Fine Particulate Formation and Ash Deposit Behavior during Sawdust/Coal Co-firing

The formation of particulate matter (PM) as well as the related ash deposit characteristic during sawdust/coal co-firing was investigated in a 25 kW down-fired multi-fuel furnace. The tested fuels included raw coal, raw sawdust and two kinds of mixtures of sawdust and coal. In this work, fine particles with aerodynamic diameter between 30 nm and 667 nm were examined, and ash deposition were collected at the identically operational conditions. The effects of both fuel properties and fuel interaction on PM formation and ash deposit behavior were evaluated. Particle size distribution and mass concentrations were determined by Electric Low Pressure Impactor (ELPI), while the ash deposit samples were collected by an air-cooled, temperature-controlled probe. The prediction from a simple model assuming "non-interacting-effects" on PM formation and ash deposition between various kinds fuels were compared with the experimental results. It indicated that a significant increase of ash deposit exists for a case of co-firing fuels, whereas fine PM concentrations decrease.