Comprehensive performance analysis and optimization of novel SCR-ORC system for condensation heat recovery

An organic Rankine cycle (ORC) system with separation, compression, and recycling of exhaust gas (SCR-ORC) based on a novel condenser is proposed. The relationship between volume, temperature, and pressure in fluid mechanics is used to change the internal space structure of condenser, so that a temperature difference is generated between the exhaust gas split in two spaces, which is used to recover the condensation heat. Then, the SCR-ORC system is used to reuse the recovered condensation heat. Further, the comprehensive performance of SCR-ORC system and novel condenser is analyzed and compared with that of ORC system and traditional condenser. Furthermore, multi-objective optimization is conducted by using thermodynamic, economic, and environmental performance as optimization objectives through the genetic algorithm with optimal combination weights method. The results indicate that when the condenser pressure drop (ΔPc) is 0.12 MPa, the waste condensation heat of traditional condenser reaches 64852.24 kW, while that of novel condenser is 38910.92 kW, the condensation heat recovery and exergy loss of novel condenser are 6114.28 kW and 2408.63 kW respectively. Compared with the ORC system, the net power output (Wnet), thermal efficiency (ηt), exergy efficiency (ηex), and annual emission reduction (AER) of equivalent carbon dioxide of SCR-ORC system with R245fa as the working fluid are increased by 6803.17 kW, 2.52%, 6.54%, and 1215.82 × 103 kg, respectively, while the payback period (PBP) is decreased by 0.59 years. It is also found that the working fluids with lower critical temperature exhibit better comprehensive performance, and the comprehensive performance of R134a is the highest among the considered working fluids.