Publications

Explosion relief panels or doors are often used in industrial buildings to reduce damages caused by gas explosions. Decades of research have contributed to the understanding of the phenomena involved in gas explosions in order to establish an effective method to predict reliably the explosion overpressure. All the methods predict a monotonic increase of the overpressure with the concentration of the gas in the range from the lower explosion limit to the stoichiometric one. Nevertheless in few cases a non-monotonic behaviour of the maximum developed pressure as a function of hydrogen concentration was reported in the literature. The non-monotonic behaviour was also observed during experimental tests performed at the Scalbatraio laboratory at the University of Pisa in a 25 m3 vented combustion test facility with a vent area of 112 m2. This paper presents the results obtained during the tests and investigates the possible explanations of the phenomena.

An energy production from the combination of dehydrogenation and combined cycle power generation is proposed. The delivered system is established from three main modules: dehydrogenation combustion and combined cycle. The heat in the system is circulated thoroughly to enhance the energy efficiency due to optimum energy recovery. The Pt/Al2O3 catalyst is applied in the dehydrogenation module due to superior activity to accelerate the dehydrogenation of MCH. The toluene emitted from the MCH is recirculated to the hydrogenation plant while the hydrogen is further utilized as the fuel in the combustion. Although the high-temperature condition is necessary to perform high yield dehydrogenation the proposed system is capable of carrying out self-heating mechanism with no external heat. With the optimum configuration the delivered system can produce 100.0 MW of electricity from 100 t/h of MCH with 50.19% of energy efficiency.

Hydrogen is considered to be a very promising potential energy carrier due to its excellent characteristics such as abundant resources high fuel value clean and renewable. Its safety features greatly influence the potential use. Several safety problems need to be analyzed before using in transportation industry. With the development of the tunnel transportation technology the safe use of hydrogen in tunnels will receive a lot of research attentions. In this article the risk associated with hydrogen release from onboard high-pressure vessels and the induced combustion in tunnels was analyzed using the Partially Averaged Navier–Stokes (PANS) turbulence model. The influences of the tunnel ventilation facilities on the hydrogen flow characteristics and the flammable hydrogen cloud sizes were studied. The tunnel layouts were designed according to the subsea tunnel. And a range of longitudinal ventilation conditions had been considered to investigate the hydrogen releases and the sizes of the flammable hydrogen cloud. Then the hydrogen combustion simulation was carried out after the fixed leaking time. The overpressures induced after the ignition of leaking hydrogen were studied. The influences of ventilation and ignition delay time on the overpressure were also investigated. The main aim was to research the phenomena of hydrogen releases and combustion risk inside subsea tunnels and to lay the foundation of risk assessment methodology developed for hydrogen energy applications on transportation.

HyRAM is a methodology and accompanying software toolkit which is being developed to provide a platform for integration of state-of-the-art validated science and engineering models and data relevant to hydrogen safety. As such the HyRAM software toolkit establishes a standard methodology for conducting quantitative risk assessment (QRA) and consequence analysis relevant to assessing the safety of hydrogen fueling and storage infrastructure. The HyRAM toolkit integrates fast-running deterministic and probabilistic models for quantifying risk of accident scenarios for predicting physical effects and for characterizing the impact of hydrogen hazards (thermal effects from jet fires thermal and pressure effects from deflagrations and detonations). HyRAM incorporates generic probabilities for equipment failures for nine types of hydrogen system components generic probabilities for hydrogen ignition and probabilistic models for the impact of heat flux and pressure on humans and structures. These are combined with fast-running computationally and experimentally validated models of hydrogen release and flame behaviour. HyRAM can be extended in scope via user contributed models and data. The QRA approach in HyRAM can be used for multiple types of analyses including codes and standards development code compliance safety basis development and facility safety planning. This manuscript discusses the current status and vision for HyRAM.

This paper describes an experimental programme on vented hydrogen deflagrations which formed part of the Hyindoor project carried out for the EU Fuel Cells and Hydrogen Joint Undertaking. The purpose of this study was to investigate the validity of analytical models used to calculate overpressures following a low concentration hydrogen deflagration. Other aspects of safety were also investigated such as lateral flame length resulting from explosion venting. The experimental programme included the investigation of vented hydrogen deflagrations from a 31 m3 enclosure with a maximum internal overpressure target of 10 kPa (100 mbar). The explosion relief was provided by lightly covered openings in the roof or sidewalls. Uniform and stratified initial hydrogen distributions were included in the test matrix and the location of the ignition source was also varied. The maximum hydrogen concentration used within the enclosure was 14% v/v. The hydrogen concentration profile within the enclosure was measured as were the internal and external pressures. Infrared video images were obtained of the gases vented during the deflagrations. Findings show that the analytical models were generally conservative for overpressure predictions. Flame lengths were found to be far less than suggested by some guidance. Along with the findings the methodology test conditions and corresponding results are presented.

The debate on low-carbon heat in Europe has become focused on a narrow range of technological options and has largely neglected hydrogen and fuel cell technologies despite these receiving strong support towards commercialisation in Asia. This review examines the potential benefits of these technologies across different markets particularly the current state of development and performance of fuel cell micro-CHP. Fuel cells offer some important benefits over other low-carbon heating technologies and steady cost reductions through innovation are bringing fuel cells close to commercialisation in several countries. Moreover fuel cells offer wider energy system benefits for high-latitude countries with peak electricity demands in winter. Hydrogen is a zero-carbon alternative to natural gas which could be particularly valuable for those countries with extensive natural gas distribution networks but many national energy system models examine neither hydrogen nor fuel cells for heating. There is a need to include hydrogen and fuel cell heating technologies in future scenario analyses and for policymakers to take into account the full value of the potential contribution of hydrogen and fuel cells to low-carbon energy systems.

Hydrogen stored or transported as ammonia has been proposed as a sustainable carbon-free alternative for fossil-fuels in high-temperature industrial processes including power generation. Although ammonia itself is toxic and exhibits both a low flame speed and calorific value it rapidly decomposes to hydrogen in high temperature environments suggesting the potential use in applications which incorporate fuel preheating. In this work the rate of ammonia-to-hydrogen decomposition is initially simulated at elevated temperatures to indicate the proportion of fuel conversion in conditions similar to gas pipelines gas-turbines or furnaces with exhaust-gas recirculation. Following this different proportions of hydrogen and ammonia are numerically simulated in independent zero-dimensional plug-flow-reactors at pressures ranging from atmospheric to 50 MPa and pre-heating temperatures from 600 K to 1600 K. Deflagration of very-lean-to-fuel-rich mixtures was investigated employing air as the oxidant stream. Analyses of these reactors provide estimates of autoignition thresholds of the hydrogen/ammonia blends which are relevant for the safe implementation and operation of hydrogen/ammonia blends or pure ammonia as a fuel source. Further operational considerations are subsequently identified for using ammonia or hydrogen/ammonia blends as a hydrogen fuel carrier by quantifying residual concentrations of hydrogen and ammonia fuel products as well as other toxic emissions within the hot exhaust products.

For massive utilization of hydrogen energy it is necessary to transport a large quantity of hydrogen by liquefied hydrogen carriers. However the current rule on ships carrying liquefied hydrogen in bulks do not address the maritime transport of liquefied hydrogen and the safety assessment of liquefied hydrogen carriage is thus very important. In the present study we spilled liquefied hydrogen and LNG (Liquefied Natural Gas) on the surface of various materials and compared the difference of their spread and dispersion. Liquefied hydrogen immediately dispersed upward compared to LNG. Furthermore we also measured the flammability limit of low temperature hydrogen gas. Its range at low temperature was narrower than the range at normal temperature.

This paper describes a 1-D numerical model for the prediction of heat and mass transfer through an intumescent paint that is applied to an on-board high-pressure GH2 storage tank. The intumescent paint is treated as a composite system consisting of three general components decomposing in accordance with independent finite reaction rates. A moving mesh that is employed for a better prediction of the expansion process of the intumescent paint is based on the local changes of heat and mass. The numerical model is validated against experiments by Cagliostro et al. (1975). The overall model results are used to estimate effect of intumescent paint on fire resistance of carbon-fibre reinforced GH2 storage.

The HyDeploy Project seeks to address a key issue for UK customers: how to reduce the carbon they emit in heating their homes. The UK has a world class gas grid delivering heat conveniently and safely to over 83% of homes. Emissions could be reduced by lowering the carbon content of gas through blending with hydrogen. Compared with solutions such as heat pumps this means that customers would not need disruptive and expensive changes in their homes. This Network Innovation Competition (NIC) funded project seeks to establish the level of hydrogen that can be safely blended with natural gas for transport and use in a UK network.

Under its Smart Energy Network Demonstration innovation programme Keele University is establishing its electricity and gas networks as facilities to drive forward innovation in the energy sector. The objective of HyDeploy is to trial natural gas blended with potentially up to 20% volume of hydrogen in a part of the Keele gas network. Before any hydrogen can be blended with natural gas in the network the percentage of hydrogen to be delivered must be approved by the Health and Safety Executive (HSE). It must be satisfied that the approved blended gas will be as safe to use as normal gas. Any approval will be given as an exemption to the Gas Safety (Management) Regulations. These regulations ensure the safe use and management of gas through the gas network in the UK. The evidence presented to the HSE comprises critically appraised literature combined with the results from a specifically commissioned experimental and testing programme. Based on engagement with all local customers this includes detailed safety checks on the network appliances and installations at Keele. Subject to approval by the HSE the hydrogen production and grid injection units will be installed and an extensive trial programme of blending will be undertaken. If hydrogen were blended at 20% volume with natural gas across the UK it would save around 6 million tonnes of carbon dioxide emissions every year the equivalent of taking 2.5 million cars off the road.

This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.