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ABSTRACT
In order to study the influence of water addition in the low-temperature pre-pyrolysis process on the coal spontaneous combustibility, programmed heating experiments were carried out to test secondary oxidation characteristics of coal which was pretreated by isothermal pyrolysis at 80°C with different water content of 5.96%, 10.11%, 13.92%, and 17.48%. The results showed that the concentration of CO and CO2 decreased, and tended to be constant along with time during the pre-pyrolysis process in which moisture had a positive effect on CO2 release. The thermostatic pre-heating at 80°C inhibited the spontaneous combustion of coal, while the presence of water during the pre-pyrolysis process showed the competitive characteristics of promoting and inhibiting the coal spontaneous combustion at the same time. From the perspective of CO and CO2 production, oxygen consumption rate, and exothermicity, it was found that the coal pre-pyrolyzed with water content of 10.11% was easiest to self-heat, followed by the cases with water content of 5.96%, 13.92%, and 17.48%, respectively. The Pearson correlation coefficient method was adopted to conduct correlation analysis on values of ∆CO/∆O2, CO/O2, and CO2/O2 concentration with respect to coal exothermic intensity. It was found that the value of CO/O2 concentration has the highest correlation with the exothermic intensity, which could be used as an index of exothermic degree in the stage of spontaneous combustion above 80°C.