Safety
Single Step Compact Steam Methane Reforming Process for Hydrogen-Cng (H-Cng) Production from Natural Gas
Sep 2011
Publication
Compressed natural gas (CNG) is being increasingly used as a clean transportation fuel. However for further reduction in emissions particularly NOx H-CNG mixture with ~ 20 % hydrogen is recommended. Presently most of the H-CNG mixture is produced by blending hydrogen with CNG. For hydrogen production Steam Methane Reforming (SMR) is a major process accounting for more than 90% of hydrogen production by various industries. In this process natural gas is first reformed to syn gas under severe operating conditions (Pressure 20-30 bar temperature 850-950 deg C) followed by conversion of CO to hydrogen in the shift reactor. Other method of hydrogen production such as electrolysis of water is more expensive. Further there are issues of safety with handling of hydrogen its storage and transportation for blending. In order to overcome these problems a single step compact process for the production of H-CNG gaseous mixture through low severity steam methane reforming of natural gas has been developed. It employs a catalyst containing nickel nickel oxide magnesium oxide and silica and has the capability of producing H-CNG mixture in the desired proportion containing 15-20 vol % hydrogen with nil CO production. The process is flexible and rugged allowing H-CNG production as per the demand. The gaseous H-CNG product mixture can directly be used as automobile fuel after compression. The process can help as important step in safe transition towards hydrogen economy. A demonstration unit is being set up at IOC R&D Centre.
Implementation of Large Scale Shadowgraphy in Hydrogen Safety Phenomena
Sep 2013
Publication
We have implemented a portable large-scale shadowgraph system for use in flow visualization relating to hydrogen safety. Previous large-scale shadowgraph and schlieren implementations have often been limited to background- oriented techniques which are subject to noise. The system built is based on a large-scale shadowgraph technique developed by Settles which allows for high-quality visualization. We have applied the shadowgraph system to complex phenomena and current issues in hydrogen safety including DDT in long channels jet releases and unconfined deflagrations. Shadowgrams taken are compared to a Z-schlieren system. This shadowgraph system allows analysis of these phenomena at longer length scales.
Experimental Study on Hydrogen/Air Premixed Flame Propagation in Closed Rectangular Channels
Sep 2019
Publication
An experimental study of hydrogen/air premixed flame propagation in a closed rectangular channel with the inhibitions (N2 or CO2) was conducted to investigate the inhibiting effect of N2 and CO2 on the flame properties during its propagation. Both Schlieren system and the pressure sensor were used to capture the evolution of flame shape and pressure changes in the channel. It was found that both N2 and CO2 have considerable inhibiting effect on hydrogen/air premixed flames. Compared with N2 CO2 has more prominent inhibition which has been interpreted from thermal and kinetic standpoints. In all the flames the classic tulip shape was observed. With different inhibitor concentration the flame demonstrated three types of deformation after the classic tulip inversion. A simple theoretical analysis has also been conducted to indicate that the pressure wave generated upon the first flame-wall contact can affect the flame deformation depending on its meeting moment with the flame front. Most importantly the meeting moment is always behind the start of tulip inversion which suggests the non-dominant role of pressure wave on this featured phenomenon.
Hydrogen-Air Explosive Envelope Behaviour in Confined Space at Different Leak Velocities
Sep 2009
Publication
The report summarizes experimental results on the mechanisms and kinetics of hydrogen-air flammable gas cloud formation and evolution due to foreseeable (less than 10-3 kg/sec) hydrogen leaks into confined spaces with different shapes sizes and boundary conditions. The goals were - 1) to obtain qualitative information on the basic gas-dynamic patterns of flammable cloud formation at different leak velocities (between 935 and 905 m/sec) for a fixed leak flowrate and 2) to collect quantitative data on spatial and temporal characteristics of the revealed patterns. Data acquisition was performed using a spatially distributed reconfigurable net of 24 hydrogen gauges with short response time. This experimental innovation permits to study spatial features of flammable cloud evolution in detail which previously was attainable only from CFD computations. Two qualitatively different gas dynamic patterns were documented for the same leak flowrate. In one limiting case (sufficiently low speed of leak) the overall gas-dynamic pattern can be described by the well-known “filling box” model. In another limited case (high velocity of leak) it is proposed to describe the peculiarities of gas-dynamic behavior of flammable cloud by the term of a “fading up box” model. From the safety view point the “fading up box” case is more hazardous than the “filling box” case. Differences in macroscopic and kinetic behavior which are essential for safety provision are presented. Empirical non-dimensional criterion for discrimination of the two revealed basic patterns for hydrogen leaks into confined spaces with comparable length scale is proposed. The importance of the revealed “fading up box” gas-dynamic pattern is discussed for development of an advanced hydrogen gauges system design and safety criteria.
Hydrogen Explosions in 20’ ISO Container
Oct 2015
Publication
This paper describes a series of explosion experiments in inhomogeneous hydrogen air clouds in a standard 20′ ISO container. Test parameter variations included nozzle configuration jet direction reservoir back pressure time of ignition after release and degree of obstacles. The paper presents the experimental setup resulting pressure records and high speed videos. The explosion pressures from the experiments without obstacles were in the range of 0.4–7 kPa. In the experiments with obstacles the gas exploded more violently producing pressures in order of 100 kPa.
Turbulent Flame Propagation in Large Unconfined H2/O2/N2 Clouds
Oct 2015
Publication
Turbulence is a key aspect in hydrogen explosions. Unfortunately only limited experimental data is available and the current understanding of flame turbulence interactions is too limited to permit safe predictions. New experimental data are presented in which the flame trajectory and pressure history are interpreted for unconfined explosions of H2/O2/N2 clouds of 7 m3. The intensity of the turbulence is varied between 0 and 5 m/s and the integral scale of the turbulence is on the order of 10 cm which is at least an order of magnitude larger than lab scale.
Modelling of Hydrogen Jet Fires Using CFD
Sep 2011
Publication
The computational fluid dynamics (CFD) software FLACS has primarily been developed to model dispersion and explosion phenomena; however models for the simulation of jet fires are under development. The aim is to be able to predict industrial fires efficiently and with good precision. Newly developed models include e.g. flame models for non-premixed flames discrete transfer radiation model as well as soot models. Since the time scales for fire simulations are longer than for explosions the computational speed is important. The recent development of non-compressible and parallel solvers in FLACS may therefore be important to ensure efficiency. Hydrogen flames may be invisible will generate no soot and tend to radiate less than hydrocarbon fuels. Due to high pressure storage the flame lengths can be significant. Simpler jet flame relations can not predict the jet flame interaction with objects and barriers and thus the heat loads on impacted objects. The development of efficient and precise CFD-tools for hydrogen fires is therefore important. In this paper the new models for the simulation of fire are described. These models are currently under development and this manuscript describes the current status of the work. Jet fire experiments performed by Health and Safety Laboratories (HSL) both free jets and impinging jets will also be simulated to evaluate the applicability and validity of the new fire models.
Modelling Heat Transfer in an Intumescent Paint and its Effect on Fire Resistance of On-board Hydrogen Storage
Oct 2015
Publication
This paper describes a 1-D numerical model for the prediction of heat and mass transfer through an intumescent paint that is applied to an on-board high-pressure GH2 storage tank. The intumescent paint is treated as a composite system consisting of three general components decomposing in accordance with independent finite reaction rates. A moving mesh that is employed for a better prediction of the expansion process of the intumescent paint is based on the local changes of heat and mass. The numerical model is validated against experiments by Cagliostro et al. (1975). The overall model results are used to estimate effect of intumescent paint on fire resistance of carbon-fibre reinforced GH2 storage.
Effect of the Position and the Area of the Vent on the Hydrogen Dispersion in a Naturally Ventilated Cubiod Space with One Vent on the Side Wall
Dec 2021
Publication
The design of ventilation system has implications for the safety of life and property and the development of regulations and standards in the space with the hydrogen storage equipment. The impact of both the position and the area of a single vent on the dispersion of hydrogen in a cuboid space (with dimensions L x W x H ¼ 2.90 0.74 1.22 m) is investigated with Computational Fluid Dynamics (CFD) in this study. Nine positions of the vent were compared for the leakage taking place at the floor to understand the gas dispersion. It was shown a cloud of 1% mole fraction has been formed near the ceiling of the space in less than 40 s for different positions of the vent which can activate hydrogen sensors. The models show that the hydrogen is removed more effectively when the vent is closer to the leakage position in the horizontal direction. The study demonstrates that the vent height of 1.00 m is safer for the particular scenario considered. The area of the vent has little effect on the hydrogen concentration for all vent positions when the area of the vent is less than 0.045 m2 and the height of the vent is less than 0.61 m.
Safe Hydrogen Fuel Handling and Use for Efficient Implementation – SH2IFT
Sep 2019
Publication
The SH2IFT project combines social and technical scientific methods to address knowledge gaps regarding safe handling and use of gaseous and liquid hydrogen. Theoretical approaches will be complemented by fire and explosion experiments with emphasis on topics of strategic importance to Norway such as tunnel safety maritime applications etc. Experiments include Rapid Phase Transition Boiling Liquid Expanding Vapour Explosion and jet fires. This paper gives an overview of the project and preliminary results.
Comparative Study of Regulations, Codes and Standards and Practices on Hydrogen Fuelling Stations
Oct 2015
Publication
This work deals with a comparative study of regulations codes and standards for hydrogen fuelling station dedicated for light duty land vehicles in the following countries: United States (California) United Kingdom Italy Germany Canada Sweden Norway Denmark and Spain.<br/>The following technical components of a hydrogen fuelling station are included in the scope of the study: the hydrogen storage systems (cryogenic or compressed gases) and buffer storage the compressor stations the high pressure buffer storage the cooling systems for hydrogen the dispensing equipments and the dispensing area. The hydride storage the pipelines on site production and the hydrogen vehicle have been excluded.<br/>The analysis performed in September 2014 in a report from INERIS DRA-14-141532-06227C BENCHMARK STATIONS-SERVICE HYDROGENE is based on documents collected by bibliographic review and information obtained through a questionnaire sent to authorities and IA HySafe members in the above mentioned countries.<br/>This paper gives a synthesis of the regulations and on permitting process in the different studied countries (including the new European Directive on the deployment of alternative fuels infrastructure in Europe) it develops the required safety barriers in the different parts of a fuelling station and specially for the dispensing area gives an overview of the different approaches for safety distances and processes to obtain licences to operate.
Hydrogen Effects on X80 Pipeline Steel Under High-pressure Natural Gas & Hydrogen Mixtures
Oct 2015
Publication
Blending hydrogen into existing natural gas pipelines has been proposed as a means of increasing the output of renewable energy systems such as large wind farms. X80 pipeline steel is commonly used for transporting natural gas and such steel is subjected to concurrent hydrogen invasion with mechanical loading while being exposed to hydrogen containing environments directly resulting in hydrogen embrittlement (HE). In accordance with American Society for Testing and Materials (ASTM) standards the mechanical properties of X80 pipeline steel have been tested in natural gas/hydrogen mixtures with 0 5.0 10.0 20.0 and 50.0vol% hydrogen at the pressure of 12 MPa. Results indicate that X80 pipeline steel is susceptible to hydrogen-induced embrittlement in natural gas/hydrogen mixtures and the HE susceptibility increases with the hydrogen partial pressure. Additionally the HE susceptibility depends on the textured microstructure caused by hot rolling especially for the notch specimen. The design calculation by the measured fatigue data reveals that the fatigue life of the X80 steel pipeline is dramatically degraded by the added hydrogen.
Experimental Investigation of Hydrogen Release and Ignition from Fuel Cell Powered Forklifts in Enclosed Spaces
Sep 2011
Publication
Due to rapid growth in the use of hydrogen powered fuel cell forklifts within warehouse enclosures Sandia National Laboratories has worked to develop scientific methods that support the creation of new hydrogen safety codes and standards for indoor refuelling operations. Based on industry stakeholder input conducted experiments were devised to assess the utility of modelling approaches used to analyze potential consequences from ignited hydrogen leaks in facilities certified according to existing code language. Release dispersion and combustion characteristics were measured within a scaled test facility located at SRI International's Corral Hollow Test Site. Moreover the impact of mitigation measures such as active/passive ventilation and pressure relief panels was investigated. Since it is impractical to experimentally evaluate all possible facility configurations and accident scenarios careful characterization of the experimental boundary conditions has been performed so that collected datasets can be used to validate computational modelling approaches.
Numerical Simulation of the Helium Dispersion in a Semi-confined Air-filled Cavity
Sep 2013
Publication
This paper deals with the build-up of concentration when a continuous source of helium is supplied in an air-filled enclosure. Our aim is to reproduce the results of a small-scale experimental study. To begin with the size of the experiment is reduced from 1/10 to 3/5 for the present analysis. Hypotheses are made in order to reduce the dimension of the real problem. Numerical simulations are carried out on fine grids without any turbulence modelling. The flow structure and the concentration profile of the resulting flow are analyzed and compared with theoretical results.
Homogeneous and Inhomogeneous Hydrogen Deflagrations in 25 m3 Enclosure
Sep 2019
Publication
Explosion venting is a frequently used measure to mitigate the consequence of gas deflagrations in closed environments. Despite the effort to predict the vent area needed to achieved the protection through engineering formulas and CFD tools work has still to be done to reliably predict the outcome of a vented gas explosion. Most of available data derived from experimental campaigns performed in the past involved homogeneous conditions while especially in the case of a very buoyant gas such as hydrogen the most probable scenario that can follow and unintended release in a closed environment foresee the ignition of a stratified inhomogeneous mixture. University of Pisa performed experimental tests in a 25 m3 facility in homogeneous and inhomogeneous conditions. The present paper is aimed to share the results of hydrogen dispersion and deflagration tests and discuss the comparison of maximum peak overpressure generated in the two scenarios. Description of the experimental set-up includes all the details deemed necessary to reproduce the phenomenon with a CFD tool.
Ignitability and Mixing of Underexpanded Hydrogen Jets
Sep 2011
Publication
Reliable methods are needed to predict ignition boundaries that result from compressed hydrogen bulk storage leaks without complex modelling. To support the development of these methods a new high-pressure stagnation chamber has been integrated into Sandia National Laboratories’ Turbulent Combustion Laboratory so that relevant compressed gas release scenarios can be replicated. For the present study a jet with a 10:1 pressure ratio issuing from a small 0.75 mm radius nozzle has been examined. Jet exit shock structure was imaged by Schlieren photography while quantitative Planar Laser Rayleigh Scatter imaging was used to measure instantaneous hydrogen mole fractions downstream of the Mach disk. Measured concentration statistics and ignitable boundary predictions compared favorably to analytic reconstructions of downstream jet dispersion behaviour. Model results were produced from subsonic jet dispersion models and by invoking self-similarity jet scaling arguments with length scaling by experimentally measured effective source radii. Similar far field reconstructions that relied on various notional nozzle models to account for complex jet exit shock phenomena failed to satisfactorily predict the experimental findings. These results indicate further notional nozzle refinement is needed to improve the prediction fidelity. Moreover further investigation is required to understand the effect of different pressure ratios on measured virtual origins used in the jet dispersion model.
Simulation of Thermal Radiation from Hydrogen Under-expanded Jet Fire
Sep 2017
Publication
Thermal hazards from an under-expanded (900 bar) hydrogen jet fire have been numerically investigated. The simulation results have been compared with the flame length and radiative heat flux measured for the horizontal jet fire experiment conducted at INERIS. The release blowdown characteristics have been modelled using the volumetric source as an expanded implementation of the notional nozzle concept. The CFD study employs the realizable k-ε model for turbulence and the Eddy Dissipation Concept for combustion. Radiation has been taken into account through the Discrete Ordinates (DO) model. The results demonstrated good agreement with the experimental flame length. Performance of the model shall be improved to reproduce the radiative properties dynamics during the first stage of the release (time < 10 s) whereas during the remaining blowdown time the simulated radiative heat flux at five sensors followed the trend observed in the experiment.
Experimental Results on The Dispersion of Buoyant Gas in a Full Scale Garage from a Complex Source
Sep 2009
Publication
The lack of experimental data on hydrogen dispersion led to the experimental project DRIVE (Experimental Data for Hydrogen Automotive Risks Assessment for the validation of numerical tools and for the Edition of guidelines) that involves the CEA (French Atomic Energy Commission) the National Institute of Industrial Environment and Risks (INERIS) the French car manufacturer PSA PEUGEOT CITROËN and the Research Institute on Out of Equilibrium Phenomena (IRPHE). The CEA has developed an experimental setup named GARAGE in order to analyze the condition of formation of an explosive atmosphere in an enclosure. This is a full scale facility in which a real car can be parked. Hydrogen releases were simulated with helium which volume fraction was measured with mini-katharometers. These thermal conductivity probes allow spatial and time volume fraction variations measurements. We present experimental results on the dispersion of helium in the enclosure due to releases in a typical car. The tested parameters are the location of the source (engine bottom of the car storage) and the flow rate. Emphasis is put on the influence of these parameters on the time evolution of the volume fraction in the enclosure as well as on the vertical distribution of helium.
Measurements of Flow Velocity and Scalar Concentration in Turbulent Multi-component Jets
Sep 2017
Publication
Buoyancy effects and nozzle geometry can have a significant impact on turbulent jet dispersion. This work was motivated by applications involving hydrogen. Using helium as an experimental proxy buoyant horizontal jets issuing from a round orifice on the side wall of a circular tube were analyzed experimentally using particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) techniques simultaneously to provide instantaneous and time-averaged flow fields of velocity and concentration. Effects of buoyancy and asymmetry on the resulting flow structure were studied over a range of Reynolds numbers and gas densities. Significant differences were found between the centreline trajectory spreading rate and velocity decay of conventional horizontal round axisymmetric jets issuing through flat plates and the pipeline leak-representative jets considered in the present study. The realistic pipeline jets were always asymmetric and found to deflect about the jet axis in the near field. In the far field it was found that the realistic pipeline leak geometry causes buoyancy effects to dominate much sooner than expected compared to horizontal round jets issuing through flat plates.
Hydrogen Fueling Standardization: Enabling ZEVs with "Same as Today" Fueling and FCEV Range and Safety
Oct 2015
Publication
Zero Emission Vehicles (ZEVs) are necessary to help reduce the emissions in the transportation sector which is responsible for 40% of overall greenhouse gas emissions. There are two types of ZEVs Battery Electric Vehicles (BEVs) and Fuel Cell Electric Vehicles (FCEVs) Commercial Success of BEVs has been challenging thus far also due to limited range and very long charging duration. FCEVs using H2 infrastructure with SAE J2601 and J2799 standards can be consistently fuelled in a safe manner fast and resulting in a range similar to conventional vehicles. Specifically fuelling with SAE J2601 with the SAE J2799 enables FCEVs to fill with hydrogen in 3-5 minutes and to achieve a high State of Charge (SOC) resulting in 300+ mile range without exceeding the safety storage limits. Standardized H2 therefore gives an advantage to the customer over electric charging. SAE created this H2 fuelling protocol based on modelling laboratory and field tests. These SAE standards enable the first generation of commercial FCEVs and H2 stations to achieve a customer acceptable fueling similar to today's experience. This report details the advantages of hydrogen and the validation of H2 fuelling for the SAE standards.
PIV-measurements of Reactant Flow in Hydrogen-air Explosions
Sep 2017
Publication
The paper present the work on PIV-measurements of reactant flow velocity in front of propagating flames in hydrogen-air explosions. The experiments was performed with hydrogen-air mixture at atmospheric pressure and room temperature. The experimental rig was a square channel with 45 × 20 mm2 cross section 300 mm long with a single cylindrical obstacle of blockage ratio 1/3. The equipment used for the PIV-measurements was a Firefly diode laser from Oxford lasers Photron SA-Z high-speed camera and a particle seeder producing 1 μm droplets of water. The gas concentrations used in the experiments was 14 and 17 vol% hydrogen in air. The resulting explosion can be characterized as slow since the maximum flow velocity of the reactants was 13 m/s in the 14% mixture and 23 m/s in the 17% mixture. The maximum flow velocities was measured during the flame-vortex interaction and at two obstacle diameters behind the obstacle. The flame-vortex interaction contributed to the flame acceleration by increasing the overall reaction rate and the flow velocity. The flame area as a function of position is the same for both concentrations as the flame passes the obstacle.
CO2-Free Hydrogen Supply Chain Project and Risk Assessment for the Safety Design
Sep 2013
Publication
We at Kawasaki Heavy Industries have proposed a "CO2-Free H2 supply chain" using abundant brown coal of Australian origin as the energy source. This chain will store CO2 generated during the process for producing hydrogen from brown coal in a project (Carbon Net) that the Australia Government is promoting. Thus Japan can import CO2-free hydrogen. The supply chain consists of the hydrogen production system the hydrogen transport/storage system and the hydrogen use system. Related to their designs we have to consider their hazards polluted scenarios and safety measures via a safety assessment process that is compliant with international risk assessment standards. To verify safety designs related experiments and analyses will be conducted. This paper describes the approach to safety design for especially the related liquid hydrogen facilities.
Influence of Pressure and Temperature on the Fatigue Strength of Type-3 Compressed-hydrogen Tanks
Sep 2011
Publication
The pressure of compressed hydrogen changes with temperature when mass and volume are constant. Therefore when a compressed-hydrogen tank is filled with a certain amount of hydrogen it is necessary to adjust the filling pressure according to the gas temperature. In this study we conducted hydraulic pressure-cycle tests to investigate the fatigue life of Type-3 compressed-hydrogen tanks when environmental temperature and filling pressure are changed. The results indicated that the fatigue life at low temperatures (−40 °C 28 MPa) and room temperature (15 °C 35 MPa) was almost equal. However the fatigue life at high temperatures (85 °C 44 MPa) was shorter than that under other conditions suggesting that stress changes caused by thermal stress affect the fatigue life of the Type-3 tank.
Overview of the DOE Hydrogen Safety, Codes and Standards Program Part 3- Advances in Research and Development to Enhance the Scientific Basis for Hydrogen Regulations, Codes and Standards
Oct 2015
Publication
Hydrogen fuels are being deployed around the world as an alternative to traditional petrol and battery technologies. As with all fuels regulations codes and standards are a necessary component of the safe deployment of hydrogen technologies. There has been a focused effort in the international hydrogen community to develop codes and standards based on strong scientific principles to accommodate the relatively rapid deployment of hydrogen-energy systems. The need for science-based codes and standards has revealed the need to advance our scientific understanding of hydrogen in engineering environments. This brief review describes research and development activities with emphasis on scientific advances that have aided the advancement of hydrogen regulations codes and standards for hydrogen technologies in four key areas: (1) the physics of high-pressure hydrogen releases (called hydrogen behaviour); (2) quantitative risk assessment; (3) hydrogen compatibility of materials; and (4) hydrogen fuel quality.
Pressure Limit of Hydrogen Spontaneous Ignition in a T-shaped Channel
Sep 2011
Publication
This paper describes a large eddy simulation model of hydrogen spontaneous ignition in a T-shaped channel filled with air following an inertial flat burst disk rupture. This is the first time when 3D simulations of the phenomenon are performed and reproduced experimental results by Golub et al. (2010). The eddy dissipation concept with a full hydrogen oxidation in air scheme is applied as a sub-grid scale combustion model to enable use of a comparatively coarse grid to undertake 3D simulations. The renormalization group theory is used for sub-grid scale turbulence modelling. Simulation results are compared against test data on hydrogen release into a T-shaped channel at pressure 1.2–2.9 MPa and helped to explain experimental observations. Transitional phenomena of hydrogen ignition and self-extinction at the lower pressure limit are simulated for a range of storage pressure. It is shown that there is no ignition at storage pressure of 1.35 MPa. Sudden release at pressure 1.65 MPa and 2.43 MPa has a localised spot ignition of a hydrogen-air mixture that quickly self-extinguishes. There is an ignition and development of combustion in a flammable mixture cocoon outside the T-shaped channel only at the highest simulated pressure of 2.9 MPa. Both simulated phenomena i.e. the initiation of chemical reactions followed by the extinction and the progressive development of combustion in the T-shape channel and outside have provided an insight into interpretation of the experimental data. The model can be used as a tool for hydrogen safety engineering in particular for development of innovative pressure relief devices with controlled ignition.
Study of Potential Leakage on Several Stressed Fittings for Hydrogen Pressures Up To 700 Bar
Sep 2011
Publication
In order to improve risk analyses and influence the design of the future H2 systems an experimental study on “real” leaks qualification and quantification was performed. In H2 energy applications fittings appeared as a significant leakage potential and subsequently explosion and flame hazards. Thus as a part of the “Horizon Hydrogène Energie” French program four kinds of commercial fittings usually employed on H2 systems were tested thanks to a new high pressure test bench – designed setup and operated by INERIS – allowing experiments to be led for H2 pressures until 700 bar. The fittings underwent defined stresses representative of H2 systems lifetime and beyond. The associated leaks – when existing – are characterized in terms of flow rate.
Catalysts for Hydrogen Removal: Kinetic Paradox and Functioning at High Concentration of Hydrogen
Sep 2009
Publication
Platinum metals dispersed on a porous carrier e.g. -Al2O3 are used as catalysts for removal of small amounts of hydrogen from the air where the excess of oxygen is significant.<br/>The recombination reaction of H2 and O2 on smooth platinum proceeds at a high rate only in gas mixes with an excess of hydrogen. When the concentration of oxygen exceeds that of hydrogen in terms of stoichiometric ratio the process slows down sharply and eventually stops completely. In research undertaken at the Karpov Institute of Physical Chemistry (Moscow) forty years ago the electrochemical mechanism of red-ox reactions was proposed as an explanation for this inhibition by excess oxygen. The results of ellipsometric analysis pointed to the formation of a protective monolayer of PtO molecules on the Pt surface in an oxygen-rich atmosphere. It was observed that the recombination reaction proceeds at a high rate with the use of a porous catalyst at any concentrations of reactant gases. The reason for that lies in the mechanism of the catalysis: the reaction proceeds at a certain depth in the porous body of the catalyst. Hydrogen which has higher mobility penetrates in larger quantity than oxygen thus creating there the stoichiometric excess. To test the proposed mechanism of recombination the catalytic reaction was studied ) with porous carriers of various thicknesses and b) with metal grids of various porosities covering the catalyst. The data obtained have confirmed unequivocally the earlier hypothesis of hydrogenation of a porous catalyst.<br/>Such insight has allowed the authors to develop more effective prototypes of catalyst for removal of hydrogen. In particular by using a porous grid cover to remove excess heat in the reaction zone of the catalyst plate we achieved a considerable expansion of the region of hydrogen concentrations where the catalyst is both effective and reliable.
Blast Wave from Hydrogen Storage Rupture in a Fire
Oct 2015
Publication
This study addresses one of knowledge gaps in hydrogen safety science and engineering i.e. a predictive model for calculation of deterministic separation distances defined by the parameters of a blast wave generated by a high-pressure gas storage tank rupture in a fire. An overview of existing methods to calculate stored in a tank internal (mechanical) energy and a blast wave decay is presented. Predictions by the existing technique and an original model developed in this study which accounts for the real gas effects and combustion of the flammable gas released into the air (chemical energy) are compared against experimental data on high-pressure hydrogen tank rupture in the bonfire test. The main reason for a poor predictive capability of the existing models is the absence of combustion contribution to the blast wave strength. The developed methodology is able to reproduce experimental data on a blast wave decay after rupture of a stand-alone hydrogen tank and a tank under a vehicle. In this study the chemical energy is dynamically added to the mechanical energy and is accounted for in the energy-scaled non-dimensional distance. The fraction of the total chemical energy of combustion released to feed the blast wave is 5% and 9% however it is 1.4 and 30 times larger than the mechanical energy in the stand-alone tank test and the under-vehicle tank test respectively. The model is applied as a safety engineering tool to four typical hydrogen storage applications including onboard vehicle storage tanks and a stand-alone refuelling station storage tank. Harm criteria to people and damage criteria for buildings from a blast wave are selected by the authors from literature to demonstrate the calculation of deterministic separation distances. Safety strategies should exclude effects of fire on stationary storage vessels and require thermal protection of on-board storage to prevent dangerous consequences of high-pressure tank rupture in a fire.
CFD and VR for Risk Communication and Safety Training
Sep 2011
Publication
There are new safety challenges with an increased use of hydrogen e.g. that people may not see dangerous jet flames in case of an incident. Compared to conventional fuels hydrogen has very different characteristics and physical properties and is stored at very high pressure or at very low temperatures. Thus the nature of hazard scenarios will be very different. Consequence modelling of ventilation releases explosions and fires can be used to predict and thus understand hazards. In order to describe the detailed development of a hazard scenario and evaluate ways of mitigation 3D Computational Fluid Dynamics (CFD) models will be required. Even with accurate modelling the communication of risk can be challenging. For this visualization in virtual reality (VR) may be of good help in which the CFD model predictions are presented in a realistic 3D environment with the possibility to include sounds like noise from a high pressure release explosion or fire. In cooperation with Statoil Christian Michelsen Research (CMR) and GexCon have developed the VRSafety application. VRSafety can visualize simulation results from FLACS (and another CFD-tool KFX) in an immersive VR-lab or on a PC. VRSafety can further be used to interactively control and start new CFD-simulations during the sessions. The combination of accurate CFD-modelling visualization and interactive use through VRSafety represents a powerful toolbox for safety training and risk communication to first-responders employees media and other stakeholders. It can also be used for lessons learned sessions studying incidents and accidents and to demonstrate what went wrong and how mitigation could have prevented accidents from happening. This paper will describe possibilities with VRSafety and give examples of use.
A Comparison Exercise on the CFD Detonation Simulation in Large Scale Confined Volumes
Sep 2009
Publication
The use of hydrogen as an energy carrier is going to widen exponentially in the next years. In order to ensure the public acceptance of the new fuel not only the environmental impact has to be excellent but also the risk management of its handling and storage must be improved. As a part of modern risk assessment procedure CFD modeling of the accident scenario development must provide reliable data on the possible pressure loads resulted from explosion processes. The expected combustion regimes can be ranged from slow flames to deflagration-to-detonation transition and even to detonation. In the last case the importance of the reliability of simulation results is particularly high since detonation is usually considered as a worst case state of affairs. A set of large-scale detonation experiments performed in Kurchatov Institute at RUT facility was selected as benchmark. RUT has typical industry-relevant characteristic dimensions. The CFD codes possibilities to correctly describe detonation in mixtures with different initial and boundary conditions were surveyed. For the modeling two detonation tests HYD05 and HYD09 were chosen; both tests were carried out in uniform hydrogen/air mixtures; first one with concentration of 20.0% vol. and the second one with 25.5% vol. In the present exercise three CFD codes using a number of different models were used to simulate these experiments. A thorough inter-comparison between the CFD results including codes models and obtained pressure predictions was carried out and reported. The results of this inter comparison should provide a solid basis for the further code development and detonation models’ validation thus improving CFD predictive capabilities.
Safety Distances: Comparison of the Methodologies for Their Determination
Sep 2011
Publication
In this paper a study on the comparison between the different methodologies for the determination of the safety distances proposed by Standard Organizations and national Regulations is presented. The application of the risk-informed approach is one of the methodologies used for the determination of safety distances together with the risk-based approach. One of the main differences between the various methodologies is the risk criterion chosen. In fact a critical point is which level of risk should be used and then which are the harm events that must be considered. The harm distances are evaluated for a specified leak diameter that is a consequence of some parameters used in the various methodologies. The values of the safety distances proposed by Standard Organizations and national Regulations are a demonstration of the different approaches of the various methodologies especially in the choice of the leak diameter considered.
Detection of Hydrogen Released In a Full-Scale Residential Garage
Sep 2011
Publication
Experiments were conducted to assess detectability of a low-level leak of hydrogen gas and the uniformity of hydrogen concentration at selected sensor placement locations in a realistic setting. A 5%2hydrogen/95%2nitrogen gas mixture was injected at a rate of 350 L/min for about 3/4 hour into a 93m3 residential garage space through a 0.09 m2 square open-top dispersion box located on the floor. Calibrated catalytic sensors were placed on ceiling and wall locations and the sensors detected hydrogen early in the release and continued to measure concentrations to peak and diminishing levels. Experiments were conducted with and without a car parked over the dispersion box. The results show that a car positioned over the dispersion box tends to promote dilution of the hydrogen cause a longer time for locations to reach a fixed threshold and produce lower peak concentrations than with no car present.
Numerical Investigation of a Mechanical Device Subjected to a Deflagration-to-detonation Transition
Sep 2011
Publication
In this work we evaluate the consequences of the combustion of a stoichiometric mixture of hydrogen-air on a mechanical device which can be considered as a long tube. In order to choose the most dangerous combustion regime for the mechanical device we devote a particular attention to the investigation of the 1D deflagration-to-detonation transition. Then once established the most dangerous combustion regime we compute the reacting flow and the stress and strain in the mechanical device. Analyses are performed using both semi-analytical solutions and Europlexus a computer program for the simulation of fluid-structure systems under transient dynamic loading.
Analysis of Transient Supersonic Hydrogen Release, Dispersion and Combustion
Sep 2017
Publication
A hydrogen leak from a facility which uses highly compressed hydrogen gas (714 bar 800 K) during operation was studied. The investigated scenario involves supersonic hydrogen release from a 10 cm2 leak of the pressurized reservoir turbulent hydrogen dispersion in the facility room followed by an accidental ignition and burn-out of the resulting H2-air cloud. The objective is to investigate the maximum possible flame velocity and overpressure in the facility room in case of a worst-case ignition. The pressure loads are needed for the structural analysis of the building wall response. The first two phases namely unsteady supersonic release and subsequent turbulent hydrogen dispersion are simulated with GASFLOW-MPI. This is a well validated parallel all-speed CFD code which solves the compressible Navier-Stokes equations and can model a broad range of flow Mach numbers. Details of the shock structures are resolved for the under-expanded supersonic jet and the sonic-subsonic transition in the release. The turbulent dispersion phase is simulated by LES. The evolution of the highly transient burnable H2-air mixture in the room in terms of burnable mass volume and average H2-concentration is evaluated with special sub-routines. For five different points in time the maximum turbulent flame speed and resulting overpressures are computed using four published turbulent burning velocity correlations. The largest turbulent flame speed and overpressure is predicted for an early ignition event resulting in 35–71 m/s and 0.13–0.27 bar respectively.
Component Availability Effects for Pressure Relief Valves Used at Hydrogen Fueling Stations
Sep 2017
Publication
There are times in engineering when it seems that safety and equipment cost reduction are conflicting priorities. This could be the case for pressure relief valves and vent stack sizing. This paper explores the role that component availability (particularly variety in flow and orifice diameters) plays in the engineer’s decision of a relief valve. This paper outlines the guidelines and assumptions in sizing and selecting pressure relief devices (PRDs) found in a typical high pressure hydrogen fueling station. It also provides steps in sizing the station common vent stack where the discharge gas is to be routed to prior being released into the atmosphere. This paper also explores the component availability landscape for hydrogen station designers and identifies opportunities for improvement in the supply chain of components as hydrogen fueling stations increase in number and size. American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section VIII (ASME BPVC Section VIII) Compressed Gas Association S-1.3 (CGA S-1.3) and American Petroleum Institute 520 (API 520) standards provide specific design criteria for hydrogen pressure relief valves. Results of these calculations do not match the available components. The available safety relief valves are 50 to 87 times larger than the required calculated flow capacities. Selecting a significantly oversized safety relief valve affects the vent stack design as the stack design requires sizing relative to the actual flowrate of the safety relief valve. The effect on the vent stack size in turn negatively affects site safety radiation threshold set back distances.
Numerical Simulations of a Large Hydrogen Release in a Process Plant
Sep 2009
Publication
This paper describes a series of numerical simulations with release and ignition of hydrogen. The objective of this work was to re-investigate the accidental explosion in an ammonia plant which happened in Norway in 1985 with modern CFD tools. The severe hydrogen-air explosion led to two fatalities and complete destruction of the factory building where the explosion occurred. A case history of the accident was presented at the 1.st ICHS in Pisa 2005.<br/>The numerical simulations have been performed with FLACS a commercial CFD simulation tool for gas dispersion and gas explosions. The code has in the recent years been validated in the area of hydrogen dispersion and explosions.<br/>The factory building was 100 m long 10 m wide and 7 m high. A blown-out gasket in a water pump led to release of hydrogen from a large reservoir storing gaseous hydrogen at 3.0 MPa. The accident report estimated a total mass of released hydrogen between 10 and 20 kg. The location of the faulty gasket is known but the direction of the accidental release is not well known and has been one of the topics of our investigations. Several simulations have been performed to investigate the mixing process of hydrogen-air clouds and the development of a flammable gas cloud inside the factory building resulting in a simulation matrix with dispersions in all axis directions. Simulations of ignition of the different gas clouds were carried out and resulting pressure examined. These results have been compared with the damages observed during the accident investigation.<br/>We have also performed FLACS simulations to study the effect of natural venting and level of congestion. The height of the longitudinal walls has been varied leading to different vent openings at floor level at the ceiling and a combination of the two. This was done to investigate the effects of congestion with regards to gas cloud formation.<br/>The base case simulation appears to be in good accordance to the observed damages from the accident. The simulations also show that the build up of the gas cloud strongly depends on the direction of the jet and degree of ventilation. The CFD study has given new insights to the accident and the results are a clear reminder of the importance of natural venting in hydrogen safety.
A Study on the Effectivity of Hydrogen Leakage Detection for Hydrogen Fuel Cell
Sep 2017
Publication
Unlike four-wheel fuel-cell vehicles fuel-cell motorcycles have little semi-closure space corresponding to the engine compartment of four-wheel fuel-cell vehicles. Furthermore motorcycles may fall while parked or running. We conducted hydrogen concentration measurement and ignition tests to evaluate the feasibility of detecting leaks when hydrogen gas leaked from a fuel-cell motorcycle as well as the risk of ignition. We found that the installation of hydrogen leak detectors is effective because it is possible to detect minute hydrogen leaks by installing leak detectors at appropriate points on the fuel cell motorcycle and risks can be reduced by interrupting the hydrogen leak immediately after detection.
Shock Initiated Ignition for Hydrogen Mixtures of Different Concentrations
Sep 2011
Publication
The scenario of ignition of fuels by the passage of shock waves is relevant from the perspective of safety primarily because shock ignition potentially plays an important role in deflagration to detonation transition. Even in one dimension simulation of ignition between a contact surface or a flame and a shock moving into combustible mixture is difficult because of the singular nature of the initial conditions. Indeed initially as the shock starts moving away from the contact surface the region filled with shocked reactive mixture does not exist. In the current work the formulation is transformed using time and length over time as the independent variables. This transformation yields a finite domain from t = 0. In this paper the complete spatial and temporal ignition evolution of hydrogen combustible mixtures of different concentrations is studied numerically. Integration of the governing equations is performed using an Essentially Non-Oscillatory (ENO) algorithm in space and Runge-Kutta in time while the chemistry is modeled by a three-step chain-branching mechanism which appropriately mimics hydrogen combustion.
Empirical Profiling of Cold Hydrogen Plumes Formed from Venting of LH2 Storage Vessels
Sep 2017
Publication
Liquid hydrogen (LH2) storage is viewed as a viable approach to assure sufficient hydrogen capacity at commercial fuelling stations. Presently LH2 is produced at remote facilities and then transported to the end-use site by road vehicles (i.e. LH2 tanker trucks). Venting of hydrogen to depressurize the transport storage tank is a routine part of the LH2 delivery and site transfer process. The behaviour of cold hydrogen plumes has not been well characterized because of the sparsity of empirical field data which can lead to overly conservative safety requirements. Committee members of the National Fire Protection Association (NFPA) Standard 2 [1] formed the Hydrogen Storage Safety Task Group which consists of hydrogen producers safety experts and computational fluid dynamics modellers has identified the lack of understanding of hydrogen dispersion during LH2 venting of storage vessels as a critical gap for establishing safety distances at LH2 facilities especially commercial hydrogen fuelling stations. To address this need the National Renewable Energy Laboratory Sensor Laboratory in collaboration with the NFPA Hydrogen Storage Task Group developed a prototype Cold Hydrogen Plume Analyzer to empirically characterize the hydrogen plume formed during LH2 storage tank venting. The prototype analyzer was field deployed during an actual LH2 venting process. Critical findings included
- Hydrogen above the lower flammable limit (LFL) was detected as much as 2 m lower than the release point which is not predicted by existing models.
- Personal monitors detected hydrogen at ground level although at levels below the LFL.
- A small but inconsistent correlation was found between oxygen depletion and the hydrogen concentration.
- A negligible to non-existent correlation was found between in-situ temperature measurements and the hydrogen concentration.
Numerical Simulation of Detonation Failure and Re-initiation in Bifurcated Tubes
Oct 2015
Publication
A numerical approach is developed to simulate detonation propagation attenuation failure and re-initiation in hydrogen–air mixture. The aim is to study the condition under which detonations may fail or re-initiate in bifurcated tubes which is important for risk assessment in industrial accidents. A code is developed to solve compressible multidimensional transient reactive Navier–Stokes equations. An Implicit Large Eddy Simulation approach is used to model the turbulence. The code is developed and tested to ensure both deflagrations (when detonation fails) and detonations are simulated correctly. The code can correctly predict the flame properties as well as detonation dynamic parameters. The detonation propagation predictions in bifurcated tubes are validated against the experimental work of Wang et al. [12] and found to be in good agreement with experimental observations.
Numerical Study of the Detonation Benchmark using GASFLOW-MPI
Sep 2019
Publication
Hydrogen has been widely used as an energy carrier in recent years. It should a better understand of the potential hydrogen risk under the unintended release of hydrogen scenario since the hydrogen could be ignited in a wide range of hydrogen concentrations in the air and generate a fast flame speed. During the accidental situation the hydrogen-air detonation may happen in the large-scale space which is viewed as the worst case state of affairs. GASFLOW-MPI is a powerful CFD-based numerical tool to predict the complicated hydrogen turbulent transport and combustion dynamics behaviours in the three-dimensional large-scale industrial facility. There is a serious of well-developed physical models in GASFLOW-MPI to simulate a wide spectrum of combustion behaviours ranging from slow flames to deflagration-to-detonation transition and even to detonation. The hydrogen–air detonation experiment which was carried out at the RUT tunnel facility is a well-known benchmark to validate the combustion model. In this work a numerical study of the detonation benchmark at RUT tunnel facility is performed using the CFD code GASFLOW-MPI. The complex shock wave structures in the detonation are captured accurately. The experimental pressure records and the simulated pressure dynamics are compared and discussed.
The Analysis of Fire Test for the High Pressure Composite Cylinder
Sep 2011
Publication
A large number of natural gas vehicles (NGV) with composite cylinders run in the world. In order to store hydrogen using the composite cylinder has also reached commercialization for the hydrogen fuel cell vehicle (FCV) which is been developing on ECO Energy. Under these increasing circumstances the most important issue is that makes sure of safety of the hydrogen composite cylinder. In case of the composite cylinder a standards to verify the safety of cylinders obey several country's standards. For NGV ISO 11439 has adopted as international standards but for FCV it has been still developing and there is only ISO/TS 15869 as international technical standards. In contents of international standards the fire test is the weakest part. The fire test is that the pressure relief valves (PRD) normally operate or not in order to prevent cylinders bursting when a vehicle is covered by fire. However with present standards there is no method to check the problem from vehicles in local flame. This study includes fire test results that have been performed to establish the fire-test standards.
Development of Uniform Harm Criteria for Use in Quantitative Risk Analysis of the Hydrogen Infrastructure
Sep 2009
Publication
This paper discusses the preliminary results of the Risk Management subtask efforts within the International Energy Agency (IEA) Hydrogen Implementing Agreement (HIA) Task 19 on Hydrogen Safety to develop uniform harm criteria for use in the Quantitative Risk Assessments (QRAs) of hydrogen facilities. The IEA HIA Task 19 efforts are focused on developing guidelines and criteria for performing QRAs of hydrogen facilities. The performance of QRAs requires that the level of harm that is represented in the risk evaluation be established using deterministic models. The level of harm is a function of the type and level of hazard. The principle hazard associated with hydrogen facilities is uncontrolled accumulation of hydrogen in (semi) confined spaces and consecutive ignition. Another significant hazard is combustion of accidentally released hydrogen gas or liquid which may or may not happen instantaneously. The primary consequences from fire hazards consist of personnel injuries or fatalities or facility and equipment damage due to high air temperatures radiant heat fluxes or direct contact with hydrogen flames. The possible consequences of explosions on humans and structures or equipment include blast wave overpressure effects impact from fragments generated by the explosion the collapse of buildings and the heat effects from subsequent fire balls. A harm criterion is used to translate the consequences of an accident evaluated from deterministic models to a probability of harm to people structures or components. Different methods can be used to establish harm criteria including the use of threshold consequence levels and continuous functions that relate the level of a hazard to a probability of damage. This paper presents a survey of harm criteria that can be utilized in QRAs and makes recommendations on the criteria that should be utilized for hydrogen-related hazards.
Mixing and Warming of Cryogenic Hydrogen Releases
Sep 2017
Publication
Laboratory measurements were made on the concentration and temperature fields of cryogenic hydrogen jets. Images of spontaneous Raman scattering from a pulsed planar laser sheet were used to measure the concentration and temperature fields from varied releases. Jets with up to 5 bar pressure with near-liquid temperatures at the release point were characterized in this work. This data is relevant for characterizing unintended leaks from piping connected to cryogenic hydrogen storage tanks such as might be encountered at a hydrogen fuel cell vehicle fuelling station. The average centerline mass fraction was observed to decay at a rate similar to room temperature hydrogen jets while the half-width of the Gaussian profiles of mass fraction were observed to spread more slowly than for room temperature hydrogen. This suggests that the mixing and models for cryogenic hydrogen may be different than for room temperature hydrogen. Results from this work were also compared to a one-dimensional (streamwise) model. Good agreement was seen in terms of temperature and mass fraction. In subsequent work a validated version of this model will be exercised to quantitatively assess the risk at hydrogen fuelling stations with cryogenic hydrogen on-site.
Modeling of Hydrogen Pressurization and Extraction in Cryogenic Pressure Vessels Due to Vacuum Insulation Failure
Sep 2017
Publication
We have analyzed vacuum insulation failure in an automotive cryogenic pressure vessel (also known as cryo-compressed vessel) storing hydrogen (H2). Vacuum insulation failure increases heat transfer into cryogenic vessels by about a factor of 100 potentially leading to rapid pressurization and venting to avoid exceeding maximum allowable working pressure (MAWP). H2 release to the environment may be dangerous if the vehicle is located in a closed space (e.g. a garage or tunnel) at the moment of insulation failure. We therefore consider utilization of the hydrogen in the vehicle fuel cell and electricity dissipation through operation of vehicle accessories or battery charging as an alternative to releasing hydrogen to the environment. We consider two strategies: initiating hydrogen extraction immediately after vacuum insulation failure or waiting until MAWP is reached before extraction. The results indicate that cryogenic pressure vessels have thermodynamic advantages that enable slowing down hydrogen release to moderate levels that can be consumed in the fuel cell and dissipated onboard the vehicle even in the worst case when the vacuum fails with a vessel storing hydrogen at maximum refuel density (70 g/L at 300 bar). The two proposed strategies are therefore feasible and the best alternative can be chosen based on economic and/or implementation constraints.
Monitoring H2 Bubbles by Real Time H2 Sensor
Sep 2017
Publication
Portable H2 sensor was made by using mass spectrometer for the outside monitoring experiment: the leak test the replacement test of gas pipe line the combustion test the explosion experiment the H2 diffusion experiment and the recent issue of the exhaust gas of Fuel Cell Vehicle. In order to check the real time concentration of H2 in various conditions even in the highly humid condition the system volume of the sampling route was minimized with attaching the humidifier. Also to calibrate H2 concentration automatically the specific concentration H2 small cylinder was mounted in the system. In the experiment when H2 gas was introduced in the N2 flow or air in the tube or the high-pressure bottle highly concentrated H2 phases were observed by this sensor without diffusion. This H2 sensor can provide the real time information of the hydrogen molecules and the clouds. The basic characterization of this sensor showed 0-100% H2 concentrations within 2ms. Our observation showed the size of the high concentration phase of H2 and the low concentration phase after mixing process. The mixed and unmixed H2 unintended concentration of cloud gas the high speed small cluster of hydrogen molecules in purged gas were explored by this real time monitoring system.
Non-monotonic Overpressure vs. H2 Concentration Behaviour During Vented Deflagration. Experimental Results
Oct 2015
Publication
Explosion relief panels or doors are often used in industrial buildings to reduce damages caused by gas explosions. Decades of research have contributed to the understanding of the phenomena involved in gas explosions in order to establish an effective method to predict reliably the explosion overpressure. All the methods predict a monotonic increase of the overpressure with the concentration of the gas in the range from the lower explosion limit to the stoichiometric one. Nevertheless in few cases a non-monotonic behaviour of the maximum developed pressure as a function of hydrogen concentration was reported in the literature. The non-monotonic behaviour was also observed during experimental tests performed at the Scalbatraio laboratory at the University of Pisa in a 25 m3 vented combustion test facility with a vent area of 112 m2. This paper presents the results obtained during the tests and investigates the possible explanations of the phenomena.
Delivering a Safe, Viable Hydrogen Economy in Australia
Sep 2019
Publication
At Woodside Energy Ltd (Woodside) safety is built into everything we do and progressing hydrogen opportunities is no exception. This paper will present information from the macro level of process safety for hydrogen at a plant level through to the consumer experience. Examples of the benefits of an integrated process safety approach will be used from Woodside’s experience pioneering the liquefied natural gas industry in Australia.<br/>This paper will underscore the reasons why Australia needs to adopt robust safety standards for hydrogen as quickly as possible in order to advance the hydrogen economy across all sectors. Focus areas requiring attention during development of standards and potential mechanisms to close will be proposed. Establishing a hydrogen economy in Australia could lower carbon emissions stabilise power grids increase renewable energy penetration and create jobs. Developing Australian standards that are fully aligned with international standards will facilitate Australia taking a leading role in the global hydrogen economy.
Experiments on the Combustion Behaviour of Hydrogen-Carbon Monoxide-Air Mixtures
Sep 2019
Publication
As a part of a German nuclear safety project on the combustion behaviour of hydrogen-carbon monoxide-air mixtures small scale experiments were performed to determine the lower flammability limit and the laminar burning velocity of such mixtures. The experiments were performed in a spherical explosion bomb with a free volume of 8.2 litre. The experimental set-up is equipped with a central spark ignition and quartz glass windows for optical access. Further instrumentation included pressure and temperature sensors as well as high-speed shadow-videography. A wide concentration range for both fuel gases was investigated in numerous experiments from the lower flammability limits up to the stoichiometric composition of hydrogen carbon monoxide and air (H2-CO-air) mixtures. The laminar burning velocities were determined from the initial pressure increase after the ignition and by using high-speed videos taken during the experiments.
A GIS-based Risk Assessment for Hydrogen Transport: A Case Study in Yokohama City
Sep 2019
Publication
Risk assessment of hazardous material transport by road is critical in considering the spatial features of the transport route. However previous studies that focused on hydrogen transport were unable to reflect the spatial features in their risk assessments. Hence this study aims to assess the risk of hydrogen transport by road considering the spatial features of the transport route based on a geographic information system (GIS). This risk assessment method is conducted through a case study in Yokohama which is an advanced city for hydrogen economy in Japan. In our assessment the risk determined by multiplying the frequency of accidents with the consequence was estimated by road segments that constitute the entire transport route. The effects of the road structure and traffic volumes were reflected in the estimation of the frequency and consequence for each road segment. All estimations of frequency consequence and risk were conducted on a GIS compiled with the information regarding the road network and population. In the case study in Yokohama the route for the transport of compressed hydrogen was virtually set from the near-term perspectives. Based on the case study results the risks of the target transport route were assessed at an acceptable level under the previous risk criteria. The results indicated that the risks fluctuated according to the road segments. This implies that the spatial features of the transport route significantly affect the corresponding risks. This finding corroborates the importance of considering spatial features in the risk assessment of hydrogen transport by road. Furthermore the discussion of this importance leads to the capability of introducing hydrogen energy careers with high transport efficiency and transport routing to avoid high risk road segments as risk countermeasures.
Improvements in Two-Step Model of Hydrogen Detonative Combustion: Model Description and Sensitivity to its Parameters
Sep 2009
Publication
In the present paper the two-stage model of detonative combustion of hydrogen is presented. The following improvements are described: accurate description of the heat release stage of combustion; the clear physics-based procedure for calculation of the parameters of the proposed model; sample calculations of the detonation wave in hydrogen/air mixtures in wide range of conditions showing that the proposed model performs well in a wide range of conditions (pressures temperatures mixture compositions). The results of the 2D simulations of the detonation cell are presented for the hydrogen/oxygen/argon mixture as example to show the performance and accuracy of the model presented in this paper.
Hydrogen Ventilation Test Facility or Underground Mining and Tunneling
Sep 2019
Publication
One of the focus areas in the heavy-duty transport industry globally is de-carbonization of trucks dozers shovels semi-trucks buses etc. Hydrogen fuel cells (FCs) technology is one considered solution for the industry due to its zero-emissions its MW scalability and capacity to store large amounts of energy for long duration continuous power operation. Underground deep mines is another option for deployment and operation of hydrogen FCs. Benefits include lower emissions improved health comfort and safety as well as reduced operating costs. Underground mining trucks loaders and other machines have power ratings up to 750 kW which proves difficult for battery and tethered electric energy. Hydrogen FCs have the ability to overcome these power and energy storage limitations. The risks and technologies associated with delivering storing and using hydrogen underground first need to be investigated and proven safe. This work presents the design construction and operation of a mining ventilation test facility (VTF) at the North-West University in South Africa that aims to quantify the risk of hydrogen in confined ventilated environments. Initial work has been conducted on measuring concentrations of hydrogen released in the temporary ventilation site and is discussed.
Numerical Study of the Near-field of Highly Under-expanded Turbulent Gas Jets
Sep 2011
Publication
For safety issues related to the storage of hydrogen under high pressure it is necessary to determine how the gas is released in the case of failure. In particular there exist limited quantitative information on the near-field properties of the gas jets which are important for establishing proper decay laws in the far-field. This paper reports recent CFD results for air and helium obtained in the near-field of the highly under-expanded jets. The gas jets are released from a 30-bar tank with the same opening (orifice). The Reynolds number based on the diameter of the orifice and corresponding gas conditions at the exit was well beyond 106 . The 3D Compressible Multi-Component Navier-Stokes equations were solved directly without relying on the compressibility-corrected turbulence models. The numerical model was initially tested on a one-component (air-air) case where a few aerospace-driven data sets are available for validation. The shock geometry is characterized through the Mach disk position and diameter. These are compared to the results known from the literature and to the scaling laws developed based on the dimensional analysis. In the second two-component (helium-air) jet scenario the density field was validated and examined together with other fields in the attempt to suggest potential initial conditions for the forthcoming far-field simulations.
Comparison of Modelling Approaches for CFD Simulations of High Pressure Hydrogen Releases
Sep 2011
Publication
Several approaches have been used in the past to model the source of a high pressure under-expanded jet such as the computationally expensive resolution of the jet shock structure and the simpler pseudo-source or notional nozzle approaches. In each approach assumptions are made introducing inaccuracies in the CFD calculations. This work assesses the effect of different source modelling approaches on the accuracy of CFD calculations by comparing simulation results to experimental data of the axial distribution of the flow velocity and H2 concentration.
Prevention of Hydrogen Accumulation Inside the Vacuum Vessel Pressure Suppression System of the ITER Facility by Means of Passive Auto-catalytic Recombiners
Sep 2017
Publication
Hydrogen safety is a relevant topic for both nuclear fission and fusion power plants. Hydrogen generated in the course of a severe accident may endanger the integrity of safety barriers and may result in radioactive releases. In the case of the ITER fusion facility accident scenarios with water ingress consider the release of hydrogen into the suppression tank (ST) of the vacuum vessel pressure suppression system (VVPSS). Under the assumption of additional air ingress the formation of flammable gas mixtures may lead to explosions and safety component failure.<br/>The installation of passive auto-catalytic recombiners (PARs) inside the ST which are presently used as safety devices inside the containments of nuclear fission reactors is one option under consideration to mitigate such a scenario. PARs convert hydrogen into water vapor by means of passive mechanisms and have been qualified for operation under the conditions of a nuclear power plant accident since the 1990s.<br/>In order to support on-going hydrogen safety considerations simulations of accident scenarios using the CFD code ANSYS-CFX are foreseen. In this context the in-house code REKO-DIREKT is coupled to CFX to simulate PAR operation. However the operational boundary conditions for hydrogen recombination (e.g. temperature pressure gas mixture) of a fusion reactor scenario differ significantly from those of a fission reactor. In order to enhance the code towards realistic PAR operation a series of experiments has been performed in the REKO-4 facility with specific focus on ITER conditions. These specifically include operation under sub-atmospheric pressure (0.2–1.0 bar) gas compositions ranging from lean to rich H2/O2 mixtures and superposed flow conditions.<br/>The paper gives an overview of the experimental program presents results achieved and gives an outlook on the modelling approach towards accident scenario simulation.
Licensing a Fuel Cell Bus and a Hydrogen Fueling Station in Brazil
Sep 2011
Publication
The Brazilian Fuel Cell Bus Project is being developed by a consortium comprising 14 national and international partners. The project was initially supported by the GEF/UNDP and MME/FINEP Brazil. The national coordination is under responsibility of MME and EMTU/SP the São Paulo Metropolitan Urban Transport Company that also controls the bus operation and bus routes. This work reports the efforts done in order to obtain the necessary licenses to operate the first fuel cell buses for regular service in Brazil as well as the first commercial hydrogen fueling station to attend the vehicles.
A Study of Barrier Walls for Mitigation of Unintended Releases of Hydrogen
Sep 2009
Publication
Hydrogen jet flames resulting from ignition of unintended releases can be extensive in length and pose significant radiation and impingement hazards. Depending on the leak diameter and source pressure the resulting consequence distances can be unacceptably large. One possible mitigation strategy to reduce exposure to jet flames is to incorporate barriers around hydrogen storage and delivery equipment. An experimental and modeling program has been performed at Sandia National Laboratories to better characterize the effectiveness of barrier walls to reduce hazards. This paper describes the experimental and modeling program and presents results obtained for various barrier configurations. The experimental measurements include flame deflection using standard and infrared video and high-speed movies (500 fps) to study initial flame propagation from the ignition source. Measurements of the ignition overpressure wall deflection radiative heat flux and wall and gas temperature were also made at strategic locations. The modeling effort includes three-dimensional calculations of jet flame deflection by the barriers computations of the thermal radiation field around barriers predicted overpressure from ignition and the computation of the concentration field from deflected unignited hydrogen releases. The various barrier designs are evaluated in terms of their mitigation effectiveness for the associated hazards present. The results show that barrier walls are effective at deflecting jet flames in a desired direction and can help attenuate the effects of ignition overpressure and flame radiative heat flux.
Tokyo Gas’ Efforts Regarding Impact Assessment on Surroundings and Emergency Response Training
Sep 2017
Publication
In Japan 82 commercial Hydrogen Refuelling Stations (HRSs) were constructed as of March 1 2017 but few impact assessments have been reported on the surroundings at HRS. In addition as HRSs become more widespread the number of HRSs around narrow urban areas will also increase. Thus the necessity of impact assessments on the surroundings of HRSs is expected to increase. In order to confirm that the influence from our HRS is not problematic to the surrounding residences we conducted an impact assessment on the surroundings at HRS by using the actual HRS construction plan. Although safety is one of the objects of an impact assessment in Japan the safety of an HRS is guaranteed by observing the High Pressure Gas Safety Act its Technical Standards and other related regulations. On the other hand if an accident such as a hydrogen leak or hydrogen fire occurs at an HRS it becomes important to prevent secondary disasters and to minimize influence on the surroundings by means of an initial response by the operators of the HRS. Therefore we have conducted training to improve the emergency response capability of the HRS operators and to prevent secondary disasters. In this paper we describe the abovementioned information with regard to an impact assessment on the surroundings and for emergency response training.
Early Community Engagement with Hydrogen in Australia
Sep 2019
Publication
Community support and acceptance is part of the licence to operate for any industry. The hydrogen industry is no different and we will need to have strong support from the broad community to establish a viable hydrogen economy in Australia.<br/>As Woodside progresses our plans for bulk hydrogen export and associated domestic opportunities stakeholder engagement throughout will be critical to success. This talk will share Woodside’s approach to community engagement and local opportunities and how we plan to draw on more than 30 years’ experience operating liquefied natural gas plants in Western Australia’s Pilbara region.<br/>At this early stage of our hydrogen work we are beginning with the end in mind: engaging the customer. We’ve worked with local Australian businesses to help raise public awareness and interest in hydrogen by producing prototype consumer products. We will share experiences from this work that underscore the value of early engagement with all stakeholders: government regulators industrial and community neighbours and end consumers to enable the hydrogen economy vision for Australia. This paper will present information on community engagement and acceptance of hydrogen in Australia.<br/>This information has come from Woodside Energy Ltd by engaging with small businesses government regulators and the community at large. As we establish community acceptance for hydrogen as an energy carrier in Australia Woodside has been working in parallel to have standards and regulations established for hydrogen in Australia. Through our work with Hydrogen Mobility Australia we are advocating the adoption of ISO standards unless there is a specific geographic or health safety and environment reason not to.
Risk Assessment of Hydrogen Explosion for Private Car with Hydrogen-driven Engine
Sep 2009
Publication
The aim of the study is to identify and quantify the additional risks related to hydrogen explosions during the operation of a hydrogen-driven car. In a first attempt the accidents or failures of a simple one-tank hydrogen storage system have been studied as a main source of risk. Three types of initiators are taken into account: crash accidents fire accidents without crash (no other cars are involved) and hydrogen leakages in normal situation with following ignition. The consequences of hydrogen ignition and/or explosion depend strongly on environmental conditions (geometry wind etc.) therefore the different configurations of operational and environmental conditions are specified.<br/>Then Event Tree/Fault Tree methods are applied for the risk assessment.<br/>The results of quantification permit to draw conclusions about the overall added risk of hydrogen technology as well as about the main contributors to the risk. Results of this work will eventually contribute to the on-going pre-normative research in the field of hydrogen safety.
Experimental Study of Ignited Unsteady Hydrogen Jets into Air
Sep 2009
Publication
In order to simulate an accidental hydrogen release from the low pressure pipe system of a hydrogen vehicle a systematic study on the nature of transient hydrogen jets into air and their combustion behaviour was performed at the FZK hydrogen test site HYKA. Horizontal unsteady hydrogen jets with an amount of hydrogen up to 60 STP dm3 and initial pressures of 5 and 16 bar have been investigated. The hydrogen jets were ignited with different ignition times and positions. The experiments provide new experimental data on pressure loads and heat releases resulting from the deflagration of hydrogen-air clouds formed by unsteady turbulent hydrogen jets released into a free environment. It is shown that the maximum pressure loads occur for ignition in a narrow position and time window. The possible hazard potential arising from an ignited free transient hydrogen jet is described.
The Crucial Role of the Lewis Number in Jet Ignition
Sep 2011
Publication
During the early phase of the transient process following a hydrogen leak into the atmosphere a contact surface appears separating hot air from cold hydrogen. Locally the interface is approximately planar. Diffusion occurs potentially leading to ignition. This process was analyzed by Lin˜a´n and Crespo (1976) for Lewis number unity and Lin˜a´n and Williams (1993) for Lewis number less than unity. In addition to conduction these processes are affected by expansion due to the flow which leads to a temperature drop. If chemistry is very temperature-sensitive then the reaction rate peaks close to the hot region where relatively little fuel is present. Indeed the Arrhenius rate drops rapidly as temperature drops much more so than fuel concentration. However the small fuel concentration present close to the airrich side depends crucially upon the balance between fuel diffusion and heat diffusion hence the fuel Lewis number. For Lewis number unity the fuel concentration present due to diffusion is comparable to the rate of consumption due to chemistry. If the Lewis number is less than unity fuel concentration brought in by diffusion is large compared with temperature-controlled chemistry. For a Lewis number greater than unity diffusion is not strong enough to bring in as much fuel as chemistry would be able to burn and combustion is controlled by fuel diffusion. In the former case combustion occurs faster leading to a localized ignition at a finite time determined by the analysis. As long as the temperature drop due to the expansion associated with the multidimensional nature of the jet does not lower significantly the reaction rate up to that point ignition in the jet takes place. For fuel Lewis number greater than unity first the reaction rate is much lower. Second chemistry does not lead to a defined ignition. Eventually expansion will affect the process and ignition does not take place. In summary it appears that the reason why hydrogen is the only fuel for which jet ignition has been observed is a Lewis number effect coupled with a high speed of sound hence a high initial temperature discontinuity.
Determination of Characteristic Parameters for the Thermal Decomposition of Epoxy Resin/carbon Fibre Composites in Cone Calorimeter
Sep 2011
Publication
The thermal degradation of two epoxy resin/carbon fiber composites which differ by their volume fractions in carbon fiber (56 and 59 vol%.) was investigated in cone calorimeter under air atmosphere with a piloted ignition. The external heat flux of cone calorimeter was varied up to 75 kW.m-2 to study the influence of the carbon fiber amount on the thermal decomposition of those composites. Thus main parameters of the thermal decomposition of two different composites were determined such as: mass loss mass loss rate ignition time thermal response parameter ignition temperature critical heat flux thermal inertia and heat of gasification. As a result all the parameters that characterize the thermal resistance of composites are decreased when the carbon fiber volume fraction is increased.
Study of Fire Risk and Accidents Emergency Disposal Technology System of Hydrogen Fuel Vehicles
Sep 2017
Publication
As the energy crisis and environment pollution growing severely the hydrogen fuel motor vehicle has got more and more attention many automobile companies and research institutions invest significant R&D resources to research and develop the hydrogen fuel vehicles. With the development of the hydrogen fuel cell vehicles and hydrogen fuel motor vehicles the hydrogen had more to more extensive application. According to the categories of the hydrogen fuel vehicles the characteristics of hydrogen fuel vehicle fire risk and accidents are analyzed in this paper. As for hydrogen fuel cell vehicles the function of its key components such as the fuel cell the high-pressure storage tank is presented firstly. Then based on the low density fast diffusion and flammable of hydrogen the probable scenarios of accident such as fuel leak jet flame are analyzed and the fire risk of the key components and the whole vehicle is evaluated. Finally the development trend of the emergency warning system of hydrogen fuel cell vehicles is analyzed and some recommendations are proposed referring to the detection pre-warning and control technologies used in the industrial sites. Aiming at the hydrogen car structure characteristics and the fire accident modes and accidents evolution rules the emergency disposal technology system for hydrogen fuel motor vehicles is put forward.
Experimental Study on High Pressure Hydrogen Jets Coming Out of Tubes of 0.1–4.2 m in Length
Sep 2011
Publication
Wide use of hydrogen faces significant studies to resolve hydrogen safety issues in industries worldwide. However widely acceptable safety level standards are not achieved in the present situation yet. The present paper deals with hydrogen leaks from a tube to ignite and explode in atmosphere. The experiments using a shock tube are performed to clarify the auto-ignition property of high pressure hydrogen jet spouting from a tube. In order to improve experimental repeatability and reliability the shock tube with a plunger system is applied where the PET diaphragm is ruptured by a needle in order to control a diaphragm burst pressure (hydrogen pressure). As a result it becomes possible to control the diaphragm burst pressure to obtain a local minimum value. The most important result obtained in the preset study is that the minimum diaphragm burst pressure for auto-ignition is found between 1.0 and 1.2 m of tube length using a longer tube than the one used in the previous study. This minimum tube size is not found elsewhere to suggest that the tube length has a limit size for auto-ignition. Furthermore auto-ignition and Mach disk at the tube exit are observed using a high speed camera which is set at the frame speed of 1x105 fps when the ignited hydrogen jet is spouted out the tube.
Ignition of Hydrogen Jet Fires from High Pressure Storage
Sep 2013
Publication
Highly transient jets from hydrogen high pressure tanks were investigated up to 30 MPa. These hydrogen jets might self-initiate when released from small orifices of high pressure storage facilities. The related effects were observed by high speed video technics including time resolved spectroscopy. Ignition flame head jet velocity flame contours pressure wave propagation reacting species and temperatures were evaluated. The evaluation used video cross correlation method BOS brightness subtraction and 1 dimensional image contraction to obtain traces of all movements. On burst of the rupture disc the combustion of the jet starts close to the nozzle on the outer shell of it at the boundary layer to the surrounding air. It propagates with a deceleration approximated by a drag force of constant value which is obtained by analysing the head velocity. The burning at the outer shell develops to an explosion converting a nearly spherical volume at the jet head the movement of the centroid is nearly unchanged and follows the jet front in parallel. The progress of the nearly spherical explosion could be evaluated on an averaged flame ball radius. An apparent flame velocity could be derived to be about 20 m/s. It seems to increase slightly on the pressure in the tank or the related initial jet momentum. Self-initiation is nearly always achieved especially induced the interaction of shock waves and their reflections from the orifice. The results are compared to thermodynamic calculations and radiation measurements. The combustion process is composed of a shell combustion of the jet cone at the bases with a superimposed explosion of the decelerating jet head volume.
Low Energy Hydrogen Sensor
Sep 2011
Publication
A new silicon-based hydrogen sensor for measurements at high concentrations near the lower flammable limit of hydrogen (40000 ppm) is presented. Due to operation at room temperature the power consumption of the sensor is smaller than that of other sensors on the market by several orders magnitude. Further development of the sensor system could lead to battery powered or even energy-independent operation. As sensor fabrication is based on semiconductor technology low-cost production can be achieved for the mass market. The sensor investigated showed good long-term stability combined with a fast response on the basis of cyclic thermal activations. This was demonstrated by a stress test that simulated the activation and measurement cycles experienced by the sensor in one year. Finite element method was used to further reduce the power consumption of the thermal activation. This resulted in an average power consumption of 2 × 10−6 W for the sensor activation.
Numerical Study on Fast Filling of 70 MPA Hydrogen Vehicle Cylinder
Sep 2011
Publication
There will be significant temperature rise within hydrogen vehicle cylinder during the fast filling process. The temperature rise should be controlled under the temperature limit (85 °C) of the structure material (set by ISO/TS 15869) because it may lead to the failure of the structure. In this paper a 2-dimensional axisymmetric computational fluid dynamics (CFD) model for fast filling of 70 MPa hydrogen vehicle cylinder is presented. The numerical simulations are based on the modified standard k − ɛ turbulence model. In addition both the equation of state for hydrogen gas and the thermodynamic properties are calculated by National Institute of Standards and Technology (NIST) database: REFPROP 7.0. The thermodynamic responses of fast filling with different pressure-rise patterns and filling times within type III cylinder have been analyzed in detail.
Flammability Profiles Associated with High-pressure Hydrogen Jets Released in Close Proximity to Surfaces
Oct 2015
Publication
This paper describes experimental and numerical modelling results from an investigation into the flammability profiles associated with high pressure hydrogen jets released in close proximity to surfaces. This work was performed under a Transnational Access Agreement activity funded by the European Research Infrastructure project H2FC.<br/>The experimental programme involved ignited and unignited releases of hydrogen at pressures of 150 and 425 barg through nozzles of 1.06 and 0.64 mm respectively. The proximity of the release to a ceiling or the ground was varied and the results compared with an equivalent free-jet test. During the unignited experiments concentration profiles were measured using hydrogen sensors. During the ignited releases thermal radiation was measured using radiometers and an infra-red camera. The results show that the flammable volume and flame length increase when the release is in close proximity to a surface. The increases are quantified and the safety implications discussed.<br/>Selected experiments were modelled using the CFD model FLACS for validation purposes and a comparison of the results is also included in this paper. Similarly to experiments the CFD results show an increase in flammable volume when the release is close to a surface. The unstable atmospheric conditions during the experiments are shown to have a significant impact on the results.
Status of the Pre-normative Research Project PRESLHY for the Safe Use of LH2
Sep 2019
Publication
Liquid hydrogen (LH2) compared to compressed gaseous hydrogen offers advantages for large scale transport and storage of hydrogen with higher densities and potentially better safety performance. Although the gas industry has good experience with LH2 only little experience is available for the new applications of LH2 as an energy carrier. Therefore the European FCH JU funded project PRESLHY conducts pre-normative research for the safe use of cryogenic LH2 in non-industrial settings. The work program consists of a preparatory phase where the state of the art before the project has been summarized and where the experimental planning was adjusted to the outcome of a research priorities workshop. The central part of the project consists of 3 phenomena oriented work packages addressing Release Ignition and Combustion with analytical approaches experiments and simulations. The results shall improve the general understanding of the behavior of LH2 in accidents and thereby enhance the state-of-the-art what will be reflected in appropriate recommendations for development or revision of specific international standards. The paper presents the status of the project at the middle of its terms.
Dynamics of Vented Hydrogen-air Deflagrations
Sep 2011
Publication
The use of hydrogen as an energy carrier is a real perspective for Europe since a number of breakthroughs now enable to envision a deployment at the industrial scale. However some safety issues need to be further addressed but experimental data are still lacking especially about the explosion dynamics in realistic dimensions. A set of hydrogen-air vented explosions were thus performed in two medium scale chambers (1 m3 and 10 m3). Homogeneous mixtures were used (10% to 30% vol.). The explosion overpressure was measured inside the chamber and outside on the axis of the discharge from the vent. The incidence of the external explosion is clearly seen. All the results in this paper and the predictions from the standards differ greatly meaning that a significant effort is still required. It is the purpose of the French project DIMITRHY to help progressing.
Self-ignition of Hydrogen-nitrogen Mixtures During High-pressure Release Into Air
Oct 2015
Publication
This paper demonstrates experimental and numerical study on spontaneous ignition of H2–N2 mixtures during high-pressure release into air through the tubes of various diameters and lengths. The mixtures included 5% and 10% (vol.) N2 addition to hydrogen being at initial pressure in range of 4.3–15.9 MPa. As a point of reference pure hydrogen release experiments were performed with use of the same experimental stand experimental procedure and extension tubes. The results showed that N2 addition may increase the initial pressure necessary to self-ignite the mixture as much as 2.12 or 2.85 – times for 5% and 10% N2 addition respectively. Additionally simulations were performed with use of Cantera code (0-D) based on the ideal shock tube assumption and with the modified KIVA3V code (2-D) to establish the main factors responsible for ignition and sustained combustion during the release.
Full Suppression of Hydrogen Explosion Using Phlegmatization Additives- Experimental Results
Sep 2011
Publication
The paper presents results of experimental investigations of different phlegmatizator substances and its binary compounds used for full hydrogen combustion suppression. The work was performed in experimental facilities of three different scales (small medium and large) at normal initial pressure and temperature range 20 ⎯ 120 °С. Ten individual substances and six binary compounds were tested in a small scale experiments. Three individual halogen containing substances capable of full suppression of hydrogen combustion were found in a series of small scale experiments (tube length – 1 m ID – 66 mm). The minimum concentration of the most effective substance was 11% at 20°С and 14% at 120°С in a small scale experiments. Medium scale confined and large scale unconfined experiments confirmed the possibility of full combustion suppression. The minimum concentration of the most effective binary mixture was found to be 12 % at 20°С in a large scale experiments.
Evaluation of the ADREA-HF CFD Code Against a Hydrogen Deflagration in a Tunnel
Sep 2013
Publication
In the present work the capabilities of the computational fluid dynamics (CFD) code ADREA-HF to predict deflagration in homogenous near stoichiometric hydrogen-air mixture in a model of a tunnel were tested. The tunnel is 78.5 m long. Hydrogen-air mixture is located in a 10 m long region in the middle of the tunnel. Two cases are studied: one with a complete empty tunnel and one with the presence of four vehicles near the center of the tunnel. The combustion model is based on the turbulent flame speed concept. The turbulent flame speed is a modification of Yakhot's equation in order to account for additional physical mechanisms. A sensitivity analysis for the parameter of the combustion model and for the mesh resolution was made for the empty tunnel case. The agreement between experimental and computational results concerning the value of the maximum pressure and the time it appears is satisfactory in both cases. The sensitivity analysis for the parameter of the combustion model showed that even small changes in it can have impact on the simulating results whereas the sensitivity analysis of the mesh resolution did not reveal any significant differences.
Numerical Simulation of Homogenous/Inhomogeneous Hydrogen-air Explosion in a Rectangular Channel
Sep 2019
Publication
Hydrogen is one of the promising energy sources in the future because it has the advantages of clean combustion products high efficiency and renewable energy. However hydrogen has the characteristics of low ignition energy wide flammable range (4% -75%) and fast burning flame speed which can cause explosion hazards. Typically the accidental release of hydrogen into confined or semi confined enclosures can often lead to a flammable hydrogen-air mixture with concentration gradients and possible flame acceleration and deflagration-to-detonation transition (DDT). The present study aims to test the capability of our in-house density-based solver ExplosionEngFoam for flame acceleration (FA) and deflagration-to-detonation transition (DDT) in homogenous/inhomogeneous hydrogen-air mixtures. The solver is based on the open source computational fluid dynamics (CFD) platform OpenFOAM and uses the modified Weller et al.’s combustion model taking into account LD and RT instabilities turbulence and non-unity Lewis number etc. Numerical simulations were conducted for both homogeneous and inhomogeneous mixtures in a long enclosed channel with 5.4 m in length and 0.06 m in height. The predictions demonstrate good quantitative agreement with the experimental measurements in flame tip position speed and pressure profiles by Boeck et al. The flow characteristics such as flame fine structure wave evolution etc. were also discussed.
European Hydrogen Safety Training Programme for First Responders: Hyresponse Outcomes and Perspectives
Sep 2017
Publication
The paper presents the outcomes of the HyResponse project i.e. the European Hydrogen Safety Training Programme for first responders. The threefold training is described: the content of the educational training is presented the operational training platform and its mock-up real scale transport and hydrogen stationary installations are detailed and the innovative virtual tools and training exercises are highlighted. The paper underlines the outcomes the three pilot sessions as well as the Emergency Response Guide available on the HyResponse’s public website. The next steps for widespread dissemination into the community are discussed.
Hydrogen Wide Area Monitoring of LH2 Releases
Sep 2019
Publication
The characterization of liquid hydrogen (LH2) releases has been identified as an international research priority to expand the safe use of hydrogen as an energy carrier. The elucidation of LH2 release behavior will require the development of dispersion and other models guided and validated by empirical field measurements such as those afforded by Hydrogen Wide Area Monitoring (HyWAM). HyWAM can be defined as the quantitative spatial and temporal three-dimensional monitoring of planned or unintentional hydrogen releases. With support provided through the FCH JU Prenormative Research for the Safe Use of Liquid Hydrogen (PRESLHY) program HSE performed a series of LH2 releases to characterize the dispersion and pooling behavior of cold hydrogen releases. The NREL Sensor Laboratory developed a HyWAM system based upon a distributed array of point sensors that is amenable for profiling cold hydrogen plumes. The NREL Sensor Laboratory and HSE formally committed to collaborate on profiling the LH2 releases. This collaboration included the integration of the NREL HyWAM into the HSE LH2 release hardware. This was achieved through a deployment plan jointly developed by the NREL and HSE personnel. Under this plan the NREL Sensor Laboratory provided multiple HyWAM modules that accommodated 32 sampling points for near-field hydrogen profiling during the HSE PRESLHY LH2 releases. The NREL HyWAM would be utilized throughout the LH2 release study performed under PRESLHY by HSE including Work Package 3 (WP3—Release and Mixing--Rainout) and subsequent work packages (WP4—Ignition and WP5—Combustion). Under the auspices of the PRESLHY WP6 (Implementation) data and findings from the HSE LH2 Releases are to be made available to stakeholders in the hydrogen community. Comprehensive data analysis and dissemination is ongoing but the integration of the NREL HyWAM into the HSE LH2 Release Apparatus and its performance as well as some key outcomes of the LH2 releases in WP3 are presented.
Validation and Recommendations for CFD and Engineering Modeling of Hydrogen Vented Explosions: Effects of Concentration, Stratification, Obstruction and Vent Area
Oct 2015
Publication
Explosion venting is commonly used in the process industry as a prevention solution to protect equipment or buildings against excessive internal pressure caused by an explosion. This article is dedicated to the validation of FLACS CFD code for the modelling of vented explosions. Analytical engineering models fail when complex cases are considered for instance in the presence of obstacles or H2 stratified mixtures. CFD is an alternative solution but has to be carefully validated. In this study FLACS simulations are compared to published experimental results and recommendations are suggested for their application.
Can the Addition of Hydrogen to Natural Gas Reduce the Explosion Risk?
Sep 2009
Publication
One of the main benefits sought by including hydrogen in the alternative fuels mix is emissions reduction – eventually by 100%. However in the near term there is a very significant cost differential between fossil fuels and hydrogen. Hythane (a blend of hydrogen and natural gas) can act as a viable next step on the path to an ultimate hydrogen economy as a fuel blend consisting of 8−30 % hydrogen in methane can reduce emissions while not requiring significant changes in existing infrastructure. This work seeks to evaluate whether hythane may be safer than both hydrogen and methane under certain conditions. This is due to the fact hythane combines the positive safety properties of hydrogen (strong buoyancy high diffusivity) and methane (much lower flame speeds and narrower flammability limits as compared to hydrogen). For this purpose several different mixture compositions (e.g. 8 % 20 % and 30 % hydrogen) are considered. The evaluation of (a) dispersion characteristics (which are more positive than for methane) (b) combustion characteristics (which are closer to methane than hydrogen) and (c) Combined dispersion + explosion risk is performed. This risk is expected to be comparable to that of pure methane possibly lower in some situations and definitely lower than for pure hydrogen. The work is performed using the CFD software FLACS that has been well-validated for safety studies of both natural gas/methane and hydrogen systems. The first part of the work will involve validating the flame speeds and flammability limits predicted by FLACS against values available in literature. The next part of the work involves validating the overpressures predicted by the CFD tool for combustion of premixed mixtures of methane and hydrogen with air against available experimental data. In the end practical systems such as vehicular tunnels garages etc. is used to demonstrate positive safety benefits of hythane with comparisons to similar simulations for both hydrogen and methane.
Experiments on the Distribution of Concentration Due to Buoyant Gas Low Flow Rate Release in an Enclosure.
Sep 2009
Publication
Hydrogen energy based vehicles or power generators are expected to come into widespread use in the near future. Safety information is of major importance to support the successful public acceptance of hydrogen as an energy carrier. One of the most important issues in terms of safety is the use of such system in closed area such as a private garage in which a fuel cell car may be parked. This kind of situation leads to the fundamental problem of the dispersion of hydrogen due to a simple vertical source in an enclosure. Many numerical and experimental studies have already been conducted on this problem showing the formation of a stably stratified distribution of concentration. Most of them consider the cases of accidental situation in which the flow rate is relatively important (of the order of 10Nl/min to 100Nl/min). We present a set of experiments conducted on a full scale facility of the size of a typical private garage with helium as a model gas for hydrogen. In this study we focus on the low flow rates that can be characteristic of chronic leaks that may not be detected by security devices of the system (of the order of 0.1Nl/min to 10Nl/min). The facility allows changing natural ventilation conditions and experiments have been conducted from the tightest which is less than 0.01ACH to that typical of a real garage say of the order of 0.1ACH.
Risk Quantification of Hydride Based Hydrogen Storage Systems for Automotive Applications
Sep 2009
Publication
For hydrogen fuelled vehicles to attain significant market penetration it is essential that any potential risks be controlled within acceptable levels. To achieve this goal on-board vehicle hydrogen storage systems should undergo risk analyses during early concept development and design phases. By so doing the process of eliminating safety-critical failure modes will help guide storage system development and be more efficient to implement than if undertaken after the design-freeze stage. The focus of this paper is the development of quantitative risk analyses of storage systems which use onboard reversible materials such as conventional AB5 metal hydrides the complex hydride NaAlH4 or other material candidates currently being researched. Collision of a vehicle having such a hydrogen storage system was selected as a dominant accident initiator and a probabilistic event tree model has been developed for this initiator. The event tree model contains a set of comprehensive mutually exclusive accident sequences. The event tree represents chronological ordering of key events that are postulated to occur sequentially in time during the accident progression. Each event may represent occurrence of a phenomenon (e.g. hydride chemical reaction and dust cloud explosion) or a hardware failure (e.g. hydride storage vessel rupture). Event tree branch probabilities can be quantified using fault tree models or basic events with probability distributions. A fault tree model for hydride dust cloud explosion is provided as an example. Failure probabilities assigned to the basic events in the fault tree can be estimated from test results published data or expert opinion elicitation. To account for variabilities in the probabilities assigned to fault tree basic events and hence to propagate uncertainties in event tree sequences Monte Carlo sampling and Latin Hypercube sampling were employed and the statistics of the results from both techniques were compared.
Overview of the DOE Hydrogen Safety, Codes and Standards Program part 2- Hydrogen and Fuel Cells, Emphasizing Safety to Enable Commercialization
Oct 2015
Publication
Safety is of paramount importance in all facets of the research development demonstration and deployment work of the U.S. Department of Energy’s (DOE) Fuel Cell Technologies Program. The Safety Codes and Standards sub-program (SC&S) facilitates deployment and commercialization of fuel cell and hydrogen technologies by developing and disseminating information and knowledge resources for their safe use. A comprehensive safety management program utilizing the Hydrogen Safety Panel to raise safety consciousness at the project level and developing/disseminating a suite of safety knowledge resources is playing an integral role in DOE and SC&S efforts. This paper provides examples of accomplishments achieved while reaching a growing and diverse set of stakeholders involved in research development and demonstration; design and manufacturing; deployment and operations. The work of the Hydrogen Safety Panel highlights new knowledge and the insights gained through interaction with project teams. Various means of collaboration to enhance the value of the program’s safety knowledge tools and training resources are illustrated and the direction of future initiatives to reinforce the commitment to safety is discussed.
A Dual Zone Thermodynamic Model for Refueling Hydrogen Vehicles
Sep 2017
Publication
With the simple structure and quick refuelling process the compressed hydrogen storage system is currently widely used. However thermal effects during charging-discharging cycle may induce temperature change in storage tank which has significant impact on the performance of hydrogen storage and the safety of hydrogen storage tank. To address this issue we once propose a single zone lumped parameter model to obtain the analytical solution of hydrogen temperature and use the analytical solution to estimate the hydrogen temperature but the effect of the tank wall is ignored. For better description of the heat transfer characteristics of the tank wall a dual zone (hydrogen gas and tank wall) lumped parameter model will be considered for widely representation of the reference (experimental or simulated) data. Now we extend the single zone model to the dual zone model which uses two different temperatures for gas zone and wall zone. The dual zone model contains two coupled differential equations. To solve them and obtain the solution we use the method of decoupling the coupled differential equations and coupling the solutions of the decoupled differential equations. The steps of the method include: (1) Decoupling of coupled differential equations; (2) Solving decoupled differential equations; (3) Coupling of solutions of differential equations; (4) Solving coupled algebraic equations. Herein three cases are taken into consideration: constant inflow/outflow temperature variable inflow/outflow temperature and constant inflow temperature and variable outflow temperature. The corresponding approximate analytical solutions of hydrogen temperature and wall temperature can be obtained. The hydrogen pressure can be calculated from the hydrogen temperature and the hydrogen mass using the equation of state for ideal gas. Besides the two coupled differential equations can also be solved numerically and the simulated solution can also be obtained. This study will help to set up a formula based approach of refuelling protocol for gaseous hydrogen vehicles.
Numerical Modelling of Flame Acceleration and Transition to Detonation in Hydrogen & Air Mixtures with Concentration Gradient
Sep 2017
Publication
Hydrogen gas explosions in homogeneous reactive mixtures have been widely studied both experimentally and numerically. However in practice combustible mixtures are usually inhomogeneous and subject to both vertical and horizontal concentration gradients. There is still very limited understanding of the hydrogen explosion characteristics in such situations. The present numerical investigation aims to study the effect of mixture concentration gradient on the process of Deflagration to Detonation Transition and the effect of different hydrogen concentration gradient in the obstructed channel of hydrogen/air mixtures. An obstructed channel with 30% blockage ratio (BR=30) and three different average hydrogen concentrations of 20 % 30% and 35% have been considered using a specially developed density-based solver within the OpenFOAM toolbox. A high-resolution grid was built with the using adaptive mesh refinement technique providing 10 grid points in half reaction length. The numerical results are in reasonably good agreement with the experimental observations [1]. These studies show that the concentration gradient has a considerable effect on the accelerated flame tip speed and the location of transition to detonation in the obstructed channel. In all the three cases the first localised explosion occurred near the bottom wall where the shock and flame interacted and the mixture was most lean; and the second localised explosion occurred at the top wall due to the reflection of shock and flame front and later develops to form the leading detonation wave. The increase in the fuel concentration was found to increase the flame acceleration (FA) and having a faster transition to detonation.
Modeling of Cryogenic Hydrogen jets
Oct 2015
Publication
In the present work the CFD modeling of cryogenic hydrogen releases in quiescent environment is presented. Two tests from the series of experiments performed in the ICESAFE facility at KIT (Karlsruhe Institute for Technology) have been simulated within the SUSANA project. During these tests hydrogen at temperature of 37K and 36K and at pressure of 19 and 29 bars respectively is released horizontally. The release at the nozzle is sonic and the modeling of the under-expanded jet was performed using two different approaches: the Ewan and Moodie approach and a modification of the Ewan and Moodie approach (modified Ewan and Moodie) that is introduced here and employs the momentum balance to calculate the velocity in the under-expanded jet. Using these approaches a pseudo-diameter is calculated and this diameter is set as source boundary in the simulation. Predictions are consistent with measurements for both experiments with both approaches. However the Ewan and Moodie approach seems to perform better.
Testing, Evaluation and Development of Hydrogen Sensors for an Underground Mining Ventilation Test Facility
Sep 2019
Publication
An underground mining ventilation testing facility (VTF) was designed and constructed at the HySA facility at the North-West University South Africa. The purpose was to evaluate risks associated with different hydrogen storage technologies in a confined environment. The work included initial calculations of hydrogen movement in specific spaces and the development of simulation tools to compare these modelled results with experimental work. For this purpose hydrogen sensors that could accurately measure hydrogen concentrations during a controlled hydrogen leak at the VTF were required. Hazardous hydrogen sensors capable of measuring >4% hydrogen are not readily available commercially. Typically hydrogen sensors rated for hazardous environments are designed for safety actions (e.g. activating emergency measures when hydrogen is detected) at concentrations of 8%. (Measuring concentrations higher than this is not required for commercial use hence there is no market for such sensors.) At the VTF it is necessary to be able to measure hydrogen concentrations >4% in order to obtain information on the flammable hydrogen concentrations at specified distances and orientations around a controlled hydrogen leak. Initial experimental work was conducted at low pressures resulting in very low hydrogen concentrations. Commercial available original equipment manufacturer (OEM) hydrogen sensors were capable of measuring 0.2% hydrogen which for the low pressures and gas flows here proved sufficient to enable us to make sensible conclusions. However higher pressures and gas flows are essential in practical use hence higher concentrations of hydrogen need to be measured. A custom sensor was developed by HySA while commercial sensors (OEM) were investigated. This work reports on the testing and evaluation of several hydrogen sensors. Results of initial ventilation tests are presented.
Structural Response for Vented Hydrogen Deflagrations: Coupling CFD and FE Tools
Sep 2017
Publication
This paper describes a methodology for simulating the structural response of vented enclosures during hydrogen deflagrations. The paper also summarises experimental results for the structural response of 20-foot ISO (International Organization for Standardization) containers in a series of vented hydrogen deflagration experiments. The study is part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA). The project is funded by the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 671461. The HySEA project focuses on vented hydrogen deflagrations in containers and smaller enclosures with internal congestion representative of industrial applications. The structural response modelling involves one-way coupling of pressure loads taken either directly from experiments or from simulations with the computational fluid dynamics (CFD) tool FLACS to the non-linear finite element (FE) IMPETUS Afea Solver. The performance of the FE model is evaluated for a range of experiments from the HySEA project in both small-scale enclosures and 20-foot ISO containers. The paper investigates the sensitivity of results from the FE model to the specific properties of the geometry model. The performance of FLACS is evaluated for a selected set of experiments from the HySEA project. Furthermore the paper discusses uncertainties associated with the combined modelling approach.
Safety of Hydrogen Powered Industrial Trucks, Lessons Learned and Existing Codes and Standards Gaps
Sep 2011
Publication
This paper provides an introduction to the powered industrial truck application of fuel cell power systems the safety similarities with the automotive application and safety lessons learned. Fuel Cell niche markets have proven their value to many early adopters. How has the automotive market provided a springboard for these niche applications? How are niche markets revealing gaps in current safety approaches? What is different about the powered industrial truck application and what new codes and standards are needed to accommodate those differences?
Engineering Safety in Hydrogen-Energy Applications
Oct 2015
Publication
Since a few years hydrogen appears as a practical energy vector and some hydrogen applications are already on the market. However these applications are still considered dangerous hazardous events like explosion could occur and some accidents like the Hindenburg disaster are still in the mind. Objectively hydrogen ignites easily and explodes violently. Safety engineering has to be particularly strong and demonstrative; a method of precise identification of accidental scenarios (“probabilities”; “severity”) is developed in this article. This method derived from ARAMIS method permits to identify and to estimate the most relevant safety barriers and therefore helps future users choose appropriate safety strategies.
Numerical Simulation of Deflagration-to-detonation Transition in Hydrogen-air Mixtures with Concentration Gradients
Oct 2015
Publication
Flame acceleration in inhomogeneous combustible gas mixture has largely been overlooked despite being relevant to many accidental scenarios. The present study aims to validate our newly developed density-based solver ExplosionFoam for flame acceleration and deflagration-to-detonation transition. The solver is based on the open source computational fluid dynamics (CFD) platform OpenFOAM®. For combustion it uses the hydrogen-air single-step chemistry and the corresponding transport coefficients developed by the authors. Numerical simulations have been conducted for the experimental set up of Ettner et al. [1] which involves flame acceleration and DDT in both homogeneous hydrogen-air mixture as well as an inhomogeneous mixture with concentration gradients in an obstucted channel. The predictions demonstrate good quantitative agreement with the experimental measurements in flame tip position speed and pressure profiles. Qualitatively the numerical simulations reproduce well the flame acceleration and DDT phenomena observed in the experiment. The results have shown that in the computed cases DDT is induced by the interaction of the precursor inert shock wave with the wall close to high hydrogen concentration rather than with the obstacle. Some vortex pairs appear ahead of the flame due to the interaction between the obstacles and the gas flow caused by combustion-induced expansion but they soon disappear after the flame passes through them. Hydrogen cannot be completely consumed especially in the fuel rich region. This is of additional safety concern as the unburned hydrogen can potentially re-ignite once more fresh air is available in an accidental scenario causing subsequent explosions. The results demonstrate the potential of the newly developed density based solver for modelling flame acceleration and DDT in both homogeneous/inhomogeneous hydrogen-air mixture. Further validation needs to be carried out for other mixtures and large-scale cases.
Dependence of Hydrogen Embrittlement on Hydrogen in the Surface Layer in Type 304 Stainless Steel
Sep 2013
Publication
Hydrogen embrittlement (HE) together with the hydrogen transport behaviour in hydrogen-charged type 304 stainless steel was investigated by combined tension and outgassing experiments. The hydrogen release rate and HE of hydrogen-charged 304 specimens increase with the hydrogen pressure for hydrogen-charging (or hydrogen content) and almost no HE is observed below the hydrogen content of 8.5 mass ppm. Baking at 433 K for 48 h can eliminate HE of the hydrogen-charged 304 specimen while removing the surface layer will restore HE which indicates that hydrogen in the surface layer plays the primary role in HE. Scanning electron microscopy (SEM) and scanning tunnel microscopy (STM) observations show that particles attributed to the strain-induced α′ martensite formation break away from the matrix and the small holes form during deformation on the specimen surface. With increasing strain the connection among small holes along {111} slip planes of austenite will cause crack initiation on the surface and then the hydrogen induced crack propagates from the surface to interior.
Humidity Tolerant Hydrogen-oxygen Recombination Catalysts for Hydrogen Safety Applications
Sep 2017
Publication
Catalytic hydrogen-oxygen recombination is a non-traditional method to limit hydrogen accumulation and prevent combustion in the hydrogen industry. Outside of conventional use in the nuclear power industry this hydrogen safety technology can be applied when traditional hydrogen mitigation methods (i.e. active and natural ventilation) are not appropriate or when a back-up system is required. In many of these cases it is desirable for hydrogen to be removed without the use of power or other services which makes catalytic hydrogen recombination attractive. Instances where catalytic recombination of hydrogen can be utilized as a stand-alone or back-up measure to prevent hydrogen accumulation include radioactive waste storage (hydrogen generated from water radiolysis or material corrosion) battery rooms hydrogen-cooled generators hydrogen equipment enclosures etc.<br/>Water tolerant hydrogen-oxygen recombiner catalysts for non-nuclear applications have been developed at Canadian Nuclear Laboratories (CNL) through a program in which catalyst materials were selected prepared and initially tested in a spinning-basket type reactor to benchmark the catalyst’s performance with respect to hydrogen recombination in dry and humid conditions. Catalysts demonstrating high activity for hydrogen recombination were then selected and tested in trickle-bed and gas phase recombiner systems to determine their performance in more typical deployment conditions. Future plans include testing of selected catalysts after exposure to specific poisons to determine the catalysts’ tolerance for such poisons.
Validated Equivalent Source Model for an Under-expanded Hydrogen Jet
Oct 2015
Publication
As hydrogen fuel cell vehicles become more widely adopted by consumers the demand for refuelling stations increases. Most vehicles require high-pressure (either 350 or 700 bar) hydrogen and therefore the refuelling infrastructure must support these pressures. Fast running reduced order physical models of releases from high-pressure sources are needed so that quantitative risk assessment can guide the safety certification of these stations. A release from a high pressure source is choked at the release point forming the complex shock structures of an under-expanded jet before achieving a characteristic Gaussian pro le for velocity density mass fraction etc. downstream. Rather than using significant computational resources to resolve the shock structure an equivalent source model can be used to quickly and accurately describe the ow in terms of velocity diameter and thermodynamic state after the shock structure. In this work we present correlations for the equivalent boundary conditions of a subsonic jet as a high-pressure jet downstream of the shock structure. Schlieren images of under-expanded jets are used to show that the geometrical structure of under-expanded jets scale with the square root of the static to ambient pressure ratio. Correlations for an equivalent source model are given and these parameters are also found to scale with square root of the pressure ratio. We present our model as well as planar laser Rayleigh scattering validation data for static pressures up to 60 bar.
From Research Results to Published Codes And Standards - Establishing Code Requirements For NFPA 55 Bulk Hydrogen Systems Separation Distances
Sep 2009
Publication
Performing research in the interest of providing relevant safety requirements is a valuable and essential endeavor but translating research results into enforceable requirements adopted into codes and standards a process sometimes referred to as codification can be a separate and challenging task. This paper discusses the process utilized to successfully translate research results related to bulk gaseous hydrogen storage separation (or stand-off) distances into code requirements in NFPA 55:Storage Use and Handling of Compressed Gases and Cryogenic Fluids in Portable and StationaryContainers Cylinders and Tanks and NFPA 2: Hydrogen Technologies. The process utilized can besummarized as follows: First the technical committees for the documents to be revised were engaged to confirm that the codification process was endorsed by the committee. Then a sub-committee referred to as a task group was formed. A chair must be elected or appointed. The chair should be a generalist with code enforcement or application experience. The task group was populated with several voting members of each technical committee. By having voting members as part of the task group the group becomes empowered and uniquely different from any other code proposal generating body. The task group was also populated with technical experts as needed but primarily the experts needed are the researchers involved. Once properly populated and empowered the task group must actively engage its members. The researchers must educate the code makers on the methods and limitations of their work and the code makers must take the research results and fill the gaps as needed to build consensus and create enforceable code language and generate a code change proposal that will be accepted. While this process seems simple there are pitfalls along the way that can impede or nullify the desired end result – changes to codes and standards. A few of these pitfalls include: wrong task group membership task group not empowered task group not supported in-person meetings not possible consensus not achieved. This paper focuses on the process used and how pitfalls can be avoided for future efforts.
HyP SA – Our safety story
Sep 2019
Publication
Australian Gas Infrastructure Group’s (AGIG’s) vision is to be the leading gas infrastructure business in Australia this means delivering for our customers being a good employer and being sustainably cost efficient. Establishing and developing a hydrogen industry is a key pathway for us to achieve our vision.
In South Australia AGIG is pioneering the introduction of hydrogen into its existing gas distribution networks through the Hydrogen Park South Australia (HyP SA) project. With safety our top priority we would like to give an overview of the safety considerations of our site our network methodology and the development of new safety procedures and culture regarding the production handling and reticulation of a 5% hydrogen blend.
We will cover three themes each having a safety story that is specific to the Australian context and to the project’s success:
The Production Plant and Site
Project site safety known hazards and risk mitigation electrical protection safety procedures lighting and security. Hydrogen storage filling and transportation.
The Network
Securing the network for an isolated safe demonstration footprint. Gas network and hydrogen safety considerations why 5%? Emergency procedures and crew training. New safety regulations blended networks. How does hydrogen perform in a blended gas with respect to leaks? How safe is the existing network and what sensors and controls are we using.
The Home
Introducing blended gas to existing homes. Appliance safety and failure mode analysis. Community engagement and education on a 5% renewable hydrogen gas blend and use in the home
.
We aim to give a comprehensive overview of delivering a safe demonstration network for the HyP SA project in terms of the three main ecosystems that the hydrogen will be present our learnings so far and the development of the safety methodologies that will be applied in the industry in the future.
In South Australia AGIG is pioneering the introduction of hydrogen into its existing gas distribution networks through the Hydrogen Park South Australia (HyP SA) project. With safety our top priority we would like to give an overview of the safety considerations of our site our network methodology and the development of new safety procedures and culture regarding the production handling and reticulation of a 5% hydrogen blend.
We will cover three themes each having a safety story that is specific to the Australian context and to the project’s success:
The Production Plant and Site
Project site safety known hazards and risk mitigation electrical protection safety procedures lighting and security. Hydrogen storage filling and transportation.
The Network
Securing the network for an isolated safe demonstration footprint. Gas network and hydrogen safety considerations why 5%? Emergency procedures and crew training. New safety regulations blended networks. How does hydrogen perform in a blended gas with respect to leaks? How safe is the existing network and what sensors and controls are we using.
The Home
Introducing blended gas to existing homes. Appliance safety and failure mode analysis. Community engagement and education on a 5% renewable hydrogen gas blend and use in the home
.
We aim to give a comprehensive overview of delivering a safe demonstration network for the HyP SA project in terms of the three main ecosystems that the hydrogen will be present our learnings so far and the development of the safety methodologies that will be applied in the industry in the future.
CFD Modeling OF LH2 Dispersion Using the ADREA-HF Code
Sep 2011
Publication
In the present work the computational fluid dynamics (CFD) code ADREA-HF has been applied to simulate the very recent liquefied hydrogen spill experiments performed by the Health Safety Laboratory (HSL). The experiment consists of four LH2 release trials over concrete at a fixed rate of 60 lt/min but with different release direction height and duration. In the modeling the hydrogen source was treated as a two phase jet enabling simultaneous modeling of pool formation spreading as well as hydrogen vapor dispersion. Turbulence was modeled with the standard k- model modified for buoyancy effects. The effect of solidification of the atmospheric humidity was taken into account. The predicted concentration at the experimental sensors? locations was compared with the observed one. The results from the comparison of the predicted concentration with and without solidification of the atmospheric humidity indicate that the released heat from the solidification affects significantly the buoyant behavior of the hydrogen vapor. Therefore the simulation with solidification of the atmospheric humidity is in better agreement with the experiment.
Hytunnel Project to Investigate the Use of Hydrogen Vehicles in Road Tunnels
Sep 2009
Publication
Hydrogen vehicles may emerge as a leading contender to replace today’s internal combustion engine powered vehicles. A Phenomena Identification and Ranking Table exercise conducted as part of the European Network of Excellence on Hydrogen Safety (HySafe) identified the use of hydrogen vehicles in road tunnels as a topic of important concern. An internal project called HyTunnel was duly established within HySafe to review identify and analyse the issues involved and to contribute to the wider activity to establish the true nature of the hazards posed by hydrogen vehicles in the confined space of a tunnel and their relative severity compared to those posed by vehicles powered by conventional fuels including compressed natural gas (CNG). In addition to reviewing current hydrogen vehicle designs tunnel design practice and previous research a programme of experiments and CFD modelling activities was performed for selected scenarios to examine the dispersion and explosion hazards potentially posed by hydrogen vehicles. Releases from compressed gaseous hydrogen (CGH2) and liquid hydrogen (LH2) powered vehicles have been studied under various tunnel geometries and ventilation regimes. The findings drawn from the limited work done so far indicate that under normal circumstances hydrogen powered vehicles do not pose a significantly higher risk than those powered by petrol diesel or CNG but this needs to be confirmed by further research. In particular obstructions at tunnel ceiling level have been identified as a potential hazard in respect to fast deflagration or even detonation in some circumstances which warrants further investigation. The shape of the tunnel tunnel ventilation and vehicle pressure relief device (PRD) operation are potentially important parameters in determining explosion risks and the appropriate mitigation measures.
Modeling of 2LiBH4+MgH2 Hydrogen Storage System Accident Scenarios Using Empirical and Theoretical Thermodynamics
Sep 2009
Publication
It is important to understand and quantify the potential risk resulting from accidental environmental exposure of condensed phase hydrogen storage materials under differing environmental exposure scenarios. This paper describes a modelling and experimental study with the aim of predicting consequences of the accidental release of 2LiBH4+MgH2 from hydrogen storage systems. The methodology and results developed in this work are directly applicable to any solid hydride material and/or accident scenario using appropriate boundary conditions and empirical data.
The ability to predict hydride behaviour for hypothesized accident scenarios facilitates an assessment of the risk associated with the utilization of a particular hydride. To this end an idealized finite volume model was developed to represent the behaviour of dispersed hydride from a breached system. Semi-empirical thermodynamic calculations and substantiating calorimetric experiments were performed in order to quantify the energy released energy release rates and to quantify the reaction products resulting from water and air exposure of a lithium borohydride and magnesium hydride combination.
The hydrides LiBH4 and MgH2 were studied individually in the as-received form and in the 2:1 “destabilized” mixture. Liquid water hydrolysis reactions were performed in a Calvet calorimeter equipped with a mixing cell using neutral water. Water vapor and oxygen gas phase reactivity measurements were performed at varying relative humidities and temperatures by modifying the calorimeter and utilizing a gas circulating flow cell apparatus. The results of these calorimetric measurements were compared with standardized United Nations (UN) based test results for air and water reactivity and used to develop quantitative kinetic expressions for hydrolysis and air oxidation in these systems. Thermodynamic parameters obtained from these tests were then inputted into a computational fluid dynamics model to predict both the hydrogen generation rates and concentrations along with localized temperature distributions. The results of these numerical simulations can be used to predict ignition events and the resultant conclusions will be discussed.
The ability to predict hydride behaviour for hypothesized accident scenarios facilitates an assessment of the risk associated with the utilization of a particular hydride. To this end an idealized finite volume model was developed to represent the behaviour of dispersed hydride from a breached system. Semi-empirical thermodynamic calculations and substantiating calorimetric experiments were performed in order to quantify the energy released energy release rates and to quantify the reaction products resulting from water and air exposure of a lithium borohydride and magnesium hydride combination.
The hydrides LiBH4 and MgH2 were studied individually in the as-received form and in the 2:1 “destabilized” mixture. Liquid water hydrolysis reactions were performed in a Calvet calorimeter equipped with a mixing cell using neutral water. Water vapor and oxygen gas phase reactivity measurements were performed at varying relative humidities and temperatures by modifying the calorimeter and utilizing a gas circulating flow cell apparatus. The results of these calorimetric measurements were compared with standardized United Nations (UN) based test results for air and water reactivity and used to develop quantitative kinetic expressions for hydrolysis and air oxidation in these systems. Thermodynamic parameters obtained from these tests were then inputted into a computational fluid dynamics model to predict both the hydrogen generation rates and concentrations along with localized temperature distributions. The results of these numerical simulations can be used to predict ignition events and the resultant conclusions will be discussed.
Hydrogen Onboard Storage: An Insertion of the Probabilistic Approach Into Standards & Regulations?
Sep 2005
Publication
The growing attention being paid by car manufacturers and the general public to hydrogen as a middle and long term energy carrier for automotive purpose is giving rise to lively discussions on the advantages and disadvantages of this technology – also with respect to safety. In this connection the focus is increasingly and justifiably so on the possibilities offered by a probabilistic approach to loads and component characteristics: a lower weight obliged with a higher safety level basics for an open minded risk communication the possibility of a provident risk management the conservation of resources and a better and not misleading understanding of deterministic results. But in the case of adequate measures of standards or regulations completion there is a high potential of additional degrees of freedom for the designers obliged with a further increasing safety level. For this purpose what follows deals briefly with the terminological basis and the aspects of acceptance control conservation of resources misinterpretation of deterministic results and the application of regulations/standards.<br/>This leads into the initial steps of standards improvement which can be taken with relatively simple means in the direction of comprehensively risk-oriented protection goal specifications. By this it’s not focused on to provide to much technical details. It’s focused on the context of different views on probabilistic risk assessment. As main result some aspects of the motivation and necessity for the currently running pre-normative research studies within the 6th frame-work program of the EU will be shown.
Pool Spreading and Vaporization of Liquid Hydrogen
Sep 2005
Publication
An essential part of a safety analysis to evaluate the risks of a liquid hydrogen (LH2) containing system is the understanding of cryogenic pool spreading and its vaporization. It represents the initial step in an accident sequence with the inadvertent spillage of LH2 e.g. after failure of a transport container tank or the rupture of a pipeline. This stage of an accident scenario provides pertinent information as a source term for the subsequent analysis steps of atmospheric dispersion and at presence of an ignition source the combustion of the hydrogen-air vapor cloud. A computer model LAUV has been developed at the Research Center Juelich which is able to simulate the spreading and vaporization of a cryogenic liquid under various conditions such as different grounds (solid water). It is based on the so-called shallow-layer differential equations taking into account physical phenomena such as ice formation if the cryogen is spilled on a water surface. The presentation will give a description of the computer model and its validation against existing experimental data. Furthermore calculational results will be analyzed describing the prediction and quantification of the consequences of an LH2 spill for different cases. They also include the comparison of an LH2 spillage versus the corresponding release of other cryogens such as liquid natural gas liquid oxygen and liquid nitrogen.
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