Simulation and optimization of flue gas waste heat utilization by organic Rankine cycle with zeotropic mixtures

Aspen HYSYS software was used to simulate the organic Rankine cycle using zeotropic mixtures for the recovery and utilization of waste heat from compressor station flue gas. Considering the environmental protection, safety, matching of critical temperature and heat source temperature, benzene, toluene, R141b and R123 were selected as the circulating working fluids. The average net output work over a period of time was proposed as the optimization objective. The cycle performance of benzene/R141b, benzene/R123, toluene/R141b and toluene/R123 as circulating working fluids were compared, and the influences of key factors were analyzed such as evaporation pressure, condensation pressure, the components of zeotropic mixtures and their molar ratios to the average net output work of the system. The best working condition was determined. The results show that when the condensing pressure is 100 kPa, the evaporation pressure is 3 000 kPa, and when the mixed working medium is benzene/R141b(molar ratio of benzene and R141b with 0.4/0.6), the average net output work of the system is the largest, which is 4.7% higher than that of benzene as the circulating working fluid. © 2021, Central South University Press. All right reserved.