Shape Up the Future with Filtration & Separation – Clean Environmentation
Professor Wallace Woon-Fong Leung, Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong
Title: Advances in Nanofiber Filtration of Nano-aerosols
Nano-aerosols/ultrafine particles (<100nm) in high concentration (50-500+ MM/m3) are found in polluted air both indoors and outdoors. Air-borne viruses are also typically in the same size range. By their small sizes, these invisible killers can be inhaled readily into our bodies causing health problems. Nanofiber filters are very effective to capture these invisible killers. This presentation will discuss various technologies being developed in the past decade on filtration of nano-aerosols to achieve high capture efficiency and to maintain low pressure drop.
Depth filtration on submicron aerosols and nano-aerosols using nanofiber filter as function of face velocity, filter thickness, and fiber packing density has been well established. This includes low Peclet number (Pe<10) condition for which diffusion dominates over convection/interception capture.
To achieve high capture efficiency for a given aerosol size, a certain basis weight (grams of nanofibers per square meter) of filter is required. When the same weight of nanofibers is divided into multiple layers, each separated by a permeable scrim material, the pressure drop of the entire filter is much reduced as compared to the case with all nanofibers all incorporated in a single layer. This novel multilayer nanofiber technology has been proven for different polymeric and natural materials.
For extended aerosol loading, a cake formed on the filter surface. The transition from depth to surface/cake filtration has been studied recently both experimentally and theoretically. It has been found that more aerosols are captured at the upstream end of the filter forming a skin layer, followed by plugging of pores in the skin layer by aerosol deposit, building of dendritic bridges above the plugged pores of the capillaries in the skin layer, and finally cake forming above the filter.
The cake formed above a nanofiber filter is quite dense, resulting in higher pressure drop across the entire filter. It can be made less dense and more permeable when a microfiber filter is installed upstream of the nanofiber filter. This composite filter technology has been proven experimentally and also by numerical simulation.
Other technologies such as cleaning of a loaded nanofiber filter by backpulse-and-backblow, and electrostatically charging of a nanofiber filter will also be discussed.
Professor Kuo-Lun Tung, Dept. of Chemical Engineering, National Taiwan University, Taipei, Taiwan
Title: Nature-Inspired Filtration Membranes: Geomimicry versus Biomimicry.
There are many lessons that one could learn from, and/or mimic in nature. In the past decades, biomimetic concept has been widely adopted for biomaterials and polymeric materials designs by scientists and biologists. The biomimetic concept has promoted a fantastic progress in the science and engineering of bio/organic materials. Nevertheless, the geomimetic concept was astonishingly few to be taken into consideration for inorganic materials development.
Recently, several new concepts to develop novel membrane materials have been proposed and new preparation methods from a fundamental understanding of formation mechanism and morphology of natural materials haven been designed. In this talk, several potential routes intentionally mimic existing biological and geological processes to develop novel organic and inorganic membranes will be surveyed.
Professor Chikao Kanaoka, Kanazawa University, Japan
Title: Fine particle filtration technology using fiber as dust collection medium.
Researches relating dust collector using fiber as particle collection body i.e., air filter, cartridge filter and nonwoven bag filter, were reviewed. Their filtration process was classified into 3 stages, i.e., Stage 1.inner filtration I, Stage 2.inner filtration II and Stage 3.surface filtration.
Collection mechanisms of fresh circular fiber have been well understood and so-called classic filtration theory is applicable except single nano-particle, where discussion about the possibility of thermal rebound is necessary. In Stage 1, effects of shape of both fiber and particle, and filter structure, non-uniformity are the important issues. In Stages 2 and 3, filtration process becomes very complicated because of many affecting parameters. Main target in Stage 2 is to develop effective scheme to describe the phenomena and to find filter structure having a large holding capacity. Most important issue in Stage 3 is to develop the effective cleaning technique to minimize the dust emission based on rational but not empirical scheme.
Keynote Speaker: Mr. Zhili Song, Shanghai Hongli Purification Technology Co., Ltd, 7/F., No.408 Changshou Rd., Shanghai, China
Title: A New Liquid-Solid filtration technology for efficient filtration of fine particles of micron and sub-micron – “Surface layer filtration”
The kinds of liquid-solid filtration technology and device in industrial productions are very much, but according to the basic mechanism of filtering are only two kinds: surface filtration (SF) and depth filtration (DF). The mechanism of SF is “screening”, namely small pores of media capture large solid particles; the mechanism of DF is “adsorption”, namely large pores of media capture small solid particles.
SF and DF are only suitable cake filtration and clarification filtration of slurries containing particles larger than 5 μm, not suitable the slurries containing particles less than 5 μm. Otherwise the energy consumptions or material consumptions will be significantly increased.
A new filtration technology of slurries containing higer propotions of sub-micron particles have been researched and developed for ten years, have been successfully applied in a lot of filtrations of ultra-fine particles.
The SLF draws the advantages of SF and DF and avoids the disadvantages of SF and DF, can get to excellent filtering efficiency and accuracy, low energy and material consumptions and long service life coincidentally.
This paper describes the emergency background, general situations. The mechanism of capture small particles by larger pores of media is “adsorption on surface layer, bridging in entrance of pores”. Wish for to reach SLF, the parameters relative to media and filters must be satisfied following mathematical model: or . If to capture out particles of 0.1-1μm from various chemical solutions, the average capillary pores diameters of media would generally be 1-25μm. At last, this paper introduces the main applications of SLF in Chinese industrial productions.
Dr. Wenping Li, Agrilectric Research Company, 3063 Highway 397, Lake Charles, Louisiana, USA
Title: Development of Adsorptive Silica Filter Aid from a Natural Resource
Amorphous silica from Rice Hull Ash has been considered as a green filter material with highly porous structure, excellent filtration properties and relatively pure chemical compositions. For decades, it has been used as a filter aid for industrial water and waste water treatment, and process filtration. As a filter aid, it is designed for suspended solids removal. For the dissolved contaminations, activated carbon or other adsorbents need to be applied. Problems with adsorbents, such as granular or powder activated carbon (AC) or other adsorbents include high cost, regeneration loss for granular, and low filtration flow rate with powder adsorbents. There is a need for development of a cost effective adsorptive filter media with both filtration and adsorption properties.
Amorphous silica from Rice Hull Ash is a material with mesoporous structure, and special functional group such as –OH, Si-H and Si-O-Si on the surface with potential adsorption capacity. The adsorptive properties of the material itself is limited due to the relatively low BET surface area of only 30-40m2/g. Increase of the surface area enhances the activation of the function groups and the adsorption capacity. Based on the concept, a high surface area adsorptive silica filter aid from RHA amorphous silica is developed. Physical, chemical, filtration and adsorption properties of the adsorptive silica filter aid, including SEM, EDX, FTIR, BET surface area, iodine and molasses numbers, pore size, pore volume, cake permeability, cake density were studied. Results indicate 10-20 times surface area increase and corresponding high adsorption capability especially for large molecules. The selective adsorption was explained by its unique the pore size and pore volume features. There is certain compromise of permeability due to increase of the surface area and change of pore size distribution, however, permeability of the adsorptive silica is still 3-6 times higher than regular powder activated carbon. Case studies on Free Fatty Acid removal for oil filtration and heavy metal removal for wastewater treatment will also be presented.
Mr. Martin Klein, MANN+HUMMEL GmbH & Co. Kulmbacher Str. 12, 95502 Himmelkron, Germany
Title: Clean, Efficient, Smart – New Trends in Cabin Air Filtration
Increasing knowledge concerning the health issues related to fine particulate matter, noxious gases and allergens in combination with increased exposure to these pollutants, especially in fast-growing markets like China and India, impose a significant demand to improve the air quality in car cabins. More and more also the fraction of PM1 (< 1μm) as well as the ultrafine particles (UFP < 0,1 μm) and their effects on human health are getting in focus. Especially vehicle passengers are exposed to high concentrations of these ultrafine particles if no suitable filtration systems are available. By adopting HEPA Filter Media Technology a superior Air Quality inside the vehicle can be established. In order to offer an optimum solution which reflects different requirements (e.g. differential pressure and life time) several aspects need to be considered that shall be addressed in this presentation by introducing results from lab as well from field tests.
In traffic jams or tunnels, gaseous pollutants like NO2 often exceed the WHO safe limits by several factors, which have led to the optimization and modification of existing activated carbons as well as the development of new types of adsorbents to keep the concentrations in the vehicle cabin at a healthy level.
For e-mobilty one central challenge is to maximize the driving range. Smart connected cabin air filter systems help to reduce the energy demand for heating and cooling and provide optimal air cleaning in each driving condition and environment.
Dr. Kyung-Ju Choi, CTO, Clean & Science, 2775 Algonquin Rd., Rolling Meadows, IL 60008, USA, Chair of KFS
Title: Will the synthetic filtration materials such as polyolefins and polytetrafluoroethylene become the next generation filter-media?
Filtration technology is a continuously advancing field for the last 50 years. Due to the excellent chemical resistance and higher filtration efficiency, while maintaining low resistance, polyethylene, polypropylene and polytetrafluoroethylene have become standard materials for several applications in air and liquid filtration. Furthermore, these materials are gaining momentum by replacing commodity cellulose or fiberglass based filtration materials. Submicron meltblown polypropylene materials are being widely used, particularly in Asian markets, realized as room air purifiers, gas turbine and cabin air applications. Polyolefin spunbond materials have been dominating the HVAC and residential markets due to its high surface electric charging characteristics and low resistance for the last 20 years. Low density polyethylene (LDPE) or linear low density polyethylene (LLDPE) split thin films have been still used in air filter market. Stretched polyolefin and polytetrafluoroethylene films have been penetrating into the conventional membrane market due to its dimensional stability, chemical inertness and user-friendliness. Additionally, the molecular orientation and crystal structure of polyolefins and polytetrafluoroethylene have been gradually improving embodied by positive advances in molecular structure and mechanical properties. Polyolefins and polytetrafluoroethylene are prevalent in today’s filtration market and are actively being refined, which makes it plausible that these materials will persevere, if not gain more popularity, in the next generation of filter-media.
Professor Eunkyong Shim, Dept. of Textile, Engineering and Chemistry, College of Textiles, North Carolina State University, Raleigh, NC, USA
Title: Nonwoven Technology for Filter Media Development
Increasing awareness of impacts of air and water pollutions on health coupled with needs for safe, energy efficient and environmental friendly industrial processes results in higher demand in filtration and separation applications in nonwovens. Development of nonwoven filter media requires control of their structure through understanding of processing mechanism and material properties. In this talk, I will discuss controlling solidity/porosity of nonwovens, creation of micro/nanofiber filter media, and filtration properties of these nonwovens. Functionalization for filter media including improving electrostatic charging characteristics and imparting ion exchange capability will be discussed.
Professor Peter P Tsai, University of Tennessee, Knoxville TN, USA
Title: Quantitative Analysis of the Factors that Determine the Filter Quality
Abstract:Two factors, penetration and pressure drop, determine the filter quality of a filter media, the lower the penetration and/or the pressure drop, the higher the filter quality. Fiber diameter and packing density are two factors that determine the penetration and the pressure drop of a filter media. Based on single fiber efficiency theory, filtration efficiency is exponentially increased with the increase of the fiber service area, which is increased with the decrease of the fiber diameter for the same weight of the media. Pressure drop is inversely proportional to the square of the fiber diameter but is proportional to a function of packing density. The filtration efficiency may or may not increase with the increase of the pressure drop. The packing density function is increased sharply with the increase of the packing density. This presentation will provide the data of filter quality of some real media having different fiber diameters with different or the same packing density. Theories are employed to explain and have a good agreement with the results of the filter quality of real samples. Therefore, theories are very valuable to design desired specifications and to predict the penetration and the packing density of a media and the filter quality of the media can be calculated.
Professor Yong Sik Ok, Korea University, Seoul, Korea
Title: SMART biochar technology: A shifting paradigm towards advanced materials and filtration/separation research
Abstract:Biochar, produced through pyrolysis of biomass under low or no oxygen conditions, has found a wide range of applications from soil fertility improvement to removal of contaminants. Initial interest in biochar is to use it as a means to capture carbon dioxide from the atmosphere; however, recent developments are seeing biochar being applied in engineering, and health care and life sciences, some of those applications have large potentials for rapid commercialization. We expect a paradigm shift towards the development of the next generation of biochar with applications in a range of new fields such as filtration and separation.