Process for preparing liquefied natural gas (LNG) from coal

The invention discloses a process for preparing liquefied natural gas (LNG) from coal. The process is specifically characterized in that only fine desulfurization is needed before methanation of synthetic gas from coal, CO2 still stays in the synthetic gas, CO2 is removed after methanation, and the synthetic gas is liquefied till the CO2 is 50*10 (vol%) to produce the LNG. The methanation process without recycle gas is adopted, and CO2 is removed by combining low-temperature separation with low-temperature methanol washing phase. CO2 is separated at the temperature of -50 to -60 DEG C under the pressure of 2.4-2.6MPa, and liquid pure CO2 obtained at a column reactor is used as a byproduct. Mixed gas of CH4 and CO2 is obtained at the tower top and delivered to a low-temperature methanol washing tower, and CO2 is removed to 50*10 (vol%). By adopting the process, CO2 can be conveniently collected as a byproduct. Meanwhile, the gas quantity of low-temperature methanol washing and the CO2 quantity are reduced. For the conventional coal-made SNG (synthetic natural gas) process, the quantity of recycle gas can be reduced by more than 50% by adopting the process.