Energy, exergy, environmental, and economic analyses and multiobjective optimization of a DSORC system for waste heat utilization in low-concentration gas power generation

This paper proposes a dual-loop ORC system with working fluid shunting (DSORC) for waste heat recovery from low-concentration gas power generation. Thermodynamic models based on pinch points position changes, environmental models based on life cycle assessment, and economic models are established to analyze energy, exergy, environmental, and economic performances of the DSORC system. Multiobjective optimization is performed by GA to reveal the best performance. The results show that the thermodynamic performance of the DSORC system is better than that of the DORC system, and the exergy destruction is smaller in the evaporative condenser, low-temperature evaporator, and low-temperature preheater of the DSORC system. The proportions of ADP and GWP are large in the weighted environmental potential of the DSORC system. The weighted environmental potential generated by the operating process is more than 97 %, but the steel consumption per unit of power generation is the most sensitive to the environmental impact. The optimal P6 is close to the maximum P6 that can be achieved for each working fluid, the optimal P2 ranges from 9.92 MPa to 10.99 MPa, and the optimal P3 ranges from 0.22 MPa to 0.23 MPa.