Optimal synthesis of expansion liquefaction cycle for distributed-scale LNG (liquefied natural gas) plant

The selection of liquefaction process is of great significance for distributed-scale LNG (liquefied natural gas) plant. This paper proposes four configuration strategies of expansion liquefaction cycle for distributed-scale LNG plant, namely multistage expanders, single precooling cycle, regeneration and mixture working fluid. FOM (figure of merit) is applied to evaluate the liquefaction cycles for distributed-scale LNG plant. Sixteen feasible liquefaction cycles are configured based on the configuration strategies and then optimized by genetic algorithm to maximum FOM for optimal synthesis. The cost analysis and exergy analysis of system are investigated. The optimized liquefaction process (Case 8) has two cycles, namely R410A precooling cycle and parallel nitrogen expansion cycle. The results show that the FOM of the optimized liquefaction cycle is 0.566 for distributed-scale LNG plant.