A Fundamental Investigation On Recovery Of Titanium From Titanium-bearing Blast Furnace Slag

There are lots of V-Ti bearing magnetite in Pan-Xi Zone, which accounts for 90.54% of total titanium resource in China. In present process, 53% Ti entries V-Ti bearing magnetite concentrate obtained by mineral separation, which was refined By blast furnace, almost all of titanium entry the slag phase and form the blast furnace slag including 22%～25% TiO₂. Nowadays, there are no effective methods to recover this slag, which is piled by large. It is not only waste of Ti resource, but polluting environment.To resolve the problem of effective utilization of Ti-bearing blast furnace slag, in this paper, based on full foundation of physical and chemical characteristics Ti-bearing blast furnace slag, directed enrichment and separation of CaTiO₃ in Ti-bearing water quenching slag and H2SO4 leaching were systematically investigated. The effects of additives and heat treatment on crystal granularity of CaTiO₃ were studied. It was shown that the additive CaO and CaF₂ are helpful to increase granularity of CaTiO₃. Under the conditions of non-melted state (1250℃), R=3.0, addition of 6% CaF₂, roasting time 4 hours and cooling speed 10℃/min, CaTiO₃ with about 30μm grain size was obtained. By flotation, rich-Ti material including 50.21% TiO₂ was obtained under the conditions of hydroxamic acid dosage 12kg/t and pH 9, but recovery was low.The effects of H₂SO₄ concentration, reaction temperature, reaction time, L/S, raw material granularity and stirring speed on the leaching rate of TiO₂ were investigated respectively in H₂SO₄ leaching process. For water quenching slag , it was shown that the leaching rate of TiO₂ was 72.26% under the conditions of H2SO4 concentration 50%, reaction temperature 100℃, reaction time 1h, L:S=10:l, raw material granularity -0.5mm and stirring speed 400r/min. For the natural cooled slag, the leaching rate of TiO₂ was only about 40% under corresponding conditions with water quenching slag.The water quenching Ti-bearing slag was investigated by double stage leaching and the effect of colloid substance CaSO₄ was decreased in the leaching process. It was shown that, under the conditions of reaction temperature 100℃, raw material granularity -0.5mm, stirring speed 400r/min, first leaching process 10%～15% H₂SO₄ concentration, reaction time 10～30min, and second leaching process 50% H₂SO₄ concentration, reaction time 2h, the leaching rate of TiO₂ was over 80%.The leaching mechanism was investigated from thermodynamic analysis, crystalshape and micrographic structure. It was shown that the Ti-bearing water quenching slag is fragile, fine granularity, loose, multi-hole and great contacte surface. CaTiO₃ was only Ti-component phase which can react with H2SO4. The slag was activated by water quenching and formed lots of non-crystal substances which have good reaction activation helped to TiO₂ of leaching. But there were lots of aluminosilicates with good crystallinity which can not react with H₂SO₄, instead of CaTiO₃ in natural cooled slag. The compacted structure of natural cooled slag leaded to bad performance of leaching.