Flow Reactors in Series

Considering a sequence of stirred reactors in series, the residence time for reactor 1 is given by 

Combining this with the performance equation (see Chapter 4) for a first-order reaction, 

By writing similar equations for f2. Fn the following expression for conversion at the end of N reactors results  

This equation has been validated by the extensive experimental results of Elridge and Piret (1950). 

For a reversible reaction, first order in both directions. 

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Thus j plug flow reactors in series with a total volume Ik, totai give the same conversion as a single reactor of volume VRttota]. 

E takes place in the liquid phase in a combination of two plug flow reactors in series as shown... 

Equal-Size Mixed Flow Reactors in Series... 

Let us illustrate the use of this method by considering three mixed flow reactors in series with volumes, feed rates, concentrations, space-times (equal to residence times because e = 0), and volumetric flow rates as shown in Fig. 6.7. Now from Eq. 5.11, noting that e = 0, we may write for component A in the first reactor... 

Determining the Best System for a Given Conversion. Suppose we want to find the minimum size of two mixed flow reactors in series to achieve a specified conversion of feed which reacts with arbitrary but known kinetics. The basic performance expressions, Eqs. 5.11 and 5.12, then give, in turn, for the first reactor... 

Figure 6.9 Graphical representation of the variables for two mixed flow reactors in series.

The optimum size ratio for two mixed flow reactors in series is found in general to be dependent on the kinetics of the reaction and on the conversion level. For the special case of first-order reactions equal-size reactors are best for reaction orders n > 1 the smaller reactor should come first for n < 1 the larger should come first (see Problem 6.3). However, Szepe and Levenspiel (1964) show that the advantage of the minimum size system over the equal-size system is quite small, only a few percent at most. Hence, overall economic consideration would nearly always recommend using equal-size units. 

Reactant A (A R, C o = 26 mol/m ) passes in steady flow through four equal-size mixed flow reactors in series (r otai = 2 min). When steady state is achieved the concentration of A is found to be 11, 5, 2, 1 mol/m in the four units. For this reaction, what must be so as to reduce from... 

The kinetics of the aqueous-phase decomposition of A is investigated in two mixed flow reactors in series, the second having twice the volume of the first reactor. At steady state with a feed concentration of 1 mol A/liter and mean residence time of 96 sec in the first reactor, the concentration in the first reactor is 0.5 mol A/liter and in the second is 0.25 mol A/liter. Find the kinetic equation for the decomposition. 

Using a color indicator which shows when the concentration of A falls below 0.1 mol/liter, the following scheme is devised to explore the kinetics of the decomposition of A. A feed of 0.6 mol A/liter is introduced into the first of the two mixed flow reactors in series, each having a volume of 400 cm. The color change occurs in the first reactor for a steady-state feed rate of 10 cmVmin, and in the second reactor for a steady-state feed rate of 50 cm /min. Find the rate equation for the decomposition of A from this information. 

A stream of fully suspended fine solids (v = 1 mVmin) passes through two mixed flow reactors in series, each containing 1 m of slurry. As soon as a particle enters the reactors, conversion to product begins and is complete after two minutes in the reactors. When a particle leaves the reactors, reaction stops. What fraction of particles is completely converted to product in this system ... 

The main individual reactions that take place in the reformer (e.g., reactions (1), (2) and (5)) will be considered separately from the overall autothermal reaction for two reasons. First, in ATR the reactor can be considered as two plug-flow reactors in series (1) a very fast POX reaction occurs at the top of the catalyst bed and utilizes a small portion of the bed and (2) a slow SR utilizes the remainder of the reactor bed. Therefore, an optimal ATR catalyst must have excellent SR eatalytic properties. Second, there may be situations in which liquid fuels are reformed using only these individual reactions e.g., diesel fuel may be reformed using only SR (reaction (2)) or only by POX (reaction (1)). 

Kramers<5> (Fig. 2.6) of a plug-flow reactor in series with an ideally mixed stirred... 

The riser will be considered as divided into zones that can be represented by a battery of piston-flow reactors in series (Figure 3). Each zone will have a length of Lj, L2, Ly etc. The following relations will apply ... 

When the reactors are of equal volume, the overall conversion is independent regardless of which reactor precedes. However, generally, the CFSTR should precede the plug flow to minimize the total reactor volume. Figure 5-37 shows the total residence time of the CFSTR and plug flow reactors in series. 

The final sequence we shall consider is a CSTR and plug-flow reactor in series. There are two ways in wlricb this sequence can be arranged (Figure... 

Danckwerts Mixing vessel and plug flow reactor in series. Both orders of the apparatus A and B give identical residence time distribution from [92]. 

This model accounts for fuel atomization and vaporization, partial oxidation, steam reforming, and anode exhaust combustion. It is asumed that the partial oxidation reaction is very fast and occurs at the top of the catalyst bed along with fuel atomization and vaporization. It is also assumed that the steam reforming initiates after all O2 is consumed in the partial oxidation reaction. Therefore, the reactor will initially be considered as two plug-flow reactors in series. Figure 2 and 3 depict the inlet conditions for the ATR model and results from the model, respectively. 

Thus, j plug flow reactors in series with a total volume... 

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