Pyrometallurgy

These are chemical processes that occur in metallurgical aggregates at high (800–2000 ° C) temperatures. Therefore, pyrometallurgy is sometimes called "high temperature chemistry." Often chemical reactions are accompanied by a change in the state of aggregation of the reacting substances: melting , sublimation , evaporation of the resulting metals or their compounds. In such processes, interactions can occur between the solid, liquid (melts) and gaseous phases in any combination.

Pyrometallurgical processes are the processes of agglomeration of metallurgical raw materials, smelting of charge materials, the manufacture of alloys, and refining of metals. In particular, it is firing , blast furnace smelting , open-hearth smelting , smelting in converters , arc and induction furnaces. Pyrometallurgy is the basis for the production of cast iron , steel , lead , copper , zinc , etc.

In pyrometallurgy, carbon reduction is often used - in cases where the metals being reduced do not form stable carbides , in addition to the above, such metals include germanium , cadmium , tin, and others. In the cases of formation of stable carbides by reduced metals instead of carbon reduction, metallothermy is often used ^[1] .

Pyrometallurgy is the main and most ancient area of ​​metallurgy. From ancient times until the end of the 19th century, metal production was based almost exclusively on pyrometallurgical processes. At the turn of the 19th and 20th centuries, another major branch of metallurgy, hydrometallurgy, acquired industrial significance. However, pyrometallurgy continues to maintain a dominant position both in the scale of production and in the variety of processes.

At the beginning of the 20th century, along with fiery heating methods, various types of electric heating (arc, induction, etc.) began to be used in metallurgy; At about the same time, electrolysis of molten chemical compounds (production of aluminum and other non-ferrous metals ) was introduced in industry.

In the 2nd half of the 20th century, plasma smelting of metals , zone smelting and electric firing smelting became widespread. Metallurgical processes based on the use of electric current distinguish into an independent area of ​​pyrometallurgy - electrometallurgy .

The main process of pyrometallurgy is ore smelting, which is carried out at such high temperatures when the products of the chemical interaction melt, forming two liquid phases - metal or sulfide and slag. Distinguish between reducing and oxidative melting.

The decisive process of reducing ore smelting is the reduction of metal oxides with the ultimate obtaining of a molten metal or its alloy with other elements. A typical reduction smelting is the production of pig iron in blast furnaces . Recovery processes are also central to the smelting of manganese, oxidized nickel, lead, and titanium ores.

The main reducing agents are carbon , carbon monoxide and hydrogen . Carbon monoxide is formed in the furnace itself when carbon is incompletely burned; the main amount of hydrogen is obtained by decomposition of natural gas injected into the furnace.

A variety of reduction melts is metallothermal production of metals, in which another metal is used as a reducing agent of a metal ( Mn , Cr , V , etc.) - with a high affinity for oxygen: Ca ; Mg ; Al , as well as Si . One of the advantages of metallothermal reduction is the production of metals that are not contaminated with carbon or hydrogen.

Typical oxidative ore smelting is the processing of rich copper sulfide ores in shaft furnaces. During smelting, the main sulfur fraction of sulfide minerals is oxidized, resulting in a significant amount of heat being released. The main target product of the smelting is the melt of FeS and Cu ₂ S sulfides - matte .

Cast iron and matte ore smelting are essentially intermediate products that require additional processing. Such treatment consists in blowing the melts with air or pure oxygen , as a result of which the impurities contained in the alloys are oxidized and pass either to slag (SiO ₂ ; MnO ; FeO and others) or to gas (CO; SO ₂ ). The process is called conversion .

Similar to conversion is the fuming process - gas purging of slag melts. It differs from converting in that the metal melt is purged with oxidizing gas, and with fumigation of the slag by reduction. And secondly, the products of oxidation of the metal melt — metal oxides — form the second liquid phase — slag, and the fumigation products of slag — reduced volatile metals (or sulfides) in the vapor state, are removed from the reaction space by a gas stream ^[2] .

• Small mountain encyclopedia . In 3 t. = Mala gіrnicha encyclopedia / (In Ukrainian). Ed. V.S. Beletsky . - Donetsk: Donbass, 2004. - ISBN 966-7804-14-3 .
• Korotich V.I. , Naboychenko S.S. , Sotnikov A.I., Grachev S.V., Furman E.L., Lyashkov V. B. (edited by V.I. Korotich). The Beginning of Metallurgy: A Textbook for High Schools. - Yekaterinburg: USTU, 2000 .-- 392 p. - ISBN 5-230-06611-3 .