 |
PPD710S - Process Plant Design and Economics 315 - 1st OPP - JUN 2023 |
|
|
1 Page 1 |
▲back to top |
nAmlBIA unlVERSITY
OFSCIEnCEAno TECHnOLOGY
FACULTY OF ENGINEERING AND THE BUILT
ENVIRONMENT
DEPARTMENT OF CIVIL, MINING AND PROCESS ENGINEERING
QUALIFICATION: BACHELORS OF ENGINEERING IN METALLURGICAL &
CHEMICAL ENGINEERING
QUALIFICATION CODE: BMET
&BCHEM
LEVEL: 7
COURSE CODE: PPD710S
COURSE NAME: PROCESS PLANT DESIGN &
ECONOMICS 315
SESSION: JUNE 2023
PAPER: THEORY
DURATION: 3 HOURS
MARKS: 100
FIRST OPPORTUNITY EXAMINATION
EXAMINER(S) Prof Vusumuzi Sibanda
MODERATOR: Prof Godfrey Dzinomwa
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.
PERMISSIBLE MATERIALS
I. Examination paper.
2. Two Graph Papers
3. Mathematical Instruments
THIS QUESTION PAPER CONSISTS OF 6 PAGES (Including this front page)
|
|
2 Page 2 |
▲back to top |
SECTIONA [SOMARKS]
Question 1 [2 marks]
How would you define Design Engineering?
[2 marks]
Question 2 [8 marks]
Give examples of constraints that need to be factored in process design to transition from;
i. Region of ALL designs to a region of POSSIBLEdesigns
ii. Region of POSSIBLEdesigns to a region of PLAUSIBLEdesigns
[8 marks]
Question 3 [10 marks]
State the main building blocks of a Process Plant Design
[10 marks]
Question 4 [10 marks]
Mineralogical analysis was done on 2 samples of ore from two areas of the same ore deposit
as part of metallurgical test-work required to develop a flowsheet to process a newly
discovered Zinc-Lead ore. Shown below are 2 micrographs derived from mineralogical
analysis of Ore A and Ore B which are both Galena - Sphalerite- Pyrite ores hosted in
siliceous gangue.
|
|
3 Page 3 |
▲back to top |
Micrograph - Ore A
Micrograph - Ore B
Ore A and Ore B are Galena - Sphalerite - Pyrite ores hosted in siliceous gangue
i.
What do you understand by the term "mineral texture".
[2 marks]
ii.
Describe the mineral textures of Ore A and Ore B.
[4 marks]
iii.
Process mineralogy is very important in Process Plant Design. Explain how the
mineralogy of Ore A and Ore B will affect the design ofthe comminution plant.
[4 marks]
Question 5 [ 15 marks]
The crushing circuit below was developed to crush both the Galena - Sphalerite - Pyrite ores above in
order to generate feed material ball milling (Ore A) and SAGmilling (Ore B) before the ore undergoes
sequential flotation. The crushing plant has been sized to process 1000 tph of ore and the apertures
on the screen panels of the three screens are; Screen 1 (150mm), Screen 2 (25mm) and Screen 3
(15mm) respectively.
|
|
4 Page 4 |
▲back to top |
The table below gives the size distribution by mass of stream 1 and stream 4.
ISize(mm)
200 150 100 so 25 10
Cum % passing for stream 1 95 55 ~5 35 25 15
Cum % passing for stream 4 100 75 65 55 f45 35
1000 tph
~---~
Screen 1- lSOmm
I.
2
3
4
Screen 2 - 25mm
3a
5
7 Crusher 2
R 6
IO
8
9
II
Screen 3 -15 mm
Assuming the screens to be 100% efficient and the bond work index of the ore is 16.5 KWh/t,
i.
Calculate the energy required to crush the ore in Crusher 1. What is the power required
by the Crusher?
[S marks]
ii.
What is the reduction ratio for this crusher?
[3 marks]
iii.
What type of crusher will be suitable for this application and why?
[2 marks]
iv.
What is the size distribution of stream 3a?
[5 marks]
|
|
5 Page 5 |
▲back to top |
Question 6 [5 marks]
As seen in the crushing circuit discussed in Question 3 classification (screening) is an integral
part of comminution circuits. What is the importance of classification in comminution circuit
design? Draw a sketches of a flowsheets where (i) screens (ii) cyclones are used.
[5 marks]
SECTION B [50 MARKS]
Question 1 [10 Marks]
What are the main assumptions for the following reactor models;
i. Plug flow reactor model (PFR)?
(3 marks]
ii. Continuous stirred tank reactor model (CSTR)?
[3 marks]
iii. Sketch and explain the Residence Time Distribution profiles for an ideal PFRand CSTR
(4 marks]
Question 2 [25 Marks]
(i) The Bond Work index is so popular for ore characterisation. Discusswhy and state one disadvantage
that is associated with this method.
[3 marks]
(ii) The circuit below shows a SAG (pancake) mill used to mill Ore Band the mill discharges on a single
deck screen that sends all the class 1 size to oversize and all class 2 and class 3 to the undersize. The
feed rate is lOtph comprising of only size class 1. Holdup mass is 4t. The selection function S1=S2and
the breakage function b21=0.6. Under these conditions, 40% of the product reports to the oversize as
illustrated.
IOtph
|
|
6 Page 6 |
▲back to top |
(a) Why does a SAG mill have a "short length" and "wide diameter" while a ball mill has a "longer
length" and "smaller diameter"?
[S marks]
(b) From the information provided calculate S2 and also provide the detailed composition of the
undersize of this mill
[12 marks]
(c) The feed size composition is changed to [000...280]and if operating conditions remain the same,
calculate the composition of the undersize now.
[S marks]
Note for perfect mixed milling this general equation applies:
Question 3 [15 marks]
What do you understand by the following in the context of economic evaluation of a mineral
beneficiation project
a. Net Present Value (NPV) [3 marks]
b. Payback period [3 marks]
c. Internal Rate of Return (IRR) [2 marks]
d. Salvage value (2 marks]
e. Direct Field costs (2 marks]
f. Fixed and Variable operating costs [3 marks]
--------------
THE END--------------