Mechanism study on the influence of in situ SO_x removal on N₂O emission in CFB boiler

Highlights: • The presence of SO₂ would hinder N₂O decomposition on CaO (1 0 0) surface. • N₂O decomposition pathway on deSO_x intermediate was proposed. • Temperature dependence of the reaction pathway was considered. • Surface recovery process was the rate-determining step for N₂O catalytic decomposition. - Abstract: The influence of in situ deSO_x process on N₂O emission in CFB boiler was studied using density functional theory calculations. The competitive adsorption of SO₂ and N₂O on pure CaO (1 0 0) surface was first studied and the reaction priority was determined. Results showed that SO₂ was more likely to adsorb on CaO (1 0 0) surface O anion site, which hindered the catalytic decomposition of N₂O on CaO (1 0 0) surface and sulfurized the CaO (1 0 0) surface under reducing atmosphere. Then a partially sulfurized CaO (1 0 0) surface was established to study the catalytic activity of deSO_x reaction intermediate on N₂O decomposition. The O atom transfer process and the surface recovery process were two key steps for N₂O decomposition and the rate-determining step was the latter one. The sulfurization of the surface could deactivate its catalytic activity on N₂O decomposition compared with pure CaO (1 0 0) surface but it was still better than that of pure CaS (1 0 0) surface. The free Gibbs energy was calculated to incorporate the temperature dependence of respective reactions. When temperature was higher than 373 K, the surface recovery was more likely to proceed via the LH route