| Blast furnace dust is one of the main by-products produced in the smelting process of ferrite and steel plants,including the main elements of ferrite,zinc and so on.How to reuse these elements has become an important issue.The method of leaching and reduction were mainly used for the treatment of zinc containing dust at present.The application of leaching for zinc containing dust is relatively extensive,but there is also a high demand for raw materials,and the problem of mismatching with the existing technology in the iron and steel plants.The initial investment of the pyrometallurgical treatment of zinc containing dust is large and the operation is complex,and this method can not be popularized in small and medium enterprises.In this thesis,zinc containing blast furnace dust was treated by the combined process of pyrometallurgical and hydrometallurgy.By controlling the temperature and the amount of carbon addition,the zinc ferrite in the blast furnace dust was selectively reduced to zinc oxide and magnetic ferrite oxide,and then the separation of zinc and ferrite was achieved by magnetic separation and acid leaching.The blast furnace dust(BF dust)was taken from a steel enterprise in Shaanxi.On the basis of thermodynamic calculation,The blue carbon was used as reducing agent in the reduction roasting of BF dust and then the calcined product was treated by magnetic separation before leaching.The influence of roasting and leaching process parameters on zinc leaching rate were studied.The element content,phase composition and morphology of all kinds of solid materials and calcines were analyzed by X ray diffraction fluorescence spectrometer(XRF),X ray diffractometer(XRD)and scanning electron microscope(SEM).Through the thermodynamic calculation of the related reaction of the Zn-Fe-C-O system and the phase analysis of the roasting products,the temperature range for reduction roasting of the blast furnace dust was determined to be 700~900?.Through the thermodynamic calculation and the phase analysis of the roasting products,the temperature range of the reduction roasting of Zn-Fe-C-O and other related reactions of blast furnace dust was determined to be 700~900?.The reduction roasting conditions were studied.When the roasting temperature is about 800,the roasting time is 2h,and the carbon addition account for50% of the weight of BF dust,the zinc ferrite in the blast furnace dust can be selectively reduced to zinc oxide and ferrite oxide.The leaching rate of zinc increased from 12.95% to 68.6% and the leaching rate of iron increased from 29.94% to 37.55%,when the BF dust was reduction roasting.The effects of sulfuric acid consumption,temperature,leaching time,stirring speed and liquid to solid ratio on the leaching rate of zinc and ferrite in roasting products were studied.The results show that the sulfate sulfuric acid consumption and temperature are the main factors influencing the leaching rate of zinc.When the leaching time is 1h,the leaching temperature is 30?,the liquid to solid ratio is 12:1,the concentration of sulfuric acid is 3mol/L,the stirring speed is 400r/min,the leaching rate of zinc and iron is 78.88% and 40.63%.The effect of magnetic separation on the leaching rate of zinc and iron in the calcined of BF dust was studied.The results show that the magnetic separation of the calcine can preliminarily separate zinc and iron.At the leaching temperature of 30?,the leaching time is 1h,the concentration of sulfuric acid is 3mol/L,the liquid to solid ratio is 12:1 and the stirring speed is 400r/min,the leaching rate of zinc and iron in the calcined BF dust after magnetic separation is 79.66% and 33.21%,respectively.Hence the iron and the zinc in the BF dust can be effectively separated by reduction roasting magnetic separation leaching process. |
PDF Full Text Request