Simultaneous Fast Decomposition of NH₄HSO₄ and Efficient NO_<i>x</i> Removal by NO₂ Addition: An Option for NO_<i>x</i> Removal in H₂O/SO₂-Contained Flue Gas at a Low Temperature

Abstract

The deposition of NH4HSO4 on the catalyst surface is the main obstacle to the stable removal of NOx in SO2-contained flue gas at a low temperature. In this work, the promotional effect of NO2 on the decomposition of NH4HSO4 is presented for the first time. The NH3-selective catalytic reduction (SCR) experiments show that the V2O5–WO3/TiO2 catalyst exhibits higher SCR activity and excellent resistance to SO2 and H2O when NO2 is present in the flue gas at 250 °C. Results from Brunauer–Emmett–Teller, scanning electron microscopy, and Fourier transform infrared spectroscopy characterizations indicate that NH4HSO4 will not excessively deposit on the surface of the catalyst because the ammonia ion of NH4HSO4 will be rapidly consumed by the NO2/NO mixture. Our study reveals that it is promising to stably and efficiently remove NOx from SO2-contained flue gas at a low temperature by properly adjusting the NO2/NO ratio.