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...

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...

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...

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...

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...

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....

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...

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...

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...

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...

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...

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.

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 [1]. 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. [4]

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...

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 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 [1]. 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...

....

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...

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...

“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...

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...

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 1^st stage filter before membrane filtration or media filtration system, the safety filter before RO membrane, the fiber media filter in the wastewater system, etc....

Cake filtration data, in the form of filtrate volume V_f = f(t), i.e. as a function of time, is commonly fitted in the linearized t/V_f–V_f–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 V_f (t)–data, which will lead to the resulting plot deviating from the ideally linear slope.

These problems can be overcome by fitting the original V_f (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...

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...

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...

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.

Related to a NaCl molecule these are:

RE_NaCL = 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.

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

TBA

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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...

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...

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...

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...

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...

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...

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...

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....

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...

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...

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...

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...

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 [1].

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 [2]. 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...

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...

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...

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...

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...

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.

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...

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 (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....

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...

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 D_u) for definite (required) solids mass fraction in the underflow (C_mu) 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 (x_90o) 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 E_T, E_T’ 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...

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...