Combustion characteristics and synergistic effects during co-combustion of lignite and lignocellulosic components under oxy-fuel condition

Co-combustion of lignocellulosic biomass and coal has been recognized as a promising route to deliver carbon neutrality. In this study, the combustion characteristics of lignocellulosic biomass main components (cellulose, hemicellulose, and lignin), one kind of lignite, and their mixtures were investigated under air and oxy-fuel conditions, respectively. The combustion reactivity of cellulose and hemicellulose was better than that of lignite, while that of lignin was worse. Under the oxy-fuel condition with the same oxygen mole fraction as air, the combustion of cellulose and hemicellulose was slightly delayed, while a distinct combustion delay was observed for lignin similar to lignite. For the co-combustion, compared to lignite, the combustion reactivity could be improved by blending cellulose and hemicellulose, while it got worse by mixing lignin. Cellulose and hemicellulose had a positive synergistic effect on the release of lignite volatiles, while lignin showed a negative synergy on it. All the lignocellulosic components showed positive synergies with lignite on the char oxidation due to the high structural porosity of lignite char and the advanced oxidation of lignocellulosic char.