Several hydrogenation processes are being considered that will require hydrogen of 95% purity. A refinery stream of 800,000 scfm (at 32oF, 1 atm), currently being used for fuel and 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 the absorbent. Because the 95% Hz must be delivered to a hydrogenation process at not less than 375 psia, it is proposed to operate the absorber at 400 psia and 100°F. If at least 80% of the hydrogen fed to the absorber is to leave in the exit gas, determine:

(a) The minimum absorbent rate in gallons per minute

(b) The actual absorbent rate if 1.5 times the minimum amount is used.

(c) The number of theoretical stages.

(d) The stage efficiency for each of the three species in the feed gas, using the O'Connell correlation.

(e) The number of trays actually required.

(f) The composition of the exit gas, taking into account the stripping of octane.

(g) If the octane lost to the exit gas is not recovered, estimate the annual cost of this lost oil if the process operates 7,900 h/year and the octane is valued at $l.00/gal.