effects of tube material on scale formation and control … · formation and control in horizontal...

The International Desalination Association World Congress on Desalination and Water Reuse 2013 / Tianjin, China REF: IDAWC/TIAN13-119

EFFECTS OF TUBE MATERIAL ON SCALE FORMATION AND CONTROL IN MULTIPLE-EFFECT DISTILLERS Authors: H. Glade, K. Krömer, A. Stärk, K. Loisel, K. Odiot, S. Nied, M. Essig Presenter: Dr. Heike Glade Senior Researcher – University of Bremen – Germany [email protected] Abstract Crystallization fouling on heat transfer surfaces is a severe problem in thermal seawater desalination and a complex phenomenon. The allowance for potential scale formation by over-sizing the heat transfer surface area, scale prevention measures, cleaning methods as well as production losses during plant shutdown for cleaning create considerable capital, operating, and maintenance costs. The choice of tube material affects the wettability, the adhesion forces between surface and deposit as well as the induction time of crystallization fouling. However, the effects of tube material on scale formation in horizontal tube falling film evaporators commonly used in multiple-effect distillation (MED) plants have been scarcely investigated. A better understanding of the effects of tube material on scale formation may help to design and operate more efficient heat exchangers. In the present study, the influence of surface properties and characteristics on crystallization fouling from seawater was investigated. Various tube materials such as copper-nickel 90/10, aluminium brass, a highly corrosion-resistant stainless steel, and a magnesium-containing aluminium alloy were tested in a horizontal tube falling film evaporator in pilot plant scale. To differentiate influential factors the tube materials were characterized. The surface roughness was determined using a tactile stylus unit (perthometer). The contact angle was measured using a drop shape analysis instrument and the surface free energy was determined with the Owens-Wendt-Rabel-Kaelble method. The crystalline scale layers formed outside the horizontal tubes of the falling film evaporator were analyzed using scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDXS), wide angle X-ray diffraction (XRD), and atomic absorption spectroscopy (AAS). Additionally, the thickness of the scale layer formed outside the horizontal tubes was measured. Novel aspects of scale formation on different tube materials used in multiple-effect distillers are presented and discussed. The tube materials show qualitative and quantitative differences with respect to scale formation. The experimental results are discussed in the light of contact angle, surface free energy, surface roughness, wettability, and adhesion forces. The experiments performed under conditions near to those in industrial multiple-effect distillers allow a closer insight into scale formation on different tube materials.

The International Desalination Association (IDA) World Congress on Desalination and Water Reuse

REF: IDAWC/TIAN13-119 -- 2 --

I. INTRODUCTION Crystallization fouling consists of deposition and removal processes. Influencing factors can be classified into three major categories, i.e. solution composition (components, concentrations, pH, supersaturation, and suspended particles), operating parameters (surface and bulk temperature, pressure, heat flux, and fluid dynamics like flow velocity, flow regime), and heat exchanger characteristics (surface free energy, topography, surface roughness) [1, 2]. Effective scale control by polymeric anti-scalants requires a precise knowledge of the effects of the solution composition, the operating parameters, and the heat exchanger characteristics on scale formation. In multiple-effect distillers with horizontal tube falling film evaporators, scale is formed on the outside of the tubes and, thus, it is difficult to be controlled. Common materials used for heat exchanger tubing in multiple-effect distillation (MED) plants are copper-nickel 90/10, aluminium brass, titanium grade 2, highly corrosion-resistant stainless steel grades such as SS 1.4565, and aluminium alloy 5052 with 2.4 – 2.8 % magnesium. The choice of tube material affects the wettability, the adhesion forces between surface and deposit as well as the induction time of crystallization fouling. So far, no simple correlation between surface free energy or surface roughness and fouling behavior has been confirmed [2 - 5], but several studies displayed a strong dependence between surface free energy or surface roughness and crystallization fouling. There are a number of contrary reports on the effects of surface energy on fouling behavior [6]. Some reports showed that foulants attached preferentially to surfaces with high surface energy, while other reports showed that foulants attached preferentially to surfaces with low surface energy. Numerous studies also indicated there was no relationship between surface energy/wettability and fouling behavior [6]. It has long been suspected that poorest foulant adhesion occurs on surfaces with low surface energies and that low energy surfaces were more resistant to build-up of fouling and easier to clean [5, 6]. Furthermore, it is assumed that increasing surface roughness and increasing quantity of surface pitting result in an increased crystallization fouling [7]. Many studies were performed with single-salt solutions such as aqueous CaSO4 or CaCO3 solutions in pipe flow systems or plate heat exchangers (e.g., [7-9]). Modern anti-fouling strategies are based on approaches increasing the duration of the induction period and, hence, decreasing the adhesive strength between crystals and heat transfer surface. The adhesion between crystals and heat transfer surface during the induction period consists of mechanical and molecular interactions [8]. The molecular interactions are described on the basis that dispersive and polar Lifshitz-van der Waals forces are of major importance for the adhesion mechanism. In addition, the Lewis acid-base interactions in polar media and the double layer forces are taken into account [8]. In recent studies (e.g., [8]), the interfacial defect model has been analyzed with respect to its ability to identify low-fouling surfaces. Since seawater is a multi-component electrolyte solution, scale formation is caused by co-precipitation of different calcium- and magnesium-containing salts. In former experiments performed in a horizontal tube falling film evaporator with artificial seawater and seawater-based model solutions, Glade et al. [10] found that the copper-nickel 90/10 tubes were covered with a two-layer scale comprising a thin, flaky magnesium-rich and calcium-free base layer underneath a thick layer of calcium carbonate crystals in the form of aragonite. Elements like Cu, Ni, Fe, Mn were often detected in the magnesium-rich scale layer. The results suggest that the Mg-rich base layer forms in the early stages and its growth ceases and aragonite crystals start to precipitate once the tube surface is completely covered with the Mg-rich scale



layer. Experiments were performed in a wide range of process conditions. With increasing salinity the amount of calcium-containing scale significantly increases. An increase in temperature and a decrease in wetting rate result in an increase in scale formation. However, the effects of tube material on scale formation and control in horizontal tube falling film evaporators commonly used in multiple-effect distillation plants have been scarcely investigated. The main objective of the current research is to contribute to understanding of mixed salt scaling on different tube materials in multiple-effect distillers under process conditions similar to those in industrial distillers. II. EXPERIMENTAL SET-UP The experimental studies were carried out in a horizontal tube falling film evaporator in pilot plant scale. The effects of tube material on scale formation were studied by performing experiments with artificial seawater. 2.1 Horizontal tube falling film evaporator The main part of the test rig is an evaporator fitted with a bank of 6 horizontal tubes arranged below each other with a ratio of tube pitch to tube outside diameter of s/d0 = 2. Saturated steam is introduced into the tubes and condensed under vacuum conditions. The test solution is distributed onto the first tube and trickles down by gravity forming a thin film flow over the horizontal tubes. The enthalpy of condensation allows the feed water to be preheated to the boiling point on the upper tube and then part of it to be evaporated on the lower tubes. The tubes with the adherent scale can be removed from the tube sheets in order to analyze the scale. The pilot plant is equipped with various components for temperature, pressure, and flow rate measurements and control. Therefore the test rig allows systematic studies by varying the process parameters and simulating process conditions in different stages of industrial MED plants. In order to consider a possible extension of the operating range of multiple-effect distillers towards higher top brine temperatures, experiments were performed at an evaporation temperature exceeding the top brine temperatures currently prevailing in industrial multiple-effect distillers. The experiments were performed at an evaporation temperature of tEV = 75°C and a condensation temperature of tCO = 80°C inside the tubes. The wetting rate,

Lm&

=Γ , (1)

was Γ = 0.1 kg/(s m). 2.2 Tube materials In the horizontal tube falling film evaporator, tubes made of copper-nickel 90/10, aluminium brass, stainless steel grade 1.4565 (super-austenitic stainless steel with high corrosion resistance) and the aluminium alloy AlMgSi0.5 containing 0.35 – 0.60 % magnesium were used.



The outer diameter of the tubes was d0 = 25 mm and the effective length was L = 453 mm. The wall thickness of the tubes was adjusted with regard to the different thermal conductivities of the materials in order to have similar heat conduction resistances and heat fluxes and to perform the tests under similar conditions. The tubes were employed with their typical surface topography as delivered by the tube suppliers. The surface roughness was determined using a tactile stylus unit (perthometer). The tube materials, thermal conductivities, outer diameters, wall thicknesses and surface roughnesses are summarized in Table 1.

Table 1: Tube Data

Alloy UNS No. Thermal conductivity [11, 12]

Outer diameter

Wall thickness

Surface roughness Ra

/ W/(m K) / mm / mm / µm

CuNi 90/10 C70600 52 (@ 20°C) 60 (@ 100°C)

25 1.0 0.37

Aluminium brass C68700 112 (@ 100°C) 25 2.0 0.38 SS 1.4565 S34565 13 (@ 20-100°C) 25 0.5 0.16 AlMgSi0.5 A96060 200-220 (@20°C) 25 1.5 0.15

2.3 Test solution In the experiments, artificial seawater based on salt mole fractions for standard artificial seawater as suggested in the formulation by Kester et al. [13] was used. Experiments were performed with artificial seawater having a salinity of 45 g/kg and an ionic strength of I = 0.94 mol/kg. After mixing the salts and stirring, the solution was aerated. The aeration tended to equilibrate the solution with atmospheric gases and removed the excess CO2 resulting from the conversion of HCO3

- to CO3

2-. The pH of the artificial seawater after aeration was between 8.1 and 8.3. All experiments were performed with 240 liters of artificial seawater for test periods of 4 hours and 50 hours. In previous experiments, this volume was found to be favorable [14, 15]. 2.4 Surface characterization In order to differentiate influential factors, the tube surfaces were characterized. The contact angle was measured using a drop shape analysis (DSA) instrument. The contact angle is the resultant of adhesive and cohesive forces and provides an inverse measure of the wettability of the surface. Measuring the contact angle by DSA, a droplet of a test liquid is placed upon the surface. By means of a CCD camera and a data processing system the image of the liquid droplet is digitized. Afterwards, the contour of the droplet is analyzed with respect to the determination of the contact angle corresponding to the wetting equilibrium [8]. Before measuring the contact angle, the surface was cleaned with isopropanol to remove any deposits, grease, oil, etc.. The surface free energy was determined on the basis of the contact angle measurements with at least two test liquids and Young’s equation. The solid/liquid interfacial free energy between droplet and tube surface in Young’s equation is calculated using the geometric mean approach (Owens-Wendt-Rabel-



Kaelble method). For metallic surfaces, the geometric and harmonic mean approaches to calculate the solid/liquid interfacial free energy should be favored since they are state of the art and have been used frequently in many research areas for the combination of wetting and adhesion [8]. 2.5 Chemical and structural characterization of the scales The crystalline scale layers formed outside the horizontal tubes of the falling film evaporator were analyzed by various methods to obtain chemical, structural, and quantitative information. Scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDXS) and wide angle X-ray diffraction (XRD) provide qualitative information on structural and chemical characteristics/properties of the scale, especially about composition, crystal structure, crystal size and orientation. The amounts of calcium and magnesium in the scale were detected by atomic absorption spectroscopy (AAS). The thickness of the scale layer was measured with a gauge based on the eddy current principle. Scale thickness was determined on the third tube from the top of the tube bank. The scale of the fourth tube was dissolved in a hot solution of acetic acid and the concentrations of Ca2+ and Mg2+ ions in the solution were measured using AAS. Furthermore, the fifth tube was analyzed using SEM, EDXS, and XRD. III. RESULTS AND DISCUSSION In the following, the contact angles and surface free energies of the different tube materials are shown. Afterwards, the effects of tube material on the composition, structure, and quantity of the scale in horizontal tube falling film evaporators are presented and discussed. 3.1 Contact angle and surface free energy Figure 1 shows the contact angles of water on the tube materials based on the DSA measurements. Decreasing contact angles are accompanied by an improved wettability of the surfaces. The order of the contact angles of water on the different metals was found to be AlMgSi0.5 < Alu Brass < SS 1.4565 < CuNi 90/10. The results suggest that the wettability of the metals is in the order of AlMgSi0.5 > Alu Brass > SS 1.4565 > CuNi 90/10 which complies with the own practical experience except for SS 1.4565 showing the lowest wettability in the pilot plant.



0

10

20

30

40

50

60

70

80

90

100

AlMgSi0.5 Alu Brass SS 1.4565 CuNi 90/10

Con

tact

ang

le /

O

Figure 1. Contact angles with water

The surface free energies of the metals calculated on the basis of the geometric mean approach (Owens-Wendt-Rabel-Kaelble method) are shown in Figure 2.

0

5

10

15

20

25

30

35

40

45


Surf

ace f

ree

ener

gy /

(mN

/m)

disperse partpolar part

Figure 2. Surface free energies of the tube materials 3.2 Effect of tube material on scale formation The SEM images in Figure 3 show the scale formed on the surface of the CuNi 90/10 tubes after a test period of 4 hours and 50 hours, respectively. The experiments were performed with artificial seawater having a salinity of 45 g/kg at a high evaporation temperature of 75°C and a wetting rate of 0.1 kg/(s m).



The tube surface is covered mainly with CaCO3 (aragonite) and Mg(OH)2 (brucite). The flaky brucite forms a thin base layer on the tube surface. Rod-shaped aragonite crystals grew up on this base layer. Some CaSO4 crystals were found on the tube surface after a test period of 50 hours.

2

1

6

Figure 3. SEM images showing the CuNi 90/10 tube surface after a test period of 4 h (top row) and 50 h (bottom row);

artificial seawater, tEV = 75°C, tCO = 80°C, S = 45 g/kg, Γ = 0.1 kg/(s m): 1- CaCO3 (aragonite), 2- Mg(OH)2 (brucite), 3- CaSO4, 6- Cu, O-containing scale

The SEM images of the scale formed on the surface of the aluminium brass tubes after a test period of 4 hours and 50 hours respectively are shown in Figure 4. Similar to the CuNi 90/10 tubes, the aluminium brass tubes were covered with a two-layer scale comprising a thin, flaky magnesium-containing base layer underneath a thick layer of calcium carbonate crystals in the form of aragonite.



20 µm

1

6

5 µm

1

Figure 4. SEM images showing the aluminium brass tube surface after a test period of 4 h (top row) and 50 h (bottom

row); artificial seawater, tEV = 75°C, tCO = 80°C, S = 45 g/kg, Γ = 0.1 kg/(s m): 1- CaCO3 (aragonite), 6- Cu, Zn-containing scale with traces of Mg, Ca.

Figure 5 shows the SEM images of the scale formed on the surface of the SS 1.4565 tubes after a test period of 4 hours and Figure 6 illustrates the tube surface after a test period of 50 hours. While the CuNi90/10, Alu Brass and AlMgSi0.5 tubes showed a relatively uniform scale layer, the scale formed on the tubes made of the stainless steel grade 1.4565 was very unevenly distributed. Some surface areas were densely covered with scale, some areas were only weakly covered and some spots were even almost uncovered, as shown in Figures 5 and 6.



1

2

Figure 5. SEM images showing the SS 1.4565 tube surface after a test period of 4 h; artificial seawater,

tEV = 75°C, tCO = 80°C, S = 45 g/kg, Γ = 0.1 kg/(s m): 1- CaCO3 (aragonite), 2- Mg(OH)2 (brucite)

1

2

Figure 6. SEM images showing the SS 1.4565 tube surface after a test period of 50 h; artificial seawater,

tEV = 75°C, tCO = 80°C, S = 45 g/kg, Γ = 0.1 kg/(s m): 1- CaCO3 (aragonite), 2- Mg(OH)2 (brucite)



The SEM images in Figure 7 show the scale formed on the surface of the AlMgSi0.5 tubes after a test period of 4 hours and 50 hours, respectively. The tube surface is densely covered with a flaky magnesium-containing scale. Some rod-shaped aragonite crystals grew up on this base layer and some CaSO4 crystals were found on the tube surface. Compared to the CuNi 90/10, aluminium brass and SS 1.4565 tube surfaces, a thicker layer of magnesium-containing scale and less CaCO3 was found on the AlMgSi0.5 tubes.

1

2

3

3

6 6

2

21 8

8

2

Figure 7. SEM images showing the AlMgSi0.5 tube surface after a test period of 4 h (top row) and 50 h (bottom row);

artificial seawater, tEV = 75°C, tCO = 80°C, S = 45 g/kg, Γ = 0.1 kg/(s m): 1- CaCO3 (aragonite), 2- Mg, O-containing scale, 3- needle-like Ca, S, O-containing scale, 6- Al, O-containing scale,

8- Al, O, Mg-containing scale

Figure 8 shows the AAS results for the masses of calcium and magnesium per unit tube surface area for the different alloys after test periods of 4 hours and 50 hours. The tube materials show qualitative and quantitative differences with respect to scale formation. After a short test period of 4 hours, most scale was found on the CuNi 90/10 tubes. Less scale was found on the aluminium brass tubes and much less scale formed on the AlMgSi0.5 tubes and SS 1.4565 tubes. After a test period of 50 hours, the scale quantity found on the CuNi 90/10 tubes was higher than that found on the SS 1.4565 tubes. The scale quantity on the aluminium brass tubes was similar to the quantity found on the SS 1.4565 tubes. After 50



hours, the lowest scale quantity was found on the AlMgSi0.5 tubes. While the magnesium mass per unit tube surface area was low on the CuNi 90/10, Alu Brass and SS 1.4565 tubes and the quantity of the magnesium-containing scale did not notably change with increasing test period, the magnesium mass in the scale per unit tube surface area was relatively high on the AlMgSi0.5 tubes and even notably increased after 50 hours. However, the quantity of the calcium containing scale was relatively low after 50 hours. The results suggest that the magnesium-containing scale has a higher affinity to the aluminium alloy.

0.16 0.20 0.19 0.19

1.03

2.13

0.06 0.070

2

4

6

8

4 50 4 50 4 50 4 50

Con

tent

/ g/

m2

time τ in h

Ca contentMg content

S = 45 g/kgtEV = 75ºCtCO = 80ºCΓ = 0.1 kg/(s m)

CuNi 90/10Ra = 0.37 µm

s = 1 mm

Alu BrassRa = 0.38 µm

s = 2 mm

SS 1.4565Ra = 0.16 µms = 0.5 mm

AlMgSi0.5Ra = 0.15 µms = 1.5 mm

Figure 8. Effects of tube material on the masses of calcium and magnesium in the scale per unit tube surface area

The polar and disperse parts of the surface free energies and the total scale quantities after a test period of 4 hours are summarized in Figure 9. The comparison of surface energy data with scale quantities in Figure 9 does not confirm the approach which is often reported in literature that foulants attach preferentially to surfaces with high surface free energy [6]. There is also no simple correlation between the polar component of the surface free energy and the fouling behavior. Kazi et al. [9] reported that the extent of fouling on different metal surfaces increases with increasing thermal conductivity of the metal (copper > aluminium > brass > stainless steel). In the current research, the wall thickness of the tubes was adjusted with regard to the different thermal conductivities of the materials in order to have similar heat conduction resistances and heat fluxes and to perform the tests under similar conditions. Thus, considerable effects of the different thermal conductivities can be excluded. AlMgSi0.5 and SS 1.4565 having the lowest surface roughness showed the lowest scale formation, but the surface roughnesses of the different tube materials were not so much different as to justify the differences in scale formation. It is more likely that corrosion products on the copper alloys can accelerate scale formation as reported in literature (e.g., [16]).



0

1

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6

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45


Ca

and

Mg

cont

ent

/ (g/

m²)

Surf

ace f

ree

ener

gy /

(mN

/m)

Disperse part Polar part Ca and Mg content in scale

Figure 9. Comparison of surface free energies and total scale quantities after a test period of 4 hours,

tEV = 75°C, tCO = 80°C, S = 45 g/kg, Γ = 0.1 kg/(s m) Furthermore, the co-precipitation of calcium- and magnesium-containing salts might play an important role. Since seawater is a multi-component electrolyte solution, scale formation is caused by co-precipitation of different calcium- and magnesium-containing salts. Due to the complexity of crystallization fouling, research has mainly been restricted to single-salt precipitation. Crystallization fouling of calcium carbonate has been studied extensively, whereas not much attention has been given to the crystallization of magnesium-containing salts. The effect of tube material on co-precipitating calcium- and magnesium-containing salts in a seawater environment is poorly understood. It is conceivable that some tube materials promote the formation of magnesium-containing scale, e.g., the magnesium-containing aluminium alloy, which in turn influences the precipitation of calcium carbonate scale. IV. CONCLUSIONS The effect of tube material on scale formation was studied in a horizontal tube falling film evaporator in pilot plant scale using artificial seawater under conditions near to those in industrial multiple-effect distillers. The tube materials show qualitative and quantitative differences with respect to scale formation. The scale formed on the tubes made of the stainless steel grade 1.4565 was very unevenly distributed. The CuNi 90/10, aluminium brass and AlMgSi0.5 tubes showed a relatively uniform scale layer. After a short test period of 4 hours, the scale quantity on the tube materials was in the order of CuNi 90/10 > Alu Brass >> AlMgSi0.5 > SS 1.4565. After a test period of 50 hours, the scale quantity was in the order of CuNi 90/10 > SS 1.4565 ~ Alu Brass > AlMgSi0.5. While the magnesium mass per unit tube surface area was low on the CuNi 90/10, Alu Brass and SS 1.4565 tubes and the quantity of the magnesium-containing scale did not notably change with increasing test period, the magnesium mass in the scale per unit tube surface area was relatively high on the AlMgSi0.5 tubes and even notably increased after 50



hours. However, the quantity of the calcium containing scale was relatively low after 50 hours. The results suggest that the magnesium-containing scale has a higher affinity to the aluminium alloy. The comparison of surface energy data with scale quantities after 4 hours does not confirm the approach which is often reported in literature that foulants attach preferentially to surfaces with high surface energy [6]. The results suggest that there is no simple correlation between surface energy data and fouling behavior and that a correlation cannot be based on surface properties of the heat transfer surface, only. The adjacent crystalline deposit has to be taken into account since the latter phase also influences molecular interaction at the interface crystal/heat transfer surface. In the ongoing research, advanced approaches such as the interfacial defect model [8] will be applied to the system in order to analyze its ability to predict the scaling tendency on different tube materials in desalination systems. V. REFERENCES 1 Zhao, X.; Chen, X.D.: A critical review of basic crystallography to salt crystallization fouling in

heat exchangers. Proc. of International Conference on Heat Exchanger Fouling and Cleaning, Crete Island, Greece, 2011.

2 Geddert, T.; Bialuch, I.; Augustin, W.; Scholl, S.: Extending the induction period of crystallization fouling through surface coating. Heat Transfer Engineering 30 (2009) 868-875.

3 Geddert, T.; Augustin, W.; Scholl, S.: Induction time in crystallization fouling on heat transfer surfaces. Chemical Engineering and Technology 34 (2011) 1303-1310.

4 Liu, Y.; Zou, Y.; Zhao, L.; Liu, W.; Cheng, L.: Investigation of adhesion of CaCO3 crystalline fouling on stainless steel surfaces with different roughness. International Communications in Heat and Mass Transfer 38 (2011) 730-733.

5 Zettler, H.U.; Weiß, M.; Zhao, Q.; Müller-Steinhagen, H.: Influence of surface properties and characteristics on fouling in plate heat exchangers. Heat Transfer Engineering 26 (2005) 3-17.

6 Zhao, Q.; Müller-Steinhagen, H.: Intermolecular and adhesion forces of deposits on modified heat transfer surfaces. Proceedings of the 4th International Conference on Heat Exchanger Fouling, Fundamental Approaches & Technical Solutions, Davos, July 8-13, 2001. In: PUBLICO Publications, Germany, 2002, 41-46.

7 Lei, C.; Peng, Z.; Day, T., Yan, X.; Bai, X; Yuan, C.: Experimental observation of surface morphology effect on crystallization fouling in plate heat exchangers. International Communications in Heat and Mass Transfer 38 (2011) 25-30.

8 Förster, M.; Bohnet, M.: Modification of molecular interactions at the interface crystal/heat transfer surface to minimize heat exchanger fouling. International Journal of Thermal Science (2000) 39, 697-708.

9 Kazi, S.N.; Duffy, G.G.; Chen, X.D.: Fouling and fouling mitigation on heated metal surfaces. Desalination 288 (2012) 126-134.

10 Glade, H.; Krömer, K; Will, S.; Detering, J.; Essig, M.; Kempter, A.; Nied, S.; Schürmann, G.: On scale formation of magnesium salts in thermal seawater desalination. Proceedings of IDA World Congress on Desalination and Water Reuse, Perth, Australia, 2011.

11 VDI-Gesellschaft (Ed.): VDI-Wärmeatlas, 10th edition, Berlin, Heidelberg: Springer-Verlag, 2006.

12 ATI Allegheny Ludlum Corporation: AL 4565 Alloy. Corrosion Resistant Stainless Steel. Technical Data Sheet, 2003.

13 Kester, D.R.; Duedall, I. W.; Connors, D. N.; Pytkowicz, R. M.: Preparation of artificial seawater, Limnology and Oceanography, 12 (1967) 176-179.



14 Glade, H.; Hermersdorf, M.; Ulrich, J.; Essig, M.; Rieger J.; Brodt, G.: Scaling in Multiple-Effect Distillers: New Approach to Study Mechanisms and Control, Proc. IDA World Congress on Desalination and Water Reuse, Bahamas, 2003.

15 Glade, H.; Wildebrand, C.; Will, S.; Essig, M.; Rieger, J.; Büchner, K.-H.; Brodt, G.: Pilot Plant Investigations on Scale Formation and Control in Multiple-Effect Distillers, Proc. IDA World Congress on Desalination and Water Reuse, Singapore, 2005.

16 Alahmad, M.: Factors affecting scale formation in sea water environments – An experimental approach. Chemical Engineering & Technology 31 (2008) 149-156.

effects of tube material on scale formation and control … · formation and control in horizontal...

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