中空纤维更新液膜传质性能的研究

研究了中空纤维更新液膜(HFRLM)技术的传质性能.以CuCl2水溶液-10%P204 煤油-盐酸为实验体系,研究结果表明,中空纤维更新液膜技术可以实现同级萃取-反萃,且总传质系数随料液相流速的增大而增大,在实验条件下,总传质系数受反萃相流速的影响较小.实验研究探讨了混合方式(料液与萃取剂混合和反萃剂与萃取剂混合)和体系分配系数对传质性能的影响.实验结果表明,由于相间分配系数的不同,总传质系数受混合方式的影响较大,以分配系数较大的一相与萃取相混合流经管程的方式对传质过程有利.     

乳化液膜传质动力学模型的研究进展

本文综述了乳化液膜传质动力学模型的发展状况：从最简化的平板模型,空心球模型到较为详尽的渐进前沿模型乃至其他传质模型;对各传质动力学模型的优缺点进行了比较和评价,指出了不同模型的应用范围。在此基础上,介绍了改进的渐进前沿模型;同时,对传质动力学模型今后的发展方向进行了预测。     

液膜脱酚的综合传质模型

本文研究了液膜传质过程中的各种复合因素,提出描述该过程的综合传质模型.考虑到液滴内外传质阻力及膜破裂等因素的影响,本模型将著名的“渐近前沿模型”作适当调整.模型参数k_o和B_m由Powell优化方法最优拟合实验值决定.实验结果证实本文所建议的传质机理模型比较符合实际,并具有适用的弹性.     

Study of Operating Condition Affecting Mass Transfer Rate in Liquid Surfactant Membrane Process

Abstract

The removal of acetic acid from its dilute solution by liquid surfactant membrane (LSM) has been investigated by batch test. Some important factors affecting the mass transfer rate, such as surfactant and its content, stirring speed, ratio of reagents, treating ratio and volume ratio of membrane phase to internal phase, have been studied. The breakage and the swelling of the emulsion have also been investigated. The transport mechanism of HAc across the membrane in the system is referred to as I-II facilitated transport mechanism.     

Mass Transfer in Liquid–Liquid Systems

A formal criterion for determining the phase controlling mass transfer in liquid–liquid systems is proposed. Experimental data on mass transfer in the continuous phase are generalized for the external and mixed mass-transfer problems.     

Hydrodynamic Effects in Liquid Membrane Transfer

Abstract

An experimental apparatus was developed which permitted the thickness of liquid membranes to be measured. The observed values for the thickness were of the order of 0.01 cm which is considerably in excess of those values previously reported in the literature. The experimentally observed data were favorably compared to the thicknesses computed using boundary layer theory. Finally, dimensional analysis was used to develop a correlation of the computed membrane thickness as a function of the droplet diameter and system properties.     

支撑液膜萃取乳酸传质模型

本文对使用支撑液膜(Supported Liquid Membrane)从水溶液中革取乳酸(HL)的过程进行了理论分析,经过适当的简化,推导出支撑液膜革取乳酸的传质模型。对模型进行了实验验证,测得了膜的弯曲因子及过程的促进因子,模型计算值与实验值相吻合,同时得出膜内载体三烷基氧磷(TRPO)与乳酸形成的萃合物分子式为HL·TRPO。     

Mass Transfer Analysis of CO2 Capture by PVDF Membrane Contactor and Ionic Liquid

Post‐combustion processes based on ionic liquids (ILs) and membrane contactors are attractive alternatives to traditional systems. Here, a gas stream composed of 15 % CO₂ and 85 % N₂ flowed through the lumen side of a hollow‐fiber membrane contactor containing poly(vinylidene fluoride)‐IL (PVDF‐IL) fibers. The IL 1‐ethyl‐3‐methylimidazolium acetate [emim][Ac] served as an absorbent due to its high chemical absorption and CO₂ solubility. The overall mass transfer coefficient (K_overall), activation energy (E_a), and resistances of the hollow‐fiber membrane were quantified. The K_overall value was one order of magnitude higher than those reported in previous works with conventional solvents, and the E_a was lower than formerly stated values for other solvents. A theoretical simulation was conducted to estimate the operational parameters required for 90 % CO₂ capture and to quantify intensification effects related to CO₂ absorption in a packed column.     

Membrane Partition and Mass Transfer in Ultrafiltration

Abstract

Through ultrafiltration experiments with a macromolecular solution of dextran and a suspension of bentonite, it is shown how the understanding of mass transfer phenomena involved in ultrafiltration can be improved if several limiting mechanisms working simultaneously over different parts of a same membrane are taken into account. This partition is determined according to the operating conditions as well as the characteristics of the treated fluid. This approach is convenient to describe an entire range of experimental variations in solvent and solute transfer through hollow fiber membranes induced either by macromolecular concentration polarization or by particles fouling. It is shown that reversible fouling can have effects as dramatic as irreversible fouling (pore plugging) in some circumstances.     

液体表面活性剂膜的传质模型

本文提出了一个新的关于液膜传质的模型.该模型不仅考虑了溶质在乳状液球内核中的渗透过程,还考虑了由表面活性剂所致的界面阻力升高效应,因而更加准确地描述了液膜体系的传质过程.该模型的另一个特点是考虑了在传质过程中膜的破裂,从而使数学模型更加迫近液膜体系的实际情况.实验结果与理论分析均表明,溶质透过乳状液外围的表面活性剂薄层的分子扩散是整个液膜传质过程的速率控制段.这一结论将导致对液膜结构更加深刻的理解,并将有助于液膜体系的改进.     

Liquid/Solid Mass Transfer in Fixed Beds

The liquid/solid mass transfer behavior of a fixed bed of cylinders was studied using the diffusion‐controlled dissolution of copper in acidified potassium dichromate. Variables studied were solution velocity and cylinder diameter. For a steady flow, the data were correlated for the conditions 25 < Re < 600 and Sc = 990 by the equation Sh = 2.65 Sc^0.33 Re^0.5. A comparison between the present data and previously obtained data for a fixed bed of Raschig rings has revealed that cylinder packing produces higher rates of mass transfer than Raschig rings.     

膜萃取过程的传质特性研究

膜萃取是一种新型的分离技术。本文在中空纤维膜器中研究了膜萃取过程的传质特性。通过四种不同体系的实验,求取了基于水相的总传质系数,提出了求算膜萃取过程中各分传质系数k_(?)、k_(?)、k_(?)的半经验关联式。研究表明,减小膜阻可以强化膜萃取过程,提高过程的总传质系数.比较和分析膜萃取过程中各部分传质阻力,可以看出,对于萃取相平衡常数m1的体系应选用疏水膜器,对于m1体系则应选用亲水膜器。     

Mass Transfer Simulation of Gold Extraction in Membrane Extractors

The extraction of gold in membrane extractors was theoretically investigated. Extraction of gold in the form of $ {\rm Au(CN)}_2^- $ in a solution of n‐heptane and synergistic extractants of LIX79+TOPO was studied. The membrane extractor consists of three sections: the tube side, the membrane, and the shell side. Conservation equations were derived for $ {\rm Au(CN)}_2^- $ in the membrane module and were numerically solved based on finite element method. Simulations were conducted through solving the momentum and mass transfer equations simultaneously. It was indicated that as the feed flows within the tube side, it moves into the membrane due to the concentration difference, and then gets swept by the moving extractants within the shell side. The distribution of solute concentration in the membrane contactor was obtained. Simulation results showed increasing the feed flow rate reduces the extraction efficiency, while doing the same for the organic phase flow rate does not change the extraction efficiency.     

乳状液膜分离Zn^2＋的界面传质阻力及传质模型

用Ｌｗｅｉｓ恒界面传质池对乳状液膜分离Ｚｎ＾２＋的传质阻力进行实验研究，结果表明由于表面活性剂单分子层的形成，使界面传质阻力占整个传质阻力的８５％。在此基础上所建立的既考虑界面传质阻力又考虑膜破碎的液膜传质模型能使用理论计算值与实验测定值符合较好。     

Mass Transfer Investigation of Liquid Membrane Transport of Gold (III) by Methyl Isobutyl Ketone Mobile Carrier

Extraction of Au^III ions by an emulsion liquid membrane (ELM) system with methyl isobutyl ketone (MIBK) as the mobile carrier and also liquid‐liquid extraction of Au^III from aqueous solutions have been studied. Experiments on the transport of the gold ions in a liquid‐liquid extraction system and stripping of the extracted ions from the organic phase as well as the extraction by a three‐phase W/O/W emulsion liquid membrane system have been performed. The results showed that even when the distribution coefficient of the diffusing species in the phases is small, the extraction by emulsion liquid membranes would be an effective process. A first‐order extraction rate was proposed and examined for the extraction system.     

Effect of Membrane Structural Characteristics on Mass Transfer in a Membrane Absorption Process

Carbon dioxide is absorbed by de-ionized water or NaOH aqueous solution in the unsteady-state membrane absorption process. A theoretical model has been developed to describe the mass transfer behavior in the liquid phase, in which the effects of membrane structural characteristics are investigated. The concentration profiles in the liquid phase are calculated as a function of time. When the membrane porosity is relatively high or the pore size is relatively small, the solute concentration profile near the membrane surface can get homogeneous instantly due to the short distance between adjacent pores. In this case, the existence of the porous membrane has less effect on the mass transfer process. However, when the membrane porosity is relatively low or the pore size is relatively large, the distance between the adjacent pores is large, so the concentration profile near the membrane surface is hard to get homogeneous during the absorption process. Therefore, the concentration profile can be influenced significantly by the membrane structural characteristics, which means that the membrane structure has a significant effect on the mass transfer in liquid phase. Moreover, the chemical reaction in the liquid phase makes it difficult for the concentration profile near the membrane surface to get homogeneous. The disturbance in the liquid phase caused by the gas flow and pressure fluctuation is also taken into account in the model, and the model results agree well with the experimental data.     

界面性质对气液传质的影响

界面性质对气液传质有重要影响。分子通过界面时需克服界面自由能，界面两侧的浓度不一致。本文导出了两者之间的关系     

强制气流作用下溶液蒸发过程的传质规律

针对强制气流作用下溶液的蒸发过程,在分析气液相间力学特性的基础上,根据Levich涡流衰减理论和边界层理论,将气流流动状态与相间传质结合,研究了湍流气流横掠液面过程中气液相间的传质变化规律,分析了雷诺数、气流流道结构及普朗特混合长度对传质的影响,得到了气液相间的湍流质扩散系数的变化规律,湍流气流横掠液面条件下的对流传质准则数Sh=0.221Sc1/3Rex1/2. 结果表明,湍流扩散系数、传质系数与气流的流动状态密切相关,气流流道结构对气液相间的传质有重要影响.     

气隙式膜蒸馏传递过程的研究

本文用气隙式膜蒸馏装置测定了膜两侧流体的温度、流量及料液浓度对膜蒸馏通量的影响,并从理论上描述了传热、传质过程,建立了可以预测膜蒸馏过程渗透通量的数学模型.实验结果与模型预测吻合较好.     

Hydraulics and Mass Transfer Efficiency of a Commercial-Scale Membrane Extractor

Abstract

In recent years there has been significant interest in utilizing microporous hollow fiber membranes for liquid-liquid extraction. The membrane extractor resembles the shell and tube heat exchanger with the tube section composed of 1000–2500 fibers/in². The diameter of each fiber is approximately 300 microns. In this process, the feed may be passed through the shell side, while the solvent is passed through the fiber side, or vice versa. Mass transfer occurs across the liquid-liquid interface formed in the pores of the fiber wall. The advantages of this technology are high throughput capacities, independence of density difference between the feed and solvent, and potentially high mass transfer areas. The mass transfer performance of an available commercial scale nonbaffled membrane extraction module was determined to be lower than expected from results obtained in smaller scale modules. Mass transfer studies of a commercial-scale membrane extraction module at the Separations Research Program have shown that a significant portion of the fibers are bypassed by the shell side fluid and consequently only a fraction of the total fiber surface area is utilized. A hydraulic study using a dye tracer technique verified this finding with an aqueous flow on the shell side. A model which incorporates mass transfer correlations reported by others has been developed and shown to have excellent agreement with the experimental data obtained. In this paper, the efficiency of the membrane extractor is compared with conventional spray, sieve tray, and packed columns; the effect of shell side bypassing is also presented.