roasting
Quick Summary
Roasting is a metallurgical process that involves heating metal-bearing compounds in the presence of air, typically below their melting points. This process is crucial in extractive metallurgy for converting metallic minerals into a form that allows for easier extraction of the metal.12
There are several types of roasting, each designed for a specific outcome:
* Oxidizing roasts convert sulfide compounds into oxides, releasing sulfur dioxide gas.2
* Sulfatizing roasts transform sulfides into sulfates.2
* Reducing roasts lower the oxide state or fully reduce an oxide to its metallic form.2
* Chloridizing roasts convert oxides into chlorides using a chlorine source.2
* Volatilizing roasts eliminate easily vaporized oxides by converting them into gases.2
* Calcination drives off carbon dioxide or chemically combined water.2
Roasting is often an exothermic reaction, meaning it releases heat. This preliminary treatment is essential before further processes like smelting or refining can be employed to extract and purify metals.21
Ask Britannica AI about this topic
Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.
copper processingRoasting, smelting, and converting…concentrate has been produced containing copper and other metals of value (such as gold and silver), the next step is to remove impurity elements. In older processes the concentrate, containing between 5 and 10 percent water, is first roasted in a cylindrical, refractory-lined furnace of either the hearth or fluidized-bed…
Read More…concentrate has been produced containing copper and other metals of value (such as gold and silver), the next step is to remove impurity elements. In older processes the concentrate, containing between 5 and 10 percent water, is first roasted in a cylindrical, refractory-lined furnace of either the hearth or fluidized-bed…
Read More
lead processingIndirect smelting…for smelting, it must be roasted to remove most of the sulfur and to agglomerate further the fine flotation products so that they will not be blown out of the blast furnace. Various fluxing materials, such as limestone or iron ore, are mixed with the ore concentrate. The mix is…
Read More…for smelting, it must be roasted to remove most of the sulfur and to agglomerate further the fine flotation products so that they will not be blown out of the blast furnace. Various fluxing materials, such as limestone or iron ore, are mixed with the ore concentrate. The mix is…
Read More
nickel processingFrom sulfide ores…another, the matte may be roasted to produce high-grade nickel oxides; these are subjected to a pressure leach, and the solution is electro- and carbonyl refined. In electrorefining, the nickel is deposited onto pure nickel cathodes from sulfate or chloride solutions. This is done in electrolytic cells equipped with diaphragm…
Read More…another, the matte may be roasted to produce high-grade nickel oxides; these are subjected to a pressure leach, and the solution is electro- and carbonyl refined. In electrorefining, the nickel is deposited onto pure nickel cathodes from sulfate or chloride solutions. This is done in electrolytic cells equipped with diaphragm…
Read More- pyrometallurgy
The most important operations are roasting, smelting, and refining. Roasting, or heating in air without fusion, transforms sulfide ores into oxides, the sulfur escaping as sulfur dioxide, a gas. Smelting (q.v.) is the process used in blast furnaces to reduce iron ores. Tin, copper, and lead ores are also smelted.
Read MoreThe most important operations are roasting, smelting, and refining. Roasting, or heating in air without fusion, transforms sulfide ores into oxides, the sulfur escaping as sulfur dioxide, a gas. Smelting (q.v.) is the process used in blast furnaces to reduce iron ores. Tin, copper, and lead ores are also smelted.
Read More - metallurgyRoasting
As stated above, for those instances in which a metal-bearing compound is not in a chemical form that permits the metal to be easily and economically removed, it is necessary first to change it into some other compound. The preliminary treatment that is commonly…
Read MoreAs stated above, for those instances in which a metal-bearing compound is not in a chemical form that permits the metal to be easily and economically removed, it is necessary first to change it into some other compound. The preliminary treatment that is commonly…
Read More 
uranium processingRoastingThe hydrometallurgical processing of uranium ores is frequently preceded by a high-temperature calcination step. Roasting dehydrates the clay content of many ores, removes carbonaceous materials, oxidizes sulfur compounds to innocuous sulfates, and oxidizes any other reductants that may interfere in subsequent leaching operations.
Read MoreThe hydrometallurgical processing of uranium ores is frequently preceded by a high-temperature calcination step. Roasting dehydrates the clay content of many ores, removes carbonaceous materials, oxidizes sulfur compounds to innocuous sulfates, and oxidizes any other reductants that may interfere in subsequent leaching operations.
Read More
zinc processingRoasting and sintering…electrolytic production of zinc, the roasting of concentrates is achieved in fluidized-bed roasters, in which finely divided and heated particles of concentrate are suspended in a rising stream of air. The sulfur content can be reduced to less than 0.5 percent, and a high-strength (10 percent) sulfur dioxide gas is…
Read More…electrolytic production of zinc, the roasting of concentrates is achieved in fluidized-bed roasters, in which finely divided and heated particles of concentrate are suspended in a rising stream of air. The sulfur content can be reduced to less than 0.5 percent, and a high-strength (10 percent) sulfur dioxide gas is…
Read More