Release of fuel-bound nitrogen in biomass during high temperature pyrolysis and gasification

Pyrolysis and gasification of two biomass feedstocks with significantly different fuel-bound nitrogen (FBN) content were investigated to determine the effect of operating conditions on the partitioning of FBN among gas species. Experiments were performed in a bench-scale, indirectly-heated, fluidized bed reactor. Data were obtained over a range of temperatures and equivalence ratios representative of commercial biomass gasification processes. An assay of all major nitrogenous components of the gasification products was performed for the first time, providing a clear accounting of the evolution of FBN. Results indicate that: (1) NH₃ is the dominant nitrogenous gas species produced during pyrolysis of biomass; (2) the majority of FBN is converted to NH₃ or N₂ during gasification; relative levels of NH₃ and N₂ are determined by thermochemical reactions which are affected strongly by temperature; and (3) N₂ appears to be produced from NH₃ in the gas phase