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

Abstract

The invention discloses a technology and a device for removing hydrogen, nitrogen and carbon monoxide from methane rich gas and producing liquefied natural gas (LNG). The technology comprises two parts, namely low-temperature liquefaction and rectification separation after flash evaporation; the low-temperature liquefaction part is finished in a cold box by using cold flow supplied by a mixed refrigerant; in the rectification separation part after flash evaporation, the hydrogen, the nitrogen and the carbon monoxide are removed by adopting a flash evaporation and rectification flow; and after the methane rich mixed gas containing the hydrogen and the nitrogen sequentially passes through the cold box, a re-boiler at the bottom of a rectification tower and the cold box and the methane components are liquefied, the methane rich mixed gas enters a rectification separation system, and the hydrogen, the nitrogen and the carbon monoxide are removed, wherein the obtained LNG product contains less than or equal to 2,000ppm of hydrogen, less than or equal to 4 percent of nitrogen and less than or equal to 6 percent of carbon monoxide. By the natural gas liquefaction technology for the methane rich gas containing the hydrogen, the nitrogen and the carbon monoxide, the hydrogen, the nitrogen and the carbon monoxide are removed, and the LNG is obtained at the same time; the technology is advanced in process route; and compared with the conventional technology, the technology has the advantage that the investment cost of equipment and the energy consumption of the system are remarkably reduced.

Description

technical field [0001] The invention provides a process and device for dehydrogenation, nitrogen and carbon monoxide from methane-enriched gas to 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 carbon monoxide. In order to obtain liquefied natural gas, they must be removed to a certain extent before they can be used as liquefied 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 material condi...

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Problems solved by technology

as attached figure 1 Shown is the methane-rich gas purification and liquefaction process, which includes low-temperature liquefaction and rectification separation; the low-temperature liquefaction part uses refrigerant to provide cooling capacity to realize the liquefaction of natural gas in a cold box; the rectification separation part uses double-tower rectification (High-pressure tower and low-pressure tower) The process removes hydrogen, nitrogen, and carbon monoxide, and the top of the low-pressure rectification tower obtains nitrogen-rich gas and carbon monoxide, and the top of the high-pressure rectification tower obtains hydrogen-rich gas; this process can obtain qualified liquefied natural gas from impurity gas removal products, but this process is relatively complicated, using two rectification towers, the investment cost of equipment is high, and it is not easy to start up and operate the device

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