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PPD710S - Process Plant Design - 2dn Opp - June 2022 |
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n Am I BI A u n IVER s ITY
OF SCIEnCE Ano TECHnOLOGY
FACULTYOF ENGINEERING
DEPARTMENT OF MINING & PROCESS ENGINEERING
QUALIFICATIONS: BACHELOR OF ENGINEERING IN METALLURGY & CHEMICAL ENGINEERING
QUALIFICATION CODE: 08BEMT & 08BECE LEVEL: 8
COURSE CODE: PPD710S
SESSION: JUNE 2022
DURATION: 3 HOURS
COURSE NAME: PROCESSPLANT DESIGN &
ECONOMICS 315
PAPER: THEORY
MARKS: 100
EXAMINER:
MODERATOR:
SECONDOPPORTUNITYQUESTIONPAPER
Mr. Thomas Moongo
Prof. Vusimuzi Sibanda
INSTRUCTIONS
1. Answer all questions.
2. Read all the questions carefully before answering.
3. Marks for each question are indicated at the end of each question.
4. Please ensure that your writing is legible, neat, and presentable.
PERMISSIBLEMATERIALS
1. Examination paper.
2. Calculator and stationery.
THIS QUESTION PAPER CONSISTS OF 6 PAGES (Including this front page)
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SECTIONA
Question 1
Explain how and why HAZOPanalysis is used during process plant design?
[30 marks]
[S marks]
Question 2
What does the below piping and instrumentation diagram symbols represent?
0
0
tp'i\\
/pie\\
\\lQY
0
(a}
(b}
(c}
(d}
(e}
[S marks]
Question 3
[9 marks]
Givea detailed explanationof different sampledivision methodsthat you could apply when evaluating
a copper ore.
Question 4
[6 marks]
Name and explain two particle size distribution models that can be applied during crushing
and screening circuit design. In your discussion provide the mathematical equations for these
models and define all relevant terms.
Question S
Define the following terminologies.
(a} Economics
(b} Net Present Value (NPV}
(c} Internal rate of return {IRR}
(d} Return on investment (ROI}
(e} Payback Period (PBP}
[S marks]
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SECTIONB
[70 marks]
Question 1
[10 marks]
Rosh Pinah Zinc Mine requires mass balance to be conducted as one of the steps done during process
design. Their plant is processing a complex ore of Lead and Zinc that contains 7.3% Pb and 8.4% Zn
and the ore is treated on a 1000 tons/day basis in a flotation circuit. In a day, two separate
concentrates amounting to 109 ton of Lead concentrate and 148 ton of Zinc concentrate are produced.
For the Lead concentrate, Lead (Pb) recovery is 94.8% and the zinc loss is 2.1%. For the Zinc
concentrate, zinc (Zn) recovery is 88.3% and the Pb loss is 1.8%. Carry out the mass balance balance
after sketching the problem using an appropriate diagram (show all your calculations) and complete
the Table below.
Table 1: Mass balance summary for Rosh Pinah Zinc Mine
===
Feed
Pb concentrate
Zn concentrate
Tailings
Question 2
[10 marks]
Namib Lead and Zinc Mine is considering undertaking experiments to improve process
efficiencies. First, they are considering determining the minimum quantity of a sample
required for metallurgical testwork for a lead ore assaying 5% Pb which must be routinely
sampled for assayto a confidence level of ±0.1% Pb, 95 times out of 100. Galena is essentially
liberated from the quartz gangue at a particle size of 150µm. Assume that the sample will be
collected during crushing to a top size of 25 mm. The mean density of Galena and Quartz is
7.50 g/cm 3 and 2.65 g/cm 3.
Question 3
[10 marks]
Rossing Uranium Mine is considering developing a model for simulating the fraction of
product size class i for a perfectly mixed mill. As a process design student who is well versed
with milling kinetics simulation, derive the equation for modelling the fraction of product size
class i for a perfectly mixed mill and for size class 1, 2 and 3. Give a sketch of the mill labelled
with all critical symbols to be used in your formulas and define them.
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Question 4
[10 marks]
All design engineers should be able to communicate with other technical experts by using appropriate
diagrams. For the following operations, develop an appropriate block flowsheet with at least five (5)
major unit processes each of the following operations:
(a) Namdeb's diamond processing plant.
(b) Namib Lead and Zinc concentrator.
[S marks]
[S marks]
Question 5
[10 marks]
Kombat Copper Mine seek advice from process design consultants regarding the below
proposed design modification in their processing plant. The rod mill is fed at the rate of 20tph
with dry solids (density 2900 kg/m 3). The cyclone feed contains 35% solids by weight and size
analysis on the rod mill discharge, ball mill discharge and cyclone feed gave the following:
Circuit equipment
Rod mill discharge
Ball mill discharge
Cyclone feed
Analysis by weight
26.9%
4.9%
13.8%
Size analysis
+2S0µm
+2S0µm
+2S0µm
Ore Feed
Water
Cyclone
Underflow
Overflow
Ball mill
Flotation
As an expert in process plant design, advice Kombat Copper Mine management on what
should be the volumetric flowrate of the feed stream to the cyclone. Draw a sketch of the
problem and show all your work.
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Question 6
[10 marks]
Swakop Uranium Mine process engineers designed a hydrocyclone which is fed with a
pulp/slurry having a specific density of 1.25 t/m 3 at a mass flowrate of 40tph for dry solids.
The underflow stream has an L/s ratio of 0.85 and the overflow stream has 10% solids. Given
that the dry solid specific density is 2.55. Calculate the following:
(a) Mass flowrate of the hydrocyclone underflow and overflow streams in tph.
(b) Volumetric flowrate of the pulp in the underflow stream in dm3/s.
[5 marks]
[5 marks]
Question 7
[5 marks]
Okorusu Flourspar processing plant was designed to treat S00t of solids per hour. The feed
pulp, containing 40% solids by weight is conditioned for 5 minutes with reagents before
pumping it to the flotation cells. For design purpose, calculate the volume of the conditioning
tank required. Assume solids density to be 2700 kg/m 3•
Question 8
A homogeneousleachingreaction
3R hasa reported rate at 215°C and 5 atm of
[5 marks]
Findthe residencetime neededfor 80% conversionof a feed to a PFR,given that
Cj = 0.0625 mol/L
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Listof Equations
Power (P) = K(J)pLD2·5 _!:'.__Sin0
Ncrit
C = fglm
= 42.3
Critical Speed N ·t - ---
en -
d
v = rnoG)m
(R 1) = Q 60LTvW(2LMIN + LT)
M=-
Cd3
s2
P = E (kWh/t) x F (t/h)
F=U+O
loglog ( R100) = mxlog(x) + c
= C1 12.13(Ar) 0·32 -10.3 for Ar< 51 mm
m =-1[-(aa1-
a)r + at]
PiP = fiP + wr;::blijsjwi -Siwiw
i>1
Screenarea= Standard Fseceredenratceap(atpchit.)y (t/hm 2)
E = lOWi(-
1
-
-
1
- -)
(~)b] Y = 100- lOOexp[-
Ff= Uu' + Oo'
C2 = 0.34(Ar) - 14.41 for Ar~51 mm
log(y) = mxlog(x) + k
_________________
THE END______________
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