| Extractive metallurgy by Brano Fecko-Cegin | |
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A metallic
oxide is fed into a furnace along with a reducing agent such as carbon.
The metal releases its combined oxygen, which recombines with the carbon
to form a new carbonaceous oxide and leaves the metal in an uncombined
form.
High furnace An example of an exothermic reaction is the oxidation of iron sulfide (FeS) to form iron oxide (FeO) and sulfur dioxide (SO2) gas:
Alternatively an endothermic reaction is the smelting reduction of zinc oxide (ZnO) by carbon monoxide (CO) to yield zinc (Zn) metal and carbon dioxide (CO2):
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For this reaction to even proceed at a reasonable rate, the heat of 1,300 to 1,350 °C (2,375° to 2,450° F).For iron the oxidizing reaction is:
Roasting is a preliminary treatment that is very commonly used to change the substance that we're working with to extract the metal into some other compound in order to remove the metal easier and more economically. There are various kinds of roasts, for example: 1. Oxidizing roasts, which remove all or part of the sulfur from sulfide metal compounds, replacing the sulfides with oxides. 2. Sulfatizing roasts, which convert certain metals from sulfides to sulfates. 3. Reducing roasts, which lower the oxide state or even completely reduce an oxide to a metal. 4. Chloridizing roasts, or chlorination, which change metallic oxides to chlorides by heating with a chlorine source such as chlorine gas, hydrochloric acid gas, ammonium chloride, or sodium chloride. 5. Volatilizing roasts that eliminate easily volatilized oxides by converting them to gases.
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