Geology Reference
In-Depth Information
ability of ventilation with inert gasses to extinguish the fire. This is why nitrogen or CO
2
gas inertization
techniques require extremely long and expensive application time to cause any reduction to the deep seated
combustion. The wetting ability of the compressed foam is essential to soak and saturate the ash, in order to reach
and cool the combustion area.
Fire Science
F
ire science teaches us that any surface that is wet with water cannot be hotter than the boiling temperature of the water,
which is roughly 212 °F. This temperature is very important in coal-mine firefighting, because coal must be hotter than
212 °F to pyrolyze or degrade by heat into volatile gasses, which burn. In other words, if it is wet, it will not burn.
Compressed Foam
I
nert gasses cannot wet the coal, like compressed foam does. When we use an inert gas to inflate the compressed
foam, we create an inert foam. When the water drains out of the foam and the bubbles burst, the inert gas is released
into the surrounding atmosphere. This helps to smother the fire by diluting the oxygen. The water that drains out of
the foam wets the coal and cools the fuel below the fire gas distillation temperature of 212 °F.
The compressed foam can be modified with the chemical stabilizers which will cause the foam to become even
more durable. This allows the foam to build upon itself, as the stream from the bore hole continues to inject more
foam. The pressure in the bore hole will begin to rise as it fills the mine from floor to ceiling. This is also known as
“
As the pressure rises from the foam pushing against the foam filled cavity, this pressure forces the
foam into cracks, crevices, and fissures that can lead off in all directions. These cracks, crevices, and fissures are
very hard to extinguish and can be hidden ignition sources that can come to life weeks or months after extinguish-
ing efforts have ceased. Additional bore holes are drilled to provide pressure relief and we often see foam coming
out of nearby bore holes, which gives us the ability to monitor the direction and progress of the foam in the mine.
We then extend the discharge hose to the relief holes that become the
roofing out.
”
“
new
”
injection sites.
Quality Control
W
e have developed an essential quality control program for the foam. This quality control program assures we
produce the right foam for the right purpose. Our quality control program is designed to test every batch of
chemical to be certain there have been no mistakes in the chemical compositions or mixing ratios. Mistakes can
produce weak or inferior foam. Weak or inferior foam cannot accomplish the planned results. For additional quality
control, we add a simple connection to our well head adaptor with a valve that can be opened at any time to see the
quality of the foam being injected into the mine (Figure 19.1.1). This sometimes presents a new problem of how to
dispose of all the test foam we have accumulated on the surface. The problem is not generally a serious one, but
involves our employees playing in the foam on their break time.
New Developments
C
AFSCO is developing new ways to use encapsulated CO
2
. The CO
2
will be captured from the source of
combustion which causes global warming such as electric power generators and other fossil-fuel combustion
processes. The CO
2
foam can then be used to extinguish deep seated coal-mine fires. The carbon encapsulated
foam can be permanently stored in the subterranean cavities. The CO
2
gas is heavier than air and will gravitate to
the lowest part of the cavity. The water and foamable agent that drains from the CO
2
foam will also gravitate to the
lowest part of the subterranean cavity where it will be pumped back to the surface where it will be recycled to
continue the creation of the new CO
2
foam.
The simplicity of the compressed-foam system allows us to use other chemicals and products such as waste fly ash,
and bottom ash created by the electric power companies that burn coal. This fly ash and bottom ash can be mixed with
water to produce a foamable slurry that can be turned into compressed foam and injected into the burned out areas,
thereby creating structurally sound, solid blocks of waste material to prevent subsidence and damage to homes and
