NOVELTY - Synthetic natural gas is prepared by removing oil, amine, benzene, and naphthalene from coke oven gas, performing heat exchange with sulfur-tolerant methanation reactor II exhaust gas (2) in heat exchanger II (16), performing heat exchange with sulfur-tolerant methanation reactor I (1) exhaust gas in heat exchanger I (15), sending to top of sulfur-tolerant methanation reactor I loaded with molybdenum-based sulfur-tolerant methanation catalyst, performing 1st sulfur-tolerant methanation and organic sulfur hydrogenation reaction, and sending exhaust gas to waste heat boiler I (12).    USE - Preparation of synthetic natural gas (claimed).    ADVANTAGE - Preparation of synthetic natural gas is simple and has low energy consumption and equipment investment, improved yield, and excellent product quality.    DETAILED DESCRIPTION - Synthetic natural gas is prepared by removing oil, amine, benzene, and naphthalene from coke oven gas, performing heat exchange with sulfur-tolerant methanation reactor II exhaust gas (2) in heat exchanger II (16), performing heat exchange with sulfur-tolerant methanation reactor I (1) exhaust gas in heat exchanger I (15), sending to top of sulfur-tolerant methanation reactor I loaded with molybdenum-based sulfur-tolerant methanation catalyst, performing 1st sulfur-tolerant methanation and organic sulfur hydrogenation reaction, sending exhaust gas to waste heat boiler I (12), recovering heat, performing heat exchange with coke oven gas, sending to top of sulfur-tolerant methanation reactor II loaded with molybdenum-based sulfur-tolerant methanation catalyst, performing 2nd sulfur-tolerant methanation and organic sulfur hydrogenation reaction, sending exhaust gas to waste heat boiler II (13), recovering heat, performing heat exchange with coke oven gas, cooling in air cooler I (10), performing gas-liquid separation in gas-liquid separation tank I (4), discharging condensed liquid from tank bottom, sending gas phase to iron oxide crude desulfurizing tower (5), desulfurizing, sending to activated carbon desulfurizing tower (6), desulfurizing, sending exhaust gas to heat exchanger III (17), performing heat exchange with methanation reactor (3) outlet gas, heating in steam heater (18), sending to top of methanation reactor loaded with nickel (Ni)-based catalyst, performing clean methanation, sending exhaust gas to waste heat boiler III (14), performing heat exchange with desulfurizing tower gas, cooling in air cooler II (11), cooling in water cooler (19), sending to gas-liquid separation tank II (7), discharging condensed liquid, performing heat exchange with gas-liquid separation tank IV (9) gas in methane precooler (20), cooling in cooler I (21), performing gas-liquid separation in gas-liquid separation tank III (8), discharging condensed liquid, cooling gas in cooler II (22), performing gas-liquid separation in gas-liquid separation tank IV, discharging gas, and sending liquid which is liquefied natural gas product to liquefied natural gas tank.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of synthetic natural gas preparation system. (Drawing includes non-English language text).    Sulfur-tolerant methanation reactor I (1)    Sulfur-tolerant methanation reactor II (2)    Methanation reactor (3)    Gas-liquid separation tank I (4)    Crude iron oxide desulfurization tower (5)    Activated carbon desulfurization tower (6)    Gas-liquid separation tank II (7)    Gas-liquid separation tank III (8)    Gas-liquid separation tank IV (9)    Air cooler I (10)    Air cooler II (11)    Waste heat boiler I (12)    Waste heat boiler II (13)    Waste heat boiler III (14)    Heat exchanger I (15)    Heat exchanger II (16)    Heat exchanger III (17)    Steam heater (18)    Water cooler (19)    Methane precooler (20)    Cooler I (21)    Cooler II (22)