CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT_NHM 13 i MC LC PHN I: TNG QUAN V BAUXITE ( B XT) ............................................. ii 1.1. Khi nim chung ......................................................................................... 1 1.1.1. Khi nim ............................................................................................. 1 1.1.2. Thnh phn cht lng v cc dng tn ti trong t nhin .................. 1 1.2. S phn b qung Bauxite Vit Nam. ..................................................... 2 1.3. Phn loi: .................................................................................................... 4 1.4. Cht lng qung Bxt v kh nng p dng cng ngh bayer Vit Nam. ........................................................................................................................... 7 1.5. ng dng .................................................................................................... 8 PHN 2. C S PHNG PHP BAYER (THY LUYN) QUNG BAUXITE SN XUT ALUMIN. ............................................................... 9 2.1.Gii thiu chung Quy trnh sn xut nhm ................................................. 9 2.2. Gii thiu s lc v phng php Bayer.................................................. 9 2.2.1. Gii thiu .............................................................................................. 9 2.2.2. Phn loi ............................................................................................. 11 2.2.3. Cng ngh ch bin qung b xt Vit Nam ................................... 11 2.3. C s l thuyt .......................................................................................... 12 2.4. C ch ....................................................................................................... 13 2.5. Thng s cng ngh .................................................................................. 14 2.6. Thit b ...................................................................................................... 15 2.7. Thuyt minh Phng php Bayer. ............................................................ 15 PHN 3. PHN KT LUN ............................................................................. 32 CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT_NHM 13 ii LI NI U Cng ngh ch bin khong sn ang dn tr thnh mt trong nhng ngnh kinh t mi nhn ca nc ta, trong cng ngh ch bin bauxit, l mt trong cc nghnh cng ngh ch lc trong tng lai.Nc ta c ngun bauxit di do c bit l vng ty bc v ty nguyn.Crtnhiucngtykhiathckhongsnkhcnhaunhngttcvmc chchunglch bintinh qung,tnggitr khong snvitnampng nhu cu ngay cng cao ca cng nghip v m bo s pht trin kinh t Nhim v ca tiu lun ny l cung cp cho moi ngi nhng kin thc mi nht v bauxit v cng ngh ch bin bauxite ca Vit Nam. Ni dung ca bi tiu lun gm 4 phn: Phn I: Tng quan chung. Phn II: c s phng php bayer Phn III:Kt lun. Mc d nhm rt c gng hon thin ti mt cch trn vn nht, nhng cng kh c th khng mc nhng sai st nht nh. V vy nhm chng Em mong Thy gp bi lm ca nhm chng em thm hon thin hn. Thnh Ph H Ch Minh, Ngy 10 Thng 02 Nm 2012 CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT1NHM 21 PHN I: TNG QUAN V BAUXITE ( B XT) 1.1. Khi nim chung 1.1.1. Khi nim B xt l nham thch c mu t trng n en, ch yu l hn hp cc hp cht v c v nhm hydoxit. Loi boxit thng gp c mu . Cc loi hnh qung boxit quan trng l bsmit, gipsit (hydragilit), diaspo, alumogel. 1.1.2. Thnh phn cht lng v cc dng tn ti trong t nhin a. Thnh phn ha hc Boxit c thnh phn tng i phc tp, nhng ch yu l hn hp cc khong nhmhydroxit,thngbnhimbnbistoxit(toramuchoqung) hocsilicoxit.Thnhphnhahccaboxitdaonggia50-63%Al2O3, 12-32 % H2O, 15-25 % Fe2O3, 2-10 % SiO2 v 2-5 % TiO2. Hm lng nhm oxit v silic oxit l nhng yu t quyt nh cht lng ca qung boxit. Nhmoxittrongqungboxitchyutrongthnhphncahydroxitnh diaxpo, bmit, gipsit hoc bayerit. Ngoi ra, nhm oxit trong boxit cn c th dng corundum v trong thnh phn khong ca nhm caolinit. GibbsitBoehmitDiaspore Thnh phnAl(OH)3o-AlO(OH)-AlO(OH) Hm lng alumina ti a (%)65,485,085,0 H tinh thn t Trc thoi Trc thoi CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT2NHM 21 Mt (g.cm-3)2,423,013,44 Nhit tch nc (C)150350450 b. Cc dng tn ti Qungbauxitecthtmthydidngthm(blanket),ti(pocket),lp (interlayered),vtcht(detrital).Thmbauxitelcclplintcvbng phng, thng gn mt t, c b dy thay i t 1 n 40 m (trung bnh t 4 n 6 m) v c th rng hng cy s. Ti bauxite l cc ti nm di mt t, cchiusuthayitdi1chon30m,nmclphoclinktvi nhau. Lp bauxite l thm hoc ti bauxite b ph lp v p xung, cho nn n bnnnhiuhnthmhoctibauxitedotrnglngcalptbntrn. Tchtbauxiterthimthyvnccutodostchtcabauxiteb xi mn t thm, ti, hay lp bauxite ni khc. 1.2. S phn b qung Bauxite Vit Nam. Kt qu thm d a cht pht hin trn lnh thVit nam c nh gi l mt quc gia c tr lng qung boxit phong ph c Min Bc v Min Nam Vit Nam. Tng tr lng qung boxit ca Vit Nam c tnh khong 8 t tn, trong c 7,6 t tn cc tnh Ty Nguyn. Vi tr lng nh vy, nc ta ng trong s cc nc c tr lng boxit ln trn th gii. CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT3NHM 21 Vit Nam c hai loi hnh qung boxit: a.Loi qung bsmit v diaspo, tp trung ch yu Min Bc Vit Nam, phn b cc tnh H Giang, Cao Bng, Lng Sn, Bc Giang). Tng tr lng d on khong trn 350 triu tn, hm lng nhm dao ng trong khong 39-65 %. Modul silic (Al2O3 /SiO2) bng 5-8.b. Loi qung gipsit, tp trung ch yu Ty Nguyn v Min Nam Vit Nam, vi tng tr lng c tnh khong 7,6 t tn. TrlngqungboxitcthmdvchngminhTyNguynv MinNamVitNamlkhong2772triutn.Trongcthcckhuvc nh sau: * Ti nguyn vng c Nng - Phc Long khong 1.570 triu tn * Ti nguyn boxit vng Lm ng tp trung hai t khong l Tn Rai v Bo Lc. - Tr lng vng khong Tn Rai khong 57 triu tn cp C1, 120 triu tn cp C2, hm lng nh sau: Al2O344,69 % SiO22,61 % Fe2O323,35 % TiO23,52 % 60% 12% 19% 5% 0% 1% 2% 1% S phn b qung Bxt ti Vit Nam k Nng Konplong - kanakBo Lc - Di Linh Bnh Phc Ven bin H GiangCao Bng Lng Sn CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT4NHM 21 MKN24,3 % - Tr lng vng t khong Bo Lc khong 378 triu tn. Nichung,qungboxitnguynkhaiLmngucchtlngkhng cao,hmlngAl2O3chkhong35-37%.Ngitaphituynraqung nguyn khai thu c tinh qung giu nhm hn. Sau khi tuyn, tinh qung boxit cc t khong Lm ng cng ch t hm lng 45 - 49% Al2O3. Hnh 1.2: Mt ct a cht Bauxite Cao Nguyn min trung. 1.3. Phn loi: Ba dng cu trc khc nhau ca bauxite c th phn loi thnh 2 nhm da vo hm lng nc khc nhau l: monohydrates v trihydrates. Trihydrates bao gm gibbsite v bhmite c tm thy chu M Latinh v vng Carib Loibauxitedotuicaxcnh.Bauxitediaspolloiginht,cn loi tr nht l hydragilit, cc loi bauxite cn li nm gia bauxite diaspo sch vhydragilitsch.Khi phong haalumosilicattrong iu kinthinnhin s to thnh tt c cc khong vt nhm oxt ngm nc keo nhm- cha lng nc khng xc nh Al2O3.xH2O. Smt ncca keo nhmtheo thi gian slmbinithnhphnkhongvt,vihydrahgilitx=3,diaspovbmit x=1. Keo nhmalumo gi bnhydragilitbmitdiaspocorundum. CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT5NHM 21 Theo Maliavkin, ty theo t s trng lng ca Al2O3 v SiO2, tt c nhm c chia lm 3 loi: -Sialit Al2O3: SiO2
1 -Alit Al2O3: SiO2 >1 -Boxit Al2O3: SiO2 >2 Nhn b ngoi bauxite c th khc nhau. Thng thng bauxite c mu , kh cng.ikhicnggpbauxitecmutrngvng,xanhthmvccmu khc. Mu chng t hm lng st oxt cao, khi hm lng st oxt thp th bauxite c mu xm hoc trng. Diaspore Hnh 1.3a: So snh cc loi BauxitCNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT6NHM 21 Hnh 1.3c: Mt mu t bazan cha qung b xt ti D n t hp B xt Nhm Lm ng. Hnh 1.3d: Mu qung nguyn khai ti k Nng, ngun nguyn liu phc v cho Nh my Alumin Nhn C. CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT7NHM 21 Hnh 1.3e: Mu qung tinh ti m b xt k Nng. Hnh 1.3f: Sulfat Nhm k thut, sn phm u tin sau qu trnh x l qung b xit tinh. 1.4. Cht lng qung Bxt v kh nng p dng cng ngh bayer Vit Nam. Cht lng qung b-xt c nh hng rt quyt nh n tnh kh thi v mt kinh t cng nh tnh cnh tranh ca cng ngh c la chn. Nhn chung, cng ngh Bayer c p dng cho loi b-xt c cht lng cao, c hm lng SiO2 thp. Ch sModunsilic (mSi) ca b-xt c ngha c bit quan trng khi la chn cng ngh v c nh hng quyt nh n hiu CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT8NHM 21 qu ca cng ngh. Ch s ny c xc nh bng t l gia thnh phn Al2O3 v SiO2 trong qung b-xt. Ch s ny cng cao cng tt (thnh phn Al2O3 cng cao, v SiO2 cng thp cng tt). Theo nh gi chung, cht lng b-xt ca VN thuc loi thp, ch khng phi l cao nh nhiu ngi lm tng. So vi b-xt ca cc nc trn th gii, b-xt ca Ty Nguyn thuc loi cht lng thp nht, i hi phi c thm cng on tuyn ra qung nguyn khai tng modun silic, v vy tnh cnh tranh khi s dng cng ngh Bayer cng l thp. Ch s mSi ca b-xt Tn Rai v Nhn C ch c 3,5-7,8 (trung bnh 4,93) trong khi ca Indonesia 14-18; Jamaica 15-25; c 11-20, n 20-25; Php 11-18; Nam T (c) 10-20; Hungary 10-13; Suriman 18-23; Hy Lp 10-19 v.v. Trong cng ngh Bayer ch s mSi s quyt nh (nh hng ti) t l thu hi ha hc ca alumina. Nh ta bit, theo l thuyt, khi p dng cng ngh Bayer cho b-xt ca Ty Nguyn c modun silic mSi=4,93, t l thu hi Al2O3 (trn c s ha hc) ti a (cha tnh n cc yu t khc) l (1-1:4,93) x 100% = 79,71%. Modunsilic cng thp, t l thu hi ny cng thp, v tnh hiu qu cng thp. Trong qu kh, chng ta c cc nghin cu c th la chn cng ngh. Kt qu cho thy, cn c quy trnh c th i vi b-xt ca tng m. M 1 thng 5 v m Tn Rai cn c hai quy trnh khc nhau, vi cc thng s cng ngh khc nhau (p sut v nhit ha tch, nng kim trung bnh, thi gian ha tch, tc ha tch, yu cu kh silic v.v.). 1.5. ng dng ng dng ch yu ca boxit l lm nguyn liu cho cng nghip luyn nhm. Ngnh cng nghip sn xut nhm kim loi tiu th 85% qung boxit trn ton th gii. Phn boxit cn li c s dng trong hai lnh vc l sn xut alumin chuyn dng (10%), bao gm alumin nung v alumin hot ha, v sn xut vt liu chu la (5%), v d gch chu la, ximng chu la v cc vt liu mi. CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT9NHM 21 PHN 2. C S PHNG PHP BAYER (THY LUYN) QUNG BAUXITE SN XUT ALUMIN. 2.1.Gii thiu chung Qu trnh sn xut nhm Hin nay trn th gii quy trnh sn xut nhm c thc hin theo 3 giai onchnhl:Khaithcbauxite,ch binaluminav luynnhm.Trong giai on ch bin alumina v luyn nhm c thc hin theo 2 quy trnh: quytrnhBayer-chbinbauxitethnhaluminavquytrnhHall-Heroult- in phn alumina thnh nhm. Hnh 2.1: Quy trnh sn xut nhm. 2.2. Gii thiu s lc v phng php Baer. 2.2.1. Gii thiu Cng ngh Bayer c Karl Bayer pht minh vo nm 1887. Khi lm vic Saint Petersburg, Nga ng pht trin t mt phng php ng dng alumina cho ngnh cng nghip dt (n c dng lm cht n mn trong vic nhum si bng), vo nm 1887 Bayer pht hin rng nhm hydroxit kt ta t dung dch kim dng tinh th v c th tch lc v ra d dng, trong CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT10 NHM 21 khi n kt ta bi s trung ha dung dch trong mi trng axt th dng st v kh ra sch. Cng ngh ny tr nn rt quan trng trong ngnh luyn kim cng vi nhng pht minh v in phn nhm vo nm 1886. Cng vi phng php x l bng xyanua c pht minh vo nm 1887, cng ngh Bayer khai sinh ra lnh vc luyn kim bng nc hin i. Ngy nay, cng ngh ny vn khng thay i v n to ra hu ht cc sn phm nhm trung gian trn th gii. Cng ngh Bayer l phng thc sn xut chnh tinh luyn qung th bauxit sn xut ra qung tinh alumina. Trong bauxit c n 30-54% l alumina, Al2O3, phn cn li l cc silica, nhiu dng xt st, v ixt titan.Alumina phi c tinh ch trc khi c th s dng in phn sn xut ra nhm kim loi. Trong tin trnh Bayer, bauxit b chuyn ha bi mt lung dung dch natri hydroxit (NaOH) nng ln ti 175C tr thnh hydroxit nhm, Al(OH)3 tan trong dung dch hydroxit theo phn ng sau: Al2O3 + 2 OH + 3 H2O 2 [Al(OH)4] Cc thnh phn ha hc khc trong bauxit khng ha tan theo phn ng trn c lc v loi b ra khi dung dch to thnh bn , qung ui hay ui qung ca loi qung bauxit. Chnh thnh phn bn ny gy nn vn nn mi trng v vn thi ging nh cc loi qung ui ca cc khong sn kim loi mu ni chung. Tip theo, dung dch hydroxit c lm lnh v hydroxit nhm dng ha tan phn lng to thnh mt dng cht rn, bng, c mu trng. Khi c nung nng ln ti 1050C (qu trnh canxit ha), hydroxit nhm phn r v nhit tr thnh alumina v gii phng hi nc: 2 Al(OH)3 Al2O3 + 3 H2O CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT11 NHM 21 2.2.2. Phn loi Hinnayvtrong tng lai,khong90%alumina trn th gii vn c sn xutbngcngnghBayer.chuyntbxtthnhalumina,ngita nghinqungvtrnvivivsodacttch,ribmhnhpnyvo bnh cha p lc cao, ri nung ln. xt nhm b phn gii bng soda ct tch, riktta,ra,vnungtchncra.Thnhphmlbtmutrngmn hn mui n m ta gi l alumina. TrongqutrnhsnxutaluminabngphngphpBayer,tytheothnh phn khong vt ca b xtm cng ngh Bayer cchia thnh 2 gii php khc nhau: a. Cng ngh Bayer chu M c p dng nu Al2O3 ca b xit dng gippsite (trihydrate Al2O3. 3H2O), c th c ho tch d dng. B xt ny thng c ha tch nhit ti a140-145oCtrongdungdchhatchcnngkimthp(120-140g/l Na2O). b. Cng ngh Bayer chu u c p dng nu Al2O3 ca b xt dng boehmite v diaspore (monohydrate Al2O3.H2O), phi ha tch nhit cao hn 200oC (240-250oC trong cc nh my hin i v c cht xc tc i vi qung diaspore) v trong dung dch ha tch c nng kim cao hn (180-250g/l Na2O). 2.2.3. Cng ngh ch bin qung b xt Vit Nam BxtTyNguynlloibxtgippsite,mlthindkhaithc.Bxt ny thuc loi gippsite-goethite, cht lng trung bnh, thng phi qua tuyn ramimbochtlng sdng cngnghBayerBcM(nhit , nng kim ho tch thp). Tuy nhin b xt ny c cha nhiu goethite nn kh nng lng km.. Choti nayc hainghincusn xutaluminatmTnRai,tnhLm ng, v m 1/5, tnh k Nng phc v cho vic lp Nghin cu kh thi pht trin 2 m ny. CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT12 NHM 21 a)Tinhqungbxtm1/5thucloibxttt(Al2O3~50,23%;SiO2~ 2,09%), thnh phn khong vt ch yu l gippsite d ho tch, do c th p dng cng ngh Bayer sn xut alumina t b xt gippsite ca Ty Nguyn, c th: -Bn qung c kh silic s b trc khi ho tch ci thin vic kh silic v kh nng lng tch bn vi hm lng cht rn 1.000-1.050 g/l. nng kimhot tnh l1603g/l,lngvithmvo2-2,2%(qung bxtkh), nhit 95-100oC, thi gian 5-6 pht. -Ho tch vi bn qung sau khi tin kh silic nhit 145oC, thi gian 60-75 pht, p sut 12-14 ata, bn ho tch ra c c = 1,36. b) Trong khi , mt nghin cu khc i vi b xt Tn Rai cho kt lun nh sau: - Bn qung qua tin kh silic trc khi ho tch ci thin vic kh silic v kh nng lng tch bn vi hm lng cht rn 900-1.100g/l, trong dung dch qua s dng, nhit 95-100oC , thi gian t bay hi c c 6-10 gi; hu kh silic nhit 100oC, thi gian ti u l 6 gi. -Hotchvibnqungsau khitinkhsilicnhit 105oC n107oC, trongdung dchcnngkimcttch210g/l(hoccaohn) viRPcn t1,10-1,12,thigian:2,5gi,psutkhquyn,bnhotchracc= 1,45 1,50. Tm li, cng ngh Bayer ch bin b xt gippsitic thuc loi cng ngh ph bin nhng cng c mt s cng on ca cng ngh ny cn c nhng chuyn gia c kinh nghim v thit k, vn hnh v ch bin th mi sn xut ra c alumina. Trong tt c mi trng hp lin quan n b xt gippsitic v alumina ct, iu cn ch trng u tin l phi da vo kt qu phn tch ca phng th nghim, m hnh ton hc, tip cn c nhng kinh nghim vn hnh nh my v c mt i ng k thut v cng nhn lnh ngh. 2.3. C s l thuyt Nhit ng hcn nn bCNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT13 NHM 21 Al(OH)3 + NaOH=Na[Al(OH)4]= NaAlO2 + 2H2O AlOOH+ NaOH +H2O =Na[Al(OH)4] = NaAlO2+2H2OAluminat natri: 2NaAlO2 = Na2O.Al2O3
Cc tp cht Fe2O3: khng tc dng vi NaOH Bn . SiO2 :SiO2 (ct thch anh) : khng tan Bn . Caolinit :Al2O3.2SiO2.2H2O +2NaOH = Na2O.Al2O3.2SiO2.3H2O Natri alumosilicat Na2O.Al2O3.2SiO2.3H2OBn TiO2 :TiO2+ NaOH = NaHTiO3 (hoc Na2O.3TiO2.2.5H2O) Natri metatitanat NaHTiO3 Bn 2.4. C ch -Khuch tn-Phn ng ha hc -Tc ha tch: K D DCJo12211+ +=o oCNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT14 NHM 21 -Min ng hc khuch tn : -Min ng hc ha hc : -Min trung gian : 2.. Thng s cng ngh Ho tch boxit bng NaOH (F.Habashi-t.51) Qung Nhit oCp sutpsiNaOH g/lThi gian hThc t Ghipxit 140 60(4.2 at)140 1 MBmit 180 120(8.4 at)350-600 2-4 Chu uiaspoNng Nng kim costic (Na2Ok) : Na2Ok= NaOH-d + Na2O Ch s costic : Dung dch tun hon : ok =3.5 4.0MNa2O = 62 g ; MAl2O3 = 102gChn : ok =3.6; Na2Ok = 300g/lit K1 1 12 1> +| |K1 1 12 1< +| |K1 1 12 1= +| |mol O Almol O Nakk], [], [3 22= o137g/lit62102x3.630062102xO NaO Akk 23 2= = =CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT15 NHM 21 Khi lng boxitAl2O3 Bauxit45100 137g/litm = 137 x 100/45 = 304 g/litNhit: T =140oC p sut : P=2-4at Ph gia ViCht tr lng : bt m2.6. Thit b Hnh 2.6. S thit b 2.7. Thuyt minh Phng php Baer. Cng ngh Bayer ch yu gm cc cng on sau: 1.Ha tch:Bxit c ho tch vi dung dch kim NaOH. Lng Al2O3 c tch ratrongdngNaAlO2hotanvctchrakhicnkhnghotan (gi l bn m ch yu l cc xt st, xt titan, xt silic). 2.Pha long 3.Khuy phn ha CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT16 NHM 21 4.C bay hi DungdchaluminateNaAlO2chnhitnnhitcnthitv cho mm Al(OH)3 kt ta. Sn phm Al(OH)3 cui cng c lc, ra v nung to thnh Al2O3 thnh phm. Hnh 2.3. Quy trinh y phng php bayer Bxtsaukhixaypthvva,ctrnvilngnhvi(nul bxt diaspo) v cho vo my nghin t cng vi dung dch st tun hon theo tnh ton. My nghin thng lm vic theo chu k kn vi my phn CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT17 NHM 21 cpkinphnrnghockiugungxon,mgnythaythhocb sung bng cc my xoy thy lc. huyn ph tp trung cc b cha, un nngbnghnn100oChochnvgiyvigi,khuytrnlin tcphnlnsilicoxtcthtngtcvikimaluminatthnh alumosilicat khng ha tan. Khi ha tch lin tc, huyn ph c bm qua thit b nung nng i vo dy tola, sau chy qua thit b tch hi, t thit b tch hi, huyn ph chy vo cc b khuy c pha long huyn ph otola. Dung dch chy ra t thit b lng, c qua lc tch hon ton cc cn ,vclmnguin70oC,sauckhuyphnha(lmvic gin on hoc lin tc). Ngi ta cho hydrat mi vo qu trnh khuy phn hatytheolngAl2O3ctrongdungdch,tsgiamiviAl2O3 trong dung dch khong 1,3 n 1,4. Sau khi khuy c a qua lng huyn ph v tch dung dch ci. Nhm oxt sau khi phn loi theo c ht c chia lm hai phn: -Phn 1 c c ht ln: c ra kim v cho i nung. -Phn 2 th cho hydrat mi vo. Dungdchcivncrahydrataicbayhitrongthitbchn khng,nngNa2Otng,hatancanatricacbonatgimkhihm lng NaOH trong duing dch tng. Trongqutrnhbayhidungdchci,phnnatricabonatgim.iuny chophptrnhNatricabonattchlytrongdungdchvginng Na2CO3 nm trong gii hn nht nh. gimtiutnNaOH,Na2CO3saukhitchkhidungdchtunhon c ha tan trong nc v kim ha bng sa vi. Dung dch kim long nhncemcbayhicngdungdchci,dungdchcbayhi c b sung kim mi, sau a vo my nghin cng Boxt. Hydrat thnh phm c kh nc v nung 1200oC S TC DNG CA CC HP CHT TRONG BXT VI KIM. 1.Silic oxt: CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT18 NHM 21 TrongqungBxt,siliccthnhphnkhlnvnhhngrtlnn qu trnh, v tc dng vi kim: SiO2 + 2NaOH = NaSiO3 + H2O Tc v mc ha tan SiO2 t do ph thuc vo nhiu yu t nh kch thc ht, nng v nhit dung dch. Silic oxt v nh hnh v c bit l gel silic oxt ngm nc, ha tan trong dung dch kim nhanh hn so vi SiO2 kt tinh thch anh, tridimitSi(OH)4, SiO2.2 H2O, Si2(OH)2 hoc SiO2.H2O ha tan nhanh trong Na2CO3 to thnh Natrisilicat. Na2CO3 + SiO2.H2O = Na2SiO3 + H2O + CO2 Na2SiO3 + NaAl(OH)4 + aqua = Na2O.Al2O3..n SiO2.mH2O + NaOH Natri alumisilicat khng ha tan trong NaOH, dng rn, ln vo cn . 2.Titan oxt TiO2 nh hng nhiu n qu trnh thu Al2O3. Titan c mt trong boxt thng dng TiO2. TiO2 + NaOH = NaHTiO2 NaHTiO2 + H2O = NaHTiO3 + NaOH Khi thm vi vo, vi s tc dng vi Titan oxt to thnh Canxititanat, gim tn tht kim. TiO2 + 2CaO +n H2O = TiO2.2CaO. nH2O 3.St oxt. Trong thc t th St oxitkhng ha tan khi tch boxt bng kim, st oxt nhiu s nh hng n qu trnh tch v ra cn . Mt vi khong vt st lm tng tc ha tch bxt. 4.Cc cht hu c. Cha lng nh trong bxt nhng sau vi ln tun hon trong dung dch s tch ly lng ln cc cht ny. Khi c mt vi, mt s cht hu c ha tan trong dung dch kim c tc dng lm tng thc thu Al2O3, cn cc cht khc ( ha tan trong benzene, nhng khng ha tan trong kim) th li lm gim thc thu Al2O3 t bxt CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT19 NHM 21 diaspo. Khi ha tch bxt c cha nhiu cht hu c tan trong benzene ny th dung dch aluminat c mu thm en v nhm oxt thu c trong qu trnh ha tch rt thp, kh cht hu c ha tan trong beenzen ny ngi ta thng thiu kt bxt hoc cho thm vi liu lng cao ( n 10% v hn na). Cc cht hu c khng ch nh hng n qu trnh ha tch bxt, nu hm lng cc cht hu c cao th nht ca dung dch aluminat tng ln r rt, gy kh khn cho vic phn cp khi nghin Bxt, lm chm qu trnh lng v ra bn , cng nh qu trnh lc trn thit b lc. Qu trnh khuy phn ha dung dch aluminat cng b chm li v nhm hydroxit nhn c c ht b hn, cht hu c nh hng rt xu n hot ng ca thit b c bay hi v n qu trnh kt tinh natri cacbonat t cc dung dch tun hon. Cc cht hu c ch c nh hng n qu trnh khuy phn ha khi chng c tch t trong dung dch n gii hn c hi, sau khi t n gii hn ny, tc khuy phn ha chm li v khi tch t trn 3% cc cht hu c (theo oxi) th thc t dung dch ngng phn ha. Ngun tp hu c ny ch yu l bxt, ngoi ra chng cn i vo dung dch do kt qu tng tc gia dung dch vi vi lc v cc cht lm ng t cht hu c thng cho vo huyn ph sau khi pha long tng tc lng ca cn . Cng vi mi nhm hydroxit v cng vi dung dch kim sau khi costc ha natricabonat cc cht hu c quay li qu trnh. ngn nga cc cht hu c tch ly trong dung dch, cn kh chng song song vi vic b sung. Cn ch rng mt phn cc cht hu c c kh i trong cc cng on: theo cn , nhm hydroxit thnh phm, natricacbonat monohydrate kt ta khi bay hi dung dch ci v cn vi sau khi costic ha natri cacbonat mu hung. Cng nhiu cht hu c tch t th chng ra khi vng quay cng nhiu bng nhng con ng ny. Thiu v trong mt s trng hp em ra bxt c th lm gim nng ti hn ca cc cht hu c trong dung dch aluminat. CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT20 NHM 21 Trong tt c cc cht hp ph cc cht hu c t dung dch aluminat cc cng on khc nhau ni trn th natricacbonat monohydrate c kh nng hp ph ln nht do hp ph nn s pht trin ca cc tinh th kt thc nhanh, cht kt ta gm nhng ht rt b, do c b mt ring ln v nng ca cc cht cao nht. natricacbonat monohydrate mang mu cc cht hu c, do cc x nghip cn gi l natricacbonat mu hung. Nhm hydroxit nhn c bng khuy phn ha cng mang mu ca cc cht hu c, mu hng nht, lng cc cht hu c hp ph trn cn ph thuc vo sn lng, thnh phn khong vt v c ht ca cun , tc l vo b mt hot tnh ca cn, cng nh cc cht hu c trong dung dch aluminat. 5.Cc cht cha cabonat. Trong bxt ch yu l cc ht cacbonat n gin, canxi cacbonat CaCO3, megezit MgCO3 v siderite FeCO3, khi ha tch bxt diaspo bng dung dch m c Na2Oth i b phn cacbon dioxit nm trong cc phn ca cacbonat, chuyn vo dung dch to thnh Na2CO3. CaCO3 + NaOH = Ca(OH)2 + Na2CO3 MgCO3 + NaOH = Mg(OH)2 + Na2CO3 Hoc di dng ion: MeCO3 + OH- = Me(OH)3 + CO32- Chiu ca cc phn ng thun nghch ny s ph thuc vo s tng quan n ha tan ca cc cacbonat v cc hydroxit tng ng. Nu dung dch tun hon c nng Na2O cao th ha tan ca cc hydroxit gim t ngt v phn ng s i theo chiu ngc li. Phn ng siderite vi NaOH phc tp hn, trong nhng iu kin ny st hai khng bn vng b oxi ha thnh macnetit, v sn phm tng tc c t tnh v phn ng km theo vic tit ra hydro. Dung dch aliminat phn hy siderir v magezit hon ton hn, v vi tc b hn so vi canxi. Fe(Mg)CO3 + 2 NaAlO2 + 4 H2O = Fe(Mg)(OH)2 + Na2CO3 + Al(OH)3 CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT21 NHM 21 Khi ha tch cc cacbonat ni trn th otocla bng dung dch aluminat, th tng tc xy ra khng phi theo s dn m tng tc vi kim t do, a n vic gim bn vng ca dung dch aluminat v lm cho n phn ha. Mc d mt vi cacbonat: canxi. Siderite lm tng tc ha tch bxt diaspo, nhng chng l nhng tp cht c hi v chng lm trung ha mt phn kim costic. Hm lng natri cacbonat cng tng th nng sut ca cc thit b c c bay hi cng gim, bi v ng nung cng nhanh b ng cn, cng nhiu natri cacbonic kt ta th khi c c lm bay hi v lng natricacbonat cn phi costic ha kim quay li cng ln. 6.Cc mui sunfua. Trong bxt, lu hunh ch yu dng pirit FeS2, v dng keo ca hp cht ny. Khi ha tch trong dung dch otocla th vic chuyn lu hunh vo dung dch aluminat i vi cc loi bxt pirit ha ph thuc vo dng khong vt v cu trc ca n. Pirit c cu trc r rt khng tng tc vi dung dch kim aluminat. Phn ln lu hunh trong dung dch tn ti di dng Na2S. Trong qu trnh ha tch, cng nh trong cc cng on khc mt phn Na2S b oxi ha bin thnh natrisunfat. Hm lng lu hunh sunfat gim khi tng hm lng silic oxit trong dung dch.Lu hunh nn c coi l cht tp v n tiu tn lng kim v lm bn dung dch aluminat do st sufua to thnh v km vi cc dung dch keo ca n. Khi s dng sunfua dng keo trong dung dch rt kh v vy bxt cha nhiu lu hunh dng keo phn tn khng dng phng php Bayer. Lm sch bxt khi cc sunfua bng cch tuyn ni v thiu, cc sunfua d ni theo bt. khi c thiu trong l l si, lu hunh chy tt v nhanh hn. Khi thiu bxt nhiu sunfua, c bit l diaspo bxt trong l lp si l bin php c bn nht chun b bxt cho ha tch otocla. CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT22 NHM 21 Cc giai on chnh trong qu trnh sn xut alumin 1.Ha tch2.Pha long3.Khuy phn ha4.C bay hiA. HA TCHCc c trng ch yu ca qu trnh ha tch bxit trong tocla l thc thu Al2O3, nng sut thit b v sut tiu tn hi v kim Cc iu kin ti u c xc nh lp bng thc nghim , quan trng nht l : 1. nghin mn ca bxit 2.S khuy trn huyn ph trong otocla 3.Nng kim hot tnh trong dd tun hon4.Nhit v thi gian ha tch5.S c mt ca vi v cc cht khc 6.Tnh lin tc hoc chu k ca qu trnh ha tch Ho tch bxit hydragilit d phn hu c th tin hnh trong cc b thng thng , khuy huyn ph bng khng kh hoc bng c gii. tng tc qu trnh v thc thu Al2O3 , dng dd kim m n 250g/l Na2O v ho tch nhit gn vi im si ca dd khong 150oC Nung nng hn na s gip tng thc thu Al2O3 , c bit vi dd long hn v t s costic thp. v vy ni chung cc x nghip u tin hnh ha tch bxit hydragilit trong ctola. Bxit bmit v diaspo lun lun ha tch trong tocla p sut khong 25 at v cao hn. tocla lun lun c ch to bng thp : chng bn v chng c n mn ca cc dd aluminat. vi nhit v p sut cao hn nhit v p sut thng dng x nghip (60 at v cao hn) th thp ccbon b n mn: trong nhng trng hp ny tocla phi c ch to bng thp hp kim t tin hn. CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT23 NHM 21 Nung nng huyn ph trong otocla c th qua b mt truyn nhit, hoc bng hi a trc tip vo huyn ph tcla. b mt truyn nhit thng dng l o hi hoc rut xon. phng php trao i nhit ny c nhng nhc im sau y : 1.p sut trong o hi phicao hn trong tcla , lm cho cu to tcla phc tp v t2.Thi gian nu ko di huyn c nung nng chm bi v sut din tch nung nng b v qu trnh truyn nhit b xu i do to thnh cn cu trong tocla 3. khuy trn huyn ph nung nng qua tng , thng dng cch khuy c gii , m vic chn kn trc cnh khuy ny phc tp v i hi phi thay i lun. nung nng nhng lng huyn ph ln cc xng alumin hin i, i hi phi c din tch trao i nhit ln, ph hp vi cc thit b nung nng kiu ng. Trong iu kin sn xut, ngi ta thng dng thit b trao i nhit c u bi v trong cc thit b ny ch c mt pha u ng l hn cng vo thn thit b , cn pha kia th chuyn ng t do theo chiu trc . Cu to ny gip cho cc ng khng b un cong v bin dng do dn di, ngay c khi c s khc nhau ln v nhit . u im ca thit b trao i nhit ny l d tho v d lm sch .Huyn ph chuyn ng theo ng, cn hi nung nng th chuyn ng trong khng gian gia cc ng. trnh tng p sut trong thit b nung nng v tocla qu mc quy nh, bm pittongc trang b p k tip xc, mc lin vi b khi ng ca ng c v cng c trang b van an ton. nh k thi kh ra khi tocla trn mi thit b c ng ng x kh , ni phn trn ca tocla vi ng tho m ng ny th ni vi ng x. Mi ng thi khi u c van kha, van ny m khng lu trc khi x ton dy tocla. T tocla cui cng ca dy huyn ph i qua thit b t bc hi v y c lm ngui n gn im si tng ng vi p sut kh quyn . Nhim CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT24 NHM 21 vch yu ca thit b t bc hi l nhanh chng gim nhit ca huyn ph qu nung trong tocla xung n mc cc cng an tip theo c th tin hnh p sut thng. Mt nhim v khc l nhanh chng tch hi ca qu trnh t bc hi, v s dng hi ny s lm gim rt nhiu lng tiu hao hi nc. Nghin Mn Ca Bxit Tc ha tch t l thun vi b mt tip xc ca bxit vi dd,Nghin mn bxit s lm tng din tch tip xc gia bxit vi dd, lm tng tc ha tch. iu khng km phn quan trng l khi nghin qung s ph v cc kt hch gia cc ht ca cc khong vt khc nhau, bc trn cc khong sn ha tan, tc l lm tng b mt tip xc gia chng vi dd tun hon.Cng iu kin nghin nh nhau, mc bc trn ( hay l t s trng lng cc ht t do ca khong vt c ch trn hm lng tng ca cc khong sn ny trong qung) cng cao th tin hnh ha tch cng tt. khi nghin cc kt hch b ph v ch yu nhng ch tip gip gia cc khong sn khc nhau, biv y bn km hn trong bn thn cc ht ca tng khong sn ring bit. t n bc trn hon ton ca khong sn , cn phi nghin n mc tt c cc ht qung sau khi nghin u b hn cc ht ban u ca khong sn ha tan.Trong bxit cc ht iaspo v bmit thng rt b, do mun bc trn chng hon ton i hi phi nghin rt mn. tuy nhin khng nht thit phi nghin bxit bc trn hon ton cc ht ni trn , bi v v trng lng cng nh v th tch, chng chim tuyt i b phn trong bxit, m i vi khong sn nhiu nht trong qung th n c th c bc trn ngay c khi kch thc cc ht sau khi nghin ln hn kch thc cc ht khong sn ban u. nghin mn c nh hng khc nhau n qu trnh ha tch , ty thuc vo cu trc , thnh phn ha hc v thnh phn khong vt ca bxit. Cc loi bxit khc nhau , nghinvi kch thc khc nhau.CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT25 NHM 21 ha tch bxit c cu trc cht ch , i hi phi nghin mn hn so vi bxit xp , trong c nhiu khe, rnh m dung mi c th xuyn qua di tc dng trc tip ca cc lc mao dn hoc do kt qu ca khuch tn . Nghin cng mn, cng lm gim chiu di ca cc khe rnh v ng mau dn , do cng lm dung mi d thm nhp vo cc ht qung v cng thc y qu trnh ha tch . Bxit cng cht cng t khe rnh , cng kh thm t v khuch tn dung mi vo ht qung, do phn nhm hydroxit c ha tch qua cc khe h cng t. Dung dch ch c th thm nhp vo cc l xp khi khng kh y c y i, m iu ny ph thuc vo thm t dd, hay l tnh ho nc ca b mt bxit. Mt s cht hu c hot tnh b mt to ra nhng mng ho nc gip cho dd d thm t v thm nhp su vo trong qung. nghin ti u ca cc ht bxit khng ging nhau. Bxit c st , nht l trong c khong sn ch yu b cch ly hon ton bi cc cht tp, i hi phi nghin mn hn so vi bxit ti xp. mt s bxit, cc ht khong sn cha alumin b bao bc bi mt lp mng mng cht tp , khng tc dng vi dd tun hon. Trong trng hp ny ha tch bxit ch tin hnh do khuch tn dung mi qua nhng lp mng ny, hoc qua l xp v khe rnh trong chng. i vi cc loi bxit ny th nghin mn l c bit cn thit, nhm ph v cc lp mng c to c to thnh bng cc cht hu c, khng tc dng vi dd aluminat, hoc bng gel silic, bao bc chung quanh cc ht iaspo.Bxit iaspo nghin mn em lm sch SiO2 bng cch khuy trn s b 80oC vi dd aluminat m c kh silic. Vic lm sch silic oxit ra khi bxit cng nhiu cng tt. Ht nghin mn s thu c alumin cao ch ha tch nht nh, tng nghin mn cn lm gim t ngt nng sut ca my nghin, cn lm chm qu trnh lng cn , do lm gim nng sut ca cc thit b lng v ra S Khuy Trn Huyn Ph Trong Otocla CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT26 NHM 21 Cng nh phn ln cc qu trnh d th, qu trnh ha tan ca khong sn cha alumin ca bxit bao gm cc giai on sau: -Thm t b mtca khong sn bng dd kim-Qu trnh tng tc thc thu gia natri hydroxit vi khong sn-Bo ha alumin v ngho natri hydroxit hot tnh trong lp b mt ca dd -Khuch tn alumin ha tan t lp bin v di chuyn kim n lp ny Thng khuch tn l giai on chm nht trong s cc giai on ni trn , quyt nh ton b tc ca qu trnh. Khuy trn huyn ph lm gim chiu dy ca lp khuch tn chung quanh ca ht boxit v ng u ha nng alumin v Na2O hot tnh, tng tc khuch tn.Nng Kim Hot Tnh Trong Dd Tun HonTng hm lng Na2O hot tnh chng nhng lm tng tc ha tch, m cn lm gim tiu tn hi nung nu bxit v gim tiu tn lao ng ; th tch ca thit b ha tch cng yu cu b hn Hm lng kim qu cao s lm otocla bng thp b n mn v nc ra cn phi nhiu hn, tng ph ti cho qu trnh bc hi v lm iu kin lm vic y xu i. Nhit v thi gian ha tchTng nhit lm tng tc ha tan, t cng kt qu nh nhau, c th gim thi gian ha tch.Nhit cng cao, p sut trong tocla cng cng cao, i hi tocla phi bn hi, chu n mn cao ca kim trong iu kin ny . khi hp th lin tc , cung cp huyn ph di nh sut cao c bit kh khn.Nhit v thi gian nung nng cng nh hng n n mt mt kim vo bn S c mt ca vi v cc cht khc Cho vi khi ha tch bxit iaspo v iaspo bmit lm cho nhm hydroxit ha tan nhanh v tt hn.CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT27 NHM 21 Khi nung nu vi kim , cc tp CaCO3 , FeCO3 trong bxit phn hy , to thnh cc hydroxit tng ng nn cho vi vo t hn, lng vi cho vo ti u thng 3-4%so vi lng boxit, c xc nh vo thc nghim v n ph thuc ng thi vo nhiu nguyn nhn : dng v thnh phn bxit, cc cht tp c trong bxit, cc iu kin ha tch .. Khi cho vi vo trong qu trnh ha tch bxit : vi r tin , khng lm bn dd aluminat v khng lm gim lng kim v mt mt Na2O trong cn .Nhng khi cho lng vi vo nhiu s to thnh canxi aluminat ngm nc , trnh mt mt lng nhm oxit ny ngi ta c th cho vo natricacbonat khi ra cn . Canxi to cc hp cht kt ta vi cc hp cht ph c trong bxit nh titan ,.. v c tch ra khi dd .Vi cn hp ph cc mu do cc tp cht to ra trong dd. Tnh lin tc hoc chu k ca qu trnh ha tch Tt c cc cng on trong sn xut alumin theo pp bayer thng tin hnh lin tc.u im ca khu ha tch lin tc so vi gin on l: a.Khng c thi gian cht ca otocla khi nhp liu v tho liu b.Tn dng c ht th tch ca otocla, vi huyn ph c in y.c.Nng sut tng cao d.Tit kim c hi nc , do huyn ph c nung nng trc khi vo otocla bng hi ca qu trnh t bc hi ca huyn ph otocla.e.Vn u t t, gim s tocla s dng v th tch nh xng f.Gi thnh ca qu trnh t hn nhiu. Ha tch boxit hydragilit d phn hy c th tin hnh trong cc b thng thng , khuy huyn ph bng khng kh hoc bng c gii . tng CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT28 NHM 21 tc qu trnh v t Al2O3 , dng dd kim m n 250g/l Na2O v ha tch nhit gn vi nhit im si ca dd khong 1050C.B.KHUY PHN HA Dung dch aluminat sau khi ha tch qua qu trnh lm long dung dch, sau c a qua qu trnh phn ha, nhit ci cn bng cng thp th cng nhiu nhm hydroxit kt ta, cn chn cc iu kin phn ha thch hp qu trnh tin hnh nhanh nht v hon ton nht , nhng ht ca nhm hydroxitkt ta khng qu ln,m cng khng qu nh. Nu kt ta cc ht nh mn hoc cc ht nhm hydroxit v nh hnh, cc cng on sau s gp kh khn , tng mt mt nhm oxit v natri oxit do bay bi nhm hydroxit v kh ra cho sn phm ht kim .Thi gian khuy phn ha dd aluminat chim hn na thi gian ca ton b qu trnh sn xut alumin, kt ta khong 50-52% nhm oxit t dd, cn khuy lin tc dd aluminat t 60-100h v thm mi nhm hydroxit mi kt ta tng tc phn ha.1. nh hng nhng iu kin khc nhaun khuy phn ha dung dch aluminat Kt qu khuy phn ha ph thuc vo cc yu t sau: Nhit dd aluminat: tng nhit ca dd s lm gim tc phn ha v vi thi gian khuy phn ha chn th thc thu Al2O3 s gim xung mt cch tng ng lm ngui th xy ra hin tng ngc li.nung nng lm tng ht ca hydrat tit ra, bi v tng nhit s lm gim tc to thnh cc mm v tng tc pht trin ca chng Nng dd aluminat:khi chn nng ca dd aluminat tin hnh khuy phn ha cn xut pht nhng suy tnh sau: a.t s costic ca dd ci phi bng 3,4 v cao hn, t s ny thc thu Al2O3t 50% vcao hn. b.Hydrat phi gm ch yu cc ht kch thc50-60m CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT29 NHM 21 c.lng Al2O3 ly c t 1m3dd trong 1 ngy m khng c t hn 15-20kg. Thay i nng trong nhng gii hn thng thng khng gy nh hng ln n ht trung bnh ca hydrat khi khuy phn ha. T s kim trong dd trc v sau khuy phn ha: gim t s costic sau khi lclm tng tc phn ha dd aluminat, tng thc thu Al2O3 , nng sut thit b phn ha v cht lng dd ci; cc dd ny ra khi thit b phn ha vi t s cao hn. gim t s ny trong cc dd c nh hng tt n khuy phn ha ch yu trong cc gi u.S lng v cht lng mi :mi hot tnh l hydrat ht mi kt ta dng lm mi s c hat tnh cao hn hydrat thng thng trong huyn ph mi s c hot tnh cao hn hydrat thng thng trong huyn ph mi x nghip. l do nhm hydroxit tun han ln ln theo thi gian v hp ph cc cht tp, iu ny lm gim nng cc im hot tnh trn b mt chung ca cc ht hydrat tnh trn n v trng lng . do nu mi dd u khuy phn ha vi mi mi kt ta th nng sut ca cng an phi tng ln. Thi gian v tc khuy: tc khuy trn t nh hng n phn ha dd; cng ha khuy trn c lm tng phn no tc phn ha.Cc tp cht: cc cht hu c c cc tc hi nu trn. Cc x nghip thng kh cc cht hu c t dd tun hon theo natri cacbonat. Khi nung nng natri cacbonat ny n 400oC th cc cht hu c ny chy i. V lng natri cacbonat mu hung khng nhiu , phng php kh ny khng cn tn km nhiu.Phng php khuy: trong sn xutdd aluminat c khuy phn ha gin on cng nh lin tc . khuy lin tc c nhc im ln lm chm qu trnh phn ha dd aluminat , do dd ban u nhanh chng b pha long khi cho dd vo thit b phn ha u tin cha dd ngho Al2O3v vi t s costic cao.nhng hin nay ngui ta khc phc c nhc im y v thu c hiu qu cao. CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT30 NHM 21 Cc nh my sn xut thng ch khuy phn ha sao cho thu c nhm hydroxit c ht t 60m tr ln ,mc d khuy phn ha c ht hydrat b tin hnh nhanh hn. Nhngvi cc ht hydroxit ht mn,nht l v nh hnh s 1.gim t ngt tc lng cc ht , gim nng sut ca cc thit b lng v ra 2.tng ph ti cng on c bay hi v tng lng tiu tn hi, v ra ht kim trong loi hydrat ny cn nhiu nc hn3.lm chm qu trnh lc, v ht b i qua vi lc cng vi nc lc, cn vi ht ln hn th lm tc vi lc4.mt mt cc hydroxit nhm dng biThit b phn ly dng hnh tr tng t nh tocla nhng kch thc nh hn, bn qung si rt mnh, nhit gim do nc bc hi thu nhit. thu hi cc git do nc bc hi mang i, trong thit b phn ly c b phn ngng ng dung dch. em bn pha long mc ch qu trnh l lm lng tt hn. kh SiO2 c han ton , sau lng gn. C. KIM HA NATRI CACBONAT TUN HONSau mi chu kca qu trnh, gn 2%kim b trung ha thnh cacbonat v khi c chi c tch ra di dng natri cacbonat mu nung, chuyn natri cacbonat v dng kim ngi ta dng un si vi sa viNa2C3 + Ca(OH)2 = 2 NaOH +CaCO3 kim ha 85% dd soda, cn lng CaO khng t hn 130% so vi lng tnh theo natri cacbonat, trong 45% dng to hydroaluminat , cn 85% cho qu trnh kim ha. Thnh phn soda c mu hung nh hng qu trnh , n cng t dd tun hon th hm lng Na2O v nhm oxit trong dd ban u cng thp. iu ny lm tng kim v tng nng sut . Nhit cn c CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT31 NHM 21 gi cao trong cc thit b kim ha, thit b lng, nhit cao t to thnh hydroaluminat, gim tn tht lng nhm oxit v gim lng tiu tn CaO. D. NUNG NHM HYDROXIT Nung l nguyn cng cui cng trong tt c cc phng php sn xut alumin . sch , ht v thnh phn pha l nhng yu t quyt nh cht lng ca alumin dng trong in phn. sch v nh hng ca n n qu trnh in phn rt ln, gy cn tr qu trnh in phn, gim hiu sut... ht c nh hng khc nhau n cc ch tiu in phn, ht b nhiu s lm tng mt mt do bay bi, cn cc ht ln th ha tan chm trong cht in phn v ng tng trn y b in phn. Khi nung khng phi ton b alumin chuyn thnh -Al2O3. trong alumin k thut ngoi -Al2O3, lun lun c cha -Al2O3 , c khi cn c mt t bmit, chng ha tan trong cht in phn vi tc khc nhau, ht m khc nhau v khc nhau v kch thc ca cc tinh th. Tt c iu ny c th nh hng ln n tin trnh in phn.Hm lng cc cht tp trong alumin hu nh han ton ph thuc vo sch ca nhm hydroxit ban u. Thng ch nhn thy vi s sai lch v hm lng Na2O, SiO2, v Fe2O3. Na2O cn li t hn do bay hi, cn SiO2 v Fe2O3 th nhiu hn do s mi mn ca tng l, c bit cc vng nhit cao bi v do giao ng nhit , gch chu la b nt v v vn. V vy , i vi l nung vn rt quan trng l chn gch chu la cng, bn , chu nhit v chu c nhng thay i nhit . vng nhit cao, l c lt bng samt c hm lng alumin cao. ht ca alumin ch yu do kch thc cc ht hydrat quyt nh, do ht ny ch xc nh khi cung cp alumin cho cc x nghip mi, cn i vi cc x nghip in phn th ht ca alumin c nh gi theo ht ca hydrat ban u. CNG NGH CH BIN BAUXITE GVHD: TS. H VN HNG HHO6BLT32 NHM 21 PHN 3. PHN KT LUN Bauxite,mttrongnhiukhongsncthkhaithcVitNam,lti nguyn thin nhin ca quc gia, tng t nh nng sn, lm sn, thy sn, v nc. Ti nguyn thin nhin cn phi c khai thc nu vic khai thc mang li phc li ti a cho ngi dn, c nh hng ti thiu n i sng cadncvmitrngtrongvngkhaithc,vgpphntchccvo cng cuc pht trin chung ca t nc.
