Schematic of stages in extraction battery

Constant underflow means constant overflow as given by Eqnation 7.5 below. 

This is the case of constant underflow where slope of the operating line 

Using the equilibrium relation and the operating line given by Equation 7.3, McCabe-Thiele procedure can be performed. This is illustrated in the following example. 

Since the oil content in final extract is 92% of original, final oil in extract (in final overflow) is given by  

The final extract contains 40% of oil so the final overflow can be given by  

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