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

Abstract

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.

Description

technical field [0001] The invention belongs to the technical field of liquefaction of natural gas, coal bed methane or other methane-rich gases, and in particular relates to a single-stage mixed refrigerant refrigeration cycle liquefaction method and device. Background technique [0002] The main component of natural gas and coalbed methane is methane, which cannot be liquefied at room temperature only by pressurization. It needs to be liquefied by natural gas liquefaction process. For example, methane under normal pressure is liquefied into LNG (liquefied natural gas) at -162°C. Its volume is only 1 / 625 of the original gas state, and its density is more than 600 times that of methane in the standard state. , 45% of water, volumetric energy density of 72% of gasoline. Because of its clean burning quality and ease of use, it is a high-quality industrial and domestic fuel, and at the same time it is very convenient for transportation and storage. [0003] At present, common...

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Problems solved by technology

However, its cooler is placed on the ground, and after the mixed refrigerant compressed by the compressor enters the cooler, it is partially liquefied in the cooler to generate a gas-liquid two-phase (in the pipeline after the cooler); in order to solve the problem of mixed cold For the problem of two-phase flow of refrigerant gas and liquid, this technology still has a gas-liquid separator to separate the gas and liquid after the cooler, and pumps the separated liquid refrigerant to the inlet of the cold box to separate the gas from the separator The refrigerant is mixed and then enters the cold box. This method still increases the number of equipment (such as separators, pumps, etc.) and control points. The circulation process and operation control are still relatively complicated, and the increase in the number of equipment also leads to an increase in input costs. , resulting in an increase in the cost of the entire production process

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