DEVICE AND METHOD FOR LIQUEFYING NATURAL GAS USING SINGLE MIXED WORKING MEDIUM AS REFRIGERATION MEDIUM

摘要

A device and a method for liquefying natural gas using single mixed working medium as refrigeration medium are provided. The device comprises a two-section mixed working medium 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 working medium is compressed step by step by using the two-section mixed working medium compressor (1), separated step by step, and gas-phase and liquid phase mixed working mediums obtained from 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 total heat exchange process match with each other better by the aid of using two-stage heat exchange, thereby flow of the mixed working medium is reduced effectively.