METHODS FOR REDUCING THE EMISSION OF NITROUS-OXIDE FROM FLUIDIZED-BEDCOMBUSTION

Two methods for the reduction of nitrous oxide emissions, afterburning and reversed air staging, are investigated in a 12 MW circulating flu idized bed boiler. With afterburning the N2O emission can be reduced b y 90% or more, using an amount of secondary fuel corresponding to 10% of the total energy input. With reversed air staging it is possible to reduce the emission of N2O to one fourth (25 ppm), without significan tly affecting the other emissions. With reversed air staging no second ary air is used in the combustor and an air-ratio of about unity is ma intained throughout the combustion chamber. Air for final combustion i s added in the cyclone outlet.