Plug-flow reactor with recycle

PLUG-FLOW REACTOR WITH RECYCLE The Basic Design Equation 

With this recycle, the conditions at R corresponding to the reactor inlet are [/4] = [/4]r, Fa = Far- Thus the PFR equation given in Chapter 4 becomes 

Integration of Equation 10.7 for a first-order reaction A — Products 

Note from Equations 10.3 and 10.5 that the recycle ratio R is given by 

The central problem in the design of an RFR is determining the optimum value of A ar to minimize the reactor volume. This can be obtained by setting 

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Plug flow reactors with recycle exhibit some of the characteristics of CSTRs, including the possibility of multiple steady states. This topic is explored by Penmutter Stah dity of (%emical Reactors, Prentice-Hall, 1972). 

For a plug flow reactor with recycle ratio R, relate the concentration change across the reactor to the overall concentration change. 

At present we have 90% conversion of a liquid feed (n = 1, C o =10 mol/ liter) to our plug flow reactor with recycle of product (R = 2). If we shut off the recycle stream, by how much will this lower the processing rate of our feed to the same 90% conversion ... 

A gas containing A (2 mol/m ) is fed (1 m /hr) to a plug flow reactor with recycle loop (0.02 m loop volume, 3 kg of catalyst), and the output composition from the reactor system is measured (0.5 mol A/m ). Find the rate equation for the decomposition of A for the following cases. Be sure to give the units of C, and k in your final expression. 

Aris (1991a), in addition to the case of M CSTRs in series, has also analyzed two other homotopies the plug flow reactor with recycle ratio R, and a PFR with axial diffusivity and Peclet number P, but only for first-order intrinsic kinetics. The values M = 1(< ), R = >(0), and P = 0( o) yield the CSTR (PFR). The M CSTRs in series were discussed earlier in Section IV,C,1. The solutions are expressed in terms of the Lerch function for the PFR with recycle, and in terms of the Niemand function for the PFR with dispersion. The latter case is the only one that has been attacked for the case of nonlinear intrinsic kinetics, as discussed below in Section IV,C,7,b. Guida et al. (1994a) have recently discussed a different homotopy, which is in some sense a basically different one no work has been done on multicomponent mixture systems in such a homotopy. 

The basic scheme of a single plug flow reactor with recycle is shown below in Fig.4.4-1. Such a reactor may be described also as a combination of perfectly mixed reactors. Other simplified configurations are described in the following cases, 4.4-l(l) and 4.4-l(2). The states are the concentration of the tracer in the perfectly mixed reactors, i.e. SS = [Ci, C2,. ]. The residence time in the... 

Another model, which will not be analyzed, is the plug-flow reactor with recycle shown in Fig. 6-1. The reactor itself behaves as an ideal tubular type, but mixing is introduced by the recycle stream. When the recycle rate becomes very large, ideal stirred-tank performance is obtained, and when the recycle is zero, plug-flow operation, results. The response data on the actual reactor are used to evaluate the recycle rate and then the conversion is estimated for a plug-flow reactor with this recycle rate. 

Parallel reactions (nonreacting products) The general case Effect of reaction order One of the reactants undergoes a second reaction Parallel-consecutive reactions Plug-flow reactor with recycle The basic design equation Optimal design of RPR Use of RPR to resolve a selectivity dilemma Semibatch reactors... 

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