Safety of hydrogen/natural gas mixtures by pipelines : ANR french project HYDROMEL

International audienceIn order to gain a better understanding of hazards linked with Hydrogen/Natural gas mixtures transport by pipeline, the National Institute of Industrial Environment and Risks (INERIS) alongside with the Atomic Energy Commission (CEA), the industrial companies Air Liquide and GDF SUEZ, and the French Research Institutes ICARE and PPRIME (CNRS) have been involved in a project called HYDROMEL. This project was partially funded by the French National Research Agency (ANR) in the framework of its PAN-H program aimed at promoting the R&D activities related to the hydrogen deployment. Firstly, the project partners investigated how a NG/H2 mixture may influence the modeling of a hazard scenario, i.e. how the addition of a quantity of hydrogen in natural gas can increase the potential of danger. Therefore it was necessary to build an experimental database of physics properties for mixtures. Secondly, effect distances in accidental scenarios that could happen on pipelines have been calculated with existing models adapted to the mixtures. This part was preceded by a benchmark exercise between all partners' models and experimental results found in the literature. Finally the consortium wrote a 'good practice guideline for modeling the effects related to the release of natural gas /hydrogen mixture'. The selected models and their comparison with data collected in the literature as well as the experimental results of this project, and the main conclusions of the guidelines are presented in this paper

Evaluation of two-phase flow models for accidental release and comparison with experimental data

International audienceUnderstanding the dynamics of a two-phase flow (liquid and gas) has been studied quite extensively over the past. This problem is indeed of direct relevance for many areas such as transportation, chemical processes and for the area of industrial risk assessment. For several years, INERIS has been conducting various experiments in order to understand the mechanisms of vaporisation during the release of products initially stored in the liquid phase, into the atmosphere. The purpose is to determine the gas fraction flowing not only in the pipeline but also in the released jet and the liquid fraction that could be trapped on the ground because of the presence of an obstacle. The studied products were propane, butane and ammonia. Various regimes of flows were tested and a database was created. Then, an evaluation of different models for calculating the two-phase flow and the droplet behaviour was based on flow regimes and experimental set-up. The first objective was to calculate the flow rate in the pipeline and predict the size of the droplets in the initial part of the jet. There was a wide scatter of the results and many difficulties arose during the determination of the flow evaporation rate. This paper presents the experimental results and conclusions on the validity of the twophase models depending on the products, experimental set-up, and pressure storage

Transport du CO2 par canalisation : évaluations des risques

Nowadays, the CCS chain (carbon capture and storage) is considered as an interesting solution to fight the global warming by reducing CO2 concentrations in the atmosphere. However, in case of massive accidental leak of CO2, which can be mixed with toxic impurities (NOx, SOx…), this could lead to toxic effects in humans located in the nearby environment. Between capture and storage, the pipeline transport is the part of the network the most vulnerable and the most difficult to protect. The development of a safe chain of CO2 then requires to develop risk assessment methods dedicated to CO2 transport by pipeline. This involves the production of new knowledge about the mechanisms of dense gas clouds dispersion, multiphase flows, and sudden process of relaxation of supercritical fluids. For this, several experiments are currently carried out at INERIS. Firstly, a thermodynamic set-up was built in order to determine the thermo-physical and thermodynamics data required for the formulation of the phase equilibrium model. Secondly, a mid-scale set-up allows to get the fluid flow pattern maps required for the formulation of the heterogeneous discharge model, the near-field particle size distribution and velocity profiles. Further tests on a larger scale are planned to check that the current results and models could be extrapolated to massive releases of CO2. Some calculations carried out with dispersion softwares seem to provide different results in terms of hazardous distances for instantaneous or continuous releases. A focus on the models used by the softwares appears necessary to get a better understanding of this difference in the risk assessment context.Les projets France Nord (Ademe) et CO2PipeHaz (Commission européenne) sont focalisés sur la compréhension des mécanismes physiques mis en jeu lors d’un rejet de CO2 dans l’atmosphère, lors du transport de CO2. Les risques liés au transport sont ciblés spécifiquement car les réseaux sont plus vulnérables et plus difficiles à protéger que d’autres éléments de la chaîne. Or, à l’occasion d’une fuite accidentelle, on craint la formation d’un nuage dense de CO2 qui maintiendrait au niveau du sol les polluants, éventuellement toxiques, véhiculés par le CO2 (SO2, H2S, NOx…). Dans ce cadre, des connaissances sont recherchées, en particulier, sur les mécanismes de formation des nuages gazeux très denses, multiphasiques et sur les processus de détente brutale des fluides supercritiques, sujet pour lesquels il n’est pas certain que les outils de modélisation disponibles soient pertinents dans le cas de création de neige carbonique lors de la détente. Ces scénarios de fuite sont donc étudiés par l’INERIS pour produire des connaissances et des outils de base qui contribuent à une meilleure maîtrise des risques des installations de transport de CO2

Assessment of the models for the estimation of the CO2 releases toxic effects

Currently, INERIS is involved in European and French projects regarding the CCS chain (carbon capture and storage). Nowadays, some people consider this chain as a future device to fight against the global warming due to high concentration of CO2 in the atmosphere. However, in case of massive accidental leak of CO2, this substance could be the origin of toxic effects for human. Now, carbon dioxide concentrations considered as potentially toxic get close to 10 0000 ppm. To estimate precisely the distances reached by this hazardous level of concentrations, an efficient understanding of the CO2 release phenomena, from the assessment of the mass flow rate to the atmospheric dispersion, is necessary. Whereas the carbon dioxide is often stored and handled under 2-phase or supercritical conditions associated to storage pressure, CO2 ice formation is possible in case of accidental leak in the atmosphere due to specific properties regarding its triple point. Then, this CO2 flakes creation may be followed by the liquid/solid CO2 pool formation on the ground. Due to the important pressure drop of the fluid during the leak, a significant expansion phase, a high rate of air entrainment and a huge temperature drop followed by a dense and cold cloud formation should be considered. Concerning these specific points, a few of atmospheric dispersion softwares take into account the carbon dioxide specific conditions of release. And moreover, some calculations carried out with other software seem to provide different results in terms of hazardous distances for instantaneous or continuous releases. A focus on the models used by the softwares appears interesting to let a better understanding of this difference in the risk assessment context

Influence of the flammable cloud geometry on the gas explosion effects

International audienc

La sécurité du captage et du stockage du CO2 : un défi pour les industries de l'énergie

National audienceL'accumulation de CO2 dans l'atmosphère induite notamment par les systèmes de production d'énergie qui utilisent des énergies fossiles est largement jugée responsable du réchauffement climatique. Une solution à court et moyen terme a été proposée qui consiste à capter à la source le CO2 dans les fumées de combustion (ou l'extraire du combustible avant combustion), puis à le transporter jusqu'à des zones de stockage géologique. La mise en oeuvre pratique soulève cependant bien des difficultés dont la sécurité. On s'interroge en particulier sur l'effet de fuite massive sur les canalisations de transport, en ayant en tête la tragédie du lac Nyos en Afrique qui a fait 1800 victimes. On présente dans ce document des résultats d'expériences consacrées à la caractérisation de ces fuites. Des moyens d'essais tout à fait originaux ont été mis en place, dont en particulier un réservoir de 2m3 capable de contenir du CO2 en phase dense (comme prévu dans les canalisations de transport), à une pression plus grande que 70 bar, reliée à une canalisation de dépotage permettant des rejets jusqu'à un diamètre d'orifice de 2 pouces. L'installation pourvue de thermocouples, de capteurs de pression et d'un système de pesée a permis de mesurer avec précision les débits massiques et l'état du fluide à l'orifice. Par ailleurs, le nuage formé à l'extérieur a été examiné en détail, dont en particulier la répartition des températures et des concentrations. A fort débit, l'incidence des forces de pesanteur se manifeste de manière nette, ce qui laisse augurer d'une très faible propension à la dispersion

Transferts thermiques des écoulements turbulents compressibles en conduites (étude par simulation numérique des grandes échelles)

Dans de nombreux dispositifs industriels comme les conduites de refroidissement des moteurs de fusées, un écoulement turbulent est en contact avec une paroi solide chaude.L'instabilité due aux courbures ajoutée au confinement créent des courants orthogonaux au flux principal d'une intensité pouvant aller jusqu'à 20% de celui-ci. Pour comprendre les interactions entre ces courants secondaires et les transferts thermiques, des résultats de simulations numériques des grandes échelles sont obtenus dans des conduites pouvant présenter des courbures et des parois chauffées. Un écoulement pleinement développé est injecté à l'entrée du domaine par la simulation synchrone d'une conduite périodique. Un modèle de viscosité turbulente a été implanté dans le code de calcul et aucune loi de paroi n'est utilisée. Une température supérieure est d'abord appliquée sur une des quatre parois d'une conduite carrée rectiligne pour une validation du code de calcul. Les mécanismes d'éjections de fluide chaud de la paroi chauffée vers le coeur de la conduite sont bien représentés et on peut observer le développement progressif de la couche limite thermique. L'évolution spatiale de l'écoulement a ensuite permis d'appliquer un flux constant.Une conduite de section rectangulaire en forme de S a ensuite été simulée. A chaque courbure, apparaît un fort flux secondaire inhérent au gradient de pression normal aux parois courbes. Ceci implique la naissance d'une paire de tourbillons longitudinaux contra-rotatifs de type "Dean" ou "Ekman" évoluant au voisinage de la paroi convexe.L'interaction entre ces courants secondaires et le mélange turbulent est étudiée suivant les modes de chauffage.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Etude bibliographique et expérimentale sur la caractérisation de l'inflammabilité du méthane enrichi en hydrogène dans le cadre d'évaluation des risques de l'injection d'hydrogène dans le réseau de gaz naturel (concept « power to gas »)

National audienc

Hardware and instrumentation to investigate massive releases of dense phase CO2

CCS (carbon capture and storage) is seen as a possibility to mitigate the global warming effect. The practical implementation of this technique faces a few challenges like safety issues. It is wondered if a massive release affecting the pipeline (may be the most vulnerable part of the CCS chain) would not lead to a disaster remembering what happened in Africa about 28 years ago (about Nyos Lake accident see Eos, 2009). Few experimental observations of large-scale CO2 releases have been made, and the physics and thermochemistry involved are not fully understood, even if considerable progress has been made theoretically.(2) In this paper, the experimental techniques used to investigate this specific problem are described and illustrated with some key results extracted from various projects. Innovative techniques were employed to control the mass flowrate, blowdown, nearfield, and farfield dispersion in the atmosphere. A 2m(3) spherical vessel able to store up to 1000kg of CO2 at a pressure above 8MPa was used. Dense CO2 was allowed to spill out via a 50mm pipe. The temperature, CO2 concentration, and density field of the outside cloud were monitored using thermocouples and concentration probes. Among other results, it was in particular shown that when the mass flowrate is large enough, body forces become significant forcing the cloud to stay on the ground