Co-combustion of sewage sludge with wood/coal in a circulating fluidised bed boiler - A study of NO and N2O emissions

Paper in proceeding, 2001

Reduction of emissions of NO and N2O from co-combustion of wet or dried sewage sludge with coal or wood is investigated. This is motivated by the high nitrogen content in sewage sludge that may give rise to high emissions. An advanced air-staging method for combustion in circulating fluidised bed is applied. It is shown that with fluidised bed combustion the emissions are low as long as the sludge fraction is not too high (say, less than 25%), and the conversion of fuel nitrogen to NO or N2O is only a few percent. However, air staging as such is not efficient for high volatile fuels, and any air supply method can be applied in such a case, in contrast to combustion of coal, when the air supply arrangement has a decisive influence.