Cut Rate, Variable Reflux

only the first two cases will be discussed because with modern computers at hand, for these two cases only a graphical solution will be of value. 

Constant Reflux. In general, the operating line of a cascade follows from a mass/molar balance and a material balance between the top and a certain stage n of the cascade. For constant reflux R = const resp. R/Pi = v = const, 

The operating line is a straight line with the slope 

Constant Cut Rate, Veriable Reflux. When the molar balance  

Once the necessary number of stages is known, the product rate Pj/F can be calculated according to  

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Figure 6.17 Graphical evaluation of the number of stages for a reflux cascade (enriching section), operated with constant cut-rate, variable reflux.

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