M

Fig. 5.1. Recycling system of reactor and distillation column

Fig. 5.2. Distillation column with reactive total reboiler

Fig. 5.3. RD column with reactive total condenser and reactive total reboiler

Fig. 5.3. RD column with reactive total condenser and reactive total reboiler

In the very early stage of conceptual process design, very little is known about the reaction kinetics, so a macrokinetic power-law expression in terms of liquidphase mole fractions should be used r=kxnHf) (5-i)

with n as apparent reaction order with respect to Aj, K as chemical equilibrium constant, and fc as the effective rate constant of forward reaction. K and fc are dependent on the temperature T but in a first step, they can be taken as constant parameters. K can be estimated from thermodynamic relations at a typical boiling temperature of the reaction mixture.

For the sake of a simplified nomenclature, the component indices are dropped by setting x = x and x1 = 1 - x. In addition, a dimensionless reaction rate r* is introduced r* - fc - (1—xKi—Id^) (5-2)

As a special case of (5.2), the rate of a first-order reaction (n = 1) is given by * x K

where xce is the mole fraction of A2 at chemical equilibrium. The vapor-liquid equilibrium is described assuming a constant relative volatility a = pf/pi > 1, which is assumed to be constant. Then, the equilibrium mole fraction of component A2 in the vapor phase, ye, is given by ye = (5.4)

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