Gas injector for blast furnace vertical shaft injection

Abstract

An injector for injecting hot gases, in particular heated reducing gases, into a furnace or reactor, comprising a tubular body (12) extending along a main axis (L) between a mounting portion (18) configured for securing the injector to the furnace and a nose portion (14) to be arranged inside the furnace, the tubular body includes an internal gas passage (20) for directing heated gas from an inlet orifice (22) at the mounting portion to at least one outlet orifice (16) at the nose portion. The tubular body (12) includes a coolant supply channel (40) and a coolant return channel (42) defined between cooperating inner and outer tubes (30, 34), where the coolant supply channel and the coolant return channel are formed as staggered helical channels extending in the same layer in the direction of the main axis.

Description

Technical Field

[0001] The present invention relates generally to the field of metallurgy and more particularly to the operation of a shaft furnace (ie blast furnace) in which hot reducing gas is fed into the furnace shaft. Background Art

[0002] With the signing of the Paris Agreement and near global consensus on the need for action to reduce emissions, all industrial sectors must develop solutions to improve energy efficiency and reduce CO2 output.

[0003] In this context, practitioners in the field of ferrometallurgy have developed new methods to reduce the environmental footprint of blast furnace steelmaking lines. In fact, despite alternative methods such as scrap smelting or direct reduction in electric arc furnaces, the blast furnace (BF) still represents today the most widely used process in steel production.

[0004] One technology developed to reduce the carbon footprint during steel production is the so-called "shaft injection", in which hot gases (mainly CO and H2) are injected into the upper part of the blast furnace, above the cohesion zone, in a part that is usually protected internally by a refractory lining or cooling elements such as plates or wall panels or plate coolers or cooling elements protruding in the inner wall of the furnace.

[0005] The injection of hot gases in a blast furnace or in a shaft furnace at shaft level (shaft injection) is cited in many publications and inventions, but has not yet been implemented in commercial blast furnaces in industrial applications.

[0006] A gas injector for shaft supply is disclosed, for example, in WO 2022 / 064046. The gas injector comprises a tubular body defining a gas passage. A coolant fluid circulates in the annular gap.

[0007] Other designs of injectors have been developed without cooling arrangements, see for example WO 2022 / 058771. However, injectors without cooling arrangements cannot take advantage of the higher strength of the materials used at low temperatures and also result in larger dimensions.

[0008] Furthermore, prior art injectors are molded from expensive high grade materials and are subject to different (heat induced) stresses at many points in their body during use, causing some parts of the injector body to exhibit different stress related expansion / dilation than other parts. This in turn reduces the life and reliability of the injector.

[0009] Therefore, one challenge is to increase the durability and flexibility of injectors operating in aggressive gas atmospheres, in abrasive conditions due to solid material flowing at very high temperatures, and in dusty environments.

[0010] Objectives of the invention

[0011] An object of the present invention is to provide a gas injector of improved design which overcomes the above mentioned drawbacks and meets the desired requirements of durability and flexibility. Summary of the invention

[0012] In order to achieve the above mentioned objectives, the present invention proposes an injector for injecting hot gas, in particular hot reducing gas. The gas injector has been specially developed for injecting hot gas, i.e. hot / heated reducing gas, into a furnace or reactor, more specifically into a metallurgical furnace or reactor, in particular a shaft furnace or blast furnace. The injector comprises:

[0013] a tubular body extending along a main axis between a mounting portion configured for fixing the injector to the furnace and a nose portion arranged inside the furnace, the tubular body comprising an internal gas passage for directing hot gases, in particular heated reducing gases, from an inlet orifice at the mounting portion to at least one outlet orifice at the nose portion;

[0014] The tubular body includes a coolant supply channel and a coolant return channel defined between cooperating inner and outer tubes, wherein the coolant supply channel and the coolant return channel are formed as staggered spiral channels extending in the main axis direction in the same layer.

[0015] The main benefit of the present invention is obtained by the arrangement of the coolant supply and return channels in the same layer. Such arrangement is possible due to the specific design of the injector of the present invention, in which the inner and outer tubes cooperate with each other to define the supply and return channels. The supply and return channels are staggered, they are close to each other in the same layer. Therefore, they are at the same height.

[0016] The present invention is designed to be compact: combining the supply channel and the return channel in the same layer is more compact than, for example, having two superimposed layers (one layer for the supply flow and the other layer for the return flow), which further gives more space for the passage of the reducing gas flowing through the injector, or reduces the overall external dimensions of the injector, in particular the outer diameter.

[0017] Another benefit of the present invention is that, due to the coolant supply and return channels, the injector is cooled, making it more wear-resistant and reliably resistant to sudden charge drops. Since the coolant channels are staggered, the two coolant flows are arranged close to each other. In other words, the channels with counter-current coolant are arranged in a staggered manner. Due to the inventive arrangement of the coolant supply and return channels formed as staggered spiral channels, the surface of the inventive injector is cooled more evenly than the surface of a conventional injector with a conventional cooling arrangement, thereby reducing thermal stresses in the material forming the tube and thus reducing deformation of the injector. This provides the desired durability and flexibility for the inventive gas injector.

[0018] Any suitable material can be used for the injector tubular body. However, the injector body (i.e., the inner tube and the outer tube) is preferably made of steel or alloy steel (or steel alloy), more preferably of stainless steel or high temperature steel. High temperature steel corresponds to steel that resists corrosion due to high temperatures and maintains strength at temperatures up to higher than conventional steel. The high temperature steel may be, for example, the following steel grades: 1.4841; 1.5415; 1.4842; 1.4659; 1.4859; 1.4889 or similar steel grades. Alternatively, the injector body may be made of copper, a copper alloy, nickel or a nickel alloy.

[0019] In a specific example, the inner tube includes two staggered helical grooves defining the supply and return passages, the helical grooves extending from the mounting portion to the nose portion where the two helical grooves are fluidly connected.

[0020] In addition, an inlet port is arranged at the mounting portion and connected to the first spiral groove, and an outlet port is arranged at the mounting portion and connected to the second spiral groove. The inlet port and the outlet port are advantageously connected to a coolant circulation system. Coolant (e.g., water) from a coolant source enters the first spiral groove via the inlet orifice, flows through the first groove toward the nose portion where the first groove and the second groove connect, and then flows back through the second spiral groove toward the mounting portion, where the coolant flows out of the second groove (towards the collector pipe) via the outlet port.

[0021] One advantage of the present invention is related to the size of the injector. As mentioned above, due to the specific design in which the coolant supply and return channels are arranged in the same layer, the total outer diameter of the injector of the present invention can be small / compact, which allows more space for passages. This is achieved by the specific design of the injector of the present invention, wherein the ratio between the outer diameter of the outer tube and the inner diameter of the inner tube is preferably less than 2.5, less than 2 or even less than 1.5. For example, in a specific example, the size of the outer diameter and the inner diameter can be as follows: 220 / 110mm, 270 / 160mm, 250 / 135mm. These values ​​are only indicative and do not limit the scope of the present invention.

[0022] In a specific example, the nose portion comprises an end face arranged with at least one outlet aperture, the end face being at least partially inclined relative to the main axis so that in use the end face faces downwards. Advantageously, the inclined end face prevents descending charge material from entering the injector, thereby reducing the risk of injector blockage or flow restriction.

[0023] Further advantageously, the inclined end face promotes uniform cooling of the nose portion of the injector of the invention in which the coolant supply and return channels are formed in the same layer, since the channel at the supply channel close to the nose tip can follow the tip at a short and substantially constant distance. This advantageously leads to uniform cooling, since the coolant cannot take shortcuts, contrary to what is known in the art, such as from FR2085511 A1, where the water flow is smaller at the top, since the path for the water is longer here and the resistance is therefore higher.

[0024] The end face may be flat or curved. Preferably, the angle between the end face and the main axis is between 10° and 60°, and more preferably 20°. However, the angle may be adjusted depending on the corresponding angle of the material in the furnace and the size of the injector.

[0025] According to the same or other specific examples, the injector includes a sealing structure between the inner tube and the outer tube. Preferably, the sealing structure includes a spiral seal between the two spiral grooves. In other words, the coolant supply channel and the coolant return channel are separated from each other by a seal arranged in a space extending between the two channels. This position of the seal advantageously reduces the bypass of the coolant from one channel to another channel, even if the outer tube is deformed during operation. The spiral seal may comprise any suitable material, however, it preferably comprises a water-swellable material, and more preferably, comprises water-swellable fibers. If one channel begins to leak, the coolant (usually water) contacts the water-swellable material, which advantageously expands and closes to form a gap, thereby preventing further leakage of the coolant.

[0026] According to the same or other specific examples, the injector further comprises a tubular protective insert disposed in the passage of the tubular body, thereby defining a central passage for the reducing gas. The insert protects the inner surface of the inner tube, thereby increasing its life and efficiency. The protective insert is disposed inside the passage and defines a central passage for the heated reducing gas.

[0027] The protective insert may be made of any suitable material; however, it is preferably made of a thermally insulating material and / or a stress-resistant material and / or a chemically resistant material. More preferably, the insert is made of a ceramic and / or a dense ceramic material, such as alumina, magnesia, zirconia or silicon carbide.

[0028] Advantageously, the thermal insulation material may be arranged between the tubular body and the protective insert. The temperature losses of the injected hot reducing gas will be reduced, resulting in higher gas reactivity and energy savings. In a specific example, the tubular protective insert has a concave outer surface, and the thermal insulation material is arranged as an outer layer in the concave outer surface. The thermal insulation material may have any desired shape; it may be supplied as one, two or more pieces, which may be formed / assembled into an outer layer around the tubular protective insert. In a preferred specific example, the thermal insulation material is arranged as two half cylinders, which are assembled into the concave outer surface of the protective insert. The thermal insulation material can generally be any material having thermal insulation properties, and preferably comprises an alumina-based ceramic material or a zirconia-based ceramic material, more preferably comprises microporous ceramics and / or ceramic fibers.

[0029] In a particular example, the injector further comprises a mounting flange extending radially from the tubular body, the mounting flange being used to at least indirectly secure the injector to the outer wall of the furnace.

[0030] According to the same or other specific examples, the injector further comprises a connecting flange surrounding the mounting portion, the connecting flange being used to connect the injector to a corresponding flange of a reducing gas supply line of a gas injection system of a metallurgical furnace.

[0031] According to another invention, the present invention also relates to a gas injection system for a furnace, in particular a blast furnace, comprising a furnace wall (or shell) at least partially covered by an internal protective layer, the gas injection system comprising at least one injector according to the present invention, wherein the injector crosses the furnace wall and the protective layer respectively.

[0032] Conventionally, the protective layer may comprise refractory material and / or cooling elements. The cooling elements may comprise cooling boxes and / or cooling panels / staves.

[0033] In the case of cooled staves with internal coolant channels, the inventive design with a single layer of coolant channels is advantageous for compactness, since the injectors can be arranged in the body of the stave, between the coolant channels or adjacent to the coolant channels.

[0034] The injector can be arranged to pass through the outer wall and the protective layer so that the injector tip is flush with the inner side of the protective layer (facing the charge / charge material) or protrudes from it. In the latter case, the injector protrudes from the inner side of the protective layer by a distance of, for example, 50 mm, 100 mm or 200 mm or possibly more.

[0035] In an embodiment, the injector is oriented perpendicular to the furnace wall (i.e., pointing toward the center of the furnace) or tangentially to the furnace wall. In a preferred embodiment, the angle between the injector and the furnace wall is between 50° and 90°. Angles below 50° may cause space problems inside the furnace. Tangential orientation helps to create eddies in the furnace, which helps to increase the distribution of the gas and mixing with the rising gas from the tuyere height, and also increases the residence time of the gas in the furnace, thereby increasing gas utilization.

[0036] According to the same or other specific examples, the gas injection system further comprises at least one guide sleeve fixed to the furnace wall and traversing the furnace wall and the wall plate. The injector is received in the guide sleeve and protrudes from the guide sleeve in the furnace. Advantageously, during operation, the sleeve protects the furnace from cooling elements during the exchange of the injectors. The guide sleeve prevents falling charge from being caught between the injector and the wall plate during the exchange process, thereby reducing the risk of significant damage.

[0037] The gas injection system may further comprise at least one mounting sleeve fixed to the furnace wall and protruding inside the furnace; the guide sleeve extending in the mounting sleeve.

[0038] According to a further aspect, the present invention also relates to a shaft furnace, in particular a blast furnace, comprising:

[0039] A metal shell defining a furnace wall;

[0040] at least one tuyeres arranged at tuyeres height for injecting hot gases into the shaft furnace, and

[0041] The gas injection system according to the present invention comprises at least one injector,

[0042] At least one injector is arranged at an injection height above the tuyere height.

[0043] It should also be noted that the injector of the present invention can be used in various operating modes of the shaft / blast furnace.

[0044] The hot reducing gas may typically be a gas containing mainly (>50% by volume) a reducing agent species such as CO or H2. In particular, the reducing gas may be "synthesis gas". The reducing gas may be injected into the furnace via an injector at a temperature between 600°C and 1200°C, in particular between 800°C and 1200°C. The reducing gas injection may be performed at a velocity between 40m / s and 200m / s.

[0045] The injection of hot reducing gas is usually carried out by a plurality of injectors according to the present invention, which are distributed around the circumference of the shaft / blast furnace, preferably at a distance between injectors within 0.5 to 2.5 m. Such equidistant injectors allow for uniform distribution of the injected gas around the furnace circumference and further help to center the rising gas flowing upward in the furnace and coming from the bosh area.

[0046] Conventionally, the gas injected through the tuyere at the tuyere height may be hot blast in order to burn the coke in the charge. Alternatively, hot reducing gas (eg, syngas) may be injected through the tuyere at a relatively high temperature with or without oxygen. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present invention will now be described as an example with reference to the accompanying drawings, in which:

[0048] Figure 1 : is a first perspective schematic diagram of a specific example of the injector of the present invention;

[0049] Figure 2 : is a second perspective schematic diagram of the injector of the present invention;

[0050] Figure 3 :for Figure 2 A cross-sectional schematic diagram of an injector;

[0051] Figure 4 :for Figure 2 A detailed perspective schematic diagram of a portion of an injector of; and

[0052] Figure 5 :for Figure 2 An exploded perspective diagram of an injector. DETAILED DESCRIPTION

[0053] Figures 1 to 5 Different views of an embodiment of an injector 10 according to the invention are shown.

[0054] The gas injector 10 is designed for injecting heated reducing gas into a furnace, in particular a blast furnace, but it can be generally used for injecting hot gas into a furnace or reactor, in particular a metallurgical furnace / reactor. The injector 10 comprises a tubular body 12 (or injector body) extending along a main axis L from a nose (front) portion 14 to a relative (rear) mounting portion 18, the nose portion having, for example, one injection hole or outlet orifice 16 (possibly more). The tubular body 12 comprises an internal gas passage 20 for guiding the hot / heated reducing gas from an inlet orifice 22 in / at the mounting portion 18 to the injection hole 16. The tubular body 12 is generally made of steel or a steel alloy or a metal alloy. In practice, the inlet orifice 22 is connected to a hot gas source, i.e., hot reducing gas (not shown) via an appropriate pipe / duct.

[0055] The mounting portion 18 includes a mounting flange 24 extending radially from the tubular body 12, which is used to at least indirectly mount (i.e., fix) the injector 10 to a furnace wall portion, typically a furnace outer wall / shell (not shown). The mounting portion 18 also includes a connecting flange 26 extending radially from the tubular body 1 and surrounding the inlet opening 22, which is used to connect the injector to a corresponding flange of a reducing gas supply pipeline of a gas injection system (not shown). Other types of connecting components for connecting the inlet orifice 22 of the injector 10 to the supply pipeline can also be used.

[0056] The injector 10 or its tubular body 12 comprises a cooling system 28, such as cooling channels connected to a coolant circulation system (not shown), in particular when, in the installed state of the injector 10, the portion surrounding the injection hole or outlet orifice 16 protrudes inside the blast furnace.

[0057] It will be appreciated that the injector 10 of the present invention has a tubular body 12 comprised of two tubes, namely an inner tube 30 and an outer tube 34. As can be seen, the outer tube 34 defines the outer wall of the injector, while the inner tube 30 defines the gas passage 20.

[0058] The tubular body 12 includes a coolant supply channel 40 and a coolant return channel 42 defined between the inner tube 30 and the outer tube 34. The supply channel 40 and the return channel 42 are formed as staggered spiral channels extending in the same layer along the main direction (defined by the axis L). The supply channel 40 extends from the inlet port 44 at the mounting portion 18 to the nose 14 of the tubular body 12, and the return channel 42 extends from the nose portion 14 to the outlet port 46 at the mounting portion 18 of the tubular body 12. The inlet port 44 and the outlet port 46 are open through the outer tube 34. The supply channel 40 and the return channel 42 are fluidically connected to each other at the nose portion 14. As can be seen from the accompanying drawings, since the supply channel and the return channel are interlaced with each other, these channels are arranged to be close to each other in the same layer. Therefore, these channels are at the same height, and the supply channel and the return channel extend adjacent to each other on the length of the tubular body 12 to form a single-layer structure.

[0059] In other words, the supply channel and the return channel are defined in the transverse direction (transverse to the main axis L) by the inner tube 30 and the outer tube 34. The supply channel and the return channel are two separate flow paths for the coolant, which are staggered or alternated (i.e., not one above the other) within the same layer defined by the inner tube 30 and the outer tube 34. The supply channel and the return channel surround the gas passage 20.

[0060] The inner tube 30 and the outer tube 34 are shaped / configured to cooperate with each other to define a coolant supply channel 40 and a coolant return channel 42. In the illustrated embodiment, the outer surface 50 of the inner tube 30 includes two staggered spiral grooves 48.1, 48.2 that define the coolant supply channel 40 and the coolant return channel 42, respectively. Thereby, these grooves are separated by a spiral ridge 48.3. In this embodiment, the inner surface 52 of the outer tube 34 is smooth and closes the coolant channel. However, other configurations are possible, for example, the outer surface of the inner tube 30 can be smooth, while the inner surface of the outer tube 34 can be machined to include two staggered spiral grooves.

[0061] The sealing structure is disposed between the inner tube 30 and the outer tube 34 of the tubular body 12. Figure 4 In a specific example, the sealing structure comprises a spiral seal 54 between the two spiral grooves 48.1, 48.2. The seal 54 is arranged in a groove in the spiral ridge 48.3. The seal 54 can generally be made of any suitable material, but water-swellable materials such as water-swellable fibers are preferred. The inner tube and the outer tube are fixed relative to each other and assembled in a sealed manner. For example, the inner tube and the outer tube can be welded at their axial ends, which also provides the required water seal.

[0062] The nose portion 14 of the injector tubular body 12 also includes an end face 56 in which the outlet orifice 16 is arranged. The end face 56 is inclined relative to the main axis L so that an angle θ is formed between the end face 56 and the main axis L, and the end face faces downward in use. The angle θ may be, for example, between 10° and 60°. According to the specific example shown, the end face 56 is flat, however, other configurations are possible, and the end face may be, for example, curved.

[0063] The injector 10 is exposed to a lot of heat in use and inside the furnace. Therefore, a protective insert 60, which acts as an insulating layer (preferably based on ceramic or refractory materials), is advantageously arranged inside the inner tube 30, and therefore in the passage 20 of the tubular body 12. The protective insert 60 has a tubular / cylindrical shape and protects the inner surface of the inner tube 30, while leaving a central passage 20.1 for the reducing gas to flow through the injector. The size of the outer diameter of the protective insert 60 generally corresponds to the inner diameter of the inner tube 30 of the tubular body 12 with some clearance. The protective insert 60 can be generally made of ceramic or dense ceramic, such as oxide ceramics, in particular magnesium oxide, aluminum oxide, zirconium oxide or silicon carbide.

[0064] An intermediate layer of thermal insulation material 64 may be arranged between the inner tube 30 and the protective insert 60. In this variation, the outer surface of the protective insert comprises a recess 62, i.e., the insert 60 has a concave outer surface and the thermal insulation material 64 is arranged in the recess 62. Figure 5As can be seen in FIG. 1 , the protective insert has a tubular shape with two end shoulders 61 on its outer surface axially delimiting an annular recess 62. The thermal insulation material 64 is configured as two semi-cylinders 64.1, 64.2 which fit into the annular recess 62 on the outer surface of the protective insert 60 ( Figure 5 ). However, other configurations are possible, and the thermal insulation material may have any other shape, such as a cylindrical sleeve, with the protective insert inserted inside the sleeve-shaped insulation material. The thermal insulation layer may be made of any suitable thermal insulation material, such as oxide ceramics.

[0065] In the installed state, Figure 1 As shown in the figure, the injector 10 is arranged to protrude slightly inside the blast furnace. The blast furnace generally comprises a hearth and a steel shell 71 (shown in dotted lines) extending vertically above the hearth forming a shaft. The steel shell constitutes the outer wall of the furnace. The inner surface of the steel shell (i.e., facing the interior of the furnace) is generally covered by cooling plates (or wall panels). Such cooling plates typically have a plate-like body made of steel or copper (alloy) with internal coolant channels through which a coolant (water) circulates. The front side of the cooling plate (i.e., facing the interior of the furnace) is also generally covered by a protective layer of steel blade inserts or refractory material (not shown in the figure). Figure 1 The dashed line 73 in the figure depicts the inside of a protective lining formed, for example, by a cooling plate with or without inserts / refractory material, and LP indicates the protrusion length, which may be about 50 mm, 100 mm or 200 mm or more.

[0066] The mounted injector 10 protrudes into the furnace interior through corresponding apertures in the housing, so that the nose portion 14 with the outlet orifice 16 is located inside the furnace, while the mounting portion 18 is outside the outer wall. In the case of cooling plates, these are provided with corresponding apertures (holes through their thickness), and the injector is arranged to pass through these apertures. The injector body 12 extends through the apertures in the furnace housing (apertures 71.1) and the apertures in the cooling plates (protective lining 71), and protrudes from the cooling plates inside the furnace (to a length LP).

[0067] The injector 10 is attached to the aperture 71.1 in the furnace shell 71 in a gas-tight manner by means of the mounting flange 24. For ease of installation and sealing purposes, a mounting sleeve 66 (made of steel, ceramic material or a suitable metal alloy) can be arranged to extend in both apertures. The mounting sleeve 66 has an outer diameter corresponding to the diameter of the two apertures (i.e., in the outer shell and the cooling plate) and has a length suitable for guiding through the shell 71. The mounting sleeve 66 comprises a corresponding mounting flange 68 fixed to the furnace wall in any suitable manner (e.g., bolting or welding, in a gas-tight manner).

[0068] A guide sleeve 70 with a corresponding flange 72 can further be fixed to the outer wall of the furnace and is arranged to extend through the furnace wall and the protective lining (cooling element and / or refractory material). The guide sleeve 70 extends in the mounting sleeve 66 and receives the injector 10, which protrudes from the guide sleeve in the furnace. The guide sleeve 70 has a length corresponding to the distance from the outer side of the shell to the front side 71 or the protective lining.

[0069] The injector 10 may be mounted to the furnace wall in any suitable manner. The injector may be oriented perpendicularly to the furnace wall (pointing towards the centre of the furnace) or tangentially to the furnace wall (i.e. at any angle below 90°, preferably above 50° relative to the furnace wall at the location of the injector).

[0070] [List of Reference Numerals]

[0071] 10: Injector

[0072] 12: Tubular body

[0073] 14: Nose

[0074] 16: outlet opening

[0075] 18: Installation

[0076] 20: Gas passage

[0077] 22: Inlet orifice

[0078] 24: Mounting flange of injector

[0079] 26: Connecting flange

[0080] 28: Cooling system

[0081] 30: Inner tube

[0082] 34: External pipe

[0083] 40: Coolant supply channel

[0084] 42: Coolant return channel

[0085] 44: Inlet orifice

[0086] 46: outlet opening

[0087] 48.1, 48.2: Staggered spiral grooves

[0088] 48.3: Spiral ridges

[0089] 50: Outer surface of inner tube

[0090] 52: Inner surface of outer tube

[0091] 54: Spiral seal

[0092] 56: End face

[0093] 60: Protective insert

[0094] 61: Shoulder

[0095] 62: concave part

[0096] 64: Thermal insulation layer

[0097] 64.1, 64.2: Half of the thermal insulation layer

[0098] 66: Install the casing

[0099] 68: flange for mounting the sleeve

[0100] 70: Casing

[0101] 72: flange of guide sleeve

[0102] L: Main axis

[0103] θ: Angle between the end face and the main axis

Claims

1. An injector for injecting hot gas into a metallurgical furnace or reactor, in particular for injecting heated reducing gas into a furnace or reactor, the injector comprising: a tubular body (12) extending along a main axis (L) between a mounting portion (18) and a nose portion (14), the mounting portion being configured for securing the injector to the furnace, the nose portion to be arranged inside the furnace, the tubular body comprising an internal gas passage (20) for directing heated gas from an inlet orifice (22) at the mounting portion to at least one outlet orifice (16) at the nose portion; The tubular body (12) includes a coolant supply channel (40) and a coolant return channel (42) defined between cooperating inner and outer tubes (30, 34), wherein the coolant supply channel and the coolant return channel are formed as staggered spiral channels extending in the same layer along the main axis direction.

2. The injector according to claim 1, wherein The inner tube comprises two staggered helical grooves (48.1, 48.2) defining the supply channel and the return channel, the helical grooves extending from the mounting portion to the nose portion, the two helical grooves being fluidly connected at the nose portion; and wherein an inlet port (44) is arranged at the mounting portion and connected to the first spiral groove; An outlet port (46) is arranged at the mounting portion and connects the second spiral groove.

3. Injector according to claim 1 or 2, wherein the ratio between the outer diameter of the outer tube and the inner diameter of the inner tube is less than 2.5, preferably less than 2 or 1.

5.

4. An injector according to any one of the preceding claims, wherein the nose portion (14) comprises an end face (56) at which the at least one outlet orifice is arranged, the end face being at least partially inclined relative to the main axis such that in use the end face faces downwards.

5. Injector according to claim 4, wherein the end surface (56) is flat or curved.

6. Injector according to claim 4 or 5, wherein the angle (θ) between the end face and the main axis is between 10° and 60°, preferably 20°.

7. An injector according to any one of the preceding claims, comprising a sealing structure between the inner tube and the outer tube.

8. The injector according to claim 7, wherein the sealing structure comprises a spiral seal (54) interposed between the two spiral grooves.

9. Injector according to claim 8, wherein the spiral seal comprises a water-swellable material, preferably a water-swellable fiber.

10. The injector according to any of the preceding claims, further comprising a tubular protective insert (60) arranged in the passage of the tubular body.

11. Injector according to claim 10, wherein the protective insert is made of a thermally insulating material and / or a stress-resistant material and / or a chemically resistant material, preferably, the insert is made of oxide ceramics, graphite and / or silicon carbide.

12. Injector according to claim 10 or 11, wherein a thermal insulation material (64) is arranged between the tubular body (12) and the protective insert (60).

13. The injector of claim 12, wherein the tubular protective insert has a concave outer surface and the thermal insulation material is provided as a peripheral layer in the concave outer surface.

14. Injector according to claim 13, wherein the thermal insulation material is provided as two half cylinders (64.1, 64.2) which fit within the concave outer surface.

15. Injector according to any one of claims 12 to 14, wherein the thermal insulation material comprises an alumina-based ceramic or a zirconia-based ceramic, preferably microporous ceramic and / or ceramic fibers.

16. Injector according to any one of the preceding claims, further comprising a mounting flange (24) extending radially from the tubular body for at least indirectly securing the injector to an outer wall of a furnace.

17. Injector according to any of the preceding claims, further comprising a connection flange (26) surrounding the mounting portion, the connection flange being used to connect the injector to a corresponding flange of a reducing gas supply line of a metallurgical furnace gas injection system.

18. Injector according to any one of the preceding claims, wherein the injector body is made of steel or a steel alloy, preferably stainless steel or high temperature steel.

19. A gas injection system for a furnace or a reactor, in particular for a blast furnace, comprising a furnace wall (71) having a protective layer, the gas injection system comprising at least one injector according to any one of the preceding claims, wherein the injector traverses the furnace wall and the protective layer.

20. The gas injection system of claim 19, wherein the injector is oriented perpendicularly or tangentially to the furnace wall, preferably the angle between the injector and the furnace wall is between 50° and 90°.

21. The gas injection system of claim 19 or 20, further comprising at least one guide sleeve (70), wherein the guide sleeve is fixed to the furnace wall and traverses the furnace wall and the wall plate, and wherein the injector is received in the guide sleeve and protrudes from the guide sleeve into the furnace.

22. The gas injection system of claim 21, further comprising at least one mounting sleeve (68) fixed to the furnace wall and protruding inside the furnace; the guide sleeve extending in the mounting sleeve.

23. A gas injection system according to any one of claims 19 to 22, wherein the coolant supply passage is connected to a coolant fluid source and the coolant return passage is connected to a coolant collector conduit.

24. A gas injection system according to any one of claims 19 to 23, wherein the protective layer comprises cooling elements and / or refractory materials, and wherein the gas injector is arranged so that the nose portion is flush with the inner side of the protective layer, or protrudes a distance (PL) relative to the inner side of the protective layer.

25. A vertical furnace, in particular a blast furnace, comprising A metal shell defining a furnace wall; at least one tuyeres arranged at tuyeres height for injecting hot gases into said shaft furnace, and A gas injection system according to any one of claims 19 to 24, Wherein the at least one injector is arranged at an injection height above the tuyere height.

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