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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
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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
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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
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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
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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
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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
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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
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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
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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.
9.1 Lng trong trng trng lc
9/62
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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
9.1 Lng trong trng trng lc
10/62
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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&=
9.1 Lng trong trng trng lc
22/62
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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 +=
9.1 Lng trong trng trng lc
23/62
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Thit b lng huyn ph (lng + rn)
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).
9.1 Lng trong trng trng lc
24/62
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Thit b lng huyn ph (lng + rn)
Thit b lng bn lin tc:
Hnh: Thit b lng 8 ngn.
Hnh: thit b lng c tm chn nghing.
9.1 Lng trong trng trng lc
25/62
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Thit b lng huyn ph (lng + rn)
Thit b lng bn lin tc:
9.1 Lng trong trng trng lc
26/62
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Thit b lng huyn ph (lng + rn)
Thit b lng bn lin tc:
9.1 Lng trong trng trng lc
27/62Hnh: Thit b lng hnh tr
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Thit b lng huyn ph (lng + rn)
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
9.1 Lng trong trng trng lc
28/62
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Thit b lng huyn ph (lng + rn)
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.
9.1 Lng trong trng trng lc
29/62
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Thit b lng huyn ph (lng + rn)
Thit b lng lin tc:
9.1 Lng trong trng trng lc
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
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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
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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
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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
===
9.2 Lng trong trng lc ly tm
34/62
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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
+
+=
9.2 Lng trong trng lc ly tm
35/62
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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
9.2 Lng trong trng lc ly tm
36/62
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Cyclone lng: Nguyn l cu to v lm vic:
9.2 Lng trong trng lc ly tm
37/62
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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
=
9.2 Lng trong trng lc ly tm
38/62
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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
=
&
9.2 Lng trong trng lc ly tm
-
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.
9.2 Lng trong trng lc ly tm
40/62
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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 ==&
&
9.2 Lng trong trng lc ly tm
41/62
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Cyclone lng h bi: Cc bc tnh thit k
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 =
9.2 Lng trong trng lc ly tm
42/62
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Cyclone lng h bi: Cc bc tnh thit k
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
9.2 Lng trong trng lc ly tm
43/62
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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
=
=
9.2 Lng trong trng lc ly tm
44/62
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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
=
=
&&
9.2 Lng trong trng lc ly tm
45/62
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Cyclone lng h bi: Chn cyclone theo catalogue
9.2 Lng trong trng lc ly tm
46/62
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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.
9.2 Lng trong trng lc ly tm
Hnh: Ghp nhiu cyclone n hot ng song song 47/62
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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%.
9.2 Lng trong trng lc ly tm
48/62
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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
9.2 Lng trong trng lc ly tm
49/62
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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
9.2 Lng trong trng lc ly tm
50/62
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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).
9.2 Lng trong trng lc ly tm
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
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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:
9.2 Lng trong trng lc ly tm
( )2m2r2
mmax RR
2p
=
= 1RR rm
g
R
mg
Rm
F
F avg2
avg
2
g
c
=
==
30
n=
2
RRR mravg
+=
52/62
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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:
9.2 Lng trong trng lc ly tm
+
=
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
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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
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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
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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.
9.3 Lng trong trng tnh in
57/62
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Cc dng thit b: phn thn dng tr hay hp, phn cha cndng chp nn.
9.3 Lng trong trng tnh in
58/62
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Phn loi: Lng tnh in kh v t
9.3 Lng trong trng tnh in
Figure: Dry type Electrostatic precipitator59/62
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Phn loi: Lng tnh in kh v t
9.3 Lng trong trng tnh in
WESP 60/62
-
H thng x l kh thi t l t dng lng tnh in kh:
9.3 Lng trong trng tnh in
61/62
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9.4 Tr lng
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