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HMY720S - Hydrometallurgy 324 - 2nd Opp - Nov 2022 |
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nAm I BIA un IVE RSITY
OF SCIEn CE Ano TECHno LOGY
FACULTYOF ENGINEERINGAND THE BUILTENVIRONMENT
DEPARTMENTOF CIVIL,MININGAND PROCESSENGINEERING
QUALIFICATION: BACHELOR OF ENGINEERING IN METALLURGY
QUALIFICATION CODE: 08BMET
LEVEL: 8
COURSE CODE: HMY720S
COURSE NAME: HYDROMETALLURGY 324
SESSION: NOVEMBER 2022
DURATION: 90 MINUTES
PAPER: 1
MARKS: 50
EXAMINER(S)
SECONDOPPORTUNITYQUESTION PAPER
Prof D Groot
MODERATOR:
Dr T Coetsee, University of Pretoria
INSTRUCTIONS
1. Answer all questions.
2. Read all the questions carefully before answering.
3. Marks for each questions are indicated at the end of each question.
4. Please ensure that your writing is legible, neat and presentable.
PERMISSIBLEMATERIALS
1. Examination paper.
2. Scientific calculator, non-programmable
THIS QUESTION PAPER CONSISTS OF 5 PAGES (Including this front page)
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Question 1
Consider a Sherritt-type cobalt refinery as shown below.
(a) Explain the chemical principles used to separate nickel from cobalt in this flowsheet, and why
it is necessary as the hydrogen reduction step is selective.
[S]
(b) Draw a modified flowsheet to recover the cobalt as cathode.
[3]
Co-Ni Sulphide
Residue
(la Ni fuflne,y)
Iron O•ida
(to Ni R•llnery)
OXJDAllOH
Co II lo Co Ill
Ni-Co
Double
Sall
Ni Double Soll
(lo NI Refinery)
Sulphuric
Acid
Co
Powder
CoS
(to .lcld L<1ac:t>)
Ammonium Sulphate
figure 10. Sherritt Cobalt Refinery Flowsheet
Question 2
The 4f (lanthanides) and Sf (actinides) elements differ considerably in their chemistries. The
chemistry of both periods of elements also differs much from the transition metals.
(a) Discuss how the 4f and Sf elements generally differ in terms of their coordination chemistry.
[3]
(b) Discuss how the ability of the Sf elements to form 1,musuacl omplex ions (as compared to
transition metals) is used in the extraction of uranium from its ores.
[S]
Question 3
Discussthe factors that affect the morphology (i.e. what the deposit looks like) of copper
electrodeposits.
[8]
Question 4
Nickel ores are found as sulfides and as laterites.
(a) Describe the operation of the Moa Bay process for laterite ores.
[5]
(b) Briefly discuss how the environmental impact of this plant could be reduced.
[2]
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Question 5
Consider a typical hydrometallurgical plant.
(a) Explain why a series of stirred tank reactors are used, instead of a single, large reactor with
the same retention time.
(3]
(b) Would a number of parallel stirred tank reactors (same number, same retention time) have
the efficiency as a series? Explain your answer.
[2]
(c) Explain how a stirred tank reactor on a plant differs from a CSTR.
[3]
(d) Discuss how the difference in performance between a real reactor and a CSTRcan be dealt
with during plant design.
[6]
Question 6
You wish to model the dissolution kinetics of calcium oxide particles in a 0.01 mol/1 solution of
hydrochloric acid. The particles are +10 -72 micron. A number of experiments are done at various
temperatures and stirring rates. It is found that the measured rate is fairly insensitive to the
temperature, but varies greatly with stirring.
Calculate the expected time for the dissolution of all particles.
[SJ
Given: density of calcium oxide: 3.34 g/cm 3; diffusion coefficient: 7.93 x 10-4cm2/s at 20 deg;
solubility of the reaction product is 74.5 g/100 ml (20 °C}.
Given information
See following pages (2).
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Table25.1Conversion-TimEexpressionfsor VariousShapesof ParticlesS, hrinking-CorMe odel
FilmDiffusionControls
Ash DiffusionControls
ReactionControls
Platplate
X0 = l -L1
-I= X11
T
-( =.,V,2_fl
T
t
-=
Xa
T
·t
L = half thickness
r=
PnL
bk-gC,'I$
Pnl2
r= 2b~,CAg
PnL
r= bk"CAg
ri:
.,.-...
.s:..:.
"t '
Cylinder
Xn= l - (Jr )i.2
.!.=Xn
T
PnR
r= 2bkKCA
8
-t = Xn+ (1- X8) ln(l - X8)
T
- PaR2
T- 4b~C
t Ag
!.= 1 -
T
(1 -
XD)1'1
-1!]!!_
r= bk"CAg
8
Sphere . !.= Xa
1-(~Y X8 =
T
PaR
r= 3bkgCAg
(11)
!.= 1-
T
3(1-
X8)2i3 +2(1-
X8)
PsR2
(10)
r=
6b9"fi,CAg
(18)
=
T
1-
(1 -
X8)113
(23)
(17) r= bkP"aCRAg
(22)
Smallparticle
Stokesregime
;t = l - (1 - X8)2i3 (30)
-&
{".)
r= PBRn
2b~C
(29)
Ag
....
..:,:
'It::
-t'.
Largeparticle
(u = constant)
!-_r= l - (1 - Xn)112 (31)
-r= (const)RC-10-1A2 &
Not applicable
Not applicable
; =1 - (1 - Xa)l13
PoRo
-r= bk~C
A&
!.= 1- (1- X11)w
'T
PoR
-r= bk"CAg
.i:,.
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1
IA
1A
!'4I 2
IIA
2A
3
4
Li Be
Uhl""'
O.!M1
.. S.l)UiulTi
9.012
11
Na
Sodium
zi.m
19
K
Po(nsium
J.<UJ98
37
Rb
R-
ll'i.-468
M- 12
Mg
2Ul5
3
1118
4
IVB
5
VB
SB
6
VIB
6B
20
Ca
Ti V Cr 38 ~48
23y] 24
Calcium
Trt#'lium \\'OI\\DUITI Cfltvmlum
Sr WZr 40.0711 ~
38
Stl'on11um
K7,C,2
41
.40 ,.
Zirtoriium
!ilZl-'
51.996
----
PeriodicTableof the Elements
13
Atomic
IIIA
Number
Symbol
,'5. 3A
B
Name
Boton
I0.811
AXlnlitMou
13
7
8
9
10
11
12 Al
VIIB
~VIII---._
7B
f
8
IB
118
Alwnlnum
\\
1B
28
269112
25
. Mn
Manr,.nest
54.933
26
Fe
Iron
27
Co
Cc:oalt
589JJ
N I Cu II Z
Nir;kel
·
sg 59]
45 •46
Rh Pd
Rhodium
102.!Mli
P1116dii>m
100.4.!
14
IVA
G 4A
C
c.tbon
12.011
14
Si
·-n-••·
15
16
17
VA
VIA
VIIA
w6A J SA
wg7A
N
N'i1.toc«i
IHXH
O
0.rrttn
_ 15_.00'J
.F
Fluorinl
__ 18.!m
18
VIIIA
SA
2
I H""e"""
~0•.'1"~.
Ne
Neon
_ _20180___
15
P
Pho,pho,,n,
,
16
S
Slilfur
32.mG
17
Cl
Chlorine
35.CS)
18
Ar .
.t.rp,
39~1!
f1'33~:"7~f341:71~5§_~1~~s1<2:'
79~
M.79!
55
56
.. Cs Ba
C-.m
"""'
131.!'n.i
m:i2a
72Hf 73Ta 74W ·75Re ~6Os 77Ir
~=~~~===: Htfnium
171!.49
0sn'llUITI
10023
ltimum
19222
78Pt 79Au
J>Satinum Gold
15'5A'l8
UJG.00,
80Hg ~81Tl
Mmu,y
Thal!Mn
200.59
204.JIO
~2Pb ~3 Bi
lHd
8dml.ltb
207.2
?l)J9,ll)
·8P4 o ·85At
' Polonkam As.1:atinf
2(WJ,982
20').987
86Rn
Radon
222.018
87
Fr
rrancivm
m.oa,
88
Ra
R•dlum
22G025
10R4 f 10D5 b
Ruthtrlordlvm
261
. ....
10S6 g
Seeborc,um
•.
10B7 h ~1H08 s 10M9 t 11O0 s 11R1 g
Bohrium
'
. ·•·
.
Kats/um Mtttnttk.m Darmstadtium Roem,entum
........ ......., ........ ___,
.
.
1C12 n ~1N3 h
Copemldurn · Nlhonium
2.9ii
. .....
11F4 l ~1M15 c 11L6 v 11T7 s
flerovi...-n Mosc:orium l.n"ffl1'10run Ten~ulne
- ....
, 80
····-·· ..
-----
1O18 g
0~
..
---
.,r r r r r r r .,.~· II II II II II 57
58 ll59
60
61 lt62
63
64
65
La;~I~L;!ad• Ce Pr Nd Pm Sm Eu Gd Tb 10y- 1~ JLJ.tiJ~I I~ Ge1d5O'7lN-2~5i
Tl~,r.t!ilu2tSn
JI \\62.500 .• H1o6r4n9iwlJn
167.250 , . IC8.934 , Y1t7t~.\\~.055
174.967
A;:~I~A~c · Th Pa U Np Pu .Am Cm Bk Cf ~~E1,1s Fm Md ,,,No Lr
Adinlum
W.029
Thorium
232.038
Protactinium
23\\.0li
UreMlffl
238.0ZI
tt.ptuntum
:m.0'8
Plutonium
2"'4W
Americium
2'3..001
Curium
247.07D
Bet\\o:elium californium
247070
251.0l(i
EinsWnil.m
knnlum
Mend.it'rlum
[254! . :zsl_()l'Jj
&1
Nobe!ium '
259.101
VI
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