Plug-flow reactors sizing

PLE 18.4 PLUG FLOW REACTOR SIZE FROM A RATE EQUATION... 

EXAMPLE 18.5 PLUG FLOW REACTOR SIZE FROM RATE ---------- CONCENTRATION DATA... 

Example 5 Percent Approach to Equilibrium For a reversible reaction with rate equation r = L[A — (1 — A)Vl6], the size function kV,./V of a plug flow reactor will be found in terms of percent approach to equilibrium ... 

Determine what size plug flow reactor, operating at 650°C and 5.0 atm, produces 85% conversion of the feed consisting of 4 kg/mols of pure phosphine per hour. 

This volume is appreciably larger than the volume of plug flow reactor calculated in Illustration 8.3 for the same reaction conditions and fraction conversion. However, the cost of such a reactor would be considerably less than the cost of a tubular reactor of the size determined in Illustration 8.3. 

Size Comparisons Between Cascades of Ideal Continuous Stirred Tank Reactors and Plug Flow Reactors. In this section the size requirements for CSTR cascades containing different numbers of identical reactors are compared with that for a plug flow reactor used to effect the same change in composition. 

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

Plug flow reactors mostly operate at essentially constant pressure but sometimes pressure drop due to friction is appreciable. Thus problems P4.05.30 and P4.05.29 reveal a significant effect of friction on conversion and reactor size. For flow in pipelines, the pressure drop is given by... 

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. 

When a value of Cg is specified, corresponding values of simultaneous solution of the last three equations. Then a plug flow reactor, for instance, can be sized as... 

What size of plug flow reactor operating at 649°C and 460 kPa can produce 80% conversion of a feed consisting of 40 mol of pure phosphine per hour ... 

For the reaction of Problem 5.21, what size of plug flow reactor would be needed for 80% conversion of a feed stream of 1000 mol A/hr at AO — 1.5 mol/liter ... 

Stoichiometry of the reaction is 2A->R + S. What size plug flow reactor (in liters) operating at 100°C and 1 atm can treat 100 mol A/hr in a feed consisting of 20% inerts to obtain 95% converson of A ... 

Regarding reactor sizes, a comparison of Eqs. 5.4 and 5.19 for a given duty and for s = 0 shows that an element of fluid reacts for the same length of time in the batch and in the plug flow reactor. Thus, the same volume of these reactors is needed to do a given job. Of course, on a long-term production basis we must correct the size requirement estimate to account for the shutdown time between batches. Still, it is easy to relate the performance capabilities of the batch reactor with the plug flow reactor. 

For a given duty the ratio of sizes of mixed and plug flow reactors will depend on the extent of reaction, the stoichiometry, and the form of the rate equation. For the general case, a comparison of Eqs. 5.11 and 5.17 will give this size ratio. Let us make this comparison for the large class of reactions approximated by the simple nth-order rate law... 

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. 

What reactor holding time will yield a product in which Cr = 0.9 mol/ liter (a) in a plug flow reactor, (b) in a mixed flow reactor, and (c) in a minimum-size setup without recycle ... 

If > U2, or the desired reaction is of higher order than the unwanted reaction, Eq. 3 shows that a high reactant concentration is desirable since it increases the R/S ratio. As a result, a batch or plug flow reactor would favor formation of product R and would require a minimum reactor size. 

Find the size of adiabatic plug flow reactor to react the feed of Example 9.5 (F q = 1000 mol/min and AO 4 mol/liter) to 80% conversion. 

Find the fraction of reactant unconverted in the real reactor and compare this with the fraction unconverted in a plug flow reactor of the same size. 

Equation 20 with Eq. 5.17 compares the performance of real reactors which are close to plug flow with plug flow reactors. Thus the size ratio needed for identical conversion is given by... 

Determine what size of plug flow reactor operating at 0°C and 1 atm would give 50% conversion of A to R for a feed rate of 100 kmol/hr of pure A. 

For a feed rate u = 3 what is the smallest size of plug flow reactor with appropriate piping (bypass or recycle or slide taps on the reactor) which will give... 

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