A straw oil used to absorb benzene (B) from coke-oven gas is to be steam-stripped in a sieve-plate column at 1 atm to recover B. Equlibrium at the operating temperature is approximated by Henry' slaw. It is known that when the oil phase contains 10 mol% B, its partial pressure is 5.07 kPa. The oil is assumed nonvolatile, and enters containing 8 mol% B, 75% of which is to be recovered. The steam leaving is 3 mol% B.

(a) How many theoretical stages are required?

(b) How many moles of steam are required per 100 mol of feed?

(c) If the benzene recovery is increased to 85% using the same steam rate, how many theoretical stages are required?