technical review - mintek · in the tailings. the minix resin was also tested successfully for...

annual report 200717

Main pic:

Solvent drying

in the AuTEK

biomedical

screening

laboratory.

TECHNICAL REVIEW

GOLD INDUSTRY

AuTEK – extending the industrial uses of gold

Project AuTEK, the joint R&D initiative between Mintek and the three major

South African gold producers to develop new industrial uses for gold, is now

nanotechnology and biomedical applications.

AuTEK Biomedical

Biomedical research under Project AuTEK, jointly funded by Harmony Gold

and Mintek, focuses on developing new types of metal-based therapeutic

agents, with the emphasis on cancer, malaria, and HIV/AIDS. The past year

in the in-house team. Mintek’s HIV BSL II biomedical laboratory was fully

commissioned, and funding received

from the Technology and Human

Resources for Industry Programme

(THRIP) allowed for the acquisition

of a Nuclear Magnetic Resonance

(NMR) instrument, which will be

commissioned in early 2008. New

development opportunities are being

investigated through networking

and collaborative approaches

to the large pharmaceutical

companies, with the emphasis

on HIV.

More than 170 compounds

have been screened so far for

anti-tumour activity, with 30

per cent showing promising

results. Structure-based

design has resulted in an increase in the “hit rate” (activity plus

selectivity) to 10 per cent. The pharmacological work is largely

undertaken at the universities of Cape Town, Western Cape, and

Pretoria, with synthetic efforts taking place in-house and at three

local universities (Cape Town, Johannesburg, and KwaZulu-

USA for possible assistance with the further development of the

most promising compounds.

Under the HIV programme, more than 100 compounds were

screened in the past year (the majority of them in-house), with an

inhibitor rate of 16 per cent. Advanced studies on 19 interesting

candidates are under way, and it is planned to submit samples to

partners in the USA for further evaluation as a step towards pre-

clinical trials.

Steady progress has also been made in the anti-malarial

programme, which like the cancer programme is also largely

university-based. More than 40 ligands have been prepared, and

“Biomedical research

under Project AuTEK,

jointly funded by Harmony

Gold and Mintek, focuses

on developing new types

of metal-based therapeutic

agents, with the emphasis

on cancer, malaria, and

HIV/AIDS.”

annual report 2007 18

Pics from

top to

bottom:

The

biomedical

laboratory –

preparation

of in vitro

cell assays.

The Atomic

Force

Microscope

in the nano-

technology

centre.

A respirator

canister and

AUROliteTM

gold-based

catalyst.

Evaluating

precious-

metal-based

catalysts

for diesel

exhaust

after-

treatment

applications.

complexation studies are in progress. Initial data from screening

tests are expected in the last quarter of 2007.

To date, the AuTEK biomedical programme has produced two

PhD and three MSc graduates, and a further eight PhD, six MSc,

and four post-doctoral candidates are currently registered. Work

under the programme has won seven awards, and resulted in

100 contributions to professional journals and conferences, with

49 being international.

AuTEK Nanotechnology

The AuTEK nanotechnology programme, which is co-funded by

electrochemistry, molecular recognition (biolabelling), and

drug delivery systems. A novel method has been developed

for producing anisotropic precious-metal nanoparticles, and

further work is being carried out to control product quality, particle

size distribution, and reproducibility with the aim of imparting

desirable electronic, magnetic, optical, and catalytic properties.

Certain systems are being investigated for their possible use in

electrochemical sensors for the detection of glucose and other

biological structures.

The production of organically stabilised gold nanoparticles

for application in molecular recognition (biolabelling) has been

successfully scaled up to 2 litre batches. These will be stabilised and

functionalised by attaching bio-molecules, with the goal of developing

malaria, HIV, and diabetes. Similar technology involving multiplexing of the

underlying structure will be utilised to adapt the particles for drug delivery a

well as diagnostics.

To ensure that South Africa remains internationally competitive in this fast-

ordinated at national level by the Department of Science and Technology (DST)

through its National Nanotechnology Strategy. One of the main pillars of this

initiative is establishing a number of innovation centres around the country. Two

centres will be established in 2007, one at Mintek and the other at the CSIR. The

primary aims of the centre at Mintek are to train young scientists who will stimulate

the growth of an emerging nanotechnology industry in South Africa, develop

prototype products, and add value to the precious metals being produced locally.

The DST, the Medical Research Council, and the Water Research Commission

will be participating in the initiative, which will initially have three focal areas around

sensors, molecular recognition, and nanotechnology for the water industry.

AuTEK Catalysis

The AuTEK catalysis programme, which is co-sponsored by AngloGold Ashanti,

seeks to develop gold catalysts for industrial applications. One of the major hurdles to

establishing a gold catalyst market has been a lack of commercially viable quantities

of material for product testing and screening. Large-scale production of gold catalysts

is not easy, owing to issues such as gold particle size, reproducibility, and deactivation,

and involves synthesis techniques that are completely different to those currently

employed in PGM catalyst production. Research at AuTEK has been directed at

overcoming these hurdles and has led to the development of the AUROliteTM range of

gold catalysts.

Under the AuTEK catalysis programme, the current production capacity of 20 kg

per batch is currently being further scaled-up to the 65 kg scale to meet demand.

Construction of the plant, which is sponsored by the DST’s Precious Metals Initiative, is


Pics from top to

bottom:

AUROliteTM

gold-based

catalyst.

Inspecting

emergency

equipment

during an ICMI

audit of a gold

plant.

Cyanide

speciation by

segmented

analysis.

Calibrating

a Cynoprobe

before

installation on a

gold plant.

expected to be complete by the fourth quarter of 2007.

AuTEK, in conjunction with the World Gold Council (WGC), is

actively marketing these gold-based catalysts under the trademark

AUROliteTM, and supplying end-users. The typical AUROlite

product range includes Au/Al2O3, Au/Fe2O3, Au/TiO2, Au/ZnO. Joint

marketing displays have been held at the North American Catalysts

Conference and Europacat – generating much interest, which has

translated into further orders. AUROlite materials have been supplied to

petrochemicals, oleochemicals, and respirators and other safety equipment.

Gold catalysts are unique in terms of their ability to catalyse oxidation

reactions at low temperature and/or by the use of molecular oxygen.

Examples of such reactions include:

• Carbon monoxide oxidation.

• Oxidation/selective oxidation of organics – e.g. glucose to gluconic acid,

cyclohexane to nylon precursors.

• Epoxidation – e.g. propene to propene oxide.

Gold catalysts have also been found to be suitable for the removal of mercury

from coal power plant emissions, and the hydrodechlorination (destruction) of

ground water pollutants such as trichloroethene.

Gold catalysts also offer the ability to oxidise the carbon monoxide in

hydrogen feedstock for fuel cells, converting it to “inert” carbon dioxide and

thereby preventing degradation of the cell’s performance. Mintek is still

seeking commercial partners to assist in the further development of this

technology, which has been tested at Johnson Matthey’s laboratories

and subsequently trademarked and patented under the name

AUROPureH2

TM.

Cyanide services

Mintek took part in full compliance audits of Sasol Polymers’

Sasolburg sodium cyanide plant and of Sasol Infrachem to assess

for compliance with the Producers’ and Transportation codes of the

International Cyanide Management Institute (ICMI). ICMI-based

“gap” audits were also undertaken at the Navachab gold mine in

Namibia and Geita in Tanzania. The audits planned for Iduapriem

and Bibiani in Ghana were re-scheduled, and will now take

place in 2007. Mintek takes the role of technical Expert Auditor

accreditation as Lead Auditor.

At the end of the year under review, the Cyanide Centre

Laboratory underwent an audit in terms of ISO 17025 (Testing

Laboratories), and Mintek expects to achieve full compliance with

this standard in mid-2007.

Mintek has built a solid foundation in soil, solution, and gas-phase

analysis and mass-balancing of cyanide, and is currently looking

at extending this expertise to other metals. As part of this process,

an advance gold-leach reactor is being commissioned that will

enable conditions such as agitation intensity, shear characteristics,

temperature, pressure, pH value, and redox potential to be

carefully monitored and controlled. The pulp can be sampled during

operation, with sub-samples taken for analysis and returned to the

leach without distorting the mass balance. Cyanide concentration and

species are monitored using the Cynoprobe on-line analyser, and a

SCADA system is used for data capture and trending. The new reactor


Pics from top

to bottom:

Apparatus

for

determining

the rate

of oxygen

uptake

during gold

leaching.

Elution

the MINIXTM

gold-selective

resin.

The control

room in

Mintek’s

DC arc

demonstration

smelting

facility.

will initially be used in development work on high-arsenic gold

ores, incorporating arsenic speciation and mass-balancing. The

equipment will eventually form part of a comprehensive facility

for characterisation and problem-solving on gold leach and

adsorption circuits, from both the process and the environmental

aspects.

Process development

An extensive suite of testwork, including mineralogy,

comminution and gravity concentration, leaching, adsorption,

and carbon-in-pulp/carbon-in-leach (CIP/CIL) modelling, was

Gold’s Modder East project. On the commercial plant, which is

being designed by Bateman, about 40 per cent of the gold will

be extracted in a gravity circuit, with the remainder recovered by

CIL. The work showed that recoveries of between 87 per cent and

new gold mine on the East Rand in almost 30 years, is scheduled

to start production in the third quarter of 2009, and will reach a level

of 110 000 ounces (3.42 tons) a year at full output.

Laboratory testwork was conducted to evaluate processing options as

part of the feasibility study, carried out by MDM Engineering, for Mano

River Resources’ New Liberty gold project in Liberia. This project is

production targeted for the latter part of 2007.

A visit was paid to CVG Minerven in Venezuela to carry out a basic

Recommendations were made regarding options for upgrading the plants’

capacities and introducing new technology, as well as for tailings re-

treatment and cyanide management. Further work, including testing of a bulk

sample for process development, is anticipated in 2007.

The MINIXTM gold-selective resin was tested in a resin-in-leach (RIL) pilot plant

at Fairview gold mine, which was run by Gold Fields in collaboration with the

then owners of the mine. Gold Fields, who supply the Biox® technology used at

Fairview, are continuing work with Mintek to reduce the thiocyanate concentration

in the tailings. The MINIX resin was also tested successfully for scavenging

dissolved gold from slimes-dam return water at a Witwatersrand gold mine.

A number of service projects were carried out for projects in Botswana, the DRC,

Ghana, Mali, Romania, Zambia, and Zimbabwe, as well as South Africa. Ongoing

testing of surfactants (wetting agents) for application in heap leaching was conducted

in collaboration with the manufacturer. A new CIP/CIL and resin-in-pulp/resin-in-leach

(RIP/RIL) computer modelling programme was developed to interface with standard

Microsoft®Windows-based processes.

PLATINUM-GROUP METALS (PGM) INDUSTRY

Demonstration of the smelting step of the proposed ConRoast process for recovering

PGMs from high-chromium low-sulphur concentrates continued until the end of the year

under review. Four major DC furnace campaigns have now been conducted, treating a

total of 28 000 tons of revert tailings and other materials with Cr2O

3 contents of up to 5

per cent, at feed rates exceeding 1 000 tons per month. During the last campaign, which

ran continuously for 17 months, the availability of the furnace was 91 per cent.

The full ConRoast process involves the smelting of dead-roasted sulphide concentrates,

with recovery of the PGMs and base metals into an iron-based alloy rather than a sulphide


Pics from top to

bottom:

A furnace tap

during the

ConRoast

smelting

campaign.

Flotation pilot

Pilanesberg

Pics 3 and 4:

The QEMSCAN

and Mineral

Liberation

Analyser

are used

extensively for

PGM process

development.

of ore types and concentrate compositions - it removes the limits

on the minimum quantities of contained base metals or sulphur, and

can tolerate the high chromite levels in concentrates characteristic

of UG2 ores without the necessity for copper cooling elements in the

furnace sidewalls.

of material was smelted in a 200 kilovolt-ampere DC arc furnace. A high

recovery was obtained, with 98% of the platinum, palladium, and rhodium

reporting to the iron alloy phase. An engineering feasibility study of the

process is under way, with Mintek providing design inputs for the proposed

commercial furnace.

Laboratory and pilot-plant testwork was carried out in support of the

feasibility study, by SRK Consulting, on Platmin’s Pilanesberg project. The

bench-scale testwork was conducted on diamond drill core samples and

the silicate and UG2 ores in industry-standard primary and secondary circuits,

were performed using ore from a trial pit excavated at the Tuschenkomst

property. The data generated during this work will be used to design the

processing plant, which will consist of separate concentrators for the silicate

ore and UG2.

A 60-ton representative sample from Ridge Mining’s Sheba’s Ridge project

was piloted to provide metallurgical design data for the feasibility study.

towards the pre-feasibility study (Annual Report 2006), with recoveries

of 86 per cent for copper, 69 per cent for nickel, and 73 per cent for

is scheduled for completion at the end of calendar 2007. According to

the pre-feasibility study, completed in March 2005, Sheba’s Ridge will

produce 24 000 ton of nickel, 12 000 tons of copper, and 390 000

ounces of PGMs and gold per annum.

Three pilot runs, plus extensive laboratory-scale work, were

completed on different ore types for Barrick Gold’s Sedibelo

project, and this work is continuing into 2007. Other investigations

were carried out for Sylvania Resources on the recovery of PGMs

from chromite tailings, and for AfriOre’s Akanani project (now

owned by Lonmin).

A considerable number of quantitative mineralogical

investigations, using the QEMScan and Mineral Liberation

characteristics of the PGMs, were carried out in conjunction with

the process development work. Mintek also worked closely with

the suppliers of both these technologies to increase the accuracy

of the results from rapid, automated scans of PGM-bearing

samples. This is a particular issue with the PGMs, because of the

overlap in spectral windows. In a new development, a quantitative

scanning electron microscope was set up on site at Mintek for

one of the major PGM producers. Mintek has been running the

instrument on the client’s behalf to provide prioritised mineralogical

support during studies of the various plant streams for mass-balance

purposes and other research projects.

As part of its research into more cost-effective comminution

technologies, Mintek commissioned a pilot-scale high-pressure grinding


Pics from top

to bottom:

A pilot-scale

high-pressure

grinding

roll .

Pouring

molten

metal into

atomiser

cup.

Product from

roll (HPGR). This is a relatively new technology, which uses the

principle of interparticle crushing between two counter-rotating

conventional crushing in certain applications, the HPGR generates

a product with very favourable characteristics for downstream

processing, from incipient crack formation to complete particle

disintegration.

Testwork has been carried out on a number of ore types, mainly

from the PGM sector. While UG2 ores are generally too abrasive

for effective processing, considerable success has been realised

with Merensky ores. The results show that incorporating a HPGR

before the primary milling stage could lead to lower comminution

costs and enhanced metallurgical performance. Locked-cycle tests

to investigate whether the HPGR could in some instances replace

the primary milling circuit have indicated that a grind of 100 per cent

passing 600 micrometres can be achieved with a circulating load of

70 per cent. Mintek is planning to install a second, larger HPGR during

2007.

Phase 1 of a study in minor element deportment in PGM smelting,

which was conducted as part of the AMIRA P671 Project, was

completed. The results showed the need for further development of

analytical techniques, which would form a basis for the likely extension

of the project.

The Platinum Development Initiative (PDI) is a collaborative programme,

supported by the three major platinum producers, to develop new industrial

uses for platinum. The initial work of the programme focused on developing

platinum-based analogues of nickel-based superalloys. Experimental

phase-diagram work on the platinum-aluminium-chromium and platinum-

nickel-ruthenium systems has been completed, while the establishment of a

thermodynamic database for the platinum-aluminium-chromium-ruthenium alloy

system is almost complete. The outstanding phase diagram work will be done

at the University of the Witwatersrand under the Centre of Excellence in Strong

Materials.

The DST-funded programme for fast-tracking the commercialisation of platinum-

base superalloys has progressed according to plan. Three projects were initially

envisaged – the glass industry, coatings, and powder metallurgy. After a review, the

glass component was terminated, since it was felt that this project could not compete

with the well-established technology offered by the major players in the sector. A R2

million physical vapour deposition system has been commissioned for the coatings

work, which is being undertaken in collaboration with the University of the Free State

alloyed buttons produced at Mintek, and are being characterised at UFS as part of a

PhD study.

An Atomijet atomisation rig, capable of producing platinum powders in the size range

from 30 to 150 micrometres has been commissioned, and an uniaxial compaction press

is being re-furbished and should be delivered in the second half of 2007.

In September, six members of the PDI research team gave presentations at the

Japanese-South African-German Workshop and Summer School in Bayreuth, Germany.

This comprised a gathering of scientists from Germany, Japan, Russia and South Africa

FERROUS METALS INDUSTRY

The titaniferous magnetite layers in the Upper Zone of the Bushveld Complex contains


Pics from top

to bottom:

Small-scale

smelting

titaniferous

magnetite.

Conducting

a ferronickel

smelting

campaign at

Mintek for

Oriel Resources

Plc.

A grinding ball

sectioned for

metallurgical

analysis.

SmartboltTM

austenitic

stainless steel.

vast resources of iron, vanadium, and titanium, but to date no

process has been developed that can economically recover

all three of these metals. The high titania levels make the ore

unsuitable for smelting in a traditional blast furnace, and the

and Vanadium, which operate the Mapochs Mine, processes the ore for

iron and vanadium, but discards the low-grade titanium slag.

Veremo Holdings has begun an evaluation of the feasibility of utilising

part of the titaniferous magnetite ore from the Bushveld Complex to

produce iron units that could be used as feed for foundries and steel plants.

The initial feasibility study includes the potential recovery of titania and

vanadium from the slag.

Approximately 5 tons of concentrate was produced from 14 tons of trenched

material and smelted in Mintek’s 200 kilovolt-ampere DC arc furnace.

The testwork was aimed at producing slag that could be used in further

development work, as well as evaluating the deportment of iron, titanium,

and vanadium under varied reducing conditions.

additions, the process could be controlled to produce good-quality iron with

high recoveries and a wide range of titania-containing slag compositions.

Further development work will investigate the feasibility of upgrading

2 and

recovering the vanadium from the slag.

Oriel Resources Plc (Oriel) has been engaged in developing its

Shevchenko Nickel project in Kazakhstan since 2004, and conducted a

major ferronickel smelting campaign at Mintek in 2005 (Annual Report

2005). Bateman was appointed in late 2004 to conduct a feasibility

study that was completed at the end of 2005 based on the work at

Mintek . The process includes an Aerofall mill and Polcal calciner

from Polysius, Germany, and the twin electrode DC arc furnace

is similar to the approach envisaged for the Koniambo ferronickel

project in New Caledonia, now owned by Xstrata.

Oriel has continued to develop the Shevchenko project and

to evaluate the selected process options so that the most

appropriate approach can be chosen for the project to proceed.

Mintek has been conducting additional testwork on these process

options for Oriel to assist with the project development.

In 2005, Mintek began a major collaborative project, funded

by the Innovation Fund and supported by Anglo Platinum, the

University of Pretoria, and an industrial partner, to develop

a more cost-effective grinding ball for the minerals industry.

Samples produced in laboratory-scale melts are undergoing

screening, and in parallel with this, reference balls are being

produced so that the casting methods can be optimised. Batch

tests of balls cast from the most promising materials are planned

Trials of the “smart” rockbolt, or SmartBoltTM, are continuing in

“highly critical” areas on two deep-level gold mines. Mintek is

working with a team of specialists towards the commercialisation of

both the SmartBolt and the HerculesTM low-nickel austenitic stainless

steel, and the Innovation Fund has indicated that it will support

commercialisation if the two projects merit it.


Pics from top

to bottom:

Spiral

separation of

chromite.

Density

fractions of

an iron-ore

sample.

The

Sarcheshmeh

mine in Iran.

The project proposals and funding agreements for the ferrous

and base metals pillars of the Advanced Metals Initiative, which

quarter of 2007. Three projects have been proposed under this

initiative, all of which are aligned strongly with the automotive

industry.

An investigation was begun on the pre-reduction of manganese

ore and the possibility of recovering energy from the liquid slag.

These processes hold potential for reducing the carbon dioxide

emissions produced during smelting, and possibly for the

production of hydrogen.

Work continued on iron ore characterisation for Kumba

Resources in support of the Sishen Expansion Project. In

addition, investigations were carried out on the upgrading of

elutriation, and magnetic separation.

Metallurgical testwork, involving investigations of the size

distribution, comminution characteristics, washability using heavy

liquid separation, and gravity separation using tables and spirals,

was conducted on material from Chromex Mining’s Mecklenburg

chromite project. The results were used as input for the detailed

design and costing exercise, and to forecast the product split into

chemical, and foundry grade).

NON-FERROUS METALS INDUSTRY

The bioleaching work package under the European Union’s BioMinE

project, which is co-ordinated by Mintek, has continued to progress well.

During the year under review, a number of project partners investigated

the process engineering development, as well as the more fundamental

technology, related to the bio-hydrometallurgical treatment of two low-grade

Integrated pilot campaigns on the complex polymetallic concentrates from both

of these deposits is scheduled to begin at Mintek in the second half of 2007,

and will run through to mid-2008. It is anticipated that a number of our European

colleagues in BioMinE will participate in this programme, which, if successful, will

lead to pre-feasibility studies. Although the resources are of European origin, the

outcome of the work will be directly relevant to similar deposits in southern Africa

and in other parts of the world. BioMinE is funded under the EU’s Sixth Framework

Programme (FP6), and is also supported by a major strategic investment by the

DST.

Large-scale piloting of Mintek’s heap bioleaching technology for chalcopyrite-

bearing copper ores continued at the Sarcheshmeh Copper Complex in southern

2005, a further three 20 kt heaps were commissioned at approximately three-monthly

Copper Industries Company (NICICO) has decided to proceed with the development

of a commercial plant, with a capacity of 12 kt of copper metal per annum, at the

Dahrezar copper mine. Mintek will be contributing to the feasibility study for the project,

which is scheduled for completion towards the end of 2007, and will remain closely

involved in the engineering and commissioning of the planned commercial plant.

The successful heap bioleaching of chalcopyritic ores depends on the generation and

preservation of heat of chemical reaction in the heap, and prolonging the permeability

of the heap. These objectives have been realised by a combination of certain heap

construction features and operational tactics, and the life cycle of each heap has been


Pics from top

to bottom:

Heap bio-

leaching at

Sarcheshmeh.

• Pregnant

leach solution

ponds.

• Pond under

construction.

• Inoculum

preparation

plant.

• Auger

sampling of

heap.

partitioned into several operating stages, each with its own targets

and criteria for completion. This approach has required a new

level of sophistication in heap leaching. For the Iranian pilot plant,

a spreadsheet-based operator advisory and administration system

has been developed, which tracks the life cycle of each individual cell

within a heap, and provides operator support for the most essential daily

decisions. These include the allocation of irrigant (intermediate leach

or to intermediate leach solution), and adjustment of the irrigation and

aeration rates to satisfy the stoichiometry of the reaction and maximise

heat accumulation within the heap. For commercial applications, a more

sophisticated package with additional features is being developed, that will

integrate with current industry-standard SCADA and database software.

As a result of the success at NICICO, Mintek has undertaken a considerable

amount of heap-bioleaching amenability testwork, which could lead to this

technology being further evaluated for application to low-grade copper, nickel

(sulphides and laterites), and uranium deposits in southern and central Africa.

Development continued on a novel technique for inoculating bacteria into

leach heaps, with the aim of obtaining a more rapid start-up and enhanced

oxidation rates, which will lead to higher heap temperatures and faster

copper leaching. A set of 6 m column leach tests were conducted on a low-

grade chalcopyrite ore, and further work is being conducted on techniques

to monitor the process. This project is being carried out with an industrial

partner, with funding from the Biotechnology Partnership and Development

(BioPAD) initiative.

Mintek is continuing with research on the development and optimisation

of molecular techniques for identifying the micro-organisms involved in

tank and heap leaching, in order to gain an improved understanding

vice

versa. Work at the University of the Free State and Rhodes University

on the production of precious-metal nanoparticles by biosynthesis

is focusing on the isolation of the proteins and enzymes involved,

with the aim of linking these to the varios sizes and shapes of

particles that are produced. A second round of THRIP funding has

been received for investigations into the bioleaching of silicate

minerals. Two MSc projects are under way, on nickel laterites (at

the University of KwaZulu-Natal) and the bio-assisted weathering

of kimberlites (at the University of the Witwatersrand), and will

be completed in March 2008. Two BTech projects are being

undertaken at Tshwane University of Technology on the biological

degradation of cyanide species.

In support of a study of a major expansion at the Nkomati

nickel mine, an 80 ton bulk sample of the Chromititic Peridotite

Mineralised Zone (PCMZ) was processed in Mintek’s milling and

The plant incorporated a scavenger cleaner circuit and employed

optimised residence times to enhance the recovery of the slow-

undertaken on a sample from the Main Mineralised Zone (MMZ).

ore, previously regarded as uneconomic, can be processed to

yield a saleable concentrate. This, together with improved metal-

price forecasts, made it possible to lower the cut-off grade applied to

portions of the resource, thus increasing the open-pit reserves.

As a result of applying the lower cut-off grades and including the


Pics from top

to bottom:

Flotation

pilot-plant

campaign on

Nkomati ore.

The Nkomati

Nickel Mine

(photo

courtesy

Nkomati

Nickel).

Pilot-plant

operators

take samples

from the

manganese

solvent-

extraction

circuit

to purify

the cobalt

electrolyte

before

electro-

Copper

electro-

the KOV

PCMZ, Nkomati’s nickel reserves have increased by 50 per

cent – to 485 377 tons. The by-product reserves have also

43 per cent, and 4.181 million ounces of PGMs, a 70 per cent

increase. Based on these positive results, LionOre and ARM

commissioned DRA to proceed with a bankable feasibility study

for the large-scale expansion of the concentrator plants.

The proposed large-scale expansion, planned for 2010, will

incorporate mining of the PCMZ, increasing annual production

to approximately 20 000 tons of nickel and extending the life of

the mine to beyond 2020. An interim expansion exploiting the

disseminated MMZ will maintain nickel production at its current

level of about 5 000 tons per year after the massive sulphide

mineralisation is depleted in 2008.

Mintek has carried out process development work for a number

of copper-cobalt projects in Zambia and the DRC. Among these

a South African mining company in the DRC for many years. The

started up in September 2006. The second phase, which will involve

cobalt metal on-site at Ruashi, is under construction.

Mintek began bench and pilot work, which would be used in the bankable

feasibility study for phase II of the project, in April 2006. Three campaigns

were conducted, and the work was completed during March 2007.

In the design of the solvent-extraction and electrowinning circuit, Mintek

worked closely with Metorex’s design company, TWP Matomo Process

Plant. The plant has been designed for a capacity of 120 000 tons of ore per

month. When the phase II expansion is completed, production at Ruashi is

expected to increase to 45 000 tons of copper cathode and approximately 3

500 tons of cobalt metal and cobalt carbonate per annum.

A major process development campaign was conducted for the KOV copper-

cobalt project, also in the DRC. A total of 27 tons of material was delivered to

laboratory tests to determine the optimum leach conditions, integrated piloting of the

leaching, copper solvent extraction and electrowinning circuit, and Aspen simulation

LME Grade A standard (higher than 99.95 per cent copper), were produced. The KOV

complex, which contains one of the world’s largest high-quality copper and cobalt

resources, is being re-developed by Nikanor plc. The project will include a major

27 500 tons per year of cobalt products.

Dense-media separation, milling, and leaching testwork were carried out to investigate a

Green Team Consultants International.

Mintek has been involved in numerous projects to remove iron and manganese from

dilute cobalt sulphate solutions by oxidative precipitation using air/SO2. This technology

is attractive as it can be done at ambient temperature, relatively low pH, and ferrous

iron is quantitatively removed within 1-2 hours. In order to produce cobalt cathode of the

desired quality, iron, manganese, copper, zinc, and aluminium must generally be removed

from the feed to electrowinning. The requirements to produce an intermediate cobalt salt

are generally less stringent, but usually iron, aluminium, and manganese still need to be

removed.


Pics from top to

bottom:

The Outotec

high-shear

impeller.

Laboratory

NicksynTM

reagent in

support of the

at Tali Nickel.

The thermal

Magnesium

Process demon-

stration plant.

The recent interest shown in this technology by emerging

copper-cobalt producers in central Africa has encouraged Mintek

to do some work to identify potential scale-up issues. Various

agitators and gas induction systems were investigated, and a high-

shear impeller designed and supplied by Outotec was selected for

further testwork on a 2 m3 scale to examine the effects of parameters

such as SO2

and temperature on the process. Optimisation tests remain to be done

on power consumption and various aspects around gas induction.

Two smelting campaigns were conducted on discard slag from BCL in

Botswana to compare the use of AC and DC furnaces for recovering

nickel and copper. The results showed that both technologies were equally

effective, and that the company could substantially improve the recoveries

in its slag-cleaning operation by adding reductant to the existing settling

furnaces.

The Mintek-developed nickel synergist (Nicksyn™) was evaluated to

optimise nickel recovery and nickel-calcium separation at Tati Nickel in

Botswana. Laboratory test work was conducted at Mintek on the feed to the

nickel solvent-extraction circuit to optimise the combination of the synergist

and the Versatic 10 commercial extractant, and the results applied on the

Activox® hydrometallurgical demonstration plant at Tati using a 0.5 ton

commercial batch of Nicksyn.

on the organic phase, which could result in gypsum formation in

the extraction circuit if the feed becomes saturated with calcium.

Previously, Tati Nickel minimised the problem by diluting the feed

stream with fresh water, but this would increase the size of the

production. Furthermore, with Versatic 10, the pH of extraction

cannot be increased as this causes higher calcium loadings -

extraction stages).

With the synergistic system, the calcium loading was about

one-tenth that obtained previously, and gypsum formation can

be completely avoided. The Versatic-Nicksyn combination also

achieved higher nickel recoveries (99.7 per cent compared

with about 99.3 per cent) using only four stages. In addition,

lower reagent losses were experienced, which can be ascribed

to the much lower pH of operation and the reduction in crude

formation.

Work continued on the production of titanium-aluminium master

alloys by aluminothermic reduction, and a project is in progress

at the University of Cape Town on the fundamental aspects of the

titanium-aluminium-oxygen-carbon-nitrogen system to determine

the best criteria for scale-up.

Following a review of the economics of the Mintek Thermal

Magnesium Process, Anglo American has decided not to pursue

commercialisation, since it is felt that it would not be able to

compete with the low-cost Chinese producers. Mintek will continue to

look for opportunities for applying the technology.


Pics from top

to bottom:

Small-scale

pressure

leaching of

a uranium

contentrate.

uranium

leach liquor.

Uranium

oxide

precipitation.

Hydro-

phobicity

a diamond-

bearing

concentrate.

INDUSTRIAL MINERALS

ambient and pressure leaching, gold diagnostic leaching,

and CIL adsorption, was done for the Buffelsfontein tailings

recovery project owned by First Uranium, the gold and uranium

subsidiary of Simmer and Jack Mines. Based in this preliminary

to recover an uranium concentrate, then pressure leaching,

solvent extraction and ion exchange using NIMCIX continuous

leach residues would be treated in a CIL plant for gold recovery.

Also for First Uranium, pilot-scale leaching was conducted on a

bulk underground sample from the Ezulweni project to produce

a feed for solid-liquid separation, countercurrent decantation,

and ion-exchange testwork. The results will be used to generate

design criteria for a possible NIMCIX plant. Both these projects

are continuing into 2007.

Testwork was completed on the development of the process

Malawi, as part of the bankable feasibility study by GRD Minproc.

Paladin gave the go-ahead for the development of the project in

February 2007, and commissioning is scheduled for the third quarter

of 2008. Kayelekera will be Paladin’s second uranium mine in southern

Africa – Langer Heinrich in Namibia, for which Mintek conducted

2007.

Mintek’s uranium business continues to grow, and an increasing number

of approaches are being received concerning proposed projects on

Witwatersrand-type materials, particularly tailings re-processing for both

uranium and gold. Some of these are potentially very large projects. Mintek’s

strength in this area is the comprehensiveness of the services it can provide,

from initial investigations up to large scale piloting.

During the year, a new laboratory facility for characterising diamonds according

to their hydrophobicity (response to grease-table recovery) and luminescence

(recovery by X-ray methods) was fully commissioned. The laboratory has met with

an extremely favourable response form major industry players, including De Beers,

SouthernEra, and Bateman, and work on optimising recovery processes has been

done for a number of projects in South Africa and overseas. Mintek has engaged

an internationally recognised expert in kimberlite petrology and diamond studies,

and this project will be expanded in 2007/08 to include diamond characterisation for

purposes of marketing valuation and population discrimination.

Ongoing heavy-liquid separation testwork was carried out for De Beers to evaluate

Mintek’s capabilities in chlorination technology were further developed with the

can handle kilogram-size samples, resulting in a much-improved mass balance.

A suite of testwork, including sample characterisation, heavy-liquid separation, shaking-

conducted on a sample of bauxite. The aim of the work was to simulate a processing


Pics from top

to bottom:

Personal

Protection

Equipment

(PPE) for

radiation

Monitoring a

bulk sample of

uranium ore.

Mintek’s HIV

Committee.

Access to

potentially

hazardous

areas is

restricted

to trained

personnel.

route to remove the quartz and hematite/goethite from the

material. It was found that around two-thirds of the total silica,

and more than half of the Fe2O

3, could be removed, which as well

as resulting in a higher-quality product, would reduce the formation

of “red mud” in the Bayer process.

QUALITY, ENVIRONMENT AND SAFETY

Mintek’s Environmental Management System underwent a successful

audit, for OHSAS 18001 (Occupational Health and Safety), will take place

in 2007, and that for IS0 9001 (Quality) the following year. Re-assessment

The Analytical Services laboratories underwent a successful surveillance

audit for ISO 17025 compliance in 2006.

At the end of the period under review, the Lost Time Injury Frequency Rate

(LTIFR) was 2.0, compared with the target of 1.0. The Client Dissatisfaction

Frequency Rate (CDFR), after consistently achieving the target of less

than 10, rose sharply in the second half of the year. This was due to late

delivery of results, and communication problems with the clients, on

several minor projects undertaken by one of Mintek’s divisions. Steps

have been taken to remedy these problems.

During 2006, two new indices were established: the Major

Environmental Incidents Frequency Rate (MEIFR) and Public

Dissatisfaction Frequency Rate (PDFR). Mintek’s MEIFR is above the

target of 5 at the moment. The upward trend is possibly the result of

as corrective action is implemented. The PDFR (which is a subset

of the MEIFR) is also above the target – however, the public

Mintek is registered as a uranium testwork facility with the NNR

and the Department of Minerals and Energy (DME). A Radiation

Protection Programme (RPP) has been incorporated as part of

the overall Safety, Health, and Environment programme, and

an internal audit schedule, incorporating site inspections by the

NNR, has been implemented.

“During the year, a new laboratory facility

for characterising diamonds according to their

hydrophobicity (response to grease-table recovery)

and luminescence (recovery by X-ray methods) was

fully commissioned.”

annual report 2007 30annual report 2007

technical review - mintek · in the tailings. the minix resin was also tested successfully for...

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