Cng ngh cracking u tin sn xut propylen Nhng nm gn y nhu cu v propylen - sn phm ch yu tng hp nha polypropylen (PP) khng

g ngng tng. Cc d bo ca Nexan, Inc. cho thy tc tng trng nhu cu PP t 5%/nm v xu hng ny cn tng hn na trong thi gian ti. Cc cng ngh mi nhm u tin to ra sn phm propylen trong qu trnh ch bin du m gm c cc phng php sau: + Qu trnh cracking naphta bng hi nc c xc tc, + Qu trnh cracking du th c xc tc - qu trnh FCC (fluid cracking catalyst), + Dehydro ha kh propan, + Tng hp propylen bng qu trnh methathesis + Chuyn ha metanol thnh propylen. Trong s cc phng php sn xut propylen k trn, hai phng php u l ph bin nht. Trong hin nay phng php cracking naphta bng hi nc chim t trng 67%, phng php FCC chim 30%, ch c 3% cho cc phng php cn li. Tuy nhin theo d bo ca CMA, Inc. n nm 2010, t trng ln lt s l: cracking naphta bng hi nc: 59%, qu trnh FCC: 33% v 8% cho cc phng php cn li. Sau y chng ta s phn tch cc qu trnh nu trn: 1. Sn xut propylen t qu trnh cracking naphta bng hi nc u tin to ra propylen Naphta l mt sn phm ca qu trnh chng tch du th (chim khong 4%) nm gia on tch xng nh v benzin nng hn. y l mt nguyn liu rt quan trng cho ngnh ha du. N l nguyn liu sn xut ra olefin trong qu trnh cracking naphta bng hi nc khng c mt oxy khng kh. Trong qu trnh ny cc hydrocacbon b chuyn ha, to ra cc sn phm olefin (etylen, propylen, butadien) v cc cht thm (benzen, toluen, xylen). Cc sn phm ny li l nguyn liu cho qu trnh tng hp tip theo cc cht khc: nha tng hp polyetylen, polypropylen, nha PS, si tng hp, ha cht cng nghip, dung mi cng nghip, v.v... Methathesis l mt phng php tuy c in nhng nay c ci tin u tin tch propylen t dng hn hp olefin trong qu trnh cracking naphta. Theo ti liu ca Hng ABB Lummus, mt khi qu trnh methathesis c tch hp vo qu trnh cracking naphta bng hi nc, c th tng hiu sut tch propylen/ etylen t 0,65/1 ln 1,1/1, ng thi lm gim gi thnh ca c 2 sn phm, tng li sut ca nh my. Vin nghin cu du m ca Php cng nghin cu cng ngh methathesis ring trn c s phn ng ca etylen vi C4 to ra propylen trn xc tc cha rni. Cng ngh ny c trin khai quy m pilot i Loan. Cng ngh mi nhm tng t l tch propylen/ etylen t 0,65/1 ln 0,85/1 cng c hng Lurgi - Oil - Gas - Chemie Franfurt (c) nghin cu. Cng ngh ny c tn l Propylur, trong olefin C4 ly t cc qu trnh cracking naphta bng hi nc, t qu trnh cracking FCC hay

raffinat t nh my sn xut butadien. Phn ng chuyn ha xy ra 420oC, p sut 1,3 - 2 bar, xc tc l zeolit dng vin. Hng UOP cng pht trin cng ngh OCP (Olefin - Cracking - Process) chuyn ha olefin C4 - C8 thnh propylen v etylen nhm tch hp vi qu trnh cracking naphta bng hi nc tng hiu sut tch propylen/ etylen n 30%, t t l 0,8/1,0 v cao hn. Trong qu trnh ny olefin phn ng trn xc tc zeolit iu kin nhit 500 - 800oC, p sut 1 - 5 bar. Cng ngh ny cng c trin khai t hp lc du ca lin doanh UOP - ATOFINA Antwerp (B). Cng ngh cracking c xc tc (PCC) sn phm olefin thnh propylen, etylen v butylen trn c s xc tc ZSM - 5 c cc hng Exxon Mobil, Lurgi, Kellogg Brown & Root pht trin. Cng ngh mi ny cho kt qu tch t nguyn liu naphta 30 - 40% propylen, 10 - 20% etylen. 2. Sn xut u tin propylen t qu trnh cracking FCC Theo cc s liu d bo, t trng propylen sn xut t qu trnh ny chim v tr th hai. Qu trnh u tin tch propylen c th thc hin hoc bng cch s dng xc tc chn lc hoc thay i thng s cng ngh. Hng UOP trin khai cng ngh Petro FCC nhm tng t l tch propylen/ propan t 6 - 8% ln 25% t qu trnh FCC. Cng ngh ny cho php qu trnh FCC lm vic cng cao hn bng cch tng cng hi lu xc tc nhng khng lm tng tiu tn nhit cho qu trnh v mt s gii php khc. Tng hp tt c cc gii php trn c th nng hiu sut tch propylen ln ti 25% trong cc nh my lc du s dng cng ngh mi FCC ca UOP. Hin nay, cc thit b lp thm cho qu trnh FCC c xc tc kiu RxCat ca UOP c cho bn rng ri. 3. Phng php dehydro ha propan (PDH) y l phng php n gin nht sn xut propylen. C th dehydro ha lng propan thnh 88% propylen. Phng php sn xut ny c nhc im l gi ca sn phm propylen ph thuc rt nhiu vo gi ca nguyn liu propan nn hiu qu kinh t ca qu trnh gia cng thp. S thc l mt s nh my PDH kiu ny thi gian trc (1980 - 1990) phi ng ca v gi nguyn liu tng qu mc chu ng. Mt s hng lc du c gng khc phc bng cc gii php ci tin cng ngh v thit k tit kim chi ph nng lng nhm gim gi thnh sn xut. Hin ti ch c 2 cng ngh PDH c s dng thc t: l qu trnh OLEFEX ca Hng UOP s dng xc tc platin v CATOFIN TECHNOLOGY ca Hng Lummus s dng xc tc Crom - Al2O3 c hiu sut chuyn ha propan thnh propylen kh cao (85%). Cc nh my ln chuyn ha propan thnh propylen thng c xy dng cc nc Trung ng, Nga, ng Nam ni c gi thnh propan thp. 4. Phng php chuyn ha metanol thnh olefin (MTO: methanol - olefin) Phng

php ny c u im ln ti nhng vng c ngun kh thin nhin di do, gi r, khng cn vn chuyn xa. Kh thin nhin u tin c chuyn ha thnh metanol, sau chuyn ha tip thnh olefin. Mt d n ln theo cng ngh ny ang c trin khai Lagos - Nigeria do lin doanh UOP v Norsk Hydro A.S. ca Na Uy lm ch u t. Nh my ny sn xut metanol theo cng ngh ca Haldor - Topsoe A.S. ln nht th gii vi cng sut 7.500 tn metanol/ ngy, m bo sn xut ra 400.000 tn/nm mi loi propylen (v etylen) v tip tc sn xut ra nha PE, PP ngay ti nh my. Cng ngh ca UOP - Norsk Hydro A.S. chuyn ha metanol thnh propylen v etylen vi t l 50/ 50. Phn ng chuyn ha din ra trong thp phn ng dng tng si iu kin: 350 - 550oC, p sut 1 - 3 bar, s dng xc tc silicoaluminophotphat. Theo phn tch ca UOP, nh my s dng cng ngh MTO xy dng Nigeria hon ton c th cnh tranh vi cc t hp ha du cracking sn xut propylen c cng cng sut. Theo tnh ton ca UOP th thi gian thu hi vn ca nh my MTO ny l 4 nm, t hn 1 nm so vi nh my cracking naphta. Hng Lurgi cng c cng ngh ca ring mnh cho qu trnh chuyn ha metanol thnh propylen. u tin metanol chuyn ha qua xc tc thnh dimetyl ete, metanol d v hi nc. Hn hp ny sau phn ng thp phn ng kiu tng si 420 - 490oC, p sut 1,3 - 1,6 bar nh xc tc zeolit to ra propylen. Cng ngh ny c trin khai sn xut th ti nh my sn xut metanol ca hng Statoil, Tjeldbergodden (Na Uy). 5. So snh cc phng php sn xut propylen C mt vi yu t cn phi xem xt khi la chn, nh gi v mt phng n sn xut propylen. Yu t hng u, quan trng nht tt nhin l ch tiu kinh t. Cc yu t ch yu xem xt khi nh gi v so snh chn mt phng php l: kh nng cung cp nguyn liu, gi nguyn liu chnh, kh nng thay th ngun nguyn liu; hiu sut propylen v sn lng v cc ng sn phm; chi ph u t xy dng nh my, v.v... Khi xc nh r ngun nguyn liu vi gi hp l v linh ng thay th ngun nguyn liu th d dng nh hng phng php no c li hn. Hiu sut chuyn ha propylen l yu t ch yu xc nh lng nguyn liu cn thit, lng sn phm ph to ra xc nh cc yu t tc ng ca n ln dng sn phm chnh (propylen). Sn lng sn phm, chi ph u t, xy dng nh my, tnh ph hp ca c s c sn cng l nhng yu t cn tnh n d n tr nn hp dn, kh thi. Vn cui cng lin quan ti chnh sch c th ca nh u t nhm tng v a dng ha sn phm cng nh tn dng cc ngun ti nguyn, ku gi, li ko u t, to cng n vic lm cho ngi lao ng ti a phng t nh my. 6. p dng phng n sn xut u tin propylen no cho ngnh

ha du Vit Nam Trn c s phn tch cc cng ngh u tin sn xut propylen, da trn hon cnh c th ca nc ta, la chn phng n 1 l: cracking naphta bng hi nc c xc tc hoc phng n 2: qu trnh cracking FCC c xc tc l hp l. Cc qu trnh ny c tch hp vi cc dy chuyn lc tch du th trong cc t hp lc - ha du ca nc ta. Cc phng n trn ngoi cc u im nh phn tch, cn ph hp vi hon cnh c th ca ngnh lc - ha du ca nc ta, l: - Cn c vo ngun nguyn liu, nc ta c tr lng hn ch v du th, cn phi nhp thm du th cho cc t hp lc ha du; Cc m kh ca nc ta cha ch yu kh metan thch hp cho sn xut in, m v c tn dng ti a cho mc ch ny. - To ra sn phm propylen l sn phm ha du c gi tr cao hn sn xut nha PP tha mn nhu cu trong nc v xut khu. Nng cao doanh s v li rng ca cc t hp lc - ha du. - Gim chi ph vn hnh nh tn dng nng lng v ph tr ca t hp lc, ha du. Gim chi ph vn chuyn, chi ph qun l chung, nng cao li ch tng th ca ton b nh my. - Chi ph u t thp hn - ch cn tch hp mt unit chuyn ha olefin u tin sn xut propylen cho mt dy chuyn sn xut nha PP vi cng sut ph hp. Trn y phn tch cc gii php nhm u tin to ra sn phm propylen trong qu trnh ch bin du kh nhm tha mn nhu cu ca th trng. Cc qu trnh a ra u c u khuyt im nht nh v phi xem xt, phn tch trong tng iu kin c th. Khng th c cu tr li n gin v nh u t cn phi la chn, so snh, cn nhc xc nh phng php sn xut no ph hp nht trong iu kin c th. Kh nng p dng cng ngh cracking hi nc to ngun nguyn liu ha du t etan v naphta nc ta (ng ngy 10.10.2007 21:41 & 1528 lt xem) Trc y, axetylen (C2H2) c s dng trong mt thi gian di lm nguyn liu u cho cc qu trnh ch bin ha du. Sau , v l do gi thnh, axetylen dn c thay th bi etylen (C2H4), propylen (C3H6) v butadien (C4H6). Hin nay, etylen lun chim u th v mt kinh t so vi axetylen. Khong nm 1930 v trong Chin tranh Th gii th nht, etylen l sn phm thu c t qu trnh ha lng v ct phn on cc kh l t cc, t qu trnh dehydrat ha ru etylic v thm ch c qu trnh hydro ha ring phn axetylen. Khi nhu cu etylen tng ln, ngi ta s dng qu trnh nhit phn cc phn on du m (kh nh, naphta) sn xut nguyn liu ny. Ngay t nm 1950, ba t hp ha du quan trng x l cc phn on du m c xy dng, mt ca BP Scotlen (30 nghn tn/nm), mt ca Petrochemicals Ltd. Lancashire (10 nghn

tn/nm) v mt ca ICI Cleverland (30 nghn tn/nm). Gia nm 1940 v 1950, cng sut trung bnh ca cc nh my vo c 10 - 50 nghn tn/nm, nhng chnh trong thp k 1950 - 1960 xut hin cc nh my ln sn xut etylen t naphta vi cng sut 300 nghn tn/nm. thu c cc lfin, ngi ta dng cng ngh cracking vi hi nc cc phn on du m. Qu trnh cracking vi s tham gia ca hi nc (gi tt l cracking hi nc) l qu trnh nhit phn cc hydrocacbon bo ha c ngun gc t kh t nhin hoc du m trong s c mt ca hi nc. Qu trnh ny trc tin sn xut etylen v propylen, l nhng nguyn liu ha du quan trng. Ty theo ngun nguyn liu s dng, ngi ta c th to ra phn on C4 giu butadien v phn on C5+ (hydocacbon c 5 nguyn t cacbon tr ln) cha nhiu cht thm, c bit l benzen. Ngoi ra, cn phi k n cc cu t nh v nng, l sn phm ca qu trnh cracking, c s dng lm nhin liu. Thc t, s a dng ca sn phm ca qu trnh cracking hi nc lm cho qu trnh ny tr thnh mt qu trnh then cht trong cng nghip ha du. Kh t nhin v cc phn on du m thu c bng qu trnh chng ct thng l cc cu t hydrocacbon bo ha c hot tnh ha hc v kh nng chuyn ha ha hc rt thp v t chn lc. Chng khng cho php to ra nhiu sn phm ha hc khc nhau. Ngc li, nh cracking hi nc, ngi ta c th thu c cc hydrocacbon khng no mch thng hoc hydrocacbon thm c kh nng phn ng rt mnh nn c rt nhiu ng dng. Tnh hnh sn xut v tiu th etylen Thng k ca ngnh Du kh cho thy kh nng sn xut etylen trn th gii t 95,6 triu tn vo nm 1999 v tng ln n 118 triu tn vo nm 2005. Sn lng propylen bng mt na sn lng etylen. Hin nay, nc ta cha sn xut c etylen v cc dn xut i t etylen nh polyetylen (PE), vinyl clorua (VCM), styren (SM), etylen oxyt (EO), v.v... Tuy nhin, nhu cu v cc mt hng cht do i t PE, poly vinyl clorua (PVC), polystyren (PS) ngy cng ln. Trnh by nhu cu tiu th cc loi cht do PE, polypropylen (PP), PVC, PS trong nhng nm qua v d bo nhu cu v tc tng trng mt s loi cht do ch yu trong nhng nm ti. p ng mt phn nhu cu v cc loi cht do ch yu ca Vit Nam, va qua chng ta xy dng v a vo vn hnh mt s nh my lin doanh sn xut PVC, cng sut 80 - 100 nghn tn/nm, i t VCM nhp khu. Hin nay, song song vi vic xy dng Nh my Lc du s 1 ti Dung Qut, chng ta ang trin khai d n sn xut PP. Ngoi ra, trong nhng nm ti chng ta cn trin khai d n sn xut PS, PE, si tng hp polyeste (PET), v.v... Trong tng lai cc d n ny u cn n nguyn liu c bn cho ha du

l etylen. D kin nhu cu etylen cho nm 2010 l 900 nghn tn/nm. Cc qu trnh cracking vi hi nc u im ca qu trnh cracking hi nc l c th s dng ngun nguyn liu a dng, t phn on nh nht nh kh t nhin, kh ha lng (LPG), cc phn on naphta, gasoil cho n cc phn on cn nng v c du th. M l nc c nhiu kh t nhin giu etan v propan, nn h thng s dng cc hydrocacbon nh ny sn xut etylen. Ngc li, chu u ngi ta thng s dng cc phn on du m lm nguyn liu cho cc qu trnh cracking hi nc. Trong khun kh bi bo ny, chng ti quan tm n cc qu trnh cracking hi nc cc nguyn liu t sn phm lc du (etan v naphta) to etylen v propylen. Bn cht ngun nguyn liu c nh hng mnh n hiu sut qu trnh cracking vi hi nc. Qu trnh c tin hnh nhit rt cao cng vi s hi lu ca nguyn liu cha chuyn ha. Cc kt qu nghin cu cho thy hiu sut etylen gim i khi nguyn liu nng hn v t l hiu sut etylen v propylen C2/C3 gim u n t etan n gasoil trong khi hiu sut ca xng cracking (C5+ -200oC) tng ln. Cracking etan M, ngi ta s dng kh etan tch t kh t nhin lm nguyn liu sn xut etylen vi hiu sut cao. Tuy vy, chn lc etylen gim khi hiu sut chuyn ha etan tng. Thc t, ngi ta lm vic chuyn ha etan 65% v sau khi hi lu etan cha chuyn ha, ngi ta thu c hiu sut etylen khong 80%. Vit Nam, m bo hiu qu kinh t cho d n sn xut etylen, cng sut ti thiu ca t hp etylen phi t trn 300 nghn tn/nm. Nhu cu etan cn c cho cng sut ny l 375 nghn tn/nm (280 triu m3/ nm). Kh ng hnh ca b Cu Long c hm lng etan cao (12 - 13,6%) rt thch hp cho vic tch etan lm nguyn liu cho sn xut etylen v pht trin cng nghip ha du. Tuy nhin theo d kin, kh nng thu gom v a kh vo b t cc m Bch H, Rng ng, Ruby/ Emerald v t cc m khc thuc khu vc b Cu Long (theo phng n cao) vo giai on cao nht, nguyn liu kh cng ch sn xut khong 210 - 220 nghn tn etylen/ nm, n nm 2015 ch cn sn xut 190 nghn tn/nm v n nm 2020 th hu nh cn ngun nguyn liu. Trong trng hp ny, nu ch da vo ngun kh ng hnh t b Cu Long th khng nguyn liu trin khai v duy tr d n trong khong 15 - 20 nm. Tim nng kh ca b Nam Cn Sn rt phong ph. Sau Lan Ty, Lan cn c cc m Rng i, Hi Thch, Mc Tinh s c a vo khai thc. Cng sut ng ng Nam Cn c th t ti 6 - 7 t m3 kh/ nm v c kh nng duy tr lu di. T 6,5 t m3 kh/ nm vi hm lng etan 4,2% ch c th tch c 230 triu m3 etan/ nm (310 nghn tn etan/ nm) v c th chuyn ha thnh

250 nghn tn etylen/ nm. Tuy nhin, cng sut ny vn nh hn so vi quy m kinh t ti thiu (300 nghn tn/nm). Kh Ty Nam t l PM - 3 - CAA v m Ci Nc vi cng sut 1,25 - 1,4 t m3/ nm c k hoch a vo C Mau cung cp cho cm kh - in - m C Mau. Kh Ty Nam t l B vi sn lng 2 - 3,5 t m3/ nm ang c d kin a vo b, ch yu cung cp cho cc nh my in - m hoc cho cc ngnh cng nghip khc. Ngun kh ny c thnh phn etan thp (di 3%) v hm lng CO2 qu cao (trung bnh 20%) v khng thch hp cho vic tch etan sn xut etylen. Nhn chung, theo cc thng tin hin c v d bo kh nng cung cp kh trong thi gian ti, trn c s hm lng etan trong kh v cng sut ti thiu phi t m bo hiu qu kinh t cho d n, cn xem xt kt hp s dng c hai ngun kh ca b Cu Long v Nam Cn Sn trin khai xy dng t hp etylen u tin nc ta. Vi cng sut d kin 300 nghn tn etylen/ nm v sn phm HDPE 200 nghn tn/nm, LL/LDPE 100 nghn tn/nm, tng vn u t c tnh l 680 triu USD. Lng etan tiu th hng nm cho t hp etylen ny khong 280 triu m3 v gi kh c th chp nhn c l 2 USD/ triu BTU. Cracking naphta Cc naphta l ngun nguyn liu chnh chu u v Nht Bn. Qu trnh cracking hi nc cc naphta c kh nng cung cp ngun sn phm rt phong ph, t hydro cho n cc phn on lng nng rt giu hp cht thm. Nhit cracking c nh hng n hiu sut thu hi etylen. Nhit cng cao cng cho hiu sut thu hi cao. i vi mt l phn ng cho, ngi ta c th xc nh s nh hng ca nhit nhit phn bng cch gi thi gian lu v hm lng hi nc khng i. Khi nhit sn phm ra khi l tng ln, hiu sut etylen tng ln trong khi hiu sut propylen v xng ca qu trnh cracking hi nc (phn on C5 -200oC) gim i. Ngi ta t c hiu sut thu hi etylen thc nghim l 30,0 - 33,4% so vi naphta nguyn liu. nhit rt cao, thi gian lu tr thnh yu t quan trng nht. Thc nghim cho thy hiu sut etylen mi nhit sn phm ra khi l u c mt gi tr nht nh. Hin ti, t c hiu sut etylen tt nht, ngi ta thao tc iu kin rt khc nghit, khong 850oC, v vi thi gian lu trong khong 0,2 - 0,4 giy. Nh , hn ch c s cc ha v c th tng c khong thi gian hot ng gia hai ln t cc. Ngoi ra, ngi ta cn nhn thy i vi cng khc nghit, hiu sut to etylen gim khi p sut ring phn ca hydrocacbon tng ln. ti u ha hiu sut to etylen, ngi ta iu chnh p sut ring phn ny bng cch pha long hn hp phn ng vi hi nc. Thc t, v l do kinh t, ngi ta thng gii hn mt gi tr khong 0,5 - 0,6 tn hi nc/ tn naphta. Cc hiu sut sn phm nhit phn

cn ph thuc vo thnh phn ha hc ca nguyn liu s dng. Thc t, tnh bn nhit ca cc hydrocacbon tng theo th t sau: parafin, naphten, hydrocacbon thm, v tnh bn nhit gim khi chiu di ca mch cacbon tng. V th, ngi ta thng nhn thy rng hiu sut to etylen cng nh propylen cao khi trong nguyn liu cha nhiu parafin. Hin nay, ngi ta thng s dng qu trnh cracking hi nc i vi nguyn liu naphta u tin sn xut propylen theo cng ngh Deep Catalytique Cracking - DCC. Hiu sut thu olefin trong dy chuyn DCC c th t c 34,49% hp cht C3 - C4; 5,59% hp cht C2. Cracking naphta cng l mt hng cng ngh quan trng c kh nng p dng sn xut cc nguyn liu ha du nc ta.