Determination of the Optimal Operating Condition of the Single Mixed Refrigerant Process for LNG FPSO

As increasing the demand of energy all over the world, the consumption of natural gas is also increasing. The offshore gas reserves are estimated to have significant portion of natural gas. In this sense, the LNG FPSO is introduced to develop the natural gas in offshore. LNG FPSO is broken into main two parts, hull and topside. The liquefaction process is regarded as primary among all topside systems in LNG FPSO. The liquefaction process condenses the pretreated natural gas into LNG which takes up about 1/600th the volume of natural gas in the gaseous state.

The single mixed refrigerant (SMR) process operates with only one mixed refrigerant to pre-cool, liquefy, sub-cool natural gas. The SMR process consists of compressors, heat exchangers, coolers, valves, phase separators and common headers. The operating conditions include the flow rate, pressure, temperature, and refrigerant composition.

In this study, the optimal operating conditions for SMR process, which is suitable for LNG FPSO, were determined by considering the power efficiency based on variation of feed gas compositions. Aspen HYSYS was utilized to obtain the optimal operating conditions.