Gas Membrane Separation Of Non-ideal Phenomena

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.