Release of Fuel-Bound Nitrogen during Biomass Gasification

Abstract

Gasification of four biomass feedstocks (leucaena, sawdust, bagasse, and banagrass) with significantly different fuel-bound nitrogen (FBN) content was investigated to determine the effects of operational parameters and nitrogen content of biomass on the partitioning of FBN among nitrogenous gas species. Experiments were performed using a bench-scale, indirectly heated, fluidized-bed gasifier. Data were obtained over a range of temperatures and equivalence ratios representative of commercial biomass gasification processes. An assay of all major nitrogenous components in the gasification products was performed for the first time, providing a clear accounting of the evolution of FBN. Important findings of this research include the following: (1) NH3 and N2 are the dominant species evolved from fuel nitrogen during biomass gasification; >90% of FBN in feedstock is converted to NH3 and N2; (2) relative levels of NH3 and N2 are determined by thermochemical reactions in the gasifier; these reactions are affected strongly by temperature; (3) N2 appears to be primarily produced through the conversion of NH3 in the gas phase; (4) the structural formula and content of fuel nitrogen in biomass feedstock significantly affect the formation and evolution of nitrogen species during biomass gasification.