Kinetic investigation of the SO₂ influence on NO reduction processes during methane reburning

The reburning technique is an economical and highly efficient method for the reduction of NOx (nitrogen oxides) emissions. The University of Leeds (UK) proposed mechanism was used to investigate the effect of SO₂ on the NO reduction during methane reburning in a plug flow reactor (CHEMKIN model) and compared with Glarborg's experimental data. The computational and experimental results show good agreement when there is no SO₂ addition, and the highest NO reduction is obtained at the optimal air/fuel ratio 0.8. With SO ₂ addition, the optimal air/fuel ratio increases from 0.8 to 0.87 with an increase of SO₂ concentration from 0 to 3000 ppm at a temperature of 1300 K. Under the fuel-lean condition, the addition of SO ₂ slightly enhances the reduction of NO during methane reburning. Under the fuel-rich condition, SO₂ addition inhibits the reduction of NO when the air/fuel ratio is in the range of 0.65-1.0. However, when the air/fuel ratio is less than 0.65, then SO₂ addition has negligible effect on NO reduction. The reaction mechanisms that influence the effect of SO₂ on NO reduction were determined by the main controlling elementary reactions obtained from sensitivity analysis.