How to obtain pure aluminum?
The history of aluminum is very old. However, it has recently been transformed into a form used today. Although aluminum is the most common metal in the world, pure aluminum does not exist naturally. Aluminum atoms are easily attached to other metals that make up the compounds.
It is also impossible to isolate aluminum by melting compounds in the furnace, such as with iron. Obtaining püre aluminum is a little bit hard. The aluminum manufacturing process is much more complex and requires a large amount of electricity. For this reason, aluminum smelting machines have always been built around energy sources, hydroelectric power plants that do not pollute the environment. But let’s start again anyway.
Aluminum Manufacturing Process
The aluminum production process can be divided into three stages;
- First, bauxite containing aluminum is removed from the ground.
- The bauxites are then made into alumina or aluminum oxide.
- Pure aluminum is produced using electrolytic reduction.
In this process, aluminum oxide is disassembled using electric current. Approximately 4- tons of bauxite is processed into 2 tons of alumina, which can be made around 1 ton of aluminum.
How Aluminum is Made?
There are various minerals in the world where aluminum can be obtained. However, the most common raw material is bauxite. Bauxite is a mineral primarily composed of aluminum oxide mixed with some other minerals. Bauxite is considered high quality if it contains more than 50% aluminum oxide.
There are many variations between bauxites and they can be structurally intact or crumb. Bauxite is usually brick red, red, or brown due to iron oxide. If the iron content is low, bauxite may be gray or white. However, bluish, purple, red, and black derivatives, yellow, dark green, and even multicolored bauxites are formed.
Approximately 90% of global bauxite stocks are found in tropical and subtropical regions, while 73% are found only in five countries:
Guinea has the highest bauxite supply of 5.3 billion tons (28.4% of global supply) and bauxite has a very high quality, with a very little contribution. They are also located very close to the surface and have factors that make mining very easy.
The most common way to use bauxite is to use mines. Special equipment is used to cut a layer removed from the surface, then these rocks are transported to factories near the mines to be taken to areas that provide grain reduction such as crushing and grinding.
However, some places require underground mines to be made, where aluminum ore is extracted from deep underground locations. One of the deepest mines in the Cheremkhovskaya-Deep mine in the Urals in Russia, the ventilation wells extend to a depth of 1550 meters.
What is Bayer Process?
Bayer Process is the process of producing aluminum oxide from Boxide.
The next stage of the production chain is the process of turning bauxite into alumina or aluminum oxide (Al2O3) white powder. The most common process for producing alumina from bauxite is the Bayer process, which was discovered 100 years ago, but is still widely used today. Approximately 90% of the alumina refineries in the world use the Bayer process. It is very efficient, only high rates of bauxite, especially low silicon, can be used.
The principle of the Bayer process is as follows:
The crystallized aluminum hydrate contained in bauxite easily dissolves in concentrated caustic soda (NaOH) at high temperatures. And when the temperature is lowered, the concentration of the solution rises again. Aluminum hydrate crystallizes, but other elements contained in bauxite should not dissolve or recrystallize before the aluminum hydrate crystallizes and should fit well. The slurry structure can be easily isolated and removed after melting the aluminum hydrate caustic soda. This mud is known as red mud.
Alumina is a direct source of aluminum in the aluminum production process, but another component is required to create the right environment for electrolysis, and this component is cryolite. It is a rare natural fluoride mineral and is artificially produced due to its scarcity in natural form. In modern metal production, cryolite is made with a mixture of hydrofluoric acid, aluminum hydroxide, and soda.
Bauxites are the most common raw material for producing alumina, but not limited to them. Alumina can be made from the nepheline line. Nepheline is formed in the form of apatite-nepheline rock (apatite is a calcium-phosphorus oxide). Along with the production process, producing alumina from Nephelin also produces soda, (a substance used in construction, production of some chemicals, food industry, etc.) and rare metal gallium. Production waste white mud can be used to make high quality cement. To create 1 ton of alumina, 4 tons of nepheline and 7.5 tons of limestone are used.
So as you can see obtaining aluminum is a detailed process. And there are so many materials to manufacture pure aluminum.
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