Uzi Mann

The limiting residence time distribution of continuous recycle systems

Abstract The limiting residence time distribution (RTD) of continuous recycle systems as the recycle ratio approaches infinity is considered. It is shown that the RTD converges to the exponential distribution whenever the system does not consist of a “dead volume” at the limit. This limiting behavior is independent of the system configuration and flow patterns. Issues concerning the proper modeling approach and the mathematical formulation of the condition that the system has no “dead volume” are discussed in detail. Some examples illustrating the importance of selecting the proper modeling approach are also provided.

New design formulation of chemical reactors with multiple reactions: I. basic concepts

Abstract A new approach to formulate the design of chemical reactors with multiple reactions is presented. The new design methodology is applicable for all reactor configurations, any number of chemical reactions, having any form of rate expressions. Reactor operations are formulated in terms the smallest set of dimensionless design equations and their solutions provide dimensionless operating curves, indicating progress of the chemical reactions, species compositions and the temperature variations without considering the reactor size or operating time. Reactor sizing represents a “point” on these operating curves and the required volume is readily determined for a specified feed rate and given reaction rates. The design is formulated using the least number of terms in each design equation, thus providing the most robust set of equations for numerical solutions. The methodology also provides new design capabilities for reactor configurations whose designs are not available in the literature. Part I presents the basic concepts of the new approach and illustrates how they are applied.