Study On High-temperature Enrichment And Flotation Separation Of Titanium Components From Ti-bearing Blast Furnace Slag

The grade of TiO₂ in Ti-bearing blast furnace slag of Panzhihua Iron and Steel Group Co.Ltd.is generally about 18%-25%,that TiO₂ disperses in various Ti-containing minerals.The traditional flotation methods failed to seperate titanium component effectively.According to the selective precipitation technology,the process mineralogy of Ti-bearing blast furnace slag,the selective enrichment and precipitation of titanium component,the surface properties and flotation behaviors of perovskite,titanaugite,and magnesium aluminum spinel?MA-spinel?,the mechanism of flotation separation of such minerals,and the modified slag flotation separation were studied in this paper.The main contents and conclusions of this paper are as follows:?1?Selective enrichment and precipitation of titanium componentThe main minerals in the Ti-bearing blast furnace slag are perovskite,titanaugite and MA-spinel,and the chemical composition is complex including CaO,SiO₂,and TiO₂?19.35%?.When perovskite is the target mineral and insure the w?SiO₂?)/w?TiO₂?proportion unchanged,adding to 2.54% CaO would promote perovskite selective enrichment and precipitation,based on the barycenter theory of CaO-SiO₂-TiO₂ ternary phase diagram.Pre-oxidation slag obtains by heat treatment at 1025°C for 30 min.The pre-oxidation process could oxidate Ti N,Ti C,and Ti?C,N?which influence the viscosity and melting temperature,thus the oxygen-potential in the slag increases.After the pre-oxidation process,Ti²⁺/Ti³⁺ change to Ti⁴⁺ which accelerates the perovskite crystal growth.The selective enrichment and precipitation process is as followed: pre-oxidation slag blending with 1.0% Fe₂O₃ is fused at 1470°C for 40 min?heating rate 4.0°C/min?,then heated preservation at 1320°C for 90 min?cooling rate 0.5°C/min?.The perovskite enrichment and precipitation effect in the modified slag is obvious,which the crystal size is 63.17 ?m,and the crystallization volume is 30.62%.Perovskite arranges in the modified slag in the shape of crosswise,graininess,and bead-like.The reasons are that perovskite precipitates firstly,then the fine perovskite crystals fuse resulting in the Ca²⁺ and TiO₃^2-concentrates decreased and perovskite growth limited.During the temperature reduces,perovskite crystals form neck in the growth limitation place.Because the neck place has the smaller radius of curvature,surface tension makes the melting point of neck place decrease.Thus,the neck place is easy to re-fuse and becomes finer,and the place where is the large radius of curvature is stabilization and makes perovskite crystals larger.?2?Flotation behaviors of minerals and the action mechanism with reagentsThe equal contents of Ti and Ca on perovskite surface,and the high contents of Al on titanaugite and MA-spinel surfaces.In the pure water,the point of zero charges of perovskite,titanaugite and MA-spinel are located at p H 5.6,4.3,and 2.9,respectively.Sodium oleate?Na OL?does not possess the good selectivity and collector performance to flotation separation of these minerals.Sodium lauryl sulfate?SLS?possesses the good collector performance,but the selectivity is weak.Octyl hydroxamic acid?OHA?possesses the good selectivity and collector performance.Sodium silicate has the selective depressant action to flotation separation of perovskite using OHA as the collector.Oxalic acid has certain depressant action,the depressant action of CMC is weak.The results of the artificially mixed minerals flotation test indicate that the perovskite concentrate with the grade of 33.57% and recovery of 49.53% of TiO₂ is obtained using the collector of OHA and it possesses better flotation index than using Na OL or SLS as the collector.When adding the sodium silicate,the perovskite concentrate with the grade of 39.44% and recovery of 50.19% of TiO₂ is obtained.Under acidic condition,the active point of OHA reacted with perovskite is Ti,the active point of OHA reacted with titanaugite and MA-spinel were Mg and Al.Under alkaline conditions,the active points of OHA reacted with perovskite are Ti and Ca,the active points of OHA reacted with titanaugite are Ca and Mg;and the active point of OHA reacted with MA-spinel were Mg and Al.Under acidic condition,the adsorption capacity of sodium silicate on perovskite is weak,and the adsorption capacity of sodium silicate on titanaugite and MA-spinel is strong.Sodium silicate is adsorbed on titanaugite and MA-spinel surface,which hindered the approach of OHA to the surface and reduced the adsorption of OHA on the titanaugite and MA-spinel surface.?3?Flotation separation technology of the modified slagWhen the pulp concentration of the modified slag is 20%,the p H of the pulp is 12.61 after stirring for 3 min,meanwhile the content of free CaO is 0.55%.When H₂SO₄ is as the regulator,the modified slag?the grade of TiO₂ is 17.12%?flotation tests indicate that the perovskite concentrate with the grade and recovery of TiO₂ does not obtain good index,and H₂SO₄ consumption is about 16.31 kg/t.The SEM and EDX analysis results indicate that the surfaces of each minerals are covered by CaSO₄ micro precipitated,leading to the bad index.Using HCl as the treatment agent,the roughing flotation results indicate that the perovskite concentrate with the grade of 29.74% and recovery of 49.95% of TiO₂ is obtained.Although the grade of TiO₂ of perovskite concentrate increases after treated by HCl,the index does not reach a better result,and the acid wastewater brings a new pollution.Therefore,exploring a new technology of perovskite flotation separation from the modified slag has an important guiding significance to separate titanium component from Ti-bearing blast furnace slag.