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Investigating fine particle emissions
21/11/2005

VTT, University of Kuopio and TTS Institute carried out a research project on fine particle emissions in small-scale wood combustion in co-operation with nine companies from 2002 – 2005. The project looked at three areas: fine particle modelling, measuring techniques and definition of emission coefficients. Fine particles are smaller than 2.5µm (PM2.5) and ultrafine particles 0.001 – 0.1 µm, and coarse particles are defined to have diameter > 2.5 µm. A fine particle model for small scale wood combustion was developed. Measuring techniques of fine particles are in the development phase and standardised methods are still lacking. The differences of measuring devices were studied by measuring simultaneously using several devices and in various periods with different situations. The essential phases are sampling and dilution of a sample to ensure reliability of measurements. VTT measured fine particle number emission using the Electrical Low Pressure Impactor and mass concentrations using the Dekati Low Pressure Impactor. Fine particles emissions are affected by many parameters like fuel quality fuel composition, combustion process, use of the appliance, and burning rate. Fuel quality and use of the appliance have major effects on emissions. They affect the soot and hydrocarbon formation, which play an important role in fine particle formation. During continuous burning (e.g. pellet burning) the combustion is better controlled and emissions are lower than during batch burning (e.g. in stoves). At the lowest, continuous burning of wood pellets resulted in fine particle emissions less than 10 mg/MJ. The emission varies especially in the interference, cleaning, on-off using and low load situations. In wood log combustion, fine particle size varies in different combustion phases: the largest is in ignition phase and the smallest in the char burning phase. More research is needed on the composition of fine particles and health effects. Additional information Heikki Oravainen, VTT (combustion measurements), heikki.oravainen@vtt.fi Jorma Jokiniemi, VTT (modelling, jorma.jokiniemi@vtt.fi Jarkko Tissari, University of Kuopio (project in general), jarkko.tissari@uku.fi Oravainen, H. Fine particle emissions from small scale wood burning appliances, Bioenergy in Wood Industry, 12 - 15 September 2005. Book of Proceedings, p. 291 – 293.