Study On The Catalytic Reduction Regeneration Process Of Complex Absorption No_x Circulating Fluid

NO_x,typical component in flue gas streams,is recognized as another main pollutants that induce acid rain and greenhouse effects.Compared with the various denitrification technologies,the liquid-phase denitrification,characterized by Fe（Ⅱ）EDTA has been demonstrated as a very promising research direction in controlling NO_x emission because of its speedy capture ability for NO_x.However,Fe（Ⅱ）EDTA is easy to be oxidized by O₂ in the process of complexing absorption of NO,which will gradually reduce its denitration capacity.The product of Fe（Ⅱ）EDTA-NO has not been reduced in time,and it is difficult to maintain high NO removal rate for a long time.Therefore,in order to promote the industrial application of Fe（Ⅱ）EDTA complex denitrification technology,the regeneration of Fe（Ⅱ）EDTA is particularly important.In this paper,based on the related theoretical research of catalytic reduction of nitrate,a new method of Fe（Ⅱ）EDTA regeneration using Pd-based metal catalysts was proposed.The influence of different parameters on the Fe（Ⅱ）EDTA regeneration was investigated and the physical and chemical properties involved in the process of catalytic reduction were studied by using modern characterization technology.Finally,a new process of Fe（Ⅱ）EDTA complex absorption coupling catalytic reduction was proposed.The main research contents and structure are as follows:（1）The preparation of Pd-based metal catalysts and their effects on the catalytic reduction of Fe（Ⅱ）EDTA-NO were studied.The investigation of catalyst support,catalyst preparation method and Pd content showed that activated carbon was the best catalyst carrier during the catalytic reduction of Fe（Ⅱ）EDTA-NO,the catalyst synthesized by the one-pot method had the best reduction effect and the optimal loading of the catalyst was 3.14%.The catalyst prepared in accordance with the above optimal conditions had a conversion rate of Fe（Ⅱ）EDTA-NO of 96.0%at 20 minutes.（2）By studying the factors of catalytic reduction of Fe（Ⅱ）EDTA complexing solution,it was found that the optimal conditions of the reaction were as follows:the initial p H of the solution was 6,the reaction temperature was 60 ^oC,the amount of Pd/AC catalyst added was 2 g/L and the amount of sodium formate added was 10 g/L.Under the optimum conditions,the conversion of Fe（Ⅱ）EDTA could reach 95%,and the denitration rate of Fe（Ⅱ）EDTA regeneration solution could be restored to 100%.Cyclic voltammetric curves showed that under the action of external electrons,NO in Fe（Ⅱ）EDTA-NO could be reduced to N₂ and NH₄⁺.In the investigation of the reaction kinetics,it was found that the reaction conformed to the first-order reaction kinetic model,the reaction rate constant was 1.5449 min^-1,the apparent adsorption constant was 0.1123 L/mg,the activation energy Ea of the reaction was 43.3492 k J/mol and the pre-factor was 2.699×10⁶.（3）A new process of Fe（Ⅱ）EDTA complex absorption coupled catalytic reduction regeneration was proposed.The results of small-scale experiment and side line experiments showed that the complex solution could maintain more than 85%denitration rate in 315 min.Compared with a fresh Fe（Ⅱ）EDTA solution,the time to maintain 85%denitration rate is approximately 26 times longer.This process not only reduced Fe（Ⅱ）EDTA-NO and Fe（Ⅲ）EDTA to Fe（Ⅱ）EDTA with the ability of NO absorption,but also solved the problem of post-treatment of complexed NO in solution.The innovation of this paper is to select an excellent Pd/AC catalyst to effectively regenerate Fe（Ⅱ）EDTA denitration solution,and the reaction mechanism of Pd/AC on catalytic reduction of Fe（Ⅱ）EDTA-NO was studied.In addition,the Fe（Ⅱ）EDTA complex absorption coupled catalytic reduction regeneration process proposed in this paper greatly enhanced the denitration performance of the solution,which will provide new ideas and methods for the industrial application of Fe（Ⅱ）EDTA denitration technology.