Bauxite rotary kiln, also called alumina rotary kiln is a kind of rotary kiln, we can see from the name, the rotary kiln is mainly for in development of alumina rotary kiln, which is mainly composed of a rotary part, supporting part, transmission device, kiln hood, kiln head tail sealing, burning device and etc. composition. Kiln supporting board and a kiln tail material returning scoop the block casting, convenient installation, with high heat resistance and corrosion resistance, wear resistance, kiln head cold air sleeve through air cooling, can, to the mouth of the kiln kiln shell and guard plate of uniform cooling the safer and more reliable. The kiln head cover adopts a large volume method, and the structure of the kiln door is opened, so that the air flow is more stable. Kiln head, a kiln tail seal using radial friction maze, scales double sealing form, has the advantages of simple structure, convenient maintenance is at present domestic most advanced seal form. Swirl type four channel coal powder burner with fuel injection ignition device used in combustion device.
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Bauxite Rotary Kiln (667 downloads)
Bauxite, also known as alumina and bauxite, the main component is alumina,the density 2.4-2.5g/cm3 and hardness of 1 ~ 3, opaque, crisp, very difficult to melt, insoluble in water, can be dissolved in sulfuric acid, sodium hydroxide solution.It is mainly for aluminum smelting and refractory materials.
Rotary kiln clinker is pale, pale yellow, and dark grey. It is mainly used for high aluminum refractory material, also can be used for production of fused corundum.
Light burning bauxite of rotary kiln,also known as the light burning powder,is the raw material of water purification agent aluminium polychloride.White or gray white,due to iron,it appears brownish yellow or light red.Density 3.9 ~ 4g/cm3, hardness 1 ~ 3, opaque, brittle.
The rotary kiln calcination process of bauxite
The rotary kiln Calcined Bauxite changes can be divided into three sections: the decomposition stage, the two stage of mullite petrochemical and crystallization sintering stage.
- Decomposition stage：400 ℃ -1200 ℃ temperature range is bauxite decomposition stage.Diaspore and kaolinite in bauxite at 400℃ start dehydration, 450-600 ℃ intense reaction, 700-800 ℃ completed.Gibbsite under high temperature gradually transformed corundum, kaolinite and dehydrated into metakaolin, more than 950 ℃ into mullite and amorphous SiO2,which is converted to cristobalite at high temperatures.
- Mullite petrochemical phase: Above 1200 ℃, corundum and SiO2 continue to react to form mullite, is known as the secondary mullite:
3AI2O3 + 2SiO2 → (≥1200 ℃) → 3AI2O3 + 2SiO2 (secondary mullite)
In the secondary mullite petrochemical, it occurs about 10% volume expansion,while below the 1300-1400 ℃,Fe2O3, TiO2 of bauxite, and other impurities with Al2O3, SiO2 can form reaction liquid,liquid phase formation is contributed to secondary mullite formation,but also makes preparation for the sintering of barite.
- Barite sintering stage：With the completion of secondary mullite petrochemical,Barite sintering rapid action is beginning.Above 1400-1500 ℃,due to the liquid phase, corundum and mullite crystals is growing,when 1500 ℃ is about 10μm, 1700 ℃ respectively 60μm and 90μm.The main factors affecting the sintered bauxite are secondary mullite petrochemical phase,liquid and structure of bauxite.
Global mined bauxite,with more than 85% by using rotary kiln to produce alumina,followed by the production of aluminum metal.10% is used in the production of alumina using non-metallic, and the remaining for non-metallurgical bauxite applications.