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

1 095 1 1 01 034 1 p p p 01 1 27 1 eq 1 is a

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Unformatted text preview: s vapor. Reflux drum temperature is 100oF, and composition of total distillate in mole fractions is 0.10 C2, 0.20 C3, and 0.70 nC4. Reflux pressure is not given, but K-values at 100oF and 200 psia are given. Assumptions: K-values are inversely proportional to pressure. Find: Pressure in the reflux drum. Analysis: As shown in Exercise 4.24, the compositions of net equilibrium vapor and liquid are independent of recycle or, in this case, reflux. Therefore, the flash equations can be applied using the total distillate composition as the feed composition. Therefore, Ψ =V/F = 0.10. The Kvalues are given by: KC2 = 2.7 200 200 200 , KC3 = 0.95 , KnC 4 = 0.34 P P P Substituting these equations into Eq. (3), Table 4.4, 200 200 200 01 1 − 0.95 . 01 1 − 0.34 . P P P f { P} = + + =0 200 200 200 1 + 01 2.7 . − 1 1 + 0.1 0.95 − 1 1 + 0.1 0.34 −1 P P P 01 1 − 2.7 . (1) Eq. (1) is a nonlinear equation that can be solved by various means. Using a spreadsheet, in a manner similar to that used to solve Exercise 4.24, we obtain P = 126 psia. Exercise 4.28 Subject: Comparison of flash calculations using three different K-value correlations. Given: A stream at 7.2oC and 2,620 kPa with the overall composition given below. Find: Phase conditions Analysis: Using the CHEMCAD process simulator, the following results are obtained using the Soave-Redlich-Kwong (SRK), Peng-Robinson (PR), and Benedict-Webb-Rubin-Starling (BWRS) correlations: K-values: Component N2 C1 C2 C3 nC4 nC5 nC6 SRK 17.5 5.73 1.07 0.327 0.098 0.036 0.0096 PR 17.6 5.71 1.12 0.337 0.102 0.032 0.0110 BWRS 16.3 6.00 0.99 0.292 0.087 0.029 0.0071 The K-values for the SRK and PR correlations are in reasonably good agreement, deviating from each other by less than 15 %. Except for C1, the BWRS correlation predicts lower values, with the biggest deviation for nC6. Product compositions: Componen t N2 C1 C2 C3 nC4 nC5 nC6 Total: SRK: f, kmol/h υ, kmol/h 1.0 0.70 124.0 52.92 87.6 11.13 161.6 6.81 176.2 2.31 58.5 0.25 33.7 0.05 642.60 74.17 PR: l, kmol/h υ, kmol/h 0.30 0.69 71.08 52.06 76.46 10.45 154.79 6.42 173.89 2.16 58.25 0.26 33.65 0.04 568.43 72.08 BWR: l, kmol/h υ, kmol/h 0.31 0.67 71.94 53.04 77.15 9.63 155.18 5.67 174.04 1.88 58.24 0.21 33.66 0.03 570.52 71.13 l, kmol/h 0.33 70.96 77.97 155.93 174.32 58.29 33.67 571.47 All three correlations predict about the same V/F ratio, which ranges from 0.1107 to 0.1154. Exercise 4.29 Subject: Equilibrium flash calculations at different temperatures and pressures Given: Mixture of 100 kmol of 60 mol% benzene (A), 25 mol% toluene (B), and 15 mol% oxylene (C). Sources of vapor pressure data. Assumptions: Ideal solutions using vapor pressure with Raoult's law. Find: Amounts and compositions of vapor and liquid products at: (a) 100oC and 1 atm. (b) 100oC and 2 atm. (c) 105oC and 0.1 atm. (d) 150oC and 1 atm. Analysis: Instead of Figure 2.4 for the vapor pressures of benzene and toluene and three vaporpressure data points for o-xylene, use the built-in vapor pressure data in the CHEMCAD pr...
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This document was uploaded on 02/24/2014 for the course CBE 2124 at NYU Poly.

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