Service Operations Management Operations Strategy Lecture 2.
Unit Operations Lecture 22 (continued)
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Unit Operations Lecture 22 (continued) 1 16 Nov 2012
description
Unit Operations Lecture 22 (continued). 16 Nov 2012. Trayed Columns (Diameter). Chap 6 (10 ,p 314, Wankat ) “Fair’s Procedure” Considers entrainment flooding (most freq.) Downcomer flooding (sometimes) – need different procedure Downcomer flooding rare if (1- h ) ≥ 10% - PowerPoint PPT Presentation
Transcript of Unit Operations Lecture 22 (continued)
Unit OperationsLecture 22 (continued)
1
16 Nov 2012
Trayed Columns (Diameter)
2
• Chap 6 (10 ,p 314, Wankat) “Fair’s Procedure”o Considers entrainment
flooding (most freq.)o Downcomer flooding
(sometimes) – need different procedure
o Downcomer flooding rare if (1- h) ≥ 10%
• Used in AspenPlus
floodufracVfunctionDia
*1,1,2
1
h
velocityfloodingtoapproachfractionalfrac
sftvelocityvaporfloodingu
flowvaporforavailablefractionAtray
flood
cs
h
James R. Fair (1920 -2010)
Trayed Columns (Diameter)
3
• Plate spacing (selected for maintenance, performance). Typ:o 12 – 16” for Dia < 5’o 24” larger columns
• Calc Dia & round up to nearest ½ foot (USA)o 2.5’ minimum dia.o If < 2.5’ consider packed
tower
V
VLfsbflood Cu
2.0
, 20
factorcapacityC
cmdynetensionsurface
fsb
,
Figure 6.23
4461*
45.0
eqn
ufGD
VAA
floodT
d
areatraytoareadowncomerratiotypicallyfloodingoffractiontypicallyf
AAd 1.0
)(8.0
In-Class Exercise
4
Data:
cmdyne
mkg
L
mkg
V
hrkg
hrkg
L
G
70
986
92.1
2883
7920
3
3
Let:
spacingtray
floodingf
AAd
"241.0
)%80(8.0
Estimate the tower diameter in meters.
Pause video and do exercise. When done, resume the video.
In-Class Exercise
5
Data:
cmdyne
mkg
L
mkg
V
hrkg
hrkg
L
G
70
986
92.1
2883
7920
3
3
Let:
spacingtray
floodingf
AAd
"241.0
)%80(8.0
Estimate the tower diameter in meters.
G = 7920kg/hr 2.2kg/sL = 2883kg/hr 0.801kg/sroe V 1.92kg/cumroe L 986kg/cumFlv = 0.016Csb,f = 0.39ft/ssurf ten 70dyne/cmu flood = 11.34ft/sAd/A = 0.1f = 0.8Dt = 0.766m
5.0
l
glv G
LF
6
Tower Diameter
AspenPlus In-Class Exercise
7
Estimate the tower diameter in meters. (by hand
and by AspenPlus)
Benzene – Toluene Separation
F = 100 kmole/hrXBZ = 0.6saturated liquidUse sieve trays
AspenPlus PFD
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Column Internals
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Base method: NRTL
Column Internals
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Not optimized by DSTWUNfeed = 15Pcol = 1.013 bar (constant)
Column Internals
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Column Internals
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Column Internals
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Column Internals
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Column Internals
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hrkg
hrkg
L
G
9.443,34
9.757,30
Column Internals
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RTPMw
V
mkg
L
368.780
392.2
1000)15.2737.110(10314.814.92013.1
35
mkg
V
V gkg
KbarmxKmol
molgbar
RTPMw
Column Internals
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Column Internals
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AspenPlus In-Class Exercise
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Estimate the tower diameter in meters. (by hand
and by AspenPlus)
Benzene – Toluene Separation
F = 100 kmole/hrXBZ = 0.6saturated liquidUse sieve trays
G = 30757.9kg/hr 8.544kg/sL = 34443.9kg/hr 9.568kg/sroe V 2.92kg/cumroe L 780.68kg/cumFlv = 0.06849Csb,f = 0.375ft/ssurf ten 18.18dyne/cmu flood = 6.00448ft/sAd/A = 0.1f = 0.8Dt = 1.68m
Column Internals
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Column Internals
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Column Internals
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Column Internals
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25
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27
28
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Overview
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• Questions from last week??• Review rigorous methods / RADFRAC• Multicomponent systems:o Residue curveso DSTWU / RADFRAC o Rules of thumb
• Complex (Enhanced) distillation• Column internals• Batch distillation
Batch (Rayleigh) Distillation
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Seader & Henley (2006)
x
xo oxy
dxWWln
• Usually for small capacity systems
• 1 column handle multi-”campaigns”
• Produce sample new products• Batch upstream processes• Feed contains solids/foulants
Material Balance:leads to Rayleigh Equation
where:][moleschargeinitialFW
chargeinitialoffractionmolexx
o
Fo
Batch (Rayleigh) Distillation
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x
xo oxy
dxWWln
a) P = constant; K = f(T) only
oo xx
KWW ln
11ln
b) Binary with = constant
o
oo
xx
xx
WW
11lnln
11ln
c) y = K x ; but K = f(T,x) Solve graphically or numerically
Multistage Batch Distillation
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Modes of operation:• Constant reflux rate or ratio• xD varies with time• easily implemented (flow sensors)• Relatively simple and cost effective
• Constant distillate composition• R or D varies with time• Requires fast response composition sensors• Sensors might not be available or only
justified for larger batch systems• Optimal control mode• xD and R varied with time• Designed to:
Minimize operation time Maximize amount of distillate Maximize profit
• More complex control scheme
Seader & Henley (2006)
to
ttooD WW
xWxWX
tD
oDot xx
xxWW
Multistage Batch Distillation
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Removing volatile impurities.
Seader & Henley (2006)Flexible, multi-purpose system
Questions?
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