Effect of fiber variation on staged membrane gas separation module performance

The effect of fiber property variations on the performance of a two-stage s ystem for gas separation was studied theoretically and experimentally. Vari ations in fiber inner diameter, slow gas permeance, or selectivity are cons idered. Variability in any of these properties is detrimental to performanc e, as characterized by product flow rate and product recovery (fraction of the feed recovered as a product), The performance decline increases as eith er property variation or product purity increase. The two-stage system can enhance performance significantly over a single sage. Permeate miring is al so beneficial to performance. Like a single stage, however, some fibers may stop producing a retentate product and consume product produced by other f ibers for sufficiently large variation in size and permeance. The theory ag rees well with experiments for the production of nitrogen from air.