Abstract Model liquid mixtures of organic compounds containing nitrogen were burned in a laboratory fluidized bed reactor at temperatures ranging from 700 to 900 °C and oxygen concentrations ranging from 2 to 15 vol%. The model solutions included binary mixtures of toluene with pyridine, quinoline, aniline, 1-aminonaphthalene, nitrobenzene and benzonitrile. Several ternary mixtures containing propanol, ethanol, pyridine, thiophene, toluene and urea were also employed. The nitrogen concentrations in the model mixtures varied within the range 0.5–5 wt%. The results showed that the dependence of the NO x emissions on temperature was influenced by the gas phase oxygen concentration. The conversion of the fuel nitrogen to NO x was less dependent on nitrogen compound type than on other factors. The conversions to NO x increased with increasing air excess for combustion and with decreasing organic nitrogen concentrations. Only a weak influence of SO 2 and in situ desulphurization on NO x emissions in the fluidized bed was observed. Addition of water, propanol or ethanol to a model burned mixture caused a significant reduction of NO x emissions.