Prevention of the Antimony Compounds at the Geothermal Power Plants with HYDRODIS® GE Products

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e-ISSN: 2651-4028

Research Article / Araştırma Makalesi

Received: 16.06.2021; Accepted: 24.09.2021 DOI: 10.30516/bilgesci.952134

Prevention of the Antimony Compounds at The Geothermal Power Plants with Hydrodis® Ge Products

Ayhan Erten

^1*

, Mustafa Eroglu

¹

İrfan Avcı

¹

, Taylan Karan

¹

, A. Efekan Çoban

¹

Abstract: The energy dema nd is increa sing da y by da y. Therefore, the renewa ble a nd susta ina ble energy of geotherma l power pla nts is very importa nt. The biggest problems seen in geotherma l power pla nts a re sedimenta tion a nd sca ling. The sca ling occurs into the wells, pipelines a nd hea t excha ngers, etc. where the geotherma l brine pa sses. Those loca tions where the elements a nd compounds in the geotherma l brine precipita te under specific conditions, forms sca les. Those sca les ca used decrea sed efficiency of energy production. During the process of energy production, the tempera ture drops inside hea t excha ngers a nd tha t ca uses the a ntimony (Sb) compounds got precipita ted a nd ca used sca ling. Those sca les nega tively a ffect hea t tra nsfer a nd eventua lly ca use less energy to be produced by ca using blocka ge of the va porizer, prehea ter, a nd filters. For this rea son, stibnite sca ling is a situa tion tha t should be ta ken into serious considera tion. Until now, different methods ha ve been developed a ga inst stibnite sca lings. As of 2020, HYDRODIS®

GE ha s been formula ted a nd developed by the Bozzetto Group, which the a im of stop the precipita tion a nd cuts the opera ting costs. In this wa y, the a ntimony compounds where possibly crea tes sca les got prevented a nd returned in the geotherma l brine to the reservoir via reinjection wells by letting production continue without a ny energy loss.

Keywords: Stibnite, a ntimony, geotherma l power pla nts, HYDRODIS® GE.

1Address: Bozzetto Group., Ista nbul/Turkey

*Corresponding author: a yha n.erten@bozzetto.com.tr

Citation: Erten, A., Eroglu, M., Avcı, İ., Ka ra n, T, Çoba n, A.E. (2021).Prevention Of The Antimony Compounds At The Geothermal Power Plants With Hydrodis® Ge Products. Bilge Interna tional Journa l of Science a nd Technology Resea rch, 5(2):

146-156.

1. INTRODUCTION

Geotherma l wells a re used to tra nsfer the hot ma gma energy under the earth’s crust to underground water. Some importa nt pla ces with hot wa ter a nd convection a nd upstrea m stea m return a re Ca lifornia , New Zea la nd, Ita ly,

Turkey, Ja pa n, a nd Icela nd. Among these countries, Turke y ha s a n importa nt position. Turkey, a s a country with rich geotherma l district hea ting, is used for greenhouse hea ting a nd spa centers with the production of bot h electricity (Ba ra n vd., 2015).

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This study wa s completed a t the Gediz Gra ben, a pa rt of the Turkey. Turkey wa s strongly a ffected by the Alpine- Hima la ya n orogenic belt, which emerged a t the confluence of the Eura sia n a nd Africa n Pla tes, resulting in crusta l thickening from tectonic compression in Ea stern Ana tolia (Haklıdır & Şengün, 2020). Alaşehir geothermal field is one of the high-tempera ture regions in the Gediz gra ben a nd is the region where the geotherma l power pla nt in this study is loca ted. Ma ny geotherma l a rea s in Turkey ha ve a re low to medium entha lpy fields, which a re the most preferred systems for genera ting electricity in bina ry power pla nts (Ba ra n vd., 2015).

Sca ling is a ma jor problem in geotherma l a pplica tions.

Blocka ge a nd sedimenta tion problems ca used by sca ling reduces power pla nt production a nd expensive clea ning a nd opera tion costs. The decrea se in energy yield a nd increa se in opera ting costs directly a ffects fina ncia l return.

Geotherma l fluid chemistry in the different types of sca ling ca n be seen in different geotherma l fields a nd sometimes in different wells of the sa me site.

The genera l cha ra cteristics of the sca les origina ting from the geotherma l fluid depend on the geologica l environment, reservoir type, physicochemica l properties, a nd hydrogeologica l a nd hydrochemica l properties, to give a n exa mple of na tura l conditions. However, other properties a re due to opera ting conditions, well depth, flow ra te, opera ting pressure, a nd opera ting tempera ture. However, a ntimony compounds, which a re formed due to the cooling of the geotherma l brine, a re a type of sca le tha t va ries a ccording to power pla nt designs, power pla nt electricity energy production dema nds, a nd ea rth crust na tura l conditions.

Antimony, a constituent of hydrotherma lly formed minera l pa ngenesis often in the triva lent sta te a s stibnite (Sb2S3), or more commonly known a s its members, in the form of thioa ntimonites of lea d, copper, silver, mercury, iron, etc.

la rge group of "sulfosa lt minera ls". Ra rely, it occurs a s a ntimony, the na tura l element or a lloys (a ntimonides), or a s the oxysulfa te kermesite (Krupp, 1988). Sca ling of stibnite a nd a ntimony-rich sulfide ha s been observed in pipelines a t geotherma l power pla nts in va rious geotherma l systems, including Ita ly, El Sa lva dor, a nd New Zea la nd (Olsen vd., 2012). Consequently, Turkey ha s sulfides of a ntimony into loca l to some geogra phic a rea s like other countries.

The identity of the species controlling a ntimony tra nsport in na tura l high-tempera ture fluids is not well known, studies to da te rely on indirect evidence such a s stibnite solubility a s a function of pH a nd dissolved sulfur (Sherma n vd., 2000).

Antimony is a silvery, white, brittle, crysta lline solid tha t exhibits poor conductivity of electricity a nd hea t. It ha s a n a tomic number of 51, a n a tomic weight of 122, a nd a density of 6.697 kg/m3 a t 26 oC (Anderson, 2012).

However, in geotherma l brines, Sb(III) is the oxida tion sta te (Brown, 2011). Stibnite is a ntimony (III) sulfide Sb2S3. Norma lly pointed (long, needle-like) occurs na tura lly a s a minera l tha t forms bla ck crysta ls (Brown, 2011). Usua lly, Sb precipita tes from geotherma l brine a s Sb2S3. At low T lea ving a hea t excha nger the deposits

produced a re a morphous, red, or ora nge “Meta stibnite”; a t high T the bla ck minera l Stibnite is sometimes produced(Weres, 2019). Sb (III) complex in a ddition to sulfur, which ma y be importa nt in severa l meta stibnite geologica l, Sb (V) a re sulfur complexes. The thioa ntimona te complexes SbS-34, SbS(HS)+, a nd Sb (HS)4+ ha ve long been known experimenta lly. Seems to conta in few minera ls.Sb(V) in fourfold coordina tion with sulphur: fa ma tinite, Cu3SbS4;potosiite,

Pb6Sn2Fe2Sb2S16;a nd stibioenergite

Cu3(Sb,As)S4(Sherma n vd., 2000). Meta stibnite is a n a morphous (non-crysta lline) colloid a nd is red-colored (Brown, 2011). However, the stibnite is norma lly observed in dua l pla nt prehea ter (Brown, 2011). In bina ry pla nts, stibnite, usua lly red a morphous form is precipita ted a s bla ck ra ther tha n crysta lline f orm (Brown, 2011). The a ntimony species likely to be present in the geotherma l brine ha ve been cha ra cterized by Krupp (Krupp, 1988).

His experiments investiga ted the equilibrium between stibnite a nd severa l soluble sulfide complexes (Sca nes, 1989). Although there ma y be a ntimony concentra tion is too low in the brine, it ma y become a lmost qua ntita tive sca ling a ntimony sulfide (Brown, 2011). Antimony sulfur solubility is very sensitive to tempera ture a nd pH cha nges.

Some studies of the dua l pla nt ma y experience both lower pH a t a lower tempera ture. Specifica lly, the stea m is condensed in a n eva pora tor a nd then a dded to the brine a n d then directed to a prehea ter where low tempera ture a nd low pH a re likely (Brown, 2011). Stibnite (sb2s3) is the most a bunda nt minera l a ntimony a nd resolution, the prima ry control over the concentra tion of a ntimony hydrotherma l fluid (Olsen vd., 2012).

Bina ry pla nts often ha ve lower brine tempera tures tha n conventiona l fla sh pla nts. Also, pH modifica tion or a ddition of brine due to the ca pa citor should ha ve a low pH. Under these conditions, a ntimony(III) sulfide (stibnite) ma y precipita te in the hea t excha ngers, ca using loss of hea t tra nsfer a nd ultima tely clogging of the hea t excha nger tubes (Brown, 2011). Mecha nica l clea ning, stea m clea ning, a nd ca ustic soda wa shing options a re a va ila ble toda y to preve n t stibnite deposits (Brown, 2011).

Although the pla nt uses a polya cryla te inhibitor to control ca lcite deposition, this wa s found to be ineffective for stibnite deposition (Sca nes, 1989). For stibnite, it is possible to develop a ntisca la nts such a s ca lcite a ntisca la nts.

Some resea rch ha s been done in this a rea , but there is no a ntisca la nt on the ma rket yet tha t is successful in preventing stibnite deposition. However, resea rch continues (Brown, 2011).

The litera ture ha s reported a few nega tive results of the tria l on stibnite. The la st development of Bozzetto Group ha s pretended stibnite sca les into the geotherma l system.

2. MATERIAL AND METHODS

As of 2020, studied by the Bozzetto Group to eva lua te the performa nce of HYDRODIS^® GE to inhibit a ntimony sulfide deposition in geotherma l brines under dyna mic

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conditions. This study wa s ca rried out in the 24 MW power plant in Alaşehir, Manisa.

In this study, the geotherma l power pla nt ha s one va porizer a nd two prehea ters. The brine inlet tempera ture a t a vera ge 170 ºC and HYDRODIS® GE was injected through power pla nts pipelines designed by Orma t Energy Converter (OEC) units. The a vera ge brine outlet tempera ture wa s average 65 ºC for the preheater outlet. Typical brine flow ra tes were 825 tonnes/hours.

In this study, we pla nned to dose the ma ximum qua ntit y a s 15 ppm a nd optimize it by week. So, the controls were provided by dosing the inhibitor a t 15 ppm in the first two weeks. After 15 ppm of the first pha se of the test, the coupons a nd filters were removed, observed physica lly, a nd a na lyzed with XRF, a nd then the optimiza tion wa s provided a ccording to the results of the a na lysis.

By the wa y, the checked coupons a nd the filters ha ve been inserted into the system without clea ning a nd were observed every week during the tria l period. During the optimiza tion study, the dosa ges were reduced from 15 ppm to 10 ppm a nd 5 ppm. Fina lly, 5 ppm dosa ge provided sta bility a nd did not cha nge the brine's chemistry.

3. RESULTS AND DISCUSSION

The brine chemistry da ta , filters, coupons were observed throughout the tria l. The following da ta which obta ined during the tria l wa s performed by the XRF a na lysis ma de

on the filters together with the physica l observa tion of them.

The XRF a na lysis of the filter sa mples wa s ca rried out with the X-MET8000 Expert XRF device. The sca le deposit wa s investiga ted using Sca nning Electron Microscopy (SEM), while providing high m a gnifica tion ima ges, SEM ca n a lso provide a semi-qua ntita tive elementa l a na lysis of the sca le deposits. SEM a na lyzes of the sa mples obta ined were ca rried out with the Fei Qua nta 250 Feg a nd EdX a na lysis with the EDX Detector (Oxford Aztec) device. The sca le deposit wa s investiga ted using X-Ra y Powder Diffra ctometry (XRD) while providing informa tion a bout the chemica l composition a nd crysta llogra phic structure of sca le deposits. XRD a na lyses were ca rried out on the Philips X’Pert Pro device. The scales on Xrd analyzed at the 2ø theta and 5-80 degrees Cu Kα radiation with a wa velength of 0.1542 nm.

3.1. The effect of HYDRODIS® GE to geothermal brine chemistry

The effect of HYDRODIS® GE products on brine chemistry is given in Figures 2,3,4 a nd 5. According to brine chemistry a na lysis, it wa s observed tha t the va lues were sta ble without a ny cha nge in the silica a nd tota l ha rdness da ta . Obta ining pa ra llel va lues a t the inlet a nd outlet of the pla nt shows tha t our product na med HYDRODIS® GE provides high stability even in optimiza tion studies with low dosa ge products without being a ffected by dosa ge cha nges.

Figure 2. The effect of HYDRODIS® GE on ec/ph of pla nt inlet of brine chemistry 2160 2180 2200 2220 2240 2260 2280 2300

4 4.55 5.5 6 6.57 7.58

25.11.2020 11:00 26.11.2020 11:00 26.11.2020 17:00 27.11.2020 15:30 30.11.2020 09:00 30.11.2020 16:00 1.12.2020 15:00 2.12.2020 09:30 2.12.2020 16:00 3.12.2020 16:00 4.12.2020 13:00 7.12.2020 14:00 8.12.2020 14:00 9.12.2020 14:00 11.12.2020 09:00 14.12.2020 13:00 15.12.2020 09:00 16.12.2020 09:00 16.12.2020 16:00 17.12.2020 15:00 18.12.2020 15:00 21.12.2020 09:00 21.12.2020 16:00 22.12.2020 13:00 23.12.2020 09:00 EC

pH

Date Plant Inlet EC/pH

pH EC (µs/cm)

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Figure 3. The effect of HYDRODIS® GE on silica a nd tota l ha rdness of pla nt inlet of brine chemistry

Figure 4. The effect of HYDRODIS® GE on EC/pH of pla nt outlet of brine chemistry 0 5 10 15 20 25

4 54 104 154 204 254 304 354 404

25.11.2020 11:00 26.11.2020 11:00 26.11.2020 17:00 27.11.2020 15:30 30.11.2020 09:00 30.11.2020 16:00 1.12.2020 15:00 2.12.2020 09:30 2.12.2020 16:00 3.12.2020 16:00 4.12.2020 13:00 7.12.2020 14:00 8.12.2020 14:00 9.12.2020 14:00 11.12.2020 09:00 14.12.2020 13:00 15.12.2020 09:00 16.12.2020 09:00 16.12.2020 16:00 17.12.2020 15:00 18.12.2020 15:00 21.12.2020 09:00 21.12.2020 16:00 22.12.2020 13:00 23.12.2020 09:00 Total Hardness

Silica

Date

Plant Inlet Silica /Total Hardness

Silica(SiO2) Total Hardness (CaCO₃)

18501900 19502000 20502100 21502200 22502300

4 4.5 5 5.5 6 6.5 7 7.5

25.11.2020 11:00 26.11.2020 11:00 26.11.2020 17:00 27.11.2020 15:30 30.11.2020 09:00 30.11.2020 16:00 1.12.2020 15:00 2.12.2020 09:30 2.12.2020 16:00 3.12.2020 16:00 4.12.2020 13:00 7.12.2020 14:00 8.12.2020 14:00 9.12.2020 14:00 11.12.2020 09:00 14.12.2020 13:00 15.12.2020 09:00 16.12.2020 09:00 16.12.2020 16:00 17.12.2020 15:00 18.12.2020 15:00 21.12.2020 09:00 21.12.2020 16:00 22.12.2020 13:00 23.12.2020 09:00 Ec

pH

Date Plant Outlet EC/pH

pH EC (µs/cm)

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Figure 5. The effect of HYDRODIS® GE on silica a nd tota l ha rdness of pla nt outlet of brine chemistry 3.2. The effect of HYDRODIS® GE to scales of filter

The effect of HYDRODIS® GE products on scales of filters a re given in Ta ble 1 a nd Figure 6. Antimony (da rk brick color) precipita tion seen in the injection filter (Sb₂S₃) was prevented after HYDRODIS® GE inhibitor dosage. It

wa s observed tha t the structures seen in the filter were a lso clea ned, a nd the color formed on the filter turned into very wea k ora nge. The fa ct tha t no sca le forma tion wa s observed in Filter B, which wa s opened for control purposes a nd regula rly monitored during the tria l period, showed tha t the surfa ce inhibitor we used works properly.

.

0 5 10 15 20 25

4 54 104 154 204 254 304 354 404

25.11.2020 11:00 26.11.2020 11:00 26.11.2020 17:00 27.11.2020 15:30 30.11.2020 09:00 30.11.2020 16:00 1.12.2020 15:00 2.12.2020 09:30 2.12.2020 16:00 3.12.2020 16:00 4.12.2020 13:00 7.12.2020 14:00 8.12.2020 14:00 9.12.2020 14:00 11.12.2020 09:00 14.12.2020 13:00 15.12.2020 09:00 16.12.2020 09:00 16.12.2020 16:00 17.12.2020 15:00 18.12.2020 15:00 21.12.2020 09:00 21.12.2020 16:00 22.12.2020 13:00 23.12.2020 09:00 Total Hardness

Silica

Date

Plant Outlet Silica /Total Hardness

Silica(SiO2) Total Hardness (CaCO₃)

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Table 1. The effect of HYDRODIS® GE products on sca les of filters. i. The filter checked before tria l, ii. The filter checked in the first week during the tria l iii. The filter checked the second week during tria l.

Date Fılter Locatıon Fılter Images Scales Images Xrf Results

i. 25.11.2020 Jes-2 Rejection B Filter

ii. 3.12.2020 Jes-2 Rejection B Filter

iii. 11.12.2020 Jes-2 Rejection B Filter

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Figure 6. The effect of HYDRODIS® GE products on sca les of filters.

3.3. The effect of HYDRODIS® GE on the scales of structures investigation with sem In the sca le sa mples exa mined by sca nning electron microscopy (SEM), it wa s observed tha t the sca le sa mples were knitted with a very tight needle network before the experiment wa s ca rried out, a nd the a ntimony combined with the free sulfur in the brine medium to form Stibnite compounds frequently a nd densely. After the HYDRODIS GE product wa s dosed, it wa s

observed tha t needle-like structures lost their pa ttern frequency a nd a ntimony produced less compounds with sulfur a nd the a mount of Stibnite decrea sed. The obta ined SEM ima ges were supported by energy-dispersive x-ra y spectroscopy (EDx) results ta ken from the regions where the ima ges were. The effect of HYDRODIS® GE products on scales of structures investiga tion with SEM a nd EDx a re given in Ta ble 2 a nd Figure 7.

. 0 5 10 15 20 25 30 35 40

20.11.202025.11.202030.11.2020 5.12.2020 10.12.202015.12.202020.12.202025.12.202030.12.2020

% Sb

Fılter Out Dates

%Sb scales on Filters

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Table 2. The effect of HYDRODIS® GE products on the sca les of structures investiga tion with sem. i. The sca les of filters a na lyzed wit h sem a nd edx before tria l, ii. The sca les of filters a na lyzed with sem a nd edx in the first week during the tria l iii. The sca les of filters a na lyzed with sem a nd edx in the second week during tria l.

Date 5-10 Micron Images 2-5 Micron Images EDx Analyses Elemental Ratio%

i. 25.11.2020

ii. 03.12.2020

iii. 11.12.2020

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Figure 7. Sca les of the structures a t the reinjection filters % sb ra tio on edx results.

3.4. Effect of HYDRODIS® GE on the scales of structures investigation with ft-ir

The pea ks in my tra nsmitta nce spectrum indica te tha t the compounds were cha nged with dosa ge.

This is to be expected, a nd even is the desired outcome, beca use there wa s no hydroca rbon pea k a round 3000 cm^-1 during the second period of tria l, indica ting tha t there a re no hydroca rbons present

on the sca les sa mples. This is a lso shown in the spectra compa ring the pre a nd post sa mples of stibnite a ga inst the ba ckground of a ir. Though the pea ks a re very simila r, the la ck of a hydroca rbon pea k shows tha t the tria l wa s successful. The two pea ks a re compa red of this ba nd a re shifted 1 0 t o 15 cm^-1 to a lower frequency, indica ting tha t the receiver ha s switched to a stronger Sb⁺³ molecule collector for S. The visible spectrum ca n be a ssigned a t ~1050 cm^-1, indica ting tha t a nother strong band ν (C=S) has formed temporarily.

.

Figure 8. Xrd pa ttern of sca les of the structures a t the reinjection filters 0

5 10 15 20 25 30 35 40 45 50

23.11.202025.11.202027.11.202029.11.2020 1.12.2020 3.12.2020 5.12.2020 7.12.2020 9.12.2020 11.12.202013.12.2020

% Sb

Date Sb Ratio on Edx%

0 200 400 600 800 1000 1200 1400 1600 1800

5 20 35 50 65 80

Intensity(a.u.)

2 Theta (deg.) 25.11.2020 3.12.2020

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The sca les were a na lyzed by XRD, FT-IR, a nd other techniques. According to Ta ble 3, the sca le cha ra cteriza tion da ta obta ined during the study showed tha t the stibnite sca les a t lower outlet tempera tures of geotherma l power pla nts ha ve been kept under control by decrea sing the speed of the crystal growing using HYDRODIS GE® polymers.

The minimum dosa ges ha ve been checked during the tria l period of the system a nd it could opera te smoothly even a t 5 ppm. The obta ined results ha ve shown tha t stibnite compounds ca n be blocked by using HYDRODIS polymer just a t the entra nce of the hea t excha nger of the geotherm a l power pla nt. In a ddition to, the fa ct tha t the products a t lo w dosa ge interva ls sta bilizes the power pla nt in a short time like one month during the prevention of the stibnite problem a nd its from the power pla nt, confirms the purpose a nd success of this study. All in a ll, in Ta ble 3. a dded to the conclusion section covers a period of not only one month

but dea ls with the before a nd a fter of the problem. The visua ls in Ta ble 3 confirm tha t the reduced to growing-up crysta lline structure a nd precipita tion on the coupons ha ve been prevented over time and that the HYDRODIS® GE products ha ve successfully protected the system. Accordin g to the results obta ined, this study showed tha t HYDRODIS® GE products can be applied in different power pla nts a nd prehea ters designed for different tempera tures under different dosa ge conditions.

Considering the sca la ble a pplica tion of power pla nts a nd the a im of susta ina ble a nd sta ble brine chemistry, we expect tha t our work ca n be beneficia l to the study of a ntimony compounds a nd provide a significa nt stra tegy for geotherma l power pla nts.

Table 3. The eva lua tion coupons a t the geotherma l power pla n

Date Coupon

Locatıon Coupon Images

8.11.2019 Plant Outlet

25.11.2020 Plant Outlet

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Acknowledgements

We would like to tha nk a ll reservoir tea m of our pa rtner for their support in this study.

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