The cooperation of Mr. Myron Black of Peerless Cement i n. Detroit, dichigan ..... The Group I1 elements consj.st of ScryLlium, magnesium, calcium, strontium ...
PCA R&D Serial No. 1154
MARCH 1981
ASSESSMENT OF WASTE FUEL USE IN CEMENT KILNS
by
',
Douglas L. Hazelwcod Francis J. Smith A.T. Kearney, Inc.
Alexandria, Virginia 223 13 Ellis M. Gartner Portland Cement Association Skokie, Illinois 60077 68-03-2586
Project Officws Leo Weitzman and Hairy Freeman Industrial Environmental Research Laboratory Cincinnati, Ohio 45268
prepared for 1
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U.S. ENVIRONMENTAL PROTECTION AGENCY Office of Reseerch and Development Washingtcn, D.C. 20460
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ASSESSMENT OF WASTE FL‘EL USE IN CEMENT KILNS by
Douglas L. Hatelwood Francis J. Smith A.T. Kearney, Inc. Alexandria, Virginia 223 13
Ellis !vl. Gartner Portland Cement Association Skokie, Illinois 60077 68-03-2586
Project Officers Lea Weitrman 2nd Harry Freeman Industrial Environmental Research Laboratory
Cincinnati, Ohio 45268 prepared for U.S . ENV IR Q NM E NT A L PR 0 TECTlO N AGE PlCY C f k e o i Research and Development ..
Wnshhgtcn. 9.C. 20460
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x : c wastes p r e c l u d e s C?eir iise J S f u e l s in most : r i r i u ~ t r 1 ; 1 1 ~ ~ : - O C P S S C cement S ~ m a n u f a c t u r e h i n g the n c t a L l e t’sce t i ,:ti .
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SECTION 4 TECHNICAL ASPECTS OF WASTE FUEL USE
This Section describes t h e t e c h n o l o g y of cement ptoduct i o n and t h e e f f e c t s of added chemicals on cement properties. Past research in the use of waste f u e l s is a l s o reviewed. A l t h o u g h Same work ha.s Seen conducted u s i n g m u n i c i p a l refuse. d i s c a r d e d automobile t i r e s and petroleum coke as supplemental f u e l s in cement k i l n s , t h i s study was limited to t h e assessment of l i q u i d o r g a n i c i n d u s t r i a l wastes a s k i l n fuels. S e m i - s o l i d wastes, such a s i n d u s t r i a l siudqes, may be shown to be f e a s i b l e k i l n fuels i n t h e f u t u r e , however, firing problems and concerns over p o t e n t i a l cement quality impacts have restricted research p r o g r a m to t h e use of liquid wastes thus f a r . CEMENT MANUFACTURING TECHNOLOGY
T h e r e are two b a s i c c e m e n t manufacturing processes: t h e process and t h e d r y process. F i g u r e s 1 and 2 illustrate the equipment c o m m l y u s e d in these processes. The w e t process involves t h e yrinzing of raw m a t e r i a l s w i t h watcr to form 3 s l u r r y containiny 30 to 4 0 p e r c e n t i a o i s t u r e . The s l u r r y is b l e n d e d , as required, and s c b s e q u e n t l y fed to t h e k i l n . T h e d r y process, on t h e o t h e r h a n d , does mt introduce water d u r i n g g r i n d i n g and t h e raw m a t e r i a l s axe f e d to t h e kiln in t h e form of a d r y powder. vet
'
The wet process was t h e o r i g i n a l cement m a n u f a c t u L i n g proc e s s , and u n t i l recently, had advantages over t h e dry process due to ease of h a n d l i n g and blending of raw m a t e r i a l s as w e l l a s yielding h i g h e r q u a l i t y clinker. However, improvements in d r y b l e n d i n g and material handling techniques, i n combination
with lower e n e r g y consumption used in t h e d r y process, has m i n i m i z e d the a d v a n t a g e s of t h e wet process. Most new cement p l a n t s or p r o d u c t i o n l i n e s now u s e t h e d r y process.
1
7
Figure 1.
Typical Wet Process K!.Xn.
T h e r 3 t e s of p o r t l a n d c c m c n k production since 1?70 a r n r e s c n t c d in T a b l e 1. Type I ana 71 cements r e p r e s e n t hpgroxim a t e l y 30-95 p e r c e n t of t o t a l U.S. c e m e n t p r c d u c t i o n s h o w n . G n l y p l a f i t s producing Type I and TI ccments h a v e Seen emplayed to d i s p o s e of waste f u e l s to d a t e . Rezause of t h e r e l a t i v e l y small c a p a c i t y f o r u t i l i z i n g p l a n t s p r o d u c i n g o t h e r cLz..ent t y p e s to d i s p o s e of w a s t e s , t h i s r e p o r t 3 d d r e s s e s only the feasibility of using k i l n s Froducing 'i';.?e 1 and I 1 portland Cements, However, therE are few differences between all five t y p e s in terms aE pyroy rocessing e o z d i t i o l l s . T h e s t a n d a r d : i n i t : of measure u s e d by the cement i n d u s t r y is t h p s h o r t t o n izquivalent to 2,OGO j=au;lris or 907 kilograms). Znr this r e a s o n , short t g n s 2nd s i m i l a r English units a r e used i n p r o s c n t i n q d a t a i n t h i s report.
? o r t ? a n d ccment clinkfr i s p r o c i ~ 1 ~!:y ~ ( 3t h e controlled h i g h t e m p e r a t c i e S t l c n i ~ gu f calcareous i n a t G r i a l ( e . q . , liinestcrle, o y s t e r .;he!,ia), argillacecus m a t e r i a l ( t i . q . , cldy, s h a l e ) , and silicc?ous m a t s r i a l s { e . q . , s a n d ) . These materials provide the 5a.;rc e l e p e n t s required in ccmrmt: c a l c i u i n , silicon, alurnizum id iron. A I L r3lemt;nts a r e u s u a l l : ; ? r e s e n t in their t u l . l y n x i d i z e c l !:ern i n :.-i.rnenr. clinker.
79, 005 81,432 86,597 79,482
1972
1973 1974 .I 9 75 1976 1977
6 7 , 776 71,922 77,852
1976
83,849 53,390 7 6 I 500 b3,400
1979 . ~
1980 (estimated) 1981. ( c s t i n a t e d )
9
3200
2830 2400 l&
0
0
w
2000
E
3
2 c
1600
w
0
=E
w l-
1200
800 400
0 PERCENT OF KILN LENGTH Figure 3 .
Typical Wet K i l n Temperature 2rofiles (1).
The p r o d u c t from t h e kiln consists of d a r k , h a r d n o d u l e s c a l l e d c l i n k e r . T h e s e n o d u l e s are 3 / 4 - i n c h e s or less in s i z e and are cooled x i t h air in a c l i n k e r cooler prior to storage and f u r t h e r processing, The hot recovered air from the cooler seLves as s e c o n d a r y air i n firing t h e k i l n s .
Part of t h e a i r from kine clinker cooler, a l o n g with combust i o n 5asc-s and water vapor i n t r o d u c e d in wet process s y s t e m s , t h r o u q t i the-kiln, into-some form of dust coll-ection The remainder of the c l i n sy:T?tem, ;nd finally ocit the s t a c k . k e r cooler gases are p a s s e d directly to the dust collection .;ysten. 'The k i l n and cooler e x h a u s t s carry e n t r e i n e d d u s t and volatilized m a t t e r from the k i l n i n t o the dust colleztion s y s Tern. Varying concentrations of nitrogen o x i d e s (NO,) and : G u l f u r a x i d e s (SO,) occur In the k i l n e x i t gases. :XISSL.S
C l i n k c r . is *?round w i t h a b o u t 3 - 6 percent .iypsum (calcium s u l f a t e ) , -:.id& '3 r . t t a r d the ccment's setting k i ; n e , t o form the f i n a i T c m e n t p r o d u c t . O t h e r ~jdditives s u c h 4s air-entraininq, 4 is -cr z i n g , and "wat..-r-prcofingc a g e n t s can be added.
.
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One of the XOST : i g n i l ; c ~ n tR C W tec!inolagl :dl d e v e L o p m e n t s ;n t h e cement i n d u s t r y I n r e c e n t y e a r s is t!ie . , u s p n s l c n p r e heater. T h i s u n i t car&o n l y be u s e d in d r y processes, w h e r e i t i s installed j u s t upstream of the kiln. The ?reheater cor.sists of a s e r i e s of cyclones c o n n e c t e d by pipes t h r o u g h which gases frcm t h e kiln p a s s upward c o u n t e r - c w ; : e n t t o the d r y raw material f i c w i a g down and a r o u n d t h e cyclones.
First, S i - s p e n s i o n p r e h e s t e r s o f f e r a number of a d v a n t a g e s . t h e y p r o v i d z conservation of e n e r g y 'chrough the t r a n s f e r of h e a t from the gas i n t o t h e raw r n a t e r i a l f e e d dust. This, i n t u r n , leads t o r o u g h l y 110 p e r c e n t calcination of t h e f e e d bei o r e it. c n t e r s t h e k i l n . The addition of a s e p a r a t e c c n h u s t i o n chamber or " p r u c a l c i n e r " LO t h e p r e h e a t e r s y s t e m cJn further i n c r e a s e the a m o u n t o f c a l c i r l a t i o n achieved. Up to 90 u e r c e n t of t h e reqyired c a l c i n a t i o n can be Q b c a i n e d w i t h s u c h s y s t e m s b e f o r e the feed e n t e r s ?.he k i l n . T?,;ese systems x c becoming increasingly p o p l a r s s they p e r m i t g r e z t e r t h r o u g h p u t f o r any g i v e n kiln s i z e .
In d e s i j n i r r g new p l a n t s , t h i use of p r e h e a t e r s with or Yithout p r c c a l c i n e r s m e z x khar. t h e r o t a r y k i l n need only be ibout h a i f tne l e n g t h as wocld be z e q u i r e d w i t h o u t a p r e h e a t e r . ; . ' r r ~ h e . ~ t : ~ c 5 :have, : however, been f o u n d to p r e s e n t m a t e r i a l flow 2i'oblerns "hen c h l o l : i n a t e d waste f u e l s a r e burned. ?REV ICIlS S T U D I E S S e v e r a l cement p l a n t s i n the T n i t z d S t a t e s and abroad h a v e exper.iniented i n t h e psst w i t h . i x ~ j u s t r i d lt l a s t e s as f u e l s o u r c e s , however, m o s t s f t h i s work has not l x r ? 2 d o c u m e n t P d . Contacts with ci_lrncr,t n L i n u f a c t u r e r s i n d i c a t e t h a t many companies h a v e c o n d u c t e d l i n i ' i c d l i u r a t i o n t r j a l s 1:;ith waste f u e l ; . T h e snajcrI t y of t h e s e .:rials h a v e Invcxivvd waste oii:; and s p e n t n o n - h a i oqcnsted solvcnts
.
T h e w a s t e f u e l ex2erixents which h a v e been d c c u n e n t e d are rzvieweu ::elow. S e c t i o n 5 c a n t s i n s detailed d i s c u s s i o n s of m i s s i n s testing r e s u i t s from tiieze s t u d i e s .
.-----------:t. Liixrence Cili5ent
-
. . .
1ZJnnua
Waste O i l E x p e r i m e n t - Xpproximatcly 330,000 y a l X o n s of u s e d S u b r i c d t i r i y a i l were b u r n e d at St. Lawrence Cement between idarch and M a y , 1974 ( 2 ) . T h e k i l n u t i l i z e d for this work was a dr:; s y s t e m w i t h d u a l f o u r - s t a g e p s e h e s t e r s equipFeci w i t h a by-pass s y s t e m , D u r i n g t h e experiment, the k i l n produced up tc ap2raximately 3,500 t o n s per day of c l i n k e r . T h e k i l n utilized in t h i s e x p e r i m e n t was oil-fired. Waste o i l was pumped and i n j e c t e d s e p a r a t e l y Ercm t h e number six o i l normally u s e d i n t h e k i l n , The heating v a l u e of t h e wastm o i l u s e d :lazied b e t w e e n about 13,600 and 19,300 BTU,/Lb or l 0 6 , O O O to L43, 100 ETU/gai. Waste t - u e l was u s e d 53r about o n e t h i r d of t h e t o t a l k i l n f u e l requirement.
The p r i n c i p a l focils of t h i s s t u d y was on t h e contaminants !.cad, z i n c , p h o s p h o r u s , and bronine p r e s e n t i n t h e waste fuels. ,'ipproximate cgncentrations of t h e s e materials i n the waste oils were:
Lead Bromine Zinc P h o s p h o r us
0.6% 6.15% G.13 r3.18
S t a c k testing r e v e a l e d RO i n c r c d s e d +iln emissions of t h e s e e l e m e n t s that could be z t t r i b u t e d t o t h e ~ a s t eo i l s , Particul a t e emissions f r o m the k i l n were a c t u a i l y foc;r!d to d e c r e a s e during p e r i o d s of waste fuel use. T h e lead, z i n c , ,ind p h o s p h o r u s p r e s e n t in the waste ail were l a r g e l y retainc2d in t h e c l i n k e r p r o d u c t . Most of t h e b r o m i n e was r e t a i n e d a s bromide i n t h e kiln dust. T h e uuality o f t h e c c m c n t was i n KO way impactcd by t h e use of waste fuels.
E x p e r i n e n t s Witti C h l o r i n q t c d X a s t e s m d PCB's-I n J u n e , 1975, St. Lawrence Cenent bcgan experiments using ;1 l n i x t u r e of c h l o r l n a t p d a l i p n a t i c materials In t h e i r d r y sclsp c n s i o n - p r e h e a t e r t i i l n ( 3 ) . It was f o u n d t h a t t h e chlorine p r e s e n t i n t h e ;qaste fuels p r e f e r e n t i a l l y formed easily volat i Li z e d a l k a l i c h l o r i d e s . A c ncrrnal k i l n temperathres- these : n a t e r i a l s 3re uoiatilized and c a r r i e d frcm t h e k i l n w i t h t h e gas stream. M a t e r i a l Guild-up problems were zncountered i n t h e k i l n s y s t e m when t h e s e alkali c h l o r i d e s c o n d e n s e d o n t h e raw :nt:!a1 in t h e r ~ r c i i c a t e r m d were r e t u r n e d to t h e kiln. This ;;rcJt'lw k e Qverccme Sy remirovinq ;f p r t i c n L 7 i ? h e k i l n ex: ? 1 1 < j t 73s I S :t -?ntrlrs t h e p r r h z a t c r syclten. .{ Y h .IU ; +. ,*?.: :?ac n~tist,be ~ e r r ~ o v n .It d t h e bypa:::: :;so i n u i : e s s e s . T5P 1f kex
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.
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- ~ w r e ~ cP ex p e r i n e n t s . ' . - 41 .1c d -
i
'L 9 p e r a t i c : : .
u:;ing a d r y : ~. *. . nwere a b o r t e d :!:is gas t!ue ;:: ?art to a
12
*
-
continual p l d g y i n g 2roblern c x p e r i m c r d d t ttie S y p a s s d u z t r e s u l t i n g f r o m i t s inadequate s i z e . I t was a l s o f o u n d that p a r ticulzte s t a c k *missions increased dramatically because of the i n a b i l i t y of t h e d u s t collection e q u i p e n t to h a n d l e t h e h i q h e r g a s f l m r a t e s r e q u i r e d to p r o p e r l y cool k h e bypass gas stream, It: was d e c i d e d , t h e r e f o r e , to continue t!ie experiments using one of t h e wet-process k i l n s of t h e St. Lawrence Cement Company,
Setwren { 7 c t o b c r , 1975 and J a n u a r y , 1 9 7 6 t b r e e experiments were c o n d u c t r d u s i n g an oil-fired/ 1,000 ton per day, wet process k i l n . Zach experiment i n v o l v e d a different chlorinated waste E u e i . The three w a s t e s 1:sed d u r i n g t h ? t e s t s a r e de. ; c r i ' x d i a T a b l e 2 on the Follosinq p a g u .
T h e :dastc €uels u s e d i n t h i s s x - p r i m e t l t had typical heating va1cl.s of ?,SO0 to i1,900 3 T U / l b or 9 4 , 6 0 0 to 117,800 FTU/gal lnci were u s e d to s u p p l e r c e n t iiumber s i x f u t r l oil use. The f u e l r c f l a c m n e n t l e v e l achieved w i t h :he ;:.astss averacred about 12
percent. Fuel. requirements for i;he k i l n '.:ere r ~ d u c e dby aparoximateLy G5 p e r c e n t of t h e a c t u c i i a i e r q y c:>ntretit of t h o wnEtes b u r n e d . T h e rema1ni:iq 3 5 p c r c z c t :2€ che wi3stes' ~ : I L . K ~ : J c c m t e n c was ex:~7encit.d in v o l . l t i t i z i n q the a l k a l i c h l o r i d e s f o r m e d by t h e a a d i tlir?n or C h I o r ine-5earing fuels. (This uti 1 i . z a t . i o n ' v a l u e is for -1 vki:>ke containing 3 0 p e r c e n t c h l o r i n e by w e i y h t 2nd would ;: i s n q e is E h e waste c-(:T.?Gs~ i i x rhangcu. ) m
T h e k e y t a c t o r i i : n i t i n g ::!:e ainouiic ITf wastes t h a t c o u l d be I n t r o d u c e r 3 i n t o t ! ? ~k i l n was ' !ie : ~ a ~ t e ! sc'; ! l o r i n e c o n t e n t . When c h l o r i n e was f e d to t h e x r l n i t t m h i g n 3 r a t e , A l k a l i chloride r i n g s were formed i n t h e k i l n w h i c h d i s r t l p t c a operations.
nna::..mum r a t e of c h l o r i n e addition c l u i n g t h e t e s t s was p e r c e n t r e l a t i - 2 9 to c i i n k e r w e i g h t . (This f i g u r e i n c l u d e s c h l o r i n e present i n t h e raw f e e d and the :lo. 6 fuel o i l . ) At r , a t e s b e l o w 0 . 7 percent, '10 process disruptians occurred, howz!ver, ! : a r i a t i o n s in kiln ci;emist?--y between , i a n t s make the t r s 2 n s f e r a b i l it y of t o l e - a n c e . ; s v e l s questionable. From these t e s t s f t is e s t i n a t ~ dt l i a t c n l o r i n e can p r o b a b l y be added t o - a i-*r*:JicaLw t prccpss .::i.n it: r a t e s up to 3.4-0.7 p e r c e n t wi2hout The
0.79
.
t
+ -
i i.;~-irptiar:. ~ ~ e ~ ; ~ : ~ ~ n s .
F
'TABLE 2 .
CONTENT OF WAS'iE FUELS USED IN CANA'rIAN TEST I I _ -
~
Contea ts (Percent)
Amount Used !;a1
waste Type
_c
Chlorinated a l i phat i c s ( a )
;om)
21,900
18.0 c h l o r o p t a p a n e L propenc, e t h y l c h l o r i d e , and d i ch loromctbane 16.5 dlchloroethans 15.6
chlatobenzenc
10.5 11.3 nu1 t ichlcrr inated butanes, b i t t e n e s , hexanes, and hexeneri
27.3 other c h l o r f n a t e d
aliphatic6 Chioririatrd aronatics ( b )
19 400
52.2
18.9 h e x a c h l o r w y c l o p e n t a d i -
ene and associated complexes ii.5 20.4
oc t a e h l o r o c y c l o p e n tene other cnlor i n a ted aromatizs
Chlor i n a t c d BE m a t i c 8 plus PCDslb)
28.5 chlorotoluene
23.3
tetrachlorobiphmyls
16.0 ttichlcrobiphtnyls 9.1 pent a c h l or nbi phen y 1s 5.5
dichlorabiphenyls
l?.6
other chlorinated aromatics
-Notes: -
(a)
AliphatiCS a t e a C l a s s of carbons compounds w i t h t h e a s r h n acorn8 in n p n c h a i n s -- - - -
(5)
hrcnaatics :t n g s .
...
re compounda containing one or acre b e n z e n e
S o ~ r c e : :4ac Qonald, L.P., "ydrocarbons i n
et.al., 'l3urnfng Waate ChiGrinated a Cement Kiln,' Fisheries and Envi-
ronmental. Canadal :4acch, 1 9 7 7 .
14
Particulate emissions ticre Eu:.inu f.3 incrcn:l;e when u h l o r inebearing wastes were b u rn e d i n t h e k i l n , T h i s is not s u r p r i s i n g since the c h l o r i n e from t h e b a s t e s will r'ombine w i t h p o t a s s i u m and siium in the k i l n to form volatile a l k a l i c h l o r i d e s w h i c h a r e carried f ~ o nthe kiln w i t h t h e e x n a u s t g a s e s . While the i n c r e a s e d dust loading exgerienced by t h e d u s t collection equipment can r e s u l t i n increased particulate m i s s i o n s , it is q u i t e feasible t h a t coilectir-n equipment can be rnodif ied to adequatel y c o n t r o l emissions i f c h l o r ine-bearing fiiel supplements a r e to be used cn a r o u t i n e basis. Particulate emissions fran t h e ::t:zck, u s u s l 1 . y a b o u t 0 . 5 p o u n d s per ton of c l i n k e r produced, incrrerased d u r i n g t h e t e s t s by a n a v e r a g e f a c t o r of 2 . 2 . D u r i ~ ? qt.22 ?rial with aliphatic wastes, p a r t i c u l a t e emissions averzged :;ix %imes t h e i r normai level.. This c o i n c i d e d with extensive r i n g iorrr;ation which reqcireci a k i l n s!-hut-dcwn. in s p i t e c f t h e h i g h emissions, masinurn g r o u n d level c m c c n t r a t i o n s ot: parricalates were calcul a t e d to be ;At l e a s t a f a c t u r C I ~ een lower t h e n the O n t a r i o s k a n u a r . ! of LO\? nicrograrris ~ P Ccubic :ze.cer. (iiccause of v a r i a tion:; r: i l n ziiernistr:, :'r:d d i i s t c o 1 1 x t i 3 f i s y s t e m efficiency, car 4 iculace e m i s s i o n d a t z i:; n ~ C r i r c c t : trar.sf s r a b l s between ?.!.:in LS ; "'
!4:
.
i
?
,i j
15
28 per ren t d i c h l o r 0methane 2 4 , 2 0 0 gallons
P C 3 in o i l
p e r c e n t krichloroe t hyler,e
Arochlor 1242 ii: r . i l 15.7 p e r c e n t total
chlorine content C h l o r o p h e n o l s and Phenoxyacids
Trichlo r e t r i f 1u o r ce t h a n e
Notes:
Source:
2,600
rja11(~s
560 sounds
94 S e r c e n t x y l e n e
2
percent W P P (a)
2
p e r c e n t MCPA ( b )
2
p e r c e n t chlorophen o l s and phenoxy acids
F r e o n TF
(a)
MCPP = 2- ( 2 - m e t h y l - 4 - c h l o r o p h e n o x y ) - p r o p i o n i c acid.
(b)
MC2A = 2-methyl-4-chlorophenox~acetic a c i d
Ahling, B , , "Combustion Test with C h l o r i n a t e d Hydroc a r b o n s i n a Cernent X i l n at S t o r a ~ i k aT z s t C e n t e r , " E w e d i s h Xater a n d , i r F o l l u t i o n R e s e a r c h I n s t i t u t e , L ; t o c k t i o ? ~ r ,:.larch 1 6 , l978. . . . . .
............................
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-.
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i3oth t h e S w e d i s h and C a n a d i a n f a c i 1 i t : es e m p l o y c l e c t r o static precipitators for controliinq d u s t e m i s s i o n s . I t appears t h a t ~ l k a l ic h l o r i d e s generated when c h l o r i n e is added to t h e k i l n have a h i g h e r resistivity t h a n typical kiln dust. T h i s ;'lay r e q u i r e " t u n i r g " of t h e precipitator s t a g e s in order to c a p t u r e t h e d u s t most e f f e 2 t i v e l y .
In tile c o u r s e of t h e e x p e r i m e n t s , t h e c l i n k e r p r o d u c t :;-;=wed d ~ c r c s s ein strength, Fi s l i g h t L e d u u t i o n i n c l i n k e r alkali c o n t e n t was r e a l i z e d . However, unlike t h e Canadian experiments, the c h a z q e was i : O t a s much as p r e d i c t e d by stoichiometric ~ ~ 3 1 culatians. T h i s d i s c r c n a n c y may be d u e to e r r o r s in c o ~ ~ t r ~ t i n q n mass b a l a n c e ::hat r e s u l t e d from a l a r q c v a r i a n c e i n m a t e r i a l f l o w rates d u r i n g the t e s t s . 110
EFFECTS OF YI'JOR
AND TRACE ELEMENTS ON
CEMENT !'4RNUFACTURR P J D USE : ; i ; n i r i c a n t p o t e n t i a l I - r x i s t s for d i s p c s i n q of many w a s t e s i n cement 2 i l . m i n a aiifc ;ind e f f i c i e n t m a n n e r . IIawever, t h e i z d i s c r i m i n a n t use cf w a s t z fl:c.ls in cement kilns can r e s u l t i n
l.:rliiccepta'31.e emission ~ C V C ~ S process , f a i l u r e s , and decreased l:i!!Ttcwt. q u a l i t y . i J i ti: :.i ccmi?iste k n o w l c d q e of t h e c o n s t i t u e n t s ~f t . ! i ~w a s t e Seina u t i l i z e d < ~ n d an u n d e r s c a n d i c g .of kiln chemi s t r y. ,_ it is g o c s i b l e to supp.lcment o r p o s s i b l y even r e p l a c e i " o n s 1 i f u c i ..::TP d i t h 1.itt.le 01 no n e g a t i v e i n p z c t s . This sub:;cction r,in!mari::es ::he l i k e l y ::E:lects 04-: typical :iasts F u e l ci:,nsti,t i ~ c n t so n t!:e cernent m a n u f a c t u r i n g process and cement quijii t y . 111 !jenc::ai, the tolerance I J € ,I p a r t i c u l a r process for c h e w ical:; " , h i l t : n a y 5e p r e s e n t in c.~ac,tc fue!.s will depend on the ' e x i s t i n c ; k i l n ::!iumistrqr. ,The k i l : i chemistry itself is dependent on t h e constituents p r e s e n t i n the raw. feedstoc!:s a n d t h e ?:tie: ( i n i is l i k e i y to v n r y bctwe,:n geographic rsgions. These basid t i i i f e r c n c c s hptween scmcnt p l j n t s p r e v e n t the 2orrnulatio.i c f ;c?t : . t > l < ? r 3 i 1 C t . !.t?vc 1s for L":emicals t h a t may be i n t r o d w e d :IICC) t,tit' c e n e ~ i t r h r o u g h rxaste f u e l s .
Group I elements consist of h y d r o g e n , l i t h i u m , sodiua, i m t s s s i u r n , rubidium, and cesium.
Hydrogen { H ) -I l y d r o g e n , introduced in t h e f o r m of w a t e r , i s very common in a l l k i l n s and a p p a r e n t l y h a s little e f f e c t on c l i n k e r properties. Lithiurn {Li)-L i t h i u m T t ' n e r a l l y occur3 i n c e m e n t i n concenttations of 0 . 0 2 p e r c e n t or less. Tt. niny be t x n e f i z i a 1 in r e t a r d i n g a ? . , a l i L > q y r c g a t er c a r t i c n s and i x p r o v l s f j b c r n 4 . i h i l i t y level;; ::p k o Oi1c F . ? r c e n t ( 7 , 8 , 9 ) .
-I=
19
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\XI--
Potassium is p r e s e n t i n most ceraent t : i i j ~ k ~lt~ ;!:ay ~ ~ ~d ~ . ; u in k i l n d u G t K C i , X2S0,; 3 r KkC'O3. ?cta:,.Siun P E P E e r e n t i a l l y forms I(2SD4 in k h e t 2 r c s c n c e of sulfur G n d oxygen. T h e s u l f a t e usually occurs i n t h e clinker as a crystalline solid solution c a l l e d a p h t h i t a l i t c or glaserite of approximate composition K3Na ( 5 0 4 ) ~ . A r c a n i t e , X z S O 4 , is diso formed i n c l i n k e r s . E x c e s s potassium in c l i n k e r tends t o e n t e r t h e belite phase, ( C a 0 ) ~SO3, f o r m i n g t h e s o - c a l i e d " a l k a l i - b e l i t e " of approximate composition R20 (CaO)23 (SO31 1 2 . Since t h e presence of a l k a l i - b e + L i t e s can d e t r i m e n t a l l y affect c e m e n t Guality, it is p r e f e r a b l e t o b a l a n c e the p o t a s s i u n with sufficient s u l f u r s u c h t h a t most of t h e c l i n k e r potassium is in t h e form of sulEates. E x c e s s i v e concentrations of potassium in t h e cement can cause alkali-aggregate r e a c t i o n s s i m i l a r tc those d i s c u s s e d u n d e r so? i urn. be p r e s e n t
b i s
T h e ASTN s;zizs a t o t a l a l k a l i specification f o r "low a l k a l i " cements as $ r e s e n t e d i n equation ( 1 ) . E x c e s s i v e a l k a l i s m a y also result in m a t z r i a l b u i l d u p w i t h i n the k i l n system and t h e formation cf r i n g s i n t h e k i l n ( l l , . L 2 , 1 3 ) . R u b i d i u m ( E b ) and C e s i u m (Cs)-F u b i d i u n and cesium g e n e r a l ' - y o c c ~ i! n~ c e m e n t s i n concent r a ~ : ~ o :oi s .:1.02 p e r c e n t or less. 'They m y be e x p e c t e d to behave v e r y simiL:.rly to potassium, t a r m i n g s t a b l e sulEates and volatile a h l o r i d e s ( 7 ) .
Grour, 11 Slements -. T h e Group I1 elements consj.st of S c r y L l i u m , m a g n e s i u m , calcium, strontium, and barium.
i 3 e r y l l i u m (BE)-Beryllium has not been measured i n cement c l i n k e r i n significant quantities. Its h c i l z V i O K i n a cement k i l n cannot be predicted d l t b o u g h d u e to t.ie stability a d i n v o l d ' : i l i t y of its o x i d e s it appears p r o b a b l e t h a t it primarily w o u l d be r e t a i n e d in t h e c l i n r c e r .
1
I'
Strontium fSr)-S t r o n t i u m f r e q u e n t l y o c c u r s in cement i n the range of 0.050 . 4 percent. I t appears to be m a r g i n a l l y harmful t o cement s t r e n g t h a n d other physical characteristics. E x c e s s i v e SrO This may c o u l d increase free lime c o n t e n t i f not c o u n t e r a c t e d . i n t u r n cause deleteriouc e x p a n s i o n s in concrete i n c o n c e n t r a t i o n s g r e a t e r than 1-2 percent (7,14,15).
Barium (Ba)-Barium is u s u a l l y found in cement c l i n k e r at levels below 0.2 p e r c e n t . I t is reported to produce s m a l l increases in cement paste shrinkage b u t may also increase strengths. E x c e s sive BaO w i l l i n c r e a s e f r e e lime content i f n o t c o u n t e r a c t e d . "ree lime concentrations above 1-2 p e r c e n t may cause deleterious e x p a n s i o n of some concretes (7,9,16). Group 111 E l - e m e n t s
T h e G r o u p III elements c o n s i s t of b o r o n , aluminum, g a l l i u m , indium, and t h a l l i u m .
.
Boron {El-Boron is u s u a l l y present i n c e m e n t in trace q u a n t i t i e s . ' B o r o n a p p e a r s t o be sensitive to t h e p r e s e n c e of other m i n o r elements a s i t exhibits G r r a t i c behavior when added to c e m e n t . Concentrations of boron oxide a s L o w as 0.04 p e r c e n t have been reported t o have d e l e t e r i o u s effects on c e m e n t i n g p - r o-p e r t i e s . However I b e n e f i c i a l effects have been o b s e r v e d i n some i n s t a n c e s (16~7).
--
Alumi. num iAl) Alurniriurn is d component of all c e m e n t s and is u s u a l l y prese n t ( i n s a l u t i o n with other compounds) i n c o n c e n t r a t i o n s of 2-7 percent as A l 2 O 3 . The ASTM l i m i t s A 1 7 0 1 c o n c e n t r a t i o n g t o six percent and t r i c a l c i u m a l u m i n a t e ( 3 C a O . A l 2 0 3 ) concentrations to eight p e r c e n t i n type I 1 p o r t l a n d cement (10). -
G a l l i urn
I
--
(Ga) G a l l i u m presumably occurs o n l y i n trace q u a n t i t i e s in cen e n t raw materials. G a l l i u m a p p a r e n t l y is commonly f o u n d .in m a 1 in concentrations of 4-10 ppm. YO information is avdila b l e cn g a l l i u m i n c p m e n t k i l l ? systems (13,19,20).'
- , , \ I iim I -r-
( I n )--
I n d i u m :l:-cs:;nabI~ ~ c u r sonly in t r a c e quantities i n c e m e n t "7:v.ls of i n d i u m i n coai are p r o b a b l y on t h e
raw a a t e r i 2 l s
~
o r d e r O f G.93 ~ . Tr,dium is relatively v o l a t i l e , i n d , i n a ' c i l n aystcr?.. likely to be : k p o s i r e d i n the L i J n d u s t . No infcrnat:m --: : v a l l a b l e on incii1:n i n c e m e n t k i l n L;ystems ( 2 0 ,
-
21).
:hail.iun i ~ i ) - ? h a l l i u m u s u a l l y occurs o n l y i n t r z c e q u a n t i t i e s i n c e m e n t raw m a t e r i a l s . 'Fhallicm c o n c e n t r a t i o n s in coal are p r o b a b l y i n t h e orcier or' 1 ppm but nay be h i g h e r . T h a l l i i l m is r a t h e r volatile and is likely to concentrate in t h e k i l n d G s t (21).
:roup CV E l e m e n t s The Group XV elements a r e carbon, silicon, jernanium, t i n , and l e a d .
: ~ it r o q e n
--
(3)
?iitroy@n is p r e s e n t as ?,be :ua-jor o m p o n c n t or the k i l n gas stream, Elitrogen c o n t a i n e d i n f u e l s is b e l i e v e d to cantribuse to k i l n 30, e m i s s i o n s . L e v e l s of nitrogen i n coal and o t h e r f u e l s ace v a r i i i b l e h u t f y e q u e n t l y a r e a s h i g h as 1-2 p e r c e n t , Raw feed m a t e r i a l s c a n t y p i c a l l y contain ~p to 0.1 p e r c e n t ~ i t r o g e nw h i l e cemenr c l i n k e r s , depending on w h e t h e r t h e y a r e pzoduced under oxidizing O K reducing conditions, w i l l c m t a i n a f r ? w p a r t s per million nitrogen up to 0 . 0 5 p e r c e n t nitrogen, respective 1y ,
?
1
--
Phosphor u s (P) P h o s p h o r u s sometines occurs at l e v e l s of m e p e r c e n t or more in raw m a t e r i a l s . I t is almost completely r a t a i r l e d b y t h e clinker. L e v e l s of the oxide, 9705, - - of 0.5 pcrcerlt or less in cement w i l l p r o b a b l y n o t a f f e c t cement p r o p e r t i e s . High l e v e l s o f "05, above 2 . 5 P e r c e n t , are known to s e r i o u s i y r e t a r d strefiqths. i n t e r m e d i a t e l z v e l s of s h o s p h o r u s a r c tolerable when balanced by the additian of E l u o r i d e s and p a s i b l y chlorides i : 6 , 2 5 ) .
A r s e n i c (As)-The ~ I r s a n i ct e n d s tc 5cl-n t h e i > x i d e s A S T O ? and A s 2 O j . S t ' n t o x i r k decomposes t o ,i:e r r : o x i c e a t a f a i r l y .LGW !:limpera. . L . -
-93oCli.
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3 i s m u t h (Bi;T h e effects of S i s n u t h o n cement p r c d w t l o n z r e n o t tinderstood. B i s m u t h t e z d s ':o.For,-n t h e t 7 x i c k s B i 9 3 3 and Bi205, eb." 7 e n t o x i d e b e i n q t!:? F r z v e l a n t t o r n at. I i l g n e r temper atur es. 3 i s m u t h ma!' Le J??osited i n t h e k i l n dust.
ro[Jjerty darnaqc. personal. I n j u r y , and r.he g r o s s contamifiation af air w i t h c o m b u s t i o n p r o d u c t s . w,rstu
I
~ 3 1storage t a n k s used for storing w d s t e fuels s h o u l d be of s t u r d y and leak-proof c o n s t r u c t i o n I n x c o r d a n c e with regulat i o n s set f o r t h by the Occupational Safety and H e a l t h A d m i n i stration ( 2 9 CFR P a r t 1910, StlCpart A , section i91tj.106). The use of a plant's e x i s t i n g s t o r a g e tanks, pumps, a n d p i p i n g m a y be f m s i b l e . However, the c o r n p a t a b i l i t y of t h e w a s t e s w i t h e x i s t i r i g equipment s h o u l d be assessed to i n s a r e th& excessive corrosion, pumping difficulties, or trapor releases do n o t occur. A p r i n c i p a l concern i n selecting e q u i p m e n t will b e t h e corrosiveness of the w a s t e s to be h a n d l e d . :daterial made of s t e e l nay be appropriate for h a n d l i n g some v a s t e s while more corrosive w a s t e s may r e q u i r e f u l l y lined systems. Equipment s u p p l i e r s w i l l be t h e b e s t source of i n f o r m a t i o n f o r m a t c h i n g e q u i r j m e n t specifications to waste characteristics. S p e c i a l c a r e s h o u l d be e x e r c i s e d i n s e l e c t i n g pump s y s t e m s . Waste f u e l pumps will. t y p i c a l l y he required to h a n d l e wastes of v a r y i n g viscosities w i t h occasicnally h i g h s o l i d s concentrations, and to d e ' l i v e r v a r i a b l e flow r a t e s w i t h h i g h p r e s s u r e s (about 100200 p s i ) f a r long p i p i n g d i s t a n c e s .
Waste-fuel storage t a n k s a n d pumps s h o u l d be 'located Gn irnperrneabie pads and s u r r o u n d e d by d i k e s , berms, OK s i m i l a r ~ ' J t ~ ~ l r t ucraepsa b l e of containing the r e s u l t s of a n y m a s s i v e :.;pill E i nerqency e q u i p m e n t , s u c h as f i r e extinguishers, b r e a t h i n g ~ ~ l a s k ss,o r b e n t materials, and shower-wash stations, s h o u l d be s i t e d In the immediate v i c i n i t y cf the storage a r e a , and employees t r a i n s d in their proper use. O f f - l o a d i n a of tank t r u c k s OK tank cars s h o ~ be ? conducted in ;t way t h a t m i n i m i z e s vapor r e l e a s e s into t t , c clir. The v a p o r s p r e s e n t i n t h e plant's storage tank w i l l . be displaced ~ it? he t a n k is fiiled and s h o u l d be p r o p e r l y contained. These f u m e s c a n a? c d s j . 1 ~r e t u r n e d to t h e transport t a n k via a closed line Setween taqk v e n t s . ;n ,iddition, sorbent t r a p s q h o u l d be p r e s *'-it 'n t h e Flant's :;tor2(3e t m k ver.ts to c o n t a i n v a p s r s e v o l v e d # I S Lir e s r i l t D E t h e r m a l expansion and ;noleefilar c i i f f u s i o n d u r i n g :.or.~ii.f.; tJrage. ..
As XI , : i t e r n a t i v e to s o r b e n t t r a p s , '1 ?:ant n a y e i c c t to v+?rit t a n k v3por.s , i i r e c t l y i n t o the kiln's f e e d a i r supply. -,,ls L. t e c h n i q u e is sometines u s e d i n lime k i l n s and k r a f t PULP nills to control +lapor emissions and odors. Such s y s t e m s gent.ral1y function ,1t:dzr n..gativc F r c s s u r e and a r e designed to k;le3 'rapor c 3 n c c n t r ~ t i o n sw e l l h e l m o n e - q u a r t e r of t h e vapor's ? m e r 'xplcs;,trp : i n i t . ~ ! o w e s r c r , i f S L c h a a;ys:tsm is r e l i e d upon -1
4
~o c:i:ninacp spillage and war kcr e x p x u ~ eCjuring a a i n t n n a n c e oFurations mrj a f t e r t r a n s f e r of v a s t c s b e t w e e n t a n k s , 3 system for f l c s h i n g waste r e s i d u e s from p i p i n g , p u m p S , and t a n k s s h o u l d be c ; ; * ? i o y e d. One p o s s i b l e s y s t e m is i l l u s t r a t e d in F i q u r e 4 . U s i n 9 s u c h a systerr,, equipment c o n t J i n i n g waste materials can 'se s e l e c t i v e l y r i n s e d w i t h a r e l s t i v e i y h a r m l e s s s u b s t a n c e such as NJO. 2 f u e l oil. A v l a i v i n g systen? s i r n i l i d r to t h e one i l l u s t r a t e d can be employed to direct t h e r i n s e o i l t h r c u g h a l l p i p i n g c o n t a i n i z g waste f u e l s , t h e t r a n s f e r hose u s e d to d r a i n t h e t a n k t r u c k , t h e w a s t e - f u e l p u m p , a n d t!ie w a s t e - f u e l s t o r z d e t a n k . T h i s w i 1 . l zllow r ? f u e i i . n , ( ; ::nd maintenance operations to be c o n d u c t e d withoat cisking s p i I . 1 2 , vzpor r e l e a s e s , or worker e x p s , s u r c s . As d n added precaution, pipiRc1 s h o u l d be arranged to a l l t h e system to be d r a i n e d ::y y r s b . i z y flow. i"rtomated i n c n i tors s h o u l d he -2rnployed to alert operators in the isvcnt ot' w a s t e - f u e l handling p r o b l e n . These systems may even be d e s i g n e d to i n s t i t u t e proper ccrrective a c t i o n s . ii
i2ressux-e t r a n s d u c c r located i n t h e waste p i p i n g a t t h e e n t r a n c e ! n t o !rhe k i l n c a n 5e employed Lo a t ? t o r n a t i c a l l y t u r n o f f the waste f u e l ;xmp i n the e v e n t s f a s d d e n pressure d r o p as would :IC e x p ? r i e n c e d i n J p i p e r u p t u r e ,>r. 7 ~ 1 Eailure. 2 Interlocks . s h o u l d z l s o be 9rovidc.d to automztically s t o p t!ie flow of waste .rid A i r Pollution Research I n s f - i- r&.; -' t e , ?-larch 16, .1378. ? ' *
T7
C a n a d i a n and S w e d i s h experiments L.,3vr- :, : e n t i F i 4 L ! ~ T + ~ GaGghter molecules d u r i n g s t a c k t e s t i n ? , .:t~:.cificsLl;), C ~ ~ O K O form, dichloromzthanc, and carbon t e t x a c h l r > r i d t ? . A l t h o u g h these compounds a l s o were d e t z c t e d in s t a c k emiss:ons d u r i n q p e r i d s when no waste f u e l s were being u s c d , t h e h ; \ j h e s t concentrations were f o w d when c h l o r i n a t e d waste f u e l s were a d d e d . I t appears that contamiEation of plant f e e d water l u r : n g t h e s p experiments c o u l d have r e s u l t e d in most of the e m i s s i a n u detected. Table 5 p r e s e n t s t h e maximum and z v e ~ a q econcentrations of orgaiiochlor1&s n c t u a l l y d e t e c t e d d u r i n g t h e S w e d i s h and Ganad i m c x p e r i n c n t s . Also p r e s e c t e d Lire ambient coilcentration.'; of these compounds o w r l a n d masses as c c v e a l c d by s e v e r a l stttdies conducted throughout the w o r l d .
Decause c;lobal background l e v e l s of c a r b o n tetrachloride a r e considerably greater than s t a c k concentrations d e t e c t e d d u t i c g a n y wzstc-tllel e x p e r i m e n t s , it apr;sars " c a t carbon tetr a c h l c r i d e emissions from cement p l a n t s b u r n i n g wasta f u e l s a r e not: 3 significant concern.
Pnissions of chloroform do not correlate well between t h e The C a n a d i a n s t u d i e s revealed peak b a c k g r o u n d ~ h ' I c r . ~ E o r concentrations m 'd:he;1 no waste f u e l s were b c i n y S n r n e d w h i c h a r e sppr oximateiy 1,300 times lower t h a n t h e S w e d i s h b a c k g r o m d emissions. T h i s larqe difference indicates t h a t t h e relatively h i s h emissions d e t e c t e d i n the Swcdisb ?xperiisc.nI:s ( a s compared to t h e Canadian r e s u l t s ) prob3bly oriqinated from contamination of t h e f e e d water used in m i x i n g t h e A-JW a e a l being f e d into t h e kiln.
Swedisn and Canaalizn s t u d i e s .
2 E t h e c?m::;SiOiIS d e t e c t e d d u r i n g the C a n a d i a n t e s t s are ltssurned to be typical, c?LLoroform smir ions w i l l n c t be 2 ::i5nifizant c o n c e r n . No ; - ? r c e p t i b l e change i n c f f - s i t e zmbierlt c o n c c n t r a r i o c s o f c h l o r o i o r x i s L _i:ely tt, .;c d e t c ? c t a b l e frcm s u c h lcw-levr31 1:missions.
C'RGANOffILORInE EMISS I3NS --
TABLE 5.
Maximum Emissions -Without With Waste Waste Pnnharn; -t.
. rue1s
n-.rb
culIIs.4CJliC
' d V . .
-
1
I
Average Global
Average Emissims
With waste
Backqround
.-
LnLorororm (b)
52
Chloroform ( c ) Dichloro-
0.018
18
29
c h l o r i d e (c) u c es :
27
0.069
m e t h a m (c) Carbon Tetra-
1 .I
Fuels
i a)
0.006
0.G04
12 0.341
0,015
14
0.036
0.120
0.063
concentraticns are e x p r e s s e d in p a r t s per billion ( p p b ) . To convert i n t o micrograms per c h i c meter (ug/m3) t h e followinq conversion
(a) A l l
,-
~,~..~--I--
I
*
~ F Chloroform S x
5,O = u g / d ppb Dichloromethane x 3.5 = ug/mL ppb Carbon retrachloride x 6 . 4
= ug,/n13
i t 1 Emission l e v e l s t a k e n from S w e d i s h experiments. ( c ) Ynission levels taken from C a n a d i a n experiments.
nor carbon tetrachloride her? d e t e c t e d during the S w e d i s h experiments,
Ne i cher d i c h l o r o m e t h a n e
A h l i n 5 , 2. , "Combustion T e s t W i t h Chiorinated Hydroca.-bons in a Cemcnt K i l n at S t o r a Vika Test C z n t c r , " Swedish Water and Air Polluting Xesearch I n s t i t u t e , Xarch 1 6 , 1978.
Sources:
1
.'.lacD o n a l d , L.P., e t . al., " B u r n i n g Waste C h l n r i nLab.>dGydrocarrbons i n a C e m e n t Kiln," F i s h e r i e s and S n v j ~.:nrnetlt Canada, :4arch, 1,377. " C h l o r o f c L z , :arbon T e t r a c h l o r i d e , and O t h e r Halordzthanes: b'in :::~?viror?rnent-l ~ s s e s s m e n," t "Jtional Acarlen:, c € S c i e n c e s , j.978, 3pc?ssc "'13Clr'
St.3'
tnrtL.;ticAl ! : o s e in
-
-
it
I:IS have , i e r n o n s t r x t e d c l e s t r :ict:ion of cx' .:*:;DS n u c h as 'CE': to beyond t h e l i m i t s of . .,,-:i';n, i t I s u n i i k t ? ! l y t h a t comy?ouncs such as - n ! i i ( j have ~ ' ~ c . ~ .~ I e~s ter ur cj t i o n . t t is l i k e l y
*->
;i
4s
4
1
I
i
1
t h a t these compounds are formed from t.he components of: fract u r e d waste molecules, or that t h e y o r i g i n a t e from contsmina-
tion of the feed water used to manufactuie t h e clinker.
It is known t h z t t h e incineration of c h l o r o p h e n o l s can result i n t h e emission of dioxins or furana w h i c h may be ext r e m e ly t . o x i c , For this reason, Swedish researchers conducted sensitive m o n i t o r i n g f o r these compounds d u r i n g t h e three trials in which c h l o r o p h e n o l s were u s e d a s wzste fuels. In one of these t r i a l s , trace amounts of what may have been heptachlorodibenzo-p-dioxin ( 7 C D D ) , o c t a c h l o r ~ i b e n z ~ - p - d i o x i n(8CDD) , or octachlorodibenzofuran (8CDF) were detected. Mass spectrometric a n a l y s i s to confirm the identity of the compounds det e c t e d was n o t possible as t h e concentrations p r e s e n t were too low. As the generation and survival of these compounds in a cement kiln cannot be r u l e d out, it is advisable that further experimental work be conducted before wastes with a potential for generating d i o x i n s or furans are allowed to be burned in cement k i l n s on a r o u t i n e b a s i s . A s d e s c r i b e d in Section 4 of t h i s report, t h e introduction of chiorine into a k i l n system will r e s u l t in increased particu l a t e loadings in the kiln exhaust gases. The c h l o r i n e released when chlorinated wastes are broken i n t o their constituent elements w i l l form volatile alkali chlorides which exist a s gaseous fumes at normal k i l n burning z m e temperatures. These alkali c h l o r i d e s , principally potassium c h l o r i d e . and p o s s i b l y sodium chloride, w i l l condense to dusts at the lower temperatures encountered outside t h e kiln and must be removed by t h e plant's dust collection equipment.
Dry cement kilns utilizing suspension p r e h e a t e r s are likely to experience material b u i l d u p or r i n $ formation problems when
burning c h l o r i n a t e d wastes and a r e , t h e r e f o r e , unlikely candidates f o r u s i n g t h i s type of waste € u e l , K i l n s which recycle a significant p o r t i o n of t h e collected kiln dust may also encounter similar problems. T h e amount of excess kiln dust formed when burning chlorina t e d wastes will probably be i n d i r e c t stoichiometric propcrtian to t h e amount of c h l o r i n e p r e s e n t in t h e wastes. Assuming t h a t all chlorine r e a c t s to form potassium chloride, up to 2.1 pounds of additional k i l n d u s t { G i l l % - g e n e r a t e d f o r - every p o m d oE c h l o r i n e i n j e c t e d i n t o t h e kiln. For an e s t h a t e d inaximum c h l o r i n e addition rate equal to 0.G p e r c e n t of clinker P r o d u c t i o n , colLection system d u s t loadings c o u l d be e x p e c t e d to increase by up to 2 5 pour,ds of dust per ton of production c a p a c i t y . 3ecause d u s t formation r a t e s a r e likely to he linked to the a l k a l i content of t h e : i l a n t ' s raw feed materials, d u s t L o a d i c g s and ?articulate e . m i x s i o n s ;nay v a r y considerably be~ W C O :p ~l a n t s
.
:0
I n p l a n t s which coutinely add c h l o r i n e t o the k i l n to reduce c l i n k e r a l k a l i c o n t c a t , t h e u s e of chlorinated w a s t e f u e l s s h o u l c i present 110 additional d u s t emission problems, Other plants, however, w i l l experience additional d u s t collection system loadings which may r e s u l t in i n c r e a s e d s t a c k emission of par ti c u l a t e s
.
The akility of control equipment to c a p t u r e t h e a d d i t i o n a l dust g e n e i a t e d when u s i n g chlorinated waste fuels is expected to v a r y greatly between cement p l a n t s . P l a n t s a l r e a d y e x p e r i e n c i n g problems meeting applicable p a r t i c u l a t e e m i s s i o n s t a n d a r d s are u n l i k e l y to be able to p r e v e n t f u r t h e r dzterioration of their emissions and are, t h e r e c o r e , unlikely c a c d i d a t e s f o r using s u c h waste f u e l s . Plants which h a v e excess dclst collect i o n capability and a r e operating b e l o w allowable p a r t i c u l a t e emission levels are much more s u i t a b l e c a x d i d a t c s for using cblorinated waste fuels. However, e v e n plants w h i c h a r e marg i n a l l y i n compliance could - t e n t i a l l y u s e c h l o r i n a t e d waste fuels without exceeding emission stawJsrds. Several process modifications could probably be employed to maintain a c c e p t a b l e emission levels. 'These i n c l u d e r e d u c i n g i n s u f f l a t i o n r a t e s of r e c o v e r e d d u s t , reducing the r a t e s at w h i m l e a c h e d d u s t i s recycled, altering k i l n drafts, and m d i * f y i p g Ailn combustion k i n e tics
.
Canadian e x p e r i m e n t s with used lubricating o i l s bzde shcwn 2 x c c l l e n t potential for t h e use of such wastes in cement kilns. 3 u r i n g t h e s e ex2er i m e n t s , mass balances were c o n d u c t e d on the a a j o r c o n t a m i n a n t s of t h e oils, lead, z i n c , bromine, and phosp h o r u s . The average concentrations of these elements i n the o i l and their r a t e of addition r e l a t i v e to clinker production a r e shown 1.n T a b l e 6. T h e a m o u n t s a7f p h o s F h o r u s and zinc i n p u t w i t h waste f u e l s were relatively insignificant i n r e l a t i o n to t h e i r concentrat i o n s i n t h e raw meal used to produce Lhe c l i n k e r . T h e i r presence in s u c h l o w amounts in waste fuels, therefore, presents n o
significant environmental risk.
Bromine appears to a c t i n a manner identical to chlorine in a k i l n s y s t e m . Bramine € r u n a waste f u e l forms volatile alkali bromides w h i c h e n t e r the e x h u s t qas stream and must be removed the k i i n ' s d u s t collection equipment, The a m o u n t of bromine introduced into the k i l n d u r i n g this experiment was p r o b a b l y two
