Emission Characterization and Efficiency Measurements of High-Efficiency Wood Boilers

Detailed gaseous and particle emissions along with thermal efficiency measurements were made on three mid-sized high-efficiency wood boilers with thermal output capacities of 150 kW (514 000 Btu h–1) (n = 2) and 500 kW (1.7 mmBtu h–1) (n = 1). Wood chips and commercial wood pellets were used as fuel. Continuous emissions of CO, NOx, SO2, fine particle mass (PM2.5), and ultrafine particle number distributions were determined using a dilution tunnel sampling system. PM2.5 and semivolatile organic compound characterization was performed. Low concentrations of CO, organic carbon (OC), and elemental carbon (EC) during steady-state boiler operation indicated good combustion conditions. Fine particle mass from wood pellets was predominantly K+ and SO42–, with <8% OC and <2% EC. Inorganic emissions (PM2.5, NOx, and SO2) were found to depend upon fuel quality, which indicates the need for wood pellet fuel standards in the U.S. Cd, Pb, Ti, Rb, and Zn were found to be enriched in PM2.5, which is of concern for human...