聚酰亚胺复合膜的制备及其在沼气提纯中的应用

Propration of polyimide composite membrane and its application in biogas purification

为解决沼气分离过程中单级膜过程产物CO_(2)纯度低及CH4的损失率较高等问题,通过界面聚合法制备了具有超高分离性能的具有聚酰亚胺分离层的复合膜,研究了操作温度、进料侧压力及切割比等因素对分离效果的影响。结果表明:该膜适用的温度及压力范围较广,不同操作条件下的膜均表现出了优异的分离性能,产出的CO_(2)纯度高,CH4的损失率低。低温、低压、低切割比有利于渗透侧高纯CO_(2)的输出;高温、高压、低切割比则有利于渗余侧CH4的回收。使用该膜模拟沼气分离,在切割比为0.1下操作,当进气压力为0.2 MPa、温度为25℃时,通过单级膜过程,渗透侧可得到99%的CO_(2),渗余侧CH4回收率可高达99%。在很宽的操作范围内,本文制备的复合膜在沼气中CO_(2)组分分离时,CH4损失率可控制在1%范围内,是理想的CO_(2)/CH4分离膜。

To solve the problems of low purity of CO2 and high loss rate of CH4 in the single-stage membrane process during biogas separation,an ultrahighly selective composite membrane with polyimide separation layer was prepared by interfacial polymerization.The effects of the operating temperature,the feed pressure,and the stage cut on the separation performance were investigated.The results showed that the membrane exhibited excellent separation performance under different operating conditions.The high purity of CO2 could be obtained on the permeate side with low CH4 loss.The low operating temperature,low feed pressure,and low stage cut were favorable for the high purity CO2 on the permeate side,while the high operating temperature,high pressure,and low stage cut were favorable for the high recovery of CH4 on the residue side.Using this membrane to separate the simulated biogas at 0.2 MPa and 25℃with a stage cut of 0.1,99%of CO2 could be obtained on the permeate side and 99%of CH4 could be recovered on the residue side through a single-stage membrane process.In a wide operating range,the composite membrane prepared in this study could control the CH4 loss within 1%when separating CO2 from biogas,which is a potential membrane for CO2/CH4 separation.