aerosol dari buku permukaan versi inggris

7/25/2019 Aerosol Dari Buku Permukaan Versi Inggris

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Surfaces, Interfaces, and Colloids: Principles and Applications, Second Edition. Drew MyersCopyright 1999

John Wiley & Sons, Inc.

ISBNs: 0!"1##0$0! %'r()'c*+ 0!"1-#!990 %lectronic+

13 Aerosols

/he preios ch'pters h'e intro(ce( seer'l cl'sses o2 colloi(s 'n( so3e o2 the

i3port'nt sr2'ce 'spects o2 their 2or3'tion, st')ili4'tion, 'n( (estrction. 3lsions,

2o'3s, 'n( (ispersions 're the 3ost co33only tre'te( 'n( intensely st(ie(

e5'3ples o2 colloi('l syste3s. /hey constitte the 3'6ority o2 pr'ctic'l 'n( i(e'l

syste3s one enconters. /here e5ists one other cl'ss o2 tre, lyopho)ic colloi(s7the

'erosols7which, 'lthogh see3ingly less i3port'nt in ' theoretic'l or 'pplie( sense,'re o2 gre't pr'ctic'l i3port'nce.

8erosols 're syste3s in which there e5ists ' con(ense( ph'se o2 one 3'teri'l

%soli( or lii(+ th't is (isperse( in ' g'seos ph'se 'n( th't h's (i3ensions th't

2'll into the colloi('l r'nge. /here 're two s)cl'sses o2 'erosols (epen(ing on

whether the (isperse( ph'se is ' lii( or ' soli(. /here c'nnot )e, o2 corse, '

(ispersion o2 one g's in 'nother. Where the (isperse( ph'se is ' lii(, thesyste3 is co33only re2erre( to 's ' 3ist;; or ' 2og.;;


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13.1. THE IMPORTANCE OF AEROSOLS

8erosols, )oth lii( 3ists 'n( soli( s3o*es, h'e ' gre't (e'l o2 technologic'l 'n(

n'tr'l i3port'nce. /echnic'lly they 're se2lly e3ploye( in co'ting oper'tions,

2ire2ighting, 3e(ic'l tre't3ents %'llergy 'n( 'sth3' spr'ys+, che3ic'l pro(ction

processes, spr'y (rying, 'n( other proce(res. =n the opposite si(e o2 the le(ger, o2corse, we h'e the s3o*e 2ro3 in(stri'l s3o*est'c*s, s3og 'n( h'4e 2ro3

in(stry 'n( 'to3o)iles, 2orest 2ires, high2lying 6et contr'ils, che3ic'l 'n( )iologic'l

we'pons, 'n( so on. oweer, the re'l i3p'ct o2 'erosols %in prely 3'ssie ter3s+

co3es 2ro3 n'tr'l sorces: clo(s, s3o*es, 'n( si3il'r n'tr'l 'ir)orne p'rticles.

8 clo( %n'tr'l+ is ' l'rge collection o2 w'ter (roplets or ice cryst'ls 3oing

throgh the 't3osphere 'n( hel( together %loosely+ )y ' 'riety o2 2orces to )e(iscsse( )elow. =ther n'tr'l 'erosols incl(e: 'ir)orne pollen (st 'n( s'n(

%i2 high enogh in the 't3osphere c'sing )e'ti2l re( snsets+ olc'nic clo(s

o2 w'ter, sl2r o5i(es %pro(cing 'ci(s+, 'n( other soli( 'n( lii( 3'teri'ls

n'tr'l che3ic'l 2ogs;; pro(ce( )y pl'nt 3et')olis3 'n( (eco3position in

(ense 2orest 're's %e.g., the S3o*y Mont'ins in the sothe'stern >nite(

St'tes+ 'n( 3'ny 3ore.

317


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318 8?=S=@S

/o('y, pro)')ly the 3ost isi)le 'erosols %to the gener'l consciosness+ 're

those reslting 2ro3 'ir polltion. Co3pose( o2 'n in2ern'l 3i5tre o2 w'ter,

soli( p'rticl'te 3'teri'ls, 'n( lii( (roplets, polltion 'erosols c'n liter'lly

represent the (eils own che3ic'l wor*shop. >n(er the in2lence o2 the sns

ltr'iolet g'4e, 'n( 'i(e( )y the e22ects o2 c't'lytic processes (iscsse( in

Ch'pter 9, the co3ple5 sops we pro(ce ('ily c'n n(ergo continos

che3ic'l ch'nges o2ten le'(ing to (is'stros reslts 2or orseles 'n( or

eniron3ent. /he e22ects o2 polltion on h3'n he'lth, on eget'tion, on

3'teri'ls 'n( strctres, 'n( on the 't3osphere itsel2 're 3ore 'pp'rent 'n(2rightening eer ('y. /o preten( th't we, the h3'n r'ce, c'n si3ply t'*e '

step )'c* ot o2 the in(stri'l reoltion 'n( retrn to )etter;; ('ys is pre

2'nt'sy %'n( 2olly+. Inste'(, we 3st i3proe or technology to re(ce the leel

o2 pollt'nts we pro(ce 'n( to control th't which is n'oi(')le so th't it

neer re'ches the open light o2 ('y. /o('y, sing so3e o2 the si3ple principles

(escri)e( )elow %'n( others 3ore co3ple5, o2 corse+, we h'e the

technologic'l c'p')ility to gre'tly i3proe or sit'tion. Wh't 're l'c*ing 're

the econo3ic 'n( politic'l 2orce o2 will to i3ple3ent wh't we *now 'n(

contine (eeloping new w'ys to control these inh')it'nts o2 the twilight 4one

we c'll 'erosols.;;

13.2. COLLOIDAL PROPERTIES OF AEROSOLS

While 'erosols 're typic'l colloi(s in th't they respon( to the s'3e 2orces

'lre'(y intro(ce(7th't is, electrost'tic 'n( 'n (er W''ls inter'ctions7the

speci'l con(itions th't pre'il in ter3s o2 the interening g'seos 3e(i3

reslts in 'n 'pp'rent 'lit'tie (i22erence 2ro3 colloi(s in lii( 3e(i'. /he

prece(ing ch'pters illstr'te( the i3port'nce o2 the interening 3e(i3 to the

ch'r'cter 'n( inter'ctions o2 colloi('l p'rticles (e to the screening e22ect o2

the continos ph'se on p'rticleAp'rticle inter'ctions. In 'erosols, 'lthogh the

2n('3ent'l rles re3'in the s'3e, the screening e22ect o2 the g'seos3e(i3 )eco3es rel'tiely insigni2ic'nt so th't ' n3)er o2 '(6st3ents in

thin*ing 3st )e 3'(e in or(er to reconcile the 'pp'rent (i22erences )etween

'erosols 'n( e3lsions, sols, 'n( other colloi('l syste3s.


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In ' 2irst 'n'lysis, we c'n i(enti2y 't le'st 2or )'sic (i22erences )etween

'erosols 'n( other colloi(s rel'te( to the (ispersion 3e(i3: %1+ )oy'ncy

e22ects, %-+ the e22ects o2 3oe3ent o2 the (ispersing 3e(i3, %#+ p'rticle

3o)ility in n(istr)e( con(itions %i.e., 2ree 2'll+, 'n( %!+ 3o(i2ic'tion o2

inter'ctions )y the interening 3e(i3. In e3lsions, 2o'3s, 'n( sols we h'e

seen th't )oy'ncy c'n )e i3port'nt in (eter3ining the st')ility o2 ' syste3

%i.e., 3'tching the (ensities o2 (isperse( 'n( continos ph'ses c'n ret'r(

cre'3ing or se(i3ent'tion+. In 'erosols, where the (ensity o2 the continos

ph'se will 'lw'ys )e signi2ic'ntly less th'n th't o2 the (isperse( p'rticle, sch

e22ects 're pr'ctic'lly none5istent7the colloi( is essenti'lly le2t to its own

(eices the s'l inter'ctions 2on( 2or 'll colloi(s, the const'nt;;


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1#.-. C=@@=ID8@ ?=?/IS =< 8?=S=@S

319

pll o2 gr'ity %'ss3ing th't we 're not ')o'r( the sp'ce shttle or MI?+,

'n( the whi3s o2 the win(s.

13.2.1. Dyna!"s o# $%e Aerosol Mo&een$

St(y o2 the (yn'3ics o2 2li( 2low is concerne( with the 2orces 'cting on

the )o(ies in the 2li(. In the e'rlier ch'pters on soli( (ispersions,

e3lsions, 'n( 2o'3s, 2li( (yn'3ics w's l'rgely ignore( in 2'or o2 the

tre;; colloi('l inter'ctions. In 'erosols, the n'tre o2 the continos

3e(i3 3'*es the s)6ect o2 2li( (yn'3ics 3ch 3ore i3port'nt to then(erst'n(ing o2 the syste3, so th't the 2ollowing (iscssion will intro(ce

' 2ew )'sic rel'tionships th't c'n )e i3port'nt in the st(y o2 'erosols.

Win(s,;; in the 2or3 o2 conection crrents or other 3oe3ents o2 the

3e(i3, 're gener'lly 3ore i3port'nt in g'ses th'n lii(s. S3'll

te3per'tre (i22erences or 3ech'nic'l 3oe3ents th't wol( )e ('3pe(

ot ic*ly in ' 3ore iscos lii( 3'y )e tr'nsl'te( oer l'rge (ist'ncesin g'ses 'n( pro(ce ' 3ch gre'ter e22ect in 'erosols. %?e3e3)er the

2'3os Chinese )tter2ly th't c'n ch'nge the we'ther in 'ns's 'ccor(ing

to ch'os)'se( theories o2 we'ther (eelop3ent+

In ' st'tic syste3 o2 rel'tiely high iscosity %rel'tie to th't o2 g'ses+,

inerti'l 2orces (e to p'rticle 3oe3ent 're sel(o3 signi2ic'nt speci2ic'lly,

iscos 2orces (o3in'te. In g'ses, the 2orces reslting 2ro3 p'rticle

3oe3ent )eco3e 3ore i3port'nt 'n( 3st )e consi(ere( in ' (yn'3ic

'n'lysis o2 the syste3. In (yn'3ic 2li( 2low 'n'lysis, the r'tio o2 inerti'l

2orces %rel'te( to p'rticle 3'ss, elocity, si4e, etc.+ to iscos 2orces %'

ch'r'cteristic o2 the 3e(i3 'n( not the p'rticles+ in ' syste3 is '

(i3ensionless n3)er ter3e( the ?eynol(s n3)er, ?e, 'n( is se( to


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F( 0.2 3R-v

-

%1#.-+

In the region 1 ?e 10#, ' tr'nsition occrs 2ro3 l'3in'r %F(v+ to tr)lent

2low %F(v-+ 'n( the rel'tionship )etween F('n( v)eco3es 3ore

co3ple5. 8lso, since (r'g 2orces 'ct'lly 'pply only to the rel'tie elocity


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32' 8?=S=@S

FI()RE 13.1. In the 3oe3ent o2 'erosol p'rticles, the type o2 2low in the g's ph'sewill

signi2ic'ntly '22ect the 2'te o2 the p'rticles.


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(ist'nce ' p'rticle will tr'el )e2ore colli(ing with 'nother p'rticle, the 3e'n

2ree p'th, , is gien )y

E% G+ NR-F

1

%1#.#+

where Nis the p'rticle n3)er (ensity.


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where


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1#.-. C=@@=ID8@ ?=?/IS =< 8?=S=@S

321

Cc

1

1.-$ 0.! e5p

1.1R

%1#.H+

R

=)iosly, the correction gien in this e'tion )eco3es 3ore i3port'nt 2or

'erosols o2 s3'ller p'rticle r'(is, or in con(itions o2 lower g's pressres

%e.g., high 'ltit(es+.

8ccor(ing to the Sto*es e'tion, the elocity o2 2ree 2'll o2 ' p'rticle in 'n

n(istr)e( gr'it'tion'l 2iel(, v2,is gien )y


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v2

m'

-R-

%1#.$+

$ R

9


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eents th't pro(ce high'ltit(e 'erosols c'n '22ect not only the color o2 or

snsets )t 'lso other 3ore it'l glo)'l 't3ospheric inter'ctions.

In w'ter, with ' iscosity 'ppro5i3'tely H0 ti3es th't o2 'ir, 3iner'l

p'rticles si3il'r to those ')oe wol( h'e se(i3ent'tion r'tes on the

or(er o2 1.$ 3 ('y1'n( -# 3 3in

1, respectiely. Sch c'lcl'tions

%esti3'tions, re'lly+ 're i3port'nt 2or 3o(eling pro)le3s o2 se(i3ent

'cc3l'tion in ('33e( reseroirs, 2or e5'3ple.

13.2.2. Collo!*al In$era"$!ons !n Aerosols

8lthogh the rles 're the s'3e, p'rticleAp'rticle %colloi('l+ inter'ctions in

'erosols c'n see3 to h'e signi2ic'ntly (i22erent 'ntit'tie 'n( 'lit'tie

ch'r'cteristics th'n in lii( 3e(i'. 8 g'seos 3e(i3, )ec'se o2 its ery

(i22erent nit (ensity, (ielectric const'nt, 'n( other properties, is ery ine22ec

tie 't screening the 2orces 'cting )etween colloi('l p'rticles.


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322 8?=S=@S

FI()RE 13.2. Bec'se o2 the low (ielectric const'nt o2 'ir, the 'ttr'ctie inter'ctions

'3ong 'erosol p'rticles is or(ers o2 3'gnit(e gre'ter th'n th't pre'iling in ' lii(3e(i3. 8n o)ios reslt o2 th't is the 'ppe'r'nce o2 hosehol( 244 )'lls;; % a+ 'n(

r'pi( (st 'cc3l'tion on sr2'ces %b+. In technology reiring ltr'cle'n

eniron3ents, the reslting pro)le3s reire 3illion(oll'r soltions.

in 'erosols will, there2ore, )e 't le'st 'n or(er o2 3'gnit(e gre'ter,

in(ic'ting th't the 'ttr'ctie 2orce )etween p'rticles will 'l3ost 'lw'ys

oerwhel3 the *inetic energy o2 the p'rticles 'n( inel'stic or stic*y

collisions will 'l3ost 'lw'ys occr.

So3e pr'ctic'l reslts o2 th't strong inter'ction incl(e hosehol( 244

)'lls, where (st p'rticles 2loccl'te 'n( 2or3 2r'ct'lli*e strctres

%ho3ogeneos 2loccl'tion


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%


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1#.#. @I>ID 8?=S=@S: MIS/S 8ND


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pr'ctic'l 'pplic'tions o2 'erosols (epen( on the presence o2 ch'rge, 's

(oes one o2 the 3ost i3port'nt process 2or (estroying nw'nte( 'erosols.

13.3. LI+)ID AEROSOLS, MISTS AND FO(S

Mists 'n( 2ogs 're colloi('l (ispersions o2 ' lii( in ' g's. /hey 3'y

there2ore )e thoght o2 's )eing roghly the inerse o2 ' 2o'3 syste3. /heinter'ctions controlling their st')ility, howeer, 're not in gener'l the s'3e

's those inole( in 2o'3 st')ili4'tion, )ec'se 3ists 'n( 2ogs (o not

nor3'lly possess the thin l'3ell'r st')ili4ing 2il3s encontere( in 3ost

2o'3s, whether o2 the spheric'l or the polyhe(r'l type.

@ii( 'erosols 3'y )e 2or3e( )y one o2 two processes, (epen(ing on

whether the (isperse( syste3 )egins 's ' lii( or n(ergoes ' ph'se ch'nge


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32- 8?=S=@S

2ro3 'por to lii( (ring the 2or3'tion process. In the 2irst c'se, since the

(isperse( 3'teri'l (oes not ch'nge ph'ses, the 'erosol is 2or3e( )y so3e

process th't ch'nges the (ispersity or nit si4e o2 the lii(. /o this cl'ss

)elong the spr'y 3ists sch 's those 2or3e( 't the )otto3 o2 ' w'ter2'll or

)y oce'n w'es, 3ists pro(ce( )y igoros 'git'tion, 'n( those 2or3e(

)y so3e (irect spr'ying or 'to3i4'tion process. /he ter3 'to3i4'tion;; is

' so3ewh't n2ortn'te choice )ec'se it h's nothing to (o with the

n'tre o2 the process )eing (escri)e( howeer, the ter3 entere( the

'erosol 2iel( 3'ny ye'rs 'go 'n( is still encontere(. 8 3ore 'pt ter3 is

ne)l'4'tion;; %clo( 2or3'tion+. @ii( 'erosols c'n 'lso )e 2or3e(

(irectly )y the 'pplic'tion o2 high electric'l potenti'ls to the lii(.

/he secon( cl'ss o2 3ists or 2ogs is th't pro(ce( )y so3e process in

which the incipient lii( ph'se is intro(ce( 's ' 'por 'n( 2or3s (roplets

's ' reslt o2 so3e eili)ri3 con(ens'tion process, or the lii( ispro(ce( 's ' reslt o2 so3e che3ic'l re'ction. /he 2or3er 3ech'nis3

incl(es, o2 corse, clo( 'n( 2og 2or3'tions, while the l'tter correspon(s

to so3e che3ic'l;; 2ogs 'n( 3ists.

13.3.1. Sray!n/ an* Rela$e* Me"%an!ss o# M!s$ an* Fo/ Fora$!on

@ii( 'erosol 2or3'tion )y spr'ying is ' ery i3port'nt in(stri'l process,

een thogh so3e o2 the 2n('3ent'l (et'ils o2 the process 're still not

ery well n(erstoo(. M'6or 'pplic'tions incl(e p'int 'pplic'tion 2el

in6ection in (iesel, g'soline, 'n( 6et engines spr'y (rying o2 3il*, eggs, 'n(

other 2oo(s the pro(ction o2 3et'l 'n( pl'stic pow(ers %spr'y cooling+

3e(icin'l nose 'n( thro't spr'ys the 'pplic'tion o2 pestici(es to crops'n( 3'ny 3ore. In 'll o2 those 'pplic'tions, it is it'lly i3port'nt th't the

ch'r'cteristics o2 the 'erosol pro(ce( )e opti3i4e( to pro(ce the (esire(

en( reslt. /heories rel'te( to the 2or3'tion o2 (rops in spr'y syste3s c'n

)e ery help2l in 'ppro5i3'ting the con(itions necess'ry to pro(ce 'n

'erosol o2 (e2ine( ch'r'cteristics. oweer, )ec'se o2 the n'tre o2 the


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necess'ry to 'rrie 't the opti33 spr'ying syste3 )y tri'l'n(error

technies )'se( on preios e5perience in the 2iel(.

8erosol sp'ys 're s'lly 2or3e( )y one o2 2or )'sic processes 's ills

tr'te( in


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1#.#. @I>ID 8?=S=@S: MIS/S 8ND


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=ther syste3s e5ist )t 're o2 3ch less signi2ic'nce in pr'ctice. =2 the

2or, the 3ost i3port'nt in(stri'lly 're sing the highpressre ori2ice 'n(

the rot'ting (is*.


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32 8?=S=@S

is encontere(. 8s ' reslt, the lii( will not 2low s3oothly in lines p'r'llel

to the w'lls o2 the ori2ice )t will 2low in co3ple5 p'tterns with e((ies,

swirls, 'n( ortices. When the lii( le'es the ori2ice in this tr)lent7or,

to se ' 3ore 2'shion')le ter3, ch'otic7st'te, the 'ngl'r 2orces in the

ortices will 'ct 'g'inst the sr2'ce tension o2 the lii( to strip o22 nits o2

lii( to 2or3 (roplets %


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/he sr2'ce tension 2orces *eeping the 6et together will )e Lr./he secon(

r'(is o2 cr'tre 2or the 6et )eing in2initely l'rge. /he critic'l r'(is 't

which ' continos 6et o2 lii( )eco3es nst')le 'n( )re'*s p to 2or3

(roplets will )e

#1L#

rc r - %1#.9+

It is (i22iclt, o2 corse, to (eter3ine the 'le o2 in ' 2lowing syste3 ths

e5peri3ent'l eri2ic'tion o2 sch 'n 'n'lysis is not ' trii'l 3'tter.

oweer, i2 one 'ss3es th't % is proportion'l to the in6ection pressre, the

pro(ct o2 the pressre 'n( r#shol( )e const'nt. In pr'ctice, the

'gree3ent is not ite e5'ct. I2 one were to se 'n e5cess pressre7th'tis, the pressre in e5cess o2 th't 't which ch'otic 2low )egins7the

'gree3ent 3ight logic'lly )e e5pecte( to i3proe.

Since theories 2or pre(icting the (rop si4e o2 ' spr'y )'se( on the ch'r'cteristics


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s'lly necess'ry to 3e'sre si4es 2or e'ch gien sit'tion. In gener'l, howeer,

the 2ollowing rles hol( 2or 3ost 2li( e6ection syste3s:

Incre'sing the sr2'ce tension o2 the lii( will (ecre'se the (rop si4e.

Incre'sing the iscosity o2 the lii( will incre'se the 'er'ge r'(is.


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1#.#. @I>ID 8?=S=@S: MIS/S 8ND


26/53

FI()RE 13.0. /here 're three principle 3ech'nis3s 2or (rop 2or3'tion in (is*

'to3i4ers: %a+ (irect 2or3'tion 't the (is* e(ge %b+ (rop 2or3'tion 2ro3 strings o2

lii( 'w'y 2ro3 the e(ge %c+ (rop 2or3'tion 2ro3 sheets 'w'y 2ro3 the e(ge. /he

locs 'n( 3ech'nis3 will 'ry 'ccor(ing to the con(itions o2 se: the

ch'r'cteristics o2 the lii( %sr2'ce tension, iscosity, (ensity, 2ee( r'te, etc.+ the

*inetic energy o2 the lii( 't the (is* e(ge %spee( o2 rot'tion, (is* (i'3eter, etc.+

the e22ects o2 the srron(ing g's 't the (is* e(ge 'n( the physic'l con2igr'tion o2

the (is* %'nes, cr'tre, etc.+.


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8?=S=@S


28/53

8 che3ic'l;; 3etho( 2or the pro(ction o2 'erosol inoles the (irect con(en

s'tion o2 (rops or p'rticles in the 'ir or other g'seos eniron3ent. In or(er

TA4LE 13.1. A S5ary o# Soe 4as!" Ro$ary A$o!er an* Fee* L!65!*

C%ara"$er!s$!"s an* T%e!r Ee"$e* E##e"$s on A&era/e Dro S!e o# $%e

Aerosol Pro*5"e*

Ch'r'cteristic

5pecte( 22ect o2 Incre'se on Drop Si4e

8to3i4er

Dis* (i'3eter

Decre'se

Dis* spee(

Decre'se


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Incre'se


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1#.#. @I>ID 8?=S=@S: MIS/S 8ND


31/53

$n!" lnPo

%1#.10+

where Pis the pressre or 'ctiity o2Ain the 'por ph'se 'n( Pois th't in the

lii( ph'se. /he r'tio P%Pois o2ten re2erre( to 's the (egree o2 spers't

r'tion o2 the syste3. 8 lii( (rop o2 r'(is rwill h'e ' sr2'ce energy e'l to

! r-, so th't the 'ct'l 2ree energy ch'nge on (rop 2or3'tion will )e

P

! r-

$n!" lnPo

%1#.11+

where )oth ele3ents to the right c'n )e written in ter3s o2 the (rop r'(is,

r. I2 is the (ensity o2 the lii( 'n(& its 3olecl'r weight, the e'tion )e

co3es

$r#


32/53

P

! r-

%1#.1-+

& R"

Po


33/53

33' 8?=S=@S

where the two ter3s 're o2 opposite sign 'n( h'e ' (i22erent (epen(ence on

r.8 plot o2 $erss re5hi)its ' 3'5i33 's illstr'te( in


34/53

ing to ' clster si4e o2 ')ot -G w'ter 3olecles. It is (i22iclt to s'y whether '

(rop o2 th't s3'll si4e 'ct'lly h's the s'3e properties 's the )l* lii(. It is

pro)')le, in 2'ct, th't the rel'tiely high sr2'ce : ol3e r'tio in sch 'n

'sse3)ly will reslt in 'n 'ct'l sr2'ce tension gre'ter th'n the tre;; )l*

'le o2 "- 3N 31. I2 ' l'rger 'le 2or is se(, the 'le o2 rc(ecre'ses. /he

s'3e occrs 's the (egree o2 spers'tr'tion incre'ses. /he ncritic'l

'ntit'tie se o2 'tion %1#.1#+ c'n )e 3isle'(ing in th't it pre(icts critic'l

clster si4es 2or ho3ogeneos ncle'tion th't 're nli*ely to occr with 3ch

2reency i2 le2t to the ch'nce o2 r'n(o3 2lct'tion processes. 'lit'tiely,

howeer, the e'tion is se2l in e5pl'ining the (i22iclty o2 2or3ing lii(

'erosols )y (irect con(ens'tion in highly pri2ie( syste3s.

I2 one co3)ines 'tion %1#.1-+ 'n( %1#.1#+, one 3'y o)t'in ' 'le 2or

the 2ree energy o2 2or3'tion o2 ' clster o2 the critic'l r'(is 2or (rop

2or3'tion, $3'5:

$3'5

! rc-

1$#&

-

%1#.1!+

#

E#-%R" l %P%P ++

-F


35/53

P

-

1$#'3

-L#

R" ln


36/53

Po

FI()RE 13.. In ncle'tion processes there will e5ist ' critic'l p'rticle r'(is,rc,

)elow which 2ree energy consi(er'tions will (rie the incipient 'erosol p'rticle to

(is'ppe'r. 8)oe rcp'rticle growth shol( occr.


37/53

1#.!. S=@ID 8?=S=@S: D>S/ 8ND SM= 331

Concept'lly, one c'n thin* o2 the ncle'tion process in the 2ollowing

ter3s. I2 the pressre or 'ctiity o2 the 'por, P,is s3'll rel'tie to Po, then

$2or ' gien clster o2 3olecles will incre'se with e'ch '((e( 3olecle.

In other wor(s, the ten(ency will )e 2or clsters s3'ller th'n rcto retrn to

the 'por ph'se.

St'tistic'lly, one 3ight e5pect to enconter clsters o2 'll si4es (e to r'n(o3

2lct'tion processes howeer, 'll e5cept the s3'llest wol( )e ery

nco33on. /here wol( there2ore )e little li*elihoo( o2 o)t'ining the critic'l

r'(is necess'ry 2or (rop 2or3'tion to occr. oweer, 's the (egree o2

spers'tr'tion incre'ses, rc(ecre'ses 'n( r'n(o3 2lct'tions )egin to reslt

in 3ore clsters with th't r'(is. =nce th't point is re'che(, the clsters )egin

to grow spont'neosly to 2or3 (rops. When ' speci2ic spers'tr'tion pressre

is e5cee(e(, there will (eelop ' ste'(y p'r'(e o2 clsters o2 the reire(

critic'l (i3ensions, reslting in the 2or3'tion o2 ' isi)le 3ist or 2og.

Con(ens'tion 'erosols c'n 'lso )e prep're( )y che3ic'l re'ctions

inoling two g'seos re'ct'nts

8%g+ B%g+ C%l or s+

In sch ' process the p'rticle si4e will )e controlle( pri3'rily )y the

concentr'tions o2 the re'ct'nts in the g's ph'se.

13.-. SOLID AEROSOLS, D)ST AND SMOE


38/53

8erosols co3pose( o2 soli( p'rticles sspen(e( in ' g's 're co33only

re2erre( to 's (st or s3o*e,;; the e5'ct ter3inology s'lly (epen(ing on

the si4e 'n( se(i3ent'tion r'te o2 the p'rticles, or the 3etho( o2 'erosol

2or3'tion. In so3e sit'tions, 'erosols 2or3e( throgh (ispersion

processes 're ter3e( (sts;; while those 'rising 2ro3 con(ens'tion

processes 're c'lle( s3o*es.;; 8ltern'tiely, so3e pre2er to l')el 's (sts

'erosols o2 s22icient p'rticle si4e to h'e rel'tiely r'pi( %e.g., notice')le

oer ' short ti3e sp'n+ se(i3ent'tion r'tes in 'ir, while s3o*es wol( )e

o2 s3'ller, lighter p'rticles. ?eg'r(less o2 the ter3inology e3ploye(, it is

cle'r th't soli( 'erosols constitte ' ery i3port'nt, 'n( s'lly

n(esir')le, co3ponent o2 3'ny 3o(ern processes.

/he 3'6ority o2 in(stri'l 'erosols %)oth w'nte( 'n( nw'nte(+ 're pro(ce(

)y processes o2 (ispersion in which s3'll p'rticles 're 2or3e( 2ro3 l'rger soli(

3'sses. S3o*e 2ro3 )rning woo( or co'l, (st in sg'r re2ineries 'n( gr'in

3ills, 3ining (sts, 'n( so3e e5h'sts 2ro3 intern'l co3)stion engines 'll

2'll into this gener'l c'tegory o2 'erosol 2or3'tion. Bec'se o2 the r'ther

r'n(o3 n'tre o2 their 2or3'tion, (sts pro(ce( )y (ispersion technies (o

not len( the3seles to 'ntit'tie 'n'lysis o2 2'ctors controlling p'rticle si4e,si4e (istri)tion, or other 2'ctors o2 potenti'l interest in 3ost colloi('l syste3s.

Con(ens'tion 'erosols, on the other h'n(, 're less


39/53

332 8?=S=@S

co33on )t incl(e those 2or3e( )y the che3ic'l re'ction o2 one or 3ore

g'seos 3'teri'ls %e.g., '33oni'+ or )y o5i('tion or )rning 3'gnesi3.

/he con(itions o2 2or3'tion )y con(ens'tion 're so3ewh't 3ore

'ccessi)le 2ro3 'n e5peri3ent'l st'n(point %e.g., control o2 re'ct'nt 2low

r'tes, te3per'tre, pressre+ 'n( there2ore 3ore '3en')le to theoretic'l

'n'lysis. In 3ost c'ses, howeer, e5perience 'n( intition 're the

i3port'nt 2'ctors where control o2 2in'l 'erosol ch'r'cteristics is i3port'nt.

Bec'se o2 the pr'ctic'l i3port'nce 'n( potenti'lly h'r32l i3p'ct o2 soli(

'erosols pro(ce( )y (ispersion processes, they h'e receie( ' gre't (e'l o2

'ttention in ter3s o2 how their pro(ction c'n )e eli3in'te( or re(ce( 'n(

their (issip'tion sppresse(. In sch wor*, the e3ph'sis is s'lly pl'ce( on

process ch'nges th't will pro(ce 2ewer or l'rger %'n( there2ore 3ore r'pi(ly

se(i3enting+ p'rticles, or, 's in the c'se o2 co'l)rning 2rn'ces, ret'r(ing the

pw'r( 3oe3ent o2 c'r)on 'erosol p'rticles so th't they c'n )e 3ore

co3pletely )rne( )e2ore le'ing the st'c*. /he sppression 'n( (estrction

o2 s3o*es 'n( (sts will )e (iscsse( 2rther l'ter.

Soli( 'erosols pro(ce( )y con(ens'tion processes, while not gener'lly 's

i3port'nt 2ro3 ' pr'ctic'l st'n(point, 're o2ten o2 3ore theoretic'l interest

)ec'se it is e'sier to control their ncle'tion 'n( growth r'te, p'rticle si4e 'n(

si4e (istri)tion, 'n( r'te o2 (is'ppe'r'nce. /hey c'n there2ore )e se( 3ore

re'(ily to st(y the 'rios theories o2 'erosol 2or3'tion 'n( (estrction. /he

con(ens'tion 3etho(s nor3'lly e3ploye( in sch st(ies c'n )e (ii(e( into

two cl'sses: che3ic'l 'n( physic'l con(ens'tion processes. 8 typic'l physic'l

3etho( 3'y inole the he'ting o2 ' 3'teri'l o2 rel'tiely low ol'tility %e.g.,

ste'ric 'ci(+ s22iciently to pro(ce ' high (egree o2 spers'tr'tion 'n(

p'ssing the 'por into ' stre'3 o2 col( g's, r'pi(ly con(ensing the 'por into '

soli( 'erosol. M'ny o2 the ele3ents o2 to)'cco s3o*e 're 'lso o2 sch '

physic'l;; origin. 8 represent'tie che3ic'l 3etho( wol( )e illstr'te( )y the

g'sph'se re'ction o2 '33oni' 'n( hy(rogen chlori(e to pro(ce ' snow o2

'33oni3 chlori(e or )y the photoche3ic'l o5i('tion o2 iron pent'c'r)onyl


40/53

wi(e 're's )y 'irpl'ne or sr2'ce (ispers'l technies. In '((ition, so3e

in(stri'l c't'lysts, whose 'ctiity (epen(s on their h'ing ' l'rge sr2'ce :

ol3e r'tio, 're e22ectiely e3ploye( in the 2or3 o2 'n 'erosol (st or s3o*e.


41/53

1#.H / DS/?>C/I=N =< 8?=S=@S

333

13.0 THE DESTR)CTION OF AEROSOLS

8erosols, li*e 2o'3s, e3lsions, 'n( (ispersions, 3'y )e either '('nt'geos

or (etri3ent'l, (epen(ing on the sit'tion. /he preios (iscssion intro(ce(

so3e o2 the 2n('3ent'l 'spects o2 'erosol 2or3'tion. =2 e'l or perh'psgre'ter pr'ctic'l i3port'nce is the estion o2 the sppression o2 'erosol

2or3'tion, the (estrction o2 n'oi(')le 'erosols, or the controlle( (eposition

o2 'erosols onto sr2'ces. erh'ps the )est 'ppro'ch to soling sch pro)le3s

is throgh 'n n(erst'n(ing o2 so3e o2 the gener'l principles inole( in their

st')ili4'tion 'n( (estrction. In th't conte5t, so3e o2 the 3ech'nis3s o2

(estrction inole( will )e essenti'lly the s'3e 's those 2or other colloi('l

syste3s: 2loccl'tion 'n( co'lescence.

/he 3etho(s o2 (estroying 'erosols, whether lii( or soli(, 're n3eros.

So3e o2 the 3ore co33on 're illstr'te( in


42/53

FI()RE 13.7.8lthogh there 're ' n3)er o2 3etho(s to control 'erosol

(isch'rges,so3e o2 the 3ost co33on incl(e %a+ )'22le 2ilters, %b+ )'g 2ilters %c+

cyclones, 'n( %d+ spr'y scr))ers.


43/53

33- 8?=S=@S

the 'er'ge p'rticle %e5cept, o2 corse, where it stic*s to ' w'll or other

sr2'ce+, le'(ing to i3proe3ents sch 's ' 3ore r'pi( se(i3ent'tion (e

to gr'ity, 3ore e22icient collection in cyclonic precipit'tors, 'n( e'sier 2ilter

')ility.

8ccor(ing to 'tion %1#.$+, the r'te o2 2'll o2 'n 'erosol p'rticle will )e

proportion'l to the r'(is s're( 'n( the (ensity o2 the p'rticle %'ct'lly the(i22erence in (ensity )etween p'rticle 'n( g's+, 'n( inersely proportion'l to

the iscosity o2 the g's.


44/53

9# 1

-

where 1is the iscosity o2 the lii( 'erosol (rop.

8 co33on 3etho( 2or re3oing 'n 'erosol %s'lly soli(s+ 2ro3 the 'ir is the

cyclone collector. 8 typic'l cyclone (esign is illstr'te( in


45/53

orte5 '5is %'n( ot o2 the collector+ 'n( centri2g'l 2orces c'rrying the p'rticle

'w'y 2ro3 the '5is 'n( tow'r( the w'll.

/he centri2g'l 2orce, Fc, is gien )y

mvt

-

Fc

%1#.1$+

d

where mis the 3'ss o2 the p'rticle, vtis its t'ngenti'l elocity, 'n( dis its (ist'nce

2ro3 the orte5 '5is. 8lthogh centri2g'l 2orces will (o3in'te the 2orce )'l'nce,

ti3e is reire( 2or the p'rticle to re'ch the w'll, so th't ' cert'in resi(ence ti3e inthe cyclone will )e reire( 'n( the (esign (i3ensions


46/53

1#.H / DS/?>C/I=N =< 8?=S=@S

330


47/53

FI()RE 13.8. =ne o2 the 3ost se( 3etho(s o2 soli( 'erosol or pow(er collection

is the cyclone collector. /he pow(erl'(en 'ir enters the collector t'ngenti'lly 'n(

the 3ore (ense pow(er is 2orce( to the w'lls )y centri2g'l 2orce. /he cle'ne(;; 'ir

then e5its the collector )y ' centr'l '5i'l (ct.

3st t'*e th't into 'ccont. In '((ition, c're 3st )e t'*en to insre th't

precipit'te( p'rticles 're not reintro(ce( into the 'ir stre'3 )y the orte5 'n(

p'rticles c'rrie( ot with the cle'n;; 'ir. 8lthogh the oper'tion o2 the typic'l

cyclone collector is (escri)e( in ter3s o2 ' (o)le spir'l 2low, the 'ct'l 2low

sit'tion is e5tre3ely co3ple5, 'n( ' gre't (e'l re3'ins to )e le'rne(.

/he cyclone collector is e5tre3ely co33on 'n( c'n )e 2on( with 3'ny

(esign 'ri'tions incorpor'te( to incre'se e22iciency or to 3eet speci2ic

nee(s. 8l3ost 'll spr'y (rying processes e3ploy cyclones 2or pri3'ry or

secon('ry pro(ct collection. =ther in(stri'l processes e3ploy the3 to

control the (isch'rge o2 nw'nte( 'erosols into the eniron3ent.

=ne 3ech'nis3 2or the (estrction o2 ' 3ist or 2og o2 ' ol'tile lii( is )y

ch'nging the (egree o2 s'tr'tion;; o2 the srron(ing g's. I2 the g's

cont'ins less th'n the s'tr'tion '3ont o2 'por o2 the lii( ph'se, the

(rop will e'por'te. /he r'te o2 e'por'tion o2 ' (rop o2 lii( o2 r'(is r

'n( 3'ss mis gien )y

dm

-


48/53

! (crE1 !

F

%1#.1"+

dt


49/53

33 8?=S=@S

where !is ' const'nt (epen(ing on the 'por (i22sion coe22icient (%c3-s

1+,

cis the concentr'tion o2 the 'por ne5t to the (rop %g c3#+, vtis the r'te o2 2'll

's gien )y 'tion %1#.$+, 'n( the other ter3s 're 's preiosly (e2ine(.


50/53

$ r

/'*e, 2or e5'3ple, ' p'rticle with ch'rge -e, r10!c3, in 'ir 't -0 C p'ssing

)etween two ertic'l electro(es H c3 'p'rt with 'n 'pplie( potenti'l o2 10$ 3

1. 8ccor(ing to 'tion %1#.1G+, the elocity o2 3igr'tion in the

FI()RE 13.9. In the electrost'tic precipit'tion o2 ch'rge( 'erosols, the 'ir is 3'(e

to p'ss )etween two oppositely ch'rge( electro(es so th't the p'rticles will )e

'ttr'cte( to 'n( '(here to the electro(e sr2'ces. I2 the con2igr'tion o2 the

electro(es is properly (esigne(, ery e22icient 'erosol re3o'l c'n )e 'chiee(.


51/53

?=B@MS 337

electric 2iel( will )e 0.09# c3 s1. I2 the p'rticle h's ' (ensity o2 # g c3

#, its

r'te o2 2ree 2'll will )e 0.0! c3 s1E. %1#.$+F. 8ss3ing th't the p'rticle

enters the electric 2iel( ei(ist'nt 2ro3 e'ch electro(e, it will re'ch the

correspon(ing electro(e sr2'ce )e2ore le'ing the 2iel( so long 's the

height o2 the electro(es is gre'ter th'n 1.0G c3.

/he 3oe3ent o2 ch'rge( 'erosol p'rticles in electric 2iel(s h's 3'ny

i3port'nt technologic'l 'pplic'tions, incl(ing electro(eposition %especi'lly 2or

p'inting 3et'llic sr2'ces sch 's 'to3o)iles+ 'n( electrophotogr'phy. It is

'lso ery i3port'nt 2or the pri2ic'tion o2 'ir in critic'l sit'tions.

8((ition'l pr'ctic'l 3etho(s o2 'erosol re3o'l incl(e 2iltr'tion 'n( cen

tri2g'tion. Centri2g'tion, o2 corse, is )'sic'lly the s'3e 'sse(i3ent'tion e5cept th't the 2orce o2 gr'ity is repl'ce( )y 'rti2ici'l 2orces

o2 gre'ter strength. 'tion %1#.$+ contines to 'pply in th't c'se,

'lthogh the 'le o2 3st )e 3ltiplie( )y the 'ppropri'te 2'ctor.


52/53

PRO4LEMS

sti3'te the critic'l (rop si4e 2or the ncle'tion o2 r'in (roplets in ' clo(

2or3'tion 't 't3ospheric pressre 'n( 'ir te3per'tre %"+ o2 1H C.

8ss3e th't the sr2'ce tension o2 w'ter is "#.0 3N 31't th't

te3per'tre. ?epe't the c'lcl'tion 2or 'ir te3per'tres o2 !H 'n( 90 C'ss3ing th't the sr2'ce tension o2 w'ter oer the te3per'tre r'nge 0A

100 C is gien )y the 2or3l' 0.1$$!""H.9G.

I2 ' (rop o2 w'ter in ' clo( 2or3'tion 'tt'ins ' (i'3eter o2 1 33, wh't will

its ste'(yst'te elocity )e 's it 2'lls

I2 w'ter (rops 're 2or3e( oer ' )oiling *ettle oer which there e5ists 'n

pw'r( conection crrent o2 0.0- 3 s1, wh't will )e the critic'l (roplet

(i'3eter 2or which the (rops will )egin to 2'll


53/53

8?=S=@S

Kien ' w'ter (rop 2'lling throgh 'ir 't -0 C 'n( 1 't3 with ' elocity o2 0.-H 3 s1, c'lcl'te the

?eynol(s n3)er o2 the 'ir.

8 (st p'rticle o2 (i'3eter ! 10"3 settles in the 'ir 't -0 C 'n( 1 't3. Wh't is its ste'(yst'te

elocity ow long will it t'*e to 2'll one 3eter

ow 3ch ti3e is reire( 2or ' spheric'l p'rticle o2 (ensity -.0 g c3#'n( 1000 n3 in (i'3eter to

2'll 1 3 n(er gr'ity 't -H C in

%'+ w'ter %)+ 'ir 't 1 't3 pressre %c+ in ' high 'c3

8erosoll'(en 'ir 't -H C is pri2ie( )y p'ssing it )etween two p'r'llel electro(es $ c3 'p'rt 't ' elocity o2

0.0H c3 s1. /he potenti'l 'cross the electro(es is 10

$ c3

1, the p'rticle ch'rge is -e,'n( the (ensity is

-.H g c3#. Wh't is the 3ini33 height o2 the electro(es th't will ensre co3plete re3o'l o2 the 'erosol

2ro3 the 'ir

/ri'ls o2 ' new process 2or prep'ring ' pow(er o2 ' te3per'treensitie 3'teri'l )y sing ' spinning

(is* spr'y cooler reslt in 'n 'er'ge p'rticle si4e too l'rge to 3eet pro(ct speci2ic'tions. Sggest

three process 3o(i2ic'tions th't 3ight reslt in ' re(ction o2 the 'er'ge p'rticle si4e th't wol( not

'22ect the pro(ction r'te 2or the pro(ct.

With re2erence to ro)le3 1#.G, i2 te3per'tre sensitiity is not ' pro)le3, wh't '((ition'l step 3ight

)e se2l to sole the p'rticle si4e pro)le3

In ' no44le 'to3i4'tion process, gien ' 2i5e( no44le (i'3eter 'n( lii( pressre, 'n incre'se in

lii( te3per'tre will %'+ incre'se the 'er'ge (roplet (i'3eter %)+ (ecre'se the (roplet (i'3eter

%c+ h'e no e22ect on (roplet (i'3eter %(+ the e22ect c'nnot )e pre(icte( )'se( on ''il')le

in2or3'tion. 5pl'in yor 'nswer.

aerosol dari buku permukaan versi inggris

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