Fueloil containing a mixture of 90 mol% propane and the rest carbon disulfide is burned to completion in 150% excess air inside a furnace. The furnace exhaust gas passes through a scrubber, where 95% of the CO2 entering is absorbed in ammoniated water and removed. In addition, some water vapor in the combustion product is condensed. Everything else exits the scrubber in the overhead gas, which is split into two streamsafter leaving the scrubber: one stream is recycled and mixed with fresh combustion gases from the furnace before entering the scrubber; the other stream is passed to a tall stack. Assume the combustion products are SO2, CO2, and H2O. Required:
a. Why do you think some of the scrubber overhead gas is recycled?
b. Draw a fully-labeled process flow diagram. If it is possible to calculate the feed rate of ammoniated water to the scrubber, do so.