Isothermal Evaporation Process Simulation Using the Pitzer Model for

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Industrial & Engineering Chemistry Research

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Isothermal Evaporation Process Simulation using Pitzer Model for the Quinary System LiCl–NaCl–KCl–SrCl2–H2O at 298.15 K Lingzong Meng,*,†,‡ Miroslaw S. Gruszkiewicz,‡ Tianlong Deng,§ Yafei Guo,§ and Dan Li† †

School of Chemistry and Chemical Engineering, Linyi University, Linyi 276000, P. R. China

‡

Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6110,

USA §

Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin University of Science

and Technology, Tianjin 300457, P. R. China


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ABSTRACT: The Pitzer thermodynamic model for liquid–solid equilibrium in the quinary system LiCl–NaCl–KCl–SrCl2–H2O at 298.15 K was constructed by selecting the proper parameters and standard chemical potential. The solubility data and water activity data of the systems SrCl2–H2O, NaCl–SrCl2–H2O, KCl–SrCl2–H2O, LiCl–SrCl2–H2O, and NaCl–KCl–SrCl2–H2O were used to evaluate the model. Good agreement between the calculated and experimental solubility data indicates that the model is reliable. The Pitzer model for the above system at 298.15 K was then used to calculate the component solubilities and conduct computer simulation of isothermal evaporation of the mother liquor

for

the

oilfield

brine

in

Nanyishan

region

of

Qaidam

Basin

(China).

The

evaporation-crystallization route and order of salt precipitation, changes in concentration and precipitation of lithium, sodium, potassium, and strontium, and water activities during the evaporation process were demonstrated. The salts crystallized from the brine in the order : KCl, NaCl, SrCl2·6H2O, SrCl2·2H2O, and LiCl·H2O. The whole evaporation-crystallization process may consist of six stages. In each stage the variation trends for the relationships between ion concentrations or water activities and the evaporation ratio are different. This result of the simulation of brines can be used as a theoretical reference for comprehensive exploitation and utilization of this type of brine resources.

Keywords: Pitzer thermodynamic model; solid–liquid equilibrium; Strontium chloride; Computer simulation of isothermal evaporation; Oilfield brine system



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1. INTRODUCTION The oilfield brines in Nanyishan region of the Qaidam Basin in China, which mostly belong to the CaCl2 type, have high contents of lithium, potassium, strontium, as well as accompanying sodium, calcium, bromine, boron, and many other useful components. The concentration of lithium of the brines in Nanyishan district is up to 0.98 g·L-1, 35.75 g·L-1 for potassium and 4.45 g·L-1 for strontium, which is much higher than those in the salt lake brines in Qinghai-Tibet Plateau.1,2 After multistep exploitation for boron, calcium, bromine, most of the oilfield brine in this type largely belongs to the complex

system

LiCl–NaCl–KCl–SrCl2–H2O.

The

phase

diagrams

(solubility

data)

and

thermodynamic studies of brine systems are the foundations in economical utilization of brine resources and description of phase chemical behavior of the brine.3 Therefore, studies of phase diagrams and thermodynamics of brine systems containing lithium and strontium are necessary and urgent to extract natural resources. Experimental work and thermodynamic modeling are usually combined to complete the description of phase equilibrium for the brine systems. It is difficult to reveal the relations of the nearby crystallization areas in the complex systems by using only the experimental results in the diagrams. Although the thermodynamic models are mainly empirical, they are very convenient for the thermodynamic property calculation and for other research.4 Moreover, the construction of the thermodynamics model needs to be affirmed with the experimental results. The Pitzer model,5-8 which gave a series of equations for ion activity coefficients and osmotic coefficients in the solution, have been widely applied in solubility predictions, thermodynamics property calculations, isothermal evaporation process simulations, technology process application, and so on.9-11 For a complete Pitzer thermodynamic model of the aquous system, the binary Pitzer parameters, mixing Pitzer parameters,


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and standard chemical potentials (µ0/RT) for the species are necessary. A number of experimental and theoretical studies on subsystems of the complex system LiCl–NaCl–KCl–SrCl2–H2O at 298.15 K have been carried out in recent decades. The solubilities of the systems NaCl–SrCl2–H2O, KCl–SrCl2–H2O, LiCl–SrCl2–H2O, and NaCl–KCl–SrCl2–H2O, which are important subsystems of the oil field brine system, have been reported at 298.15 K,12-16 but the solubility data for the quinary system at 298.15 K is still lacking. The Pitzer parameters for the species in the complex system have also been reported many times in the literatures,17-24 but some of the parameters are very different in different sources, so it’s necessary to select a consistent set parameters out of these results to construct the model for this quinary system. In this paper, the new Pitzer thermodynamics model for liquid–solid equilibrium in the five-component system was constructed by choosing the proper parameters and standard chemical potential values. Then, the Pitzer model for the system at 298.15 K was used to conduct a computer simulation of isothermal evaporation for the mother liquor of oilfield brine. The evaporation-crystallization route, the order of salt crystallization, changes in ion concentration and precipitation of lithium, sodium, potassium, and strontium, and water activities during the evaporation process were demonstrated.

2. MODEL APPROACH The Pitzer model, which is extended by Harvie and Weare, consists of semi-empirical equations for the ion activity coefficients and osmotic coefficients.5-8 The model can be constructed with the parameters and standard chemical potentials and validated by comparing the calculated data (e.g., solubility data, osmotic coefficients, activity coefficients, and water activities) with the experimental data not applied in the parameter fitting. The solubility data were calculated in this paper to affirm the model accuracy. The compositions of the solution and coexisting solid minerals can be identified with these equations.



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The equations used in the Pitzer model are described in the references.7 The solubility product constant (Ksp) and activity products (Kap) of a hydrated salt Mν1Xν2·ν0H2O at a stated temperature and pressure is shown in equations (2) and (3). Mυ1Xυ2·ν0H2O = ν1Mυ2+ + ν2Xυ1- +ν0H2O

(1)

lnKsp =υ1ln(m′MγM) +υ2ln(m′XγX) +υ0lnαw = (µ0 Mυ1Xυ2·υ0H2O −υ1µ0 Mυ2+ −υ2µ0Xυ1- − υ0µ0H2O)/RT

(2)

lnKap =υ1ln(mMγM) +υ2ln(mXγX) +υ0lnaw

(3)

lnaw = − øMW∑mi

(4)

In expressions (2) to (3), m and m′ are the concentration (mol·kg−1) and saturated concentration of the ions, respectively. In equation (4), aw and Mw represent the water activity and molecular mass of water (kg·mol-1), and mi contains all species in the solution.

3. MODEL PARAMETERIZATION The Pitzer model of Song and Yao for the system (Li+,Na+,K+,Mg2+//Cl-,SO42-–H2O) at 298.15 K has been used successfully in predicting thermodynamic properties for Chinese salt lake brines. 23 The parameters and standard chemical potentials for the species in this model were fitted again using the osmotic coefficients, activity coefficients or the solubility data to suit the different brine concentration in Chinese salt lake brines, especially for lithium concentration (up to 20 mol·kg-1).23 Considering the real situation for the system LiCl–NaCl–KCl–SrCl2–H2O, the parameters and standard chemical potentials used in this research for the quinary system were taken from the literature.23,24 Pitzer binary parameters β(0), β(1), CØ for SrCl2 can be obtained from Clegg et al.,17 Phutela and Pitzer,19 and Holmes et al.20-21. The mixing Pitzer parameters containing strontium are available from Clegg et al.17 and Reddy and Ananthaswamy,18 and Guo et al.22. Combining the standard chemical potentials for the species containing strontium from literature24 and solubility product constant (as Ksp) for


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SrCl2·6H2O17,25, the standard chemical potentials for Sr2+ can be calculated using equation (2). All three kinds of parameters required in the quinary system: Pitzer binary parameters, mixing parameters and standard chemical potentials, are listed in Tables S1, S2, and S3, Supporting Information, respectively. 3.1. Parameter Evaluation of the SrCl2–H2O system. Literature data for water activities in unsaturated binary system SrCl2–H2O were used to evaluate the Pitzer binary parameters for SrCl2. In view of the large deviation between the binary parameters from Holmes et al.20,21 and those from Clegg et al.17 or Phutela and Pitzer,19 and additionally considering that the parameters from Phutela and Pitzer19 have been evaluated earlier,19 we evaluated only the binary parameters from Clegg et al.17 Note that the three parameters for SrCl2 from Clegg et al.17 were used in the present prediction are to maintain consistency with this study. C(ø), not C(0) and C(1), was used in this study. The biggest deviation between the water activities calculated with three binary parameters from Clegg et al.17 and these with four binary parameters from Clegg et al.17 were 0.0008 except the point (3.52, 0.7094), which shows that the three binary parameters for SrCl2 from Clegg et al.17 are good enough for this model. The water activities of SrCl2 solutions at different concentration were predicted with the two set of binary parameters in Table S1, as shown in Figure 1. The two set of calculated water activities agree well with each other, which indicates that the three binary parameters for SrCl2 from Phutela and Pitzer19 and from Clegg et al.17 are both equally reliable for the current model. The binary parameters for SrCl2 used in this present prediction for the quinary system are taken from Phutela and Pitzer.19 3.2. Mixing Parameters Evaluation. The solubilities in the literatures for systems NaCl–SrCl2–H2O, KCl–SrCl2–H2O, LiCl–SrCl2–H2O, and NaCl–KCl–SrCl2–H2O are applied to validate the Pitzer mixing ion interaction parameters related to strontium.12-16 The experimental and calculated solubility data of the invariant points of the four systems with different sets of parameters are tabulated in Table S4,



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Supporting Information. The calculated solubilities are in accordance with the measured data, which confirms that the SrCl2 binary parameters of either Phutela and Pitzer19 or Clegg et al.17 can be successfully used for solubility calculations. Using the calculated solubilities with the binary parameters for SrCl2 from literature19 and measured solubility data12-16, using the binary parameters for SrCl2 from literature,19 the phase diagrams for these systems were plotted, as shown in Figures 2–5. The results in Table S4 shows that the mixing parameters θNa,Sr and ΨNa,Sr,Cl fitted to the saturated solution molalities are more accurate than these fitted for ionic strengths under 7.0 mol·kg-1. The coincident results in the KCl–SrCl2–H2O system in Figure 3 shows the Pitzer mixing parameters θK,Sr and ΨK,Sr,Cl in literature18 are reliable. The solubility data from Shi et al.25 are relatively more reliable. Comparisons in the NaCl–KCl–SrCl2–H2O system showed that the measured solubility data are in accordance with the predicted values except for the solubility curve cosaturated with KCl and SrCl2·6H2O. This confirms the reliability of the Pitzer mixing interaction parameters found in the literature. The deviation for the solubility curve cosaturated with KCl and SrCl2·6H2O is the same as that in the KCl–SrCl2–H2O system. Therefore, the calculated phase diagram for the quaternary system are relatively more reliable than the experimental values. For the system LiCl–SrCl2–H2O, the mixing parameters θLi,Sr and ΨLi,Sr,Cl fitted only using the water activities22 were elected for the model because of the smallest deviations between the experimental and calculated water activity data (Figure S1, Supporting Information). The Pitzer model can mainly predict the solubility data for SrCl2·6H2O but shows a remarkable deviation for the solubility curve saturated with the salt SrCl2·2H2O in Figure 4. The Pitzer model for the system LiCl–SrCl2–H2O is relatively reliable for its reliable parameters and solubility product constants of LiCl·H2O10,23, SrCl2·2H2O25 and SrCl2·6H2O17,25. Therefore, the experimental data14,15 for the solubility curve


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saturated with SrCl2·2H2O, which deviate from the model calculation, are not accurate enough in our estimation. The main reason may be that the presence of lithium can lead to significant experimental errors in strontium determination especially at high Li/Sr ratios.26 It should be noted the calculated solubility isotherm in Figure 4 is nearly the same as that in Figure 4 in the literature,22 especially for the curves saturated with SrCl2·6H2O. The primary reason is that the equilibrium constants of SrCl2·6H2O is the same, but the mixing parameters and equilibrium constants of SrCl2·2H2O in this study are different from those in the literature.22 The solubility product constant of SrCl2·2H2O is not given in the literature.22

4. MODEL APPLICATION 4.1 Solubility Prediction. The solubility data of the quinary system LiCl–NaCl–KCl–SrCl2–H2O were predicted to exploit the mother liquor of the oilfield brine in Nanyishan region of Qaidam Basin. Considering the brine from Nanyishan district is firstly saturated with KCl after evaporation, therefore, we calculated the solubility data of the system saturated with KCl. The calculated dry-salt diagram is shown in Figure 6. The Jänecke indices of NaCl and SrCl2, whose units are mol/100 mol dry salt (mLiCl + mKNaCl + 2mSrCl2), are used as abscissa and ordinate values. The dry-salt phase diagram saturated with KCl consists of four crystallisation zones (LiCl·H2O, NaCl, SrCl2·6H2O and SrCl2·2H2O), five univariant solubility curves cosaturated with LiCl·H2O + NaCl, LiCl·H2O + SrCl2·2H2O, SrCl2·2H2O + SrCl2·6H2O, NaCl + SrCl2·6H2O and NaCl + SrCl2·2H2O, and two invariant points cosaturated with LiCl·H2O + NaCl + SrCl2·2H2O and NaCl + SrCl2·2H2O + SrCl2·6H2O. The crystallization areas decrease in the sequence NaCl, SrCl2·6H2O, SrCl2·2H2O and LiCl·H2O. 4.2 Isothermal Evaporation Calculation. The isothermal evaporation calculation was carried out in this study. The brine with known compositions was used in the isothermal evaporation. There is no



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precipitation of solid salts before evaporation, which shows that the activity products of the salts (Kap) are below the solubility product constants (Ksp). After subtracting a certain amount of water from the brine, the activity products of all the salts were calculated to compare with the solubility product constants. If the activity product of some salt was higher than its solubility product constant (Kap≥Ksp), it indicated that the salt was saturated. Otherwise, more water needed be subtracted from the brine until some salt was saturated. After subtracting a certain amount of the saturated salt and water from the brine, the activity products of the other salts were calculated again to compare with the solubility product constants. These steps were repeated until the final invariant point was reached. For this evaporation calculation, the method of continually subtracting water and the saturated salt was adopted. It is possible to obtain from this calculation the evaporation-crystallization route and the order of mineral crystallization, the variation in brine composition, the saturation points of sodium, potassium, strontium and lithium salts, and the variation in water activities during evaporation. 4.2.1 Evaporation-Crystallization Route and Order of Salt crystallization. After multistep exploitation of boron, calcium, and bromine from oilfield brine in Nanyishan region of Qaidam Basin, the mother liquor was used for the calculation. The original composition of the ions used in the calculation was cited from literature,1 as shown in Table 1. The unit of molality (mol·kg-1) was used in the theoretical calculation, so the amount of brine containing 1 kg water was used for convenience. The calculated composition of the solution and the masses of the minerals precipitating out from the liquid phase when a new salt becomes saturated, are tabulated in Tables 1 and S5, Supporting Information. The phase diagram of the quinary system LiCl–NaCl–KCl–SrCl2–H2O saturated with KCl in Figure 7 was used to discuss the evaporation process for the oilfield brine from Nanyishan district. Point A shows the composition of the original brine, which is not saturated with respect to any of the


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salts, located in the NaCl crystallization region in the dry-salt diagrams in Figure 7. From point A to point B, the ion concentrations become high continuously with the water loses, but no salts precipitating out from the brine, so the positions from A to B are the same in the dry-salt diagrams. Then the liquid phase gets into the area saturated with KCl, with only KCl precipitating out, the positions from B to C are still the same in Figure 7. Sodium chloride is saturated at point C, which is in the NaCl crystallization region in Figure 7, with KCl and NaCl precipitating out. From B to C, the evaporation ratio is only from 49.75% to 51.22%, and only 5.69% pure KCl can be obtained. KCl and NaCl get saturated nearly at the same time. SrCl2·6H2O begins to precipitate out from the liquid phase at point D, accompanied by the precipitation of KCl and NaCl. From C to D, the evaporation-crystallization path follows the line from the point of NaCl to C, then to point D in Figure 7. As the evaporation continues, SrCl2·6H2O begins to dissolve and SrCl2·2H2O begins to form at the point E. The concentration of the liquid phase become stable for a while at E until SrCl2·6H2O disappears. Then the evaporation-crystallization path goes on along with the invariant line EF. Lithium chloride becomes saturated at the point F, which is also the dry salt point. The composition of the liquid phase becomes stable till the brine is dried. As shown in Tables 1 and S5, and Figure 7, the salts precipitate out from the brine in order of KCl, NaCl, SrCl2·6H2O, SrCl2·2H2O, and LiCl·H2O, and the whole evaporation process can be separated into six stages: water evaporation stage (AB), KCl crystallization stage (BC), NaCl crystallization stage (CD), SrCl2·6H2O crystallization stage (DE), SrCl2·2H2O crystallization stage (EF), and LiCl·H2O crystallization stage. The main points of the evaporation-crystallization path are B, C, D, E, and F, which

are

tabulated

in

Tables

1

and

S5.

A

point worth

emphasizing is that

the

evaporation-crystallization paths for the real brine are not always in agreement with the solubility



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isotherms in phase diagram because the brine system is more complicated than this quinary system. However, the phase diagram can still supply the theoretical foundation for exploitation of brine resources. 4.2.2 Concentration and Precipitation of Li+, Na+, K+, and Sr2+. The relations between the concentrations of Li+, Na+, K+, and Sr2+ and the evaporation ratio for the water are shown in Figure 8. As shown in Table 1 and Figure 8(a), lithium salts can’t crystallize from the solution before point F. The lithium ion concentration of the mother liquor gradually increases from 0.16 to 19.87 mol·kg-1 with the evaporation ratio from 0 to 99.17%, which benefits the lithium recovery. The lithium concentration first increases slowly with increasing evaporation ratio, but subsequently a small increase in evaporation ratio causes rapid increase up to saturated concentration. The trend for the curves in Figure 8(a) changes whenever new solid precipitates out. The activity products (lnKap) for LiCl·H2O, which remain below the solubility product constant (lnKsp) for LiCl·H2O during the evaporation process before point F, were also calculated, as shown in Figure 9. The variation trend for the curve in Figure 9 is nearly the same as that in Figure 8(a), which shows that lnKap for LiCl·H2O is positively correlated with lithium concentration. The concentration of SO42- in the original oilfield brine of the Nanyishan district is about 0.0019 mol·kg-1,1 so Li2SO4·H2O will become saturated during the evaporation process. However, further discussion of this aspect is beyond the scope of this research, which is confined only to the subsystem LiCl–NaCl–KCl–SrCl2–H2O for analysis of the evaporation process. The concentrations for Na+, K+, and Sr2+change with evaporation ratio are shown in Figures 8(b), 8(c) and 8(d). The concentrations of ions in the solution gradually increase to maximal value, and then decrease if the salt containing this ion begin to precipitate out. The variation trends for the curves of the


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ion concentrations in each stage from B to F are different. Sodium concentration increases with the positive slope with the evaporation ratio increasing before Point C, but decreases with the negative slope to Point F. The precipitation ratios for NaCl are 98.71% at point D and 99.84% at point E where SrCl2·6H2O begins to precipitate from the solution. Potassium concentration firstly increases before point B, and then decreases from B to E, at last, increases at the stage EF. Pure KCl can be obtained at the stage BC, but only 5.69% for total KCl. The precipitation ratios are 96.71% at point D and 99.14% at point E. Strontium concentration gradually increases before point D to reach the peak concentration of 1.6323 mol·kg-1, and then sharply decreases during the stage DF to 0.0137 mol·kg-1 at point F. 78.74% of SrCl2·6H2O precipitates out before SrCl2·2H2O forms in the brine, which is the biggest amount for SrCl2·6H2O we can get from the brine. 99.81% of strontium chloride precipitates out before LiCl·H2O begins forming. From Tables 1 and S5, and Figure 8, we can choose the best time to remove the salts during the evaporation process. For example, we can obtain NaCl and KCl without strontium at point D from the solution, and remove the salts as soon as SrCl2·2H2O appears, to get the maximum amount of SrCl2·6H2O. The whole thermal evaporation process illustrate that the useful mineral (lithium, potassium and strontium) with high purity can be extracted from the brine resources with this method. 4.2.3 Water Activity Calculation. The thermodynamic properties, which are important parameters for the solutions, can also be obtained during the evaporation using the Pitzer model of the system LiCl–NaCl–KCl–SrCl2–H2O. The water activities, which are related to the concentration of the solution, were calculated during the evaporation process in this study, as shown in Table 1 and Figure 10. The maximum water activity value is at point A during the evaporation. With the evaporation ratio gradually increasing, initially the water activity decreases slowly, while above evaporation ratio of 90% a small increase in evaporation ratio causes a sharp decrease to reach the minimum water activity of



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Page 14 of 26

0.1064 at point F. The variation trend for the curves in each stage in Figure 10 is different. Therefore, water activity of the brine can be measured to determine the current stage of mineral crystallization.

5. CONCLUSIONS The

Pitzer

thermodynamic

model

for

liquid–solid

equilibrium

in

the

quinary

system

LiCl–NaCl–KCl–SrCl2–H2O at 298.15 K was constructed by selecting the proper parameters in the literatures. The solubility data of the NaCl–SrCl2–H2O, KCl–SrCl2–H2O, LiCl–SrCl2–H2O, and NaCl–KCl–SrCl2–H2O systems, not applied in the parameter fitting, were applied to evaluate the model. Good agreement between the computation value and measured solubilities illustrates that the model is reliable. Next, the phase diagram (solubilities) of the quinary system were obtained with this model. The model was also used to conduct a computer simulation of isothermal evaporation of the mother liquor for the oilfield brine in Nanyishan region of Qaidam Basin. The evaporation-crystallization route and the order of salt crystallization were demonstrated using the diagrams of the quinary systems. The minerals were crystallized out of the brine in the order of KCl, NaCl, SrCl2·6H2O, SrCl2·2H2O, and LiCl·H2O, and the whole evaporation process may consist of six stages. The variation in concentration and precipitation of lithium, sodium, potassium, and strontium, and water activities during the evaporation process, which are the theoretical basis in the brine resource exploitation, were calculated. The variation trends in each stage for the curves between ion concentrations or water activities and the evaporation ratio are different. This result of the simulation of brines can be used as a theoretical reference for comprehensive exploitation and utilization of this type of brine resources.

■ AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. Tel. and Fax: +86-539-8766600.


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Notes The authors declare no competing financial interest.

■ ACKNOWLEDGMENTS This work was supported by the NNSFC (21406104, 21276194, 21306136 and U1406113), and the Key Laboratory of Salt Lake Resources and Chemistry, Qinghai Institute of Salt Lake, Chinese Academy of Sciences (KLSLRC-KF-13-HX-4). M.S.G.’s effort was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences.

■ ASSOCIATED CONTENT Supporting Information Information as mentioned in the text. This information is available free of charge via the Internet at http://pubs.acs.org.

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brines of sodium sulfate subtype. Acta Geol. Sin-Engl. 2010, 84, 1708–1714. (11) Song, P. S.; Yao, Y.; Sun, B.; Li, W. Pitzer model of thermodynamics for the Li+, Na+, K+, Mg2+/Cl−, SO42−– H2O system (in Chinese). Sci. China Chem. 2010, 40, 1286–1296. (12) Ding, X. P.; Sun, B.; Shi, L. J.; Yang, H. T.; Song, P. S. Study on phase equilibria in NaCl–SrC12–H2O ternary system at 25 °C .Inorg. Chem. Ind. 2010, 42, 9–11.

(13) Shi, L. J.; Sun, B.; Ding, X. P.; Song, P. S. Phase Equilibria in Ternary System KCl–SrCI2–H2O at 25°C. Chin.J. Inorg.Chem. 2010, 26, 333–338.

(14) Blidin, V. P. Heterogeneous Equilibrium in Aqueous Ternary Systems of Lithium Chloride and the

Chlorides of Barium, Strontium, and Calcium (in Russian). Dokl. Akad. Nauk SSSR 1952, 84, 947−950.

(15) Kydynov, M. K.; Lomteva, S. A.; Druzhinin, I. G. Solubility of Ternary Systems of Lithium, Sodium, and

Strontium Chlorides at 25 °C (in Russian). Issled. Obl. Khim. Tekhnol. Miner. Solei Okislov 1965, 146−150.


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(16) Filippov, V. K.; Fedorov Y. A.; Charykov, N. A．Thermodynamics of phase equilibria in the potassium, strontium, sodium, chloride，water (K+, Sr2+/Cl−–H2O, Na+, Sr2+/Cl−–H2O and Na+, K+, Sr2+/Cl−–H2O) system at at 25 °C. Zhurnal Obshchei Khimii. 1990, 60, 492−499.

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NaCl + SrCl2 + H2O at 298.15 K and Representation with an Extended Ion-Interaction Model. J. Chem. Eng. Data 2005, 50, 1162−1170.

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Strontium Chloride at Elevated Temperatures. J. Chem. Eng. Data 1987, 32, 76−80.

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Electrolytes with One or Both Ions Univalent. J. Phys. Chem. 1973, 77, 2300-2308.

(25) Partanen, J. I. Re-evaluation of the Mean Activity Coefficients of Strontium Chloride in Dilute Aqueous Solutions from (10 to 60) °C and at 25 °C up to the Saturated Solution Where the Molality Is 3.520 mol·kg-1. J.

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Captions


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1. Chemical Composition of the Liquid Phases during Isothermal Evaporation of the mother liquor for the oilfield

brine in Nanyishan region of Qaidam Basin

Figure 1. Calculated water activities of the system SrCl2−H2O at 298.15 K. —, data from literature;17 ○, calculated data with

three binary parameters in literature;17 ▲, calculated data with binary parameters in literature.19

Figure 2. Measured and predicted phase diagrams of the ternary system NaCl–SrCl2–H2O at 298.15 K. —, predicted isotherm

curve with SrCl2 binary parameters from literature19 and mixing parameters to the saturated molalities from literature;17 △ ,

measured data from literature;12 ■, measured data from literature.16

Figure 3. Measured and predicted phase diagrams of the ternary system KCl–SrCl2–H2O at 298.15 K. —, predicted isotherm

curve with three SrCl2 binary parameters from literature19 and mixing parameters from literature;18 △ , measured data from

literature;13 ■, measured data from literature.16

Figure 4. Measured and predicted phase diagrams of the ternary system LiCl–SrCl2–H2O at 298.15 K. —, predicted isotherm

curve with three SrCl2 binary parameters from literature19 and mixing parameters from literature;22 ■, measured data from

literature;14 △ , measured data from literature.15

Figure 5. Measured and predicted phase diagrams of the quaternary system NaCl–KCl–SrCl2–H2O at 298.15 K. —, predicted

isotherm curve; △ , measured data in literature.16

Figure 6. Predicted phase diagrams of the quinary system LiCl–NaCl–KCl–SrCl2–H2O at 298.15 K saturated with KCl.

Figure 7. Evaporation-crystallization route of the mother liquor for the oilfield brine in Nanyishan region of Qaidam Basin at

298.15 K. —, evaporation-crystallization path; …, solubility curves.

Figure 8. Relationship between the ion concentrations and evaporation ratio of the water during the evaporation process.

Figure 9. Relationship between lnKap for LiCl·H2O and evaporation ration of the water during the evaporation process.

Figure 10. Relationship between water activities and evaporation ration of the water during the evaporation process. Table 1. Chemical Composition of the Liquid Phases during Isothermal Evaporation of the mother liquor for the oilfield brine in Nanyishan region of Qaidam Basin



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

evaporation

chemical components of the liquid phase/(mol·kg-1)

no.

aw a

+

ratio/%

Li

A

0.00

0.1646

B

49.75

C

+

+

sequence of salt precipitation

-b

K

Sr

2.2738

1.0659

0.0592

3.6227

0.8727

0.3275

4.5248

2.1212

0.1178

7.2092

0.7215

KCl

51.22

0.3374

4.6612

2.0608

0.1214

7.3022

0.7164

KCl + NaCl

D

96.37

4.5379

0.8102

0.9656

1.6323

9.5784

0.5385

KCl + NaCl + SrCl2·6H2O

E

98.36

10.0294

0.2173

0.5581

0.7669

12.3385

0.3431

KCl + NaCl + SrCl2·6H2O + SrCl2·2H2O

F

99.17

19.8738

0.0594

0.9312

0.0137

20.8918

0.1064

KCl + NaCl + SrCl2·2H2O + LiCl·H2O

a

Na

+

Cl

Calculated for the water. bCalculated in view of the charge balance of ions.


Page 20 of 26

1.00

aw 0.95 0.90 0.85 0.80 0.75 0.70 -0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-1

3.5

m( SrCl2) /( mol·kg ) Figure 1. Calculated water activities of the system SrCl2−H2O at 298.15 K. —, data from literature;17 ○, calculated data with

three binary parameters in literature;17 ▲, calculated data with binary parameters in literature.19

4

-1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


m( SrCl2) /( mol·kg )

Page 21 of 26

3

2

1

0 0

1

2

3

4

5 -1

m( NaCl) /( mol·kg )

6

7

Figure 2. Measured and predicted phase diagrams of the ternary system NaCl–SrCl2–H2O at 298.15 K. —, predicted isotherm

curve with SrCl2 binary parameters from literature19 and mixing parameters to the saturated molalities from literature;17 △ ,

measured data from literature;12 ■, measured data from literature.16




4

-1

3

2

1

0 0

1

2

3

4 -1

m( KCl) /( mol·kg )

5

6

Figure 3. Measured and predicted phase diagrams of the ternary system KCl–SrCl2–H2O at 298.15 K. —, predicted isotherm

curve with three SrCl2 binary parameters from literature19 and mixing parameters from literature;18 △ , measured data from

literature;13 ■, measured data from literature.16

4

-1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

3

2

1

0 0

5

10

15

-1

m( LiCl) /( mol·kg )

20

Figure 4. Measured and predicted phase diagrams of the ternary system LiCl–SrCl2–H2O at 298.15 K. —, predicted isotherm

curve with three SrCl2 binary parameters from literature19 and mixing parameters from literature;22 ■, measured data from

literature;14 △ , measured data from literature.15


Page 22 of 26

Page 23 of 26

KCl

100

m(KCl)/(mol/100 mol S)

80

60

KCl 40

20

NaCl 0 0

SrCl2

20

40

60

80

100

NaCl

m(NaCl)/(mol/100 mol S)

Figure 5. Measured and predicted phase diagrams of the quaternary system NaCl–KCl–SrCl2–H2O at 298.15 K. —, predicted

isotherm curve; △ , measured data in literature.16

100 SrCl2

SrCl2· 6H2O

1.0

60

Part enlargement 0.8

0.6

40

0.4

NaCl

20

0

SrCl 2· 2H2O

80

m(SrCl 2)/(mol/100 mol S )

m(SrCl2)/(mol/100 mol S)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.2

LiCl· H2O

0.0

0

LiCl

20

40

NaCl

60

80


100

NaCl

0.0

0.5

1.0

1.5

2.0


Figure 6. Predicted phase diagrams of the quinary system LiCl–NaCl–KCl–SrCl2–H2O at 298.15 K saturated with KCl.



80

SrCl2· 6H2O

m(SrCl2)/(mol/100 mol S)

100 SrCl2

60

D

40

20

NaCl

E 0

C(B)(A)

F 0

LiCl

20

40

60

80

100

NaCl


Figure 7. Evaporation-crystallization route of the mother liquor for the oilfield brine in Nanyishan region of Qaidam Basin at

298.15 K. —, evaporation-crystallization path; …, solubility curves.

20

6

(a)

(b)

F

B -1

m(Na )/(mol· kg )

15

E

10

+

+

-1

m(Li )/(mol· kg )

5

D

5

C

4 3

A

2

D E

1

B C

A 0

0

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

Evaporation Ratio/%

0.4

0.6

Evaporation Ratio/%

0.8

F 1.0

2.0

3.0

(d)

(c) 2.5 2.0

D

1.5

-1

m(Sr )/(mol· kg )

B C

-1

m(K )/(mol· kg )

1.0

2+

1.5

+

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 26

1.0

D

A

F

E

0.5

E

0.5

BC

A

F

0.0

0.0 0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

Evaporation Ratio/%

0.4

0.6

0.8

Evaporation Ratio/%

Figure 8. Relationship between the ion concentrations and evaporation ratio of the water during the evaporation process.


1.0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


14 12

F

10

lnKap (LiCl)

Page 25 of 26

E

8

D

6 4

BC

2

A

0 -2

0.0

0.2

0.4

0.6

0.8

1.0

Evaporation Ratio/% Figure 9. Relationship between lnKap for LiCl·H2O and evaporation ration of the water during the evaporation process.

1.0

0.8

A

aw

BC

0.6

D 0.4

E

0.2

F 0.0 0.0

0.2

0.4

0.6

0.8

1.0

Evaporation Ratio/% Figure 10. Relationship between water activities and evaporation ration of the water during the evaporation process.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

TOC Graphic


Page 26 of 26

Isothermal Evaporation Process Simulation Using the Pitzer Model for

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