Rio Tinto and Alcoa Announce World’s First Carbon-Free Aluminum Smelting Process

Rio Tinto and Alcoa Corporation announced a revolutionary process to make aluminum that produces only oxygen as a by-product, eliminating all direct greenhouse gas emissions from the traditional smelting process.  In Canada alone, use of the technology could eliminate the equivalent of 6.5 million metric tonnes of greenhouse gas emissions, if fully implemented at existing aluminum smelters in the country.  That represents an amount roughly equal to taking nearly 1.8 million light-duty vehicles off the road.

The conventional Hall–Héroult process (invented in 1886) for smelting aluminum involves dissolving alumina (Al2O3) in molten cryolite, and electrolyzing the molten salt bath, typically in a purpose-built cell with carbon electrodes.  The mixture is electrolyzed by passing a low voltage direct current at 100–300 kA through it, causing liquid aluminum metal to be deposited at the cathode.  Oxygen from the alumina combines with carbon from the anode to produce mostly carbon dioxide.

The cells operate 24 hours/day; temperature in the cells is maintained via electrical resistance.  Oxidation of the carbon anode increases the electrical efficiency at a cost of consuming the carbon electrodes and producing carbon dioxide.

The new Rio Tinto/Alcoa process eliminates the carbon, using proprietary materials instead; the only by-product is oxygen. 

Read more at  Rio Tinto and Alcoa Announce World’s First Carbon-Free Aluminum Smelting Process; Apple Assist; Elysis JV to Commercialize