Antiscalant Patel Des 1999

Presented at the Conference on Desalination and the Environment, Las Palmas, Gran Canaria, 912 November, 1999.European Desalination Society and the International Water Association.

0011-9164/98/$09.50 1998 Elsevier Science B.V. All rights reserved

Desalination 124 (1999) 6374

New antifoulants for deposit control in MSF and MED plants

Suresh Patel*, Michael A. Finan

Process Additives Division, FMC (UK) Corporation Ltd., Tenax Road, Trafford Park, Manchester M17 1WT, UKTel. +44 (161) 872-2323, ext. 3350; Fax +44 (161) 875-3171/5

Abstract

New products based on enhanced maleate chemistry have been developed to control the broad range of depositsfound in thermal desalination plants. To investigate the performance characteristics of enhanced maleate products,laboratory tests were developed to measure the control of fouling species. The test methods developed for and usedin this study provide a further understanding of the key mechanisms of deposit control by additives. The advanceperformance of products based on enhanced maleate chemistry compared with conventional products currently inuse in MSF and MED plants will be presented. Individual product data sets have been combined to produce productperformance profiles which can then be used in the selection of additive appropriate to the fouling characteristics ofthe desalination plant. The enhanced maleates have been successfully tried in both MSF and MED plants. Six monthsdata from a 23,000m3/d plant in Saudi Arabia, operated at a top brine temperature of 110C, will be presented. Also12- month operational data from an 8000m3/d MED plant in Europe, top brine temperature 62C, will be presented.The results from these extended field evaluations have confirmed the initial laboratory results.

Keywords:Calcium carbonate; Magnesium hydroxide; Seawater; Scale; Inhibitor; Dispersant; Desalination; MSF;MED; Belgard EV2030; Belgard EV2050; Field trials

1. Introduction

The main process for production of pure wa-ter from seawater is currently practiced by multi-stage flash (MSF) and multi-effect desalination(MED). The major problem encountered is thedeposition of scale onto the heat transfer surfaces

*Corresponding author.

which results in a serious loss of efficiency andproduction [1]. Without effective scale control,this can lead to the eventual shutdown of the plantfor cleaning.

The scales that are generally encountered canbe divided into two main classes: (1) alkalinescales, e.g., calcium carbonate and magnesiumhydroxide and (2) non-alkaline scales, e.g., cal-cium sulphate.

S. Patel, M.A. Finan / Desalination 124 (1999) 637464

The alkaline scales result from the thermal de-composition of bicarbonate ion present in sea-water.

2HCO3- ====> CO32- + H2O + CO2 (1)

The calcium ions present in the seawater reactwith the carbonate ions to form calcium carbon-ate.

Ca2+ + CO32- ====> CaCO3 (2)

Furthermore, the carbonate formed in reaction (1)may react with water in the following manner:

CO32- + H2O ====> CO2 + 2OH- (3)

The hydroxyl ions formed can react with magne-sium present in the seawater to form magnesiumhydroxide:

Mg2+ + 2OH- ====> Mg(OH)2 (4)

The rate of formation of calcium carbonate andmagnesium hydroxide in seawater depends ontemperature, pH, concentration of bicarbonateions, rate of CO2 release, concentration of Ca2+

and Mg2+ ions, and total dissolved solids. Calciumcarbonate is the major scale that is formed up to aseawater temperature of 90C, whereas magne-sium hydroxide is mainly formed above tempera-tures of 95100C. This is due to the increase information of hydroxyl ions with increasing tem-perature [see Eq. (3)]. Also, calcium carbonateand magnesium hydroxide possess low solubilitiesand have an inverse solubility, that is with in-creasing temperature their solubility decreases.

The non-alkaline scale found is calcium sul-phate which exists in three forms: anhydrite(CaSO4), hemihydrate (CaSO41/2H2O) and dihy-drate (CaSO22H2O). All these forms of calcium

sulphate are more soluble than calcium carbonateand magnesium hydroxide, and will form whenthe seawater is supersaturated with respect tocalcium sulphate.

Marshall and Slusher [2] determined the solu-bilities of the three forms of calcium sulphate atdifferent temperatures and different seawaterconcentration factors. These results may be usedto estimate under what conditions an MSF plantcan be operated before calcium sulphate scalingbecomes a problem. Hence in most MSF plants,calcium sulphate scaling is prevented by con-trolling the temperature and concentration factorof the brine within the precipitation limits, that isa maximum temperature of 120C and a concen-tration factor of 2 based on standard seawater.

Another foulant that can occur is by the in-gress of fine silt usually when the seabed is dis-turbed during rough sea conditions, dredgingactivities, etc. [3]. This increases the suspendedsolids content of the feed seawater and can causeblockages of pumps, pipework and deposition onheat transfer surfaces. The silt can also combinewith calcium carbonate and/or magnesium hy-droxide forming a mixed scale. In addition, someantiscalants adhere strongly to silt by adsorption,hence reducing the concentration of the additivein the bulk solution to control chemical fouling,e.g., calcium carbonate and magnesium hydrox-ide. This could lead to severe fouling of the plantif the additive concentration is not increased.

To control this scaling problem on heat trans-fer surfaces in MSF and MED plants, the follow-ing methods may be used: (a) acid treatment, (b)additive treatment, and (c) mechanical cleaning.

The first method involves the addition of acidwhich undergoes the following reactions:

HCO3- + H+ ====> H2O + CO2

This method of scale control is effective but has anumber of drawbacks. These are:

S. Patel, M.A. Finan / Desalination 124 (1999) 6374 65

1. Stoichiometric amounts of acid must beadded to the seawater; usually a large quantity ofacid is required and is hazardous.

2. Addition of excess acid would give rise tocorrosion problems [4].

3. From Eq. (5), large volumes of CO2 are re-leased, hence additional equipment in the form ofa decarbonator is required to remove the CO2produced.

Due to these drawbacks, the second method ismore practical. Chemical additives are used tocontrol the formation of scale by having threshold,crystal growth inhibition and crystal distortionproperties. The threshold properties may be de-fined as maintaining the calcium and magnesiumions in solution. Some of these threshold additiveshave a marked effect on the crystal habit of thescaling compound, such that the crystal eitherstops growing or is distorted. The distorted crys-tals are less likely to adhere to each other and tometal surfaces. Polymers based on polycarboxylicacid type chemistry also have the additional ad-vantage of having dispersion properties of calciumcarbonate, magnesium hydroxide and silt. Poly-mers can adsorb onto the particulate surfaces andimpart a like charge, hence repelling neighbouringparticles, thereby keeping the particles suspendedin solution.

The chemical additives that are currently inuse have one or more of these properties. Theseare polyphosphates, phosphonates, polyacrylatesand polymaleates. They are either used on theirown or in combination with a mechanical cleaningmethod, namely sponge ball cleaning. The lattermethod removes any soft scale (which is formedin the presence of an additive) that is deposited ona heat transfer surface [5,6].

Polyphosphates are rarely used in MSF andMED plants as these tend to cause additional scalein the form of thick muddy deposits [7] as calciumphosphate or mixed scale including phosphateions, which can strongly adhere to the heat trans-fer surfaces and is difficult to remove.

In this study a new range of antifoulants, en-hanced maleates [8], have been studied and com-pared to the conventional additives currently inuse. In order to compare these additives, a numberof tests were designed to provide not only theperformance characteristics of the individualadditive but also to identify the key mechanism bywhich these additives retard scale under desalina-tion conditions.

The objective of this work was to generate per-formance profiles of individual additives such thatthe appropriate additive can be matched to thefouling characteristics of the desalination plantand field tested on MSF and MED plants.

2. Experimental

2.1. Calcium carbonate deposition testThis test measures the additives ability to

control calcium carbonate deposition by threemechanisms: (1) threshold, (2) nucleation at theheated metal surface and (3) crystal growth inhi-bition at the metal surface.

This test method utilizes a synthetic seawater(Table 1). This water, containing an additive, ispumped at constant flow rate through a coil 1.1mm (ID) 316 stainless steel capillary tube

Table 1

Synthetic seawater chemistry used in calcium carbonatedeposition test

Calcium, mg/l as Ca2+

Magnesium, mg/l as Mg2+

Chloride, mg/l as Cl-

Sodium, mg/l as Na+

Carbonate, mg/l as CO32-

Sulphate, mg/l as SO42-

Potassium, mg/l as K+

Total dissolved solids, mg/lpH

4001,20018,71110,5221842,62339534,0378.6


Fig. 1. Calcium carbonate deposition test rig.

immersed in water bath at 90C. Any calciumcarbonate deposition reduces the bore of the tubeand causes an increase in pumping pressure. Therate of change in pressure across the capillary tubewas monitored by a pressure transducer and plot-ted against time on a chart recorder. Two mg/l ofadditive was maintained during the test, and thetime to reach a P of 1psi (6.895kPa) was meas-ured. The set-up of this equipment is shown inFig. 1. The greater the time to reach P of 1psi,the better the additive at controlling calciumcarbonate deposition.

2.2. Calcium carbonate crystal growth inhibitiontest

This test is designed to measure the additivesability to stop the growth of calcium carbonatecrystals in the bulk solution phase. A 100 cm3

synthetic water (Table 2) containing 20mg ofcalcium carbonate crystals was placed in a waterbath at 85C for 30 min. The solution was filteredthrough a 0.45 filter and the soluble calciumdetermined in the filtrate by titration with EDTA.This test was repeated with 4 mg/l additive pres-

ent. Also a standard solution was made containingno carbonate ions and the above test repeated. Tocalculate the percentage inhibition of each addi-tive, the following equation was used:

% inhibition = ([Ca2+]Additive - [Ca2+]Blank/

[Ca2+]Standard - [Ca2+]Blank) 100

where [Ca2+]Additive is the concentration of solubleCa2+ in an additive-containing solution (mg/l),

Table 2Synthetic seawater chemistry used in the crystal growthinhibition test




Sodium, mg/l as Na+



12537519,29011,94018131,9118.8


[Ca2+]Standard is the concentration of soluble Ca2+ ina standard solution (mg/l), and [Ca2+]Blank is theconcentration of soluble Ca in a blank solution(mg/l). The higher the percentage inhibition, thebetter the crystal growth inhibition of calciumcarbonate.

2.3. Magnesium hydroxide inhibition test

This test measures the threshold properties ofadditives to control magnesium hydroxide.

One thousand cm3 seawater (Table 3) washeated to 90C while the pH was maintained at 8throughout the 30 min test. The turbidity of thesolution at the end of the test was measured usinga Hach spectrophotometer. The above test wasrepeated with 10 mg/l additive present; hence, thelower the turbidity reading obtained with an addi-tive, the greater the inhibition to magnesiumhydroxide. The percentage inhibition was cal-culated using the following equation:

% inhibition = 100 - K where

K = (TAdditive - TStandard)/(TBlank - TStandard) 100

and TAdditive is the turbidity of the additive solution(NTU), TStandard the standard solution (NTU), andTBlank the blank solution (NTU).

Table 3Analysis of natural seawater




Sodium, mg/l as Na+



Potassium, mg/l as K+


4601,36819,85010,8021242,65042835,6828.4

In addition, the blank solution was repeatedand then filtered through a 0.45 filter and thedeposit collected, then dried in an oven at 50Cfor 48h. This deposit was analyzed by x-ray pow-der diffraction and was found to be brucite.

2.4. Mixed calcium carbonate and magnesiumhydroxide scale dispersancy test

The ability of additives to suspend particles ofcalcium carbonate and magnesium hydroxide ismeasured in this test. A mixed calcium carbonateand magnesium hydroxide scale was prepared bycirculating 5l of seawater (Table 3) over a 316stainless steel heat exchanger at 90C for 4 days,and the seawater volume was maintained by ad-justing for any loss due to evaporation. Through-out the 4 days, the seawater pH was maintained at8.5 and the bulk solution temperature was main-tained at 85C.

One hundred cm3 of this solution was filteredthrough a 0.45 filter and the deposit stored at50C for 48h. This deposit was analyzed by x-raypowder diffraction and found to be a mixed scaleof calcium carbonate and magnesium hydroxide.

One hundred cm3 of this solution was placedin a Hach spectrophotometer and the turbidityfollowed over 30 min. This test was the blank run.This was repeated, except that the solution con-tained 10 mg/l additive. The greater the turbiditymaintained by the additive, the higher the disper-sancy. The equation used to calculate the percent-age efficiency of the additives is shown below:

% efficiency = (TdAdditive - TdBlank) / (TdStandard - TdBlank ) 100

where TdAdditive is the turbidity of the additivecontaining solution (NTU), TdStandard is the turbid-ity of start of the test (NTU), and TdBlank is theturbidity of blank solution (NTU).

The higher the percentage efficiency obtained


by an additive, the better the dispersion activity tomixed calcium carbonate and magnesium hy-droxide scale.

2.5. Calcium sulphate inhibition testThis test measures the threshold properties of

additives to control calcium sulphate. A 100 cm3

of synthetic water containing 2495 mg/l calciumand 7200 mg/l sulphate (full water chemistry is in

Table 4Synthetic water chemistry used in calcium sulphateinhibition test


Sodium, mg/l as Na+




2,4956,3982,70219,29035,38588.5

Table 5Additives

Abbreviation Chemical type Commercialproduct

PMA-1

PMA-2

PMA-3

EM-1

EM-2PAA

P-NATE

Homopolymer of polymaleic acidTerpolymer of polymaleic acidCopolymer of polymaleic acidPolycarboxylic acid

Polycarboxylic acidPolyacrylate

Phosphonate

Belgard EV

Belgard EV2000

Sokalan PM10i, Kao KC550Belgard EV2030, Belgard EV2035Belgard EV2050Degussa POC 2020Albrivap DSB, Aquamax LT-19

Table 4) was stored at 70C for 24 h. This testwas repeated with the additive under test. Also astandard solution was made containing no sul-phate ions. The solutions were filtered through a0.45 filter and the soluble calcium determinedby titration with EDTA. The percentage inhibi-tion is calculated using the equation given in thecalcium carbonate crystal inhibition test.

2.6. Additives tested in this study

The additives [3,912] evaluated in this studyare given in the Table 5.

3. Results and discussion3.1. Calcium carbonate control

3.1.1. Calcium carbonate depositionThe results, presented in Fig. 2, show the en-

hanced maleates, EM-1 and EM-2, polyacrylateand phosphonate, to be good inhibitors of thedeposition of calcium carbonate on a heat ex-changer surface. The mechanism by which cal-cium carbonate deposition is controlled by theseadditives is predominantly by threshold and re-tarding the nucleation of calcium carbonate nucleion the heated metal surface, whereas the maleatesPMA-l, PMA-2 and PMA-3 show poor depositioncontrol of calcium carbonate.

3.1.2. Calcium carbonate crystal growth inhi-bition

The results in Fig. 3 show that PMA-1 andPMA-2 have excellent crystal growth inhibition tocalcium carbonate compared to PMA-3. Thissuggests that not all polymaleates have the samecrystal growth inhibition properties in the bulksolution phase. The enhanced maleates both showcrystal growth inhibition properties, but EM-1 isalmost twice as effective as EM-2. The poly-acrylate has poor inhibition and the phosphonatehas mediocre crystal growth inhibition to calciumcarbonate.


Fig. 2. Calcium carbonate deposition control.

Fig. 3. Calcium carbonate crystal growth inhibition.

Overall, the two tests show all the additivestested can control calcium carbonate depositionbut the mechanism by which they function varies.The additive that demonstrates the best calciumcarbonate control is EM-1, closely followed byEM-2.

3.2. Magnesium hydroxide control

This test was developed to measure the differ-ences in threshold activity between additives tocontrol magnesium hydroxide deposition. Theresults, presented in Fig. 4, indicate that EM-1

and PMA-3 have excellent magnesium hydroxidecontrol. The polyacrylate and PMA-1 have me-diocre magnesium hydroxide control. No magne-sium hydroxide control is found with PMA-2,EM-2 and phosphonate. Hence PMA-2, EM-2 andthe phosphonate would not control magnesiumhydroxide deposition by the threshold mechanism.

3.3. Dispersion properties

The dispersion properties of additives becomeessential if the saturation index of a brine forcalcium carbonate and magnesium hydroxide are


Fig. 4. Inhibition of magnesium hydroxide.

very high, so that precipitation would occur rap-idly, then threshold inhibitors are likely to be lesseffective compared to additives with good disper-sion properties.

A mixed scale of calcium carbonate and mag-nesium hydroxide was prepared in situ fromnatural seawater in a small recirculating rig witha heat exchanger to mimic the type of scale foundi a desalination plant [13]. The additives evalu-a d in this dispersancy test is presented in Fig. 5.Ta

the mixed scale. PMA-1 shows mediocre disper-sion properties, whereas the poly-acrylate andphosphonate have very little or no dispersionproperties.

3.4. Calcium sulphate controlCalcium sulphate starts to form in a desali-

nation plant if the concentration factor of the brineis increased and/or top brine temperature is high.Therefore, additives used in desalination plants

Fig. 5. Dispersion of mixed calcium carbonate and magnesium hydroxide scale.n te

he results indicate that PMA-2, PMA-3, EM-1nd EM-2 have excellent dispersion properties to

should possess some activity to control calciumsulphate.


Fig. 6. Inhibition of calcium sulphate.

Additives were evaluated for calcium sulphateinhibition, and the results are presented in Fig. 6.The best calcium sulphate inhibitor is PMA-1,whereas PMA-2, EM-1 and EM-2 show mediocrecalcium sulphate inhibition properties. Less than20% calcium sulphate inhibition is obtained withPMA-3, polyacrylate [14] and phosphonate. Thelast three additives should not be used for calciumsulphate control.

3.5. Performance profilesThe test data were used to generate perfor-

mance profiles of individual additives using radardiagrams. The larger the area occupied by theadditives, the better the multi-functional scalecontrol properties.

Fig. 7 shows the comparison of PMA-1 withPMA-2. This profile clearly shows that PMA-1 isbetter overall than PMA-2, but PMA-2 has betterdispersion properties. Both products would beused differently, i.e., PMA-1 in high-temperatureMSF plants where both calcium carbonate andmagnesium hydroxide control is required, andPMA-2 in low-temperature MSF plants wherecalcium carbonate inhibition and dispersion prop-erties from the additive would be required.

Fig. 8 shows that PMA-3 is significantly dif-ferent from PMA-1 as it has very good dispersionand magnesium hydroxide properties but poorcalcium carbonate and calcium sulphate control.PMA-3 would be used in high- temperature plantsbut would rely predominantly on its dispersiveproperties to control calcium carbonate and wouldnot be used when calcium sulphate is likely toform.

Fig. 9 shows that EM-1 has superior multi-functional properties compared to PMA-1 tocontrol calcium carbonate and magnesium hy-droxide but slightly lower activity against calciumsulphate. This would suggest that EM-1 wouldmake an excellent inhibitor for high temperatureMSF plants where calcium carbonate and magne-sium hydroxide would be the predominant scalelikely to occur.

Fig. 10 shows that EM-2 has excellent calciumcarbonate deposition control and disper-sancy butpoor magnesium hydroxide control. Hence, EM-2would be used in low-temperature plants wherecalcium carbonate control is required.

Fig. 11 shows the polyacrylate to be a goodcalcium carbonate deposition control agent andmagnesium hydroxide inhibitor. Again, withpolyacrylate, the top brine temperature of MSF


Fig. 7. Performance profiles of PMA-1 and PMA-2.

Fig. 9. Performance profiles of PMA-1 and EM-1.

plant would be restricted such that calcium sul-phate control is not required and dispersion ofeither mixed scale or silt is not required.

Fig. 12 shows the phosphonate to be a goodcalcium carbonate inhibitor but has virtually nodispersion properties and should be restricted touse in low-temperature plants. However, if disper-sion properties are required in a low- temperatureplant, then the phosphonate would not be suitable.

This analysis clearly shows that EM-1 has thebest performance profile for scale control incurrent high temperature MSF plant and EM-2

Fig. 8. Performance profiles of PMA-1 and PMA-3.

Fig. 10. Performance profiles of PMA-1 and EM-2.

has the best performance profile for use in currentMED plants.

4. Field trials

To follow-up on the laboratory data on theenhanced maleates, EM-1 and EM-2, the follow-ing trials were conducted:

4.1. MSFThe field trial was carried out for 6 months

in a longitudinal MSF unit (24 stages in five


Fig. 11. Performance profiles of PMA-1 and polyacrylate. Fig. 12. Performance profiles of PMA-1 and phos-phonate.

Fig. 13. Heat transfer coefficient for HIS. Six-month operation with 2 mg/l EM-1.

modules, the first module consisting of six stages,the next three modules consisting of five stageseach, with the last module consisting of threestages, which is designated as the heat rejectionsection) in Saudi Arabia operating at 110C topbrine temperature, 23,000 m3/d distillate pro-duction, recycle brine concentration ratio of 1.3,EM-1 dose rate of 2 mg/l and ball cleaning twotimes per week (nine cycles/operation).

The heat transfer data collected are shown inFig. 13. A deterioration of heat transfer indicatesscaling on heat transfer surfaces. Fig. 13 indicatesan initial gradual drop in heat transfer over the

first 18 days but then is constant for the remainingperiod of the test. This would be a typical profilethat is found in all plants if good scale control isachieved. This indicates that some scale is initiallyformed, but then no further deposition occurredduring the test period. This was confirmed in thevisual inspection of the brine heater at the end ofthe field trial. In addition, the GOR in Fig. 14increases with time, indicating increase in pro-duction of distillate. This improvement may bedue to the seawater temperature increase andreduction in condensate temperature.


Fig. 14. GOR. Six-month operation with 2 mg/l EM-1.

Fig. 15. GOR. 4 ppm (for 51 days), then 3 mg/l of EM-2.

The results from plant performance and visualinspection at the end of the field trial showed EM-1 to be a very effective antifoulant.

4.2. MEDA field trial was conducted on a 12-effect

desalination unit with thermocompression inEurope for 12 months, producing 8000 m3/d

distillate water at a top brine temperature of 62C[15]. The ejectocompressors are fed with 43 barsteam raised by dedicated boilers. EM-2 wasdosed at 3 mg/l. The results in Fig. 15 show theGOR remains virtually constant throughout thetest period. Visual inspection was carried out atthe end of the field trial, and the evaporator cellsincluding the heat exchanger tubes were found tobe clean.


The results from these extended field evalua-tions have confirmed the initial laboratory resultsthat EM-1 is an excellent antifoulant for high-temperature MSF plants and EM-2 is an excellentantifoulant for MED plants.

5. Conclusions

The laboratory investigation shows that addi-tives vary in performance depending on the typeof mechanisms by which they function to controlor retard scale formation. The enhanced maleateswere found to be superior antifoulants comparedto those currently available commercially.

The enhanced maleates can be differentiatedsince EM-1 has all the multi-functional propertiesrequired to control deposition and can be used inhigh-temperature plants. EM-2 has excellentcalcium carbonate inhibition and dispersion prop-erties and hence can be used in low-temperatureplants. The extended field trials for EM-1 andEM-2 demonstrate their in use scale control per-formance and confirm the initial laboratory re-sults.

References[1] S.M. Zubair, M.O. Budair and A.A. Al-Shakhs,

AES, 27 (1992) 279.[2] W.L. Marshall and J. Slusher, J. Chem. Eng. Data,

13(1) (1968) 183.[3] Y. Fukumoto, K. Isobe, N. Moriyama and F. Pujo-

das, Desalination, 83 (1991) 65.[4] O.D. Linnikov, V.L. Podbereznyi, E.A. Anokhina,

and O.V. Guseva, Desalination, 89 (1993) 311.[5] H. Bohmer, Desalination, 93 (1993) 171.[6] F. Al-Bakeri and H. El Hares, Desalination, 92

(1993) 353.[7] A.M. Shams El Din, Desalination, 61 (1987) 89.[8] S. Patel and M.J. Lees, EP-818423, 1998.[9] M.A. Finan, S. Smith, C.K. Evans and J.W.H. Muir,

Desalination, 73 (1989) 341.[10] S. Al-Zahrani, A.M. Al-Ajlan and A.M. Al-Jardan,

Desalination, 97 (1994) 17.[11] S.A. Al-Saleh and A.R. Khan, Desalination, 97

(1994) 87.[12] S.A. Al-Saleh and A.R. Khan, Desalination, 97

(1994) 97.[13] M. Al-Ahmed and F.A. Aleem, Desalination, 93

(1993) 287.[14] M.C. Van Der Leeden and G.M. Van Rosmalen,

Desalination, 66 (1987) 185.[15] C. Temstet, G. Canton, J. Laborie and A. Durante,

Desalination, 105 (1996) 109.

Abstract1. Introduction2. Experimental2.1. Calcium carbonate deposition test2.2. Calcium carbonate crystal growth inhibition test2.3. Magnesium hydroxide inhibition test2.4. Mixed calcium carbonate and magnesium hydroxide scale dispersancy test2.5. Calcium sulphate inhibition test2.6. Additives tested in this study

3. Results and discussion3.1. Calcium carbonate control3.1.1. Calcium carbonate deposition3.1.2. Calcium carbonate crystal growth inhi-bition

3.2. Magnesium hydroxide control3.3. Dispersion properties3.4. Calcium sulphate control3.5. Performance profiles

4. Field trials4.1. MSF4.2. MED

5. ConclusionsReferencesTables and figuresTable 1Table 2Table 3Table 4Table 5Fig. 1.Fig. 2.Fig. 3.Fig. 4.Fig. 5.Fig. 6.Fig. 7.Fig. 8.Fig. 9.Fig. 10.Fig. 11.Fig. 12.Fig. 13.Fig. 14.Fig. 15.

Antiscalant Patel Des 1999

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