An approximate heuristic design procedure is used for the columns in the conventional process. The optimum number of trays is assumed to be equal to 2 times the minimum, and the optimum reflux ratio is assumed to be 1.2 times the minimum. The assumptions and specifications use up 9 of the 12 design degrees of freedom, leaving 3 that can be used to optimize the process. Three design optimization variables were selected:
1. Molar holdup in the reactor VR
2. Composition (mole fraction) of reactant B in reactor zB
The chemical equilibrium constant at 366 K [(Keq)366] and the relative volatilities (constant or temperature dependent) are specified for each case. Equimolal overflow is assumed in the distillation columns, which means that neither energy balances nor total balances are needed on the trays for steady-state calculations. Other assumptions are isothermal operation of the reactor, theoretical trays, saturated liquid feed and reflux, total condensers, and partial reboilers in the columns. Additional assumptions and specifications are the following:
1. In all cases the net production rates are set by fixing the fresh feed flowrate of pure component A at F0A to 12.6mol/s and B at F0B to 12.6mol/s.
2. The amount of reactant A lost in product stream Di is constant at Aioss = 0.63 mol/s (xD1,A = 0.05 mol fraction). There is no B and D going overhead (xD1B = xD1D = 0).
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