Recycled alloys

The output from brass mills in the United States is spHt nearly equally between copper and the alloys of copper. Copper and dilute copper alloy wrought products are melted and processed from electrically refined copper so as to maintain low impurity content. Copper alloys are commonly made from either refined copper plus elemental additions or from recycled alloy scrap. Copper alloys can be readily manufactured from remelted scrap while maintaining low levels of nonalloy impurities. A greater proportion of the copper alloys used as engineering materials are recycled than are other commercial materials. 

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There are significant advantages in recycling alloy scrap at a smelter like Sudbury ... 

Key words recycling alloys, amorphous alloys, alloy coatings, laser surfacing, laser alloying. 

Catalytic methanation processes include (/) fixed or fluidized catalyst-bed reactors where temperature rise is controlled by heat exchange or by direct cooling using product gas recycle (2) through wall-cooled reactor where temperature is controlled by heat removal through the walls of catalyst-filled tubes (J) tube-wall reactors where a nickel—aluminum alloy is flame-sprayed and treated to form a Raney-nickel catalyst bonded to the reactor tube heat-exchange surface and (4) slurry or Hquid-phase (oil) methanation. 

Fresh reducing gas is generated by reforming natural gas with steam. The natural gas is heated in a recuperator, desulfurized to less than 1 ppm sulfur, mixed with superheated steam, further preheated to 620°C in another recuperator, then reformed in alloy tubes filled with nickel-based catalyst at a temperature of 830°C. The reformed gas is quenched to remove water vapor, mixed with clean recycled top gas from the shaft furnace, reheated to 925°C in an indirect fired heater, and injected into the shaft furnace. For high (above 92%) metallization a CO2 removal unit is added in the top gas recycle line in order to upgrade the quaUty of the recycled top gas and reducing gas. 

Lead [7439-92-17, Pb, is an essential commodity ia the modem iadusttial world, ranking fifth ia tonnage consumed after iron (qv), copper (qv), aluminum (see Aluminumand aluminum alloys), and 2iac (see Zinc and zinc alloys). In 1993, the United States accounted for 30% of the 4,450,000 metric tons of refined lead consumed by the Western world. Slightly over half of the lead produced ia the world now comes from recycled sources (see Recycling, NONFERROUS LffiTALS). 

The recovery of vanadium from these slags is of commercial interest because of the depletion of easily accessible ores and the comparatively low concentrations (ranging from less than 100 ppm to 500 ppm) of vanadium in natural deposits (147,148). In the LILCO appHcations the total ash contained up to 36% 20 (147). Vanadium is of value in the manufacture of high strength steels and specialized titanium alloys used in the aerospace industry (148,149). Magnesium vanadates allow the recovery of vanadium as a significant by-product of fuel use by electric utiUties (see Recycling, nonferrous LffiTALS). 

A conservative estimate of the total value of the products from the mineral industry is ca 3.9 trillion ia terms of 1992 dollars (4). This estimate does not include the value of products derived from secondary sources such as recycling (qv) or reclamation. Secondary recovery is significant for certain commodities. For example, in 1992 ca 30% of the world steel (qv) production, 46% of the world refined lead output, 15% of the world refined copper (qv) production, and ca 30% of the aluminum (see Aluminumand ALUMINUM alloys) output from the Western world were clearly identified as being derived from scrap. The value of the world mineral commodity export trade in 1992 was ca 616,698 million ia 1992 dollars. This accounted for ca 18% of all commodities exported (4). 

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. 

Much of the technology used in the reclamation of metals from metal-bearing wastes was developed by the mining iadustries. The primary means of recycling metal from metal and alloyed scrap is via pyrometaHurgy (see Metallurgy). 

Cobalt. There is no U.S. mine production of cobalt. Refining of imported nickel—cobalt mattes has not occurred since the mid-1980s. About 1600 t of secondary cobalt was recycled from scrap by 13 faciUties in the United States representing - 22% of total U.S. consumption. The price of the metal was around 44/kg. Most is imported from Zaire and Zambia. Increasing quantities are coming from Russia. Historically, the price of cobalt has been quite volatile and dependent on the pohtical environment in those countries. Cobalt is used in superaHoys, 40% catalysts, 14% paint driers, 11% magnetic alloys, 10% and cemented carbides and other uses, 16%. 

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