Japan
CO2-Free Hydrogen Supply Chain Project and Risk Assessment for the Safety Design
Sep 2013
Publication
We at Kawasaki Heavy Industries have proposed a "CO2-Free H2 supply chain" using abundant brown coal of Australian origin as the energy source. This chain will store CO2 generated during the process for producing hydrogen from brown coal in a project (Carbon Net) that the Australia Government is promoting. Thus Japan can import CO2-free hydrogen. The supply chain consists of the hydrogen production system the hydrogen transport/storage system and the hydrogen use system. Related to their designs we have to consider their hazards polluted scenarios and safety measures via a safety assessment process that is compliant with international risk assessment standards. To verify safety designs related experiments and analyses will be conducted. This paper describes the approach to safety design for especially the related liquid hydrogen facilities.
Influence of Pressure and Temperature on the Fatigue Strength of Type-3 Compressed-hydrogen Tanks
Sep 2011
Publication
The pressure of compressed hydrogen changes with temperature when mass and volume are constant. Therefore when a compressed-hydrogen tank is filled with a certain amount of hydrogen it is necessary to adjust the filling pressure according to the gas temperature. In this study we conducted hydraulic pressure-cycle tests to investigate the fatigue life of Type-3 compressed-hydrogen tanks when environmental temperature and filling pressure are changed. The results indicated that the fatigue life at low temperatures (−40 °C 28 MPa) and room temperature (15 °C 35 MPa) was almost equal. However the fatigue life at high temperatures (85 °C 44 MPa) was shorter than that under other conditions suggesting that stress changes caused by thermal stress affect the fatigue life of the Type-3 tank.
A Study on the Effectivity of Hydrogen Leakage Detection for Hydrogen Fuel Cell
Sep 2017
Publication
Unlike four-wheel fuel-cell vehicles fuel-cell motorcycles have little semi-closure space corresponding to the engine compartment of four-wheel fuel-cell vehicles. Furthermore motorcycles may fall while parked or running. We conducted hydrogen concentration measurement and ignition tests to evaluate the feasibility of detecting leaks when hydrogen gas leaked from a fuel-cell motorcycle as well as the risk of ignition. We found that the installation of hydrogen leak detectors is effective because it is possible to detect minute hydrogen leaks by installing leak detectors at appropriate points on the fuel cell motorcycle and risks can be reduced by interrupting the hydrogen leak immediately after detection.
Comparison of Liquid Hydrogen, Methylcyclohexane and Ammonia on Energy Efficiency and Economy
Mar 2019
Publication
Among several candidates of hydrogen storage liquid hydrogen methylcyclohexane (MCH) and ammonia are considered as potential hydrogen carriers in terms of their characteristics application feasibility and economic performance. In addition as a main motor in the hydrogen introduction Japan has focused and summarized the storage methods for hydrogen into these three methods. Each of them has advantages and disadvantages compared to each other. This study focuses on the effort to analyze and clarify the potential of these three hydrogen storages especially in terms of physical characteristics energy efficiency and economic cost. Liquid hydrogen faces challenges in huge energy consumption during liquefaction and boil-off during storage. MCH has main obstacles in largely required energy in dehydrogenation. Lastly ammonia encounters high energy demand in both synthesis and decomposition (if required). In terms of energy efficiency ammonia is predicted to have the highest total energy efficiency (34–37%) followed by liquid hydrogen (30–33%) and MCH (about 25%). In addition from cost calculation ammonia with direct utilization (without decomposition) is considered to have the highest feasibility for being massively adopted as it shows the lowest cost (20–22 JPY/Nm3-H2 in 2050). However in case that highly pure hydrogen (such as for fuel cell) is demanded liquid hydrogen looks to be promising (24–25 JPY/Nm3-H2 in 2050) compared to MCH and ammonia with decomposition and purification.
Monitoring H2 Bubbles by Real Time H2 Sensor
Sep 2017
Publication
Portable H2 sensor was made by using mass spectrometer for the outside monitoring experiment: the leak test the replacement test of gas pipe line the combustion test the explosion experiment the H2 diffusion experiment and the recent issue of the exhaust gas of Fuel Cell Vehicle. In order to check the real time concentration of H2 in various conditions even in the highly humid condition the system volume of the sampling route was minimized with attaching the humidifier. Also to calibrate H2 concentration automatically the specific concentration H2 small cylinder was mounted in the system. In the experiment when H2 gas was introduced in the N2 flow or air in the tube or the high-pressure bottle highly concentrated H2 phases were observed by this sensor without diffusion. This H2 sensor can provide the real time information of the hydrogen molecules and the clouds. The basic characterization of this sensor showed 0-100% H2 concentrations within 2ms. Our observation showed the size of the high concentration phase of H2 and the low concentration phase after mixing process. The mixed and unmixed H2 unintended concentration of cloud gas the high speed small cluster of hydrogen molecules in purged gas were explored by this real time monitoring system.
A GIS-based Risk Assessment for Hydrogen Transport: A Case Study in Yokohama City
Sep 2019
Publication
Risk assessment of hazardous material transport by road is critical in considering the spatial features of the transport route. However previous studies that focused on hydrogen transport were unable to reflect the spatial features in their risk assessments. Hence this study aims to assess the risk of hydrogen transport by road considering the spatial features of the transport route based on a geographic information system (GIS). This risk assessment method is conducted through a case study in Yokohama which is an advanced city for hydrogen economy in Japan. In our assessment the risk determined by multiplying the frequency of accidents with the consequence was estimated by road segments that constitute the entire transport route. The effects of the road structure and traffic volumes were reflected in the estimation of the frequency and consequence for each road segment. All estimations of frequency consequence and risk were conducted on a GIS compiled with the information regarding the road network and population. In the case study in Yokohama the route for the transport of compressed hydrogen was virtually set from the near-term perspectives. Based on the case study results the risks of the target transport route were assessed at an acceptable level under the previous risk criteria. The results indicated that the risks fluctuated according to the road segments. This implies that the spatial features of the transport route significantly affect the corresponding risks. This finding corroborates the importance of considering spatial features in the risk assessment of hydrogen transport by road. Furthermore the discussion of this importance leads to the capability of introducing hydrogen energy careers with high transport efficiency and transport routing to avoid high risk road segments as risk countermeasures.
Tokyo Gas’ Efforts Regarding Impact Assessment on Surroundings and Emergency Response Training
Sep 2017
Publication
In Japan 82 commercial Hydrogen Refuelling Stations (HRSs) were constructed as of March 1 2017 but few impact assessments have been reported on the surroundings at HRS. In addition as HRSs become more widespread the number of HRSs around narrow urban areas will also increase. Thus the necessity of impact assessments on the surroundings of HRSs is expected to increase. In order to confirm that the influence from our HRS is not problematic to the surrounding residences we conducted an impact assessment on the surroundings at HRS by using the actual HRS construction plan. Although safety is one of the objects of an impact assessment in Japan the safety of an HRS is guaranteed by observing the High Pressure Gas Safety Act its Technical Standards and other related regulations. On the other hand if an accident such as a hydrogen leak or hydrogen fire occurs at an HRS it becomes important to prevent secondary disasters and to minimize influence on the surroundings by means of an initial response by the operators of the HRS. Therefore we have conducted training to improve the emergency response capability of the HRS operators and to prevent secondary disasters. In this paper we describe the abovementioned information with regard to an impact assessment on the surroundings and for emergency response training.
Experimental Study on High Pressure Hydrogen Jets Coming Out of Tubes of 0.1–4.2 m in Length
Sep 2011
Publication
Wide use of hydrogen faces significant studies to resolve hydrogen safety issues in industries worldwide. However widely acceptable safety level standards are not achieved in the present situation yet. The present paper deals with hydrogen leaks from a tube to ignite and explode in atmosphere. The experiments using a shock tube are performed to clarify the auto-ignition property of high pressure hydrogen jet spouting from a tube. In order to improve experimental repeatability and reliability the shock tube with a plunger system is applied where the PET diaphragm is ruptured by a needle in order to control a diaphragm burst pressure (hydrogen pressure). As a result it becomes possible to control the diaphragm burst pressure to obtain a local minimum value. The most important result obtained in the preset study is that the minimum diaphragm burst pressure for auto-ignition is found between 1.0 and 1.2 m of tube length using a longer tube than the one used in the previous study. This minimum tube size is not found elsewhere to suggest that the tube length has a limit size for auto-ignition. Furthermore auto-ignition and Mach disk at the tube exit are observed using a high speed camera which is set at the frame speed of 1x105 fps when the ignited hydrogen jet is spouted out the tube.
Localized Plasticity and Associated Cracking in Stable and Metastable High-Entropy Alloys Pre-Charged with Hydrogen
Dec 2018
Publication
We investigated hydrogen embrittlement in Fe20Mn20Ni20Cr20Co and Fe30Mn10Cr10Co (at.%) alloys pre-charged with 100 MPa hydrogen gas by tensile testing at three initial strain rates of 10−4 10−3 and 10−2 s−1 at ambient temperature. The alloys are classified as stable and metastable austenite-based high-entropy alloys (HEAs) respectively. Both HEAs showed the characteristic hydrogen-induced degradation of tensile ductility. Electron backscatter diffraction analysis indicated that the reduction in ductility by hydrogen pre-charging was associated with localized plasticity-assisted intergranular crack initiation. It should be noted as an important finding that hydrogen-assisted cracking of the metastable HEA occurred not through a brittle mechanism but through localized plastic deformation in both the austenite and ε-martensite phases.
Effects of Alloying Elements Addition on Delayed Fracture Properties of Ultra High-Strength TRIP-Aided Martensitic Steels
Dec 2019
Publication
To develop ultra high-strength cold stamping steels for automobile frame parts the effects of alloying elements on hydrogen embrittlement properties of ultra high-strength low alloy transformation induced plasticity (TRIP)-aided steels with a martensite matrix (TM steels) were investigated using the four-point bending test and conventional strain rate tensile test (CSRT). Hydrogen embrittlement properties of the TM steels were improved by the alloying addition. Particularly 1.0 mass% chromium added TM steel indicated excellent hydrogen embrittlement resistance. This effect was attributed to (1) the decrease in the diffusible hydrogen concentration at the uniform and fine prior austenite grain and packet block and lath boundaries; (2) the suppression of hydrogen trapping at martensite matrix/cementite interfaces owing to the suppression of precipitation of cementite at the coarse martensite lath matrix; and (3) the suppression of the hydrogen diffusion to the crack initiation sites owing to the high stability of retained austenite because of the existence of retained austenite in a large amount of the martensite–austenite constituent (M–A) phase in the TM steels containing 1.0 mass% chromium
Development of Hydrogen Behavior Simulation Code System
Oct 2015
Publication
In the Fukushima Daiichi Nuclear Power Station (NPS) accident hydrogen generated by oxidation reaction of the cladding and water etc. was leaked into the NPS building and finally led to occurrence of hydrogen explosion in the building. This resulted in serious damage to the environment. To improve the safety performance of the NPS especially on the hydrogen safety under severe accident conditions a simulation code system has been developed to analyze hydrogen behaviour including diffusion combustion explosion and structural integrity evaluation. This developing system consists of CFD and FEM tools in order to support various hydrogen user groups consisting of students researchers and engineers. Preliminary analytical results obtained with above mentioned tools especially with open source codes including buoyancy turbulent model and condensation model agreed well with the existing test data.
Safety Requirements for Liquefied Hydrogen Tankers
Oct 2015
Publication
R&D projects for establishing hydrogen supply chain have already been started in Japan in collaboration among the industry government and universities. One of the important subjects of the project is development of liquefied hydrogen tankers i.e. ships carrying liquefied hydrogen in bulk. In general basic safety requirements should be determined to design ships. However the existing regulations do not specify the requirements for hydrogen tankers while requirements for ships carrying many kinds of liquefied gases are specified in “International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk” (IGC Code) issued by the International Maritime Organization i.e. a special organization under the United Nations. Therefore the basic safety requirements for hydrogen tankers should be developed. We conducted bibliographic survey on the IGC Code ISO/TR 15916:2004 “Basic considerations for the safety of hydrogen systems” and so on; in order to provide safety requirements taking into account the properties of liquid and gaseous hydrogen. In this paper we provide safety requirements for liquefied hydrogen tankers as the basis for further consideration by relevant governments.
Dependency of Equivalence Ratio on Hydrogen Cylindrical Detonation Induced by Direct Initiation
Sep 2011
Publication
A hydrogen fuel is expected to expand its demand in the future. However hydrogen has to be treated with enough caution because of wide combustible conditions and easiness to ignite. Detonation accidents are caused in hydrogen gas such as the explosion accident in Fukushima first nuclear plant (2011). Therefore it is necessary to comprehend initiation conditions of detonation to prevent its detonation explosion. In the present study cylindrical detonation induced by direct initiation is simulated to understand the dependency of equivalence ratios in hydrogen-oxygen mixture. The several detailed kinetic models are compared to select the most appropriate model for detonation in a wide range of equivalence ratios. The Petersen-Hanson model is used in the present study due to the best agreement among the other models. In the numerical results of cylindrical detonation induced by direct initiation a cellular structure which is similar to the experimental smoked foil record is observed. The local pressure is up to 12 MPa under the condition at the standard state. The ignition process of cylindrical detonation has two stages. At the first stage the normalized cell width /L1/2 at each equivalence ratio increases linearly. At the second stage cell bifurcations appear due to a generation of new transverse waves. It is observed that a transverse wave transforms to a transverse detonation at the end of the first stage and after that some disturbance is developed to be a new transverse wave at the beginning of the second stage.
Auto-ignition Mechanism Near the Boundary Layer for High-pressure Hydrogen Release into Circular and Rectangular Tubes
Oct 2015
Publication
The accidents that hydrogen ignites without ignition source are reported in several cases which phenomenon is called “auto-ignition.” Since the use of high pressure hydrogen will be increased for the hydrogen society it must be necessary to understand auto-ignition mechanism in detail to prevent such accidents. In this study we performed three-dimensional numerical simulations to clarify the autoignition mechanism using the three-dimensional compressive Navier-Stokes equations and a hydrogen chemical reaction model including nine species and twenty elementary reactions. We focus on the effects of the shape of the cross-section on the hydrogen auto-ignition mechanism applying for a rectangular and cylindrical tube. The results obtained indicate that the Richtmyer-Meshukov instability involves these auto-ignition.
Fundamental Study on Accidental Explosion Behavior of Hydrogen/Air Mixtures in Open Space
Sep 2011
Publication
In this study the flame propagation behavior and the intensity of blast wave by an accidental explosion of a hydrogen/air mixture in an open space have been measured simultaneously by using soap bubble method. The results show that the flame in lean hydrogen/air mixtures propagated with a wrinkled flame by spontaneous instability. The flame in rich hydrogen/air mixtures propagated smoothly in the early stage and was intensively wrinkled and accelerated in the later stage by different type of instability. The intensity of the blast wave of hydrogen/air mixtures is strongly affected by the acceleration of the flame propagation by these spontaneous flame disturbances.
Overview of the New Combined Gasoline/Hydrogen Supply Station and Relevant Regulations in Japan
Sep 2007
Publication
When a hydrogen supply station is to be installed in Japan three fundamental laws must be taken into consideration: the High Pressure Gas Safety Law the Building Standards Law and the Fire Service Law. The High Pressure Gas Safety Law in particular regulates procedures for safety concerning hydrogen supply stations. This law came under review accompanying consideration of the potential utilization of fuel cell vehicles and hydrogen stations. At that time the Japan Petroleum Energy Center (JPEC) investigated safety technology for hydrogen supply stations and prepared a draft of the law. Since then a new combined gasoline/hydrogen supply station compliant with the revised law was established on December 2006. There are a large number of safety precautions incorporated into this station model which conform to the law. As a result of these modifications it was possible to reduce the safe setback distance. In this paper we present an overview of the new hydrogen supply station model the safety precautions and the regulations the station is based on.
Numerical Investigation of Detonation in Stratified Combustible Mixture and Oxidizer with Concentration Gradients
Sep 2019
Publication
Hydrogen leakage in a closed space is one of the causes of serious accidents because of its high detonability. Assuming the situation that hydrogen is accumulated in a closed space two-dimensional numerical simulation for hydrogen oxygen detonation which propagates in stratified fuel and oxidizer with concentration gradient is conducted by using detailed chemical reaction model. The concentration gradient between fuel and oxidizer is expressed by changing the number of hydrogen moles by using sigmoid function. Strength of discontinuity at the boundary is controlled by changing the gain of the function. The maximum pressure history shows that the behaviour of triple points is different depending on the strength of discontinuity between the two kind of gas. In without concentration gradient case the transverse waves are reflected at the boundary because of the sudden change of acoustic impedance ratio between two kind of gas. In contrast in with concentration gradient case the transverse wavs are not reflected in the buffer zone and they are flowed into the oxidizer as its structures are kept. As a result the confined effect declines as the strength of discontinuity between the two kind of gas is weakened and the propagating distance of detonation changes
Performance Evaluation of the Miniaturized Catalytic Combustion Type Hydrogen Sensor
Oct 2015
Publication
Fast response and high durability hydrogen sensor is required in the safety management of hydrogen station and fuel cell vehicle. We had developed the catalytic combustion type hydrogen sensor in the shape of the miniature beads. It is using the optimized Pd-Pt/Al2O3 catalyst and the Pt micro-heater coil. Both warm-up time and response time of this sensor achieved less than 1 second by downsizing the element to 200μm diameter. Furthermore we improved the resistance of sensor poisoning to silicone vapor and confirmed long term stability within +/-10% of output error up to 8 years. Therefore we assume that our sensor technology contribute to hydrogen safety.
Hazard Identification Study for Risk Assessment of a Hybrid Gasoline-hydrogen Fueling Station with an Onsite Hydrogen Production System Using Organic Hydride
Oct 2015
Publication
Hydrogen infrastructures are important for the commercialization of fuel cell vehicles. Hydrogen storage and transportation are significant topics because it is difficult to safely and effectively treat large amounts of hydrogen because of hydrogen hazards. An organic chemical hydride method keeps and provides hydrogen using hydrogenation and dehydrogenation chemical reactions with aromatic compounds. This method has advantages in that the conventional petrochemical products are used as a hydrogen carrier and petrochemicals are more easily treated than hydrogen because of low hazards. Hydrogen fueling stations are also crucial infrastructures for hydrogen supply. In Japan hybrid gasoline-hydrogen fuelling stations are needed for effective space utilization in urban areas. It is essential to address the safety issues of hybrid fueling stations for inherently safer station construction. We focused on a hybrid gasoline-hydrogen fuelling station with an on-site hydrogen production system using methylcyclohexane as an organic chemical hydride. The purpose of this study is to reveal unique hybrid risks in the station with a hazard identification study (HAZID study). As a result of the HAZID study we identified 314 accident scenarios involving gasoline and organic chemical hydride systems. In addition we suggested improvement safety measures for uniquely worst-case accident scenarios to prevent and mitigate the scenarios.
Complex Metal Hydrides for Hydrogen, Thermal and Electrochemical Energy Storage
Oct 2017
Publication
Hydrogen has a very diverse chemistry and reacts with most other elements to form compounds which have fascinating structures compositions and properties. Complex metal hydrides are a rapidly expanding class of materials approaching multi-functionality in particular within the energy storage field. This review illustrates that complex metal hydrides may store hydrogen in the solid state act as novel battery materials both as electrolytes and electrode materials or store solar heat in a more efficient manner as compared to traditional heat storage materials. Furthermore it is highlighted how complex metal hydrides may act in an integrated setup with a fuel cell. This review focuses on the unique properties of light element complex metal hydrides mainly based on boron nitrogen and aluminum e.g. metal borohydrides and metal alanates. Our hope is that this review can provide new inspiration to solve the great challenge of our time: efficient conversion and large-scale storage of renewable energy.
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