A Preliminary Experimental Study On Coal Oxidation Kinetics Based On Thermal Analysis Technology

The study of coal oxidation is very important in preventing coal fire. In this dissertation, 11 kinds of coal with different ranks were collected for experiments. The author studies the the oxidation character, with the coal particle size in 120 mesh and heating rage of 30℃to 800℃, by thermal analysis kinetics means.The coal oxidation process were divided into 5 phases:moisture content vaporizing & desorbing, gain weight, oxidation & decomposition, combustion and mass stable phases, and the first four phases were mainly studied. We have calculated oxidation dynamical parameters activation energy and pre-exponential factor, then found the most probably mechanism function closed to Bagchi method by analysing the experimental data with Coats-Redfern integration method and Archar differential method. It is shown that the activation energy is different at various phases on coal of different rank. At the phase of low-temperature oxidation: the activation energy of lignite is more than bituminous and bituminous; while the high-temperature oxidation, the lower of the coal rank, the less of activation energy is. The pre-exponential fact respects the chemical reaction rate, which increases with the activation energy increasing. The gas releasing rules and character at the whole coal oxidation phases were studied by TG-DSC-GC combination techniques.At the phase of low-temperature oxidation: the index-gas and the auxiliary index-gas on distinguishing spontaneous combustion were discovered. At higher temperature, the maximum combustion rage and the oxygen consumption volume on all kinds of coal were also discovered.The oxidation character on the whole phases of coal oxidation was obtained according to the gas realease rules. The coal oxidation reaction is:from slow to rapid,multi-steps, competitive, parallel and mutation process. The coal oxidation & decomposition process is very complex, the general reaction equations about the process of coal oxidation is established. According to GC analysis data,and the LINEST(known_y's,known_x's,const,stats) function about linear-piecewise regression analysis, the general reaction rate equations is obtained at different oxidiation phases.