Method and apparatus for single-stage mixing cryogen refrigerating cycle liquefied natural gas

The invention discloses a method for liquefying natural gas by the refrigeration cycle of a single stage mixed refrigerant, which comprises the following steps: raw natural gas passes through a heat exchanger in an ice chest to exchange heat with the mixed refrigerant, and is cooled and liquefied; wherein, in sequence, the mixed refrigerant is first pressurized by a compressor, cooled by a cooler, directly enters the heat exchanger to be precooled without gas-liquid separation, goes out of the heat exchanger for depressurization and temperature reduction and then returns to the heat exchanger to exchange the heat of the natural gas and liquefy the natural gas, as well as is vaporized to gaseous mixed refrigerant and returns to the compressor for the next cycle; by reducing the outlet pressure of the compressor, or boosting the position of the outlet cooler of the compressor or using a way that the mixed refrigerant goes in and out of the ice chest both from the lower part, the method solves the problem of two phase flow of gas and liquid; can reduce the investment of the equipment such as a gas-liquid separator, a pump and the like, simplify the cycle process and operation control and reduce the manufacture cost as well. The invention also discloses a device applied to the method.