Aluminium is the third most common element on Earth after oxygen and silicon Free Essays

Aluminium is the third most common element on Earth after oxygen and silicon. The aluminium industry had a Gross Domestic Product of $3.1 billion in1997/98, ranking the aluminium industry amongst Australia’s leading manufacturers and employs over 16000 people directly. We will write a custom essay sample on Aluminium is the third most common element on Earth after oxygen and silicon or any similar topic only for you Order Now The total value of export earnings was about $6.3 billion in 1998/99, second only to coal as an export industry for Australia. These facts underline the fact that the aluminium industry is a major asset to Australia and is world competitive. Aluminium is important to us currently and is used from everything from soft drink cans to car bodies to window frames. Aluminium is lightweight, strong, long-lasting, highly corrosion resistant as a protective oxide coating is naturally generated, is an excellent heat and electricity conductor, has good reflective properties, is very ductile, completely impermeable and odourless and totally recyclable. Despite this, less than 200 tonnes in 1885 were produced compared to approximately 22 million tonnes in 1998 – plus some 5 million tonnes of recycled Aluminium. This is because aluminium is so highly oxidized that it can be only refined using huge amounts of electricity and electricity did not become readily available until this century. Thus, it is known as the metal of the 20th century. There are three process involved in the manufacture of Aluminium: Bauxite mining, alumina refinery and aluminium smelting. Raw Materials – Cryolite (Na3AlF6). Sodium Aluminium Fluoride. This reduces the temperature needed to electrolyse the aluminium reducing the cost. It was originally obtained from mines in Greenland, but the supply has depleted and it is now produced synthetically. – Aluminium fluoride (AlF3), calcium fluoride (CaF2) and Lithium Fluoride (LiF) which play the part of reducing the melting point of the mixture. – Alumina (Al2O3). This is obtained from bauxite, a red rock-like material, which also contains a lot of unwanted substances. Bauxite is mined in Western Australia, Queensland and Northern Territory. Bauxite mining leaves a lot of barren areas which will be investigated later. Bauxite and alumina are stored in storage bunkers. To produce aluminium metal, bauxite has to be concentrated, thus removing most impurities. Bauxite is crushed and washed to remove some of the clay and sand then dried in kilns. This is because crushed bauxite is easier to transport. The ore is loaded onto trucks, railway cars, or conveyor belts and transported to ships or refinery. The concentration of bauxite into alumina is called the Bayer process as shown below. Note that the red mud from the refinery must be carefully disposed of and this will be explore in Environmental factors. The Chemical Process To refine aluminium from alumina which contains both aluminium and oxygen, electrolysis is used, in a process known as the Hall-Heroult process. Alumina has to be liquefied (it is mixed with cryolite to reduce melting temperatures) and each cell is supplied with four to six volts and 150,000 amps of electricity. The sequence of creation is: All pots are covered so that exhaust gases are drawn into a large fume duct (will be explored later). As this involves consumable anodes, the pots cannot be sealed and every time a pot is opened, a small quantity of volatile gases escapes. For the safety and comfort of workers, the potroom needs to be well ventilated and the workers need breathing protection equipment. So much electricity is needed in this process that many smelters are located near hydro-electric plants or have their own power stations such as Alcoa which mines brown coal to generate electricity that meets 50% of its energy requirements. Approximately 16 kWh of energy is needed to produce one kg of molten metal in the Hall-Heroult Process compared to a theoretical energy of 6.34 kWh per kg of molten metal. Two main causes of this are the reoxidation of aluminium metal by carbon dioxide and high temperature, as well as side reactions wasting energy. Computers are now being used to monitor each pot continuously and set a best voltage for any particular condition reducing energy consumption. Covering the top of the anodes with an insulator to prevent them burning off and improved quality of carbon anodes reduces energy loss. Australia’s comparatively has a low consumption of power for each kilogram of aluminium produced. Research is currently being done to find an alternative extraction process and the two main ways are through carbon reduction and electrolysis of aluminium chloride. The Product Aluminium, Al a Group III element is the product that results. Its properties and uses were discussed above. Other than the pure substance, alloys are also made containing copper, magnesium, manganese, chromium, silicon, nickel, iron and zinc. Quality control issues include the issue that normal refining processes do not remove all the impurities from aluminium, so most commonly used industrial aluminium already has small amounts of impurities alloyed with it. Fortunately, this makes aluminium stronger but remains easy to bend. Some alloys are less suitable for extrusion than others, requiring higher pressures, allowing only low extrusion speeds and/or having less than acceptable surface finish and section complexity. Aluminium sheets which are rolled from ingots are not flat when produced from the rolling mills. To flatten it, they are stretched between heavy-duty hydraulically-operated grips. A Micro Alignment Telescope with sweep optical square is used to check the flatness within specified tolerance to ensure the quality. One random sample for each batch of the aluminium and its alloy ingots undergo an optical spectrometry analysis to ensure that the results lie within the limits determined by Australian specification. The by-products and waste products of this product are carbon dioxide and fluoride gases as well as sulphur and nitrogen oxides. Carbon dioxide gas is a greenhouse gas and large amounts of fluorides are toxic. Sulphur and nitrogen oxides are acid rain gases. Therefore these need to be controlled and this will be investigated below in Environmental Factors. The aluminium and its alloy ingots or its processed equivalents are packed and distributed through shipping. Approximately 78% of all aluminium produced in Victoria is exported. Location Australia has six aluminium smelters located in Tasmania (one), Victoria (two), New South Wales (two) and Queensland (one). However Bauxite mines are in Queensland, Northern Territory and Western Australia. This is because the energy costs are too high to set up a plant near the mines but in Tasmania, Victoria and New South Wales electricity is cheap. As lots of electricity is used in the electrolysis, it is cheaper to transport the bauxite to the smelters than to set up a smelter near the mines and pay higher costs for electricity. Other factors that are taken into account include the labour force available (generally higher near cities), transportation of the aluminium produced (so the smelter has to be near ports, railway stations or highways), geographic factors (smelters are built in residential areas where the land is cheap) and legal factors (whether the sounds and the activities such as the fumes released and the transportation of aluminium using trucks would affect nearby residential properties who could sue). Environmental By recycling aluminium, approximately 95% of the energy (approximately 2 billion kWh of electricity) otherwise required to produce the primary metal aluminium can be saved. This makes the aluminium cheaper to manufacture as well as reduce the rapid depletion of non-renewable fossil fuels to produce electricity. When land is mined for Bauxite, active reforestation must be carried out to ensure the stability of the environment as well as ensuring that the soil left over doesn’t erode and cause mud slides. Extreme care must be taken with the handling and disposal of red mud from the refineries. This is usually pumped into dams which are sealed with impervious material to prevent pollution of surrounding countryside. The manufacture of aluminium produces carbon dioxide, a greenhouse gas, fluoride gas, a toxic gas and other exhaust gases (such as the sulphur and nitrate oxides) that can potentially be harmful. To combat their pollution, all pots are covered and the fumes are drawn into a fume duct where the gases pass through beds of alumina which adsorbs over 99%of the fluoride. All cryolite needs to be manufactured synthetically and suitable fluorides are expensive and so they need to be recovered. The gases then pass through dust filter bags and a dry scrubber and treatment facilities to remove the greenhouse and other gases and only clean air is released. Although manufacture of aluminium uses a lot of energy and other options to mine aluminium are being investigated (as shown above), the use of aluminium itself has saved a large amount of energy because they are strong and light. It is estimated that 1,230 litres of petrol was saved in cars that used 64 kg of aluminium instead of other metals and this saved more than five times the energy required to produce each kilogram of aluminium used in the car. How to cite Aluminium is the third most common element on Earth after oxygen and silicon, Papers