Abstract
This work investigated the applicability of heterogeneous and pseudo-homogeneous models to predict the dynamic behavior of a fixed-bed catalytic reactor. Some issues concerning the dynamic behavior of the system were discussed, such as the prediction of the inverse response phenomenon. The proposed models (Het- erogeneous I and II and Pseudo-homogeneous) were able to predict with qualitative similarity the main characteristics of the dynamic behavior of a fixed-bed catalytic reactor, including the inverse response. The computational time demanded for the solution of the heterogeneous models was 10 to 50% longer than in the case of the pseudo-homogeneous model, making the use of the former suitable for applications where computational time is not the major restriction (off-line applications). On the other hand, when on-line applications are required, the simplified model (Pseudo-homogeneous model) showed to be a good alternative because this model was able to predict (qualitatively) the dynamics of the reactor using a faster and easier numerical solution.
Highlights
Nowadays, the economic feasibility of many commodity production processes characterized by large throughputs relies on computer-based operations, in which a good process model is important, but necessary
This work investigated the applicability of heterogeneous and pseudo-homogeneous models to predict the dynamic behavior of a fixed-bed catalytic reactor
The proposed models (Heterogeneous I and II and Pseudo-homogeneous) were able to predict with qualitative similarity the main characteristics of the dynamic behavior of a fixed-bed catalytic reactor, including the inverse response
Summary
The economic feasibility of many commodity production processes characterized by large throughputs relies on computer-based operations, in which a good process model is important, but necessary This is especially true for fixed-bed catalytic reactors, whose nonlinear and complex behavior makes it difficult to obtain their best performance (high conversion). The location of regions with unstable behavior can change in space and time and is dependent on input disturbances and control actions For these reasons, the detailed formulation of the model considering the equations in dynamic mode is necessary to ensure the reliability of such complex predictions. When on-line applications are required, simplified models that reproduce the essential characteristics of the system are preferred because computational time is a major restriction in these cases Bearing this in mind, the object of the present studies was the development of dynamic models of fixed-bed catalytic reactors based on the heterogeneous and pseudo-homogeneous approaches. The models show different degrees of details and the analyses of the dynamic behavior of a fixed-bed catalytic reactor that promotes the oxidation of ethanol into acetaldehyde allowed to identify the differences in the predictions generated by each model as well as to determine which model is more adequate for a specific application, either off- or on-line
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