Ky Thuat Xu Ly Khi Thai

7/29/2019 Ky Thuat Xu Ly Khi Thai

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Bi ging: K Thut X L Kh Thi

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MC LC

MC LC ............................................................................................................................. 1Chng 1: NHIM KHNG KH ..................................................................................... 31.1 NGUN GC PHT SINH...................................................................................... 31.1.1 Ngun nhim t nhin ............................................................................................ 31.1.2 Ngun nhim nhn to ............................................................................................ 41.2 NH HNG CA CC CHT NHIM MI TRNG KHNG KH ........ 61.2.1 nh hng ca cc cht nhim n sc kho con ngi ....................................... 61.2.2 nh hng ca cc cht nhim n ng vt ......................................................... 71.2.3 nh hng ca cc cht nhim n thc vt .......................................................... 71.2.4 nh hng ca cc cht nhim n vt liu ........................................................... 81.2.5 Hu qu ton cu ca cht nhim khng kh .......................................................... 91.3 S LAN TRUYN CHT NHIM TRONG KHNG KH ............................. 13

Chng 2: CNG NGH X L BI ............................................................................... 192.1 KHI NIM CHUNG V BI V PHN LOI.................................................. 192.1.1 Khi nim................................................................................................................. 192.1.2 Phn loi .................................................................................................................. 202.1.3 Vn tc gii hn ca ht bi: ................................................................................... 202.1.4 Chiu cao hiu qu ca ng khi: ............................................................................ 212.2 BUNG LNG BI V THIT B LC BI QUN TNH ............................... 252.2.1 Bung lng. .............................................................................................................. 252.2.2 Thit b lc bi qun tnh. ........................................................................................ 292.3 THIT B LC BI LY TM ................................................................................ 302.3.1 Thit b lc bi ly tm kiu nm ngang ................................................................... 30

2.3.2 Thit b lc bi ly tm kiu ng. ............................................................................ 332.4 LI LC BI ....................................................................................................... 362.4.1 Gii thiu chung. ..................................................................................................... 362.4.2 Cc dng khc nhau ca li lc bi: ...................................................................... 372.5 THIT B LC BI BNG IN ......................................................................... 402.5.1 S cu to v nguyn l lm vic ........................................................................ 402.5.2 Sc ht tnh in - vn tc di chuyn ca ht bi .................................................... 422.5.3 Phn loi: ................................................................................................................. 432.5.4 Phng trnh ca thit b lc bi bng in: ............................................................ 432.5.5 Hiu qu lc theo c ht ca thit b lc bi bng in:.......................................... 452.6 THIT B LC BI KIU T. ........................................................................... 46

2.6.1 Bung phun - Thng ra kh rng. .......................................................................... 472.6.2 Thit b kh bi c lp m bng vt liu rng c ti nc. ............................ 472.6.3 Thit b lc bi (ra kh )c a cha nc si bt. ................................................. 50Chng 3: CC PHNG PHP X L KH THI CNG NGHIP .......................... 523.1 C S L THUYT CA CC QU TRNH X L KH THI ..................... 523.1.1 Hp th kh bng cht lng ...................................................................................... 523.1.2 Hp ph kh bng vt liu rn .................................................................................. 603.1.3 X l nhim bng qu trnh thiu t ................................................................... 703.1.4 X l nhim bng phng php sinh hc ............................................................. 793.2 CNG NGH X L KH SUNFUIOXIT SO2 ................................................. 863.2.1 Hp th kh SO2bng nc ..................................................................................... 863.2.2 X l kh SO2bng vi CaCO3hoc vi nung CaO........................................... 88


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3.2.3 X l SO2bng cht hp th hu c....................................................................... 903.2.4 X l SO2bng cc cht hp ph th rn ................................................................ 933.2.5 Hp ph kh SO2bng than hot tnh ...................................................................... 933.2.6 X l kh SO2bng than hot tnh c ti ncQu trnh LURGI ....................... 95

3.2.7 X l kh SO2bng nhm oxt kim ho................................................................. 963.2.8 X l kh SO2bng mangan oxt (MnO)................................................................. 983.2.9 X l kh SO2bng vi v olomit trn vo than nghin...................................... 1003.2.10 So snh li ch kinh t ca mt s phng php x l kh SO2 ............................ 1023.3 CNG NGH X L KH IHIRO SUNFUA H2S ........................................ 1033.3.1 X l H2S bng Natri cacbonat, amoni cacbonat, hoc kali phtpht ................... 1033.3.2 X l kh H2S bng dung dch amoniac ................................................................ 1053.3.3 X l kh H2S bng than hot tnh ......................................................................... 1053.3.4 X l H2Sbng cht hp ph st oxt Fe2O3 ......................................................... 1063.3.5 X l H2S bng Natri thioasenat Na4As2S5O2 ....................................................... 1083.3.6 X l H2S bng xt NaOH..................................................................................... 109

3.4 CNG NGH X L KH NIT OXIT NOx ..................................................... 1103.4.1 Hp th NOxbng dung dch amoni cacbonat....................................................... 1103.4.2 Hp th kh NOxbng nc................................................................................... 1113.4.3 Hp ph kh NOxbng silicagel, alumogel v than hot tnh................................ 1123.4.4 Gim thiu c xc tc lng kh NOxbng cc cht gy phn ng kh khc nhau....

........................................................................................................................... 1123.4.5 Gim thiu s pht sinh kh NOxbng cc iu chnh qu trnh chy .................. 1153.5 CNG NGH X L KH FLO V HP CHT CA FLO. ........................... 1163.5.1 Hp th kh florua bng nc. ............................................................................... 1163.5.2 Kh kh flo v florua bng dung dch xt NaOH. ................................................. 1173.6 CNG NGH X L KH CLO.......................................................................... 1183.6.1 Kh kh clo bng sa vi. ...................................................................................... 1183.6.2 X l kh clo theo phng php axit. .................................................................... 1203.7 CC PHNG PHP X L NHIM MI .................................................. 1213.7.1 Khi nim chung v mi v cc cht c mi ......................................................... 1213.7.2 Chng nhim mi i vi mi trng bn trong nh ......................................... 1233.7.3 X l nhim mi bng phng php hp th ..................................................... 1243.7.4 X l nhim mi bng phng php hp ph .................................................... 1243.7.5 X l nhim mi bng phng php thiu t ................................................... 124Ti Liu Tham Kho .......................................................................................................... 126


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Chng 1

NHIM KHNG KH

1.1 NGUN GC PHT SINHNgun gy nhim khng kh l ngun sinh ra cc cht nhim.Da vo ngun gc pht sinh: ta c ngun nhim t nhin v ngun nhim

nhn to

1.1.1 Ngun nhim t nhin1. nhim do hot ng ca ni laHot ng ca ni la phun ra mt lng khng l nham thch nng v nhiu

khi bi vi cc cht nhim nh tro bi, kh SO2, NOx, H2S, CH4c tc hi nngn v lu di ti mi trng. Khng kh cha bi s lan ta i rt xa do n c

phun ln rt cao.

2. nhim do chy rngChy rng do cc nguyn nhn t nhin cng nh cc hot ng thiu thc

ca con ngi. Khi rng b chy nhiu cht c hi bc ln v lan to ra mt khuvc rng ln nhiu khi vt ra khi bin gii quc gia c rng b chy. Cc cht nhim nh khi, bi, kh SOx NOx, CO, THC.

3. nhim do bo ctHin tng bo ct thng xy ra nhng vng t tr v kh khng c lp

ph thc vt c bit l sa mc. Ngoi vic gy ra nhim bi, n cn lm gimtm nhn.

4. nhim do i dngDo qu trnh bc hi nc bin v bi nc do sng p vo b c ko theo

mt lng mui (ch yu l NaCl v cn li l cc cht MgCl2, CaCl2, KBr) b gia vo t lin. Khng kh c nng mui cao s gy han g vt liu, ph hucng trnh xy dng.

5. nhim do thc vtCc cht nhim do thc vt sn sinh ra v lan to vo kh quyn l:

- Cc hp cht hu c d bay hi hydrocacbon. - Cc bo t thc vt, nm: chng thng c nng cc i vo ma h.- Phnhoa c kch thc t 10 n 50mCc chtny thng gy ra bnh d ng, bnh ng h hp i vi c th con

ngi.

6. nhim do phn hy cc cht hu c trong t nhin


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Do qu trnh ln men cc cht hu c khu vc bi rc, m ly ca vi sinh vts to ra cc kh nh metan (CH4), cc hp cht gy mi hi thi nh hp cht nit(ammoniac - NH3), hp cht lu hunh ( hydrosunfua - H2S, mecaptan) v thm chc c cc vi sinh vt.

7. nhim do cc cht phng x.Trong lng t c mt s khong sn v qung kim loi c kh nng phng xa.

Cng phng x cng mnh v cng gy nguy him cho con ngi khi nhngvt cht phng x c trong mi trng khng kh xung quanh.

8. nhim c ngun gc t v tr.C rt nhiu ht vt cht nh b xm nhp vo bu kh quyn ca tri t mt

cch thng xuyn lin tc. Bi v tr c mt trong lp kh quyn trn cao v hpth gn 50% nh sng mt tri v ch pht x li mt phn nh xung mt t.

Ngi ta chia cc ht bi v tr thnh hai nhm tu thuc vo thnh phn hohc ca chng:

- Bi t cc thin thch: cha cc nguyn t Na, Mg, Al, Si, K, Ca, Ti, Cr.- Bit cc Sierit (thin thch st, niken) cha Fe, Co, Ni.1.1.2 Ngun nhim nhn toNgun nhn to cng kh a dng, ch yu l do hot ng giao thng vn ti,

hot ng cng nghip (y l 2 ngun nhim chnh th), ngoi ra cn mtphn nh t sinh hot ca con ngi v hot ng nng nghip.

1.Ngun nhim giao thng vn ti.Sn sinh ra t ng khi, ng x ca xe c, my bay, tu b cha nhiu kh

CO, NO2 , NO , SO2 , SO3, ht bi Pb, benzen v cc dn xut ca benzen gy ungth

c im ni bt ca ngun nhim giao thng vn ti l ngun nhim rtthp, di ng, s lng ln nn rt kh kim sot.

2.Ngun nhim cng nghip.Do qu trnh t nhin liu thi ra cc cht c qua ng khi.

Do bc hi, r r, tht thot trn dy chuyn sn xut sn phm v trn ccng ng dn ti.

c im ca ngun thi t cc nh my l nng cht c hi rt cao v tptrung trong mt khng gian nh.

Mi ngnh sn xut c nhng cht nhim c trng ring ca ngnh .V d : - sn xut giy : bi , thit b nu dung dch sulfit : kh SO2 , SO3,

- sn xut thy tinh : l nu thy tinh : bi, NOx , SO2, - nh my thuc l : bi, mi hi v nictin

3.Ngun nhim t sinh hot ca con ngi.


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Ch yu l bp un v l si s dng nhin liu than , ci, du ha v kht, nhng nhn chung ngun ny nh ch gy nhim cc b.

Ngoi ra , vic ht thuc l cng l mt nguyn nhn gy nhim mi trngkhng kh, c hi n sc khe do to ra cc cht c nh : axeton, nphanil,nicotin v nhiu cht gy ung th.

Cng rnh, mi trng nc mt b nhim, bc hi hay phn hy to ra cckh gy mi hi nh : H2S , NH3 , CH4 Kh thot ra t cc h x.Cc cng trnh xy dng, khai thc gy nhim bi v ting n.

Nhn chung cc ngun nhim ny l nh nhng li gy ra nhim cc btrong mt nh hay trong mt phng.

4.Ngun nhim do hot ng nng nghipHot ng nng nghip to ra 15% tng s cc cht kh gy hiu ng nh knh

nh :+ CO2to ra do qu trnh t rng lm ry, do ha hon.

+ CH4 sinh ra t cc cnh ng m t hay t cc qu trnh phn gii ym khcht hu c nh : mn, phn gia sc Nhn xt:

V khi lng tuy ngun nhim nhn to t hn ngun nhim t nhinnhng li c hi hn rt nhiu do thi ra nhiu cht c hi hn v li gn khudn c ni c mt dn s ng.

Ngoi ra, cn c cc cch phn loi ngun nhim khc nh:Da vo tnh cht hot ng, gm c:

- Ngun pht thi lin tc- Ngun pht thi gin an- Ngunpht thi tht thngDa vo v tr thi, c hai loi:

- Ngun c nh: ng khi nh my, bp sinh hot, ni la- Ngundi ng: giao thng vn tiDa vo m hnh tnh ton, c 3loi:V cao:

- Ngun thp: h thng thng gi, xng sn xut- Nguncao: ng khi cao.V mt hnh th:

- Ngun im: ng khi- Ngun ng: ng giao thng mt xe chy ln,- Ngunmt: bi rc,V phng din nhit:


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- Ngun nng- Ngun ngui

1.2 NH HNG CA CC CHT NHIM MI TRNG KHNG KH Bt k mt cht no dng kh, lng hay rn khi thi vo mi trng khng kh

vi nng va gy nh hng trc tip n i sng v hot ng ca conngi, ng thc vt, n cc b mt v cnh quan mi trng u c gi l cht nhim

C 3 cch phn loi cht nhim khng kh:

Cch th nht: Da vo ngun gc pht sinh ngi ta chia cht nhim ralm hai loi:

- Cht nhim s cp: l cht nhim sinh ra trc tip ti ngun. Nh khi tthan th cht nhim s cp l: bi, SO2, CO, CO2, NO2

- Cht nhim th cp: l cht nhim sinh ra trong qu trnh bin i hoa1hc gia cc cht nhim s cp vi nhau hoc gia cc cht nhim s cp vicc cht c sn trong khng kh. V d nh H2SO3l cht nhim th cp sinh rado SO2tc dng vi H2O.

Cch th hai: Da vo trng thi vt l, cht nhim chia ra lm 3 loi:- Cht nhim dng rn: bi, khi- Cht nhim dng hi (lng): hi dung mi hu c, hi axit, hi thy

ngn

- Cht nhim dng kh: kh v c, kh hu c.. Cch th ba: Da vo kch thc cht nhim khng kh c chia ra lm 2

loi:

- Phn t: cc cht kh- Ht:bi, khi, sng1.2.1 nh hng ca cc cht nhim n sc kho con nginh hng ca cc cht nhim khng kh n sc kho con ngi: ph thuc

vo nng v thi gian tip xc.

Kh CO: l mt loi kh c do n phn ng mnh vi hng cu trong muv to ra cacboxyl hemoglobin (COHb) lm hn ch s trao i v vn chuyn oxyca mu i nui c th. i lc ca CO i vi hng cu gp 200 ln so vi oxi.Hng cu trong mu hp thu CO nhiu hay t ph thuc vo nng CO trongkhng kh, thi gian tip xc ca c th vi khng kh nhim v mc hotng ca c th.

Bnh thng nng COHb trong mu c gi mc 0.4% do kh CO snsinh bn trong c th khng ph thuc vo cc ngun bn ngoi. Khi hm lngCOHb trong mu t 2 5% bt u c du hiu nh hng n h thn kinh trung

ng. Khi hm lng COHb trong mu tng n 10 20% cc chc nng hot


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ng ca cc c quan khc nhau trong c th b tn thng. Nu hm lng COHbtng n 60% - tng ng vi nng kh CO trong khng kh l 1000ppm thtnh mng b nguy him v dn n t vong.

Kh CO khng li hu qu bnh l nghim trng lu di hoc gy ra khuyttt nng n i vi c th. ngi b nhim CO khi ri khi ni nhim, nng COHb trong mu gim dn do CO thot ra ngoi quang h hp.

Kh NOx: Tc hi ca NOxtng i chm v kh nhn bit, ch yu l gyra bnh mn tnh v ng h hp nh vim x phi mn tnh.

Kh SO2: c mi kht ngt ngt. Nhng ngi tip xc thng xuyn vikh SO2khong 5ppm hoc hn th nhy v mi gim. Nu tip xc nng caohn gy xut tit nc nhy v sng ty thnh kh qun.

Kh H2S: khng mu, d chy vc mi trng thi, gy chy nc mt; vimmt, vim tuyn h hp

Kh Cl: c mu xanh, mi hng cay. Gy hi i vi mt, da, ng h hp.ht th khng kh c Cl, s cm thy kh th, bng rt da, cay mt v nhn b m.

Kh NH3: trong khng kh tn ti dng lng, kh, khng mu, c mi khaihc. Lm vim da, vim mt v ng h hp.

Kh O3: Gy vim mt, chy nc nhy ng h hp, kh c hng, au u,lon nhp th.

Bi: Gy tn thng i vi mt, da, h h hp v h tiu ho. Gy ra bnhhen suyn, bnh phi

1.2.2 nh hng ca cc cht nhim n ng vtCc cht nhim khng kh thm nhp vo c th ng vt bng hai con

ng: con ng h hp do ht th khng kh b nhim v con ng tiu ha don c, l cy b nhim c.

Nhng cht nhim ch yu gy hi cho ng vt l:

Kh SO2: gy tn thng lp m trn cng ca b my h hp, gy bnh khthng v suy tim.

Kh CO: lm suy gim kh nng vn chuyn oxy ca hng cu trong mu. Kh HF: gy vim kh qun, vim phi cc loi chut lang v th. Vi

nng cao trn 8mg/m3HF c th gy cht do vim phi nng. Ngoi ra, khi n cc cha nhng hp cht ca flo, cc loi cu, b thng b hng rng.

1.2.3 nh hng ca cc cht nhim n thc vtThc vt c nhy cm vi nhim mi trng cao hn so vi ngi v ng

vt. S sinh trng bnh thng ca thc vt i hi phi c cc yu t: nhsng, nhit , m,cht dinh dng v trng thi thch hp ca t trng. Thnhng, nhim khng kh li ng vai tr quan trng trong s ph hy trng thicn bng ca cc yu t ny.


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trnh bng , gch, knh, sn khi c gi mnh, tng t nh qu trnh x l b mtbng my phun ct.

3.i vi vt liu sn:Lp sn trn b mt sn phm, thit b, dng c hoc cng trnh c th b tc

ng bi bi dng rn hoc lng c cha nhiu hp cht ha hc khc nhau, gy ras mi mn hoc phn ng phn hy cht sn. Tc hi gy ra trn c hai phngdin kinh t v m quan khng nhng i vi cng trnh v vt thng thng mcn i vi c cc tc phm ngh thut, hi ha.

Kh H2S trong khng kh nhim c phn ng trc tip vi cc hp cht cach trong sn to thnh PbS lm cho mu sn b xn ti.

4.i vi vt liu dt.Nhng nguyn liu dt vi nh bng, len, si tng hp l nhng vt liu

nhy cm vi cc cht nhim gc axit. Kh SO2lm gim bn do ca si, vi.Kh SO2cng c phn ng vi thuc nhum lm cho thuc nhum km cht lng,khng t c mu sc mong mun hoc h hng. Bi trong khng kh cng gytc hi ng k cho may mc, lm cho qun o bn nhanh, b mi mn nhanh,nht l khi bi c cha cc thnh phn nh SO2, H2S

Ngoi ra cng cn ni thm rng: cc yu t mi trng khc nh nhit , nhsng, m, gi cng tham gia vo vic gy tc hi cho sn phm dt may.

5.i vi vt liu in, in t.Nguyn nhn thng thng khin cho cc thit b in cng sut thp b trctrc l do bi bm trn cc cng tc tip xc, cu dao lm cho mch in khng

thng sut khi ng in. S vic c th nguy hi hn, nu trong bi c cha cchp cht n mn kim loi. Bi cng c th bm trn cc b phn cch in cang dy cao th, khi gp m, sng hoc ma, lp bi m c th tr thnh vtdn in v gy ra hin tng phng in rt nguy him. Ngi ta cng nhn thyrng: u bt paladium gc niken ca cng tcin b n mn v hnh thnh lp gmu xanh cch in. Kt qu ny do thnh phn nitrat c mt trong bi gy nn.

6.i vi vt liu giy, da thuc, cao su.Kh SO2gy tc hi mnh i vi giy v da thuc, lm cho bn, dai cachng b gim st. Cn cao su th rt nhy cm vi ozon. Ozon lm cho cao su b

cng gin, gim sc bn v nt n.

1.2.5Hu qu ton cu ca cht nhim khng kh1.Ma axit.Maaxit l s kt hp ca ma, sng m, tuyt, ma vi axit sunfuric, axit

nitric c nng long (pH < 5,6). Oxit lu hunh, oxit nit sinh ra do qu trnh tchy cc nhin liu khong chng b oxi ha trong kh quyn trong thI gian di tvi gi n nhiu ngy v bin thnh axit sunfunric v axit nitric ri theo ma tuytri xung mt t. T nhng nm 1950, nc M xut hin cc trn ma axit.


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Nm 1979, Trung Quc, ma axit ln u tin xut hin, ch yu khu vc sngTrng Giang, pha ng cao nguyn Thanh Hi v bn a T Xuyn.

Thng thng, nu kh quyn han tan trong sch, khng b nhim bi ccloi kh SO

2v NO

xth pH ca nc ma khang 5.6 tc l thuc tnh axit do kh

CO2 trong kh quyn tc dng vi nc nc ma. Khi kh quyn b nhim khSO2 v NOxth pH nc ma s nh hn 5.6 v ta s c ma axit. Khi pH ca ncma nh hn 4.5 bt u c tc hi i vi c v thc vt.

Cc nguy hi ca ma axit ch yu l lm cho sng h b axit ho, cy ci bkh ho, cc loi c b cht, e do sc khe con ngi. Da vo di chuyn ca gi,my ma axit c th i t vng ny n vng khc nn phm vi nguy hi cng rngln.

- Rng b hy dit. Ma axit lm tn thng l cy, tr ngi qu trnh quanghp, lm cho l cy b vng a v ri rng. Ma axit lm cho cht dinh dng trong

t b tan mt, c tc dng ph hoi s c nh m ca vi sinh vt v s phn giicc cht hu c, lm gim mu m ca t. Ma axit cn cn tr s sinh trngca b r lm suy gim kh nng chng bnh v su hi. Ton chu u ckhong 14% rng b nhng cn ma axit tn ph, ring nc c b tn ph ti50%. Rng trn th gii b ma axit tn ph, tn tht v g hng nm vt qu10 t la.

- Nc h b axit ho. Ma axit lm nhim ngun nc trong h v phhng cc loi thc n, uy hip s sinh tn ca cc loi c v cc sinh vt khc tro ngnc. Thy in c hn 9 vn h th 22% h b axit ho vi mc khcnhau; 80% nc h ca min Nam Na Uy b axit ho.

- Sn lng nng nghip b gim. Ma axit l yu kh nng quang hp cacy, ph hoi cc t chc bn trong, khin cho cy trng mc rt kh khn. Maaxit cn c ch vic phn gii cc cht hu c v c nh m trong t, ra tri ccnguyn t dinh dng trong t (Ca, Mg, K) lm cho t b ngho ho. Theo iutra ca Nht Bn, ma axit lm mt s cy ng cc v la m b gim ti 30% snlng. Ma axit cn ho tan cc kim loi c hi (Hg, Cd, Al...) do lm gim gitr s dng cu sn phm nng nghip, thm ch khng th dng c.

SO2, NO2

SO2 nng, H2O H2SO4NO2 HNO3

Ma axit


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Hnh 1.1: Chu trnh to ma axit trong kh quyn

- Lm tn hi n sc kho con ngi. Kh SO2 l cht ch yu gy ra maaxit, rt nguy him cho sc khe con ngi. Khi ht phi SO2vi nng nht nhh hp s b kch thch mnh. Liu SO

2gy nguy him sau 30 n 60 pht ht th l

260-130 mg/m3. c tnh chung ca SOxl ri lon chuyn ho protein v ng,thiu vitamin B v C, c ch enzym oxydaza. Hp thu lng ln SO2c kh nnggy bnh cho h to huyt v to ra methemoglobin tng cng qu trnh xy haFe2+ thnh Fe3+.

- Gy ra n mn cc vt kin trc. Thnh c Aten ni ting, tng nhn s caAi cp, dob nhng trn ma axit m ngy cng b xm thc hng dn.

2.Hiu ng nh knh.Bc x cc i t mt tri xung tri t l bc x sng ngn gm cc tia trng

thy c bc sng = 0,4 0,8m, cc tia cc tm = 0,1 0,4m v mt phn cctia cn hng ngoi = 0,8 5m.

Bc x cc i t mt t vo bu tri l bc x sng di thuc vng hngngoi c bc sng t = 3 60m.

Cc cht nhim khng kh nh CO2, CH4, N2O, CFC (cloroflorocacbon), O3v hi nc l nhng cht gn nh trong sut i vi tia sng ngn, ngc li ivi cc bc x sng di, tia hng ngoi th chng hp th rt mnh.

Hiu ng nh knh chnh l hin tng cc cht nhim khng kh nh CO2,CH4, CFC, N2O, O3, hi nc cn tr, hp th nng lng bc x t mt t ri to

nhit vo bu kh quyn lm cho nhit kh quyn nng ln.Cc cht CO2, CH4, N2O, CFC, O3, hi nc c gi l kh nh knh.

S gia tng nhit do hiu ng nh knh c tc ng mnh m n nhiu mtca mi trng:

- Nhit tri t tng s lm bng tan v dng cao mc nc bin. Nh vynhiu vng sn xut lng thc tr ph, cc khu ng dn c, cc ng bng ln,nhiu o thp c th b chm di mc nc bin.

- Lm thay i iu kin sng bnh thng ca cc sinh vt. Mt s loi sinhvt thchnghi c s pht trin thun li. Trong khi nhiu loi s b thu hp

khng gian sng hoc b tiu dit do khng kp thch nghi vi nhng bin i mitrng sng.

- Kh hu ton cu s b bin i su sc, cc i kh hu c xu hn g dichuyn v pha hai cc ca tri t. Ton b iu kin sng ca cc quc gia b xotrn. Hot ng sn xut nng nghip, lm nghip, thu sn b nh hng nghimtrng.

- Nhiu loi bnh tt mi i vi con ngi xut hin, cc loi dch bnh lantrn, sc kho ca con ngi b suy gim.

Cc biu hin ca s bin i kh hu tri t:-

S nng ln ca kh quyn v tri t ni chung.


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- S thay i thnh phn cht lng kh quyn c hi cho mi trng sng cacon ngi v cc sinh vt trn tri t.

- S dng cao mc nc bin do tan bng dn ti s ngp ng ca cc vngt thp, cc o nh trn bin.

- S di chuyn cc i kh hu tn ti hng nghn nm trn cc vng khcnhau ca tri t, dn ti nguy c e do s sng ca cc loi sinh vt, cc h sinhthi v hot ng bnh thng khc ca con ngi.

- S thay i cng hot ng ca qu trnh hon lu kh quyn, chu trnhtun hon nc trong t nhin v cc chu trnh sinh a ho khc.

- S thay i nng sut sinh hc ca cc h sinh thi, cht lng v thnh phnca thu quyn, thch quyn, sinh quyn, th nhng quyn.

Gii php khc phuc:

Ti hi ngh thng nh v mi trng hp ti Rio Janero nm 1992, cc qucgia trn th gii thng qua Cng c khung v bin i kh hu ca Lin HpQuc. Cng c khung v bin i kh hu t ra mc tiu: n nh nng cckh nh knh trong kh quyn mc c th ngn nga c s can thip ca conngi i vi h thng kh hu. Mc n nh phi t mt khung thi gian chocc h sinh thi thch nghimt cch t nhin vi s thay i kh hu, m bo vicsn xut lng thc khng b e do v to kh nng pht trin kinh t mt cch bnvng. Cc quc gia tham gia cng c phi tun th 5 nguyn tc sau:

- Cc nc phi bo v h thng kh hu.-

Cn phi xem xt y nhng nhu cu ring v hon cnh c th ca ccnc ang pht trin.

- Cc nc phi thc hin nhng bin php phng nga, ngn nga v gimnh nguyn nhn gy bin i kh hu.

- Cc quc gia c quyn v phi y mnh s pht trin bn vng.- Cc quc gia phi hp tc y mnh mt h thng kinh t quc t m ca v

tng tr.Cng c khung v bin i kh hu t ra cc gii php nhm khc phc s nngln ca ton cu nh:

- Bo ton v nng cao kh nng ca cc b hp th kh nh knh nh: cc khurng nhit i v n i, cc sinh khi bin v i dng, cc h sinh thi bin,ven b v t lin khc.

- Hp tc trong vic chun b s thch ng vi cc tc ng ca s thay i khhu nh qun l tng hp vng b bin, qun l ti nguyn v nng nghip, phchi cc khu vc b nh hng bi hn hn, l lt v sa mc ho.

- Tng cng hp tc trong nghin cu v trao i thng tin khoa hc, cngngh, k thut, kinh t ca cc quc gia nng cao thm hiu bit v nguyn nhnv nh hng ca bin i kh hu cng nh hu qu kinh t x hi ca cc chin

lc ng ph vi bin i kh hu.


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- 13 -

- Tng cng v hp tc trong gio dc, o to v truyn b i chng linquan n bin i kh hu, ng thi khuyn khch s tham gia ca cng ng vo

bo v h thng kh hu ton cu.

3.S suy gim tng ozon.S r r v pht thi cc cht CFC (cloroflorocacbon),cacbon tetraclorua (CCl4)

l nguyn nhn chnh gy suy gim tng ozon.

Khi cc cht ny khuch tn n tng bnh lu th chng b tn cng bi cc t iacc tm v phn hu thnh cc nguyn t Cl. Chnh nguyn t Cl ny l nguynnhn gy suy gim tng ozon.

Cl + O3 = ClO + O2ClO + O3 = Cl + 2O2

Nh vy mt nguyn t Clo bin nhiu phn t O3 thnh O2thng thng.

Hu qu ca s suy gimtng ozon:- Tng kh nng mc bnh ung th da- Tng kh nng mc bnh v mt, c bit l bnh c thu tinh th. - Ph hu h thng min dch ca con ngi v ng vt. - Gim nng sut cy trng.- Lm mt cn bng h sinh thi ng thc vt bin.Cc gii phpbo v tng ozon:Trc s gia tng mc suy thoi tng ozon, cc quc gia trn TG k kt

Cng c vin v bo v tng ozon v Nghi nh th Montreal v cc cht lm suygim tng ozon.

Cng c vin c k kt nm 1985 gm 21 iu khon c mc ch c bn lxy dng hp tc v hnh ng quc t nhm nghin cu tng ozon, bo v tngozon trc cc hot ng ca con ngi v bo v sc kho con ngi trc nhngthay i ca tng ozon. Cc quc gia tham gia c nhim v:

- Hp tc trong quan trc, nghin cu, trao i thng tin hiu r v nh gitt hn nh hng ca cc hot ng con ngi ti tng ozon v nhng nh hngn sc kho con ngi v mi trng do bin i tng ozon.

- Chp nhn cc bin php v hp tc trong vic phi hp cc chnh sch kim sot, hn ch hoc ngn chn cc hot ng c nh hng c hi do s bini hoc gy ra s bin i tng ozon.

- Hp tc trong h thng ho cc bin php v tiu chun nht tr thchin cng c v cc vn bn km theo.

- Hp tc vi cc c quan quc t c thm quyn thi hnh c hiu qu cngc v cc vn bn lin quan.

1.3 S LAN TRUYNCHT NHIM TRONG KHNG KH


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- 14 -

Mt cht sau khi thi vo khng kh, chng s khuch tn i cc ni. Cc yu tiu kin kh hu, a hnh mt t v thnh phn kh v bi thi nh hngn s phn b cht nhim trong khng gian v theo thi gian.

a.nh hng ca gi:Gi hnh thnh cc chuyn ng ri ca khng kh trnb mt t ng vai tr chnh trong s pht tn cht nhim. Hai yu t quan trngcn quan tm l hng gi v tc gi. Nng cht nhim s tng khi tc gi gim

b.Nhit : nhit khng kh c nh hng n s phn b nng cht nhim trong khng kh tng gn mt t. tng ny thng thng cng ln caonhit cng gim nhng trong mt s trng hp c hin tng ngc li khicng ln cao (trong mt tm cao no ) nhit khng kh cng tng. Hin tngny gi l s nghch o nhit. Khi c nghch nhit khng kh tr nn rt n nhv cn tr mi chuyn ngthng ng ca tng b phn kh do lc ni gy ra.

n nh do nghch nhit to ra cn lm hn ch s trao i nng lng gi ca likhng kh st mt t vi gi cc lp kh quyn trn cao v do lm cn tr qutrnh khuch tn cc cht nhim theo c phng ng ln phng ngang m huqu l lm cn tr s pht tn gy nng m c ni gn mt t. Trong qu kh tng xy ra nhng ln c nghch o nhit mt vi vng li tc hi ln nhs kin ng c kh ca thnh ph Lun n.

Nghch o nhit c hnh thnh do nhiu nguyn nhn khc nhau:

- Lm lnh lp khng kh t bn trn.- Lm nng lp khng kh t bn di.- Chuyn ng ca dng khng kh lnh bn di lp khng kh m.- Chuyn ng ca dng khng kh m trn lp khng kh lnh.Nghch nhit do nguyn nhn th nhtgy ra l dng nghch nhit bc x. Dng

nghch nhit ny thng xut hin quanh nm vo na m n sng sm, nhng vma ng c th ko di c ban ngy khi nng lng bc x mt tri khng sc

ph v lp nghch nhit. c bit nhng vng kh hu lnh khi mt t c lptuyt bao ph, nghch nhit c th ko di t 5 7 ngy bi v tuyt phn x rt tttia nng mt tri ng thi l vt pht x mnh cc tia hng ngoi.

Nguyn nhn th haithng xut hin vng p sut cao khi c lp my che

ph trn bu tri v hp th nng lng bc x t mt tri chiu xung. Lp nghchnhit ny thng c cao t 400 500 m n 4000 5000 m trn mt t.Nguyn nhn th bal trng hp dng khng kh lnh t cc vng t cao vo

ban m trn xung cc thung lng to thnh lp khng kh lnh nm di lpkhng kh m v dn n nghch o nhit y thung lng. Trng hp ny nuc ngng t xy ra th lp sng gi s hnh thnh v lm cho nh nng mt tri vo

ban ngy khng th xuyn qua c, khi nghch nhit c th ko di vi ngy vch khi no c gi mnh hoc bo n mi b qut sch khi thung lng.

Nguyn nhn th tthng xy ra khi c dng khng kh t pha khut gi casn ni thi xung chn ni. Khng kh ny s c m ln theo qu trnh nn p


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- 15 -

on nhit v n len vo bn trn lp khng kh lnh st mt t di chn nigy ra hin tng nghch nhit vi cng mnh v c th ko di.

Ti cng mt a im v cng mt thi gian c th c hai lp nghch nhitcng song song tn ti: mt lp st mt t n cao 100 n 200m v mt lp cao t 900 n 1100m.

Tm li nghch nhit c th c hnh thnh v c tng cng trong cc iukin sau y:

Thi tit trong nm: v ma ng nghch nhit thng ko di do mt trikhng sc lm m mt t ph v lp nghch nhit.

Kh nng hp thu v nh nhit ca mt t: mt t tr tri khng c cy hpth v nh nhit nhanh hn so vi mt t c lp thc vt che ph do to iukin thun li cho vic hnh thnh nghch nhit. cng tng t nh vy khi mt tc lp tuyt bao ph.

Sng m, my nht l my thp v che knh bu tri lm cho bc x mt trikhng sc lm m mt t.

S di chuyn cc khi khng kh m hoc lnh t sn ni xung ng bnghoc t cc truyn t cao xung thung lng.

Tt c cc dng nghch nhit d st mt t hay trn cao u cn tr s xotrn ca kh quyn v do dn n s tch t cht nhim, lm cho nng cht nhim c th tng ln rt cao, gy tc hi nghim trng n mi trng sinh thi cakhu vc.

c.nh hng ca ma: Ma c tc dng lm sch mi trng khng kh, ccht ma s ko theo cc ht bi v ha tan mt s cht c hi trong khng kh riri xung t gy nhim t v nhim nc.

Nh vy, ma thc y vic loi b cc cht nhim ra khi khng kh nhngli gp phn chuyn cc cht nhim ny vo t, nc

Ma lm sch bi trn cc l cy, do lm tng kh nng ht bi ca cc dycy xanh cch ly bo v khu dn c.

d.nh hng ca sng m: Sng m dy c v ko di xc nh hin tnglng ng trong lp kh quyn ti mt t . y l yu t kh tng bt li cho skhuch tn cht nhim trong khng kh. Chng gp phn gy ra hin tng nghch

o nhit v chng c th l nguyn nhn to thnh khi m c hi. . c nhiu trng hp khi m gy tai nn th thm cho dn c. V vy tn shnh thnh, mt v n nh ca sng m mt a phng no cn c

phn tch cn thn trong vic thit k cc cng trnh x l kh thi v thi khe.a hnh mt t: nh hng n trng gi trong khu vc v do nh

hng n vic pht tn cht thi. Dng b mt, loi thm thc vt cng c nhhng n s pht tn cht thi.

ahnh, g gh ca mt t v cng trnh nh ca c nh hng rt ln nchuyn ng ngang ca khng kh trn mt t.

a hnh:


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- 16 -

Trng hp a hnh khng bng phng, trn nglan truyn lung khi gpvt cn c dng nh ni i, vc su, thng lng trng vn tc gi s b thayi, mc ri ca kh quyn b nh hng v do lung khi s b bin dng,ko theo l s phn b nng cht nhim trong lung khi cng nh trn mt

t b thay i. pha n gi ca sn i lung khi chuyn ng theo cc ng dng ca

khng kh v do c xu hng va va p vo sn i va b ht ngc ln cao,v vy nng cht nhim trn mt t s tng cao so vi trng hp a hnh

bng phng. pha khut gi ca ngn i, bc tranh cng phc tp hn do c hin tng

qun gi lm cho cht nhimb t ng li trong khu vc ny v khng lan ta raxa hn na.

Cng trnh, nh ca:Khi gi thi qua cng trnh, cc g sc cnh ca cng trnh s ht lung gi lncao to ra ri c cng v kch thc ln hn nhiu so vi ri t nhin ca

bn thn lung gi, lm cho lung gi c kh nng b thay i c vn tc ln chiuhng chuyn ng.

Nh ca, cng trnh gp phn lm thay i trng vn tc ca khng kh. pha trc cng trnh vn tc chuyn ng ca khng kh tng ln, pha sau vntc kh gim li to nn vng gi qun v phi n mt khong cch xa vn tc khmi t c gi tr ban u.

Cc vng gi qun s lm cho nng cht nhim tng cao ln, c bit lvi cc ngun nhim thp.

Vng gi qun (bng kh ng) phthuc vo cc yu t:

- Kch thc ca cng trnh, chiu cao nh, chiu rng nh. - Cng trnh ng c lp hay nm trong cm nh.- Khong cch gia cc cng trnh trong cm nh. - Hnggi thi: trng hp bt li nht l khi gi thi trc giao vi nh. V kch thc cng trnh ngi ta phn bit:

Nh hp: nu b rng nh b2.5 Hnh, trong Hnhchiu cao ca nh

Hnh 1.2 Lung khi lan truyn khi gp vt cn i ni


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Nh rng : nu b rng nh b>2.5 Hnh

V khong cch gia cc nh trong cm cng trnh: nu hai nh cch nhau trn

10 ln chiu cao ca ngi nh ng trc (theo chiu gi): ta c th xem nhngngi nh l ng c lp.

Di y l s bng kh ng ng vi cc trng hp khc nhau:

Hnh 1.3a: Nh hp ng c lp


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Hnh 1.3b: Nh rng ng c lp

Hnh 1.3c: Nh hp ng trc nh khc

Hnh 1.3d: Nh rng ng trc nh khc


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Chng 2

CNG NGH X L BI

2.1 KHI NIM CHUNG V BI V PHN LOI2.1.1 Khi nimCc phn t chtrn th ri rc c th c to ra trong cc qu trnh nghin,

ngng kt v cc phn ng ho hc khc nhau. Di tc dng ca cc dng khhoc khng kh, chng chuyn thnh trng thi l lng v trong nhng iu kinnht nh chng to thnh nhng vt cht m ngi ta gi l bi.

Bi l mt h thng gm hai pha: pha kh v pha rn ri rc - cc ht c kchthc nm trong khang t kch thc nguyn t n kch thc nhn thy c

bng mt thng, c kh nng tn ti l lng trong thi gian di ngn khc nhau.

Sol kh cng l h thng vt cht ri rc gm cc ht th rn v th lng dngl lng trong thi gian di khng hn nh. Tc lng chm ca cc ht sol kh rt

b. Nhng ht nh nht ca sol kh c kch thc gn bng kch thc cc nguyntln, cn nhng ht ln nht c kch thc khong 0,2 1m.

Khi nim v sol kh th c th ng ngha vi bi. Cc sol kh c th c kchthc ng nht hoc khng ng nht.

Kch thc ca ht bi c hiu l ng knh, di cnh ca ht hay lry, kch thc ln nht ca hnh chiu ca ht.

ng knh tng ng tca ht bi c hnh dng bt k l ng knh hnh

cu c th tch bng th tch ca ht bi. Vn tc lng chm vcca ht bi l vn tc ri ca ht trong mi trng tnh

di tcdng ca trng lc. vn tc lng chm ph thuc vo kch thc ca ht,hnh dng v khi lng n v ca n cng nh khi lng n v v nht cami trng.

ng knh lng chm cca ht bi l ng knh ht bi hnh cu m vn tcri v khi lng n v ca n bng vn tc ri v khi lng n v ca ht chnh dng phi chun ang xem xt.

ng knh lng chm ca ht c xc nh theo cng thc sau y rt ra t l

thuyt v s lng chm ca ht bi:

mH

b

C

,

)(

18107

Trong :: nht ng lc ca mi trng (kh, nc) Pa.s b, : khi lng n v ca bi v ca mi trng, g/cm

3

H: chiu cao ri (lng) ca ht, cmg: gia tc trng trng, m2/s

: thi gian ri, s


20/126


- 20 -

2.1.2 Phn loi1.Da vo ngun gc pht sinh:- Bi t nhin- Binhn to.2.Da vo thnh phn ha hc:- Bi v c:- Bihu c:3.Da vo kch thc ht:- Bi th, ct bi: gm t cc ht bi rn c kch thc ht > 75m.- Bi: ht cht rn c kch thc nh hn bi th (5 75m) c hnh thnh

t cc qu trnh c kh nh nghin, tn, p

- Khi: gm cc ht vt cht c th l rn hoc lng c to ra trong qutrnh t chy nhin liu hoc qu trnh ngng t c kch thc ht t 1 - 5m. Ht

bi c ny c tnh khuch tn rt n nh trong kh quyn.

- Khi mn: gm nhnght rn rt mn, kch thc ht < 1m- Sng: ht cht lng c kch thc < 10m. Loi ht ny mt nng

lm gim tm nhn th c gi l sng gi. Nhnght bi c tc hi nht i vi sc khe con ngi l khi chng c th

thm nhp su vo tn phi trong qu trnh h hp, kch thc < 10m. Ngi tagi c bi ny l bi h hp.

2.1.3 Vn tc gii hn ca ht bi:Vn tc gii hn ca mt ht bi c ng knh khi ri trong mi trng

c xc nh theo cng thc:

18

)( 2gv bgh

Khi ht bi ri trong khng kh rth khi lng n v ca khng kh nh hn

rt nhiu ln so vi khi lng n v b ca ht bi d ngi ta c th b quai lng v cng thc trn s tr thnh:

18

2gv bgh

Ta c th p dng cng thc trn tnh thi gian v khong cch lng ngca bi trn mt t t mt cao Hno ng vi vn tc gi cho trc. mt sgi thit phi a ra c th p dng cng thc trn cho ph hp:

- Ht bi dng hnh cu v tun theo nh lut Stokes- Chiu caoHca ng khi c xem l chiu cao hiu qu m ti ht bi

c vn tc ban u bng khng v bt u ri t do trong kh quyn


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Hnh 2.1: Lung khi t ngun im cao trong h trc xyz

- Bi thot ra khi ng khi c lm ngui tc khc n nhit mi trngxung quanh.

- Khng c xo trn mnh trc v trong khi riKhng c tc ng qua li gia cc ht bi c kch thc khc nhau.2.1.4 Chiu cao hiu qu ca ng khi:Trn hnh 2.1 th hin hnh dng ph bin ca ng khi. Ti ming ng khi,

nh vn tc pht, lung khi c mt ng nng ban u lm cho n c xu hngbc thng ng ln trn. Mt khc, do nhit ca khi cao hn nhit khng khxung quanh, lung khi chu tc dng ca lc ni do chn lch nhit gy ra.Cng vi lc nng, lung khi chu tc ng ca lc gi theo phng ngang do nh cao nht ca lung khi s nm cch ming ng khi mt khong cch nhtnh no xui theo chiu gi. Khi t cao y tc l lc ng nng ban u ca

lung khi b trit tiu v nhit khi tr nn cn bng vi nhit khquyn do ktqu ca qu trnh ho trn vi khng kh xung quanh, lung khi sgi phng nm ngang song song vi chiu gi.

Mt s cng thc tnh nng cao ca lung gi:

1. Cng thc ca Davidson W.FDa theo kt qu thc nghim tin hnh trn ng kh ng ca Bryant nm

1949, Davidson W.F a ra cng thc sau y c gi l cng thc BryantDavidson.

mT

T

uDh

khoi

),1()( 4.1

Cng thc trn c th phn bit thnh hai thnh phn:Thnh phn nng do vn tc ban u ca khi:


22/126


- 22 -

mu

Dhv ,)(4.1

V thnh phn do sc ni gy ra bi chn lch nhit :

mTT

uDh

khoi

t ,)(4.1

Trong cc cng thc trn:D- ng knh ming ng khi, m.

- vn tc ban u ca lung khi ti ming ng khi, m/s

u - vn tc gi, m/s

Tkhoi - nhit tuyt i cakhi ti ming ng khi, K.

T - chnh lch nhit gia khi v khng kh xung quanh, oC hoc K.

2. Cng thc ca Bosanquet- carey v Halton:Cng thc ca Bosanquet v cng s c da trn l thuyt kt hp vi thc

nghim, trong nng do ng nng v nng do chnh lch nhit l hms ca khong cch x k t chn ng khi xui theo chiu gi. Cc cng thc cxy dng cho iu kin trung tnh ca kh quyn.

nng cao do ng nng ban u:

)8,01(max,

max,x

hhh

v

vv

uL

uhv

1max,

43,01

77,4

nng cao do lc ni (chnh lch nhit ):

1

3

1137,6

Tu

zTgLht

Trong z l hm s ca X m:

157,3 L

uxX

Khi

1

1

12 L

T

gTu


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- 23 -

Hm s )(Xfz c cho di dng biu sau:

nng tng cng ca lung khi :tv hhh

V chiu cao hiu qu ca ng khi :

hhH 75,0

Trong :

L1lu lng khi thi nhit T1, m3/s

T1 nhit tuyt i m ti khi lng n v ca khi cn bng vi khilng n v ca khng kh xung quanh (mt cch gn ng c th xem T1 Txq)

11 TTT khi - hiu s gia nhit ca khi ti ming khi v nhit T1.

3. Cng thc ca Holland:Da vo kt qu kho st lung khi t nhng ng khi nh vng Oak Rige,

Holland J.Z. y ban nng lng nguyn t ca M a ra cng thc xc nh nngcao ca lung khi, c gi l cng thc Oak Rige :

uQDh h /)10.1,45,1(5

Dh, - tnh theo m

u - vn tc gi tnh theo m/s

Qh- cng nhit ca lung kh thi ra mi trng xung quanh:

scaltLCQ ph /,

Trong :

Cp- t nhit ng p ca khi, cal/kg.oC

- khi lng n v ca khi, kg/m3

t - chnh lch nhit ca khi v khng kh xung quanh, oC

Cng thc ny nn p dng cho iu kin trung tnh ca kh quyn. i vi iu kinn nh kt qu tnh cn tng thm 10 20%, ngc li trong iu kin kh quyn khng n

nh th gim bt 10 20%.

X

Z

0 20 40 60 80 100

2

4

6

8


24/126


- 24 -

4. Cng thc ca Briggs G.A.Cc phng php hin i xc nh nng ca lung kh trong iu kin kh

quyn n nh hon ton p ng c yu cu do c s l thuyt kh r rng v c thtin hnh quan trc, o c thc t tng i n gin b sung cho l thuyt. trong iukin n nh, giai on u ca s pht trin lung khi di tc dng ca lc ni, ri

bn trong ca lung chim u th so vi ca khng kh xung quanh. Tuy nhin trongiu kin trung tnh v khng n nh ca kh quyn, lung khi un ln nhng cui cngcng t c cao m ti ri bn ngoi tr nn ng k hn so vi ri bntrong lung . Lc lung khi ngng pht trin. Trng hp ny rt phc tp cho cngvic nghin cu v quan st , tuy nhin li l trng hp kh ph bin.

Briggs G.A (1975) nghin cu trng hp ni trn v a ra cng thc sau y pdng choiu kin c tc dng ca lc ni l ch yu:

mxu

Fh ,6,1 3/2

3/1

Trong :

F- lc ni ban u ca lung khi c xc nh theo cng thc:

342

/,4

smT

TTDgF

khoi

xqkhoi

xf- khong cch t ngun n im kt thc nng cao trung bnh ca lung khi:

KhiF< 55m4/s3 th xf= 50F0,625

KhiF 55m4/s3 th xf= 120F0,4Ring i vi cp trung tnh ca kh quyn, Briggs G.A cn a ra cng thc:

mhuu

Fh ,)

.(54.1 3/13/2

*

Trong : /* u gi l vn tc ma st. i vi mt t bng phng c thm c

hoc trng trt nng nghip smu /7.06.0*

h: chiu cao thc ca ng khi

Trng hp nghch nhit, cng thc Briggs c dng sau:

mu

Fh ,6.2

3/1

Khi tri ng gi, nng ca lung khi c xc nh theo cng thc:

mz

T

T

gFh ,)(1.5 8/34/1


25/126


- 25 -

5. Cng thc ca M.E. Berliand v ca mt s tc gi khc ca NgaCn c vo s liu thc nghim v so snh kt qu tnh ton nng cht nhim trn

mt t, Berliand v cng s (1964) a ra cng thc xc nh nng cao lung khi nhsau:

xqTu

TgL

u

Dh

3

1010

6.1875.1

Trong :10u - vn tc gi o c ct o gi trm kh tng, tc o cao

10m.

L - lu lng khi thi ti ming ng khi, m3/s

2.2 BUNG LNG BI V THIT B LC BI QUN TNH2.2.1 Bung lng.

1.Cuto v nguyn l hot ng:Nguyn tc hot ng: cc ht bi c gi li trong bung lng di tc dng

ca trng lc.

Bung lng c cu to rt n gin: l mt khng gian hnh hp c tit dinngang ln hn nhiu ln so vi tit din ng ng dn kh vo cho vn tc dngkh gim xung rt nh, nh th ht bi thi gian ri xung chm y ditc dng ca trng lc v b gi li trong .

Bung lng c p dng lng bi th c kch thc ht t 60 - 70m trln.

2.L thuyt tnh ton:a.Mt s quy nh v gi thit:Bung lng c cu to hnh hp nm ngang chiu di l, chiu caoHv b rng

B.

Hnh 2.1. Cc bung lng bi1- Kh vo; 2- Kh sch thot ra; 3- X bi; 4- Van iu chnh; 5- Ca dn v sinh

a) Bung lng n gin b) Bung lng nhiu sn

BH


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- 26 -

Vn tc dng kh mang bi trn ton b tit din ngang ca bung lng l un trng vn tc ca dng kh trong bung lng bi l khng i

Htbi chuyn ng ngang theo dng kh c vn tc bng vn tc dng kh.

Ht bi ri di tc dng ca trng lc theo phng thng ng khi chm cy trc im N ca bung lng coi nh b gi li trong bung lngNu L l lu lng dng kh - m3/s th vn tc chuyn ng ngang uca ht bi

s c xc nh theo cng thc sau:

BH

Lu , m/s

Thi gian lu li ca dng kh(ca bi) trong bung lng:

L

lBH

u

l , s

Khi ht bi thuc bt k loi vt liu g c ng knh ri vi vn tc vv ic mt an htrong thi gian xc nh th:Nu h < H: ht bi b dng kh mang theo ra ngoi phm vi ca bung lng.Nu h H: tt c cc ht bi c kch thc bng hoc ln hn u b gi li

trong bung lng.Nh vy t s h/Hng vi cc c ng knh khc nhau ca ht bi th hin

c phn bi c kch thc cho b gi li trong bung lng v t ta c thxc nh c hiu qu lc theo c ht ca bung lng.

Gi tr hc th xc nh theo cng thc sau:

TBvh , mi vi nhng ht bi c kch thc nh < 75m th:

18

)( 2gvv bghTB

Trong :

- nht ng lc ca mi trng kh, Pa.sb, - khi lng ring ca ht bi v ca khng kh, g/cm

3.

g - gia tc trng trng, m/s2.

ng knh b nht ca ht bi hay ng knh gii hn m bung lng c thgi li c ton b l:

gBl

L

gl

uH

bb

o)(

18

)(

18min

Ta c th phn bit cc trng hp sau: i vi ht bi c kch thc b th thi gian k t lc bt u ri n lc ht

bi t vn tc gii hn vghrt ngn so vi thi gian lu , lc ta c:vTB = vgh


27/126


- 27 -

i vi ht bi c kch thc ln hn th sau mt qung ng khng phi lqu ngn so vi ht bi mi t c vn tc ri gii hn vgh. Lc qungng ht bi ri cn c phn thnh hai on:

on u l on m ht bi ri c gia tc cho n lc vn tc ri t khong99% vgh.

on tip theo l on m ht bi ri vi vn tc vgh = const cho n cui thigia .

Nu trong khong thi gian ca dng kh trong bung lng m nhng ht biln cha kp t vn tc gii hn th ton b ng ri c ca chng u phixc nh theo vn tc tc thi:

)1(/ Z

ghgh eZvvh

b.Hiu qu:Gi thit rng mi c ht bi trong dng kh i vo bung lng c phn bu n trn ton tit din ngang ban u ca n, tc l s lng ht bi c bt k

t l thun theo chiu cao h, do nu gi () l hiu qu lc ca bung lng ivi c ht , ta s c:

%100)(

)( H

h

Trong h() l chiu cao ng vi ng knh ht; xc nh theocng thcsau:

glB

hL

b

18

T ta thu c biu thc hiu qu lng i vi c ht nh sau:

,%555,5 2)(

L

glBb

c.Bin php nng cao hiu qu lc ca bung lng :Mun nng cao hiu qu lc i vi mt c ht nht nh no th:

- Mt l h()phi tng trong khiH= const- Hai l gi h()khng i v gim chiu cao Hca bung lng vI iu kin

m bo nng sut lc tc lu lng kh cn lc khng thay i.Ta c th thc hin theo cch th 2 bng cch chia bung lng thnh nhiu tng

u nhau. Chiu cao ca mi tng lHiv lu lng i quaLiu gim xung theomt t l nh nhau.

Hiu qu lc s tng ln nln:u im: nh chia thnh nhiu tng nn kch thc ca bung lng c thu

gn, t chim din tch nhng vn lc c mt lu lng kh ln vi hiu sut lccao.

Nhc im: kh dn v sinh khi bi bm trn cc tng. i khi ngi ta phI

dng bin php phun nc p lc mnh ty ra.


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3.Cc dng khc ca bung lng bi:Trong thc t p dng bung lng vi nguyn l ri t do ca ht bi trong ch

chuyn ng chy tng ca khng kh l c nhiu hn ch l kch thc bunglng ln, lu lng khng kh cn lc khng c nhiu. khc phc cc nhcim ni trn G.S .V.V Baturin xut loi bung lng c tm chn thnh nhiungn:

Dng khng kh chuyn ng theo ng dch dc t ngn ny sang ngn khc,do ht bi khng nhng ri di tc dng ca trng lc m cn b va p vocc tm chn do lc qun tnh gy ra, nh m kch thc bung lng c gimnh v hiu qu lng tng cao.

Ngoi loi bung lng c tm chn thnh nhiu ngn, ta cn thy mt s loibung lng khc tn dng lc qun tnh ca nhiu tc gi khc nhau sau y:

Nh hnh 2.2a ngi ta s dng tm chn ca gi vo to ra s thay it ngt chiu hng chuyn ng ca dng kh, nh bi d tch ra khi dngkh v ri xung phu cha. gim bt tn tht p sut, ngi ta c th thay tmchn bng cc ngot cong ca cc ng dn kh vo v dn kh ra nh hnh 2.2b

Hnh 2.3: Thit b lng bi qun tnh

ac vch ngn; b- vi ch quay kh nhn; c- c chp m rng; d- nhp kh ngang hng.

Kh sch

Bi Bi

Kh schKhbi

dcba

Khbi

Bi

Kh sch

Kh bi

Bi

Kh bi

Kh sch

Kh vo Kh ra

Hnh 2.2 Bung lng c tm chn


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- 29 -

Bunglng c cu to cho hnh 2.2c, trong tc lng ng ca cc htbi kh c tng cng bi dng kh chuyn ng thng ng hng xung di.ng dn kh c dng hnh loa vi mc ch gim bt vn tc ca dng kh st y

bung lng loi tr kh nng lm cho bi lng ng y phu b bc ngc

tr ln.

2.2.2 Thit b lc bi qun tnh.Nguyn l c bn: lm thay i chiu hng chuyn ng ca dng kh mt

cch lin tc, lp i lp li bng nhiu loi vt cn c hnh dng khc nhau. Khidng kh i hng chuyn ng th bi do c sc qun tnh ln s gi hngchuyn ng ban u ca mnh v va p vo cc vt cnri b gi li hocmt ng nng v ri xung y thit b.

1. Thit b lc qun tnh Venturi:Khi dng chy b thu hp tit din th bi s b p st vo thnh vt cn v ltvo cc khe 2 ri vo by bi 3. ti y dng kh s b ht ngc tr lnri thot

ra ngoi, cn bi trong by 3th ri xung phu cha bi ca thit b.

2. Thit b lc bi kiu mn chn un cong:Dng kh i qua khe h gia cc tm chn ca dy trc s b chn li bi cc

tm chn ca dy ng sau v do 1o n s thay i hng chuyn ng theo ccg hnh vng cung ca tm chn i tip n cc dy tm chn tip theo. Trongqu trnh thay i hng chuyn ng, bi s b gi li trong lng mng v rixung phu cha bi ca thit b. tn tht ct p ca dng kh i qua thit b vokhong 10 25Pa.

Hnh 2.4: Thit b lc bi kiu qun tnh Venturi

Hnh 2.5: Thit b lc bi kiu mn chn un cong


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- 30 -

X bi

Kh clc bi

Kh mang bi

Tm l

sch

Hnh 2.6: Thit b lc bi qu tnh kiu l sch

3. Thit b lc qun tnhkiu l sch:

Trong thit b ny c t cctm chn song song nhau vcho gc vi hng chuynng ban u ca dng kh. Nhs thay i hng chuyn ngca dng kh mt cch t ngt,

bi s dn li ng thot vc x vo thng cha cngvi khong 10% lu lng khthi.

u im ni bt ca loi

thit b ny l tn tht p sut rtnh.Loi thit b ny thng

c s dng nh mt cp lcth t trc cp lc tinh khcnh xiclon, lc ti vi v.v..

2.3 THIT B LC BI LY TM2.3.1

Thit b lc bi ly tm kiu nm ngang

1.S cu to v nguyn l hot ng:Thit b lcbi ly tm kiu c cu to kh n gin. Thit b bao gm mt ng

bao hnh tr bn ngoi 1, bn trong c li hnh tr hai u bt trn v thon 2 mbo chy bc c tt. Khng kh mang bi i vo thit b c cc cnh hngdng 3 to thnh chuyn ng xoy. Lc ly tm sn sinh t dng chuyn ng xoytc dng ln cc ht bi v y chng ra xa li hnh tr ri chm vo thnh ng baov thot ra khe hnh vnh khn 4 ri vo ni tp trung bi.

Bi

Bi

Kh schthot raKh vo

3 1 2 4 6 5Qu o gii hn

Hnh 2.7: S cu to thit b lc bi kiu nm ngang


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- 31 -

Khng kh sch theo ng loa 5vi cnh hng dng kt hp vi van iu chnh6thot ra ngoi.

Nh vy dng kh i t u ny ra n u kia ca thit b trn cng mt chiu.Do ngi ta cn gi l thit b lc ly tm mt chiu.

Trn hnh 2.7 l cc dng ming, rnh hoc khe thot bi v kh sch ca thitb lc bi ly tm nm ngang:

2. L thuyt tnh ton:S n gin ha ca thit b lc bi ly tm kiu nm ngang phc v tnh

ton c th hin hnh 2.8:Cc kch thc chnh ca thit b:

1r -bn knh li hnh tr, m

Kh sch

a. b.

Khsch

Bi Bi

d.c.

Kh sch

Bi

Kh

sch

Tm chn hnhvnh khn

Kh schKhsch

Khsch

Bi

Bi

Bie. f. g.

Hnh 2.8: Cc dng ming, rnh, khe thot kh


32/126


- 32 -

Hnh 2.9: S n gin cathit b ly tm nm ngang

2r -bn knh ng bao hnh tr bn ngoi (v thit b), m

l- chiu di lm vic ca thit b, m Ta giLl lu lng th tch dng khng kh mang bi i vo thit b lc, m3/s

v l h s nht ng lc cakhng kh nhit tv p sut khquyn.

Dng khng kh i vo thit bnh cnh hng dng nn c vn tcquay l n vng/s.

Phng trnh qu o ca ht bitheo thng s :

)

9

2exp( 2220

nyy b

)( 212

2 rr

Lx

Vi y0l tung ban u ca htbi trn trc y ti mt ct u tin cathit b.

Kh thng s ta thu cphng trnh qu o ca ht bitrong h trc OXY: Kxeyy 0 vi

L

rrnK b

21

22223

9

2

ng knh gii hn ca ht bi:

)ln()(

5.4

1

2

22

1

2

2

3min r

r

lnrr

L

b

o

, m

minc ngha l ng knh bnht m ton b c ht ln hn hoc

bng ng knh ny s b gi lihon ton trong thit b lc v do ngi ta cn gi l ng knh gii hn ca ht bi.

Hiu sut lc theo c ht ca thit b:

%1002

1

2

2

22

2)(

rr

rr

Hoc:

%100

1

)exp(1

2

1

2

)(

r

r


33/126


- 33 -

%100)exp(1

)exp(12

2

)(

o

Vi:

L

rrlnb

21

2223

9

4

ng biu din hiu qu lc c dng nh sau:

2.3.2 Thit b lc bi ly tm kiu ng.1.Cu to v nguyn l lm vicThit b lc bi ly tm kiu ng

thng c gi l xiclon c cu to rt adng, nhng v ngyun tc c bn th baogm cc b phn hnh:

Khng kh mang bi i vo thit bng 1 ni theo phng tip tuyn vi thnhnh tr ng 2. Phn di ca thn hnhtr c phiu 3 v di cng ng x 4. Bntrong hnh tr c ng thot kh sch 5 lp

cng trc ng vi thn hnh tr.Nh ng dn 1 lp theo phng tip

tuyn, khng kh s c chuyn ng xoyc bn trong thn hnh tr ca xiclon vkhi chm vo ng y hnh phiu, dngkhng kh b di ngc tr ln nhng vngi c chuyn ng xoy c ri cui cng theo ng 5 thot ra ngoi.

Trong dng chuyn ng xoy c, cc ht bi chu tc dng bi lc ly tm lmcho chng c xu hng tin dn v pha thnh ng ca thn hnh tr ri chm vo

100

()%

o max 0

Kh bi

Kh sch

1

4

3

2

5

Dk

6a

6b

Hnh 2.10: xiclon


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- 34 -

, bt ng nng v ri xung y phiu. Trn ng x 4 ngi ta c lp van 6 x bi vo thng cha.

Thng thng y phiu c p sut m, do khi m van 6 khng kh bnngoi s b ht vo xiclon t di ln trn v c th lm cho bi lng ng y

phiu bay ngc ln v theo khng kh thot ra ngoi qua ng 5 lm mt tc dngca vic lc bi.

trnh tnh trng trn ngi ta dng van kp, trc khi x bi ngi ta ngvan 6a ri mi m van di 6b.

2.L thuyt tnh ton:S tnh ton cng nh cc

thnh phn vn tc chuyn ngttrong xiclon hon ton ging nh

trng hp thit b lc ly tm nmngang v do mi cng thc rt ra c i vi thit b lc lytm nm ngang u p dng ccho thit b ly tm kiu ng -xiclon.

iu khc bit cn lu y l trong cng thc thay vcho chiu di l ta dng chiu caolm vic Hpca xiclon:

1hHHp Trong :

H - chiu cao thn hnh tr ca xiclon, m.

h1 - chiu cao ng dn vo, m.Vn tc ban u vEca dng khng kh ng dn vo ti tit din a x b:

'ba

LvE

, m/s

S vng quay n ca dng khng kh trong thn xiclon:

)()17.0(

21 rrvn E

, vg/s

Thit b lc bi ly tm kiu ng - xiclon c cu to rt a dng, tu theo hngsn xut m kch thc tng i ca chng rt khc nhau. Mt khc nhiu tc gikhc nhau mc d cng da trn nguyn l chung ging nhau nhng a ra s tnh ton cng nh cch tip cn vn khng hon ton ging nhau, do c rtnhiu dng cng thc khc nhau xc nh ng knh gii hn oca ht bi mvi ng knh y chng b gi li ton b trong xiclon.

Mt s cng thc tiu biu xc nh o:

Rosin v cng s (1932):

Hx

Kh sch

Kh bi

h1

HtH

Dk

6a

6b

Hnh 2.11: xiclon


35/126


- 35 -

)21(3

2r

y

nv

yg

Eb

o

Lapple v cng s (1940):

Eb

onv

r

)(3 1

Gardiner:

Eb

onv

rr

)(

)(3 12

Davies (1952):

4

2

12 )(1

)(8

3

r

r

Hv

r

Eb

o

Muchlrad (1954):

)1

1(

3

2

32

4

2ff

f

rnv

gr

oEb

o

Kamenhep P.N (1959):

1

2ln3r

r

n b

Ko

Baturin V.V (1965):

Eb

onv

rr

)(3 12

Trong cc cng thc trn:

o - ng knh gii hn ca ht bi, m.

Hrr ,, 21 - ln lt l bn knh ng trong (ng thot kh sch), ng ngoi (vxiclon) v chiu cao, m.

y - khong cch ban u ca ht bi n thnh xiclon, m.

K

,,,

- ln lt l h s nht ng lc, h s nht ng, khi lng n vv trng lng n v ca khng kh: Pa.s, m2/s, kg/m3, kG/m3.

bb , - khi lng v trng lng n v ca bi: kg/m3, kG/m3.

Ev - vn tc khng kh ng dn vo xiclon, m/s. 2/21 rrro -bn knh trung bnh u vo ca xiclon, m.

2

1

rr

f- t s bn knh ng trong v ng ngoi ca xiclon.

n2 - vn tc gc ca dng khng kh trong xiclon, s-1.


36/126


- 36 -

2.4 LI LC BI2.4.1 Gii thiu chung.Cc c tnh quan trng ca li lc bi l: hiu qu lc, sc cn kh ng, thi

gian ca chu k hot ng trc khi thay mi hoc hon nguyn.Qu trnh lctrong li lc bi c th chia thnh hai giai an:Trong giai an u xy ra qu trnh gi bi trong lp li sch, trong lc

xem rng s thay i cu trc ca li lc do bi bm v do cc nguyn nhn khcl khng ng k. Giai an ny gi l giai an n nh, hiu qu lc v sc cnkh ng ca li lc trong giai an ny c xem nh khng thay i theo thigian. Giai an ny thng rt ngn ngi

Giai an hai ca qu trnh lc c gi l giai an khng n nh do s thayi cu trc ca lp li lc bi nhiu ht bi b gi li trong , nh hng ca

m hoc bi cc nguyn nhn khc lm cho sc cn kh ng v hiu qu lc cali lc thay i r rt.Vi li lc bi th cc ht c ng knh t 0.1 0.5m lt qua li nhiu

nht, cn cc ht c kch thc ln hn hoc nh hn li b gi li. Qu trnh gibi trong li lc din ra trn c s nhng hin tng sau y: Khi dng kh mangbi i qua li lc, cc ht bi tip cn vi cc si ca vt liu lc v ti xy racc tc ng tng h gia ht bi v vt liu lc. Cc tc ng tng h ny phthuc vo kch thc , vn tc ca ht, loi vt liu lc cng nh s c mt ca lctnh in, lc trng trng

Cc dng chnh ca tc ng tng h gia ht bi v vt liu lc l; va pqun tnh, thu bt do tip xc v khuch tn.

Cc yu t nh hng n hiu qu lc:nh hng ca kch thc ht bi.Qu trnh thu gi trong li lc ph thuc rt nhiu vo kch thc ht bi. i

vi ht bi c kch thc nh hn 0.3m th hin tng khuch tn ng vai tr chyu, cn bi c kch thc ln hn th hin tng tip xc v va p qun tnh mi

bt u pht huy tc dng.nh hng ca vn tc kh i qua li lc.Vn tc lc c nh hng tri ngc nhau i vi qu trnh thu gi bi v do

khuch tn v do va p qun tnh. nh hng ca ng knh si vt liu lc.ng knh ca si vt liu lc cng c nh hng quyt nh i vi qu trnh

thu gi bi do tt c cc tc ng gy ra. V d, h s lt li i vi bi c=0.65m qua li lc c c si D=1m nh hn 2000 ln so vi li lc c c siD=50m. V vy ch to li lc c hiu qu cao ngi ta c gng s dng loivt liu si nh nht c th c vi bn cho php. nh hng ca ln cht (rng) ca li lc.


37/126


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Khi ln cht ca vt liu si trong li lc tng th hiu qu thu gi bi docc tc ng va p qun tnh, va chm tip xc tng cao ng k, trong khi hiuqu do khuch tn ch thay i t.

2.4.2 Cc dng khc nhau ca li lc bi:1. Li lc kiu tm.Kt cu ca loi li lc ny rt n gin: gm mt khung hnh vung hoc ch

nht, hai mt l tm tn c l v gia xp nhiu tm li thp chng ln nhau to thnh nhiu l rng zc zc. Ngoi li thp, vt liu m c th c thay th

bng si kim loi ri, m xp bng si tng hp hoc khu s, khu kim loi, khunha. B dy ca vt liu trong tm li lc nm trong khong 50 100mm.

Qu trnh gi bi xy ra trong li lc kiu tm ch yu l di tc ng ca vap qun tnh. cho bi khng b cun theo dng kh sau khi bm trn si li,

ngi ta dng du cng nghip tm t ton b li lc lc ta c li lc kiutm tm du. Ngoi tc dng gi bi, du cn bo v cho li lc khng b han g.

Sau thi gian s dng khong 50 250h, khi bi bm nhiu lm cho sc cnkh ng ca li lc tng qu mc cho php, ngi ta lm sch li lc bng cchra trong nc x phng, phun nc p lc cao hoc ht bi. Sau lm kh vtm du mi dng tip.

Li lc kiu tm thng c s dng lc bi trong khng kh thi vo cah thng thng gi, iu ho khng kh vi nng bi ban u khng qu 5mg/m3.

2. Li lc tm du t ra.Loi li lc ny bao gm nhng tm lc bng li thp treo trn gung quay

tun t nhng cc tm lc vo mt thng ng du pha di ca thit b, nhth bi bm vo cc tm lc s b r ra v lng xung y thng du. nh k xcn trong thng du v b sung du mi. Tc quay ca gung t 1,8 3,5mm/ph, cng c loitc quay nhanh hn 1 3 mm/s. Nng sut lc t t 8000 10000 m3/m2h. Sc cn kh ng 100Pa. Hiu qu lc t 96 98%.

Thit b lc t ra c ch to thnh n nguyn din tch b mt lm vickhong 2 2,5 m2. c din tch b mt lc cn thit, ngi ta c th ghp nhiun nguyn li vi nhau.

3. Li lc kiu rul t cun.Vt liu s dng cho li lc kiu rul t cun l loi d th, xp, b dy 50

mm ( trng thi t do, khng b p). Tm vt liu lc di 20 30m c cunquanh mt trc t trong hp bn trn thit b lc v u kia c ci vo trc quay pha di ca thit b. Trc quay bn di c truyn ng bng ng c.

Tm lc c ta trn dn li thp cng vo khung ca thit b to thnh bmt lc dng kh i qua lun lun p tm lc vo dn li thp, lm cho tm lckhng b chng hay b x rch.

Trn li lc b tr u o (cm bin) chnh lch p sut gia hai mt ca tm

lc. khi chnh lch p sut t n gii hn quy nh, ng c s t ng quay v


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- 38 -

cun on tm lc ht kh nng lm vic tri ln thit b mt on tm lcmi. C nh vy cho n khi ton b cuc vt liu lc cun ht xung trc di.Lc ngi ta thay cun vt liu lc khc.

Li lc c th xem thuc loi thit b lc bi cp III, thng c s dngtrong cc h thng thng gi v iu ho khng kh mt cch c lp hoc c sdng nh cp lc th trc cc thit b lc cp II hoc cp I.

4. Li lc bng ti vi hoc ng tay o.Li lc bng ti vi c th lit vo thit b lc bi cp II vi hiu qu lc c

th thay i trong phm vi rt rng t 10 90% i vi c ht di micrmet.

a.Cu to:Li lc bng ti vi gm

nhiu ti vi dt t cc loi si

khc nhau nh si len, gai, sibng vi, si thu tinh lngvo khung li thp bo v.Trong cng nghip thngdng loi ti vi hnh ng vlp vo mt thit b hon chnhc km cc b phn c giihoc bn c gii gi bi vc gi l thit b lc ng tayo.

Thit b gm nhiu ngtay o c ng knh t 125 300mm, chiucao t 2 3.5mu di c lin kt vo bny c l trn bng ngknh ng tay o hoc lng vokhung v c ng u trn vo

bn c l.

b.Nguyn l hot ng:Kh cn lc c a vo phu cha bi ri theo cc ng ti vi i t trong rangoi hoc t ngoi vo trong i vo ng gp kh sch v thot ra ngoi. Khi bi

bm nhiu trn mt trong hoc mt ngoi ca ng tay o lm cho sc cn cachng tng cao nh hng n nng sut lc, ngi ta tin hnh hon nguyn bngcch rung gi bi kt hp vi thi kh ngc t ngoi vo trong ng tay o hoc

pht khng kh nn kiu xung lc khng kh i t trong ra ngoi ng tay o.

S rung lc chc khi ti sinh c hiu qu nht i vi cc ti vi theo hngdc, nhng nh vy ti vi b mn mnh, c bit phn di. S rung lc cn phingn v t ngt nhng khng qu mnh trnhnhng lc chc ln tc ng vovi.

Bi

Kh bi

Kh sch

Hnh 2.12: Lc tay o

ng gom kh sch

B phn gi bi

Phu cha bi

ng tay o


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Cng on rung lc cc ti vi theo phng dc nh sau: nng thanh treo ln 7 10 cm, sau cho ri t do t cao ny cng vi ti vi gy xc va p. Vicnng v th ti vi c lp i lp li 5 n 15 ln ph thuc vo cc tnh cht ca

bi. Phng php ti sinh ny kh hiu qu v s dng cho cc vi nng. S dao

ng cc ti vi nm ngang thng c s dng cho vi mng vi b mt nhn.Khi tin hnh ti sinh vi, lp bi lng bm bn ngoi b bong ra v rt xung

phu cha bi, nhng bn trong vi vn cn li mt lng ln bi nm gia cc siv bm trn x, do khi ti s dng thit b vn gic hiu sut lc cao.

Thit b lc c ch to thnh nhiu n nguyn v lp ghp nhiu nnguyn thnh mt h thng c nng sut lc p ng yu cu. h thng lmvic c lin tc, qu trnh hon nguyn c tin hnh nh k v tun t chotng n nguyn hoc tng nhm n nguyn trong lc cc n nguyn khc trongh thng vn lm vic theo chu k lc bnh thng. Kh thi ngc hay kh nn pht

ra trong qu trnh hon nguyn c dn sang cc n nguyn khc ca h thng nhp vo vi dng kh cn lc.Nng sut v hiu qu lc ca thit b lc ti vi hoc ng tay o ph thuc rt

nhiu vo cht liu vi lc.c. Tnh ton:Sc cn ca thit b lc khng nn vt qu 750 1500 Pa v ch trong trng

hp c bit c th cho php ln n 2 2.5 kPa. Khi sc cn tng cao c th xy rahin tng nh ng tay o b rch ng khu, b bt ra khi cc mi lin kt vihp thit b...

tnh mt cch gn ng din tch b mt lc yu cu, cn xc nh lu lngtng cng ca kh i qua thit b lc.Din tch b mt lc (b mt ca tt c cc ng tay o) c th xc nh theo

cng thc:

2

221

21 ,mSq

LLSSS

Trong :S1- din tch b mt lc ca tt c cc n nguyn cng lm vic ng

thi, m2.

S2din tch b mt vi lc ca cc n nguyn cn tin hnh chu khon nguyn, m2.

L1- lu lng kh cn lc c k n lng kh thm nhp vo thit bqua khe h, m3/ph.

L2 lu lng kh thi gi bi, m3/ph c th nhnphmSL /,)8.15.1( 322

q - nng sut lc n v ca vi lc, m3/m2.ph


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Tr s q c th nhn nh sau tu thuc vo loi vi lc:

Vi lc Len hoc vi bngsi

Vi bng si tnghp

Vi bng si thutinh

Nng sut lc nv q, m3/m2.ph 0.6 1.2 0.5 1 0.3 0.9

S lng ng tay o hoc s n nguyn thit b lc c xc nh theo cngthc:

0S

Sn

Trong S0din tch b mt ca mt ng tay o, hoc b mt lc ca mt nnguyn mt cch tng ng, m2.

2.5 THIT B LC BI BNG IN2.5.1 S cu to v nguyn

l lm vic

Thit b lc bi bng in gmmt dy kim loi nhn tit din b 1c cn theo trc ca ng kim loi2 nh c i trng 3.

Dy kim loi c cch in

hon ton vi cc b phn xungquanh ti v tr 4 v c np inmt chiu vi in th cao, khong50000V tr ln. l cc m cathit b. cc dng l ng kim loivao bc xung quanh cc m vc ni t. di in th cao mdy kim loi c np, n s to ra

bn trong ng cc dng mt intrng mnh v khi dng kh mang

bi i qua, nhng phn t kh trongdng kh s b ion ha ri truynin tch m (electron) cho ht bidi cc tc ng va p qun tnhv /hoc khuch tn ion. Nh thcc ht bi b ht v pha cc dng, ng li trn b mt trong ca ng hnh tr,mt tch in v ri xung phiu cha bi 5.

Ngoi loi thit b lc bi bng in kiu ng, ngi ta cn c th to ccdng ht bi bng cc tm bn t song song hai bn cc dy cc m v lc tac thit b lc bng in kiu tm bn.

Bi

Kh bn

Kh sch

1

2

3

4 5

Hnh 2.13. Thit b lc bi tnh in dng ng1- in cc lng; 2- in cc qung sng;

3- Khung; 4- B phn gi bi; 5- Cch in.


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Cc kiu thit b lc bi bng in ny gi l loi mt vng, tc l vng ion hav vng ht bi cng kt hp lm mt. Nhc im ca loi thit b ny l i hi

phi c ngun in cao p 50 100kV. Vi in p cao nh th nhng hin tngph khng mong mun thng xy ra nh to ra kh NOx, ozon v.v..v kh phc tp

trong khu cp in. trnh nhng nhc im trn, ngi ta ch to loi thit blc bi hai vng.

Trong thit b lc bi hai vng, ngun in c in th 220V c cp vo bphn nn dng v tng in p to thnh ngun in mt chiu vi in p 13 v6.5kV. in p 13kV c ni vo in cc dng bng dy thp mnh ng knh4 8mm t cch nhau c 30mm ca vng ion ha, cn vng thu bi l cc in ccm dng xen k di dng tm bn t cch nhau 10mm, cc m ni t v ccdng ni vi ngun in 6.5kV.

Hiu qulc ca thit b lc bng in ph thuc ch yu vo kch thc ca

ht bi, cng ca in trng v thi gian ht bi nm trong vng tc dng cain trng.

Hnh 2.14: Thit b lc bi bng in kiu tm

Tm bn ccdng ht bi


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Hnh 2.15: S nguyn l ca thit b lc

bi bng in hai vng.2.5.2 Sc ht tnh in - vn tc di chuyn ca ht biMc d loi thit b lc bi bng in mt vng c nhng nhc im trn

nhng c p dng kh ph bin v cc qu trnh vt l xy ra trong cng ddng l gii bng cc m hnh l ha do ch xem xt loi ny.

Di mt in p ti hn, cc phn t kh hoc khng kh b ion ha in ccnp in v phn chia thnh cc ion dng v m.

Cc ion dng tp trung m c gn in cc m v to thng qung sngcorona xung quanh in cc. nu in p c khng ch di gii hn nguy himth s khng xy ra tia la in gy s c v tn hao nng lng. Cc ion kh mangdu - s di chuyn v pha cc dng v trn ng chuyn ng chng va p vocc ht bi lm cho cc ht bi b tch in m, nh bi b ht vo cc bn ccthu bi. Qu trnh tch in ca nhng ht bi xy ra rt nhanh do s lng ion dyc v kch thc ca chng nh hn nhiu so vi ngay c ht bi di micromet;kt qu l hu ht bi c tch in ngay t tit din vo ca thit b.

in lng m ht bi c th tch c t l thun vi bnh phng ca ngknh ht.

in lng q m ht bi hnh cu ng knh tch c trong in trng c

cng Ecc xc nh theo cng thc sau:2 coEpq

Trong :2

3

D

Dp ,Dl hng s tnh in ca ht bi.

i vi a s loi bi Dnm trong khong 28 v p = 1,5 2,4. i vi bikhng dn in c th lyp =1,75, bi kim loi thD = v lc p = 3.

o - h s thm thu in, )./(,10.854.812 mVCo

cE - cng in trng ion ha tc thay i in p trn n v chiu di,

V/m.


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- 43 -

q - in lng, culong (C)

- ng knh ht bi, m

Cng thc trn p dng i vi bi c ng knh m 5,0 khi qu trnh tch

in ca ht bi xy ra di tc ng va p qun tnh ca ion vo ht bi l chyu.

i vi bi c kch thc b ( m 2,0 ) qu trnh tch in xy ra ch yu ldo khuch tn ion v luc in lng q ca ht bi s xc nh theo cng thc:

eq810

Trong : e - in tch ca electron, e = 1,6.10-19CNh vy, in tch cc i m ht bi c ng knh 0.5m nhn c t l

thun vi bnh phng ng knh, cn ht bi vi di 0.2 m - t l thun ving knh.

i vi c bi m 5,02,0 c hai tc ng va p v khuch tn u xy rav tc tch in nhanh nht l bi c m 3,0

Lc tnh in tc dng ln ht bi 0.5m ca in trng ht Ep:22 poe EEpF , ivi thit b lc bi bng in mt vng Ep =1.

2.5.3 Phn loi:Mt s loi thit b lc bng in l: kiu ng, kiu tm bn, kiu mt vng,

kiu hai vng.

Thit b lc bi bng in kiu 2 vng thng c p dng lc bi trongcc h thng thng gi, cn kiu mt vng c p dng rt rng ri lc bitrong hu ht cc lnh vc cng nghip.

Ngoi cc kiu nu trn, ngi ta cn phn bit cc kiu khc ca thit b lcbi bng in sau y:

Tu thuc vo chiu hng chuyn ng ca dng kh i qua thitb lc, ta cthit b lc kiu ngang v kiu ng.

V bin php lm sch, thi bi ra khi thit b lc ngi ta phn bit thnh loikh v t.

Trong thit b lc bng in loi kh, bi bm trn cc in cc (c in cc thubi ln in cc ion ho) c lm sch bng phng php c kh nh rung, va p bi ri xung phu cha ri bng h thng bn co hoc trc vt bi c thi rangoi.

Trong thitb lc bng in loi t, bi bm trn cc in cc c ty rabng cch phun nc, gii nc. Nc c th c phun hoc gii mt cch lintc hoc gin on tng chu k. Khi phun nc lin tc, ngi ta ch to thnhmng nc mng chy trn b mt ca in cc thu bi, nh th bi b ht vo incc lp tc c mng nc cun tri xung thng cha m t c kh nng b dngkh lm tung ra v mang theo ra ngoi.

2.5.4 Phng trnh ca thit b lc bi bng in:


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Trng hp thit b lc bi bng in kiu ng, bn knh ng cc dng ht bil R, ng knh dy kim loi cc m gia rt nh so vi R ta c th b qua.

Ta chn trc x trng vi dy cc m - trc ca ng hnh tr, trc y vung gctheo phng bn knh ca hnh tr.

Nu dng kh chuyn ng trong ng vi vn tc trung bnh v nh - ch chy tng th trng vn tc trn mt ct ngang ca ng s c dng parabon. Vntc dng kh chy dc theo trc x ti tung y bt k s tnh bng:

)1(2

2

maxR

yvvx ,

Trong vmaxl vn tc cc i ti tm ca tit din ng, ng bng 2 ln vntc trung bnh ca dng kh trong ng:

2max22

R

Lvv TB

Ll lu lng dng kh i qua ng.Chiu di ca ng hnh tr ht bi b gi li rong ng l:

R

Ll

3

4

l vn tc di chuyn ca ht bi di tc dng ca lc tnh in.

Khi chuyn ng ca kh trong ng l chy ri th trng vn tc trn mt ctngang ca ng gn nh l hnh ch nht, vn tc tm cng nh xa tm u bng

nhau constR

Lv

2, lc ta c:

R

LvRl

Trong trng hp thit b l kiu tm bn, khi tm bn t cch nhau 2a v cchiu cao l hvi ch chy ri ca kh gia tm bn ta c:

h

Lval2

0 vmax

vx

Hnh 2.16: S tnh ton thit b lc bi bng in kiu ng


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- 45 -

a

a

l

Cx

Co

x dx

Hnh 2.17: S tnh ton hiu qu lc cathit b lc bi bng in kiu tm bn

Cn lu l chuyn ng ca dng kh trong thit b lc bi bng in trn thct l mang tnh cht chy ri.

2.5.5 Hiu qu lc theo c ht ca thit b lc bi bng in:Trng hp thit b lc bi bng in kiu tm bn.Gi thit rng s phn b nng bi trn tit din ngang ca thit b l nh

nhau v khng ph thuc vo khong cch t ch vo n tit din xem xt. Gi tr tuyt i ca nng bi dctheo chiu dica thit b gim dn. mc

lc bi ca thit b c xc nh theo tr s trung bnh ca nng b trn tan titdin ngang ca thit b. Ta k hiu tr s nng trung bnh ni trn ti mt ct khong cch x tnh t u vo ca thit b l Cx

Col nng ca bi gn bn cc ht bi c th biu din di dng sau: xo CC

Trong :

- h s t l - hng s i vi mi mt bt k gi thit rng quy lutphn b nng trn mt ct lkhng thay i theo x.

Ta c: )exp(12av

lCC

Trong :

C1, C2nng bi ban u v cui cng ca kh trc v sau blc, mg/m3.

l - chiu di ca tm bn, m.v - vn tc trung bnh ca dng kh i gia cc tm bn, m/s.

Hiu qu lc ca thit b c biu din qua nng u v cui ca bi trongkh i qua b lc theo biu thc:

1

21

C

CC

Thay gi tr C2vo biu thc ny ta c:


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)exp(1av

l

Trng hp thit b lc bikiu ng:

Thay v khong cch a ta s c bn knh R ca cc ht bi hnh tr, cn trc xl trc ca hnh tr v ng thi l cc ion ha ca b lc. Hiu qu lc ca thit b lc bi bng in kiu ng l:

)exp(1Rv

l

2.6 THIT B LC BI KIUT.Qu trnh lc bi trong thit b lc kiu t c da trn nguyn l tip xc

gia dng kh mang bi vi cht lng, bi trong dng kh b cht lng gi li v thi

ra ngoi di dng cn bn. Phng php lc bi bng thit b lc kiu t c thxem l n gin nhng hiu qu rt cao

u im:

- Thit b lc bi kiu c d ch to, gi thnh thp nhng hiu qu lc bicao

- C th lc bi c kch thc di 0,1m- C th lm vic vi kh c nhit v m cao m mt s thit b lc bi

khc khng th p ng c nh b lc ti vi, b lc bng in.

- Thit b lc bi kiu c khng nhng lc bi m cn lc c kh c hibng qutrnh hp th, bn cnh n cn c s dng nh thit b lm ngui vlm m kh m trong nhiu trng hp trc thitb lc bi bng in phi cn nn.

Nhc im:

- Bi c thi ra di dng cn bn do co th lm phc tp cho h thngthot nc v s l nc thi.

- Dng kh thot ra t kh t thit b lc c m cao v c th mang theo cnhng git nc lm hang ng ng, ng khi v cc b phn khc pha sauthit b lc.

- Trng hp kh thi c cha cht n mn cn bo v thit b v h thngng ng bng sn chng g hoc phi ch to thit b v ng ng bng vt liukhng han g.

Cht lng c s dng ph bin nht trong thit b lc bi kiu t l ncThit b lc bi kiu t c chia thnh cc loi sau y ty thuc vo nguyn

l hot ng ca chng:

- Bung phun, bung ra kh rng- Thit b lc c lp in bng vt liu rng v c ti t- Thit b lc c a st kh hoc a si bt


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- Thit b lc c lp vt liu ht di ng- Thit b lc theo nguyn l va p qun tnh- Thit b lc theo nguyn l ly tm- Thit b lc venturi2.6.1 Bung phun - Thng ra kh rng.Bung phun hoc thng ra kh rng c

s dng rt ph bin lc bi th trong khthi ng thi lm ngui kh nh l cp lcchun b v gia cng bi trc thit b lc bngin nhm gim nng bi ban u v iuchnh in tr sut ca bi.

Cu to v nguyn l hot ng:Nc c phun t trn xung di vdng kh c dn ngc chiu t di lntrn. Cng c th b tr vi phun t bn phaxung quanh v phun theo phng ngang vodng kh.

dng kh phn b c u n trn titdin ngang ca thit b, ngi ta c b tr b

phn phn phi kh tit din vo ca dngkh.

Nu cc kh cn lm sch gy tc dng hahc vi v thit b th mt trong v c ltlp bo v l vt liu bn axit.

Nu dng thp rng lm ngui kh th nc cp vo thp c p sut cao 20atqua m phun vi l phun c ng knh 1- 2mm. trnh tc vi phun, nc phic lc trc.

Nu dng thp rng lm ngui kh v thu bi th cng phun dch thtng n 3 5m3 cho 1000m3 kh.

Mc thu bi trong thp ra rng s tng khi tng lng dch th c phun vo

v khi tng b mt git dch th tip xc vi cc ht bi.Vn tc dng kh trong thit b khang 0.6 1.2 m/s. nu vn tc kh ln hn

nc c th b dng kh mang theo nhiu m tm chn nc khng kh nng cn li

2.6.2 Thit b kh bi c lp m bng vt liu rng c ti nc.Thit b kh bi c lp m rng c ti nc con gi l thp ra kh hay

(scrubber)

Cu to:gm mt thng tit din trn hoc ch nht bn trong c cha mt lpm bng vt liu rng v c ti nc. Lp vt liu rng thng dng l ccloi khu c hnh dng khc nhau lm bng kim loi mu, s, nha.

Hnh2.18. Thp ra kh rng1- Kh vo; 2- Kh sch ra; 3- Cht lng

a vo h thng phun; 4- X bi


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Hnh 2.19. Thp ra kh c lp m1- Kh vo; 2- Kh sch ra; 3- Cht lng

a vo h thng phun; 4- X bi; 5- Lpvl m; 6- Tm c l

Cc thng s k thut c bn ca lp m rng l:

- Din tch b mt n v Sadin tch b mt tip xc ca 1m3vt liu rng,m2/m3.

- Din tch tit din rng trn1m2 tit din ngang ca lp vt liurng So, m

2/m2, tr s So ng thicng l th tch rng ca 1m3vt liurng, m3/m3.

- ng knh tng ng calp vt liu rng: m

S

Sd

a

otd ,4

- Sc cn kh ng ca lp vtliu rng:

td

KK

dS

vHp

0

2

2

Trong : - h s sc cn khng ca lp vt liu rng.

Kv - vn tc kh i quatit din sng ca lp vt liu rng,m/s.

H chiu cao lp vtliu rng, m.

K - khi lng n v ca kh, kg/m3.

H s sc cn ph thuc vo ch chuyn ng ca kh trong thit b thngqua chun s Raynon: aKKKK Sv /4Re

Khi ReK< 80: 85.0Re400

K

Khi 80< ReK< 400: 45.0Re70

K

Khi ReK> 400: 2.0Re5.16

K

Nguyn l hot ng:Kh i t di ln xuyn qua lp vt liu rng, khi tipxc vi b mt t ca lp vt liu rng bi s bm li cn kh sch thot rangoi. Mt phn bi b nc cun tri xung thng cha v c x di dng bn.nh k ngi ta s ra lp vt liu rng.

Nhc im ca loi thit b ny l khi vn tc kh cao th thit b ny khnghot ng c do c hin tng sc nc (nc b thi ngc tr ln v c thdng tro vo ng ng thot kh sch)


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- 49 -

2 3 4 2

1 56

kh kh

Hnh 2.20: Thit b phun nc c lp m rng kiu nm ngang1.Vi phun, 2.V v khung, 3.H thng ti, 4. Phn khng ti nc ca

lp m thay chotm chn nc, 5. B cha cn bn, 6. Lp vt liu rng

Ngoi loi thp phun kiu ng vi chuyn ng ngc chiu ca kh v nc,ngi ta cn ch to loi thit b phun c lp vt liu rng kiu nm ngang. Laithit b ny c th lm vic vi vn tc kh ln (c th t 10m/s). Do kch thcca thit b s c gn nh hn.

Lng nc phun trong thit b ny thng nm trong khong 0.150.5l/m3.Hiu qu lc t 90% i vi c bi >2m.

Hiu qu lc ca thit b phun nc kh bi c lp m bng vt liu rng c

th c xc nh bng cng thc sau: Stk

d

H

qS onO ))(1(exp(1

Trong :

- hng s thc nghim ph thuc vo loi vt liu rng.dong knh hoc kch thc c trng ca cc loi khu dng lm

vt liu rng.qn - lng nc b gi li trong lp vt liu rng

man Sq m3/m3;

m - b dy ca lp nc lng t b mt tip xc ca lp vt liurng.Stk - chun s Stoke i vi h thng kh v bi vi kch thc c

trng doca khu vt liu rng.

oKbK dvStk 18/2

Di y l tr s do v ca cc khu khc nhau: do, mm

- Khu Raschig, khu yn nga Berl, khu intalox: 12,7 0,192-

Khu Berl, khu Raschig, khu Pall 25,4 0,19


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38,0 0,165

- Thancc 76 127 0,03

2.6.3 Thit b lc bi (ra kh )c a cha nc si bt.Nguyn l lm vic: nc

c cp vo a va to mt lp nc c b caothch hp, dng kh i t dcln trn qua a c l, lmcho lp nc si bt. Bi

trong kh tip xc vi b mtca bong bng nc v b gili ri theo nc chy xungthng cha.

a c l dng trong thitb l l trn c ng knh do= 48mm hoc rnh song songc b rng b = 45 mm. Dintch sng ca a nm trongkhang 0.20.25m2/m2. khi s

dng thit b vi mc ch valc bi va lm ngui kh thdin tch sng ca a c thln n 0.40.5m2/m2.

Thit b lc bi t kiu a si bt c khnng lc c bi c kch thc lnhn hoc bng 5m vi hiu qu lc tng i cao.

Hiu qu lc bi ca thit b lc bi c a cha nc si bt c th c xcnh theo cc cng thc sau, khng nhng ph thuc v chiu cao lp bt m cn

ph thuc vo cc thng s vt l ca bi:

i vi bi thm t:04,0

2005,0

2)(]

)([89,0

on

Kb

po

nK

dg

v

hhg

Lv

i vi bi kh thm t:

235,02

005,0

2)(]

)([89,0

on

Kb

po

nK

dg

v

hhg

Lv

Trong ngoi cc k hiu quen thuc cn c:

oh - chiu cao ca l trn a c l (tc b dy ca a)

Hnh 2.21. Thp si bt

1- Kh vo; 2- Kh sch thot ra; 3- Cht lng avo h thng phun; 4- X bi; 5- Lp cht lng sibt; 6- a dc l


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ph - chiu cao tm phn x, m

od - ng knh ca l trn trn a c l, m

n - h s nht ng lc ca nc, Pa.s

Kv - vn tc ca kh qua tit din sng ca a c l, m/s


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Chng 3

CC PHNG PHP X L KH THI CNG NGHIP

3.1C S L THUYT CA CC QU TRNH X L KH THI3.1.1 Hp th kh bng cht lngHp th kh bng cht lng l qu trnh ho tan cht kh trong cht lng khi

chng tip xc vi nhau. C cu ca qu trnh ny c th chia lm 3 bc:

- Khuch tn cc phn t cht nhim th kh khng khi kh thi n b mtcht lng hp th.

- Thm nhp v ho tan cht kh vo b mt ca cht hp th. -

Khuch tn cht kh ho tan trn b mt ngn cch vo su trong lngkhi cht lng hp th.

1. Mt s vn c bn ca qu trnh trao i cht.Hin tng dn nhit trong cht kh l kt qu ca s chuyn ng hn lan

ca cc phn t kh, lm chng b xo trn v dn ti s cn bng nng lng giacc phn t. Nh c chuyn ng ny m s khc bit cc b ca nng cht khtrong hn hp s gim dn ngay c khi khng c s can thip ca ngai lc nhkhuy, lc

Ta xem xt mt hn hp gm haicht A v B trong bnh ng cng nhit

v p sut. s lng phn t trongmt n v th tch l n, trong nA ls lng phn t A v nB l s lng

phn t cht B, ta s c BA nnn .ng hc cht kh chng t rng cng nhit v p sut s lng phnt n mi im khc nhau ca bnh lnh nhau.

Gi thit rngs lng phn t nA

v nBthay i theo phng Z, trong nAnhiu hn pha di ca bnh, cnnBnhiu hn pha trn ca bnh. Lc ta c s chuyn ng ca phn t At di y bnh i ln trn v cc phnt cht B t bn trn chuyn ng xung di.

S lng phn t cht A t di i ln qua mt ct O-O s c xc nh theobiu thc:

dZ

dnDN AABA

= nA + nB

NA

NB

0

Z

Hnh 3.1: Biu din qu trnh trao icht ca hai cht A v B trong hn hp


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V s lng t cht B t trn i xung qua mt ct O -O s l:

dZ

dnDN BBAB

Trong :ABD - h s khuch tnca cht A trong hn hp A-B

BAD - h s khuch tn ca cht B trong hn hp B-A

dZ

dnA ,dZ

dnB - ln lt l gradian mt phn t cht A v B theo

phng Z.

T cc iu kin BA nnn v n= const ta rt ra c:

dZ

dnA = -

dZ

dnB

m bo iu kin n= const, s lng phn t ni chung i qua mt phngO-O phi bng khng ( 0 BA NN ). Do BAAB DD - tc l h s khuch tncht A v cht B trong hn hp A-B l bng nhau. V vy ta c th vit ngn gn hs khuch tn lD

Phng trnh khuch tn cn c th c biu din qua gradian nng :

dZ

dCDm AA (nh lut Fick)

Trong :

mA - dng khi lng cht A iqua n v th tch trong n v thigian, kg/m2.s hoc mol/m2.sCA - nng cht A, kg/m

3hoc mol/m3.

Z - l khong cch, m.D - h s khuch tn, m2/s.

2. Trao i cht v l thuyt hai lp bin (hai lp mng). trao i mt lng cht nhim t kh thi vo cht lng hp th, cn phi

trao i cc phn t qua vng ranh gii gi l lp bin (mng, phim). Cc phn ti qua lp bin t hai pha, mt s t pha cht kh, mt s t pha cht lng. Cng

trao i thc ph thuc vo cc yu t tc ng nh: nhit , p sut, nng , ho tan. Nng phn t pha cht kh ph thuc vo c hai hin tng khuchtn: khuch tn ri v khuch tn phn t. Thng thng khuch tn ri c tc dnglm cho nng phn t c u n trong khi kh cn khuch tn phn t c tcdng lm cho cc phn t kh chuyn ng v pha lp bin. pha cht lng cngxy ra hin tng tng t nh trn, trong khuch tn ri c hnh thnh gicho nng c u n trong ton b khi cht lng, cn khuch tn phn tdch chuyn cc phn t n lp bin v i vo pha kh. Nu cc phn t ca kh iqua lp bin v i vo cht lng c phn ng ho hc vi cht lng hoc b gi li

bng cc qu trnh vt l khc lm cho chng khng th quay tr li khi kh th

cng trao i thc ca kh vo cht lng s tng.


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tin cho phn tch l gii, ta xem rng lp bin ngn cch gia cc pha khv lng gm c hai lp: mt lp bin kh v mt lp bin lng ngi ta gi ll thuyt hai lp bin (hai lp mng) vc th hin hnh 3.2.

Cng trao i cht t pha ny sang pha kia l t l thun theo din tch tipxc v th nng trao i cht vi h s t l kc gi l h s trao i cht.

Xt ring l tng lp bin ta c th vit phng trnh trao i cht nh sau:i vi lp bin kh:

)( AiAGGA ppkN

i vi lp bin lng:

)( ALAiLA CCkN Trong :

NA - cng trao i cht ca cht A qua n v din tch ca lp bin,mol/m2.h hoc kg/m2.h.

pAG- p sut ring ca cht kh A trong khi kh( cch xa lp bin), atm hocmmHg.

pAi - p sut ring ca cht kh A thuc pha kh trong lp bin kh trn b mtcht lng, atm hoc mmHg.

CAi - nng cht A thuc pha lng trong lp bin cht lng, kg/m3hoc g/l.

CAL - nng cht A thuc pha lng trong khi cht lng (cch xa lp binlng), kg/m3hoc g/l.

kG - h s trao i cht thuc pha kh ca lp bin kh tnh theo chnh lch psut ring, mol/m2.h.atm hoc kg/m2.h.atm, kg/m2.h.mmHg.

kL - h s trao i cht ca lp bin cht lng tnh theo chnh lch nng ,mol/m2.h.kg/m3hoc kg/m2.h.kg/m3 m/h.

3. Cc phng trnh ca qu trnh hp th:Hp th kh l thu mt cht kh hoc hi bng cht lng nh cc qu trnh vt

l v ho hc. Trong qu trnh hp th, cht b hp th c ho tan vo trong pha

lng - cht hp th.

Pha kh

Pha lngKhuch tn phn t

Khuch tn phn t Lp bin kh

Lp bin cht lng

yAi

yAG pAG

pAi

xAi CAi

xAL CAL

Hnh 3.2: M hnh hai lp bin ngn cch gia hai pha kh v lng


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hp th c cht nhim, cc phn t cht nhim cn c khuch tnn b mt lp bin ngn cch, i qua c hai lp bin kh v lng v cui cng thmnhp vo khi cht lng. C ngha l cng trao i thc ca phn t qua milp bin l nh nhau, do ta c:

)()( ALAiLAiAGGA CCkppkN

Phng trnh trn cn c th c biu din qua chnh lch ca t sut mol cacht kh cn hp th trong pha kh cng nh trong pha lng:

)()( ALAixAiAGyA xxkyykN

Trong :

AiAG yy , - ln lt l t sut mol ca cht A trong khi kh v trong lp bin

kh st b mt ngn cch.

AiAL xx , - ln lt l t sut mol ca cht A trong khi cht lng v tronglp

bin cht lng st b mt ngn cch.

yx kk , - ln lt l h s trao i cht ca lp bin lng v lp bin kh tnh

theo chnh lch t sut mol, mol/m2.h.T sut mol l t s gia s mol cht kh A trn tng s mol ca c cht A v B

trong hn hp kh A - B. i vi pha lng: l t s gia s mol ca cht kh Atrn tng s mol ca dung mi v cht ho tan.

Nng C, p sut p, p sut ton phn P v t sut mol c lin quan cht chvi nhau ( Pyp ii ), do :

LMx kk v Gy Pkk Trong :

M - Khi lng n v ca pha lng.

P- p sut ton phn ca pha kh.Trong qu trnh hp th bng cht lng, cht nhim ho tan A cn c

khuch tn ra khi pha kh v thm nhp vo pha lng, chng thng c gi thitrng hai pha kh v lng trong hai lp bin lun lun trng thi cn bng trn ttc cc im ca b mt tip xc v khng c mt tr lc no ng k xy ra i viqu trnh khuch tn gia hai lp bin ca b mt tip xc. Kt qu l cc i lng

CAi, pAihoc xAi v yAilun nm trong mi quan h cn bng. iu c ngha ltng cp cc i lng CAi v pAi, xAi v yAitrong cng thc nu bit i lngny th xc nh c i lng kia. Trong lc cc i lng y AGtrong khi khv xALtrong khi cht lng khng trng thi cn bng v rng nu trng thi cn

bng th qu trnh khuch tn s khng xy ra na.Nng A trong pha kh gim rt nhanh t yAGn yAi tiim st b mt

ngn cch. Trn b mt ngn cch yAi v xAi trng thi cn bng. Trong pha lngnng cht A th hin qua t sut mol xAcng nhanh chng t tr s xAitrn bmt ngn cch n tr s xALtrong lng khi cht lng.


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4. Tnh ton thit bhp th:Thit b hp th c chc nng to ra b mt tip xc cng ln cng tt gia hai

pha kh v lng. C rt nhiu kiu khc nhau ca thit b hp th, nhng c th phnchia lm bn loi chnh sau:

- Bung phun, thp phun: trong cht lng c phun thnh git nh trongth tch rng ca thit b v cho dng kh i qua.

- Thit b sc kh: kh c phn tn di dng bong bng i qua lp chtlng. Qu trnh phn tn kh c th thc hin bng cch cho kh i qua tm xp, tmc l hoc bng cnh khuy c hc.

- Thit b hp th kiu si bt: kh i qua tm c l bn trn c cha lp ncmng.

- Thit b hp th c lp m bng vt liu rng. Cht lng c ti trn lpm rng v chy xung di to ra b mt t ca lp

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