Los ntawm Bauxite rau Alumina: Cov Txheej Txheem Bayer
Thawj aluminium yog ua nyob rau hauv ob theem sib txawv: refining bauxite rau hauv alumina, thiab txo cov alumina rau hlau. Kwv yees li plaub mus rau tsib tonnes ntawm bauxite yield txog ob tonnes ntawm alumina, uas nyob rau hauv lem tsim ib tonne ntawm thawj txhuas. Cov theem refining yog cov txheej txheem Bayer, txoj kev alkaline uas siv cov solubility ntawm txhuas hydroxide hauv cov dej qab zib kub kub.
Kev zom zaub mov:crushed bauxite yog zom nyob rau hauv sodium hydroxide tov ntawm 140-300℃nyob rau hauv roughly 35 atm siab, yog li cov txhuas oxides yaj raws li sodium aluminate thaum silica thiab hlau nyob li insoluble residue.
Kev piav qhia:sedimentation thiab pom nyob rau hauv cov tso tsheb hlau luam qhia cais cov cawv cev xeeb tub los ntawm kev nplua, hlau - nplua nuj residue hu ua av nkos liab.
Dej nag:Cov cawv yog txias thiab noob nrog aluminium hydroxide crystals, uas loj hlob thiab khom tawm ntawm kev daws.
Calcination:rotary kilns calcine hydroxide ntawm li 1100℃kom muab smelter-qib alumina, feem ntau 99.5% Al₂O₃.
Kev lag luam kev lag luam refinery yog tus thawj coj los ntawm caustic soda thiab kev siv lub zog, thiab qib alumina yuav tsum nruj tswj hwm rau theem thib ob kom ua haujlwm ruaj khov.
Hall-Héroult Electrolysis: Txoj Kev Txom Nyem
Hlau aluminium yog tsim los ntawm Hall-Héroult txheej txheem, nyob rau hauv uas alumina yog yaj nyob rau hauv ib tug molten cryolite-raws li electrolyte (Na₃AlF₆ nrog txhuas fluoride thiab calcium fluoride ntxiv) ntawm txog 940-965℃. Direct tam sim no dhau los ntawm consumable carbon anodes los ntawm da dej mus rau ib tug carbon-lined cathode. Lub alumina yog txo electrochemically, molten aluminium sau rau hauv qab ntawm tes thiab yog siphoned tawm, thiab cov carbon anodes yog oxidized rau carbon dioxide.
Tag nrho cov tshuaj tiv thaiv ntawm tes yog 2Al₂O₃ + 3C → 4Al + 3CO₂. Kev txo cov hlwb niaj hnub ua haujlwm ntawm 93-95% kev ua haujlwm tam sim no, thiab cov khoom siv tsis siv neeg taw tes tuav cov alumina concentration hauv da dej ntawm kwv yees li 2-4% kom cov tshuaj tiv thaiv nyob ruaj khov thiab zam cov teebmeem anode.
Lub zog thiab cov khoom siv ntsuas ntsuas
Smelting yog ib qho hluav taws xob- kev lag luam hnyav, thiab kev siv yog ib qho loj tshaj tus nqi thiab emissions lever. Cov duab qhia txog kev txo cov kab niaj hnub:
| Parameter | Yam nqi |
|---|---|
| Alumina noj | 1.90 - 1.95 t ib tonne ntawm txhuas |
| Kev siv carbon anode | 0.40 - 0.45 t ib tonne ntawm txhuas |
| Kev siv hluav taws xob | 12.5 - 15 MWh ib tonne ntawm txhuas |
| Zoo tshaj - hauv - chav kawm tshwj xeeb lub zog | 12.3 - 13.0 kWh ib kg, ua tiav nrog kev ua kom zoo ntawm busbar thiab cov nyiaj sib nqus teb |
| Nruab nrab zog siv nyob rau hauv Suav teb | txog 13,500 kWh ib tonnes |
| Cell khiav hauj lwm kub | 940 - 965 degree |
| Tam sim no efficiency | 93 - 95% |
| Inert anode kev loj hlob hlwb | txog 15 kWh ib kg, tsis muaj carbon dioxide generated ntawm lub anode |
Pov tseg cov cua sov rov qab los ntawm cov pa hluav taws xob thiab lub lauj kaub roj yog lub hauv paus tseem ceeb ntawm kev ua haujlwm zoo, thiab cov cua sov rov qab tau nce ntxiv rau hauv cheeb tsam cua sov thiab rau preheating alumina lossis anode raw khoom. Cov kab tsim nrog slotted anodes thiab dynamic voltage tswj zaum ntawm qis kawg ntawm kev noj ntau yam, thaum lub hlwb laus tuaj yeem tshaj 15 kWh ib kg.
Cov teebmeem Anode thiab PFC Emissions
Yog tias alumina concentration hauv da dej poob qis qis dua 1.5%, lub xov tooj ntawm tes tsis tuaj yeem txhawb nqa ib txwm electrolysis thiab qhov hluav taws xob nce siab, feem ntau siab dua 8 V. Thaum lub sij hawm cov teebmeem no, cov roj fluorocarbon tsim ntawm lub anode, feem ntau yog tetrafluoromethane thiab hexafluoroethane, los ntawm ib sab cov tshuaj tiv thaiv ntawm cryolite da dej nrog carbona, piv txwv li 4 4Al + 12NaF + 3CF₄.
Perfluorocarbons yog lub tsev cog khoom muaj zog heev: tshaj 100- xyoo qab ntug tetrafluoromethane nqa lub ntiaj teb ua kom sov muaj peev xwm ntawm kwv yees li 6,600-7,400 thiab hexafluoroethane kwv yees li 11,100-12,200 npaug ntawm cov pa roj carbon dioxide, nyob ntawm seb cov ntaub ntawv siv li cas. Automated alumina noj, cell voltage xyuas thiab computer tswj tau txiav anode nyhuv zaus mus rau hauv qab 0.1 txheej xwm ntawm tes ib hnub twg nyob rau hauv cov nroj tsuag zoo, thiab qhia thoob ntiaj teb PFC emissions los ntawm txhuas smelting tau poob li ntawm 85% txij li thaum 1990.
Liab av nkos: ntim, txaus ntshai thiab siv
Bauxite residue, los yog av nkos liab, yog cov khib nyiab loj ntawm alumina refining. Ntiaj teb no tiam yog kwv yees li ntawm 180 lab tonnes ib xyoo, thiab cov residue yog alkaline, nrog pH feem ntau ntawm 10 thiab 13 thiab 2-6% residual sodium hydroxide, yog li cia yuav tsum tau engineered los tiv thaiv to thiab plua plav.
Qhuav stacking tau dhau los ua txoj kev tswj hwm zoo dua vim tias nws txo qis cov hneev taw los ntawm kwv yees li ib nrab thiab tshem tawm qhov kev pheej hmoo ntawm kev puas tsuaj los ntawm kev puas tsuaj los ntawm cov dej ntub dej. Kev siv tseem txwv tab sis nthuav dav los ntawm ntau txoj hauv kev: rov qab los ntawm cov hlau, titanium thiab lub ntiaj teb tsis tshua muaj, siv 8-12% cov av nkos liab ua cov silica thiab alumina hauv geopolymer thiab cement sib xyaw, thiab cov kua qaub leaching kom rov qab tau cov dej qab ntsev thiab ua kom cov seem seem.
Cov lus nug nquag
Q: Qhov txawv ntawm bauxite, alumina thiab txhuas yog dab tsi?
Bauxite yog cov mined ore, alumina (aluminium oxide) yog qhov ua kom zoo li nruab nrab muab rho tawm los ntawm nws, thiab txhuas yog cov hlau tsim thaum alumina raug txo nyob rau hauv ib qho electrolytic cell.
Q: Vim li cas aluminium smelting thiaj li siv zog?
Lub aluminium-oxygen daim ntawv cog lus hauv alumina muaj zog heev, yog li kev tawg nws yuav tsum muaj qhov txuas ncaj qha tam sim no. Txawm tias cov hlwb zoo tshaj plaws xav tau ntau dua 12 kWh ntawm hluav taws xob ib kilogram ntawm cov hlau, uas yog vim li cas smelters tau tsim qhov twg lub hwj chim pheej yig thiab ruaj khov.
Q: Dab tsi yog qhov kub ntawm qhov txo cell khiav ntawm?
Lub cryolite-raws li electrolyte melts ntawm ze li ntawm 950 degree, thiab cov hlwb feem ntau ua haujlwm ntawm 940 thiab 965 degree, uas yog siab txaus kom cov da dej molten tab sis tsawg txaus los txwv cov fluoride poob thiab siv zog.
Q: Vim li cas cov teebmeem anode tseem ceeb?
Lawv nkim lub zog, cuam tshuam kev ua haujlwm ntawm tes thiab tsim cov perfluorocarbons nrog lub ntiaj teb ua kom sov siab heev. Kev pub noj tsis siv neeg thiab kev tswj hluav taws xob tsis tshua muaj tshwm sim, thiab qhov zaus ntawm cov teebmeem yog tus qauv qhia kev ua haujlwm rau lub smelter.
Q: Ntau npaum li cas cov av nkos liab tsim ib tonne ntawm hlau?
Bauxite residue tiam yog nyob ntawm qib ore tab sis feem ntau nyob rau hauv thaj tsam ntawm ib mus rau ob tonnes ntawm qhuav residue ib tonne ntawm alumina tsim, yog li kev tswj cov seem yog ib qho tseem ceeb ntawm cov nqi ntawm thawj cov khoom.
Q: Puas yog lwm yam aluminium hloov pauv rau thawj hlau?
Recycled aluminium yuav tsum tsuas yog ib feem me me ntawm lub zog xav tau rau thawj smelting thiab tuaj yeem rov ua dua tsis tau poob nws cov khoom tseem ceeb, txawm hais tias alloy sorting txwv ntau npaum li cas cov hlau thib ob tuaj yeem siv rau hauv kev thov.
