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air-fuel equivalence ratio and timescales of kinetic reaction and oxygen transport were used to analyze the combustion of underground coal fires at different temperature stages. At high temperature stage, due to the fast rate of kinetic reaction, oxygen concentration transported from galleries or cracks was lower than that required by theoretical kinetic reaction. Thus the oxygen consumption rate of coal combustion was controlled by oxygen transport rate and the coal fires were incomplete combustion because of lean oxygen concentration. According to the Single-Particle Reaction- Diffusion model proposed by Krishnaswamy, a formula to estimate oxygen consumption rate of underground coal fires with lean oxygen concentration and incomplete combustion at high temperature was developed. A numerical case study was conducted to analyze and examine the proposed formula. The investigated results show that the proposed formula can effectively estimate oxygen consumption rale controlled by oxygen transport at high temperature. [ABSTRACT FROM AUTHOR]

To analyze the oxidation kinetics reason that self-ignition tendency of coal with different metamorphic degree are different, based on the basic assumptions of coal adiabatic self-heating process, a oxidation kinetics analysis on the reaction characteristics of the process was made combined with the Arrhenius equation, then this paper studied four feature parameters: adiabatic process apparent activation energy (Ec), the critical temperature ( Tc) and the average heating rates each stages of the adiabatic process, (Rhm,Rjs), finally, the relationship between each characteristic parameter and coal metamorphic level was made by numerical fitting. It is show that the oxidation kinetics characteristics are characterized by the four parameters (Ec, Tc, Rhm and Rjs) in the difficulty degree of coal self-ignition reaction (Ec),the difficulty degree of control ( Tc) and the heating speed (Rhm and Rjs) ;with the increase of coal metamorphic grade, Ec has a logarithmic relation with it, Tc has a linear relation, however, Rhm and Rjs have a negative exponent relation. The difference of self-ignition tendency of coal with different metamorphic degree is studied on oxidation kinetics, and it is of great significance to self-ignition control. [ABSTRACT FROM AUTHOR]