Law of substance separation on cross-flow filtration in turbulent flow

Cross-flow filtration is a filtration process for separation of a disperse phase from liquids. Suspension flows tangentially to a membrane and the filtrate is drawn off perpendicular to the direction of flow. Formation of a filter cake on the membrane is thus prevented, reduced, or its composition, modified. The principle of the separation is based on tow opposing effects: on the one hand, the particles are transported by the filtration flux to the membrane where they cause and increase in concentration; on the other hand, concentration differences are again reduced by the turbulence of the cross-flow and by Brownian motion of the particles. The two mechanisms compete with each other and depend upon particle size in different ways. An energetic comparison of the two effects yields the separation law of cross-flow filtration as a steady state solution of the Fokker-Planck equation. The separation law has an exponential form and assigns each particle size a separation probability with which it reaches the membrane. Once on the membrane the particles may form a filter cake, flow through the pores or return to the bulk flow. If the particles remain on the membrane the ranges of layer-free and cake-forming filtration can be calculated from the hydro-dynamic and geometric conditions of the cross-flow filter. Conventional cake filtration is regarded as limiting case. In continuous cross-flow filtration process a low separation probability through the filtration pressure on selection of the filter medium resistance.     

Relation of Structure,Properties and Performance of Fibrous Media for Gas Filtration

The relation between the structure, permeability and filtration performance of needled nonwoven filter media is reported. Surface treated and untreated fabrics were studied, including microporous coated, laminated e‐PTFE, heated calendered and surface singed materials. Surface treatments appear to impart higher packing densities, but mean pore size is governed by the type of treatment with microporous and PTFE having the smaller values. Filtration performance was determined from graphs of pressure drop with filtration duration, differences in filtration efficiencies and the dust concentrations in gas emissions. Except for the singed materials, the treated fabrics depicted surface filtration and the untreated depth filtration. The trend for singed fabrics showed initial depth followed by surface filtration. Markedly higher filtration efficiencies were obtained with surface filtration, which corresponded with higher rates of pressure drop. Surface treatments, giving smaller mean pore sizes, resulted in higher filter cake resistance owing to low particle penetration through the base fabric.     

Einfluss ausgewählter Medienstrukturparameter auf das Betriebsverhalten von Ölnebelfiltern

The relevant mechanisms in oil mist filtration and their impact on operational behavior of the filters have received increasing attention in research over the last few years and are qualitatively well understood by now. However, so far the relationship between structural properties of the filter media and the operational behavior of the filters is relatively unknown. For the identification of filtration‐relevant structural parameters, textile properties of different filter media were characterized with various methods. The operational behavior of the characterized filter media was then examined and compared.     

Heißgasfiltration

Even if already numerous hot gas filter systems are installed, hot gas filtration with all its aspects is still not known enough. Hot gas filtration offers significant advantages in many cases. Processes can be simplified or intensified, process efficiency can be increased, contamination of products or blocking by condensation or desublimation can be prevented, and downstream equipment can be protected. The paper describes the fundamental particularities of filtration at higher temperatures and provides an overview of filter media and filter systems for hot gas filtration. Moreover, applications of hot gas filtration are presented.     

Electrospun soy‐protein‐based nanofibrous membranes for effective antimicrobial air filtration

Soy proteins are gaining more and more attention because of its multifunction and biodegradability. Silver nanoparticles (AgNPs) are introduced into the nanofibers to prevent growth of microorganisms over the filter media. In the present study, the multifunctional and antimicrobial nanofibrous membranes were prepared by electrospinning the soy protein isolate (SPI)/polymide‐6 (PA6)‐silver nitrate system followed by ultraviolet reduction. The morphology of SPI/PA6 nanofibrous membranes was characterized by scanning electron microscopy. Antibacterial property of nanofibrous membranes were investigated against Escherichia coli and Bacillus subtilis. The optimized fiber membrane exhibited over 95% filtration efficiency of PM_0.3 (particulate matter size less than 0.3 μm). The successful synthesis of SPI/PA6‐AgNPs nanofibrous membranes would make it to be the potential candidate for novel antibacterial and high‐performance air filter. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45766.     

二次盐水过滤用的超精密澄清过滤技术

分析了３类可用于二次盐水过滤的超精密澄清过滤技术,介绍了刚性微孔聚乙烯管压滤机连续多年在盐水二次过滤的使用中所取得的主要效果。     

陶瓷膜过滤技术在煤制乙二醇工艺中的应用

介绍了陶瓷膜过滤技术在煤制乙二醇工艺中应用,通过试验和分析,采用微孔陶瓷膜过滤器较好的解决了煤制乙二醇过程中微细颗粒精密过滤技术难题,提升煤制乙二醇成品的品质。     

Reuse of greywater and rainwater using fiber filter media and metal membrane

As water resources become more limited and waste discharge becomes increasingly problematic, the concept of water reuse is becoming important. Recently, use of greywater and rainwater as alternative water resources has drawn attention. However, lack of useful information on the combined use of greywater and rainwater hinders wide application of these systems.In this study, novel treatment options including lignocellulose filter media and metal membranes were examined to reuse greywater and rainwater in office buildings. Laboratory scale experiments were performed to evaluate the potential of these technologies. The fiber filter media was useful to control first flush rainwater but was not enough to produce water for non-potable use in buildings. Thus, the metal membrane filtration was attempted to reject particulate pollutants. The removal efficiency of various pollutants and the membrane permeability were examined using metal membranes with different pore sizes.     

A case study of simulating submicron aerosol filtration via lightweight spun-bonded filter media

The most common method of filtration is via fibrous nonwoven media. Fibrous filters are generally characterized by their collection efficiency and pressure drop. Traditional computational studies in this area are typically based on unrealistic 2-D geometries with the fibers simply placed in a lattice (regular array) perpendicular to the flow. The traditional approaches however, do not permit studying the relation between the 3-D structure of a filter media and its performance. In this study, for the first time, a virtual 3-D web is generated based on the fiber orientation information obtained from analyzing microscopic images of lightweight spun-bonded filter media. Pressure drop and collection efficiency of our virtual filter are simulated and compared with the previous 2-D analytical and numerical models as well as experiment. Our pressure drop calculation, unlike the previous models, showed a perfect agreement with the predictions of the Davies’ empirical equation. The collection efficiencies obtained from simulating a thin spun-bonded filter media challenged with submicron particles having diameters ranging from 50 to 500 nm showed a similar trend as that of the previous 2-D models. For the solid volume fraction (SVF), filter thickness, and the fiber and particle diameters considered in this study, we found collection efficiencies higher than that of the above mentioned 2-D models with a relatively good agreement with experimental data obtained from a TSI 8130 filter tester.     

微孔滤膜过滤器的改进探讨

针对仪器分析教学各种过滤的不同要求,对常规的全玻璃微孔滤膜溶剂过滤器进行了改进。改进后的微孔滤膜过滤器可以用于实验中油/水相溶剂和样品的处理,满足了不同的仪器分析教学实验操作需要,实现了微孔滤膜溶剂过滤器的多功能化,为实验教学节省了开支。     

Experimental Study on Filtration Performance of Flat Sheet Multiple-Layer Depth Filter Media for Intake Air Filtration

Depth filter media are usually composed of multiple layers to attain optimal values of main filtration parameters such as pressure drop and particle collection efficiency (PCE). Understanding the performance of the single layers that make up the filter media can contribute to attaining these optimum values. For the purpose of this study, we have developed two samples of depth filter media, 2LM and 3LM, composed of two and three layers, respectively. Samples of the media and single layers have been prepared in flat sheet form. Filtration performance of these samples has been evaluated using a lab-scale flat sheet filter media test unit with KCl as the test aerosol. Results from these tests have been compared with those from an automated filter tester (AFT) with NaCl as the test aerosol. These media have been characterized based on filter media properties and data from the filtration performance tests and the effect of layers on filtration performance has been observed. Pressure drop data from the tests with a standard test unit and our laboratory test unit are similar, and the difference in data is attributed to high inlet concentration of KCl particles. The overall filtration performance is strongly dependent on the final layer regarding pressure drop and particle of two- and three-layer filter media. Other constituent layers can be seen as contributors to the dust-holding capacity of the filter media and can reduce the dust load for the final layer.

Copyright 2013 American Association for Aerosol Research     

湿法磷酸净化中液固分离过程的实验研究

针对湿法磷酸净化过程中存在的液固分离问题,采用离心过滤的方法,探讨了磷酸预处理脱色液的过滤特性,研究了分离因素、滤饼厚度、过滤介质等因素对过滤的影响。实验结果表明,当分离因素约为252,滤饼厚度约为20 mm,采用涤纶加密型滤布时,过滤效果最佳。     

Einsatzkriterien für textile Filtermedien

Criteria for the use of textile filter media . The chemical, thermal and mechanical requirements that have to be taken into consideration for the selection of a filter medium, with regard to the kinds of synthetic fibers (related to today's filter uses), for the different procedures involved in wet and dry filtration are described. The influence of the structure of the filter fabric, in both pore and mesh and it's effect on filter efficiency is shown. The requirements for making-up are explained and the possible types of elements for use in textile filter media are mentioned.     

A study on the effects of laminating temperature on the polymeric nanofiber web

The use of fine fiber has become an important design tool for filter media. Nanofibers-based filter media have some advantages such as lower energy consumption, longer filter life, high filtration capacity, easier maintenance, low weight rather than other filter media. The nanofibers-based filter media made up of fibers of diameter ranging from 100 to 1,000 nm can be conveniently produce by electrospinning technique. Common filter media have been prepared with a layer of fine fiber on typically forming the upstream or intake side of the media structure. The fine fiber increases the efficiency of filtration by trapping small particles, which increases the overall particulate filtration efficiency of the structure. Improved fine fiber structures have been developed in this study in which a controlled amount of fine fiber is placed on both sides of the media to result in an improvement in filter efficiency and a substantial improvement in lifetime. In the first part of this study, the production of electrospun nanofibers is investigated. In the second part, a different case studyis presented to show how they can be laminated for application as filter media. Response surface methodology (RSM) was used to obtain a quantitative relationship between selected electrospinning parameters and average fiber diameter and its distribution.     

Electrospun nanofibers with application in nanocomposites

The use of fine fiber has become an important design tool for filter media. Nanofibers-based filter media have some advantages such as lower energy consumption, longer filter life, high filtration capacity, easier maintenance, low weight rather than other filter media. The nanofibers-based filter media made up of fibers of diameter ranging from 100 to 1,000 nm can be conveniently produce by electrospinning technique. Common filter media have been prepared with a layer of fine fiber on typically forming the upstream or intake side of the media structure. The fine fiber increases the efficiency of filtration by trapping small particles, which increases the overall particulate filtration efficiency of the structure. Improved fine fiber structures have been developed in this study in which a controlled amount of fine fiber is placed on both sides of the media to result in an improvement in filter efficiency and a substantial improvement in lifetime. In the first part of this study, the production of electrospun nanofibers is investigated. In the second part, a different case studyis presented to show how they can be laminated for application as filter media. Response surface methodology (RSM) was used to obtain a quantitative relationship between selected electrospinning parameters and average fiber diameter and its distribution.     

玻纤滤材过滤阻力的预测

过滤阻力和过滤效率是玻纤空气滤材的关键参数。实际应用中,为了优化滤材阻力和效率之间的矛盾,通常会选择多种尺寸的纤维搭配使用。对这种滤材的过滤阻力进行预测,对于高性能滤材的研制具有重要意义,而目前对玻纤滤材过滤阻力的理论计算大部分还局限于单种纤维的理想情况。本文将针对由多种玻纤原料制备的滤材,根据不同玻纤的比表面积,利用Kozeny-Carman方程计算由此制备的滤材过滤阻力。这种方法计算的过滤阻力理论值与实际测量值非常接近,相关系数R2=0.996 9,可为过滤材料的优化设计提供一定的依据。     

Particle Filtration for Determination of Pore Size Characteristics of Microporous Membranes: Applicability to Plasma Separation Membranes

Abstract

Pore characteristics of microporous membranes were studied by filtration with aqueous solutions containing spherical particles of uniform diameter. The rejection values for four types of plasma separation membranes of microporous structure show good linearity to particle size with high correlation on log-normal probability coordinates. The mean pore size of 94 to 866 Å and standard deviation of 1.51 to 2.13 were obtained for these membranes. Such membranes have mean pore sizes of about one order of magnitude larger than that for synthetic dialysis and hemofiltration membranes in addition to having wider pore distributions. The mean pore sizes obtained by this study relate closely to sieving properties of macromolecules from blood.     

Experimental Analysis of Fine–Particle Migration during Ceramic Filtration Processes

Slip casting and filter pressing are ceramic forming processes which can be affected by the migration of fine particles during filtration. Fine particles can be carried along with the filtrate and deposited within the ceramic compact and /or filter medium, thereby clogging and reducing the permeabilities of the porous media. This in turn affects the growth rate as well as the porosity of the compact. Evidence of clogging of the ceramic compact and filter medium was obtained by (1) SEM analysis of the compact and filter media, (2) surface area measurements of cross sections of compacts, and (3) measurements of the thickness of compacts as a function of casting time.     

高分子精密微孔过滤机在化工生产上的应用

高分子精密微孔过滤机是一类过滤、排渣、再生与耐腐蚀等性能很优异的新型精密过滤机。本文叙述该类过滤机的主要特点,并系统介绍了其在化工生产上的各种精密滤饼过滤、精密澄清过滤以及各种化工生产废水等领域的主要应用。     

膜技术在废水处理中的应用

本文介绍了膜技术处理废水的基本原理及其特点，综述了反渗透、微滤、超滤、液膜和电渗析等传统膜技术在废水处理的应用，以及纳滤膜、充气膜、膜生物反应器、渗透蒸发和胶团强化超滤法等新型膜技术在废水处理的发展及其应用，指出了膜技术在处理废水中存在的主要问题，并对膜技术处理废水的发展前景作了展望。