Research On Simultaneous Desulfurization And Denitrification By Combining Liquid-phase Oxidation With Limestone-gypsum System

With the development of the Industry, the atmospheric pollution of our country became more and more serious. SO2and NOx are the main atmospheric contaminant. In the Twelfth Five-Year Plan period, the country continues controling the SO2emission, and brings the NOx emission into the amount control. So the coal-fired flue gas must be desulfurized and denitrified before it is discharged.The limestone-gypsum technology, whose process is simple and desulfurization efficiency is high, is the most widely used FGD technology among the world presently, but it’s inefficient on the removal of NOx. The author achieved simultaneous desulfurization and denitrification by adding liquid-phase oxidant to the limestone serum to improve the existing desulfurization technology.(1) Based on the conditions of oxidization and reduction of the nitrogen compound, while the reduction potential of the oxidant is higher than0.996V, the NO could be oxidized and absorbed. Exploratory experiments showed that, in the alkaline solution, NaC102and Na2S2O8have good oxidative effect on NO.(2) In the alkaline solution, studied the oxidation ability of NaC102. Research showed that, NaC102alkaline solution could oxidize and remove NO. When NaC102concentration was0.02mol/L, pH was10, temperature was70℃and gas flux was0.4L/min, disposed the simulated gas whose NO concentration was from0.02%to0.06%, the denitrification rate could reach above94%. The denitrification rate rose while the NaClO2concentration or reaction temperature increased, and decreased while gas flux or NO concentration increased, the suitable pH range for denitration was from7to10.(3) Under the conditions of CaCO3solid content40g/L, NaC102additive dosage1.6g/L, initial pH10, temperature70℃and gas flux0.5L/min, disposed the simulated gas whose SO2and NO concentration were separately0.06%to0.2%and0.03%to0.07%by NaC102/CaC03, the desulfurization rate were all above98%. While SO2concentration was0.08%, and the NO concentration was from0.04%to0.06%, the denitrification rate were all above88%, the maximum could reach96%. The tail gas all reached the discharge standards.(4) Research showed that, Na2S2O8could also oxidize and remove NO. The denitrification rate rose while the Na2S2O8concentration or temperature increased, and decreased while gas flux increased, the suitable pH range for denitration was from2to3and9to12. Under the conditions of CaCO3solid content40g/L, Na2S2O8concentration0.15mol/L, pH9, temperature70℃and gas flux0.5L/min, disposed the simulated gas whose SO2and NO concentration were separately0.06%to0.2%and0.03%to0.08%by Na2S2O8/CaCO3, the desulfurization rate were all above99.2%. While SO2concentration was0.08%, and NO concentration was from0.03%to0.06%, the denitrification rate were all above88.8%, the maximum could reach95%. The tail gas all reached the discharge standards, too.