FR2658181A1 - Regenerable reactive fluid for energy storage, and plant for the production and use of hydrogen using such a fluid - Google Patents

Abstract

The invention relates to a regenerable reactive fluid for energy storage, and to a plant for the production and use of hydrogen using such a regenerable reactive fluid. According to an essential characteristic of the invention, this fluid consists of a suspension of a metal powder in water, the said powder being obtained from at least one metal taken from the group consisting of aluminium, magnesium, zinc and iron, with addition of at least one adjuvant which promotes the sedimentary and/or chemical stability of the said suspension with time, the said fluid thus being capable of releasing energy in the form of heat and hydrogen at the time of the initiation of a decomposition reaction of water by the said metal. The associated plant contains a hydrogen generator (100) comprising at least one reactor (101, 102), having an inlet (110) for continuously supplying with the regenerable reactive fluid and surmounted by a cooling element (120) at the outlet of which the hydrogen can be recovered, and preferably also a unit for the catalytic combustion of the hydrogen (130), and a recovery or condensation heat exchanger (140). Application especially to any use using hydrogen as chemical and energetic vector (carrier), and in particular to the production of a chemical boiler.

Description

 The present invention relates to the field of energy storage, and more particularly that of regenerable reactive fluids for storing energy and releasing this energy at least in the form of heat, and preferably also in the form of hydrogen.

 Beyond the old techniques of sensible heat storage (for example using gravel), or more recent techniques of latent heat storage (for example using phase change materials or PCM, or certain specific mineral or organic compounds ), we investigated thermochemical energy storage techniques using endo and exothermic chemical reactions that are reversible or reversible. This type of storage makes it possible to use chemical compounds as cold storage energy.

 It has thus been proposed to use, for example, calcium oxide or magnesium oxide. These two products lead, by hydration, to the corresponding hydroxide with use of heat, the regeneration being ensured by decomposition of the oxide hydroxide in a subsequent phase.

 Calcium oxide used, in the form of powder or granules arranged in water, may for example allow to obtain a heat production of the order of 1.25 MJ per kg of calcium oxide.

 This type of technique, besides its limitation to the production of heat, offers results that remain mediocre, mainly because of the poor heat conduction of the calcium oxide which is always in the form of a divided solid.

 As a result, it is particularly attractive to use metal-based regenerable reactive fluids, because the storage density in J / kg can reach high values, in particular by reaching the storage density level of the domestic fuel, which However, it is not regenerable.

 There is a growing trend towards the use of hydrogen, both as a chemical and energetic vector, because it has a high energy content, and it is also a "clean" fuel (total absence of pollutants to combustion), unlike hydrocarbons whose combustion generates a release of unburnt toxic and carbon dioxide.

 The storage of hydrogen in the gaseous state (or more rarely liquid, as is the case, for example, in the aerospace field) has drawbacks (risks of explosion, and weight of the storage bottles if we want to avoid underground storage under pressure), which led to study the use of metal hydrides to store the hydrogen in adsorbed form. However, metal hydrides are still very expensive, and their use is still difficult to control.

 The state of the art is also illustrated by French Patent No. 2,288,548, in which there is described a reactor for hydrogen production synthesis carburation, in which it is intended to decompose in water containing sodium hydroxide. caustic, aluminum which abounds releases pure hydrogen, with bubbling of the liquid, according to an oxidation-reduction reaction of water.

 Such a system is actually difficult to exploit.

 Indeed, the supply of the reactor is completely discontinuous, and it is therefore difficult to control: the figures of the aforementioned patent illustrate the gravimetric feed mode used, being effected by spilling aluminum elements ( in bars, sheets, powder, or waste) in the upper part of the reactor then open. Therefore, in addition to the difficulty of preserving the hermetic integrity of the reactor and the need for human intervention, the flow rate of hydrogen remains completely random.

 The state of the art can be further supplemented by Japanese Patent Application No. 63-89401, in which a continuous hydrogen production system is described which comprises a vessel containing water, in which At the top of the tank is provided a feed hopper of aluminum powder, this powder thus falling on the successive inclined trays: the hydrogen is bubbled in an aqueous solution of soda, and emerges back to countercurrent in the liquid-solid medium.

 Such a system is also difficult to exploit in practice: in addition to the random flow of hydrogen, due to the discontinuous gravimetric feed in aluminum powder, and the difficulty of maintaining the hermetic integrity of the tank (because of the feeding in solid form leaving an interstitial porosity complicating the control of the tightness of the supply system, and therefore of the entire installation), drawbacks already noted for the previous system, should be added the need to provide a tank large because of the heterogeneity of the phase it contains, as well as the risk of fouling inclined trays. In addition, the installation necessarily includes an intermediate storage of hydrogen to try to regulate the hydrogen supply flow rate, which poses a problem for the safety of the environment. Finally, this system is actually limited to an application in laboratory, but remains in fact impracticable industrially.

 The object of the invention is to design a more efficient regenerable reactive fluid, allowing an easy and safe storage of hydrogen in the form of a fluid, and which is at the same time stable over time (chemical and sedimentative stability), all by having a very high energy density.

 The object of the invention is also to propose a regenerable reactive fluid whose viscosity is compatible with its transport and its pumping by conventional methods, and the formulation of which can be defined with a sufficiently high precision to be able to control the flow of hydrogen, to produce hydrogen only on demand, without the need for intermediate storage.

 The object of the invention is also to propose a regenerable reactive fluid whose composition can be determined according to the type of application concerned, depending on whether one is primarily interested in the heat or the volume of hydrogen that one seeks to obtain, and also according to the storage temperatures concerned.

 Another object of the invention is to provide a plant for the production and use of hydrogen employing a regenerable reactive fluid of the aforementioned type, which can be fed continuously with regenerable reactive fluid, while remaining of simple and compatible structure. with very diverse applications, both direct (fuel cells, engines, chemical reagents), and indirect (with a combustion of hydrogen produced, especially for domestic heating, thus allowing the realization of a real "boiler chemical").

 Another object of the invention is to provide such an installation capable of continuous supply and withdrawal, without requiring any human intervention, whose efficiency is high, and whose operation is both flexible and easily controllable.

 It is more particularly a regenerable reactive fluid energy storage, characterized in that it consists of a suspension of metal powder in water, said powder being obtained from at least one metal taken from the group consisting of aluminum, magnesium, zinc, and iron, with addition of at least one adjuvant promoting the sedimentative and / or chemical stability of said suspension over time, said regenerable reactive fluid being thus susceptible to release energy in the form of heat and hydrogen upon initiation of a reaction of decomposition of water by said metal.

 More particularly, the metal powder is an atomized powder whose average particle size is of the order of 10 to 30 μm.

 According to a particularly advantageous embodiment, the regenerable reactive fluid comprises at least one adjuvant constituted by a polymer derived from cellulose; in particular, the adjuvant used is constituted by a carboxymethyl cellulose (CMC), or is constituted by a hydroxyethyl cellulose (HEC).

 Alternatively, the regeneratable reactive fluid comprises a carboxymethyl cellulose (CMC) adjuvant and a hydroxyethyl cellulose (HEC) adjuvant.

 For some applications, it is advantageous to provide that the regenerable reactive fluid also comprises an additive improving the resistance of the suspension to microorganisms, such as formalin, and / or an additive promoting the chemical stability of the suspension, such as sodium silicate.

 Advantageously, the contents of metal powder and adjuvants or additives are chosen so that the viscosity of said fluid is compatible with its transport and its pumping, for example being at most equal to 8 Pa.s, and preferably between 3 and 6. Not.

 According to a preferred embodiment, the metal powder is an aluminum powder, and the aluminum and water masses are in a ratio of between 0.45 and 0.6, and preferably close to 0.5.

 According to an advantageous formulation, the regenerable reactive fluid comprises adjuvants or additives whose approximate mass percentages are divided into 2% of sodium silicate and 1.7 to 1.9% of hydroxyethyl cellulose (HEC), with the addition of a saline solution for substantially lowering the freezing point of said fluid for external storage thereof, in particular a saline solution such that the mass ratio NaCl / H 2 O is between 0.19 and 0.23.

 Alternatively, the regenerable reactive fluid comprises adjuvants or additives whose approximate mass percentages are divided into 1% formalin, 2% sodium silicate, and 1.6 to 2% hydroxyethyl cellulose (HEC).

 According to another variant, the regenerable reactive fluid comprises adjuvants or additives whose approximate mass percentages are divided into 1% formalin, 2% sodium silicate, 0.5 to 1% hydroxyethyl cellulose (HEC), and 2.3 to 2.6% carboxymethylcellulose (CMC).

 According to another variant, the regenerable reactive fluid comprises adjuvants or additives whose approximate mass percentages are divided into 1% formalin, 2% sodium silicate, 0.5 to 1% hydroxyethyl cellulose (HEC), and 2.8 to 3.2% carboxymethylcellulose (CMC).

 The invention also relates to an installation for the production and use of hydrogen employing a regenerable reactive fluid comprising at least one of the abovementioned characteristics, this installation being characterized in that it comprises a hydrogen generator comprising at least one hermetically sealed reactor of perfectly agitated type, having a continuous feed inlet regenerable reactive fluid and surmounted by a cooling element at the output of which the hydrogen can be recovered. As the metal supply is obtained by a continuous fluid, the seal is then easily controllable, which was not the case for the known techniques.

 According to a particular embodiment in which the aforementioned installation is usable as a chemical boiler, this installation is remarkable in that it further comprises a hydrogen combustion unit and, downstream thereof, a heat exchanger. heat.

 Preferably, the combustion unit is a catalytic reactor of conventional type, for example a fixed bed of beads or a block of monolith impregnated with catalyst, making it possible to recover hydrogen by catalytic combustion; in particular, the catalytic reactor is connected to the outlet of the cooling element via a filtration module for stopping the fine particles entrained, a non-return valve, and a venturi-mixer allowing the diluted hydrogen to be diluted in compressed air.

 Also preferably, the heat exchanger is a conventional type of exchanger, either direct (bubble column) or indirect (condensing), allowing a better recovery of the combustion gases.

 It is furthermore interesting that the above-mentioned plant also comprises an additional heat recovery unit using the metal-water suspension resulting from the water decomposition reaction, said additional unit comprising a conventional type exchanger, for example an exchanger. cylindrical coaxial.

 In this case, it is advantageous for the exchanger of the additional unit to be connected to the reactor or to at least one of the reactors of the hydrogen generator via a precipitation / filtration module, the water pipe passing through said exchanger being connected to the inlet of the heat exchanger provided downstream of the combustion unit to thereby allow a preheating of a portion of the primary fluid of said exchanger of the additional unit; in particular, an emulsion venturi is provided upstream of the heat exchanger provided downstream of the combustion unit, to which the water pipe passing through the exchanger of the additional unit arrives, a recirculation pump being in further provided, preferably upstream of said emulsion venturi.

 It is also interesting, for an installation in which the regenerable reactive fluid is constituted by a suspension of aluminum powder in the water, that this installation comprises a first reactor comprising inferiorly a continuous feed inlet regenerable reactive fluid and an additional sodium feed inlet, and a second reactor in series with said first reactor and having a lower continuous withdrawal outlet of the products of the reaction.

 Other characteristics and advantages of the invention will emerge more clearly in the light of the following description and of the single figure of the appended drawing, relating to a particular embodiment of a plant for the production and use of hydrogen. , using a regenerable reactive fluid according to the invention.

 As has been indicated above, the regenerable reactive fluid is constituted, according to an essential characteristic of the invention, by a suspension of metal powder in water, said powder being obtained from at least one metal taken in the group consisting of aluminum, magnesium, zinc and iron, with addition of at least one adjuvant promoting the sedimentative and / or chemical stability of said suspension over time, so that this regenerable reactive fluid is thus capable of releasing energy in the form of heat and hydrogen during the initiation of a reaction of decomposition of water by said metal.

 Although it may be envisaged, in some particular cases, to use mixtures or alloys made from several metals of the above-mentioned group, a single metal will generally be used to constitute the suspended powder in water.

 The choice of the metal will generally be guided by the type of application concerned, depending on whether one is primarily interested in the recoverable heat or the volume of hydrogen that one seeks to obtain, but also by the type of industrial infrastructure available.

 In theory, it would be possible to consider any metal M whose electrochemical potential is lower than that of hydrogen, so as to obtain a decomposition of water leading to the production of hydrogen, according to the reaction M + n H2 M - OH (OH) n + n / 2H 2. In fact, for practical reasons of implementation, it seemed preferable to be limited to the aforementioned group of metals.

 As such, aluminum appears to be the most advantageous metal in this group of metals.

 Indeed, aluminum is a more reducing metal than the usual metals (copper, lead, iron, zinc). Its high valence leads to the release of 1.5 moles of hydrogen per mole of aluminum.

 Aluminum, although an eminently oxidizable metal, is, however, unalterable in the air at ordinary temperature, because a thin layer (0.01 to 0.1 microns) is formed cold on its surface. very compact amorphous alumina which protects it from deep oxidation.

In addition, between 0 and 1000C, pure water does not attack the aluminum of good purity. There is simply an increase in the thickness of the oxide layer.

Alumina acts as a protective layer, thus preserving the aluminum from any oxidation during its integration with the regenerative reactive fluid.

 Aluminum reacts in the presence of soda because the soda dissolves the protective layer of alumina and allows the attack of aluminum. The reaction releases energy in the form of heat and hydrogen.

The aluminum after reaction is in the form of hydroxide.

Overall aluminum reacts on water according to reaction
Al + 3H2O NaOfl Al (OH) 3 + 3/2 H2 + 480.6 KJ / Mol
The energy is released during the reaction in the form of heat for 52%, and in the form of hydrogen for 48%. For an aluminum mass percentage of 31.4 in the regenerable reactive fluid, and knowing that the heat of combustion of hydrogen is 295.5 KJ / Mol, the available energy is 10.74 MJ per kg of fluid regenerable reagent (5.59 MJ in the form of heat and 5.15 MJ in the form of hydrogen). It may be noted that the equivalent heating value is 92.3 MJ per liter of crude aluminum and 44.4 MJ per liter powdered aluminum, still 34.2 MJ per kg of aluminum powder, against 41.8 MJ / kg for heating oil.

 The aluminum hydroxide obtained after reaction is a solid product that can be reconverted into aluminum, following the traditional processes of the aluminum industry (calcination, electrolysis, etc.).

 In practice, a suspension of atomized aluminum powder will preferably be chosen such that the aluminum and water masses are in a ratio of between 0.45 and 0.6, for example close to 0.5.

The average particle size of the aluminum powder is of the order of 10 to 20 μm, in particular around 15 μm.

 This atomized aluminum powder may for example be obtained by the Hall process, in which compressed air at very high pressure is expanded around the orifice of a nozzle fed with liquid aluminum. This jet of compressed air creates a vacuum around the orifice, which causes the aluminum to rise and burst into fine droplets. The pulverized aluminum is then aspirated by vacuum in cyclones.

 In the case of magnesium, no basic supply is necessary to trigger or initiate the decomposition reaction of water, but it must however provide heating means for the water in which the powder is suspended is carried at a temperature of the order of 70 ° C. (it is well known that the reaction is only initiated from a temperature threshold.) The reaction is exothermic, as for aluminum, but gives a little less hydrogen and a little more heat for a given mass of suspension with a regenerable reagent fluid of stoichiometric formulation.

 For a zinc powder, it is necessary to provide a strong base (soda, potash ...) as for aluminum. The choice of zinc is certainly good in theory, but we must recognize that there are currently few existing structures for its industrial exploitation. In addition, the sedimentation stability is more difficult to control than with aluminum, so it is necessary to provide for this purpose intermittent stirring means. The reaction is again exothermic, and allows in fact to obtain mostly hydrogen for a small amount of heat released.

 With an iron powder, the conditions of the initiation of the reaction are relatively severe, since the presence of a water vapor at a temperature of at least 200 ° C (the reaction is, it is appropriate to As a result, the applications of this type of regenerable reactive fluid will be essentially focused on the industry interested in producing hydrogen.

 Tables I and II which follow gather comparative data of different types of regenerable reactive fluids organized according to a suspension of metal powder in water.

 Table I indicates, for each type of metal concerned (distinguishing for iron two FeII and FeIII oxidation levels distinguishing for iron two levels of Fe oxidation and the molar mass M m (in kg mol1), the density of the metal mass fraction Xm of a stoichiometric formulation (it being understood that the mass of adjuvants or additives - to which it will be returned later - was not taken into account for this comparison), and the density approximate minimum # (in kg / m3) of such a metal-water slurry (again without regard to adjuvants or additives).

TABLE I

<tb> Metal <SEP> Mm <SEP> d <SEP> Xm <SEP> SE <SEP>
<tb> Mg <SEP> 24.31x10-3 <SEP> 1.74 <SEP> 0.403 <SEP> 1 <SEP> 208
<tb> Al <SEP> | <SEP> 26.98x10-3 <SEP> | <SEP> 2.7 <SEP> | <SEP> 0.333 <SEP> | <SEP> 1 <SEP> 265
<tb> Zn <SEP> 65.38x10-3 <SEP> 7.14 <SEP> 0.645 <SEP> 2 <SEP> 245
<tb> FeII <SEP> 0.608 <SEP> 2 <SEP> 130
<tb><SEP># 55,85x10-3 <SEP><SEP># 7,86
<tb> FeIII <SEP> 0.508 <SEP> 1 <SEP> 800
<Tb>
Table II indicates, for each type of metal concerned, the enthalpy 5 H of the water-metal reactions (in KJ.mol-1), the quantity Q of heat produced per kg of regenerable reagent fluid of stoichiometric formulation (in MJ / kg), the H2 volume of hydrogen produced by the reaction per kg of regenerable reactive fluid (in Nm3 / kg, the Normals-m3 referred to the normal conditions being in fact more telling than a rise in mol of hydrogen released by number moles of metal), and finally the percentage r due to gas.

TABLE II

<tb> Metal <SEP> | <SEP>#H<SEP><SEP> | <SEP> Q <SEP> | <SEP> VH2 <SEP> | <SEP> r
<tb><SEP> Mg <SEP> - <SEP> 352.6 <SEP> - <SEP> 5.84 <SEP> 0.371 <SEP> 44.7
<tb><SEP> Al <SEP> - <SEP> 414.8 <SEP> - <SEP> 5,12 <SEP> 0.415 <SEP> 50.8
<tb><SEP> Zn <SEP> - <SEP> 70.47 <SEP> - <SEP> 0.69 <SEP> 0.221 <SEP> 80.2
<tb><SEP> FeII <SEP> + <SEP> 3.51 <SEP> + <SEP> 0.038 <SEQ> 0.244 <SEQ> 98.7
<tb><SEP> FeIII <SEP> + <SEP> 33.27 <SEP> + <SEP> 0.30 <SEP> 0.306 <SEP> 92.2
<Tb>
As has been said above, the regenerable reactive fluid is a suspension of metal powder in water, with addition of at least one adjuvant promoting the sedimentative and / or chemical stability of said suspension over time.

 In fact, it is first of all sought to limit as much as possible the sedimentation of the metal powder in the water, in order to obtain a pseudo-homogeneous fluid. This can be achieved by using a suitable adjuvant, such as a polymer derived from cellulose: two families of cellulosic polymers can be cited as such, namely carboxymethylcelluloses (CMC denoted) and hydroxyethylcelluloses (denoted HEC), separately or in combination.

 It should be noted that hydroxyethylcelluloses provide an advantageous effect of gelling in the absence of movement, which is of interest for the regenerable reactive fluid. It should also be noted that carboxymethylcelluloses also have the effect of reducing the viscosity: although this is only a secondary result, it is nonetheless favorable for transport and pumping. regenerable reactive fluid.

 Moreover, it may be advantageous to provide in addition two other types of additives, namely an additive improving the resistance of the suspension to microorganisms, such as formalin, and / or an additive promoting the chemical stability of said suspension, such as sodium silicate.

 In general, the regenerable reactive fluid has a freezing point of -4 ° C. However, it may be advantageous, in the case of certain particular applications, to lower this freezing point further so as to reduce the freezing point. allow external storage of the regenerable reactive fluid, in which case another additive will be provided, for example in the form of a saline solution, for lowering the freezing point of the regenerable reactive fluid to-150C, for example a saline solution such as the NaCl / H 2 mass ratio is between 0.19 and 0.23.

 Moreover, as indicated above, the viscosity of the regenerable reactive fluid is a parameter whose role is important for the transport of said fluid, in order to allow a continuous supply and very flexible for an installation using such a device. regenerable reactive fluid. In this respect, it is advantageous to adjust the contents of metallic powder and adjuvants or additives so that the viscosity of the regenerable reactive fluid is compatible with its transport and its pumping, for example being at most equal to 8 Pa.s, this viscosity preferably being between 3 and 6 Pa.s.

 The following Table III gathers the data relating to the formulation of different regenerable reactive fluids in which the metal powder is here an atomized powder of aluminum, according to a suspension such that the aluminum and water masses are in a ratio ranging from 0.45 to 0.6.

These data thus detail, as a purely illustrative example, the composition of five regenerable reactive fluids (noted
Compositions A to E) as adjuvants or additives, said data being expressed in percentages by weight.

 In the case of adjuvants consisting of cellulosic polymers, particular types of carboxymethylcellulose (CMC) and / or hydroxyethylcellulose (HEC) are provided. Thus, in Table III, two hydroxyethylcelluloses (HEC), sold respectively under the name "HEC-MBR" and "HEC-HBR", and a carboxymethylcellulose (CMC) sold under the name "CMC" are found in Table III. -7M IC ".

One of the five compositions (Composition A) in
Table III comprises as additive a saline solution, whose weight ratio noted NaCl / H 2 O is here between 0.19 and 0.23, aimed at lowering the freezing point of the regenerable reactive fluid, as explained above.

adjuvant
<tb> or <SEP> Composition <SEP> A <SEP> Composition <SEP> B <SEP> Composition <SEP> C <SEP> Composition <SEP> D <SEP> Composition <SEP> E
<tb> Additive
<tb> Formol <SEP> 1 <SEP>% <SEP> 1 <SEP>% <SEP> 1 <SEP>% <SEP> 1 <SEP>%
<tb> Silicate <SEP> of <SEP> Sodium <SEP> 2 <SEP>% <SEP> 2 <SEP>% <SEP> 2 <SEP>% <SEP> 2 <SEP>% <SEP> 2 <SEP >%
<tb> HEC-MBR <SEP> 1.7 <SEP> to <SEP> 1.9 <SEP>% <SEP> 1.6 <SEP> to <SEP> 2 <SEP>% <SEP> 0.6 <SEP> to <SEP> 1 <SEP>%
<tb> HEC-HBR <SEP> 0.5 <SEP> to <SEP> 1 <SEP>% <SEP> 0.5 <SEP> to <SEP> 0.8 <SEP>%
<tb> CMC-7MIC <SEP> 2,3 <SEP> to <SEP> 2,6 <SEP>% <SEP> 2,8 <SEP> to <SEP> 3,2 <SEP>% <SEP> 2 , 8 <SEP> to <SEP> 3.2 <SEP>%
<tb> NaCl / H2O <SEP> 0.19 <SEP> to <SEP> 0.23
<Tb>

 It should be noted that Compositions D and E are relatively close, and that the weight percentage of cellulosic polymers can be mentioned synthetically, indicating a percentage of 0.5 to 1% for the HEC adjuvant, and 2.8 3.2% for CMC adjuvant.

 In general, it goes without saying that the ranges of mass percentages indicated in Table III are given for information only, and that they can not in any way limit the scope of the invention.

 With regard to their chemical and / or sedimentative stability, and their viscosity, the five compositions A to E correspond to relatively comparable regenerable reactive fluids.

The storage temperatures of these regenerable reactive fluids, ensuring safe storage, range from -2 ° C to 50 ° C for each of Compositions B to E, and from -15 ° C to 50 ° C for
Composition A. In reality, suspensions of this type are able to resist without problem for two hours if they are subjected to a temperature up to 70 ° C.

 These suspensions should preferably be stored away from light. Their lifespan varies from two to five months depending on the case, being more precisely of the order of two months with Composition A, and of the order of four to five months with Compositions B to E.

 The above data can easily be applied to the case of magnesium, zinc and iron. However, in the case of suspensions based on iron or zinc, the concentrations of the stabilizer used (CMC and / or HEC) should be increased compared to those indicated in Table III, since the minimum density of the suspensions metal-water concerned is significantly larger (it is more than twice that of water, as shown in Table I).

 The various regenerable reactive fluids which have just been described are thus quite suitable for storage, transport and pumping in a pseudo-homogeneous phase, and are capable of releasing energy on demand in the form of heat and heat. hydrogen, when initiating a reaction of decomposition of water by the metal used. In addition, it is possible to combine the advantages of stability over time (in particular chemical and sedimentative stability) and a very high energy density. Finally, the formulation of the regenerable reactive fluid can be precisely defined, which in particular makes it possible to control the flow of hydrogen in a completely satisfactory manner.

 The possible applications of the regenerable reactive fluids in accordance with the invention are numerous, and both direct (fuel cells, engines, chemical reagents), and indirect (with combustion of hydrogen), allowing in particular the realization of a "chemical boiler".

 This latter application is particularly advantageous because the regenerable reactive fluid according to the invention makes it possible to obtain a non-polluting alternative energy source: in fact, hydrogen produces only water during its combustion, and therefore none of the pollutants usually encountered (carbon dioxide, hydrocarbons, or aromatics, nitrogen compounds, sulfur compounds).

 For example, it is possible to develop a chemical boiler based on a process for producing hydrogen using a regenerable reactive fluid, and preferably an aluminum-based regenerable reactive fluid. This then makes it possible to avoid the hydrogen storage and transport steps usually encountered with conventional techniques, in order to make room for the transport of a compound in liquid form in pseudo-homogeneous phase (pseudo-liquid). In addition, aluminum is safe, so that such a chemical boiler concept is very interesting in the building sector, to organize space heating.

 Combustion can be envisaged either by burner or in catalytic form, and in the latter case it suffices then to provide downstream a conventional or direct contact heat exchanger system (submerged combustion type or bubble column).

 We will now describe, with reference to the single figure of the drawing, an installation for the production and use of hydrogen using a regenerable reactive fluid according to the invention.

 This installation illustrates the concept of a chemical boiler, with here a catalytic combustion of the hydrogen obtained, as well as a recovery of the heat produced at several levels.

 According to an essential aspect of the invention, the installation comprises a hydrogen generator 100 comprising at least one hermetically sealed reactor and of perfectly stirred type (here two reactors 101, 102 arranged in series), having a feed inlet. continuously regenerable reagent fluid and surmounted by a refrigerant element 120 at the output of which the hydrogen can be recovered.

 The installation illustrated here uses a regenerable reactive fluid comprising an atomized powder of aluminum suspended in water. In the case of other metals, it will be seen that it is sufficient to slightly modify the structure of the reactor (s) to organize the heating necessary to trigger the reaction of decomposition of water by the metal.

 The first reactor 101 consists of a hermetically closed enclosure 103, in the lower part of which are provided on the one hand an inlet 110 for continuous supply of regenerable reactive fluid (the regenerable reactive fluid is transported by a pipe 112, and pumped by conventional pumping means not shown here), and on the other hand an additional inlet 111 for supplying soda (the sodium hydroxide solution, for example at 2 moles / liter, is transported by a pipe 113, and pumped by conventional pumping means not shown). In the upper part, a sealed cover 118 carries an agitator 175 whose fin is close to the bottom of the enclosure 103, and an associated drive motor 116 disposed outside said enclosure. The reaction medium 104 is thus continuously agitated, and its temperature is identified by a sensor 117 mounted on the cover 118. Finally, there is provided, in the lower part of the enclosure, a draw-off valve 114.

 Although this is not mandatory, here a second reactor 102 is provided which is practically identical to the first reactor 101, and in series with it via a connection 107.

 This second reactor thus comprises a hermetically sealed enclosure 104, surmounted by a tight cover 119, and it is equipped with an agitator 175 with its associated motor 116, a temperature sensor 117, and a lower take-off valve. 114. In the lower part of this second reactor, there is provided here an outlet 115 continuously withdrawing the products of the reaction, leading through a pipe 154 to heat exchange means which will be described later.

 A connection in the upper part of the two reactors 101, 102 is provided by tubes 108, 109, leading to the lower inlet of the cooling element 120. This cooling element 120 is of conventional design and has a cold water coil internally. , of which only the inlet 122 and the outlet 123 have been shown, said outlet leading through a pipe 155 to the aforementioned heat-exchange means, and on which it will be returned later.

The reaction scheme in the hydrogen generator 100 is as follows (a) dissolution of the protective film A1203:
A13 + - 4 OH H-- o (Al (OH) 4) + 2H2O
2 (b) oxidation with formation of solid Al (OH) 3
al; + 3 H2O --- o Al (OH) 3 + 3/2 H2
Al (OH) 3 crystallizes (nucleation) on the surface of aluminum crystals
and AL (OH) 3 already present.

(c) dissolution of the crystallized solid phase on the surface of the metal
Al (OH) 3; NaOH ---> NaAl (OH) 4
The balance sheet is
AI + 3 H2O + NaOH --- r 3/2 H2 + NaAl (OH) 4
In the first reactor 101, which is fed continuously with regenerable reactive fluid and sodium hydroxide, the reaction self-initializes at room temperature, and stabilizes in steady state at 90-95 C, after a transient regime whose duration is of a few minutes.

 If the reaction is complete in the first reactor 101, the second reactor 102 is still useful because it serves as an expansion vessel for the formed foam and buffer reactor before emptying. If the reaction is not complete in the first reactor 101, this reaction is completed in the second reactor 102 (this can be very useful when using a high feed rate of regenerable reactive fluid, since thus keep an identical overall time of passage).

 Thus, the use of a second reactor constitutes a significant advantage for the installation.

 The hydrogen formed and the water vapor rise through the tubes 108, 109 to the cooling element 120, and the water vapor recondenses on contact with the cold coil of said cooling element, so that the hydrogen escaping through a high outlet 121 of the refrigerant element then becomes available for the intended use.

 In the case where it is envisaged to use an atomized powder other than an aluminum or zinc powder, the structure of the reactor (s) of the hydrogen generator 100 should be modified somewhat.

 For example, with a magnesium powder, the enclosure will be double jacket, to organize a hot water circulation, with further heating electric resistance (this direct heating mode is preferable to a heater operated upstream of the reactor, which could generate a problem of bubbling resulting from a reaction initiated too early).

 In the case of iron, the inlet 111 will serve as a supply of water vapor whose temperature is at least 200 ° C, and naturally will also be provided heating means such as those already mentioned for a magnesium powder .

 The installation illustrated here is usable as a chemical boiler: it comprises, downstream of the hydrogen generator 100, a hydrogen combustion unit 130, downstream of which is provided a heat exchanger 140.

 The combustion of hydrogen could naturally be carried out in a traditional manner by means of a burner. Means embodying a catalytic combustion are illustrated here, so that the combustion unit 130 is a catalytic reactor, making it possible to recover hydrogen by catalytic combustion.

 Recall briefly that a catalyst is a body that acts as a chemical accelerator, here combustion. It participates in transient intermediate reactions and is found intact at the end of the reaction. The principle of catalytic combustion is already widely used in the industry: after-combustion of fumes (catalytic converter), catalytic radiant panels with natural gas.

 Catalytic combustion has two characteristics: it occurs without a flame and at a temperature below the normal autoignition temperature. This mode of combustion has the advantage of not releasing any nitrogen oxide since it is carried out at low temperature, in addition to the possibility of obtaining high combustion efficiencies.

Finally, a well sized catalytic reactor easily withstands variations in the hydrogen flow rate without yield drop.

 The catalytic reactor 130 chosen here is a fixed bed of alumina balls impregnated with palladium, which can be distinguished from the central column 132 with its end flanges 133, 134, and the outer shell 131 with its external communications 135, 136 for the cooling fluid (air or water). The catalytic combustion temperature is furthermore controlled by means of an associated sensor 139. The hydrogen is diluted in air and the reaction is self-initialized at ambient temperature: the yields obtained (measurement by mass spectrometry) are then from 99 to 100% from 1800C. In a variant, it is possible to use a monolith block impregnated with catalyst, or else a system of two coaxial cylinders (of horizontal axis) between which the catalyst is placed.

 The operating conditions of a catalytic combustion reactor are characterized by the specific volume flow rate in liters per hour per gram (1 / hr 1), which is the volume flow rate of fuel gas per gram of catalyst: for a given catalyst , combustion will be total at a given specific volume flow, and a given minimum combustion temperature (the temperature favors combustion).

 At fixed specific volumetric flow, the catalytic combustion is even better than the temperature (directly related to the amount of hydrogen to be burned) is high. These results were obtained at the laboratory scale for hydrogen flow rates of the order of 20 I / h. For the reaction device, a specific volume flow rate of 120 to 150 l / h / g is chosen for a temperature of 200 to 400 ° C. in a steady state, a combustion rate of 100% is then ensured.

 The catalytic reactor 130 is connected to the outlet of the refrigerating element 120 by a first duct 124 leading here to a venturimixer 127, then by a second duct 129 downstream of said venturi-mixer. Furthermore, there is provided, between the refrigerating element 120 and the venturi-mixer 127, a filtration module 125 making it possible to stop the fine particles that could have been entrained, as well as a non-return valve 126. Venturi mixer 127 has an air inlet 128, so that the incoming hydrogen, filtered, in said venturi, is sucked in and diluted in the compressed air (a dilution of 3 to 4% is usually retained to preserve the safety of Installation). It goes without saying that the venturi-mixer could be replaced for any other equivalent gas / gas device.

 In the lower part of the catalytic reactor 130, the combustion gases exit at a temperature of about 300.degree. C., via a pipe 137 leading firstly to an emulsion venturi 160 (to promote the exchange), then, via a pipe 138, to a heat exchanger 140 of conventional type, either direct (bubble column) or indirect (condensing), allowing a better recovery of the combustion gases.

 There is illustrated here an exchanger 140 in the form of a bubble column, but one could also use a known system with water tank and recirculation (submerged combustion) or a known system of water spray in a hot gas . The bubble column 140 is here conventionally surmounted by a first expansion tank assembly 141, with an upper air outlet 146 and an outlet side tube 142, said lateral tube leading via a pipe 143 to a second set of expansion tank 144, downstream of which is provided a pipe 145 leading to the inlet of a recirculation pump 170 whose output reaches the inlet of the emulsion venturi 160.

 The heat exchanger 140 which has just been described constitutes a first level of heat recovery: indeed, at the outlet of the catalytic combustion, it is the combustion gases (excess air + steam of combustion water) at a temperature of 200 to 400 ° C which are recovered in the direct-contact heat exchanger of the bubble column type (or submerged combustion) where the combustion water recondenses.Then the heat of combustion and the sensible heat and latent of the combustion water that are recovered.

 The installation described here also comprises two other levels of heat recovery, which is another possible advantage further improving the possibilities of this installation.

 The installation comprises an additional heat recovery unit 150 using the solid-liquid suspension that results from the water decomposition reaction: this additional unit 150 comprises a conventional type of exchanger 151, for example a coaxial cylindrical exchanger liquid / liquid. Here, the continuous withdrawal line 154 makes it possible to convey the products extracted in the lower part of the second reactor 102, whose temperature is of the order of 70.degree. C., firstly towards a precipitation-filtration module 152 (allowing to retain the solid particles that can be obtained), then, through a pipe 153, to the exchanger 151, the waste thus cooled out through an associated pipe 158.On thus manages to preheat a portion of the primary fluid of the exchanger.

 In addition, the water outlet 123 of the cooling element 120 leads, via a pipe 155, to the aforementioned coaxial exchanger 151, at the outlet of which a pipe 156 connects to the outlet pipe 157 of the pump. recirculation 170 (said conduit 157 leading to the emulsion venturi 160). Thus, heat recovery is still provided at the level of the refrigerant overcoming the two stirred reactors which are adiabatic: the water of the refrigerant is heated, for example to 30 ° C, after allowing the recondensation of the vapor, so that the The heat of the reaction is thus recovered in the form of latent and sensitive heat at the level of the hydrogen and the entrained and recondensed water vapor.

 Finally, with regard to the regulation of the installation, fixed control and safety instructions are available: reactor temperatures (sensors 117), catalytic combustion temperature (sensor 139), liquid levels in the reactors (sensors not shown in the figure). The valves can be solenoid valves, and the supply pumps can be controlled by an external signal (for example in the form of temperature sensors, pressure and levels connected to relays). There are also means for controlling the stirring and regulating the flow of combustion air by means of sensors connected to the feed pumps (a stop of agitation involving an immediate shutdown of the pump or pumps). supply, the air flow being adjusted to the regenerative reactive fluid supply flow rate, and therefore the flow rate of hydrogen produced).

 The invention is not limited to the embodiments that have just been described, but on the contrary covers any variant using, with equivalent means, the essential characteristics appearing in the claims.

Claims (23)

 1. Regenerable reactive energy storage fluid, characterized in that it consists of a suspension of metal powder in water, said powder being obtained from at least one metal selected from the group consisting of aluminum, magnesium, zinc, and iron, with addition of at least one adjuvant promoting the sedimentative and / or chemical stability of said suspension over time, said regenerable reactive fluid being thus capable of releasing energy under form of heat and hydrogen during the initiation of a reaction of decomposition of water by said metal.  2. Regenerable reactive fluid according to claim 1, characterized in that the metal powder is an atomized powder whose average particle size is of the order of 10 to 30 microns.  3. Regenerable reactive fluid according to claim 1 or 2, characterized in that it comprises at least one adjuvant consisting of a polymer derived from cellulose.  4. Regenerable reactive fluid according to claim 3, characterized in that the adjuvant used is constituted by a carboxymethyl cellulose (CMC).  5. Regenerable reactive fluid according to claim 3, characterized in that the adjuvant used consists of a hydroxyethyl cellulose (HEC).  6. Regenerable reactive fluid according to claim 3, characterized in that it comprises an adjuvant consisting of a carboxymethyl cellulose (CMC) and an adjuvant consisting of a hydroxyethyl cellulose (HEC).  7. Regenerable reactive fluid according to one of claims 1 to 6, characterized in that it also comprises an additive improving the resistance of the suspension vis-à-vis microorganisms, such as formalin.  8. Regenerable reactive fluid according to one of claims 1 to 7, characterized in that it also comprises an additive promoting the chemical stability of the suspension, such as sodium silicate.  9. regenerable reactive fluid according to one of claims 1 to 8, characterized in that the contents of metal powder and adjuvants or additives are chosen so that the viscosity of said fluid is compatible with its transport and its pumping, being by example at most equal to 8 Pa.s, and preferably between 3 and 6 Pa.s.  10. Regenerable reactive fluid according to one of claims 1 to 9, wherein the metal powder is an aluminum powder, characterized in that the aluminum and water masses are in a ratio between 0.45 and 0.6, and preferably close to 0.5.  11. Regenerable reactive fluid according to claims 5, 8 and 10, characterized in that it comprises adjuvants or additives whose approximate mass percentages are divided into 2% sodium silicate and 1.7 to 1.9% d hydroxyethylcellulose (HEC), with furthermore a saline solution making it possible to substantially lower the freezing point of said fluid with a view to external storage thereof, in particular a saline solution such as the NaCl / H 2 mass ratio. is between 0.19 to 0.23.  12. regenerable reactive fluid according to claims 5, 7, 8 and 10, characterized in that it comprises adjuvants or additives whose approximate mass percentages are divided into 1% formalin, 2% sodium silicate, and 1 6 to 2% hydroxyethyl cellulose (HEC).  13. Regenerable reactive fluid according to claims 6, 7, 8 and 10, characterized in that it comprises adjuvants or additives whose approximate mass percentages are divided into 1% formalin, 2% sodium silicate, 0, 5 to 1% hydroxyethyl cellulose (HEC), and 2.3 to 2.6% carboxymethyl cellulose (CMC).  14. regenerable reactive fluid according to claims 6, 7, 8 and 10, characterized in that it comprises adjuvants or additives whose approximate mass percentages are divided into 1% formalin, 2% sodium silicate, 0, 5 to 1% hydroxyethyl cellulose (HEC), and 2.8 to 3.2% carboxymethyl cellulose (CMC).  15. Installation for the production and use of hydrogen employing a regenerable reactive fluid according to any one of the preceding claims, characterized in that it comprises a hydrogen generator (100) comprising at least one reactor hermetically closed and perfectly agitated type (101, 102), having a continuous feed inlet regenerable reactive fluid and surmounted by a refrigerant element (120) at the outlet of which hydrogen can be recovered.  16. Installation according to claim 15, usable as a chemical boiler, characterized in that it further comprises a hydrogen combustion unit (130) and, downstream thereof, a heat exchanger (140). .  17. Installation according to claim 16, characterized in that the combustion unit (130) is a catalytic reactor of conventional type, for example a fixed bed of beads or a monolith block impregnated with catalyst, to enhance the hydrogen by catalytic combustion.  18. Installation according to claims 15 and 17, characterized in that the catalytic reactor (130) is connected to the outlet of the cooling element (120) via a filter module (125) for stopping fine particles entrained, a check valve (126), and a venturi-mixer (127) or other gas / gas device for diluting the hydrogen sucked in compressed air.  19. Installation according to claim 16, characterized in that the heat exchanger (140) is a conventional type of exchanger, either direct (bubble column) or indirect (condensing), allowing a better recovery of gases from combustion.  20. Installation according to one of claims 16 to 19, characterized in that it also comprises an additional heat recovery unit (150) using the metal-water suspension resulting from the decomposition reaction of water, said additional unit comprising a heat exchanger (151) of conventional type, for example a coaxial cylindrical exchanger.  21. Installation according to claim 20, characterized in that the exchanger (151) of the additional unit (150) is connected to the reactor (102) or to at least one of the hydrogen generator reactors (100). ) via a precipitation-filtration module (152), the pipe (155, 156) of water passing through said heat exchanger being connected to the inlet of the heat exchanger (140) provided downstream of the combustion unit (130) to thereby preheat a portion of the primary fluid of said exchanger (151) of the additional unit (150).  22. Installation according to claim 21, characterized in that an emulsion venturi (160) is provided upstream of the heat exchanger (140) provided downstream of the combustion unit (130), to which the water pipe (155, 156) passing through the exchanger (151) of the additional unit (150), a recirculation pump (170) being further provided, preferably upstream of said emulsion venturi.  23. Installation according to one of claims 16 to 22, wherein the regeneratable reactive fluid is constituted by a suspension of aluminum powder in water, characterized in that it comprises a first reactor (101) comprising inferiorly an inlet (110) continuously supplying regenerable reactive fluid and an additional inlet (111) for supplying sodium hydroxide, and a second reactor (102) in series with said first reactor and having a lowering outlet (115) continuously the products of the reaction.