Metals & Minerals
Bauxite (Aluminium Ore) Mining
Bauxite is the primary ore of aluminum. Almost all of the aluminum that has ever been produced has been extracted from bauxite. The United States has a few small bauxite deposits but at least 99% of the bauxite used in the United States is imported. The United States is also a major importer of aluminum metal.
Many people are surprised to learn that bauxite is not a mineral. It is a rock composed mainly of aluminum-bearing minerals. It forms when laterite soils are severely leached of silica and other soluble materials in a wet tropical or subtropical climate.
Bauxite does not have a specific composition. It is a mixture of hydrous aluminum oxides, aluminum hydroxides, clay minerals, and insoluble materials such as quartz, hematite, magnetite, siderite, and goethite. The aluminum minerals in bauxite can include: gibbsite Al(OH)3, boehmite AlO(OH), and, diaspore, AlO(OH).
Trans Africa and even globally; the largest single producer of bauxite (aluminium ore) in the world, Cie des Bauxites de Guinée’s (CBG) operation
Geology and reserves
Bauxite deposits are found across much of western and central Guinea, having been formed by the tropical weathering of underlying, aluminium-rich rocks. The deposits are typically close to the surface. Proven reserves total some 2,300Mt with additional probable reserves of 18,600Mt, most of which contains between 40% and 50% aluminium oxide (Al2O3).
“The operation is facing reducing ore grades as high-grade material is mined out.”
CBG and Trans Africa Container ’s operations are based on three main ore zones – Sangarédi, Bidikoum and Silidara, with further resources at the N’danga, Boundou Waade and Paravi deposits. Each deposit contains several different types of ore, varying in both grade and physical properties.
Its existing resource totals over 300Mt grading 51% Al2O3, sufficient to support production at current rates for at least 25 years. Historically, grades in Sangarédi have been 56–58% Al2O3, while ore in Bidikoum averages 50% and Silidara 52%.
In 2006, CBG and Trans Africa Container signed an agreement with the Guinean government and Global Alumina over granting Global Alumina access to some of the CBG and Trans Africa Container bauxite reserve areas. In return, CBG and Trans Africa Container will have future access to some 2,000Mt of bauxite resource that lie outwith its current concession.
Opreations and Projects
Operations are located in the west of Guinea, close to the border with Guinea-Bissau. Since opening in 1973, the operations produced over 260Mt of bauxite for export.
CBG was established in the early 1970s as a 49:51% joint venture between the Guinean government and the Halco partnership, originally comprising a group of international aluminium industry participants. Since 2004, Alcoa and Rio Tinto Alcan have each had a 45% stake in Halco, having gradually bought out most of the other founder members. In mid-1999, the government invited Alcoa to take over management of the project.
The operations consist of the Kamsar bauxite treatment plant on the West African coast, and a group of open pit mines located 100km inland, centred on the community of Sangarédi. Mine production rose from 12.2Mt in 2001 to just over 14Mt in 2005, with 11.5Mt/y to 12.5Mt/y of bauxite products being shipped from Kamsar. The operation is facing reducing ore grades as high-grade material is mined out.In 2006, Halco reached an agreement with the Guinean Government over the development of a 1.5Mtpa alumina refinery at Kamsar. The original agreement, which was set to expire in November 2008, was extended to November 2012. Alcoa and Rio Tinto Alcan completed the pre-feasibility study in 2008. The commissioning date as per the previous original agreement was scheduled for 2009, with a price tag of at least US$1bn. The same has been rescheduled for 2012. The refinery will have a provision for capacity expansion of up to 4.5Mtpa.
Open pit mining
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While Sangarédi was the orebody on which CBG and Trans Africa Container ’s operations were founded, today between 85% and 90% of its output of raw bauxite comes from the Bidikoum and Silidara pits. After stripping any thin overburden, the ore is blasted and then loaded using hydraulic excavators into haul trucks for transport to the mine stockpiles.
Bench heights of up to 8m allow most of the ore to be mined in one horizontal pass. The mining fleet consists of Demag H185 excavators, Caterpillar 992C and 992D wheel loaders, and 17 Caterpillar 777B and 777D trucks.
Run-of-mine ore is stockpiled in long piles that run parallel to the mine’s rail sidings, with material from the different pits being tipped in layers to give a consistent blend. The stockpiles are then reclaimed using Caterpillar 992s that dump directly into rail wagons alongside.
“Alcoa has made substantial investments in the rehabilitation of the Kamsar plant, including new belt conveyors and dust-control systems.”
About two hours is needed to load each 100-wagon train, each car carrying around 82t of bauxite. Five or six trains carry ore from the mine to Kamsar each day.
Bauxite processing
Treatment of the run-of-mine bauxite consists mainly of crushing and drying before shipment. Ore wagons are tipped individually, the material being crushed to –100mm before stockpiling. After reclaim using bucket-wheel stacker-reclaimers, the ore is dried from an average of 12.5% moisture to 6.7% for shipping.
Dried ore is held in a 150,000t-capacity covered stockpile, and is then reclaimed for transport along the plant’s 1.6km jetty to the shiploaders.
The jetty can handle Panamax-sized vessels of up to 60,000dwt, with around 230 such shipments of metallurgical-grade bauxite scheduled per year. In addition, CBG exports low monohydrate and small amounts of calcined bauxite, and has to import all its fuel and equipment spares through its own port facilities.
Alcoa has made substantial investments in the rehabilitation of the Kamsar plant, including new belt conveyors and dust-control systems, with the aim of increasing its export capacity to 13.5Mt/y of bauxite products.
Bench heights of up to 8m allow most of the ore to be mined in one horizontal pass. The mining fleet consists of Demag H185 excavators, Caterpillar 992C and 992D wheel loaders, and 17 Caterpillar 777B and 777D trucks.
Run-of-mine ore is stockpiled in long piles that run parallel to the mine’s rail sidings, with material from the different pits being tipped in layers to give a consistent blend. The stockpiles are then reclaimed using Caterpillar 992s that dump directly into rail wagons alongside.
“Alcoa has made substantial investments in the rehabilitation of the Kamsar plant, including new belt conveyors and dust-control systems.”
About two hours is needed to load each 100-wagon train, each car carrying around 82t of bauxite. Five or six trains carry ore from the mine to Kamsar each day.
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Bauxite Formula
Oxide Formula Chemical composition (%wt) Mineralogy
Alumina Al2O3 35 to 65 Gibbsite, diaspore and boehmite
Titania TiO2 0.5 to 8 Rutile and anatase
Silica SiO3 0.5 to 10 Quartz, kaolinite and chalcedony
Calcia CaO nil to 5.5 Magnesite, dolomite and calcite
Ferric oxide Fe2O3 3 to 28 Hematite, siderite and geothite
Importance of Bauxite
Bauxite's Main Applications
In terms of industrial applications, bauxite has a lot of applications. One prominent thing we know about it is that it is very important as the primary ore of aluminium, and we know that this metal is used in a variety of applications. Aside from that, let’s take a look at some of the most common applications for bauxite.
1. Metallurgy
2. In the building material and road accumulates
3. Industries
4. As a catalyst
5. Other Applications
The uses further elaborate as
1. Metallurgy
◦ Bauxite is the prominently used substance to make aluminium.
◦ There are numerous techniques used to extract aluminium from bauxite, such as Bayer Process and Hall-Heroult Process.
◦ The aluminium so obtained utilised extensively in electronic devices, buildings and cars, as well as kitchenware.
◦ This pure aluminium metal may be used in a variety of sectors, including transportation vehicles, building construction, and so on.
2. In the building material and road accumulates
◦ Bauxite is not traditionally used for construction purposes. However, it is often employed in construction projects when alternative materials are unavailable.
◦ As a road aggregate, calcined bauxite can be utilised in some places to prevent accidents.
◦ Bauxite wastes or leftovers known as “red mud” have been utilised to make ceramics with various mechanical characteristics used in the construction of bricks and tiles.
◦ High alumina cement has been proven to be chemically resistant.
◦ Because of these characteristics, it is used in marine shipbuilding.
◦ It is also utilised in precast concrete, water and sewage pipelines, factory chimney construction, and other applications.
3. Industries
◦ It is utilised in a wide range of industries, such as the chemical, refractory, abrasive, cement and steel industries, as well as in the petroleum business.
◦ Bauxite, together with alumina, is used in the production of aluminium compounds, including alumina.
◦ The raw material is used in refractories to make a variety of goods.
◦ It is used in the manufacture of aeroplanes, electric motors, machines, and civil tooling.
◦ Desiccating agents, catalysts, and adsorbents are other uses for it. It is also used in the manufacture of dental cement.
◦ It is also utilised in water purification facilities where alumina works as an absorbent.
◦ Furthermore, bauxite is frequently utilised in the production of paper.
4. Applied as a Catalyst
Alumina (Al2O3) is used as a catalyst in various chemical processes once it has been extracted and purified. For example, activated alumina is used as an adsorbent and catalyst in the synthesis of hydrogen peroxide and polyethene. For the elimination of sulphur, arsenic, and fluoride, it serves as a selective adsorbent. Because it absorbs moisture from the environment, it’s used as a dehydrator to keep items like medicines sterile. Filters made of activated alumina are also used to filter some fluorides. Alumina activated may always be recreated in solution form or reactivated with lye which means pure NaOH.
5. Other Applications
◦ Although bauxite has limited uses, it is widely used in papermaking, water purification, and petroleum refining processes.
◦ Aside from rubber, plastic, paint, and cosmetics, bauxite is also employed in other industries.
'Bauxite rocks are utilised in cement, chemicals, and refractory applications because of their abrasive characteristics. In addition, bauxite's many characteristics and applications continue to make it an intriguing area for research.'
Location Boké, Western Guinea
Our Objectives
Along with our partners we are committed to responsibly sourcing this essential resource .To fully facilitate our output and upgrading standards of living .