WO2024009200A1

WO2024009200A1 - Hydrogen storage with absorption/desorption carried out in a flduized bed

Info

Publication number: WO2024009200A1
Application number: PCT/IB2023/056878
Authority: WO
Inventors: Gregory John Ash
Original assignee: Africa South Hydrogen Proprietary Limited
Priority date: 2022-07-05
Filing date: 2023-07-01
Publication date: 2024-01-11

Abstract

A method of storing hydrogen in a hydrogen capture material includes contacting the hydrogen capture material (100) in loose particulate format with gaseous hydrogen inside a pressure-tight vessel (12) at a predetermined contact temperature and at a corresponding predetermined contact pressure that promote capturing and storing of hydrogen by the hydrogen capture material (100) through adsorption and/or absorption of hydrogen on or by the hydrogen capture material (100) from the gaseous hydrogen, such that the hydrogen capture material (100) captures and stores at least some hydrogen through adsorption and/or absorption of hydrogen on or by the hydrogen capture material (100) from the gaseous hydrogen as a result of such contact. The hydrogen capture material (100) in loose particulate format is fluidized by contact of the gaseous hydrogen with the hydrogen capture material and the gaseous hydrogen acts as a working fluid to achieve and/or maintain the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture material.

Description

HYDROGEN STORAGE WITH ABSORPTION/DESORPTION CARRIED OUT IN A FLDUIZED BED

FIELD OF INVENTION

THIS INVENTION relates to hydrogen storage. The invention provides a method of storing hydrogen in a hydrogen capture medium. The invention also provides a method of recovering hydrogen stored in a hydrogen capture medium, from the hydrogen capture medium. The invention further provides a hydrogen storage system.

BACKGROUND TO THE INVENTION

HYDROGEN IS A DESIRABLE STORE OF ENERGY, as it converts to heat or electrical energy without creating a carbon or other undesirable waste product. Hydrogen can also be produced from water without creating carbon or other undesirable waste products.

A limiting factor to widespread adoption of hydrogen as an energy store is the difficulty of storing and transporting it (or transport and storage together in the case of mobile applications such as trains, ships, buses, trucks), because of its low energy to volume ratio as a gas and the potentially explosive nature of gaseous hydrogen especially when compressed.

It is known that certain materials have a capacity for reversible storage of hydrogen, for hydrogen selectively to be adsorbed and/or absorbed on and/or by and desorbed from such materials. Such materials include metals in elemental metallic format and metal alloys.

There is a need to provide for the storage of hydrogen in a compact, cost effective and safe way that allows rapid uptake and release of the gas, which need the present invention seeks to address through exploitation of the abovementioned capacity of certain materials for reversible storage of hydrogen.

SUMMARY OF INVENTION

IN ACCORDANCE WITH A FIRST ASPECT OF THE INVENTION, THERE IS PROVIDED a method of storing hydrogen in a hydrogen capture medium, the method including contacting the hydrogen capture medium, in particulate format, with gaseous hydrogen such that at least some hydrogen of the gaseous hydrogen is captured and thus stored by the hydrogen capture medium through adsorption and/or absorption of hydrogen from the gaseous hydrogen on or by the hydrogen capture medium as a result of such contact.

In this specification, the terms “adsorption” and “absorption” are used not only to include physical interactions within the conventional scope thereof, but also to include chemical interactions. Therefore, in respect of hydrogen being adsorbed on and/or absorbed by the hydrogen capture medium, the invention includes within its scope that a chemical reaction may take place between the hydrogen capture medium and the hydrogen that is adsorbed on and/or absorbed by the hydrogen capture medium. The same applies to “desorption”. The nature of the interaction relevant to any particular hydrogen capture medium would be readily determinable by those skilled in the art from literature references or through routine experimentation.

The hydrogen capture medium may be provided in loose particulate format.

In one, preferred, embodiment of the invention, contacting the hydrogen capture medium with the gaseous hydrogen is effected such that the hydrogen capture medium is fluidized by such contact.

To allow for fluidization, the hydrogen capture medium may be provided as a bed of loose particles, wherein contacting the gaseous hydrogen with the bed of loose particles of hydrogen capture medium is performed such that the contact fluidizes the bed. This may include supplying gaseous hydrogen to the bed at a volumetric feed flow rate of a magnitude sufficient to fluidize the bed. Such supply may also be at a predetermined supply pressure of a magnitude sufficient to optimize hydrogen adsorption and/or absorption by the bed, e.g. to fluidize the bed.

It will be appreciated that, in respect of the hydrogen capture medium being in particulate format, it is implied that the hydrogen capture medium would be a solid material. Thus, the hydrogen capture medium may consist of a solid hydrogen capture material, in particulate format. The hydrogen capture medium may be of, and the hydrogen capture material may therefore be, a material that is capable of capturing, and thus storing, hydrogen thereon and/or therein through adsorption and/or absorption of hydrogen on or by the hydrogen capture material from gaseous hydrogen when contacted by gaseous hydrogen.

In one embodiment of the invention, the hydrogen capture material would typically comprise a metal. In such a case, the hydrogen capture material may be either in elemental metallic format or a metal compound.

When the hydrogen capture material is in elemental metallic format, the hydrogen capture material may for example be palladium (Pd). Persons skilled in the art would appreciate that numerous other examples exist and that Pd is therefore not the only possible hydrogen capture material in elemental metallic format, which is identified herein only as an example.

When the hydrogen capture material is a metal compound, it would typically be a metal alloy, i.e. a compound of two or more metals.

For example, the hydrogen capture material may be selected from TiFe, Ti0.22Cr0.39V0.39, Tii.iCrMn, TiFeo.85Mno.o5, LaNi₄.9Sn₀.i , NaAl, and Lao.8Ceo.2Ni5 and metal alloys of metal alloy hydrides selected from AI(BH₄)3, AIH₃, BaReH₉, Ca(BH₄)2, FeTiHu, KBH₄, LaNi₅H₆, LiAIH₄, LiBH₄, LiH, Mg(BH₄)₂, Mg₂FeH₆, Mg₂Ni₅H₄, MgH₂, Mn(BH₄)₂, NaAIH₄, NaBH₄, and Zn(BH₄)₄, wherein the hydride denotes the form of the metal alloy in which hydrogen has already been adsorbed or absorbed on or by the metal alloy. Persons skilled in the art would appreciate that numerous other examples exist and that the metal alloys and metal alloy hydrides identified here are therefore not the only possible metal alloy hydrogen capture materials, these being identified herein only as examples.

The present invention is, in fact, not distinguished in any particular hydrogen capture material. Instead, the invention is distinguished in a novel and inventive approach to storing hydrogen in and/or on and, in respect of the second aspect of the invention, to recovering hydrogen stored in and/or on, a hydrogen capture medium of the type described herein. Contacting the hydrogen capture medium with gaseous hydrogen may be effected at a predetermined contact temperature that promotes capturing and storing of hydrogen by the hydrogen capture medium through adsorption and/or absorption of hydrogen on or by the hydrogen capture medium from the gaseous hydrogen.

Typically, the predetermined contact temperature would be associated with a corresponding predetermined contact pressure at which, at the predetermined contact temperature, capturing and storing of hydrogen by the hydrogen capture medium through adsorption and/or absorption of hydrogen on or by the hydrogen capture medium from the gaseous hydrogen is promoted.

Therefore, the method may include contacting the hydrogen capture medium with gaseous hydrogen a predetermined contact temperature, being the abovementioned predetermined contact temperature, and at a corresponding predetermined contact pressure, being the abovementioned predetermined contact pressure, that promote capturing and storing of hydrogen by the hydrogen capture medium through adsorption and/or absorption of hydrogen, from the gaseous hydrogen, on or by the hydrogen capture medium.

The predetermined contact temperature and corresponding predetermined contact pressure, at which adsorption and/or absorption of hydrogen from the gaseous hydrogen on or by the hydrogen capture medium is promoted, would depend on the hydrogen capture medium that is used and would be readily determinable by persons skilled in the art from literature references and through routine experimentation.

Examples of predetermined contact temperatures and pressures of some metal alloys that may be used in the method of the invention, include those set out in Table 1 , below:

Table 1 : Metal alloy contact temperature and pressure examples for adsorption/absorption of hydrogen

Achieving and/or maintaining the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium may at least in part be driven by the temperature of the gaseous hydrogen that is contacted with the hydrogen capture medium.

In other words, the gaseous hydrogen that is contacted with the hydrogen capture medium may be used, or may be employed or may act, as a working fluid to achieve and/or maintain the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium.

The term “working fluid” is in this context used in a heat transfer sense, meaning that it is the temperature of the gaseous hydrogen that drives any required temperature change to achieve and/or maintain the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium. The gaseous hydrogen is therefore used, and the method therefore includes using, the gaseous hydrogen to bring the hydrogen capture medium to a temperature that promotes adsorption and/or absorption, in the case of this first aspect of the invention, and that promotes desorption, in the case of the second aspect of the invention, such a temperature being the abovementioned predetermined contact temperature.

Put differently, the gaseous hydrogen that is contacted with the hydrogen capture medium may provide a contact environment that is at the predetermined contact temperature, thereby to bring the hydrogen capture medium to the predetermined contact temperature and thus effect contacting between the gaseous hydrogen and the hydrogen capture medium at the predetermined contact temperature.

In one embodiment of the invention, for the gaseous hydrogen to be used, employed, or to act as a working fluid in achieving and/or maintaining the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium or, put differently, to provide a contact environment that is at the predetermined contact temperature, the gaseous hydrogen may be subjected to temperature treatment prior to being contacted with the hydrogen capture medium.

Such temperature treatment may be performed selectively to cool or heat the gaseous hydrogen, as may be required for the gaseous hydrogen to be contacted with the hydrogen capture medium at the predetermined contact temperature.

Therefore, the method may include subjecting the gaseous hydrogen that is contacted with the hydrogen capture medium to temperature treatment upstream of the hydrogen capture medium, selectively to cool or heat the gaseous hydrogen as may be required to achieve and/or maintain the predetermined contact temperature in contacting the hydrogen capture medium with the gaseous hydrogen.

The extent and nature of the temperature treatment may be determined with reference to a temperature of the hydrogen capture medium or a temperature to which the hydrogen capture medium is cooled or heated independently of its contact with the gaseous hydrogen (e.g. through indirect heat exchange with a heat transfer medium, induction, etc.).

Thus, the method does not exclude, and may in fact include, cooling or heating the hydrogen capture medium independently of its contact with the gaseous hydrogen, in which case combined -

(i) cooling or heating of the capture medium independently of its contact with the gaseous hydrogen, and

(ii) contact of the gaseous hydrogen with the capture medium, would provide the predetermined contact temperature. In another embodiment, the hydrogen capture chamber herein referenced may, itself, be subjected to temperature treatment to achieve and maintain the predetermined contact temperature.

More typically, however, the temperature treatment may selectively heat or cool the gaseous hydrogen to the predetermined contact temperature. Thus, achieving the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium would typically, and in fact preferably, result from or be driven by the temperature of the gaseous hydrogen. Put differently, as mentioned above, in having been heated or cooled to the predetermined contact temperature, the gaseous hydrogen that is contacted with the hydrogen capture medium may thus provide a contact environment that is at the predetermined contact temperature.

While both cooling and heating have been referenced above as possible temperature treatments it would, in relation to this first aspect of the invention, be more typical for cooling to be employed in a case in which adsorption and/or absorption of hydrogen on or by the hydrogen capture medium is desired.

The hydrogen capture medium may be provided, and contacting of the hydrogen capture medium with gaseous hydrogen may therefore be performed, inside a hydrogen storage chamber.

The hydrogen storage chamber may be pressure-tight, i.e. it may be capable of withstanding internal pressures exceeding atmospheric pressure. For example, the hydrogen storage chamber may be capable to withstanding internal pressures of up to 3MPa, or even up to 35MPa.

The hydrogen storage chamber may for example be provided by a pressure-tight vessel. In one embodiment of the invention, the pressure-tight vessel may be a pressure-tight tank.

Contacting the hydrogen capture medium with the gaseous hydrogen at the predetermined contact temperature and the predetermined contact pressure may therefore be performed inside the hydrogen storage chamber, such that the predetermined contact temperature and the predetermined contact pressure are provided and maintained inside the hydrogen storage chamber.

In other words, a contact environment, as referenced above, at the predetermined contact temperature and predetermined contact pressure may be provided inside the hydrogen storage chamber to promote adsorption and/or absorption of hydrogen by the hydrogen capture medium when contacting the gaseous hydrogen with the hydrogen capture material, wherein, in one embodiment of the invention, the predetermined contact temperature may be provided by the gaseous hydrogen.

The hydrogen storage chamber may have an inlet, through which to feed gaseous hydrogen into the hydrogen storage chamber to be contacted with the hydrogen capture medium.

The hydrogen storage chamber may also have an outlet, through which to withdraw gaseous hydrogen from the hydrogen storage chamber.

Gaseous hydrogen that may be withdrawn from the hydrogen storage chamber may, for example, be or comprise gaseous hydrogen comprising unabsorbed hydrogen, i.e. gaseous hydrogen fed into the hydrogen storage chamber and having been contacted with the hydrogen capture medium but not having had hydrogen absorbed and/or adsorbed from it. Such gaseous hydrogen may be described as “excess” gaseous hydrogen.

Gaseous hydrogen withdrawn from the outlet may, in other words, comprise or consist of excess gaseous hydrogen, which would be in excess with reference to the volume of hydrogen, or the volumetric rate of hydrogen over time, that the hydrogen capture medium is able to adsorb and/or absorb.

In an embodiment of the invention in which stored hydrogen is recovered from the hydrogen capture medium as gaseous hydrogen, such as in accordance with the second aspect of the invention, gaseous hydrogen that is withdrawn from the outlet may comprise or consist of a hydrogen product gas. This foresees that, in such an embodiment, either one or both of excess gaseous hydrogen and a hydrogen product gas may be recovered through the outlet at a particular time.

As alluded to above, there would typically be excess hydrogen to withdraw from the outlet if the volumetric feed flow rate at which gaseous hydrogen is fed to the hydrogen capture chamber exceeds the rate at which hydrogen can be adsorbed on and/or absorbed by the hydrogen capture medium and, by extension, if the hydrogen capture medium is saturated with hydrogen and therefore can no longer adsorb and/or absorb hydrogen thereon and/or therein. The excess may, in chemical terms, be a stoichiometric excess. As also alluded to above, in an embodiment of the invention other than the method of this first aspect of the invention, more specifically an embodiment in which hydrogen is recovered, as gaseous hydrogen, from a hydrogen capture medium storing hydrogen, e.g. in accordance with the method of the second aspect of the invention, gaseous hydrogen that is withdrawn from the hydrogen storage chamber through the outlet may, alternatively additionally, be or comprise a hydrogen product gas.

The outlet may comprise at least one outlet valve.

The outlet valve may be configured automatically to release excess gaseous hydrogen and/or hydrogen product gas from the hydrogen storage chamber above a predetermined release pressure, for release thereof, inside the hydrogen storage chamber. Therefore, the outlet valve may be a pressure relief valve.

Additionally, or alternatively, the outlet valve may be configured to be selectively opened to allow such release and shut to prevent such release, independent of pressure.

When the outlet valve is a pressure relief valve, the pressure relief valve may be an adjustable pressure relief valve, in the sense that the pressure at which the valve would release gaseous hydrogen from the hydrogen storage chamber may be selectively changed, e.g. respectively to release excess gaseous hydrogen and to release hydrogen product gas from the hydrogen storage chamber.

Typically, the outlet would comprise two outlet valves, preferably each being a pressure relief valve, selectively operable or respectively selectable to release gaseous hydrogen from the hydrogen storage chamber at respective predetermined release pressures, which may be different, and each being capable of being selectively opened or shut independent of pressure.

As described in more detail below, including with reference to the second aspect of the invention, providing more than one outlet valve, and more specifically providing two outlet valves, would typically be motivated respectively to provide respectively for recirculation of gaseous hydrogen, and more specifically for recirculation of excess gaseous hydrogen, to the hydrogen storage chamber, and for release of a hydrogen product gas from the hydrogen storage chamber. One valve may therefore be a gaseous hydrogen recirculation valve and the other may be a hydrogen product gas release valve.

In being provided for release of a hydrogen product gas from the hydrogen storage chamber, in accordance with the method of the second aspect of the invention, having two valves would also allow for hydrogen product gas to be released from the hydrogen storage chamber while gaseous hydrogen is simultaneously being recirculated.

In the context of the method of the present, first, aspect of the invention, however, no simultaneous withdrawal or release of a hydrogen product gas while gaseous hydrogen is being recirculated is provided for, however. Thus, any additional valve that is provided at the outlet of the hydrogen storage chamber for the release of a hydrogen product gas from the hydrogen storage chamber would typically remain shut during the performance of the method of this first aspect of the invention.

Therefore, in the method of this, first, aspect of the invention, the gaseous hydrogen recirculation valve would operate to release excess gaseous hydrogen from the hydrogen storage chamber, including to maintain the predetermined contact pressure inside the hydrogen storage chamber, as hereinafter described in more details, while the hydrogen product gas release valve would remain shut.

In operating to release excess gaseous hydrogen from the hydrogen storage chamber, for recirculation to the hydrogen storage chamber, the gaseous hydrogen recirculation valve would release excess gaseous hydrogen from the hydrogen storage chamber with reference to a gaseous hydrogen recirculation release pressure, which would be a pressure inside the hydrogen storage chamber at which excess gaseous hydrogen would be released from the hydrogen storage chamber for recirculation.

The method may include continuously supplying gaseous hydrogen to the hydrogen capture medium. In other words, contacting the hydrogen capture medium with gaseous hydrogen may include continuously supplying gaseous hydrogen to the hydrogen capture medium.

Continuous supply of gaseous hydrogen to the hydrogen capture medium may be, as alluded to above, at a volumetric feed flow rate. As also alluded to above, the volumetric feed flow rate may be sufficient to effect fluidization of the hydrogen capture medium in the preferred embodiment of the invention in which such fluidization is effected.

The volumetric feed flow rate may either be constant over time or may change over time, e.g. as a result of changes in the hydrogen capture medium. Such changes in the hydrogen capture medium may include break-up of particles thereof during hydrogen storage through adsorption. Typically, over time, there may therefore be periods of time during which the volumetric feed flow rate is constant and periods of time during which the volumetric feed flow rate changes.

In this specification, the term “constant” may be interpreted, in one sense, as preferably free of any variation in the relevant parameter. In another sense, it may be interpreted as being “substantially constant” meaning that slight, functionally immaterial, variations in the relevant parameter may be present over time. Where the term “constant” is used, the relevant parameter may therefore be exactly the same over time or may vary functionally immaterially over time.

Supply of gaseous hydrogen to the hydrogen capture medium may furthermore also be at a predetermined supply pressure, as has also been alluded to above. The predetermined supply pressure may typically be greater than the predetermined contact pressure at which the gaseous hydrogen is contacted with the hydrogen capture medium.

It will be appreciated that the continuous supply of gaseous hydrogen, and particularly the volumetric feed flow rate and the predetermined supply pressure, may, as noted above, be of such a nature and magnitude (i.e. “sufficient”) that the hydrogen capture medium is continuously fluidized by such continuous supply of gaseous hydrogen in order to optimize hydrogen adsorption and/or absorption by the hydrogen capture medium.

Feeding of gaseous hydrogen into the hydrogen storage chamber to be contacted with the hydrogen capture medium would typically be performed through a single inlet. However, discharge of gaseous hydrogen inside the hydrogen storage chamber to be contacted with the hydrogen capture medium would typically be performed through a plurality of discharge nozzles. In one embodiment of the invention, gaseous hydrogen that is supplied to the hydrogen capture medium may comprise, or optionally consist of, fresh gaseous hydrogen, i.e. gaseous hydrogen that had not previously been contacted with the hydrogen capture medium. Such fresh gaseous hydrogen may be obtained from a fresh gaseous hydrogen supply source.

The method may further include recovering uncaptured hydrogen, as gaseous hydrogen, and more specifically as excess gaseous hydrogen as described above, from the hydrogen capture medium.

Thus, when the method is performed using the hydrogen storage chamber, the method may include continuously feeding gaseous hydrogen into the hydrogen storage chamber while recovering uncaptured hydrogen, as gaseous hydrogen, and more specifically as excess gaseous hydrogen, from the hydrogen storage chamber. Such recovery may be continuous but would more typically be intermittent.

Recovering uncaptured hydrogen, as gaseous hydrogen, and more specifically as excess gaseous hydrogen, from the hydrogen storage chamber may include releasing gaseous hydrogen, comprising uncaptured hydrogen (i.e. excess gaseous hydrogen), from the hydrogen storage chamber.

Releasing such excess gaseous hydrogen from the hydrogen capture chamber may be effected when the pressure inside the hydrogen storage chamber is at, or exceeds, the predetermined contact pressure, i.e. reaches the gaseous hydrogen recirculation pressure. Thus, excess gaseous hydrogen so released may be released at or above the predetermined contact pressure, at the gaseous hydrogen recirculation pressure.

Release of excess gaseous hydrogen from the hydrogen storage chamber may, under simultaneous feeding of gaseous hydrogen into the hydrogen storage chamber at the volumetric feed flow rate, maintain the predetermined contact pressure inside the hydrogen capture chamber.

In other words, the method may include withdrawing, or more typically releasing, excess gaseous hydrogen from the hydrogen storage chamber at the gaseous hydrogen recirculation pressure such that the predetermined contact pressure is maintained inside the hydrogen storage chamber.

Put differently, maintaining the predetermined contact pressure inside the hydrogen storage chamber may include withdrawing, or releasing, excess gaseous hydrogen from the hydrogen storage chamber.

Withdrawal or release of excess gaseous hydrogen to maintain the predetermined contact pressure inside the hydrogen storage chamber may, as alluded to above, typically be effected as and when the pressure inside the hydrogen storage chamber reaches or exceeds the predetermined contact pressure, by reaching the gaseous hydrogen recirculation release pressure. Such release may, for example, be automatic, through a pressure relief valve such as the gaseous hydrogen recirculation valve referenced above. Such a valve may therefore be configured for automatic release of gaseous hydrogen from the hydrogen storage chamber at the gaseous hydrogen recirculation release pressure, to maintain the pressure inside the hydrogen storage chamber at the predetermined contact pressure.

In performing the method of this, first, aspect of the invention, the predetermined contact pressure would therefore be achieved inside of the hydrogen storage chamber through continued feeding of gaseous hydrogen into the hydrogen storage chamber without release thereof from the hydrogen storage chamber while the pressure inside the hydrogen storage chamber is below the predetermined contact pressure, until the predetermined contact pressure has been reached or has been exceeded inside of the hydrogen storage chamber, thus reaching the gaseous hydrogen recirculation release pressure. The predetermined contact pressure would then be maintained inside of the hydrogen storage chamber by releasing excess gaseous hydrogen from the hydrogen storage chamber at the gaseous hydrogen recirculation release pressure, to restore the pressure inside the hydrogen storage chamber to the predetermined contact pressure.

Release of gaseous hydrogen, more specifically excess gaseous hydrogen, from the hydrogen storage chamber to maintain the predetermined contact pressure inside the hydrogen storage chamber may, as needed, be continuous over time, or may be intermittent. When the method includes recovering gaseous hydrogen comprising unabsorbed hydrogen (i.e. excess gaseous hydrogen, as referenced above) from the hydrogen capture medium, the method may also include recirculating gaseous hydrogen comprising uncaptured hydrogen, recovered from the hydrogen capture medium (i.e. excess gaseous hydrogen as referenced above), to the hydrogen capture medium, as recirculated gaseous hydrogen, such that the gaseous hydrogen that is contacted with the hydrogen capture medium comprises recirculated gaseous hydrogen.

Thus, when the method is performed using the hydrogen storage chamber, the method may include recirculating gaseous hydrogen comprising uncaptured hydrogen, released from the hydrogen storage chamber as a result of the pressure inside the hydrogen storage chamber reaching or exceeding the predetermined contact pressure and thus having reached the gaseous hydrogen recirculation pressure, or to maintain the predetermined contact pressure inside the hydrogen storage chamber, as recirculated gaseous hydrogen into the hydrogen storage chamber, such that the gaseous hydrogen that is fed into the hydrogen storage chamber comprises recirculated gaseous hydrogen.

Such recirculation may originate from the outlet of the gaseous hydrogen chamber, which outlet may therefore comprise a gaseous hydrogen recirculation outlet. The gaseous hydrogen recirculation outlet may comprise the gaseous hydrogen recirculation valve. In addition, the outlet may comprise a hydrogen product gas outlet. The hydrogen product gas outlet may comprise the hydrogen product gas release valve referenced above, which would typically be shut in performing the method of this, first, aspect of the invention.

Gaseous hydrogen that is supplied to the hydrogen capture medium, e.g. by being fed into the hydrogen storage chamber, may therefore comprise, or optionally consist of, recirculated gaseous hydrogen.

When the method includes recirculating gaseous hydrogen comprising unabsorbed hydrogen, recovered from the hydrogen capture medium (i.e. excess gaseous hydrogen that is recirculated as recirculated gaseous hydrogen), to the hydrogen capture medium, the method may include supplementing the recirculated gaseous hydrogen with fresh gaseous hydrogen to the extent necessary to maintain volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

It follows that, to maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber, gaseous hydrogen supplied to the hydrogen capture medium may selectively comprise - fresh gaseous hydrogen; recirculated gaseous hydrogen; or a combination of fresh gaseous hydrogen and recirculated gaseous hydrogen.

In summary, broadly speaking, contacting the hydrogen capture medium with gaseous hydrogen may therefore include - continuously feeding gaseous hydrogen into the hydrogen storage chamber at a volumetric feed flow rate that is sufficient to fluidize the hydrogen capture medium and to achieve and maintain the predetermined contact pressure inside the hydrogen storage chamber, while releasing uncaptured hydrogen, as excess gaseous hydrogen, from the hydrogen storage chamber to achieve and maintain the predetermined contact pressure inside the hydrogen storage chamber; and recirculating the excess gaseous hydrogen, as recirculated gaseous hydrogen, into the hydrogen storage chamber, such that the gaseous hydrogen that is fed into the hydrogen storage chamber comprises recirculated gaseous hydrogen.

The composition of the gaseous hydrogen that is supplied to the hydrogen capture medium, e.g. by being fed into the hydrogen storage chamber, may accordingly be selected such that a supply of gaseous hydrogen to the hydrogen capture medium makes use of recirculated gaseous hydrogen when recirculated gaseous hydrogen is available and such that the gaseous hydrogen is supplied to the hydrogen capture medium at a volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

In a case in which there is temperature treatment of gaseous hydrogen that is supplied to the hydrogen capture medium, e.g. in being fed into the hydrogen storage chamber, it would be appreciated that such temperature treatment would therefore be performed either on fresh gaseous hydrogen, or on recirculated gaseous hydrogen, or on a mixture thereof, depending on the composition of the gaseous hydrogen that is supplied to the hydrogen capture medium.

The composition of gaseous hydrogen supplied to the hydrogen capture medium may change over time, since the capacity of the hydrogen capture medium to store hydrogen would become diminished as the hydrogen capture medium becomes saturated with hydrogen.

More specifically, under a continuous volumetric supply of gaseous hydrogen, when the hydrogen capture medium does not store any hydrogen or while the hydrogen capture medium is in the process or adsorbing and/or absorbing hydrogen and is therefore still hydrogen lean from a hydrogen storage perspective, fresh gaseous hydrogen may initially exclusively or predominantly be provided from the source of fresh gaseous hydrogen as gaseous hydrogen feed to the hydrogen capture medium, with little to no excess gaseous hydrogen being released from or recirculated to the hydrogen storage chamber.

As hydrogen is adsorbed and/or absorbed by the hydrogen capture medium, however, and the capacity of the hydrogen capture medium to store hydrogen diminishes, or if excessive fresh gaseous hydrogen is supplied to the hydrogen capture medium compared to the rate of adsorption and/or absorption of hydrogen by the hydrogen capture medium, there would be excess gaseous hydrogen, comprising uncaptured hydrogen (as also referenced above) inside the hydrogen storage chamber to recover and recirculate to the hydrogen capture medium, as recirculated gaseous hydrogen (as also referenced above), which the method of the invention provides to exploit when possible.

The recirculation of recirculated gaseous hydrogen to the hydrogen capture medium in turn reduces the volume of fresh gaseous hydrogen that is required to achieve and maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

Ultimately, when the hydrogen capture medium is saturated with hydrogen, there would be no more adsorption and/or absorption of hydrogen by the hydrogen capture medium. Thus, all gaseous hydrogen supplied to the hydrogen capture medium would continuously be recirculated as recirculated gaseous hydrogen and would be sufficient to maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber. At such a time, no further fresh gaseous hydrogen would be required to maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

It will be understood that the method may therefore include supplementing recirculated gaseous hydrogen with fresh gaseous hydrogen to the extent necessary to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture medium and to achieve and maintain the predetermined contact pressure inside the hydrogen storage chamber.

Advantageously, the extent of the requirement to supply fresh gaseous hydrogen to the hydrogen capture medium to maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber in combination with recirculated gaseous hydrogen, may be used as an indicator of the extent of saturation of the hydrogen capture medium. When there is no more such requirement, it may be concluded that the hydrogen capture medium is saturated with hydrogen.

Such a conclusion may also be drawn if the volumetric feed flow rate of gaseous hydrogen into the hydrogen storage chamber is equal to a volumetric flow rate at which gaseous hydrogen is recovered from the hydrogen capture medium, e.g. is released from the hydrogen storage chamber (referenced hereinafter as the volumetric rate of recovery of gaseous hydrogen from the hydrogen capture medium).

Such a conclusion may also be drawn if there is an absence of a temperature differential between the gaseous hydrogen that is fed into the hydrogen storage chamber and the recirculated gaseous hydrogen when the recirculated gaseous hydrogen is recovered from the hydrogen capture medium.

Therefore, the method may include measuring, typically electronically, the volumetric rate of supply of fresh gaseous hydrogen to the hydrogen capture medium to maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber and concluding, typically electronically, that the hydrogen capture medium is saturated with hydrogen if such a volumetric rate of supply is or approximates zero (0).

The method may also include measuring, typically electronically, the volumetric rate of recovery of gaseous hydrogen from the hydrogen capture medium, e.g. the volumetric rate of release of gaseous hydrogen from the hydrogen storage chamber, over time, and concluding, typically electronically, that the hydrogen capture medium is saturated with hydrogen if such volumetric rate of recovery or release over time approximates or is equal to the volumetric feed flow rate.

The method may also include measuring, typically electronically, the temperature of the gaseous hydrogen that is fed into the hydrogen storage chamber (T1) and the temperature of the recirculated gaseous hydrogen when it is recovered from the hydrogen capture medium, i.e. is withdrawn or released from the hydrogen storage chamber when the hydrogen storage chamber is used (T2), and concluding, typically electronically, that the hydrogen capture medium is saturated with hydrogen if a differential between such temperatures (T3) is or approximates zero.

As suggested above, such measuring and the drawing of such conclusion/s may be performed electronically. For example, the measuring and drawing of such conclusion/s may be performed by an electronic control system, which would also exert corresponding control over the valves herein described, e.g. to effect the pressurized condition of the hydrogen storage chamber as hereinafter described.

Such a control system may for example comprise an electronic processing unit in communication with a flow sensor that measures the volumetric rate of supply of fresh gaseous hydrogen to the hydrogen capture medium and/or respective flow sensors that measure the volumetric feed flow rate and the volumetric rate of recovery of gaseous hydrogen from the hydrogen storage chamber and/or respective temperature sensors that measure the temperature of the gaseous hydrogen that is fed to the hydrogen storage chamber and the temperature of the gaseous hydrogen released from the hydrogen storage chamber when it is released from the hydrogen storage chamber. In summary, broadly speaking, the method may therefore include - electronically measuring a temperature (T1) of gaseous hydrogen that is fed into the hydrogen storage chamber; electronically measuring a temperature (T2) of gaseous hydrogen that is withdrawn from the hydrogen storage chamber; electronically calculating a temperature differential (T3) as T1 minus T2; electronically measuring the volumetric rate of supply of fresh gaseous hydrogen supplementing recirculated hydrogen to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the hydrogen storage chamber; electronically measuring a volumetric rate of recovery of recirculated gaseous hydrogen from the hydrogen storage chamber; electronically measuring the volumetric feed flow rate of gaseous hydrogen to the hydrogen storage chamber; and electronically concluding that the hydrogen capture material is sufficiently saturated with hydrogen, if

T3 is or approximates a value of zero (0), and/or the volumetric rate of supply of fresh gaseous hydrogen to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the hydrogen storage chamber is or approximates zero (0), and/or the volumetric rate of recovery of recirculated gaseous hydrogen is equal to or approximates the volumetric feed flow rate.

Supply of gaseous hydrogen to the hydrogen capture medium, e.g. feeding of gaseous hydrogen into the hydrogen storage chamber, may, in response to such a conclusion (i.e. that the hydrogen capture medium is saturated with hydrogen), be ceased, typically automatically, thus providing a pressurized hydrogen storage chamber at a storage pressure.

Such ceasing of supply of gaseous hydrogen to the hydrogen capture medium may, with reference to utilization of the hydrogen storage chamber, include closing the gaseous hydrogen recirculation outlet, e.g. using the gaseous hydrogen recirculation valve referenced above, while also closing a fresh gaseous hydrogen supply conduit against fresh gaseous hydrogen supply. Such closure may be in addition to ceasing of gaseous hydrogen supply to the hydrogen storage chamber, through, for example, ceasing of recirculation of recirculated gaseous hydrogen and supplementing such recirculated gaseous hydrogen with fresh gaseous hydrogen.

Optionally, with the gaseous hydrogen recirculation outlet closed, the method may, however, include continuing to feed fresh gaseous hydrogen into the hydrogen storage chamber for a limited period of time, thereby to achieve the storage pressure. This may particularly be required if the storage pressure is above the predetermined contact pressure.

The storage pressure may be at or above the predetermined contact pressure.

It will be appreciated that, thus, the hydrogen storage chamber would comprise solid hydrogen capture medium saturated with hydrogen and, in addition, pressurized gaseous hydrogen providing the storage pressure inside of the hydrogen storage chamber.

Transport of stored hydrogen and pressurized gaseous hydrogen in the pressurized hydrogen storage chamber, through transport of the hydrogen storage chamber, would thus be allowed.

As a safety precaution, it is provided that the hydrogen storage chamber would be configured to withstand internal pressures significantly higher than the predetermined contact pressure, to provide for possible increases in pressure through release of stored hydrogen by the capture medium as a result of temperature fluctuations.

In operation, in performing the method of this first aspect of the invention starting with a hydrogen storage chamber comprising hydrogen capture medium as hereinbefore described, the method may therefore include, initially, before any gaseous hydrogen has been contacted with the hydrogen capture medium, contacting the hydrogen capture medium with gaseous hydrogen from a supply of fresh gaseous hydrogen, i.e. gaseous hydrogen that has not yet been contacted with the hydrogen capture medium, e.g. supplied along a fresh gaseous hydrogen supply conduit, inside the hydrogen storage chamber, by feeding fresh gaseous hydrogen into the hydrogen storage chamber at the volumetric feed flow rate and at the predetermined supply pressure sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

The fresh gaseous hydrogen may be subjected to temperature treatment upstream of the hydrogen capture medium, for the fresh gaseous hydrogen to be used, employed, or act as a working fluid to achieve and maintain, i.e. to provide a contact environment inside the hydrogen storage chamber at, the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium.

Feeding of fresh gaseous hydrogen into the hydrogen storage chamber would result in the pressure inside the hydrogen storage chamber increasing, as gaseous hydrogen comprising unabsorbed hydrogen (i.e. excess gaseous hydrogen) accumulates inside the hydrogen storage chamber.

Once the predetermined contact pressure has been achieved or exceeded inside the hydrogen storage chamber (i.e. when the gaseous hydrogen recirculation release pressure is reached), gaseous hydrogen comprising unabsorbed hydrogen (i.e. excess gaseous hydrogen) would, typically automatically through an outlet valve such as the first- mentioned pressure relief valve, i.e. the gaseous hydrogen recirculation valve, hereinbefore described, be released from the hydrogen storage chamber downstream of the hydrogen capture medium through the gaseous hydrogen recirculation outlet, to maintain the predetermined contact pressure inside the hydrogen storage chamber. As stated, such release would occur at the abovementioned gaseous hydrogen recirculation release pressure, which may be at or above the predetermined contact pressure.

The method may then include recirculating the excess gaseous hydrogen withdrawn, i.e. released, from the hydrogen storage chamber through the gaseous hydrogen recirculation outlet, as recirculated gaseous hydrogen, to the hydrogen storage chamber and, thus, to the hydrogen capture medium, at a volumetric feed flow rate and predetermined supply pressure sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

Optionally, the method may include supplementing the recirculated gaseous hydrogen with fresh gaseous hydrogen from the fresh gaseous hydrogen supply source, to maintain the volumetric feed flow rate at which the recirculated hydrogen is fed into the hydrogen storage chamber and the predetermined supply pressure sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

The method may then further include subjecting the recirculated gaseous hydrogen, and the fresh gaseous hydrogen if used, to temperature treatment upstream of the hydrogen capture medium, for the recirculated gaseous hydrogen, and the fresh gaseous hydrogen, to be used, employed, or act as a working fluid to achieve and maintain the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium, i.e. provide a contact environment inside the hydrogen storage chamber at the predetermined contact temperature.

Once the conclusion that the hydrogen capture medium is saturated with hydrogen has been reached, e.g. by the control system, as hereinbefore described, the method may include ceasing, typically automatically, supply of gaseous hydrogen to the hydrogen storage chamber once the storage pressure has been reached inside the hydrogen storage chamber as a result of continued feeding of gaseous hydrogen into the hydrogen storage chamber, and closing or closing off the hydrogen storage chamber pressure tightly at the storage pressure.

The method may therefore include pressure-tightly closing, or closing off, the hydrogen storage chamber at a storage pressure above the predetermined contact pressure and at a temperature that does not exceed the predetermined contact temperature. Such closing, or closing off, may be performed electronically in response to the conclusion that the hydrogen capture material is sufficiently saturated with hydrogen

Thus, the method of the invention provides a hydrogen storage chamber comprising hydrogen capture medium laden with hydrogen, closed off and pressurized with gaseous hydrogen at the predetermined storage pressure.

IN ACCORDANCE WITH A SECOND ASPECT OF THE INVENTION, THERE IS PROVIDED a method of recovering, in gaseous form, hydrogen that has been stored by a hydrogen capture medium through adsorption and/or absorption of the hydrogen on or by the hydrogen capture medium, the method including contacting the hydrogen capture medium with gaseous hydrogen such that hydrogen is desorbed from the hydrogen capture medium as gaseous hydrogen as a result of such contact.

Storage of hydrogen “by” the hydrogen capture medium therefore includes storage of hydrogen in and storage of hydrogen on the hydrogen capture medium, respectively by one or both of adsorption and absorption, within the meanings of these terms hereinbefore characterized.

In relation to this, second, aspect of the invention, it must be understood that reference to the “hydrogen capture medium” is to hydrogen capture medium storing hydrogen to be recovered, typically being saturated with hydrogen, unless otherwise indicated. This is in contrast to the hydrogen capture medium of the method of the first aspect of the invention, which is hydrogen capture medium that is, at least initially, in a condition in which hydrogen would be stored therein instead of released therefrom. Hydrogen capture medium in such a condition would typically be a hydride of the hydrogen capture medium.

The hydrogen capture medium may therefore be as described with reference to the first aspect of the invention, including that it may be provided in loose particulate format as a bed thereof, subject to the abovementioned proviso that, in the case of the method of this, second, aspect of the invention, the hydrogen capture medium stores hydrogen that has been adsorbed on and/or absorbed by the hydrogen capture medium. Thus, when the hydrogen capture material is a metal alloy, the hydrogen capture medium may, in this second aspect of the invention, typically be a metal alloy hydride.

The hydrogen that is stored by the hydrogen capture medium may have been so stored by performing the method of the first aspect of the invention. The method of this, second, aspect of the invention may therefore include, as a prior step, performing the method of the first aspect of the invention.

It follows that terms that characterize the method of this, second, aspect of the invention that align with terms of the method of the first aspect of the invention may be as characterized with reference to the method of the first aspect of the invention, except where otherwise indicated. Contacting the hydrogen capture medium with the gaseous hydrogen may, as described with reference to the first aspect of the invention, be effected such that the hydrogen capture medium is fluidized by such contact. Put differently, the hydrogen capture material in loose particulate format may be fluidized by contact of the gaseous hydrogen with the hydrogen capture material. In other words, gaseous hydrogen supplied to the hydrogen capture medium may be so supplied at a volumetric feed flow rate, and typically also at a predetermined supply pressure, sufficient to fluidize the hydrogen capture medium.

Contacting the gaseous hydrogen and the hydrogen capture medium may be effected at a predetermined contact temperature and at a corresponding predetermined contact pressure (as mentioned above) that promote desorption of hydrogen from the hydrogen capture medium as gaseous hydrogen. The volumetric feed flow rate, and typically also the predetermined supply pressure, may therefore also be sufficient to achieve and/or maintain the predetermined contact pressure for contact of the gaseous hydrogen with the hydrogen capture medium.

It should be understood that the predetermined contact temperature and the predetermined contact pressure that are referenced, or that apply, in relation to this, second, aspect of the invention would typically be different from the predetermined contact temperature and predetermined contact pressure characterized with reference to the method of the first aspect of the invention, since the conditions for adsorption and/or absorption of hydrogen on or by a particular hydrogen capture medium and the conditions for desorption of hydrogen, as gaseous hydrogen, from the same hydrogen capture medium, would be different.

The predetermined contact temperature and corresponding predetermined contact pressure, at which desorption of hydrogen from the hydrogen capture medium is promoted, would depend on the hydrogen capture medium that is used and would be readily determinable by persons skilled in the art from literature references and through routine experimentation.

Examples of predetermined contact temperatures and pressures of some other metal alloys include those set out in Table 2, below: Table 2: Metal alloy contact temperature and pressure examples for desorption of hydrogen

As in the case of the method of the first aspect of the invention, achieving and/or maintaining the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium may at least in part be driven by the temperature of the gaseous hydrogen that is contacted with the hydrogen capture medium.

In other words, as in the case of the method of the first aspect of the invention, the gaseous hydrogen that is contacted with the hydrogen capture medium may be used, or may be employed or may act, as a working fluid to achieve and maintain the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium. As before, the term “working fluid” is in this context used in a heat transfer sense, meaning that it is the temperature of the gaseous hydrogen that drives any required temperature change to achieve and/or maintain the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium.

Put differently, and as also noted above in relation to the method of the first aspect of the invention, the gaseous hydrogen that is contacted with the hydrogen capture medium may therefore provide a contact environment that is at the predetermined contact temperature, being a temperature at which desorption of hydrogen stored by the hydrogen capture medium, as gaseous hydrogen, is promoted.

The method may therefore include subjecting the gaseous hydrogen that is contacted with the hydrogen capture medium to temperature treatment upstream of the hydrogen capture medium, selectively to cool or heat the gaseous hydrogen as may be required to achieve and/or maintain the predetermined contact temperature in contacting the hydrogen capture medium.

Thus, the method may include subjecting the gaseous hydrogen that is contacted with the hydrogen capture medium to temperature treatment upstream of the hydrogen capture medium, selectively to cool or heat the gaseous hydrogen as may be required to achieve and/or maintain the predetermined contact temperature in contacting the hydrogen capture medium.

(i) cooling or heating of the hydrogen capture medium independently of its contact with the gaseous hydrogen, and

(ii) contact of the gaseous hydrogen with the hydrogen capture medium, would provide the predetermined contact temperature. In another embodiment, the hydrogen capture chamber herein referenced may, itself, be subjected to temperature treatment to achieve and maintain the predetermined contact temperature.

More typically, however, the temperature treatment may selectively heat or cool the gaseous hydrogen to the predetermined contact temperature.

Thus, achieving the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium would typically, and in fact preferably, result from or be driven by the temperature of the gaseous hydrogen. Put differently, as mentioned above, in having been heated or cooled to the predetermined contact temperature, the gaseous hydrogen that is contacted with the hydrogen capture medium may provide a contact environment that is at the predetermined contact temperature.

While both cooling and heating have been referenced above, as possible temperature treatments, it would, in relation to this second aspect of the invention, be more typical for heating to be employed in a case in which desorption of hydrogen from the hydrogen capture medium, as gaseous hydrogen, is desired.

Preferably, the temperature treatment selectively heats or cools the gaseous hydrogen that would be contacted with the hydrogen capture medium to the predetermined contact temperature.

The hydrogen capture medium may be provided, and contacting of the hydrogen capture medium with gaseous hydrogen may therefore be performed, inside a hydrogen storage chamber, which may be a hydrogen storage chamber as described with reference to the first aspect of the invention.

Contacting the hydrogen capture medium with the gaseous hydrogen at the predetermined contact temperature and the predetermined contact pressure may therefore be performed inside the hydrogen storage chamber, such that the predetermined contact temperature and the predetermined contact pressure are provided and maintained inside the hydrogen storage chamber. In other words, a contact environment, as also referenced above, at the predetermined contact temperature and predetermined contact pressure may be provided inside the hydrogen storage chamber to promote desorption, of hydrogen by the hydrogen capture medium when contacting the gaseous hydrogen with the hydrogen capture material. As noted above, in one embodiment of the invention the predetermined contact temperature may be provided by the gaseous hydrogen.

Contacting the hydrogen capture medium with gaseous hydrogen may include continuously supplying gaseous hydrogen to the hydrogen capture medium, e.g. by continuously feeding gaseous hydrogen into the hydrogen storage chamber. It will be appreciated that such continuous supply may, as described above, be such that the hydrogen capture medium is continuously fluidized.

As has also been indicated above, gaseous hydrogen that is supplied to the hydrogen capture medium, e.g. by being fed into the hydrogen storage chamber, may be supplied at a volumetric feed flow rate, and typically also at a predetermined supply pressure, sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

The hydrogen storage chamber may, before contacting the hydrogen capture medium with gaseous hydrogen at the predetermined contact temperature and predetermined contact pressure, be in a condition in which it is, or was, pressurized with gaseous hydrogen at a storage pressure and at a storage temperature different from the predetermined contact temperature and predetermined contact pressure, which pressure and temperature do not promote, i.e. that avoid, desorption of hydrogen from the hydrogen capture medium as gaseous hydrogen. Typically, such a storage temperature may be a temperature below the predetermined contact temperature and such a storage pressure may be a pressure above the predetermined contact pressure.

In such a case, the method may include that, at least initially, the gaseous hydrogen that is contacted with the hydrogen capture medium at the predetermined contact temperature and at the predetermined contact pressure such that hydrogen is desorbed from the hydrogen capture material as gaseous hydrogen as a result of such contact, either comprises or, more typically and preferably consists of, gaseous hydrogen with which the hydrogen storage chamber is, or was previously, pressurized.

Thus, in recovering hydrogen from the hydrogen capture medium inside the hydrogen storage chamber, pressurized gaseous hydrogen contained inside the hydrogen storage chamber, typically being located above the hydrogen capture medium, may be withdrawn from the outlet of the hydrogen storage chamber, more specifically from the gaseous hydrogen recirculation outlet, and recirculated to the inlet of the hydrogen storage chamber.

Such recirculated gaseous hydrogen may then be supplied to and contacted with the hydrogen capture medium at the predetermined contact temperature and at the predetermined contact pressure.

In such a case, as in the case of the method of the first aspect of the invention, the recirculated gaseous hydrogen may be used, or employed, or may act as a working fluid as hereinbefore described, which may include subjecting the recirculated gaseous hydrogen to temperature treatment as hereinbefore described.

As an alternative, or in addition, the gaseous hydrogen that is contacted with the hydrogen capture medium at the predetermined contact temperature and at the predetermined contact pressure to effect desorption of hydrogen from the hydrogen capture medium may either comprise or consist of fresh gaseous hydrogen from a fresh gaseous hydrogen supply source. In one embodiment of the invention, fresh gaseous hydrogen may be used to supplement recirculated gaseous hydrogen to achieve and/or maintain the volumetric feed flow rate at which gaseous hydrogen is supplied to the hydrogen capture medium sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

As a further alternative, or in addition, the gaseous hydrogen that is contacted with the hydrogen capture medium at the predetermined contact temperature and at the predetermined contact pressure to effect desorption of hydrogen from the hydrogen capture medium may either comprise or consist of gaseous hydrogen desorbed from the hydrogen capture medium as a result of the hydrogen capture medium having been contacted with recirculated gaseous hydrogen or fresh gaseous hydrogen. The method may therefore include recirculating, preferably continuously, desorbed gaseous hydrogen to the inlet of the hydrogen storage chamber.

Pressurized and/or desorbed gaseous hydrogen that is withdrawn from the hydrogen storage chamber for recirculation to the inlet of the hydrogen storage chamber may be withdrawn, or released, from the hydrogen storage chamber freely, i.e. continuously and without any determination of volumetric flow rate.

Contacting the hydrogen capture medium with gaseous hydrogen may therefore, as noted above, include withdrawing desorbed gaseous hydrogen from the outlet of the hydrogen storage chamber, and more specifically through the gaseous hydrogen recirculation valve, recirculating it to the inlet of the hydrogen storage chamber, and feeding it into the interior of the hydrogen storage chamber at the volumetric feed flow rate, and typically also at the predetermined supply pressure, sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

Such recirculation may, as mentioned above, be continuous, i.e. not dependent on a predetermined pressure within the hydrogen storage chamber that causes the recirculation to be intermittent, for example. Therefore, for example, the gaseous hydrogen recirculation valve, as referenced in relation to the method of the first aspect of the invention, may, in performing the method of this, second, aspect of the invention, be fully open for the duration of the performance of the method of this second aspect of the invention.

Given that the temperature adjustment of the hydrogen capture medium by the recirculated hydrogen will cause desorption of the hydrogen from the hydrogen capture medium as gaseous hydrogen, the pressure within the hydrogen storage chamber will rise due to accumulation of gaseous hydrogen inside the hydrogen storage chamber. Such a pressure increase would continue, under continuous recirculation of gaseous hydrogen, until such time as a hydrogen product gas release pressure is reached upon which a valve, typically a pressure relief valve on the outlet, more one specifically the hydrogen product gas outlet, will open, allowing a hydrogen product gas to be released for use. Such valve would typically be the second valve characterised with reference to the first aspect of the invention, i.e. the hydrogen product gas release valve described with reference to the method of the first aspect of the invention, and its opening, and thus withdrawal of the hydrogen product gas, may therefore occur concurrently with recirculation of gaseous hydrogen.

It will be appreciated that the gaseous hydrogen that is contacted with the hydrogen capture medium at the predetermined contact temperature and at the predetermined contact pressure to effect desorption of hydrogen from the hydrogen capture medium may therefore, selectively, comprise only gaseous hydrogen that pressurized the hydrogen storage chamber before such contact, or only fresh gaseous hydrogen, or only recirculated desorbed gaseous hydrogen, or any combination of two or more hereof, each of which may be supplied to the hydrogen capture medium, e.g. by being fed into the interior of the hydrogen storage chamber, at the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

Most typically, in performing the method starting with a hydrogen storage chamber comprising hydrogen capture medium storing hydrogen and pressurized gaseous hydrogen, the hydrogen capture medium would be contacted, at a volumetric feed flow rate, and typically at the predetermined supply pressure, sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber, with - recirculated gaseous hydrogen that pressurizes, or previously pressurized, the hydrogen storage chamber, typically at the predetermined contact temperature and at the predetermined contact pressure, and then with recirculated desorbed gaseous hydrogen, optionally mixed with fresh gaseous hydrogen, at the predetermined contact temperature and at the predetermined contact pressure.

The method may also include continuing recirculation after hydrogen desorption from the hydrogen capture medium has commenced, thus recirculating desorbed gaseous hydrogen to the hydrogen storage chamber. Such recirculation and continued desorption of hydrogen as gaseous hydrogen would result in the pressure inside of the hydrogen storage chamber increasing, up to a point at which the hydrogen product gas release pressure referenced herein is reached, at which time release of hydrogen product gas would occur.

Therefore, in summary, typically and preferably, the gaseous hydrogen that is contacted with the hydrogen capture medium at the predetermined contact temperature and at the predetermined contact pressure such that hydrogen is desorbed from the hydrogen capture material as gaseous hydrogen as a result of such contact, comprises or consists of pressurized gaseous hydrogen contained in the hydrogen storage chamber, the method therefore including - withdrawing pressurized gaseous hydrogen contained in the vessel from the vessel; recirculating such gaseous hydrogen to the vessel at a volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the vessel; and contacting the gaseous hydrogen so recirculated with the hydrogen capture material at the predetermined contact temperature and at the predetermined contact pressure such that the hydrogen capture material is fluidized by such contact and such that hydrogen is desorbed from the hydrogen capture material as gaseous hydrogen as a result of such contact.

Contacting the hydrogen capture medium storing hydrogen with gaseous hydrogen at the predetermined contact temperature and at the predetermined contact pressure causes desorption of hydrogen from the hydrogen capture medium and release thereof from the capture medium as gaseous hydrogen.

Such a release of gaseous hydrogen would, at the volumetric feed flow rate of gaseous hydrogen that is fed into the hydrogen storage chamber, sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber, cause, as indicated above, an increase in pressure inside of the hydrogen storage chamber, which pressure increase would be determinative of release of gaseous hydrogen from the hydrogen capture medium as a hydrogen product gas, typically through the hydrogen product gas outlet and through the hydrogen product gas release valve once the hydrogen product gas release pressure has been reached inside the hydrogen storage chamber. It is emphasized that such withdrawal or discharge would typically be automatic at or above the hydrogen product gas release pressure, e.g. through a pressure-sensitive valve such as the second pressure relief valve, more specifically the hydrogen product gase release valve, referenced in relation to the method of the first aspect of the invention.

In other words, release of gaseous hydrogen through desorption of hydrogen from the hydrogen capture medium as a result of the contacting the hydrogen capture medium with gaseous hydrogen increases the pressure inside of the hydrogen storage chamber and causes automatic discharge of gaseous hydrogen from the hydrogen storage chamber as a hydrogen product gas, as referenced above, above a predetermined hydrogen product gas release pressure, as referenced above.

Discharge or release of gaseous hydrogen from the hydrogen storage chamber may originate from the outlet of the hydrogen storage chamber, which may therefore comprise hydrogen product gas outlet hereinbefore described, preferably in addition to the gaseous hydrogen recirculation outlet referenced in relation to the method of the first aspect of the invention.

The method may include continuously recirculating gaseous hydrogen to the hydrogen storage chamber, including while hydrogen is being desorbed from the hydrogen capture medium and while hydrogen product gas is being released from the hydrogen capture medium. Such gaseous hydrogen may be recirculated from the hydrogen storage chamber, being recovered from the hydrogen storage chamber through the gaseous hydrogen recirculation outlet of the hydrogen storage chamber.

Thus, a hydrogen product gas, comprising gaseous hydrogen released from the hydrogen capture medium, may be obtained.

IN ACCORDANCE WITH A THIRD ASPECT OF THE INVENTION, THERE IS PROVIDED a hydrogen storage system for selective storage and recovery of hydrogen by or from a hydrogen capture medium in accordance with the methods of the first and second aspects of the invention respectively, the system comprising - a hydrogen storage chamber containing a hydrogen capture medium in its interior, the hydrogen storage chamber having an inlet to and an outlet from its interior; a gas dispersal system located downstream of the inlet of the hydrogen storage chamber and upstream of the hydrogen capture medium and providing gas inlet openings into the hydrogen storage chamber, optionally having a plurality of gas feed nozzles located inside the interior of the hydrogen storage chamber, to feed gaseous hydrogen into the interior of the hydrogen storage chamber in use; a gaseous hydrogen recirculation outlet provided by the outlet of the hydrogen storage chamber, for gaseous hydrogen to be released from the hydrogen storage chamber, at a gaseous hydrogen recirculation pressure, and be recirculated to the gas dispersal system as recirculated gaseous hydrogen, in use; a gaseous hydrogen recirculation pump located and configured to supply gaseous hydrogen from the gaseous hydrogen recirculation outlet and/or fresh gaseous hydrogen from a fresh gaseous hydrogen supply source to the gas dispersal system in use; and a hydrogen product gas outlet provided by the outlet of the hydrogen storage chamber, for gaseous hydrogen to be released from the hydrogen storage chamber, and thus from the system, in use, as a hydrogen product gas, at a hydrogen product gas release pressure inside the hydrogen storage chamber, for use.

The hydrogen storage chamber, the hydrogen capture medium, the inlet to the hydrogen storage chamber the gas dispersal system, the gaseous hydrogen, the outlet from the hydrogen storage chamber, the gaseous hydrogen recirculation outlet, the gaseous hydrogen product gas outlet, the gaseous hydrogen recirculation valve, the hydrogen product gas release valve, and all other components of the system described directly or indirectly in or by terms also used to characterize the method aspects of the invention, including the control system itself, may be as characterized with reference to the method aspects of the invention, or may be configured to perform the functions characterized in terms of the method aspects of the invention.

The gas dispersal system may be located to feed gaseous hydrogen into the interior of the hydrogen storage chamber, in use, preferably such that the hydrogen capture medium is fluidized by such feeding of gaseous hydrogen into the interior of the hydrogen storage chamber.

In one embodiment of the invention, with respect to a particular operative orientation of the hydrogen storage chamber, the gas dispersal system may be located at a base of the hydrogen storage chamber, such that the hydrogen capture medium essentially rests on or is supported by the gas dispersal system, or a part thereof.

The system may also include a gas cooling device and a gas heating device located downstream of the gaseous hydrogen recirculation pump and upstream of the gas dispersal system, respectively to be supplied with fresh and/or recirculated gaseous hydrogen by the gas recirculation pump and selectively to cool or heat such gaseous hydrogen before it is fed to the gas dispersal system and into the interior of the hydrogen storage chamber.

The system may be adapted to prevent loss of capture medium from the storage chamber, e.g. by means of baffles and/or filters located in the path of flow of gaseous hydrogen in the system.

The system may also comprise stirring means, to stir the hydrogen capture medium to assist its fluidization.

The gaseous hydrogen recirculation outlet and the hydrogen product gas outlet may be provided by one or more outlet valves, as characterised with reference to the first and second aspects of the invention respectively, i.e. comprising the gaseous hydrogen recirculation valve and the hydrogen product gas release valve. The outlet valves may be a pressure-sensitive, or pressure relief, outlet valves, for gaseous hydrogen to be discharged, or released, automatically from the hydrogen storage chamber as a hydrogen product gas, and thus from the system, at a predetermined release pressures inside the hydrogen storage chamber, which predetermined release pressures may respectively be the hydrogen product gas release pressure and the gaseous hydrogen recirculation release pressure. The valves may, however, also be configured to be made fully open or fully shut, independent of pressure.

Where the gaseous hydrogen recirculation outlet and the hydrogen product gas outlet comprise respective outlet valves, as is preferred, the system may be adapted such that the valves are respectively selectable, or opened, or closed, or activated for discharge, or release, of gaseous hydrogen from the hydrogen storage chamber. Alternatively, a single, adjustable valve may be provided, which may be adjustable in respect of its release pressure. More specifically, the gaseous hydrogen recirculation outlet preferably comprises a gaseous hydrogen recirculation valve that is configured automatically to release gaseous hydrogen from the interior of the hydrogen storage chamber at the gaseous hydrogen recirculation pressure and that can selectively be opened and shut independent of pressure.

Furthermore, the hydrogen product gas outlet preferably comprises a hydrogen product gas release valve that is configured automatically to release gaseous hydrogen from the interior of the hydrogen storage chamber at the hydrogen product gas release pressure and that can selectively be opened and shut independent of pressure.

The system may include a control system, for controlling operation of the system to perform the methods of the first and second aspects of the invention respectively.

The control system may be an electronic control system, comprising an electronic processing unit configured to control the system as hereinbefore and hereinafter described, selectively to perform the methods of the first and second aspects of the invention respectively.

In one respect, the control system may be configured to operate the recirculation pump, i.e. to activate the pump and pump gaseous hydrogen, comprising fresh gaseous hydrogen and/or recirculated gaseous hydrogen, i.e. from the fresh gaseous hydrogen supply source and/or from the gaseous hydrogen recirculation outlet, into the interior of the hydrogen storage chamber at a volumetric feed flow rate, and typically at a predetermined supply pressure, sufficient to achieve and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain a predetermined contact pressure inside of the hydrogen storage chamber selected to promote either adsorption and/or absorption of hydrogen from the gaseous hydrogen on or by the hydrogen capture medium or desorption of hydrogen previously adsorbed and/or absorbed on or by the hydrogen capture medium at a predetermined contact temperature, such a predetermined supply pressure preferably being greater than the predetermined contact pressure.

In another respect, the control system may be configured to supplement gaseous hydrogen from the recirculation outlet with fresh gaseous hydrogen from the fresh gaseous hydrogen supply source to the extent necessary to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the hydrogen storage chamber.

In another respect, the control system may be configured to direct flow of gaseous hydrogen, driven by the gaseous hydrogen recirculation pump, selectively to the gas cooling device or to the gas heating device, and selectively to activate the gas cooling device or the gas heating device, if activation is needed, for the gaseous hydrogen to be selectively heated or cooled to the predetermined contact temperature.

In another respect, the control system may be configured to measure pressure inside the interior of the hydrogen storage chamber.

In another respect, the control system may be configured to release, through the gaseous hydrogen recirculation outlet and preferably at the gaseous hydrogen recirculation release pressure, excess gaseous hydrogen from the interior of the hydrogen storage chamber to maintain the predetermined contact pressure inside of the hydrogen storage chamber, and then recirculating such excess gaseous hydrogen, as recirculated gaseous hydrogen, to the gas dispersal system through operation of the recirculation pump. The control system may in this regard be in operative communication with a valve of the gaseous hydrogen recirculation outlet, and more specifically with the gaseous hydrogen recirculation valve.

Alternatively, such release of gaseous hydrogen, as recirculated gaseous hydrogen, through the gaseous hydrogen recirculation outlet, may occur automatically, particularly when the valve of the gaseous hydrogen recirculation outlet comprises a pressure relief valve, more specifically the gaseous hydrogen recirculation valve, configured, or calibrated, for automatic release of gaseous at or above the predetermined contact pressure, and more specifically at the gaseous hydrogen recirculation pressure.

Preferably, in this regard, the control system is configured selectively to - shut the hydrogen product gas release valve and set the gaseous hydrogen recirculation valve to operate as a pressure relief valve at the gaseous hydrogen recirculation pressure, and open the gaseous hydrogen recirculation valve and set the hydrogen product gas release valve to operate as a pressure relief valve at the hydrogen product gas release pressure.

In another respect, and as alluded to above, the control system may be configured to maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber, using fresh gaseous hydrogen from the fresh gaseous hydrogen supply source, recirculated gaseous hydrogen, or a combination thereof, wherein, when recirculated gaseous hydrogen is available, then at least recirculated gaseous hydrogen is supplied to the hydrogen storage chamber and is supplemented with fresh gaseous hydrogen only to the extent necessary to maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

The control system may further be configured - to measure a temperature (T1) of gaseous hydrogen that is fed into the hydrogen storage chamber; to measure a temperature (T2) of gaseous hydrogen that is withdrawn from the hydrogen storage chamber; to calculate a temperature differential (T3) as T1 minus T2; to measure a volumetric rate of supply of fresh gaseous hydrogen supplementing recirculated hydrogen to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the hydrogen storage chamber; to measure a volumetric rate of recovery of recirculated gaseous hydrogen from the hydrogen storage chamber through the gaseous hydrogen recirculation outlet; to measure the volumetric feed flow rate of gaseous hydrogen supplied to the hydrogen storage chamber through the inlet of the hydrogen storage chamber; and to conclude that the hydrogen capture material is sufficiently saturated with hydrogen, if -

In this regard, and in another respect, the control system may include a fresh gaseous hydrogen supply volumetric flow meter located to measure, and that measures in use, the volumetric rate at which fresh gaseous hydrogen, required to achieve or maintain the predetermined gaseous hydrogen feed flow rate constant over time, is withdrawn from the fresh gaseous hydrogen supply source. It will be appreciated that, thus, if sufficient recirculated gaseous hydrogen is available to maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber using the recirculation pump, then no fresh gaseous hydrogen would be required.

Furthermore, the control system may include a gaseous hydrogen feed volumetric flow meter located to measure, and that measures in use, the volumetric feed flow rate at which gaseous hydrogen is fed to the hydrogen storage chamber over time.

In another respect, the control system may include a gaseous hydrogen recovery volumetric flow meter located to measure, and that measures in use, the volumetric rate of recovery, e.g. discharge or release, of gaseous hydrogen, and more specifically recirculated gaseous hydrogen, from the hydrogen storage chamber over time.

In another respect, the control system may be configured to close or close off the hydrogen storage chamber pressure-tightly, or to cease feeding of gaseous hydrogen into the interior of the hydrogen storage chamber, and thus provide a pressurized condition at a storage pressure after, it has been noted by the control system that, at the volumetric feed flow rate of gaseous hydrogen fed into the hydrogen storage chamber through the gas dispersal system, sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber, the volumetric flow rate of fresh gaseous hydrogen supply over time is, or approximates, zero (0).

In another respect, the control system may be configured to withdraw, from the hydrogen storage chamber in the pressurized condition, pressurized gaseous hydrogen from the hydrogen storage chamber through the gaseous hydrogen recirculation outlet and to pump such gaseous hydrogen into the interior of the hydrogen storage chamber at the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber.

The methods and system of the first to third aspects of the invention may further provide for passage of ultrasonic waves through the hydrogen capture medium when contacting the hydrogen capture medium with the gaseous hydrogen.

Such passage may increase kinetic energy that is imparted onto the hydrogen capture medium in being contacted with the gaseous hydrogen.

THE INVENTION EXTENDS TO applications of hydrogen stored and/or recovered in accordance with the invention, including, for example, as a source of hydrogen for propulsion of a vehicle (whether for electricity generation or as a fuel in an internal combustion engine), bulk storage of hydrogen at locations where benefit may be derived from using stored hydrogen to generate electricity or for chemical purposes, the bulk transport of hydrogen from production facilities or depots to where it is required and the activation of capture medium, e.g. of metal alloys / metal hydrides, for use as activated capture medium.

In exploiting the invention to activate the hydrogen capture medium, the methods of the invention may include successively and repeatedly charging the hydrogen capture medium with hydrogen in accordance with the method of the first aspect of the invention and discharging hydrogen from it until the hydrogen capture medium has fractured into irregular particles.

BRIEF DESCRIPTION OF DRAWINGS The invention will now be described in more detail by way of non-limiting example, with reference to the accompanying drawings.

In the drawings:

FIGURE 1 shows a hydrogen storage system in accordance with the invention;

FIGURE 2 shows a gas dispersal system of the storage system of Figure 1 ;

FIGURE 3 shows a plot of concentration of hydrogen in LaNi^Sno i for temperatures of 25 °C and 130 °C;

FIGURE 4 shows adsorption/absorption and desorption curves of the metal hydride;

FIGURE 5 shows the absorption and desorption curves, or PCT curves (Pressure, Concentration, Temperature) of LaNi^Snoi for 20 °C and 60 °C;

FIGURE 6 shows the metal hydride reactor tank used in the example, including the view of the 4 nozzles creating the fluidisation at the bottom of the tank;

FIGURE 7 process and instrumentation diagram (P&ID) created for the test setup

FIGURE 8 shows adsorption/absorption results from Test 4A;

FIGURE 9 shows desorption results from Test 4B; and

FIGURE 10 shows a sorption graph for the whole of Test 4.

DETAILED DESCRIPTION OF THE INVENTION

REFERRING TO THE DRAWINGS, and in particular to Figure 1 , reference numeral 10 generally indicates a hydrogen storage system in accordance with the third aspect of the invention, for selectively performing the methods of the first and second aspects of the invention.

The hydrogen storage system 10 comprises a hydrogen storage chamber in the form of a hydrogen storage vessel that comprises a tank 12 that is located in a substantially upright orientation.

The tank 12 is a pressure tank, capable of withstanding up to about 3MPa (30atm) of internal pressure, or even up to as much as 300bar of pressure, alternatively even up to 35MPa (350 atm). The tank 12 defines an interior 14 that holds a hydrogen capture medium 100 in accordance with the invention. The hydrogen capture medium 100 comprises a hydrogen capture material in particulate solid format, arranged as a packed bed thereof inside the interior 14. In accordance with the invention, the hydrogen capture medium 100 is of a hydrogen capture material which may be a metal, e.g. a metal in elemental metallic form, or a metal compound, e.g. a metal alloy.

In use, the hydrogen capture medium 100 would be contacted with gaseous hydrogen inside the interior 14 by feeding gaseous hydrogen into the interior 14 from beneath the packed bed of hydrogen capture medium 100, e.g. in the manner described below with reference to Figure 1 , preferably such that gaseous hydrogen thus fed into the interior 14 fluidizes the hydrogen capture medium 100, respectively for hydrogen of the gaseous hydrogen to be captured (through adsorption and/or absorption), and thus stored, by the hydrogen capture medium 100, in accordance with the method of the first aspect of the invention, or for hydrogen previously captured by the hydrogen capture medium by adsorption and/or absorption to be desorbed and thus recovered from the hydrogen capture medium 100 as gaseous hydrogen, in accordance with the method of the second aspect of the invention.

The tank 12 comprises a base 16 that provides a gas dispersal system, which is also referenced by reference numeral 16. The gas dispersal system 16, in turn, comprises a lower base member 16.1 and an upper base member 16.2 of the tank 12. The upper base member 16.2 is vertically spaced from the lower base member 16.2 in the illustrated configuration of the tank 12.

The lower base member 16.1 and upper base member 16.2 define a gaseous hydrogen feed chamber 16.3 therebetween, below the interior 14.

The upper base member 16.2 is apertured, defining a plurality of inlet openings 16.4 (only some of which are referenced, by way of example). The openings 16.4 are provided with nozzles, as described hereinafter, noting that the provision of such nozzles is optional, but preferred.

Gaseous hydrogen that is in use fed into the gaseous hydrogen feed chamber 16.3 can thus pass into the interior 14 through the openings 16.4. The tank 12 further comprises a roof 22 and side walls 24 that extend between the roof 22 and base 16.

The side walls 24 comprise a cylindrical portion 24.1 and an optional flared portion 24.2, thus defining lower, cylindrical and upper, flared portions of the interior 14. Flaring of the upper, flared portion of the interior 14 may in use serve to slow the rise of gaseous hydrogen and particles of the capture medium that in use rise inside the interior 14 such that the medium particles fall back down into the body of the tank 12.

In the roof 22 of the tank 12 an outlet 30 is defined, leading into an outlet conduit 54 which will be described in more detail below.

The outlet 30 is optionally shielded from direct gas contact and from the hydrogen capture medium 100 by a cone shaped baffle or shield 28 which projects centrally downwardly from the roof 22.

The baffle 28 defines apertures (not shown) around its upper edge to allow passage of gaseous hydrogen therethrough. The apertures are fitted with filters (not shown) capable of preventing hydrogen capture medium from leaving the tank 12 through the outlet conduit 54. Typically, the filter is configured to prevent passage of particles larger than about 1 micron.

The upper base member 16.2 of the gas dispersal system 16 is shown in more detail in Figure 2.

As mentioned above, the openings 16.4 in the upper base member 16.2 may be mounted with nozzles. Such nozzles may, for example, be Tuyere-type nozzles, fitted within the tank 12 such that they extend through and project beyond the upper base member 16.2, thereby preventing hydrogen capture medium held in the tank 12 from falling through the upper base member 16.2 under the effect of gravity and thus into the gaseous hydrogen feed chamber 16.3.

More specifically, as shown in Figure 2, each opening 16.4 may open into a feed conduit 16.5 and each opening 16.4 and its associated conduit 16.5 may be covered by an inverted cone-shaped diverter 16.6 which would be mounted to the feed conduit 16.5 of its associated opening 16.4.

Each diverter 16.6 comprises a conical body that terminates in an apex. The apex of each diverter 16.4 is spaced above an outlet of their associated inlet conduits 16.5, such that the body of each diverter 16.6 extends downwardly and partly covers their associated inlet conduits 16.5. Thus, a gas supply mouth 16.4 that circumscribes each inlet conduit 16.5 is defined by each diverter 16.6.

It will be appreciated that the abovementioned configuration provides for gaseous hydrogen that is fed into the interior 14 to be directed operatively downwardly onto the upper base member 16.2 as opposed to operatively upwardly into the interior 14. Thus, accumulation of hydrogen capture medium 100 on the upper base member 16.2 is prevented, and preferred fluidization of the hydrogen capture medium 100 is promoted. Egress of hydrogen capture medium through the openings 16.4 is also prevented.

As mentioned above, the tank 12 has an outlet 30 in its roof 22, which leads into an outlet conduit 54.

The outlet conduit 54 branches - through a hydrogen product gas outlet, into a hydrogen product gas conduit 56, from which hydrogen product gas can be withdrawn, or released, from the interior 14, and through a gaseous hydrogen recirculation outlet, into a gaseous hydrogen recirculation conduit 58, along which gaseous hydrogen recovered, e.g. withdrawn or released, from the interior 14 may be recirculated, as recirculated gaseous hydrogen, to the interior 14 and therefore to the hydrogen capture medium 100.

The hydrogen product gas conduit 56 is provided with a valve 60, which is a hydrogen product gas release valve, to allow withdrawal of hydrogen product gas from the interior 14 based on the pressure inside of the interior 14 when desorption of hydrogen from the hydrogen capture medium is effected, as discussed below in more detail.

More specifically, the valve 60 is a pressure relief valve, configured automatically to release gaseous hydrogen from the interior 14 above a predetermined release pressure, more particularly at a hydrogen product gas release pressure. The valve 60 may also be selectively opened or shut.

Release of gaseous hydrogen from the interior 14 at the hydrogen product gas release pressure would typically in use only occur from the pressurized condition of the tank 12, as hereinafter described, to release hydrogen product gas from the tank 12 in performing the method of the second aspect of the invention. In performing of the method of the first aspect of the invention, i.e. in effecting adsorption and/or absorption of hydrogen, the valve 60 would typically be shut.

During performance of the method of the second aspect of the invention, i.e. in effecting desorption of hydrogen, the valve 60 would typically operate, or be set as, as a pressure relief valve or would be controlled to be open or shut by the control system hereinafter described, at the hydrogen product gas release pressure.

The gaseous hydrogen recirculation conduit 58 has a valve 61 similar to the valve 60, which is a gaseous hydrogen recirculation valve.

The valve 61 is also a pressure relief valve that automatically releases gaseous hydrogen from the interior 14 above a predetermined release pressure, more specifically at a gaseous hydrogen recirculation pressure. The valve 61 may also be selectively opened or shut.

Configuration of the valve 61 is such that the gaseous hydrogen recirculation pressure is at or above a predetermined contact pressure, and more specifically at a gaseous hydrogen recirculation release pressure, at which gaseous hydrogen fed into the interior 14 is to be contacted with the hydrogen capture medium 100, selectively to store hydrogen in and recover hydrogen from the hydrogen capture medium, thereby to maintain the predetermined contact pressure inside the interior 14. As herein described the predetermined contact pressure would be a pressure at which, at a corresponding predetermined contact temperature, adsorption and/or absorption of hydrogen by the hydrogen capture medium is promoted.

During performance of the method of the first aspect of the invention, i.e. in effecting adsorption and/or absorption of hydrogen, the valve 61 would typically function as a pressure relief valve, to establish and maintain the predetermined contact pressure through intermittent or continuous release of gaseous hydrogen, and more specifically excess gaseous hydrogen, from the interior 14 when the pressure inside the interior 14 reaches the gaseous hydrogen recirculation release pressure. During performance of the method of the second aspect of the invention, i.e. in effecting desorption of hydrogen, the valve 61 would typically be open, to allow for free and continuous recirculation of gaseous hydrogen from and to the interior 14.

Therefore, in use, with reference to the valve 61 , to store hydrogen in the hydrogen capture medium 100 at the predetermined contact pressure that promotes such storage, in accordance with the method of the first aspect of the invention, continuous feeding of gaseous hydrogen into the interior 14 would result, without any release of gaseous hydrogen from the interior 14, in the pressure inside the interior 14 increasing. Such pressure increase would continue until the predetermined contact pressure that promotes hydrogen storage is reached or exceeded, and the gaseous hydrogen recirculation pressure is thus reached, with gaseous hydrogen then being released from the interior 14 by the valve 61 to maintain the predetermined contact pressure inside the interior 14. The valve 61 is therefore the means by which the pressure inside the interior 14 of the tank 12 is regulated for achieving and maintaining the predetermined contact pressure for hydrogen storage. The valve 60 would in such a case be shut.

The valve 61 is therefore the means by which the pressure inside the interior 14 of the tank 12 is regulated for achieving and maintaining the predetermined contact pressure for hydrogen storage by the hydrogen capture medium 100, and thus also determining the gaseous hydrogen recirculation pressure.

Furthermore, in use, with reference to the valve 60, to recover hydrogen stored in the hydrogen capture medium 100, in accordance with the method of the second aspect of the invention, continuous feeding of gaseous hydrogen into the interior 14 and release of hydrogen from the hydrogen capture medium 100 as gaseous hydrogen would result, without any release of gaseous hydrogen from the interior 14, in the pressure inside the interior 14 increasing. In a preferred embodiment in which the valve 61 is open in performing the method of the second aspect of the invention, such a pressure increase may extend across the entire system 10. Such pressure increase would continue, subject to continued withdrawal and recirculation of excess gaseous hydrogen through the valve 61 , until the predetermined contact pressure that promotes hydrogen storage is reached or exceeded, which would typically be the same as the hydrogen product release pressure, with gaseous hydrogen then being released from the interior 14 by the valve 60, which would be set as a pressure relief valve.

The valve 60 is therefore the means by which the pressure inside the interior 14 of the tank 12 is regulated for achieving and maintaining the predetermined contact pressure for hydrogen recovery from the hydrogen capture medium 100, and thus also determining the hydrogen product gas release pressure.

As mentioned above, the valves 60, 61 may be configured such that they may be selectively shut or fully opened, typically by the control system hereinafter described, against any release of gaseous hydrogen.

As also mentioned above, when performing the method of the first aspect of the invention, the valve 60 would be shut while the valve 61 would operate as a pressure relief valve at the gaseous hydrogen recirculation pressure, to maintain the predetermined contact pressure for hydrogen storage inside the interior 14.

As also mentioned above, when performing the method of the second aspect of the invention, the valve 61 would be fully open while the valve 60 would operate as a pressure relief valve at the hydrogen product gas release pressure, to maintain the predetermined contact pressure for hydrogen recovery inside the interior 14

The recirculation conduit 58 is, downstream of the valve 60, met by a fresh gaseous hydrogen feed conduit 62, downstream of which the recirculation conduit 58 leads, as a pump inlet conduit 64, to a gas recirculation pump 66.

The fresh gaseous hydrogen feed conduit 62 is also provided with an open/shut valve 67 to control feed of fresh gaseous hydrogen from a fresh gaseous hydrogen supply source.

A gaseous hydrogen feed outlet conduit 68 leads from the recirculation pump 66, to a three-way valve 70 having an inlet 70.1 , a first outlet 70.2, and a second outlet 70.3. A heating device gaseous hydrogen supply conduit 78 connects the first outlet 70.2 to a gaseous hydrogen heating device 80. A cooling device gaseous hydrogen supply conduit 82 connects the second outlet 70.3 to a gaseous hydrogen cooling device 84.

A heating device outlet conduit 86 and a cooling device outlet conduit 88 lead from the heating device 80 and the cooling device 84 respectively, and connect to a manifold conduit 90, respectively through first and second inlet openings 92, 94 of the manifold conduit 90.

An outlet 96 of the manifold conduit 90 provides a gaseous hydrogen feed chamber inlet opening in the lower base member 16.1 of the gas dispersal system 16, thus leading into the gaseous hydrogen feed chamber 16.3.

The system 10 further includes a control system (not illustrated), for controlling operation of the system 10.

The control system is configured to control and operate the recirculation pump 66 to supply gaseous hydrogen, including recirculated gaseous hydrogen when supplied to the pump 66 along recirculation conduit 58 and fresh gaseous hydrogen supplied to the pump 66 along feed line 62, to the interior 14 at a volumetric feed flow rate, and typically at a predetermined supply pressure, sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the interior 14.

Configuration of the control system in this regard is such that fresh gaseous hydrogen is only used to supplement recirculated gaseous hydrogen to the extent necessary to achieve and maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the interior 14.

The control system is also configured to measure the volumetric rate of supply of fresh gaseous hydrogen along the fresh gaseous hydrogen supply conduit 62, that is required to maintain the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the interior 14, and to conclude that the hydrogen capture medium is saturated with hydrogen if such a supply is or approximates zero (0).

The control system is also configured to measure the volumetric rate of recovery of gaseous hydrogen, and more specifically excess gaseous hydrogen, from the interior 14 along the recirculation conduit 58, over time, and to conclude that the hydrogen capture medium is saturated with hydrogen if such volumetric rate of recovery over time approximates or is equal to the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the interior 14.

The control system is also configured to measure the temperatures of the gaseous hydrogen that is supplied to the gas dispersal system 16 (T1) and of the recirculated gaseous hydrogen that is recovered along the recirculation conduit 58 (T2), and to conclude that the hydrogen capture medium is saturated with hydrogen if there is no differential, or not a significant differential (T3, as T1 minus T2), between such temperatures.

The control system is also configured selectively to - shut the hydrogen product gas release valve and set the gaseous hydrogen recirculation valve to operate as a pressure relief valve at the gaseous hydrogen recirculation pressure, when performing the method of the first aspect of the invention, and open the gaseous hydrogen recirculation valve and set the hydrogen product gas release valve to operate as a pressure relief valve at the hydrogen product gas release pressure, when performing the method of the second aspect of the invention.

The control system is an electronic control system, configured to perform the abovementioned control, operation, measuring, and concluding electronically, using an electronic processing unit that is in communication with the recirculation pump 66 and respective flow and temperature sensors that measure the volumetric rate of supply of fresh gaseous hydrogen to the hydrogen capture medium, the volumetric feed flow rate at which gaseous hydrogen is supplied to the interior, the volumetric rate of recovery of gaseous hydrogen from the interior 14 through the gaseous hydrogen recirculation outlet, and the temperatures of gaseous hydrogen fed to the interior 14 and of the recirculated gaseous hydrogen.

The control system is also configured to discontinue pumping of gaseous hydrogen to the interior 14 based on the conclusion being drawn that the hydrogen capture medium 100 is saturated with hydrogen. Such configuration may be for discontinuation to be effected at a desired storage pressure inside the interior 14, which may be or may exceed the predetermined contact pressure. Thus, the control system would effectively close or close off the interior 14 and provide a pressurized condition of the system 10, wherein the interior 14 comprises hydrogen saturated capture medium and pressurized gaseous hydrogen at the storage pressure.

The control system is further configured, from the pressurized condition of the system 10, to withdraw pressurized gaseous hydrogen from the interior 14 and recirculate such hydrogen to the gas dispersal system 16 at a volumetric feed flow rate and at a predetermined supply pressure sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the hydrogen storage chamber, at the predetermined contact temperature at which, at the corresponding predetermined contact pressure, release of hydrogen from the hydrogen capture medium 100 is promoted, to monitor pressure inside of the interior 14, and to release hydrogen from the interior through the gas product outlet line 56 by opening valve 60 if the hydrogen product gas release pressure is detected. Such release may, however, be automatic at the hydrogen product gas release pressure, in which case the control system would be configured to open the hydrogen product gas release valve 60 for operation as a pressure relief valve as hereinbefore described.

In use, to effect hydrogen capture and storage, fresh gaseous hydrogen is pumped / released into the fresh gaseous hydrogen feed conduit 62 at first pressure, that is typically equal to the predetermined contact pressure, as determined by the type of hydrogen capture medium 100 and the predetermined contact temperature at which contacting of the gaseous hydrogen with the hydrogen capture medium 100 would be effected, from a hydrogen supply source, by opening the valve 67.

The fresh gaseous hydrogen feed conduit 62 delivers the fresh gaseous hydrogen to the recirculation pump 66 along the pump inlet conduit 64 which, in turn, delivers the gaseous hydrogen, at the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the interior 14, to the three-way valve 70 at a second pressure, being a predetermined supply pressure, that preferably exceeds the predetermined contact pressure.

In effecting hydrogen capture and storage, gaseous hydrogen is directed by the valve 70 to the cooling device 84 along the cooling device gas supply conduit 82, to be cooled to the predetermined contact temperature at which adsorption/absorption of gaseous hydrogen by the capture medium 100 would be promoted, whether in combination with independent cooling of the hydrogen capture medium 100 or not. While, in the case of absorption/adsorption, cooling is more typical, the possibility that heating may occur using the heating device is not excluded.

Heating or cooling of the gaseous hydrogen to be fed into the interior 14 is effected so that the gaseous hydrogen would act as working fluid to achieve and/or maintain the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture medium 100.

Cooled gaseous hydrogen then passes, at the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the interior 14 and at the predetermined supply pressure, along the manifold conduit 90 and is delivered to the gas inlet chamber 26, from where it feeds into the interior 14 through the openings 16.4 and associated nozzles described above, thus contacting and fluidizing the hydrogen capture medium bed 100.

Contacting the hydrogen capture medium 100 with cooled gaseous hydrogen, in addition to achieving and maintaining the predetermined contact temperature, prevents an excessive rise in temperature in the hydrogen capture medium 100 which may otherwise be caused by an exothermic reaction that takes place between the hydrogen capture medium 100 and the gaseous hydrogen as hydrogen is absorbed by the hydrogen capture medium 100. Contact between the gaseous hydrogen and the fluidized hydrogen capture medium 100 causes hydrogen to be adsorbed/absorbed by the capture medium 100. Excess gaseous hydrogen, comprising unabsorbed hydrogen, rises beyond the capture medium bed 100 and leaves the interior 14 through the outlet 30, being directed along the recirculation conduit 58 to be recirculated to the interior 14 by the recirculation pump 66, in this respect optionally combining with fresh gaseous hydrogen from the fresh gas supply source along supply line 62, to maintain the volumetric feed flow sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the interior 14.

When the control system concludes that the hydrogen capture medium 100 is saturated with hydrogen, as hereinbefore described, and the desired storage pressure is detected inside the interior 14, the control system discontinues supply of gaseous hydrogen to the interior 14, thus closing or closing off the interior at the storage pressure. Thus, a transportable tank 12 comprising hydrogen stored in saturated solid capture medium 100 and pressurized residual gaseous hydrogen is provided as a storage condition of the system 10.

To effect hydrogen recovery, with the system 10 in the storage condition as described above, pressurized gaseous hydrogen is withdrawn from the storage camber 14 along the recirculation conduit 58 by opening the valve 61 fully and, using the recirculation pump 66, is delivered by the pump 66 at the volumetric flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the interior 14 and at the predetermined supply pressure to the valve 70 which directs the gas to the heating device 80, where it is heated to the predetermined contact temperature for hydrogen recovery from the hydrogen capture medium 100, subsequent to which it is fed into the interior 14 along the manifold conduit 90 and gas dispersal system 16, such that the gas contacts the bed of capture medium 100 preferably such that the bed 100 is fluidized. Thus, again, the gaseous hydrogen to be fed into the interior 14 is heated so that it would act as the working fluid in achieving and/or maintaining the predetermined contact temperature inside the interior 14 in contacting the gaseous hydrogen with the hydrogen capture medium 100.

Contact between the heated gaseous hydrogen and the saturated capture medium 100 results in gaseous hydrogen being released from the capture medium. Continued recirculation, at the volumetric feed flow rate sufficient to fluidize and/or maintain fluidization of the hydrogen capture medium and/or achieve and/or maintain the predetermined contact pressure inside of the interior 14, of initial residual gaseous hydrogen and gaseous hydrogen released from the capture medium 100 (i.e. “desorbed” gaseous hydrogen), results in an accumulation of hydrogen inside the interior 14 and a resulting rise in pressure.

Detection, by the control system, of such a rise in pressure inside the interior 14 would result, if a threshold pressure is reached, such as the hydrogen product gas release pressure, in the control system opening the valve 60, or would result in the valve 60 being opened automatically if it is set as a pressure relief valve once the pressure reaches the hydrogen product gas release pressure, for product gaseous hydrogen to be discharged from the interior 14.

The tank 12 is made of a composite material and can contain 3 Mpa (30 atm), or even up to 35MPa (350 atm), of pressure. The tank 12 may, instead, be made of any other suitable material.

EXAMPLE

Introduction

THIS EXAMPLE describes the test protocol followed to prove the concept of the invention of this first to third aspects of the present invention.

This test protocol gives the step-by-step details of the tests conducted on a particular metal hydride, lanthanum pentanickel (LaNi₅) alloyed with tin (Sn) (“metal alloy”), as hydrogen capture medium, and the results recorded during testing to exemplify the operation of the invention exploiting a fluidized particulate metal hydride with gaseous hydrogen as the heat transfer working fluid and fluidizing gas.

The metal alloy reacts with hydrogen to produce a hydride and heat, which must be withdrawn through cooling to allow the reaction to run to completion. In accordance with the invention this cooling is achieved by pre-cooling the hydrogen used to fluidise the metal alloy. Conversely, the metal hydride of the metal alloy (i.e. the metal alloy in a condition in which it stores hydrogen), when heated, produces in free hydrogen gas and the metal alloy. The heating is in accordance with the invention effected by heating the hydrogen used to fluidize the hydride.

To show that -

1) fluidisation of the metal alloy, in particulate format, in a container, such as a tank, with hydrogen as the fluidisation medium, is an effective way of performing adsorption and/or absorption of hydrogen by the metal alloy (by forming a hydride of the metal alloy);

2) fluidisation of the resulting metal hydride of the metal alloy is an effective way of performing desorption of hydrogen from said hydride; and

3) hydrogen can effectively be used as the working fluid to transfer and remove heat to and from the hydrogen capture medium.

Choice of hydrogen capture medium

The metal alloy / hydride used in these experiments (LaNi^Sno i).

In order to set the baseline performance, the materials that were used were scrutinised, specific to the precise alloy. The baseline was established from “Metal hydride hydrogen compression: recent advances and future prospects”, from 2016, by authors Volodymyr A. Yartys (Institute for Energy Technology), Mykhaylo Lototskyy (UWC), Vladimir Linkov (UWC), David M. Grant (University of Nottingham) and others.

Figure 3 shows the plot used by these researchers to determine the concentration of H in their metal hydride. This metal hydride (LaNi^Sno i) is the same alloy used in the presently reported tests. It shows that there is 141 .4 NL/kg H present in the metal hydride between a temperature of 130 °C and 25°C. This is once full absorption has taken place, starting in the form LaNi4.9Sno.1H6 before desorption has started. In the paper “Improvement of hydriding kinetics of LaNi5-type metal alloy through substitution of nickel with tin followed by palladium deposition”, the authors of that paper demonstrate how palladium (Pd) deposition influences that performance of the metal hydride. See Figure 4 in this regard.

Through the analysis of the abovementioned academic literature sources, the baseline for the metal hydride to be used was set.

Figure 5 shows the pressure, concentration and temperature (PCT) diagram for the metal hydride that was used in the presently reported tests and provides the clear absorption and desorption curves for the alloy at temperatures of 20 °C and 60 °C.

Technical details of experimental setup

System concept description

The system used to perform the tests herein reported consisted of a network of high pressure 316SS tubing, looped through a gaseous hydrogen recirculation pump, a gaseous hydrogen heat exchanger coil, a metal hydride reactor tank, and then past a junction point back into the line from a fresh hydrogen supply source (hydrogen cylinder) to the pump, creating a loop for closed cycle system testing.

Four points were measured for pressure and temperature. These were -

• Point 1 - upstream of the pump

• Point 2 - after the pump, before the heat exchanger coil

• Point 3 - after the heat exchanger coil, before the metal hydride fluidisation tank

• Point 4 - after the tank

Metal hydride fluidization tank

The metal hydride fluidisation tank (referred to in this example as “reactor” from time to time) consisted of a 1000 mm long tube, 50mm in diameter (OD) and a thickness of 2mm. It had a 250 mm base plate of 5mm thick at the bottom and an inlet port and chamber that made up about the bottom 50mm of the reactor. 50mm above the bottom, a separator plate with 4 fluidisation nozzles, each having 8 equidistant holes on the sides, in a 150° downward direction from vertically up, were provided. Reference is in this regard made for Figure 6.

Metal hydride

The metal hydride being tested was, as indicated above, an alloy of lanthanum pentanickel (LaNi5) with tin (Sn), of which alloy the molecular formula is LaNi4.9Sno.i .

The density of the metal hydride is somewhere between 7950 and 8210 kg/m3. Based on research literature, -8080 kg/m³ was used for calculation purposes. This density was not experimentally confirmed.

The metal hydride wastaken to have the properties set out in table 3:

Table 3: Properties of the metal hydride used in experiments

Working/heat transfer fluid

Gaseous hydrogen was used as the working fluid for heat transfer. A tube coil was installed for use as an indirect heat exchanger, to transfer heat to the gaseous hydrogen. A 9 m coil, with an approximate diameter of 210mm, made from 8mm OD, 316SS tube, was installed as a heat exchanger after the pump outlet.

Methodology

The methodology for testing is described here in this section, including the sensors, data acquisition system used, and various other relevant aspects of the test setup.

Test facility

A test room and control room were constructed for the purpose of the tests.

The test room was a 3 x 3m (9 m²) room, with insulation panels for walling and a lifted room region for ventilation of buoyant H2 gas, should there be discharge or leakage.

An adjacent control room comprising a 3 x 3m (9 m²) room, totally sealed from the outside to ensure no potential ingress of hydrogen gas that could create a safety hazard, was also constructed.

Test setup

A test setup was built using the following material:

• 8mm OD 316 SS tubing (ASTM 269), suitable for up to -400 bar.

• Double ferrule compression 316SS fittings for high pressure joint application, also up to -400 bar

• Various components including needle valve, ball valves, check valves, pressure regulating valves, pressure gauges, pressures sensors, temperature sensors, temperature gauges, the MH fluidising reactor, gas circulating pump, H2 cylinder, main pressure regulator and filter elements.

A process and instrumentation diagram (P&ID) created for the test setup is provided as Figure 7. The following test setup description refers to Figure 7:

• ABSORPTION/ADSORPTION: During absorption, in this set up, no pressure relief valve (PRV) valve was present between the outflow from the fluidisation tank and the recirculation pump as will be the case usually. Rather, the predetermined pressure was set by adjusting the pressure of fresh gas supplied from the cylinder. This sets the tank pressure at the required level for absorption. The amount of “excess” hydrogen gas flow through recirculating system from the tank was not constant. It varies according to how much hydrogen is being pumped into the fluidisation chamber less the amount absorbed into the metal hydride at any point in time. The rate of absorption is dependent on pressure and temperature of the system. The temperature of the system is reduced by pre-cooling the hydrogen by passing it through the heat exchanging stainless steel coil to a temperature where the metal hydride is at the most optimal temperature for absorption.

• The pump outflow of hydrogen is essentially constant and is sufficient to maintain fluidisation of the metal alloy in the tank and will draw any extra hydrogen needed to achieve this from the fresh gas supply via needle valve V1 and through the mass flow meter QM1 . The primary means of knowing when the tank is “full” is when the inflow of fresh gas required to do this is zero (or a predetermined low flow rate) through valve V1 and gas flow meter QM1. At that point no hydrogen is being absorbed into the metal alloy and all the gas being pumped to fluidise the medium is passing out of the tank through the pressure relief valve to the recirculation system.

• In practice a comparison of feed flow rate and flow rate out of the tank could also indicate a “full” status when the two are approximately the same. In these experiments, we did not monitor flow rates at those points.

• A third way to determine full is when there is no further exothermic reaction happening - so the temperature of hydrogen entering and leaving becomes the same, (ie in this setup T3 and T4 become essentially equal).

DESORPTION: During desorption, the control is different. The relief valve on the circuit on diagram is set to a low pressure sufficient to maintain recirculation flows but low enough to allow desorption and valves V1 and V2 are tight shut. The pump sucks a sufficient essentially constant volume per time out of the previously pressurised tank to recirculate, heat treat and cause fluidisation - irrespective of pressure in the tank. As the hydride desorbs hydrogen, the pressure in the tank therefore increases and the pressure relief valve opens at the predetermined pressure to allow hydrogen to leave the system for use. The tank is empty when there is no more hydrogen desorbing and so the pressure in the tank falls below that required to open the relief valve. During desorption, the endothermic reaction of desorption removes heat from the incoming fluidising hydrogen (i.e.: T4 is lower than T3). When the tank is “empty” the temperatures of hydrogen entering the tank and leaving it therefore tend towards equalising.

Gaseous hydrogen

The gaseous hydrogen used for the tests was hydrogen 5.0 (UN1049 - Hydrogen Compressed) rated at 173 bar at 20 °C, 0.62 kg H₂.

Material safety data sheet reference from Air Products for this gas product is MSDS 067A. The tank was filled January 2023 and specified an expiry date in 2028. The UN1049 hydrogen product is 99.999% (5N) hydrogen with trace amounts of CO2, N2 and other non-combustible gases.

An Afrox Scientific gas regulator W019220, rated for H2 use, was used as the main pressure regulator to the system, capable of 300 bar max input and 16 bar max output.

Recirculation pump

The pump used for the circulation of the gaseous hydrogen was a Maximator Air-amplifier GPLV-5, which is a single stage, double acting, positive displacement pump with a pressure ratio capability of up to 1 :5 (1 bar to 5 bar). It is an ATEX rated pump due to its non-electrical drive nature, being an air driven pump. The pump can be driven at various input (drive) pressure levels ranging from a minimum of 4 bar to maximum of 10 bar. At the desired max flow rate of 120 L/min, this pump consumes more than 300 L/min of air at 4 bar. It was noted that there was a chance of a minute amount of gaseous hydrogen that would leak through the piston sleeve and be blown out by the driven air exhaust. This was not quantified in the tests herein reported.

A petrol driven compressor was acquired to ensure that the circulation pump can be run at required speed for continued operation during tests. The compressor has a 150 L tank and can supply 360 L/min continuous at 8 bar.

Heating and cooling of gaseous hydrogen

The cooling and heating of gaseous hydrogen was done primarily through a heat source of heat sink, with a long coil of 8mm tube submerged in it. The tube was made from 3x 3m pieces of ASTM 269, 316 SS tube, with helix diameter of 210 mm and a pitch of roughly 25mm.

Cooling method

Cooling of the gaseous hydrogen was accomplished using an indirect heating method. This involved submerging a coil of 9m length into a bucket of ice water at 0 °C.

Heating method

Heating of the gaseous hydrogen was done indirectly, using two heating methods:

1 ) A 9m coil submerged in an oil bath heated by an element (hot water urn)

2) Heat tracing on the out-going section of the tube from the heat exchange coil.

Method 1 : Hot Oil bath

• Method: oil heating method

• Brand: Cryspa Gold Premium Sunflower Frying Oil

• 230 C boil point; 232 deg C smoke point

• Specific Heat: 3.1927 kJ/kg.K

• Volume heated: 19.5 Litres

• Heating mechanism: 3.5 kW hot water heating urn In addition to the hot oil bath, the outgoing tube of the heat exchanger coil was wrapped in heat tracing with an output of 22 W/m heat. The heat tracing was wound directly and tightly against the tube of approximately 700mm in length. 3.5 m of heat tracing was used, totalling and additional 77W of heat input into the tube. The heat tracing raised the temperature of the pipe to roughly 130-140 °C and was able to increase the temperature of the H2 from around 90 °C to ~120 °C.

Test data collection equipment

The test equipment included a data acquisition unit, pressure and temperature sensors and a flow meter. Additional pressure gauges and temperatures gauges were used for visual indication of temperature and pressure. Sensors and calibration

The following sensors were used for the experiment:

Table 4: Sensors used

* 6a and 6b sensors used the same channel. Due to both P2 and P3 being on the same side of the pump, and due to the DAQ unit used only having 8 analogue 4-20 mA signal channels.

Other indicator gauges and sensors were used as follows:

Table 5: Other indicator gauges and sensors

Each of the temperature sensors came with 3 m of cable, prepared and crimped to the probes. Pressures sensors used instrumentation cable (0.75 m², 4 core) and were wired to the terminals of each sensor, down to the termination point on the electrical panel.

Gas flow meter

The gas flow meter used was a Universal Flow Monitors manufactured FlowStream OFM Multigas series flow meter, with Part No. OFM-EF-2P56-N-X1 A-D17. It is a Multigas flow meter, capable of measuring air, argon, CO2, helium, hydrogen, methane, nitrogen and oxygen (“OFM”). It has a housing made of anodized Aluminium (“E”) with A-Excellent rating for hydrogen, with seals made of Viton (“F”), a fluoropolymer elastomer, which has an A-Excellent rating in compatibility with hydrogen gas. The “N” dictates that the calibration gas used was nitrogen gas. The X1A describes that it delivers a 4-20 mA signal and the D17 that it comes with 17 feet of cable (5.18m). The sensor specification sheet describes capability of 1 -100 SLPM air measurement and 1-200 SLPM for hydrogen.

Electronic scale

An electronic scale (Scaletronics HCS3033D) with accuracy of 0.1 gram was used to weigh the metal alloy used for the experiments. Data acquisition unit/ system

The data acquisition system used was a USB-1208FS-Plus, 12 bit, 12 channel data acquisition unit from Measurement Computing. There are 8 analogue input (Al) channels that can take -10 to 10V signals. For interfacing with the sensors, 250 Ohm resistor were bridged between the 10V Al input terminals of the DAQ in order to read the 4-20 mA signals of the pressure, temperature and flow sensors, creating a 1 -5 V signal.

All sensors were used on 11 -bit Single ended (SE) function for data recording.

Table 6: Details of the DAQ unit used for data collection and recording

Where applicable, these accuracies and precision of the DAQ and the sensors were considered. For SE application, only 11 -bit measurement is applicable. The data recording and viewing software used was DAQami, downloaded from Measurement Computing.

The sampling rate initially was set at 1 Sps (although Test 1 was done at 50 Sps). However, it was seen that more resolution is required and this was increased to 2 Sps for Test 3 and Test 4, and ultimately to 10 Sps for Test 5 and Test 6, and onwards. This latter resolution allowed the visibility of the transient pressure created by the pump.

Material compatibility

Generally, stainless steel 316 was used for the components and the wetted areas of sensors. Where different materials were used, it was ensured that the materials are compatible in use with hydrogen gas. Some of the materials used included:

• Viton - seals on flow sensor

• PTFE - seals on valves

• Anodized aluminium - flow sensor housing

• Stainless steel 316 or 316 L - all tubing, joints, double compression fittings, valve bodies.

• Copper seals - seals for instrument seal interface (standard for instrumentation fittings)

Handling of the alloy metal hydride

The metal hydride was understood to be pyrophoric when coming into contact with air. Specifically, it was understood that the metal hydride that was used was activated LaNi4.9Sno.1-

An inert atmospheric chamber (IAC) was constructed, with sealed glove access in which to handle the metal hydride and pre-filled with Argon gas.

Within this chamber, the metal alloy which was in crystalline form was ground down into a fine powder. The tank was placed on the scientific scale, the instrument was zeroed and the alloy powder was gradually filled into the tank until the desired experimental weight was obtained.

During the assembly, 500.2g of the metal hydride powder was loaded into the metal hydride reactor, thus establishing a bed thereof, before the reactor was sealed.

Test protocol

The following were followed in sequence.

Filling cycle (hydrogen adsorption/absorption)

For the Fill Cycle or Absorption cycle for hydrogen into the metal hydride, the following steps were adhered to: 1 ) Set point 4 relief valve to ~6 Bar

2) Set gaseous hydrogen pressure regulator to ~6 bar.

3) Open valve V2

4) Close valves V3 and V4

5) Zero flow mass meter totaliser (press button A2 until “tot” displayed, then press and hold. After approximately 5 seconds cycling zeroes appear, keep holding until all zeros steady).

6) Place heat exchange coil in ice

7) Start recording of data

8) Open needles valve from gaseous hydrogen tank (V1 )

9) Switch on pump

10) Watch Q output - when it is zero, tank is full

11 ) Switch off pump

12) Wait 5 min, then stop data recording

13) Label data set

Emptying cycle (hydrogen desorption)

For the Empty Cycle or Desorption cycle for hydrogen into the metal hydride, the following steps are to be adhered to:

1 ) Close needle valve (V1 )

2) Close valve V2

3) Open valves V3 and V4

4) Zero H flow meter (as above)

5) Place heat exchanger coil in hot oil containing tea urn

6) Set relief valve to ~2.5 Bar

7) Keep valve V4 tight shut

8) Start recording data

9) Switch on pump

10) When pressure P4 starts increasing indicating that desorption and fluidisation occurring, open V4 to discharge hydrogen through the flow meter QM1

11 ) Watch QM1 , T3 and T4 and P4. When tank is empty T3 is effectively equal to T4, QM1 is effectively zero and P4 falls to setting of relief valve (PRV) 12) Switch off pump

13) Wait 5 min, then Stop data recording

14) Label data set

Test results

The following test cycles were performed - which resulted in the test protocol above which was used in tests 4 and 5.

• Test 1 - Flow determination of pump in closed cycle test

• Test 2 - First Absorption test

• Test 3 - First Desorption test

• Test 4 - 2^nd Absorption and Desorption Test

• Test 5 - 3^rd Absorption and Desorption Test, using automatic pressure relief blow off and then manual pulsatile relief.

In this report, only test 4 was thoroughly analysed.

Table 7: Details of the tests including sample rate and scaling factors used

Tests 0, 1, 2, and 3

These tests, namely tests 0, 1 , 2 and 3 were the initial test runs to fine tune various parts of the test setup and ensure proper data logging has occurred.

• Test 1 was the initial functional check test, with the first charge and discharge test, conducted on 3 June 2023.

• Test 2 was the first proper heat run test, followed by charge and discharge test, conducted on 6 June 2023.

• Test 3 was a charge and discharge test run with additional checks on sensors, done on 8 June 2023.

Test 4 (split into parts A and B)

Test 4A was an absorption test - selected sensor readings are presented in Figure 8.

Note the temperature of hydrogen entering the tank (at T3 - blue/top-to-middle trace) was initially high as test three had just been completed to empty the tank.

The cooling by passing the hydrogen through the coil immersed in water and ice rapidly brings the temperature down.

As would be expected, while the input hydrogen was warm, there was no flow of fresh hydrogen from the storage tank into the system (yellow/bottom trace).

As soon as the recirculating hydrogen started cooling, hydrogen acting as a working fluid cooled the metal alloy in the tank and it therefore started taking up hydrogen.

This allowed fresh hydrogen to flow into the system (yellow/bottom trace) since insufficient hydrogen was being recirculated to maintain fluidization.

The T4 temperature of hydrogen leaving the tank and re-circulating (red/middle-to-top trace) rose as soon as the exothermic reaction between the alloy and the hydrogen began. As the amount of unreacted metal alloy diminishes, T4 slowly falls until at the “tank full” state they are essentially equal. Note that at this point the flow of new gas into the system also falls to near zero. The residual slight difference between T3 and T4 reflects heat stored in the metal hydride which has not yet been cooled by inflowing cool hydrogen.

Test 4B was a desorption test - selected sensor readings are presented in Figure 9.

As in test 4A the input hydrogen temperature (T3) starts low (at the end of test 4A) and rapidly climbs as the hydrogen is heated in the coil immersed in hot oil. Despite being fed with warming hydrogen, the temperature of the gas leaving the tank initially falls. This is as expected as it reflects the endothermic reaction of desorption of hydrogen from the metal hydride when the pressure in the tank was lowered. As expected hydrogen was then released via the pressure relief vlave through the flow meter to waste (yellow/bottom trace).

This in practice would be hydrogen available for use on emptying the tank. The pulsatile nature of the yellow trace reflects the pulsatile pump we used to cause fluidization - so each stroke of the pump caused better fluidization and a burst of released hydrogen.

Unfortunately, the filters that were used were not fine enough and the high hydrogen flow rates caused entrainment of the powdered metal hydride which made the relief valve “sticky”. The resultant flow was therefore not continuous but in discrete bursts at high flow rates.

In comparing overall results to expected results, with reference to Figure 10, as can be seen in the sorption curves for this metal hydride, the approximate maximal amount of hydrogen that would be expected to be absorbed / adsorbed by 500 g of the hydride when it is taken from zero atmospheric pressure to 6 bar (7 bar absolute) is 80NI (160/kg).

The approximate maximal amount of hydrogen expected to be released when heated to 60 degrees and taken from that “full state” at 6 bar down to a pressure of 2 bar absolute is 72NL.

The actual amounts absorbed and desorbed were as shown in the table below. Table 8: Results of Sorption tests on Test 4 and the volumes of H2 measured

Test 4 proved all three of the objectives for this stage of the research. It was proven specifically that hydrogen can be used to fluidise a metal hydride and simultaneously to act as a heat transfer fluid to cause absorption and desorption of hydrogen by that metal hydrides at the expected gravimetric density.

It is of note that T4 exit temperature only reached 40 degrees during test 4B - implying that hydrogen that was recirculated was not adequately heated. As a result, during the subsequent test (test 5) where the hydride was heated to a higher temperature to ensure that the tank was fully empty a further 20.03 SL of hydrogen was recovered. This should be added to the hydrogen recovered during test 4B given a total recovery of 81 .9 SL which is then greater than that which was expected.

The fact that less hydrogen appears to have been put into the tank in test 4A than was recovered in total from tests 4B and 5.0 is similarly due to incomplete emptying of the tank in test 3.

Discussion of test results

The tests herein reported were conducted to prove the core conceptual features of invention, namely

1) fluidisation of the metal alloy in a container, with hydrogen as the fluidisation medium, is an effective way of performing adsorption / absorption of hydrogen by the metal alloy (forming a hydride);

2) fluidisation of the resulting metal hydride is an effective way of performing desorption of hydrogen from said hydride; and

3) hydrogen can effectively be used as the working fluid to transfer and remove heat to and from the metal hydride reactor. From the results of Test 4, it is believed that these objectives have been achieved since - a) the expected exothermic (absorption) and endothermic (desorption) profiles were shown; b) fresh gas flow was shown to be absorbed by the metal alloy in volumes as expected; and c) on desorption, pressure increased downstream of the tank as would be expected with hydrogen release from the hydride and outflow hydrogen was measure leaving the system as expected in test 4.

DISCUSSION

THE PRESENT INVENTION has multiple advantages that contributes toward seeking to meet the need identified in the background to the invention. These include that recirculation of gaseous hydrogen allows a sufficient volume of hydrogen gas to be contacted with the hydrogen capture medium to achieve fluidization and affords multiple opportunities for hydrogen to be adsorbed or absorbed by the hydrogen capture medium.

When any gas is used to fluidize a particulate solid, the gas initially rises through the material in a few columns and escapes the solid material without fluidizing it. In an open system with a limitless supply of gas (such as air) continued pumping over time achieves the fluidized state. With hydrogen being the gas, the system cannot be open as the objective is to contain hydrogen. If hydrogen was simply blown into the base of the container via a diffuser, the pressure of gas above the material would rapidly rise and prevent more hydrogen being introduced. This invention includes a pump which takes this uncaptured hydrogen off the top of the tank and re-introduces it to the bottom of the tank to allow adequate gas flow to cause fluidization and to re-expose the hydrogen to the medium to allow its ab or adsorption.

Typically, ab- or adsorption of hydrogen is an exothermic process and has been found to be slowed and even stopped by rising temperature of the hydrogen capture medium. To achieve maximal uptake, it has been found desirable to cool the hydrogen capture medium. This is usually achieved by building a cooling system into the tank. In this invention, the cooling and recirculation of hydrogen contacted with hydrogen capture medium, optionally combined with fluidization, provides an advantageously efficient approach of effecting temperature control.

Conversely, releasing the hydrogen from the hydrogen capture medium has been found to be promoted by heating the hydrogen capture medium. Again, the present invention avoids the need to employ a heating system in the tank, since the invention achieves heating by, instead, heating the recirculated hydrogen which heats the material as the hydrogen fluidizes it.

Fluidization is also advantageous from the perspective that hydrogen capture media, such as metal hydrides, typically fracture and become finer and finer particles which pack until hydrogen can no longer permeate between them to react with anything save the surface particles. Fluidization by its nature separates the partciles s that they become an emulsion within a bath of hydrogen achieving maximal contact each cycle. In addition, capture media such as metal hydrides require activation by means of exposure to high pressure hydrogen and / or mechanical fracturing by ball-milling. This changes the shape of particles to be more irregular so that they do not pack as tightly, thereby allowing the hydrogen to penetrate the material. This invention spaces the particles by fluidizing them so that they are surrounded by hydrogen - irrespective of their shape. Activation of the metal hydrides is therefore avoided.

While the invention has been described in detail with respect to a specific embodiment and/or example thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily conceive of alterations to, variations of and equivalents to these embodiments. Accordingly, the scope of the present invention should be assessed as that of the claims and any equivalents thereto, which claims shall be appended hereto upon completion of this patent application.

A significant advantage of fluidization of the capture medium is that the particles of the medium are separated from each other, thus allowing more intimate contact of hydrogen with the particles across their surfaces.

A further advantage of fluidization for temperature dependant processes is that fluidization has been shown to result in a very even distribution of temperature throughout the vessel with an absence of hotspots or cold spots - so that reaction is rapid and complete and controllable without formation of unwanted products because of such typical uneven temperatures in other systems.

Claims

1. A method of storing hydrogen in a hydrogen capture material capable of capturing and thus storing hydrogen therein through adsorption and/or absorption of the hydrogen on or by the hydrogen capture material from gaseous hydrogen, the method including contacting the hydrogen capture material in loose particulate format with gaseous hydrogen inside a pressure-tight vessel at a predetermined contact temperature and at a corresponding predetermined contact pressure that promote capturing and storing of hydrogen by the hydrogen capture material through adsorption and/or absorption of hydrogen on or by the hydrogen capture material from the gaseous hydrogen, such that the hydrogen capture material captures and stores at least some hydrogen through adsorption and/or absorption of hydrogen on or by the hydrogen capture material from the gaseous hydrogen as a result of such contact, wherein the hydrogen capture material in loose particulate format is fluidized by contact of the gaseous hydrogen with the hydrogen capture material; and the gaseous hydrogen acts as a working fluid to achieve and/or maintain the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture material.

2. The method according to claim 1 , which includes subjecting the gaseous hydrogen that is contacted with the hydrogen capture material to temperature treatment upstream of the vessel, selectively to cool or heat the gaseous hydrogen as may be required to achieve and/or maintain the predetermined contact temperature in contacting the hydrogen capture material with the gaseous hydrogen.

3. The method according to claim 2, wherein the temperature treatment selectively heats or cools the gaseous hydrogen to the predetermined contact temperature.

4. The method according to any one of claims 1 to 3, wherein contacting the hydrogen capture material in loose particulate format with gaseous hydrogen includes - continuously feeding gaseous hydrogen into the vessel at a volumetric feed flow rate that is sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the vessel, while releasing uncaptured hydrogen, as excess gaseous hydrogen, from the vessel to achieve and maintain the predetermined contact pressure inside the vessel; and recirculating the excess gaseous hydrogen, as recirculated gaseous hydrogen, into the vessel, such that the gaseous hydrogen that is fed into the vessel comprises recirculated gaseous hydrogen.

5. The method according to claim 4, which includes supplementing the recirculated gaseous hydrogen with fresh gaseous hydrogen to the extent necessary to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the vessel.

6. The method according to claim 5, which includes electronically measuring a temperature (T1) of gaseous hydrogen that is fed into the vessel; electronically measuring a temperature (T2) of gaseous hydrogen that is withdrawn from the vessel; electronically calculating a temperature differential (T3) as T1 minus T2; electronically measuring the volumetric rate of supply of fresh gaseous hydrogen supplementing recirculated hydrogen to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the vessel; electronically measuring a volumetric rate of recovery of recirculated gaseous hydrogen from the vessel; electronically measuring the volumetric feed flow rate of gaseous hydrogen to the vessel; and electronically concluding that the hydrogen capture material is sufficiently saturated with hydrogen, if

T3 is or approximates a value of zero (0), and/or the volumetric rate of supply of fresh gaseous hydrogen to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the vessel is or approximates zero (0), and/or the volumetric rate of recovery of recirculated gaseous hydrogen is equal to or approximates the volumetric feed flow rate.

7. The method according to any one of claims 1 to 6, which includes pressure- tightly closing, or closing off, the vessel at a storage pressure above the predetermined contact pressure and at a temperature that does not exceed the predetermined contact temperature.

8. The method according to claim 6 and claim 7, wherein pressure-tightly closing, or closing off, the vessel at the storage pressure above the predetermined contact pressure and at a temperature that does not exceed the predetermined contact temperature is performed electronically, and automatically, in response to the conclusion that the hydrogen capture material is sufficiently saturated with hydrogen.

9. A method of recovering, in gaseous form, hydrogen that has been stored by a hydrogen capture material through adsorption and/or absorption of the hydrogen on or by the hydrogen capture material, wherein the hydrogen capture material is provided in loose particulate format inside a pressure-tight vessel in combination with pressurized gaseous hydrogen at a pressure and temperature that avoids desorption of hydrogen from the hydrogen capture material as gaseous hydrogen, the method including contacting the hydrogen capture material with gaseous hydrogen at a predetermined contact temperature and at a corresponding predetermined contact pressure that promote desorption of hydrogen from the hydrogen capture material as gaseous hydrogen such that hydrogen is desorbed from the hydrogen capture material as gaseous hydrogen as a result of such contact, wherein the hydrogen capture material in loose particulate format is fluidized by contact of the gaseous hydrogen with the hydrogen capture material; and the gaseous hydrogen acts as a working fluid to achieve and/or maintain the predetermined contact temperature in contacting the gaseous hydrogen with the hydrogen capture material.

10. The method according to claim 9, which includes subjecting the gaseous hydrogen that is contacted with the hydrogen capture material to temperature treatment upstream of the vessel, selectively to cool or heat the gaseous hydrogen as may be required to achieve and/or maintain the predetermined contact temperature in contacting the hydrogen capture material.

11. The method according to claim 10, wherein the temperature treatment selectively heats or cools the gaseous hydrogen to the predetermined contact temperature.

12. The method according to any one of claims 9 to 11 , wherein the gaseous hydrogen that is contacted with the hydrogen capture medium at the predetermined contact temperature and at the predetermined contact pressure such that hydrogen is desorbed from the hydrogen capture material as gaseous hydrogen as a result of such contact, comprises or consists of pressurized gaseous hydrogen contained in the vessel and wherein the method therefore includes - withdrawing pressurized gaseous hydrogen contained in the vessel from the vessel; recirculating such gaseous hydrogen to the vessel at a volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the vessel; and contacting the gaseous hydrogen so recirculated with the hydrogen capture material at the predetermined contact temperature and at the predetermined contact pressure such that the hydrogen capture material is fluidized by such contact and such that hydrogen is desorbed from the hydrogen capture material as gaseous hydrogen as a result of such contact.

13. The method according to any one of claims 9 to 12, wherein release of gaseous hydrogen through desorption of hydrogen from the hydrogen capture material as a result of the contacting the hydrogen capture material with gaseous hydrogen increases the pressure inside of the vessel and causes automatic discharge of gaseous hydrogen from the vessel as a hydrogen product gas above a predetermined hydrogen product gas release pressure.

14. The method of any of claims 9 to 13, which includes a prior step of performing the method of any one of claims 1 to 8.

15. A hydrogen storage system for selective storage and recovery of hydrogen by or from a hydrogen capture medium in accordance with the method of any one of claims 1 to 8 or any one or claims 9 to 14 respectively, the system comprising - a hydrogen storage vessel containing a bed of loose particulate hydrogen capture material in its interior, the vessel having an inlet to and an outlet from its interior; a gas dispersal system located downstream of the inlet of the vessel and upstream of the hydrogen capture medium and providing gas inlet openings into the vessel, optionally having a plurality of gas feed nozzles located inside the interior of the vessel, to feed gaseous hydrogen into the interior of the vessel in use, wherein the gas dispersal system is located to feed gaseous hydrogen into the interior of the vessel such that the bed of hydrogen capture material is fluidized by such contact; a gaseous hydrogen recirculation outlet provided by the outlet of the vessel, for gaseous hydrogen to be released from the vessel, at a gaseous hydrogen recirculation pressure, and be recirculated to the gas dispersal system as recirculated gaseous hydrogen, in use, the gaseous hydrogen recirculation outlet comprising a gaseous hydrogen recirculation valve that is configured automatically to release gaseous hydrogen from the interior of the vessel at the gaseous hydrogen recirculation pressure and that can selectively be opened and shut independent of pressure; a gaseous hydrogen recirculation pump located and configured to supply gaseous hydrogen from the gaseous hydrogen recirculation outlet and/or fresh gaseous hydrogen from a fresh gaseous hydrogen supply source to the gas dispersal system; a gas cooling device and a gas heating device located downstream of the gaseous hydrogen recirculation pump and upstream of the gas dispersal system, respectively to be supplied with recirculated and/or fresh gaseous hydrogen by the gas recirculation pump and selectively to cool or heat such gaseous hydrogen before it is fed to the gas dispersal system and into the interior of the vessel; a hydrogen product gas outlet provided by the outlet of the vessel, for gaseous hydrogen to be released from the vessel, and thus from the system, in use, as a hydrogen product gas, at a hydrogen product gas release pressure inside the vessel, for use, the hydrogen product gas outlet comprising a hydrogen product gas release valve that is configured automatically to release gaseous hydrogen from the interior of the vessel at the hydrogen product gas release pressure and that can selectively be opened and shut independent of pressure; and an electronic control system comprising an electronic processing unit that is configured electronically, independently, - to activate the pump, to pump gaseous hydrogen from the recirculation outlet and/or from the fresh gaseous hydrogen supply source into the interior of the vessel at a volumetric feed flow rate sufficient to achieve and/or maintain fluidization of the hydrogen capture material and/or to achieve and/or maintain a predetermined contact pressure inside the vessel, to supplement gaseous hydrogen from the recirculation outlet with fresh gaseous hydrogen from the fresh gaseous hydrogen supply source to the extent necessary to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain a predetermined contact pressure inside the vessel selected to promote either adsorption and/or absorption of hydrogen from the gaseous hydrogen on or by the hydrogen capture material or desorption of hydrogen previously adsorbed and/or absorbed on or by the hydrogen capture material at a predetermined contact temperature; to direct flow of gaseous hydrogen driven by the gaseous hydrogen recirculation pump, selectively to the gas cooling device or to the gas heating device and selectively to activate the gas cooling device or the gas heating device, if activation is needed, for the gaseous hydrogen to be selectively heated or cooled to the predetermined contact temperature, selectively to shut the hydrogen product gas release valve and set the gaseous hydrogen recirculation valve to operate as a pressure relief valve at the gaseous hydrogen recirculation pressure, and open the gaseous hydrogen recirculation valve and set the hydrogen product gas release valve to operate as a pressure relief valve at the hydrogen product gas release pressure, to measure a temperature (T1) of gaseous hydrogen that is fed into the vessel; to measure a temperature (T2) of gaseous hydrogen that is withdrawn from the vessel; to calculate a temperature differential (T3) as T1 minus T2; to measure a volumetric rate of supply of fresh gaseous hydrogen supplementing recirculated hydrogen to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the vessel; to measure a volumetric rate of recovery of recirculated gaseous hydrogen from the vessel through the gaseous hydrogen recirculation outlet; to measure the volumetric feed flow rate of gaseous hydrogen supplied to the vessel through the inlet of the vessel; and to conclude that the hydrogen capture material is sufficiently saturated with hydrogen, if -

T3 is or approximates a value of zero (0), and/or the volumetric rate of supply of fresh gaseous hydrogen to maintain the volumetric feed flow rate sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the vessel is or approximates zero (0), and/or the volumetric rate of recovery of recirculated gaseous hydrogen is equal to or approximates the volumetric feed flow rate; to close or close off the vessel pressure-tightly, or to cease feeding of gaseous hydrogen into the interior of the vessel, and thus provide a pressurized condition at a storage pressure based on the conclusion that the hydrogen capture material is sufficiently saturated with hydrogen, and from the pressurized condition of the vessel, to withdraw pressurized gaseous hydrogen from the vessel through the gaseous hydrogen recirculation outlet and pump such gaseous hydrogen into the interior of the vessel at the volumetric feed flow rate that is sufficient to fluidize the hydrogen capture material and to achieve and maintain the predetermined contact pressure inside the vessel.