13.3 A gas stream containing a valuable hydrocarbon (MW = 44) is scrubbed with a nonvolatile oil (MW=300, specific gravity =

0.90) in a tower packed with 1-inch Raschig rings. The entering gas analyzes 20 mole percent hydrocarbon with the remainder being an inert gas (MW = 29). The gas stream enters the column at 5000 lb/hr-ft2, and hydrocarbon-free oil enters the top at 10,000 lb/hr-ft. The column is 4 ft in diameter. Ninety-five

percent of the valuable hydrocarbon is to be recovered. Use the equilibrium relationship and the equations for k,a and ka given below. Estimate the height of packing required.