Comprehensive study on co-combustion behavior of pelletized coal-biomass mixtures in a concentrating photothermal reactor

Abstract

Co-combustion of biomass offers a great potential to reduce CO2 emissions but rarely mentioned co-combustion behavior of pelletized coal-biomass mixtures and inconclusive results based on single determinants formed obstacle for industrial application. In this study, ignition and flame characteristics, reaction and kinetic parameters and pollutant generation path were comprehensively investigated. Intrinsic combustion experiments were carried with the gas phase maintaining at room temperature in a concentrating photothermal reactor at heating rate over 200 °C/s. Same “homogeneous” ignition was evidenced while advanced devolatilization but more intense slagging behaviors were identified with the increase of biomass proportion. With the biomass proportion increased from 0% to 40%, the activation energies during devolatilization to ignition decreased non-linearly from 47.44 kJ/mol to 8.03 kJ/mol, indicating the existence of synergistic effect. CO exhibited relative high generation rates and the generation rate increased with the biomass content. Three fitted CO peaks were identified during co-combustion, which were contributed by devolatilization of coal and biomass, and combustion of char, respectively. First increased and then decreased NO emission with the increase of biomass proportion was evidenced for the higher N content in biomass but enhanced reduction by char and NH radicals with higher biomass proportion.