A kind of composite refrigeration natural gas liquefaction method

Abstract

The invention relates to a method for natural gas liquefaction, in particular to a method for composite refrigeration natural gas liquefaction by adopting propane and ethylene refrigerant stepwise refrigeration and nitrogen expansion cycle. The method for composite refrigeration natural gas liquefaction is used for heat exchange of pretreated natural gas and a composite refrigerant in a cold box heat exchanger, so as to liquefy the natural gas into liquefied natural gas. The method comprises the steps of first making the pretreated natural gas enter a primary cold box to be subject to refrigeration cycle heat exchange with propane to -30 DEG C to -60 DEG C; making the natural gas enter a secondary cold box to be subject to refrigeration cycle heat exchange with ethylene to -90 DEG C; and finally making the natural gas enter a third-stage cold box to be subject to expansion refrigeration cycle heat exchange with nitrogen to -150 DEG C to -160 DEG C to form finished liquefied natural gas. According to the method for liquefying the natural gas, the refrigerant is a pure substance, no ratio problem occurs, and the refrigerant is stable to operate. Low temperature level refrigerant nitrogen is non-combustible fluid, space is saved better in plane arrangement, and the operational safety is higher.

Description

technical field [0001] The invention relates to a natural gas liquefaction method, in particular to a compound refrigeration natural gas liquefaction method using propane, ethylene refrigerant cascade refrigeration and nitrogen expansion cycle. Background technique [0002] Refrigerated natural gas liquefaction processes typically include three methods: cascade refrigeration, mixed refrigerant refrigeration, and expansion refrigeration. Chapter 3 of the book "LNG Technology" written by Machinery Industry Press, Gu Anzhong, etc. introduces the principles and methods of the three processes. Different refrigeration processes can be used alone and applied to natural gas liquefaction devices. . [0003] Cascade refrigeration usually uses three refrigerants: propane, ethylene, and methane. It consists of three independent refrigeration cycle systems. Each refrigeration cycle contains three heat exchangers. In the cascade liquefaction process, the refrigerant with a higher boiling...

AI Technical Summary

Problems solved by technology

The disadvantage is that if all LNG production uses nitrogen expansion refrigeration, the energy consumption of the process will be high

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