Biting the Dust
Biting the Dust
Open cut or underground, dust is the enemy of mining operations. Mobile dust monitors and road-condition monitors are just two of the recent innovations the Australian mining industry is deploying in the battle against dust suppression.
Large machines operating in a harsh environment - whether it's above or below ground - generate dust, masses of it. Dust may seem innocuous but it's damaging: inhaled in quantity, over time, it can cause 'black lung' and other pneumoconiosis-related diseases.
Indeed, it is so deleterious to human health that government agencies such as the Environmental Protection Agency (EPA) and the Department of Planning have implemented 'police and enforce' dust emission standards.
Mine operators also take dust emissions seriously: mine personnel can shut down production on a site if they judge dust levels to be too high for work to continue safely.
According to Australian Diversified Engineering (ADE) sales manager Eric Tomicek, "New mines have limits on 'fugitive dust emissions' as part of their licencing requirements, so operations need to comply with best-practice dust suppression efforts.
"It looks bad if a community can see dust around, and it can impact on how the mine is perceived in the community - especially where you have mines in more inhabited areas such as the Hunter Valley in New South Wales," Tomicek say. "As a result, mining companies install dust monitors on the perimeters of the site to measure fugitive dust.
"It's a pretty serious business: by law, companies need to upload their dust emission measurements to a website where anyone can see them and - at the least in the Hunter Valley - on dry, windy days where there is likely to be a lot of dust in the air, the EPA will drive around, and fly up and down over the mines with a helicopter, to monitor dust levels," he says.
With so much at stake, dust suppression is a perennial hot topic, and mine operators throw millions of dollars at the problem every year. One of the difficulties, argues operations and technical director for Reynold's Soil Technologies (RST) David Handel, is that there's no simple, one-fits-all solution.
"A lot of people are selling silver bullets, and companies want to buy silver bullets," Handel explains.
"The problem is that mine sites vary so much: the conditions at a mine site in Queensland are completely different from [those at] one in Western Australia, and Tasmania is different again. Because everything needs a different approach, there's no panacea offered by one product."
Handel and Tomicek agree that good dust suppression on roads starts with good roads. By building haul roads incorrectly, companies are creating their own problems, in part because fine particles - in other words, dust - are needed to help bind roads together.
One innovation in dust suppression on haul roads is the use of super-concentrates instead of water. "It's more expensive per litre," says Handel, "but it minimises shipping and application costs. In some applications, where a mine used to use 10,000 litres or more of water, it's now using 2000 litres of super-concentrate."
Another is the development of a water truck that delivers the same amount of water no matter what the speed of the vehicle. "At low speed, [a normal truck] can deliver too much water," explains Tomicek. "But a haul truck on a mine site has priority, which forces the water truck to speed up, which means less water being sprayed onto the road. If it's done at a defined rate, operators know how much water has been applied."
As well as efforts to reduce the production of dust through better design and construction of haul roads and more effective road-dust dampening systems, work is going into reducing the amount of dust produced by other mining activities, such as blasting, Handel says.
"Originally developed for Citic Pacific (CP) Mining in Western Australia, which had a problem with asbestos on the site, there's a system that reduces the amount of explosive energy required by replacing [the usual blasting compound] with plasma gel, which attenuates the energy in the blast. This gets better fragmentation and nice even rock break, with less fines, which improves material handling as well as reducing dust."
Both Tomicek and Handel argue that it's vital mine operators take a more holistic approach to dust suppression, and that they deploy tools that can measure the effectiveness of any dust suppression measures being used.
"You'll have a mine site with perimeter dust monitors - but if the site gets shut down due to high dust levels, you won't know where it's coming from," Handel says. "So companies really need to look at putting in place dust-monitoring systems that will monitor a specific area, such as a haul road, a blast face or a stockpile."
Dust monitoring within a site, using technologies such as those developed by Proof Engineers (amoung others), is a good first step towards acquiring an accurate picture of how much dust is circulating and where it is coming from.
Tomicek and Handel also contend that change management is a major piece of the puzzle.
"A lot of time, people think they're doing the right thing but they may actually be creating a problem," says Handel. "So it comes down to education.
"People need to realise they can't just come in with a technology and expect it to do everything, without providing resources, without change management, without training people.
"It's a bit like expecting you can wash your hair once with a new shampoo and not do it again for 12 months."