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CCB 2053: Mass Transfer Design, Semester May 2014

Assignment 1

Deadline for Submission: 14 August 2014, Thursday, before

5pm. (Total marks = 25 %)

Answer ALL questions:

1. A gas mixture at 2.026 x 105 Pa total pressures contains air and SO2 is brought

into contact in a single stage equilibrium mixer with pure water at 293 K. The

partial pressure of SO2 in the original gas is 1.52 x 104 Pa. The inlet gas contains

5.70 total kg mol and inlet water 2.20 total kg mol. The exit gas and liquid leaving

are in equilibrium. Calculate the amount and compositions of the outlet phases.

Use Equilibrium data from Figure below.

[5 marks]

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2. It is desired to absorb 90% of the acetone in a gas containing 1.0 mol % acetone

in air in a countercurrent stage tower. The total inlet gas flow to the tower is 30.0

kg mol/h, and the total inlet pure water flow to be used to absorb the acetone is

108 kg mol H2O/h. The process is to operate isothermally at 300 K and a total

pressure of 101.3 kPa. The equilibrium relation for the acetone (A) in the gas-

liquid is yA= 2.53xA. Determine the number of theoretical stages required

graphically. Repeat, using the analytical Kremser equation.

[5 marks]

3. A feed mixture weighing 200 kg of unknown composition containing water, acetic

acid, and isopropyl ether is contacted in a single stage with 280 kg of a mixture

containing 40 wt % acetic acid, 10 wt % water, and 50 wt % isopropyl ether. The

resulting raffinate layer weighs 320 kg and contains 29.5 wt % acetic acid, 66.5

wt % water, and 4.0 wt % isopropyl ether. Determine the original composition of

the feed mixture and the composition of the resulting extract layer. Use

equilibrium data in Table A.3-24.

[5 marks]

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4. An aqueous feed solution of 1000 kg/h of acetic acid-water solution contains 30.0

wt % acetic acid and is to be extracted in a countercurrent multistage process

with 2500 kg/h pure isopropyl ether to reduce the acid concentration to 2.0 wt %

acid in the final raffinate. Use equilibrium data in Table A.3-24.

(a) Calculate the amounts and compositions of the exit streams.

[5 marks]

(b) Determine the number of theoretical stages required.

[5 marks]

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