thermophysical properties and phase behavior of a co

THERMOPHYSICAL PROPERTIES AND PHASE BEHAVIOR OF A CO2-RICH NATURAL GAS Antonin Chapoy, Mahmoud Nazeri, Mahdi Kapateh, Rod Burgass, Bahman Tohidi Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh, UK

Christophe Coquelet

MINES ParisTech, Fontainebleau, France

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2014 GPA Convention April 13 -16

Outline • • • • • •

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Introduction / Background VLE / Phase Envelope Hydrate / dehydration Viscosity / density Frost Points Conclusions


Introduction / Background • Significant gas deposits with relatively high CO2 concentrations (US, East Asia...) – From 40 to 70 mole% CO2

• Models / correlations developed for methane rich fluids are not necessary applicable • Experimental data for such systems are scarce • Knowledge gained is transferrable between CCS and acid gas production/processing/injection

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Introduction / Background • 3 years project in collaboration with MinesParisTech (Armines) started in 2011 • Main objective: developing a reliable thermodynamic package for CCS fluids • CO2 originating from capture processes is generally not pure and can contain impurities such as: – H2O, CH4, C2H6,C3H8, N2, H2, O2, Ar, CO, NyOx, H2S, SO2… • The main aim of the proposed project was to investigate the phase behavior and properties of CO2-rich stream containing impurities • For testing model, some CO2 rich NGs were studied 4


Research Topics • Phase Equilibria (VLE, Phase Envelope) • Hydrates

– Saturated or low water content (dehydration)

• Solubility, water content, pH in brines • Phase behavior with glycols • Transport properties – Density, viscosity, speed of sound

• Frost/ dry ice • Interfacial Properties • Mercury content 5


Type of Fluids investigated • From binary to multicomponent systems Comp. CO2 Methane Ethane Propane n-Butane i-Butane n-Pentane Nitrogen Hydrogen Oxygen Argon CO Total

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MIX 1 95.64 0.6261 0 0 0 0 0 1.41 0.8175 0.08 1.21 0.2127 100

MIX 2 89.83 0 0 0 0 0 0 5.05 0 3.07 2.05 0 100

MIX 3 69.99 20.02 6.612 2.58 0.3998 0.3997 0 0 0 0 0 0 100

MIX 4 49.93 39.99 3.510 1.530 0.501 0.499 0.513 3.524 0 0 0 0 100

MIX 5 95.97 0 0 0 0 0 0 2.028 0.605 0.783 0.611 0 100

MIX 6 69.99 7.901 7.015 4.968 2.067 2.049 0 6.009 0 0 0 0 100


Fluids investigated in this work Comp. CO2 Methane Ethane Propane n-Butane i-Butane Nitrogen Oxygen Argon Total

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MIX 2 89.83 0 0 0 0 0 5.05 3.07 2.05 100

MIX 3 69.99 20.02 6.612 2.58 0.3998 0.3997 0 0 0 100


Models • Classical SRK 72 equation of state for systems without polar components • sCPA – SRK 72 for systems with water/glycols/alcohol RT a(T ) 1 RT P= − − Vm − b Vm (Vm + b ) 2 Vm

SRK part

(

 ∂ ln( g )  ∑ x i ∑ 1 − X Ai 1 + ρ ∂ρ  i Ai 

)

Association part

• For Hydrate: Solid solution theory of van der Waals and Platteeuw  H w

f

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 ∆µw = fw exp − RT  β

β −H

β −H

 where ∆µw  

 = µw − µ = RT ∑ v m ln1 + ∑ Cmj f j  m j   β

H w


Phase Equilibria – Vapour Liquid Equilibria • Between CO2 and components of the stream and between components • Data needed for EoS model ----> Engineering calculations • Saturation pressure/ phase envelope of multicomponent systems for validation

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Why Measure VLE? • Lack of data -- > especially for toxic gases or close to CO2 critical conditions CO2

CO

N2

O2

Ar

H2

NO

CH4

C2H6

C3H8

NO2

SO2

H2S

N2O

CO2 CO N2 O2 Ar H2 NO CH4 C2H6 C3H8

NO2

SO2 H2S

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What we have covered so far CO2 CO2 CO N2 O2 Ar H2 NO CH4 C2H6 C3H8 NO2 SO2 H2S

CO

N2

O2

Ar

H2

NO

NEW

NEW

NEW

NEW

NEW

NEW

[6570]+CD

CR

[67]

[9093]

[90] [90]

[8283] [9497]

NEW

CH4

C2H6

C3H8

NO2

SO2

H2S

N2O

[1936] [7982]

[37 49] [8485]

[47,5061]

CD

[6264]+CD

NEW

[141]

[84-88]

ND

NEW

[89]

NEW

[99109] [106109]

[100102]

NEW

ND

[104105]

ND

DWA

NEW

ND

ND

CRYO

CD

[107108]

ND

CRYO

NEW

CRYO

[140]

NEW

ND

NEW

ND

NEW

ND

[110119]

[111112, 120]

[121123]

ND

NEW

ND

ND

[124]

ND

ND

[29]

NEW

ND

ND

ND

[99]

ND

NEW

ND

[125]

DWA DWA

CR

[126131] [132134] [136139]

NEW NEW NEW

ND

ND

ND

ND ND

N2O

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VLE Apparatus Schematic illustration of the cell used for VLE studies Capillary Sampler Cooling Fluid in/out Equilibrium Cell Cooling Jacket Temperature Probe Window

Specifications – Ti Rig – 200 ml – Maximum working P : 3,000 psia / 200 bar – -30 °C < T < 120 °C – -22 °F < T < 250°F Phase sampling: ROLSI™

Pressure Transducer 2-way valve Magnetic Motor

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Typical Experimental / Modelling Results 1400

Tuned kij

9 8

1200

7

1000

P / MPa

6

800

5 4

600

3

400

2

200

1 0

P / psia

10

kij =0

0

0

0.2

0.4

x1,y1

0.6

0.8

1

Vapour – Liquid Equilibria in the H2S + CO2 Binary System 13


Phase Envelope • Experimental setup Main Characteristics: Titanium piston vessel Pmax: 10,000 psia /700 bar Tmin: -110°F /-80 oC Tmax: 350°F / 180oC

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Phase Envelope – Procedures (BP) 1600

T = 20.2°C / 68.4°F System: MIX 2

1500

P /psia

1400

2 Phases Region

1300 1200 1100 1000

Single Phase Region 0

15

5

10

15

V / cm3

20

25

30


Phase Envelope – Procedures (BP) 1250 1200

Cooling

1150

Eq. Pts 2 phases

1100

Eq. Pts 1 phases

Eq. Pts 1 phases

1100

1050 1000

1000 950

900

900

10

15

T/ °C

16

1050

950 5

Eq. Pts 2 phases

1150

P / psia

P / psia

1200

Heating

20

5

10

15

20

T/ °C


Phase Envelope – Procedures (DP) 810

Cooling 790

Heating Dew Point

P / psia

770

780 770

750

760 750

730

740 730

710 690

720

8

10

12

14

10

11

16

12

13

18

14

20

T/ °C 17


Validation: Phase Envelope -76

-40

-4

32

68

104 1200

80 70

1000

P /bar

60

800

50

600

40 30

P / psia

90

T/ °F

400

20 200

10 0

0 -60

-40

-20

T/ °C

0

20

40

Exp. and predicted Phase Envelope (Blue and Red Lines: SRK-EoS with tuned kij; Dotted lines: PR-EoS with kij=0). 18


Validation: Phase Envelope -76

-40

T/ °F

32

68

104

80

1100

70

900

60

P /bar

1300

50

700

40

500

30

P /psia

90

-4

300

20

100

10 0

-100 -60

-40

-20

0

T/ °C

20

40

Exp. and predicted Phase Envelope (Blue and Red Lines: SRK-EoS with tuned kij; Dotted lines: PR-EoS with kij=0). 19


Dehydration Requirement • Knowledge of the maximum allowable water content in CO2rich fluids is critical for a safe transport of CO2 to storage sites – Hydrates, corrosion

• Limited data are available on the phase behavior of CO2 in presence of hydrates – GPA RR80 and RR99 (also published in SPE) – Unfortunately the reliability of these studies has been recently questioned in a few papers (ex BRE: Hendrick et al., GPA Convention 2010) – Gap in data at low temperature (T35% reduction in density

ρ / kg.m-3

-100 -150 -200

>60% reduction in density

-250

MIX 3

-300 CH4 -350 0

2500

5000

7500

10000

12500

15000

17500

20000

P / psia

Density difference between pure CO2 and mixtures at 122°F / 50°C 36


Frost Point/ Dry ice • VSE of CO2-mixtures important issue

– safety assessment of CO2 pipelines – possibility of solid or ‘dry ice’ discharge during an accidental release or rapid decompression

• Removal of CO2

– A technique has been suggested based on frosting CO2 at low temperature and separating the CO2 solid from natural gas

• No data for multicomponent systems

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Frost Point/ Dry ice - Equipment

BT 2.15 Calorimeter 38

Cross-sectional view of the SETARAM BT 2.15

Internal Block


Experimental Procedure

Operation line online monitoring

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Onset point (melting point) calculation procedure


Frost Point/ Dry ice - Equipment

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P /psia

40

Specifications: • Working pressure: 30,000 psia / 2000 bar • Constitutive metal: Stainless steel • Internal volume: ±1% error in Viscosity) Q: Flow rate, cm3/Sec (no effect on the accuracy of the viscosity) L: Length of Capillary tube, cm L = 1477.8 cm D: Calculated Internal Diameter, cm D = 0.029478 cm (calculated by knowing the length and volume of the tube)

η: Viscosity, cP C: Unit Conversion Factor

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C = 6894757

Viscosity – CS approach CS Theory: Viscosity at Critical Point: Pure Fluids: Reference Fluid

Mixtures: Critical Parameters Mixture Parameter 55

Viscosity – Modelling - Pedersen

Mixture Parameter:

MBWR EOS

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Viscosity – Modelling - Pedersen Fenghour et al. (1998)

Reference Fluid, CO2, Viscosity: Viscosity at Zero-density: Reduced effective cross section: Reduced Temperature: Energy Scaling Parameter: Excess Viscosity:

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