UNDERGROUND MINE FIRES
Comment - Foam extinguishment of coal mine fires, especially abandoned coal mine fires, has never really had a thorough and comprehensive field test. The technology advances over the past 20 years can potentially provide a workable alternative to "doing nothing" or excavation. Funding for a demonstration has been continuously elusive. Unfortunately, the number of fires remains constant, and the alternative costs are continuously increasing.
In order to extinguish a coal mine fire it is necessary to keep the fire zone in a non-combustible condition, in this case, free of air, until the fire is extinguished, and then maintain that condition until the temperature is reduced to a suitable level. This requires two performance characteristics for foam extinguishment to be successful: (1) filling the fire zone with foam, and (2) keeping the fire zone filled with foam. In order to achieve these goals, the foam system - feed rate of foam and the decay rate of foam - must be high enough to achieve filling, and then the foam, itself, must be "permanent" enough to allow the cooling to proceed. Various combinations of drain time and feed rate can potentially achieve this goal, but simple economics defines that extended drain time foams are the best choice.
This is no more complicated than filling a bucket with water - the delivery rate (foam feed) must be greater than the leakage rate (drain time) or the bucket will never fill.
This argument is not unique to abandoned coal mine fires, as any book on the subject of fire fighting will describe the same balance requirements for water extinguishment or conventional foam extinguishment.
The Office of Surface Mining is proceeding with a foamed fire extinguishment at the Percy Mine Fire, North Union Township, Fayette County, Pennsylvania. The bids were due on October 2, 1997. The drain time specification for the extinguishment foam is ten minutes or greater, but without specifying the percent drained - 1% or 99%, makes a big difference, so it is unlikely to be successful - foamman's opinion. The results, when available, will be interesting.
On Sunday, December 21, 1997, the Pittsburgh Post-Gazette published a lengthy story about this mine fire. No specific conclusions were presented, just the fact that the fire has been burning for more than 20 years. Hopefully, Mike Bucsko, the reporter, will follow the story to its conclusion.
On August 5, 1998, I received an e-mail message from Richard Balogh, Office of Surface Mining, Pittsburgh, PA. He explains that the objective of the Percy Mine Fire project is NOT extinguishment, "...but it is an attempt at creating a mine level barrier to the advance of the fire toward Youngstown. Unfortunately adequate funding is not available to attempt to extinguish the fire. Once the barrier is created, the project responsibility will remain with the Commonwealth of Pennsylvania, Department of Environmental Protection."
He continues, "[w]e are using the fire fighting foam to lower temperatures as needed to permit the placement of foaming cement to create the barrier. Secondarily, we are trying the foam in some intensely burning areas to see what foam application characteristics provide the maximum amount of quenching/cooling."
Jump ahead 2003 -
Aqueous foam has finally been used to extinguish a fire in an active mine. Mark Cummins of Cummins Industries has used a proprietary foam composition and 100% nitrogen expansion gas for extinguishment of a fire at the Pinnacle Mine in West Virginia. A brief description has been published in International Longwall News and is posted here for convenience - "New Multi-Class Foam Suppresses Fire."
Everybody is doing it now, April, 2004 -
A recent announcement has revealed that U.S. Foam, Longview, TX, has extinguished a mine fire in Utah using their "Hellfighter System", which is not further defined. This extinguishment was apparently executed at the Skyline Mine in October, 2002, but has just now been announced for patent protection reasons. This extinguishment also used 100% nitrogen expansion gas. A patent application on the subject has been filed and published:
Ozment, A., U.S. 2004 0016552, filed July 16, 2003
"Methods and Apparatus for Fighting Fires in Confined Areas"