Taking into account all dust emissions on site to formulate a dust management plan is essential to implementing cost effective solutions.
This is the view taken by environmental scientists with project delivery firm Sinclair Knight Merz (SKM), said to be a leader in dust management in the Pilbara region of Western Australia.
Senior environmental scientist with SKM Karen Roberts said that dust management was often viewed entirely from an engineering perspective before considering site management and procedural opportunities for dust reductions.
“SKM examines all potential emissions from the mine or ship loading facility, determine appropriate dust reduction strategies, including procedural, management and engineering, and help prioritise controls based on cost effectiveness,” Roberts said.
“This includes emissions from vehicles dumping to stockpiles, crushing and screening, front end loaders, dozers, transfer stations, and wind erosion from stockpiles.
“The company also examines open areas and identifies how worker behaviour and awareness can assist with reducing dust emissions.”
This approach achieves the most cost effective reductions, according to Roberts.
“For instance, if vehicles are a source of dust, scientists determine why and examine solutions such as use of chemical suppressants, sealing roads, reducing speeds and installing wheel shaker grids between dusty and non-dusty areas,” Roberts said.
“If wind erosion is a problem, we determine if open areas need to be open and if so, determine whether access can be restricted or vegetation, polymers or mulching used to reduce emissions.
“If crushers or conveyors are producing dust SKM investigates if they are being properly maintained, if water sprays are working adequately, if conveyor skirts have been correctly fitted and if gates are being left open.”
Roberts said that the company’s monitoring technique involved determining dust emission characteristics by using calibrated hand held monitors.
“A back calculation method is used to convert the emission rate into grams per second which can then be used in a dispersion model,” Roberts said.
“Once all sources have been characterised the model can be run and the largest contributors to dust levels at a receptor, such as an office, residence or rare flora, can be determined.
“The largest emitters can be targeted and the most appropriate and cost effective reduction strategies can be implemented.”
Roberts said that further monitoring was conducted once the dust reduction strategy had been implemented to ensure that the predicted reduction had been achieved, and to assist with ongoing management of dust from the facility.
SKM has experience in dust management on projects such as Rio Tinto Iron Ore projects at Cape Lambert, Dampier and Paraburdoo, and Alcoa Kwinana.
The firm also undertook the BHP Billiton Iron Ore Dust Identification, Characterisation and Abatement Project as part of the Mine and Port Developments Joint Venture with Fluor in the Pilbara region of Western Australia.
“This project used laboratory testing undertaken by BHP Billiton Iron Ore at its research laboratories in Newcastle to determine the dust characteristics of all iron ore products through Port Hedland, and to determine the emission rate for site sources,” Roberts said.
“The emission rates were then incorporated into a Dispersion Model and validated against ambient air quality monitoring data within Port Hedland.
The validated model was then used to determine the sources that had the greatest impact on Port Hedland and appropriate reductions strategies implemented.”
Roberts and SKM environmental (atmospheric) scientist Jon Harper will present a paper on The Importance of Monitoring and Modelling in Dust Management at the Dust Management in Mining Conference in Brisbane 19 to 21 September 2007.
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