Publications

Passive auto-catalytic recombiners (PARs) have the potential to be used in the future for the removal of accidentally released hydrogen inside confined areas. PARs could be operated both as stand-alone or backup safety devices e.g. in case of active ventilation failure.

Recently computational fluid dynamics (CFD) simulations have been performed in order to demonstrate the principal performance of a PAR during a postulated hydrogen release inside a car garage. This fundamental study has now been extended towards a variation of several boundary conditions including PAR location hydrogen release scenario and active venting operation. The goal of this enhanced study is to investigate the sensitivity of the PAR operational behaviour for changing boundary conditions and to support the identification of a suitable PAR positioning strategy. For the simulation of PAR operation the in-house code REKO-DIREKT has been implemented in the CFD code ANSYS-CFX 15.

In a first step the vertical position of the PAR and the thermal boundary conditions of the garage walls have been modified. In a subsequent step different hydrogen release modes have been simulated which result either in a hydrogen-rich layer underneath the ceiling or in a homogeneous hydrogen distribution inside the garage. Furthermore the interaction of active venting and PAR operation has been investigated.

As a result of this parameter study the optimum PAR location was identified to be close underneath the garage ceiling. In case of active venting failure the PAR efficiently reduces the flammable gas volume (hydrogen concentration > 4 vol.%) for both stratified and homogeneous distribution. However the simulations indicate that the simultaneous operation of active venting and PAR may in some cases reduce the overall efficiency of hydrogen removal. Consequently a well-matched arrangement of both safety systems is required in order to optimize the overall efficiency. The presented CFD-based approach is an appropriate tool to support the assessment of the efficiency of PAR application for plant design and safety considerations with regard to the use of hydrogen in confined areas.

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.

Nomograms for assessment of hazard distances from a blast wave generated by a catastrophic rupture of stand-alone (stationary) and onboard compressed hydrogen cylinder in a fire are presented. The nomograms are easy to use hydrogen safety engineering tools. They were built using the validated and recently published analytical model. Two types of nomograms were developed – one for use by first responders and another for hydrogen safety engineers. The paper underlines the importance of an international effort to unify harm and damage criteria across different countries as the discrepancies identified by the authors gave the expected results of different hazard distances for different criteria.

The deterioration of the mechanical properties of metal induced by hydrogen absorption threatens the safety of the equipment serviced in hydrogen environments. In this study the hydrogen concentration distribution in 2.25Cr-1Mo-0.25V steel after hydrogen charging was analyzed following the hydrogen permeation and diffusion model. The diffusible hydrogen content in the 1-mm-thick specimen and its influence on the mechanical properties of the material were investigated by glycerol gas collecting test static hydrogen charging tensile test scanning electron microscopy (SEM) test and microhardness test. The results indicate that the content of diffusible hydrogen tends to be the saturation state when the hydrogen charging time reaches 48 h. The simulation results suggest that the hydrogen concentration distribution can be effectively simulated by ABAQUS and the method can be used to analyze the hydrogen concentration in the material with complex structures or containing multiple microstructures. The influence of hydrogen on the mechanical properties is that the elongation of this material is reduced and the diffusible hydrogen will cause a decrease in the fracture toughness of the material and thus hydrogen embrittlement (HE) will occur. Moreover the Young’s modulus E and microhardness are increased due to hydrogen absorption and the variation value is related to the hydrogen concentration introduced into the specimen.

We at Kawasaki have proposed a “CO2 free H2 chain” using the abundant brown coal of Australia as a hydrogen source. We developed the basic design package and finished the Front End Engineering Design (FEED) in 2014. There are not only the hazards of the processing plant system but also the characteristic hazards of a hydrogen plant system. We considered and carried out Hazard Identification (HAZID) as the most appropriate approach for safety design in this stage. This paper describes the safety design and HAZID which we practiced for the CO2-Free Hydrogen Supply Chain FEED.

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.

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.

Renewable generation technologies (e.g. photovoltaic panels (PV)) are often installed in buildings and districts with an aim to decrease their carbon emissions and consumption of non-renewable energy. However due to a mismatch between supply and demand at an hourly but also on a seasonal timescale; a large amount of electricity is exported to the grid rather than used to offset local demand. A solution to this is local storage of electricity for subsequent self-consumption. This could additionally provide districts with new business opportunities financial stability flexibility and reliability.<br/>In this paper the feasibility of hydrogen based electricity storage for a district is evaluated. The district energy system (DES) includes PV and hybrid photovoltaic panels (PVT). The proposed storage system consists of production of hydrogen using the renewable electricity generated within the district hydrogen storage and subsequent use in a fuel cell. Combination of battery storage along with hydrogen conversion and storage is also evaluated. A multi-energy optimization approach is used to model the DES. Results of the model are optimal battery capacity electrolyzer capacity hydrogen storage capacity fuel cell capacity and energy flows through the system. The model is also used to compare different system design configurations. The results of this analysis show that both battery capacity and conversion of electricity to hydrogen enable the district to decrease its carbon emissions by approximately 22% when compared to the reference case with no energy storage.

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.

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.