Design of metallic nickel hollow fiber membrane modules for pure hydrogen separation

Cost‐effective and robust nickel (Ni) membrane for H₂ separation is a promising technology to upgrade the conventional H₂ industries with improved economics and environmental benignity. In this work, Ni hollow fibers (HFs) with one closed end were fabricated and assembled into a membrane module for pure H₂ separation by applying vacuum to the permeate side. The separation behavior of the HF module was investigated both experimentally and theoretically. Results indicate that H₂ recovery can be improved significantly by changing the operation conditions (temperature or feed pressure). Ni HF is a promising membrane geometry, but the negative effect of pressure drop when H₂ passes through the lumen cannot be ignored. Under the vacuum operation mode, there is little difference in term of H₂ recovery efficiency whether the feed gas flow is controlled in countercurrent or recurrent operation. This work provides important insight to the development of superior membrane H₂ separation system. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3662–3670, 2018     

镍基非对称中空纤维膜用于乙醇自热重整制氢

采用纺丝-烧结技术制备了具有内表面致密皮层的外支撑式金属镍非对称中空纤维膜,并用于乙醇自热重整（EATR）制氢,研究了温度、进料流速、吹扫气流速、水醇比（S/C）以及氧醇比（O₂/C）等操作条件对膜制氢性能的影响。结果表明,金属镍非对称中空纤维膜既具有优异的EATR催化活性,又有良好的透氢性能。在500～1000℃、S/C=4、O₂/C=0.8的条件下乙醇可完全转化,H₂产率和H₂渗透通量可分别达到81.59%和13.99 mmol/（m²·s）,增加进料中氧气含量可显著抑制膜表面积炭,但同时也会降低氢气产率和一氧化碳选择性。     

Characterization of crosslinked hollow fiber membranes

As the applications for polymeric membranes expand, new challenges arise. One of the largest of these challenges is the plasticization caused by strongly swelling penetrants such as carbon dioxide at elevated pressures. A considerable amount of material research has investigated crosslinking of dense film membranes to increase plasticization resistance. This paper extends such materials research to include more practically relevant asymmetric hollow fibers. Crosslinkable polyimide fibers were spun and an ester crosslinking reaction was studied using chemical and spectroscopic techniques to characterize the extent of crosslinking and to relate the effect of the reaction on fiber stability. CO₂ permeance and CO₂/CH₄ selectivity were studied at a variety of pressures and temperatures over time to yield indications of real-world separation performance.     

The removal of toxic heavy metal cations by polysulfonebenzylthiourea reactive hollow fiber ultrafiltration membranes

The hollow fiber asymmetric matrix membranes were prepared with phase inversion by utilization of the chloromethyl polysulfone/polyethylene glycol/DMAC casting solution and chloromethyl polysulfone as membrane materials. The effects of composition of spinning casting solution and process parameters of dry–wet spinning on the structure of hollow fiber matrix membrane were investigated. Through the reaction between matrix membrane and thiourea, the highly qualified polysulfonebenzylthiourea reactive hollow fiber ultrafiltration membranes were able to afford. The adsorption isotherms of the polysulfonebenzylthiourea hollow fiber membrane for Cd²⁺ and Zn²⁺ were determined and the effects of mobile phase conditions and the operating parameters on removal performance of the polysulfonebenzylthiourea hollow fiber membrane for Cd²⁺ and Zn²⁺ were also investigated. The experimental results showed that adsorption isotherms of Cd²⁺ and Zn²⁺ could be described by the Langmuir isotherm, the polysulfonebenzylthiourea hollow fiber membrane could be operated at high feed flow rate, and a large‐scale removal of Cd²⁺ and Zn²⁺ could be realized. According to required recovery of Cd²⁺ and Zn²⁺ and the saturation degree of polysulfonebenzylthiourea hollow fiber membrane, the optimum loading amount of Cd²⁺ and Zn²⁺ should be selected in the actual removal of Cd²⁺ and Zn²⁺. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of several types of polyvinyl butyral hollow fiber membranes by thermally induced phase separation

Hollow fiber membranes were prepared by thermally induced phase separation from three types of polyvinyl butyral (PVB) and a blend of two of these polymers. Although the difference in the chemical composition of the PVB polymers used was not remarkable, their respective membrane performances were quite different. With a high phase separation temperature the pore size of the prepared membrane was large, because structure growth occurred for a long time. Water permeability tests of the wet membranes showed the results that corresponded to the pore sizes of the membranes. By contrast, the results for the dried membrane appeared to be related to the hydrophilicity of the PVB polymer and independent of pore size in the wet condition. Although the membrane with high wettability had low mechanical strength, the membrane from the polymer blend of two different PVB polymers showed adequate wettability and mechanical strength. This produced a hollow fiber membrane with favorable characteristics for application in water treatment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polyvinyl alcohol/polysulfone (PVA/PSF) hollow fiber composite membranes for pervaporation separation of ethanol/water solution

Polysulfone (PSF) hollow fiber membranes were spun by phase‐inversion method from 29 wt % solids of 29 : 65 : 6 PSF/NMP/glycerol and 29 : 64 : 7 PSF/DMAc/glycol using 93.5 : 6.5 NMP/water and 94.5 : 5.5 DMAc/water as bore fluids, respectively, while the external coagulant was water. Polyvinyl alcohol/polysulfone (PVA/PSF) hollow fiber composite membranes were prepared after PSF hollow fiber membranes were coated using different PVA aqueous solutions, which were composed of PVA, fatty alcohol polyoxyethylene ether (AEO₉), maleic acid (MAC), and water. Two coating methods (dip coating and vacuum coating) and different heat treatments were discussed. The effects of hollow fiber membrane treatment methods, membrane structures, ethanol solution temperatures, and MAC/PVA ratios on the pervaporation performance of 95 wt % ethanol/water solution were studied. Using the vacuum‐coating method, the suitable MAC/PVA ratio was 0.3 for the preparation of PVA/PSF hollow fiber composite membrane with the sponge‐like membrane structure. Its pervaporation performance was as follows: separation factor (α) was 185 while permeation flux (J) was 30g/m²·h at 50°C. Based on the experimental results, it was found that separation factor (α) of PVA/PSF composite membrane with single finger‐void membrane structure was higher than that with the sponge‐like membrane structure. Therefore, single finger‐void membrane structure as the supported membrane was more suitable than sponge‐like membrane structure for the preparation of PVA/PSF hollow fiber composite membrane. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 247–254, 2005     

新型中空纤维膜接触器用于乙醇/水体系分离的探索

引言 醇/水体系分离一直是化工生产中的重要环节,高效的醇/水分离技术能够使醇的产量大大提高,满足日益增长的工业生产需求.传统的分离方法如精馏、萃取等已经相当成熟,但是这些方法在工业生产过程中能耗巨大,越来越受到面临能源资源匮乏的当代社会的关注和制约.在此背景下,面向高效、节能的新型膜接触分离器应运而生,如Alan等[1]指出,工业化或半工业化的过程已经包括膜吸收、膜萃取以及渗透蒸馏等多个耦合分离单元[2-6].     

稀释剂对TIPS法等规聚丙烯中空纤维微孔膜孔径及其连通性的影响

热致相分离（TIPS）法制备等规聚丙烯（iPP）中空纤维微孔膜,邻苯二甲酸二丁酯（DBP）与邻苯二甲酸二辛酯（DOP）的混合溶剂作为制膜稀释剂。干/湿氮气流量法测定了α（稀释剂中DBP的质量分数）和β（铸膜液中聚合物的质量分数）对膜样品的平均孔径及其分布的影响,并采用膜孔曲折因子定量表达膜孔连通性。发现全部膜样品均体现窄孔径分布特征。对于相同的β, α增加导致平均孔径及膜孔连通性下降。α=0.20时,β增加,膜的平均孔径先增加后降低,膜孔曲折因子稍下降; α=0.35或0.50时,β增加,膜的平均孔径降低,膜孔曲折因子下降。膜孔连通性体现了膜内部的拓扑结构,共溶剂组成和铸膜液固含量能够调节iPP中空纤维微孔膜的孔径及其连通性。     

PVDF-ZrO2复合中空纤维膜在乳化油废水中的应用

针对普通聚偏二氟乙烯(PVDF)中空纤维膜具有疏水性强、易污染的应用缺陷,在制备纳米粒子掺杂改性的PDVF-ZrO2复合中空纤维膜前期工作基础上,表征了其微观结构,并考察了其在油水体系中的分离效果。微观结构检测表明,随着ZrO2含量的增大,复合膜的断面微观结构完成由指状大孔向海绵状结构的转化。PDVF-ZrO2复合膜的接触角和牛血清蛋白(BSA)吸附实验结果显示其亲水性及抗污染性能均得到了提高。进一步考察了PDVF-ZrO2复合中空纤维渗透分离性能,ZrO2纳米粒子质量分数为0.3%时,显示了最佳的渗透性能。在乳化油废水处理过程中,在油质量浓度为1 g/L,操作压力为0.1MPa、搅拌强度为20 r/min条件下,通量为105 L/(m2.h),TOC去除率为95.4%,表明具有较好的废水处理效果。     

中空纤维渗透汽化膜分离研究现状与展望

本文综述了中空纤维渗透汽化膜分离的研究进展,包括中空纤维支撑膜的制备、复合膜的制备方法、中空纤维渗透汽化膜的工业应用和中空纤维渗透汽化膜传质特性等几个方面,对这个方面所存在的问题以及今后发展方向进行了展望.     

Fundamental understanding of the effect of air‐gap distance on the fabrication of hollow fiber membranes

The objectives of this work are, fundamentally, to understand hollow fiber membrane formation from an engineering aspect, to develop the governing equations to describe the velocity profile of nascent hollow fiber during formation in the air gap region, and to predict fiber dimension as a function of air‐gap distance. We have derived the basic equations to relate the velocity profile of a nascent hollow fiber in the air‐gap region as a function of gravity, mass transfer, surface tension, drag forces, spinning stress, and rheological parameters of spinning solutions. Two simplified equations were also derived to predict the inner and outer diameters of hollow fibers. To prove our hypotheses, hollow fiber membranes were spun from 20 : 80 polybezimidazole/polyetherimide dopes with 25.6 wt % solid in N,N‐dimethylacetamide using water as the external and internal coagulants. We found that inner and outer diameters of as‐spun fibers are in agreement with our prediction. The effects of air‐gap distance or spin‐line stress on nascent fiber morphology, gas performance, and mechanical and thermal properties can be qualitatively explained by our mathematical equations. In short, the spin‐line stresses have positive or negative effects on membrane formation and separation performance. A high elongational stress may pull molecular chains or phase‐separated domains apart in the early stage of phase separation and create porosity, whereas a medium stress may induce molecular orientation and reduce membrane porosity or free volume. Scanning electron microscopic photographs, coefficient of thermal expansion, and gas selectivity data confirm these conclusions. T_g of dry‐jet wet‐spun fibers is lower than that of wet‐spun fibers, and T_g decreases with an increase in air‐gap distance possibly because of the reduction in free volume induced by gravity and elongational stress. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 379–395, 1999     

CO2/CH4 separation using inside coated thin film composite hollow fiber membranes prepared by interfacial polymerization

Carbon dioxide(CO_2) is greenhouse gas which originates primarily as a main combustion product of biogas and landfill gas. To separate this gas, an inside coated thin film composite(TFC) hollow fiber membrane was developed by interfacial polymerization between 1,3–cyclohexanebis–methylamine(CHMA) and trimesoyl chloride(TMC). ATR-FTIR, SEM and AFM were used to characterize the active thin layer formed inside the PSf hollow fiber. The separation behavior of the CHMA-TMC/PSf membrane was scrutinized by studying various effects like feed gas pressure and temperature. Furthermore, the influence of CHMA concentration and TMC concentration on membrane morphology and performance were investigated. As a result, it was found that mutually the CHMA concentration and TMC concentration play key roles in determining membrane morphology and performance. Moreover, the CHMA-TMC/PSf composite membrane showed good CO_2/CH_4 separation performance. For CO_2/CH_4 mixture gas(30/70 by volume) test, the membrane(PD1 prepared by CHMA 1.0% and TMC 0.5%) showed a CO_2 permeance of 25 GPU and the best CO_2/CH_4 selectivity of 28 at stage cut of 0.1. The high CO_2/CH_4 separation performance of CHMA-TMC/PSf thin film composite membrane was mostly accredited to the thin film thickness and the properties of binary amino groups.     

聚氯乙烯中空纤维多孔膜研究进展

介绍了聚氯乙烯(PVC)膜材料的特点及其中空纤维膜的3种主要制备方法,即溶液相转化法、双螺杆挤出纺丝-拉伸法和同质增强法。分别阐述了PVC中空纤维膜3种制备方法的技术路线和致孔机理,并回顾了其研究进展,展望了PVC中空纤维膜的发展及应用前景。     

Preparation and membrane performance of poly(ethylene-co-vinyl alcohol) hollow fiber membrane via thermally induced phase separation

Poly(ethylene-co-vinyl alcohol) (EVOH) hollow fiber membranes with ultrafiltration performance were prepared from EVOH/glycerol systems via thermally induced phase separation (TIPS). The diluent glycerol was used as bore liquid to make a lumen of the hollow fiber for the purpose of prevention of the diluent evaporation and the larger pores formation at the inner surface of the hollow fiber. The obtained hollow fiber membranes showed asymmetric structures with skin layer near the outer surface, the larger pores just below the skin layer and the smaller pores near the inner surface. The formation of the larger pores near the outer surface was due to the enhanced pore growth by the water penetration. Some primary factors affecting the structure and performance of the membranes such as ethylene content (EC) in EVOH, cooling water bath temperature and take-up speed were studied extensively. The water permeability can be improved by increasing the water bath temperature and the take-up speed and by decreasing the EC. Both the pore size at the outer surface and the connectivity between the pores have to be considered together to understand the experimental result of the water permeability and the solute rejection.     

二乙胺导向合成中空纤维负载型SAPO-34分子筛膜

采用价格低廉的二乙胺为模板剂，通过球磨晶种诱导二次生长法制备中空纤维负载型SAPO-34分子筛膜用于CO₂/CH₄气体分离。系统考察了诱导晶种大小、膜合成液中二乙胺含量、铝源含量与晶化时间对膜结构形貌以及分离性能的影响。结果表明：相比于原始晶种，球磨晶种诱导制备SAPO-34分子筛膜层更加致密。随着膜合成液中二乙胺含量增加，膜表面分子筛晶体逐渐由SAPO-11向SAPO-34转变，当二乙胺含量过高时，载体表面未形成SAPO-34膜。当合成液中铝源含量较低时，分子筛膜晶化不够完全，当铝源含量过高时，膜表面晶体粒径逐渐减小甚至难以成核，膜层厚度减薄，不易生成连续的膜层。随着晶化时间的增加，膜层厚度逐渐增加，膜表面趋于致密。当膜合成液摩尔组成为1.0Al₂O₃∶0.9P₂O₅∶0.6SiO₂∶2.0DEA∶100H₂O，晶化时间为36 h时，球磨晶种诱导制得的SAPO-34分子筛膜分离性能最佳，膜的CO₂渗透性为1.11×10^?6 mol·m^?2·s^?1·Pa^?1，CO₂/CH₄分离选择性达80。     

Enhancing CO2 absorption efficiency using a novel PTFE hollow fiber membrane contactor at elevated pressure

The internal structure design of membrane module is very important for gas removal performance using membrane contactor via physical absorption. In this study, a novel membrane contactor developed by weaving polytetrafluoroethylene (PTFE) hollow fibers was applied to remove CO₂ from 60% N₂ + 40% CO₂ mixture (with CO₂ concentration similar to that of biogas) at elevated pressure (0.8 MPa) using water as absorbent. Compared with the conventional module with randomly packed straight fibers, the module with woven PTFE fibers exhibited much better CO₂ absorption performance. The weaving configuration facilitated the meandering flow or Dean vortices and renewing speed of water around hollow fibers. Meanwhile, the undesired influences such as channeling and bypassing were also eliminated. Consequently, the mass transfer of liquid phase was greatly improved and the CO₂ removal efficiency was significantly enhanced. The effects of operation pressure, module arrangement, feed gas, and water flow rate on CO₂ removal were systematically investigated as well. The overall mass‐transfer coefficient (K_OV) varied from 1.96 × 10^?5 to 4.39 × 10^?5 m/s (the volumetric mass‐transfer coefficient K_La = 0.034–0.075 s^?1) under the experimental conditions. The CO₂ removal performance of novel woven fiber membrane contactor matched well with the simulation results. © 2017 American Institute of Chemical Engineers AIChE J, 64: 2135–2145, 2018     

Pervaporative separation of butanol using a composite PDMS/PEI hollow fiber membrane

In the study, the separation and purification of butanol was carried out using the composite hollow fiber membrane having the active layer of polydimethylsiloxane (PDMS) on the macroporous support of polyetherimide (PEI). The pervaporation results with the initial butanol concentration showed a trade-off between flux and separation factor. However, both the flux and the separation factor increased as the operating temperature increased. The pervaporation results showed the butanol flux and the separation factor were higher than those of the reported results. In this study, butanol was concentrated by the pervaporation as a feasibility study for the biofuel applications.     

Multichannel mixed‐conducting hollow fiber membranes for oxygen separation

A multichannel mixed‐conducting hollow fiber (MMCHF) membrane, 0.5 wt % Nb₂O₅‐doped SrCo_0.8 Fe_0.2O_3‐δ (SCFNb), has been successfully prepared by phase inversion and sintering technique. The crystalline structure, morphology, sintering behavior, breaking load, and oxygen permeability of the MMCHF membrane were studied systematically. The MMCHF membrane with porous‐dense asymmetrical microstructure was obtained with the outer diameter of 2.46 mm and inner tetra‐bore diameter of 0.80 mm. The breaking load of the MMCHF membrane was 3–6 times that of conventional single‐channel mixed‐conducting hollow fiber membrane. The MMCHF membrane showed a high oxygen flux which was about two times that of symmetric capillary membrane at similar conditions as well as a good long‐term stability under low oxygen partial pressure atmosphere. This work proposed a new configuration for the mixed‐conducting membranes, combining advantages of multichannel tubular membrane technology and conventional hollow fibers. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1969–1976, 2014     

中空纤维更新液膜处理含镍电镀废水

利用自制疏水聚偏氟乙烯(PVDF)中空纤维膜组件对中空纤维更新液膜处理含镍电镀废水过程中的影响因素进行了研究,考察了液膜两侧液相浓度、流速、萃取剂P204所占油相比例等因素对镍去除率的影响.并把中空纤维更新液膜和中空纤维支撑液膜处理效果进行了对比.     

Two‐dimensional simulation of hollow fiber membrane fabricated by phase inversion method

In the steady fabricating process, two‐dimensional hollow fiber membrane near the spinneret was numerically simulated using the finite element method (FEM). The unknown positions of free surface and moving interface were calculated simultaneously by the velocity and pressure fields. The effects of seven relevant parameters, i.e., inertia term, gravity term, dope flow rate, bore flow rate, dope viscosity, tensile force, end velocity and non‐Newtonian on the velocity and diameter profile were studied. On the basis of the simulated results, the inertia term in hollow fiber‐spinning process was safely neglected in low speed, while the effect of gravity was not be neglected. Besides, the outer diameter of the fibers increased with an increase of dope flow rate and bore flow rate; Large tensile force or large end velocity could cause large deformation in the air gap; larger viscous dope solution tended to make less deformation in the air gap. It was found that an increase of the dope flow rate at small dope flow rate resulted in an increase of the inner diameter, while at large dope flow rate, it decreased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2067–2074, 2006