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O Compute Keq from built-r expression

Figure 9.15 Setting up chemical equilibrium model.

O Compute Keq from built-r expression

Figure 9.15 Setting up chemical equilibrium model.

Figure 9.16 Steady-state conditions with chemical equilibrium.

Figure 9.16 Steady-state conditions with chemical equilibrium.

Stage

Figure 9.17 Composition profiles with chemical equilibrium.

Stage

Figure 9.17 Composition profiles with chemical equilibrium.

The resulting design flowsheet is given in Figure 9.16 and should be compared with the one for the kinetic model given in Figure 9.12. The differences are striking. The reflux ratio required to achieve the same product purities drops from 5.05 to 2.74, which corresponds to a very large reduction in energy consumption (from 35.0 to 18.2 MW). The diameter of the column is reduced from 7.4 to 4.8 m.

The composition profiles are quite different between the two cases. Figure 9.17 presents the results for the equilibrium design. A comparison with Figure 9.14b shows that the reac-tant compositions are much smaller for the equilibrium model (peak methanol concentration = ~ 5 mol%) compared with those for the kinetic model (peak methanol concentration = ~ 25 mol%).

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