In the production process of polyester, the condensation reaction is gradually carried out, and the molecular weight of polymer is improved continuously. The reaction belongs to the reversible balanced reaction and reaction equilibrium constant is small, thus the balance is guaranteed by continuously removing small molecules generated by the reaction under the vacuum operation conditions. In the early stage of the production process, the viscosity of the system is small, and the small molecules are relatively easy to enter the gas phase, thus the process is carried out by reaction control; and in the later stage of the production process, the operation viscosity of the system is gradually increased, thus the process is carried out by diffusion control. Therefore, most of the polyester industry adopts multistage condensation, and uses a horizontal surface renewal reactor with good mass transfer performance as a final condensation reactor.
In the patents of a series of disclosed disk reactors, the described structure mainly comprises a sealed transverse cylinder. The cylinder is arranged with a material inlet and a material outlet thereon, and is pivoted with a driving shaft therein. The driving shaft is fixedly arranged with plural groups of ring disks. A plural of parallel axial film-drawing steel plates is fixedly arranged on the ring disk or on the side portion of the ring disk. The disk reactor employs the ring disks or axial film-drawing steel plates to form a vertical film or a parallel film during operation, so as to increase the amount of material liquid film carried in the internal space of the reactor, increase the mass transfer area of the reactor, and effectively improve the stirring efficiency. The disk reactor has good reaction effect when the material viscosity is low in the early stage of reaction. However, with the deepening of the reaction and the increase of the material viscosity, such structure hinders the material flow to cause slow reaction speed. Furthermore, the retention time of the material on the surface of the reactor is too long, which results in excessive heating time to cause crosslinking side reaction.