How do you optimize a multi-stage membrane system for gas separation?

Optimization involves: stage cut (permeate/feed ratio) - higher cut improves recovery but reduces purity; pressure ratio across membrane - higher ratio improves driving force but increases compression costs; recycle streams - improve recovery at cost of larger membrane area and compression. Configuration options: single-stage, two-stage cascade, two-stage with recycle. Trade-offs between purity, recovery, membrane area, and compression costs are optimized using process simulators. For hydrogen recovery, two-stage with recycle often achieves >99% purity with >95% recovery.