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When the dust settles

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Dust suppression techniques have come a long way from turning a hose on a dusty process.

Today, dust suppression techniques utilise a smart combination of valves, instrumentation and controllers that identify the wetting needs of a specific zone at a specific time for precise dust control.

Modern dust suppression is about optimising water usage and making the most of maintenance free hardware life cycles.

The mining boom, coupled with growing demand from the new markets China and India, means effective dust control is more important than ever before.

Cooee general manager Frank Vos told Australian Mining that minesites are beginning to feel the pinch and are consequently pushing production levels to ensure expectations are met.

“In the end, it all comes down to productivity,” Vos said.

“Mine operators need to know just how much their haul road is costing them.”

According to Vos, water trucks as the sole method for dust control is ineffective and inadequate.

In order to achieve effective dust control with water trucks, every inch of the haul road must be watered down.

Haul trucks are unable to overtake the water trucks for safety reasons, which in turns slows traffic.

“Another issue with water trucks is that they speed up road degradation,” Vos said.

“By using water to keep dust down, it breaks up the tension on the road, so minesites are forced to employ graders to regenerate the road. The problem is, graders generally travel at speeds of 8km/h which also effects the flow of traffic.”

Vos recommended mine operators trial other dust suppression techniques that will complement a minesite’s water truck technology.

“In the past, some products required haul roads to be closed for 12 hours. Newer products realise haul roads need to be immediately trafficable," Vos said.

Water is, without fail, the main suppression medium on minesites and there are many dust suppression treatments that can utilise water more effectively.

Most involve the use of chemicals that agglomerate dust particles into larger sized particles, which decreases the tendency for dust particles to become airborne.

These chemicals are often used on coal stockpiles.

In addition surfactants are also used to make water ‘wetter’, allowing the water to penetrate more effectively into road surfaces by decreasing the surface tension effects.

Micro Fresh Filters business development manager Stephen Gledhill told Australian Mining that the number one improvement in dust control is the use of other technology to complement water trucks.

Generally speaking, the chemicals used in alliance with water trucks, provide durable control and suppression of fugitive dust caused by wind and vehicle movements.

The dust suppression chemicals mix into the water during vehicle movement and can be applied during normal operations, with no need to stop traffic.

“The risk of vehicle collision on busy haul roads is much higher when visibility is reduced.

“Dust suppressants must be an economical water management tool that in no way interfere adversely with minesite operations, safety or the environment,” he said.

Combating the problem

Bürkert Fluid Control Systems Hunter Valley representative Keith Dumbrill told Australian Mining that fixed-position dust suppression is the best way to avoid interference with mine operations, as it may be built into site infrastructure as needed.

The problem of locally mounted dust suppression hardware being adversely affected by the demanding environment is removed by using a new pneumatic actuation concept that removes the need for internal piloting.

Remotely piloted pneumatic ‘slave’ valves are unaffected by the fine particle pollution found in recycled dust suppression water.

These valves deliver joint benefits of strong feed air delivery to the site of actuation (without drop-off) and long service life, as all sensitive components are removed from the demanding environment.

“The introduction of pneumatic valves opened the potential for incorporating high-level pneumatic control functionality or complete automation systems for more efficient and reliable water usage,” Dumbrill said.

“With precise control, dust suppression systems optimise when and where water is deployed.”

According to Dumbrill, precise control and precise dust suppression is vital to a minesite because it is directly linked with the occupational health and safety of the employees, members of surrounding communities, as well as environmental pollution.

“Effective dust suppression stops the inhalation of coal dust,” he said.

“The same issue is related to members of local communities which, in the absence of effective dust suppression, can be blanketed with gritty dusk when wind conditions are right.”

Mt Thorley Warkworth coal mine in the Hunter Valley is used to being on the receiving end of an extensive build up of gritty black coal dust. Knowing this can occur, the minesite is constantly monitoring wind and dust levels to minimise the impact the dust may have on near neighbours.

The dust can clogs pipes, mechanical parts and other equipment that has not been specifically engineered for the demanding environment.

Rio Tinto Hunter Valley environmental specialist Andrew Speechly told Australian Mining that dust suppression was vital to the productivity of a minesite.

“In the event of high volumes of dust, production equipment such as draglines are stood down to mitigate off-site impacts,” he said.

According to Speechly, there has been considerable attention paid to the development and deployment of new technology over the past few years.

Rio Tinto Coal Australia’s (RTCA) Mt Thorley Warkworth site employed Burkert Fluid Control Systems to suppress the dust with coal processing, transportation and the operation OH&S issues that can result from gritty black coal dust.

More than nine million tonnes per annum (Mtpa) of feed coal is mined at the Mt Thorley Warkworth operation and delivered to the Coal Preparation plant, where it is off loaded into the dump hoppers.

Processing yields 5.8 Mtpa of saleable coal.

Due to the movements of considerable volumes of coal, dust suppression in these areas is critical, and is achieved by wetting coal with water. This water is recycled and reused.

In the past, pipes, valves and solenoid valves (actuated with water) were clogged with scale due to poor water integrity, voiding the dust suppression system.

These faults occurred approximately once per month on the solenoid valve, necessitating the removal of the coil in order to clean the blocked internal parts of the pilot valve.

Today, the Mt Thorley Warkworth operation is investigating the use of Modular control to increase the efficiency of water carts operating within the pits.

“The modular system will allow the carts to be directed automatically and advise operators of locations within the pit that require watering,” Speechly said.

“This will improve efficiency by overcoming the issue of water carts being over allocated to certain areas of the pit and not others.”

Stephen Gledhill

Business Development Manager

Micro Fresh Filters

stephen_gledhill@microfreshfilters.com

www.microfreshfilters.com

Andrew Speechly

Hunter Valley Environmental Specialist

Rio Tinto Coal Australia

info@rtca.riotinto.com.au

www.riotintocoalaustralia.com.au

Frank Vos

General Manager

Cooee

fvos@cooeeproducts.com.au

www.cooeeproducts.com.au

Keith Dumbrill

Hunter Valley Burkert representative

Burkert Fluid Control Systems

www.burkert.com.au

sales.au@burkert.com

 

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