Corresponding author: Phone: +44(0)1314 513797 Fax +44(0)1314 513 797 E-mail: [email protected]HYDRATE AND PHASE BEHAVIOUR MODELLING IN CO 2 -RICH PIPELINES Antonin Chapoy*, Rod Burgass, Bahman Tohidi Hydrates, Flow Assurance & Phase Equilibria Research Group, Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh EH14 4AS, Scotland, UK ABSTRACT CO 2 transport will be a key part of any Carbon Capture and Storage (CCS) system. Generally for CCS, flow assurance modelling of these pipelines has been restricted to pure CO 2 systems; however CO 2 streams coming from capture processes are not pure and contain various components. These fluids have a certain level of moisture, so dehydration is needed before delivering CO 2 rich fluid to the export pipeline, in order to prevent potential hydrate formation, two-phase flow and corrosion in the export line. In this paper, a rigorous and generalized model is presented to predict the phase behaviour, hydrate dissociation pressures and the dehydration requirements of CO 2 rich gases. A statistical thermodynamic approach, with the Cubic-Plus-Association equation of state, is employed to model the phase equilibria. The hydrate-forming conditions are modelled by the solid solution theory of van der Waals and Platteeuw. Predictions of the developed model are first validated using simple systems and then for more complicated synthetic multicomponent systems. Keywords: Gas Hydrates; Carbon dioxide; Water; Thermodynamic Model. NOMENCLATURE List of symbols P Pressure T Temperature y Composition Abbreviations AAD Absolute Average deviation CPA Cubic Plus Association EoS Equation of State ppm Part per million H Hydrate phase L liquid phase I Ice phase V vapour phase Subscript Cal Calculated property exp Experimental property W Water property Sat Saturation INTRODUCTION As nearly forty percent of untapped hydrocarbon fields contain high concentrations of CO 2 and H 2 S (Lallemand et al. 2012 [1]). There is a requirement for accurate predictions of thermophysical properties, essential for sound design of production facilities for such hydrocarbon systems. For example, in South East- Asia, the CO 2 content is higher than 70 mole% in some gas fields. The presence of such high concentrations of CO 2 in the stream can lead to challenging flow assurance and processing issues. Such compositions can lead to many technical challenges, flow assurance issues, as well as a significant increase in processing costs. The presence of high concentrations of CO 2 means that higher strength/specification transport pipelines are required in order to reduce the risk of ductile fracture. The presence of water may result in ice and/or gas hydrate formation, leading to pipeline restriction and blockage. Where natural gas is compressed for transportation purposes it is necessary to know the effect of CO 2 concentration in the stream on the physical properties of the fluid, i.e., the system's bubble Proceedings of the 8th International Conference on Gas Hydrates (ICGH8-2014), Beijing, China, 28 July - 1 August, 2014
HYDRATE AND PHASE BEHAVIOUR MODELLING IN CO2-RICH PIPELINES
Antonin Chapoy*, Rod Burgass, Bahman Tohidi Hydrates, Flow Assurance & Phase Equilibria Research Group, Institute of Petroleum
Engineering, Heriot-Watt University, Edinburgh EH14 4AS, Scotland, UK
ABSTRACTCO2 transport will be a key part of any Carbon Capture and Storage (CCS) system. Generally for CCS, flow assurance modelling of these pipelines has been restricted to pure CO2 systems; however CO2 streams coming from capture processes are not pure and contain various components. These fluids have a certain level of moisture, so dehydration is needed before delivering CO2 rich fluid to the export pipeline, in order to prevent potential hydrate formation, two-phase flow and corrosion in the export line.In this paper, a rigorous and generalized model is presented to predict the phase behaviour, hydrate dissociation pressures and the dehydration requirements of CO2 rich gases. A statistical thermodynamic approach, with the Cubic-Plus-Association equation of state, is employed to model the phase equilibria. The hydrate-forming conditions are modelled by the solid solution theory of van der Waals and Platteeuw. Predictions of the developed model are first validated using simple systems and then for more complicated synthetic multicomponent systems.Keywords: Gas Hydrates; Carbon dioxide; Water; Thermodynamic Model.
NOMENCLATUREList of symbolsP Pressure T Temperaturey Composition
Abbreviations AAD Absolute Average deviationCPA Cubic Plus AssociationEoS Equation of Stateppm Part per millionH Hydrate phaseL liquid phaseI Ice phaseV vapour phase
SubscriptCal Calculated propertyexp Experimental propertyW Water propertySat Saturation
INTRODUCTION
As nearly forty percent of untapped hydrocarbon fields contain high concentrations of CO2 and H2S (Lallemand et al. 2012 [1]). There is a requirement for accurate predictions of thermophysical properties, essential for sound design of production facilities for such hydrocarbon systems. For example, in South East-Asia, the CO2 content is higher than 70 mole% in some gas fields. The presence of such high concentrations of CO2 in the stream can lead to challenging flow assurance and processing issues. Such compositions can lead to many technical challenges, flow assurance issues, as well as a significant increase in processing costs. The presence of high concentrations of CO2 means that higher strength/specification transport pipelines are required in order to reduce the risk of ductile fracture. The presence of water may result in ice and/or gas hydrate formation, leading to pipeline restriction and blockage. Where natural gas is compressed for transportation purposes it is necessary to know the effect of CO2
concentration in the stream on the physical properties of the fluid, i.e., the system's bubble
Proceedings of the 8th International Conference on Gas Hydrates (ICGH8-2014),Beijing, China, 28 July - 1 August, 2014
point pressure. This will allow accurate assessment of the compression requirement. A preliminary literature survey showed that there is limited or no experimental data on the above systems. Therefore, using non validated conventional thermodynamic models may lead to inaccurate estimation of reservoir size, fluid properties (e.g., dew point), or other unexpected problems, e.g., two‐phase flow when only one phase was expected, higher dehydration requirements to avoid hydrate/ice problems, etc...(Chapoy et al., 2009, SPE 123778 [2]). In this work, experimental measurements of the locus of incipient hydrate-liquid water-vapor curve for a CO2-rich natural gas (70 mole % of CO2 and 30 mole % of light hydrocarbons CH4 to nC4) in equilibrium with liquid water are presented at pressures up to 40 MPa. New experimental data are reported for water content in equilibrium with hydrates at about 10 MPa and temperature range from -40 to 50°F (-40 to 10°C). The Cubic-Plus-Association (CPA-EoS) or the Soave-Redlich-Kwong (SRK) equation of state combined with the solid solution theory of van der Waals and Platteeuw (1959) [3] as developed by Parrish and Prausnitz (1972) [4] was employed to model the fluid and hydrate phase equilibria as previously described by Chapoy et al. [5, 6, 7, 8]. The predictions of the thermodynamic model were compared with the experimentally measured properties (saturation pressure, dew point, hydrates).
EXPERIMENTALThe majority of the setups and procedures used in this paper were described in detail in [5, 6, 7, 8]. A brief description of each setup is given below.
MaterialsCarbon dioxide (CO2) was purchased from BOC and has a certified purity higher than 99.995 vol%. Composition of the CO2-rich synthetic mixtures prepared by BOC is given in Table 1. De-ionized water was used in all hydrate tests.
Saturation and Dew Pressure Measurements and ProceduresThe equilibrium setup consisted of a piston-type variable volume (maximum effective volume of 300 ml), titanium cylindrical pressure vessel with mixing ball, mounted on a horizontal pivot with associated stand for pneumatic controlled rocking mechanism (Figure 1). Rocking of the cell
through 180 degrees at a constant rate and the subsequent movement of the mixing ball, ensured adequate mixing of the cell fluids. Cell volume, hence pressure, can be adjusted by injection/withdrawal of liquid behind the moving piston.
Figure 1 Schematic illustration of equilibrium rig used for saturation pressure measurements
Components Composition, mole%
CO2 BalanceO2 0.783±0.016%Ar 0.611±0.012%N2
H2
2.028 ±0.041%0.605±0.012%
Table 1 Composition, mole%, of the synthetic multicomponent mixture used in this study as prepared and certified by BOC.
The rig has a working temperature range of -70 to 180°C, with a maximum operating pressure of 700 bar. System temperature is controlled by circulating coolant from a cryostat within a jacket surrounding the cell. The equilibrium cell and pipework were thoroughly insulated to ensure constant temperature. The temperature was measured and monitored by means of a PRT (Platinum Resistance Thermometer) located within the cooling jacket of the cell (accuracy of 0.05 °C). A Quartzdyne pressure transducer with an accuracy of ± 0.3 bar was used to monitor pressure. The bubble point was determined by
changing the volume of the cell and finding the break over point in the pressure vs. volume curve as shown in Figure 2.
Figure 2 Plot showing an example of bubble point determination from plot of change in cell pressure, P, versus volume, V, from test for with the 90 mole% CO2–rich fluid at 10.1°C
Figure 3 Plot showing an example of dew point determination from plot of change in cell pressure, P, versus volume, V, from test for with the 90 mole% CO2–rich fluid.
A typical test to determine the dew point is as follows: To obtain the dew point using the isochoric method the cell is loaded with the test sample and is set to 5 degrees above the estimated dew point temperature. The pressure of the cell is then increased by pumping a mixture of water and glycol into the piston side to reach the desired pressure. The cell is cooled until the system has clearly become two phase. The cell temperature is then step heated, allowing sufficient time for equilibration, until the system has clearly become single phase again. Throughout the process the cell is rocked using a pneumatic pivoting system to ensure all of the cell constituents are thoroughly
mixed and equilibrium is reached. The system pressure and temperature are recorded every minute using a logging program. The recorded data is then processed to determine the system pressure at each temperature step. This process results in two traces with very different slopes on a pressure versus temperature (P/T) plot, one in the single phase and one in the 2 phases region. The point where these two traces intersect is taken as the dew point (Figure 3)
Hydrate Dissociation MeasurementsDissociation point measurements were conducted using the isochoric step-heating method developedin this laboratory. Figure 4 shows the apparatus used to determine the phase equilibrium conditions. The phase equilibrium is achieved in a cylindrical cell made of Hastelloy. The cell volume is about 80 cm3 and it can be operated up to 400 barbetween -30 and 50°C.
Figure 4 Schematic illustration of high-pressure hydrate rig
Water Content Measurements and ProceduresThe core of the equipment for water content measurement has been originally described by Chapoy et al. (2012) [5]. The setup comprises of an equilibrium cell and a device for measuring the water content of equilibrated fluids passed from the cell. The equilibrium cell is similar to the one described in the saturation pressure measurements. The moisture/water content measurement set-up consists of a heated line, a Tuneable Diode Laser Adsorption Spectroscopy (TDLAS) from Yokogawa and a flow meter. The estimated experimental accuracy of water content is ±5 ppm mole.
THERMODYNAMIC MODELLINGA general phase equilibrium model based on the uniformity of component fugacities in all phases is used to predict the water activity and the hydrate suppression temperature of aqueous solutions of salt and alcohol. A description of the thermodynamic model and parameters can be found elsewhere [5, 4, 5, 6].In summary, the statistical thermodynamics model uses the Cubic Plus equation of state for fugacity calculations in all fluid phases. The CPA EoS combines the well known Soave-Redlich-Kwong (SRK) EoS (Soave, 1972 [7]) for describing the physical interactions with the Wertheim’s first-order perturbation theory (1987) [8], which can be applied to different types of hydrogen-bonding compounds.
RESULTS AND DISCUSSIONS
Figure 5 Experimental and predicted phase envelope of the synthetic mixture. Lines: bubble and dew lines predictions using the SRK-EoS; Dotted lines: bubble and dew lines predictions using the SRK-EoS with kij =0.
Bubble point and dew point measurements were carried out for the multicomponent mixture from about -20 to about 20°C. The results are and plotted in Figure 5. As shown in Figure 5, the SRK-EoS model can predict the phase envelope of the multi-component systems with good accuracy, the predictions are in better agreement at higher temperature conditions. The predicted critical temperature and pressure are 28°C and 8.1 MPa, respectively.
Figure 6 Pressure vs. temperature diagram for carbon dioxide + water. Black curves: Model predictions (Hydrate stability zone); Dotted lines: Model predictions (bubble lines); () : data from Deaton and Frost (1946) 错误！未找到引用源。; : data from Larson (1955) 错误！未找到引用
源。; : data from Takeuchi and Kennedi (1964)错误！未找到引用源。; (): data from Ng and Robinson (1985) 错误！未找到引用源。 ; : data from Nakano et al. (1998) 错误！未找到引
用源。; : data from Chapoy et al. (2009) 错误！
未找到引用源。.
The thermodynamic model was compared to the stability zone of CO2 hydrate in presence of a free water phase. As seen in Figure 6, the experimental(collected from the open literature) and predicted phase boundaries for carbon dioxide hydrates are in good agreement. The water content in the CO2
rich phase in equilibrium with liquid water predicted by the model has also been compared to literature data from 25°C/298.15K (Figure 7), 150°C/423.15 K (Figure 8) and 205°C/478.15 K (Figure 9) and pressure to 150 MPa. As seen in Figure 7 (below the critical point of pure CO2), different phases can be found in the carbon dioxide – water system at this temperature: a water rich liquid phase, a carbon dioxide rich vapour phase and a carbon dioxide rich liquid phase. At the VLL point, two water content values can be found, one in the vapour phase and one in the liquid CO2 rich phase. Most literature data at 298.15 K are in good agreement with each other and with the model, except for the recent data of Hou et al. (2013) [18] which are 2-3 times higher than the other literature data, especially in the liquid region. Below the VLL locus, the water content is decreasing with pressure. Above the VLL locus in the liquid CO2 phase, pressure has a limited influence (in the pressure range
investigated) on the water content. Above the critical point of pure CO2 as seen in Figure 4 and 5, the model can predict accurately the distribution of water in the CO2 rich phase. The data of Takenouchi and Kennedy [5] are out of line with other literature data at 150°C/423.15 K
Figure 7 Water Content in the vapour and liquid phases of carbon dioxide in equilibrium with liquid water at 298.15 K. Black Lines: Model predictions; () Experimental data from Wiebe and Gaddy (1941) 错误！未找到引用源。; () Experimental data from Gillepsie and Wilson (1982) 错 误 ！ 未 找 到 引 用 源 。 ; () Experimental data from Nakayama et al. (1987) 错误！未找到引用源。; () Experimental data from King et al. (1992) 错误！未找到引用源。 ;(): Experimental data from Hou et al. (2013) 错误！未找到引用源。.
Figure 8 Water Content in carbon dioxide in equilibrium with liquid water at 423.15 K. Black lines: Model predictions; (): Experimental data from Takenouchi and Kennedy (1964) 错误！未
找到引用源。 ; () Experimental data from Gillepsie and Wilson (1982) 错误！未找到引用
源。; (): Experimental data from Tabasinejad et
al. (2011) 错误！未找到引用源。 ; ():Experimental data from Hou et al. (2013) 错误！
未找到引用源。.
The experimental data on water contents for CO2
in equilibrium with hydrates in a wide range of temperature from -10 to -50°C up to 10 MPa have been generated in this work.
Figure 9 Water Content in carbon dioxide in equilibrium with liquid water at 478.15 K. Black lines: Model predictions; : Experimental data from Tabasinejad et al. (2011) 错误！未找到引用
源。 .
Figure 10 Water Content in the vapour and liquid phases of carbon dioxide in equilibrium with hydrates or liquid water. Black lines: Model predictions; (): this work at 263.15 K; (): this work at 253.15 K; (): this work at 243.15 K; ():this work at 233.15 K; (): this work at 223.15 K.() Experimental data at 288.15 K from Gillepsie and Wilson (1982) 错误！未找到引用源。; () Experimental data at 288.15 K from King et al. (1992) 错 误 ！ 未 找 到 引 用 源 。 ; ():Experimental data at 288.15 K from Valtz et al. (2004) 错误！未找到引用源。.
The results from this work are plotted in Figure 10along with literature experimental data and predicted values. As can be seen there is good agreement between experimental results andpredicted values, validating the model predictions.
Figure 11 Plot showing equilibrium water content measurements for CO2 at 8.89 MPa at different temperatures on step-heating and step-cooling.
In a previous work by Youssef et al. (2009) [22], the measurement of hydrate formation and dissociation temperature of CO2 hydrates, in the absence of any aqueous phase, by measurement of the water content in the vapour phase was demonstrated. It was decided to conduct a similar test but with liquid CO2 in the absence of any aqueous phase.
Initially a small amount of water, 0.15 ml, was injected into the cell. The temperature was then reduced to -10 °C and the cell was vacuumed prior to injecting high purity CO2. The pressure in the cell was maintained constant at 8.89 MPa by adjusting the cell volume as required. The test was started at a temperature of 15.0 °C, therefore significantly higher than the expected hydrate formation temperature. The temperature was then reduced step-wise, measuring the water content of the equilibrium liquid CO2. Once the temperature was below the predicted hydrate formation temperature, at the set pressure, the temperature was reduced to -24.0 °C in order to give sufficient sub-cooling to form hydrates. The temperature was then increased step-wise again, measuring the water content at each temperature once equilibrated.
The water content measurements at each temperature are plotted in Figure 11. As can be seen from Figure 11, the measured water contents
for the step-cooled temperatures between 15.0 °C and -4.9 °C are close to 1100 ppm mole water. On cooling to -24.0 °C the water content reduces significantly indicating hydrate formation. On step-heating the water content increases at each temperature as would be expected for liquid CO2
in equilibrium with hydrates. The results show that this method can be used to indicate hydrate formation and dissociation using water content measurements. The results from this test with liquid CO2 combined with those reported by Youssef et al. (2009) [22] with vapour CO2
demonstrate that it should be possible to identify hydrate formation/dissociation using water content measurements. It is also worth noting that the model accurately predicts the hydrate dissociation of CO2 + 1000 ppm water mixture (Figure 11).
Figure 12 Predicted and experimental hydrate stability of the CO2-rich stream in presence of distilled water. (), this work; Black lines: hydrate stability zone predicted using the CPA-EoS model using an aqueous mole fraction of 0.8; (), dry system saturation points, this work; Dotted lines: phase envelope of the dry system (no water) using the SRK-EoS. Broken lines: pure CO2 hydrate stability zone predicted using the CPA-EoS model.
The experimental hydrate dissociation conditions for the mixture in equilibrium with water are plotted in Figure 12 along with the prediction of the dry multicomponent mixture phase envelopeand the pure CO2. Pure CO2 and the multicomponent mixture form structure I hydrate.As seen in the figure, we have first a vapour + hydrate + liquid water line, then a vapour +liquid rich CO2 + hydrate + liquid water line and finally a liquid rich CO2 + hydrate + liquid water line. The bubble point of the mixture is higher than pure CO2, hence hydrates would be more stable in the
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0.11
0.12
-20 -15 -10 -5 0 5 10
y w/ m
ole
%
T/ oC
Heating
Dissociation point
Cooling
sCPA-SRK 72
0
5
10
15
20
25
30
35
40
260 270 280 290 300
P/M
Pa
T / K
liquid region, as the vapour +liquid rich CO2 + hydrate + liquid water line is intersecting the bubble line at higher temperature. For this system the thermodynamic model is in excellent agreement with the new experimental data in the vapour phase region (>0.2 K) and within 0.5-0.8°C above the dew line. The ratio between the water mole fraction and the mixture fraction has a limited effect in this range of aqueous fraction as nitrogen, oxygen and argon are weak structure II hydrate formers.
The experimental water content data in equilibrium with hydrates for pure CO2 and the multi-component systems are plotted along with predictions of the thermodynamic model in Figure 13. As can be seen from the figure the experimental and predicted data are in good agreement with some deviation (AAD≈ 5%). As expected, for the multi-component systems, less water can be dissolved than in pure CO2, because the amount of water that can be dissolved in small molecules such as N2, O2… is far lower at the same temperature and pressure than in liquid CO2. As seen in this figure, the water contents for the multi-component system are between the water contents of pure CO2 and pure CH4, however there is no direct relation between the CO2 composition in these fluids and the reductions observed compared to the water content in pure CO2. The water content is on average about 10-30% lower than in pure CO2 for the multi-component system.
Figure 13 Plot showing experimental water content data and predictions for the water content of pure CH4, pure CO2 [6] and the CO2-rich stream at 13.8 MPa and different temperatures. (), pure CO2, this work; Red lines: water content predictions using the CPA-EoS model for pure CO2; (), multicomponent system; Blue dotted lines: predictions using the CPA-EoS model for the multicomponent system; (), multicomponent
system, this work; Brocken red lines: predictions using the CPA-EoS model for methane.
CONCLUSIONSKnowledge of the phase behaviour of CO2 rich systems is currently of great importance for both the energy industry and ultimately the environment. As discussed in this work, very limited reliable experimental data are available in the literature on the vapour/liquid-liquid equilibria for CO2-water system. Very few data sets are available for CO2 hydrate formation in under saturated conditions. It is, therefore, planned to extend this work to a wider range of temperature to further validate/improve the developed thermodynamic model.In this communication the phase behaviour and some properties of CO2-rich stream have been studied, such as the phase envelope, the hydrate stability, dehydration requirement of the mixture. Models have been developed to calculate and predict these properties.
The main impacts of the high CO2 concentration are summarized below:
(i) The single liquid phase region of the CO2-rich mixture is 2-5 MPa higher than for pure CO2 in the studied temperature range(ii) More water can be dissolved in the stream compared to pure CH4, hence the dehydration requirement for this type of fluid could be more stringent (iv) The developed models are in good agreement with the measured experimental data.
Future work will concentrate on the determination and modelling of properties for other types of natural gases (different CO2 concentrations, impact of H2S, etc.).
ACKNOWLEDGMENTSThis work is part of an ongoing Joint Industrial Project (JIP) conducted jointly at the Institute of Petroleum Engineering, Heriot-Watt University and the CTP research Center of MINES ParisTech. The JIP is supported by Chevron, GALP Energia, Linde AG, OMV, Petroleum Expert, Statoil, TOTAL and National Grid Carbon Ltd, which is gratefully acknowledged.
[1] Lallemand F. et al. Solutions for the treatment of highly sour gases, Digital Refining, April 2012.
[2] Chapoy A, Burgass R, Tohidi B. Effect of common impurities on the phase behaviour of carbon dioxide rich systems: Minimizing the risk of hydrate formation and two-phase flow.In: the SPE Offshore Europe Conference, Aberdeen, Scotland, 2009.
[3] Van der Waals JH, Platteeuw JC. Clathrate solutions. Adv. Chem. Phys. 1959;2: 2-57.
[4] Parrish WR, Prausnitz JM. Dissociation pressures of gas hydrate formed by gas mixture. Ind. Eng. Chem. Process. Des. Develop. 1972;11:26-34.
[5] Chapoy A., Haghighi H., Burgess R., Tohidi, B. On the Phase Behaviour of the Carbon Dioxide - Water Systems at Low Temperatures: Experimental and Modelling. J. Chem. Therm. 2012:47;6-12.
[6] Chapoy A., Nazeri M., Kapateh M., BurgassR., Coquelet C., Tohidi B. Effect of impurities on thermophysical properties and phase behaviour of a CO2-rich system in CCS, International Journal of Greenhouse Gas Control, 2013:19; 92-100.
[7] Haghighi H, Chapoy A, Tohidi B. Freezing Point Depression of Electrolyte Solutions: Experimental Measurements and Modeling Using the Cubic-Plus-Association Equation of State. Industrial and Engineering Chemistry Research 2008; 47:3983-3989
[8] Burgass R, Chapoy A, Duchet-Suchaux P, Tohidi B, Experimental water content measurements of carbon dioxide in equilibrium with hydrates at (223.15 to 263.15) K and (1.0 to 10.0) MPa, The Journal of Chemical Thermodynamics, 2014:69;1-5.
[9] Deaton WM, Frost EMJ. Gas hydrate composition and equilibrium data. Oil Gas J. 1946;45:170-178.
[10] Ng HJ, Robinson DB. Hydrate formation in system containing methane, ethane, propane, carbon dioxide or hydrogen sulphide in the presence of methanol. Fluid Phase Equilibr. 1985;21:144-155.
[11] Takenouchi S, Kennedy GC. Dissociation pressures of the phase CO2-5.75H2O. Geol. Notes no. 293. Institute of Geophysics, University of California, Berkeley, 1964;383-390.
[12] Larson SD. Phase studies of the two-component carbon dioxide-water system, involving the carbon dioxide hydrate. Ph.D. Thesis, University of Illinois, Urbana-Champaign, 1955.
[13] Nakano S., Moritoki M., Ohgaki K. High-Pressure Phase Equilibrium and Raman Microprobe Spectroscopic Studies on the CO2 Hydrate System. J Chem. Eng. Data. 1998:43;807-810
[14] Wiebe R, Gaddy VL. Vapor phase composition of the carbon dioxide-water mixtures at various temperatures and at pressures to 700 atm. J. Am .Chem. Soc. 1941;63:475-477.
[15] Gillespie P.C., Wilson G.M., 1982. Vapor–liquid and liquid–liquid equilibria: water–methane, water–carbon dioxide, water–hydrogen sulfide, water–n-pentane, water–methane–n-pentane, Research report RR-48, Gas Processors Association, Tulsa.
[16] Nakayama T., Sagara H., Arai K., Saito S.High pressure liquid-liquid equilibria for the system of water, ethanol and 1,1-difluoroethane at 323.2 K. Fluid Phase Equilib., 1987:38;109-127.
[17] King MB, Mubarak A, Kim JD, Bott TR. The mutual solubilites of water with supercritical and liquid carbon dioxide. J. Supercrit. Fluids. 1992;5:296-302.
[18] Hou S-X., Maitland G.C., Trusler J.P. M.,Measurement and modeling of the phase behavior of the (carbon dioxide+ water) mixture at temperatures from 298.15 K to 448.15 K. The Journal of Supercritical Fluids,2013:73;87-96.
[19] Takenouchi S., Kennedy GC.. Dissociation pressures of the phase CO2-5.75H2O. Geol. Notes no. 293. Institute of Geophysics, University of California, Berkeley, 1964;383-390.
[20] Tabasinejad F., Moore R. G., Mehta S. A., Van Fraassen K. C., Barzin Y., Rushing J. A., Newsham K. E., Water Solubility in Supercritical Methane, Nitrogen, and Carbon Dioxide: Measurement and Modeling from 422 to 483 K and Pressures from 3.6 to 134 MPa. Ind. Eng. Chem. Res. 2011:50; 4029–4041.
[21] Valtz A, Chapoy A, Coquelet C, Paricaud P,Richon D. Vapour - liquid equilibria in the carbon dioxide – water system, measurement
