WO2020126401A1

WO2020126401A1 - Assembly and method for injecting a gaseous combustion agent

Info

Publication number: WO2020126401A1
Application number: PCT/EP2019/082987
Authority: WO
Inventors: Benoit Grand; Sarah Juma; Xavier Paubel; Jean-Baptiste SENECHAL
Original assignee: L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude
Priority date: 2018-12-21
Filing date: 2019-11-28
Publication date: 2020-06-25
Also published as: JP2022514328A; CN113195976A; EP3671038A1; ES2894624T3; MX2021007420A; EP3671038B1; BR112021011579A2; US20220074592A1

Abstract

Assembly for injecting a gaseous combustion agent into a combustion zone, the assembly comprising a chamber (11), at least one primary injector (21) for carrying a primary flow of the gaseous agent from the chamber (11) towards the combustion zone (1) and for injecting the said primary flow into the combustion zone (1), at least one secondary injector (22) for carrying a secondary flow of the agent from the chamber (11) towards the combustion zone (1) and for injecting the said secondary flow into the combustion zone (1), a pressure detector (30) for detecting a gaseous pressure or a variation in gaseous pressure in the chamber (11), a regulating system (31) for regulating a bore section of the at least one secondary passage fluidically connecting the at least one secondary injector (22) to the chamber (11), a control system (32) connected to the pressure detector (30) and to the regulating system (31), the control system (32) operating the regulating system (31) in such a way that the bore section of the at least one secondary passage is regulated according to the pressure or to the pressure variation detected by the pressure detector (30).

Description

ASSEMBLY AND METHOD FOR INJECTION OF AN AGENT

GAS COMBUSTION

The present invention relates to an assembly for injecting a gaseous combustion agent into a combustion zone, a burner comprising such an assembly and the use of such an assembly / burner in a combustion process.

In industrial combustion processes, for example in order to transform a charge (melting, reheating, recycling furnace, etc.), certain flame characteristics are sought, in particular a shape and a length of flame adapted to the enclosure. of combustion and / or the charge that one wishes to heat, in order to obtain a determined heat transfer profile and to optimize the quality of production and the service life of the equipment.

The flame characteristics are in particular determined by the nature of the combustion agents (fuel and oxidizer) and the way in which they are introduced into the combustion zone (flow rates, speeds, distribution in space, etc.).

Thus, from EP-A-0763692 a burner is known which comprises a first interior passage for supplying oxidant rich in oxygen (at least 80% of O2), an intermediate passage for supplying fuel externally surrounding the first passage for oxidizer supply and a second external oxidant supply passage externally surrounding the fuel supply passage. According to EP-A-0763692, the burner includes means for varying the oxidizer flow rate injected through the first interior passage, which makes it possible to control a characteristic of the flame such as the flame length and the brightness.

Likewise, it is known from EP-A-1016825 to use a burner comprising a first interior passage for supplying oxidant, an intermediate passage for supplying fuel externally surrounding the first passage for supplying oxidant and a second external oxidant supply passage externally surrounding the fuel supply passage for heating a transfer channel for molten glass during glass production and adjusting the flame length generated by means of said burner by modifying the proportion of the total oxidant flow rate passing through the first oxidant supply passage.

The burners mentioned above are burners with concentric and adjacent injection of fuel and oxidizer generating a flame of essentially circular section. Other burners generate flames called "flat flames" and / or inject at least part of the oxidant at a distance from the injection of the fuel, or even inject at least part of the fuel at a distance from the injection of the oxidant.

Thus EP-A-2143999 describes a burner comprising:

• at least two passages of gaseous fuel;

• at least one pass of oxidant and

• at least one outlet surface in which the at least one pass of gaseous fuel or the at least one pass of oxidant terminate.

This known burner also includes:

Means suitable for supplying an oxidant flow, as well as means for injecting said oxidant flow into the at least one oxidant passage and

Means capable of providing at least one flow of gaseous fuel, as well as means for injecting this flow of gaseous fuel into the at least two passages of gaseous fuel,

this in order to generate at least one jet of oxidant and at least two jets of gaseous fuel which meet in a combustion zone downstream of the burner.

According to EP-A-2143999, the at least two gas fuel passages each have an internal passage and an external coaxial passage.

A means for controlling the flow of gaseous fuel regulates the flow of gaseous fuel through the interior passages and the exterior passages, respectively, by means of a gaseous fuel distributor.

This allows you to control both the heat transfer profile and the flame length.

If it is thus known that it is possible to modify certain characteristics, and in particular the length of the flame generated by adjusting the distribution of the flow of fuel or oxidizer over several concentric passages / injectors, known burners do not include any means of feedback to adjust the burner operation and therefore the target characteristic of the flame in real time.

It has now surprisingly been discovered that it is possible to produce such a feedback system on the basis of a detected pressure of the gaseous combustion agent before its distribution. The present invention relates to an assembly for injecting, into a combustion zone, a gaseous combustion agent chosen from gaseous fuels and gaseous oxidants. The set includes a room and the agent is introduced into the set through an entrance to this room.

The assembly includes at least one primary injector for transporting a primary flow of the agent from the chamber to the combustion zone and for injecting said primary flow into the combustion zone. To this end, the at least one primary injector is fluidly connected to the chamber by means of at least one passage called the primary passage.

The assembly also includes at least one secondary injector for transporting a secondary flow rate from the chamber agent to the combustion zone and for injecting said secondary flow flow into the combustion zone. The at least one secondary injector is in turn fluidly connected to the chamber by means of at least one passage called the secondary passage. The at least one secondary passage has an adjustable flow section.

An adjustment system, for example in the form of a valve, makes it possible to adjust this flow section of the at least one secondary passage.

The assembly also includes a pressure detector for detecting a pressure or a variation in gas pressure in the chamber as well as a control system connected to the pressure detector.

The control system is also connected to an adjustment system and controls said adjustment system, so that the flow section of the at least one secondary passage of the assembly is regulated according to the pressure or the variation. pressure detected by the assembly pressure sensor.

According to one embodiment, the control system, which can be an analog or digital control system, is adapted to control the control system so that the gas pressure in the chamber is located in a pressure zone predetermined by adjusting the flow section of the at least one secondary passage.

According to yet another embodiment, the control system is adapted to control the adjustment system so that the gas pressure in the chamber corresponds to a predetermined value by adjusting the flow section of the at least one secondary passage. .

It should be noted that the predetermined pressure zone or range can be constant over time, but that it can also vary over time, for example: Depending on the process steps, such as for example, a melting process or a reheating process, in which the assembly is used, a process which can be cyclic or non-cyclic,

• depending on the power required in the combustion zone or

• as a function of a feedback parameter other than the pressure in the chamber of the assembly.

The above remarks also apply to the predetermined gas pressure value. As indicated above, the assembly control system can be an analog or digital system. It can be mechanical, for example pneumatic or hydraulic. Preferably, the control system is digital. According to a preferred embodiment, the control system is programmable. In this case, for the implementation of the injection assembly according to the invention, the control system is programmed so as to control the adjustment system so as to actuate the adjustment system as a function of the pressure or of the pressure variation detected by the pressure detector. The gas pressure or the variation in gas pressure detected by the pressure detector is then transmitted to the programmable control system: for example by means of a wired connection or by a wireless connection.

The adjustment system may include various means for adjusting the flow section of the at least one secondary passage, such as one or more adjustable valves positioned in the at least one secondary passage between the chamber and the at least a secondary injector, or the movement of a mechanical element acting as a shutter of the at least one secondary passage, this movement being generated for example by translation, by rotation (screwing) or by deformation of a mechanical element linked to the shutter or by modification of the magnetic state of a metallic element.

According to a simple and reliable embodiment, the adjustment system is provided with at least one shutter capable of adjusting the flow section of the at least one secondary passage by closing it at least partially.

Such an adjustment system can in particular take the following form. The at least one secondary passage connecting the at least one secondary injector fluidly to the chamber has an internal surface in the form of a funnel and the adjustment system comprises a shutter having a corresponding external surface and which can be moved along the longitudinal axis of the passage secondary. When the shutter is thus moved along said longitudinal axis, the external surface of the shutter approaches or moves away from the internal surface of the secondary passage and the flow section of said passage is reduced, respectively enlarged.

It should also be noted that it may be advantageous to design the adjustment system in such a way that the flow section of the at least one secondary passage is never completely closed. Indeed, in order to ensure sufficient cooling of the at least one secondary injector and / or to avoid clogging of the at least one secondary injector (for example because of deposits of condensable substances present in the atmosphere of the combustion zone or the formation of soot resulting from the overheating of the gaseous fuel in contact with at least one secondary injector) a minimum gas flow through the at least one secondary injector may be necessary. It is however also conceivable to provide such a minimum gas flow by means other than the adjustment system defined above such as for example fluid passages shorting the shutter and of reduced size in order to simply ensure this minimum flow.

The assemblies are typically made of metal, the injectors or at least the downstream ends (injection ends) often being advantageously made of metals with high resistance to heat and oxidation, such as alloys of austenitic nickel steels. -Chrome Inconel® type or nickel-free alloys Kanthal® type.

The assembly according to the invention may more particularly comprise at least one pair of a primary injector with a secondary injector, a pair in which one of the primary injector and the secondary injector surrounds the other of the primary injector and the secondary injector.

The primary injector can thus surround the secondary injector or the secondary injector can surround the primary injector of the torque.

According to an advantageous embodiment, the primary torque injector is surrounded by the secondary torque injector.

According to a particular embodiment, the primary injector and the secondary torque injector are concentric. However, in some cases, a non-concentric arrangement may be useful.

It should be noted that such a torque configuration does not exclude the presence of other elements and in particular the presence of one or more other injectors in or around one or the other of the torque injectors. For example, according to a particular embodiment, the fluid can be a gaseous oxidizer, such as a gas containing at least 80% vol and preferably at least 90% vol of oxygen. The primary torque injector is located in the center and is surrounded by the secondary torque injector, preferably concentrically. An injector for injecting fuel into the combustion zone is located between the primary injector and the secondary torque injector, so that the fuel injector surrounds the primary oxidizer injector and is surrounded by G secondary oxidizer injector, the assembly thus forms part of a burner for the combustion (at least partial) of the fuel with the oxidizer and in which the flow section of G secondary injector and therefore also the distribution of the oxidant between the flow primary and secondary flow are regulated by the control system by means of the adjustment system according to the gas pressure or the variation of gas pressure in the chamber of the assembly detected by the pressure detector.

According to another analogous embodiment, the fluid is a gaseous fuel, such as natural gas. The primary torque injector is located in the center and is surrounded by the secondary injector, preferably concentrically. An injector for injecting oxidant into the combustion zone is located between the primary injector and the secondary torque injector, so that the oxidant injector surrounds the primary fuel injector and is surrounded by the secondary fuel injector. The oxidizer is preferably a gas containing at least 80 vol% and more preferably at least 90 vol vol. The assembly thus forms part of a burner for the combustion (at least partial) of the fuel with the oxidizer and in which the flow section of the secondary injector and therefore also the distribution of the fuel between the primary flow and the secondary flow of fuel are regulated by the control system by means of the adjustment system according to the gas pressure or the variation of gas pressure in the chamber of the assembly detected by the pressure detector.

The assembly according to the invention may comprise a single primary injector and a single secondary injector and in particular a single pair of a primary injector with a secondary injector. According to an alternative embodiment, the assembly according to the invention comprises several primary injectors and / or several secondary injectors and in particular several pairs of a primary injector with a secondary injector.

According to a particular embodiment, the at least one secondary injector of the assembly is spaced from the at least one primary injector of the assembly without the at least one primary injector of the assembly surrounds a secondary injector of the assembly and without the at least one secondary injector of the assembly surrounds a primary injector of the assembly.

In this case, the at least one primary injector can in particular extend in a first plane, while the at least one secondary injector extends in a second plane, the second plane being parallel to the first plane. In this way, it is possible to inject the primary flow and the secondary flow of the combustion gas agent into the combustion zone in two parallel planes.

According to an alternative embodiment, the at least one primary injector extends in a first plane and the at least one secondary injector extends in a second plane, the first plane and the second plane intersecting downstream of said primary injectors and secondary, that is to say inside the combustion zone into which the gaseous combustion agent is injected.

The assembly according to the invention may comprise at least two primary injectors and / or at least two secondary injectors, preferably at least two primary injectors and at least two secondary injectors. This is particularly advantageous in the case where, as described above, the at least one primary injector extends in a first plane and the at least one secondary injector extends in a second plane different from the first plane.

For the injection of the gaseous agent into the combustion zone, the inlet of the assembly, which is also the inlet of the chamber of the assembly, is fluidly connected to a source of gaseous fuel, preferably at a source of gaseous fuel chosen from natural gas, biogas, propane, butane, residual gases from steel or methane reforming processes, hydrogen, any mixture of said gaseous fuels, or from a source of an oxidizer gaseous, preferably having an oxygen content of 21 to 100% vol, preferably greater than 21% vol and in particular of at least 80% vol, more preferably at least 90% vol.

Such a source can be a reservoir of the gaseous agent in gaseous form or in liquefied form, a supply conduit transporting said gaseous agent or a generator of said gaseous agent.

The invention also relates to an installation comprising several assemblies according to any one of the embodiments described above. In this case, it may be preferable for this installation to include a common control system capable of controlling, preferably independently, the adjustment system of each set of the installation as a function of the gas pressure or the gas pressure variation detected by the pressure detector of said assembly.

As indicated above, the assembly can be incorporated into a burner.

Such a burner according to the invention therefore comprises an assembly according to any one of the above embodiments for the injection into a combustion zone of a gaseous combustion agent chosen from a gaseous fuel and a gaseous oxidant.

Such a burner typically also includes at least one additional injector for injecting an additional fluid into the combustion zone. As a general rule, when the gaseous agent injected by the assembly is a gaseous fuel, the at least one additional injector is suitable for injecting a gaseous oxidant into the combustion zone and when the gaseous agent injected by l the assembly is a gaseous oxidizer, the at least one additional injector is suitable for injecting a fuel (gaseous or non-gaseous) into the combustion zone.

According to one embodiment, the burner comprises a block with an inlet face and an outlet face opposite the inlet face. The combustion zone is located downstream from the outlet face.

Unlike the assembly, the block is typically made of refractory material, such as a cement, or a material of the electrofused type, or a pressed material, composed mainly of alumina and / or zirconia and / or silica and / or magnesia or a mixture of these components in varying proportions depending on the application process.

The assembly is then attached to the inlet face of the block so that the burner injectors, and therefore also the injectors of the assembly, are positioned in one or more perforations which pass through the block from the face of entry to the exit face.

Thus, a burner according to the invention can, for example comprise such a block with one or more first perforations which end at a first level in the outlet face of the block as well as one or more additional perforations which end in the face second level located below or above the first level. The assembly includes at least two and preferably at least three primary injectors and secondary injectors for transporting and injecting gaseous fuel into the combustion zone. Each of the primary injectors forms a pair with one of the secondary injectors. According to one embodiment, each of the primary injectors surrounds one of the secondary injectors. According to a preferred embodiment, each of the secondary injectors surrounds one of the primary injectors. These couples, by example in triplicate, are positioned in the first perforation (s) which end at the first level. The burner also has several additional injectors for transporting and injecting oxidant into the combustion zone. Said additional injectors are positioned in the additional passage (s) of the block so as to allow the injection of oxidant into the combustion zone above or below the gaseous fuel. The additional injectors may extend in a plane parallel to the plane of the torques of a primary injector with a secondary injector. According to another embodiment, the additional injectors can define a plane for injecting the oxidizer which cuts the plane of the torques in the combustion zone downstream of the outlet face where the oxidant injected by the additional injectors mixes and reacts with the fuel injected by the couples.

As already indicated above, others and in particular one or more other injectors due to G primary injector and the secondary torque injector may be present in or around either of G primary injector and the injector secondary of the couple.

According to a first embodiment, the additional passage or passages terminate in the outlet face of the block above the first passage or passages. According to another embodiment, the additional passage or passages terminate in the outlet face of the block below the first passage or passages.

According to a third embodiment, the block comprises one or more additional passages which terminate in the outlet face at a level situated above the first level and in which or which are at least two and preferably at least three injectors additional for the oxidizer, as well as one or more additional passages which terminate in the outlet face of the block below the first level and in which one or more are at least two and preferably at least three additional injectors for the oxidizer. This embodiment makes it possible to inject, depending on the needs of the process, oxidant into the combustion zone above, below or above and below the gaseous fuel.

The invention also relates to an oven comprising an internal combustion zone and equipped with at least one assembly according to the invention for the injection of a gaseous combustion agent chosen from gaseous fuels and gaseous oxidizers in said combustion zone . As indicated above, the at least one assembly can be part of a burner according to the invention, in which case the oven is equipped with at least one burner according to the invention. The present invention can in particular advantageously be implemented in an oven selected from furnaces for manufacturing or reheating glass or enamels, furnaces for manufacturing or recycling or reheating metals such as rotary ovens or aluminum reverberators , copper or lead, cast iron, steel, etc.

Another aspect of the present invention is a combustion process in which a gaseous combustion agent chosen from gaseous fuels and oxidizers is injected into a combustion zone by means of an assembly according to the invention, said assembly possibly being part of a burner according to the invention.

According to this method, the pressure detector of each assembly detects the gas pressure or a variation of the gas pressure in the chamber of this assembly, the adjustment system of the assembly regulates the flow section of its at least one secondary passage , and the control system controls the adjustment system so that the flow section of the at least one secondary passage of each assembly is regulated as a function of the pressure or of the pressure variation detected by the pressure detector this set.

As already described above in the context of the installation and the furnace according to the invention, in the case where several assemblies are used in the process, each assembly can have its own control system connected to the pressure detector and to the system adjustment, the control system controlling the adjustment system so that the flow section of the at least one secondary passage is regulated as a function of the pressure or of the pressure variation detected by the pressure detector of said assembly. Often advantageously, however, a common control system can control the adjustment system of each assembly according to the pressure or the pressure variation detected by the pressure detector of the assembly in question. As also already indicated above, the adjustment system of the assembly can be controlled so that the gas pressure in the chamber of the assembly is within a predetermined pressure zone or even so that the gas pressure in the chamber of the assembly corresponds to a predetermined value.

The gaseous combustion agent injected into the combustion zone by means of the assembly is a gaseous fuel chosen from natural gas, biogas, propane, butane, residual gases from steel or methane reforming processes, l hydrogen or any mixture of the gases mentioned above, or a gaseous oxidizer, preferably having an oxygen content from 21 to 100% vol, preferably greater than 21% vol and in particular at least 80% vol, more preferably at least 90% vol.

The process according to the invention is particularly useful for carrying out combustion inside a combustion zone in the context of a process such as the manufacture or recycling of glass or enamels, the manufacture or recycling or reheating of metals such as aluminum, copper, lead, cast iron, steel, etc.

The invention and its advantages will be better understood in the light of the following examples: (reference being made to FIGS. 1 to 5) in which:

FIG. 1 schematically represents an assembly comprising a primary injector (21) with a concentric secondary injector (22), the secondary injector (22) surrounding G primary injector (21);

FIG. 2 schematically represents an assembly comprising a primary injector (21) with a concentric secondary injector (22), the primary injector (21) surrounding G secondary injector (22);

FIG. 3 schematically represents an assembly comprising a primary injector (21) with a non-concentric secondary injector (22), separated by a distance, FIGS. 4 and 5 schematically represent two views of the assembly incorporated in a burner for injection in a combustion zone (1) of a gaseous combustion agent.

Figures 1, 2, and 3 show a fluid inlet chamber (11). The primary injector (21) is fluidly connected to the chamber (1 1) by means of a primary passage (23). The secondary injector is fluidly connected to the chamber (1 1) by means of a secondary passage (24). The secondary passage (24) has an adjustable flow section. An adjustment system (32) makes it possible to adjust this flow section of the secondary passage (24) using a shutter (33). Figures 1, 2 and 3 also show a pressure detector (30) for detecting a gas pressure or a variation in gas pressure in the chamber (11) and a control system (31) connected to the pressure detector (30). The control system is also connected to and controls the adjustment system (32).

FIG. 4 schematically represents an assembly comprising three primary injectors (21) each surrounded by its concentric secondary injector (22), a chamber (11). The primary injectors (21) are fluidly connected to the chamber (1 1) by the primary passages (23). The secondary injectors (22) are fluidly connected to the chamber (1 1) by the secondary passages (24). The secondary passage has an adjustable flow section. An adjustment system (32) makes it possible to adjust this flow section of the secondary passage (24) by means of a shutter (33). A pressure detector (30) is present for detecting a pressure or a variation in gas pressure in the chamber (1 1). A control system (31) is connected to the pressure detector (30). This control system is also connected to and controls the adjustment system (32).

In FIGS. 4 and 5, the burner comprising a block (40) with an inlet face (41) and an outlet face (42) opposite the inlet face, as well as additional injectors (50 ) for injecting an additional fluid into the combustion zone (1).

The automatic adjustment by feedback system according to the present invention can advantageously be implemented in various combustion processes such as the production of glass.

Glass furnaces mainly use air preheated to over 1000 ° C as an oxidizer. This hot air is obtained when passing through regenerators (stack of refractory bricks). The volume of oxidizer injected into the oven at this temperature level constitutes a significant amount of movement.

During the oven campaign, it may be necessary to increase the production beyond the capacity of the regenerators which cannot supply a larger quantity of hot air because of the limitation of the output of the fans. A similar problem arises when the condition of the bricks does not or no longer allow the desired preheating temperatures to be obtained.

The installation of burners operating with an oxygen-rich oxidant (oxy-burner) then appears to be a particularly suitable solution. These burners are generally installed in the openings available near the regenerators. Oxy-combustion (i.e. combustion with an oxidizer containing at least 80% vol and preferably at least 90% vol of oxygen) generating a volume of smoke 4 times lower than combustion at l air and with at least equivalent efficiency, the flames coming from the oxy-burners (hereinafter "oxy flames" are very disturbed by the flames, called "aero flames", coming from regenerators operating with hot air, because of the least amount of movement of the oxy flame. These disturbances can create interference of the oxy flame with the molten solid and unburnt matter and thus problems with glass quality or energy efficiency. These problems are all the more important when the power (and therefore the flows of the combustion agents) of the oxy-burners is reduced for phases of lower production increase. It is therefore essential to maximize the pulse or amount of movement of the oxyfires throughout the power range of the oxy-burners.

Systems like those described in document EP 2143999 allow manual adjustment of the flow of gaseous fuel between two injections (primary and secondary) in order to maximize the fuel pulse and thus guarantee the stability of the flame of the oxy-burner. However, these manual systems require a constant adjustment on the part of operators of the distribution of fluids, without being able to easily assess in real time the impact of these adjustments on the process. To avoid these adjustments and any quality problems, operators most often adjust the power on the air burners (regenerator) resulting in excess oxygen consumption and an increase in production costs.

The present invention can advantageously be used in this case by defining a predefined pressure range or a predefined pressure making it possible to ensure an automatic distribution of flow between the primary and secondary injections so as to maximize the pulse of the oxy flame whatever the total fuel flow.

For example, in the case of a production increase of 4%, the power of an oxy-burner can be 800 kW whereas for a production increase of 8%, the power of an oxy-burner can be of 1.8 MW. It has been determined that a pressure of 300 mbarg at the distribution chamber between the two fuel injections ensures a very stable flame both at 800 kW and at 1800 kW. The automatic adjustment according to the invention of the distribution of fuel as a function of the gas pressure in the chamber when the power varies will thus optimize production costs, limit quality defects and optimize energy consumption.

Claims

1. Assembly for the injection into a combustion zone of a gaseous combustion agent chosen from gaseous fuels and gaseous oxidizers, the assembly comprising:

• a room (1 1) having an entrance through which the agent is introduced into the assembly,

• at least one primary injector (21) for transporting a primary flow of the agent from the chamber (1 1) to the combustion zone (1) and for injecting said primary flow into the combustion zone ( 1), said at least one primary injector being fluidly connected to the chamber (1 1) by means of at least one primary passage (23),

• at least one secondary injector (22) for transporting a secondary flow of the agent from the chamber (11) to the combustion zone (1) and for injecting said secondary flow into the combustion zone, said at least one secondary injector being fluidly connected to the chamber by means of at least one secondary passage (24),

said assembly also comprising:

• a pressure detector (30) for detecting a gas pressure or a variation in gas pressure in the chamber,

• an adjustment system (31) for adjusting a flow section of the at least one secondary passage, and

• a control system (32) connected to the pressure detector and to the adjustment system, the control system controlling the adjustment system so that the flow section of the at least one secondary passage is regulated according to the pressure or the pressure change detected by the pressure sensor.

2. An assembly according to claim 1, in which the control system controls the adjustment system so that the gas pressure in the chamber is within a predetermined pressure zone or so that the gas pressure in the chamber corresponds to a predetermined value by adjusting the flow section of the at least one secondary passage.

3. Assembly according to any one of the preceding claims, in which the adjustment system is provided with at least one shutter (33) capable of adjusting the flow section of the at least one secondary passage.

4. Assembly according to any one of the preceding claims, comprising at least a pair of a primary injector with a secondary injector, a pair in which one of the primary injector and the secondary injector surrounds the other of the primary injector and secondary injector.

5. An assembly according to any one of claims, comprising at least two primary injectors and / or at least two secondary injectors, preferably at least two primary injectors and at least two secondary injectors.

6. Installation comprising several assemblies according to any one of the preceding claims, the installation preferably comprising a common control system which is connected to the pressure detector of each assembly and which is capable of controlling the adjustment system of each assembly in function of the gas pressure or of the variation in gas pressure detected by the pressure detector of said assembly.

7. Burner comprising an assembly according to any one of the preceding claims for the injection into a combustion zone of a gaseous combustion agent chosen from a gaseous fuel and a gaseous oxidizer and at least one additional injector for the injection of '' an additional fluid in the combustion zone.

8. Burner according to claim 7, comprising a block (40) with an inlet face (41) and an outlet face (42) opposite the inlet face (41), burner in which the the assembly is attached to the inlet face (41) of the block (40) so that the burner injectors are positioned in one or more perforations passing through the block from the inlet face to the outlet face.

9. Burner according to claim 8, in which the primary and secondary injectors of the assembly form couples of a primary injector with a secondary injector, the couples being positioned in at least one first perforation of the block (40) and the at least one additional injector being positioned in at least one additional perforation of the block (40).

10. Burner according to claim 9, comprising at least two couples and at least two additional injectors, in which the couples define a first fluid injection plane and in which the injectors define a second injection plane of the additional fluid different from the first plane, the second plane being parallel to the first plane or oriented so as to cut the first plane in the combustion zone downstream of the outlet face (42).

11. Oven comprising an internal combustion zone and comprising at least one assembly according to any one of claims 1 to 5 for the injection of a gaseous combustion agent chosen from gaseous fuels and gaseous oxidizers in the combustion zone internal of the oven, the at least one assembly optionally forming part of a burner according to any one of claims 7 to 10.

12. Oven according to claim 11 comprising several assemblies, the oven preferably comprising a common control system which is connected to the pressure detector of each assembly and which is capable of controlling the adjustment system of each assembly as a function of the gas pressure or of the variation in gas pressure detected by the pressure detector of said assembly.

13. Combustion method in which a gaseous combustion agent chosen from gaseous fuels and oxidizers is injected into a combustion zone by means of an assembly according to any one of claims 1 to 5, said assembly being optionally part of 'a burner according to any one of Claims 7 to 10, process in which:

• the assembly pressure detector detects the gas pressure in the assembly chamber,

The assembly adjustment system regulates the flow section of the at least one secondary passage, and • the assembly control system controls the assembly adjustment system so that the flow section of the at least one secondary passage is regulated as a function of the pressure or of the pressure variation detected by the assembly pressure detector.

14. The method of claim 13, wherein the control system controls the control system so that the gas pressure in the chamber is within a predetermined pressure zone or so that the gas pressure in the chamber of the assembly corresponds to a predetermined value by adjusting the flow section of the at least one secondary passage of the assembly.

15. Method according to one of claims 13 and 14, wherein the gaseous combustion agent is a gaseous fuel chosen from natural gas, biogas, propane, butane, residual gases from steel or reforming processes. methane, hydrogen or any mixture of at least two of these gaseous fuels or a gaseous oxidant having an oxygen content of 21 to 100% vol, preferably greater than 21% vol and in particular at least 80% vol, more preferably at least 90% vol.