Stable oxides of aluminum, also known as bauxite in the mining, ceramics and materials sciences industries are what is called Alumina. Alumina demand is still expected to rise due to the country’s rapid progress in electrolytical aluminum and ceramics.
You can extract alumina from any ore using many different methods, such as the Bayer Method, soda lime sintering process and Bayer-sintering mixed method. This method accounts for 95% to all of the global alumina supply. Although the acid method has seen great advancements since the 1970s it is still not used in industry.
Bayer’s process for the development of products made from alumina.
Austrian Bayer (K.J.Bayer), invent it in 1888. It works by using NaOH solution of caustic soda to melt and dissolve aluminum in bauxite. This gives rise to sodium aluminate. Once the solution has been separated from its red mud residue, the temperature can be decreased and an aluminum hydroxide seed crystal is made. After long stirring the solution, the sodium alkali is separated and made into aluminum hydroxide. It’s then calcined at temperatures of 9501200. Obtained alumina products. After precipitation of aluminum oxide, the mother liquor is obtained. This solution is recycled following evaporation.
Gibbsite, diaspore and boehmite have different crystal structures. Because they dissolve in different caustic soda solutions, it is important to provide different dissolution conditions, especially different temperature. You can dissolve gibbsite bauxite at 125140. The diaspore bauxite is to be dispersed at 240260. To this, lime (3%) should be added.
Bayer process The advantages to producing alumina products
It is here that the Bayer Process has made significant progress.
2. Large-scale, continuous equipment operation
2. Production process automation
3. Energy-saving techniques such as fluidized roasting and high pressure enhanced dissolution
4. The production of sandy aluminum to meet flue gas and aluminum electrolysis. Bayer has many advantages
The economic effect of the Bayer Process is determined by the quality of the bauxite, mainly the SiO2 content in the ore, which is usually expressed by the aluminum-silicon ratio of the ore, that is, the weight ratio of the Al2O3 to the SiO2 content in the ore. Because in the dissolution process of the Bayer Process, SiO2 is transformed into sodalite-type hydrated sodium aluminosilicate (Na2O·Al2O3·1.7SiO2·nH2O), which is discharged along with the red mud. For every kilogram of SiO2 present in the ore, there will be approximately 1 kilogram Al2O3 as well as 0.8 kgs NaOH. A lower aluminum-silicon ratio in bauxite means that the Bayer process has a less economic effect. The Bayer Process produced a bauxite with an aluminum-silicon content of 7-8 until the mid 1970s. The decreasing resources of high-grade gibbsite-type Bauxite has made it more important to research how to utilize other types of low grade bauxite. Also, new technologies that save energy have been developed.
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