Dynamics of other reactor configurations

No other reactor configuration (batch, semibatch, plug flow) exhibits the range of dynamic behavior of the CSTR. However, over a finite time interval, other configurations can sometimes exhibit a narrower range of dynamic behavior. If a semibatch reactor is operated such that the rate of reaction is just balanced by the rate of dilution from the feed, a pseudo-steady state may exist. In this case, the concentration of reactants and products in the reactor will remain constant over the time interval necessary to fill the reactor [27]. This may be exploited to provide constant polymer properties during the filling and start-up of a CSTR or CSTR train. 

Plug flow reactors are subject to the same sorts of instabilities as batch reactors (since the kinetics are essentially those of a batch reactor). In addition, the problem of reduced heat transfer due to polymer build-up on the inside surface of the reactor is compounded by the fact that polymer near the wall may be more viscous (due to low temperature or high conversion). The resultant velocity gradient will result in continuing build-up on the walls as the viscous polymer near the walls has a longer residence time than the less viscous material near the center of the tube. This effect will lead to reduced heat transfer, and an even greater tendency toward thermal instability. 

---