Electrometallurgical process

The same arrangement is applied for electrometallurgical processes where insoluble anodes are used and the liberated gas is allowed to esoape freely into the atmosphere. 

Figure 3.1. Schematic of electrometallurgical processes used to purify metals. Shown is the (a) Downs cell used to purify sodium metal and (b) Hall cell used to purify aluminum metal. Reproduced with permission from Chemistry The Central Science, 8th ed., Brown, LeMay, Bursten. Copyright 2002 Prentice-Hall.

The high resistance of titanium diboride, TiB2, to many metal melts, particularly aluminum, has led to its use as an electrode and crucible material for electrometallurgical processes. 

R. Combes, B. Tremillon, F. De Andrade, M. Lopes and H. Ferreira, Definition and Use of an Oxoacidity Function O for the Comparison of Acidity Levels at 1000 K of Some Chloride Melts Involved in Electrometallurgical Processes, Anal. Lett. 15A (1982) 1585-1600. 

The PRISM NFRC uses an established electrometallurgical separations process employed by the aluminum industry for separating aluminum from alumina. This electrometallurgical process has been proven and deployed on a laboratory and engineering scale for nuclear materials by both ANL and Idaho National Laboratory [23]. Separations are accomplished in a molten salt bath that uses an electrical potential in the solution to separate used fuel. The uranium and TRUs plate out on an anode and are subsequently removed from the solution. 

With the NFRC process, nonproliferation concerns are alleviated by the intrinsic diversion resistance of tihe electrometallurgical process [11,24]. All TRUs (Np, Pu, Am, Cm) are separated en masse in one step of the electrometallurgical process the combined constituents are not usable for military purposes without complex additional processes. These TRUs are continually recycled in the PRISM until they are fissioned completely [25,26], which localizes the material on-site thereby avoiding risks of theft or diversion during transport. 

Boron is used as an alloying element for steel. For that reason, the alloy ferroboron, with 20% boron, is manufactured in electrometallurgical processes and used as a raw material. Low boron contents, as low as 0.003% B, have a marked effect on the hard-enability of steels with medium high carbon contents. It leads to hardening through the component section without alloying the steel with expensive elements such as chromium and nickel. Boron steels of this type have been very much utihzed for agricultural machinery. 

In electrometallurgy, electrolysis is used to produce metals from their compounds. For example, the Hall process is an electrometallurgical process crucial to aluminum production. The main source of aluminum is bauxite, AI2O3 n H2O. A hydrometallurgi-cal process, the Bayer process, separates bauxite from the irou aud silicon dioxide with which it is usually found. In this process, the bauxite is heated in a concentrated aqueous NaOH solution under high pressure. The aluminum oxide dissolves, leaving the other oxides behind in solid form. 

Electrochemical processes in melts are often attended by side reactions and phenomena complicating the primary process. This is true, in particular, for the technically very important class of reactions in which a number of metals (calcium, barium, and others) are obtained electrometallurgically from molten salts. In many of these processes the metal that is deposited (sometimes in a highly disperse state) is found to interact with the corrosive melt for example, in a reaction such as... 

See for example Electrometallurgical Techniques for DOE Spent Fuel Treatment Final Report, National Research Council, National Academy Press, Washington, D.C., 2000 Alternatives for High-Level Waste Salt Processing at the Savannah River Site, National Research Council, National Academy Press, Washington, D.C., 2000. 

The design of connection of the electrodes to the current conductors depends on the nature of the process. There is a considerable difference between the connections used in electrolyzers where periodical removal of electrodes from the bath is required and the connections used in electrolyzers where the electrodes are not removed and form a fixed part of the equipment. The first case is encountered mainly in electrometallurgical refining processes where anode scraps and cathodes with the deposited metal are removed. In such oases... 

In electrolyzers where during the operation no replacement of the electrolyte is required (e. g. electrometallurgical refining processes) mixing can be carried out by a suitably designed stirrer or by gas (air) which is led in through a perforated pipe which reaches to the bottom of the vessel. 

Several processes for the extraction of copper by electrometallurgical methods have been devised. The Marchese patent2 aimed at the decomposition of copper matte and deposition of the copper simultaneously in a sulphuric-acid electrolyte with a copper-matte anode and a copper cathode. In Siemens and Halske s patent3 the copper of the ore was oxidized to the cupric state by an acid solution of ferric sulphate, and the copper deposited electrolytically in a second vessel with a diaphragm separating the cathode and the anode. Neither process has been commercially successful. 

Many processes used to produce or refine metals are based on electrolysis. Collectively these processes are referred to as electrometallurgy. Electrometallurgical procedures can be broadly differentiated according to whether they involve electrolysis of a molten salt or of an aqueous solution. 

By changing the head end treatment steps, other types of fuel can be accommodated in this nonaqueous process. For example, an initial Li/Li20 step can be added to convert oxide fuel to the metallic form. To be compatible with the electrometallurgical treatment just described, the electrorefiner requires the spent fuel to be in a metallic form. 

R.G. Agnew, L.D. Kowal, and D. Young, Process Optimisation at INCO s Cobalt Refinery, International Symposium on Electrometallurgical Plant Practice, eds. P.L. Claessens and G.B. Harris (Montreal, Canada Canadian Institute of Mining, Metallurgy and Petroleum, 1990), 221-231. 

Simpson, M.F. et al. 2001. A description of the ceramic waste form production process from the demonstration phase of the electrometallurgical treatment of EBR-II spent fuel. Nuclear Technology 134(3) 263-377. 

Westphal, B.R. et al. 2008. On the development of a distillation process for the electrometallurgical treatment of irradiated spent nuclear fuel. Nuclear Engineering and Technology 40(3) 163. 

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