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K. Li - One of the best experts on this subject based on the ideXlab platform.
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decolorization of dye containing aqueous solutions by the polyelectrolyte enhanced ultrafiltration peuf process using a hollow fiber Membrane Module
Separation and Purification Technology, 2006Co-Authors: Nyi Nyi Kyaw, K. LiAbstract:Polysulfone (PSf) asymmetric hollow fiber Membranes with molecular weight cut-off (MWCO) of 13,000 Da have been prepared and employed for removal of the triphenylmethane dyes including malachite green (MG), brilliant green (BG) and new fuchsin (NF) from aqueous solutions. Several water-soluble polymers such as poly(diallydimethyl ammonium chloride) (PDADMAC), poly(sodium-4-styrenesulfonate) (PSS) and polyvinyl alcohol (PVA) have been examined for the polyelectrolyte-enhanced ultrafiltration (PEUF). The experimental results indicate that all the three triphenylmethane-type dyes can be removed effectively using the PSf hollow fiber ultrafiltration Membrane with the aid of the anionic PSS polymer. The enhancement is primarily due to the formation of complexes between the anionic polymer and the cationic dye molecules through electrostatic attraction. The cationic and nonionic polymers such as PDADMAC and PVA are not suitable for the decolorization of MG, BG and NF aqueous solutions. The decolorization performances of the PSf Membrane Module can be fully restored by the back-washing operation using alcohol after each experiment.
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mixed conducting ceramic hollow fiber Membranes for air separation
Aiche Journal, 2005Co-Authors: K. LiAbstract:Mixed conducting ceramic hollow-fiber Membranes, which possess an asymmetric structure, were prepared by a combined phase inversion and sintering technique where precursors of the hollow fibers were first spun using a polymer solution containing suspended LSCF powders and were then sintered at elevated temperature. By controlling the weight ratio of the LSCF powder to the polymer binder, sintering temperature, and time, the LSCF hollow fibers with gastight properties have been prepared and evaluated using an apparatus developed during the course of this study. Using the gastight LSCF hollow fibers, a Membrane Module was assembled for air separation. The performances of the Module for air separation have been studied under various operating modes and at different temperatures and feed flow rates both experimentally and theoretically. The results reveal that the surface exchange reaction at the downstream side is much more important than that at the upstream side, especially for lower operating temperatures. The porous inner surface of the prepared LSCF hollow-fiber Membranes substantially favors the oxygen permeation when air is fed in the shell side of the Membrane Module. At high operating temperatures, oxygen permeation can be enhanced by the countercurrent flow operation. Vacuum operation favors the oxygen permeation kinetically in the LSCF hollow-fiber Membrane Modules. © 2005 American Institute of Chemical Engineers AIChE J, 2005
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selective removal of trace h2s from gas streams containing co2 using hollow fibre Membrane Modules contractors
Separation and Purification Technology, 2004Co-Authors: Dongliang Wang, K. LiAbstract:Removal of trace H2S from gas streams containing high concentration of CO2 was carried out in a polyvinylidene fluoride porous asymmetric hollow fibre Membrane Module, using an aqueous solution containing 2 M sodium carbonate as absorption medium. Effects of gas/liquid flow ratio, CO2 concentration and operating pressures on the extent of H2S removal, H2S selectivity and overall mass transfer coefficients were investigated. The selectivity for H2S was about one order of magnitude higher than that in conventional-packed towers. Using feed gas mixtures containing 1000 ppm H2S with CO2 concentrations ranging from 5–23 vol.%, the H2S removal efficiency of nearly 100% was attained with less than 5 vol.% of CO2 permeated and absorbed. Experimental results indicate that the Membrane Module used was very efficient in the selective removal of trace H2S to ultra-low concentration even at high gas/liquid flow ratio.
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removal of h2s to ultra low concentrations using an asymmetric hollow fibre Membrane Module
Separation and Purification Technology, 2002Co-Authors: Dongliang Wang, K. LiAbstract:Removal of H2S to ultra-low concentrations using an asymmetric hollow fibre Membrane Module was studied from gas streams containing 17.9–1159 ppm H2S. The absorption medium used was 2 M sodium carbonate (NaCO3) aqueous solution. A porous polyvinylidene fluoride (PVDF) asymmetric hollow fibre Membrane was used as the barrier between the liquid and gas phases. The effect of various operating conditions on H2S outlet concentration and mass transfer coefficient was examined. The operating conditions examined included the feed gas concentration, the gas velocity (resident time), the liquid velocity, and the gas pressure. The PVDF hollow fibre Membrane Module was found to be very efficient in purification of gas streams containing soluble toxic gases. With the feed concentrations of 17.9–1159 ppm H2S, complete removal of H2S can be reached at very short resistance time (<0.1 s) and low liquid/gas flow ratio. The mass transfer coefficient strongly depends on the gas phase pressure and gas flow rate.
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an ultrathin skinned hollow fibre Module for gas absorption at elevated pressures
Chemical Engineering Research & Design, 1996Co-Authors: K. LiAbstract:An ultrathin skinned hollow fibre Membrane Module coupled with a liquid absorbent was investigated experimentally for the removal of CO 2 from a gas mixture. The Module consists of a bundle of hollow fibres having a dense skin layer at the outer edge of the fibre. The gas mixture containing 4% CO 2 was introduced into the hollow fibre lumen and was in countercurrent contact with the liquid (either water or NaOH solution) fed into the Module shell. The overall mass transfer coefficients of carbon dioxide were obtained in the gas phase. A study ofmass transfer in the Membrane Module indicates that the overall mass transfer coefficients, K AG, are controlled by both the liquid film and Membrane resistances. It was also shown experimentally that the use of the ultrathin skinned hollow fibres Module for CO 2 absorption has two advantages. Firstly, the dense skin layer of the hollow fibre Membrane eliminates the wetting problem commonly encountered in microporous Membranes. As a result, the mass transfer operations are stable with long term exposure of the Membrane to the liquid absorbent. Secondly, operations of the feed pressure are flexible. The feed gas pressure of 200 k P a higher than the liquid pressure was maintained without any noticeable bubble formation in the liquid phase. The higher operating pressure in the gas phase suggests that the reduction of the mass transfer rate due to the higher Membrane resistance could be compensated by an elevation of the feed gas pressure, i.e. increase of the driving force.
Lizhi Zhang - One of the best experts on this subject based on the ideXlab platform.
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coupled heat and mass transfer in an application scale cross flow hollow fiber Membrane Module for air humidification
International Journal of Heat and Mass Transfer, 2012Co-Authors: Lizhi ZhangAbstract:Abstract This study is a step forward from previous researches involving hollow fiber Membrane contactors for air humidification. A real application-scale cross-flow hollow fiber Membrane Module is investigated. The air stream flows transversely across the fiber bundle while being humidified. The novelty is that the shell-and-tube Module is converted to a parallel-plates heat mass exchanger in the model set up. The equations governing the heat and moisture transfer from the water to the air, through the Membranes, are described. The equations are then normalized with newly defined dimensionless parameters, which summarize the operating conditions and have clear physical meanings. Following this step, the two-variable two-dimensional partial differential equations are numerically solved. Tests are conducted to validate the model. Effects of varying operating conditions on system performance are discussed. It is found that the system is dominated by mass transfer in Membranes with a total Lewis number larger than 10. The packing density has a direct influence on performances. In contrast, the geometry of fiber packing arrangement has a negligible effect. This is tremendously different from the traditional metal tube bundles for sensible-only heat transfer.
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conjugate heat and mass transfer in a hollow fiber Membrane Module for liquid desiccant air dehumidification a free surface model approach
International Journal of Heat and Mass Transfer, 2012Co-Authors: Lizhi Zhang, Simin HuangAbstract:Abstract Conjugate heat and mass transfer in a hollow fiber Membrane Module used for liquid desiccant air dehumidification is investigated. The Module is like a shell-and-tube heat exchanger where the liquid desiccant stream flows in the tube side, while the air stream flows in the shell side in a counter flow arrangement. Due to the numerous fibers in the shell, a direct modeling of the whole Module is difficult. This research takes a new approach. A representative cell comprising of a single fiber, the liquid desiccant flowing inside the fiber and the air stream flowing outside the fiber, is considered. The air stream outside the fiber has an outer free surface (Happel’s free surface model). Further, the equations governing the fluid flow and heat and mass transfer in the two streams are combined together with the heat and mass diffusion equations in Membranes. The conjugate problem is then solved to obtain the velocity, temperature and concentration distributions in the two fluids and in the Membrane. The local and mean Nusselt and Sherwood numbers in the cell are then obtained and experimentally validated.
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heat and mass transfer in a randomly packed hollow fiber Membrane Module a fractal model approach
International Journal of Heat and Mass Transfer, 2011Co-Authors: Lizhi ZhangAbstract:Abstract Hollow fiber Membrane Modules are widely used in various industries. The disordered nature of hollow fiber distributions in the Module exhibits the existence of a fractal structure formed by the voids between the fibers. The area fractal dimension of the voids on the Module cross section is obtained. Then the shell side flow distribution and convective heat and mass transfer are investigated based on the fractal theory developed. An experimental work where an air flow in the shell side is humidified by a water flow in the tube side is performed to validate the model. It is found that the model predicts the flow distribution and the heat and mass transfer deteriorations well with local data for a triangular array. With the model, friction factor and Sherwood number deteriorations which take into account of the degree of irregularity, in terms of fractal dimension, are analyzed. The results show that the higher the packing density is, the less the fractal dimension is, and the less the non-uniformity of the flow distribution is. The Sherwood and Nusselt numbers of a randomly distributed fiber Module are only 1–5% of a uniformly spaced tube array. Correlations are proposed for the estimation of friction factor and Sherwood numbers considering the degree of irregularity. The predictions are also compared to the available mass transfer correlations in the literature.
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coupled heat and mass transfer in a counter flow hollow fiber Membrane Module for air humidification
International Journal of Heat and Mass Transfer, 2011Co-Authors: Lizhi Zhang, Simin HuangAbstract:Abstract Hollow fiber Membrane based air humidification offers great advantages over the traditional methods because the liquid water droplets are prevented from mixing with the process air, while water vapor can permeate through the Membranes effectively. The novelty in this research is that the coupled heat and moisture transport in a hollow fiber Membrane Module for air humidification is investigated, both numerically and experimentally. The air stream and the water stream flow in a counter flow arrangement. It is found that the Membranes play a key role in humidification performances. For sensible heat transfer, both the liquid side and the Membrane side resistance can be neglected, while the total heat transfer coefficients are determined by the air side heat transfer coefficients. In contrast, in mass transfer, only the liquid side resistance can be neglected, while the total mass transfer coefficients are co-determined by Membrane properties and the air side convective mass transfer coefficients.
Raja Ghosh - One of the best experts on this subject based on the ideXlab platform.
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purification of equine igg using Membrane based enhanced hybrid bioseparation technique a potential method for manufacturing hyperimmune antibody
Biotechnology and Bioengineering, 2008Co-Authors: Lu Wang, Raja GhoshAbstract:Hyperimmune equine IgG is widely used as antivenom and anti-rabies agents. This article discusses a Membrane based enhanced hybrid bioseparation technique for efficient and scalable purification of equine immunoglobulin G (IgG) from horse serum. This technique is an improved version of a standard hybrid bioseparation technique developed within our group earlier for fractionation of human plasma proteins (Ghosh. 2004. J Membr Sci 237: 109–117). In the presence of a high antichaotropic salt concentration, equine IgG is selectively and reversibly captured within a stirred cell Membrane Module from horse serum, partly due to precipitation and microfiltration, and partly due to hydrophobic interaction based Membrane adsorption, while the impurities are washed out from the device. The reversibly sequestered IgG is then released by lowering the salt concentration which favor both dissolution of the precipitated IgG and desorption of the Membrane bound IgG. The enhanced hybrid bioseparation technique improves the IgG recovery from the Membrane Module by switching from a stirring to non-stirring mode during the IgG release phase. It also reduces Membrane fouling by an appropriate pH switch. The effects of operating conditions on equine IgG capture were first systematically studied. The enhanced hybrid bioseparation technique was followed by an ultrafiltration step to remove ammonium sulfate and low molecular weight impurities. The equine IgG purity obtained under optimized conditions was 88% and its recovery was over 90%, both being significantly higher than corresponding values obtained using currently used purification techniques. Biotechnol. Bioeng. 2008;99: 625–633. © 2007 Wiley Periodicals, Inc.
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effect of Module design on the efficiency of Membrane chromatographic separation processes
Journal of Membrane Science, 2006Co-Authors: Raja Ghosh, Tiffany WongAbstract:Abstract The efficiency of Membrane chromatography is critically dependent on Membrane Module design. This paper discusses the vital role of fluid flow distribution and collection within a Membrane Module in Membrane chromatographic processes. The performances of Membrane Modules of three different diameters based on a new design which enhanced both feed flow distribution and effluent collection were compared with corresponding conventional Modules. Protein bioseparation being one of the major applications of Membrane chromatography, these studies were carried out using lysozyme as test solute. The lysozyme binding capacities of cation-exchange Membranes housed in the different Modules were measured both in the breakthrough mode and in the pulse chromatographic mode. The Membrane Modules based on the new design showed significantly higher lysozyme binding capacities than the corresponding conventional Modules. The binding capacity enhancement due to Module design increased with increase in Membrane diameter. With the largest diameter Membrane Module, the breakthrough binding capacity enhancements with the new design were in the range of 110–112%. With the same diameter Membrane Module the maximum binding capacity enhancements in the pulse chromatographic mode was found to be around 135%. The reasons for the increase in binding efficiency are explained.
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enhancement of Membrane permeability by gas sparging in submerged hollow fibre ultrafiltration of macromolecular solutions role of Module design
Journal of Membrane Science, 2006Co-Authors: Raja GhoshAbstract:Permeability in Membrane filtration processes suffers from two major limiting factors: concentration polarization and Membrane fouling. Gas-sparging, which involves bubbling of a gas in close proximity of a Membrane, is known to minimise both of these. Gas-sparged Membrane filtration is carried out either by pressurising a gas-sparged feed side or by using suction to draw the permeate through a Membrane from the un-pressurised, gas-sparged feed side. The first approach is mainly used in ultrafiltration processes. The second approach which is easier to implement and is widely used in microfiltration processes. This paper discusses the enhancement of permeability by gas-sparging in suction-driven, submerged hollow fibre ultrafiltration using two different Membrane Module types. These Modules were prepared using hollow fibre Membranes having nominal MWCO of 150 kDa and were used to ultrafilter polysaccharide solutions. Depending on the operating conditions and on the Module design, gas-sparging enhanced effective hydraulic permeability by as much as 115%. The extent of Membrane fouling was also significantly lower in the gas-sparged mode. The effectiveness of gas-sparging was found to be greater with one Membrane Module type, clearly highlighting the effect of Module design on process efficiency.
E Chardon - One of the best experts on this subject based on the ideXlab platform.
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submerged hollow fibre Membrane Module design options and operational considerations
Desalination, 2002Co-Authors: Anthony G. Fane, Sheng Chang, E ChardonAbstract:A new Membrane Module concept, the submerged hollow fibre Membrane, has been widely accepted for the wastewater Membrane bioreactor. This paper focuses on operational considerations and design aspect of the submerged hollow fibre Membrane Module. Experiments with both crossflow and ‘dead-end’ submerged systems have demonstrated that bubbling is effective in enhancing filtration performance, but the effect of gas flow rate is constrained because of the limited effect of bubbling on turbulence in two-phase flow. The experimental results also indicated that Module configuration exerts crucial effects on the performance of the system. A better filtration performance can be obtained with vertical axial fibre orientation, small fibre diameters, and a loose fibre bundle. A model describing the filtration behavior of the submerged hollow fibre at steady state shows that when the maximum initial flux is lower than the critical flux, the flux distribution along the fibre can be estimated according to a dimensionless parameter x = 4LRi−32Rm−12 which includes fibre length and radius and hydraulic resistance. When the average imposed flux is lower than the critical flux but the maximum local initial flux is higher than the critical flux, a steady state can be achieved after an initial deposition over some of the fibre length. The filtration resistance caused by the initial deposition becomes significant when the fibre radius is smaller than 0.2 mm, particularly with long fibre lengths and high ratios of average imposed flux to critical flux. The simulation also suggested that the optimal combination of fibre radius and length goes to small radius and short length.
In Seop Chang - One of the best experts on this subject based on the ideXlab platform.
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effect of internal pressure and gas liquid interface area on the co mass transfer coefficient using hollow fibre Membranes as a high mass transfer gas diffusing system for microbial syngas fermentation
Bioresource Technology, 2014Co-Authors: Muhammad Yasin, Shinyoung Park, Yeseul Jeong, In Seop ChangAbstract:Abstract This study proposed a submerged hollow fibre Membrane bioreactor (HFMBR) system capable of achieving high carbon monoxide (CO) mass transfer for applications in microbial synthesis gas conversion systems. Hydrophobic polyvinylidene fluoride (PVDF) Membrane fibres were used to fabricate a Membrane Module, which was used for pressurising CO in water phase. Pressure through the hollow fibre lumen ( P ) and Membrane surface area per unit working volume of the liquid ( A S / V L ) were used as controllable parameters to determine gas–liquid volumetric mass transfer coefficient ( k L a ) values. We found a k L a of 135.72 h −1 when P was 93.76 kPa and A S / V L was fixed at 27.5 m −1 . A higher k L a of 155.16 h −1 was achieved by increasing A S / V L to 62.5 m −1 at a lower P of 37.23 kPa. Practicality of HFMBR to support microbial growth and organic product formation was assessed by CO/CO 2 fermentation using Eubacterium limosum KIST612.