Emissions of NOx and N2O during co-combustion of dried sewage sludge with coal in a circulating fluidized bed combustor

Emissions of NO_x and N₂O were measured during mono-combustion of dried sewage sludge and co-combustion with coal in a bench-scale circulating fluidized bed combustor (CFBC). The results were compared with previous results obtained using a bubbling fluidized bed combustor (BFBC). The increase in NO_x with sludge ash accumulation in the combustor was less for the CFBC than the BFBC, partly because of the higher attrition rate of sludge ash in CFBC resulting from the higher gas velocity. The influence of sludge ash on the formation of NO_x in CFBC was less than that in BFBC during sludge combustion. The effects of fuel type on NO_x and N₂O emissions were also evaluated.