A single stage spiral wound membrane is used to remove CO2 from a natural gas stream. Feed is supplied at 20 MSCFD, 850 psig and contains 93% CH4 and 7% CO2. The retentate leaves at 835 psig with 2% CO2 and the permeate leaves at 10 psig with 36. 6% CO2. The permeance of CO2 through the membrane is reported to be 5. 5 x 10^-2 ft3(STP)/(ft2·hr·psi). Assuming Patm = 15 psia, find the:
(a) percent recovery of methane in the retentate stream [90. 1%]
(b) area of the membrane, ft2, assuming both a linear and log-mean driving force. How do these two approximations compare to the actual area of 33,295 ft2?
(c) permeance of CH4 ft3(STP)/(ft2·hr·psi) and the selectivity of the membrane, a12. [a12 = 19. 3]
Note: MSCFD = 10^6 ft3(STP)/day
