Experimental study on three additives used for the removal of nitrite, a byproduct of ozone oxidation denitration technology

Abstract

Nitrogen oxides resulting from fossil fuel combustion are one of the major atmospheric pollutants. Ozone oxidation flue gas denitration technology has garnered significant attention for its benefits such as high efficiency, low temperature and simultaneous removal of multiple pollutants. However, the large amount of nitrite in the absorption products makes it prone to secondary pollution. A cost-effective and harmless treatment of the by-product nitrite will promote the ozone oxidation denitration technology. This study focused on investigating three different additives (ammonium chloride, ammonium carbonate, and urea) that can be added to react with nitrite and remove it in a harmless way. The effects of reaction temperature, initial nitrite ion concentration, reaction molar ratio, and initial pH on nitrite removal efficiency were explored. Combined with a wet spraying system, the synergistic removal of NOx/SO2 and by-product nitrite has also been studied. The experimental results revealed that with appropriate operating conditions and additives, the by-product nitrite can be efficiently removed while the system can achieve efficient removal of NOx/SO2. Among the three additives, ammonium carbonate was found to have the best overall removal effect. However, urea had an advantage over the other two additives in highly acidic and low-temperature slurry.