Minimum solvent/feed ratio

Both maximum and minimum limits exist of the solvent/feed ratio. The maximum is the value that locates the mix point M on the binodal curve near the solvent vertex, such as point Mmla on Figure 14.7(b). When an operating line coincides with a tieline, the number of stages will be infinite and will correspond to the minimum solvent/feed ratio. The pinch point is determined by the intersection of some tieline with line RnS- Depending on whether the slopes of the tielines are negative or positive, the intersection that is closest or farthest from the solvent vertex locates the operating point for minimum solvent. Figure 14.9 shows the two... 

Countercurrent Operation 466 Minimum Solvent/Feed Ratio 468 Extract Reflux 468... 

The position of the difference point can also be situated on the other side of the triangular diagram. There are also some restrictions with respect to the necessary minimum solvent/feed ratio. Further details can be found elsewhere [20, 21 ]. 

If a line from point AR should coincide with a tie line, an infinite number of stages will be required to reach this condition. The maximum amount of solvent for which this occurs corresponds to the minimum solvent/feed ratio which can be used for the specified products. The procedure for determining the minimum amount of solvent is indicated in Figure 7.13. All tie lines below that marked JK are extended to line SRn to give intersections with line SRN as shown. The intersection farthest from S (if on the left-hand side of the diagram) or nearest S (if on the right)... 

Solution, (a) Prior to investigating the maximum and minimum solvent/feed ratios, which occur, respectively, at the minimum and maximum number of stages, we develop the solution for S/F= 1.5. 

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