| High iron content gibbsite-type bauxite, located in Guigang, Binyang and Hengxian of Guangxi is the largest gibbsite-type bauxite as known in China. There are amount of valuable metals but no effective processes and technology for the utilization of this ore. In the thesis, iron-aluminum-silicon separation process has been studied. The mineralogy of high iron content gibbsite-type bauxite, Fe-Al separation process and mechanics, as well as Al-Si separation from high-alumina content slag were also studied main points as follows:Mineralogy analysis indicates that the main minerals in high iron content gibbsite-type bauxite are gibbsite, goethite, raphisiderite and kaolin. There are also a small amount of diaspore, illite, anatase, quartz, chlorite, etc. The content of alumina, silica and total iron are 26.35%,8.32%,31.22% respectively, and the ore is also associated with titanium, gallium, vanadium and other valuable metals. Aluminum is scattered into gibbsite, goethite and silicates whose content is 45.01%,23.68%,23.15% respectively.98.59% iron is dispered in hematite and goethite. This ore is characterized as relatively high iron oxides content, but low alumina content, A/S ratio is only 3.17. Aluminiferous minerals and ferrous minerals are fine in size and conjoint and substituted with each other.Fine high iron content bauxite and sodium salt additives are mixed intensively, the mixture is pelleted or briquetted, roasted, grinded and separated by magnetic separation in turn, metallic iron and high-alumina slag are obtained. Under the conditions of T-2, T-3 and T-4 dosage were 15%, 2% and 25% respectively, iron and aluminum were able to be deeply separated after reduced at 1050℃for 60 min. Roasted ore was grinded with 50% bulk concentration and-0.074mm content reached 96.69%, the magnetic filed intensity was 97.5mT. A metallic iron concentrate with 93.73% total iron grade,1.21% Al2O3 could be obtained. The recovery rate of iron reached 93%. Iron mainly existed in the form of metallic iron in the concentrate; alumina and silica were combined with additives entered into sodium aluminosilicate.Thermodynamics of reactions of additives showed that alumina and silica inclined to combine with sodium oxide and formed sodium aluminosilicates. Ferric iron oxide was easier to be reduced to ferrous iron and metallic iron. The formations of peridot and iron aluminate were restrained. Therefore, the complex structure between Fe-Al-Si was destroyed; Fe-Al separation could be achieved.Microstructure of the roasted ore indicated that T-2 enhanced the separation of metallic iron grains from non-magnetics, T-3 accelerated reduction of iron oxide, and T-4 made the aggregation of metallic iron grains. The suitable reduction temperature and time is necessary to enlarge the size of metallic iron grains.Through the optimization of leaching parameters, including temperature, sulfuric acid concentration, liquid-solid ratio, time and stirring speed, leaching of alumina and silica may reach 84% and 88% when the appropriate sulfuric acid concentration was 20%, leaching temperature was 25℃, leaching time was 60min, liquid-solid ratio was 10:1 and stirring speed was 100r/min. Leaching dynamics results show the alumina leaching is coincided with the internal diffusion reaction, so as silica.When the tempeture was 30℃, the dosage of activated carbon was 0.8g/L, stirring speed was 160r/min and the time was 15min,82.3% silica and 3.69% alumina were adsorpted by activated carbon, and the A/S value of acid leached solution reached upto 16.13. |
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