A \(25 \mathrm{wt} \%\) solution of dioxane in water is to be extracted continuously at the rate of \(1000 \mathrm{~kg} / \mathrm{h}\) in countercurrent fashion with pure benzene to remove \(95 \%\) of the dioxane. Equilibrium data are given in Problem 7.15.

(a) What is the minimum solvent requirement?

(b) If \(800 \mathrm{~kg} / \mathrm{h}\) of solvent is used, how many theoretical stages are required?

(c) What is the number of real stages if the Murphree stage efficiency, expressed in terms of extract compositions, is \(\mathbf{E}_{M E}=0.5\) ?

Problems 7.17 to 7.19 refer to the system cottonseed oil (A)-liquid propane (B)-oleic acid (C) at \(372 \mathrm{~K}\) and \(42.5 \mathrm{~atm}\). Equilibrium tie-line data taken from Treybal (1980) in weight percent are given in Table 7.8. Oleic acid is a monounsaturated fatty acid found naturally in many plant sources and in animal products. It is an omega-nine fatty acid and considered one of the healthier sources of fat in the diet. It is commonly used as a replacement for animal fat sources that are high in saturated fat. As a fat, oleic acid is one of the better ones to consume. As a replacement for other saturated fats, it can lower total cholesterol level and raise levels of high-density lipoproteins (HDLs) while lowering low-density lipoproteins (LDLs), also known as the "bad" cholesterol.

Problem 7.15:-

Water-dioxane solutions form a minimum-boiling-point azeotrope at atmospheric pressure and cannot be separated by ordinary distillation methods. Benzene forms no azeotrope with dioxane and can be used as an extraction solvent. At \(298 \mathrm{~K}\), the equilibrium distribution of dioxane between water and benzene is as follows (Treybal, 1980):

(a) Determine the minimum solvent rate required.

Data From Problem 7.17 to 7.19:-

Problem 7.17:-

Generate the Janecke diagram and the distribution curve for the system cottonseed oil (A)-propane (B)-oleic acid (C) at \(372 \mathrm{~K}\) and \(42.5 \mathrm{~atm}\).
Problem 7.18:-

If \(100 \mathrm{~kg}\) of a cottonseed oil-oleic acid solution containing \(25 \mathrm{wt} \%\) acid is extracted twice in crosscurrent fashion, each time with \(1000 \mathrm{~kg}\) of pure propane, determine the compositions (wt\%) and the weights of the mixed extract and the

final raffinate. Make the computations on a solvent-free basis using the Janecke diagram generated in Problem 7.17.
Problem 7.19:-

If \(1000 \mathrm{~kg} / \mathrm{h}\) of a cottonseed oil-oleic acid solution containing \(25 \mathrm{wt} \%\) acid is to be continuously separated into two products containing 2 and \(90 \mathrm{wt} \%\) acid (solvent-free compositions) by countercurrent extraction with propane, calculate:

(a) The minimum number of theoretical stages required.

(b) The minimum external extract/reflux ratio required.

(c) For an external extract/reflux ratio of 4.5, the number of theoretical stages, the position of the feed stage, and the quantities, in \(\mathrm{kg} / \mathrm{h}\), of the important streams.

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Table 7.8 Equilibrium Tie-Line Data for System Cottonseed Oil (A)-Propane (B)-Oleic Acid (C) at 372 K and 42.5 Atm Oil Propane Acid Oil Propane Acid 63.5 36.5 0.0 2.30 97.7 0.00 57.2 37.3 5.5 1.95 97.3 0.76 52.0 39.0 9.0 1.78 97.0 1.22 42.7 39.5 13.8 1.50 96.6 1.90 39.8 41.5 18.7 1.36 95.9 2.74 31.0 42.7 26.3 1.20 95.0 3.80 26.9 43.7 29.4 1.10 94.5 4.40 21.0 46.6 32.4 1.00 93.9 5.10 14.2 48.4 37.4 0.80 93.1 6.10 8.3 52.2 39.5 0.70 92.1 7.20 4.5 54.4 41.1 0.40 93.5 6.10 0.8 55.5 43.7 0.20 94.3 5.50 Source: Data from Treybal (1980).