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Experimental study on low-temperature oxidation of an Australian coal

Wang, H., Dlugogorski, B.Z. and Kennedy, E.M. (1999) Experimental study on low-temperature oxidation of an Australian coal. Energy & Fuels, 13 (6). pp. 1173-1179.

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Low-temperature oxidation of an Australian coal is examined in an isothermal flow reactor, operated at atmospheric pressure and 50 °C. Strong dependence of the rates of consumption of oxygen and the formation of carbon dioxide are observed on coal particle size and oxygen concentration in the gas stream. Following an induction period, oxygen consumption proceeds at a quasi steady state rate indicating that this process is limited by oxygen diffusion in the pores of coal particles. The rate of carbon dioxide production decreases with time, due to the progressive reduction in the number of active sites at the internal surfaces of pores in coal particles. This points to the kinetic control of CO 2 production. The apparent reaction order for oxygen consumption at quasi steady state varies between 0.63 for large and 0.41 for small particles, with the latter number providing the best estimate of the intrinsic order. Fitting the rate of CO 2 production to the expression developed by Kam et al. for higher temperatures suggests that, under the present experimental conditions, CO 2 is formed via parallel pathways of (i) direct oxidation of coal to CO 2 and (ii) formation and subsequent decomposition of solid coal-oxygen complexes, with carbon dioxide produced mainly via the first pathway at long times. The results presented in this paper have applications to self-heating and spontaneous combustion of coal.

Item Type: Journal Article
Publisher: American Chemical Society
Copyright: © 1999 American Chemical Society
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