CSIRO research in minerals processing and metal production FEBRUARY 2010 GOLD RECOVERY Together two compounds answer gold recovery woes Page 9 IN SITU LEACHING Mining gold without a mine Page 3 IRON ORE Cast-iron future for Australia hinges on research Page 6 By TIM TREADGOLD ALBERT Einstein and Sir Isaac Newton had their scientific explanations for gravity, but goldminers have never really cared how it works, just as long as gravity helps separate gold from lighter minerals. Some of the earliest gold processing techniques – from panning, sluicing and dry-blowing, when no water was available – were early, simple uses of gravity. e same force is at work in a thoroughly modern gold-extraction technique, which is at the heart of the InLine Pressure Jig (IPJ) of Gekko Systems, a company based in the historic Victorian goldmining city of Ballarat. While the jig is much faster and far more efficient than the original gravity separating techniques used by oldtimers, Gekko was keen to better understand the science inside the device so they could optimise its performance. Enter CSIRO’s computational fluid dynamics (CFD) team, which was happy to take up the challenge. Gekko wanted to know what happens inside the closed world of its IPJ in order to provide a more detailed description to its clients and market it more successfully. Dr Chris Solnordal, project leader and a senior member of the CFD team, says the assignment required constructing a computer model that replicated the jig’s internal workings. “We had to incorporate into the model all of the factors at work in the jig, from the round shape of the vessel, the nature of the slurry being injected, the flow rate, and the effect of a pulsing (or jigging) action on the slurry,” Dr Solnordal says. “e result is a model that explains why Gekko’s IPJ achieves high recoveries of both fine and coarse mineral particles.” Dr Solnordal says one of the most important factors revealed in the computer GOLD CFD sheds light on the curious workings of a gold jig CONTINUED PAGE 2 modelling was the circular shape of the vessel itself and the central slurry injection point from which slurry disperses in all directions. “As the slurry slows down there is a greater opportunity for the gold to drop out onto the ‘gold pan’. “Other jigs lack the circular shape and are more like long channels, so the flow rate across the screen where heavy material falls out stays constant … it’s not spreading out, it’s like water flowing down a river.” As the gold drops out of the slurry Key points p CFD has been used to understand how a gold jig works p An important finding was how the vessel’s circular shape and central slurry injection point helps performance p Optimum operating parameters for different applications were identified Gekko Systems InLine Pressure Jig in operation. PHOTO: GEKKO SYSTEMS
Transcript
CSIRO research in minerals processing and metal production February 2010
gOld ReCOveRyTogether two compounds answer gold recovery woesPage 9
In SItu leaChIngMining gold without a mine Page 3
IROn OReCast-iron future for Australia hinges on researchPage 6
By tIm tReadgOldAlbert einstein and Sir Isaac Newton had their scientific explanations for gravity, but goldminers have never really cared how it works, just as long as gravity helps separate gold from lighter minerals.
Some of the earliest gold processing techniques – from panning, sluicing and dry-blowing, when no water was available – were early, simple uses of gravity.
The same force is at work in a thoroughly modern gold-extraction technique, which is at the heart of the Inline Pressure Jig (IPJ) of Gekko Systems, a company based in the historic Victorian goldmining city of ballarat.
While the jig is much faster and far more efficient than the original gravity separating techniques used by oldtimers, Gekko was keen to better understand the science inside the device so they could optimise its performance.
enter CSIrO’s computational fluid dynamics (CFD) team, which was happy to take up the challenge.
Gekko wanted to know what happens inside the closed world of its IPJ in order to provide a more detailed description to its clients and market it more successfully.
Dr Chris Solnordal, project leader and
a senior member of the CFD team, says the assignment required constructing a computer model that replicated the jig’s internal workings.
“We had to incorporate into the model all of the factors at work in the jig, from the round shape of the vessel, the nature of the slurry being injected, the flow rate, and the effect of a pulsing (or jigging) action on the slurry,” Dr Solnordal says.
“The result is a model that explains why Gekko’s IPJ achieves high recoveries of both fine and coarse mineral particles.”
Dr Solnordal says one of the most important factors revealed in the computer
gOld
CFD sheds light on the curious workings of a gold jig
ConTinued PAGe 2
modelling was the circular shape of the vessel itself and the central slurry injection point from which slurry disperses in all directions.
“As the slurry slows down there is a greater opportunity for the gold to drop out onto the ‘gold pan’.
“Other jigs lack the circular shape and are more like long channels, so the flow rate across the screen where heavy material falls out stays constant … it’s not spreading out, it’s like water flowing down a river.”
As the gold drops out of the slurry
Key pointsp CFd has been used to understand how a gold jig worksp An important finding was how the vessel’s circular shape and central slurry injection point helps performancep optimum operating parameters for different applications were identified
Gekko Systems InLine Pressure Jig in operation. Photo: Gekko SyStemS
PROCESS February 20102
CSIRO Process Science and engineering Ph +61 3 9545 8500 Fax +61 3 9562 8919
InsidePage 3: Mining gold without a mine Page 4: old gold tailings power solar energy’s futurePage 5: Sustainable options sought for falling grades; SamplesPageS 6, 7 and 8: Cast-iron future for Australia hinges on researchPage 9: Together two compounds answer gold recovery woes; new look offers insight into age-old scale problem Page 10: organic reactions safely exploredPage 11: efforts to prove new recovery method pay off; Cultivating a competitive edgePage 12: Leader’s Forum; Tim Treadgold
Process is a publication of CSiRo’s mineral resources domain. it does not purport to be comprehensive or to render professional advice. Articles submitted by external contributors reflect the views of authors and not CSiRo. All material in this publication is subject to copyright. For permission to reproduce any part or all of an article, please contact the editor. Print Post Approved 349181/01684.
This publication is printed on Monza Satin recycled paper.
it falls onto a screen covered in ragging (a layer of rocks or lead shot), which is pulsed, causing the gold-rich material to percolate down into a hutch – a conical region with an exit chute and pipe – for extraction and possible reprocessing for enhanced separation, or as a finished product.
Dr Solnordal says other factors at work in the Gekko IPJ include encapsulation of the process. This meant it could be run under pressure, facilitating faster pumping and processing while eliminating the gas-liquid interface where particles might otherwise accumulate.
“Gekko’s request to us was to help them gain a greater understanding of what’s happening inside their vessel,” he says. “They obviously had their ideas, but you can’t see inside it.
CFd sheds light on the curious workings of a gold jig FRoM PAGe 1
Science and technology for a competitive edgep The minerals industry has emerged from the global financial crisis in surprisingly good shape. demand is on the increase and is forecast to grow further, fuelled by the rapidly expanding economies of China and india.
Australia’s position in the global minerals market is not a given. We will need to use all our smarts to maintain our market share.
in today’s globalised world there are many players keen to grow their market share in mineral commodities. Some of these players have the advantage of superior grade resources that are easily exploitable.
in Australia, we are increasingly facing adverse conditions. our historically high-grade resources are quickly depleting. our industry is increasingly relying on lower-grade, harder-to-access reserves. environmental constraints are quickly becoming more stringent – think carbon emissions and minor element pollutants.
Science and technology offer a competitive edge for the nation in today’s mineral commodity business.
Science and technology provide the basis for cost-effective processing solutions for lower-grade commodities in poorly accessible places. Science and technology also underpin environmentally sustainable process routes – process routes with low intrinsic carbon emissions and significantly reduced environmental impact.
Research also shows ways to enter new markets with novel, value-added products and services, hence increasing the Australian industry’s resilience and competitive position.
The current issue of Process illustrates how CSiRo’s research in mineral processing and metal production addresses issues of global competitiveness. We hope that it gives you a flavour of how it could also help your activities to remain competitive and successful.
At CSiRo, we remained focused on generating the technology required to help Australia’s minerals industry gain a competitive edge.
COMMeNTbarT FOlliNk
ChieF, CSiRo PRoCeSS SCienCe And enGineeRinG
“Through our modelling, Gekko can see whether the IPJ is operating the way the company thinks it is and possibly find ways of improving the design.”
The ensuing CFD model is essentially a Gekko jig built inside a computer, with key inputs including a liquid the density of gold-rich slurry entering a circular vessel at a specified flow rate, which is then tracked to see how and when heavier particles, such as gold, drop out.
“The important part was being able to model the jigging motion of the screen, so we included the ragging and the characteristic shape of the bed of material on the ragging.
“What we learned is that encapsulation and pressure caused a recirculation of the slurry. Heavy material was falling down as you would normally
see in this type of gravity-based system, but in the Gekko jig there was also a pulsating recirculation that showed the material flowing back in and not just out.
“That meant finer material, which might otherwise have gone to the tailings as waste, was being encouraged to move back into the system, increasing residence time and capturing more gold.”
Gekko r&D manager tim Hughes says the CFD modelling helped the company to identify optimum operating parameters for different applications. “As a follow up we are considering the next level of CFD testing with the discrete element method (DeM) to further investigate the potential for design optimisation.”
CSIRO Process Science and engineering on the web www.csiro.au/minerals
3February 2010 PROCESS
require further detailed study, including a close look at the nature of the rocks in an orebody, the effect of permeability enhancement methods on gold recovery, the time it would take for the lixiviants to pass through the rocks, the number and spacing of drill holes, and other costs such as piping and tanks to hold the liquids.
“The critical targets we have set are to achieve 50 per cent gold recovery with a breakthrough time, which is the time it takes between injecting and extracting the fluids, of 20 days. Widening the hole spacing through permeability enhancement methods is also a key focus of the research, as it offers the potential to substantially reduce capital costs,” he says.
The plan now is to identify several deposits on which field-based studies can be carried out, preferably with a number of partners interested in the science involved and prepared to co-fund the next phase of work, which has been earmarked to receive A$657,000 in CSIrO funding, with A$150,000 being sought from industry sponsors.
A number of mining companies and government geological surveys have expressed interest in supporting the next phase of research. Field studies involving the injection of lixiviants are likely to start in 2011, once permits and environmental approvals have been obtained.
By tIm tReadgOld IN AuStrAlIA, extracting minerals without first digging and crushing the ore is largely confined to uranium. Yet in theory, Australia’s remote and marginal gold deposits – not suited to conventional mining – could be made economically viable if a CSIrO study on in situ (or in-place) leaching of gold delivers on its early promise.
Paul roberts, who leads the in situ leaching research for the Minerals Down under Flagship, says early laboratory tests with a number of chemicals had successfully recovered gold from near-surface oxide (or weathered) ores.
“There are a number of steps we need to take to establish the commercial potential of in situ oxide gold ore leaching, but we can already see a strong financial case to support the science,” he says.
In its most simple form, in situ leaching involves drilling holes in a mineralised structure, pumping liquids that dissolve or attract the target mineral down the holes, and then recovering the pregnant liquid for processing. An estimated 20 per cent of the world’s uranium is recovered in this way.
However, gold is different and faces two challenges to in situ leaching: the identification of chemicals other than cyanide that will target gold, and addressing the permeability of oxide gold ores. These are less permeable than the rocks in typical uranium in situ leach operations, meaning that without artificial permeability enhancement, gold extraction rates are likely to be too low.
The first challenge, to find a replacement for cyanide – traditionally used as the lixiviant (a chemical used to extract or attract gold) in gold processing – has led to the successful use of sodium thiosulfate and ferric eDtA (or ferric ethylenediaminetetraacetic acid).
However, as if the hunt for gold-scouring chemicals was not tough enough the original in situ work on ore from a Western Australian (WA) goldmine was derailed by the presence of iron sulfide, also known as pyrites, or ‘fool’s gold’, which broke down the lixiviants.
“It was at that point that we changed the approach, looking at what had been achieved; we refocused on gold deposits
without pyrite and that led us to look at weathered gold deposits,” Mr roberts says.
Across the southern portion of WA, and over the border in South Australia, there are many potential heavily weathered targets where the pyrite has been leached out over the eons.
refocusing research work onto oxide gold deposits soon delivered better results, with gold recoveries rising to between 60 per cent and 95 per cent in bottle roll tests, with the higher level considered good even by conventional gold processing standards.
However, the most eye-catching aspect of the work was a financial model which showed that, with the right type of ore deposit, gold might be extracted by an in situ leaching method involving some permeability enhancement at an operating cost of between A$400 and A$650 an ounce – about half the current gold price and enough to have most gold companies thinking carefully about adding a new extraction technique to their armoury of technologies.
The second challenge – to improve permeability – has led the team to consider permeability enhancement methods, consisting of either mechanical rock breakage via hydraulic fracturing methods or explosives and/or chemical dissolution of gold-hosting minerals to improve lixiviant access to the gold itself. Studies on developing these options have only just begun.
Mr roberts says a number of issues
3
In SItu leaChIng
Mining gold without a mine
In situ leaching is a promising alternative to conventional open pit mining for marginal gold deposits.
Ph
oto
: P
ete
r S
ea
Ge
r /
iSto
ck
PROCESS February 20104
QuaRtz ReCOveRy
CSIRO Process Science and engineering Ph +61 3 9545 8500 Fax +61 3 9562 8919
By ReBeCCa thyeR tAIlINGS FrOM Australia’s gold-rush could help a Victorian company strike it rich in a modern-day venture to produce speciality, high-value feedstocks that could be used in solar-grade silicon production. If successful, the work has the potential to increase solar energy use.
Creswick Quartz already recovers quartz (SiO2) from the waste tailings of late 19th century alluvial gold mines and supplies it as architectural-quality quartz to landscape and construction industries and to niche markets.
These quartz deposits – at Creswick, west of Melbourne – are of a high quality with low impurity levels, giving the company the option to produce higher-quality quartz for use as feedstock in pure silica and silicon production. It is a possibility Creswick Quartz has been exploring with the Minerals Down under Flagship.
leading the project is CSIrO scientist Dr Hal Aral. He says the goal is to develop a commercially viable and environmentally sustainable quartz-purification process that produces metallurgical and solar-grade silicon feedstock, all from the waste tailings of Victoria’s early gold industry.
The purification process has the potential to lead to cheaper silicon solar cells – something that depends critically on the availability of inexpensive solar-
grade silicon feedstock – and, with that, increase solar energy use.
Already, physical and chemical treatment is showing that the research team can produce various particle sizes that are 99.995 per cent pure silica, a step towards the goal of 99.999 per cent pure silica that is needed for solar-grade silicon production.
Silicon (Si) occurs naturally in many silicate minerals, but the most important source for silicon production is quartz. With the right processes, Creswick Quartz could supply high-quality, fine-particle-sized (down to 10 to 20 microns) and lump (20 to 80 millimetre) quartz suitable for both metallurgical and solar-grade silicon production.
Metallurgical-grade silicon usually has a purity of 98 to 99.5 per cent, mostly because the purity of the quartz feedstock is low.
However, Creswick’s inherently high-purity lump quartz has an advantage over many. It is low in boron, phosphorus and lithium and is suited to ultra-high metallurgical-grade silicon production.
Solar-grade silicon – at 99.999 to 99.9999 per cent pure silicon – is manufactured from scraps of semiconductor-grade silicon which, in turn, is produced from metallurgical-grade silicon. Semiconductor-grade silicon processing includes chlorination and
complex downstream work, which Dr Aral says is tedious and expensive, eventually making the final cost of silicon products very high.
Additionally, the demand for solar-grade silicon is now greater than the amount of scrap the electronics industry can supply. It means the industry is looking for high-purity, fine-particle-sized feedstocks for solar-grade silicon production.
Creswick Quartz CeO Chris Karamountzos says the company has been busy extensively drilling to expand its existing reserves in order to meet increasingly global demand for feedstock,
For the research team, the next stage is to demonstrate the CSIrO-developed physical and chemical treatment processes at a large scale.
Dr Aral says his team wants to create a process that produces high-purity feedstocks and which also uses less energy and produces less greenhouse gases than existing processes.
The work is an example of how researchers and industry are working towards a new level of sustainability, he says. “The aim is to convert old mining tailings into new, high-value feedstocks.”
crushing and sizing plant at creswick Quartz. Photo: creSwIck Quartz
Old gold tailings power solar energy’s future
CSIRO Process Science and engineering on the web www.csiro.au/minerals
5February 2010 PROCESS
lIFe CyCle aSSeSSment
Sustainable options sought for falling gradesBy ReBeCCa thyeRCONVeNtIONAl concentrating and smelting could prove to be the most sustainably appropriate processing routes for copper and nickel as ore grades fall, work by the Minerals Down under Flagship has shown.
This is the case when pyrometallurgical processing is suitable and where no additional grinding is required, says CSIrO senior project engineer terry Norgate, a specialist in using life cycle assessment (lCA) to investigate and evaluate the environmental impacts of processes.
However, he found that the most appropriate processing option changes if fine grinding (down to five micrometres) is needed. Instead the best processing route is heap leaching and direct smelting for copper ores and in situ leaching for nickel ores.
With the lower-grade ores expected to be used in the future likely to need extra processing, sustainability concerns are becoming more prominent. It prompted Mr Norgate to try to identify the most sustainable processing routes for these ores in terms of energy consumption and greenhouse gas emissions.
“Falling ore grades and more complex ore bodies anticipated in the future can be expected to lead to increased energy consumption and associated greenhouse gas emissions for primary metal production,” he says, with sustainability concerns seeing the mineral processing and metal
Samplesnew aluminium research clusterp A new collaboration will see scientists from CSiRo and five universities research sustainable energy-efficient technologies for the Australasian aluminium industry.
Primary production of aluminium is highly energy-intensive and reducing the amount of energy used will assist the industry in maintaining competitiveness.
The ‘Breakthrough technologies for primary aluminium’ research cluster brings together researchers from Swinburne university of Technology, the university of Auckland, the university of nSW, the university of Queensland, and the university of Wollongong with CSiRo scientists.
“The cluster collaboration addresses a fundamental need of the aluminium industry,” CSiRo’s Light Metals Flagship director dr Raj Rajakumar says.“it complements and extends CSiRo’s existing research activities into aluminium production technologies with low carbon footprints.”
The collaboration, an initiative of CSiRo’s national Research Flagships Collaboration Fund, has collective investment of more than $8 million over three years.
new laterite heap leach technologyp Another collaborative cluster will see CSiRo working with the universities of South Australia (through the ian Wark Research institute), Queensland, Melbourne and British Columbia to examine ways of enhancing heap leaching of nickel laterite.
The majority of Australia’s nickel resources occur as nickel laterite deposits, which tend to be lower-grade and are complex and expensive to treat using conventional methods.
heap leaching is a promising next-generation technology that offers a potentially simpler and less costly processing alternative.
however, significant technical challenges are preventing the adoption of heap leaching, including excessive acid consumption (caused by unwanted side reactions) and maintaining high permeability within the heaps.
The cluster, led by the ian Wark Research institute, is looking to overcome problems associated with the lower-grade deposits through the development of radically new and improved pretreatment and agglomeration methods.
production sector come under increasing pressure to address these issues. “but choosing the most appropriate processing route for low-grade ores is not always clear.”
With this in mind, Mr Norgate used lCA to examine various processing routes for extracting metal from low-grade ores – down to ores containing less than 0.1 per cent metal. He examined conventional concentrating and smelting, direct-ore smelting, heap leaching, pressure leaching and in situ leaching for copper and nickel ores to answer the question: ‘What’s best for low grade ores – smelting, leaching or concentrating?’
The study results suggest that no definitive answer can be given to that question, with the most appropriate route for processing low-grade ores – in terms of embodied energy and greenhouse gas emissions – largely dependent on the ores’ mineralogy.
Also, Mr Norgate says that this ‘first-pass comparison’ of various processing routes did not include economic considerations. “Such issues will strongly influence the route eventually chosen,” he says.
The potential impacts of some emerging technologies, which could also influence the route chosen, were not considered. These include:n�ore sorting – which could be used to
reduce the amount of ore (and hence energy) required for direct smelting; and
n�waste heat recovery – for example, from smelting slags, mattes and other by-product streams – which could be used to reduce the energy consumption of both the conventional and direct smelting routes.
He says industry can take on board the study’s results, especially as future grades fall. “Although there is often very little choice as to which processing route is used – because this largely depends on ore mineralogy – the results showed what the most sustainable routes are likely to be as ore grades fall.”
“ Falling ore grades and more complex ore bodies anticipated in the future can be expected to lead to increased energy consumption and associated greenhouse gas emissions for primary metal production,” teRRy nORgate
PROCESS February 20106
CSIRO Process Science and engineering Ph +61 3 9545 8500 Fax +61 3 9562 8919
By JulIan CRIBBtHe rAVeNOuS blast furnaces and steelworks of Asia are calling for a whole new level of mineral sophistication as they progressively eat their way through the world’s high-grade iron ore resources.
With no shortage of slightly lower-grade ores, Australia needs to both maintain and enhance demand for these ores.
This is where Minerals Down under Flagship researchers are hard at work on the technologies that will shape tomorrow’s market demand for Australia’s $30 billion iron ore export sector – technologies that will help open up opportunities for vast new orebodies with slightly lower iron content or trickier mineral composition.
Theme leader Dr ralph Holmes says Australia has about a billion tonnes of known top-grade hematite ores left. “but we have absolutely no shortage of slightly lower-grade hematite/goethite ores as well as magnetite ores. However, these ores may contain magnetite or higher levels of impurities such as phosphorus, alumina and silica,” he says. “Our work is looking at ways to help industry exploit the ores from these deposits.”
The key to developing Australia’s new iron ore resources lies in gaining a precise understanding of the chemical composition, mineralogy and texture of the different iron ore types; the ability to predict how they will perform as lump ore in blast furnaces, fines in sintering machines or as concentrates in the production of iron ore pellets, both singly or in blends with other ores, and how best to process them.
It is about equipping every tonne of ore to leave Australia with a body of
knowledge for optimising its performance and, hence, its value to the customer and its return to the miner, Dr Holmes says.
At the heart of this, CSIrO’s iron ore classification scheme is growing to embrace ore types from new deposits in Australia and overseas. It now includes ores from countries such as Guinea, Sierra leone, Peru, brazil and China, as well as Western Australia’s midwest, Yilgarn and Irvine Island. The aim is to assess and predict the processing characteristics of current and future Australian ores, as well as the ones they may be blended with in customer’s steelworks to make the best sinter and pellets.
“brazilian iron ore can be higher grade than Australian ore, but the ores are complementary and when combined correctly produce very good sinter,” Dr Holmes says. “One of our goals is to help customers identify the optimal blends of Australian ores with brazilian, Chinese, Indian or other ores that they are using.”
In line with this, an Australian iron ore deposit database has been created to provide a clear up-to-date picture of the nation’s main iron ore reserves, their tonnage and chemical features, such as phosphorus levels.
“The rationale was to evaluate the true potential wealth of our untapped iron ore resources. We started by acquiring raw data from the Western Australian (WA) Department of Mines and Petroleum,
CaSt-IrOnIROn ORe
CSirO is designing technology to shape future demand for australia’s $30 billion iron ore export sector, in particular ways to create opportunities for vast new orebodies.
which was then stored in a structured way, filters applied and content validated for final delivery through Google earth visualisation software.
“We are currently building a secure hosted site for the database so external users can access it.”
Among the findings from the database, for example, is that in addition to our remaining one billion tonnes of high-grade ore, Australia has at least eight billion tonnes of high-phosphorus iron ore in WA alone, as well as large resources of lower-grade ore.
However, ores with more than 0.1 per cent phosphorus adversely affect the strength of the steel produced from them – unless the phosphorus is reduced.
“The database has given us a good grasp of the phosphorus issue facing the iron ore industry and where the priority areas are,” Dr Holmes says. “It has increased our confidence in the approaches we are taking to unlock the value of
Australian high-phosphorus iron ores.” Dr Holmes says the team has recently
lodged a patent application for a process that may halve the phosphorus content of an ore using low concentration leaching agents and reduced heat inputs, in preparation for a future when such reserves will emerge as significant frontline exports.
Working closely with iron ore companies large and small, the Flagship team is using this mass of data about the
australia has at least eight billion tonnes of high-phosphorus iron ore in Wa alone.
Future FOr auStralIa hIngeS On reSearCh
7February 2010 PROCESS
CSIRO Process Science and engineering on the web www.csiro.au/minerals
Future FOr auStralIa hIngeS On reSearCh
scale and quality of reserves to help design potential product blends and flowsheet options for the beneficiation of lower-grade ores.
“This will increase the understanding of available ore resources, prolong the life of mines and maximise market acceptance of final products at the same time,” Dr Holmes says.
Another new technology developed
by the Flagship is ‘recognition’, an optical image analyser for automated identification of minerals and textures in iron ore and sinter samples. A user-defined expert system, it can be trained to recognise minerals, associations and ore textures based on their colour, reflectance, hardness, porosity and mineral associations. Dr Holmes says it can greatly reduce the uncertainty involved in manual classification.
Another key focus of the team’s research is on fine-tuning the sintering process, which produces approximately two-thirds of the world’s blast furnace feedstock. researchers are using x-rays and other analytical tools (see breakout on page 8) to define in unprecedented detail the cascade of chemical events that occur when iron ore fines are heated with fuel and fluxes to make sinter. The goal is to
Photo: robert weber / iStock
ConTinued on PAGe 8
PROCESS February 20108
CSIRO Process Science and engineering Ph +61 3 9545 8500 Fax +61 3 9562 8919
Cast-iron future for australia hinges on research FRoM PAGe 7
tailor sinter recipes to produce stronger and higher-yielding sinter, save energy, and reduce waste and emissions.
The group recently completed a major industry-funded project on the sintering of higher alumina content iron ores found in some new Australian deposits. This will help industry to meet the challenge of rising alumina content and maximise use of these ores in steel mills worldwide.
Another significant impurity in Australian iron ores is kaolinite and the group has recently published new findings on ways to remove it using cationic flotation. The team has established that, unlike silica impurities that float strongly with ether diamine, high doses of ether monoamine are needed to induce strong flotation of kaolinite, particularly in acidic solutions. In addition, they established that the flotation recovery of kaolinite increases with ionic strength, which is the opposite of what happens with oxides.
researchers are also working with a number of smaller mining houses to develop better methods of exploiting magnetite ores. The bulk of Australian ore mined today is hematite and goethite,
but the continent also harbours tens of billions of tonnes of lower-grade (35 to 45 per cent iron) magnetite in which there is rising global interest due to the strong demand for steel.
“Magnetite ores are more straightforward to upgrade than hematite/goethite ores, although you need to watch the silica content of the concentrate,” Dr Holmes says. “We can help by characterising the gangue minerals present in the ore, and identify the best processing techniques for a particular ore. This can assist small companies gain entrance to the market or increase their market share by exploiting some of these lower-grade ores using the most cost-effective processes and designing the process to suit the ore.”
In a more futuristic venture, the team is working with indigenous microbes found in Australian iron ores to develop bioflotation and bioflocculation processes for separating mineral contaminants from iron ore using the polysaccharides and enzymes excreted by the bugs. The advantage of this approach, should promising laboratory trials bear fruit at
People have been sintering iron ore to feed blast furnaces for centuries, but the complex and subtle chemistry at the heart of the process remains mysterious.
now a CSiRo team is turning to the power of the Australian Synchrotron to establish what really goes on inside one of the most important industrial processes of the modern world.
iron ore fines and fluxes are mixed and loaded into a hot stage inside the powder diffraction beamline of the Synchrotron, and irradiated with x-rays while being heated to between 1300ºC and 1400ºC as the team seeks to diagnose each step in the delicate shifts in mineral phases that take place when sinter is formed. The goal is to generate new insights that will lead to better sinter and more efficient blast furnace operations among Australia’s main customers for this essential mineral product.
Project leader ian Madsen, an authority in x-ray diffraction, says the work is a very fundamental study of sinter formation’s mechanisms. “The technique is x-ray diffraction and the tool is the
very high intensity x-ray capability of the Synchrotron. We’ll be using both natural and synthetic minerals to understand what really happens.”
More than two-thirds of the ferrous materials used to feed the world’s blast furnaces is in the form of sinter – an aggregate formed by firing iron ore fines with coke and a calcium-rich flux, explains CSiRo principal research scientist Mark Pownceby.
“The critical component is a binding phase known as SFCA – silico-ferrite of calcia and alumina – which influences how strong the sinter will be. This is the ‘glue’ that holds it together for efficient and stable blast furnace operation. We want to understand each step in the formation of mineral phases that occur in sintering.”
The team believes that a clearer insight into sintering chemistry will lead steel producers, who are increasingly compelled to use lower-grade ores, to better ways to blend various ore types and achieve the right mixture of iron ore fines and fluxes for improved blast furnace performance – and a more competitive product.
Sinter mysteries explored
larger scales, is that it can be used to more selectively reject impurities from iron ores. “It’s a possible process for the future, not for now,” Dr Holmes adds.
In another important advance for the environmental sustainability of iron-making, the team has tested new sampling and quenching methods as a means of quantifying the emission of dioxins during sintering. The team has successfully demonstrated the use of urea, ammonium sulfate and anthracite as potential inhibitors for dioxin formation, with the result that dioxin emissions were cut by as much as 60 to 80 per cent.
Industry partnership is also flourishing, with the recent announcement that bHP billiton and CSIrO have entered into an agreement that has led to bHP billiton relocating its Carbon Steel Materials research group to CSIrO’s Queensland Centre for Advanced technologies (QCAt) in brisbane.
“This will significantly enhance r&D links between the two organisations in the iron ore, manganese and coke-making areas,” Dr Holmes says. “As part of this co-location, bHP billiton is relocating its two pilot-scale coke ovens from Newcastle to QCAt and research will be contracted out to CSIrO.”
together, all these developments will help build a more secure and prosperous iron ore sector for Australia into the future in which, potentially, more processing will occur onshore before export to add further value to the nation’s iron ore reserves.
andre Poliakov using recognition software: an optical image analyser for automated identification of minerals and textures in iron ore and sinter samples. PhoTo: JASon STARR
CSIRO Process Science and engineering on the web www.csiro.au/minerals
9
By ReBeCCa thyeR AN elutION PrOCeSS that combines the benefits of chloride and sulfite is showing it has the potential to be a key step in a new gold thiosulfate leaching and recovery system.
The process uses both chloride and sulfite in a synergistic mixture to elute (or strip) the gold thiosulfate complex from the resin used to adsorb the gold after it is leached from its ore using the cyanide alternative – thiosulfate.
traditionally, cyanide is used to recover gold from ores, and then activated carbon is used to recover the precious metal from the ensuing cyanide solution. However, many refractory ore types do not respond well to this process and as regulations on using cyanide become stricter, industry may need to look for other recovery methods.
Although thiosulfate offers an alternative means of dissolving gold from ore, there is a crux: activated carbon does not work well in recovering the gold from the thiosulfate leach solution.
This is where the new Minerals Down under Flagship’s elution process, which also sees the eluant and resin recycled,
elution circuits over this period,” he says. Dr Jeffrey says that many operations
have refractory ore types that do not respond well to the traditional cyanidation process. “These ores contain carbonaceous material that ‘steals’ the gold from the cyanide solution. This phenomena is known as preg-robbing.”
The gold ‘stolen’ by the carbonaceous material is lost as recovery moves to the next step. This is because it is finer than the screens used to recover the activated carbon pellets.
Thiosulfate leaching coupled with resin adsorption and elution is one of the potential technologies for processing these ore types.
“An alternative step in the gold recovery process would offer companies a solution for these preg-robbing ores. And with environmental regulations often changing the way cyanide can be used, industry is on the look-out for alternatives to use with a range of different ore types, not just for the preg-robbing ores,” Dr Jeffrey says.
Jeffrey, working through the Parker CrC for Integrated Hydrometallurgy Solutions, says a small-scale pilot has validated the work.
“It ran for 40 days with continuous loading of the resin, followed by elution and resin recycling, and then gold recovery by electrowinning. There was no decline in performance of either the adsorption or
eleCtROn BaCKSCatteR dIFFRaCtIOn
New look offers insight into age-old scale problem By ReBeCCa thyeR exploiting a defect found in the mineral scale that builds up in autoclaves during high-pressure acid leaching could provide a potential means of removing the scale and reducing associated industry costs.
Taking a new research approach to an old industry problem – that of jarosite build-up in autoclaves during the high-pressure acid leaching of nickel laterites – Minerals down under Flagship researcher dr Jian Li identified extended crystal defects in the jarosite build-up. her work, with dr nick Timms and dr Steve Reddy from Curtin university’s Applied Geology department (via the Parker Centre), is an important finding. That is because jarosite solubility preferentially increases with extended defects. A potential avenue for scale removal could therefore be solutions that exploit the
defect-rich scale’s solubility, she says.dr Li and her Curtin university
collaborators made the discovery using electron backscatter diffraction (eBSd) to characterise the scale’s crystallographic microstructure and provide a model for scale growth. it is the first time eBSd has been used to do so in an industry situation like this.
The approach was taken, she says, because it was necessary to understand how the scale formed and then to devise solutions that may prevent or reduce that growth, control autoclave conditions to alter the scale’s physical characteristics to make it easier to remove, and provide alternative descaling agents.
Being able to look at a costly industry problem – one that decreases processing efficiency, is laborious to remove and
involves temporary plant closures and production losses – through ‘new eyes’ was valuable, she says. “eBSd provided detailed microstructural information, the kind of information that no other techniques can quite offer.”
dr Li expects more opportunities to use eBSd for mineral-processing-related research to arise from this work. “This is the first study that has used eBSd to analyse scale from a real processing plant. And although we don’t see a direct impact on industry from this work at this point in time, we do have a better understanding of eBSd’s capability and we’ll apply this technique for more industry-related problems should the opportunity occur.”
mrs Danielle hewitt sampling for gold thiosulfate recovered using the patented ion exchange resin process. Photo: DarryL PeronI
CSIRO Process Science and engineering Ph +61 3 9545 8500 Fax +61 3 9562 8919
The Parker Centre is a Cooperative Research Centre comprising four Core Research Participants (CSiRo
Process Science and engineering, Curtin university of Technology, Murdoch university and the university of Queensland), 10 Core industry Participants from the minerals industry, and 12 Supporting Participants.
www.parkercentre.com.au
Parker CentrePROCESS10
By ReBeCCa thyeR A PurPOSe-buIlt wet oxidation facility is helping Parker Centre researchers to develop and improve technologies for the alumina industry.
The unique facility gives researchers the opportunity to unravel some of the fundamental chemistry involved in oxidising complex organic mixtures at the high pressures and temperatures found in the bayer process, the principal means of refining bauxite to produce alumina.
The new facility, located within the Australian Minerals research Centre at CSIrO’s Waterford site, has been specifically designed for research projects in the Parker Centre and CSIrO’s light Metals Flagship.
The facility will also be available as a problem-solving tool for industry clients.
research scientist Dr Allan Costine says the system can also be used to measure hydrogen production – a major safety concern when using wet oxidation technology.
Wet oxidation is used to remove organic impurities from bayer process liquors to improve process efficiency and final product quality. As its name suggests, it works by adding oxygen at high
temperature and pressure to degrade the liquor’s organic compounds.
However, because hydrogen can be produced under these conditions, it creates the potential for explosive mixtures to form if oxygen is also present. As such, existing wet oxidation technology limits the oxygen supply, but this also limits the effectiveness of the oxidation process.
“An alternative approach is to address the hydrogen production side of the equation,” Dr Costine says, and this is where the new facility comes in. “It gives us the means to safely monitor hydrogen and oxygen concentrations on a continuous basis using online electrochemical gas sensors.”
On the safety front, the facility’s equipment has been designed for use with potentially explosive gas mixtures. Key safety features include fail-safe shut-off for the oxygen supply, a hydrogen alarm, and non-return valves on all key gas lines. All instruments in the autoclave area have an intrinsically safe rating to avoid the potential for thermal or spark ignition. The facility was also subjected to a rigorous hazard and operability (HAZOP) study as part of the commissioning process.
Dr Costine says the new wet oxidation facility gives researchers a unique
capability to solve specific problems for clients, as well as investigate the fundamentals of organic degradation reactions under extreme conditions.
“We can now investigate reactions under the conditions of a range of high temperature unit processes, including digestion and evaporation as well as wet oxidation, which are directly relevant to the bayer process,” he says.
The facility has already been used to confirm that an organic compound of a kind found in bayer liquors can be oxidised at 250°C under a nitrogen atmosphere. The production of hydrogen, directly measured in the off-gases, demonstrated that water can act as an oxidant under these conditions.
The wet oxidation facility can also be used to conduct measurements of the production of hydrogen and volatile organic compounds in similar processes used by other industries, such as paper and pulp.
Dr allan costine (standing) and mr mark Schibeci in the new wet oxidation facility. Photo: cSIro
the wet oxidation facility can be used as a problem-solving tool for industry.
CSIRO Process Science and engineering on the web www.csiro.au/minerals
11February 2010 PROCESS
p does the minerals industry matter to Australia today? You bet! it comprises eight per cent of Australia’s gross domestic product and in 2008-09 generated more than A$159 billion in export earnings – a record result even with the global economic downturn.
But will things stay the same? no! The roller-coaster of the past three years shows how dramatic global economic change can be. Furthermore, it’s clear that the nature of our resources continues to shift: our high-grade ores are depleting, the ores are becoming harder to access, and competition from countries such as Brazil
tools for automation and process control, and new ways to extract value from low-grade or complex ores.
other technologies will help the industry improve its environmental performance by reducing greenhouse gas emissions, water use and waste production.
in production and manufacturing, new technologies to produce light metals and the products made from them will help reduce manufacturers’ costs while improving environmental performance.
CSiRo is committed to delivering the science and technology needed to ensure the minerals industry remains economically competitive and environmentally sustainable. We trust that industry will match this commitment by investing and implementing these technologies in partnership with us.
it’s clear 2010 is shaping up to be an exciting year!
and india is increasing. As a result, the minerals industry needs a
competitive edge. history shows that science and technology comprise a major mechanism for achieving that successful edge.
CSiRo, through its Minerals down under and Light Metals Flagships, is delivering the science and technology the industry needs at all stages of the value chain.
For exploration this includes technologies that produce integrated data sets to enable three-dimensional visualisation of the earth’s crust. These techniques help to direct exploration and reduce exploration costs.
Reductions in the costs of mining and improved worker safety will be helped by new remotely operated and geologically intelligent surface mining technologies, and non-entry mining technologies.
Technologies to improve mineral processing include new online measurement
OPeN SPaCe Dr STeve MOrTONCSiRo GRouP exeCuTiVe
– MAnuFACTuRinG,
MATeRiALS And MineRALS
By ReBeCCa thyeR A 280-HOur-lONG, small-scale pilot operation involving CSIrO researchers and rio tinto staff has ‘proved in practice’ CSIrO’s direct solvent extraction (DSX) process to recover nickel and cobalt from laterite leach solutions.
The successful operation was stage five of a journey that Minerals Down under Flagship researchers – working through the Parker CrC for Integrated Hydrometallurgy Solutions – and rio tinto technology and Innovation staff have taken to further develop the technology to suit rio tinto’s leach solution and to test how well it works.
lead scientist, CSIrO’s Dr Chu Yong Cheng, says stage five is the most important for any new solvent-extraction process. Called the fully continuous stage it is essentially a small-scale pilot operation. “A lot of effort went into this operation: it was run continuously with extraction, scrubbing and stripping, over two shifts a day with hundreds of samples taken.”
However, that effort was justified because its success means the process has been proved “in practice and not just in
nICKel PROCeSSIng
efforts to prove new recovery method pay off
flowsheets and potentially low capital and operating costs.
The latest stage in testing the SSX technology involved further optimising operating conditions for extraction, scrubbing and stripping in a fully counter-current operation mode and collecting data for plant design and operation. It followed on from previous work, including batch and semi-continuous stages, which helped the research team determine optimum conditions for the DSX circuit.
Dr Cheng says the latest results – now being evaluated by rio tinto – could be used for further, larger-scale pilot work, plant design and operation. “More test work could be carried out to further improve the operation and accumulate more data for plant design and operation.”
Mark Godfrey says the nickel and cobalt recovery results are very good. “Confirmation that there is no gypsum precipitation makes this an outstanding process and continued testing and development of DSX for nickel laterite processing is warranted.”
principle”, he says.Mark Godfrey, rio tinto principal
adviser for hydrometallurgy, says DSX offers a simple and selective process for the full recovery of the nickel and cobalt from nickel leach solutions.
The core of the DSX process is the CSIrO-developed synergistic solvent extraction (SSX) technology, which rio tinto had earlier identified as a possible way of streamlining nickel processing.
SSX uses organic solvent reagents to directly separate nickel and cobalt from impurities including magnesium, calcium and manganese without intermediate precipitation and re-leach steps, and does so with high selectivity, simple process
Cultivating a competitive edge
Dr wensheng zhang with the fully continuous pilot plant used to test cSIro’s direct solvent extraction process. Photo: DarryL PeronI
PROCESS February 201012
CSIRO Process Science and engineering Ph +61 3 9545 8500 Fax +61 3 9562 8919
By tIm tReadgOldSenior Resources Writer*MAKING MONeY FrOM magnetite has been one of the biggest challenges faced by the Australian iron ore industry, but if a series of recent developments deliver as promised, decades of doubt will be dispelled and a major new export industry will be launched.
until recently magnetite, which requires more processing than other iron ores, such as hematite, has only been used in a handful of isolated examples, such as the small Savage river mine in tasmania, where magnetite is converted into iron pellets, and at OneSteel’s Whyalla mines in South Australia.
What happened at Whyalla is the best illustration of why magnetite has played second fiddle to other ores, despite being available in massive deposits around Australia.
until a few years ago OneSteel (and its predecessor, the steel division of bHP) only used hematite in its Whyalla blast furnaces because of its higher natural iron content.
rising iron ore prices saw OneSteel recognise an export opportunity, switching its Whyalla operations to magnetite and exporting the hematite.
OneSteel recognised the key problem with magnetite, the processing cost to upgrade it from around 30 per cent iron content, versus 55 per cent to 60 per cent for hematite. The low grade and high shipping costs meant magnetite was best suited to domestic consumption, especially if close to a steel mill; it has not been considered suitable for export – with Savage river a notable (but small) exception.
times change. High-grade resources of hematite are limited. Magnetite is abundant, and Chinese steel mills have traditionally used magnetite as a pelletised feedstock in their steel mills.
rather than seeing magnetite as a poor relation to hematite, the game became one of finding a way to connect an Australian resource with Chinese demand. The biggest step in that direction was taken in late November, with the start of construction at the Karara magnetite processing facility of a local company, Gindalbie Metals, and its
the magnetite iron-ore revolution is coming
Market expansion possible with idea-testing lab
provides titanium and other corrosion-resisting alloys to many industry clients.
We remain committed to continually evaluating and re-evaluating our products to suit new uses and help mineral processors address economic, environmental and social sustainability pressures.
The process industries and the companies like ours that support them are in a constant state of evolution, with the drive for efficiency improvements demanding new process development or increasing the effectiveness of existing processes.
research is vital to this, and companies, big and small, rely on CSIrO to provide that specialty.
It WAS A SIMPle IDeA, to broaden the market for one of our key products – the rtF4 agitator hydrofoil – but one that required specialised help to accomplish.
The rtF4 hydrofoil, sold through our Chemical Plant & engineering (CP&e) division, had proven itself as being efficient and having lower power consumption than competing products in process applications, so we decided to explore the possibility of marketing it to the mineral processing industry.
However, there was a caveat, the rtF4 would need to be scaled up.
leaDer’S FOruM TONy SayChieF exeCuTiVe oFFiCeR,
CeM inTeRnATionAL PTY LTd
WWW.CeM-inT.CoM.Au
As a small-to-medium-sized enterprise, being able to test if this was possible was beyond our skills and facilities. but by turning to CSIrO, we were able to employ researchers to test if our equipment could offer similar advantages in larger operations.
It could and it does. That initial research is helping our company to build a new market. This illustrates how companies can work with the nation’s top research provider to grow their business.
today, CeM International continues to have a significant interest in the processing side of the minerals industry. Our CP&e division provides specialised filtration and agitation equipment, while our titanium International division
Chinese partner, AnSteel, near Geraldton in Western Australia.
The business case behind Karara is a classic ‘half-way’ solution. rather than going all the way and producing iron pellets (like Savage river), the magnetite ore is taken only to a concentrate stage. It is this material that will be shipped to a pellet-making plant in China, and the pellets then fed directly into a blast furnace.
Karara is the most ambitious attempt yet at ‘monetising’ Australian magnetite. Other projects will follow, including the proposed Southdown mine of Grange resources near Albany on WA’s south coast, and a series of major potential processing developments in the Pilbara region.
In time, and if the business case of Karara can be successfully demonstrated, Australia’s long dormant resource of magnetite will become a major income earner.
*Tim Treadgold is a former senior resources writer and columnist for brW and now writes for MiningNews.net, the eureka report and Forbes magazine among others.
Cem International has a significant interest in the mineral processing industry.
