Dust suppression units - Types, Efficiency and GRT's Superior Dosing units

What are dust suppression units?

Dust suppression using water alone aims to bind and capture dust particles using either wetting at low pressure or misting and fogging at high pressure to match the particle size of dust particles. It is achieved through the use of dust suppression units which produce droplets and fine mists and fogs of dust suppressant solutions that bind and attach to dust particles. The nozzles nebulize the dust suppression solution to smaller particles to match the size of small particulate matter. To give more surface coverage dust suppression units can be vertically adjustable with a horizontal rotation that treats a wide area. In previously penned articles, we discussed advantages and disadvantages of fog cannon dust suppression and went on to compare wet vs dry dust suppression systems. The prime focus of our article this week is to understand wet dust suppression units with emphasis on the following points:              

• What are the different types of dust suppression units?
• The science behind the efficiency of dust suppression units?
• Superior dust suppression units utilised by GRT 

What are the different types of dust suppression units? 

There are several different types of dust suppression units on the market. These are used for dust suppression in demolition sites, for environmental repair, landfills, stockpiles in mining, civil earthworks and any other application that requires dust suppression. We look at some examples and what they offer.

Skid self-contained dust suppression unit has an independent dust suppression system ideal for use in larger indoor or outdoor spaces. Equipped with a fog cannon installed on a manual telescopic mast, which raises to 4m and has a range of 20m. It features a 1000L plastic water tank, which supplies water for 160 minutes. It also has a built 4Kva generator making it fully self-contained.

The 240V large dust suppression unit is perfectly suitable for any outdoor job and can spray from 10 degrees to 50 degrees with a spray range of 13m. It is extremely light and portable and can be used for a variety of different applications in small working areas.

The dust fighter dust suppression unit offers a spray coverage of 6500m2 (without wind) and a spray distance of 50m (without wind). It offers adjustable speed to suit different-sized sites and applications.

The 5000 Liter Honda Powered Aqua-V AquaMax Unit consists of a triple deflector system that easily suppresses dust with the added convenience of a remote actuator for in-cab on/off control. Each deflector is individually controlled by ball valves for directional spray control.

The V22 Dust Controller is a long projection range dust suppression unit with a complete revolution pivot function and is most suitable for covering large areas. The nozzle head and outer nozzle ring generate a finely atomized mist, which binds the dust particles and prevents them from spreading. 

What is the science behind the efficiency of dust suppression units? 

The very direct question in this section should rather be how does dust suppressant droplet size affect binding of the dust particle? Well, for your larger dust suppressant droplets, which are produced at low pressure but at very close proximity to the dust, suppression site the intention is to achieve wetting. Wetting deals with the larger dust particles but it has its limitations when it comes to smaller dust particle sizes. Larger dust suppressant droplets fall to the ground, wetting everything in its path. The smaller dust particle follows streamlines, where it is swept around the dust suppressant droplet without being bound by the dust suppressant particle.

However, when the dust suppressant particles are atomized to form a mist, the correct size dust suppressant droplet facilitates efficient dust suppression. The dust particle and dust suppressant droplet collide and bond together falling down the airstream without wetting. The working principle behind the negative-pressure mist curtain dust suppression unit is based on the Venturi effect. When a confined flow passes through a reduced cross-section, the flow velocity increases, with its flow velocity being inversely proportional to the cross-section it is passing through. From Bernoulli’s law, it is known that fluid pressure decreases as flow velocity increases, so low pressure will occur near a high-velocity flow, resulting in the adsorption effect. The mechanism of dust particles capture by mist droplets is based on aerodynamics and factors which contribute to effective capture include inertial collision, interception, diffusion, gravity effect, electrostatic effect and coagulation. 

Superior dust suppression units – GRT’s automated dosing units

The previously mentioned units focus on water-alone, ignoring the fact that water is chemically incompatible with the dust it is trying to manage. GRT utilises automated dosing units to change and improve the characteristics of the water to optimise the chemical and physical performance of the dust control system. These have been designed and manufactured in Australia and range from simple hand-operated pumps to fully automated dosing units used by the world’s largest mining and quarrying companies.

GRT’s dosing units inject GRT products such as GRT Haul-Loc or GRT: Activate into the flow stream of the water at your standpipe or hydrant fill points at GRT’s recommended dosage rates, calibrated to the rate of flow in the water supply pipe. The units are tailor-made for each customer to suit their individual needs and ensure accurate dosing of the product with the following options:

• Solar-powered, generator or mains power compatible. 
• Manual, remote control, or automated start. 
• Permanently fixed, mobile skids/bunds, truck, miner or drill-mounted units available. 
• Can be dual purposed to also dose different GRT products. 

Another typical application of GRT’s automated dosing units is in blast pattern dust control. GRT DC: Binder prevents dust generation from the hazardous piles of drill cuttings produced by drill & blast activities. Using GRT’s automated dosing units, the product is accurately dosed at low dosage rates into the site water carts and then sprayed over the drill pattern. GRT’s specialized long-chain polymer (LCP) technology ensure a little goes a long way. 

Superiority in dust suppression units ensures that clients get value for their investment whilst providing a safe working environment for workers and communities within the vicinity of dust-generating activities. GRTs automated dosing units complement the different chemical technologies that suppress dust at its source. 

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REFERENCES 

Colinet et al. 2010. Best Practices for Dust Control in Coal Mining. IC 9517. Department of Health and Human Services. 

Colinet et al. 2010. Best Practices for Dust Control in Metal/Nonmetal Mining. IC 9521. Department of Health and Human Services. 

Dust suppression. Retrieved 19/06/21. 

Dust suppression unit. Retrieved 19/06/21. 

Dust suppression units. Retrieved 19/06/21.

Ma et al. 2020. Effect of spraying on coal dust diffusion in a coal mine based on a numerical simulation. Environmental Pollution. 264. 114717. 1-15. 

Logachev, I.N. and Logachev, K.I. 2014. Industrial Air Quality and Ventilation: Controlling Dust Emissions. CRC Press. Taylor & Francis Group. 

Peng et al. 2019. Research on mine dust suppression by spraying: Development of an air assisted PM10 control device based on CFD technology. Advanced Powder Technology. 

Peng et al. 2020. Optimization of external spray negative-pressure mist-curtain dust suppression devices for road headers based on a multi-factor orthogonal experiment. Journal of Cleaner Production. 275. 123603. 1 – 17. 

Wang, P., Zhang, K., and Liu, R. 2019. Influence of air supply pressure on atomization characteristics and dust-suppression efficiency of the internal-mixing air-assisted atomizing nozzle. Powder Technology. 

Xu et al. 2019. Multi-factor numerical simulation study on spray dust suppression device in coal mining process. Energy. 

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