Phương pháp lắng

Chng 9Phn Ring Cc H Khng ng Nht

Bng Phng php Lng

Trnh by khi nim v phn loi h khng ng nht (KN).Gii thiu cc qu trnh lng (lng trng lc, lng ly tm v lngtnh in) v cc loi thit b lng (cu to, nguyn l lm vic vthng s tnh ton c bn) tch ring tng pha ca cc hKN (h bi, huyn ph).

Hong Minh Nam

Nguyn Hu Hiu

1/62

9.0 H khng ng nhtH khng ng nht (KN) hay h d th: hn hp kh hay lngc ln cc ht rn hay lng.Phn ring h KN: tch cc ht rn hay lng l lng ra khi h.Mc ch:

Thu hi cc ht (nu c gi tr kinh t cao); Ngn nga khng to thnh cc hp cht gy nh

hng n qu trnh hay thit b tip theo; X l kh hay lng trc khi thi ra mi trng.

c trng ca h KN:o S pha: 2;o Pha phn tn (pha trong): ht rn hay lng phn tn trong

mi trng kh hay lng khc;o Pha lin tc (pha ngoi): bao quanh cc ht rn hay git

lng phn tn, l mi trng pha kia phn tn vo.Phn loi:

H kh KN phn ring h kh KN H lng KN phn ring h lng KN 2/62

9.0 H khng ng nhtH kh KN: ht rn hoc lng trong mi trng khPhn loi: da vo s hnh thnh H c hc: bi (ht rn hoc cht lng) phn tn trong mi

trng kh do qu trnh c hc (p, nghin, sng, trn),phun,... Kch thc bi: 550m;

H ngng t: ht kh hoc hi dng rn hoc lng trong mitrng kh do qu trnh ngng t hi, phn ng gia hai kh,sy, chy,... Kch thc ht: 0,30,001m;o Khi = kh dng rn/khng kh: do chy khng hon ton v ngng t

hi nco Sng m = hi dng lng/khng kh: ngng t hi nc thnh git mn

trong khng kh

c im: (Ht+ht)/h ngng t Ht ln/h c hc; Ht ln/h c chy ht nh/h ngng t; dht < 1m: chuyn ng hn lon (chuyn ng Brown); dht < 0,1m: khng b lng di tc dng ca trng lc l lng.

3/62

9.0 H khng ng nhtH kh KN: Cc ht bi c kch thc nm gia h c hc v h ngng t

Cc phng php phn ring C hc: lc c hc, trng trng, ly tm; t: h c thi hoc sc qua lp cht lng; Lc: kh + bi vt ngn xp (gi bi) kh sch in trng: kh + bi in trng c in th cao (bi

b lng) kh sch. 4/62

9.0 H khng ng nhtH lng KN: rn, lng hoc kh l lng trong mi trng lng.Phn loi:

H huyn ph: rn/lng; H nh tng: lng/lng; H bt: kh/lng.

Huyn ph:o Ph bin trong cng nghip v k thut;o nht = f(nng , kch thc pha rn);o Da vo kch thc ht:o Huyn ph th: dht > 100 mo Huyn ph mn: 0,5 m < dht < 100 m, quan st qua knh

hin vi v cc ht chuyn ng Browno Cht lng c: dht = 0,1 m, mc phn tn ht ln,

chuyn ng Brown mnh, khng lng di tc dng catrng lc

o Dung dch keo: dht < 0,1 m dphn t5/62

H lng KN:Nh tng:

Khng bn, d phn lp di tc dng ca trng lc (chtlng c nh trn v cht lng c ln di to b mtphn pha)

Cht tr nh: tng bn cho h, c tc dng to v b mtcc ht lng ngn s lin kt b mt

Pha phn tn v pha lin tc c th chuyn ha ln nhau tyvo nng pha phn tn

nht = f(nng pha phn tn), khi max c nng chuyn pha

Cc phng php phn ring: lng, lc v ly tm

9.0 H khng ng nht

6/62

9.1 Lng trong trng trng lc(gravity settling processes)

Kt qu ca qu trnh lng thu c pha lin tc l pha lng(nc trong) hoc pha kh (kh sch) v pha phn tn dng cnlng.Vn tc lngLng t do ca mt tp hp ht ng nht, n nh: trong qutrnh lng cc ht cn khng thay i hnh dng, kch thc,khng va chm vo nhau v vo thnh bnh.Kho st qu trnh ri ca mt ht cn hnh cu tm hiu ctrng cho qu trnh lng ca cc ht cn trng thi ny.

Lng (settling/sedimentation/precipitation)l qu trnh phn ring da vo s khcnhau v khi lng ring v kch thcca hai pha di tc dng ca trng lc(trng lc, ly tm, tnh in,...).

7/62

Xc nh vn tc lng, vsXt ht hnh cu c khi lng m v ng knh d.Trong mi trng lu cht tnh: t = 0; tc ri ca ht, v = 0 vv tng dn di tc dng ca lc trng trng, Fg, ng thi xuthin lc cn ca mi trng vi b mt ht, Fd. Ngoi ra, c lcy Archimedes, FA.Phng trnh chuyn ng ca ht

gVF;2

vSF;gVF

dt

dvmF

pfA

2

fpdppg

A,d,gi

i

=

==

==

p, f: khi lng ring ca ht v lu cht; Vp: th tch ht; : h s tr lc,ph thuc vo ch chy v hnh dng ht; Sp: tit din ln nht ca httheo phng vung gc vi hng chuyn ng; v: vn tc ca ht.

Fg

Fd

FA

6

dV

4

dS

3

p

2

p

=

=

9.1 Lng trong trng trng lc

8/62

Xc nh vn tc lng, vsg t = 0: Fd = 0 (cha chuyn ng, = 0)

Ht c kch thc khng i, vn tc ri ca ht s tng dn theothi gian: t > 0: Fd 0 v tng dn n khi: Fd = F, ht t trng thi cnbng v lng vi vn tc khng i vs (vn tc lng). Thi gian ht c vn tc lng l rt ngn (0,20,5 s) so vi tng thi gianlng.

( ) gVFFF pfpAg ==

( )

( )s/m,

dg

3

4v

gV2

vSFF

f

fp

sg

pfp

2

sgf

pd

=

=

=

Ht hnh cu, vn tc lng:

Fd

F

d

Vn tc lng: vn tc khng i ca ht ri trongmi trng lu cht tnh trng thi cn bng lc.


9/62

Xc nh vn tc lng, vsgVn tc lng: vn tc khng i ca ht ri trong mi trnglu cht tnh trng thi cn bng lc.

c im ca vsg:

vs vb: vn tc lng l vn tc ri u ca ht trong mi trng lu chtng yn, vn tc cn bng l vn tc chuyn ng ca dng lu cht aht vo trng thi l lng (tng si).

vs = f(d, p, Re)

ng knh ht, d:

Ht hnh cu: d = dh; Ht hnh khng cu (bt k):: h s hnh dng ht. 1,3trn; 1,52gc cnh; 1,72di kim; 2,33bn mng.

Ht c kch thc khc nhau:

n: s c ht trong khi ht, xi: phn khi lng ca c ht di.

f

sg

f

sgf dvdvRe

=

= Ch lng

3pe V24,1dd ==

==

n

1 i

i

e

d

x

1dd


10/62

Xc nh vn tc lng, vsg: theo ch lng da vo Re Lng dng (lng theo Stokes): lc cn ca mi trng tun

theo nh lut Stokes.

Lng qu (lng theo Alen): lc cn ca mi trng tuntheo cng thc Alen.

Lng chy ri (lng theo Newton-Rittinger):

Da vo chun s Archimedes (Ar)

( ) s/m,18

gdvdv3F;

Re

24;2,0Re fp

f

2

sgsgfd === f: lng chm v p < f: lng ni

B mt lng:

Th tch huyn ph trong thit b:

( )fpsg fv =

max,sg

ss

v

VA

&

=

ssm VtV&=


22/62

Thit b lng huyn ph (lng + rn)

Thit b lng gin on: Tnh thng s thit b

Th tch thit b:

ts: thi gian lng (s), 0,8: h s cha y

Thit b lng dng tr vi ng knh:

Thit b lng dng khi: tit din ch nht, chn trc chiurng W Chiu di thit b:

Chiu cao thit b:

H1: chiu cao phn lng, H2: chiu cao phn cha cn

Phn cha cn thng c thit k dng nn d tho cn.

3ssmTB m,

VtVV

=

=

&

m,A4

D sTB =

m,W

AL =

m,HHH 21 +=


23/62


Thit b lng bn lin tc:

Nguyn tc lm vic: dng huyn ph c np v dng nctrong c tho lin tc, nhng cn c tho theo chu k.

Huynph

Nctrong

tng nng sut thit b vgim kch thc: to b mtlng bi cc tm chnnghing (thit b dng hnhkhi) hoc cc chp hnh nnxp chng ln nhau (thit bdng tr).


24/62



Hnh: Thit b lng 8 ngn.

Hnh: thit b lng c tm chn nghing.


25/62




26/62




27/62Hnh: Thit b lng hnh tr


Thit b lng lin tc: nhp liu, tho nc trong v ly cn c thchin lin tc. Thu cn: dng kh nn hoc dng co gt.

Hnh: Thit b lng kiu rng co.

1. B lng

2. Mng

3. Bnh rng truyn ng

4. Cnh khuykiu rng co


28/62


Thit b lng lin tc:

Hnh: Thit b lng hnh phu.

. Phu cha

. a phn phi

. Mng chanc trong

. ng tho cn

5. ng dn khng kh nnHnh: Thit b lng x l

nc thi bnh vin.


29/62


Thit b lng lin tc:


30/62Hnh:

Trng lc ly tmLc ly tm:

To trng lc ly tm:Lng xycln (cyclone): dng hn hp quay xung quanh ngtm c nhLng ly tm (centrifugal): thng hnh tr cha cht lng quay xungquanh ng tm ca nChun s Frude (Fr): t s gia lc ly tm v lc trng trng

Yu t phn lynh gi sc mnh ca trng lc ly tm

=

=

==g

r

mg

rm

F

FFr

22

G

c

rmF 2c =

F

Hnh: To trnglc ly tm

9.2 Lng trong trng lc ly tm(centrifugal settling processes)

31/62

9.2 Lng trong trng lc ly tmTc lngTrong trng lc ly tm, ht cu chu tc dng ca cc lc:Lc ly tm:

Lc trng trng (b qua v ht b):Lc cn:

Lc Archimedes:

PT chuyn ng ca ht cu:

rVrmF 2pp2

c ==

mgFg =

2

vSF

2

fpd

=

rVF 2pfA =

2

vSr

dt

dv

2

vSrVrVF

dt

dvm

2

fp

p

fp2

2

fp

2

pf

2

pp

d,A,ci

i

=

==

=

32/62

Tc lngiu kin cn bng lc: ht chuyn ng vi tc khng i ltc lng.

Ch lng dng:

n: s vng quay trong 1 giy (1/s), vt: vn tc tip tuyn (m/s)

scvv0dt

dv==

Re

24,

dvRe

f

scf =

=

( ) s/m,vg

r

18

gdv sg

2

fp

f

2

sc =

=

rg

vrv,n2

2

tt ===

9.2 Lng trong trng lc ly tm

33/62

Tc lngCh lng qu :

Chun s Archimedes:

Ch lng chy ri:

d

Rev

Re

5,18,

9,13

ArRe

f

fsc6,0

715,0

==

=

( )2

f

ffp

3 gdAr

=

d

RevAr71,1Re;44,0

f

fsc

===


34/62

Tc lng thc: qu trnh lng ca cc ht cn chu nhhng ca nng th tch (hay phn th tch).

: h s hnh dng ht;1: h s lu n nng th tch,

: phn th tch, ; xp: phn khi lng ca pha rn tronghn hp;2: h s lu n nht:

f, p: nht ca pha lin tc v pha phn tn, h bi 2 = 1

21scsr vv =

+= 5,4)1(25,0 321

p

mpx

=

( )pf

pf

232

3

+

+=


35/62

Cyclone lng (cyclone settling/separator):Cu to v nguyn l lm vic:

Dng hn hp theo ng dn voca cyclone theo phng tiptuyn vi vn tc 1225 m/s. Dngquay trn trong rnh gia ng tmv v tr. Di tc dng ca lc lytm cc ht rn vng ra thnh thitb v lng xung y, cn pha lintc (kh sch) theo ng tm rangoi. Cn lng ri xung y, rinh van gi a ra ngoi. Van gic nhim v a cn lng ra,nhng khng cho kh i vocyclone.

Hnh: Cyclone lng bi

1. ng tm

2. V trlng

3. y nnthu cn

4. Ca vo

5. Ca thocn

Kh sch


36/62

Cyclone lng: Nguyn l cu to v lm vic:


37/62

Cyclone lng: Thng s k thutVn tc dng hn hp trong cyclone:

: bn knh quaytrung bnh

R1: bn knh ngoi ca ng tm,R2: bn knh trong ca v tr cyclone.

Thi gian lng:

S vng quay ca dng hn hp:

Kch thc ht b nht c th lng ch lng dng:

avgmc rv =

( ) 2RR

R/Rlg3,2

RRr 21

12

12avg

+=

=

sr

12sc

R

R sr

scv

RRt

v

drt

2

1

==

=2

tn sc

( )( ) avgfp

12

rn

RR9d

=


38/62

Cyclone lng: Thng s k thutB mt lng ca cyclone: b mt xung quanh ca v tr

H: chiu cao ca v tr cyclone.Bn knh v tr:

Tn tht p sut ca dng qua cyclone:

i vi cyclone, c = 60180v tc qui c

2

sr

mavgsc m,

v

VHr2A

&

==

m,

hv

Hv1

hv

Hv1R

R

t

sr

t

sr1

2 +

=

2

vp

2

qf

c

=

2

2

mq

R

Vv

=

&


Cyclone lng: c im C kt cu n gin Hiu qu phn ring cao Hiu sut phn tch =f(c tnh h phn ring, kch thc

cyclone, vn tc dng chy, kch thc hat,) Tng nng sut v hiu qu ca qu trnh phn ring th lm

tng yu t phn ly:

gr

v

g

r

tb

2

ttb

2

=

=

Phi gim bn knh trung bnh(rtb): ch to cc cyclone b,t thm cnh hng dng. Cccyclone nh to thnh t hp

cyclone.


40/62

Cyclone lng h bi: Cc bc tnh thit k

Thng dng cyclone theo ch lngdng. ng knh ht b nht c th lng:

Chn tc dng vo: vm,i = 1225 m/s

Chn t l chiu cao v chiu rng catit din ch nht ca vo: h/w = 24

Kch thc ca vo:

( )( )

avgfp

12

rn

RR9d

=

w/h

hw;

w/hv

Vv

Vh

i,m

mi,m

m ==&

&


41/62


Hnh: H Thng Lc Bi Cyclone

Chn tc dng kh ra:vm,o = 48 m/s

ng knh ng tm:

Chn b rng rnh gia ng tm vv tr:

Tc trung bnh ca dng chytrong cyclone (theo kinh nghim):

Bn knh ngoi ca ng tm:R1 = r1+

r1: bn knh trong v : chiu dy ng Bn knh trong ca v tr cyclone:

R2 = R1 + r

o,m

mct

v

V4d

=

&

wRRr 12 =

4,1

vv

i,m

avg,m =


42/62


Hnh: H Thng Lc Bi Cyclone

Tnh bn knh trung bnh ca vng quay dng kh trong cyclone. Tnh tc gc Tnh tc lng Tnh th tch phn lm vic ca cyclone:

Chiu cao v tr cyclone:

K = 1,25: h s d tr chiu cao Kim tra b mt lng v bn knhv tr Chiu cao phn nn cha cn:

;dc: ng knh l tho cn, = 50o60o: gc nghing nn

scmw tVV&=

( )2122w

RR

KVH

=

= tg2

dRH c2n


43/62

Cyclone lng h bi: Cc bc tnh thit k Tnh s vng quay ca dng hn hp Xc nh yu t phn ly

Kim tra ch lng v kchthc hat nng pha phntn (bi) trong kh sch ra khing tm xp

Tnh hiu sut ca cyclone Tnh vn tc qui c v tr lc

ca cyclone

gr

v

g

r

avg

2

avg,mavg

2

=

=


44/62

Cyclone lng h bi: Chn cyclone Cyclone l loi thit b lng c tiu chun ha. Cho trc t s p/f = 350750; = 60180 Tnh s b vn tc qui c

Tnh s b ng knh cyclone theo nng sut cho

Lm trn D v chn D theo catalogue Tnh li vn tc qui c

Tnh kim tra tr lc ca cyclone, nu p thuc khong choth t yu cu

Cc kch thc ca cyclone c cho trong catalogue theo D.

s/m 45,2v,p2

v 'qf

'

q

=

'

q

m'

2

'

v

V4R2D

==

&

2

2

m

2

mq

R

V

D

V4v

=

=

&&


45/62

Cyclone lng h bi: Chn cyclone theo catalogue


46/62

Cyclone lng h bi: Cc dng cycloneCyclone chm: khi yu cu nng sut phn ring lnghpnhiu cyclone n hot ng song song.Cyclone t hp: khi cn tng hiu qu ca qu trnh phn ring ghp nhiu cyclone thnh phn (kch thc b) hot ngsong song.


Hnh: Ghp nhiu cyclone n hot ng song song 47/62

Cyclone lng h bi: Cc dng cycloneCyclone t: khi cn tng hiu qu ca qu trnh lm schkhb tr thm h thng phun sng trong cyclone. Hiu sutlm sch rt cao: 99%.


48/62

Cyclone lng huyn ph (cyclone thy lc-hydrocyclone):c im:

4,037,0d

d

2

3 =

o Dng phn ring h lng-rn vi cyclone n hoc t hp;

o p sut dng vo cao, pm =23 at;o Qu trnh phn ring huyn ph trong cyclone

tng i phc tp, p dng vo ch tng nmt gi tr gii hn, vt qu gi tr ny th qutrnh phn ly s b nh tr;

o Hiu qu ca qu trnh phn ly ph thuc vot s:

d2: ng knh ng tho nc trong;d3: ng knh ca tho bn (huyn ph c).d3 =(0,1670,2)Dd2 =(0,140,3)DD: ng knh cyclone


49/62

Cyclone lng huyn ph (cyclone thy lc-hydrocyclone):Thng s c bn:ng knh ng vo:

: h s lu lngNng sut cyclone:

K: h s,

Cng sut my bm: to p sutcho cyclone hot ng

Hm: p lc ca huyn ph vo cyclone:

: hiu sut, 0,5; D = 300350 mm, lm m c huyn phD =100 mm, lm trong pha lng D= 1015 mm.

mm

m1

/p2

V4d

=

&

m3m pKDdV =&

m3

2

1

Dd22

dK

=

kW,1000

gHVN mmm

=&

m,g

pH

m

mm

= Hydrocyclone


50/62

My ly tm lng (settling centrifugal separator):Cu to v nguyn l lm vic: gm thng hnh tr quay xung quanhng tm vi vn tc gc . Thng quay c th t thng ng (my ly tmng-vertical decanter centrifuge) hoc nm ngang (my ly tm ngang-horizontal decanter centrifuge).


Hnh: My ly tm ng 3 chnKhi rotor quay, b mt thong ca cht lng lng parabol v vi ln th b mt nysong song vi thnh rotor.

Rm

RrMy ly tm ng

51/62

My ly tm lng (settling centrifugal separator): Loi ngThng s c bn:p sut ln nht ca cht lng tc dng ln rotor (thnh, y vnp) b qua ct p thy tnh:

Rr: bn knh trong ca rotor, Rm: bn knh b mt thong ca chtlng trong rotor,

: h s cha y, = h/H; H: chiu cao rotor, h: chiu cao banu ca cht lng.Yu t phn ly:

Tc gc:

Bn knh quay trung bnh ca khi cht lng:


( )2m2r2

mmax RR

2p

=

= 1RR rm

g

R

mg

Rm

F

F avg2

avg

2

g

c

=

==

30

n=

2

RRR mravg

+=

52/62

My ly tm lng (settling centrifugal separator): Loi ngThng s c bn:Nng sut:

J: nghing thy lc ca dng chyTc lng cc i:

Thi gian lng:

Quan h gia thi gian lng v tc lng cc i:


+

=

r

m4

m

2

m

2

r

4

m

4

r

f

fm

R

RlnRRR

4

R3R

2

J9V&

( )f

r

2

fp

2

max,sc18

Rdv

=

( )m

r

fp

22

fsc

R

Rln

d

18t

=

( )sc

mrrmax,sc

t

R/RlnRv =

53/62

My ly tm lng (settling centrifugal saparator): Loi nm ngang9.2 Lng trong trng lc ly tm

Khi rotor quay, b mt thong ca cht lng trong rotor l mt vng trn tm O1cch tm O ca rotor mt khong lch tm:

Trng tm ca khi cht lng t ti O2 cch tm O ca rotor khong

Khi ln, tm O1 s trng vi tm O v bn knh b mt thong ca chtlng trong rotor cng c tnh theo my ly tm ng.

Hnh: My ly tm nm ngang

2

ge

=

2

R1x

=

O1

O2

O e

x

54/62

Cu to v nguyn l lm vic

9.3 Lng trong trng tnh in (Electrostatic precipitator-ESP)

Gm mt bn in cc dng v m t song song v ni vi ngun in mtchiu. Gia hai bn in hnh thnh trng tnh in. Khi hiu in th gia haibn ln th cc phn t kh b ion ha s dch chuyn v bn cc tri du.Khi h kh bi chuyn ng ngang qua khng gian ca bn cc, cng b tchin v chuyn ng v cc dng v lng .

55/62

iu kin thc hin qu trnh Trng tnh in mnh to lc in trng (lc

coulomb); tch in cho h bi: 108 ion/cm3.

9.3 Lng trong trng tnh in

Tc lng:

n: s in t, e: in tchin t, E: in th intrng

d3

neEv

f

se =

56/62

Cc yu t nh hng: Kch thc v tnh cht vt l ca bi: ht cng ln th qu trnh

lng cng nhanh; iu kin phn ring: nng bi, nhit , m v tc

ca h bi; Hnh dng, kch thc v khong cch cc in cc.


57/62

Cc dng thit b: phn thn dng tr hay hp, phn cha cndng chp nn.


58/62

Phn loi: Lng tnh in kh v t


Figure: Dry type Electrostatic precipitator59/62

Phn loi: Lng tnh in kh v t


WESP 60/62

H thng x l kh thi t l t dng lng tnh in kh:


61/62

9.4 Tr lng

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