|
A
Quarterly
R
& D Abstract Service
By IIME
MINERALS
ENGINEERING
--A
Global Alert Service
Issue No.
66 & 67
JULY
2005/OCTOBER 2005
Editors:
R
Singh
K
K Bhattacharyya
S
C Maulik
Compilation
: Mrs. A Dhawan
Indian
Institute of Mineral Engineers
C/o
Mineral Processing Division
National
Metallurgical Laboratory
Issue
nos. 68 & 69
January
2006/ April 2006
1.
Extraction of molybdenum from spent catalyst by salt-roasting
B.B.
Kar, B.V.R. Murthy and V.N. Misra
Regional
Research Laboratory, Bhubaneswar, 751013 India
biswabandita@rrlbhu.res.in
International
Journal of Mineral Processing, Volume 76, Issue 3, June
2005, Pages 143-147
Spent
hydro-refining catalysts mainly consists of 20–22% MoO3,
5–6% NiO, 4–5% S, 1–2% Co3O4,
1.3–1.5% Fe2O3, 3–4% SiO2,
and the balance is Al2O3. In the
present study, one such spent catalyst was roasted with
sodium chloride to recover molybdenum by converting
it into sodium molybdate. The sodium molybdate was further
purified by chemical treatment to obtain a pure grade
molybdenum trioxide. Various parameters like temperature,
time and NaCl addition have been studied, and conditions
for the maximum recovery of molybdenum have been established.
2.Densification
of iron(III) sludge in neutralization
Wee
Yong Gan, Cordelia Selomulya*, Geoff Tapsell and Rose
Amal
*ARC
Centre for functional Nanomaterials, School of Chemical
Engineering and Industrial Chemistry, University of
New South Wales, Sydney NSW 2052, Australia
c.selomulya@unsw.edu.au
International
Journal of Mineral Processing, Volume 76, Issue 3, June
2005, Pages 149-162
Acid
mine drainage (AMD), of which iron is a substantial
component, is a potential by-product in the mining industry.
Conventional neutralization is a common approach to
treat AMD, although it creates a major disposal problem
due to the generation of voluminous sludge. Sludge recirculation
improves solid density by slowing down the rate of neutralization
and allowing the growth of precipitates, while existing
solids act as seed particles by providing necessary
surface area for precipitation. The mechanisms of iron
sludge densification are not fully understood, mainly
because of the complex nature of iron chemistry, and
the variety of amorphous, polymeric oxides that could
be formed. In this work, the effects of alkaline reagents,
flocculant addition, and dosing sequence, on the precipitation
of iron (III) hydroxide and densification of the recycled
sludge were investigated. Slowly dissolving lime (Ca(OH)2)
was found to be more effective than caustic (NaOH) in
producing sludge with higher solid contents. Polymers
addition created stronger aggregates that could withstand
shearing without significant size reduction, but the
overall sludge density was lower than those produced
without flocculant. Conditioning the sludge at pH between
3.5 and 4.5 by adding fresh lime in a specific dosing
manner appeared to be conducive to the growth of large
agglomerates. The final sludge solid content of ~15
wt.% was considerably higher than others produced under
different conditions. The plate-like structures of precipitates
generated with more recycles in this instance, possibly
helped ease the release of entrapped water between solids
during shearing, thus producing sludge with higher solid
density.
3.
Pelleting flocculation—an alternative technique to optimise
sludge conditioning
W.
Walaszek and P. Ay
Chair
of Mineral Processing, Brandenburg University of Technology,
Siemens-Halske-Ring 8, 03046 Cottbus, Germany
walaswi@tu-cottbus.de
International
Journal of Mineral Processing, Volume 76, Issue 3, June
2005, Pages 173-180
The
process of pelleting flocculation, a further development
of classical flocculation technology, is defined as
a formation of wet pellets directly in a liquid medium.
Apart from well described mechanisms of flocculation
like perikinetic and orthokinetic flocculation, the
mechanism responsible for the formation of dense agglomerates
is the mechanical syneresis guaranteed by the appropriate
reactor form. Upon the two established models in the
literature: the series system and the parallel system,
experiments were performed to simulate a layer-by-layer
particle deposition on the so-called “mother seeds”
conforming to the parallel system. The present paper
deals with the results originating from laboratory scale
experiments with model sludge, kaolin suspension. The
layering process was conducted in the presence of different
cationic flocculants and the resulting relationships
with respect to their nature and to the applied energy
level have been assessed. The achieved agglomerates
exhibit an “onion like” structure with densities up
to 1.42 g/cm3 and solid matter content up to 48% after
gravity dewatering. Thus generated sludge agglomerates
reveal the optimisation potential for sludge treatment
manifested by improved characteristics achieved during
the conditioning.
4.
Examination of the jarosite–alunite precipitate addition
in the raw meal for the production of Portland and sulfoaluminate-based
cement clinkers
M.
Katsioti, P.E. Tsakiridis*, S. Agatzini-Leonardou and
P. Oustadakis
*
School of Mining and Metallurgical Engineering, Lab
of Metallurgy, National Technical University University
of Athens, 9, Iroon Polytechniou street, 157 80 Zografou,
Athens Greece
ptsakiri@central.ntua.gr
Int
Journal of Mineral Processing, Volume 76, Issue 4, August
2005, Pages 217-224
The
aim of the present research work was to investigate
the possibility of adding a jarosite–alunite chemical
precipitate, a waste product of a new hydrometallurgical
process developed to treat economically low grade nickel
oxides ores, in the raw meal for the production of Portland
cement clinker. The precipitate was also tested in the
production of non-expansive, sulfoaluminate-based cement
clinker, as a substitute for gypsum because of its high
sulfate content. For the Portland clinker, two samples
of raw meals prepared, one with ordinary raw materials
(reference sample) and another with 1% jarosite–alunite
precipitate. Both raw meals were sintered at 1450 °C.
For the sulfoaluminate-based clinker, one raw meal contained
20% gypsum (reference sample) whereas the other contained
11% of the precipitate. Both raw meals were sintered
at 1300 °C. The results of chemical and mineralogical
analyses as well as the microscopic examination showed
that the use of the jarosite–alunite precipitate did
not affect the mineralogical characteristics of the
so produced Portland cement clinker. In the case of
sulfoaluminate-based cement clinker, there was confirmed
the formation of the sulfoaluminate phase (C4A3SŻ),
the most typical phase of this cement type.
5.
Effect of frothers on bubble size
Rodrigo
A. Grau, Janusz S. Laskowski and Kari Heiskanen
Helsinki
University of Technology, Helsinki, Finland
Rodrigo.Grau@hut.fi
Int
Journal of Mineral Processing, Volume 76, Issue 4, August
2005, Pages 225-233
The
size of bubbles in flotation cells was measured using
the UCT bubble size meter and the HUT bubble size analyser.
While both methods provided similar critical coalescence
concentration (CCC) values for the three tested frothers,
they also revealed important differences. Using the
HUT bubble size analyser, which does not impose any
lower bubble size limit, it was possible to find differences
in bubble size measured for three frothers at concentrations
exceeding the corresponding CCC values. Frothers affect
both the break-up phenomena in the impeller/stator zone
in flotation cell, and bubble coalescence. While longer
chain polyglycols (e.g. DF-1012) are able to produce
larger stable bubbles than the short chain DF-250 and
DF-200 polyglycols, the CCC values for DF-1012 are lower
than those for DF-250 and DF-200.
6.
A new technique for extracting zirconium form Egyptian
zircon concentrate
Aly
M. Abdel-Rehim
Alexandria
University, 69 Sultan Hussein St Shallalat, Alexandria,
Egypt
A_rehim@hotmail.com
Int
Journal of Mineral Processing, Volume 76, Issue 4, August
2005, Pages 234-243
Zircon
is the most important commercial source of zirconium,
its compounds and alloys. Several methods are used for
industrial processing of zircon for production of zirconium
dioxide and tetrachloride. These methods include sintering
of zircon with sodium carbonate or sodium hydroxide
or calcium oxide or calcium carbonate and with potassium
fluorosilicate, chlorination of zircon mixture with
coal in blast furnace and carbidization of zircon in
a mixture of coal in electric arc furnace. All these
methods are carried out at high temperatures and have
many disadvantages.
The
present work illustrates a study of a new technique
for extracting zirconium from Egyptian zircon concentrate
by its simultaneous ball-milling and pressure alkaline
leaching, to improve the recovery of zirconium from
zircon. Experiments were carried out in stainless steel
ball-mills of cylindrical shape under different conditions
of temperature, pressure and time. The ball-mills were
heated and mechanically rotated in an electric furnace
by means of roll mechanism. The filtrate after leaching
of zircon, containing excess of sodium hydroxide was
regenerated by its treatment with calcium hydroxide
for purification from silicon impurity. Then, the solution
was evaporated to the desired concentration (500 g/l
Na2O) and recycled to the reactor of leaching.
The
results obtained show that complete recovery of zirconium
from zircon (99.7%) by simultaneous ball-milling and
alkaline leaching was attained at 250 °C within 3 h,
using amount of sodium hydroxide 150% of theoretical
requirement (satisfying favourable conditions of zirconate
cake for subsequent acid leaching).The standard free
energy (ΔFo)
and equilibrium constant (K) of the reaction of zircon
with sodium hydroxide were calculated as—19.58 k cal
mol--1 and 2.29 1014, respectively.
The kinetics of the technological alkaline processing
of zircon in ball-mall autoclaves was studied over the
temperature range 150–275 °C.
7.
Effect of contaminant carbonaceous matter on the sorption
of gold by pyrite
H.
Tan, D. Feng, J.S.J. van Deventer * and G.C. Lukey
Department
of Chemical and Biomolecular Enginering, The University
of Melbourne, Melbourne Parkville, Vic. 3010, Australia
*
jannie@unimelb.edu.au
Int
Journal of Mineral Processing, Volume 76, Issue 4, August
2005, Pages 244-259
The
effect of carbon or graphite coating on the adsorption
of gold cyanide on pyrite was investigated with pure
pyrite and a pyrite concentrate. In the carbon or graphite
contaminated pyrite systems carbon and graphite not
only acted as gold sorbents, but also enhanced gold
adsorption on pyrite. The carbon coating enhanced gold
adsorption on pyrite to a larger extent, in comparison
with the graphite coating. The carbon or graphite coating
on pyrite reduced the negativity of the pyrite surfaces,
and hence improved the physical adsorption of gold cyanide
on pyrite. In addition, the highly conductive coating
of carbon or graphite on pyrite could enhance electron
transfer in the electrochemical reactions occurring
in the chemical adsorption of gold and gold reduction
on pyrite. The preg-robbing by pyrite or the graphite-coated
pyrite was reduced and further eliminated at higher
cyanide concentrations. However, gold adsorption on
the carbon-coated pyrite could not be prevented even
at higher cyanide concentrations due to gold adsorption
on the carbon coating. In comparison with pure pyrite,
the pyrite concentrate had a higher capacity adsorbing
gold, due to the presence of carbonaceous matter in
the pyrite concentrate. Fine grinding intensified the
smearing of carbon or graphite on the mineral particles,
resulting in a larger extent of enhancement in the preg-robbing
of the concentrate by the carbon or graphite coating.
A diagnostic elution of the preg-robbing pyrite samples
indicated that the reduction of gold at the pyrite surfaces
was the dominant mechanism for gold adsorption on pyrite,
followed by physical and chemical adsorption. Surface
topological studies by SEM/EDX showed that gold adsorbed
at defect sites on pyrite surfaces. For the pyrite with
a 5% carbon coating, gold was observed to adsorb not
only at the defect sites, but also at the smooth surfaces
with carbon present. For the pyrite with a 5% graphite
coating, carbon was also found at the pyrite surfaces,
but gold was only detected at the defect sites. XPS
studies revealed that part of the gold physically and
chemically adsorbed on pyrite or pyrite coated with
carbon or graphite. Some gold cyanide was reduced at
the pyrite surfaces, with the sulphide ions of pyrite
being oxidised to elemental sulphur.
8.
Effects of surfactant adsorption and surface forces
on thinning and rupture of foam liquid films
Emil
D. Manev and Anh V. Nguyen*
*Discipline
of Chemical Engineering, School of Engineering, The
University of Newcastle, New South Wales 2308, Australia
Anh.Nguyen@newcastle.edu.au
Int
Journal of Mineral Processing, Volume 77, Issue 1, September
2005, Pages 1-45
The
properties of thin liquid films (TLF) are of paramount
significance for colloidal disperse systems, and a number
of industrial processes, including froth flotation.
In flotation, the bubble–particle attachment is controlled
by the thinning and rupture of the intervening liquid
film between an air bubble and a mineral particle. The
froth evolution and its transient stability are also
a function of the drainage and rupture of liquid films
between air bubbles. Surface-active substances (surfactants)
are used as flotation reagents to control the behavior
of the liquid films. This paper presents a review of
our research in the area of surfactant adsorption, surface
forces and liquid films. It mainly focuses on the validation,
application and extension of the Stefan–Reynolds theory
on the liquid drainage. The extension of the Stefan–Reynolds
theory comprises surface forces (disjoining pressure),
surface tension variation, caused by the adsorption
and diffusion of surfactants. Both the experimental
and theoretical results are mostly related to the free
(foam) films formed between two bubbles but can be principally
extended to emulsion films between two oil drops and
wetting films between an air bubble and a solid surface.
9.
Aggregate size and density after shearing, implications
for dewatering fine tailings with hydrocyclones
George
V. Franks, Peter D. Yates, Noel W.A. Lambert and Graeme
J. Jameson
Centre
for Multiphase Processes, Chemical Engineering, The
University of Newcastle, Callaghan, NSW, 2308, Australia
george.franks@newcastle.edu.au
Int
Journal of Mineral Processing, Volume 77, Issue 1, September
2005, Pages 46-52
Experiments
have been conducted in a shear cell in order to provide
insight into the separation of flocs by size and density
in a hydrocyclone. The size of the aggregates was measured
after shearing at a rate comparable to that found within
a typical hydrocyclone. Two types of coal tailings from
the Hunter Valley, NSW Australia with average sizes
of about 0.4 µm and 10 µm were investigated. The size
of aggregates after shearing was measured for a range
of different polymeric flocculants of varying molecular
weight and charge density. Under certain conditions
90% of the aggregates from the submicron tailings have
size greater than 38 µm after shear at 1200 s-1
for 30 s. The aggregates produced from the 10 µm tailings
had over 90% larger than 82 µm with the flocculants
tested. The size of the aggregates remained sufficiently
large after shearing to be suitable for hydrocyclone
dewatering. The density of the aggregates was calculated
from the aggregate size and mass fractal dimension.
The small difference between the density of the aggregates
and water was found to be the factor limiting their
velocity under the applied centrifugal acceleration.
10.
Dynamic adsorption of sodium dodecylbenzene sulphonate
and dowfroth 250 onto the air–water interface
C.M.
Phan, A.V. Nguyen* and G.M. Evans
*
Discipline of Chemical Engineering, School of Engineering,
The University of Newcastle, University Drive, Callaghan,
NSW 2308, Australia
anh.nguyen@newcastle.edu.au
Minerals
Engineering, Volume 18, Issue 6, May 2005, Pages 599-603
Surface
active agents (surfactants) are widely used to control
the interfacial properties of the gas–liquid and liquid–1
interfaces in the froth flotation separation process.
The dynamic adsorption of the surfactants is critical
to flotation which is a kinetics-controlled process.
This paper examines the dynamic adsorption of sodium
dodecylbenzene sulphonate and Dowfroth 250, which is
a commercial mixture of polyglycols used to control
the dispersion of air in flotation. The dynamic adsorption
process was modelled based on either the diffusion-controlled
or kinetics-controlled theories. The numerical computation
was applied to solve the non-linear governing equations.
The dynamic adsorption of the surfactants was measured
in terms of the dynamic surface tension using the pendant
drop method. Comparison between the theoretical results
and experimental data shows that the kinetics-controlled
model for the surfactant adsorption describes the experimental
data better for both surfactant systems.
11.
Selective flotation of enargite from chalcopyrite by
electrochemical control
H.
Guo and W.-T. Yen
Department
of Mining Engineering, Queen's University, Kingston,
Ontario, Canada K7L 3N6
hguo@nrcan.gc.ca
Minerals
Engineering, Volume 18, Issue 6, May 2005, Pages 605-612
Voltammetric
studies, contact angle measurements, collector and collectorless
microflotation tests were carried out in this study
to investigate the oxidation properties and flotation
characteristics of enargite as well as chalcopyrite.
Selective flotation of enargite from chalcopyrite under
varied pulp potentials was conducted to investigate
the feasibility of enargite removal from a chalcopyrite
concentrate.The test results indicate that chalcopyrite
began to oxidize quickly at a much lower potential than
enargite. Enargite could be floated well at a potential
higher than +0.2V vs. SCE while chalcopyrite was completely
depressed at a potential higher than +0.2V vs. SCE.
Selective flotation revealed that enargite can be successfully
removed from chalcopyrite through controlling the pulp
potential higher than +0.2V and lower than +0.55 V vs.
SCE.
12.
Heap leaching kinetics are proportional to the irrigation
rate divided by heap height.
H.M.
Lizama, J.R. Harlamovs, D.J. McKay and Z. Dai
Teck
Cominco Metals Ltd, Teck Cominco Research, PO Box 2000,
Trail, BC, Canada, V1R 4S4
hector.lizama@teckominco.com
Minerals
Engineering, Volume 18, Issue 6, May 2005, Pages 623-630
Zinc
sulphide ore was leached in columns of various heights
and under various irrigation rates. Sphalerite and pyrite
bioleaching kinetics agreed with the colonization shrinking
core model where an initial colonization phase was followed
by a steady rate phase. Columns irrigated at the same
rate showed colonization rate constants (µ) of both
sphalerite and pyrite that increased linearly with the
inverse of column height. Similarly, the shrinking core
rate constants (k)
were also inversely proportional to heap height. When
the irrigation rate was physically adjusted to compensate
for height, columns ranging from 1 m to 8 m tall showed
leaching curves that were identical. In essence, sphalerite
and pyrite heap bioleaching kinetics were proportional
to the irrigation rate divided by the height (L/h). The relationships governing the colonization and shrinking core
rate constants were different for sphalerite and pyrite.
Sphalerite bioleaching was favoured over pyrite at lower
values of L/h. The degree of sulphur oxidation was favoured at higher values
of L/h.
13.
Chromium(VI) biosorption characteristics of Neurospora
crassa fungal biomass
Sibel
Tunali, Ismail Kiran and Tamer Akar
Department
of Chemistry, University of Osmangazi, Campus of Meselik,
26480, Eskisehir, Turkey
stunali@ogu.edu.tr
Minerals
Engineering, Volume 18, Issue 7, June 2005, Pages 681-689
The
removal of Cr(VI) from aqueous solutions by live and
pretreated Neurospora crassa fungal biomass was investigated
in the batch mode. The influence of solution pH, contact
time and initial metal ion concentration as well as
pretreatment of biomass on the biosorption efficiency
were studied. All pretreatment methods were found to
increase the biosorption capacity of biomass in comparison
with the live biomass and biosorption capacity of acetic
acid pretreated biomass was found to be 15.85 ± 0.94
mg/g biomass under optimum conditions. The adsorption
constants were found from the Freundlich isotherm model
at 25 °C. The biosorbent was regenerated using 10 mM
NaOH solution with up to 95% recovery and reused five
times in biosorption–desorption cycles successivelly.
The biosorption mechanism of biosorbent was also evaluated
by chemical and instrumental analysis including infrared
spectroscopy, scanning electron microscopy and X-ray
energy dispersion analysis.
14.
Dissolution of wollastonite and its flotation and surface
interactions with tallow-1,3-diaminopropane (duomeen
T)
S.
Prabhakar, K. Hanumantha Rao and W. Forsling
National
Metallurgiccal Laboratory, Madras Centre, Complex Taramani,
Chennai 600 113
swaprabha@yahoo.com
Minerals
Engineering, Volume 18, Issue 7, June 2005, Pages 691-700
Wollastonite
finds an important place among industrial minerals due
to its high chemical and thermal resistance and also
as a substitute for asbestos. With the depletion of
high-grade ores and increased demand, it becomes inevitable
to process low-grade ores. Flotation can be employed
effectively for processing these ores. Flotation behavior
of wollastonite was studied using tallow-1,3-diaminopropane
as collector in the Hallimond micro-flotation cell.
The flotation recoveries obtained were correlated with
contact angle measurements. Dissolution studies clearly
bring out the incongruent dissolution of wollastonite,
resulting in a silica rich layer on the surface of the
mineral. The release rates of calcium and silicon decrease
with the particle size. Maximum flotation obtained at
1 × 10-5 M diamine concentration. DRIFT studies
indicate that the intensity of alkyl chain bands increases
with increasing diamine concentration, thus corroborating
increased presence of diamine on wollastonite resulting
in maximum contact angle and flotation recovery. Surface
free energy values of wollastonite were determined by
different approaches using contact angle data of well-defined
components of polar and apolar liquids. An attempt has
been made to correlate between the flotation response
and the surface free energy values of wollastonite in
the presence diamine.
15.
The FF (flocculation–flotation) process
Jailton
J. da Rosa and Jorge Rubio*
Laboratorio de Tecnologia
Mineral e Ambiental, Departamento de Engenharia de Minas,Pgem
- Universidade Federal do Rio Grande do Sul, Av Oswaldo
Aranha 991512, 90035- 190 Porto Alegre, RS Brazil..*
jrubio@ufrgs.br
Minerals Engineering,
Volume 18, Issue 7, June 2005, Pages 701-707
A
new on-line flocculation system (FF) has been developed
which is coupled with a rapid flotation to remove the
aerated flocs (flocs with entrained and entrapped bubbles).
These aerated flocs are formed only in the presence
of high molecular weight polymers and bubbles and under
high shearing (and head loss) in special “flocculators”.
The air excess air abandons the flotation tank (a centrifuge
or a column) by the top and the flocs float after very
short residence times (within seconds). The aerated
flocs are large units (some millimetres in diameter)
having an extremely low-density. Process efficiency
was found, in all cases, to be a function of the trilogy,
head loss, type (and concentration) of flocculants and
air flow rate. Mechanisms involved appear to include
small bubble formation and their rapid occlusion (entrapment)
within flocs, nucleation of bubbles at floc/water interfaces,
polymer coiling as a result of “salting out” effects
at the aqueous/air interface and plug flow type of mixing
(flocculation) instead of perfect. Successful examples
of emulsified oil and solids removal from water are
shown and because in all cases were obtained high efficiencies
(>90% removal), at high hydraulic loadings (>130
m h-1) it is believed that this kind of flocculation–flotation
appears to have a great potential in solid/liquid or
liquid/liquid separation.
16.
Recent advances in bias and froth depth control in flotation
columns
J.
Bouchard, A. Desbiens and R. del Villar*
LOOP
, Department of Mining, Metallurgical and Materials
Engineering, Universite Laval, Quebec, QC, Canada GiK
7P4
rene.delvillar@gmn.ulaval.ca
Minerals
Engineering, Volume 18, Issue 7, June 2005, Pages 709-720
This
paper reviews recent work done at Université Laval in
the field of column flotation instrumentation and control.
The presented control results rely on froth depth and
bias sensors. This work establishes that flotation column
control could be substantially improved by using different
control methods, such as nonlinear, multivariable, and
feedforward control. The emphasis is placed on the way
the available information, from sensors and quantitative
or even qualitative relationships, may be used to reach
the control objectives. Laboratory and pilot-scale results
illustrate the discussion.
17.
Using the SUPASIM flotation model to diagnose and understand
flotation behaviour from laboratory through to plant
Martyn
P. Hay
E Mail: martynhay@worldonline.co.za
Eurus
Mineral Consultants PO Box 1249, Cramerview, Gauteng,
2060, South Africa
Minerals
Engineering, Volume 18, Issue 8, July 2005, Pages 762-771
For
a model to be successful it must address the concerns
and needs of a target audience. Further, the model must
demonstrate the same patterns of behaviour as the real
system, and need only be complex enough to meet this
objective. If the model is too complex it can become
unusable to those who need it most.With this in mind,
SUPASIM has been developed for the practical metallurgist
requiring only laboratory flotation rate data as input.
Some 35+ successful plant simulations have been completed
since 1985. The approach of SUPASIM is to characterise
an ore, organise information in an understandable way
and add structure to the complex flotation situation
and hence support the metallurgist to interpret the
relationship between variables and optimise the flotation
process.The paper describes the basis on which the model
was developed and sets out to provide an insight into
interpreting laboratory flotation kinetics and their
physical meaning in a production plant and the influence
floatable gangue has on float performance and plant
design. A case study illustrates how the ratio of slow
floating mineral to gangue can influence circuit design
and improve recovery on a plant scale.
18.
Investigation of the role and interactions of a dithiophosphate
collector in the flotation of sulphides from the Merensky
reef
J.
Wiese, P. Harris and D. Bradshaw
Mineral
Processing Research Unit, University of Cape Town, P
Bg, Rondebosch 7700, S Africa
jenny@chemeng.uct.ac.za
Minerals
Engineering, Volume 18, Issue 8, July 2005, Pages 791-800
Platinum
group elements (PGE) are recovered by flotation from
the Merensky reef in the Bushveld Complex, South Africa.
The reef contains approximately 1% sulphide minerals
in the form of chalcopyrite, pentlandite and pyrrhotite.
The PGEs are strongly associated with these sulphide
minerals. Different reagent combinations are used in
the flotation process to extract the valuable minerals
from the reef. Batch flotation tests were conducted
on a typical ore from the Merensky reef to investigate
the role of dithiophosphate (DTP) and copper sulphate
(CuSO4) addition on the flotation response
of the ore using both guar and caboxymethyl cellulose
(CMC) type polymeric depressants. Differences in the
flotation response of the individual minerals present
in the ore to the different reagent combinations were
observed. These differences and the reasons for the
differences are discussed.
19.
The effect of agitation on the flotation of platinum
ores
D.A.
Deglon
Mineral
Processing Research Unit, Department of Chemical Engineering
, University of Cape Town, Private Bag Rondebosch, Cape
Town 7700, South Africa
dad@chemeng.uct.ac.za
Minerals
Engineering, Volume 18, Issue 8, July 2005, Pages 839-844
Flotation
is routinely used for the beneficiation of platinum
ores for which the bulk of world production is from
South Africa. Most South African platinum concentrators
use mechanically agitated flotation cells which operate
with power intensities higher than the typical industrial
range of 1.0–2.0 kW/m3. This is due to the general philosophy
in the platinum industry that increasing power intensity
is beneficial to the flotation of finer particles. This
paper investigates the influence of agitation on flotation
with reference to results from tests on two pilot-scale
mechanical flotation cells on South African platinum
concentrators. Flotation tests were conducted on a 60
l forced-air flotation cell and a bank of four 150 l
induced-air flotation cells over a range of impeller
speeds, air flow rates and feed types. Flotation results
demonstrate that increasing the level of agitation generally
has a beneficial effect on the rate of flotation of
platinum ores but that this is accompanied by significant
decreases in concentrate grade. These decreases may
be due to increases in entrainment or in the rate of
flotation of poorly liberated (low grade) particles
or floatable gangue. However, since platinum ores are
measured in parts per million, relatively small amounts
of additional gangue reporting to concentrate will impact
significantly on concentrate grade.
20.
A CIP simulation technique using excel built-in functionality
J.W.
Coetzee and S. Lalloo
Department
of chemical Engineering, Cape Technikon, P. O. Box 652,
Cape Town 8000, S Africa
coetzeew@cput.ac.za
Minerals
Engineering, Volume 18, Issue 8, July 2005, Pages 845-848
Carbon-in-pulp
(CIP) operations are used extensively in the gold mining
sector to recover aurocyanide form solution. In this
study, an attempt was made to model these operations
by making use of various simplifying assumptions in
order to simulate the effect of changing operating conditions
on plant performance. A pragmatic approach was followed
as the developed simulation is aimed at industrial scale
applications. The model is based on the assumptions
that leaching and adsorption rates are a function of
the difference in concentration between metallic gold
and aurocyanide, and aurocyanide and gold adsorbed onto
the activated carbon respectively. This type of model
proved to be effective for plant data simulation purposes
and could be solved using a Newtonian search algorithm
where the errors between predicted outputs and plant
data is minimized.
21.
Beneficiation of a gold bearing enargite ore by flotation
and As leaching with Na-hypochlorite
L.
Curreli, M. Ghiani, M. Surracco and G. Orrů
Department
of Geoengineering and Environmental Technologies (DIGITA)
University of Cagliari, 09123Cagliari. Italy
curreli@unica.it
Minerals Engineering,
Volume 18, Issue 8, July 2005, Pages 849-854
The
deep mineralized bodies of the Italian Serrenti-Furtei
gold-bearing deposit, located in southern Sardinia,
contain substantial amounts of enargite-luzonite and
pyrite with subordinate tennantite, covellite, chalcopyrite
and arsenopirite. The gold, which occurs as grains of
between a few tens of micrometres and submicron size,
is not amenable to direct cyanidation. These ores are
beneficiated by bulk flotation using sulphydryl collectors
and the resulting concentrates are then pyrometallurgically
processed to produce gold and copper. However, the concentrates
contain significant amounts of arsenic, severely reducing
their market value; the abatement of this highly toxic
metal in the flue gas to comply with stringent emission
limits, increases processing costs significantly.In
order to reduce the arsenic content in the concentrates
and hence the penalties incurred, we carried out an
investigation on enargite leaching using sodium hypochlorite
to selectively dissolve the arsenic.By suitably adjusting
the main influencing variables, leaching was found to
be effective, achieving 96% arsenic removal without
significant Au and Cu losses, increasing the commercial
value per tonne of concentrate.
22.
A review of pyrrhotite flotation chemistry in the processing
of PGM ores
J.D.
Miller, J. Li, J.C. Davidtz and F. Vos
Department
of Metallurgical Engineering, University of Utah, Salt
Lake City, UT 84112, USA
jdmiller@mines.utah.edu
Minerals
Engineering, Volume 18, Issue 8, July 2005, Pages 855-865
The
chemistry of pyrrhotite flotation using xanthate collectors
is reviewed with respect to the processing of PGM ores
and the recent results from captive bubble contact angle
measurements at the University of Utah are presented.
In some cases a low flotation recovery of PGM may be
due to the surface state of pyrrhotite particles under
conventional flotation conditions (open to air and pH
9.0).
Thermodynamically
pyrrhotite is not stable and reacts relatively quickly
with its environment. Natural/collectorless flotation
of pyrrhotite is observed only under a low oxidation
potential in acidic solution. Its surface is easily
oxidized to ferric hydroxide/oxide under conventional
flotation conditions, creating a hydrophilic state at
the pyrrhotite surface and low flotation recovery even
though xanthate collectors can be adsorbed. Under these
conditions, activation by copper is not easily achieved.
These observations reported in the literature have been
confirmed by captive bubble contact angle measurements.
Based on the analysis of previous research, conditions
for improved pyrrhotite flotation and increased PGM
recovery are suggested.
23.The
optimization of an improved method of fine coal dewatering
M.
Le Roux, Q.P. Campbell, M.S. Watermeyer and S. de Oliveira
School
of Chemical And Minerals Engineering, North West University,
Private Bag X6001, Internal Box 553, Potchefstroom 2520,
South Africa
chimlr@puk.ac.za
Minerals
Engineering, Volume 18, Issue 9, August 2005, Pages
931-934
An
improved method of dewatering fine coal (-500 µm) by
vacuum filtration was developed and optimized. Tests
on a bench scale vacuum filter showed that when a filter
cake was deliberately damaged, causing the airflow through
the cake to increase and the applied vacuum to decrease,
a lower final moisture content could be achieved as
well as a higher rate of dewatering.
This
method was optimized, taking into account the optimum
time to inflict the damage to the filter cake during
a single dewatering cycle. The amount and character
of the inflicted damage to the filter cake was also
investigated. It was found that the optimum time to
inflict the damage was as soon as possible after the
point of 100% saturation, decreasing the final moisture
percentage from 29% to 24%. The configuration of the
damage had no significant influence to the final moisture
content of the filter cake. This led to believe that
the air flow through the cake during dewatering is mainly
hindered by a layer of ultra fine coal that will form
at the top of a filter cake. Further investigation showed
this layer to be approximately a third from the top
of the filter cake, relating to a particle size of between
120 and 130 µm.
24.Pasting
characteristics of hematite/quartz systems
C.A.O.
Hernandez, A.C. De Araujo, G.E.S. Valadăo* and S.C.
Amarante
*Department
of technological studies, Mineracoes Brasileiras Reunidas
S A ; Av de Ligacao 3580 CEP 34000 000 Nova Lima, MG
Brazil
gvaladao@denim.ufmg.br
Minerals
Engineering, Volume 18, Issue 9, August 2005, Pages
935-939
Iron
ore tailings are currently disposed underwater in tailings
dams as slurries containing from 30% to 50% of solids
by weight. Conventional or high capacity thickeners
are used to recycle most of the process water at the
beneficiation plants. The underflow slurry stream of
this unit operation feeds tailing basins either by gravity
or by pumping. Alternatively, the preparation of pastes
from tailings is a very attractive method since it allows
their surface disposal without the need of large dam
embankments and it also permits co-disposal with mine
waste rock in controlled piles. In some specific cases,
filling up exhausted open pits by co-disposal of tailings
in a paste form and waste rock can be employed with
several environmental related advantages. In the present
work some physical and rheological characteristics of
the slurries and pastes, prepared in different hematite/quartz
systems, are presented and compared with some physical,
chemical and mineralogical characteristics of the solids.
25.
Process data visualisation with biplots
S.
Gardner, N.J. Le Roux and C. Aldrich
Department of Process
Engineering, University of Stellenbosch, Private Bag
XI, Matieland 7602, Stellenbosch, South Africa; E mail:
cal@sun.ac.za
Minerals
Engineering, Volume 18, Issue 9, August 2005, Pages
955-968
In
this paper a modern methodology of biplots is introduced
as a means for monitoring the behaviour of process systems.
This sophisticated methodology allows for the projection
of high-dimensional data to a low-dimensional subspace
that can be visualised by a human operator. The projections
are highly graphical in nature, and rich in information
regarding variation in process variables, correlations
among these variables, as well as class separation,
taking into account the multivariate character of the
data. Moreover, as is shown by way of two case studies,
process disturbances can be visualised and explored
quantitatively by superimposing alpha-bags on biplots.
26.
Influence of dry grinding on talc and kaolinite morphology:
inhibition of nano-bubble formation and improved dispersion
Marek
Zbik and Roger St. C. Smart
Applied
Centre for structural and Synchrotron Studies, University
of South Australia, Mawson Lakes, Adelaide 5095, Australia
roger.smart@unisa.edu.au
Minerals
Engineering, Volume 18, Issue 9, August 2005, Pages
969-976
The
effects of dry grinding in a porcelain ball mill and
a chrome steel ring mill on the structure and morphology
of talc and kaolinite minerals and mixtures have been
studied. It is well known that ground talc is easier
to make down as a suspension than unground talc and
that it displays better rheological behaviour in the
slurry. Morphological and structural studies (SEM, TEM,
AFM, XRD) of both ground and unground talc and kaolinite
samples have revealed new factors accounting for this
behaviour during make down as a mineral suspension in
water. Short-term (<1 min) grinding in the ring mill
not only breaks the platelets, which lowers the aspect
ratio, but also disaggregates most of the particles.
In both talc and kaolinite, this action destroys voids
in aggregates. In talc, it also destroys the splayed
ends of the sheets at the particle edges. Both actions
reduce trapped nano-bubbles and their tendency to reduce
wetting and promote flotation. Platelets of talc, during
grinding, also become more stepped and damaged on basal
surfaces as a result of abrasion. Abrasion on basal
surfaces exposes additional edge area, which increases
the proportion of reactive sites and assists dispersion
of talc in aqueous solution. Prolonged grinding (60
min) of mixtures (10% talc) produces rounded aggregates
that are composed of nm-sized colloidal particles. These
colloids and aggregates are strongly hydrophilic. Structural
observations (XRD and electron diffraction patterns)
indicated that crystalline structure destruction occurs
during prolonged grinding in the ring mill making both
minerals totally amorphous. This does not occur after
mixing (15 min) in the porcelain ball mill.
27.
The effect of mechanical milling on the carbothermic
reduction of hematite
Jalil
Vahdati Khaki, Mohamad Reza Aboutalebi, Shahram Raygan
*
Iran
University of Science and Technology, , Tehran, Iran
*
Graduate student at Iran University of Science and Technology
and Instructor at University of Tehran, Tehran, Iran
Mineral
Processing and Extractive Met Review
V 25,(1) Jan–Mar 2004 ; 29 - 47
Mechanochemical
synthesis of materials deals with the chemical reactions
that occur during milling. These reactions may include
the reduction of metal oxides and chloride to pure metals.
Mechanical milling can also be used to activate the
high temperature reactions. In this paper, a brief review
of the research carried out on the reduction of mechanically
activated iron oxides is presented. Typical results
of experiments recently performed by the authors are
reported. Experimental results clearly show that mechanical
milling can decrease the reduction temperature and increase
the reduction rate significantly. An overview of the
further studies to be done in this field is also presented
28
Recent developments in processing ocean manganese nodules—a
critical review
Amitava
Mukherjee *, Ashok M. Raichur, K. A. Natarajan, M. Modak
**
*
Department of Metallurgy, Indian Institute of Science,
, Bangalore, India
**
Department of Chemical Engineering, Indian Institute
of Science, , Bangalore, India
Mineral
Processing and Extractive Met Review v 25( 2) Apr–Jun
2004 ; 91
- 127
This
article reviews the state of the art in processing and
extracting ocean manganese nodules. It briefly reviews
the mining sites where abundant rich nodules occur and
also describes the metal distribution in nodules. The
physicochemical characteristics of the nodules, touching
upon different facets such as mineralogy, geochemistry,
moisture content, and textural properties of the nodules,
are discussed in detail. In the extraction aspects of
the nodules, is article reviews two different extraction
routes often mentioned in the literature during the
last two decades, namely hydrometallurgical and biohydrometallurgical
treatments. The hydrometallurgical techniques include
leaching by mineral acids, ammoniacal leaching, leaching
at high temperature, and pressure and leaching with
reducing agents. Reduction of manganese dioxide by organics
and its probable application in leaching of nodules
is described in a detailed manner. The biohydrometallurgy
section extensively reviews the bioreduction phenomenon
for manganese dioxide and suggests possible application
in leaching of nodules. Projected future developments
in the field, with an eye on commercialization, are
also discussed.
29.
Trends in red mud utilization – a review
R.
K. Paramguru, P C Rath , V. N. Misra
Regional
Research Laboratory, Council of Scientific and Industrial
Research, Bhubaneswar, India
Mineral
Processing & Extractive Met Review
Vol 26, (1) Jan-Mar 2005 ;1 - 29 P.
Red
mud is the major waste material produced during alumina
production following the Bayers process. Depending on
the quality of the raw material processed, 1–2.5 tons
of red mud is generated per ton of alumina produced.
The treatment and disposal of this residue is a major
operation in an alumina plant. A lot of research and
developmental activities are going on throughout the
world to find effective utilization of red mud, which
involves various product developments. This article
attempts to review these developments
30.
Effect of Temperature on Coal Flotation Performance—A
Review
S.
Bhattacharya and R. D. Pascoe*
Department
of Fuel and Mineral Engineering, Indian School of Mines,
Dhanbad, Jharkhand, India
*
Camborne School of Mines, University of Exeter, Redruth,
Cornwall, U.K
Mineral
Processing and Extractive Met Review
v26 (1)Jan-Mar 2005
;31 – 61 p
Though
substantial coal-washing activities are carried out
in a tropical climate, in the 70-yr history of coal
flotation, the effect of diurnal and seasonal variations
in temperature as an operational variable has received
only limited attention. This review examines the current
knowledge on the effect of temperature on coal flotation
performance and finds that coals with strong natural
hydrophobicity do not seem to be affected by a variation
in pulp temperature. Difficult-to-float coals, however,
appear to float well within a temperature range of 20–35°C
with considerable improvement in all flotation indices,
concentrate yield and ash, recovery of combustibles,
flotation rate, and tailing ash as compared to their
values at higher or lower temperature.
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