NOx removal from the flue gas of oil-fired boiler using a multistage plasma-catalyst hybrid system

The study on removal of NOx from the flue gas of oil-fired boiler has been carried out using non-thermal plasma cum catalyst hybrid reactor at 150 °C. Propylene (C3H6) was used as a reducing agent. A multistage plasma-catalyst hybrid reactor was newly designed and successfully operated to clean up the flue gas stream having a flow rate of 30 Nm3/h. TiO2 and Pd/ZrO2 wash-coated on cordierite honeycomb were used as catalysts in the present study. Though the plasma-catalyst hybrid reactor with TiO2 showed good activity on the removal of NO yet it removed only 50–60% of NOx because a significant portion of NO oxidized to NO2. On the contrary, the plasma-catalyst hybrid reactor with Pd/ZrO2 removed about 50% of inlet NO with a negligible amount of NO oxidation into NO2. The plasma/dual-catalysts hybrid system (front two units of plasma-Pd/ZrO2 + rear two units of plasma/TiO2) proved to be very promising in NOx removal in the presence of C3H6. DeNOx efficiency of about 74% has been achieved at a space velocity of 3300/h at 150 °C.