Mining Project: Improved Float Dust Controls in Underground Coal Mines
To reduce the risks associated with accumulations of combustible and explosive materials.
The accumulation of float coal dust (FCD) in underground mines is an explosion hazard that threatens all underground coal workers. This hazard is addressed by the application of rock dust to maintain an incombustible content of the total dust on mine surfaces at a minimum of 80%, but inadequate rock dusting practices can leave miners exposed to an explosion risk. Therefore, the development of controls aimed at reducing FCD accumulation in mine entries will provide another layer of protection in preventing mine explosions.
While dust controls and rock dusting are the main methods used to reduce this hazard, improved float dust source controls will reduce the accumulation of FCD, in turn improving the efficacy of current rock dusting practices. Since 2001, U.S. coal mine disasters have resulted in 59 fatalities, and 80% of these were attributed to explosions that were enhanced by the accumulation of float coal dust in the mine entries. While the occurrence of dust-fueled explosions is relatively low—three documented instances in 2001, 2006, and 2010—these incidents represented 31%, 36%, and 60% of the underground coal mining fatalities for their respective years. These explosions typically occur when methane gas ignites and the resulting pressure wave re-entrains coal dust that has settled out of the ventilating air onto the floor, roof, and ribs of the mine entries.
To address this problem, this project has three research aims, which will be achieved as described below:
- Evaluate the use of enclosures and/or chemical treatments for controlling emissions of FCD from non-cutting processes. This aim will use both laboratory testing and in-mine testing to examine additional source controls of float dust that are not directly related to the cutting of coal. The aim builds upon the research of a previous FCD project by using a transfer point water spray system in-mine that can be modified to allow for chemical treatments.
- Evaluate in the field and optimize the full-scale water curtain to reduce FCD accumulations in longwall returns. A full-scale water curtain aimed at reducing the amount of airborne float coal dust that accumulates in a longwall return was developed through laboratory testing as part of this project’s predecessor. Through the current project, the water curtain will be deployed on a longwall section and evaluated using a continuous float dust monitor.
- Develop a water-powered longwall shearer scrubber to capture FCD generated by cutting. Through a combination of computational fluid dynamics (CFD) and laboratory studies, this aim will focus on the design and evaluation of a water-powered scrubber for float dust that can be used on a longwall shearer.
The anticipated impact of this research is that the three FCD controls developed will be used by the mining industry to reduce accumulations of combustible material or to improve the ratio of rock dust to combustible material on deposition surfaces, thereby increasing the efficacy of current rock dusting practices and reducing the likelihood of a dust-fueled mine explosion. A reduction of combustible material along with non-caking rock dust may provide an opportunity for a business case for future rock dusting practices. There is also potential for controls developed in this project to have application in other industries that seek to control combustible dust.
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