Oxy-fuel combustion kinetics of biomass: insights from multi-heating-rate experiments and kinetic analysis

Oxy-fuel combustion of biomass, when integrated with renewable energy sources, offers a promising pathway for producing high-value green methanol, thereby alleviating pressures related to carbon neutrality. However, fundamental kinetic data for biomass oxy-fuel combustion remain insufficient and require further validation. This study investigated the oxy-fuel combustion kinetics of typical biomass under both slow and fast heating conditions using thermogravimetric analysis and a micro fluidized-bed reactor, respectively. Kinetic results indicate that under slow-heating conditions, biochar combustion in an oxy-fuel atmosphere exhibits accelerated reaction rates. The activation energies for corn straw biochar and rice husk biochar decrease by 13.08 kJ/mol and 8.79 kJ/mol, respectively, compared to combustion in air, with corresponding reaction orders of 1.284 and 1.325. Under fast-heating conditions, the activation energies for volatile release are 74.76 kJ/mol for corn straw and 85.66 kJ/mol for rice husk. Although the trend in activation energy for biochar combustion remains consistent with that under slow heating, a more pronounced reduction is observed for rice husk biochar. Low-heating-rate kinetics capture activation energy dynamics, while high-rate data access the intrinsic reaction. This study provides a scientific foundation and critical data to support the development and application of biomass oxy-fuel combustion technology.