Measurements of NOx emissions from biomass combustion in small to large-scale power plants

• NO X emissions from four different fuels and furnaces are compared. • NO X emissions and flue gas control vary greatly between the furnaces. • Fuel-N conversion to NO correlates with fuel-N, regardless of combustion technology. • CH/N, H/N, and O/N ratios show similar correlations with fuel-N to NO conversion. • NO X emissions depend on both fuel-bound nitrogen and combustion technology. NO X emissions from thermal conversion are among the most serious gaseous emissions. The role of combustion technology and combusted biomass or biogenic residue on these emissions is not yet fully understood. This study investigates the gas composition at four different biomass-fueled combustion power plants, focusing on nitrogen species. The thermal energy input of the industrial-sized combustion facilities are 0.9 MW th , 40.4 MW th , 105 MW th and 154 MW th . These four facilities with different combustion technologies also employ different fuels, e.g., wood chips, waste wood, straw and pencil residues. The measurements are conducted simultaneously with a two-measuring point approach entailing flue gas measurements near the particle filter and stack, and gas measurements in the combustion chamber. A specially designed high-temperature probing lance is implemented to collect gas from the combustion chamber before the gas is analyzed with a Fourier-transformed infrared spectrometer (FTIR). The resulting NO X emissions are dependent on the fuel and the combustion technology. The conversion of the fuel-bound nitrogen to NO X at the stack, which ranged between 1.1% and 5%, correlates with the fuel nitrogen content and the elemental composition of the fuel across the combustion plants. Moreover, NO was the main nitrogen species detected inside the combustion chambers.