MTO-II Tutorial-IV (11.02.2021)
Ques.1. 3000 kg/hr of an acetic acid water solution containing 30% acetic acid by weight is to be extracted
counter currently with isopropyl ether to reduce the acid concentration to 3% in the solvent free raffinate
product. Determine (1) minimum solvent rate required? The number of theoretical stages if the solvent is
used in double amount to that of minimum amount of the solvent?
(10)
LLE data:
Aqueous
Phase
(Mass %
(100
x)
wt% HAC
Ether
Water
(100
y)
wt% HAC
Ether
Water
Organic
Phase
(Mass %)
0
1
5
10
25.5
36.7
44
45
46.5
44.8
1
99
0
1.4
97.6
0.33
1.9
93.1
1.4
2.15
87.85
3.6
3.4
71.1
11.4
4.4
58.9
21.6
9.6
46.4
30.1
11.6
43.4
31.9
16.6
36.9
36.2
31.3
23.9
44.8
99.4
0.60
98.95
0.72
97.6
1
95
1.4
84.7
3.9
6.9
71.5
59.1
10.8
56.3
11.8
48.7
15.1
31.3
23.9
Ques. 2. A ternary mixture M containing acetic acid, water, and diethyl ether is obtained as an intermediate
product in the reactor section of a plant. The mixture is completely miscible above 30 °C but separates in
to two layers at lower temperatures. As it is simpler to pump a homogeneous fluid, the mixture is pumped
at 33 °C to the LLE unit of the plant. In LLE pant, the mixture enters a separating unit, where it is cooled
to the operating temperature used in the extraction system. The mutual solubility data is given for the
temperature used in the counter current extraction battery.
The water rich solution from the separating unit is charged as feed to the first unit of the counter current
system. The initial ternary mixture contains 0.242 mass fraction acid and the mass fraction of the acid on
solvent free basis is 0.35. The solvent added to the nth stage is S, which is saturated with water. The
overflow solution (extract) from the first stage is in equilibrium with a water rich solution containing 0.125
mass fraction acid and the E1/R0 = 1.92.
(15)
Determine
a.
b.
c.
d.
Composition of the original mixture
Composition of R0 and E0
Composition of underflow
Number of the theoretical stages
Data:
yc
xc
0
0
0.05
0.065
0.10
0.115
0.15
0.16
0.20
0.20
0.25
0.24
0.30
0.285
Solubility Data:
Aqueous Phase
(wt %
Organic Phase
(wt %)
Acetic acid
Ether
Water
Acetic acid
Ether
Water
0
7.5
92.5
0
97
0
12.5
10
77.5
13
80
13
24
13
63
24
60
24
30.5
30
39.5
30
40
30