Technology and device for removing hydrogen and nitrogen from methane-rich gas through rectification and producing liquefied natural gas

Abstract

A technology and a device for removing hydrogen and nitrogen from methane-rich gas through rectification and producing liquefied natural gas. The technology comprises two parts: low-temperature liquefaction and rectification separation, wherein the low-temperature liquefaction includes following steps: firstly feeding the methane-rich gas containing hydrogen and nitrogen into a refrigerating box and liquefying a methane component in the refrigerating box with a mixed refrigerant for providing cooling capacity; and the rectification separation includes: directly feeding the liquefied methane-rich gas containing hydrogen and nitrogen into a single rectifying column to perform rectification for removing the hydrogen, the nitrogen and a less amount of carbon monoxide, wherein a gas mixture containing the hydrogen, the nitrogen and the less amount of the carbon monoxide is obtained at the top of the rectifying column; passing the gas mixture through the refrigerating box for recycling the cooling capacity and discharging the gas mixture out from the refrigerating box; and feeding back a liquid phase at the bottom of the rectifying column to the refrigerating box for being supercooled and then discharging the liquid phase out from the system to obtain a liquefied natural gas product which is not more than 500 ppm in the content of the hydrogen, is not more than 2% in the content of the nitrogen and is not more than 2% in the content of carbon monoxide. The invention provides a technology in which liquefied natural gas is produced by liquefying the methane-rich gas and meanwhile the hydrogen, the nitrogen and the carbon monoxide are removed. The technology is simple in processes and is low in equipment investment cost.

Description

technical field [0001] The invention provides a process and device for rectifying methane-rich gas to dehydrogenate nitrogen and produce liquefied natural gas. Coal-based synthesis gas, coke oven gas, and methanized coke oven gas contain not only methane, but also nitrogen, hydrogen, and a small amount of carbon monoxide. In order to obtain liquefied natural gas, it must be removed to a certain extent before it can be used as liquefied natural gas. Natural gas (LNG) product output. Background technique [0002] Under the pressure of environmental protection and energy cost, the proportion of natural gas as primary energy in various fields of society is gradually increasing, and its application fields have gradually expanded to power generation, automobile gas, industrial gas, urban residential gas, chemical gas, etc. , the market demand is increasing rapidly. The traditional natural gas pipeline supply method is still the mainstream, but due to the limitations of raw mater...

AI Technical Summary

Problems solved by technology

The use of flash evaporation will inevitably cause a large amount of methane to be carried in the flash gas, and the amount cannot be precisely controlled, which will cause a large loss of methane components

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