Empirical modelling of oxidation behaviours of coals stored under different conditions

Abstract

ABSTRACTIn this study, oxidation behaviours of lignite samples stored under different conditions (deep freezer;-25°C, nitrogen tank; 18°C and oven; 30°C) for 16 weeks were investigated. Therefore; oxygen consumption rates of the coal having two size fractions (74 μm and 500 μm) and activation energies were calculated by oxygen analyser and TG/DTG analysis, respectively. In addition, the ignition temperatures and combustion risk index values of coal samples were determined by the crossing point method. As a result, the activation energies were determined to be between 28.0413 and 39.5839 kJ/mol. It was also determined that the consumption of oxygen increased after the temperature of the coal reaching 90°C. At the beginning of the storage period, lignite samples with a fine particle size in the ‘medium risk’ class in terms of the propensity to spontaneous combustion were included in the ‘high risk’ class at the end of the process. Finally, the relationship among all the obtained experimental results was outlined for the first time by creating a numerical model through the design of experiment (DOE) and it was seen that the coal samples stored in the deep freezer had advantages in terms of oxidation behaviour compared to the other two storage conditions.