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MC LCTI LIU THAM KHO ................................................................................................... 64PHN I - GII THIU CHUNG
PHN II - GII THIU V DY CHUYN
SN XUTPHN III - TNH TON THIT B CHNH
PHN IV - KT LUN
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PHN IGII THIU CHUNG
I. L THUYT V CHNG CT :1. Khi nim :
- Chng ct l qu trnh dng tch cc cu t ca hn hp lng
cng nh hn hp kh lng thnh cc cu t ring bit da vo bay hikhc nhau ca cc cu t trong hn hp (ngha l khi cng nhit , p suthi bo ho ca cc cu t khc nhau).
- Thay v a vo trong hn hp mt pha mi to nn s tip xcgia hai pha nh trong qu trnh hp thu hoc nh kh, trong qu trnh chngct pha mi c to nn bng s bc hi hoc ngng t.
- Chng ct v c c kh ging nhau, tuy nhin s khc nhau cn bnnht ca 2 qu trnh ny l trong qu trnh chng ct dung mi v cht tanu bay hi (ngha l cc cu t u hin din trong c hai pha nhng vi tl khc nhau), cn trong qu trnh c c th ch c dung mi bay hi cn chttan khng bay hi.
- Khi chng ct ta thu c nhiu cu t v thng th bao nhiu cut s thu c by nhiu sn phm. Nu xt h n gin ch c 2 cu t thta s thu c 2 sn phm :
Sn phm nh ch yu gm cu t c bay hi ln (nhit si nh)
Sn phm nh ch yu gm cu t c bay hi nh (nhit si ln)
- i vi h Benzen Toluen Sn phm nh ch yu gm benzen v mt t toluen. Sn phm y ch yu l toluen v mt t benzen.
2. Phng php chng ct :Cc phng php chng ct c phn loi theo :
- p sut lm vic : p sut thp p sut thng p sut cao
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Nguyn tc lm vic : da vo nhit si ca cc cu t, nunhit si ca cc cu t qu cao th ta gim p sut lm vic gim nhit si ca cc cu t.
- Nguyn l lm vic :
Chng mt bc Chng li cun theo hi nc Chng ct
- Cp nhit y thp : Cp nhit trc tip Cp nhit gin tip
Vy: i vi h Benzen Toluen, ta chn phng php chng ct lintc p sut thng.
3. Thit b chng ct :Trong sn xut, ngi ta thng dng nhiu loi thit b khc nhau
tin hnh chng ct. Tuy nhin, yu cu c bn chung ca cc thit b vnging nhau ngha l din tch tip xc pha phi ln. iu ny ph thuc vomc phn tn ca mt lu cht ny vo lu cht kia. Nu pha kh phn tnvo pha lng ta c cc loi thp mm, nu pha lng phn tn vo pha kh tac thp chm, thp phun, y ta kho st 2 loi thng dng l thpmm v thp chm.
Thp mm : thn thp hnh tr, thng ng pha trong c gn ccmm c cu to khc nhau, trn pha lng v pha hi cho tip xc vinhau. Tu theo cu to ca a, ta c :
- Thp mm chp : trn mm b tr c chp dng trn, xupap, .- Thp mm xuyn l : trn mm c nhiu l hay rnh. Thp chm (thp m) : thp hnh tr, gm nhiu bc ni vi nhau
bng mt bch hay hn. Vt chm c cho vo thp theo mt tronghai phng php sau : xp ngu nhin hay xp th t.
II. GII THIU V NGUYN LIU :Benzen & Toluen :
Benzen: l mt hp cht mch vng, dng lng khng mu v c mi thmnh.Cng thc phn t l C6H6. Benzen khng phn cc,v vy tan tt trongcc dung mi hu c khng phn cc v tan rt t trong nc. Trc yngi ta thng s dng benzen lm dung mi. Tuy nhin sau ngi tapht hin ra rng nng benzen trong khng kh ch cn thp khong 1ppmcng c kh nng gy ra bnh bch cu, nn ngy nay benzen c s dng
hn ch hn
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Cc tnh cht vt l ca benzen:
o Khi lng phn t: 78,11o T trng(200C): 0,879
o
Nhit si: 80o
Co Nhit nng chy: 5,50C
Toluen: l mt hp cht mch vng, dng lng v c tnh thm ,cng thcphn t tng t nh benzen c gn thm nhm CH3. Khng phn cc,do toluen tan tt trong benzen.Toluen c tnh cht dung mi tng t benzennhng c tnh thp hn nhiu, nn ngy nay thng c s dng thaybenzen lm dung mi trong phng th nghim v trong cng nghip.
Cc tnh cht vt l ca toluen:
o Khi lng phn t : 92,13o T trng (20oC) : 0,866o Nhit si : 111oCo Nhit nng chy : -95 oC
Cc phng thc iu ch :
o i t ngun thin nhinThng thng cc hidrocacbon t c iu ch trong phng thnghim, v c th thu c lng ln n bng phng php chng ctthan , du m.
o ng vng v dehiro ha ankaneo Cc ankane c th tham gia ng vng v dehidro ha to thnh hidro
cacbon thm nhit cao v c mt xc tc nh Cr2O3, hay cc limloi chuyn tip nh Pd, Pt
CH3(CH2)4CH3 3232/ OAlOCr
C6H6
o Dehidro ha cc cycloankaneCc cycloankane c th b dehidro ha nhit cao vi s c mt
ca cc xc tc kim loi chuyn tip to thnh benzen hay cc dnxut cu benzen
C6H12 P dP t/
C6H6
o i t acetylenun acetane trong s c mt cu ca xc tc l than hot tnh hay
phc ca niken nh Ni(CO)[(C6H5)P] s thu c benzen
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3C2H2 x t C6H6
o T benzen ta c th iu ch c cc dn xut ca benzen nh toluenbng phn ng Friedel-Crafts (phn ng ankyl ha benzen bng cc
dn xut ankyl halide vi s c mt cu xc tc AlCl3 khanC6H6 + CH3- Cl 3A lC l C6H5-CH3
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PHN IIGII THIU V DY CHUYN SN XUT
Ta thit k h thng chng luyn lin tc loi thp a chp tch hn
hp 2 cu t benzen toluen p sut thng.S nguyn l dy chuyn sn xut c trnh by trn ( Hnh 1 )
Qu trnh lm vic ca dy chuyn nh sau :
Nguyn liu u vo F a vo thng cha nguyn liu (1) c bm (2)bm ln thng cao v (3) . T thng cao v nguyn liu qua van lu lng (4)vo thit b gia nhit hn hp u (5) < y l thit b trao i nhit dng ngtrm > . Nguyn liu c i trong ng t di ln , gia nhit bng hi ncbo ha nhit si sau vo thp chng luyn (6).
Thp chng luyn gm 2 phn :
Phn t a tip liu tr ln : on luyn
Phn t a tip liu tr xung : on chng
Trong thp , hi i t di ln gp cht lng i t trn xung v theo chiu caoca thp , nhit cng ln cao cng thp nn khi hi qua cc a t di ln, cu t c nhit si cao s ngng t li v cui cng trn nh ta thuc hn hp gm hu ht cc cu t d bay hi l Benzen . Hi ny i vothit b ngng t hi (7) < hi i ngoi ng , nc lnh i trong ng v t diln > y c hi ngng t li . Mt phn cht lng sau khi ngng t i vthp a trn cng , 1 phn khc i qua thit b lm lnh (9) lm lnh nnhit cn thit ri i vo thng cha sn phm nh (10) , c bm (11)a ra ngoi .Cht lng i t trn xung di gp hi c nhit cao hn , 1phn cu t c nhit si thp (cu t d bay hi ) c bc hi v do nng cu t kh bay hi trong cht lng ngy cng tng . Cui cng y
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thp ta thu c hn hp lng gm hu ht cc cu t kh bay hi l Toluen .Sn phm y i qua van iu chnh (14) ra thit b trao i nhit . un situn hon v bc hi hn hp y thp . Mt phn khc tho ra lin tc avo thng cha sn phm y (15) khng ch bng cc van .
Nc ngng ca cc thit b gia nhit (5),(12) c tho qua cc thit b thonc ngng (16),(13) thit b chng luyn ny : hn hp u a vo lintc , cc sn phm nh , y ly ra lin tc
Ch thch:
1. Thng cha nguyn liu u
2. Bm sn phm nh
3. Thng cao v
4. Van o lu lng
5. Thit b gia nhit hn hp u
6. Thp chng luyn
7. Thit b ngng t hi lu
8. Van iu chnh hi lu
9. Thit b ngng t lm sch sn phm nh
10. Thng cha sn phm nh
11. Bm sn phm nh
12. Thit b gia nhit sn phm y
13,16 . Van tho nc ngng
14.Van iu chnh sn phm y
15.Thng cha sn phm y
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PHN IIITNH TON THIT B CHNH
I.TNH CN BNG VT LIU TRONG THP CHNGLUYN
1. Cn bng vt liu:
F = P + W (1)Cn bng vt liu cho cu t d bay hi ( Benzen )
F.xf = P.xp + W.xw (2)
Trong : - F : Hn hp u ( Kg/h)
- P : Lng sn phm nh (Kg/h)
- W : Lng sn phm y (Kg/h)
Xf : Nng hn hp u tnh theo % khi lng cu t d bayhi (%)
Xp : Nng hn hp sn phm nh tnh theo % khi lng cacu t d bay hi
Xw : Nng hn hp sn phm y tnh theo % khi lng cacu t d bay hi
Thay s liu cho vo 2 phng trnh (1) , (2) theo gi thit :
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F = 2,7 Kg/s = 9720 Kg/h
Xf= 25% = 0,25
Xp= 98% = 0,98
Xw = 1,5% = 0,015
Ta c h :
9720
0,98 0,015 9720.0,252367,047( / )
7352,953( / )
P W
P W P Kg h
W Kg h
+ =
+ ==
=
2.Tnh chuyn nng
+ Chuyn nng khi lng sang nng phn molTa c cng thc chuyn i :
1
A A
A AA
A B A A
A B A B
x x
M MX
x x x x
M M M M
= =
+ +
Trong : ;A Bx x nng ca cu t d bay hi v kh bay hi
MA , MB khi lng ca cu t d bay hi v kh bay hi
MA=Mbenzen= 78 ; ts=81,1
o
C
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MB=Mtoluen= 92 ; ts = 110oC
p dng cng thc trn ta c :
Nng phn mol hn hp u
0,25
78 0,28220,25 0,75
78 92
fx = =
( Phn mol )
Nng phn mol ca sn phm nh theo benzen :
0,98
78 0,98300,98 0,0278 92
px = =
( Phn mol )
Nng phn mol ca sn phm y theo benzen :
w
0,015
78 0,0176
0,015 0,98578 92
x = =
( Phn mol )
+Xc nh s bc thay i nng :
Ta c bng s liu :
X 0 5 10 20 30 40 50 60 70 80 90 100
y 0 11,8 21,4 38 51,1 61,9 71,2 79 85,4 91 95,9 100
ts 110,6 108,3 106,1 102,2 98,6 95,2 92,1 89,4 86,8 84,4 82,3 80,2
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Da vo bng s liu ta v c ng cn bng
ng lm vic ca on luyn i qua im:x=y=xp=0,9830
ng lm vic ca on chng i qua im :
x=y=xw=0,0176
Giao im ca 2 ng lm vic c ta :
x=y=xf=0,2822
Gi s:
- Hn hp u i vo thp nhit si
- S mol ca pha hi i t di ln trn bng nhautrong mi tit din thp
- Hi i ra khi thp c ngng t hon ton
- un si y thp bng hi gin tip .
- S mol cht lng khng i theo chiu cao trongon chng v on luyn
- Sn phm y i ra khi thp hon ton lng
o trc tip trn th ta c : y*f= 0,492
*
min *0, 9830 0, 492 2,340, 492 0, 2822
p f
f f
x yRy x
= = =
Ta ly cc gi tr Rx>Rmin trn th ta v c cc ng lm vic khc nhauca on chng v on luyn vi tung B khc nhau :
+ Rx=Rmin .b
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+1
p
x
xB
R=
+
( b = 1,2 . 2,5 )
b = 1,3 => Rx= 3,042 , B = 0,243
b = 1,6 => Rx= 3,744 , B = 0,207
b = 1,9 => Rx= 4,446 , B = 0,180
b = 2,2 => Rx= 5,118 , B = 0,159
b = 2,5 => Rx= 5,85 , B = 0,143T vi mi ng nng lm vic , ta tm c 1 s a l thuyt
khc nhau.
Ta c bng s liu
Rx 3,042 3,744 4,446 5,118 5,85Nx 19 15 15 13 12
Nx(Rx+1) 76,798 71,16 81,69 79,924 82,2
T s liu trn ta dng thi quan h gia Nx(Rx +1) v Rx .
T im cc tiu ca th ta tm c
Rth = 3,744
T th ta tm c s bc thay i nng :
Nx = 15Ta c phng trnh ng lm vic ca on luyn
1 1
px
x x
xRy x
R R= +
+ +
3, 744 0, 9830
3,744 1 3,744 1y x= +
+ +
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y = 0,789 x + 5,727
Ta c phng trnh ng lm vic ca on chng
' ' 11 1
xw
x x
R f f y x xR R
+ = ++ +
Vi0,2822
0,2870,9830
Ff
P= = =
' '
' '
3, 744 0, 287 1 0, 287.0,0176
3, 744 1 3, 744 10, 849 0, 0026
y x
y x
+ = +
+ +
= +
II. TNH NG KNH THP
ng knh c xc nh theo cng thc :
0, 0188 ( )( . )
tb
y y tb
gD m
=
Trong : gtb lng hi trung bnh i trong thp (kg/h )
( . ) y y tb tc hi trung bnh i trong thp ( kg/m2s)
1. Tnh ng knh on luyn
a, Lng hi trung bnh i trong on luyn
C th tnh gn ng bng trung bnh cng ca lng hi i rakhi a trn cng ca thp (gd ) v lng hi i vo a di cng caon luyn (g1)
1 ( / )2
dtb
g g g kg h
=
Lng hi i vo on luyn c xc nh theo h phng trnhcn bng vt liu v h phng trnh cn bng nhit lng sau :
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ra = 94,108 = 394,013.103 (J/kmol)
rb = 90,3265 = 378,175.103 ( J/kmol )
rd = 394,013.103.0,9830 + (1- 0,9830).378,175.103
= 393,744.103 (J/kmol)
Ta c lng hi i ra khi nh thp gd (kg/h)
gd= Gr+ Gp = Gp(1+Rth) [II-181]
gd = 2367,047(1+3,744) = 11229,291 (Kg/h)
Vy lng lng hi lu
Gr = 11229,291 2367,047 = 8862,224 (Kg/h)
Phn t lng trung bnh ca hn hp nh thp :
78.0,9830 + 92 (1-0,9830) = 78,238
=>11229,291
143,527( / )78,238
d g kmol h= =
2367,047
30,254( / )78,238
pG kmol h= =
8862,224 113, 272( / )78,238
rG kmol h= =
Thay vo h phng trnh ta c :
1 1
1 1 1
3 3
1 1
30,254
. .0, 2822 30, 254.0, 9830
(368,191.10 10, 383.10 . ) 56512895, 09
g G
g y G
g y
= +
= +
+ =
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Gii h phng trnh ta c :
1
1
1
121,429
151, 683( / )0,422
G
g kmol hy
=
= =
Vy lng hi trung bnh i trong on luyn l :
1
2
dtb
g gg
+= [II-181]
143,527 151,683
147, 605( / )2
tb g kmol h+= =
Nng trung bnh on luyn :
1 0,9830 0, 422 0,7025( )2 2
dtb
y y y mol+ += = =
Phn t lng trung bnh ca hi trong on luyn :
78.0,7025 + 92(1-0,7025) = 82,165
=> gtb = 82,165 . 147,605 = 12127,965 (Kg/h)
- Khi lng ring trung bnh
+ Vi pha hi
Khi lng ring trung bnh ca hn hp c xc nh theo cngthc :
31 1 2[ (1 ) ].273 ) /22,4.
tb tbytb
y M y M kg m
T
+ = [II-183]
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Trong M1,M2 khi lng mol ca benzen v toluen
T : nhit trung bnh lm vic ca thp , hay caon chng , on luyn tnh theo %
ytb1: Nng phn mol ca benzen
1 11 ( )
2
d ctb
y y y mol
+=
1, 1d cy y nng u v cui ca on luyn
1 1 1 2. (1 )tb tb y M y M + l phn t lng trung bnh
ca on luyn = 82,165Nhit trung bnh ca hn hp trong on luyn
80,62 100, 490,51
2
o
tbt C+
= =
Thay vo cng thc ta c :
382,165.273 2, 7547( / )22,4.(90,51 273)
ytb kg m = =+
+ Vi pha lng
Khi lng ring trung bnh ca hn hp c tnh theo cng thc
1 1
1 2
11 [ 183]tb tb
xtb xtb xtb
x x II
+ +
Trong :1tbx phn khi lng trung bnh ca benzen trong
pha lng
xtb : khi lng ring trung bnh ca pha lng
tnh theo nhit trung bnh
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on luyn vi t = 90,51oC ta c :
3
1
3
2
803, 439( / )
797, 49( / )
xtb
xtb
kg m
kg m
=
=
[I-9]
1 2, xtb xtb l khi lng ring trung bnh ca benzen toluen
tinh khit ca pha lng theo nhit trung bnh
Nng lng trung bnh ca on luyn :
25% 98%61,5%
2
+=
Thay vo cng thc [II-183] ta c :
3
1 0, 615 1 0, 615
803, 439 797, 49
801,138( / )
xtb
xtb kg m
= +
=
Vn tc kh i trong thp c xc nh theo cng thc2
[ ]( . ) 0, 065 ( . ) ( / y y tb xtb ytbh kg m s = [II-184]
Trong : , xtb ytb : Khi lng ring trung bnh ca pha lng v pha kh
theo nhit trung bnh (kg/m3)
h : Khong cch gia cc a (m)
gi tr h chn theo ng knh thp
[ ] : h s sc cng b mt
Khi < 20 yn/cm th [ ] = 0,8
< 20 yn/cm th [ ] = 1
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1 2
1 2
1
hh
a a
= +
on luyn vi t = 90,51oC theo [I-300] c
3
1
3
2
3 3
3 2
19, 98.10 ( / )
20.396.10 ( / )
1 0, 615 1 0, 615
19,98.10 20,396.10
20,138.10 ( / ) 20.138( / ) 20
[ ] 1
benzen
toluen
hh
hh
N m
N m
N m dyn cm
= =
= =
= +
= = > =
Chn h = 0,45
Vy
2
2
( . ) 0, 065.1 0, 45(801,138.2, 7547) ( /
( . ) 2, 048( / . )
y y tb
y y tb
kg m s
kg m s
=
=
Thay vo cng thc tnh D ta c :
12127,9650, 0188 1, 4467( )
2,048D m= =
Chn D = 1,4 , h =0,45 l ph hp
Vy vn tc kh i qua on luyn l :
2 2
1 2 2
0,0188 . 0,188 .12127,9650, 7939( / )
1, 4 . 1, 4 .2, 7547tb
ytb
ytb
gm s
= = =
2. Tnh ng knh on chng
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Lng hi trung bnh i trong on chng c xc nh gnng theo cng thc
' ''
1
2ntb
g gg
+= [II-182]
Trong : 'tbg l lng hi i vo on chng .
V lng hi ra khi on chng = lng hi i vo on luyn ' 1ng g=
nn ta c th vit :
'' 1 1
2tb
g gg += [II-182]
Trong : '1g : l lng hi i vo on chng
'
1G : lng lng . Hm lng lng'
1x c xc nh
theo phng trnh cn bng vt liu v cn bng nhit lng sau :
' '
1 1 w
' ' '
1 1 1 w w
' ' ' '
1 1 1 1
.
. .
n
n n
G g G
G x g y G x
g r g r g r
= +
= + = =
[II-182]
Trong : '1 wy y= tm trn ng cn bng ng vi xw= 0,0176 -> yw= 0,015
(phn mol )' ' '
1 1 1. (1 ).a br r y y r = +
Trong :'
1r n nhit ha hi hn hp u v a th nht ca
on chng
Nhit si ca hn hp a th nht ca on chng vi nng
benzen l 1,5% l tw = 109,91o
C
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Da vo [I-254] v ni suy ta c :
3
3
' 3 3
1
' 3
1
88,543( / ) 370,710.10 ( / )
86,538( / ) 362,318.10 ( / )370,710.10 .0,015 (1 0,015).362,318.10
362,444.10
a
b
r Kcal kg J kmol
r Kcal kg J kmol r
r
= =
= =
= +
=
Phn t lng trung bnh ca hn hp y :
M= 78.0,0176+92.(1-0,0176) = 91,7536
w
7352,95380,138( / )91,7536G kmol h= =
' ' '
1 . (1 )n a n n br r r y y r = = + l n nhit ha hi ca hn hp i vo a trn
cng ca on chng [II-182]
Thay vo h phng trnh ta c :
' '
1 1' ' '
1 1 1
' 3 3 3
1
80,138
.0,015 80,138.0,0176
.362,444.10 151,683.(368,191.10 10,383.10 .0,422)
G g
G x g
g
= + = + = +
Gii h phng trnh ta c :
'
1
'
1
'
1
234, 24( / )
154,1( / )0, 016( )
G kmol h
g kmol h x mol
=
= =
Lng hi trung bnh i trong on chng l :
'' 1 1 151,683 154,1 152,8915( / )
2 2tb
g g g kmol h
+ += = =
Nng trung bnh ca on chng l :
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N : KTTP GVHD : PHM TH THU HOI
'
1 12
0, 422 0,0150,2185( )
2 2tb
y y y mol
+ += = =
Phn t lng trung bnh ca hi i trong on chng :M =78.0,2185+92(1-0,2185) = 88,941
gtb= 152,8915.88,941 = 13598,3229 (Kg/h)
Khi lng ring trung bnh .
+ Vi pha hi
Khi lng ring trung bnh c tnh theo cng thc :
' 32 1 2 2[ . (1 ). ].273 ( / )22,4.
tb tbtb
y M y M kg m
T
+ =
Trong : M1 , M2 khi lng mol ca benzen toluen
T : nhit lm vic ca oank chng ( oK)
2tby : Nng phn mol ca benzen
2 22 ( )
2d c
tb
y y y mol
+=
2 2,d cy y Nng ti 2 u on chng
Nhit trung bnh ca hn hp trong on chng :.
100,4 109,91 105,1552
o
tbt C+= =
' 388,941.273 2,866( / )
22,4.(105,155 273)tb kg m = =+
V thay M = 2 1 2 2[ . (1 ). ]tb tb y M y M + =88,941 l phn t lng trung
bnh ca hi trong on chng
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N : KTTP GVHD : PHM TH THU HOI
+ Vi pha lng
Khi lng ring trung bnh c tnh theo cng thc :
2 2
1 2
11 [ 183]tb tb
xtb xtb xtb
x x II
= +
xtb: khi lng ring trung bnh ca pha lng tnh
theo nhit trung bnh .
on chng t = 105,155oC
31
3
2
787,33( / )
782,845( / )
benzen xtb
toluen xtb
kg m
kg m
= =
= =[I-9]
Nng trung bnh ca on chng l
25% 1,5%13,25%
2
+=
Thay vo cng thc ta c :
2
1 0,1325 1 0,1325
787,33 782,845
783, 436( / )
xtb
xtb kg m
= +
=
Vn tc kh i trong thp :
2
[ ]( . ) 0, 065 ( . ) ( / y y tb xtb ytbh kg m s = [II-184]
Trong : , xtb ytb : Khi lng ring trung bnh ca pha lng v
pha kh theo nhit trung bnh (kg/m3)
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N : KTTP GVHD : PHM TH THU HOI
h : Khong cch gia cc a (m)
gi tr h chn theo ng knh thp
[ ] : h s sc cng b mtKhi < 20 yn/cm th [ ] = 0,8
< 20 yn/cm th [ ] = 1
1 2
1 2
1
hh
a a
= +
on chng t = 105,155oC
3
1
3
2
3 3
3 2
18,155.10 ( / )
18, 859.10 ( / )
1 0,1325 1 0,1325
18,155.10 18,859.10
18, 762.10 ( / ) 18, 762( / ) 20
[ ] 0,8
benzen
toluen
hh
hh
N m
N m
N m dyn cm
= =
= =
= +
= =