High-Efficiency Removal of NOx From Flue Gas by Multitooth Wheel-Cylinder Corona Discharge Plasma Facilitated Selective Catalytic Reduction Process

In this paper, a plasma-assisted selective catalytic reduction (SCR) process was employed for the conversion of nitrogen oxides (NO
_x
) from flue gas to nitrogen (N
₂
) and water (H
₂
O) using V
₂
O
₅
-WO
₃
/TiO
₂
catalyst over a broad reaction temperature (125 °C–550 °C) range. Ammonia (NH
₃
) was used as a reducing agent, and nonthermal plasma was generated in a multitooth wheel-cylinder corona discharge reactor driven by a dc power supply. In order to optimize the geometry of the corona discharge reactor, the discharge power and the NO oxidation efficiency were compared for different discharge gaps and sawtooth slice numbers of the multitooth wheel electrode, respectively. The effects of reaction temperature, water vapor, and SO
₂
concentration on the plasma facilitated SCR of NO
_x
were also investigated. The experimental results showed that shorter discharge gap (11 mm) appeared to be more advantageous with respect to NO oxidation. NO oxidation efficiency was less affected by sawtooth slice number. The plasma-assisted SCR process enhanced the catalytic activity of SCR catalyst and exhibited a remarkable improvement in NO
_x
removal efficiency at a temperature range of 125 °C–300 °C. The presence of water vapor in plasma-assisted SCR process significantly improved the NO
_x
removal, especially at low temperature. The addition of SO
₂
suppressed the NO
_x
removal in plasma-assisted SCR process; however, the NO
_x
removal was greatly promoted by the presence of SO
₂
and H
₂
O, indicating that water vapor can significantly ameliorate the SO
₂
inhibiting effect in the plasma-assisted SCR process.