The increasing demand of fine particles in suspensions requires new processes which can provide such dispersed particle collectives. These suspensions are for example 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 succeeding 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 novel cross-sectional fractionation technique is being presented, 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...

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. Using developments and applications in artificial intelligence algorithms in industrial processes, and data from a filtration process consisting of three pressure filters and their auxiliary equipment in a Zinc concentration plant, it will be shown that optimization algorithms subjected to the operative, resource consumption, and quality constraints are viable to provide key operational information...

In all industries, efficient filtration is a key process step in achieving high product quality. One of the most common products used for filtration is the filter press, which has gone through a lot of changes over the decades. Among the latest innovations in filter press development is the use of artificial intelligence (AI) on mobile devices.

One of the challenges for filter press operators is estimating when the best time will be, from an economic perspective, to clean the machine or even change the filter cloths in order to avoid any damage to the filter press and achieve filter press efficiency at the most constant level possible.

By collecting process parameters and making use of AI, ANDRITZ has found a way of providing its customers with a tool that can tell the customer, when the filter press will need to be cleaned and the filter cloths will have to be changed.

By using process parameters such as pressure, temperature and feed in combination with the Lenser I-Plate, it’s easy to say when the optimum time is to terminate the cycle, thus saving time and energy as well as avoiding unnecessary mechanical strain on the plates and cloths.

These programs are a part of the ANDRITZ Intelligent Filter Press, and they are explained in this paper by means of examples...

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MEMS are Micro-Electro-Mechanical Systems. They are small components that combine logic elements and micromechanical structures in one chip and can process mechanical, electrical and chemical information. MEMS are very small and can be placed at positions which previously could not be reached. The measuring results are less influenced by the measuring devices. The energy requirement for the measurements and transmission of the information is very low. MEMS are able to generate this energy by themselves, they take energy from vibrations, from temperatures or pressure changes.

These properties allow measurements in filter equipment and having the results available during the running process. Further it enables corrections in the manufacturing process which previously were not possible. These corrections are used to protect employees, to improve quality of products, to increase capacities and to protect product equipment and machinery.

The target is, that the filter press learns and initiates appropriate actions, documenting these and informing the user. However, control over the process always remains with the user. For different tasks there are different types of MEMS; combinations of sensors are more and more usual. One of the most common sensor-combination is the accelerometer with gyroscope and the sensor for temperature. This sensor-combination allows monitoring all movements in the filter press. It provides information about position of plates in the filter, that means if plates or equipment is moving or bent due to high forces. It includes also the movement of membranes at membrane plates and allows for example the measuring of cake thickness in chambers in closed filter press. An additional common sensor-combination is used to measure pressures and temperatures in filter presses. These sensors allow...

Integrated continuous manufacturing processes of active pharmaceutical ingredients (APIs) and fine chemicals provide key benefits concerning product quality control, scale‑up capability, and a reduced time‑to‑market. Thereby, the crystallization step, which is used in approximately 90 % of API productions, mainly defines the final API properties. Especially, the final product purity is influenced directly by the crystallization step and should be optimized to ensure both consistent purity and particle size distribution (PSD). Upcoming challenges are the solid-liquid separation as well as washing and drying steps to meet specific product specifications regarding residual moisture reduction and preservation of PSD. The overall goal is to create an end-to-end small-scale continuous manufacturing process for the typical API production scale of 250 ‑ 1000 kg per year, starting from raw material treatment to final dosage form. Versatile approaches and concepts are available for small-scale continuous crystallization, divided into the main concepts of mixed-suspension mixed-product removal and tubular crystallizers. Continuous solid-liquid separations, on the other hand, are rather scarce.

In the framework of our research, we patented the Continuous Vacuum Screw Filter (CVSF) for small-scale solid-liquid separation, washing, and drying of particle suspensions. The modular set-up of the CVSF offers a maximized flexibility and thus rapid adaptability to changing market demands and product requirements. This contribution shows the general working principle of the CVSF as well as the results of the systematic apparatus and process characterization...

For the production or purification of temperature-sensitive products, crystallization followed by solid-liquid separation is a common process. Typically, the individual process steps are carried out batch-wise and on different devices, which in turn entails a number of disadvantages. These include deficits in the area of process efficiency, the risk of product contamination during transfer between the individual apparatuses as well as the need for transport equipment (e.g. pumps or pipelines) and the implementation of existing safety standards.

To minimize the mentioned problems, the development of integrated, (quasi-) continuous plant concepts becomes more and more significant. One example of such a concept is the so-called Enhanced Belt Crystallizer, which is an advanced version of the Belt Crystallizer and combines the process steps crystallization, ripening and solid-liquid separation on a single device.

In the poster contribution, the basic concept and its technical implementation will be presented. Subsequently, the plant functionality is demonstrated using lysozyme as a material system. Thus, the conventional production and separation process is successively transferred to the Enhanced Belt Crystallizer...

Pharmaceutical products (APIs) are produced mainly by crystallization to form a high purity product with controlled particle size distribution in suspension. The isolation (filtration, washing, and drying) process is needed to separate the pure product crystals from the impure mother liquor to produce dry, free-flowing particles while preserving the particle size distribution achieved by crystallization.

Drying is the last and critical processing step in the isolation and purification of API crystals which is performed to remove the residual solvent remaining after filtration and washing. The effectiveness of the drying process affects the quality attributes of the final drug product. Traces of residual solvent may also affect the stability of the formulated product. API dissolves in the residual solvent left during drying tends to create "sticky" points at the contacts between particles, promoting solid bridges and being responsible for particle agglomeration. The residual moisture content and composition, solvent polarity, surface tension, and viscosity significantly impact agglomeration. The drying process can also impact on final drug product leading to non-uniform powder flowability, inconsistent drug product dissolution profile, and bioavailability.

The aim of this work was to quantify the correlation between the mass of material deposited during drying and lump formation.....

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...

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. The cleaning procedures consist of the...

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 pores are filled with liquid. To reduce the residual moisture of the filter cake, mechanical dewatering measures are a more cost-effective alternative to thermal drying. An innovative method for mechanical dewatering is filter cake compaction by using an oscillatory shear and a low normal pressure. After the successful testing on a laboratory scale, the present work was concerned with the transfer of the compaction process to a continuous filter apparatus. For this purpose, a module for the compaction of compressible filter cakes under oscillatory shear was developed and implemented on an existing indexing vacuum belt filter...

Microfibrillated cellulose (MFC) has gained a lot of attention during present decade owing to its sustainability potential, availability for surface modification and mechanical properties. Commercial scale up of this material is, however, restricted due to the lack of an energy efficient production and transportation process. One of the main factors, in the present process solution, that increases the energy demand during the production and transportation is the high water content of the process streams and the final product. MFC is often produced in dilute suspension and hence a lot of water needs to be separated to allow for an economical transportation and/or further modifications. Although dewatering of MFC is a key factor to commercial scale up of the process, progress is still needed. Current suggested methods for the water removal greatly rely on drying techniques, all of which are rather energy intensive and may lead to irreversible particle aggregation which can cause difficulties in dispersibility.

A preceding mechanical dewatering step, with a lower energy demand than that of the drying, may be added to reduce the total energy demand of the production process. The most common method of solid-solvent separation is mechanical dewatering by filtration; however, it is not suitable for MFC due to the large surface area subjected to the liquid flow and because of mechanical interlockings and friction between the fibrils that may cause extensive filtration resistance. A means to aid the filtration is to apply an additional force to the particles in the solution. In this context, an electro-assisted filtration technique, in which an electric field is applied across part of the filter chamber may prove to be beneficial. The application of an electric field introduces several electrokinetic phenomena which can be beneficial to the dewatering process.

Considering the benefits of electric field and complexity of the material to be filtered; an electro-assisted filtration of MFC produced...

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...

Cake filtration is a common process, which is used in various industrial sectors (e.g. chemical, pharmaceutical, energy) for solid-liquid separation. Frequently the filter cake is washed in a subsequent process step by a displacement washing with a molecularly miscible liquid to remove impurities or valuable substances dissolved in the pore liquid. The aim here is to achieve a given residual impurity content with minimum use of wash liquid and equipment allocation in order to achieve the most economical process.

The physical principles of displacement washing of saturated filter cakes have been known for many years, the research findings are already being applied in practice. However, previous research work is based on highly simplifying assumptions, e.g. a homogeneous cake geometry and structure and no deformation of the cake surface due to wash water application.

In reality, deviations from these simplifying assumptions frequently occur, which can negatively and uncontrollably influence the course and result of a filter cake washing process. This leads to an increased demand of wash liquid and/ or an extension of the process time. The presented study is mainly concerned with imperfections caused by the wash liquid application and the interaction with the cake surface. The main focus lies on the reproducible experimental creation of imperfections as well as their description and quantification...

To facilitate integrated end to end pharmaceutical manufacturing using digital design, a digital tool capable of transferring material property information between operations to predict the product attributes in integrated purification processes has been developed. The focus of the work reported here combines filtration and washing operations commonly used in active pharmaceutical ingredient (API) purification and isolation by combining predicted and experimental data generated during upstream crystallization process. In detail, this work focuses on the development of a mechanistic model-based workflow for the optimization of an integrated filtration and washing model, with a view to minimize impurities in the isolated cake...

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 sepa- ration 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 back- washes a planar filter medium with an effective diameter of 100 mm. The process var- iables 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...

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Water resource management is a key sustainability challenge for steelmakers in order to improve the production cycle as the water scarcity grows. Water is used extensively in the steel industry for cooling process for e.g. continuous casting or hot rolling. In the hot rolling mills filtration is required to remove the suspended particles that remain in the water following the decantation process. To maintain the efficiency of the production cycle as well as to protect the operational environment from corrosion and microbial growth, cost-effective fine particle filtration is required to efficiently remove suspended solids contaminants build up.

Herein, Sofi Filtration conducted a pilot study as part of the WHAM EU project. In this pilot operation Sofi's technology was tested against sand filter technology in an Italian steel mill. A research study was carried out for a cooling water of a hot rolling mill by feeding both technologies with the same water in conjunction and sampling for the Total Suspended Solids. The effluent from a hot rolling mill contains oil and other compounds containing elements such as iron, copper, boron, and manganese.

The pilot operation result shows that...

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...

Centrifugal filtration is widely applied in the bio/pharma and chemical industries, as well as in laboratory-scale scientific research. This unit operation comes with its complexities in terms of modelling and simulation which, along with the scarcity of computational resources, has resulted in simplified mathematical models that are not adequate for industrial applications. Recently, with the increased availability of computational resources, Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD) coupling has become a candidate for modelling centrifugal filters with differing geometries and complexities. Here, the aim is to model cake formation in a vertical, basket-type centrifugal filter focusing on the solid phase as a first step.

To achieve this, simulations are carried out for two selected aqueous suspensions: calcium carbonate (CaCO₃) and microcrystalline cellulose (MCC). LIGGGHTS^® (DEM) software is used to carry out the simulations. The particles are...

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...

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...

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...

Bioremediation technologies such as bio-augmentation, bio-stimulation or natural attenuation have widely been proposed as cost-effective means for soil treatment of contaminated sites. These techniques rely on the use of bacteria to degrade or immobilize recalcitrant pollutants. Although bioremediation has many advantages compared to the traditional technologies, it is important to recognize that some scientific challenges need to be met, due in part to our lack of understanding of microorganism interactions in different hydrologic environments. The design of efficient bioremediation strategies can be improved by a better understanding of the complex interplay of physical, chemical, and biological factors affecting bacteria transport and filtration. Differences in transport and filtration behavior can be caused by bacteria surface properties that will influence interactions with the surfaces of solid soil particles. Bacteria transport and filtration is more complex in the vadoze zone, when compared to that occurring in the saturated zone, due to the presence of air phase in the pores. Bacteria may interact with these multiples interfaces (air-water-solid) and this may highly influence the mechanisms of filtration as well as the amount of bacteria retained. The objective of this work was to investigate bacteria filtration mechanisms under saturated and unsaturated flow conditions....

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...

Hydrocyclone separator is a device that uses centrifugal force to separate multiphase substances with different densities. It is widely used in wastewater treatment, oil-water separation and other fields. While the development of hydrocyclone, the separation efficiency and treatment capacity become the factors limiting the application of this technology. On the one hand, the high treatment capacity requires the hydrocyclones with large diameter, on the other hand, the separation efficiency of hydrocyclone will decrease with the increase of diameter. The parallel connection of hydrocyclones is a solution to increase the treatment capacity. However, compared with the single hydrocyclone, the separation efficiency of parallel hydrocyclones will decrease.

A new type of common bucket is designed to solve the problem of the decline of separation efficiency of parallel hydrocyclones, which can make the parallel rotating flow field produce inherent stability, and reduce the negative influence of the air core on the separation performance through the self liquid sealing. In this paper, the influence of the common bucket on the stability of parallel flow field in liquid bucket and the separation performance is studied by numerical simulation...

Cake filtration is a common process, which is used in various industrial sectors (e.g. chemical, pharmaceutical, energy) for solid-liquid separation. Frequently the filter cake is washed in a subsequent process step by a displacement washing with a molecularly miscible liquid to remove impurities or valuable substances dissolved in the pore liquid. The aim here is to achieve a given residual impurity content with minimum use of wash liquid and equipment allocation in order to achieve the most economical process.

The physical principles of displacement washing of saturated filter cakes have been known for many years, the research findings are already being applied in practice. However, previous research work is based on highly simplifying assumptions, e.g. a homogeneous cake geometry and structure and no deformation of the cake surface due to wash water application.

In reality, deviations from these simplifying assumptions frequently occur, which can negatively and uncontrollably influence the course and result of a filter cake washing process. This leads to an increased demand of wash liquid and/ or an extension of the process time. The presented study is mainly concerned with imperfections caused by the wash liquid application and the interaction with the cake surface. The main focus lies on the reproducible experimental creation of imperfections as well as their description and quantification...

A well-known and frequently used method for solid-liquid separation in the industrial environment is cake filtration using gas differential pressure fields. Due to dissolved impurities within the pore liquid of the filter cake, usually a displacement washing is performed as an additional process step. The reduction of these impurities within the filter cake is to be accomplished by requiring the least possible amount of wash liquid, time and filter area. In order to meet given specifications in terms of residual impurity content, the amount of wash liquid and/or wash time have to be adjusted, as well as potential predewatering and postdewatering steps.

The underlying transport mechanisms during displacement washing are widely understood and allow the design and operation of industrial processes based on laboratory experiments under certain assumptions. However, little attention is paid to the gap between these laboratory experiments and a real process, which can be caused by various imperfections (e.g. reslurrying of the filter cake during wash water application, inhomogeneous filter cake structure, uneven filter cake height, etc.). These imperfections can usually be neglected on small scale equipment but may dominate real processes on a larger scale, leading to an increase in washing effort and cost. This ongoing study is concerned with replicable geometric imperfections of the filter cake and their effect on the displacement washing process. Their impact is investigated in experimental studies, as well as theoretical studies applying the dispersion model. The aim is not only their qualitative, but also their quantitative evaluation on the course of the washing process...

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Numerical modeling at pore-scale which is based on high-resolution CT images has proven its validity and importance in many areas. It is especially important in the case of heterogeneous porous media (e.g., broad pore size distribution with potential for channeling effects) and chemical heterogeneity (e.g., nonuniform distribution of the size and locations of the washcoat particles/coating layer in the case of catalytic filters, nonuniform distribution of the size and locations of active carbon particles in air filters, etc.). Typically the reactive transport is described by convection and diffusion processes in the pore space and by homogeneous reactions within the reactive particles (washcoat, active carbon, etc.). Note that earlier we have addresses heterogeneous reactions, here we concentrate on homogeneous reactions, mainly in connection with catalytic filters. To be more precise, the reactions are heterogeneous at nanoscale, however here our investigations are carried out at micron scale, and the nanoscale heterogeneous reactions are averaged to homogeneous reactions at micron scale. To tackle pore scale simulation of reactive transport Fraunhofer ITWM has developed PoreChem Software which is a highly scalable solver for multispecies reactive flow in porous media. PoreChem uses a voxelized representation of geometry, includes implementation of numerical solution of Stokes(-Brinkman) equation for the flow problem and convection-diffusion-reaction equations for species transport, and can be used for problems with up to tens of billions of voxels.

In [1] PoreChem was used for pore scale simulations in the case of first order reaction. The role of the geometrical and chemical heterogeneity was highlighted. Nevertheless, reduction of the whole Selective Catalytic Reduction (SCR) process to a first order reaction has limited applicability and neglects reactions in the non-porous region and complex chemical transformations in the washcoat. Thus, in the current paper, we discuss several complex reactions...

Sludges from civil and industrial WWT plants and from agri-food industry are a growing problem throughout the EU, due to a production trend growth faster than the availability of disposal plants (landfills and incinerators), and due to the tightening of regulatory constraints and chemical-physical limits that make the spreading in agriculture as a soil improver possible. For this reason, the urgency to reduce the volumes of sludges to be disposed of, improving the performance of dehydration technologies, is increasingly pressing.

This work reports the comparative study of the dehydration performance of the sludge module of the innovative industrial process B-PLAS®, applied to sewage sludge from different sources: WWT primary sludge, WWT post anaerobic digester sludge, WWT mixed sludge, sludge from anaerobic digester of a biogas plant treating agri-food waste.

The study focuses on the first part of the process (sludge module), evaluating the solid-liquid separation performance by means of a filter press, without the use of polyelectrolytes or other filtration conditioning, depending on the operating conditions of the hydrothermal carbonization reactor, in particular temperature, pressure and residence time.The results show...

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In the field of solid-liquid separation, membrane filter plates have been established in filter presses. Using membrane filter plates, a higher solid content of sludges can be achieved in less time compared to chamber filter plates. In membrane filter presses capacity and quality of cake and filtrate depend on a lot of factors and in particular on condition of filter cloth and membranes.

With the developed JZ-Analysis-System, information in the filter plate pack, a so-called Black Box, are made transparent. Now collected data refer to leaking membranes, blinded or damaged filter cloth, cake thickness distribution in different chambers and filling degree of the complete filter. This information is transmitted wirelessly from the plate pack to smartphones, to laptops or is sent to the control centre. All these data are available during the running process, during squeezing the membrane plates, and allow a fast reaction already during the process.

If squeeze medium is lost, the Analysis-System will indicate the number of the affected membrane plate and the operator is able to change this plate during the next cake discharge. No additional searching for the plate is necessary. If filter cloths are blinded, broken or not fixed properly, the Analysis System will indicate the corresponding chambers again during the running filtration process and the filter cloths can be corrected during cake discharge. After the squeezing step our Analysis-System will indicate, if the complete filter is overfilled or underfilled. This will influence the results of...

In hydraulic filters, electrostatic charges are generated by triboelectric effect occurring every time hydraulic fluids are traversing insulating filter medias. For this reason, generation of electrostatic charges is a phenomenon always present in hydraulic filtration systems when insulating materials such as paper and glass fiber are used. In most cases, when systems are not able to dissipate the electric charges, accumulation of this latter results in strong ESD (ElectroStatic Discharges), which are detrimental for both filter element integrity and environmental safety. In practice, when ESD occur internally within filter housing they consist in a local electrical-breakdown of hydraulic oil (namely sparks) followed by an extremely high local increase of temperature (in the order of thousands of Celsius degree) leading to irreversible damages of filter element components (filters media, sealing parts, end-cups) and hydraulic fluids. Moreover, an electrostatic potential is induced on filter housing and may reach values close to air electrical-breakdown (⁓50kV). If this occurs, electrical arcs develop in air and along pipelines bringing to high-risk industrial environment (explosion, electrical shocks, etc.) for humans and hydraulic system components (filter indicators, pumps, electrical apparatus).

As discussed in previous section, ESDs are the results of an unbalanced situation between electric charge generation and dissipation. This work aims at developing a robust and standardized method, which is able to evaluate and quantify these two electrostatic phenomena occurring within hydraulic filters...

In the context of the bioeconomy, the trend towards improving fish stocks worldwide is increasingly moving towards fish farms. The project described here aims to develop an overall system for marine animal husbandry. Starting with the design of an online controlled measurement system for monitoring water quality parameters for sensitive shrimp species and other edible fish in tank farms, improved and flexible sensors will be used for the desired application, while providing high coverage of relevant parameters. Furthermore, the developed measuring instruments are used to monitor the standards to be met for the cultivation of insects by using biogenic waste materials. To achieve this goal, water quality is of crucial importance and can be kept stable in this sensitive ecosystem by the adaptable online sensor technology. The cost of an entire measurement system is usually very high for existing techniques due to the large number of parameters to be covered in different ways, and the economic benefits for the development of sensors for parameters that are not often in demand is necessarily high, so this is the starting point for development. The first prototype shows a stable data recording of the measured values of a multitude of simultaneously recorded parameters at low costs, with the planning to integrate further parameters into the system in the future for a greater flexibility at application sites...

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...

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 of 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 ideal, 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 identifying initial parts of an experiment where cake filtration may not be the dominant process. 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. The method was tried on a dataset of 225 cake filtration experiments and was found to be superior to the linearized regression method by reducing errors due to time offset and transformation of the dependent variable. New findings...

The separation of solid particles from liquids via filtration is a key unit operation in the pharmaceutical sector. This processing step normally occurs after crystallization of an Active Pharmaceutical Ingredient (API) and could include several wash cycles in order to deliquor the cake and remove any residual solvents and other impurities below specified limits.

In this work we detail a digital design approach via mechanistic model-based workflow for the modelling of a filtration unit, with a view to developing an optimized continuous filtration model...

Al-melts contain non-metallic inclusions, which have a negative influence on mechanical properties. Therefore, ceramic foam filters are widely applied for the cleaning of the Al-melt by removing these solid impurities.

With increasing inclusion size it is well known that particle separation within a ceramic foam filter (CFF) is increasing. In contrast, especially particles in the single-digit µm range are difficult to separate at the filter struts due to weaker transport mechanism. Hence, larger amounts of impurities may remain in the ingot.

Moreover, a clustering of these inclusions, when not separated in the CFF, turns out to be detrimental in terms of material properties.

The application of CFF with elevated number of pores per inch (ppi), in this case 30, is a common solution for removing impurities in the given size range but is strongly dependent on the exerted casting process. But the usage of 30 ppi filters in the case of sand casting is already critical due to freezing of the melt in the filter and leads to abortion of the casting process.

A promising technique is the additional appropriation of ceramic fibres with diameters much smaller than the filter strut thickness. Already minor amounts of fibres increase the surface for potential particle separation and hence increase filtration efficiency. Furthermore, SEM analysis indicates...

“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...

The optimization of industrial, civil and agricultural processes for higher resource efficiency, separation of rain and black water and the increasing awareness of water value lead to a decreasing wastewater discharge resulting in higher concentrated wastewaters.

Emerging contaminants, MicroPollutants (MPs) and MicroPlastics (MPlas), have become important for municipal and industrial wastewater treatment, as surface water high quality is the fundament of drinking water quality.

Industrial chemicals and Active Pharmaceutical Ingredients (API) lead to increase heterogeneous organic chemical loads, which are often poorly degraded in conventional municipal wastewater treatment plants (WWTP).

First mover plants are tackling this issue with quaternary treatment steps, using ozonization or carbon-based sorption processes to remove MPs and to retain plastic fragments. The processes are anyway still subject to optimization due to incomplete oxidation products, Powdered Activated Carbon (PAC) loss and sustainability.

This project develops a technological innovative solution, revamping an existing industrial candle filtration product, towards a tailored solution for MPs adsorption through PAC and MPlas retention, within a unique process combination.

The innovative filtration process combines an engineered mixture of PAC and a filter aid (cellulose) with pre-coat filtration. The main challenges are hydraulic performance, resources optimization and MPs and MPlas elimination performance. Testing several carbon/filter aid combinations in laboratory scale, allows insights in the MPs and MPlas removal performance. To evaluate the optimization of hydraulic performance and of resource conservative PAC/filter aid mixture, experimental design is used during test set-up and results’ statistical evaluation. Best operation settings are characterized by...

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...

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Microplastics (MP) are ubiquitous in the aquatic environment and need to be removed. A new method uses organosilanes, based on Green Chemistry, for the removal of MP from various waters. When organosilanes are added to water containing MP, they attach to the surface of the microplastics, collect them, form agglomerates and fix them chemically. The trick is that MP agglomerates then float onto the surface and do not sink down to the ground. An easy separation with a skimmer leads to a reproducible MP removal efficiency of > 95%, independent of polymer type and concentration.

To ensure the functionality of the removal processes - and to generally identify microplastics hotspots and sources in the global watercycle -, microplastics in the water need to be quantified. However, microplastics´ monitoring in waters with conventional methods is very complex, time-consuming and expensive. Therefore, we developed a new approach to detect microplastics fast and inexpensive using fluorescent dyes. Those are selective for microplastics, which makes them easily detectable using a fluorescent imaging device. In the sense of a future circular economy, we also investigate ways to reuse and recycle the microplastics agglomerates from the treated water. One promising approach is the use in concrete production. Another, but less favorable approach, is energy production.

Summarized, Wasser 3.0 applies a holistic concept for the detection, removal, and reuse of microplastics from wastewater, industrial process water, seawater, and freshwater systems. It achieves environmental protection, sustainability, and resource efficiency with low-tech, low-maintenance and low-cost solutions...

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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...

Modern water-diesel separators employ a so-called two-stage approach, which combines both hydrophilic and hydrophobic materials to collect and separate the suspension of water. The hydrophobic layer (sieve) is designed to have a low wettability such that the collected mass retains almost spherical and falls along the sieve due to gravity. In general, the droplets exhibit complicated and various interactions with the sieve: partial clogging, retention (breakthrough), and drainage (rolling or sliding). In addition, those interactions interfere with the flow fields yielding an additional pressure drop, which in turn affect the dynamics. On the other hand, the choice of the material of the sieve affects its efficiency and the overall pressure drop. The sieves are characterized by the wettability condition, open-area ratio, and the mean fiber diameter. Thus, studying the effect of the properties of the sieves on the dynamics of a single droplet is vital to quantify the mechanisms in the process of liquid-liquid separation.

The present work uses the computational fluid dynamics (CFD) package OpenFOAM®*, coupled with an improved scheme designed for an accurate computation of the surface tension force for capillary dominated regimes in the framework of the volume of fluid (VoF) method. Fully resolving simulations are carried out to simulate the interaction of water droplets in a diesel fuel flow with a screen mesh. This study yields correlations, which...

Monitoring of product compositions is essential for the control of unit processes. Nowadays, it is given a clear preference to in-line solutions. Product quality parameters have to be observed in almost real-time and the sensor should be used for different applications. This contribution introduces the Multi-Reflectance-Spectroscopy (MRS) as an innovative technique based on multiwavelength reflectometry for in-situ quality/process control of suspensions and emulsions. This technology is fast, has no direct contact to the sample and is applicable without any chemicals and sampling.

Using machine learning approaches, the measuring signals can be correlated with quality parameters of dispersions (e.g., suspended solid concentration or particle size) with high accuracy. We present exemplary the potential of machine learning methods improving prediction-accuracy in process industry and give various example applications and results of suspensions and emulsions...

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...

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...

ANDRITZ is paving the way for sustainable improvements in the availability, productivity and quality of solid/liquid separation processes by leveraging advances in digitalization and IIoT. One excellent illustration of this process-focused innovation is RheoScan, which draws on Artificial Intelligence (AI) to achieve measurable savings in terms of investment and operating costs.

Sludge thickening and dewatering processes require the injection of polymer as flocculants, necessary to allow solid/liquid separation by filtration. But polymer can be pricey in terms of running costs and environmental impact. In traditional set-ups, the initial polymer dose is selected by the machine operator and rarely adjusted throughout the day, regardless of changes in the sludge characteristics or production needs.

Metris addIQ RheoScan, the first optical measurement system on the market, applies an intelligent camera system that detects the clear belt area and actual sludge viscosity during the thickening and dewatering process. With support of AI, Metris addIQ RheoScan ensures that the thickening and dewatering equipment always uses the optimum dose of polymer. It automatically adjusts and optimizes the polymer dose 24/7 and provides maximum flexibility to control and monitor the entire operation remotely, eliminating the need for on-site supervision.

The results of case studies in environmental and mining applications...

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...

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 are carried out in the context of the AiF project IGF 19305 BR. The overarching goal is to expand comprehension of the interaction of several influence parameters such as steam temperature, boiling temperature of the VOC, filter cake resistance and height. The presentation shows the results of the investigations and demonstrates the advantages of processing VOC contaminated solids by SPF. Furthermore, it is shown that....

Agglomeration is an issue that causes many problems during secondary processing of pharmaceuticals, requiring material to need further processing and thus costing additional time and resources to ensure a satisfactory outcome. A potential source of agglomeration is the particle contact established during filtration; This leads to robust agglomerates forming during drying when these contacts are cemented in place with precipitating material. Here we present a two-dimensional model for the formation of packed bed structures during filtration, in order to better understand the distribution and properties of the inter-particle contacts. The model uses circular particles of different sizes, mimicking bimodal particle size distributions often encountered in practice. The statistics of packing and void formation, along with the distribution of inter-particle contacts, are presented and discussed in the context of filtration and drying...

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...

Filter cakes resulting from the filtration of concentrated suspensions in continuously operating filters are often dried thermally afterwards to obtain the dry product. Mechanical dewatering can significantly reduce the moisture in the filter cake and thus the energy required for thermal drying. In gas differential pressure dewatering, the liquid present in the pore system of the filter cake is removed after overcoming the inlet capillary pressure. As can be seen in the figure on the left, the emptied pores of the filter cake lead to an undesired gas throughput. This has economic and technical disadvantages, because the gas throughput has to be compensated by the vacuum pump [1-2]. In this contribution, the investigations for the development of a filter media is presented, which can avoid this gas throughput....

The filtration of organic particles is increasingly becoming the focus of science. Organic single-celled organisms such as microalgae or yeast are an efficient supplier of important proteins, unsaturated fatty acids, oils, colourants and vitamins. They are therefore interesting raw materials in the food, chemical, bioindustry and pharmaceutical sectors. One disadvantage is still the comparatively high harvesting costs. These are caused by a high compressibility of the organic microparticles, which considerably reduces the filtrate flow. Increasing the pressure, for example via centrifugation, is also uneconomical due to the additional acceleration of the considerable water content. As a possible economical continuous option, thin film filtration of small cake heights (< 1 mm) on drum filters offers a process with which the pressure loss across the filter cake can be kept constantly low. Thin film filtration is based on the formation of a thin filter cake with immediate decrease after dehumidification. However, the removal of pasty thin filter cakes remains a challenging process. Due to the cake heights of < 1 mm, the risk of damaging the filter medium is high with the commonly removal via scrape. Therefore, an alternative cake discharge via a roller is used. According to the current state of research, an effective prediction of the cake removal behaviour and fouling of the membrane is not possible for thin film filtration.

In the context of this study, the influences of an inorganic particle system (titanium dioxide) and a biological particle system (yeast) are shown...

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...

A sewage sludge is the by-product of wastewater treatment (WWTP), and is mainly composed of water and the rest of its mass is the dry solids (DS). Prior to the transport and valorisation of these sludges, a liquid-solid separation is necessary. Various processes allow this aim, but their performance is limited and can be enhanced to avoid the use of processes like thermal drying which consume high amounts of energy, that need to be limited.

Electro-dewatering (EDW) is a hybrid process in which a conventional filtration-compression process is combined with the application of an electric field in order to enhance sludge dewatering (with lower energy consumption compared to a conventional drying process).
Previous studies have proposed an empirical model that reveals a relationship between the evolution of DS over time. This mathematical model includes a kinetics coefficient that is proportional to the sludge’s properties. This model was developed for EDW carried out under a constant electric current (I-EDW), unlike most of the studies presented in the literature where a constant voltage (U-EDW) is commonly used. Although less studied in the literature, the I-EDW mode remains an interesting operating mode as mentioned in some previous studies.

The objectives of this study are: (i) to evaluate the influence of the physicochemical parameters on the response of the process (notably the kinetics of the liquid-solid separation), and (ii) to incorporate the influencing parameters on the kinetics into the model...

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...

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,..