Abstract:

As one of the key technologies of the whole device for large scale floating liquid natural gas (FLNG) equipment, liquefaction process is mainly dominated by foreign companies at present. Mixed refrigerant liquefaction process has the advantages of simple process, less equipments, high efficiency and lower power consumption, so it has been widely applied to liquefaction plant on land. It will also be adopted in the offshore FLNG which is about to put into production firstly in the world. Mixed refrigerant liquefaction process can be divided into different types of processes, and different liquefaction processes have different characteristics and scope of application. HYSYS software is used to simulate the three mixed refrigerant cycles under various conditions of feed flow, methane component ratio and heavy components ratio. Energy consumption and device features of different processes are compared. Processes which are suited to different liquefaction capacities are analyzed. The results show that, the ratios of power consumption of propane pre-cooled mixed refrigerant (C₃MR), double mixed refrigerant (DMR) and single mixed refrigerant (SMR) are 0.3309, 0.2254 and 0.2451 respectively in the condition of 65000 m³/d natural gas inflow. Mixed refrigeration process which has the largest number of key equipments is C₃MR, followed by the DMR, and the minimum is SMR. C₃MR requires the most refrigeration while SMR requires the least. With the change of methane content in the feed gas, the ratio of power consumption of C₃MR changes the most, while those of DMR and SMR change less.

Key words: FLNG, mixed refrigerant liquefaction process, sensitivity analysis, offshore adaptability