Reactor Selection and Operating Conditions for Parallel Reactions

3 Reactor Selection and Operating Conditions for Parallel Reactions  

In this section, we will discuss the qualitative aspects of selecting the reactor and operating conditions for parallel reactions. We will assume that component A undergoes two irreversible reactions, of which the former gives the desired product, R, and the latter the nondesired product, S  

In the case of a gas-phase system, the product purity can, in our example, be increased by a higher total pressure or a reduced amount of inert components. If a low value for ca is desired, then a CSTR is the correct choice for the reactor. The reactor should further be operated so that as high a value for the conversion, pa, as possible is obtained. In gas-phase reactions, the desired reaction is now promoted by the low total pressure and a high amount of inert components in the system. 

Undesirable parallel reactions can thus force us to select a CSTR, although the low production capacity requires a considerably larger reactor volume than in the case of a PFR or a BR. 

FIGURE 3.19 Concentration evolvements of the components for a composite reaction in a (a) CSTR, and (b) PFR. 

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