Inhibiting effect of CO2 on the oxidative combustion thermodynamics of coal

Abstract

A thermal analysis experiment was conducted in O₂/N₂/CO₂ and O₂/N₂ atmospheres (O₂ concentrations were 21, 14, 8, and CO₂ concentrations were 0, 39, 46, 52) to investigate the thermal behavior of coal oxidation and combustion. Results demonstrated that an elevated CO₂ concentration or decreased O₂ concentration had a delaying effect on the thermogravimetric analysis and differential scanning calorimetry (DSC) curves; moreover, the characteristic temperatures were substantially augmented. When the O₂ concentration was 21 vol%, the total heat released by coals A (highly volatile bituminous coal) and B (anthracite coal) decreased by 5.8% and 4.1%, respectively, after CO₂ addition. The comprehensive combustion performance index was also lowered. The DSC curve can be divided into two exothermic peaks, and the ratio of the peak 1 to peak 2 areas decreased with the addition of CO_2, which indicated that CO₂ inhibited the oxidation of the active functional groups of coal structures. Apparent activation energy in O₂/CO₂/N₂ was less than that in O₂/N₂.