Studies On No Absorption With Ferrous Triethanolamine Solution

In rencent years, nitrogen oxides (NOx),which are considered one kind of major air pollutants, could cause acid rain and photochemical smog, thus threaten human life and health at a large extent. Whether in the domestic or overseas, dry denitrification methods, especially SCR and SNCR, are the most popular denitrification processes in industrial application. But SCR and SNCR both have some disadvantages, such as expensive investment, catalyst poisoning and release of other secondary pollutants.The advantages of wet denitrification methods are simple equipment and relatively low energy consumption. Although NO absorption with ferrous chelate solution has been studied worldwidely, this method did not apply to industry, due to the fact that ferrous chelate can be easily oxidized into ferric chelate by O2in the flue gas. Despite of the resistance to O2of ferrous thiochelate, this kind of ligands are relatively high cost and complex. Thus, this article proposes NO absorption with ferrous triethanolamine (TEA) solution, adding reductant to regenerating ferric triethanolamine. Firstly, this paper investigated NO removal efficiency and reaction rate with Fe2+TEA solution and then compared the results with NO absorption by Fe2+EDTA solution. And then, category, reaction order, mass transfer coefficient, enhancement factor and reaction rate constant of this reaction are analyzed and calculated. At last, the effect of adding sodium hydrosulfite (Na2S2O4) into Fe2+TEA solution is investigated.NO absorption with Fe2+TEA solution was studied in bubbling reactor. Results show that1:2is the most appropriate molar ratio of Fe2+TEA solution. pH value of solution influences NO removal efficiency dramatically, due to the fact that the solubility and redox potential of Fe2+TEA are depended on pH value. When pH value is13, NO removal efficiency by Fe2+TEA can reach90%. When concentration of Fe2+TEA increased from0.03mol/L to0.18mol/L, NO removal efficiency increased from50%to90%. Although with the increase of inlet concentration of NO, NO removal efficiency has declined slightly, it can maintain about80%. This complexation reaction is exothermic reaction, therefore, the increase of reaction temperature will result in the decrease of NO removal efficiency, when reaction temperature is30℃and80℃, respectively, the NO removal efficiency is80%and54%, respectively. The existence of O2in the feed gas led NO removal efficiency decrease dramatically, but compared to Fe2+EDTA solution, Fe2+TEA solution show more resistance to O2. In addition, reaction rate of Fe2+TEA and NO was studied. Experiments suggest that reaction rate of Fe2+TEA and NO increased with the increase of pH value and concentration of Fe2+TEA solution. In the meantime, reaction rate drops sharply because of increase of O2content in flue gas. But under same condition, the difference of reaction rate between Fe2+TEA and Fe2+EDTA is4><10"6mol/min. The complexing process of Fe2+TEA and NO is the fast reaction of order1and second order reaction rate constant was calculated as7.61x108m3kmol-1s-1under the conditions of Fe2+TEA concentration0.125mol/L,25℃and pH value13. Employing Na2S2O4as reductant, the reduction efficiency of Fe3+TEA can reach62%under the conditions of [Fe3+TEA]/[Na2S2O4]=1:2,[Fe3+TEA]=0.05mol/L and20℃.