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BI GING

QU TRNH LC TCH VT LGing vin bin son: GVC. ThS. Trn Vn TinTn mn hc : Qu trnh Lc tch vt l S VHT : 5 (75 tit) Ti liu hc tp: + Sch, gio trnh chnh: 1. Bi ging QU TRNH LC TCH VT L, Trn Vn Tin 2. Tp Cc hnh v, s , cu to thit b ch nh trong Bi ging, Trn Vn Tin 3. Procds de Sparation, tp 2, 655 trang, Jean-Pierre Wauquier NXB TECHNIP Paris, 1998. (Ch : Bi ging ny c bin son theo cun Procds de Sparation. Cc hnh v, s , cu to thit b ch nh trong Bi ging, sinh vin tra trc tip theo s th t ca hnh trong cun Procds de Sparation.) + Sch tham kho: 1. Nguyn Bin. Cc Qu trnh, Thit b trong Cng ngh Ha cht v Thc phm, tp 4: Chng luyn, Hp th, Trch ly, Kt tinh, Hp ph, Sy. NXB KH&KT H Ni, 2002. 2. Nguyn Bin. Tnh ton Qu trnh, Thit b trong Cng ngh Ha cht v Thc phm, tp 1&2. NXB Khoa hc v K thut H Ni, 2001. 3. Nguyn Bin, Vn i, Long Thanh Hng, inh Vn Hunh, Nguyn Trng Khung, Phan Vn Thm, Phm Xun Ton, Trn Xoa. S tay Qu trnh v Thit b Cng ngh Ha cht, tp 1&2. NXB Khoa hc v K thut H Ni, 2004.

Chng m u : TNG QUAN V MN HC QU TRNH LC TCH VT L1. S tt c cc loi qu trnh trong nh my lc du (Hnh 1.1a) 2. S tt c cc loi phn xng trong nh my lc du (Hnh 1.2) 3. Vai tr ca Cng ngh Lc du trong nh my lc du Du th c to thnh t hn hp phc tp gm rt nhiu cc hp cht, phn ln l hydrocarbon. thu c cc sn phm du m p ng c cc tiu chun k thut thng mi, u tin cn phi thc hin mt qu trnh phn ring du m nguyn khai thnh nhiu phn on khc nhau. Cc phn on ny, tip sau phi c tinh luyn lm sch, hay phi tri qua cc qu trnh chuyn ha ha hc, c bit l nhm phc v cho cc nhu cu ca ngnh ha du sau ny. Nguyn l c s ca mt cng on phn ring c minh ha trong Hnh 1.1. Hn hp ban u (du th hoc hn hp khc, A, B, C...) c phn ring ra thnh cc cu t khc nhau hay cc phn on khc nhau nh nhng tnh cht c trng, v d bng khong nhit si. Mt cng on nh vy thng thng i hi s tiu tn nng lng (un si trong chng luyn hay lm lnh trong kt tinh) hay i hi s tr gip ca mt tc nhn phn ring chn lc (dung mi trch ly, hp th, cht hp ph). Trong cc trng hp ni ring ca lc du th, cc qu trnh lc tch vt l bo m c 3 chc nng chnh sau: Cc qu trnh phn on

2Qu trnh chng ct kh quyn cho php phn on du th thnh cc phn on khc nhau: kh du ha lng LPG, xng, kerosen, gazol, fuel... c cho v d trn Hnh 1.2. Vi cc qu trnh chuyn ho ho hc, trong hu ht cc trng hp, sau khi thc hin qu trnh, dng sn phm thng phi tri qua mt cng on phn on nhm mc ch thu c cc sn phm c cht lng p ng cc tiu chun k thut nghin cu. Cc qu trnh tun hon li Hu ht cc cng on chuyn ha ha hc u c c trng bi s chuyn ha tng chng khng hon ton, tip li l mt cng on phn ring tch ring v tun hon li cc cu t cha c chuyn ha, v h s chuyn ho tu thuc qu trnh thng nm trong khong 10-90% (Hnh 1.3). Nh vy, s cn thit gia tng ch s octan IO ca cc ngun xng c s nhm sn xut ra cc loi xng khng ch, dn n vic phi tin hnh cc qu trnh ng phn ha cc n-parafin thnh cc iso-C5 v C6. Cc n-parafin khng c chuyn ha khi i ra khi qu trnh ng phn ha s c tch ra bi cc ry phn t c kch thc 5Ao v c ti tun hon, nhm t kt qu ng phn ha hon ton cc parafin ny. Cc qu trnh lm sch - Lm sch cho nguyn liu trc khi phn ng: tch cc loi tp cht (nh H2S, mercaptan c trong hn hp kh trn ry phn t 13X) m chng c phn ng ph vi xc tc trong nguyn liu u l rt cn thit cho cc cng on h lu, v trong cc cng on c xc tc, cht xc tc rt nhy phn ng vi cc tp cht c trong nguyn liu. - Lm sch hon thin cht lng to sn phm (tch aromatic, parafin sn xut du nhn, tch aromatic cho nhin liu). - Lm sch p ng yu cu l mt vi sn phm thu c phi c tinh khit cao ng dng cho cc nhu cu ca ha du (v d sn xut H2, i/n-parafin, BTX ... tinh khit). - Lm sch nhm tch trit cc tp cht c hi c trong cc cht thi l kh, nc t nh my ra mi trng (nh hp th H2S bng dung mi amin). Gio trnh ny cp ch yu n qu trnh phn ring cc hn hp ng nht. Cc hn hp ny cn c tch thnh cc nhm cu t hay thm ch thnh cc cu t tinh khit nh cc qu trnh lc tch vt l (hay qu trnh truyn cht) kh phc tp. Cc qu trnh ny, ty tng trng hp, s i hi t mt hay mt tp hp cc cng on tinh ch li mt cch chn lc mt vi cu t trong phn on ban u.

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Chng 1 : NG DNG QU TRNH CHNG CT, HP TH TRONG CNG NGH LC DU1.1. CHNG CT KH QUYN DU TH 1.1.1. Cc quy trnh cng ngh ca phn xng chng ct kh quyn du th 1.1.1.1. Quy trnh cng ngh thng dng Chng ct kh quyn l 1 cng on cn bn ca quy trnh cng ngh lc du, cng on ny ra i t cui th k XIX. V n l cng on u tin trong quy trnh cng ngh lc du, nn chng ct kh quyn lun phi x l lng ln nht nguyn liu v n ng vai tr quyt nh trong vn hnh nh my lc du. Nng sut ca cng on thay i t 300.000 n hn 10 triu tn du th/nm. Gi thnh ca 1 phn xng chng ct kh quyn nng sut 10 triu tn du th/nm vo thi im nm 1994 l khong 120-150 triu USD. Trn phng din tng qut, t nguyn liu l du th, qua phn xng chng ct kh quyn, ta s thu c cc phn on sn phm du th nh sau: a. Mt phn on kh (C1-C4) v xng (C5-C10,11, ts=30-180oC) phn on hn hp kh-xng ny, thng thng sau khi c x l hydro ( tch S, N, O...), v sau khi c tch ring kh ra khi xng, chng s l nguyn liu cho cc cng on: a.1. X l kh: -tch ring C1-C2 lm kh t dng trong nh my - tch ring C3 v ring C4 l cc dng kh ho lng (v. 5.3). a.2. Sn xut xng: tu thuc yu cu m phn on xng c th c phn on nhm mc ch sn xut cc sn phm sau: + Xng ng c t: Phn on xng ly trc tip t du m c tr s octan rt thp: t 30-60, trong khi yu cu v tr s octan cho xng ng c t nht phi ln hn 70. Do vy phi dng 4 bin php khc nhau nng cao cht lng xng nh sau: - Dng cc ph gia ch: tetrametyl ch hoc tetraetyl ch c tc dng ph hu cc hp cht trung gian hot ng (peroxyt, hydroperoxyt) v do lm gim kh nng b chy kch n tc l lm tng kh nng chy iu ho, kt qu l tr s octan ca xng c nng cao. Tuy nhin, lng ph gia ch khi cho vo xng cng ch lm tng nhiu nht t 6 n 12 n v octan, trong khi n li rt c, do vy bin php ny hin nay b loi b. - Dng cc ph gia khng cha ch nh cc hp cht cha oxy (gii php tm thi): metanol (RON=127-136, rt c, khng dng na), etanol (RON=120-135), MTBE (Metyl Tert-Butyl Ete, RON=115-123), ETBE (Etyl Tert-Butyl Ete, RON=110-119), TAME (TertAmyl Metyl Ete, RON=111-116), ... Trong cc loi trn, etanol c s dng nhiu nht chu M (10-22%), tip n l MTBE (ti 15%). V d: ch vi 10% etanol ho vi 90% mt loi xng c RON=87, s cho hn hp xng mi c RON=90-92; cn vi 15% MTBE ho vi 85% cng vi loi xng c RON=87, s cho hn hp xng mi c RON=91-92. - Pha trn xng c tr s octan cao nh xng alkyl ho, izome ho, ... vo xng c tr s octan thp. - Hin i ho cc nh my lc du (gii php lu di) bng vic trang b cc phn xng sn xut xng c tr s octan cao nh phn xng RC (xng ti to xc tc, IO=95), FCC (xng cracking xc tc, IO=92), ...

4+ Xng ng c my bay: y l loi xng cao cp, c tr s octan bng 100 tr ln. Thng n l hn hp xng pha trn ca xng cracking xc tc vi cc thnh phn c tr s octan cao. + Xng lm dung mi: dng lm dung mi ho tan trong cng nghip sn, cao su, keo dn...; ngoi ra cn dng lm dung mi trch ly cht bo (du m ng thc vt) trong cng nghip hng liu, dc liu... Thng thng xng dung mi c ly trc tip t du m l xng parafin (hexan, heptan, octan...) c hm lng aromatic thp ( FeS + H2 Sulfure st to thnh 1 lp ph b mt bo v thit b, nhng khi c HCl do mui to thnh khi thy phn: MgCl2 + 2H2O --> Mg(OH)2 + 2HCl n s tc dng vi HCl: FeS + 2HCl -->FeCl2 + H2S v H2S li tip tc ph hy Fe. Lng HCl sinh ra ph thuc ch yu vo hm lng cn MgCl2 m n chim t 10-20% tng khi lng mui. Cn clorua ny trong thc t s b thy phn n 95% 350oC, trong khi cn CaCl2 (10%) cng nhit ny ch b thy phn 10%. 1.1.2.2. n mn do S nhit cao S tn ti di dng hp cht v c v hu c c trong du th v sinh ra trong qu trnh x l. S n mn thp C thng thng do S xy ra rt mnh trong vng nhit khong 300420oC v tc n mn tng ng c th vt qu 1mm/nm. Khi tc n mn t n 0,3mm/nm, s c cc nguy c v nghn tc do cn FeS, km theo kh nng chy n thit b. Phng php bo v l dng cc loi thp hp kim trong vng nhit trn vi thnh phn 5%Cr v 0,5%Mo nht l i vi cc ng truyn nhit trong l t. vng c tc chy cao, s n mn cng c gia tng, do phi s dng thp hp kim 12% Cr v thm ch c th dng n 15%. 1.1.2.3. n mn do acid naphtenic (nhm COOH vi vng C5, C6) Cc acid naphten l cc hp cht c khi lng phn t thay i, chng rt n mn trong khong nhit 220-420oC. T nhit 420 tr ln, chng b phn hy v hin tng n mn cng bin mt. S n mn tr nn km nhit di 300oC v tr nn nghim trng k t 350oC. V vy s n mn din ra trong ton b l, trong cc ng ng trao i nhit v y thp. N cng r nt hn khi tc lun chuyn lu cht tng cao. x l, nn dng loi thp hp kim Cr v Mo. 1.1.2.4. S mi mn S mi mn ch yu din ra trong cc ng ng vn chuyn lu cht v cc ng ng pha nh thp khi tc lun chuyn lu cht tr nn cao v khi c nhiu khuu ng trn ng ng.

91.1.3. Tch mui trong du th 1.1.3.1. Nhng tc hi ca mui: n mn ho hc v n mn c hc a. mui ca du th, s nhim mn t nc bin Qu trnh tch mui trong du th l mt phn on rt quan trng trong nh my lc du v n s quyt nh n s hot ng tt hay khng tt ca cc qu trnh x l sau ny. Phn ln cc ging du khi khai thc s cho du th c ln mui, ch yu l mui NaCl, nhng chng cng c km theo cc mui kim loi kim th. mui ny c mang n t nc ca va hay t nc thm nhim; mui ph thuc vo v tr cu trc ca ging du v vo tnh cht vt l ca cha. Hn na mui cn thay i theo tui ca ging du Mt khc vic xut nhp, vn chuyn du th s lm mui ca du th tng ln. Trong sut qu trnh vn chuyn, s giu thm v mui bin c th ln n 10-18 ppm (Bng 5.4). Nh vy, nc bin l nguyn nhn chnh gy nn mui trong du th. Du th sau khi tri qua qu trnh x l tch mui mt phn ti m du, ri li b giu thm v mui trong sut qu trnh vn chuyn trn bin, s c a v nh my lc du. Ti y n s tri qua phn on tch mui trc khi a vo cng on chng ct kh quyn. Ngoi ra cn cc cht nhim khc hin din trong du th l cn khong cht, cht han g, sulfur st,...tc hi ch yu ca nhng cht nhim bn ny l chng c th gy ra cc h nh tng bn vng rt kh ph hy. Mui trong du th ch yu l mui Chlorure m s phn b chng gn ng nh sau: NaCl: 70-80% khi lng MgCl2: 20-10% khi lng CaCl2: 10% khi lng Cc mui ny hin din di dng tinh th hoc di dng ion ha trong nc c trong du th (khi n nh my lc du, hm lng nc trong du th l C4. 2.3.5.1. Cc qu trnh ch s dng mt dung mi, Qu trnh Shell/UOP Nm 1961, cng ty Hong gia H Lan Shell cng tc vi hng UOP M pht minh ra 1 qu trnh ch s dng mt dung mi sulfolan. So snh vi dung mi glycol, dung mi sulfolan c nng sut ln hn i vi cc hp cht aromatic, nhit si cao hn, n nh nhit tt nht v nhy km hn i vi s oxy ha. S qu trnh Shell/UOP c trnh by trong Hnh 7.32.

Cc qu trnh s dng mt dung mi duy nht mt cch tng qut bao gm 4 cng on chnh sau: 1. Trch ly cc hp cht aromatic bng dung mi sulfolan, 2. Tch nc v parafin-naphten ra khi phn trch bng chng ct trch ly, 3. Ti sinh dung mi cho phn trch bng chng ct thng thng, 4. Ti sinh dung mi cho phn lc bng vic dng nc ra ko dung mi ra.Nguyn liu c nhp vo mc thp ca thp trch ly, thp ny cng nhn dung mi sulfolan c km theo khong 1% nc nh thp, v y cc hydrocarbon c tun hon li. Thit b trch ly l thit b tip xc bng a quay RDC, hay l mt thp mm xuyn l tng ng vi khong chc bc l thuyt. N hot ng nhit khong 100oC, di p sut t 2-4 bar. T l dung mi c iu chnh sao cho tha mn vi cc tiu chun k thut v hiu sut thu aromatic v thng nm trong khong 3/1 dn 5/1 theo khi lng. Phn trch th c t thp trch ly c chuyn v nh thp chng ct trch ly c khong ba chc mm, hot ng p sut kh quyn vi t s un si tun hon ph hp cho cc hp cht aromatic y thp t c cc ch tiu k thut v hm lng cc hp cht khng aromatic. Hi nh bao gm cc hp cht khng aromatic, mt phn cc hp cht aromatic nh nht v nc b li cun theo do ng ph (c cng nhit si) vi cc hydrocarbon. Sau khi ngng t, pha hydrocarbon c lng v chuyn tr li v thp trch ly. Phn trch c lm sch ht cc cht khng phi aromatic (ch cn Ar v dung mi) c chuyn v thp bc hi cc hp cht aromatic (cng c khong ba chc mm), n c sc hi nc chn thp. Thp hot ng p sut thp (300-400mmHg) nhit y m bo n nh nhit ca dung mi, khong 180oC. Qu trnh iu khin thp c thc hin sao cho nh thu c hp cht aromatic c cc tiu chun k thut thch hp, v y dung mi ti sinh c tun hon v li thp trch ly. Nc thu hi thit b ngng t nh thp bc hi s qua cng on ra phn lc th ko ht dung mi sulfolan ra khi phn lc, sau c x l sao cho tch loi cc vt hp cht hydrocarbon khng aromatic b ha tan v c tun hon tr li trong thp bc hi. 2.3.5.2. Cc qu trnh s dng 2 dung mi

Cc qu trnh s dng hai dung mi, mt cch tng qut bao gm 5 cng on

53 chnh sau: 1. Trch ly (ln 1) cc hp cht aromatic , dng 2 dung mi ng thi (DMSO v C4): li dng tnh chn lc ca DMSO-aromatic v ca C4-naphten v parafin m tch c aromatic ra khi naphten v parafin 2. Trch ly li (ln 2), ch dng 1 dung mi C4: li dng tnh chn lc ca C4aromatic m tch c aromatic ra khi DMSO (thu c phn ln DMSO tinh khit) 3. Tch DMSO b ko theo cc phn lc ra nh ca 2 thp trch ly: li dng tnh chn lc ca nc-DMSO m tch c DMSO ra khi cc phn lc . 4. Tch hn hp nc-DMSO bng chng ct chn khng nhm thu hi trit DMSO (0,3 bar do DMSO d b phn hy v nhit) 5. Thu hi dung mi C4 t 2 phn lc ra khi thp ra bng 2 thp chng ct p sut cao: nh cc thp thu c C4 cho tun hon tr li, cn y cc thp ta thu c cc dung dch trch v lc tinh khit. Cc qu trnh s dng 2 dung mi khc bit vi cc qu trnh trn do cc giai on lm sch cc hp cht thm v ti sinh dung mi khng c thc hin bng chng ct trch ly v stripping m bng trch ly li vi mt dung mi ph. Dung mi ph phi t b trn ln vi dung mi chnh v d dng phn tch c vi cc hp cht hydrocarbon ca nguyn liu bng phng php chng ct.Cc qu trnh khc nhau c ngh, ni bt nht l vi cc dung mi tetraethylenglycol (Union Carbide), NFM (Snam Progetti), DMSO (IFP) c s dng nh dung mi trch ly v mt parafin c th hoc d bay hi hn hoc t bay hi hn cc hp cht hydrocarbon ca nguyn liu, c s dng nh dung mi trch ly li. Qu trnh DMSO-Butan, s cng ngh c trnh by trong Hnh 7.33, c pht trin bi IFP t u nhng nm 1960 v c cng nghip ha vo nm 1967. Nguyn liu c nhp vo trong thp trch ly khu vc trung gian. DMSO, c gia thm 4-6 % nc c a vo nh v Butan c a vo y thp. Qu trnh trch ly c thc hin nhit trung bnh khong 30oC v p sut 4-6 bar tuyt i nhm gi cho butan th lng. T l dung mi (DMSO/nguyn liu) c khng ch sao cho bo m c hiu sut thu aromatic ty theo thnh phn nguyn liu. Thng t l ny trong khong 3/1 n 6/1. T l Butan/nguyn liu c iu chnh ty theo cc ch tiu k thut tinh khit ca cc hp cht aromatic; t l ny thng khong 0,15/1. Phn lc th n t thit b trch ly c ra bng nc tch loi DMSO ha tan trong , sau c chng ct phn tch butan, butan c tun hon. Phn trch c a n thit b trch ly li cho tip xc ngc dng vi butan cng mt iu kin p sut v nhit nh trong thp trch ly. T l lu lng butan/trch c xc nh sao cho trch ly li c hon ton cc hp cht aromatic v trung bnh bng 0,31/1 theo khi lng. DMSO c ti sinh nh vy c cho tun hon trc tip v thp trch ly. Butan, c mang theo aromatic c ra bng nc loi DMSO bo ha c trong ri c chng ct v c tun hon v thp trch ly li. Nc ra cc hydrocarbon c cha DMSO c chng ct chn khng (200 mmHg) v c tun hon v thit b ra bng nc, nm nh cc thp trch ly. DMSO c thu hi v c ti nhp vo trong dng dung mi. Hiu qu ca s ny l dng DMSO m khng s c nguy c phn hy n. Mt thun li khc ca s ny l n c kh nng trch ly cc hp cht aromatic ca mt phn on rng, do vic phn tch aromatic/dung mi bng chng ct khng cn l vn na. Tuy nhin cn lu rng phn on cng rng th lu lng dung mi trch ly v trch ly li cng ng k i vi mt n v aromatic c trch ly. V vy c mt gii hn kinh t v x

54l cc phn on rng v nu vt qu gii hn ca phn on rng cho php th khng th p dng mang tnh cng nghip i vi trch ly cc hp cht BTX. 2.3.5.3. Cc qu trnh cng ngh in hnh a. Qu trnh Udex Qu trnh Udex c pht trin kt hp bi cc hng UOP v Dow Chemical Co., bng dung mi c c s DEG v c p dng t nm 1952. Trrong khong chc nm, n l qu trnh duy nht sn xut aromatic c ngun gc t du m vi tinh khit ln hn 99,8% v hiu sut trung bnh d 95%. Ngy nay n khng cn c quan tm nh l mt qu trnh c tnh cnh tranh na. DEG trong thc t cho nng sut aromatic tng i thp, dn n s dng cc t l dung mi ln trong qu trnh trch ly, t 6 -20, ty theo nguyn liu. Cc dung mi hiu nng cao hn thay th n. b. Qu trnh Arosolvan ca Lurgi Qu trnh ny thc hin vi dung mi c s l NMP. Trong th h u tin c cng nghip ha vo nm 1962, NMP c cng thm nc (12-14 %) ti u ha hiu qa trch ly ca n. Sau , xut hin mt dung mi hn hp NMP-glycol dn n mt qu trnh tit kim hn v nng lng, do n trnh c s ha hi nc d cng vi cc hydrocarbon trong giai on lm sch phn trch bng chng ct trch ly. T l ca glycol ph thuc vo hm lng aromatic ca nguyn liu v thng nm trong bin 40-50%. Mt c im ca qu trnh l thit b trch ly Lurgi, c thit k trn nguyn l chng cht cc thit b khuy trn-lng v c thun li l d dng c ngoi suy cho n ng knh thp khong 8m. Cc tnh cht tan ca NMP dn n vic tin hnh qu trnh trch ly nhit gn vi mi trng, khong 50oC. c. Qu trnh Tetra ca Union Carbide Qu trnh ny ly tn gi ca dung mi m n s dng: l dung mi tetraethylen glycol cng vi 4% nc. N c bit n vo nm 1968. S thay th DEG bng TETRA c kh nng ha tan ln hn cho php chia hai t l dung mi v nh vy lm tng ln 80% nng sut x l. Vi cc thit b mi, Union Carbide a ra cc cu trc bn trong c bit ca thp. l cc mm xuyn l c nhiu ng chy chuyn kiu MU (Multiple Upcomer) i vi thp trch ly v chng cho php cc lu lng ln hn cc mm thng thng, v cc mm c ng chy chuyn kiu MD (Multiple Downcomer) i vi cc thp stripping cc hp cht khng aromatic. Thp ny trong thc t cn phi c cc cu trc bn trong t l vi cc lu lng lng/hi cao, m c hiu qu. ng nc ra cc hp cht aromatic v phn lc, cng nh qu trnh lm sch dung mi bng hp th, th ph hp vi qu trnh Tetra. d. Qu trnh Morphylex ca Krupp-Koppers Qu trnh ny c hot ng vi dung mi NFM c 4% nc. Qu trnh trch ly c thc hin trong thp c mm xuyn l kiu thng dng nhit cao khong 180oC. S chung ca qu trnh c hai im cng ngun gc so vi cc s trc. Mt ngun gc lin quan n thp stripping cc hp cht khng aromatic c bit nh l thp chng ct trch ly hon ton, ngha l bi s nhp dung mi tinh khit vo nh v do c mt khu vc ct v mt khu vc chng. u im ca s b tr ny l gii hn c s i ln ca cc hp cht aromatic trong phn ct distilat, mt mt iu ny cng gii hn lng nc c ha hi

55cng vi cc hp cht aromatic ny do ng ph, v mt khc gii hn s tun hon hydrocarbon v thp trch ly. Mt ngun gc khc nm ng nc ra cc hp cht hydrocarbon: nc i qua nh ca 2 thit b stripping c s dng cho ra phn lc, ri th nc c ni li vi dung mi c ti sinh n t y thp stripping cc hp cht aromatic nhm hydrate ha li dung mi trc khi tun hon v thp trch ly. 2.3.6. T l thu hi v tinh khit ca cc hp cht aromatic Tt c cc qu trnh trnh by u c th sn xut cc hp cht aromatic c cc ch tiu k thut v tinh khit nghim ngt nht, ty theo tnh hnh x l hon thin ti mt t nhm loi cc hp cht hydrocarbon cha bo ha l cc hp cht kh phn tch nht khi aromatic. Cc d liu cho theo v d trong Bng 7.28 i vi cc trng hp lm vic ca cc qu trnh Udex, Sulfolan, Arosolvan v DMSO, cho thy rng t l thu hi mi mt hp cht aromatic gn nh nhau i vi qu trnh ny so vi qu trnh khc. Ngc li, i vi tt c cc qu trnh, t l thu hi gim kh nhanh t benzen (>99,5%) n xylen (95-96%). T l ny tr nn nh (trung bnh 70%) i vi cc hp cht aromatic c 9 nguyn t C. 2.3.7. Cc d liu kinh t S so snh v kinh t chnh xc cc qu trnh l khng th thc hin c, do cc thng tin ban hnh khng bao gi c lin quan n cng mt trng hp c s. Chng ta v vy s gii hn trnh by trong Bng 7.29 cc d kin u t v tiu th m chng c th c ch trong vic nh gi kinh t s b mt d n. Cc d kin ny c lin quan vi c ng dng gii thiu trong Bng 7.28. Ch c mt hng dn ng ni m ta c th rt ra t y l: qu trnh Udex khng c tnh cnh tranh, nh chng ta nu. kt lun, qu trnh sn xut Benzen v toluen, hay sn xut Benzen, Toluen v Xylen t mt phn on C6-C7 hay phn on C6-C8 ca dng sn phm cracking hi hay ca dng sn phm reforming xc tc cn n cc qu trnh c tri qua chn chnh tt trong cng nghip, c kh nng cp cho cc hp cht aromatic cc ch tiu k thut nghim ngt nht cng vi hiu sut tt nht. Cc qu trnh ny c phn bit vi nhau do bn cht ca dung mi trch ly, chnh dung mi quyt nh n mt kha cnh khong thay i p dng v cc iu kin lm vic. Tuy nhin tht kh khn phn bit c chng trong ln phn tch th nht trn k hoch kinh t. S la chn mt qu trnh cho mt p dng c bit, v vy, phi c da trn s nghin cu su sc, c bit phi lu n tt c cc thng s a phng. 2.4. THIT B TRCH LY LNG LNG 2.4.1. Tng quan Nhm t c hiu qu cao, cu to thit b trch ly cn phi tha mn: Din tch tip xc ln nht gia cc pha (khu vc b mt tip xc), nhm lm cho cc qu trnh trao i pha d dng i vi mt dng hnh hc nht nh, cc iu kin vn hnh, c bit l nhit , c nh hng trc tip (thng qua cc h s phn b) hoc gin tip (t trng, nht...) n hiu qu trch ly. Vic la chn cng ngh v thit k cc cu trc bn trong cho mt h trch ly lng-lng c nh hng bi nhiu tiu chun nh sau: Lu lng tng (quyt nh n ng knh thp D) Cht lng sn phm (quyt nh n chiu cao thp H)

56 S khc nhau v t trng gia 2 pha (quyt nh n tc chuyn khi, H) T l cc pha (lng pha nh/lng pha nng, H) c trng ca s phn tn ( n nh, s to thnh nh tng bn..., quyt nh n s phn pha) S c mt ca cc cht rn (sn phm ca s phn hy, cn..., quyt nh n s phn pha) Cc iu kin vn hnh (nhit , p sut..., quyt nh n cu to thp) Khuynh hng ng cu (quyt nh n thi hn v sinh thp) Thi gian lu (quyt nh n nguy c phn hy cc sn phm) Tnh n mn (quyt nh n bn TB) Tnh bt chy ca mt trong cc sn phm (quyt nh n an ton) Din tch v chiu cao ca TB trch ly (quyt nh n mt bng phn xng) Cc quy ch c bit v vn hnh v an ton...

Hin tng trn ngc S trn ngc l mt hin tng din ra dc trc c khuynh hng ko di thi gian lu ca pha lin quan. Trong thc t, khi hin tng ny xy ra, mt phn pha lin quan c khuynh hng quay trn trong thit b trch ly, iu ny lm ko di thi gian lu ca pha trong khi mt phn khc ca pha s b bt buc phi vn chuyn nhanh hn, v tr ca phn pha ny b chim bi v tr ca phn pha b trn ngc. S trn ngc c hai hu qu tai hi n hiu nng ca thit b trch ly: Gim st hiu qu do s trn ngc mt phn ca mt hoc c hai pha Gim nng sut biu kin ca thit b trch ly, mt phn ca dng quay vng v do nhp liu mt cch v ch cho thit b Trong trng hp ca cc sn phm nhy cm, s gia tng thi gian lu ca mt phn sn phm c th gy nn s phn hy ca n. Cc nh ch to thit b thung ch trng vo s gim thiu hin tng trn ngc. (Hnh 7.34a) 2.4.2. H thng thit b trch ly Cc loi thit b trch ly c gp li thnh 2 nhm theo c ch tip xc pha c hay khng c tc ng ca nng lng c hc (khuy trn, a quay ...) trc tip ln hn hp cc pha ang tip xc vi nhau. Nhm khng c tc ng ca nng lng c hc gi l thit b trch ly loi tnh, nhm c tc ng ca nng lng c hc gi l thit b trch ly loi ng. Cc thit b trch ly loi tnh trong ng lc 2 pha tip xc vi nhau l nh chnh lch khi lng ring. Pha c lu lng nh phn tn vo trong lng pha lin tc. Thp ny c thun li l c nng sut ln song hiu qu chuyn khi li thp do b hin tng trn ngc mnh. Loi ny thng c dng khi qu trnh trch ly l n gin, dung mi d dng ko cu t cn tch ra khi pha lc. Nhm mc ch ci thin qu trnh phn tn ca cc pha (tc l tng hiu qu chuyn khi) bng cch hn ch ti a hin tng trn ngc, gia tng thi gian lu ca pha phn tn ng thi ci thin cht lng ca s phn tn, cc thit b trch ly c trang b thm cc kt cu bn trong nh cnh khuy, a quay hay cc c cu dao ng nhn nng lng c hc t bn ngoi, l cc thit b trch ly loi ng. 2.4.2.1. H thng thit b trch ly loi tnh a. My trn dng (Hnh 7.35)

57Cc my trn dng, cn gi l my trn tnh cho php khuy trn cc pha trong mt h thng ng dng. Dng c trn l do cu trc zic zac bn trong ch khng phi do nng lng bn ngoi tc ng. Chng c th c s dng nh cc my trn trong cc h thng trn lng. Chng cho php s phn tn kh tt, tn tht p sut nh v nh vy vn tc chy trong ng s rt u n, iu ny s lm gim thi gian lu. Cc thit b loi ny thng c ng dng trong cc qu trnh trch ly n gin. b. Thp phun to sng (Hnh 7.36) l mt h thng n gin nht, trong pha lin tc chy t do v c cho tip xc vi pha phn tn, pha ny i ngc dng qua pha lin tc. Cc h thng phun to sng n gin (khng c b phn ti phn phi pha phn tn) c dnh cho cc qu trnh trch ly d dng nht, v hiu qu chuyn khi ca chng nh. c. Thp so le (Hnh 7.37) Thp so le nhm ci thin hiu qu cc thp phun to sng. Cc tm so le dng a trn, k tip mt a hnh vnh khn hoc cc a hnh vin phn lp ngc nhau. S tip xc gia pha nng v pha nh c thc hin cho dng. Cc tm so le ny thc hin s khuy trn li ca pha phn tn.

Hiu qu ca mt h thng nh vy cng khng cao lm (0,05-0,2 bc l thuyt mt a thc t, gi tr ny cng ln ngha l hiu sut trch ly ca thp loi ny cng cao, ngha l m bo mt s bc trch ly nht nh, thp s khng cn cao, chi ph u t cho thp s nh), nhng chng c cc khu vc chuyn tip ln v cc cu trc a n gin l l do ng dng chng cho cc h thng c th ng cu v n mn.d. Thp mm c l (Hnh 7.38) Cc dng thp khng ngn hoc ngn n gin (a, b, c), trong cc dng pha chuyn ng lin tc t u ny n u kia thp, do vy hiu qu tip xc trn ln rt thp. Vi cc thp loi mm, sau mi ngn cc pha li tip xc li vi nhau, nh vy tng s lng cc giai on tip xc qua mi ngn: tip xc-lng phn pha-tip xc-lng phn pha nh vy, hiu qu trao i khi tng ln nhiu. Cc mm ca thp trch ly ny bo m c cc chc nng thu gp, ti trn sau ti phn tn pha phn tn. Hiu qu ca cc thp trch ly ny c ci thin r rng (khong 0,7 bc l thuyt mt mm) v cho d hin tng ng cu v n mn d xy ra, chng vn thng c u tin chn hn l cc thp loi thp so le. e. Thp m (Hnh 7.39)

Vt liu m ch c tc dng lm tng b mt tip xc ca 2 pha. Tt c cc loi m nh: m vng, yn nga, m cu trc u c th c s dng ty theo trng hp.Trong thi gian u, cc loi m yn nga (selle) bng cramique c s dng rng ri nhng hin nay chng khng cn c s dng na trong cc trng hp c bit cho d chng c u im chng n mn m tt nhng chng li c hn ch l: Tn tht p sut ln v nng sut gim (do h s trng nh, v m dy chim nhiu ch) Tnh d gy v khi sn xut (gy v khi c s gin n cc tng m) v khi lp t

58Cc m yn nga v m vng bng cramique c thay th bi cc m yn nga v m vng bng kim loi (IMPT ca Norton, vng Pall, CMR ca Glitsch, v.v.), chng d s dng hn, vng chc hn v cho php gim thiu kch thc thp.

Khuynh hng hin nay l s dng cc loi m cu trc nhm ci thin hn na hiu nng chuyn khi, tuy nhin vic s dng cng b hn ch do: Gi thnh kh ln C bn n mn yu hn (m cu trc c cu to mnh mai hn m yn nga v m vng) Kh khn trong vic tho lm v sinh.

m c kch thc cng nh (ng knh m nh) th hiu qu cng cao nhng nng sut cng gim v kh nng ng cu cng gia tng. Hiu sut chuyn khi ca thp m thng kh cao: bng 0,5-4 bc l thuyt/1m m.Thp m thng c s dng trong cc trng hp sau y: X l cc phn on du nhn bng furfural Tch loi H2S khi cc phn on du m Trch ly cc hp cht aromatic t cc phn on C6-C8 (qu trnh Duosol) Trch ly cc hp cht phnol t cc dng thi ca nh my lc du v ca qu trnh cc ha (qu trnh Phnosolvant) 2.4.2.2. H thng thit b trch ly loi ng a. Thit b trn-lng (Hnh 7.40) Trong cc h thng ny, giai on 1 l qu trnh khuch tn pha ny vo pha kia c thc hin nh nng lng bn ngoi (cnh khuy) trong 1 thit b trn, sau n giai on lng phn pha c thc hin trong 1 thit b lng ring. Hiu qu ca mi giai on ca thit b loi ny c th t n 90%. Cc thit b trn-lng c in m 2 giai on l tch bit nhau, s dng n gin nhng chim din tch mt bng ln. Chng c gp nhiu nht trong cc nh my c lu lng x l ln. Cc thit b l tch bit, d vn hnh cho tng qu trnh ring, nh vy vn tc khuy trn ln v vn tc lng cng ln v trong mi trng tnh. Mt dng thit b trn-lng c bit dng cho qu trnh trch ly cc hp cht aromatic, trong cc thit b trn-lng c chng cht ci ny ln ci khc trong cng mt thp (thp trch ly Mehner, Hnh 7.41). Cc thit b trn-lng c nh gi cao v hiu qu tng giai on cao v c linh ng cao (c th ng dng cho nhiu loi nguyn liu). Tuy nhin chng li c nhc im l gi c cao i vi cc h thng nhiu giai on v thng thng i hi phi c mt bng ln. b. Cc h thng quay

b.1. RDC v ARDC (Thit b tip xc a quay v thit b tip xc a quay khng i xng-Rotating Disc Contactor v Asymmetric Rotating Disc Contactor) Thit b RDC (Hnh 7.42) l 1 thp hnh tr trong c gn cc a c nh hnh vnh khn. Gia thp l 1 trc quay c gn cc a trn. Vng hot ng c to thnh khong gia a quay v a c nh. gn nh v y thp l cc vng lng (ni tho sn phm) c phn cch khi vng hot ng gia thp bi mt tm li nhm mc ch hn ch s khuy trong cc vng lng. Thit b ARDC (Hnh 7.43a) l mt s pht trin ca thit b RDC, trong trc c t lch tm nhm to 1 vng lng tng phn cho cc pha tng tng a. Phn

59 nh i vo trong RDC t vng pha di v i qua RDC ngc dng vi pha nng c a vo t vng pha trn. Mt trong cc pha c phn tn vo trong mi ngn nm gia hai vng c nh v kch thc ca cc git lng c iu khin bi vn tc quay ca a.Trong thit b RDC, ngoi tr cc vng ngoi ra, khng c s ni tip ca qu trnh phn tn v qu trnh kt dnh. S chuyn ng ca cht lng c to thnh t hai thnh phn, s quay v chuyn ng dc chm, c iu khin bi cc a quay v cc a vnh khn. Ngy nay, li c mt s thp RDC c s dng cc trng thi tnh khi RDC hot ng ging thp so le. l v cc l do ch yu sau: Cn gia tng cc i nng sut Tit kim nng lng trong sn xut Trong trng hp hiu qu trch ly ca thp RDC c nh l khng tha mn yu cu, ngi ta c th lp thm mt thp b sung, thng l thp m, hon tt cho thp RDC c nh hn l dng thp RDC quay. b.2. Cc thp trch ly quay khc (Hnh 7.43b, c, d) Cc loi thp trch ly khc c thit k nhm mc ch: t c hiu qu trch ly cao Gim thiu s trn ngc Ci thin s ti trn pha phn tn trong cc bc Cc thp trch ly quay c s dng trong rt nhiu ng dng quan trng: i vi thp RDC: trch ly cc hp cht aromatic (qu trnh Shell, Sulfolan) i vi thp Kuhni: trch ly cc hp cht aromatic (qu trnh IFP, DMSO) Cc thp trch ly khc nh thp Kuhni cng c s dng trong cng nghip ha cht, dc phm, x l nc thi, ... c. Cc thp trch ly lun phin Trong cc thp trch ly lun phin, s phn tn c bo m bi qu trnh khuy nh cc tc ng trc tip n khi lng ca cht lng v nh tc dng ca cc mm c l. Chng ta phn bit hai nhm thit b theo phn ng l: Cc thit b trong cc mm trng thi ng Cc thit b trong cc mm l c nh cn khi cht lng c khuy bi cc xung ng u n. c.1. Cc thit b c mm ng Thit b trch ly Karr (Hnh 7.44) c cu to bi mt dy cc mm c l (55-60% khu vc t do, l ng knh t 7-14mm) c mc vo nhau nh mt trc khuy chuyn ng dc lun phin. cc khong u n, c mt vng c gi vo nhm gim hin tng trn ngc. Nhm hng b c cu ny di ng dc v trnh s tip xc kim loi vi kim loi gia b c cu vi thp, cc vng bng PTFE (vt liu polyme) c ng knh ngoi ln hn so vi cc mm kim loi c t ngoi cng. Cc thp trch ly mm ng c s dng : Trch ly cc hp cht aromatic (qu trnh Union Carbide bng TEG) Trch ly cc hp cht phnol c trong nc thi nh my lc du (qu trnh Chempro)

60c.2. Cc thp xung Trong cc thp trch ly xung, cc cu trc bn trong c c nh cn khi cht lng c trong thp c khuy bi cc xung u n. Cu hnh ny c li im ln v n gim thiu c s lng cc chi tit c kh chuyn ng. Cc thp xung c phn bit vi nhau ch yu bi: B phn bn trong thp c th c to thnh t: cc mm tnh (mm c l chim ton b khu vc thp, hoc c cc a v vng Hnh 7.45.a) hoc m (Hnh 7.45.b) Phng cch to xung cho khi cht lng: c hc (v d bi mt ng thi chn thp Hnh 7.45.a) hoc kh ng (Hnh 7.45.b) Trong khi trong cc thp c mm tnh (tr thp xung) ch c mt pha chuyn qua cc l ca mm cn pha kia i qua cc ng chy chuyn, th trong cc thp xung c hai pha u chuyn lun phin qua cng cc l. iu ny bo m cho s phn tn ca mt trong cc pha v bo m s khuy, do bo m s ng th ha ca pha lin tc gia hai bc. Ngy nay cc thp xung ngy cng c s dng cho nhiu ng dng khc nhau nh x l dng thi, cng nghip dc phm... d. Cc thp trch ly ly tm Nhm d dng phn tch cc pha, mt vi nh thit k a ra cc thp trch ly c to ra mt trng trng lc nhn to c gia tc. Cc thit b ny c rt nhiu li im: Kh nng x l cc pha c t trng gn nhau Thi gian lu nh (p dng cho cc sn phm khng bn) Th tch thit b nh Chng t c s dng trong cng ngh du m do cc nhc im sau: Cc h thng c kh c vn tc ln ( tin cy, bo tr km) Gi cao Lu lng thp Kt lun Mt cch tng qut, vic chn la mt thit b trch ly chu nh hng ln bi kinh nghim tch lu c i vi mi ng dng. iu ny c bit r rng khi thit k mt cng on mi ca mt qu trnh c kim chng hoc khi thay th mt thit b ca mt cng on ang tn ti. Vic p dng ng mt qu trnh mi thng bt u t cc giai on th cc pilote (unit-pilote), trong phng th nghim sau mc bn cng nghip. Vic la chn cc thit b ny p dng mc cng nghip phi c tin hnh theo cc quy trnh nu trn v cc quy tc ngoi suy t cc thit b trch ly thng ng tin cy. Cc nh cng nghip v vy s c khuynh hng da vo nhng kinh nghim thu c t cc pilote v ch s gp rt t ri ro khi th mt kiu thit b trch ly mi cho mt cng on cng nghip.

61

Chng 3 : NG DNG QU TRNH KT TINH TRONG CNG NGH LC DU3.1. TNG QUAN 3.1.1. Mc ch ca qu trnh kh parafin Khi ra khi cng on trch ly bng dung mi, dung dch lc (hay chnh l du gc trong tng lai), c tch loi hu ht cc hp cht thm c trong n. Do vy ch s nht ca n c nng ln n gi tr yu cu. Dung dch lc ch yu bao gm cc phn t: Hp cht parafin c mch thng, di, t nhiu phn nhnh v cc hp cht naphten. Trong , cc hp cht parafin mch thng t phn nhnh c khuynh hng kt tinh ngay nhit thng s cn tr s chy ca du bi trn. Trong khi , du nhn cn tho mn kh nng lu bin trong hp carter nhit thp (20oC chng hn). Nh vy, cn phi loi b cc phn t parafin c im kt tinh cao trong hu ht cc loi du gc.

Mc ch ca qu trnh tch parafin l lm gim im vn c (cloud point) v im chy (pour point) ca du gc nhn c t qu trnh trch ly cc hp cht thm bng cch loi b cc phn t parafin c nhit kt tinh cao. thc hin iu , phng php c s dng l kt tinh cc phn t parafin thnh dng rn bng cch lm lnh, sau tch chng ra khi du ( trng thi lng) bng phng php lc. y r rng l lnh vc c u th ca qu trnh kt tinh so vi cc phng php lc tch vt l khc v do trong thc t qu trnh ny ng vai tr quan trng trong vic sn xut cc loi du gc c cht lng cao.3.1.2. Nguyn liu v sn phm

Nguyn liu ca cng on kh parafin l dung dch lc n t phn xng trch ly cc hp cht thm.Sn phm t cng on tch parafin bao gm: - Du gc kh parafin - Sn phm c tnh parafin c tn gi l "Gatsch" hay "Slack War". Gatsch c th c bn ngay (m khng cn tinh ch) cho mt s ng dng c bit (chng hn nh sn xut cc vt liu chng thm). Tuy nhin, thng th hm lng du cn li trong gatsch l kh cao (10-25%) i vi hu ht cc ng dng ca parafin. V vy, n cn c tri qua cc cng on x l b sung khng ch hm lng du cn li trong parafin sn phm phi nh hn 0,5-2%V. y l cng on c tn gi l kh du mm (dshuilage) m n c cng mt nguyn l nh qu trnh kh parafin, chnh l qu trnh kt tinh. Sau n cng on tch parafin rn bng phng php lc. S khc nhau gia hai qu trnh l nhit vn hnh. Thc vy, nhit s vo khong t -15 n -25 oC (tu thuc vo yu cu im chy cn t c. Nhit thp kt tinh c phn du mm, cn nu ch cn kt tinh parafin th +2 n +5 l ) i vi qu trnh tch parafin trong khi qu trnh kh du mm c thc hin trong khong t +2 n +15 oC (nhit cao hn kt tinh parafin ra khi du mm lng). Sau qu trnh kh du mm ta nhn c cc sn phm sau: - Sn phm trung gian gia du kh v parafin c tn gi l du mm (base molle). - Parafin (tn gi chung). Sau , sn phm ny c th cn phi tri qua 1 qu trnh tch

62lc na phn thnh cire v parafin (tn gi ring). T l ca cc sn phm thu c t 2 qu trnh trn, thng thng l: du kh parafin : 75%; du mm : 13%; parafin : 12%

S khc bit gia Cire v parafin c th tm tt nh sau:- Parafin l mt cht rn cng, i tinh th (tinh th c kch ln) c mu trng, tu theo cht lng m c th nng chy cc nhit khc nhau v lun ln hn 50oC. - Cire l mt cht rn d dt mng thuc loi vi tinh th (tinh th c kch thc nh) c mu t trng n vng sm, nng chy trn 70oC. Thng th cc parafin c to thnh t cc phn on nh (c nht 100oC nh hn 20 mm2/s). Trong khi , Cire l sn phm t cc cn nng (c nht 100oC v khong 35 mm2/s).

Cire v parafin c rt nhiu ng dng thc t nh: - Trng ln giy carton, ln hp, ln b cha...;-Cch nhit;-Sn xut nn;-Lm cht chng thm;-Sn xut keo dn;-Sn xut xi nh g .v.v.Hnh 9.1 m t cc sn phm thu c t qu trnh kh parafin. ng thng cho chia biu thnh 2 min. Min pha trn biu din thnh phn v hiu sut parafin, min pha di-ca du kh. nghing ca ng thng phn pha s cng b khi chn lc (ca dung mi) cng cao. Trong thc t, ng ct phn pha l ng cong chm chm, iu c ngha l sn phm s cha nhiu tp cht hn. Bng 9.1 nu ln cc tnh cht vt l ca du kh, gatsch, parafin v du mm thu c t qu trnh kh parafin m nguyn liu l du lc nh ( trch ly aromatic) ca du th Bin Bc. Sau qu trnh kh parafin, du kh cn phi tri qua qu trnh hon thin kh mu, mi mi t c cc tiu chun ca du nhn gc. Du gc c rt nhiu ng dng quan trng trong nhiu lnh vc c lit k trong Bng 9.2. 3.2. KT TINH KH PARAFIN BNG DUNG MI Qu trnh kh parafin trong du nhn c s dng nhiu nht hin nay da trn phng php kt tinh vi s c mt ca mt dung mi. Dung mi ny, tn ti dng lng, s ci thin ng k cc iu kin cn bng nhit ng ca h. Mt dung mi l tng phi ho tan tt du nhn (phn du khng cha parafin) v kt ta hon ton parafin c trong du nguyn liu. Mt khc, parafin khi kt ta phi t to thnh mng tinh th khng qu cht ch nhm to iu kin cho du nhn (phn du khng cha parafin) dng lng c th i qua trong qu trnh lc v sau. Do , bin s hot ng u tin ca qu trnh tch parafin chnh l kiu loi dung mi c s dng. Mt dung mi tt cho qu trnh kh parafin cn c cc tnh cht: - ho tan v chn lc: c ho tan tt i vi du nhn v c chn lc kt ta tt i vi parafin trong qu trnh kt tinh. - C im si thp: sau khi tch parafin dung mi cn c loi khi cc sn phm bng phng php chng ct. im si thp cho php tit kim c nng lng tiu tn trong cng on ny. - Nhit ho hi v nhit dung ring nh vi cng mt l do nh trn. - im ng c thp: dung mi cn gi c trng thi lng trong sut thi gian lc. - Khng c hi, khng n mn, r v sn c.

63* C rt nhiu dung mi hoc hn hp dung mi p ng c cc yu cu k thut nu trn, trong c 1 s qu trnh ra i t xa xa nhng do cc nguyn nhn v mi trng m hin khng cn c s dng na nh: Hn hp ca acton v benzen, ra i nm 1927; Hn hp ca chlorure-ethylen v benzen, ra i nm 1930, hin c 2 qu trnh ny khng cn c s dng na do c; Propan, ra i nm 1932, hin khng cn c s dng do thit b phi lm vic di p sut propan ha lng. * Mt s loi dung mi cn ang c s dng nh cc hn hp ca Methyl-isobutylcton; Tricloro-hylen; Dichloro-methan v hn hp ca methyl-ethyl-cton v toluen (MEKToluen). Benzen (hin nay khng cn c s dng do c tnh cao) v toluen l nhng dung mi tuyt vi cho du nhn v chng ha tan rt tt du nhn (phn naphten v aromatic) nhng ng thi chng cng ho tan kh tt parafin (t kt ta c parafin) v do chng t c s dng nh mt dung mi ring r. Ngc li, Acton v Cton bc cao (methyl-ethyl-cton, methyl-propyl-cton) chng khng ho tan tt i vi du nhn v li cng khng ha tan parafin nn s kt ta tt parafin (v do c tnh chn la tt l khng ha tan parafin). Hn na, mng li tinh th parafin kt ta c nh loi dung mi ny li ph hp tt cho qu trnh lc v t lu gi du nhn trong cc tinh th ca chng. Ta gi chng l cc anti-solvant do khi trong hn hp vi toluen, chng c tc dng lm gim cc c tnh ca dung mi Toluen (l ho tan parafin). Cc hp cht ny c kh nng ho tan trung bnh nhng b li chng li c chn lc kt ta parafin cc k tt. Ta nhn thy rng hn hp ca hai dng dung mi trn cho php ta tin gn n mt dung mi l tng. Trong thc t, ta thng dng nht l hn hp ca methyl-ethyl-cton v Toluen. Dung mi methyl-ethyl-cton thng c vit tt l MEK (Methyl-Ethyl-Keton). Trong tng s cc qu trnh tch parafin hin nay, hn hp dung mi MEK-Toluen chim ti 80%, do trong phn tip theo ta ch nghin cu loi dung mi ny. Cc c tnh ca MEK v Toluen c cho trong Bng 9.3. 3.2.1 Qu trnh kh parafin bng dung mi MEK-Toluen (Hnh 9.2) Ta phn bit 3 giai on sau: Giai on kt tinh hay giai on lm lnh bng dung mi: thc hin qu trnh kh parafin bng cch lm lnh cho hn hp u gm nguyn liu (l du kh aromatic t qu trnh trch ly trc ) v dung mi MEK-Toluen. Kt thc giai on ny, hn hp i ra l 1 hn hp lng-rn (cn gi l Slurry) bao gm 2 pha:

- 1 pha lng ng nht cha phn ln du kh (~90% lng du kh) v 1 lng ln dung mi.- 1 pha rn dng tinh th cha nhiu parafin v ngm 1 lng nh du kh (~10%) v lng nh dung mi cn li. Giai on lc bng thit b lc chn khng thng quay: tch pha rn dng tinh th ra khi pha lng ng nht cha phn ln du kh Giai on chng 2 pha thu c hon nguyn dung mi

64Trc khi i su vo vic phn tch s qu trnh kh parafin, chng ta xem xt mt vi thng s c nh hng n qu trnh nh: bn cht nguyn liu, thnh phn dung mi, nhit lm lnh lc cui, t l dung mi-nguyn liu, tc lm lnh. 3.2.2. nh hng ca bn cht nguyn liu Bn cht nguyn liu c nh hng rt r rng n qu trnh kh parafin. C th l hiu qu ca qu trnh lc ph thuc trc tip vo hnh dng, cu trc tinh th parafin c to thnh trong giai on kt tinh, m cu trc ny li hon ton ph thuc vo bn cht (tnh cht vt l) ca nguyn liu. Tht vy, nguyn liu cng nht bao nhiu th tinh th to thnh cng c dng vi tinh th by nhiu (kch thc rt nh), iu s lm cho giai on lc cng kh khn. V vy, cc phn on ct nng, nht thu c thp chng chn khng khi dng lm nguyn liu cho qu trnh kh parafin th hiu qu kt tinh parafin v nng sut lc t c s thp hn so vi khi nguyn liu l phn on nh. Cc phn ct nh c nht thp, ly pha nh thp chng chn khng, gi l du Light Neutral. Cc phn ct nng c nht cao hn, ly pha thp (du DSV), gi l Heavy Neutral. Cn du chn khng (du DAO) thu c t qu trnh kh asphalt bng dung mi ca cn RSV gi l Bright Stock hoc BSS (Bright Stock Solvent). Hnh 9.3 minh ha iu ny bng vic biu din s ph thuc ca vn tc lc vo nht ca nguyn liu. Bng 9.5 lit k cc iu kin lm vic ca qu trnh kh parafin cho mt s loi nguyn liu u khc nhau. 3.2.3. nh hng ca thnh phn dung mi MEK-Toluen Khng ch bn cht ca dung mi c nh hng n qu trnh kt tinh, khi s dng dung mi hn hp, thnh phn cc hp cht to nn dung mi cng ng vai tr rt quan trng. Tht vy, nh trnh by trong phn trn, dung mi MEK c kh nng ho tan nh i vi du nhn (phn naphten v aromatic) v li cng khng ha tan parafin nn s kt ta tt parafin (v do c tnh chn la tt l khng ha tan parafin). Trong khi , Toluen li ho tan tt du nhn ng thi cng ha tan thm c mt phn parafin. V vy, cn phi ti u ho t l hai dung mi ny trong hn hp dung mi t c hiu qa cao nht khi s dng l: ha tan tt nht du nhn v kt ta tt nht parafin. Bng 9.6 minh ho cho nh hng ca thnh phn dung mi khi x l cng mt loi phn on c nht 40oC l 30mm2/s. Ta nhn thy khi tng t l MEK th: - Nhit cui ca giai on kt tinh s khng qu thp (-12 oC so vi -17 oC m vn t c im chy khng i l -7 oC nh trng hp u). iu ny s lm gim ng k tiu tn nng lng trong qu trnh kt tinh. - Tc lc tng rt nhiu (t 80 ln n 172 l/m2.h), nh vy ta c th gim thiu b mt lc. y l im ht sc quan trng v cc thit b lc thng quay c mc u t v bo tr rt ln (20 MF cho 1 thit b lc 120 m2). - Hm lng du b lu gi trong parafin nhiu hn, ngha l hiu sut thu hi du kh parafin cng thp. Tuy nhin, trong khong t l MEK thng dng (50 n 75%), nh hng ny l khng ng k lm.

65Ta thy rng dng nh l c li hn khi tng t l MEK tuy nhin trong thc t khi t l MEK qu cao s lm xut hin thm mt pha th ba l pha du mi b kt ta (gm ch yu l parafin) ngoi hai pha du/dung mi v parafin/dung mi c. S xut hin ca pha th ba s gy ra: - Tt gim hiu sut thu hi du. - H thp ch s nht ca du kh (do mt nhiu parafin trong pha du kt ta). - Nhanh chng bt kn li lc do s c mt ca pha du kt ta. xc nh nng gii hn ca MEK trong dung mi, ta trn du tch parafin vi dung mi hn hp c cha cc t l khc nhau ca MEK, sau lm lnh chng, ri ghi li cc nhit ti bt u xut hin pha th ba. Kt qu nhn c khi tin hnh th nghim trn vi du c nht 100oC l 20mm2/s v im chy l -6oC cho ta ng cong phn pha trn gin Hnh 9.4 Trn gin c xy dng mt ng thng tn gi ng "lc". ng thng ny cho php xc nh nhit lc cn thit t c sn phm c im chy l -6oC theo t l MEK c trong dung mi. ng cong "Phn pha" gii hn vng c xut hin pha th ba. V d: i vi hn hp dung mi c cha 40% MEK, cn phi lc -19oC t c sn phm c im chy -6 oC (chnh lch nhit l 13oC, tn nhiu nng lng). Cng vi hn hp dung mi c thnh phn , hin tng phn pha s xy ra -28oC. T l MEK cho php ln nht l 75% (giao im gia ng lc v ng phn tch pha). t l ny, nhit lc l -12oC v chnh lch nhit l 6oC. 3.2.4. nh hng ca nhit lm lnh lc cui (hay l nhit lc) Mc ch ca qu trnh kh parafin l nhm h thp im chy ca du kh bng cch h thp nhit lm lnh lc cui. Cn ch rng vic h qu thp nhit lm lnh lc cui s c nhc im l tiu tn nng lng, ng thi li cn lm gim t nhiu ch s nht v hiu sut thu hi du kh. V vi nguyn liu c nht khc nhau th gim ca 2 thng s trn cng khc nhau nh c trnh by trong Bng 9.7. iu ny li cng c thy r trong Hnh 9.9. Khi im chy c h thp n -13oC (so vi -10oC) th lng parafin kt tinh tch c s nhiu ln, lng du kh cn li s t i v ng thi ch s nht cng b gim. Nh vy, gi tr nhit lm lnh lc cui m qu trnh kh parafin cn phi thc hin hon ton ph thuc vo gi tr im chy ca sn phm du kh thu c. Cn lu rng tiu chun k thut v im chy ca du nhn mi vng kh hu trn th gii l khc nhau v thng thng x n i, im chy l thp v x nhit i l cao. 3.2.5. nh hng ca t l dung mi-nguyn liu Do tc dng ca hn hp dung mi l ha tan tt du kh (Toluen) v kt ta tt parafin (MEK), iu c ngha l dung mi s tch tt parafin ra khi du kh. V vy t l dung mi-nguyn liu cng ln th hiu qu qu trnh cng cao nh c th hin trn Hnh 9.10. Ta thy khi t l dung mi-nguyn liu cng ln th: hiu sut thu hi du kh cng tng (khng nhiu lm); hm lng du kh b ngm bi parafin gim rt nhiu; tc lc tng kh nhiu lc ban u, sau gim nh. 3.2.6. nh hng ca tc lm lnh

66Tc lm lnh trong giai on lm lnh c nh hng n kch thc ca tinh th v do vy s nh hng n giai on lc tch du kh ra khi parafin. Thc nghim ch ra rng: * khi tc lm lnh l qu chm s gy nn s hnh thnh cc tinh th dng hnh xon c nhiu lp d lm bt tc khng cho du kh i qua lp tinh th sp lp ny; * khi tc lm lnh l qu nhanh s gy nn s hnh thnh cc tinh th dng hnh kim c kch thc rt nh, chng d lm bt tc li lc dn n khng cho du kh i qua li. Nh vy, mt khong gi tr tc lm lnh thch hp cn c xc nh v n thng nm trong khong t 3-5oC/pht ty theo bn cht nguyn liu. 3.3. S CNG NGH KT TINH KH PARAFIN 3.3.1. S nguyn l phn xng tch parafin khng kh du mm (Hnh 9.16) 3.3.2. S nguyn l phn xng tch parafin c kh du mm Sn phm ca qu trnh kh parafin gm c du kh parafin v parafin cha lng du kh ln (10 n 25%) thng gi l gastch hay slack wax. Gastch khng m bo sch khi lm nguyn liu cho mt s chu trnh sn xut h ngun, do cn phi c tip tc x l nhm gim hm lng du xung cn chng 0,5 n 2% th tch. iu ny c thc hin trong phn xng kh du mm Hnh 9.17. Mc ch ca phn xng kh du mm l sn xut parafin sn phm thng phm, cn du mm ch l th phm. y l phn xng hot ng cng da trn nguyn tc kt tinh c nhit lm vic cao hn nhit trong phn xng kh parafin. Sn phm cui l parafin v du mm. Thc nghim cho thy khi nhit lc cng cao, parafin nhn c s c im chy cng cao, parafin cng cng nhng hiu sut thu hi parafin sn phm li gim. V mt kinh t s c li hn khi tin hnh kh du mm ngay khi bnh tinh th va i ra khi b phn lc parafin do trong bnh tinh th vn cn cha mt lng dung mi kh ln v gim c phn chi ph u t cho phn xng chng ct dung mi. Cng on ny c tn gi l cng on tch parafin c kh du mm vi s nguyn l nh trn Hnh 9.17. Trong c 2 s trn ta thy mt phn xng tch parafin bao gm cc cm chnh sau: - Cm kt tinh c nhim v lm lnh hn hp nguyn liu v dung mi nhm kt tinh parafin. - Cm lc u tin c nhim v loi du kh ra khi bnh tinh th parafin (gastch), cm lc th hai c nhim v loi du mm ra khi parafin. - Cm chng ct gm hai nhm thp chng ct i vi phn xng tch parafin khng kh du v ba nhm thp vi phn xng tch parafin c kh du. Cm chng ct m trch vic tch dung mi khi du kh, khi du mm v khi parafin. - H thng dung mi c nhim v: thu hi dung mi i ra t cc thp chng ct v cung cp dung mi cho cc hn hp nguyn liu. Ngoi ra, cn phi tnh n cm thit b lm lnh m bo kh nng lm lnh cho qu trnh kt tinh. Bng 9.8 gii thiu thng s vn hnh ca phn xng kh du mm sn xut parafin. Qua bng ny ta thy r nh hng ca nhit lc ln hiu sut thu hi cng nh ln cht lng sn phm parafin nhn c.

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Chng 4 : NG DNG QU TRNH HP PH TRONG CNG NGH LC DU4.1. TNG QUAN Cng nghip lc du v x l kh ng dng rt nhiu qu trnh hp ph, nhm 2 mc ch chnh nh sau: - Lm sch v sy kh (tch nc, tch CO2, tch lu hunh...) - Thu hi cc cu t kh qu v tch cc hn hp kh thnh cc cu t ring bit (sn xut hydro, tch i/n Parafin, O2/N2, ...) Bng 10.1 gii thiu cc ng dng chnh ca qu trnh hp ph trong cng nghip lc du v x l kh. Cht c gi l sn phm chnh l nhng cht c gi tr, l i tng quan tm ca qu trnh, thng thng chng c lu lng ln v chng l cc cht khng b hp ph gim chi ph nh (cc cht 1,2,3,4 trong Bng 10.1). Nhng i khi, cho d n ch c rt t, nhng l sn phm qu him cn phi thu hi, khi n va l sn phm chnh va l cht b hp ph (cc cht 5,6,7,8,9 trong Bng 10.1). Cht b hp ph lun lun l cht c lu lng nh. Cc loi cht hp ph thng c s dng trong cng nghip du kh, v hnh dng l cc cht rn c cu trc vi mao qun, c tng hp t qu trnh sn xut, l: than hot tnh, ry phn t carbon, oxyt nhm hot tnh (Al2O3), silicagel, st kh mu v c bit l cc loi zeolit. Zeolit thng tn ti dng kt t ng bnh nh cht gn kt v c ch to c hnh dng cc vin bi, vin thi tr c kch thc ph hp vi cc ng dng cng nghip. V cu to vt l, n l 1 dng tinh th c cu trc vi mao qun, ng knh l mao qun rt nh v mi loi zeolit li c cc ng knh khc nhau nhm gi li (hp ph) hoc cho i qua (khng hp ph) cc phn t c cc ng knh phn t khc nhau. V cng thc ha hc, zeolit l phc cht ca oxyt nhm (AlO2), oxyt silic (SiO2) v kim loi kim (Na, K) hoc kim th (Ca, Ba), c ngm nc. Cng thc tng qut ca zeolit l: Mx/n[(AlO2)x(SiO2)y],wH2O M l 1 trong cc cation Na, K, Ca, Ba; n l ha tr ca M; x, y l cc s nguyn vi y/x 1; w l s phn t nc c trong mng. Bng 10.2 gii thiu cc loi cht hp ph thng c s dng vi cc tnh cht c trng ca chng. Mt cht hp ph c gi l tt khi n c: - B mt hot ng (F) ln, dn n b mt tip xc K-R s ln, - Th tch (V) ca cc l vi mao qun nh, tc tng th tch cc khong khng gian trng, khng tip xc K-R s nh, tc l b mt hot ng ln (V ngc vi F) - ng knh l vi mao qun nh, iu ny cho php tch c phn t c kch thc rt nh ra khi phn t c kch thc ln hn. Da trn ng knh l ngi ta phn ra loi l mao qun ln (>500A), l mao qun trung (20-500A), vi l mao qun (