Design of a membrane plant for gas sweetening based on new polyimide membranes

A family of four new polyimides was synthesized with different CO₂ and CH₄ transport properties from fluorinated diaminotriphenylmethane and four different dianhydrides. The transport properties were used to simulate a gas membrane sweetening process in order to study their effect on the economy of the process. The membrane with the highest CO₂/CH₄ selectivity achieved the best performance for getting the product into specification, requiring less membrane area, obtaining higher methane recovery and lower gas processing cost (GPC). The effect of pressure feed was obtained by adding a second compressor to the feed stream; the results showed that the GPC exhibited an opposite trend to that of typical studies, increasing it with pressure; an explanation of this behavior is presented. The effect of feed flow on the GPC remained constant and presenting a linear behavior with membrane selectivity.