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Dust Dust Management MANAGING MINING RISKS

Effective dust control solutions for respirable and nuisance dusts

Dry fog dust control solution on a conveyor
Dry Fog on a Conveyor Transfer at a coal mine in Queensland

Dust issues in all aspects of mineral mining and processing are commonplace and a nuisance and danger to workers and equipment. MARC Technologies, a wholly-owned subsidiary of ALS Limited, has the experience and know-how to apply class-leading solutions and technologies that provide effective dust control to manage dust problems, down to respirable levels.

Effective dust control nozzle

Since dust generation can occur wherever a product is disturbed or stockpiled, processes such as truck dumps, crushing, screening, conveyor transfers, stacking and reclaiming, train loading and unloading, and ship loading and unloading all have the potential to create harmful emissions and require an effective control method to suppress dust. 

dust control droplet size agglomeration

Dry Fog Dust Suppression Systems

There are many technologies available for dust mitigation but few can effectively suppress airborne, respirable dust. For example, water sprays can be used to wet the product’s material surface to prevent dust generation, but this can cause issues with carryback and belt wear.

Dry fog dust control on a bucket wheel reclaimer

Dry Fog on a bucketwheel conveyor at a coal terminal in Columbia

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Additionally, once the product is disturbed, unwetted dry surfaces can be exposed and dust liberated. Furthermore, water sprays are ineffective in suppressing airborne and respirable dust because their droplet size is too large to attach to surrounding dust particles in the airstream.

As a result, the dust migrates around the water droplets and can escape the area. Dry Fog adds less than 0.05% moisture by volume to the product, and as such can be used with moisture-sensitive materials such as cement and clinker, phosphates and bauxite.

Dust Solutions Inc. (DSI) Dry Fog™ systems use an ultra-sonic nozzle, air and water to produce fog particles less than 10 microns. Dry to the touch, this fog is used to scrub out airborne, respirable dust by binding with like size particles and dropping them out of suspension.

Dry Fog™ uses around 1/5th of the water used in a traditional water spray which eliminates issues with carryback and belt wear. Blockages are rare since the nozzle’s venturi design includes relatively large water and air orifices, and the nozzle vibrates slightly when in operation, which prevents the nozzle from being blocked externally. The systems also offer dual filtration to factor out the poor quality water supply.

NESCO PRESSURE MISTING SYSTEMS

With over 1000 installations in the US and beyond, NESCO is a well-established and well respected high pressure misting dust suppression system that mitigates dust generation by forcing controlled amounts of moisture into the product. This, in turn, minimises the liberation of dust further down the process, allowing less water to be used downstream. A single NESCO system can typically treat multiple areas such as truck dumps, primary, secondary and tertiary crushers, screens and stackers.

Screen for a lithium plant in Western Australia, before NESCO startup

Screen for a lithium plant in Western Australia, before NESCO startup

The systems run at around 15 bar, which allows for the generation of finer droplet sizes, which is important for control of fugitive dust. This also means that NESCO is effective in controlling dust within the material handling process by mounting sprays in strategic positions to knock down generated dust. Sprays into areas such as crushers also allow moisture penetration into newly exposed dry surfaces and this lessens subsequent dust generation downstream.

Screen for a lithium plant in Western Australia, after NESCO startup dust control on

Screen for a lithium plant in Western Australia, after NESCO startup

Dusttamer Windfences for effective dust control

DustTamer™ Windfences is also an effective dust control method for larger areas such as stockpiles. DustTamer systems drastically reduce wind velocity within a shielded area by exerting a drag force on oncoming wind and allowing a portion of the wind to penetrate the screen, evening out wind pressures on either side of the fence.  

Stockpile windfence designed to prevent dust escaping the area

Stockpile windfence designed to prevent dust escaping the area

Controlling the top surface of the pile with water cannons offers limited protection, and this has to be constantly applied, and there are detrimental and unwanted effects with excess water on the material. 

Windfence in combination with Dry FogTM around a ROM bin

Windfence in combination with Dry FogTM around a ROM bin

Windfences, use permanent structure, and hard-wearing, UV stable knitted polyester material that is strong enough to be used in cyclonic regions, and are guaranteed for 20 years, with many installations that have been installed for many more with no replacement of material. 

Smaller windfence panels can also be used around ROM bin structures, large hoppers and to clad troublesome transfer or crushing towers to mitigate escaping dust by reducing the wind velocity through the structure. Used in conjunction with other effective dust control measures such as Dry Fogtm, these can add up to an effective dust control method that has minimal running costs.

DSI systems are supplied by MARC Technologies, who have been successfully delivering dust control solutions to the mining and industrial sectors since 1995.  MARC Technologies is a wholly-owned subsidiary of the Brisbane based ALS, providing a global presence. www.marctech.com.au

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