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CONFIDENTIAL EH/OCT 2009/CPE521
UNIVERSITI TEKNOLOGI MARA
FINAL EXAMINATION
COURSE
COURSE CODE
EXAMINATION
TIME
PROCESS UNIT OPERA TION
CPE521
OCTOBER 2009
3 HOURS
INSTRUCTIONS TO CANDIDATES
1 . This question paper consists of five (5) questions.
Answer ALL questions in the Answer Booklet. Start each answer on a new page..
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CONFIDENTIAL 2 EH/OCT 2009/CPE521
QUESTION 1
a) Many biological and inorganic or organic substances occur in a mixture of differentcomponents in a solid. In order to separate the desired solute constituent or remove anundesirable solute component from the solid phase, the solid is contacted with a liquidphase. Explain the leaching process for biological substances and inorganic or organicmaterials by citing an example for each of the process.
(4 marks)
b) Leach oil is to be ex tracted from palm kernel in a countercurrent m ulti-batch extractorwhere hexane is used as the extracting solvent. The process is to treat 2880 kg/h ofpalm kernel consisting of 69.44 wt inert solid (B), 28.4 7 wt of oil (A) and also 2.09wt of hexane (C). The fresh solvent mixture contains 1 350 kg/h hexane and 25 kg/h oil.The leached solids are to contain 125 kg/h oil. The concentration of insoluble solid in thesolution mixture (A/) for the slurry underflow is essentially constant at 2.0 kg insoluble
solid/kg soluble retained.
i) Calculate the amo unts (LN, \A,) and compositions (yN, x-,) of the two exit strea ms .(18 marks)
ii) Calculate the number of theoretical stages.(3 marks)
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CONFIDENTIAL 3 EH/OCT 2009/CPE521
QUESTION 3
A feed stream containing 51 mol methano l and the rema inder methyl ethyl ketone is fedas a two phase mixture that is 80 vapor to a distillation column at 1 .013 bar. It is desired toseparate this mixture into a stream containing 80 mol me thanol and a stream containing95 mol methyl ethyl ketone. The column has a total condenser and a partial reboiler. Theequilibrium data for methanol at 1.013 bar are given in Table 1.
Table 1 Equilibrium data for methanol at 1.013 bar
xA
00.047
0.1
0.1530.201
0.310
0.420
YA
00.1590.252
0.3280.386
0.486
0.572
xA
0.614
0.713
0.809
0.8570.903
0.948
1
yA
0.6930.7510.817
0.8560.895
0.939
1
i) From the equilibrium data in Table 1 , construct the vapo r-liquid equilibrium curve.(2 marks)
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CONFIDENTIAL 4 EH/OCT 2009/CPE521
QUESTION 4
a) Describe and explain the following phenomena which occur in gas absorption:
i) Loading pointii) Flooding point
(4 marks)
b) It is desired to remove 92 of the ammon ia from the entering gas stream from a chem icalreactor contains 25 mol amm onia and the rest inert gases. The total flow is 1 81 .4 kgmol/h to an absorption tower at 303K and 1.013 x 10
5 Pa pressure, where water
containing 0.005 mol fraction ammonia is in the scrubbing liquid. The equilibrium data forAmm onia-Water system are given in Appendix 1 .
i) Construct the equilibrium curve for Am monia-Water system(2 marks)
ii) Determine the minimum flow L min(5 marks)
iii) Using 1.5 times the minimum flow, plot the equilibrium and operating line.(5 marks)
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CONFIDENTIAL APPENDIX 1 EH OCT 2009 CPE521
A.3-22 Equilibrium Data for Ammonia-Water System
Mote FractionNHs inLiquid xA
0
0.0126
0.0167
0.0208
0.0258
0.0309
0 0405
0 0503
0.0737
0.0960
0.137
0.175
Partial Pressure ofNH2
in Vapor pA mm Hg)
20°C 293 K)
0
12
15
18.2
24.931.7
50.0
69.6
114
166
30°C 303 K)
0
11.5
15.3
19.3
24.4
29.6
40.151.0
79.7
110
179
260
Mole Fraction NH3
in Vapor yA\ P — 1 Atm
20°C
0
0.0158
0.0197
0.0239
0.03280.0416
0.0657
0 0915
0.150
0.218
30°C
0
0 0151
0 0201
0.0254
0 0321
0.0390
0.05270 0671
0.105
0.145
0 235
0 342
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