Burner and method of operation

Abstract

This invention relates to specific burners, and more particularly to non-premixed or partially premixed fuel burners with the flexibility to enrich the burner with oxygen. Therefore, the burner can be used in applications requiring operation in both air-fuel and / or oxygen-fuel and / or air-oxygen-fuel modes, depending on the furnace operation requirements. The invention further relates to a furnace including a burner and a method of operating the burner.

Description

Technical Field

[0001] This invention relates to burners, and more particularly to industrial burners for gaseous fuels, and especially to burners that can be used as both air-fuel burners and air-oxygen-fuel burners. Prior Technology

[0002] In the existing technology, many high-temperature heating or melting preheating furnaces are designed with air-fuel burners in mind.

[0003] Due to increased product demand, manufacturers are seeking to improve the productivity of their current operating plants. Additionally, increased scrutiny from emissions regulators requires improvements in the efficiency of current furnace operations and reductions in emissions.

[0004] In addition, the need for decarbonization has increased pressure to switch to low-carbon intensity fuels (such as hydrogen and ammonia) in industries with medium to high heating applications.

[0005] There are several potential methods to address these challenges.

[0006] First, fuel-flexible burners can be used, which can operate on any gaseous fuel, such as natural gas (NG), liquefied petroleum gas (LPG), biogas, syngas, hydrogen, ammonia, or other gases, while meeting the emission and thermal efficiency standards of heating or melting furnaces. Designing fuel-flexible gaseous fuel burners presents several challenges, depending on the burner type and design.

[0007] In addition to the wide range of variations in the combustion behavior of these fuels (well documented in the combustion literature), differences in the calorific value, reaction rate, and flammability limits of gaseous fuels also present challenges in burner design. For example, one challenge is that when H2 is introduced to replace NG, the total gas volumetric flow rate begins to increase for the same MMBtu rating of the burner. This increased volumetric flow rate will affect the nozzle exit velocity, which, based on burner design, can influence flame stability, flame heating distribution, and burner emission characteristics.

[0008] Secondly, air-oxygen fuel (AOF) burners are a viable option because they allow the use of pure oxygen or oxygen-enriched air as the oxidant, replacing a portion of the air used as an oxidant. AOF burners contribute to increased plant productivity and thermal efficiency for several reasons, well documented in the literature [Baukal Jr, Charles E. Oxygen-enhanced combustion. CRC press, 2010]. Key reasons include increased plant thermal efficiency with reduced nitrogen diluent, thus decreasing heat absorbed and carried away by nitrogen, and higher peak temperatures enabling higher heat transfer rates through flame radiation.

[0009] The amount of process benefit from using an AOF burner depends on the burner's total oxygen enrichment. Baukal Jr., Charles E. Oxygen-enhanced combustion. CRC press, 2010 shows a graph of available energy versus oxidant composition at different exhaust temperatures. The inventors observed that available heat increases rapidly with initial air enrichment levels as high as 35%-45%, but process benefits increase more slowly with further increases in enrichment level. This is considered important because available heat is an indirect measure of thermal efficiency. The graph provides some guidance on where furnace operators can potentially choose to operate the burner and / or furnace at intermediate enrichment levels to optimize the balance between process benefits and oxygen costs.

[0010] A further challenge for AOF burners is NOx emissions, as the increased enrichment locant in the air increases the tendency for NOx formation in the burner due to the increased local oxygen concentration. Thermal NOx formation continues to increase to a certain enrichment locant (which, depending on the burner design, may peak somewhere between 40% and 60%). By further increasing the enrichment locant beyond 40%-60%, NOx emissions begin to decrease as local N2 concentrations begin to decline, and NOx formation continues to decrease as burner operation moves towards pure oxygen-fuel burners.

[0011] Therefore, the primary objective of this invention is to provide an advantageous burner that mitigates or overcomes one or more of the aforementioned challenges. This invention provides a fuel-flexible burner. This burner also allows operation in air-fuel and / or air-oxygen-fuel modes without any burner modifications. Furthermore, this burner produces low NOx under all such operating conditions.

[0012] The specific existing technology design of the burner can be summarized as follows:

[0013] EP 3 967 925 A1 describes a burner with different internal sections compared to the present invention.

[0014] US 5308239 and US 5871343 disclose burners with an air-oxygen fuel design that have a different concept and NOx design strategy than this invention.

[0015] US 8727767 discloses a flat flame burner that operates in a different mode compared to the present invention.

[0016] AU 684296B2 discloses an air-fuel and air-oxygen fuel burner with a different design compared to the present invention, wherein air rotates around the fuel and oxygen jets. Summary of the Invention

[0017] Generally speaking, this invention relates to burners, and more particularly to burners that can be used in high-heating applications, especially burners that need to operate in air-fuel, oxygen-fuel, and / or air-oxygen-fuel modes depending on the furnace operation requirements.

[0018] Specifically, this invention relates to the subject matter as defined in the scope of the invention application.

[0019] The present invention provides a burner that can be used in applications where, depending on the furnace operation requirements, the burner needs to operate in both air-fuel and air-oxygen-fuel modes.

[0020] The burner of the present invention helps to address the above challenges by providing a novel burner design that is fuel-flexible (e.g., working with NG or H2 and / or NG / H2 mixtures), provides operational flexibility between air-fuel and air-oxygen fuel modes, and offers low NOx and CO emissions in both air-fuel and air-oxygen fuel modes.

[0021] Generally speaking, the burner of the present invention can be used in any application requiring high heating, particularly in applications such as steam methane reforming, reheat furnaces in the steel industry, or secondary melting furnaces.

[0022] In its general form, the present invention provides a burner (1) comprising an ignition source (10), a primary fuel conduit (20), a primary oxidizer conduit (30) for supplying a primary oxidizer, and a secondary fuel conduit (40) for supplying secondary fuel. The primary fuel conduit includes a primary fuel outlet (22) having multiple primary fuel outlet holes (23) for supplying primary fuel to an ignition chamber (25). The ignition chamber (25) is positioned within the primary fuel conduit (20) extending from the primary fuel outlet (22) to the end plane (24) of the primary fuel conduit. The primary fuel conduit wall (29) includes a plurality of vent holes (28) at the location of the ignition chamber (25), the primary oxidizer conduit includes an intermediate annular conduit (35) in the downstream portion (5) of the burner, the intermediate annular conduit (35) is configured to allow the primary oxidizer to be divided into two parts, such that a first part is introduced into the ignition chamber (25) via the plurality of vent holes (28) to mix with the primary fuel, and a second part is introduced into a swirler section (33), which is further composed of the primary oxidizer conduit, and the secondary fuel conduit has a secondary fuel outlet (44) at its downstream end.

[0023] The present invention further provides a furnace including the burner of the present invention and a method for operating the burner.

[0024] The following section reveals specific (further) advantages of the burner of the present invention. Simple Explanation of the Diagram

[0025] The invention will now be described in conjunction with the accompanying drawings, wherein the same element symbols denote the same elements.

[0026] Figure 1A is an exemplary side view of the downstream portion of an exemplary burner of the present invention, including its cross-section at the downstream end. It particularly shows the connectors of the respective conduits and the preferred arrangement with a central axis.

[0027] Figure 1B is an exemplary side cross-sectional view of the downstream portion of an exemplary burner of the present invention, including its cross-section at the downstream end. It particularly shows the connectors of the respective conduits and the preferred arrangement with a central axis.

[0028] Figure 2A is an exemplary side cross-sectional view of the downstream portion of the burner of the present invention, showing, for example, the flow of various components, such as primary and secondary fuels, primary oxidant (e.g., air, oxygen or a combination thereof), and optional staged oxidant, which is diverted to the vent section and the cyclone section.

[0029] Figure 2B is an exemplary cross-sectional view of the downstream portion of the burner of the present invention, highlighting various components and optional components such as vent holes, turbulence generator plates, and ducts for staged oxidizers.

[0030] Figure 3A is an exemplary side cross-sectional view of the downstream portion of the burner of the present invention, highlighting certain distances, diameters, etc., such as the dimensions of various conduits (or individual pipes), and certain distances between the outlet plane and the outlet.

[0031] Figure 3B is an exemplary cross-sectional view of the downstream portion of the burner of the present invention, highlighting certain distances, diameters, etc., and indicating that D0 is the diameter of the primary fuel outlet orifice and D1 is the diameter of the purge air outlet orifice.

[0032] Figure 4 is an exemplary cross-sectional view of the downstream portion of the burner of the present invention, highlighting angles β and θ, and the use of a primary fuel plate as the primary fuel outlet and an optional air scavenging plate for the main oxidizer (section). It further illustrates how consecutive holes in different rows can be staggered by half the included angle between two consecutive holes in a row.

[0033] Figure 5 includes a schematic diagram of a first-stage fuel conduit according to an embodiment of the present invention, highlighting the omnidirectional arrangement of the vent (with diameter P1) and indicating the optional air premixing orifice, and further emphasizing the angle α, which is the angle between the centers of two consecutive orifices measured at the center of the conduit.

[0034] Figure 6A is an exemplary side cross-sectional view of the downstream portion of the burner of the present invention, which, for example, emphasizes the flow and interaction of primary fuel and main oxidant.

[0035] Figure 6B is a corresponding view of an embodiment including the aforementioned partial premixing as an optional feature. The scavenging holes on the wall of pipe 2 transfer a small portion of the main oxidant to the primary fuel line.

[0036] Figure 6C shows a related view, highlighting, for example, the interaction between secondary fuels and staged oxidizers.

[0037] Figure 7A is a schematic diagram of the operating state of the burner, showing steps 1 and 2 for operating an embodiment of the burner of the present invention.

[0038] Figure 7B is a schematic diagram of the operating state of the burner, showing steps 3 and 4 of an embodiment of the burner of the present invention.

[0039] Figure 8 shows a comparison of experimental results (normalized NOx data) obtained using the exemplary burner of the present invention and the prior art.

[0040] Figure 9A is an exemplary side cross-sectional view of an alternative embodiment of the present invention, which involves an alternative type of (partial) premixing of primary fuel and main oxidant (e.g., air), such as using a "stepped design".

[0041] Figure 9B is an exemplary cross-sectional and side-sectional view of an alternative embodiment of the present invention, which relates to an alternative type of (partial) premixing of primary fuel and main oxidant (e.g., air), such as using a "stepped design".

[0042] Figure 9C is an exemplary cross-sectional and side-sectional view of an alternative embodiment of the present invention, which relates to an alternative type of (partial) premixing of primary fuel and main oxidant (e.g., air), such as using a "stepped design".

[0043] Figure 10 shows an exemplary cross-sectional view of an embodiment of the present invention involving an ignition cup (75) and an oxidant venting cup (76), and the figure shows the respective distances L0, L01, L1, etc.

[0044] Figure 11 further illustrates some features of the burner of the present invention discussed in Example 1 (such as anchor points and stabilized surfaces).

[0045] Figure 12 illustrates other burner designs mentioned in this example. Implementation

[0046] This invention generally provides burners and other objects as defined in the claims of this invention.

[0047] The burner of the present invention overcomes the challenges of the prior art in various ways.

[0048] For example, the burner can operate in air-fuel mode in a cold furnace (i.e., average temperature <400 F during the burner's start-up sequence) without requiring oxygen assistance or a continuous ignition source. The burner can also operate stably in lean fuel, low flame temperature mode. The burner produces a stable flame (without any stripping) over a very wide 1:30 descent range, even with equivalence ratios as low as 0.25. This is an important feature, especially when the refractory is relined. The burner can operate in air-fuel mode to cure the refractory using air-fuel methods, which typically produce a lower maximum flame temperature compared to oxy-fuel or air-oxy-fuel methods. These characteristics allow for controlled preheating of the process furnace, enabling the process to start up and reach steady-state conditions within the timeframes required by the process requirements.

[0049] Furthermore, the oxidant back pressure (air and oxygen and / or enriched air) in the burner of this invention eliminates the need for any external secondary compression device for such flows. This feature helps reduce burner operating costs and minimizes any maintenance associated with such activities.

[0050] Furthermore, the burners of this invention offer low NOx efficiency and can operate at (relatively visible) lower speeds compared to some burners that require high supply pressures and speeds of Mach number 1 or higher. Increased supply requirements could potentially increase the operating costs of the burners. NOx formation is primarily through the formation of rapid and thermal NOx. As will be readily understood by those skilled in the art, the formation of thermal NOx depends on three parameters: local oxygen concentration, local nitrogen concentration, and local temperature.

[0051] This burner employs multiple strategies to achieve low NOx efficiency. Three fluids, preferably air, fuel, and oxygen / oxygen-enriched air, are supplied through spatially separated outlets / ports, thereby simultaneously reducing the interaction of O2, N2, and high temperature at a localized location.

[0052] Furthermore, this burner design enables localized interactions between fuel / air and fuel / O2 combustion, thereby helping to increase the separation of the high-temperature zone (fuel / O2 combustion) from air and, consequently, N2.

[0053] Furthermore, this burner design allows for rapid and thorough mixing of the air-fuel mixture at the ignition point. This is achieved through a unique burner cup tip (ignition chamber) design that incorporates air entrainment in the fuel jet, allowing for a lower peak temperature compared to the typical characteristics of non-premixed burners. The lower peak temperature, compared to conventional air-fuel non-premixed combustion, helps reduce the formation of hot NOx.

[0054] While fuel and / or oxidizer staging is a generally known technique for reducing peak temperatures in the flame and reducing NOx formation, this burner may involve oxidizer staging to help reduce peak temperatures and thus reduce NOx formation through distributed combustion.

[0055] Furthermore, the burner of the present invention can be further optimized by a fixed fuel split ratio, so that no active control is required when switching from air-fuel mode to air-oxygen-fuel mode, thereby reducing the cost of burner operation.

[0056] Finally, the two fuel supply ports play an important role in optimizing burner operation to account for changes in fuel composition, such as from NG or H2 to NG / H2 fuel mixtures based on the fuel supplier.

[0057] This burner allows for starting / ignition with a low equivalence ratio (lean fuel start) as low as 0.25, especially when it is impossible to reduce the airflow rate below a certain setpoint, while minimizing the start-up fuel flow for safety reasons. The equivalence ratio is defined as the ratio of the actual fuel / air molar ratio to the stoichiometric fuel / air molar ratio.

[0058] Specifically, in the first embodiment of this document, a burner (1) is provided, comprising an ignition source (10); a primary fuel conduit (20) comprising a primary fuel outlet (22) having multiple primary fuel outlet holes (23) for supplying primary fuel to an ignition chamber (25) located within the primary fuel conduit (20) and extending from the primary fuel outlet (22) to an end plane (24) of the primary fuel conduit, wherein the wall (29) of the primary fuel conduit surrounding the ignition chamber (25) comprises a plurality of vent holes (28); and a main oxidizer conduit (30) for supplying main oxidizer, comprising a portion (5) located downstream of the burner. The intermediate annular conduit (35) is configured to allow the diversion of the main oxidant, such that a first portion is introduced into the ignition chamber (25) through the plurality of vent holes (28) to mix with the primary fuel; the secondary fuel conduit (40) is used to supply secondary fuel and has a secondary fuel outlet (44) at its downstream end, wherein at least in the downstream portion (5) of the burner (1), the primary fuel conduit (20) is surrounded by the main oxidant conduit (30) and the secondary fuel conduit (40), and in the downstream portion, there are a primary fuel outlet (22), an ignition chamber (25), an intermediate annular conduit (35) and a secondary fuel outlet (44).

[0059] As used herein, the phrase "downstream portion of a burner having" certain outlets refers to a downstream portion that includes all said outlets. Furthermore, said portion further includes a cyclone section and / or a vent.

[0060] The term "downstream portion" may be used interchangeably with the term "downstream section" in this document.

[0061] In a preferred embodiment herein, at least in the downstream portion (5) of the burner (1), the main oxidizer conduit (30) and the secondary fuel conduit (40) are arranged substantially concentrically around the primary fuel conduit (20), and in this downstream portion there are a primary fuel outlet (22), an ignition chamber (25), an intermediate annular conduit (35) and a secondary fuel outlet (44).

[0062] In certain embodiments of the invention, one or more given concentric conduits are arranged around one or more given other conduits, the conduits being arranged around the other in a section corresponding to at least 20%, preferably at least 30%, particularly at least 40%, especially at least 50%, and in some embodiments at least 75% of the total length of the burner, wherein said section includes a primary fuel outlet, a main oxidizer outlet, a secondary fuel outlet, and an auxiliary oxidizer outlet. Furthermore, where a swirler section and / or a vent ring are also present, said portion preferably further includes a swirler section or a vent ring.

[0063] In this document, the 'total length' of the burner of the present invention is determined by establishing the distance between the farthest upstream end of all conduits and the farthest downstream end of all conduits.

[0064] In another preferred embodiment, the primary fuel conduit, the main oxidant conduit, and the secondary fuel conduit (and optionally the auxiliary oxidant conduit) are arranged concentrically around the central ignition source along their entire length.

[0065] In a preferred embodiment of the invention, a given catheter is arranged concentrically around another catheter, resulting in the formation of a corresponding ring.

[0066] Therefore, in the preferred embodiment herein, the burner is configured such that one or more fuels or oxidants flow through at least one annular zone. In this invention, such an annular zone may be further characterized by including other elements of the respective conduits as defined elsewhere herein (such as outlet orifices, vents, swirler sections, etc.).

[0067] Similarly, in the preferred embodiments described herein, the burner is characterized in that one or more outlets of the duct are configured as annular rings. In this invention, such annular rings may be characterized in that they contain other elements as defined elsewhere herein (such as outlet orifices, vents, swirler sections, etc.).

[0068] Generally speaking, in this invention, if a catheter has a smaller diameter than one (or more) other catheters and is arranged inside the other catheters, then the catheter is described as being "surrounded" by the other catheters (or each of the other catheters).

[0069] However, in order to be 'surrounded' by another conduit, a given conduit does not need to be completely surrounded by another conduit, and may extend further downstream and / or upstream from the other conduit. Various definitions apply herein, where a given element is referred to as being 'arranged around' another element.

[0070] In a preferred embodiment, the catheter described as being surrounded by (one or more) other catheters shares its longitudinal axis with (one or more) other catheters.

[0071] In a preferred embodiment, the ignition chamber (25) extends from the primary fuel conduit outlet plane (55) to the intermediate annular conduit outlet plane (56).

[0072] In some preferred embodiments, the ignition chamber (25) is characterized by at least two (preferably two or three) steps on its wall, each step comprising a row of vent holes (28).

[0073] In some preferred embodiments, the ignition chamber (25) includes a section having an outer diameter that is less than or equal to the inner diameter of the primary fuel conduit (20).

[0074] In some preferred embodiments, the ignition chamber (25) further includes a section having an inner diameter greater than the outer diameter of the primary fuel conduit (20) but a smaller outer diameter than the inner diameter of the intermediate annular conduit (35).

[0075] More specifically, in a particular set of embodiments, the burner is characterized in that the ignition chamber (25) extends from the primary fuel outlet (22) to the intermediate annular duct outlet plane (56), wherein the wall surrounding the ignition chamber (25) includes at least two (preferably two or three) steps of an annular duct with an increased diameter, each of the at least two steps including a plurality of vent holes (28).

[0076] In another specific embodiment, the burner is characterized in that the ignition chamber (25) extends from the primary fuel outlet (22) to the intermediate annular conduit outlet plane (56), wherein the wall surrounding the ignition chamber (25) comprises two sections, wherein i) the first section extends from the primary fuel outlet (22) to the primary fuel conduit end plane (24), wherein the primary fuel conduit wall (29) surrounding the section comprises a plurality of vent holes (28), and ii) the second section has an inner diameter greater than the outer diameter of the primary fuel conduit (20), but the second section has an inner diameter smaller than the inner diameter of the intermediate annular conduit (35). The burner has an outer diameter and includes a plurality of additional vent holes (28), wherein iii) the burner optionally further includes an air purging plate (73) having a purging hole (32) extending between the outer diameter of the first section and the inner diameter of the second section, and iv) the burner optionally further includes two mechanical mixer plates (74), each of which is located downstream of and adjacent to the two sections, and v) an air purging plate (73) having a purging hole (32) existing between the outer diameter of the second section and the inner diameter of the intermediate annular duct (35).

[0077] Preferably, the mechanical mixer plate (74) has a disc-shaped structure that interrupts the fuel flow from the primary fuel outlet (23). Specifically, the first mechanical mixer plate has a disc-shaped structure (mechanical mixer 1) that interrupts the fuel flow from the "external series" of the primary fuel outlet (23). The disc interrupts this fuel jet, facilitating rapid mixing of fuel and air within the ignition chamber.

[0078] Preferably, the air purging plate (73) is a disc containing purging holes (32). More preferably, the plate / disc is located between the fuel conduit wall (29) and the intermediate conduit wall located inside the conduit (35).

[0079] In another specific embodiment, the burner is characterized in that the ignition chamber (25) extends from the primary fuel outlet (22) to the intermediate annular conduit outlet plane (56), wherein the wall surrounding the ignition chamber (25) comprises two sections, wherein i) the first section has an outer diameter smaller than the inner diameter of the primary fuel conduit (20) and comprises a plurality of vent holes (28), wherein the wall (29) of the primary fuel conduit surrounding the first section comprises a plurality of vent holes (28), and wherein the first section further comprises allowing the primary oxidant to additionally enter the ignition chamber (25) along the flow direction between the two annulus of the primary fuel outlet orifice. The components, ii) the second section has an inner diameter greater than the outer diameter of the first fuel conduit (20), but the second section has an outer diameter smaller than the inner diameter of the intermediate annular conduit (35), and includes a plurality of additional vent holes (28), and wherein the burner optionally further includes iii) an air purging plate (73) having a purging hole (32) between the outer diameter of the first section and the inner diameter of the second section, and iv) the burner optionally further includes an air purging plate (73) having a purging hole (32) between the outer diameter of the second section and the inner diameter of the intermediate annular conduit (35).

[0080] In some preferred embodiments, the ignition chamber (25) includes an ignition cup (75) and an oxidizer venting cup (76). Preferably, the ignition cup (75) is contained in a first section of the ignition chamber (25), and the oxidizer venting cup (76) is contained in a second section of the ignition chamber (25), wherein the second section is located downstream of the first section.

[0081] More specifically, in a particular set of embodiments, the burner is characterized in that the ignition chamber (25) extends from the primary fuel outlet (22) to the intermediate annular conduit outlet plane (56), wherein the wall surrounding the ignition chamber (25) comprises two sections, wherein i) the first section has an outer diameter less than or equal to the outer diameter of the primary fuel conduit (20) and comprises a plurality of vent holes (28), wherein the wall surrounding the first section comprises a plurality of vent holes (28), and wherein the first section further comprises a component that allows the primary oxidant to further enter the ignition chamber (25) along the flow direction, ii) the second section has an inner diameter greater than the outer diameter of the primary fuel conduit (20), but the second section has an outer diameter smaller than the inner diameter of the intermediate annular conduit (35), and comprises another plurality of vent holes (28). Preferably, the burner further includes an air purging plate (73) with purging holes (32) located between the outer diameter of the first section and the inner diameter of the second section. Preferably, the burner further includes an air purging plate (73) with purging holes (32) located between the outer diameter of the second section and the inner diameter of the intermediate annular duct (35). Preferably, the burner optionally further includes a mechanical mixer plate (74) located downstream of and adjacent to the first section.

[0082] Preferably, in this document, the burner further includes an ignition source (10) which preferably terminates in the ignition chamber (25).

[0083] In some embodiments, the ignition source (10) is a central ignition source having a central axis (15) and a conduit end plane (16).

[0084] In a preferred embodiment of this document, the main shaft (2) of the burner (1) coincides with the central shaft (15) of the ignition source (10).

[0085] Preferably, at least in the downstream portion (5) of the burner (1), the central ignition source (10) is surrounded by the primary fuel conduit (20), the main oxidant conduit (30) and the secondary fuel conduit (40), and optionally the plurality of auxiliary oxidant conduits (50).

[0086] In some embodiments, the main shaft (2) of the burner (1) coincides with the central shaft (15) of the ignition source (10).

[0087] Furthermore, regarding the ignition source (10), it may be designated as 'pipe 1' in this document.

[0088] The (central) ignition source may also be referred to as the 'igniter' in this article.

[0089] In this paper, the outer diameter of the ignition source (10) can be defined as D2.

[0090] As shown, for example, in Figure 2A, the burner may further include a central ignition source wall (19). Thus, the central ignition source wall (19) may have an outer diameter D2.

[0091] Furthermore, the central ignition source is preferably located at the center of the burner, preferably along its entire length, especially in which the other ducts of the burner are arranged concentrically around the central ignition source.

[0092] Furthermore, regarding the primary fuel conduit (20), which may be designated as "pipe 2" herein, it is a gas fuel conduit.

[0093] In this paper, the inner diameter of the primary fuel conduit (20) can be defined as D3.

[0094] Therefore, the wall of the primary fuel conduit (29) may have an inner diameter D3.

[0095] In some embodiments, the primary fuel conduit end plane (24) corresponds to the ignition chamber end plane (26).

[0096] The primary fuel conduit (20) further includes a primary fuel outlet (22). In some embodiments, the primary fuel outlet (22) is configured as a plate including a primary fuel outlet orifice (23), particularly as an air purging plate including a primary fuel outlet orifice (23).

[0097] As shown, for example, in Figures 1A and 1B, the primary fuel conduit (20) may further include a specific primary fuel connector (21).

[0098] In this document, as shown, for example, in Figure 3A, the distance between the primary fuel outlet (22) and the primary fuel conduit end plane (24) and / or the ignition chamber end plane (26) can be defined as L0. Therefore, in some embodiments, the primary fuel outlet (22) is recessed by a distance L0 from the primary fuel conduit end plane (24) in the upstream direction. Preferably, the primary fuel conduit end plane (24) corresponds to the ignition chamber end plane (26).

[0099] In the burner described herein, the primary fuel conduit (20), more specifically the primary fuel outlet (22), further includes a primary fuel outlet orifice (23). Therefore, the primary fuel outlet (22) may also be designated herein as a 'fuel distribution nozzle'. The outlet / nozzle may be described as having multiple orifices that introduce the primary fuel into the ignition chamber.

[0100] In this paper, the diameter of the primary fuel outlet orifice (23) can be defined as D0. Preferably, D0 / D2 is between 0.04 and 0.5.

[0101] In a particular embodiment, the primary fuel outlet orifice (23) is located on a concentric circle surrounding the center of the primary fuel outlet plate. Preferably, the total number of concentric circles is in the range of 2 to 7, more preferably, the total number of concentric circles is between 2 and 5. Preferably, the orifice is circular. The orifice can be any other shape, such as star-shaped, triangular, double-star-shaped, rectangular, etc.

[0102] Not wanting to be bound by theory, this size significantly contributes to the ability to quickly mix fuel with the surrounding air.

[0103] In this paper, as shown for example in Figure 4, the circumferential angle defined by the center of the main shaft (2) of the burner and the two adjacent primary fuel outlet holes (23) can be defined as angle θ.

[0104] In the burner described herein, the primary fuel conduit (20) further includes a vent (28).

[0105] In this paper, the inner diameter of the vent (28) can be defined as P1. Preferably, P1 / D2 is between 0.05 and 0.4.

[0106] In a particular embodiment, the vent holes (28) are arranged in rows around the primary fuel conduit. Preferably, there will be no more than 5 rows of vent holes; more preferably, no more than 3 rows of vent holes. Preferably, the holes are circular. The holes can be any other shape, such as star-shaped, triangular, double-star-shaped, rectangular, etc.

[0107] In this document, as shown, for example, in Figure 5, the axial distance between the two rows of vent holes (28), measured between their centers, can be defined as H.

[0108] In this paper, the circumferential angle defined by the center of the main shaft (2) of the burner and the two adjacent vent holes (28) can be defined as angle α.

[0109] In a particular embodiment herein, the primary fuel conduit (20) further includes an air premixing orifice (27), preferably upstream of the primary fuel outlet (22).

[0110] In this paper, the diameter of the air premixing orifice (27) can be defined as P0. Preferably, P0 / D2 is between 0.02 and 0.2.

[0111] In a particular embodiment, the air premixing orifices (27) are arranged in rows around the primary fuel conduit. Preferably, there are no more than five rows of premixing orifices. More preferably, there are no more than three rows of premixing orifices. Preferably, the orifices are circular. The orifices can be any other shape, such as star-shaped, triangular, double-star-shaped, rectangular, etc.

[0112] In this paper, the distance between the primary fuel conduit wall (29) and the intermediate annular conduit wall (37) can be defined as L4.

[0113] Furthermore, regarding the main oxidant conduit (30), it may be designated herein as "pipe 3", and in particular as air pipe.

[0114] In this paper, the inner diameter of the main oxidant conduit (30) can be defined as D4.

[0115] Therefore, the wall (39) of the main oxidant conduit can have an inner diameter D4.

[0116] In this document, the distance between the intermediate annular conduit end plane (36) and the main oxidant conduit end plane (38) can be defined as L2. Therefore, in some embodiments, the intermediate annular conduit end plane (36) is recessed from the main oxidant conduit end plane (38) by a distance L2 in the upstream direction.

[0117] In the burner described herein, the main oxidizer conduit (30) further includes an intermediate annular conduit (35).

[0118] In this invention, the intermediate annular conduit (35) is configured to allow the main oxidant to be divided into two parts, such that the first part is introduced into the ignition chamber (25) via a plurality of vent holes (28) as defined above.

[0119] The first portion is preferably about 20% of the total volumetric flow rate. In a particular embodiment, the first portion is in the range of 2% to 40%, preferably in the range of 10% to 25%.

[0120] In a preferred embodiment herein, the first portion of the primary oxidant enters the ignition chamber at a right angle to the primary fuel outlet (via the peripheral wall of the chamber).

[0121] Therefore, in the preferred embodiment of this document, the first portion of the primary oxidant enters the ignition chamber in a direction perpendicular to the flow direction of the primary fuel.

[0122] Not wanting to be bound by theory, this method uses vigorous mixing of fuel and 'ignition' air to reduce peak flame temperature compared to a typical diffuse flame. This is considered important for minimizing NOx emissions from the flame. Furthermore, the air introduction method also keeps the peripheral walls cool by protecting them from direct contact with the flame.

[0123] In this document, the distance between the primary fuel conduit end plane (24) and the intermediate annular conduit end plane (36) can be defined as L1. Therefore, in some embodiments, the primary fuel conduit end plane (24) is recessed from the intermediate annular conduit end plane (36) by a distance L1 in the upstream direction.

[0124] In a preferred embodiment of the invention, the burners are characterized in that the main oxidant conduit (30) further includes a cyclone section (33).

[0125] Therefore, the intermediate annular conduit (35) is preferably configured to allow the main oxidant to be divided into two parts, with the second part being introduced into the hydrocyclone section (33).

[0126] In particular, in a preferred embodiment herein, the annular conduit (35) is configured to allow the main oxidant to be divided into two parts, such that the first part is introduced into the ignition chamber (25) via the plurality of vent holes (28) to mix with the primary fuel, and the second part is introduced into a cyclone section (33) that further includes the main oxidant conduit.

[0127] To avoid being bound by theory, a second portion of the air introduced into the swirler section creates a strong tangential flow field in the combustion chamber, which increases the mixing rate between the oxidizer and the fuel, while also producing a compact flame and a flame without significant soot.

[0128] Similarly, to avoid being bound by theory, the use of vortex generators to rotate air is well-known in the field of combustion. The main function of the vortex is to provide tangential flow to, for example, the air leaving tube 3, and to create a recirculation zone at the center. This recirculation zone brings the hot combustion gases back to the burner outlet plane, thereby providing a continuous ignition source for new reactants. The upper and lower limits of the vortex angle are determined by the furnace length and the burner combustion rate.

[0129] Preferably, the vortex angle is 5-60 degrees, more preferably 30-45 degrees.

[0130] As used herein, the vortex angle is defined as the angle between a plane nominally tangent to the outlet of the cyclone blades and a plane parallel to the main axis of the burner.

[0131] Preferably, in this paper, the vortex number (defined herein as the ratio of the axial flux of tangential momentum to the axial flux of axial momentum) is in the range of 0.1 to 1.5.

[0132] In some embodiments, the main oxidant conduit (30) further includes a scavenging hole (32) located on the air scavenging plate (73), particularly in the flow direction parallel to the main shaft (2) of the burner.

[0133] In this document, the diameter of the cleaning holes (32) can be defined as D1. Preferably, D1 / D2 is between 0.04 and 0.5.

[0134] In a particular embodiment, the cleaning holes (32) are arranged in a circular manner on different concentric diameters, in 1-7 rows, preferably 1-3 rows of holes with concentric diameters. Preferably, the holes are circular in shape. The holes can be any other shape, such as star-shaped, triangular, double-star-shaped, rectangular, etc.

[0135] In this paper, the circumferential angle defined by the center of the main shaft (2) of the burner and the two adjacent cleaning holes (32) can be defined as angle β.

[0136] The main oxidant conduit (30) may further include a specific main oxidant connector (31).

[0137] Furthermore, regarding the secondary fuel conduit (40), which may be designated as "pipe 4" herein, it is a gaseous fuel conduit.

[0138] In this paper, the inner diameter of the secondary fuel conduit (40) can be defined as D5.

[0139] Therefore, the secondary fuel conduit wall (49) may have an inner diameter D5.

[0140] In some embodiments, the burner (1) is further included in a turbulence generator (47) within the secondary fuel conduit (40).

[0141] The turbulence generator may also be referred to herein as a component for generating turbulence or a turbulence generator component. Each may comprise one or more turbulence generator disks or turbulence generator plates. Preferably, the turbulence generator component is arranged at an additional wall of the secondary fuel conduit, the additional wall being positioned adjacent to the wall of the main oxidizer conduit.

[0142] In this document, the distance between the main oxidant conduit end plane (38) and the secondary fuel conduit end plane (46) can be defined as L3. Therefore, in some embodiments, the main oxidant conduit end plane (38) is recessed from the secondary fuel conduit end plane (46) by a distance L3 in the upstream direction. Preferably, the secondary fuel conduit end plane (46) corresponds to the end plane of the co-oxidant conduit (50).

[0143] The secondary fuel conduit (40) may further include a specific secondary fuel connector (41).

[0144] In a preferred embodiment of the invention, as also shown in FIG. 2B, the burner further includes a plurality of oxidant conduits (50) for supplying an oxidant (e.g., air, oxygen, or a combination thereof). Hereinafter, the latter may also be designated as 'oxidant'. The plurality of oxidant conduits (50) may further include an oxidant connector (51).

[0145] Preferably, these catheters are arranged as the outer ring of the catheter. These catheters are used for oxygen enrichment. In a preferred embodiment of the invention, the oxidant conduits (50) may have turbulence generating devices (57) to increase the mixing of the jet with the combustion atmosphere and / or may be angled inward toward the center of the burner (preferably 0.2 to 25 degrees, more preferably 0.25 to 10.0 degrees, more preferably 0.5 to 5.0 degrees).

[0146] In a preferred embodiment, the oxidant is 80% to 100% oxygen by volume purity. In a preferred alternative embodiment, the oxidant is 23% to 50% (volume) oxygen-enriched air.

[0147] Without being bound by theory, this configuration helps to spatially separate the oxygen / oxygen-enriched air inlet from the fuel inlet, thereby enabling delayed mixing and combustion, and producing a flameless / low NOx burner.

[0148] In this document, as shown, for example, in Figure 3B, the distance between the centers of the two oxidant conduits (50) positioned relative to each other with respect to the main shaft (2) of the burner can be defined as D6.

[0149] In this paper, the inner diameter of such oxidant conduits (50) can be defined as D7.

[0150] Therefore, the wall (59) of the oxidant conduit can have an inner diameter D7.

[0151] In this paper, the angle defined by the center of the main shaft (2) of the burner and the two adjacent oxidant conduits (50) can be defined as angle η.

[0152] The burners of this invention are designed to operate using any gaseous fuel, such as natural gas (NG), hydrogen (H2), LPG, biogas, syngas, ammonia, or other gases.

[0153] Therefore, according to the present invention, the primary fuel used in the burner can be any gaseous fuel. In a preferred embodiment, it is selected from the group consisting of natural gas (NG), hydrogen (H2), LPG, biogas, syngas, and ammonia. In other embodiments, it is selected from natural gas (NG), a mixture of NG / H2 and hydrogen.

[0154] According to the present invention, the secondary fuel is any gaseous fuel. In a preferred embodiment, it is selected from the group consisting of natural gas (NG), hydrogen (H2), LPG, biogas, syngas, and ammonia. In other embodiments, it is selected from natural gas (NG), a mixture of NG / H2 and hydrogen.

[0155] In a preferred embodiment, the primary oxidant is air.

[0156] Generally, there are no particular limitations on the specific properties of the fuel and oxidant used with the burner of the present invention. Furthermore, in some embodiments, the material flowing through a particular conduit (e.g., fuel or oxidant) may be replaced with a material (e.g., oxidant or fuel) that is the same as or different from the material disclosed above. For example, an oxidant may be used instead of the secondary fuel in the burner (1). In this particular embodiment, fuel flows through the primary fuel conduit (20) of the burner (1), while the oxidant flows through the main oxidant conduit (30), the secondary fuel conduit (40), and optionally the oxidant conduit (50). Alternatively, in some embodiments, secondary fuel may be used instead of the main oxidant. In this embodiment, fuel flows through the primary fuel conduit (20) and the main oxidant conduit (30) of the burner (1), while the oxidant or fuel flows through the secondary fuel conduits (40) and optionally the oxidant conduit (50). In other words, any combination of fuel or oxidant may flow through the primary fuel conduit (20), the main oxidant conduit (30), the secondary fuel conduit (40), and optionally the auxiliary oxidant conduit of the burner (1).

[0157] As used herein, the 'outlet plane' of a given conduit refers to a plane defined downstream in a direction perpendicular to the main axis of the conduit, where the fuel or oxidant is no longer confined by the two walls.

[0158] As used herein, the 'catheter end plane' of a given catheter refers to a plane defined at the downstream end of the catheter along a direction perpendicular to the main axis of the catheter.

[0159] In the preferred embodiments herein, D3 / D2 is 1.5 to 4.5, particularly 2.0 to 3.0.

[0160] In the preferred embodiments herein, D4 / D2 is 3.0 to 9.0, particularly 3.5 to 5.5.

[0161] In the preferred embodiments herein, D5 / D2 is 5.0 to 11.0, particularly 5.5 to 7.0.

[0162] In the preferred embodiments herein, L1 / L4 is 0.5 to 2.5, particularly 1.0 to 2.0.

[0163] In the preferred embodiments herein, L0 / D3 is 0.25 to 1.0, particularly 0.4 to 0.6.

[0164] In the preferred embodiments herein, (L1+L2) / D3 is 0.25 to 1.0, particularly 0.4 to 0.6.

[0165] In the preferred embodiments herein, L3 / D4 is 0.05 to 0.25, particularly 0.1 to 0.2.

[0166] In the preferred embodiments herein, D6 / D2 is 9.0 to 22.0, particularly 10.0 to 14.0.

[0167] In the preferred embodiments herein, D6 / D5 is 1.75 to 2.5, particularly 1.8 to 2.1.

[0168] In the preferred embodiments herein, D7 / D2 is 0.15 to 1.0, particularly 0.25 to 0.75.

[0169] In the preferred embodiments described herein, H / P1 is 1.25 to 2.5.

[0170] In the preferred embodiment described herein, angle α is 3 to 30 degrees, such as 10 to 20 degrees. The ratio of the area of ​​all vents 28 in a row (having a diameter P1) to the surface area of ​​the cylinder with an outer diameter D2 and a height P1 is between 10% and 55%.

[0171] To avoid being bound by theory, a lower range of angle α helps to separate the orifices so that they are not too close to interfere with the mixing of fuel and air, while a higher range of angle α prevents the orifices from being too far apart and ensures sufficient fluid communication between adjacent jets to enhance fuel-air mixing and ignition in the ignition chamber.

[0172] Each series can be symmetrically interleaved to provide a three-dimensional mixing effect. This mixing is crucial for providing a reliable ignition system for the burner at lean equivalence ratios as low as 0.25.

[0173] In the preferred embodiment described herein, angle β is 5-40 degrees.

[0174] The air purging plate (73) has a porosity in the range of 2% to 15% (defined by dividing the total open area on the plate that allows the air to flow by the cross-sectional area of ​​the plate).

[0175] To avoid being bound by theory, a lower angle β helps separate the orifices, preventing them from becoming too close and creating air-rich areas, while a higher angle β prevents the orifices from becoming too far apart, ensuring sufficient fluid communication between adjacent jets to mutually support the chemically active flame radicals that provide ignition, thereby enhancing flame stability. Sufficient air is used for fuel-air mixing, and a low-velocity zone and recirculation zone are created to provide a flame anchoring zone. This flame anchoring position is crucial for maintaining the flame without extinguishing it, for example, in extreme cases such as when the primary fuel is reduced to 10% of the burner's maximum combustion rating and the secondary fuel is cut off / shut down.

[0176] In some embodiments, the burner includes different series of holes, and the consecutive holes in the different series of holes are staggered by half the included angle between two consecutive holes in a series.

[0177] In the preferred embodiment described herein, the angle θ is 10-40 degrees.

[0178] The primary fuel outlet plate (72) has a porosity in the range of 2% to 25% (defined by dividing the total open area on the plate that allows airflow by the cross-sectional area of ​​the plate).

[0179] To avoid being bound by theory, a lower range of angle θ helps to separate the orifices, preventing them from getting too close when the two fuel jets become too close to prevent air entrainment in the fuel jets, while a higher range of angle θ prevents the orifices from being too far apart and ensures sufficient coupling between the two jets to provide a stable flame, a wide range of descent, and equivalence ratio overall.

[0180] In the preferred embodiment of this document, the angle η is 10-70 degrees, particularly 40-60 degrees.

[0181] In some embodiments, the burner includes different rows of holes, and consecutive holes in different series of holes are staggered by half the included angle between two consecutive holes in a row.

[0182] In a preferred embodiment, the burner (1) is configured such that the velocity of the primary fuel at the outlet of the primary fuel outlet (23) is between 30 ft / s and 500 ft / s, particularly between 40 ft / s and 400 ft / s.

[0183] Without being bound by theory, the velocity of first-stage fuel was determined to significantly contribute to its ability to mix rapidly with the surrounding air. This velocity range provides a stable flame without any stripping.

[0184] In a preferred embodiment, the burner (1) is configured such that the velocity of the main oxidant at the oxidant section outlet (34) is between 5 ft / s and 300 ft / s, particularly between 10 ft / s and 200 ft / s.

[0185] To avoid being bound by theory, the maximum achievable primary oxidant (preferably air) velocity is typically determined by the available pressure from the blower. The inventors have discovered that such velocities, along with appropriate vortex angles, provide adequate mixing of the air and both fuels, and maintain a stable flame even in cold furnaces across a wide range of burner operations.

[0186] In a preferred embodiment, the burner (1) is configured such that the velocity of the secondary fuel is between 20 ft / s and 200 ft / s, particularly between 40 ft / s and 120 ft / s.

[0187] To avoid being bound by theory, the velocity of the secondary fuel is determined to provide sufficient mixing with the swirling air, thereby achieving a stable flame. A secondary fuel velocity below the low-velocity limit can cause unreacted fuel to accumulate near the furnace wall. This fuel can then burn there, causing overheating of the reburner top wall. In a preferred embodiment, the burner (1) is configured such that the velocity of the oxidant is between 50 ft / s and 500 ft / s, particularly between 100 ft / s and 300 ft / s.

[0188] To avoid being bound by theory, the velocities of staged oxidizers / co-oxidizers are typically kept high, allowing the enriched air or oxygen jet to entrain surrounding combustion gases and reduce the local oxygen concentration before this high-oxygen-concentration jet encounters the fuel and / or partially burned fuel / air mixture. This facilitates delayed mixing of the fuel and oxidizer, contributing to spacious combustion and lower thermal NOx. An upper limit is set so that the momentum is not high enough to cause delayed mixing, resulting in unburned fuel leaving the furnace. This is especially important if the furnace width or length is small. Furthermore, further increasing the velocity will increase the supply pressure requirements. Increased supply pressure will necessitate a secondary compression unit, which increases the operating costs of the burner.

[0189] In a preferred embodiment, the burner of the present invention operates in such a manner that... i) During startup, approximately 100% of the total thermal power of the burner (defined as the sum of the products of the calorific value (higher or lower) and the flow rate of each fuel) is provided by that primary fuel; and / or ii) During normal operation, about 25 to 65%, preferably 45 to 65%, of the total calorific value of the burner is provided by the primary fuel, and the remainder is provided by the secondary fuel. The remaining portions are preferably supplied by the secondary fuel.

[0190] In a preferred embodiment, the burner is configured such that i) the volumetric flow rate of the oxidant in the ignition chamber is about 5-25% of the total main oxidant flow rate; and / or ii) the volumetric flow rate of the premixed oxidant is about 2-10% of the total main oxidant flow rate; and / or iii) the volumetric flow rate of the oxidant transferred to the auxiliary oxidant conduits (50) is about 2-5% of the main oxidant flow rate.

[0191] In a specific conduit, the volumetric flow rate of any fluid is divided between different outlets by relating the cross-sectional area of ​​individual outlets to the total cross-sectional area of ​​the outlets of other conduits. In doing so, the fluid pressure and the pressure difference between two adjacent conduits are important criteria for determining the directional flow of the fluid. For example, Figure 6B shows the sample area markings of an oxidant conduit. The cross-sectional areas of the vent (28), air scavenging hole (32), oxidant section outlet (34), and premixing hole (27) are A0, A1, A2, and A3, respectively.

[0192] A0 = (A0 + A1 + A2 + A3) / 5 - 25%

[0193] A3 = (A0 + A1 + A2 + A3) / 2 - 10%

[0194] Therefore, in the preferred embodiment of this article, the cross-sectional areas of the vent hole (28), the air removal hole (32), the oxidant section outlet (34) and the premixing hole (27) are A0, A1, A2 and A3, respectively, wherein A0 = 5-25% of (A0+A1+A2+A3).

[0195] Similarly, in the preferred embodiment of this article, the cross-sectional areas of the vent hole (28), the air removal hole (32), the oxidant section outlet (34) and the premixing hole (27) are A0, A1, A2 and A3, respectively, wherein A3 = 2-10% of (A0+A1+A2+A3).

[0196] Preferably, in this document, the secondary fuel conduit (40) is located close to the main oxidant conduit (30), wherein D5 / D4 is preferably between 1.05 and 1.40, and more preferably between 1.1 and 1.25. This allows the flow and ignition of the secondary fuel to be initiated by heat from the primary fuel flame (which acts as the ignition flame for the secondary fuel), without requiring a furnace temperature higher than the auto-ignition temperature of the secondary fuel and / or without requiring an ignition source to ignite the secondary fuel. Further specific embodiments of the invention are described in the accompanying drawings, which have been summarized above and can be further described in detail below:

[0197] As shown, for example, in Figure 6A, a portion of the primary oxidant (typically 2%-40% of the total, preferably 10%-25%, such as about 20%) is introduced into the ignition chamber via the peripheral wall of a chamber perpendicular to the fuel distribution nozzle. This is used to vigorously mix the fuel and 'ignition' air so that ignition can reliably and repeatedly occur in a gas mixture within the combustible range of fuel concentration, while also reducing the peak flame temperature compared to a typical diffuse flame. This is considered important for minimizing NOx emissions from the flame. Furthermore, the method of air introduction also keeps the peripheral wall cooled by protecting it from direct contact with the flame. The fuel distribution plate (72) (the term may be used interchangeably herein with 'primary fuel outlet plate') is recessed by a length of L0+L1 to provide more length for the fuel jet to partially or completely develop and partially premix with the 'ignition cup' air.

[0198] More specifically, in a preferred embodiment, the distribution plate is recessed from the hot side of the burner by a length of L0+L1+L2 or L01+L1+L2 (as also shown, for example, in Figure 10). More specifically, a portion of the main oxidant (typically about 20% of the total) is introduced into the "ignition cup," and the "oxidant venting cup" enters through the peripheral wall of the chamber, which is perpendicular to the fuel distribution nozzle. The first portion entering the "ignition cup" mixes vigorously with a portion of the fuel and the "ignition" oxidant, allowing the mixture composition in the "ignition cup" to ignite the flame across a wide range of fuel and oxidant flow rates. The second portion entering the "oxidant venting cup" mixes with the fuel, resulting in a lower peak flame temperature compared to a typical diffuse flame. This is important for minimizing NOx emissions from the flame. Furthermore, the method of oxidant introduction also keeps the peripheral wall cool by protecting it from direct contact with the flame. The first portion of fuel in the "ignition cup" mixes with the "ignition oxidant." The mechanical mixer plate breaks up the fuel jet in this first section to mix with the ignition oxidizer. A second portion of the jet on plane 2, fuel recessed at L01+L1, provides sufficient length for the fuel jet to fully or partially develop and partially premix with the oxidizer in the oxidizer venting cup. This feature helps stabilize the flame over a wider range of equivalence ratios.

[0199] As shown, for example, in Figure 6B, these air premixing holes 27 enable fluid communication between the primary oxidant and the primary fuel upstream of the fuel distribution plate (72). The number and diameter of these holes, and the number of rows of holes, can be predetermined based on the area ratio of hole A3 to the vortex air outlet area, as well as the pressures of the air and primary fuel. The pre-calculated ratio depends on the amount of air required in the primary fuel during startup.

[0200] As highlighted in Figure 6C, there is an interaction between secondary fuels and staged oxidizers, and the importance of primary / secondary fuel and oxidizer staging. Primary and secondary fuels, in addition to contributing to NOx emission reduction, also help accommodate varying volumetric fuel flow rates when switching between NG and NG / H2 mixtures in this design. Furthermore, the "secondary fuel" helps create a "pseudo" isolation layer between the primary oxidizer and staged oxidizers, which can be approximately 90-100% oxygen pure, potentially helping to reduce the contact between N2 present in the primary oxidizer and the high-concentration oxygen jet from the primary oxidizer jet. Oxidizer staging is considered important for spatially separating the oxygen / oxygen-enriched air port from the fuel port, as it helps delay the mixing between fuel and oxidizer and facilitates spacious combustion that helps reduce thermal NOx formation. Additionally, the relatively high velocity of the staged oxidizer helps the oxygen / oxygen-enriched air jet entrain furnace gases, which helps reduce local oxygen concentrations, thereby contributing to reduced thermal NOx emissions.

[0201] Generally, the advantageous features of the present invention include the following, all of which correspond to other preferred embodiments of the first state: - The characteristic of the first-state burner may be that it is fuel-flexible (and, for example, allows the use of NG, H2, NG+H2 mixtures). This burner allows for reliable start-up in a cold furnace (below the auto-ignition temperature of the fuel) using an air-fuel mode. - The characteristic of the first-state burner is its flexible operation (and for example, it can operate as an air-fuel or air-oxygen-fuel burner). Therefore, the burner can switch between air-fuel (holding mode) and air-oxygen-fuel (melting mode) modes according to the operational needs of, for example, reheating or secondary melting furnaces, without any significant changes to the burner's control system. - The characteristic of the first-state burner is that it does not require water cooling. - The characteristics of a first-state burner may be that it allows for low NOx levels, for example, keeping NOx levels within environmental limits, especially through low NOx designs for both air-fuel and air-oxygen fuel modes. - The characteristic of the first-state burner is that it allows for low CO levels in both air-fuel and air-oxygen fuel modes. - The characteristic of the first-state burner is that the low back pressure of the combustion air and oxygen eliminates the need for any secondary compression device. - The characteristic of the first-state burner is that it can operate in air-fuel mode when oxygen is unavailable, regardless of the average furnace temperature. - The characteristic of the first-state burner is that the use of a single fuel, air and oxidant flow to supply fluid helps to reduce the total cost of skids, diverter valves and / or any complex control mechanisms. - The characteristic of the first-state burner is a reduction ratio of 1:30. - The characteristic of the first-state burner is that it produces a lean fuel-stabilized flame that does not extinguish under high excess air (equivalence ratio as low as 0.25). - The characteristic of the first-state burner is that it can achieve stable and reliable ignition and combustion under cold furnace conditions with an equivalence ratio as low as 0.25. In a particular embodiment of this document, the first-state burner is characterized by low back pressure of the main oxidant and oxygen / oxygen-enriched airflow, so that a secondary compressor unit is not required to increase the supply pressure.

[0202] In a second aspect of the invention, a furnace comprising a burner according to a first aspect of the invention is provided.

[0203] The preferred embodiment of the furnace of the present invention corresponds to the embodiment of the burner of the present invention described above. Therefore, preferably, the furnace is further defined according to any of the above embodiments of the burner described in the context of the first example.

[0204] This includes embodiments relating to the aforementioned advantages of the burner in the first state, and such embodiments are also discussed herein with regard to the respective furnaces of the second state.

[0205] In some preferred embodiments, the furnace is selected from a group consisting of furnaces used for steam methane reforming, reheat furnaces in the steel industry, and secondary melting furnaces.

[0206] In a third aspect of the present invention, a method is provided for operating a burner of the first aspect and / or for operating a furnace of the second aspect.

[0207] Those familiar with this technique will easily understand that the method described has no particular limitations.

[0208] In some embodiments, the method includes the following steps: i) starting the burner, ii) gradually increasing the combustion rate of the burner, iii) starting the secondary fuel, iv) further gradually increasing the combustion rate of the burner, and v) optionally supplying the oxidant to the burner.

[0209] In a specific embodiment of the third state, step i) includes activating the main oxidant, the igniter, and the primary fuel.

[0210] Generally, further preferred embodiments of the method of the present invention correspond to the embodiments of the burner of the present invention described above, wherein the burner used in the method is further defined by additional product features. In other words, preferably, the method of the present invention is further defined according to any of the above embodiments of the burner described in the context of the first example.

[0211] Furthermore, a further preferred embodiment of the method of the present invention relates to further method features, which are based on any features described above in conjunction with the burner of the present invention.

[0212] Furthermore, the advantages of the present invention include the following, all of which correspond to a further preferred embodiment of the third state sample: - The third-state method is characterized by its fuel flexibility (and, for example, allows the use of NG, H2, or NG+H2 mixtures). This, for example, allows for reliable startup of cold furnaces using an air-fuel configuration. - A characteristic of the third-state method is its operational flexibility (and, for example, its ability to operate as an air-fuel or air-oxygen-fuel burner). Therefore, the method can switch between air-fuel (holding mode) and air-oxygen-fuel (melting mode) modes according to the operational needs of, for example, reheating or secondary melting furnaces, without requiring any significant changes to the burner's control system. - A characteristic of the third-state method is that it does not require water cooling. - A characteristic of the third-state approach is that it allows for low NOx levels, for example, keeping NOx levels within environmental limits, particularly for both air-fuel and air-oxygen fuel modes. - The characteristic of the third-state method is that the low back pressure of combustion air and oxygen eliminates the need for any secondary compression device. - The characteristic of the third-state method is that it can be carried out in an air-fuel mode when oxygen is unavailable, regardless of the average furnace temperature. - The third-state approach is characterized by using a single fuel, air, and oxidant stream to supply fluids, which helps reduce the total cost of skids, diverter valves, and / or any complex control mechanisms.

[0213] Furthermore, in general, in this document, a preferred embodiment of any of the second to fourth states corresponds to a preferred embodiment of the first state.

[0214] Generally, when applied to any feature in the embodiments of the invention described in this specification and the claims of this invention, the article "a / an" as used herein means one or more. The use of "a / an" does not limit the meaning to a single feature unless such limitation is explicitly stated. The article "the" preceding a singular or plural noun or noun phrase indicates one or more specific specified features and may have a singular or plural implied meaning depending on the context in which the article is used. The adjective "any" refers to any number of one, some, or all.

[0215] Furthermore, if an embodiment is described herein by using terms such as "comprising", other embodiments described herein by using terms such as "composed of" instead of the terms "comprising" are also envisioned. Other specific embodiments

[0216] This invention also relates particularly to the following items:

[0217] Project 1: A burner (1) comprising a primary fuel conduit (20) having a primary fuel outlet (22) having multiple primary fuel outlet holes (23) for supplying primary fuel to an ignition chamber (25), wherein a plurality of vent holes (28) are included around the wall of the ignition chamber (25); a main oxidizer conduit (30) for supplying main oxidizer, comprising an intermediate annular conduit (35) located in a downstream portion (5) of the burner, the intermediate annular conduit (35) being configured To allow for the diversion of the main oxidant, a first portion is introduced into the ignition chamber (25) via the plurality of vent holes (28) to mix with the primary fuel, and a second portion is optionally introduced into the oxidant section (33). Preferably, the burner further includes a plurality of oxidant conduits (50) for supplying an auxiliary oxidant, particularly wherein, at least in the downstream portion (5) of the burner (1), the primary fuel conduit (20) is surrounded by the main oxidant conduit (30) and the plurality of oxidant conduits (50).

[0218] Project 2 The burner as described in Project 1, wherein the burner further includes a secondary fuel conduit (40) for supplying secondary fuel and having a secondary fuel outlet (44) at its downstream end, wherein at least in the downstream portion (5) of the burner (1), the primary fuel conduit (20) is surrounded by the main oxidant conduit (30) and the secondary fuel conduit (40), and in the downstream portion there is a primary fuel outlet (22), an ignition chamber (25), an intermediate annular conduit (35) and a secondary fuel outlet (44).

[0219] Item 3: A burner as described in Item 1 or 2, wherein the burner further comprises a plurality of oxidant conduits (50) for supplying an oxidant, particularly wherein, at least in the downstream portion (5) of the burner (1), the primary fuel conduit (20) is surrounded by the main oxidant conduit (30), the secondary fuel conduit (40), and the plurality of oxidant conduits (50), and the downstream portion further comprises an oxidant outlet (54).

[0220] Item 4: A burner as described in any of the preceding items, wherein the burner (1) further includes an ignition source (10), particularly wherein the ignition source (10) terminates in the ignition chamber (25), particularly wherein the ignition source (10) is a central ignition source having a central axis (15) and a conduit end plane (16), particularly wherein the main axis (2) of the burner (1) coincides with the central axis (15) of the ignition source (10), particularly wherein at least in the downstream portion (5) of the burner (1), the central ignition source (10) is surrounded by the primary fuel conduit (20), the main oxidant conduit (30) and the secondary fuel conduit (40), and optionally the plurality of auxiliary oxidant conduits (50).

[0221] Item 5: A burner as described in any one of Items 1 to 4, wherein the ignition chamber (25) is located within the primary fuel conduit (20) and extends from the primary fuel outlet (22) to the end plane (24) of the primary fuel conduit, wherein the wall (29) of the primary fuel conduit surrounds the ignition chamber (25) and includes a plurality of vent holes (28).

[0222] Item 6 (see, for example, Figure 9A): a burner as described in any of Items 1 to 4, wherein the ignition chamber (25) extends from the primary fuel outlet (22) to the intermediate annular duct outlet plane (56), wherein the wall surrounding the ignition chamber (25) includes at least two (preferably two or three) steps of an annular duct with an increased diameter, each of the at least two steps including a plurality of vent holes (28).

[0223] Item 7 (see, for example, Figure 9B): A burner as described in any of Items 1 to 4, wherein the ignition chamber (25) extends from the primary fuel outlet (22) to the intermediate annular duct outlet plane (56), wherein the wall surrounding the ignition chamber (25) comprises two sections, wherein i) the first section extends from the primary fuel outlet (22) to the primary fuel duct end plane (24), wherein the primary fuel duct wall (29) surrounding the section comprises a plurality of vent holes (28), and ii) the second section has a larger than the The first section has an inner diameter of the outer diameter of the first fuel conduit (20), but the second section has an outer diameter smaller than the inner diameter of the intermediate annular conduit (35), and includes a plurality of additional vent holes (28). Optionally, the burner further includes iii) an air purging plate (73) with purging holes (32) extending between the outer diameter of the first section and the inner diameter of the second section, and iv) two mechanical mixer plates (74), each of which is located downstream of and adjacent to the two sections.

[0224] Item 8 (see, for example, Figure 9C): A burner as described in any of Items 1 to 4, wherein the ignition chamber (25) extends from the primary fuel outlet (22) to the intermediate annular conduit outlet plane (56), wherein the wall surrounding the ignition chamber (25) comprises two sections, wherein i) the first section has an outer diameter smaller than the inner diameter of the primary fuel conduit (20) and comprises a plurality of vent holes (28), wherein the wall (29) surrounding the first section comprises a plurality of vent holes (28), and wherein the first section further comprises a component that allows the primary oxidant to enter the ignition chamber (25) in the flow direction between the two rings of the primary fuel outlet orifice, and ii) the second section has an inner diameter larger than the outer diameter of the primary fuel conduit (20), but the second section has an outer diameter smaller than the inner diameter of the intermediate annular conduit (35), and comprises a plurality of additional vent holes (28).

[0225] Item 9: A burner as described in any of the preceding items, wherein the ignition chamber (25) includes an ignition cup (75) and an oxidizer vent cup (76), preferably wherein the ignition cup (75) is contained in a first section of the ignition chamber (25) and the oxidizer vent cup (76) is contained in a second section of the ignition chamber (25), wherein the second section is located downstream of the first section.

[0226] Item 10: Burner as described in any of the preceding items, i) The end face (24) of the primary fuel conduit corresponds to the end face (26) of the ignition chamber; and / or ii) The primary fuel conduit further includes an air premixing orifice (27) upstream of the primary fuel outlet (22); and / or iii) The main oxidant conduit (30) further includes a scavenging hole (32) in the flow direction parallel to the main shaft (2) of the burner; and / or iv) The main oxidant conduit (30) further includes a hydrocyclone section (33), particularly wherein the intermediate annular conduit (35) is configured to allow the main oxidant to be divided into two parts, wherein the second part is introduced into the hydrocyclone section (33); and / or v) The burner (1) is further included in the turbulence generator (47) in the secondary fuel duct (40).

[0227] Item 11: A burner as described in any of the preceding items, wherein the end plane (24) of the primary fuel conduit corresponds to the end plane (26) of the ignition chamber.

[0228] Item 12: A burner as described in any of the preceding items, wherein the primary fuel conduit further includes an air premixing orifice (27) upstream of the primary fuel outlet (22).

[0229] Item 13: A burner as described in any of the preceding items, wherein the main oxidant conduit (30) further includes a purging hole (32) in the flow direction parallel to the main shaft (2) of the burner.

[0230] Item 14: A burner as described in any of the preceding items, wherein the main oxidant conduit (30) further comprises an oxidant section (33), the oxidant section being a cyclone section (33), particularly wherein the intermediate annular conduit (35) is configured to allow the main oxidant to be divided into two parts, wherein the second part is introduced into the cyclone section (33).

[0231] Item 15: A burner as described in any of the preceding items, wherein the burner (1) further includes a turbulence generator (47) in the secondary fuel conduit (40), particularly wherein the turbulence generator includes one or more turbulence generator disks.

[0232] Item 16: A burner as described in any of the preceding items, wherein... i) The diameter of the primary fuel outlet orifice (23) is defined as D0, where D0 / D2 is between 0.04 and 0.5; and / or ii) The diameter of the cleaning holes (32) is defined as D1, wherein D1 / D2 is between 0.04 and 0.5; and / or iii) The outer diameter of the ignition source (10) is defined as D2, and the inner diameter of the primary fuel conduit (20) is defined as D3, wherein D3 / D2 is 1.5 to 4.5, particularly 2.0 to 3.0; and / or iv) The outer diameter of the ignition source (10) is defined as D2, and the inner diameter of the main oxidant conduit (30) is defined as D4, wherein D4 / D2 is 3.0 to 9.0, particularly 3.5 to 5.5; and / or v) The outer diameter of the ignition source (10) is defined as D2, and the inner diameter of the secondary fuel conduit (40) is defined as D5, wherein D5 / D2 is 5.0 to 11.0, particularly 5.5 to 7.0; and / or vi) The outer diameter of the ignition source (10) is defined as D2, and the distance between the centers of the two oxidant conduits (50) positioned relative to each other with respect to the main shaft (2) of the burner is defined as D6, wherein D6 / D2 is 9.0 to 22.0, particularly 10.0 to 14.0; and / or vii) The inner diameter of the secondary fuel conduit (40) is defined as D5, and the distance between the centers of the two oxidant conduits (50) positioned relative to each other with respect to the main shaft (2) of the burner is defined as D6, wherein D6 / D5 is 1.75 to 2.5, particularly 1.8 to 2.1; and / or viii) The diameter of these air premixing holes (27) is defined as P0, where P0 / D2 is between 0.02 and 0.2; and / or ix) The inner diameter of such vents (28) is defined as P1, wherein P1 / D2 is between 0.05 and 0.4; and / or x) The distance between the end plane (24) of the primary fuel conduit and the end plane (36) of the intermediate annular conduit is defined as L1, and the distance between the wall (29) of the primary fuel conduit and the wall (37) of the intermediate annular conduit is defined as L4, wherein L1 / L4 is 0.5 to 2.5, particularly 1.0 to 2.0; and / or xi) The distance between the end plane (24) of the primary fuel conduit and the end plane (36) of the intermediate annular conduit is defined as L1, the distance between the end plane (36) of the intermediate annular conduit and the end plane (38) of the main oxidant conduit is defined as L2, and the inner diameter of the primary fuel conduit (20) is defined as D3, wherein (L1+L2) / D3 is 0.25 to 1.0, particularly 0.4 to 0.6; and / or xii) The distance between the end plane (38) of the main oxidizer conduit and the end plane (46) of the secondary fuel conduit is defined as L3, and the inner diameter of the main oxidizer conduit (30) is defined as D4, wherein L3 / D4 is 0.05 to 0.25, particularly 0.1 to 0.2; and / or xiii) The distance between the primary fuel outlet (22) and the end plane (24) of the primary fuel conduit and / or the end plane (26) of the ignition chamber is defined as L0, and the inner diameter of the primary fuel conduit (20) is defined as D3, wherein L0 / D3 is 0.25 to 1.0, particularly 0.4 to 0.6; and / or xiv) The distance between the two rows of vents (28), measured between their centers, is defined as H, and the inner diameter of the vents (28) is defined as P1, wherein H / P1 is 1.25 to 2.5; and / or xv) The angle defined by the centers of the main shaft (2) of the burner and the two adjacent vent holes (28) is defined as angle α, wherein angle α is 3 to 30 degrees; and / or xvi) The angle defined by the centers of the main shaft (2) of the burner and the two adjacent cleaning holes (32) is defined as angle β, wherein angle β is 5-40 degrees; and / or xvii) An angle defined by the centers of the main shaft (2) of the burner and the two adjacent primary fuel outlet holes (23) is defined as angle θ, where angle θ is 10-40 degrees; and / or xviii) The angle defined by the center of the main shaft (2) of the burner and the two adjacent oxidant conduits (50) is defined as angle η, wherein angle η is 10-70 degrees, particularly 40-60 degrees.

[0233] Item 17: A burner as described in any of the preceding items, wherein the diameter of the primary fuel outlet orifice (23) is defined as D0 / D2, wherein D0 is between 0.04 and 0.5.

[0234] Item 18: A burner as described in any of the preceding items, wherein the diameter of the cleaning holes (32) is defined as D1, wherein D1 / D2 is between 0.04 and 0.5.

[0235] Item 19: A burner as described in any of the preceding items, wherein the outer diameter of the ignition source (10) is defined as D2 and the inner diameter of the primary fuel conduit (20) is defined as D3, wherein D3 / D2 is 1.5 to 4.5, particularly 2.0 to 3.0.

[0236] Item 20: A burner as described in any of the preceding items, wherein the outer diameter of the ignition source (10) is defined as D2 and the inner diameter of the main oxidant conduit (30) is defined as D4, wherein D4 / D2 is 3.0 to 9.0, particularly 3.5 to 5.5.

[0237] Item 21: A burner as described in any of the preceding items, wherein the outer diameter of the ignition source (10) is defined as D2 and the inner diameter of the secondary fuel conduit (40) is defined as D5, wherein D5 / D2 is 5.0 to 11.0, particularly 5.5 to 7.0.

[0238] Item 22: A burner as described in any of the preceding items, wherein the outer diameter of the ignition source (10) is defined as D2, and the distance between the centers of the two oxidant conduits (50) positioned relative to each other with respect to the main shaft (2) of the burner is defined as D6, wherein D6 / D2 is 9.0 to 22.0, particularly 10.0 to 14.0.

[0239] Item 23: A burner as described in any of the preceding items, wherein the inner diameter of the secondary fuel conduit (40) is defined as D5, and the distance between the centers of the two oxidant conduits (50) positioned relative to each other with respect to the main shaft (2) of the burner is defined as D6, wherein D6 / D5 is 1.75 to 2.5, particularly 1.8 to 2.1.

[0240] Item 24: A burner as described in any of the preceding items, wherein the diameter of the air premixing orifice (27) is defined as P0, wherein P0 / D2 is between 0.02 and 0.2.

[0241] Item 25: A burner as described in any of the preceding items, wherein the inner diameter of the vent (28) is defined as P1, wherein P1 / D2 is between 0.05 and 0.4.

[0242] Item 26: A burner as described in any of the preceding items, wherein the distance between the end plane (24) of the primary fuel conduit and the end plane (36) of the intermediate annular conduit is defined as L1, and the distance between the wall (29) of the primary fuel conduit and the wall (37) of the intermediate annular conduit is defined as L4, wherein L1 / L4 is 0.5 to 2.5, particularly 1.0 to 2.0.

[0243] Item 27: A burner as described in any of the preceding items, wherein the distance between the end plane (24) of the primary fuel conduit and the end plane (36) of the intermediate annular conduit is defined as L1, the distance between the end plane (36) of the intermediate annular conduit and the end plane (38) of the main oxidizer conduit is defined as L2, and the inner diameter of the primary fuel conduit (20) is defined as D3, wherein (L1+L2) / D3 is 0.25 to 1.0, particularly 0.4 to 0.6.

[0244] Item 28: A burner as described in any of the preceding items, wherein the distance between the end plane (38) of the main oxidizer conduit and the end plane (46) of the secondary fuel conduit is defined as L3, and the inner diameter of the main oxidizer conduit (30) is defined as D4, wherein L3 / D4 is 0.05 to 0.25, particularly 0.1 to 0.2.

[0245] Item 29: A burner as described in any of the preceding items, wherein the distance between the primary fuel outlet (22) and the end plane (24) of the primary fuel conduit and / or the end plane (26) of the ignition chamber is defined as L0, and the inner diameter of the primary fuel conduit (20) is defined as D3, wherein L0 / D3 is from 0.25 to 1.0, particularly from 0.4 to 0.6.

[0246] Item 30: A burner as described in any of the preceding items, wherein the distance between the two rows of vent holes (28), measured between the centers of the two rows of vent holes (28), is defined as H, and the inner diameter of the vent holes (28) is defined as P1, wherein H / P1 is 1.25 to 2.5.

[0247] Item 31: A burner as described in any of the preceding items, wherein the angle defined by the center of the main shaft (2) of the burner and the two adjacent vent holes (28) is defined as angle α, wherein angle α is 3 to 30 degrees.

[0248] Item 32: A burner as described in any of the preceding items, wherein the angle defined by the centers of the main shaft (2) of the burner and the two adjacent cleaning holes (32) is defined as angle β, wherein angle β is 5-40 degrees.

[0249] Item 33: A burner as described in any of the preceding items, wherein the angle defined by the center of the main shaft (2) of the burner and the two adjacent primary fuel outlet holes (23) is defined as angle θ, wherein angle θ is 10-40 degrees.

[0250] Item 34: A burner as described in any of the preceding items, wherein the angle defined by the centers of the main shaft (2) of the burner and the two adjacent oxidant conduits (50) is defined as angle η, wherein angle η is 10-70 degrees, particularly 40-60 degrees.

[0251] Item 35: A burner as described in any one of Items 17 to 34 above, wherein i) D3 / D2 is between 1.5 and 4.5, especially between 2.0 and 3.0; and / or ii) D4 / D2 is 3.0 to 9.0, especially 3.5 to 5.5; and / or iii) D5 / D2 is between 5.0 and 11.0, especially between 5.5 and 7.0; and / or iv) D6 / D2 is between 9.0 and 22.0, especially between 10.0 and 14.0; and / or v)D6 / D5 is 1.75 to 2.5, and for special series it is 1.8 to 2.1.

[0252] Item 36: A burner as described in any one of items 11 to 29 above, wherein i) L1 / L4 is 0.5 to 2.5, especially 1.0 to 2.0; and / or ii) L0 / D3 is 0.25 to 1.0, especially 0.4 to 0.6; and / or iii) (L1+L2) / D3 is 0.25 to 1.0, especially 0.4 to 0.6; and / or iv) L3 / D4 is 0.05 to 0.25, especially 0.1 to 0.2; and / or v)H / P1 is 1.25 to 2.5.

[0253] Item 37: A burner as described in any one of items 17 to 36 above, wherein i) Angle α is between 3 and 30 degrees; and / or ii) Angle β is 5-40 degrees; and / or iii) Angle θ is 10-40 degrees; and / or iv) Angle η is 10-70 degrees, especially 40-60 degrees.

[0254] Item 38: A burner as described in any of the preceding items, wherein the burner (1) is configured such that at the outlet of a given duct... i) The velocity of the primary fuel (preferably at the outlet of the orifice 23) is between 30 ft / s and 500 ft / s, particularly between 40 ft / s and 400 ft / s; and / or ii) The velocity of the primary oxidant is between 5 ft / s and 300 ft / s, particularly between 10 ft / s and 200 ft / s; and / or iii) The velocity of the secondary fuel is between 20 ft / s and 200 ft / s, particularly between 40 ft / s and 120 ft / s; and / or iv) Optionally, the velocity of the oxidant is between 50 ft / s and 500 ft / s, particularly between 100 ft / s and 300 ft / s.

[0255] Item 39: A burner as described in any of the preceding items, wherein the velocity of the first-stage fuel is between 30 ft / s and 500 ft / s, particularly between 40 ft / s and 400 ft / s.

[0256] Item 40: A burner as described in any of the preceding items, wherein the velocity of the primary oxidant is between 5 ft / s and 300 ft / s, particularly between 10 ft / s and 200 ft / s.

[0257] Item 41: A burner as described in any of the preceding items, wherein the velocity of the secondary fuel is between 20 ft / s and 200 ft / s, particularly between 40 ft / s and 120 ft / s.

[0258] Item 42: A burner as described in any of the preceding items, wherein the velocity of the oxidant is between 50 ft / s and 500 ft / s, particularly between 100 ft / s and 300 ft / s.

[0259] Item 43: A burner as described in any of the preceding items, wherein the vortex angle is 5-60 degrees, preferably 30-45 degrees.

[0260] Item 44: A burner as described in any of the preceding items, wherein the burner (1) is configured in such a way that... i) During startup, approximately 100% of the total thermal power of the burner is provided by the primary fuel; and / or ii) During normal operation, approximately 25 to 65%, preferably 45 to 65%, of the total calorific value of the burner is provided by the primary fuel, and the remainder is provided by the secondary fuel.

[0261] Item 45: A burner as described in any of the preceding items, wherein the burner (1) is configured such that, during startup, approximately 100% of the total thermal power of the burner is provided by the primary fuel.

[0262] Item 46: A burner as described in any of the preceding items, wherein the burner (1) is configured such that during normal operation, about 25 to 65%, preferably 45 to 65%, of the total thermal power of the burner is provided by the primary fuel.

[0263] Item 47: A burner as described in any of Items 45 and 46, wherein the remainder of each is supplied by the secondary fuel.

[0264] Item 48: A burner as described in any of the preceding items, wherein the burner (1) is configured in such a way that... i) The volumetric flow rate of the oxidant in the ignition chamber is approximately 5-25% of the total main oxidant flow rate; and / or ii) The volumetric flow rate of the premixed oxidant is approximately 2-10% of the total main oxidant flow rate; and / or iii) The volumetric flow rate of the co-oxidant transferred to the co-oxidant conduit (50) is about 2-5% of the main oxidant flow rate.

[0265] Item 49: A burner as described in any of the preceding items, wherein the burner (1) is configured such that the volumetric flow rate of the oxidant in the ignition chamber is about 5-25% of the total main oxidant flow rate.

[0266] Item 50: A burner as described in any of the preceding items, wherein the burner (1) is configured such that the volumetric flow rate of the premixed oxidant is about 2-10% of the total main oxidant flow rate.

[0267] Item 51: A burner as described in any of the preceding items, wherein the burner (1) is configured such that the volumetric flow rate of the oxidant transferred to the oxidant conduits (50) is about 2-5% of the flow rate of the main oxidant.

[0268] Item 52: A burner as described in any of the preceding items, wherein the burner (1) is configured such that, during normal operation, depending on the operating requirements, the burner can be reduced from 100% design combustion rate to a reduction position of approximately 1:30.

[0269] Item 53: A burner (1) as described in any of the preceding items, wherein the central ignition source (10) forms the "tube 1" of the burner.

[0270] Item 54 The burner (1) as described in any of the preceding items, wherein the primary fuel conduit (20) forms the "pipe 2" of the burner.

[0271] Item 55: A burner (1) as described in any of the preceding items, wherein the main oxidant conduit (30) forms the "pipe 3" of the burner, the pipe being particularly an air pipe.

[0272] Item 56: A burner (1) as described in any of the preceding items, wherein the secondary fuel conduit (40) forms the "pipe 4" of the burner.

[0273] Item 57: The burner (1) as described in any of the preceding items, wherein the oxidant conduit (50) is each designated as a 'stage oxidant conduit' or a 'stage oxidant'.

[0274] Item 58: The burner (1) as described in any of the preceding items, wherein all such conduits except for such oxidant conduits (50) share a common central axis.

[0275] Item 59: A burner (1) as described in any of the preceding items, wherein all such conduits, except for such oxidant conduits (50), are arranged concentrically around a common longitudinal axis at least in the downstream portion (5).

[0276] Item 60: The burner (1) as described in any of the preceding items, wherein all such conduits are substantially straight.

[0277] Item 61: A burner (1) as described in any of the preceding items, wherein the burner (1) comprises a configuration substantially as depicted in any of the accompanying drawings or any combination thereof.

[0278] Item 62: A furnace comprising a burner (1) as described in any one of items 1 to 61.

[0279] Item 63: The furnace as described in Item 62, wherein the furnace is selected from a group consisting of a furnace for steam methane reforming, a reheat furnace in the steel industry, and a secondary melting furnace.

[0280] Item 64: A furnace as described in Item 63, wherein the furnace is further characterized by any of the features described in any of Items 1 to 61.

[0281] Item 65: A method for operating a burner (1) as described in any one of Items 1 to 61 or a furnace as described in any one of Items 62 to 64, the method comprising the following steps i) Start the burner, ii) Optionally increase the combustion rate of the burner, iii) Start the secondary fuel, iv) Gradually increase the combustion rate of the burner to that of the burner. v) Optionally, the oxidant is supplied to the burner.

[0282] Item 66: The method of Item 65, wherein step i) comprises starting the primary oxidizer, the igniter and the primary fuel. Example

[0283] The following examples are provided to further illustrate the nature of the invention, but are by no means intended to limit it in any way.

[0284] Example 1

[0285] A test burner was manufactured and tested at 5 MMBtu / hr in our industrial-scale combustion laboratory with NG as primary and secondary fuel, air as the main oxidant, and oxygen as the co-oxidant.

[0286] The burner was successfully tested in start-up, incremental and air-fuel as well as air-oxygen fuel modes. The burner performs well and indicates that the burner produces a stable flame in both air-fuel and air-oxygen fuel modes without any external support.

[0287] The curves in Figure 8 illustrate the comparison of normalized NOx data from laboratory tests of the invention and prior art ( Figure 12 ). Normalized NOx values ​​were defined as the ratio of NOx (ppm) produced by the burner type to the maximum NOx (ppm) produced between the different burners. In the present instance, the NOx data has been normalized by the NOx generated by the prior art as it yields the maximum NOx (ppm). The total burner combustion rate, burner equivalent ratio, and fuel composition were identical for both burners.

[0288] The results indicate that the NOx emissions of the present invention are about 30% to 70% lower than the existing technology (without oxygen fractionation and with 75% oxygen fractionation) (depending on the oxygen enrichment site of the burner). Under these test conditions, CO emissions in the exhaust flue were kept below 20 ppm.

[0289] The fact that the present invention is capable of producing significantly lower NOx in air-fuel and air-oxygen-fuel modes is due to a number of unique features of this burner.

[0290] In the air-fuel mode, the burner provides improved performance in terms of NOx emissions because the bleed hole (28) provides air in the ignition cup that can be entrained with a fuel jet before the fuel leaves the outlet plane of the burner. This enhanced mixing through a unique burner cup tip (ignition chamber) design thereby permits a reduction in peak temperature relative to the common characteristics of non-premixed burners. The lower peak temperature of this burner flame simulates the peak temperature of partially premixed air–fuel combustion rather than non-premixed combustion.

[0291] In the air-oxygen-fuel mode, the burner produces a stable flame while producing lower NOx compared to the existing technology.

[0292] Three fluids—air, fuel, and oxygen / oxygen-enriched air—are supplied via spatially separated outlets / ports, thereby simultaneously reducing the interaction of O2, N2, and high temperature at a localized position. First, in the central region of the burner, the air-fuel flame operates in a fuel-enriched environment that reduces peak temperature compared to stoichiometric combustion (equivalence ratio = 1). Second, vent holes (28) supply air in the ignition cup, which can entrain fuel jets before the fuel leaves the burner's outlet plane. As discussed above, this enhanced mixing, achieved through a unique burner cup tip (ignition chamber) design, allows for a lower peak temperature compared to non-premixed burners. The lower peak temperature helps reduce thermal NOx formation.

[0293] In addition, the radial splitting position of the oxygen injection nozzle and the central flame is crucial for minimizing thermal NOx formation. Firstly, the radial splitting of the oxidizer jet and the secondary fuel outlet enables delayed mixing of the central fuel flame and the oxidizer, thus achieving distributed combustion. Thermal NOx formation is primarily influenced by temperature, nitrogen concentration, and oxygen concentration. Delayed mixing achieves distributed combustion that lowers the peak combustion temperature. Furthermore, the entrainment of furnace gas to dilute the oxidizer stream helps reduce local oxygen concentration before these high-oxygen-concentration jets encounter the fuel and / or partially burned fuel / air mixture. Therefore, the tendency for the burner to form thermal NOx is reduced.

[0294] Finally, the turbulent-induced injection of secondary fuel between the primary oxidant (air) and the auxiliary oxidant allows for the creation of a "pseudo" isolation layer (near the burner outlet) of partially burned fuel between the primary oxidant and the staged oxidant. This pseudo isolation layer can potentially help reduce the contact between N2 present in the primary oxidant and the high-concentration O2 jet from the auxiliary oxidant jet in a high-temperature atmosphere.

[0295] In air-fuel mode, the burner is able to produce a stable flame at a high descent of 1:30 and an equivalence ratio of 0.25. This efficiency is due to the unique configuration of the burner hardware, including the position of the air scavenger plate (73), its stepped design, and the axial flow of air through the air scavenger plate (73), thereby providing a stable flame anchoring position. As shown in Figure 11, the burner provides multiple flame anchoring positions depending on the burner's total combustion rate. In air-fuel mode, the flame is anchored in two positions: one near the air scavenger plate (73) and the other on the inner periphery of the cyclone outlet plane. In air-oxygen-fuel mode (higher oxygen enrichment level) and in air-fuel mode under descent conditions and low equivalence ratios, the flame remains anchored at the air scavenger plate (73) without any extinguishing, because a recirculation zone is set in the area created by the stepped design of the air scavenger plate (73). In addition, the air purging plate (73) has a recessed L1 on the swirl outlet plane (34), which allows the flame to be anchored relatively unaffected by the furnace atmosphere.

[0296] The burner's design features allow for radial and axial removal of oxidizer from the ignition cup, while keeping the surrounding walls cool by protecting it from direct contact with the flame.

[0297] The robust flame anchoring mechanism of this type of burner, as described above, provides additional benefits for burner operation, allowing switching from air-fuel mode to air-oxygen-fuel mode without any burner modifications. The stable anchoring position allows the oxidizer to supply a higher proportion of oxygen while maintaining a stable flame at the center without stripping. The oxygen supplied by the oxidizer can be up to 90% of the total oxygen required for the stoichiometric combustion of the fuel. If the furnace is above the fuel's auto-ignition temperature, and if necessary, the burner can operate in full oxygen-fuel mode.

[0298] In this invention, the creation of two fuel supply conduits with unique injection technology (one conduit with multiple fuel jets and the second conduit with a turbulence generator tip) and an ignition cup feature provides fuel flexibility to the burner, resulting in a stable flame anchoring. For the same heat input to the burner, as the hydrogen fraction in the fuel increases, the fuel velocity increases because a higher hydrogen (calorific value of hydrogen is approximately 330 Btu / scf) volumetric flow rate is required to match the heat input of NG (calorific value of NG is approximately 1000 Btu / scf). This increased velocity can lead to flame stripping or affect the burner's heat release rate. In the novel burner, the flame anchoring position helps to form a stable flame at the center. This stable flame at the center acts as the ignition flame for the fuel supplied by the secondary fuel conduit. Therefore, this burner can produce a stable flame with NG and / or NG / H2 mixtures.

[0299] Finally, the burner ignites well at equivalence ratios as low as 0.25. This allows the burner to be started / ignited at low equivalence ratios (lean fuel start). This is possible because the unique design of the ignition cup provides a zone in which ignition can be initiated and sustained while still remaining below the overall burner flammability limit of natural gas. A portion of the primary oxidizer is introduced into the ignition chamber via the peripheral wall of a chamber perpendicular to the fuel distribution nozzle. This is used to vigorously mix the fuel and 'ignition' air to ensure reliable and repeatable ignition of the gas mixture with fuel concentrations within the flammability range.

[0300] Example 2

[0301] The following examples illustrate a non-limiting, illustrative, detailed method of operating the burner (1) according to the present invention, as depicted in Figures 7A and 7B:

[0302] Step 1: Start the main oxidizer (this will also allow some air to pass through the cup), start the igniter located in the center of the burner, and start the primary fuel. This ignites the main flame.

[0303] Step 2: Once the flame is ignited, the burner's combustion rate gradually increases to a certain rate of MMBtu / hr. At this point, the secondary fuel is activated. Because the secondary fuel outlet port is located close to the primary fuel flame, the secondary fuel is ignited by the energy provided by the combustion of the primary fuel.

[0304] Step 3: Increase the combustion rate of the burner to achieve the desired combustion rate.

[0305] Step 4: When required by the process, an oxidant can be supplied to the burner.

[0306] 1: Burner 2: Spindle 5: Downstream section 10: Ignition source, central spark igniter 15: Central axis 16: Catheter tip plane 19: Central Ignition Source Wall 20: Primary fuel conduit 21: Primary fuel connector 22: Primary fuel export 23: Primary fuel outlet orifice 24: First-stage fuel duct end plane 25: Ignition Room 26: Ignition chamber end plane 27: Air premixing hole 28: Vent hole 29: Primary fuel duct wall 30: Main oxidant conduit 31: Main Oxidant Connector 32: Clean the hole 33: Oxidizing agent section, hydrocyclone section 34: Oxidant Section Outlet 35: Intermediate annular catheter 36: Intermediate annular conduit end plane 37: Intermediate annular catheter wall 38: Main oxidant conduit end plane 39: Main oxidant conduit wall 40: Secondary fuel conduit 41: Secondary fuel connector 44: Secondary fuel export 46: Secondary fuel duct end plane 47: Turbulence Generator 49: Secondary fuel duct wall 50: Co-oxidant conduit 51: Co-oxidant Connector 54: Export of oxidizing agents 55: Primary fuel duct outlet plane 56: Intermediate annular conduit outlet plane 57: Turbulence Generating Device 59: Co-oxidant conduit wall 72: Primary fuel outlet plate 73: Air Purification Panel 74: Mechanical mixer plate 75: Ignition Cup 76: Oxidizing agent release cup A0: Cross-sectional area A1: Cross-sectional area A2: Cross-sectional area A3: Cross-sectional area, hole D0: Diameter D1: Diameter D2: Outer diameter D3:Inner diameter D4:Inner diameter D5:Inner diameter D6: Distance D7: Inner Diameter H: Distance L0: Distance L01: Distance L1: Distance L2: Distance L3: Distance L4: Distance P0: Diameter P1:Inner diameter α: Angle β: Angle η: Angle θ: angle

Claims

1. A burner (1) comprising a primary fuel conduit (20) having a primary fuel outlet (22) having multiple primary fuel outlet orifices (23) for supplying primary fuel to an ignition chamber (25), wherein the wall surrounding the ignition chamber (25) includes a plurality of vent holes (28), a main oxidant conduit (30) for supplying a main oxidant, comprising an intermediate annular conduit (35) located in a downstream portion (5) of the burner, the intermediate annular conduit (35) being configured to allow diversion of the main oxidant such that a first portion is introduced into the ignition chamber (25) via the plurality of vent holes (28) to mix with the primary fuel, and a second portion is introduced into an oxidant section (33), wherein the burner further comprises a plurality of auxiliary oxidant conduits (50) for supplying an auxiliary oxidant. In particular, at least in the downstream portion (5) of the burner (1), the primary fuel conduit (20) is surrounded by the main oxidant conduit (30) and the plurality of auxiliary oxidant conduits (50); wherein the ignition chamber (25) extends from the primary fuel outlet (22) to an intermediate annular conduit outlet plane (56), wherein the wall surrounding the ignition chamber (25) includes at least two (preferably two or three) steps of an annular conduit with an increased diameter, each of the at least two steps including a plurality of vent holes (28).

2. The burner as claimed in claim 1, wherein the burner further comprises a primary and secondary fuel conduit (40) for supplying primary and secondary fuel and having a primary and secondary fuel outlet (44) at its downstream end, wherein at least in the downstream portion (5) of the burner (1), the primary fuel conduit (20) is surrounded by the main oxidant conduit (30) and the secondary fuel conduit (40), and in the downstream portion there are a primary fuel outlet (22), an ignition chamber (25), an intermediate annular conduit (35) and a secondary fuel outlet (44).

3. The burner as claimed in claim 2, wherein at least in the downstream portion (5) of the burner (1), the primary fuel conduit (20) is surrounded by the main oxidant conduit (30), the primary and secondary fuel conduits (40), and the plurality of auxiliary oxidant conduits (50).

4. The burner as claimed in any one of claims 1 to 3, wherein the ignition chamber (25) is located within the primary fuel conduit (20) and extends from the primary fuel outlet (22) to the end plane (24) of the primary fuel conduit, wherein the wall (29) of the primary fuel conduit surrounds the ignition chamber (25) and includes a plurality of vent holes (28).

5. A burner as claimed in any one of claims 1 to 3, wherein the wall surrounding the ignition chamber (25) comprises two sections, wherein i) a first section extends from the primary fuel outlet (22) to a primary fuel conduit end plane (24), wherein the primary fuel conduit wall (29) surrounding the section comprises a plurality of vent holes (28), and ii) a second section has an inner diameter greater than the outer diameter of the primary fuel conduit (20), but the second section has an outer diameter smaller than the inner diameter of the intermediate annular conduit (35), and comprises another plurality of vent holes (28), and wherein iii The burner optionally further includes an air purging plate (73) having one of the purging holes (32) extending between the outer diameter of the first section and the inner diameter of the second section, and iv) the burner optionally further includes two mechanical mixer plates (74), each of which is located downstream of and adjacent to the two sections, and v) the burner optionally further includes an air purging plate (73) having one of the purging holes (32) existing between the outer diameter of the second section and the inner diameter of the intermediate annular duct (35).

6. A burner as claimed in any one of claims 1 to 3, wherein the wall surrounding the ignition chamber (25) comprises two sections, wherein i) the first section has an outer diameter smaller than the inner diameter of the primary fuel conduit (20) and comprises a plurality of vent holes (28), wherein the wall (29) surrounding the first section comprises a plurality of vent holes (28), and wherein the first section further comprises a component that allows the primary oxidant to enter the ignition chamber (25) in the flow direction between two rings of the primary fuel outlet orifice. ii) The second section has an inner diameter greater than the outer diameter of the first fuel conduit (20), but the second section has an outer diameter less than the inner diameter of the intermediate annular conduit (35), and includes a plurality of additional vent holes (28), and wherein iii) the burner optionally further includes an air purging plate (73) having a purging hole (32) between the outer diameter of the first section and the inner diameter of the second section, and iv) the burner optionally further includes an air purging plate (73) having a purging hole (32) between the outer diameter of the second section and the inner diameter of the intermediate annular conduit (35).

7. The burner as claimed in any one of claims 1 to 3, wherein the ignition chamber (25) includes an ignition cup (75) and an oxidizer vent cup (76), preferably wherein the ignition cup (75) is contained in a first section of the ignition chamber (25) and the oxidizer vent cup (76) is contained in a second section of the ignition chamber (25), wherein the second section is located downstream of the first section.

8. A burner as claimed in any one of claims 1 to 3, wherein the burner (1) further comprises an ignition source (10), particularly wherein the ignition source (10) terminates in the ignition chamber (25), particularly wherein the ignition source (10) is a central ignition source having a central axis (15) and a conduit end plane (16), particularly wherein the main axis (2) of the burner (1) coincides with the central axis (15) of the ignition source (10), particularly wherein at least in the downstream portion (5) of the burner (1), the central spark igniter (10) is surrounded by the primary fuel conduit (20), the main oxidant conduit (30) and the secondary fuel conduit (40), and the plurality of oxidant conduits (50).

9. The burner as claimed in any one of claims 1 to 3, wherein i) the end plane (24) of the primary fuel conduit corresponds to the end plane (26) of the ignition chamber; and / or ii) the primary fuel conduit further includes an air premixing orifice (27) upstream of the primary fuel outlet (22); and / or iii) the main oxidizer conduit (30) further includes a scavenging orifice (32) in a flow direction parallel to the main shaft (2) of the burner.

10. The burner as claimed in any one of claims 1 to 3, wherein the burner (1) further includes a turbulence generator (47) in the secondary fuel conduit (40).

11. The burner as claimed in any one of claims 1 to 3, wherein i) the diameter of the primary fuel outlet orifice (23) is defined as D0, wherein D0 / D2 is between 0.04 and 0.5; and / or ii) the diameter of the scavenging orifices (32) is defined as D1, wherein D1 / D2 is between 0.04 and 0.5; and / or iii) the outer diameter of the ignition source (10) is defined as D2, and the inner diameter of the primary fuel conduit (20) is defined as D3, wherein D3 / D2 is between 1.5 and 4.5, particularly between 2.0 and 3.0; and / or iv) the outer diameter of the ignition source (10) is defined as D2, and the inner diameter of the main oxidizer conduit (30) is defined as D4, wherein D4 / D2 is between 3.0 and 9. 0, particularly 3.5 to 5.5; and / or v) the outer diameter of the ignition source (10) is defined as D2, and the inner diameter of the secondary fuel conduit (40) is defined as D5, wherein D5 / D2 is 5.0 to 11.0, particularly 5.5 to 7.0; and / or vi) the outer diameter of the ignition source (10) is defined as D2, and the distance between the centers of the two oxidant conduits (50) positioned relative to each other with respect to the main shaft (2) of the burner is defined as D6, wherein D6 / D2 is 9.0 to 22.0, particularly 10.0 to 14.0; and / or vii) the inner diameter of the secondary fuel conduit (40) is defined as D5, and the distance between the centers of the two oxidant conduits (50) positioned relative to each other with respect to the main shaft (2) of the burner is defined as D5. The distance between the centers of the fuel conduit (50) is defined as D6, where D6 / D5 is 1.75 to 2.5, particularly 1.8 to 2.1; and / or viii) the diameter of the air premixing holes (27) is defined as P0, where P0 / D2 is between 0.02 and 0.2; and / or ix) the inner diameter of the vent holes (28) is defined as P1, where P1 / D2 is between 0.05 and 0.4; and / or x) the distance between the end plane of the primary fuel conduit (24) and the end plane of the intermediate annular conduit (36) is defined as L1, and the distance between the wall of the primary fuel conduit (29) and the wall of the intermediate annular conduit (37) is defined as L4, where L1 / L4 is 0.5 to 2.5, particularly 1.0 to 2.0; and / or xi) the distance between the end plane (24) of the primary fuel conduit and the end plane (36) of the intermediate annular conduit is defined as L1, the distance between the end plane (36) of the intermediate annular conduit and the end plane (38) of the main oxidant conduit is defined as L2, and the inner diameter of the primary fuel conduit (20) is defined as D3, wherein (L1+L2) / D3 is 0.25 to 1.0, particularly 0.4 to 0.6; and / or xii) the distance between the end plane (38) of the main oxidant conduit and the end plane (46) of the secondary fuel conduit is defined as L3, and the inner diameter of the main oxidant conduit (30) is defined as D4, wherein L3 / D4 is 0.05 to 0.25, particularly 0.1 to 0.2; and / or xiii) wherein the distance between the primary fuel outlet (22) and the end plane (24) of the primary fuel conduit and / or the end plane (26) of the ignition chamber is defined as L0, and the inner diameter of the primary fuel conduit (20) is defined as D3, wherein L0 / D3 is 0.25 to 1.0, particularly 0.4 to 0.6; and / or xiv) the distance between the two rows of vent holes (28) measured between their centers is defined as H, and the inner diameter of the vent holes (28) is defined as P1, wherein H / P1 is 1.25 to 2.5; and / or xv) the inner diameter of the oxidant conduit (50) is defined as D7, wherein D7 / D2 is between 0.15 and 1.0, particularly 0.25 to 0.

75.

12. A burner as claimed in any one of claims 1 to 3, wherein i) the ratio of the area of ​​all vent holes in a column to the surface area of ​​the cylinder with an outer diameter D2 and a height P1 is between 10% and 55%; and / or ii) the purging air plate (73) has a porosity within the limit of 2% to 15% (defined by dividing the total open area on the plate that allows air flow by the cross-sectional area of ​​the plate); and / or iii) the primary fuel outlet plate (72) has a porosity in the range of 2% to 25% (defined by dividing the total open area on the plate that allows fuel flow by the cross-sectional area of ​​the plate); and / or iv) the angle defined by the center of the main shaft (2) of the burner and the two adjacent oxidant conduits (50) is defined as angle η, wherein angle η is 10-70 degrees, particularly 40-60 degrees.

13. A burner as claimed in any one of claims 1 to 3, wherein the burner (1) is configured such that at the outlet of a given duct, i) the velocity of the primary fuel is between 30 ft / s and 500 ft / s, particularly between 40 ft / s and 400 ft / s; and / or ii) the velocity of the primary oxidant is between 5 ft / s and 300 ft / s, particularly between 10 ft / s and 200 ft / s; and / or iii) the velocity of the secondary fuel is between 20 ft / s and 200 ft / s, particularly between 40 ft / s and 120 ft / s; and / or iv) the velocity of the auxiliary oxidant is between 50 ft / s and 500 ft / s, particularly between 100 ft / s and 300 ft / s.

14. A burner (1) comprising a primary fuel conduit (20) having a primary fuel outlet (22) having multiple primary fuel outlet orifices (23) for supplying primary fuel to an ignition chamber (25), wherein the wall surrounding the ignition chamber (25) includes a plurality of vent holes (28), a main oxidant conduit (30) for supplying a main oxidant, comprising an intermediate annular conduit (35) located in a downstream portion (5) of the burner, the intermediate annular conduit (35) being configured to allow diversion of the main oxidant such that a first portion is introduced into the ignition chamber (25) via the plurality of vent holes (28) to mix with the primary fuel, and a second portion is introduced into an oxidant section (33), wherein the burner further comprises a plurality of auxiliary oxidant conduits (50) for supplying an auxiliary oxidant. In particular, at least in the downstream portion (5) of the burner (1), the primary fuel conduit (20) is surrounded by the main oxidant conduit (30) and the plurality of auxiliary oxidant conduits (50); wherein the oxidant section (33) is a swirler section (33), and in particular, wherein the intermediate annular conduit (35) is configured to allow the main oxidant to be divided into two parts, wherein a second part is introduced into a swirler section (33).

15. The burner as claimed in claim 14, wherein a vortex angle in the cyclone section (33) is 5-60 degrees, preferably 30-45 degrees.

16. The burner (1) as described in any one of claims 1 to 3, wherein the burner (1) is operated such that i) during startup, about 100% of the total thermal power of the burner is provided by the primary fuel; and / or ii) during normal operation, about 25 to 65%, preferably 45 to 65%, of the total thermal power of the burner is provided by the primary fuel, and the respective remainder is provided by the secondary fuel.

17. A burner as claimed in any one of claims 1 to 3, wherein the burner (1) operates such that i) the volumetric flow rate of the oxidant in the ignition chamber is about 5-25% of the total main oxidant flow rate; and / or ii) the volumetric flow rate of the premixed oxidant is about 2-10% of the total main oxidant flow rate; and / or iii) the volumetric flow rate of the oxidant transferred to the auxiliary oxidant conduits (50) is about 2-5% of the main oxidant flow rate.

18. The burner (1) as described in any one of claims 1 to 3, wherein the burner (1) is operated in such a way that, during normal operation, depending on the operating requirements, the burner can be reduced from 100% design combustion rate to a reduction position of about 1:

30.

19. A method for operating a burner (1) as claimed in any one of claims 1 to 15, the method comprising the steps of i) starting the burner, ii) gradually increasing the combustion rate of the burner, iii) starting primary and secondary fuels, iv) further gradually increasing the burner to the combustion rate of the burner, and v) optionally supplying the oxidant to the burner.

20. The method as described in claim 19, wherein step i) comprises starting the primary oxidant, an ignition source, and the primary fuel.

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