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picture1_Carbon Steel Pdf 181097 | 2011042692804 1303766884 1


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File: Carbon Steel Pdf 181097 | 2011042692804 1303766884 1
how aluminium is made new zealand aluminium smelters limited the process nzas uses the hall heroult process to reduce an electric current o approimately amps carbon anode alumina to aluminium ...

icon picture PDF Filetype PDF | Posted on 30 Jan 2023 | 2 years ago
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                       How Aluminium is Made
                       NEW ZEALAND ALUMINIUM SMELTERS LIMITED
                                                                                The Process
                                                                               NZAS uses the Hall-Heroult process to reduce                 An electric current, o approˆimately ƒ‰Š,……… amps 
                           CARBON ANODE                                        alumina to aluminium metal. The basic inputs are             or ‚ines ƒ,  „  and ‹,……… amps or ‚ine ‡, 
                                                                               alumina, electricity and carbon.                             flows into the cells through carbon anodes which 
                                                                                                                                            orm the positive electrode and also supply the 
                                                 OER                         In this process, alumina undergoes an electro-               carbon or the reduction reaction. The current 
                      METAL BAT  
                      NTERACE           2Al O  +3C    4Al + 3CO              chemical reaction in individual reduction cells. 
                                             2 3                 2                                                                          passing through the aluminaŒbath solution reduces 
                                                                               These cells are long steel shells lined with                 the alumina to aluminium and oˆygen. The 
                                                                               reractory brics and carbon and are connected               aluminium is deposited at the cathode, while the 
                                       ALMNM                               electrically in series. The carbon lining o the cell        oˆygen is attracted to the carbon anode. The cells 
                                                                               orms the cathode.                                           operate at temperatures o around ‰Š…°‘.
                                                                               Alumina Al    is ed into the cells at regular 
                                                                                                                                          There are ƒ† carbon anodes in ‚ines ƒ,  „  cells 
                                                                               intervals where it is dissolved in a bath o molten          and … carbon anodes in ‚ine ‡ cells. Aluminium 
                                                                               cryolite sodium aluminium fluoride .                        rods are attached to suspend them in the reduction 
                                                                               NZAS has our reduction lines€ ‚ines ƒ,  „                 cells. The anodes, which are largely consumed 
                                                                               each containing …† individual cells and ‚ine ‡              in the reaction, are replaced by rota ater around 
                                                                               containing ‡† cells.                                         Š days in the cell. ’sed anodes called butts, are 
                                                                                                                                            crushed and used in the production o new anodes 
                                                                                                                                            which are manuactured using petroleum coe, 
                      The equation for the basic reaction is                                                                                li“uid pitch and the recycled carbon material.
                      2Al O  +3C     4Al + 3CO  
                                     2         3                                                                               2
                  ”olten aluminium, which collects in the bottom 
                  o the cell, is siphoned o and transported to the 
                  cast house. •ach cell in ‚ine ƒ,  „  produces                            Tonnes                              Tonnes                              Tonne 
                  approˆimately ƒ,‡‹… g o molten aluminium and                             Bauƒite        ‚                    Alu„ina ‚                           Alu„iniu„
                  each cell in ‚ine ‡ produces approˆimately ƒ,–… g            4                                   2                                   €
                  o molten aluminium every ‡ hours.
                  —ases generated in the process are collected and 
                  filtered through fluoride scrubbing e“uipment             Metal Castin ­ 
                  beore being released to the atmosphere.                  ”olten aluminium is transported to the ”etal               Two ingot casting machines, each capable o 
                                                                            ›roducts cast house in lined crucibles carried by          casting up to ƒ.‹ tonnes per hour, cast, stac, 
                  Apart rom alumina, the primary re“uirement in            special purpose crucible transport vehicles. •ach          strap and weigh the ingots into one tonne bundles, 
                  the smelting o aluminium is a constant availability      crucible holds about five tonnes o molten metal.          ready or transport.
                  o electricity at a competitive price. Around ƒ‡,‹…… 
                  ™‘šh o electricity, two tonnes o alumina and           The metal is tipped into the holding urnaces.             œillet, rolling bloc and T bar are cast using a 
                  ‡‹ gs o carbon are re“uired to produce one             The holding urnaces are heated and hold                   vertical direct chill casting process producing up to 
                  tonne o aluminium.                                       the aluminium at –…°‘, the desired casting                seven metre lengths. œillet can be cast in a variety 
                                                                            temperature.                                               o diameters. Ater casting, billet is placed in a 
                                                                                                                                       homogenising urnace or reheating and cooling 
                                                                            Aluminium is cast as  g ingot, rolling bloc            under controlled conditions. This ensures a uniorm 
                                                                            and T bar lengths, or alloyed with other metals to         crystalline structure throughout.
                                                                            produce billet.
                   Raw Materials
                    €  œauˆite is the ore rom which aluminium metal             4  The raw materials are miˆed and ormed into carbon         †  The smelter’s main emission control e“uipment are 
                   is ac“uired. œauˆite is mined at šeipa on ‘ape žor          anodes weighing approˆimately ƒ,ƒ‹ g or all ‚ines.         the ™ry Scrubbers, where dust particles and fluoride 
                   ›eninsula in north Ÿueensland. It is shipped to ¡io Tinto    They are then baed at temperatures o up to ƒ,ƒ……°‘ or      gases are removed rom cell emissions. There are ƒ dry 
                   Alcan žarwun and Ÿueensland Alumina ‚imited, in              up to ƒŠ days. This baing process improves the strength      scrubbers at NZAS which collect more than ‰‰ per cent 
                   —ladstone on the central Ÿueensland coast or refining.      and conductivity o the anode. ›itch volatiles are released   o the fluoride gases rom process emissions. 
                    2                                                           and burnt to provide eˆtra heat.                               ‡
                       The fine white alumina powder Al    is transported                                                                       ‘hemical reduction o alumina to aluminium taes 
                                                                               …
                   by ship to NZAS rom the alumina refineries. ¢our                 The carbon anodes are attached to aluminium rods         place in individual reduction cells connected in an 
                   tonnes o bauˆite produce two tonnes o alumina, which       using molten cast iron to enable them to be suspended         electrical circuit. The smelter has our reduction lines. 
                   produces one tonne o aluminium.                             rom cell superstructures. They are then sprayed with         ¡eduction ‚ines ƒ,  „  are housed in buildings Š…… 
                    3                                                           approˆimately † g o molten aluminium to reduce              metres long and all contain …† reduction cells. ‚ines ƒ, 
                       The electrical current re“uired or the smelting         airburn in the cell. They are distributed by an overhead       „  are ¥aiser ›Š‰ technology. 
                   process flows in the reduction cell through carbon blocs    conveyor to a distribution point where they are truced to     ˆ
                   anodes  to the cathodes in the bottom o the reduction      the cells via an Anode Transport £ehicle AT£ .                   ¡eduction ‚ine ‡ comprises more recent ‘™…… 
                   cells. The anodes are made rom petroleum coe, li“uid                                                                     technology and is …… metres in length, connected in an 
                   pitch and recycled carbon anodes which are returned                                                                        electric circuit. ‚ine ‡ contains ‡† reduction cells.
                   rom the reduction process.
                   €                    2                       3                        4                        …                            †                            ‡                        ˆ
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