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Coal dust combustion in a stirred reactor: evaluation of combustion and extinction mechanics in coal dust explosion flames.
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, OFR 67-83, 1981 Jan; :1-78
The relative effects of seven additives (N2, He, CO2, fly ash, KHCO3, NaCl, and NH4H2PO4) on extinction limits of coal dust flames have been studied in a 200-cm3 jet-stirred reactor. Conditions in the reactor are known to be comparable to those at the head of a coal dust explosion flame. KHCO3, NaCl, and NH4H2PO4 are commercial fire retardants and are presumed to be chemically active, but test results support the presumption only for NaCl and NH4H2PO4. Curves of weight-of-additive to suppress the flame and temperature at extinction were obtained as a function of stoichiometry. For all but the NaCl and NH4H2PO4, 20% to 30% additive in the mixture of coal plus air plus additive is required for extinction of maximum combustibility. With NaCl and NH4H2PO4, the figures were 13% and 4%, respectively. The extinction mechanism is presumed to be chain termination of volatiles combustion. Extinction temperatures were found to be substantially independent of kind of additive, with essentially constant values in the fuel-rich region, and declining as fuel concentration decreased.
Coal dust; Additives; Dust explosions; Fire retardants; Combustion; Safety; Test chambers; Nitrogen; Helium; Carbon dioxide; Fly ash; Sodium chloride; Potassium carbonates; Flammability testing; Ammonium phosphate
CP; Final Contract Report
NTIS Accession No.
OFR 67-83; Contract-J0199018
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, OFR 67-83
Ohio State University
Page last reviewed: May 5, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division