Exergy, Exergoeconomic, Exergoenvironmental Analysis and Working Fluid Picking of an Integrated Liquefied Natural Gas Cold Energy Utilization System Consisting of an Organic Rankine Cycle and Two-Stage Turbine Organic Flash Cycle

A novel integrated system is suggested herein to recover liquefied natural gas (LNG) cold energy more reasonably and effectively, containing an organic Rankine cycle (ORC), a two-stage turbine organic flash cycle (TTOFC), and an LNG expansion cycle. R134a-R32, R134a-Propylene, R152a-Propylene, and R152a-R32 are picked as the working fluid combinations for the system. A comprehensive study, including the net outpower power, exergy, exergoeconomic, and exergoenvironmental analysis, is conducted. The effects of the turbine 1 inlet temperature, the ORC working fluid mass flow in the heat exchanger 3, the pump 5 outlet pressure, and the inlet pressure for the flash tank in the TTOFC on the performance of the above three criteria are presented. The NSGA-II method is used for three-objective optimization and another design with ORC and single-stage turbine organic flash cycle is set to compare with the new combined cooling, heating, and power system. The results show that R134a-R32 is the best combination. In the R134a-R32 combination, the total capital cost is 25.64 $ h(-1), and the total environmental impact is 53.75 mPts h(-1).