Method for liquefying high-low pressure nitrogen double-expansion natural gas

Abstract

The invention discloses a method for liquefying high-low pressure nitrogen double-expansion natural gas, which comprises the following steps: compressing and cooling nitrogen gas, and then introducing the nitrogen gas into the pressurizing end of a low-pressure pressurizing machine for pressurization; after cooling the nitrogen gas to a temperature of between 30 and 45 DEG C by a second after cooler, introducing the nitrogen gas into the pressurizing end of a high-pressure pressurizing machine to obtain high-pressure nitrogen gas which is cooled to a temperature of between 30 and 45 DEG C by a first after cooler; introducing the cooled high-pressure nitrogen gas into a main heat exchanger, cooling the nitrogen gas and raw natural gas to a temperature of 70 DEG C below zero and 30 DEG C below zero by the low-pressure nitrogen gas at the outlet of a low-pressure expander, taking out a current of the nitrogen gas which is introduced into a high-pressure expander for expansion refrigeration and then is introduced into the low-pressure expander for expansion refrigeration to obtain low-pressure nitrogen gas, and simultaneously cooling, liquefying and super-cooling the raw natural gas by the low-pressure nitrogen gas continuously and then leading out the raw natural gas from the main heat exchanger; and throttling the raw natural gas led out of the main heat exchanger by a throttle valve, separating the raw natural gas by a separation tank to obtain liquefied natural gas which is introduced into a storage tank, and returning the gas into the main heat exchanger for recovering cold. The method is applicable to high-low pressure areas and has high liquefaction rate which can reach 100 percent.

Description

technical field [0001] The invention relates to a natural gas liquefaction method, in particular to a high-low pressure nitrogen double-expansion natural gas liquefaction method. Background technique [0002] With the development of society, the amount of oil reserves is decreasing, and the greenhouse effect is becoming more and more obvious; people's requirements for green energy are also becoming stronger and stronger, so natural gas has been widely used. However, the extracted natural gas is all gaseous, and it is almost impossible to transport it, which greatly restricts its use. The liquefaction ratio of natural gas is 591. If the natural gas is liquefied, the volume will be reduced by 591 times, and transportation will become possible. Therefore, a large number of natural gas liquefaction devices have appeared. The liquefaction process of natural gas mainly includes nitrogen expansion refrigeration process, nitrogen-methane expansion refrigeration process, mixed worki...

AI Technical Summary

Problems solved by technology

However, there is no high-low pressure nitrogen expansion refrigeration liquefaction process. Here we mainly introduce the high-low pressure nitrogen double-expansion natural gas liquefaction process. This process is a kind of nitrogen double-expansion process.

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