Azeotropic Distillation
CHEN 4460 – Process Synthesis,
Simulation and Optimization
Dr. Mario Richard Eden
Department of Chemical Engineering
Auburn University
Lab Lecture No. 3 – Sequencing of Azeotropic Distillation Columns
October 2, 2012
Contains Material Developed by Dr. Daniel R. Lewin, Technion, Israel
Introduction
•
When two or more components differ in boiling by less
than approximately 50C 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 57.8C,
methanol (2), which boils at 64.7C and n-hexane (3),
which boils at 68.7C.
A.
Sketch any boundaries across which the residue curves
cannot traverse.
B.
Sketch the residue curves for three feed compositions:
Mole Fractions
Component
I
II
III
1
0.70
0.15
0.15
2
0.15
0.70
0.15
3
0.15
0.15
0.7
Example 1
•
Note the existence of
compositions are in mol %:
four
azeotropes,
Azeotrope
where
T oC
Methyl acetate (65%), methanol (35%) Binary
53.5
Methanol (51%), n-hexane (49%) Binary
50.0
Methyl acetate (60%), n-hexane (40%) Binary
51.8
Methyl acetate (31%), n-hexane (40%), methanol (29%) Ternary
49.0
Example 1 – Solution
 Plot pure components on
vertices with Tb
 Plot all azeotropes
diagram with Tb
(2) 64.7
B oC
on
0
(3)
He
xa
ne
0.8
tha
Me
<<
0.2
<<
0.4
0.6
)
l (2
no
 Plot the residue curves
connecting all azeotropes,
azeotropes & vertices, and
finally vertices & vertices
with arrow heads pointing
towards increasing boiling
point temperatures
1
50oC
0.6
0.4
o
49 C
0.8
0.2
1
(3) 68.7
C oC 0
53.5oC
0
0.2
0.4
MA (1) >>
o
0.6 51.8 C
0.8
A oC
1(1) 57.8
Example 1 – Solution
 Plot pure components on
vertices with Tb
 Plot all azeotropes
diagram with Tb
(2) 64.7oC
on
0
(3)
He
xa
ne
0.8
tha
Me
<<
0.2
<<
0.4
0.6
)
l (2
no
 Plot the residue curves
connecting all azeotropes,
azeotropes & vertices, and
finally vertices & vertices
with arrow heads pointing
towards increasing boiling
point temperatures
1
50oC
0.6
 Plot
additional
residue
curves that “arch” towards
intermediate temperatures
on the way to the end point
0.4
o
49 C
53.5oC
0.8
0.2
1
(3) 68.7oC 0
0
0.2
0.4
MA (1) >>
o
0.6 51.8 C
0.8
Feed I
o
1(1) 57.8 C
Example 1 – Solution
 Plot pure components on
vertices with Tb
 Plot all azeotropes
diagram with Tb
(2) 64.7oC
on
0
(3)
He
xa
ne
0.8
tha
Me
<<
0.2
<<
0.4
0.6
)
l (2
no
 Plot the residue curves
connecting all azeotropes,
azeotropes & vertices, and
finally vertices & vertices
with arrow heads pointing
towards increasing boiling
point temperatures
1
50oC
0.6
 Plot
additional
residue
curves that “arch” towards
intermediate temperatures
on the way to the end point
0.4
o
49 C
53.5oC
0.8
0.2
1
(3) 68.7oC 0
0
0.2
Feed III
0.4
MA (1) >>
o
0.6 51.8 C
0.8
Feed I
o
1(1) 57.8 C
Example 1 – Solution
 Plot pure components on
vertices with Tb
 Plot all azeotropes
diagram with Tb
(2) 64.7oC
on
0
(3)
He
xa
ne
0.8
tha
Me
<<
0.2
Feed II
<<
0.4
0.6
)
l (2
no
 Plot the residue curves
connecting all azeotropes,
azeotropes & vertices, and
finally vertices & vertices
with arrow heads pointing
towards increasing boiling
point temperatures
1
50oC
0.6
 Plot
additional
residue
curves that “arch” towards
intermediate temperatures
on the way to the end point
0.4
o
49 C
53.5oC
0.8
0.2
1
(3) 68.7oC 0
0
0.2
Feed III
0.4
MA (1) >>
o
0.6 51.8 C
0.8
Feed I
o
1(1) 57.8 C
Example 1 – Solution
 Plot pure components on
vertices with Tb
 Plot all azeotropes
diagram with Tb
on
 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.
F
A
40%
B
60%
Component
Boiling Temperature (K)
A
360
B
400
C
370
Azeotrope I Azeotrope II Azeotrope III Azeotrope IV
50%
55%
C
50%
45%
Temp
350 K
360 K
55%
30%
45%
45%
25%
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
360 K
III, 330 K
I, 350 K
IV, 315 K
400 K
II, 360 K
C
370 K
Example 2 – Solution
S2
360 K
F
B2
M1
D2
D1
M2
B1
III, 330 K
F
M1
S1
D1
B2
I, 350 K
M2
D2
S1
S2
IV, 315 K
B1
400 K
II, 360 K
C
370 K