Ponchon-Savarit diagram

Alternative approaches are to be found in the hterature. Derivations of the above equations are given in numerous texts (2,10—12), which also describe graphical or analytical solutions to the problem. Many of these have direct analogues in other separation processes such as distillation (qv) and hquid—hquid extraction, and use plots such as the McCabe-Thiele diagram or Ponchon-Savarit diagram. 

FIG. 18 81 Composition diagrams for leaching calculations a) right-triangular diagram (h) modified Ponchon-Savarit diagram,... 

The graphical technique most frequently used in distillation is the x-y or McCabe-Thiele diagram (1). The H-x, or Ponchon-Savarit diagram (2,3), is herder to visualize and cannot be readily extended to multicomponent distillation. Due to their limited application, H-x diagrams were excluded from this book, and are discussed elsewhere (4-6). 

Ponchon-Savarit diagram. 26 Ponter underwetting theory, 516, 517 Porter rivulet model. 542 Porter and Jenkins packing HETP, 532-534 regime transition. 332 Poynting factor. 7 Prado and Fair tray efficiancy, 375 PRO/II. 169, 170,180... 

With the reflux ratio fixed, one can step off the number of trays for a binary column using a McCabe-Thiele diagram or, if one wishes to account for heat effects, a Ponchon-Savarit diagram (Treybal. 1968), establishing the number of trays needed and where to feed the column. 

In general the Ponchon-Savarit diagram is somewhat more difficult to use than the constant 0 / (McCabe-Thiele) diagram, but it is the exact solution for theoretical plates assuming that the enthalpy data employed are correct. 

Equilibrium values from the upper Ponchon-Savarit diagram are used to construct the equilibrium curve in the lower McCabe-Thiele diagram as follows. For a given tie-line, a vertical line is drawn down from the end-point on the N-y curve on to the diagonal (x = y) in the lower diagram. A horizontal line is then drawn to the left to meet the vertical from the other end-point of the tie-line on the N-x curve. The intersection gives a point on the equilibrium curve. This procedure is repeated. 

To produce crystals containing 95 per cent Ba(N03)2 at the top and 95 per cent Pb(N03)2 at the bottom from a 50 per cent feedstock, using a reflux ratio of 1.36, four theoretical stages would be adequate as shown. The upper Ponchon-Savarit diagram could also be used to determine the number of theoretical stages. 

F. Generalize. This procedure is similar to the one we used for binary flash distillation in Figure 2-9. Thus, there is an analogy between distillation calculations on enthalpy-conposition diagrams (Ponchon-Savarit diagrams) and extraction calculations on triangular diagrams. 

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