Transcript Advances in Stonedusting - AiroDust

Advances in stonedusting
1

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.
2
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.
3
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………….
4
7.5% Methane
Explosion
5
7.5% Methane
Explosion
6
7.5% Methane
Explosion
7
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.
8
Coal dust explosion
1 kg
9
Coal dust explosion
75kg
10
Coal dust explosion
75kg
11
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.
12
Wet stone dusting
13
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
14
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.
15
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.
16
Surface full scale
trials
17
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.
18
Underground Trials
19
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 v’s Airo-Dust testing, facilitated by
Skillpro Services.
20
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.
21
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.
22
Explosion Testing
23
Explosion Testing

On average 40% more stonedust was lifted from the Airo-Dust
trays compared to the stonedust lifted from the Dry dust trays.
4000
3000
0
1420
3315
1845
2300
1810
3035
820
500
1485
1000
1755
2855
1754
1500
3218
2000
2075
2500
3462
Loss of stone dust (g)
3500
6
10
11
12
13
14
Dry stone dust trays
3462
1754
1755
2075
1810
1845
820
Slurry additive process trays
3218
2855
1485
3035
2300
3315
1420
Explosion test number
24
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)
25
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
26
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.
27
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 AiroDusters can be supplied.

The Airo-Dust additive is supplied and serviced Australia wide
by ITW’s Applied Australia or nominated overseas agent.
28
Equipment
29
Equipment
30
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.
31
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
32
Airo-Dusting
33