Plug flow reactor continuous tracer

Non-ideal reactors are described by RTD functions between these two extremes and can be approximated by a network of ideal plug flow and continuously stirred reactors. In order to determine the RTD of a non-ideal reactor experimentally, a tracer is introduced into the feed stream. The tracer signal at the output then gives information about the RTD of the reactor. It is thus possible to develop a mathematical model of the system that gives information about flow patterns and mixing. 

Continuous tracer addition to a plug flow reactor... 

How can tracer methods help us in solving these two problems We know that reactor performance, as measured by conversion of the limiting reactant or by product selectivity, is a function of kinetics, flow pattern and mixing pattern in the reactor. The flow and mixing phenomena in various reactor geometries are complex, and we are currently unable to characterize them completely (at an economical cost). The only reactors that we know how to design, predict their performance and scale up with confidence, are those that behave as the two ideal reactor types, i.e. the plug flow (PFR) and the continuous flow stirred tank reactor (CSTR). 

For readable discussions of plug flow and the concept of dispersion the reader is referred to the literature [1, 2, 17]. Here we shall confine ourselves to a brief illustration of axial and radial dispersion. Let us consider the behavior of a tracer introduced into a stream flowing through a packed bed reactor, as sketched in Fig. 7.12. Here (a) shows the axial dispersion or spread by the time it reaches the exit of a tracer pulse introduced uniformly over the cross-sectional area of the column at a given axial position. Figure 7.12b depicts the radial dispersion of a tracer introduced continuously at a point source. 

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