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(CENG101)[2009](s)final~1021^_10019.pdf
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DEPARTMENT OF CHEMICAL ENGINEERING
Hong Kong University of Science and Technology
Final Exam - Spring Semester 2009/2010

CENG 101 C Chemical Process Principles
Friday, 22 May 2009, Time: 12:30 C 15:30 p.m. LTC

Instructions to Students
1.
Write your NAME and COURSE CODE on each answer book and this question sheet.

2.
The percentage marks are shown with each question.

3.
Start each question on a new page and number all pages.

4.
You can use books or notes.

5.
Calculator is permitted.

6.
Read questions carefully.

7.
Return examination QUESTION SHEETS together with your answers.


A mixture of isooctane, n-pentane, and water is required to be separated for pure products. The following information is known:
Boiling point (oC) melting point (oC) Solubility in water Solubility in benzene Mol% in feed
Isooctane 99.3 -107.38 no yes 50
n-pentane 36.1 .129.8 0.01g/100ml (20oC) yes 40
water 100 0 yes no 10

Please propose a separation train with brief explanations for your choice and sequence of the separators. (10 marks)
Ammonia is oxidized with air to form nitric oxide in the first step of the production of nitric acid. Two principal reactions occur:
4NH3 (g) + 5O2 (g) = 4NO (g) + 6H2O (g) r=-904.7 KJ (R1) 4NH3 (g) + 3O2 (g) = 2N2 (g) + 6H2O (g) r=-1256.5 KJ (R2)
Calculate the required heat exchange rate with the reactor in kW. (20 marks)

3 A 1-m3 closed container is filled with moist air saturated with water vapor at 30 oC, Suppose the moisture would not affect the pressure significantly..
a) How much water vapor is in the container? (2 marks)
b) If it is heated to 50 oC, what is the relative humidity? (3 marks)
c) If it is cooled down to 15 oC, how much of water is condensed? (2 marks)
d) How much heat is released from the cooling process from b) to c)? (3 marks)

4 An aqueous slurry at 30 oC containing 10.0wt% solids is fed to an evaporator in which enough water is vaporized at 1 atm to produce a product slurry containing 25.0wt% solids. Heat is supplied to the evaporator by feeding saturated steam at 2.0 bar (absolute) into the coil immersed in the slurry. Calculate the minimum flowrate of the steam flow rate for a slurry feed rate of 1.00 Ton/h. The heat capacity of the solid can be taken as half that of liquid water. Cp of water can be taken as 4.19 kJ/kg oC. (10 marks)
5 500 kg of a 20.0wt% acetic acid/80.0wt% water solution is mixed with 500 kg methyl isobutyl ketone (MIBK). After equilibration, how many kilograms of extract (MIBK-rich phase) and raffinate (water-rich phase) are produced? What is the composition (wt%) of each phase? (10 marks)
6 Acetaldehyde is synthesized by the catalytic dehydrogenation of ethanol:
C2H5OH = CH3CHO + H2 (R3)
Fresh feed of pure ethanol at 25 oC, 1 atm is blended with a recycled stream
(95.0mol% ethanol and 5.00mol% acetaldehyde) at 70 oC, and the combined stream is
heated and