Abstract: Based on the Chinese bauxite character and the status of the traditional sintering process, the intensified sintering process was studied. In the charge, the mass ratio of alumina to silica is 9.62, calcium ratio 1.3-2.0, alkali ratio 1.0, and then the charge is sintered above 1250℃. It is convenient for sinter to be leached, and the secondary reaction appears little. The slurry after sinter leaching is transferred into autoclave for desilicification at about 170℃, and the siliceous modulus of solution reaches more than 200. Then some lime is added for deep-desilication at normal pressure, the siliceous modulus of solution increases more than 600 even if the Al2O3 content is more than 200g/L.The SiO2 coefficient in hydrate garnet from deep-desilication is more than 0.28. Under conditions of the addition of seed and application of novel technology of carbonization, the contents of Na2O and SiO2 in product are less than 0.37% and 0.025%, respectively. When surfactant is added into spent liquor in the evaporation, the concentration of Na2OT can reach more than 300g/L, and the scale on the heating surface can be abated obviously. With the application of intensified sintering process the output of every rotary kiln increases by 19.7%, in the same time the energy consumption of alumina production decreases by 24.71%.
Study and application of intensified sintering processfor alumina production
Abstract：
Based on the Chinese bauxite character and the status of the traditional sintering process, the intensified sintering process was studied. In the charge, the mass ratio of alumina to silica is 9.62, calcium ratio 1.32.0, alkali ratio 1.0, and then the charge is sintered above 1 250 ℃. It is convenient for sinter to be leached, and the secondary reaction appears little. The slurry after sinter leaching is transferred into autoclave for desilicification at about 170 ℃, and the siliceous modulus of solution reaches more than 200. Then some lime is added for deep-desilication at normal pressure, the siliceous modulus of solution increases more than 600 even if the Al2O3 content is more than 200 g/L.The SiO2 coefficient in hydrate garnet from deep-desilication is more than 0.28. Under conditions of the addition of seed and application of novel technology of carbonization, the contents of Na2O and SiO2 in product are less than 0.37% and 0.025%, respectively. When surfactant is added into spent liquor in the evaporation, the concentration of Na2OT can reach more than 300 g/L, and the scale on the heating surface can be abated obviously. With the application of intensified sintering process the output of every rotary kiln increases by 19.7%, in the same time the energy consumption of alumina production decreases by 24.71%.
Table 2 Effect of temperature on sinteringprocess under different conditions
In addition, there are K2O 7%, Na2Os 1.5% in charge, sintering time is 20 min. Sinter leaching conditions: temperature 90 ℃; time 20 min; amount of sinter 350 g/L. Solution for sinter leaching: Na2Ok 77.12 g/L, Na2Oc 12 g/L, Al2O3 70.55 g/L.
Fig.1 Relationship of Al2O3 extraction ratio and time at different temperature in sinter leaching process (Sinter leaching condition: amount of sinter, 350 g/L; Solution for sinter leaching: Na2Ok 85 g/L, Al2O3 78.55 g/L, Na2Oc 13 g/L, αk 1.78; Green liqor: Al2O3 203-210 g/L, SiO2 10-11 g/L)
