THE EMISSIONS AND CONTROL OF NO(X) AND N2O IN PRESSURIZED FLUIDIZED-BED COMBUSTION

Using the Otaniemi pressurized fluidized bed combustion test rig a study has been made of the emissions and control of NOx (NO + NO2) and N2O in different operating conditions for three types of solid fuel (peat, bituminous coal and brown coal). The influence of operating parameters, including bed temperature, excess air level, pressure, etc., were investigated. The results showed that NOx emissions were low and the excess air level was a dominant variable, and N2O emission was mostly dependent on the burning temperature. Ammonia injection and air staging are effective as NOx reduction techniques. Both techniques can reduce the NOx up to 60% dependent on the fuel type and the amount of ammonia or degree of air staging. The oxygen level and temperature of ammonia injecting position were significant factors in NOx reduction in ammonia injection operations. The N2O emissions, however, were always increased as a consequence of NOx reductions.