1. CO2PipeHaz
An Integrated, Multi-scale Modelling
Approach for the Simulation of Multiphase
Dispersion from Accidental CO2 Pipeline
Releases in Realistic Terrain
R.M. Woolley, M. Fairweather,
C.J. Wareing, S.A.E.G. Falle
University of Leeds, UK
S. Brown, H. Mahgerefteh, S. Martynov
University College London, UK
Simon E. Gant
Health and Safety Laboratory, UK
EC FP7 Projects Technical Workshop:
Leading the way in CCS implementation
14 – 15 April 2014, UCL, UK
C. Proust, J. Hebrard, D. Jamois
INERIS, France
V.D. Narasimhamurthy, I.E. Storvik,
T. Skjold
GexCon AS, Norway
D.M. Tsangaris, I.G. Economou, G.C.
Boulougouris, N. Diamantonis
NCSRD, Greece

2. INERIS (France)
Prof. C. Proust
National Research
Centre for Physical
Sciences (Greece)
Prof. I. Economu,
Dr. D. Tsangaris
University of Leeds
(UK)
Prof. M. Fairweather
University College
London, (UK)
Prof. H. Mahgerefteh
Dalian University of
Technology (China)
Prof. Y. Zhang
GexCon AS (Norway)
Dr. J.A. Melheim,
Health and Safety
Laboratory (UK)
Dr. M. Wardman
Dr. S. Gant
Project Partners

3. Outline
Introduction – Work in context
Experimental Configuration
Realistic Industrial Release Case
In-pipe and Release Condition Modelling
Thermodynamic Property Modelling
Near-field Multi-phase Dispersion Model
Far-field Dispersion Model
Decision Support Tools
Conclusions

4. Schematic of CO2 pipeline release and dispersion scenario
Introduction - Work in Context
Until P = Patm
Far-FieldNear-
field
Transfer of data
between models
Integration of numerical models
Output from in-pipe
modelling

5. Φ
45°
E
Φ (mm) E (mm) e (mm)
5.8 9 5
8.9 15 10
11.8 15 12
25 15 10
50 No screw No screw
2 m3 vessel Connection to the discharge pipe End of the discharge pipe
General view discharge orifice
Experimental Configuration

6. Experimental Configuration
Mast No :1 2 3 4 5
6
Release point
2 m3 vessel
Masts :
N°1 @ 1m
N°2 @ 2m
N°3 @ 5m
N°4 @ 10m
N°5 @ 20m
N°6 @ 37m
0
+20
+30
+110
+140
+170
-20
-30
-40
-60
-130
-140
+40
+60
-10
+10
Release point is 1.5 m above
ground
: Thermocouple K ± 0.25°C
: O2 analyser ± 0.01% v/v

7. Experimental Configuration
Near-field instrumentation
Test Number Observed Mean
Mass Flow
Rates / kg s-1
Ambient
Temperature / K
Air Humidity
/ %
Reservoir
Pressure /
bar
Nozzle
Diameter / mm
11 7.7 276.15 >95 83 12
12 24.0 276.15 >95 77 25
13 40.0 276.65 >95 69 50
High-speed camera still
of a 9mm release
R.M. Woolley, M. Fairweather, C.J. Wareing, S.A.E.G. Falle, C. Proust, J. Hebrard, D. Jamois, 2013,
Experimental Measurement and Reynolds-Averaged Navier-Stokes Modelling of the Near-Field Structure of
Multi-phase CO2 Jet Releases, Int. J. Greenh. Gas Con., 18, 1, 139-149.

8. Hypothetical release at a site in UK using a realistic
pipeline route:
Task involves:
Selection of pipeline release scenario
Outflow predictions (UCL)
Near-field predictions (University of Leeds)
Far-field CFD predictions (GexCon and HSL)
Comparison to risk assessment tools (HSL)
Realistic Industrial Release Case

9. Pipe diameter 36” (ext. 914 mm, int. 870 mm)
Wall thickness 22 mm
Length 217 km
Pressure 150 bar
Temperature 10 ºC
Composition 100% CO2
Failure mode Full-bore guillotine rupture
Upstream flow No pump or reservoir
Block valves None
0
100
200
300
400
500
600
0 50 100 150 200
Distance (km)
PipelineElevation(m)
Elevation (m)
Rupture Location
Pipeline outflow results
found to be insensitive to
terrain
Realistic Industrial Release Case

10. 0
1
2
3
4
5
6
7
8
0 20 40 60 80
Crater Length (m)
CraterDepth(m)
Historical Nat. Gas
Assumed CO2
Crater dimensions assumed, based on natural gas incident data
12 m
30 m
1 m
45º
4 m
Plan View Side View
12 m
0
5
10
15
20
25
30
35
0 20 40 60 80
Crater Length (m)
CraterWidth(m)
Realistic Industrial Release Case

11. In-pipe and Release Condition Modelling
Tasks:
To develop a multiphase
heterogeneous outflow model for
predicting CO2 discharge rate and fluid
state during pipeline failure
Validate against large and small scale
experimental data from INERIS and
DUT
Method:
1D transient CFD
Finite Volume method
Godunov 1st order scheme
Harten, Lax, van Leer (HLL) solver
Explicit time integration
Model closure required for the
thermo-physical properties of the
phases (liquid, vapour and solid)
Brown, S., Martynov, S., Mahgerefteh,H.,
Proust, C., 2013.
A Homogeneous Equilibrium Relaxation
Flow Model for the Full Bore Rupture of
Dense Phase CO2 Pipelines.
Int. J. Greenh. Gas Con. 17, 349-356.

12. 0.1
1.0
10.0
100.0
1000.0
10000.0
-100 -80 -60 -40 -20 0 20 40
Temperature, °C
Pressure,bar
Saturation
Melting
Sublimation
Phast
UCL
Solid
Liquid
Vapour
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
0 50 100 150 200
Time (s)
Totalmassreleaserate(kg/s)
UCL
Phast
Starting Condition
(150 bar, 10 ºC)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 50 100 150 200
Time (s)
Liquidmassfraction(w/w)
UCL
Phast
UCL
Phast
In-pipe and Release Condition Modelling
S. Brown, S. Martynov, H. Mahgerefteh, C. Proust, 2013, A Homogeneous Equilibrium Relaxation Flow Model for
the Full Bore Rupture of Dense Phase CO2 Pipelines, Int. J. Greenh. Gas Con., 17, 349-356.

13. For CO2 and CO2 mixtures, the Physical Properties Library
(PPL) developed by NCSRD can be used to obtain the
following properties:
Volumetric (density, compressibility)
Energy related (enthalpy, entropy, heat capacity)
Derivative (Joule-Thomson, speed of sound)
Transport (viscosity, diffusivity, thermal conductivity)
and these properties can be obtained:
Cubic equations of state (Redlich-Kwong, Soave-Redlich-Kwong,
Peng-Robinson, Peng-Robinson-Gasem, )
Specialized equations of state (GERG, Span and Wagner, Yokozeki)
Advanced equations of state (SAFT/PC-SAFT/tPC-PSAFT)
Thermodynamic Property Modelling

14. Thermodynamic Property Modelling
CO2 Speed of soundCO2 Joule-Thompson
coefficient
Predictions of CO2 properties obtained using SAFT approach
N.I. Diamantonis, G.C. Boulougouris, E. Mansoor, D.M. Tsangaris, I.G. Economou, 2013, Evaluation of Cubic,
SAFT, and PC-SAFT Equations of State for the Vapor-liquid Equilibrium Modeling of CO2 Mixtures with other
Gases, Ind. Eng. Chem. Res., 52, 10, 3933-3942.

15. Near-field Multi-phase Dispersion Model
Conservative, upwind, finite volume
code solving the Reynolds-averaged
Navier-Stokes equations for mass,
momentum, total energy, and mean
of mixture fraction.
Adaptive Mesh Refinement with a
hierarchy of grids – Solution
computed on all grids. Mesh is then
refined where solution varies rapidly.
For shock calculations - an HLL
(Harten, Lax, van Leer) Riemann
solver is used.
Coordinates: axisymmetric
cylindrical polar or full three-
dimensions.

16. Non-ideal Equation of State
Internal energy on the saturation line for the improved equation of state.
C.J. Wareing, R.M. Woolley, M. Fairweather, S.A.E.G. Falle, 2013, A Composite Equation of State for the Modelling
of Sonic Carbon Dioxide Jets, AIChE J., 59, 10, 3928-3942.
Gas Phase: Peng-Robinson Eqn of State
Liquid Phase:
Span & Wagner
Eqn of State
Latent heat: DIPPR data
Solid phase: DIPPR data
Near-field Multi-phase Dispersion Model

17. Temperature Predictions of INERIS Releases - Liquid Release
Test 8
x = 1m
d = 40
160
180
200
220
240
260
280
300
Temperature/K
Test 6
x = 1m
d = 112
Test 7
x = 1m
d = 85
160
180
200
220
240
260
280
300
Temperature/K
Test 6
x = 2m
d = 225
Test 7
x = 2m
d = 170
Test 8
x = 2m
d = 80
Test 6
Pressure = 95 bar, diameter = 9 mm
Test 7
Pressure = 85 bar, diameter = 12 mm
Test 8
Pressure = 77 bar, diameter = 25 mm
-1.2 -0.8 -0.4 0.0 0.4 0.8 1.2
160
180
200
220
240
260
280
300
Temperature/K
y / m
Test 6
x = 5m
d = 562
-1.2 -0.8 -0.4 0.0 0.4 0.8 1.2
y / m
Test 7
x = 5m
d = 424
-1.2 -0.8 -0.4 0.0 0.4 0.8 1.2
y / m
Test 8
x = 5m
d = 200
Near-field Multi-phase Dispersion Model

18. X = 0.0
3-D crater geometry - 2 axisymmetric boundaries
Z = 0.0
Near-field Multi-phase Dispersion Model

19. Near-field Multi-phase Dispersion Model
Total velocity x = 0.0 CO2 Dense Phase
Fraction x = 0.0

20. Far-field Dispersion Model (FLACS)
Compressible form of unsteady 3-dimensional RANS equations:
Mass, momentum, enthalpy, mass and mixture fractions
Turbulence: k - ε equations with sub-grid models
Second-order accurate Finite-Volume formulation
Staggered Cartesian grids
Terrain and geometry implementation:
Distributed porosity concept
Cut-cell method
Features of the commercial code FLACS:

21. Far-field Dispersion Model (FLACS)
Multi-phase dispersion: Euler-Lagrange model
Non-compressible spherical particles: solids and droplets
Point-particle method (Loth, 2000)
Two-way coupling between the continuous phase (gas) and the
dispersed phase (particles):
Source terms in the mass, momentum and energy equations
Particle-turbulence interaction: source terms in k - ε equations
Droplet vaporization and particle deposition on obstacles are
modelled
Particle-particle interactions not considered.
Particle momentum equation: simplified Maxey and Riley’s equation
Buoyancy and drag forces are considered
Instantaneous fluid velocity seen by the particle: modeled by
stochastic differential equations - modified Langevin equation

22. Far-field Dispersion Model (ANSYS-CFX)
Lagrangian particle-tracking for solid CO2 particles
Sublimation: accounts for mass and heat transfer, and particle size
reduction
Initial particle diameter assumed 20 μm
Humidity:
Transported water vapour and dispersed water droplets
Numerics:
Finite volume, high-order upwind-biased convection scheme, ~0.6M cells

23. Terrain data purchased from Ordnance Survey
3D far-field geometry imported into FLACS and CFX
Imported terrain in FLACS Imported terrain in CFX
Release location
10 km
5 km
Far-field Dispersion Model

24. Terrain imported in FLACS using CP-8 objects (which employs
porosity-concept rather than the cut-cell method).
A coarse grid of ≈ 350,000 was adopted for this test run.
Wind profile: 2 m/s, Pasquill class ‘D’, reference height 10 m and
ground-roughness 0.1 m
Release location
Wind direction
Sensors are placed 2m
above the local ground
Far-field Dispersion Model

25. Time variation of volume fraction at different sensor locations
Far-field Dispersion Model

26. Far-field Dispersion Model
Predicted CO2 jet in the vicinity of the crater using
FLACS (left) and CFX (right)

27. Far-field Dispersion Model
CFX predicted steady-state CO2 cloud, defined using
three different mean CO2 concentrations: 1% v/v
(left); 2% v/v (middle); 4% v/v (right), and coloured
according to the distance from the crater source.

28. 28
TASKS:
Incorporate the predictive capabilities as
described, as well as current knowledge
and good practice, into decision support
tools.
Demonstrate the usefulness of tools to
identify potential hazards by examining
harm from vapour concentration and
population density
Decision Support Tools

29. 29
Risk Assessment Studies

30. • 1%, 10% and 50%
fatality contours for
indoor and outdoor
populations weather
condition and release
point (standard TROD)
• figure shows 1% fatality
contour for outdoor
populations
• 72 wind directions
(figure shows 4
directions)
• overlay with
representative
population data
Societal Risk Calculation

31. Conclusions
The process of simulating a hypothetical ‘realistic’ release
from a buried 0.914 m (36 inch) diameter, 217 km long pipeline
has been demonstrated.
The work has demonstrated that it is feasible, in principle, to
simulate such industrially-relevant flows.
In view of the fact that most routine pipeline risk assessments
will be carried out using integral or other phenomenological
models that assume dispersion over flat terrain, it would be
useful to use the models demonstrated here to determine
under what set of conditions such models might provide
unreliable results.
Finally, from an emergency-planning perspective, it would be
useful to further develop and validate models that are able to
predict the extent of the visible CO2 plume, as well as its
extent in terms of its instantaneous hazardous CO2
concentrations.

32. Acknowledgements & Disclaimer
The research leading to the results described in this
presentation has received funding from the European
Union 7th Framework Programme FP7-ENERGY-2009-1
under grant agreement number 241346.
The presentation reflects only the authors’ views and the
European Union is not liable for any use that may be made
of the information contained therein.