Selective catalytic reduction (SCR)

Process mechanism

In the SCR denitrification process, NO_x in the flue gas reacts selectively with the reductant and produces N₂ and H₂O with the presence of V₂O₅/TiO₂ based catalysts under the temperature of 300 to 420 ℃. The reductant is typically anhydrous ammonia, aqueous ammonia or urea. The reaction using ammonia (anhydrous/aqueous) as the reductant for a selective catalytic reduction process can be described as the following:

4NH₃+4NO+O₂ →4N₂+6H₂O        (1)

4NH₃+2NO₂+O₂ →3N₂+6H₂O       (2)

NO+NO₂+2NH₃ →2N₂+3H₂O        (3)

Process flow

For a typical SCR process, the SCR reactor is installed between the economizer and the air reheater. The following figure shows the process flow:

Performance

Denitrification efficiency: 70-95%

Ammonia slip ≤ 3ppm

SO₂/SO₃ conversion <1%

System pressure drop <800 pa

System utilization >98%