UNIVERSITY OF TRIPOLI

FACULTY OF ENGINEERING

CHEMICAL ENGINEERING DEPARTMENT

MASS TRANSFER II (CHE 422), DR. SABRI MRAYED SPRING 2015

Tutorial Sheet # 4

1. An ethylene glycol-methyl ethyl ketone (MEK) solution that contains 40 wt% of ethylene

glycol and 60 wt% MEK is to be contacted with pure water in a continues single-stage

extraction process. The flow rate of the glycol solution and the water are 40 kg/min and 60

kg/min, respectively. (a) Determine the compositions of the extract and raffinate phases, and

(b) find the flow rate of each phase.

2. For the system in problem (1), calculate the minimum and maximum amount of water for the

same operation and the corresponding extract and raffinate flow rate and compositions.

3. Pure water is used to separate a chloroform-acetone mixture in a three-stage crosscurrent

extraction process. The feed contains 45 wt% chloroform and 55 wt % acetone, and flows at a

rate of 100 kg/min. Pure water is added each stage at a rate of 50 kg/min. (a) Determine the

compositions of the extract and raffinate phases for each stage, and (b) find the flow rate for

the streams leaving the contactors. The extraction process is carried out at 25 C.

Equilibrium data are as follows:

Mutual solubility data

Acetone Water Chloroform

57.3 7.3 35.4

60.5 11 28.5

60 18 22

59.2 23 17.8

58.5 27 14.5

56.6 32.4 11

55.5 34.4 10

54 37.4 8.6

53.2 38.8 8

51.6 41.4 7

49 45.4 5.6

Tie-line data

Solvent layer (wt%) Raffinate layer (wt %)

Acetone Water Chloroform Acetone Water Chloroform

3 96 1 9 1 90

8.3 90.5 1.2 23.7 1.3 75

13.5 85 1.5 32 1.6 66.4

17.4 81 1.6 38 2 60

22.1 76.1 1.8 42.5 2.5 55

31.9 66 2.1 50.5 4.5 45

44.5 51 4.5 57 8 35

4. 1000 kg/h of a 45 wt% acetone in water solution is be extracted at 25 C in a continuous, countercurrent system with pure 1,1,2-trichloroethane to obtain a raffinate containing 10 wt%

acetone. Using the following equilibrium data, determine with upright triangle diagram: (a)

determine the minimum flow rate of solvent, (b) the number of stages required for a solvent

rate equal to 2 times the minimum, and (c) the flow rate and compositions of each stream

leaving each stage.

LLE

Water phase, wt% Chloroform phase, wt%

Water

(B )

Trichloroethane

(C)

Acetone

(A)

Water

(B )

Trichloroethane

(C)

Acetone

(A)

35 10 55 13 27 60

43 7 50 4 46 50

57 3.00 40 3 57 40

68 2 30 2 68 30

79 1 20 1.5 78.5 20

89.5 0.5 10 1 89 10

Tie-line data

Raffinate

Wt % acetone

Extract

Wt %acetone

44 56

29 40

12 18

5. A water solution of 100 kg/h containing 1.5 wt % nicotine in water is stripped with a kerosene

stream of 2000 kg/h containing 0.05 wt % nicotine in a countercurrent stage tower. The exit

water is to contain only 10 % of the original nicotine. Calculate the number of theoretical

stages needed. (x is the wt fraction of nicotine in the water solution, and y is the wt fraction of

nicotine in the kerosene)

x y x y

0.001010 0.000806 0.00746 0.00682

0.00246 0.001959 0.00988 0.00904

0.005 0.00454 0.0202 0.0185

6. 2 kg/s of a feed containing 60 wt % A and 40 wt % B is to be extracted by solvent C in cross-

current extractor of three stages. The flow of solvent C is being 0.91 kg/s to each stage. What

are the compositions and flow rates of the raffinate and extract leaving the third stage?

Equilibrium data

Raffinate phase wt% Extract phase wt%

A B C A B C

70 25 5 71.6 4.8 33.6

60 37 3 62.6 2.5 34

50 8 2 52 3.1 .9

40 58.5 1.5 41.9 3.1 55

30 68.5 1.5 31.9 3 65.1

20 79 1 22 2.9 75.1

10 89 1 11.1 2.1 86.8

7. If counter current operation is used for the same conditions of the feed in problem (5) (2 kg/s

of composition 60% A and 40 % B) and the total amount of solvent C (3 0.91 kg/s) and if the

maximum concentration of A in the final raffinate leaving is as in the cross-current operation

described in problem 5. Show whether or not the number of stages increase, decrease, or the

same as in problem 5.

8. A feed of 13500 kg/h consists of 8 wt% acetic acid in water. Acetic acid will be removed from

the solution by extraction with pure methyl isobutyl ketone at 298 K. If the raffinate is to

contain only 1 wt % of acetic acid, estimate the kilograms/hour of solvent required if a single

stage used. Assume that water and methyl isobutyl ketone are insoluble. Fir this system [y =

0.657 x], where y is kg of acetic acid per kg of methyl isobutyl ketone, and x is the kg of

acetic acid per kg of water.