The invention discloses a process and a device for preparing LNG (
Liquefied Natural Gas) and co-producing
carbon dioxide from
coke oven gas, belonging to the field of
chemical industry. The
coke oven gas subjected to fine desulfurization is divided into two paths, the first path directly enters a
methanation section, the second path enters a CO conversion
tower, CO is converted into CO2 through a
water gas conversion reaction, and H2 is generated at the same time; the converted gas is cooled by a
heat exchanger I2 or a steam boiler and then enters an
alcohol amine
decarburization tower, CO2 is partially or almost completely removed by spraying an
alcohol amine solution, and the
alcohol amine solution is heated and regenerated to obtain high-purity CO2 as a chemical
raw material; the decarburized gas and the first path of gas are converged and then enter a
methanation section, and H2 reacts with CO and CO2 in three
methanation reactors which are connected in series and in parallel to generate CH4. The device comprises a main pipeline, a CO conversion
tower, a
heat exchanger, an alcohol amine decarbonization tower, an alcohol amine regeneration tower, a methanation reactor and the like. According to the invention, large-air-volume circulation and a compressor are avoided, the cost is saved, high-purity CO2 is co-produced, the CO / CO2 content and temperature rise can be flexibly regulated and controlled, and temperature runaway is prevented.