Device and method for producing polyoxymethylene dimethyl ether DMM3-5

The invention discloses a device and method for producing polyoxymethylene dimethyl ether DMM3-5. A gaseous product which contains methanal and is prepared through two methods serves as a starting material, the gaseous product does not pass through an absorption tower, that is to say, an aqueous solution is not prepared, the gaseous product is discharged from an outlet of a methanol oxidation reactor, heat exchange and fine dehydration are conducted, the treated gaseous product is introduced into an extraction catalytic distillation tower which integrates gas phase extraction, liquid phase catalysis and liquid phase distillation to be subjected to a polycondensation reaction, technological processes such as the polycondensation reaction and fractionation are completed in one step, and original tedious processes are simplified. According to the device and method for producing polyoxymethylene dimethyl ether DMM3-5, a new technical route for producing polyoxymethylene dimethyl ether is created; compared with the prior art, a large quantity of equipment, pipelines and internal part facilities are omitted; the technological processes are optimized; the investment is saved, and the production cost is reduced; energy conservation and emission reduction are achieved to the maximum extent; the solid foundation is laid for large-scale, continuous and intensive production.