Aluminum is the third most abundant element on the earth’s crust. It comprises 8% of the soil and rocks of the planet. It is only found in chemical compounds with other elements like silicon, oxygen and sulphur. Metallic aluminum that is pure can be produced economically from aluminum oxide ore.
Manufacturing aluminum involves two phases, the Bayer process of bauxite ore refinement to obtain the aluminum oxide and the Hall-Heroult process that involves smelting aluminum oxide in order for the pure aluminum to be released.
In the Bayer process, bauxite is crushed mechanically then the crushed ore is combined with caustic soda. It is placed in a grinding mill to produce slurry that contained fine ore particles. This will be pumped into a digester and heated at 230 degrees F and maintained for an hour or so. It will then undergo series of flash tanks for pressure reduction and heat recovery to be used in the refining process.
The slurry will be pumped into the settling tank, the impurities not dissolved will settle into the bottom of the vessel. After that, the rest of the liquid that resembles like coffee will be pumped through series of cloth fibers. Then the filtered liquid wll be pumped in a series of six-story-tall tanks for precipitation. The crystals settling at the bottom of the tank will be removed. It will be moved into the kiln for calcining and after that, the crystals will undergo a cooler.
The Hall-Heroult process, reduction pot is used. Its bottom is lined with carbon to act as the electrode. In the reduction pot, the alumina crystals are dissolved in molten cryolite. The direct current will pass through the solution resulting to breaking the bond between the oxygen atom and aluminum. The oxygen released will be attracted to the carbon rods forming carbon dioxide.
Crucible is transferred down the potline and collects 9,000 lb of molten aluminum. The metal is moved into a holding furnace and cast as ingots. Pouring the molten aluminum in a long horizontal mold is the common technique used. As the metal passes through the mold, its exterior is cooled with water and cause the aluminum to solidify.