Injector burner for metallurgical furnaces

Abstract

The present invention relates to an injector burner (1) for the simultaneous injection of at least one fuel gas and pure oxygen or oxygen in a concentrated mixture into a metallurgical melting furnace. The injector burner (1) has a double nozzle configuration comprising a first internal nozzle (10) and a second nozzle (20). The first nozzle (10) has a convergence / divergence shape defined by a constriction (13) formed upstream of its outlet end (11), and the first discharge conduit (10") is provided with an oxygen inlet (61). The second nozzle (20) has a shape that converges towards its outlet end (21), and the second discharge conduit (20") is provided with one or more inlets (70, 71, 72) for one or more fuel gases. The injector burner 1 includes rectifiers (31, 32) located in the second discharge conduit (20") in an intermediate axial position.

Description

Technical Field

[0001] The project that led to this application has received funding from the Coal and Steel Research Fund under grant number 101034081.

[0002] The present invention relates to an injector burner for metallurgical furnaces, particularly for electric arc furnaces used in steel production.

Background Art

[0003] In the field of furnaces used in the steel industry, particularly in the field of electric arc furnaces, it is known to provide an opening in the side wall of the furnace chamber through which devices such as burners, injectors, lances, etc. can be inserted.

[0004] In particular, it is known to use auxiliary burners that can add additional energy to the energy supplied by the electric arc to promote and accelerate the melting of metals.

[0005] It is known to use injectors that can introduce gas or particulate matter into the furnace chamber and into the bath of molten metal and slag generated therein. These can be fixed to the wall or movable within the furnace using a suitable manipulator (in which case they are sometimes called lances). Injectors are often used to generate supersonic gas flows or high-speed jets of particulate matter. Injectors and lances, in addition to functioning as gas injectors or burners, make it possible to introduce additives (e.g., coal, lime, other particulate matter) used during the metallurgical process into the bath of molten metal. Auxiliary burners, injectors, and lances are hereinafter referred to as "injectors".

[0006] To achieve maximum efficiency, these injectors must be placed as close as possible to the melting chamber within the furnace. In this configuration, the injectors are intended to operate at furnace operating temperatures (which can reach 1500°C to 1700°C) and are exposed to potential splashes of liquid steel and slag. Therefore, these injectors are equipped with internal forced water cooling circuits.

[0007] In particular, injector burners suitable for simultaneously injecting fuel gas and oxygen-rich gas are already known in the prior art.

[0008] For example, an injector burner is known that has an inlet for an oxidizing gas (oxygen) and one or more inlets for a fuel gas (hydrogen, methane, propane, butane, LPG, or waste gas from other processes). The oxygen and fuel gas exit through separate openings provided in the head of the injector burner, facing the inside of the metallurgical furnace. The oxygen is supplied through a central nozzle (Laval) having a profile capable of achieving supersonic speeds. The fuel gas, on the other hand, is supplied through an annular nozzle concentric with the central nozzle and having a profile capable of reaching subsonic speeds.

[0009] The annular nozzle provides optimal axial symmetry for both the flame (initial burner phase) and the shrouding of the oxygen jet during the decarburization injection phase (end of the cycle).

[0010] More specifically, if it is desirable to decarburize the steel in a flat liquid bath stage, the nominal flow rate is achieved, and the Laval is sized accordingly (thus meeting the supersonic design requirements).

[0011] Depending on the wall's installation distance, fuel must be injected around the oxygen jet to ensure that it has a sufficiently effective jet when penetrating the liquid bath (ideally coherent, i.e., at an axial velocity equal to or at least supersonic Ma>1, the velocity at which it exits the Laval nozzle).

[0012] By burning the fuel on the surface layer of the O2 jet, a thin flame is generated around the jet. Because it is hot and low density, the oxygen jet flows into a "diluted conduit" and therefore dissipates at a slower speed. As a result, the jet reaches the liquid bath coherently or at least supersonic, ensuring better penetration and more effective decarburization.

[0013] Experiments have shown that this encapsulation effect is even more effective when the fuel is hydrogen (or contains hydrogen).

[0014] Therefore, it is clear that such enveloping is more effective when a flow of fuel is generated around the jet, and thus the flame surrounds it 360°, i.e., in a ring.

[0015] However, it was found that the dual nozzle configuration described above may not always ensure optimal axial symmetry in the enveloping of the flame and oxygen jet. This phenomenon is thought to be due to the fuel gas supply conditions, particularly signs of internal turbulence and preferential flow, as long as the fuel gas is not injected into the injector burner in a axially symmetric and uniform manner at specific locations.

[0016] Therefore, in the field of injector burners for metallurgical furnaces, there is a need to improve the aforementioned injector burners to reduce this phenomenon and ensure better axial symmetry in the envelopment of the flame and oxygen jet. [Overview of the Initiative] [Means for solving the problem]

[0017] The main objective of the present invention is to eliminate all or part of the aforementioned problems of the prior art by providing an injector burner for a metallurgical furnace having a structural configuration that ensures better axial symmetry in the envelopment of the flame and oxygen jet.

[0018] A secondary object of the present invention is to provide an injector burner for a metallurgical furnace that is not subject to prominent wear phenomena caused by thermal stress.

[0019] Another secondary object of the present invention is to provide an injector burner for a metallurgical furnace that can supply hydrogen as a fuel without being subject to corrosion phenomena and without complicating its plant configuration.

Brief Description of the Drawings

[0020] The technical features of the present invention related to the above-mentioned objects can be clearly understood from the content of the following claims, and the advantages will become more readily apparent in the following detailed description with reference to the accompanying drawings that represent one or more pure, exemplary and non-limiting embodiments.

[0021] [Figure 1] It is a front perspective view of an injector burner according to a first preferred embodiment of the present invention. [Figure 2] It is an orthogonal side view of the injector burner of FIG. 1. [Figure 3] It is a perspective view of the injector burner of FIG. 1, with some parts removed to better show another part. [Figure 4] It is an orthogonal cross-sectional view of the injector burner of FIG. 1 according to the cross-section IV-IV shown in FIG. 2. [Figure 5] It is an orthogonal cross-sectional view of the injector burner of FIG. 1 according to the cross-section V-V shown in FIG. 1. [Figure 6] It is a perspective cross-sectional view of the injector burner of FIG. 2 according to the cross-section VI-VI shown in FIG. 2. ​​​​​​​​​​It is an orthogonal view in a plan view of the injector burner of FIG. 8. [Figure 11] It is a perspective view of the injector burner of FIG. 8, with some parts removed to better show other parts. [Figure 12] It is an orthogonal cross-sectional view of the injector burner of FIG. 8 according to the cross-section XII-XII shown in FIG. 9. [Figure 13] It is an orthogonal cross-sectional view of the injector burner of FIG. 8 according to the cross-section XIII-XIII shown in FIG. 10. [Figure 14] It is a perspective cross-sectional view of the injector burner of FIG. 9 according to the cross-section XIV-XIV shown in FIG. 9. [Figure 15] It is a perspective view of the components of the injector burner of FIG. 8, partially shown in cross-section, regarding the rectifier with differentiated cross-sections. [Figure 16] It is a different perspective view of the components of the injector burner of FIG. 8, partially shown in cross-section, regarding the rectifier with differentiated cross-sections.

[0022] Elements or parts of elements common to the embodiments described below are denoted by the same reference numerals.

Mode for Carrying Out the Invention

[0023] The injector burner for a metallurgical furnace according to the present invention is generally denoted by reference numeral 1 in the accompanying drawings as a whole.

[0024] ​​​​​​​​​According to a general embodiment of the present invention, the injector burner 1 has an axially symmetric development with respect to the longitudinal axis X.

[0027] More specifically, the injector 1 extends along the injector axis X between the head section and the rear section. • Head section 2. This is intended to be inserted into the opening of the furnace, with its front surface 2' facing directly into the interior of the furnace. • Rear section 3. This is intended to be located outside the reactor and is provided with connections to one or more fuel gas supply pipes 70, 71, 72, oxygen 61, and cooling fluids 51, 52.

[0028] As shown in Figures 4, 5, 12, and 13, the injector 1 has a dual nozzle configuration comprising the following: • First internal nozzle 10. • A second nozzle 20 is arranged concentrically around the outside of the first nozzle 10.

[0029] Both nozzles 10 and 20 are coaxial with the injector axis X.

[0030] The first nozzle 10 is integrated coaxially with the first tubular supply body 10' to form the first discharge conduit 10''.

[0031] Next, the second nozzle 20 is integrated coaxially with the second tubular supply body 20' to form the second discharge conduit 20''.

[0032] The second discharge conduit 20" is concentric with the first discharge conduit 10" on the outside and has an annular flow cross-section.

[0033] The first nozzle 10 has a convergence / divergence shape defined by a constriction 13 formed upstream of its outlet end 11, thereby enabling the generation of a gas jet at supersonic speeds. The outlet end 11 of the first nozzle 10 defines a circular orifice 11' coaxial with the injector axis X, which opens onto the front surface 2' of the head portion 2.

[0034] Preferably, the first nozzle 10 is a De Laval nozzle.

[0035] Furthermore, in the first discharge conduit 10'' where the first nozzle 10 is provided, an oxygen inlet 61 is provided in the first tubular supply body 10', that is, on the upstream side of the constricted portion 13.

[0036] The second nozzle 20 has a shape that converges toward the outlet end 21 toward the injector axis X, and is capable of generating a gas jet that is continuous with the jet generated by the first nozzle 10 at subsonic speed.

[0037] In particular, as shown in Figures 4, 5, 12, and 13, the outlet end 21 of the second nozzle 20 defines an annular opening 21', which is concentric with the circular orifice 11' defined by the outlet end 11 of the first nozzle 10, and also opens on the front surface 2' of the head portion 2.

[0038] Furthermore, the second discharge conduit 20'', which is provided with the second nozzle 20, is provided with one or more inlets 70, 71, 72 for one or more fuel gases in the second tubular supply body 20', that is, on the upstream side of the second nozzle 20. In particular, according to the embodiments shown in Figures 1 to 7, the second discharge conduit 20'' may be provided with two separate inlets 71, 72 for one or more fuel gases, and according to the alternative embodiments shown in Figures 8 to 16, a single inlet 70 for fuel gases may be provided.

[0039] Operationally, in the injector burner 1, oxygen and fuel gas exit from separate openings: the circular orifice 11' of the first nozzle 10 at subsonic or supersonic speeds (depending on the supplied flow rate), and the annular opening 21' of the second nozzle 20 at subsonic speeds.

[0040] The annular opening 21' of the second nozzle 20 allows for better axial symmetry in both the flame (initial burner stage) and the decarburization injection stage (end of cycle).

[0041] More specifically, if it is desirable to decarburize the steel in a flat liquid bath stage, the nominal flow rate is achieved by sizing the first nozzle (preferably a Laval nozzle), thereby achieving the supersonic design conditions.

[0042] Depending on the wall installation distance, fuel must be injected around the oxygen jet to ensure that it has a sufficiently effective jet when penetrating into the liquid bath (ideally coherent, i.e., at an axial velocity equal to or at least supersonic Ma>1, the velocity at which it exits the Laval nozzle). By burning the fuel on the surface layer of the O2 jet, a thin flame is generated around the jet. Because it is hot and low density, the oxygen jet flows into a "diluted conduit" and therefore dissipates at a slower speed. As a result, the jet reaches the liquid bath coherently or at least supersonic, penetrating better and ensuring a more effective decarburization.

[0043] Experiments have shown that this engulfing effect is even more effective when the fuel is hydrogen (or contains hydrogen). Therefore, it is clear that such engulfing is more effective when a fuel flow is generated around the jet, and thus the flame surrounds it 360°, i.e., in a ring.

[0044] Injector 1 is equipped with the cooling circuit described below.

[0045] The first discharge conduit 10" is surrounded at least by the first nozzle 10 by the first tubular housing 14, which defines a first annular circulation chamber 100 for the cooling fluid around the first discharge conduit 10".

[0046] Preferably, as shown in Figures 4, 5, 12, and 13, the first tubular housing 14 extends axially so as to surround the first tubular supply 10'.

[0047] Next, the second discharge conduit 20'' is surrounded at least at the second nozzle 20 by a second tubular housing 24, which defines a second annular circulation chamber 200 for the cooling fluid around the second discharge conduit 20''. Conveniently, as shown in Figures 4, 5, 12, and 13, the second tubular housing 24 extends axially to surround only the second nozzle 20 and does not extend to the second tubular supply 20'.

[0048] Therefore, the injector burner 1 has a concentric tubular structure. Starting from the inside, in order, it has a first discharge conduit 10'' with a first nozzle 10, a first tubular housing 14 defining a first circulation chamber 100, a second discharge conduit 20'' with a second nozzle 20, and a second tubular housing 24 defining a second circulation chamber 200.

[0049] According to the present invention, the injector burner 1 includes at least one rectifier 31 or rectifier 32 located in the second discharge conduit 20" at an intermediate axial position between the second nozzle 20 and the one or more fuel gas inlets 70, 71, 72.

[0050] As shown in Figures 4, 5, 12, and 13, the rectifier 31 or 32 is interposed across the entire annular flow cross-section of the second discharge conduit 20" in the intermediate axial position.

[0051] In operation, the rectifier 31 or 32 ensures that the second (annular) nozzle is supplied uniformly, and the jet generated by the second annular nozzle is circumferentially uniform in terms of velocity (magnitude (modulus) and direction) around the central oxygen jet generated by the first nozzle.

[0052] Surprisingly, this allowed us to confirm that it ensured better axial symmetry in the enveloping of the flame and oxygen jet.

[0053] Conveniently, the injector 1 may include two or more rectifiers 31 or 32 arranged in series.

[0054] As already noted, the second nozzle 20 is integrated coaxially with the second tubular supply body 20' to form the second discharge conduit 20''.

[0055] Conveniently, the second tubular feeder 20' has a cylindrical cross-section. The rectifier 31 or 32 is positioned inside the second tubular feeder 20' upstream of the second nozzle 20 and its outlet end 21.

[0056] According to two preferred embodiments shown in the attached drawings, the rectifier 31 or 32 is comprised of an annular body having a plurality of through holes 310 or 320, each of which has an axial extension parallel to the injector axis X.

[0057] Conveniently, a cavity defining a common outflow chamber 4 is open on the front surface 2' of the head section 2, and both nozzles 10 and 20 open at the bottom of that chamber.

[0058] Preferably, as shown particularly in Figures 4, 5, 12, and 13, the outflow chamber 4 has the shape of a cylindrical cup and is coaxial with the injector axis X.

[0059] The inner side wall 40 of the chamber is coplanar with the outlet end 21 of the second nozzle 20. In other words, the inner side wall 40 of the chamber is a cylindrical extension of the outer edge of the annular opening defined by the second nozzle 20. In other words, the cylindrical cup has the same diameter as the outer rear edge of the second annular nozzle 20.

[0060] In terms of operation, the presence of the cylindrical cup-shaped outlet chamber 4 makes the following possible. • To accommodate two concentric flows of oxygen and fuel over a length sufficient to ensure their alignment, initial mixing, and stabilization. • To protect the annular nozzle (second nozzle) and the rubber nozzle (first nozzle) from blockage caused by material scattering.

[0061] It was possible to confirm that these effects are synergistically enhanced by the presence of the rectifier 31 or 32. The rectifier 31 or 32 ensures that the flow within the cylindrical cup is uniform and does not displace inward from one side. In other words, the centering of the flow and the uniform flow across the entire cross-section of the cup enhance the function of the cylindrical cup from the standpoint of preventing splashing.

[0062] To maximize the two effects mentioned above, the cylindrical cup must accommodate the cylindrical extension of the outer edge of the annular nozzle, and the forward annular portion of the first nozzle located downstream of the constriction 13 (hereinafter also referred to as the "tip of the first nozzle") must be as small as possible (outer radius minus inner radius in terms of "radial thickness"), so that the additional cross-section of the cup is minimized with respect to the sum of the outlet cross-section of the central nozzle 10 (either the first nozzle or the Laval nozzle) and the outlet cross-section of the annular nozzle 20 (or the second nozzle).

[0063] Preferably, the outflow chamber 4 is completely housed inside the head portion 2.

[0064] Preferably, the front surface 2' of the head portion 2 is perpendicular to the injector axis X.

[0065] During operation, especially when the injector burner 1 is driven by hydrogen, the flame may already be ignited inside the cup-shaped outlet chamber 4.

[0066] To avoid localized (very harmful) thermal overloads in some parts of the outlet chamber 4, the following conditions must be ensured. • Maximum circumferential flow uniformity. • Maximum cup filling uniformity (internal flow).

[0067] These conditions are met by the present invention (the presence of at least one rectifier). In fact, if rectifiers 31 or 32 are not present, non-uniformity of the flow occurs, causing the flame to move from one side into the cup, thereby creating a localized heat load that cannot be resolved by cooling.

[0068] However, it is also advisable to ensure the following requirements are met. • Uniform and efficient cooling in the circumferential direction of both the front and inner surfaces of the cup (to protect them from melting and / or damage to the material). • Efficient and uniform circumferential cooling of the tip of the first nozzle 10 (Laval nozzle).

[0069] Conveniently, the first requirement is satisfied by the injector burner 1 comprising a third circulation chamber 300 for a cooling fluid (preferably water), which extends inside the head portion 2 parallel to the front surface 2' and around the outlet chamber 4.

[0070] Preferably, as shown in Figures 4, 5, 12, and 13, the third circulation chamber 300 preferably has a certain L-shaped cross-section and defines an annular circuit concentric with the outflow chamber 4.

[0071] In particular, the first branch of the L-shaped cross section is parallel to the front surface 2', and the second branch of the L-shaped cross section is parallel to the side wall of the outflow chamber 4.

[0072] Conveniently, the third circulation chamber 300 has an L-shaped cross-section so as to be offset with respect to the surface to be cooled, as described below. • Minimize the cross-section (however, a minimum allowable channel thickness is given due to the risk of internal contamination and dead zones). • Maximize the velocity of the cooling fluid (preferably water), thereby maximizing heat exchange. This prevents the cooling fluid from being centrifuged outwards, resulting in more cooling of the outer part of the burner (which is already protected by the mounting case) and less cooling of the cup area that is being protected.

[0073] Conveniently, the third circulation chamber 300 is fluidly connected to the second circulation chamber 200.

[0074] The second circulation chamber 200 is dedicated to cooling the second discharge conduit 20" and is used specifically to cool the second nozzle 20.

[0075] In particular, the second circulation chamber 200 is divided into two circumferential sectors by two partitions 210, 220, which are angularly spaced around the injector axis X and preferably positioned opposite each other, defining two flow conduits 201, 202 connected in series with each other.

[0076] The two flow conduits 201 and 202 of the second circulation chamber 200 are preferably connected in series with each other by the third circulation chamber 300.

[0077] In terms of operation, according to the preferred embodiment shown in the attached drawings, the cooling of the second nozzle 20 is connected to the cooling of the front surface 2' and the cup 4.

[0078] More specifically, the cooling fluid first enters one of the two flow conduits 201, passes through its end to the third circulation chamber 300, and comes into direct contact with the front and cup, i.e., the metal (e.g., copper) that is in direct contact with the heat-loaded surface. After traveling through the entire third circulation chamber 300 (a 360° annular path), the cooling fluid enters the other axial flow conduit 202 of the second circulation chamber 200 and proceeds towards the rear of the injector 1. Preferably, after leaving the second circulation chamber 200, as will be described later, it enters the first circulation chamber 100 through the external bypass conduit 53.

[0079] Conveniently, according to the two embodiments shown in the attached drawings, the third circulation chamber 300 is separated from the second circulation chamber 200 by a wall 303, which extends circumferentially around the outflow cavity 4 and has an L-shaped radial cross-section. The wall is provided with two openings, an inlet 301 and an outlet 302, which are fluidly connected to one of the two conduits 201 and 202 of the second circulation chamber 200.

[0080] The first circulation chamber 100 is dedicated to cooling the first discharge conduit 10”, and in particular functions to cool the tip of the first nozzle 10, which is the region that experiences the most thermal stress in the first discharge conduit 10”.

[0081] The first circulation chamber 100 is preferably divided into multiple axial sectors by multiple axial partitions 110, 120, 130, 140, which define axial flow conduits 101, 102, 103, 104 connected in series with each other.

[0082] In operation, the flow of the cooling fluid is guided as follows: The cooling fluid enters from the rear of one of the axial flow conduits 101, 102, 103, or 104 via bypass 53, moves toward the front (where the heat load is), and due to a partition wall that forces a change of direction, follows this path along the aforementioned axial flow conduit n times (four times in the case shown in the attached diagram), and finally reaches outlet 52.

[0083] Considering the small space available in the inner portion of injector 1 (corresponding to the first supply conduit 10'), the best solution for cooling is to use a path divided into axial conduits in an alternating sliding direction on the opposite side, and it was possible to confirm that a high heat exchange coefficient can be obtained by utilizing the collision effect of the flow directed toward the tip of the first nozzle 10. Considering the reduced size of the inner portion in the region of the tip of the first nozzle 10 (Laval nozzle), the heat conduction of the metal (preferably copper) is sufficient to ensure cooling and circumferential uniformity of temperature.

[0084] This is not the case for the outer portion of injector 1 (corresponding to the second supply conduit 20', outlet chamber 4, and front 2'), but it is preferable that it also be made of copper. In fact, due to the larger dimensions involved, a third circulation chamber (L-shaped cross-section) and a perfectly uniform cooling action provided by the most uniform heat load possible in the cup (obtained by the rectifier) ​​are required.

[0085] Conveniently, the first circulation chamber 100 is fluidly connected (preferably in series) to the second circulation chamber 200.

[0086] Preferably, the first circulation chamber 100, the second circulation chamber 200, and the third circulation chamber 300 are connected in fluidic series to each other, particularly as described above, in order to form a single circuit.

[0087] More specifically, the injector burner 1 includes an inlet 51 for the cooling fluid formed in the second circulation chamber 200 and an outlet 52 for the cooling fluid formed in the first circulation chamber 100. The direction of the cooling fluid flow may be reversed.

[0088] According to the embodiments shown in Figures 1 to 7, the holes 310 of the rectifier 31 may have a constant cross-sectional area.

[0089] Preferably, in the case of holes 310 having a certain cross-sectional area, the ratio of the total cross-sectional area of ​​all holes 310 of the rectifier 31 to the total annular area of ​​the rectifier 31 is in the range of 0.2 to 0.8, more preferably in the range of 0.30 to 0.40. The total annular area of ​​the rectifier 31 corresponds to the inner annular cross-sectional area of ​​the second tubular feed body 20' (in which the first tubular housing 14 for the first discharge conduit 10'' is coaxially inserted) at the installation position of the rectifier.

[0090] Conveniently, the rectifier 31 is configured to minimize pressure drop while avoiding an increase in flow velocity.

[0091] According to the embodiments shown in Figures 8 to 16, each hole 320 of the rectifier may have a cross-section that is differentiated in the axial direction between a cylindrical inlet portion 321 having a constant cross-sectional area and an outlet portion 322 having a constant cross-sectional area that is larger than the area of ​​the inlet portion 321.

[0092] Preferably, in the case of a hole 320 having two parts with different cross-sectional areas, the ratio of the total cross-sectional area of ​​all holes 320 of the rectifier 32 in the cylindrical inlet portion 321 to the total annular area of ​​the rectifier 32 is in the range of 0.01 to 0.2, more preferably in the range of 0.02 to 0.1. The total annular area of ​​the rectifier 32 corresponds to the inner annular cross-sectional area of ​​the second tubular feed body 20' (in which the first tubular housing 14 for the first discharge conduit 10'' is coaxially inserted) at the installation position of the rectifier.

[0093] Preferably, in the case of a hole 320 having two parts with different cross-sectional areas, in each hole, the ratio of the axial extension of the exit portion 322 to the diameter of the inlet portion is in the range of 3 to 30, more preferably in the range of 6 to 12.

[0094] The rectifier 32 is preferably made of a material with high wear resistance. For example, the rectifier 32 may be made of wear-resistant steel, or it may be provided with a surface wear-resistant coating (for example, a layer of titanium nitride, tungsten carbide, or DLC (diamond-like carbon)).

[0095] When using hydrogen as the fuel gas instead of methane, a flow rate 3.33 times higher than that of methane is required to achieve the same output. Because there are no excessive velocities or cross-sections in the fuel line, two or more fuel inlets are necessary. This complicates the plant engineering of the reactor where injector 1 is installed.

[0096] By using a rectifier 32 provided with a bore 320 having two parts with different cross-sections, hydrogen can be used, and the volumetric flow rate can be reduced at the same power level (for example, because it has a single fuel inlet), without the problem of erosion.

[0097] More specifically, in order to reduce volumetric flow rate and the size of the fuel supply conduit, it is necessary to ensure that the gas reaches a higher pressure in the injector burner. In fact, as pressure increases, velocity decreases. This can be achieved by creating a large constriction within the conduit. However, this would result in extremely high velocity as the gas passes through it immediately downstream.

[0098] Ideally, there is no high enough velocity to reach a choking state; that is, unless the velocity of sound is reached within the bore, there is no significant pressure drop. Considering the fact that hydrogen has a velocity of sound of 1190 m / s at room temperature, while methane has a velocity of sound of 420 m / s at room temperature, as the hydrogen content increases, corrosion phenomena (e.g., originating from particulate matter transported within the pipe) become considerably more severe. This raises the question of finding a safe embodiment.

[0099] A bore 320 is provided with two sections having different cross-sectional areas (i.e., defining a chamber adapted to house and dissipate the jet before it enters the burner conduit), and the rectifier 32, made of a wear-resistant material, fully addresses these needs and clearly ensures the complete functionality described above.

[0100] This configuration, which involves a rapid expansion of the cross-sectional area, is intended to allow for the expansion of the gas flow; in other words, it is intended to confine the jet generated at the inlet to the outlet and allow it to completely dissipate within it.

[0101] Conveniently, the fuel gas can be supplied to the injector burner 1 in the form of hydrogen, in the form of a hydrocarbon gas, in particular in the form of natural gas, or a mixture thereof.

[0102] Conveniently, the hydrogen and hydrocarbon-containing gases may be supplied separately to the second nozzle 20 using at least two separate inlets and mixed together in the second discharge conduit 20" located upstream of the rectifier 31 or 32.

[0103] The present invention relates to a method for the simultaneous injection of at least one fuel gas and pure oxygen or oxygen in a concentrated mixture into a metallurgical melting furnace.

[0104] This method provides, in particular, the use of the injector burner 1 described above, according to the present invention.

[0105] This method provides supplying pure oxygen or oxygen in a mixture to a first nozzle 10 and supplying one or more fuel gases to a second nozzle 20.

[0106] This method includes selective use of the injector burner 1 in accordance with the following: • Burner operation mode. Under over-expanded subsonic or supersonic conditions, oxygen is supplied at a flow rate that generates an oxygen jet at the outlet of the first nozzle 10. Alternatively, • Injector operating mode. Oxygen is supplied at the outlet of the first nozzle 10 at a flow rate such that it generates an oxygen jet under suitable supersonic conditions or under-expansion supersonic conditions.

[0107] In both operating modes, the one or more fuel gases are supplied to the second nozzle 20, which, in conjunction with the jet generated by the first nozzle, continuously generate a gas jet at subsonic speed.

[0108] According to the present invention, since the flow of one or more fuel gases is subjected to the action of the rectifiers 31 and 32 upstream of the second nozzle 20, the second nozzle is supplied uniformly, and the jets produced by the second nozzle surrounding the central oxygen jet produced by the first nozzle are uniform in velocity (both magnitude and direction) in the circumferential direction.

[0109] According to one embodiment of the method according to the present invention, in use, in both operating modes, the second nozzle 20 is supplied with either pure hydrogen or a predetermined proportion of hydrogen in the supply flow from the beginning.

[0110] According to an alternative embodiment of the method according to the present invention, when used in burner operating mode, the proportion of hydrogen in the supply flow to the second nozzle is gradually increased by reducing the proportion of another fuel gas, until it reaches a point where pure hydrogen or hydrogen in a predetermined proportion is supplied.

[0111] Preferably, during use, in injector operation mode, the proportion of hydrogen in the supply flow to the second nozzle is the same as the proportion of hydrogen supplied to the second nozzle at the end of use in the previous burner operation mode.

[0112] The present invention makes it possible to obtain the numerous advantages that have already been partially described.

[0113] The injector burner 1 for metallurgical furnaces according to the present invention has a structural configuration that ensures better axial symmetry in the envelopment of the flame and oxygen jet.

[0114] The injector burner 1 for metallurgical furnaces according to the present invention does not experience significant wear phenomena caused by thermal stress.

[0115] The metallurgical furnace injector burner 1 according to the present invention can supply hydrogen as fuel without being subjected to corrosion phenomena and without complicating the plant configuration.

[0116] Thus, the present invention achieves its intended purpose.

[0117] Clearly, in practice, it is possible to envision forms and configurations different from those described above without departing from the current scope of the present invention.

[0118] Furthermore, all details may be replaced with technically equivalent elements, and the dimensions, shapes, and materials used may be arbitrary as needed.

Claims

1. An injector burner (1) for the simultaneous injection of at least one fuel gas and pure oxygen or oxygen in a concentrated mixture in a metallurgical melting furnace, The injector burner (1) extends along the injector axis (X) between the head portion (2) and the rear portion (3), The head portion (2) is intended to be inserted into the opening of the furnace, with its front surface (2') facing directly into the interior of the furnace. The rear section (3) is intended to be located outside the reactor and is provided with connections to one or more supply conduits for one or more fuel gases (70, 71, 72), oxygen (61), and cooling fluids (51, 52). The injector burner (1) has a double nozzle configuration comprising a first internal nozzle (10) and a second nozzle (20) arranged concentrically outside the first nozzle (10). The first nozzle (10) is integrated coaxially with the first tubular feed body (10') to form the first discharge conduit (10"), and the second nozzle (20) is integrated coaxially with the second tubular feed body (20') to form the second discharge conduit (20"), the latter being concentric with the first discharge conduit (10") on the outside. The first nozzle (10) has a convergence / divergence shape defined by a constriction (13) located upstream of its outlet end (11), and can generate a gas jet at supersonic speeds, and the first discharge conduit (10") is provided with an oxygen inlet (61). The second nozzle (20) has a shape that converges toward the injector axis (X) at its outlet end (21), and is capable of generating a gas jet that is continuous with the jet generated by the first nozzle at subsonic speed, and the second discharge conduit (20") is provided with one or more inlets (70, 71, 72) for one or more fuel gases. The first discharge conduit (10") is surrounded at least at the first nozzle (10) by a first tubular housing (14) that defines a first annular circulation chamber (100) for the cooling fluid around the first discharge conduit (10"), and the second discharge conduit (20") is surrounded at least at the second nozzle (20) by a second tubular housing (24) that defines a second annular circulation chamber (200) for the cooling fluid around the second discharge conduit (20"), The injector burner (1) comprises a rectifier (30) positioned in the second discharge conduit (20") at an intermediate axial position between the second nozzle (20) and one or more fuel gas inlets (70, 71, 72), wherein the rectifier (30) is interposed across the entire annular flow cross-section of the second discharge conduit (20") at the intermediate axial position.

2. The injector burner (1) according to claim 1, wherein a cavity defining a common outflow chamber (4) opens on the front surface (2'), and both nozzles (10, 20) open at the bottom of the chamber.

3. The chamber (4) has the shape of a cylindrical cup and is coaxial with the injector shaft (X). The injector burner (1) according to claim 2, wherein the inner side wall (40) of the chamber (4) is coplanar with the outlet end (21) of the second nozzle (20).

4. The injector burner (1) according to claim 2 or 3, wherein the chamber (4) is completely housed inside the head portion (2).

5. The injector burner (1) according to any one of claims 1 to 4, wherein the front surface (2') of the head portion (2) is perpendicular to the injector axis (X).

6. The injector burner (1) according to any one of claims 1 to 5, comprising a third circulation chamber (300) for a cooling fluid, which extends inside the head portion (2) parallel to the front surface (2') and around the outlet chamber (4).

7. The third circulation chamber (300) preferably has a certain L-shaped cross-section and defines an annular circuit concentric with the outflow chamber (4), The injector burner (1) according to claim 6, wherein the first branch of the L-shaped cross section is parallel to the front surface (2') and the second branch of the L-shaped cross section is parallel to the side wall of the outflow chamber (4).

8. The injector burner (1) according to claim 6 or 7, wherein the third circulation chamber (300) is fluidly connected to the second circulation chamber (200).

9. The injector burner (1) according to any one of claims 1 to 8, wherein the second circulation chamber (200) is divided into two circumferential sectors defining two flow conduits (201, 202) connected in series with respect to each other by two partition walls (210, 220) arranged at an angle apart around the injector axis (X).

10. The injector burner (1) according to claim 9, as dependent on claim 8, wherein the two flow conduits (201, 202) of the second circulation chamber (200) are connected in series with each other by the third circulation chamber (300).

11. The injector burner (1) according to any one of claims 1 to 10, wherein the first circulation chamber (100) is fluidly connected, preferably in series, to the second circulation chamber (200).

12. The injector burner (1) according to any one of claims 1 to 11, wherein the first circulation chamber (100) is divided into a plurality of axial sectors that define axial flow conduits (101, 102, 103, 104) connected in series with respect to a plurality of axial partitions (110, 120, 130, 140).

13. The first circulation chamber (100), the second circulation chamber (200), and the third circulation chamber (300) are connected to each other in a fluid series manner. The injector burner (1) according to any one of claims 6 to 12, comprising an inlet (51) for cooling fluid provided in the second circulation chamber (200) and an outlet (52) for cooling fluid provided in the first circulation chamber (100).

14. The rectifier (30) is composed of an annular body provided with a plurality of through holes (310 or 320), An injector burner (1) according to any one of claims 1 to 13, wherein each through-hole has an axial extension parallel to the injector axis (X).

15. The injector burner (1) according to claim 14, wherein the hole (310) of the rectifier (31) has a constant cross-sectional area.

16. The injector burner (1) according to claim 14 or 15, wherein the ratio of the total cross-sectional area of ​​all holes (310) of the rectifier (31) to the total annular area of ​​the rectifier (31) is in the range of 0.2 to 0.8, preferably in the range of 0.30 to 0.

40.

17. The injector burner (1) according to any one of claims 1 to 14, wherein each hole (320) of the rectifier (32) has a cross-section that is axially differentiated between a cylindrical inlet portion (321) having a constant cross-sectional area and an outlet portion (322) having a constant cross-sectional area that is larger than the area of ​​the inlet portion (321).

18. The injector burner (1) according to claim 17, wherein the ratio of the total cross-sectional area of ​​all holes (320) of the rectifier (32) in the cylindrical inlet portion (321) to the total annular area of ​​the rectifier (32) is in the range of 0.01 to 0.2, preferably in the range of 0.02 to 0.

1.

19. In each hole (320), the ratio of the axial extension of the outlet portion (322) to the diameter of the inlet portion (321) is in the range of 3 to 30, more preferably in the range of 6 to 12, the injector burner (1) according to claim 17 or 18.

20. The injector burner (1) according to claim 17, 18, or 19, wherein the rectifier (32) is made of a material having high wear resistance.

21. The injector burner (1) according to any one of claims 1 to 20, wherein the fuel gas is provided in the form of hydrogen, in the form of a hydrocarbon gas, in particular in the form of natural gas, or a mixture thereof.

22. An injector burner (1) according to any one of claims 1 to 21, wherein hydrogen and hydrocarbon-containing gases are supplied separately to a second nozzle (20) using at least two separate inlets (71, 72) and mixed together in a second discharge conduit (20") located upstream of a rectifier (31, 32).

23. A method for the simultaneous injection of at least one fuel gas and pure oxygen or oxygen in a concentrated mixture in a metallurgical melting furnace, using an injector burner (1) according to any one of claims 1 to 22, Pure oxygen or oxygen in a mixture is supplied to the first nozzle (10), and one or more fuel gases are supplied to the second nozzle. The method includes using the injector burner in a manner that selectively follows either a burner operating mode or an injector operating mode. In this burner operating mode, oxygen is supplied at a flow rate such that it generates an oxygen jet at the outlet of the first nozzle (10) under subsonic or supersonic conditions with over-expansion. In this injector operating mode, oxygen is supplied at the outlet of the first nozzle 10 at a flow rate that generates an oxygen jet under suitable supersonic conditions or under-expansion supersonic conditions. In both operating modes, the one or more fuel gases are supplied to the second nozzle, and together with the jet generated by the first nozzle, a gas jet is continuously generated at subsonic speed. A method wherein one or more fuel gas flows are subjected to the action of the rectifiers (31, 32) upstream of the second nozzle (20), so that the second nozzle is supplied uniformly, and the jets produced by the second nozzle surrounding the central oxygen jet produced by the first nozzle are circumferentially uniform in velocity, size, and direction.

24. The method according to claim 23, wherein, in both operating modes during use, the second nozzle (20) is supplied with either pure hydrogen or a predetermined proportion of hydrogen in the supply stream from the outset.

25. The method according to claim 23, wherein, when used in burner operating mode, the proportion of hydrogen in the supply flow to the second nozzle is gradually increased until it reaches a point where pure hydrogen or hydrogen in a predetermined proportion is supplied.

26. The method according to claim 25, wherein, in the injector operating mode, the proportion of hydrogen in the supply flow to the second nozzle is the same as the proportion of hydrogen supplied to the second nozzle at the end of use in the previously performed burner operating mode.

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