Titanium has a great effect on the digestion of bauxite in the Bayer process because it reacts readily at high temperatures in alkaline sodium aluminate solution. Under this consideration, the hydrothermal conversion ...Titanium has a great effect on the digestion of bauxite in the Bayer process because it reacts readily at high temperatures in alkaline sodium aluminate solution. Under this consideration, the hydrothermal conversion of Ti-containing minerals in the system of Na2O-Al2O3- SiO2-CaO-TiOz-H2O with increased temperatures was studied based on the thermodynamic analysis and systematic experiments. The results show that anatase converts to AlaTi2SiO12 at low temperatures （60-120℃）, which is similar to anatase in crystal structure. As the temperature continues to rise, Al4Ti2SiO12 decomposes gradually and converts to Ca3TiSi2（Al2Si0.5Ti0.5）O14 at 200 ℃ When the temperature reaches 260℃, CaTiO3 forms as the most stable titanate species for its hexagonal closest packing with O^2- and Ca^2＋. The findings enhance the under-standing of titanate scaling in the Bayer process and clarify the mechanism of how additive lime improves the digestion of diaspore.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.U1202274 and51504059)China Postdoctoral Science Foundation Funded Project(No.2015M581352)the Fundamental Research Funds for the Central Universities of China(Nos.N140203005 and N140204015)
文摘Titanium has a great effect on the digestion of bauxite in the Bayer process because it reacts readily at high temperatures in alkaline sodium aluminate solution. Under this consideration, the hydrothermal conversion of Ti-containing minerals in the system of Na2O-Al2O3- SiO2-CaO-TiOz-H2O with increased temperatures was studied based on the thermodynamic analysis and systematic experiments. The results show that anatase converts to AlaTi2SiO12 at low temperatures （60-120℃）, which is similar to anatase in crystal structure. As the temperature continues to rise, Al4Ti2SiO12 decomposes gradually and converts to Ca3TiSi2（Al2Si0.5Ti0.5）O14 at 200 ℃ When the temperature reaches 260℃, CaTiO3 forms as the most stable titanate species for its hexagonal closest packing with O^2- and Ca^2＋. The findings enhance the under-standing of titanate scaling in the Bayer process and clarify the mechanism of how additive lime improves the digestion of diaspore.
