Simultaneous removal of nitrogen oxides and sulfur dioxide using ultrasonically atomized hydrogen peroxide.

ABSTRACT

A new method was developed for denitrification and desulfurization using hydrogen peroxide with the aid of an ultrasonic nebulizer to obtain high removal efficiency of NOx and SO2. Comparing with the atomizing nozzles having the aperture size of 0.01~0.02 mm, the droplets generated using the ultrasonic nebulizer show the smallest d50 value of 7.2 µm, with 72% possessing the size less than 10 µm. Based on the numerical simulation of the vaporization rate of droplets, it is indicated that the droplets with the size of 7.2 µm can be vaporized totally at very short residence time (0.11 s) under 130 °C. Effects of influence factors including the reaction temperature, the initial H2O2 concentration, pH value, and the flue gas flow rate were studied on the removal efficiencies of NO and SO2. Using the in-series double-oxidation subsystems with H2O2 concentration of 6 wt%, pH 5.0, and the reaction temperature of 130 °C, the removal efficiencies of SO2 and NO are respectively 100% and 89.3% at the short residence time of 1.8 s, and the removal efficiency of NO can be increased to 100% as the residence time is longer than 3.7 s. It is confirmed that the ultrasonically atomized H2O2 can indeed enhance the removal efficiencies of NO and SO2 at the optimal temperature, owing to the fast vaporization rate of fine droplets as well as the formation of more active radicals to be captured by NO and SO2 simultaneously. The results here provide a promising route to remove effectively the emissions of NO and SO2 simultaneously. Graphical abstract.