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Electrometallurgy is a method inmetallurgy that uses electrical energy to produce metals by electrolysis. It is usually the last stage in metal production and is therefore preceded bypyrometallurgical orhydrometallurgical operations.[1] The electrolysis can be done on a molten metal oxide (smelt electrolysis) which is used for example to produce aluminium from aluminium oxide via theHall-Hérault process. Electrolysis can be used as a final refining stage in pyrometallurgical metal production (electrorefining) and it is also used for reduction of a metal from an aqueous metal salt solution produced by hydrometallurgy (electrowinning).
Electrometallurgy is the field concerned with the processes of metalelectrodeposition. There are seven categories of these processes:
Molten OxideElectrolysis in steelmaking is utilizing electrons as the reducing agent instead ofcoke as in conventionalblast furnace. For steel production, this method uses an inert anode (Carbon, Platinum, Iridium or Chromium-based alloy)[4] and places iron ore in the cathode. The electrochemical reaction in this Molten Oxide cell can reach up to 1600 °C, a temperature that melts iron ore and electrolyte oxide.[5] Then the molten iron ore decompose following this reaction:[6]
The electrolysis reaction will produce molten pure iron as a main product and oxygen as its by-product. Because this process does not add coke in the process, no CO2 gas is produced. So no directgreenhouse gas emission. Moreover, if the electricity to run such cells comes from renewable sources, this process may have zero emissions. This technology also can be implemented for producing Nickel, Chromium, and Ferrochromium.
Currently the Massachusetts-based Boston Metal company is in a process to scale up this technology to an industrial level.[6]
The purpose of this method is to reduce carbon content from steel. This process is suitable for secondary steelmaking industry which recycling steelscrap that has variety of carbon content in their feedstock.[7] This method aim to replace current conventional method that utilizingBasic Oxygen Furnace (BOF) to reduce carbon content of iron by blowing oxygen to make it react with carbon and forming CO2.
In electrorefining, decarburization process happened in electrochemical cell that composed of inert electrode, slag and steel. During the process, current passing through the cell and made slag and steel melted. Oxygen ion from slag decompose and oxidize carbon on steel and to form CO. That decarburizing reaction occurs in three steps as follows:[7]
The total reaction from this cell is:[7]
The SiO2 comes from the slag, based on the reaction above, besides producing CO gas. This method also produces pure silicon (depending on the slag). The benefit of this direct decarburization process is that it does not produce CO2, but rather CO, which is not considered as greenhouse gas.
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