Occurrence and Production of Aluminum

Abstract

Abstract Production of primary aluminum involves two independent processes to transform the ore to the metal. It starts with the mineral bauxite, which has the highest grade of commercially mined metal ores, and is also the most easily purified. Bauxite typically contains about 50% aluminum oxide, while the rest of the mineral consists of oxides of iron, silicon, titanium, and other metals. Aluminum oxide (Al 2 O 3 ), or alumina, is extracted from bauxite by means of the Bayer process. Then the alumina is electrolyzed in large electrolysis cells to produce molten aluminum by the Hall–Héroult process, named after the inventors. These two industrial processes were invented in 1886 and 1887, and for almost 130 years they have resisted numerous attempts to replace them with new alternative processes. The aluminum industry is presently facing three main challenges: the economy, its electric energy consumption, and its carbon footprint. The economy has been difficult for several years, due to low metal prices, high global aluminum inventory, and current overcapacity and oversupply. Electric power dominates the cost, because even under ideal conditions alumina needs a large amount of energy to be reduced to aluminum, and in addition the process as conventionally conducted is not very energy efficient. Furthermore, the production of alumina and aluminum generates significant amounts of CO 2 , both from the chemistry of the reduction process itself and from the electric power plants based on fossil fuels such as coal and natural gas. However, there are positive signs for the aluminum industry as well. The world will continue to need aluminum, and experts expect a doubling of the world's aluminum production from 2010 to 2020.