【作者】 刘君腾；

【导师】 张卫东；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2009， 博士

【摘要】 中空纤维更新液膜（HFRLM）是一种新型的液膜技术,其区别于其他传统液膜过程最主要的特点是:在中空纤维管内流动的是液-液两相混合物,分散相（液膜相）液滴在流场作用下,实现更新,强化传质。本文主要以Cr（Ⅵ）为实验体系,研究了HFRLM的传质机理。通过溶剂萃取实验,研究了磷酸三丁酯（TBP）对Cr（Ⅵ）的萃取效果,以及NaOH对络合物的反萃效果,确定了萃取、反萃过程的反应方程式。采用大块液膜（BLM）实验考察了TBP作为载体对Cr（Ⅵ）的迁移性能,并类比于一级不可逆连串反应,建立了BLM传质过程的动力学模型,分析了溶质在BLM过程中的传递情况,讨论了分配系数对传质过程的影响。借助显微摄像技术,研究了中空纤维管内液-液两相的流体流动情况,获得了最直观的视觉信息,考察了中空纤维管内液滴及流动液膜的存在形态,证实了HFRLM基本理论的正确性。通过分析、总结观测结果,将中空纤维管内的流体流型划分为6大类,绘制了液-液两相流型图,对HFRLM的操作参数选择进行指导。借鉴气体分子碰撞理论和液滴聚并、破碎的相关研究成果,建立了描述液滴与流动液膜碰撞、聚并的数学模型,为定量描述由液滴引起的传质强化,深入研究中空纤维更新液膜的传质机理提供了理论基础。以阻力串联模型为基本出发点,将溶质在中空纤维管内的传质步骤分解为流动液膜与液滴之间传质、滴内传质和滴外传质3个步骤。鉴于壳程非理想流动的复杂性,同时采用理论分析和实验检验两种方法,确定了适用于本文的壳程传质关联式。在中空纤维管内,采用“表面更新扩展模型”描述液滴与流动液膜之间碰撞引起的传质强化现象;采用Higbie溶质渗透模型计算滴外传质系数。HFRLM传质过程的模型化研究,有助于其传质机理的深入分析,对HFRLM技术的放大设计以及工业化应用具有一定的指导意义。采用示踪实验讨论了HFRLM的稳定性问题,结果表明HFRLM稳定性良好,泄漏率基本低于0.01%。以传质模型为指导,系统地研究了各种体系（如Cr（Ⅵ）、Cu（Ⅱ）、青霉素）在HFRLM过程中的传质行为。从传质阻力和传质推动力两个方面,分析了液膜过程的传质机理。萃取、反萃分配系数在液膜传质过程中具有重要地位,mm’不仅影响传质的类型、速率,甚至决定了传质过程能否发生。混合方式极大地影响着HFRLM过程中各分传质阻力对总阻力的贡献,其对传质速率的影响巨大。采用HFRLM技术处理含铬废水,具有处理速度快、效果好等优点,去处率高达99.8%,废水处理后Cr（Ⅵ）含量低于0.5 mg·L^-1,满足国家排放标准。HFRLM技术在废水处理过程无二次污染产生,浓缩后废水可回收使用,是实现电镀废水闭路循环的有效手段之一。中空纤维更新液膜技术经济、环境效益显著,在电镀含铬废水处理方面有广阔的应用前景。更多还原

【Abstract】 Hollow fiber renewal liquid membrane(HFRLM) is a novel liquid membrane process.The main characteristic of HFRLM,which different from other liquid membrane processes,is that the flow in the tube-side is a liquid-liquid two-phase.In the flow fields,the dispersion phase(liquid membrane phase) renews the flow liquid membrane and so enhances the transport rate.In this thesis,a study on the mechanism of HFRLM mass transfer process is investigated using Cr(Ⅵ) as the main experimental system.The extraction efficiency of Cr(Ⅵ) by tri-n-butyl phosphate(TBP) and the stripping efficiency of complex by NaOH were studied by means of solvent extraction experiments.The extractive and stripping reactions were confirmed.The transport performance of Cr(Ⅵ) through bulk liquid membrane(BLM) process using TBP as mobile carrier was evaluated.A kinetic model was developed assuming that the Cr(Ⅵ) transport through BLM can be explained by a irreversible first-order reaction.The mass transfer behavior of Cr(Ⅵ) in BLM process was analyzed and the effect of the distribution coefficient on the mass transfer process was discussed.With the help of digital microscope camera technique,the liquid-liquid two-phase flow in the hollow fiber was investigated and a large of visual information was obtained.The existence of the droplets and the flow liquid membrane in the hollow fiber was proved.The correctness of the HFRLM basic theory was confirmed.According to the video,the flow pattem of the two-phase in the hollow fiber was divided into 6 kinds and a flow pattern diagram was drawn,which would be help for the determination of the operation parameters.Make reference to the molecule collision theory as well as the study of the droplet coalescence/breakage behavior,a mathematic model was proposed to describe the collision and coalescence between the droplet and the flow liquid membrane.This model provides a theory basis for the quantitative calculation of the mass transfer intensification and the deep investigation of HFRLM mass transfer mechanism.On the basis of the resistance-in-series model,the mass transfer process in the tube-side was divided into 3 steps:(1) the transport between the flow liquid membrane and the droplet,(2) the transport in the droplet and(3) the transport out of the droplet.In view of the complexity of the non-ideality in the shell side,both theory analysis and experimental verification were used to determine the appropriate shell side mass transfer correlation.Inside of the hollow fiber,the surface-renewal-stretch model was used to describe the mass transfer intensification phenomena caused by the collision between the droplets and the flow liquid membrane.Higbie permeation theory was used to describe the mass transfer process out of the droplet.The modeling study of HFRLM,would be helpful for the deep analysis of the mass transfer mechanism,and also give guidance to the HFRLM scaling up design and industrial application.The stability of the HFRLM was studied by monitoring the leakage of the tracer.Results show that the stability of the HFRLM was good and the leakage is less than 0.01%.Under the guidance of the mathematical model,the mass transfer behavior of various systems(such as Cr(Ⅵ),Cu(Ⅱ) and PG) through the HFRLM was studied systematically.The mechanism of the liquid membrane mass transfer process was analyzed from the point of view of the resistance and the driving force.The extraction/stripping distribution coefficient play an important role in the liquid membrane process.They affect the type and the rate of the transport,and even determine whether it will take place or not.The contribution of the individual mass transfer resistance to the overall resistance was affected greatly by the mixing method.HFRLM was used for chromium(Ⅵ)-containing wastewater treatment, which had advantages of rapidness and excellent treatment.The removal efficiency of chromium(Ⅵ) is bigger than 99.8%,and the Cr(Ⅵ) concentration in the treated outlet wastewater is less than 0.5 mg·L-1,which is lower than national discharge standards.No second-pollution in the whole treatment process,and the concentrated solution could be reused.HFRLM and has obvious economic and environmental benefits.HFRLM can be widely used in treatment of chromium(Ⅵ)-containing industrial wastewater.更多还原