Thermogravimetric analyses of oxy-fuel co-combustion of semi-coke and bituminous coal

Abstract Semi-coke is blended with bituminous coal in oxygen-enriched atmospheres to be efficiently used as an energy source. Combustion characteristics and kinetic behavior of blends under oxygen-enriched atmosphere are studied with thermogravimetric analysis. The ignition temperature of each sample in 21%O 2 /79%CO 2 atmosphere is about 15 °C higher than that in air. The burnout behavior of semi-coke is significantly improved when N 2 is replaced by CO 2 at the same oxygen concentration. Increasing oxygen concentration can improve ignition and burnout behaviors further. Differential thermogravimetry (DTG) curves of semi-coke show quite different behaviors in air and 21%O 2 /79%CO 2 atmospheres. There are two distinct peaks in air, while in 21%O 2 /79%CO 2 , there is only one. Activation energies of blends are obtained by Starink method at four heating rates. These activation energy values are, then, used to determine the most probabilistic mechanism function of each stage by Malek method. The results show that the activation energy usually decreases with the increase of the conversion degree and the proportion of bituminous coal. The average activation energy in air atmosphere is slightly smaller than that in 21%O 2 /79%CO 2 atmospheres. It is worth noting that the activation energies of the blends increase with the increase of oxygen concentrations.