CAFS married with nitrogen brings mine fire under control
Volume 24 Number3
What started as a roof fall became a carbon monoxide release in the working area of a coal mine and caused a complete shut down at Consolidated Buchanan No. 1 coal mine in Virginia. Multi-million dollar mining machinery sat entombed and at risk.
Within 72 hours of notification on July 16, 2007, CAFSCO mobilized and responded to the incident with a nitrogen foam injection plan. Massive amounts of nitrogen have been used to dilute oxygen in coal mine environments as a method to suffocate fires. This method of fire control is expensive and time consuming.? It can take months of high volume nitrogen injection to dilute the toxic mine gases to a safe limit. Rather than inject massive amounts of nitrogen into the mine to dilute the CO2?- an effective but time consuming and expensive undertaking - CAFSCO requested Chemguard to develop a more stable Class A foam that would help reduce the volume of costly nitrogen and improve the dissipation rate. In other words, control the density and the drainage time of the environmentally-friendly bubbles.
Because that compressed foam is a semi-solid, nitrogen-enhanced foam, it displaces the toxic gases while slowly releasing conservative amounts of nitrogen, maintaining dilution in the foamed areas of the mine.?The foam has penetrating and wetting characteristics that saturate the interior of the mine from floor to ceiling, entering all cracks and crevices, effectively soaking out all sources of ignition. Compressed foam is generated with a commercial air compressor and a water pump that uses a fire hose to convey the dense and durable foam bubbles to bore holes that are drilled or punched into the selected areas of the coal mine.
Using this nitrogen method to inject over 700 million gallons of compressed nitrogen foam, into a five square mile area, CAFSCO displaced carbon monoxide and toxic gasses out of the mine and into a gas recovery system which had the capability of separating the methane from the toxic gases. The methane recovered was used for commercial applications. Using the Class A foam concentrate can shorten recovery time and cut costs in toxic gases dissipation and fire fighting operations in subsurface environments.
Gas injection with CO2?can have limited beneficial effects on a fire burning in a sub-surface coal mine. The gas migrates through burned out channels and takes the same path that the combustion ventilation takes. The gas, when heated, tends to rise and travels in the roof areas of the burned out channels before exiting the coal mine with the combustion gases. If the CO2?does not get heated by the fire, it remains heavier than air and will seek paths in the refuse that flow out of the lower areas of the coal mine. In either case, CO2?by itself is not very efficient in controlling combustion because it cannot cool the carbonaceous Class A fuel in the way a liquid can. Carbon dioxide produces carbonic acid when it comes in contact with the water, which is produced as a by-product of the original combustion. This acid can cause additional pollution problems in a coal mine.
A liquid such as water will not reach the upper areas of the burned out voids and channels in the coal mine and will always flow to the lowest parts of the coal mine, missing the combustion that always tends to rise to the top of the areas involved. Water does not penetrate into the Class A fuels that have been covered with the products of combustion such as the carbonaceous soot that is water repellant. It is extremely difficult to use water to soak out a coal mine fire. The pollution caused from run-off is extremely hazardous because its been in contact with the products of combustion.
?Mark Cummins, the original inventor of the Compressed Air Foam System (CAFS), U.S. Patents 4318443 and 4457375, discovered compressed foam bubbles are unique from all other types of foam that are comprised of thin films of surfactant treated water which encapsulate a small amount of air that is 78 percent inert nitrogen and 21 percent oxygen that is not available as a free gas to feed the fire because it is encapsulated in the bubbles. When the wet bubbles contact the extreme heat of combustion, the water in the bubbles explodes into steam and expands in the form of gas volume 1,700 times the volume of the original water. This expansion causes a positive pressure in the area of combustion, which prevents free air oxygen from entering the area from any direction. All of the burned out channels and voids begin to exhaust away from this area with no incoming air or ventilation to feed the fire. CAFSCO's experience allows us to control the most intense sub-surface fires involved in deep coal mine fires.
Surfactants in the foaming agents are similar to common dishwashing detergents and are not harmful to the environment. In fact, they stop the vast toxic releases from the products of combustion because they are very hydrophilic (carbon loving). Foam bubbles act as a filter to attract the toxic hydrocarbon gases and keep the carcinogens, such as benzene, inside the coal mine instead of allowing them to exhaust to the outside air.? The water in the thin films of the bubbles cools every contacted surface, fills the voids in the channels and voids from floor to ceiling and blocking any unwanted ventilation of gases in or out of the coal mine. The surfactants also cause the water that is released from the bubbles to penetrate deep into the Class A matter everywhere it contacts a surface, and reduces or completely stops any run-off water pollution.?
CAFSCO have applied for patents for several other concepts using compressed foam.? The foam bubble provides the perfect environment for a microbe population that can conscientiously consume the oxygen?and create the CO2?that helps extinguish the fires and prevent new fires from occurring in the subterranean environment.
?The unique environment of the bubble provides the necessary water, nutrients and gases needed for the selected microbes to become healthy and vigorous and to begin to multiply into hungry masses looking for new sources of carbon to consume. The compressed foam is the best method to transport and to apply the living environments of the bubbles to the areas within the coal and oil bearing seams beneath the earth's surface, where the microbes can find the new sources of carbon to begin the process of converting the carbon in the oil and coal into beneficial, and in some cases, clean burning fuel gases.
General Electric Research Division?is discussing the possibility of a joint venture with CAFSCO to use microbe knowledge and compressed foam technology to provide a new way of getting clean energy out of the coal and oil without having to dig or pump the carbon from below the earth's surface. There will be no waste left on the surface and the CO2?produced from the natural gas power plants will be used to feed the?algae ponds that turn it into oxygen and diesel fuel.
According to scientific documentation, the more fire means the more CO2, which has been used to extinguish fires for many years. The reason fire fighters have not noticed it or used it until now is because they use water to fight fires. Water only absorbs heat faster than it is being created by the fire and, in extreme fires and heat, steam from the water (H2O) is only one phase away from separating into its elements, hydrogen (an explosive gas) and oxygen, (the gas that makes hydrogen explode).
Firefighters cannot do much with the CO2?produced by the fire when they use water. But foam is a different ball game. The surfactants in the foam are carbon loving, which means the surfactant molecules attach to the carbon by electron bonding. That is why the CAFS foam cleans the air of CO2?and explosive coal dust when it is sprayed through an entry. The foam also cools the massive amount of CO2?produced by the fire. The CO2?is heavier than air when cooled, and when the CAFS foam is used to block the ventilation of this gas, it becomes an effective fire extinguishing agent that helps put the fire out in areas where the foam has not reached or cannot reach. That is the secret. It is simple, but it can be developed into a new technology.
Through 30 plus years of experience with the use of CAFS, subsurface fires create a unique situation that allows CAFSCO to tailor a complete site specific, turn-key injection plan to extinguish extreme fires or use the unique ability of specialized enhanced foam to extinguish hidden ignition sources.
CAFSCO research continues to develop earth friendly microbiological methods to create inert environments in the sealed areas of coal mines.
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