Aluminum Smelting Industry Explained

Bauxite rock consists of alumina, water molecules and other minerals. The Bayer process extracts alumina through heating and dissolving the particles, then further refining the compound through filtering. After separating the alumina from bauxite, the smelter will discard the other materials.

Carl Josef Bayer created The Bayer Process in 1888. Bayer, who had a career in the textile industry, developed this process to extract alumina to dye cotton. 

While working on this process, Bayer discovered how to dissolve sodium aluminate during extraction by heating bauxite ore and a sodium hydroxide solution known as caustic soda in a pressure vessel. 

Bauxite can contain several compounds in addition to aluminum. While each compound present in the bauxite requires different extraction methods, the overall process remains the same. The particular aluminum component will determine the exact extraction method. After separating the residue, the gibbsite undergoes a cooling and seeding process with the fine-grained aluminum hydroxide to become precipitated. 

During extraction, the bauxite’s aluminum oxide converts into the soluble sodium aluminate. The silica dissolves while other compounds present in the bauxite remain solid. Any impurities or red mud undergo a filtration process using a rotary sand trap. This waste product has a high calcium and sodium hydroxide content. 

Charles Martin Hall and Paul Héroult created the first commercially viable way to extract aluminum in 1886 with the Hall-Héroult process. This process dissolves alumina in molten synthetic cryolite to lower the melting point for electrolysis. Cryolite also provides the additional benefits of making it easy for alumina to dissolve, conducting electricity and having a lower density than aluminum.

During the electrolysis process, the liquid aluminum deposits at the cathode while the oxygen from the alumni simultaneously combines with the carbon to create carbon dioxide. Typical aluminum smelters require large amounts of energy to function correctly. This need for energy means smelters are often close to large power stations.

On the industrial scale, the Hall-Héroult process of aluminum smelting requires a great deal of power, producing aluminum through electrolysis. Dissolved aluminum separates and moves to a collection area. Energy demands for this process are high, affecting the alumina smelting and aluminum market.

Due to new sustainability drivers and environmental impacts, aluminum smelting in the scrap and secondary market is gaining popularity. This is the process of recycling aluminum scrap into aluminum that can be reused to form a green aluminum closed-loop process.

Many manufacturing facilities have adopted the secondary aluminum smelting process, leading to significant economic and environmental benefits. Currently, more than half the aluminum in automotive and construction applications is from a recycling facility. This trend continues to grow due to the many benefits, such as requiring less energy and reducing landfill waste and greenhouse emissions.

After collecting the aluminum for the secondary aluminum smelting process, this scrap is de-coated to remove contaminants on the surface. Then, the aluminum shreds move to the recycling furnace to melt and reform in ingots and billets. After the reforming process, the aluminum is ready for processing into new aluminum products.