Recovering and reusing organic solvents rather than discharging them into a waste stream is an important part of the operation of most chemical plants. The magnitude of the recovery efforts can be staggering. In recent years the Eastman Kodak company used 3.6 billion pounds of solvents and recovered 3.5 billion pounds (97%). Eastman's instillation of a $26 million acetone recovery system reduced acetone emissions by 50% in the division that had been responsible for most of these emissions.
In an acetone recovery process, a gas stream containing 20.0 mole% acetone and the remainder nitrogen leaves a chemical plant at 90oC and 1 atm. The stream is cooled at a constant pressure in a condenser enabling some of the acetone vapour to be recovered as liquid. The nitrogen and uncondensed acetone are discharged to the atmosphere.
a) Two cooling fluids are available - cooling tower water at 20oC and a refrigerant at -35oC. For each fluid determine the % acetone recovery, assuming that the coolant temperature equals the condenser temperature.
b) In a real system, the condenser temperature can never be as low as the initial cooling fluid temperature. Explain why this is the case and how this would affect solvent recovery.
c) What other factors might determine which of the coolants you decide to use.
d) What are the major benefits of recovering the acetone?