Selectivity refers to the role of catalyst and in the presence of oxygen conditions, NH3 first and NOx occur reduction removal reaction, producing nitrogen and water, without oxidation reaction with oxygen in smoke gas, its main reaction formula is:

4NO+4NH3+O2 →4 N2+6H2O ((1)

2NO2+4NH3 +O2 → 3 N2+6H2O ((2))

Ka tɛ̈n ye catalyst tɔ̈u, a ka chemical reaction ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈n ye tɛ̈

O kɔrɔ la, a lëu bɛ̈n ya tɛ̈ɛ̈r bɛ̈n ya tɛ̈ɛ̈r bɛ̈n ya tɛ̈ɛ̈r.