626. These standards define key parameters for testing such as flow rate, aerosol concentration, count median diameter, geometric standard deviation, and ambient conditions. Some standards also specify the test equipment. Still, measurements that are compliant to the standards requirements don’t necessarily result in consistent penetration test results. While count median diameter and the geometric standard deviation are accurate means to define a sub-micrometer particle size distribution, the aerosol undergoes changes in the aerosol path of the filter tester that can change the size distribution.
When TSI developed a new model filter tester, the model 8130A, which replaced the model 8130, TSI executed a detailed test matrix in order to obtain continuity of measurement results between models. It consisted of:
- Two types of test aerosol, NaCl and Emery Oil
- Different types of flat-sheet media
- Different flow rates
In conclusion, these tests showed an excellent agreement between the models 8130A and 8130 for every media/aerosol combination and at different flow rates with measured penetrations typically within ±10% of the global mean.
To apply these results to in-line production filter testing requires...
One step beyond: From the experimental investigation of discharging methods to numerical optimization potential of electret filter media
M. Kerner*, S. Antonyuk, Technische Universität Kaiserslautern; K. Schmidt, IT for Engineering (it4e) GmbH; S. Schumacher, C. Asbach, Institute of Energy and Environmental Technology e.V. (IUTA), Germany
Electret filter media are commonly used in aerosol filtration to remove particles from gases. They provide a high initial particle removal efficiency combined with a low pressure drop as the fibers of the electret filter media are electrostatically charged. In addition to the mechanical deposition mechanisms (diffusion, impaction and interception), charged particles are deposited by the Coulomb effect and any (charged or uncharged) particles by dielectrophoresis.
The high initial particle deposition is reduced with increasing filter life, as already deposited particles attenuate the electrostatic effects mentioned above. In the worst case, the electrostatic effects have vanished and the aged electret filter media become conventional mechanical filter media. With regard to the application, it is necessary that even the aged filter media achieve a minimum filtration efficiency. For this reason, testing standards for electret filter media take into account ageing by discharging the electret filter media or the entire filter with isopropanol.
In this work experimental investigations on the influence of discharging methods on ten different corona charged and triboelectrically charged electret filter media are performed by means of deposition experiments. The focus is on the discharging methods with isopropanol prescribed in DIN EN 779 (liquid isopropanol) and its replacement ISO 16890-4 (isopropanol vapor)...
Modelling of the mechanical aging behaviour of PLA-based nonwovens and monofilaments under filter application-relevant conditions
R. Taubner*, Saxon Textile Research Institute (STFI), Germany, C. Schippers*, L. Tsarkova, Deutsches Textilforschungszentrum Nord-West gGmbH (DTNW); J. S. Gutmann, University Duisburg-Essen (UDE), Germany
Nonwovens and felts from synthetic fibers (polyester, polypropylene) or from glass fibers are the mostly used filter media in air filtration. These materials offer high efficiency, long service life and a good price-performance ratio. However, the modern growing trend to replace petroleum-based fibers with bio-based and bio-degradable polymers dictates a new challenge for researchers, filter developers and manufatures.
Presented research focuses exploring PLA fibers as an alternative material for applications in air filtration. Particular emphasis was made on the characterisation of the mechanical properties of PLA monofilaments under aging conditions, which are relevant for the applications as filter media, with an aim to quantify the biodegradability of the PLA based materials. Furthermore, the air filtration characteristics of the PLA nonwovens depending on the textile media parameters were tested.
Multiple methodologies were used to characterise structural changes and mechanical properties PLA monofilaments before and after respective aging treatments. The results of the DSC analysis, tensile stress tests, 3D optical microscopy and scanning electron microscopy were...
Changing a filter – A change of principle
T. Stoffel*, DELBAG GmbH, Germany
The new filter classes based on ISO 16890 are already looking back upon more than four years since their approval, not only by national European bodies of standardization but industrial associations around the globe. Still, large portions of the facility management business segment have not yet fully embraced their existence. Even under the old standards, maintenance crews were more often than not confused about when to change filters in an air treatment system. To even add to their misperception, historically, various recommendations have in the past led to considerable confusion with installers of air filters about the legally required or economical optimum time to change the filter.
This essay should look back at the insecurity caused in the past related to filter change intervals. We will engage in the difference between the final pressure drop measured on the former EN779:2012 and the recommended air filter change intervals stated in the former EN13779. Both of these standards have long been replaced for some time: ISO 16890 for air filters and the ISO 16798 for air treatment systems. Unfortunately, none of the two regulations have given our global strive adapt the layout of air treatment systems and service thereof - to configure to real ambient conditions - any simplicity, or given more safekeeping for the consumer. Neither have the requirements for energy efficiency made the configuration and timely service of air filters any easier.
The European Energy Efficiency Directive was first passed by the European legislation 2009. It introduced an unprecedented SFP value to calculate the specific fan performance and the fans overall energy consumption in 2009 to asses each component of an air treatment system. Since then the filter community has relentlessly been heavily scrutinizing the SFP’s lack of evaluating the dynamic change of energy consumption caused by air filters.
Guided by the Eurovent energy ratings system for air filters, the EU is expected to pass a motion in 2021 to update the European Energy Efficiency Directive that shall plan to reflect new change interval for filters that will fulfill both initial claims. Not only will the service life of a filter reflect the ambient conditions, but it will moreover guide users to change intervals that will minimize energy costs induced by the air filters design and filter medium...
Test methods for indoor air cleaners with alternative test aerosols and considering ultrafine particles
S. Schumacher*, A. Banda Sanchez, A. Caspari, U. Schneiderwind, C. Asbach, Institut für Energie- und Umwelttechnik (IUTA) e.V., Gemany
In the light of the growing awareness for air pollution, indoor air cleaners are meanwhile widely used to improve the indoor air quality. The market is expected to continue growing strongly during the COVID-19 pandemic as air cleaners may contribute to minimizing infection risks by filtration of virus-carrying droplets. Up to now, there are various national standards to test indoor air cleaners that determine the clean air delivery rate (CADR) as a measure for the cleaning performance. In the light of developing the first international testing standard ISO/IEC 63086 for air cleaners, there is the chance to harmonize and complement the current test methods. In this context, this work deals with the choice of suitable test aerosols and methods for considering ultrafine particles.
Most of the national standards use cigarette smoke as test aerosol. However, the aerosol properties such as concentration, agglomerate size, particle morphology and charge state are expected to strongly depend on the combustion conditions. Furthermore, tobacco smoke is carcinogenic and cigarettes are comparably expensive. However, for introducing an alternative test material to an international standard, different aspects have to be considered. Primarily, the new method has to yield highly repeatable results that allow a comparison between the performances of different appliances. Secondly, it is important for the testing institutions that all materials are globally available at reasonable costs, are easy to handle without risks for the operator and the properties are independent of the supplier. Thirdly, for the manufacturers and consumers it is desirable that the results using the new test material do not strongly differ from the results from the previous national standards using other test materials. Although the latter is not a strict requirement, it may facilitate the introduction of the new test method and increase the acceptance by the consumers.
With this motivation, we investigated the performance of three air cleaners using different filtration technologies with respect to NaCl, KCl and DEHS and compared it to results derived with cigarette smoke. We show that the CADR can be very reproducibly measured with all investigated test aerosols and does not strongly depend on the choice of the material. This means that the filtration efficiency curves in the relevant particle size range are sufficiently flat and discharging effects by the test aerosol are negligible at the low exposures involved.
Concerning the particle size, recent national testing standards typically consider only particles larger than about 0.3 µm since considerably smaller particles are not accessible by optical particle counters. However, a test method considering smaller particles, especially in the ultrafine particle (UFP) size range <0.1 µm, is highly desirable for different reasons: Firstly, it is know that the relevance for health effects increases with decreasing particle size, since smaller can enter deeper the human respiratory system and have a higher surface to volume ratio. Furthermore, the largest fraction of the number size distribution of typical indoor aerosols lies in this size range and is thus most representative for real conditions. Finally, a previous study has shown that the efficiency of air cleaners can considerably degrade with decreasing particle size, especially when using of electret filters (Schumacher, 2018).
For these reasons, we investigated two different methods for determination of a CADR for UFP. As test aerosol, potassium chloride (KCl) particles were generated from an aqueous solution and dispersed in a 30 m³ test chamber, where the air cleaner was located. The first approach used a condensation particle counter (CPC) to measure the total concentration of particles larger than several nanometers, depending on the exact type of CPC used. By fitting the exponential decay curves with and without air cleaner, the CADR was derived. The method is easy to perform, but has the disadvantage that there is generally a dependence on the exact size distribution of the test aerosol. We investigated how large this effect is and how reproducibly size distributions can be generated by using different atomizers.
To circumvent the dependence on the particle size distribution, the CADR was alternatively determined by measuring the decay rates for monodisperse fractions in the UFP range using a differential mobility analyzer (DMA) adjusted to classify one certain particle size. As disadvantage, this restricts information on the cleaning performance to a specific particle size and has worse statistics because of the substantially lower particle concentrations. The results from both methods were evaluated and compared. The findings from the study shall drive the development of new methods in the recently published IEC 63086 testing standard for air cleaners...
Impact of roadside filtration devices on the concentration levels of road traffic pollutants at an urban traffic hotspot
T.K. Müller, T. Warth*, MANN+HUMMEL GmbH, Germany
In recent years, air quality in German cities has improved continuously, but hotspots in several cities still do not comply with the 2008/50/EC immission limit values. Currently, most exceedance events in Germany are related to NO₂ values being too high. In contrast, excessive particulate matter (PM) concentrations pose the greatest challenge from a worldwide perspective. A novel approach to locally improve the contaminant level is to employ outdoor air filtration devices, as e.g. the MANN+HUMMEL Filter Cube.
Stuttgart’s ‘Am Neckartor’ area is the most prominent air quality hotspot in Germany and therefor offers an ideal location for the exemplary investigation into the effectiveness of filtration devices at an urban traffic hotspot. As part of a public-private field testing project, 23 outdoor air filtration devices (MANN+HUMMEL Filter Cube) with a nominal flow rate of 14.500 m³/h per unit were installed in the ‘Am Neckartor’ area beside federal highway B14. The employed filters were equipped with high capacity activated carbon filter media capable of reducing the local NO2 and PM concentrations. The focus of this publication is set on the proof of concept investigations conducted at the Neckartor site...
Using ultrafine aerosols to understand service life of air filters for gas turbine applications
A. Corradi*, G. Costa, Ahlstrom-Munksjö ; J. A. Marval Díaz, P. Tronville, Politecnico di Torino, Italy
The concentration of airborne particulate pollution and the size distribution of the mass of the particles captured during air filters service life affect strongly how their airflow resistance changes throughout their operation. Therefore, the ageing process of air filters depends strongly on the place and on the system where they are employed. Urban and industrial areas are very challenging because of the high concentration of atmospheric sub-micrometer particles which clog fibrous filter media quickly. In fact, smaller particles get into the fibrous matrix (deep filtration) and occupy the space available among the fibers. Larger particles tend to deposit on the top of the filtering material (surface filtration) and increase much less its airflow resistance.
Depending of the type of filter material, natural ageing can show very different behaviors. For sure it is very useful to compare service life of filter elements in severe conditions. However, such testing programs should last six to twelve months to be meaningful and reliable. Moreover, the trend observed in data sets obtained during various years may differ because of the season or atmospheric conditions.
These considerations are relevant and of practical interest for most air filters and especially for those used in gas turbine air intake systems. In fact, their service life, maintenance costs and energy implications are strongly influenced by the type of airborne particulate pollution in a specific place and system. The availability of a repeatable and reproducible laboratory procedure to predict the natural ageing process, as closely as possible, is highly desirable. This procedure would allow to design and to optimize the filter media and the filter cartridge geometry, together with the combination of the most appropriate prefiltration choice.
For this reason, Ahlstrom-Munksjö and Politecnico di Torino carried out a research project to develop a new synthetic ultrafine aerosol able to clog a full scale filter element in laboratory in a few hours...
Modeling and simulation of moisture penetration and wearing time of face masks
M. Böhle, A. Schwarzwälder, Technische Universität Kaiserslautern; R. Kirsch, S. Osterroth* , Fraunhofer Institute for Industrial Mathematics (ITWM), Germany
The year 2020 has shown an increasing awareness of the use of face masks and respirators in order to protect the wearer or the surrounding people against infections.
Two protection concepts can be distinguished: self-protection and external protection. In the first concept, the wearer wants to protect himself or herself against infectious pathogens or viruses in the surrounding. Depending on the availability, corresponding filter masks should be preferably used by people working in health and nursing care. In the second concept, the wearer protects people in the surrounding from being infected.
A reliable protection does not only depend on the filtration properties of the mask material. In the literature, it is discussed whether moisture penetration decreases the filtering efficiency [1, 2]. If this is the case, the safety is reduced . The most critical state is reached when the mask is imbrued entirely (moisture breakthrough) since the moisture can serve as an "infection bridge" spanning across the depth of the filter material. This holds for highly efficient filter masks (e.g. FFP-2), but even more so for masks to protect others: Coughing and sneezing can lead to the detachment of potentially infectious droplets from the outer surface, which will then spread into the vicinity . In standard test procedures such as DIN EN 14683 , DIN EN 149 , or 42 CFR Part 84 , the temperature and the moisture content are considered as constant and static. The test material is adjusted to given conditions. However, when breathing out, the face mask is exposed to moisture and the temperature (body heat) is different from the surrounding.
Most wearing time recommendations are reference values, based on an average usage scenario. The speed and intensity of the moisture penetration of a mask depend heavily on the physical stress level of the wearing person [7, 8]. The time it takes until the moisture breaks through cannot be derived in a simple way ("rule of thumb") from the physical activity, which is usually fluctuating. In general, a visual check of the mask is neither feasible without aid nor reliable enough to detect a moisture breakthrough.
Specialized computer simulation tools have proven to be very useful for the innovation and optimization of filtration devices. Previous studies were mostly focused on filtration efficiency and have not considered the moisture transport. Additionally, the breathing behavior was modeled using an idealized sinusoidal profile.
The present work is devoted to the adaptation of well-known transport models to the transport of moisture in porous media...
Effect of washing on the performance of surgical masks
N. Bardin-Monnier, A. Charvet*, O. Dufaud, D. Thomas, J.C. Appert-Collin, N. Bernard, F. Huin, M. Lebrun, Université de Lorraine; C. Dessale, F. Aantoine, CIC-IT, France
Medical face masks are intended to limit the transmission of infective agents during surgical procedures. These masks are used by surgical staff but also by patients and general public for the reduction of the infection spreads during epidemic or pandemic situations. Before the pandemic, type II surgical masks were recommended in the care services, IIR type for the medical staff during a care with a risk of projection (operating rooms) and FFP2 masks during particular care of a patient requiring special precautions. Note that surgical masks can be worn up to 4h and FFP2 up to 8h. During the pandemic, FFP2 are recommended for invasive medical gesture or maneuvers in the respiratory sphere of a patient carrying SARS-Cov-2; type IIR surgical masks for all other types of care. As they present low and highly variable collection efficiency (with filtration velocity and particle size), surgical masks do not provide a protection comparable to FFP2. As a consequence, wearing them protects the others instead of oneself. The tension on the supply of these single-use devices, due to the pandemic of COVID-19, leads to study the potential reuse of medical face masks after washing.
The objective of this study is to verify if, after washing, medical face masks still comply with EN14863+AC in terms of filtration efficiency, breathability and blood penetration resistance...
A novel filter material is deactivating viruses and bacteria and binds allergenic proteins from pollen
E. Gottschall, P. Pfeuffer, K. Gottschall*, KLAWEGO GmbH & Co. KG, Germany
A novel equipment of filter media is presented, exhibiting antiviral, antibacterial, and antiallergenic properties. The equipment of various base materials, like glass fibers, activated carbon particles or fibers of cellulose, polyamide, polyester, or polypropylene with cross-linked poly(vinylamine) yields a so far unknown efficacy against microorganisms of different origin. Filter media are now produced according to various manufacturing processes e.g. wet-laid, meltblown. spunbond, staple fibers, and carbon activation.
Using a microglass fiber based HEPA filter of H13 quality the following data have been reached. According to ISO 18184 after two hours 4.9 powers of ten were inactivated relating to the bacteriophage MS 2 starting from one million viruses per ml. Already after 20 seconds >99,95% were inactive. The corresponding H13 filter material, not equipped with poly(vinylamine), destroyed only 80% of the virus after two hours. The effectiveness against bacteria was even higher by one decade. According to ISO 20743 in total 5.9 powers of ten were depleted relating to Staphylokokkus Aureus. With respect to Klebsiella Pneumoniae the number was even 6.3 powers of ten. In addition, 99% of the allergenic inventory of birch pollen was retained, as determined via a specific Elisa assay. Different to a usual viruzide or bacterizide equipment, no soluble biozide ingredients are used. There is a bare physical effect, generated by the attraction of opposite charges. The cross-linking of the polymer yields a very stabile coating. A polymeric mesh is generated, temperature resistant up to 200°C and not soluble any more. The sample capacity was high. One cm2 of filter material were binding the pollensome content of 80 mg pollen.
Until now filter materials are retaining only an unknown fraction of viruses contained in aerosols, fine dust, and suspended matter. The prescribed test procedures using DEHS droplets or potassium chloride particles are not representative for the ability to retain or deactivate viruses or allergens. Also the growth of bacteria inside filter materials has been often reported. Until today unequipped filters have been a reservoir for various germs. From now on it is possible to deactivate the retained viruses and bacteria, using any type of filter, ranging from HVAC- applications, cleanroom filters to FFP 3 masks. The result is a significantly reduced risk of infection for the user...
PALAS - Quick and reliable test of community masks with regard to the new EN Guideline CWA 17553
S. Schütz*, M. Schmidt, PALAS GmbH, Germany
Community mask are the most common national strategies to in Europe to lift legal relationships caused by covid pandemic. Uniform security standards across Europe can be part of this, to contain the COVID-19 pandemic across borders. The CWA assist producer who switched their production to non-medical mask, the so-called community masks.Therefore, an upcoming new EU directive CWA 17553 will be released by CWA with the title “Community face coverings – Guide to minimum requirements, methods of testing and use”.
Even before that Palas already started a development of a fast, economical and easy to handle measurement device the Mas-Q-Check. The Mas-Q-Check was developed by Palas to subject protective masks to a quick, simple and yet meaningful test before use. A particle counting measurement device is used, which is able to detect efficiencies in the size range of viruses and bacteria. The system can also be used for training purposes as it immediately shows the efficiency of protective masks.
The mask is placed on the test head before use. Using a high-resolution aerosol spectrometer, the particle contamination (size and quantity) in the ambient air is measured. Afterwards the device switches automatically and determines the value of the particle contamination behind the protective mask. This can be repeated automatically several times.
Measurement of the size-resolved filtration efficiency of various face mask materials using the aerodynamic aerosol classifier
S. Payne*, J. Symonds, Cambustion Ltd, UK
Face coverings are widely worn in public spaces under many countries’ COVID-19 laws and guidelines. The intention is that coverings over the mouth and nose will protect others (rather than the wearer) against the spread of infection by capturing virus-laden droplets in exhaled air, coughs and sneezes. These commonly consist of layers of woven fabric. Surgical masks are intended for health care staff to protect patients during surgical procedures and in other medical settings. Respiratory filtering half masks are intended to protect the wearer and are regulated as personal protective equipment (PPE) for inhaled air only.
Numerous recent studies have emphasised the possibility of airborne coronavirus transmission. While the World Health Organisation (WHO) defines droplets as ≥5-10 μm diameter and aerosols as <5 μm, both can be generated as a continuum of particle sizes during various respiratory activities including coughing, talking and singing.
It is therefore of interest to investigate the particle size-resolved filtration properties of various face mask materials, for both inhalation and exhalation flows and across a wide particle size range. A suitable instrument for achieving this is the Aerodynamic Aerosol Classifier (AAC), which can select particle sizes between 25 nm and >5 μm by using a rotating cylinder to balance opposing centrifugal and drag forces for the desired aerodynamic diameter, so that particles move across a sheath flow to the outlet. This principle of aerosol selection is independent of the charge state and produces a truly monodisperse aerosol with a high transmission efficiency limited only by diffusion and impaction losses.
This study uses an AAC to select monodisperse test particles by aerodynamic diameter in order to assess the filtration performance of various face covering materials, in both flow directions and at filter face velocities representative of inhalation and exhalation flow rates. These coverings included:-
- Disposable filtering half masks conforming to the FFP1, FFP2 and FFP3 classes specified in EN 149
- Disposable surgical masks consisting of non-woven fabrics
- Cloth face coverings with woven fabrics of various thread counts and layered structures
How face masks help stop COVID-19
K.-J. Choi*, Clean & Science Co., Ltd., USA
The Centers for Disease Control and Prevention (CDC) continues to recommend that persons in the U.S. wear masks in public settings “around people who don’t live in your household and when you can’t stay 6 feet away from others.” Masks help stop the spread of COVID-19. In many states there is a legal requirement to wear masks in public buildings and spaces. This presentation will cover the nature of COVID-19 virus particles, the current test methods of facemask filtration, and the test results comparing N-95 mask, surgical mask, and cloth mask.
Continous hydrodynamic fractionation of fine particles using crossflow
P. Lösch*, K. Nikolaus, S. Antonyuk, Technische Universität Kaiserslautern, Germany
The increasing demand of fine particles in suspensions leading to new processes which can provide such dispersed particle collectives. These suspensions are often intermediates for the production of coatings, structured reinforced plastic or for printed electronics. While production processes like precipitation or crystallization are often generating particles with broad particle size distributions, a suceeding process step of classification is necessary. In known separation processes, such as sedimentation, filtration or centrifugation, the particles are either classified according to a certain grain size or sorted by a physical characteristic. However, in many applications in which finely dispersed multicomponent mixtures of particles with sizes < 10 μm with different properties are to be separated in industrially relevant quantities, the usage of a single separating feature is often no longer sufficient. In this contribution, a cross-sectional filtration technique is being developed, which is a promising method for the highly specific separation of micro- and sub-micron suspensions...
Automatic fractionation of particles from lithium-ion batteries in a tubular centrifuge with model-based control
T. Sinn*, M. Gleiß, H. Nirschl, Karlsruhe Institute of Technology (KIT), Germany
The process industry is currently undergoing various changes at the moment. For economic and ecological reasons, resource-efficiency is more and more requested, meaning the optimal exploitation of energy and materials through by optimal operation of existing production plants. However, when processes are too complex, conventional practices are often not able to operate the process satisfactorily close to the optimum. The same challenge arises when specific product properties are demanded, but the process changes its behavior during operation. Accurate setting of operational parameters is required, which must be realized through a sensible control strategy. In such complex cases, a model-based control is a potentially sound solution.
At the same time, mobility is about to undergo a fundamental transformation towards electric vehicles. This will certainly entail a growing demand for materials needed in batteries (Li, Mn, Co for example) as well as increase the urgency to develop recycling processes for end-of-life batteries.
This work treats the investigation of centrifugation as a potential step in a battery recycling chain. The well-known unit operation is examined as the key step – separation of battery constituents for further selective treatment – in a newly developed direct recycling approach for Li-ion battery cathodes. The partially nano-sized particulate cathode material enters a tubular centrifuge to fractionate the constituents. In order to assure the separation of only one species from the watery suspension, the operational parameters must be carefully set. Due to the progressive sediment build-up inside the rotor, the separation conditions in tubular centrifuges change accordingly. If this is not counteracted, centrate properties are time-dependent and the desired fractionation output is not attained. To achieve complete fractionation over the entire operation time, continuous control of the operating parameters, that are rotational speed and volumetric flow rate, is realized in form of...
Modeling of shape and density fractionation in tubular centrifuges
M. Winkler*, H. Nirschl, Karlsruhe Institute of Technology (KIT), Germany
Classification is an established process in solids processing technology to divide particulate products into defined fractions based on their size. However, complex particle systems with strict specifications regarding product-relevant properties often require a different approach. Thus, multi-dimensional fractionation is needed in which both geometric (particle size and shape) and material (density, interfacial properties) separation characteristics are considered. If a task involves the efficient separation of nanoparticles based on their shape, size or solid density, high centrifugal forces are required. Due to their advantageous throughput rates and extreme operating conditions, tubular centrifuges are well suited for this application.
During separation, a low concentrated suspension is fed into the tube centrifuge rotor with a constant volumetric flow rate. Suspended nanoparticles settle along the radial and axial coordinates inside a fluid reservoir. Their sedimentation velocity is determined by their geometric and chemical properties and the operating conditions of the apparatus. Fractions with sufficiently low settling rates are transported beyond the rotor weir and enter the fine product stream. The removed solids accumulate along the separation zone on the inner rotor wall. To gain process knowledge and estimate the separation result for a well characterized product, dynamic process simulation is an effective tool. Previous studies focused on the one-dimensional classification of fines, whereby only one separation characteristic, the particle size, and its distribution, was considered in the calculation. This work strives to further extend well established one-dimensional model equations by an additional separation criterion, i.e. the shape or aspect ratio of individual particles. The numerical calculation of the particle transport behavior in tubular centrifuges shall thus be given a broader range of applications and help to identify advantageous operating parameters and apparatus specifications.
This study includes the generation of multi-dimensional density distributions that define a property range of non-spherical particles as a function of at least two geometric features...
Filtration 4.0 - How filtration processes profit from IIoT solutions
W. Perron, ANDRITZ Separation Inc., USA
In many industries, efficient filtration is the key process step to achieve constantly high product quality. One of the most common technologies used for filtration is the filter press. Technology group ANDRITZ has combined findings gathered from Industrial Internet of Things (IIoT) with automation solutions for the filter press, creating new mechanisms and features that promise an increase in product quality and a decrease in operating costs as a result of process optimization.
Intelligent filter press features include solutions to increase efficiency, reduce downtime, and also enhance safety and monitoring functions. The key distinguishing functions of intelligent filter presses are monitoring of dry substance, intelligent washing cycles, monitoring of oil and filtrate quality, and intelligent pressure control. Two of these solutions use a Smart Sensor inside the filter press that monitors the press and constantly compares the values reported with the nominal values so that the filter press can be stopped automatically if there are deviations from the norm. This provides an opportunity to increase efficiency, for example by suggesting an automatic washing cycle to keep the quality of the end product at a constant, high level. And it also improves safety by stopping the filter press in case of a pressure loss. This feature increases operating safety enormously. In addition, the oil levels and oil quality are measured constantly, ensuring continuing smooth operation and reducing OPEX costs by avoiding unnecessary oil changes.
Another central function of the intelligent filter press that increases efficiency is the monitoring of dry substance with Smart Sensors inside the filter press during the process. This enables the operator to stop filtration at the right time and reduce fluctuations in the cake moisture content.
The intelligent filter press is often combined with intelligent filter elements, such as the LENSER intelligent filter plate and the Metris addIQ SmartFILTERCLOTH, to increase its usability. The SmartFILTERCLOTH is a filter cloth tagged with an RFID chip to help monitor use and suggest replacing a filter cloth at the right time, thus ensuring ideal filter cloth service.
The intelligent filter press and its features will be explained...
Setting the grounds for a dynamic adjustment of the operational parameters of a press filter using ai to compensate for slurry quality changes
J. Bruzzo*, J. Koskela, S. Manninen, K. Kettunen, Flowrox Oy, Finland
The step of solid/liquid separation (pressure filtration for the case of this study) is usually one of the last steps in the chain of raw material transformation in concentration plants adding tremendous value to the product being handled. As in every production process, it is expected that the resulting products (cake) comply with a series of prescribed conditions in terms of planned production, operational expenses (resource consumption), and quality. Sound world-class asset management of the solid/liquid separation equipment is key to meet these operative requirements and might well be the difference between reaching budgeted profits or wasting company money continuously.
Nonetheless, not even the most rigorous world-class asset management structure can completely foresee the level of impact that deviated process variations in equipment upstream can have on the filtration step. Nor the reactive measures taken by the filtration team can guarantee to compensate for these process deviations in time to keep production, consumables, and quality in the budgeted levels.
Filtration units such as pressure filters are provided with rigid settings, a fixed set of stages to be followed or physical conditions to be met during each filtration cycle regardless of the quality of the slurry being fed to the filter. This rigidity makes continued reactive adjustments an untenable endeavor. Constant supervision is needed to manually change these filtration settings to accommodate to slurry conditions to get the best possible output from the filter. Unfortunately, this task is labor-intensive, and having constant supervision plays against the limited organizational structure in place. Many cycles can be run before a suitable action is taken in the filtration settings or ideally before the deviation is corrected in the upstream process. There seems to still prevail an independency of pipelined processes, where changes in key variables are not automatically communicated to the rest of the actors across the production chain introducing thus negative consequences.
This paper aims to set the grounds for migrating from a manual and close-to-obsolete filter supervision to a novel automatized adaptive supervision-free response philosophy...
In-situ cleaning process of chamber filter presses with sensor-controlled and demand-oriented automation
P. Morsch*, M. Gleiß, H. Nirschl, Karlsruhe Institute of Technology (KIT); R. Werner, D.U. Geier, T. Becker, Technical University of Munich, Germany
Cleaning plants for the chemical industry is essential to avoid cross-contamination, especially in batch operation, and thus to ensure safe production. This applies in particular to solid-liquid separation processes and to filtration. Due to the difficult to clean surfaces of filter cloths, these devices have special requirements for cleaning. The cleaning of filters is therefore often designed conservatively, which is equivalent to excessive cleaning. A demand-oriented cleaning method based on image analysis offers a lot of optimization potential in this area, especially to reduce the required cleaning agent, document the cleaning result and reduce the amount of wastewater....
Regeneration of filter press fabrics in the mining sector
B. Fränkle*, Karlsruhe Institute of Technology (KIT), Germany
Generally, filter media used in filter presses have a limited operation life. Beside mechanical damage, there is a growing deposition of fine particles with increasing filtration cycles, the so-called blinding, inside the filter cloth. Resulting decreasing pore diameters not only affect the efficiency of the filtration process itself by increasing the filter medium resistance, but also makes it more difficult to regenerate the filter press between the individual cycles, e.g. leading to an insufficient cake discharge. Since tailings filtration requires handling of large process flows containing a significant fraction of particles in the lower micrometer range an investigation into media rejuvenation is of interest.
Therefore, the regeneration of three industrial used cloths from a gold, silver and an iron ore mine provided by FLSmidth differing in cycle amount, material, weave and fiber type is investigated by using different agents as well as changing exposure times and concentrations and ultrasound. The effectiveness of the different cleaning procedures is evaluated based on the process engineering parameters permeability and pore size in flow measurements and permeability tests. Subsequently, an additional elementary analytical examination of selected sample states is carried out to determine whether the composition of the tailings influences the regenerability. Possible negative effects on the mechanical properties of the cloths, both by the high number of filtration cycles and by the cleaning process, are analyzed by means of tensile tests...
Description of the properties of filter media for surface filtration in automatic filters
T. Buchwald*, U.A. Peuker, Technical University Bergakademie Freiberg, Germany
Whenever large quantities of liquids need to be cleaned of small amounts (in the ppm–range) of suspended solids, automatic filters are used, which clean the filter medium after a certain threshold (time or pressure drop) is reached. Commonly, the medium is backwashed with filtrate and the resulting liquid containing the concentrated particles is discarded. In order to determine the efficiency of a filter medium in regards to separation size, solids capacity and tendency to blocking, all relevant process variables need to be constantly monitored.
This is achieved in a laboratory filtration apparatus, which semi-automatically backwashes a planar filter medium with an effective diameter of 100 mm. The process variables pressure drop, volumetric flow rate, the liquid’s turbidity at the inlet and outlet of the medium, and the cleaned filter resistance are monitored. In addition, the cut size of the filter medium is determined before and after a filtration test.
The collected data can be used to sufficiently describe the behavior of filter media during operation as well as the change of its properties due to blinding by particles and mechanical/hydrodynamic stresses.
The paper discusses the treatment of the acquired data and how conclusions can be drawn for the development of new filter media for clarifying filtration applications. In a current research project, new nonwoven filter media are developed...
Undersaturated zones: an integral part of a cake washing process
A. Brueckner*, T. Sprott, B. Hoffner, Mannheim University of Applied Sciences, Germany
In several industries cake washing is used for a specific purification of a wet filter cake. A mostly unavoidable part of these single or multi-stage washing processes are dewatering zones, where the filter cake is undersaturated by deliquoring. In order to prevent potential mixing of different liquids on the cake surface, undersaturated zones after cake formation (pre-dewatering) and between two wash stages (intermediate dewatering) are necessary. However, the uncertainty about the extent of the undersaturation step leads to a time consuming and costly process. In addition to the necessary separation of the different liquids on the cake surface, further positive effects of undersaturation will clarify with laboratory experiments.
Previous investigations show that an undersaturated filter cake cannot be re-moistened to full saturation but can only reach an equilibrium saturation S<1. However, the kinetics of the saturation increase exceeds the kinetics of the saturation decrease by far. At this point various issues of remaining gas bubbles on the residual impurity X* are addressed and evaluated experimentally.
This work deals with the question how an undersaturation zone prior to a washing step influences the course of a washing process, esp. with regard to the main washing regimes (displacement/ dispersion/ diffusion). The investigation is based on...
Tasty wash liquor – Coffee extraction from the perspective of filter cake washing
M. Kuhn*, V. Hargarten, H. Briesen, Technical University of Munich; T. Sprott, B. Hoffner, Mannheim University of Applied Sciences, Germany
Coffee is a valuable trading commodity and an important good of consumption. In recent years, the coffee beverage was additionally promoted as luxury food similar to red wine in a movement called the “third wave” of coffee. Within the “third wave” also various brewing methods have been (re-)discovered and coffee extraction itself has seen a growing interest. This trend, in turn, brought along an increasing number of academic studies on coffee extraction, a process whose influence on the final beverage has been underestimated for a long time. Recent modeling approaches now describe coffee extraction in terms of mass transfer rates, diffusion, dispersion, and convection. A first comparison of coffee extraction with filter cake washing shows that similar physical effects prevail in both cases and that measured concentrations at the outlet exhibit a comparable dynamic behavior. This analogy motivates a systematic juxtaposition of the two fields of research.
In this contribution, we therefore compare recent insights on coffee extraction with approaches and findings on filter cake washing. Physical phenomena and their incorporation in the corresponding washing and extraction models are discussed. The explanatory power of different modeling approaches is examined and the potential of transferring models and process strategies between filter cake washing and coffee extraction is assessed...
Parameter estimation in cake washing – considerations of quality and quantity of experimental data and ther impact on simulation results
T. Sprott, A. Brueckner, B. Hoffner, Mannheim University of Applied Sciences, Germany
The parameter-based simulation, in which measured values are used to determine simulation parameters, is a common method in engineering science. Both quantity and quality of measured data usually restrict the quality and statement of accuracy of the simulation. In this respect, it must be differentiated whether an impreciseness of a simulation results from
- errors of each individual measurement.
- an insufficient number of data points, which may also represent only a small range of measurement.
- a combination of both.
A multi-stage countercurrent filter cake washing is a good example of such a parameter-based simulation. Generally, washing processes are designed with data from nutsche filter experiments. However, nutsche filter experiments are time consuming, costly and inaccurate in order to reproduce a multi-stage countercurrent washing process. This is mainly due to the fact, that the wash liquor concentrations of all washing stages (except the last one) have to be determined iteratively for each wash ratio.
A validated parameter-based simulation gives the opportunity to simulate a multi-stage washing process with the need of just a single stage washing curve. This reduces the experimental effort significantly. However, the influence of quality and quantity of measured data on the simulation results have to be taken into account. Examples will show...
Quasi-continuous production of defined crystals on an integrated belt filter
T. Dobler*, H. Nirschl, Karlsruhe Institute of Technology (KIT), Germany
Increasing global competition, existing but not exhausted resource and energy saving potential as well as constantly changing sales markets and the desire for individual products with a high product quality require innovative solutions in almost all economic sectors. In the chemical industry, these include, in addition to a modular design, the conversion of batchwise operation into its continuous form, increasing the degree of automation and the integration of different process steps in one process apparatus.
Taking these aspects into account, a novel plant concept for the quasi-continuous particle synthesis and separation was developed. A high degree of automation as well as the combination of different unit operations (crystallization, solid-liquid separation and drying) in one plant ensures considerable savings in energy and resources. Furthermore, an intelligent control system in combination with innovative measurement technology allows the targeted adjustment of particle properties and an increase in product quality and quantity.
The basis of the apparatus is a belt filter in which the vacuum trays are replaced by functional units. While there are temperature control modules in the crystallization and drying area, filtration segments are located in the solid-liquid separation zone below the belt. The individual functional units can be arranged in any order, which in turn guarantees high plant flexibility and allows rapid adaptation to new material systems and existing customer requirements.
In the course of the presentation, the basic apparatus concept and its technical implementation will be discussed and the results of experimental considerations will be presented.
A novel modular small-scale apparatus for continuous solid–liquid separation and washing of crystal suspensions
C. Steenweg*, A. Seifert, G. Schembecker, K. Wohlgemuth, Technical University Dortmund, Germany
Control of product quality, such as particle size distribution (PSD), residual moisture and purity, is of high importance during pharmaceutical and fine chemical production processes. Each process step in the whole process chain can affect all following steps and thus may interfere with reliable in-spec production. During the last decade, a shift towards continuous manufacturing can be observed to eliminate the batch-to-batch variability. Thus, novel process concepts are required to replace or extend unit operations that have predominantly been batch operations, such as crystallization and subsequent solid-liquid separation, washing and drying.
Various concepts for continuous crystallization for small volume flow rates of 10 ‑ 100 mL min‑1 are available improving the critical quality attributes . However, within the crystallization process chain, further process steps like filtration, washing, and drying are required to obtain the final solid and dry product. Such techniques have been scarcely investigated in continuous operation mode in the typical API production scale of 250 - 1000 kg a-1.
Only few equipment concepts for the continuous downstream of crystalline products have been commercialized by now. Alconbury Weston Ltd. offers a quasi-continuous automated batch filtration with a semi-continuous inlet and solid discharge. Disadvantageously, buffer tanks for the slurry inlet are required, which entails several drawbacks regarding product quality, traceability and process efficiency. [2,3]
Continuus Pharmaceuticals Inc. provides a continuous rotary plate filter that was tested for volume flow rates in the range of 20 - 100 mL min-1. However, this device does not enable a deliquoring and further thermal drying of the crystals and the filter cake may not be uniformly dispersed radially on the filter medium. 
Thus, innovative process solutions for integrated downstream product design are required. We aspire to design, set up, and characterize an innovative continuous process concept for solid-liquid separation, washing, and drying of crystal suspensions that is connectable to different continuous small-scale crystallizers such as a MSMPR cascade, a continuous oscillatory baffled crystallizer or a slug flow crystallizer with small volume flow rates between 10 - 100 mL min-1.
This contribution will show the characterization of the innovative apparatus for small-scale continuous solid-liquid separation and washing...
Highly efficient extraction of egg yolk powder thanks to continuous filtration and drying
M. Rahmann*, BHS-Sonthofen GmbH, Germany
Significant savings, greater yield and increased throughput – a pharmaceutical company benefits from various improvements as a result from switching to a continuous extraction process and leaving the traditional batch operation behind. Key components that make these improvements possible are the Indexing Belt Filter and the AVA continuous horizontal dryer from BHS-Sonthofen.
Previously egg yolk powder extraction was a complicated slurrying process with dilution washing, having a series of equipment and resulting in tremendous resources requirements. The user replaced this complex batch process with a continuous process. BHS analyzed the existing process and tested alternative options in the laboratory. As a result they recommended the use of a belt filter as the most suitable solution in combination with a continuous, efficient contact dryer.
BF belt filter from BHS increases yield of phospholipids
HTK-T continuous dryer dries egg yolk powder gentle and energy efficient
Pickering emulsions: Quantification of separation, consolidation and filtration behaviour in dependence on centrifugal forces
M.-K. Assi, S. Boldt, D. Lerche*, LUM GmbH, Berlin, Germany; A. Drews, WTH Applied University, Berlin
Pickering emulsions as multiphase reaction systems for the production of sustainable hydrophobic substances are gaining increasing interest [1,2]. For process design, knowledge on the separation of the two phases (aqueous catalyst phase and product containing oil phase) is essential. Membrane filtration has been shown as a potential candidate . However, up to now, detailed investigations of this process, especially regarding the properties of the filter cake, are not available.
In this paper we present data of water in oil (1-dodecene) emulsions (vol. phase ratio 1:3) stabilized by silica particles of different polarity (HDK H2000, HDK H20, Wacker Chemie AG, Germany; silanol content of 25% and 50%, respectively). Nanofiltration membranes of MWCO = 900 Da (oNF-3, BORSIG Membrane Technology GmbH, Gladbeck, Germany) and ultrafiltration membranes of MWCO = 1000 Da (ETNA01PP, Alfa Laval, Denmark) served as filter media...
Simulation of cake formation over time in centrifugal filtration
D. Serper*, P. Oinas, Aalto University, Finland
Centrifugal filtration is a commonly used solid-liquid separation method, which is often preferable over other separation methods when solid product quality depends on the low moisture content. The method’s superiority in dewatering capacity is due to its driving force - rotational speed - which makes it a powerful tool to be used in various key industries such as biotechnology, pharmaceutical, and forest products.
Rotational speed results in a pressure drop that aids rapid sedimentation of the solids while liquids are slower to reach to the walls due to their lower density. After this transient settling period, the process continues solely as cake filtration. The complexity of the system increases with the effect of the rotation-related pseudo-forces such as centrifugal force and Coriolis force. Additionally, the rotation can result in turbulence, complicating the system further, as do the compressibility of the cake and the properties of the solid phase. Existing literature is very limited and mostly concentrated on one-dimensional linear flow, and on spherical, uniformly sized particles. This knowledge gap makes investment in this method excessively risky, although various industries are driven to use the method due to their product specification needs.
A unique approach to narrow the theory gap on this key downstream operation has been developed. The novelty this model lies in the inclusion of the effects of turbulence, particle shape irregularity and particle size distribution simultaneously on the COMSOL multiphysics platform. The model developed is utilized to simulate limestone cake formation from aqueous suspensions in centrifugal filtration. The results will...
Batch filter centrifuges - Software supported and reliable scale-up with minimal experimental effort
I. Nicolaou, NIKIFOS Ltd, Cyprus
The reliable scale-up and optimization of soft is a big filtration challenge due to the complex phenomenology. That is why pilot tests are necessary. By not considering the up-to date theory for the steps cake formation, cake washing and cake deliquoring, such pilot tests are carried out unsystematically. Such approach is usually too time consuming and uneconomical. In this paper it will be explained how a cobination of laboratory and pilot tests can minimize the experimental effort for a reliable centrifuge scale-up. A novel, theory and computer based approach for the analysis of laboratory and pilot test data will be presented. This theory considers in a big extent the real phenomenology in the centrifuges like intermittent suspension and wash liquid feeding, cake compressibility and depending on the cake compression different cake heights and cake resistances for each step.
It will be explained, which suspension and cake characterizing parameters (so called efficiency parameters) are needed for reliable performance predictions for all steps: cake formation, cake washing and cake deliquoring. Taking a real case as example, it will be demonstrated by using the software CENTRISTAR how the test measurements can be analyzed and judged and how the efficiency parameters can be determined...
Innovative two stage water filter
J. Roßbauer*, Grünbeck Wasseraufbereitung GmbH; M. Wilkens*, Hengst SE, Germany
“Water is life!” this simple sentence shows how important clean drinking water becomes, even in industrial countries. Due to this, the company Grünbeck, as a leader in water treatment solution and the company Hengst, known for leading filtration solutions in industrial and automotive applications, joined to start a cooperation to develop an innovative filter solution for hygienic water treatment applications.
The main target of the development is to find a mobile filtration solution for leisure vehicles, which can adapt to nearly all drinking water tanks to provide hygienic and pure water.
To ensure a filtration system which is reliable for nearly all drinking water standards a two-stage filter system with a minimum amount of auxiliary materials – for example without any kind of glue within the filter element – has been developed.
The filter element consists of two innovative filter stages with active carbon as, for example, an agent for the removal of chlorine and an additional material for the removing of pathogens and colloids.
Due to the use of the Hengst Energetic concept and ultra-sonic welding processes it is possible to produce a filter element that only consist of the filter materials and plastic components (end cap and inner tube), without any kind of glue or further materials.
The filter element is evaluated by several parameters, especially by retention of chlorine, turbidity and germ reduction...
Separation of varnish from turbine oil by adsorption technology
E. Barega*, T. van der Linde, John Crane Indufil, Netherlands
Recent developments in industrial turbines to improve efficiency resulted in higher firing temperatures. As a result of these extreme operating conditions, oil oxidation products and varnish are formed. At present, one of the solutions offered to remove varnish is filtration. However, filtration increases the energy consumption in cooling and later heating the lubrication oil. Additionally, filtration cannot remove the soluble varnish and frequent replacement of filters is required. Compared to filtration, adsorption provides a higher capacity due to its high specific area. Besides this, adsorption can remove both soluble and insoluble varnish. Nevertheless, some currently used adsorbents release unwanted substances such as water. Moreover, the adsorbents need to be replaced after use.
This paper presents a technology to remove varnish from lubrication oil using a polymeric adsorbent material...
Environmentally friendly oil removal from water surfaces by adsorption on bio-inspired textiles
L. Beek*, M. Akdere, T. Gries, RWTH Aachen University; P. Ditsche, M. Mail, W. Barthlott, University of Bonn, Germany
The contamination of water with oil is a significant threat to water quality and the biotic environment. Major accidental spills from tankers or drilling platforms have led to environmental disasters, but minor contaminations such as spills from heating oil or leaks of engine oil from cars or ships in the port area represent a major ecological challenge too. Over 30 million litres of oil leaked into inland waters in 2014 alone.
Current methods for the elimination of oil spills on water surfaces include active working pumps, chemicals or materials, which absorb oil. The latter have to be cleaned or disposed of afterwards. In this study, we present a new method of cleaning water surfaces contaminated with oil, which neither needs pumping nor chemicals. The new technique was inspired by the adsorbing abilities of the floating fern Salvinia at the University of Bonn, which has a longstanding tradition in biomimetic applications of such superhydrophobic surfaces. The most well-known example is probably the Lotus Effect. The leaves have a sophisticated micro-structure surface, which retains a thick air-layer under water. If oil is present on the surface of the water, it replaces this air-layer and is adsorbed and transported on the surface. This ability is based on the effect of the hierarchical micro-structure of the leaf’s surface and its water repellent chemistry. Our investigations have shown...
Microfiber disc filter for water & wastewater treatment
S. Choi*, G. Kim, Digiwatec; Y. Kim, Hanyang University; K. Koh, CtoC; S. Kim, EE Company, Korea
Materials such as plastic, cotton, fiberglass, wool, and paper have been widely applied as economical and effective filter materials in the field of water purification and water treatment in the form of cartridge filters. In addition, plastic-based fiber materials are applied to filter devices in the form of media and filter yarns, because they have better filtration performance than conventional filter media such as sand, but have a narrow installation area and a feature of backwashing.
In this study, a plastic microfiber material was used to form a circular disk and utilized not only the excellent filtration characteristics of the microfiber fibers, but also the excellent cleaning characteristics of the circular disk structure.
A filter in which tens of microfiber circular disk filters were stacked was subjected to a performance comparison test with a cartridge filter and a media filter. It was confirmed that the microfiber disk filter can control the filtration performance through changes in the filtration thickness and filtration speed of the filter, and form a turbulent flow between the disks, thereby providing excellent backwash performance. The multi-array structure in which tens of microfiber disk filters with smaller and larger diameter are arranged alternately is intended to improve filtration and backwash performance. Through conducting the optimization and field performance tests with the various water qualities, we plan to commercialize the microfiber disc filter as the 1st stage filter before membrane filtration or media filtration system, the safety filter before RO membrane, the fiber media filter in the wastewater system, etc....
The advantages of nonlinear regression of cake filtration experiments
T. Buchwald, U. Peuker, Technical University Bergakademie Freiberg, Germany
Cake filtration data, in the form of filtrate volume Vf = f(t), i.e. as a function of time, is commonly fitted in the linearized t/Vf–Vf–plot to gain knowledge on the specific cake resistance and the filter medium resistance. There are some apparent shortcomings to this method, most commonly errors in the determination of the Vf (t)–data, which will lead to the resulting plot deviating from the ideally linear slope.
These problems can be overcome by fitting the original Vf (t)–equation nonlinearly. This can be achieved by any modern statistical software. The method offers many advantages, most prominently the effective determination of the true time offset superposed on the time data. Data with non–constant pressure can be fit by use of the pressure–time integral. Moreover, additional models can be incorporated into the nonlinear equation, which can give information on, for example, cake compressibility. Additional knowledge may be gained in the beginning of the filtration process by fitting models for blocking filtration.
The paper presents a method for nonlinear parameter estimation of cake filtration data...
How programmable materials can be used to design woven filter media with optimized backwashing properties
R. Kirsch, S. Osterroth, S. Rief*, Fraunhofer Institute for Industrial Mathematics (ITWM), Germany
Global challenges such as sustainable development, climate change, renewable energy, or individual mobility increase the necessity for a much more efficient and sustainable use of our resources. Programmable materials have the potential to initiate a paradigm shift since they can perform system functions through their internal design. This allows for increased functional integration while simultaneously reducing system complexity. Programmable materials are materials whose inner structure is designed and manufactured in such a way that properties and behavior can be controlled and reversibly changed by external stimuli, e.g. temperature changes or chemical agents. Moreover, new manufacturing methods make it possible to specifically produce these structures in the micrometer range. These methods include for example, additive processes like 3D-printing.
In this paper, the focus is on the use of programmable materials in the area of effective filter cleaning. More precisely, we investigate weaves in a liquid filtration application. In the regular filtration step, it is desirable to have high filtration efficiencies, a low pressure drop and a high dust holding capacity. Low pressure corresponds to energy savings and low operating costs. The dust holding capacity ensures efficient use of operational capacity. When certain limits are reached, the backwashing step is performed to clean the filter medium from deposited dust. Thereby, the filter medium does not need to be replaced and maybe used several filtration cycles. However, backwashing cannot clean the medium entirely and the motivating question is: What is the potential to improve the backwashing efficiency by geometrical changes of the filter medium using programmable materials? Backwashing efficiency means short regeneration time, low clean water consumption and minimal particulate residues. We answer the above question by...
FILOS – Protocol & report for the filtration of suspensions a novel software tool for planning, analysing, judging, saving and reporting of measured and calculated test data
I. Nicolaou*, NIKIFOS Ltd, Cyprus
In this paper a novel and powerful module of the Filtration Software FILOS for entering and saving all known and measured data for every experiment of a given Filtration test series will be presented. Each experiment belongs to a definite test series and every series belongs to a definite project. Projects and Series as well as experiments of each series, test goal and tested steps for each experiment are listed in the first column (see figure below). The second column displays the geometrical parameters of the test apparatus and basic material data for the tested suspension. The data for each tested step (Cake Formation and the optional Steps: Cake Washing, Cake Squeezing and Cake Deliquoring) are displayed in a separate column. The Protocol is also a Calculator because it calculates and displays from the entered measured data the values of many important parameters, which enable the judgment of each experiment. All data of one test series can be transferred to the FILOS-Analysis modules for Detailed judgment and determination of the necessary efficiency parameters for the filter performance simulation. Highest flexibility regarding input and calculated parameters enables the use of Protocol even as a Simulator, which can be used even for the planning of the experiments. The Series Overview Table displays for comparison reasons all important input and calculated parameters for all experiments of the current test series...
Bernoulli offers a solid basis for crystallization
H. Meldau*, Sulzer Escher Wyss, Germany
The state of knowledge about crystallization is associated with the names Mersmann, Mullin and Randolph and Larson, who showed 40 years ago that the average crystal size in stirred crystallizers is < 1 mm
Crystallization and crystal solvation are opposing physical processes in the tiny cosmos of nanoparticles. They occur in the boundary layer on the crystal surface. The reaction enthalpy that is implemented in these processes is 3890 J / mol for NaCl.
1 Mol = 6.022 1023 Particle
1 J = 0,624x1019 eV
Related to a NaCl molecule these are:
RENaCL = 40,31 x 10-3 eV
Where's the energy that is permanently fed into the process? It is converted into kinetic energy, which serves various consumers or degrees of freedom in the turbulence area and thereby releases many molecules.
This locally increasing supersaturation with hydrated ions is neither visible nor measurable. However, the effect is convincing. A large number of very small crystal nuclei form spontaneously while releasing energy. Waste heat resulting from this process increases the temperature of the suspension insignificant. But the formation of these small crystal nuclei are extremely undesirable. The reduction of energy supplied helps here.
It is not necessary to keep crystals in suspension. A slowly sinking crystal should not be stopped and its growth should not be disturbed by unnecessary energy input. If the crystal is down, it can be transported with little energy back to the place where supersaturation is generated.
The Bernoulli principle makes this possible with many economic consequences.
Magnetic seeded filtration as a holistic solid-liquid separation concept
F. Rhein*, H. Nirschl, Karlsruhe Institute of Technology (KIT), Germany
The demands on separation technology have steadily increased over recent years. Highly specific, selective separation techniques that are also suitable for fine particles in dilute suspensions, are needed more and more. In this work, magnetic seeded filtration (MSF) is presented as a separation concept that is capable of handling these challenges. Here, magnetic seed particles are added to a suspension and after agglomeration with the target particles, the agglomerates are removed by magnetic separation. However, the necessity of adding magnetic material is economically and ecologically questionable and is the main point of criticism against the process.
In the scope of this work, it was shown that high separation efficiencies of up to 95% on a broad parameter scale are achievable with MSF, even in dilute suspensions with particle concentrations of under 10-2vol%. Moreover, the electrostatic interactio..n
Adsorption of microplastic particles on the surface of freshwater plants
A.-C. Swertz*, E. Schmidt, University of Wuppertal, Germany
Plastic litter is a severe problem of modern society gaining more attention in recent times. The term “microplastics” is often used in this context referring to small plastic particles or fibres with a diameter < 5 mm. These particles are not only widespread in marine environments but can also be detected in inland water bodies and soils. Although modern sewage treatment plants can retain most of the incoming microplastic, a small fraction finds its way into rivers with the final effluent.
At the Institute of Particle Technology of the University of Wuppertal, the adsorption behaviour of microplastics on the surface of freshwater plants was studied.
As a first step, a benchtop experiment was realised to observe the general interaction of plastic microparticles (e. g. PE and PVC) with common freshwater plants as rigid hornwort (Ceratophyllum demersum) or eelgrass (Valisneria sp.). The adsorption of microplastics on the plant’s surface has been analysed using light microscopy with visible and UV-light as shown in figure 1.
As the lab experiment could successfully show that microplastics have a strong adsorption behaviour on the surface of aquatic plants, the contamination of plants from inland water bodies were analysed. For this purpose plant material was collected from different spots in Ruhr river. Parts of these plants were examined using light microscopy with visible and UV light, as shown in figure 1.
The method of the lab experiments and the first results regarding the distribution of aquatic plants with adsorbed microplastics in the environment will be presented in this paper...
abcr eco_antimic – a multivariable, antimicrobial material applicable for all surfaces and reducing biofilms
C. Hussal*, J.Schuricht, abcr GmbH, Germany
More and more microorganisms, especially Methicillin-resistant Staphylococcus aureus (MRSA) or Escherichia coli (E.coli), are coming into focus because of their health-endangering properties. Almost on all surfaces touched by people bacteria can be found. Surfaces must be regularly disinfected with strong detergents in order to prevent the reproduction of bacteria and to limit transmission paths. A solution prevent reproduction or formation of biofilms are functionalized surfaces as coatings, with a ‘immediate’ killing effect or are at least toxic for reproduction. However, these substances do not stop at the human body. Therefore, new and sensible solutions are needed against the formation of multi-resistant germs.
A proven alternative to equip all surfaces antimicrobial - even in water-bearing systems - is abcr eco_antimic from the company abcr GmbH.
The material provides an enormously wide range of applications as a surface-active substance in respect of incubation time, effectiveness and duration of action. The substance can be used as a coating or as part of the matrix and then shows practically no wear and tear and a long-lasting effect over several years. In addition, the material is characterized by the fact that it shows no mobility. The human body isn’t affected. Challenging applications can be found on all contact surfaces, e.g. in hospitals, sanitary facilities, on medical equipment. A further field of application is the reduction of biofilms in water-bearing systems.
abcr eco_antimic has already been successfully used in various applications and a large number of patents and the biocide approval exist. How the material works and what results have been achieved will be shown in our presentation...
Hydrocyclone for reduction of abrasive wear in sand trap piping of wastewater treatment plants
T. Senfter*, B. Stern, M. Berger., M. Pillei, M. Kraxner, MCI Management Center Innsbruck; H. Erber Innsbruck Municipal Administration, Austria
Sand traps are typically installed in wastewater treatment plants for the removal of abrasive particles from the inlet flow. The particle rich water at the lower stage of the sand trap is pumped to a second sedimenter, which is connected to a sand washer.
Particles, which cannot be separated by the second sedimeter, are pumped back to the inlet of the wastewater treatment plant. This leads to a recirculation of the non-separable particles and results in abrasive wear in the first stages of the wastewater treatment plant.
For the removal of these particles a hydrocyclone was installed in the recirculation line of a wastewater treatment plant (capacity 400.000 population equivalents) in Austria. The system was investigated in terms of optimum operational parameters (high separation efficiency, low pressure drop) and separated particles properties (particle size distribution, composition). The hydrocyclone was operated in bypass-mode with an inlet flow rate of 3 m³/h and 1.93 kg/h of particles (average) were separated. The separated particles (median diameter 1.1 mm) consisted of 50.12% organic and 49.88 % anorganic material (average).
It was shown, that...
High-performance micro particle separation by modified hydrocyclone technology
S. Porkert*; A. Scholl, L. Busse, ECOFARIO, Germany
ECOFARIO is a Munich-based green-tech startup that was founded in 2018 and has developed and patented a break-through separation process based on hydrocyclone technology to target the global problem of microplastic and microparticle pollution.
This technology will be installed modularly as an end-of-pipe solution in municipal or industrial sewage treatment plants or in industrial process water circuits. There, it will significantly reduce the microparticle load with a special focus on microplastics and the associated pollutants. This will result in enhanced water quality, fewer purification costs, and lower negative environmental impact. Common processes such as micro-, nano- and ultrafiltration are based on active filter media. By eliminating the physical filter, ECOFARIO’s technology can treat volume flows of any size with long product life cycles without the need for flushing sequences, cleaning chemicals, or other filter-based drawbacks.
The technology's main benefit is that the microparticles (microplastics) are separated from the surrounding water solely by gravitation and fluid forces. Within the technology’s key components...
Alkaline Leaching behavior of zinc from Egyptian zinc ore and filtration performance at various pressure difference
D.M. Abdo*, E.A. Abdel-Aal, Central Metallurgical Research and Development Institute (CMRDI), Egypt
This study was performed in two phases of work. In the first stage, alkaline leaching of zinc from Egyptian zinc ore at the Um Gheig area was examined and the influence of the operating variables including stirring speed, leaching temperature, NaOH concentration and liquid to solid ratio was determined experimentally. The optimum condition was found to be NaOH concentration of 4 M, liquid to solid ratio of 20 ml/g, temperature of 80 °C and a stirring speed of 400 rpm for time 2 hrs, in the range of investigated parameters. Under these conditions, the highest recovery of zinc was obtained to be 86.52%. In the second stage, the filtration process was examined under various pressure difference ranging from 0.66 to 0.80 bar. The finding reveals that...
Filter press solid liquid separation: comparative study on cake drying and washing performances with different plate designs.
N.M. Finocchiaro*, F. Kaswalder, A. Grosso, Aqseptence Group s.r.l., Italy
In the last few years, sludge treatment with filter presses has become more and more common in the mining industry as well as in other sectors. These machines offer great advantages: first, the dewatering level that can be reached with filter presses is much higher compared with other separation technologies, and this grants a substantial water recovery level. Moreover, filter presses are very versatile machines that can easily adapt to changes in both production capacity and solids concentration.
The mining sector requires higher and higher performances, in particular on residual moisture content in cake and machine’s throughput. The optimization of the filter press process parameters is therefore essential to meet customers’ needs.
This paper presents the results of two case studies where we compared different plate designs by conducting bench-scale simulations.
The first case study described in this paper is focused on the analysis of cake drying performances with different plate types. Plates used had different arrangements such as different membrane types and a different positioning of drainage holes. The parameter monitored was the residual moisture content in cake. This study was carried out on a coal concentrate.
The second case study was focused on the fluid dynamics of the washing liquor inside the filtration chamber in case of cake washing. The movement of a fluid inside the chamber was analysed by using a tracer...
1½-Way CFD-DEM coupling with DNSlab: The optimal compromise between modeling depth and computer resources demand for the 3D simulation of microscale fluid-particle-processes
K. Schmidt*, IT for Engineering (it4e) GmbH; V. Puderbach, S. Antonyuk, Technische Universität Kaiserslautern, Germany
Microscale fluid-particle processes, especially such as filtration of solid particles from liquid by porous media, involve the effect of the fluid flow on the particles as well as the effect of the particles on the fluid flow. For the simulation of such processes, where the CFD method is used to model the fluid flow and the DEM method to model particle-particle and particle-structure interactions, several approaches of coupling these two methods can be applied with different modelling depths and demands regarding computer resources. Using the it4e simulation software DNSlab, different variants of coupling the CFD and the DEM method have been implemented and evaluated regarding their suitability especially for microscale fluid-particle processes...
Grey-box modelling of decanter centrifuges by coupling a numerical model with neural networks
P. Menesklou*, M. Gleiß, H. Nirschl, Karlsruhe Institute of Technology (KIT), Germany
Continuously operating decanter centrifuges are often used for solid-liquid separation in the chemical and mining industries. Simulation tools can assist in the configuration and optimisation of the separation apparatus, which means controlling the quality characteristics of the product. Increasing computation power has led to a renewed interest in grey-box modelling. The name is deduced from the fact that in the simplest case the model consists of two kinds of models. The white-box model is a representative example of known mathematical and physical relationships, such as analytical equations or numerical models, which often contain multiple assumptions. The black-box model, typically a regression model or neural network, requires a training data set and correlates a model, which is predicting output parameter as a function of input parameters. Combining both has the advantage that effects, which cannot be modelled with the assumptions of the white-box model, can be predicted by the black-box model if appropriate training data is selected for it.
In this presentation a grey-box model for the simulation of the mechanical dewatering of a finely dispersed product in decanter centrifuges will be discussed. Here, the white-box model is a numerical and dynamic process model, which considers the settling behaviour, the sediment consolidation and the sediment transport. The black-box model is a neuronal network trained with experimental data. Now, the simulation tool is able to check the accuracy of the model on the one hand, and on the other hand, effects that have not been modelled so far can be learned using training data with a neural network, thus extending the range of validity....
Method development for the resolved numerical simulation of mechanical solid-liquid separation in decanter centrifuges
H. Wettich*, M. Gleiß, H. Nirschl, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
The sustainable and efficient use of resources and plants while providing a high product quality is the challenge for the process industry in this century. Nearly 60 % of the processes in the chemical industry involve the production, processing and usage of particulate systems. One basic process operation is the separation of solids from liquids. For the separation of finest solid particles from liquids, continuously operating decanter centrifuges are commonly used on an industrial scale. The design of these apparatuses is based on simplified black box models for the stationary state. Though, the physical behavior of the separation process as well as sediment formation and its transport remain unconsidered in this approach. For the selection of a suitable apparatus as well as the optimum adjustment of the operating parameters, a large number of experiments on a pilot scale are necessary. However, changes in the material properties of the initial suspension can lead to a significantly different process behavior, so that different running parameters are required for an optimal operation of the apparatus.
Here, one challenge is that the process takes place on different time and length scales: The characterization of the disperse phase takes place at the smallest scale. Solids phase characteristics influence the separation-related material functions such as sedimentation, consolidation and sediment transport. In combination with the adjustable operating parameters, this defines residence time behaviour and flow conditions. Advancing digitalization can make an important contribution to a sustainable development under consideration of all scales. CFD simulation allows the resolved observation of the physical processes in the separation apparatus.
In this presentation, a simulation approach will be discussed which takes sedimentation, sediment formation and solids transport into account...
Re-wetting during belt filter press operation
G. Krammer*, F. Mazzi, Graz University of Technology; R. Raberger, Andritz AG, Austria
Belt filter presses are widely used for the separation of solid particles from liquids. In a first stage, the free draining liquid of a suspension is removed by a gravity table. This pre-thickened suspension is further compacted by feeding it through two converging filter belts, i.e., the wedge zone to form a filter cake that is sufficiently stable to cope with increasing press forces exerted on the cake during a sequence of subsequent rollers. With the diameters of the rollers decreasing, the operation parameters belt speed and belt tension as well as the geometric set-up resulting in the enlacement lengths, the gradual, though step-wise increase of the exerted areal pressure as well as the respective exposure time of the cake are ensured to meet the targeted cake dryness and specific throughput.
Under the premise that no gas bubbles are present in the cake during its formation, mere press filtration results in a filter cake that is fully saturated by liquid. Further reduction of the liquid content is accomplished by liquid evaporation (thermal drying or desorption) or liquid displacement by gas blowing. However, a filter cake that has elastic properties will expand when the pressure is released. Under the premise that adjacent free liquid is present and sufficient time is given, such an expanding filter cake can pick up liquid that was removed from the cake already previously. However, when time is too short and/or liquid for re-wetting is lacking, a filter cake is obtained with a saturation below one, i.e., with a higher cake dryness and shrinking cracks may form.
In the laboratory two different aqueous suspension were investigated, hard coal and a waste material containing metal and organic matter. Mimicking the belt filter process, the free liquid was drained before the pre-thickened suspension was compacted by applying normal pressure. The resulting filter cake was fed to a laboratory roller test set-up at conditions typical for large-scale applications. The filter cake dryness was determined with and without a liquid suction and storage layer positioned between the rubberized and dense roller and the filter medium. The results show...
Compaction of compressible filter cakes by oscillating shear
T. Yildiz*, H. Nirschl, Karlsruhe Institute of Technology (KIT), Germany
Cake filtration is a proven method for separating solid particles from a suspension. After cake formation, there is a particle network whose porse are filled with liquid. To reduce the residual moisture of the filter cake, mechanical dehumidification measures are a more cost-effective alternative to thermal drying. After cake formation, gas pressure is applied to the filter cake, allowing the liquid to be largely displaced from the pores of the particle network. This can lead to the formation of shrinkage cracks, especially in fine-particle products, which result in higher gas consumption and thus higher process costs. It is known from previous research activities that shrinkage cracks during liquid removal can be prevented by pre-compaction of the filter cake. Since the required pressing pressure can be very high, depending on the particle system, and this measure is therefore often not feasible on a continuous technical scale, alternative compaction methods are desirable. An innovative method is the application of an oscillating shear into the filter cake using significantly lower pressing pressure, which has already been successfully tested on a laboratory scale for mineral materials with low and medium compressibility.
In order to further clarify the applicability of the process, the compaction behavior of other products under oscillating shear must be investigated. For this purpose, experimental studies under variation of process parameters such as the vibration frequency and the number of applied oscillations were carried out on a laboratory plant using a new model product with high compressibility. In the course of the lecture the compaction behaviour under oscillating shear of the highly compressible model product will be presented. In addition to the consideration of the new product class, the influence of different agglomeration states on the behaviour of the product under the vibration-enhanced compaction will be shown...
Enhancing egyptian phosphate filtration rate during chemical processing into phosphoric acid
E.A. Abdel-Aal*, Central Metallurgical Research and Development Institute (CMRDI), Egypt
This study was carried out to enhance the filtration rate of phosphoric acid from phosphogypsum during chemical processing of Egyptian phosphate using Dihydrate process. Enhancing the filtration rate was applied using different additives and/or increasing the filter speed. The obtained results are compared with the filtration rates from different international phosphates from Florida, Morocco, Tunisia and others. In industry, better filtration rate of phosphoric acid means higher production as well as less capital and operation costs. Chemical techniques for enhancing the filterability are reaction with the suitable surface–active agent or mixing with a poly acrylamide polymer just before filtration while the physical technique is related to decreasing the cake thickness via increasing rotation speed of filter under the standard applied vacuum. The applied additives include but not limited to surfactants, aluminum bearing materials, oxidizing agents, blending of two phosphate ores, …etc. Phosphoric acid is produced under simulate industrial Dihydrate process. To understand effect of additive from fundamentals point of view, induction time was measured under different supersaturation ratios. The results show that...
Floc characterization with turbiscan apparatus: Which useful information for sludge thichening and dewatering ?
P. Ginisty, I. Igwet, IFTS - Institute of Filtration & Techniques of Separation; R. Ramsch, Formulaction, France
Sludge is produced by wastewater treatment and is in the form of a liquid slurry with a water content of 95-99% and the is treated (treatment principle represented by the figure below) to be compatible with its final destination (use in agriculture, incineration, landfilling…)
Effectiveness and cost of sludge treatment and disposal operations are strongly affected by its volume, so reduction of volume is certainly a pillar for the development of sustainable management systems. To this purpose, thickening and dewatering are the necessary steps to improve sludge solids concentration and most of these operations require flocculation pretreatment to obtain an efficient separation process between water and solids.
Treatment optimization is very empirical as operators should continuously adapt the machines performances to sludge and flocs properties and variations of these properties over time. If some methods are classically used for sludge characterization, relatively few are available for flocs and levels of knowledge of flocs behavior remains low. It is necessary to take into account the water release from flocs, depending of the constraints in the mechanical dewatering machines. Only free water, sum of the supernatant water and bulk water, respectively present between and inside the flocs can be removed by mechanical processes but flocculation can modify the ratio between free and bound water .
Laboratory methods and devices should be tested to get more knowledge about flocs properties and behavior, too help the selection of polymers and corresponding dosage and to collect data about their dewaterability. Among them, drainage and CST tests vs mixing time, basket spin tests with shearing, limit dryness determination can give useful information . It is also necessary to take into account how the way of floc formation can influence their properties.
This paper presents flocs characterization by Turbiscan apparatus. Its allows detection at an early stage all kinds of destabilisation such flocculation, sedimentation, coalescence… 20 to 50 times faster than the visual detection. The Turbiscan works on...
Compressibility in filter aid filtration with cellulose depending on the loading
D. Neuber*, Urs A. Peuker, Technical University Bergakademie Freiberg, Germany
Filter aid filtration, also known as precoat filtration, is used to separate very small, colloidal or gelatinous impurities from a generally low–concentrated suspension. It is a very flexible application in solid-liquid separation due to the wide range of available filter aids with different particle sizes and modifications. The aim of using filter aids is building up a stable permeable network in which submicron particles can be separated from the liquid to gain a particle–free filtrate. The most commonly used filter aids in industry are kieselguhr, perlite and cellulose, which each have their own advantages and disadvantages depending on the field of application, due to their different structure and origin.
Kieselguhr, fossil skeletons of diatoms, builds up a very stable filter cake, has a large surface area and there is a great wealth of experience in handling it. In comparison, cellulose is a renewable resource, no threat to health, and better disposable, but forms a significantly more compressible filter cake. This leads to a porosity change over the cake height and mainly to a decrease in porosity in the lower filter layers close to the filter medium. The pores are getting narrower, leading to higher flow velocities and higher shear rates. Separated solid particles can remobilise again and re-enter into filtrate. Such redispersion negatively affects the process behaviour of the precoat filtration. For optimization of filter aid filtration processes with cellulose, these effects of compression need to be investigated.
In this work, the compression behaviour of cellulose filter cakes depending on titanium dioxide loading is investigated by using a Compression-Permeability-Cell. The results show...
An optimal control method for filter-aid filtration processes with compressible cakes
P. Pergam*, J. Steinhäuser, M. Kuhn, H. Briesen, Technical University of Munich, Germany
Adding filter aids to filtration processes is a well-established technique for separating hard-to-handle suspensions. Filter aids deliver reinforcement of the cake structure and increase the cake’s permeability. Newly developed filter-aid materials (e.g. cellulose fibers) offer environmental and health benefits. However, contrary to traditionally-used rigid filter aids (e.g. kieselgur, perlite) above mentioned additives suffer from an increased compressibility due to their softer material structure and their fibrous morphology. Thus, their dosage is more challenging to handle in praxis. Unsuitable concentrations will have a great impact on filtration performance, because lower-layer blocking (“skin effect”) leads to rapid increase in overall differential pressure. In this preliminary study, we aim to find optimal dosage strategies using an optimal control (OC) approach.
Kuhn et al. [1, 2] successfully applied OC on filter-aid filtrations with incompressible cakes. Assuming the absence of depth filtration effects, they found the optimal time-dependent filter-aid dosage to be proportional to the time-varying impurities contained in the suspension. The focus of the present work lies on dead-end filter-aid filtration processes operated in constant flow mode, but here with compressible filter cakes. As a neuralgic case study, we try to find the optimal time-dependent filter-aid concentration trajectory for a constant concentration of impurities in the suspension...
Investigations on the process strategy of aqueous two-phase flotation (ATPF)
L. Jakob*, M. Heinzmann, H. Nirschl, Karlsruhe Institute of Technology (KIT), Germany
The purification of industrial enzymes from complex biosuspensions represents a major challenge for the bioprocess. Many separation steps are necessary to capture the target protein from the fermentation broth and to increase the purity up to the final product. Losses and energy costs of the individual steps sum up and purification costs for enzymes usually represent more than 50% of production costs.
Flotation of enzymes in aqueous two-phase systems (aqueous two-phase flotation, ATPF) combines selectivity of extraction with high mass transfer of flotation. Proteins attach themselves with their hydrophobic part to rising bubbles and are transported from bottom into top phase. This allows to perform "Capture" and "Clean" in one step. ATPF promises to be an efficient alternative to conventional purification processes of biotechnological products by eliminating several separation steps, warranting mild conditions and high product concentration in an aqueous top phase. However, more research is needed to develop the new technology on its way to an industrial use.
Especially the process design needs to be investigated. Looking on common foam separation techniques for bio-products, a cylindrical flotation cell might be preferred for ATPF as well. During a long ascent during bottom phase the bubbles might collect more target molecules and transfer them into top phase of the aqueous two-phase system. On the contrary a horizontal flotation tank, like used in mineral flotation, would provide high throughput and should be preferred for continuous flotation.
In this talk, fundamental perceptions how an optimized ATPF-process should be realized will be presented...
Novel method for removal of microplastics from various waters using organosilanes
K. Schuhen*, Wasser 3.0 gGmbH, Germany
Microplastics (MP) are ubiquitous in the aquatic environment and need to be removed. A new method uses organosilanes for the removal of MP form various waters.
When adding organosilanes to water containing MP, they attach to the surface of the microplastics, collect it in agglomerates and fix it chemically.
The clou is, that MP agglomerates are floating on the surface and not sinking down to the ground. An easily separation with a skimmer leads to MP removal efficiency to reproducible > 95 % independent of polymer type and concentration.
Characterization of protein crystal sediments with microcomputer tomography
B. Radel*, H. Nirschl, Karlsruhe Institute of Technology (KIT), Germany
Due to advances in the microbial production of target molecules, product titers after fermentation have increased in recent years. In the case of proteins, such high titers are a challenge for downstream processing. Typically, centrifugation and several chromatography steps separate the target protein from the impurities and the mother liquor. High titers in the mother liquor require large chromatography columns and large amounts of solvents making the downstream process expensive. Additional precautions regarding toxicity and explosive properties may be required when using organic solvents. Therefore, alternative methods such as selective preparative protein crystallization are becoming more and more interesting for the pharmaceutical industry. Another positive aspect of crystalline proteins is a longer shelf life and different drug release properties. After the crystallization step, the protein crystal must be separated from the mother liquor. Dead-end cake filtration is often used for this solid-liquid separation step. Compared to conventional crystals, protein crystals have a lower mechanical stability. Even at low pressures, crystal breakage or abrasion can occur, which worsens the filtration behavior.
In current research Nowotny et al. have modified the amino acid sequence of the enzyme alcohol dehydrogenase from Lactobacillus brevis in order to improve the crystallization properties. Kubiak et al. used cross-linking of lysozyme crystals, which increased the mechanical stability. For cost reasons, the screening of such modifications is typically carried out on a small scale with only a few milliliters of sample volume. Typical filtration experiments in e.g. a nutsche filter require much larger volumes.
To characterize the filtration behavior, we have developed a 3D printed filtration cell which, in combination with an optical analytical centrifuge, enables a filtration experiment with a sample volume of approx. 300µL. Thus, the influence of protein engineering and crystal modification on filtration can be determined on a small scale. The flux density function, which describes sedimentation and filtration properties as a function of the solids volume fraction, is calculated from experimental data obtained with the filtration cell...
3D information about the multiphase processes in the pore space of a filter cake using X-ray tomography
E. Löwer*, T. Leißner, U.A. Peuker, Technical University Bergakademie Freiberg, Germany
Predicting the dewatering of porous structures is the key to evaluate the efficiency of mechanical solid-liquid separations: The investigation of the developing liquid distribution and the characterization of the saturation process usually requires experimental data/support points. Direct computed tomographic insights into the structure of the filter cake allow the tracking of micro processes during the desaturation process. The used ZEISS Xradia 510 Versa X-ray microscope used combines classic X-ray tomography with microscopy optics, which makes significantly smaller imaging voxel sizes possible.
The investigated geometric filter cake properties depend mostly on the distributed particle properties, which are deterministically coupled to each other. Typical technically relevant size distributions (narrow monomodal, logarithmic normal distribution or bi-modal distributed particle sizes) are investigated in 2D and 3D analyses of the individual particles (size, shape) and in tomographic characterization of the resulting filter cake. The size range of the particles is selected under the condition that the weight force remains the dominant size with respect to the interaction forces of the particles (x10 > 20 µm). The structural information about the pore system is systematically evaluated and quantified by characteristic parameters (integral and local porosity, horizontal and vertical pore radius, coordination number, pore connectivity, tortuosity, local contact angle) of the system.
In addition to the completely saturated cake structures, the mentioned parameters are also determined on dewatered filter cakes...
Steam pressure filtration - Combination of water insoluble liquids and dewatering with steam
S. Esser*, U.A. Peuker, Technical University Bergakademie Freiberg, Germany
Steam pressure filtration (SPF) has been established in the field of solid-liquid separation for the last 20 years, while the field of application is steadily expanding. The treatment of solvent-loaded solids, e.g. following a solid-liquid extraction presents a challenge in practice. This challenge becomes even more complicated if the solvents used are volatile organic compounds (VOC) which are poorly soluble in water and thus bio-incompatible. A complete mechanical separation of the VOC from the solid is not possible and a following drying process is usually energy intensive and expensive.
In comparison with conventional filtration, in SPF the saturated filter cake is treated with saturated or superheated steam instead of gas, which results in excellent washing and dewatering behaviour of the filter cake.
Due to the uniform mechanical displacement of the suspension liquid, the SPF promises a lower residual VOC load of the filter cake in contrast to conventional filtration at the end of the mechanical displacement phase. The end of mechanical displacement is defined as the time of steam breakthrough in SPF or gas breakthrough in conventional filtration.
The filtrate accumulated up to these times is pure VOC in both processes. Another steam flow through the filter cake, which in this context can also be seen as steam stripping, further reduces the VOC load of the filter cake. The driving force here is the minimization of the thermodynamic potential to the thermic equilibrium. The energy required to evaporate the VOC is supplied by the vapor phase in form of enthalpy of vaporization of water condensing on the particle surface. In this process phase, the filtrate is collected as a two-phase mixture of VOC and water according to the vapor composition at the outlet of the filter.
The investigations on SPF in combination with a water-insoluble liquid phase were carried out in the context of the already completed AiF project IGF 19305 BR. The presentation gives an overview on the project and a summary of the results....
Innovative filter module to separate microplastics from wastewater
A. Lanfermann*, T. Barthels, M. Nießen, P. Abels, Fraunhofer Institute for Laser Technology ILT; G. Klass, C. Doisl, Klass-Filter GmbH; C. Riester, LaserJob GmbH; B. Hoche, Lunovu GmbH; T.Q. Pham, OptiY GmbH, Germany
The pollution by microplastics is currently a major topic in the society. Microplastics are defined as plastic particles with a diameter < 5 mm. They are divided into primary microplastics, deliberately introduced particles in e.g. shower gels or soap, and secondary microplastics, e.g. plastic bags dissolved by UV light. Both types of microplastics get in our wastewater and later in the wastewater treatment plants (WWTPs). Bigger particles can be separated reliably in the WWTPs but small particles < 63 µm are not filtered and are released in our rivers and seas. But exactly these small particles are the dangerous ones for our flora and fauna because they accumulate in the tissues of humans, animals and plants as well as in the soil. This fact makes it necessary to develop better filter systems to separate even particles < 63 µm out of wastewater.
The project aims to develop a filter to separate microplastic particles down to 10 µm from wastewater. The basis of this filter is the Klass cyclone filter that has an actual pore size of 100 µm and is used in different cleaning processes for wastewater and canal water. To adapt this cyclone filter to the challenge of filtrate microplastics, the project team develops a new filter insert with pore sizes of 10 µm. At the end of the project a prototype will be built and tested in a WWTP to evaluate the function of the filter. The new developed filter insert consists of...
Cyclonplus - A novel software for the analysis of hydocyclone test data and the design and performance calculation of hydrocyclones
I. Nicolaou*, NIKIFOS Ltd, Cyprus
In this paper a novel software for the theory based analysis of hydrocyclone test data and the design and performance calculation of hydrocyclones (parallel connection considered) with reliable and physically based mathematical models is presented. The reliability is due to the used adaptation parameters, which depend on the given suspension and the given cyclone geometry and can be determined by analysis of test data. Characteristic to this tool is the highest flexibility regarding the input parameters. For example, we can design a hydrocyclone (diameter D, number of cyclones in parallel connection n, underflow (apex) diameter Du) for definite (required) solids mass fraction in the underflow (Cmu) and simultaneously demand a definite clarification or classification result for the overflow, as for example 90% of the solids in the overflow should have a particle size smaller than a definite entered size (x90o) and additionally demanding a definite flow rate Q and definite pressure drop Dp. The program calculates and displays for each simulation the particle size distributions, the flow rates and the solids content of overflow and underflow as well as the total efficiencies ET, ET’ and the grade efficiency curves G(x) and G’(x) of the hydrocyclone.
What makes the program more user-friendly is that all calculations including tables and graphs are taking place/displayed in one window with automatically updating of the diagram and table with any change of the input parameters. Any material or setting parameter can be systematically varied and its influence on any result parameter can be studied. For example we can study how the diameter of the hydrocyclone influences the cut size, the total efficiency, the particle size distribution and solids content of the overflow and underflow...
Sedimentation of bidisperse polymer suspensions in aqueous polymer solutions
T. Sobisch*, U. Schuldt, D. Lerche, LUM GmbH, Germany
Basically, separation processes can be described by extended Stokes law taking into account volume concentration of disperse phase (hindrance) and rheological behaviour of continuous phase. To deduce separation behaviour under high gravity in centrifuges one can assume that separation velocity scales linearly with acceleration in Newtonian liquids. Situation in non-Newtonian liquids is much more complex, however, this is often characteristic for industrial separation tasks, e.g. during downstream bioprocessing. Modelling of the separation processes gets even more complicated when taking into account polydispersity of real-world suspensions.
To contribute to a better understanding, model investigations were performed with monodisperse polymer particles (6 and 15 µm) and their bidisperse mixtures in aqueous solutions of carboxmethyl cellulose (CMC). Measurements were conducted as function of centrifugal acceleration and at gravity.
In dependence on CMC concentration and particle size the investigations led to interesting findings. Dissolved CMC induced flocculation affecting sedimentation even for micron-sized model particles if viscous forces are sufficiently high. At high CMC concentrations shear-thinning like separation behaviour was observed, and in case of the smaller polymer particles also a lack of traceable separation below a critical centrifugal force. Sedimentation velocity as function of centrifugal acceleration could be well described by a linear approach if the velocity is normalized for acceleration. In case of shear-thinning like separation the slope of the normalized linear dependence is positive, but zero for Newton-like behaviour. Due to interaction with dissolved polymers settling of larger and smaller particles in bidisperse systems is not independent. Remarkably, sedimentation velocity of the larger particles is slowed down by...
Membrane bioreactor for the cleaning of surface water of a solid waste treatment site
T. Garstenauer*, B. Mayr, EnviCare, Austria
At solid waste treatment facilities, waste is partially stored outdoor on sealed surfaces. Therefore, rainwater might be considerably polluted with organic and inorganic compounds, depending on the leaching behaviour of the waste pile.
The discharge of rainwater is by law only allowed into storm water or combined wastewater sewers. If it is going to be discharged into a receiving water body, anthropogenic polluted surface water has to be treated according to the state of the art. The so-called first flush, the rainwater from the first 15 minutes during heavy rain events, has to be collected, stored and cleaned properly. Normally the water quality after the first flush already allows for direct discharge.
High fluctuating quantities and qualities of this surface water with differing temperature causes high demands on the treatment technology. In the case presented in this paper the COD (Chemical Oxygen Demand) concentration in the inflow ranges from 50 mg/l to 1,000 mg/l, in addition there can also be fluctuating and substantial nitrogen and phosphorus loads. In biological treatment plants, the retention of activated sludge has to be guaranteed for sudden heavy rain events as well as for longer dry periods. Membrane bioreactors meet both criteria while in a conventional sedimentation-based system, the activated sludge flocs will be washed out.
In membrane bioreactors (MBR) biological wastewater treatment is combined with membrane technology. Organic compounds, nitrogen and phosphorus are removed in aerobic processes. Ultrafiltration membranes prevent biomass and inert particles from wash-out. In this case hollow fibre membranes with a cut off of 50 nm are used.
This paper presents the design, construction and operation of an MBR plant for the cleaning of surface water of a solid waste treatment site...
Technical and economical evaluation of a membrane-based filtration process to remove micropollutants, resistant bacteria/genes and nutrients from treated wastewater
M. Werner*, D. Schreier, MICRODYN-NADIR, Germany; A. Merz, Darmstadt University of Applied Sciences, Germany
Since the last decade, the global concern regarding the release of harmful substances to the aquatic ecosystem is growing.
Chemical substances referred to as “micropollutants” originate from the production and use of products such as pharmaceuticals, biocides, pesticides, industrial and domestically applied chemicals, or personal care. These substances are frequently entering the aquatic ecosystem occasionally and via diffuse paths. The main path of entry represents industrial and municipal wastewater which is collected and treated in wastewater treatment plants (WWTPs) and subsequently discharged to waterbodies.
In addition to micropollutants the emergence and increasing spread of antibiotic resistant bacteria (ARB) and genes (ARG) holds a growing risk to environmental and public health. In several studies ARB and ARG have been extensively detected in wastewater. Published data illustrated a significantly higher proportion of ARG in raw and treated wastewater compared to surface water. The prevalent conditions in WWTPs, especially the biological treatment, tend to favour the accumulation and distribution of ARB to receiving waterbodies.
To deal with micropollutants in the outlet of WWTPs, processes e.g. ozonation, granulated activated carbon filtration and powdered activated carbon filtration have been implemented in plants all over Central Europe to further purify treated wastewater. However, those processes do not guarantee a removal of ARB/ARG. The challenge to significantly reduce micropollutants and separate ARB/ARG from treated wastewater led to a rising demand for additional filtration processes and triggered the development and application of membrane-based filtration processes which provide a physical barrier for harmful substances.
Such a process represents the “BIO-CEL® Activated Carbon process”, a combination of submerged ultrafiltration (UF) membranes, the dosage of Powdered Activated Carbon (PAC) and precipitants. A detailed description of the process can be found in M. Werner, M06 FILTECH 2019. In order to provide a customized solution for advanced wastewater treatment, MICRODYN-NADIR has been operating pilot plants at five locations since 2016 by testing different feed water as...
Old RO membranes end-of-life : from autopsy to reuse as NF/UF/MF or IEM in Water and WasteWater Treatments and at the end as an alternative fuel production
M. Pontié*, Angers University; S. Awad, IMT Atlantique, France; M. Shabani, Modares University, Iran; F. Seibel, V. Barbosa Briao, Universidade de Passo Fundo, Brazil
The overall objective of the present work is to estimate the degradation level of old reverse osmosis (RO) membranes end-of-life, sampled from different countries (Senegal, Mauritania, Tunisia, Brazil, Israel) in terms of water permeability, salts rejection, roughness changes and chemical analysis (i.e. ATR-FTIR, wettability, zetâ potential…) by following a membrane autopsy, in order to help the management of aged RO elements as new NF/UF/MF or also IEM.
The overall objective of the present work was to estimate by membrane autopsy the level of performances degradation of old RO membranes in order to envisage their reuse application as NF or UF or MF or IEM. A mechanistic approach using the Spiegler–Kedem–Katchalsky model helps us to observe that the old RO membrane acquired by use a convective mass transfer contribution vs diffusional. We defined a novel adimentionnal Peclet number (denoted Pe′) usable to distinguish between diffusional and convective mass transfer in NF, showing a new classification of NF membranes orienting the choice of a NF membrane for a done application. Furthermore, SEM/AFM and EDX experiments show crystals (i.e. CaCO3) and bacteria deposited as fouling agents, roughness increase for the old membrane (from 73 to 220 nm) due to (bio)foulants deposition or scaling. Transmembrane streaming potential (link to zetâ potential) measurements help us to observe a displacement of the isoelectric point (IEP) of the pristine RO membrane i.e 5.7±0.3 to 4.5±0.3 in comparison to the old one showing chemical modifications of the inner active layer suspected due to (bio)fouling residuals. With such old RO as NF/UF/MF or IEM and before end-of-life, new applications were engaged i.e. water defluoridation, water softening and wastewaters treatment in a microbial fuel cell.
Furthermore, the possibility to transform old RO spacers to alternative fuels via pyrolysis is studied...
Membrane distillation for the production of pharmaceutical-grade water
C. Nellessen*, T. Klein, Wilhelm Werner GmbH; H.-J. Rapp, DEUKUM GmbH; F. Rögener, Technical University Cologne, Germany
The water used for pharmaceutical applications is subject to strict regulations. Water quality as well as processing measures are clearly defined. In the European Union, the quality of water for pharmaceutical use is determined by the European Pharmacopeia (Ph.Eur.). Within the current pharmacopoeias, a distinction is made between purified water (PW) and water for injection (WFI) [EU2017].
PW is used for the production of medical products that are neither pyrogen-free nor sterile. Pyrogens are substances that cause fever in humans during parenteral intake (bypassing the intestine, e.g. intravenously). WFI is water for the production of medical products, solutions and dilutions for parenteral use. Drinking water is the raw material for both, PW and WFI production according to the respective national regulations [EU2017].
The Ph. Eur. sets limits and requirements for the quality of PW and WFI. Some parameters are depicted in Table 1....
Membrane distillation (MD) is investigated worldwide as a low cost, energy saving alternative to conventional separation processes such as distillation and reverse osmosis (RO). The porous and hydrophobic membranes used in MD processes allow the passage of vapors only and retain all nonvolatile components and liquids on the retentate side, thus the product obtained is theoretically 100% pure water vapor. Therefore, it is important that the dry pores must not be wetted by the liquid feed, which is directly in contact with the membrane. Due to the low required temperature level, the use of waste heat as well as solar thermal energy and geothermal energy is possible for the MD.
MD processes can be categorized into four basic module configurations, which play a fundamental role in separation efficiency and processing cost: direct contact membrane distillation (DCMD), air gap membrane distillation (AGMD), sweeping gas membrane distillation (SGMD), and vacuum membrane distillation (VMD).
A MD test plant was build up in the technology center of Wilhelm Werner Reinstwassertechnik GmbH, using membrane modules in AGMD configuration provided by DEUKUM GmbH. The condensate runs out of the module through gravity at the bottom. Different membranes were investigated. First results show that...
Nanofiltration versus reverse osmosis for brackish water desalination process considering wide range of salinity: pilot scale investigation
H. Dach*, M. Pontié, Angers University, France; A. Lhassani, Fez University, Morocco
The most commonly used technology for brackish water desalination is Reverse Osmosis (RO), due to its lower energy consumption. Newer generation membranes, such as Nanofiltration (NF) and ultra-low pressure Reverse Osmosis (ULPRO) membranes may provide the opportunity to reduce feed pressures and operating costs associated with RO desalination while providing similar permeate water quality. Since NF membranes are supplied in the same configurations as RO membranes, utilities could replace RO with NF spiral-wound elements without the need for significant additional capital investment. In this study, the tradeoffs in choosing NF and ULPRO membranes over RO were investigated including whether or not significantly lowering operating pressures/costs would result in diminished permeate water quality...
Possibilities for increasing the efficiency of decentralized production of potable water from seawater using membrane processes
T. Peters*, Membrane Consulting, Germany
Increasing demand for water resources is straining available supplies to an unprecedented degree, sparking the emergence of many innovative technologies for enhancing the efficiency of i. a. pressure driven membrane processes.
For more than five decades there has been remarkable growth in the need for quality water purification by all categories of users. The increasingly broad range of requirements for water quality has motivated the water treatment industry to refine existing techniques, combine methods and explore new water purification technologies.
Although great improvements have been made, misconceptions still exist. Therefore, it is necessary to increase the understanding of the capabilities of available technologies and how these technologies might be applied. Thereby it has to be considered that in principle and by experience there are no two water treatment problems exactly alike. There will always be slight differences with more than one technically acceptable and scientifically-sound solution to any given water treatment problem. As guideline shall be considered “each case is different”.
Based on activities and involvement of the author in seawater desalination in the last 40+ years with focus on optimization and improvement of seawater reverse osmosis desalination plants it can be stated, that actually sustainable, environmental sound and cost saving solutions, that are familiar to real experts in this market, often are not considered by potential user as it should be or could be. This applies mainly to the areas „seawater intake and pre-treatment“, „pumping and energy saving devices“ in combination with renewable energy sources at e. g. off-grid situations, „post-treatment“ (mineralization), „brine mining” and “machine learning (ML)” as part of Artificial Intelligence (AI) for optimizing the control of the function of desalination plants.
Facing the actual situation and the future demand, the user of such plants should obtain “best of the best” solutions if arguments as “cost saving”, “long-term sustainability” and “environmental sound” are of importance. Thereby the success achieved at centralized huge seawater reverse osmosis desalination plants should be adapted as far as possible to decentralized and small plants in order to increase the resource efficiency and to reduce the related carbon footprint during manufacturing, commissioning and operation of such units.
Selected example for such solutions for decentralized plants will be presented...
Modification of commercial UF membranes by plasma polymerization: Impact on structural / physicochemical properties and filtration performances
S. Déon* , Z. Koubaa, E. Korzhova, P. Fievet, Université de Bourgogne Franche-Comté; A. Airoudj, V. Roucoules, Université de Haute-Alsace, France
Commercial membranes often exhibit difficulties in rejecting multivalent cations, such as heavy metals, due to their usual negative charge. To face this drawback, it is proposed in this study to tailor surface properties of a GK membrane (Osmonics) by allylamine plasma polymerization. The impact of two polymerization durations on both structural/physicochemical properties and filtration performances was investigated. Impact on performances was investigated through permeation flux and ion rejection by cross-flow filtration of single salt solutions as well as ternary and quaternary ion mixtures (containing mono- and divalent anions and cations). Meanwhile, the properties of the modified membranes, namely mean pore radius, roughness, hydrophobicity, and surface zeta potential were estimated to discuss the impact of modification on filtration performances.
It is first proved that modification by cold plasma polymerization is an adequate and sustainable modification technique since...
Electrospray deposition of polyelectrolytes for tailoring physicochemical properties and enhancing filtration performances of commercial UF membranes
S. Déon*, E. Korzhova, P. Fievet, Université de Bourgogne Franche-Comté, France
Compared with reverse osmosis and tight nanofiltration membranes, ultrafiltration membranes allow large permeation flux with relatively low applied pressures. Unfortunately, rejection performances are often low due to large pores and especially that of divalent cations (such as heavy metals) is impeded by the usual negative charge of commercial membranes. Hence, the widespread use of nanoporous membranes in the removal of ionic contaminants requires the adjustment of their physicochemical properties to allow adequate ion rejection and fouling mitigation. In this study, it is proposed to tailor physicochemical properties of a commercial low molecular weight cut-off ultrafiltration membrane by electrospray deposition (ED) of polyethylenimine (PEI) and polystyrene sulfonate (PSS). This self-assembly of positive and negative polyelectrolyte layers is based on electrostatic attraction between polymers (membrane and polyelectrolytes) exhibiting opposite charge sign. The electrospray deposition is a common technique which, up to now, has not often been used for membrane modification. This technique consists in spraying fine droplets of polymer solution on the membrane surface under a high voltage between the needle containing the solution and the metallic support on which the membrane is stuck. Compared with classical dip-coating technique, the advantages of this process are the small quantities of polymer required and the inhomogeneous polymer dispersion at the membrane surface.
It is shown in this study that it is possible, with adequate conditions, to adjust the charge of the membrane surface from −40 to +40 mV by...
Bilayer composite membranes: fabrication and optimization for improved gas permeability
S. Farrukh*, F. Yousaf, National University of Sciences & Technology (NUST), Pakistan; X. Fan, University of Edinburgh, UK
Membranes with high gas permeability are greatly attractive to both academia and industry. As single layer dense membranes are being utilized in industries for separation and purification of gases such as CO2, CH4 and N2. The selectivity of these membranes is good and depends on polymer selection. However, the permeability of single layer dense membranes is very low. According to Robeson’s curve, selectivity and permeability of gases have inverse relationship. To address this point, composite membranes with superior performance can be employed for CO2 separation from CH4 and N2. Herein, we report comparison between high performance composite membranes of Cellulose acetate (CA)/ γ-CD(Cyclodextrin)MOF and Polyurethane(PU)/γ-CD-MOF supported on a porous structure of Poly vinyl alcohol (PVA). Fourier Transform Infra-Red spectroscopy was used to study the existence of different functional groups in the membranes. The presence of γ-CD-MOF in the membranes was also confirmed by X-Ray Diffraction. Universal Testing Machine was used to determine the maximum tensile strength of the prepared membranes. Scanning Electron Microscopy shows good dispersion of γ-CD-MOF and it also displays defect free selective and porous layers. The resultant membranes show excellent...
New PANFLUTE ultrafiltration membrane: Filtration and anti-fouling performance with complex water composed of water/oil/particles
El hadji Ibrahima Ndiaye, H. Nabet, J.-M. Pereuilh, S. Nowe, M. Jacob, Total; J.M. Espenan; Polymem SA; N. Abidine, ABC Membranes Sarl, France, J.-M. Pandraud, Clean Membranes, Inc., USA
Water plays a vital role in the production of petroleum. Producing oil or gas generates a large quantity of produced water, which is extracted with the hydrocarbons. The management of produced water is a critical challenge for operators. Produced water can be successfully reused for well injection or safely discharged to the environment, to do so, it is necessary to efficiently remove the hydrocarbons and the suspended solids. Separation processes using membrane technology have been developed to meet these challenges, but capital cost (mainly for offshore installations) and operability (fouling) remain crucial challenges.
It is well known that polyacrylonitrile (PAN) membranes have good hydrophilicity and chemical stability, but the utilization of PAN in hollow-fiber membranes has only met limited success with hydrocarbons. However, Clean Membranes developed a novel variation of the PAN polymer by grafting it with PEO to form a proprietary amphiphilic comb copolymer, polyacrylonitrile-graft-poly (ethylene oxide) (PAN-g-PEO). Hollow fiber membranes made with PAN-g-PEO were demonstrated by Clean Membranes to have exceptional capabilities for separating hydrocarbons from produced water without fouling, but these early membranes lacked sufficient mechanical strength for commercial applications. Clean Membranes subsequently collaborated with ABC Membranes and Polymem to develop and manufacture a novel in-out, multi-bore PAN-g-PEO UF membrane named PANFLUTE. Laboratory studies conducted by ABC Membranes using their proprietary PANFLUTE structural membrane design demonstrated good filtration performance in terms of wettability, permeability, and resistance to irreversible fouling with complex water composed of water/oil/particles.
Despite the success of ABC Membranes’ laboratory studies, it was understood that the expected benefits of treating oily water with PANFLUTE could best be achieved by working with a leader in the oil and gas industry, utilizing their test platforms and conducting the tests under their control. Clean Membranes, ABC Membranes, and Polymem teamed with Total to conduct this testing. This paper reports on the early data derived from these tests and the preliminary evaluation of PANFLUTE for the treatment produced water in the oil and gas industry...
A new pvdf ultrafiltration hollow fiber with durable performances for mbr and tertiary filtration
O. Lorain*, J.M. Espenan, I. Duchemin, Polymem SA, France
The history of the choice of the material for hollow fiber ultrafiltration fabrication is very interesting. At the beginning, in the late 1980s, cellulose acetate (CA) was chosen because it was the most hydrophilic material, ideal for the filtration with low fouling and low need for chemical cleaning. However, due to its low biological resistance and sensitivity to high pH, in the late 1990s, the use of this material declined, and it was completely replaced by polysulfone (PSU) and polyethersulfone (PES). To compensate the low hydrophilicity of these materials, the membranes were doped with hydrophilic additives like PVP during the manufacturing process. Then in the 2000s, and particularly in the United States, where the membranes market was rapidly evolving at this time, PSU and PES hollow fiber manufacturers faced problems of severe hollow fiber breakage. This was due to the use of large amount of chlorine during cleaning which degraded both the polymers backbone and the hydrophilic additives. A new fluorinated material, the polyvinylidene fluoride (PVDF), was then used to make membranes more resistant. With PVDF, the fibers no longer break, however the chlorine during chemical cleaning steps continued to degrade the hydrophilic additives causing an unexpected increase in irreversible fouling of the membranes over time. In addition, the release of the additives which are located on the surface of the pores, involved an increase in the size of the pores of the UF membrane leading also to an unexpected decrease of the rejection performances of the membranes.
Polymem with its partner Arkema have developed a new PVDF material incorporating an innovative amphiphilic di-block copolymer which is anchored in the polymer backbone during the early stages of membrane fabrication. Compared to conventional additives, this new hydrophilic polymer is not degraded by chlorine and the membrane retains its hydrophilicity throughout its service life. In addition, the pores size does not change, keeping the same rejection performances...
A dynamic transport model to predict evolution of nanofiltration performances in partial recycling and diafiltration modes
S. Déon* , B. Lam, P. Fievet, Université de Bourgogne Franche-Comté, France
Although many knowledge models describing the rejection of ionic compounds by nanofiltration membranes are available in literature, they are all used in full recycling mode. In these previous works, both permeate and retentate streams are recycled in order to maintain constant concentrations in the feed solution. However, such “steady state” approaches are not relevant for real applications. Indeed, nanofiltration of real effluents is implemented either in partial recycling (retentate only) or diafiltration modes, for which the permeate stream is collected during filtration. In these conditions, concentrations progressively evolve over time and classical models fail to predict performances.
Here, an improvement of the classic “Donnan Steric Pore Model”, which includes both volume and concentration variations over time is proposed. The model is based on...