Th nghiem qua trnh thiet b

Cot chem

Contents

2I. TRCH YEU:

21.Muc ch th nghiem

22.Phng phap th nghiem:

23.Ket qua th nghiem:

3II. C S LY THUYET:

31.o giam ap cua dong kh:

32.He so ma sat fck theo Rec khi cot kho:

43.o giam ap (Pc khi cot t:

54.iem lut cua cot chem:

6III. THIET B VA PHNG PHAP TH NGHIEM:

61.Thiet b th nghiem:

62.Cac so lieu lien quan en cot chem:

63.Phng phap th nghiem:

7IV. KET QUA TH NGHIEM:

20V. BAN LUAN:

21VI. PHU LUC:

22VII. TAI LIEU THAM KHAO:

I. TRCH YEU:

1. Muc ch th nghiem

Khao sat ac tnh ong lc hoc lu chat va kha nang hoat ong cua cot chem bang cach xac nh:

Anh hng cua van toc dong kh va long len ton that ap suat (o giam ap) khi i qua cot.

S bien oi cua he so ma sat cot kho fck theo chuan so Reynolds (Re) cua dong kh va suy ra cac he thc thc nghiem.

S bien oi cua tha so ( lien he gia o giam ap cua dong kh qua cot kho va qua cot t theo van toc dong long.

Gian o gii han kha nang hoat ong cua cot (gian o ngap lut va gia trong).

2. Phng phap th nghiem:

Cho dong kh vi cac lu lng khac nhau qua cot co cha cac vat chem bang s. Lan lt khao sat o giam ap khi ch co dong kh chuyen ong qua cot (cot kho) va khi co dong kh chuyen ong qua cot ket hp vi dong long chay t tren xuong vi lu lng khac nhau (cot t).3. Ket qua th nghiem:

G%L = 0L = 0.2L = 0.4L = 0.6L = 0.8L = 1L = 1.2

Pck1Pck2P1P2P1P2P1P2P1P2PP

10112333434445

15435555688889

2065787781012121517

258712111113161418163040

3010915161520222826183254

35131322221926283128263658

40161528282629313436424566

451819313233343538424958112

502222363641404442505266140

552727404146465150596088

6031314646535462627078128

6537355054626270728893

704141606271748286106110

75474766698282100102124138

80535376788794112111

8559598886107106132129

9066669998122118

957373112108132133

1008181124123151148

II. C S LY THUYET:

1. o giam ap cua dong kh:

o giam ap (Pck cua dong kh qua cot phu thuoc vao van toc khoi lng G cua dong kh qua cot kho (khong co dong chay ngc chieu). Khi dong kh chuyen ong trong cac khoang trong gia cac vat chem tang dan van toc th o giam ap cung tang theo. S gia tang nay theo luy tha t 1,8 en 2,0 cua van toc dong kh.

(Pck = (Gnvi n = 1,8 2,0.

(1)Khi co dong long chay ngc chieu, cac khoang trong gia nhng vat chem b thu hep lai. Dong kh do o di chuyen kho khan hn v mot phan the tch t do gia cac vat chem b lng chat long chiem c. Khi tang van toc dong kh len, anh hng can tr cua dong long tang len eu an cho en mot tr so ti han cua van toc kh, luc o o giam ap cua dong kh tang vot len. iem ng vi tr so ti han cua van toc kh nay c goi la iem gia trong. Neu tiep tuc tang van toc dong kh qua tr so ti han nay, anh hng can tr ho tng gia dong long va dong kh rat ln, (Pc tang mau chong khong theo phng trnh (1) na. Dong long luc nay chay xuong cung kho khan, cot chem iem lut.

ng bieu dien log((Pc/Z) (o giam ap suat cua dong kh qua mot n v chieu cao cua phan chem trong cot) d kien nh trnh bay tren hnh 1.

2. He so ma sat fck theo Rec khi cot kho:

Chilton va Colburn e ngh mot he thc lien he gia o giam ap cua dong kh qua cot chem kho vi van toc khoi lng cua dong kh qua cot.

, N/m2

Z: chieu cao phan chem, m.

G: van toc khoi lng dong kh da tren mot n v tiet dien cot, kg/s.m2.

Dh: kch thc ac trng cua vat chem, m.

(g: khoi lng rieng cua pha kh, kg/m3.

(h: he so ieu chnh dung cho vat chem rong.

(w: he so hieu chnh anh hng cua thanh cot len o xop cua cot chem.

Sherwood tong hp ket qua cua mot so nghien cu va a ra tr so sau cho vong s Raschig:

(h = 0,35

(w = 1

Tuy nhien, Zhavoronkov e ngh mot he thc khac chnh xac hn v a a c tr so o xop cua cot chem vao he thc:

, N/m2

Vi:

(: o xop cua vat chem.

ng knh tng ng cua vat chem, m.

a: dien tch be mat rieng cua vat chem, m2/m3.

He so ma sat fck la ham so theo chuan so vo th nguyen Rec, vi Rec c tnh theo cong thc sau:

(: o nht cua dong kh, kg/ms.

Zhavoronkov a xac nh c khi dong kh chuyen t che o chay tang sang che o chay roi ng vi tr so Rec = 50. Trong vung chay roi, 50 < Rec < 7000 vi cot chem ngau nhien. Ta c:

Tuy nhien, cac he thc tong quat tren khong c chnh xac lam v khong xem xet c toan bo anh hng cua hnh dang vat chem.

3. o giam ap (Pc khi cot t:

S lien he gia o giam ap cot kho (Pck va cot t (Pc co the bieu dien nh sau:

(Pc = ((PckDo o co the d kien fc = (fck

Vi (: he so phu thuoc vao mc o xoi ti cua dong long L, kg/m2s.Leva e ngh anh hng cua L len ( nh sau:

( = 10(Lhaylog( = (L

Gia tr ( tuy thuoc vao loai, kch thc, cach thc sap xep vat chem (xep ngau nhien hay theo th t) va o ln cua lu lng dong long L. Th du vi vat chem la vong s Raschig 12,7mm, chem ngau nhien, o xop ( = 0,586; gia tr cua L t 0,39 en 11,7 kg/m2s va cot hoat ong trong vung di iem gia trong.

( = 0,084Mot so tai lieu con bieu dien s phu thuoc gia t so vi he so xoi ti nh sau:

Khi A< 0,3 cho vat chem bang s co d < 30mm, ta co:

4. iem lut cua cot chem:

Khi cot chem b ngap lut, chat long chiem toan bo khoang trong trong phan chem, cac dong chay b xao tron manh liet, hien tng nay rat bat li cho s hoat ong cua cot chem. Goi gia tr cua GL tng ng vi trang thai nay la GL*.

Zhavoronkov ket luan rang trang thai ngap lut xay ra khi hai nhom so sau co s lien he nhat nh vi nhau cho moi cot.

va

Vi fck: he so ma sat cot kho.

v: van toc dai cua dong kh ngay trc khi vao cot, m/s.

(t: o nht tng oi cua chat long so vi nc, neu chat long la nc th (t = 1.

Do o s lien he (1, (2 tren gian o log(1 - log(2 se xac nh mot gian o lut cua cot chem, phan gii han hoat ong cua cot chem di ng nay.

III. THIET B VA PHNG PHAP TH NGHIEM:

1. Thiet b th nghiem:

Gom co:

1. Cot thuy tinh, ben trong la cac vong s Raschig xep chem ngau nhien.

2. He thong cap kh gom co:

Bm (quat) thoi kh BK.

Ong dan kh.

Ap ke sai biet ch U.

Lu lng ke kh F co o chia t 8 en 100%.

3. He thong cap nc gom:

Thung cha nc bang nha N.

Bm chat long BL.

Lu lng ke long Fl co o chia t 0,2 den 3,5 galon/ph2. Cac so lieu lien quan en cot chem:

Cot thuy tinh:

ng knh d = 0,09 m.

Chieu cao H = 0,805 m.

Chieu cao phan chem Z = 0,6 m.

Vat chem xep ngau nhien, vong Raschig ng knh 12,7mm, be mat rieng a = 370 380 m2/m3, o xop ( = 0,586.

ng knh ong thep ay cot D = 0,09m.

3. Phng phap th nghiem:

1) Khoa lai tat ca van long (t 1 en 4).

2) M van 5 va khoa van 6.

3) Cho quat chay trong 5 phut e thoi het am trong cot. Tat quat.

4) M van 1 va 2, sau o cho bm chay.

5) M van 3 va t t khoa van 1 e ieu chnh mc long ay cot ngang bang vi ong nh mc g. Tat bm va khoa van 3.

6) o o giam ap cua cot kho:

Khoa tat ca cac van long lai. M van 6 con van 5 van ong. Cho quat chay roi t t m van 5 e chnh lu lng kh vao cot.

ng vi moi gia tr lu lng kh a chon ta oc (Pck tren ap ke U theo mmH2O. o xong tat quat, ngh 5 phut.

7) o o giam ap khi cot t:

M quat va ieu chnh lu lng kh qua cot khoang 15 20%.

M van 1 va cho bm chay. Dung van VL tai lu lng ke e chnh lu lng long (lu lng ke long co vach chia 0,1; 0,2; ;1,6). Neu VL a m toi a ma phao van khong len th dung van 1 e tang lng long.

ng vi lu lng long a chon (v du: 0,1; 0,2) co nh, ta chnh lu lng kh va oc o giam ap (Pc giong nh (Pck trc o. Chu y la tang lng kh en iem lut th thoi.

Chu y:

1) Trong qua trnh o o giam ap cua cot t can canh gi mc long ay cot luon on nh chieu cao ay bang cach chnh van 4. Neu can, tang cng van 2 e nc trong cot thoat ve bnh cha (van 2 dung e xa nhanh khi giam lu lng kh).

2) Khi tat may phai tat bm long BL trc, m toi a van 4 sau o tat quat BK.

3) Neu s xuat e nc tran vao ong dan kh th m van xa nc pha bang.

IV. KET QUA TH NGHIEM:

Bang 1: Cac tr so ket qua khi cot kho L = 0G%G (kg/m2.s) Pck (mm H2O)Pck (N/m2)Pck/Z (N/m)fckRecklogGlogPck/Z

100.085219.632.670.73747.469-1.0711.514

150.127329.4491.62070.925-0.8961.690

200.169439.265.331.53094.380-0.7721.815

250.211878.4130.671.464117.836-0.6762.116

300.2541098163.331.411141.850-0.5952.213

350.29614137.2228.671.368165.305-0.5292.359

400.33816156.8261.331.332188.761-0.4712.417

450.3820196326.671.301212.216-0.4202.514

500.42323225.4375.671.274236.230-0.3742.575

550.46527264.64411.250259.686-0.3332.644

600.50733323.45391.229283.141-0.2952.732

650.5538372.4620.671.209307.155-0.2602.793

700.59244431.2718.671.191330.611-0.2282.857

750.63449480.2800.331.175354.066-0.1982.903

800.67656548.8914.671.160377.522-0.1702.961

850.71963617.410291.146401.536-0.1433.012

900.76169676.211271.133424.991-0.1193.052

950.80378764.412741.121448.447-0.0953.105

1000.84589872.21453.671.109471.902-0.0733.162

o th LogPck/Z theo LogG vi L = 0

Bang 2: Cac tr so ket qua trng hp cot t L = 0,2

G%G (kg/m2.s)Pc (mm H2O)Pc (N/m2)Pc/Z (N/m)fcRec (kg/m2s)

100.085329.4491.10643.1041.500

150.127439.265.332.16043.1041.333

200.169658.8982.29543.1041.500

250.211988.21471.64743.1041.125

300.25414137.2228.671.97543.1041.400

350.29617166.6277.671.66143.1041.214

400.33820196326.671.66543.1041.250

450.3824235.23921.56143.1041.200

500.42329284.2473.671.60643.1041.261

550.46534333.2555.331.57443.1041.259

600.50737362.6604.331.37843.1041.121

650.5540392653.331.27343.1041.053

700.59243421.4702.331.16443.1040.977

750.634706861143.331.67943.1041.429

800.676102999.616662.11343.1041.821

850.7191041019.21698.671.89243.1041.651

900.76111010781796.671.80643.1041.594

950.8031141117.218621.63843.1041.462

1000.8451171146.619111.45843.1041.315

o th Pc/Z theo G vi L = 0.2

Bang 3: Cac tr so ket qua trng hp cot t L = 0,4 G%G (kg/m2.s) Pc (mm H2O)Pc (N/m2)Pc/Z (N/m)fcRec (kg/m2s)

100.085439.265.331.47486.2092.000

150.12754981.672.70086.2091.667

200.169768.6114.332.67886.2091.750

250.2111098163.331.83086.2091.250

300.25413127.4212.331.83486.2091.300

350.29620196326.671.95486.2091.429

400.33822215.6359.331.83286.2091.375

450.3828274.4457.331.82186.2091.400

500.42336352.85881.99486.2091.565

550.46552509.6849.332.40786.2091.926

600.50774725.21208.672.75686.2092.242

650.5579774.21290.332.51386.2092.079

700.59284823.213722.27486.2091.909

750.63494921.21535.332.25486.2091.918

800.6761071048.61747.672.21686.2091.911

850.7191281254.42090.672.32886.2092.032

900.7611461430.82384.672.39786.2092.116

950.8031641607.22678.672.35786.2092.103

1000.84517517152858.332.18186.2091.966

o th Pc/Z theo G vi L = 0.4

Bang 4: Cac tr so ket qua trng hp cot t L = 0,6 G%G (kg/m2.s) Pc (mm H2O)Pc (N/m2)Pc/Z (N/m)fcRec (kg/m2s)

100.08554981.671.843129.31292.500

150.127658.8983.240129.31292.000

200.169878.4130.673.060129.31292.000

250.21113127.4212.332.379129.31291.625

300.25417166.6277.672.399129.31291.700

350.29625245408.332.443129.31291.786

400.338302944902.498129.31291.875

450.3835343571.672.277129.31291.750

500.42354529.28822.991129.31292.348

550.46589872.21453.674.120129.31293.296

600.50793911.415193.464129.31292.818

650.5594921.21535.332.991129.31292.474

700.59298960.41600.672.653129.31292.227

750.6341161136.81894.672.782129.31292.367

800.6761461430.82384.673.024129.31292.607

850.7191641607.22678.672.983129.31292.603

900.7611871832.63054.333.071129.31292.710

950.8032262214.83691.333.248129.31292.897

gi tr G = 85% th hin tng lt bt uo th Pc/Z theo G vi L = 0.6

Bang 5: Cac tr so ket qua trng hp cot t L = 0,8 G%G (kg/m2.s) Pc (mm H2O)Pc (N/m2)Pc/Z (N/m)fcRec (kg/m2s)

100.08554981.671.843129.31292.500

150.127658.8983.240129.31292.000

200.169878.4130.673.060129.31292.000

250.21113127.4212.332.379129.31291.625

300.25417166.6277.672.399129.31291.700

350.29625245408.332.443129.31291.786

400.338302944902.498129.31291.875

450.3835343571.672.277129.31291.750

500.42354529.28822.991129.31292.348

550.46589872.21453.674.120129.31293.296

600.50793911.415193.464129.31292.818

650.5594921.21535.332.991129.31292.474

700.59298960.41600.672.653129.31292.227

750.6341161136.81894.672.782129.31292.367

800.6761461430.82384.673.024129.31292.607

850.7191641607.22678.672.983129.31292.603

900.7611871832.63054.333.071129.31292.710

950.8032262214.83691.333.248129.31292.897

gi tr G = 75% th hin tng lt bt u

o th Pc/Z theo G vi L = 0.8

o th

o th mo ta anh hng cua G (lu lng khong kh) len P/Z (chenh lech ap suat qua mot n v chieu cao) va tng quan so sanh gia cac lu lng chay L khac nhau

o th mo ta anh hng cua LogG len Log(P/Z) (o giam ap suat qua mot n v chieu cao) va tng quan so sanh gia cac lu lng chay L khac nhau

o th mo ta anh hng cua Re len logfck va logfc va tng quan so sanh gia cac lu lng L khac nhauo th mo ta quan he gia Log (he so phu thuoc vao mc o xoi ti cua dong long) va cac lu lng L tai mot vai v tr di iem gia trong ( ay chon cac v tr G = 20, 30, 40% lam v du) Bang 8: Cac tr so ket qua khi cot lut

L (galon/ph)G* (%)L (kg/s)L/G*G* (kg/m2.s)v (m/s)12log1log2

0.60.850.060.070590.8030.6441.8390.072931.62158-1.1371

0.80.750.0790.105330.8030.5632.57360.097241.51287-1.0122

Gian o lut cua cot log1 theo log2

Gian o lut cua cot chem

Bang 9: Cac ket qua, he thc thc nghiemMoi lien heKet qua thc nghiem

Pck/Z theo G tai L = 0

Pc/Z theo G tai L = 0.2Pc/Z theo G tai L = 0.4

Pc/Z theo G tai L = 0.6

Pc/Z theo G tai L = 0.8

Pc/Z theo G tai L = 1

Pc/Z theo G tai L = 1.2y = 1637.x2 + 155.3x + 8.959y = 3411.x2 + 367.4x + 37.88y = 3281.x2 - 7.168x + 46.79y = 3533.x2 + 148.1x + 50.76y = 8450.x2 - 1068.x + 189.8y = 9497.x2 - 1553.x + 213.4y = 14767x2 - 1296.x + 109.3

Moi lien heKet qua thc nghiem

Logfck theo Reck L = 0

Logfc theo Reck L = 0.2

Logfc theo Reck L = 0.4

Logfc theo Reck L = 0.6

Logfc theo Reck L = 0.8

Logfc theo Reck L = 1

Logfc theo Reck L = 1.2y = -0.238x + 0.976y = -0.342x + 1.414

y = -0.264x + 1.284y = -0.346x + 1.547

y = -0.321x + 1.551

y = -0.198x + 1.394

y = 0.092x + 0.947

Moi lien heKet qua thc nghiem

Log theo Ltai G = 20% : y = 5.410x - 0.003tai G = 30% : y = 6.431x + 0.08tai G = 40% : y = 4.827x + 0.128

V. BAN LUAN:

1. Da vao o th va so lieu thc nghiem ta thay:

oi vi cot kho: khi G tang th o giam ap tang theo ng thang.

oi vi cot t: khi G tang th o giam ap cung tang theo nhng chia thanh tng vung ro ret nh gian o trong ly thuyet a e cap. Khi lu lng long cang tang th cot cang de gan en iem lut hn. Sau iem gia trong th gia tr (P tang len rat nhanh, ot ngot. oan thang trong vung nay rat doc nen ta rat kho van hanh cot chem che o si bt nay mac du cot chem hoat ong tot nhat che o o.Thc t khi tin hanh thi nghim khi ti im lut ta dng thi nghim do o trn thi khng co vung sau im gia trong.2. Gian o f theo Re c lap e nham bieu dien s phu thuoc cua tr lc vao lu lng cua dong lu chat. Neu lu lng dong lu chat cang ln th he so ma sat f gia hai pha cang tang. Lap o th nham xac nh c lu lng hp ly e van hanh cot e tr lc nho va thu c hieu suat truyen khoi tot nhat gia hai pha vi nhau ma cot van khong b lut. Tuy nhien trong o th tren th ta lai thay ieu ngc lai tc la khi lu lng tang len th tr lc lai giam dan, ket qua nay thu c do anh hng cua sai so trong qua trnh th nghiem. Neu biet 1 trong hai gia tr Re hoac f th co the dung o th e xac nh gia tr con lai nh sau: T gia tr f hoac Re a biet, ke mot ng thang ng theo phng ngang hoac theo phng ng, cat o th f_Re tai mot iem. T giao iem o, ke mot ng thang vuong goc vi truc con lai th se xac nh c gia tr can tm.

3. S lien he gia cac oi tng tng oi gan vi vi d oan. Cu the la cac moi lien he sau:

Log((Pck/Z) va logG la phu thuoc tuyen tnh vi nhau theo ng thang giong nh ly thuyet a nhan nh.

(Pc/Z va G cung gan nh c chia thanh hai vung ro ret: vung di iem gia trong va vung tren iem gia trong. +Vung di iem gia trong th (P tang cham va eu an nen cac iem nay thu c gan nh cung nam tren mot ng thang. +Vung tren iem gia trong th (P tang nhanh, ot ngot nen oan thang rat doc; neu tang lu lng long va kh len cao na se tien en iem lut cua cot.

Log( va L: hoan toan phu thuoc tuyen tnh vi nhau nen c the hien thanh mot ng thang tren o th.

4. Tuy nhien trong qua trnh lam th nghiem cung co nhieu sai so. Nhng nguyen nhan dan en sai so co the la do:

Lu lng dong long khong on nh do bm

Lu lng dong kh khong on nh do quat

Cot nc duy tr ay cot khong am bao yeu cau lam cho nc xam nhap vao ong o o chenh ap lam anh hng en ket qua.

Sai so khi oc va trong thao tac th nghiem.

ieu kien th nghiem khong nh nhau cac lan o.

Chu y:

Khi chnh xong lu lng dong kh va dong long xong phai tien hanh oc ngay ket qua.

Gia qua trnh th nghiem phai dng khoang 10 phut e lam nguoi thiet b, on nh he thong roi mi tiep tuc van hanh thiet b.Neu s suat e nc tran vao ong dan kh th m van xa nc pha sau bang.VI. PHU LUC:

1. Tnh fck bang cong thc:

2. Tnh fc bang cong thc:

fc = (.fck3. Tnh Reck bang cong thc:

(: o nht cua khong kh lay 450C.

4. Tnh ( bang cong thc:

(Pc = (.(Pck

5. Tnh chuyen oi lu lng:

Lu lng kh:

V = 0.286 m3/ph

(K: khoi lng rieng cua dong kh lay 450C.

Tra c cac thong so cua dong kh:

(K = 1.1305 kg/m3

( = 1928.10-8kg/m.s

Lu lng long:

4.586 la he so quy oi t galon sang lt.(L: khoi lng rieng cua long lay nhiet o 30oCVi F: tiet dien cua cot chem, tnh bang cong thc:

0,0064 (m2)6. Tnh iem lut cua cot chem

Vi fck: he so ma sat cot kho

v: van toc dai cua dong kh ngay trc khi vao cot, m/s

v = G/FTrong o G: lu lng dong kh (m3/s)

td : o nht tng oi cua chat long so vi nc . Neu chat long la nc th td = 1.VII. TAI LIEU THAM KHAO:[1] Tap the CBGD bo mon May - Thiet b, Th nghiem Qua trnh-Thiet b, ai hoc Bach Khoa Tp.HCM.

[2] Giao trnh truyen khoi ,GS.TSKH.Nguyen Bin, ai hoc Bach khoa Ha Noi

[3] Vu Ba Minh, Truyen khoi, ai hoc Bach Khoa Tp.HCM.

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