Growing attention to mining-related environmental issues has stimulated the search for new approaches to dust management. In particular, the challenges associated with controlling haul-road fugitive dust emissions have led regulatory agencies to examine these emissions in greater detail. Studies conducted by the U.S. Environmental Protection Agency indicate that, typically, haul trucks contribute heavily to the total fugitive airborne dust generated at a mine site. With the continuing demand for natural resources, there will be rising interest in the management and control of haul road dust emissions.
ATMOS Global (ATMOS Australia Pty Ltd.), an Australia-based consulting company specializing in advanced dust impact forecasting, management and control, works with a wide range of companies from a broad range of industries to accurately assess complex air quality risks associated with their operations, increase the efficiency of the recommended risk mitigation measures and improve their environmental strategy and communications. ATMOS Global has been developing and pioneering advanced 3-D Numerical Weather Prediction and complex air quality modeling, forecasting and management tools for almost two decades.
ATMOS Global recently launched ATMOS-5D+, the haul-road dust control version of ATMOS-5D, which was released in 2010 and is described as a risk-based dust forecasting and management solution designed to meet the increasingly complex needs for dust control in mining and other industrial sectors. According to the company, ATMOS-5D+ is a unique multi-agent autonomous technology that complements and enhances the efficiency of traditional management practices used for haul-road dust control.
Dr. Orestis Valianatos, president and CEO of ATMOS Global, explained that, “ATMOS-5D+ sets guidelines for cost-effective courses of fact-based dust management action leading to safer working conditions, reduced environmental consequences and higher productivity, by offering mine operators an opportunity to anticipate, identify and decide a few days in advance—before adverse dust impacts are predicted to happen—what the response to these potential dust impacts will be.”
ATMOS-5D+ works in tandem with ATMOS Global’s Dust Alert+, which Valianatos said is the world’s first artificial intelligence, multi-factor, multi-criteria, dust-impact early warning system. “ATMOS-5D+ and DustAlert+ combine state-of-the-art meteorological and air quality forecasting concepts and apply mathematical and physical sciences proficiency to the task of delivering more than 25,000 highly specialized site-level dust impact forecasts every year,” said Valianatos.
ATMOS Global’s daily dust impact forecasts are delivered to customers’ sites via a Web-based interface from ATMOS Global’s main facility. According to the company, its database allows mine operators to use a variety of fixed and mobile devices (computers, smartphones and tablets) and communication channels to interact with forecasting information.
ATMOS-5D+ and DustAlert+ allow users to adopt an integrated approach that can be customized to accommodate variations in dust management strategies associated with various types of mining activities. These systems are configured to respond to site specific circumstances and to evolve with the growing requirements of the mining operations by allocating dust management resources according to predicted potential dust impacts.
Protecting by Predicting
Western Areas is an Australia-based miner whose main asset is the Forrestania nickel project, located 400 km east of Perth, comprising two mines: Flying Fox and Spotted Quoll. Flying Fox is one of the highest grade nickel mines in Australia and has been in production since 2006. The company’s second mine, Spotted Quoll, began high-grade nickel ore production from the Tim King open-pit during the first half of 2010. Spotted Quoll underground mine development (the Hanna decline) commenced in April 2011. Ore from both mines is processed at the 500,000-mtpy Cosmic Boy nickel concentrator.
At Spotted Quoll, an environmentally sensitive ‘receptor’—a population of the Declared Rare Flora (DRF) species Eucalyptus steedmanii listed under the Western Australian Wildlife Conservation Act—was identified within 50 ft of the edge of the proposed open pit early in the mine planning stages. A key priority has been to protect this plant population from adverse dust impacts associated with mining activities.
According to Valianatos, based on advance dust-impact risk advice provided by ATMOS-5D+ and DustAlert+, Western Areas makes decisions regarding dust mitigation measures using site specific fugitive dust emissions profiles (calculated by using ATMOS Global’s DustFinder software) of TSP, PM10, PM2.5 and other fractions associated with site mining activities that can include drilling and blasting, bulldozing, excavating, loading and unloading, ore crushing and screening, conveying, waste rock handling, topsoil stripping and stockpiling activities, as well as dust from exposed mining areas, stockpiles and haul roads. Western Areas also is provided with high-resolution, site-specific weather information generated daily by ATMOS-5D to help assess the risk level for each event.
The system, according to the company, allows Western Areas to prepare an effective response days before potential dust impacts. ATMOS-5D and DustAlert+ were instrumental in assisting Western Areas to reduce annual total dust deposition recorded at the location of the sensitive vegetation in close proximity to the open-pit by 24.2%, even as the annual rate of mining increased by 44.3% for the Spotted Quoll site (2010 versus 2011). Monitoring has proven that there has been no visible decline in the health of the DRF population since Spotted Quoll commenced operation.
The dust impact forecasting and management information has become an integral part of Western Areas’ employee training programs, and Western Areas and ATMOS Global were jointly nominated by the W.A. Department of Mines and Petroleum as finalists for the 2011 Golden Gecko Awards for Environmental Excellence for implementation of ATMOS-5D at the Spotted Quoll project.
Dust Supression in the Pit
Dust Control Technology, a global leader in open area dust suppression, recently introduced its newest and largest design, the DustBoss DB-100. Engineered specifically to deliver the power to reach the working face of a surface mine, the new dust suppressor has a range of more than 100 m, giving it ample reach to cover stockpiles 200- to 300-ft high. The giant atomized misting unit stands nearly 10-ft tall, and can cover a massive area of 280,000 square feet (more than 26,000 square meters) from a single location.
The DB-100 was designed with input from some of the leading mining companies in the world, with data collected from numerous site visits, where visibility around massive working areas can be profoundly impacted by dust. “Most operations use water trucks to wet down haul roads before trucks enter the area for loading,” said DCT Vice President Aaron Valencic. “Unfortunately, the technique is only marginally effective on surface dust, and it has no effect at all on airborne particles.”
Water trucks also don’t address dust from the loading operation itself, as their reach is limited only to the area around the driving surface. “This new unit will reach all the way to the working face, knocking down dust from the shovel right as it picks up or drops material,” he said. “With the improved visibility and air quality, mining companies can maintain a safer and more productive workplace.”
According to CEO Edwin Peterson, the unit was developed specifically for large-scale mining, coal operations and bulk material handling. “It was originally an idea of our late co-founder, Barry Brown,” Peterson said. “He had the vision to create a mine-grade open-pit dust suppression design that was extremely powerful and exceptionally reliable. Although he did not get to see it built, I know he’d be proud to see it become a reality.”
Peterson said that in applications such as mining, which require high dependability even under extreme working conditions, the simplest designs are usually the most successful. “During the design phase, we talked with mine managers, maintenance staff and supervisors to see what was most important to them,” he said. “The range and performance were key, but nearly every one of them also stressed reliability. Downtime is very expensive, and they want to spend their days on core activities, not dealing with equipment breakdowns.”
To address that need, DCT engineered an extremely rugged and efficient design. Like all of the company’s fan-driven atomizers, the DB-100 delivers both power and dependability by using a straightforward, direct drive fan motor. It has no drive belts, diesel engines or complex worm gear systems that could present breakdown problems in the difficult service environment of a mine or coal yard.
Despite its impressive size, the DB-100 requires minimal maintenance, with lubrication of fan motor bearings recommended every 10,000 hours, while the oscillation motor is lubricated for life. All DustBoss models are covered by a three-year/3,000 hour warranty and complete satisfaction guarantee.
Prototype Proves Successful
DCT made the announcement after extremely positive trials at a large coal handling operation, where migrating dust was creating a nuisance. The DB-100 demonstrated its effectiveness in managing dust from the facility’s stockpiles, which had proven too large for a competitor’s dust suppression equipment previously tested by the utility.
The new design represents the culmination of two years’ development time, and is based on 40 years of engineering experience in atomized mist technology. “Effective dust suppression is a complex equation,” Peterson said. “In addition to droplet size and air speed, there are dozens of variables that affect a machine’s performance. The size and precise shape of the barrel are critical, for example, as a successful design must control the laminate air flow to achieve the optimal plume and distance.
“But the design really is the sum of all its parts, in that every component is specifically engineered to maximize performance, including the integrated fan and nozzle components, inlet valves, propellers, vanes, pumps and filters. Failure to optimize any one of those details will detract from the unit’s effectiveness,” Peterson said.
The new machine’s 60 hp fan is fed by a manifold of 30 brass nozzles that are specifically sized and positioned for the new design. The DB-100 features simple, user-defined 359˚ oscillation, along with adjustable elevation from -7˚ to 45˚. It can also be outfitted with a dosing pump to accurately meter in surfactants or tackifiers to further enhance binding of dust particles. A 10 hp (7.5 kW) booster pump elevates water pressure as high as 200 psi for outstanding droplet production, and the DB-100 can be set up to run potable or non-potable water.
A wye delta starting system reduces initial energy requirements, and DCT recommends a minimum of 10 PSI water pressure. The units include an in-line filter and 1-1/2 in. cam-and-groove quick disconnect female coupling. They can be ordered with international motors to meet standards for any location around the world.
Because it can run unattended for long periods, the DB-100 can free up manpower and equipment by eliminating the need for water trucks or sprinklers, delivering a short payback period for many users. The versatile device is also well suited to automated control, and can be wired to operate according to a wide range of sensor inputs, including weather conditions and even specific air particulate levels.