Smelting nonferrous metals

Many nonferrous metals can be extracted by reduction smelting, eg, copper, tin, nickel, cobalt, silver, antimony, and bismuth. Blast furnaces are sometimes used for the smelting of copper or tin, but flash and reverberatory furnaces are more common for metals other than lead. 

The obvious destination for nickel waste is in the manufacture of stainless steel, which consumes 65% of new refined nickel production. Stainless steel is produced in a series of roasting and smelting operations. These can be hospitable to the various forms of nickel chemical waste. In 1993, 3 x 10 t of nickel from nickel-containing wastes were processed into 30 x 10 t of stainless steel remelt alloy (205,206) (see Recycling, nonferrous metals). This quantity is expected to increase dramatically as development of the technology of waste recycle coUection improves. 

The principal direct raw materials used to make sulfuric acid are elemental sulfur, spent (contaminated and diluted) sulfuric acid, and hydrogen sulfide. Elemental sulfur is by far the most widely used. In the past, iron pyrites or related compounds were often used but as of the mid-1990s this type of raw material is not common except in southern Africa, China, Ka2akhstan, Spain, Russia, and Ukraine (96). A large amount of sulfuric acid is also produced as a by-product of nonferrous metal smelting, ie, roasting sulfide ores of copper, lead, molybdenum, nickel, 2inc, or others. 

Primary smelting and refining of copper 3334 Primary production of aluminum 3339 Primary smelting and refining of nonferrous metals, except copper and aluminum 3341 Secondary smelting and refining of nonferrous metals... 

Seeondary smelting and refining and alloying of nonferrous metals and alloys 3341... 

The nonferrous metals industry is divided into 61 subcategories by the type and source of the metal to be smelted and/or refined and by similar wastewater sources. Twenty-six of these subcategories... 

Tables 3.39 and 3.40 illustrate TRI releases and transfers for the primary nonferrous metals smelting and refining industry. For this industry as a whole, chlorine comprises the largest number of TRI releases. This is reflected in the fact that chlorine is a byproduct of the magnesium industry and the largest reporter is a magnesium facility. The other top releases are copper compounds, zinc compounds, lead compounds, and sulfuric acid.

Nonferrous metal hydroxide sludge wastes contain a large quantity of water, and the content of valuable metals is too small to allow economical smelting of these wastes. However, the wastes are a burden on the environment and they can only be deposited in special garbage dumps, which are very costly. Therefore a method for processing and recovery of the valuable materials and metal in the waste is highly desirable. 

Tetronics A process for treating dusts from electrical arc furnaces for making steel and nonferrous metals. Volatile metals (zinc, lead, cadmium) are recovered, and residual slag is nontoxic and suitable for landfill. The dusts, mixed with coal dust and a flux, are fed to a furnace heated by a plasma gun. The metal oxides present are selectively reduced and the vapors of zinc, lead, and cadmium are condensed in a modified Imperial Smelting furnace. Developed by Tetronics Research Development Company, United Kingdom, and first commercialized for steel dusts at Florida Steel, Jackson, TN, in 1989. Seven plants were operating in several countries in 1992. 

Reduction smelting, of nonferrous metals, 16 143-144 Reductive alkylation... 

Iron oxides are used as the flux in smelting of nonferrous metals (e.g. lead) (Pettifer, 1981). The oxide removes the siliceous and other impurities and also serves to keep the slag fluid. A further use of iron oxides (FeOOH) is in the removal of H2S from coal gas, i. e. 

It is used in antiseptics and medicines, as a flux in smelting, soldering and welding operations, as a deoxidizer in nonferrous metals, as a neutron absorber for atomic energy shields, in rocket fuels, and as extremely hard abrasive boron carbide (harder than corundum). See also Boron. 

Orkla A complex process for recovering sulfur from pyrite. The ore was smelted with coke, limestone, and quartz, with very little air at 1,600°C, and the iron was removed as a slag. The copper and other nonferrous metals formed a matte with the sulfur. Pyrolysis of this matte removed half of the sulfur. An air blast removed the other half without oxidizing it. Developed by the Orkla Mining Company, Norway, between 1919 and 1927. First commercialized at Thamshavn, Norway, in 1931, but the plant closed in 1962. The process was used for many years in Spain, Portugal, and Hungary. 

Current uses of arsenic are in pesticides, cotton desiccants, and wood preservatives. Arsenic is also used as a bronzing and decolorizing agent in the manufacture of glass, and in the production of semiconductors (Tanaka, 2004), as a desiccant and defoliant in agriculture, and as a byproduct of the smelting of nonferrous metals, particularly gold and copper, from coal residues (Hall, 2002). 

The average Zn content of the lithosphere is —80 p,g g and the most abundant sources of Zn are the ZnS minerals sphalerite and wurtzite and to a lesser extent smithsonite (ZnCOa), willemite (Zn2Si04), and zincite (ZnO) (Reimann and de Caritat, 1998). The smelting of nonferrous metals and the burning of fossil fuels and municipal wastes are the major Zn sources contributing to air pollution. 

Arsenic was recovered as arsenic trioxide in about 20 countries from the smelting or roasting of nonferrous metal ores or concentrates. The most common separation methods are volatilization from the ores, and sublimation of arsenic trioxide occurs during the roasting stage of these ores. 

---