Investigation on co-combustion of semi-coke and bituminous coal in oxygen-enriched atmosphere: Combustion, thermal conversion, and kinetic analyses

Semi-coke is the solid pyrolysis product of low-rank coal, with high carbon content and difficult to ignite and burn out. The blending of semi-coke with bituminous coal can realize a large amount of utilization of semi-coke. In this paper, the combustion, thermal conversion, and kinetic analyses of semi-coke blending with bituminous coal are investigated under oxygen-enriched conditions (30% O2 atmosphere). Compared with 20% O2 atmosphere, the ignition and burnout temperatures are reduced by 10, 7, 8, 12, 7 °C and 129, 76, 85, 115, and 152 °C for the semi-coke blending ratios of 0, 30, 50, 70 and 100% under 30% O2 atmosphere. Oxygen-enriched combustion can effectively decrease the ignition temperature and improve the combustion performance of the mixture. In 30% O2 and 20% O2 atmospheres, the synergy effect of the co-combustion process is different. Under the 30% O2 atmosphere, semi-coke, and bituminous coal have a strong synergistic effect, which can reduce burnout temperature. However, under 20% O2 atmosphere, the burnout temperature of the mixture will increase. At a higher blending ratio of semi-coke, the effect of oxygen-enriched conditions on co-combustion is greater, and high oxygen concentration will make the interaction of the mixture combustion process more intense. Compared with bituminous coal, the activation energy of the mixture gradually increases with the increase of the blending ratio of semi-coke, and different combustion stages correspond to different mechanism functions, respectively. The research results can provide ideas for the utilization of semi-coke under oxygen-enriched conditions.