BSTILL - Binary Batch Distillation Column

This distillation equipment is as described in Sec. 3.3.3.2. For convenience a column containing seven theoretical plates and reboiler is assumed, together with constant volume conditions in the reflux drum. The example is based on that of Luyben (1973, 1990). 

The component balance for the more volatile component on any plate n yields dX, 

It may be noted that the liquid holdup on the plates is set rather large. This is necessary to avoid very slow rates of computation. 

CONSTANT HOLDUP BINARY BATCH DISTILLATION COLUMN EQUILIBRIUM PLATE BEHAVIOUR 

CONSTANT MOLAR OVERFLOW AND CONSTANT PLATE HOLDUP CONSTANT HOLDUP IN REBOILER AND SURGE DRUM 

The component balance for plate n, based on the more volatile component, is 

5 Simulation Tools and Examples of Chemical Engineering Processes 

For the reflux drum and condenser, assuming constant holdup 

Startup is at initially total reflux, with the reflux value set at an arbitrarily high value, R = Rinit. Once the distillate composition, XO, exceeds the set point composition, XOset, control of reflux ratio is effected by varying the reflux ratio according to the proportional control relationship RC=KC (X0set-X0). The change from initial startup to controlled withdrawal of distillate is effected by means of the logical control variable Flag . 

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