Distillation-reaction transformed composition variables

The transformed variables describe the system composition with or without reaction and sum to unity as do Xi and yi. The condition for azeotropy becomes X, = Y,. Barbosa and Doherty have shown that phase and distillation diagrams constructed using the transformed composition coordinates have the same properties as phase and distillation region diagrams for nonreactive systems and similarly can be used to assist in design feasibility and operability studies [Chem Eng Sci, 43, 529, 1523, and 2377 (1988a,b,c)]. A residue curve map in transformed coordinates for the reactive system methanol-acetic acid-methyl acetate-water is shown in Fig. 13-76. Note that the nonreactive azeotrope between water and methyl acetate has disappeared, while the methyl acetate-methanol azeotrope remains intact. Only... 

Residue curve maps have shown to provide valuable insights and design assistance for nonideal systems, particularly for reactive distillation. Transforming the composition variables according to Doherty s approach allows to define a reaction invariant space of... 

Another type of nonlinear control can be achieved by using nonlinear transfonnations of the controlled variables. For example, in chemical reactor control the rate of reaction can be controller instead of the temperature. The two are, of course, related through the exponential temperature relationship. In high-purity distillation columns, a transformation of the type shown below can sometimes be useful to "linearize the composition signal and produce improved control while still using a conventional linear controller. 

Equation 14.37 shows that composition is not a convenient measure of azeotropy in reactive distillation. For equilibrium reactive mixtures, it is more convenient to use transformed variables that represent the equivalent amounts of reactants present in the equilibrium mixture. Thus, for the reaction... 

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