Study On Integration Technique And Mechanism Of Removal SO₂and NO From Flue Gas By NaClO₂/NaClO Compound Absorbent

At present，the pollution control of sulfur dioxide and nitrogen oxidesin coal-fired flue gas is the main task of air pollution control areas. So far,the research on the single desulfurization and denitration has been a lot ofmethods at home and abroad. There are hundreds of desulfurization anddenitrification methods, but only a dozen on industrial application. Thecommon feature of these processes is: one technology only removals onepollutant by a set of specialized equipment. This "one to one" governacemode exist many problems such as the large investment, high operatingcosts and much occupied land. As the environmental protectionrequirements increasing gradually and the emission standards continuing tohigher level, in addition to desulfurization, denitrification, the furthercontrol mercury, PM2.5, and the governance of the greenhouse gases CO₂were been required. The pollution control chain of flue gas is getting longerand longer, the energy companies can’t afford the more and higherenvironmental costs. Therefore, to develop the new technologies andequipments of simultaneous desulfurization and denitrification has becomean emerging research direction at home and abroad. It is urgent to realize the industrialized integrated technology of desulfurization anddenitrification.Based on the high efficiencies and low cost of desulfurizationdenitrification with NaClO solution, a new type of NaClO₂/NaClOcomposite absorption liquid by adding NaClO₂was designed. At the sametime, the experimental study on simultaneous desulfurization anddenitrification was made in the small scale level of the spray tower device.With the comprehensive consideration of test result and the workingcondition of practical project, the optimum operating parameters wereconfirmed. The test result showed that the optimum operating parameterswere: the concentration of NaClO₂and NaClO were2mmol/L and4mmol/L,respectively; the pH value of the absorbent was5.5; the L/G was20L/m3;the reaction temperature was50℃. In the optimum test condition, thedesulfurization and denitrification efficiencies could respectively retain99.7%and93.9%.Through the determination of various substances in solution which isbefore and after the reaction of simultaneous desulfurization anddenitrification, the existence of the chlorine dioxide and chlorine wasproved. At the same time, they are the intermediate product of chlorousacid and hypochlorous acid and the main oxide material for the compositeabsorbing solution. Then, the two-phase gas-liquid reaction process ofsimultaneous desulfurization and denitrification by sodium chlorite/sodium hypochlorite solution was revealed. Furthermore, the reaction equationswere summed up.Through calculate the molar reaction enthalpy, molar formation Gibbsfunction, constant of reaction rate and partial pressure of NO and SO₂, thecalculation results show that the simultaneous desulfurization anddenitrification is available. Then, considering the economic applicability,the economic benefits of the composite absorption solution was assessed.This study designs a new technology of simultaneous desulfurizationand denitrification by composite NaClO₂/NaClO absorption solution, it wasbased on the judgment of the status of the coal-fired flue gas treatment andprospects of development. The new method has many advantages such ashigh efficiency to desulphurization and denitrification, low-cost absorbent,simple equipment, simple operation and easy to implement automaticcontrol, the overall costs can be acceptable. So it has fine theoreticalsignificance and application promotion prospect.