Transcript Lecture 13

“Chemical Engineering Equilibrium
Separations”
Lectures 12 & 13
12 Oct 2012
1
Overview
• AspenPlus:
o Shortcut methods: DSTWU
o Rigorous method: RADFRAC
• Efficiencies
• Introduction to multicomponent distillation
2
AspenPlus: DSTWU
3
Tray Operation
a)
b)
c)
d)
e)
Spray
Froth *
Emulsion
Bubble
Cellular foam
4
Types of Trays
a) Sieve
b) Valve
c) Bubble cap
5
Typical Flow Pattern
6
Operation
Typically
columns operated
at 50% - 85% of
flooding.
Figure 6.21 Limits of stable operation in a trayed tower.
[Reproduced by permission from H.Z. Kister, Distillation Design,
McGraw-Hill, New York (1992).]
Seader et.al., 2012
7
Operation
Video:
FRI (Fractionation Research, Inc.) non-profit research consortium
“Design and Performance of Fractionating Devices”
http://www.fri.org/
8
Operation
Typically
columns operated
at 50% - 85% of
flooding.
Figure 6.21 Limits of stable operation in a trayed tower.
[Reproduced by permission from H.Z. Kister, Distillation Design,
McGraw-Hill, New York (1992).]
Seader et.al., 2012
9
Efficiencies
Assumed equilibrium
stages, but may not reach
equilibrium on a stage;
why?
Flooding!
10
Efficiencies
EO 
Overall column efficiency:
Murphree efficiency: E MV 
y out  y in
y
*
out
 y in
N equil
N actual

actual vapor conc . change
vapor conc . change at equil .
E MV 
y n  y n 1
y  y n 1
*
n
( eqn 7  41 )
E MV  1  e
 N OG
11
Efficiencies
12
Efficiencies
Seader & Henley, 2006
13
Efficiencies
E MV
P.C. Wankat, 2nd., 2007
14
Overview
• Questions on homework??
• McCabe-Thiele graphical technique (binary systems)
•Condensers
•Reboilers
• Binary Shortcut Methods
• AspenPlus:
o Shortcut methods: DSTWU
o Rigorous method: RADFRAC
• Efficiencies
• Introduction to multicomponent distillation (chapter 9)
15
Questions?
16