Designing Heterogeneous Reactors for Stability

A study of the nonlinear kinetics of heterogeneous reactors can lead to basic design criteria which are useful in designing stability into a given reactor. The design of most reactors is usually based upon other physical parameters such as reactivities, heat transfer surfaces, metallurgical conditions, and operating lifetimes. The question of reactor stability is often deferred on the design schedule until these other parameters have so closely bounded the design that only incidental changes are possible. It is fortunate that many reactors are naturally stable over wide ranges of design conditions. Nonlinear kinetics have been examined in two ways in the past. The first method is to modify the basic reactor kinetic equations to include the effects of temperature, pressure, or poisoning. Solutions of these equations generally can be obtained with some approximation being needed. The second method consists of obtaining the transfer function of a simple reactor and modifying the characteristics of this reactor by feedback networks. The first method has been used successfully by Weinberg and Ergen for homogeneous reactors and by Lipkin and others for heterogeneous reactors. The second method is an engineering one which is capable of giving considerable information over a wide range of variables and will be used in this paper with suitable approximation to examine the stability of heterogeneous reactors.