WO2024184175A1 - Device for producing a hydrogen – gaseous hydrocarbon mixture - Google Patents

Abstract

The present invention relates to a device (1) for producing a mixture of gaseous hydrocarbon and hydrogen, which device is intended to be arranged upstream of at least one burner of a gas boiler, characterised in that it comprises at least: - a Venturi tube (2), - a first inlet opening (3) for gaseous hydrocarbon, - an outlet opening (4) for the mixture of gaseous hydrocarbon and hydrogen produced by the device (1), - a second inlet opening (5) for hydrogen, - a hydrogen regulation and safety unit (6) connected to the second inlet opening (5) and to the neck of the Venturi tube (2), and - a pressure switch (7) measuring the pressure of the hydrogen entering through the second inlet opening (5), - a differential pressure switch (8) between the inlet and the neck of the Venturi tube (2), and - an electronic control box (9) for regulating the supply of hydrogen.

Description

DESCRIPTION

TITLE: DEVICE FOR PRODUCING A HYDROGEN MIXTURE -

HYDROCARBON GAS

Technical field of the invention

The present invention relates to the general field of gas burners, in particular for boilers. It relates more specifically to a device for producing a variable mixture of hydrogen and gaseous hydrocarbon arranged to be placed upstream of at least one gas burner for a gas boiler, but also to a method of implementing said device on a gas burner.

State of the art

In the field of gas burners for boilers in particular, it is known to use a gaseous hydrocarbon, which is most often made up of methane. Gaseous hydrocarbons offer many economic and even environmental advantages since gaseous hydrocarbons have relatively low levels of pollutant emissions compared to other fossil fuels such as coal or oil.

However, for obvious ecological reasons, it is now essential to reduce all pollutant emissions, particularly carbon dioxide emissions, which are responsible for almost 65% of the greenhouse effect of anthropogenic origin.

To reduce pollutant emissions generated by gaseous hydrocarbons, one solution is to mix them with a quantity of hydrogen representing a ratio of around 20% or even more. The interest in mixing hydrogen in a gaseous hydrocarbon is multiple. First of all, it obviously allows to reduce CO2 emissions and the consumption of fossil gas. This last aspect also has a geopolitical interest by limiting the dependence of countries on countries producing gaseous hydrocarbons. In addition, the hydrogen - gaseous hydrocarbon mixture also has an economic interest, because hydrogen is a means of storing electricity produced by renewable energy sources, and can be produced at times when the production of electricity from renewable energy sources is higher than consumption. Finally, the combustion of hydrogen produces a significant quantity of water vapor, increases the temperature dew point of the burnt gases and promotes condensation in the heat exchanger of the associated boiler.

Thus, the devices known to produce a mixture of gaseous hydrocarbon and hydrogen are such that the mixture is ensured upstream of the gaseous hydrocarbon distribution network using a mixer. This type of mixer is conventionally composed of proportional valves associated with a flow measurement and an electronic component ensuring the gaseous hydrocarbon/hydrogen ratio. The major drawback to this type of mixer is the complexity of ensuring proportional dosing regardless of the flow rate of gaseous hydrocarbon consumed, which limits the use of this type of device to research applications and network infrastructures.

Furthermore, with this type of known mixers, the mixture of hydrogen and gaseous hydrocarbon is obtained for higher hydrogen and gaseous hydrocarbon pressures than those used for supplying burners operating only with gaseous hydrocarbon, which implies installing additional expansion stages to lower the supply pressure of said burners.

Finally, since the mixing is carried out upstream of the gaseous hydrocarbon distribution circuit, this type of mixer is not suitable for producing a mixture of gaseous hydrocarbon and "green" hydrogen, the latter being produced from renewable energy sources and, preferably, locally.

In the field of gas burners, air/hydrocarbon gas mixers are already known, such as those disclosed in US patent application US 2006/292505 or European patent application EP 4 043 788, associated with a pneumatic gas regulator allowing a dosage of 7 to 10% gas for 90 to 93% air regardless of the air flow rate. This type of mixer is based on the principle of the Venturi effect, named after the Italian physicist Giovanni Battista Venturi, which is the name given to a phenomenon of fluid dynamics, according to which a flowing fluid undergoes a depression where the flow section narrows. Thus, this type of mixer comprises a variable flow air duct connected to a Venturi tube having a progressive narrowing of section and creating at the neck (narrowest section of the Venturi tube) a depression proportional to the air flow rate. In this type of mixer, the gaseous hydrocarbon is then injected at the neck of way to mix with air. Furthermore, to ensure a constant air/hydrocarbon gas mixture ratio regardless of the air flow rate, the hydrocarbon gas pressure upstream of the throat is regulated to a pressure practically equal to the air pressure upstream of the Venturi tube. The advantage of this technology is to ensure precise, constant dosing on which the air/hydrocarbon gas mixture flow rate can be adapted over a relatively wide range. However, this type of mixer has a number of drawbacks. Indeed, it is not suitable for producing a mixture of hydrocarbon gas and hydrogen and it can penalize air systems with a significant pressure drop.

Summary of the invention

The aim of the present invention is therefore to propose a device for producing a mixture of gaseous hydrocarbon and hydrogen arranged to be placed upstream of at least one burner of a gas boiler and advantageously close to a production of green hydrogen, said device being compact and quick to set up and making it possible to mix hydrogen at a variable rate in gaseous hydrocarbon depending on the flow rate of the latter without any harmful impact on the burner, whatever its technology, and as soon as said burner is in operation, said device being able to be easily adjusted by a person who has had training in burner adjustments.

In accordance with the invention, there is therefore proposed a device for producing a mixture of gaseous hydrocarbon and hydrogen arranged to be placed upstream of at least one burner of a gas boiler, remarkable in that it comprises at least:

- a Venturi tube,

- a first inlet orifice arranged at the inlet of said Venturi tube and arranged to be connected to a supply pipe,

- an outlet orifice arranged at the outlet of said Venturi tube and arranged to be connected to a pipe for discharging the mixture of gaseous hydrocarbon and hydrogen produced by said device,

- a second inlet port arranged to be connected to a hydrogen supply pipe,

- a hydrogen safety and regulation group connected by its inlet to said second inlet port and by its outlet to the neck of said Venturi tube and making it possible to regulate the hydrogen pressure at the neck of said Venturi tube proportionally to the gaseous hydrocarbon supply pressure at the first inlet port,

- a pressure switch measuring the pressure of hydrogen entering said device through its second inlet port,

- a differential pressure switch detecting a pressure difference between the inlet and the neck of said Venturi tube, and

- an electronic control unit for regulating the hydrogen supply to the device using said hydrogen safety and regulation group based on the pressure measurements of the pressure switch and the differential pressure switch in manual mode or in automatic mode.

The Venturi tube is advantageously shaped to generate a maximum pressure difference between its inlet and neck, while limiting the pressure loss between the first inlet port and the outlet port of the device.

According to an advantageous embodiment, the hydrogen safety and regulation group comprises, depending on the direction of circulation of the hydrogen, at least:

- a cut-off solenoid valve connected to the second inlet port of the device and allowing or not the supply of hydrogen to the Venturi tube,

- a pressure regulator associated with a servo-regulator and connected to the output of the cut-off solenoid valve, and making it possible to regulate the hydrogen pressure at the neck of said Venturi tube proportionally to the gaseous hydrocarbon supply pressure at the first inlet orifice, and

- a flow limiter connected between the pressure regulator outlet and the neck of the Venturi tube to limit the hydrogen flow at the neck of said Venturi tube.

Preferably, the cut-off solenoid valve is electrically powered and controlled by the electronic control unit so that in automatic mode, the cut-off solenoid valve opens and authorizes the supply of hydrogen, only when the hydrogen pressure measured by the pressure switch is greater than or equal to a first threshold value, and when the pressure difference between the inlet and the neck of the Venturi tube measured by the differential pressure switch is greater than or equal to a second threshold value, said first and second threshold values being predetermined according to the applications of the device and respectively set on the pressure switch and the differential pressure switch.

The pressure regulator is advantageously of the normally closed type and comprises a valve which moves between a "closed" position in which it comes to bear on a seat, with partial sealing, so as to limit the passage of hydrogen through said seat, and an "open" position in which it no longer rests on said seat so as to allow greater circulation of hydrogen upstream of the flow limiter, said valve being connected by a rod to a deformable membrane.

According to an even more advantageous embodiment, the servo-regulator comprises a needle movable between an "open" position in which it allows the circulation of hydrogen taken upstream of the pressure regulator to the membrane of said pressure regulator on the side opposite the valve, and a "closed" position in which it comes to bear on a seat, in a partial seal, so as to limit the passage of said hydrogen and to allow the movement of the membrane of said pressure regulator to return the valve to its closed position, a movable membrane for moving said needle from its open position to its closed position, and vice versa, pressure means tending to keep said needle pressing against the membrane and return means tending to return said membrane to a position such that it keeps the needle in its open position, said membrane being subjected, on the one hand, to the pressure of the gaseous hydrocarbon taken at the first inlet orifice determining a set pressure and, on the other hand, to the pressure of the hydrogen taken downstream of the pressure regulator.

According to an even more advantageous embodiment, the return means of the servo-regulator are associated with an adjustment screw making it possible to adjust the force of said return means.

The flow limiter is preferably of the screw type and comprises an adjustment screw, the screwing or unscrewing of which allows respectively to reduce or increase the flow of hydrogen injected at the neck of the Venturi tube and to modulate the ratio of hydrogen in the mixture produced by the device.

The invention also relates to a method for implementing a device according to the invention upstream of at least one burner of a gas boiler, remarkable in that it comprises at least the following steps: a) switching off the device, the latter delivering only gaseous hydrocarbon, its hydrogen safety and regulation group not being electrically powered, b) positioning the burner on an operating point corresponding to its maximum power, then measurement of the oxygen content in the fumes leaving the gas boiler, c) putting the hydrogen safety and regulation group into manual mode, then measurement of the oxygen content present in said fumes, d) adjusting the flow rate of injected hydrogen using the hydrogen safety and regulation group in relation to the data from a chart representing the change in the oxygen content in the fumes leaving the gas boiler as a function of the hydrogen content injected, e) switching off the device, the latter only delivering gaseous hydrocarbon, its hydrogen safety and regulation group not being electrically powered, f) positioning the burner at an operating point corresponding to its minimum power, then measurement of the oxygen content in the fumes leaving the gas boiler, g) putting the hydrogen safety and regulation group into manual mode, then measurement of the oxygen content present in said fumes, h) adjusting the flow rate of injected hydrogen using the safety and regulation group hydrogen regulation in relation to the data of said chart, i) placing the safety and hydrogen regulation group in automatic mode.

Advantageously, the method comprises, before step a), a step of creating the chart showing the evolution of the oxygen level in the fumes as a function of the hydrogen level present in the fumes leaving the gas boiler, this creation step being based on the following input data:

- excess air applied to said burner,

- the range of variation of the hydrogen rate,

- the nature of the gaseous hydrocarbon and the nature of the hydrogen.

Brief description of the figures

Other advantages and characteristics will emerge more clearly from the following description of an embodiment of the invention with reference to the appended figures in which:

[Fig 1] is a schematic view of a device for producing a variable mixture of gaseous hydrocarbon and hydrogen according to the invention,

[Fig 2] is a perspective view of a device of Figure 1, [Fig 3] is another perspective view of the device of Figure 2 partially shown,

[Fig 4] is a bottom view of the device of Figure 2,

[Fig 5] is a partial schematic vertical sectional view of the device of Figure 2 along the V-V axis of Figure 2,

[Fig 6] is a schematic view of an example of an abacus allowing the implementation of the device of figure 2 on a burner of a gas boiler, said abacus representing the evolution of oxygen in the fumes as a function of the hydrogen level in the gas.

Description of the embodiments

With reference to Figure 1 and in accordance with the invention, the device 1 for producing a variable mixture of gaseous hydrocarbon and hydrogen arranged to be placed upstream of at least one gas boiler burner comprises at least:

- a Venturi tube 2,

- a first inlet orifice 3 arranged at the inlet of said Venturi tube 2 and arranged to be connected to a gaseous hydrocarbon supply pipe,

- an outlet orifice 4 arranged at the outlet of said Venturi tube 2 and arranged to be connected to a pipe for discharging the mixture of gaseous hydrocarbon and hydrogen produced by said device 1,

- a second inlet port 5 arranged to be connected to a hydrogen supply pipe,

- a hydrogen safety and regulation group 6 connected by its inlet to said second inlet orifice 5 and by its outlet to the neck of said Venturi tube 2,

- a pressure switch 7 measuring the pressure of hydrogen entering said device 1 through its second inlet orifice 5,

- a differential pressure switch 8 detecting a pressure difference between the inlet and the neck of said Venturi tube 2, and

- an electronic control box 9 for regulating the hydrogen supply to the device 1 using said hydrogen safety and regulation group 6 as a function of the pressure measurements of the pressure switch 7 and the differential pressure switch 8 in a manual mode or in an automatic mode. Here, the term "inlet" or "outlet" refers to elements or parts of elements of the device 1 located on the side of the inlet or outlet of a fluid depending on its flow direction.

Furthermore, the term "pressure switch" here refers to a device used to relay information on pressure variations of a fluid inside an element, said pressure switch being able to be of any type such as, for example, mechanical, electrical, electronic or even pneumatic.

The Venturi tube 2 is shaped to generate a maximum pressure difference of between 5 and 10 mbar between the inlet and the neck of said Venturi tube 2, while limiting the pressure drop between the first inlet orifice 3 and the outlet orifice 4 of the device 1 of between 1 and 4 mbar. This particular configuration is necessary to allow the system to admit a significant level of hydrogen at the neck of the Venturi tube 2, while limiting the pressure drop of the gas mixture produced upstream of a burner of a gas boiler, i.e. at the outlet orifice 4 of the device 1, so as to always have a gas mixture in conditions guaranteeing optimal operation of the associated burner.

Another advantage of this particular configuration of the Venturi tube 2 is that it allows operation with a low-pressure hydrogen supply (which must be slightly higher than the gaseous hydrocarbon supply pressure, of the order of 5 to 10 mbar). This particular configuration therefore helps to reduce the risks of gas leaks inside the premises receiving the device 1.

Finally, this configuration of the Venturi tube 2 with a high depression between its inlet and its neck allows, on the one hand, an adaptation to variations in the pressure of gaseous hydrocarbon without disturbing the rate of hydrogen injected at the level of said neck and, on the other hand, to guarantee a safe admission of hydrogen.

The first inlet port 3 and the outlet port 4 of the device 1 are advantageously materialized by male connectors with a gas thread fixed to the Venturi tube 2.

Furthermore, the second inlet orifice 5 is advantageously materialized by a flange provided with a female connector with a gas thread.

According to an advantageous embodiment, with reference to FIGS. 2 to 5, the hydrogen safety and regulation group 6 comprises, depending on the direction of circulation of the hydrogen, at least: - a cut-off solenoid valve 10 connected to the second inlet port 5 of the device 1,

- a pressure regulator 11 associated with a servo-regulator 12 and connected to the output of the cut-off solenoid valve 10, and

- a flow limiter 13 connected between the outlet of the pressure regulator 11 and the neck of the Venturi tube 2.

The cut-off solenoid valve 10 allows the hydrogen supply to be authorized or not to the Venturi tube 2. The cut-off solenoid valve 10 is electrically powered and controlled by the electronic control unit 9 in automatic mode or in manual mode, the transition from one mode to the other being ensured by a switch of said electronic control unit 9. Thus, in automatic mode, the cut-off solenoid valve 10 opens and authorizes the hydrogen supply, and therefore the passage of the latter, only when the hydrogen pressure measured by the pressure switch 7 is greater than or equal to a first threshold value, and when the pressure difference between the inlet and the neck of the Venturi tube 2 measured by the differential pressure switch 8 is greater than or equal to a second threshold value, said first and second threshold values being predetermined according to the applications of the device 1 and respectively set on the pressure switch 7 and the differential pressure switch 8.

The control of the cut-off solenoid valve 10 by the electronic control unit 9 as a function of the values measured by the pressure switch 7 and the differential pressure switch 8 is important, because it makes it possible to guarantee the safety of the device 1 by only admitting hydrogen into said device 1 when the hydrogen is available at a sufficient pressure and when a consumption of the mixture of hydrogen and gaseous hydrocarbon produced is effective (consumption detected by a pressure difference between the inlet and the neck of the Venturi tube 2), for example when the associated burner is in operation. Furthermore, when the device 1 is switched off, the cut-off solenoid valve 10 is closed and no hydrogen is injected at the neck of the Venturi tube 2.

In fact, the large difference in density between the gaseous hydrocarbon and the hydrogen leads, during periods of non-consumption of the gas mixture produced, to a separation of the gases. This phenomenon can lead to an accumulation significant hydrogen in the line upstream of the associated burner, and generate dangerous ignition conditions for said burner.

Furthermore, in the event of the use of hydrogen produced locally from non-controllable renewable energy sources, the quantity of hydrogen available is not always sufficient, which implies preventing the introduction of hydrogen from the supply line in the event of too low hydrogen pressure, in order to avoid the reflux of gaseous hydrocarbon into the hydrogen line.

The hydrogen safety and regulation group 6 also comprises a pressure regulator 11 associated with a servo-regulator 12 making it possible to regulate a hydrogen pressure upstream of the flow regulator 13.

With reference to FIG. 5, the pressure regulator 11 conventionally comprises a valve 14 movable between a "closed" position in which the valve 14 bears on a seat 15, in a partial seal, so as to limit the passage of hydrogen through said seat 15 and obtain the desired hydrogen pressure upstream of the flow limiter 13 for a low flow rate of gaseous hydrocarbon, and an "open" position in which the valve 14 no longer bears on said seat 15 so as to have a flow rate and a hydrogen pressure upstream of the flow limiter 13 adapted to a higher flow rate of gaseous hydrocarbon. Said valve 14 is connected by a rod 16 to a deformable membrane 17. Furthermore, the pressure regulator 11 is of the normally closed type and comprises return means 18 tending to return said valve 14 to its closed position.

Here, the term "partial sealing" refers to a seal obtained, in a conventional manner, by a metal-metal contact which is not perfect in principle, and cannot therefore be absolute, this type of sealing allowing a low gas flow rate to pass through.

With reference to Figure 5, the servo-regulator 12 comprises a needle 19 movable between an "open" position in which it allows the circulation of hydrogen taken upstream of the pressure regulator 11 to the membrane 17 of said pressure regulator 11 on the side opposite the valve 14, and a "closed" position in which it comes to bear on a seat 20, according to a partial seal, so as to limit the passage of said hydrogen and to allow the movement of the membrane 17 of said pressure regulator 11 to return the valve 14 to its closed position. Said servo-regulator 12 further comprises a movable membrane 21 for moving said needle 19 from its open position to its closed position, and vice versa, and means pressure 22 tending to keep said needle 19 pressing against the membrane 21. Said membrane 21 is subjected, on the one hand, to the pressure of the gaseous hydrocarbon taken at the first inlet orifice 3 of the device 1 determining a set pressure and, on the other hand, to the pressure of the hydrogen taken downstream of the pressure regulator 11. Furthermore, the servo-regulator 12 comprises return means 23 tending to return said membrane 20 to a position such that it keeps the needle in its open position.

With reference to Figure 5, the pressure regulator 11 - servo-regulator 12 assembly operates as follows. Thus, if the hydrogen pressure downstream of the pressure regulator 11 is higher than said set pressure, then the membrane 21 will move the needle 19 from its open position to its closed position and the hydrogen taken upstream of the pressure regulator 11 will flow in a reduced manner to the membrane 17 of the pressure regulator 11 on the side opposite the valve 14, which has the effect of moving the valve 14 of said pressure regulator 11 from its open position to its closed position, of reducing the hydrogen pressure downstream of the pressure regulator 11, until equilibrium is obtained between the hydrogen pressure downstream of the pressure regulator 11 and the set pressure. Conversely, if the hydrogen pressure downstream of the pressure regulator 11 is lower than said set pressure, then the membrane 21 will move the needle 19 from its closed position to its open position and the hydrogen taken upstream of the pressure regulator 11 will flow significantly to the membrane 17 of the pressure regulator 11 on the side opposite the valve 14, which has the effect of moving the valve 14 of said pressure regulator 11 from its closed position to its open position, of increasing the hydrogen pressure downstream of the pressure regulator 11, until equilibrium is obtained between the hydrogen pressure downstream of the pressure regulator 11 and the set pressure.

The return means 23 are further associated with an adjustment screw 24 which makes it possible to adjust the force of said return means 23, in order to finely adjust the settings and to introduce a variation in the hydrogen rate between the minimum power and the maximum power of the gas burner.

The hydrogen safety and regulation group 6 also comprises a flow limiter 13 for limiting the flow of hydrogen entering the Venturi tube 2. With reference to FIG. 5, said flow limiter 13 is of the screw type and comprises an adjustment screw 25, the screwing or unscrewing of which allows respectively to reduce or increase the flow rate of hydrogen injected at the neck of the Venturi tube 2 and, consequently, to modulate the ratio of hydrogen in the mixture produced by the device 1 according to the invention.

It is understood that the device 1 thus configured makes it possible to regulate the hydrogen pressure proportionally to the gaseous hydrocarbon supply pressure, that is to say at the level of the first inlet orifice 3 of said device 1, which has the effect of automatically compensating for pressure variations in the gaseous hydrocarbon supply network. Furthermore, even if the hydrogen supply pressure must be slightly higher than the gaseous hydrocarbon supply pressure, the depression at the mixing point of the hydrogen and the gaseous hydrocarbon located at the neck of the Venturi tube 2 is sufficient to ensure the regulation of the flow rate of injected hydrogen.

Furthermore, it is understood that maintaining the hydrogen level in the device 1 according to the invention is, regardless of the flow rate of gaseous hydrocarbon, completely autonomous and independent of the burner on which it is implemented. In addition, the hydrogen intake management is integrated into said device 1 and is of the electromechanical type, which makes the management of said device 1 accessible to any heating engineer and/or boiler room operator equipped with standard means.

However, in order to ensure the correct adjustment and operation of the device 1, the invention also relates to a method of implementing said device on a gas boiler burner.

Said method consists in deducing the level of hydrogen present in the mixture of hydrogen and gaseous hydrocarbon produced by the device 1 according to the invention as a function of the oxygen content present in the fumes leaving the gas boiler. This method is intended to be carried out by heating engineers who are used to adjusting burners using a combustion analyzer measuring the level of oxygen in the fumes and a chart representing the change in the level of oxygen in the fumes as a function of the level of hydrogen present in the fumes (see Figure 6).

For this, the method of implementing said device on a gas boiler burner comprises at least the following steps: a) switching off the device 1, the latter device 1 only delivering gaseous hydrocarbon, its hydrogen safety and regulation group 6 not being not electrically powered, b) positioning the burner at an operating point corresponding to its maximum power, then measuring the oxygen level in the fumes leaving the gas boiler, c) putting the hydrogen safety and regulation group 6 into manual mode, then measuring the oxygen level present in said fumes, d) adjusting the flow rate of injected hydrogen using the hydrogen safety and regulation group 6 in relation to the data from a chart representing the change in the oxygen level in the fumes leaving the gas boiler as a function of the hydrogen level injected, e) switching off the device 1, the latter device 1 only delivering gaseous hydrocarbon, its hydrogen safety and regulation group 6 not being electrically powered, f) positioning the burner at an operating point corresponding to its minimum power, then measuring the oxygen level in the fumes leaving the gas boiler, g) putting the hydrogen safety and regulation group 6 into manual mode, then measuring the oxygen level of oxygen present in said fumes, h) adjustment of the flow rate of hydrogen injected using the hydrogen safety and regulation group 6 in relation to the data of said chart, i) putting the hydrogen safety and regulation group 6 into automatic mode.

Before step a), the method advantageously includes a step of creating the chart showing the evolution of the oxygen level in the fumes leaving the gas boiler as a function of the level of hydrogen injected.

This creation step is based on the following input data:

- excess air applied to said burner,

- the range of variation of the hydrogen rate (for example from 2 to 50%),

- the nature of the gaseous hydrocarbon and the nature of the hydrogen.

Once these input data are known, the theoretical stoichiometric air flow rate in the gaseous hydrocarbon in the absence of hydrogen injection is deduced. Then, the flow rate of the mixture of hydrogen and gaseous hydrocarbon admitted is calculated as a function of the hydrogen content, because the density of said mixture varies as a function of the hydrogen content in said mixture. With an air flow rate injected by a fan at constant burner level, we can then obtain the value of the excess air as a function of the hydrogen level in said mixture, from which we deduce the oxygen level present in the fumes leaving the gas boiler.

Thus, in the end, for a given type of gaseous hydrocarbon, we obtain a chart representing the evolution of the oxygen level in the fumes leaving the gas boiler as a function of the hydrogen level present in the mixture injected into the burner for different values of air flow rate injected into said burner, said chart having on the abscissa a scale giving the hydrogen level in the mixture produced by device 1 between 0 and 60%, and on the ordinate a scale giving the oxygen level present in the fumes leaving the gas boiler between 3 and 10%. The example of the chart shown in Figure 6 shows the change in the oxygen level in the fumes leaving the gas boiler as a function of the hydrogen level present in the mixture injected into the burner for different values of the oxygen level in the fumes leaving the gas boiler in the absence of hydrogen present in the mixture, these values of said oxygen level ranging from low to high from 3.5 to 6%, which corresponds to conventional gas boiler adjustment values.

It is understood that with the particular configuration of the device 1 according to the invention, the hydrogen content in the mixture produced by said device 1 will be between 0 and 60%. This content is particularly suitable for a gas burner, because beyond 60% the other equipment associated with said gas burner may no longer operate safely.

The device 1 for producing a variable mixture of gaseous hydrocarbon and hydrogen according to the invention finds a particular application for supplying at least one gas burner of a boiler, but it goes without saying that said device 1 could be adapted to be implemented on other equipment such as, for example, a mixing station for a chemistry laboratory or even an industrial welding process.

Finally, it goes without saying that the examples of device 1 in accordance with the invention which have just been described are only particular illustrations, in no way limiting of the invention.

Claims

1. Device (1) for producing a mixture of gaseous hydrocarbon and hydrogen arranged to be placed upstream of at least one gas burner, characterized in that it comprises at least: - a Venturi tube (2), - a first inlet port (3) arranged at the inlet of said Venturi tube (2) and arranged to be connected to a supply pipe, - an outlet orifice (4) arranged at the outlet of said Venturi tube (2) and arranged to be connected to a pipe for delivering the mixture of gaseous hydrocarbon and hydrogen produced by said device (1), - a second inlet port (5) arranged to be connected to a hydrogen supply pipe, - a hydrogen safety and regulation group (6) connected by its inlet to said second inlet port (5) and by its outlet to the neck of said Venturi tube (2) and making it possible to regulate the hydrogen pressure at the neck of said Venturi tube (2) proportionally to the gaseous hydrocarbon supply pressure at the first inlet port (3), - a pressure switch (7) measuring the pressure of hydrogen entering said device (1) through its second inlet port (5), - a differential pressure switch (8) detecting a pressure difference between the inlet and the neck of said Venturi tube (2), and - an electronic control box (9) for regulating the hydrogen supply to the device (1) using said hydrogen safety and regulation group (6) as a function of the pressure measurements of the pressure switch (7) and the differential pressure switch (8) in manual mode or in automatic mode. 2. Device (1) according to claim 1 characterized in that the Venturi tube (2) is shaped to generate a maximum pressure difference of between 5 and 10 mbar between its inlet and neck, while limiting the pressure loss between the first inlet orifice (3) and the outlet orifice (4) of the device (1) of between 1 and 4 mbar. 3. Device (1) according to any one of claims 1 or 2, characterized in that the hydrogen safety and regulation group (6) comprises according to the direction of hydrogen flow at least: - a cut-off solenoid valve (10) connected to the second inlet port (5) of the device (1) and allowing or not the supply of hydrogen to the Venturi tube (2), - a pressure regulator (11) associated with a servo-regulator (12) and connected to the outlet of the cut-off solenoid valve (10), and making it possible to regulate the hydrogen pressure at the neck of said Venturi tube (2) proportionally to the gaseous hydrocarbon supply pressure at the first inlet orifice (3), and - a flow limiter (13) connected between the outlet of the pressure regulator (11) and the neck of the Venturi tube (2) making it possible to limit the flow of hydrogen at the neck of said Venturi tube (2). 4. Device (1) according to claim 3 characterized in that the cut-off solenoid valve (10) is electrically powered and controlled by the electronic control unit (9) so that in automatic mode, the cut-off solenoid valve (10) opens and authorizes the supply of hydrogen, only when the hydrogen pressure measured by the pressure switch (7) is greater than or equal to a first threshold value, and when the pressure difference between the inlet and the neck of the Venturi tube (2) measured by the differential pressure switch (8) is greater than or equal to a second threshold value, said first and second threshold values being predetermined according to the applications of the device (1) and respectively set on the pressure switch (7) and the differential pressure switch (8). 5. Device (1) according to any one of claims 3 or 4, characterized in that the pressure regulator (11) is of the normally closed type and comprises a valve (14) movable between a "closed" position in which it rests on a seat (15), with a partial seal, so as to limit the passage of hydrogen through said seat (15), and an "open" position in which it no longer rests on said seat (15) so as to allow greater circulation of hydrogen upstream of the flow limiter (13), said valve (14) being connected by a rod (16) to a deformable membrane (17). 6. Device (1) according to claim 5 characterized in that the servo-regulator (12) comprises a needle (19) movable between an "open" position in which it allows the circulation of hydrogen taken upstream of the pressure regulator (11) to the membrane (17) of said pressure regulator (11) on the side opposite the valve (14), and a "closed" position in which it comes to bear on a seat (20), according to a partial seal, so as to limit the passage of said hydrogen and to allow the movement of the membrane (17) of said pressure regulator (11) to return the valve (14) to its closed position, a movable membrane (21) to move said needle (19) from its open position to its closed position, and vice versa, pressure means (22) tending to keep said needle (19) pressing against the membrane (21) and return means (23) tending to return said membrane (20) to a position such that it maintains the needle in its open position, said membrane (21) being subjected, on the one hand, to the pressure of the gaseous hydrocarbon taken at the level of the first inlet port (3) determining a set pressure and, on the other hand, to the pressure of the hydrogen taken downstream of the pressure regulator (11). 7. Device (1) according to claim 6 characterized in that the return means (23) of the servo-regulator (12) are associated with an adjustment screw (24) making it possible to adjust the force of said return means (23). 8. Device (1) according to any one of claims 3 to 7, characterized in that said flow limiter (13) is of the screw type and comprises an adjustment screw (25), the screwing or unscrewing of which allows respectively to reduce or increase the flow of hydrogen injected at the neck of the Venturi tube (2) and, consequently, to modulate the ratio of hydrogen in the mixture produced by the device (1). 9. Method for implementing a device (1) according to any one of claims 1 to 8 upstream of at least one burner of a gas boiler, characterized in that it comprises at least the following steps: a) switching off the device (1), the latter delivering only gaseous hydrocarbon, its hydrogen safety and regulation group (6) not being electrically powered, b) positioning the burner at an operating point corresponding to its maximum power, then measuring the oxygen level in the fumes leaving the gas boiler, c) putting the hydrogen safety and regulation group (6) into manual mode, then measuring the oxygen level present in said fumes, d) adjusting the flow rate of injected hydrogen using the hydrogen safety and regulation group (6) in relation to the data of a chart representing the change in the oxygen level in the fumes leaving the gas boiler as a function of the hydrogen level injected, e) switching off the device (1), the latter only delivering gaseous hydrocarbon, its hydrogen safety and regulation group (6) not being electrically powered, f) positioning the burner at an operating point corresponding to its minimum power, then measuring the oxygen level in the fumes leaving the gas boiler, g) putting the hydrogen safety and regulation group (6) into manual mode, then measuring the oxygen level present in said fumes, h) adjusting the flow rate of injected hydrogen using the hydrogen safety and regulation group (6) in relation to the data of a chart representing the change in the oxygen level in the fumes leaving the gas boiler as a function of the hydrogen level injected, data from said abacus, i) putting the hydrogen safety and regulation group (6) into automatic mode. 10. Method according to claim 9, characterized in that it comprises, before step a), a step of creating the chart showing the evolution of the oxygen level in the fumes leaving the gas boiler as a function of the level of hydrogen injected, this creation step being based on the following input data: - excess air applied to said burner, - the range of variation of the hydrogen rate, - the nature of the gaseous hydrocarbon and the nature of the hydrogen.