Stirred Tank Reactor Some Practical Considerations

STIRRED TANK REACTOR SOME PRACTICAL CONSIDERATIONS 

The mechanically agitated contactor, referred to also as the stirred tank reactor (STR), is the most commonly used reactor for small and medium volume production in organic synthesis. Therefore, we shall summarize the important practical features of this reactor, which should also be applicable to CSTR. 

Several types of impellers are used. The most common are the simple marine impeller and the highly efficient double-motion stirrer. The reactors are always suitably baffled. 

For reactions with a sizable heat effect, heat is abstracted in several ways reflux condenser, internal coil, external heat exchanger, cooling jacket, and half-round pipes wound on the reactor body. The overall heat transfer coefficient with water in the tank for a water-cooled or steam-heated jacketed vessel is 0.15-1.7, for a tank with water-cooled half-round pipe is 0.3-0.9, and for a tank with water-cooled internal coil is 0.5-1.2kW/m K (Rose, 1981). 

Reactors are usually available only in standard sizes. It is much cheaper to buy an oversized tank that conforms to the nearest standard than to have a reactor of actual calculated dimensions specially fabricated. 

---

STIRRED TANK REACTOR SOME PRACTICAL CONSIDERATIONS... 

Stirred tank reactor Some practical considerations... 

In practice, the continuous mass polymerization is rather complicated. Because of the high viscosity of the copolymerizing mixture, complex machinery is required to handle mixing, heat transfer, melt transport, and devolatilization. In addition, considerable time is required to establish steady-state conditions in both a stirred-tank reactor and a linear-flow reactor. Thus, system start-up and product grade changes produce some off-grade or intermediate grade products. Copolymerization is normally carried out between 100 and 200°C. Solvents are used to reduce viscosity or the conversion is kept to 40-70%, followed by devolatilization to remove solvents and monomers. Devolatilization is carried out from 120 to 260° C... 

---