Los ntawm Bauxite rau Alumina: Cov Txheej Txheem Bayer
Bauxite yog lub ntsiab ore ntawm txhuas, lub pob zeb uas muaj 40% mus rau 60% txhuas oxide ua ke nrog hlau oxide, silica thiab lwm yam impurities. Thawj theem extraction, tus txheej txheem Bayer, cais cov txhuas oxide ntawm cov impurities.
Crushed bauxite yog tov nrog kub, concentrated sodium hydroxide tov thiab zom nyob rau hauv lub siab ntawm qhov kub ntawm ib ncig ntawm 150 mus rau 250 degrees Celsius. Cov txhuas oxide dissolves los ua sodium aluminate, thaum hlau oxide, silica thiab lwm yam impurities nyob twj ywm raws li cov khoom seem hu ua av nkos liab. Lub slurry yog lim kom tshem tawm cov av nkos liab, tawm hauv cov kua ntshiab sodium aluminate.
Tom qab ntawd aluminium hydroxide yog precipitated los ntawm cov tshuaj los ntawm noob thiab txias, thiab cov precipitate yog ntxuav thiab calcined nyob rau hauv rotary kilns los yog kua - txaj calciners ntawm txog 1000 degrees Celsius kom tsav tawm dej. Cov khoom yog dawb alumina hmoov, ze li ntawm ntshiab txhuas oxide.
Los ntawm Alumina mus rau Aluminium: Hall -Heroult txheej txheem
Alumina muaj qhov melting point saum 2000 degrees Celsius, uas yuav ua rau ncaj qha melting uneconomic. Lub Hall-Heroult txheej txheem dissolves alumina nyob rau hauv molten cryolite, ib tug fluoride ntxhia, txo cov kev khiav hauj lwm kub mus txog 950 degrees Celsius.
Lub zog ncaj qha tam sim no, feem ntau yog 150,000 txog 600,000 amperes, hla lub cell ntawm carbon anodes thiab carbon-lined cathode. Ntawm lub cathode, cov ntaub ntawv txhuas ua kua thiab sau rau hauv qab ntawm tes; ntawm anodes, oxygen reacts nrog cov pa roj carbon monoxide tso tawm carbon dioxide. Cov kua txhuas yog siphoned los ntawm lub xov tooj ntawm tes thiab cam khwb cia rau hauv ingots, billets los yog slabs rau kev ua ntxiv.
Zog thiab ib puag ncig kev xav
Electrolysis yog lub zog siv zog: tsim ib tonne ntawm thawj txhuas yuav tsum tau kwv yees li 13 mus rau 15 megawatt- teev hluav taws xob, uas yog vim li cas cov smelters nyob ze rau qis- cov nqi hluav taws xob, suav nrog cov nroj tsuag dej. Cov txheej txheem tseem emissions carbon dioxide los ntawm cov anodes, thiab cov av nkos liab los ntawm Bayer txheej txheem yuav tsum tau ua tib zoo tswj nyob rau hauv engineered cia chaw.
Cov kev cuam tshuam no piav qhia txog qhov muaj zog ib puag ncig rau kev rov ua dua tshiab: melting scrap aluminium siv li ntawm 5% ntawm lub zog ntawm thawj cov khoom lag luam thiab zam lub voj voog bauxite thiab cov av nkos liab tag nrho, uas yog vim li cas cov khoom siv rov ua dua tshiab tau muab ntau qhov kev xav tau thoob ntiaj teb.
Alternative thiab Emerging Routes
Lwm txoj kev rho tawm muaj nyob tab sis tsis tshua muaj. Acid leaching tuaj yeem rho tawm cov txhuas los ntawm qee cov ore thiab cov khoom siv khib nyiab, tab sis feem ntau kim dua thiab nyuaj dua li cov txheej txheem Bayer. Kev tshawb fawb txuas ntxiv ntawm inert anodes uas yuav tshem tawm cov pa roj carbon dioxide emissions ntawm electrolysis, thiab ntawm cov qauv siv tau zoo dua, tab sis Bayer thiab Hall -Heroult cov txheej txheem tseem yog cov pob txha ntawm cov khoom siv txhuas.
Cov lus nug nquag
Q: bauxite yog dab tsi thiab nws tuaj qhov twg?
Bauxite yog cov pob zeb liab liab uas muaj 40-60% txhuas oxide (alumina) ua gibbsite, boehmite lossis diaspore minerals, mined tsuas yog hauv Australia, Guinea, Tuam Tshoj, Brazil thiab Is Nrias teb; kwv yees li 4-6 tonnes ntawm bauxite yog xav tau los tsim 1 tonnes ntawm txhuas.
Q: Dab tsi tshwm sim hauv Hall-Heroult electrolysis cell?
Alumina yog yaj nyob rau hauv molten cryolite ntawm li 950-970℃thiab faib los ntawm ib tug hluav taws xob tam sim no rau molten txhuas ntawm cov pa roj carbon cathode thiab carbon dioxide ntawm carbon anode; cov txheej txheem khiav tsis tu ncua nrog alumina pub thiab anode hloov.
Q: Lub zog siv hluav taws xob ntau npaum li cas yog thawj aluminium siv?
Cov kauj ruam electrolysis feem ntau siv 13-15 kWh ib kilogram ntawm txhuas, thiab niaj hnub smelters nruab nrab ntawm 14,000-15,500 kWh ib tonne; qhov no yog vim li cas aluminium smelters yeej ib txwm nyob ib sab ntawm lub zog pheej yig xws li chaw nres tsheb hydroelectric.
Q: Cov av nkos liab yog dab tsi thiab yuav ua li cas rau nws?
Cov av nkos liab yog cov hlau- nplua nuj alkaline seem tshuav tom qab txheej txheem Bayer, txog 1-1.5 tonnes ib tonne ntawm alumina; nws tau muab khaws cia rau hauv cov pas dej tailings uas tau tswj xyuas kom zoo, thiab cov txheej txheem tshiab yuav rov qab tau cov hlau, cov av tsis tshua muaj los yog siv rau hauv cov cement thiab cov khoom siv hauv tsev kom txo cov av pov tseg.
Q: Yuav ua li cas aluminium ntau lawm ua kom huv?
Cov smelters niaj hnub siv inert los yog prebaked anodes nrog fume kev kho mob los txiav emissions, hydro thiab txuas ntxiv zog kom txo tau cov pa roj carbon hneev taw, thiab kev lag luam recycles txheej txheem seem sab hauv; Kev tsim cov txhuas los ntawm cov hlau siv dua tshiab tsuas yog siv li 5% ntawm lub zog ntawm cov khoom tsim thawj.
Q: Nws siv ntau npaum li cas bauxite los ua ib tonne ntawm txhuas?
Raws li txoj cai ntawm tus ntiv tes xoo, kwv yees li 4-5 tonnes ntawm bauxite tau ua kom zoo rau hauv kwv yees li 2 tonnes ntawm alumina, uas yog tom qab ntawd smelted rau hauv li 1 tonne ntawm thawj txhuas. Qhov sib piv pes tsawg yog nyob ntawm qib ntawm cov ore thiab kev ua haujlwm ntawm cov refinery thiab smelter.