Reactivity and Leaching of Wood Ash Pellets Dehydrated by Hot Air and Flue Gas

Companies that generate a large amount of wood ash will need an industrial process to agglomerate the ash and lower its reactivity, because untreated ash is a dust hazard for workers and is difficult to spread evenly on forest soil. In addition, untreated ash can cause burning damage to vegetation owing to its alkalinity and rapid release of salts. Production of large amounts of wood ash agglomerates demands an effective dehydration process. The reactivity and release of inorganic constituents from wood ash pellets dehydrated at room temperature using hot air and flue gas was investigated. Our results imply that flue gas-treated pellets have significantly lower reactivity in terms of pH and electrical conductivity, and release less Ca and more Mg compared to pellets dried at room temperature or in hot air. Ash pellets dehydrated in hot air are very reactive, and release more Ca than pellets dried in other ways. The formation of syngenite during the flue-gas treatment decreases K release from the ash pellets.