Container for storing hydrogen

Abstract

The invention relates to a container (10) for storing hydrogen at a pressure of more than 700 bar, comprising a casing (1) which surrounds a storage volume (3), wherein the pressure exerted by the hydrogen in the storage volume (3) and the stresses can be absorbed by the casing (1), and the container (10) comprises an inner layer (2), which separates the storage volume (3) from the casing (1) in a gas-tight manner such that direct contact between the hydrogen and the material of the casing (1) is prevented. The inner layer (2) rests against the casing (1) in a form-fitting and / or force-fitting manner, and the container (10) has a connection (5) for filling and emptying the storage volume (3). According to the invention, the casing (1) consists of a high-strength metal, and the inner layer (2) consists of a metal which is resistant to hydrogen, in particular hydrogen embrittlement.

Description

[0001] Containers for storing hydrogen

[0002] The invention relates to a container for storing hydrogen according to the preamble of patent claim 1 and to a high-pressure storage device for hydrogen according to patent claim 11.

[0003] Hydrogen is currently becoming increasingly important for energy storage and supply in both industrial and private sectors. Liquefied hydrogen gas applications require temperatures below the critical temperature, which for hydrogen is -239.96°C, requiring significant cooling to achieve this temperature. However, hydrogen can be stored relatively efficiently in high-pressure containers at ambient temperatures, although this requires high pressures.

[0004] In addition to high-pressure storage, new challenges are also being posed for the equipment used to handle hydrogen itself. Components that come into direct contact with hydrogen, such as compressor units, piping, valves, sealing rings, and connections, must be adapted to the requirements of hydrogen. For example, the choice of materials, or rather the selection of hydrogen-compatible materials, is limited, and components must be adapted and redesigned accordingly. Ranges of around 1000 bar and above are particularly interesting for hydrogen storage, as relatively economical quantities of hydrogen, i.e., 50 kg and more at ambient temperature per cubic meter of container volume, can be stored stationary in these pressure ranges. A pressure of 1500 bar at 15°C results in almost 60-65 kg H2 per m 3 Storage volume, compared to 40 kg H2 at 700 bar.

[0005] Common hydrogen storage variants known from the state of the art also overlap with the storage forms of other gases. Different forms of hydrogen are known: for example, compressed gaseous hydrogen (CGH2; at 350 bar and 15°C), liquid hydrogen (LH2; at 1 bar and -253°C), cryogenically compressed hydrogen (CCH2 at 300 bar and -253°C), and solid hydrogen below a temperature of -259.2°C. Due to its complex handling, the latter is increasingly found in finely scaled application formats, such as in research.

[0006] For high-pressure applications in corrosive or material-damaging liquid and gaseous media, the state of the art generally uses ferritic / martensitic steels, as well as austenitic stainless steels, duplex and superduplex alloys, or nickel-based alloys. Since the mechanical and physical properties of these materials vary greatly, they are specifically used for different components according to their properties. For example, austenitic stainless steels are currently used for flanges, pipelines, and valve bodies in the medium-pressure segment, and duplex alloys are used for higher pressures. Martensitic stainless steels and nickel-based alloys are used for seals. Highly stressed valve spindles and valve seats are often made of martensitic, precipitation-hardened stainless steels and additionally coated.The required physical and mechanical properties are achieved through optimization and targeted adjustment of heat treatment, work hardening, and forming processes, e.g., forging, rolling, etc. With regard to hydrogen, no ferritic / martensitic microstructure components may be present in the material; this excludes the material groups of duplex steels and tempering steels for use with hydrogen.

[0007] Various concepts for hydrogen storage are known from the prior art. Plastic containers with different structures are typically used for this purpose. For example, DE10 2012 002 996 A1 discloses a container made of a moldable material having an inner and an outer shell, wherein the container comprises epoxy resin, plastic, metal, or glass. Furthermore, WO2021 130098A1 discloses a method for producing a component for storing or distributing compressed gas with a core material comprising aluminum or an aluminum alloy. The core material is coated on the compressed gas side with a ductile aluminum alloy and / or pure aluminum. EP 3 862 619 A1 discloses a hydrogen pressure container capable of preventing hydrogen-induced rupture of a cylinder.In a hydrogen pressure vessel according to one embodiment, a gap portion is provided between an internally threaded portion of a cylinder into which the lid is screwed and a resin sealing member, in which an inner peripheral surface of a cylinder is spaced from an outer peripheral surface of a lid. The cylinder has a first through-hole for discharging gas in the gap portion into a relief pipe and a second through-hole for introducing oxygen-containing gas into the gap portion formed therein.

[0008] In the currently emerging market for hydrogen refueling stations, higher pressure levels allow for greater local storage of larger quantities, significantly extending refueling intervals. State-of-the-art hydrogen refueling systems are often designed with three pressure levels: low-pressure, medium-pressure, and high-pressure banks, with a minimum pressure of 300–350 bar in the low-pressure bank to ensure a filling pressure of 300 bar for refueling cars. Buses and trucks, however, require 700 bar. As future refueling concepts tend toward even higher pressures, it will be necessary in the future to design and produce high-pressure banks to accommodate these higher pressures, and, above all, to feed them with even higher pressure storage units. High-pressure storage tanks for hydrogen up to 750 or a maximum of 1000 bar are currently available on the market, in Type I-IV variants. These are filled via connections that are just below or equal to DN 20 mm.This currently results in filling times that can take several hours for large storage facilities. The concepts for correspondingly large storage systems with high capacities rely on the interchangeability of filled storage systems. For example, with ship storage facilities, it is currently common practice for an empty storage facility to be exchanged for a previously filled one in port, as filling directly in port and the resulting layover time for the ship would take too long.

[0009] Space savings through higher pressures per volume, resulting in higher storage capacity and shorter filling times, are the direction development should take to make hydrogen more attractive as an energy storage medium. However, this is directly related to the adequate design of compressor-cooler units to prevent system overheating. Since hydrogen filling stations currently typically operate at pressures of 300-700 bar, these concepts also consider filling cycles that may be shorter or longer depending on storage capacity and demand.

[0010] The disadvantage of the containers known from the prior art is that they allow gas pressures of up to approximately 700 bar, which is insufficient for growing demand both in terms of temperature and storage capacity. On the other hand, containers known from the prior art that allow higher pressures have a complex structure and usually only allow a few charging and discharging cycles before they need to be replaced. The object of the present invention is therefore to provide containers for hydrogen that allow hydrogen to be stored at high pressures while still having a simple structure.

[0011] This object is achieved in a container of the type mentioned above with the characterizing features. According to the invention, the shell is made of a high-strength metal, and the inner layer is made of a metal resistant to hydrogen, in particular hydrogen embrittlement.

[0012] In contrast to the smaller pressure storage vessels in the medium-pressure range, which are used in the prior art, for example in vehicles, and which consist of CFRP-reinforced casing with polymer inner layers, the present invention enables stationary containers and hydrogen storage systems as well as systems for industrial storage and for hydrogen filling stations for refueling vehicles. With the inventive features of a two-part metallic container consisting of a casing made of high-strength heat-treated steel and a hydrogen-impermeable inner layer made of aluminum or austenite, the corrosion resistance can be increased and the number of filling cycles can be significantly increased. This corresponds to Class Type I for metallic pressure vessels. In the present invention, the high-strength and more hydrogen-sensitive casing acts as a carrier of the mechanical stresses, while the inner layer made of aluminum or austeniteAustenite with high hydrogen impermeability protects the shell from hydrogen embrittlement.

[0013] The inventive design of the pressure vessel or container allows it to be filled with hydrogen at pressures of 1500 bar and more. The most critical component of the pressure vessel is the shell, made of high-strength metal such as heat-treated steel. It is manufactured using hot forming, in contrast to conventional high-pressure pipes, which are drilled. Through hot forming and subsequent heat treatment, the mechanical properties are optimized to both minimize raw material usage and save weight. The advantage of the containers according to the invention lies in the possibility of non-cutting production and the optimized microstructure, which, in the case of the forged part, for example, is significantly finer and more homogeneous and achieves higher mechanical properties.

[0014] In the context of the present invention, the term "shell" refers to the entire envelope or casing of the storage volume or inner layer. The term "shell" is defined as extending beyond the purely geometrical shell of a cylinder. Thus, in the present invention, in advantageous embodiments of the container, the term "shell" also encompasses the lid and base.

[0015] Particularly advantageous embodiments of the container are further defined by the features of the dependent claims:

[0016] It is advantageous for the casing to consist of several parts that can be screwed or connected to one another. The modular design allows the individual parts of the container to be easily manufactured and then joined together to form the container during final assembly.

[0017] Preferably, the shell consists of a substantially cylindrical central part, a base, and a lid, wherein the central part is open at both ends, and wherein the lid and the base are each insertable into one of the open ends of the shell and connected to the shell, in particular detachably, preferably via threads. Thus, for example, individual parts, such as the lid or the base, can be combined with central parts of different sizes or lengths, thus producing containers with different storage volumes while maintaining the same lids or bases.

[0018] Advantageously, it can be provided that the casing, in particular the lid, has a conical recess, wherein the conical recess has a tapered profile in the direction of the outer side of the casing, wherein the container comprises a plug which is arranged in the casing, wherein the plug is designed opposite to the conical recess and is inserted therein in such a way that the plug can be pressed or pressed into the conical recess by means of the pressure in the storage volume and wherein the connection is arranged or formed in the plug.

[0019] In order to advantageously achieve a form and frictional connection and an ideal fit of the inner layer to the shell, it can be provided that the inner layer is joined to the shell by internal high-pressure forming, wherein in particular by means of an autofrettage process an internal stress is applied in the inner layer and / or the shell by the internal high-pressure forming.

[0020] In order to detect defects or cracks in the inner layer in good time, it can be provided that a sniffer hole is arranged in the shell, in particular in the cover, to detect leaks in the inner layer. In a preferred embodiment, it can be provided that the shell is made of a steel alloy, in particular of a heat-treatable steel, preferably of the steel alloy 1.6580 or 1.6952, and the inner layer, and in particular the plug, is made of an aluminum alloy or steel alloy, in particular of an austenitic steel, preferably from the group of steel alloys 1.44xx, particularly preferably 1.4404 or 1.4571 or 1.4301 or 1.4435. The specified material numbers always refer to the materials specified in the standard EN 10027-2.

[0021] To store hydrogen in the container as easily as possible, the shell, particularly the wall thickness, can be designed to withstand a pressure in the storage volume of up to 1500 bar. The ability to store hydrogen at high pressures advantageously eliminates the need for additional cooling to maintain it in liquid form in the container. Thus, the storable weight of hydrogen also increases with increasing pressure.

[0022] Advantageously, the jacket and the inner layer can be designed to withstand temperature fluctuations from -40°C to 230°C. This allows for easy handling, particularly during filling and storage of the container, without the need for additional cooling or heating of the container or without reaching temperatures unfavorable for the material.

[0023] A further aspect of the invention provides for an efficient storage device for hydrogen. According to the invention, this is achieved in a high-pressure storage device for hydrogen comprising a number of containers connected to one another in series and / or in parallel and combined into a bundle, in which the containers are designed as containers according to the invention.

[0024] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0025] The invention is schematically illustrated below with reference to particularly advantageous but non-limiting embodiments in the drawings and is described by way of example with reference to the drawings:

[0026] Figure 1 shows a first embodiment of the container according to the invention in a sectional view, Figure 2 shows the container according to Figure 1 in a plan view and

[0027] Figure 3 shows an embodiment of a hydrogen storage device according to the invention in an isometric view.

[0028] Figure 1 shows a first embodiment of the container 10 according to the invention in a sectional view. The cutting axis is guided through the center of the container 10 and shows a cross-section of the container 10. The container 10 comprises a jacket

[0029] 1 which surrounds a storage volume 3 in which hydrogen can be stored under pressure. The pressure exerted by the hydrogen in the storage volume 3 is absorbed by the jacket 1, thus establishing the stability of the container 10. The jacket 1 thus absorbs the pressure and stresses of the hydrogen compressed in the storage volume 3 and prevents the container 10 from bursting. An inner layer 2 is arranged between the storage volume 3 and the jacket 1 of the container 10. The inner layer 2 is arranged over its entire surface in the inside of the jacket 1 and thus separates the storage volume 3 from the material of the jacket 1. The inner layer

[0030] 2, the jacket 1 is separated from the storage volume 3 and the hydrogen contained therein in a gas-tight manner, preventing contact between the hydrogen and the material of the jacket 1. The inner layer 2 rests positively against the jacket 1, whereby the pressure or stresses exerted on the inner layer 2 are absorbed by the jacket 1, thus ensuring the stability of the container 10.

[0031] The shell 1 is made of a high-strength metal that absorbs the forces exerted by the hydrogen stored in the storage volume 3. According to the invention, the shell 1 is made of a steel alloy, in particular a high-strength tempering steel, for example the steel alloy 1.6580 or 1.6952. These steel alloys are particularly high-strength and are particularly well suited for the production of the shell 1, as they enable high strengths with simple manufacturing options, for example through hot forming. By means of a subsequent tempering heat treatment, the mechanical characteristics can optionally be optimized, so that the container 10 or shell 1 of the container 10 can be manufactured using non-cutting technology and with an optimized microstructure, which in the case of forged parts, for example, is significantly finer and more homogeneous and therefore achieves higher mechanical characteristics.

[0032] The container 10 further has a connection 5. The connection 5 connects the storage volume 3 to the outside or the surroundings of the container 10, and the filling channel 51 of the container 10, through which the storage volume 3 is filled with hydrogen, is closed by the connection 5. Hydrogen is supplied to or removed from the storage volume 3 via the connection 5 and the filling channel 51. The connection 5 can have different dimensions adapted to the size of the storage volume 3. For example, different connections 5 and sizes of the connections 5, e.g., with 1 / 4 inch, are known in the prior art.

[0033] The material of the inner layer 2 consists of a hydrogen-resistant metal, so that it does not experience hydrogen embrittlement upon contact with hydrogen. Particularly suitable materials for the inner layer 2 include, for example, aluminum alloys or high-alloy steels. Austenitic steels are particularly preferred for the inner layer 2. Of the group of austenitic steels, the group of steel alloys 1.44xx and, for example, the steel alloy 1.4404 or 1.4571 or 1.4301 or 1.4435 have proven particularly suitable in the tests underlying the invention. Austenitic steels exhibit particularly good hydrogen resistance for the formation of the inner layer 2 and, at the same time, are also easily formable.

[0034] In a preferred embodiment of the container 10 according to the invention, the casing 1, as shown in Figure 1, is constructed from several individual parts. The container 10 preferably has a cylindrical central part 11 which forms the cylindrical wall of the casing 1. A lid 13 is arranged at the upper end of the casing 1 or the cylindrical central part 11. On the end of the cylindrical central part 11 opposite the lid 13, a base 12 is arranged in the region of the base of the casing 1 or the container 10. The central part 11 has threads at each of its ends via which the base 12 or the lid 13 are screwed into the cylindrical central part 11. The central part 11, the base 12 and the lid 13 thus form the casing 1 of the container 10, which ensures the stability of the container 10.

[0035] As an alternative to the embodiment shown in Figure 1, the base 12 and the cover 13 can also be connected to the central part 11 via other, preferably detachable, connections. For example, in the case of weldable materials, they can be welded to the central part 11, or they can be connected to the central part 11 via press connections or other connection variants known from the prior art.

[0036] The embodiment of the container 10 or the casing 1 shown in Figure 1, consisting of the central part 11, the lid 13, and the base 12, allows for simple production of the container 10, which can be carried out in large quantities and in variable dimensions. For example, the length of the central part 11 can be easily adapted to the required storage quantity of hydrogen by making it longer for a larger required storage volume, while still allowing the same lid 13 and base 12 to be used.

[0037] The inner layer 2 is applied to the inner circumference of the shell 1 so that the shell 1 absorbs all the forces exerted on the inner layer 2 by the hydrogen compressed in the storage volume 3. The inner layer 2 is introduced into the interior of the shell 1 during the manufacture of the container 10 and is then attached or adapted to the shell 1 by internal high-pressure forming. The shell 1 thus acts as a die for the inner layer 2. In the case of the embodiment in Figure 1, the shell 1 is therefore first partially manufactured by connecting the central part 11 to the base 12, and then the inner layer 2 is inserted into the interior of the partially prefabricated shell 1. The cover 13 is then inserted into the central part 11 and connected or screwed to it, so that the inner layer 2 is arranged inside the shell 1 and forms the storage volume 3.Subsequently, the storage volume 3 formed by the inner layer 2 and the shell 1 is pressurized, and the inner layer 2 is deformed. The pressure in the storage volume 3 presses the inner system 2 against the shell 1, thereby deforming it such that the inner layer 2 rests fully on the shell 1. By applying pressure to the storage volume 3, the inner layer 2 undergoes autofrettage, which leads to an increase in load-bearing capacity through the targeted induction of compressive residual stresses.

[0038] Optionally, the shell 1 can also be subjected to autofrettage by selectively applying internal pressure to the storage volume 3 or by internal high-pressure forming. Autofrettage can generate targeted residual stresses in the shell 1 and / or the inner layer 2. The targeted induced residual stresses increase the strength under load caused by the hydrogen stored in the storage volume 3.

[0039] In a preferred optional embodiment of the container 10 according to the invention, it has a conical recess 14. The conical recess 14 is arranged, for example, as shown in Figure 1, in the lid 13 or at other locations in the casing 1. The conical recess 14 has a tapered profile towards the outside of the casing 1, i.e. towards the surroundings of the container 10, as a result of which the inside diameter of the cone or the recess 14 is larger in the area of ​​the storage volume 3 than on the outside of the casing 1 or the container 10. A plug 6 is inserted into the conical recess 14 and is designed to be opposite to the conical recess 14. The plug 6 therefore has the same pitch as the cone, so that the entire surface of the cone rests in the recess 14. The internal pressure of the gas or liquid present in the storage volume 3 causes the cone to be compressed.Hydrogen therefore pushes the plug 6 towards the outside of the casing 1 and thereby presses or pressed into the recess 14.

[0040] As shown in Figures 1 and 2, the connection 5 can preferably be formed in the plug 6. The material of the plug 6 comprises a similar or identical material to the inner layer 2, which is resistant to hydrogen and prevents a reaction between the material of the plug 6 and the hydrogen. The plug 6 thus makes it possible to connect the interior of the container 10, i.e., the storage volume 3, to the environment while simultaneously preventing hydrogen from contacting the material of the casing 1 or the material of the cover 13 shown in Figure 1.Thus, the design of the plug 6 of the shell 1 as well as the inner layer 2 provides a simple structure of the container 10 with which hydrogen can be stored under high pressure, wherein the forces generated by the pressure of the hydrogen inside the storage volume 3 can be easily absorbed by the shell 1 and at the same time hydrogen only comes into contact with materials that are resistant to hydrogen or on which hydrogen has no negative effects.

[0041] In order to be able to easily store hydrogen with a high density and at the same time at almost room temperature in the container 10, the jacket 1 or the middle part 11 of the lid 13 and the base 12 are designed in such a way in their wall thickness and structure that they can absorb a pressure of up to 1500 and more in the storage volume 3.

[0042] In order to enable universal use of the container 10, the material of the casing 1 and the inner layer 2 are designed, and the wall thickness and coating are such that they can be filled with hydrogen at different temperatures and can also withstand temperature fluctuations during filling and removal of hydrogen. In particular, they can withstand temperature fluctuations from -40 °C to 230 °C. As mentioned at the beginning, the storage of hydrogen, particularly in large quantities with high availability, is a problem in the prior art. For this purpose, a hydrogen storage device 100 is provided according to the invention, the preferred embodiment of which is shown in Figure 3. The hydrogen storage device 100 comprises a number of containers 10, in this embodiment ten containers 10, which are connected via a holder 101 to form a common hydrogen storage device 100. The containers 10 orTheir connections 5 can, for example, be connected to one another in series or in parallel via a pipe system. Furthermore, it is optionally possible for some of the containers 10 to be arranged in series and these in turn parallel to other containers 10 in the hydrogen storage unit 100. This makes it possible, for example, for the containers 10 to be filled with hydrogen in parallel or serially, one after the other, and thus provide a large storage volume 3 together, or, as in the case of a parallel arrangement of containers 10, for them to be able to release a larger quantity of hydrogen via the respective connection 5 at the same time. The containers 10, which are combined or connected in the hydrogen storage unit 100, are designed like a container 10 according to the invention. The containers 10 therefore each have a casing 1 which is gas-tightly insulated from the storage volume by an inner layer 2.

[0043] As shown in the preferred embodiment in Figures 1 and 2, the container 10 or its shell 1 can have a so-called sniffer hole 7. The sniffer hole 7 connects the area surrounding the shell 1 or the container 10 with the outside of the inner layer 2. Any leakage in the inner layer 2 can be detected through the sniffer hole 7, since hydrogen escaping from the inner layer 2 passes through the sniffer hole 7 into the area surrounding the container 10 and can be easily detected there. The sniffer hole 7 can be arranged in the lid 13, as shown by way of example in Figures 1 and 2, since this is particularly easily accessible.

Claims

Patent claims 1. A container (10) for storing hydrogen at a pressure of more than 700 bar, comprising a jacket (1) surrounding a storage volume (3), wherein the pressure and stresses exerted by the hydrogen in the storage volume (3) can be absorbed by the jacket (1), wherein the container (10) comprises an inner layer (2) which separates the storage volume (3) from the jacket (1) in a gas-tight manner, so that direct contact of the hydrogen with the material of the jacket (1) is prevented, wherein the inner layer (2) bears positively and / or non-positively against the jacket (1), and wherein the container (10) has a connection (5) for filling and emptying the storage volume (3), characterized in that the jacket (1) is made of a high-strength metal and the inner layer (2) is made of a metal which is resistant to hydrogen, in particular hydrogen embrittlement.

2. Container (10) according to claim 1, characterized in that the casing (1) consists of several parts which are designed to be screwed or connected to one another or into one another.

3. Container (10) according to claim 2, characterized in that the jacket (1) consists of a substantially cylindrical central part (11), a base (12) and a lid (13), wherein the central part (11) is open at both ends and wherein the lid (13) and the base (12) are each insertable into one of the open ends of the jacket (1) and are connected to the jacket, in particular detachably, preferably via threads.

4. Container (10) according to one of the preceding claims, characterized in that the casing (1), in particular the lid (13), has a conical recess (14), wherein the conical recess (14) has a tapered course in the direction of the outer side of the casing (1), - wherein the container (10) comprises a plug (6) which is arranged in the casing (1), wherein the plug (6) is formed opposite to the conical recess (14) and is inserted therein in such a way that the plug (6) can be pressed or pressed into the conical recess (14) by means of the pressure in the storage volume (3) and - wherein the connection (5) is arranged or formed in the plug (6).

5. Container (10) according to one of the preceding claims, characterized in that the inner layer (2) is joined to the shell (1) by internal high-pressure forming, wherein, in particular, a residual stress is applied in the inner layer (2) and / or the shell (1) by means of the internal high-pressure forming in the course of an autofrettage process.

6. Container (10) according to one of the preceding claims, characterized in that a sniffer bore (7) for detecting leaks in the inner layer (2) is arranged in the casing (1), in particular in the lid (13).

7. Container (10) according to one of the preceding claims, characterized in that the casing (1) consists of a steel alloy, in particular of a tempering steel, preferably of the steel alloy 1 .6580 or 1 .6952.

8. Container (10) according to one of the preceding claims, characterized in that the inner layer (2), and in particular the plug (6), consists of an aluminum alloy or steel alloy, in particular of an austenitic steel, preferably from the group of steel alloys 1.44xx, particularly preferably 1.4404 or 1.4571 or 1.4301 or 1.4435.

9. Container (10) according to one of the preceding claims, characterized in that the casing (1), in particular in the wall thickness, is designed to withstand a pressure in the storage volume (3) of up to 1500 bar.

10. Container (10) according to one of the preceding claims, characterized in that the jacket (1) and the inner layer (2) are designed to withstand temperature fluctuations from -40°C to 230°C.

11. High-pressure storage device (100) for hydrogen comprising a number of containers (10) which are connected to one another in series and / or in parallel and combined to form a bundle, characterized in that the containers (10) are designed according to one of claims 1 to 10.

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