Chemical and leaching characteristics of ash from combustion of coal, peatand wood in a 12 MW CFB - a comparative study

The chemical characteristics of fly ash samples from combustion of three fu els: coal, peat and wood chips, have been studied. The ash materials were c ollected in the 12 MW CFB at Chalmers University of Technology during full load combustion with similar standard combustion parameters. The samples we re characterized in terms of chemical composition, mineralogy and leaching behavior. The special characteristics of the mineral matter in each fuel we re reflected in the leaching results. Upon reaction with moderate amounts o f water secondary mineral phases such as ettringite and calcite, were forme d. These compounds were shown to affect the leaching rates for calcium and sulfate as well as the pH of the leachates. (C) 1998 Elsevier Science Ltd. All rights reserved.