France
Development of a Model Evaluation Protocol for CFD Analysis of Hydrogen Safety Issues – The SUSANA Project
Oct 2015
Publication
The “SUpport to SAfety aNAlysis of Hydrogen and Fuel Cell Technologies (SUSANA)” project aims to support stakeholders using Computational Fluid Dynamics (CFD) for safety engineering design and assessment of FCH systems and infrastructure through the development of a model evaluation protocol. The protocol covers all aspects of safety assessment modelling using CFD from release through dispersion to combustion (self-ignition fires deflagrations detonations and Deflagration to Detonation Transition - DDT) and not only aims to enable users to evaluate models but to inform them of the state of the art and best practices in numerical modelling. The paper gives an overview of the SUSANA project including the main stages of the model evaluation protocol and some results from the on-going benchmarking activities.
Hydrogen Storage: Recent Improvements and Industrial Perspectives
Sep 2017
Publication
Efficient storage of hydrogen is crucial for the success of hydrogen energy markets (early markets as well as transportation market). Hydrogen can be stored either as a compressed gas a refrigerated liquefied gas a cryo-compressed gas or in hydrides. This paper gives an overview of hydrogen storage technologies and details the specific issues and constraints related to the materials behaviour in hydrogen and conditions representative of hydrogen energy uses. It is indeed essential for the development of applications requiring long-term performance to have good understanding of long-term behaviour of the materials of the storage device and its components under operational loads.
The CALIF3S-P2remics Software – An Application to Underexpanded Hydrogen Jet Deflagration
Sep 2019
Publication
To assess explosion hazard the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) is developing the P2REMICS software (for Partially PREMIxed Combustion Solver) on the basis of the generic CFD solver library CALIF3S (for Components Adaptive Library for Fluid Flow Simulation). Both P2REMICS and CALIF3S are in-house IRSN softwares released under an open-source license. CALIF3S-P2REMICS is dedicated to the simulation of explosion scenarii (explosive atmosphere formation deflagration or detonation and blast waves propagation) for hydrogen as more generally for any explosive gas or gas/dust mixture. It is based on staggered space discretizations and implements fractional-steps time algorithms well suited for massively parallel computations. A wide range of experiments is used for the software validation. Among them we focus here on a free underexpanded hydrogen jet deflagration performed in two steps: first the hydrogen is released in air up to obtain a steady jet (dispersion phase) then the deflagration is triggered. For the dispersion phase simulation a notional nozzle approach is used to get rid of the description of the shocked zone located near the nozzle. Then a so-called turbulent flame velocity approach is chosen for the deflagration simulation. The computations allow to highlight the complex flow structures induced by the inhomogeneity fuel concentration in the jet. A large dispersion of results is observed depending on the chosen correlation for the turbulent flame speed.
Hydrogen Effect on Fatigue and Fracture of Pipe Steels
Sep 2009
Publication
Transport by pipe is one the most usual way to carry liquid or gaseous energies from their extraction point until their final field sites. To limit explosion risk or escape to avoid pollution problems and human risks it is necessary to assess nocivity of defect promoting fracture. This need to know the mechanical properties of the pipes steels. Hydrogen is considered to day as a new energy vector and its transport in one of the key problems to extension of its use. Within the European project NATURALHY it has been proposed to transport a mixture of natural gas and hydrogen. 39 European partners have combined their efforts to assess the effects of hydrogen presence on the existing gas network. Key issues are durability of pipeline material integrity management safety aspects life cycle and socio-economic assessment and end-use. The work described in this paper was performed within the NATURALHY work package on ’Durability of pipeline material’. This study makes it possible to emphasize the hydrogen effect on mechanical properties of several pipe steels as X52 X70 or X100 in fatigue and fracture and in two different environments: air and hydrogen electrolytic.
CFD Benchmark Based on Experiments of Helium Dispersion in a 1m3 Enclosure–intercomparisons for Plumes
Sep 2013
Publication
In the context of the French DIMITRHY project ANR-08-PANH006 experiments have been carried out to measure helium injections in a cubic 1 m3 box - GAMELAN in a reproducible and quantitative manner. For the present work we limit ourselves to the unique configuration of a closed box with a small hole at its base to prevent overpressure. This case leads to enough difficulties of modelisations to deserve our attention. The box is initially filled with air and injections of helium through a tube of diameter 20 mm is operated. The box is instrumented with catharometres to measure the helium volume concentration within an accuracy better than 0.1%. We present the CFD (Fluent and CASTEM ANSYS-CFX and ADREA-HF) calculations results obtained by 5 different teams participating to the benchmark in the following situation: the case of a plume release of helium in a closed box (4NL/min). Parts of the CFD simulations were performed in the European co-funded project HyIndoor others were performed in the French ANR-08-PANH006 DimitrHy project.
CFD design of protective walls against the effects of vapor cloud fast deflagration of hydrogen
Oct 2015
Publication
Protective walls are a well-known and efficient way to mitigate overpressure effects of accidental explosions (detonation or deflagration). For detonation there are multiple published studies whereas for deflagration no well-adapted and rigorous method has been reported in the literature. This article describes the validation of a new modelling approach for fast deflagrations of H2. This approach includes two steps. At the first step the combustion phase of vapor cloud explosion (VCE) involving a fast deflagration is substituted by equivalent vessel burst problem. The purpose of this step is to avoid the reactive flow computations. At the second step CFD is used for computations of pressure propagation from the equivalent (non reactive) vessel burst problem. After verifying the equivalence of the fast deflagration and the vessel burst problem at the first step the capability of two CFD codes such as FLACS and Europlexus are examined for modelling of the vessel burst problem (with and without barriers). Finally the efficiency of finite and infinite barriers used for mitigation of the shock is investigated
Feasibility of Hydrogen Detection by the Use of Uncoated Silicon Microcantilever-based Sensors
Sep 2013
Publication
Hydrogen is a key parameter to monitor radioactive disposal facility such as the envisioned French geological repository for nuclear wastes. The use of microcantilevers as chemical sensors usually involves a sensitive layer whose purpose is to selectively sorb the analyte of interest. The sorbed substance can then be detected by monitoring either the resonant frequency shift (dynamic mode) or the quasi-static deflection (static mode). The objective of this paper is to demonstrate the feasibility of eliminating the need for the sensitive layer in the dynamic mode thereby increasing the long-term reliability. The microcantilever resonant frequency allows probing the mechanical properties (mass density and viscosity) of the surrounding fluid and thus to determine the concentration of a species in a binary gaseous. Promising preliminary work has allowed detecting concentration of 200 ppm of hydrogen in air with non-optimized geometry of silicon microcantilever with integrated actuation and read-out.
Review of Methods For Estimating the Overpressure and Impulse Resulting From a Hydrogen Explosion in a Confined/Obstructed Volume
Sep 2009
Publication
This study deals with the TNO Multi-Energy and Baker-Strehlow-Tang (BST) methods for estimating the positive overpressures and positive impulses resulting from hydrogen-air explosions. With these two methods positive overpressure and positive impulse results depend greatly on the choice of the class number for the TNO Multi-Energy method or the Mach number for the BST methods. These two factors permit the user to read the reduced parameters of the blast wave from the appropriate monographs for each of these methods i.e. positive overpressure and positive duration phase for the TNO Multi-Energy method and positive overpressure and positive impulse for the BST methods. However for the TNO Multi-Energy method the determination of the class number is not objective because it is the user who makes the final decision in choosing the class number whereas with the BST methods the user is strongly guided in their choice of an appropriate Mach number. These differences in the choice of these factors can lead to very different results in terms of positive overpressure and positive impulse. Therefore the objective of this work was to compare the positive overpressures and positive impulses predicted with the TNO Multi-Energy and BST methods with data available from large-scale experiments.
Comparisons of Helium and Hydrogen Releases in 1 M3 and 2 M3 Two Vents Enclosures: Concentration Measurements at Different Flow Rates and for Two Diameters of Injection Nozzle
Oct 2015
Publication
This work presents a parametric study on the similitude between hydrogen and helium distribution when released in the air by a source located inside of a naturally ventilated enclosure with two vents. Several configurations were experimentally addressed in order to improve knowledge on dispersion. Parameters were chosen to mimic operating conditions of hydrogen energy systems. Thus the varying parameters of the study were mainly the source diameter the releasing flow rate the volume and the geometry of the enclosure. Two different experimental set-ups were used in order to vary the enclosure's height between 1 and 2 m. Experimental results obtained with helium and hydrogen were compared at equivalent flow rates determined with existing similitude laws. It appears for the plume release case that helium can suitably be used for predicting hydrogen dispersion in these operating designs. On the other hand – when the flow turns into a jet – non negligible differences between hydrogen and helium dispersion appear. In this case helium – used as a direct substitute to hydrogen – will over predict concentrations we would get with hydrogen. Therefore helium concentration read-outs should be converted to obtain correct predictions for hydrogen. However such a converting law is not available yet.
High-pressure PEM Water Electrolysis and Corresponding Safety Issues
Sep 2009
Publication
In this paper safety considerations related to the operation of proton-exchange membrane (PEM) water electrolysers (hydrogen production capacity up to 1 Nm3/h and operating pressure up to 130 bars) are presented. These results were obtained in the course of the GenHyPEM project a research program on high-pressure PEM water electrolysis supported by the European Commission. Experiments were made using a high-pressure electrolysis stack designed for operation in the 0–130 bars pressure range at temperatures up to 90 °C. Besides hazards related to the pressure itself hydrogen concentration in the oxygen gas production and vice-versa (resulting from membrane crossover permeation effects) have been identified as the most significant risks. Results show that the oxygen concentration in hydrogen at 130 bars can be as high as 2.66 vol %. This is a value still outside the flammability limit for hydrogen–oxygen mixtures (3.9–95.8 vol %) but safety measures are required to prevent explosion hazards. A simple model based on the diffusion of dissolved gases is proposed to account for gas cross-permeation effects. To reduce contamination levels different solutions are proposed. First thicker membranes can be used. Second modified or composite membranes with lower gas permeabilities can be used. Third as reported earlier external catalytic gas recombiners can be used to promote H2/O2 recombination and reduce contamination levels in the gas production. Finally other considerations related to cell and stack design are also discussed to further reduce operation risks.
High Pressure Hydrogen Fires
Sep 2009
Publication
Within the scope of the French national project DRIVE and European project HyPER high pressure jet flames of hydrogen were produced and instrumented.<br/>The experimental technique and measurement strategy are presented. Many aspects are original developments like the direct measurement of the mass flow rate by weighing continuously the hydrogen container the image processing to extract the flame geometry the heat flux measurement device the thermocouples arrangement…<br/>Flames were observed from 900 bar down to 1 bar with orifices ranging from 1 to 3 mm. An original set of data is now available about the main flame characteristics and about some thermodynamic aspects of hydrogen releases under high pressure.<br/>A brief comparison of some available models is presented.
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.
Hydrogen Ironmaking: How It Works
Jul 2020
Publication
A new route for making steel from iron ore based on the use of hydrogen to reduce iron oxides is presented detailed and analyzed. The main advantage of this steelmaking route is the dramatic reduction (90% off) in CO2 emissions compared to those of the current standard blast-furnace route. The first process of the route is the production of hydrogen by water electrolysis using CO2-lean electricity. The challenge is to achieve massive production of H2 in acceptable economic conditions. The second process is the direct reduction of iron ore in a shaft furnace operated with hydrogen only. The third process is the melting of the carbon-free direct reduced iron in an electric arc furnace to produce steel. From mathematical modeling of the direct reduction furnace we show that complete metallization can be achieved in a reactor smaller than the current shaft furnaces that use syngas made from natural gas. The reduction processes at the scale of the ore pellets are described and modeled using a specific structural kinetic pellet model. Finally the differences between the reduction by hydrogen and by carbon monoxide are discussed from the grain scale to the reactor scale. Regarding the kinetics reduction with hydrogen is definitely faster. Several research and development and innovation projects have very recently been launched that should confirm the viability and performance of this breakthrough and environmentally friendly ironmaking process.
Experimental Study of the Effects of Vent Geometry on the Dispersion of a Buoyant Gas in a Small Enclosure
Sep 2011
Publication
We present an experimental study on the dispersion of helium in an enclosure of 1 m3 with natural ventilation through one vent. Three vent geometries have been studied. Injection parameters have been varied so that the injection Richardson number ranges from 2·10−6 to 9 and the volume Richardson number which gives the ability of the release to mix the enclosure content ranges from 8·10−4 to 900. It has been found that the vertical distribution of helium volume fraction can exhibit significant gradient. Nevertheless the results are compared to the simple analytical model based on the homogenous mixture hypothesis which gives fairly good estimates of the maximum helium volume fraction.
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.
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.
Safety Strategy for the First Deployment of a Hydrogen- Based Green Public Building in France
Sep 2011
Publication
HELION a subsidiary of AREVA in charge of the business unit Hydrogen and energy storage is deploying for the first time in a French public building a hydrogen-based energy storage system the Greenergy Box™. The 50 kWe system is coupled with a photovoltaic farm to ensure up to 45% electrical autonomy and power backup to the building. The safety system and siting measures of the complete hydrogen chain are described. The paper also highlights the work accomplished with Fire Authorities and Public to gain the acceptance of the project and allow the deployment of four other hydrogen-based green buildings.
Syngas Explosion Reactivity in Steam Methane Reforming Process
Sep 2013
Publication
During the synthesis of hydrogen by methane steam reforming mixtures composed of H2 CH4 CO and CO2 are produced in the process. In this work the explosion reactivity of these mixtures on the basis of detonation cell size and laminar flame speed is calculated using a reactant assimilation simplification and a kinetic approach. The detonation cells width are calculated using the Cell_CH Kurchatov institute method and the laminar flame velocities are calculated with Chemkin Premix using different detailed chemical kinetic mechanisms. These calculations are used to define if these mixtures could be considered having a medium or a high reactivity for risk assessment in case of leak in the hydrogen plants.
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 Explosion on a Pressure Swing Adsorption Facility
Sep 2011
Publication
Computational fluid dynamic simulations have been performed in order to study the consequences of a hydrogen release from a pressure swing adsorption installation operating at 30 barg. The simulations were performed using FLACS-Hydrogen software from GexCon. The impact of obstruction partial confinement leak orientation and wind on the explosive cloud formation (size and explosive mass) and on explosion consequences is investigated. Overpressures resulting from ignition are calculated as a function of the time to ignition.
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