Particle size distribution of the fly ash from biomass combustion

The particle size distributions of the fly ash have been determined with an Andersen cascade impactor for various biomass fuels in different furnaces and under different operating conditions. Particle diameters are calculated as aerodynamic diameters (unit particle density of rho = 1.0 kg/dm(3)). For native wood, chipboard fuel, urban waste wood and hay, unimodal particle size distributions were found with mean diameters <0.25 mu m. More than 80 weight% of the particle mass was found as aerosol with diameters < 1 mu m. Bark is the only fuel found so far which exhibits a bimodal particle size distribution. Flue gas recirculation leads to lower amounts of aerosol particles in under stoker furnaces.