Synthesis of cascade refrigeration systems integrated with chemical processes

Abstract A nonlinear programming model is presented for the synthesis of cascade refrigeration systems with alternate working fluids, optimized over a continuous range of operating temperatures. A technique for the lumping of temperature intervals is developed, which often increases the efficiency of optimization without adversely affecting the solution. The model allows for the efficient integration of heat pumps with temperature intervals having negative cold deficits, often leading to less costly designs. Results are presented for an ethylene separation train.