Hydrogen energy high-pressure storage and transportation equipment refers to the high-pressure equipment used for hydrogen energy storage and transportation. The high-pressure hydrogen storage equipment includes fixed high-pressure hydrogen storage containers and high-pressure hydrogen cylinders, while the high-pressure hydrogen transmission equipment includes road hydrogen transmission equipment and hydrogen pipelines. High pressure hydrogen storage and transportation equipment has potential leakage and explosion hazards due to its large reserves, frequent charging and discharging and easy to cause hydrogen embrittlement.
In recent years, several accidents have occurred at home and abroad. In june2019, a hydrogen leakage explosion accident occurred on a long tube trailer in Santa Clara, California, USA; In the same month, a hydrogen storage vessel explosion accident occurred in sanwicka, Norway; In August, 2021, the hose of a hydrogen tank car burst and deflagration occurred in Shenyang. This has sounded an alarm for the safe storage and transportation of hydrogen energy. With the rapid development of hydrogen energy, the types and quantity of hydrogen energy high-pressure storage and transportation equipment in China are growing rapidly, the service conditions are extreme, the risk degree is increasing, and the safety assurance is facing new challenges.
Basic features
Compared with compressed natural gas storage and transportation equipment, hydrogenation reactor and other high-pressure equipment, hydrogen energy high-pressure storage and transportation equipment has the following three basic characteristics.
Hydrogen is easy to leak, flammable, explosive and has large reserves. Once it fails, it will cause serious harm
Compared with gasoline and natural gas, hydrogen has the characteristics of small density, large diffusion coefficient, low ignition energy, wide combustion and explosion range, fast combustion flame speed, easy leakage, flammability and explosion. High pressure hydrogen storage and transportation equipment has large hydrogen storage capacity. For example, according to gb50516-2010 technical code for hydrogen refueling stations (version 2021), the maximum hydrogen capacity of a single hydrogen storage high-pressure vessel in the primary, secondary and tertiary hydrogen refueling stations is 20001500800kg respectively. Once it leaks and explodes, it will cause serious harm. If hydrogen is ignited immediately after leakage, hydrogen jet fire will be formed; If it leaks into the confined space, it is easy to form flammable hydrogen cloud. Once ignited, it will produce deflagration and detonation, which will seriously endanger the safe operation of equipment and the safety of people's lives and property.
High pressure of compressed hydrogen, with risk of hydrogen embrittlement
As shown in the figure, the hydrogen storage pressure of hydrogen energy high-pressure storage and transportation equipment is high. These equipment operate under high-pressure hydrogen environment for a long time, and their hydrogen materials are prone to performance degradation due to hydrogen embrittlement.
The hydrogen embrittlement of metallic materials is mainly manifested in the decrease of toughness, the acceleration of fatigue crack growth rate, and the decrease of the threshold value of stress intensity factor of hydrogen induced cracking.
Hydrogen embrittlement of non-metallic materials is mainly manifested in the changes of elastic modulus, tensile strength and friction coefficient caused by hydrogen dissolution, and hydrogen bubbles and cracks caused by rapid pressure reduction.
Service performance is affected by many factors and complicated mechanism, and it is difficult to control
The service performance of hydrogen energy high-pressure storage and transportation equipment is comprehensively affected by many factors, such as materials (tensile strength, chemical composition, microstructure, etc.), environment (hydrogen pressure, ambient temperature, hydrogen purity, etc.), stress (load, structure, loading mode, etc.) and manufacturing (forming process, heat treatment, surface quality, etc.).
Generally, the higher the strength of the material, the faster the fatigue crack growth rate, and the lower the threshold value of the stress intensity factor of hydrogen induced cracking; The higher the hydrogen pressure, the higher the hydrogen embrittlement sensitivity; The lower the loading frequency is, the more serious the hydrogen embrittlement is; Stress intensity factor range Δ When k is small, hydrogen has little effect on the fatigue crack growth rate, but Δ When k exceeds a certain value, the effect is significant; The greater the surface roughness of the hydrogen facing material, the more serious the damage of high pressure hydrogen to the fatigue performance of the equipment.
In addition, there may be coupling among the factors. For example, it has been found that when the hydrogen pressure is less than 40MPa, the hydrogen embrittlement sensitivity of Cr Mo steel decreases with the decrease of loading frequency. It is very difficult to predict and control the service performance of hydrogen energy high-pressure storage and transportation equipment because of many influencing factors and complex mechanisms.
Development status
01 hydrogen storage high pressure equipment
Stationary hydrogen storage high pressure vessel
Fixed hydrogen storage high-pressure vessels are mainly used in hydrogenation stations, hydrogen energy storage, emergency power stations, etc. at present, they are most widely used in hydrogenation stations. According to the structural characteristics, fixed hydrogen storage high-pressure vessels in China mainly include single-layer steel hydrogen storage high-pressure vessels and multi-layer steel hydrogen storage high-pressure vessels.
The single-layer steel hydrogen storage high-pressure vessel mainly includes spinning type hydrogen storage high-pressure vessel and single-layer integrally forged type hydrogen storage high-pressure vessel. The spinning type hydrogen storage high-pressure vessel is formed by spinning seamless steel pipes, and its design pressure is usually not more than 50MPa. At present, it is mainly used in 35MPa hydrogenation station. This kind of container has the advantages of simple structure, low manufacturing cost and mass production, but its volume is limited. At present, the water volume of a single container usually does not exceed 1000L. Therefore, it is mostly used in the form of container groups (some as many as 21 containers). It is necessary to strengthen the research on the interaction mechanism between multiple containers and its impact on failure behavior under extreme conditions such as fire and impact. In addition, most of these vessels are made of Cr Mo steel (mainly 4130X), which is highly sensitive to hydrogen embrittlement.
The multi-layer steel hydrogen storage high-pressure vessel mainly includes steel strip staggered multi-layer hydrogen storage high-pressure vessel and laminated plate wrapped hydrogen storage high-pressure vessel. Compared with single-layer steel hydrogen storage high-pressure vessels, such vessels have higher hydrogen storage pressure and larger volume. For example, the volumes of 50MPa and 98mpa steel strip staggered multi-layer hydrogen storage high-pressure vessels reach 7.3 and 1m3 respectively. In addition, austenitic stainless steel with good hydrogen embrittlement resistance is often used as the hydrogen facing material of such vessels, which is conducive to preventing the failure caused by hydrogen embrittlement. However, the structure of such vessels is complex, the manufacturing cycle is long, and the quality requirements for welded joints are high.
With the continuous support of the national 973 Plan Project "basic research on the design and manufacture of large bearing parts of high-pressure hydrogen system" and the national key R & D plan project "Research on performance testing and quality evaluation technology of hydrogen energy storage and transportation equipment", after more than 20 years of efforts, China has realized the independent control of fixed hydrogen storage high-pressure vessels. According to statistics, by the end of 2021, China has built 191 hydrogenation stations and more than 1500 fixed hydrogen storage high-pressure vessels in service.
High pressure hydrogen cylinder
High pressure hydrogen cylinders are mainly used for hydrogen energy transportation, such as hydrogen fuel cell passenger cars, logistics vehicles, buses, forklifts, heavy trucks, ships, UAVs, etc. Hydrogen fuel cell forklift trucks mainly use steel high-pressure hydrogen cylinders, and the rest use aluminum lined carbon fiber fully wound hydrogen cylinders (hereinafter referred to as type III cylinders) and plastic lined carbon fiber fully wound hydrogen cylinders (hereinafter referred to as type IV cylinders). In addition to the basic features of hydrogen energy high-pressure storage and transportation equipment, high-pressure hydrogen cylinders also have the following features:
(1) The volume and weight are limited. Due to the space in the vehicle, the volume of the gas cylinder is usually no more than 450L. The lighter its weight, the more conducive it is to improve the performance of the whole vehicle and reduce the cost;
(2) The filling requirements are special. The filling speed of the cylinder is fast and real-time communication with the hydrogenation machine is required. The filling time of the passenger car is usually 3~5min. The rapid filling of hydrogen will lead to temperature rise, which will affect the performance of the cylinder;
(3) The service life is long, and the design service life is usually 10~15 years, or even longer;
(4) The use environment is complex and changeable. The use environment is related to the region and road conditions where the vehicle is located, and there are risks such as mechanical damage and environmental erosion.
Under the leadership of the special equipment safety supervision bureau of the State Administration of market supervision, the overall development idea of China's high-pressure hydrogen cylinders is: the structure is from type III to type IV, and the pressure is from low to high.
At present, type III bottles with nominal working pressures of 35MPa and 70MPa have been independently designed, manufactured and mass produced. The mass hydrogen storage density is 3.8% ~ 4.5%, reaching the international advanced level. They are widely used in hydrogen fuel cell vehicles such as hydrogen fuel cell electric vehicles. At present, there are more than 40000 in service. Type IV bottles have been developed and applied abroad earlier. Hexagon of the United States, Toyota of Japan and Iljin of Korea have developed 70MPa type IV bottles, and the mass hydrogen storage density has reached 5.7%. The Ministry of science and technology approved and supported the research on "70MPa vehicle mounted high-pressure hydrogen storage bottle technology" in 2019. In 2019 and 2020, China issued the group standards t/catsi02005-2019 liquefied petroleum gas high density polyethylene tank glass fiber fully wound cylinder and t/catsi02007-2020 vehicle compressed hydrogen plastic tank carbon fiber fully wound cylinder, which effectively promoted the development of type IV cylinders in China. At present, the production capacity of lpg- type IV cylinder in China has exceeded 1million / year, and type IV hydrogen cylinder products have also been put on the market.
02 high pressure hydrogen transmission equipment
Road hydrogen transmission equipment
Road hydrogen transmission equipment transmits and distributes hydrogen through roads, railways, etc. it is suitable for occasions with short distance and less hydrogen consumption, mainly including long tube trailers and tube bundle containers. China has mature experience in designing, manufacturing and using long tube trailers and tube bundle containers. The nominal working pressure of this kind of equipment is usually 20~30mpa, the volume is not more than 3000l, and the hydrogen transport capacity of a single vehicle is not more than 500kg. The transportation efficiency is low and the cost is high. In order to improve the hydrogen transportation volume of a single vehicle, the Ministry of science and technology included the "high-pressure and large capacity tube bundle container hydrogen storage technology for highway transportation" in the key special project of "renewable energy and hydrogen energy technology" in 2020, and developed a large capacity carbon fiber wound hydrogen storage bottle and tube bundle container above 50MPa.
Hydrogen pipeline
Hydrogen pipelines have the characteristics of many types, large diameter and pressure range, large quantity and wide range. The classification and use are shown in the above figure.
Fig. 3 Classification and application of hydrogen pipeline
Fig. 3 Classification and application of hydrogen pipeline
At present, several long-distance hydrogen transmission pipelines with a total length of more than 5000km have been built in Europe and the United States. In contrast, although China has accumulated rich experience in the design, construction, operation and maintenance of hydrogen industrial pipelines and special pipelines, the construction of long-distance hydrogen transmission pipelines started late.
03 specifications and standards
In order to guide the healthy development of hydrogen energy high-pressure storage and transportation equipment, China attaches great importance to the formulation of specifications and standards, and has formulated a series of standards in terms of test methods and products. As shown in the figure.
At present, China is organizing the drafting of relevant national standards such as hydrogen storage pressure vessel, hydrogen cylinder combination valve, periodic inspection of hydrogen cylinder, hydrogen filling agreement of hydrogen refueling station, etc.
Facing challenges
01 security
Safety and reliability are the most basic requirements for hydrogen energy high-pressure storage and transportation equipment. At present, such equipment still has risks in terms of regulations, technology and management.
In terms of regulations, the existing safety technical specifications for special equipment lack basic safety requirements for hydrogen energy storage and transportation equipment above 35MPa;
In terms of technology, there are some risks, such as lack of material hydrogen environmental performance data, improper selection of product design methods, poor consistency of product performance, insufficient equipment inspection and detection ability and lack of methods;
In terms of management, there are risks that the equipment does not match the use scenario (for example, the gas cylinder is directly used for hydrogen storage in the hydrogenation station), and blind import of foreign products.
In addition, with the gradual transformation from the demonstration stage to the commercial stage, the pressure of the on-board hydrogen supply system of hydrogen fuel cell electric vehicles has gradually developed from 35MPa to 70MPa, and the design pressure of the hydrogen storage vessel in the hydrogenation station has gradually increased from 50MPa to 98mpa, which puts forward higher safety requirements for the hydrogen energy high-pressure storage and transportation equipment.
02 lightweight
Lightweight is the basic requirement for high-pressure hydrogen storage and transportation equipment such as on-board high-pressure hydrogen cylinders, long tube trailers and tube bundle containers. The realization of lightweight is not only beneficial to improve the power performance of the whole vehicle, but also to improve the endurance of fuel cell electric vehicles, as well as the hydrogen transport capacity of long tube trailers and tube bundle containers.
In order to promote the lightweight development of China's hydrogen energy high-pressure storage and transportation equipment, the technical index of the national key R & D plan project "70MPa vehicle mounted high-pressure hydrogen storage bottle technology" requires that the mass hydrogen storage density shall not be less than 5.0%. For long tube trailers, tube bundle containers and other equipment, at present, the main ways to achieve lightweight are to increase the hydrogen storage pressure and optimize the composite material structure. The technical indicators of the national key R & D plan project "high pressure, large capacity tube bundle container hydrogen storage technology for highway transportation" require that the nominal working pressure is not less than 50MPa and the mass hydrogen storage density is not less than 5.5%.
03 low cost
Hydrogen energy high-pressure storage and transportation equipment accounts for a high proportion of the cost in hydrogen refueling stations, hydrogen fuel cell electric vehicles and other systems. For example, in a 70MPa hydrogenation station with a filling capacity of 800kg/ day, the proportion of hydrogen storage containers in the cost is about 15%, and the larger the hydrogenation station is, the higher the proportion of hydrogen storage containers in the cost is. Therefore, reducing the cost of hydrogen energy high-pressure storage and transportation equipment is of great significance to reduce the overall cost of the hydrogen energy industry. Doe released the cost target of fixed hydrogen storage containers and hydrogen cylinders for fuel cell vehicles: the final cost target of 1kg hydrogen stored in fixed low-pressure (16MPa) hydrogen storage containers is $450, and that of medium pressure (43mpa) and high-pressure (92.5mpa) containers is $600; The final cost target of 1kg hydrogen stored in on-board hydrogen cylinders is $266.
At present, on the premise of meeting the basic requirements such as safety, reducing the cost is still a challenge for hydrogen energy high-pressure storage and transportation equipment. In the construction cost of hydrogen energy high-pressure storage and transportation equipment, the material cost accounts for the highest proportion. Therefore, the development of high-performance and low-cost hydrogen resistant materials can effectively reduce the equipment cost. In addition, the equipment cost can also be reduced by optimizing the structure, improving the design method and manufacturing process, and realizing large-scale production.
