Energy and Exergy Investigation of Two Modified Single Mixed Refrigerant Processes for Natural Gas Liquefaction

Abstract Liquefaction processes consume a high amount of energy, and any attempt to achieve lower energy consumption and higher exergy efficiency would lead to a remarkable enhancement in the process efficiency. In the present study, two mini-scale modified single mixed refrigerant processes for natural gas liquefaction are simulated. The specific power consumption and total avoidable exergy destruction rate are optimized using the genetic algorithm tool. As a result of the energy optimization of the base case process, the specific energy consumption and the total exergy destruction rate are reduced by 19.4% and 25.4%, respectively. On the other hand, the maximum total exergy efficiency of 47.51 % is obtained through the exergy optimization of the process. The results related to the process configuration with a pump shows a higher exergy efficiency. Moreover, the minimum specific power consumption of 0.221 kWh/kg LNG is obtained through the optimization of the exergy destruction rate function.