Device for producing a hydrogen - gaseous hydrocarbon mixture

Abstract

A device for producing a mixture of gaseous hydrocarbon and hydrogen arranged to be disposed upstream of at least one burner of a gas boiler. The device includes a Venturi tube, a first gaseous-hydrocarbon inlet opening, an outlet opening for the mixture of gaseous hydrocarbon and hydrogen produced by said device, a second hydrogen inlet opening, a hydrogen safety and regulation unit connected to said second inlet opening and to the neck of said Venturi tube and, a pressure switch measuring the pressure of hydrogen entering said second inlet opening, a differential pressure switch between the inlet and the neck of said Venturi tube, and an electronic control unit for regulating the hydrogen supply.

Description

TECHNICAL FIELD

[0001] The present invention relates to the general field of gas burners, in particular for boilers. More specifically, it relates to a device for producing a variable mixture of hydrogen and gaseous hydrocarbon arranged to be disposed upstream of at least one gas burner for a gas boiler, but also a method for implementing said device on a gas burner.BACKGROUND

[0002] In the field of boiler gas burners in particular, using a gaseous hydrocarbon, which the majority of the time consists of methane, is known. Gaseous hydrocarbons offer many economic and even environmental benefits since gaseous hydrocarbons have relatively low pollutant emission levels compared with other fossil fuels such as coal or oil.

[0003] However, for obvious ecological reasons, it is now essential to reduce all emissions of pollutants, including carbon dioxide emissions responsible for nearly 65% of the anthropogenic greenhouse effect.

[0004] To reduce the emissions of pollutants generated by gaseous hydrocarbons, one of the solutions is to mix the latter with a quantity of hydrogen representing a ratio of around 20% or more. The advantage of mixing hydrogen into a gaseous hydrocarbon is multiple. Firstly, this obviously reduces CO2 emissions and fossil gas consumption. The latter aspect is also of geopolitical interest by limiting the dependence of countries on gaseous hydrocarbon-producing countries. In addition, the hydrogen-gaseous hydrocarbon mixture also has an economic interest, as hydrogen is a means of storing electricity produced by renewable energy sources, and can be produced at times when electricity production from renewable energy sources is greater than consumption. Finally, the combustion of hydrogen produces a significant amount of water vapour, increases the dewpoint temperature of the burnt gases and promotes condensation in the heat exchanger of the associated boiler.

[0005] Thus, the devices known to produce a mixture of gaseous hydrocarbon and hydrogen are such that the mixture is provided upstream of the gaseous hydrocarbon distribution network using a mixer. This type of mixer is traditionally composed of proportional valves associated with a flow measurement and an electronic member providing 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.

[0006] Moreover, with this known type of mixer, the hydrogen and gaseous hydrocarbon mixture is obtained for higher hydrogen and gaseous hydrocarbon pressures than those used for supplying burners operating solely with gaseous hydrocarbon, which involves installing additional expansion stages to lower the supply pressure of said burners.

[0007] 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.

[0008] In the field of gas burners, air / hydrocarbon mixers are already known, such as those disclosed in US patent application 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 fluid dynamics phenomenon, according to which a flowing fluid undergoes a pressure drop where the cross-section of flow narrows. Thus, this type of mixer includes a variable-flow air duct connected to a Venturi tube having a progressive narrowing of cross section and creating at the neck (the narrowest cross-section of the Venturi tube) a pressure drop proportional to the air flow. In this type of mixer, the gaseous hydrocarbon is then injected at the neck so as to mix with the air. In addition, to ensure a constant air / gaseous hydrocarbon mixture ratio regardless of the air flow, the gaseous hydrocarbon pressure upstream of the neck is regulated to a pressure almost equal to the air pressure upstream of the Venturi tube. The advantage of this technology is to ensure precise, constant dosing to which the air / gaseous hydrocarbon mixture flow rate can be adapted over a relatively large range. However, this type of mixer has a certain number of drawbacks. This is because it is not suitable for producing a mixture of gaseous hydrocarbon and hydrogen and can be detrimental to aeraulic systems with a significant pressure drop.SUMMARY

[0009] The purpose of the present invention is therefore to propose a device for producing a mixture of gaseous hydrocarbon and hydrogen arranged to be disposed upstream of at least one burner of a gas boiler and advantageously in the vicinity of a production of green hydrogen, said device being compact and quick to install and making it possible to mix hydrogen in gaseous hydrocarbon at a variable rate according to the flow rate of the latter without adversely affecting the burner, regardless of its technology, and as soon as said burner is in operation, said device being easily adjustable by a person having been trained in burner settings.

[0010] According to the invention, a device is therefore proposed for producing a mixture of gaseous hydrocarbon and hydrogen arranged to be disposed upstream of at least one burner of a gas boiler, comprising at least:

[0011] a Venturi tube,

[0012] a first inlet opening disposed at the inlet of said Venturi tube and arranged to be connected to a supply pipe,

[0013] an outlet opening disposed at the outlet of said Venturi tube and arranged to be connected to a pipe for discharge of the mixture of gaseous hydrocarbon and hydrogen produced by said device,

[0014] a second inlet opening arranged to be connected to a hydrogen supply pipe,

[0015] a hydrogen safety and regulation unit connected by its inlet to said second inlet opening 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 opening, and

[0016] a differential pressure switch detecting a pressure difference between the inlet and the neck of said Venturi tube, remarkable in that it comprises at least:

[0017] a pressure switch measuring the pressure of hydrogen entering said device through its second inlet opening,

[0018] an electronic control box for regulating the hydrogen supply to the device using said hydrogen safety and regulation unit according to the pressure measurements of the pressure switch and the differential pressure switch according to a manual mode or according to an automatic mode.

[0019] 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 opening and the outlet opening of the device.

[0020] According to an advantageous embodiment, the hydrogen safety and regulation unit comprises, in the direction of flow of the hydrogen at least:

[0021] a shutoff solenoid valve connected to the second inlet opening of the device and allowing enabling or not the supply of hydrogen to the Venturi tube,

[0022] a pressure regulator associated with a servo-regulator and connected to the outlet of the shutoff 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 port, and

[0023] a flow limiter connected between the outlet of the pressure regulator and the neck of the Venturi tube for limiting the hydrogen flow at the neck of said Venturi tube.

[0024] Preferably, the shutoff solenoid valve is electrically supplied and controlled by the electronic control box so that, in automatic mode, the shutoff solenoid valve opens and enables 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 adjusted on the pressure switch and the differential pressure switch.

[0025] The pressure regulator is advantageously of the normally closed type and comprises a valve movable between a “closed” position in which it comes into contact with a seat, in a partial seal, so as to limit the passage of hydrogen through said seat, and an “open” position in which it is no longer in contact with said seat so as to allow greater circulation of hydrogen towards the upstream of the flow limiter, said valve being connected by a rod to a deformable membrane.

[0026] According to an even more advantageous embodiment, the servo-regulator comprises a needle movable between an “open” position in which it allows the flow of the 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 abuts 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 to move said needle from its open position to its closed position, and vice versa, pressure means tending to hold said needle in contact with the membrane and return means tending to return said membrane to a position such that it holds 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 opening determining a setpoint pressure and, on the other hand, to the pressure of the hydrogen taken downstream of the pressure regulator.

[0027] According to an even more advantageous embodiment, the return means of the servo-regulator are associated with an adjusting screw making it possible to adjust the force of said return means.

[0028] The flow limiter is preferably of the screw type and comprises an adjustment screw the screwing in or unscrewing of which respectively makes it possible to reduce or increase the hydrogen flow injected at the neck of the Venturi tube and to modulate the hydrogen ratio in the mixture produced by the device.

[0029] 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:

[0030] a) switching off the device, the latter delivering only gaseous hydrocarbon, its hydrogen safety and regulation unit not being electrically supplied,

[0031] b) positioning the burner at an operating point corresponding to its maximum power, then measuring the oxygen content in the fumes leaving the gas boiler,

[0032] c) putting the hydrogen safety and regulation unit in manual mode, then measuring the oxygen content present in said fumes,

[0033] d) adjusting the flow rate of hydrogen injected using the hydrogen safety and regulation unit with respect to the data of a nomogram representing the change in the oxygen level in the fumes leaving the gas boiler as a function of the hydrogen level injected,

[0034] e) switching off the device, the latter delivering only gaseous hydrocarbon, its hydrogen safety and regulation unit not being electrically supplied,

[0035] f) positioning the burner at an operating point corresponding to its minimum power, then measuring the oxygen content in the fumes leaving the gas boiler,

[0036] g) putting the hydrogen safety and regulation unit in manual mode, then measuring the oxygen content present in said fumes,

[0037] h) adjusting the flow rate of hydrogen injected using the hydrogen safety and regulation unit with respect to the data of said nomogram,

[0038] i) putting the hydrogen safety and regulation unit in automatic mode.

[0039] Advantageously, the method comprises, before step a), a step of creating the nomogram showing the change in the oxygen level in the fumes as a function of the hydrogen level present in the fumes leaving the gas boiler, this creation step relying on the following input data:

[0040] the excess air applied to said burner,

[0041] the range of variation of the hydrogen content,

[0042] the nature of the gaseous hydrocarbon and the nature of the hydrogen.BRIEF DESCRIPTION OF THE FIGURES

[0043] Other advantages and features will appear better from the following description of an embodiment of the invention, with reference to the appended figures, wherein:

[0044] FIG. 1 is a schematic view of a device for producing a variable mixture of gaseous hydrocarbon and hydrogen according to the invention,

[0045] FIG. 2 is a perspective view of a device of FIG. 1,

[0046] FIG. 3 is another perspective view of the device of FIG. 2 partially depicted,

[0047] FIG. 4 is a view from below of the device of FIG. 2,

[0048] FIG. 5 is a partial schematic partial view in vertical section of the device of FIG. 2 along the axis V-V′ of FIG. 2,

[0049] FIG. 6 is a schematic view of an example the nomogram allowing the implementation of the device of FIG. 2 on a burner of a gas boiler, said nomogram representing the change in oxygen in the fumes as a function of the hydrogen level in the gas.DETAILED DESCRIPTION

[0050] With reference to FIG. 1 and in accordance with the invention, the device 1 for producing a variable mixture of gaseous hydrocarbon and hydrogen arranged to be disposed upstream of at least one gas boiler burner includes at least:

[0051] a Venturi tube (2)

[0052] a first inlet opening 3 disposed at the inlet of said Venturi tube 2 and arranged to be connected to a gaseous-hydrocarbon supply pipe,

[0053] an outlet opening 4 disposed at the outlet of said Venturi tube 2 and arranged to be connected to a pipe for discharge of the mixture of gaseous hydrocarbon and hydrogen produced by said device 1,

[0054] a second inlet opening 5 arranged to be connected to a hydrogen supply pipe,

[0055] a hydrogen safety and regulation unit 6 connected by its inlet to said second inlet opening 5 and by its outlet to the neck of said Venturi tube 2,

[0056] a pressure switch 7 measuring the pressure of hydrogen entering said device 1 through its second inlet opening 5,

[0057] a differential pressure switch 8 detecting a pressure difference between the inlet and the neck of said Venturi tube 2, and

[0058] an electronic control box 9 for regulating the hydrogen supply of the device 1 using said hydrogen safety and regulation unit 6 according to the pressure measurements of the pressure switch 7 and the differential pressure switch 8 according to a manual mode or according to an automatic mode.

[0059] “Inlet” or “outlet” here means the elements or parts of elements of the device 1 located on the inlet or outlet side of a fluid according to its direction of flow.

[0060] Furthermore, “pressure switch” here means a member used to relay information on pressure variations of a fluid within an element, said pressure switch being of any type such as, for example, mechanical, electrical, electronic or pneumatic.

[0061] The Venturi tube 2 is shaped to generate a maximum pressure difference 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 opening 3 and the outlet opening 4 of the device 1 to between 1 and 4 mbar. This particular configuration is necessary to allow the system to admit a high hydrogen content 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 opening 4 of the device 1, so as to always have a gas mixture under conditions guaranteeing optimal operation of the associated burner.

[0062] Another advantage of this particular configuration of the Venturi 2 tube is to allow 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 contributes to reducing the risks of gas leakage inside the premises receiving the device 1.

[0063] Finally, this configuration of the Venturi tube 2 with a high pressure drop between its inlet and its neck allows, on the one hand, adaptation to variations in the gaseous-hydrocarbon pressure without disturbing the hydrogen rate injected at said neck and, on the other hand, guaranteeing an intake of hydrogen in complete safety.

[0064] The first inlet opening 3 and the outlet opening 4 of the device 1 are advantageously implemented by male couplings with a gas thread fastened to the Venturi tube 2.

[0065] Moreover, the second inlet opening 5 is advantageously implemented by a flange provided with a female coupling with a gas tapping.

[0066] According to an advantageous embodiment, with reference to FIGS. 2 to 5, the hydrogen safety and regulation unit 6 comprise, in the direction of flow of the hydrogen, at least:

[0067] a cutoff solenoid valve 10 connected to the second inlet opening 5 of the device 1,

[0068] a pressure regulator 11 associated with a servo-regulator 12 and connected to the output of the shutoff solenoid valve 10, and

[0069] a flow limiter 13 connected between the outlet of the pressure regulator 11 and the neck of the Venturi tube 2.

[0070] The shutoff solenoid valve 10 enables or not the supply of hydrogen to the Venturi tube 2. The shutoff solenoid valve 10 is electrically powered and controlled by the electronic control box 9 in automatic mode or in manual mode, switching from one mode to the other being provided by a switch of said electronic control box 9. Thus, in automatic mode, the shutoff solenoid valve 10 opens and authorises the supply of hydrogen, and therefore the passage thereof, 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.

[0071] Control of the shutoff solenoid valve 10 by the electronic control box 9 according to 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 admitting hydrogen into said device 1 only 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. Moreover, when the device 1 is switched off, the shutoff solenoid valve 10 is closed and no hydrogen is injected at the neck of the Venturi tube 2.

[0072] This is because the large density difference between gaseous hydrocarbon and hydrogen leads to a separation of the gases during periods of non-consumption of the gas mixture produced. This phenomenon may lead to a significant accumulation of hydrogen in the pipeline upstream of the associated burner, and cause dangerous ignition conditions for said burner.

[0073] In addition, in the case of the use of hydrogen produced locally from non-controllable renewable energy sources, the amount of hydrogen available is not always sufficient, which involves preventing the introduction of hydrogen from the supply line in the event of excessively low hydrogen pressure, in order to prevent the backflow of gaseous hydrocarbon into the hydrogen line.

[0074] The hydrogen safety and regulation unit 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.

[0075] With reference to FIG. 5, the pressure regulator 11 conventionally comprises a valve 14 movable between a “closed” position in which the valve 14 comes into contact with a seat 15, in a partial seal, so as to limit the passage of hydrogen through said seat 15 and to obtain the desired hydrogen pressure upstream of the flow limiter 13 for a low gaseous hydrocarbon flow, and an “open” position in which the valve 14 is no longer bearing on said seat 15 so as to have a hydrogen flow rate and pressure upstream of the flow limiter 13 adapted to a greater gaseous hydrocarbon flow rate. Said valve 14 is connected by a rod 16 to a deformable membrane 17. Moreover, 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.

[0076] The term “partial seal” here refers to a seal being obtained, in a conventional manner, by a metal-to-metal contact that is in principle not perfect, and which cannot in fact be absolute, this type of seal allowing a low gas flow through.

[0077] With reference to FIG. 5, the servo-regulator 12 comprises a needle 19 movable between an “open” position in which it allows the flow of the 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 into contact with a seat 20, in 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 pressure means 22 tending to hold said needle 19 in abutment 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 opening 3 of the device 1 determining a setpoint pressure and, on the other hand, to the pressure of the hydrogen taken downstream of the pressure regulator 11. Moreover, the servo-regulator 12 comprises return means 23 tending to bring said membrane 20 back into a position such that it holds the needle in its open position.

[0078] Referring to FIG. 5, the assembly consisting of pressure regulator 11 and servo-regulator 12 operates as follows. Thus, if the pressure of the hydrogen downstream of the pressure regulator 11 is higher than said setpoint 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 circulate in a reduced manner up to the membrane 17 of the pressure regulator 11 on the side opposite to 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, and reducing the hydrogen pressure downstream of the pressure regulator 11, until equilibrium between the hydrogen pressure downstream of the pressure regulator 11 and the setpoint pressure is obtained. Conversely, if the pressure of the hydrogen downstream of the pressure regulator 11 is lower than said setpoint 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 substantially up 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, and increasing the pressure of the hydrogen downstream of the pressure regulator 11, until equilibrium is obtained between the hydrogen pressure downstream of the pressure regulator 11 and the setpoint pressure.

[0079] The return means 23 are further associated with an adjusting screw 24 for adjusting the force of said return means 23, in order to finely adjust the settings and introduce a variation in the hydrogen rate between the minimum power and the maximum power of the gas burner.

[0080] The hydrogen safety and regulation unit 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 adjusting screw 25 the screwing in or unscrewing respectively and which makes it possible to reduce or increase the hydrogen flow rate injected at the neck of the Venturi tube 2 and, therefore, to modulate the hydrogen ratio in the mixture produced by the device 1 according to the invention.

[0081] It is well understood that the device 1 thus configured makes it possible to regulate the hydrogen pressure proportionally to the gaseous hydrocarbon supply pressure, i.e. at the first inlet opening 3 of said device 1, which has the effect of automatically compensating for the pressure variations of the gaseous hydrocarbon supply network. Furthermore, even if the hydrogen supply pressure must be slightly higher than the gaseous-hydrocarbon supply pressure, the vacuum at the hydrogen and gaseous hydrocarbon mixing point located at the neck of the Venturi tube 2 is sufficient to regulate the injected hydrogen flow rate.

[0082] Furthermore, it is well understood that the maintenance of the hydrogen rate in the device 1 according to the invention is, regardless of the flow rate of gaseous hydrocarbon, totally autonomous and independent of the burner on which it is implemented. In addition, the hydrogen intake management is integrated in 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 common means.

[0083] However, in order to ensure proper adjustment and proper operation of the device 1, the invention also relates to a method for implementing said device on a gas boiler burner.

[0084] Said method consists in deducing the hydrogen content 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 implemented by heating engineers who are used to adjusting burners using a combustion analyzer measuring the oxygen level in the fumes and a diagram representing the change in the oxygen level in the fumes as a function of the hydrogen level present in the fumes (see FIG. 6).

[0085] For this purpose, the method for implementing said device on a gas boiler burner comprises at least the following steps:

[0086] a) switching off the device 1, the latter the device 1 delivering only gaseous hydrocarbon, its hydrogen safety and regulation unit 6 not being electrically supplied,

[0087] b) positioning the burner at an operating point corresponding to its maximum power, then measuring the oxygen content in the fumes leaving the gas boiler,

[0088] c) putting the hydrogen safety and regulation unit (6) in manual mode, then measuring the oxygen content present in said fumes,

[0089] d) adjusting the flow rate of hydrogen injected using the hydrogen safety and regulation unit 6 with respect to the data of a nomogram representing the change in the oxygen level in the fumes leaving the gas boiler as a function of the hydrogen level injected,

[0090] e) switching off the device 1, the latter the device 1 delivering only gaseous hydrocarbon, its hydrogen safety and regulation unit 6 not being electrically supplied,

[0091] f) positioning the burner at an operating point corresponding to its minimum power, then measuring the oxygen content in the fumes leaving the gas boiler,

[0092] g) putting the hydrogen safety and regulation unit 6 in manual mode, then measuring the oxygen content present in said fumes,

[0093] h) adjusting the flow rate of hydrogen injected using the hydrogen safety and regulation unit 6 with respect to the data of said nomogram,

[0094] i) putting the hydrogen safety and regulation unit 6 in automatic mode.

[0095] Before step a), the method advantageously includes a step of creating the nomogram showing the change in the oxygen level in the fumes leaving the gas boiler as a function of the injected hydrogen level.

[0096] This creation step is based on the following input data:

[0097] the excess air applied to said burner,

[0098] the range of variation of the hydrogen content (for example from 2 to 50%),

[0099] the nature of the gaseous hydrocarbon and the nature of the hydrogen.

[0100] Once these input data are known, the theoretical stoichiometric air flow rate in the gaseous hydrocarbon is deduced in the absence of hydrogen injection. Then the flow rate of the admitted hydrogen and gaseous hydrocarbon mixture 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 a constant air flow injected by a fan at the burner, it is then possible to obtain the value of the excess air as a function of the hydrogen content in said mixture, from which the oxygen content present in the fumes leaving the gas boiler is deducted.

[0101] Thus, in the end, for a given type of gaseous hydrocarbon, a nomogram representing the change in the oxygen rate in the fumes leaving the gas boiler as a function of the hydrogen rate present in the mixture injected into the burner for various values of air flow rate injected at said burner, said nomogram having on the X-axis a scale giving the hydrogen rate in the mixture produced by the device 1 between 0 and 60%, and in on the Y-axis a scale giving the oxygen content present in the fumes leaving the gas boiler between 3 and 10%. On the example nomogram shown in FIG. 6, the change in the oxygen content in the fumes leaving the gas boiler is shown as a function of the hydrogen content present in the mixture injected into the burner for various values of the oxygen content in the fumes leaving the gas boiler in the absence of hydrogen present in the mixture, these values of said oxygen content ranging from low to high of 3.5 to 6% which corresponds to conventional gas boiler setting values.

[0102] It is well 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 rate is particularly suitable for a gas burner, as above 60% the other equipment associated with this gas burner may no longer operate safely.

[0103] The device 1 for producing a variable mixture of gaseous hydrocarbon and hydrogen according to the invention has a particular application for supplying at least one gas burner of a boiler, but it goes without saying that said device 1 may be adapted to be implemented on other equipment such as, for example, a mixing station for a chemical laboratory or an industrial welding process.

[0104] Finally, it goes without saying that the examples of a device 1 in accordance with the invention that have just been described are merely particular, and in no way limiting, illustrations of the invention.

Claims

1-10. (canceled)11. A device for producing a mixture of gaseous hydrocarbon and hydrogen arranged to be disposed upstream of at least one gas burner, comprising: at least:a Venturi tube,a first inlet opening disposed at the inlet of said venturi tube and arranged to be connected to a supply pipe,an outlet opening disposed at the outlet of said Venturi tube and arranged to be connected to a pipe for discharge of the mixture of gaseous hydrocarbon and hydrogen produced by said device,a second inlet opening arranged to be connected to a hydrogen supply pipe,a hydrogen safety and regulation unit connected by its inlet to said second inlet opening and by its outlet at 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 opening, anda differential pressure switch detecting a pressure difference between the inlet and the neck of said Venturi tube,a pressure switch measuring the pressure of hydrogen entering said device through its second inlet opening, andan electronic control box for regulating the hydrogen supply of the device using said hydrogen safety and regulation unit according to the pressure measurements of the pressure switch and the differential pressure switch according to a manual mode or according to an automatic mode.

12. The device according to claim 11, wherein the venturi tube is shaped to generate a maximum pressure difference between 5 and 10 mbar between its inlet and neck, while limiting the pressure drop between the first inlet opening and the outlet opening of the device to between 1 and 4 mbar.

13. The device according to claim 11, wherein the hydrogen safety and regulation unit comprises, in the direction of flow of the hydrogen, at least:a shutoff solenoid valve connected to the second inlet opening of the device and enabling or not the supply of hydrogen to the Venturi tube,a pressure regulator associated with a servo-regulator and connected to the outlet of the shutoff 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 opening, anda flow limiter connected between the outlet of the pressure regulator and the neck of the Venturi tube making it possible to limit the hydrogen flow at the neck of said Venturi tube.

14. The device according to claim 13, wherein the shutoff solenoid valve is electrically supplied and controlled by the electronic control box so that, in automatic mode, the shutoff solenoid valve opens and enables 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 adjusted on the pressure switch and the differential pressure switch.

15. The device according to claim 13, wherein the pressure regulator is of the normally closed type and comprises a valve movable between a “closed” position in which it abuts against a seat, in a partial seal, so as to limit the passage of hydrogen through said seat, and an “open” position in which it is no longer abutting against said seat so as to allow greater circulation of the hydrogen upstream of the flow limiter, said valve being connected by a rod to a deformable membrane.

16. The device according to claim 15, wherein the servo-regulator comprises a needle movable between an “open” position in which it allows the flow of the 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 abuts 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 membrane movable to move said needle from its open position to its closed position, and vice versa, pressure means tending to hold said needle in contact with the membrane and return means tending to return said membrane into a position such that it holds 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 opening determining a setpoint pressure and, on the other hand, to the pressure of the hydrogen taken downstream of the pressure regulator.

17. The device according to claim 16, wherein the return means of the servo-regulator are associated with an adjusting screw making it possible to adjust the force of said return means.

18. The device according to claim 13, wherein said flow limiter is of the screw type and comprises an adjusting screw the screwing in or unscrewing of which respectively makes it possible to reduce or increase the hydrogen flow rate injected at the neck of the Venturi tube and, therefore, to modulate the hydrogen ratio in the mixture produced by the device.

19. A method for implementing a device according to claim 11 upstream of at least one burner of a gas boiler, comprising:a) switching off the device, the latter delivering only gaseous hydrocarbon, its hydrogen safety and regulation unit not being electrically supplied,b) positioning the burner at an operating point corresponding to its maximum power, then measuring the oxygen content in the fumes leaving the gas boiler,c) putting the hydrogen safety and regulation unit in manual mode, then measuring the oxygen content present in said fumes,d) adjusting the flow rate of hydrogen injected using the hydrogen safety and regulation unit with respect to the data of a nomogram 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, the latter delivering only gaseous hydrocarbon, its hydrogen safety and regulation unit not being electrically supplied,f) positioning the burner at an operating point corresponding to its minimum power, then measuring the oxygen content in the fumes leaving the gas boiler,g) putting the hydrogen safety and regulation unit in manual mode, then measuring the oxygen content present in said fumes,h) adjusting the flow rate of hydrogen injected using the hydrogen safety and regulation unit with respect to the data of said nomogram,i) putting the hydrogen safety and regulation unit in automatic mode.

20. The method according to claim 19, wherein, before step a), a step of creating the nomogram showing the change in the oxygen level in the fumes leaving the gas boiler as a function of the injected hydrogen level, this creation step being based on the following input data:the excess air applied to said burner,the range of variation of the hydrogen content,the nature of the gaseous hydrocarbon and the nature of the hydrogen.

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