Aluminum manufacture

Cryolite. Cryohte constitutes an important raw material for aluminum manufacturing. The natural mineral is accurately depicted as 3NaF AIF., but synthetic cryohte is often deficient in sodium fluoride. Physical properties are given in Table 4. 

Product Utilization. The principal appHcation for chromium phosphate coatings is as a paint base for painted aluminum extmsions and aluminum beverage can stock. In these appHcations, extremely demanding performance criteria are met by the chromium phosphate conversion coatings. As an example, the Architectural Aluminum Manufacturer s Association Voluntary Specification 605.2-92 requires humidity and salt spray testing for 3000 hours and allows only minimal incidence of paint failure after testing (26). 

Anthracite. Anthracite is preferred to other forms of coal (qv) in the manufacture of carbon products because of its high carbon-to-hydrogen ratio, its low volatile content, and its more ordered stmcture. It is commonly added to carbon mixes used for fabricating metallurgical carbon products to improve specific properties and reduce cost. Anthracite is used in mix compositions for producing carbon electrodes, stmctural brick, blocks for cathodes in aluminum manufacture, and in carbon blocks and brick used for blast furnace linings. 

In 1892 the electrolysis of brine was discovered as a method for making both sodium hydroxide and chlorine. This rapidly grew in importance and since the 1960s it has been the only method of manufacture. Among electrolytic industries it is the second largest consumer of electricity, aluminum manufacture being the largest. 

The cooling tower, which is an efficient air scrubber can easily become a catchall for contaminants resulting from the location of the tower or from the industrial process. In arid areas, ingress of sand contributes to fouling, which reduces efficiency and contributes to biofilm and under-deposit corrosion. In coastal areas, sand laden with chlorides can cause corrosion of stainless steel components and impair chemical corrosion inhibitor performance. Heavy industries, such as steel or aluminum manufacture, produce severely contaminated cooling water resulting from direct contact with metal slags and lubricants. 

The formation of large quantities of coke is a severe drawback unless the coke can be put to use. Calcined petroleum coke can be used for making anodes for aluminum manufacture, and a variety of carbon or graphite products such as... 

Aluminum oxide is used in the production of aluminum manufacture of abrasives, refractories, ceramics, electrical insulators, catalyst and catalyst supports, paper, spark plugs, crucibles and laboratory works,... 

Manganese Pyrolusite (Mn02) Reduction of oxide by carbon or aluminum Manufacturing alloys with iron and other metals... 

Aluminum Manufacture of abrasives, smelting Fibrosis initiated from short exposures... 

While these divestitures were taking place, traditional fine chemicals manufacturers were able to enjoy new contracts for the synthesis of active ingredients from companies involved in crop protection products and pharmaceuticals. Many European companies were the beneficiaries of the new trend. In Switzerland the leader was Lonza, which became independent in 1999 when its mother company, Alu Suisse, merged with the Canadian aluminum manufacturer Alcan. Other Swiss firms—such as Siegfried AG, EMS-Dottikon, Cilag, and Orgamol, Rohner, now part of Dynamit Nobel—took advantage of these developments. Clariant entered the field on a big scale in 2000 with its acquisition of BTP. 

Electrochemistry Chemistry that involves the flow of electrical current such as silver plating and aluminum manufacturing. 

Aluminum manufacture Aluminum is the most abundant metallic element in Earth s crust, but until the late nineteenth century, aluminum metal was more precious than gold. Aluminum was expensive because no one knew how to purify it in large quantities. Instead, it was produced by a tedious and expensive small-scale process in which metallic sodium was used to reduce aluminum ions in molten aluminum fluoride to metallic aluminum. 

The industrially most important minerals for aluminum manufacture are the bauxites (laterite). Bauxite is not a uniform material, but comprises a mixture of different aluminum oxide hydrates and hydroxides [e.g. boehmite, y-AIO(OH), diaspore, a-AlO(OH)] with aluminum silicates, iron and titanium oxides etc. with between 35 and 70% (mostly 50 to 65%) aluminum oxide. 

Most important raw materials for aluminum manufacture are the bauxites mixtures of AIO(OH) and AKOH) with SiOs, FesOi, TiOs, etc (AbOj-content generally 30 to 65%)... 

Industrial aluminum manufacture currently almost exclusively by the Hall-Heroult process... 

Al production is energy intensive, energy eost making up 25 to, S()% of aluminum manufacturing costs in Western industrialized countries... 

Most of the a-aluminum oxide is utilized for aluminum manufacture (ca. 0.5 t aluminum/t AI2O3). In the USA over 90% of the aluminum oxide production is utilized in the manufacture of aluminum, the rest being utilized in the manufacture of refractory, grinding, ceramic, glass and enamel products and electrocorundum. It is also used as a filler in polymers (polyesters, epoxides). 

In the period 1977 to 1981 a pilot plant for aluminum manufacture from aluminum chloride was operated in the USA by Alcoa. In this period most of the anhydrous aluminum chloride produced in the USA was consumed in this plant. 

Explain why fluoride emissions are often of concern in aluminum manufacturing process. 

Use Production of aluminum potassium compounds, millstones, substitute for bauxite in aluminum manufacture, decolorizing and deodorizing agent, fertilizer. 

Use Metallurgical additive, high-temperature electrical conductor, refractory, cermet component, coatings resistant to attack by molten metals, aluminum manufacture, super alloys. 

Hall, Charles Martin (1863-1914). Invented method of aluminum manufacture by electrochemical reduction of alumina. Parallel discovery by Heroult in France. 

Petroleum Coke. Petroleum coke is an important raw material from petroleum for the chemical industry. Unlike most petroleum raw materials which go into organic synthesis, petroleum coke is important in inorganic technology. Anodes for aluminum manufacture consume 600,000 tons of petroleum coke annually—18% of U.S. petroleum coke production. About 0.7 pound of petroleum coke is consumed for every pound of aluminum produced. The next most important chemical use is in the manufacture of graphite electrodes for the steel industry, a use which consumes about 5% of current coke production. 

The National Institute of Environmental Health Sciences is funding research at the State University of New York at Albany to determine at aquatic bioavailability of PAHs from sediments collected near discharge points from two aluminum manufacturing plants in the Massena area of the St. 

Petroleum coke, obtained by subjecting the distillation bottoms to pyrolitic polymerization and thermal decomposition in a delayed or fluid coker, is used in the manufacture of calcium and silicon carbides, electrodes for aluminum manufacturing, and graphite. It also finds use as a utility fuel and as a construction material in foundry and blast furnaces. 

Figure 21.28 The electrolytic cell in aluminum manufacture. Purified AI2O3 is mixed with cryolite (NasAIFg) and melted. Reduction at the graphite furnace iining (cathode) gives molten Al. Oxidation at the graphite rods (anodes) slowly converts them to CO2, so they must be replaced periodically.

OTHER COMMENTS used as an adsorbent, in abrasive and aluminum manufacturing, in paper, spark plugs, fluxes and heat resistant fibers, and in chromatographic analysis. 

Brewis has recently discussed the nature of adhesives used for aluminum. The two major aluminum manufacturers. Aluminum Company of America (ALCOA) and Reynolds Metals, have published small useful volumes on all aspects of aluminum bonding, although these volumes are not recent.Another excellent detailed discussion of aluminum adhesives, particularly from the viewpoint of durability, is given by Minford of ALCOA,... 

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