Front end combination purification technique for producing liquefied natural gas from mixture gas rich-containing methane

Abstract

The invention discloses a front-end combined purification process used to produce liquefied natural gas from mixed gas richly containing methane, which comprises four unit parts: acid gas removal, drying and dehydration, heavy hydrocarbon removal and demercuration. The mixed gas firstly undergoes a purification treatment through composite amine solution, CO2, H2S and HCN acid gases in the mixed gas are removed to the concentration less than or equal to 20ppm; the moisture in the gas is removed to a dew point at normal pressure less than or equal to minus 70 DEG C through isopiestic drying and dehydration treatment, then heavy hydrocarbon components above C5 are removed to the concentration less than or equal to 10ppm through temperature-changing pressure-changing absorption and purification treatment; finally the mercury content is removed to the value less than or equal to 0.001mu g/Nm<3> through the demercuration of demercuration adsorbent. The process has better purification effect than the conventional process route, improves the utilization rate of the raw materials and decreases the energy consumption during the purification; and the operation indexes of the units are easier to control.

Description

technical field [0001] The invention belongs to the front-end purification treatment technology of methane-rich gas low-temperature liquefaction. Specifically, for an industrial device that obtains liquefied natural gas (LNG) from a mixed gas rich in methane, it is necessary to remove the acid gas components, water, and high-carbon hydrocarbons contained therein before the mixed gas is subjected to cryogenic liquefaction. The precision required for liquefaction is the only way to ensure the safe and stable operation of the liquefaction separation process and equipment. Background technique [0002] Under the pressure of environmental protection and energy costs, the proportion of natural gas as a primary energy source in various fields of society is gradually increasing, and its market demand is also increasing rapidly. The traditional pipeline transportation supply method is still the mainstream, but due to the limitation of raw material conditions and user distribution, a...

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Problems solved by technology

The specific performance is as follows: ① Existing devices usually use the MEA solution process to remove acid gases (CO2, H2S, HCN). Due to the instability of the solution system, especially when the mixed gas contains organic sulfur, the solution is prone to irreversible degradation, often As a result, the acid gas components in the gas after the purification of the amine system exceeded the standard; ②The existing devices all adopt a single-stage temperature and pressure swing adsorption process for dehydration and removal of high-carbon hydrocarbons. It is regeneration gas, and the amount of regeneration gas is very large, accounting for about 25% to 60% of the process gas, which reduces the liquefaction rate of the gas; second: moisture and heavy hydrocarbons are removed on the same adsorbent, resulting in partial load of drying and purification Large, forcing the system to reduce the load operation, reducing the production capacity of the entire liquefaction unit

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