Information on the sulfur content of bark and its contribution to SO2 emissions when burned as a fuel

Abstract

Conjecture exists about the SO2 emissions resulting from the burning of wood residues since current New Source Performance Standards for large power boilers permit the use of the Btu in wood residues in calculating allowable SO2 emission rates. The concern is based on available knowledge of the sulfur content of bark and wood residues which, if stoichiometrically converted to SO2 would account for SO2 levels of about 130 ppm in the flue gas. This information is apparently the background for selection of an emission factor of 0.375 Ib SO2/million Btu of wood residue fired that is included in EPA resource documents. This paper describes a field study carried out to determine the amount of SO2 generated when burning representative bark. The study involved a sulfur fuel balance around the combustion device by determining sulfur content of the bark fed, and sulfur leaving the boiler in solid and gaseous forms, namely ash, fly ash, and SO2. The study showed that Just over 5 % of the sulfur contained in the bark was emitted as SO2 which amounted to 0.001 to 0.02 Ib SO2/million Btu in the bark fed. The remainder of the sulfur was accounted for in the ash combustion products. The findings support the conclusion that the sulfur content of wood is not stoichiometrically converted to SO2. © 1980 Air and Waste Management Association.