Ternary System Without Inerts

5.1.1 Column Configuration

In the two-product reaction system, the column has both bottoms and distillate products coming from the two ends of the column. The two reactant feedstreams are fed into the middle section of the column. With a one-product reaction system without inerts, the column has only a bottoms or a distillate product. If product component C is heavier than reactant components A and B, there is a bottoms stream but no distillate. The column operates at total reflux with all of the overhead vapor condensed and returned to the column as reflux. There is no need to have a rectifying section because there is no distillate and no need to maintain any composition at the top of the column.

Thus, the column configuration in the one-product ternary system without inerts is quite different than the two-product configuration. Figure 5.1 gives the flowsheet. There are only stripping and reactive sections.

5.1.2 Chemistry and Phase Equilibrium Parameters

Table 5.1 gives kinetic and vapor-liquid phase equilibrium parameters used in the numerical case considered in this chapter. The forward reaction rate parameters are the same as those used in the two-product case. The activation energy of the backward reaction is the same, but the preexponential factor of the backward reaction is changed because the backward reaction is only first order in the concentration of product C.

The backward reaction depends on only 1 mol fraction, so a smaller value of kB is needed to achieve the same conversion (the product of 2 mol fractions is smaller than 1 mol fraction). Therefore, equilibrium constant KEq is increased to 20 from the previous value of 2.

The vapor pressures of reactants A and B are the same as in the two-product system. The vapor pressure of heavy product C is assumed to be the same as D in the quaternary system. Relative volatilities are constant.

Distillation Column Control
Figure 5.1 Ternary reactive distillation column without inerts.

TABLE 5.1 Kinetic and Vapor-Liquid Equilibrium Parameters for Base Case

Activation energy (kcal/mol)

Forward 30

Backward 40 Specific reaction rate at 366 K (kmol s

Forward 0.008

Backward 0.0004

Chemical equilibrium constant at 366 K 20

Heat of vaporization (kcal/mol) 6.944 Molecular weights (g/mol)

A and B 50

C 100

Liquid density (kg/m3) 700

Vapor Pressure Constants Aj

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