The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Hermann Nirschl - One of the best experts on this subject based on the ideXlab platform.
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The influence of Filter Cloth on cake discharge performances during backwashing into liquid phase
Separation and Purification Technology, 2021Co-Authors: Patrick Morsch, Harald Anlauf, Hermann NirschlAbstract:Abstract In industrial solid/liquid separation, the removal of fine particles in a suspension with a significant amount of solids content can be a challenging task. Cake filtration in particular is a useful principle for separation of such suspensions. This separation occurs in a wide array of industrial production applications and has some advantages compared to other separation principles. To achieve the required performance, different types of Filters can be used. One commonly used type is operated semi-continuous and use backwashing to discharge the Filter cake. The regeneration of the Filter Cloth is as important as the actual filtration step. In the case of a properly regenerated Filter Cloth, the filtrate flow at the beginning of each step is still the same, while the initial filtrate flow decreases for and inefficient regeneration. This regeneration of the Filter Cloth depends strongly on the interaction between the particle system and the Filter Cloth. In the case of backwashing filtration, a clear difference could be observed between multifilament and monofilament fabrics. For multifilament Filter Cloths, it is possible to calculate the minimum required cake thickness for a complete discharge by means of the total resistance, i.e. the product of the specific cake resistance multiplied by the cake thickness. For 3 investigated fabrics with mesh size ≤ 20 µm, a complete cake discharge could be achieved by all 3 model particle systems. It is noticeable that the minimum required cake thickness decreases with increasing specific resistance. As soon as the cake thickness with the respective specific cake resistance of the particle system exceeds the value 5∙1010 m−1, a complete discharge can be observed. The cake thicknesses found within the same particle system were very similar between the 3 fabrics investigated. Based on this observation, the release of cakes from multifilament fabrics appears to be dominated by cohesion of particles in the cake. The adhesion from the first particle layer to the fabric does not seem to be a significant influencing factor. The situation is different for monofilament fabrics. This behaviour is different from the multifilament fabrics in the cake thickness. Here, smaller cake minimum required cake thicknesses were observed for small specific cake resistances. This is due to the particle deposition mechanism within the fabric. A lower specific cake resistance is associated with a larger particle size and/or a different particle shape (greater deviation from the ideal sphericity). Larger particles relative to the mesh size of the Filter fabric preferably form a clean interface between the particle layer and the Filter fabric (surface deposition). This leads to a lower interference and better cake discharge. This behaviour could be estimated by dividing the Filter media resistance (determined by a particle system whose particle size is significantly larger than the mesh size of the fabric), by the specific cake resistance multiplied by a particle shape-dependent factor (Eq. (2) ). The shape-dependent factors were determined to be 0.03 for orthorhombic, 0.15 for flaky and 0.46 for needle-shaped particles and thus increases with increasing deviation from the ideal sphericity. By including the Filter medium resistance, the influence of the fabric and the adhesion of particles to the fabric is to be expected. Validity of this model was proven with 6 Filter Clothes with ≤ 22 µm mesh (3 twill and 3 plain weave). Similar behaviour between multifilament fabric and monofilament fabric could only be observed with the required minimum backwashing volume for a complete discharge. The required necessary backwash volume is always ≤ 2 l/m2. In summary, this study shows the regeneration performance of different Filter Cloth types (multifilament and monofilament) can be predicted by different models.
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Influence of regeneration variables during backwashing treatment into gas-phase after liquid filtration
Separation and Purification Technology, 2020Co-Authors: Patrick Morsch, Pascal Ginisty, Harald Anlauf, Hermann NirschlAbstract:Abstract In industrial solid/liquid separation, the removal of fine particles occurs in a wide array of industrial production applications and can be found in nearly every process plant. Especially the cake filtration is emphasized as advantageous principle for separation of suspension with a low solids content (0.01–1 v/v %). To maintain the separation performance, it is required to replace or regenerate the used Filter Cloth. The latter one can occur through backwashing treatment into liquid or gas phase whereby the gas discharge required an upstream drying process. The main task of that regeneration procedure is a most complete Filter cake discharge to reduce the flow resistance of the Filter for the subsequent filtration step. Recommendations for advantaged process variables doesn’t exist and should be evaluate during this investigation. Investigations regarding to the regeneration procedure has shown, that the cake discharge into gas phase has significant differences to the discharge into liquid phase. Whereas the discharge into gas phase is created through an impulse, the liquid discharge can be interpreted as a slide on the Filter Cloth surface. Moreover, the backwashing variables are highly different (influence of backwashing pressure, Filter cake thickness) between the different backwashing environments as a result of the characteristic surface forces. In this work, main attention is given to the particle system (particle size and Filter cake thickness), the different weave types, assembly of the Filter Cloth and, of course, the backwashing pressure. The difference between a discharge in gas phase and liquid phase is described and its effect on the quality of the regeneration.
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Description of the Filter Cloth deformation during backwashing filtration
Separation and Purification Technology, 2020Co-Authors: Patrick Morsch, Harald Anlauf, Maurus Bauer, Christoph Kessler, Hermann NirschlAbstract:Abstract The separation of fine particles with Filter Cloth is a commonly used technique to remove particles from process streams under low-cost and low-maintenance conditions. Such kind of Filter apparatus can be found, i.e., in front of distillation columns with the adjusted size. Here, it is possible to have a Filter apparatus with Filter elements ≤ 2.5 m in length and ≤ 100 elements in one vessel. For a constant and stable process conditions, a periodical regeneration of the Filter Cloth is absolute required. One option for realizing this procedure is discharging the built-up Filter cake in liquid phase (backwashing filtration). Due to the reverse flow, a deformation of the Filter Cloth occurs. This deformation depends on the assembly situation, mechanical pre-loading of the weave, the environment of the system, the weave type and, of course, the backwashing pressure. The interaction of this variables results in an adjusting of the space between the Filter elements and correspond with the required backwashing volume in l/m2. Influence of a contact between two Filter elements is not known but can have a negative impact in case of remaining Filter cake on surface. Too much space reduces the economy of the apparatus because less Filter surface needs the same apparatus footprint. Thus, by knowing how the Filter Cloth expand, the space can be adjusted on the particular separation task. This can lead to an improvement of the Filter surface per apparatus footprint and can be advantageously compared to competing separations procedures. The deformation of the Filter Cloth during the backwashing treatment is described and discussed in the context of this investigation on the basis of elementary mechanics.
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Optical dirt detection for a demand-controlled cleaning of woven Filter Cloth
Separation and Purification Technology, 2018Co-Authors: Richard-sebastian Moeller, Hermann NirschlAbstract:Abstract To cope with ever rising quality demands while in constant transition to flexible product lines, cleaning should be considered an integral part of any process design and processing operation. For many unit operations feasibility has been proven. However, in the cross-sectional technology of solid-liquid separation, progress in hygienic design of filtration equipment did not keep pace. As an answer we propose a closed-loop control for cleaning intensity and present a method to evaluate the cleanliness of any woven Filter Cloth. The weave’s periodicity is evaluated automatically, based on a reported algorithm. By means of image analysis, particle deposits are detected as irregularities on the near-regular weave pattern. Employing background subtraction, we do not rely on overall contrasts in color or brightness between Cloth and soiling. If there is a contrast, we reliably find single particles (of 200 µm in our example), as we demonstrate on different color channels of RGB images. The proposed algorithm was implemented in Matlab and executed on a desktop PC in on-line speed. It will enable economical, safe and reliable cleaning of belt Filters and Filter presses.
Patrick Morsch - One of the best experts on this subject based on the ideXlab platform.
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The influence of Filter Cloth on cake discharge performances during backwashing into liquid phase
Separation and Purification Technology, 2021Co-Authors: Patrick Morsch, Harald Anlauf, Hermann NirschlAbstract:Abstract In industrial solid/liquid separation, the removal of fine particles in a suspension with a significant amount of solids content can be a challenging task. Cake filtration in particular is a useful principle for separation of such suspensions. This separation occurs in a wide array of industrial production applications and has some advantages compared to other separation principles. To achieve the required performance, different types of Filters can be used. One commonly used type is operated semi-continuous and use backwashing to discharge the Filter cake. The regeneration of the Filter Cloth is as important as the actual filtration step. In the case of a properly regenerated Filter Cloth, the filtrate flow at the beginning of each step is still the same, while the initial filtrate flow decreases for and inefficient regeneration. This regeneration of the Filter Cloth depends strongly on the interaction between the particle system and the Filter Cloth. In the case of backwashing filtration, a clear difference could be observed between multifilament and monofilament fabrics. For multifilament Filter Cloths, it is possible to calculate the minimum required cake thickness for a complete discharge by means of the total resistance, i.e. the product of the specific cake resistance multiplied by the cake thickness. For 3 investigated fabrics with mesh size ≤ 20 µm, a complete cake discharge could be achieved by all 3 model particle systems. It is noticeable that the minimum required cake thickness decreases with increasing specific resistance. As soon as the cake thickness with the respective specific cake resistance of the particle system exceeds the value 5∙1010 m−1, a complete discharge can be observed. The cake thicknesses found within the same particle system were very similar between the 3 fabrics investigated. Based on this observation, the release of cakes from multifilament fabrics appears to be dominated by cohesion of particles in the cake. The adhesion from the first particle layer to the fabric does not seem to be a significant influencing factor. The situation is different for monofilament fabrics. This behaviour is different from the multifilament fabrics in the cake thickness. Here, smaller cake minimum required cake thicknesses were observed for small specific cake resistances. This is due to the particle deposition mechanism within the fabric. A lower specific cake resistance is associated with a larger particle size and/or a different particle shape (greater deviation from the ideal sphericity). Larger particles relative to the mesh size of the Filter fabric preferably form a clean interface between the particle layer and the Filter fabric (surface deposition). This leads to a lower interference and better cake discharge. This behaviour could be estimated by dividing the Filter media resistance (determined by a particle system whose particle size is significantly larger than the mesh size of the fabric), by the specific cake resistance multiplied by a particle shape-dependent factor (Eq. (2) ). The shape-dependent factors were determined to be 0.03 for orthorhombic, 0.15 for flaky and 0.46 for needle-shaped particles and thus increases with increasing deviation from the ideal sphericity. By including the Filter medium resistance, the influence of the fabric and the adhesion of particles to the fabric is to be expected. Validity of this model was proven with 6 Filter Clothes with ≤ 22 µm mesh (3 twill and 3 plain weave). Similar behaviour between multifilament fabric and monofilament fabric could only be observed with the required minimum backwashing volume for a complete discharge. The required necessary backwash volume is always ≤ 2 l/m2. In summary, this study shows the regeneration performance of different Filter Cloth types (multifilament and monofilament) can be predicted by different models.
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Influence of regeneration variables during backwashing treatment into gas-phase after liquid filtration
Separation and Purification Technology, 2020Co-Authors: Patrick Morsch, Pascal Ginisty, Harald Anlauf, Hermann NirschlAbstract:Abstract In industrial solid/liquid separation, the removal of fine particles occurs in a wide array of industrial production applications and can be found in nearly every process plant. Especially the cake filtration is emphasized as advantageous principle for separation of suspension with a low solids content (0.01–1 v/v %). To maintain the separation performance, it is required to replace or regenerate the used Filter Cloth. The latter one can occur through backwashing treatment into liquid or gas phase whereby the gas discharge required an upstream drying process. The main task of that regeneration procedure is a most complete Filter cake discharge to reduce the flow resistance of the Filter for the subsequent filtration step. Recommendations for advantaged process variables doesn’t exist and should be evaluate during this investigation. Investigations regarding to the regeneration procedure has shown, that the cake discharge into gas phase has significant differences to the discharge into liquid phase. Whereas the discharge into gas phase is created through an impulse, the liquid discharge can be interpreted as a slide on the Filter Cloth surface. Moreover, the backwashing variables are highly different (influence of backwashing pressure, Filter cake thickness) between the different backwashing environments as a result of the characteristic surface forces. In this work, main attention is given to the particle system (particle size and Filter cake thickness), the different weave types, assembly of the Filter Cloth and, of course, the backwashing pressure. The difference between a discharge in gas phase and liquid phase is described and its effect on the quality of the regeneration.
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Description of the Filter Cloth deformation during backwashing filtration
Separation and Purification Technology, 2020Co-Authors: Patrick Morsch, Harald Anlauf, Maurus Bauer, Christoph Kessler, Hermann NirschlAbstract:Abstract The separation of fine particles with Filter Cloth is a commonly used technique to remove particles from process streams under low-cost and low-maintenance conditions. Such kind of Filter apparatus can be found, i.e., in front of distillation columns with the adjusted size. Here, it is possible to have a Filter apparatus with Filter elements ≤ 2.5 m in length and ≤ 100 elements in one vessel. For a constant and stable process conditions, a periodical regeneration of the Filter Cloth is absolute required. One option for realizing this procedure is discharging the built-up Filter cake in liquid phase (backwashing filtration). Due to the reverse flow, a deformation of the Filter Cloth occurs. This deformation depends on the assembly situation, mechanical pre-loading of the weave, the environment of the system, the weave type and, of course, the backwashing pressure. The interaction of this variables results in an adjusting of the space between the Filter elements and correspond with the required backwashing volume in l/m2. Influence of a contact between two Filter elements is not known but can have a negative impact in case of remaining Filter cake on surface. Too much space reduces the economy of the apparatus because less Filter surface needs the same apparatus footprint. Thus, by knowing how the Filter Cloth expand, the space can be adjusted on the particular separation task. This can lead to an improvement of the Filter surface per apparatus footprint and can be advantageously compared to competing separations procedures. The deformation of the Filter Cloth during the backwashing treatment is described and discussed in the context of this investigation on the basis of elementary mechanics.
Jérémy Olivier - One of the best experts on this subject based on the ideXlab platform.
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Measurement of adhesion strengths and energy between calcium carbonate cake and Filter Cloth
2016Co-Authors: Pascal Ginisty, B. Legoff, Jérémy Olivier, Jean Vaxelaire, Hervé Tabuteau, J. PaixaoAbstract:Various devices in liquid-solid separation require mechanical cake discharge using different technologies. An incomplete cake discharge causes yield losses, cycle time increase, irregular cake formation, high mechanical constraints which decrease medium life time, excess consumption of cleaning liquors….Currently, cake discharge is only assessed qualitatively by observations of Filter Cloth after discharge or quantitatively by weighing recovered solids. A prototype has been developed to carry out reliable and repeatable measurements by removing Filter Cloth from Filter cake by shearing. This study presents results of experiments performed with calcium carbonate (which forms sticky cakes) and discusses the conditions of cake formation and cake detachment from Filter Cloth. It highlights the role of two main parameters : Filter Cloth characteristics and pressure.
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Electro-dewatering of activated sludge: Electrical resistance analysis
Water research, 2016Co-Authors: Jean-baptiste Conrardy, Jean Vaxelaire, Jérémy OlivierAbstract:Abstract The significant risk of ohmic heating and the high electric energy consumption at terminal stages of the dewatering are two problems that hamper the development of the electro-dewatering (EDW) technology. In the future prospect of studying these two issues, it is important to provide and analyse quantitative data relative to the behavior of the electric resistance in EDW. It was the main goal of this study. It showed that the electric resistance of the complete system (cake + Filter Cloth) depended on the cake dryness. It increased sharply when the solids content exceeded around 45%.The solids loading also influenced the apparent resistance at the beginning of the process. The electric resistance of the Filter Cloth represented about 20% of the total resistance. It remained relatively constant over the process except at the terminal stage where it generally increased sharply. The use of conductive Filter, such as metallic Cloth, enabled to decrease the electric resistance and reduce the energy consumption of the process. The electric resistance decreased across the cake from the anode to the cathode. This behavior may be explained by several phenomena such as the ions migration and their interaction with the solid, the decrease of dry solids content from the anode to the cathode and the gas presence at the anode (due to electrolysis reaction).
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Electro-Dewatering of Activated Sludge: Electrical Resistance Analysis
Water Research, 2016Co-Authors: Jean Vaxelaire, Jérémy Olivier, Jean-baptiste ConrardyAbstract:The significant risk of ohmic heating and the high electric energy consumption at terminal stages of the dewatering are two problems that hamper the development of the electro-dewatering (EDW) technology. In the future prospect of studying these two issues, it is important to provide and analyse quantitative data relative to the behavior of the electric resistance in EDW. It was the main goal of this study. It showed that the electric resistance of the complete system (cake + Filter Cloth) depended on the cake dryness. It increased sharply when the solids content exceeded around 45%. The solids loading also influenced the apparent resistance at the beginning of the process. The electric resistance of the Filter Cloth represented about 20% of the total resistance. It remained relatively constant over the process except at the terminal stage where it generally increased sharply. The use of conductive Filter, such as metallic Cloth, enabled to decrease the electric resistance and reduce the energy consumption of the process. The electric resistance decreased across the cake from the anode to the cathode. This behavior may be explained by several phenomena such as the ions migration and their interaction with the solid, the decrease of dry solids content from the anode to the cathode and the gas presence at the anode (due to electrolysis reaction). \textcopyright 2016 Elsevier Ltd.
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Sludge Dewatering: Influence of operating parameters on dryness limit determination
2014Co-Authors: Pascal Ginisty, Jérémy Olivier, Romain Girault, Julian Tosoni, Emilie Dieudé-fauvel, Jean VaxelaireAbstract:Dewatering process efficiency, classically assessed by a parameter "dryness limit", is strongly, affected by conditioned sludge properties and by operating conditions. The medthod to measure its parameters is based on a filtration-compression test, which depends significantly on operating conditions. A standard method is under progess in France to develop a better controlled procedure. This paper presents the impact of solids load, pressure and compression time, Filter Cloth, flocculation conditions, pre-thickening and storage time on the dryness limit for different kinds of sludge. A comparison with industrial devices was also made.
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Pressurised electro-osmotic dewatering of activated and anaerobically digested sludges: electrical variables analysis.
Water research, 2012Co-Authors: Morgane Citeau, Jérémy Olivier, Jean Vaxelaire, Akrama Mahmoud, O. Larue, Eugène VorobievAbstract:Abstract Pressurised electro-osmotic dewatering (PEOD) of two sewage sludges (activated and anaerobically digested) was studied under constant electric current (C.C.) and constant voltage (C.V.) with a laboratory chamber simulating closely an industrial Filter. The influence of sludge characteristics, process parameters, and electrode/Filter Cloth position was investigated. The next parameters were tested: 40 and 80 A/m 2 , 20, 30, and 50 V—for digested sludge dewatering; and 20, 40 and 80 A/m 2 , 20, 30, and 50 V—for activated sludge dewatering. Effects of Filter Cloth electric resistance and initial cake thickness were also investigated. The application of PEOD provides a gain of 12 points of dry solids content for the digested sludge (47.0% w/w) and for the activated sludge (31.7% w/w). In PEOD processed at C.C. or at C.V., the dewatering flow rate was similar for the same electric field intensity. In C.C. mode, both the electric resistance of cake and voltage increase, causing a temperature rise by ohmic effect. In C.V. mode, a current intensity peak was observed in the earlier dewatering period. Applying at first a constant current and later on a constant voltage, permitted to have better control of ohmic heating effect. The dewatering rate was not significantly affected by the presence of Filter Cloth on electrodes, but the use of a thin Filter Cloth reduced remarkably the energy consumption compared to a thicker one: 69% of reduction energy input at 45% w/w of dry solids content. The reduction of the initial cake thickness is advantageous to increase the final dry solids content.
Jean Vaxelaire - One of the best experts on this subject based on the ideXlab platform.
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Measurement of adhesion strengths and energy between calcium carbonate cake and Filter Cloth
2016Co-Authors: Pascal Ginisty, B. Legoff, Jérémy Olivier, Jean Vaxelaire, Hervé Tabuteau, J. PaixaoAbstract:Various devices in liquid-solid separation require mechanical cake discharge using different technologies. An incomplete cake discharge causes yield losses, cycle time increase, irregular cake formation, high mechanical constraints which decrease medium life time, excess consumption of cleaning liquors….Currently, cake discharge is only assessed qualitatively by observations of Filter Cloth after discharge or quantitatively by weighing recovered solids. A prototype has been developed to carry out reliable and repeatable measurements by removing Filter Cloth from Filter cake by shearing. This study presents results of experiments performed with calcium carbonate (which forms sticky cakes) and discusses the conditions of cake formation and cake detachment from Filter Cloth. It highlights the role of two main parameters : Filter Cloth characteristics and pressure.
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Electro-dewatering of activated sludge: Electrical resistance analysis
Water research, 2016Co-Authors: Jean-baptiste Conrardy, Jean Vaxelaire, Jérémy OlivierAbstract:Abstract The significant risk of ohmic heating and the high electric energy consumption at terminal stages of the dewatering are two problems that hamper the development of the electro-dewatering (EDW) technology. In the future prospect of studying these two issues, it is important to provide and analyse quantitative data relative to the behavior of the electric resistance in EDW. It was the main goal of this study. It showed that the electric resistance of the complete system (cake + Filter Cloth) depended on the cake dryness. It increased sharply when the solids content exceeded around 45%.The solids loading also influenced the apparent resistance at the beginning of the process. The electric resistance of the Filter Cloth represented about 20% of the total resistance. It remained relatively constant over the process except at the terminal stage where it generally increased sharply. The use of conductive Filter, such as metallic Cloth, enabled to decrease the electric resistance and reduce the energy consumption of the process. The electric resistance decreased across the cake from the anode to the cathode. This behavior may be explained by several phenomena such as the ions migration and their interaction with the solid, the decrease of dry solids content from the anode to the cathode and the gas presence at the anode (due to electrolysis reaction).
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Electro-Dewatering of Activated Sludge: Electrical Resistance Analysis
Water Research, 2016Co-Authors: Jean Vaxelaire, Jérémy Olivier, Jean-baptiste ConrardyAbstract:The significant risk of ohmic heating and the high electric energy consumption at terminal stages of the dewatering are two problems that hamper the development of the electro-dewatering (EDW) technology. In the future prospect of studying these two issues, it is important to provide and analyse quantitative data relative to the behavior of the electric resistance in EDW. It was the main goal of this study. It showed that the electric resistance of the complete system (cake + Filter Cloth) depended on the cake dryness. It increased sharply when the solids content exceeded around 45%. The solids loading also influenced the apparent resistance at the beginning of the process. The electric resistance of the Filter Cloth represented about 20% of the total resistance. It remained relatively constant over the process except at the terminal stage where it generally increased sharply. The use of conductive Filter, such as metallic Cloth, enabled to decrease the electric resistance and reduce the energy consumption of the process. The electric resistance decreased across the cake from the anode to the cathode. This behavior may be explained by several phenomena such as the ions migration and their interaction with the solid, the decrease of dry solids content from the anode to the cathode and the gas presence at the anode (due to electrolysis reaction). \textcopyright 2016 Elsevier Ltd.
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Sludge Dewatering: Influence of operating parameters on dryness limit determination
2014Co-Authors: Pascal Ginisty, Jérémy Olivier, Romain Girault, Julian Tosoni, Emilie Dieudé-fauvel, Jean VaxelaireAbstract:Dewatering process efficiency, classically assessed by a parameter "dryness limit", is strongly, affected by conditioned sludge properties and by operating conditions. The medthod to measure its parameters is based on a filtration-compression test, which depends significantly on operating conditions. A standard method is under progess in France to develop a better controlled procedure. This paper presents the impact of solids load, pressure and compression time, Filter Cloth, flocculation conditions, pre-thickening and storage time on the dryness limit for different kinds of sludge. A comparison with industrial devices was also made.
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Pressurised electro-osmotic dewatering of activated and anaerobically digested sludges: electrical variables analysis.
Water research, 2012Co-Authors: Morgane Citeau, Jérémy Olivier, Jean Vaxelaire, Akrama Mahmoud, O. Larue, Eugène VorobievAbstract:Abstract Pressurised electro-osmotic dewatering (PEOD) of two sewage sludges (activated and anaerobically digested) was studied under constant electric current (C.C.) and constant voltage (C.V.) with a laboratory chamber simulating closely an industrial Filter. The influence of sludge characteristics, process parameters, and electrode/Filter Cloth position was investigated. The next parameters were tested: 40 and 80 A/m 2 , 20, 30, and 50 V—for digested sludge dewatering; and 20, 40 and 80 A/m 2 , 20, 30, and 50 V—for activated sludge dewatering. Effects of Filter Cloth electric resistance and initial cake thickness were also investigated. The application of PEOD provides a gain of 12 points of dry solids content for the digested sludge (47.0% w/w) and for the activated sludge (31.7% w/w). In PEOD processed at C.C. or at C.V., the dewatering flow rate was similar for the same electric field intensity. In C.C. mode, both the electric resistance of cake and voltage increase, causing a temperature rise by ohmic effect. In C.V. mode, a current intensity peak was observed in the earlier dewatering period. Applying at first a constant current and later on a constant voltage, permitted to have better control of ohmic heating effect. The dewatering rate was not significantly affected by the presence of Filter Cloth on electrodes, but the use of a thin Filter Cloth reduced remarkably the energy consumption compared to a thicker one: 69% of reduction energy input at 45% w/w of dry solids content. The reduction of the initial cake thickness is advantageous to increase the final dry solids content.
Harald Anlauf - One of the best experts on this subject based on the ideXlab platform.
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The influence of Filter Cloth on cake discharge performances during backwashing into liquid phase
Separation and Purification Technology, 2021Co-Authors: Patrick Morsch, Harald Anlauf, Hermann NirschlAbstract:Abstract In industrial solid/liquid separation, the removal of fine particles in a suspension with a significant amount of solids content can be a challenging task. Cake filtration in particular is a useful principle for separation of such suspensions. This separation occurs in a wide array of industrial production applications and has some advantages compared to other separation principles. To achieve the required performance, different types of Filters can be used. One commonly used type is operated semi-continuous and use backwashing to discharge the Filter cake. The regeneration of the Filter Cloth is as important as the actual filtration step. In the case of a properly regenerated Filter Cloth, the filtrate flow at the beginning of each step is still the same, while the initial filtrate flow decreases for and inefficient regeneration. This regeneration of the Filter Cloth depends strongly on the interaction between the particle system and the Filter Cloth. In the case of backwashing filtration, a clear difference could be observed between multifilament and monofilament fabrics. For multifilament Filter Cloths, it is possible to calculate the minimum required cake thickness for a complete discharge by means of the total resistance, i.e. the product of the specific cake resistance multiplied by the cake thickness. For 3 investigated fabrics with mesh size ≤ 20 µm, a complete cake discharge could be achieved by all 3 model particle systems. It is noticeable that the minimum required cake thickness decreases with increasing specific resistance. As soon as the cake thickness with the respective specific cake resistance of the particle system exceeds the value 5∙1010 m−1, a complete discharge can be observed. The cake thicknesses found within the same particle system were very similar between the 3 fabrics investigated. Based on this observation, the release of cakes from multifilament fabrics appears to be dominated by cohesion of particles in the cake. The adhesion from the first particle layer to the fabric does not seem to be a significant influencing factor. The situation is different for monofilament fabrics. This behaviour is different from the multifilament fabrics in the cake thickness. Here, smaller cake minimum required cake thicknesses were observed for small specific cake resistances. This is due to the particle deposition mechanism within the fabric. A lower specific cake resistance is associated with a larger particle size and/or a different particle shape (greater deviation from the ideal sphericity). Larger particles relative to the mesh size of the Filter fabric preferably form a clean interface between the particle layer and the Filter fabric (surface deposition). This leads to a lower interference and better cake discharge. This behaviour could be estimated by dividing the Filter media resistance (determined by a particle system whose particle size is significantly larger than the mesh size of the fabric), by the specific cake resistance multiplied by a particle shape-dependent factor (Eq. (2) ). The shape-dependent factors were determined to be 0.03 for orthorhombic, 0.15 for flaky and 0.46 for needle-shaped particles and thus increases with increasing deviation from the ideal sphericity. By including the Filter medium resistance, the influence of the fabric and the adhesion of particles to the fabric is to be expected. Validity of this model was proven with 6 Filter Clothes with ≤ 22 µm mesh (3 twill and 3 plain weave). Similar behaviour between multifilament fabric and monofilament fabric could only be observed with the required minimum backwashing volume for a complete discharge. The required necessary backwash volume is always ≤ 2 l/m2. In summary, this study shows the regeneration performance of different Filter Cloth types (multifilament and monofilament) can be predicted by different models.
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Influence of regeneration variables during backwashing treatment into gas-phase after liquid filtration
Separation and Purification Technology, 2020Co-Authors: Patrick Morsch, Pascal Ginisty, Harald Anlauf, Hermann NirschlAbstract:Abstract In industrial solid/liquid separation, the removal of fine particles occurs in a wide array of industrial production applications and can be found in nearly every process plant. Especially the cake filtration is emphasized as advantageous principle for separation of suspension with a low solids content (0.01–1 v/v %). To maintain the separation performance, it is required to replace or regenerate the used Filter Cloth. The latter one can occur through backwashing treatment into liquid or gas phase whereby the gas discharge required an upstream drying process. The main task of that regeneration procedure is a most complete Filter cake discharge to reduce the flow resistance of the Filter for the subsequent filtration step. Recommendations for advantaged process variables doesn’t exist and should be evaluate during this investigation. Investigations regarding to the regeneration procedure has shown, that the cake discharge into gas phase has significant differences to the discharge into liquid phase. Whereas the discharge into gas phase is created through an impulse, the liquid discharge can be interpreted as a slide on the Filter Cloth surface. Moreover, the backwashing variables are highly different (influence of backwashing pressure, Filter cake thickness) between the different backwashing environments as a result of the characteristic surface forces. In this work, main attention is given to the particle system (particle size and Filter cake thickness), the different weave types, assembly of the Filter Cloth and, of course, the backwashing pressure. The difference between a discharge in gas phase and liquid phase is described and its effect on the quality of the regeneration.
-
Description of the Filter Cloth deformation during backwashing filtration
Separation and Purification Technology, 2020Co-Authors: Patrick Morsch, Harald Anlauf, Maurus Bauer, Christoph Kessler, Hermann NirschlAbstract:Abstract The separation of fine particles with Filter Cloth is a commonly used technique to remove particles from process streams under low-cost and low-maintenance conditions. Such kind of Filter apparatus can be found, i.e., in front of distillation columns with the adjusted size. Here, it is possible to have a Filter apparatus with Filter elements ≤ 2.5 m in length and ≤ 100 elements in one vessel. For a constant and stable process conditions, a periodical regeneration of the Filter Cloth is absolute required. One option for realizing this procedure is discharging the built-up Filter cake in liquid phase (backwashing filtration). Due to the reverse flow, a deformation of the Filter Cloth occurs. This deformation depends on the assembly situation, mechanical pre-loading of the weave, the environment of the system, the weave type and, of course, the backwashing pressure. The interaction of this variables results in an adjusting of the space between the Filter elements and correspond with the required backwashing volume in l/m2. Influence of a contact between two Filter elements is not known but can have a negative impact in case of remaining Filter cake on surface. Too much space reduces the economy of the apparatus because less Filter surface needs the same apparatus footprint. Thus, by knowing how the Filter Cloth expand, the space can be adjusted on the particular separation task. This can lead to an improvement of the Filter surface per apparatus footprint and can be advantageously compared to competing separations procedures. The deformation of the Filter Cloth during the backwashing treatment is described and discussed in the context of this investigation on the basis of elementary mechanics.