Propration of polyimide composite membrane and its application in biogas purification
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 poly imide 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.
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