Alumina
Bauxite is a stable aluminum oxide. It can also be used as bauxite for mining, ceramics, and material science. Alumina demand is still expected to rise due to the rapid growth of the country’s electrolytical aluminum and ceramics industries.
Many methods can be used to remove alumina from an ore. These include the Bayer process, soda lime sintering and combined Bayer-sintering. Bayer Process, which accounts for 95% worldwide alumina output, has been the preferred method of producing alumina. Although the acid process has seen great advancements since the 1970s it is still not used in industry.
Bayer developed the Bayer process to produce alumina products
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 then 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 conditions, especially different dissolution temperatures. You can dissolve gibbsite bauxite at 125140. The diaspore bauxite is to be dispersed at 240260. To this, lime (3%) should be added.
Bayer processes are able to produce alumina products with many advantages
It is here that the Bayer Process has made significant progress.
1. Continuous operation and large-scale equipment
2. Automation of production processes
3. You can reduce your energy consumption by using high-pressure dissolution and fluidized baking.
4. Sandy alumina is produced to produce aluminum electrolysis, flue gas and the need for dry purification. Bayer: The benefits
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 one kilogram of Al2O3 as well as 0.8 kgs of NaOH. A lower aluminum-silicon ratio in bauxite means that the Bayer process has a less economic impact. 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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Aluminum Oxide
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