Pilot-Scale Investigation of Plasma-Chemical Reactions in Microwave-Driven Flue Gas Treatment

The growing need for effective air pollution control technologies has prompted significant interest in innovative flue gas treatment methods. This study investigates the plasma-chemical mechanisms and pollutant abatement performance of a pilot-scale microwave-assisted plasma reactor operating at 915 MHz and up to 75 kW for simultaneous removal of SO ₂ , NO _x , and CO ₂ from combustion flue gas. Plasma treatment induced radical-driven oxidation of NO, substantially enhancing the aqueous solubility of nitrogen oxides and thereby improving ammonia scrubbing efficiency. However, excessive plasma power resulted in thermal NO _x formation, governed by local gas temperature, highlighting the critical need for optimized specific energy input. A logarithmic correlation between plasma power and NO _x concentration was derived, enabling estimation of power thresholds necessary to suppress thermal NO formation. Complete or near-complete SO ₂ removal and high CO ₂ capture efficiency (50–100%) were achieved, demonstrating the synergistic coupling of plasma activation with alkaline scrubbing. These findings demonstrate the viability of microwave-assisted plasma technology as a flexible and efficient solution for integrated flue gas pollutant control with potential for industrial-scale deployment in coal-fired power plants and other combustion facilities.