Separation Process Principles- 2n - Seader &amp; Henley - Solutions Manual

# Given vapor liquid equilibrium data at 1 atm and

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Unformatted text preview: 13 Subject: Azeotrope for the chloroform-methanol system at 101.3 kPa. Given: Vapor-liquid equilibrium data from Section 13, p. 11 of Perry's Handbook, 6th edition. Find: From data, construct y-x and T-x-y plots. Azeotrope conditions Analysis: See plots below. From these plots, a minimum-boiling azeotrope occurs at 53.5oC with a composition of 65 mol% chloroform and 35 mol% methanol. Exercise 4.14 Subject: Azeotrope for the water-formic acid system at 101.3 kPa. Given: Vapor-liquid equilibrium data from Section 13, p. 14 of Perry's Handbook, 6th edition. Find: From data, construct y-x and T-x-y plots. Azeotrope conditions Analysis: See plots below. From these plots, a maximum-boiling azeotrope occurs at 107.6oC with a composition of 42 mol% water and 58 mol% formic acid. Exercise 4.15 Subject: Partial vaporization of a water (A) -isopropanol (B) mixture at 1 atm. Given: Vapor-liquid equilibrium data at 1 atm and vapor-pressure data. Find: (a) (b) (c) (d) (e) Construct T-x-y and y-x diagrams. Composition of vapor when a 60 mol% A - 40 mol% B mixture is at its bubble point. Composition of vapor and liquid for 75 mol% vaporization of mixture in Part (a). K-values and α-values at 80 and 89oC. Comparison of parts (a), (b), and (c) to results from using Raoult's and Dalton's laws. Analysis: (a) The following are plots of the given equilibrium data, including the purecomponent normal boiling points. Exercise 4.15 (continued) Analysis: (a) continued Exercise 4.15 (continued) Analysis: (b) From the y-x plot on the previous page, the composition of the first bubble of vapor is 57 mol% isopropanol and 43 mol% water. See the q-line on the diagram. (c) For 75 mol% vaporization, use the inverse lever-arm rule on the T-x-y diagram or plot a q-line on the y-x diagram. For the latter, from the equation above Eq. (4-6), the slope of the q-line is [(V/F)-1]/(V/F) = (0.75-1.0)/0.75 = -0.333. The construction is shown on the y-x diagram, where the intersection with the equilibrium curve gives xA = 0.14 and yA = 0.50. (d) Can not compute the K-values or α at 80oC, because this temperature is below the lowest boiling mixture, which is the azeotrope. At 89oC, the T-x-y diagram gives the following compositions from the line shown on the above diagram: yB = 0.35, yA = 0.65 xB = 0.035, xA = 0.965 From Eq. (2-19) for the definition of the K- value, KB = yB 0.35 = = 10 xB 0.035 KA = yA 0.65 = = 0.67 xA 0.965 From Eq. (2-21) for the definition of the relative volatility, α, noting that at 89oC and 1 atm, isopropanol is more volatile, K 10 α B,A = B = = 15 KA 0.67 (e) To calculate T-x-y curves from vapor pressure data, using Raoult's and Dalton's laws, Eq. (2-44 ) applies, as well as the sum of the mole fractions in the phases in equilibrium. Thus, s s yA PA T yB PB T KA = = , KB = = (1, 2) xA P xB P yA + y B = 1 , xA + x B = 1 (3, 4) Equations (1) to (4) can be reduced to the following equations for the mole fractions of benzene in terms of the K-values: 1 − KB , y A = KA x A (5, 6) KA − KB If...
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