Batch Reactor with Two Reactants

The results presented in the previous section are for the simple reaction A — B. In this section we consider the reaction A + B — C. For the pure batch reactor in which the two reactants are initially charged to the vessel, the results are quite similar to those found in the simple A — B reaction. The effects of various design and kinetic parameters are essentially the same because both reactants are charged in their stoichiometric amounts. 

For fed-batch operation, however, there is a significant difference between the reaction A — B and the reaction A + B — C. One of the reactants can be charged to the reactor. Then the other can be fed at a rate consistent with the heat transfer capacity of the system. 

The following numerical example illustrates the dynamics of a fed-batch reactor with two reactants. 

The kinetics used are those given in Chapter 2 (Table 2.2). The desired operating temperature is 340 K. The diameter of the reactor is 2 m, giving a total volume of 12.57 m3 and jacket heat transfer area of 25.13 m2. The reactor is initially charged with 6.285 m3 of pure B with a composition CB = 8.01 kmol/m3. The initial reactor temperature is 300 K. 

Two temperature controllers are used. The first manipulates the flowrate of the A feed. A 45 min ramp in this reactor temperature controller is used with Kci = 0.5 and Tj2 = 20 min. Two 30-s lags are included in the loop. The span of the temperature transmitter is 50 K, and the maximum flowrate FA0 of the reactant A is 0.004 m3/s. The second temperature controller setting the flowrates of the hot and cold streams to the jacket is proportional-only with a 330 K setpoint and a gain of 0.05. The maximum cold water and hot water flowrates are 0.005 and 0.002 m3/s, respectively. 

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