nd European Summer School on Hydrogen 2 nd European Summer School on Hydrogen 2 Safety Safety Belfast, 30 July – – August 8, 2007 August 8, 2007 Belfast, 30 July Risk Management and Hydrogen Safety Risk Management and Hydrogen Safety Andrei V. Tchouvelev Andrei V. Tchouvelev
Acknowledgement Acknowledgement Financial Support Presented research was supported in part by Natural Resources Canada through the activities of the Codes and Standards Working Group of the Canadian Transportation Fuel Cell Alliance, by the research performers, A.V.Tchouvelev & Associates Inc., TISEC Inc., and the Hydrogen Research and by the collaborating industrial partners 2 2
Concept of Risk Management Concept of Risk Management Risk management – coordinated activities to direct and control an organization with regard to risk. Risk management generally includes risk assessment, risk treatment, risk acceptance and risk communication . ISO / IEC Guide 73: 2002 3 3
Scope Scope Quantitative risk comparison of hydrogen and natural gas refuelling options Project Scope Sourcing Hydrogen Natural Gas Options Compressed Compressed Gas Delivery Gas Pipeline Reforming fuel On-Site comparison Generation scenario Electrolysis 4 4
Generic Station Configuration for QRA Generic Station Configuration for QRA The generic station consists (regardless of technology) of the following major components or “boxes”: 1. fuel delivery / on-site production (will also include purification for reformer technology); 2. compression; 3. storage; 4. dispensing / vehicle interface (vehicles themselves are excluded). 5 5
Qualitative RA – – TIAX FMEA Study TIAX FMEA Study Qualitative RA FMEA for Hydrogen Fueling Options, CEC-600-2005-001 Design Baseline Considerations: 6 6
Hazard Identification Hazard Identification Example of HazID analysis (via FMEA) for a electrolyser 7 7
Failure Scenarios Selection Failure Scenarios Selection Tube Trailer: • S1: Small horizontal leak during unloading • S2: Catastrophic horizontal leak during unloading Electrolyser: • S3: Catastrophic internal leak at hydrogen rinser • S4: Venting of catastrophic internal leak • S5: H2 Leak outdoors between compressor and storage Reformer: • S6 (and S9): NG supply line leak outdoors • S7: NG line leak between NG compressor and reformer • S8: Catastrophic internal leak at PSA unit CNG Station: • S10: CNG leak outdoors between compressor and storage Gas Storage: • S11: Horizontal jet release (H2 and CH4) at equal pressure and orifice • S12: Venting of H2 and CH4 at equal flow rate 8 8
Tube Trailer Failure Scenarios Tube Trailer Failure Scenarios Small leak via 1 mm orifice, 2640 psig: Catastrophic leak via ½” OD orifice, 2640 psig: LFL horizontal extent 4.26 m LFL horizontal extent 40.5 m 9 9
Electrolyser Failure Scenarios Electrolyser Failure Scenarios Hydrogen release and dispersion from a hydrogen rinser fitting through a ¾” opening at 10 bar 10 10
Electrolyser Failure Scenarios Electrolyser Failure Scenarios Hydrogen release and dispersion from a hydrogen rinser through a ¾” opening at 10 bar � Hydrogen release and dispersion: • Duration of sonic release – 0.7 sec • Total release duration – 1.0 sec • Quantity of released hydrogen – 0.5 Nm3 0.02 sec 1.0 sec 11 11
Outdoor Release Comparison Outdoor Release Comparison Release of H2 and CH4 outdoors between compressor and storage towards storage via 1 mm orifice, 4’ from storage Flame length 0.4 m Flame length 3.4 m H2 line flow 1.25 kg/h at 6000 psig CH4 line flow 18 kg/h at 4000 psig 12 12
Horizontal Jets Comparison Horizontal Jets Comparison Storage: hydrogen and CNG release and dispersion from a shut-off valve fitting through a ½” OD at 4125 psi • Leak orifice ½” OD, 8.48 mm ID • Leak direction/location: horizontal leak 1 m above the ground • Domain size: symmetric, 100m by 8 m by 25 m. • Water volume of cylinders: 2.811 m 3 • Initial stagnation pressure: 284.4 bars • Choked leak duration: H 2 : 80 sec , CH 4 : 240 sec • Simulation time: 0-90 sec for CH 4 , 0-60 sec for H 2 13 13
Steady state CFD results: H 2 vs. CH 4 Steady state CFD results: H 2 vs. CH 4 � Steady CFD results by PHOENICS 3.6.1 � Horizontal leak 1m above the ground, OD ½” (ID 8.48 mm) orifice � High pressure 284 bars � � � � H 2 : 43 m, CH 4 : 68 m 14 14
Transient CFD results: H 2 vs. CH 4 Transient CFD results: H 2 vs. CH 4 15 15
Natural Gas (CH4) Storage Venting Natural Gas (CH4) Storage Venting Venting (sonic and subsonic) of CH4 outdoors: 2,000 scfm, 9 m/s wind, LFL (5% vol.) profile – Fluent, RNG k-e Sonic, 1” orifice, LFL 1.8 m extent Subsonic, 3” orifice, LFL 4.8 m extent 16 16
Hydrogen Storage Venting Hydrogen Storage Venting Venting (sonic) of H2 outdoors: 2000 scfm, 9 m/s wind, LFL (4% vol.) profile – Fluent, RNG k-e Sonic, 1” orifice, LFL 5.5 m extent 17 17
Natural Gas (CH4) Storage Venting Natural Gas (CH4) Storage Venting Blow-off Velocities for H2 and CH4 (slide by C. Moen, SNL) 18 18
Jet Fire Thermal Radiative Flux Jet Fire Thermal Radiative Flux Model References � Y. R. Sivathanu and J. P. Gore, 1993. � W. Houf and R. Schefer (SNL), 2004-6. � Has been recently validated by SNL for free H 2 jet flames � T. Mogi et al (AIST), 2005. � Used for verification purposes � TNO “Yellow Book”, Part 2, p.6.48, 1997. � Used for vertical flares � Still needs to be validated for hydrogen 19 19
Tube Trailer Thermal Effects Tube Trailer Thermal Effects Scenario 1: � Small leak via 1 mm orifice, 2640 psig � LFL horizontal extent 4.26 m 20 20
Tube Trailer Thermal Effects Tube Trailer Thermal Effects Scenario 2: � Catastrophic leak via ½” OD orifice, 2640 psig � LFL horizontal extent 40.5 m 21 21
Storage Horizontal Jet Thermal Effects – – Storage Horizontal Jet Thermal Effects Methane Methane Scenario 11: � Catastrophic leak via 8.48 mm orifice at 282 bars from CNG storage system 22 22
Storage Horizontal Jet Thermal Effects – – Storage Horizontal Jet Thermal Effects Hydrogen Hydrogen Scenario 11: � Catastrophic leak via 8.48 mm orifice at 282 bars from H 2 storage system 23 23
Storage Venting Thermal Effects Storage Venting Thermal Effects Thermal Flux from CNG and H2 Storage Venting 24 24
Ignition Probabilities Approach Ignition Probabilities Approach Developed by DNV with input from AVT � Starting point – historical data review RELEASE RELEASE GAS CRUDE CLASS I CLASS II CLASS RATE RATE LEAK III CATEGORY (kg/s) Small < 1 0.010 0.010 0.006 0.004 0.002 Large 1 – 50 0.070 0.030 0.018 0.012 0.007 Massive > 50 0.300 0.080 0.049 0.031 0.018 Historical Ignition Probability Data for Hydrocarbons (Cox, Lees & Ang) 25 25
Ignition Probabilities Considerations Ignition Probabilities Considerations � All considered H2 leaks are less than 1 kg/s � Historically reported ratio of immediate to delayed ignition probability is 2 to 1 � What is realistic probability for H2 – 1% seems low � Key considerations in comparison with methane: � For a given mass leak, H2 would produce appr. 8 times bigger flammable cloud than methane (their LFL’s are close) Delayed ignition probability is proportional to the flammable � cloud size. Hence, 1 kg/s leak for methane is “equivalent” in volume to 0.125 kg/s for H2 � Though the flammable range of H2 (4 to 75% vol.) is 7.3 times greater than that of methane (5 to 15% vol.), for both gases the size of a cloud above 15 % vol. is about 16% of the total size of cloud above LFL 26 26
Ignition Probabilities Considerations Ignition Probabilities Considerations Minimum ignition energy vs H2 concentration in air As presented by M.Swain on May 24, 2004 Hydrogen Concentration Minimum Ignition Energy Required (mJ) 29% (stoicheometric) 0.02 10% 0.15 9% 0.21 8% 0.33 7% 0.56 6% 1.0 5% 3.0 4% 10.0 27 27
Adopted Ignition Probabilities Adopted Ignition Probabilities As proposed by DNV RELEASE HYDROGEN HYDROGEN HYDROGEN HYDROGEN RATE RELEASE TOTAL IMMEDIATE DELAYED CATEGORY RATE IGNITION IGNITION IGNITION (kg/s) PROBABILITY PROBABILITY PROBABILITY Small Leak < 0.125 0.012 0.008 0.004 Large Leak 0.125 – 6.25 0.08 0.053 0.027 Massive Leak > 6.25 0.35 0.23 0.12 Flammable H2 Not 1 - 1 gas mixture Applicable within closed systems 28 28
Frequencies & Probabilities Analysis – – Frequencies & Probabilities Analysis Fault and Event Trees Fault and Event Trees Example: Scenario 1 Tube Trailer Small Leak 29 29
Risk Estimation Risk Estimation Risk Metrics � Location Specific Individual Risk (LSIR) where the summation is extended for all scenarios and: Fs is the frequency of the scenario S P F is the probability of death in the scenario for an individual at the location The frequency of the scenario is taken as: where F O is the end outcome frequency calculated from the post-incident event trees with the formula: where F i , is the failure frequency of the initiating event for the scenario calculated using a fault tree analysis P b is the probability of an individual segment of the event tree such as probability of immediate ignition or probability of delayed ignition 30 30 30
Recommend
More recommend
