Stripping minimum

The corresponding estimate of minimum stripping-agent flow rate for a stripper is obtained as... 

Smin = minimum stripping factor at minimum flow rate for air... 

Minimum stripping factor at corresponding minimum air flotvrate ... 

The minimum stripping medium (steam or gas) lean oil ratio is estimated by a trial and error procedure based on key component ... 

Minimum stripping is analogous to minimum reflux. The discussion in Sec. 2.2.6 is also valid to minimum stripping. To determine minimum stripping, draw a line from the bottom composition point on the 45° diagonal line to the intersection of the 4-line with the equilibrium curve. From Eq. (2.30), the slope of this line is (1 + Smin)/Smill and its intercept on the y axis is -xfl/Smin. 

One useful limit for a stripping column is the maximum L/G ratio, which corresponds to the minimum stripping gas flowrate (minimum G/L ratio) required for a desired separation. The maximum L/G is the slope of the line which begins at the point (To, Xi) and intersects the equilibrium line. As shown in Figure 6.7, the (L/G)max occurs as one rotates the operating line clockwise around (Xi, Tq) until it intersects the equilibrium line. This can occur at a tangent pinch point and not necessarily at the end of the column Xm, Ym). 

For optimal stripping, temperatures should be high and pressures low. However, temperatures should not be so high as to cause decomposition, and vacuum should be used only if necessary. The minimum stripping agent flow rate, for a specified value of < 5 for a key component K corresponding to an infinite number of stages, can be estimated from an equation obtained from (12-60) with N = oo... 

The complex formulation effect previously discussed is found in all cases studied, whatever the formulation variable. Hence, the minimum drop size is attained at some formulation distance from t timum in both A regions, as schematically indicated in Fig. 19. However, the exact position of this minimum strip depends on stirring condititms and physicochemical properties. 

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