Energy efficiency and economic analysis of a novel polygeneration system based on LNG cold energy utilization and wet flue gas waste heat recovery

The polygeneration systems based on liquefied natural gas (LNG) cold energy recovery are limited by high investment costs, low efficiency due to low-grade heat sources, and low LNG cold energy utilization efficiency. In this paper, a novel polygeneration system based on LNG cold energy utilization and wet flue gas waste heat recovery was proposed. This system was designed to utilize low-grade wet flue gas as a heat source, and to effect waste heat recovery and low-temperature carbon dioxide (CO₂) capture from the flue gas. A thermodynamic and economic model was developed to analyze the performance of system. Parameter analysis and exergy analysis were conducted to examine the impact of thermodynamic parameters on system performance. Furthermore, the initial investment cost and daily average income of the system were evaluated. To optimize the performance of system, a genetic algorithm was employed. The results demonstrate that the cooling output and total power output of the proposed system are 17.60 kW and 448.00 kW, respectively, and a carbon capture rate of 92.86 % with an exergy efficiency of 38.95 % is achieved. The estimated investment payback period is 1.32 years. Based on the optimization results, the exergy efficiency of the system reaches 45.26 % and the total power output of the optimized system is 505.08 kW. These findings provide important theoretical groundwork and technical support for the widespread application of LNG in cryogenic power generation and carbon capture.