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Process Synthesis

In RD, the reaction is superimposed on distillative separation. On the one hand, this results in synergistic effects, such as a shift in the chemical equilibrium as a result of products being removed and distillation limits being exceeded owing to the reaction, while, on the other hand, it is precisely these synergies which make RD so extraordinarily complex. It should be borne in mind that today's Eastman Kodak process was not patented until 60 years after the first MeAc patent.

A vital aim of process synthesis is therefore to reduce the complexity of RD in order to enable simple solutions of this sort to be recognized quickly. To analyze processes involving reversible reactions systematically, a comprehensive process synthesis strategy has been developed. One element of this strategy is the analysis of RD lines. RD lines enable the feasibility of RD processes to be examined simply. The simplification is based on the fact that, according to the Gibbs phase rule (Fig. 2.2), the number of degrees of freedom of a system in physical and chemical equilibrium is reduced by the number of independent equilibrium reactions. Thus, in the case of a liquid-boiling system composed of three components A, B, C, which react according to A + B o C, only one concentration has to be defined in order to fix the composition, unlike the case of a system without a reaction where two concentrations have to be defined.

In order to be able to handle these concentration parameters appropriately, various authors have developed transformation methods [4]. These transformation methods enable RD to be described by a system of equations that is known from conventional distillation. The transformation converts the concentration para-

Transformation of the system A + B ^ C • Gibbs phase rule: F = C - Ph - R + 2

— —Chemical equilibrium

-► Transformation

Reaction path

Fig. 2.2 Gibbs rule C

Fig. 2.2 Gibbs rule C

— —Chemical equilibrium

-► Transformation

Reaction path

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