First plug flow reactor

The first distinction to be drawn, as far as heat transfer is concerned, is between the plug-flow and continuous well-mixed reactor. In the plug-flow reactor shown in Fig. 13.1, the heat transfer can take place over a range of temperatures. The shape of the profile depends on... 

Volume of CFSTR and plug flow reactors with respect to conversion level for a first order reaction... 

This relation is identical with that which would be obtained from equation 8.2.10 for a plug flow reactor with first-order kinetics. 

Comparison of performance of a series of N equal-size CSTR reactors with a plug flow reactor for the first-order reaction... 

Comparison of the fractional yields of V in mixed and plug flow reactors for the consecutive first-order reactions. A A- V W. (Adapted from Chemical Reaction Engineering, Second Edition, by O. Levenspiel. Copyright 1972. Reprinted by permission of John Wiley and Sons, Inc.)... 

The F(t) curve for a system consisting of a plug flow reactor followed by a continuous stirred tank reactor is identical to that of a system in which the CSTR precedes the PFR. Show that the overall fraction conversions obtained in these two combinations are identical for the case of an irreversible first-order reaction. Assume isothermal operation. 

Two Reactions, Different Orders—In the case of a desired second-order reaction and an undesired first-order reaction, such as A + B - C and A — D, where C is the desired product, the batch, semi-batch, or plug-flow reactor is preferred. 

A feed containing Ca0 = 1.5 and Cb0 - 1.75 lbmol/cuft is charged at the rate of 100 cuft/hr to a CSTR followed by a plug flow reactor with half the residence time of the CSTR. The concentration leaving the system is to be Ca2 = 0.4. Find the composition C.1 leaving the CSTR and the sizes of the two reactors. Also, find the concentrations with the same sizes when the PFR is first. 

For a first order reaction, the volumes of a CSTR and of a plug flow reactor are to be compared for the same conversion. 

At present the liquid phase reaction, A + B = C + D, takes place in a plug flow reactor. A conversion of 96% is obtained with Ca0 = Cb0 = 1 mol/liter. A mixed reactor 10 times the volume of the PFR is connected in series. Find conversions with the PFR first and with the PFR second in series. In the PFR,... 

The flow through a plug flow reactor effecting a first order reaction is increased by 20%. In order to maintain conversion at its former value, the temperature is to be raised. If the reaction has an activation energy of 4 kcal/gmol and the initial temperature is 150 C, what will be the new temperature Would the required elevation in temperature be different if the reactor were a CSTR ... 

It is proposed to carry out to within 90% of equilibrium a gas phase reaction, A B, which is first order, by passage through a plug flow reactor at 500 C and 1 atm. The pure reactant enters at 350 C and the available data are,... 

A first order reversible reaction, A B, is carried out in a plug flow reactor, starting with pure A. The specific rate and equilibrium constants are functions of temperature, k = A exp (-E/T)... 

A plug flow reactor is operated with a ratio 3 = R /V of recycle flow to fresh flow. The reaction is first order. Find the ratio Cr/Cf of the effluent and feed concentrations. 

The complexity of the turbulent reacting flow problem is such that it is best to deal first with the effect of a turbulent field on an exothermic reaction in a plug flow reactor. Then the different turbulent reacting flow regimes will be described more precisely in terms of appropriate characteristic lengths, which will be developed from a general discussion of turbulence. Finally, the turbulent premixed flame will be examined in detail. 

Fig. 10. Conversion in an exothermic reversible first-order reaction carried out in (a) a plug-flow reactor and (b) a continuous stirred tank reactor.

For fairly high degrees of conversion, with both first- and second-order reactions, the volume of a tubular reactor in which laminar flow occurs is about 30—50% greater than that of the plug-flow reactor in... 

Now, for a constant-density first-order reaction, the integrated form of the design equation for a plug-flow reactor, eqn. (66), may be rewritten... 

For a first-order reaction which is not accompanied by any change in density, the design equation for a plug-flow reactor can be integrated to give... 

As Table 5 shows, the volume of a continuous stirred tank with a certain performance is greater than that of the corresponding plug-flow reactor. The volume ratio with a second-order reaction is markedly greater than when first-order kinetics apply and this effect is greater at high conversions where both ratios can be very large. 

Mixed Versus Plug Flow Reactors, First- and Second-Order Reactions... 

Thus in Fig. 6.1, and in terms of the limiting component A, the size ratio of mixed to plug flow reactors is represented by the region between the first-order and the second-order curves. 

Consider N plug flow reactors connected in series, and let X2,.. . , be the fractional conversion of component A leaving reactor 1, 2,.. . , A. Basing the material balance on the feed rate of A to the first reactor, we find for the /th reactor from Eq. 5.18... 

With Eqs. 6b and 7 we can compare performance of N reactors in series with a plug flow reactor or with a single mixed flow reactor. This comparison is shown in Fig. 6.5 for first-order reactions in which density variations are negligible. 

At present the elementary liquid-phase reaction A + B R + S takes place in a plug flow reactor using equimolar quantities of A and B. Conversion is 96%, Cao = Cbo = 1 mol/liter. If a mixed flow reactor ten times as large as the plug flow reactor were hooked up in series with the existing unit, which unit should come first and by what fraction could production be increased for that setup ... 

For an irreversible first-order liquid-phase reaction (C q = 10 mol/liter) conversion is 90% in a plug flow reactor. If two-thirds of the stream leaving the reactor is recycled to the reactor entrance, and if the throughput to the whole reactor-recycle system is kept unchanged, what does this do to the concentration of reactant leaving the system ... 

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