Basic Research On The Recovery Of Valuable Metals From Spent SCR Catalysts

Under the general environmental trend of“Jinshan Yinshan is not as good as Lvshui Qingshan”,the selective catalytic reduction?SCR?denitration process has the advantages of high denitration efficiency,good selective reduction and little influence by the composition of the flue gas.It is widely used in the world.The SCR catalyst is mainly composed of noble metal oxides such as V,W and Ti.The service life is generally 3 to 5 years.If it is not properly disposed after disposal,it will cause serious pollution to the environment and waste of resources.To this end,the disposal of the spent SCR catalyst produced by the SCR process will be one of the major problems in building a harmonious society and realizing the green development of the heavy chemical industry.At present,China's spent SCR catalysts are mostly used for landfill disposal,which not only causes waste of land resources and environmental pollution,but also causes the loss of valuable precious metals.In order to develop spent SCR catalyst recycling technology,realize the harmless disposal of spent catalyst and its precious metal resource utilization;this study analyzes the industrial denitration methods and the harmless treatment principle of spent SCR catalyst,and through thermodynamic calculation,an innovation method for recovering the main V,W and Ti metal pyrometallurgy in spent SCR catalysts is proposed.That is,the spent SCR catalyst?vanadium-titanium?of a domestic thermal power plant is mixed with carbon,iron and lime and other raw materials,ball-making and drying,and then fusion and reduced in a DHL-400 DC arc furnace,and melted at a high temperature.It becomes Fe-V-W alloy and high-titanium slag,and the cooled and separated Fe-V-W alloy and high-titanium slag will be used for the smelting of alloy steel and the titanium white industry,respectively.In addition,in the process of realizing the harmless and resource treatment of the above-mentioned spent SCR catalyst,it was found that the powder physical properties of the spent catalyst are important process parameters in the feeding and smelting reduction process of the DC arc furnace,and therefore,the physical properties of spent SCR powder were tested.The physical parameters of the spent SCR catalyst powder determined in this study mainly include the angle of repose,the collapse angle,the difference angle,the flat angle,the dispersity,the apparent density and the tap density,etc,and summed up and analyzed the change of the above physical parameters with the diameter of SCR catalyst particles.For the industrial treatment of spent SCR catalyst?such as the accumulation of spent SCR catalyst in the plant,the choice of transport tools used in the transportation process,the loading methods in the smelting plant,the design of the high silo?provides basic test data;The SCR catalyst also provides experimental research data for the design of DC arc furnaces for the smelting of high titanium slag and iron alloys.This has potential value for the re-resource utilization of high-risk waste-spent SCR catalyst,and it is of great significance for building an ecologically harmonious society.The spent SCR catalyst,carbon powder and iron powder are mixed in a certain proportion,pelletized,and melted into a high-temperature molten Fe-V-W alloy and high-titanium slag liquid phase by a DC arc furnace,and after being cooled and separated by slag/iron,SEM,Xrd and other analytical methods were used to detect the chemical composition and phase of the slag/iron two-phase sample.The theoretical basis of the recycling of spent SCR catalyst was studied by experimental data,and the carbothermal reduction/melting separation behavior and mechanism were discussed.The results show that the recovery rate of the valuable metal changes with C/O,temperature,basicity and time.The optimal industrial parameters for recovering valuable metal elements in spent SCR catalysts were determined by experiments:molten pool temperature is 1650?,the C/O is 1.0,basicity is 1.0and melting time is 10 minutes.The complete separation of ferroalloy containing V and W and high titanium slag was successfully achieved.Under these condition,the recovery rates of Fe,V,W and TiO₂ reached 99%,97%,92%and 94%,respectively.This is of great practical significance and economic value for the development of spent SCR catalyst recycling technology,the construction of a harmonious society and the realization of sustainable development.