Aluminum secondary production

Consists of clay, mud, and silt, mainly aluminum silicates Dense fine-grained rock containing mainly clay Contains silicates secondary product... 

In the secondary production of aluminum, scrap is usually melted in gas- or oil-fired reverberatory furnaces of 14,000 to over 45,000 kg capacities. The furnaces have one or two charging wells separated from the main bath by a refractory wall that permits only molten metal into the main bath. The principal processing of aluminum-base scrap involves the removal of magnesium by treating the molten bath with chlorine or with various fluxes such as aluminum chloride, aluminum fluoride,... 

The technique generally used to minimize the degree of change in crystallinity of the milled product is to eliminate the water or other solvents from the product, usually by packaging the material within a suitable barrier (for example, aluminum foil laminate). Other techniques include the production of a 100% crystalline material, which may eliminate the effects of moisture. This technique, however, may require a secondary production stage of armealing or a period to allow the product to equilibrate under controlled storage conditions. 

The presence of plumboferrite [ PbFe407] in the Tyne River sediments was reported by Hudson-Edwards et al. (1996), and the mineral has also been identified as a secondary product in tailings (Morin et al., 1999). Although aluminum hydroxides play a prominent role in geochemical modeling, few occurrences of such material have... 

Aluminum metal can be produced either from bauxite ore or from recychng aluminum scrap. Electrowinning of aluminum ore is sufficiently expensive that the secondary production industry commands much of the market. Electrowinning aluminum from alumina is a highly energy-intensive process, which is why the world s major primary aluminum smelters are located in areas that have access to low-cost energy and abundant power resources (e.g., hydroelectric, natural gas, coal or nuclear), while secondary producers tend to be located near industrial centers, where aluminum scrap is largely available. 

HF,perfluoro carbon, and carbonyl sulfide into the environment. In contrast, secondary production of aluminum, using scrap input, requires only remelting—a far cleaner process with little or no hazardous waste. 

Metallurgical processes By-product coke ovens Foundries gray iron Foundries steel Secondary aluminum Secondary copper Secondary zinc Uranium refining... 

Powders from Colloidal Sol-Based Compotdtions. A common example of the synthesis of a single oxide from a colloidal precursor, following a well-known method (Yoldas, 1975), involves hydrolysis of aluminum secondary butoxide by addition of excess water, formation of boehmite, AlOOH and peptization of boehmite by an add to obtain a colloidal sol. Oh et al. (1996), to dte an application, prepared such colloidal sols and also seeded a part ofsuch a sol with 15 wt% ofa-alumina(<0.12/im). Up to 350°C, both the solid products were amorphous. However, seeding caused early (950°C) crystallization of the a-phase, while the unseeded conqiosition led to a late crystallization (1150°C) of the same phase. 

Other Compounds. Primary and secondary amines add 1,4- to isoprene (75). For example, dimetbylamine in ben2ene reacts with isoprene in the presence of sodium or potassium to form dimetby1(3-metby1-2-buteny1)amine. Similar results are obtained with diethylamine, pyrroHdine, and piperidine. Under the same conditions, aniline and /V-metbylaniline do not react. Isoprene reacts with phenol in the presence of aluminum phenoxide (76) or concentrated phosphoric acid (77) to give complex products. 

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). 

In general, if the desired carbon—phosphoms skeleton is available in an oxidi2ed form, reduction with lithium aluminum hydride is a powerful technique for the production of primary and secondary phosphines. The method is appHcable to halophosphines, phosphonic and phosphinic acids as well as thein esters, and acid chlorides. Tertiary and secondary phosphine oxides can be reduced to the phosphines. 

Alkaline earth metal alkoxides decompose to carbonates, olefins, hydrogen, and methane calcium alkoxides give ketones (65). For aluminum alkoxides, thermal stability decreases as follows primary > secondary > tertiary the respective decomposition temperatures are ca 320°C, 250°C, and 140°C. Decomposition products are ethers, alcohols, and olefins. 

Scrap that is unsuitable for recycling into products by the primary aluminum producers is used in the secondary aluminum industry for castings that have modest property requirements. Oxide formation and dross buildup are encountered in the secondary aluminum industry, and fluxes are employed to assist in the collection of dross and removal of inclusions and gas. Such fluxes are usually mixtures of sodium and potassium chlorides. Fumes and residues from these fluxes and treatment of dross are problems of environmental and economic importance, and efforts are made to reclaim both flux and metal values in the dross. 

Nonferrous metallurgy is as varied as the ores and finished products. Almost every thermal, chemical, and physical process known to engineers is in use. The general classification scheme that follows gives an understanding of the emissions and control systems aluminum (primary and secondary), beryllium, copper (primary and secondary), lead (primary and secondary), mercury, zinc, alloys of nonferrous metals (primary and secondary), and other nonferrous metals. 

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