Xstrata: Selling Formulae for Efficiency

The IsaMill has been a significant success for Brisbane, Australia-based Xstrata Technology (XT), most recently at Red Dog (see E&MJ, January/February 2009) and at Pan Australian’s Phu Kam copper-gold operation in Laos where an M10,000 mill rated at 3MW is using MT1 ceramic media. The smallest version, the M1000 with 500 kW power is in use at the Macraes gold operation in New Zealand.

Red Dog also utilizes XT’s Jameson Cell flotation technology, the latest (Mark IV) version of which has been provided with a specially designed flexible hose to connect the downcomer, rather than the rigid slurry hose used previously. The first cell with this modification has been installed at the CHPP plant built by the Thiess Sedgman joint venture for the Lake Vermont Resources operation near Dysart in the Bowen Basin, Queensland, Australia.

But IsaMill and the Jameson Cell are not the only XT products, nor is XT the only unit within the Xstrata Group providing process technology for third party use. Just as MIM in Australia had commercialized its technology development operation before being acquired by Xstrata, so Falconbridge in Ontario, Canada had also decided to offer its expertise to third parties. Today this service is provided by the Xstrata Process Support Group from Falconbridge, near Sudbury, and covers the processing chain from Process Mineralogy through to pyrometallurgy and hydrometallurgy, with services from small scale bench testing, through large scale pilot testing to venture style project analysis.

Focus on Energy Efficiency

A key focus for Xstrata process engineers is the containment or reduction of energy consumption without loss of process efficiency. So Xstrata Technology is concentrating on improving energy efficiency through the way processing circuits are designed to suit specific ores and on how the whole processing chain is integrated to get maximum benefit from minimum grinding power. Joe Pease, the company’s CEO, argues that improvements in energy efficiency of up to 50% can often be achieved by combining Xstrata Technology’s existing tools: basic quantitative mineralogy, grinding models, new grinding technologies, reproducible laboratory flotation tests, and basic smelting thermodynamics.

Quantitative mineralogy can characterize ores and reveal the implications for concentrator and smelter designs. The most benefit is gained by asking two simple questions, says Pease: in roughing, how coarse can you grind and still get high recovery; and in cleaning how fine do you need to grind rougher concentrate to make a high grade product?

The focus in roughing is on liberating enough gangue to allow the mineral to be recovered to a small stream for further processing; in cleaning the focus is on mineral liberation and a trade must be established between the energy needs of grinding and downstream smelting or leaching.

Too often the rougher feed is ground too fine but the cleaner feed not fine enough, raising energy consumption downstream. The reluctance to regrind finer may be due to anticipated sliming problems and/or the adverse effect of steel grinding media fragments on flotation. But fine grinding with inert media, for instance in the IsaMill, avoids these problems.

Albion Process

Similarly focused on reduced energy demand, but perhaps less well-known than XT’s IsaMill, Jameson Cell, ISASMELT and ISAPROCESS technologies is the company’s Albion Process. Developed to treat concentrates from refractory base and precious metals ores it uses ultrafine grinding to yield activated, highly reactive mineral particles that are leached in simple atmospheric tanks. The result, says XT, is a simple, low energy process that uses conventional mine site equipment and can be applied economically at large or small scales. Capital expenditure and maintenance costs are low and operation is simple so Albion can be significantly more attractive than pressure or bacterial leaching alternatives.

Since 2006 the patented process has been marketed for Xstrata by Core Resources who also bought the company’s Hydrometallurgy Research Laboratories and provides independent testing services under the name HRL Testing. Mike Hourn, XT’s Hydrometallurgy manager, told E&MJ that so far two licenses have been granted, one to the Las Lagunas project in the Sanchez Ramirez province of the Dominican Republic and the other for the Certej gold project in Romania.

At Las Lagunas the Australian-based company Envirogold Ltd is building a plant designed to process over 800,000mt/y of refractory pyritic tailings to yield 87,000 oz/y gold and 510,000 oz/y silver. The tailings come from the nearby Pueblo Viejo mine. The IsaMill, an M3000, will regrind the material ready for oxidative leaching. This operation is beginning start-up and should reach full production in 2010-11, Mike Hourn said. UK-based European Goldfield is meanwhile progressing the Certej project through detailed design with the intention of producing 160,000 oz/y gold.

Pyrometallurgy

In another fresh implementation of an XT technology Mopani Copper Mines in Zambia is installing the first ISACONVERT plant at its Mufulira, Zambia smelter expansion. Having commissioned an ISASMELT unit at Mufulira in mid-2006 MCM are now expanding converting capacity. ISACONVERT has been under development has been under development for 15 years,

Ball Mills, BIOX and H2SO4 from Bateman

The Dutch-based but primarily South African company Bateman Engineering is actively expanding both its equipment and technologies portfolio. Working with the CITIC engineering group in China, Bateman Engineered Technologies (BET) aims to become a large-scale player in mill supply, while late in 2008 Bateman announced it would buy the proprietary and patented BIOX refractory ore treatment process. And at the Ambatovy nickel project in Madagascar Bateman Engineering will construct a 5,500mt/day sulphuric acid plant under a $36-million fixed price lump sum contract.

Near Groblersdal in Mpumalanga, South Africa, the Ridge Mining plc subsidiary Blue Ridge Platinum (Pty) Ltd is completing a new platinum operation. Having conducted the pre-feasibility and feasibility studies, Bateman Engineering was given responsibility for the total $59-million lump sum turnkey contract to design, engineer and construct the PGM concentrator in 2007. A primary crusher will supply 115,000 mt/month of PGM ore to one primary and one secondary ball mill that form a typical MF2 circuit in conjunction with flotation cells. The primary ore will supply coarse ground material for the primary flotation circuit and the secondary mill will grinding the tails from primary flotation ready for secondary flotation. The two concentrate streams will be combined for filtration and shipment to a toll treatment facility.

The two mills were built by CITIC in China and supplied to the project by BET under its exclusive license to market CITIC mills in Southern Africa. They were dry commissioned in China and shipped from Shanghai to Durban in South Africa on a bulk break basis as some sections were too big to be containerized. These sections required special attention during transport as they were exposed to the weather but critical parts were shipped in containers. Unusually, the two mills were the first major process equipment units to be installed at Blue Ridge.

Elsewhere BET has secured a ball mill order for the Inca Pacific Magistral copper-molybdenum project in Peru, to be delivered in September 2010 and is reportedly working on the design of a SAG mill for London-headquartered Highland Gold Mining’s Mayskoye gold project near Pevek in Siberia, Russia.

BIOX Technology

This acquisition, from the Gold Fields Group, is subject to certain conditions but Bateman Engineering intends to incorporate the business within the Bateman Engineering Projects Strategic Business Unit as a Center of Excellence within the Bateman Engineering Group. A second technology, ASTER (Activated Sludge Tailings Effluent Remediation), was also included in the sale. ASTER is being tested in a number of pilot plants as a method for efficiently removing thiocyanate and cyanide from leach solutions, Bateman says.

Where gold is encased within particles of sulphide mineral such as arsenopyrite, pyrite and pyrrhotite, preventing cyanide from leaching the gold, the BIOX process uses a combination of three naturally occuring bacteria to digest and destroy these sulphide minerals so that cyanidation can proceed. The bacteria—Acidithiobacillus Ferrooxidans, Acidithibacillus Thioxidans and Leptosprillum Ferrooxidans—require nutrients during the process which can typically take four to six days depending on the mineralogy of the feed. After oxidation the BIOX product is washed and neutralized with limestone and/or lime, creating environmentally acceptable precipitates and the neutralized effluent can be thickened to return the water content for use in the milling, flotation and BIOX process sections.

Eleven commercial BIOX plants have been commissioned over the past 20 years, eight of which are currently in operation, Bateman says. Of these the oldest is in South Africa at the Fairview mine, treating 62 mt/d of concentrate while the largest is the 1,069-mt/d-concentrate first phase of the Kokpatas plant in Uzbekistan owned by Navoi Mining and Metallurgical Combinat. Bateman has been in discussions concerning doubling the capacity of this plant. The company believes being able to offer the Biox technology will also strategically position Bateman Engineering for several gold opportunities in the future.

Sulphuric Acid, Canadian Style

Bateman’s construction contract at the Ambatovy project covers erection and commissioning up to handover for hot commissioning of two 2,750-mt/day sulfur burning acid plants. It follows on from the successful completion of the about $100 million engineering and procurement contract for the plants, which Dynatec Madagascar SA awarded to Bateman in August 2007. The process engineering involved in this earlier phase was undertaken with Noram Engineering and Constructors Ltd, the Canadian company who own the acid plant technology used and with whom Bateman Engineering has a long term technology license agreement. The first plant should be completed late in 2009.

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