Graphical and Shortcut Methods Binary Systems

At a given point in time, the amount of liquid in the reboiler is and its composition in terms of the mole fraction of the lighter component is The distillate rate and composition at time / are D mol/h and Xg, respectively. The internal liquid and vapor flows at the same instant areL and P mol/h, assumed constant from tray to tray. A material balance at / around an envelope that includes the condenser and a column section from the condenser to any tray gives the following operating line equation if the holdups are neglected  

The operating line equation at time when the reboiler liquid amount and com- 

A material balance around the condenser relates the L/V ratio to the reflux ratio 

The graphical procedure is applicable to any binary batch distillation process and is not limited to operations at constant reflux ratio or constant distillate composition. 

FIGURE 17.2 Graphical method for constant reflux ratio. 

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