Advanced exergoeconomic evaluation of a mini-scale nitrogen dual expander process for liquefaction of natural gas

Abstract A mini-scale nitrogen dual expander process for the production of liquefied natural gas was evaluated by conventional and advanced exergoeconomic analyses. The main indicators of the analyses were calculated and analyzed to determine the effect of equipment cost and performance on process total cost. Results of the conventional analysis indicated that the compressors have the highest total costs including mainly investment cost. However, the total cost of the other components mainly consists of exergy destruction cost resulting in small exergoeconomic factors. Regarding results of the advanced analysis, most of exergy destruction cost of the compressors and the expanders is avoidable endogenous that reveals a high potential for improvement. However, a large portion of the investment cost of the equipment is unavoidable endogenous. The largest share of total avoidable cost belongs to EXP-1 (59%) followed by EXP-2 (33%) which exhibits the highest priority of the expanders for improvement. This also indicates that these components are the most important components from economic point of view. Sensitivity of the analyses indicators to the main influencing parameters, maximum and minimum pressures of the cycle and the refrigerant flow rate was also investigated.