Characterization difference of coals with different spontaneouscombustion tendencies during oxidation stage
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Abstract:
Low temperature oxidation experiments of three coal samples with different spontaneous combustion tendencies were carried out. Activation energies and characteristic temperatures of coal oxidation process conversion were obtained by the computational model based on the relationship between CO volume fraction and coal temperature change. With the experimental results of TG-DSC(theremogravimetric analysis-differential scanning calorimetry), the change laws of activation energy and oxidation characteristics of three coal samples in low temperature were analyzed. The results show that 1) during the low temperature oxidation, the CO generation amount, the oxygen consumption amount and the oxygen consumption rate increase with the enhancement of spontaneous combustion tendency. Temperature inflections that CO generation amount and oxygen consumption rate increase sharply are the same during the experiment of different coal samples. And the stronger the spontaneous combustion is, the lower the temperature inflection is, and the change of CO volume fraction shows obvious stages. 2) The change laws of activation energy of coals with different spontaneous combustion tendencies are significantly different. When coal temperature reaches the active temperature, activation energy decreases rapidly, and the mutation points of activation energy are corresponding to the conversion characteristic temperatures in coal oxidation process. 3) According to the characteristic temperature and the change law of activation energy, the low temperature oxidation process could be divided into four stages, namely surface oxidation, thermal oxidation, accelerated oxidation and deep oxidation.
