Post on 11-Feb-2016
description
CHEN 4460 – Process Synthesis, Simulation and Optimization
Dr. Mario Richard EdenDepartment of Chemical Engineering
Auburn University
Lab Lecture No. 3 – Sequencing of Azeotropic Distillation ColumnsOctober 4, 2011
Contains Material Developed by Dr. Daniel R. Lewin, Technion, Israel
Azeotropic Distillation
Introduction• When two or more components differ in boiling by
less than approximately 50C and form a nonideal liquid solution, the relative volatility may be below 1.10.
• Then ordinary distillation may be uneconomic, and if an azeotrope forms even impossible.
• In that event, the following separation techniques, referred as enhanced distillation by Stichlmair, Fair, and Bravo, should be explored:– Extractive distillation– Salt distillation– Pressure-swing distillation– Homogeneous azeotropic distillation– Heterogeneous azeotropic distillation– Reactive distillation
Example 1• Given that methyl acetate (1), which boils at
57.8C, methanol (2), which boils at 64.7C and n-hexane (3), which boils at 68.7C.
A. Sketch any boundaries across which the residue curves cannot traverse.
B. Sketch the residue curves for three feed compositions:
Mole FractionsComponent I II III
1 0.70 0.15 0.152 0.15 0.70 0.153 0.15 0.15 0.7
Example 1• Note the existence of four azeotropes, where
compositions are in mol %:
Azeotrope T oCMethyl acetate (65%), methanol (35%) Binary 53.5Methanol (51%), n-hexane (49%) Binary 50.0Methyl acetate (60%), n-hexane (40%) Binary 51.8Methyl acetate (31%), n-hexane (40%), methanol (29%) Ternary
49.0
Example 1 – Solution
1
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
10.80.60.40.2 0
B
C A 1
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
10.80.60.40.2 0
<< Methanol (2)
(2) 64.7oC
<<
Hexa
ne (3
)
(3) 68.7oC
MA (1) >>
(1) 57.8oC 1
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
10.80.60.40.2 0
<< Methanol (2)
(2) 64.7oC
<<
Hexa
ne (3
)
(3) 68.7oC
MA (1) >>
(1) 57.8oC
53.5oC
51.8oC
50oC
49oC
1
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
10.80.60.40.2 0
<< Methanol (2)
(2) 64.7oC
<<
Hexa
ne (3
)
(3) 68.7oC
MA (1) >>
(1) 57.8oC
53.5oC
51.8oC
50oC
49oC
Plot pure components on vertices with Tb
Plot all azeotropes on diagram with Tb
Plot the residue curves connecting all azeotropes, azeotropes & vertices, and finally vertices & vertices with arrow heads pointing towards increasing boiling point temperatures
Example 1 – Solution Plot pure components
on vertices with Tb
Plot all azeotropes on diagram with Tb
Plot the residue curves connecting all azeotropes, azeotropes & vertices, and finally vertices & vertices with arrow heads pointing towards increasing boiling point temperatures
Plot additional residue curves that “arch” towards intermediate temperatures on the way to the end point
1
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
10.80.60.40.2 0
<< Methanol (2)
(2) 64.7oC
<<
Hexa
ne (3
)
(3) 68.7oC
MA (1) >>
(1) 57.8oC
53.5oC
51.8oC
50oC
49oC
Feed I
Example 1 – Solution Plot pure components
on vertices with Tb
Plot all azeotropes on diagram with Tb
Plot the residue curves connecting all azeotropes, azeotropes & vertices, and finally vertices & vertices with arrow heads pointing towards increasing boiling point temperatures
Plot additional residue curves that “arch” towards intermediate temperatures on the way to the end point
1
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
10.80.60.40.2 0
<< Methanol (2)
(2) 64.7oC
<<
Hexa
ne (3
)
(3) 68.7oC
MA (1) >>
(1) 57.8oC
53.5oC
51.8oC
50oC
49oC
Feed IFeed III
Example 1 – Solution Plot pure components
on vertices with Tb
Plot all azeotropes on diagram with Tb
Plot the residue curves connecting all azeotropes, azeotropes & vertices, and finally vertices & vertices with arrow heads pointing towards increasing boiling point temperatures
Plot additional residue curves that “arch” towards intermediate temperatures on the way to the end point
1
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
10.80.60.40.2 0
<< Methanol (2)
(2) 64.7oC
<<
Hexa
ne (3
)
(3) 68.7oC
MA (1) >>
(1) 57.8oC
53.5oC
51.8oC
50oC
49oC
Feed IFeed III
Feed II
Example 1 – Solution Plot pure components
on vertices with Tb
Plot all azeotropes on diagram with Tb
Plot the residue curves connecting all azeotropes, azeotropes & vertices, and finally vertices & vertices with arrow heads pointing towards increasing boiling point temperatures
Plot additional residue curves that “arch” towards intermediate temperatures on the way to the end point
Example 2• A stream consisting of a mixture of A, an organic
component, and water, B, which forms an azeotrope. A separation process is to be designed to obtain pure products A and B. The plant manager suggests that you investigate the possibility of using component C as MSA. Componen
tBoiling Temperature (K)
A 360B 400C 370
F Azeotrope I
Azeotrope II
Azeotrope III
Azeotrope IV
A 40% 50% 55% 30% B 60% 55% 45% 45% C 50% 45% 25%
Temp 350 K 360 K 330 K 315 K
Example 2
• Indicate the location of the azeotropes on a ternary diagram, as well as representative residue curves.
• Suggest a process for the separation of A and B into pure products and show its operating lines on the ternary diagram.
• Draw a PFD for your process. Indicate flow rates of all internal and external streams as multiples of the flow rate of F.
Example 2 – Solution
C
I, 350 KIII, 330 K
II, 360 K
IV, 315 K
360 K
370 K400 K
Example 2 – Solution
C
I, 350 KIII, 330 K
II, 360 K
IV, 315 K
360 K
370 K400 K
D2
B2
S1
F
B1
M1
S2
D1M2
B2B1
D2D1F M1 S1
S2
M2