Selective catalytic reduction

Selective catalytic reduction (SCR) is a means of converting nitrogen oxides, also referred to as x with the aid of a catalyst into diatomic nitrogen (2), and water (O). A reductant, typically anhydrous ammonia (3), aqueous ammonia (OH), or an urea (2) solution, is added to a stream of flue or exhaust gas and is reacted onto a catalyst. As the reaction drives toward completion, nitrogen (2), and carbon dioxide (2) in the case of urea use, are produced.