Apa yang sebenarnya bergerak
Bauxite is red soil. It is refined into alumina, and alumina is smelted into aluminium by passing an enormous electric current through it. Because that last step is essentially electricity in solid form, the smelter is built next to cheap power rather than next to the mine — often on a different continent.
- Materialnya
- Bauxite
- Varietasnya
- Gibbsitic bauxite, roughly 45% alumina, low silica
- Titik awal
- Guinea — The Boké plateau, part of the largest bauxite reserve base in the world
Langkah demi langkah, perbatasan demi perbatasan
Guinea · Boké, Guinea dipegang oleh Mining consortia with the Guinean state (Penambang)
Scraping the plateau
Bauxite lies at or near the surface under a thin overburden. It is ripped and loaded — no blasting, no grinding, no flotation. The simplest large-scale mining there is.
Mengapa di sini: Tropical weathering over millions of years made this. West Africa and northern Australia have most of it.
China · Kamsar, then Chinese and Gulf refineries dipegang oleh Traders and refiners (Pedagang)
Rail to the coast, then a Capesize
Railed to a purpose-built port and loaded onto bulk carriers. Guinea ships hundreds of millions of tonnes a year of what is, physically, dirt.
Mengapa di sini: An export ban would force refining onshore — several countries have tried exactly that with different minerals.
China · Alumina refinery dipegang oleh Refiner (Pemurni)
The Bayer process
Digested in hot caustic soda under pressure. The alumina dissolves; the iron and silica do not, and settle out as red mud. The dissolved alumina is then precipitated and calcined to a white powder.
Apa yang terjadi pada sisanya: Red mud is the largest single waste stream in the metals industry by volume, and it is caustic. Storing it safely is the defining problem of this step.
Mengapa di sini: Refineries sit near ports and near smelters. Some are in Guinea now, but most of the capacity is not.
United Arab Emirates · Smelter, wherever power is cheap dipegang oleh Smelter (Pemurni)
Electricity, made solid
Alumina is dissolved in molten cryolite at about 960 °C and an enormous direct current is passed through it. Aluminium collects at the bottom; the carbon anodes are consumed and must be constantly replaced.
Apa yang terjadi pada sisanya: Roughly 125 tonnes of carbon anode is burned away — and that carbon started life as petroleum coke, from an oil refinery.
Mengapa di sini: Iceland, the Gulf, Quebec, Siberia, Yunnan. All the same answer: cheap, reliable, uninterruptible electricity.
Germany · Rolling and extrusion mills dipegang oleh Fabricators (Produsen)
Frames, cans, cables, car bodies
Cast into billet and slab, then extruded or rolled. Recycled aluminium needs about a twentieth of the energy of primary, which is why scrap is worth so much.
Mengapa di sini: Four tonnes of Guinean soil for one tonne of metal — and once it exists, it can be melted and reused indefinitely.
Ini adalah contoh terhitung. Contoh ini mengikuti kuantitas awal yang dinyatakan melalui hasil dan perolehan tipikal yang dipublikasikan, sehingga proporsinya dapat diperiksa; ini bukan catatan pengiriman tertentu. Fakta rute — negara mana saja, proses apa saja, dan mengapa material tersebut tidak dapat begitu saja ditangani di tempat lain — dikompilasi dari laporan publik.