Done and dusted

Meteorological forecasts and dispersion models are helping minesites win the war against dust. Jessica Darnbrough writes for Australian Mining.

Dust control has come a long way from using a hose as the primary solution to a dusty process.

Today, minesites are looking for pro­active solutions to dust control.

Minesites are starting to look to weather bureaus in much the same way psychics look to the stars for guidance

and information.

Meteorological forecasts combined with atmospheric dispersion models and planned operating data are helping to determine the likelihood of dust on the surrounding environment.

Sinclair Knight Merz’s senior atmo­spheric scientist Jon Harper told Aus­tralian Mining that long range forecasts

and dispersion models allow minesites to find out what will happen tomorrow and react today.

“By using long range forecasts mine­sites are able to predict down to the hour what the weather conditions are going to be like and what the probability of dust is in the area, allowing the site enough time to get active and target the storm before it targets the site,” he said.

“A facility can either adjust their oper­ational plans or implement dust reduc­tion strategies to reduce the predicted impact.”

Harper said dust emissions from min­ing, material processing and ship load­ing operations are an environmental issue of increasing concern to government regu­lators and the community.

These could be generated from wind, when wind speed exceeds a threshold velocity, or from mechanical processes that generate and potentially release par­ticulate matter.

These processes include material move­ment (such as grinding operations, drop­ping at conveyor transfer points, stack­ing, reclaiming and ship loading), blasting and vehicular movement over unsealed or dust laden surfaces.

Dust monitoring programs historic­ally focused on ambient dust concentra­tions using a range of methodologies in­

clud­ing High Volume Air Samplers (HVAS), Tapered Element Oscillating Microbal­ance (TEOM) and Beta Attenuation Mon­itors (BAM).

While all three are able to provide information to a facility, they have the drawback of requiring 240 V power and are normally located at, or adjacent to, a sensitive receptor.

“This complicates the process of using these monitors as part of a dust man­agement strategy as by the time an issue with dust is realised it is often too late to adequately rectify the situation,” Harper said.

Wind effect

According to Harper, light scattering tech­niques such as the MetOne E-Sampler are increasingly being used on facilities.

“These monitors can be operated using a 12 V power source which means it is possible to locate them in isolated locations and use solar power to charge a deep cycle battery,” he said.

“The dust concentrations and meteor­o­logical parameters recorded by the mon­itors are relayed to a computer for pro­cessing. If the concentrations could result in adverse impacts, then a computer will initiate a series of warnings including text messages or emails to mine management or specifically designed sirens.”

According to Harper, however, this is still a reactive method that requires the prompt attention of personnel to initiate the chosen controls and reduction strate­gies.

“It would be preferable to know in advance if the expected meteorological conditions are conducive to a facility hav­ing an issue at a receptor,” he said.

“Previously facilities have relied solely on generalised weather forecasts that are applicable to a large area and may not capture specific localised meteorological events such as katabatic winds and the timing of sea breezes.”

“With advances in our understand­ing of meteorological parameters, the development of reliable forecasting ­software and the increasingly powerful personal computers, it is now possible to obtain accurate meteorological forecasts for spe­cific locations.

“To use the forecasting to its full po­tential the meteorological data should be coupled to an atmospheric dispersion model and planned operating data to increase understanding of the potential impacts.”

According to the Australian Bureau of Meteorology, minesites can, and often are, supplied with information specific to their location.

“We can tailor information to suit the specific needs of each industry,” Aus­tralian Bureau of Meteorology’s duty

forecaster Richard Russell told Australian Mining.

“The information supplied to each site is designed to their specific need and will talk in trends.

“We can predict the 10 minute wind speed average for a mine or, conversely, let them know what is likely to occur from hour to hour,” Russell said.

“Currently, we do forecasts for the La Trobe Valley, however, this isn’t so much with regards to the likelihood of

wind as it is to the likelihood of a fire.

Moisture control

Andre Wyzenbeek from John Morris Scientific agreed that a proactive solution was the best solution.

“Weather stations, on the surface, don’t seem that impor­tant. However, if you know that the wind is picking up then you can wet the areas that have low moisture levels,” Wyzenbeek told Australian Mining.

According to Wyzenbeek, measuring moisture is another method minesites are employ­ing in their fight against airborne particulates.

“If you can measure the amount of moisture in the ground you can determine whether or not the area needs watering and thus if it is an area that could contribute to the dust problem onsite,” Wyzenbeek said.

“Water is a precious resource, as are wetting agents, so there is no point wetting something to prevent dust if the area is already sufficiently moist.

“It is just a waste of re­sourc­es.”

Jon Harper

Environmental Scientist

SKM

08 9268 9650

jharper@skm.com.au

Andre Wyzenbeek

John Morris Scientific

02 9417 8877

Andrew@johnmorris.com.au

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