An experimental study was made of the oxidation of bituminous coal in the temperature range 80-180°C. The weight increase of the sample, and oxygen consumption during oxidation were measured. Two different flow configurations were used to determine the oxygen consumption rate: a continuous flow technique (CF) in which reactor effluent gases were analyzed by gas chromatography; and a pulse feed (PF) technique in which small and known amounts of various N2/O2 mixtures were injected into a carrier gas stream before the gas entered the reactor; the oxygen up-take was measured by G.C. analysis. The PF technique yielded the reaction rate in the first moments of oxidation, during which the oxygen consumption rate was relatively high. The effect of temperature, oxygen partial pressure, particle size, and gas flow rate were evaluated. The rate of oxidation decreased with increasing time of oxidation: the lower the temperature, the faster the rate decreased. At 100°C the rate was independent of particle size, indicating full chemical control while at 160° the rate was affected by internal diffusion, since oxidation of larger particle sizes resulted in a decrease in the rate. The rate was also affected by the time during which previously oxidized samples were kept in an inert atmosphere (restoration time): the restoration of reactivity increased with restoration time. Initial rates measured by the PF technique were used to obtain the activation energy and the order of reaction. Activation energies of 8-9 Kcal/mole and an order of reaction of about 0.9 were found,. © 1988 Combustion Institute.

An experimental study on oxidation rates of coal at low temperature

PETARCA, LUIGI;TOGNOTTI, LEONARDO;
1988

Abstract

An experimental study was made of the oxidation of bituminous coal in the temperature range 80-180°C. The weight increase of the sample, and oxygen consumption during oxidation were measured. Two different flow configurations were used to determine the oxygen consumption rate: a continuous flow technique (CF) in which reactor effluent gases were analyzed by gas chromatography; and a pulse feed (PF) technique in which small and known amounts of various N2/O2 mixtures were injected into a carrier gas stream before the gas entered the reactor; the oxygen up-take was measured by G.C. analysis. The PF technique yielded the reaction rate in the first moments of oxidation, during which the oxygen consumption rate was relatively high. The effect of temperature, oxygen partial pressure, particle size, and gas flow rate were evaluated. The rate of oxidation decreased with increasing time of oxidation: the lower the temperature, the faster the rate decreased. At 100°C the rate was independent of particle size, indicating full chemical control while at 160° the rate was affected by internal diffusion, since oxidation of larger particle sizes resulted in a decrease in the rate. The rate was also affected by the time during which previously oxidized samples were kept in an inert atmosphere (restoration time): the restoration of reactivity increased with restoration time. Initial rates measured by the PF technique were used to obtain the activation energy and the order of reaction. Activation energies of 8-9 Kcal/mole and an order of reaction of about 0.9 were found,. © 1988 Combustion Institute.
Petarca, Luigi; Tognotti, Leonardo; Zanelli, S.; Bertozzi, G.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/9062
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