Smelting, aluminum

Alternating current is converted to direct current (dc) for the smelting cells by siUcon rectifiers. High conversion efficiency (over 99%) and minimum capital costs are achieved when the rectified voltage is 600—900 V dc. Because aluminum smelting cells operate at 4.5—5.0 V, 130 or more cells are coimected in series, forming what the industry calls a potline, which may operate at 50—360 kA. 

Nonmineralized SGA flows freely, and is often known as sandy alumina because it easily covers the cryoflte bath of aluminum electrolysis cells (see Aluminum compounds, introduction). Properties typical of a sandy SGA are shown in Table 1. Aluminum smelting technology in the United States is primarily based upon sandy alumina. Older European smelting technology, however, is based upon a poor flowing, low bulk density, highly mineralized SGA called floury alumina, composed principally of a-Al O. ... 

Alumina Product Data Bulletins L o. CHE920, CHE 922, Alcoa, Bauxite, Arkansas Alcoa Chemie, Lausanne, Switzerland Alcan Chemicals, Qeveland, Ohio Kaiser Chemicals, Cleveland, Ohio Malakoff Industries (Reynolds), Malakoff, Texas Baikowski, Charlotte, North Carolina Criceram (Pechiney), Cedex, Prance Union Carbide Specialty Powders, IndianapoHs, Indiana Sumitomo Aluminum Smelting, Tokyo, Japan Showa Alumina Industries SAL, Tokyo, Japan VAW Aluminum, Germany Martinswerke, Germany Pechiney, Prance Arco Specialty Chemicals, Newton Square, Pennsylvania. 

Pitch. The principal outlet for coal-tar pitch is as the binder for the electrodes used in aluminum smelting. These are of two types. Older plants employ Sn derberg furnaces, which incorporate paste electrodes consisting of a mixture of about 70% graded petroleum coke or pitch coke and 30% of a medium-hard coke-oven pitch. This paste is added periodically to the top of the monolithic electrode as it is consumed. The more modem smelters employ prebaked electrodes requiring less binder, about 18%. 

Where considerable quantities of energy are used in the process, relatively cheap and abundant sources of energy need to be available (for example, alumina and aluminum smelting, steel making). 

Primary Aluminum Smelting (kg/T Chlorine Demagging (kg/T of Magnesium Wet Processing Primary Copper Primary Copper Secondary Primary Lead1 Primary Zinc (kg/T of... 

If you work in an industry that uses hexachloroethane, such as aluminum smelting, or a chemical plant, you could be exposed by breathing it or touching it. About 8,500 people in the United States are exposed to hexachloroethane at work. 

One case study was identified where a man who had been occupationally exposed to hexachloroethane was treated for a liver tumor (Selden et al. 1989). Exposure had occurred over a period of 6 years as a result of the presence of hexachloroethane in a degassing agent used during aluminum smelting. However, the hexachloroethane reacted at the 700 C use-temperature, releasing a gas that was 96% hexachlorobenzene with small amounts of other chlorinated compounds. Because there was occupational exposure to a mixture of chlorinated compounds rather than just hexachloroethane, it is highly unlikely that the tumor was the result of hexachloroethane exposure alone. Occupational exposure to mineral oil mists for 20 years was also part of the subject s employment history. 

The application of toxicokinetic modeling to the assessment of interactive effects between hexane, ketones and aromatic compounds. Investigation of dermal absorption of polycyclic aromatic compounds (PAHs). Research indicates dermal absorption of PAHs in a number of industries including aluminum smelting, coke ovens, creosote production and others is significantly more important than previously recognized. 

The Advanced Recovery Systems, Inc. (ARS) developed the patented, ex situ DeCaF hydrometallurgical technology to decontaminate fluoride by-products and to recover recyclable metals. The technology uses a proprietary acid mixture to digest the fluoride matrix, freeing radioactive contaminants (e.g., uranium, thorium, or radium) and hazardous contaminants (e.g., lead, arsenic, or chromium). Radioactive elements are recycled or disposed. Metals are also recycled, and fluoride is recovered as a high-value salt for aluminum smelting. 

The aluminum smelting industry has similar conditions to pulp. Demand can be - and has been - met during the last decade by very large-scale, low-cost new capacity in countries endowed with privileged natural resources and/or low conversion costs such as India, the CIS, China, and the Middle East. These low-cost... 

Primary aluminum smelting subcategory-NSPS for anode and cathode paste plant wet air pollution control 1-davMax. Monthly Ava. mg/kg (lbs./106 lbs) 0.000 0.000 ... 

Secondary aluminum smelting subcategory-Applicability Yes 40 CFR 421, Subpart C EPA1984d... 

Abramson MJ, Wlodarczyk JH, Saunders NA, et al. 1989. Does aluminum smelting cause lung disease Am Rev Respir Dis 139 1042-1057. 

White DM, Longstreth WTJ, Rosenstock L, et al. 1992. Neurologic syndrome in 25 workers from an aluminum smelting plant. Arch Intern Med 152 1443-1448. 

Many symptoms of aluminum toxicity are similar to those of Alzheimer s disease and osteoporosis. This suggests that long-term accumulation of aluminum in the brain may contribute to the development of Alzheimer s disease. In addition, an unidentified protein not found in normal brain tissue has been discovered in the brain tissue of Alzheimer s patients. Because aluminum is excreted by the kidneys, toxic amounts of aluminum also may impair kidney function. People who worked in aluminum smelting plants for long periods have been found to experience dizziness, impaired coordination, and losses of balance and energy. Accumulation of aluminum in the brain was cited as a possible cause for these symptoms as well. This has caused concern, especially as it relates to neurotoxicology (Alzheimer s disease).19-21... 

In autumn 2006, the national power company of Iceland blocked two glacial rivers near the mountain of Karahnjukar in order to flood a wilderness area of 22 square miles and create a reservoir that would supply power for a new aluminum smelting facility built by the American company, Alcoa. The hydroelectric dam, the tallest of its kind in Europe, was expected to generate 4600 GWh of electricity each year, and the smelter had the capacity to process 344,000 metric tons of aluminum annually. In addition to the 400 jobs the project was expected to provide, Alcoa also claimed that theirs would be the safest, most environment-friendly smelter on Earth. Some Icelanders contested this assertion, however, by pointing out the 45 miles of tunnels, 31 miles of high-tension power lines, and the sulfur dioxide fumes associated with... 

The concentrations of TriCDTs, TeCDTs, and PeCDTs in soil and sediment samples, gas samples from waste incineration and aluminum smelting, ash from an aluminum smelting plant, a car shredder, and from combustion of wood chips, peat and refuse derived fuel, different effluents from a pulp and paper mill, and crab, carp, and lobster tissue samples, are presented in Table 1. 

TriCDTs and TeCDTs have been determined in aerosol, particle, and gas phase samples from an aluminum smelting plant. The concentrations of TriCDTs ranged from 40 to 900 ng/Nm3, the concentrations of TeCDTs from 10 to 400 ng/Nm3, and those of PeCDTs from 1 to 160 ng/Nm3 [14]. Due to the scarce number of pure TeCDT model compounds available, the isomerism of most of the TeCDTs in the samples could not be determined. In any case, the concentrations of 2378-TeCDT seemed to be very low. The number of individual TeCDTs in the samples from the aluminum smelter was much higher than the... 

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