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Experiments and Simulations of Large Scale Hydrogen-Nitrogen-Air Gas Explosions for Nuclear and Hydrogen Safety Applications
Sep 2023
Publication
Hydrogen safety is a general concern because of the high reactivity compared to hydrocarbon-based fuels. The strength of knowledge in risk assessments related to the physical phenomena and the ability of models to predict the consequence of accidental releases is a key aspect for the safe implementation of new technologies. Nuclear safety considers the possibility of accidental leakages of hydrogen gas and subsequent explosion events in risk analysis. In many configurations the considered gaseous streams involve a large fraction of nitrogen gas mixed with hydrogen. This work presents the results of a large scale explosion experimental campaign for hydrogen-nitrogen-air mixtures. The experiments were performed in a 50 m3 vessel at Gexcon’s test site in Bergen Norway. The nitrogen fraction the equivalence ratio and the congestion level were investigated. The experiments are simulated in the FLACS-CFD software to inform about the current level of conservatism of the predictions for engineering application purposes. The study shows the reduced overpressure with nitrogen added to hydrogen mixtures and supports the use of FLACS-CFD-based risk analysis for hydrogen-nitrogen scenarios.
Safe Design for Large Scale H2 Production Facilities
Sep 2023
Publication
To contribute to a more diverse and efficient energy infrastructure large quantities of hydrogen are requested for industries (e.g. mining refining fertilizers…). These applications need large scale facilities such as dozens of electrolyzer stacks from atmospheric pressure to 30 bar with a total capacity ranging from 100 up to 400 MW and associated hydrogen storage from a few to 50 tons.
Local use can be fed by electrolyzer in 20 feet container and stored in bundles with small volumes. Nevertheless industrial applications can request much bigger capacity of production which are generally located in buildings. The different technologies available for the production of hydrogen at large scale are alkaline or PEM electrolyzer with for example 100 MW capacity in a building of 20000 m3 and hydrogen stored in tube trailers or other fixed hydrogen storage solution with large volumes.
These applications led to the use of hydrogen inside large but confined spaces with the risk of fire and explosion in case of loss of containment followed by ignition. This can lead to severe consequences on asset workers and public due to the large inventories of hydrogen handled.
This article aims to provide an overview of the strategy to safely design large scale hydrogen production facilities in buildings through benchmarks based on projects and literature reviews best practices & standards regulations. It is completed by a risk assessment taking into consideration hydrogen behavior and influence of different parameters in dispersion and explosion in large buildings.
This article provides recommendations for hydrogen project stakeholders to perform informed-based decisions for designing large scale production buildings. It includes safety measures as reducing hydrogen inventories inside building allocating clearance around electrolyzer stacks implementing early detection and isolation devices and building geometry to avoid hydrogen accumulation.
Local use can be fed by electrolyzer in 20 feet container and stored in bundles with small volumes. Nevertheless industrial applications can request much bigger capacity of production which are generally located in buildings. The different technologies available for the production of hydrogen at large scale are alkaline or PEM electrolyzer with for example 100 MW capacity in a building of 20000 m3 and hydrogen stored in tube trailers or other fixed hydrogen storage solution with large volumes.
These applications led to the use of hydrogen inside large but confined spaces with the risk of fire and explosion in case of loss of containment followed by ignition. This can lead to severe consequences on asset workers and public due to the large inventories of hydrogen handled.
This article aims to provide an overview of the strategy to safely design large scale hydrogen production facilities in buildings through benchmarks based on projects and literature reviews best practices & standards regulations. It is completed by a risk assessment taking into consideration hydrogen behavior and influence of different parameters in dispersion and explosion in large buildings.
This article provides recommendations for hydrogen project stakeholders to perform informed-based decisions for designing large scale production buildings. It includes safety measures as reducing hydrogen inventories inside building allocating clearance around electrolyzer stacks implementing early detection and isolation devices and building geometry to avoid hydrogen accumulation.
Public Perception of Hydrogen: Response to an Open-ended Questions
Sep 2023
Publication
Widespread use of hydrogen and hydrogen-based fuels as energy carriers in society may enable the gradual replacement of fossil fuels by renewable energy sources. Although the development and deployment of the associated technologies and infrastructures represent a considerable bottleneck it is generally acknowledged that neither the technical feasibility nor the economic viability alone will determine the extent of the future use of hydrogen as an energy carrier. Public perception beliefs awareness and knowledge about hydrogen will play a significant role in the further development of the hydrogen economy. To this end the present study examines public perception and awareness of hydrogen in Norway. The approach adopted entailed an open-ended question examining spontaneous associations with the term ‘hydrogen’. The question was fielded to 2276 participants in Wave 25 of the Norwegian Citizen Panel (NCP) an on-line panel that derives random samples from the general population registry. The analysis focused on classifying the responses into negative associations (i.e. barriers towards widespread implementation of hydrogen in society) neutral associations (e.g. basic facts) and positive associations (i.e. drivers towards widespread implementation of hydrogen in society). Each of the 2194 responses were individually assessed by five researchers. The majority of the responses highlighted neutral associations using words such as ‘gas’ ‘water’ and ‘element’. When considering barriers vs. drivers the overall responses tend towards positive associations. Many respondents perceive hydrogen as a clean and environmentally friendly fuel and hydrogen technologies are often associated with the future. The negative sentiments were typically associated with words such as ‘explosive’ ‘hazardous’ and ‘expensive’. Despite an increase in the mentioning of safety-related properties relative to a previous study in the same region the frequency of such references was rather low (4%). The responses also reveal various misconceptions such as hydrogen as a prospective ‘source’ of clean energy.
Purging Hydrogen Distribution Pipelines: Literature Review, Description of Recent Experiments and Proposed Future Work
Sep 2023
Publication
The aim of the H21 project is to undertake measurements analysis and field trials to support the safe repurposing of Great Britain’s natural gas distribution network for hydrogen. As part of this project work has been ongoing to identify aspects of existing natural gas procedures that will need to be modified for hydrogen and to support the development of new procedures. This has included a review of the scientific basis of current displacement purging practices analysis of the potential implications of switching from natural gas to hydrogen and experimental support work. The reduced density and viscosity of hydrogen means that minimum purging velocities should (in principle) be higher for hydrogen to avoid stratification and ensure adequate removal of the purged gas during pipeline purging operations. A complicating factor is the high molecular diffusivity of hydrogen (roughly three times that of natural gas) which causes hydrogen to mix over short distances more rapidly than natural gas. Current models for pipeline purging do not take into account the mixing effect related to molecular diffusion. The wider flammable limits lower ignition energy and greater potential for combustion to transition from deflagration to detonation with hydrogen means that indirect purging with nitrogen is currently being investigated for distribution pipelines. This paper reviews the ongoing analysis of hydrogen pipeline purging and discusses a potential future scientific programme of work aimed at developing a new pipeline purging model that accounts for molecular diffusion effects.
Hydrogen Recombiners for Non-nuclear Hydrogen Safety Applications
Sep 2023
Publication
Hydrogen recombiners are catalyst-based hydrogen mitigation systems that have been successfully implemented in the nuclear industry but have not yet received serious interest from the hydrogen industry. Recombiners have been installed in the containment buildings of many nuclear power plants to prevent the accumulation of hydrogen in potential accidents. The attractiveness of hydrogen recombiners for the nuclear industry is due to the confined state of the containment building where hydrogen cannot be vented easily and its passive design where no power or actions are needed for the unit to operate. Alternatively in the hydrogen industry most applications utilize ventilation to mitigate potential hydrogen accumulation in confined areas and passive safety is not essential. However many applications in the hydrogen industry may utilize hydrogen recombiners from a different approach. For instance recombiners could be utilized in emerging hydrogen areas to minimize the costs of ventilation upgrades or built into hydrogen appliances to avoid vent connections. The potential applications for recombiners in the hydrogen industry have different atmospheric conditions than the nuclear industry which may impact the catalyst in the units and render them less effective. Thus experiments have been performed to investigate the limits of the recombiner catalyst and if modifications to the catalyst can extend their use to the hydrogen industry. This paper will present and discuss the applications of interest conditions that may affect the catalyst and results from experiments investigating the catalyst behaviour at temperatures less than 0 °C and carbon monoxide concentrations up to 1000 ppm.
Public Facing Safety and Education for Hydrogen Fueling Infrastructure
Sep 2023
Publication
Building safe and convenient fuelling stations is key to deploying the arrival of commercial/public-use fuel cell electric vehicles (FCEVs). As the most public-facing hydrogen applications second only to the FCEVs hydrogen stations are an efficient tool to educate the public about hydrogen safety and normalize its use to fill up our vehicles. However as an emerging technology it is the industry’s responsibility to ensure that fuelling infrastructures are designed and maintained in accordance with established safety standards and thus that the fuelling process is inherently safe for all users. On the other end it is essential that consumers have all the necessary information at reach to help them feel safe while fuelling their zero-emission vehicles.<br/>This paper will provide a snapshot of the safety systems used to help protect members of the public using hydrogen fueling stations as well as the information used to educate people using this equipment. This will cover the different processes involved in hydrogen fueling stations the dangers that are present to customers and members of the public at these sites and the engineering design choices and equipment used to mitigate these dangers or prevent them from happening. Finally this paper will discuss the crucial role of understanding the dangers of hydrogen at a public level and showing the importance of educating the public about hydrogen infrastructure so that people will feel comfortable using it in their everyday lives.
Buoyant Jet Model to Predict a Vertical Thermal Stratification During Refueling of Gaseous Hydrogen Tanks in Horizontal Position with Axial Injection
Sep 2023
Publication
Thermodynamic modeling of hydrogen tank refueling i.e. 0 dimension (0D) model considers the gas in the tank as a single homogeneous volume. Based on thermodynamic considerations i.e. mass and energy balance equations the gas temperature and pressure predicted at each time step are volume-averaged. These models cannot detect the onset of the thermal stratification nor the maximum local temperature of the gas inside the tank.<br/>For safety reasons the temperature must be maintained below 85 °C in the composite tank. When thermal stratification occurs the volume-averaged gas temperature predicted by 0D models can be below 85 °C while local temperature may significantly exceed 85 °C. Then thermally stratified scenarios must be predicted to still employ 0D models safely.<br/>Up to now only computational fluid dynamics (CFD) approaches can predict the onset of the thermal stratification and estimate the amplitude of thermal gradients. However CFD approaches require much larger computational resources and CPU time than 0D models. This makes it difficult to use CFD for parametric studies or a live-stream temperature prediction for embedded applications. Previous CFD studies revealed the phenomenon of jet deflection during horizontal refueling of hydrogen tanks. The cold hydrogen injected into the warm gas bulk forms a round jet sinking down towards the lower part of the tank due to buoyancy forces. The jet breaks the horizontal symmetry and dumps the cold gas towards the lower part of the tank.<br/>The jet behavior is a key factor for the onset of the thermal stratification for horizontally filled tanks. Free round jets released in a homogeneous environment with a different density than the jet density were extensively investigated in the literature. A buoyant round jet modeling can be applied to predict the jet deflection in the tank. It requires initial conditions that can be provided by 0D refueling models. Therefore 0D models coupled with a buoyant round jet modeling can be used to predict the onset of the thermal stratification without CFD simulation. This approach clarifies the validity domain of 0D models and thus improves the safety of engineering applications
Gas Leak Detection Using Acoustics and Artificial Intelligence
Sep 2023
Publication
Gas leak detection on a production site is a major challenge for the safety and health of workers for environmental considerations and from an economic point of view. In addition flammable gas leaks are a safety risk because if ignited they can cause serious fires or explosions. For these reasons Acoem Metravib in collaboration with TotalEnergies One Tech R&D Safety has developed for the past four years a system called AGLED for the early detection localization and classification of such leaks exploiting acoustics and artificial intelligence driven by physics. Numerous tests have been conducted on a theater representative of gas production facilities created by TotalEnergies in Lacq (France) to build a robust learning database of leaks varying in flowrates exhaust diameters and also types (hole nozzle flange...). Moreover to limit the number of false alarms a relearning strategy has been implemented to handle unexpected disturbances (wildlife human activities meteorological events...). The presented paper describes the global architecture of the system from noise acquisition to the gas leak probability and coordinates. It gives a more in-depth look at the relearning algorithm and its performance in various environments. Finally thanks to a complementary collaboration with Air Liquide an example of test campaign in a real industrial environment is presented with an emphasis on the improvement obtained through relearning.
Design for Reliability and Safety: Challenges and Opportunities in Hydrogen Mobility Assets
Sep 2023
Publication
Safety and reliability are important performance attributes of any engineered system where humanmachine interactions are present. However they are usually approached as afterthoughts or in some cases unintended consequences of the system design and development process that must be addressed and verified in subsequent design stages. In plain words safety and reliability are often seen as constraints that add layers of complexity and extra costs to the minimum functional system of interest. No longer. Shell Hydrogen is embedding the Design for Reliability and Safety approach to engineer our products and assets in such a way that safety and reliability are at the core of a concurrent engineering process throughout the system lifecycle. This has been achieved in practice by leveraging systems reliability and safety engineering methods along with the experience and expertise of Shell Hydrogen original equipment manufacturers and system integrators in designing building and operating hydrogen assets for mobility applications.<br/>The challenges in implementing this approach are many ranging from access to historical data on equipment and component safety and reliability performance to lack of standardization in the industry when dealing with hydrogen related hazards. In this paper we will describe the approach in more detail some of our early successes and failures during deployment and the continual improvement journey that lies ahead.
Design of Long-Life Wireless Near-Field Hydrogen Gas Sensor
Sep 2023
Publication
A wireless near-field hydrogen gas sensor is proposed which detects the leaking hydrogen near its source to achieve fast response and high reliability. The proposed sensor can detect leaking hydrogen in 100ms with nearly no delay due to hydrogen diffusion in space. The overall response time is shortened by orders of magnitude compared to conventional sensors according to simulation results. Over 1 year of maintenance interval is empowered by wireless design based on Bluetooth low energy protocol.
Very Low-cost Wireless Hydrogen Leak Detection for Hydrogen Infrastructure
Sep 2023
Publication
A unique hydrogen leak detection strategy is the use of powerless indicator wraps for fittings and other pneumatic elements within a hydrogen facility. One transduction mechanism of such indicators is a color change that is induced by a reaction between a pigment and released hydrogen. This is an effective way to detect hydrogen leaks and to identify their source before they become a safety event however this technology requires visual (manual) inspection to identify a color change or leak. One improvement in this strategy would be to improve the communication of the visual response to an end-user. Element One (E1) has previously developed and introduced DetecTape® a self-fusing silicone non-reversible hydrogen leak detecting tape for application to potential leak sites in hydrogen piping valves and fittings and it has been successfully commercialized with excellent feedback. Element One’s sensors can be fabricated using either pigments or thin films which both change color and conductivity. Neither change requires an external power source. The conductivity change may be communicated as a wireless transmission such as passive radio frequency identification devices (RFID) to an appropriate receiving system where it may be remotely monitored to achieve higher levels of safety and reliability at low cost. Element One will report on its recent progress in the commercial development of remotely monitored hydrogen leak detection using several wireless protocols including passive RFID.
Hydrogen Dispersion Following Blowdown Releases into a Tunnel
Sep 2023
Publication
This paper presents work undertaken by the HSE as part of the Hytunnel-CS project a consortium investigating safety considerations for fuel cell hydrogen (FCH) vehicles in tunnels and similar confined spaces. The test programme investigating hydrogen dispersion in tunnels involved simulating releases analogous to Thermally activated Pressure Relief Devices (TPRDs) typically found on hydrogen vehicles into the HSE Tunnel facility. The releases were scaled and based upon four scenarios: cars buses and two different train designs. The basis for this scaling was the size of the tunnel and the expected initial mass flow rates of the releases scenarios. The results of the 12 tests completed have been analysed in two ways: the initial mass flow rates of the tests were calculated based upon facility measurements and the Able-Noble equations of state for comparison to the intended initial flow rate; and observations of the hydrogen dispersion in the tunnel were made based on 15 hydrogen sensors arrayed along the tunnel. The calculated mass flow rates showed reasonable agreement with the intended initial conditions showing that the scaling methodology can be used to interpret the data based on the full-scale tunnel of interest. Observations of the hydrogen dispersion show an initial turbulent mixing followed by a movement of the mixed hydrogen/air cloud down the tunnel. No vertical stratification of the cloud was observed but this effect could be possible in longer tunnels or tunnels with larger diameters. Higher ventilation rates in the tunnel resulted in a reduction of the residence time of the hydrogen and a slight increase in the dilution.
Deflagration-to-detonation Transition Due to a Pressurised Release of a Hydrogen Jet. First Results of the Ongoing TAU_NRCN-CEA Project
Sep 2023
Publication
A sudden release of compressed gases and the formation of a jet flow can occur in nature and various engineering applications. In particular high-pressure hydrogen jets can spontaneously ignite when released into an environment that contains oxygen. For some scenarios these high-pressure hydrogen jets can be released into a mixture containing hydrogen and oxygen. This scenario can possibly lead to a wide range of combustion regimes such as jet flames slow or fast deflagrations or even hazardous detonations. Each combustion regime is characterized by typical pressures and temperatures however fast transition between regimes is also possible.<br/>A common project between Tel Aviv University (TAU) Nuclear Research Center Negev (NRCN) and Commissariat à l’Energie Atomique et aux énergies alternatives (CEA) has been recently launched in order to understand these phenomena from experimental modelling and numerical points of view. The main goal is to investigate the dynamics and combustion regimes that arise once a pressurized hydrogen jet is released into a reactive environment that contains inhomogeneous concentrations of hydrogen steam and air.<br/>In this paper we present the first numerical results describing high-pressure hydrogen release obtained using a massively parallel compressible structured-grid flow solver. The experimental arrangements devoted to this phenomenon will also be described.
Sudden Releases of Hydrogen into a Tunnel
Sep 2023
Publication
This paper presents work undertaken by the HSE as part of the Hytunnel-CS project a consortium investigating safety considerations for fuel cell hydrogen (FCH) vehicles in tunnels and similar confined spaces. The sudden failure of a pressurised hydrogen vessel was identified as a scenario of concern due to the severity of the consequences associated with such an event. In order to investigate this scenario experimentally HSE designed a bespoke and reusable ‘sudden release’ vessel. This paper presents an overview of the vessel and the results of a series of 13 tests whereby hydrogen was released from the bespoke vessel into a tunnel at pressures up to 65 MPa. The starting pressure and the volume of hydrogen in the vessel were altered throughout the campaign. Four of the tests also included congestion in the tunnel. The tests reliably autoignited. Overpressure measurements and flame arrival times measured with exposed-tip thermocouples enabled analysis of the severity of the events. A high-pressure fast-acting pressure transducer in the body of the vessel showed the pressure decay in the vessel which shows that 90% of the hydrogen was evacuated in between 1.8 and 3.2 ms (depending on the hydrogen inventory). Schlieren flow imagery was also used at the release point of the hydrogen showing the progression of the shock front following initiation of the tests. An assessment of the footage shows an estimated initial velocity of Mach 3.9 at 0.4 m from the release point. Based on this an ignition mechanism is proposed based upon the temperature behind the initial shock front.
Pressure Evolution from Head-on Reflection of High-speed Deflagration in Hydrogen Mixtures
Sep 2023
Publication
Our previous reported experiments revealed that the reflection of high-speed deflagrations in hydrogenair and hydrogen-oxygen mixtures produces higher mechanical loading and reflected pressures than reflecting detonations. This surprising result was shown to correlate with the onset of detonation in the gases behind the reflected shock. We revisit these experiments with the aim of developing a closed-form model for the pressure evolution due to the shock-induced ignition and rapid transition to detonation. We find that the reflection condition of fast deflagrations corresponds to the chain-branching crossover regime of hydrogen ignition in which the reduced activation energy is very large and the reaction characteristic time is very short compared to the induction time. We formulate a closed-form model in the limit of fast reaction times as compared to the induction time which is used to predict a square wave pressure profile generated by self-similar propagation of internal Chapman-Jouguet detonation waves followed by Taylor expansion waves. The model predictions are compared with Navier-Stokes numerical simulations with full chemistry as well as simple Euler calculations using calibrated one-step or twostep chain-branching models. Both simplified numerical models were found to be in good agreement with the full chemistry model. We thus demonstrate that the end pressure evolution due to the reflection of high-speed deflagrations can be well predicted analytically and numerically using relatively simple models in this ignition regime of main interest for safety analysis and explosion mitigations. The slight departures from the square wave model are investigated based on the physical wave processes occurring in the shocked gases controlling the shock-to-detonation transition. Using the two-step model we study how the variations of the rate of energy release control the pressure evolution in the end gas extending the analysis of Sharpe to very large rates of energy release.
Modeling of Tube Deformation and Failure under Conditions of Hydrogen Detonation
Sep 2023
Publication
In case of accidental conditions involving high-speed hydrogen combustion the considerable pressure and thermal loads could result in substantial deformation and/or destruction of the industrial appliances. Accounting of such effects in the safety analysis with CFD tools can provide critical information on the design and construction of the sensitive appliances’ elements. The current paper presents the development and the implementation of a new 3D-technique which makes possible to perform simulations of the gas-dynamic processes simultaneously with adaptation of the geometry of complex configurations. Using the data obtained in the experiments on the flame acceleration and DDT in the tubes of industrial arrangements performed in MPA and KIT the authors performed a series of the combustion simulations corresponding to the experimental conditions. The combustion gas-dynamics was simulated using COM3D code and the tube wall material behavior was modelled using finite-element code ABAQUS - © Dassault Systèmes with real-time data exchange between the codes. Obtained numerical results demonstrated good agreement with the observed experimental data on both pressure dynamics and tube deformation history.
SSEXHY Experimental Results on Pressure Dynamics from Head-on Reflections of Hydrogen Flames
Sep 2023
Publication
In the past few years CEA has been fully involved at both experimental and modeling levels in projects related to hydrogen safety in nuclear and chemical industries and has carried out a test program using the experimental bench SSEXHY (Structure Submitted to an EXplosion of HYdrogen) in order to build a database of the deformations of simple structures following an internal hydrogen explosion. Different propagation regimes of explosions were studied varying from detonations to slow deflagrations.<br/>During the experimental campaign it was found that high-speed deflagrations corresponding to relatively poor hydrogen-air mixtures resulted in higher specimen deformation compared to those related to detonations of nearly stoichiometric mixtures. This paper explains this counter-intuitive result from qualitative and quantitative points of view. It is shown that the overpressure and impulse from head-on reflections of hydrogen flames corresponding to poor mixtures of specific concentrations could have very high values at the tube end.
Fuel Cell Vehicle Hydrogen Emissions Testing
Sep 2023
Publication
The NREL Hydrogen Sensor Laboratory is comprised of researchers dedicated to furthering hydrogen sensor technology and detection methodology. NREL has teamed up with researchers at Environment and Climate Change Canada (ECCC) and Transport Canada (TC) to conduct research to quantify hydrogen emissions from Fuel Cell Electric Vehicles (FCEV). Test protocols will have a large effect on monitoring and regulating the hydrogen emissions from FCEVs. How emissions are tested will play an important role when understanding the safety and environmental implications of using FCEVs. NREL Sensor Laboratory personnel have partnered with other entities to conduct multiple variations of emissions testing for FCEVs. This experimentation includes testing different models of FCEVs under various driving conditions while monitoring the hydrogen concentration of the exhaust using several different test methods and apparatus. Researchers look to support regulatory bodies by providing useful data that can support more consistent and relevant safety and environmental standards. We plan to present on the current test methods and results from recent emissions measurements at ECCC.
Effect of Methane Addition on Transition to Detonation in Hydrogen-Air Mixtures Due to Shock Wave Focussing in a 90 - Degree Corner
Sep 2023
Publication
The main purpose of this work is to investigate the influence of methane addition in methane-hydrogen-air mixture (φ = 0.8 – 1.6) on the critical conditions for transition to detonation in a 90-deg wedge corner. Similar to hydrogen-air mixtures investigated previously [1] methane-hydrogen-air mixtures results showed three ignition modes weak ignition followed by deflagration with ignition delay time higher than 1 μs strong ignition with instantaneous transition to detonation and third with deflagrative ignition and delayed transition to detonation. Methane addition caused an increase in the range of 3.25 – 5.03% in the critical shock wave velocity necessary for transition to detonation for all mixtures considered. For example in stoichiometric mixture with 5% methane in fuel (95% hydrogen in fuel) in air the transition to detonation velocity was approx. 752 m/s (an increase of 37 m/s from hydrogen-air) corresponding to M = 1.89 (an increase of 0.14 from hydrogen-air) and 75.7% (an increase of 4.7% from hydrogen-air) of speed of sound in products. Also similar to hydrogen-air mixture the transition to detonation velocity increased for leaner and richer mixture. Moreover it was observed that methane addition in general increased the pressure limit at the corner necessary for transition to detonation.
X-ray Absorpton Spectroscopy Study on Hydrogen Recombination Catalysts of Palladium Nanoparticles on Titanium Oxide under Wet Condition
Sep 2023
Publication
Hydrogen recombination catalyst is useful tool for reducing hydrogen in closed area. The catalyst is known to be poisoned under wet condition in long time use. The study is focused on the behavior of pre-oxidized Pd nanoparticle as the hard-used catalyst in high humidity environment by comparison of alumina and titanium oxide supports using in situ X-ray absorption spectroscopy technique. The reduction of surface oxide layer of Pd/TiO2 was promoted by water during hydrogen recombination although the reduction reaction of Pd/Al2O3 was inhibited by water.
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