Technology for preparing natural gas from synthesis gas

The invention relates to a technology for preparing natural gas from synthesis gas. Sulfur-containing components in raw synthesis gas are removed firstly, desulfurized gas containing CO2 enters a methanation device and is subjected to a methanation reaction, and coarse SNG (synthetic natural gas) product gas is obtained; CO2 in the coarse SNG product gas is removed, a qualified SNG product is prepared, and methane-rich gas obtained in the CO2 removing process returns to the methanation reactor and is utilized as diluent gas to control the reaction temperature rise of the methanation reactor. Compared with the prior art, not only is the reaction temperature rise of the methanation reactor controlled, but also circulating gas flow rate of a circulating gas compressor can be greatly reduced,so that system energy consumption and equipment investment are remarkably reduced. 本发明涉及种合成气制天然气的工艺，先脱除原料合成气中的含硫组分，含CO2的脱硫气进入甲烷化装置内发生甲烷化反应，得到粗SNG产品气。粗SNG产品气再脱除CO2制得合格的SNG产品，在CO2脱除过程中得到的富甲烷气体返回至甲烷化反应器，用作稀释气，起到控制甲烷化反应器反应温升的作用。与