Enhancing NOx removal in a high-gravity rotating packed bed with gaseous ClO2 oxidation-absorption: Kinetic, mass transfer, and cost analysis

Abstract

The application of ClO2(g) for NO oxidation presents a promising approach to improving air pollution control technology. In this study, an integration of ClO2(g) with absorption using a high-gravity rotating packed bed (HiGee RPB) was proposed for NOx removal. The results showed that ClO2(g) has a comparable oxidation efficiency (close to 100%) to O3 in converting NO to NO2, while the dosage of ClO2(g) required was two times smaller than that of O3. The gas-phase oxidation kinetic analysis between ClO2(g)-NOx, using an ideal plug flow model, simulated the potential amount of NOx species produced in a short reaction distance in the pipeline. Furthermore, at higher gas-liquid ratios and in high-gravity fields, the effective mass transfer interfacial area for NO2 absorption was mainly controlled by the liquid film rather than droplet behavior, resulting in decreased absorption capacity. The empirical model for predicting the gas-side mass transfer coefficient confirmed that the interaction between mass transfer performance and chemical absorption was independent. Therefore, selecting the appropriate absorbent is a key factor in achieving high-loading NO2 concentrations after oxidation by ClO2(g). Another interesting finding is that balancing system energy consumption and the target treated NOx concentration played a critical role in enhancing the NOx absorption capacity. The cost analysis showed that substituting existing scrubbers with RPB processes could facilitate NOx absorption capacity (g-NOx/kWh) with cost-effectiveness. Overall, this study provides valuable insights into the development of effective and efficient NOx removal technologies, and future research in this area can build on these findings.