Simulation of fuel-bound nitrogen evolution in biomass gasification

Fuel bound nitrogen (FBN) in biomass can be converted to molecular nitrogen (N/sub 2/) or pollutants such as oxides of nitrogen (NO/sub x/), ammonia (NH/sub 3/) and hydrogen cyanide (HCN) during high temperature gasification. Since earlier studies have indicated that the partitioning of FBN among gasification products is determined by kinetics rather than equilibrium, a kinetics model of a fluidized bed gasifier was developed. This model considers 109 elementary chemical reactions and about 30 C, H, O, N species. It was assumed that biomass gasification comprises an initial instantaneous devolatilization and pyrolysis step, that divides the biomass into char and volatiles, followed by heterogeneous and homogeneous reactions between the volatiles, oxidizer(s) and char. Simulation results agree well with experimental data and indicate that most of the FBN is partitioned between NH/sub 3/ and N/sub 2/. As gasification temperature increases, a significant fraction of the NH/sub 3/ is converted to N/sub 2/.