Determination of global kinetics of coal volatiles combustion

Values of global kinetic constants for the combustion of coal volatiles have been determined for the first time for volatiles from three coals (two bituminous coals and a Texas lignite). The combustion rates of the volatiles were found to vary over an order of magnitude at flame temperatures. The activation energies varied from 12.1 to 17.4 kcal/mole and the frequency factors varied from 1.6 * 10;The volatiles were pyrolyzed from crushed coal drawn on weighed trays through a gas-fired muffle furnace, and they were burned at the top of a tube in an intense back-mix volume treated theoretically as a stirred reactor. Two types of experiment were carried out: partial combustion measurements near the stoichiometric for all coals from which the global kinetics were determined; and extinction limits for the Pittsburgh ;In a final result, comparison of calculated isothermal pyrolysis times and volatiles combustion times indicates that combustion may be slower than or of the same order as pyrolysis, indicating a need for consideration of finite volatiles combustion kinetics in coal flame modeling.