This paper presents experimental results of NO<sub>x</sub> emission measurements for combustion of two kinds of coal in a bubbling fluidized bed combustor. The tested fuels were Czech brown coal (CBC) and German young brown coal (GYC). These fuels have different nitrogen contents. The experiments were performed in the pilot scale BFB experimental unit with power output of 500 kW. The influence of several parameters on NO<sub>x</sub> formation are investigated in this paper. The parameters studied here include the effect of the nitrogen content in the fuel, the effect of the oxygen concentration in the bed, the effect of bed temperature, the effect of air staging, and the effect of fluidization velocity. Significantly different behaviour of the fuels was found. Although GYC has a lower nitrogen content than CBC, it is more reactive and produces higher NO<sub>x</sub> emissions. The biggest dependence of NO<sub>x</sub> production for CBC was found for the effects of air staging and fluidization velocity. As the fluidization velocity increases and the amount of secondary air decreases, there is an increase in NOx emissions. The oxygen concentration in the bed has the strongest effect on the NO<sub>x</sub> production of GYCs. With increasing oxygen concentration, the production of NO<sub>x</sub> also increases. On the basis of the NO<sub>x</sub> measurements, the N-NO conversion factor was calculated and the effect of the operating parameters on this conversion factor was investigated.
NOx EMISSIONS FROM BUBBLING FLUIDIZED BED COMBUSTION OF LIGNITE COAL
