Polymerization Kinetics and Reactor Design

Abstract

An informal review is given of the author's view of the present state of engineering knowledge in polymerization kinetics and the present state of the art in the design of polymerization reactors. The discussion focuses on key areas where information for reactor design is needed and relates them to the design and scale-up of the reactor. Special emphasis is given to the effect of reactor configura tion. Optimization methods and the importance of proper control strategy are also discussed.*"phe recent advances in polymerization kinetics and design of polymerization reactors have been aptly summarized in recent reviews (1-4) which include most of the published articles. We therefore decided that instead of repeating these efforts we would devote this review to taking stock of our opinion of where we stand today and what problems must be solved to bring the design of polymerization reactors to the same level as conventional reactor design.Basically, polymerization is a complex chemical reaction, and there fore most of the concepts developed with respect to the design of re actors for such reactions apply also to the design of polymerization reactors. Thus, what are the significant differences of polymerization as compared with other complex chemical reactions that merit special attention? Let us briefly consider what is the information generally needed for the successful design and control of a chemical reactor.Assume we already have a process giving a desired product. What we need for design is:( 1 ) Specifications and tolerances for the product quality, the yields needed, etc.(2) An engineering kinetic model allowing us to predict the effect of changes in the process parameters (temperature, inlet concentration, transport processes ) on the yield and desired products. 56 57(3) A description of the transport processes occurring in the re actor; in other words, a flow model and an evaluation of the effect of transport processes on the kinetics.With this information in hand, we can then undertake to consider: (4) A suitable design configuration allowing safe scale-up and easy control.(5) Optimization of design and operating conditions. (6) Control strategy to ensure conformance to specifications. The body of this review takes up these points in order. Product SpecificationsPerhaps the most characteristic feature of polymerization reactor engineering is the fact that in a majority of cases the specifications are not given in terms which are suitable for reactor design. Let us assume for a moment that we have a simple polymerization process, where only one type of polymer is possible and that we know the kinetics sufficiently to predict the effect of all variables. What we are going to predict are molecular weight distributions (MWDs). However, product specifica tions are given in completely different terms: mechanical strength, elec trical properties, corrosion resistance, performance in molding and extrusion equipment, etc. While for this simple case all these properties should be completely specified by the MWD, wha...

Influence of mixing on the performance of periodic chemical reactors

“…Also, utilization of an isothermal model reveals the strong dependence of some polymerization processes on concentration nonuniformities alone. In closing this section it should be noted that experimental realization of precisely the situation shown in Figure 1 has been proposed by Shinnar and Katz (1972) for simulation of small deviations from perfect mixing.…”