Experimental Studies on Particle Emissions from Grate Fired Biomass Combustion Boilers

Fine particle emissions were measured at two commercial grate fired boilers operating on moist fuel residues. The aim of this study was to characterize fine particle emissions with a view to pinpoint parameters influencing the emissions. Additionally effectiveness of used flue gas cleaning techniques was assessed. The results show that large quantities of fine particles are emitted to the atmosphere from both boilers. From 1 MW boiler equipped only in multicyclone 4.8*107 of particles/cm3 (particles with diameter smaller than 0.6 μm) are emitted to the atmosphere. From 6 MW boiler equipped in multicyclone, ESP and flue gas condenser 1.7*106 of particles/cm3 (< 0.6 μm) end up in the atmosphere. Significant fluctuations in the coarse mode (1-10 μm) number concentration over time were observed in 1 MW boiler (between 100 and 10000 particles/cm3) and these were much higher than in 6 MW boiler (between 6000 and 11000 particles/cm3). Operating load showed to have a significant influence on coarse particles number concentration. Collection efficiency of ESP was assessed for about 96% by number and 83% by mass. Number concentration of particles passing through the flue gas condenser was close to unaltered, while mass concentration was reduced by half