Device for recovery of light hydrocarbons and co-production of LNG from tail gas of Fischer-Tropsch synthesis and method thereof

Abstract

The invention discloses a method for recovery of light hydrocarbons and co-production of LNG from tail gas of Fischer-Tropsch synthesis. The method comprises the following steps: tail gas from a Fischer-Tropsch synthesis unit passes through a supercharging decarburization unit to remove a CO2 component and then remove H2O therein; the purified tail gas is cooled and then enters a dethanizer; light hydrocarbons are removed from the tail gas in the dethanizer, cooled at the bottom of the dethanizer and then enters a downstream process unit; the tail gas at the top of the dethanizer enters a demethanizer; liquid methane flows out of the demethanizer and cryogenic treatment is continuously carried out to obtain LNG which enters an LNG storage tank; after the tail gas at the top of the demethanizer is reheated, H2, CO and N2 therein are separated; a separated permeate gas with an appropriate H2/CO ratio returns the Fischer-Tropsch synthesis unit or a PSA hydrogen production device; and the N2-containing tail gas is emptied or used as a fuel gas. By the use of the method for recovering light hydrocarbons from the tail gas, operating cost of the device can be reduced effectively, yield of hydrocarbon products is raised, and LNG is coproduced. Then, good economic benefit can be obtained.

Description

technical field [0001] The invention relates to a method for recovering light hydrocarbons and co-producing LNG from the tail gas of Fischer-Tropsch synthesis. Background technique [0002] Fischer-Tropsch synthesis was discovered in the 1920s from synthesis gas (CO+H 2 ) catalyzes the reaction of synthesizing hydrocarbon liquid fuels on a catalyst, which was discovered by German chemists Fischer and Tropsch, also referred to as Fischer-Tropsch synthesis or F-T synthesis. Fischer-Tropsch synthesis, as a method for synthesizing hydrocarbon liquid fuels from synthesis gas, has been industrialized in China. Syngas can be obtained from coal or biomass gasification. China is rich in coal biomass resources, but oil resources are relatively insufficient. With the development of economy and society, the demand for liquid fuels continues to increase. Fischer-Tropsch synthesis is used to convert coal or biomass The use of liquid fuel plays an important role in alleviating the shortag...

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Problems solved by technology

[0004] Since the effective components of Fischer-Tropsch synthesis are CO and H 2 , the presence of hydrocarbons in the Fischer-Tropsch synthesis tail gas reduces the partial pressure of effective components, increases the load on the Fischer-Tropsch synthesis reactor system, and makes equipment investment and operating costs relatively high

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