Study On Simultaneous Removal Of So₂ And No From Coal-Fired Flue Gas By NaClO₂ /NaClO Compound Absorbent

The main pollutants of coal-fired flue gas are fly ash, SO₂, NO_x, Hg and greenhouse gas CO₂.The traditional treatment technologies always remove only one pollutant in a device, results in it's large investment, high cost for operation and much occupation of land. With the improvement of environmental requirements, the enterprises will be overwhelmed if they still follow the traditional idea. The technology of simultaneous desulfurization and denitrification and multi-pollutant integrated technology both quickly become the study points for their advantages to solve the problems exist in the traditional methods.Based on the good desulfurization and denitrification efficiencies and the consideration of cost about NaClO₂, NaClO was selected as an addition. The effects of operating parameters to the removal efficiencies by NaClO₂/NaClO compound absorbent were studied in a self-designed spraying tower. With the comprehensive consideration of test result and the working condition of practical project, the optimum operating parameters were confirmed. The test result showed that the desulfurization and denitrification efficiencies could respectively retain 99.8% and 94.0% in the following test condition: the concentration of NaClO₂ and NaClO were 6mmol/L and 18mmol/L, respectively; the pH value of the absorbent was 6; the initial concentration of SO₂ and NO were 2850mg/m³ and 670mg/m³, respectively; The reaction temperature was 55℃; the flue gas flux was 20 m³/h; the L/G was 20L/m³.Through the contrast test, the reaction mechanism was analyzed and the possible reactions and the overall chemical reaction equations were all put forward. Then, molar reaction enthalpy, molar formation Gibbs function, partial pressure of NO and SO₂ and constant of reaction rate were calculated by thermodynamic methods. The calculation results show that the simultaneous desulfurization and denitrification were available. Furthermore, the amount of usage of NaClO₂ and cost to retain the same removal efficiency of NO for the compound absorbents in different mixture ratio (NaClO₂ to NaClO) were compared.NaClO₂/NaClO compound absorbent has the advantage of high removal efficiencies but low investment, so this research provides an excellent reference for the forward development of NaClO₂ absorbent.