There is a need to create targeted membranes designed for specific practical problems such as the separation of hydrogen sulfide from oil and accompanying gas, the separation of CO₂ from different process streams or the conditioning of biogas. These processes require integrated membrane systems possessing stability of membrane material under the process conditions. Due to its outstanding chemical resistance, good mechanics and stability at the presence of different organic compounds (including C₃₊ hydrocarbons), poly(4-methyl-1-pentene) (PMP) is suitable for the use in the mentioned petrochemical separation processes. The scope of this work is the production of hollow fiber (HF) membranes from the semicrystalline PMP via the environmental friendly melt spinning process and the corresponding permeation performance in a membrane module for gas separation...

More than 2 million m² of HJS Sintered Metal Filter (SMF^®) material have been produced within the last 15 years, with a peak production of 300.000 m² p.a.. The SMF^® material is a thin (< 0.5 mm) porous sintered metal in which a precisely defined stainless steel powder is sintered with an expanded metal carrier. This results in a thin, mechanically and thermally very stable filter medium, which can be treated in further processing similar to sheet metal. The SMF^® basis material is industrially manufactured as quasi endless sheet with a width of 125 to 130 mm. Approved for hot gas and exhaust filtration, the material is further processed into filter modules that are designed for the named applications.

These SMF^® modules are proven for a very large number of exhaust gas filtration applications used by vehicle manufacturers for applications that are subject to the current European emission legislation and thus strict requirements for particle number reduction. Furthermore, there are first applications in the industrial filtration of gases. In addition to the thermal robustness of the filter material, the high retention capacity and good cleanability of inert filtrate is also a key factor.

The aim is to use the known advantages of the thin foldable SMF^® material, such as sharp separation efficiency or good cleanability, for new industrial filtration applications...

Today aerosols are produced in many industrial processes like machining or in pneumatic compressors. The harmfulness of these industrially produced droplets often lies in the liquid itself as it can be toxic or cancerous while exhaled natural aerosols can carry viruses or other pathogens. For health protection, the filtration of these aerosols is an important task. The wetting properties of the fibers have a large influence on the filtration efficiency and coalescence of droplets on the fibers. Oleophilic fibers are better in capturing the oil aerosols while the drainage increases with oleophobic fibers. For improved efficiency and drainage properties, a mixed-wet fiber system could therefore be advantageous.

Deposition of droplets and the resulting coalescence is highly complex and extremely dependent on the wetting properties. Describing these processes in filter-scale simulations is computationally extremely demanding, if not infeasible. We present a new approach for simulating oil mist deposition and droplet coalescence correctly accounting for the wettability of the fibers, especially for mixed-wet filter media. The aim is to gain a more realistic pressure loss of a fibrous filter structure which takes the presence of the filtered phase into account as well as the coalescence of the liquid phase on the fibers depending on the wettability and the fluid parameters...

During the COVID-19 pandemic, face coverings have been widely worn in public spaces to capture respiratory particles produced by the wearer and reduce spread of infection. 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.

In this study the filtration properties of various face mask materials were investigated across a broad range of particle sizes. The interception mechanism is important for large particle capture, for which aerodynamic diameter is the most useful measure of size. 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...

The concept of optimisation is considered one of the keyways of permanently resolving issues impacting OPEX and helping a business be sustainable. This study shows how measure the gap between the present and optimised operation levels of a dust collector system and decide on how convenient it is to proceed given existing conditions by focussing on particular areas of expertise – performances, reliability of technology, quality and savings.

In this case study, the existing dust collectors on kiln / raw mill of the cement plant are not performing according to the design conditions, the initial guaranteed value of pressure drop is always exceeded inevitably leading to the main following conditions:

• premature bags failure, mainly due to overcleaning to manage the very high pressure drop across the filter
• extremely high compressed air consumptions
• high power consumptions of the fan

Some examples of the criticalities highlighted by a preliminary analyse were related to the internal filter design, the exit available area reduced, the bottom, vertical and lateral gas velocity. Rendering the existing filter with a 3D model suitable for running a CFD simulation combined with a tailored process data collection campaign, allow both to perform a detailed gas behave analysis and rectify the mechanical criticalities affecting the equipment performances. This novel “OTP OPTIMISE PERFOMANCES^R” approach passes through the deep process analysis and equipment validation and the study of a comprehensive solution to optimize the existing bagfilter with low impact modifications and saving capex.

The main results have been...

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:

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..

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...

Many products of daily life and industrial use are based on suspension and emulsions. Monitoring of product compositions is essential for the control of unit processes. Nowadays, it is given a clear preference of in-line solutions. Changes in product quality have to be detected continuously and quickly to adjust the production process.

Measurements based on optical methods are used widespread. Optical response is fast, do not need to measure direct inside the sample and work without any chemicals and sampling.

This contribution introduces an optical method for in-situ measurement of suspensions and emulsions based on reflectance. The so called Multi reflectance spectroscopy (MRS) technology is an innovative technique based on multiwavelength reflectometry and capable of predict dispersion quality parameter such as suspended solid concentration or particle size...

The homogeneity of filter media is important for material selection and quality control, along with the specific weight (nominal grammage) and the distribution of the local weight. Cloudiness or formation is a concept used to describe deviations from homogeneity in filter media. There are various image analysis methods for measuring cloudiness differing in the exact definition of this term. Cloudiness concepts based on the range of interaction [1], the coefficients of the Laplace pyramid [2,3], or the power spectrum [4,5] have been suggested. Measured cloudiness is reproducible. However, cloudiness measured with varying instruments usually cannot be compared. We have developed a theoretically sound cloudiness index and a method to measure it from the power spectrum. The eligible frequency band depends on the image acquisition. Reproducibility of the method is guaranteed as long as the non-woven sample attenuates the light proportional to the material thickness. Our method is hence well suited to build a technical standard on it.

Following [4,5], we suggest to derive the cloudiness index from the power spectrum of the relative local area weight, averaged over a selected frequency range. Here, relative local area weight means local area weight divided by specific weight. This cloudiness measure has various advantages over popular alternatives, both in terms of the information contained and the robustness of the measurement [5]. The power spectrum captures the energy density in a broad spectral range. Moreover, under certain conditions, the structure of a nonwoven is fully characterized by the specific weight, the variance of the local weight, and the power spectrum. Consequently, the power spectrum is the parameter that exclusively reflects the cloudiness.

Here, we address questions arising from practical application. The most prominent is the choice of the spectral band to properly capture a non-woven’s cloudiness relevant for the physical properties as well as meeting visual perception. The band...

The largest pore size often called the first bubble point (FBP) is one of the most critical properties of a porous material. It determines the barrier properties of the membrane and affects the flux of permeating species across the membrane. The first bubble point test is used to confirm the pore-size rating, which is among others the key selection criterion for membrane filters. This is especially important in water filtration applications and in the pharmaceutical and medical industries as it indicates the extent of particle size that can effectively be retained.

The ASTM F-316-03 defines the first bubble point at the pressure at which the first continuous gas bubbles are detected. The “bubble point” method as described in ASTM F-316 is based on a visual determination, and thus it is influenced by the subjectivity and precision of the operator.

In this work, we present the determination of the largest pore size in different filtration media by using an automated first bubble point tester POROLUX™50 and a capillary flow porometer POROLUX™1000...

The continuous development of new products in pharma and biotechnology leads to a need of required processes for further processing. Especially proteins or vaccines, which are obtained from cell suspensions, require separation processes for further processing. To achieve the best filterability for a special application, the membranes, woven or nonwoven filter materials with tailor-made structure have to be developed For the design and dimensioning of filtration processes, standardized laboratory tests are usually performed [1,2]. To cover a wide range of processes, the standardized tests require a quite large filtration area and a large amount of the suspension to be filtered. For cost reduction in both the use of valuable pharmaceutical products and newly developed membranes, it is advisable to reduce the required material input. A new possibility is to perform the filtration experiments by means of analytical photo-centrifugation filtration (ACF) which allows a simple and fast membrane characterization and filterability with high throughput [3,4]. With ACF it is possible to analyze up to 12 different...

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.

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...

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...

The Lenzing Group stands for the ecologically responsible production of high-quality, specialty fibers made from the renewable raw material wood. The LENZING^TM Lyocell manufacturing process is distinguished by its conversion efficiency and closed cycle design, which recovers, purifies and re-uses the process solvent and process water...

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...

Bekipor® filter media consists of one or more sintered web layers of very fine metallic fibers (1 to 40µ). The multi-layered structure of the media provides superior filtration efficiency, high contaminant (dirt) holding capacity and low pressure drop, which increases the on stream lifetime of the filter element. Unlike alternative materials with binder, fiber migration is not an issue as the fibers are physically bonded together. Bekipor^® metal fiber media has the advantage of high corrosion and temperature resistance, high heat dissipation and mechanical resistance. All of the characteristics are highly beneficial in many applications. Bekipor^® sintered metal fiber media are widely used for over 40 years in liquid and gas filtration for various industries such as polymer production, chemical processes, power generation or oil filtration. Filters made out of Bekipor^® metal fiber media are cost effective, as they will lead to minimal downtime and maintenance. Moreover, the filter elements can be easily cleaned off-line to be reused. This all leads to the best Total Cost of Ownership (TCO).

An overview of the design and manufacturing of this media will be provided. A recent independent testing of the Bekipor^® sintered metal fiber media compared its filtration performances in term of filtration efficiency, permeability, and dirt holding capacity to commercially available woven wire mesh and sintered metal powder. This study shows that...

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....

The core element of every filter unit is the filter medium. To select a filter medium for a specific filtration task, also commercial aspects and the ability to form the medium into the desired design without damaging it have to be considered. Nevertheless, the main request is to ensure, that the medium complies with the filtration requirements of the process. Thus, the pore size needs to be selected so small that the desired purity of the filtrate is achieved. At the same time, the filter medium needs to be able to withstand the chemical, thermal and mechanical stresses which occur. For a resource-saving filtration process, the filter medium should have a high permeability and a large dirt-holding capacity, which is associated with a long service life. For filtration processes with a large dirt load which has to be separated, the filter medium should be easily cleaned e. g. by pulse-jet or back flushing. Many of these filtration properties mentioned are contrary to each other and cannot be combined in one filter medium at the same time. For example, a high separation efficiency due to a small pore size is always associated with a high flow resistance.

There is a wide range of filter media of different structure made of various materials. For demanding process conditions, for instance in the form of high process pressures and temperatures or if sharp-edged particles have to be deposited, metallic filter media and in particular metal woven wire meshes are often used. Dutch Twilled Weaves as one of the weaving types of woven wire meshes are established filter media for the deposition of finest particles down to the single-digit micrometer range and to realize highest separation performances already in the unloaded state. To achieve these small pore cross-sections, the weft wires need to be woven as closely together as possible. This results in a fabric with a low porosity, low free passage area and low number of pores, and thus a high pressure loss and power consumption of the filtration process. Furthermore, the narrowest pore cross section is located inside the fabric, which is why this weaving type is very difficult to clean. Frequent replacements of the filter elements made from them is necessary, which leads to high maintenance costs and long plant downtimes.

An alternative weaving type to produce finest wire meshes are the so called Betamesh-PLUS fabrics. In these plain weave fabrics, the wire diameters of the warp and weft as well as the pitches are combined in such a way that these fabrics are characterized by...

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, PoreSizer^TM (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...

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 [1]. 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....

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...

Croft Filters manufactures customised filtration solutions for industrial processes. Most filtration media are manufactured conventionally but almost all manufacturing processes involve both automated and hand operations. Filter media design is driven by the required filtration level. Delivering the filtration media with the maximum open area will provide a greater efficiency. However, operational pressures may require the woven wire mesh to be supported, or consist of one or more layers also with support. This decreases the overall open area and increases the pressure drop across the filter. Any changes in design that can decrease the pressure drop across the filter will increase the efficiency of the filtration media.

Selective Laser Melting (SLM) Additive Manufacturing (AM) technology manufactures components layer by layer which delivers design freedom to produce complex geometry components. The manufacturing process has been utilised to create innovative AM filters.

The aim is to demonstrate the wide range of added value that the AM process can deliver to improve filtration filter media efficiency as well as filtration media through an alternative manufacturing process...

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...

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 [1], 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 [2]. 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 [3]. Deformations of filter media are observed in air filtration, too. In [4], 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...

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...

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...

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...

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.

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) 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...

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...

In the last years, the demand for better air quality has continuously increased. Especially indoor air quality IAQ is of concern and reliable filtration solutions are more important than ever to provide a safe and healthy environment in occupied buildings. Therefore, tailored filter media with an enhanced filtration efficiency for HVAC (heating, ventilation, air conditioning) applications is required. At the same time, it is needed to focus on energy conservation, which is favorable for the environment and additionally reduces the energy costs. To decrease the energy consumption of HVAC units, the filter media needs to have a low pressure drop during its complete time of usage. Based on those requirements, IREMA-Filter has set the goal to develop a new generation of pleatable filter media that combines a high filtration efficiency with a decreased pressure drop.

The filters that are made with the new media are tested and described by DIN EN ISO 16890. This standard categorizes HVAC filters depending on the fractional efficiency for aerosol removal during testing. ePM1 results are reported for aerosol (DEHS) that has an aerodynamic diameter of 1 µm and less. This particle size range is of major concern due to its negative effects on human health.

During the test for DIN EN ISO 16890 a filter’s performance is tested twice, under initial conditions (new filter) as well as after an isopropyl alcohol (IPA) vapor treatment which removes all of the electrostatic charges within the material. After this discharge step the filter can pass the ePM1 test successfully, if its minimum efficiency is at least 50% regarding aerosol diameters smaller than 1 µm (0,3-1,0 µm). Previously the mechanical efficiency (after discharge) that was needed to pass this requirement generally was linked to a high pressure drop of the filter.

IREMA-Filter developed an enhanced type of synthetic filter material that combines high initial efficiency with high mechanical efficiency while keeping the pressure drop low due to its unique integrated prefilter fiber design. Based on this innovation a new generation of synthetic filter media for ePM1 applications is achieved with an extended service life and improved energy consumption footprint. The following table shows...

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.

Key advantages:

1. 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....

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.

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.

PlasmaMAX^TM 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 PlasmaMAX^TM 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...

One major contributing factor that limits the service life of conventional filter media is blinding. This is caused by the constant ingress and accumulation of particulate matter inside the structure of the filter media. If unaddressed, this blinding results in a reduction in the cycle count or increased cycle times, reduced production rates and a decrease in throughput, an increase in the number of wash cycles, poor cake release, increased filter maintenance, premature wearing and holing leading to bypass and early failure as well as unscheduled changeovers leading to reduced machine availability and capacity.

Historically, the filtration properties of the fabric have been improved with surface chemical applications to address the above-mentioned limitations. The surface treatment eventually washes off during the process and the achieved benefits diminish with time and do not last the full lifetime of the media. To address this issue, Lotus Range™ filter fabrics have been invented with new release enhancing properties engineered directly into the yarn itself. This means that the achieved benefits can be seen throughout the service life of the filter media.

Multiple field trials were carried out in the mining and minerals as well as the chemical industry to validate this newly engineered technology. As a result of the anti-scale and anti-blinding properties, service life of the media was dramatically increased and fewer change overs meant greater machine availability and production output. The efficient cake discharge lead to a direct reduction in cycle time, this benefit can additionally reduce manpower and ultimately create a safer working environment. Efficient washing minimised solids residue and blinding which effectively results in lowered costs by washing with reduced frequency and less water consumption.

Overall the performance...