5. A spiral-wound permeator assembly using a novel polymeric membrane material with thickness z = 100 m is tested for CO2 removal from coal-bed methane containing 15 mol% CO in an enhanced natural gas recovery project. At a slipstream feed rate of 70 L/min, at 25 bar and 25 C, the corresponding molar flow rate of the feed is 1.18 mol/s. The permeator produces a 45.4 L/min total permeate flow that is 80 mol% CO2, and a retentate containing 87 mol% CH4. The feed and the retentate absolute pressures are both 25 bar, and there is negligible pressure drop throughout the permeator. The membrane surface area is 100 m. Assume that the partial pressures of the gas species are uniform throughout the feed and permeate sides of the membrane. (a). Calculate the permeabilities (mol m/m s Pa) of CO2 and CH4, and the membrane selectivity, assuming the permeate exits at 1 bar and 25 C. (b). What feed pressure (bar) is required to obtain a retentate that is 99 mol% CH4? Assume the total feed rate remains 1.18 mol/s, and the permeate still contains 80 mol% CO2.