1. What is alumina?
Aluminum oxide, also known as aluminum trioxide, is a dehydrated product obtained from bauxite through Bayer process, sintering process, and other processes. It is a white powder or sand like substance.
2. What are the quality indicators of alumina?
The quality indicators of alumina mainly include chemical composition and physical properties. According to the provisions of the national standard GB/T24487-2022 for alumina, the main chemical composition indicators include AL2O3, SiO2, Fe2O3, Na2O, CaO, and ignition reduction content; The main physical performance indicators include specific surface area and particle size.
How is alumina classified?
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According to different uses, alumina can be divided into two categories: one is used as a raw material for electrolytic aluminum, called metallurgical grade alumina; The other type is non metallurgical alumina used in fields such as ceramics, chemicals, pharmaceuticals, etc., called special alumina, also known as chemical alumina. Currently, the majority of global alumina is used for electrolytic aluminum smelting and production, while only about 5% is used for other purposes.
What quality standards are used in the alumina industry?
At present, there are two aluminum oxide standards issued and implemented in China: one is the national standard “Aluminum Oxide” (GB/T24487-2022), which is applicable to aluminum oxide produced from bauxite, recycled aluminum oxide raw materials, and other raw materials used for the production of metal aluminum by molten salt electrolysis. It is also applicable to aluminum oxide used as raw materials for the production of corundum, ceramics, refractory products, and other aluminum oxide chemical products; The second is the industry standard “Metallurgical Grade Aluminum Oxide” (YS/T803-2012), which is only applicable to the aluminum oxide used in the production of electrolytic aluminum by the molten salt electrolysis method, that is, metallurgical grade aluminum oxide.
5. What are the main production costs of alumina?
The production cost of alumina mainly includes raw material costs and manufacturing expenses. Among them, the cost of raw materials mainly includes bauxite, caustic soda, and energy, with the proportion of these items accounting for approximately 39.7%, 15.6%, and 25% in 2022, respectively; Manufacturing costs mainly include labor costs, depreciation, and repair costs, accounting for approximately 15.7% of the total.
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What are the production processes for alumina?
The production process of alumina mainly includes Bayer method and sintering method. The process flow of Bayer method roughly includes the following main steps: crushing bauxite and mixing it with caustic soda to produce qualified raw ore slurry; Pre desilication, dilution, and sedimentation separation of red mud for the original ore slurry; The precipitate is decomposed into aluminum hydroxide through seed crystallization; Aluminum hydroxide is separated, washed, and roasted to obtain alumina.
The sintering process involves the following main steps: producing fine abrasive slurry from bauxite, limestone, and soda ash in proportion; After sintering, dissolution, and desilication procedures, prepare sodium aluminate solution; After the solution undergoes carbonation decomposition, the precipitated aluminum hydroxide and sodium carbonate mother liquor are separated; Roast aluminum hydroxide to form alumina.
What is the relationship between aluminum oxide and electrolytic aluminum?
Aluminum oxide is the main raw material for the production of electrolytic aluminum. Usually, 4 tons of bauxite can produce 1.92 tons of aluminum oxide and then 1 ton of electrolytic aluminum.
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