Separation of air into N₂ and O₂ is widely practiced. Cryogenic distillation is most economical for processing 100 to 5,000 tons of air per day, while pressure-swing adsorption is favorable for 20 to 50 tons/day. For small-volume users requiring less than 10 tons/day, gas permeation finds applications where for a single stage, either an oxygen-enriched air (40 mol% O₂) or 98 mol% N₂ can be produced. It is desired to produce a permeate of 5 tons/day (2,000 lb/ton) of 40 mol% oxygen and a retentate of nitrogen, ideally of 90 mol% purity, by gas permeation. Assume pressures of 500 psia (feed side) and 20 psia (permeate). Two companies who can supply the membrane modules have provided the following data:

Determine the required membrane area in m² for each company. Assume that both module types approximate crossflow.

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Module type PM for O₂, barrer/μm PM0₂/PMN2 Company A Hollow-fiber 15 3.5 Company B Spiral-wound 35 1.9