Primary Measures to Reduce the Emissions of Nitrogen Oxide in Circulating Fluidized Bed Boilers

During the combustion of coal in a circulating fluidized bed boiler the conversion of the fuel\uadbond nitrogen to either nitrogen oxides or nitro\uadgen can be influenced by design and operational measures. The paper gives a summary of results obtained in a series of tests on a 40 MW circulating fluid\uadized bed boiler in Nykoping, designed by Gota\uadverken Energy. In this commercial boiler it was not possible to study the influence of primary to secondary air addition independent of thebed temperature. For this reason, a smaller boiler designed by the same manufacturer was adapted to permit independent variations of the primary air ratio and the bed temperature. The results from the 40 MW and the 8 MW boilers are compared and the influence of the distribution of the air supply and of the bed temperature on the reduction of nitrogen oxide emissions are dis\uadcussed