EP2931653A1

EP2931653A1 - Pyrotechnic process for providing very highly pure hydrogen and associated device

Info

Publication number: EP2931653A1
Application number: EP13818261.3A
Authority: EP
Inventors: Jean-Philippe Goudon; Pierre Yvart; Fabrice MANTELET; Frédéric LESAGE
Original assignee: Herakles SA
Current assignee: ArianeGroup SAS
Priority date: 2012-12-12
Filing date: 2013-12-09
Publication date: 2015-10-21
Also published as: WO2014091127A1; US20150321909A1; US9624102B2; KR20150093824A; FR2999167B1; CA2894471A1; FR2999167A1

Abstract

The subject matter of the present invention is a pyrotechnic process for providing very highly pure hydrogen (G) and also a device (100) suitable for implementing said process. Said process comprises: the combustion of at least one solid pyrotechnic charge which generates hydrogen-containing gas (4a, 4b, 4c, 4d) for the production of a hot hydrogen-containing gas (G1) under pressure, containing at least 70% by volume of hydrogen; and the purification of at least one part of said hydrogen-containing gas (G1) under pressure, by passage through a metallic membrane for separating the hydrogen (9) maintained at a temperature above 250°C, advantageously between 300 and 600°C, so as to obtain, at the outlet of said membrane (9), a hydrogen-containing gas (G) containing at least 99.99% by volume of hydrogen.

Description

Pyrotechnic method for providing very high purity hydrogen and associated device

The present invention relates to a pyrotechnic process for providing hydrogen of very high purity. Said method is advantageously used to power fuel cells, portable or onboard. The present invention also relates to a device suitable for implementing said method.

The invention is particularly applicable in the context of the hydrogen supply of low and medium power (1 to 100 watts) fuel cells, used in the aeronautical and military fields, such as those equipping the drones and those equipping the infantrymen . The electrical powers targeted in this context are about ten times greater than the powers consumed by portable electrical appliances, such as mobile phones. The scope of the invention can be extended to onboard fuel cells of higher power, a few tens of kilowatts, used, for example, for the supply of aeronautical emergency power generators.

Fuel cells are alternative sources of electrical energy that provide a response to new energy and environmental requirements. Fuel cells have a potential energy density on board at least 4 times higher than that of lithium batteries. They do not release greenhouse gases.

The production of hydrogen to fuel fuel cells is therefore a technical problem of topicality, object of many researches.

Processes have already been described for the production of hydrogen by cracking hydrocarbons, thermolysis (thermal decomposition in the absence of oxidant) of hydrides and hydrolysis of hydrides.

Another developed route is based on the use of pyrotechnic solid materials generating hydrogen by combustion. It makes it possible to overcome the problem of permanent storage of fluid (liquid or gaseous). She is particularly interesting in that said materials have a high stability in storage conditions and great simplicity of use.

Such pyrotechnic solid materials generating hydrogen have in particular been described in patent applications EP 1 249 427, EP 1 405 823, EP 1 405 824, EP 1 496 035 and EP 2 265 545. They are in the form of blocks. , pellets, discs or grains. Their composition generally contains a hydrogenated reducing component of inorganic hydride, borazane or polymeric type of aminoborane (polyaminoborane) and an inorganic oxidizing component. Their combustion generates, with a good yield (~ 11 to 13% theoretical mass, ie ~ 70 mole / kg), hydrogen. Their combustion temperature (~ 800 K, depending on the formulations), not excessive (see below), is high enough that the reaction is self-sustaining after ignition. The self-sustaining combustion of these materials is favored by the pressurization in the combustion chamber. Such materials produce hydrogenated gas with a high hydrogen content, containing at least 70% by volume of hydrogen.

The gases supplying a fuel cell must be free, or at least contain extremely low levels, of species, such as CO, NH ₃ , (¾ and H ₂ S, capable of poisoning the catalyst of said battery. must also be at suitable temperatures (less than 473 K, ideally less than 350 K so far, to spare the battery membrane) and at low overpressures (ideally a few millibars up to 5 bar) compared to the Finally, the particle content of said gases must be very low.

With reference to such specifications, the composition of pyrotechnic solid materials hydrogen generators is in principle optimized to generate the least possible such gaseous species poisons for (the catalyst) the battery (in any case, the gases hydrogenated products produced by these materials are always likely to contain, at low rates, poison species for the cell and it is appropriate to purify them to deliver to said cell a hydrogen of purity greater than 99.9% by volume, to guarantee its life) and to burn at a moderate temperature (it is always desirable to lower the temperature of the hydrogenated gases produced by the combustion of these materials at a temperature of about 800 K (see above), to deliver to the cell hydrogen at a temperature below 473 K, ideally less than 350 K). The hydrogenated gases produced by the combustion of said materials are also conveniently filtered to trap the solid particles they carry (particles that have not been retained in the gangue resulting from the combustion). The filters used for trapping said solid particles comprise, for example, an arrangement of one or more corrugated metal grids or an arrangement of metallic elements having pores (of a few millimeters to a few nanometers in diameter).

The patent application FR 2 906 805 describes a method for providing non-pressurized hydrogen which is in the way specified above. Said method comprises the combustion, at high pressure, of at least one solid pyrotechnic charge in at least one combustion chamber, said combustion generating hydrogen and the flow rate of said hydrogen generated in at least one tank of larger volume. This document does not really address the technical problem of purification of generated hydrogen. Nor does it address the technical problem of managing the temperature of said generated hydrogen.

Furthermore, those skilled in the art are aware of purification devices (selective filtration) of hydrogenated gases, containing metal hydrogen separation membranes, composed for example of palladium or a metal alloy containing palladium. In this regard, reference can be made to the teaching of "Palladium-based alloy membranes for separation of high purity hydrogen from hydrogen containing gas mixture", in Platinum Metal rev., 2011, 55, (1), 3-12, to the teaching of "Hydrogen, 3. Purification" in Ullmann's Encyclopedia of Industrial Chemistry, Vol. 18, p. 309-333, (2011-10-15), to the teaching of the patent application WO 2006/067156, or that of the patent application FR 2 790 751. The effectiveness of these membranes is optimal when they are at temperatures close to 300-600 ° C (said membranes are then activated) and the hydrogenated gas is supplied under pressure (which allows the permeation of hydrogen through said membranes), typically from a few bars to 50 bar , with respect to the delivery pressure (~ atmospheric pressure) of the purified hydrogen (out of said membranes). In these conditions, the hydrogen delivered by the membrane reaches purities of 99.999%. These operating conditions (temperature and pressure) are easily manageable during the production of hydrogen in an industrial environment by cracking hydrocarbons, but the implementation of such cracking require complex architectures on portable or embedded systems. In addition, hydrocarbon cracking (as well as thermolysis of a hydride) are energy consuming operations. Moreover, in a context of hydrogen generation by hydrolysis of a hydride, the heating of the membrane is most often carried out by means of electrical resistors, which is also disadvantageous in terms of energy. The process described in application US 2007/0084879, which associates hydrogen generation by hydrolysis or thermolysis of a hydride and purification of said hydrogen generated by passage through a membrane of the palladium membrane type (other types of membranes being cited), thus appears hardly interesting from the energy point of view.

The use of metal hydrogen separation membranes, although leading to hydrogen of high purity, therefore remains always restrictive due to the operating conditions of said membranes in temperature and pressure. To the inventors' knowledge, this use has never been directly associated with the pyrotechnic production of hydrogenated gas. The inventors recommend such an association, which is particularly interesting with reference to the technical problem summarized below: the provision of hydrogen of very high purity, under advantageous conditions from the point of view of energy (the combustion (upstream) of a pyrotechnic loading requiring little energy and generating (downstream) a hot gas under pressure.This pressure is obviously appropriate (see below) and, with reference to the temperature parameter, the implementation of the process of the The invention can be optimized (see the advantageous variants of implementation of the method of the invention specified below)), and from the point of view simplicity and size of the associated device, perfectly suitable for portable or embedded systems.

With reference to the technical problem of the provision (on demand) of very high purity hydrogen (under particularly interesting implementation conditions), the Applicant proposes therefore a high-performance solution, based on the combustion of at least one pyrotechnic solid charge generating hydrogenated gas (hydrogenated gas already containing a substantial level of hydrogen), then the purification, by a metal membrane of hydrogen separation, of at least a portion of the hydrogenated gas generated (generally hydrogenated gas generated), to obtain hydrogen of very high purity; said hydrogen of very high purity particularly suitable for supplying a fuel cell. Said solution is analyzed in terms of method and device.

According to its first object, the present invention therefore relates to a method for providing hydrogen of very high purity. Said method comprises:

the combustion of at least one solid pyrotechnic charge generating hydrogenated gas for the production of a hydrogen gas, hot, under pressure, containing at least 70% by volume of hydrogen; and

the purification of at least a portion of said hydrogenated gas under pressure, by passing through a hydrogen separation metal membrane maintained at a temperature above 250 ° C., advantageously between 300 and 600 ° C., to obtain at the outlet of said membrane, a hydrogenated gas containing at least 99.99% by volume of hydrogen.

The combustion of the at least one pyrotechnic charge is triggered, per se known, by the user system as soon as the operational energy requirement appears. It generates, in a manner known per se, within the (each) combustion chamber containing the (a) pyrotechnic charge, hydrogenated gas, hot (~ 800 K, see above) at high pressure (the operating pressure the at least one combustion chamber is generally between 10 ⁶ Pa and 10 ⁷ Pa (between 10 and 100 bar)). Several pyrotechnic charges (identical or not, generally identical), each arranged in a combustion chamber, can be ignited simultaneously or sequentially according to the hydrogen demand. The pyrotechnic charge (s) used are suitable for generating a hydrogenated gas containing at least 70% by volume of hydrogen. This text gives further details on such loads. The hydrogenated gas generated is delivered, hot, under pressure (generally at a pressure less than or equal to 10 bar, more generally at a pressure of a few bars), when leaving the combustion chamber in which it has been generated, hot, at high pressure. The person skilled in the art knows how to adjust the area of the delivery orifice (or even the delivery ports, if the combustion chamber concerned has more than one) of the gas to regulate the pressure and the rate of delivery of said gas.

In the context of the implementation of the process of the invention, at least a part of the pyrotechnically generated hydrogen gas, under pressure, is brought into contact (passed through) with a metal membrane for separating hydrogen (membrane hot, activated) for its purification. It should be understood that at least a portion of the hydrogenated gas delivered has passed through such a membrane, regardless of the exact arrangement of the combustion chamber (s) (in operation) present and membrane (s) present ( s). Thus, it is possible in particular that a single combustion chamber delivers in a single membrane or in several membranes arranged in parallel, that n combustion chambers are connected to a single membrane or that each of the n chambers is connected to a membrane. .. Moreover, "a" membrane has been mentioned but it is easy to understand that it is not possible to exclude from the scope of the invention a purification carried out successively on at least two membranes arranged in series. In any event, in the context of the process of the invention, at least part of the hydrogenated gas recovered from the combustion chamber (s) is purified by passage through (at least) a membrane. For the sake of simplification of the description of the process of the invention, reference is made hereinafter to the metal separation membrane. It has been reported that at least a portion of the pyrotechnically generated hydrogen gas is thus purified. In general, all the hydrogenated gas generated is thus purified but it can not be excluded from the scope of the present invention that part of the pyrotechnically generated hydrogen gas is not oriented for purification towards the metal membrane but used at another end (for other purposes).

The membrane is supplied with hydrogenated gas (generated pyrotechnically) under pressure and containing at least 70% by volume of hydrogen. It delivers this hydrogenated gas, not pressurized because of the pressure drop that it undergoes within said membrane, and containing at least 99.99% by volume of hydrogen. It thus makes it possible to substantially rid the said hydrogenated gas of gaseous species, other than hydrogen, which are present therein. In particular, it makes it possible to rid it of poisonous species for a fuel cell. It therefore also makes it possible to lower the pressure of said hydrogenated gas. The hydrogenated gas obtained at the exit of said membrane is therefore the hydrogen of very high purity not pressurized desired. It is perfect for fuel cell power supply.

The metal membrane for separating hydrogen (used, in the context of the implementation of the process of the invention, for purifying hydrogenated gas produced pyrotechnically, immediately after its production) is of the type described in the art. prior. It is preferably a palladium membrane or an alloy including palladium.

It is understood that the method of the invention comprises feeding the metal separation membrane with hydrogenated gas produced under pressure, which of course is favorable to the permeation of said gas through said membrane. Whatever the exact variant of implementation of the method of the invention, it is therefore a pressurized gas that feeds the metal separation membrane. The pressure of the gas generated during the first step of the process is thus used for the implementation of the second step of said process.

With reference to the temperature parameter of the gas to be purified, it is possible to specify the following. Given the current technologies of metal membrane hydrogen separation, technologies undoubtedly called to evolve, it is preferable to inject into the hot membrane hydrogen gas at a temperature not too high, typically less than 473 K (200 ° C) (the operation of the membranes is currently optimal hot with "cold" gases). Since the pyrotechnically produced gas is at about 800 K (~ 527 ° C), it is recommended to cool it before it enters the membrane.

For carrying out the purification of hydrogenated gas under pressure, in the context of the process of the invention, the gas is passed through (at least) a membrane heated to a temperature above 250 ° C., advantageously a temperature between 300 and 600 ° C. The heating of the membrane, for its maintenance at a suitable temperature, can be carried out according to conventional methods, for example by means of an electrical resistance. It is also conceivable to heat the membrane with the hot hydrogen gas produced by the combustion of the at least one pyrotechnic charge. This heating mode is not, in the current state of the membrane technologies (whose filtration operation is optimal hot with injection of hydrogen gas "cold"), really recommended. In the context of the implementation of advantageous variants of the process of the invention (see below), there is, to ensure at least partly this heating, transfer of calories generated by the combustion of the at least one pyrotechnic charge and / or taken from the gaseous products generated by the combustion of the at least one pyrotechnic charge, at the metal separation membrane. This makes it possible to avoid, at least to minimize, the heat input required by means of an energy consuming system (such as an electrical resistance) to maintain said membrane at a temperature where it is effective, or even very efficient.

So :

according to an advantageous variant of implementation of the method of the invention (pyrotechnic generation of hydrogenated gas and purification of at least a part thereof), the heat produced by the combustion of the at least one pyrotechnic charge is partly used to carry out the purification, ie to continuously heat the metal separation membrane. Heat transfer conveniently takes place by thermal conductivity, a conductive heat exchanger then connecting the combustion chamber (s) with the metal membrane. Said heat exchanger, thermal bridge, can exist in different forms, more or less materialized. It may consist of the air filling the spaces (advantageously confined and minimized) between said combustion chamber (s) and said membrane or preferably of a material (solid) arranged in said spaces, material ( such as a metal in the form of beads, filings or particles) which advantageously has a high thermal conductivity (typically 50 W / mK (for steel) to 380 W / mK (for copper)). It is already understood that the method of the invention is advantageously implemented with optimization of such a transfer of the combustion heat to the filtration membrane (optimization at the distances involved, the contacts made and the thermal conductivity of the material used to materialize the thermal bridge);

according to another advantageous variant of implementation of the method of the invention including a continuous heating of the membrane, independent of the preceding one (use of part of the combustion heat generated at the level of the chamber ( s) during the implementation of the purification) but which advantageously accumulates with it, the hydrogenated gas produced (hot, mentioned above a combustion temperature of about 800 K) is cooled before its purification (it is understood that the at least part of the hydrogenated gas generated hot to be purified can thus be cooled and that generally all of said gas is thus cooled). Such cooling is appropriate with reference to the passage through the metal membrane (see above) and the subsequent use of said gas, purified (for example to supply a fuel cell). The hydrogenated gas produced may in particular be cooled (at least partially or completely) by being circulated with heat exchange (its circulation pipe then acting as a heat exchanger), before coming into contact with the metal separation membrane. . Very advantageously, the heat thus transferred from the hot hydrogen gas is returned (in part) to the metal membrane. Thus, in addition to a portion of the heat of combustion, part of the heat carried by the produced (hot) hydrogen gas can be used to heat the metal membrane. The purification of the hydrogenated gas can thus be implemented with optimal use of the calories generated during combustion.

The method of the invention comprising the combustion and purification steps specified above is therefore advantageously implemented with recovery of part of the amount of heat generated during combustion to carry out the purification; it is very advantageously implemented with recovery of a part of the quantity of heat generated during combustion to carry out the purification and with cooling of the hydrogenated gas produced, a part of the quantity of heat extracted during said cooling being itself also recovered to implement the purification. Incidentally Here, the heat of the hydrogenated gas produced is in fact also heat generated during combustion. The distinction made above (with reference to the recovery of calories) is with reference to the location of the heat exchanges 1) at the level of the at least one combustion chamber, 2) at the level of the circulation, excluding the chamber of combustion. combustion, hydrogenated gas delivered.

In the context of the implementation of the process of the invention, the at least part of the hydrogenated gas produced (generally all of it) intended to be purified, is further advantageously filtered before coming into contact with the metal separation membrane, in order to be rid (at least in part) of the solid particles it contains (combustion residues of the pyrotechnic charge entrained, not trapped in the combustion gangue). Filtration can be implemented conventionally (see introduction to this text). Assuming that at least a portion of the hydrogenated gas produced is also cooled before purification, it is advantageously filtered and then cooled.

The process of the invention, as described above, therefore advantageously comprises the following 4 successive steps:

- production (pyrotechnics) of hot hydrogenated gas under pressure,

filtering at least a portion of said hot hydrogenated gas under pressure,

cooling said at least a portion of said hot hydrogenated gas under filtered pressure, and

purifying said at least a portion of said hot hydrogenated gas under cooled filtered pressure;

implemented, preferably, with recovery of part of the amount of heat generated during combustion to carry out the purification;

implemented, even more preferably, with recovery of a portion of the amount of heat generated on combustion and a portion of the amount of heat extracted during cooling to carry out the purification. These 4 successive steps are generally implemented with filtration, cooling and purification of all the hydrogenated gas produced pyrotechnically.

With reference to the temperature parameter of the purified gas, it is generally possible to specify the following. The temperature of the purified gas must not be excessive in view of the use made of it. It has been stated above that, in order to supply a fuel cell, the temperature of the gas must not exceed 473 K.

With reference to the start-up (start-up) phase of the process of the invention (with a cold membrane), the following can be indicated.

The membrane must undergo a "preheating" phase ensuring its temperature conditioning.

In a context of use of electric resistance heating means, no problem arises. In other contexts, the following can be done in particular.

According to a first variant of starting up the process of the invention, hydrogenated gas produced by the combustion of at least one solid pyrotechnic charge generating hydrogenated gas is injected hot (without cooling) into the membrane and ensures its preheating. Once the membrane thus preheated (made operational), the hot hydrogenated gas produced (at least in part, generally in all) is advantageously cooled before being brought into contact with the membrane raised to its operating temperature (see above). above that the functioning of the membranes is optimal when hot with "cold" gases). For its cooling (as indicated above), the hydrogenated gas produced (at least in part, generally in all) can in particular be circulated in a pipe with heat exchange (its circulation pipe then acting as heat exchanger) , before coming into contact with the metal separation membrane. According to this first start-up variant, it may be considered that the method self-initializes.

According to a second variant of start-up of the method of the invention, an additional (preheating) pyrotechnic charge is used to supply the necessary calories (at least a part of them) to the temperature setting of the membrane, before the passage of hydrogenated gas in said membrane during the implementation of the method. The preheating of the membrane can then be achieved either by direct thermal transfer (between the pyrotechnic combustion preheating charge, more precisely the combustion chamber containing it and the membrane) or by indirect thermal transfer via the gases generated by the combustion of the charge. pyrotechnic preheating circulated in a heat exchanger "in contact with" the membrane). The pyrotechnic preheating charge advantageously consists of a solid propellant charge. The solid propellant involved is not necessarily a generator of a gas consisting essentially of hydrogen. A standard composite solid propellant may be suitable. In the context of this second variant of starting the process, in addition to the heat produced by the combustion of the preheating charge, the heat produced by the combustion of the at least one pyrotechnic charge can also be partly used to preheat the membrane. metallic separation.

It is now proposed to give details of the pyrotechnic charges suitable for the implementation of the method of the invention.

Said loadings may consist of loadings of the prior art, consisting of at least one product of conventional type, ie of the block, disc, pellet, grain type ... with a composition of: oxidizing component (s) type (s) ) Inorganic (s) + Hydrogenated Reducing Component (s) (see Introduction to this text). In any event, the at least one pyrotechnic charge used for the implementation of the method of the invention is selected to pyrotechnically generate a hydrogenated gas containing at least 70% by volume of hydrogen. It is indeed from such a hydrogenated gas that purification on membrane generates the hydrogen of very high purity desired.

Particularly suitable for the implementation of the method of the invention, the pyrotechnic charges consist of at least one pyrotechnic product containing, for at least 96% of its mass, at least one inorganic oxidizing component and at least one hydrogenated reducing component selected inorganic hydrides, borazane and polyaminoboranes. The at least one inorganic oxidizing component (generally only one inorganic oxidizing component is present but the presence of at least two in a mixture can not be excluded) and the at least one specific hydrogenated reducing component (generally a single hydrogenated reducing component as identified above is present but the presence of at least two in a mixture can not be excluded) therefore represent at least 96% by weight (or even at least 98% by weight, or even 100% by weight) of the mass of the pyrotechnic product (s) ( s) advantageously used (s) to generate, according to the invention, the combustion gases. The optional 100% supplement is generally composed of additives, such as process auxiliaries, stability, desensitization with static electricity (such as Si0 ₂ ) and / or ballistic, combustion modifiers. The presence of impurities is not excluded.

With reference to said at least one hydrogenated reducing component, it is possible, in no way limiting, to specify the following. 1) The at least one inorganic hydride that may be present in the composition of the pyrotechnic products used is advantageously a borohydride, very advantageously an alkaline or alkaline earth borohydride. Preferably, said at least one inorganic hydride is selected from sodium borohydride, lithium or magnesium. Pyrotechnic products used in the method of the invention therefore preferably contain in their composition, such as organic hydride, NaBH _4, LiBH ₄ or Mg (BH ₄₎ _2.

2) The at least one hydrogenated reducing compound, however, preferably consists of borazane or a polymer of aminoborane (a polyaminoborane). Particularly preferably, borazane is the only hydrogenated reducing compound present in the composition of the pyrotechnic products used.

With reference to said at least one inorganic oxidizing component, it is possible, in no way limiting, to specify the following.

It is advantageously chosen from those used according to the prior art in the technical field of fuel cells; i.e. among:

perchlorates (it very advantageously consists of ammonium perchlorate),

dinitroamides ("dinitramides") (it very advantageously consists of ammonium dinitroamidure), nitrates (it very advantageously consists of strontium nitrate), and

metal oxides (it advantageously consists of iron oxide (Fe ₂ O ₃ ), vanadium oxide (V ₂ Os), aluminum oxide (Al ₂ O ₃ ), titanium oxide; (Ti0 ₂ ), manganese oxide

(MnO ₂ ), preferably iron oxide (Fe ₂ O 3)).

The pyrotechnic products (constituting the pyrotechnic charges) used in the process of the invention therefore very advantageously contain NH ₄ ClO ₄ , NH ₄ N (NO ₂ ) ₂ , Sr (NO 3) 2 or Fe ₂ O 3.

In the context of this variant, the pyrotechnic product (s) used preferably contains in its (their) composition:

from 40 to 80% by weight of at least one hydrogenated reducing component as identified above (generally of such a hydrogenated reducing component), and

from 20 to 60% by weight of at least one inorganic oxidant (generally of such an inorganic oxidant).

They contain, particularly preferably:

from 55 to 75% by weight of at least one hydrogenated reducing component as identified above (generally of such a hydrogenated reducing component), and

from 25 to 45% by weight of at least one inorganic oxidant (generally of such an inorganic oxidant).

It is generally also very advantageous for said pyrotechnic product (s) to contain (s) more than 50% by weight of hydrogenated reducing component (s). , even more advantageous that said (s) product (s) pyrotechnic (s) contains (s) more than 70% by weight of hydrogenated reducing component (s). It has been understood that the said hydrogenated reducing component (s) present constitute (s) the hydrogen reserve.

It is recalled here, for all practical purposes, that the at least one pyrotechnic charge used for the generation of hydrogenated gases consists of at least one pyrotechnic product (generally several) in the form of grains, pellets, disks or blocks. These grains, pellets and blocks have any shape, for example spherical, ovoid or cylindrical. Grain generally a mass of a few milligrams, pellets a mass of a few tenths of grams to a few grams, discs of a few tens of grams to a few hundred grams and blocks of a hundred grams to a few kilograms.

The processes for obtaining these solid pyrotechnic products are known methods, described in particular in the EP patent applications identified on page 2 of this text.

It is understood that said at least one pyrotechnic charge used generally contains several pyrotechnic products (although the use of a single product, such as a block, is not excluded). In such a context, all the products constituting said at least one load do not necessarily have the same composition (or the same shape). However, they are all generators of hydrogenated gas within the meaning of the invention.

Said at least one pyrotechnic charge burns upon ignition. The ignition device generally consists of an igniter, in connection with the user system, via a sealed passage supporting the operating pressure, and possibly at least one ignition relay charge. Advantageously, when the user system allows it, the igniter is triggered by mechanical stress (for example by means of a piezoelectric relay or a primer striker), in order to avoid any unnecessary consumption of electrical energy for trigger the system. Thus, the process of the invention is advantageously triggered by mechanical stress.

In view of the above, it is understood that the method of the invention is particularly suitable for supplying, in very pure hydrogen, portable or on-board fuel cells. The hydrogen of very high purity delivered out of the metal membrane of hydrogen separation associated with the at least one combustion chamber, is ideal for such use.

The invention can actually be analyzed as a process for supplying very high purity hydrogen of a fuel cell; said method comprising the pyrotechnic process for providing hydrogen of very high purity, as described above (including high pressure combustion and then purification on metal membrane for hydrogen separation of at least a portion (generally all) hydrogenated gas produced) followed by delivery of said high purity hydrogen to said fuel cell. It should be noted, however, that the very high purity hydrogen obtained on demand by the process of the invention can quite well be used in other contexts.

According to its second object, the present invention relates to a pyrotechnic device for providing (on demand) hydrogen of very high purity. Said device is suitable for implementing the method described above, is in fact suitable for an advantageous implementation variant thereof (advantageous with reference to heat exchange). It typically includes:

at least one combustion chamber provided with at least one delivery orifice that is suitable for the arrangement and the high-pressure combustion, within it, of a solid pyrotechnic charge generating hydrogenated gas and for the delivery of hot hydrogenated gas, under pressure, via said at least one delivery port;

at least one metal membrane for separating hydrogen, suitable for the purification of hydrogenated gas, having an inlet face and an outlet face; said metal membrane for separating hydrogen being arranged in a reservoir so that a void volume is formed in said reservoir upstream of its inlet face; and

means for delivering the purified gas;

said combustion chamber (s) and metallic membrane (s) for hydrogen separation being placed in communication via at least one pipe so that hydrogenated gas delivered from the combustion chamber (s) is directed to at least one metal membrane for separating hydrogen and being arranged in a heat-insulated enclosure; said delivery means being adapted to ensure the delivery of gas, purified within the said (s) membrane (s) metal (s) for separation of hydrogen, out of said lagged enclosure.

The device of the invention is generally designed to direct all the hydrogenated gas generated towards the at least one metal membrane for separating hydrogen, but, as indicated above, it can not be ruled out that it contains means, arranged between the said minus a combustion chamber and said at least one metal membrane for separating hydrogen to derive a portion of said generated hydrogen gas.

It has already been understood, in consideration of the foregoing, that many arrangements of the combustion chamber (s) and membrane (s) present are possible, it being understood that the gas of very high purity to be delivered must be purified by passage through through at least one membrane. Note that the use of a single membrane in combination with at least one combustion chamber is recommended and that the following arrangement: at least one annular combustion chamber disposed around a metal membrane for separating hydrogen is particularly preferred (especially with reference to the transfer of heat of combustion to the membrane).

It will further be understood that the (each) metallic hydrogen separation membrane is arranged in a reservoir (the device comprising a membrane in its reservoir can be described as a purification chamber), so that an empty volume is provided in said reservoir upstream of the inlet face of said membrane (of each membrane). This empty volume is intended for the storage of species (CO, H ₂ O, NH _3, etc.) separated from hydrogen by said membrane (in operation). The inlet face of a membrane is obviously that intended to receive the hydrogenated gas under pressure to be purified and the exit face that by which the purified hydrogenated gas unpressurized (containing more than 99.99% hydrogen) is issued.

Characteristically, the combustion chamber (s) and metal membrane (s) separating the device of the invention (chamber (s) and membrane (s) placed in communication) are arranged in a heat-insulated enclosure, the means for delivering the purified gas delivering said gas out of said lagged enclosure. This arrangement is appropriate to confine the various constituent elements of the device and aims to best preserve the heat of combustion and to ensure at least heat transfer: heat of the combustion chambers and hot gas transport pipes to the (the) membranes (s).

For an optimization of said heat transfers, it is recommended that: the lagged enclosure contains a material providing a thermal bridge between said at least one combustion chamber (+ at least one tubing present) and said at least one metal separation membrane; said material being advantageously of high thermal conductivity (see above). We have seen that air is (at least) likely to provide such a thermal bridge but a material with higher thermal conductivity, such as a metal (in the form of beads, chips or particles) is certainly more efficient . In fact, it is recommended to "fill" said enclosure insulated with a material of high thermal conductivity. The heat of combustion is thus "confined" in the lagged enclosure and its transfer to the at least one membrane can be optimized.

The device of the invention is also likely to comprise gas cooling means, currently pyrotechnically generated hydrogen gas (at least a part thereof), thus arranged downstream of the at least one combustion chamber of the device. Said cooling means are arranged upstream of the at least one metal separation membrane. They aim to protect the said at least one membrane from the excessive heat of the combustion gases. They protect in the same way any upstream device using hydrogenated gas of very high purity.

It has been seen, in the context of the process, that calories taken during this cooling are advantageously transferred to the at least one membrane present. Thus, according to an advantageous embodiment, the cooling means of the hydrogenated gas generated pyrotechnically consist of at least a portion of at least one tubulure putting in communication at least one combustion chamber and at least one metal separation membrane; said at least one portion snaking around said at least one metal separation membrane. Any tubing circulating hot gases generated, snaking around a metal separation membrane, is thus able to perform the function of heat exchanger.

Note that arranged in a material, a fortiori high thermal conductivity, any pipe can theoretically provide some cooling of the hot gas circulating in it ... that the heat exchanger explained above is not necessarily present in a material providing a thermal bridge between the at least one combustion chamber and the at least one membrane ... However, it is understood that in order to be able to ensure maximum heat transfer to the at least one membrane present (and thus to increase its efficiency), it is advantageous to accumulate, within the heat-insulated enclosure, the presence of a material ensuring the thermal bridge specified above (material advantageously having a high thermal conductivity) and that of a heat exchanger (consisting of at least one part of hot gas circulation pipe between at least one combustion chamber and at least one membrane) around said at least one membrane.

As regards the arrangement of said at least one combustion chamber, it is possible, in no way limiting, to indicate the following. Said at least one combustion chamber is per se known. It generally consists of a mechanical assembly containing an ignition device or initiation module (such a module advantageously triggers ignition by mechanical biasing, and such a module therefore advantageously comprises a piezoelectric relay or a primer striker ( see above)), a device for maintaining the main pyrotechnic charge (whose various constituent elements (the presence of a single block is however expressly provided for) may be loose or arranged, so as to limit the bulk ) and possibly a pyrotechnic pellet ignition relay. The loading (which can therefore be monoblock) is generally maintained in a basket, so that the combustion residues are retained in said basket (they constitute a gangue). When said loading consists of several elements, they are stabilized within said basket. This limits and the size and the mechanical stresses of said elements in response to the vibrations of the system. Said at least one combustion chamber comprises at least one delivery orifice for the delivery (under pressure) of the gases generated within it (at high pressure).

Said at least one metal membrane for separating hydrogen from the device of the invention is known per se. It consists, as indicated above, advantageously in a palladium membrane or an alloy containing palladium.

The device of the invention may also contain gas filtration means, currently hydrogenated gas generated pyrotechnically (at least a part thereof), able to rid said gas of at least a portion of the solid combustion residues it contains, arranged downstream of the at least one combustion chamber and upstream of the at least one metal separation membrane, advantageously arranged upstream of the cooling means when such means are present. Such filtration means may for example comprise, as indicated in the introduction to this text, an arrangement of one or more corrugated metal grids or an arrangement of metal elements having pores (from a few millimeters to a few nanometers in diameter). .

The means for delivering the purified gas generally comprise essentially a conventional pipe. They are advantageously suitable for delivering said gas to the user system. Said user system, as indicated above, advantageously consists of at least one fuel cell. Thus, the device of the invention, as described above, is therefore advantageously arranged upstream of at least one fuel cell.

The device of the invention (at least one device of the invention) is advantageously integrated into the structure of a system, in particular a portable or embedded system, for example an airborne system. It can thus be integrated into the structure of an airborne vehicle, for example the fuselage or wings of such a machine.

It is now proposed to illustrate the invention, in no way limiting, by the appended figure (Figure 1). Said single figure schematizes in section a device of the invention (according to a preferred embodiment) suitable for implementing the method of the invention (according to a preferred implementation variant).

The device 100 shown diagrammatically in said FIG. 1 comprises an insulated envelope 1 enclosing four annular combustion chambers 3a, 3b, 3c, 3d each containing a pyrotechnic charge generating hydrogenated gas 4a, 4b, 4c, 4d, and each provided with an orifice 5a, 5b, 5c, 5d opening into a pipe 6. Said four annular combustion chambers 3a, 3b, 3c, 3d are arranged in contact with a material of high thermal conductivity 2, for example iron filings, so too enclosed in the said insulated jacket 1. The tubing 6 is connected to a particle filter 7, and then winds (in its part 6, within the high thermal conductivity material 2, to connect to a tank 8 containing a hydrogen separation membrane 9 (the inlet face of said membrane 9 is referenced 9a, its outlet face 9b), at its distal end with respect to its connection with the tubing 6, the reservoir 8 is provided with a pipe 10 in communication with a fuel cell 11.

The reservoir 8 has an empty volume 8 'on the side of its connection with the tubing 6, which serves to store the gaseous residues separated from the hydrogen by the membrane 9.

Each combustion chamber 4a, 4b, 4c, 4d contains an initiation module 12 of its pyrotechnic charge 4a, 4b, 4c, 4d.

The operation of this device 100 is specified below. One (several) of the 4 hydrogen generating pyrotechnic charges 4a, 4b, 4c, 4d included in the combustion chambers 3a, 3b, 3c, 3d is (are) lit (simultaneously or sequentially) by means of its ( their) initiation module 12. The combustion of the said charge (s) generates, in the combustion chamber (s) that closes (s), hydrogen gas G0 hot at a high pressure (2 to 3.10 ⁶ Pa (20 to 30 bar), for example). Part of the heat of combustion produced in the combustion chamber (s) is absorbed by the high-conductivity material 2. The hot hydrogen gas at high pressure G0 is delivered via the orifice (s) of delivery 5a, 5b, 5c, 5d. It is conveyed, under pressure (at a lower pressure (than the pressure indicated above, operating pressure of the combustion chamber (s) in operation), generally from a few bars to ten bars) in the 6. Said gas delivered under pressure is referenced Gl in FIG. 1. It also exchanges heat with the material with a high thermal conductivity 2. It is freed (at least in part) of the solid combustion residues it contains ( solid residues not trapped in the gangue resulting from the combustion which remains in the combustion chamber (s) having worked (s)) by passing through the particulate filter II is injected, cooled, still under pressure, in the tank 8 containing the metal separation membrane 9. The cooling implemented is optimized to the extent that said gas G1 is circulated around the membrane 9 (more precisely of the reservoir 7 enclosing it), within the material with high thermal conductivity 2. Said high conductivity material 2 therefore transfers heat from the chamber (s) (s) ) of combustion having worked and tubing 6 (gas G1)) to the hydrogen separation membrane 9, which heats up accordingly. The temperature rise of the membrane 9 is thus simultaneous with the production of the hydrogenated gases and favors the efficiency of separation of the hydrogen by said membrane 9. The hot hydrogenated gas G1, after having snaked in the tubing 6, penetrates in the tank 8 (by the empty volume 8 and in contact with the separation membrane 9 (with its inlet face 9a) .The hydrogen is separated by the membrane 9 from the other gaseous species (present in a very small amount) It emerges from said membrane 9 by the outlet face 9b thereof and is delivered downstream, at a purity higher than 99.99%, to the fuel cell 11.

Claims

1. pyrotechnic method for providing hydrogen of very high purity (G), characterized in that it comprises:

the combustion of at least one solid pyrotechnic charge generating hydrogenated gas (4a, 4b, 4c, 4d) for the production of a hydrogen gas (G1), hot, under pressure, containing at least 70% by volume of hydrogen; and

the purification of at least a portion of said hydrogenated gas under pressure (G1), by passing through a metal membrane for separating hydrogen (9) maintained at a temperature above 250 ° C., advantageously between 300 and 600 ° C, to obtain, at the exit of said membrane (9), a hydrogenated gas (G) containing at least 99.99% by volume of hydrogen.

2. Method according to claim 1, characterized in that a part of the amount of heat produced by the combustion of said at least one solid pyrotechnic charge generating hydrogenated gas (4a, 4b, 4c, 4d) is used for heating said membrane metallic separation (9).

3. Method according to claim 2, characterized in that said part of the quantity of heat produced by the combustion of said at least one solid pyrotechnic charge generating hydrogenated gas (4a, 4b, 4c, 4d) is transferred to said metal membrane of separation (9) via a material (2), acting as a thermal bridge, preferably with high thermal conductivity.

4. Method according to any one of claims 1 to 3, characterized in that it further comprises the cooling of at least a portion of said produced hydrogen gas (G1), prior to purification.

5. Method according to claim 4, characterized in that a portion of the amount of heat extracted during said cooling is used to heat said metal separation membrane (9).

6. Method according to any one of claims 1 to 5, characterized in that it further comprises the filtration of at least a portion of said product hydrogen gas (G1) to rid it at least in part of the solid combustion residues it contains, said filtration being carried out upstream of its purification.

7. Method according to any one of claims 1 to 6, characterized in that it comprises, successively, the production of said hydrogenated gas (G1), the filtration of at least a portion of said hydrogenated gas (G1) to rid it at least in part solid combustion residues contained therein, cooling said at least a portion of said filtered hydrogenated gas (G1) and purifying said at least a portion of the hydrogenated gas (G1) filtered and cooled.

8. Method according to any one of claims 1 to 7, characterized in that said at least one solid pyrotechnic hydrogen gas generator (4a, 4b, 4c, 4d) is a pyrotechnic charge consisting of at least one pyrotechnic product containing, for at least 96% of its mass, at least one inorganic oxidizing component and at least one hydrogenated reducing component selected from inorganic hydrides, borazane and polyaminoboranes.

9. Process according to claim 8, characterized in that the said at least one hydrogenated reducing component chosen from inorganic hydrides is chosen from inorganic borohydrides, advantageously alkaline borohydrides and non-earth alkalis, very advantageously lithium borohydrides. and magnesium.

10. The method of claim 8, characterized in that said at least one hydrogenated reducing component is selected from borazane and polyaminoboranes; in that said at least one hydrogenated reducing component is advantageously borazane.

11. A method according to any one of claims 8 to 10, characterized in that said at least one inorganic oxidizing component is selected from perchlorates, dinitroamides, nitrates and metal oxides; advantageously among ammonium perchlorate, ammonium dinitroamide, strontium nitrate and iron oxide.

12. Method according to any one of claims 8 to 11, characterized in that said at least one pyrotechnic product contains:

from 40 to 80% by weight of said at least one hydrogenated reducing component (generally of such a hydrogenated reducing component), and from 20 to 60% by weight of said at least one inorganic oxidizing component (generally of such an inorganic oxidizing component);

in that said at least one pyrotechnic product advantageously contains:

from 55 to 75% by weight of said at least one hydrogenated reducing component (generally of such a hydrogenated reducing component), and

from 25 to 45% by weight of said at least one inorganic oxidizing component (generally of such an inorganic oxidizing component).

13. Method according to any one of claims 8 to 12, characterized in that said at least one pyrotechnic product contains more than 50%, preferably more than 70% by weight of said at least one hydrogenated reducing component.

14. Method according to any one of claims 1 to 13, characterized in that it is implemented for feeding at least one fuel cell (11).

15. pyrotechnic device (100) for providing hydrogen of very high purity (G), suitable for implementing the method according to any one of claims 1 to 14, characterized in that it comprises:

at least one combustion chamber (3a, 3b, 3c, 3d) provided with at least one delivery orifice (5a, 5b, 5c, 5d) suitable for the arrangement and for the combustion at high pressure, within it , a solid pyrotechnic charge generating hydrogenated gas (4a, 4b, 4c, 4d), as well as the delivery of hot hydrogen gas, under pressure, (G1) via said at least one delivery orifice (5a, 5b) , 5c, 5d);

at least one metal membrane for separating hydrogen (9), suitable for purification of hydrogenated gas, having an inlet face (9a) and an outlet face (9b); said metal hydrogen separation membrane (9) being arranged in a reservoir (8) so that a void volume (80 is formed in said reservoir (8) upstream of its inlet face (9a);

means for delivering the purified gas (10); said combustion chamber (s) (3a, 3b, 3c, 3d) and metal membrane (s) of hydrogen separation (9) being placed in communication via at least one pipe (6) so that hydrogenated gas delivered from the combustion chamber (s) (3a, 3b, 3c, 3d) is directed towards at least one metal membrane for hydrogen separation (9) and arranged inside a heat-insulated enclosure (1); said delivery means (10) being able to ensure the delivery of gas, purified within said hydrogen metal separation membrane (s) (9), out of said enclosure insulated (1).

16. Device (100) according to claim 15, characterized in that it comprises at least one annular combustion chamber (3a, 3b, 3c, 3d) arranged around at least one metal separation membrane (9).

17. Device (100) according to claim 15 or 16, characterized in that said insulated enclosure (1) contains a material (2) providing a thermal bridge between said combustion chamber (s) (3a, 3b, 3c, 3d) and metallic membrane (s) (9); said material (2) being advantageously of high thermal conductivity.

18. Device (100) according to any one of claims 15 to 17, characterized in that it further comprises gas cooling means (G1), arranged downstream of the at least one combustion chamber (3a, 3b, 3c, 3d) and upstream of the at least one metal separation membrane (9).

19. Device (100) according to claim 18, characterized in that said means consist of at least a portion (6 ') of the at least one tubulure (6) communicating the at least one combustion chamber (3a, 3b , 3c, 3d) and the at least one metal separation membrane (9); said portion (6 ') snaking around said at least one metal separation membrane (9).

20. Device (100) according to any one of the claims

15 to 19, characterized in that said at least one metal separation membrane (9) is a palladium membrane or an alloy containing palladium.

21. Device (100) according to any one of claims 15 to 20, characterized in that it further contains filtration means (7) of the gas (G1), able to rid it of at least a portion of residues combustion solids it contains, arranged downstream of the at least one combustion chamber (3a, 3b, 3c, 3d) and upstream of the at least one metal separation membrane (9), advantageously arranged upstream of the means cooling means (7) when such means (7) are present.

22. Device (100) according to any one of claims 15 to 21, characterized in that it is arranged upstream of at least one fuel cell (11).