546.2 Ibmol/h 6.192 cfs y, mol% C2 C3 nC4 60.2573 nC5 32.5874 пСs 0.0006 0.4817 Rect 6.6730 Bottom tray 230.5° F 150 psia x, mol% C2 0.0001 Сз nC4 39.1389 nC5 пСв 0.1448 621.3 Ibmo/h 171.1 gpm 43.0599 17.6563
Fuel cell automotive systems are being considered that willrequire hydrogen of 95% purity. A refinery stream of 800,000 scfm (at 32oF, 1 atm), containing 72.5% H2, 25% CH4, and 2.5% C2H6, is available. To convert this gas to the required purity, oil absorption, activated charcoal adsorption, and membrane separation are being considered. For oil absorption, an available n-octane stream can be used as absorbent. Because the 95% H2 must be delivered at not less than 375 psia, it is proposed to operate the absorber at 400 psia and 100oF. If at least 80% of the hydrogen fed to the absorber is to leave in the exit gas, determine the: (a) minimum absorbent rate in gpm; (b) absorbent rate if 1.5 times the minimum amount is used; (c)number of theoretical stages; (d) stage efficiency for each of the
three species in the feed gas, using the O’Connell correlation; (e)number of trays actually required; (f) exit gas composition, accounting for octane stripping; and (g) if the lost octane in part (f) is not recovered, estimate its value if the process operates 7,900 h/yearand the octane is valued at $1.00/gal. Would the octane preclude use of this hydrogen in fuel cells?
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