6.2 Multiple-Reactor System Plug flow reactors in series and/or in parallel N plug flow reactors in series with a total volume V gives conversion as a single plug flow reactor of volume V. For reactors in parallel V/F or t must be the same for each parallel line.Any other way of feeding is less efficient. 11
11 • Plug flow reactors in series and/or in parallel • N plug flow reactors in series with a total volume V gives conversion as a single plug flow reactor of volume V. • For reactors in parallel V/F or τ must be the same for each parallel line. Any other way of feeding is less efficient. 6.2 Multiple-Reactor System
EXAMPLE 6.I OPERATING A NUMBER OF PLUG FLOW REACTORS The reactor setup shown in Fig.E6.1 consists of three plug flow reactors in two parallel branches.Branch D has a reactor of volume 50 liters followed by a reactor of volume 30 liters.Branch E has a reactor of volume 40 liters.What fraction of the feed should go to branch D? Branch D v=50.liters =30 liters V=40 liters Branch E Figure E6.1 12
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SOLUTION Branch D consists of two reactors in series;hence,it may be considered to be a single reactor of volume Vp 50 +30 80 liters Now for reactors in parallel V/F must be identical if the conversion is to be the same in each branch.Therefore. 份。-（月 Or Fo=Vp= Therefore,two-thirds of the feed must be fed to branch D. 13
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.Equal-size mixed flow reactors in series In plug flow,the concentration of reactant decreases progressively through the system;in mixed flow,the concentration drops immediately to a low value. CA in N>30 Plug flow Five mixed flow reactors,N=5 Single mixed flow reactor,N=1 CAout Volume through reactor system Figure 6.3 Concentration profile through an N-stage mixed flow reactor system compared with single flow reactors. 14
14 •Equal-size mixed flow reactors in series In plug flow, the concentration of reactant decreases progressively through the system; in mixed flow, the concentration drops immediately to a low value
Consider a system of N equal-size mixed reactors connected in series.Density changes will be assumed to be negligible C-1,X-1 CN-1,XN-1 C0,X0=0 C1,X1 C2,X2 F00 CN XN:U Figure 6.4 Notation for a system of N equal-size mixed reactors in series. 15
15 Consider a system of N equal-size mixed reactors connected in series. Density changes will be assumed to be negligible