Experimental Study On Simultaneous Desulfurization And Denitrification By ClO₂ Oxidation With Calcium Based Absorption

Coal is the main energy consumption in China.In 2014,the total consumption of coal was 3.51 billion tons,producing annual emissions of SO₂ and NOx 21.176 million tons and 23.378 million tons,respectively.Conventionally,the most successful processes in the application for the removal of SO₂ and NOx are wet limestone-gypsum wet flue gas desulfurization?WFGD?technology and selective catalytic reduction?SCR?,respectively.SO₂ and NOx from flue gas is removed by installing separate wet flue gas desulfurization and denitrification equipments,which have many disadvantage,such as expensive investment and operation costs.To solve the existing problems of wet flue gas desulfurization process and develop a wet simultaneous denitrification and desulfurization technologies with compact structure,low investment and operating costs,no second pollution desulfurization and realizingproduct to the resources is in urgent need of the coal-fired flue gas treatment.In this paper,a new technology combining CaCO3 slurry absorbent with chlorine dioxide gas oxidation for flue gas simultaneous desulfurization and denitrification was put forward.The ClO₂ dosage amount,initial concentration of NO and the influence of the presence of SO₂ on the NO oxidation efficiency was studied during the gas phase oxidation period.And the concentration,pH and temperature of CaCO3 slurry absorbent,liquid to gas ratio was studied respectively.The experimental results show that: in the gas phase oxidation period: NO oxidation efficiency increased with the increase of ClO₂ dosage;Under the condition of a given ClO₂/NO mole ratio,the initial NO concentration have little effect on NO oxidation efficiency,when there is SO₂,with the increase of initial SO₂ concentration,NO oxidation efficiency reduced.For a given initial concentration of SO₂ 1000 mg/m3,NO initial concentration 509 mg/m3,when the ClO₂ and NO mole ratio was 0.8,NO oxidation efficiency could be 95%;In liquid phase absorption,CaCO3 slurry mass concentration 9%,initial pH of 7,temperature of 55 o C,L/G of 18 L/m3,the final desulfurization efficiency can reach 100%,denitrafication efficiency reached about 81%.Finally,the products in gas oxidation section and liquid phase CaCO3 slurry absorption section were analyzed.By experimentalobservations and data analysis,the reaction mechanism of gas-phase oxidation stage and liquid absorption section were analyzed.Based on this,a possible reaction mechanism was proposed,which theoretically explained the possible reaction pathway in desulfurization and denitrification process in the combined process.The process can achieve high removal efficiency of SO₂ and NOx,especially does not change the original equipment in limestone-gypsum method.Just injecting chlorine dioxide gas into flue gas can achieve high desulfurization and denitrification efficiency,thus leading to low cost of desulfurization and denitrification.The process has good practical and theoretical value.