Biomass reburning has emerged as a promising method for reducing nitrogen oxide (NO) emissions. However, a comprehensive

understanding of reburning reactions using biomass remains limited. In particular, the char contribution to NO 

reduction requires further clarifi cation, especially when using rice husk. This study investigates the contribution of rice 

husk char to NO reduction during the reburning process in a drop-tube furnace. The eff ects of reaction temperature, NO 

concentration, and equivalence ratio on the contribution of the homogeneous and heterogeneous reactions were analyzed. 

Results showed that increasing the reburning temperature enhanced the heterogeneous reaction by promoting CO release 

from the char surface, thereby increasing the char’s contribution to the overall reburning reaction. As the initial NO concentration

increased, NO reduction increased for both rice husk and its char; however, due to the limited amount of fuel 

for reburning reactions, the rate of increase in NO reduction decreased. The homogeneous reaction decreased above a 

certain equivalence ratio because oxygen limitation reduced the conversion of intermediate species into N 2 . In contrast, 

the char reaction increased and eventually reached saturation with an increasing equivalence ratio, further enhancing char 

contribution. These fi ndings provide valuable insights for optimizing biomass reburning systems, particularly by clarifying 

the distinct role and operational dependencies of heterogeneous char-NO reactions.