Anodes are carbon blocks used as conductors in the electrolysis process by which aluminum is produced. The raw materials used in the production of anodes are:
- petroleum cokes – during the oil refining process a residue of which petroleum coke can be made remains. The large water molecules in the carbon residue are broken or torn by heating and then petroleum coke is formed. This product is suitable as a raw material.
- coal tar pitch – by distillation of crude tar, the residual coal tar pitch is obtained. After heating this material, it can be used as a raw material for anodes.
- anode butts – in the production process to make aluminum, the anodes in the furnace do get burned for the biggest part. The residues that remain are collected and crushed into smaller pieces. These butts get shipped to the Netherlands and they are reused as raw material. As a result, there is very little anode waste.
These three raw materials are combined after various operations and the mixture is then vibrated in a mold into the desired shape. The anode is baked to a temperature of 1090 °C for two weeks. The anode now possesses the properties that are important for the customer, such as high density, high conductivity, and low reactivity. After baking, the anode is packaged and transported to the customer.