Study On Precipitation, Separation, Growth Of Rutile Phase In Modification Of High-titanium Slag

The grade of TiO2in high-titanium slag which produced by directly reduced and melting-separation from vanadium-titanium magnetite is quilt lower; it’s just40-60%. This slag cannot be used as the raw material for titanium sponge or direct chlorination. So it needs to get higher grade rutile by modified to enrich treatment.Based on the distribution characteristics of titanium in the Ti-bearing slag, a method which combined with "transformed into rutile-precipitation and growing up-separation" was proposed in this paper. Firstly, high titanium slag was modified, most of the titania was transformed into rutile. After that, the rutile phase was coarsening and growing up in a suitable heat treatment condition. Finally, the rutile was separated by acid leaching, alkali leaching and acid leaching.Research on the process of modifying high-titanium slag and transforming into rutile has been carried out. The results is showed that adding acidic oxides SiO2or P2O5will help the impurities in anosovite turned into silicate or phosphate, and the TiO2can be precipitated in rutile phase.The effect of heat treatment on the precipitation and growing up of rutile phase has been researched. It is showed that a lower cooling rate is conducive to the rutile phase’s coarsening and growing up. Besides of this, raising the heat treatment temperature is also availed the coarsening and growing up of rutile, as it can break the "heredity" effect of rutile.The precipitation and coarsening kinetics of rutile in modification of high titanium slag under cooling conditions were discussed. The volume fraction of rutile during the cooling process can be approximately described by JMAK equation, i.t.X=1-exp(-c/αn), and n=0.3387, c=1.531e1718-T The average size of rutile can be described as follows: αr3=A(T)(1+e (α+c)p), and p=0.71, b=1.15e1718-T In this article, the separation process of rutile phase has been studied. Some technology condition affected on the grade of rutile has been discussed. In acid leaching process, the optimized technology is that, leaching temperature is90℃, leaching time is4h, and the ration of solid to liquid is1:20. In alkali leaching process, the optimized technology is that, the concentration of NaOH isl.5mol/L, leaching temperature is90℃, leaching time is6h, and the ration of solid to liquid is1:20. After being acid leaching and alkali leaching, the grade of rutile is82.36%, and the recovery is97.52%. By multi-stage leaching, the grade can be obtained to92.7%, and the recovery is94.1%.