Exergoeconomic Analysis and Optimization of a Combined Cooling, Heating, and Power System Based on a Super-Trans-Subcritical Regenerative Cycle Using the Liquefied Natural Gas Cold Energy and Steam Methane Reforming Waste Heat Available to Purchase

This article designs and analyzes a combined cooling, heating, and power system based on the step utilizing liquefied natural gas cold energy and steam methane reforming flue gas waste heat. The system performance is evaluated through thermodynamic analysis, exergoeconomic analysis, and multi-objective optimization of the system. The influence of the turbine inlet pressure P₄, split ratio x, and mole fraction of carbon tetrafluoride N_R14 on the system performance is analyzed. The results show that increasing P₄ and T₁₀ can improve the net work output, the thermal efficiency, the exergy efficiency, and lower the average unit cost. Reducing x, P₁₄, and N_R14 can reduce the average unit cost, and improve the exergy efficiency. The system energy is mainly distributed in the heat exchangers. In the actual optimal state, the thermal efficiency, exergy efficiency, and average unit cost of the system are 72.35%, 52.16%, and 31.24 $/GJ, the annual net economic value is 1.507 × 10⁶ $, and the discounted payback period is 3.38 years. The research results are conducive to capturing carbon dioxide from flue gas, saving resources, and protecting the environment.