Extractive metallurgy, hydrogen

In metallurgy, hydrogen sulfide is used to precipitate copper sulfide from nickel—copper-containing ore leach solutions in Alberta, Canada, or to precipitate nickel and cobalt sulfides from sulfuric acid leaching oflaterite ores in Moa Bay, Cuba (120) (see Metallurgy, extractive metallurgy). 

As a primary approach toward "Hydrogen Economy", the H2S by-product obtained from fossil fuels or by extractive metallurgy of sulfide ores should be considered as more important for H2 recovery than for the sulfur which can be recovered. 

Yannopoulos, J.C., The Extractive Metallurgy of Gold, Van Nostrand Reinhold, New York, 1991, 224. Magdeburg-P A high-pressure hydrogenation process developed by Lurgi in World War II. 

The most important applications of hydrogen sulfide involve the production of sodium sulfide and other inorganic sulfides. Hydrogen sulfide obtained as a by-product often is converted into sulfuric acid. It also is used in organic synthesis to make thiols or mercaptans. Other applications are in metallurgy for extracting nickel, copper, and cobalt as sulfides from their minerals and in classical qualitative analytical methods for precipitation of many metals (see Reactions). It also is used in producing heavy water for nuclear reactors. 

Calcined materials are those which have been processed by incineration or burning which drives off volatiles and oxidizes the substances to varying degrees, often leaving a product better disposed for subsequent chemical processing. Calcination is often used in metallurgy to prepare ore for extraction, as in the case when pyrites (e.g., iron sulphide ore) is calcined to iron oxide. Petroleum coke is calcined to drive off volatiles, mostly hydrogen and methane. 

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