Reducing Gas Injection System

Abstract

A reducing gas injection system (10) for a blast furnace having a blast furnace wall (30), comprising: a reducing gas distribution pipe (20); and one or more injection devices (40) attached to the blast furnace wall at shaft level, wherein the reducing gas distribution pipe (20) is attached to the blast furnace wall (30) or a supporting structure thereof, and the injection devices (40) include a nozzle body (42) having a peripheral wall extending along a longitudinal axis from a front end having at least one injection hole (41) to an opposite rear end having an inlet (43), the nozzle body including an internal gas channel for directing reducing gas from the inlet (43) to the injection hole (41), and the nozzle body (42) is attached through an opening in the blast furnace wall (30) so that the front end having the injection hole (41) is located inside the blast furnace (31). a nozzle body (42) including a peripheral mounting portion configured to gas-tightly connect the injection device to the opening in the blast furnace wall, the nozzle body (42) including a peripheral mounting portion configured to gas-tightly connect the injection device to the opening in the blast furnace wall, the inlet (43) being fluidly connected to a reducing gas distribution pipe (20) by an injection device support, the injection device support including a supply pipe (51) connected to the reducing gas distribution pipe (20), an elbow (52) connected to the supply pipe (51), and an injection pipe (53) connected to the elbow (52), the injection pipe (53) being gas-tightly flanged to the inlet (43) of the injection device (40) and gas-tightly attached to the injection pipe (53) and / or an outlet of the elbow including at least one Cardan compensation joint (531).

Description

[Technical Field]

[0001] The present invention relates generally to the field of metallurgy, and more particularly to the operation of a blast furnace in which hot reducing gas is supplied to the blast furnace shaft. [Background technology]

[0002] With the Paris Agreement and near-global consensus on the need for action on emissions, it is imperative that each industrial sector considers how it can improve energy efficiency and develop solutions to reduce CO2 emissions.

[0003] In this context, actors in the field of ferrous metallurgy have developed new methods to reduce the environmental damage in the blast furnace iron-making route. Indeed, despite the existence of alternative methods such as scrap melting or direct reduction in electric arc furnaces, the blast furnace (BF) still represents the most widely used process for iron and steel production today.

[0004] Among the techniques developed to reduce blast furnace CO2 emissions, it has been proposed to introduce hot reducing gas, typically synthesis gas (syngas) (consisting primarily of CO and H2), directly into the shaft of the blast furnace. This is also known as "shaft feeding" and refers to the introduction / injection of hot reducing gas (syngas) through the outer wall of the furnace into the ferrous oxide gas-solid reduction zone above the hot blast (tuyere) level, i.e., above the bosh and preferably above the cohesive zone. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to propose a viable reducing gas injection system for supplying hot reducing gas to the shaft of a blast furnace, which can be implemented in existing blast furnaces. A further object of the present invention is to provide a compact and cost-effective system for the gas-tight connection of the hot synthesis gas piping with the injection points in the shaft of the blast furnace, preferably allowing relative movement of the two systems. [Means for solving the problem]

[0006] In order to overcome the above problems, the present invention provides, in a first aspect, The reducing gas injection system a reducing gas distribution pipe; - one or more injectors mounted on the (outside of) the blast furnace wall at shaft level, The reducing gas distribution pipe is attached (configured) to the blast furnace wall or its supporting structure, the one or more injection devices include a nozzle body having a peripheral wall extending along a longitudinal axis from a front portion having at least one injection hole to an opposite rear portion having an inlet port, the nozzle body including an inner gas channel configured to guide a reducing gas from the inlet port to the injection hole(s); the nozzle body is mounted through an aperture in the wall of the blast furnace so that a front part with injection hole(s) is located inside the blast furnace and the rear part with an inlet is located outside the wall of the blast furnace, preferably the mounting is a flange mounting; The nozzle body includes a peripheral mounting portion configured to gas-tightly connect the injection device to the opening in the blast furnace wall. the inlet is in fluidic connection with the reducing gas distribution pipe by an injector stock, the injector stock including a supply pipe connected to the reducing gas distribution pipe, an elbow connected to the supply pipe, and an injector pipe connected to the elbow; The present invention proposes a reducing gas injection system for a blast furnace, comprising a blast furnace wall, the injection pipe being flange-mounted gas-tightly to the inlet of the injection device and the outlet port of an elbow containing the injection pipe and / or at least one compensation system, which may be a cardan joint.

[0007] Injection of reducing gas into the shaft of a blast furnace has been cited in many publications, but has not yet been implemented in industrial applications in commercial blast furnaces.

[0008] One challenge with integrating shaft injection compared to the known hot air injection at the tuyere level is the nature of the reducing gas: at the tuyere the gas is simply hot air, whereas with shaft injection the gas is a reducing gas, typically a synthesis gas (syngas) containing large amounts of highly flammable hydrogen and CO, the latter of which is also toxic to humans.

[0009] Therefore, maintaining a gas-tight connection between the main gas distribution pipe and the injection points of the blast furnace is of utmost importance. This is all the more true when one realizes that the high temperatures of the reducing gas (up to about 1100°C) and the high temperatures inside the blast furnace at shaft level cause thermal expansion and deformation of the blast furnace wall, the reducing gas distribution pipe, the injectors, and the injector supports, resulting in non-negligible relative displacements and stresses throughout the reducing gas injection system. The injector supports must therefore compensate for these relative displacements without allowing the reducing gas to escape by leakage.

[0010] In the case of tuyere systems, the front of the blowpipe is pressed against the tuyere, which is built into the wall of the blast furnace, by a spring tie rod system. While this provides some compensation for lateral movement, this solution is not sufficiently gas-tight when using reducing gases such as syngas. Therefore, in contrast to the attachment of a tuyere support to the tuyere, the injection pipes of current reducing gas injection systems are gas-tightly attached to the injection device by flange mounting. This solves the gas-tightness problem, but it compromises the ability to compensate for the above-mentioned relative displacement of the elbow and injection pipe.

[0011] Cardan compensation joints are known in the art of tuyere stocks and are described in U.S. Patents 3,662,696, 3,766,868, 4,023,832, 4,027,605, 4,987,838 and 5,462,433, which are incorporated herein by reference. Another advantageous Cardan compensation joint is described in DE 20 2012 011 622.3, which is also incorporated herein by reference. The tuyere support of the referenced patent offers the advantage that differential deformations during use and manufacturing imperfections between the tubular segments of the tuyere support can be compensated for by using a Cardan compensation joint in combination with a bellows-type compensator which generally has very few corrugations.

[0012] However, in conventional tuyere supports, such Cardan type compensating joints are used in the downcomer section of the tuyere support, i.e., upstream of the elbow, rather than downstream thereof.

[0013] The inventors have found that the loss of flexibility caused by conventional attachment of spring tie rod systems in the tuyere system can be advantageously balanced by introducing a Cardan type compensating joint downstream of the elbow bend, for example at the elbow outlet (near the elbow attachment to the injection pipe) and / or internally within the injection pipe, without compromising gas tightness.

[0014] In order to further compensate, as far as possible, for any further relative movements between the reducing gas distribution pipe and the injection device(s), the supply pipe preferably also comprises at least one further Cardan compensation joint. In an advantageous embodiment, two Cardan compensation joints are foreseen, one near the inlet of the supply pipe and the other near the outlet of the supply pipe.

[0015] Ease of maintenance and time savings during maintenance are very important, especially when the number of injection points and therefore the number of connections is large. For this purpose, quick couplings to the two corresponding flanges of the injection pipe, together with hooks on the injection pipe, can be foreseen. In an embodiment, the injection pipe is flange-mounted in a gas-tight manner to the injection device inlet by bolts or hooks, the use of hooks allowing for faster assembly and disassembly. Advantageously, gas tightness is further improved by using metal and / or soft seals between the first mounting flange at the rear of the nozzle body and the second mounting flange of the injection pipe. Even more advantageously, all flanges of the injection device support are provided with metal and / or soft seals. The seals can be of various materials and shapes, such as flat or O-ring type.

[0016] Furthermore, the flange mounting can also be opened to connect a drill to free blocked injection equipment on the rear flange during maintenance, and will therefore be constructed to withstand the forces involved in such a case.

[0017] Alternatively, at least in the case of minor obstruction of the injection device or simply for inspection, the elbow is preferably provided with a maintenance and inspection port concentric with the longitudinal axis of the injection device, to which a cover, a view glass and / or a camera are preferably removably attached. The camera and the view glass can be used simultaneously, for example by using a suitably positioned beam splitter. Since at shaft level, in contrast to at tuyere level, the interior of the blast furnace is dark, the camera is preferably a thermal and / or infrared camera and / or can be provided with an additional light source.

[0018] In a particularly advantageous embodiment, partial or increasing clogging of the injector can also be detected by integrating a flow detector, or preferably a skin flow or thermocouple, at any position of the injector support that protrudes into the gas flow or is integrated into the refractory lining. Indeed, if the gas flow is significantly reduced or stopped, the temperature readings of the thermocouple will decrease, indicating the need for inspection and maintenance.

[0019] The front area of ​​the injection device, i.e. the area including the injection holes, can be flush with the inner blast furnace wall in its recess or in the part that projects into the inside of the blast furnace. If a cooling plate is attached to the inside of the blast furnace wall, the front area of ​​the injection device can be flush with the inside of the cooling plate in its recess or projecting into the inside of the blast furnace.

[0020] In this latter case, the front of the injection device is adapted to fit through a corresponding opening in a cooling plate attached to the inside of the blast furnace wall.

[0021] It should be noted that if the front region of the injection device projects inside the blast furnace, it is foreseeable that there will be a number of injection holes in the projecting part of the injection device, said injection holes advantageously pointing in different directions, such as straight (along the longitudinal axis of the injection device), perpendicular to the longitudinal axis of the injection device or at any suitable angle, downwards and / or to one or both sides.

[0022] In the case of a protruding type injection device, it may be necessary or desirable to provide a protruding cover located above the injection device that is configured to protect the front of the nozzle body that protrudes into the inside of the blast furnace from descending burden material.

[0023] Furthermore, it is preferred to provide a cooling system in front of the injection device. Alternatively, a separate cooling nose can be attached around the protruding part (in whole or in part) of the injection device in the blast furnace, whereby this cooling nose not only provides thermal protection but also protection from wear. For this reason, the injection device and / or the separate cooling nose can be cooled with (pressurized) water and are generally made of materials such as copper, copper alloys such as copper / nickel alloys, cast iron, cast steel, etc.

[0024] Although the injection device can be made from multiple pieces, it is preferred that the injection device, including the nozzle body with the peripheral wall extending from the front along a longitudinal axis and with at least one injection hole, be made from one piece. Thus, in embodiments, the injection device is a single piece that may or may not protrude into the interior of the blast furnace.

[0025] Furthermore, the injectors can be oriented perpendicular to the blast furnace wall (towards the center of the blast furnace) or tangentially (i.e., at any angle less than 90°, preferably greater than 10° relative to the blast furnace wall at the location of the injectors). The reducing gas injection system can include 15 to 60 injectors, preferably 20 to 40 injectors.

[0026] It is also important to note that the distribution piping does not generally need to be a closed peripheral collector as is the case with conventional bustle pipes. However, this area of ​​the shaft is typically cluttered with coolant distribution piping for the cooling plate and / or support structure. Therefore, if sufficient space is not available in a given blast furnace environment, the reducing gas distribution piping can be divided into several sections (e.g., four quadrants) located around the blast furnace, each section being supplied by a separate reducing gas supply line from the reducing gas source.

[0027] In another embodiment, where space at shaft level is limited, the reducing gas distribution pipe can be mounted above the hot blast bustle pipe but below the level of the injectors (either attached to it or, preferably, to the blast furnace or its supporting structure), so that the injector support supply pipe is connected to the top side of the reducing gas distribution pipe and the injector support faces upwards.

[0028] In view of the temperature rise of the reducing gas, the inner surface of the reducing gas distribution pipe, the injector support, and optionally the injector are lined with a layer of refractory insulating material to protect the reducing gas injection system.

[0029] In a second aspect, the present invention proposes a blast furnace installation for producing pig iron, comprising a blast furnace and at least one reducing gas injection system as described herein, wherein the injection device(s) are mounted at shaft level. Another advantage of the present invention is that the reducing gas distribution pipe can be mounted above or below the level of the injection devices, for example, depending on the availability of sufficient space. Even if the reducing gas distribution pipe is divided into several sections located around the blast furnace, it is possible to arrange some of the reducing gas distribution pipe sections above and below the injection device level.

[0030] The term "fluid connection" means that two devices are connected by conduits or pipes so that a fluid, e.g., a gas, can flow from one device to another. This term includes means for varying this flow, such as valves or fans to regulate mass flow, compressors to regulate pressure, etc., and control elements, such as sensors, actuators, etc., that are necessary or desirable for properly controlling the operation of the blast furnace as a whole or of each element within the blast furnace installation.

[0031] As used herein, the expressions "at shaft level" and "into the shaft of the blast furnace" refer to injection of material above the hot blast (tuyere) level, i.e., above the bosh, preferably above the agglomeration zone, in the ferrous oxide gas-solid reduction zone.

[0032] "About" in this context means that a given numerical value covers a range of values ​​from -10% to +10% of said numerical value, preferably from -5% to +5% of said numerical value. [Brief explanation of the drawings]

[0033] Preferred embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: [Figure 1] FIG. 1 is a three-dimensional schematic diagram illustrating one embodiment of a reducing gas injection system mounted in the shaft of a blast furnace. [Figure 2] FIG. 10 is a partial cross-sectional view of one embodiment of an injector support mounted between a reducing gas distribution pipe and an injector. [Figure 3] FIG. 10 is a detailed view of another embodiment of a portion of a reducing gas injection system, more particularly showing another embodiment of an injection device up to an elbow. [Figure 4] 4 is a detailed view of yet another embodiment of a portion of a reducing gas injection system, more particularly showing an alternative embodiment of the injection apparatus up to the elbow relative to that of FIG. 3. [Figure 5] 1A and 1B are schematic diagrams showing a protective cover for an injection device in a side view and a front view, respectively.

[0034] Further details and advantages of the invention will become apparent from the following detailed description of some non-limiting embodiments, which refers to the accompanying drawings.

[0035] Although the injection of hot reducing gas in the shaft of a blast furnace has been mentioned in many publications, industrial application has not yet been implemented in a commercial blast furnace.

[0036] One challenge with integrated shaft injection compared to hot air injection at the tuyere is the nature of the gas: at the tuyere, the gas is simply hot air, whereas with shaft injection, the gas is typically syngas, containing large amounts of highly flammable hydrogen and CO, the latter of which is toxic to humans.

[0037] Therefore, maintaining an airtight connection between the main gas distribution pipe and the injection point at the blast furnace is of utmost importance.

[0038] The outlet of the injector can have different designs, ranging from a simple opening or a tuyere-like opening, to injectors with, for example, specific replaceable inserts, protective covers over the outlet of the injector, separate cooled noses, etc., and preferably with multiple injection points facing in different directions.

[0039] In the tuyere area, the connection between the hot gas piping, especially the bustle pipe, and the tuyere is realized by the tuyere support, which has two main functions: - a gas connection between the hot blast piping and the tuyere built into the shell of the blast furnace at tuyere level; -To allow compensation of the relative movements between the tuyere integrated into the blast furnace shell and the hot blast piping connected to the free-standing steel structure of the blast furnace installation. The relative movement is relatively important due to the fact that different temperatures exist in the system.

[0040] A conventional tuyere support consists of several parts, the main parts being the downcomer, elbow, and blowpipe. The hemispherical front of the blowpipe is pressed against the tuyere, which is built into the wall of the blast furnace, by a spring tie rod system. The tuyere support elements are connected to a cardan-type compensating joint on the downcomer, allowing movement in two directions. These two-dimensional movements are sufficient to hold the blowpipe hemisphere in place on the seat in the nose of the tuyere. This movable metallic seat connection is sufficient for conducting hot air into the blast furnace.

[0041] A conventional tuyere itself is a relatively complex system consisting of a tuyere body and a tuyere nose, the latter of which projects into the blast furnace, and more specifically into the blast furnace raceway. This area is characterized by very high temperature levels, typically 2000 to 2500°C, and very high gas velocities. Also, because molten slag and iron particles are found at this level of the blast furnace, it is clear that the tuyere nose is subject to damage and must be replaced periodically.

[0042] Blast furnaces usually employ a large number of tuyere nozzles, typically between 10 and 40 depending on the make of the furnace.

[0043] The inventors have identified that in the present reducing gas injection system, the injection equipment itself may potentially be simplified compared to the tuyere in the tuyere area for the following main reasons: - shaft areas of the furnace with lower temperature levels, without a thick refractory lining, allowing cooling by cooling plates and / or cooling boxes and / or external water film cooling; - Typical temperature levels of 900 to 1100°C for reducing gases, -Lower flow rates and therefore smaller diameter piping required, -Lower pressure levels.

[0044] One of its advantageous effects is that the small diameter of the injectors increases the space between them and facilitates their connection to the blast furnace shell with flanged bolted connections including metal and / or soft seals. A further advantage of the small diameter of the injectors is that it allows the openings in the blast furnace wall and cooling plate to be kept small. This in turn ensures that the solution can be easily retrofitted into existing blast furnaces without the need to replace the cooling plate.

[0045] More particularly, with regard to the use of flange mounting to attach the injection device support to the injection device, tightness can be further controlled by applying a certain torque when tightening the flange bolts. Typical means for verifying tightness, such as soapy water, can be used.

[0046] However, by using a flanged mounting of the injector to the reducing gas distribution pipe, the injector support must be able to compensate for any relative movements of the injector support and the reducing gas distribution pipe with respect to the injector. The present invention therefore proposes a combination of a flanged mounting and a Cardan type compensating joint between the injector and the outlet of the elbow.

[0047] 1 shows a schematic three-dimensional partial cutaway view of one embodiment of a reducing gas injection system 10 of the present invention for injecting a reducing gas, such as syngas, into the shaft of a blast furnace, said system being mounted at shaft level to the blast furnace wall 30 or its supporting structure (not shown). The reducing gas distribution pipe 20 of the reducing gas injection system here covers the entire circumference of the blast furnace at shaft level and is fed by a reducing gas supply line 22 and connected to a plurality of injectors 40, each of which projects slightly inside the blast furnace 31 through corresponding openings in a cooling plate 60, with a single injection hole 41 per injector.

[0048] The reducing gas distribution pipe 20 is gas-tightly connected to the injector 40 via an injector support which includes a supply pipe 51 attached to an elbow 52 which is fastened to an injector pipe 53 which is in turn connected by a flange 535 to a corresponding flange 44 of the injector 40. In this embodiment, a Cardan compensation joint 531 is provided in the injector pipe 53.

[0049] 1 to 4, the supply pipe 51 is attached to the lower side of the reducing gas distribution pipe and faces downwards, i.e., the injector level is below the reducing gas distribution pipe level. However, an "upside-down" embodiment of the reducing gas injection system is also explicitly provided, in which the injector level is above the reducing gas distribution pipe level, i.e., the supply pipe is connected to the upper side of the reducing gas distribution pipe and extends upwards.

[0050] 2 shows in more detail another embodiment of the reducing gas injection system, which includes a reducing gas distribution pipe 20 attached to the inlet 43 of the injection device 40 and connected to an injection device support with its supply pipe 51, its elbow 52, ​​and its injection pipe, and with its refractory lining 21. In this embodiment, the injection pipe 53 also has a Cardan compensation joint 531 inside. Note that each element of the injection device support is preferably also provided with a refractory lining, but this lining has been omitted from the drawing for simplicity.

[0051] Preferably, the supply pipe 51 is provided with two Cardan compensation joints 511, 512 to further compensate for relative movement of the reducing gas distribution pipe with respect to the elbow 52. All parts of the injection device support are preferably mounted together with corresponding flanges and, if desired, provided with corresponding seals (not shown).

[0052] The injection devices 40 are hermetically fastened to openings in the blast furnace wall 30. If cooling plates 60 are present, these are provided with corresponding openings. Advantageously, the injection devices 40 or their nozzle bodies 42, in particular if the part surrounding the injection holes 41(s) projects into the inside 31 of the blast furnace, comprise a cooling system 45, such as cooling channels connected to a cooling water circulation system.

[0053] A service access port 521 is provided in the rear of the elbow, the central longitudinal axis of which corresponds to the central longitudinal axis of the injection device 40 .

[0054] 3 is a detailed view of yet another embodiment showing only the downstream portion of the supply line (not shown) of the reducing gas injection system, with the same or equivalent features numbered the same as in the reference numerals above and below.

[0055] As shown in more detail in this drawing, the injection device is gas-tightly mounted by a mounting flange 46 to the blast furnace wall 30 .

[0056] The service access port 521 has a removable cover 524 with a central opening aligned with the central longitudinal axis of the injection device 40. The opening is fitted with a shut-off valve 525 equipped with an inspection system that combines a view glass 523 and a camera 522.

[0057] In this embodiment, the Cardan compensation joint 531 is provided in the injection pipe 53 .

[0058] FIG. 4 is similar to FIG. 3 except that in FIG. 3 a Cardan compensation joint 531 is provided in the outlet portion of elbow 52.

[0059] In an embodiment, a protruding cover can be arranged above the injector(s) and configured to protect the front of the nozzle body protruding into the furnace from descending heavy materials. Protection of the injector nozzle body against abrasion by such descending heavy materials (sinter / pellets and coke) can be achieved, for example, by a smooth or corrugated steel shell. The principle of this protruding cover 100 is shown in FIG. 5 , which forms a kind of cap extending in the longitudinal direction L of the injector. It covers the protruding length of the injector (shown by the dashed line). As can be seen from the figure, the cover 100 has a curved steel cross section, more specifically, a rounded inverted V-shape. The apex 100.1 of the V is located above the injector 40, and two branches 100.2 extend on either side of the injector 40, optionally even below the injector. The cover 100 can be directly or indirectly liquid-cooled. Coolant channels can be arranged, for example, under the shell. [Explanation of symbols]

[0060] 10. Reducing gas injection system 20. Reducing gas distribution pipe 21 Refractory lining 22 Reducing gas supply line 30 Blast furnace wall 31 Inside the blast furnace 40 injection device(s) 41 Injection hole(s) 42 Nozzle body 43 Intake port 44 First mounting flange (rear of nozzle body) 45 Cooling System 46 Mounting flange (for mounting injection device to blast furnace shell) 51 Supply pipe 511, 512 Further cardan compensation joints 52 Elbow 521 Maintenance and inspection hatch 522 Camera 523 Observation Glass 524 Cover 525 Valve 53 Injection tube 531 Cardan Compensating Joint 535 Further mounting flange (on said injection pipe) 60 cooling plate 51+52+53 Injection device support 100 Cover 100.1 Vertex 100.2 Two Branches

Claims

1. A reducing gas injection system (10) for a blast furnace comprising a blast furnace wall (30), - a reducing gas distribution pipe (20), one or more injection devices (40) mounted on the blast furnace wall at shaft level, A reducing gas distribution pipe (20) is attached to the blast furnace wall (30) or its supporting structure; The injection device (40) includes a nozzle body (42) having a peripheral wall extending along a longitudinal axis from a front portion having at least one injection hole (41) to an opposite rear portion having an inlet (43); the nozzle body includes an internal gas channel for guiding a reducing gas from the inlet (43) to the injection hole (41); The nozzle body (42) is mounted through an opening in the blast furnace wall (30) so that a front part with an injection hole (41) is located inside the blast furnace (31), while a rear part with an inlet (43) is located outside the blast furnace wall; the nozzle body (42) including a peripheral mounting portion configured to gas-tightly connect the injection device to the opening in the blast furnace wall; the inlet (43) is fluidly connected to the reducing gas distribution pipe (20) by an injector support, the injector support including a supply pipe (51) connected to the reducing gas distribution pipe (20), an elbow (52) connected to the supply pipe (51), and an injection pipe (53) connected to the elbow (52); The injection pipe (53) is gas-tightly flanged to the inlet (43) of the injection device (40), and the injection pipe (53) and / or the outlet of the elbow includes at least one Cardan compensation joint (531).

2. 2. The reducing gas injection system (10) of claim 1, wherein at least one Cardan compensation joint (531) of the injection pipe (53) is connected to an elbow (52).

3. 3. The reducing gas injection system (10) according to claim 1 or 2, wherein the front region of the injection hole (41) projects into the inside (31) of the blast furnace.

4. 4. The reducing gas injection system (10) according to any one of claims 1 to 3, wherein the supply pipe (51) comprises one or more further Cardan compensation joints (511, 512).

5. 5. The reducing gas injection system (10) of claim 1, wherein the injection device (40) is gas-tightly attached to the opening in the blast furnace wall (30) by a flange (46) and with bolts or hooks.

6. 6. The reducing gas injection system (10) according to claim 1, wherein the injection pipe (53) is flange-attached gas-tightly to the inlet (43) of the injection device (40) by bolts or hooks.

7. 7. A reducing gas injection system (10) according to any one of claims 1 to 6, wherein the injection device (40) comprises the nozzle body (42) having the peripheral wall extending from the front along the longitudinal axis and having at least one injection hole (41), and the injection device (40) is made of one piece.

8. 8. The reducing gas injection system (10) of any one of claims 1 to 7, wherein the elbow (52) comprises a service access port (521) concentric with the longitudinal axis of the injection device (40).

9. 9. The reducing gas injection system (10) of claim 1, wherein a gas flow detector or thermocouple is mounted within the injector support, the gas flow detector or thermocouple projecting into the gas flow or integrated into the refractory lining of the injector support.

10. 10. The reducing gas injection system (10) of claim 1, wherein a front portion of the injection device is configured to be mounted through an opening in a cooling plate (60) mounted inside the blast furnace wall (30).

11. 11. The reducing gas injection system (10) of claim 10, wherein a cooling system (45) is provided in front of the injection device.

12. 12. The reducing gas injection system (10) according to any one of claims 1 to 11, wherein the inner surfaces of the reducing gas distribution pipe (20), the injection device (40), and the injection device support (51+52+53) are lined with a layer of refractory insulating material.

13. The reducing gas injection system (10) of any one of claims 1 to 12, comprising 20 to 60 injection devices (40).

14. 14. The reducing gas injection system (10) of any one of claims 1 to 13, wherein the injection device (40) is oriented perpendicular or tangential to the blast furnace wall (30).

15. 15. The reducing gas injection system (10) of any one of claims 1 to 14, wherein the reducing gas distribution pipe (20) is divided into several sections located around the furnace, each section being supplied by a separate reducing gas supply line.

16. 16. The reducing gas injection system (10) of claim 1, wherein a protruding cover (100) is disposed above the injection device and configured to protect a front portion of the nozzle body protruding into the furnace interior from descending heavy materials.

17. 17. A blast furnace installation for producing pig iron, comprising a blast furnace and at least one reducing gas injection system (10) according to any one of claims 1 to 16, the injection device being mounted at shaft level.

18. A reducing gas injection system (10) as described in claim 6, wherein the injection pipe (53) is flange-mounted with an airtight metallic and / or soft seal between a first mounting flange (44) at the rear of the nozzle body and a second mounting flange (535) of the injection pipe (53).

19. A reducing gas injection system (10) as described in claim 8, wherein a cover (524), an observation glass (523) and / or a camera (522) are removably attached to the maintenance and inspection port (521).

20. A reducing gas injection system (10) as described in claim 11, wherein the cooling system (45) is fluid-cooled and connected to the cooling system of the cooling plate (60).

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