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

# Exercise 44 subject degrees of freedom analysis for a

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Unformatted text preview: it if the vapor feed rate, the outlet temperature of the partial condensate, and the cooling water outlet temperature were specified. Exercise 4.3 Subject: Degrees of freedom analysis for an adiabatic, two-phase flash. Given: Continuous, adiabatic flash of one feed into vapor and liquid products Assumptions: Exiting streams are in equilibrium Find: (a) (b) (c) (d) (e) Analysis: Number of variables. All equations relating variables. Number of equations. Number of degrees of freedom Preferred specifications (a) Variables are those appearing in Figure 4.36 N V = 3C + 9 (b) C Component material balances 1 Energy balance 1 Pressure identity for two exiting streams 1 Temperature identity for two exiting streams 3 Mole fraction sums for three streams C Vapor-liquid equilibrium equations (c) NE = 2C + 6 (d) ND = NV - NE = (3C + 9) - (2C + 6) = C + 3 (e) Specify the feed completely ( feed rate, temperature, pressure and C - 1 mole fractions) plus exiting pressure. Exercise 4.4 Subject: Degrees of freedom analysis for a non-adiabatic three-phase flash. Given: Continuous, non-adiabatic flash of a liquid feed to produce a vapor and two liquid phases as shown in Figure 4.33. Assumptions: The three exiting phases are in equilibrium. Find: Number of degrees of freedom. Analysis: The variables are the heat transfer rate and four each of stream flow rates, temperatures, pressures, and C mole fractions. Thus, NV = 4C + 13. The equations are: C Component material balances 1 Energy balance 2 Pressure identities for three exiting streams 2 Temperature identities for three exiting streams 4 Mole fraction sums for four streams 2C Phase equilibrium relations: KiI = yi / xiI and KiII = yi / xiII Therefore, NE = 3C + 9 Number of degrees of freedom = ND = NV - ND = (4C + 13) - (3C + 9) = C + 4 Exercise 4.5 Subject: Application of Gibbs phase rule to seven-phase system of Figure 4.31. Given: One gas and six liquid phases in equilibrium. Assumptions: Gas phase includes N2 , O2 , and argon. Find: Number of degrees of freedom by Gibbs phase rule. Possible set of specifications to fix system. Analysis: From Eq. (4-1), Number of degrees of freedom = C - number phases + 2 Number of components = 9 (N2 , O2 , argon, n-hexane, aniline, water, phosphorus, gallium, and mercury. Number of phases = 7 Number of degrees of freedom = 9 - 7 + 2 = 4 Specify T, P, and mole fractions of argon and oxygen in the air. Exercise 4.6 Subject: Partial vaporization of a mixture of benzene and ethyl alcohol. Given: Vapor-liquid equilibrium data (T-x-y) for benzene-ethyl alcohol at 1 atm and vapor pressure data for benzene and ethyl alcohol. Initial mixture contains 25 mol% benzene. Assumptions: Phase equilibrium Find: (a) Bubble point. (b) Composition of vapor at bubble point. (c) Composition of liquid at 25 mol% vaporization. (d) Composition of liquid at 90 mol% vaporization. (e) Same as part (c), except vapor is removed and then additional 35 mol% is vaporized. (f) Plot of temperature vs. mol% vaporized for parts (c) and (e). (g) Repeat of parts (a) to (f) assuming ideal solutions Analysis: See plot of T-x-y data on next page, as drawn with a s...
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