Equivalences and lower ignition limits of coal dust and methane mixtures

Technical Report · Sun Jan 01 00:00:00 EST 1967

OSTI ID:7081247

Singer, J M; Cook, E B; Grumer, J

This study was undertaken to obtain some fundamental information about hazardous mixtures of coal dust and methane (firedamp) likely to occur in mines. Fuel concentration limits for ignition of mixtures of coal dust, methane, and air have been determined by a hot-gas ignition method. The limiting concentration of each of the two fuels was usually less than that corresponding to its lean flammability limit in air. The lean limits of flammability of coal dust vary with the type and size of the dust; in this study coal dust concentrations were less than 80 mg/liter. Ignition jets were turbulent pulses (emerging from a channel of 0.5-cm diam) resulting from explosions of stoichiometric mixtures of methane, oxygen, and nitrogen. The objectives were to establish quantitative relations between concentrations of each fuel at ignition limits of hybrid mixtures and to study the mechanism of ignition by hot turbulent gases. Empirical equations were fitted to concentrations for four coals, namely, Pittsburgh seam (sizes A, B, and C), Sewell No. 2 seam, Pocahontas No. 3 seam, and anthracite. Equivalences of coal dust to methane were computed from these equations; equivalence being defined as -..delta..c/..delta..m where c is the coal dust concentrated and m is the methane concentration, each in milligrams per liter of air. It was found that the equivalence increases as the temperature of the hot-gas jet decreases. In general, the equivalence is also an inverse function of volatile content of the coal and a direct function of the particle size. However, volatile content in itself is not a sufficient correlating variable, nor is the specific surface area of the coal dust. Some evidence of a synergistic combination of coal dust and methane was obtained in certain concentration ranges.

• Research Organization: Bureau of Mines, Washington, D.C. (USA)
• OSTI ID: 7081247
• Report Number(s): BM-RI-6931
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
COAL FINES
IGNITION
COAL MINES
SAFETY
METHANE
AIR
COAL
DUSTS
MIXTURES
PARTICLE SIZE
ALKANES
CARBONACEOUS MATERIALS
CRYOGENIC FLUIDS
DISPERSIONS
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUELS
GASES
HYDROCARBONS
MINES
ORGANIC COMPOUNDS
SIZE
014000* - Coal
Lignite
& Peat- Combustion
016000 - Coal
Lignite
& Peat- Health & Safety
012000 - Coal
Lignite
& Peat- Mining