Plug flow reactor yield limits

Neither B nor the undesirable products are present in the feedstream. Determine the maximum yields of B that can be obtained in the limit where the conversion level approaches 100% for both a plug flow reactor and a continuous flow stirred tank reactor. 

In all cases studied, the membrane reactor offered a lower yield of formaldehyde than a plug flow reactor if all species were constrained to Knudsen diffusivities. Thus the conclusion reached by Agarwalla and Lund for a series reaction network appears to be true for series-parallel networks, too. That is, the membrane reactor will outperform a plug flow reactor only when the membrane offers enhanced permeability of the desired intermediate product. Therefore, the relative permeability of HCHO was varied to determine how much enhancement of permeability is needed. From Figure 2 it is evident that a large permselectivity is not needed, usually on the order of two to four times as permeable as the methane. An asymptotically approached upper limit of... 

In order for a membrane reactor to produce yields of HCHO greater than in a plug flow reactor, the membrane must be permselective for this species. The more permselective the membrane is to formaldehyde the better the membrane reactor performs until the formaldehyde is approximately one thousand times more permeable than methane. At this limit, the concentration of HCHO is essentially equal on both sides of the membrane at all times. No further improvement is possible by increasing the diffusivity of the formaldehyde further because there is... 

Note that the first reaction is autocatalytic in component B. Reactant A is the limiting component. Component B is the desired product while C and D are by-products. Both reactions have moderate heats of reaction and relatively low activation energies. To maximize the yield of 23, a plug-flow reactor was selected. The economic objectives are throughput and yield. What is the appropriate partial control scheme for this reactor ... 

Neither V nor any of the undesirable product species are present in the feed stream. For both a plug flow reactor and a single continuous flow stirred-tank reactor determine the maximum yields of V that can be obtained in the limit at which the conversion of A approaches 100%. Prepare plots of the effluent concentrations of all species versus reactor space time for each type of reactor. To quantify the concentration of the undesired products in the effluent, consider the dimerization reaction (2A D) as the only significant reaction. 

The usual practice of maintaining a constant conversion is optimal with respect to the maximum possible yield under some limiting conditions (Szepe and Levenspiel 1968 Chou et al. 1967). Consider an isothermal, plug-flow reactor. Suppose the deactivation kinetics are such that the fractional catalytic activity A can be described by ... 

In the limit as CAF approaches zero, the overall yield approaches unity. If the plug flow and stirred tank reactors are operated at less than... 

If a tubular-flow reactor is equipped with a recycle arrangement, as shown in Fig. 7, the mixing pattern is somewhere between the two ideal limits of plug flow and ideal back-mixing. Such a system can be useful for controlling product distribution from a complex reaction. Consider the simultaneous occurrence of reactions (17) and (105) where reaction (105) is second-order and B is the desired product. The discussion above would suggest that plug flow would enhance the relative yield of B but back-... 

In the complete-conversion limit as Caf approaches zero, the overall yield in the CSTR approaches unity. If the plug flow and stirred-tank reactors are operated at less than complete conversion, equations (D) and (F) indicate that at the same conversion the yield from the CSTR will always exceed that from the PFR. 

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