Abstract: A system and a method for liquefying natural gas using single mixed refrigerant as refrigeration medium are provided. The system comprises a two-stage mixed refrigerant compressor (1), coolers (21, 22), gas-liquid separators (31, 32), throttling devices (51, 52), a plate-fin heat exchanger group (8) and a LNG storage tank (9). The method of the present invention reduces the power consumption for gas compression by compressing and separating the mixed refrigerant stage by stage. The heat exchange curves of cold fluid and hot fluid in the total heat exchange process match with each other better by the aid of using multiple-stage heat exchange, which can reduce the flow of the mixed refrigerant. Further, the system of the present invention has a good adaptability to load-variable operation of the apparatus, and thus can effectively avoid abnormal liquid-flooding at the bottom of the cold box.

Abstract: A system and a method for liquefying natural gas using single mixed refrigerant as refrigeration medium are provided. The system comprises a two-stage mixed refrigerant compressor (1) driven by a motor, two coolers (21, 22), a liquid pump (4), three gas-liquid separators (31, 32, and 6), two throttling devices (51, 52), a plate-fin heat exchanger group (7) and a LNG storage tank (8). The method comprises the following steps: the mixed refrigerant is compressed step by step by using the two-stage mixed refrigerant compressor (1), separated step by step, and gas-phase and liquid phase mixed refrigerant streams obtained from the separation flow into different passages of the heat exchanger group (7) respectively for throttling and heat exchanging. Heat exchange curves of cold fluid and hot fluid in the whole heat exchange process match with each other better by using two-stage heat exchange, thereby flow of the mixed refrigerant is reduced effectively.