Temperature pyrometallurgy

Thermal properties such as thermal capacity, thermal expansion, melting temperature, thermal decomposition and sublimation are all important in considering processes to which minerals may be directly subjected in a pyro way. As for example, roasting or calcination or any pyro pre-treatment of a mineral concentrate is greatly influenced by its thermal properties. The chapter on pyrometallurgy deals with these aspects. 

In the broadest sense, coordination chemistry is involved in the majority of steps prior to the isolation of a pure metal because the physical properties and relative stabilities of metal compounds relate to the nature and disposition of ligands in the metal coordination spheres. This applies both to pyrometallurgy, which produces metals or intermediate products directly from the ore by use of high-temperature oxidative or reductive processes and to hydrometallurgy, which involves the processing of an ore by the dissolution, separation, purification, and precipitation of the dissolved metal by the use of aqueous solutions. 4... 

Hydrometallurgy Traditionally the winning of metals from their ores has been achieved by pyrometallurgy the reduction of relatively concentrated metallic ores at high temperatures. The reactions of the blast furoace form a typical example (see also page 377) ... 

The chemical processing of ores to recover the metal values in pure form is commonly referred to as extractive metallurgy as presently practiced it is subdivided into hydrometallurgy and pyrometallurgy. Hydrometallurgy involves reacting the ore at low or moderate temperatures with a hquid solvent that will selectively dissolve the valuable metal or metals, separating the dissolved metals from each other by... 

In pyrometallurgy (high temperature dry smelting), however, hydrogen is much less effective as a reductant, but carbon becomes important. For reasons we discuss in Section 17.8, the concentrate to be reduced is usually in the form of a metal oxide, so the reductant has to be something that has a greater affinity for the available oxygen atoms than has the... 

Metals are important resources and have a wide range of applications. Metals are often extracted from ores. Once the ore is mined, the metals must be extracted, usually by chemical or electrolytic reduction. Pyrometallurgy uses high temperatures to convert ore into raw metals, while hydrometalluigy employs aqueous chemistry for the same purpose. The methods used depend on the metal and their contaminants. Most metals are obtained by hydrometallurgical processes such as aqueous acids or alkalis are predominantly used to dissolve the metal oxides, sulfides, or silicates. Electrowinning and solvent extraction are frequently used to recover and concentrate the metals. A limited number of high-temperature molten salts have also been used for the recovery of refractory metals, such as titanium and aluminum, from their ores... 

How a pure metal is obtained by reduction from its combined form depends on the standard reduction potential of the metal (see Table 19.1). Table 20.2 outlines the reduction processes for several metals. Most major metallurgical processes now in use involve pyrometallurgy, procedures carried out at high temperatures. The reduction in these procedures may be accomplished either chemically or electrolyticaUy. 

Pyrometallurgy, metallurgy at high temperatures, is considered with particular attention to iron. Hydrometallurgy, the extraction of metals using aqueous solutions, is discussed with particular attention to aluminum. 

A large number of metallurgical processes utilize high temperatures to alter the mineral chemically and to ultimately reduce it to the free metal. The use of heat to alter or reduce the mineral is called pyrometallurgy. Pyro means "at high temperature.")... 

When common oxides, such as for instance of lead, are reduced, they form molten metal. Zinc oxide does not exactly follow the other oxides, because zinc has such a high vapor pressure at the temperature needed that it disappears as a vapor, from which the metal has to be condensed. In view of these facts, it is not strange that the pyrometallurgy of zinc was delayed and so also was knowledge about zinc in its metallic form. 

The methods commonly used for purifying metals are distillation, electrolysis, and zone refining. Pyrometallurgy refers to metallurgical processes carried out at high temperatures. 

The above techniques that involve high-temperature processes are known as pyrometallurgy. Another common technique involves the electrolytic reduction of metal compounds, often referred to as hydrometallurgy or electrorefining, depending on whether the procedure is carried out before or after the metal has already been separated from its ore, respectively. Hydrometallurgy consists of three steps ... 

HydrometaUurgy is often more economical than pyrometallurgy, due to the high energy costs associated with the elevated temperatures needed for calcination and roasting. 

Proton a positively charged particle in an atomic nucleus. (2.5 18) Pure substance a substance with constant composition. (1.9) Pyrometallurgy recovery of a metal from its ore by treatment at high temperatures. (21.8)... 

Pyrometallurgical Processes The metallurgical method based on roasting an ore, followed by reduction of the oxide to the metal, is called pyrometallurgy, the prefix pyro- suggesting that high temperatures are involved. Some of the characteristics of pyrometallurgy are as follows ... 

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