Research On The Complex Absorption Coupling Electrochemical Regeneration Integrated Denitrification Process

The key to wet flue gas denitrification is to increase the solubility of NO in water.The ferrous chelate can be rapidly complexed with NO,so that the solubility of NO in the ferrous chelate solution is more than 100 times that of pure water,which is a research method of flue gas denitration technology.There are two drawbacks to this method.One is that the ferrous iron is easily deactivated by oxidation,and the other is the subsequent treatment of the absorption liquid.In this paper,there are two disadvantages in the complex absorption and denitrification method.The ferritic complex absorption liquid is regenerated by direct electroreduction method.The mechanism and optimization conditions of the ferrous chelate complexation NO absorption process and electroreduction process are studied.A complex absorption-regeneration overall process capable of stable operation under oxygen-rich conditions.The article is expanded from the following three sections:1.The process optimization of ferrous chelate complexation for NO absorption was studied.The absorption capacity of ferrous chelates for NO is always less than the theoretical value.After the concentration is increased from 0.03mol·L-1 to 0.09mol·L-1,the ferrous utilization rate decreases from 71.09%to 49.01%.In addition to the complexation reaction of NO,the absorption process also has a disproportionation reaction of NO under the action of ferrous iron to form NO3-/NO2-and N2O.It was found that when the ratio of ferrous iron to ligand was 1:1 and the concentration of ferrous chelate was 0.07mol·L-1 under the condition of adding supporting electrolyte,the highest removal rate of NO was 82.88%,ferrous iron.The utilization rate is 60.56%.For the choice of reactor,from the two aspects of stability and efficiency,the double-chamber membrane reactor is selected and the absorption process is separated from the electroreduction regeneration process to achieve the best NO removal effect.2.The process optimization of electroreduction regeneration complex absorption liquid was studied.The single factor method was used to investigate the effects of voltage,pH,O2 content,SO2,CO2 and other factors on electrical reduction.According to the experimental results,the reduction voltage of 7V can be selected to maintain the NO removal rate above 53%,and it will not cause a strong hydrogen evolution reaction.The initial reduction pH was chosen to be 6.5,and the reduction peak current was high for both Fe(III)and NO.02 can oxidize ferrous iron to ferric iron.The higher the content,the faster the oxidation rate,and the inhibition of NO absorption.Therefore,a larger reduction current is needed to increase the reduction rate to resist the influence of O2.SO2 promotes the absorption of NO,and the reaction with O2 has a higher priority than ferrous iron,which can significantly reduce the oxidation rate of ferrous iron.CO2 does not complex with ferrous chelates,but affects absorption efficiency by affecting the pH of the absorbing solution.The experiment also found that the cathode reduction products were H2,N2O,N2 and NH4+,and the amount produced was related to the ratio and the reduction potential.The more negative the potential,the higher the ratio of NH4+ and H2 in the product.The potential is-0.58V,no H2 is produced,the electron utilization rate of NH4+ is only 17.37%,the potential is-1.01V,H2 is precipitated,the electron utilization rate of NH4+is increased to 26.06%,the potential is-1.4V,and the H2 production is further.Increased,the electron utilization rate of NH4+ reached 42.07%.3.The deficiencies of the electroreduction method and the feasibility analysis of the improved method were studied.In view of the slow reduction rate of electroreduction regeneration method,it is attempted to increase the reaction rate by adding Zn powder to the system.It is found that although Zn powder has high reactivity,it cannot be regenerated in the cathode under conditions suitable for complex absorption,and Hydrolysis reaction and chelation reaction may even adversely affect the absorption process;for the accumulation of NH4+ in the absorption liquid,NH4+ can be eliminated by electrooxidation on the anode through the cation exchange membrane,but the degradation rate of NH4+ on the graphite electrode is higher.Slow,you need to find more suitable oxidation conditions.