In addition to considering mixing and heat transfer, the design of continuous solution polymerization reactors also needs to pay special attention to the residence time distribution. In order to obtain a narrower residence time distribution, using multiple fully mixed reactors in series is one method, or a laminar flow reactor can be used to reduce the number of reactors and equipment investment.
When multiple fully mixed kettles are connected in series, the number of kettles generally ranges from 3 to 8. The more there are, the narrower the residence time distribution and the greater the investment. Therefore, various factors need to be balanced in the design. The agitator type of each reactor can be different. The polymerization first kettle is a low viscosity system, and using a turbine or blade agitator in combination with a baffle in turbulent flow can achieve good mixing, allowing the catalyst to be fully mixed with the monomer. The viscosity gradually increases, and when entering the transition basin operation, the agitator can use multi-stage counter current impellers, wide blade curved surface axial flow impellers, and turn on turbine impellers. In the later stage of the reaction, the viscosity of the system is higher, and it enters the laminar flow zone for operation. The agitator adopts screw belt, broken screw belt and other types, and the agitator adopts near wall design or scraper design according to the viscosity of the kettle material.
In order to narrow the residence time distribution, make the flow closer to laminar flow, and suppress axial backmixing, the equipment can be designed with a shape with a large aspect ratio. The agitator can be designed with a structure with good radial mixing and weak axial backmixing, such as a frame agitator or a skewed frame agitator. However, due to low viscosity, the first kettle is generally still designed as a full mixing kettle.