Formation and reduction of pollutants in CFBC: From heavy metals, particulates, alkali, NOx, N2O, SOx, HCl

Abstract

Due to the advantages of fluidized bed combustors a wide range of different fuels is utilized. The fuels range from anthracite, medium and low rank coals to peat, wood residues, biomass waste, sewage sludge and other sludges to plastics and municipal solid waste. Because of this wide range of fuels pollutants such as heavy metals, particulates, alkali, NO, NO2, N2O, SO2, SO33 and HCl may be formed during the fuel conversion process depending on the fuel and operating conditions. These pollutants may lead to difficulties in operation of the fluidized bed combustor e.g. because of slagging and fouling the heat transfer may decrease or the efficiency of the SCR catalyst. High concentrations in the flue gas may lead to health problems and pollution of the environment. This work investigates the conversion routes of the pollutants from the fuel to the final flue gas. It is discussing the different chemistry of the pollutants and their possible interactions inside the combustor. Primary measures to avoid pollutant formation and reduction paths are demonstrated. Areas for further research are recommended.