Research On Escaping Of Fluorine, Potassium And Sodium Of Bayan-obo Iron Concentrate In The Sintering Process

The fluorine content in Bayan obo iron ore concentrate has been controlled around0.5%with continuous improvement of modern mineral processing technology. But the influenceto metallurgical industry by fluorine hasn’t been eliminated, for alkali metals such as sodiumand potassium hasn’t been under effective control. Fluorine has a combined action withsodium and potassium on the produced pellets to a big pellet reducing inflation, low pelletstrength, low sinter strength of binding phase, broad melting range of sinter and pellet andso on. Therefore, this issue has done a research on the escape of fluorine, potassium andsodium during the roasting process of Bayan obo iron ore concentrate, which has not onlyprovided theoretical foundation for improving the roasting or sintering process of Bayan oboiron ore concentrate, but also has brought theoretical direction for supplement and perfectionof the special roasting technology. Finally the comprehensive utilization rate of iron oreconcentrates containing fluorine will be improved. This paper are mainly divided into twoparts:In the first part, Factsage6.2is used to analysis the phase formation of fluorite,potassium feldspar and natrium pyroxene, which are the main form of F, K and Na in thesintering process. The results show that Potassium feldspar decomposition reaction starts at1102℃, and generates leucite (KAlSi2O6) and SiO2; When CaF2and CaO are added into thepotassium feldspar, the silicon aluminate generate in the system, and Ca2SiO4generates at980℃, when fledspar disintegrate at1090℃, the cuspidine generates at the same time.When the temperature reached1270℃, the cuspidine disintegrate and the Ca2Al2SiO7generate, KF and KCaF3are also generated; Sodium pyroxene starts to decomposite at965.7℃; When CaF2and CaO are added, Ca2Fe2O5and Ca2SiO4generate after the Sodiumpyroxene decompositied, and cuspidine generates at1120℃. When the temperature reached1200℃, the cuspidine disintegrate and the Ca3SiO5generated. And NaF generates in thesintering process. The second part is mainly focus on potassium feldspar-CaF2-CaO system and natriumpyroxene-CaF2-CaO system. Coats-Redfern and Flynn-Wall-Ozawa method is used toanalysis of dynamic characters and calculate the fluoride escaping heat. The results provedthat the kinetics energy of potassium feldspar-CaF2-CaO system is E=49.4941kJ/mol witha parameter of A=13.9427. Its dynamic calculation used the Ginstling-Brounstein equation.The reaction theory of this reaction is three dimensional diffusion and the mechanismfunction is G （α）=123(1)32.The kinetic energy of the system of natriumpyroxene-CaF2-CaO is E=48.0036kJ/mol with a kinetic parameter of A=17.4685. Itsdynamic function used for calculation is the Valensi equation. The reaction theory is a twodimensional diffusion and the mechanism function is G（α）=α (1α)ln(1).The results of this study have significance meaning for the improvement of Bayan Oboore concentrate sintering technology and the reduction of the harmful elements such as F, K,and Na in the blast furnace iron production.