1.What yog qhov tseem ceeb ntawm cov tshuaj lom neeg cov kev cai lij choj koom nrog hauv cov txheej txheem bayer rau rho tawm alumina (al₂o₃) los ntawm Bauxite ore?
Qhov tseem ceeb ntawm cov neeg siv khoom hauv Bayer bayer rau alumina extraction
①Bauxite zom
Bauxite (feem ntau xh₂o thiab immerities) reacts nrog concentrium hydroxide (Naoh) thiab siab los ua cov sodium aluminate (Naalo₂):
AL2O3o {3}}}} → 2Na} {} {} {} {} {13 {} h2 o
Qhov no yaj tau alumina thaum tawm hauv impurities li fe₂o₃ thiab tio₂ undissolved13.
②Silica Tshem Tawm
Silica (sitio₂) hauv Bauxite reacts nrog Naoh tsim soluble silium silicate silicate (na₂sio₃), uas tom qab precipitated raws li cov khoom lag luam cia (DSP):
Sio 2+2 naoh {3+ h2osio2}} → naoh → → naoh → → naoh {sio3 Se
DSP tsim tiv thaiv Silica kev sib kis hauv cov Alumina kawg 20134.
③Nas Hau ntawm Aluminium Hydroxide
Sodium Aluminate daws yog txias, diluted, thiab noob nrog al (Oh) ₃ crystals los nag dawb hydroxide:
Naalo 2+2 → h2o → al (Oh) 3 ↓ + h2 o} h2 o ↓ ↓) 3 ↓ + naoh
Qhov no thim rov qab txoj kev txawv txav, yielding Ntshiab Al (Oh) ₃13.
④Kho rau alumina
Aluminium hydroxide yog calcined ntawm ~ 1000 degree tshem dej thiab tsim anhydrous alumina (al₂o₃):
2al (Huag) 3 → al2o {{{{}} h2o ↑ 2O ↑ (Oh) 3 {{{{} h2 o ↑
Qhov no yields zaum kawg smelting-qib alumina rau electrolysis1.
⑤Rov qab siv ntawm naoh
Tus neeg siv Naoh daws los ntawm nag lossis daus rov qab thiab siv dua hauv cov qib plab zom mov, txo qis kev noj haus,
Naoh (refenerated) → rov ua rau kauj ruam 1NaOh (repenerated) → rov ua dua tshiab rau kauj ruam 1
Qhov no kaw-lub voj tsim kev txhim kho cov txheej txheem kev ruaj khov.
2.Yow chav tsev-héricecrip cov txheej txheem electrolysis ua kom zoo nkauj, thiab muaj dab tsi ua cryolite (Na₃alf₆) thiab carbon anodes ua si?
①Kev siv hluav taws xob Electrolyte
Alumina (Al₂o₃) yog yaj nyob rau hauv Molten Cleolite (Na-₃alf₆), txo qis lub taw tes melting los ntawm ~ 2072 degree (ntshiab al₂o₃) rau ~ 950 degree. Cryolite ua raws li cov kuab tshuaj thiab ion tus saib xyuas, ua kom electrolysis ua kom electrolysis thaum txo hluav taws xob siv hluav taws xob12.
②Electrochemical tshua muaj
Nyob rau Cathode (carbon-kab cell):
Aluminium ions (al³n) yog txo qis rau molten metallic aluminium:
Al 3++3 e} e- → al (l) al 3++3 e- → al (l)
Molten Aluminium sau ntawm cov xov tooj ntawm tes hauv qab rau cov sijhawm tapping34.
③Ntawm cov carbon anode:
Oxide ions (O²⁻) oxidize, reacting nrog carbon tsim cov pa roj:
O2- + C → CO2 (g) +4 e-} e-o2- + c {+4 e
Qhov no siv cov pa roj carbon anodes, xav tau hloov ntau zaus15.
Lub luag haujlwm ntawm cryolite
Txhim kho ionic conductivity ntawm molten da dej.
Stabilizes Alumina Qhov kawg, tswj kev muaj mob ion (alleter thiab o²⁻) rau kev txhawb nqa electrolysis24.
④Kev Siv Zog
Cov txheej txheem yuav tsum tau ~ 13-15 kw kg ntawm txhuas vim yog cov hluav taws xob siab rau kev tswj kom muaj qhov kub thiab tsav tsheb redox. Cov Hlwb Niaj Hnub Niaj Hnub No Siv cov qauv ntsug hluav taws xob los txhim kho kev ua tau zoo35.
⑤Cuam tshuam ib puag ncig
Carbon anode oxidation generates ntau dua, koom tes rau tsev cog khoom pa pa tawm. Kev siv dag zog kom tau INTAL INTAL Anodes (piv txwv li, ceramics) tsom rau tshem tawm kev tso tawm ncaj qha.
3.Qhov kev siv zog yuav cov kev teeb meem muaj sia nyob rau hauv txhuas smelting, thiab ua li cas niaj hnub smilters chaw ua haujlwm zoo?
①Kev Xav Tau Loj & Cov Khoom Siv Hluav Taws Xob
Cov cuab yeej siv hluav taws xob sib xyaw-hériceured electrolysis yuav tsum ~ 13-15 kg ntawm pob hluav taws xob, nrog ~ 67% ntawm cov tshuaj pleev pob zeb thoob ntiaj teb (~ 12-16.5 T CO₂EQ ib tuj ntawm txhuas) 56.
②Cov kev daws teeb meem tshiab: Kev hloov mus rau lub zog txuas ntxiv (piv txwv li, hnub ci, hydro) thiab cov phiaj xwm kev ua kom zoo dua txo cov pa roj carbon ntau dua. Smelters hauv cheeb tsam zoo li Iceland siv geothermal thiab hydrohower kom ua tiav ze-xoom-emission Production ntau lawm58.
③Kev tswj hwm kub ntxhov heev
Tsoos smelting poob lub zog tseem ceeb li nkim kub kub (piv txwv li, tso pa tawm thiab tso pa tawm), nrog tsuas yog ~ 50% hluav taws xob siv tau zoo.
④Cov kev daws teeb meem tshiab: Ua ntej pib ua kom sov lub tshuab ceev kev ntes pov tseg kom muaj cov khoom siv kub, txhim kho cov cua sov ua kom zoo dua qub, txhim kho tag nrho lub zog hluav taws xob los ntawm 10-15% 68.
Kev txwv electrolytic cell
Cov laus cell tsim (xws li, Söderberg Anodes) txom nyem los ntawm ntau dua kev tiv taus ntau dua thiab luv dua lifespans, nce lub zog pov tseg.
⑤Cov kev daws teeb meem tshiab: Rov mus nrogInert Anodes(Piv txwv li, ceramics) tshem tawm cov carbon anode noj thiab cov pa sib cais, thaumVertrode kev teeb tsaTxo kev puas tsuaj tawm tsam, txiav lub zog siv los ntawm ~ 20% 35.
Txheej Txheem Txheej Txheem Tawm & Broproducts
Cov pa roj carbon anode oxidation tso tawm qhob noom, thiab alumina impurities (piv txwv li, fluorine compounds) pab rau tsev cog khoom roj emissions56.
⑥Cov kev daws teeb meem tshiab: Cov pa roj carbon ntes thiab cia (CCS) cov tshuab thiab txhuam cov thev naus laus zis cuab ntxiab. Kaw lub voj fluoride rov qab siv cov kev phom sij ntawm cov khoom noj cuam tshuam35.
⑦Daim phiaj xwm ruaj khov & lub zog hloov tau
Smelters xav tau ruaj khov, lub zog siab, kev sib koom ua ke nrog kev sib koom ua ke nrog kev txuas ntxiv txuas ntxiv.
4. Vim li cas thiaj li tshem tawm ntawm cov impurities zoo li silica (SIDO₂) thiab hlau oxides (Fe₂o₃) tseem ceeb) tseem ceeb thaum ua kom zoo dua qub, thiab cov qauv dab tsi ua tiav qhov no?
①Ensuring alumina purity rau electrolysis
Silica reacts nrog sodium hydroxide (Naoh) thaum lub sij hawm zom zom mov Hlau oxides (Fe₂o₃) nyob tsis muaj insoluble tab sis nyuaj alumina zoo yog tias tsis tshem tawm lick.
②Tiv thaiv kev vam meej ntawm naoh noj
Uncontrolled silica xaus kev noj haus ntau dhau naoh, nce nqi ua haujlwm. Cov hau kev hydrometallurgical zoo li xaiv ua leaching nrog cov kua qaub lossis cov hauv paus txiav qhov no los ntawm phiaj thaum lub sij hawm khaws cia alumina tawm tswv yim23.
③Zam kev ua rau muaj kev phom sij los ntawm kev tsim
Silica tuaj yeem ua ntej li cov khoom lag luam seem (DSPs), sib sau nplai hauv cov tshuaj tiv thaiv thiab txo cov kev ua kom sov. Tswj kev zom su (piv txwv li, kub, Naoh concanced) suppress DSP tsim [.
④Txhim Kho Cov Txheej Txheem Ua Si
Hlau oxide impide pab rau "av nkos liab" pov tseg, uas ua rau muaj kev pheej hmoo ib puag ncig. Kev sib cais ua kom tau sib cais ua ke (piv txwv li, sib nqus sib cais rau fe₂o₃) txo cov av nkos liab thiab txhim kho qhov chaw ua haujlwm zoo.
⑤Txhim Kho Zog Txuag Txuag Zog
Impurities nce melting kub hauv smelting. Kev kho mob ua ntej ntawm Sintering lossis Hydrometallurgical Cov kev tshem tawm cov sido thiab Fe₂o₃ Upfront, kev txo lub zog xav tau nyob rau hauv cov txheej txheem electrolysis.
5.Txoj kev txhawj xeeb ib puag ncig tshwm sim los ntawm cov av nkos liab (bauxite seem) pov tseg, thiab rov ua dua tshiab ecological kev cuam tshuam ecological?
①Kev lom zem ua kom huv si & dej paug
Liab Mud lub siab alkalinity (pH 10-13) thiab cov hlau hnyav (piv txwv li cov hlau, vanadium, tshuaj lom dej hiav txwv thiab haus dej.
②Me quav: Ruaj paus seem ntawm carbonation (kev txhaj tshuaj) mus rau neutalize ph. Cov txheej txheem hlau rov ua kom tiav rau kev rov qab siv cov khoom siv phom sij rau kev rov ua haujlwm hauv alloys lossis catalysts12.
Av loj siv & kev phom sij cia
Ntau txhiab tus tons ntawm cov av liab tau khaws cia rau hauv lub pas dej tauv, uas cov kev pheej hmoo pheej hmoo tsis txaus ntseeg (piv txwv li 2010 ujka spill nyob rau hauv Hungary). Kev ntim khoom tseem noj cov av loj heev.
③Me quav: Siv av liab nyob hauv kev tsim kho-cement ntau lawm(Hloov 30% clinker) lossisrooj ceramics(Cov av nplaum hloov). Geopolymer Technologies hloov cov khoom seem rau hauv cov ntaub ntawv tsim tsev34.
Cov pa phem los ntawm hmoov av
Qhuav liab gud generates cov hmoov av, ua rau muaj kev ua pa thiab av degradation.
④Me quav: Siv phytostabilization-cog cov nroj tsuag hlau-tiv taus cov nroj tsuag (piv txwv, willows) kom immobilize hmoov av thiab cov hlau. Tsho tiv no nrog geotextiles lossis biomass25.
Cov Khoom Khib thiab Cov Kab Hlau
Cov av liab muaj cov hlau muaj txiaj ntsig (piv txwv li, muaj 20-50% hlau, cov av tsis tshua muaj) tab sis feem ntau pov tseg.
⑤Me quav: Rho tawmHlau oxidesNtawm smelting lossis sib nqus sib cais rau steelmaking. Hydrometallurgical cov hau kev rov qab tau rov qab scandium thiab titanium rau aerospace \/ Zog siv14.
Kev cuam tshuam av & Ecosystem Kev Cuam Tshuam
Tsis kho cov av nkos liab av av, muab cov av thaiv av.
Me quav: Nruab nrab cov seem nrog gypsum lossis acids rauKho Kom ZooHauv kev ua liaj ua teb (ntxiv hlau, phosphorus). Pilot txoj haujlwm hauv Is Nrias teb thiab Tuam Tshoj ua kom tau zoo dua cov qoob loo ntawm cov av cog qoob loo.
