MC LC mc Trang
MC LC ................................................................................................... 1 YU CU V NH GI HON THNH M UN .................................... 6 BI 1 .......................................................................................................... 7 NGUN GC DU M V KH ................................................................. 7 M bi: HD A1 ............................................................................................ 7 Gii thiu .................................................................................................... 7 Mc tiu thc hin ...................................................................................... 7 Ni dung chnh ........................................................................................... 7 1.1. Ngun gc v c ................................................................................. 7 1.2. Ngun gc hu c ............................................................................... 8 1.3. Cu hi v bi tp .............................................................................. 10 BI 2 ........................................................................................................ 11 THNH PHN HA HC V PHN LOI DU M ................................ 11 M bi: HD A2 .......................................................................................... 11 Gii thiu .................................................................................................. 11 Mc tiu thc hin .................................................................................... 11 Ni dung chnh ......................................................................................... 11 2.1. Thnh phn hydrocacbon trong du m ............................................ 11
2.1.1. Hydrocacbon parafinic ......................................................... 11 2.1.2. Hydrocacbon naphtenic ....................................................... 12 2.1.3. Hydrocacbon thm (aromatic) ............................................. 13 2.1.4. Hydrocacbon loi hn hp naphten aromat .................. 142.2. Cc thnh phn phi hydocacbon ....................................................... 14
2.2.1. Cc cht cha lu hunh .................................................... 14 2.2.2. Cc cht cha nit .............................................................. 15 2.2.3. Cc cht cha oxy ........................................................... 16 2.2.4. Cc kim loi nng ............................................................. 16 2.2.5. Cc cht nha v asphanten ........................................... 16 2.2.6. Nc ................................................................................ 172.3. Phn loi du m .......................................................................... 17
2.3.1.
Phn loi du m da vo bn cht ha hc ................... 171
2.3.2.2.4.
Phn loi du m theo bn cht vt l ............................. 18Thnh phn v phn loi kh ......................................................... 19
2.4.1. 2.4.2.
Phn loi .......................................................................... 19 Thnh phn ...................................................................... 19
2.5. Cu hi v bi tp ......................................................................... 20 BI 3 ........................................................................................................ 21 CC C TNH CA DU TH V SN PHM DU M ...................... 21 M bi:HDA3 ............................................................................................ 21 Gii thiu .................................................................................................. 21 Mc tiu thc hin .................................................................................... 21 Ni dung chnh ......................................................................................... 21 3.1. Tnh bay hi ...................................................................................... 21 3.2. Tnh bt chy ..................................................................................... 22 3.3. Tnh lu chuyn................................................................................. 23
3.3.1. T trng ............................................................................... 23 3.3.2. nht ............................................................................... 23 3.3.3. Tnh lu chuyn trong iu kin lnh .................................. 243.4. Tnh n mn v s c hi ca cc sn phm du m ...................... 25 3.5. Cc bin php bo qun cc sn phm du m ................................ 25 3.6. Cu hi v bi tp .............................................................................. 26 BI 4 ........................................................................................................ 27 NG DNG CA CC PHN ON DU M ....................................... 27 M bi: HD A4 .......................................................................................... 27 Gii thiu .................................................................................................. 27 Mc tiu thc hin .................................................................................... 27 Ni dung chnh ......................................................................................... 28 4.1. Phn on kh ................................................................................... 28
4.1.1. 4.1.2.
Kh lm nguyn liu tng hp ha du ............................. 28 Kh lm nhin liu t ....................................................... 29
4.2. Phn on xng ................................................................................ 34
4.2.1. Thnh phn ha hc ........................................................ 34 4.2.2. Xng lm nhin liu ............................................................. 34 4.2.3. Cc ng dng khc ca xng........................................... 454.3. Phn on kerosen ....................................................................... 46
4.3.1. Thnh phn ha hc............................................................ 462
4.3.2. 4.4.1. 4.4.2.4.5.
ng dng ......................................................................... 47 Thnh phn ha hc ........................................................ 50 ng dng ca phn on gasoil nh ............................... 50Phn on gasoil nng (Phn on du nhn) ............................. 52
4.4. Phn on gasoil nh ........................................................................ 50
4.5.1. Thnh phn ha hc ........................................................ 52 4.5.2. ng dng ca phn on sn xut du nhn ................ 53 4.5.3. ng dng ca phn on sn xut sn phm trng .............................................................................................. 574.6. Phn on cn du m (cn gudon) ............................................. 57
4.6.1. Thnh phn ha hc............................................................ 57 4.6.2. ng dng ca phn on cn gudron ................................. 584.7. Cu hi v bi tp ......................................................................... 60 BI 5 ........................................................................................................ 62 CC C TRNG VT L V S NH GI CHT LNG DU M 62 M bi: HD A5 .......................................................................................... 62 Gii thiu .................................................................................................. 62 Mc tiu thc hin .................................................................................... 62 Ni dung chnh ......................................................................................... 62 5.1. Xc nh cc c trng vt l ca phn on du m ....................... 62
5.1.1. Thnh phn chng ct phn on ................................... 62 5.1.2. p sut hi bo ha ......................................................... 63 5.1.3. T trng ............................................................................ 64 5.1.4. t nht ........................................................................... 65 5.1.5. ng cong im si thc ............................................... 66 5.1.6. im anilin........................................................................ 67 5.1.7. Nhit chp chy .......................................................... 68 5.1.8. Nhit ng c, im ng c v im kt tinh ......... 69 5.1.9. Nhit chy ........................................................................ 70 5.1.10.Hm lng nc trong phn on du m ........................ 70 5.1.11.Tr s octan ......................................................................... 715.2. nh gi cht lng ca du m qua cc c trng sau .............. 71
5.2.1.
Thnh phn hydrocacbon trong du m ........................... 713
5.2.2. T trng ............................................................................ 72 5.2.3. H s c trng K ............................................................ 72 5.2.4. Hm lng cc hp cht cha cc nguyn t d th 72 5.2.5. nht ............................................................................ 73 5.2.6. Nhit ng c ............................................................ 74 5.2.7. Nhit chp chy .......................................................... 74 5.2.8. Hm lng cc conradson ............................................... 74 5.2.9. Kim loi nng trong du ................................................... 745.3. Cu hi v bi tp ......................................................................... 75 TI LIU THAM KHO ............................................................................. 76
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GII THIU V M UNV tr, ngha, vai tr m un: L m un u tin trc khi hc vin hc vo kin thc chuyn ngnh, l tin cho hc vin tip cn vi lnh vc du kh sau ny. Mc tiu ca m un: M un nhm trang b cho hc vin c kin thc c bn mt cch khi qut nht v chuyn ngnh ha du. Gip cho hc vin d dng tip thu cc kin thc chuyn ngnh. Bit c ngun gc ca du m v s hnh thnh du m Bit c thnh phn ha hc ca du m Nm c cc ng dng ca du m trong i sng
Mc tiu thc hin ca m un: Hc xong m un ny hc vin c kh nng: M t c thnh phn ha hc ca du m Phn loi c du m nh gi c cht lng ca du th v sn phm du thng qua cc tnh cht ha l c trng. M t c cc ng dng ca cc phn on du m. Ni dung chnh/cc bi ca m un: Bi 1: Ngun gc ca du m v kh Bi 2: Thnh phn ha hc v phn loi du m Bi 3: Cc c tnh ca du th v sn phm du m Bi 4: ng dng ca cc phn on du m Bi 5: Cc c trng vt l v s nh gi cht lng du m
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CC HNH THC HC TP CHNH TRONG M UN
-
Hc trn lp cc kin thc c bn v ha hc du m v kh T nghin cu ti liu lin quan n ha hc du m v kh Tham quan cc thit b ha du-Kho cu th trng cung cp du th v kh trn th gii v Vit Nam
YU CU V NH GI HON THNH M UN V kin thc Gii thch c cc phn ng trong qu trnh hnh thnh du m v kh. M t c thnh phn ca du th M t c ng dng ca cc phn on du m Nm c cc c trng ha l ca du th v nh gi cht lng du th v sn phm du. V k nng Tr li c cc cu hi trong qu trnh hc. Nghin cu tm kim ti liu lin quan n qu trnh hc Lm c cc tiu lun v t chc thuyt trnh trc lp. Hc hi v gip bn hiu tt cc ni dung ca m un, lm c s hc m un tip theo. V thi Nghim tc trong hc tp v tm kim ti liu. Ch ng tm kim cc thng tin trn mng.
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BI 1 NGUN GC DU M V KH M bi: HD A1Gii thiu Du m v kh l nhng khong cht phong ph nht trong t nhin, chng c mt nhiu ni trong lng t. gip cho vic tm kim cc khu vc cha du kh, ta i nghin cu ngun gc ca du kh l rt quan trng C rt nhiu kin tranh lun v ngun gc ca du kh, nhng ch yu l hai gi thuyt: Gi thuyt v ngun gc v c Gi thuyt v ngun gc hu c
Mc tiu thc hin Hc xong bi ny hc vin c kh nng: M t ngun gc ca du m v kh Ni dung chnh 1.1. Ngun gc v c Theo gi thuyt ny trong lng Tri t c cha cc cacbua kim loi nh Al4C3, CaC2. Cc cht ny b phn hy bi nc to ra CH4 v C2H2: Al4C3 CaC2 + + 12H2O 2H2O 4Al(OH)3 Ca(OH)2 + + 3CH4 C 2 H2
Cc cht khi u (CH4, C2H2) qua qu trnh bin i di tc dng ca nhit , p sut cao trong lng t v xc tc l cc khong st, to thnh cc hydrocacbon c trong du kh. chng minh cho iu , nm 1866, Berthelot tng hp c hydrocacbon thm t axetylen nhit cao trn xc tc. Nm 1901, Sabatier v Sendereus thc hin phn ng hydro ha axetylen trn xc tc Niken v st nhit trong khong 200 3000C, thu c mt lot cc hydrocacbon tng ng nh trong thnh phn ca du. Cng vi hng lot cc th nghim nh trn, gi thuyt v ngun gc v c ca du m c chp nhn trong mt thi gian kh di.
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Sau ny, khi trnh khoa hc v k thut ngy cng pht trin th ngi ta bt u hoi nghi lun im trn v: phn tch c (bng cc phng php hin i) trong du m c cha cc Porphyrin c ngun gc t ng thc vt. Trong v qu t, hm lng cacbua kim loi l khng ng k. Cc hydrocacbon thng gp trong cc lp trm tch, ti nhit t khi vt qu 150-2000C (v p sut rt cao), nn khng nhit cn thit cho phn ng ha hc xy ra. Chnh v vy m gi thuyt ngun gc v c ngy cng phai m do c t cn c. 1.2. Ngun gc hu c l gi thuyt v s hnh thnh du m t cc vt liu hu c ban u. Nhng vt liu chnh l xc ng thc vt bin, hoc trn cn nhng b cc dng sng cun tri ra bin. trong nc bin c rt nhiu cc loi vi khun hiu kh v ym kh, cho nn khi cc ng thc vt b cht, lp tc b chng phn hy. Nhng phn no d b phn hy (nh cc cht Albumin, cc hydrat cacbon) th b vi khun tn cng trc to thnh cc cht d tan trong nc hoc kh bay i, cc cht ny s khng to nn du kh. Ngc li, cc cht kh b phn hy (nh cc protein, cht bo, ru cao phn t, sp, du, nha) s dn lng ng to nn lp trm tch di y bin; y chnh l cc vt liu hu c u tin ca du kh. Cc cht ny qua hng triu nm bin i s to thnh cc hydrcacbon ban u: RCOOR RCOOH RCH2OH R-CH=CH2 + H2 + H2O RCOOH RH + R-CH=CH2 R-CH2-CH3 + CO2 + H2O ROH
Theo tc gi Petrov, cc axt bo ca thc vt thng l cc axit bo khng no, s bin i to thnh -lacton, sau to thnh naphten hoc aromat: Thuyt ngun gc hu c ca du m cho php gii thch c nhiu hin tng trong thc t. Chng hn nh: du m cc ni hu nh u
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khc nhau, s khc nhau c th l do vt liu hu c ban u. V d, nu vt liu hu c ban u giu cht bo th c th to ra loi du parafinic Du c sinh ra ri rc trong cc lp trm tch, c gi l m. Do p sut y cao nn chng b y ra ngoi v buc phi di c n ni mi qua cc tng cha thng c cu trc rng xp. S di chuyn tip tc xy ra cho n khi chng gp iu kin thun li c th li y v tch t thnh du m. Trong qu trnh di chuyn, du m phi i qua cc tng xp, c th s xy ra s hp ph, cc cht c cc b hp ph v li cc lp , kt qu l du s nh hn v sch hn. Nhng nu qu trnh di chuyn ca du b tip xc vi oxy khng kh, chng c th b oxy ha dn n to cc hp cht cha cc d nguyn t, lm du b gim cht lng. Khi du tch t v nm trong cc m du, qu trnh bin i hu nh t xy ra nu m du kn. Trong trng hp c cc khe h, oxy, nc kh quyn c th lt vo, s xy ra bin cht theo chiu hng xu i do phn ng ha hc. Cc hydrocacbon ban u ca du kh thng c phn t lng rt ln (C30 C40), thm ch cao hn. Cc cht hu c ny nm trong lp trm tch s chu nhiu bin i ha hc di nh hng ca nhit , p sut, xc tc (l khong st). Ngi ta thy rng, c ln chm su xung 30 mt, th nhit trong lp trm tch tng t 0,54 1,200C, cn p sut tng t 3 7,5 atm. Nhng vy su cng ln, nhit , p sut cng tng v trong cc lp trm tch to du kh, nhit c th ln ti 100 2000C v p sut t 200 1000 at. iu kin ny, cc hydrocacbon c phn t ln, mch di, cu trc phc tp s phn hy nhit, to thnh cc cht c phn t nh hn, cu trc n gin hn, s lng vng thm t hn Thi gian di cng l cc yu t thc y qu trnh cracking xy ra mnh hn. Chnh v vy, tui du cng cao, ln chm cng su, du c to thnh cng cha nhiu hydrocacbon vi trng lng phn t cng nh. Su hn na c kh nng chuyn ha hon ton thnh kh, trong kh metan l bn vng nht nn hm lng ca n rt cao. Cng chnh v vy, khi tng
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chiu su ca cc ging khoan thm d du kh th xc sut tm thy kh thng cao hn. 1.3. Cu hi v bi tp 1. 2. 3. 4. 5. Theo thuyt ngun gc v c th du m c hnh thnh nh th no? Ti sao thnh phn cc m du li khc nhau? Bng chng no chng t du m c ngun gc hu c? Ti sao trong qu trnh di c du li bin i cht lng, theo chiu hng no? V sao? V sao tui du cng cao th cng cha nhiu hydrocacbon vi trng lng phn t cng nh?
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BI 2 THNH PHN HA HC V PHN LOI DU M M bi: HD A2Gii thiu Du m l mt hn hp rt phc tp, trong c hng trm cu t khc nhau. Mi loi du m c c trng bi thnh phn ring, nhng v bn cht, chng u c cc hydrocacbon l thnh phn chnh, chim 60 n 90% trng lng du, cn li l cc cht cha oxy, lu hunh, nitTrong kh cn cha cc kh tr nh: N2, He, Ar. Mt iu cn lu l tuy du m trn th gii rt khc nhau v thnh phn ha hc, nhng li rt ging nhau v thnh phn nguyn t (hm lng C dao ng trong khong 83 n 87%, cn H t 11 n 14%). Mc tiu thc hin Hc xong bi ny hc vin c kh nng: M t c thnh phn ca du m Phn loi du m Thnh phn hydrocacbon trong du m Cc thnh phn phi hydrocacbon trong du m Phn loi du m Thnh phn v phn loi kh
Ni dung chnh
2.1. Thnh phn hydrocacbon trong du m Hydrocacbon l thnh phn chnh ca du, hu nh cc loi hydrocacbon (tr olefin) u c mt trong du m. Chng c chia thnh cc nhm parafin, naphten, aromat, hn hp naphtenaromat. 2.1.1. Hydrocacbon parafinic Hydrocacbon parafinic (cn gi l alcan) l loi hydrocacbon ph bin nht. Trong du m chng tn ti ba dng: kh, lng, rn. Cc hydrocacbon kh (C1C4), khi nm trong du, do p sut cao nn chng tn ti th lng v ha tan trong du m. Sau khi khai thc, do p sut gim, chng thot ra khi
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du. Cc kh ny gm metan, etan, propan v butan gi l kh ng hnh, ngoi ra cn c mt lng rt nh pentan bay hi ra cng. Trong du m c hai loi parafin: nparafin v izoparafin, trong n parafin chim a s (2530% th tch) chng c s nguyn t t C1 n C45. Cc n parfin c s nguyn t cacbon bng hoc ln hn C18, nhit thng chng l cht rn. Cc parafin ny c th ha tan trong du hoc to thnh cc tinh th l lng trong du. Khi hm lng cc parafin ln qu cao, du c th b ng c, gy kh khn cho qu trnh vn chuyn. Hm lng ca chng cng cao, nhit ng c ca du cng ln. Khi bm v vn chuyn cc loi du ny phi p dng cc phng php sau: Gia nhit ng ng, cho thm ph gia, tch bt parafin rn ti ni khai thc h im ng c. Cc parafin rn tch t du th l nguyn liu qu tng hp ha hc, iu ch cht ty ra tng hp, t si nhn to, phn bn, cht do Cc izo parafin thng ch nm phn nh v phn c nhit si trung bnh ca du. Chng thng c cu trc n gin, mch chnh di, nhnh ph t v ngn, nhnh ph thng l nhm metyl. Cc izo parafin c s cacbon t C5 n C10 l cc cu t rt qu, chng lm tng kh nng kh nng chng kch n (tng tr s octan) ca xng. 2.1.2. Hydrocacbon naphtenic Naphtenic (xyclo parafin) l mt trong s hydrocacbon ph bin v quan trng trong du m. Hm lng c th thay i t 30 n 60% trng lng. Chng thng dng vng 5, 6 cnh, cng c th dng ngng t 2 hoc 3 vng. Cc hydrocacbon naphtenic c mt trong cc phn on nh (thng l mt vng v t nhnh ph) hoc phn nhit trung bnh v cao (khi l cc cu t c nhiu vng v nhnh ph di).(CH2)11-CH3
R
R
(CH2)10-CH3 H3C CH3 CH3
R
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Hydrocacbon naphtenic l thnh phn rt quan trng trong nhin liu ng c v du nhn. Cc naphtenic mt vng lm cho xng c cht lng cao; nhng hydrocacbon naphtenic mt vng c mch nhnh di l thnh phn rt tt cho du nhn v chng c nht cao v t thay i theo nhit . c bit, chng l cc cu t rt qu cho nhin liu phn lc, do chng c nhit chy cao, ng thi gi c tnh linh ng nhit thp. Hydrocacbon naphtenic trong du m cn l nguyn liu qu t iu ch cc hydrocacbon thm: benzen, toluen, xylen (BTX), l cc cht khi u trong sn xut t si tng hp, cht do v thuc nhum Du m cha nhiu hydrocacbon naphtenic l nguyn liu tt cho sn sut du nhn c cht lng tt. Chng li c nhit ng c thp nn gi c tnh linh ng, khng gy kh khn cho qu trnh bm, vn chuyn, phun nhin liu. 2.1.3. Hydrocacbon thm (aromatic) Hydrocacbon thm thng gp l loi mt vng v ng ng ca chng (benzen, toluen, xylen). Cc cht ny thng nm trong phn nh v l cu t lm tng kh nng chng kch n ca xng. Cc cht ngng t 2, 3 hoc 4 vng thm c mt trong phn c nhit si trung bnh v cao ca du m; hm lng cc cht ny thng t hn.
CH3 CH3 CH3 bezen toluen xylen naphtalen
antraxen
pyren
diphenyl
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Khc vi nhin liu xng, nhin liu phn lc v diezen, nu hm lng aromat nhiu th chng lm gim cht lng ca cc loi nhin liu do kh t bc chy v to cc, to cn trong ng c. Cc cu t aromat mt vng c nhnh ph di l nguyn liu qu sn xut du nhn c nht v ch s nht cao. 2.1.4. Hydrocacbon loi hn hp naphten aromat Loi ny rt ph bin trong du, chng thng nm phn on c nhit si cao. Mt s hydrocacbon hn hp naphten aromat thng gp trong du m c cu trc nh sau:
tetralin
indan
xyclohexylbenzen
2.2. Cc thnh phn phi hydocacbon 2.2.1. Cc cht cha lu hunh Trong thnh phn phi hydrocacbon cc hp cht lu hunh l ph bin nht, chng lm xu i cht lng ca du th. Cc loi du cha t hn 0,5% lu hunh l loi du tt, du cha t 2% lu hunh tr ln l loi du xu. Cc cht cha lu hunh thng dng sau: - Mercaptan - Sunfua - Disunfua - ThiophenS
R-S-H R-S-R R-S-S-R
- Lu hunh t do
S, H2S
Lu hunh dng mercaptan: mercaptan l cc hp cht c nhm SH lin kt trc tip vi gc hydrocacbon, chng khng bn v d phn hy nhit cao: 2RSH RSH3000C
R-S-R + H2S R-CH=CH2 + H2S
5000C
Cc cht mercaptan thng c trong phn on nhit si thp, gc hydrocacbon thng t C1 C8.14
Lu hunh dng sunfua v disunfua: cc cht ny thng c cc phn on c nhit si trung bnh v cao. Gc hydrocacbon c th l mch thng, vng no hoc vng thm. V d:
SR
(CH2)n
SR
Lu hunh dng thiophen: cc hp cht cha lu hunh dng thiophen c cu trc mch vng, nh:
S thiophen
S benzothiophen
S dibenzothiophen
Thiophen l loi cht cha lu hunh ph bin nht (chim t 45 92% trong tt c cc dng hp cht cha lu hunh ca du m). Chng thng c phn nhit si trung bnh v cao ca du. Lu hunh dng t do: l lu hunh dng nguyn t v dng H 2S. Da vo hm lng lu hunh dng H2S c trong du m ngi ta phn thnh hai loi du: du chua lng H2S > 3,7 ml/ 1 lit du, du ngt lng H2S < 3,7 ml/ 1 lit du. 2.2.2. Cc cht cha nit Cc cht cha nit thng c rt t trong du m (0,01 n 1% trng lng), chng nm trong phn on c nhit si cao, thng c 1, 2 hoc 3 nguyn t Nit. Nhng hp cht c mt nguyn t nit thng c tnh baz v l loi chnh. Mt s v d v cc hp cht cha mt nit nh sau:N izo-quinolin
N pyridin
N quinolin
N acridin
N H pyrol
N H indol
N H cacbazol
N H benzocacbazol
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2.2.3. Cc cht cha oxy Cc cht cha oxy trong du m thng tn ti di dng axit, xeton, phenol, ete, estetrong cc axit v phenol l quan trng hn c, chng thng nm nhit si trung bnh v cao. Cc phenol thng gp l:OH OH OH
phenol
CH3 crezol
naphtol
2.2.4. Cc kim loi nng Hm lng cc kim loi c trong du thng khng nhiu (vi phn triu). Chng c trong cu trc ca cc phc kim loi, ch yu l phc ca hai nguyn t V v Ni. Ngoi ra cn c mt lng rt nh cc nguyn t khc nh Fe, Cu, Zn, Ti Hm lng kim loi nng nhiu s nh hng n qu trnh ch bin xc tc, chng s lm ng c xc tc. V vy, i vi qu trnh cracking v reforming, yu cu hm lng ny khng c qu 5 n 10 ppm. 2.2.5. Cc cht nha v asphanten Nha v asphanten l nhng cht cha ng thi cc nguyn t C, H, O, S, N; c phn t lng rt ln (500 600 vC tr ln). Nhn b ngoi chng u c mu sm, nng hn nc, v khng tan trong nc. Chng u c cu trc h vng thm ngng t cao, thng tp trung nhiu phn nng, nht l trong cn du m. Tuy nhin cng c th phn bit c nha v asphanten theo cc c im sau y: Nha Trng lng phn t: 600 vC D tan trong dung mi hu c. Khi tan to dung dch thc thm ha: 0,14 0,25 1000 vC Kh tan trong dung mi hu c. Khi tan to dung dch keo thm ha: 0,2 0,7 Asphanten Trng lng phn t: 1000 2500
Cc cht nha v asphanten thng c nhiu phn nng, c bit l phn cn sau khi chng ct, chng u lm xu i cht lng ca du m. S c mt ca chng trong nhin liu s lm cho sn phm b sm mu, khi chy
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khng ht s to cn, u c xc tc. Tuy nhin, du m no cha nhiu nha v asphanten s l ngun nguyn liu tt sn xut nha ng 2.2.6. Nc Trong du m, bao gi cng c ln mt lng nc nht nh, chng tn ti dng nh tng. Cc nguyn nhn dn n s c mt ca nc trong du m, l: nc c t khi thnh nn du kh do s ln chm ca cc vt liu hu c di y bin v nc t kh quyn ngm vo cc m du. Nc trong du m cha mt lng rt ln cc mui khong. Cc cation v anion thng gp l: Na+, Ca2+, Mg2+, HCO3-, SO42-Ngoi ra cn mt s oxit khng phn ly dng keo nh: Al2O3, Fe2O3, SiO2. Khi khai thc du, lng, nc s tch ra khi du. Trong trng hp nc to thnh h nh tng bn vng, lc mun tch nc phi dng ph gia ph nh. Cn ch mt s mui khong trong nc b thy phn to ra axit, gy n mn thit b theo phn ng: MgCl2 MgCl2 + + 2H2O 2H2O Mg(OH)2 Mg(OH)Cl + + 2HCl HCl
2.3. Phn loi du m Du th mun a vo cc qu trnh ch bin hoc bun bn trn th trng, cn phi xc nh xem chng thuc loi no: du nng hay nh, du cha nhiu hydrocacbon parafinic, naphtenic hay aromatic, du c cha nhiu lu hunh hay khng. T mi xc nh c gi tr trn th trng v hiu qu thu c cc sn phm khi ch bin. C nhiu phng php phn loi du m, nhng thng da vo ch yu hai phung php, l: da vo bn cht ha hc v bn cht vt l. 2.3.1. Phn loi du m da vo bn cht ha hc Phn loi theo bn cht ha hc c ngha l da vo thnh phn cc loi hydrocacbon c trong du. Nu trong du, h hydrocacbon no chim phn ch yu th du m s mang tn loi . V d, du parafinic th hm lng hydrocacbon parafinic trong phi chim 75% tr ln. Tuy nhin trong thc t, khng c bt k m du no li c thun chng mt loi hydrocacbon nh vy, nh vy thng ch c du trung gian; v d, mt loi du no c: hn
17
50% parafinic, ln hn 25% naphtenic v cn li l cc loi khc th c gi l du napten-parafinic C nhiu phng php khc nhau phn loi theo bn cht ha hc: Phn loi theo Nelson, Waston v Murphy: theo cc tc gi ny, du m c c trng bi cc h s K, l mt hng s vt l quan trng, c trng cho bn cht ha hc ca du m, c tnh theo cng thc:3
K
T d
T: nhit si trung bnh ca du th, tnh bng Reomuya (0R), 10R=1,250C. d: t trng ca du th, xc nh 15,60C (600F) so vi nc cng nhit . Gii hn h s K c trng phn chia du m nh sau: Bng 2.1. H s K c trng ca cc h du m khc nhau Du m h parafinic Du m h trung gian Du m h naphtenic Du m h aromatic K=13 12,15 11,5 10,5 K=12,10 K=11,45 K=10
2.3.2. Phn loi du m theo bn cht vt l Cch phn loi ny da theo t trng, bit t trng c th chia du th theo ba cp. 1. 2. 3. Du nh: Du trung bnh: Du nng:
d15 4 d15 4 d15 4
0,830 0,830 0,884 0,884
Hoc c th phn du theo 5 cp sau: 1. 2. 3. 4. 5. Du rt nh: Du nh va Du hi nng: Du nng: Du rt nng
d15 4 d15 4 d15 4 d d15 4 15 4
0,830 0,830 0,850 0,850 0,865 0,865 0,905 0,905
18
Ngoi ra trn th trng th gii cn s dng 0API thay cho t trng v0
API c tnh nh sau:0
API
141,5 d15,6 15,6
131,5
Du m c 0API cng nh th du cng nng. 2.4. Thnh phn v phn loi kh 2.4.1. Phn loi Kh hydrocacbon trong t nhin c phn loi theo ngun gc nh di y: Kh thin nhin: L cc kh cha trong cc m kh ring bit. Trong kh ny thnh phn ch yu l metan (chim t 70 99%), cn li cc kh khc nh etan, propan v rt t butan. Kh ng hnh: l kh nm ln trong du m, c hnh thnh cng vi du, thnh phn ch yu l cc kh propan, butan, pentan Kh ngng t (Condensate): Thc cht l dng trung gian gia du v kh (phn cui ca kh v phn u ca du), bao gm cc hydrocacbon nh propan, butan v mt s hydrocacbon lng khc nh pentan, hexan, thm ch hydrocacbon naphtenic v aromatic n gin. iu kin thng, kh ngng t dng lng. Kh ngng t l nguyn liu qu sn xut LPG v s dng trong tng hp ha du. 2.4.2. Thnh phn c trng ch yu ca kh thin nhin v kh du m bao gm hai phn: phn hydrocacbon v phi hydrocacbon. Cc hp cht hydrocacbon: Ch yu l cc kh metan v ng ng ca n nh: etan, propan, n butan, izo butan, ngoi ra cn mt t cc hp cht C5, C6. Hm lng cc cu t trn thay i ty theo ngun gc ca kh. V d, trong kh thin nhin cha ch yu l metan, cc kh nng C3 n C4 rt t; cn trong kh ng hnh, hm lng cc kh C3, C4 cao hn. Cc hp cht phi hydrocacbon: Ngoi thnh phn chnh l hydrocacbon, trong kh thin nhin v kh du m cn cha cc hp cht khc nh: CO2, N2, H2S, H2, He, Ar, NeTrong cc loi kh k trn, thng kh N2 chim phn
19
ln. c bit, c nhng m kh cha He vi hm lng kh cao nh cc m kh t nhin M. Ngi ta c th s dng cc m kh lm ngun nguyn liu sn xut cc kh tr, thu hi H2S phc v cho cng nghip. 2.5. Cu hi v bi tp 1. 2. 3. 4. 5. 6. Nu vn tt cc thnh phn chnh trong du th, ti sao trong du th khng c mt ca olefin? Khi nim v h s c trng K? Lin quan n thnh phn du th nh th no? K tn cc loi du trung gian? Phn bit kh t nhin v kh ng hnh? nh hng ca cc hp cht Lu hunh n cht lng du th? Phn bit du chua v du ngt. Phn bit nha v asphanten. Tc hi ca nha v asphanten i vi nhin liu?
20
BI 3 CC C TNH CA DU TH V SN PHM DU M M bi:HDA3Gii thiu s dng cc sn phm du kh mt cch c hiu qu v bo m an ton cho ngi s dng, chng ta phi bit c cc c tnh ca sn phm. T xut cc bin php bo v sn phm trong qu trnh tn tr v bo qun mt cch hiu qu nht. Mc tiu thc hin Hc xong bi ny hc vin c kh nng: M t cc tnh cht ca du th v cc sn phm du m xut cc bin php hp l tn tr v bo qun du m trnh
s bay hi. Ni dung chnh 3.1. Tnh bay hi Tnh bay hi c trng cho kh nng chuyn t dng lng sang dng hi ca mt sn phm. Ty thuc vo nhit , p sut mt cht c th tn ti dng ny hay dng khc, hay cc dng nm cn bng vi nhau. i vi cc nguyn cht, p sut xc nh, s ha hi xy ra nhit khng i. Khi p sut tng th nhit ha hi tng. p sut do pha hi gy ra nm cn bng vi pha lng nhit xc nh gi l p sut hi. i vi cu t nh d bay hi th p sut hi cng cao v nhit si cng thp. Ngc li cu t cng nng cng kh bay hi th p sut hi cng thp v nhit si cng cao. Nhng i vi cc sn phm du kh c c trng bi khong nhit si. V d phn on xng, khong nhit si t 300C n 1800C. Trong qu trnh s dng cc sn phm nng lng phi chuyn t dng lng khi tn tr sang dng hi khi s dng. V vy n i hi phi c giai on ha hi, i vi cc sn phm du kh, s ha hi xy ra nhit tng dn trong qu trnh ha hi. Mt khc, mt c im rt quan trng c lin quan21
n qu trnh ha hi l s ha hi tiu th nng lng. Ngc li qu trnh ngng t l qu trnh ta nhit. y l cc c tnh cn phi ch khi s dng cc sn phm du kh, v n dn n vn nh: lm h nhit mi trng, kh khi ng ng c iu kin lnh 3.2. Tnh bt chy Chy l qu trnh oxi ha mt cht din ra rt nhanh v km theo ta nhiu nhit, y l qu trnh phc tp, trong phn ng oxy ha l c s ca qu trnh t chy cc sn phm du kh bng oxi (khng kh) th s to thnh cc sn phm chy CO2, H2O, SO2Nhit tr ca cc cht c th tham kho bng 3.1 (C, H, S) + O2 CO2 + H2O + SO2 + Q Cc sn phm du kh c nhit tr cao, t l H/C cng cao v hm lng lu hunh cng thp th nhit tr cng cao. Nhng qu trnh chy xy ra hon ton nht thit phi hi t cc iu kin sau: Cn thit phi a sn phm sang dng hi. S dng lng thch hp khng kh v sn phm: qu trnh chy
xy ra th t l nhin liu v khng kh phi nm trong khong gia gii hn chy di v gii hn chy trn.Vng chy c
D khng kh
D nhin liu
Gii hn chy di
Chy hp thc
Gii hn chy trn
% Nhin liu trong khng kh
Cn c nng lng khi mo: tia la in ca buri, ngn la mi hoc nhit cao. Bng 3.1. Nhit chy ca mt s cht Cht t C H S Sn phm chy Kh CO2 Hi H2O Kh SO2 Nhit tr (kcal/ kg) 8133 29100 2322
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3.3. Tnh lu chuyn S lu chuyn ca cc sn phm du kh thng qua hai thng s: t trng v nht, l hai thng s thay i theo nhit , khi nhit tng t trng v nht gim, nh hng ny l ng k. 3.3.1. T trng T trng l t s gia trng lng ring ca mt vt mt nhit nht nh v trng lng ring ca mt vt khc c chn l chun, xc nh cng v tr. i vi cc loi sn phm du lng u ly nc ct nhit 40C v p sut 760 mmHg lm chun. T trng ca du m, hoc mt phn on du m nhit t trn trng lng ring ca nc 40C, ta c th ghi dt4. d so snh, t trng c biu th cng mt nhit , phn ln cc nc u ly 200C (d204) hoc 15,60C (tng ng vi 600F) so vi nc cng nhit . mt s nc cn biu th t trng bng 0API. Cng thc chuyn i t trng sang 0API nh sau:0
API
141,5 d15,6 15,6
131,5
T trng ca sn phm du m thay i rt nhiu khi nhit thay i, nhng khng ph thuc vo p sut. Tuy nhin nu p sut cao th c nh hng cht t. 3.3.2. nht nht l tnh cht ca mt cht lng, c xem l ma st ni ca cht lng v cn tr s chy ca cht lng. Nguyn nhn c nht l do i lc c hc gia cc ht cu to nn cht lng. nht ca du m c lin quan n qu trnh bm vn chuyn, s bi trn, s phun nhin liu trong cc ng c. nht ph thuc vo nhit , khi nhit tng nht gim. nht ng lc ( hoc ): nht ng lc biu th cho cc cht lng dng khng c gia tc, c tnh bng cng thc: Trong : l thi gian chy ca cht lng
23
l hng s nht k, khng ph thuc vo nhit m ch ph thuc vo kch thc hnh hc ca nht k. Nu nht ln phi dng nht k c ng knh mao qun ln; cn nht ca cht lng cn o nh, th dng nht k c ng knh mao qun nh; sao cho thi gian chy ca cht lng khng qu 200 giy. nht ng lc c tnh bng poaz (P) hay centipoaz (cP). 1 P=100 cP=0,1 N.s/ m2=1 dyn.s/ cm2=1 g/cm.s nht ng hc ( ): nht ng hc l t s gia nht ng lc hc v khi lng ring ca n (c hai u xc nh cng nhit v p sut): d
Trong :
l nht ng hc, tnh bng stc (St) hoc centistc (cSt) l nht ng lc d l khi lng ring, g/cm3 1 St=1 cm2/s=100 cSt
Cc sn phm du kh c nht cng cao th tnh lu ng cng thp. nht cn nh hng n kh nng bm, kh nng phun sng v kh nng bi trn. 3.3.3. Tnh lu chuyn trong iu kin lnh Khi nhit ca sn phm du kh gim, nht tng dn n tnh lu chuyn gim. Nu tip tc gim nhit , bt u xut hin cc vi tinh th rn, cc tinh th ny to dn n mt lc no lu cht s c li v ng khi lm cn tr qu trnh lu chuyn. Kh nng kt tinh ph thuc vo cc hydrocacbon c mt trong sn phm v c xp theo th t tng dn nh sau: Aromatic < Naphtenic < iso-parafinic < n-parafinic Nh vy kh nng kt tinh ch yu l do n-parafinic v tng dn khi s nguyn t cacbon tng. V d nhit kt tinh ca mt s n-parafinic c cho trong bng 3.2.
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Bng 3.2. Nhit kt tinh ca n-parafinic nparafinic -138 (0C) T0kt nC4H10 nC8H18 -57 nC16H34 +18 nC26H54 +56 nC44H90 +86
3.4. Tnh n mn v s c hi ca cc sn phm du m Khi t chy cc sn phm du kh s sinh ra mt lng ln kh thi gm: CO2, CO, SO2, NOx v mui than gy nhim bu kh quyn, c hi i vi con ngi v thc vt. Ngoi ra trong khi thi cn c mt lng ch gy nh hng n sc khe cng ng. Cc hp cht ch hu c i vo c th ngi qua phi v rut thm ch c th hp th qua da. nh hng c hi ca ch hu ht l i vi h thn kinh. Cc triu chng nhim c r rng l mt ng, c nhng gic m kinh hong, mt tp trung, km n, bun nn, ri lon cm xc Cc hp cht SOx sinh ra trong khi thi khi gp hi nc trong khng kh to thnh axit gy n mn ng c. SO2 + 1/2O2 SO3 + H2O SO3 H2SO4
Ngoi ra trong cc sn phm du kh c th cha cc hp cht axt m chng c mt nh cc ph gia hoc cc sn phm bin cht to thnh trong qu trnh tn tr, cc hp cht lu hunh m ch yu l cc hp cht mercaptan (RSH), cc hp cht oxi, cc axit hu c (RCOOH). S c mt ca chng s gy nn qu trnh n mn ng ng v cc thit b tn tr. 3.5. Cc bin php bo qun cc sn phm du m Phi bo qun mi loi sn phm du m trong cc phng tin cha ring, m bo gi gn tt cht lng v khng c cht bn v nc ri vo sn phm. Trong qu trnh s dng b ngm, phi nh k o mc sn phm du m v kim tra tnh trng ho rnh xung quanh b. Khi pht hin thy mc sn phm gim nhiu hoc c hin tng r chy phi tm nguyn nhn v tin hnh sa cha kp thi.
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Cc sn phm du m cha trong phuy phi c bo qun ring tng loi trong cc nh kho, di cc mi che hoc trn cc bi l thin c san bng. Ch c php cha sn phm d bay hi trong cc phuy bng kim loi. Khi tip xc vi cc sn phm du m l cc cht d bt la v c tnh c hi phi s dng cc phng tin bo h lao ng. Cc ch xut nhp sn phm du m v qun l cc phng tin vn chuyn phi theo ng cc quy nh. Cc b kim loi ca cc dn xut, cc ng dn, cc vi phun trong thi gian xut nhp sn phm du m phi c tip t. Cc cu thang ln xung, cc tay vn, cc ca np ca cc phng tin cha ng v vn chuyn phi chc chn v sch s m bo an ton lao ng. 3.6. Cu hi v bi tp 1. 2. 3. 4. 5. 6. 7. 8. nh hng ca bay hi n qu trnh thit k cc bn b cha nh th no? Nhng yu t no nh hng n qu trnh lu chuyn ca cc sn phm du kh? Cc iu kin qu trnh chy xy ra? Chy hp thc l g? ngha chung v ring ca t trng i vi cc sn phm du m? Cc bin php bo qun cc sn phm du m? Cc nguyn nhn gy nn hao ht sn phm du? Cc bin php chng hao ht?
26
BI 4 NG DNG CA CC PHN ON DU M M bi: HD A4Gii thiu Du m mun s dng c th phi tin hnh phn chia thnh tng phn on nh. Qu trnh phn chia da vo phng php chng ct thu c cc khong nhit si khc nhau. u tin, khi khai thc do c s gim p sut nn phn on kh b tch ra, thng t C 1 n C4 v mt lng rt t C5, C6. Sau , ty thuc vo gii hn nhit si m ta thu c cc phn on sau: Phn on xng: nhit si nh hn 1800C, bao gm cc thnh phn t C5-C11. Phn on kerosen: nhit si t 180 n 2500C, cha cc hydrocacbon t C11-C16. Phn on gasoil nh (cn gi l phn on iezen): nhit si t 250-3500C cha cc thnh phn t C16-C21. Phn on gasoil nng (cn gi l phn on du nhn), nhit si t 350 n 5000C, bao gm C21 n C25, thm ch n C40. Phn on cn gudron nhit si trn 5000C, gm cc thnh phn c s nguyn t cacbon t C41 tr ln, gii hn cui cng c th n C80. Cc phn on k trn c ng dng trong nhiu mc ch khc nhau, nhng ch yu c s dng lm nhin liu hoc to cc sn phm ha hc. c th s dng vi hiu qu cao nht cc sn phm du m, cn phi nm vng cc c im, tnh cht ca tng phn on. Mc tiu thc hin Hc xong m un ny hc sinh c kh nng: M t c cc phn on du m M t c ng dng ca cc phn on du m
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Ni dung chnh 4.1. Phn on kh Phn on kh bao gm cc hydrocacbon C1 n C4, mt lng rt t C5, C6. Cc kh ny c th khai thc t m kh hoc tch ra khi khoan du. Kh c ng dng lm nguyn liu cho cng nghip tng hp ha du v lm nhin liu t. 4.1.1. Kh lm nguyn liu tng hp ha du 4.1.1.1. Tng hp amoniac Amoniac (NH3) l nguyn liu ban u tng hp phn m. Qu trnh tng hp s dng ch yu l kh thin nhin qua cc qu trnh sau: u tin chuyn ha thnh kh tng hp (qu trnh reforming hi nc) CH4 CH4 CO N2 + + + + O2 H2O H2O 3H2 CO CO + + 2H2 3H2 H2 + Q
CO2 + 2NH3
Sau khi loi b CO l tip n giai on tng hp amoniac: Xc tc cho phn ng ny l cc oxyt nh Fe2O3, Fe3O4, FeO, Al2O3, Cr2O3, TiO2Phn ng ny xy ra p sut cao (25 n 100MPa), nhit 5000C. 4.1.1.2. Tng hp metanol Metanol l mt trong nhng nguyn liu v dung mi quan trng trong cng nghip ha hc. Metanol cn c coi l nhin liu l tng v n c kh nng chy hon ton khng gy nhim mi trng, ngoi ra n c s dng lm ph gia tng tr s octan cho xng. C th tng hp metanol bng cch oxy ha khng hon ton metan theo phn ng sau: CH4 + [O] CH3OH Xc tc s dng trong qu trnh ny c th l: Cc kim loi Fe, Ni, Cu, Pd cc oxyt ca chng, hoc hn hp oxyt v kim loi. Ngy nay trong cng nghip, xc tc c s dng l V2O5 vi nguyn liu l h CH4, O2, NO v cc nhit khc l nhit , p sut.
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Trong cng nghip ha cht, metanol c s dng nh l mt bn sn phm cho nhiu qu trnh tng hp cng nghip. Phn ln metanol dng cho iu ch formandehit v mt s cht quan trng nh: Cloruametyl (CH3Cl), metyl amin (CH3NH2), axit axetic (CH3COOH), vinylmetyl ete (CH3O-CH=CH2), metyl mercaptan (CH3SH) Nh vy, oxy ha trc tip metan c th thu c sn phm l metanol v formaldehyt. Vic s dng NOx nh l cht khi mo hoc cht oxi ha cho phn ng em li nhng hiu qu r rt. Thnh phn sn phm thu c khi oxy ha trc tip metan c th tham kho hnh 4.1. 4.1.2. Kh lm nhin liu t Hin nay trong cng nghip s dng cc loi l t vi nhiu loi nhin liu truyn thng khc nhau nh D.O, F.O, than, in Phc v cho cng on gia nhit ca cc cng ngh sn xut khc nhau nh: nung, sy, hp. Lng nhin liu s dng trong lnh lc ny rt ln, do vy vic chuyn i nhin liu cng c ngha to ln. Chuyn ha kh thnh nhin liu t l hng s dng quan trng v c hiu qu cao, do cng ngh ha lng kh v ang pht trin trn phm vi ton cu. 4.1.2.1. Kh t nhin ha lng (LNG) ngha quan trng nht ca vic ha lng kh t nhin l gim c 600 ln th tch, lm cho cng vic tn tr, vn chuyn v bo qun tr nn thun li hn rt nhiu. Trong qu trnh ha lng kh t nhin, cc kh c nhit si thp s c lm lnh xung di im sng ca n. Nhit ngng t ti cc p sut khc nhau i vi mi cu t ca kh t nhin c cho bng 4.2 Bng 4.1. Nhit ngng t ca mt s kh Kh Metan Etan Etylen Propa n Propyl en29
Nhit ngng t (0C) ti cc p sut khc nhau (Psi) 1,0 3,4 6,85 17,1 34,2 - 159 - 144 - 133 - 92 - 71 - 91 - 63 - 44 - 15,5 _ - 104 - 80 - 62 - 8,3 _ - 46 - 12 + 12 _ _ - 49 - 18 - 56 _ _
Metanol Axetylen Formaldehyt Dan xuat C1 Kh tong hp Etan Polyetylen Etylen Propylen Meta n
Khai thac
Etylen Propylen
Lam sach
C3+
Cracking
Butadien Chat thm Xang
Tach kh
Reforming
Xuat khau Propan Butan
Vinyl axetylen
Propin
Butylen
Butadien Cao su
PVA
Polypropylen
Nha epoxy
Thuy tinh hu c
MTBE, ETBE
Hnh 4.1. S o chuyen hoa kh thanh cac san pham hoa hoc
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Kh t nhin ha lng c s dng lm nhin liu trong nhiu ngnh kinh t quc dn nh nng lng, cng nghip, giao thng vn ti, kh t dn dng, v t ra c u th hn hn so vi cc loi nhin liu khc. Chng hn nh trong ngnh nng lng, s dng kh t nhin sn xut in s lm gim gi thnh t 30 n 40%. Xy dng nh my chy bng kh t, vn u t s gim 20% so vi nh my chy bng than. Ngy nay, khong 20% tng lng kh tiu th trn th gii l phc v cho vic sn xut ra nng lng v d tnh con s ny trn th trng s tng mnh trong nhng nm ti. Nhiu nh my chu trnh hn hp kh ln ang c xy dng, v tng nhanh trong khi nhiu nh my nng lng sn c ang c trang b li tng hiu qu v gim cht thi NOx v SOx. Mt s h thng tm c ln cung cp hi qu trnh cng c s dng, gi l nhit-nng lng kt hp (Combined heat and power-CHP). Hin trn th gii vic s dng kh cho pht in l rt ph bin. cc nc c ngun kh thin nhin di do, kh c s dng cho my pht in chim t l rt cao (khong 80% sn lng kh khai thc c). Bi v vic s dng kh c tnh u vit nh sau: 4.1.2.2. t gy nhim mi trng. Chi ph u t cho cng ngh s dng kh thp. Hiu sut nhit cao. Thi gian xy dng ngn. Din tch xy dng nh my nh. Gi thnh sn xut 1 Kwh in t kh thp hn so vi cc loi nhin Kh du m ha lng (LPG)
liu khc. Thnh phn ch yu ca LPG bao gm cc hydrocacbon parafinic nh propan, butan. Ngoi ra, ty thuc vo phng php ch bin m trong thnh phn ca n c th c mt mt lng nh olefin nh propylen, butylen.
30
Khi ha lng, th tch ca cc hydrocacbon gim, v d mt lt propan lng cho 270 lt hi 1 atm, 1 lt butan lng cho 238 lit hi 1 atm. V vy cng nh LNG, LPG c th vn chuyn, tn tr mt cch d dng v thun tin. Nhit lng ta ra khi t LPG rt ln (khong 10900 n 13000 kcal/ kg tng ng vi vi nhit lng ca 1,5 n 2 kg than ci, 1,3 lit du ha hay 1,5 lit xng). Vi nhit lng c th s dng cho cc l cng nghip, lm nhin liu cho ng c t trong thay cho xng (trong cc loi t), lm nhin liu dn dng. Ngy nay trn th gii c xu hng s dng LPG thay cho nhin liu xng chy t, do n c nhiu u im hn hn so vi cc loi nhin liu khc l nhin liu chy hon ton, khng c khi, khng c tro, khng ln cc tp cht gy n mn cc phng tin bn b cha, khng gy nhim. Hm lng kh thi c hi nh NOx, COx rt t. Vit Nam, nhu cu tiu th LPG ngy cng tng, c th tham kho bng 4.2. Bng 4.2. Nhu cu tiu th LPG ti Vit Nam (tn) Nm Lng LPG sn xut LPG, ngi ta va nn va lm lnh n nhit ha lng ca cht kh. V d, propan ha lng -42,10C; izo butan -110C; n butan -0,50C. Cc c trng ca LPG thng phm c tham kho trong bng trong bng 4.4. v bng 4.5. Bng 4.3. Nhit chy ca cc hydrocacbon khc nhau Hydrocacbon Etan Etylen Propan Propylen n butan Kcal/ kg 250C 11350 11270 11080 10940 10930 1995 55.000 1997 249.000 2000 310.000 2003 650.000
31
izo butan Buten izo-pentan
10900 10800 10730 Loi LPG 100% 100% Butan (Butang as) 0,580 3,2 0,0 0,4 99,4 0,2 10920 0,541 9,2 0,0 51,5 47,5 1,0 10980 Hn hp 50% Propan, 50% Butan
Bng 4.4. c tnh l, ha ca LPG thng phm
Thnh phn
Propan (Propang as)
T trng (150C) p sut hi, kg/ cm2 (400C) Thnh phn: C2 (etan) C3 (propan) C4 (butan) C5 (pentan) Nhit chy (kcal/ kg)
0,507 13,5 1,7 96,2 1,5 0,0 11070
Qua phn phn tch, so snh, nh gi v tng quan gi thnh trn n v nhit tr v hiu sut t chy gia cc loi nhin liu truyn thng, nhin liu kh thin nhin v LPG cho thy nu xt v phng din chi ph, th vic chuyn i cc nhin liu truyn thng sang s dng nhin liu kh thin nhin v LPG s tit kim c ng k chi ph cho nhin liu tnh trn u sn phm. Kh t c th t c nhit tr cung cp cao mt cch nhanh chng v cng h nhit nhanh khi ngng s dng. y l u im ln ca kh trong qu trnh nung, un, nu. Theo ti liu ca Unique Gas cung cp, hiu qu v nhit tr ca vic s dng kh vi cc loi nhin liu khc l:
Bng 4.5. So snh nhit tr ca cc nhin liu
32
Nhin liu in Ci Than ci Than Du F.O Du D.O Du th Du ha Nhin liu phn lc Xng ng c Kh du m ha lng (LPG) Kh thin nhin ha lng
Nhit tr (Kcal/ kg) 860 2662 6582 8171 10175 10675 10175 10840 11000 11400 11400 11845 12400
T trng
0,92 0,99 0,82 0,90 0,80 0,87 0,78 0,84 0,71 0,79
Bn cnh vic gim nhim mi trng kh dng kh thin nhin v LPG cn tit kim c khong 30 50% thi gian un nng do kh c nhit chy cao hn cc loi nhin liu khc v c hiu sut cao gp 1,5 ln so vi cc loi cht t khc. y l loi nhin liu sch, hiu sut chy cao, khng sinh khi v to mui khi chy. V nguyn tc LPG c s dng nh l mt ngun nguyn liu tin li sch s nht trong cc loi nhin liu thng dng. LPG c chia thnh 5 lnh vc s dng chnh: Dn dng v thng nghip: nu n, si m, n gas trong cc h dn, cc ca hng n ung v khch sn. Cng, nng nghip: sy thc phm, nung gm s, hn ct t: nhin liu cho xe con, xe taxi Pht in: chy my pht in turbin. Ha du: sn xut etylen, propylen, butadien cho ngnh nha v c bit sn xut MTBE l cht lm tng tr s octan.
33
4.2. Phn on xng 4.2.1. Thnh phn ha hc Phn on xng bao gm cc hydrocacbon t C5 n C10, C11 c khong nhit si di 1800C. C 3 loi hydrocacbon parafinic, naphtenic, aromatic u c mt trong phn on. Tuy nhin thnh phn s lng cc hydrocacbon rt khc nhau, ph thuc vo ngun gc du th ban u. Chng hn, t h du parafinic s thu c xng cha parafin, cn t du naphtenic s thu c xng c nhiu cu t vng no hn. Ngoi hydrocacbon, trong phn on xng cn c cc hp cht lu hunh, Nit v Oxy. Cc cht cha lu hunh thng dng hp cht khng bn nh mercaptan (RSH). Cc cht cha Nit ch yu dng pyridin; cn cc cht cha oxy rt t, thng dng phenol v ng ng. Cc cht cha nha v asphanten u cha c. 4.2.2. Xng lm nhin liu 4.2.2.1. ng c xng ng c xng l mt kiu ng c t trong, nhm thc hin chuyn ha nng lng ha hc ca nhin liu khi chy thnh nng lng c hc di dng chuyn ng quay. ng c xng bao gm ng c 4 k v ng c 2 k, trong ng c 4 k ph bin hn. Chu trnh lm vic ca ng c 4 k c th hin trong hnh 4.1. Xng t thng nhin liu ca phng tin c bm chuyn n b ch ha kh (Carburettor), hoc h thng phun nhin liu c in t. Ti y n c phun sng v phi trn vi khng kh to thnh hn hp chy. Hn hp nhin liu v khng kh sau c a vo xylanh ng c thng qua ng gp u vo v van ht.
34
4 1 2
5 1: Xi lanh 2: Piston 3: Thanh truyen 3 4, 5: Supap
Ky hut
Ky nen
Ky chay
Ky xa
Hnh 4.2: Chu trnh hoat ong trong ong c 4 ky
K ht: Piston i t im cht trn xung im cht di, van ht m ra ht hn hp xng v khng kh vo xylanh. Lc ny van thi ng. K nn: Piston i t im cht di ln im cht trn, lc ny van ht ng li nn hn hp xng v khng kh. Khi b nn, p sut tng (6-12 kg/cm2) dn n nhit tng (250 3500C), chun b cho qu trnh chy tip theo. K chy: Khi piston ln n im cht trn th bugi nh la, s t chy hn hp xng v khng kh. Khi chy, nhit nng bin thnh c nng y piston xung im cht di, ng thi truyn chuyn ng qua thanh truyn lm chy my. K x: Lc ny piston b y xung im cht di, v do qun tnh ca bnh piston tip tc i ln, van x s m ra kh chy thot ra ngoi v khi piston ln im cht trn th xylanh thi sch kh thi, van thi s ng li. Khi piston bt u i xung th van ht li m ra v bt u cho mt chu trnh mi 4.2.2.2. Bn cht ca qu trnh chy trong ng c xng ng c lm vic bnh thng th trong xylanh, cc mt la phi lan truyn u n, ht lp n n lp kia, vi tc khong 15 n 40 m/s. Nu mt la lan truyn vi tc qu ln (ngha l s chy din ra cng mt lc trong xylanh) th xem nh l qu trnh chy khng bnh thng v c gi l chy kch n. l s chy rt nhanh hn hp nhin liu v khng kh trong
35
bung t do nhit v p sut gia tng nhanh tip theo s chy khi u ca hn hp chung quanh bugi. 4.2.2.3. nh hng ca thnh phn nhin liu n tnh cht chy trong ng c. Tr s octan. Mt trong nhng tnh cht quan trng ca nhin liu xng l phi c kh nng chng li s kch n. c trng gi l tr s octan. Tr s octan l mt n v o quy c dng c trng cho kh nng chng kch n ca nhin liu, c o bng phn trm th tch ca izo-octan (2,2,4 trimetylpentan C8H18) trong hn hp chun vi n-heptan (n C7H16), tng ng vi kh nng chng kch n ca nhin liu iu kin tiu chun. S dng thang chia t 0 n 100, trong n heptan c tr s octan bng khng v izo octan c quy c bng 100. V nguyn tc, tr s octan cng cao cng tt, tuy nhin phi ph hp vi tng loi ng c. Xng c tr s octan t 80 n 83 thng c s dng cho cc loi xe c t s nn nh hn 7,5. Xng c tr s octan t 90 n 95 thng c s dng trong cc loi xe c t s nn cao trn 9,5 nh cc loi xe ua, xe t cao cp C hai phng php xc nh tr s octan, phng php nghin cu (gi l tr s octan theo RON) v phng php mt (gi l tr s octan theo MON). im khc nhau ca hai phng php ch yu l do s vng quay ca mt th nghim. Theo RON: L tr s octan ca xng th hin khi s dng trong ng c iu kin tc v ti trng trung bnh. S vng quay ca mt th nghim l 600 vng/ pht. Theo MON: L tr s octan ca xng c trng cho iu kin hot ng khc nghit hn, l nhit u vo ca hn hp cao, ti trng ln, v ng c phi tri qua ch van tit lu m ht tc cao. S vng quay ca mt th nghim l 900 vng/ pht.
36
Thng thng, tr s octan theo RON thng cao hn MON. Mc chnh lch phn nh: mt mc no tnh cht ca nhin liu thay i khi ch lm vic ca ng c thay i, cho nn mc chnh lch cn gi l nhy ca nhin liu i vi ch lm vic thay i ca ng c. Mc chnh lch gia MON v RON cng thp cng tt. Mi loi xng khc nhau c chng kch n cng khc nhau. Ngi ta thy rng: Cc hydrocacbon phn t nh nh parafin mch nhnh, cc aromat ch chy c sau khi im ha, c ngha l loi ny c kh nng chng kch n tt. Cc n parafin d dng chy ngay c khi ngn la cha lan truyn ti, gy ra s chy kch n. C th sp xp kh nng chng kch n ca cc hydrocacbon nh sau: Hydrocacbon thm > olefin mch nhnh > parafin nhnh > naphten c nhnh > olefin mch thng > naphten > n parafin. Nh vy, trong xng cha cng nhiu hydrocacbon thm hoc izo-parafin th tr s octan cng cao. Tr s octan ca mt s hydrocacbon ring r c th tham kho bng 4.6. Bng 4.6. Tr s octan ca mt s hydrocacbon khc nhau Hydrocacbon Cc parafin: Propan n butan izo butan n pentan izo pentan Cc olefin: Propylen Buten 2 101,4 99,6 84,9 86,5 16,5 13,1 105,7 93,6 > 100 61,9 92,3 100 90,1 99 61,9 90,3 5,7 3,5 0 2,0 Tr s octan PP RON PP MON chnh lch
37
Hydrocacbon Penten 1 Hexen 1 Cc naptalen: Xyclopentan Xyclohexan Metyl xyclohexan Etyl xyclohexan Cc thm: Benzen Toluen o-Xylen m-Xylen p-Xylen 1,3,5-Trimetyl bezen Izo-Propyl bezen 4.2.2.4. hydrocacbon
Tr s octan PP RON 90,9 76,4 100 83 74,8 46,5 PP MON 77,1 63,4 85 78,6 71 40,8
chnh lch 13,8 13,0 15 4,4 3,8 5,7
113 115 > 100 > 100 > 100 > 100 108
111,6 102,1 100 > 100 > 100 114 99,3
1,4 12,9 8,7
Cc phng php nng cao cht lng ca xng
Phn on xng ly trc tip t du m c rt t izo parafin v hydrocacbon thm, nhiu n parafin, do tr s octan rt thp (ch t t 30 n 60), trong khi yu cu v tr s octan cho xng ng c phi ln hn 80. V vy phi dng nhng bin php khc nhau nng cao cht lng ca xng, ngi ta dng cc phng php sau y: a. Phng php dng ph gia
38
Bn cht ca phng php ny l dng mt s ha cht pha vo xng nhm hn ch mt s qu trnh oxy ha ca cc hydrocacbon khng gian trc mt la khi chy trong ng c. Cc loi ph gia c chia lm hai nhm: Ph gia ch bao gm cc cht nh tetrametyl ch (TML), tetretyl ch (TEL), c tc dng ph hy cc hp cht trung gian hot ng (peroxyt, hydroperoxyt) v do lm gim kh nng b chy kch n. Kt qu l tr s octan ca xng thc t c tng ln. C ch dng ph gia ch nh sau: Phn hy TML trong ng c:t0C
Pb(CH3)4Pb + O2+ O2
PbPbO2
+
4CH3
t0C
To cht khng hot ng:R-CH3 R-CH2OOH
R-CH2OOH + PbO2
RCHO + PbO + H2O + 1/2O2
Kt qu l bin cc peroxyt hot ng thnh cc aldehit (RCHO) bn vng, lm gim kh nng chy kch n. Nhng ng thi PbO kt ta s bm trn thnh xylanh, ng dn, lm tc ng nhin liu v tng mi mn. Do vy ngi ta dng cc cht mang a PbO ra ngoi. Cc cht mang thng dng l C2H5Br hoc C2H5Cl, c ch tc dng nh sau:C2H5Br2HBr + PbOt 0Ct0C
C2H4PbBr2
+
HBr
+ H 2O
Cc sn phm PbBr2, H2O l cht lng, c nhit si thp s bc hi v c kh thi a ra ngoi. Hn hp ph gia ch v cht mang gi l nc ch. Nc ch rt c nn phi nhum mu phn bit. b. Phng php ha hc Ph gia ch nh phn tch phn trn, ch l ph gia khi cho vo xng lm tng tr s octan nhiu nht (t 6 n 12 n v octan). Tuy nhin do tnh c hi m hin nay nhiu quc gia ban hnh lut cm s dng loi ph gia ny. Vit Nam, t thng 7 nm 2001 bt u chin dch khng s dng xng ch.
39
C mt s bin php hu hiu t tr s octan cao hn khi khng s dng ch: Pha trn xng c tr s octan cao (nh xng alkyl ha, izomer ha) vo nhin liu c tr s octan thp. Nng cp v a thm cc thit b lc du sn xut hn hp xng c tr s octan cao. S dng cc ph gia khng cha ch, nh cc hp cht cha oxy: etanol, MTBE, ETBE, MTBA, TAME Trong cc ph gia cha oxy ni trn, etanol v MTBE c s dng vi s lng nhiu nht. Chng hn nh M, MTBE c pha trn ti 15% th tch, etanol ti 10% th tch. Brazil pha trn ti 22% etanol vo xng trong nhiu nm. Metanol khi dng pha ch thng c tr s octan cao tng t nh cc cht ph gia khc. u im ln nht ca ph gia ny l: gi tng i r, kh nng iu ch ph gia ny trong thin nhin tng i d dng. Metanol c th iu ch t cc nguyn liu th khc nhau. Nhc im ln nht ca ph gia ny l kh nng tan v hn ca n trong nc c th dn ti nhng hu qu khng tt. Etanol khng c s dng rng ri nh metanol, n ch c s dng ch yu cc quc gia c sn ngun nguyn liu thin nhin l ma nh Brazil. Nhc im ca ph gia ny l ht m rt nhiu, lm tng nguy c chy n ca nhin liu v lm tng RPV ca nhin liu. Ph gia Tert butyl alcol l sn phm trung gian ca oxyt propylen. C khong 800.000 tn TBA c sn xut trn ton th gii hng nm, trong khong 400.000 tn c sn xut chu u. Hin nay TBA c s dng pha ch vi metanol (t l 1: 1) hn hp theo t l ny s lm gim kh nng phn cch gia hai pha ca metanol, ng thi ci thin RPV ca hn hp. Nhc im ca ph gia ny l nhit chy mm kh cao (v vy khng tn cha xng c ph gia ny nhit thp) v c kh nng ht m cao tuy khng nhiu nh metanol v etanol.40
Ph gia Metyl tert butyl ete (MTBE) khi pha vo xng khng lm thay i RPV ca nhin liu. Kh nng ha tan vi nc ca MTBE thp hn nhiu so vi cc loi ru khc do vy lng nc ln vo nhin liu s t hn nhiu, s dng MTBE t nguy him hn so vi cc ph gia khc v nguy c gy chy n t hn so vi ru. Tuy nhin nhc im ln ca ph gia ny l gi thnh cao, ch pha vo xng c ti a 15 20% nn tr s octan tng khng nhiu. MTBE c iu ch bng phng php tng hp cc izo butylen, m izo butylen khng phi l loi nguyn liu d kim. Bn cnh vic tng tr s octan, hn hp ca xng vi ph gia cha oxy gip gim thi hydrocacbon v CO t xe c s dng nhin liu. C th thy r tr s octan ca mt s cht cha oxy in hnh trong bng 4.7. Bng 4.7. Tr s octan ca cc ph gia cha oxy Ph gia cha oxy Metanol Etanol Tert butyl alcol (TBA) Metanol / TBA (50/50) Metyl tert butyl ete (MTBE) Tert amylmetyl ete (TAME) Etyl tert butyl ete (ETBE) RON 127 136 120 135 104 110 115 123 115 123 111 116 110-119 Xng reformi ng MON 99 104 100 106 90 98 96 104 98 105 98 103 95-104 Xng Cracki ng Xng Alkyl ha
Bng 4.8. c im ca mt s loi xng Xng nh chng ct trc tip T du Cc c tnh th naphteni c RON ban u 77 T du th trung gian 69 T du th parafinic 65 93 93 97
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Xng nh chng ct trc tip T du Cc c tnh th naphteni c thm 0,5% nc ch T trng d415 p sut hi bo ha Reid (bar) Thnh phn ct (ASTM): - Nhit si u - Nhit si 10% - Nhit si 50% - Nhit si 90% - Nhit si cui 52 69 83 103 109 42 56 68 84 107 40 55 71 93 97 87 0.721 0.43 T du th trung gian 85 0.685 0.59 T du th parafinic 82 0.682 0.59
Xng reformi ng
Xng Cracki ng
Xng Alkyl ha
99 0.76 0.45 37 60 115 170 180
98 0.74 0.55 37 50 100 188 195
101 0.71 0.45 37 65 107 119 147
Trn th trng hin nay, cc loi xng cho t thng dng l Mogas 90, 92. Mt s ch tiu c trng ca xng ch v xng khng ch xem bng 4.9. Bng 4.9. Mt s loi xng t ang lu hnh trn th gii hin nay Phn loi Ch tiu c trng cho s phn loi Tr s octan, min 1. Xng ch thng dng gm cc loi: Xng A-72 Xng A-76 Xng Mogas-83 Xng Mogas-86 MON 72 MON 76 RON 83 RON 86 0.24 0.15 0.20 Hm lng ch, g/l, max
2. Xng ch/ khng ch cht lng cao gm:
42
Phn loi
Ch tiu c trng cho s phn loi Tr s octan, min Hm lng ch, g/l, max 0.4/0.015 0.4/0.015 0.4/0.015 0.013 Phng php th ASTM D2699
-
Xng Mogas-90 Xng Mogas-92 Xng Mogas-97
RON 90 RON 92 RON 97 RON 97 Xng khng ch RON 92 RON 97 97 70 120 190 210 2.0 4.0 3.0 1A 5.0 360 0.05
3. Xng khng ch c bit Ch tiu 1. Tr s octan, min Theo phng php RON Theo phng php MON 2. Thnh phn phn on, 0C 10% V, max 50% V, max 90% V, max im si cui, max Cn cui, % V, max Cn v hao ht % V, max 70 120 190 210 2.0 4.0 3.0 1A 5.0 360 0.1 92 -
Bng 4.10. Ch tiu cht lng xng khng ch
TCVN 26981995
3. axit, mg KOH/ 100ml, max 4. n mn tm ng 500C, 3h, max 5. Hm lng nha thc t mg/ 100ml, max 6. n nh oxy ha, pht, min 7. Hm lng lu hunh tng, % kh.
TCVN 2695 1995 TCVN 2694 1995 ASTM D381 ASTM D1266 ASTM D1266
43
Ch tiu l., max 8. 9. Hm lng ch, g/l, max p sut hi bo ha/ Reid 0
Xng khng ch RON 92 0.013 83 5 10 RON 97 0.013 83 5 10
Phng php th
ASTM D3237 ASTM D4953 ASTM D3606 ASTM D4815
37,8 C, kPa, max 10. Hm lng benzen, %kh.l., max 11. Hm lng MTBE, % V, max Phn loi 1. Xng ch thng dng 2. Xng ch c cht lng 3. Xng khng ch c cht lng 4. Xng khng ch c bit 4.2.2.5. Xng my bay
Bng 4.11. Tng quan v s phn loi xng t trn th gii hin nay Ch tiu c trng cho s phn loi Tr s octan, min MON 72, RON 80 MON 86, RON 92 MON 85, RON 92 MON 90, RON 95 Hm lng ch t 0.15 n 0.8 g/l T 0.15 n 0.6 g/l Max: 0.015 g/l Khng
Xng my bay thuc loi xng cao cp, khng th ly c t mt loi xng thun nht m thng l hn hp ca mt s thnh phn c bit nhm thu c xng c phm cht tt. Xng my bay phi c nhng tiu chun cn thit sau y. Tr s octan bng hoc ln hn 100, ngoi ra phi m bo tr s octan khi hn hp chy thiu xng, tha khng kh v hn hp chy tha xng, thiu khng kh. ng c my bay khi lm vic c hai qu trnh: qu trnh ct cch bao gi cng phi s dng cng sut ti a, lng xng trong hn hp phi c tng ti a (gi l hn hp giu). Trong qu trnh bay, c lc ng c phi gim cng sut, lng xng gim (hn hp ngho). Tr s octan trong trng hp hn hp giu gi l tr s phm . Ngi ta th hin tr s octan ca xng my bay
44
bng phn s, trong : t s l tr s octan, mu s l tr s phm . V d xng loi B 100/ 130 th 100 l tr s octan, 130 l tr s phm . Thnh phn ct phn on ca xng my bay phi ly hp (t 40 n 1800C) trnh c nhiu cu t nh to nt hi trong h thng cp liu, v c nhiu cu t nng, v khi chy s chy khng hon ton to cn. Hm lng olefin phi thp (< 3%) trnh s trng hp to nha, lm cho xng b bin mu v khng bo qun c lu. Xng my bay thng l xng pha trn, v d, xng loi B 100/ 130 thu c bng cch trn xng cracking xc tc vi nhng thnh phn cao octan nh izo-octan. Xng B 91/ 115 l xng pha trn gia xng cracking xc tc, xng chng ct trc tip v thnh phn cao octan. Bng 4.13 cho bit ch tiu cht lng ca xng my bay theo tiu chun ca Lin X (c). Cc ng dng khc ca xng Ngoi cng dng chnh l nhin liu, xng cn c s dng lm dung mi hoc nguyn liu cho tng hp ha du. 4.2.3.1. Xng lm dung mi Phn on xng c s dng lm dung mi trong cng nghip sn, cao su, keo dn, ngoi ra cn s dng trch ly cht bo, trong cng nghip hng liu, dc liu Trong cc loi dung mi, ph bin l xng parafinic v aromatic. Thng thng xng dung mi ly trc tip t du m l xng parafinic, c hm lng hydrocacbon thm thp. Cc lnh vc ng dng khc nhau ca xng xem bng 4.12. 4.2.3.2. Xng lm nguyn liu cho tng hp ha du Xng s dng lm nguyn liu cho tng hp ha du cn gi l phn on naphtalen. T phn on ny ngi ta sn xut c cc hydrocacbon thm khc nhau nh benzen, toluen, xylen. Ngoi ra, cn thu c cc olefin nh nh etylen, propylen, butadien thu c cc hydrocacbon thm (BTX), ngi ta s dng cc phn on hp khi chng ct.45
Bng 4.12. Cc ng dng ca xng dung mi Loi dung mi A B C D E F G White Spirit 40 60 70 95 100 100 30 135 Khong si0
Mc ch s dng Keo, cao su, ty vt m Trch ly du m, cht bo, ch to nc hoa Trch ly du m, cht bo, cng nghip cao su Kh nc ca ru Cng nghip cao su, sn, ty bn Cng nghip cao su, sn. Trch ly hng liu, sn xut dc liu. Sn, vecni (thay du thng)
C 100 80 100 103 130 160 75 205
Phn on 60 Phn on 80 toluen cao nht. Phn on 105 xylen cao nht.
850C: Phn on cha metyl xyclopentan, xyclohexan 1000C: Phn on cha naphten C7, cho hiu sut 1400C: Phn on cha naphten C8, cho hiu sut
cho hiu sut benzen cao nht.
Xng dng ch bin ha hc cn phi rt sch, v nu trong xng c nhiu S, N, O s lm ng c xc tc trong qu trnh ch bin. V vy yu cu v hm lng cc cht d th v kim loi nng c trong xng phi nh sau: Hm lng S Hm lng N Hm lng As (10 15). 10-4 % trng lng 5. 10-6 % trng lng 1. 10-4 % trng lng 1. 10-7 % trng lng
Hm lng Hg, Pb
Phn on kerosen Phn on ny cn gi l du la: c nhit si t 180 n 250 0C, bao gm cc hydrocacbon c s cacbon t C11 n C16. 4.3.1. Thnh phn ha hc Trong phn on ny, hu ht l cc parafin, rt t izo parafin. Cc hydrocacbon naphtenic v thm mt vng nhiu nhnh ph ngoi ra cn c mt46
cc hp cht hai hoc ba vng, c bit loi naphten v thm hai vng chim a s. 4.3.2. ng dng Phn on kerosen s dng ch yu cho hai mc ch: lm nhin liu phn lc v du ha dn dng, trong nhin liu phn lc l ng dng chnh. 4.3.2.1. Kerosen lm nhin liu phn lc ng c phn lc (Hnh 4.2). Tuabin chnh ch s dng mt phn ng nng ca sn phm chy bung t nhm lm quay tuabin my nn, phn ng nng quan trng cn li s c gin n qua tuy-e ra ngoi vi tc rt ln, to nn mt phn lc tc ng ln ng c, y ng c tin ln pha trc. y l ng c phn lc tuabin.Khng kh 1 3 2 4 Sn phm chy
Hnh 4.3. ng c phn lc Ch thch: 1. Tuabin my nn khng kh a vo bung t. 2. Tuabin chnh, bin mt phn ng nng ca dng kh thnh chuyn ng quay, lm quay tuabin my nn. 3. Bung t chnh 4. Bung t ph nh hng ca bn cht nhin liu n qu trnh chy: nhin liu dng trong ng c phn lc c ch to t kerosen hoc t hn hp gia phn on kerosen vi phn on xng.
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Yu cu ca nhin liu phn lc l d chy bt k iu kin p sut v nhit no, chy iu ha, khng b tt trong dng khng kh c tc xoy ln. m bo c nhit tr cao, nhin liu khng cha nhiu thnh phn aromatic m ch yu l parafinic v naphtenic. Nhng an ton cho my bay hot ng cao ln, nhit thp cn hn ch thnh phn parafinic d b kt tinh v tng cng thnh phn naphtenic nhiu vng. Cn phi ch n kh nng to cn, to cc ca nhin liu gy nh hng xu n tnh nng hot ng ca ng c. Kh nng c xp theo chiu gim dn nh sau: Aromatic > olefin > izo-parafin, naphten > n-parafin nh gi kh nng to cn cacbon, ngi ta dng i lng chiu cao ngn la khng khi, l chiu cao ti a ca ngn la khng c khi tnh bng mm, khi t nhin liu trong n du tiu chun. Chiu cao ngn la khng khi cng cao chng t nhin liu chy cng hon ton. Chiu cao cng thp, kh nng to cn cacbon cng ln. Nhng thnh phn khng phi hydrocacbon cha trong nhin liu u c nh hng xu n tnh cht s dng ca nhin liu. Cc hp cht lu hunh khi chy to ra cc cht c tnh axit gy n mn nhit thp. Cc hp cht cacbon cn gy ra cn cacbon trong bung t. Cc hp cht oxy, nh axit naphtenic, phenol u lm tng kh nng n mn cc thng cha, ng dn nhin liu v cc sn phm to ra do n mn (cc mui kim loi ca axit naphtenic) li gp phn to cn to tro khi chy bm vo bung t, ch yu l bugi, vi phun, tuy-e thot sn phm gy tr ngi cho qu trnh. Cc hp cht Nit lm nhin liu km n nh, bin mu ca nhin liu. cc kim loi nht l Vanadi, Natri nm trong sn phm chy nhit cao 6500C n 8500C khi p vo cc tuabin s gy n mn hp kim hoc gy ph hoi cc chi tit tuabin, v vy hm lng kim loi v tro trong nhin liu phi rt nh, khong vi phn triu. 4.3.2.2. Kerosen lm du ha dn dng.
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T phn on kerosen, vi khong si 200 n 3100C c th sn xut du ha, s dng lm du ha dn dng nh thp sng, un nu. c tnh quan trng ca du ha l chiu cao ngn la khng khi. m bo ngn la sng, p, r, u, chiu cao ny phi ln hn 20 mm. Thnh phn ha hc ca du ha nh hng cn bn n s chy. Du ha c cha nhiu thnh phn hydrocacbon thm trong khi chy s to nhiu mui khi. Cht keo v axit naphten lm tc bt trong mung n, lm gim nh sng khi t chy. Trong thnh phn ca du ha dn dng ch c parafinic v naphten c s nguyn t cacbon trong phn t t 10 n 14. y l cc cht chy tt cho ngn la xanh, nhit tr cao. Nu trong nhin liu cha nhiu lu hunh, khng nhng gy c hi trc tip cho ngi s dng m cn lm cho bng n m i, khng m bo cng chiu sng ca ngn la. Ch tiu v du ha dn dng ca Vit Nam xem bng 4.13. Bng 4.13. Ch tiu du ha dn dng theo tiu chun Vit Nam Cc ch tiu Mu Saybolt Axit tng, mg KOH/g Chiu cao ngn la khng khi, mm Thnh phn ct phn on, 0C - im si u - im ct 50% - im si cui - Cn trung bnh Hm lng lu hunh, %Kl im chp chy cc kn, 0C Lng nha thc t, mg/100ml ASTM D1266 ASTM D93 ASTM D381 Min 144 Min 200 Min 277 Max 1,00 Max 0,1 Min 36 Max 1,0 Phng php th ASTM D156 ASTM D3242 ASTM D1322 Mc quy nh Min 20 Max 0,002 Min 19
49
nht 200C, cSt n mn tm ng, 2h/1000C Khi lng ring 150C, g/cm3 4.4. Phn on gasoil nh
ASTM D445 ASTM D130 ASTM D1298
Max 3,5 1,0 Max 0,83
Gasoil nh, cn gi l phn on du izen, c khong nhit si t 250 n 3500C, cha cc hydrocacbon t C16 n C21. 4.4.1. Thnh phn ha hc Phn ln trong phn on ny l cc n-parafin, izo-parafin cn hydrocacbon thm rt t. Hm lng cc cht cha S, N, O tng nhanh. Lu hunh ch yu dng disunfua, d vng. Cc cht cha oxy ( dng axit naphtenic) c nhiu v t cc i phn on ny. Ngoi ra cn c cc cht dng phenol nh dimetylphenol. Trong gasoil xut hin nha, song cn t, trng lng phn t ca nha cn thp (300 n 400 .v.C). 4.4.2. ng dng ca phn on gasoil nh Phn on gasoil ca du m ch yu c s dng lm nhin liu cho ng c izen 4.4.2.1. ng c izen 1-Thanh truyn; 2-Xylanh; 3-Piston; 4,7-Vi phun nhin liu 5-Van np khng kh; 6-Van thi sn phm; 8-im cht trn 9-im cht di5 6
4 2
7
8 3 9 1
Hnh 4.4. M hnh bung t ca ng c izen
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ng c xng c t s nn thp hn so vi ng c izen. Vi ng c xng, t l l t 7/1 n 11/1, cn ng c izen l t 14/1 n 17/1, v vy ng c izen c cng sut ln hn ng c xng trong khi tiu hao cng mt lng nhin liu. Nguyn l lm vic: Khi piston i t im cht trn xung im cht di, van np m ra, khng kh c ht vo xy lanh; sau van np ng li, piston li i t im cht di ln im cht trn, thc hin qu trnh nn khng kh. Do b nn, p sut tng, dn n nhit tng c th ti 500 n 7000C. Khi piston ln n gn im cht trn nhin liu c phun vo xy lanh (nh bm cao p) di dng sng, khi gp khng kh nhit cao s t bc chy. Khi chy p sut tng mnh y piston t v tr im cht trn xung im cht di thc hin qu trnh dn n sinh cng c ch v c truyn qua h thng thanh truyn lm chy my. Piston sau li i t im cht di ln im cht trn thi sn phm chy ra ngoi qua mt van thi v tip tc thc hin chu k mi. 4.4.2.2. Bn cht ca qu trnh chy Nhin liu sau khi phun vo xylanh khng t chy ngay m phi c mt thi gian oxy ha su cc hydrocacbon trong nhin liu, to hp cht cha oxy trung gian, c kh nng t bc chy. Khong thi gian gi l thi gian cm ng hay thi gian chy tr. Thi gian cm ng cng ngn cng tt, lc nhin liu s chy iu ha. Nh vy, c thi gian chy tr ngn th trong nhin liu phi c nhiu cc cht n parafin, v cc cu t ny d b oxy ha, tc l d t bc chy, cn cc izo parafin v cc hp cht hydrocacbon thm rt kh b oxy ha nn thi gian chy tr di, kh nng t bc chy km. C th sp xp th t theo chiu gim kh nng oxy ha (tc l thi gian cm ng) ca cc hydrocacbon nh sau: n parafin < naphten < n olefin < izo naphten < izo parafin < izo olefin < hydrocacbon thm. 4.4.2.3. Tr s xetan c trng cho kh nng t bc chy ca nhin liu izen, ngi ta s dng i lng tr s xetan. Tr s xetan l n v o quy c, c trng cho kh51
nng t bc chy ca nhin liu izen, l mt s nguyn, c gi tr ng bng gi tr ca hn hp chun c cng kh nng t bt chy. Hn hp chun ny gm hai hydrocacbon: n xetan (C16H34) quy nh l 100, c kh nng t bc chy tt v -metyl naphtalen (C11H10) quy nh l 0, c kh nng t bc chy km. Cc hydrocacbon khc nhau u c tr s xetan khc nhau: mch thng cng di, tr s xetan cng cao, ngc li, hydrocacbon thm nhiu vng, tr s xetan thp. Nu tr s xetan qu cao s khng cn thit v gy lng ph nhin liu, mt s thnh phn nhin liu trc khi chy, nhit cao trong xylanh b thiu oxy nn phn hy thnh cacbon t do, to thnh mui. Nu tr s xetan thp s xy ra qu trnh chy kch n do: trong nhin liu c nhiu thnh phn kh b oxy ha, khi lng nhin liu phun vo trong xylanh qu nhiu mi xy ra qu trnh t chy, dn n chy cng mt lc, gy ta nhit mnh, p sut tng mnh, ng c run git, gi l chy kch n. tng tr s xetan c th thm vo nhin liu cc ph gia thc y qu trnh oxy ha nh: izo propylnitrat, n butylnitrat, amylnitratvi lng khong 1,5% th tch, cht ph gia c th lm tng tr s xetan ln 15 n 20 n v. 4.5. Phn on gasoil nng (Phn on du nhn) Vi khong si t 350 n 5000C, phn on ny bao gm cc hydrocacbon t C21 n C35 hoc c th ln ti C40. 4.5.1. Thnh phn ha hc Do c phn t lng ln, thnh phn ha hc ca phn on du nhn rt phc tp: Cc n-parafin v izo-parafin t, naphten v thm nhiu. Dng cu trc hn hp tng. Hm lng cc hp cht ca S, N, O tng mnh: hn 50% lng lu hunh c trong du m tp trung phn on ny, gm cc dng nh disulfua, thiophen, sulfua vng Cc cht Nit thng dng ng ng ca pyridin, pyrol v cacbazol. Cc hp cht oxy dng axit. Cc kim loi nng nh V, Ni, Cu, PdCc cht nha, asphanten u c mt trong phn on.
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Thng thng ngi ta tch phn on du nhn bng cch chng ct chn khng phn cn du m, trnh phn hy cc cht nhit cao.Xng Du thChng ct p sut thng
Kerosen Diezel Cn mazutChng ct Chn khng
Cc phn on du nhn
4.5.2. ng dng ca phn on sn xut du nhn 4.5.2.1. Cng dng ca du bi trn a. Cng dng lm gim ma st Mc ch c bn ca du nhn bi trn gia cc b mt tip xc ca cc chi tit chuyn ng nhm gim ma st. My mc s mn ngay nu khng c du bi trn. Nu chn ng du bi trn th h s ma st gim t 100 n 1000 ln so vi ma st kh. Khi cho du vo my vi mt lp dy, du s xen k gia hai b mt. Khi chuyn ng, ch c cc phn t du nhn trt ln nhau. Do my mc lm vic nh nhng, t b mn, gim c cng tiu hao v ch. b. Cng dng lm mt Khi ma st, kim loi nng ln, nh vy mt lng nhit sinh ra trong qu trnh . Lng nhit ln hay nh ph thuc vo h s ma st, ti trng, tc . tc cng ln th lng nhit sinh ra cng nhiu, kim loi s b nng lm my mc lm vic mt chnh xc. Nh trng thi lng du chy qua cc b mt ma st em theo mt phn nhit truyn ra ngoi, lm cho my mc lm vic tt hn. c. Cng dng lm sch Khi lm vic, b mt ma st sinh ra mn kim loi, nhng ht rn ny s lm cho b mt cng tc b xc, hng. ngoi ra c th c ct, bi, tp cht ngoi ri vo b mt ma st. Nh du nhn lu chuyn qua cc b mt ma st, cun theo cc tp cht a ra cacte du v c lng lc i. d. Cng dng lm kn
53
Trong cc ng c c nhiu chi tit truyn ng cn phi lm kn v chnh xc nh piston xylanh, nh kh nng bm dnh to mng, du nhn c th gp phn lm kn cc khe h, khng cho hi b r r, m bo cho my lm vic bnh thng. e. Bo v kim loi B mt my mc, ng c khi lm vic thng tip xc vi khng kh, hi nc, kh thilm cho kim loi b n mn, h hng. nh du nhn c th lm thnh mng mng ph kn ln b mt kim loi nn ngn cch c vi cc yu t trn, v vy kim loi c bo v. 4.5.2.2. Phn loi du nhn Du nhn s dng cho mc ch bi trn (gi l du ng c) Du nhn khng s dng cho mc ch bi trn (du cng nghip) Trong thc t, du ng c chim mt t l kh ln trong cng nghip sn xut du bi trn ni chung (khong 40%) v c s dng ph bin. 4.5.2.3. a. Cc c trng c bn ca du bi trn nht nht ca mt s phn on du nhn l mt i lng vt l c trng cho tr lc do ma st ni ti ca n sinh ra khi chuyn ng. Do vy nht c lin quan n kh nng bi trn ca du nhn. thc hin nhim v bi trn, du nhn phi c nht thch hp, phi bm chc ln b mt kim loi v khng b y ra ngoi, ngha l n phi c ma st ni ti nh. nht ca du nhn ph thuc ch yu vo thnh phn ha hc. Cc hydrocacbon parafinic c nht thp hn so vi cc loi khc. chiu di v phn nhnh ca mch hydrocacbon cng ln, nht s tng ln. Cc hydrocacbon thm v naphten c nht cao. c bit s vng cng nhiu th nht cng ln. Cc hydrocacbon hn hp gia thm v naphten c nht cao nht. Theo ngha s dng, du nhn c 2 loi chnh, l:
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nht ca du nhn thng c o bng poaz (P), centipoaz (cP), hoc stc (St), centistc (cSt). b. Ch s nht Mt c tnh c bn na ca du nhn l s thay i nht theo nhit . Thng thng, khi nhit tng, nht s gim. Du nhn c xem l du bi trn tt khi nht ca n t b thay i theo nhit , ta ni rng du c ch s nht cao. ngc li nu nht thay i nhiu theo nhit , c ngha l du c ch s nht thp. Ta c th xc nh ch s nht VI theo ton hnh 4.4. Cch xc nh nh sau: t thc ni 2 im gi tr nht 400C v 1000C, im ct s l gi tr ch s nht VI cn tm.
Hnh 4.5. Ton xc nh ch s nht VI 4.5.2.4. Sn xut du nhn thc hin c chc nng bi trn tt, du nhn phi c nht kh cao duy tr c mng du lin tc, mt khc ch s nht phi cao khi my mc lm vic nhit thng, cng nh nhit cao nht t b thay i (c ngha l du phi c ch s nht cao). t c mc ch trn, nguyn liu tt nht sn xut du nhn gc l:
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-
Cc n parafin sau khi tch bt cc cht c phn t lng qu ln trnh s kt tinh. Cc hydrocacbon naphtenic hoc thm t vng, c nhnh ph di; cc cu t ny l nguyn liu l tng sn xut du nhn gc, v chng va c nht cao (tnh cht ca cc vng naphten, vng thm); va cho ch s nht cao (tnh cht ca nhnh ph-parafin).
Sau khi c du nhn gc, sn xut du nhn thng phm, ngi ta phi pha thm cc ph gia nhm mc ch tng cng cc tnh cht sn c, hoc to ra nhng kh nng m trong du nhn gc cha c. Ph gia pha ch du bi trn phi p ng c cc yu cu: tan trong du gc, n nh ha hc, khng c hi, c tnh tng hp, bay hi thp v khng phn ng ha hc vi nhau. Cc loi ph gia thng l: Ph gia chng oxy ha bao gm cc dn xut ca phenol,H CH3 H3C C CH3 OH CH3 C CH3 phenyl- -naphtylamin CH3 R N R
amin nh:
2,6-tert-butyl-p-crezol
-
Ph gia tng ch s nhtCH3 H2C C CH3 poly-izo-butylen n H2C CH3 C n COOCH3
polymetylmetacrylat
-
Ph gia c ch n mn
56
CH3 S H N N N benzothiazol H3C C CH2 S tecpen sunfua
-
Ph gia ty raSO3R Ca SO3R Ca OH SO3R
4.5.3. ng dng ca phn on sn xut sn phm trng Cc sn phm trng l tn gi ca ba loi nhin liu: Xng, kerosen, izen. l cc loi nhin liu c s dng nhiu nht, quan trng nht. lm tng s lng cc nhin liu ny, c th tin hnh phn hy gasoil nng bng phng php cracking hoc hydrocracking. Vi cch ny, c th bin cc cu t C 21 n C40 thnh xng (C5 n C11), kerosen (C11 n C16), izen (C16 n C20), nh vy, nng cao hiu sut s dng ca du m. 4.6. Phn on cn du m (cn gudon) 4.6.1. Thnh phn ha hc Gudron l phn cn li sau khi phn tch cc phn on k trn c nhit si ln hn 5000C, gm cc hydrocacbon c s nguyn t cacbon ln hn C41, gii hn cui cng c th ln n C80. Thnh phn ca phn on ny rt phc tp. C th chia thnh 3 nhm chnh sau: 4.6.1.1. Nhm cht du Nhm cht du bao gm cc hydrocacbon c phn t lng ln, tp trung nhiu cc hp cht thm c ngng t cao, cu trc hn hp nhiu vng gia thm v naphten, y l nhm hp cht nh nht, c t trng xp x bng 1, ha tan trong xng, n pentan, CS2 nhng khng ha tan trong cn. Trong phn on cn nhm du chim t 45 n 60%.57
4.6.1.2.
Nhm cht nha
Nhm ny dng keo qunh: gm hai nhm thnh phn l cht trung tnh v cht axit. Cc cht trung tnh c mu en hoc nu, nhit ha mm nh hn 100 C, t trng ln hn 1, d dng ha tan trong xng, naphtalen. Cht trung tnh to trong nha c tnh do dai v tnh dnh kt. Hm lng ca n nh hng trc tip n tnh ko di ca nha, chim khong 10 n 15% khi lng ca cn gudron. Cc cht axt l cht c nhm COOH, mu nu sm, t trng ln hn 1, d ha tan trong cloroform v ru etylic, cht axit to cho nha c tnh hot ng b mt. Kh nng kt dnh ca bitum ph thuc vo hm lng cht axit c trong nha, n ch chim khong 1% trong cn du m. 4.6.1.3. Nhm asphanten Nhm asphanten l nhm cht mu en, cu to tinh th, t trng ln hn 1, cha phn ln cc hp cht d vng c kh nng ha tan mnh trong cc disunfua (CS2). un 3000C khng b nng chy m b chy thnh tro. Ngoi ba nhm cht chnh ni trn, trong cn gudron cn c cc hp cht c kim ca kim loi nng, cc cht cacbenkhng tan trong cc dung mi thng thng, ch tan trong pyridin 4.6.2. ng dng ca phn on cn gudron Phn on gudron c s dng trong nhiu mc ch khc nhau nh sn xut bitum, than cc, nhin liu t l. Trong cc ng dng trn, sn xut bitum l ng dng quan trng nht. 4.6.2.1. a. Sn xut bitum Thnh phn ha hc ca bitum Bitum l hn hp phc tp ca nhiu loi cht, trong hm lng cc nguyn t thu c nh sau:0
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Bng 4.14. Thnh phn nguyn t ca bitum Cacbon Hydro Lu hunh Nit Oxy (C) (H) (S) (N) (O) 80 87% 10 15% 2 8% 0,5 2% 1 5%
Trong cc nguyn t k trn, hm lng cacbon v hydro chim mt t l tng i ln. Qua thy rng nhm du l b phn ch yu to thnh bitum. Cc cht asphanten quyt nh tnh rn ca bitum, c ngha l mun bitum cng rn th hm lng asphanten cng cao. Cc cht nha quyt nh tnh do v kh nng gn kt ca bitum Cc cht du lm tng kh nng chu ng sng gi, nng ma ca bitum. Mt loi bitum tt, chu thi tit tt, c cao th phi c thnh phn nh sau: 25% nha, 15 n 18% asphanten, 52 n 54% du. T l gia asphanten v nha khong 0,5 n 0,6. T l nha so vi du t 0,8 n 0,9. Cn du m cha nhiu parafinic rn l nguyn liu xu nht sn xut bitum. Bitum s c bn thp, tnh gn kt km do c nhiu hydrocacbon khng phn cc. Ngc li cn du m loi aromatic hoc naphten aromtic l nguyn liu rt tt sn xut bitum. b. Mt s tnh cht c trng ca bitum xuyn kim: l i lng c trng cho qunh ca bitum, c tnh bng milimt chiu su ln xung ca kim t di ti trng 100g trong thi gian 5 giy 250C. ln kim cng nh, bitum cng qunh. dn di: l i lng c trng cho tnh do ca bitum, c tnh bng cetimet khi ko cng mt mu c tit din quy nh 250C vi tc ko l 5 cm/ pht. dn di cng ln th tnh do ca bitum cng cao. Tnh n nh nhit: khi nhit thay i, tnh cng, tnh do ca bitum cng thay i. Nu s thay i cng nh th tnh n nh ca bitum cng cao.
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Tnh n nh vi thi gian: L kh nng ca bitum chng li tc ng ca mi trng xung quanh. Do nh hng ca thi gian m tnh cht v thnh phn ca bitum thay i. S thay i gi l s ha gi ca bitum. Tnh n nh ca bitum du m tng i cao, thng th sau 10 n 15 nm s dng, cc tnh cht ca n mi thay i r rt. 4.6.2.2. ng dng ca phn on cn lm nhin liu t l C th s dng trc tip phn on cn du m lm nhin liu t l. Nhit nng ca nhin liu ny vo khong 9.000-10.000 kcal/ kg. T l gia C v H cng thp, nhit nng ca du cng cao. Nu trong nhin liu ny c hm lng cc kim loi nng ln, khi chy s to thnh hp kim vi st c nhit nng chy thp, dn n thng l. 4.7. Cu hi v bi tp 1. 2. 3. 4. 5. 6. Ti sao phi ha lng kh? Nu cc ng dng c bn ca kh t nhin ha lng (LNG) v kh du m ha lng (LPG). V sao LPG c th s dng lm nhin liu cho ng c xng? Bn cht ca qu trnh chy trong ng c xng. Tr s octan l g? Thnh phn ca cc hydrocacbon nh hng th no n tr s octan? nh hng ca thnh phn hydrocacbon n tnh cht chy ca nhin liu trong ng c xng. Cc gii php nng cao tr s octan ca xng? C ch tc dng ca ph gia ch v ph gia oxygen trong vic nng cao tr s octan ca xng? 7. 8. 9. Nu cc ng dng c bn ca xng? Bn cht ca qu trnh chy trong ng c izen. Tr s xtan? Cng dng ca du bi trn, mt vi ch tiu chnh ca du bi trn? Ch s nht? 10. Cc yu cu v qu trnh chy ca nhin liu trong ng c phn lc, t cho bit cc ch tiu cn c ca loi nhin liu ny?
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11. Khi nim v chiu cao ngn la khng khi? nh hng ca thnh phn ha hc ca nhin liu n ch tiu ny nh th no? 12. nh hng ca thnh phn ha hc n tnh t bc chy ca nhin liu trong ng c iezen? 13. Cc yu cu ca ph gia trong du bi trn?
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BI 5 CC C TRNG VT L V S NH GI CHT LNG DU M M bi: HD A5Gii thiu nh gi cht lng cc loi du th v cc sn phm du, s chnh lch gi tr gia loi du th ny vi loi du th khc, ngi ta da vo cc c trng ha l ca chng. Trn c s nh gi ng cht lng mi c hng s dng v cng ngh ch bin hp l. Mc tiu thc hin Hc xong bi ny hc vin c kh nng: M t c cc c trng vt l ca du th v cc sn phm du. nh gi cht lng du m thng qua cc i lng vt l Ni dung chnh 5.1. Xc nh cc c trng vt l ca phn on du m 5.1.1. Thnh phn chng ct phn on Thnh phn ct l mt trong nhng ch tiu quan trng cn phi xc nh i vi cc sn phm trng nh xng, kerosen, izen. Theo thnh phn ct phn on c th bit c cc loi sn phm thu v khi lung ca chng. Cc phn on du bao gi cng gm rt nhiu cc n cht khc nhau vi nhit si thay i. Do vy c trng cho tnh cht bay hi ca mt s phn on l nhit si u v nhit si cui. Qu trnh chng ct c thc hin trong b chng ct tiu chun Engler. Cho 100 ml mu vo bnh. Gia nhit nhit t t, tc thng thng t 4 n 5 ml sn phm trong 1 pht. Khi c git lng u tin rt xung bnh hng th nhit si lc l nhit si u, tip ghi li nhit si ng vi 10, 20, 30, 90% th tch. n khi no ct thy ngn trong nhit k t cc i tt xung t ngt th l nhit si cui.
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T cc gi tr , ta dng th ph thuc gia % sn phm chng ct c v nhit si gi l ng cong chng ct. Mi mt loi nhin liu, c c trng bi thnh phn chng ct nht nh. Nhng nhn chung, nu cng l xng, hoc cng l kerosen th yu cu v khong nhit si gn nh nhau. Thnh phn ct phn on xng ng c c ngha rt quan trng. Nhit si t 10 n 30% c ngha quyt nh kh nng khi ng ca ng c. Khong nhit cng thp ng c cng d khi ng khi my ngui. Tuy nhin thp qu, d to nt hi trong h thng cp nhin liu gy hao tn nhin liu. Nn nhit si 10% khng vut qu 700C. Nhit ct 50% c ngha quyt nh kh nng tng tc ca ng c v qu trnh t nng ng c. Nu nhit ct 50% qu cao khi thay i tc , lng nhin liu trong my t, cng sut gim iu khin xe kh khn. Do vy nhit ct 50% (t 40% n 70%) cng thp cng tt v d dng tng s vng quay ca ng c ln mc ti a trong thi gian ngn nht. Tuy vy nu qu thp s to nt hi gy tht thot nhin liu (v vy khng nn vt qu 1400C). Nhit ct 90% c ngha v mt kinh t, nu nhit 90% cao, xng khng bc hi hon ton trong bung t. Xng trng thi lng theo xylanh vt qua xecmng vo cate cha du, lm long du nhn, lm gim kh nng bi trn v mi mn ng c. Nhit ct cui nh gi mc bay hi hon ton v lm long du nhn. Nu nhit si cui cao qu tr du nhn s b ra tri trn thnh xylanh, mi mn piston, v th nhit si cui khng qu c 2050C. 5.1.2. p sut hi bo ha p sut hi bo ha l mt trong cc tnh cht vt l quan trng ca cc cht lng d bay hi. y chnh l p sut hi m ti , th hi cn bng vi th lng. Cht lng c p sut hi bo ha cng ln th iu kin bo qun, tn tr v vn chuyn cng phi nghim ngt, tun th cht ch cc bin php an ton phng chng chy n.
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p sut hi bo ha Reid l p sut tuyt i 1000F (37,80C) c trng c trng cho kh nng bay hi ca phn on xng. l p sut hi bo ha o c iu kin ca bom Reid 37,80C. i lng ny cng ln bay hi cng cao. p sut hi bo ha c xc nh trong dng c tiu chun gi l bm Reid (hnh 5.1).
4
5
h 1
2
3
Hnh 5.1. Bom Reid 1- Bung khng kh; 2- Bung lng; 3- Bnh n nhit; 4- p k thy ngn; 5- Van
Cho xng vo bnh 2, ni thng vi bnh 1, ri cho vo bnh n nhit, sau khi n nh nhit (37,80C) trong 15 pht th m vn ni ton b h thng vi p k thy ngn. chnh lch h s cho bit p sut hi bo ha ca xng cn o. bc hi ca xng cng cao, chnh h cng ln. 5.1.3. T trng T trng l t s gia trng lng ring ca mt vt mt nhit nht nh v trng lng ring ca mt vt khc c chn l chun, xc nh cng v tr. i vi cc loi sn phm du lng u ly nc ct nhit 4 0C v p sut 760 mmHg lm chun.
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T trng ca du m, hoc mt phn on du m nhit t trn trng lng ring ca nc 40C, ta c th ghi dt4. d so snh, t trng c biu th cng mt nhit , phn ln cc nc u ly 200C (d204) hoc 15,60C (tng ng vi 600F) so vi nc cng nhit . mt s nc in hnh l M cn biu th t trng bng 0API. Cng thc chuyn i t trng sang 0API nh sau:0
API
141,5 d15,6 15,6
131,5
T trng ca sn phm du m thay i rt nhiu khi nhit thay i, nhng khng ph thuc vo p sut. Tuy nhin nu p sut cao th c nh hng cht t. C th xc nh t trng bng phng php nh: dng ph k, cn thy tnh, picnomet. Phng php picnomet l ph bin nht, dng cho bt k loi cht lng no. Phng php ny da trn s so snh trng lng ca du vi nc ct trong cng th tch v cng nhit . 5.1.4. t nht nht l tnh cht ca mt cht lng, c xem l ma st ni ca cht lng v cn tr s chy ca cht lng. nguyn nhn c nht l do i lc c hc gia cc ht cu to nn cht lng. nht ca du m c lin quan n qu trnh bm vn chuyn, s bi trn, s phun nhin liu trong cc ng c. nht ph thuc vo nhit , khi nhit tng nht gim. nht ng lc ( hoc ): nht ng lc biu th cho cc cht lng dng khng c gia tc, c tnh bng cng thc: Trong : l thi gian chy ca cht lng l hng s nht k, khng ph thuc vo nhit m ch ph thuc vo kch thc hnh hc ca nht k.
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Nu nht ln phi dng nht k c ng knh mao qun ln; cn nht ca cht lng cn o nh, th dng nht k c ng knh mao qun nh; sao cho thi gian chy ca cht lng khng qu 200 giy. nht ng lc c tnh bng poaz (P) hay centipoaz (cP). 1 P=100 cP=0,1 N.s/ m2=1 dyn.s/ cm2=1 g/cm.s nht ng hc ( ):ng nht ng hc l t s gia nht ng lc hc v t trng n (c hai u xc nh cng nhit v p sut): d
Trong :
l nht ng hc, tnh bng stc (St) hoc centistc (cSt) l nht ng lc d l trng lng ring, g/cm3 1 St=1 cm2/s=100 cSt
Xc nh nht ng hc bng cch o thi gian chy ca du qua nht k mao qun Pinkvic. nht quy c ( nht Engler): nht quy c hay nht biu kin, cn gi l nht Engler l t s gia thi gian chy ca 200 ml mu nhit th nghim v 200 ml nc ct 200C qua ng nh trong dng c o nht:0 t E 20
t 0
Trong :t 0
0
t E 20 l nht Engler nhit t.
l thi gian chy ca mu nhit t l thi gian chy ca nc 200C
5.1.5. ng cong im si thc xc nh thnh phn phn on ca du m, thng tin hnh chng ct trong b chng ct tiu chun vi cc iu kin quy nh cht ch, gi l chng phc tp (va chng va luyn).
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Qu trnh chng ct nhng vy s cho phn chia cao. Sau dng th quan h nhit si-phn trm sn phm chng ct so vi du th (% th tch hoc trng lng). th ny gi l ng cong im si thc. T kt qu thu c xc nh im si thc, c th xc nh thnh phn cc phn on ca du m c nhit si n 2000C, 3000C n 4850C (hnh 5.2).100 90 80 70 60 50 40 30 20 10 0 0 100 200 300 400 500 600
% Khi lng
Nhit , 0C
Du th Bch H
Du th i Hng
Hnh 5.2. ng cong chng ct im si thc ca du th Bch H v i Hng
Ni chung, ng cong im si thc l mt ng cong quan trng nht ca du m. N cho php nh gi c thnh phn ca cc phn on c nhit si khc nhau. Ngoi ra cn gip cc nh cng ngh xc nh phng n ch bin t yu cu v cht lng v s lng cc phn on mong mun. 5.1.6. im anilin im anilin l nhit thp nht trong iu kin xc nh, anilin l sn phm tng ng ha tan vo nhau to thnh mt hn hp ng nht. Khi thnh phn ha hc khc nhau th gi tr ca im anilin khc nhau. Hydrocacbon thm c im anilin thp hn so vi cc loi hydrocacbon khc rt nhiu (v hydrocacbon d dng tan trong anilin hn). Trong cng mt loi hydrocacbon th im anilin tng ln theo trng lng phn t. im anilin thng thng c xc nh qua phng php th tch bng nhau gia anilin v sn phm. Anilin dng xc nh phi khng c mu, va mi chng ct. Ch dng phn chng ct trong khong 10 n 90%.
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Phng php im anilin thng c s dng xc nh thnh phn cc hydrocacbon thm c trong phn on. hm lng hydrocacbon thm cng ln, im anilin cng thp. 5.1.7. Nhit chp chy Nhit chp chy l nhit ti , khi phn on du m c t nng, hi hydrocacbon s thot ra to vi khng kh xung quanh mt hn hp m nu a ngn la n gn chng s bng chy ri pht tt nh l mt tia chp. Nh vy nhit chp chy lin quan n hm lng cc sn phm nh trong phn on. Du cng c nhiu cu t nh, nhit chp chy cng thp. Phn on xng: Nhit chp chy khng quy nh, thng l m. Phn on kerosen: Nhit chp chy t 28 n 600C, thng thng 400C. Phn on izen: Nhit chp chy cc kn t 35 n 860C, thng thng l 600C. Phn on du nhn: Nhit chp chy t 130 n 2400C. C hai phng php xc nh nhit chp chy: Phng php cc kn v phng php cc h. Phng php cc kn thng p dng i vi i vi cc sn phm d bay hi nh kerosen, k c izen. Phng php cc h thng p dng i vi cc sn phm khng bay hi nh du nhn. Phng php cc kn bao gi cng cho nhit chp chy thp hn so vi phng php cc h. Xc nh nhit chp chy c ngha rt quan trng trong vic tn cha v bo qun nhin liu. Nu nhit chp chy ca nhin liu thp, khi bo qun trong b cha ngoi tri nng nng phi phng c tia la in gn trnh chy n. i vi nhin liu izen cho xe tng, nu nhit chp chy thp, c ngha l hm lng cc cu t nh nhiu, rt nguy him cho ngi ngi trong v xe tng phi lm vic trong iu kin kn hon ton.
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Khi xc nh nhit chp chy ca mt phn on no , thy nhit chp chy khc thng, c th ngh rng trong phn on ln cc nhin liu nh. 5.1.8. Nhit ng c, im ng c v im kt tinh ng c l mt tnh cht ca du m v sn phm du m. Chng b mt tnh linh ng khi nhit h thp. Tnh linh ng mt i l do s to thnh nhng mng kt tinh parafin hoc do nht tng mnh. Mng tinh th parafin to thnh v trong nhng sn phm du m gm hn hp hydrocacbon c nhit ng c khc nhau. Khi lm lnh n mt nhit nht nh, nhng parafin c phn t lng ln kt tinh trc, nhng hydrocacbon c phn t lng nh hn s chui vo khung ting th , dn n s vn c trc khi ng c. Thng thng im vn c ln hn im ng c t 3 n 50C. S ph thuc nhit ng c vo hm lng parafin c biu din qua biu thc sau:0 Tdd
K1
K 2 lgC
Trong C l hm lng parafin rn c trong phn on (% trng lng) K1, K2 l cc hng s Trong trng hp hm lng parafin thp, s ng c l do khi gim nhit , nht tng mnh lm cho c khi nhin liu ng c li. Nhng tnh trn ph thuc rt nhiu yu t nh: t l, cu to cc hydrocacbon trong sn phm du m, kiu lm lnh, nht, lng cc cht nha v asphanten, hm lng nc im ng c: l nhit cao nht m sn phm du lng em lm lnh trong iu kin nht nh khng cn chy c na. im vn c: l nhit m khi sn phm em lm lnh trong nhng iu kin nht nh, n bt u vn c do mt s cu t bt u kt tinh. im kt tinh: l nhit sn phm bt u kt tinh c th nhn thy bng mt thng.69
5.1.9. Nhit chy Nhit chy l lng nhit ta ra khi t chy mt lng nhin liu vi iu kin l nhit ca nhin liu trc khi t v sn phm chy l 200C. Nhit chy l mt trong nhng c tnh ch yu ca nhin liu. Khi t chy hon ton cc nhin liu kh, nhin liu lng hoc nhin liu rn u to thnh CO 2 v H2O v ta nhit theo phn ng:C xHy x y O2 4 xCO2 y H2 O Q 2
Trong trng hp nhin liu cha lu hunh s to thnh SO2 Nc to thnh c th th lng hoc th hi. Gi tr nhit lng cao (Qcao) l lng nhit ta ra khi tt c nc trong sn phm chy trng thi lng, Qcao=Q1 + Q2:C xHy x y O2 4 xCO2 y H2 O Q 2
H2Ohi phm chy trng thi kh.
H2Olng + Q2
Gi tr nhit lng thp (Qthp) l lng nhit ta ra khi tt c nc trong sn Hiu gia nhit lng trn v nhit lng di chnh l nhit lng cn thit nc chuyn t trng thi lng sang trng thi hi, nhit lng ny gi l nhit ha hi ca nc. 5.1.10.Hm lng nc trong phn on du m Nhn chung nc khng ha tan trong du m v cc phn on ca du m. Nhng khi tng nhit th ha tan ca nc trong du m s tng ln. S c mt ca nc trong mt s phn on du gy nguy him cho qu trnh s dng, chng hn: Nu trong du bin th c nc s lm gim cch in. Trong nhin liu phn lc c nc s gy nguy him, v my bay lm vic cao ln, nhit h rt thp (khong 500C), lng nc c trong nhin liu s to thnh cc tinh th nc l tc vi phun, gy gin on cung cp nhin liu.
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Trong sn sut LPG, khi dn n s h nhit , nc s to thnh cc tinh th nh gy tc van gim p. Do vy cn phi tch nc ra khi cc phn on sao cho hm lng nc cng nh cng tt. 5.1.11.Tr s octan Tr s octan l i lng c trng cho kh nng chng kch n ca nhin liu. C hai phng php xc nh tr s octan, l phng php nghin cu (RON) v phng php mt (MON). Bn cht ca phng php ny l so snh bn chng kch n ca nhin liu th nghim v nhin liu tiu chun, biu th bng tr s octan. bn chng kch n ca izo-octan qui c bng 100 v ca n-heptan bng 0. 5.2. nh gi cht lng ca du m qua cc c trng sau xc nh gi tr ca du th trn th trng, ng thi nh hng cho cc qu trnh s dng, ch bin, tnh ton cng sut thit b cho nh my lc du, vic phn tch, xc nh cc ch tiu ca du th l rt cn thit. C rt nhiu c tnh quan trng, trong phn ny ch a ra cc tnh cht tiu biu nht, lin quan n s dng v qu trnh cng ngh ch bin chng. 5.2.1. Thnh phn hydrocacbon trong du m Hydrocacbon l thnh phn quan trng nht ca du th, trong du chng chim t 60 n 90% trng lng. Du cha cng nhiu hydrocacbon th cng c gi tr kinh t cao. Ph thuc vo hm lng ca tng loi: pararfin, naphten, aromat m c th sn xut c cc sn phm nhin liu c cht lng khc nhau. Du cha naphten, aromat s cho php sn xut xng c tr s octan cao. Du cha nhiu n-parafin s l ngun to ra nhin liu izen c cht lng tt, nhng hm lng parafin rn cao qu s lm tng im ng c ca du, gy kh khn cho qu trnh vn chuyn, bc rt, phi p dng cc bin php h im ng, gy tn km. Du trung gian naphten-parafinic s l nguyn liu tt sn xut ra du nhn c ch s nht cao. Khi khai thc c du th, nht thit phi xc nh hm lng v c tnh ca cc hydrocacbon c trong du. C nhiu phng php xc nh chng71
nhng ph bin l phng php ha l nh sc k kh, ph hng ngoi (IR) v t ngoi (UV). 5.2.2. T trng Da vo t trng c th s b nh gi du m thuc loi nng hay nh, mc bin cht thp hay cao. Theo t trng, ph bin ngi ta chia du thay 3 cp: Du nh: Du trung bnh: Du nng:
d15 4 d15 4 d15 4
0,830 0,830 0,884 0,884
Du th cng nh, hiu sut v cht lng cc sn phm trngthu c khi chng ct cng cao; du cng cha t lu hunh, cng mang nhiu c tnh parafinic hoc trung gian naphtenic parafinic. Du cng nng th cha cng nhiu cc cht d nguyn t, cc cht nha v asphanten, khng thun li sn xut
