Do an Chung Cat Benzen Va Toluen1.Diendandaihoc.vn

8/2/2019 Do an Chung Cat Benzen Va Toluen1.Diendandaihoc.vn

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AMH Qu trnh & Thit b GVHD : Phannh Tun

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B GIO DC V O TO CNG HA X HI CH NGHA VITNAM

TRNG I HC BCH KHOA c lp T do Hnh phcThnh ph H Ch Minh

Khoa: Cng ngh Ha & Thc phmB mn: Qu trnh v Thit b

NMN HC: N MN HC QT&TB. M S: 605040H v tn sinh vin: V Tin DngLp: HC06MBNgnh (nu c): My & Thit B

1. u n: Thit k thp mm chp chng ct hn hp Benzen Toluenc nng sut 200 l/h tnh theo sn phm nh

2. Nhim v (ni dung yu cu v s liu ban u):- Nng nhp liu: F = 40%phn khi lng

- Nng sn phm nh: D = 98% phn khi lng

- Nng sn phm y: W = 1% phn khi lng

- Ngun nng lng v cc thng s khc t chn3. Ni dung cc phn thuyt minh v tnh ton:

Xem phn mc lc4. Cc bn v v th (loi v kch thc bn v):

Gm 2 bn v A1: bn v quy trnh cng ngh v bn v chi tit thit b5. Ngy giao n: 6/10/20096. Ngy hon thnh n: 18/01/20107. Ngy bo v hay chm: 25/01/2010

Ngy 6 thng 10 nm 2009CH NHIM B MN NGI HNG DN

(K v ghi r h tn) (K v ghi r h tn)

Su tm bi:www.daihoc.com.vn


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NHN XT NCn b hng dn. Nhn xt:_________________________________________________________________________________________________________________________________________________________________________________________________________________________________im:______________ Ch k: ________________

Cn b chm hay Hi ng bo v. Nhn xt: ____________________________________________________________________________________________________________________________________________________________________________________________________________________im:______________ Ch k: ________________

im tng kt:



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LI M U

Khoa hc k thut ngy cng pht trin ng gp to ln cho nn cng nghip ncta ni ring v th gii ni chung. Mt trong nhng ngnh c ng gp v cng to ln l ngnh cng nghip h hc, c bit l ngnh sn xut cc h cht c bn.

Hin nay, cc ngnh cng nghip cn s dng rt nhiu h cht c tinh khitcao. Nhu cu ny t ra cho cc nh sn xut h cht s dng nhiu phng php nng cao tinh khit ca sn phm nh : trch ly, chng ct, c c, hp thu Tutheo c tnh yu cu ca sn phm m ta c s la chn phng php cho ph hp. ivi h benzen toluen l h 2 cu t tan ln vo nhau, ta chn phng php chng ct nng cao tinh khit cho benzen.

n mn hc Qu trnh & Thit b l mt mn hc mang tnh tng hp trong qutrnh hc tp ca cc k s Cng ngh H hc tng lai. Mn hc ny gip sinh vin c thtnh tn c th : quy trnh cng ngh, kt cu, gi thnh ca mt thit b trong sn xuth cht - thc phm. y l ln u tin sinh vin c vn dng cc kin thc hc gii quyt cc vn k thut thc t mt cch tng hp.

Nhim v ca n l thit k thp mm chp chng ct hn hp Benzen Toluen p sut thng vi nng sut theo sn phm nh(Benzene) l 200 lt/h c nng 98% phn khi lng benzen, nng sn phm y l 99% khi lngToluene,Nng nhp liu l 40% khi lng Benzene, nhp liu trng thi lng si.



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Ti liu tham kho .......................................................................................... 54

Chng 1 :TNG QUAN

I. L THUYT V CHNG CT :1. Khi nim :



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- Chng ct l qu trnh dng tch cc cu t ca hn hp lng cng nh hn hpkh lng thnh cc cu t ring bit da vo bay hi khc nhau ca cc cu t trong hnhp (ngha l khi cng nhit , p sut hi bo h ca cc cu t khc nhau).

- Thay v a vo trong hn hp mt pha mi to nn s tip xc gia hai phanh trong qu trnh hp thu hoc nh kh, trong qu tr nh chng ct pha mi c tonn bng s bc hi hoc ngng t.

- Chng ct v c c kh ging nhau, tuy nhin s khc nhau cn bn nht ca2 qu trnh ny l trong qu trnh chng ct dung mi v cht tan u bay hi (ngha l cccu t u hin din trong c hai pha nhng vi t l khc nhau), cn trong qu trnh cc th ch c dung mi bay hi cn cht tan khng bay hi.

- Khi chng ct ta thu c nhiu cu t v thng th bao nhiu cu t s thuc by nhiu sn phm. Nu xt h n gin ch c 2 cu t th ta s thu c 2 snphm :

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 phngphp chng ct c phn loi theo :

- p sut lm vic : p sut thp p sut thng p sut cao

Nguyn tc lm vic : da vo nhit si ca cc cu t, nu nhit si cacc 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 lin tc psut 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 vn ging nhau ngha l din

tch tip xc pha phi ln. iu ny ph thuc vo mc phn tn ca mt lu cht nyvo lu cht kia. Nu pha kh phn tn vo pha lng ta c cc loi thp mm, nu pha lngphn tn vo pha kh ta c 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 cc mm c cu tokhc nhau, trn pha lng v pha hi cho tip xc vi nhau. Tu theo cu to caa, ta c :

- Thp mm chp : trn mm b tr c chp dng trn, xupap, .



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- 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 trong hai phng php sau: xp ngu nhin hay xp th t.

So snh u nhc im ca cc loi thp :

Thp chm Thp mm xuyn l Thp chp

uim

- Cu to kh n gin.- Tr lc thp.- Lm vic c vi cht lngbn nu dng m cu cca cht lng.

- Tr lc tng ithp.- Hiu sut kh cao.

- Kh n nh.- Hiu sut cao.

Nh

c im

- Do c hiu ng thnh hiusut truyn khi thp.- n nh khng cao, khvn hnh.

- Do c hiu ng thnh khitng nng sut th hiu ngthnh tng kh tng nngsut.- Thit b kh nng n.

- Khng lm vic cvi cht lng bn.- Kt cu kh phc tp.

- C tr lc ln.- Tiu tn nhiuvt t, kt cuphc tp.

Vy :qua phn tch trn ta s dng thp mm chp chng ct h Benzen Toluen.

II. GII THIU V NGUYN LIU :1. Benzen & Toluen :

Benzen: l mt hp cht mch vng, dng lng khng mu v c mi thm nh.Cng

thc phn t l C6H6. Benzen khng phn cc,v vy tan tt trong cc dung mi hu ckhng phn cc v tan rt t trong nc. Trc y ngi ta thng s dng benzenlm dung mi. Tuy nhin sau ngi ta pht hin ra rng nng benzen trong khngkh ch cn thp khong 1ppm cng c kh nng gy ra bnh bch cu, nn ngy naybenzen c s dng hn ch hnCc tnh cht vt l ca benzen:

o Khi lng phn t: 78,11o T trng(200C): 0,879o Nhit si: 80oCo Nhit nng chy: 5,50C

Toluen: l mt hp cht mch vng, dng lng v c tnh thm ,cng thc phn t

tng t nh benzen c gn thm nhm CH3. Khng phn cc,do toluen tan tt trongbenzen.Toluen c tnh cht dung mi tng t benzen nhng c tnh thp hn nhiu,nn ngy nay thng c s dng thay benzen lm dung mi trong phng th nghim vtrong cng nghip.Cc tnh cht vt l ca toluen:

o Khi lng phn t : 92,13o T trng (20oC) : 0,866o Nhit si : 111oC



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o Nhit nng chy : -95 oCCc phng thc iu ch :

o i t ngun thin nhinThng thng cc hidrocacbon t c iu ch trong phng th nghim, v cth thu c lng ln n bng phng php chng ct than , 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 lim loi chuyn tip nh Pd,PtCH3(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 tckim loi chuyn tip to thnh benzen hay cc dn xut cu benzenC6H12 PdPt/ 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 benzen3C2H2 xt C6H6o T benzen ta c th iu ch c cc dn xut ca benzen nh toluen bng phn

ng Friedel-Crafts (phn ng ankyl ha benzen bng cc dn xut ankyl halidevi s c mt cu xc tc AlCl3 khanC6H6 + CH3- Cl 3

AlCl C6H5-CH32. Hn hp benzen toluen :

Ta c bng thnh phn lng (x) hi (y) v nhit si ca hn hp Benzen Toluen 760 mmHg.(Tham kho STT1)

x (% phnmol)

0 5 10 20 30 40 50 60 70 80 90 100

y (% phnmol)

0 11,8 21,4 38 51,1 61,9 71,2 79 85,4 91 95,9 100

t (oC) 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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AMH Qutrnh & Thit b GVHD :Phan nh Tun

Trang 11

hkgVD DD /8,161809.2,0.

hkmolM

DD

D

/07,2

Phng trnh cn bng vt cht:

WDF xWxDxF

WDF

...

hkmolF

hkgF

hkmolW

hkgW

/87,4

/4.402

/8,2

/6,240

F= 402,4 kg/h D = 161,8 kg/h W = 240,6 kg/hF = 4,87 kmol/h D = 2,07 kmol/h W = 2,8 kmol/h

4.0Fx 98,0Dx 01,0Wx 44.0Fx 983,0Dx 012,0Wx

III. XC NH CH S HI LU THCH HP :* Ch s hi lu ti thiu :T s hon lu ti thiu l ch lm vic m ti ng vi s mm l thuyt l

v cc. Do , chi ph c nh l v cc nhng chi ph iu hnh (nhin liu, nc vbm) l ti thiu.



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Hnh 1: th cn bng pha ca hBenzen Toluen ti P = 1atm

Da vo hnh 1 ta c xF = 0,44 yF* = 0,643

T s hon lu ti thiu : 44,0643,0 3.64,0983,0**

min FFFD

xy yxR = 1,68

T s hon lu lm victnh theo cng thc kinh nghim: R = 1,5Rmin = 1,5.1,68 =2,52

Theo Phng php th tch thp nh nht ta c: V = S.HVi S din tch tit din ngang ca thp; H chiu cao thp. Mt khc din tch tit

din thp t l vi lng hi, lng hi ny li t l vi lng hon lu hay S t l viR. Chiu cao thp t l vi s a l thuyt N lt. Vy th tch thp t l vi gi tr N lt.(R+1).Ln lt cho cc gi tr R v tm th tch thp, ng vi gi tr no nh nht ca th tch thpth R l t s hon lu ti u.

R 5 4.5 4 3.5 3 2.5 2

Nlt 12 13 14 16 15 15 18(R+1).Nlt 72 71.5 70 72 60 52.5 54

Biu din trn th:



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Theo th trn ta chn gi tr t s hi lu thch hp R = 2,48

IV . PHNG TRNH NG LM VIC - S MM L THUYT:1 . Phng trnh ng lm vic ca on ct:

y =11

R

xx

R

R D =148,2

983,0148,2

48,2

x

= 0,771.x + 0,2842 . Phng trnh ng lm vic phn chng:

-Phng trnh ng lm vic ca phn chng

y= xR

fR

1

-1

1

R

fxW =1,37x -0.0044

vi f=WF

WDxx

xx

= 012,044,0

012,0983,0

=2,27

R+1 .Nlt

R



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Hnh 2: th xc nh s mm l thuyt chng h Benzen Toluen ti P = 1atm

3 . S a l thuyt :

th xc nh s a l thuyt :Dng ng lm vic ca thp bao gm ng lm vic phn ct v phnchng. Trn th y-x ta ln lt v cc ng bc thang t xc nh c sa l thuyt l14.56 a, ta ly trn 15

T th, ta c : 15 a bao gm : 6 mm ct1 mm nhp liu6 mm chng (5 mm chng + 1 ni

un)Tm li, s a l thuyt l Nlt = 15 mm.

V . XC NH S MM THC T:

c nhiu phng php xc nh s mm thc ca thp, ngoi tr cc nh hng cathit k c kh thp th ta c th xc nh s mm thc da vo hiu sut trung bnh:Nt = Nlt/htbTrong : Nt s a thc t, Nlt - s a l thuyt, htb hiu sut trung bnh cathit b

htb =n

nnnn n ....321

Trong ni - hiu sut ca cc bc thay i nng , n - s v tr tnh hiu sut

x

y

x



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Trong trng hp ny ta tnh

htb =3

WFD nnn

Vi Dn Fn Wn - ln lt l hiu sut a trn cng, hiu sut a nhp liu v hiusut a di cng

- Xc nh Dn ta c : T(nhit nh thp) = 800C, xD = 0,983 suy ra yD = 0,994 s dng bng

I.101 trang 91 STT1 tra v ni suy cc gi tr nht mB = 0,316.10-3 N.s/m2, mT =

0,319.10-3 N.s/m2. nht ca hn hp lg mhh = xD.lgmB (1- xD).lg mT (theo cng thc I.12

trang 84 5 ) mhh = 0,316. 10-3 N.s/m2 (= 0.316cP)

V bay hi tng i a =x

x

y

y

1.

1=

983.0983.01

.994.01

994.0

= 2,87

a. mhh = 2,87.0,316 = 0,905, theo hnh IX.11 trang 171 th Dn = 0,53- Xc nh Fn , tng t nh trn ta c:

TF(nhit a nhp liu) = 94

0

C, xf = 0,44 suy ra yD = 0,643 s dng bng I.101trang 91 5 tra v ni suy cc gi tr nht mB = 0,277.10-3 N.s/m2, mT = 0,291.10

-3N.s/m2. nht ca hn hp lg mhh = xD.lgmB (1- xD).lg mT (theo cng thc I.12

trang 84 STT1) mhh = 0,293. 10-3 N.s/m2 (= 0,293 cP)

V bay hi tng i a =x

x

y

y

1.

1=

44.0

44.01.

643.01

643.0

= 2,29

a. mhh = 2,29.0,293 = 0,672, theo hnh IX.11 trang 171 th Dn = 0,58-Xc nh wn , tng t nh trn ta c:

Tw(nhit a di cng) = 1100C, xw = 0,012 suy ra yD = 0,065 s dng bng

I.101 trang 91 5 tra v ni suy cc gi tr nht m

B= 0,239.10-3 N.s/m2, m

T=

0,250.10-3 N.s/m2. nht ca hn hp lg mhh = xD.lgmB (1- xD).lg mT (theo cng thc I.12

trang 84 5 ) mhh = 0,249. 10-3 N.s/m2 (= 0,249 cP)

V bay hi tng i a =x

x

y

y

1.

1=

012.0

012.01.

0365.01

0365.0

= 3,12

a. mhh = 3,12.0,249 = 0,777, theo hnh IX.11 trang 171 th Dn = 0.62

htb =3

WFD nnn =3

62,058,053,0 = 0.58

Suy ra s mm thc :Nt = Nlt/htb = 15/0,58 = 25,8 ly trn 26 mm



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Chng4 :TNH TON THP CHNG CT

* ng knh thp chng ct (Dt) :

tbyy

tbg

).(0188,0

.3600.

4VD

tb

tbt

(m)

Vtb:lnghi trung bnh i trong thp m3/h.

tb :tc hi trung bnh i trong thp m/s.gtb : lng hi trung bnh i trong thp Kg/h.Lng hi trung bnh i trong on chng v on ct khc nhau.Do ,ng knh on chng v on ct cng khc nhau.

I. ng knh on ct :1 . Lng hi trung bnh i trong thp on ct:

21gg

gd

tb

kg/h

gd : lng hi ra khi a trn cng ca thp kg/hg1: lng hi i vo a di cng ca on ct kg/h

Xc nh gd:gd = D.(R+1) =2,07.(2,48+1) = 7,204 kmol/h

= 563,93 kg/h(V MhD =78.yD+(1-yD).92 = 78,28 kg/kmol)

Xc nh g1 : T h phng trnh :

dd

D

rgrg

xDxGyg

DGg

..

...

11

1111

11

(IV.1)

Vi:G1 : lng lng a th nht ca on ct .r1 : n nhit ho hi ca hn hp hi i vo a th nht ca on ctrd : n nhit ho hi ca hn hp hi i ra nh thp .* Tnh r1 : t1 = tFs = 94

oC , tra bng I.212, trang 254, [5] ta c :n nhit ho hi ca Benzen : rB1 = 383,1 kJ/kg.n nhit ho hi ca Toluen : rT1 = 371,3 kJ/kg.Suy ra : r1 = rB1.y1 + (1-y1).rT1 = 373,1y1 - 11,8y1

r1 = 373,1y1 - 11,8y1 kJ/kg

* Tnh rd : tD = 80

o

C , tra bng I.212, trang 254, [5] ta c :n nhit ho hi ca Benzen : rBd = 393,3 kJ/kg.n nhit ho hi ca Toluen : rTd = 378,3 kJ/kg .Suy ra : rD = rBd.yD + (1-yD).rTd = 393,3.0,99 + 378,3.0,01

rD = 393,15 kJ/kg(vi xD = 0,983 suy ra yD theo phn khi lng l 0,99)

* x1 = xF = 0,4(ta coi n)



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Gii h (IV.1) , ta c : G1 = 593,3 kg/hy1 = 0,524 (phn khi lng benzen)g1 = 755,1 kg/h

Vy : gtb = 5,6592

1,75593,563

kg/h

2 . Tc hi trung b

nhi trong thp on ct

:Vn tc hi i trong thp on ct:

ytbxtbtbyy hw ..065,0. Vi : rxtb : khi lng ring trung bnh ca pha lng kg/m

3 .rytb : khi lng ring trung bnh ca pha hi kg/m

3 .h: khong cch mm (chn h = 0,3 ng vi D = 0,6-1,2m)

: h s tnh n sc cng b mtXc nh rytb :

273.4,22

273.92.178.

tb

tbtbytb t

yy

Vi: + Nng phn mol trung bnh : ytb = 21 Dyy = 2 99,0468,0 = 0,725

+ Nhit trung bnh on ct : ttb =2

1 Dtt =2

5,805,98 = 89,5 oC

Suy ra : rytb =2,752 kg/m3.

Xc nh rxtb :

Nng phn mol trung bnh : xtb =2

DF xx =2

983,044,0 = 0,692

Suy ra :92).1(.78

.78

tbtb

tbtb xx

xx

= 65,5 %.

ttb = 89,5oC , tra bng I.2, trang 9, [5], ta c :

3/804 mkgbenzen 3/798 mkgtoluen

toluen

tb

benzen

tb

xtb

xx

11

rxtb = 802 kg/m3

Xc nh : h s tnh n sc cng b mtTa c:

cmdynmNhhTBhh

/7,10/10.7,1010.5,21

1

10.3,21

1111 333

Vi: B =21,3.10-3

N/m, T = 21,5.10-3

N/m (s liu tra t bng I.242 trang 300STT1)

Ta thy hh < 20 theo STT2 tr184 chn = 0,8

smkghw ytbxtbtbyy ./33,1752,2.802.3,0.8,0.065,0..065,0.2

m

g

tbyy

tb 419,033,1

5,659.0188,0

).(0188,0D t



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Tc hi trung bnh i trong on ct:

smw

wy

tbyy

y /483,0752,233,1.

'

II. ng knh on chng :1 . Lng hi trung bnh i trong thp on chng :

2

1,,

, gg

g

n

tb

; kg/hgn : lng hi ra khi on chng ; kg/h.g1: lng hi i vo on chng ; kg/h.

Xc nh gn : gn = g1 = 755,1 kg/hXc nh g1 : T h phng trnh :

1111

1'

11'

1'

1'

.'.''.'

..'.

rgrgrg

xWygxG

WgG

nn

WW (IV.2)

Vi : G1 : lng lng a th nht ca on chng .

r1 : n nhit ho hi ca hn hp hi i vo a th nht ca onchng.* Tnh r1 : xW =0,012(phn mol) tra th cn bng ca h ta c : y*W

=0,016(phn mol), tng ng vi nng khi lng l y*W = 0,014(phn khilng)

t1 = tW = 110oC, tra bng I.212, trang 254, [5], ta c :

n nhit ho hi ca Benzen : rB1 = 370,56 kJ/kg.n nhit ho hi ca Toluen : rT1 = 362,20 kJ/kg. r1 = rB1.yW + (1-yW).rT1 =362,3 kJ/kg

* Tnh r1 : t1 = tFs = 94oC , tra bng I.212, trang 254, [5] ta c :

n nhit ho hi ca Benzen : rB1 = 383,1 kJ/kg.

n nhit ho hi ca Toluen : rT1 = 371,3 kJ/kg.r1 = rB1.y1 + (1-y1).rT1 = 378,9 kJ/kg* W = 240,6 kg/hGii h (IV.2) , ta c : x1 = 0,0135 (phn mol)

G1 = 1030,3 kg/hg1 = 789,7kg/h

Vy : gtb = 4,7722

1,7557,789

kg/h

2 . Tc hi trung bnh i trong thp on chng:Vn tc hi i trong thp on chng :

ytbxtbtbyy hw ..065,0. Vi : rxtb : khi lng ring trung bnh ca pha lng kg/m3 .

rytb : khi lng ring trung bnh ca pha hi kg/m3 .

h: khong cch mm (chn h = 0,3 ng vi D = 0,6-1,2m) : h s tnh n sc cng b mt

Xc nh rytb : 273.4,22

273.92.178.

tb

tbtbytb t

yy



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Trang 19

Vi: + Nng phn mol trung bnh : ytb =2

1 Dyy =2

014,0468,0 = 0,241

+ Nhit trung bnh on chng : ttb =2

1 Wtt =2

1105,98 = 104,2oC

Suy ra : rytb =2,96 kg/m3.

Xc nh rxtb :Nng phn mol trung bnh : xtb =

2WF xx =

2012,044,0

= 0,226

Suy ra :92).1(.78

.78

tbtb

tbtb xx

xx

= 18,8 %.

ttb =2

WF tt = 211093

101,5oC , tra bng I.2, trang 9, 5 , ta c :

3/793 mkgbenzen 3/788 mkgtoluen

toluen

tb

benzen

tb

xtb

xx

11

Suy ra: rxtb = 789 kg/m3

Xc nh : h s tnh n sc cng b mtTa c:

cmdynmNhhTBhh

/3,10/10.3,1010.5,21

1

10.8,18

1111 333

Vi: B =18,8.10-3 N/m, T = 21,5.10

-3 N/m (s liu tra t bng I.242 trang300 5 )

Ta thy hh < 20 theo STT2 tr184 chn = 0,8

38,196,2.7,789.3,0.8,0.065,0..065,0. ytbxtbtbyy hw

mg

tbyy

tb 444,038,1

4,772.0188,0

).(0188,0D t

Tc hi trung bnh i trong on chng:

smw

wytb

tbyy

y /466,096,238,1.

'

Kt lun :hai ng knh on ct v on chng khng chnh lch nhau quln nn ta chn ng knh ca ton thp l : Dt = 0,50 m.

Khi tc hi ch lm vic thc:

+ Phn ct : lv = 339,0752,2.50,0

5,659.0188,0.

.0188,02

2

2

2

tbyt

tb

Dg

m/s

+ Phn chng :lv = 369,096,2.50,0

4,772.0188,0

.

.0188,02

2

2

2

tbyt

tb

D

g

m/s.

* chiu cao thp chng ct (Dt) :H = Nt(H+ d) + (0,8 1), m (cng thc IX.54- STT2 -Tr.169)



20/55


Trang 20

Trong Nt - s a thc t; d b dy ca a, m; 0,8 1 khong cch cho php nh v y thit b, m; H khong cch gia cc a, mH = 26.(0,25 +0,004 ) +0,8 = 7,4 m ly trn l H = 7,5 mTrong b dy a d = 0,004 m tnh phn b dy a

Vy kt lun chiu cao thp H = 7,5 m III. Tr lc ca thp chp :

Tr lc ca thp chp bao gm: tn tht p sut khi dng kh i qua a kh, tntht do sc cng b mt, tn tht tht do lp cht lng trn a v b qua sbin i chiu cao lp cht lng trn aTr lc ca thp chp c xc nh the cng thc:

2/,. mNPNP dtt

Trong Ntt s a thc t ca thp; dP - tng tr lc ca mt a, N/m2

dP = kP + sP + tP

kP - tr lc a kh, N/m2

sP - tr lc a do sc cng b mt, N/m2

tP - Tr lc ca lp cht lng trn a, N/m2

Tr lc ca a kh kP :

kP = 2

. 02wy

Trong : - h s tr lc, thng chn = 4,5 5( y ta chn = 5);

y - khi lng ring ca pha hi, kg/m3; w0 tc kh qua rnh chp, m/s

Vi khi lng ring pha hi i trong ton thp:3/856,2

2

96,2752,2mkgy

Vn tc kh trung bnh i qua mt rnh ca chp(phn tnh tn chp ta chn mta 10 chp, mt chp 10 rnh), vy:

smw /4,3510

1

10

1

2

339.0369,00

Suy ra: kP =2

20

2

/3,80452

4,35.586,2.5

2

.mN

wy

Tr lc do sc cng b mt sP , N/m2

sP =td

.4, N/m2

Trong - sc cng b mt, N/m; dt ng knh tng ng ca khe

rnh chp,mKhi rnh chp m hn tn: d t =

xf.4

y xf - din tch tit din t do ca rnh. xf = a.b = 5.10 = 50mm2 vi a,b l

b rng v chiu cao ca rnh chp, mm. - chu vi rnh chp, = 2.(a+b) =30mm

Suy ra: dt = mmmfx 310.67,667,6

30

50.4.4



21/55


Trang 21

Vy sP =2

3

3

/296,610.67,610.5,10.4.4

mNdt

, vi l sc cng b mt trung bnh

ca phn chng v phn ct, nh ta tnh phn vn tc hi i trong thp th ct = 10,7.10

-3 N/m, chng= 10,3.10-3 N/m,

suy ra = 310.5,102

chungct N/m

Tr lc ca cht lng trn a tP , N/m2 (tr lc thy tnh)

tP =

2

.b

hg bb , N/m2

Trong b chiu cao khe chp, m; b - khi lng ring bt, kg/m3; hb

chiu cao ca lp bt trn a, m; g gia tc trng trng, m/s2+ Khi lng ring bt b = 0,5 x = 0,5.795,5 = 379,75 kg/m

3, vi x - khilng ring trung bnh pha lng phn chng v phn ct,

x =3/5,795

2802789

2mkgchungct

+ hb chiu cao lp bt ly bng hai ln chiu cao lp cht lng trn a, theophn tnh ton cho a th chiu cao lp cht lng trn a l 25mm, vy hb =50mm+b chiu cao khe chp, tnh tn phn chp ta c b = 10mmSuy ra:

tP =2/6,167

2

01,005,081,9.75,379

2. mN

bhg bb

Tng tr lc ca 1 a:

dP = kP + sP + tP = 8045,3 + 6,296 + 167,6 = 8219,2N/m2

Tr lc ca tn thp:

2/39,164382,8219.25. mNPNP dtt Kt lun: Tr lc ca tn thp P = 16438,39 N/m2



22/55


Trang 22

CHNG 5:CN BNG NHIT LNG

I. CN BNG NHIT LNG CHO THIT B NGNG T :Qnt =(R+1)D.rD kW

Qnt : nhit ngng t, kW Vi rD = Dx .rB +(1- Dx ).rT Ti xD = 0,98 tra bng IX-2a trang 135 STT2 ta c TD = 80 . Ti nhit ny tac: rB= 392,4.10

3 J/kg v rT=377,8.103 J/kg

rD = 0,98 x 392,4.103 + 0,02 x 377,8.103 = 392,108.103 J/kg

Do Qnt =3600

2,07.78,28. 392,108 (2.48+1) = 61,42 kW

II. CN BNG NHIT LNG CHO THIT B GIA NHIT DNG NHP LIUN NHIT SI : QF =CF .F(TF - TVo), kW

Ti xF = 0,44 ni suy t bng IX-2a trang 146 STT2 ta c TF = 94oC

Nhit dung ring ca nhp liu tra nhit trung b nh t =2

2594 =59,5oC

ti nhit ny ta c CB=1930 J/kg , CT=1900 J/kg (Bng I.153 TR171-172 5 ).

Ta c CF= Fx CB + (1- Fx )CT = 0,4.1930+ (1-0,4).1900 = 1913,2 J/kg Do

QF=1913,2.3600

4,87.86,4(94 -25) = 15,43 kW

Nu coi tn tht trn ng nhp liu bng 5% th QF = 1,05.15,43=16,2 KwIII. CN BNG NHIT LNG CHO THIT B LM NGUI SN PHM YT NHIT 110OC XUNG 35OC :

QW = WCW(TW- TWra), kW

Nhit dung ring c xc nh nhit trung b nh T=2

35110 =72,5oC . Ti

nhit ny ta ni suy t bng I.153 TR171-172- 5 ta c : CB=1983 J/kg,CT=1952J/kgNn CW = wx CB + (1- wx )CT = 0,01. 1983 + (1-0,01).1952= 1952,31 J/kg

Do QW= 360091,862,8.

.1952,31.(110-35)=11,86, kWIV. CN BNG NHIT LNG CHO THIT B LM NGUI SN PHM NH

T NHIT 80OC XUNG 35OC :QD =CD.D(TD- TDra), kW



23/55


Trang 23

Nhit dung ring cng c xc nh nhit trung b nh T=2

3580 =57,5oC .

Ti nhit ny ta ni suy cc gi tr nhit dung ring bng I.153 TR171-172- 5 :CB=1877.5 J/kg , CT=1850 J/kgTng t ta tnh c CD=1877 J/kg

Do QD = 3600 4,86.07,2 .1877 .(80-35)=5,13 kW

V. NHIT LNG CUNG CP CHO Y THP :T cn bng nhit lng ta c:QT = Qnt + QW + QD QF + Qf=1,05.( 61,42 + 11,86 + 5,13- 16,2 ) = 65,32 kW

Qf: l lng nhit tn tht, ta ly khong 5% tng lng nhit c ch cung cp choy thp



24/55


Trang 24

CHNG 6:TNH TON C KH

I . THN THP :1.B dy thn :

V thit b hot ng p sut thng nn ta thit k thn hnh tr bng phngphp hn h quang in, kiu hn gip mi 2 pha. m bo cht lng ca snphm v kh nng n mn ca benzen i vi thit b, ta chn thit b thn thit bl thp khng g m X18H10T. Thn thp c ghp vi nhau bng mi ghp bch.

V thp lm vic vi nhit ln hn 100

0

C nn cn phi bc cch nhit cho thp. Cc thng s cn tra v chn phc v cho qu trnh tnh ton: Nhit tnh ton: t = tmax + 20 = 110 + 20 = 130

0C p sut tnh ton :V thp hot ng p sut thng nn ta coi p sut tnh tn bng vi p sut thy tnhln nht tc dng ln y thp. iu kin nguy him nht chn tnh ton lthp cha y Toluene nhit 300C khi khi lng ring ca Toluene T =856,5 kg/m3

Nn: P = (Hthn + 2Hnp).g.T = (7,5 + 2.0,15).9,81.856,5 = 61328 N/m2 0,0613

N/mm2Vi dung tch thp nh hn 30m3 ta chn theo bng 1.1 tr10- Tnh tn thit k chi tit

thit b ha cht du kh H L Vin th p sut tnh tn P = 0,01N/mm2

, nn ta chn psut tnh ton theo iu kin nguy him nht nh trn tnh.vi Hnp = h + ht = 125 +25 =150 mm(tnh phn y np).H s b sung do n mn ha hc ca mi trng:Chn h s b sung do n mn ha hc Ca = 1 mm ng sut cho php tiu chun: ca X18H10T[]* = 140 N/mm2 (Hnh 1.2, trang 16, 7 H s hiu chnh: = 1 ng sut cho php: [] = []* = 140 N/mm2 (chn = 1) H s bn mi hn:V dng phng php hn h quang in kiu hn gip mi hai phah = 0,95 (Bng XIII.8, trang 362, 6 ) Tnh b dy: Cho thn tr hn chu p sut trong

25161895,0061,0

140][hP

Nn ta tnh b dy thn theo cng thc 5.3 tr96 7 B dy ti thiu: S =

mmDP

h

t 197,095,0.140.2

500.105,0

][2

.

S + Ca = 0,197 + 1 = 1,197 mm



25/55


Trang 25

Quy trn theo chun: S = 2 mm, tuy nhin da vo bng 5.1 trg 94 - 7 Tnh kim tra bn: Cho thn tr hn chu p sut trong

iu kin: 1,0

t

a

D

CS 1,0

500

14

0,006 0,1 (tha)

Nn:)14(500

)14(95,01402

)(

)(][2][

at

ah

CSD

CSP

= 1,586 > P = 0,061 N/mm2 : tha

Vy kt lun: b dy thn thp S = 4mm, ng knh ngi thp Dn = 500 + 2.4 =508mm

II. Tnh Tn Chp :Chn chp s dng trong thp l chp trn+ ng knh ng hi: dh = 26 mm+ S chp phn b trn a: n = 10 chpChn s chp n = 10, vi khong cch gia tm ca hai chp 100mm + Chiu cao chp tnh t mt a n nh chp 70mm+ ng knh trong ca chp 46mmVi: ch - b dy chp, thng ly 2 mm - 3 mm, ta chn 2 mmSuy ra ng knh ngi ca chp 50mm+ Khong cch t mt a n chn chp S = 15 mm+ Chiu cao g chy trn 45mm+ Chiu cao khe chp

x

yy

g

wb

.

.2

Vi 5,310.05,0..3600

245.4

...3600

422

nd

Vw

h

yy , Vy lu lng hi i trong thp,

m3/h; - h s tr lc ca achp, thng ly bng 1,5 -2; y x - khi lng ring

trung bnh ca pha hi v pha lng, kg/m3

Suy ra

790.81,98,2.5,3.2 2

b 0,0218 m, chn b = 25 mm

+ Chn b rng khe chp 5mm+ Chn khong cch ln nht t g chy chuyn n thn thp 60mm(b dy 4mm) + Chn khong cch t g chy trn n thn thp 80mm(b dy 4mm)+ B tr cc chp trn a sao cho 3 chp lin tip nhau to thnh hnh tam gic u

III. Tnh Ton y v Np Thit B

Chn y v np c dng hnh ellip tiu chun, c g, lm bng thp X18H10T

Ta c: 2594095,0105,0

140][hP



26/55


Trang 26

Nn b dy y v np chu p sut trong tnh theo cng thc 6.9 ( Tnh tn cc chi titthit b ha cht v du kh H L Vin)

ahk

t CPR

S ]..[2

.

Trong S b dy y np, mm;t

tt

h

DR

.4

2

bn knh cong bn trong nh

y(np), m; h - h s bn mi hn (ly bng 0,95); ][ k - gii hn bn ko ca vt liu

vi X18H10T th [k] =540.106 N/m2; P p sut tnh tn N/m2; Ca h s n mn, mm

00105,0001,095,0.10.540.2

105,0.500

]..[2

.6

ahk

t CPR

S

Ta thy S Ca = 0,05 < 10mm nn ta cng thm 2 mm na cho b dy (theo hngdn trg 386 STT2) suy ra S = 3,05 mm ly theo chun S = 4 mm

V y np tiu chun nn ta c: t

t

D

h = 0,25 do Rt = Dt = 500 mm

V chn cc kch thc theo STT2 tr382:

+ ht =125 mm+ Chiu cao g: hg= h = 25 mm+Din tch b mt trong: Sy = 0,31 m

2+Th tch cha ca y(np):Vycha = 27,6.10

-3 m3

Tnh kim tra bn:

105,0586,1)14(500

)14(95,0.140.2

)(

)(][2][

125,0006,0500

14

PCSR

CSP

D

CS

at

ah

t

a

Vy tha iu kin bn. Kt lun chn kch thc y np:

+ ht =125 mm

+ Chiu cao g: hg= h = 25 mm+Din tch b mt trong: Sy = 0,31m2

+Th tch cha ca y(np):Vycha = 27,6.10-3 m3

+ Rt = Dt = 500 mm

IV.Bch ghp thn v np:Mt bch l b phn quan trng dng ni cc phn ca thit b cng nh ni cc

b phn khc vi thit b. Cc loi mt bch thng s dng: Bch lin: l b phn ni lin vi thit b (hn, c v rn). Loi bch ny ch

yu dng thit b lm vic vi p sut thp v p sut trung bnh. Bch t do: ch yu dng ni ng dn lm vic nhit cao, ni cc b

bng kim loi mu v hp kim ca chng, c bit l khi cn lm mt bchbng vt liu bn hn thit b.

Bch ren: ch yu dng cho thit b lm vic p sut cao.Chn bch c ghp thn, y v np lm bng thp CT3, cu to ca bch l bch

phng hn kiu 1 theo bng XIII.27 trg417 STT2.



27/55


Trang 27

Vi Dt = 500 mm v p sut tnh ton P = 0,061 N/mm2 chn bch c cc thng s

sau theo bng XIII.27 trg418 STT2:

Dt D Db D1 Do hBu-lngdb Z

(mm) (ci)

500 630 580 550 511 22 20 16

Trs bng IX.5 trang 170 6 ng vi ng knh trong 500mm ta chn s a gia hai

bch l 4, vy tng s bch cn dng l 25,614

251

4N B

tN

Ta chn 7 bch ghp thn kn ca mi ghp bch ch yu do vt m quyt nh. m lm bng cc vt

liu mm hn so vi vt liu bch. Khi xit bu lng, m b bin dng v in y l ncc ch g gh trn b mt ca bch. Vy, m bo kn cho thit b ta chn ml dy aming, c b dy l 3 mm.

Tnh kim tra b dy ca bch theo cng thc 7.1 trg 148 Tnh tn cc chi tit thit bha cht v du kh -H L Vin :

Cnh tay n ca mment gy un:

l1 =2

1DDb =2

550580 = 15 mm

l2 = 2

sDD tb

= 2

4500580

= 38 mmS b dy thit b, mmP p sut ca mi trng trong thit b N/mm2

db ng knh ngoi ca bulong, mm

b][ - ng sut cho php ca vt liu lm bulong

bi][ - ng sut cho php ca vt liu lm bchK, h s. Vi

2

2

1 )(][

.7,0].[

][..61,0

b

l

bbi

bb d

DPZ

l

l

Kdth



28/55


Trang 28

: h s

Ta thy rng trong cng thc tnh t c K, nn ta chn trc gi tr t tnh K, gi tr tc chn theo STT2.Chn t = 20mm suy ra K = 0,887, thay vo tnh t = 18,22 ta th y gi tr t chn v t tnhtn sai lch khng ng k (nh hn 5%) nn chn b dy bch h = t = 20 mm Tm li kch thc bch l:

Dt D Db D1 Do hBu-lng

db Z(mm) (ci)500 630 580 550 511 22 20 16

V. ng knh cc ng dn Bch ghp cc ng dn :

ng dn thng c ni vi thit b bng mi ghp tho c hoc khng thoc. Trong thit b ny, ta s dng mi ghp tho c.

i vi mi ghp tho c, ngi ta lm on ng ni, l on ng ngn cmt bch hay ren ni vi ng dn: Loi c mt bch thng dng vi ng c ng knh d > 10mm. Loi ren ch yu dng vi ng c ng knh d 10mm, i khi c th dng

vi d 32mm.ng dn c lm bng thp X18H10T.Bch c lm bng thp CT3 , cu to ca bch l bch lin khng c.

1. ng dn sn phm y:Nhit ca cht sn phm y tw = 110

oCTi nhit ny th: Khi lng ring ca benzen : B = 780,25 kg/m

3 Khi lng ring ca toluen : T = 778,39 kg/m

3

1)()21(

.21 22

2 t

S

D

l

D

D

l

DK

bt

t

19,138152,01)

55038.2580().

38151(2,01).2().1( 2

2

122

2

1

ll

DlD

ll

l

b



29/55


Trang 29

Nn:39.778

99,01

25,780

01,011

T

F

B

F

F

xx

F = 778,4 kg/m

3

Chn loi ng ni cm su vo thit b.Chn vn tc cht lng trong ng ni l vF = 0,32 m/s. (theo bng 2.2 trg370

STT1)

ng knh trong ca ng ni:Dy =

32,0..4,778.3600

6,240.4

...3600

.4

FF

F

v

G= 0,0189 m = 18,9 mm

Chn ng c Dy = 25 mm.Tra bng XIII.32, trang 434, 6 Chiu di on ng ni l = 90 mm.Tra bng XIII.26, trang 410, 6 Cc thng s ca bch ng vi P = 0,25 N/mm2 l:

Dy Dn D Db D1 h Bu lngdbmm ci

25 32 100 75 60 12 10 4

2. ng dn nguyn liu:Nhit ca cht lng nhp liu l tF = 94

oCTi nhit ny th: Khi lng ring ca benzen : B = 802,3 kg/m

3 Khi lng ring ca toluen : T = 780 kg/m

3

Nn: 9,8102665,01

34,818

2665,011

TF

B

F

F

xx

F = 789,5 kg/m3

Chn loi ng ni cm su vo thit b.Chn vn tc cht lng trong ng ni l vF = 0,32 m/s. (theo bng 2.2 trg370

STT1)ng knh trong ca ng ni:

Dy =32,0..5,789.3600

4,402.4

...3600

.4

FF

F

v

G= 0,023 m = 23 mm

Chn ng c Dy = 25 mm. (theo bng XIII.32 STT2)Tra bng XIII.32, trang 434, [6] Chiu di on ng ni l = 90 mm.Tra bng XIII.26, trang 410, [6] Cc thng s ca bch ng vi P = 0,25 N/mm2 l:

Dy Dn D Db D1 hBu lng

db Zmm ci

25 32 100 75 60 12 10 4



30/55


Trang 30

3. ng dn hi ra khi thp :Nhit ca pha hi ti nh thp l tD = 80,5

oC.Khi lng ring ca pha hi ti nh thp:

)2735,80(

273

4,2228,781

HD

HDHD RT

PM = 2,7 kg/m3

Chn vn tc hi ra khi nh thp l vHD = 20 m/s.(theo bng 2.2 trg370 STT1)Lng hi vo thit b ngng t : GD = D.(R + 1) = 161,8.(2,48 + 1) = 563,06 kg/hng knh trong ca ng ni:

Dy =207,23600

06,5634

.3600

.4

HDHD

D

v

G= 0,031 m = 31 mm

Chn ng c Dy = 40 mm.(theo bng XIII.32 STT2)Tra bng XIII.32, trang 434, 6 Chiu di on ng ni l = 100 mm.Tra bng XIII.26, trang 411, 6 Cc thng s ca bch ng vi P = 0,25 N/mm2 l:

Dy Dn D D D1 hBu lng

db Zmm ci

40 45 130 100 80 12 12 44. ng dn hi vo y thp:

Nhit ti y thp l 1100C khi lng ring ca pha hi ti y thp3/92,2

)273110(273

4,2286,911

mkgRT

PM

HW

HWHW

Chn vn tc hi vo y thp l vHD = 20 m/s.(theo bng 2.2 trg370 STT1)

ng knh trong ca ng niVi lu lng hi i vo y thp g1 = 789,7kg/h = 0,22kg/s = 0,075m

3/s

Suy ra Dy = ..

075,0.40,069 m = 69 mm

Chn ng c Dy = 70 mm.(theo bng XIII.32 STT2)Tra bng XIII.32, trang 434, 6 Chiu di on ng ni l = 110 mm.Tra bng XIII.26, trang 412, 6 Cc thng s ca bch ng vi P = 0,25 N/mm2 l:

Dy Dn D D D1 hBu lng

db Z

mm ci70 76 160 130 110 12 14 8

5. ng dn lng hon lu :Nhit dng hn lu tR = 80,5

oC.Chn vn tc ca dng ny vo thp l v = 0,3 m/s. (theo bng 2.2 trg370 5 ) Khi lng ring ca benzen : B = 813,46 kg/m

3 Khi lng ring ca toluen : T = 806,56 kg/m

3



31/55


Trang 31

Nn:56,806

9765,0146,813

9765,011

T

D

B

D

D

xx

D = 813,3 kg/m

3

ng knh trong ca ng ni:

Dy =3,0..9,812.3600

88,416.4

...3600

..4

v

RG

D

D = 0,023 m = 23 mm

Chn ng c Dy = 25 mm. (theo bng XIII.32 6 )Tra bng XIII.32, trang 434, [6] Chiu di on ng ni l = 90 (mm).Tra bng XIII.26, trang 409, [6] Cc thng s ca bch ng vi P = 0,25 N/mm2 l:

Dy Dn D Db D1 hBulng

db Zmm ci

25 32 100 75 60 12 10 4

VI. Tnh ton chn , tai treo :1. Tnh trng lng ca ton thp:Tra bng XII.7, trang 313, [6] Khi lng ring ca thp CT3 l: CT3 = 7850 kg/m

3Khi lng ca tm bch ghp thn v np :

mbch = 7850022,0500,0630,04

.8..4

.8 22322

CTt hDD = 159,3 kg

Khi lng ca thn thit b :

mthn =4

.(D2ng D

2t).Hthn . X18H10T = 7900.5,7.500,0508,0.

422

= 375 kg

Khi lng ca y (np) thp:my(np) =2. Sb mt .y . X18H10T = 2.0,31 . 0,004 . 7900 = 19,9 kg

Khi lng mm, ta c 25 mm v thit b un siMmm = khi lng chp + khi lng a di chp + khi lng ng chychuyn(bao gm c phn g chy trn) + khi lng ng hi Ta ly khi tng th ca mt mm bng 2 ln khi lng mm khng c l v ngchy chuyn cng vi b dy mm l 4mm, suy ra:

Mmm = 2. 4

. D2t. 1 . X18H10T = 2. 4

.0,52. 0,004 . 7900 = 12,4 kg

Tng khi lng mm M = 12,4.25 = 310 kgKhi lng Toluene gi s cha y thp trong trng hp nguy him nht

Mtoluene =4

. D2t. Ht . toluene =4

. 0,52. 7,5 . 856,5 = 1260 kg

Khi lng ca ton thp:m = Mbch + Mthn + My(np) + Mmm + Mtoluene = 159,3 +375 +19,9 + 310 +1260

= 2124,2 kg2.Tnh chn thp:

Chn chn : thp c trn bn chn.Vt liu lm chn thp l thp CT3.



32/55


Trang 32

Theo aythiet b

Tructhiet

b

Ti trng cho php trn mt chn : Gc =4

81,92142,2

44

mgP = 0,5253.104 N

m bo an tn ta chn Gc = 1.104 N

Tra bng XIII.35, trang 437, 6 chn chn c cc thng s sau:

F.104 q.10-6 L B B1 B2 H h s l dm2 N/m2 mm

85,4 0,29110 80 95 110 180

120 6 40 18

Tnh khi lng gn ng mt chn :Th tch mt chn :

V1 chn = [2.(H s).s. B2 + L. s. B].10-9

= [2.(180 6).6.110 + 110.6.80].10 -9 = 2,69.10-3 m3

Khi lng mt chn :m1 chn= V1 chn . CT3 = 2,69.10-3.7850 = 21,1kg

3. Tnh tai treo thp:Chn tai treo: Tai treo c gn trn thn thp v ta vo gin gi thp vng trong qutrnh lm vicChn vt liu lm tai treo l thp CT3Ti trng trn mt tai treo chn bng vi ti trng trn mt chn Gc = 1.10

4 NTra bng XIII.36, trang 438, STT2 chn tai treo c cc thng s sau:

F.104 q.10-6 L B B1 H S l a d mm2 N/m2 mm57,0 0,44 90 65 75 140 6 35 15 14 1,0

Khi lng mt tai treo: mtai treo = 1,0 kgTra bng XIII.37, trang 439, STT2 Chn tm lt tai treo bng thp CT3 c cc thng s sau(tra theo Gc = 2,5.10

4N): Chiu di tm lt: H = 260 mm Chiu rng tm lt: B = 140 mm B dy tm lt: SH =6 mm



33/55


Trang 33

Th tch mt tm lt tai treo:Vtm lt = B.SH.H

= 140. 6. 260. 10-9 = 0,2184.10-3 m3Khi lng mt tm lt tai treo:

mtm lt = Vtm lt. CT3 = 0,2184.10-3.7850 = 1,714 kg

Chng7 :TNH TN THIT B PH

I . THIT B NGNG T SN PHM NH:Chn thit b ngng t v ng loi TH, t nm ngang.ng truyn nhit c lm bng thp CT3, kch thc ng 20 x 2: ng knh ngoi: dn = 20 mm = 0,02 m B dy ng: t = 2 mm = 0,002 m ng knh trong: dtr = 0,016 m

Chn: Nc lm lnh i trong ng vi nhit vo tV = 30

oC v nhit ra tR = 40oC.

Dng hi ti nh i ngoi ng vi nhit ngng t tngng = 80,5oC

1. Sut lng nc lm lnh cn dng :Cn bng nhit: Qnt = (R + 1).GD.rD = Gn.(hR hV) = Gn.CpTQnt = (R + 1).D.rD = 61,42 kJ/s theo tnh tn phn cn bng nhit

Lng nc cn dng:VR

ntn hh

QG

2 =

7,1255,167

42,61

= 1,47 kg/s

Trong hR, hv enthanpy ca nc nhit trung bnh

Cttt rvf0354030

2

1

2

1

2. Hiu s nhit trung bnh :Chn kiu truyn nhit ngc chiu, nn:

405,80305,80

)405,80()305,80(log

Lnt = 45,32 K.

3. H s truyn nhit:H s truyn nhit K c tnh theo cng thc:



34/55


Trang 34

ngng

t

n

1r

1

1K

, W/m2.K

Vi: n : h s cp nhit ca dng nc lnh W/m

2.K

ngng : h s cp nhit ca dng hi ngng t W/m2

.K rt : nhit tr qua thnh ng v lp cu.3.1.Xc nh h s cp nhit ca nc i trong ng :

Nhit trung bnh ca dng nc trong ng: 40302

1

2

1 rvf ttt .

Ti nhit ny th: Khi lng ring ca nc: n = 994 kg/m

3 nht ca nc: n = 7,23.10

-7 m2/s H s dn nhit ca nc: n = 0,626 W/mK Chun s Prandtl: Prn = 4,90Chn vn tc nc i trong ng: vn = 0,6 m/s

S ng:6,0.016,0.

4.

99447,1

..4

.22

ntrN

n

vd

Gn = 18,26 ng

Tra bng V.II, trang 48, 6 chn n = 19 ng Vn tc thc t ca nc trong ng:

22 016,019994

47,144

trn

nn dn

Gv = 0,39 m/s.

Chun s Reynolds :

7.

10.23,7

016,039,0Re

n

trnn

dv

= 8630,7

Ta thy 2300 < Ren < 10000 cp nhit xy ra ch chy qu p dng cng thc (10), trang 6, Hng dn TNQTTB hay cng thc V.44 6 trang 16 cng thc xc nh chun s Nusselt:

lv

nnn CNu

25,0

43,0

Pr

Pr.Pr.

Trong : 1 h s tnh n nh hng ca h s cp nhit theo t l gia chiudi L v ng knh d ca ng khi Re < 10000, tng ng l = 1,2

H s C ph thuc Re, ng vi nRe = 8630,7 ta c C = 30Tnh Prv: Prvc xc nh nhit trung bnh ca thnh ng

H s cp nhit ca nc i trong ng trong: n = trnn

d

.Nu

3.2.Nhit ti qua thnh ng v lp cu :

t

wwt r

ttq

21 , (W/m2).

Trong : tw1 : nhit ca vch tip xc vi hi ngng t,

oC tw2 : nhit ca vch tip xc vi nc lnh,

oC



35/55


Trang 35

21 rrrt

tt

B dy thnh ng: t = 0,002 m H s dn nhit ca thp khng g: t = 16,3 W/mK Nhit tr lp bn trong ng: r1 = 1/5000 m

2.K/W

Nhit tr lp cu ngoi ng: r2 =1/5800 m2

.K/WNn: rt = 0,0005 m2.K/W

3.3.Xc nh h s cp nhit ca hi ngng t ngoi ng :iu kin:- Ngng t hi bo ha.- Khng cha khng kh khng ngng.- Hi ngng t mt ngoi ng.- Mng cht ngng t chy tng.- ng nm ngang.

p dng cng thc (3.65), trang 120, [4]i vi ng n chic nm ngang th:

4

nW1ngng

32

1 ).dt-.(t

.g.r.725,0

Tra hnh V.20, trang 30, STQTTB Tp 6 h s ph thuc vo cch b tr ngv s ng trong mi dy thng ng l tb = 0,7 (v xp xen k v s ng trong midy thng ng l 9) H s cp nhit trung bnh ca chm ng: ngng = tb1 = 0,71Dng php lp: chn tW1 = 52

oCNhit trung bnh ca mng cht ngng t: tm = (tngng + tW1) = (80,5 + 52) =66,25 oC

Ti nhit ny th: Khi lng ring ca benzene : B = 828,92 kg/m

3 Khi lng ring ca toluene : T = 820,34 kg/m

3

Nn:34,820

9765,01

92,828

9765,011

A

D

N

D xx

= 828,71 kg/m3

nht ca benzene : B = 3,67.10-4 N.s/m2

nht ca toluene : T = 3,51.10-4 N.s/m2

Nn: lg = xDlgB + (1 xD)lgT = 0,98.lg(3,67.10-4) + (1 - 0,98)lg(3,51.10-4)

= 3,67.10-4 N.s/m2 H s dn nhit ca sn phm nh : D = 0,1436 W/mK

n nhit ngng t ca sn phm nh xc nh t f: r = 390 kJ/kgNn:

KmW ./66,101152).0,02-.(80,53,67.10

1436,0.28,718.390.10725,0

).dt-.(t

.g.r.725,0 24

4-

323

4

nW1ngng

32

1

ngng = 1 .0,7 = 708,2 W/m2K

qngng = ngng (tngng tW1) = 708,2.(80,5 - 52) = 20183,7 W/m2

qt = qngng = 20183,7 (W/m2) (xem nhit ti mt mt l khng ng k)



36/55


Trang 36

tw2 = tw1 - qtrt = 52 20183,7.2,867.10-4 = 46,20C

Prw2 = 3,83

83,752,1.83,3

9,4.9,4.30

Pr

Pr.Pr.

25,0

43,0

25,0

43,0

l

v

nnn CNu

n = KmWdNu

tr

nn 2

/8,2966016,0

626,0.83,75.

qn = n (tW2 tf) = 2966,8.(46,2 - 35) = 33228,2 W/m

2

Kim tra sai s:

=ngng

nngng

q

qq 100% =

7,20183

2,332287,20183 100% = 55,7% sai s

qu ln, khng tha ta lp li cc bc tnh nh trn vi cc gi tr khcca tw1

SHi Ngng tLn

Tnh tngng tw1 tm t1 angng qngng1 80.5 60 70.25 20.5 1414.474 28996.71912 80.5 61 70.75 19.5 1432.27 27929.25973 80.5 59 69.75 21.5 1397.732 30051.234

Kt lun: vy chn ln tnh lp li th nht vi: tw1 = 600C c sai s nh nht, v

tw2 = 45,60C

3.4.Xc nh h s truyn nhit:

474,1414

10005,0

8,2947

11

K = 646,742 W/m2K

4. B mt truyn nhit:B mt truyn nhit c xc nh theo phng trnh truyn nhit:

F =32,45742,646

100061,42

. log

tK

Qnt = 2,1 m2 d tr b mt truyn nhit ta chn

F = 2,5 m25. Cu to thit b:S ng truyn nhit: n = 19 ng. ng c b tr theo hnh lc gic u.



37/55


Trang 37

Chiu di ng truyn nhit: L =

2

ddn

F

trn = 0,604 m chn L = 0,7 m

S chng : 1 chngS ng trn ng cho: b = 5 ng

Tra bng trang 21, [3] Bc ng: t = 1,2d = 1,2.0.02 = 0,024 mS ng tt c : 19p dng cng thc (V.140), trang 49, [6]:ng knh trong ca thit b: D = t(b-1) + 4dn = 0,024.(5-1) + 4.0.02 = 0,17mly trn 0,2m

II . THIT B UN SI Y THP :Chn thit b un si y thp l ni un Kettle.ng truyn nhit c lm bng thp X18H10T, kch thc ng 38 x 3: ng knh ngoi: dn = 38 mm = 0,038 m B dy ng: t = 3 mm = 0,003 m ng knh trong: dtr = 0,032 m

Hi t l hi nc 2,5at i trong ng 38 x 3. Tra bng 1.251, trang 314, 6 : Nhit ha hi: OH2r = rn = 2189500 J/kg

Nhit si: OH2t = tn = 126,25oC

Dng sn phm ti y c nhit : Trc khi vo ni un (lng): tS1 = 110,2

oC Sau khi c un si (hi): tS2 = 110,6

oC1. Sut lng hi nc cn dng:Tra bng 1.251, trang 314, [5] Nhit ha hi ca nc 2,5 at = OH2r = 2189,5 kJ/kg

hkgskgrr

D /05,113/0315,05,2189.95,0

32,56.95,0

Q-Q-Q+Q+QQ-Q-Q+Q+Q2

fFDWnt

2

fFDWnt2

2. Hiu s nhit trung bnh:Chn kiu truyn nhit ngc chiu, nn:

6,11025,1262,11025,126

ln

)6,11025,126()2,11025,126(log

t = 15,85 K.

3. H s truyn nhit:H s truyn nhit K c tnh theo cng thc nh i vi tng phng:

S

t

n

1r

11K

,W/m2.K

Vi: n : h s cp nhit ca hi t W/m

2.K S : h s cp nhit ca sn phm y W/m

2.K. rt : nhit tr qua thnh ng v lp cu.



38/55


Trang 38

3.1.Nhit ti qua thnh ng v lp cu:

t

2w1wt

r

ttq

, W/m2.

Trong : tw1 : nhit ca vch tip xc vi hi t trong ng,

oC

tw2 : nhit ca vch tip xc vi sn phm y ngoi ng,o

C21

t

tt rrr

B dy thnh ng: t = 0,003 m H s dn nhit ca thp khng g: t = 16,3 W/mK (Bng XII.7, trang 313,

STQTTB 6 ) Nhit tr lp bn trong ng: r1 = 1/5800 m

2.K/W (Bng 31, trang 419, [4]) Nhit tr lp cu ngoi ng: r2 =1/5800 m

2.K/WNn: rt = 5,289.10

-4 m2.K/W

3.2.Xc nh h s cp nhit ca dng sn phm y ngoi ng:p dng cng thc (V.89), trang 26, [6]:

S = 7,77 . 10-2.

0,37

s

0.11745,0

0,775,00,3330,033

h

h

T.c.

q...

r.

Nhit si trung bnh ca dng sn phm ngoi ng:

2

6,1102,110

221

SSS

ttt = 110,4 (oC) tS = 110,4 + 273 = 383,4 K

Ti nhit si trung bnh th: Khi lng ring ca pha hi trong dng sn phm ngoi ng:

)2734,110(273

4,22921

S

HWh

RT

PM = 2,91 kg/m3

Khi lng ring ca benzen : B = 780,52 kg/m3

Khi lng ring ca toluen : T = 781,64 kg/m3

Nn: 00128,064,781

00365,01

52,780

00365,011

T

W

B

W xx

= 781,636 kg/m3

nht ca toluen : T = 2,994.10-4 N.s/m2

nht ca benzen : B = 2,71.10-4 N.s/m2

Nn: lg = xWlgB + (1 - xW)lgT = 0,0043.lg(2,71.10-4) + (1 - 0,0043)lg(2,994.10-

4) = 2,993.10-4 N.s/m2

H s dn nhit ca hn hp : = 0,149 W/mK Sc cng b mt ca benzen : B = 0,01755 N/m Sc cng b mt ca toluen : T = 0,0183 N/m

Nn:TB

TB

= 0,009 N/m

Nhit dung ring ca benzen : cB = 2157,45 J/kg.K Nhit dung ring ca toluen : cT = 2108,19 J/kg.K



39/55


Trang 39

Nn: c = cN Wx + cA. (1 - Wx ) = 2108,37 J/kgK

Nhit ha hi ca Benzen: rB = 370636,47 J/kg Nhit ha hi ca toluen : rT = 362262,87 J/kgNn: r = rN Wx + rA. (1 - Wx ) = 362293,45 J/kg

3.3.Xc nh h s cp nhit ca hi t trong ng:

p dng cng thc (3.65), trang 120, [4]: 4trW1nn

3n

2nn

n).dt-.(t

.g..r725,0

Dng php lp: chn tW1 = 124,8 (oC)

Nhit trung bnh ca mng nc ngng t: tm = 126,525oC

Ti nhit ny th: Khi lng ring ca nc: n = 937,935 kg/m

3 nht ca nc: n = 2,25.10

-4 (N.s/m2) H s dn nhit ca nc: n = 0,686 W/mK

Nn: n = 10849,76103 (W/m2K)

qn = n (tn tW1) = 15732,15 W/m2

qt = qn = 15732,15349 W/m2 (xem nhit ti mt mt l khng ng k) tw2 = tw1 - qtrt = 116,68

oCS = 2481,544 W/m

2K (vi q = q t) qS = S (tW2 tS) = 15579,58 W/m

2Kim tra sai s:

=n

Sn

q

qq 100% = 0,97% < 5% (tha)

Kt lun: tw1 = 124,8oC v tw2 = 116,68

oC


544,24811

10.289,576103,18491

14

K = 988,73 W/m2K


F = 17,485,5173,889

100032,56. log

tK

Q m2 ly d b mt truyn nhit F = 4,5 m2

5. Cu to thit b:Chn s ng truyn nhit: n = 37 ng. ng c b tr theo hnh lc gic u.


2trn ddn

F

= 1,107 m chn L = 1,2 m

Tra bng V.II, trang 48, STQTTB 6 S ng trn ng cho: b = 7 ngChn bcng: t = 1,2dn = 1,2.0,038 = 0,046 m

p dng cng thc (V.140), [6]:ng knh trong ca thit b: D = t(b-1) + 4dn = 0,43(m)



40/55


Trang 40

III . THIT B LM NGUI SN PHM NH :Chn thit b lm ngui sn phm nh l thit b truyn nhit ng lng ng.

ng truyn nhit c lm bng thp X18H10T, kch thc ng trong : 16x1,6;kch thc ng ngoi : 25x2,5.

Chn: + Nc lm lnh i trong ng 16x1,6 (ng trong) vi nhit u : t1=27oC, nhit cui : t2 = 40oC.

+ Sn phm nh i trong ng 25x2,5 (ng ngoi) vi nhit u : tD =80,5oC, nhit cui : tD = 35

oC.Cc tnh cht l hc ca nc lm lnh c tra ti liu STQTTB tp 1ng

vi nhit trung bnh ttbN =2

21 tt =33,5oC:

+ Nhit dung ring: cN = 4,181 kJ/kg.+ Khi lng ring: N = 994,4 (Kg/m

3).+ nht ng lc: N = 0,7371.10

-3 (N.s/m2).+ H s dn nhit: N = 0,6242 (W/m

oK).

Cc tnh cht l hc ca sn phm nh c tra ti liu tham kho 6 ngvi nhit trung bnh ttbD = 75,57

2355,80

2'

DD tt oC:

+ Nhit dung ring: cD= 1909,84 (J/kg.).+ Khi lng ring: D = 837,91 (Kg/m

3).+ nht ng lc: D = 0,407.10

-3 (N.s/m2).+ H s dn nhit: D = 0,149 (W/m

oK).1 . Sut lng nc cn dng lm mt sn phm nh:

Sut lng sn phm nh:GD = 161,8 kg/h = 0,045 kg/s.

Lng nhit cn ti tnh phn cn bng nhit lng cho thit b lm ngui snphm nh QD = 5,13 kW :

Sut lng nc cn dng:

GN =)2840.(181,4

13,5

).( 12

ttc

Q

N

D = 0,102 kg/s = 368,1 kg/h

2 . Xc nh b mt truyn nhit :B mt truyn nhit c xc nh theo phng trnh truyn nhit:

Ftb =log. tK

Qt

,m2

Vi: + K : h s truyn nhit.+ tlog : nhit trung bnh logarit.

Xc nh tlog :Chn kiu truyn nhit ngc chiu, nn:

038,20

2735

405,80ln

)2735()405,80(log

t K.

Xc nh h s truyn nhit K:H s truyn nhit K c tnh theo cng thc:



41/55


Trang 41

Dt

N

rK

111

,W/m2.oK

Vi: + N : h s cp nhit ca nc trong ng W/m2.oK.

+ D : h s cp nhit ca sn phm nh W/m2.oK.

+ rt : nhit tr ca thnh ng v lp cu.* Xc nh h s cp nhit ca sn phm nh ng ngoi:Vn tc ca sn phm nh i trong ng ngoi:

475,0)016,002,0.(

4.

91,837

045,0

)..(

4.

2222

ngtrD

DD dD

Gv m/s.

ng knh tng ng: dtd = Dtr dng = 0,02- 0,016 = 0,004 (m).Chun s Reynolds :

62,599110.407,0

91,837.004,0.475,0.Re

3.

D

DtdDD

dv

< 10000 : ch chy

chuyn tip, cng thc xc nh chun s Nusselt c dng:

lv

DDD CNu

25,0

43,0

PrPr.Pr.

Trong :+ l : h s hiu chnh ph thuc t l chiu di ng vi ng knh

ng, chn l =1. H s C = 19,5+ PrD : chun s Prandlt ca sn phm nh 57,75

oC, nn

149,0

84,1909.10.407,0.Pr

3

D

DDD

c

= 5,223.

+ Prw1 : chun s Prandlt ca sn phm nh nhit trung bnh cavch.

Suy ra:25,0

1Pr01,83

w

DNu

H s cp nhit ca sn phm nh trong ng ngoi:

D = 25,01

25,01 Pr

8,3095

004,0.Pr

149,0.01,83.

wwtd

DD

d

Nu

Nhit ti pha sn phm nh:

)75,57(Pr

8,3095).( 125,0

1

1 w

w

wtbDDD tttq W/m2

Vi tw1 : nhit ca vch tip xc vi sn phm nh (ngoi ng nh).* Nhit ti qua thnh ng v lp cu:

t

wwt r

ttq 21 , W/m2.

Trong :+ tw2 : nhit ca vch tip xc vi nc (trong ng nh).

+ 21 rrrt

tt

B dy thnh ng: t = 1,6 mm.



42/55


Trang 42

H s dn nhit ca thp khng g: t = 17,5 W/m.K.Nhit tr trung bnh ca lp bn trong ng vi nc sch:

r1 = 1/5000 m2.oK/W.

Nhit tr lp cu pha sn phm nh: r2 = 1/5800 (m2. K/W).

Suy ra: rt = 1/2155,9 (m2. K/W).

Vy: qt = 2155,9.(tw1-tw2)* Xc nh h s cp nhit ca nc trong ng nh:Vn tc nc i trong ng:

798,00128,0.

4.

4,994

102,0

.

4. 22 trN

NN d

Gv (m/s).

Chun s Reynolds :

94,1377910.7371,0

4,994.0128,0.798,0.Re

3.

N

NtrNN

dv

> 104 : ch chy

ri, cng thc xc nh chun s Nusselt c dng:25,0

2

43,08,0 )Pr

Pr.(PrRe..021,0

w

NNNlNNu

Trong :+ l : h s hiu chnh ph thuc vo ReN v t l chiu di ng vi

ng knh ng : ReN = 13779,94, chn l =1.+ PrN : chun s Prandlt ca nc 34

oC, nn PrN = 5.+ Prw2 : chun s Prandlt ca nc nhit trung bnh ca vch.

Suy ra:25,0

2Pr

9,107

w

NNu

H s cp nhit ca nc trong ng:

N = 25,02

25,02 Pr

90,5265

0128,0.Pr

6242,0.49,128.

wwtr

NN

d

Nu

Nhit ti pha nc lm lnh:

)34(Pr

90,5265).( 225,0

2

2 ww

tbNwNN tttq W/m2

Chn: tw1 = 50,5oC :

Cc tnh cht l hc ca sn phm nh c tra ti liu tham kho 5 ng vi nhit tw1=50,5

oC:+ Nhit dung ring: c = 1906,38 J/kg..+ nht ng lc: = 0,423.10-3 N.s/m2.+ H s dn nhit: = 0,138 W/m

oK.

Khi : Prw1 = 84,5138,0

38,1906.10.423,0. 3

c

T (IV.9): qD = 02,14438)5,5075,57.(84,5

8,309525,0

W/m2.

Xem nhit ti mt mt l khng ng k: qt = qD = 02,14438 W/m2.

T (IV.10), ta c: tw2 = tw1 -9,2155

tq = 43,8oC



43/55


Trang 43

Tra ti liu tham kho [4 (tp 1)], Prw2 = 4,10

T (IV.11): qN = 7,16650)348,43.(95,3

90,526525,0

W/m2.

Kim tra sai s:

=7,16650

7,1665002,14438

D

DN

q

qq= 13,29% sai s ny chp nhn

c nn ta chnVy: tw1 = 50,5

oC v tw2 = 43,8oC.

Khi : 28,372595,3

9,526525,0

N W/m2.oC

45,199184,5

8,309525,0

D W/m2.oC

05,810

9,2155

1

28,3725

1

25,1991

11

K W/m2.oC

T (IV.7), b mt truyn nhit trung bnh:

038,20.05,810

5,13.103tbF = 0,316 m

2

Suy ra chiu di ng truyn nhit :

L 99,6

2

0128,0016,0.

316,0

m

Chn: L = 8 m,(d tr khong 15%).

Kim tra: 506250128,0

5,7

trd

Lth l = 1: tho.

Vy: thit b lm mt sn phm nh l thit b truyn nhit ng lng ng vichiu di ng truyn nhit L = 8 m, chia thnh 2 dy, mi dy 4 ng ming

1 m.

IV . THIT B LM NGUI SN PHM Y :Chn thit b lm ngui sn phm y l thit b truyn nhit ng lng ng.ng truyn nhit c lm bng thp X18H10T: Kch thc ng trong: 16 x 1,6 Kch thc ng ngoi: 25 x 2,5

Chn: Nc lm lnh i trong ng trong vi nhit vo tV = 27

oC v nhit ra tR =43oC.

Sn phm y i trong ng ngoi vi nhit vo tWS = 110,2oC v nhit ra

tW = 35oC.

1. Sut lng nc lm lnh cn dng:



44/55


Trang 44

Nh phn cn bng nhit lng trn tnh, ta c lng nhit trao i QW = 11,86kWTra bng 1.250, trang 312, ST I Enthalpy ca nc 27oC = hV = 113,13kJ/kg

Enthalpy ca nc 43oC = hR = 180,17 kJ/kg

Sut lng nc cn dng:VR

n hh

QG = 13,11317,180

3600.86,11

= 636,8 kg/h


2735

432,110ln

)2735()432,110(log

t = 27,82 K.

3. H s truyn nhit:H s truyn nhit K c tnh theo cng thc:

Wt

n

rK

111

W/m2.K

Vi: n : h s cp nhit ca dng nc lnh W/m

2.K W : h s cp nhit ca dng sn phm y W/m

2.K rt : nhit tr qua thnh ng v lp cu.

3.1.Xc nh h s cp nhit ca nc trong ng:Kch thc ca ng trong: ng knh ngoi: dn = 16 mm = 0,016 m B dy ng: t = 1,6 mm = 0,0016 m ng knh trong: dtr = 0,0128 mNhit trung bnh ca dng nc trong ng: tf= (tV + tR) = 35

oCTi nhit ny th: Khi lng ring ca nc: n = 994 kg/m

3 nht ca nc: n = 7,23.10

-7 m2/s H s dn nhit ca nc: n = 0,626 W/mK Chun s Prandtl: Prn = 4,9Vn tc nc i trong ng:

22 0128,09943600

8,3664

3600

4

trn

n

n d

Gv = 1,383 m/s

Chun s Reynolds :

7.

10.23,7

0128,0383,1Re

n

trnn

dv

= 24484.65 > 104 : ch chy ri

p dng cng thc (11), trang 7, 6 cng thc xc nh chun s Nusselt:25,0

2

43,08,0

Pr

Pr.PrRe..021,0

w

nnnlnNu



45/55


Trang 45

Trong : 1 h s tnh n nh hng ca h s cp nhit theo t l gia chiudi L v ng knh d ca ng v Re, ta chn 1 = 1 theo bng trang 7 - 6

H s cp nhit ca nc trong ng: n =tr

nn

d

.Nu

3.2.Nhit ti qua thnh ng v lp cu:

t

2w1wt

rttq

, W/m2

Trong : tw1 : nhit ca vch tip xc vi sn phm y (trong ng trong),

oC tw2 : nhit ca vch tip xc vi nc lnh (ngoi ng trong),

oC

21

t

tt rrr

B dy thnh ng: t = 0,003 m H s dn nhit ca thp khng g: t = 16,3 W/mK Nhit tr lp bn trong ng: r1 = 1/5000 m

2.K/W

Nhit tr lp cu ngoi ng: r2 =1/5800 m2

.K/WNn: rt = 5,565.10

-4 m2.K/W

3.3.Xc nh h s cp nhit ca dng sn phm y ngoi ng:Kch thc ca ng ngoi: ng knh ngoi: Dn = 25 mm = 0,025 m B dy ng: t = 2,5 mm = 0,0025 m ng knh trong: Dtr = 0,02 mNhit trung bnh ca dng sn phm y ngoi ng: tW = (tWS + tWR) = 72,6

oC.

Ti nhit ny th: Khi lng ring ca Benzen : B = 822,029 kg/m

3 Khi lng ring ca Toluen : T = 814,196 kg/m

3

Nn: 001228,0196,814

00365,01

029,822

00365,011

A

W

N

W xx

= 814,224 kg/m3

nht ca Benzen : B = 3,409.10-4 N.s/m2

nht ca Toluen : T = 3,315.10-4 N.s/m2

Nn: lg = xWlgB + (1 - xW)lgT = 3,316.10-4 N.s/m2 H s dn nhit ca sn phm y : W = 0,146 W/mK

Nhit dung ring ca Benzen : cB = 1980,28 J/kgK Nhit dung ring ca Toluen : cT = 1941,04 J/kgKNn: c = cB Wx + cT. (1 - Wx ) = 1941,18 J/kgK

p dng cng thc (V.35), trang 12, STQTTB 6 :

c

Pr = 4,42

Vn tc ca dng sn phm y ngoi ng:



46/55


Trang 46

)016,0020,0(224,8143600

6,2404

)(3600

42222

ntr

W

dD

Gv = 0,73 m/s

ng knh tng ng: dt = F4

Dtr dn = 0,02 0,016 = 0,004 m

Chun s Reynolds :

410.316,3224,814004,073,0Re

tvd = 7169,89 < 104 : ch chy chuyn tip

p dng cng thc (10), trang 6, 6 cng thc xc nh chun s Nusselt:25,0

1

43,0

Pr

Pr.Pr.

wlW CNu

Trong : 1 h s tnh n nh hng ca h s cp nhit theo t l gia chiudi L v ng knh d ca ng.

Tra bng 2, trang 6, 6 chn 1 = 1,9Tra bng 2, trang 6, 6 chn C = 27

H s cp nhit ca dng sn phm y ngoi ng: W =t

W

d

.Nu

Dng php lp: chn tW1 = 60oC

Ti nhit ny th: nht ca benzen : B = 3,86.10

-4 N.s/m2 nht ca toluen : T = 3,78.10

-4 N.s/m2Nn: lgW1 = xWlgB + (1 xW)lgTW1 = 3,78.10

-4 N.s/m2 H s dn nhit ca sn phm y : W = 0,1275 W/mK Nhit dung ring ca Benzen : cB = 1935,25 J/kgK Nhit dung ring ca Toluen : cT = 1904 J/kgK

Nn: cW1 = cB Wx + cT. (1 - Wx ) = 1904,3 J/kgK

Ta c:

1275,0

3,1904.10.78,3Pr

4

1

111

W

WWW

c

= 5,66

Nn:

74,6971,49,4

.88,4.9,1.27PrPr

.Pr.25,0

43,0

25,0

1

43,0

wlW CNu

W = .KW/m2192004,0

1189.0.03,101. 2t

W

d

Nu

qW = aW (tW tW1) = 2219 (76,2 60) = 25740,44 W/m

2 qt = qW = 25740,44 W/m

2 (xem nhit ti mt mt l khng ng k)

tw2 = tw1 - qtrt = 41,2 oC PrW2 = 4,31 Nun = 153,4 an = 4801,55 W/m

2Kqn = an (tW2 tf) = 28809,33 W/m

2

Kim tra sai s:



47/55


Trang 47

=W

nW

q

qq 100% = 0,106 chn khong ~ 5% l ph hp nn kt

qu ny chp nhn cKt lun: tw1 = 60

oC v tw2 = 41oC


2219

110.565,5

55,4081

11

4

K = 798,62 W/m2K


F =82,723600

100086,11

. log

tKQ = 0,12 m2

5. Cu to thit b:Chiu di ng truyn nhit: L =

2

ddn

F

trn = 2,12 m chn L = 2,5 m

Kim tra:0128,0

5,2

trd

L = 195 > 50 l = 1: tha

Kt lun: Thit b lm ngui sn phm y l thit b truyn nhit ng lng ngvi tng chiu di ng truyn nhit L = 2,5 m, chia thnh 5 hng ng mi hng c ng di0,5 m

V . THIT B UN SI NHP LIUChn thit b gia nhit nhp liu l thit b trao i nhit kiu ng chm.ng truyn nhit c lm bng thp X18H10T, kch thc ng 38 x 3: ng knh ngoi: dn = 38 mm = 0,038 m B dy ng: t = 3 mm = 0,003 m ng knh trong: dtr = 0,032 mHi t l hi nc 2,5at i trong ng 38 x 3. Tra bng 1.251, trang 314,STQTTB 6 : Nhit ha hi: OH2r = rn = 2189500 J/kg

Nhit si: OH2t = tn = 126,25oC

Dng sn phm ti y c nhit :

Trc khi vo ni un (lng): tF = 30 oC Sau khi c un (lng si): tS2 = 94

oC6. Sut lng hi nc cn dng:Tra bng 1.251, trang 314, [5] Nhit ha hi ca nc 2,5 at = OH2r = 2189,5 kJ/kg

hkgskgr

D /74/0074,05,2189.95,0

15,43Q

2

F2



48/55


Trang 48


9425,126

3025,126ln

)9425,126()3025,126(log

t = 58,95 K.

8. H s truyn nhit:H s truyn nhit K c tnh theo cng thc nh i vi tng phng:

Ft

n

rK

111

,W/m2.K

Vi: n : h s cp nhit ca hi t W/m

2.K F : h s cp nhit dng nhp liu W/m

2.K. rt : nhit trqua thnh ng v lp cu.3.5.Nhit ti qua thnh ng v lp cu:

t

FF

t r

tt

q

21

, W/m2

.Trong : tF2 : nhit ca vch tip xc vi hi t pha v,

oC tw1 : nhit ca vch tip xc vi nhp liu trongng,

oC

21

t

tt rrr

B dy thnh ng: t = 0,003 m H s dn nhit ca thp khng g: t = 16,3 W/mK (Bng XII.7, trang 313,

STQTTB 6 ) Nhit tr lp bn trong ng: r1 = 1/5800 m

2.K/W (Bng 31, trang 419, [4]) Nhit tr lp cu ngoi ng: r2 =1/5800 m2.K/WNn: rt = 5,289.10

-4 m2.K/W3.6.Xc nh h s cp nhit ca dng nhp liu trong ng:Ti nhit si trung bnh th ca dng nhp liu tFtb = 62

0C: Khi lng ring ca benzen : B = 836 kg/m


3

Nn: 0012,0828

4,01

836

4,011

T

F

B

F xx

= 831,2 kg/m3

nht ca toluen : T = 3,81.10-4 N.s/m2

nht ca benzen : B = 3,9.10-4 N.s/m2

Nn: lg = xFlgB + (1 xF)lgT = 0,4.lg(3,9.10-4) + (1 - 0,4)lg(3,81.10 -4) = 3,85.10-4 N.s/m2

H s dn nhit ca hn hp : = 0,149 W/mK Nhit dung ring ca benzen : cB = 2157,45 J/kg.K Nhit dung ring ca toluen : cT = 2108,19 J/kg.KNn: c = cN Fx + cA. (1 - Fx ) = 2108,37 J/kgK



49/55


Trang 49

p dng cng thc (V.35), trang 12, 6 ]:F

FFF

cPr

= 1,94

Vn tc dng nhp liu i trong ng:

22 032,02,8313600

4,4024

3600

4

tr

FF d

Gv = 0,167 m/s.

Chun s Reynolds :

410.85,3

2,831032,0167,0Re

F

FtrFF

dv

= 11534,71 > 104 : ch chy ri

p dng cng thc (3.27), trang 110, [4] Cng thc xc nh chun s Nusselt:25,0

2

43,08,0

Pr

Pr.PrRe..021,0

F

FFFlFNu

Trong : 1 h s tnh n nh hng ca h s cp nhit theo t l chiu di vng knh ng.

3.7.Xc nh h s cp nhit ca hi nc i pha v :

p dng cng thc (3.65), trang 120, [4]: 4trW1n

32

n).dt-.(t

.g..r725,0

n

nnn

Dng php lp: chn tF1 = 122,8oC

Nhit trung bnh ca mng nc ngng t: tm = 126,25oC

Ti nhit ny th: Khi lng ring ca nc: n = 937,935 kg/m

3 nht ca nc: n = 2,25.10

-4 N.s/m2 H s dn nhit ca nc: n = 0,686 W/mK

Nn: n = 10849,76 W/m2K

qn = n (tn tW1) = 16820,49 W/m2

qt = qn = 16530,1 W/m2 (xem nhit ti mt mt l khng ng k)

tF2 = tF1 - qtrt = 116oC Vi tF2 = 116

0C th tnh cht ca dng nhp liu trong ngKhi lng ring ca benzen : B = 775 kg/m

3Khi lng ring ca toluen : T = 780,5 kg/m

3

Nn: 00128,05,780

4,01

775

4,011

T

F

B

F xx

= 781,25 kg/m3

nht ca benzene : B = 2,27.10-4 N.s/m2

nht ca toluene :T = 2,39.10-4 N.s/m2

Nn: lg = xFlgB + (1 xF)lgT = 0,4.lg(3,9.10-4) + (1 - 0,4)lg(3,81.10 -4)

= 2,32.10-4 N.s/m2

H s dn nhit ca hn hp : = 0,128 W/mKNhit dung ring ca benzen : cB = 2168,45 J/kg.KNhit dung ring ca toluen : cT = 2118,19 J/kg.K

Nn: cF = cN Fx + cA. (1 - Fx ) = 2130,37 J/kgK

p dng cng thc (V.35), trang 12, 6 :F

FFF

c

Pr = 3,31



50/55


Trang 50

25,0

2

43,08,0

PrPr

.PrRe..021,0

F

FFFlFNu = 704,56

F = 2818,23 W/m2K (vi q = qt)

qF = F (tF2 tF) = 17134,8 W/m2

Kim tra sai s:

=n

Sn

q

qq 100% = 1,8% < 5% (tha)

Kt lun: tw1 = 122,8oC v tw2 = 116

oC


23,2818

110.289,5

76,10849

11

4

K = 1024,69 W/m2K

9. B mt truyn nhit:

B mt truyn nhit c xc nh theo phng trnh truyn nhit:F = 25,0

95,5869,1024100043,15

. log

tK

Q m2 ly d b mt truyn nhit F = 0,5 m2

10.Cu to thit b:Chn s ng truyn nhit: n = 19 ng. ng c b tr theo hnh lc gic u.


2trn ddn

F

= 0,523 m chn L = 0,6 m

Tra bng V.II, trang 48, 6 S ng trn ng xuyn tm ca hnh su cnh l 3 nVI . BNCAO V :

1. Tn tht ng ng dn:Chn ng dn c ng knh trong l dtr = 80 mmTra bng II.15, trang 381, [5] nhm ca ng: = 0,2 mm = 0,0002 m (n

mn t)Tn tht ng ng dn:

g2

v.

d

lh

2

F1

1

111

m

Trong : 1 : h s ma st trong ng ng. l1 : chiu di ng ng dn, chn l1 = 30 m.

d1: ng knh ng dn, d1 = dtr = 0,08m. 1 : tng h s tn tht cc b. vF : vn tc dng nhp liu trong ng dn

1.1.Xc nh vn tc dng nhp liu trong ng dn :Cc tnh cht l hc ca dng nhp liu c tra nhit trung bnh:

tF =2

94302

FSFV tt = 62 oC



51/55


Trang 51

Ti nhit ny th: Khi lng ring ca benzen : B = 836 kg/m


3

Nn:149,833

4,01

295,843

4,011

A

F

N

F

F

xx

F = 832 kg/m

3

nht ca benzen : B = 4,335.10-4

N.s/m2

nht ca toluen : T = 4,045.10

-4 N.s/m2F = 4,129.10

-4 N.s/m2Vn tc ca dng nhp liu i trong ng:

22 08,08323600

56,17174

3600

4

trF

FF d

Gv = 0,114 m/s

1.2.Xc nh h s ma st trong ng ng :Chun s Reynolds :

4

10.129,4

83208,0114,0Re

F

FtrFF

dv

= 18461,54 > 4000 : ch chy ri

Chun s Reynolds ti hn: Regh = 6(d1/)8/7 = 5648,513

Chun s Reynolds khi bt u xut hin vng nhm: Ren = 220(d1/)9/8 =

186097,342V Regh < ReF < Ren ch chy ri ng vi khu vc qu .

p dng cng thc (II.64), trang 379, [5]: 1=25,0

F1 Re

100

d.46,1.1,0

= 0,031

1.3.Xc nh tng h s tn tht cc b : Ch un cong :

Tra bng II.16, trang 382, [5]: Chn dng ng un cong 90o

c bn knh R viR/d =2 th u1(1 ch) = 0,15.ng ng c 6 ch un u1 = 0,15. 6 = 0,9

Van :Tra bng 9.5, trang 94, [1]: Chn van cu vi m hon ton th van(1 ci) = 10.ng ng c 2 van cu van = 10. 2 = 20

Lu lng k : l1= 0 (coi nh khng ng k). Vo thp : thp = 1

Nn: 1 = u1 + van + ll = 21,9

Vy:

81,92

114,0.9,21

08,0

30031,0

2

1

h = 0,022 m

2. Chiu cao bn cao v:Chn : Mt ct (1-1) l mt thong cht lng trong bn cao v. Mt ct (2-2) l mt ct ti v tr nhp liu thp.Ap dng phng trnh Bernoulli cho (1-1) v (2-2):

z1 +g.

P

F

1

+

g

v

.2

21 = z2 +

g.

P

F

2

+

g

v

.2

22 +hf1-2



52/55


Trang 52

z1 = z2 +g.2

vv

g.

PP2

1

2

2

F

12

+hf1-2

Trong : z1: cao mt thong (1-1) so vi mt t, hay xem nh l chiu cao bn cao

v Hcv = z1.

z2: cao mt thong (2-2) so vi mt t, hay xem nh l chiu cao t mt tn v tr nhp liu:z2 = hchn + hy + (nttC 1)h + 0,4

= 0,18 + 0,150 + (14 1)0,25 + 0,4 = 3,98 m P1 : p sut ti mt thong (1-1), chn P1 = 1 at = 9,81.10

4 N/m2 P2 : p sut ti mt thong (2-2)Xem P = P2 P1 = nttL .PL = 12. 2040= 24485 N/m

2 v1 : vn tc ti mt thong (1-1), xem v1 = 0 m/s. v2 : vn tc ti v tr nhp liu, v2 = vF = 0,32 m/s. hf1-2 : tng tn tht trong ng t (1-1) n (2-2):hf1-2 = 0,662m

Vy: Chiu cao bn cao v: Hcv = z2 +g.2

vv

g.

PP2

1

2

2

F

12

+hf1-2

= 3,98 +81,92

032,0

832.81,9

24485 2

+ 0,662

= 8,78 mChn Hcv = 10 m.

VII . BM :1. Nng sut:Nhit dng nhp liu l tF = 30

oC.

Ti nhit ny th: Khi lng ring ca benzen : B = 869,25 (kg/m

3) Khi lng ring ca toluen : T = 855,39 (kg/m

3)

Nn:39,855

2665,01

25,869

2665,011

A

F

N

F

F

xx

F = 858,78 (kg/m

3)

nht ca benzen : B = 5,91.10-4 (N.s/m2)

nht ca toluen : T = 5,39.10-3 (N.s/m2)

Nn: lgF = xFlgB + (1 xF)lgTF = 5,541.10

-4 (N.s/m2)Sut lng th tch ca dng nhp liu i trong ng:

hkgQF /4,402= 0,5 m3/h

Vy: chn bm c nng sut Qb = 0,5 (m3/h)

2. Ct p:Chn : Mt ct (1-1) l mt thong cht lng trong bn cha nguyn liu. Mt ct (2-2) l mt thong cht lng trong bn cao v.p dng phng trnh Bernoulli cho (1-1) v (2-2):



53/55


Trang 53

z1 +g

P

F.1

+

g

v

.2

21 + Hb = z2 +

g

P

F.2

+

g

v

.2

22 +hf1-2

Trong : z1: cao mt thong (1-1) so vi mt t, chn z1 = 1m. z2: cao mt thong (2-2) so vi mt t, z2 = Hcv = 10m.

P1 : p sut ti mt thong (1-1), chn P1 = 1 at. P2 : p sut ti mt thong (2-2), chn P2 = 1 at. v1,v2 : vn tc ti mt thong (1-1) v(2-2), xem v1= v2 = 0 m/s. hf1-2 : tng tn tht trong ng t (1-1) n (2-2). Hb : ct p ca bm.

2.1.Tnh tng tr lc trong ng:Chn ng knh trong ca ng ht v ng y bng nhau: dtr = 50 mmTra bng II.15, trang 381, [5] nhm ca ng: = 0,2 mm = 0,0002 m (nmn t)Tng tr lc trong ng ht v ng y

hf1-2 =g2

v.

d

ll 2Fh

tr

h

Trong : lh : chiu di ng ht.Chiu cao ht ca bm: Tra bng II.34, trang 441, [5] hh = 4,3 m Chn lh = 6 m. l : chiu di ng y, chn l = 15 m. h : tng tn tht cc b trong ng ht. : tng tn tht cc b trong ng y. : h s ma st trong ng ht v ng y. vF : vn tc dng nhp liu trong ng ht v ng y m/s.

22 050,03600

5,24

3600

4

tr

bF d

Qv = 0,36 m/s

Xc nh h s ma st trong ng ht v ng y :Chun s Reynolds :

410.541,5

78,85805,036,0Re

F

FtrFF

dv

= 27122,63 > 4000 : ch chy ri

Chun s Reynolds ti hn: Regh = 6(dtr/)8/7 = 3301,065

Chun s Reynolds khi bt u xut hin vng nhm: Ren = 220(dtr/)9/8 =

109674,381

V Regh < ReF < Ren ch chy ri ng vi khu vc qu .

p dng cng thc (II.64), trang 379, [5]: =25,0

Ftr Re

100

d.46,1.1,0

= 0,03124

Xc nh tng tn tht cc b trong ng ht : Ch un cong:

Tra bng II.16, trang 382, [5]: Chn dng ng un cong 90o c bn knh R vi R/d= 2 th u1(1 ch) = 0,15.



54/55


Trang 54

ng ht c 2 ch un u1 = 0,15. 2 = 0,3 Van :

Tra bng 9.5, trang 94, [1]: Chn van cu vi m hon ton th v1(1 ci) = 10.ng ht c 1 van cu v1 = 10Nn: h = u1 + v1 = 10,3

Xc nh tng tn tht cc b trong ng y : Ch un cong:

Tra bng II.16, trang 382, [5]: Chn dng ng un cong 90o c bn knh R vi R/d= 2 th u2(1 ch) = 0,15.

ng y c 4 ch un u2 = 0,15. 4 = 0,6 Van :

Tra bng 9.5, trang 94, [1]: Chn van cu vi m hon ton th v2(1 ci) = 10.ng y c 1 van cu v2 = 10

Vo bn cao v : cv = 1Nn: = u1 + v1 + cv = 11,6

Vy: hf1-2 =81,92

32,0.6,113,1005,020603124,0

2

= 0,2 m

2.2.Tnh ct p ca bm:Hb = (z2 z1) + hf1-2 = (10 1) + 0,2 = 9,2 m

3. Cng sut:Chn hiu sut ca bm: b = 0,8.

Cng sut thc t ca bm: Nb =8,03600

81,978,8582,95,0

.3600

.

b

Fbb gHQ

= 13,45 WKt lun: m bo thp hot ng lin tc ta chn 2 bm li tm loi XM, c:- Nng sut: Qb = 0,5 m

3/h- Ct p: Hb = 9,2 m- Cng sut: Nb = 13,45 W

KT LUNVi quy trnh cng ngh tnh tn trn ta thy rng mt lng nhit ng k cn

gii l ngng t sn nh, gii nhit sn phm nh v gii nhit cho sn phm y chac tn dng gia nhit cho dng nhp liu. Nhng trong qu trnh tnh tn gianhit cho dng nhp liu ti trng thi lng si nu tn dng nhit th cha gianhit ti lng si trong khi phi tn thm thit b, ng ng lm tng chi ph caphn xng. Vn tn dng nhit l mt vn thc t rt c quan tm, n nh lmt gii php nng cao hiu qu ca qu trnh v tit kim nng lng, nhng tronggii hn v thi gian, kh nng v kinh nghim thc t nn em cha phn tch tnh tonnh gi ng mc cc qu trnh. n mn hc l mt mn hc tng hp v n mangli cho em nhiu kinh nghim tnh tn thit k hn chnh mt qu tr nh trong snxut.



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