Faculty of Engineering United Arab Emirates University Quiz #3 CHME 300: Introdu
ID: 701460 • Letter: F
Question
Faculty of Engineering United Arab Emirates University Quiz #3 CHME 300: Introduction to Chemical Eng. Quiz 3 (Time: 20 min) Name: An absorber is used to remove acetone from a nitrogen carrier gas. The feed containing 21.3 wt% acetone enters the absorption tower at a rate of 200 kg/h The absorbing liquid is water. which enters at a rate of 1000 kg/h The exit gas stream contains 08 wt% acetone and 29 wt % water vapor, and the exit liquid stream is free of nitrogen. Perform a degree of freedom analysis and calculate the mass fraction of acetone in the exiting liquid stream.Explanation / Answer
Assume one hour then you have 200 kg of gas which is 21.3% acetone. So you have 200 x 0.213 = 42.6 kg acetone and 200 - 42.6 = 157.4 kg N2
The exit gas is 100 - 0.8 - 2.9 = 96.3% N2 so the total mass of the exit gas is 157.4/0.963 = 163.4 kg assuming none of the N2 dissolves in the water.
The mass of acetone in the exit gas is 163.4 x 0.008 = 1.31 kg. So the mass of acetone dissolved in the water is 42.6 - 1.31 = 41.29 kg
The exit gas also contains 163.4 x 0.029 = 4.74 kg water
If we start with 1000 kg water and loose 4.74 kg the mass of water left is 995.3 kg
So the exit stream of water has 995.3 kg water and 41.29 kg acetone. The total mass leaving is 1036.5 kg and the mass fraction of acetone
41.29/1036.5 = 0.0398 or 3.98%
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