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Going greener in the Gold Fields - Australian Mining

Thursday, 7 July 2016

While the mining downturn has heavily impacted the iron ore and coal industries, the gold market has remained strong, soaring to nearly $US1300 per ounce in June and becoming this year’s best performing asset. Gold Fields is among the top gold producers in the world and with its implementation of Aggreko’s gas powered generators at its Western Australian mines, it has reaffirmed its commitment to becoming the global leader in sustainable gold mining. Australian Mining visited its Granny Smith Gold Mine on the official opening of the power station, discovering some of its history along the way.

A brief history 

Discovered in 1979 by Raymond Smith, the Granny Smith Gold Mine was named after his wife Laurende who had just become grandmother. Located 20km south of Laverton in the state’s Eastern goldfields region, it initially consisted of the Goanna, Granny, and Windich ore zones as well as five satellite deposits, with first gold produced in January 1990. By 1995, the deposits in the zones had depleted, until the discovery of the Wallaby deposit, 11km south west of the mine, in 1998. Since first ore was processed in 2001, the Wallaby deposit has become the mine’s sole source of gold; with the mine eventually transitioning from open pit to underground mining in 2006. 

Following a series of owners including Canyon Resources, Delta Gold, and Barrick Gold, the operation was acquired by Gold Fields in 2013, WA’s largest underground gold mining company.

Gold Fields has eight operations in four countries including Ghana, South Africa, Peru, and Australia. Granny Smith is one of four mines the company owns in Australia, with the others including Darlot, St Ives and the combination of Agnew and Lawlers.

It has an annual production rate of 2.2 million ounces of gold and as of last year, its Australian operations accounted for 46 per cent of its total gold production. 

Granny Smith’s gold production and processing 

The site has 468 employees on site as well as a number of contractors, with 10 per cent of the total being women.

During a brief introduction to the site, Granny Smith Gold Mine general manager Ian Suckling said “We’d like that to be more but that’s the current status of it.”

Despite being the youngest in the Gold Field’s Australian portfolio, Granny Smith provides a substantial amount of gold and Suckling said the mine’s production to date has been seven million ounces of gold, which equates to around 230 tonnes.

“It’s a fair amount of gold; in today’s gold price that might be $12 billion. Twenty-six per cent of the gold comes from the Wallaby underground mine which was started in 2004, and that’s the base load. That’s the core source of our production at the moment,” he said.

“Although we have a lot of very good exploration potential around here, we’re keen to, and we think, very capable of, supplementing that, but at the moment Wallaby’s the go.”

In 2014 and 2015 the operation produced more than 300,000 ounces of gold, however their current rate is yet to hit that standard.

“The guidance for this year is a little short of those figures but we have a very good future in front of us,” Suckling said, remaining positive about the reserves they have, saying, “We have exploration results that demonstrate that there’s plenty of gold still beneath where we are today.”

“Last year there was a big uptick in our reserves [with] 7 million tonnes at 6 grams per tonne of gold. There were about 1.3 million ounces of gold in reserve.”

The ore is mined depending on the ore body geometry, using either the long hole open stoping or inclined room and pillar methods. It is processed using carbon in pulp technology (CIP).

“Once its mined we crush it, we put it through a semi autogenous grinding mill. We then put through a series of leaching processes where we have cyanide that extracts the gold from the solution and activated carbon that extracts the gold in solution onto the carbon which is processed on through to extract the gold from that carbon and we end up producing what we call dore, which is over 90 per cent gold, and we ship that to the mill for refining,” Suckling said.

“And we do get 30 per cent of our gold ore [out of] a gravity process which is newly installed and that’s given us a number of efficiencies,” he added.

The site also has a carbon reactivation gold recovery facility, a fine grind retreatment plant, and a tailings thickener.

Apart from gold production, Granny Smith also has a community focus, supporting the Laverton community by providing programs for schools and being involved in the town’s cultural activities.

“We support the arts and cultural centre in town along with other mining industries in the district and we do programs to encourage people to obtain skills that they can use either in employment or in their personal lives,” Suckling said. 

From diesel to gas power

With Gold Field’s central vision to become the global leader in sustainable gold mining, their implementation of Aggreko’s ‘Next Generation Gas’ generators at Granny Smith, signals a growing trend toward the shift from diesel to gas power.

Aggreko provides temporary power and temperature control solutions such as diesel and gas generators, power plants, chillers, and air conditioners for a range of industries with 211 locations in more than 53 countries worldwide.

Their fleet of 20,000 generators range from 10Kw to 2MW with their services including delivering and operating 200MW gas fired power plants in Africa, providing generators for outdoor events, using chillers to reduce temperatures in refineries, and providing ships with onboard power generators. They also supply power for broadcasting of major sporting events such as the Olympics and music festivals; recently powering this year’s Eurovision Song Contest.

Gold Fields capitalised on Aggreko’s gas generators, with all four of their mines in WA operated using these rather than diesel generators.

The move comes after the installation of APA Group and Anglo Gold Ashanti’s 293km, $140 million gas pipeline in the Eastern Goldfields; extending from the current Murrin Murrin/Yarraloola terminal of the main Goldfields Gas Transmission Pipeline to AngloGold Ashanti Australia’s Sunrise Dam Gold Mine and through to Tropicana.

The WA minister for state development, finance, and innovation, Bill Marmion, said the pipeline presented a game changer for the industry, not only in its potential to create jobs in the future, but also to provide a cleaner fuel to several other mines in the region.

During the new power station’s opening ceremony, Gold Fields executive vice president Richard Weston said the company took advantage of connecting to the pipeline, enabling them to upgrade their 25 year old generating facility which was “nearing the end of its useful life”.

“[It presents] a new foundation for reducing our carbon dioxide emissions by more than 15 per cent per year, equivalent to 85,000 tonnes over the next ten years, which makes the operation eligible for the Australian Emissions Reduction Fund,” he said.

The fund was created as an incentive for Australian businesses to cut their greenhouse gas levels, with an overall goal of reducing emissions to five per cent less than the level it was in 2000 by 2020.

Aggreko managing director George Whyte said the installation of these gas systems highlights a growing trend of mining operations moving from diesel power.

“I think there is definitely a growing trend of transitioning from diesel to gas, at the moment, getting accessibility of the gas is one challenge,” he said.

He also said the the Granny Smith gold mine power station “is one of the most technologically advanced modular systems in the world”.

“Our mining clients have faced a challenging market place and power generation is a significant proportion of operating costs. Our global capability offers additional flexibility which reduces investment and operational risk,” he said.

The giant blue grey containers housing the engines were a distance away from the old fuel mill, emitting a constant thrum as we made our way around them.

Speaking to Australian Mining, Adam Hentschel head of operations at Aggreko Australia Pacific, said the station comprises twenty-four 1.5 megawatt engines.

“So if you think of it in terms of your car engine that might be about 100kW, each one of those is about 15 times as powerful as a car engine but it runs flat-out all the time.”

Hentschel added that the generators were a result of a five-year development program and if one engine stops failsafes ensure another will automatically start.

Explaining the process, he said, “The gas comes in to the generators, it’s converted into electricity by the alternator, it’s transferred to the switch room where then its marshalled into a single power source then sent through transformers up into the overhead line and then it runs down to the process plant and then the other power is distributed back up over to the mining operation.”

George Whyte said, “The new 33kV distribution system will meet the daily power needs of the entire mine of 24MW with 8MW allocated to the Wallaby underground mine and the remaining 16MW for the processing plant, associated facilities, and camp.”

He went on to say it also features a high pressure gas conditioning infrastructure with heat recovery technology that enhances power station efficiency and reduces gas pressure from the Eastern Goldfields gas network.

While the gas station is being used, Granny Smith’s old diesel mill will remain as a reserve.

“Gas is not available everywhere, that’s why diesel engines are still used in a lot of mines if they haven’t got any connection to gas,” Hentschel said.

“So the other thing that’s occurring now in the market as well is people are putting gas into tanks and then shipping it by road.

“Particularly with the low cost diesel fuel at the moment it is a particular challenge but I think what you’ll find in coming years, as diesel starts increasing [in price] and, it may not be for a little while, even tank gas or truck gas will be coming more cost effective than diesel.”

Hentschel also told Australian Mining the engines are designed to last a long time and have modular capabilities, as they can be added or removed depending on the power needs of the operations.

“We’ve actually got 1500 of those engines in our fleet. So what then happens is that fleet tends to move around. A lot of these ones are contracted for quite a long period of time, quite often for six months or six years or however long they’re needed, and depending on whether the mine site needs more power, we can add boxes.”

With the new gas station, Granny Smith is not only extending the site’s life, it’s signalling the continued stability of the gold market. 


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