Oxygen enrichment method for a burner of an industrial furnace

Abstract

The invention relates to a method for oxygen enrichment of the reactants of a burner (1) positioned on a wall (2) of an industrial furnace (3), characterized in that the enrichment is carried out inside the furnace, by oxygen supplied by at least two lances (4) passing through the wall of the furnace and whose ends (41) open into the furnace in the vicinity of the burner.

Description

METHOD FOR OXYGEN ENRICHED IN AN INDUSTRIAL FURNACE BURNER Designation of the technical field concerned

[0001] The invention relates to industrial furnaces for heating metal products equipped with burners, in particular preheating furnaces before rolling. Technical problems that the invention addresses

[0002] Reheating furnaces play a crucial role in the steelmaking process, where steel products are heated to high temperatures for subsequent operations, e.g. rolling in hot rolling mills.

[0003] However, these ovens contribute significantly to emissions of carbon dioxide (CO2) and nitrogen oxide (NOx), which must be reduced with stricter regulations.

[0004] Today, most reheating furnace modernization projects aim to reduce the carbon footprint of the process, leading to an increasing demand for cleaner and more sustainable technologies in industrial processes.

[0005] The adoption of oxygen enrichment is a promising solution for reducing emissions in steel reheating furnaces.

[0006] Oxy-combustion offers several advantages over traditional air combustion, including reduced fuel consumption thanks to higher combustion efficiency and compatibility with existing infrastructure. The transition to oxy-combustion contributes to global efforts to decarbonize the steel industry.

[0007] As the steel industry continues to evolve, there is growing recognition of the need to adopt sustainable practices and reduce environmental impacts. By leveraging emerging technologies such as oxy-combustion and implementing strategic measures to mitigate CO2 and NOx emissions, steel producers can not only meet regulatory requirements but also achieve long-term sustainability goals while maintaining their competitiveness in the global market. Technical background

[0008] Steel reheating furnaces are an integral part of the steelmaking process. These furnaces use burners with different configurations, including side, vault, and front burners.

[0009] In recent years, side burners have become the most widely used due to their ability to deliver high power outputs, allowing for product heating with a limited number of burners compared to top and front burners. Having fewer burners simplifies oven design and heating control.

[0010] However, side burners require the product to be heated evenly across its entire length and width. This is difficult to achieve with conventional axial flames, which concentrate most of the heat along the burner's axis.

[0011] By distributing heat more evenly throughout the product, wide flame burners help mitigate problems such as overheating and underheating, thereby improving product quality and uniformity, as described in Applicant WO2015078862.

[0012] Furthermore, steel reheating furnaces are wide, requiring very long flames reaching 7 to 8 meters to properly heat the center of the product. However, to avoid overheating the center of the product, it is necessary to adjust the flame length.

[0013] Modulated flame burners alternate between two flame modes: short flame and long flame. Short flames are designed to heat the area close to the burner, while long flames are designed to heat the area further away. By adjusting the number of times the short flame mode is used and the number of times the long flame mode is used in a defined cycle, the temperature profile along the product can be controlled.

[0014] Oxygen enrichment of the oxidizer can be achieved using several methods, including direct enrichment of the combustion air or the use of oxygen lances.

[0015] Although each method has its advantages and limitations, the use of oxygen lances is the most suitable method for modernizing existing reheating furnaces.

[0016] It allows for high levels of enrichment, reaching up to 50% oxygen, with low capital and operating costs. This is important in many cases, as the availability of oxygen at a reasonable price is a prerequisite. If the fuel consumption savings are outweighed by the additional cost of oxygen, the idea is only attractive for environmental reasons, without any economic benefit. This could hinder its adoption by industry.

[0017] US8075303 teaches the use of oxygen lances to inject oxygen directly into the furnace. However, conventional techniques generally involve a lance installed at a distance from the burner, usually between 0.7 and 1.2 m.

[0018] The injection is typically sonic or supersonic to disrupt the aerodynamics of the existing burner. This arrangement creates a highly staged and dilute combustion. The air is reduced at the burner, resulting in one or more incomplete combustion stages. The products are then oxidized by oxygen in the final stage. This configuration promotes NOx reduction and a low flame temperature.

[0019] The drawback of this technique is that the initial flame structure is completely altered. Maintaining the flame structure is crucial because flames that should be short are extended and deflected towards the high-speed oxygen jet. Burners with modulated flame length lose their function and control, as well as their flexibility in adjusting the product's temperature profile.

[0020] We can see in a diagram representing the longitudinal temperature profile of the vault, with the length of the oven in the axis of the flame, in millimeters, on the x-axis, and the temperature of the vault in degrees Celsius on the y-axis.

[0021] The temperature profile of the dome reveals the longitudinal temperature profile of the flame. The solid line corresponds to the burner operating in air-combustion mode, without oxygen injection. The dashed line corresponds to the burner operating with the injection of air enriched to 30% oxygen (compared to 21% in ambient air) via an oxygen lance positioned at a connection 90 cm from the burner axis.

[0022] Compared to air combustion, the flame, which is supposed to heat close to the burner, is stretched and heats further into the furnace. Orienting the nozzle towards the burner axis can help, but doesn't solve the problem. Any speed, position, or angle of injection creates this stretching effect.

[0023] Figures 2 and 3 show diagrams representing the cross-sectional temperature profile of the dome at different distances from the burner, with the distance to the burner axis in millimeters on the x-axis and the temperature of the dome in degrees Celsius on the y-axis.

[0024] In, the burner operates without oxygen injection, whereas in, the burner operates with oxygen injection according to the state of the art on one side of the burner, at the point represented by an arrow on the x-axis.

[0025] It is observed that with the injection of oxygen, the flame is deflected towards the oxygen jet.

[0026] In a reheating oven, the burners are usually arranged on the side walls of the oven, opposite each other. Ideally, their flames reach the middle of the oven.

[0027] Stretching the flame can therefore be a disadvantage, particularly in relatively narrow ovens. Longer opposing flames cross in the middle of the oven and deflect each other in opposite directions, generally resulting in one flame rising and another descending.

[0028] For burners positioned on a plane above the product, the tip of one flame rises towards the oven roof, while the tip of the flame from the burner on the opposite side of the oven descends towards the product. This impact on the roof and the product will cause overheating of both the roof and the top surface of the product.

[0029] For burners positioned on a surface below the product, one flame tip rises towards the product and the other descends towards the base. Similarly, the base and the lower skin of the product will be affected in the lower areas.

[0030] The resulting overheating of the product, with more oxygen on the product's surface, leads to greater scale formation.

[0031] Furthermore, the temperatures of the oven's roof and hearth are used to calibrate the mathematical model used to calculate the power distribution within the oven in order to produce a desired heating curve. If the temperature values ​​deviate from the expected values ​​due to flame tip deviations, this will result in poor energy distribution management within the oven, potentially compromising product temperature control and the oven's energy efficiency.

[0032] From this, we can understand that the structure of the flame has limits and requirements that must be met for proper furnace operation, especially burners with a modulated length wide flame concept.

[0033] The invention relates to a method for modernizing existing furnaces as well as new furnaces.

[0034] According to a first aspect of the invention, a method for enriching the reactants of a burner positioned on the wall of an industrial furnace with oxygen is proposed, the burner being supplied with oxidant and fuel, characterized in that the enrichment is carried out in the furnace, by oxygen supplied by at least two lances passing through the wall of the furnace arranged radially on either side of the burner, outside of it, and symmetrically with respect to the axis of the burner, and whose ends of the lances open into the furnace, the enrichment of the reactants with oxygen being obtained by enriching at least a part of the oxidant of the burner with oxygen before it reacts with fuel from the burner.

[0035] For example, the end of a lance is a few centimeters to a few tens of centimeters away from the burner, for example 20 cm.

[0036] The invention makes it possible to achieve oxygen enrichment on existing burners, without making any modifications to these burners and their oxidizer and fuel supply circuits.

[0037] The modification is limited to drilling a hole in the furnace wall near the burner and inserting oxygen lances through the resulting openings. The invention thus allows for easy oxygen enrichment of existing burners at a limited cost.

[0038] The invention allows oxygen to be injected using lances while preserving the structure of the flame.

[0039] According to one embodiment of the invention, the oxygen enrichment of the reactants is carried out at a point where at least part of said reactants is in combustion in lack of air.

[0040] Supplying oxygen where combustion is lacking air helps to prevent, or limit, the formation of nitrogen oxides (NOx).

[0041] Advantageously according to the invention, the burner comprising oxidizer ducts opening into the furnace through oxidizer orifices, the momentum of the oxygen exiting the end of a lance is lower than that of the oxidizer exiting the proximal oxidizer orifice of the end of the lance.

[0042] The oxidizer jet remains the driving force and drives the oxygen jet, as well as the fuel, which helps to maintain the geometry of the flame.

[0043] Advantageously, the momentum of the oxygen exiting the tip of a lance is less than half, and preferably less than one-tenth, of that of the oxidizer exiting the proximal oxidizer orifice of the tip of the lance.

[0044] The low momentum of the oxygen jets means that they do not disturb the oxidizer jets. Thus, the invention makes it possible to achieve oxygen enrichment on existing burners without disrupting the flame structure.

[0045] Since the length and width of the flame remain unchanged, the temperature distribution within the furnace is not altered, and the temperature profile of the products being heated is maintained. Therefore, oxygen enrichment has no impact on furnace operation.

[0046] The furnace operator can carry out oxygen enrichment whenever desired, without the need to make changes to the burner settings to correct a variation in heat distribution within the furnace.

[0047] Advantageously according to the invention, the quantity of oxygen supplied by the lances to a burner is between 1% and 40% of the quantity of oxygen required to obtain complete combustion of the fuel of said burner.

[0048] The oxygen supply from the nozzles is accompanied by a decrease in the oxidizer flow rate, in a proportion sufficient to maintain the same overall air / gas ratio, or more precisely, the same oxygen / gas ratio. The burners most often operate with excess air, for example, with 5% excess air.

[0049] The maximum amount of oxygen supplied by the nozzles is limited because it is necessary to maintain sufficient momentum in the oxidant to retain its capacity to carry oxygen and fuel, and not to alter the geometry of the flame.

[0050] Since the installation of oxygen lances is carried out without modification of the existing burner, it is not possible to reduce the diameter of the orifices of the burner's oxidant ducts to modify the momentum of the oxidant jets.

[0051] For the same reason, it would not be advantageous to inject oxygen-enriched air through the lances because it would be necessary to further reduce the momentum of the oxidizer passing through the burner.

[0052] The amount of oxygen supplied by the oxygen injection lances to a burner can be adjusted according to the availability of oxygen or its cost.

[0053] The higher the amount of oxygen supplied by the oxygen injection lances, the lower the energy consumption of the furnace will be.

[0054] By comparing the additional cost resulting from the injection of oxygen by the lances and the savings achieved by a reduction in the energy consumption of the furnace, the furnace operator can decide on the most advantageous quantity of oxygen injected by the oxygen lances.

[0055] According to a second aspect of the invention, a combustion system for an industrial furnace is proposed, comprising a burner positioned on a wall of the furnace and at least two lances passing through the wall of the furnace capable of enriching with oxygen, in the furnace, at least a part of the reactants of the burner so as to implement a process according to the first aspect of the invention.

[0056] For example, oxygen lances are positioned horizontally, parallel to the burner's longitudinal axis. They can also be angled so that their longitudinal axis intersects that of the burner in the furnace.

[0057] According to one embodiment of the invention, the burner comprises oxidizer ducts opening into the furnace through oxidizer orifices and at least one fuel duct opening into the furnace through a fuel orifice, characterized in that the positioning of the lances is such that it leads to an oxygen enrichment of at least a part of the burner oxidizer before it reacts with the burner fuel.

[0058] According to one embodiment of the invention, the burner comprises a first group of oxidizer ducts opening into the furnace through a first group of orifices and a second group of oxidizer ducts opening into the furnace through a second group of oxidizer orifices. The oxidizer from the first group of ducts interacts with the burner fuel before the oxidizer from the second group of ducts. The tips of the nozzles are positioned near the second group of oxidizer orifices so that the oxygen supplied by the nozzles primarily enriches the oxidizer supplied by the second group of oxidizer ducts with oxygen.

[0059] According to another embodiment of the invention, the burner has a staggered oxidizer configuration enabling it to operate in a first mode, referred to as long flame mode, where the flame has a first length, or in a second mode, referred to as short flame mode, where the flame has a second length shorter than the first. The burner comprises a first group of oxidizer ducts opening into the furnace through first orifices used when the burner operates in long flame mode, and a second group of oxidizer ducts opening into the furnace through second oxidizer orifices when the burner operates in short flame mode. The positioning of the oxygen lances is such that the burner is capable of operating in both modes with oxygen enrichment provided by the lances.

[0060] Since oxygen enrichment is not limited to a single operating mode, the advantages resulting from operation with oxygen enrichment are taken advantage of in both operating modes of the burner.

[0061] The burner's operation remains independent of oxygen injection via the nozzles. Thus, the transition from short-flame to long-flame operation, or vice versa, and the frequency of flame length changes, remain unchanged by oxygen injection.

[0062] According to one embodiment of the invention, the burner comprises oxidizer ducts opening into the furnace through oxidizer ports and at least one fuel duct opening into the furnace through a fuel port. The burner is configured such that the impulse of the oxidizer jets exiting the oxidizer ducts drives fuel towards the oxidizer jets, leading to the start of combustion in the absence of air. The positioning of the nozzles is such that oxygen is supplied at the start of combustion in the absence of air.

[0063] This arrangement of the nozzles helps to limit nitrogen oxide emissions.

[0064] Advantageously according to the invention, the end of the lances is formed by a converging nozzle capable of creating a coherent jet of oxygen.

[0065] Using a converging nozzle capable of creating a consistent jet offers several advantages, including:

[0066] - Increased oxygen injection speed: The nozzle's convergent design accelerates the flow of injected gas by progressively decreasing the cross-section. This generates a higher velocity at the nozzle outlet.

[0067] - Improved mixing of reactants: A higher injection speed helps create a more homogeneous mixture of reactants. A homogeneous mixture is essential for more efficient and complete combustion, thus reducing the formation of hot spots and the resulting NOx emissions and unburned combustion products.

[0068] In summary, the use of a convergent nozzle for oxygen injection optimizes combustion conditions, thereby improving energy efficiency, reducing pollutant emissions, and contributing to the safety and control of the combustion process.

[0069] The nozzle can be made of durable metallic or ceramic material that can withstand high temperatures.

[0070] The tip of the lance can be positioned slightly recessed from the inner wall of the furnace to protect the nozzle from radiation, especially when the nozzle is not gas-cooled. The recess in the inner wall can be small with a ceramic nozzle, due to its high temperature resistance, and larger with a metal nozzle, which has lower temperature resistance.

[0071] Under extreme conditions, the lance can be cooled by an external fluid circulating through a jacket that is part of the lance or external to the lance.

[0072] The invention makes it possible to reduce the environmental impact of the operation of the furnace, in particular by reducing CO2 emissions linked to the reduction of fossil fuel consumption which results from the enrichment of the oxidant with oxygen. Brief description of the figures

[0073] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for understanding which reference should be made to the attached drawings in which:

[0074] is a diagram illustrating the longitudinal temperature profile of the vault of a reheating furnace for a burner operating with and without oxygen injection according to the prior art,

[0075] is a diagram illustrating the cross-sectional temperature profile of the dome at different distances from the burner for burner operation without oxygen injection,

[0076] is a diagram illustrating the cross-sectional temperature profile of the dome at different distances from the burner for burner operation with oxygen injection according to the prior art,

[0077] is a schematically and partially represented front view of a furnace wall on which a burner is mounted according to the prior art.

[0078] is a schematic and partially represented vertical cross-sectional view of the wall of the lasagna on which the burner is mounted according to the prior art.

[0079] is a view similar to that after the addition of two injection lances according to an exemplary embodiment of the invention,

[0080] is a view similar to that after the addition of the two injection lances according to the embodiment shown in the invention,

[0081] is a diagram illustrating the longitudinal temperature profile of the vault of a reheating furnace for a burner operating in long flame mode with and without oxygen injection, according to an exemplary embodiment of the invention.

[0082] is a diagram illustrating the longitudinal temperature profile of the vault of a reheating furnace for a burner operating in short flame mode with and without oxygen injection according to the exemplary embodiment of the invention of the,

[0083] is a schematically and partially represented longitudinal cross-sectional view of a pre-rolling reheating furnace according to an exemplary embodiment of the invention,

[0084] is a partial and schematic representation of a lance according to an exemplary embodiment of the invention, comprising a metallic nozzle 61, and,

[0085] is a partial and schematic representation of a lance according to an example of an embodiment of the invention, comprising a nozzle 61 made of ceramic material. Detailed description of the invention

[0086] A partially represented front view from inside a pre-rolling preheating furnace 200 shows a wall 300 of the furnace comprising a burner 1 according to the prior art. The burner includes an opening 8 made of refractory material with a central gas pipe 7.

[0087] It comprises a first series of four air ducts 5 arranged at a first distance from the central gas pipe, and a second series of four air injectors 6 arranged at a second distance from the central gas pipe, the second distance being smaller than the first. The injectors in the same series are equidistant from the central gas pipe.

[0088] Two of the air injectors from the first series of injectors and two of the air injectors from the second series of injectors are positioned on a vertical plane P passing through the axis of the burner and the other two air injectors from the first series of injectors and two other air injectors from the second series of injectors are positioned on a horizontal plane also passing through the axis of the burner.

[0089] The burner is configured to operate in two modes of operation, a first mode where the oxidizer is supplied only by the injectors of the first series of injectors and a second mode where the oxidizer is supplied only by the injectors of the second series of injectors.

[0090] The first operating mode generates a long flame while the second leads to a short flame.

[0091] Thus, by playing with the operating time of the burner in each of the two operating modes, it is possible to adjust the temperature distribution in the oven and thus the temperature profile of the products.

[0092] The wall 300 of the furnace 200 is partially represented, in vertical section along plane P passing through the vertical axis of burner 1.

[0093] The burner 1 further includes a first combustion air inlet 10 supplying the first set of air injectors 5 and a second combustion air inlet 11 supplying the second set of air injectors 6. The first set of air injectors 5 opens into the furnace 200 through orifices 51, the second set of air injectors 6 opens into the furnace through orifices 61 and the central gas pipe 7 opens into the furnace through orifice 71.

[0094] This is similar to that of the one shown, partially represented, in front view from inside a preheating furnace 2 before rolling, a wall 3 of the furnace comprising a burner 1 similar to that of the one shown. Two lances 4 have been added for oxygen injection, arranged horizontally according to this embodiment of the invention.

[0095] In this representation, viewed from the front from inside the oven, only the ends 41 of the spears are visible.

[0096] For clarity in the diagram, the 4 lances are arranged vertically on plane P, on either side of the burner and symmetrically along the burner's axis. On the furnace, the lances can be positioned on other planes, for example, a horizontal plane.

[0097] The wall 3 of furnace 2 is partially represented in vertical section along plane P passing through the vertical axis of burner 1. The lances 4 pass through the wall 3 of the furnace, which has been previously drilled to receive them.

[0098] In this example, the lances 4 have at their end a nozzle 42 whose tip 41 is slightly recessed from the hot face of the oven wall 3 in order to limit its temperature. This is particularly advantageous when the nozzle 42 is metallic.

[0099] In this example of an embodiment, the lances are arranged horizontally. They are parallel to the fuel ducts 4 and the oxidizer ducts 5.

[0100] They can also be inclined at a chosen angle so that the longitudinal axes of the lances converge towards a point located on the axis of the gas pipe 7 at a determined distance from the opening. This distance from the point of convergence is chosen according to the nature of the burner, in particular the arrangement of the oxidizer and fuel ducts, the nature of the burner's main fuel, the shape(s) of the flame in normal burner operation, without the lances, and the nature of the fuel supplied by the lances.

[0101] The number, position and mode of operation of the combustion ducts, some of which may or may not be supplied depending on the operating regime of the burner, are taken into account in particular when deciding on the position and inclination of the lances.

[0102] The position and inclination of the lances can be determined in particular by numerical simulation or by tests.

[0103] The end 41 of the lances can also be found in the oven, when the material of the nozzle tolerates a higher temperature and / or when the flow of gas in the lance allows sufficient cooling of the lance and in particular of its nozzle.

[0104] Figures 8 and 9 show a diagram representing the longitudinal temperature profile of the vault, with the length of the oven in the axis of the flame, in millimeters, on the x-axis, and the temperature of the vault in degrees Celsius on the y-axis.

[0105] In these figures, the solid line curve represents burner operation without oxygen lance 4. The dashed line curve represents burner operation with an injection of air enriched to 30% oxygen by two lances 4, as shown in the diagram.

[0106] This corresponds to the operation of the burner in long flame mode and this corresponds to the operation of the burner in short flame mode.

[0107] It can be seen from these figures that with the addition of oxygen lances according to the invention, the structure of the flame is preserved in both operating modes of the burner, short flame and long flame.

[0108] The structure of the flame is preserved because it remains dominated by the aerodynamics of the air jets.

[0109] The participation of added oxygen in the reaction is delayed until the final stage. The flame root is not significantly affected, which helps maintain relatively cool roots, thus preserving the burner's mechanical structure.

[0110] The diagram schematically illustrates another application of the invention for a preheating oven 20 before rolling. The oven is shown in longitudinal section, with the products to be reheated, not shown, circulating from left to right. In this example, two lances 4 are arranged on either side of each burner 100 on a horizontal plane. This arrangement is advantageous in this type of oven where a flat flame is desired to distribute heat over the products.

[0111] The illustration partially and schematically shows a lance 4 according to an example of an embodiment of the invention, comprising a metallic nozzle 42.

[0112] Laillumer partially and schematically illustrates a lance 4 according to another embodiment of the invention, comprising a nozzle 42 made of ceramic material.

Claims

A method for enriching the reactants of a burner (1) positioned on a wall (2) of an industrial furnace (3) with oxygen, the burner being supplied with oxidizer and fuel, characterized in that the enrichment is carried out in the furnace, by oxygen supplied by at least two lances (4) passing through the wall of the furnace arranged radially on either side of the burner, outside of it, and symmetrically with respect to the axis of the burner, and whose ends (41) of the lances open into the furnace, the enrichment of the reactants with oxygen being obtained by enriching at least a part of the burner's oxidizer with oxygen before it reacts with fuel from the burner. Enrichment process according to claim 1, characterized in that the oxygen enrichment of the reactants is carried out at a point where at least part of said reactants is in combustion in lack of air. Method according to claim 1, the burner (1) comprising oxidizer conduits (5, 6) opening into the furnace through oxidizer orifices (51, 61), characterized in that the momentum of the oxygen exiting the end (41) of a lance (4) is lower than that of the oxidizer exiting the proximal oxidizer orifice (51, 61) of the end of the lance. Method according to the preceding claim, characterized in that the momentum of the oxygen exiting the end (41) of a lance (4) is less than half, and preferably less than one-tenth, of that of the oxidant exiting the proximal oxidant orifice (51, 61) of the end of the lance. A method according to any one of the preceding claims, characterized in that the quantity of oxygen supplied by the lances (4) to a burner is between 1% and 40% of the quantity of oxygen required to obtain complete combustion of the fuel of said burner. Combustion system of an industrial furnace (3) comprising a burner (1) positioned on a wall (2) of the furnace, characterized in that it comprises at least two lances (4) passing through the wall of the furnace capable of enriching with oxygen, in the furnace, at least a part of the reactants of the burner so as to implement a process according to one of claims 1 to 5. Combustion system according to the preceding claim, the burner (1) comprising oxidizer conduits (5, 6) opening into the furnace through oxidizer orifices (51, 61) and at least one fuel conduit (7) opening into the furnace through a fuel orifice (71), characterized in that the positioning of the lances (4) is such that it leads to an oxygen enrichment of at least a part of the burner oxidizer before it reacts with the burner fuel. Combustion system according to the preceding claim, the burner (1) comprising a first group of oxidizer conduits (6) opening into the furnace through a first group of orifices (61) and a second group of oxidizer conduits (5) opening into the furnace through a second group of oxidizer orifices (51), the oxidizer from the first group of conduits (6) interacting with fuel from the burner before the oxidizer from the second group of conduits (5), characterized in that the end (41) of the lances is positioned in the vicinity of the second group of oxidizer orifices (51) so that the oxygen supplied by the lances enriches with oxygen mainly the oxidizer supplied by the second group of oxidizer conduits (5). Combustion system according to claim 6, the burner (1) having a staged oxidizer making it suitable for operation in a first mode, called long flame mode, where the flame has a first length or in a second mode, called short flame mode, where the flame has a second length less than the first length, the burner comprising a first group of oxidizer conduits (50) opening into the furnace through first orifices (51) used when the burner operates in long flame mode and a second group of oxidizer conduits (6) opening into the furnace through second oxidizer orifices (61) when the burner operates in short flame mode, characterized in that the positioning of the oxygen lances (4) is such that the burner is suitable for operation in its two modes of operation with oxygen enrichment by the lances. Combustion system according to claim 6, the burner (1) comprising oxidizer conduits (5, 6) opening into the furnace through oxidizer orifices (51, 61) and at least one fuel conduit (7) opening into the furnace through a fuel orifice (71), the burner being configured so that the impulse of the oxidizer jets at the outlet of the oxidizer conduits (5, 6) drives fuel towards the oxidizer jets leading to the start of combustion in lack of air, characterized in that the positioning of the lances (4) is such that oxygen is supplied at the start of combustion in lack of air. System according to any one of claims 6 to 10, characterized in that the end of the lances (4) is formed by a converging nozzle (42) capable of creating a coherent jet of oxygen.

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