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Water
90.0
0.1
83.47
Total:
100.0
300.1
92.30 Extract
291.38
9.79
6.63
307.80 Compared to the CS results, a higher temperature, lower pressure, smaller CO2 flow rate, and
higher number of equilibrium stages are required. Unlike the CS result, the above is not the
optimal result, but is feasible depending on the reliability of the PR EOS with the WS mixing
rules. Energy balances were made around each stage, resulting in stage temperatures varying
from 355 to 365 K. Exercise 12.1
Subject: Revision of ratebased equations to account for entrainment and occlusion.
Given:. Ratebased model Eqs. (124) to (1218).
Find: Modified equations
Analysis:
Entrainment:
Let φj = ratio of entrained liquid (in the exiting vapor) that leaves Stage j to the liquid leaving
Stage j, yi ,n and yiI,n . Then, the entrained component liquid flow rate leaving Stage j =
φjxi, (1 + rjL ) L j .
Correspondingly, the entrained component liquid flow rate entering Stage j =
φj+1xi,j+1 (1 + rjL 1 ) L j +1 .
+
Occlusion:
Let θj = ratio of occluded vapor (in the exiting liquid) that leaves Stage j to the vapor
leaving Stage j, (1 + rjV )V j . Then the occluded component vapor flow rate leaving Stage j =
θj yi,j (1 + rjV )V j .
Correspondingly, the occluded component vapor flow rate entering Stage j = θj1 yi,jV
1 (1 + r j −1 )V j −1 .
The liquidphase component material balance, Eq. (124), and vaporphase component
material balance, Eq. (125), become, respectively, M iLj ≡ (1 + rjL + φ j ) L j xi , j − L j −1 xi , j −1 − φ j +1 (1 + rjL 1 ) L j +1 xi , j +1 − f i ,Lj − N iLj = 0, i = 1, 2, ..., C
,
+
,
M iV, j ≡ (1 + rjV + θ j )V j yi , j − V j +1 yi , j +1 − θ j −1 (1 + rjV−1 )V j −1 yi , j −1 − f iVj + N iV, j = 0,
, i =1, 2, ...., C The liquidphase energy balance, Eq. (126), and vaporphase energy balance, Eq. (127),
become , respectively, E jL ≡ (1 + rjL + φ j ) L j H jL − L j −1 H jL−1 − φ j +1 (1 + rjL 1 ) L j +1 H jL+1 − H jLF
+
E V ≡ (1 + rjV + θ j )V j H V − V j +1 H V+1 − θ j −1 (1 + rjV−1 )V j −1H V−1 − H VF
j
j
j
j
j C
i =1 C
i =1 fi ,Lj + Q L − e L = 0
j
j f iVj + QV + eV = 0
,
j
j The total phase material balances, Eqs. (1216) and (1217), become, respectively,
M TL, j ≡ (1 + rjL + φ j ) L j − L j −1 − φ j +1 (1 + rjL 1 ) L j +1 −
+
V
M T , j ≡ (1 + rjV + θ j )V j − V j +1 − θ j −1 (1 + rjV−1 )V j −1 − C
i =1
C i =1 f i ,Lj − N T , j = 0
f iVj + N T , j = 0
, Exercise 12.2
Subject: Revision of ratebased equations to account for a chemical reaction in the liquid
phase.
Given:. Ratebased model Eqs. (124) to (1218).
Assumption: Perfect mixing in the liquid on a stage.
Find: Modified equations for:
(a) chemical equilibrium
(b) kinetic rate law
Analysis: Let the chemical reaction be:
ν A A + ν B B ⇔ ν R R + νSS
where: νι = stoichiometric coefficient of component i where it is (+) for products R and
S, and () for reactants A and B.
Let the change in flow rate of component i in the liquid on stage j...
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 Spring '11
 Levicky
 The Land

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