Safety

Unstable hydrogen-air flame behavior randomities are important for industrial safety hydrogen infrastructure safety and nuclear power plant hydrogen safety problems. The paper is devoted to an experimental and theoretical study of the uncertainty in the acceleration of a premixed laminar unstable hydrogen flame. The results of experiments on spherical flame propagation in hydrogen-air mixtures with a hydrogen content of 10 to 60% are presented. The experiments were repeated up to 30 times in the same mixtures. A statistical analysis of the experimental results has been carried out. The scatter of the experimental data depending on the hydrogen content in the mixture was estimated. It was found to be between 8 to 17% for different mixtures with the same flame radius and mixture composition. Similar results were obtained using the numerical integration of the Sivashinsky equation of flame propagation.

Hydrogen gas storage place has been increasing daily because of its consumption. Hydrogen gas is a dream fuel of the future with many social economic and environmental benefits to its credit. However many hydrogen storage tanks exploded accidentally and significantly lost the economy infrastructure and living beings. In this study a protection wall under a worst-case scenario explosion of a hydrogen gas tank was analyzed with commercial software LS-DYNA. TNT equivalent method was used to calculate the weight of TNT for Hydrogen. Reinforced concrete and composite protection wall under TNT explosion was analyzed with a different distance of TNT. The initial dimension of the reinforced concrete protection wall was taken from the Korea gas safety code book (KGS FP217) and studied the various condition. H-beam was used to make the composite protection wall. Arbitrary-Lagrangian-Eulerian (ALE) simulation from LS-DYNA and ConWep pressure had a good agreement. Used of the composite structure had a minimum displacement than a normal reinforced concrete protection wall. During the worst-case scenario explosion of a hydrogen gas 300 kg storage tank the minimum distance between the hydrogen gas tank storage and protection wall should be 3.6 m.

Hydrogen as a clean fuel offers a practical pathway to achieve net-zero targets. However due to its physical and chemical characteristics there are some safety concerns for large-scale hydrogen utilisation particularly in process safety management. Leakage of gaseous hydrogen especially in semi-confined spaces such as tunnels can lead to catastrophic outcomes including uncontrolled fire and explosion. The current paper describes the outcome of an experimental and numerical study that aims to understand the dispersion of leaked light gas in a semi-confined space to support the adoption of hydrogen. A dispersion chamber with dimensions of 4m × 0.3m × 0.3m was constructed to investigate a baseline gas leakage scenario. To reduce the risk of the experiment in the laboratory helium is utilised as a surrogate for hydrogen. Computational fluid dynamics simulations are con ducted using FLACS-CFD to model the dispersion of leaked gas in different scenarios focusing on the impact of the ventilation velocity leakage rate and slope. The results from comprehensive numerical simulations show that ventilation is a critical safety management measure that can significantly reduce the growth of flammable clouds and mitigate the fire and explosion risk. Even with the lowest ventilation velocity of 0.25 m/s an improvement in the gas concentration level of 29.34% can be achieved in the downstream chamber. The current results will help to further enhance the understanding of hydrogen safety aspects.

The recent growth of the net of hydrogen fuelling stations increases the demands to transport compressed hydrogen on road by battery vehicles or tube-trailers both in composite pressure vessels. As a transport regulation the ADR is applicable in Europe and adjoined regions and is used for national transport in the EU. This regulation provides requirements based on the behaviour of each individual pressure vessel regardless of the pressure of the transported hydrogen and relevant consequences resulting from generally possible worst case scenarios such as sudden rupture. In 2012 the BAM (German Federal Institute for Materials Research and Testing) introduced consequence-dependent requirements and established them in national transport requirements concerning the “UN service life checks” etc. to consider the transported volume and pressure of gases. This results in a requirement that becomes more restrictive as the product of pressure and volume increases. In the studies presented here the safety measures for hydrogen road transport are identified and reviewed through a number of safety measures from countries including Japan the USA and China. Subsequently the failure consequences of using trailer vehicles the related risk and the chance are evaluated. A benefit-related risk criterion is suggested to add to regulations and to be defined as a safety goal in standards for hydrogen transport vehicles and for mounted pressure vessels. Finally an idea is given for generating probabilistic safety data and for highly efficient evaluation without a significant increase of effort.

The energy world is changing rapidly pushed also by the need for new green energy sources to reduce greenhouse gas emissions. The fast development of renewable energies has created many problems associated with grid management and stability which could be solved with storage systems. The hydrogen economy could be an answer to the need of storage systems and clean fuel for transportation. The Electrochemical Hydrogen Compressor (EHC) is an electrochemical device which could find a place in this scenario giving a solution for the hydrogen purification and compression for storage. This work analyzes through experimental and modeling studies the performance of the EHC in terms of polarization curve Hydrogen Recovery Factor (HRF) and outlet hydrogen purity. The influence of many input parameters such as the total inlet flow rate the hydrogen inlet concentration the contaminant in the feed and the cathode pressure have been investigated. Furthermore the EHC performance have been modelled in a 1D + 1D model implemented in Matlab® solving the Butler-Volmer system of equations numerically. The experimental campaign has shown that high purities can be obtained for the hydrogen separation from N2 and CH4 and purities over 98% feeding He. An increase in the cathode pressure has shown a slight improvement in the obtained purity. A comparison between PSA unit and EHC for a mixture 75% H2 – 25% CH4 at different outlet hydrogen pressure and purity was performed to analyze the energy consumption required. Results show PSA unit is convenient at large scale and high H2 concentration while for low concentration is extremely energy intense. The EHC proved to be worthwhile at small scale and higher outlet hydrogen pressure.

Global warming is an accepted fact of life on Earth posing grave consequences in the form of weather patterns with life-threatening outcomes for inhabitants and their cultures especially those of island countries. These wild and unpredictable weather patterns have persuaded authorities governments and industrial leaders to adapt a range of solutions to combat the temperature rise on Earth. One such solution is to abandon fossil fuels (hydrocarbons) for energy generation and employ renewable energy sources or at least use energy sources that do not generate greenhouse gases. One such energy carrier is hydrogen which is expected to slowly replace natural gas and will soon be pumped into the energy distribution pipeline network. Since the current energy distribution network was designed for hydrocarbons its use for hydrogen may pose some threat to the safety of urban society. This is the first time an overview article has examined the replacement of hydrocarbons by hydrogen from a totally different angle by incorporating material science viewpoints. This article discusses hydrogen properties and warns about the issue of hydrogen embrittlement in the current pipeline network if hydrogen is to be pumped through the current energy distribution network i.e. pipelines. It is recommended that sufficient study and research be planned and carried out to ensure the safety of using the current energy distribution network for hydrogen distribution and to set the necessary standards and procedures for future design and construction.

Hydrogen offers the UK a unique opportunity to deliver on our Net Zero ambitions enabling deep decarbonisation of the parts of the energy system that are challenging to electrify balancing the energy system by providing large scale long duration energy storage and reducing pressure on electricity infrastructure. The UK Government in recognition of the centrality of hydrogen to the future energy system has set a 10GW hydrogen production ambition to be achieved by 2030. This ambition and its supporting policies such as the Hydrogen Business Model the Low Carbon Hydrogen Standard and the Hydrogen Transport and Storage Business Models will unlock private sector investment and kick-start the UK’s hydrogen activity. Encouragingly the UK has a positive track record of deploying low carbon technologies. The  combination of the UK’s world leading policies and incentive schemes alongside a vibrant  Research Development and Innovation (RD&I)  and engineering environment has enabled rapid  deployment of technologies such as offshore wind  and electric vehicles. Yet despite being world leaders  in deployment early opportunities for regional  supply chain growth and job creation were not fully  realised and taken advantage of from inception. The  hydrogen sector is therefore at a tipping point. To  capitalise on the economic opportunity hydrogen  offers the UK must learn from prior technology  deployments and build a strong domestic hydrogen  supply chain in parallel to championing deployment.

Hydrogen is unique amongst low carbon  technologies. It represents a significant economic  opportunity with future hydrogen markets estimated  by the Hydrogen Innovation Initiative to be worth  $8tn and hydrogen technology markets estimated to reach $1tn by 20501 but crucially it is also still a nascent market. Unlike many other low carbon technologies where supply chains are already well established hydrogen supply chains are embryonic meaning that the UK has an opportunity to anchor these supply chains here and establish itself as a global leader.

The UK is well placed to capitalise on this opportunity with favourable geography and geology  that enables us to produce and store hydrogen cost effectively coupled with a strong pipeline of hydrogen projects a stable policy environment that is attractive to investors and a wealth of transferable skills and expertise from the oil and gas industry.

We must ensure that alongside our focus on deployment we are also investing in technology and supply chains. Not only will this deliver exponential economic benefits from the projects supported by Government but it will also enable us to tackle increasing global supply chain constraints. Hydrogen UK estimated in its Economic Impact Assessment that hydrogen could deliver 30000 jobs annually and £7bn of GVA by 2030

It is important to be targeted and strategic in our investment and activities and recognise that hydrogen represents a wide range of technologies and the UK should not expect to lead in every area. Hydrogen UK with the support of the Hydrogen Delivery Council has undertaken analysis of the hydrogen value chain building on UK strengths and identifying the high value items that can deliver significant impact and benefit to the UK. We have also conducted widespread engagement with project developers to identify the barriers to utilising UK technology in projects and with technology developers to identify the challenges and barriers to investing and siting development and manufacturing in the UK.

The report can be found on Hydrogen UK's website.

Proton exchange membrane electrolyzer cell (PEMEC) will play a central role in future power-to-H2 plants. Current research focuses on the materials and operation parameters. Setting up experiments to explore operational accident scenarios about safety feasibility is not always practical. This paper focuses on building mathematical and prediction models of hydrogen and oxygen mixing scenarios of PEMEC. A mathematical model of the PEMEC device was customized in the Aspen Custom Model (ACM) software and integrated various critical Physico-chemical phenomena as the original data set for the prediction model. The results of the mathematical simulation verified the experimental results. The prediction model proposes an artificial neural network (ANN) framework to predict component distribution in the gas stream to prevent hydrogen-oxygen explosion scenarios. The presented approach by training ANN to 1000 sets of hydrogen-oxygen mixing simulation data from ACM is applicable to bypass tedious and non-smooth systems of equations for PEMEC.

For the safe and efficient utilization of hydrogen-enriched natural gas combustion in industrial gas-fired boilers the present study adopted a combination of numerical simulation and field tests to investigate its adaptability. Firstly the combustion characteristics of hydrogen-enriched natural gas with different hydrogen blending ratios and equivalence ratios were evaluated by using the Chemkin Pro platform. Secondly a field experimental study was carried out based on the WNS2- 1.25-Q gas-fired boiler to investigate the boiler’s thermal efficiency heat loss and pollutant emissions after hydrogen addition. The results show that at the same equivalence ratio with the hydrogen blending ratio increasing from 0% to 25% the laminar flame propagation speed of the fuel increases the extinction strain rate rises and the combustion limit expands. The laminar flame propagation speed of premixed methane/air gas reaches the maximum value when the equivalence ratio is 1.0 and the combustion intensity of the flame is the highest at this time. In the field tests as the hydrogen blending ratio increases from 0% to nearly 10% with the increasing excess air ratio the boiler’s thermal efficiency decreases as well as the NOx emission. This indicates that there exists a tradeoff between the boiler thermal efficiency and NOx emission in practice.

In recent years new chemical release agents based on silane are being used in the tire industry. Silane is an inorganic chemical compound consisting of a silicon backbone and hydrogen. Silanes can be thermally decomposed into high-purity silicon and hydrogen. If silane is stored and transported in Intermediate Bulk Containers (IBCs) equipped with safety valves in vented semi-confined spaces such as ISO-Containers hydrogen can be accumulated and become explosive mixture with air. A conservative CFD analysis using the GASFLOW-MPI code has been carried out to assess the hydrogen risk inside the vented containers. Two types of containers with different natural ventilation systems were investigated under various hypothetical accident scenarios. A continuous release of hydrogen due to the chemical decomposition of silane from IBCs was studied as the reference case. The effect of the safety valves on hydrogen accumulation in the container which results in small pulsed releases of hydrogen was investigated. The external effects of the sun and wind on hydrogen distribution and ventilation were also evaluated. The results can provide detailed information on hydrogen dispersion and mixing within the vented enclosures and used to evaluate the hydrogen risks such as flammability. Based on the assumptions used in this study it indicates that the geometry of ventilation openings plays a key role in the efficiency of the indoor air exchange process. In addition the use of safety valves makes it possible to reduce the concentration of hydrogen by volume in air compared to the reference case. The effect of the sun which results in a temperature difference between two container walls allows a strong mixing of hydrogen and air which helps to obtain a concentration lower than both the base case and the case of the pulsed releases. But the best results for the venting process are obtained with the wind that can drive the mixture to the downwind wall vent holes.