Công nghệ chế biến khí

Sy kh kh bng phng php hp th dng MEG

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1 LHDK52 Bi Quang Hiu

Li M u Kh ng hnh v kh thin nhin khai thc t lng t thng bo ha hi

nc v hm lng hi nc ph thuc vo p sut, nhit , v thnh phn ha hc

ca kh. Mi mt gi tr nhit v p sut tng ng vi hm lng nc cc i

c th nht nh. Hm lng m tng ng vi hi nc bo ha ti a c gi l

m cn bng.

Hm lng hi nc trong kh ng hnh v kh thin nhin cn phi bit v

hi nc c th b ngng t trong cc h thng cng ngh x l sau ny, hnh thnh

cc hydrat ( cc tinh th cht rn ) d ng cc chim cc khong khng trong cc

ng dn hay cc thit b, ph v iu kin lm vic bnh thng i vi cc dy

chuyn khai thc, vn chuyn v ch bin kh. Ngoi ra s c mt ca hi nc v

cc hp cht cha lu hunh ( H2S v cc cht khc ) s lm gim nhit tr ca kh,

lm gim hot tnh xc tc trong cc qu trnh ch bin v l tin thc y n

mn kim loi, lm gim tui th v thi gian s dng ca cc thit b, cng trnh.

Trc nhng nguy c v tc hi to ln ca hi nc c mt trong kh thin

nhin v kh ng hnh trong cc quy trnh cng ngh th vic lm kh kh sao cho

t yu cu v tiu chun k thut l mt nhim v bt buc m bo kh nng

hot ng n nh v hiu qu ca cc dy chuyn cng ngh ch bin cc sn phn

kh sau ny. Kh c sy kh vi mc ch tch hi nc v to ra cho kh c nhit

im sng theo nc thp hn vi nhit cc tiu m ti kh c vn

chuyn hay ch bin.

Do vy, trong phm vi ca n ny, chng ta s tnh ton cc thng s thp

ca qu trnh lm kh kh bng phng php Hp th dng MonoEtylenGlycol

(MEG).

Em xin chn thnh cm n s hng dn nhit tnh ca thy gio, TS. Nguyn

Danh Nhi, B mn Lc Ha Du, i Hc M a Cht gip em hon thnh

n ny. Trong qu trnh thc hin n khng th trnh khi nhng sai st, mong

thy ng gp kin n c hon thin.

H Ni, ngy 02 thng 11 nm 2011

SV. Bi Quang Hiu


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Chng I - Tng quan v qu trnh cng ngh sy kh kh

I. C s l thuyt

Hydrat l nhng hp cht c th tn ti mt cch bn vng di dng tinh th.

Thc cht l nhng dung dch rn, trong cc phn t nc dung mi nh cc lin

kt hydro to thnh khung hydrat. Trong cc khoang ca khung ny cc phn t

kh c kh nng to hydrat nh metan, etan, propan, isobutan, nit, H2S, CO2, argon

s chim ch. Cc hydrocacbon vi phn t ca n c th xm nhp vo khung

cng vi cc phn t kh c kch thc nh hn, dn ti thay i p sut cn bng

trn cc hydrat. Mc chim ch trong khung ca cc phn t kh to hydrat i

vi thnh phn kh cho ch yu ph thuc vo p sut v nhit ca h. Cc

tinh th hydrat hnh thnh trn b mt phn chia pha ca h kh-nc. Nc t do

cn li sau khi hnh thnh cc hydrat ch tip tc chuyn thnh trng thi hydrat

khi c s khuy trn cc pha v khi c nhng iu kin nhit ng thch hp. Khi

khng c s khuy trn th qu trnh khuch tn ca kh qua lp mng cng ca cc

hydrat rt kh khan v s pht trin lin tc ca cc hydrat s khng xy ra.

iu kin hnh thnh cc hydrat ngoi ra cn ph thuc vo hm lng ca

mui c trong nc, hm lng ca chng tng s dn n gim nhit bt u

to thnh hydrat. Nhit ny cng ph thuc vo thnh phn kh, v d nhit

bt u to thnh hydrat ca metan khi c mt propan, CO2, H2S s thp hn so vi

khi vng mt cc cht ny. Hnh dng ca hydrat rt a dng, n c xc nh bi

thnh phn kh v cc iu kin nhit ng hc. Thng thng v hnh dng chng

ging nh nc hay tuyt m nn.

Nhm ngn nga s hnh thnh cc hydrat ngi ta s dng rng ri phng

php c ch tc l phng php a vo dng kh cc cht khc nhau gi l cc

cht c ch lm h nhit to thnh hydrat nh methanol, glycol v phng

php lm kh (tch nc) kh da trn c s tch hi nc ra khi kh bng cc cht

hp th lng hoc rn.

- Phng php c ch: thc cht l cho cht c ch vo dng kh m, cht c ch

s tan trong nc t do, kt qu l lm gim p sut hi nc v h nhit to

thnh hydrat. Hin nay cc cht c ch ngn nga s to thnh hydrat thng dng

nht l:

o S dng cht c ch l methanol, cn c khu vc kh hydrat v khu vc

kh axit.

o S dng cht c ch glycol


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Trong thc t thng s dng cc loi glycol: EG, DEG,TEG vi nng

khong 60 - 80 % khi lng. Vic la chn mt loi glycol s dng t

hiu qu cao chomt qu trnh x l kh no ph thuc vo :

T ng c v nht ca dung dch glycol ;

h T to hydrate i vi nng glycol cho ;

kh nng ha tan ca glycol trong HC ngng t ;

thnh phn kh.

h T im sng ca kh ph thuc vo loi cht c ch,nng ca n v

T kh tip xc vi cht c ch .

Nhng u im m cc glycol c c

Glycol Metanol

Khng gy c vi ngi v mi

trng.

Gy c hi vi ngi v mi trng.

C p sut hi bo ha rt thp v c

kh nng thu hi rt cao bng phng

php vt l n gin l c c cc dung

dch nc cha glycol.

p sut hi bo ha cao do vy kh

tch ra khi dng kh, vic ti sinh n

rt phc tp nn vic tiu hao cht c

ch l ln.

Nhit si cao nn kh b bay hi.

Trnh mt mat khi thit b.

Nhit si thp nn kh nng tht

thot l rt cao.

Khng gy n mn cho thit b. Mt s phn xng i khi cn thit k

thm cc thit b loi axit c th sinh

ra.

- Phng php hp ph: cc phng php hp ph cho php t im sng theo

m trong khong 100200oC v sy su kh n im sng -85 -100oC. Cc

cht hp ph c th chia thnh : Boxit l khong thin nhin cha ch yu l oxit

nhm ; oxit nhm hot ha l Boxit lm sch ; cc loi Gel l nhng hp cht

cu to t oxit silic v alumogel ; cc ry phn t l cc zeolite. Cc cht hp ph

c b mt ring rt ln ( 500-800 m2/g ) v b mt ny c to thnh t cc mao

qun hay mng tinh th. Cc qu trnh hp ph c th thc hin gin on trong

cc thit b vi tng thp hp ph c nh hoc lin tc vi cc thit b cha cc


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lp hp ph chuyn ng. Tuy nhin cc qu trnh lin tc rt t kh c s dng

do cc thit b cng ngh rt phc tp.

- Phng php thm thu kh: Cho n nay, qu trnh dehydrat ha bng thm thu

kh hu nh khng cn c s dng trong cng nghip x l kh na do nhng

yu cu k thut qu cao ca qu trnh. dshydrat ha kh bng thm thu phi

la chn nhng hp cht cao phn t thch hp c ij rt ln, khong 200.000 (vi

loi mng mng ng th v khng h c khuyt tt) v khong 300 500 (vi

loi chm si rng). Hn na, phi chp nhn mt lng C1 thm thu qua mng

lc mng lc c chn c b mt ring khng qu ln.

- Phng php hp th: phng php hp th c s dng rng ri sy kh kh

ti cc cng trnh ng dn kh cng nh trong cc nh my ch bin kh. Cht hp

th sy kh l nhng dung dch nc m c ca mono- , di- v trietylenglycol.

S sy kh kh bng cc cht hp th ny da trn s khc bit v p sut ring

phn ca hi nc trong khng kh v trong cht hp th. Gi tr im sng ca

kh c m bo bng dung dch Glycol.

So snh u nhc im ca cc dung mi hp th nc:

u im Nhc im

MEG

t tan trong kh ngng t. Dung

dch m c khng b ng c.

nht thp tng kh nng tip

xc vi hn hp kh. C kh nng

ngn nga to hidrat cao hn DEG

v TEG

p sut hi bo ha cao

hn DEG v TEG. Nhng

ha tan trong HC cao

hn DEG v TEG

DEG

ht m cao, kh bn khi c mt

cc hp cht lu hunh, O2 v

CO2 nhit thng. Dung dch

m c khng b ng c.

nhit cao c chn lc cao

Tiu hao do tht thot cao

hn TEG. Khi ti sinh kh

thu c DEG nng

>95%. im sng thp

hn so vi TEG. Gi thnh

cao

TEG

ht m cao. To im sng

cho kh sy cao (27.8 47.3oC)

bn cao khi c mt cc hp cht

lu hunh, O2 v CO2 nhit

i hi chi ph u t cao.

Dung dch TEG c kh

nng to mng khi c mt

cc HC nh. ha tan


5 | P a g e


u im Nhc im

bnh thng. Khi ti sinh d thu

c nng cao >99%. Dung

dch khng b ng c. bay

hi TEG thp hn DEG

ca cc HC nh trong TEG

cao hn DEG

Metanol

Gi thnh r. c s dng ch

yu trong cc h thng vn

chuyn. iu kin thng dung

dch m c khng b ng c.

C nht thp nht nn kh nng

tip xc vi hn hp kh l cao

hn cc glicol

C p sut ring phn cao

ln kh tch ra khi kh khi

ti sinh. Tiu hao ln

c tnh vt l ca cc Glycol v Metanol (dng lm kh kh)

C TNH VT

L MEG DEG TEG TREG METANOL

Cng thc

HC-

CH2-

CH2-OH

HO-

(CH2-

CH2-

O)2-H

HO-

(CH2-

CH2-

O)3-H

HO-

(CH2-

CH2-

O)4-H

CH3OH

KLPT 62.1 106.1 150.2 194.2 32.04

im si p

sut 760mmHg,

(oC)

197.3 224.8 285.5 314 64.5

p sut hi

25oC, (mmHg)

0.12


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C TNH VT

L MEG DEG TEG TREG METANOL

nht

ng

lc

(cP)

25oC

16.5 28.2 37.3 44.6 0.52

60oC

4.68 6.99 8.77 10.2 -

Sc cng b mt

25oC (dyn/cm) 47 44 45 45 22.5

Ch s khc x

25oC

1.430 1.446 1.457 1.457 20.328

Nhit dung ring

25oC (kj/kg.oC) 0.75 0.71 0.69 0.67 0.78

im chp chy

cc kn (oC)(flash

point)

115.6 123.9 1.769 204.4 12.0

im chp chy

cc h (oC) (fire

point)

118.3 143.3 165.6 190.6 -

Nhit

phn

hy

oF 329 328 404 460 -

oC 165 206.7 206.7 237.8 -


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II. S nguyn tc cng ngh sy kh kh bng phng php hp th

dng Glycol [1]

Thit b Dng vt cht

1. Thp hp th I. Kh nguyn liu m

2, 4. T.B Trao i nhit II. Kh lm kh

3. TB thi kh tch HC ha tan III. Dng glycol giu

5. Thp ti sinh IV. Dng kh thi ra

6. TB gia nhit V. Dng glycol b sung nu cn

7. TB lm ngui VI. Dng glycol ti sinh (glycol ngho)

8. Bn cha VII. Dng hi nc (cha 1 t glycol)

9. Bm

iu kin hot ng

- Thp hp th (1): + Nhit thp (15 38oC) + p sut cao (60 85 bar) - Thp ti sinh (5):

+ Nhit cao: Tnh (115oC) Ty Tp.hy glycol

+ p sut thp (1 1.2 bar)


8 | P a g e


Chng II - Tnh ton cc thng s c bn ca thp lm

kh kh bng phng php hp th dng

MonoEtylenGlycol I. D liu ban u [3]

- Thnh phn kh :

Cu t C1 C2 C3 n-C4 i-C4 n-C5 n-C6 N2 He

%V 82.0 4.7 3.8 2.5 2.8 1.5 1.2 1.0 0.5

- Nhit kh nguyn liu : 50oC

- Lu lng kh nguyn liu : 5.106 (std m3/ngy m)

- p sut kh nguyn liu : 68 bar

- p sut kh kh : 66 bar

- im sng kh kh : 10oC

- Cht hp th MEG (Mono Etylen Glycol)

- Lu lng ring cht hp th 30 (Kg/Kg H2O)

II. Yu cu tnh

- Nng ti thiu ca Glycol

- Lng dung dch tun hon/h (kg/h, kmol/h)

- S a l thuyt ca thp

- ng knh thp

- Chiu cao thp

III. Cc bc tnh ton [1]

Bc 1 : C th ha cc s liu ban u

Lu lng kh nguyn liu V = 5.106 std m3/ngy m = 208333,33 std m3/h

p sut kh nguyn liu 68 bar = 6,8 MPa

p sut kh kh 66 bar = 6,6 MPa

Khi lng phn t trung bnh ca kh nguyn liu

Trong : Mi khi lng phn t ca cu t i

Ci phn trm cu t i

Suy ra, M = 21,68 vC


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Bc 2 : Xc nh nng Glycol ti sinh ti thiu

Da vo nhit tip xc (c nhn bng nhit ca kh cn sy kh) v

im sng ca kh sy kh xc nh nng ca Glycol ti sinh ti thiu min

cn thu c im sng cho trc ca kh thng qua s hnh II.5 (trang 96

[1]), gin ny phn nh cc gi tr cn bng, m trong iu kin thc t khng t

c, nn xc nh nng Glycol theo th ny ta phi nhn im sng ca

kh thp hn gi tr cho 5-8oC.

Ta chn nhit im sng thp hn gi tr cho 5oC, tc nhit im

sng l 5oC. Da vo th hnh II.5 suy ra :

Nng Glycol ti dinh ti thiu min = 96%

Bc 3 : Xc nh hm m ca kh cn sy kh

Da vo th hnh II.1 (trang 90 [1]) hoc s IV.1a (trang 79 [2]) ta

xc nh hm m ca kh cn sy kh w1 v ca kh sy kh w2

Vi kh nguyn liu iu kin T = 50oC ; 6,8 Mpa

w1 = 1,80 g/m3 = 0,0018 (kg/m

3)

Vi kh kh p sut 6,6 MPa v c nhit im sng l 10oC

w2 = 0,21 g/m3 = 0,00021 (kg/m

3)

Bc 4 : Tnh lu lng cht hp th ti sinh

L1 = V.(w1 w2).l (kg/h)

Trong :

V l th tch kh nguyn liu (std m3/h)

l l lu lng ring cht hp th (kg/kg H2O)

w1 , w2 l hm m ca kh cn sy kh v kh sy kh (kg/ m3

)

Suy ra, L1 = 208333,33*(0,0018 0,00021 )*30 = 9937,5 (kg/h)

Bc 5 : Tnh nng Glycol bo ha xc nh theo phng trnh cn bng vt

cht da trn m trong pha lng v kh

( )

Ta chn nng ban u ca dung dch Glycol l 1 = 96,5 % ln hn nng ti

thiu ca Glycol l min = 96%

T suy ra :

( )

( )


10 | P a g e


Bc 6 : Tnh lng dung dich Glycol bo ha sau khi hp th

( )

( ) ( )

Mt khc, khi lng phn t trung bnh Mtb ca dung dch glycol bo ha c th

coi xp x bng: 0,934*62 + (1 0.934)*18 = 59,09 vC

Suy ra,

( )

Bc 7 : Tnh hng s cn bng theo phng trnh

*( ) +

( )

Trong M0 l khi lng phn t ca cht hp th MEG nn M0 = 62 vC

*( ) +

( )

Bc 8 : Xc nh yu t hp th A theo cng thc

Trong :

L l lu lng lng dung mi vo thp tnh ra Kmol/h

V lu lng kh cn lm kh tnh ra Kmol/h

- Xc nh L t L1 : theo tnh ton trn ta c L1 = 9937,5 (kg/h). Khi lng

phn t trung bnh ca dung mi hp th c tnh theo cng thc:

( )

Suy ra,

( )

- Xc nh V:

o theo trn ta c V = 208333,33 (std m3/h)

Suy ra V =

(kmol/h)

Vy :

Bc 9 : H s tch m thc t ca qu trnh hp th


11 | P a g e


Bc 10 : H s tch l thuyt khi tnh ton c ch n lng nc trong

glycol ti sinh

Trong :

X0 l nng phn mol ca nc trong cht hp ph ti sinh

Yn+1 l phn mol nc trong kh cn sy kh

Do :

Bc 11 : Tnh s a l thuyt

Ta c:

Trong ,

n l s a l thuyt ca thp hp th

A l yu t hp th tnh bc 8.

Suy ra:

Bc 12 : Tnh s a thc t

Theo kinh nghim thc t th hiu sut lm vic ca a l t 0,25-0,4

Ta chn hiu sut lm vic ca a l : = 0,3

Vy s a thc t ca thp hp th l 10 a


12 | P a g e


Bc13 : Tnh ng knh thp hp th

( )

Trong :

T l nhit lm vic ca thp, ly bng nhit kh nguyn liu (K)

T = 50oC = 323 K

P p sut lm vic ca thp,

P = (Pkh ng.liu + Pkh kh)/2 = (6,8 + 6,6)/2 = 6,7 (MPa) 67 (atm)

vn tc tuyn tnh ca dng kh trong thp (0,05-0,15 m/s)

Chn = 0,13 m/s

Q l lu lng kh nguyn liu, c quy i t iu kin tiu chun v iu

kin lm vic ca thp, (m3/s)

Theo u bi v [4], ta c cc d liu trong bng sau, trong Yi l

phn mol ca cc cu t trong hn hp kh, Tci v Pci l nhit v p

sut ti hn ca cc cu t.

Cu t C1 C2 C3 nC4 iC4 nC5 nC6 N2 He

Yi 0,82 0,047 0,038 0,025 0,028 0,015 0,012 0,01 0,005

Tci (K) 190,4 305,28 369,67 425,01 407,98 469,5 507,2 123,11 5

Yi*Tci 156,13 14,35 14,05 10,63 11,42 7,04 6,09 1,23 0,025

Pci (MPa) 4,61 4,88 4,25 3,8 3,65 3,37 3,01 3,4 0,23

Yi*Pci 3,78 0,23 0,16 0,095 0,10 0,05 0,04 0,03 0,0012

T bng trn, ta tnh c nhit gi ti hn v p sut gi ti hn

ca hn hp : pTc v pPc

pTc = Yi*Tci = 220,96 (K)

pPc = Yi*Pci = 4,49 (MPa)

Vy, suy ra nhit v p sut gi rt gn ca h: pTr v pPr

pTr = Tlm vic / pTc = 323/220,96 = 1,46

pPr = Plm vic / pPc = 6,7/4,49 = 1,49

Da vo th Hnh 3.2, trang 52 [4], ta tra c h s nn z:

z = 0,844

Vy, vi s mol khng i, trong iu kin lm vic ca thp, ta c lu

lng thc l:

( )


13 | P a g e


Suy ra :

(

)

( )

Nh vy ng knh thp khong D = 0,6 (m)

Bc 14 : Tnh chiu cao thp hp th

H = Ntt *d + h

Trong :

d l khong cch gia 2 a 0,5-0,6 m

h l chiu cao vm nh v y thp 1-1,2 m

Chn d = 0,5 m v h = 1,1 m

o H = 10*0,5 + 1,1 = 6,5 (m)

Vy chiu cao thp l 6,5 (m)

IV. Kt lun

Nh vy, vi s liu u bi cho, ta tnh c cc thng s ca thp hp th nh

sau :

Cc thng s tnh ton Kt qu

Nng ti thiu ca MEG 96%

Lng dung dch tun hon 9937,5 kg/h

S a l thuyt ca thp 3,04

ng knh thp 0,6 m

Chiu cao thp 6,5 m


14 | P a g e


Ti liu tham kho [1]. MA. Berlin, VG. Gortrencop, HP. Volcop. Ngi dch Hong Minh Nam,

Nguyn Vn Phc, Nguyn nh Soa, Phan Minh Tn. Hiu nh Nguyn nh

Soa. Cng ngh ch bin kh thin nhin v kh du m, HKT-TPHCM.

[2]. Nguyn Th Minh Hin (2004), Cng ngh ch bin kh t nhin v kh ng

hnh, NXB KHKT, H Ni.

[3]. S liu t thy gio, TS. Nguyn Danh Nhi, H M a Cht.

[4]. John M. Campbell. (1992), Gas Conditioning and Processing, Vol 1, Oklahoma.


15 | P a g e


Mc lc Li M u ........................................................................................................................... 1

Chng I - Tng quan v qu trnh cng ngh sy kh kh................................................... 2

I. C s l thuyt ............................................................................................................ 2

II. S nguyn tc cng ngh sy kh kh bng phng php hp th dng Glycol [1] . 7

Chng II - Tnh ton cc thng s c bn ca thp lm kh kh bng phng php hp th

dng MonoEtylenGlycol ........................................................................................................ 8

I. D liu ban u [3] ...................................................................................................... 8

II. Yu cu tnh ............................................................................................................ 8

III. Cc bc tnh ton [1] ............................................................................................. 8

IV. Kt lun ................................................................................................................ 13

Ti liu tham kho ............................................................................................................... 14

Mc lc ............................................................................................................................... 15

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