Method and system for synthesizing toluene diisocynate by gas-phase phosgene method

The invention provides a method and a system for synthesizing toluene diisocynate by a gas-phase phosgene method, and relates to the technical field of toluene diisocynate production, the system comprises a phosgene reaction circulation system, a condensation system and a recovery system which are communicated in sequence; the phosgenation reaction circulating system comprises a phosgenation reactor, a reaction circulating tank and a reaction circulating cooler which are communicated in sequence, gas-phase phosgene is input from the top of the phosgenation reactor, gas-phase toluenediamine is input from the side face of the phosgenation reactor, and the solvent consumption and the phosgene online amount are reduced in cooperation with circulating use of reaction circulating liquid; the safety performance of the system is improved, and meanwhile, the yield of toluene diisocynate is increased to 95%. The gas-phase mixed gas is subjected to condensation, compression and rectification separation, so that the puri