The Industrial Production of Aluminium and Its Recycling - Essay Example

Industrial Production and Recycling of Aluminum Introduction Aluminum is widely used in the production of a variety of products, including aircraft, vehicles, computers, and power lines. It owes its wide range of applications to its physical qualities. Aluminum’s malleability, luster, and light weight make it the metal of choice of artists, industrialists, and artisan who use aluminum as a chief ingredient in consumer goods, wiring, sculpture, jet aircraft, and cookware. Although it is the most abundant metal in the Earth’s crust, aluminum naturally occurs as an impure substance or as compounds (Totten and MacKenzie, 2005). Bauxite ores are the main source of the world’s aluminum. Mining and extracting aluminum from mountains and ores consume a great amount of energy and financial investments. Today, while industrialists prize aluminum as an important metal from reusable resources, environmentalists denigrate the extensive mining of aluminum and the use of aluminum in the manufacture of cans, kitchen wares, and other products because of their adverse ecological impact. Aluminum mining not only degrades the environment, but poses health problems and workplace safety issues among miners. On the other hand, aluminum end products, such as cans, foil, and kitchen wares, eventually make their way to tons of metal trashes in every city’s landfill (Green, 2007). Aluminum Production Industrial production of aluminum starts with bauxite mining and refining. The bauxite ore is crushed in the mining site. Then, the crushed materials are screened and stockpiled prior to the delivery to an alumina plant. Some mining companies wash crushed core and remove unwanted materials, like silica and clay, from it. This not only upgrades the quality of crushed bauxite ore, but its price as well. In the alumina plant, the crushed core is further crushed to a particle size mostly efficient for alumina extraction before treating it with hot (175 °C ) sodium hydroxide liquor (Bayer process). The Bayer process coverts aluminum oxide to sodium aluminate (Kogel et al., 2006): Al2O3 + 2 NaOH + 3 H2O → 2 NaAl(OH)4 When the solution cooled off, aluminum hydroxides precipitation occurs: NaAl(OH)4 → Al(OH)3 + NaOH The aluminum hydroxide then is heated at 980°C (calcined) to produce aluminum oxide or alumina (Al2O3) and give off water vapor: 2 Al(OH)3 → Al2O3 + 3 H2O The alumina produced by the Bayer process undergoes Hall–Héroult process to produce aluminum. After the digestion process, the insoluble part of the bauxite, called red mud, and fine solids are removed before precipitating the aluminum trihydrate crystals. Then, the crystals are calcined in fluidized bed calciners or rotary kilns to produce alumina (Al2O3). In the production of primary aluminum, electrolytic reduction of alumina is being done. The alumina is broken into aluminum and oxygen by dissolving it in a molten bath of fluoride compounds. An electric current is passed through the bath and the dissociated oxygen gas reacts with carbon in the electrode, producing carbon monoxide and carbon dioxide. On the other hand, the molten aluminum goes to the bottom of individual pots or cells. The aluminum in the cells is removed under vacuum into tapping crucibles (Kogel et al., 2006). Secondary aluminum production makes use of dross, chips, and scraps as raw materials. These materials undergo shredding, magnetic separation, drying, sieving, and so on in order to take out undesirable materials that affect air emissions and aluminum quality. The collected aluminum materials are subjected to smelting in rotary kilns under a salt cover. This is the most common process because the salt slag can be processed and used gain. Smelting in hearth and induction furnaces, on the other hand, requires less salt and consumes less energy. However, this process is only suitable for high-grade aluminum scrap (Balomenos,Panias,and Paspaliaris, 2011). Other processes require additional refining steps to get the desired quality of aluminum fitted for specific applications. These additional processes are necessary because alloying elements from aluminum scraps are often difficult to remove. The demagging process or removal of magnesium from melt requires a treatment involving hexachloroethane and chlorine. In order to reduce the use of toxic chemicals in the secondary aluminum production, different grades of aluminum scrap should be collected and reutilized separately (Green, 2007). While the secondary aluminum production process requires additional chemical treatment for the refinement of aluminum outputs, it consumes less energy that the primary production process. The latter consumes 164 GJ/t of aluminum produced, while the former uses 10 to 20 GJ per metric ton (Balomenos,Panias,and Paspaliaris, 2011). Recycling Aluminum Most Earth’s aluminum reserves are contained in bauxite, which naturally occurs around the globe, particularly in India, Jamaica, China, Guinea, and Brazil (Samuel, 2003). In these countries, mining of bauxite provides employment to a large portion of their working population and contributes largely to economic development. However, these economic benefits come with health and environmental costs. Bauxite mining is an open-pit process and the bauxite refining process makes use of sodium hydroxide, which produces an alkaline toxic waste as a by-product. This toxic waste, also called as red mud, has been a source of groundwater contamination in countries where bauxite mining is prevalent (Liu and Muller, 2012). In addition, both bauxite refining process and Hall-Héroult process of aluminum production consume great amounts of electricity. Thus, aside from environmental human health issues, aluminum production may aggravate the world’s energy problem. The apparent adverse impact of bauxite mining to the environment and stricter mining regulations made industry leaders to consider aluminum recycling. Aluminum can be recast without losing its natural malleability and luster. As compared with other scrap metals, heating aluminum scrap generates a small quantity of waste product called “dross,” which can further be refined to recover pure aluminum (Liu and Muller, 2012). The collection, recycling, and recasting of aluminum is not a new process in today’s society. It has been practiced since 1970s, following a great demand for aluminum beverage can, which became the industry’s standard for a beverage container because of it is light, recyclable, and cheap (Das, 2011). Since 1990s, municipal recycling and aluminum segregation programs have been established in the U.S. and Europe. Nowadays, aluminum is one of the most commonly recycled metals in the world and aluminum scrap is one of the globally traded scrap metals. Collection of Aluminum Packaging Materials and Containers in U.A.E. Aluminum has been used as the base material for packaging consumer goods, from simple foil-type packaging materials to beverage cans. The recycling industry in U.A.E. is active in refining and re-exporting non-ferrous metals amounting to some 70,000 to 100,000 tons monthly (Das, 2011). Households, corporate offices, and business centers in U.A.E. are required by the government to carry out segregation of solid waste materials. The recycling of aluminum in U.A.E. can be described into three levels. In the first level, the segregated light aluminum packaging materials from households and business offices are collected, while in the second level, the collected secondary raw materials are further segregated into various grades. At the final level, the aluminum-based materials are re-melted according to their grade. In order to persuade people on the benefits of recycling aluminum, one should make them realized that, along a pretty good industrial recycling industry, a robust informal economy for aluminum scrap exists. People should know that they can earn from salvaged aluminum just like scavengers and pickers of aluminum cans, automobile parts, siding, alloy wheels, and wiring. Thus, by letting people realized that, aside from helping in reducing the impact of bauxite mining to the environment, they can earn by collecting aluminum scraps and selling them by the pound or kilogram to large brokers. In this way, people can be encouraged to collect aluminum-based waste materials. In addition to market-based recycling, people can also generate earnings through artisanal recycling. They can sell aluminum scraps to sculptors and artists who create artworks from metals and waste materials. One can also creatively produce new items from scrap aluminum and have them promoted through social networking or blogging sites. Artisanal recyclers commonly use homemade furnaces in designing and creating functional and decorative hardware, artwork, and household utensils (Samuel, 2003). By having these unique stuffs promoted on the Internet, netizens may notice them and share them with other netizens through social media. In this manner, one can help in making people realized some other things that can be creatively done on waste materials. References Balomenos, E, Panias, D., and Paspaliaris, I. (2011) Energy and exergy analysis of the primary aluminum production processes: A review on current and future sustainability. Mineral Processing & Extractive Metallurgy Review 32, 69–89 Das, S.K. (2011) Aluminum Recycling in a carbon constrained world: Observations and opportunities. JOM 63, (8) 137–140 Green, J. A. S. (2007) Aluminum recycling and processing for energy conservation and sustainability. Materials Park, Ohio: ASM International Kogel, J. E., Trivedi, N.C., Barker, J.M., and Krukowski, S.T. (Eds.). (2006) 7th edn. Industrial minerals & rocks: Commodities, markets, and uses. Littleton, Colo: Society for Mining, Metallurgy, and Exploration Liu, G. and Muller, D.B. (2012) Addressing sustainability in the aluminum industry: A critical review of life cycle assessments. Journal of Cleaner Production 35, 108-117 Samuel, M. (2003) A new technique for recycling aluminum scrap. Journal of Materials Processing Technology 135, 117-124 Totten, G.E. and MacKenzie, S.D. (Eds.). (2005) Handbook of Aluminum. New York: Marcel Dekker Read More