sulfide scale formation and control

7/30/2019 Sulfide Scale Formation and Control

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Geothermics, Vol. 20, No. 5/6, pp. 343--353, 1991.P r i n t e d i n G r e a t B r i t a in . 0375-6505/91 $3 .00 + 0 .00P e r g a m o n P r e s s p l c 1 9 9 1 C N R .

S U L F I D E S C A L E F O R M A T I O N A N D C O N T R O L : T H EC A S E O F L E A D S U L F I D EN . A N D R I T S O S a nd A. J. K A R A B E L A S

Chemical Process Engineering Research Institute, and Department of Chemical Engineering,University of Thessaloniki, P.O. Box 1517, GR 540 06 Thessaloniki, Greece(Received March 1991; accepted or publication September 1991)

A b s t r a c t - - T h e m a i n c h a r a c t e r i s t i c s o f s c a l e e n c o u n t e r e d i n a t y p i c a l h i g h e n t h a l p y / h i g h s a l i n i t y g e o -t h e r m a l f i el d ( M i l o s is l a n d ) a r e s u m m a r i z e d . T h e r e s u l t s o f s c a l e s a m p l e a n a l y s i s , c o u p l e d w i t h t h e r e s u l t so f l a b o r a t o r y e x p e r i m e n t s w i t h m o d e l f l u i d s , p o i n t i n t h e d i r e c t i o n o f d e s i g n a n d o p e r a t i n g c o n d i t i o n s ,w h i c h m a y s i g n i f i ca n t l y m i t i g a t e t h e s c a l i n g p r o b l e m s . C a r e f u l l y c o n t r o l l e d b r i n e a c i d i f ic a t i o n a p p e a r s t ob e a v a l i d o p t i o n , w o r t h t e s t i n g i n t h e f ie ld . E n c o u r a g i n g r e s u l t s a r e a l s o o b t a i n e d i n t h i s st u d y o n t h e u s e o fo r g a n i c s c a l e i n h i b i t o r s . T h e i r e f f e c t i v e n e s s , h o w e v e r , m u s t b e a s s e s s e d u n d e r f i e l d c o n d i t i o n s o f h i g ht e m p e r a t u r e a n d s a l i ni t y.

I N T R O D U C T I O NT h e f o r m a t i o n o f s c a l e o n e q u i p m e n t s u r f a c e s e x p o s e d t o g e o t h e r m a l f l u i d s c a n h a v e s e r i o u se c o n o m i c c o n s e q u e n c e s , a r is in g o u t o f e n e r g y l o s s e s , i n c r e a s e d c o s t o f c le a n i ng a n d m a i n t e n -ance , l o ss o f p roduc t io n , o r even aba ndon ing a p roduc ing we l l . Wi th i n t ens if i ed e f fo r t s t o u seg e o t h e r m a l r e s o u r c e s f o r e n e r g y p r o d u c t i o n a n d f o r o t h e r i n d u s t r i a l a p p l i c a t i o n s , t h e r e i s a ni n c r e a s e d i n t e r e s t in u n d e r s t a n d i n g t h e s c al in g p ro c e s s . A n i m p r o v e d u n d e r s t a n d i n g m a y l e a d t omeasu res fo r mi t i ga t ing th i s p rob lem.T h e g r e a t c o m p l e x i t y o f t h e s c al e f o r m a t i o n p r o c e s s r e s u lt s f r o m t h e l a r g e n u m b e r o f s p e c ie sf o u n d i n a g e o t h e r m a l f lu id a n d f r o m t h e p l e t h o r a o f p o s s ib l e ph y s i c a l m e c h a n i s m s i n v o lv e d .T h e l a t te r m a y i n c l u d e m a s s , m o m e n t u m a n d h e a t t r a n s f e r , a s w e l l a s c h e m i c a l r e a c ti o n s a t t h ee q u i p m e n t s u r f a ce s . F u r t h e r m o r e , t h e d i v e r s it y o f f lu id c o m p o s i t i o n f r o m s i te t o s it e a n d t h ev a r i a t io n o f p r o c e s s e s a lo n g t h e f l o w p a t h m a k e t h e g e n e r a l iz a t i o n o f b o t h t h e m e c h a n i s m srespons ib l e fo r t he sca l e fo rmat ion and the p reven t ive measu res d i f f i cu l t .

T h e c o m p o s i t i o n o f th e s c a l e i n g e o t h e r m a l p l a n t s is c o m m o n l y v e r y c o m p l e x a n d d e p e n d s o nm a n y p a r a m e t e r s , s u c h a s t h e t e m p e r a t u r e a n d p r e s s u r e o f th e f l ui d , t h e h i s to r y o f w a t e r - r o c ki n t e ra c t i o n s a n d t h e o p e r a t i n g c o n d it i o n s . L o w a n d m o d e r a t e t e m p e r a t u r e b r i n e s ( T < 1 50 C )y ie ld , a s a ru l e , sca l e cons is t i ng o f ca l c ium ca rbo na te (O we n and Miche l s , 1984 ; Cors i , 1986).There a re a few excep t ions t o t h i s ru l e , such as t he geo the rmal we l l s i n t he Pa r i s Bas in , wherere l a t i ve ly l a rge concen t ra t i ons o f ch lo r ide and d i sso lved su l f i de re su l t i n i ron su l f i de sca l edepo s i t s (Cr i au d and F ou i l l ac , 1989). H igh en tha lpy and low sa l in it y f lu ids u sua l ly fo rm s i li casca l e (e .g . ce r t a in we l l s i n Ice l and) . On the o th e r hand , h igh t emp era tu re l i qu ids wi th h igh TDScon te n t y i e ld bo th s i l iceous and su l f ide sca le , w i th l ead su l f ide be ing one o f t he m a jo rcons t i t uen t s . A typ i ca l exam ple o f t he l a t t e r case i s t he sca l e depos i t ed i n t he Mi los geo the rm alp l a n t. K a r a b e l a s et al. (1989) p res en t ana lyses o f t he b r ine and o f seve ra l sca l e samples f rom th i splant .

T h e o b j e c t i v e o f t h e w o r k p r e s e n t e d h e r e i s t w o f o l d ; i, e . t o d o c u m e n t t h e n a t u r e a n d t h ecom pos i t i on o f t he sca l e enco un te red in a fa i r ly t yp i ca l h igh sa l in i t y /h igh e n tha lpy f i e ld , such ast h e M i l o s g e o t h e r m a l f ie l d, a n d t o u n d e r s t a n d t h e m e c h a n i s m o f s c a le f o r m a t i o n t h r o u g h343


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344 N . A n d r i t s o s a n d A . J . K a r a b e la sT a b l e 1 . H i g h e n t h a l p y g e o t h e r m a l a r e a s w i t h s u lf i de s c a li n g p r o b l e m s a n d s c a le c h a r a c t e r i st i c s

T D S P b F e S S u l fi d e c r y s t a ll i n eG e o t h e r m a l a r e a ( g d m 3 ) ( m g d m - 3 ) ( m g d m 3 ) ( m g d m - 3 ) p h a s e sS a l t o n S e a , C a l i f o r n i a ( 1 ) 2 5 0 8 0 2 0 0 0 1 5 - 3 0 C u 9 S 5 , C u s F e S 4 , C u 2 S , F e S 2N i l a n d , S a l t o n S e a , 1 7 0 - 2 5 0 2 0 - 1 0 0 2 0 0 - 1 9 0 0 1 0-- 30 P b S , Z n S , C u F e S 2 , C u 2 S

C a l i f o r n i a ( 2 )A s a l W e l l s , D j i b o u t i ( 3 ) 1 2 8 n . r . 1 0 ~ 2 P b S , Z n S , A g 2 SM i l o s p l a n t , G r e e c e ( 4 ) 1 1 0 2 2 (I 2 - 4 P b S , F e 0. 95 S , Z n SC e r t a i n w e l l s a t C e r r o 3 0 - 4 0 n . r . n . r . n . r . F e S , F e S 2 , P b SP r i e t o , M e x i c o ( 5 )R e y k j a n e s , I c e l a n d ( 6 , 7 ) 3 0 n . r . i 1 F e S , C u S , Z n S ( 3 - 4 % P b i ns c a l e )K r a f l a , I c e l a n d ( 7 ) 1 - - 0 . 0 2 9 F e S , F e S 2 , C u F e S 2D o g g e r , F r a n c e * ( 8 ) 6 - 3 5 - - 0 . 1 - 3 0 . 1 - 8 0 F e 9 S s, F e S , F e S 2

* L o w E n t h a l p y A r e a ; n . r. n o t r e p o r t e d ; ( 1 ) S k i n n e r e t a l . ( 1 9 6 7 ) ; ( 2 ) A u s t i n e t a l . ( 1 9 7 7 ); ( 3 ) a s r e p o r t e d b y C r i a u da n d F o u i l l a c ( 1 9 8 9 ) ; ( 4 ) K a r a b e l a s e t a l . ( 1 9 8 9 ) ; ( 5 ) M e r c a d o e t al . ( 1 9 8 9 ) ; ( 6 ) L f n d a l ( 1 9 8 9 ) ; ( 7 ) K r i s t m a n n s d 6 t t i r ( 1 9 8 9 ) ;a n d ( 8 ) C r i a u d a n d F o u i l l a c ( 1 9 8 9 ).

laboratory experiments. In this paper, sulfide scale formation in high enthalpy geothermalplants is reviewed first. A discussion follows on the mechanism of lead sulfide deposition inpipes, elucidated by conducting once-through experiments in a 13 mm i.d. pipeline undercorrtrolled conditions, which resemble those prevailing in a geothermal plant. The experimentalfindings serve as the basis for commenting on certain methods of mitigating the sulfide scalingproblem and for assessing the most important one, i.e. the pH modification of the brine. Finally,some results are reported on the use of our experimental set-up for testing potential inhibitors ofsulfide scaling.

SULFIDE DEPOSITION IN GEOTHERMAL PLANTSRegarding the mechanism of sulfide scale formation, two opposing phenomena take place as

the br ine flashes (Owen and Michels, 1984). For mildly acidic fluids, such as that of Milos, mostof the sulfide species enter the vapor phase in the form of H2S, causing a desirable decrease ofthose species in the residual brine. However, the pH rise due to the simultaneous release ofcarbon dioxide and the hydrolysis of carbonate ions favors the precipitation of heavy metals assulfides. The heavy metals at the high temperatures of the brines are mainly transported aschloride complexes. Additionally, the precipitation of metal sulfides is promoted by two otherfactors, i.e. the t emperature decrease, since the solubility of most sulfides significantly increaseswith temperature, and the "enrichmen t" of the residual brine in heavy metals because of steamseparation. As an example, in the case of Milos plant the solubility of galena in the residual brineis estimated to decrease approximately 50 times, by using Helgeson' s (1969) data or 600 times byfollowing Seward (1984). These estimates are based on the assumptions that after flashing 50%of the fluid is separated as steam and that the pH of the residual brine increases by one unit,whereas the temperature declines by 20C.Table 1 presents the major crystalline sulfide phases identified in certain geothermal fields,along with the concentration of lead, iron and sulfide ions in the respective brines. The lowenthalpy field of Dogger, France, with severe iron sulfide scaling, is also included. However , inthe latter case the origin of the scale forming ions is distinctly different from that in highenthalpy/high salinity fields. The corrosion of mild steel casing due to high chloride content is

considered responsible for the large concent ration of iron in the fluid, while the sulfide ions arepossibly products of bacterial reduction of sulfates (Criaud and Fouillac, 1989).


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S u l fi d e S c a le F o r m a t i o n a n d C o n t r o lTable 2. Characteristics and analysis of scale samples from the Milos geothermal plant

345

Sample A Sample B Sample C Sample DLocation Flashing valve Pipe between hot Pipe section -3 0 m Pipe section -10 0 mwater collecting downstream from downstream fromtank and reinjection reinjection pumps reinjection pumps

pumpsThickness - - 6--8 mm 4-6 mm 2-3 mmCrystalline PbS, Fe0.95S fl-ZnS, a-Zn S, PbS, Feo .95 S, -ZnS, Fe0.95S, a-Zn S,phases Fe0.95S fl-ZnS, PbS fl-ZnS, PbSElement Composition(wt%)Na 0.3 0.8 1.1 2.3K 0.1 0.3 0.4 0.6Mg 0.1 0.2 0.2 0.3Ca 0.1 0.1 0.1 0.1Mn 0.1 0.6 0.5 0.8

Pb 40.7 3.7 3.0 3.0Fe 15.4 30.0 39.6 27.1Zn 0.8 13.5 7.8 13.0Cu 0.3 0.6 0.3 0.1Ni 0.1 0.0 0.0 0.0Ag 0.5 0.0 0.0 0.0Si 2.9 6.4 4.6 7.2C1 0.5 1.2 2.2 3.6SO~- 0.3 0.3 1.0 0.5

D e s p i t e t h e l o w c o n c e n t r a t i o n o f h e a v y m e t a l s ( p a r ti c u l ar l y o f l e a d ) a n d t h e l i m i te dava i l ab i li t y o f su l f ide spec i es i n the M i los b r ine (a s we l l a s i n o the r b r ines ) , a s i gn if i can t am oun to f su l f i des i s depos i t ed . Su l f ide depos i t i on i s mos t p ronounced c lose t o t he f l a sh ing va lve ando c c u r s a t l o w e r r a t e s f u r t h e r a l o n g t h e f l o w p a t h . I n p a r ti c u l a r, P b S c o m p r i s e s a l m o s t 6 0 % o f t h es c a le a t t h e f la s h in g v a lv e , b e c o m i n g m u c h l e s s a b u n d a n t f u r t h e r d o w n s t r e a m . T h e s a m e t r e n dw a s a l s o o b s e r v e d a t S a l t o n S e a ( A u s t i n e t a l . , 1977); P bS was by fa r t he ma in su l f ide depos i t edjus t dow ns t re am o f t he f ir s t s t age con t ro l va lve , wh i l e a t t he t h ird and fo u r th s t age on ly t races o fP b S c o u l d b e d e t e c t e d .

T a b l e 2 p r e s e n t s c h a r a c t er i s ti c s a n d a n a l y s e s o f a r e p r e s e n t a t i v e p a r t o f s c al e s a m p l e s f r o mvar ious pos i t i ons i n t he M i los geo the rm al p l an t . A schem at i c il l u s tra t i on o f t h is p l an t and som es c a le a n a l y s e s f r o m t h e i ni ti al o p e r a t i o n o f th e p l a n t c a n b e f o u n d i n K a r a b e l a s et a l . (1989).A t o m i c a b s o r p t i o n a n d i n d u c e d c o u p l e d p l a s m a s p e c t r o s c o p y w e r e e m p l o y e d f o r t h e a n a l y si s o fan ions , w h i l e ch lo r ides were de t e rm ined by ti t ra t i on wi th s i lve r n i tra t e an d su l fa t e s by l i qu idc h r o m a t o g r a p h y . T h e c o l o r , h a r d n e s s , t h i c k n e s s a n d c o m p o s i t i o n o f t h e d e p o s i t s v a ry c o n s id e r -a b l y in t h e v a r i o u s l o c a t i o n s o f t h e M i l o s p la n t . T h e s c a le s a m p l e s c o r r e s p o n d t o p l a n t o p e r a t i o nwi th p r im ary f l a sh ing a t 24 ba r , t hus suppres s ing s i li ca supe rsa tu ra t i on and fo rm at ion o f si li cad e p o s i t s , C e r t a i n l y , s e v e r a l in t e r r u p t i o n s o c c u r r e d d u r i n g t h e 1 1 - m o n t h p e r i o d o f p l a n to p e r a t i o n , r e s u lt in g i n b a n d s o f d e p o s i ts , d i s p l a y e d b y a ll s a m p l e s w i th t h e e x c e p t i o n o f s a m p l eA .

An in t e res t i ng fea tu re o f some depos i t s i s t he p resence o f a s i l i ca - r i ch i n i t i a l t h in l aye r ,b e t w e e n t h e p i p e m e t a l a n d t h e m a i n s u lf id e b a n d , a s c o n c l u d e d b y X - r a y m i c r oa n a l y s is a n dS E M o b s e r v a t i o n s . I t is q u i t e p o s s i b le t h a t t h e s u l f id e s d o n o t d e p o s i t d ir e c t ly o n t o t h e p i p e w a l land tha t a s i l ica subs t ra t e fac i l i t a t e s the i r d epos i t i on , a s f ir s t sugges t ed b y Aus t in et a l . (1977).F u r t h e r m o r e , t h e s o l u b i l it y o f t h e h e a v y m e t a l s u l fi d es ( a n d t o a l e s s e r e x t e n t t h e k i n e t ic s o fp r e c i p i ta t i o n o f e a c h s u l f id e ) p o s s i b ly d e t e r m i n e s t h e s e q u e n c e o f t h e ir d e p o s i t i o n . I t i s , i n d e e d ,obs e rv ed tha t ga l ena (P bS) i s t he f i r st ou t o f t h ree ma jo r su l f ides to p rec ip i t a t e nea r t he f l a sh ingp o i n t , a s o n e w o u l d e x p e c t o n t h e b a s i s o f th e i r s o l u b il it y .


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346 N. Andritsos and A. J. Karabelas

O= _ .

e e

c -Ome .o

Q.

0 . 2 0

0 . 1 5

0 , 1 0

0 , 0 5

13 C=26.0 1 C = 3 . 5

[ ][ ]/[ ]/ [ ]

o \0 1 2 3 4 5pH

F ig . ] . Pb S d e p o s i t i o n r a t e as a f u n c t i o n o f p H a n d c onc en t r a t i o n ( Pb S co n ce n t r a t i o n , C , i n m g d m ~ )

LEAD SULFIDE DEPOSITION IN THE LABORATORYThe influence of various parameters on lead sulfide deposition in pipes was studied under

controlled conditions, in order to elucidate the mechanism of sulfide scaling in geothermalplants (Andritsos and Karabelas , 1991a,b). In brief, solutions of lead and sulfide ions at a fixedpH were mixed to form a solution supersaturated in PbS, which flowed in a 13 mm i.d. pipelinewith two test sections. Initial deposition rates were obtained by weighing the mass of PbSdeposited on special stainless steel or teflon coupons. The effect of pH, PbS concentration,temperature and liquid salinity on the deposition rate and the deposit morphology wereinvestigated. Additional experiments on deposit removal were carried out recently. The mainpoints of that work, which are relevant to this discussion, are summarized as follows:(a) Appreciable lead sulfide deposition occurs in a narrow pH range, associated with thesolubility of lead sulfide. The deposition curve exhibits a bell shape (as illustrated in Fig. 1 fortwo lead sulfide concentrations) , with the maximum at the so-called "threshold pH"; i.e. the pHfor spontaneous nucleation in the bulk. The threshold pH can be easily determined from lightabsorbance measurements . Above that range, bulk precipitation occurs immediately uponmixing of the reagent solutions and only some loose PbS flocs can be seen on the pipe walls.These flocs consist of numerous tiny PbS crystals (dp < 100 nm).

(b) The diffusion of lead and sulfide ions onto the pipe surface appears to be the controllingmechanism of sulfide deposition, for the conditions investigated (Re = 3000-12,000, T = 20-50C). At high temperatures, though , it is quite possible that surface reaction may also play arole, because of the high diffusivity values.(c) Detachment of the deposited particles (particle erosion) does occur, but the rate isgenerally small, as has been demonstrated by independent experiments. Dissolution of thedeposited particles is also observed for pH values lower than 3, where the solubility of leadsulfide is not negligible. The fraction removed by erosion does not seem to depend on the flowrate in the range of Reynolds numbers between 6000 and 12,000. On the other hand, the natureof the deposits (single particles, aggregates) appears to influence marked ly the detachmen t rate.(d) The morphology of the deposits is influenced by liquid salinity and, to a lesser extent, bytemperature . Larger particles are formed at relatively low supersaturat ion ratios and in the pipesection next to the entry point. I t is interesting to recall here that the same trend is observed in


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Su l f ide Sca le Format ion and Con t ro l 347the PbS c rys t a l s found in t he Mi los sca l e samples . The l a rges t pa r t i c l e s (>10 /~m) a re encoun-t e re d in t he samp le f rom the f l a sh ing va lve . PbS pa r t i c l e s f rom ze ro -sa l i n i ty l i qu ids have a cub ics h a p e , w h i l e o c t a h e d r o n o r t r u n c a t e d o c t a h e d r o n - s h a p e d c r y s t a l s a r e o b t a i n e d f r o m s a l i n el iqu ids . A no the r ch a rac t e r i s t i c o f t he de pos i t ed c rys t a l f rom sa l ine l iqu ids is t ha t t hey " fu se"w i t h e a c h o t h e r a s th e d e p o s i t i o n p r o g r e s s e s , r e s u lt i n g i n a s t r o n g a d h e r e n c e t o t h e s u b s t r a t e .T h e m i c r o g r a p h s o f F ig . 2 d e p i c t t h e s i m i la r it y o f s h a p e s b e t w e e n P b S p a r t i c le s d e p o s i t e d i n t h el ab f rom sa l ine l iqu ids and th ose i n sca l e samples .

P R E V E N T I O N A N D C O N T R O L O F S U L F I D E SC A L E F O R M A T I O NT o t a l p r e v e n t i o n o f su l fi d e s c a le f o r m a t i o n s e e m s a l m o s t i m p o s s i b l e a t p r e s e n t . H o w e v e r ,

c e r t a in c o n v e n i e n t m e a s u r e s m a y s u p p r e s s t h e a m o u n t o f sc a le f o r m i n g in g e o t h e r m a l p l a nt s .Th e ma in app roac hes i n th i s d i rec t i on a re t he chem ica l mod i f i ca t ion o f t he b r ine (e .g . pHr e d u c t i o n ) , t h e c a r e f u l d e s ig n o f t h e p l a n t , t h e s e l e c ti o n o f a p p r o p r i a t e o p e r a t i n g c o n d i t i o n s ,and the use o f add i t i ves (ma in ly c rys ta l g row th inh ib i to rs ) . T he l eas t p re fe ra b l e app roac h toc o n t r o l s c a l e f o r m a t i o n i s th e r e m o v a l o f s c a le b y c h e m i c a l o r m e c h a n i c a l m e a n s d u r i n g p e r i o d i cp l an t i n t e r rup t ions , un l ess t h i s c l ean ing i s ca r r i ed ou t on a l im i t ed sca l e du r ing regu la r p l an tm a i n t e n a n c e .

S o m e t y p i ca l m e a s u r e s t o b e t a k e n i n t h e s e l e c t io n o f d e s ig n a n d o p e r a t i n g c o n d i t io n s , a r eo u t l i n e d b e l o w :

I t w a s c l e ar l y d e m o n s t r a t e d i n th e M i l o s p l a n t t h a t t h e c a r e f u l a d j u s t m e n t o f p r im a r y f la s h in gpressu re , a t a su f f i c i en t ly h igh l eve l , d ras t i ca l l y reduced sca l e fo rmat ion by keep ing so l id ssa tu ra t i on re l a t i ve ly l ow. Th i s p ress u re a d jus tm en t was qu i t e e f fec t i ve on s i li ca depo s i t i on , bu tappa ren t ly d id no t i n f luence su l f i de scal ing .

L a r g e p i p e d i a m e t e r s m a y o f f e r s o m e a d v a n t a g e s i n r e d u c i n g s u l fi d e s c a li n g, p r o v i d e d t h a t ad i f fus ion con t ro l l ed m echan i sm i s re spo ns ib l e fo r t he su l f i de c rys t a l li za t i on on to t he p ipe wa l l s ,a s has been ind i ca t ed in t he t e s t s w i th PbS .

T h e p r e v e n t i o n o f s h u t -d o w n s a n d o f o p e r a t i n g c o n d i t i o n c h a n g e s m a y b e o f h e lp i n c e r ta i nc a s e s , b y a v o i d in g t h e f o r m a t i o n o f b a n d s o f d e p o s i ts o f d i f f e r e n t s tr e n g t h . S u c h d e p o s i t s c ans o m e t i m e s b e s h a t t e r e d a n d d i s l o d g e d f r o m t h e p i p e w a l l s, t r a n s f e r r e d b y t h e f l o w , a n d f in a ll ya c c u m u l a t e d a n d c e m e n t e d a t c e r ta i n p l a c e s , s u c h a s t h e e l b o w s o f v e r ti c a l e x p a n s i o n r i se r s .

F ina l ly , f la sh ing in the w e l lbo re sho u ld be av o ided b y ma in t a in ing h igher p r essu re i n the we l l .R e a m i n g o f th e w e l l is th e m o s t e f f e c t iv e w a y t o r e m o v e t h e d e p o s i t s in t h e c a s in g ( T h o m a s a n dGudmundsson , 1989) , bu t i t i s ra the r d i f f i cu l t t o remove sca l e f rom the s lo t t ed l i ne r . Su r facee q u i p m e n t p l u g g e d b y s ca l e c a n b e c l e a n e d e a s i e r a n d m o r e e c o n o m i c a l l y th a n t h e w e l l b o r e .U n d e r s t a n d i n g t h e m e c h a n i s m o f P b S d e p o s i t i o n i n p i p e l in e s m a y h e l p a s s e s s t h e p Hreduc t ion t echn ique , w i th spec i a l a t t en t ion to t he Mi los p l an t . Th i s me thod i s fu r the r d i scussedbe low, a long wi th a f i r s t a t t empt t o eva lua t e chemica l add i t i ves a s po t en t i a l su l f i de sca l einhibi tors .p H R e d u c t i o n

T h e m e t h o d o f s u lf id e s c al e c o n t r o l b y r e d u c in g t h e p H o f a g e o t h e r m a l b r i n e i s b a s e d o n t h ewel l know n fac t t ha t t he so lub i l i ty o f su l f ides i nc reases m arke d ly i n ac id ic so lu t ions . In t he rangeof pH va lues t ha t a re t yp i ca l o f h igh sa l i n it y and h igh en tha lpy b r ines (pH < 6 ) , a t en - fo ldinc rease o f t he su l f i de so lub i l i ty i s ob t a ined by reduc ing the pH by one un i t . P rov id ed tha t t hedepo s i t i on be hav io r o f PbS f rom a rea l b r ine i s s im i l a r t o t ha t f rom a syn the t i c one (F ig . 1 ) , evena s m a ll r e d u c t i o n o f p H m a y s o m e t i m e s r e d u c e d r a s t ic a ll y t h e a m o u n t o f d e p o s it s . I t isno t e wo r thy tha t a t pH v a lues l ess t han 5 , t he ra t e s o f nuc l ea t ion and g row th o f si li ca pa r t i c le sd e c r e a s e c o n s i d e r a b l y ( M a c r i d e s et al . , 1980). C onse que n t ly , a reduc t ion o f pH wi ll a lso have a


6/11

N . A n d r i t s o s a n d A . J . K a r a b e l a s

Zig . 2 . M ic rographs dep ic t ing PbS c rys ta ls in (a ) sca le sample A , (b ) sca le sample C and (c ) exper im enta l depos i ts wisa l ine wa te r (0 .2 M in NaCI) .


7/11

Sulf ide Scale Formation and ControlTable 3. Com parison b etw een solubil it ies of hea vy metalsulfides (from H elgeson, 1969) and the concentration of thecorresponding hea vy metals in the Milos brine (T = 230C,Salinity = 2 M NaC1)

Concentration Solubility,in brine mg dm -3 M 2+Metal (mg dm -3) pH = 4.3 pH = 5.3Pb 1.8 7.3 0.75Zn 3.3 39.0 4.10Fe 20.0 17.5 1.80Cu 0.2 0.2 2.00

349

b e n e f i c i a l e f f e c t o n t h e f o r m a t i o n o f s il ic a d e p o s i t s . H o w e v e r , t w o n e g a t i v e f a c t o r s m u s t a l s o b ec o n s i d e r e d i . e . t h e p o s s i b l e c o r r o s i o n o f p ip e s a t l o w p H v a l u e s a n d t h e c o s t o f a c i d .

T h e m e t h o d o f b r i n e a c i d i f ic a t io n h a s b e e n s u c c e s s fu l l y a p p l i e d i n s e v e r a l c a se s . I t h a s b e e ns h o w n i n a n u m b e r o f e x p e r i m e n t s ( G r e n s a n d O w e n , 1 97 7) th a t l o w e r i n g t h e p H o f t h e S a l to nS e a g e o t h e r m a l b r i n e h a s b e e n e f f e c t i v e i n r e d u c i n g o r e l im i n a t i n g t h e f o r m a t i o n o f s u lf id e a n ds i l ic e o u s s c a l e . G a l l u p ( 1 9 8 9 ) r e p o r t s t h a t i n h i b i t i o n o f i r o n - s i l i c a t e s c a l e i s a c h i e v e d b y lo w e r i n gt h e p H b y o n l y 0 .1 t o 0 .3 u n it s . A l s o , H a r r a r ( 1 9 8 1 ) n o t ic e s t h a t th e p H r e d u c t i o n i n l a b o r a t o r ye x p e r i m e n t s i n h i b it s t h e d e p o s i t i o n o f b o t h s i li ca a n d s u lf id e s . H o w e v e r , f o r c o m p l e t e s c a lep r e v e n t i o n t h e b r i n e p H s h o u l d b e r e d u c e d t o a b o u t 3 , w h i c h t e n d s t o i n c r e a s e s ig n i f ic a n t ly t h ec o r r o s i o n r a t e o f s t e e l. I n a n o t h e r e x a m p l e , b r i n e a c i d i fi c a t io n r e d u c e d t h e r a t e o f s il ic a sc a l ef o r m a t i o n a h u n d r e d t im e s ( R o t h b a u m et al., 1979) .

T a b l e 3 sh o w s t h a t t h e c o n c e n t r a t i o n s o f c e r t a i n s c a le f o r m i n g h e a v y m e t a l io n s e x c e e d t h es o l u b il it i e s o f th e c o r r e s p o n d i n g s u lf id e s f o r t h e c o n d i t i o n s o f t h e M i l o s b r in e . T h e s e s o l u b il it i e sa r e c a l c u l a t e d a c c o r d i n g t o H e l g e s o n ( 1 9 6 9 ), f o r a f l ui d w i t h a 2 M s a l i n it y a t 2 30 C a n d m u s t b ec o n s i d e r e d a p p r o x i m a t e . T h u s , t h e r e d u c t i o n o f b ri n e p H b y o n e u n i t ( e .g . b y i n j e ct io n o fh y d r o c h l o r i c a c i d ) m a y p r e v e n t s c a le f o r m a t i o n , e v e n i f a m i ld s u p e r s a t u r a t i o n i n c e r t a i n s u lf id e ss ti ll e x i s ts , a s i n d i c a t e d i n T a b l e 3 .Crystal growth inhibi tors and inhibi tor evaluation

T h e i n h ib i to r s a r e m o d e r a t e l y l a r g e m o l e c u l e s t h a t a r e r e a d i ly a d s o r b e d o n t h e g r o w t h - a c t i v es i te s o f t h e c r y s t a l su r f a c e s , t h u s b l o c k i n g t h e g r o w t h p r o c e s s ( N a n c o l l a s a n d Z a w a c k i , 1 9 8 4) .T h e m a i n f a m i l ie s o f c h e m i c a l s u s e d a s i n h i b i to r s a r e o r g a n i c p h o s p h o n a t e s , p o l y a c r y l a t e s , a n dm a l e i c a c i d d e r i v a ti v e s . C r y s t a l g r o w t h i n h i b i t i o n is c o n s i d e r e d t h e c h e a p e s t a n d m o s t e f f ic i e n tm e t h o d o f c o n t ro l l in g c a r b o n a t e s ca le f o r m a t i o n i n g e o t h e r m a l i n st a ll a ti o n s ( V e t t e r a n dC a m p e l l , 1 9 7 9) . S c a le c o n t r o l c a n s o m e t i m e s b e a c h i e v e d b y t h e i n j e c t i o n o f a c o m m e r c i a li n h i b i t o r i n c o n c e n t r a t i o n s a s lo w a s 1 m g d m - 3 . D e s p i t e t h e s u c c e ss i n p r e v e n t i n g c a r b o n a t es c a l i n g , n o i n h i b i t o r is k n o w n t o e f f i c i e n t l y s u p p r e s s t h e f o r m a t i o n o f s u lf i d e a n d s i li c a s c a l e sf r o m h i g h e n th a l p y a n d h i g h T D S b r i n e s ( H a r r a r e ta l . , 1 9 8 0 ; C o r s i , 1 9 8 6 ) . O n e r e a s o n f o r th i s i st h a t o r g a n i c i n h i b i t o r s a r e i n g e n e r a l u n s t a b l e a t t e m p e r a t u r e s h i g h e r t h a n - 1 8 0 C .

T h e m a i n t a r g e t o f t h is p a r t o f t h e w o r k i s n o t t o u n c o v e r t h e a c t iv e g r o u p s o f t h e i n h i b i t o r o rh o w i t a ff e c ts c r y st a l g r o w t h , b u t r a t h e r t o d e m o n s t r a t e t h a t t h e e x p e r i m e n t a l s y s t em e m p l o y e df o r t h e d e p o s i t i o n s t u d i e s c a n b e e f f e c t i v e l y u s e d t o d e t e r m i n e t h e e f f i c i e n c y o f a p o t e n t i a la d d i ti v e . F o r a p r e l i m i n a r y i n v e s t ig a t io n a c o m m e r c i a l p r o d u c t ( B e l c h e m 2 0 6 G o f W a t e r -C h e m ) w a s t e s t e d f o r e f f e c t i v e n e s s i n s ca l e i n h ib i t io n . T h i s a d d i t i v e is a m i x t u r e o f s e v e r a lc h e m i c a ls i n c l ud i n g p h o s p h o n a t e s a n d p o l y c a r b o x y l a te s . H o w e v e r , i ts e x a c t id e n t i ty w a s n o tr e v e a l e d .

L i g h t a b s o r b a n c e m e a s u r e m e n t s o f a P b S so l c a n b e u s e d to d e t e r m i n e t h e p H r a n g e o f


8/11

350 N . A n d r i t s o s a n d A . J . K a r a b e la s1.2

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R C = OEl C=1 C=50 C=25

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F i g . 3 . E f f e c t o f a d d i t i v e c o n c e n t r a t i o n o n t h e a b s o r b a n c e o f P b S s o ls . A d d i t i v e c o n c e n t r a t i o n , C , i n m g d m 3.

a p p r e c i a b l e d e p o s i t io n a n d t h e p H o f t h e m a x i m u m d e p o s i t io n r a t e , a s p o i n t e d o u t i n A n d r i t s o sa n d K a r a b e l a s ( 1 99 1 a ). C o n s e q u e n t l y , t h e a b s o r b a n c e m e a s u r e m e n t s o f s o ls , in w h ic h t h ep o t e n t i a l i n h i b i t o r i s a d d e d a t a c e r t a i n c o n c e n t r a t i o n , c o m p r i s e t h e i n i ti a l s t a g e o f t h ee x p e r i m e n t a l p r o c e d u r e , b e f o r e c a r r y i n g o u t l a b o r a t o r y o r p i l o t p l a n t e x p e r i m e n t s .

E q u i m o l a r s o l u t io n s o f P b 2 + a n d S2 - , f i l te r e d t h r o u g h a 0 .1 0 / am m e m b r a n e , w e r e m i x e du n d e r m i l d m a g n e t i c s t ir r in g i n a b e a k e r c o n t a i n i n g 1 00 c m 3 o f d i st il l ed a n d f i l te r e d w a t e r a t t h ea p p r o p r i a t e p H a n d a d d i t iv e c o n c e n t r a t i o n . I m m e d i a t e l y a f t e r m ix i ng , a s a m p l e f r o m t h eb e a k e r w a s t r a n s f e r r e d i n to a s p e c t r o p h o t o m e t r i c c u v e tt e a n d i ts a b s o r b a n c e w a s m o n i t o r e d f o r1 0 m i n . F i g u r e 3 p r e s e n t s t h e i n i ti a l a b s o r b a n c e c u r v e s a s a f u n c t i o n o f p H f o r f o u r a d d i t i v ec o n c e n t r a t i o n s a t 2 5 C. T h e P b S c o n c e n t r a t i o n i n e a c h s o l w a s 2 6 m g d m - 3 , c o m p u t e d b ya s s u m i n g t h a t a c o m p l e t e r e a c t i o n t a k e s p l a c e . F o r t h e z e r o a d d i t i v e c o n c e n t r a t i o n t h e d i s t i n c ts h a r p r is e o f t h e a b s o r b a n c e c u r v e a t th e t h r e s h o l d p H is w e l l r e p r o d u c e d . H o w e v e r , w i thi n c r e a s i n g a d d i t i v e c o n c e n t r a t i o n , t h e s h a r p r i s e g r a d u a l l y d e c l i n e s a n d t h e a b s o r b a n c e s a r em a r k e d l y l o w e r t h a n t h o se f o r t h e z e r o a d d i t iv e c o n c e n t r a t i o n . T h e h i g h e r th e a d d i t iv ec o n c e n t r a t i o n , t h e l o w e r t h e a b s o r b a n c e v a l ue s . T h e t e m p o r a l v a r i a t io n o f th e s o l a b s o r b a n c e ,f o r s e v e r a l fi x e d a d d i t i v e c o n c e n t r a t i o n s , is d e p i c t e d i n F i g. 4 . T h e p H o f t h e s e m e a s u r e m e n t s i s1 . 45 , a t w h i c h b u l k p r e c i p i t a t i o n i s o b s e r v e d a l m o s t i n s t a n t a n e o u s l y f o r th e z e r o a d d i t i v ec o n c e n t r a t i o n s o l . It is c l e a r l y e v i d e n t i n t h e s e m e a s u r e m e n t s t h a t t h e a d d i t i v e r e t a r d ss i gn i f ic a n t ly t h e p r e c i p i t a t i o n o f l e a d s u l f id e . H o w e v e r , e v e n f o r t h e h i g h e s t a d d i t i v e c o n c e n -t r a t io n u s e d , 2 5 m g d m - 3 , t h e p r e c i p i ta t i o n is n o t c o m p l e t e l y in h i b i te d . T h e a b s o r b a n c e c u r v ef o r th e 2 5 m g d m - 3 a d d i t iv e c o n c e n t r a t i o n i m p l i e s t h a t d e p o s i t i o n i n t h e p i p e l i n e m a y n o t o c c u ra l o n g a c o n s i d e r a b l e i n it ia l p i p e l e n g t h .

E a c h p i p e l i n e r u n t o s t u d y t h e e f f e c t i v e n e s s o f t h e a d d i t i v e l a s te d f o u r h o u r s . F o r a l l r u n s t h ep H w a s 1 . 4 5 , t h e R e y n o l d s n u m b e r 6 0 0 0, a n d t h e t e m p e r a t u r e 2 5 C , e x c e p t f o r t h e z e r o s a li n it yr u n , w h e r e t h e t e m p e r a t u r e w a s 20 C . T h e e x p e r i m e n t a l p r o c e d u r e i s d e s c r i b e d in A n d r i t s o sa n d K a r a b e l a s ( 1 9 9 1 a ). T h e a d d i t i v e w a s d i s s o l v e d u n d e r s t ir r in g i n a 1 . 5 m 3 w a t e r t a n k .

F i g u r e 5 sh o w s d e p o s i t i o n c u r v e s f o r t h r e e a d d i t i v e c o n c e n t r a t i o n s , a ll o t h e r p a r a m e t e r s b e i n gc o n s t a n t . I n a l l c a s e s w i t h a p p r e c i a b l e d e p o s i t s , d e p o s i t i o n i s s e e n t o b e l i n e a r w i t h t i m e .H o w e v e r , a s h o r t i n d u c ti o n p e r i o d is o b s e r v e d w i t h a ll n o n - z e r o a d d i t iv e c o n c e n t r a t i o n s , e v e nf o r a c o n c e n t r a t i o n o f i m g d m - 3 . T h e d e p o s i t i o n r a t e s a t t h e t w o t e s t s e c t i o n s a r e p r e s e n t e d i n


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0 * ~ *0 3 4 5T i n l ~ ( h )F i g . 5 . E f f e c t o f a d d i t i v e c o n c e n t r a t i o n o n P b S d e p o s i t i o n i n t h e f i rs t t e s t s e c t io n . A d d i t i v e c o n c e n t r a t i o n , C , i n

m g d m - 3 .

F i g. 6 . T h e d e p o s i t i o n r a t e i s d e f i n e d a s t h e s l o p e o f t h e l i n e a r d e p o s i t i o n c u r v e , w h i c h m a y n o tp a s s th r o u g h z e r o . T h e d e p o s i t io n r a t e f o r z e r o c o n c e n t r a t i o n is c o r r e c t e d fo r t h e t e m p e r a t u r ed i f f e r e n c e . A l t h o u g h s o m e i n h ib i ti o n o f d e p o s i t f o r m a t i o n i s d e t e c t a b l e e v e n f o r t h e 1 m g d m - 3c o n c e n t r a t i o n , a p p r e c i a b l e i n h i b it io n t a k e s p l a c e f o r c o n c e n t r a t io n s a b o v e 1 2 m g d m -3 .

M i c r o s c o p i c a l l y , th e a d d i t i v e c a u s e s a s m a l l d e c r e a s e i n t h e e q u i v a l e n t l e n g t h o f P b S c r y s t a l sd e p o s i t e d o n t h e m e t a l s u b s tr a t e . F u r t h e r m o r e , a g r e a t e r d e g r e e o f a g g r e g a t io n is o b s e r v e d w i t hi n c r e a s i n g a d d i t i v e c o n c e n t r a t i o n . F o r c o n c e n t r a t i o n s a b o v e 2 0 m g d m - 3 t h e d e p o s i t s a r e o n l yin t h e f o r m o f a g g r eg a t e s , s o m e t h i n g t h a t c a n b e o b s e r v e d e v e n m a c r o s c o p i c al l y . A c h a r a c t e r -


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5 1 0 1 5 2 0 2 5A d d i t iv e C o n c . ( ra g d m "3 )

F i g . 6 . Effect of ad ditiv e concentration on the in itial deposition rate of PbS in both test sectio ns (Pb Sconc. = 26 mg dm -3, T = 20C, Re = 6000, pH = 1.45).i st ic o f th e d e p o s i t s f o r c o n c e n t r a t i o n s g r e a t e r t h a n 1 0 m g d m - 3 is t h a t t h e y a r e n o t u n i f o r m l yd i s t r ib u t e d o n t h e s u b s t r a t e .

T h e a f o r e m e n t i o n e d l a b o r a t o r y e x p e r i m e n t s d e m o n s t r a t e t h a t t he r e i s a n a d d it iv e t h a ti n h ib i ts t h e f o r m a t i o n o f P b S d e p o s i t s , w h e n i ts c o n c e n t r a t i o n i n t h e l iq u id r o u g h l y m a t c h e s t h a to f le a d i o n s. T h e s e p r e l i m i n a r y r e s u l ts a r e g e n e r a l l y e n c o u r a g i n g , a l t h o u g h i t is q u e s t i o n a b l ew h e t h e r t h is a d d i ti v e c a n f u n c ti o n a t th e h i g h t e m p e r a t u r e o f t h e M i l o s b r i n e ( > 2 0 0 C ) .A d d i t i o n a l w o r k i s o b v i o u s l y r e q u i r e d t o e x a m i n e w h e t h e r s u c h a d d i ti v e s c a n h a v e a b en e f i ci a le f f e c t u n d e r f i el d c o n d i t i o n s .

C O N C L U D I N G R E M A R K SH e a v y m e t a l s u l f id e s c o m p r i s e a s i gn i fi c an t p a r t o f s c a le s f o r m i n g i n g e o t h e r m a l i n s t a l la t i on s ,

e s p e c i a l l y in t h o s e h a n d l i n g h i g h s a l i n it y b r i n e s . S u l f i d e s a r e d e p o s i t e d i n si g n i fi c a n t q u a n t i t i e sd o w n s t r e a m o f t h e g e o t h e r m a l f lu id f la s h in g p o i n t , w h e r e a su d d e n s u p e r s a t u r a t i o n i n c e r t a i nm i n e r a l s o c c u r s . T h e d e p o s i t i o n r a t e o f su l fi d es t e n d s t o d e c r e a s e w i t h d i s t a n c e f r o m t h a t p o i n t .

A p a r t f r o m t h e a c i d i f ic a t io n o f t h e b r i n e , n o e f f e c t i v e m e a s u r e s t o m i t i g a t e s il ic a a n d s u l fi d es c a li n g p r o b l e m s h a v e b e e n r e p o r t e d i n th e l i t e r a tu r e . A c i d i fi c a t io n t o r e d u c e s o m e w h a t t h e p Ho f t h e M i l o s g e o t h e r m a l f l u i d s e e m s t o b e a t e c h n i c a l l y f e a s i b l e m e t h o d t o c o n t r o l s u l f id e s c a li n g .H o w e v e r , a d d i t io n a l w o r k i s r e q u i r e d t o e s t i m a t e t h e c o s t o f t r e a t m e n t a n d i n p a r ti c u l a r t o a s se s st h e c o r r o s i o n p o t e n t i a l o f t h e t r e a t e d b r i n e .

T h e i n j e c t i o n o f c r y s t a l g r o w t h i n h i b i t o r s h a s n o t s o f a r y i e l d e d e n c o u r a g i n g r e s u l t s in th e f i e lda s a p r e v e n t i v e m e a s u r e a n d s h o u l d b e f u r t h e r i n v e s t ig a t e d . A c o m m e r c i a l i n h i b it o r t e s t e du n d e r l a b o r a t o r y c o n d i t i o n s i n t h e p r e s e n t s t u d y s h o w s a s i g n i f i c a n t i n h i b i t i o n c a p a b i l i t y a tc o n c e n t r a t i o n s s i m i l a r to t h o s e o f th e d e p o s i t in g s p e c i e s ( P b S ) . H o w e v e r , n o d e f in i te c o n c l u s i o nc a n b e d r a w n o n t h e e f f e c t i v e n e s s o f t h i s o r o t h e r i n h i b i t o r s , u n l e s s t h e y a r e t e s t e d a t h i g ht e m p e r a t u r e a n d h i g h s a l in i ty c o n d i t i o n s s u c h a s t h o s e c h a r a c t e r i z i n g t h e M i lo s b r i n e .Acknowledgements--This work has been supported by the C omm issionof European Comm unities under contracts No.EN3G-0040-GR and No. JOUG-0005-C, and by the G reek Secretariat for R esearch and Technology.


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Su l f i d e Sc al e F o r ma t i o n an d C on t r o l 353REFERENCES

A n d r i t s o s , N . a n d K a r a b e l a s , A . J . ( 1 9 8 9 ) L a b o r a t o r y s t u d i e s o f P b S sc a l e f o r m a t i o n i n s t e e l p i p e s . Geothermics 18 ,17-24 .A n d r i t s o s , N . a n d K a r a b e l a s , A . J . ( 1 9 9 1 a ) C r y s t a l l i z a t io n a n d d e p o s i t f o r m a t i o n o f l e a d s u l f id e f r o m a q u e o u s s o l u t i o n s .I . D e p o s i t i o n r a t e s . J. Colloid Interface Sci. 145 , 158-169 .A n d r i t s o s , N . a n d K a r a b e l a s , A . J . ( 1 9 9 1 b ) C r y s t a l l i z a t i o n a n d d e p o s i t f o r m a t i o n o f l e a d s u lf i d e f r o m a q u e o u s s o l u t i o n s .I I . M o r p h o l o g y o f t h e d e p o s i t s . J. Colloid Interface Sci. 145, 170-181.A u s t i n , A . L . , L u n d b e r g , A . W . , O w e n , L . B . a n d T a r d if f , G . E . ( 1 9 7 7) T h e L L L G e o t h e r m a l S t a t u s R e p o r t , J a n u a r y1 9 7 6 - J a n u a r y 1 9 77 . L a w r e n c e L i v e r m o r e L a b o r a t o r y , L i v e r m o r e , C A , U C R L - 5 0 0 4 6- 7 6 .C o r s i , R . ( 1 9 8 6 ) S c al i n g a n d c o r r o s i o n i n g e o t h e r m a l e q u i p m e n t : p r o b l e m s a n d p r e v e n t i v e m e a s u r e s . Geothermics 15 ,8 3 9 - 8 5 6 .C r i a u d , A . a n d F o u i l l a c , C . ( 1 9 8 9 ) S u lf i d e s c a l i n g i n l o w e n t h a l p y g e o t h e r m a l e n v i r o n m e n t : a s u rv e y . Geothermics 18 ,7 3 - 8 2 .G a l l u p , D . L . ( 1 9 8 9 ) I r o n s i l ic a t e sc a l e f o r m a t i o n a n d i n h i b i t i o n a t t h e S a l t o n S e a g e o t h e r m a l f ie ld . Geothermics 18 , 97-104.G r e n s , J . Z . a n d O w e n , L . B . ( 1 9 7 7 ) F i e l d e v a l u a t i o n o f s c a l e c o n t r o l m e t h o d s : a c i d i fi c a t io n . Geotherm. Resour. Counc.Trans., 119-121 .H a r r a r , J . E . ( 1 9 8 1 ) F i n a l R e p o r t o f B r i n e C h e m i s t r y a n d S c a l i n g a t t h e S a l t o n S e a g e o t h e r m a l f i e l d , 1 9 7 % 1 9 7 9 .L a w r e n c e L i v e r m o r e L a b o r a t o r y , L i v e r m o r e , C A , U C I D - 1 8 9 1 7 .H a r r a r , J . E . , L o c k e , F . E . , O t t o , C . H . , L o r e n s e n , L . E . , F r e y , W . P . a n d S n e ll , E . O . ( 1 98 0 ) O n - l i n e T e s t s o f O r g a n i cA d d i t i v e s f o r t h e I n h i b i t i o n o f t h e P r e c i p i t a t i o n o f S i l ic a f r o m H y p e r s a l i n e G e o t h e r m a l B r i n e . I V . F i n a l T e s t s o fC a n d i d a t e A d d i t i v e s . L a w r e n c e L i v e r m o r e L a b o r a t o r y , L i v e r m o r e , C A , U C I D - 1 8 5 3 6 .H e l g e s o n , H . G . ( 1 96 9 ) T h e r m o d y n a m i c s o f h y d r o t h e r m a l s y st e m s a t e l e v a t e d te m p e r a t u r e s a n d p r e s s u re s . Am. J. Sci.267, 7 2 % 8 0 4 .K a r a b e l a s , A . J . , A n d r i t s o s , N . , M o u z a , A . , M i t r a k a s , M . , V r o u z i , F . a n d C h r i s t a n i s , K . ( 1 9 8 9) C h a r a c t e r i s ti c s o f s c a l e sf r o m t h e M i l o s G e o t h e r m a l P l a n t . Geothermics 18, 169-174.K r i s t m a n n s d 6 t t i r , H . ( 1 9 8 9 ) T y p e s o f s c a l in g o c c u r r i n g b y g e o t h e r m a l u t i l iz a t i o n in I c e l a n d . Geothermics 1 8 ,1 8 3 - 1 9 0 .L f n d a l , B . ( 1 9 8 9 ) S o l i d s d e p o s i t i o n i n v i e w o f g e o t h e r m a l a p p l i c a t i o n s i n R e y k j a n e s a n d S v a r t s e n g i , s o u t h w e s t e r nI c e l a n d . Geothermics 1 8 , 2 0 7 - 2 1 6 .M a k r i d e s , A . C . , T u r n e r , M . a n d S l a u g h t e r , J . ( 1 9 8 0 ) C o n d e n s a t i o n o f si l ic a f r o m s u p e r s a t u r a t e d s i li ci c a c id s o l u ti o n s . J .Colloid Interface Sci. 7 3 , 3 4 5 - 3 6 7 .M e r c a d o , S . , B e r m e j o , F . , H u r t a d o , R . , T e r r a z a s, B . a n d H e r n a n d e z , L . ( 1 9 89 ) S ca l e i n c id e n c e o n p r o d u c t io n p i p e s o fC e r r o P r i e t o g e o t h e r m a l w e l l s . Geothermics 18, 17-24.N a n c o l l a s , G . H . a n d Z a w a c k i , S . J . ( 1 9 8 4 ) I n h i b i t o r s o f c r y s t a l li z a t i o n a n d d i s s o l u t i o n . I n Industrial Crystallization( e d i t e d b y J a n c i c , S . J . a n d d e J o n g , E . J . ) , p p . 5 1 - 5 9 . E l s e v i e r , A m s t e r d a m .O w e n , L . B . a n d M i c h e l s , D . E . ( 1 9 8 4 ) Geochemical Engineering Reference Manual. D e p t . o f E n e r g y , R e p . N o D O E /SF/11520/T1 .R o t h b a u m , H . P . , A n d e r t o n , B . H . , H a r r i s o n , R . F . , R o h d e , A . G . a n d S l a tt c r , A . ( 1 97 9 ) E f f e c t o f s i li c ap o l y m e r i z a t io n a n d p H o n g e o t h e r m a l s c a li n g . Geothermics 8 , 1 -20 .S e w a r d , T . M . ( 1 9 8 4 ) T h e f o r m a t i o n o f l e a d ( I I ) c h l o r i d e c o m p l e x e s t o 3 00 C: a s p e c t r o p h o t o m e t r i c st u d y . Geochim.Cosmochim. Acta 4 8 , 1 2 1 - 1 3 4 .S k i n n e r , B . J . , W h i t e , D . E . , R o s e , H . J . a n d M a y s , R . E . ( 1 9 6 7 ) S u l f id e a s s o c i a t e d w i th S a l to n S e a g e o t h e r m a l b r i n e .Econ. Geol. 62 , 316-330 .

T h o m a s , D . M . a n d G u d m u n d s s o n , J . S . ( 1 9 8 9 ) A d v a n c e s i n t h e s t u d y o f so l i d s d e p o s i t i o n i n g e o t h e r m a l s y s t e m s .Geothermics 18 , 5 -15 .V e t t e r , O . J . a n d C a m p e l l , D . A . ( 1 9 7 9 ) C a r b o n a t e s c a l e c o n t r o l i n h i b i t i o n i n R e p u b l i c ' s E a s t M e s a g e o t h e r m a lo p e r a t i o n s . Geotherm. Resour. Counc. Trans. 3 , 757-760 .

sulfide scale formation and control

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