Influence of RTD on the Reactor Performance

The result can be generalized RTD will diminish the conversion and the specific reactor performance for reactions with a positive reaction order (w 0). 

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In this chapter, residence time distribution (RTD) of ideal and nonideal reactors along with the method of determination are described in detail. The influence of nonideality and RTD on the reactor performance, the target product yield, and selectivity, including complex reactions, is presented. 

Figure 3.16 Influence of RTD on the performance of tubular reactors. First order reaction, k = 0.1 min . ...

Several sophisticated techniques and data analysis methodologies have been developed to measure the RTD of industrial reactors (see, for example, Shinnar, 1987). Various different types of models have been developed to interpret RTD data and to use it further to predict the influence of non-ideal behavior on reactor performance (Wen and Fan, 1975). Most of these models use ideal reactors as the building blocks (except the axial dispersion model). Combinations of these ideal reactors with or without by-pass and recycle are used to simulate observed RTD data. To select an appropriate model for a reactor, the actual flow pattern and its dependence on reactor hardware and operating protocol must be known. In the absence of detailed quantitative models to predict the flow patterns, selection of a model is often carried out based on a qualitative understanding of flow patterns and an analysis of observed RTD data. It must be remembered that more than one model may fit the observed RTD data. A general philosophy is to select the simplest model which adequately represents the physical phenomena occurring in the actual reactor. 

The influence of residence time distribution (RTD) on performance, selectivity and yield is the same in microreactors as in conventional reactors. Therefore, the eflfects are well understood. Nonetheless, the demonstration of this at the microscale has hardly been reported so far. However, some experimental techniques have been developed to measure RTDs in microchannel flows which allow comparison between different types of flows or flows run at different parameters so that at least optimal flow conditions with regard to RTD can be found. 

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