Continuing our series on the aluminum industry, this blog will look into how powdered aluminum oxide, also known as alumina or Al2O3, is turned into solid aluminum metal.
Aluminum is found in many places in everyday life, from beverage cans to airplane parts, automobile components, power lines and even cooking utensils. It has become an indispensable part of the infrastructure of our lives, which is why we are looking to expand our portfolio to offer a wider variety of Al materials to our customers.
To review, alumina starts as bauxite that is mined from the ground and then heated with various chemicals and purified to alumina. The yield from bauxite to Al2O3 is roughly 2:1. This powdered Al2O3 is further purified to aluminum, with another yield of roughly 2:1, so each pound of aluminum metal starts with 4 pounds of bauxite.
The Hall-Heroult process is utilized to transform the powdered Al2O3 into Al metal. This process uses a carbon-lined steel vat to hold the alumina and cryolite (Na3AlF6), while carbon electrode rods are then placed above the vat. The vat is heated to just under 1000°C which melts the cryolite, and the molten cryolite is then able to dissolve the alumina. Finally, an electric current is set up between the carbon vat lining and the upper electrodes causing the Al2O3 to break apart, and the molten Al to collect at the bottom of the vat. The Al metal collected at this stage is typically 99.8% pure and will require further processing to be used for the various Al Alloys we use in society today.
Every stage of the entire process requires quality control, the incoming bauxite is screened for compositional analysis. The red mud by-product is screened for environmental compliance with the effluent. The alumina powder is screened for purity, and to ensure that the process is complete. The smelting process has a series of checkpoints. The incoming alumina and cryolite are screened for purity, as is the final metal. Even the steel vat, the carbon lining of the vat, and the electrodes above will have been checked at some point in their life cycle.
At the end of their life cycle, hopefully all of these materials will be recycled, which introduces a whole new set of checkpoints. All of these checkpoints are opportunities for reference materials to be used. Powdered geological materials, liquid ICP standards, and metal standards all have their place in the cycle. LGC Industrial offers many of these materials already, and we are currently developing our own line of powdered geological materials which will be released in the coming year. Until then, browse our one of our existing product catalogs to find the reference materials you require.
Written by Kim Halkiotis, Posted by: ARMI MBH (www.armi.com)