Yx diagram

Figure 12.7 yx diagram for the ethane/heptane system. (Reproduced by permission from F, H. Ban-David, AIChE J., 2 426, 1956.) 

Figure 10.6 yx diagram forethaneln-heptane. (Reproduced by permission from. . H. Barr-David, AlChEJ., vol. 2, p. 426—427, 1956.) 

A PT diagram for the ethane/heptane system is shown in Fig. 12.6, and a yx diagram for several pressures for the same system appears in Fig. 12.7. According to convention, one plots as y and x the mole fractions of the more volatile species in the mixture. The maximum and minimum concentrations of the more volatile species obtainable by distillation at a given pressure are indicated by the points of intersection of the appropriate yx curve with the diagonal, for at these points the vapor and liquid have the same composition. They are in fact mixture critical points, unless y = x = 0 or y = x = 1. Point A in Fig. 12.7 

The phase equilibrium data, or Equation 5.12, are first plotted on a YX diagram 

When cmiditions required for die two simide cases just described are not met, the opoating curves may be located on the XA-yx diagram by appropriate use of the triangular diagram, as described below. 

In Fig. 12.9-la a typical equilibrium diagram is shown where solute A is infinitely soluble in solvent C, which would occur in the system of soybean oil (/l)-soybean inert solid meal (B)-hexane solvent (C). The upper curve of N versus for the slurry underflow represents the separated solid under experimental conditions similar to the actual stage process.The bottom line of N versusx, where N = Oon the axis, represents the overflow liquid composition where all the solid has been removed. In some cases small amounts of solid may remain in the overflow. The tie lines are vertical, and on a yx diagram, the equilibrium line is y = on the 45° line. In Fig. 12.9-lb the tie lines are not vertical, which can result from insufficient contact time, so that all the solute is not dissolved adsorption of solute A on the solid or the solute being soluble in the solid B. 

---