气体膜分离中非理想现象的研究

【作者】 魏关锋；

【导师】 贺高红；

【作者基本信息】 大连理工大学 ， 化学工程， 2000， 硕士

【摘要】 自从氢气回收和富氧分离大规模工业化以来，人们对气体在膜中的渗透机理进行了大量的研究。然而随着科学研究的深入和生产实践的发展，膜过程中原本存在的一些现象和出现的一些新现象对分离的影响变得更加突出，这些因素影响膜分离的效果，使分离过程与理想状况发生偏离。本文以空气分离与气体脱湿为例，考察了一些非理想因素对分离效果的影响。 空气分离是一类常规的膜-气分离体系，实验中发现浓度极化和组分竞争等因素同时存在于这个膜分离过程中，然而对这些因素单独进行研究并不容易，因此引入一个总包参数Ni，对这些因素对分离效果发生的作用综合进行研究。实验考察了温度、尾气量、进气压力对分离过程的影响，发现：温度的升高、尾气量的增加有利于消除实际分离过程与理想分离过程的偏离状况，而压力的增加使实际分离过程与理想的分离过程偏离程度增加。这三种因素是通过浓度极化、组分竞争等非理想因素影响实际膜分离器分离效果的。 对膜法气体脱湿而言，同样存在一些非理想因素对分离效果产生重大的影响。基于Kelvin方程和膜的结构考虑，水蒸气可能在疏松多孔的支撑层内发生毛细冷凝现象。因此，这类膜-气体系有自己独特的渗透行为，不能仅用溶解扩散机理对其传质与分离行为进行解释。本文主要研究了吹扫气、进气压力及水氧（氮）比对分离过程影响的一些规律。结果表明吹扫气的引入、毛细凝聚现象的发生能够强化过程的传质与分离，有利与分离效果的提高。本文建立了水蒸气在膜中的渗透机理模型，计算了毛细凝聚现象对水蒸气传质过程的影响。更多还原

【Abstract】 Since hydrogen recovery and oxygen enrichment are industrialized on large scale, a lot of researching work have been done on gas permeation mechanism in membrane. However with the thorough study and fast development of industrial practice activity, some phenomena existed and some new ones happening in membrane separation process have more and more significant effect on membrane separation. These factors make the actual separation processes diverge from that of ideal separation. In this paper air separation and gas dehydration are took for examples to study the effects on separation results of some nonideal elements.Oxygen and Nitrogen enrichment is a kind of general membrane-gas separation system. In experiment many factors including concentration polarization and component competition are found coexist at the same time, but it is difficult to study them solely. So a parameter Ni is introduced in this paper, which can be used to estimate the inilunce of all these factors on separation. Temperature, retentate gas quantity and feed gas pressure are studied on their effcts on separation. Experiment results show that the higer the temperature i~ and the more retentate gas use, the little difference that lies between actual and ideal separation processes. On the contrary, raising feed pressure lead the actual separation to departing from the ideal one. These three factors exert influnce on separation through concentration polarization and component competition.As regard to gas dehydration, there are also some obvious nonideal factors which have important effects on separation. On considering Kelvin equation and the structure of composite membrane, capillary condensation phenomenon occur in tiny pores of the spongy support layer. Hence this kind of membrane-gas system has its own permeation characteristic, whose transport and separationbehavior can not be clarified only by 揝olution-diffusion mechanism? A new mechanism was established. In this paper , the necessary of sweep gas, the ratio of water versus oxygen (Nitrogen) of the feed gas as well as its pressure are studied to examine their effects on separation process. From the experiment results some conclusions can be drawn that the introducing of sweep gas to permeat side and the occuring of capillary condensation in membrane enhance water transport while repress the oxygen (Nitrogen) transport and so enlarge the separation factor, in other words, their effects is beneficial to membrane separation result. In this paper a permeation mechanism of water vapor through membrane is set up and the effect of capillary condensation on transport of water vaper is calculated.更多还原