Completely Mixed Tank

The tank is free of tracer at t = 0 and the transport of the tracer concentration starts at t = 0. The tracer balance for the completely mixed tank is:

After separating the variables and considering t = 0, c = 0, the solution is:

Figure 6.9 presents an example of a completely and an incompletely mixed tank reactor with a short circuit flow.

In the incompletely mixed tank, the tracer was measured after only relatively short times at high concentrations in the effluent, as could be expected from a tank (with a short circuit flow) and at a lower concentration after longer times because of the slow transport into eddy flow regions.

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short circuiting flow

death water region

Fig. 6.9 Retention time distribution F(l) for a CSTR compared with one from a reactor with a short circuiting flow and eddy water regions.

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