Advances in stonedusting

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Advances in stonedusting
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• I will talk about and show footage relating to
• the basics about Stonedust
• methane and coal dust explosions
• why previous wet dusting attempts failed
• ACARP project C16014 - Advances in wet slurry
  dusting
• how the slurry additive process works
• and look at the equipment involved in the process
• Some information within this presentation is well
  known by the coal industry. It has been included
  to provide a summary of how various elements
  interact.

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Stone dust

• Stone dust or calcium carbonate is used in
  underground coal mines as a primary inerting
  agent, in the prevention of coal dust explosions.
• The application of dry stone dust creates large
  quantities of airborne dust along the ventilation
  circuit, requiring the extraction of inbye
  personnel.
• In a methane explosion, a pressure pulse travels
  through the immediate area of the mine.
• This wave raises any dust into suspension, both
  coal and stonedust.
• Areas treated with adequate quantities of stone
  dust, will render the dust cloud inert and a coal
  dust explosion will not occur.

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Methane

• The ignition of methane in an underground mine is
  not common but does occur.
• Friction sparks from continuous miner and shearer
  drum picks have provided ignition sources for
  methane gas.
• Other potential sources are cable flashes, belt
  friction, heating and open fires.
• Given the right conditions a methane explosion
  itself is most explosive at 9 general body and
  has deadly consequences.
• The following footage is a weaker explosion that
  compares to a typical 10 metre overdrive allowed
  to accumulate a methane concentration of only
  7.5.
• If an ignition source is present.

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7.5 Methane Explosion
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7.5 Methane Explosion
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7.5 Methane Explosion
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Coal dust

• Minimising the make of coal dust and reducing
  float dust is an ongoing challenge for all coal
  operations.
• Areas that were stone dusted once, if left
  unmaintained, accumulate coal dust deposits
  providing fuel for an explosion to propagate.
• Only 4-5mm of dry dust will be lifted in a weak
  methane explosion. The more float dust
  accumulated, the less of the underlying stone
  dust will be lifted.
• We saw that a methane explosion creates a fire
  ball that travels behind the shock wave and hits
  the dust cloud.
• Insufficient quantities of stonedust in
  suspension will allow the coal dust to ignite
  will obvious catastrophic consequences.

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Coal dust explosion1 kg
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Coal dust explosion75kg
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Coal dust explosion75kg
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Wet stone dusting

• Wet dusting was always viewed as an opportunity
  to help overcome reductions in cutting times due
  to stoppages caused by stone dusting.
• The onset of 7 day operations compounded the
  problem and attempts were made to apply stone
  dust as a slurry.
• This allowed crews to continue production while
  wet dusting was carried out in the ventilation
  intakes of the panels.
• Wet dusting is a process of creating a stone dust
  / water slurry and pumping it onto the mines
  walls.
• The intent was to replicate the conventional dry
  dusting without the need to withdraw inbye
  personnel.

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Wet stone dusting
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Why wet dusting does not work

• The application of wet dusting was proven however
  the final product failed to provide adequate
  inerting qualities.
• When stone dust comes in contact with water the
  particles partly dissolve.
• As the slurry dries, the dissolved solution moves
  between the stonedust particles forming a bonding
  bridge that locks the particles together.
• This is referred to as The Caking Effect.
• This caking reduces the amount of stone dust
  raised into suspension, creating enough doubt on
  its effectiveness as an inerting agent.
• Inspectors in NSW and Qld rightfully issued
  directives restricting the use of slurry dusting

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ACARP project C16014

• Australian Coal Association Research Program
  (ACARP) contracted Mining Attachments to research
  and develop a wet slurry treatment process that
  could overcome the caking effect.
• Applied Australia were requested to engineer an
  additive that would work but had to be end user
  friendly.
• In 2006 the additive was ready to be trialled and
  tested on large scale.
• The 3 stage project spanned over two years.
• Surface full scale spray trials
• Underground spraying trials
• Full scale explosion testing
• Industry monitors were required to assess each
  stage objectives were achieved, before advancing
  onto the next.

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Airo-Dust Additive

• Airo-Dust Additive has been designed with the
  primary focus of providing a safe product for use
  in the underground mining environment
• The MSDS outlines all the health and safety
  requirements.
• Non-combustible
• Operators wear standard PPE
• Classified Non-dangerous goods
• Warnings in regards to skin, eyes, inhalation and
  ingestion are similar to those of concentrated
  household dishwashing detergent
• pH of the additive is between 6-8 (water 7.0
  neutral)
• The required dosage of 10 litres of additive is
  required to treat one tonne of stone dust.
• Airo-Dust Additive is a trademark of Illinois
  Tool Works Inc.

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Surface full scale trials
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Surface full scale trials

• Samples were taken during the surface spraying
  trials and sent for particle size distribution.
• Results showed little change to the original
  particle sizes, supporting the anti caking
  ability of the process.
• A simulated explosion demonstrated that the
  treated wet dust could be put into suspension.
• The project moved to Cook Colliery, one of many
  operations that supported the project.
• Mining Attachments fit for purpose equipment was
  mobilised onsite and the first underground trials
  began.

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Underground Trials
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Underground Trials

• The experience gathered from the 6 months of
  trials allowed the necessary time to refine the
  process with dedicated personnel allowed to focus
  on achieving the projects aims.
• Industry monitors evaluated the underground
  trials, operating the equipment and viewing other
  areas of the mine previously dusted using the new
  slurry additive process.
• The project then moved into the final stages of
  conducting full scale explosion testing by third
  parties.
• The new slurry additive process was named
  Airo-Dust.
• The CSIR explosion testing facility in
  Kloppersbos South Africa, hosted comparative Dry
  vs Airo-Dust testing, facilitated by Skillpro
  Services.

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Explosion Testing

• The testing facility comprises of a 200m steel
  pipe tunnel that has a methane mixing station and
  ignition centre one end and the other end is
  open.

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Explosion Testing

• Trays were prepared prior to testing.
• Prior to each test explosion, trays were weighed
  and secured into the tunnel.
• After the blast the loss of stone dust from each
  tray was recorded.
• High and low speed video footage captured each
  blast.

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Explosion Testing
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Explosion Testing

• On average 40 more stonedust was lifted from the
  Airo-Dust trays compared to the stonedust lifted
  from the Dry dust trays.

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Explosion Testing

• On average the depth of dust lifted by the
  explosions also varied.
• 4-5mm in the case of the Dry dust trays
• in most cases the Airo-Dust trays were empty
  (30mm)

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Explosion Testing

• Full details of this project including all the
  results from the explosion and underground
  testing can be obtained on line by visiting
• www.acarp.com.au Project number C16014

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How the Airo-Dusting process works

• Stonedust slurry is made by mixing two parts
  stonedust with 1 part water.
• The Airo-Dust additive is dosed into the pump out
  line which provides a protection barrier around
  the stone dust particles, minimising the caking
  effect.
• Air is entrained into the line to create a foam.
  The product is highly vesicular, trapping
  millions of tiny air pockets or voids in the
  product as it dries.
• From the explosion testing it was evident that a
  methane pressure wave is able to penetrate these
  voids, smashing through the surface and raising
  the stonedust into suspension.

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How the Airo-Dusting process works

• The equipment consists of a mixing tank and
  paddle, slurry pumps, additive pumps and the foam
  generation equipment.
• The system is non adjustable making the process
  less complicated and simple to use.
• The additive is accurately dosed into the pump
  out line and delivers a steady stream of shaving
  cream like slurry to either a hand held nossel or
  machine spray bars.
• Existing equipment can be modified or new custom
  made Airo-Dusters can be supplied.
• The Airo-Dust additive is supplied and serviced
  Australia wide by ITWs Applied Australia or
  nominated overseas agent.

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Equipment
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Equipment
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Getting started

• A copy of the final ACARP report has been sent to
  both NSW and Queensland inspectors for review.
• The NSW DPI have assembled a review committee to
  firstly review the ACARP report and secondly
  participate in the initial underground trials in
  NSW.
• This will allow the Airo-Dusting process to be
  viewed from both a technical and practical
  perspective.
• Operations can now make application to the NSW
  DPI to use the Airo-Dusting process underground.

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Current participating sites

• Grasstree Mine
• 1 x existing wet duster modified into an
  Airo-Duster
• 2 x new Airo-dusters
• Greenside Colliery (South Africa)
• 1 x new Airo-Duster
• North Goonyella
• 1 x Hire Airo-Duster
• Centennial Coal (Mandalong, Clarence, Springvale)
• DPI application pending
• Vale (Integra Coal)
• DPI application pending

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Airo-Dusting