Composite Metal Oxide/Semi-coke Collaborative And Efficient Desulfurization And Denitration Catalyst

SO2and NO in coal-fired flue gas are the main atmospheric pollutants and the main cause of acid rain, so to control the emission has become the focus in China’s environmental protection. Dry flue gas desulfurization and denitrification technology, due to its no secondary pollution, recyclable resources and catalyst, grows gradually popular in flue gas purification. Activated carbon is widely used in gas purification technology as an excellent catalyst support material, but its relatively high price gives rise to a high running cost of the flue gas purification apparatus, thus it is necessary to find an efficient and low-cost carrier material. Semi-coke, produced in low-temperature carbonization of coal, has a wealth of pores, a large specific surface area and a surface distributed a great number of oxygen-containing groups. This provides favorable conditions for SO2and NO adsorption and catalytic conversion. For the phenomenon that desulfurization products affect the activity of DeNOx active substance in the catalytic process, a function-regionalized, collaborative and efficient desulfurization and denitration catalyst was developed by composing alkaline earth metal and transition metal oxides. The main research is as follows:(1) Semi-coke activation. The generated specific surface area of Semi-coke was still insufficient in the formation process, so activation treatment was needed to improve the ratio of surface area and to further enrich the pores. In this paper, steam, zinc chloride, zinc nitrate, and potassium hydroxide were used as activators for raw semi-coke activation. Conclusions drawn from Experiments were as follows:steam activation noticeably opened up the closed pores, and enhanced semi-coke’s pore volume and specific surface area; zinc chloride activation reduced the hydrogen content in semi-coke and enlarged the pore volume; nitric acid activation not only removed the ash from semi-coke microporous surface to increase the specific surface area, but also increased the surface density of the oxygen-containing groups; Potassium hydroxide activation changed the pH of the semi-coke surface and could react with the carbon in the semi-coke at a certain temperature to create new porosity, increase the pore volume and the specific surface area.(2) The preparation of function-regionalized desulfurization and denitrification catalyst and its performance evaluation. Using currently available oxide/semi-coke desulfurization and denitration catalyst to dispose of flue gas, NO physically adsorbed would be replaced by SO2; simultaneously, sulfuric acid, the desulfurization product, could react with the DeNOx active to result in a corresponding sulfate, making the catalyst inactive. In this paper,10%BaO was added to the active material contained at the shell of the catalyst particles to enhance the DeNOx catalytic active’s activity, stability and the adsorption of NO. Catalyst core mainly loaded0.5%V2O5, oxidized SO2into SO3, and stored in micropores. Catalyst particle shell loaded1%of CuO. with NH3, NO directly reduced to N2, to achieve the subregional catalyzation of DeNOx shell and core desulfurization.(3) Study of the catalyst regeneration. By comparing and analyzing four catalyst regeneration methods, the thermal regeneration method, washing regeneration method, NH3reduction regeneration method and H2reduction regeneration method, the following results have been concluded:the thermal regeneration method slightly improved the desulfurization activity of the regenerated catalyst from97.83%to98.67%, while the denitrification activity declined from76.14%to72.11%; washing regeneration method greatly reduced the desulfurization and denitrification performance, the desulfurization rate dropping to77.69%and the denitrification rate63.81%; NH3regeneration reduction method could basically restore the desulfurization and denitrification performance of the catalyst; H2reduction regeneration method could only recover the denitrification activity, and the desulfurization rate dropped by6.86%. In summary, NH3regeneration method was superior to other methods in catalyst regeneration.