Aluminum Smelting Industry Explained
The History of Aluminum Smelting
The modern aluminum smelting technique traces its roots to 1886. An Ohio chemistry student named Charles Martin Hall discovered a process to separate aluminum from molten material. At the same time, French chemist Paul T. Héroult made the same discovery. Both scientists received credit, and their technique became known as the Hall-Héroult process. It is the predominant aluminum smelting technique in use worldwide.
Although abundant in the earth's crust, pure aluminum is virtually impossible to find. Until the development of the Hall-Héroult process, the available quantities of pure aluminum amounted to samples. The Hall-Héroult process enabled the mass production of aluminum. In 1888, Hall founded the first industrial smelting operation, and global production has grown ever since.
What is Aluminum Smelting?
While aluminum is an abundant element in the Earth's crust, it is rarely available in its natural form. The smelting process is essential to access aluminum for use for building and construction materials. The mineral bauxite is responsible for the commercial viability of aluminum, and smelting is the process of extracting aluminum from bauxite.
Aluminum production first begins with smelters extracting aluminum from bauxite (sedimentary rock) during a two-step aluminum smelting process. The Bayer process separates alumina from bauxite. Also known as aluminum oxide, alumina then undergoes the Hall-Héroult process, producing pure aluminum. Each step decreases material quantity by half. For example, four units of bauxite will yield two units of alumina. Refining two units of alumina will amount to one unit of pure aluminum.
The Aluminum Smelting Process Explained
The Bayer Process
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.
The Hall-Héroult Process
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.
The Secondary Aluminum Smelting Process
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.
What Does the Outlook Look Like for Aluminum Smelters?
When it comes to aluminum trading and market outlook, projections forecast growth in demand for the commodity. By 2025, demand for aluminum is likely to grow by over 4% globally. The worldwide demand increase of over 3 billion tons is due mainly to the growing use of aluminum in construction, transportation and consumer goods industries.
Increased demand is taking a toll on global supply, leading to multiple calls for production. Since 2014, aluminum stocks at the London Metal Exchange have dropped 75%. While aluminum can undergo a recycling and reclamation process, new production demands continue to grow as more products adopt aluminum frames, components and hardware.
Consulting for Aluminum Producers and Smelting Companies
Aluminum is gaining momentum over other metals as a top choice across industries. Aluminum producers with an established alumina smelting network are poised to reap the gains from a growing and competitive alumina smelting market. If you are an aluminum smelter, gain an edge with aluminum consulting services by HARBOR.
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Market Studies: Get the latest market mapping studies and outlook projection for the range of aluminum products.
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