CO 2 PipeHaz Dispersion of accidentally released CO 2 Olav R Hansen J A Melheim O J Taraldset M Ichard Olav R. Hansen , J. A. Melheim, O. J. Taraldset, M. Ichard GexCon AS CCS from Cradle to Grave CCS from Cradle to Grave The technical and safety challenges Birmingham, UK, 22-23 March 2012
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CO2PipeHaz-Accidential-Release GexCon Hansen Birmingham 2012 · • The terrain downwind spill pond sloped upwards at about 7 degrees for 80m before levelingdegrees for 80m, before
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CO2PipeHaz
Dispersion of accidentally released CO2Olav R Hansen J A Melheim O J Taraldset M IchardOlav R. Hansen, J. A. Melheim, O. J. Taraldset, M. IchardGexCon AS
CCS from Cradle to GraveCCS from Cradle to GraveThe technical and safety challenges
Birmingham, UK, 22-23 March 2012g , ,
Outline
• Background• Modelling challenges
FLACS CFD l• FLACS CFD solver• Particle modelling• Wind and dispersion modelling• Wind and dispersion modelling• Further work
Lake Nyos incident Cameroon
• Lake in volcanic crater• Lake in volcanic crater • Supersaturated water• 1986:
• Sudden release of CO2 from deep water• About 1.6 million tons CO2 released from the lake surface
CO fl d i t b ll d kill d b t 1700• CO2 flowed into nearby valleys and killed about 1700 people in a range of 25 kilometers
US statistics
CO d f EOR• CO2 used for EOR• 13 accidents in 22 years in 5600 km of pipelines (1986-2008)• 6 equipment failures 2 operator error 2 corrosion 3 unknown6 equipment failures, 2 operator error, 2 corrosion, 3 unknown • No reported injuries and fatalities
Background
• Hazardous gasg• Pure CO2 is lethal at high concentration. Presence of
impurities such as amines, H2S, CO,…• Pipe-lines will be located in populated areasPipe lines will be located in populated areas
• Unclear regulation • Risk assessment and risk management will be demanded
DNV d d ti 1• DNV recommended practice:1• The risks to people in the vicinity of the pipeline shall be robustly
assessed and effectively managed down to an acceptable level.M j id t h d i k t h ld b f d t• Major accident hazard risk assessment should be performed to provide estimates of the extent and severity…
1 DNV-RP-J202, April 2010. DESIGN AND OPERATION OF CO2 PIPELINES
Modelling challenges
• Supersonic two-phase CO2 jet with bli ti d d iti INERIS FLIE test with sublimation and deposition
• Condensation of humidity in air• Atmospheric boundary layer flow at
S esflashing propane 1.25 kg/s
various stability conditions• Modelling of terrain and vegetation and
their influence on the flow• Thermal stratification caused by cold
and dense cloud
FLACS – GexCon CFD model
• Release & Dispersion (gas, pool-spread & evaporation, flashing) • Explosion (main feature, wide functionality), far field pressure waves
Risk assessments mitigation accident/incident investigation and more• Risk assessments, mitigation, accident/incident investigation and more• Efficient geometry import from dgn-files (and some other formats)• Ventilation (including helideck studies, natural ventilation, HVAC)• About 100 end-users in 20 countries world-wide
GexCon explosion test3 kg methane1.5 bar overpressure
CO2 dispersion demo case
• Constant release of gaseous CO2(100 kg/s at -70°C)(100 kg/s at 70 C)
• Jet release above ground. Horizontal and aligned with the wind direction
• Neutral atmospheric conditions• Neutral atmospheric conditions• Wind: 5 m/s @ 10 m from south• Terrain imported from USGS DEM
and merged with manually added buildings
0.25% isosurface videoGround level concentrations(blue > 0.5%, red > 5%)
CO2 dispersion demo case
• High momentum jet gives good mixing with ambient air
• Cloud follows terrain and it disperses• Cloud follows terrain and it disperses slowly after jet dominated region
• Highly turbulent jet, then decay of turbulence and stratification caused by dense cloud
Two phase jet models
y≥
P0 Ps(T0)P0 Patm
≥>
yi
A1U1αg1
A2U2αg2
Jet expansion -Entrainment
Jet deflection -ImpingementFlashing
1. Homogeneous model• Gas phase is saturatedGas phase is saturated
• Massive dense gas release experiments ─ Validate modelling of the influence of massive
omplexit g
releases on the flow field ─ Burro & Coyote, Maplin Sands, REDIPHEM
ty
• Massive large-scale CO2 release experiments• Most realistic, ultimate validation case• Liaohe Oilfield in 2012 by DUT (WP2.2)
Criteria for a “good” dispersion model
• Model Evaluation Protocol2 (MEP) for LNG is the most comprehensive approach p pp
• The MEP contains a structure for complete model evaluation => all models would need to be validated against key experimental databe validated against key experimental data and is a key part of the model evaluation.
• The parameters compared are:• The parameters compared are:─ maximum concentration along an arc at a
given distance from the sourcel d idth l t i─ cloud width along an arc at a given
distance from the source─ concentrations at specific sensor locations─ temperature at specific sensor locations
• Statistical Performance Measures (SPM) criteria have to be met to pass the MEPp
• FLACS generally well within the acceptance criteria. ─ Obstructed Falcon tests challenging, source not well defined?
October 2011: US Department of Transportation accepted FLACS as first CFD tool for LNG studies (NFPA-59A)
CO2 stack releases (not focus in CO2PipeHaz)
CCS facilities need to send CO2 to stack from time to time• Dense gas, will fall to ground during low winds• May often contain toxic components (H2S, amines, …)• Integral models can not predict low winds or geometry / terrain
S f d i b f• «Safe design» can be very unsafe• CFD modeling can investigate challenges and find optimal measures
(change of design, fans, stack extension, heating …)( g g g )
Example 5 m/s wind, 3 m/s wind, 2 m/s wind and 1 m/s wind
Ground level concentrations 2 m/s, 1 m/s wind
Summary
• Dispersion analysis of both accidental and controlled releases will most likely be required in risk assessment y qstudies before a pipeline can transport CO2
• Massive releases of cold CO2 in obstructed areas enforce the need for transient 3D CFD simulationsthe need for transient 3D CFD simulations
• Validation is essential for software predicting dispersion used for risk assessmentsused for risk assessments
• FLACS has shown that it predict dispersion of LNG vapour within the MEP criteria
B tt d l d d f t bl l i d─ Better models are needed for very stable low-wind conditions and obstructed area
• Large-scale validation experiments for massive releases of CO2 are very important
Acknowledgements & Disclaimer
The research leading to the results described in this presentation has received funding from the Europeanpresentation 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 thereinof the information contained therein.
Modelling challenges
DNV RP-202: • In many assessments, integral models should provide acceptable
modelling capability, but in areas where the combined effects of topography, buildings, pits, etc. and the heavy gas properties of the released CO2 may have a significant effect on the exposure of people or livestock, more detailed simulations using advanced dispersion tools (e.g. Computational Fluid Dynamics (CFD)) h ld b id dshould be considered.