Study On Removal Nitrogen Oxides By Recycle NaCl Electrolysis Under Low Temperature From Industrial Exhaust Gases

In view of the limitations of NO_x control under low temperature and shortcoming of produce a large number of wastewater through wet method we developed a technique,which has the advantages of low investment and running cost,as well as high NO_x removal efficiency.In this paper,we used sodium chloride?NaCl?electrolyte as the denitration agent to remove NO_x in flue gas.The specific content of each part was as follows:Firstly,the product of NaCl electrolyte which had electrolysis without membrane was studied.The effects of various operating parameters such as the concentration of chloride and current were discussed.The electrolyte was analysised by five-step iodometry.Results showed that the main product was ClO^-.The higher of initial concentration of NaCl would lead to the higher ClO^-concentration.With the increase of current,the concentration of ClO^-increasing first and decreasing afterwards.When the cuttent was 4 A,the electrolyte could reach the highest concentration of ClO^-.Secondly,the effects of various operating parameters on the removal of NO_x using NaClO solution which was produced by electrolytic sodium chloride without membrane were discussed.Results showed that the NO and NO_x removal efficiency in 60 min was stable.The higher of initial concentration of NaCl,current and the lower flue gas flow rate would lead to the higher nitrogen removal efficiency.In the various operating parameters,pH was one of the most important factors to affect nitrogen removal efficiency.Under the optimal experimental conditions,the NO_x removal efficiency could reach 57.40%when pre-electrolytic time of 25min,initial concentration of 70 g/L NaCl,current of 2 A,NO initial concentration of 505±10mg/m³,flue gas flow rate of 1035 ml/min and pH of 5.Thirdly,the different additives were discussed on NaCl cycle electricity method.Results showed that cobalt sulfate,sodium chlorite,sodium chlorate,hydrogen peroxide and potassium permanganate all could increase the NO removal efficiency.As potassium permanganate would increase the NO and NO_x removal efficiency obviously,this paper,chooseing potassium permanganate as additive.To choose the feasible operating condition,NaClO/KMnO₄ solution to removal nitrogen under different ways were discussed.Results showed that MnO₄^-regeneration could not achieve by circular electrolysis method and using NaClO/KMnO₄ solution under non-electrolytic way would also attain high nitrogen removal efficiency.Using NaClO/KMnO₄ complex system to denitration,recycle electrolysis and then adding KMnO₄ in the recycle electrolyte.In this way,would avoid wastewater discharge and improving denitration efficiency of recycle NaCl electrolysis's method at the same time.Finally,under the non-electrolytic system,effects of various operating parameters on the removal of NO_x using NaClO/KMnO₄ solution were discussed.Results showed that when the NaClO/KMnO₄ mole ratio of 5,solution pH of 5,NO initial concentration of 500.89 mg/m³,solution volume of 1500 ml,the NO and NO_x removal efficiency could reach 85.05%and67.69%respectively.According to the analysis of solution after reaction,it was found that Mn²⁺?NO₃^-and NO₂^-were the main product in the solution.