Despite volatile markets and decreasing commodity prices, global gold mining company AngloGold Ashanti continues to explore advanced ways of cultivating mining safety, increasing production, and curbing production costs, says AngloGold Ashanti investor relations and group communications global group senior VP Stewart Bailey.
Among the most recent technology innovations that the South Africa-based company has developed is the reef-boring machinery that extracts gold-bearing ore without explosives being used. The machine works with the help of a unique ultrahigh-strength backfill (UHSB) liquid which is poured into the drilled reef holes to assist in maintaining the integrity of the rock.
“AngloGold Ashanti’s technology research programmes have been well documented in recent years, as we have continuously worked to improve safety and productivity and reach the gold that cannot be extracted using conventional methods,” Bailey tells Mining Weekly.
Through the AngloGold Ashanti Technology Consortium which was established in 2010, the company is aiming to reach a new benchmark in safety, enabling it to mine at greater operational depths.
The key component of the new mining method currently being developed by the company is the use of mechanical reef-boring technology to extract gold-bearing reef, thereby minimising dilution.
According to AngloGold Ashanti, the new technological initiatives are a response to the limitations of conventional mining methods, which involve the gold-bearing reef being mined along with waste rock to create an excavation site large enough to accommodate equipment and people. As the work face is advanced and the rock extracted, the enlarged excavation causes significant dilution of grade by up to 200% or more.
The thin gold-bearing reef mixed with the waste rock is then transported through the extensive mine infrastructure at depth, across large horizontal distances and up to surface. This method is inefficient, owing to the depth and distance involved, coupled with the fact that waste is transported along with the reef. Gold is also lost at various transition points throughout the production chain.
If proven to be commercially viable, AngloGold Ashanti’s innovations can provide the mining firm with a strong positive differentiator and preserve the long-term optionality of the company provided by the unmined gold that remains in support pillars accross its South African mines, according to the company’s Technology Consortium.
If successful, the technology could unlock the potential to develop significant gold resources and create new jobs, while stimulating the growth of the manufacturing and services industries in the mining sector, which are currently subjected to a climate of falling commodity prices, exhausted mineral resources and soured labour relations, as well as the technical and financial sustainability challenges that ultradeep mines face in Africa.
Test Sites
Bailey notes that AngloGold Ashanti’s Technology Consortium established test sites at the TauTona mine, south-west of Johannesburg, and at the Great Noligwa mine, in the Free State, to further test and develop its new technologies, which allow for mining at greater depths and the extraction of sterilised elements of its orebodies.
He further indicates that global significant milestones were reached in 2014 when gold was extracted from the trial sites at TauTona, where the main shaft pillar yielded grades in excess of 200 g/t.
The successful trials resulted in the commissioning of three mid-range, specially designed rigs at TauTona, while a small-range prototype rig was delivered to Great Noligwa for further testing.
The company is now further investigating the possible use of reef-boring applications and the inclusion of UHSB technology to allow for the deployment of small-scale prototype mining machines initially targeting mining opportunities that are not currently possible using conventional practices
Bailey notes that the construction of the underground backfill plant at TauTona has been completed and commissioned. He further explains that the plant uses a semiautomated process to prepare the USHB liquid used to fill the holes at the TauTona prototype sites. which are expected to be safer and result in high productivity gains.
“These innovative technologies aim to enhance the efficiencies and extend the life-of-mine of deep-level mining operations in South Africa,” Bailey says.
In addition, he adds that Anglo-Gold Ashanti continues to expand its prototype base with site-equipping work in other areas, with par- ticular focus on its West Wits mines.
Headquartered in Johannesburg, AngloGold Ashanti has 19 gold min- ing operations in nine countries, as well as several exploration programmes in established and new gold producing regions.