(EDTA) - Flue Gas Denitrification In The Presence Of Fe 2 2

The main component of the nitrogen oxide in flue gas is NO. NO can hardly dissolve in water, so chelating agent such as Fe IIEDTA was used to absorb NO. The main problem in this approach is that FeIIEDTA can be easily oxidized to Fe IIIEDTA by O2 in flue gas.Because Fe III(EDTA) is not capable of binding NO, the denitration capacity of the liquid decreases quickly. According to recent researches, if pyrite slurry with added Fe IIEDTA was used to scrub flue gas, the coexisting SO2 and O2 can promote the leaching of pyrite to produce Fe2+ which may suppress the oxidation of Fe IIEDTA. In the meantime, SO2 can be catalytically oxidized to SO42-.In this study, a bubbling reactor was used as the main equipment. N2, O2, NO, and SO2 were used in certain proportion to simulate flue gas. The effects of solid-liqid ratio,the reaction temperature, pH, and concentrations of gas components were studied on the NO removal efficiency, the ferrous ion concentration, the fraction of iron leached, etc., in process of NO removal by pyrite slurry with added Fe IIEDTA in the presence of SO2. The main liquid products of denitrification were measured and analyzed.Experimental results showed that the removal efficiency of NO and the concentration of Fe2+ increased with increasing solid-liqid ratio, showing that pyrite can suppress the oxidation of Fe IIEDTA, while the fraction of leached iron decreased with increasing solid-liqid ratio. When the reaction temperature and pH were less than 60 ℃and 6, respectively, the NO removal efficiency, the concentration of Fe2+, and the fraction of leached iron inceased with increasing temperature and pH. But when the reaction temperature was above 60 ℃ and pH was above 6, the NO removal efficiency, the concentration of Fe2+, and the fraction of leached iron decreased with further increase of temperature and pH. So the ideal temperature and pH are about 60 ℃ and 6, respectively.With the increase of oxygen concentration, the removal efficiency of NO and the concentration of Fe2+ decreased because of the oxidation of Fe IIEDTA by O2, while the fraction of leached iron increased. With the increase of NO and SO2 concentrations, the removal efficiency of NO, the concentration of Fe2+,, and the fraction of leached iron inceased. Experiments under different experimental conditions all showed that the iron leaching process could be described by the reaction-controlled shrinking core model. The measured results of denitrification liquid products all showed that the removed NO wasmainly converted to ammonium.