Continuously Operated Isothermal Ideal Tubular Reactor

3 Continuously Operated Isothermal Ideal Tubular Reactor 

For isothermal operation (for non-isothermal operation see Section 4.10.3.3), a first-order reaction with respect to reactant A (rA = fecA) and constant volume, Eq. (4.10.24) leads to  

If we compare the values of Xa calculated by Eqs. (4.10.19), (4.10.20), (4.10.25) and (4.10.26) for a given value of Da, we see that for a positive reaction order the conversion in a PFR is always higher than in a CSTR (see also Section 4.10.2.7). This effect can also be explained without any mathematics The mean concentration in a PFR is somewhere between the in- and outlet value, whereas in a CSTR we have a constant but always lower reactor concentration that equals the outlet concentration. Thus for a positive value of the reaction order, the mean reaction rate in a PFR is higher. For a zero-order the difference in the reaction rate vanishes, and only for the rare case of a negative reaction order is the CSTR superior to a PFR. 

4 Continuously Operated Isothermal Tubular Reactor with Laminar Flow 

The following simple model system may illustrate this situation. Let us assume we have two ideal PFRs, each with the same volume. Both reactors are run in parallel. If we assume a first-order reaction with a rate constant of 1 s and a residence time in each reactor of 1 s we obtain a conversion of 63.2% in each reactor [Eq. (4.10.25)]. But if we divide the total volume rate unequally, the residence times 

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Continuously Operated Non-isothermal Ideal Tubular Reactor... 

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