WO2008095515A1

WO2008095515A1 - Container for the storage of compositions comprising hydrogen

Info

Publication number: WO2008095515A1
Application number: PCT/EP2007/002375
Authority: WO
Inventors: Klaus Nohl
Original assignee: Hydrodivide Ag
Priority date: 2007-02-05
Filing date: 2007-03-17
Publication date: 2008-08-14
Also published as: DE102007006416A1

Abstract

The invention relates to a container for the storage of compositions comprising hydrogen, the interior of which is coated with at least one hydride-forming metal having a hydrogen desorption temperature of more than 60°C. The container may be labeled as hydrogen-proof, and is particularly suitable for the storage of gases comprising hydrogen, metal hydrides, nanotubes charged with hydrogen, porous nanocubes charged with hydrogen, and metal-doped polymers charged with hydrogen.

Description

Container for storage of hydrogen-containing compositions

The present invention relates to a container for storing hydrogen-containing compositions, in particular hydrogen.

Hydrogen-containing compositions, in particular hydrogen-containing gases, are usually stored in so-called pressure gas containers of unalloyed steel or aluminum. These usually consist of a cylindrical part which is closed by two outwardly curved bottoms or flat bottoms, wherein on one side usually a screwed valve is provided.

Pressure vessels typically have one or more safety-related accessories to protect the vessel from inadmissible operating conditions (exceeding the design pressure or temperature). Equipment with safety function are u. a .: o safety valve (pressure relief in the environment or in a

Collecting system), o rupture disc (pressure relief usually at large dissipated

Mass flow or use at low response pressures), o Pressure limiter (switching off the pressure generator, for example compressor,

Heating), o Temperature limiter (switching off the heating source), o Vacuum breaker (protection against external overpressure), o Water sprinklers (external heat supply for cooling, for example in case of fire).

Due to their safety risk, pressure vessels are subject to various legal regulations.

If a pressure vessel is severely damaged in its strength and this leads to a wall-penetrating crack during operation, then significant stress spikes occur at these fractures, leading to further tearing of the container to lead. This tearing may cause the container to be ejected rocket-like by the escaping gas pulse several tens to hundreds of meters. Furthermore, there are considerable hazards due to thrown-out debris. When large containers burst, pressure peaks occur when installed in rooms, which can lead to considerable building damage.

Other hazards that may need to be considered: o throwing away unsecured quick-release couplings that can be opened under pressure, o releasing toxic gases, o escaping hot gases, o bursting due to external overpressure, if this operating case was not taken into account in the design (implosion o) formation of an explosive atmosphere, o rapid pressure increase in exothermic reactions, o low-temperature embrittlement at impermissibly low temperatures and o crushing by moving parts.

Due to these dangers, damage to the pressure vessels, such as external corrosion, must be avoided as far as possible. The corrosion of the outer wall can be triggered by an aggressive atmosphere, such. As seawater, halogenated detergents or by acid-forming gases. Containers whose walls are colder than the ambient temperature are particularly vulnerable to external corrosion. Especially with black containers, care must be taken to ensure adequate corrosion protection and trouble-free execution of the vapor barrier.

Furthermore, the following causes can lead to bursting of the pressure vessel: o manufacturing errors, such. B. defective execution of welded joints; o Material defects or use of unsuitable or incorrect materials; o poor execution of repairs; o extensive rusting of the container with the result of tearing the

Container wall under operating pressure; o special forms of corrosion that significantly affect the material properties, such. B. stress corrosion cracking, aging of the material at high temperatures, low temperature embrittlement; o external mechanical trauma, which the pressure vessel does not withstand, z. B. starting a container by a vehicle, o thermal influences such. B. an inadmissible heating (fire,

Fire damage) of the container, which reduces the strength of the material; o errors in pressure control and failure to respond to the safety valve or pressure relief valve; o Vacuum damage.

Due to its small molecular diameter, the storage of hydrogen (H ₂ ) presents a particularly great challenge. The hydrogen molecules usually penetrate into the structure of the metallic material, where they attach themselves to defects of the lattice. The associated change in the metal structure leads to internal stresses and embrittlement of the metal. In mechanical stress, defects and dislocations are formed, which are known to be "traps" for the hydrogen. This eventually causes cracks that spread from the inside to the outside. As a result, hydrogen storage and other metallic or non-metallic articles that are exposed to hydrogen for a long time become brittle and release diffused hydrogen to the environment.

The present invention is therefore based on the object of demonstrating possibilities for better storage of hydrogen-containing compositions, especially of hydrogen. In particular, the loss to the environment should be prevented or at least minimized and the safety during storage should be further increased. At the same time should be as cost-effective Solutions are sought and particularly suitable application areas are shown.

These and other objects, which can be derived directly from the above description, are achieved by the provision of a container having all the features of the present patent claim 1. Particularly expedient embodiments of the container are provided in the dependent claims. The further claims describe particularly expedient methods for producing the container and particularly favorable fields of application.

The solution of the present invention allows a comparatively simple and cost-effective storage of hydrogen-containing compositions, in particular of hydrogen-containing gases and of hydrogen. By preventing the embrittlement of the container, the risk of cracking and the loss of stored hydrogen-containing gas, in particular hydrogen, prevented by the wall or at least significantly reduced, so that a comparatively long storage can be achieved with relatively little environmental hazard.

The present invention relates to a container, d. H. an object having in its interior a cavity which serves in particular the purpose of separating its contents from its environment. The container may in principle be closed to receive a hydrogen-containing composition, in particular a compressed hydrogen-containing gas.

"Hydrogen-containing compositions" in the context of the present invention designate all compositions which are capable of releasing molecular hydrogen into the environment, in particular molecular hydrogen (H ₂ ), physical gas mixtures containing molecular hydrogen, and compositions containing hydrogen in physically bound form Hydrogen, based on the total weight of the composition to be stored, is preferably at least 50%, preferably at least 75%, particularly preferably at least 90%, in particular at least 95%.

The structurally ideal shape for the container is the ball and it is particularly preferred for very high internal pressures or very large volume (gas tank) as a design. Most, however, the cylindrical shape is used. The jacket is preferably closed on both sides by flat or curved bottoms (dished bottoms or basket bottom plates), wherein on one side preferably an inlet and outlet valve is screwed.

The construction and dimensioning of the container suitably meets the legal requirements, in particular the EC Directive 97/23 / EC, Article 1, paragraph 2.1.1 (Pressure Equipment Directive) and the 14th GPSGV, § 2, paragraph 1a (Pressure Equipment Ordinance).

The container is preferably made of a gas-tight material as possible. The use of unalloyed steel and / or aluminum, in particular unalloyed steel has proven particularly useful in this context. Very particular preference is given to iron-carbon alloys which, based on their total weight, contain less than 2.06% by weight of carbon and preferably less than 1.0% by weight, particularly preferably less than 0.5% by weight. , In particular, contain less than 0.1 wt .-% of other alloying constituents other than iron.

In the context of the present invention, the inside of the container is coated with at least one hydride-forming metal, the coating covering as much as possible the entire surface which may come into contact with the composition to be stored. Another advantage is the most complete possible coating of the valve parts that can come into contact with the stored composition. Conveniently, at least 99% of the total surface area to be stored with the Composition can come into contact, coated with the hydride-forming metal,

Hydride-forming metals are known per se and refer to metals capable of forming metal hydrides, i. H. Compounds of metals with hydrogen, to form. In principle, metal hydrides resemble solutions of hydrogen in metals or alloys in which hydrogen molecules are first adsorbed on the surface of the metal and then incorporated into the metal grid as elemental hydrogen. The incorporation of hydrogen into the metal grid is in principle reversible. In general, metals take up the hydrogen below a certain temperature and / or above a certain pressure and a metal hydride is formed, whereby the incorporation (absorption) of the hydrogen into the metal lattice is usually accompanied by a sharp change of the original metal lattice. Conversely, the metal hydride releases hydrogen (desorption) again as the temperature is raised and / or the pressure is reduced, with the release of hydrogen in turn associated with a change in the metal lattice. Due to the desorption of hydrogen, especially in repeated absorption-desorption processes (a-ß phase transitions), a fairly brittle metal hydride is formed in most metals, but it is insensitive to air and water. This effect is commonly known as "hydrogen embrittlement" and occurs with all prior art hydrogen storage devices.

To avoid this embrittlement, the hydride-forming metal coating of the invention is characterized by a hydrogen desorption temperature of greater than 6O ⁰ C, preferably greater than 12O ⁰ C, in particular of greater than 200 ° C from. In this case, the hydrogen desorption temperature denotes the temperature at which a metal laden with hydrogen begins to release the hydrogen back to the environment. The measurement of the desorption temperature is preferably carried out under atmospheric pressure (1033 mbar) under a nitrogen atmosphere. Within the scope of a particularly preferred embodiment of the present invention, a pressure vessel according to the prior art is internally coated with, for example, a LaMg ₂ Ni alloy. The LaMg ₂ Ni alloy has a strictly ordered crystal structure, which is retained even after hydrogen uptake. The hydrogen atoms penetrate into the metal lattice via the regular interstices and in each case acquire one of the electrons which are freely mobile in the alloy. In this way, the hydrogen atoms combine chemically with the nickel atoms: This results in insulating NiH ₄ molecules. This process is reversible only at temperatures above 200 ⁰ C. As a result, the LaMg ₂ Ni- hydride does not embrittle and protects the underlying container material as a hydrogen barrier. It should be noted that not every metal is suitable for forming such a hydrogen barrier. Rather, it is important that the desorption of the metal meets the criterion of the invention.

For the purposes of the present invention, particularly suitable hydride-forming metals include hydride-forming metallic elements, such as. As palladium or magnesium, hydride-forming intermetallic compounds, such as ZrMn ₂ , LaNi ₅ or Mg ₂ Ni, and hydride-forming alloys, such as. B. LaMg ₂ Ni, TiNi-Ti ₂ Ni or Mg-Mg ₂ Ni. Furthermore, hydride-forming alkali aluminum compounds which can form so-called. Alanates are particularly advantageous.

The thickness of the hydride-forming metal layer is preferably less than 1 mm, preferably less than 50 .mu.m, very particularly preferably less than 1 .mu.m, in particular less than 50 nm. For reasons of mechanical safety, the thickness of 10 nm should preferably not be undershot. For layer thicknesses greater than 1 mm, there may be problematic stresses due to different thermal expansion coefficients.

The application of the hydride-forming metal layer can be carried out in a manner known per se. Advantageously, the metal is first applied to the inside of the container, preferably by vapor deposition, coating from the liquid phase, in particular by chemical deposition or physical Deposition (hot dip of metal), electrochemical coating (deposition of metals from solutions of their salts at the cathode), vapor deposition, in particular by chemical vapor deposition (CVD) or physical vapor deposition (PVD) Film formation by solids or gases), sputtering, plating, thermal spraying (melting of powdered metals in a burner into droplets that strike and form a layer at high speed on the material to be coated) or electron beam evaporation.

The layer thus applied settles in the first filling of the container with a hydrogen-containing composition in metal hydride. In the first reaction phase, the so-called σ-phase, catalytically split hydrogen molecules, that is to say hydrogen atoms, are dissolved into the metal lattice as interstitial or interstitial atoms on the metal surface. If the pressure in the pressure vessel now increases, the hydrogen concentration in the metal grid or in the intermetallic bond also increases. When saturation of the σ phase is reached, the metal hydride forms. This is called the beta phase. Since this reaction is exothermic, the heat of reaction should be dissipated with thicker layers in order to avoid a standstill of the reaction. This yff phase is in the case of the metal hydride coating according to the invention with a desorption temperature greater than 6O ⁰ C, z. B. a LaMg2Ni alloy, stable up to this desorption temperature. Pressure and temperature fluctuations below the desorption temperature do not harm the hydrogen barrier.

If necessary, a leveling layer may be provided below the hydride-forming metal layer to compensate for any differences in thermal expansion coefficient between the vessel and the hydride-forming metal layer and / or the metal hydride to be formed. For this purpose, the thermal expansion coefficient of the compensation layer preferably between that of the metal hydride to be formed and that of the container material.

For further mechanical protection of the hydrogen barrier, the hydride-forming metal layer can be coated with a polymer or metal layer. The application of the polymer or metal layer is carried out by methods of the prior art.

In addition, the container of the present invention preferably includes one or more safety-related accessories to protect the container from improper operating conditions (exceeding the design pressure or temperature). For this purpose suitable safety accessories are known per se and include in particular the aforementioned parts.

The filling of the container can be done in a known per se.

The container according to the invention is particularly suitable as a pressure vessel for the storage of compressed hydrogen-containing gases. Furthermore, it can also be used as a so-called "metal hydride reservoir." A metal or a metal alloy is introduced into the container according to the invention and the hydrogen is dissolved in this metal or metal alloy Metal hydride: The metal or metal alloy is loaded with hydrogen by pressure, which can be expelled again by reducing the pressure and applying light heat.

At least during the loading and unloading times prevails in this type of memory according to the prior art, a hydrogen overpressure, which leads to the known damage. Appropriately, the hydrogen barrier is therefore particularly against mechanical damage, eg. B. by a polymer layer protected. The same as for the metal hydride storage also applies to the hydrogen storage by means of "nanotubes", "porous nanocubes", "metal-doped polymers" and other similar storage media Further details on such media can be found in the current literature, in particular M. Hirscher, M. Becher, J Nanoscience, Nanotech, 2003, Vol 3, No 1/2; PJF Harris: Carbon Nanotubes and related Structures; K. Atkinson et al., Fuel CeIIs Bulletin, 28, 9-12, 2002; AC Dillon et al., NREL Rev. Let., 94, 175501, 2005; T. Appl., Phys., A, 72, 129, 2001; M. Hirscher, M. Becher, T., et al. Hydrogen Storage in Carbon Nanotubes; OM Yaghi et al., Science, VoI 300, 2003; http://www.kompetenzcluster.org/cn/nanotechnik/leuchttuerme/single-view-lighthouse/article/816/316/; //www.3sat.de/3sat.php?http://www.3sat.de/nano/cstuecke/83664/index.html; http://www.heise.de/tp/r4/artikel/24/ 24184 / 1.html; Transition Metal Ethylene Complexes as High Capac ity Hydrogen Storage Media E. Durgun, S. Ciraci, W. Zhou, and T. Yildirim; http://www.nanowelten.de/ausstellung/katalog_more.asp?Exponat=M24_Nanotub es; Liu et al., Science 286 (1999) 1127-9, the disclosure of which is incorporated herein by reference.

The desorption temperature of the hydrogen storage material (metal hydride storage, "nanotubes", "porous nanocubes", "metal-doped polymers", etc.) is suitably smaller than the desorption temperature of the hydride-forming coating according to the invention and is preferably less than 12O ⁰ C, more preferably less than 100 ⁰ C, in particular smaller 8O ⁰ C. It is conveniently also determined at atmospheric pressure (1033 mbar) under a nitrogen atmosphere.

The storage of the container according to the invention provided with a metal hydride layer is not particularly limited. Conveniently, however, during the useful life of the container, the intended or unintentional heating of the metal hydride, which has formed from the hydride-forming metal coating, to a temperature above the hydrogen desorption temperature of the metal hydride avoided as possible.

The hydrogen containers according to the invention are so dense that they could be sent by post and the storage of hydrogen-powered vehicles in garages could be allowed.

Claims

claims:

1. Container for storage of hydrogen-containing compositions, characterized in that the inside of the container is coated with at least one hydride-forming metal having a hydrogen desorption temperature greater than 6O ⁰ C.

2. A container according to claim 1, characterized in that the coating covers at least 99% of the total surface, which may come into contact with the composition to be stored.

3. Container according to claim 1 or 2, characterized in that the hydride-forming metal palladium, magnesium, ZrMn ₂ , LaNi ₅ , Mg ₂ Ni ₁ LaMg ₂ Ni, TiNi-Ti ₂ Ni, Mg-Mg ₂ Ni or an alanate-forming Metal covers.

4. Container according to at least one of the preceding claims, characterized in that the hydride-forming metal has a hydrogen desorption temperature under normal pressure of greater than 90 ° C.

5. Container according to at least one of the preceding claims, characterized in that the coating is between 10 nm and 1 mm thick.

6. A container according to at least one of the preceding claims, characterized in that below the hydride-forming metal layer, a leveling layer is arranged, whose thermal expansion coefficient is between that of the metal hydride and that of the container material.

7. Container according to at least one of the preceding claims, characterized in that a protective layer is disposed over the hydride-forming metal layer.

8. A process for producing a container according to at least one of the preceding claims, characterized in that one has a Provide container on its inside with a hydride-forming metal coating.

9. The method according to claim 8, characterized in that applying the metal by vapor deposition, coating from the liquid phase, electrochemical coating, vapor deposition, sputtering, plating, thermal spraying or evaporation by electron beam.

10. Use of a container according to at least one of claims 1-7 for the storage of compressed hydrogen-containing gases.

11. Use of a container according to at least one of claims 1 for the storage of metal hydrides.

12. Use of a container according to at least one of claims 1-7 for the storage of hydrogen-loaded nanotubes, loaded with hydrogen porous nanocubes and / or hydrogen-loaded metal-doped polymers.

13. A container for storage of hydrogen-containing compositions, characterized in that the inside of the container is coated with at least one metal hydride having a hydrogen desorption temperature greater than 6O ⁰ C.

14. A container according to claim 13, characterized in that it is at least partially filled with a hydrogen-containing composition.