New Molten Salt Electrolysis Using Plasma Arc Electrode

Conventional smelting with a carbon reductant is not used to obtain metals with high affinity for oxygen. Molten salt electrolysis is often used for the extraction of such metals. Although no carbon dioxide emission is expected in principle, huge amounts of CO2 are generated in actual molten salt electrolysis, where graphite electrodes are used as anodes. This is why the graphite is an indispensable material for high-temperature molten salt. For example, more than 1.2 tons of CO2 are emitted per 1.0 ton production of aluminum in a conventional molten salt electrolysis. We are developing a CO2-free process using arc electrodes. Alumina (Al2O3) mixed cryolite and AlF3 are used as test materials. Electrolysis is conducted in a stainless steel chamber under an inert Ar atmosphere. The arc is generated as a gaseous anode using a water-cooled plasma torch in constant current mode. The production of aluminum was confirmed by the experiment.