Aluminum is the most used and widespread metal on the planet, comprising of around 8.8 percent of the crust. Aluminum does not exist in free form because of its high chemical reactivity. Most people do not know that there are no mining sites for aluminum anywhere in the world. Only a few rocks and minerals possess aluminum elements and hence ideal for industrial production. The aluminium manufacturing process is as follows.
1. Crushing and grinding
The raw material that contains aluminum components is known as bauxite. The recovery of alumina starts by first of all passing the bauxite through the screens so as to organize it in sizes. The bauxite is then crushed into fine uniformly sized materials.
The materials are then channeled into enormous grinding mills that contain sodium hydroxide, also known as caustic soda solution at extreme pressure and temperature. The grinding mills move in a circular motion grinding the ore into a fine consistency. The material is then removed from the mills. At this stage, the resulting solution is called slurry. The solution is a mixture of undissolved bauxite components (silicon, iron, titanium) – also called red mud, and sodium aluminate.
The slurry is then put into a digester containing a chemical that dissolves the alumina. The slurry is heated up to 145 degree Celsius. It stays in the digester from half an hour to a few hours. More sodium hydroxide is added so as to dissolve the aluminum elements in the slurry. The slurry is then pumped into some flash tanks to decrease the pressure as well as heat before channeling it into settling tanks.
Gravity is the key element in settling chamber. However, a few chemicals put to catalyze the process. The impurities in the slurry will eventually separate out. These impurities include iron and sand – they settle at the bottom of the tank.
The liquor that is at the brim of the tank is then directed via filters. This process cleans and washes the solution to recover caustic soda and alumina. The remaining red mud is directed into storage ponds to be dried through evaporation.
The material that these filters catch is known as filter cake and is cleaned to get rid of caustic soda and alumina. The filtered solution is cooled and then pumped into the precipitators.
Inside the precipitators, seed crystals of alumina hydrate are added to catalyze the precipitation of the virgin aluminum, particles while the solution cools down. The alumina crystals start to form around the seeds and settle at the bottom of the tank. The alumina crystals are then transferred to the thickening tanks and filtered into the calcination kilns.
This process involves removing water from alumina hydrate.
The alumina is then converted to metallic aluminum by smelting. This is the final stage in the aluminium manufacturing process. The smelting process has to produce aluminum from alumina. It is a continuous process that takes place at least 24 hours to complete. Smelters produce aluminum that is 99 percent pure.
To learn more about the aluminium manufacturing process, check out Lixil. Lixil is a company that specializes in making aluminum structures and products all over America.