Optimization of mixed-refrigerant system in LNG liquefaction process

LNG liquefaction is an energy intensive process. For this reason, various liquefaction processes for saving energy exist. Searching optimal process condition is very difficult because of its high nonlinearity. Pressure level, refrigerant flowrate, and refrigerant composition are key operation variables to reduce energy consumption. These variables play an important role in affecting the overall performance. Compressor is a major energy-consumption unit in LNG plant and it spends much energy depending on operating conditions. In this paper, searching optimal condition is carried out by using simultaneous optimizations. NLP model is applied for the SMR process. The optimization result shows that refrigerant composition is a major key variable and half of energy consumption can be reduced by changing operating conditions and refrigerant composition only.