Apparatus with hydrogen collection unit

Abstract

An apparatus (100, 200) suitable for utilizing hydrogen, comprising: a hydrogen preparation unit (102) configured to supply a gaseous hydrogen-containing medium containing at least 85 volume percent hydrogen at a pressure between a lower limit and an upper limit; a hydrogen collection unit (101, 201) including one or more pipe elements (300, 301) that together define an interior space bounded by a wall; and a hydrogen treatment unit (103) configured to treat and / or use the hydrogen-containing medium, wherein the apparatus (100, 200) is configured to perform the steps of supplying the hydrogen-containing medium from the hydrogen preparation unit (102) to the hydrogen collection unit (101, 201) and supplying the hydrogen-containing medium from the hydrogen collection unit (101, 201) to the hydrogen treatment unit (103), wherein the upper pressure limit is 50 bar or less, and each of the one or more pipe elements (300, 301) is cast from nodular cast iron having a tensile strength of 600 MPa or less.

Description

[Technical Field]

[0001] The present invention relates generally to collectors for hydrogen applications, and more particularly to fuel rails for hydrogen combustion engines. The present invention particularly provides a collector solution that, with appropriate material selection, has sufficient resistance to hydrogen embrittlement while at the same time providing low material costs and good feasibility. [Background technology]

[0002] In recent years, hydrogen has been attracting attention as a promising alternative fuel and energy carrier. For example, hydrogen combustion engines that use hydrogen as fuel for vehicle drive systems and fuel cells that use hydrogen to generate electrical energy have been developed.

[0003] However, the use of hydrogen in engines and other applications poses additional challenges at the level of the materials used in the systems. Indeed, a major risk associated with the use of hydrogen is the occurrence of hydrogen embrittlement or hydrogen embrittlement (the diffusion of hydrogen into the structure of a material), which leads to localized embrittlement of the material and the risk of cracking or brittle fracture. In particular, parameters that contribute to a specific activation energy, such as increased pressure and temperature, increase the risk of hydrogen embrittlement.

[0004] Therefore, special attention must be paid to the selection of appropriate materials for components that come into contact with hydrogen-containing media during storage, transportation, or handling. For example, collectors and fuel rails are critical components in hydrogen combustion engines. The fuel rail forms part of the hydrogen supply system and temporarily buffers nearly pure hydrogen before mixing with air to deliver the hydrogen-air mixture to the cylinders. While the pressure levels within collectors and fuel rails are not as high as those in hydrogen storage tanks, for example, the collector walls are in continuous contact with nearly pure hydrogen, so the risk of hydrogen embrittlement is still present. Therefore, the inspection requirements for such components are particularly stringent. Even if the nominal operating pressure level is as low as 3.5 bar, for example, they must be resistant to hydrogen embrittlement at the highest pressure levels that can occur within a fuel rail, such as 10 bar. Furthermore, even if hydrogen is only buffered and flows briefly within the fuel rail, the requirement for hydrogen embrittlement resistance must be guaranteed in the case of near-permanent exposure to hydrogen under steady-state conditions.

[0005] In general, the prior art teaches that certain porous materials, such as cast iron, are susceptible to hydrogen embrittlement and therefore unsuitable for use with hydrogen. For example, an online paper titled "Identifying Unique Hydrogen Fuel Cell System Demands and How to Meet Them" (October 22, 2020, https: / / www.oemoffhighway.com / engines / fuels-fluids / fuel-tanks-systems / article / 21199105 / identifying-unique-hydrogen-fuel-cell-system-demands-and-how-to-meet-them) teaches suitable materials for critical components of hydrogen fuel cells. The paper states that traditional low-grade stainless steels behave like cast iron and are therefore at high risk of hydrogen embrittlement. Furthermore, in an academic paper titled "Hydrogen embrittlement of nodular cast iron" (Patrik Sahiluoma et al., 2020), the hydrogen embrittlement sensitivity of ferritic nodular cast iron was investigated for the purpose of selecting materials for long-term underground storage containers for spent nuclear fuel. From the experimental study conducted focusing on high temperature as a hydrogen activation factor, it was concluded that the investigated cast iron is a material with high sensitivity to hydrogen embrittlement.

[0006] To mitigate the risk of hydrogen embrittlement, the prior art suggests using specific high-grade materials for hydrogen applications. For example, a paper titled "Review: Hydrogen Embrittlement of Metals and Alloys in Combustion Engines" (Maricruz Saborio Gonzalez et al., 2017) provides an overview of materials currently used for various components of internal combustion engines using hydrogen-enriched fuels. It generally states that non-porous materials should be selected to avoid hydrogen permeation. In particular, the use of certain metals, alloys, and steel grades is recommended, including aluminum, aluminum alloys, titanium steel, stainless steel, copper, bronze, Monel metals, Inconel, titanium, austenitic stainless steel, and alloy steels containing titanium oxide and aluminum oxide.

[0007] The aforementioned online paper titled "Identifying Unique Hydrogen Fuel Cell System Demands and How to Meet Them" (October 22, 2020, https: / / www.oemoffhighway.com / engines / fuels-fluids / fuel-tanks-systems / article / 21199105 / identifying-unique-hydrogen-fuel-cell-system-demands-and-how-to-meet-them) discusses suitable materials for key components of hydrogen fuel cells. The paper recommends using higher-grade stainless steels with a certain nickel content, which are more resistant to hydrogen embrittlement and more reliable.

[0008] US2018 / 0058312A1 presents a "hydrogen fuel reformer" that converts fuel into hydrogen. The converted hydrogen can be used, for example, in a fuel cell or fed to a combustion chamber. Due to its high temperature, the hydrogen discharged from the reformer must be cooled in a so-called "fuel reformer cooler." This means that the hydrogen temporarily remains in the cooler, creating a risk of hydrogen diffusion into the wall. To mitigate the risk of hydrogen embrittlement, the patent application proposes the application of a special layer or coating. Examples of such "hydrogen embrittlement prevention layers" include nitride layers, such as silicon nitride layers, or nickel-based alloy layers or coatings.

[0009] In summary, the above-mentioned prior art recommends the use of high-grade materials, such as stainless steel or alloy steel, or special coatings in combination with hydrogen. However, these methods, due to their reduced sensitivity to hydrogen embrittlement, have further drawbacks, for example, in terms of cost and feasibility. Indeed, high-grade materials, such as stainless steel or alloy steel, are expensive, which significantly impacts costs, especially in large engines, when such expensive materials must be used. Furthermore, for components requiring a double-wall structure, such as hydrogen collectors and fuel rails, it is preferable to thin the double wall to reduce the space occupied and facilitate the integration of the collector into the engine. However, because the above-mentioned high-grade materials do not allow for thin-wall casting, components such as collectors must be manufactured by welding. As a result, compact collector design and simple integration into the engine are difficult. Finally, the presence of welds inevitably creates weak points in the manufactured components, which is detrimental to robustness and durability.

[0010] The object of the present invention is to provide a solution that overcomes one or more of the drawbacks of the prior art solutions, more specifically to propose a collector for hydrogen applications that, by appropriate material selection, has sufficient resistance to hydrogen embrittlement and at the same time keeps material costs low, giving good feasibility. Summary of the Invention

[0011] According to a first aspect of the present invention, the above-mentioned object is achieved by an apparatus suitable for utilizing hydrogen, as defined in claim 1, comprising: a hydrogen preparation unit configured to supply a gaseous hydrogen-containing medium containing at least 85 volume percent hydrogen at a pressure between a lower limit and an upper limit depending on the operating conditions of the apparatus, the lower limit being less than or equal to the upper limit; a hydrogen collection unit in communication with the hydrogen preparation unit, the hydrogen collection unit comprising one or more pipe elements which together define an interior space bounded by a wall; a hydrogen processing unit in communication with the hydrogen collection unit, the hydrogen processing unit configured to process and / or use the hydrogen-containing medium; If the device, during operation, - supplying a hydrogen-containing medium from the hydrogen preparation unit to the hydrogen collection unit for flowing and / or temporarily buffering the hydrogen-containing medium in the interior space, the walls being in contact with the hydrogen-containing medium, the pressure in the interior space being equal to or lower than the upper limit value, and the temperature being equal to or lower than 100°C; - supplying a hydrogen-containing medium from the hydrogen collection unit to the hydrogen-processing unit; The upper pressure limit is 50 bar or less, Each of the one or more pipe elements is a casting made from nodular cast iron having a tensile strength of 600 MPa or less.

[0012] In other words, the present invention relates to an apparatus suitable for utilizing hydrogen. Hydrogen utilization refers to an application or system in which a hydrogen-containing medium is utilized, for example, where the hydrogen-containing medium is processed, used, transported, stored, etc. In a possible embodiment, the apparatus is a hydrogen combustion engine. Other embodiments relate to apparatus in which hydrogen is processed or handled, such as fuel cells, turbines, compressors, etc.

[0013] The apparatus includes a hydrogen preparation unit adapted to supply a gaseous hydrogen-containing medium. The hydrogen-containing medium is a gas or gas mixture containing at least 85% by volume of hydrogen. In one embodiment, the volume percentage of hydrogen present in the medium is, for example, 85%, 90%, or 95%. The preparation unit functions as a hydrogen supply device adapted to supply the hydrogen-containing medium under desired conditions. In particular, the preparation unit supplies the medium at a specific pressure. For example, the hydrogen preparation unit includes one or more supply lines and one or more pressure controllers. The pressure supplied by the preparation unit may also assume other values ​​depending on the operating state of the apparatus. For example, if one or more pressure reducing valves or pressure regulating valves are provided, the pressure is adjusted to a set value or a desired value depending on the actual power output. In an operating mode corresponding to a low power output, the hydrogen-containing medium is supplied by the preparation unit at a set pressure lower than that at the nominal power output. For example, if the pressure reducing valve fails, an overpressure valve may also be provided to release the overpressure when a certain discharge value is reached. In this way, the pressure of the hydrogen-containing medium supplied by the preparation unit is always between a lower limit and an upper limit, depending on the current operating state. That is, during operation of the device, the hydrogen preparation unit supplies the hydrogen-containing medium at a pressure at least equal to the lower limit and at most equal to the upper limit. For example, the upper limit of the pressure may occur when the pressure reaches a certain discharge value and the overpressure valve is activated. In this case, the hydrogen-containing medium is supplied by the hydrogen preparation unit at a pressure equal to the discharge value, which corresponds to the upper limit that may occur. In this way, a certain pressure level is achieved that varies between the lower limit and the upper limit, depending on the current operating state. In one embodiment, the lower limit and the upper limit may be equal to each other, so that the preparation unit always supplies the same pressure during operation.

[0014] The apparatus includes a hydrogen collection unit. The collection unit is a component through which the hydrogen-containing medium flows and / or is temporarily buffered and / or stored. The collection unit is composed of one or more pipe elements, tubes, or pipes. The pipe elements together define an interior space in which the medium is present. The interior space is delimited by an inner wall or walls that come into contact with the medium when it is present. In one embodiment, the hydrogen collection unit corresponds to a gas rail, hydrogen rail, or fuel rail used in a hydrogen combustion engine. The hydrogen collection unit is connected to a hydrogen preparation unit. That is, the preparation unit and the collection unit are in fluid communication, and the medium supplied by the preparation unit reaches the collection unit by a direct connection or via one or more intermediate supply lines or pipelines.

[0015] The apparatus includes a hydrogen processing unit adapted for processing and / or using a hydrogen-containing medium. In one embodiment, the hydrogen processing unit corresponds to a cylinder and injector combination such as would be present in a hydrogen combustion engine. The hydrogen processing unit is connected to a hydrogen collection unit. That is, the collection unit and the processing unit are in fluid communication, and the medium can flow from the collection unit to the processing unit by a direct connection or via one or more intermediate supply lines or pipelines.

[0016] During operation of the apparatus, the hydrogen collection unit is supplied with hydrogen-containing media delivered from the hydrogen preparation unit. Furthermore, the hydrogen-containing media is delivered or distributed from the hydrogen collection unit to the hydrogen processing unit. During operation of the apparatus, the hydrogen-containing media flows through a collector and / or is temporarily buffered or stored in the collector before being delivered to the processing unit. While the hydrogen-containing media is in the collection unit, the inner walls of the collection unit are in contact with the hydrogen-containing media. Within the hydrogen collection unit, the hydrogen-containing media is present at a temperature of 100°C or less. For example, the temperature is within the range of -20°C to 100°C, and the hydrogen is gaseous. Within the hydrogen collection unit, the hydrogen-containing media is present at a specific pressure. This pressure is equal to the pressure of the media delivered by the hydrogen preparation unit, and is achieved, for example, by an expansion system or a pressure controller. As a result, during operation of the apparatus, the pressure within the hydrogen collection unit is between the aforementioned lower and upper limits, depending on the operating state of the apparatus. Therefore, the pressure level within the hydrogen collection unit is at most equal to the upper limit. All pressure values ​​(bar) given are overpressure or gauge pressure values ​​measured relative to atmospheric pressure.

[0017] The upper pressure limit is less than or equal to 50 bar. For example, the upper pressure limit is equal to 50 bar, which means that during operation of the device, depending on the current operating state, the pressure in the collection unit delivered by the preparation unit is between the lower pressure limit and 50 bar, with the lower pressure limit being less than or equal to 50 bar. In another embodiment, the upper pressure limit is equal to 10 bar, which means that during operation of the device, depending on the current operating state, the pressure is between the lower pressure limit and 10 bar. For example, the lower pressure limit is equal to 0.3 bar, and the pressure in the collection unit varies within the range of 0.3 bar to 10 bar. In a possible embodiment, the upper pressure limit is less than or equal to 50 bar and greater than or equal to 5 bar. For example, the upper pressure limit is equal to 5 bar, 10 bar, 20 bar, 30 bar, 40 bar, or 50 bar.

[0018] The hydrogen collection unit consists of one or more pipe elements. Each of these pipe elements is a casting made from nodular cast iron. Cast iron is an alloy of iron and carbon, with a carbon content typically exceeding 2% by weight. Castings are obtained by pouring liquid cast iron into a mold and allowing it to solidify. The solidification rate, the presence of specific alloying elements, and the heat treatment applied determine the final material structure and, therefore, the material's final properties. Nodular cast iron is a type of cast iron in which unbound free carbon exists in the form of nodules or spheres within the solidified cast iron. In English, this is called "nodular cast iron," "ductile cast iron," "ductile iron," "spheroidal graphite iron," or "spheroidal graphite cast iron." The matrix contains ferrite and / or pearlite. Nodular cast iron refers to a group of materials whose material properties differ depending on their microstructure. For example, the matrix microstructure can be primarily ferritic or primarily pearlitic.

[0019] The hydrogen collection unit consists of one or more castings, each of which can withstand a maximum of 600 MPa or 600 N / mm 2 In one embodiment, it relates to nodular cast iron according to standard EN-GJS-400, having a tensile strength in the range of 400 MPa to 500 MPa. In another embodiment, it relates to nodular cast iron according to standard EN-GJS-500, having a tensile strength in the range of 500 MPa to 600 MPa.

[0020] This type of cast iron is a common material that is widely used and offers advantages in terms of cost and feasibility. In particular, parts can be easily cast in a variety of shapes and dimensions without the need for welding to create specific components. However, because cast iron has a porous structure, it is generally expected that when it comes into contact with hydrogen, the hydrogen will easily diffuse into the material's porous structure, making the material highly susceptible to hydrogen embrittlement. Therefore, prior art discourages the use of such porous materials in combination with hydrogen, recommending instead the use of higher-grade materials such as stainless steel or alloy steel, or the use of special coatings.

[0021] Surprisingly, however, it was discovered that cast iron, despite its porous structure, can be used in combination with hydrogen if certain pressure and temperature conditions are met and the appropriate type of cast iron is selected. In fact, it was found that cast irons from the nodular cast iron group with tensile strengths of up to 600 MPa absorbed very little hydrogen even when exposed to steady-state, nearly pure hydrogen for long periods at temperatures up to 100°C and pressures up to 50 bar. Furthermore, for this type of material, the effect on the plastic region under these hydrogen conditions was minimal, i.e., there was no loss of tensile strength and only a slight decrease in elongation.

[0022] As a result, the material can be used in hydrogen collection units where the above conditions apply. For example, nodular cast iron can be used to manufacture fuel rails in hydrogen-burning engines, where nearly pure hydrogen is typically present in the fuel rail at temperatures up to 100°C and pressures up to 10 bar. Indeed, the present invention allows the use of common materials such as cast iron to meet current stringent testing requirements for such components. Testing must ensure resistance to hydrogen embrittlement at the highest pressure levels that can occur in a fuel rail, e.g., 10 bar, even if the nominal operating pressure level is lower, e.g., 3.5 bar. Furthermore, resistance to hydrogen embrittlement must be guaranteed even in cases of near-permanent steady-state hydrogen exposure, even if in practice hydrogen buffering and flow within the fuel rail is only brief.

[0023] In summary, it has been surprisingly discovered that it is possible to use common materials despite the challenging application that involves the significant risk of hydrogen embrittlement from continuous exposure to nearly pure hydrogen and the activation energy associated with overpressure.

[0024] This has the advantage that the material costs of the hydrogen collection unit are significantly lower than if higher-grade materials were used. Furthermore, the use of cast iron also contributes to excellent feasibility. In particular, the use of cast iron allows the collector to be cast with thin walls, which allows for a compact design and easy integration of the collector into the engine, despite the double-wall requirement. Finally, welding in the collection unit can be eliminated, thereby improving robustness and durability.

[0025] Optionally, according to claim 2, the upper pressure limit is between 5 bar and 50 bar. In possible embodiments of the device, the pressure delivered by the hydrogen preparation unit in the hydrogen collection unit is, for example, between the lower limit and 5 bar, or between 10 bar and 20 bar, or between 30 bar and 40 bar, or between 50 bar and 10 bar. This means that the hydrogen-containing medium present in the collection unit is always under a certain overpressure, or in any case, operating conditions occur in which this overpressure is applied. An increase in pressure is associated with providing hydrogen with a specific activation energy, which increases the risk of hydrogen diffusing into the wall material. Despite this increased risk with increasing pressure, it was surprisingly found that nodular cast iron can be used for the collector wall.

[0026] Optionally, the upper pressure limit is at least 9 bar, and in possible embodiments the pressure in the collection unit is always 9 bar or greater.

[0027] Optionally, the upper pressure limit is equal to 10 bar, and in this embodiment of the device, depending on the operating conditions of the device, the pressure in the hydrogen collection unit is between the lower limit and 10 bar, for example, the lower limit is 0.3 bar and the nominal operating pressure level is about 3.5 bar.

[0028] Optionally, according to claim 3, the device is a hydrogen combustion engine, the gaseous hydrogen-containing medium serves as a gaseous fuel containing at least 85% by volume of hydrogen; one or more pipe elements of the hydrogen collection unit together form a fuel rail; the hydrogen processing unit comprises one or more injectors and a combustion chamber for each injector; The hydrogen combustion engine is in operation. - temporarily buffering the hydrogen-containing medium in the fuel rail at a pressure between a lower and upper limit and at a temperature not exceeding 100 ° C, depending on the operating mode of the hydrogen-burning engine; - configured to distribute a hydrogen-containing medium from a fuel rail to an injector for combustion in the combustion chamber.

[0029] A hydrogen combustion engine is an internal combustion engine that uses hydrogen or a mixture containing hydrogen as fuel. Various types are possible in various configurations. For example, it may be a dual-fuel type where the engine can run on diesel or a mixture of hydrogen and diesel, with diesel being used to ignite the hydrogen in the hydrogen mode. Another embodiment may be an engine that can run on hydrogen only and uses spark or electric ignition to initiate ignition of the hydrogen.

[0030] In hydrogen combustion engines, a fuel or gas rail is present, which functions as a hydrogen collection unit and forms part of the hydrogen supply system. Typically, hydrogen or a hydrogen-containing gas mixture is supplied from a storage tank, where the gas is stored at high pressure, e.g., 200 bar or higher. A hydrogen preparation unit, which includes, e.g., an expansion system and a pressure controller, then adjusts the hydrogen-containing fuel to the desired pressure depending on the engine's operating mode. The pressure delivered by the preparation unit varies between a lower limit and an upper limit, e.g., 50 bar or lower, depending on the operating mode. For example, during nominal engine operation, the delivery pressure is 3.5 bar, and the maximum delivery pressure may reach 10 bar, which can occur when the overpressure valve is activated.

[0031] After the preparation unit, the hydrogen-containing fuel is collected in a fuel rail, where it is temporarily buffered. Within the fuel rail, the temperature is below 100°C and the pressure is equal to the pressure supplied from the hydrogen preparation unit. While buffering and flowing within the fuel rail, the hydrogen-containing fuel contacts the inner wall of the fuel rail. The fuel rail is composed of one or more pipe elements, each of which is a casting made of nodular cast iron with a tensile strength of 600 MPa or less. The hydrogen-containing fuel is supplied from the fuel rail to the injectors, for example, via one or more supply lines. Thus, the fuel rail serves to accumulate or temporarily store the hydrogen-containing fuel and distribute it to the injectors.

[0032] Each injector is provided with a combustion chamber, e.g., a cylinder, configured to combust fuel to generate motive power. Typically, a hydrogen-containing fuel, with a high hydrogen content, is mixed with air just before the hydrogen-air mixture is inhaled through the cylinder inlet valve. The injector and combustion chamber thus form part of a hydrogen processing unit, and motive power is generated by combustion of the fuel, as is known in conventional internal combustion engines. Ignition of the fuel can be achieved in a variety of ways, including diesel injection or spark ignition.

[0033] Optionally, according to claim 4, the nodular cast iron is of the grade EN-GJS-400, EN-GJS-450, or EN-GJS-500 according to the European standard DIN EN 1563. Within the listed grades, there may be several variations, such as EN-GJS-400-15, EN-GJS-400-18-LT, EN-GJS-450-15, and EN-GJS-450-10. Other names may be used to refer to the same group of materials according to other standards and regulations. For example, EN-GJS-400 corresponds to GGG40 according to the older standard DIN 1693. Other equivalent grades of EN-GJS-400 include ISO 1083 400-15, Chinese GB1348 QT400-15, US ASTM A536 60-40-18, Japanese FCD400, Italian GS400-12, French FGS400-12, Spanish FGE42-12, Belgian FNG42-12, Australian AS1831 400-12, and Norwegian SJK-400. For EN-GJS-400 grade cast iron, the tensile strength is 400 MPa or more and 500 MPa or less. For EN-GJS-500 grade cast iron, the tensile strength is 500 MPa or more and 600 MPa or less. On the one hand, the cast iron must contain spheroidal graphite, not flake graphite, and on the other hand, the tensile strength must be sufficiently low. Generally, the grades of cast iron described are materials that neck under load before breaking.

[0034] Optionally, according to claim 5, the nodular cast iron has a tensile strength of 400 MPa to 500 MPa. For example, the cast iron complies with the grade EN-GJS-400 according to European standard DIN EN 1563.

[0035] In one embodiment, one or more castings are made from ferritic or pearlitic nodular cast iron. For example, it refers to a ferritic cast iron with a predominantly ferritic microstructure, meaning that the nodular cast iron is composed of nodular graphite and a matrix, with more ferrite present in the matrix than other structures, such as pearlite. For example, the ferrite content in the cast iron is at least 75%, meaning that the cast iron is composed of graphite, ferrite, and other components, with the volume fraction of ferrite in the overall material being at least 75%. For example, by volume, the graphite content is 12% to 13%, the ferrite content is 75% to 85%, and the pearlite content is 2% to 10%. In another embodiment, the casting process produces a pearlitic cast iron with a predominantly pearlitic matrix, thereby resulting in a cast iron with a desired tensile strength of 600 MPa or less, or in the range of 400 to 500 MPa. For example, the pearlite content in cast iron is at least 55%, which means that the cast iron is composed of graphite, pearlite, and other components, and the volume fraction of pearlite in the entire material is at least 55%. For example, the graphite content is 12% to 13% by volume, the pearlite content is 55% to 65%, and the ferrite content is 20% to 35%.

[0036] Optionally, according to claim 6, the hydrogen preparation unit is configured to supply the gaseous hydrogen-containing medium at a pressure of 3-4 bar, e.g., 3.5 bar, at nominal operating conditions of the device, e.g., the device is a hydrogen combustion engine and at nominal engine load the pressure in the gas rail is 3-4 bar, e.g., 3.5 bar.

[0037] Optionally, according to claim 7, the lower pressure limit is between 0.1 bar and 1 bar, for example 0.3 bar. The lower pressure limit is the lowest pressure value occurring in the collection unit, for example when operating at low power. In a possible embodiment of the device, the lower limit is equal to 0.3 bar, and a pressure of 0.3 bar or more is always present in the hydrogen collection unit during operation of the device.

[0038] Optionally, according to claim 8, each pipe element is double-walled, and the pipe element includes a second wall arranged around the first wall, the second wall being at least partially separated from the first wall by a cavity. Thus, the collection unit is double-walled, with the first wall in contact with the hydrogen-containing medium and the second wall separated from the first wall by an intermediate cavity. Optionally, the two walls are joined at one or more locations around the periphery or along the length, so that the two walls are not completely separated from each other, but the intermediate cavity exists over a significant portion. The double-walled construction of the collector has the advantage that even if there is a leak through the first wall, hydrogen is not released into the environment because the second wall forms an additional barrier. This contributes to improved safety. In certain applications, a double-walled construction is a requirement imposed by inspection standards.

[0039] Optionally, according to claim 9, the pipe element comprises a tube section and a branch section, each of the tube sections includes a sleeve having an end configured to be connected to an adjacent tube section, whereby the connected tube sections form a continuous tube, and the tube sections have transverse openings formed in the sleeve; Each of the branch segments includes a sleeve having an end configured to be connected to the tube segment at the location of the lateral opening, thereby forming a branch in the continuous tube. Thus, a pipe element is composed of two types of components. The first type relates to tube pieces that typically extend longitudinally and are open at one or both ends. By connecting several tube pieces, a continuous pipe is obtained. The second type relates to branch pieces, configured, for example, as elbow-shaped elements. Each tube piece has a lateral opening to which a branch piece can be connected. In this way, by assembling the tube pieces and branch pieces, a continuous pipe with one or more branches is formed. Typically, the continuous pipe is supplied with a hydrogen-containing medium delivered by a hydrogen preparation unit, which distributes the medium to the hydrogen treatment unit via the branches. For example, each branch piece forms the supply for an injector and the associated cylinder.

[0040] Optionally, according to claim 10, the hydrogen preparation unit comprises an expansion system disposed between the high-pressure line and the low-pressure line and having one or more pressure controllers, the expansion system configured to reduce the pressure of the hydrogen-containing medium supplied via the high-pressure line to a pressure between a lower limit and an upper limit in the low-pressure line, the low-pressure line being connected to the hydrogen collection unit. Thus, the hydrogen preparation unit comprises a high-pressure line, an expansion system, and a low-pressure line. In one embodiment, the high-pressure line of the device is supplied directly from the hydrogen main at a specified supply pressure. In another embodiment, the device comprises a tank connected to the high-pressure line for storing the hydrogen-containing medium at a pressure above 50 bar. Typically, the gaseous hydrogen-containing medium is stored in the tank at a high pressure, e.g., 200 bar, 350 bar, 500 bar, or 700 bar. For example, the hydrogen-containing medium is supplied from the tank via a high-pressure line, e.g., a high-pressure fuel line. The expansion system comprises one or more pressure controllers, e.g., pressure regulating valves or overpressure valves, which reduce the pressure of the medium supplied via the high-pressure line to a lower level. The resulting low-pressure level depends on the actual conditions of the apparatus and may vary, for example, within a range of 0.3 bar to 50 bar, or 0.3 bar to 10 bar. A low-pressure line connected to the expansion system allows the hydrogen-containing medium to be supplied to the hydrogen collection unit at a low-pressure level. For example, the tank, high-pressure line, expansion system, low-pressure line, and hydrogen collection unit together form a hydrogen supply system configured to supply the hydrogen-containing medium to the hydrogen processing unit at suitable conditions.

[0041] Optionally, according to claim 11, the one or more pressure controllers include one or more pressure regulating valves configured to reduce the pressure of the hydrogen-containing medium supplied via the high-pressure line to a set value between a lower limit and an upper limit. For example, there are one or more pressure regulating or reducing valves that reduce the pressure to a specific desired value or set pressure between 0.3 bar and 3.5 bar depending on the actual power output. Also, optionally, according to claim 11, the pressure controller includes one or more overpressure valves configured to reduce the pressure of the hydrogen-containing medium supplied via the high-pressure line to a discharge value equal to the upper limit. This means that if there is an overpressure valve set to a specific discharge value, and the overpressure valve is activated, for example due to a pressure regulating valve failure, the overpressure is discharged to the discharge value, and the pressure in the hydrogen collection unit also becomes this discharge value. Therefore, the discharge value set for the overpressure valve matches the aforementioned upper pressure limit.

[0042] Optionally, according to claim 12, the device is a hydrogen combustion engine with an output of at least 500 kW. It therefore relates to high-power engines suitable for example for ships, rail transport and power plants. In various embodiments, it relates to hydrogen combustion engines with, for example, 6, 8, 12 or 16 cylinders and an output in the range of 1000 kW to 3000 kW.

[0043] According to a second aspect of the present invention, the above mentioned object is achieved by the use of a hydrogen collection unit, as defined by claim 13, said use comprising: - providing a hydrogen collection unit comprising one or more pipe elements that together define a walled interior space; - providing a gaseous hydrogen-containing medium containing at least 85% by volume of hydrogen; flowing and / or temporarily buffering and / or storing a hydrogen-containing medium in the interior space at a temperature of -100°C or less and at a pressure between a lower limit and an upper limit, wherein the wall is in contact with the hydrogen-containing medium and the lower limit is less than or equal to the upper limit; The upper pressure limit is 50 bar or less, Each of the one or more pipe elements is a casting made from nodular cast iron having a tensile strength of 600 MPa or less.

[0044] It therefore relates to the use of a hydrogen collection unit in which, during use, a gaseous hydrogen-containing medium containing at least 85% hydrogen by volume is present. The medium is buffered or stored in a collector and / or the medium flows through the collector. In one embodiment, the hydrogen collection unit is a fuel rail or gas rail of an internal combustion engine. In another embodiment, the hydrogen collection unit is a storage tank in which the hydrogen-containing medium is stored. During use of the hydrogen collection unit, the pressure of the gaseous hydrogen-containing medium is between a lower limit and an upper limit. In one embodiment, the pressure in the collector varies depending on the specific operating conditions. In another embodiment, the lower limit is equal to the upper limit, and the pressure remains the same while the medium is in the collector. The upper limit of the pressure in the hydrogen collection unit is a maximum of 50 bar. In one embodiment, the upper limit of the pressure is between 5 bar and 50 bar, for example, 10 bar. The hydrogen collection unit is composed of one or more pipe elements, which together define an interior space bounded by a wall. The pipe elements may have two open ends, or one open end and one closed end, or both ends may be closed.

[0045] Optionally, according to claim 14, the use comprises: - providing a hydrogen preparation unit in communication with the hydrogen collection unit; - providing a hydrogen processing unit in communication with the hydrogen preparation unit; - supplying, by means of a hydrogen preparation unit, a hydrogen-containing medium at a pressure that varies between a lower limit and an upper limit depending on the operating conditions of the device; - supplying a hydrogen-containing medium from a hydrogen preparation unit to a hydrogen collection unit, wherein the hydrogen-containing medium flows into and / or is temporarily buffered in the interior space; - supplying a hydrogen-containing medium from a hydrogen collection unit to a hydrogen processing unit; - treating and / or using the hydrogen-containing medium in a hydrogen processing unit. Thus, the hydrogen collection unit is used in a hydrogen-utilizing device, which device is defined according to the first aspect of the present invention.

[0046] Optionally, according to claim 15, the hydrogen collection unit is a fuel rail used in a hydrogen combustion engine, the hydrogen-containing medium serves as a fuel containing at least 85% by volume of hydrogen; the hydrogen processing unit comprises one or more injectors and a combustion chamber for each injector; The use in question is: - temporarily buffering the hydrogen-containing medium in the fuel rail at a temperature below 100°C and at a pressure that varies between lower and upper limits depending on the operating mode of the hydrogen-burning engine; - distributing a hydrogen-containing medium from a fuel rail to an injector; - combusting the hydrogen-containing medium in the combustion chamber. Thus, the hydrogen collection unit is a fuel rail or gas rail used in a hydrogen combustion engine. [Brief explanation of the drawings]

[0047] [Figure 1] FIG. 1 is a schematic diagram of an apparatus suitable for utilizing hydrogen, according to one embodiment of the present invention. [Figure 2] FIG. 2 is a three-dimensional view showing a hydrogen combustion engine according to one embodiment of the present invention. [Figure 3] FIG. 3 is a three-dimensional view of a hydrogen combustion engine according to one embodiment of the present invention, with the exhaust banks removed to reveal the internal components. [Figure 4] FIG. 4 is a front view showing a hydrogen combustion engine according to one embodiment of the present invention. [Figure 5] FIG. 5 is a rear view showing a hydrogen combustion engine according to one embodiment of the present invention. [Figure 6] FIG. 6 is a three-dimensional view of a pipe piece according to one embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view of a tube piece according to one embodiment of the present invention. [Figure 8] FIG. 8 is a three-dimensional view of a branch piece according to one embodiment of the present invention. [Figure 9] FIG. 9 is a cross-sectional view of a branch piece according to one embodiment of the present invention. [Figure 10] FIG. 10 is a three-dimensional view of a branch piece connected to a tube piece according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0048] FIG. 1 shows a schematic diagram of an apparatus 100 suitable for hydrogen utilization according to one embodiment of the present invention. For example, the apparatus 100 may be a hydrogen combustion engine 200, as further shown in FIGS. 2-5. The apparatus 100 includes a hydrogen preparation unit 102, a hydrogen collection unit 101, and a hydrogen processing unit 103. The hydrogen preparation unit 102 includes a high-pressure line 109, an expansion system 106, and a low-pressure line 110. The high-pressure line 109 is connected to a tank 104. The low-pressure line 110 is connected to the hydrogen collection unit 101. A gaseous hydrogen-containing medium containing at least 85 volume percent hydrogen is stored in the tank 104. Storage in the tank is typically at high pressure, such as 200 bar, 350 bar, 500 bar, or 700 bar. The expansion system 106 includes a pressure controller, which allows the pressure of the hydrogen-containing medium to be reduced to a lower value in the low-pressure line 110. The pressure reached in the low-pressure line 110 depends on the operating state of the device 100 and always lies between a lower limit and an upper limit, the upper limit being less than or equal to 50 bar, for example 10 bar. The hydrogen-containing medium is fed at the achieved low pressure via the low-pressure line 110 to the hydrogen collection unit 101.

[0049] In the collection unit 101, the medium is temporarily buffered and distributed to the hydrogen processing unit 103. The tank 104, the high-pressure line 109, the expansion system 106, the low-pressure line 110, and the hydrogen collection unit 101 together form a hydrogen supply system 105 configured to supply a suitably conditioned hydrogen-containing medium to the hydrogen processing unit 103. The hydrogen-containing medium is processed or used in the hydrogen processing unit 103. In the illustrated embodiment, the hydrogen-containing medium is used in a cylinder 111 of an internal combustion engine. The hydrogen-containing medium is supplied to the engine cylinder 111 via a gas injector 108. Before entering the cylinder 111, the hydrogen-containing medium is mixed with air 107.

[0050] 2 to 5 show a hydrogen combustion engine 200. The embodiment shown relates to a 12-cylinder engine in a V-configuration with a maximum power output of 2000 kW, typically used to propel large ships and trains.

[0051] The hydrogen combustion engine 200 includes a fuel rail 201 or gas rail 201, which corresponds to the hydrogen collection unit 101 in FIG. 1. Gaseous hydrogen-containing fuel is delivered to the gas rail 201 from a low-pressure fuel line 202. The gas fuel contains at least 85% hydrogen by volume, and in possible embodiments, 90% or 95% hydrogen by volume, making it nearly pure hydrogen. The low-pressure fuel line 202 forms part of a hydrogen preparation unit, not shown in FIGS. 2-5. To this end, the hydrogen preparation unit 102 includes a high-pressure fuel line 109 and a pressure controller 106, as in FIG. 1. Also as in FIG. 1, the fuel is stored at high pressure in a tank 104, not shown in FIGS. 2-5.

[0052] The pressure controller 106 regulates the hydrogen-containing fuel to a low pressure level depending on the operating state of the hydrogen engine 200. In the illustrated embodiment, the pressure controller 106 includes at least one pressure regulating or reducing valve. These valves allow a desired or set pressure to be achieved depending on the actual engine power. This desired pressure level is approximately 3.5 bar during nominal operation and 0.3 bar at low power. The preparation unit is also provided with at least one overpressure valve, which is activated if the pressure does not decrease as desired, for example, due to a failure of the pressure regulating valve. The overpressure valve is set to a discharge value of 10 bar, so that the maximum pressure value that can occur after the pressure controller 106 is 10 bar. As a result, the pressure of the gas fuel supplied via the low-pressure fuel line 202 is always between 0.3 bar and 10 bar. This is also the pressure in the fuel rail 201. The temperature in the fuel rail 201 is usually not much higher than ambient temperature, at most 100°C.

[0053] 3, the exhaust bank 205 has been omitted for clarity. As can be seen in FIG. 3, the fuel rail 201 is made up of a number of pipe segments 300, 301. There are two different types of pipe segments: a tube segment 300 and a branch segment 301. The tube segments 300 connected to each other form a continuous pipe. One end of this continuous pipe is connected to the low-pressure fuel line 202, and the other end is closed by an end plate 303. Furthermore, each tube segment 300 has a branch segment 301 fixed thereto for supplying hydrogen to one of the cylinders.

[0054] The pipe elements 300, 301 together define an internal space in which the gaseous fuel flows and is temporarily buffered. This internal space is bounded by a wall, the inner surface of which is in contact with the hydrogen-containing fuel. As a result, the inner wall of the fuel rail 201 is in continuous contact with nearly pure hydrogen, and unless a hydrogen-compatible material is used for the wall, there is a significant risk of hydrogen diffusion into the wall material. This risk is further amplified by the pressure present within the fuel rail 201, and testing is required to ensure resistance to hydrogen embrittlement at the highest pressure level that can occur (10 bar in this case).

[0055] Hydrogen is supplied from a gas rail 201 to twelve injectors, one for each cylinder, as indicated by reference numeral 203 in Figures 2 and 3. Before entering the cylinders 203, the hydrogen is mixed with air supplied via line 204. This is further illustrated in the front view of Figure 4, where the hydrogen flow is indicated schematically by reference numeral 400 and the air flow by reference numeral 401. The hydrogen-air mixture 402 is drawn into the cylinders, compressed, and ignited. In various embodiments, ignition is accomplished in different ways. In a dual-fuel engine, ignition is accomplished by injection of a pilot fuel, e.g., 15% diesel fuel. In a spark-ignition engine, spark ignition is utilized. In both embodiments, the conditions in the fuel rail are similar: nearly pure hydrogen is held there at a pressure of up to 10 bar. After ignition, the hydrogen in the cylinders burns, generating the driving stroke. Exhaust gases then exit the cylinders via line 302, as shown in Figure 3.

[0056] 6 and 7 show a tube segment 300. The tube segment 300 is double-walled, with a first wall 701 defining an interior space 600. The inner surface of the first wall 701 is in contact with the hydrogen-containing fuel. A second wall 702 is disposed around the first wall 701, defining a cavity 703 between the two walls 701, 702. The tube segment 300 further includes a sleeve 603 having open ends 601, 602. The ends 601, 602 are configured to be connected to another tube segment 300. Cover plates 303 may be disposed on the ends 601, 602. The sleeve 603 is provided with a side opening 604 and a side opening 700.

[0057] 8 and 9 show branch piece 301 configured as an elbow. Branch piece 301 is double-walled, with a first wall 801 defining an interior space 800. The inner surface of first wall 801 is in contact with the hydrogen-containing fuel. A second wall 802 is disposed around first wall 801, with a cavity 803 disposed between the two walls 801, 802. The two walls 811, 812 are joined to each other at two locations 805, 806. Branch piece 301 further includes a sleeve 813 having open ends 811, 812. End 811 is configured to be connected to tube piece 300.

[0058] As shown in Figure 3, several connected tube sections 300 form a continuous tube into which hydrogen is supplied. Figure 10 shows how a branch piece 301 is connected to the tube section 300 at the side opening 604. In this way, hydrogen can be supplied from the tube section to the cylinders of a first line of six cylinders. Similarly, the branch piece 301 can be connected to the other side opening 700 to supply hydrogen to the cylinders of a second line of six cylinders.

[0059] The double-walled construction of the pipe elements 300, 301 is necessary to meet safety requirements. Meanwhile, a compact design of the fuel rail 201 is also necessary to allow for easy integration into the engine 200. In particular, the distance between the two cylinder heads, determined by the engine's V-angle, is a constraint, and the intake / exhaust collectors must also be located in this space between the two cylinder heads between the two banks. To enable this compact design of the gas rail 201, despite its double wall, the walls of the pipe elements 300, 301 must be sufficiently thin. In the illustrated embodiment, this is achieved by thin-wall casting, with each of the tube pieces 300 and branch pieces 301 being made from cast iron. Considering the risk of hydrogen diffusion into the walls of the gas rail 201, a material must also be selected that offers sufficient resistance to hydrogen embrittlement under the prevailing pressure and temperature conditions. Therefore, in the present invention, nodular cast iron with a tensile strength of up to 600 MPa is selected.

[0060] In particular, in the embodiment shown, each of the pipe elements 300, 301 is made of nodular cast iron conforming to the grade EN-GJS-400-15, the typical properties of which are as follows: Yield point: 250 MPa or more, tensile strength: 400 MPa or more, elongation: 15% or more. A typical stress-strain curve measured in air shows necking before fracture. ·Density: 7.3g / cm 3 , Brinell hardness: 130 to 180. Typical chemical composition: C: 2.5-3.8%, Si: 0.5-2.5%, Mn: 0.2-0.5%, P: ≦0.08%, S: ≦0.02%.

[0061] The inventors have carried out experimental studies to arrive at the surprising discovery that the cast iron described above is sufficiently resistant to hydrogen embrittlement and therefore can be used in fuel rails for hydrogen combustion engines. This experimental study concerns a first and a second series of tests.

[0062] In the first series of tests, various materials were investigated for their compatibility with hydrogen. In particular, the following grades were investigated: EN-GJS-400-15, EN-GJS-700, Mk11C, and RVS316. The last grade is a stainless steel with an austenitic microstructure and was included in the study as a control material compatible with hydrogen environments. The first three grades of material were cast irons, and microstructural analysis was performed using 5 x 8 x 50 mm specimens. The microstructures of the investigated cast irons were as follows: EN-GJS-400-15: Spheroidal graphite (13%), ferrite (77%), pearlite (10%). This is therefore a predominantly ferritic nodular cast iron. Most of the graphite particles are between 60 μm and 120 μm in size, with smaller particles between 15 μm and 30 μm. The density is 73 particles / mm 2 Contains spherical particles, 126 particles / mm 2 The overall grain density of Ti-rich inclusions was observed in this material. EN-GJS-700: Spheroidal graphite (13%), ferrite (1%), pearlite (86%). This corresponds to a predominantly pearlitic nodular cast iron with a tensile strength of at least 700 MPa. Most of the graphite particles were between 15 μm and 30 μm in size, with only a few smaller particles. The density was 150 particles / mm 2 Contains spherical particles, 171 particles / mm 2 The overall particle density was confirmed to be 1.06. The inclusions were mainly Mg oxides. Mk11C: flake graphite (12%), pearlite (88%). This corresponds to flake graphite cast iron. 34% of the graphite particles are between 30µm and 60µm in size, and 33% are between 60µm and 120µm in size. Smaller graphite particles are also found. The density is 1026 particles / mm 2 The overall graphite particle density was confirmed. The presence of MnS was also detected along with Mo-rich particles.

[0063] For each material grade, multiple specimens were exposed to hydrogen at room temperature and 10 bar pressure for 1,000 hours. The 10 bar pressure level was chosen because it is the design pressure of the proposed hydrogen combustion engine, i.e., the maximum pressure that can occur in the gas rail. The specimens were not subjected to load during hydrogen exposure. For each material grade, multiple specimens were also prepared that were not exposed to hydrogen.

[0064] After exposure to hydrogen, a first evaluation test was carried out to determine which specimens had taken up hydrogen. For this purpose, measurements were carried out on two specimens of 5 x 8 x 50 mm for each material grade: one specimen was exposed to hydrogen and the other was not. The hydrogen concentration was measured based on a melt extract in a G8 GALILEO (Bruker).

[0065] The measurement results are summarized in the following table (Table 1). Material EN-GJS-700 (pearlitic nodular cast iron, tensile strength over 700 MPa) and material Mk11C (flaky graphite cast iron) showed clear hydrogen absorption, with both materials absorbing approximately 0.3 ppm of hydrogen. This sensitivity to hydrogen absorption is consistent with prior art teachings that cast irons are generally prone to hydrogen absorption. For RVS316 (stainless steel), no significant hydrogen absorption was observed. The differences measured between exposed and unexposed specimens were within the standard deviation of the measurements. This result is also consistent with expectations, as stainless steels are generally considered to exhibit good resistance to hydrogen absorption. However, surprisingly, material EN-GJS-400-15 (ferritic nodular cast iron, tensile strength over 400 MPa) was also found to absorb almost no hydrogen, despite being a porous cast iron. TIFF2026500655000002.tif94170

[0066] Further evaluation of the first series of tests involved carrying out tensile tests on specimens exposed to hydrogen and comparing the results with identical tensile tests carried out on specimens not exposed to hydrogen. Here, round bar tensile specimens were used and the tests were carried out according to standard NBN EN ISO 6892-1 Method B. In this case, the hydrogen-exposed RVS316 (stainless steel) specimens behaved similarly to specimens that were not exposed to hydrogen. Therefore, RVS316 appears to be less susceptible to hydrogen embrittlement, which is as expected. When specimens of EN-GJS-700 (pearlitic nodular cast iron, tensile strength over 700 MPa) and Mk11C (flake graphite cast iron) were exposed to hydrogen, their mechanical properties were significantly reduced compared to specimens of the same material that were not exposed to hydrogen. The hydrogen-exposed specimens exhibited premature fracture accompanied by brittle fracture. For example, the hydrogen-exposed Mk11C specimens exhibited Rm values ​​of 271 MPa and elongation to failure of 0.16%, while the unexposed specimens exhibited Rm values ​​of 291 MPa and elongation to failure of 0.29%. For example, when EN-GJS-700 specimens were exposed to hydrogen, Rm values ​​of 617 MPa and elongation to failure of 1.5% were measured, while the unexposed specimens exhibited Rm values ​​of 696 MPa and elongation to failure of 3.1%, respectively. Therefore, both cast irons were clearly susceptible to hydrogen embrittlement, which is consistent with the general teachings of the prior art regarding the combination of cast iron and hydrogen. Finally, specimens of the material EN-GJS-400-15 (ferritic nodular cast iron, tensile strength above 400 MPa) exposed to hydrogen showed no degradation of mechanical properties compared to specimens of the same material not exposed to hydrogen. Premature fracture due to hydrogen exposure did not occur, and specimens after maximum load showed ductile fracture. Contrary to what would be expected based on the teachings of the prior art, this cast iron does not appear to be susceptible to hydrogen embrittlement under the test conditions described.

[0067] In the second series of tests, we first further verified the hydrogen compatibility of the EN-GJS-400-15 material. For this purpose, we used the EN ISO 11114-4 Method A fracture test, more specifically the "disk burst test." This test allows us to calculate the "embrittlement index (EI)." An EI value of 2 or less indicates the material's suitability for compressed hydrogen cylinders. The tests were performed using helium and hydrogen as test gases, with the applied pressure increasing at 10 bar / min. The test specimens were 58 mm diameter, 2 mm thick disks. The burst pressure under helium was 605 bar (pR_He) and under hydrogen was 485 bar (pR_H2). After applying the thickness correction factor specified in standard EN ISO 11114-4, p'R_He and p'R_H2 were calculated, and from these the EI index value was calculated (EI = p'R_He / p'R_H2). The measured EI value of the EN-GJS-400-15 specimen was 1.2, which indicates that the material is compatible with hydrogen. The disk rupture test was also repeated on a specimen of the EN-GJS-400-15 material, applying a pressure increasing at 1.5 bar / min. Similar results were obtained, with EI values ​​ranging from 1.2 to 1.3.

[0068] In the above tests, various specimens were used with the material EN-GJS-400-15, which has a predominantly ferritic structure, e.g., 77% or 82% ferrite. Nodular cast iron with the same tensile strength level of 400 MPa to 500 MPa can be produced with an appropriate casting process to obtain a predominantly pearlitic structure. Similar tests were also performed on the material EN-GJS-400, which has a predominantly pearlitic structure of 12% graphite, 61% pearlite, and 27% ferrite. Based on the tests performed, this material was also found to be hydrogen compatible.

[0069] Finally, a third series of tests was conducted to further investigate the effect of pressure on the onset of hydrogen embrittlement. Tensile tests, more specifically "slow strain rate tests" (SSRT), were conducted in air, 10 bar, and 50 bar hydrogen atmospheres. SSRT tests were performed at a constant deformation rate of ds / dt = 0.018 mm / min (corresponding to an elongation of 0.036% / min). Multiple specimens were tested. All were made of EN-GJS-400-15 grade cast iron. The specimens had graphite contents ranging from 12% to 13%, ferrite contents ranging from 83% to 85%, and pearlite contents ranging from 2% to 5%.

[0070] During the SSRT test, stress-elongation curves were measured and mechanical properties were measured after the test was completed. The results are summarized in the table below (Table 2). TIFF2026500655000003.tif85170

[0071] Test (1), performed in air, yielded the highest measured elongation at break (Epsilon_break) and necking, demonstrating the material's high plasticity. Test (2), also performed in air, yielded a lower elongation at break compared to test (1), confirming the variability of material properties observed in as-cast materials. Tests (3), (4), and (5) were performed in hydrogen at 10 bar pressure. In all cases, the measured tensile strength (Rm, ultimate tensile strength) was greater than 420 MPa, and the elongation at break exceeded 10%. Therefore, this material is not considered to exhibit embrittlement behavior in a 10 bar hydrogen atmosphere. Test (6) was performed in hydrogen at 50 bar pressure. The measured elongation at break and necking at break were lower than those measured in the 10 bar test. This indicates that hydrogen embrittlement increases with increasing hydrogen pressure, but not to the extent that full embrittlement behavior is observed in test (6). Therefore, a pressure value of 50 bar can be considered as the upper limit of the allowable pressure for the EN-GJS-400-15 material in combination with hydrogen. This is also confirmed by the shape of the measured tensile-elongation curve in test (6), which shows that in the plastic part, no completely continuous curve was measured, but the curve shows a discontinuous course at three points, with a sudden decrease in tension at approximately the same elongation before fracture.

[0072] Finally, the fracture surfaces of the various specimens were examined by fractography. Tests at 50 bar showed a larger brittle fracture zone on the fracture surface than tests at 10 bar, while tests in air showed no brittle fracture zone on the fracture surface.

[0073] Based on a series of tests conducted, the inventors have come to realize that flake graphite cast iron, as well as nodular cast iron with high tensile strength, i.e., tensile strength exceeding 600 MPa, is unsuitable for use with hydrogen. Generally, these unsuitable cast irons are materials that do not neck before fracture unless exposed to hydrogen in air. In contrast, nodular cast irons with sufficiently low tensile strength, i.e., up to 600 MPa, are considered suitable for use with hydrogen under the conditions found in hydrogen collectors. For tensile strengths not exceeding 600 MPa, both ferritic and pearlitic nodular cast irons are considered suitable. These nodular cast irons have a porous structure and are considered suitable for use with hydrogen, despite the general advice in the prior art not to use cast iron with hydrogen. One possible explanation for the suitability of these nodular cast irons with sufficiently low tensile strength is that hydrogen collects in the cavities around carbides, significantly reducing the ductility of the material and causing more brittle fracture. However, in nodular cast irons with sufficiently low tensile strength, the matrix around the carbides can compensate for the decrease in ductility caused by hydrogen without significantly reducing the tensile strength, thereby effectively avoiding the occurrence of brittle fracture.

[0074] While the present invention has been described based on specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the details of the illustrative embodiments set forth above, and that various modifications and adjustments can be made without departing from the scope of the present invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, and the field of application of the present invention is defined not by the foregoing description but by the appended claims, and all changes that come within the meaning and scope of the claims are therefore incorporated herein. In other words, this is considered to include all modifications, variations, or equivalents that fall within the field of application of the underlying basic principles and whose essential attributes are claimed in this patent application. Furthermore, readers of this patent application will understand that the words "comprising" or "comprise" do not exclude other elements or steps, and that the word "a" does not exclude a plurality. Any references in the claims should not be construed as limiting the scope of the claims to which they apply. When used in the specification or claims, terms such as "first," "second," "third," "a," "b," "c," and the like are used to distinguish between similar elements or steps and do not necessarily denote a sequential or chronological order. Similarly, terms such as "top," "bottom," "above," and "below" are used for descriptive purposes and do not necessarily denote relative locations. It is to be understood that such terms may be interchanged in appropriate circumstances, and that embodiments of the invention may function in accordance with the invention in other orders or directions than those described or illustrated.

Claims

1. An apparatus (100, 200) suitable for utilizing hydrogen, said apparatus (100, 200) comprising: a hydrogen preparation unit (102) configured to provide a gaseous hydrogen-containing medium containing at least 85 volume percent hydrogen at a pressure between a lower limit and an upper limit depending on the operating conditions of the device (100, 200), said lower limit being equal to or less than said upper limit; a hydrogen collection unit (101, 201) in communication with said hydrogen preparation unit (102), said hydrogen collection unit comprising one or more pipe elements (300, 301) which together define an interior space bounded by a wall; a hydrogen treatment unit (103) in communication with said hydrogen collection unit (101, 201), the hydrogen treatment unit (103) being adapted to treat and / or use said hydrogen-containing medium, The device (100, 200), during operation, - supplying the hydrogen-containing medium from the hydrogen preparation unit (102) to the hydrogen collection unit (101, 201) for flowing and / or temporarily buffering the hydrogen-containing medium in the interior space, the walls being in contact with the hydrogen-containing medium, the pressure in the interior space being below the upper limit and the temperature being below 100°C; - supplying said hydrogen-containing medium from said hydrogen collection unit (101, 201) to said hydrogen treatment unit (103), The upper limit of the pressure is 50 bar or less, 10. The apparatus according to claim 9, wherein each of said one or more pipe elements (300, 301) is a casting made from nodular cast iron having a tensile strength of 600 MPa or less.

2. 2. The device (100, 200) of claim 1, The upper pressure limit is between 5 and 50 bar, for example equal to 10 bar.

3. 10. The device (200) according to any one of the preceding claims, the device is a hydrogen combustion engine (200); - the gaseous hydrogen-containing medium functions as a gaseous fuel containing at least 85% by volume of hydrogen; - one or more pipe elements (300, 301) of said hydrogen collection unit (101) together form a fuel rail (201); - said hydrogen treatment unit (103) comprises one or more injectors and a combustion chamber (203) for each injector; The hydrogen combustion engine (200), during operation, - temporarily buffering a hydrogen-containing medium in the fuel rail (201) at a pressure between said lower and upper limits and at a temperature of 100°C or less depending on the operating mode of said hydrogen combustion engine (200); - An apparatus configured to distribute said hydrogen-containing medium from said fuel rail (201) to said injectors for combustion in said combustion chamber (203).

4. A device (100, 200) according to any one of the preceding claims, The device is characterized in that the nodular cast iron complies with the grade EN-GJS-400 or EN-GJS-450 or EN-GJS-500 according to European standard DIN EN 1563, preferably with the grade EN-GJS-400 according to European standard DIN EN 1563.

5. A device (100, 200) according to any one of the preceding claims, The apparatus is characterized in that the nodular cast iron has a tensile strength of 400 MPa to 500 MPa.

6. A device (100, 200) according to any one of the preceding claims, the hydrogen preparation unit (102) is configured to supply the gaseous hydrogen-containing medium at a pressure of 3-4 bar, e.g., 3.5 bar, under nominal operating conditions of the apparatus (100, 200).

7. A device (100, 200) according to any one of the preceding claims, The device, characterized in that the lower limit of the pressure is between 0.1 bar and 1 bar, for example 0.3 bar.

8. A device (100, 200) according to any one of the preceding claims, 1. The device according to claim 1 , wherein each of said pipe elements (300, 301) is made of a double wall, said pipe elements (300, 301) comprising a second wall (702, 802) arranged around said wall (701, 801), said second wall (702, 802) being at least partially separated from said wall (701, 801) by a cavity (703, 803).

9. A device (100, 200) according to any one of the preceding claims, The pipe element (300, 301) comprises a pipe piece (300) and a branch piece (301), - each of said tube pieces (300) comprises a sleeve (603) having ends (601, 602) adapted to be connected to adjacent tube pieces (300), whereby the connected tube pieces (300) form a continuous tube, said tube pieces (300) having transverse openings (604) formed in said sleeve (603); - each of the branch pieces (301) comprises a sleeve (813) having an end (811) configured to be connected to a piece of pipe (300) at the location of the transverse opening (604), thereby forming a branch in the continuous pipe.

10. A device (100, 200) according to any one of the preceding claims, the hydrogen preparation unit (102) comprises an expansion system (106) arranged between a high-pressure line (109) and a low-pressure line (110) and having one or more pressure controllers, the expansion system (106) being configured to reduce the pressure of the hydrogen-containing medium supplied via the high-pressure line (109) to a pressure in the low-pressure line (110) between the lower limit value and the upper limit value, and the low-pressure line (110) is connected to the hydrogen collection unit (101, 201).

11. 11. The device (100, 200) according to claim 10, the one or more pressure controllers include one or more pressure regulating valves configured to reduce the pressure to a set value between the lower limit and the upper limit, and / or one or more overpressure valves configured to reduce the pressure to a discharge value equal to the upper limit.

12. 4. The apparatus (200) of claim 3, The apparatus is characterized in that the hydrogen combustion engine (200) has an output of at least 500 kW.

13. Use of a hydrogen collection unit (101, 201), - providing a hydrogen collection unit (101, 201) comprising one or more pipe elements (300, 301) which together define a walled interior space; - providing a gaseous hydrogen-containing medium containing at least 85% by volume of hydrogen; - flowing and / or temporarily buffering said hydrogen-containing medium and / or storing said hydrogen-containing medium in said interior space at a temperature of up to 100°C and at a pressure between a lower limit and an upper limit, wherein said wall is in contact with said hydrogen-containing medium and said lower limit is less than or equal to said upper limit, The upper limit of the pressure is 50 bar or less, 10. The use of claim 9, wherein each of said one or more pipe elements (300, 301) is a casting made from nodular cast iron having a tensile strength of 600 MPa or less.

14. In the use according to claim 13, - providing a hydrogen preparation unit (102) in communication with said hydrogen collection unit (101, 201); - providing a hydrogen treatment unit (103) in communication with said hydrogen preparation unit (102); - supplying, by said hydrogen preparation unit (102), said hydrogen-containing medium at a pressure that varies between said lower and upper limits depending on the operating conditions of said device (100, 200); - supplying said hydrogen-containing medium to said hydrogen collection unit (101, 201) from said hydrogen preparation unit (102), said hydrogen-containing medium flowing into said interior space and / or being temporarily buffered in said interior space; - supplying said hydrogen-containing medium from said hydrogen collection unit (101, 201) to said hydrogen treatment unit (103); - treating and / or using said hydrogen-containing medium in said hydrogen treatment unit (103).

15. 15. The use according to claim 14, the hydrogen collection unit (101) is a fuel rail (201) used in a hydrogen combustion engine (200); - the hydrogen-containing medium functions as a fuel containing at least 85% by volume of hydrogen; - said hydrogen treatment unit (103) comprises one or more injectors and a combustion chamber (203) for each injector; The use in question is: - temporarily buffering said hydrogen-containing medium in said fuel rail (201) at a temperature below 100°C and at a pressure that varies between said lower and upper limits depending on the operating mode of said hydrogen combustion engine (200); - distributing said hydrogen-containing medium from said fuel rail (201) to said injectors; - combusting said hydrogen-containing medium in said combustion chamber (203).

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