SCHOOL OF CHEMISTRY & PHYSICS
UNIVERSITY OF KWAZULU-NATAL, WESTVILLE CAMPUS
APCH322 : INDUSTRIAL CHEMISTRY
JUNE 2015 MAIN EXAMINATION
DURATION: 3 HOURS
TOTAL MARKS: 100
External Examiner:
Internal Examiner/s:
Prof P Baker(UWC)
Dr K Pruessner (UKZN)
Prof SB Jonnalagadda (UKZN)
Instructions:
 This paper is divided into two sections. Answer Section A and
Section B in separate answer books.
 Answer any five of the six questions. All questions carry equal
marks (20).
 Scientific calculators may be used but all working must be
shown.
 This paper consists of 11 pages, including a Periodic Table.
Graph sheets are provided.
Students are requested, in their own interests to write legibly
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH322 Industrial Chemistry
SECTION/ PART A - MASS BALANCES
Re 
dv 

 
 = km
d
H
P
v2

z
g 2g
hf 
4 x f x L x v2
2gd
Question 1:
1.1.
[20]
Oil with a kinetic viscosity of 8.29 x 10–6 m2 s–1 flows through a 205 m long, 0.250 m diameter
cast-iron pipe. If the flow rate is 0.236 m3 s–1, calculate the friction head loss.
Km = 3.5 mm, f = 0.0069.
1.2.
[6]
A furnace is burning natural gas which is about 100% CH4 in a steady-state process. If the air
supply is adjusted to provide 130% excess air, what is the composition (in mol%) of the stack
gas on a wet basis? Assume complete combustion. Include a flow chart in your answer.
[12]
1.3.
Define the terms
(a) yield
(b) selectivity.
[2]
Page 2 of 10
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH322 Industrial Chemistry
Question 2:
2.1.
[20]
The distillation column in the figure below separates 10000 kg hr-1 of a 50% benzene - 50%
toluene mixture. The product D recovered from the condenser at the top of the column
contains 95% benzene. The bottoms W from the column contain 96% toluene. The vapor
stream V entering the column from the top is 8000 kg hr-1. A portion of the product from the
condenser is returned to the column as reflux. The rest is withdrawn for use elsewhere.
Assume that the compositions of the stream at the top of the column (V), the product
withdrawn (D) and the reflux are identical because the vapor is condensed completely. Find
the ratio of the amount refluxed to the product withdrawn.
8000 kg hr-1
V
Condenser
0.95 benzene
0.05 toluene
D
10000 kg hr-1
F
0.5 benzene
0.5 toluene
Dist.
Column
R
0.04 benzene
0.96 toluene
W
[8]
2.2.
A water solution containing 10% acetic acid is added to a water solution containing 30%
acetic acid flowing at a rate of 20 kg min-1. The product P of the combination leaves at a rate
of 100 kg min-1. What is the composition of P? Include a flowchart in your answer.
[5]
Page 3 of 10
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH322 Industrial Chemistry
2.3.
200 moles of SO2 and 100 moles of O2 are fed to a reactor. Only 50 moles of O2 react
according to 2SO2 + O2 -> 2SO3. Use the extent of reaction to find the final stack gas
composition (in mol%).
[5]
2.4.
Define the terms
(a) ORSAT analysis
(b) excess oxygen
[2]
Page 4 of 10
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH322 Industrial Chemistry
Question 3:
3.1.
[20]
Antimony is obtained by heating pulverized stibnite (Sb2S3) with scrap iron and drawing off
the molten antimony from the bottom of the reaction vessel:
Sb2S3 + 3Fe → 2Sb + 3FeS
Suppose that 0.600 kg of stibnite and 0.250 kg of iron turnings are heated together to give
0.200 kg of Sb metal.
Calculate (a) the limiting reactant, (b) the percentage of excess reactant, (c) the degree of
completion (fraction of Fe reacted), (d) the percent conversion (fraction of Sb2S3 reacted).
[10]
3.2.
Wet lumber (5 wt % H2O) is dried to 1 wt % H2O in a hot-air drier. Air fed to the drier contains
0.5 wt % H2O. Moist air leaving the drier contains 2 wt % H2O. What is the output of dry
wood from 100 kg hr-1 of wet lumber, and how much air is required to dry 100 kg hr-1 of wet
lumber? Include a flowchart in your answer.
[10]
Page 5 of 10
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH322 Industrial Chemistry
SECTION / PART B – ENERGY BALANCES
Data: Mean molar mass of air = 29 g; Molar composition of air: N2 79% and O2 21 %
Question 4:
4.1
[20]
Saturated steam at 1 atm is discharged from a turbine at a rate of 2300 kg h-1. Superheated
steam at 300oC and 1 atm is needed as a feed to a heat exchanger; to produce it, the turbine
discharge stream is mixed with superheated steam available from a second source at 400 oC
and 1 atm. The mixing unit operates adiabatically. Calculate the amount of superheated steam
at 300oC produced and required volumetric flow rate of the 400 oC steam.
The specific volume of steam at 400 oC and 1 atm (≈ 1 bar) is 3.11 m3 kg-1. Specific enthalpies
of the two feed streams and the product stream are obtained from the steam tables and are
shown on the flowchart.
[8]
Turbine discharge
2300 kg H2O(v) h-1
1 atm, saturated (100oC)
H = 2676 kJ kg-1
MIXER
300oC, 1 atm
m2 (kg H2O(v h-1)
H = 3074 kJ kg -1
400oC, 1 atm
m1 (kg H2O(v)/h)
300oC, 1 atm
H = 3278 kJ kg-1
4.2
Using certain catalyst material 80% conversion of CO2 to CH4 is achieved in presence of
stoichiometric proportion of H2. Estimate the energy in kW that must be provided or removed
if the gases enter at 200oC and leave at 500oC.
Feed: 100 mol of CO2 and 400 mol H2 per min
[12]
Data: Hfº CO2 (g) = - 393.5 kJ mol-1
Hfº H2O (v) = - 241.83 kJ mol-1
Hfº CH4 (v) = -74.85 kJ mol-1
CP CO2/ J oC-1 mol-1 = 44.93
CP H2 /J oC-1 mol-1 = 29.12
CP H2O /J oC-1 mol-1 = 35.81
CP CH4(v)/J oC-1 mol-1 = 34.21 + 5.47 x10-2 T
Page 6 of 10
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH322 Industrial Chemistry
Question 5:
5.1
[20]
A gas with analysis of 20 mole % CO, 20 % H2 and 60 % N2 is burned with 300 % XS air which
enters at 25 oC. If the exit gas leaves at 25 oC, calculate the standard heat of reaction per unit
volume (kJ m-3) of entering gas measured at standard conditions.
Data : At STP, To = 273 K; Vo = 22.415 dm3 = 22.415 x 10-3 m-3
CO
H2
5.2
ΔHoC (kJ mol-1)
-282.99
-285.84
[4]
It is desired to volatilize the iron from a reaction mixture by treating it with chlorine gas and
driving off the ferric chloride formed. The reaction is
Fe2O3(s) + 3C(s) + 3Cl2(g) → 3CO(g) + 2FeCl3(g)
The solid charge (10 wt% Fe2O3 and 90 wt% C) is introduced into the reactor at 50 °C. The Cl2
gas is used in 10% excess and introduced at 200 °C. The reactor is kept at the vapourisation
point of FeCl3 (300 °C) at which the liquid FeCl3 is vapourised and swept out by the gases
formed.
Calculate the heat that must be added or removed from the reactor per gram of charge in
order that the temperature will be maintained at 300 °C. Use the following relevant data:
FeCl3:
Hºfusion (280 °C) = -43095 J mol-1
Hºvapourization (300 °C) = 26108 J mol-1
Hºf (25 °C) = -403.34 kJ mol-1
Cp (solid) = 121 J mol-1 C-1
Cp (liquid) = 102.5 J mol-1 C-1
Solid charge: Cp = 1.26 J g-1 C-1
Cp Cl2(g)/J mol-1 C-1 = 33.6 + 1.367 x 10-2 T – 1.607 x 10-5 T2
Cp CO(g) = 29.72 J mol-1 C-1
Cp C(s) = 13.1 J mol-1 C-1
[16]
Page 7 of 10
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH322 Industrial Chemistry
Student number:
(If you are answering the question, tear this sheet and attach with the answer book)
Question 6:
6.1
[20]
1000 kg of a saturated solution of AgNO3 at 100 C are cooled to 20 C and the crystals are
filtered out. The wet filter cake, which contains 80% solid crystals and 20% saturated solution
by mass, passes to a dryer in which the remaining water is removed. Calculate the fraction of
AgNO3 in the feed stream eventually recovered as dry crystals and the amount of water that
must be removed in the drying stage.
100 g of H2O can dissolve 952 g of AgNO3 at 100 C
100 g of H2O can dissolve 222 g of AgNO3 at 20 C
[8]
6.2
Potassium chloride is to be extracted by pumping hot water (80 C) down to the deposit,
letting the system come to equilibrium and then pumping the saturated solution of KCl back to
the surface. The solution is then cooled to 10 C and the precipitated KCl is harvested. The
solution is then reheated to 80 C and the cycle completed.
a)
Complete the following phase diagram and label each region in.
b)
Use the phase diagram for KCl and H2O given below to determine the amount of KCl harvested
per hour if 1000 kg h-1 of H2O at 80 C is used.
[8]
Page 8 of 10
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH322 Industrial Chemistry
Student number:
(If you are answering the question, tear this sheet and attach with the answer book)
.
Page 9 of 10
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH322 Industrial Chemistry
Student number:
(If you are answering the question, tear this sheet and attach with the answer book)
6.3
If moderate to large amounts of isopropyl alcohol (IPA) are added to a PCE-water system, the
alcohol may partition into both the PCE (tetrachloroethylene) and water phases, bringing
about significant changes to PCE viscosity, density, solubility, and interfacial tension (Lunn and
Kueper, 1996). If sufficient isopropyl alcohol (IPA) is added, complete solubilisation of PCE in
the alcohol-water mixture can result. Phase diagram expressed in weight fractions of such
ternary system is provided. Estimate the amount of IPA to be added to a mixture of 100 kg
each of PCE and water to solubilize the both in IPA.
[4]
END OF QUESTION PAPER.
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