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Surfactants testing offers encouraging outcomes

 

In quarrying, the containment and reduction of dust emissions is an ongoing concern and challenge. An Australian business with experience across the extractive industries has devised a dust reduction solution using the best equipment and testing techniques in modern science.

Quarry Mining and Construction Equipment Pty Ltd (aka Quarry Mining) is a privately owned Australian business with an entrepreneurial spirit and a passion for customer service.  The company has been supplying the Australian mining, quarrying and tunnelling industries with drilling consumables and related products for more than 38 years. 

Quarry Mining’s team of experienced personnel ensures the highest level of technical and product service to projects.  

The company’s head office and manufacturing base is located at Beresfield, New South Wales, with offices in Mackay, Queensland, Melbourne, Victoria and a heat treatment plant in Sydney, NSW. The company is committed to delivering ongoing solutions including on-site support product trialling and procedures training.

Quarry Mining’s managing director is Kari Armitage, who has a track record of working collaboratively with researchers and customers to solve industry problems in a cost-effective way.

“Over the years we have worked on many R&D [research and development] projects with our customers who often come to us with their unique problems for us to help them solve,” she said. “Our team has over 150 years of combined experience in underground mining and construction, mostly ‘hands-on‘ operating drill rigs and hand-held bolters, so we understand the challenging and often hazardous environments that are mines, tunnels and quarries. 

“Health and safety is at the forefront of our customer’s minds and we are always looking at new ways we can engage and partner with them to solve current and emerging issues,” Armitage added. “More stringent workplace exposure standards for both coal and silica respirable dust have recently been introduced in response to a rapid rise in the number of reported cases of occupational dust diseases such as black lung and silicosis. We saw an opportunity to develop and trial a dust suppressant product so we could assist our customers address this critical issue.”

Effective from 1 July, 2020, the acceptable Work Exposure Standard (WES) for respirable crystalline silica in nearly all jurisdictions across Australia is the eight-hour time-weighted average (TWA) of 0.05 mg/m3 under the Work Health and Safety Regulations 2011. (Tasmania is the only jurisdiction to not lower the WES from a TWA of 0.1mg/m3.)

The Quarry Mining team sought the counsel of Mark Shepherd, the compliance and industry support manager at Coal Services and the chairman of the NSW Standing Dust Committee. Shepherd’s advice was to establish some sound baseline data under a controlled environment testing regime with stringent test methods and measurable outcomes for comparison. This work would be critical to the success of any dust suppressant product.  Acting upon this guidance, further investigation lead Quarry Mining to a team of researchers at Curtin University’s Western Australian School of Mines in Kalgoorlie who were active in this space. Their established wind tunnel (Figure 1) was ideal for Quarry Mining’s experimental work and significant meaningful outcomes have eventuated from this work using samples of dust sourced from different sites around the country. 

Some leading types of engineering controls for dust suppression are: 

  • Automation involving total removal of workers from dusty environments.
  • Water infusion to increase the moisture content in-situ.
  • High pressure water and atomising sprays to optimise water spray dust capture using very fine water droplets.
  • Foams used to blanket broken ground and dust.
  • Surfactants used to increase the wetability of coal and silica dusts. 
The Dosatron water-powered dosing pump is a simple, clever, and proven system that can be installed directly in the water supply line.

SURFACTANTS FOR DUST SUPPRESSION

Surfactants, an abbreviation for surface acting agents, are a simple and cost-effective control measure to reduce water tension, thereby improving the wetting capability of water droplets and increasing dust capture efficiency.

“Surfactants have been used across the industry for decades but failed to gain a foothold in a meaningful way as field performance was so unreliable,” Quarry Mining’s business development manager Neil Alston said. “One of our customers challenged us to build a wind tunnel so we could validate performance in a more controlled environment.  We took up the challenge and went about designing the test equipment but found the design had to be underpinned by complex and expensive CFD [computational fluid dynamics] modelling. An alternative was to collaborate with University researchers and to use existing experimental equipment. We discovered a team of researchers at Curtin University’s WA School of Mines in Kalgoorlie who were active in this space, so we approached them to work with us. Their established wind tunnel was ideal for our experimental work. 

“Despite Covid-19 restrictions during 2020, we successfully scoped and conducted a series of experiments with our commercial surfactant product called DUST KING and we were suitably impressed with the results,” Alston said. “Three variants of the DUST KING product were tested with respirable size fraction thermal coal, coking coal and silica dust suspended in fine water droplets. Of greatest interest was silica dust as this rock type is present in all mines, tunnels and quarries.”

The test results showed DUST KING at a one part to 3000 parts water (or 1:3000) dose rate improved the mean suppression efficiency for the capture of crystalline silica dust from 23.8 per cent (water only) to 37.7 per cent and for DUST KING B the improvement was even greater at 50.2 per cent (see Figure 2).  Similar results have been confirmed in underground trials at production faces with the product applied using small dosing units connected into the water spray circuit.

Figure 1. A schematic diagram of the wind tunnel: (1) dust generation part, (2) spray part, (3) dust measurement part, (4) dust collection part.

DRILLING AND PROCESSING APPLICATIONS

DUST KING can be applied in many versatile ways to suit each project.  It can be fed through the drill rigs themselves, applied through spray systems on to stockpiles, conveyors or transfer points and is also applicable for use with fog cannons.

Quarry Mining can tailor the dosing method to suit customer requirements. As agents for the highly reputable USA TEI brand, the company has the expertise and can offer the TEI range of water misting units available in sizes to suit specific equipment.

Figure 2. Wind tunnel test results. Mean suppression efficiency of crystalline silica with three variants of DUST KING surfactant products.

HAUL ROADS APPLICATIONS

Beyond underground mines and tunnels, DUST KING also works effectively to reduce dust on haul roads in surface operations. Haul road dust impacts are wide-ranging and include: 

  • Safety (visible dust).
  • Health of workers (respirable dust).
  • Environmental (fugitive dust emissions).
  • Water consumption.
  • Plant and roadway maintenance costs. 

The same DUST KING product used to improve the suppression efficiency of water sprays works progressively on haul roads to initially dampen the surface, bind the loose or fine dust particles and then, after repeat applications, strengthen and waterproof the road surface. Once the tough outer layer forms, moisture is retained rather than evaporates with water only. The durability of the upper layer (skin), will be a function of weather and traffic type and flow.  Even if the skin degrades over time, the larger particles are less likely to become airborne and the skin can be more readily re-formed. 

The product is readily applied to haul roads at open cut mines and quarries by dosing water carts with either pneumatic or electric pump systems tailored to customer requirements. 

“A remote solar-powered dosing system has been implemented at a large open cut mine in central WA,” Alston explained. “Water cart operators have a remote fob in the cab which when activated is used to deliver a fixed amount of DUST KING product safely and reliably into the water cart during each fill. The water carts become more effective as dust suppression with each application.”

Haul road dust impacts include reduced visibility, respirable dust risks, fugitive dust emissions, excessive water consumption, and plant and roadway maintenance costs.

 

The tough upper layer skin developed on the roadway surface.

Quarry Mining has also developed a dosing system suitable for quarries and civil applications. The Dosatron water-powered dosing pump is a simple, clever, and proven system that can be installed directly in the water supply line. Water as the power source, activates the Dosatron, which takes up the required percentage of concentrate injecting into the water. Inside the Dosatron dosing pump, the concentrate is mixed with the water, and the water pressure forces the solution downstream. Once the dosage is set, the required dose of product is maintained precisely, regardless of variations in flow and pressure. 

The system includes: 

  • A D8WL3000 Dosatron pump suited to a 1:3000 dose rate at a maximum flow rate of 150 litres per minute and a maximum pressure of eight bar.
  • A 200-litre moulded polyethylene tank.
  • A protective steel cage fitted with forklift tynes.

The DUST KING product has now been independently tested and successfully trialled at various underground and surface operations to deliver a substantial improvement in dust suppression. A range of dosing system designs is now available to suit customer requirements. “We have come a long way in the last 18 months gathering reliable laboratory and field data, so our customers have confidence in our product before use at their own operations,” Kari Armitage said. “DUST KING has given us the opportunity to strengthen the bond with our drilling customers, primarily in underground mines and tunnels, and allowed us to foster new relationships with open cut mines and quarries with the collective goal of reducing dust disease across all these industries.” •

For more information, visit the Quarry Mining & Construction Equipment website: quarrymining.com/products/dust-suppression/

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