Enhanced oxidative removal of NO by UV/in situ Fenton: Factors, kinetics and simulation

A series of experiments on the oxidative removal of NO from flue gas using a novel in situ Fenton (IF) system was performed in the presence of ultraviolet light (UV). The comparison tests revealed that the in situ Fenton system facilitated by UV (UV/IF) has a better oxidation ability of NO than that of the IF system due to the photochemical effect on the generation of oxidative species like (center dot OH). Both of the aforementioned oxidation efficiencies were higher than that of the conventional Fenton system (CF) depending on the premix of Fe2+ and H2O2 solutions, which attribute to the improvement of (center dot OH) yield and valid utilization with continuous addition of fresh reagents and UV radiation. In follow-up experiments, the effects of UV power, gas flow rate, reagent temperature, Fe2+/H2O2 molar ratio, initial pH, initial concentration of NO and SO2 and volume fraction O-2 and CO2 on the oxidative removal of NO by UV/IF method were investigated respectively. Moreover, the results of kinetic analysis indicated that NO oxidation was confirmed to have a pseudo-first-order kinetics pattern. The rate constants decreased slightly with increasing liquid temperature, and then the apparent activation energy of NO oxidation reactions in the UV/IF system was calculated as -5.62 kJ/mol by the Arrhenius equation. Furthermore, the reaction mechanism and application prospects concerning NO oxidative removal by using the UV/IF system was speculated in brief. Finally, the computational fluid dynamics (CFD) simulations revealed that the improvement of axial and radial gas hold-up would enhance the gas-liquid contact and accelerate the oxidation reactions on the interface. In addition to reasonable control of process parameters, the optimization of reactor interior structure needs to be carried out via CFD simulation and experimental validation in future research, both are favourable to promote the NO oxidation efficiency and large-scale development of this technology. (C) 2021 Published by Elsevier B.V.

Automated summary

The in situ Fenton system facilitated by UV showed better oxidation ability of NO compared to the IF system due to the photochemical effect on oxidative species generation. The oxidation efficiencies of both systems were higher than that of the conventional Fenton system, and could be further optimized by controlling process parameters like UV power, gas flow rate, and reagent temperature. Further research on reactor interior structure optimization via computational fluid dynamics simulations and experimental validation is recommended to enhance NO oxidation efficiency and promote large-scale development of this technology.