Experimental investigation of nitrogen species release from different solid biomass fuels as a basis for release models

Experimental data on the release of NOx precursors from solid biomass fuels during thermal conversion are necessary to study N release in general and to supply reliable data for the purpose of packed bed and gas phase conversion model development and validation. In this work the release of NOx precursors was studied at a lab-scale pot furnace (batch reactor) by taking measurements during the conversion process of solid biomass in a packed bed. The investigations were carried out with relevant woody biomass fuels, which cover a broad range of fuel N contents: sawdust, bark, waste wood and MDF board. The most important NOx precursor detected above the fuel bed under fuel rich conditions was NH3, while HCN was almost insignificant with the exception of sawdust. NO was detected mainly under air rich conditions. Furthermore, the experimental data were utilised to derive release functions for the relevant NOx precursors NO, NH3 and HCN. The release functions were implemented in an in-house empirical packed bed combustion model, which serves as a basis for a subsequent CFD N species gas phase calculation.