Setting the example in the fight against dust

The Hi-Quality Group is a family-owned Australian business that specialises in natural quarry and recycled products, transport services and waste management solutions. The group manages seven quarry, recycling and processing sites throughout New South Wales and a single quarry in Bulla, Victoria, about 30km northwest of the Melbourne CBD and less than 13km from Melbourne?s Tullamarine Airport.
{{image2-a:r-w:250}}Hi-Quality Group?s Bulla Quarry contains predominantly basalt deposits, with deeper reserves of sand and clay. Consequently Hi-Quality?s end products include basalt concrete aggregates that have been certified for use in concrete and asphalt applications. Its sand deposits are also suitable for ready mix concrete applications and concrete and asphalt production. The Bulla site?s products include pebbles and washed sand.
Hi-Quality is also managing a prescribed industrial waste landfill and recycling facility at the Bulla premises, accepting disposable materials such as cleanfill Category C contaminated soil, asbestos waste and acid-sulphate soil. The landfill facility abides by all Victorian Environmental Protection Agency (EPA) approvals and requirements.
To meet customer demand, which is currently outweighing supply, Hi-Quality Group engaged a mobile crushing contractor to produce its concrete aggregate to specification at the Sunbury site. This includes end products of 20mm, 14-10mm and 7mm aggregate and a 5?m (micron) crusher dust.
The biggest challenge for Hi-Quality?s contractor on this project (who for the purposes of this article asked not to be specifically named) was dust mitigation. It was required as part of the contract to abide by EPA and Victorian Department of Environment and Primary Industries requirements agreed to by Hi-Quality at the Bulla site. The nature of the basalt at the Bulla site means that when it is crushed into fines, it generates significant amounts of dust.
Various attempts by the contractor?s mobile crew to control the dust with water proved difficult and in some instances created more complications. Spraying water onto the grizzly bars led to blockage, screens had to be cleaned out at least once a day and water would carry excess fines into the end product, putting it out of spec.
The mobile crushing contractor was familiar with Polo Citrus, a specialist supplier in natural orange oil and biodegradable technology that has developed a range of products to reduce dust emissions in most extractive industry applications, so engaged the company to find a solution at the Bulla quarry site.
Polo Citrus? key ?weapon? against dust in crushing applications has been Polo BDS, a biodegradable dust suppression agent. Unlike traditional dust control agents, Polo BDS employs foam micro-bubbles at the application point and downstream prior to crushing and screening.
?The dust particles adhere to the foam and go through the crushing and screening process,? Polo Citrus business development manager Adam Gelly explained. ?The airborne dust particles that would go airborne stick to the foam. The foam dries as it goes through the rest of the process and the dust falls off. In most cases, the foam will last right through to the stackers, so you?re likely to get dust suppression right through to the stockpiles, up to about 90 per cent better in most cases.?
In turn, the foam, when mixed with a single litre of water, expands up to 100 times to capture the airborne particles. This means the plant only has to provide six litres of water per minute, resulting in considerable water savings. Gelly added that the foam also dries more quickly, reducing material build up on belts and in the plant, leaving a better quality product at the end of the process ? that is, no ?dripping? stockpiles?.
Polo Citrus managing director Brett Aisen said that while there are other suppliers that offer similar dust suppressant agents, they are not quite like Polo BDS. ?Our concentrate has been designed around our foaming unit,? he emphasised. ?We built them both to match. The concentrate wouldn?t work with any other piece of equipment.
?Our product?s different, our equipment?s different, it?s been built to purpose,? Aisen added. ?The quarrying industry doesn?t need the bells and whistles, they need a robust product that?s reliable. And the product itself, the concentrate, was redesigned a couple of years ago to actually go out to market with a price decrease, to make it cheaper, and to make it more cost-effective. So it?s very much designed for the quarry industry. We?re very much aware of the costs and we?ve tried to build a product that fits the purpose.?
To date, Polo Citrus has installed over 100 foam units throughout Australia, notably for clients such as Hazell Bros, Boral Contract Crushing and M&M Crushing. The company?s dust solutions have also been exported to ?half a dozen? operations in New Zealand, three in France and four in Norway. Polo Citrus is looking to further expand its dust solutions into Europe.
Polo Citrus delivered the Polo BDS foam unit, along with a 1000 litre container of the solution, to the mobile crushing contractor at Hi-Quality?s Bulla Quarry. Two pipes are run from the unit and the solution container to the mobile plant ? one spray bar into the feed hopper of the impactor and the other into the feed bowl of the cone. The solution is then sprayed over the aggregate as it passes the transfer points.
?It takes air, water and power, it?s derived back to a system,? Gelly elaborated of the process. ?The water and solution are combined in a mixing chamber and then they head through a vent where the air is added. Likewise, the solution is made into a foam, the foam is pumped up through 40mm lines to the areas where the most dust is generated and it is sprayed on the material that goes through the plant. It has a flow-on effect throughout the plant right through to the stacker.?
The mobile crushing contractor was pleased with the way the Polo BDS successfully reduced the dust overflow in its mobile operations and assisted the crew. The mobile plant operators found that the Polo BDS could minimise their water usage and reduce the downtime in cleaning screens from once or twice a day to just once every two days.
The contractor stated that other quarry operators that experience dust problems would benefit from employing Polo BDS. ?Thanks to Polo Citrus, we?re getting a better quality product because we?re not using up water and carrying the fines over into the aggregate. That means the end user is getting a product that?s in spec ? and that?s essential to our business,? he said.

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