Homogenous and Heterogenous Reactions for Formation and Destruction of N2O - Results from the 12 MW CFB-boiler at Chalmers

Influence of homogeneous and/or heterogeneous reactions for formation and destruction of N2O under fluidized-bed combustion conditions has been subject of discussion during the two previous workshops on N2O (Lisbon, Tsukuba). The research program on N2O emissions from combustion at the Chalmers circulating fluidized bed (CFB) boiler has been focused on projects that further elucidate the various reaction paths connected with N2O. These projects include tests where NH3, CH3CN, NO and N2O were injected into three locations in the combustion chamber when burning fuels of different volatile content. Apart from this, measurements of local concentrations of nitrogen species including NH3 and HCN in the entire combustion chamber have been carried out with bituminous coal as fuel. The present paper summarizes the results from these tests. It is concluded that both homogeneous and heterogeneous reactions are important for the formation and destruction of N2O. Furthermore, the various regions (bottom, top) of the CFB play different roles for the effective formation of the N2O emitted