ABSTRACT
The discussion of ideal reactors in Chapter 3 was limited to reactors that were either isothermal or adiabatic. Isothermal operation is often desirable, but it is hard to achieve in a large reactor with an exothermic reaction because of the difficulty in removing the heat that is released. For stirredtank reactors of fixed proportions, the rate of heat generation goes up with the cube of the diameter, but the wall area goes up only as the diameter squared. Similarly for a tubular reactor, the heat generation rate per unit length varies with the square of the diameter, but the wall area is proportional to the diameter. Therefore, for both reactor types, heat transfer becomes more difficult when the diameter is increased. Furthermore, there is more chance of unstable behavior for the larger reactors operating with a higher-temperature driving force for heat transfer. A reactor operating satisfactorily at the desired temperature may be close to the stability limit and may jump to a much higher temperature after just a slight change in feed concentration or jacket temperature.
