No aluminium without coal tar pitch
Aluminium is extracted from its oxide, alumina, using an electrolytic process. Electric current runs between two carbon electrodes (a positive and negative) in a high-temperature liquid bath of dissolved aluminium oxide.
The process relies on the anodes that are manufactured by mixing petroleum cokes with coal tar pitch, which functions as a binder. The mixture is formed into blocks of the required size and subsequently baked to about 1100°C. During the baking cycle, the coal tar pitch reacts to form graphitic structured coke and becomes electrically conductive.
Coal tar pitch is the only carbon binder that meets the requirements of the aluminium production process.
ca. 70 kilograms of coal tar pitch are needed to produce 1 tonne of aluminium.