Multi-objective optimization of organic Rankine cycle system for the waste heat recovery in the heat pump assisted reactive dividing wall column

Abstract

The application of heat pump (HP) technique to reactive dividing wall column (RDWC) achieving energy-saving has received more and more attention, however, massive low-temperature (<100 °C) waste heat would be hereby produced. Therefore, in this work, the organic Rankine cycle (ORC) is adopted to effectively convert the produced waste heat of the compressed stream to clean energy (i.e., electricity). The HP assisted RDWC (HP-RDWC) of diethyl carbonate process is taken as an example, the ORC system with five working fluids candidates are explored. The operating parameters of the ORC system (e.g., flow rate of working fluid and inlet pressure of evaporator) are optimized based upon the maximum net revenue and ORC thermal efficiency through the improved multi-objective genetic algorithm. The optimal ORC system is determined by considering the economic (i.e., net revenue) and thermodynamic efficiency (i.e., ORC efficiency) performances. The results illustrated that the net revenue of the ORC system with R123 and R600a could achieve 175,807.2 US$ and 133,665.5 US$ with ORC efficiency of 15.57 and 16.19%. In addition, total annual cost of the HP-RDWC integrated ORC processes with working fluids R123 and R600a could be reduced by 11.78% and 10.30%, respectively.