Residue curve maps plotting

E. Check. The residue curve map plotted from the process simulator agrees with the map in Doherty and Malone (2Q01). The predicted distillate conposition for the first column determined from the mass balance calculation on Figure 11-11 is 31% methanol and 69% methyl butyrate. This agrees quite well with the results from the simulator. The literature states that Figure 11-lOa should be successful for separating this type of mixture. Thus, we are quite confident that the process is feasible. 

Plotting residue curves maps (RCM) allows the designer to anticipate problems by the separation of nonideal mixtures, namely when dealing with homogeneous and heterogeneous azeotropes. By reactor selection, it may foresee problems incurred by the recycle of some reactants. 

A residue curve map (RCM) consists of a plot of the phase equilibrium of a mixture submitted to distillation in a batch vessel at constant pressure. RCM is advantageous for analyzing ternary mixtures. More exactly, a residue curve shows explicitly the evolution of the residual liquid of a mixture submitted to batch distillation. 

Summing up, the influence of the kinetics of a chemical reaction on the vapor-liquid equilibrium is very complex. Physical distillation boundaries may disappear, while new kinetic stable and unstable nodes may appear. As result, the residue curve map with chemical reaction could look very different from the physical plots. As a consequence, evaluating the kinetic effects on residue curve maps is of great importance for conceptual design of reactive distillation systems. However, if the reaction rate is high enough such that the chemical equilibrium is reached quickly, the RCM simplifies considerably. But even in this case the analysis may be complicated by the occurrence of reactive azeotropes. 

Doherty and Malone, op. cit., chap. 5]. Unlike a binary y-x plot, relative-volatility information is not represented on an RCM. Therefore, it is difficult to determine the ease of separation from a residue curve map alone. The steady states of Eq. (13-116) are the constant-composition trajectories corresponding to dxjd = 0 for all i = l,. . . , c. The steady states therefore correspond to all the pure components and all the azeotropes in the mixture. 

Generating residual curve maps We go back to reaction R3 and assume a temperature-independent value oiK=2. We also assume that A has a constant volatility relative to R of 5, and B a relative value of 3. The first step is to generate the RCM for the nonreactive mixture of A, B, and R. This is just a triangular plot of the binary liquid phase compositions AB, BR, RA. The procedure consists of the following steps ... 

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