Method for preparing liquefied natural gas by using coke-oven gas

The invention discloses a method for preparing liquefied natural gas by using coke-oven gas, which mainly comprises the steps of methanation reaction, low-temperature separation and liquefaction, wherein the methanated gas first enters a membrane separation device to allow a major part of H2 to be removed by membrane separation, then enters a low-temperature device after being pressurized and finally enters a rectification column after being cooled; a tower kettle reboiler is heated by a raw material gas and an overhead condenser is supplied with cold by throttling and evaporation of methane which is a tower bottom; under the rectification action of the rectification tower, methane with a purity of over 99.5 percent is obtained in the tower kettle, and a mixture of H2, N2 and CH4 is obtained in the tower top; the methane obtained in the tower kettle is heated again and then delivered to be liquefied as a gas product; and the mixed gas of H2, N2 and CH4 obtained at the tower top is heated again and then delive