Pilot-Scale Demonstration of Microwave-Assisted Plasma Technology for Integrated SO2, NOx, and CO2 Removal from Flue Gas

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 sulfur dioxide (SO2), nitrogen oxides (NOx), and carbon dioxide (CO2) from combustion flue gas. Plasma treatment induced radical-driven oxidation of nitric oxide (NO), substantially enhancing the aqueous solubility of nitrogen oxides and thereby improving ammonia scrubbing efficiency. However, excessive plasma power resulted in thermal NOx formation, governed by local gas temperature, highlighting the critical need for optimized specific energy input. A logarithmic correlation between plasma power and NOx concentration was derived, enabling estimation of power thresholds necessary to suppress thermal NO formation. Complete or near-complete SO2 removal and high CO2 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.