C s Ha lcho M phng

Mc lcPhn 1. ng ha hc ............................................................................................... 1Khi nim v ng ha hc......................................................................... 1Tnh ton tc phn ng vi cc bc khc nhau ....................................... 11.2.1. Phn ng bc 0 ........................................................................................ 11.2.2 Phn ng bc 1 ......................................................................................... 21.2.3 Phn ng bc 2 ......................................................................................... 21.2.4 Phn ng bc 3 ......................................................................................... 31.2.5 Phn ng bc n ......................................................................................... 31.2.6 Phn ng thun nghch ............................................................................. 41.2.7 Phn ng song song ................................................................................. 51.2.8 Phn ng ni tip ..................................................................................... 5L thuyt phn ng ..................................................................................... 61.3.1 nh hng ca nhit n tc phn ng ........................................... 61.3.2 L thuyt phn ng .................................................................................. 7Phn ng d th ........................................................................................... 81.4.1 C ch phn ng d th............................................................................. 81.4.2 ng hc ca phn ng xc tc d th .................................................... 101.4.3 Phng trnh ng hc tng qut ca phn ng d th ............................ 10Phn 2. Nhit ng ha hc .................................................................................... 13Hai nguyn l c bn ca nhit ng hc .................................................. 132.1.1. Nguyn l 1........................................................................................... 132.1.2. Nguyn l 2........................................................................................... 162.1.3. Nguyn l 3........................................................................................... 17Cn bng pha ............................................................................................ 172.2.1. iu kin cn bng pha ......................................................................... 172.2.2. Quy tc pha Gibbs ................................................................................. 17

2.2.3. Hng s cn bng pha............................................................................ 17Cn bng ho hc ..................................................................................... 18S chuyn dch cn bng - Nguyn l Le Chatelier .................................... 19Nhit ng hc cc hn hp kh ................................................................ 202.5.1 Kh l tng ........................................................................................... 202.5.2 Kh thc ................................................................................................. 202.5.3 Phng php tnh ton cc i lng nhit ng ca kh thc ................ 21Nhit ng hc v M phng .................................................................... 212.6.1 Cc H nhit ng trong m phng (Property Packages) ........................ 212.6.2 Tnh cn bng pha h nhiu cu t ......................................................... 24Ti liu tham kho .................................................................................................. 35

Phn 1. ng ha hc

Khi nim v ng ha hcng ha hc nghin cu din bin ca qu trnh bin i ha hc cc cht thhin: c ch phn ng tc phn ng yu t nh hng ti tc phn ng(nhit , p sut, nng ..).i lng quan trng nht ca ng ha hc l: vn tc phn ng (v) v hng stc (k). iu kin xy ra phn ng ha hc: iu kin theo ng ha hc:Theo l thuyt phn ng v thc nghim cc phn ng ha hc ch c thxy ra nu c va chm gia cc phn t vi nhau v cc va chm ny phi c nng lng vt qua nng lng ti thiu (nng lng hot ha ca phnng) l Ea. nh lut tc dng khi lng:L nh lut c s dng ph bin nht trong phn ng ha hc. nhlut nu rng:v = k. Cau.Cbv....Trong : v- l tc ca phn ng.k- hng s tc phn ng.u,v- bc ca cht tham gia phn ng A, B...n= u+ v+ .. l bc chung ca phn ng.

Tnh ton tc phn ng vi cc bc khc nhauDa theo nh lut tc dng khi lng c th chia thnh cc trng hp sau:1.2.1. Phn ng bc 0ABTc phn ng:dCv = k= dt

dC k dt C kt H

1

t=0

H= -Co

do , Co- C = kt1.2.2 Phn ng bc 1AB

Xt phn ng:

- p dng nh lut tc dng khi lng:v = k. Cu

(C- nng ca A ti thi im t v u= 1).

v= k.C

(1)

- Mt khc, c th tnh tc phn ng theo cng thc sau:Vn tc phn ng bng bin thin nng ca cht tham gia hoc l sn phm theothi gian. C cng thc nh sau:dCv =(2)dt(biu thc c du - nu l cht tham gia, khng c du - khi l sn phm)dCdC k dt- T (1) v (2):= k.C Cdt- lnC= kt + H(3)nu t= 0 C= Co (nng cht A lc ban u) v H= -lnCoC1 Cln o kt C= Co. e-ktDo , t biu thc (3)vk= .ln oCtC1.2.3 Phn ng bc 2a. Vi nng ban u khc nhauA

+

B

P

t=0

Co = a

b

0

t=t

C = ax

bx

x

v=

dxdx= h.(a-x).(b-x) kdtdt(a x).(b x)

Tin hnh gii tch phn trn ta c:1bxln kt Hba ax

tga = k (b-a)

t = 0, x= 01b H= b a ln av k =

1a(b x)lnt (b a) b(a x)

t

2

b. Vi nng ban u bng nhauTin hnh gii tng t nh trn nhng vi trng hp a= b1 1 ktC Co

1.2.4 Phn ng bc 3Phn ng:

A+B+C

SP

2A + B

SP

3A

SP

n gin trng hp ny ch xt vi nng cc cht ban u bng nhauCoA CoB CoC (CA= CB= CC)

Theo nh lut tc dng khi lng v cng thc xc nh vn tc phn ng:dCv= k.C3 = dtC

Tch phn 2 v:Do

t

dC1 11 kdt ( 2 2 ) kt3C2 C C0Co01 11k= 2 2 2t C C0

1.2.5 Phn ng bc nTng qut xt cho phn ng bc n. Gi s nng cht ban u bng nhau. Theonh lut tc dng khi lng v cng thc xc nh vn tc phn ng:dCdC kC n n kdtdtCLy tch phn hai v:dC1 k dt kt HnC(n 1)C n 11C= Co H=(n 1)Co n 1

Ti t= 0

Do , cng thc tng qut l:11 ktn 1(n 1)C(n 1)Co n 11 11 k= n 1 n 1 (n 1)t CCo

3

1.2.6 Phn ng thun nghchL dng phn ng thng xuyn gp trong cc qu trnh m phng.Phn ng thun nghch bc 1k

1

A

k2

B

t=0

a

b

t=t

ax

b+x

t=

a xc

b + xc

Theo nh lut tc dng khi lng:vt= v1= k1.(a-x)vn= v2= k2.(b+x)Phn ng t cn bng khi: vt= vnk1.(a-xcb)= k2.(b+xcb)do

xcb=

k1a k2bk1 k2

vn tc chung ca phn ng:vc= vt- vn = k1.(a-x)- k2.(b+x)p dng nh lut tc dng khi lng:v=

dCdCdCdx= A Bdtdtdtdt

do

dxk a k 2b k1 (a x) k2 (b x) = (k1 k2 )( 1 x)dtk1 k2

dxdx (k1 k2 )( xcb x) (k1 k2 )tdtxcb x

Ly tch phn 2 v:x

t

ln

xcb (k1 k2 )txcb x

Vy

x1k1 k2 ln cbt xcb x

dx0 xcb x 0 (k1 k2 )dt

4

1.2.7 Phn ng song song

Phn ng hu c t mt cht ban u xy ra theo rt nhiu hng khc nhau,cho cc sn phm khc nhau. Do , xem xt phn ng song song l mt hnggii quyt vn phc tp ny.Phn ng song song bc 1:A

k1

B

k2

C

Phn ng 1:

dx1 k1 (a x)dt

Phn ng 2:

dx2 k2 ( a x)dt

Trong :

a l nng ban u ca cht A;x l nng phn ng ca A ti thi im t.x1, x2 l nng ca sn phm B, C ti thi im t.

Do

x= x1+ x2

Tc chung:

dx dx1 dx2= k1(a-x)+ k2(a-x)dt dt dt

dx (k1+ k2)dtaxx

t

Ly tch phn 2 v:

dx0 a x (k1 k2 )0 dt

ln

1ak k1 k2 lnt ax

a (k1 k2 )tax

1.2.8 Phn ng ni tip1A

k

t=0

a

t=t

ax

2B

k

xy

5

C

y

Giai on 1:v1=

A BdC A dx k1 (a x) a x a.e k t x a.(1 e k1t )dtdt1

Giai on 2:v2=

B CdCC dy k2 ( x y )dtdt

CC= y =

a k1 (1 e k1t ) k2 (1 e k2t ) k1 k2

L thuyt phn ng1.3.1 nh hng ca nhit n tc phn ngNhit nh hng ln nht n tc phn ng. Khi nhit phn ng thay i,tc phn ng thay i theo phng trnh hm s m. Do , kho st s thay i catc phn ng theo nhit l iu thit yu trong phn ng ha hc.a. Quy tc thc nghim Van HoffThc nghim cho thy khi nhit tng ln th vn tc ca phn ng tng rt nhanhv c tng ln 10oC th tc phn ng tng ln 24 ln.Gi l h s nhit th l s ch vn tc ca phn ng tng ln bao nhiu lnkhi nhit tng ln 10o.

= vt 10vt

Trong :

vt+10 hng s tc nhit t+10v hng s tc nhit t

Tuy nhin, ch nn p dng cng thc ny khi khong bin thin nhit vdh vc = vktMun tng vn tc phn ng cn phi tng vn tc khuch tn vkt. Phn ng xy ra vng ng hcKhi , vn tc phn ng vng ng hc chm hn rt nhiu vn tc phn ngca vng khuch tn.vdh> vkt vc = vdhMun tng vn tc phn ng th phi tng vn tc phn ng ca vng ng hc. Phn ng vng qu Khi xy ra phn ng trong vng qu , vn tc phn ng vng khuch tn gnbng vi vn tc phn ng trong vng ng hc.

vkt vdhKhi phi xem xt qu trnh phn ng c vng khuch tn v vng ng hc,nghin cu nh hng ca c hai vng n tc phn ng xy ra.1.4.3 Phng trnh ng hc tng qut ca phn ng d thPhn ng:

S P

nXc nh vn tc ng hc: vdh k1.cs

trong :

k1 hng s vn tc ng hcCs nng S trn b mt xc tc

10

n gin, xt bc n = 1

vdh = k1.CS

Vn tc khuch tn c tnh theo nh lut Fick.

trong :

dq = - D..gradC.dtdq lng cht khuch tn trong mt n v thi gian dtD h s khuch tndxgradC =chnh lch nng trn khong chiu di dldt - khong cch

Xc nh vn tc khuch tnGi Cx l nng cht S trongmi trng phn ng, vi khongcch l v nng trn b mtxc tc l Cs.Do nng cht phn ngti b mt xc tc c tnh theobiu thc:

C Cxdx sdl

p dng nh lut Fick.dq D. .

Cs Cx

dt

Xt trong mt n v th tch V, ta c:dq D..(Cs Cx ).dtV V .dqdC vktVdt

t

dC

do

vkt

D..(Cs Cx )V .

t

D.nn vkt .(Cs Cx )V .

Xt cc trng hp sau: Trong vng qu :vkt= vdh

11

k1.Cs = .(Cs Cx)

Cs (k1 + ) = .CxCs= k .Cx1

Gi

kc=

k1. v k1. .Ccxk1 k1

Trong vng khuch tn: k1> vc = .Cx Trong vng ng hc: k1> vc = k1.CsNhn chung phn ng xc tc d th xy ra rt phc tap. gii quyt c th cnda vo nhng iu kin cng ngh v l thuyt ca qu trnh ang phn tch.

12

Phn 2. Nhit ng ha hcNhit ng ho hc l khoa hc nghin cu cc quy lut iu khin s trao i nnglng, c bit nhng quy lut c lin quan ti cc bin i nhit nng thnh cc dngnng lng khc.

Hai nguyn l c bn ca nhit ng hc2.1.1. Nguyn l 1 ca nhit ng ho hc nghin cu cc hin tng bin i nnglng trong cc qu trnh bin i ho hc hoc cc phn ng ho hc xy ra trongnhng iu kin khc nhau da trn c s nh lut bo ton nng lng caLomonoxop. Nguyn l 1 cn c gi l nguyn l bo ton nng lng.Nguyn l 1 ca nhit ng ho hc nghin cu mi quan h gia nhit v cnglin quan ti nng lng lm bin i trng thi ca h. Thng s c trng cho qu trnhbin i trng thi ca h l ni nng (gin tip thng qua thng s nhit dung).Tn ti mt hm trng thi U gi l ni nng, dU l mt vi phn ton phn.S bin i ni nng U ca h chuyn t trng thi 1 sang trng thi 2 bng tngi s ca tt c cc nng lng trao i vi mi trng trong qu trnh bin i ny.U = U2 U1 = WA QA = WB QB = .i vi mt bin i v cng nh:dU= W QTrong :

dU - vi phn ton phn W, Q - Khng phi l mt vi phn ton phn

Khi Trong :

2

= 1 = + U l ni nng ca hW c nng m n trao i vi mi trngQ nhit nng m n trao i vi mi trng

Nhit dung ng vai tr c bit quan trng khi nghin cu nguyn l 1 ca nhitng hc. Nhit dung thng c trng cho iu kin v trng thi bin i. Khi bini ni nng trong mt h cng pha c thnh phn c nh th thng c xc nhqua nhit dung. Nu h cng pha bin i trong mt khong nhit t T1 n T2 thnhit dung theo nhit trung bnh:

CT1 T2

QT2 T1

13

Trong , Q l nhit lng lm cho nhit ca h thay i t T1 n T2 nhngkhng lm thay i thnh phn pha trong h.Nhit dung ring ng p (CP): l nhit lng cn thit nng nhit ca mtmol cht nguyn cht ln 1 K iu kin p sut khng i v trong khong nhit khng c s chuyn pha. = (

( ))

Nhit dung ring ng tch (CV): l nhit lng cn thit nng nhit ca 1 molcht nguyn cht ln 1 K iu kin th tch khng i v trong khong nhit khng xy ra s chuyn pha. = (

( ))

Tnh nhit dung ca cht rn:Nhit dung phn t ca cht rn c th coi bng tng s nhit dung cc nguyn ttrong cht rn.Cng thc xc nh Cp:CP= Cv.(1+ 0,0214.Cv.

T)Tch

Tnh nhit dung ca cht kh:Vi kh thc c th dng phng trnh thc nghim thu c theo phng phpbnh phng cc tiu c dng:

CP a bT cT 2Trong , cc h s a, b, c c trng cho mi cht.Tnh nhit dung ca cht lng:Do cha c l thuyt hon chnh v trng thi lng do cha c nhiu kt lun vnhit dung trong cht lng. Thc nghim cho thy rng, nhit dung cht lng thng caohn nhit dung cht rn v nhit dung cht kh. Hiu ng nhit ca phn ng - nh lut HessHiu ng nhit ca mt phn ng ch ph thuc vo trng thi u v trng thi cuica cc cht tham gia v cc cht to thnh ch khng ph thuc vo trng thi trung gian.Cc h qu ca nh lut Hess:+ Hiu ng nhit ca phn ng thun bng hiu ng nhit ca phn ng nghchnhng mang du ngc nhau.

14

Hth = - Hng+ Nhit sinh hay nhit to thnh ca mt cht l nhit lng thot ra hay thu vokhi to thnh 1 mol cht t cc n cht bn vng iu kin .+ Hiu ng nhit ca mt phn ng bng tng nhit sinh ca cc cht cui tr itng nhit sinh ca cc cht u.

H = HS(sanpham) - HS (thamgia)+ Nhit chy ca mt mol cht l nhit lng thot ra khi t chy hon ton 1 molcht thnh cc oxit cao nht bn iu kin .Do , hiu ng nhit ca mt phn ng bng tng nhit chy ca cc cht tham giatr i tng nhit chy ca cc cht to thnh. Cng ca qu trnh bin iXt i vi kh l tng:p

nRTV

Cng ca qu trnh dn 1 mol kh c th vit di dng:V2

V2

V1

V1

A pdV A pdV RT .

VdV RT ln 2VV1

Xt qu trnh ng tch:Cng p.dV trong iu kin ng tch bng 0, do Q dU . Ngha l tt c nhitthu c thit b iu nhit u c dng thay i ni nng ca kh. Nhit dungng tch c xc nh bng quan h: Q U CV T V T V

Kh l tng c ni nng khng ph thuc th tch nn c th vit dU=CVdT i vimt phn t kh hoc c th vit dU=nCvdT cho n phn t kh. Ni nng bin i t T1n T2 c th tnh theo cng thc:2

= 1

Xt qu trnh bin i ng p:Cng thc hin trong qu trnh c th xc nh:A

V2

p.dV p V

2

V1

15

V1

2.1.2. Nguyn l 2 ca nhit ng hcTn ti mt hm trng thi gi l entropi, k hiu l S. Vy dS l mt vi phn tonphn. Gi s c mt bin i thun nghch v cng nh trong h trao i vi mitrng nhit T mt nhit lng Qtn , s bin i entropi trong qu trnh ny cxc nh bi:

Qtn

dS

T

n v ca S l: j.K-1 hoc cal.K-1.Nu s bin i l bt thun nghch ngha l qu trnh t xy ra th:

dS

QbtnT

ng dng ca nguyn l 2Nguyn l 2 c s dng d on kh nng c t xy ra ca phn ng ha hc.Trc ht xem xt s ph thuc ca entropi vo nhit .Khi nhit thay i entropi ca h cng thay i. Gi s qu trnh xy ra p=const v trong khong nhit kho st. Khi : Qp dH C p dT

Gi s s bin i l thun nghch:2

= 1 2 = 1

Nu trong khong nhit kho st Cp rt t bin i2

=

1

2= 1

Tng t nu s bin i xy ra iu kin th tch khng i: =

21

iu kin phn ng c th t xy rap dng hm th nhit ng: G= H-T.S. Khi h chuyn t trng thi ny sang trngthi khc tc l phn ng t xy ra. Khi , c phng trnh:G = (H TS)

G =H - TS

Phn ng t xy ra khi v ch khi: G < 0 H - TS < 0Hoc theo nguyn l 2 th:

S 016

2.1.3. Nguyn l 3 ca nhit ng hcEntropi ca cc cht nguyn cht di dng tinh th hon ho khng tuyt ibng khng.Trong mc ch s dng cho m phng th nguyn l 3 c s dng rt t nnkhng a ra trong ti liu ny.

Cn bng phaPha l tp hp tt c cc phn ng th ca mt h c thnh phn, tnh cht vt l,ha hc ging nhau v c b mt phn chia vi cc phn khc ca h.Cn bng pha trong cc h d th, cc cu t khng phn ng ha hc vi nhaunhng xy ra cc qu trnh bin i pha ca cc cu t.2.2.1. iu kin cn bng phaXt h c lp gm pha nm cn bng vi nhau.iu kin tng qut xy ra cn bng pha l: nhit , p sut v th ha ca micu t mi pha l nh nhau.2.2.2. Quy tc pha GibbsBc t do ca h (k hiu: C) l s thng s trng thi cng c th thay i mtcch c lp m khng lm bin i s pha ca h.Cng thc xc nh quy tc pha Gibbs:C= K - + 2T biu thc trn xc nh c rng: Khi s cu t c lp K tng th bc t do ca h s tng. Khi s pha tng th bc t do ca h gim.Nu gi cho p sut hoc nhit ca h khng i th:C=K- +12.2.3. Hng s cn bng phaHng s cn bng pha l i lng c trng cho s phn b ca cc cu t gia ccpha iu kin cn bng. K hiu l K.K=Trong :

yixi

yi Phn mol ca cu t i trong pha hi.xi - Phn mol ca cu t i trong pha lng.

17

xc nh hng s cn bng pha c th dng th c rt ra t cc s liu thcnghim, s dng cc cng thc thc nhim v dng phng php gii tch c c s tnhng phng trnh trang thi m rng.+ S dng cc phng trnh trng thi xc nh hng s cn bng phaBng vic gii cc phng trnh trng thi RK:P

RTa 0,5v b T v(v b)

c s dng nhng thng s hiu chnh, c th xc nh c hng s cn bng phanhng ni chung l rt phc tp.+ S dng nhng cng thc thc nghimCc cng thc tnh ton gn ng c cc nh khoa hc nghin cu v a ra phcv cho qu trnh tnh ton gn ng K.+ S dng thHng s cn bng K c xc nh ti nhng iu kin nhit v p sut i vitng cu t. Sau c xy dng thnh cc ng th.

Cn bng ho hcCn bng ca phn ng ha hc c c trng bi hng s cn bng. Xt phn ngha hc sau:aA + bB cC + dDNu cc cht tham gia phn ng th kh, khi c cn bng K c gi l Kpc xc nh bng biu thc:PCc .PDdKp = a bPA .PB

Kp ch ph thuc vo nhit .Mt s cng thc lin quan: = l mi quan h gia entanpi t do iu kin chun vi hng s cn bng pha Kp. = ( ) l phng trnh ng nhit vanHoff.

18

Ngoi hng s cn bng Kp , trong qu trnh tnh ton cn s dng cc hng s cnbng pha khc: Kc, Kn, KN. Mi lin h gia cc hng s cn bng:Kp = Kc(RT)n Vi R= 0,082Kp = KN.P n = (

)

Trong :

n= (c+d) (a+b)Kp hng s cn bng tnh theo p sutKc hng s cn bng tnh theo nng KN hng s cn bng tnh theo phn molNi

ni ni

Kn hng s cn bng tnh theo mol

S chuyn dch cn bng - Nguyn l Le Chatelier nh hng ca p sutNu mt h ang trng thi cn bng m ta tng p sut chung ca h th cn bngca phn ng s chuyn dch theo chiu ca phn ng to thnh s phn t kh t hn vngc li. C ngha l: Nu mt h ang trng thi cn bng m ta thay i p sutchung ca h th cn bng ca phn ng s chuyn dch theo chiu ca phn ng no ctc dng chng li s thay i .i vi h kh, p sut c nh hng rt ln ti cn bng ca qu trnh. i viphn ng trong h lng th p sut c nh hng rt hn ch. Cn vi phn ng lng kh th cn bng cn ph thuc nhiu vo h s phn ng. nh hng ca nhit =

=

Phng trnh Gibbs Hemholtz

( )( )= 2Phng trnh ng p vanHoff

19

(

) = 2

Khi , c th xt c chiu chuyn dnh cn bng khi nhit thay i:- Nu > 0 (phn ng thu nhit) khi tng nhit , cn bng ca phn ng schuyn dch theo chiu phn ng thun.- Nu < 0 (phn ng ta nhit) khi tng nhit , cn bng ca phn ng schuyn dch theo chiu phn ng nghch.Kt lun: Nu mt h ang trng thi cn bng m ta thay i nhit ca h thcn bng ca phn ng s chuyn dch theo chiu ca phn ng no c tc dng chng lis thay i .Trong khong nhit hp c th coi = khi tch phn phng trnhng p vanHoff ta c: (2 ) 11 ()=( ) (1 ) 2 1

Nhit ng hc cc hn hp kh2.5.1 Kh l tngMt hn hp kh c gi l kh l tng khi tha mn nhng yu cu sau:- Cc phn t cht kh c coi l cc cht im.- Cc phn t kh ch tng tc vi nhau khi va chm.c trng cho h kh l tng l phng trnh trng thi kh l tng:PV const hoc PV= nRTT

Tuy nhin, kh l tng khng c trong thc t, ch c p dng gii thch cchin tng vt l.2.5.2 Kh thcMt hn hp kh thng thng l hn hp kh thc tha mn nhng c im sau:- Cc phn t kh khng c coi l cht im, chng c khi lng v kch thcxc nh.- Cc phn t kh tham gia tng tc vi nhau.Mt s phng trnh trng thi m t h kh thc c s dng ph bin:20

Phng trnh Van der Waals:a P 2 . v b RTv

Trong : a, b l cc h s tng quan; v l th tch mol.Phng trnh Benedict Webb Rubin (BWR):2 3 C P RT Bo RT Ao o2 . 2 bRT a . 3 aa 6 c 2 . 1 . 2 eT T

Trong : Ao, Bo, Co. a, b, c, a , l cc hng s quan h.P l p sut, T l nhit tuyt i, l t trng mol.Phng trnh Redlich Kwong (RK):P

RTa 0,5v b T v(v b)

Trong : a, b l cc hng s quan h; v l th tch mol.Phng trnh Peng Robinson (PR):P

RTa(T )v b v ( v b ) b (v b )

Trong : a, b l cc hng s quan h; v l th tch mol.2.5.3 Phng php tnh ton cc i lng nhit ng ca kh thc T cc phng trnh trng thi T cc th thc nghim

Nhit ng hc v M phng2.6.1 Cc H nhit ng trong m phng (Property Packages)Cc h nhit ng l nhng modul c xy dng sn trong cc phn mm mphng trong ha hc. Cc h nhit ng c la chn ph hp vi nhng tnh cht khcnhau ca hn hp nguyn liu u vo, t cc hn hp n gin (ch c cc cu thydrocacbon) n hn hp rt phc tp (nh hn hp du, cc dung dch in phn,).Cc h nhit ng gip xc nh c khi qut nht tnh cht ca t loi nguynliu, gip m hnh ha cc h ha hc mt cch chnh xc nht c th.Sau y s xem xt mt s h nhit ng c s dng ph bin trong m phngcng ngh ho hc v du kh.

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Phng trnh trng thi (EOS)Cho cc ng dng vi oil, gas hoc ha du cc phng trnh trng thi Peng Robinson c ngh s dng trong Hysys. Cc phng trnh PR, SRK ang tip tcci tin, c iu chnh cho ph hp vi tng h c th nh PRSV, ZJ, LKP. Trong ccphng trnh c s dng th PR l phng trnh trng thi h tr ti a v c pdng a dng nht. Phng trnh SRK yu cu nhp vo trng thi cn bng v tnh chtnhit ng hc trc tip. Trong cng nghip ha hc vi cc h iu kin khng ltng th phng trnh trng thi PRSV c s dng ph bin.Phng trnh trng thi PR c cc ty chn: PR, Sour PR, PRSVPhng trnh trng thi SRK c cc ty chn: SRK, Sour SRK, KD, ZJ. Activity ModelsMc d phng trnh trng thi rt ng tin cy trong d on hu ht tnh cht cahydrocacbon lng trong mt khong rng cc iu kin hot ng. Tuy nhin ng dngca n b gii hn vi cc thnh phn phn cc hay khng phn cc. Vi cc h phn cchay khng phn cc c s dng phng php tip cn khc.Trong thc tin ca ngnh cng nghip ha hc, cc phng trnh trng thi t cs dng t hn do mi qu trnh thc tin u s dng phng trnh trng thi gn ng,do sai s gy ra trong h thng l rt ln. khc phc nhng nhc im ny ccnh khoa hc tin hnh thc nghim v xy dng ln nhng phng trnh gn ngph hp vi iu kin thc t. Cc phng trnh c nhm chung vo mt nhm lActivity Models. WilsonPhng trnh Wilson, c Grant M. Wilson sut vo nm 1964 l phng trnhu tin cc h s ca phng trnh c s dng biu din nng lng d Gibbs. Ncung cp mt h nhit ng ph hp hi quy h s cn bng bc hai t cc s liu.Mc d phng trnh Wilson l phc tp hn v i hi thi gian tnh ton lu hnso vi phng trnh Van Laar hoc Margules nhng n c th i din cho hu ht cccht lng khng l tng .- Thc hin tnh ton hi quy cc h s tng tc bc 2 t cc s liu nhit ng.- Tnh ton chnh xc v nhanh chng cho h khng l tng.- Tuy nhin khng th d on c tch pha lng lng v vy khng nn s dngcho c qu trnh pha trn.

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NRTLPhng trnh NRTL (Non-Random-Two-Liquid) c sut bi Renon vPrausnitz nm 1968 l mt phn m rng ca phng trnh Wilson ban u. N s dngphng php thng k v l thuyt v vi phn cht lng nghin cu v cu trc chtlng. Nhng khi nim ny kt hp vi m hnh ca Wilson to thnh phng trnh ckh nng tnh ton cc h s VLE, LLE v VLLE. Cng nh phng trnh Wilson,NRTL m hnh nhit ng lc hc ph hp v c th tnh ton bc 3 hoc cao hn sdng phng trnh vi phn t cc s liu cn bng. M hnh NRTL tng ng nhWilson cho cc h VLE.- Phng trnh NRTL kt hp nhng u im ca Wilson v Van Laar.- Qu trnh tnh ton rt nhanh.- C th s dng cho h LLE ph hp.- Tuy nhin do kt hp nhiu cng thc thc nghim nn c nhiu sai s xut hintrong qu trnh tnh ton v NRLT ph thuc vo rt nhiu hng s gn ng. UNIQUACPhng trnh UNIQUAC (UNIversal QUAsi Chemical) c Abram v Prausnitz ngh nm 1975 s dng phng php thng k v l thuyt quasi-chemical caGuggenheim nghin cu cu trc ca h lng. Phng trnh tnh ton cc h s LLE,VLE v VLLE c chnh xc rt cao so vi s dng NRTL.Phng trnh UNIQUAC cho chnh xc cao v chi tit hn bt k m hnh nhitng khc.- u im chnh ca UNIQUAC l tnh ton rt chnh xc cc h s VLE, LLE vc p dng rng ri vi h khng phn ly, ch s dng hai thng s iu chnh trong hs bc hai.- Cc thng s ch ng trong mt khong nhit tng i hp.- Phng trnh UNIQUAC s dng cc cu t c sn ging nh phng trnhWilson. Khi s thay i nng trn b mt tri vi nng mol, th phng trnhUNIQUAC s dng cho cc h c hnh dng v kch thc rt khc nhau nh polyme.- Phng trnh UNIQUAC c p dng trong mt khong rng vi hn hp chanc, alcol, nitrit, amine, este, keton, andehyt, halogen, hydrocabon halogen vhydrocacbon.

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C nhiu h nhit ng c m t trong phn mm m phng. Trn y ch nu ranhng phng trnh quan trng v cc trng hp c th s dng. Tuy nhin trong tngh c th phi c bc nh gi v la chn h nhit ng ph hp th mi nhn c ktqu tnh ton ng n, chnh xc.C rt nhiu h nhit ng c th c khai bo cho mt h hoc l ch mt h duynht. Vic la chn tng h nhit ng c th cn phi c xem xt v nghin cu mtcch k lng trc khi bt u mt qu trnh m phng. Bng di y a ra mt s htiu biu v mt vi la chn h nhit ng ph hp.Cc h

H nhit ng

Tch nc TEG

PR

Nc chua

PR, Sour PR

Qu trnh lm lnh kh

PR, PRSV

Phn tch khng kh

PR, PRSV

Thp chng ct kh quyn

PR, PR Options, GS

Thp chng ct chn khng

PR, PR Options, GS