METHOD AND ARRANGEMENT FOR REDUCING NITROGEN OXIDE EMISSIONS FROMA FLUIDIZED BED COMBUSTION

摘要

The invention relates to a method and arrangement for use in the combustion chamber (2) of a fluidized bed boiler (1) having a bubbling fluidized bed (5) operative in the bottom portion thereof, the method serving to reduce emissions of nitrogen oxides generated in fluidized bed combustion. In the method, primary air (4) is injected into the combustion chamber (2) upward from the bottom (3) of said combustion chamber (2), fuel (6) is fed into the fluidized bed (5) and secondary air (7) is injected into the combustion chamber (2) at a distance above the fluidized bed (5). Into the combustion chamber (2) is injected circulating gas into a region remaining between the top level of the fluidized bed (2) and the inlet point of the secondary air (7) or at the level of the secondary air inlet (7) separately from the inlet of the secondary air.