Many extraction systems are partially miscible at high concentrations of solute but close to immiscible at low solute concentrations. At relatively low solute concentrations both McCabe-Thiele and triangular diagram analyses are applicable. Use chloroform to extract acetone from water. Equilibrium data are given in Table 13-6. Find number of equilibrium stages required for a countercurrent cascade if feed is \(1000.0 \mathrm{~kg} / \mathrm{h}\) of a \(10.0 \mathrm{wt} \%\) acetone, \(90.0 \mathrm{wt} \%\) water mixture. Solvent is chloroform saturated with water (no acetone). Flow rate of stream \(\mathrm{E}_{0}=1371 \mathrm{~kg} / \mathrm{h}\). We desire an outlet raffinate concentration of \(0.50 \mathrm{wt} \%\) acetone. Assume immiscibility and use a weight ratio graphical analysis. Convert equilibrium to weight ratios. Compare results with Problem 13.D3.

Problem 13.D3.

Use chloroform to extract acetone from water. Equilibrium data are given in Table 13-6. Find number of equilibrium stages required for a countercurrent cascade if feed is \(1000.0 \mathrm{~kg} / \mathrm{h}\) of a \(10.0 \mathrm{wt} \%\) acetone, \(90.0 \mathrm{wt} \%\) water mixture. Solvent is chloroform saturated with water (no acetone). Flow rate of stream \(E_{0}=1371 \mathrm{~kg} / \mathrm{h}\). Outlet raffinate concentration is \(0.50 \mathrm{wt} \%\) acetone. Use a triangle diagram and compare results with Problem 13.D19.

Problem 13.D19

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TABLE 13-6. Weight % equilibrium data for the system water-chloroform-acetone at 1 atm and 25C* Water Phase, wt% Chloroform Phase, wt% XD Water x5 Chloroform XA Acetone yo Water ys Chloroform YA Acetone 99.19 0.81 0.00 0.5 99.5 0.00 82.97 1.23 15.80 1.3 70.0 28.7 73.11 1.29 25.60 2.2 55.7 42.1 62.29 1.71 36.00 4.4 42.9 52.7 45.6 5.1 49.3 10.3 28.4 61.3 34.5 9.8 55.7 18.6 20.4 61.0