was also considered. Additionally, flow reactor studies on HCN oxidation, which is an important NO/N20 precursor, with and without SO2 present were performed. It was shown that with increasing temperature or increasing oxygen concentration the emissions of NO increase. N20 emissions increase only slightly with increasing oxygen concentration and show a maximum around a bed temperature of 800ยฐC. A mechanism of homogeneous catalysis operated by SO2 is considered responsible of free radicals (i.e. H, O, OH) recombination under fuel lean conditions. Thus higher SO2 levels increase the emissions of CO, while NO decreases significantly. Due to the reduced destruction by radicals and the lower selectivity in HCN oxidation towards NO, N20 emissions increase at higher temperatures. Apart from the homogeneous interaction between SO2 and NOx and N20 emissions, the addition of limestone has a significant effect due to heterogeneous catalysis at active Cat sites. So the selectivity of HCN and NH3 oxidation towards NO is increased in the presence of limestone. The homogeneous tests in the flow reactor confirm the results obtained in the laboratory-scale FB. SO2 inhibits the conversion of HCN and combustible gases (i.e. CH4, CO and H2). It increases the selectivity of HCN oxidation to N20 compared to NO, by changing the formation paths but also decreasing the N20 destruction by the O radical. Modelling results are generally in good agreement with the experimental results.