EP2367751A1

EP2367751A1 - Device for producing hydrogen by means of an electron cyclotron resonance plasma

Info

Publication number: EP2367751A1
Application number: EP09753152A
Authority: EP
Inventors: Denis Hitz; Marc-Yves Delaunay
Original assignee: Commissariat a lEnergie Atomique CEA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2008-09-30
Filing date: 2009-09-29
Publication date: 2011-09-28
Also published as: FR2936505B1; US20110262313A1; FR2936505A1; WO2010037960A1

Abstract

The invention relates to a device (1) for producing hydrogen by means of a electron cylcotron resonance plasma, said device having a magnetic mirror configuration such that the module of the magnetic field has a non-point minimum essentially equal to the magnetic resonance field, and the magnetic field extends at least partially along the chamber (2), such that the plasma has the form of a sheet of plasma. Said device comprises water vapour injection means (14) for injecting the water vapour in the form of a supersonic jet, said means being provided with a planar nozzle (24) and a knife-edge (25) along the axis of the chamber (2) of the device, a selective cryogenic condenser (11) freezing the oxygen along the column of plasma generated in the chamber (2), and means for recovering (13) hydrogen produced from the decomposition, the oxygen being trapped by the at least one cryogenic condenser (11).

Description

Electron cyclotron resonance plasma hydrogen production device

The present invention relates to a device for producing hydrogen from an electron cyclotron resonance plasma.

Hydrogen (H ₂ ) appears today as a very interesting energy vector, which is expected to become increasingly important and which could, in the long term, be a good substitute for oil and fossil fuels, whose reserves will decline sharply in the coming decades. In this perspective, it is necessary to develop efficient processes for the production of hydrogen.

Although many processes have been described for producing hydrogen from different sources, many of these processes are unsuitable for limiting greenhouse gases.

A first technique is to use steam reforming. This is a technique for converting light hydrocarbons such as methane into synthesis gas by reaction with water vapor on a catalyst. The two main chemical reactions of this method are the production of synthesis gas and the conversion of CO: CH ₄ + H ₂ O → co + 3H ₂

CO + H ₂ O → CO ₂ + H ₂ the overall balance being CH ₄ + 2H ₂ O → co ₂ + 4H ₂

One of the major problems of this synthetic route is that it generates, as by-products, significant amounts of greenhouse gases of CO ₂ type.

A second method is to use a partial oxidation technique: it is an exothermic technique and generally without oxidation catalyst of products such as natural gas, heavy oil residues, coal. The production of synthesis gas is given by the reaction: C _n H _n + (Y ₂ ) O ₂ → nCO + (Y ₂ ) H ₂

The conversion of carbon monoxide is given by the reaction: nCO + nH ₂ 0 → nCO ₂ + nH ₂ .

Like reforming, this technique produces a significant amount of carbon dioxide.

It may also be mentioned a third technique using the direct thermal decomposition of water; such a technique would require extremely high temperatures of the order of 3000 to 4000 K (the use of a catalyst makes it possible to reduce this temperature, which nevertheless remains very high, close to 1400 K). This production technique is envisaged by using high temperature nuclear reactors cooled by a gaseous coolant such as helium (in the case of so-called fourth generation reactors of the HTR "High Temperature Reactor" type). By its principle, it is a technique that is related to the production of uranium. The other disadvantage is that it is unthinkable to use this method for small productions of hydrogen.

A fourth way is to perform an electrolysis of water: it is a technique of dissociation of water by passage of an electric current according to the reaction: H ₇ O → H ₇ + -O ₇

This reaction, whose enthalpy is ΔH = 285 kJ.mol ^-1 (at 298 K and 1 bar) is carried out according to the following method: an electrolyte cell consists of two electrodes, an anode and a cathode, connected to a DC generator The electrodes are immersed in an electrolyte serving as a conducting medium.This electrolyte is generally an acidic or basic aqueous solution, a proton exchange membrane (H ⁺ ) or an oxygen ion conducting membrane (O ^{2). "} ).

This technique poses some difficulties, however; thus the electrodes corrode in time. Moreover, such a process requires the permanent adjustment of the concentrations and the use of membranes which are either fragile for organic membranes or low yield for mineral membranes.

A fifth solution is to perform a decomposition of water by thermochemical cycle (CTC): this process uses a series of chemical reactions. An example is the use of the iodine-sulfur cycle based on the decomposition of two acids at high temperature: sulfuric acid produces oxygen and sulfur dioxide, and hydroiodic acid produces hydrogen and hydrogen. 'iodine.

The disadvantage of this technique is the implementation of rather complex chemical reactions producing, in addition to hydrogen, many other elements such as sulfur in the case of the iodine-sulfur cycle or the Fe ₃ O ₄ and the HBr in the case of the UT-3 cycle.

A sixth way considered is biomass: obtained by photosynthesis of carbon dioxide and water, it uses solar energy to produce molecules of the type C ₆ H ₉ O ₄ . Then there is a thermochemical treatment according to the reaction:

C ₆ H ₉ O ₄ + 2H ₂ o + ssou → βco + ¹ Y ₂ H ₂

Gasification with water vapor at about 900 ° C. then produces synthesis gas (CO + H ₂ O). A hydrogen supplement is then obtained by the "gas shift" reaction:

6CO + 6H ₂ O → 6CO ₂ + 6H ₂

Again, the main disadvantage of this technique lies in its production of carbon dioxide.

A seventh technique involves the photo-electrolysis of water: it is a process that uses the dissociation of the water molecule by an electric current produced by the illumination of a semiconductor photocatalyst (TiO ₂ , AsGa ).

This process does not produce greenhouse gas gas but has a relatively low conversion efficiency. Another method of producing hydrogen gas by microwave plasma is proposed in document WO2006 / 123883. This method uses the dissociation of gaseous molecules by impact electronic. The disclosed method consists of injecting microwave frequencies into a dielectric tube containing a gas or a vapor of the type H ₂ O or CH ₄ under reduced pressure, of the order of 50-300 torr. This microwave power causes the ionization and / or dissociation of the gas, thereby releasing hydrogen (initiation of a microwave plasma). At the end of the tube, a palladium separator separates the hydrogen gas diffusion.

Another method of producing hydrogen from water molecules is described in WO2005 / 005009. The disclosed method involves placing the water molecules in an electromagnetic field to excite the molecules by thermal agitation until their excitation energy exceeds the binding energy of the H and O atoms composing the water molecule.

Another method of producing hydrogen by injecting water vapor into a plasma is described in US2004 / 0265137. This patent describes a process for obtaining hydrogen from the dissociated vapor in a plasma. The document mentions in particular the use of the electron cyclotron resonance (ECR) to produce said plasma. Compared to the hydrogen production methods previously mentioned, the use of a RCE plasma machine has many advantages:

- continuous and stable operation;

- no implementation of high temperatures;

- no wear (very long usage time due to lack of filament or electrodes);

- no production of carbon or carbon compounds;

- no use of chemical complexes;

- low cost, if the magnetic structure is made of permanent magnets. However, despite the advantages mentioned above, a major problem of such a plasma machine that breaks, by electronic impact, the bonds of the water molecule, is the separation of the products formed. The insertion of a dielectric is a possible solution. This method, however, has the disadvantage of using rare and expensive compounds.

In this context, the present invention aims to provide a device for producing hydrogen by electron cyclotron resonance plasma from water, allowing efficient dissociation of water molecules and simple separation of the products formed. not necessarily requiring significant magnetic fields.

To this end, the invention proposes a device for producing hydrogen with an electron cyclotron resonance plasma comprising: a vacuum-sealed chamber intended to contain a plasma,

means for injecting water vapor into said chamber,

means for injecting a high-frequency wave inside said chamber,

a magnetic structure for generating a magnetic field in said chamber and for generating a plasma along the magnetic field lines, the module of said magnetic field having a magnetic mirror configuration with at least one electronic cyclotron resonance zone for dissociating the molecules at least partially; of water introduced in the vapor phase and for at least partially ionizing the products of the dissociation, said device being characterized in that said magnetic mirror configuration is such that the modulus of said magnetic field exhibits a non-punctual, substantially constant and substantially equal minimum the magnetic field corresponding to the electron cyclotron resonance, extended at least partially along said chamber, so that said plasma has the shape of a plasma ply; said steam injection means injecting said vapor in the form of a supersonic jet, said injection means comprising a planar nozzle and a debarker, said debarker being adapted to shape said jet of vapor so as to that it is directed along the axis of said chamber; said device comprising: at least one selective cryogenic condenser for freezing the oxygen resulting from the dissociation without freezing the hydrogen resulting from the dissociation, said at least one selective cryogenic condenser freezing the oxygen along said plasma sheet generated in said chamber; means for recovering the hydrogen resulting from the dissociation, the oxygen being trapped by said at least one cryogenic condenser. Vacuum chamber means a chamber in which a working pressure of less than or equal to 5.10 ^"3 mbar prevails, said working pressure corresponding substantially to the partial pressure of water vapor injected into the chamber.

The term magnetic field substantially equal to the magnetic field corresponding to the electron cyclotron resonance, a magnetic field equal to ± 10% near the magnetic field corresponding to the electron cyclotron resonance. Magnetic field that is substantially constant in the resonance magnetic field is understood to mean a magnetic field that does not deviate by more than 10% from the resonance magnetic field.

Thanks to the invention, an efficient hydrogen production is obtained from the steam. The device according to the invention is based on the combined use of a cyclotron resonance plasma of electrons and at least one selective cryogenic condenser. This non-CO ₂ emitting device uses no electrodes, ohmic heating, membrane or high temperatures.

Thanks to the principle of electron cyclotron resonance plasma, at the passage of the neighborhood of the resonance zone, the electrons acquire energy. They will then be able to dissociate the water molecules, then ionize the dissociation products. Thanks to the electroneutrality of the plasma, these ions will follow the electrons along the magnetic field lines.

According to the invention, the mirror configuration of the magnetic field forms a profile of the magnetic field comprising a non-local minimum, called a "flat field" minimum, whose value of the magnetic field module is equal to the value of the magnetic resonance field at ± 10% This value of the modulus of the minimum magnetic field, equal to or very close to the electron cyclotron resonance is extended at least partially along the sealed chamber of the device, typically over a length greater than 10 cm, between the two maxima of the magnetic field , thereby obtaining an extended sheet of hot plasma. The value of the module inside the chamber is constant over the entire height of said chamber for a given z on the axis of the chamber. In this way, the electrons will be able to acquire a large amount of energy in order to efficiently dissociate the water molecules and to ionize the dissociation products. In addition, the oxygen resulting from the dissociation of the water molecules will be trapped more efficiently all along the sealed chamber and over a great length.

By observing the phase diagrams of the hydrogen and oxygen elements for the low temperatures represented in FIG. 1, the operating pressure of the considered plasma machine being less than 5.10 ^-3 mbar, it is noted that for a temperature of between 5K and 35K, the oxygen is cryocondensed while the hydrogen remains in gaseous form.Thus, by using one or more cryogenic condensers forming the wall of the plasma chamber, cooled to a temperature such that the two elements, hydrogen and oxygen, composing the plasma are in different phases (hydrogen gas and solid oxygen), one can trap the oxygen in solid form without trapping the hydrogen that will be recovered by other means.The temperature of the condenser depends on the partial pressures of hydrogen from of the initial density of the plasma which is itself a function of the microwave frequency injected. Then use hydrogen recovery means such as a conventional pumping system (turbomolecular pump for example) to pump hydrogen. It is also possible to advantageously use the fact that the ionized particles follow, by electroneutrality of the plasma, the electrons which are guided by the magnetic field lines.

Indeed, if the device for cryocondensation of oxygen is placed in the magnetic field lines, then it can advantageously be place hydrogen cryocondensation devices outside the magnetic field lines.

It will be noted that, although using an electromagnetic field, the device according to the invention does not use a method of thermal agitation of the water molecules, but on the other hand breaks the atomic bonds by collisions with the electrons of the plasma.

According to a particularly advantageous embodiment of the invention, said chamber comprises means for injecting water vapor injecting water vapor along the longitudinal axis AA 'of the chamber directly into the hot plasma.

The device according to the invention may also have one or more of the following characteristics, considered individually or in any technically possible combination:

said at least one selective cryogenic condenser for freezing oxygen forms the inner wall of said chamber;

said at least one cryogenic selective condenser for freezing oxygen is located at said minimum non-point magnetic field;

said at least one selective cryogenic condenser for freezing oxygen is an annular condenser surrounding said plasma present in said chamber;

said at least one selective cryogenic condenser for freezing the oxygen resulting from the dissociation without freezing the hydrogen resulting from the dissociation is at a temperature of between 6 and 40 ° C. for a mean pressure substantially equal to 5.10 ^-3 mbar in said chamber;

said device comprises a plurality of selective cryogenic condensers for freezing the annular oxygen surrounding said plasma; said device comprises a second cryogenic condenser for freezing the oxygen resulting from the dissociation placed at the end of said a chamber between said magnetic mirror configuration and said hydrogen recovery means;

said magnetic structure comprises a plurality of permanent magnets; said plurality of permanent magnets has the same sense of magnetization;

said magnetic structure comprises permanent magnets whose poles face each other in the zone of injection of the water vapor;

said magnetic structure comprises permanent magnets whose poles face each other in the hydrogen recovery zone;

said permanent magnets located in the water vapor injection zone have a different polarity of said permanent magnets located in the hydrogen recovery zone;

said magnetic structure comprises permanent magnets of different sizes and having either the same magnetization or different magnetizations;

said magnetic structure comprises coils at ambient temperature and / or superconducting coils at low or high critical temperature, said low or high Tc; said device comprises non-dissociated water recovery means, said non-dissociated water recovery means being substantially arranged along the steam injection axis (AA ');

said non-dissociated water recovery means forms a diaphragm around said steam injection means, so as to define the shape of the jet of water vapor;

said means for recovering non-dissociated water are formed by a cryogenic condenser;

said device comprises at least one non-dissociated water reinjection system in the vapor phase and issuing from said non-dissociated water recovery means;

said device comprises a mesh having a mesh for stopping the propagation of high frequency waves; said grid is inserted between the plasma of the chamber and said at least one selective cryogenic condenser for freezing the oxygen resulting from the dissociation, so as to protect said at least one cryogenic condenser of the high frequency waves; said grid is formed by a metal mobile cylinder comprising solid portions and perforated portions for the at least partial protection of said at least one cryogenic condenser of the high frequency waves;

said device comprises an enclosure capable of recovering oxygen when the temperature of said at least one cryogenic condenser for freezing oxygen is high;

said means for recovering the hydrogen resulting from the dissociation are placed outside said magnetic mirror configuration:

said means for recovering the hydrogen resulting from the dissociation comprise a pump for pumping hydrogen in the gas phase;

said means for recovering the hydrogen resulting from the dissociation comprise at least one cryogenic condenser for freezing the hydrogen; said device comprises an enclosure capable of recovering hydrogen when the temperature of said at least one cryogenic condenser for freezing hydrogen is high;

said means for injecting a high-frequency wave inside said chamber comprises an input window placed in a high magnetic field so that the plasma diffuses towards the chamber and thus avoid impacts of the plasma on said window ;

said module of said minimum magnetic field is between 90% of said electronic cyclotron resonance value and said electronic cyclotron resonance value; said device comprises means for injecting high-frequency multifrequency waves. Other features and advantages of the invention will emerge clearly from the description which is given below, as an indication and in no way limiting, with reference to the appended figures, among which:

FIG. 1 is a representation of the phase diagrams of hydrogen and oxygen with the corresponding values at the triple point of each element;

- Figure 2 shows a top view of a first embodiment of the device according to the invention;

- Figure 3 shows a top view of a second embodiment of the device according to the invention;

- Figure 4 shows a top view of a third embodiment of the device according to the invention;

- Figure 5 shows a top view of a fourth embodiment of the device according to the invention; - Figure 6 shows a top view of a fifth embodiment of the device according to the invention;

- Figure 7 shows a top view of a sixth embodiment of the device according to the invention.

In all the figures, the common elements bear the same reference numbers.

Figure 1 has already been described above with reference to the general presentation of the invention.

FIG. 2 is a simplified representation of a device 1 for producing hydrogen by an electron cyclotron resonance plasma according to a first embodiment of the invention. The device 1 comprises:

a sealed chamber 2 of parallelepipedal shape (hereinafter referred to as an enclosure thereafter) under vacuum;

- eight bars of permanent magnets 3, 4, 5, 6, 7, 8, 9, 10 placed outside the chamber 2 (the bars typically have a height of between a few centimeters and 1 m, or more if necessary) ; a first cryogenic condenser 11 for trapping the oxygen forming the side wall of the sealed chamber 2;

a second cryogenic condenser 12 for trapping the oxygen located perpendicular to the axis AA 'of the chamber 2; a pump 13 for recovering hydrogen in gaseous form;

water vapor injection means 14 in the chamber 2 composed of a chamber in which steam prevails, this chamber being connected to the sealed chamber 2 by a nozzle 24 so as to create a supersonic jet water vapor. The jet of water vapor is shaped with debarkers 25 consisting of pipes in which circulates a liquid whose temperature is around 5 ° C. The water vapor which comes into contact with the debarkers 25 is immediately condensed and flows along the debarkers 25. The jet of steam is thus limited in radial dimension and is oriented along the longitudinal axis AA 'of the chamber 2;

means for propagation of high-frequency waves 15 of microwave type low frequencies or substantially equal to 2.45 GHz, formed by a waveguide or a coaxial cable equipped with a high frequency window sealed inside from bedroom 2;

a cryogenic condenser 16 for trapping non-dissociated water vapor so as to have a high directivity of the steam jet;

a non-dissociated water recycling pump 17 in the vapor or liquid phase;

The chamber 2 is evacuated, the vacuum being effected by means of pumping ad hoc. In order to have the least impurities in the chamber 2, a residual vacuum of at least 10 ^-4 mbar is required During operation of the device 1, the working pressure of the chamber 2 is typically less than or equal to 5.10 ^"3 mbar, this pressure being related to the partial pressure of water vapor injected into the chamber 2. The magnetic structure, formed by the eight bars of permanent magnets 3, 4, 5, 6, 7, 8, 9, 10 surrounding the chamber 2, produces inside the chamber 2 an axial magnetic field whose configuration of the module corresponds to a magnetic mirror type configuration whose profile has at least two maxima (B _max ) at abscissae located respectively in the injection and extraction zones and a non-point minimum (Bmin) extended at least partially along of room 2 and located between the two maxima (B _max ). The two maxima (B _max ) have a value greater than the value of the magnetic field (B _rθS ) for which the electron cyclotron resonance is obtained. The minimum (B _m m) is a so-called flat field minimum, the value of which is equal to or slightly less than the value for which electronic cyclotron resonance is obtained over a large abscissa length.

The magnetic mirror configuration is a so-called minimum-B configuration: the electrons of the plasma are confined in a magnetic well. The shorter the length of the minimum-B, the greater the resonance field, the faster the electrons will lead to better dissociation of water vapor from oxygen and hydrogen. Thanks to the principle of electron cyclotron resonance, at the passage of the resonance zone, the electrons will acquire energy. They will then be able to dissociate the water molecules and then partially ionize the dissociation products. The electrons follow magnetic field lines thanks to Laplace's law; and, thanks to the electroneutrality of the plasma, these ions will follow the electrons on the magnetic field lines.

The microwaves injected into the plasma tend to propagate through the plasma to the resonance zone. Indeed, the transfer of energy from the microwave power injected into the electrons of the plasma occurs at a magnetic field location (B _rθS ) such that the electron cyclotron resonance condition is established, that is to say when there is equality between the pulsation of the high frequency wave ω _HF and the cyclotron pulsation of the electron: where q _θ is the charge of the electron (Cb); B _rθS is the magnetic field corresponding to the resonance (T); m _θ is the mass of the electron.

A microwave generator, not shown, is placed outside the chamber 2; this generator injects high frequency waves into the chamber 2 via the propagation means 15. The frequency range of the microwaves can range from GHz to 100 GHz, the most common generator being the 2.45 GHz magnetron commonly used to domestic microwave ovens. For a frequency of 2.45 GHz, there is a resonance magnetic field B _rθS = 0.0875 T. However, for miniature hydrogen production devices (for embedded systems for example), it is also possible to use transistors power. Indeed, there are now field effect transistors capable of delivering about 60 W at 14.5 GHz.

Advantageously, the input window of the high frequency waves is placed in a zone of strong magnetic field, for example at the first maxima (B _max ) of the profile 20 of the module of the axial magnetic field, so that the plasma diffuses in the direction of the plasma chamber 2 and not to the entrance window, so as to avoid any bombardment of this window by the plasma, thus ensuring an unlimited lifetime. It is also possible to use so-called "overdense" plasmas (in English) where the plasma frequency is greater than the microwave frequency. The use of "over-dense" plasmas makes it possible advantageously to increase the electronic density and therefore to increase the efficiency of the system.

The steam injection means 14 in the chamber 2 are preferably placed near the microwave propagation means (however, another location may also be chosen for reasons of convenience). Water is introduced into the plasma chamber 2 in the form of a supersonic vapor jet in order to obtain a high directivity of water vapor in order to direct the water vapor directly into the hot plasma towards the resonance zone of the chamber 2. This jet is from a nozzle 24 itself serving as an orifice to an enclosure where the water vapor is. Debarbers 25 are placed at the outlet of the nozzle 24 in order to define the angular opening of the jet. These debarkers 25 consist of pipes in which circulates a liquid whose temperature is close to 5 ° C (a lower temperature would lead to solidification of the water on the debarkers). The water vapor which comes into contact with the debarkers 25 is immediately condensed and flows along the debarkers 25.

In order to further improve this directivity by reducing the size of the jet of steam, a cryogenic condenser 16, formed for example by a cryogenic ring, is placed at the level of the first maxima (B _max ) of the magnetic field, whose profile 20 represents the modulus of the magnetic field along the chamber 2. The cryogenic condenser 16, whose temperature is around 200 K, is used as a diaphragm for the purpose of trapping by cryocondensation the water vapor located in the outer part of the jet of steam. The condenser 16 also avoids the non-dissociated water saturation of the main cryogenic condensers 11 and 12 necessary for the dissociation of the ionized elements. When the cryogenic condenser 16 is saturated with water, a device, not shown, makes it possible to isolate the condenser

16 in order to regenerate it. For this, the device heats the cold walls of the condenser to recover water cold walls in liquid or gaseous form to be reinjected into the device 1 by the pump 17 recycling.

The cryogenic condenser 16 can be interchangeably replaced by a liquid condenser comprising a vertical pipe in which a pressure gradient is established (from 10 ^"3 mbar to 10 ² mbar or 1 bar). vapor in the liquid form, flows along the vertical pipe by gravity and is advantageously recycled via the pump

17 recycling. However, if the recycling tubing is short, the gradient pressure in the tubing can remain low and the water can be fed back into the device 1 directly in the vapor phase.

The magnetic structure is formed by the rod-shaped permanent magnets 3, 4, 5, 6, 7, 8, 9 and 10 having the same magnetization direction for all the magnets. The orientation of the permanent magnets 3, 4, 5, 6, 7, 8, 9 and 10 is such that the magnetic profile 20 has a magnetic mirror configuration formed by a non-point minimum-B, said to "minimum field" flat "extended over a large part of the length of the device along the axis AA 'and located between two maximum values (B _max ) of the magnetic field. The maximum values of the field are quite high, of the order of 0.15 T to 0.3 T, so as to limit the axial leakage of the plasma; the maximum values can also reach several Tesla.

The value of the minimum-B is a value equal to or less than the value of the resonance magnetic field (B _rθS ) of the order of 90% of B _rθS , that is to say approximately 0.08T. This value of the magnetic field equal to or slightly less than the electron cyclotron resonance is extended over a large part of the length of the device, of the order of 25 cm. Thus, the electrons will be able to acquire a large amount of energy in order to effectively dissociate the water molecules over the entire length of the device 1. It is also possible to use a multi-frequency microwave injection source whose combination of the bandwidths of each frequency forms a broad frequency band leading to the formation of a large resonance zone; the width of the resonance zone substantially corresponding to the bandwidth of the microwave source. Due to the flat minimum-B magnetic configuration, the plasma in the form of a long column extends over a large part of the chamber, with a high density at the outlet of the vapor jet and a pressure gradient along the chamber 2. The device 1 does not provide for radial confinement of the plasma due to the radial inhomogeneity of the magnetic field. In this case, the ionized particles forming the plasma tend to undergo a radial drift, according to a phenomenon known in plasma physics. Cryogenic condensers 11 and 12 are cold-walled condensers, called cryo-panels or cryogenic panels. The condenser 11 is advantageously placed on the inner surface of the chamber 2 so as to condense the desired ionized particles. The cold walls of the condenser 1 1 have a temperature of around 20 - 3OK, for example, so as to condense all the elements present in the chamber 2 except the hydrogen which remains in gaseous form at this temperature under the working pressure of 0.1 Pa. .

In fact, according to the phase diagrams of FIG. 1, at the operating pressure of the enclosure 2, that is to say at least 5.10 ^"3 mbar, at a temperature of between 6K and 4OK (preferentially between 5K and 30K), it is possible to cryocondense oxygen while keeping hydrogen in gaseous form.

It will be noted that the various components resulting from the dissociation of water are essentially; H ₂ , O ₂ , OH, H, O, O ⁺ , H ⁺ , H ₂ ⁺ , O ₂ ⁺ , OH ^" All the ionized elements neutralize each other before touching a wall (ie a cold wall of a cryovial panel is another wall), while the neutral elements recombine to give stable elements: H ₂ , O ₂ , H ₂ O.

The cryogenic condenser 12 is advantageously placed in the axis of the vapor jet 14 outside the plasma before a hydrogen pumping system, so as to condense the ionized oxygen particles and the undissociated water vapor. The oxygen resulting from the dissociation of the water being trapped over the entire length of the device 1, it is then sufficient to pump the hydrogen axially to the other end of the device 1 and to send it to a compressor (not shown) .

A high frequency grid 21 (HF) is placed in front of the cryopannels 1 1 so as to protect the cryopannels and to prevent their heating by the microwaves, the mesh of the RF grid (21) being determined as a function of the wavelength of the microwave. It will be noted that, according to the grid shown in FIG. 2, a tile on the abscissa substantially corresponds to 1 cm. The dimensions of each magnet have been calculated so as to obtain, in the plasma chamber, a long resonance zone, where the electrons take enough energy to dissociate the water molecules and at least partially ionize the dissociation products.

The best dissociation rate of the water being obtained for pressures lower than 5.10 ^"3 mbar, this value is considered as a maximum pressure in the chamber 2, especially since the electrons would no longer be magnetically guided if the we increase this pressure beyond

5.10 ^"3 mbar.

Figure 3 is a variant of the previous figure (the means in common between the devices 1 and 30 have the same reference numbers and perform the same functions). The device 30 according to this second embodiment differs from the device 1 of FIG. 2 in that it comprises a plurality of cryogenic condensers 31, 32, 33, 34 with cold walls of the cryo-panel type or cryogenic panel placed at the same time. 2. Typically according to this embodiment, each cryogenic condenser 31, 32, 33, 34 among the four shown is placed between a succession of magnets.

A metal cylinder 35, movable along the axis AA 'is inserted between the condensers 31, 32, 33, 34 and the plasma. The metal cylinder 35 is used as a screen for protecting the condensers 31, 32, 33, 34. The cylinder 35 comprises solid portions and perforated portions 37 by a mesh, said mesh corresponding to the wavelength of the microwaves used.

When all the perforated parts are placed in front of the condensers 31, 32, 33, 34, the oxygen dissociated by the plasma is trapped by the cold walls of the condensers 31, 32, 33, 34. The cold walls of the condensers 31, 32, 33, 34 have a temperature close to 20 -3OK for example so as to condense all the elements present in the chamber 2 except the hydrogen which remains in gaseous form. In a second position of this movable cylinder, the solid parts are placed in front of the cold walls of the condensers 31, 32, 33, 34. In this position, the device is stopped allowing the recovery of oxygen by regeneration of the cold walls of the condensers 31, 32, 33, 34 by heating them. Figure 4 is a variant of the previous figure (the means in common between devices 30 and 40 have the same reference numbers and perform the same functions). The device 40 according to this third embodiment differs from the device 30 of FIG. 3 in that it comprises a mobile metal cylinder 41 having a particular arrangement of the solid parts 36 and the perforated parts 37.

The arrangement of these solid parts 36 and of these grid portions 37 is such that in a first position of the cylinder 41 three cryogenic condensers, for example 31, 32 and 34 are in operation, that is to say they trap the hydrogen elements, and a cryogenic condenser, for example 33, is in a regeneration process. In this way, the device 40 can operate without interruption. As soon as a wall of a condenser 31, 32, 33, or 34 is saturated, it is sufficient to move the movable cylinder 41 in different positions so as to mask the oxygen saturated wall plasma in order to regenerate it during operation of the device.

According to a particular embodiment of the invention, it is possible to arrange the different condensers 31, 32, 33, 34 at different distances from the center of the chamber 2 where the hot plasma is seated. For example, the condenser 34 placed near the jet of steam will be further away from the center of the chamber 2 so as to protect it from splashing water from the jet of steam that would come to freeze excessively on the cold wall. The condenser 31 located near the hydrogen recovery system in gaseous form can be placed closer to the plasma or the center of the chamber 2 so as to pump the last oxygen atoms remaining in this zone. Figure 5 is a variant of the previous figure (the means in common between the devices 40 and 50 have the same reference numbers and perform the same functions). The device 50 according to this fourth embodiment differs from the device 40 of Figure 4 in that it comprises a nose 51 of ferromagnetic material to increase the efficiency of the magnetic mirror located in the microwave injection zone. The added piece is a substantially elongated piece of iron or ferro-cobalt for example and including the means of propagation of high-frequency waves 15 and surrounding the stream of water vapor 14.

In this way, the arrangement and the material of the nose 51 make it possible to increase the first maxima (B _max ) of the profile 53 without modifying the minimum-

B remaining identical to the embodiments detailed above, the profile 53 representing the intensity of the axial magnetic field present in the chamber 2.

In this way, the maximum value B _max of the profile 53 may be three times greater than the maximum value B _max of the profile 20 detailed in the preceding embodiments of the invention illustrated with reference to FIGS. 2 to 4, which ensures better confinement of the plasma.

The value of the minimum-B is equal to or slightly less than the value of the magnetic resonance field (B _rθS ) of the order of 90% of B _rθS , that is to say approximately 0.08T. This value of the magnetic field equal to or slightly less than the electron cyclotron resonance is extended over a large part of the length of the device, of the order of 25 cm.

Figure 6 is a variant of the previous figure (the means in common between the devices 50 and 60 have the same reference numbers and perform the same functions). The device 60 according to this fifth embodiment differs from the device 50 of FIG. 5 in that it comprises a second ferromagnetic nose 52 placed at a second maxima B _max of the profile 56.

Thus according to this fifth embodiment, the profile 56 representing the intensity of the magnetic field has two maximas whose intensity is higher than the maxima of the previous embodiments, thus ensuring better confinement of the plasma.

Figure 7 is a simplified representation of a sixth embodiment of a device 70 for producing hydrogen by an electron cyclotron resonance plasma.

The device 70 comprises: a sealed chamber 72 of parallelepipedal shape (hereinafter referred to as an enclosure thereafter) under vacuum;

- eight bars of permanent magnets 73, 74, 75, 76, 77, 78, 79, 80 placed outside the chamber 72 (the bars typically have a height of between a few centimeters and 1 m, or more if necessary);

a first cryogenic condenser 81 for trapping the oxygen forming the lateral wall of the sealed chamber 72;

a second cryogenic condenser 82 for trapping the oxygen situated perpendicular to the axis of the chamber 72;

a pump 83 enabling the recovery of the hydrogen in gaseous form;

water vapor injection means 84 in the chamber 72 composed of an enclosure containing water vapor, this chamber being connected to the sealed chamber 72 by a nozzle 94 so as to create a supersonic jet water vapor. The stream of water vapor is shaped with debarkers 95 consist of pipes in which circulates a liquid whose temperature is around 5 ° C. The water vapor which comes into contact with the debarkers 95 is immediately condensed and flows along the debarkers 95. The jet of steam is thus limited in radial dimension and is oriented along the longitudinal axis AA 'of the chamber 72;

- Microwave type high frequency wave injection means 85, formed by a waveguide or a coaxial cable equipped with a sealed high frequency window inside the chamber 72;

a cryogenic condenser 86 for trapping non-dissociated water vapor so as to have a high directivity of the steam jet;

a pump 87 for recycling water that is not dissociated in the vapor or liquid phase.

The chamber 72 is evacuated, the vacuum being effected by means of pumping ad hoc. In order to have the least impurities in the 2, a residual vacuum of at least 10 ^-4 mbar is required During the operation of the device 70, the working pressure of the chamber 72 is typically less than or equal to 5.10 ^-3 mbar, this pressure being related to the partial pressure of water vapor injected into the chamber 2. The magnetic structure is formed by the eight bars of permanent magnets 73, 74, 75, 76, 77, 78, 79, 80 surrounding the chamber 2.

The magnet bars 75, 76, 79, 80 have the same direction of magnetization along the longitudinal axis of the chamber 72, corresponding to the magnetization direction of the bars 3, 4, 5, 6, 7, 8, 9 and as shown in the preceding figures.

In a manner similar to the previously described description, the magnetic profile 90 has a magnetic mirror-type configuration formed by a non-punctual minimum-B, referred to as a "flat-field minimum" extended at least partially along the chamber 2 and situated between two maximum values (B _max ) of the magnetic field. The maximum values of the field (B _max ) are quite high, of the order of 0.15 T to 0.3 T, so as to limit the axial leakage of the plasma.

The bars of magnets 73, 74, 77, 78 are placed at the ends of the enclosure 2 and their direction of magnetization is perpendicular to the magnetization direction of the magnets 75, 76, 79, 80, the field lines created by these magnets 73, 77 and 74, 78 being in opposition. The setting up of magnets with a direction of magnetization perpendicular to the direction of the longitudinal axis AA 'of the enclosure makes it possible to reduce the size of the magnets 75, 76, 79, 80 which make it possible to obtain a mirror configuration magnetic with a minimum-B flat field slightly less than or equal to the magnetic field of resonance.

In this way, the magnets located around the chamber 2 occupies less space than in the previous representations, which makes it possible to simplify the installation of the means for regenerating the cold walls of the cryogenic condensers present inside the chamber 2 .

According to a variant of Figure 6, the magnets 75, 79 and the magnets 76, 80 may be of different sizes thus changing the magnetic profile. By for example, the magnets 76 and 80 may be smaller in size so as to provide an axial magnetic field with a value of the minimum-B, in the vicinity of the water vapor injection, close to the resonance magnetic field and a value the minimum-B lower than the resonance magnetic field at the zone of the chamber 2 near the extraction of hydrogen. This variant makes it possible to have less energetic electrons at a zone close to the extraction of hydrogen with better confinement in order to be able to dissociate the water molecules still present in this zone. For this, we realize in this area a more conventional confinement with a profile with a strong field gradient, lowering the minimum-B and keeping the values of maxima (B _max ) constant.

The invention has been mainly described with a means for extracting the gaseous hydrogen at the end of the chamber 2 and pumping the hydrogen axially; however, it is also possible to equip the device according to the invention with a hydrogen extraction means pumping hydrogen from the chamber radially at the end of the chamber of the device. Indeed, in the case of the use of a simple magnetic mirror configuration as shown in Figures 2 to 7, there may be a significant particle flow in the axis of the machine, the flow of particles being 'as much lower when B _max is big. Radical pumping of the hydrogen makes it possible to obtain 100% pure hydrogen.

The invention has been mainly described, in the embodiments illustrated with reference to FIGS. 2 to 7, with a hydrogen extraction at the end of the chamber effected by suction of the hydrogen in gaseous form by means of 'a pump. It is also possible, according to the invention, to introduce into the chamber 2 at the level of the hydrogen extraction zone and outside the magnetic field lines cold-wall cryogenic condensers for trapping hydrogen, such as cryo-panels solid or perforated and whose wall temperature is less than 5K. Thus, hydrogen and oxygen are fixed on walls independent cold that it will be enough to heat independently of each other to separately recover the hydrogen and oxygen in liquid form or in gaseous form.

The invention has mainly been described with a magnetic configuration comprising a minimum-B equal to or less than the value corresponding to the magnetic resonance field whose value of the minimum-B is a constant value over a certain length of the chamber of the device corresponding to the distance between the two maxima (B _max ); however, in another embodiment of the invention, the minimum-B of the magnetic configuration may oscillate around a minimum value, while remaining very close to this minimum value over a large distance from the chamber of the device corresponding to the distance between the two maxima (B _max ).

The invention has been mainly described with a parallelepiped chamber surrounded by a magnetic structure formed by magnet bars and comprising cryogenic condensers in the form of a plate; however, the invention is also feasible with a cylindrical sealed plasma chamber surrounded by a magnetic structure formed by circular magnets and having cryogenic ring-shaped condensers positioned along the length of the plasma chamber.

The invention has been mainly described with a parallelepiped chamber surrounded by a magnetic structure formed by bars of magnets; however, part of the magnetic structure surrounding the plasma chamber such as the upper magnet bars may also be used as lower magnet bars of a magnetic structure surrounding a second sealed plasma chamber.

Finally, the invention has been mainly described with an axial magnetic field, however, it is also possible to add a radial component to the axial magnetic field, for the dissociation for example of other elements requiring the use of a magnetic field. radial and / or to prevent radial leakage of the plasma due to drift particles and thus ensure better confinement of the plasma.

Of course, the invention is not limited to the embodiment just described. Thus, if it is desired to treat a larger quantity of water, it is possible to increase the dimensions of the apparatus while making sure to have resonance zones in the plasma chamber. Thus, we can increase the length of the minimum-B equal to or slightly less than the resonance as needed up to several meters. Note that the longer the tray of the minimum-B, the more effective the device according to the invention.

It is also possible to use coils (superconducting or not) of magnetic field to create more intense fields.

Although the invention has been more particularly described for low frequency microwave frequencies of the order of 2.45 GHz, it is of course possible to use higher microwave frequencies, as well as two microwave injections with neighboring frequencies so as to obtain a value of minimum-B between the two resonance values, as well as several injections of microwaves whose bandwidth of each (a few MHz) leads to a very wide frequency bandwidth and therefore to a more resonant zone large.

Claims

Apparatus (1, 70) for producing electron cyclotron resonance hydrogen comprising: - a vacuum sealed chamber (2, 72) for containing a plasma,

means for injecting water vapor (14, 84) into said chamber (2, 72),

means for injecting (15, 85) a high-frequency wave inside said chamber (2, 72),

a magnetic structure (3, 4, 5, 6, 7, 8, 9, 10, 73, 74, 75, 76, 77, 78, 79, 80) for generating a magnetic field in said chamber (2, 72) and generating a plasma along the magnetic field lines, the module of said magnetic field having a magnetic mirror configuration with at least one electron cyclotron resonance zone for at least partially dissociating the water molecules introduced in the vapor phase and for ionizing at least partially the products of the dissociation, said device being characterized in that said magnetic mirror configuration is such that the module of said magnetic field has a non-punctual minimum, substantially constant and substantially equal to the magnetic field corresponding to the electron cyclotron resonance and extended at least partially along said chamber (2, 72), so that said plasma is in the form of a plasma web; said steam injection means (14, 84) injecting said vapor in the form of a supersonic jet, said injection means (14, 84) comprising a planar nozzle (24, 94) and a debarker (25); , 95), said debarker (25, 95) being adapted to shape said stream of steam so that it is directed along the axis (AA ') of said chamber (2, 72); said device (1, 70) comprising: at least one cryogenic condenser (1 1, 31, 32, 33, 34, 81) selective for freezing the oxygen resulting from the dissociation without freezing the hydrogen resulting from the dissociation, said at least one cryogenic condenser (11, 31 , 32, 33, 34, 81) selective oxygen-freezing along said plasma ply generated in said chamber (2, 72);

means for recovering (13, 83) the hydrogen resulting from the dissociation, the oxygen being trapped by said at least one cryogenic condenser (1 1, 31, 32, 33, 34, 81).

2. Device (1, 70) according to claim 1 characterized in that said at least one cryogenic condenser (1 1, 31, 32, 33, 34, 81) selective for freezing oxygen forms the inner wall of said chamber ( 2, 72).

3. Device (1, 70) according to one of claims 1 to 2 characterized in that said at least one cryogenic condenser (1 1, 32, 33, 34, 81) selective for freezing oxygen is located at said minimum non-point magnetic field.

4. Device (1, 70) according to one of claims 1 to 3 characterized in that said at least one selective cryogenic condenser for freezing oxygen is an annular condenser surrounding said plasma present in said chamber (2, 72 ).

5. Device (1, 70) according to one of claims 1 to 4 characterized in that said at least one cryogenic condenser (1 1, 31, 32, 33, 34, 81) selective for freezing oxygen from the dissociation without freezing the hydrogen resulting from the dissociation is at a temperature between 6 and 4OK for a mean pressure substantially equal to 5.10 ^"3 mbar in said chamber (2, 72).

6. Device (1, 70) according to one of claims 1 to 5 characterized in that it comprises a plurality of cryogenic condensers selective for freezing annular oxygen surrounding said plasma.

7. Device (1, 70) according to one of claims 1 to 6 characterized in that it comprises a second cryogenic condenser (12, 82) for freezing the oxygen from the dissociation placed at the end of said chamber (2, 72) between said magnetic mirror configuration and said hydrogen recovery means (13, 83).

8. Device (1, 70) according to one of claims 1 to 7 characterized in that said magnetic structure (3, 4, 5, 6, 7, 8, 9, 10, 73, 74, 75, 76, 77 , 78, 79, 80) comprises a plurality of permanent magnets.

9. Device (1, 70) according to claim 8 characterized in that said plurality of permanent magnets (3, 4, 5, 6, 7, 8, 9, 10, 76, 75, 79, 80) has the same sense of magnetization.

10. Device (1, 70) according to one of claims 1 to 9 characterized in that said magnetic structure (73, 77) comprises permanent magnets whose poles face each other in the steam injection zone. water.

11. Device (1, 70) according to one of claims 1 to 10 characterized in that said magnetic structure (74, 78) comprises permanent magnets whose poles face each other in the hydrogen recovery zone.

12. Device (1, 70) according to claim 10 and claim 1 1 characterized in that said permanent magnets located in the steam injection zone have a different polarity of said permanent magnets located in the recovery zone. hydrogen.

13. Device (1, 70) according to one of claims 1 to 12 characterized in that said magnetic structure (3, 4, 5, 6, 7, 8, 9, 10, 73, 74, 75, 76, 77 , 78, 79, 80) comprises permanent magnets of different sizes and having either the same magnetization or different magnetizations.

14. Device (1, 70) according to one of claims 1 to 13 characterized in that said magnetic structure comprises coils at room temperature and / or superconducting coils at low or high critical temperature, said low or high Tc.

15. Device (1, 70) according to one of claims 1 to 14 characterized in that it comprises means (16, 86) for recovery of non-dissociated water, said means (16, 86) of recovery of the undissociated water being substantially arranged along the axis (AA ') of injection of the steam.

16. Device (1, 70) according to claim 15 characterized in that said means (16, 86) for recovering non-dissociated water forms a diaphragm around said steam injection means (14, 84). , so as to delimit the shape of the jet of water vapor.

17. Device (1, 70) according to one of claims 15 to 16 characterized in that said means (16, 86) for recovering non-dissociated water are formed by a cryogenic condenser.

18. Device (1, 70) according to one of claims 1 to 17 characterized in that it comprises at least one system (17, 87) for reinjection of non-dissociated water in the vapor phase and issued from said recovery means (16, 86) undissociated water.

19. Device (1, 70) according to one of claims 1 to 18 characterized in that it comprises a mesh (21, 35) having a mesh for stopping the propagation of high frequency waves.

20. Device (1, 70) according to claim 19 characterized in that said grid (21) is inserted between the plasma of the chamber (2) and said at least one cryogenic condenser (1 1, 31, 32, 33, 34 , 81) selective for freezing the oxygen resulting from the dissociation, so as to protect said at least one cryogenic condenser (1 1, 31, 32, 33, 34, 81) of the high frequency waves.

21. Device (1, 70) according to one of claims 19 to 20 characterized in that said mesh (35) is formed by a metal movable cylinder having solid portions (36) and perforated portions (37) for protection at least partially of said at least one cryogenic condenser (31, 32, 33, 34) of the high frequency waves.

22. Device (1, 70) according to one of claims 1 to 21 characterized in that it comprises a chamber capable of recovering oxygen when the temperature of said at least one cryogenic condenser (1 1, 31, 32, 33 , 34, 81) to freeze oxygen is high.

23. Device (1, 70) according to one of claims 1 to 22 characterized in that said means (13, 83) for recovering hydrogen from the dissociation are placed outside said magnetic mirror configuration .

24. Device (1, 70) according to one of claims 1 to 23 characterized in that said means (13, 83) for recovering hydrogen from the dissociation comprise a pump for pumping hydrogen gas phase .

25. Device (1, 70) according to one of claims 1 to 24 characterized in that said means (13, 83) for recovering hydrogen from the dissociation comprise at least one cryogenic condenser for freezing hydrogen.

26. Device (1, 70) according to claim 25 characterized in that it comprises an enclosure capable of recovering hydrogen when the temperature of said at least one cryogenic condenser for freezing hydrogen is high.

27. Device (1, 70) according to one of claims 1 to 26 characterized in that said injection means (15, 85) of a high-frequency wave inside said chamber (2, 72) comprises an input window placed in a high magnetic field so that the plasma diffuses towards the chamber (2, 72) and thus avoid impacts of the plasma on said window.

28. Device (1, 70) according to one of claims 1 to 27 characterized in that said module of said minimum magnetic field is between 90% of said electron cyclotron resonance value and said electronic cyclotron resonance value.

29. Device (1, 70) according to one of claims 1 to 28 characterized in that it comprises means for injection of high-frequency multifrequency waves.