Co-pyrolysis and co-combustion characteristics of low-rank coal and waste biomass: Insights into interactions, kinetics and synergistic effects

Abstract

This study delves into the investigation of the co-pyrolysis, co-combustion characteristics, and kinetic behaviors of straw and low-rank coal, aiming to inform strategies for their optimal combustion as potential solid fuels. As the biomass proportion increases, the synergistic effect during co-pyrolysis gradually diminishes. The addition of straw char into coal char notably enhances the ignitability and combustibility of coal char. In the co-combustion process, both synergistic and antagonistic effects (Interaction index varies from −13.52 kJ⋅mol⁻¹ to 12.62 kJ⋅mol⁻¹) exist between carbonized straw and coal char, while the synergistic effect was dominant. The first-order chemical reaction (O₁) and diffusion-controlled reaction (D₃ and D₄) are the most effective mechanisms (all the correlation coefficient R₂ > 0.97) for the co-combustion process. The proportion of straw char in the blend is recommended to be maintained at 20 wt% because of the lowest total combustion activation energy (92.35 kJ⋅mol⁻¹) and the most pronounced synergistic effect (Interaction index ΔX = 13.6). These findings offer valuable theoretical guidance for promoting the sustainable utilization of low-rank coal and biomass waste resources, fostering a more eco-friendly and efficient energy landscape.