PURPOSE: To prepare synthetic natural gas with a high calorific value, by performing a specified treatment of coke oven gas to which CO-rich producer gas has been added.
CONSTITUTION: Gas 21 generated in a battery of coke ovens 1 is led into a group of processing units 2 for removal of tar, desulphurization, removal of ammonia, etc. to produce refined coke oven gas 24. CO-rich gas 25 generated in a producer 3 is passed through a dust collector 4 and a desulfurizer 5 and is mixed with the gas 24 to obtain a raw material gas 26. The gas 26 is led into a 1st- step reaction tower 9 through a pressurizing unit 7 and a gas purifier 8 of a synthetic natural gas production equipment 6 for reaction of CO with H2 in the presence of a catalyst to form 1-4 C hydrocarbon and obtain intermediate gas 29. The gas 29 is fed into a 2nd-step reaction tower 9' for interaction of remaining CO2 and H2 in the presence of a catalyst to form CH4 and is then introduced into an adsorption unit 11 filled with adsorbent having a molecular sieve function for removal of incombustible and low-calorie components.