PFR reactors

A PFR reactor gives a better result at the same temperature. Equation (5.6) gives bout ain = 0.814 for the PFR at 283.8K. However, this is not the optimum. With only one optimization variable, a trial-and-error search is probably the fastest way to determine that 7)... 

CSTR cascade and a PFR reactor. Note how rapidly PFR behavior is approached as N increases. Levenspiel has also included lines of constant kx on this figure, and these lines may be useful in solving certain types of design problems, as we will see in Illustration 8.10. 

For the autocatalytic reaction described in Example 15-10 and the data given there, calculate the volume of a combined CSTR + PFR reactor arranged as in Figure 17.7. 

Thus, for known kinetics and a specified residence time distribution, we can predict the fractional conversion of reactant which the system of Fig. 9 would achieve. Recall, however, that this performance is also expected from any other system with the same E(t) no matter what detailed mixing process gave rise to that RTD. Equation (34) therefore applies to all reactor systems when first-order reactions take place therein. In the following example, we apply this equation to the design of the ideal CSTR and PFR reactors discussed in Chap. 2. The predicted conversion is, of course, identical to that which would be derived from conventional mass balance equations. 

Table 11.2 gives the total holding times for two values of K, both for a series of CSTRs with minimal total volume and for a series of equal-sized mixed reactors. Total holding times for equal-sized mixed reactors have been calculated using a zero finding routine. The last value in Table 11.2 is the dimensionless holding time for a PFR reactor with Michaelis-Menten kinetics, calculated by means of the following equation ... 

A reactant A in liquid will be converted to a product P by an irreversible first-order reaction in a CSTR or a PFR reactor with a reactor volume of 0.1 m . A feed solution containing 1.0 kmol m of A is fed at a flow rate of 0.01 m min", and the first-order reaction rate constant is 0.12 min . ... 

Ihe same reaction in Problem 7.1 is proceeding in two CSTR or PFR reactors with a reactor volume of 0.05 m connected in series, as shown in the figure below. 

Selectivity A significant respect in which CSTRs may differ from batch (or PFR) reactors is in the product distribution of complex reactions. However, each particular set of reactions must be treated individually to find the superiority. For the consecutive reactions A => B => C, Fig. 7-5b shows that a higher peak value of B is reached in batch reactors than in CSTRs as the number of stages increases the batch performance is approached. 

The material balance on a PFR reactor accomplishing a first-order reaction at constant density is ... 

The reaction described by the data i Tables 2-1 and 2-2 is to be carried out in a PFR. The entering molar flow rate is 5 mol/s. Calculate the reactor volume necessary to achieve 80% conversiou in a PFR. (a) First, use one of the integration formulas given in Appendix A.4 to determine the PFR reactor volume, (b) Next, shade the area in Figtae 2-1 which when multiplied by would give the PFR volume, (c) Make a qualitative sketch of the conversion, X, and the rate of reaction, down the length (volume) of the reactor. 

The reactions are elementary and take place in the gas phase. The reaction is to be carried out isothermally and as a first approximating pressure drop will be neglected. The feed consists of hydrogen gas, carbon monoxide, j carbon dioxide, and steam. The total molar flow rate is 300 mo /s. The entering pressure may be varied between 1 atm and 160 atm and the entering temperature between 300 K and 400 K. Tubular (PFR) reactor volumes between 0.1 m and 2 m are available for use. 

J. Snyder and B. Subramaniam, Chem. Eng. Sci., 49, 5585 (1994)]. Ethylbenzene is fed at(a rate of 0.00344 kmol/s to a 10.0-m PFR reactor along with inert steam at (a total pressure of 2.4 atm. The steam/ethylbenzene molar ratio is initially [i.e., parts (a) to (c)] 14.5 1 but can be varied. Given the following data, find the exiting molar flow rates of styrene, benzene, and toluene for the following inlet temperatures when the reactor is operated adiabatically. 

No reaction vector in the AR boundary can point out of the AR. If this were the case, the AR could be extended further by PFR reactors, which have trajectories that are always tangent to the rate vectors. 

Fig. 11.6. Effect of temperature on reactor conversion with all other experimental conditions the same. The catalyst in the bed is RU/AI2Q3. , Rh-Al203 membrane A, RU-AI2O3 membrane O, Pd-Al203 membrane V, Pt-AkOs membrane A, AI2O3 membrane , conventional PFR reactor. Reproduced...

The PFR reactor volume necessaiy to achieve conversion is 2165 dm . This volume could result from a bank of 100 PFRs that are each 0.1 m in diameter with a length of 2.8 m (e.g.. see Figures I-8(a) and (b)). 

The CSTR volume was 6.4 m- and the PFR volume wa.s 2.165 When we combine Figures E2-2.1 and E2-3. i on the same graph, we see that the crosshatched area above the curve is the difference in the CSTR and PFR reactor volumes. 

Comparing the CSTR and PFR Reactor Volumes and Reactor Sequencing... 

We will solve ihe preceding set of equations to find the PFR reactor vo) using both hand calculations and an ODE computer solution. We carry out the 1 calculation to help give an intuitive understanding of how the parameters X, and vary with conversation and temperature. The computer solution allows us to rea plot the reaction variables along the length of the reactor and also to study the r tion and reactor by varying the system parameters such as Qo and Tfl. 

The mean residence time for the optimized PFR reactors in Example 6.4 is about 0.8 h and boni is about 3.4 kg mol m . Find the optimal temperature profile T(z) that maximizes the concentration of component B in the competitive reaction sequence of Equation 6.1 for a PFR subject to the constraint that t = 0.8 h. Assume ajn = 4.5 kg mol m . ... 

CDP4-P Fairly straight forward California registration problem where you must carry out a number of calculations involving conversion factors to calculate CSTR and PFR reactor volumes and a batch reaction time. 

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