Reduction of Emissions of Sulphur and Chlorine from Combustion of High Volatile Waste Fuels (Sludge) in Fluidised Bed

Abstract: Co-combustion of sewage sludge with coal or wood as base fuels may cause high emissions of sulphur dioxide and hydrogen chlorine to the atmosphere. The conventional technique for sulphur capture in fluidised bed combustion using coal, lime addition, works well under co-combustion conditions with coal as base fuel but not with wood. The concentration of SO2 certainly plays a role, but phosphorous, originating from the sewage sludge, forms calcium phosphate that may interfere with the sulphur capture reactions normally taking place when lime is added to the bed. Lime addition to the fluidized bed during combustion of pulp&paper sludge, not containing phosphorous and with similar sulphur levels as for the sewage sludge, gives a normal sulphur capture. Adding hydrated lime to a bag filter is an alternative to lime addition to the bed that can be used when fuels with high content of phosphorous are co-combusted with wood. Hydrated lime also captures chlorine in the bag filter