Experimental investigation on combustion characteristics and kinetics during Co-Firing bituminous coal with ultra-low volatile carbon-based solid fuels

Abstract

With the rapid development of low-rank coal chemistry industry, the production of ultra-low volatile carbon-based solid fuels (pyrolyzed and gasified semi-cokes) with inferior combustion performance has been continuing a rising trend. The semi-cokes blended with bituminous coal in utility boiler is considered as a promising approach to realize the efficient and clean utilization of low-rank coal. Nevertheless, the co-combustion features and kinetics of ternary blending are still unclear and less work has focused on the thermal interactions between bituminous coal and various semi-cokes. Here, the thermogravimetric experiments were employed to elucidate the co-firing characteristics of various carbon-based solid fuels. The results show that the ignition temperatures of blended fuel are decreased by co-firing bituminous coal, and the ignition temperature of blend is lower than that of linear additivity. Under the conditions of 70% pyrolyzed semi-coke blended with 30% bituminous coal, the ignition temperature is reduced by 9.3% and the burnout temperature is increased by 70.6% with the heating rate raised from 10 °C/min to 40 °C/min. The apparent activation energy of blend is higher than linear additivity when the pyrolyzed semi-coke proportion is lower than 40%. The negative effects of semi-cokes on blends are reduced when the bituminous coal is blended with both pyrolyzed and gasified semi-cokes. The ignition temperature, burnout temperature and combustion index change linearly with the fraction of semi-coke. The results could provide guidance for the clean and efficient utilization of semi-cokes in utility boiler.