Effects of Preexponential Factor

In this section the rate constants are reduced or increased at 366 K by adjusting the preexponential factors while fixing the activation energies at 30,000 and 40,000 cal/mol (high activation energy case). These can be viewed as two different systems or the scenarios of changing catalyst activity. The optimal feed tray location and percentage of energy savings are of interest.

Low Reaction Rate Constant. Here we consider a lower reaction rate constant with relative volatilities aC/aA/aB/aD = 8/4/2/1. The specific reaction rates at 366 K are changed to 60% of the nominal values (kF = 0.0048 and kB = 0.0024).

Because the reaction rates are almost 60% smaller, under the conventional feed arrangement the vapor rate increases by a factor of 30% to meet product specifications compared to the nominal case (Table 18.2). Product D takes a slightly lower value than the base case (Fig. 18.5a), and more energy is required to separate the product from the reactants.

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