Example: marketing

Hall-Héroult – Prebake Cell – Pechiney technology – …

Aluminium Production Introduction The aluminium production process Hall-H roult PrebakeCell Pechiney technology Inert anodeAluminium Production: introAluminium can be produced by using anodesand cathodesin the aluminium smelter. The main components of anodes are petroleum coke, a product from the distillation of oil, and coal tar pitch, a distillation product extracted from the tar that is obtainedin coking plants. A part of the anode material, the so-called anode butts, is returned by the aluminium smelters to be reused as raw material. Petroleum coke and anode butts are crushed, dried if necessary, graded, ground, heated and mixed with an exact amount of pitch and finally kneaded. An optimal composition is yet another prerequisite for good anode quality. Depending on the anode format the compound will be moulded to a 'green anode' either in a press or in a vibrating machine.

Aluminium Production • Introduction • The aluminium production process – Hall-Héroult – Prebake Cell – Pechiney technology – Inert anode

Tags:

  Inter, Pechiney

Information

Domain:

Source:

Link to this page:

Please notify us if you found a problem with this document:

Other abuse

Transcription of Hall-Héroult – Prebake Cell – Pechiney technology – …

1 Aluminium Production Introduction The aluminium production process Hall-H roult PrebakeCell Pechiney technology Inert anodeAluminium Production: introAluminium can be produced by using anodesand cathodesin the aluminium smelter. The main components of anodes are petroleum coke, a product from the distillation of oil, and coal tar pitch, a distillation product extracted from the tar that is obtainedin coking plants. A part of the anode material, the so-called anode butts, is returned by the aluminium smelters to be reused as raw material. Petroleum coke and anode butts are crushed, dried if necessary, graded, ground, heated and mixed with an exact amount of pitch and finally kneaded. An optimal composition is yet another prerequisite for good anode quality. Depending on the anode format the compound will be moulded to a 'green anode' either in a press or in a vibrating machine.

2 After forming, the anodes are baked at approx. 1150 C to carbonize the pitch binder and eliminate the volatile parts of the pitch. After cleaning, inspecting and packaging, the anodes are ready for delivery. Anodes can be produced in allshapes and sizes. Click here for a picture of the Anode production processsteps. Click here for a short overview of the aluminium production Hall-H roult-ElectrolysisAnode production process steps1) Petroleum coke storage2) Butt storage3) Liquid pitch storage4) Sampling5) Drying6) Grading7) Crushing8) Grinding9) Sifting10) Intermediate storage11) Metering12) Preheating13) Mixing and kneading14) Homogenizing/cooling15) Pressing16) Vibrating17) Baking18) Inspecting19) Packaging, storage20) DispatchCathodeblocksCathodesin aluminumelectrolysis-content Productionof primaryaluminium Aluminium electrolysis Electrolysiscelllining Aluminium electrolysiscell Electrolysiscell-General data Western worldcathodedemand Cathodeblock production Classificationof cathodeblocks Cathodeblocks-selectioncriteria Graphite layerstructure Chemical/ structuralchangesduringheattreatment Advantages of graphite Rapport expansioncurves Disadvantagesof graphite Graphitizedcathodes: Pot resultsvssemi-graphiticblocks Graphitizedcathodes: Positive impacton technicalresults Graphitizedcathodes.

3 Achievedpotlife(publisheddata) WearReductionCathodes made from carbon and graphite are applied for the production of primary aluminumelectrolysis-contentElectrolysis cell Cathodeblocks GraphitizedblocksAluminium electrolysisGeneral chemicalreaction2 Al2O3 (dissolved) + 3 C (s) 4 Al (liquid) + 3 CO2(gas)Cathodereaction:4 Al3+(bath) + 12 e- 4 Al (liquid)or4 AlF4-(bath) + 3 e- Al (liquid) + 4F -Anode reaction:3 C (solid anode) + 6 O2- 3 CO2 (gas) + 12 e-ElectrolysiscellbottomliningRequiremen tsto thecelllining electricallyconductive resistantagainsthigh temperature lowchemicalreactionwithbathcomponents no alloy-formationwithliquid aluminium Single candidate: CARBON/GRAPHITET echnologicalchallengeTremendousincreaseo verpastcenturyin Cellsize Efficiency ProductivityDemandforsubstantial cathodecarbondevelopmentsMain targetsReductionin power consumptionIncreasein potlifeCellCathode:cCathodeBlocksdSidewa llBlockseRamming PastefGlues/CementsgRefractoryInsulation hCarbonAnodeiMoltenCryolitejLiquid AluminiumhijAluminium electrolysiscellElectrolysiscell-General dataCathodeBlock10 -20 blocks/pot= 8 -26 t/potSidewallBlocks2 -7 t/potRamming Paste2 -10 t/potSteel Shell8 -15 m long.

4 3 -4 m widePot Amperage100 330+kAPot Voltage4 -5 VPotline100 -300 cellsconnectedin seriesPotlife1500 -3000 daysWestern worldcathodedemand(*cathode= bottomblocksand sidewallblocks)37 kt23 kt10 kt8 kt11 ktTotal Total worldworld: 101 : 101 ktkt12 ktCathodeblock productionExtrusionExtrusionAnthraciteAn thraciteGraphiteGraphitePetrolcokePetrol cokeBinderBinderpitchpitchBakingBakingGr aphitizationGraphitizationMachiningMachi ningClassificationof cathodeblocksAnthracitic/ Semi-graphiticbasedon anthracite(gas orelectricallycalcined)withorwithoutaddi tionsof graphite; bakedat ~1200 CGraphiticbasedon 100% graphiteaggregate; bakedat ~1200 CGraphitizedbasedon petroleum/pitchcoke; bakedat ~ 800 Cfollowedbygraphitizationat over2500 CCathodeblocks-selectioncriteria Lowsodiumexpansion Lowelectricalresistivity High thermal conductivityGraphite layerstructureChemical/ structuralchangesduringheattreatmentMars hand Griffiths, Int.

5 Symp. on Carbon, Japan 1982 Advantages of graphite1) LowelectricalresistivityLowercathodevolt agedropLessenergyconsumption2) High thermal conductivityUniform temperaturedistributionLesssludgedeposit ionon cathodesurface3) High thermal shockresistanceNo roddingcracks4) LowsodiumuptakeNo cathodelaminationsResult: Higherpotamperage/ potmetal productivityRapport expansioncurves00,10,20,30,40,50,6030609 0120time (min)expansion (%)amorphousgraphiticgraphiteDisadvantag esof graphite MechanicaldatalowerthananthraciteMechani calwear High thermal conductivityLongerelectricalpreheatingti meDissipation of moreheatintorammingpaste Change in currentdistributionIncreasedhorizontal currentsin themetal pad Larger differential expansionCollectorbarscanmovein theslotaftercoolingGraphitizedcathodesPo t resultsvssemi-graphiticblocks Plant APlant BPlant C(180 kA)(280 kA)(300 kA) Production increase (%)+ + + Cathode drop ( )- Energy from cath.

6 Drop (kWh/t)- 142- 221- 246 Energy from red. ACD (kWh/t)+ 48-- 154 Total energy (except )- 94- - 400 Instability ( )+ 1+ 4- 11 (P. Homsi; 6th Australasian Aluminium Smelting technology Conference & Workshop)GraphitizedcathodesPositive impacton technicalresults Enhancedproductionoutput-highercurrentef ficiency-increasedpotamperage Lowercathodedrop Constantorimprovedspecificenergyconsumpt ion Improvedpotstability,allowinga reductionof theanode-to-cathodedistance (ACD)GraphitizedcathodesAchievedpotlife( publisheddata) 130 kA pot(lowamperagepot)114 months 180 kA potsup to 84 months 300 kA pots65 monthsWearReductionof graphitizedcathodesApproachCreatea 'harder' Improvedrawmaterials Optimizedcomposition/ formulation Densification Useof RefractoryHard Material (RHM) Reduceddegreeof graphitizationThealuminium production processThe raw material for the extraction of aluminium is aluminium oxide, also called alumina, produced from bauxite.

7 Direct current of a very high intensity is passed through the anodes in the process. The anodes are part of the chemical reaction. For the production of 1 ton of aluminium, approximately 400 kg anodes ton of Aluminiummetal is required. The aluminium production process is also called the Hall-H of the general processOverview of the aluminium production4 tPrebake Cell:Pre-bake technology uses multiple anodes in each cell which are pre-baked in a separate facility and attached to "rods" that suspend the anodes in the cell. New anodes are exchanged for spent anodes -"anode butts" -being recycled into new derberg technologyS derbergtechnology uses a continuous anode which is delivered to the cell (pot) in the form of a paste, and which bakes in the cell electrolytic cell or pot is an electro-chemical reactor with anodes arranged horizontally or vertically.

8 In case S derberganodes are used, the anode is delivered to the cell as a paste that is baked in-situ. In S derbergcells the power supply is either horizontal, as with HSS (horizontal stud S derberg) cells or vertical, as is the case with VSS (vertical stud S derberg) Pechiney anode technology covers all steps of anode manufacturing:-Raw materials selection and anode characterization-Green process-Baking process-Anode handling and rodding-RecyclingThe anodes are baked in open type bake ovens, using the following technology :-low gas consumption (2300 to 2600MJ/t)-low packing coke consumption-consistent level of baking-low tar and fluoride emissions-long fluewall life (130 to 160 cycles)For the brickwork maintenance, the fluewalls can continuously bereplaced without reducing the production of the furnace.

9 Copyright websitePechiney anode/wettable cathode The aluminium industry has employed the Hall-Heroultprocessfor more than 100 years to produce aluminium. The new inert anode technology is believed toreduce the anode, labor, maintenance and environmental costs associated with running a smelter. The wettable cathodes also holds potential for reduced costs and increased operating efficiencies. Due to the fact that inert anodes would not use carbon, the smelting process would not create carbon dioxide, carbon monoxide or other greenhouse gases.(from An Aluminium Revolution Thomas Van Leeuwen, CFA)Inert anode/wettable cathode technology :The inert anode/wettable cathode invention relates to productionof a metal by electrolytic reduction of a metal oxide to a metal and oxygen.

10 A preferred embodiment relates to production of aluminum by electrolytic reduction of alumina dissolved in a molten salt bath. An electric current is passed between an inert anode and acathode through the salt bath, thereby producing aluminum at the cathode and oxygen at the anode. The inert anode preferably contains at least one metal oxide and copper, more preferably the oxides of at least two different metals and a mixture or alloy of copper and silver.(from An Aluminium Revolution Thomas Van Leeuwen, CFA)Inert anode/wettable cathode technology (2):The cermet materials used in anodes are deemed inert because, unlike carbon, they do not react with oxygen generated by electrolysis of alumina. The cermet materials also have relatively low solubility in the electrolyte. However, inert electrodes are subject to corrosion through several different mechanisms.


Related search queries