Lab- and pilot-scale wet scrubber study on the redox-mediated simultaneous removal of NO and SO using a CaCO-based slurry with KI as a redox catalyst.

This study presents a novel approach that integrates ozone-driven chemical oxidation to convert NO into soluble NO, followed by the simultaneous absorption of NO and SO into a CaCO-based slurry using the redox catalyst potassium iodide (KI). Using cyclic voltammetry, we demonstrate the redox properties of the I/2I couple, which facilitates NO reduction into soluble NO and catalyst regeneration through sulfite (SO)-driven reduction, thus establishing a closed catalytic cycle within the components of flue gas. In lab-scale wet-scrubbing tests, we explore the effect of various operational parameters (i.e., KI concentration, pH, and SO concentration), with a 15 h stability test demonstrating >60% NO and >99% SO removal efficiency when the pH is controlled between 7.5 and 8.5. A successful pilot-scale implementation conducted at an inlet flow rate of 1000 m h further confirmed the reproducibility of the proposed redox-catalytic cycle. Our study offers a cost-effective, sustainable, and scalable solution for effectively mitigating NO and SO emissions at low temperatures.