Thermoeconomic analysis and evaluation of single-stage mixed-refrigerant natural gas liquefaction process

In terms of the great investment and high energy consumption of natural gas liquefaction process system, the technological economy of the process equipment can be evaluated reasonably through thermoeconomic analysis. The process flow was simulated with HYSYS based on the actual process and operation data of a natural gas liquefaction plant. Thereby, the thermoeconomic cost balance and auxiliary equations of each equipment were constructed based on economic and exergic analysis to analyze the thermoeconomic cost of streams. Besides, the technological economy of equipment was evaluated with the relative cost difference and the exergo-economic factor based on the fuel-product definition of the equipment and the thermoeconomic cost of each stream. Meanwhile, the optimization direction of each equipment was pointed out, and the influence degree of energy cost and non-energy cost on the unit thermoeconomic cost of the product was analyzed. The results show that the exergoeconomic factors of No. 3 compressor and No. 2 refrigerant pump in the process system are relatively high, and it is necessary to reduce their investment cost or the operation and maintenance cost. Additionally, energy cost is the main factor affecting the production cost of liquefied natural gas, and the unit thermoecomnomic cost of liquefied natural gas increases by 8.7% if the energy cost is increased by 10%. Generally, the research results could provide guidance and suggestions on the optimization, operation and maintenance of the natural gas liquefaction process system.