Oxidation And Absorption Of NO_x In The Flue Gas In The Liquid Phase And Removal Of The Nitrite

This paper utilizes the method of oxidation-reduction denitration technology, to realize the efficient removal of NOx in the flue gas, and reduct the nitrogen transferred to liquid to harmless N2. This article examines the effect of chlorate oxidants (NaCIO, NaClO2 and ClO2) at different factors on NO oxidation efficiency and NO2 absorption properties with Na2S solution under different conditions, and analyzes the dynamics of the absorption reaction. Na2SO3 can reducts NO2" from the denitration waste liquid to N2, experimental studies the NO2- removal efficiency at different influences to obtain optimum conditions, while compares the efficiency with urea and ammonium. Main conclusions as follows:The test shows NO oxidation efficiency can reach 100% with NaC102 and ClO2 oxidizing agents in optimal conditions, but 50～60% by NaCIO. The ClO2 gas also has a high oxidation efficiency. NaC103/NaC10 and NaClO2/NaClO mixtures are more effective and economic than separate oxidants. The concentration of ClO2 is most rich when the concentration ratio of NaC102/NaC10 is 2.5 in acid condition, cooperates oxidation with mixtures. Oxidants will react with subsequent reductant results the competition with absorption of NO2 and reductant consumption. The products of oxidation reaction are mainly Cl-, NO2, NO2- and NO3-, and ClO2 will oxidize NO2- to NO3-.Experimental studies absorption characteristics of NO2 by Na2S solution in bubbling reactor, the results show that:when Na2S concentration was in the range of 15.8 and 47.5 mmol/L, the effect of NO2 concentration on absorption efficiency was poor; however, it was obvious when the concentration of Na2S solution was 0.30～3.25 mmol/L; Oxygen in the simulated flue gas did not decrease NO2 absorption efficiency, but it leaded to extra consumption of Na2S. NO2 absorption efficiency could be strengthened by 0.1% NaOH in Na2S solution. With the NO content in NOx increasing, the absorption efficiency of NOx declined. Even in the condition of NaOH, the synergistic effect between NO and NO2 on absorption have not been observed at 0.5 oxidation degree of NOx. The reaction is endothermic reaction, so the absorption rate increases with temperature raised and gas flow rate increased. Adding Na2SO3 in the Na2S solution, NO2 absorption efficiency increases with Na2SO3 concentration increased, while the efficiency maintain 90% at last. The absorbed NO2 was converted into N2 and NO2- by Na2S solution. The reaction between Na2S and NO2 is pseudo-second order reaction relevant to NO2 and Na2S first order, respectively.The experiment Na2SO3 reduction NO2- shows the optimum reaction condition is:when the ratio of SO32-/NO2- concentration is 3:2, pH of the solution is 5 and the temperature is 35 ℃, the removal efficiency of NO2-can be up to 99%. Compared with urea and ammoniums, Na2SO3 reduction NO2- will not produce secondary pollutions and easy operation. It can be combined with flue gas denitration process by Na2SO3 as well as to achieve the disposal of NOx completely.