thiet ke phan xuong cracking xuc tac

7/31/2019 Thiet Ke Phan Xuong Cracking Xuc Tac

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n tt nghip Thit k phn xng Cracking xc tc

Nguyn Vit Hun Ho Du K44-QN HBK HN1http://www.ebook.edu.vn

M u

Hin nay, trn th gii, mt hng xng du l mt mt hng quan trng

v c bit quan trng .N chnh l mu huyt ca nn kinh t quc dn vquc phng cho bt k mt quc gia no.

V Vit Nam ,nhu cu tiu th sn phm du kh ang tng ln cng

vi s tng trng ca nn kinh t quc dn v quc phng.Tuy nhin sn

phm xng Vit Nam hin nay u c nhp khu t nc ngoi.Phn ln

t Singapore vi ba u ni tip nhn l H Ch Minh, Nng v Qung

Ninh. V t ba u ni tip nhn ny ,sn phm c phn phi ti cc kho

trung chuyn trn ton quc. Trong tng lai vic nhp sn phm xng du l

diu khng c li cho nn kinh t ca c nc. V vy m c th p ng

nhu cu xng cho ngi tiu dng th nht thit phi c nh my lc v ch

bin ,trong quan trng hn c l phi c phn xng sn xut xng du [8].

Ngi ta c th sn xut xng bng nhiu cc qu trnh ch bin khc

nhau nh l cracking xc tc, Reforming xc tc, izome ha ...V..V...trong

cracking xc tc l qu trnh ch yu sn xut xng . Tiu chun quan

trng ca nhin liu dng cho ng c xng l ch s octan . Ch s ny cng

cao th kh nng chng kch n cng cao. Thot tin th ngi ta thc hin

cracking phn on du m c nhit si trong khong 490 800 K bng

nhit , nhng vi phng php ny th hiu qu rt thp v sn phm cha

nhiu hydrocacbon phn t thp . n khong nhng nm 1930 , qu trnh

cracking nhit c thay th bng cracking xc tc , vi cht xc tc l

Aluminosilicat t nhin. V u tin ngi ta s dng lp xc tc tnh nhng

m n cng cha mang li hiu sut v cht lng xng cao nh mong mun ,

n li c qa nhiu nhc im chnh v nhng l do nh vy cho nn ngi ta

thay th n bng qu trnh Cracking c lp xc tc chuyn ng .

C rt nhiu cng ngh khc nhau cho qu trnh Cracking c lp xc tc

chuyn ng. Nhng ngy nay ngi ta dng ph bin l cng ngh ca FCC.

Vi cng ngh ny cho ngi ta thu c nhiu xng v cht lng cng tt

hn rt nhiu , phn no cng p ng

c nhu cu xng du hin nay.


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Phn ITng quan l thuyt qu trnh

cracking xc tc

Trong cng ngh ch bin du m cc qu trnh chuyn ha ha hc

di tc dng ca cht xc tc chim mt t l rt ln v ng vai tr v cng

quan trng . Cht xc tc trong qu trnh chuyn c kh nng lm gim nng

lng hot ha ca phn ng v vy m tng tc phn ng ln rt nhiu .

Mc khc , khi c mt cht xc tc th phn ng c kh nng tin hnh nhit

thp hn iu ny rt quan trng i vi nhng phn ng c hiu ngdung nhphn ng hydro ha , alkyl ha , polime ha v.v...

S c mt cht xc tc va thc y nhanh qu trnh chuyn ha ha

hc , va c kh nng to ra nhng nng cn bng cao nht , c ngha l

tng hiu sut ca qu trnh .iu quan trng nht l cht xc tc c kh nng

tng nhanh khng ng u gia cc loi phn ng m v phng din nhit

ng l chng xy ra cng lc trong qu trnh , trong iu kin nh nhau ,

ngi ta gi y l tnh cht chn la ca xc tc. Ngi ta nghin cu rt

nhiu loi cht xc tc v ngi ta cng li dng tnh cht chn la ca n m

hng phn ng ca qu trnh ch bin theo chiu c li nhm thu c

nhng sn phm chnh t hiu sut v cht lng tt nh mong mun.

Chnh v l do cho nn p ng ngy cng nhiu nhu cu dng

xng du th ngi ta nghin cu v ci tin dn qu trnh cracking xc tc

. Qu trnh cracking xc tc vi dy chuyn cng ngh FCC l u im hnc.


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Chng IMc ch v ngha Bn Cht Ha Hc

vc ch phn ng

I. Mc ch v ngha ca qu trnh cracking xc tc

Cracking xc tc chim mt v tr c bit quan trng trong cng

nghip ch bin du m . Lng du m dng ch bin bng cracking xc

tc l tng i ln.V d nh : vo thng mt nm 1965 tng lng du m

n

c m ch bin l 1500 tn/ngy trong c 800 tn/ngy (tc khong53%) c ch bin bng cracking xc tc[3-trang62]

Qu trnh cracking xc tc l mt qu trnh ch yu sn xut xng

cho t v mt t cho xng my bay.Chnh v vy m khng c nh my lc

du no li thiu phn xng cracking xc tc.

Mc ch qu trnh cracking xc tc [1,2,3] l bin i phn on du

m c nhit si cao thnh cc cu t xng c cht lng cao, ngoi ra cn

thu thm mt s sn phm ph khc nh gasoil nng , gasoil nh, kh,...Qu

trnh cracking xc tc thc cht l qu trnh cho tip xc nguyn liu vi cht

xc tc trong iu kin qui nh v ch cng ngh ,cc phn ng c li xy

ra nhm thu dc sn phm c cht lng tt v hiu sut ln, ng thi cc

phn ng ph c hi cng xy ra nh phn ng to cc bm trn b mt cht

xc tc lm cho xc tc gim hot tnh.Do vy m cn phi tin hnh ti sinh

xc tc.II. C ch phn ng : [1,2,3,4,5,6,7]

Trong iu kin m chng ta tin hnh qu trnh cracking xc tc, mt

s lng ln cc phn ng ha hc xy ra v chng quyt nh cht lng hiu

sut ca qu trnh. l cc phn ng sau:


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1. Phn ng phn hu cc mch C C, phn ng crackingL phn ng phn hu b gy mch nhng phn t c kch thc ln

(trng lng phn t ln) thnh nhng phn t c kch thc nh hn (trng

lng phn t nh hn). y l phn ng chnh ca qu trnh.

+ Phn hu parafin to olefin v parafin c trng lng phn t nh hn

CnH2n+2 CmH2m + CpH2p+2 (n = m + p)

+ B gy mch olefin to olefin nh hn

CnH2n CmH2m + CpH2p (n = m + p)

+ Hydrocacbon thm c nhnh bn b b gy to thnh parafin v

hydrocacbon thm c nhnh nh hn

ArCnH2n+1 ArCmH2m+1 + CpH2p (n = m + p)

+ Naphten b b gy m vng to cc olefin (tr vng hexan)

CnH2n CmH2m + CpH2p (n = m + p)

naphten olefin olefin

CnH2n C6H12 + CmH2m + CpH2p (n = m + p+ 6)

naphten xyclohexan olefin olefin

2. Phn ng ng phn ho (izome ho)L phn ng to ra nhng hydrocacbon c cu trc mch nhnh (cu t

lm tr s octan tng ln).

n-olefin izo-olefin

n-parafin izo-parafin

3. Phn ng chuyn di hydro di tc dng ca xc tcNh c xc tc m c s phn b li hydro cho nn lm no c mt

s hydrocacbon i (sn phm phn hu), v vy lm tng c tnh n nh

ho hc ca sn phm thu.

Naphten + olefin hydrocacbon thm + parafin

4. Phn ng trng hp

Ch yu xy ra vi hydrocacbon i.


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CnH2n + CmH2m CpH2p (n + m = p)

5. Phn ng alkyl ho v kh alkyl hoPhn ng alkyl ho xy ra nhit thp, lm gim hiu sut kh.

ArH + CnH2n Aromat CnH2n+1

Hydrocacbon thm olefin alkyl thm

Phn ng kh alkyl ho ngc vi phn ng alkyl ho, xy ra nhit

cao v to nhiu kh.

6. Phn ng ng

ng t to ccPhn ng ny ch yu xy ra i vi cc hydrocacbon thm a vng, xy

ra khi nhit cao.

S to cc trong qu trnh cracking xc tc l khng mong mun, v cc

to thnh thng bm trn b mt xc tc, gim hot tnh b mt xc tc,

gim thi gian lm vic ca xc tc.

Hiu ng nhit ca cc phn ng trn khc nhau v du cng nh v gi

tr. a s cc phn ng phn hu l phn ng thu nhit mnh, cn cc phn

ng nh phn ng ng phn ho, chuyn v hydro, polyme ho v phn ng

ngng t l cc phn ng to nhit yu. Hiu ng nhit tng cng ca qu

trnh cracking xc tc l thu nhit, vi gi tr thay i t 100 n 400 kJ/kg

nguyn liu, tu theo bn cht ca nguyn liu c s dng trong qu trnh.

Hin nay, vn cha c s nht tr hon ton trong vic gii thch c ch xc

tc qu trnh cracking.Nhng nhn chung th ph bin hn l gii htch theo c

ch ioncacbonic.Cc ioncacbonic ny c to ra khi m cc phn t

2H2 H22


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hydrocacbon ca nguyn liu tc dng vi tm axit ca xc tc.Theo thuyt

ny th qu trnh cracking xc tc xy ra theo 3 giai on chnh sau y:

a. To ioncacboni

- Paraffin : Cc hydrocacbon paraffin, trong qu trnh tin hnhcracking xc tc, n s b hp th trn trung tm axit Lewis ca cht xc tc

to ra ion cacboni :

V d : Cracking n-hexan ( 2 -trang 109 )

CH3-CH+-CH2-CH2-CH2-CH3

CH3-CH2-CH2-CH2-CH2-CH3 +H2

CH3-CH2-CH2-CH2-CH2-CH3in tch dng khng bao gi nhn c cacbon bc mt.

Tng qut c th vit :

A (H + )

CnH2n+2 CnH2n+1 + H2

Ngoi ra , Parafin cng c th b hp th trn nhng tm axit Bronsted :

CnH2n+1 +H2

CnH2n+2 + H+ CnH2n+3

CmH2m+1 + CpH2p

- Olefin: y l thnh phn khng c trong nguyn liu ban u ca qu

trnh m n c to ra do s phn hy cc hydroccbon thm ,Parafin ,

naphten ,...Olefin l hp cht rt hot ng ,nh vy m n tham gia vo phn

ng to Ion cacboni do s tc dng ca olefin vi tm axit Bronsted ca xctc:

Ion cacboni to thnh do s tc dng ca olefin vi tm axit Lewis ca

xc tc:

+ H+ (xt)+

R1 CH C R2 + (xt)

H

R1 CH C R2

H H


7/109



hoc l

CnH2n + H+ Cn

+H2n+1

CnH2n + L C+

nH2n+1 + LH

Ion cacboni to thnh trong cc phn ng tun theo quy tc nht nh.

Nh khi olefin tc dng vi H+(xt) th xc sut to alkyl bc 2 ln hn alkyl

bc mt.

Khi olefin c lin kt i cacbon bc 3 th ion cacboni bc 3 d to

thnh hn cacbon bc 2.

T hydrocacbon naphten:

Khi hydrocacbon naphten tc dng vi tm axit ca xc tc hay cc ion

cacboni khc s to ra cc ion cacboni mi tng t nh qu trnh xy ra vi

parafin.

T hydrocacbon thm :ngi ta quan st thy s to thnh ion

cacbonil s kt hp trc tip ca H+ vo nhn thm

Cc hydrocacbon thm c mch bn di th s to thnh ion cacboni

cng ging nh trng hp parafin.

RH + R+

H Al O Si

O

Oolefin

Al O Si

O

O

CH3 CH2 CH CH2+

CH3 CH2 CH2 CH2+

d to thnh hnCH3 CH2 CH CH2 H+

(xt)+

d to thnh hnH+

(xt)+CH3 CH C CH3

CH3

CH3

CH3 CH2 C CH3+

CH3CH3 CH CH CH3

+

H+CH2 CH3

+

CH2 CH3H+


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Thi gian sng ca cc ion cacboni c to ra dao ng t phn triu

giy n hng pht. Cc ion cacboni ny to ra nm trong lp cc phn t hp

ph, chng l nhng hp cht trung gian rt hot ng i vi nhiu phn ng

xy ra khi cracking.

b. Giai on bin i ion cacboni

Cc ion cacboni l nhng hp cht rt hot ng ,chnh v vy khi c

to ra t giai on trn li nhanh chng tham gia vo cc phn ng bin i

khc nhau nh :

Phn ng ng phn ho, chuyn di ion hydro, nhm metyl to cu

trc nhnh.

RCCCC CCCCR

n nh ca ion cacboni theo bc l gim dn nh sau :

C3+ (bc 3) > C2+ (bc 2) > C3+ (bc 1)

- Ion cacboni tc dng vi phn t trung ho to thnh ion cacboni mi

v phn t mi (hydrocacbon no hay i) theo phn ng vn chuyn ion

hydrit.

C+nH2n+1 + CmH2m CnH2n + C+

mH2m+1

C+nH2n+1 + CmH2m+2 CnH2n+2 + C+

mH2m+1

Phn ng cracking: Cc ion cacboni c s nguyn t cacbon ln xy ra

s phn hu v t mch v tr so vi nguyn t cacbon tch in. Sn

phm phn hu l mt phn t hydrocacbon trung ho v ion cacboni mi c

s nguyn t cacbon nh hn

R CH2 CH CH3+

CH3

R C CH2+

CH3

R CH CH2+

++


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.

Nu ba lin kt CC v tr th lin kt CC v tr [A] l c xc sut

t mch ln nht, sau n v tr [B] v cui cng n v tr [C].

Vi ion cacboni mch thng:

i vi ion cacboni l ng ng ca benzen, v d nu p dng quy tc

v tr bnh thng th v tr rt bn vng. Chnh v vy m ngi ta cho

rng proton phi c kt hp vi mt trong nhng lin kt CC trong nhn

thm to thnh nhng hp cht trung gian, sau mi phn hu theo quy tc

nu trn. Khi phn hu, in tch ion cacboni s dch chuyn theo s sau:

Nh vy trong hydrocacbon thm hiu ng tch in nhn thm l

nguyn nhn quan trng hn so vi nguyn nhn l s bin i ion cacboni

bc hai thnh bc ba.

Cc ioncacboni l ng ng ca Benzen m c mch nhnh cng di th

tc xy ra cng lnv cng d. V d nh ioncacboni izobutyl-benzen c

tc ln hn 10 ln so vi ioncacboni izopropyl-benzen .

Cc nhm metyl , etyl , rt kh b t ra khi nhn Benzen ( v l nng

lng lin kt ln ) v do kh to c ion CH3+ v C2H5

+. iu ny gii

thch c v sao trong xng cracking xc tc li c hm lng hydrocacbon

c mch nhnh bn ngn l ln v cng gii thch c l v sao trong sn

phm kh ca qu trnh cracking li nhiu hydrocacbon mch nhnh.

R C C C C C C+

C

C

[A] [B]

[C]

+

CH3 CH CH2 R+

RCH3 CH CH2+

C

C C+

C

CH C+

+C

C C

C+

H


10/109



c. Giai on dng phn ng

Giai on ny xy ra khi cc ion cacboni kt hp vi nhau hoc chng

nhng hay nhn nguyn t hydro ca xc tc to thnh cc phn t trung

ho. Nhn chung , nhng phn ng ha hc xy ra trong qu trnh cracking

xc tc l rt phc tp.

III. ng hc cho qu trnh cracking xc tc.[4,5,6,7,14]

V ng hc, cracking xc tc l mt th d in hnh v xc tc d th.

Qu trnh cracking xc tc c th xy ra cc giai on sau:

1- Qu trnh khuch tn nguyn liu n b mt xc tc (khuch tn

ngoi).2- Khuch tn hi nguyn liu n cc tm hot tnh trong l xp ca

xc tc (khuch tn trong).

3- Hp ph nguyn liu trn tm hot hot tnh xc tc.

4- Cc phn ng ha hc trn b mt xc tc.

5- Kh hp ph cc sn phm cracking v nguyn liu cha tham gia

phn ng ra khi b mt v ra khi l xp ca xc tc.6- Tch cc sn phm cracking v nguyn liu cha tham gia phn ng

ra khi vng phn ng.

Tc chung ca qu trnh nh vy s c quyt nh bi giai on no

chm nht. Phn ng xy ra trong vng ng hc hay vng khuch tn hon

ton ph thuc vo bn cht ca xc tc c s dng, ph thuc vo bn cht

ca nguyn liu v vo ch cng ngh ca qu trnh. Cc nghin cu cho thy, nu qu trnh cracking xc tc nguyn liu l gazoil nh (nguyn

liu mu) trn xc tc dng cu khi kch thc ht xc tc t 3 5 mm v

nhit l 450 5000C th phn ng xy ra vng trung gian gia ng hc

v khuch tn. Cn khi cracking lp si (FCC) ca xc tc nhit 480

5300C th phn ng xy ra vng ng hc.


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Tc ca phn ng cracking xc tc, trong a s cc trng hp c

miu t bng phng trnh bc mt c dng:

k = v0.n.ln(1 x) (n 1)x

y: k: tc ca phn ng (mol/g.h)

v0 : tc truyn nguyn liu (mol/h)

n: s mol sn phm c to thnh t 1 mol nguyn liu

x: mc chuyn ha (phn mol).

i vi phn on du trn xc tc zeolit, phng trnh bc 1 li c dng

sau:

k=vo/(1-x)

y v0 l tc th tch khng gian truyn nguyn liu (m3/m3.h).

IV. Cracking xc tc cc hp cht hydrocacbon ring

l.[1,2,3,4,5,6,7]

1. S bin i cc hydrocacbon parafinCc hp cht parafin l cu t quan trng ca phn on gazoil. Cc

nghin cu qu trnh cracking xc tc parafin s gip cho php tin hnh mhnh ha cc hin tng ca qu trnh.

Ging nh qu trnh cracking nhit, qu trnh cracking xc tc, cc

hydrocacbon parafin cng b phn hy to thnh phn t olefin v parafin c

trng lng phn t b hn.

Phng trnh tng qut:

CnH2n+2 CmH2m+2 + CpH2p (p, m < n)Nu mch parafin cng di th s phn hy xy ra ng thi mt s ch

trong mch ch khng phi ch xy ra hai u mt ca mch nh qu trnh

cracking nhit. Cc hydrocacbon parafin c trng lng phn t thp th kh

nng phn hu km.

+


12/109



V d: i vi butan C4H10 nhit 5000C; v0 = 1 h

1 ch c 1 % trng

lng b phn hy. Tuy nhin tc phn hy ca n vn ln hn gp 6 ln so

vi khi phn hu n thun di tc dng ca nhit.

Ngoi ra cn b kh hydro nhng mc nh.

Khi trng lng phn t ca parafin tng ln th kh nng phn hy v

tc phn hy cng tng ln. Tc phn hy ca parafin di tc dng ca

xc tc ln hn nhiu so vi khi phn hu iu kin cracking nhit. Tnh hp

ph chn lc ca xc tc trc tin v cao nht l i vi hydrocacbon olefin.

V vy parafin khng nm trong lp hp ph ha hc m nm ngoi gii hn

ca lp ny. Song nng lng b mt xc tc vn c tc ng n parafin cho

nn to ra nhng khu vc c nng cc phn t hydrocacbon cao m c lin

kt CC yu. Nh vy lm gim nng lng hot ha khi phn hu.Nng lng hot ha ca phn ng cracking parafin gim dn nu chiu

di mch hydrocacbon parafin tng.

Bng 1 : Nng lng hot ha ca cc n-parafin in hnh

Hydrocacbon nC6H14 nC7H16 n-C8H18

E kcal/mol 36 29 24

V vy khi cracking, mch hydrocacbon parafin cng di, cng d b b

gy. V d khi cracking xc tc cc parafin nhit 5500C nh sau:

C4H10 C2H6 C2H4+ (30%)

C4H6 H2+ (10%)

t C, xc t co

(60%)CH4 C3H6+


13/109



Bng 2:

Hydrocacbon n-C5H12 n-C7H16 n-C12H26 n-C12H26

% cracking 1 3 18 42

Cho nn cc parafin c trng lng phn t ln khi phn hu to thnh

parafin c trng lng phn t nh hn v c th b phn hu tip tc:

Cc parafin c cu trc mch nhnh tham gia phn ng phn hy vi tc

ln hn cc parafin mch thng:

S phn nhnh v s lng nhnh ca parafin c vai tr rt quan trng

trong qu trnh cracking. N c lin quan n kh nng to ion cacboni v do

n s quyt nh c tc to thnh sn phm. iu ny c chng

minh t cc s liu % chuyn ha parafin C6 khi cracking trn xc tc

aluminosilicat nh di y:

t C, xc t co

C9H20 C5H10+CH3 (CH2)12 CH3

t C, xc t co

C5H12 C4H8+C9H20

(phn hu 42%)t C, xc t c

o

C4H8 C4H10+C8H18n-

(phn hu 49%)izo- izo-C4H10 C4H8+C8H18t C, xc tc

o


14/109



Bng 3:

C6 % chuyn ho

CCCCCC 14CCCCC

C

25

CCCCC

C

25

CCCC

C C

12

C

CCCC

C

10

Khi cracking n-hexan nhit 5500C trn xc tc axit, s phn b cc

sn phm xy ra nh sau:

Bng 4:

Hydrocacbon H2 CH4 C2 C3 C4 C5

%V 9 12 19 49 8,5 1,6

S phn b ny khng i xng nhau qua C3. S c mt mt lng ln H2

v metan cho thy rng cng mt lc xy ra nhiu phn ng, c th c c phn

ng cracking nhit cng vi cc phn ng ca ion cacboni nh nu trn.

Phn ng chnh to sn phm s ph thuc vo tng quan gia cc phn ng

cracking (theo quy tc ) v phn ng vn chuyn hydro ca ion cacboni.


15/109



Do cracking xc tc m lm gim kch thc ca ion cacboni R+ cc ion

c kch thc nh nh+CH3 hay+C2H5 s kh to ra (do ct mch v tr so

vi cacbon mang in tch). V th trong sn phm u tin to ra C3 hay C4

nhiu hn C1 v C2 so vi qu trnh cracking nhit.

Ngoi ra cc parafin cn tham gia phn ng ng phn ha, chuyn di

hydro v nhm metyl, nguyn t cacbon tch in:

2. S bin i ca hydrocacbon olefin (1,2,3)Nh ni trn , Olefin khng c mt trong thnh phn nguyn liu m

n c to ra do cc phn ng ca qu trnh v tnh hp ph chn lc cao

nht ca xc tc l hydrocacbon olefin trong qu trnh cracking xc tc, chonn iu kin cracking xc tc cc hydrocacbon olefin chuyn ha vi tc

nhanh hn hng nghn n hng chc nghn ln so vi khi cracking nhit.

Hydrocacbon olefin c mt trong hn hp phn ng l do phn ng

cracking parafin, naphten hay alkyl thm. Hydrocacbon olefin l nhng hp

cht hot ng hn, trong giai on u tin ca qu trnh, chng tham gia

phn ng to ion cacboni bi qu trnh hp th mt proton vo lin kt i.

Ion cacboni va to ra s b cracking theo quy tc , khi to thnh mt

olefin nh hn v mt ion cacboni bc mt m ion ny c th li proton

trn b mt ca xc tc hay c th ng phn ha thnh ion cacboni bc hai.

V d: RCH=CHCH2CH2R1 + H+

RCH2CHCH2CH2R1 RCH2CH=CH2 + CH2CH2R1

CH3CH2R1 R1CH=CH2 + H2

n- izo-C5H11C5H11+ +

izo-C5H12+

izo-C5H11+

C4H10+ C4H9++

RRH R1+

+

+ R1H+

R2 olefin++

+ +

+


16/109



Cc hp cht olefin nh C2 C5 va to thnh t tham gia vo cc phn

ng cracking, m chng thng tham gia vo cc phn ng vn chuyn hydro

v phn ng a t, kt qu l dn n to ra parafin v cc. Khi cracking cc

olefin t C5 tr ln, ngoi phn ng ct mch theo qui tc , ngi ta cn quan

st thy c xy ra phn ng dime ha. V d khi cracking penten quan st

thy cc phn ng sau:

H+ + C=CCCC CH3CHCH2CH2CH3

CH3CH=CH2 + CH2CH3

2C5 C10 C3 + C7

C7 C3 + C4

Chnh v xy ra cc phn ng trn m trong sn phm c t l C3/C4 bng

2. Phn ng cracking penten l phn ng lng phn t, trong khi phn ng

cracking hepten li l phn ng n phn t, ngha l khng c s cnh tranh

ca phn ng dime ha:

C7 C3 + C4 (vi C3/C4 = 1)

Cn i vi hexen, tc ca qu trnh n phn t khng nhanh hn so

vi qu trnh lng phn t. T l gia tc phn ng n phn t vi phn

ng a phn t, i vi penten, hexen, hepten tng ng bng 0 : 0,2 : 7. Gi

tr ny cho thy tc cracking olefin C7 ln hn nhiu ln so vi tc

cracking n-heptan (l parafin). So vi qu trnh cracking nhit, tc phn

ng ca olefin trong cracking xc tc ln hn rt nhiu.

Ngoi phn ng ct mch, cc hydrocacbon olefin cn tham gia phn ng

ng phn ha:

CH3 C CH2

CH3

CH3 CH CH CH3

CH2 CH CH2 CH3


17/109



Tc phn ng ng phn ha tng khi trng lng phn t ca olefin

tng. Cc olefin cn tham gia phn ng trng hp to ra phn t c trng

lng ln hn.

Cc olefin cn phn ng vi hydro to thnh parafin:

Cc olefin trong qu trnh cracking xc tc cn tham gia phn ng ngng

t, ng vng to hydrocacbon thm a vng v vng thm a t l cc:

3. S bin i cc hydrocacbon naphtenic:Cc hydrocacbon naphtenic tham gia phn ng trong qu trnh cracking

xc tc vi tc ln hn 500 4000 ln so vi khi cracking nhit. Trong

iu kin cracking xc tc naphtenic tham gia phn ng alkyl, kh hydro v

phn b li hydro to hydrocacbon thm, parafin v hydro.

V d:

Phn ng phn hy vng naphten to izo-parafin:

CH3 CH2 CH CH22 CH3(CH2)5 CH CH2

CH2 CH CH2 CH3

CH2 CH CH CH2CH2 CH2CH2 CH2 +

+R CH2 CH2 H2 R CH2 CH3

CH2 CH2 CH2 CH2 CH2 CH2 H2+ + + 3

CH2 CH CH2 CH2 CH2 CH3H2 H2 H2

H2+ 2CH2 CH2 CH3

C3H8 +

+ H23

CH3 CH3 CH2 CH2 CH2 CH CH3

CH3


18/109



* Phn ng ng phn ha vng naphten

Phn ng chuyn v cc nhm bn:

Sn phm khi cracking naphten c tnh cht no nhiu hn so vi cracking

parafin. Trong cc phn ng phn hu, cc phn t c to thnh a s c s

cacbon nhiu hn C3. Cracking xc tc naphten cho hiu sut sn phm lng

cao, ngha l hiu sut s cao hn, cho nn naphten l thnh phn l tng

nht trong nguyn liu cracking xc tc.

4. S bin i ca hydrocacbon thm (1,2,3)Cc hydrocacbon thm m c gc alkyl nh bn th rt kh b cracking

ngay c khi c mt ca cht xc tc , v vng benzen c bn cao .V vy

m trong qu trnh cracking xc tc, cc hp cht alkyl thm do vng thm c bn cao hn nn trc tin s xy ra qu trnh ct nhnh alkyl (3-trang92 )

. Nhng toluen c bn rt ln, v th khng th tch nhm metyl hay etyl

trong iu kin cracking. Mch alkyl cng di th cng d b b gy v nu

mch alkyl li c nhnh th tc ct nhnh cn ln hn nhiu. iu ny d

dng gii thch khi xem xt nng lng hot ha ca hydrocacbon thm. (1-

trang 112, 2-trang 114, 3-trang 92,93 )

CH3

CH2 CH3

CH3

CH3

CH3

CH3


19/109



Bng 5:

Loi hydrocacbon thm Nng lng hot ho (kcal/mol)

C6H5C2H5 50

C6H5C4H9 34

C6H5CHCH2CH3

CH3

19

C6H5CHCH3CH3

17,5

V d: Khi cracking xc tc propyl benzen, phn ng xy ra nh sau:

C6H5CH2CH2CH3 C6H6 + CH3CH=CH2

Cn khi cracking nhit li xy ra theo hng khc:

C6H5CH2CH2CH3 C6H5CH3 + CH2=CH2

Cc phn ng khc li xy ra trong qu trnh

cracking xc tc hydrocacbon thm l:

Phn ng ng phn ho: Cc hydrocacbon thm cha nhiu gc metyl

d tham gia phn ng ng phn ho do s chuyn v cc nhm metyl theo

vng benzen.

V d:CH3

CH3

t C, xc t co

CH3

CH3

CH3CH3t C, xc t co

para-xylen meta-xylen octo-xylen


20/109



Hydrocacbon thm cn tham gia phn ng chuyn v nhm metyl

ngoi phn t: (1,2,3)

Hydrocacbon thm c nhnh alkyl di c th khp vng to

hydrocacbon thm d vng:

Cc hydrocacbon thm a vng xy ra phn ng ngng t v to cc:

hay

Cc hydrocacbon thm a vng ngng t cao to cc d hp ph trn b

mt xc tc. V vy chng km hm qu trnh lm nh hng n qu trnh

cracking cc loi hydrocacbon khc.

Trong iu kin ca cracking xc tc, cc bin i ca hydrocacbon

ring l c th tm tt nh sau:

2t C, xc t c

o

CH3

CH3

CH3

+

CH3

CH3CH3

t C, xc tco

CH2 CH2 CH2 CH3

CH2 CH2 CH2 CH3

H25+

2 + CH2 CH2

2H2 H22


21/109



Olefin v parafin

Parafin Olefin v hydro

izo-parafin

Cc hp cht olefin c trng lng thp

Parafin v dien

Olefin Parafin hay naphten v hydrocacbon thm

Polyme, cc

Olefin v parafin

Naphten Xyclohexan v olefin

Hydrocacbon thm

Olefin

Parafin v alkyl thm c mch bn ngn

Hydrocacbon thm ng phn ho, chuyn v nhm alkyl

(alkyl thm) Sn phm ngng t, cc

Ngoi ra cn xy ra cc phn ng bc 2 nh:

Naphten + Olefin Hydrocacbon thm v parafin

Hydrocacbon thm + Olefin Sn phm ngng t, cc

V. Cracking phn on du m (1,11,12)

cracking xc tc phn on du m, do qu trnh rt phc tp, nn

thc t khng th miu t tt c cc phn ng ho hc xy ra trong qu trnh.

Do ngi ta thng a ra s kho st cc hng phn ng chnh trongqu trnh cracking xc tc. V d khi nguyn liu l phn gazoil chng ct

chn khng, ta c th dng s sau:

LCO - phn on du nh ca cracking xc tc

HCO - phn on du nng ca cracking xc


22/109


23/109



chng IIxc tc ca qu trnh Cracking

Xc tc l mt trong nhng lnh vc khoa hc k thut lun c nhiu

ngi quan tm v nghin cu, c bit l xc tc dng cho cng nghip ha

du , trong c qu trnh cracking . Nh vo kh nng lm gim nng lng

hot ha ,nh vo tnh xht chn lc phn ng , ...m hiu sut cng nh cht

lng ngy cng tng ln .

S pht trin v ci tin qu trnh cracking xc tc trong cng nghip

ch bin du m, ngoi vic ci thin v nguyn liu, h thng thit b, ch cng ngh v.v..., th ta thy rng ci chnh l do s ci tin trong vic s dng

cc cht xc tc. Phn ng cracking xc tc ch yu xy ra trn b mt xc

tc, chiu hng ca phn ng ph thuc rt nhiu vo bn cht ca xc tc.

Xc tc c dng trong qu trnh cracking thng l xc tc rn, xp, c

ngun gc thin nhin hay tng hp, vi b mt ring ln. Xc tc cracking

u tin c dng l t st thin nhin c tnh axit (v d loi

montmorillonit).

V d: Lin X vo nhng nm 1919 - 1920 dng xc tc AlCl 3

trong h thng cracking sn xut xng.

Xc tc AlCl3 tin hnh nhit thp 200 3000C. Nhng trong qu

trnh s dng ngi ta thy c nhiu nhc im sau: Xc tc b mt mt

nhiu do to phc vi cc hydrocacbon ca nguyn liu, iu kin tip xc

gia xc tc v nguyn liu khng tt, cho hiu sut v cht lng xng thp.

V sau ngi ta nghin cu s dng aluminosilicat v nh hnh m u

tin l t st bentonit. Vo nm 1936 Lin X s dng xc tc

aluminosilicat quy m cng nghip. Ngi ta tin hnh tng hp

aluminosilicat trong cc nh my ch to xc tc. Sau trong cng nghip

ch bin du m ngi ta dng ph bin xc tc aluminosilicat tng hp v

n c hot tnh v chn lc tng i cao. Xc tc ny tng c s


24/109



dng trong cng nghip cracking sut 30 nm. Tuy vy, hin nay vic ci

thin xc tc vn khng ngng pht trin v n cui thp nin 60 ca th k

20, ngi ta chuyn sang ch yu dng xc tc cha zeolit.

M vo nm 1972 s dng khong 80% cht xc tc cha zeolit cho

qu trnh cracking xc tc. Hng nm M tiu th 130 nghn tn xc tc,

trong ch c 14 nghn tn l khng cha zeolit.

I. Vai tr ca xc tc trong qu trnh cracking (1,2,3,12,14)

Xc tc trong qu trnh cracking c tm quan trng rt ln. N c kh

nng lm gim nng lng hot ha ca phn ng, do vy m tng mc

phn ng ln rt nhiu. Dng xc tc cho php qu trnh tin hnh iu kinmm hn. V xc tc c tnh chn lc nn hng qu trnh ch bin theo

nhng phn ng c li nhm thu c sn phm phn ng c cht lng v

hiu sut cao.

II. Nhng yu cu cn thit i vi xc tc

Xc tc cho qu trnh cracking i hi nhng yu cu sau:

1. Hot tnh xc tc phi cao: [1-trang120]Hot tnh xc tc l yu cu quan trng nht i vi xc tc dng trong

qu trnh cracking.

V mc ch ca cracking l nhn xng, nn phng php dng hiu sut

xng thu c nh gi hot ng ca xc tc s n gin hn, hot tnh

ca xc tc cng cao s cho hiu sut xng cng ln. Do vy, hot tnh ca

xc tc thng c biu din thng qua ch s hot tnh. l gi tr ca

hiu sut xng (%KL) khi cracking nguyn liu mu trong iu kin phng th

nghim.

Hot tnh xc tc ph thuc vo tnh cht vt l - ha hc ca xc tc,

m trc ht l ph thuc vo thnh phn ha hc ca xc tc cng nh ph

thuc vo iu kin cng ngh ca qu trnh. Trong thc t sn xut, da vo

hot tnh ca xc tc, ngi ta phn xc tc thnh cc loi nh sau:

+ Xc tc c hot tnh cao, hiu sut xng > 45%


25/109



+ Xc tc c hot tnh trung bnh, hiu sut xng t 30 n 40%

+ Xc tc c hot tnh thp, hiu sut xng < 30%.

Bng 6: Tnh cht ca xc tc FCC

Thnh phn ho hc, %

Oxyt nhm 13

Oxyt silic 87

Oxyt cc nguyn t t him 2 4

Oxyt natri 0,02 0,2

Trng lng rt, g/cm3 0,8 0,9

hot tnh n nh 55 60

hot tnh theo ASTM 75 80

bn do mi mn, % 94 96

Thnh phn c ht, %

n 20 m

n 40 m

n 100 m

< 2 3

15 25

96 98

B mt ring, m2/g 400 450

2. chn lc xc tc phi caoXc tc cn c chn lc cao cho ta xng c cht lng cao v hiu

sut ln, v trong kh cracking c nng ln cc hydrocacbon c cu trc

nhnh.

Trc tin cht xc tc lm tng tc ca cc phn ng c li trong

nhng iu kin nhit v p sut nht nh, sau c tc dng lm gim


26/109



tc cc phn ng ph ,nht l nhng phn ng gy ng c xc tc nh

phn ng to cc (6 - trang 104)

Trong qu trnh cracking, chn lc ca xc tc quyt nh kh nng

to cc sn phm c gi tr ca n, l cc cu t xng c tr s octan cao.

Ngi ta c th nh gi chn lc bng cch xc nh t l gia hiu sut

xng v cc (hay kh) cng mt su bin i. Xc tc thng c nh

gi ng thi hot tnh v chn lc ca n so vi xc tc mu khi tin

hnh trong cng mt iu kin cracking. T s gia hiu sut xng v cc

(hay kh) cng ln th chn lc xc tc cng cao. Sau mt thi gian lm

vic c hot tnh v chn lc ca xc tc u b gim do c nhng thayi v tnh cht ca xc tc trong iu kin lm vic.

3. n nh phi ln: (1,2,3,14)Xc tc ch to ra cn phi gi c nhng c tnh ch yu (hot tnh,

chn lc) sau mt thi gian lm vic lu di. Cht xc tc c thi gian lm

vic lu di th gi thnh chi cho cht xc tc cng thp ( cho d tin mua xc

tc c t ) hn so vi khi mua xc tc r m thi gian lm vic ngn.

n nh xc tc c trng cho kh nng khng thay i cc tnh cht

trong qu trnh lm vic. Xc tc c n nh cng cao cng tt trong qu

trnh s dng.

4. m bo bn c v bn nhit: [3]Trong qu trnh lm vic, xc tc c xt vi nhau v c xt vi thnh

thit b lm cho xc tc d b v, do lm tn tht p sut qua lp xc tc

tng ln, lm mt mt xc tc ln. V vy m xc tc phi m bo bn c.

Khi lm vic nhit c th thay i, khi nhit cao qu m nu xc

tc khng c bn nhit th c th b bin i cu trc dn n lm gim cc

tnh cht ca xc tc.

6. Xc tc phi m bo thun nht caoXc tc cn ng nht v thnh phn, v cu trc, v hnh dng, v kch

thc. Khi kch thc khng ng u s to ra nhng vng phn lp v c tr


27/109



lc khc nhau v do s phn lp theo kch thc nn s ph v ch lm

vic bnh thng ca thit b. Mt khc khi kch thc khng ng u lm

tng kh nng v vn dn n mt mt xc tc. Cu trc l xp khng ng

u s lm gim b mt tip xc dn n lm gim hot tnh xc tc.

7. Xc tc phi bn vi cc cht lm ng c xc tcXc tc phi chng li c hiu qu tc dng gy ng c ca nhng hp

cht ca nit, lu hunh, cc kim loi nng ko di thi gian lm vic ca

xc tc.

8. Xc tc phi c kh nng ti sinh

y l yu cu quan trng trong qu trnh s dng xc tc. Xc tc ckh nng ti sinh tt s nng cao c hiu qu v nng sut ca qu trnh,

lng tiu hao xc tc cng gim xung.

9. Xc tc phi d sn xut v r tin:y cng l yu t quan trng gp phn nh hng cho cc nh nghin

cu v sn xut.

III. zeolit v xc tc cha Zeolit

1. Xc tc Zeolit [1,2,3,12,13,14]Zeolit l hp cht ca alumino - silic, l cht tinh th c cu trc c bit.

Trong htin nhin c khong 40 loi Zeolit c pht hin . Song cc ng

dng quan trng trong lp hp ph , tch lc xc tc ...ch yu l nh vo

Zeolit nhn to . Ngy nay , ngi ta tng hp c khong 200 loi Zeolit ,

tuy nhin trong ch c mt s t c s dng trong cng nghip ( 14-trang

122).

1.1 Thnh phn ha hc ca Zeolit :

Cu trc ca chng c c trng bng mng cc l rng, rnh, rt nh

thng vi nhau. Cc cht zeolit c ch to cng vi cc xc tc

aluminosilicat hay vi t st thin nhin, ri sau c x l bng phng

php c bit hp thnh xc tc cha zeolit. Xc tc cha zeolit ny c hot


28/109



tnh cao, c chn lc tt v li c gi thnh va phi, v th ngy nay chng

c s dng rt rng ri.

V thnh phn ha hc ca zeolit, ngi ta c th biu din bng cng

thc phn t nh sau:

(Me+)x[(Al2O3)x.(SiO2)y]z.2H2O

Trong : Me - l cation bi tr in tch

x,y - l cc h s tng ng

z - s phn t nc kt tinh trong Z ( 2-trang 193, 6-trang 123)

n v cu trc c bn ca Zeolit l t din TO4, l mt cation T c

bao quanh bi 4 ion O-2. Nu T l Si th SiO4 l t din trung ha in tch ,

nu l nhm Al (+3) th t din AlO-4 mang mt in tch m:

O2-

O2- O2-

Si4+

O2-

Hnh 2: T din SiO4

O2-

O2- O2-

Al3+

O2-

Hnh 3 : T din AlO-4

S thay th Si+4 bng nhm Al+3 lm xut hin mt in tch m trong

mng tinh th v n c b tr bi cation b tr in tch hay cation i.

Tnh cht ca Zeolit c thay th bi cc cu trc v hnh thi ca

chng ,tc l s sp xp trt t ca t din , phn th tch rng , s tn ti cc

mao qun v cc l ,kch thc ca cc mao qun v cc l. Ngoi ra tnh cht

ca Zeolit cn ph thuc vo t l Si/Al v cation b tr in tch (K+ , Na +...)


29/109



Quy tc Lowenstion xc nh rng : 2 nguyn t nhm khng th tn ti

ln cn nhau , ngha l trong cu trc Zeolit khng th tn ti cc lin kt Si-

O-Si v Si-O-Al . V vy m t l Si/Al lun lun ln hn hoc bng 1.

1.2 cu trc ca Zeolit:

V cu to, zeolit c to thnh t cc n v cu trc c bn gi l n

v cu trc Sodalit (hnh 4). Nu cc n v ny ni vi nhau theo cc mt 4

cnh, ta c zeolit loi A. Nu ni vi nhau theo mt 6 cnh, ta c zeolit loi X

hay Y c cu trc tng t nh faurazit (hnh 5).

Hnh 4. n v c bn ca zeolit

Zeolit A Zeolit X

Hnh 5. Cu trc ca zeolit A v X, Y

Si4+O

2

O2

Al3+


30/109



Ngy nay ngi ta ch to c hng trm loi zeolit, chng c c

trng bi kch thc cc ca s khc nhau [1-trang 117].

V d c trng ca mt s loi zeolit c dng ph bin trong cracking

xc tc c dn ra bng sau:

Bng 7 : c trng c bn ca mt vi loi zeolit

Zeolit Thnh phn ho hc ng knh l trung bnh,

A Na2O.Al2O3.2SiO2.4,5H2O 3,6 3,9

X Na2O.Al

2O

3.2,5SiO

2.6H

2O 7,4

Y Na2O.Al2O3.4,8SiO2.8,9H2O 7,4

Mordenit Na8O(Al2O3)8(SiO2)40.24H2O 6,7 7,0 (2,9 5,7)

ZSM-5 v 11 5,4 5,6

2. Zeolit v xc tc cha Zeolit dng cho qu trnh cracking [1-trang

118,119]Khi ch to xc tc cracking, hm lng natri (Na) cn phi gim ti cc

tiu bi v s c mt ca Na nhit cao v c mt hi nc, n lm gim i

ng k hot tnh cng nh chn lc ca xc tc cracking.

Khi thay th Na bng cc cation kim loi ha tr ln hn 2 hay bng 2,

th d nh canxi (Ca), reni (Re) hay cc nguyn t t him, s lm thay i

c trng cu trc ca zeolit. Kch thc l tng ln, ng thi khi li to

ra cc tm axit lm hoi tnh ca xc tng ln.

Ngi ta cho thy rng, zeolit cha oxyt silic cng nhiu, lng oxyt

nhm cng t th axit ca n cng tng. ng nhin khi tng t s oxyt

silic/oxyt nhm, khng c dn n ph hy cu trc ca zeolit. Hay ni

cch khc l t s ny cng ch tng n mt gii hn nht nh.

Qu trnh cracking xc tc thng dng zeolit loi X, Y c cha cc

nguyn t t him hay dng trao i ion v c x l bng cc phng


31/109



php c bit, ng thi kt hp vi cc hp phn lm tng bn c, bn

nhit hay iu chnh kch thc l xp. Zeolit c hot tnh cracking ln, v th

ngi ta thng dng n dng hn hp vi xc tc v nh hnh hay

aluminosilicat tinh th v c gi l xc tc cha zeolit. Trong sn xut xc

tc, ngi ta trn 10 n 20% (KL) zeolit v vi hp phn nh vy, xc tc

cng rt hot ng, hn hn xc tc aluminosilicat thng thng. Hn na

cc ch tiu kinh t cng t tt hn.

Trong cng nghip, ngi ta ch to xc tc cha zeolit hai dng chnh.

Xc tc dng cu v xc tc dng bt. Xc tc dng bt v sau ci tin

thnh xc tc vi cu th

ng

c p dng cho qu trnh cracking lp si(FCC), cn xc tc dng cu vi kch thc ht t 3 n 5 mm thng c

dng cho qu trnh cracking xc tc chuyn ng (TCC).

Zeolit c hai loi kch thc l xp: kch thc ca s v kch thc l

ln, khi a chng vo trn ln vi aluminosilicat, chng ta s iu chnh

c cu trc l ca chng nhn c kch thc l trong gii hn thch

hp nht, nhm tng chn lc ca xc tc. V d, trong xc tc cha zeolit

loi A, kch thc l ca n khng vt qu 4 n 5 . Trong cc l nh vy

propylen c th chuyn qua t do, nhng iu li khng xy ra i vi izo-

butylen. Do trn xc tc nh vy c th tin hnh qu trnh polyme ho

chn lc propylen c trong hn hp vi izo-butylen m khng phi phn tch

chng. Hay t zeolit vi kch thc 5 c th dng lm xc tc cracking

chn lc n-parafin c trong hn hp vi izo-parafin, v trong iu kin , izo-

parafin b cracking khng ng k.

Xc tc cha zeolit X v Y c kch thc l khong 8 n 10 c

dng cracking nguyn liu c thnh phn phn on rng (v d gazoil).

Khi cc phn t ln ca nguyn liu vn c th d dng ti b mt ca xc

tc, cn cc phn t nh hn c th tip xc vi cc tm hot tnh b mt

trong ca xc tc. V cc l hp cht cao phn t nn chng thng tp trung


32/109



b mt ngoi ca xc tc v do vy to iu kin thun li cho qu trnh t

chy cc khi ti sinh xc tc.

Zeolit loi X, Y, ZSM-5 (11) l loi c cc tnh cht thch hp nht cho

qu trnh cracking xc tc. Kch thc l ln ca chng xp x 10 s cho

php khuch tn d dng cc phn t ca nguyn liu vo b mt l xp ca

chng cng nh khuch tn sn phm ra ngoi. V vy chng c s dng

ch to xc tc cracking cng nghip. Thng thng cc zeolit ny l loi

trao i cation (H+, NH4+ hay cation a ha tr) kt hp vi cc phng php

x l thch hp v phi trn vi aluminosilicat v nh hnh. Loi xc tc ny

c hot tnh cao hn hng trm ln v c chn lc cao hn so vi xctc aluminosilicat thun khit. Hiu sut xng tng ln t nht l 20%, trong

khi hiu sut cc v kh li gim khi tin hnh cng mt iu kin.

th gii cc cht xc tc cracking c nhiu hng sn xut, l:

Grace, Engel Grard, Mobil, Fihtrol, AK20, Crosfiel, Catalystics.

Cc c trng c bn ca xc tc cracking l: thnh phn, trng lng

rt, cu trc xp, hot tnh, thnh phn c ht v bn.Ngoi nhng u im trn xc tc cha zeolit vn cn mt s nhc

im nh sau:

+ Gi thnh sn xut chng cao

+ Nu s dng xc tc zeolit nguyn cht th tc trao i cht ca qu

trnh phc hi v trao i nhit b hn tc chnh bn thn phn ng xc

tc. V vy m ta dng xc tc cha zeolit (zeolit tm trn cht mang, 2 20%

trn aluminosilicat tng hp).

Ni tm li, xc tc cha zeolit cho qu trnh cracking c nhiu u im

hn hn cc xc tc khc, nn hin gi y cc nc cng nghip ch bin

du m v kh tin tin, ngi ta ln lt thay th xc tc cha zeolit cho

aluminosilicat tng hp. Hin nay ngi ta ang s dng xc tc zeolit siu

bn, n p ng c mi yu cu ca xc tc trong qu trnh cracking.


33/109



III. Nhng thay i tnh cht ca xc tc khi lm vic [1,3,12,13]

[1-trang122]

Xc tc cracking trong qu trnh lm vic b gim hot tnh v chn

lc. Hin tng ny ngi ta gi l qu trnh tr ho xc tc. Qu trnh tr ho

xc tc cng nhanh nu ta tin hnh qu trnh iu kin cng ngh kh

khn, kht khe tng (v d nhit qu cao, thi gian tip xc qu di,

nguyn liu xu). Ngoi ra cn xy ra cc qu trnh khc lm tng tc tr

ho. Chng ta c th phn qu trnh tr ho xc tc lm hai qu trnh chnh,

l s tr ho do tc dng ca cc cht lm ng c xc tc v s tr ho do

tc dng lm thay i cc tnh cht l - ho ca xc tc.

Nguyn nhn ca s tr ho xc tc c th l do:

Tc dng ca cc c t nh NH3, CO2 ca cc hp cht luhunh m c bit l H2S nhit cao.

S tch t cc kim loi nng di dng cc oxyt lm thay i chcnng ca xc tc.

S tc ng ca nhit cao v hi nc.Cc hp cht kh tc dng vi xc tc c th chia lm 3 nhm:

- Nhm khng tc dng vi xc tc nhit thp hn 6200Cnh CO, CO2 v NH3.

- Nhm lm gim hot tnh ca xc tc nhng khng lm gim chn lc nh hi nc.

- Nhm lm gim chn lc ca xc tc (H2S nhit trn4250C v NH3 , SO2, SO3 nhit trn 620

0C).

T kinh nghim thao tc cng ngh cracking cho thy, hot tnh ca xc

tc c th c duy tr nu ta thm hi nc vo nguyn liu, hay vic x l

trc v sau khi ti sinh xc tc. Thm hi nc khi ch bin nguyn liu c

lu hunh s c tc dng m v khi li lm tng qu trnh n mn thit b


34/109



v sn phm ca qu trnh n mn li lm nhim bn xc tc, dn ti lm

gim hot tnh, chn lc ca xc tc.

Tc dng ng thi ca nhit cao v ca hi nc lm gim hot tnh

tng cng ca xc tc. Khi p dng lp si (FCC), do cn phi duy tr iu

kin cc t lng ng trn xc tc v xc tc khng b qu nhit khi ti

sinh, ngi ta phi a vo mt lng nh hi nc. Hn na, cng cn phi

trnh s to cc qu t, v iu dn ti ph v cn bng nhit ca h l phn

ng v ti sinh, do nhit to ra trong qu trnh ti sinh khng b nhit

thu vo ca cc phn ng cracking trong l phn ng.

Hm lng cc trn xc tc khi ra khi l phn ng ph thuc vo lngxc tc tun hon trong h thng. i vi a s cc qu trnh FCC, khi dng

xc tc zeolit, lng cc to ra thng chim vo khong 1,3 n 1,8% KL

xc tc, cn sau khi ti sinh l 0,1 n 0,05% KL.

Cc hp cht c kim v cc hp cht cha nit trong nguyn liu u l

cc phn t lm gi ho nhanh xc tc. Nhiu nghin cu ch ra rng, s c

mt ca cc hp cht nit trong nguyn liu lm gim hiu sut xng v cc

sn phm trng. V d, hm lng nit tng t 0,1 n 0,4% KL, hiu sut

xng b gim i ti 2 ln, cn hiu sut gazoil nh cng b gim, ng thi

lm tng hiu sut cn nng v gazoil nng. Khi tng nhit , tc dng c hi

ca cc hp cht nit s gim.

S u c xc tc bi cc kim loi cng c nhiu nghin cu

cp ti v ch r c ch tc dng ca chng n hot tnh ca xc tc. Khi

lng ng cc oxyt kim loi nng trn xc tc s dn ti lm gim su

cracking v gim hiu sut xng do tng qu trnh to cc.

Khi hm lng cc hp cht lu hunh trong nguyn liu tng th hm

lng cc kim loi nng nh niken v vanadi cng tng theo, v a phn chng

u tp trung phn cn nng v phn on nha - asphan. V d, trong du

m c lu hunh th c ti 90% phc cht porphirin cha vanadi, cn trong

du cha t lu hunh th l phc vi niken.


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V. Ti sinh xc tc [1,2,3]

Xc tc trong qu trnh cracking lm vic c mt thi gian s c mt

lng cc to ra do mt s phn ng c hi, cc s bm ln b mt xc tc

lm che ph cc tm hot ng ca xc tc. iu dn n gim hot tnh

ca xc tc v vy hiu qu qu trnh cracking xc tc b gim. xc tc lm

vic bnh thng (cc tnh cht ca xc tc khng b thay i) th ngi ta

phi tin hnh ti sinh xc tc. ti sinh xc tc ngi ta cn phi tin hnh

t cc bng khng kh nng trong l ti sinh. Kt qu ca qu trnh t chy

cc s sinh ra CO v CO2. Cc phn ng ny to nhiu nhit. Ngoi ra cn c

phn ng kh cc hp cht l

u hunh. Cc phn ng xy ra khi ti sinh c thmiu t nh sau:

C + O2 CO2 Q = 33,927 34,069 MJ/kg

C + O2 CO Q = 10,629 10,314 MJ/kg

CO + O2 CO2 Q = 23,650 23,755 MJ/kg

H2 + O2 H2O Q = 1210,043 1210,252 MJ/kg

S + O2 SO2 Q = 9,132 9,222 MJ/kg

SO2 + O2 SO3

MeO + SO3 MeSO4

MeSO4 + 4H2 MeO + H2S + 3H2

Nhit lng to ra c dng cp nhit cho xc tc mang vo l phn

ng, ngoi ra cn tn dng sn xut hi nc dng trong nh my.

Kh nng ti sinh c th nh gi bng cng chy cc, cng

chy cc cng cao, qu trnh ti sinh cng nhanh, th tch thit b ti sinh yu

cu cng nh. Cng chy cc ph thuc vo nhiu yu t: nhit , p

sut ring phn ca oxy, hm lng cc bm trn xc tc, cht xc tc v.v...

Yu t nhit nh hng ln cng chy cc: Qua nghin cu ta

thy nhit khong 540 6300C tin hnh ti sinh xc tc l tt nht.

Nhit ti sinh ph thuc nhiu vo cht xc tc c dng v loi l

12

121

2


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ti sinh. Mc ti sinh cn phi khng ch cht ch khng ch bo m

hot tnh ca xc tc m cn m bo vn v sinh mi trng, v th khng

nn c mt CO trong kh khi thi. Hn na, qu trnh chy cng khng

xy ra nhit qu cao hay tch nhit cc b dn ti ph hu xc tc. Cn

nu nhit qu thp th tc ti sinh s chm, cc bm trn xc tc chy

khng trit . Sau khi ti sinh, hm lng cc cn li trn xc tc phi l cc

tiu (lng cc cn cn li t 0,1 n 0,3% KL xc tc) khi phc ti a

hot tnh ca xc tc.

Tc ti sinh c th biu din theo phng trnh:

RT

En

OHO CPKPV

+= )1(K22 21

Trong :

V - tc ti sinh

PO2, PH2O - p sut ring phn ca oxy v hi nc

C - hm lng cc bm trn xc tc

n - bc phn ng theo cacbon

K1, K2 - hng s.

Vy tng tc ti sinh th ta phi tng nhit ti sinh (hiu qu

nht vng ng hc), tng p sut ring phn ca oxy trong khng kh, gim

ng knh cc ht xc tc.

Xc tc c ng knh l xp cng ln v ng u th qu trnh ti sinh

cng nhanh v oxy d khuch tn. Tuy vy iu ny b gii hn bi bn ca

xc tc v mt s tnh cht khc ca n.

Qu trnh ti sinh xc tc bng phng php t cc cha gii quyt

c vic kh cc kim loi nng hp ph trn xc tc. V vy hon thin

qu trnh ti sinh ngi ta tin hnh thm qu trnh trao i ion kh cc

kim loi nng, iu ny gii quyt c s nng cao c hiu qu ca qu

trnh ti sinh xc tc.


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VI. Cc dng hnh hc ca xc tc [1,2,3]

Xc tc dng bi:

Xc tc dng bi c kch thc t 1 n 150 m. Phn ln l cc phn

xc tc c kch thc 40 80 m.

Xc tc dng vi cu:

C kch thc ht t 10 n 150 m. So vi xc tc dng bi, xc tc

dng vi cu trong qu trnh lm vic b mi mn t hn v mt mt xc tc t

hn. Xc tc dng bi v dng vi cu thng c dng trong h thng

cracking xc tc vi lp xc tc gi si.

Xc tc ht cu ht ln:

ng knh cc ht xc tc t 3 n 6 mm. bn c ca loi ny tt,

trong qu trnh lm vic t b mi mn v t b v vn. Xc tc dng ny c

s dng trong h thng vi lp xc tc chuyn ng.

Xc tc dng tr:

C

ng knh t 3 n 4 mm, chiu cao t 3 n 5 mm. bn c km.Trong qu trnh s dng xc tc d b v vn, lm tiu hao xc tc ln. Xc

tc loi ny ch dng trong h thng cracking vi lp xc tc tnh.


38/109



CHng IIINGuyn Liu V Sn PHm

Ca QuTRnh Cracking Xc Tc

I. Nguyn liu ca qu trnh cracking xc tc: [1,2,3,4,5,6,7]

Nguyn liu c bn cho qu trnh cracking xc tc l phn ct chn

khng ca cn du th khi chng ct kh quyn. Chng thng cha 5 10%

phn on si n 3500C v c nhit si cui ti 520 5400C. Trong nhiu

trng hp, ngi ta cng c th dng c phn on nh ca chng ct kh

quyn, phn on kerosen-gazoil ca cracking nhit hay cc ho v c th cphn rafinat ca qu trnh kh asphan mazut v gudron trong sn xut du

nhn hoc l phn on mazut ca du t kim loi. Cc c trng quan trng

nht ca nguyn liu c nh hng quyt nh n cc ch tiu ca qu trnh

cracking l thnh phn phn on, hng s c trng K, thnh phn nhm

hydrocacbon, hm lng nha - asphan, hm lng cc tp cht nit, lu

hunh, kim loi v cc ho.

Khi cracking trn xc tc cha zeolit, do c hot tnh cao m nh hng

ca thnh phn phn on ca nguyn liu khng phi l yu t quan trng.

Quy lut thng thng l khi tng phn nh (hay cn gi l nh) ca

nguyn liu, hiu sut hydrocacbon loi C3, C4 v xng u tng ln, cn hiu

sut H2 v cc gim xung. Nu nguyn liu l phn ct chn khng c t

phn on nng (


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cht lng sn phm. V d s phn b ca hp cht lu hunh vo sn phm

cracking nh sau (% KL so vi nguyn liu): H2S: 20 n 30; xng: 2 n 5;

phn on si trn 1950C: 30 n 60; cc: 5 n 10.

Trong nguyn liu cracking xc tc khng nn c mt cc phn on nh

c nhit si < 2000C v khi phn hu s to nhiu kh lm gim hiu sut

xng v gim c tr s octan ca xng. Nguyn liu khng cho php cha hm

lng ln hydrocacbon thm a vng (v trong qu trnh d ngng t to cc

bm trn b mt xc tc), asphan v cc tp cht cha N v S.

Nguyn liu cng nng cng cha nhiu asphan v kim loi, khi cracking

cn phi qua x l bng hydro ho lm sch nhn c nguyn liu c chtlng cao cho qu trnh cracking xc tc.

Ni tm li, trc khi a nguyn liu vo qu trnh cracking xc tc,

chng ta phi nghin cu k cht lng ca nguyn liu, loi xc tc dng v

tu theo iu kin k thut, hiu qu ca cc phng php lm sch nguyn

liu yu cu nguyn liu dng m ngi ta quyt nh phng php lm sch

nguyn liu cho thch hp.

Trong cng nghip cracking xc tc, ngi ta c th s dng mt trong

cc nhm nguyn liu sau:

Nhm 1: l nhm nguyn liu nh c tn l phn on kerosen - sola

nhn c t qu trnh chng ct trc tip v c gii hn si t 210 n 3600C.

Chng c t trng trung bnh t 0,860 n 0,830. Trong lng phn t trung

bnh vo khong 190 200. y l nhm nguyn liu tt nht dng sn

xut xng t v xng my bay.

Nhm 2: l nhm nguyn liu ly t phn on gazoil chng ct chn

khng c nhit si t 300 n 5000C (hay 5500C). Nhm ny c cc c

trng l t trng trung bnh t 0,880 n 0,920, trng lng phn t trung bnh

t 280 n 330.


40/109



Nhm 3: l nhm nguyn liu c thnh phn rt rng, c gii hn si

t 210 5000C.

Nhm 4: l nhm nguyn liu c nhit si t 300 4500C.

[1-trang 125]

Bng 8:c tnh 4 nhm nguyn liu ca qu trnh cracking xc tc

Ch tiu Nhm 1 Nhm 2 Nhm 3 Nhm 4

T trng 0,8300,870 0,8300,920 0,8700,885 0,8700,875

Thnh phn

phn ont0 si u (0C) 200 215 300 315 225 235 n 250

t0 si 10% (V) 225 240 335 355 290 305 275 300

t0 si 50% 260 270 420 445 390 400 335 375

t0 si 80% 490 500 385 450

t0 si 90% 290 320 520 540

t0 si cui 315 360 540 550

(95%)

515 520

(95%)

420 490

(95%)

Hm lng S

(%) TL 0,2 0,6 0,6 1,8 0,35 0,75 0,5 1,4

cc % TL 0,2 0,9 0,2 0,3 0,05 0,2

Trong s cc nhm nguyn liu k trn th nhm gazoil chn khng l

ph bin nht trong qu trnh cracking xc tc. Trong nhng nm gn y, khi

nguyn liu tt ngy mt cn dn v nht l khi ch to c xc tc cracking

mi v cng ngh mi c hiu qu hn, ngi ta tin ti s dng nguyn liu

ngy cng nng hn, cht lng xu hn m vn cho php nhn c xng vi

nng sut cao v cht lng tt. l xu hng ci tin qu trnh cracking

xc tc trong hin i v trong tng lai.


41/109



II. Cc sn phm ca qu trnh cracking xc tc [1,2,3]

Cht lng ca sn phm cracking xc tc thay i trong mt khong rt

rng v ph thuc vo nhiu yu t nguyn liu, loi xc tc v cc thng s

cng ngh ca qu trnh. Trong thc t qu trnh cracking xc tc thng nhn

c cc sn phm sau:

1. Sn phm kh

Hiu sut kh cracking chim khong 10 25% lng nguyn liu em

cracking. Hiu sut ny ph thuc vo iu kin cracking. Thnh phn ca kh

cracking ph thuc vo bn cht ca nguyn liu v bn cht ca xc tc.

Bng 9:Kh hydrocacbon % khi lng

C1 C2

C3

C4

C5

10 25

25 30

30 50

10 20

Sn phm kh c a n b phn tch kh. Sau khi phn on, kh khc s dng lm nhin liu kh.

Cn phn on propan propylen v butan butylen c dng lm nguyn

liu cho qu trnh alkyl ho hay nguyn liu tng hp ho du v ho hc. Phn

on C5 c pha vo xng. Trong phn on C3, hm lng propylen c th t

ti 70 80%. Trong phn on C4, hm lng buten l 45 55%, hm lng izo-

butan l 40 60% v hm lng n-butan nh, ch vo khong 10 20%.

2. Xng cracking xc tcXng l sn phm chnh ca qu trnh, hiu sut xng cracking xc tc thng

thu c t 30 55% lng nguyn liu em cracking. Hiu sut xng v cht

lng xng ph thuc vo cht lng nguyn liu, xc tc v ch cng ngh.

Nu nguyn liu c hm lng hydrocacbon naphten th cho hiu sut v

cht l

ng xng cao. Nu nguyn liu c hm l

ng ln parafin th nhn

c


42/109



xng c tr s octan thp. Trong nguyn liu c hm lng lu hunh cao th

xng nhn c c hm lng lu hunh ln, thng chim khong 15%

trng lng lu hunh cha trong nguyn liu.

Xng nhn c t qu trnh c t trng khong 0,72 0,77. Tr s octan

theo phng php nghin cu (RON) khong 87 91.

Thnh phn ho hc ca xng cracking xc tc khc hn vi xng

cracking nhit v xng chng ct trc tip. Xng cracking xc tc c tr s

octan cao hn, c cha 9 10% trng lng hydrocacbon thm. Ni chung

xng cracking xc tc l cu t c bn ch to xng thng phm.

Phn on xng cc dy chuyn cng ngh Lin bang Nga thng c

nhit si cui l 1950C, cn cc nc khc thay i c th l 204 hay

2200C. Chng c tnh cht c trng c trnh by bng sau:[1-trang 126]

Bng 10 : c trng ca xng Cracking xc tc

204d

Hm lng S (% KL)

Tr s octan (sch)RON

MON

Thnh phn hydrocacbon (%)

Hydrocacbon thm

OlefHin

Naphten

Parafin

0,72 0,77

0,01 0,20

87 95

78 85

25 40

15 30

2 10

35 60(izo-parafin chim phn chnh)

3. Phn on si cao hn 1950CPhn on ny c chia thnh:

Phn on 195 3500C v phn cn c nhit cao hn 3500CPhn on 195 270

0

C dng ch to nhin liu kerosen


43/109


44/109



dng lm cu t pha cho nhin liu diezen, c th lm nguyn liu sn xut b

hng hay lm cu t pha long mazut.

Gazoil nh c c tnh sau:

T trng 204d = 0,83 0,940

Thnh phn ho hc gm:

Lu hunh 1,7 2,4% trng lng

Hydrocacbon olefin 6%

Hydrocacbon thm 30 50%

Cn li l hydrocacbon parafin v naphten.* Gazoil nng:

L sn phm cn ca qu trnh. Cht lng ca n ph thuc ch cng

ngh, ngun nguyn liu v cht lng gazoil nh.

Gazoil nng c nhit si > 3500C, c t trng 204d = 0,89 0,99, n

cha mt lng ln tp cht c hc. Hm lng lu hunh trong cao hn

khong 1,5 ln so vi nguyn liu ban u.Dng lm nguyn liu cho cracking nhit v cc ho hoc lm nhin liu

t l. Ngy nay ngi ta cn dng n lm nguyn liu sn xut b hng.


45/109



Phn IITnh Ton V Thit K Dy ChuynCng Ngh CrackingXc Tc

Chng I. Cc yu t nh hng nqu trnh cracking xc tc

nh hng n cc ch tiu lm vic ca qu trnh cracking xc tc

khng ch l nguyn liu v cht xc tc m cn c cc thng s cng ngh

ca qu trnh. Cc thng s cng ngh bao gm: nhit , p sut, tc np

liu khng gian th tch hay trng lng (cn gi l tc np liu ring), bi

s tun hon xc tc v mc bin i hay su chuyn ho.

I. Nhit [1,2,3,4,5,6,7]

Qu trnh cracking xc tc thng tin hnh nhit 480 5500C. Khi

tin hnh tng nhit , lc u hiu sut xng tng v sau t n cc i

ri gim xung. iu ny l do qu trnh phn hu tng, lm phn hu c cc

cu t xng va c to thnh.

Khi tng nhit , phn ng phn hu tng nhng ng thi cc phn

ng bc 2 nh dehydro cng tng, lm tng hiu sut hydrocacbon thm v

olefin. Khi trong sn phm kh hm lng C1 C3 tng, cn C4 gim, t

trng v tr s octan tng ln.


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Hnh 6

Bng 12. nh hng ca hydrocacbon n hiu sut v cht lng ca sn

phm vi nguyn liu l phn on xola (du m Lin X)

Cc thng sNhit trung bnh trong TBP

415 452 480 513

Hiu sut cc sn phm (%TL)

Kh kh 2,31

Kh bo 5,00 5,13 8,34 18,80

Xng 30,29 7,49 9,41 9,45

Gazoil nh 59,20 30,72 32,45 37,42

Gazoil nng 53,30 46,30 28,10

Cc 3,20 3,30 3,50 6,60

Tng cng 100,00 100,00 100,00 100,00

su chuyn ho (%TL) 40,80 46,70 53,70 71,90

Tr s octan ca xng (RON)

khng c pha ch 84,10 91,70 93,70 94,40

c pha 0,8 ml TEP/ 1lt xng 93,00 98,20 98,20 98,50

T trng ca xng 15

15d 0,748 0,748 0,757

390 420 450 480 510 540 425 450 475 500 5250C

30

20

10

0

4

6

810

Hiusutxngv

kh,

Hiusutcc,%TL

NC(sch),%

95

100

90

85

80 40

50

60

70

80

%V

Nhit cracking, 0C

Ch s octan

chuyn ho


47/109



II. p sut [1,2,3,4,5,6,7]

Qu trnh cracking xc tc thng tin hnh p sut d 1,4 1,8 at.

iu kin ny phn ng xy ra pha hi.

Khi tng p sut, hiu sut xng tng ln, hiu sut kh C1 C3 gim,

hm lng olefin v hydrocacbon thm gim, hm lng hydro-cacbon no

tng v do vy cht lng xng gim (tr s octan NO gim).

Vy khi tng p sut s tng hiu sut xng, cn hiu sut kh gim,

nhng qu trnh to cc tng. Vic tng p sut ca qu trnh cracking xc tc

khng c hiu qu kinh t cao. V vy ch tin hnh p sut thng.

Bng 13. chuyn ho C, hiu sut sn phm v thnh phn

RH ca xng ph thuc vo nhit phn ng [1-trang130]

Nhit,

0C

C,

%KILN

SP

tng,

%KL

Xng,

%KILN

Kh,%KL

Cc,

%KL

Cn,

%KL

M

tmt,%KL

RHno,

%V

RHO,

%V

RH

a,

%V

400 64,5 81,5 49,2 11,6 3,7 32,3 3,2 66,8 7,7 25,3

420 70,2 76,7 49,7 16,0 4,5 27,0 2,8 61,9 8,5 29,6

435 72,1 74,4 49,1 18,2 4,8 25,3 2,6 56,5 9,6 33,9

450 75,5 69,9 47,5 22,2 5,8 22,4 2,1 50,8 10,8 38,4

470 74,4 61,9 38,6 29,5 6,5 22,5 2,9 39,6 13,9 46,5

485 74,9 59,7 33,2 32,6 7,8 24,7 2,4 28,6 15,0 56,4

500 73,8 52,5 31,3 37,2 7,2 21,0 3,2 28,6 14,8 56,4


48/109



Hnh 7: nh hng p sut n hiu sut v cht lng xng

III. Mc chuyn ho Ci vi hydrocacbon tinh khit, khi tham gia phn ng, mc chuyn

ho c o bng lng sn phm to thnh theo thi gian. Nhng i vi

phn on phc tp nh phn on du m, trong cracking xc tc ngi ta li

o lng xng l sn phm chnh v sn phm nh kh v cc. Nu gi y l %

th tch ca sn phm vi im si cui cao hn im si cui ca xng, th

chuyn ho C

c tnh theo biu thc:C = 100 y

ng nhin cch xc nh nh vy cha st vi thc t. hiu chnh

theo s bin i ho l trong qu trnh to xng v kh, ngi ta xc nh mc

bin i theo cng thc sau:

C = 100 y(100 z)

y z l % xng c trong nguyn liu.IV. Tc np liu ring [1]

Tc np liu ring (hay tc khng gian np liu) l t l gia lng

nguyn liu c np trong mt n v thi gian trn lng xc tc trong

reactor (hay t l v th tch ca chng) v c k hiu bng M/H/M hay

V/H/V (V/V/H).

0,5 1,0 1,5 2,0 2,5 3,0 3,5 kG/cm2

50

40

30

20

85

90

95

O%V

80

% xng

% NO


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Nu P l p sut trong reactor v c tnh bng (at) th chuyn ho C

c lin quan vi M/H/M theo biu thc:

M/H/M

P.K

C100

C=

Phng trnh biu din p dng rt ng vi trng hp xc tc c nh,

y khng xy ra s chuyn ng ri hay s xo trn ca hi nguyn liu v

sn phm. Trong trng hp cracking xc tc vi lp si ca xc tc (FCC),

chuyn ho C l ph hp vi cng thc sau:

M/H/M

P.K

100C1100

C2=

K l hng s tc tng cng ca qu trnh.

Ta thy rng khi tng tc np liu ring, s lm gim chuyn ho.

Cn khi gim tc np liu ring th chuyn ho tng, v rng tc np

liu l i lng ngc vi thi gian phn ng. Khi s dng xc tc c hot

tnh cao, ta c th tng tc np liu v nh

vy s tng

c nng sut cathit b.

Hnh 8.

M/H/M0,2 1,0 2,0 3,0

70

50

30

10

6

10

%KL%V

2

% xn% xng

Cc

2 4 6 8 10

chu n chu n ho

Cc

80

60

40

20

6

10

2

%KL%V

X/RH

nh hng ca tc np liu ring nh hng ca t l X/RH


50/109



Trong thc t, nu dng xc tc aluminosilicat v nh hnh, tc np

liu th tch ch t t 4 5 h1. Nhng nu dng xc tc cha zeolit, tc

np liu th tch l 80 120 h1 khi tnh trong ng ng ca reactor v t 20

30 h1 khi tnh trong lp si ca reactor.

Khi tng tc np liu, nu ta tng nhit phn ng, s tng tr s

octan ca xng v tng hiu sut olefin trong kh. l phng php chnh

iu khin ch sn phm propylen v buten trong qu trnh cracking xc

tc.

V. T l lng xc tc/nguyn liu (X/RH) hay bi s tun hon

xc tc [1,3]

Khi dng xc tc cha zeolit, cho php gim t l X/RH xung cn 10/1

so vi xc tc v nh hnh l 20/1. Nu khi dng cng ngh xc tc chuyn

ng vi kch thc ht xc tc t 3 5 mm, t l X/RH cn thp hn na, ch

khong 2/1 5/1.

Khi thay i t l X/RH s lm thay i nhit ca reactor, thay i

thi gian lu ca xc tc trong reactor v l ti sinh, ng thi cng lm thay

i c lng cc bm trn xc tc trong mt chu trnh.

Nu ch n nh, tng t l X/RH s lm tng chuyn ho, tng

hiu sut cc/nguyn liu, nhng hm lng cc bm trn xc tc li gim

xung. iu ny c gii thch l do lng cc c dn ra mt lng

xc tc ln hn. Khi gi tc np liu M/H/M l khng i, nu tng t l

X/RH th thi gian tip xc gia xc tc v nguyn liu gim, v nh vy hot tnh trung bnh ca xc tc tng ln. l l do t hiu qu cao ca qu

trnh vi xc tc lp si (FCC). Nh t hiu qu cao m cho php gim kch

thc ca thit b. Nhng d dng nhn thy rng, nu tng cao qu mc

tun hon xc tc s lm nh hng n qu trnh tch hi bm trn xc tc v

lm nh hng n qu trnh ti sinh l ti sinh v cc trang thit b km

theo.


51/109



Ni chung thng s bi s tun hon xc tc rt quan trng trong qu

trnh cracking xc tc, n nh hng khng nhng ln hiu sut v cht lng

sn phm n cc thng s khc m cn nh hng n vic xc nh kch

thc cc thit b chnh ca qu trnh. V vy ta phi chn c thng s ny

mt cch ti u.

VI. Hiu ng nhit

Hiu ng nhit ca qu trnh bng tng hiu ng nhit ca cc phn ng

ring bit ca qu trnh, hiu ng nhit ph thuc vo su chuyn ho.


52/109



Chng II

I. Lch s pht trin cng ngh cracking xc tc [1,2,3]

Qu trnh cracking xc tc c nghin cu t cui th k 19, nhng

mi n nm 1923, mt k s ngi Php tn l Houdry mi ngh a qu

trnh p dng vo cng nghip. V n nm 1936 nh my cracking xc tc

u tin ca Cng ty Houdry Praess Corporahon c xy dng M. Dy

chuyn cracking xc tc u tin ny c a vo cng ngh ch bin du,

l h thng cracking xc tc trong lp xc tc tnh, h thng lm vic gin

on. V sau ny, h thng loi trn i vo lch s v n c nhng nh

cim sau:

+ Qu trnh lm vic gin on nn nng sut thit b thp

+ Ch lm vic ca h thng khng n nh v vic iu chnh cc

thng s k thut ca h thng kh khn, phc tp trong vn hnh

+ Trong qu trnh lm vic hot tnh ca xc tc thay i lin tc lm

nh hng n cht lng sn phm v cn bng vt cht ca h thng.

Nm 1941, xut hin qu trnh cracking vi lp xc tc chuyn ng

thay th cho qu trnh Houdry. Vic tin hnh cracking v ti sinh xc tc

c thc hin cc thit b ring bit.

+ Thit b phn ng (reactor)

+ Thit b ti sinh (regenerator)

Xc tc t thit b phn ng vo thit b ti sinh v ngc li hoc bng

t chy, hoc bng cng bc. Xc tc lm vic c cha cc chuyn ng

vo l ti sinh, cn xc tc ti sinh vo l phn ng to thnh mt chu trnh

lin tc. Dy chuyn loi ny Nga c tn gi l loi 43-1 v 43-102, cn

nc khc c tn l Thermofor (TCC) hay Houdry Flow. Tuy nhin cc dy

chuyn ny cng v sau cng lin tc c ci tin so vi dy chuyn ban u

khu vn chuyn xc tc ( dng vn chuyn bng hi thay cho vn chuyn

bng c hc).


53/109



Nm 1942, dy chuyn cracking xc tc lp si (FCC) u tin c

a vo hot ng vi cng sut 12.000 thng nguyn liu/ngy. Loi dy

chuyn ny c tn l Up Flow (model I). Trong dy chuyn ny, xc tc c

a ra t nh l phn ng v l ti sinh.

Sau , vo nm 1944 ngi ta tng ng knh ca cc thit b phn

ng v ti sinh, qu trnh tch hi sn phm c thc hin ngay trong thit b

phn ng, ti sinh xc tc dng tng si v qu trnh thi cng ngy cng

c ci tin cho xc tc chuyn ng t pha di v ly ra ngoi y

thit b. Dy chuyn c thit b hot ng nh vy mang tn l Dow Flow

model II, v l dng nguyn thu ca thit b phn ng v ti sinh lp sihin i ngy nay. Tip theo, ngi ta cng ci tin c hnh dng ca xc tc.

Xc tc ph bin l loi c dng hnh vi cu, nn gim c s mt mt xc

tc hay s mi mn thit b, nng cao hiu qu tch ca cc xyclon.

Trong dy chuyn model I, t l xc tc/nguyn liu u (X/RH) ch t

gii hn cc i l 3, nhng model II t l X/RH c th tng ln t 3 10.

n nm 1946, model III l loi cn bng p sut c thit k bi hng

M. W. Kellogg.

Nm 1947, hng UOP thit k loi FCC trong thit b phn ng v

thit b ti sinh chng ln nhau trn cng mt trc. n nm 1951, loi Orthor

Flow u tin ca M. W. Kellogg xut hin. Sau hng Standard Oil thit

k mt loi FCC mi gi l model IV, l ci tin ca model III v dy

chuyn cng ngh model IV u tin p dng trong cng nghip vo nm

1952.

Cng vi thi gian, FCC ngy cng c ci tin c c hiu sut,

cht lng xng cao hn v c th dng nguyn liu ngy cng nng hn, vi

cht lng nguyn liu ngy cng xu hn. [1-trang 132].

II. La chn cng ngh cracking xc tc

Qua lch s pht trin ca qu trnh cracking xc tc, ng thi qua phn

tch nh gi cc yu cu khc nh ch lm vic, nguyn liu xc tc... ta


54/109



thy qu trnh FCC c rt nhiu u im v thun li, h thng ny c s

dng ngy cng ph bin trong cng nghip du m, n c cc hng cng

nghip hng u trong lnh vc ny nh UOP, Kellogg, Shell, IFP, Exxon...

nghin cu hon thin hn nhm mc ich t nng sut hiu qu cao nht,

s dng nguyn liu nng hn, tit kim c xc tc... v phi l kinh t

nht.

Qua thc t dng h thng cracking xc tc lp si s dng xc tc dng

bi hay vi cu, ngi ta thy n c nhiu u im hn h thng cracking xc

tc trong lp xc tc chuyn ng. Nhng u im l:

+ Cc thit b chnh ca qu trnh l thit b phn ng v thit b ti sinhu c cu to rt n gin, so vi cc dng thit b khc ca qu trnh

cracking thc t chng l hnh rng.

+ S tun hon xc tc t thit b phn ng n thit b ti sinh v ngc

li l nh s vn chuyn lin tc ca hi v kh trong mt gii hn rng.

+ Do s khuy trn mnh m ca xc tc v hi nguyn liu dn n s

ng nht v nhit trong ton b th tch lp xc tc thit b phn ng

cng nh thit b ti sinh, khc phc c hin tng qu nhit cc b.

+ H thng ny c kh nng ch bin cc dng nguyn liu khc nhau,

nh t nguyn liu l phn on kerosen n nguyn liu nng l mazut, lm

tng tnh vn nng ca h thng.

+ H thng ny c cng sut lm vic ln v c thi gian tip xc ngn

(thi gian tip xc gia nguyn liu v xc tc l cc tiu) dn n vic t

c hiu sut xng cc i v olefin nh khng xy ra phn ng ngng t bc

hai m to xng. ng dng phng php ti sinh (chy hon ton CO trong

thit b ti sinh) dn n t hm lng ct cn rt thp trong xc tc.[1v 3]

Qua cc u im ta chn s cng ngh xc tc lp si FCC vi

thi gian tip xc ngn cho qu trnh cracking xc tc.


55/109



III. Dy chuyn FCC vi thi gian tip xc ngn

Trc ht nguyn l ca qu trnh cracking xc tc c th miu t bng

s sau:

Qu trnh cracking xc tc thng c tin hnh iu kin cng ngh

sau:

Nhit 470 5500C

p sut trong vng lng ca l phn ng 0,27 MPa

Tc khng gian th tch truyn nguyn liu tu theo dy chuyn

cng ngh c th t 1 120m3/m3.h

Xc tc l zeolit mang tnh axit.

1. S dy chuyn FCC thi gian tip xc ngn:Dy chuyn cng ngh FCC gm ba b phn chnh:

Reactor Ti sinh v vn dng nhit ca kh khi

Phn on phn chia sn phm.

Nguynliu

Chun bx l

Lphn ng

Sn phmqua chng tch

Xc tc lm vic

Xc tc ti sinh

L ti sinhxc tc


56/109



a) Thuyt minh dy chuyn cng ngh1. B cha nguyn liu u 15. Thit b gia nhit2. Bm 16. ng dn hi sn phm3. Van tit lu 17. Thit b phn ng FCC4. L t 18. Thp ti bay hi5. Thit b phn ly tch cn bn 19. B phn ng ng6. B cha sn phm 20. Xyclon 2 cp7. Thit b trao i nhit 21. Thit b ti sinh xc tc8. Thit b lm mt bng khng kh 22. Van l9. Thit b lm lnh bng nc 23. Bung lng tch10. Thp chng tch sn phm 24. Ni hi tn dng nhit11. B lng tch 25. Thit b tn dng nhit12. Thp tch kh 26. My nn kh13. Thp n nh14. Thit b phn dng

2. Nguyn l hot ng:+ B phn Reactor - ng ng:

Nguyn liu mi t b cha nguyn liu (1) c cho qua thit b trao

i nhit ng chm, nguyn liu mi c th c trn vi phn tun hon

(HCO) (6),(l phn on du nng ca qu trnh cracking xc tc ) v cn y

thit b (5), sau cho qua l t nng nguyn liu cracking Nguyn liu

cracking c tip xc vi xc tc nng ti sinh i vo y ca ng

ng(19), khi nguyn liu bay hi cng vi hn hp ca hi nng v xc

tc c i ln pha trn ti nh ca ng ng, ng thi xy ra cc phn ng

cracking xc tc. Hu ht nguyn liu u tham gia phn ng v chuyn ho

trong ng ng, cn reactor c dng nh mt thit b tch xc tc v hi

hydrocacbon.


57/109



Mt b phn c thit k c bit, b tr gn van chn, dng hi nc

thi xc tc v du, lm nh vy s hn ch n mc ti a hin tng trn

quay tr li ca xc tc v hi kh lm vic. Vng ng ng v b phn

tch hi ca reactor c thit k cho qu trnh FCC vi thi gian tip xc

ngn gia xc tc v du. Sau khi tch khi xc tc, hi sn phm nng (16)

c chuyn ti ct phn on. Xc tc lm vic (10) c cho qua vng

tch hi (cn gi l b phn ra xc tc) bng cch thi hi nc vo. B phn

ra khng ch lm nhim v ui ht hydrocacbon hp ph trn xc tc m

cn lm ti cc ht xc tc chng khng dnh vo nhau trc khi sang l

ti sinh. Cn iu chnh mt tc hi thch hp cho nhim v ny. Cn thitphi kim tra cht ch thi gian lu ca xc tc trong b phn ra trnh

phi dng qu nhiu khng kh trong l ti sinh. p sut trong reactor c

khng ch bng b phn iu chnh p sut ca ct phn on.

+ L ti sinh v khi tn dng nhit ca khi l:

Xc tc c cha cc (cc bm trn xc tc) c chuyn qua van iu

khin (23) v khng ch bi b kim tra mc xc tc trong l phn ng, sau

i vo l ti sinh. Xc tc vo l ti sinh theo hng tip tuyn vi thnh

l. Mc ch chnh ca ti sinh l t chy cc bm trn xc tc lm vic

bng oxy ca khng kh, khi to thnh CO, CO2, hi nc, nh vy m

tr li b mt hot tnh cho xc tc. Sau khi nn, khng kh t c cho

vo y l ti sinh, qua li phn phi trn c hiu qu khng kh v xc

tc. S chy cng xy ra trong lp si v t c iu , tc ca

khng kh phi t ln hn 1 m/s. Xc tc ti sinh c chuyn vo ngng sau khi ui c sch kh qua mt van l m s hot ng van ny

c khng ch, iu khin t ng nh b phn iu chnh nhit ca

reactor, ri sau xc tc c trn vi nguyn liu cracking v hon thnh

mt chu trnh. ng thi ngi ta tho xc tc bn gi ho ra, b sung xc

tc mi m bo hot tnh n nh ca xc tc theo thi gian lm vic.


58/109



Kh ca qu trnh chy cc v cc ht xc tc chuyn ng t pha c

vo pha long nh l ti sinh, qua hai cp xyclon gi li cc ht xc tc

v tch kh. Sau , kh khi c qua bung lng (23) tch tip bi xc

tc, ri qua b phn tn dng nhit( 24), tip theo kh khi c lm sch bi

xc tc bng lc in(26) ri i ra ngoi theo ng khi.

+ B phn phn chia sn phm:

Hi sn phm (16) c np vo ct phn on chnh chia thnh cc

sn phm khc nhau, xng v phn nh hn c cho qua b phn ngng t

ri vo thit b tch kh. Sau khi tch kh, ta nhn c phn on C1,C2( I ),

cc sn phm ny c th c dng lm kh nguyn liu cho dy chuyn.Phn on C3,C4(II) cha nhiu propylen v buten c dng lm nguyn liu

cho dy chuyn alkyl ho v sn phm tip theo l xng kh butan

T ct phn on chnh, ta cn nhn c cc phn on sn phm nh

naphta nng, LCO v HCO. Phn HCO c th cho tun hon li mt phn , v

cui cng l phn du cn c lm sch khi bn xc tc (5). Mt phn

sn phm nh ca thit b tch bn xc tc cng c cho tun hon cng vi

HCO.

IV. Hng pht trin v ci tin

ca FFC trong lc du

T thp nin 90 tr li y, qu trnh

FFC vn khng ngng c ci tin c v

cng ngh v xc tc to cho FFC trong

tng lai ph hp vi yu cu ca cng

ngh lc - ho du, ng thi cho php s

dng c nguyn liu nng hn, nhim

bn hn, ngha l vi cht lng nguyn

liu ngy cng xu hn. T mc tiu ,

cc nh thit k v cng ngh t ra cc nhim v chnh sau:


59/109



1- Ci tin v cng ngh thch ng vi nguyn liu c cht lng xu

m hiu sut xng hay phn ct vn t cc i, gim lng cc, nng cao

cht lng ca xng.

2- Ch to v ci tin cht xc tc c bn nhit, bn c cao, bn vi

cc c t, c hot tnh cao v n nh, d ti sinh v c thi gian lm vic lu

di hn.

3- Chn la cc thng s lm vic ti u bng cc cng ngh iu khin

v kim tra tin tin, hin i.

4- Ci tin cc trang thit b cng vi cng ngh khng nhng nng

cao cht lng sn phm m cn cho php kt hp sn xut cc nguyn liucho tng hp ho du v ho hc. V d nh nhn etylen, propylen, buten...

Ch trong vng vi chc nm tr li y, ngoi vic nng cao, ci tin v

p dng xc tc mi c hiu qu, ngi ta thit k cc dy chuyn FCC

hin i sn xut c khng nhng nhiu xng vi cht lng cao hn m

cn cho php nhn cc nguyn liu cho tng hp ho du. Thnh cng ,

trc ht phi k n qu trnh FCC vi thi gian cracking ngn v siu ngn

(MSCC), hay qu trnh cracking su (DCC).


60/109



Tnh Ton thit b chnh

I. S liu ban u

+ Nng sut : 2400.000 kg/m3

Bng 1: T trng v hiu sut ca sn phm

Sn phm Hiu sut (%TL) T trngkg/m3

Kh 17 1.22

Xng 48 0.764Gazoil nh 17 0.933

Gazoil nng 13 0.942

Cc 5

+thnh phn ha hc ca cc l : C =87%(TL) ;H2=9%(%TL) ;

S=4(%TL)

Khi chy th 90% cacbon bin thnh CO2 v 10% bin thnh CO

+ Nhit lp si ca xc tc trong l phn ng 485 0C

+ Nhit lp si ca xc tc trong l ti sinh 600 0C

+ Nhit cc sn phm crackinh khi i ra t l phn ng 450 0C

+ Nhit phn ng crackinh xc tc 105 kcal/1 kg xng

+ Ti ng vn chuyn ca l phn ng v ti vng kh lp hp ph c

a vo 5% v 3% hi nc (so vi nguyn liu)

+ Hi nc qu nhit a vo l phn ng c nhit l 450 0C

+ p sut lp si trn xc t c 1050 mmHg


61/109



II. Cn bng vt cht

- S ngy lm vic l 350 ngy

- S ngy ngh sa cha l 15 ngy

*nng sut thit b theo nguyn liu l

Gnl=24350

1000000.2400

=285714,286 kg/h

- Lng kh crackinh l

Gk=Gnl 17.0 = 2857140,286 17.0 = 48571.429 kg/h

- Lng xng l

Gx=Gnl 48.0 =285714,286 48.0 =137142,857 kg/h

- Lng gazoil nh l

Gg= Gnl 17.0 =285714,286 17.0 =48571,429 kg/h

- Lng gazoil nng l

Gn= Gnl 13.0 =28571 4,286 13.0 =37142,857 kg/h

- Lng cc l

Gc=Gnl 05.0 =285714,286 05.0 =14285,286 kg/h

Vy tng sn phm lGk + Gx + Gg + Gn +Gc = 48571,429 +137142,857 +48571,429

+37142,857 + 14285,714 =285714,286 kg/h

* tng hiu sut xng ca qu trnh th ngi ta cho tun hon mt phn

Gazoil nngv h s tun hon khong 0,3 .Vy lng Gazoil tun han li

l :

Gth = Gn 03.0 =37142,857 03.0 =11142,857 kg/h

- Tiu hao hi nc l

Gn =Gnl ( 0.03 + 0.05) =285714,286 08.0 =22857,143 kg/h


62/109



* Bng 2 : Cn bng vt cht

Sn phm S lng (kg/h)

*Dng nguyn liu vo

+Nguyn liu 285714,286

+Gazoil tun hon 11142,857

* Tng vo 296857,143

*Dng sn phm ra

+kh 48571,429

+xng 137142,857

+Gazoil nh 48571,429

+Gazoil nng 37142,857

+ Cc 14285,714

+Gazoil tun hon 11142,857

* Tng ra 296857,143

III: Cn Bng Nhit Lng

1. Xc nh nhit chy ca ccq = a1. qCO2 + a2.qCO + a3.qH2O kcal/kg

Trong :

a1 :l phn cacbon trong cc c t chy thnh CO2

a 2 : l phn cacbon trong cc

c t chy thnh COa 3 : hm lng hydro trong cc

qCO2 : lng nhit ta ra khi t chy 1kg cc thnh CO2

qCO2=6137 kcal/kg

qCO2 :lng nhit ta ra khi t chy 1kg cc thnh CO

qCO=2450 kcal/kg

qH2o :lng nhit ta ra khi t chy 1kg cc thnh nc


63/109



qH2O = 28905 kcal/kg

_ Theo ti liu thc nghim ta c :

a1 = 0.85 9.0 ; a2= 0.05 01.0 ; a3= 0.046 056.0

+ suy ra:

q =0.86 8137 + 0.1 2450 +0.045 28905 =8543,545 kcal/kg

Nhit lng mang rakhi l phn ng gma) do sn phm crackinh v hi nc

Q/1 = Gk.Ck.485 + Gx.qx

485 + Gg.qg485 + Gn.q

n485 + Gth.q

th485 + Gn .q

n485

_ Hm nhit ca hi xng ,gazoil nh , gazoil nng v phn hi l

u

ctnh theo cng thc sau :

qdt=

1(0,403t + 0,000405 t2)

Trong :

: t trng ca cc sn phm lng

t : nhit oc

Suy ra :

qx485 =764,0

1(0,043 .485 + 0,000405 .4852)

=322,633 kcal/kg

qg

485= 933,0

1

(0,043.485 + 0,000405 4852

)

= 301 kcal/kg

qn485 =942,0

1(0,403 .485 + 0,000405 .4852)

=299,4 kcal/kg


64/109



qth485=934,0

1( 0,403 .485 + 0,000405 .4852)

=300,83 kcal/kg

Hm nhit ca hi nc qu nhit 485 0 C l ;:

q H2O485 =833,6 kcal/kg

t nhit ca kh crackinh l Ck=0,38 kcal/kg0 C

Vy :

Q/1 = 48571,429 . 0,38 . 485 +137142,857 . 332,633

+48571,429 .301 +37142,857 .299,4 + 11142,857 .300,83

+285714,286 .833,6 = 321834060,3 kcal/kg

b) do xc tc lm vic v cc mang ra :Q/2 = (Gxt.C1 +Gc .C2)t

Trong :

C1 : l t nhit ca xc tc C1 = 0,27 kcal/kg0 C

C2 : l tt nhit ca cc C2 = 0,6 kcal/kg0

CGxt : l khi lng xc tc tun hon gia l phn ng v l ti sinh

Ta c: Gxt = n. Gnl kg/h

Vi n l bi s tun hon

Gxt = 5. 2875714,286 = 1428571,43 kg/h

Vy :

Q/

2 = (2785. 0,27 + 14285,714 .0,6)485=4521838,524 kcal/h

c) do tiu hao cho phn ng crackinh xc tc :

Q/3 =Gx .i kcal/h

Trong :

i : l nhit ca phn ng crackinh xc tc i = 105 kcal/1 kg xng

Gx : lng xng to thnh


65/109



Suy ra :

Q/3 = 137142,857 .105 =14399999,99 kcal/h

d) Nhit mt mt vo mi trng ly bng 5% lng nhit cn bngQ/4 = ( Q

/1 + Q

/2 + Q

/3 ) 05,0 =2673131,59 kcal/h

* Nhit mang vo phn ng gm c

a) Do nguyn liu nng : Q1= Gnl . qnl kcal/h

trong :

Gnl : lng nguyn liu ban u kg/h

Qnl: hm nhit ca nguyn lu

b) Do xc tc ti sinh

Q2 = Gnl .n .C1.t2 kcal /h

Trong :

Gnl : lng nguyu n liu ban u kg/h

n :bi s tun hon

C1

: t nhit ca xc tc C1

= 0,27 kcal/kg o C

T2 : nhit trong l phn ng t2 = 5800 C

Suy ra :

Q2 = 285714,286 .5 .0,27 .580 = 226063285,9 kcal/h

c) do hi nc :Q3= Gn .q

n485 = 22857,143 .833,6 = 19053714,4 kcal/h

e) do gazoil tun hon vo thit b l :Q4 = Gth .. q

th290 kcal/h

Trong :

Gth : lng Gazoil tun hon li kg/h

q th290 : hm nhit ca xc tc tun hon li

qth290 =

1(0,043t2 + 0,000405 t

22)


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=934,0

1(0,043 .290 + 0,000405 . 2902)

=156,172 kcal/kg

trong :

t2 : nhit ca xc tc tun hon li

suy ra :

Q4 = 11142,857 .156,172 =1740202,263 kcal/h

Vy lng nhit mang vo l phn ng l

Q1 + Q2 + Q3 +Q4=Q1 + 246857202,6 kcal/h

T phng trnh cn bng nhit lng ca l phn ng ta c

Q1 +Q2 + Q3 + Q4 = Q/

1 + Q/

2 + Q/

3 + Q/

4

Q1 = (Q/

1 + Q/

2 + Q/

3 + Q/

4) - ( Q2 + Q3 +Q4)

=553835763,4 246857202,6 = 306978560,8 kcal/h

vy hm nhit ca nguyn liu l :

qnl = Qnl1Q = 268,285714 8,306978560 = 1074,425 kcal/kg

III. Tnh ng knh l phn ng

1. Xc nh ng knh l phn ng theo cnh thc sau :

D = 1,128 s (m)

Trong :

S : l din tch tit din ngang ca l phn ng (m

2

)

S =.3600

V(m2)

V : th tch hi i qua tit din t do ca l phn ng (m3/h)

: tc cho php ca hi trong tit din t do ca l phn ng

(m/s) , theo ti liu : = 0,60 (m/s)

*Xc nh i l

ng V theo cng thc sau :


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V =p273

)t273(Mi

Gi4,22

p +

MiGi :Lu lng hi trong l phn ng.

tp :Tc trong l phn ng.

P: p sut tut i bn trn lp gi si ca l phn ng ly bng 0,2at

tnh i lngMi

Gita phi xc nh dc trng lng phn t

trung bnh ca kh Cracking:

Mtb =1460

429,48571= 33,27

Suy ra: Mi

Gi=

27,33

429,48571+

105

137142+

200

429,48571+

340

857,37142

+18

143,22857 +248

857,11142 = 4432,91 Kcal / h

Vy V =2x273

)485273(91,4432x4,22 += 137852,13 m3/ h

Gi tr ca i lng V va tnh c l ln nht v th tch tng cng

ca tt c cc sn phm Cracking s ln hn th tch ca nguyn liu

Suy ra: S = 6,0x3600 13,137852 = 63,8 m2

Vy ng knh l phn ng:

D = 1,128 S = 1,128 8,63 = 9,0 m


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2. Chiu cao l phn ng:

Xc nh chiu cao ton b l phn ng theo cng thc:

Hn = h + h1 + h2 + h3 + h4 + h5 , m

h: chiu cao lp gi si.

h1: chiu cao ca vng chuyn tip t lp gi si n vng tch

h2: chiu cao vng tch; h2 = 6m

h3: chiu cao vng phn ly; h3 = 6m

h4: chiu cao vng t Xyclon; h4 = 6m


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h5: chiu cao nh l phn ng, nh l phn ng c dng bn cu nn

thng ly n bng 0,5D

h5 =

thiet ke phan xuong cracking xuc tac

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