A system for improving the recovery rate of liquefied natural gas

Abstract

The invention discloses a system for improving liquefied natural gas recovery rate and relates to the field of liquefied natural gas production. The system comprises a raw material gas conveying pipe, a compressor, a methanation reactor, a liquefied natural gas purification tower and pipelines, and the system is characterized by being further provided with a pressure swing adsorption device which is provided with a pressure swing adsorption tower, wherein the raw material gas conveying pipe is connected with the compressor, the compressor is connected with the methanation reactor, the methanation reactor is connected with the liquefied natural gas purification tower which is connected with the pressure swing adsorption tower, the pressure swing adsorption tower is connected with the raw material gas conveying pipe or the liquefied natural gas purification tower, and the devices are communicated by virtue of corresponding pipelines. The system disclosed by the invention is simple to operate and cost-saving, the energy consumption is reduced, and the recovery rate of the liquefied natural gas can reach over 99.8%.

Description

technical field [0001] The invention relates to the field of liquefied natural gas production, in particular to a system for improving the recovery rate of liquefied natural gas. Background technique [0002] In the process of producing liquefied natural gas (LNG for short) from methane-rich mixed gas, especially in coke oven gas and other gas sources containing more hydrogen and nitrogen and other non-condensable gases, in order to reduce the non-condensable gas at the top of the liquefied natural gas purification tower To improve the recovery rate of liquefied natural gas, the method usually adopted is to reduce the temperature of the top of the liquefied natural gas purification tower, or even increase the cooler with liquid nitrogen as the refrigerant. A small amount of methane will be entrained, which is an important factor affecting the recovery rate of methane in LNG plants. And as the efficiency of the heat exchanger at the top of the liquefied natural gas tower dec...

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Problems solved by technology

And as the efficiency of the heat exchanger at the top of the liquefied natural gas tower decreases, the methane in the vented air at the top of the tower will increase, reducing the methane recovery rate of the liquefied natural gas plant, resulting in an increase in energy consumption per unit of liquefied natural gas production

[0003] Chinese Patent Application Publication No. CN102079999A discloses a method for producing liquefied natural gas and synthesis gas by using coke oven gas as raw material. The inlet of the methane collection unit is mixed with the purified gas by pressure swing adsorption to separate H2, N2, CO and methane in the purified gas to obtain synthesis gas and methane-rich gas, because the content of non-condensable gas and methane in the liquefied natural gas cold box is several times Coal gas mixed with non-condensable gas is used as the raw material of the pressure swing adsorption methane enrichment unit, so that a part of methane will still be entrained in the synthesis gas obtained by the pressure swing adsorption device, which fails to improve the methane recovery rate of LNG and reduce the energy consumption of LNG. The role of consumption

[0004] Chinese Patent Application Publication No. CN102942972A discloses a method for producing liquefied natural gas using coke oven gas, which discloses the use of PSA molecular sieves to remove N2 from non-condensable gases, vacuum desorbs methane adsorbed by PSA molecular sieves, and returns more than 90% of the methane content in the desorption to coke oven gas In the method of recycling, since the content of methane in the desorption gas is as high as 90%, part of the methane will be released from the adsorption waste gas, thereby reducing the recovery rate of methane

Also fails to address increased LNG recovery

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