While there are many materials that fall under the combustible dust category that make you think, “really, that’s combustible?,” coal dust is certainly not one of them. And unfortunately, the coal industry’s attempt to use a more advantageous type, Powder River Basin (PRB) coal has only increased their combustible dust risk. Found in southeast Montana and northeast Wyoming, PRB coal has a lower sulfur content and is more plentiful than traditional Appalachian bituminous coal. It’s also more combustible. Producing more dust than regular bituminous coal, it has low BTU and high moisture content, making spontaneous combustion a real concern. In fact, small fires are reported almost weekly in the industry. The PRB coal-user’s group has addressed the issue by developing stringent recommendations and practices for fire-prevention. These include guidelines on CO2 monitoring, coal storage, and of course best maintenance practices.
The NFPA also addresses coal in NFPA 120 Standard for Fire Prevention and Control in Coal Mines. There is also a chapter on coal dust in NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations that addresses:
- coal storage and cautions about spontaneous heating and how that can be limited in the coal pile storage through separation of different types of coal that are not chemically compatible, working the pile to prevent dead pockets of coal, and locating the pile away from heat sources
- storage in bins, silos and bunkers including the provision of dust tight barriers between boiler houses and the area above the silos, bunkers, or bins
- dust suppression and control including methods to control dust, proper cleaning methods, warning against the use of vigorous sweeping or compressed air and the use of listed vacuum cleaners for the dust environment or the use of low velocity water
- coal conveying and handling structures with attention to designing the structures to limit the ledges for the accumulation of dust by utilizing beam shields or placing the structural members exterior to the building; the section also addresses the use of approved equipment in the areas, the electrical classification of the areas and means to reduce the hazard of static electricity through permanent bonding and grounding
- fire protection being recommended in coal handling structures, conveyors, bag-type dust collectors
