Beneficiation technology of high silicon bauxite

First, flotation desiliconization

Flotation Removal of silicon is one effective way to improve the domestic and international quality bauxite ore, is used more methods. A lot of work has shown that: aluminum mineral flotation collectors effective and sulfonates of fatty acids; hexametaphosphate adjusting agents are sodium phosphate, tannic acid, sodium pyrophosphate, soda, sodium carbonate and the like. Reverse flotation is better with amine collectors; when the pH of the slurry is 7-8, silicate minerals such as chlorite can be effectively selected with cationic amine collectors, and sodium hexametaphosphate is available. Helps the dispersion of the pulp.

The experimental study of kaolinite-diaspore bauxite in Shandong, Shanxi, Henan and other places shows that when the ore is ground to -200 mesh, 97% (or -300 mesh accounts for 90%), sodium carbonate and sulfide Sodium is a regulator, sodium hexametaphosphate is an inhibitor, and oxidized paraffin soap and tar oil (or fatty acid of azelaic acid waste) are used as collectors. The flotation desiliconization effect is better, and its flotation semi-industrial test The results are shown in Table 1. It can be seen that the conventional aluminum flotation method can increase the aluminum-silicon ratio of aluminum ore from about 5 to over 8.

Table 1 Semi-industrial flotation results of bauxite in various mining areas in China

In addition, for low-aluminum-silicon ratio ore (alloy-to-silicon ratio of 2 to 2.6) such as Shandong Tanshui and Liaoning Xiaoshi, the small test results also prove that the concentrate-aluminum-silicon ratio can be increased to 3.5-4.0, and the recovery of Al ₂ O ₃ The rate can reach 50% to 70%, which makes the low-quality bauxite which could not be used originally, can be used as a raw material for sintering aluminum.

Second, flocculation and desiliconization

For fine-grained gibbsite-type bauxite, it can be desiliconized by selective flocculation when there is more mud. The ore is first finely ground to -5 μm to 30% to 40%, then the modifier soda and caustic soda, the dispersant sodium hexametaphosphate are added, and the polyacrylamide polymer is used for selective flocculation to suspend the suspension. Separating from the sediment, the key to this technology is the use of highly efficient selective flocculants.

Third, bacterial leaching desiliconization

Because of the small minerals in bauxite, mechanical enrichment is limited, so many scholars believe that bacterial beneficiation is one of the most promising methods. The process utilizes silicon-consuming bacteria to destroy the structure of aluminum silicic acid, such as by destroying a kaolin molecule into alumina and silica, and converting SiO ₂ into a soluble matter, thereby separating the alumina insoluble matter. This method is particularly suitable for the treatment of colloidal ultrafine bauxite.

At home and abroad, a lot of research work has been done on the leaching and desiliconization of bauxite and minerals, and some progress has been made. For example, a foreign mine ore is a trihydrate bauxite ore, containing 43.6% Al ₂ O ₃ , 13.8% SiO ₂ , 22% TiO ₂ and 9.1% Fe ₂ O ₃ . The original ore is ground to -0.074mm. Grading deliming, +0.3mm particle size for magnetic separation, non-magnetic products for aluminum concentrate, fine mud and magnetic products for fine grinding and leaching, leaching temperature 30 ° C, liquid-solid ratio 1:5, leaching time 9d, dip The liquid zeolite adsorbs alumina, and then the aluminum and silicon are separated. The semi-industrial test results are shown in Table 1.

Table 1 Semi-industrial test results of bacterial beneficiation

Fourth, chemical desiliconization

The refractory bauxite or kaolinite of the fine-grained inlay is closely symbiotic with the aluminum mineral in a microcrystalline fine structure, which is difficult to select by conventional beneficiation methods and can be treated by chemical methods. At present, the development of chemical desiliconization is mainly pre-baking (or not roasting)-leaching to remove silicon and iron , and the processes include pre-baking, leaching desiliconization, solid-liquid separation and the like.

In the United States, it is possible to obtain 4.4 to 6.85 products suitable for sintering treatment from an aluminum-containing raw material having an aluminum-silicon ratio of 0.76 to 0.86: when the ratio of the original ore-aluminum to silicon is 2, it can be increased to 16.6 to 27.5. In Australia, the original ore is calcined at 1000 ° C for 60 min, then leached with 10% NaOH solution for 2 h, 77% of SiO ₂ can be removed, and the recovery of aluminum can reach 96% to 98%, aluminum to silicon ratio It can be increased from 2.4 to 8.9 to 9.8. The former Soviet Union leached directly with 200-237g/L Na ₂ O _k sodium aluminate solution without treating the high-silicon gibbsite ore. The liquid-solid ratio was 7-10, and the leaching was carried out at 95 °C for 4-6 hours. The ratio of aluminum to silicon in raw ore is 4.39, and the ratio of aluminum to silicon in desiliconized concentrate can reach 7-8.

China's Shandong Aluminum Plant, for the bauxite containing Fe ₂ O ₃ 4% and aluminum to silicon ratio of 4 to 5, is calcined at (1000 ± 100) °C, with a NaCO ₃ -containing NaOH solution at a pressure of 3 kg / cm ² Leaching for 15 minutes can make the ratio of concentrate to aluminum to silicon 12 to 13. The concentrate is dissolved by the Bayer process, and excess lime is added from the conventional 4% to 5% excess to 15% to 20%; and the recycled alkali solution of 210 to 300 g/L Na ₂ Ok is used at 60 to 32 kg/cm ² . The boiled and leached, the Al ₂ O ₃ dissolution rate is 87.5%, the chemical alkali consumption is 16 to 38 kg/t, and the Al ₂ O ₃ desiliconization efficiency is 57% to 62%.

The above describes several methods for desiliconization of high-silicon bauxite, and in the actual production process, it is often the combined process of these methods, and the desiliconization effect is better than any one alone.