Effect Of Bayan Obo Rare-earth Tailing On Catalytic Denitration Process

Environmental pollution caused by China’s coal-based energy utilization is an important factor restricting the development of thermal power industry,among which nitrogen oxide(NO)will be the focus of environmental protection treatment of coal-fired power stations after dust and sulfur oxide(SOx).In the study of catalytic denitrification,many catalysts for catalytic reduction of NO,such as transition metal oxides and rare earth metal oxides,have been developed,but most of the catalysts used are prepared by artificial synthesis.Although the denitrification effect is significant,it still has a great shortage as an industrial application,which is mainly reflected in the problems of expensive raw materials and complex production process.Bayan ebo tailings contain transition metals and rare earth metals and other active components needed by common denitrification catalysts,which are likely to be directly used as denitrification catalysts.However,the denitrification performance and mechanism of this natural mineral have never been studied.In this paper,the catalytic denitration of rare earth tailings in bayan obo was studied to realize high value utilization of rare earth tailings.In this paper,the Rare-Earth tailings in bayan obo are taken as the main research object.Based on the analysis of the degree of dissociation of mineral monomers in the Rare-Earth tailings and the continuous generation relationship,the mineral phases of the Rare-Earth tailings are divided into two types: single mineral phases and continuous ore phases.Among them,the single mineral facies contains the isolated mineral facies of iron ore,Rare-Earth minerals,fluorite and other monomers,while the continuous ore facies contains the continuous mineral facies of iron ore,Rare-Earth minerals,fluorite and other minerals.In this paper,the catalytic denitrification performance and mechanism of hematite and cerofluorocarbon monomer phases with obvious catalytic activity in Rare-Earth tailings were studied respectively,and the combined mechanism of hematite-cerofluorocarbon coupling phases in Rare-Earth tailings was studied.A physical model of iron oxide(Fe2O3)was established for hematite,a physical model of Ce-Fe oxide(Ce-Fe)Ox doped with iron was established for cerium fluoride,and a physical model of Ce O2-Fe2O3 loaded with cerium oxide was established for hematite-cerofluorocarbon-ore coupling structure in Rare-Earth tailings.Firstly,the catalytic semi-coke reduction of NO from Rare-Earth tailings was studied.In this paper,a test platform for catalytic denitrification activity in a fixed bed reactor was built by using a vertical tubular furnace.The experimental results show that the Rare-Earth tailings can effectively catalyze the semi-coke reduction of NO.Temperature and oxygen content are important factors affecting the denitrification rate,and the catalytic denitrification capacity of Rare-Earth tailings increases with the increase of temperature and oxygen content.When the content of oxygen was 5% and the temperature was 700 oC,the denitrification rate of Rare-Earth tailings was 81.45%,which was 23.19% higher than that of single semi-coke.Secondly,the physical models of iron oxide and cerium iron oxide are studied.By comparing the denitrification performance of ferric oxide with hematite,cerium oxide with cerium fluorocarbide,the experimental errors are all within 6%,indicating the correctness of the iron oxide model and cerium oxide model established for hematite and cerium fluorocarbide in the monomer mineral phase of Rare-Earth tailings.By comparing the denitrification rate of iron oxide,cerium iron oxide and Rare-Earth tailings(46.3%,71.5%,76.4%),the catalytic performance of cerium iron oxide is higher than that of iron oxide,while that of Rare-Earth tailings is stronger than that of iron oxide and cerium iron oxide.The experimental results show that hematite and cerium fluorocarbon in Rare-Earth tailings have good catalytic activity of semi-coke reduction and denitrification.Then,the combined catalysis of hematite-cerofluorocarbon coupling in Rare-Earth symbiosis was studied.By comparing the catalytic denitrification performance of hematite,cerofluorocarbon and Rare-Earth tailings in bayan obo ore,the conclusion is that the catalytic activity of Rare-Earth tailings is higher than that of cerofluorocarbon and hematite.The hypothesis that the catalytic activity of hematite-cerofluorocarbon-eutectic coupling was higher than that of hematite and cerofluorocarbon-eutectic monomers was verified by magnetic separation technology.Based on the structural characterization and surface characteristics analysis of Ce O2-Fe2O3,it is found that the Fe2O3 loaded with cerium oxide has more active sites and oxygen vacancies,so it has excellent catalytic denitrification performance,which explains the rationality of the experimental results.By comparing the denitrification performance of the iron-based oxides loaded with cerium oxide with that of the hematite-cerofluorocarbon ore streptents,the experimental errors are all within 5%,indicating the correctness of the iron-based oxide model loaded with cerium oxide established by the hematite-cerofluorocarbon ore streptents loaded with Rare-Earth tailings.Finally,the mechanism of cerium-iron oxide catalytic semi-coke denitrification was studied by temperature programmed experiment.The experimental results show that the denitrification rate of cerium oxide is much higher than that of cerium oxide and cerium oxide,and the catalytic denitrification effect of cerium oxide is better than that of pure iron oxide and cerium oxide due to the co-catalysis of Ce-Fe.The structure and surface characteristics of cerium oxide were analyzed and it was found that cerium oxide formed Ce-Fe solid solution.When Fe3+ with a small ion radius replaces Ce4+ with a large ion radius,a substitutional solid solution is formed,and abundant oxygen vacancy is induced by the charge balance principle.As the surface active site of cerium oxide catalyst,oxygen vacancy can improve the migration rate of surface oxygen and lattice oxygen,and enhance the catalytic performance of cerium oxide catalyst.Oxygen transfer theory was used to analyze the mechanism of co-catalytic denitrification of cerium iron oxide.Cerium-iron oxide reduced NO by C/CO through oxidation-reduction cycle,providing theoretical basis for the co-catalytic mechanism of cerium iron oxide.The research results provide theoretical basis for the application and development prospect of Rare-Earth tailings in the field of catalysis.