WO2011023865A1

WO2011023865A1 - Improved equipment for producing hydrogen

Info

Publication number: WO2011023865A1
Application number: PCT/FR2010/000585
Authority: WO
Inventors: Pascal Morand; Fabien Aupretre
Original assignee: Compagnie Europeenne Des Technologies De L'hydrogene
Priority date: 2009-08-28
Filing date: 2010-08-27
Publication date: 2011-03-03
Also published as: FR2949479B1; FR2949479A1

Abstract

The invention relates to equipment for producing hydrogen, comprising: a circuit for supplying purified water; an electrolysis cell arranged to electrolyze the water received at the inlet and separating the water into a water/O₂ mixture and a water/H₂ mixture at the outlet; a first chamber (6) for separating a water/O₂mixture, connected, at the inlet thereof, to said circuit for supplying purified water and to the outlet for the water/O₂mixture of said cell, and connected at the outlet thereof to a circuit for extracting O₂ and to the inlet of said cell for the water; a second chamber (16) for separating a water/H₂ mixture, connected at the inlet thereof to the outlet for the water/H₂ mixture of said cell, and connected at the outlet thereof to circuit for extracting H₂ and to an outlet of the cell for the water; a pipe (33) connecting the first and second chambers, including a solenoid valve (34) capable of controlling a transfer of water from the second chamber (16) to the first chamber (6) in order to adjust the water level between the two; and a recombination device (35) arranged between said pipe (33) and adapted to substantially remove any trace of H₂ in the water from the second chamber (16) before the first chamber (6).

Description

Improved hydrogen production facility

The present invention relates to an installation for producing gaseous hydrogen by electrolysis of water.

It applies in particular, but not exclusively, to the supply of hydrogen for storage, for example in a metal hydride, or its consumption in a fuel cell. We know the need to reduce our production of greenhouse gases and use renewable energies.

Hydrogen is an alternative to hydrocarbons because it is an easily storable energy carrier, unlike electricity, and its oxidation releases a very important energy (285 kJ / mole).

Several ways are known to produce hydrogen gas; the most advantageous is to electrolyze the water molecule because it is a high efficiency reaction that does not produce CO2 in contrast to the massive processes that are reforming methane and hydrocarbons.

Three major types of electrolysers are known for the electrolysis of water:

alkaline electrolysers, which are characterized by the use of a liquid electrolyte which allows the transfer of the hydroxyl ions (OH-) from the cathode to the anode, - the electrolysers at high temperature, the electrolyte of which is a ceramic; this technology is only at the demonstrator stage,

membrane electrolysers, the electrolyte of which is a proton conduction ion exchange membrane. PEM membrane electrolysers (Proton Exchange Membrane) have many advantages, including: the absence of electrolyte circulation, which simplifies installation and facilitates pressure management (very high resistance to high pressure differentials),

a high chemical and electrochemical stability, leading to long lifetimes,

- high yields,

the possibility of operating at low or high pressure,

the ability to operate at high current densities

very high purities of gas (very low permeation of hydrogen through the membrane therefore less hydrogen in oxygen and therefore more safety),

the possibility of restarting the electrolyzer rapidly even after a prolonged shutdown,

the ability to safely produce over the entire flow range of the electrolyser. A disadvantage of membrane electrolysers PEM is that they must be fed with extremely pure water because the impurities pollute the membrane. These types of electrolysers require the incorporation of water purification systems, resin or otherwise, before electrolysing water. If the electrolyser rejects purified water, this results in greater water consumption and thus a premature loss of effectiveness of the resins and the need to change or regenerate them more often.

There is therefore a particular advantage, on this type of electrolyser, to avoid any loss of purified water and thus to recover and recycle all water possible.

Nevertheless, the recycling of this water can pose related problems. Indeed, the recycling of water can lead to the simultaneous presence of H2 and O2, which can recombine into a detonating mixture that would be dangerous for the installation and its environment. For this purpose, the invention proposes a hydrogen production plant, comprising

a circuit for supplying purified water,

an electrolysis cell arranged for electrolysing water received at the inlet, separating at the outlet a mixture of water-O 2 on the one hand, and a mixture of water-H2 on the other hand,

a first chamber adapted to separate a water-O 2 mixture, connected at the inlet to said purified water supply circuit and at the outlet of the water-O 2 mixture of said cell, and connected at the output to an extraction circuit for O2 and at an inlet of said cell for water,

a second chamber adapted to separate a water-H2 mixture, connected at the inlet to the outlet of the H2-water mixture of said cell, and connected at the output to an extraction circuit for the H2 and to an inlet of the cell for the water,

a duct connecting the first and second chambers, comprising a solenoid valve capable of controlling a transfer of water from the second chamber to the first chamber in order to regulate the water level therebetween, and

- A recombination device arranged in said pipe and adapted to substantially remove any trace of H2 in the water from the second chamber before the first chamber. In practice, the electrolysis means of the water may consist of a stack of several electrochemical cells PEM membrane mounted in series, which is called a "stack". The "stack" is supplied with direct current by a generator whose output voltage can be adjustable. The electrolysis installation of the water may comprise purified water recycling loops:

between the "stack" and the water-hydrogen separation chamber,

between the "stack" and the water-oxygen separation chamber,

between the first chamber, the oxygen purifier and the pure water storage tank,

between the second chamber, the hydrogen purifier and the pure water storage tank. These loops and recycling circuits are intended to recycle the purified water instead of dispersing it. Thus the plant according to the invention converts into H2 and O2 all the water it consumes, the recombination device ensuring the safety of the installation.

The first and second chambers play an important role in the invention because a large volume of water is entrained with the gases leaving the electrolysis cell.

Advantageously, the invention proposes to use as first and second chambers liquid level regulators, very compact, which has several advantages: the dead volume is low; however, the standards applicable to the safety of pressure vessels set thresholds expressed in maximum pressure x volume;

- This allows to design a very compact installation.

These level regulators continuously deliver a signal depending on the liquid level, which can be operated by a computer, particularly when the maximum level or the minimum level of liquid is reached.

The water supply circuit can be connected to running water and has several water purification units, which can be of different types (for example resin and / or activated carbon) for better purification. In addition, the water supply circuit of the installation is remarkable in that instead of directly feeding the electrolysis stack, it feeds the first chamber, using the fact that regulators are used. level to fulfill this separation function. In another variant, the water supply circuit can be connected to a deionized water storage tank. A conductivity sensor mounted on the circuit Water supply means electrolysis allows to continuously check the degree of purity of water.

The gas extraction circuits may each comprise a gas purification unit whose function is to retain the water vapor, this water being recycled to the storage tank. For better extraction of the water vapor with a view to a particular use of the gas, for example the filling of a hydride with hydrogen, the said gas purification unit may comprise a Peltier-effect gas cooler or an exchanger. of heat coupled to a cold group.

The two gas circuits may each have an output pressure regulating means which may be for example a pressure regulator which is both a pressure sensor and a proportional solenoid valve. As a safety measure, the circuits H2 and 02 of the hydrogen production plant according to the invention can be provided with means for evacuation of the gases, for example proportional valves or vents, intended to bring down the pressure instantly. case of overpressure. In the variant of the installation described above, the operating pressure is about 10 bar.

However the installation can operate at higher pressure, for example up to 50 bar and beyond; it then has the advantage of delivering gases at higher pressure for storage and thus avoid compression stages, whose performance is poor, downstream of the installation.

In this case, for safety reasons, it is no longer possible to directly return the water that has traveled the hydrogen loop to the storage or to the oxygen loop because of a larger amount of dissolved hydrogen. D must be provided in addition buffer storage for the recovery of this water and allow its degassing before driving, for example by pumping, to the purified water storage tank. The installation according to the invention may comprise a control / command unit comprising an industrial programmable controller whose inputs are connected to the sensors of the installation (water levels, pressure, temperature, conductivity, gas flow, amperage. .) and whose outputs are connected to the actuators of the installation (circulation means, solenoid valves, generator ...).

The programmable logic controller executes a sequence of instructions stored in one of its components, which allows a user to control the hydrogen production plant, for example according to several modes of operation, in particular:

a "Hydrogen Production" mode, in which the user-supplied setpoint data are the flow and operating pressure of the plant; the gases produced can be used for any application requiring hydrogen and / or oxygen;

a "hydrogen storage" mode, in which the user-supplied setpoint data are the flow rate and the filling pressure of the tank; by the very design of the installation, the increase in pressure is progressive and, in the case of a hydride recharge, this avoids a rise in temperature of the hydride and thus ensures optimum filling;

a "hydrogen consumption" mode, for example fuel cell power supply being tested, in which the setpoint data is an initial flow rate, regulated by the pressure to take into account the consumption of the battery.

Execution of a mode of operation results in the realization of a succession of phases, for example:

Preparation to start,

- Polarization of the electrolyser,

Starting the electrolysis,

Purge, Pause,

Production,

Pause,

General stop.

During the production phase, the programmable logic controller executes the following algorithms:

1) Regulation of the pressure and the water level, especially in the H2 circuit. In fact, on the one hand, the stoichiometric decomposition of water leads to 2 moles of hydrogen per one mole of oxygen, and on the other hand, each time a proton crosses the membrane of the electrolysis cell, less a molecule of water passes through it as well.

As a result, the water level and the pressure rise more rapidly in the water - hydrogen separation chamber than in the water - oxygen separation chamber. This can be a source of difficulty because some PEM membranes have to work in near equipressure. This algorithm is described below.

2) Adaptation of the voltage setpoint across the "stack" as a function of temperature. It is known that the efficiency of the decomposition reaction of water in an electrolysis cell of water increases with temperature.

The temperature sensor is designed to measure the temperature of the water at the outlet of the electrolysis stack, this measurement being used by the programmable logic controller to adapt the voltage across said electrolysis stack as a function of the user supplied gas flow rate.

3) Continuous calculation of the gas flow produced. The installation according to the invention may comprise gas flow sensors, but surprisingly it has appeared that the flow rate calculated by a coulometry equation is much more accurate than the measurement of the sensors. Thus the flow of hydrogen produced is calculated by the PLC using the following formula:

D = A * N * 3600 / (2 * e * Nv * VO), in which:

D is the flow rate in Normal liters per hour (Nl / h),

N is the number of cells in the "stack",

A is the current that flows through "stack" in amperes,

e is the charge of the electron (1.6 10-19 Coulomb),

Nv is the number of Avogadro (6,02,1023),

VO is the volume of one mole in Nl (22.4 liters).

As a control, the calculated result can be compared by the controller to the measurement of a flow sensor installed in the hydrogen circuit.

4) Continuous measurement of the conductivity of the water. If a critical water quality threshold defined by the manufacturer of the "stack" is exceeded, the PLC starts a procedure to stop the installation. For example, a conductivity threshold of 1 μS / cm or resistivity of 1 megOhm.cm can be used. As a reminder, according to the ASTM standard, a water whose conductivity is less than 0.055 μS / cm or whose resistivity is greater than 18 megOhm.cm is called ultrapure water type 1.

Advantageously, the installation may further comprise means for controlling the temperature of the feed water of the electrolysis "stack" enabling it to operate in very different climates. Indeed, the electrolysis "stack" produces heat and at high temperatures, this can lead, especially for high power installations, to excessive operating temperatures.

The installation can therefore include means for cooling the "stack", for example using heat exchangers on the water supply circuit. Similarly, when the operating temperature of the installation is too low (outside temperature too low and / or to raise the "stack" temperature faster to increase the yield), it may be advantageous to warm up. "Stack".

The installation can therefore include means for heating the "stack" using calories of a hot group, for example by providing heat exchangers on the water supply circuit. Other features and advantages of the invention will appear better on reading the following description, taken from examples given for illustrative and non-limiting purposes, taken from the drawings in which:

FIGS. 1 and 2 show functional diagrams of an installation operating at low pressure using a "stack" whose two compartments work in equipressure (FIG. 1a) and operating at high pressure using a "stack" whose two compartments work together equipressure (Figure Ib);

- Figures 3 and 4 show functional diagrams of plant variants using temperature control means, operating at low pressure (Figure 2a) and at high pressure (Figure 2b);

FIG. 5 is a schematic representation of a chamber of one of the installations of FIGS. 1 to 4,

FIGS. 6 and 7 are diagrammatic representations of elements of a recombination device that can be used in one of the installations of FIGS. 1 to 4, and

- Figure 8 is a flowchart of the water level regulating function in the first chamber and the second chamber.

The drawings and the description below contain, for the most part, elements of a certain character. They can therefore not only serve to better understand the present invention, but also contribute to its definition, if any.

Upstream, the installation is fed by a purified water supply circuit, connected to the running water network and which comprises, mounted in series, a regulator of pressure 2, water purification units 3, a purified water storage tank

I may comprise a level sensor, and, mounted on a pipe 7, a circulation means 8, for example a lifting pump, and a solenoid valve 9. The solenoid valve 9 and the lifting pump 8 are actuated to supply water the electrolysis stack 4 via a first chamber 6 when the water level in this chamber 6 reaches a minimum level.

In the example described here, the "stack" 4 comprises one or more PEM membrane electrolysers which are powered by a DC generator 5.

By means of circulation, the present means any element able to allow the circulation of a fluid from one point to another. This includes pumps of all types, and, depending on the relative position of the elements, gravity.

At the outlet of the first chamber 6, the circuit comprises a first circulation means 10, a conductivity probe 12 placed in bypass of a flow sensor 13 which is connected to a water purification unit 11. the purification unit

I 1 supplies the "stack" 4 in pure water.

The water conductivity sensor 12 is placed on the water return circuit in the loop 02 to check the degree of purification of the water, and the flow sensor 13 is used to check for the presence of a flow. feeding the "stack" 4 in water. Alternatively the flow sensor 13 may be replaced by a flow meter, especially if the circulation means 10 is a variable flow pump.

In the example described here, a temperature sensor 14 is further placed at the outlet of the water-O 2 mixture of the "stack" 4. The sensor 14 makes it possible to measure the temperature of the water at the outlet of the "stack", which makes it possible to control the operation of the "stack" 4. In a variant, the sensor 14 could be placed at the outlet of the water-H2 mixture of "Stack" 4. The gases are produced by electrolysis of water in the electrolysis "stack" 4 supplied with direct current by the generator 5 and driven by the circulation of water. There are two loops of water circulation:

a loop 02 maintained by the first circulation means 10, comprising a first chamber 6 whose main function is the separation of a water-O2 mixture that it receives, and the water purification unit 11,

an H2 loop maintained by a second circulation means 15, comprising a second chamber 16 whose main function is the separation of a H2-water mixture that it receives, a flow sensor 18 to check for the presence of a flow rate; feeding the "stack" 4 in water, and a water purification unit 17.

Again, the flow sensor 18 can be replaced alternatively by a flow meter, especially if the circulation means 15 is a variable flow pump.

It should be understood that, in the context of the invention, the expression "separation" designates the operations necessary to transform the input mixture into two separate outputs which each receive one of the components of this mixture.

Thus, as input, in the water-O2 or water-H2 mixture, the water is in liquid form, and the O2 OR H2 is in gaseous form, part of which can be dissolved in water.

In each respective chamber, the mixture then undergoes a transformation, so that two separate outlets are collected on the one hand pure water, and on the other hand the gas (O2 or H2 respectively). As will be seen below, it is nevertheless possible that the pure water still contains H2 at the outlet, and that the H2 at the outlet still contains water. Purification devices for each of these elements are provided for this purpose. The gases produced are thus led to extraction circuits respectively of hydrogen and oxygen. The H2 extraction circuit comprises a purification unit 19 for removing moisture and traces of oxygen in H2, an analysis unit 20 for checking the residual concentration of impurities in H2, a pressure regulator 21, and a pressure sensor 22. The analysis unit 20 makes it possible to detect a too great pressure and then causes the H2 degassing to a vent 23. This unit represents an important security, which is consequently placed on a separate branch of that which comprises the pressure regulator 21 and the outlet of H2 30. The analysis unit 20 may comprise a pressure sensor which makes it possible to control the efficiency of the regulation carried out by the regulator 21. hygrometer, as well as an O2 detector, to ensure the purity of the H2 gas. The pressure sensor 22 placed at the outlet of the hydrogen line makes it possible to control the "hydrogen storage" and "hydrogen consumption" modes and makes it possible to detect an excessive pressure downstream of the electrolyser.

The O 2 extraction circuit comprises a purification unit 24 for removing moisture and traces of hydrogen in O 2, an analysis unit for checking the residual concentration of H2 in oxygen and a pressure regulator 26.

The analysis unit 25 makes it possible to detect an excessive pressure and then causes the O 2 to vent to a vent 27. This unit represents a significant safety, which is consequently placed on a branch different from that which comprises the pressure regulator. 26 and the exit of O2 29. The analysis unit 25 may comprise a pressure sensor which makes it possible to control the efficiency of the regulation carried out by the regulator 26. It may also comprise a hygrometer, as well as an H2 detector, to ensure the purity of the O2 gas.

Alternatively, the analysis units 20 and 25 could be included in the branches of the regulators 21 and 26. In this case, the controller and the analysis unit can be interchanged in each branch. The condensed water from the purifiers 19 and 24 is led to the storage tank 1 respectively by pipes 31 and 32 through unrepresented circulation means.

The first chamber 6 and the second chamber 16 are respectively connected to the oxygen 27 and hydrogen 23 vents, for example by safety valves, so as to release gas in case of overpressure, or on order respectively of the analysis units 25 and 20.

Alternatively, the safety valves can be replaced or supplemented by a solenoid valve. This allows a fast decompression on command of the automaton, or directly of the analysis unit 25 or 20.

A pipe 33 connects the first chamber 6 and the second chamber 16. The circulation in the pipe 33 is controlled by a solenoid valve 34, it makes it possible to regulate the water level in the second chamber 16 by evacuating water to the first room 6.

However, this water is likely to contain a greater or lesser amount of H2. This quantity is all the more important as the operating pressure is high. However, the first chamber 6 receives a water that contains O2. Therefore, there is a risk to introduce the water from the second chamber 16 into the first chamber 6.

This risk is notably that 1Η2 and 1O2 recombines into an extremely dangerous explosive mixture for the installation and its environment.

To prevent this risk, a recombination device 35 is arranged in the pipe 33 to reduce the H2 content of the water drawn from the second chamber 16. The recombination device 35 catalyzes the recombination of H2 with H2O, so that before entering the first chamber 6, there is less H2, ideally more or almost more.

The installation may further comprise a control / command unit comprising a programmable controller 36 connected to display and input means 37. The inputs of the programmable logic controller 36 are connected:

to the level sensors respectively of the first chamber 6 and the second chamber 16,

at the level sensor of the pure water storage tank 1,

to the pressure regulators 21 and 26,

the H2 pressure sensor 22,

at the temperature sensor 14,

at the conductivity probe 12,

to purification units 19 and 24,

to analysis units 20 and 25,

the water flow sensors 13 and 18,

to the current generator 5,

electrolysis stack 4.

The outputs of the PLC 31 are connected:

- the lifting pumps 8 and circulation pumps 10 and 15,

to solenoid valves 9 and 34,

to the pressure regulators 21 and 26, to the DC generator 5,

to purification units 19 and 24

to analysis units 20 and 25,

the security means of the vent lines 02 and H2.

Figure 2 shows a block diagram of a variant of the installation intended to operate at high pressure.

In this variant the equipment or their assembly must be adapted to greater pressures, for example 50 bar.

In this variant, if the H2 and O2 gas analyzers 25 do not support the high pressure, it is possible to put them in parallel in their respective extraction circuits after expansion of the gases and to connect them to the H2 23 and O2 vents. 27.

A pressurized neutral gas supply, shown in phantom, comprising a cylinder of pressurized inert gas 39 and a solenoid valve 38, can be used to pressurize the plant. It can also be used to inerter the custom installation of the analysis units 20 and 25.

As in the low pressure variant, the installation can be controlled by a control / command unit, comprising a programmable controller 36 and display and input means 37. The programmable logic controller can also control the solenoid valve 38 on the control panel. supply of gas under pressure.

In the variant shown in Figures 3 and 4 (which respectively correspond to Figures 1 and 2), the installation further comprises at least one heat exchanger 42 between the water outlet of the first chamber 6 and the feed of "Stack" 4. This exchanger can be used to cool the water through a coolant circulating in a cooling circuit, shown in broken lines, depending on the temperature measured for example by the temperature sensor 14. In the cooling function, the heat transfer fluid circulates through a circulation means, for example a circulation pump 41, between the exchanger 42 and a second heat exchanger 40 in contact with a cold source. The second exchanger 40 may be an air / liquid or liquid / liquid exchanger, so as to evacuate excess calories.

Advantageously it is possible to recover all or part of these calories to heat the water contained in the storage tank 1 via a heat exchanger 45 that can be located in the storage tank 1 or outside thereof .

These calories can also be recovered elsewhere depending on the placement of the exchanger 45, for example at the lift 8 or downstream thereof. Solenoid valves 43 and 44 make it possible to direct the coolant either towards exchanger 45 or directly to exchanger 40.

The solenoid valves 43 and 44 and the pump 41 are of course connected to the outputs of the programmable controller 36, the temperature sensors 14 and 46 being connected to an input of the programmable controller 36. Similarly, the exchanger 40 can be connected to an output of the PLC to control the power of the exchange.

In this example, as a function of the temperature measured in the storage tank by a temperature sensor 46, the automaton actuates the solenoid valves so that the temperature of the water contained in the tank 1 remains within a range of temperature close to the operating temperature of the electrolyser.

This preheating system has the advantage of limiting thermal fluctuations related to the injection of water for example at room temperature from the tank 1 into the first chamber 6 which is at the operating temperature of the electrolyser. Indeed, the injection of "cold" feed water into the electrolyser causes a transient drop in the operating temperature, the amplitude of which varies according to the quantity and the temperature of the injected water. However, a decrease in temperature causes an increase in the electrolysis voltage (E) and the enthalpy voltage (V), which implies a reduction in the electrolysis efficiency.

In practice, at constant supply voltage, the amount of current flowing through the stack and therefore the production of hydrogen decreases.

In the case of constant flow operation, it is necessary to keep a constant current density and therefore to increase the supply voltage which results in an increase in the energy consumption of the system until the optimal operating temperature is reached again.

This pre-heating is therefore beneficial because it effectively cools the "stack" 4 while improving efficiency, which represents an optimal use of calories lost by the Joule effect at the electrolyzer.

This has the additional advantage of stabilizing the operation of the "stack" 4 under essentially stable pressure and temperature, which is beneficial for catalytic recombination. Figure 5 shows schematically the chambers used to achieve the water-O2 and water-H2 separation.

This separation is, as we have seen above, an operation which aims to recover separately the pure liquid water on one side, and the gas on the other. For this, rooms 6 and 16 are mainly based on the effect of gravity. Thus, a chamber comprises a body 50 of generally cylindrical shape placed vertically in the installation. In the figure shown here, the cylinder is higher than wide, because the flow is not too important. In high flow variants, the body 50 may take a wider than tall shape. What matters is the layout of the inputs and outputs to achieve gravity separation. The body 50 has a first inlet 52 for the mixture water + O2 or water + H2 disposed in an upper part of the body. Thus, the mixture "falls" into the body and the liquid / gas separation is performed by gravity.

The body 50 also has a second inlet 54 and a third inlet 56.

In the case of the first chamber 6, the second inlet 54 can receive the water from the second chamber 16 and / or the inert gas, and the third inlet 56 can receive the water from the lift 8. In the in the case of the second chamber 16, the second inlet 54 is used as an outlet towards the pipe 33, and the third inlet 56 makes it possible to receive the inert gas.

For both chambers, the body has a first outlet 58 for the gas connected to the respective extraction circuits, and a second outlet 60 for the water to be recycled in the feed of the "stack" 4.

The body 50 finally has a first recess 62 and a second recess 64, respectively slightly below the level of the first inlet 52 and slightly above the level of the second inlet 54, which can receive respective level sensors to determine the level. of liquid up and down in the room. FIG. 6 represents a filter that can be used to produce the recombination device 35. The filter comprises a peripheral ring 66 made of steel arranged to be housed in the pipe 33. The peripheral ring 66 substantially houses a disk 68 at its center. a filter on which is deposited a catalyst, for example platinum black, which is intended to catalyze the recombination reaction of H2 contained in the water flowing therethrough.

The filter 35 may be arranged upstream or downstream of the solenoid valve 34, and further has a porosity calculated to cause a pressure drop for the water flowing through it. This loss of charge makes it possible to increase the travel time in line 33, and therefore the amount of H2 that is recombined in pure water.

FIG. 7 represents a complement for the filter 35. Indeed, it can be complicated to control the porosity of the filter 35 and / or to obtain a sufficient pressure drop.

A valve with variable opening 70, for example a needle valve can then be used in addition. The opening is adjusted by a small electric motor step. The pressure drop is thus adapted to the difference in pressure.

Finally, as an alternative to FIGS. 6 and 7, the recombination device 35 can be made in the form of a reservoir introduced into the pipe 33, whose walls are covered with platinum black, and whose shape and volume are adapted to cause the desired pressure drop.

In order to further reduce the amount of H2 at the first chamber 6, recirculation loops through the recombiner 35 may also be provided downstream thereof. FIG. 8 details the algorithm for level and pressure regulation in the second chamber 16.

The water levels in chambers 6 and 16 as well as the pressures in the H2 and O2 circuits are measured continuously.

When the water level reaches the maximum level in the second chamber 16, the O2 pressure regulator 26 is opened so as to lower the pressure on the oxygen side and consequently increase the pressure difference between the loop H2 and the O2 loop.

When this difference is sufficient, in practice when it reaches 0.2 bar, the solenoid valve 34 on the pipe 33 between the chambers 6 and 16 is open so that water passes from the chamber 16 to the chamber 6, while maintaining said gap so that the second chamber 16 partially empties into the first chamber 6.

The solenoid valve 34 and the O2 pressure regulator 26 are closed when one of the following two conditions is fulfilled:

the water reaches the maximum level in the first chamber 6,

the water reaches the minimum level in the second chamber 16.

This closure is not necessarily total: it aims to raise the pressure at the respective chamber. The invention described herein can not be limited to the described embodiments only. It includes all the equivalents that the skilled person will consider.

In addition, the Applicant has described a number of variants that can be combined with each other. The disclosure of the present therefore relates to all combinations of these variants with each other, and not only on the juxtaposition of the variants described.

Claims

claims

1. A plant for producing hydrogen, characterized in that it comprises:

a circuit for supplying purified water,

an electrolysis cell arranged for electrolysing water received at the inlet, separating at the outlet a mixture of water-O 2 on the one hand, and a mixture of water-H 2 on the other hand,

a first chamber (6) adapted to separate a water-O 2 mixture, connected at the inlet to said purified water supply circuit and at the outlet of the water-O 2 mixture of said cell, and connected at the output to a circuit of extraction for O2 and at an inlet of said cell for water,

a second chamber (16) adapted to separate a water-H2 mixture, connected at the inlet to the outlet of the H2-water mixture of said cell, and connected at the output to an extraction circuit for the H2 and at an inlet of the cell for water,

- a pipe (33) connecting the first and second chambers, comprising an electro valve (34) adapted to control a transfer of water from the second chamber (16) to the first chamber (6) to achieve a level control of water between them, and

- A recombination device (35) arranged in said pipe (33) and adapted to substantially remove any trace of H2 in the water from the second chamber (16) before the first chamber (6).

The hydrogen production plant according to claim 1, wherein the recombination device (35) comprises a recombinant H2 recombination catalyst in water, and the recombination device (35) is further adapted to create a pressure drop in the pipe (33).

3. Hydrogen production plant according to claim 1 or 2, wherein said electrolysis cell (4) comprises at least one membrane PEM (Proton Exchange Membrane).

The hydrogen production plant according to any one of the preceding claims, wherein said purified water supply circuit is connected to a running water system and comprises, connected in series, a pressure regulator (2), at least one water purification unit (3), a purified water storage tank (1), a third means for circulation (8), a solenoid valve (9), said solenoid valve (9) and said circulation means (8) being actuated to supply water to said first chamber (6).

5. Hydrogen production plant according to one of the preceding claims, wherein the first chamber (6) is connected to an O2 extraction circuit which comprises:

an O2 purification unit (24) carrying out a water extraction, the extracted water being reinjected into said purified water storage tank (1) via a pipe (31),

a gas analysis means (25),

an O2 pressure regulating means (26), and

a first gas evacuation means (27) for lowering the pressure by releasing 1 O 2 in the event of overpressure in said O 2 extraction circuit;

6. Hydrogen production plant according to one of the preceding claims, wherein the second chamber (16) is connected to an H2 extraction circuit comprises:

an H2 purification unit (19) carrying out a water extraction, the extracted water being reinjected into said purified water storage tank (1) via a pipe (32),

a gas analysis means (20),

a means for regulating the pressure of H2 (21), and

a second gas evacuation means (23), so as to lower the pressure by releasing H2 in case of overpressure in said H2 extraction circuit;

The hydrogen production plant according to claim 6, further comprising a control / control unit, comprising:

a programmable controller (36) designed to control the operation of said installation by executing a sequence of instructions stored in one of its components, the inputs of which are connected to said first and second chambers (6, 16), to a level sensor of the pure water storage tank (1), to said regulators of pressure (21, 26), said electrolysis cell (4), a conductivity sensor (12) and a flow sensor (13) mounted on the inlet of said electrolysis cell (4) to said gas analysis means (20, 25), said H2 pressure sensor (22), said gas purification units (19, 24), a current generator (5) which supplies said electrolysis cell (4). ), a temperature sensor (14) disposed at the output of said electrolysis cell (4), and whose outputs are connected to said first, second and third circulation means (8, 10, 15), to said solenoid valves (9). , 34), said DC generator (5), said pressure regulators (21, 26), said purification units (19, 24), and

- Display and input means (3), connected to said programmable controller (36).

The hydrogen production plant according to claim 7, wherein said control / control module is adapted to control the operation of said plant according to a plurality of possible modes of operation comprising: a hydrogen production mode, wherein the user-supplied setpoint data is the flow and operating pressure of the plant, regardless of the use of the hydrogen and / or oxygen produced, or

a hydrogen storage mode, in which said plant supplies a hydrogen storage means and the user-supplied setpoint data are the flow rate and the filling pressure of the tank, or

- A hydrogen consumption mode, wherein said installation feeds a hydrogen consumption means and the setpoint data is an initial flow rate, regulated by the pressure to take into account the consumption of the battery.

9. Hydrogen production plant according to claim 7 or 8, wherein said programmable controller (36) regulates the produced gas flow as a function of the temperature measured by the temperature sensor (14), by varying the voltage generated. by the DC generator (5) and applied across the terminals of said electrolysis cell (4) as a function of the gas flow setpoint supplied by the user.

10. Hydrogen production plant according to one of claims 7 to 9, wherein said programmable controller (36) executes in a loop the following sequence of instructions:

at. take the measurement of the water level in the second chamber (16),

b. if the water level in the second chamber (16) reaches the maximum level:

vs. open the O2 pressure regulator (26),

d. measure the pressure in the O2 and H2 extraction circuits, e. if the pressure difference between said H2 extraction circuit and said O2 extraction circuit is greater than a threshold, open the solenoid valve (34) mounted on the pipe (33) provided between the first and second chambers (6, 16) while maintaining said gap so that the second chamber (16) partially empties into the first chamber (6),

f. when the water level in the second chamber (16) reaches a minimum level or when the water level in the first chamber (6) reaches a maximum level, closing said solenoid valve (34) and the O2 pressure regulator (26)

repeat from a.