Manufacturing method of alumina
I. Introduction
Alumina is an important raw material for the production of chemicals, which is widely used in ceramics, electronics, metallurgy and other fields. Therefore, it is of great significance to study the manufacturing methods of alumina to improve production efficiency, reduce cost and improve product quality. This article will introduce several common manufacturing methods of alumina.
II. Aluminum hydroxide method
Aluminum hydroxide method is one of the most commonly used methods in the production of alumina. The principle of this method is to convert the alumina in bauxite into aluminum hydroxide through chemical reaction, and then get alumina through calcination. The specific steps are as follows:
1. Dissolution of bauxite: Bauxite is mixed with sodium hydroxide solution to convert alumina into sodium aluminate.
2. Separation: Separate the sodium aluminate solution from the impurities by filtering, washing and other steps.
3. Acidification: An acidifying agent such as sulfuric acid or hydrochloric acid is added to the sodium aluminate solution to convert the sodium aluminate into aluminum hydroxide precipitate.
4. Filtration and washing: The aluminum hydroxide precipitate is separated from the mother liquor and washed to neutrality.
5. Calcination: Aluminum hydroxide is calcined at high temperature to obtain the alumina product.
Aluminum hydroxide method has the advantages of simple process, convenient operation and stable product quality, so it is widely used in alumina production.
Third, Bayer method
Bayer method is an important method in alumina production, applicable to the treatment of high-grade bauxite. The principle of this method is to use sodium hydroxide solution to dissolve alumina in bauxite at high temperature and pressure to get sodium aluminate solution, and then get aluminum hydroxide through the steps of cooling, crystallization, separation, and finally calcination to get alumina. The specific steps are as follows:
1. batching: mix bauxite, sodium hydroxide and circulating mother liquor in a certain proportion to make raw slurry.
2. High-pressure dissolution: Dissolve the raw ore slurry under high temperature and high pressure to get sodium aluminate solution.
3. Dilution and cooling: Dilute and cool down the sodium aluminate solution to precipitate aluminum hydroxide.
4. Separation and washing: Separate the aluminum hydroxide from the mother liquor by filtration and washing, and wash to neutral.
5. Calcination: The aluminum hydroxide is calcined at high temperature to obtain the aluminum oxide product.
Bayer method has the advantages of short process, low energy consumption, high product quality, etc., but the equipment investment is larger, suitable for large-scale production.
Four, sintering method
Sintering method is a traditional method in alumina production, suitable for processing low-grade bauxite. The principle of this method is to mix bauxite, sodium hydroxide and lime and other raw materials to sinter, get clinker, and then dissolve the alumina in the clinker with dilute alkali solution to get sodium aluminate solution, and finally get alumina after crystallization, separation, calcination and other steps. The specific steps are as follows:
1. batching: mix bauxite, sodium hydroxide and lime and other raw materials in a certain proportion.
2. Sintering: The mixture is sintered at high temperature in a rotary kiln to obtain clinker.
3. Dissolution: Dissolve the clinker by mixing it with dilute alkali solution to get sodium aluminate solution.
4. Crystallization and Separation: Aluminum hydroxide is precipitated and separated from the mother liquor by steps such as cooling and crystallization.
5. Calcination: Calcine the aluminum hydroxide at high temperature to get the alumina product.
Sintering method has the advantages of strong adaptability of raw materials and stable product quality, but the process is long and energy consumption is high.
V. Conclusion
Three common methods of alumina manufacturing, such as the aluminum hydroxide method, the Bayer method and the sintering method, have been introduced above. Different methods have different advantages and disadvantages and scope of application, and the suitable production method should be selected according to the actual situation. At the same time, with the continuous progress of science and technology, the manufacturing technology of alumina is also improving, and there will be more new technologies and new methods applied to alumina production in the future.
