Efficient falling film type sulfur trioxide evaporator

The invention belongs to the technical field of sulfur trioxide production, and discloses an efficient falling film type sulfur trioxide evaporator to solve the problems in evaporators in the prior art, the evaporator comprises a shell pass shell, a flue gas inlet, a flue gas outlet, a concentrated sulfuric acid outlet, a concentrated sulfuric acid inlet, a tube bundle, a lower tube box, an upper tube box and the like, a sieve plate distribution disc is arranged at the bottom of the cofferdam cylinder, an inlet impingement plate is arranged in the cofferdam cylinder close to the concentrated sulfuric acid inlet, annular impingement plates are arranged on the cofferdam cylinder at intervals in the annular direction, a plurality of liquid discharge pipes are arranged on the sieve plate distribution disc, a gas rising pipe is further arranged on the sieve plate distribution disc, and a heat exchange pipe in the pipe bundle penetrates through an upper pipe plate and then is connected with a pipe fitting. The inle