Double-wall spray gun for injecting reducing agent and oxygen into blast furnace through tuyere

Abstract

The invention relates to a double-wall lance for injecting a reducing agent and oxygen through a tuyere, comprising: a. An inner tube (5) for injecting a reducing agent (2); b. An outer tube (6) for injecting oxygen (3), the outer tube surrounding the inner tube (5); c. An end portion (7, 7a, 7b, 7c) closing the lance (1) and having:-a front face (11a, 11b, 11c) having a diameter D and comprising: i. A reductant outlet orifice (8a, 8b, 8c); ii. A front face perimeter (9a, 9b, 9c) comprising a plurality of primary oxygen outlet holes (10a, 10b, 10c); -a cap (12a, 12b, 12c) surrounding the end portion (7, 7a, 7b, 7c) and extending over a length L starting from a front face (11a, 11b, 11c) of the end portion (7, 7a, 7b, 7c) to a free end edge (14a, 14b, 14c), the length L of the cap (12a, 12b, 12c) being greater than 21.3% of a diameter D of the front face (11a, 11b, 11c). The invention also relates to a method for injecting a hot reducing gas into a blast furnace through a tuyere (4) using such a double-wall lance.

Description

Technical Field

[0001] This invention relates to a double-walled lance for injecting reducing agent and oxygen through a tuyer, and to a method for injecting hot reducing gas into a blast furnace through a tuyer. Background Technology

[0002] In a blast furnace, blast air (also known as hot blast air because it typically has a temperature exceeding 900°C) is injected into the furnace through the tuyeres. Prior to this injection, the blast furnace has been charged with the raw materials needed for pig iron production, such as coke, briquettes, pellets, iron ore, and sintered iron. Coke is charged into the blast furnace as the primary reducing agent. The iron-containing charge gradually heats up and is reduced to iron in the furnace hearth. The iron eventually softens and melts in the lower part of the furnace, forming what is known as the remelting zone. Below this level, coke remains the only solid material in the lower part of the furnace (coke reservoir) and the blast furnace hearth. Pulverized coal (PC) is generally considered the primary auxiliary reducing agent. Pulverized coal is injected into the blast furnace through a sub-lance introduced into the tuyeres. As the reducing agent partially combusts with the oxygen in the blast air, injecting the blast air along with PC particles into the coke reservoir creates a void zone in front of the tuyeres called the raceway. The size of this cavity is related to several parameters, among which the force of the gas jet at the tuyeres outlet is crucial. This force can be expressed as: I (N) = Qm (kg / s) x V (m / s), where I is the force, Qm is the mass flow rate of the gas leaving the tuyeres, and V is the gas velocity. In standard blast furnace operation, this force is approximately 700 N.

[0003] Over the past few decades, efforts have been made to reduce CO2 emissions from blast furnace operations. One of the solutions developed, described in patent application WO 2010 / 106387 (named TGRBF, or Top Gas Recirculation Blast Furnace), involves processing the gas discharged from the blast furnace and reinjecting at least a portion of the resulting reducing gas back into the blast furnace through a conventional tuyer located at the top of the hearth. The difference between this and the “conventional” operation of a blast furnace, and in the currently preferred version of this novel operation, lies in replacing all the hot blast with recirculated reducing gas. However, in this configuration, the specific consumption of the recirculated reducing gas is significantly lower than that of the hot blast in conventional operation, and it also potentially has a lower temperature. This results in a lower gas velocity at the tuyeres outlet compared to conventional hot blast operation, corresponding to a significantly lower gas flow force, and particularly below 300 N.

[0004] Therefore, injecting gas into the blast furnace creates a smaller swirling zone. The size of this swirling zone is important because it affects the gas distribution in the lower part of the furnace, the heat load on the furnace walls (which can be critical in this high-temperature zone), and also the efficiency of partial combustion of the reducing agent (such as pulverized coal) injected through the tuyeres. This can cause unburned particles to accumulate in the lower part of the furnace and disrupt its permeability. Melting conditions at the softening zone may also be affected.

[0005] Therefore, a device is needed that allows for an increase in the size of the resulting swirling zone when hot reducing gas is injected at the normal tuyeres when the blast furnace is operating in TGR-BF mode, while protecting the sub-gun material from unacceptably high temperatures. Summary of the Invention

[0006] This problem is solved by the double-walled spray gun of the present invention, which includes: a. Inner tube, used for injecting the reducing agent; b. Outer tube, which is used to inject oxygen, surrounds the inner tube; c. An end portion located at the outlet of the spray gun and within the vent, the end portion enclosing the spray gun and having: - Front face, which has a diameter D and includes: i. Reducing agent outlet hole, which is located at the front of the inner tube to allow the reducing agent to leave; - Front perimeter, which includes a plurality of main oxygen outlet holes located at the front of the outer tube to allow oxygen to leave; cap, which has an open end and an annular wall surrounding the end portion and extends over a length L from the front perimeter of the end portion to the edge of the free end. Among them, the length L of the cap end (12a, 12b, 12c) is greater than 21.3% of the diameter D of the front face (11a, 11b, 11c).

[0007] The spray gun of the present invention may also include the following optional features, either individually or according to all possible combinations of technologies: - The cap extends over a length L greater than 12 mm from the front face of the end portion to the edge of the free end.

[0008] - The cap extends over a length L of at least 13 mm from the front face of the end portion to the edge of the free end.

[0009] - The total surface area of ​​the main oxygen outlet orifice is at least 30% of the surface area of ​​the front periphery of the end portion of the spray gun. - The inner tube wall is made of solid material. - The main oxygen outlet holes are spaced apart along the perimeter of the front face. - The number of main oxygen outlet holes shall be at least seven. -The main oxygen outlet orifice has a trapezoidal shape. - The front surface periphery further includes auxiliary oxygen outlet holes, which are located around the periphery of the front surface between the main oxygen outlet holes. -The total surface area of ​​the auxiliary oxygen outlet orifice is at most 10% of the surface area of ​​the front periphery of the end portion of the spray gun. - The reducing agent outlet hole is located in the same transverse plane as the free end edge of the cap, or extends beyond the free end edge of the cap. -Preferred embodiments according to the present invention: i. The annular wall arrangement around the front perimeter is perpendicular to the cap. ii. The reducing agent outlet hole extends beyond the free end edge of the cap. iii. The front perimeter includes seven main oxygen outlet holes, and iv. The auxiliary oxygen outlet hole is shaped like a stadium.

[0010] - Alternatively, the front periphery is arranged converging towards the opening end of the cap, and the reducing agent outlet hole is located in the same transverse plane as the free end portion of the cap. -According to another preferred embodiment of the invention, including this converging arrangement, the front periphery includes eight main oxygen outlet holes, and the auxiliary oxygen outlet holes have a circular shape. -According to another preferred embodiment of the invention, which also includes such a converging arrangement, the front periphery includes seven main oxygen outlet holes, and the auxiliary oxygen outlet holes have a stadium shape.

[0011] The present invention also relates to a method for injecting thermal reducing gas into a blast furnace through a tuyer, the method comprising: a. Inject the thermal reducing gas into the air vent. b. Inject the reducing agent into the inner tube of the double-walled spray gun as described above, which is then inserted into the air vent. c. Inject oxygen-carrying gas into the outer tube of the double-walled spray gun, and d. To bring the oxygen-carrying gas into contact with the reducing agent before it is injected into the blast furnace.

[0012] Preferably, the thermal reducing gas includes the top gas of the blast furnace recirculation. Attached Figure Description

[0013] Referring to the accompanying drawings, other features and advantages of the invention will become apparent from the following description of the invention, which is given by way of indication and is by no means limiting, in which: - Figure 1 This is a general cross-sectional view of the double-walled spray gun located in the air vent of the present invention; - Figure 2 This is a perspective view of the end portion of the first embodiment of the double-walled spray gun of the present invention; - Figure 3 yes Figure 2 Front view of the end portion of a double-walled spray gun; - Figure 4 Demonstrates when using Figure 2 The trajectory of coal particles inside the duct during the double-walled spray gun; - Figure 5 This is a perspective view of the end portion of the second embodiment of the double-walled spray gun of the present invention; - Figure 6 yes Figure 5 Front view of the end portion of a double-walled spray gun; - Figure 7 yes Figure 5 A cross-sectional view of the end portion of a double-walled spray gun; - Figure 8 Demonstrates when using Figure 5 The trajectory of coal particles inside the duct during the double-walled spray gun; - Figure 9 This is a perspective view of the end portion of the third embodiment of the double-walled spray gun of the present invention; - Figure 10 yes Figure 9 Front view of the end portion of a double-walled spray gun; - Figure 11 Demonstrates when using Figure 9 The trajectory of coal particles inside the duct during the double-walled spray gun; The elements in the accompanying drawings are illustrative and may not be drawn to scale. Detailed Implementation

[0014] refer to Figure 1 The lance 1 of the present invention is introduced obliquely into a tuyer 4, which has an end portion 16 and an outlet orifice 17 to allow hot gas to be injected into the blast furnace. The end portion 7 of the lance 1 is located in the end portion 16 of the tuyer 4 upstream of the outlet orifice 17. The hot gas 18 flowing through the tuyer 6 has a temperature from 700°C to 1300°C and may be recirculated top gas. The recirculated gas preferably contains more than 70% CO / H2 mixture, more preferably more than 80% and ideally more than 90%, wherein the CO2 / H2O mixture is limited to less than 5%, and preferably less than 3%, with the remainder being mainly nitrogen N2.

[0015] The spray gun 1 of the present invention includes an inner tube 5 for a reducing agent and an outer tube 6 surrounding the inner tube 5, thus defining an annular tube through which oxygen flows. The reducing agent may be natural gas, coking gas, fuel oil, or pulverized coal. Preferably, the reducing agent is pulverized coal. The axis of the end portion 7 of the double-walled spray gun 1 is slightly inclined to inject the reducing agent 2 and oxygen 3 into the hot gas 18 along the longitudinal axis XX' of the vent 4.

[0016] The exothermic combustion reaction between the reducing agent and oxygen occurs near the outlet of the spray gun 1 due to the injection of oxygen, which increases the impact force of the gas jet at the outlet 17 of the vent 4. The temperature of the flame can reach almost 3000°C in some locations, while temperatures exceeding 1100°C at the end portion 7 of the spray gun 1 may cause irreversible damage to the spray gun 1.

[0017] According to the invention, the end portion 7 of the spray gun 1 has: a front face having a diameter D and including a reducing agent outlet orifice; and a front face periphery including a plurality of main oxygen outlet orifices surrounding the reducing agent outlet orifice. In this combination of arrangements of oxygen outlet orifices, the end portion 7 of the spray gun 1 includes a cap surrounding the end portion 7 and extending over a length L from the front face of the end portion. According to the invention, the length L of the cap is greater than 21.3% of the diameter D of the front face. Preferably, the length L is greater than 12 mm, and more preferably at least 13 mm. It has been found that this minimum length of the cap allows hot spots greater than 1100°C to be avoided at the end portion 7 of the spray gun 1.

[0018] The minimum length of the cap must be considered in conjunction with the arrangement and surface of the oxygen outlet orifice, because the oxygen outlet orifice directly contributes to combustion and thus contributes to the increase in temperature near the spray gun, while increasing the length of the cap causes the temperature near the spray gun to decrease.

[0019] Advantageously, the total surface area of ​​the main oxygen outlet orifice is at least 30% of the surface area of ​​the front periphery of the end portion of the nozzle, thus allowing the injection of the required amount of oxygen to achieve acceptable combustion power. Preferably, the total surface area of ​​the main oxygen outlet orifice does not exceed 60% of the surface area of ​​the front periphery.

[0020] More advantageously, the front periphery further includes a plurality of auxiliary oxygen outlet holes located between the main oxygen outlet holes. Preferably, the total surface area of ​​the auxiliary oxygen outlet holes is no more than 10% of the surface area of ​​the front periphery of the front face of the end portion of the spray gun, and more preferably between 3% and 10% of the surface area of ​​the front periphery.

[0021] Advantageously, the end portion of the cap is rounded to avoid the formation of heat-sticking points.

[0022] In order to position the combustion close to the outlet of the spray gun 1, the wall of the inner tube 5 is made of solid material to avoid any damage along the inner tube 5.

[0023] Furthermore, to ensure a uniform distribution of oxygen flow within the vent, the main oxygen outlet holes are spaced apart along the perimeter of the front face. This arrangement produces a uniform temperature distribution within the vent 4. While the main oxygen outlet holes can be spaced evenly along the perimeter of the front face, it is advantageous for them to be spaced irregularly along the perimeter of the front face to avoid interference from vibrations.

[0024] To optimize the contact between oxygen and reducing gas downstream of the nozzle tip, and thus optimize the combustion of the reducing gas, the number of main oxygen outlet holes is at least seven. In the example described later, the front periphery includes seven or eight main oxygen outlet holes.

[0025] The shape of the main oxygen outlet orifice is also designed to optimize the combustion reaction while maintaining combustion power at an acceptable level. For this purpose, the main oxygen outlet orifice has a trapezoidal shape, with its maximum width on one side of the annular wall of the cap.

[0026] In the context of this invention, it has been found that adding an auxiliary oxygen outlet hole located between the main oxygen outlet holes allows for the recirculation of restricted gases (particularly CO) within the cap, thereby further reducing the temperature at the end portion 7 of the spray gun 1 and minimizing hot spots. For this purpose, the total surface area of ​​the auxiliary oxygen outlet hole is between 3% and 10% of the surface area of ​​the front face. The auxiliary oxygen outlet hole can have a circular or stadium shape. The shape of the auxiliary oxygen outlet hole must be adjusted according to other structural parameters of the spray gun.

[0027] Another technical feature of the spray gun of the present invention is the relative position of the reducing agent outlet orifice and the free end edge of the cap. In this respect, it has been found that, in order to avoid the recirculation of coal particles within the cap, the reducing agent outlet orifice should be in the same transverse plane as the free end edge of the cap, or should extend beyond the free end edge of the cap.

[0028] The shape of the periphery of the front surface through which the injected oxygen passes can be adjusted to optimize the efficiency of injection through the vent. For this purpose, the periphery of the front surface can be arranged perpendicular to the annular wall of the cap or converge toward the open end of the cap. In both configurations, the relative position of the reducing agent outlet orifice to the free edge of the cap is adjusted depending on the selected shape option.

[0029] The present invention also relates to a method for injecting thermal reducing gas into a blast furnace through a tuyeres using the aforementioned dual-jet lances. The method includes the following steps: - Inject the heat-reducing gas into the air vent. - Inject the reducing agent into the inner tube of the double-walled spray gun inserted into the air vent. - Inject oxygen-carrying gas into the outer tube of the double-walled spray gun, and - To allow the oxygen-carrying gas to come into contact with the reducing agent before being injected into the blast furnace.

[0030] For environmental reasons, thermal reducing gases advantageously include the top gas of the blast furnace recirculation.

[0031] The following describes three preferred embodiments of the spray gun 1 according to the present invention.

[0032] exist Figures 2 to 4 In the first embodiment of the spray gun of the present invention shown, the end portion 7a of the double-walled spray gun 1a has a front face 11a having a diameter D of 56.5 mm and including a circular reducing agent outlet hole 8a forming the free end of the inner tube 5. The circular reducing agent outlet hole 8a is surrounded by a periphery 9a of the front face located between the inner tube 5 and the outer tube 6. The end portion 7a of the spray gun 1a is slightly inclined to inject the reducing agent 2 and oxygen 3 into the gas 18 along the longitudinal axis XX' of the vent 4. Figure 1 ).

[0033] The end portion 7a further includes a cap 12a made of an annular wall 13a, which is generally truncated conical. The cap 12a extends from the front face 11a to the rounded free end edge 14a. The cap has a length of 16 millimeters, such that the length of the cap is 28.3% of the diameter of the front face.

[0034] The front periphery 9a is arranged perpendicular to the annular wall 13a of the cap and includes seven main oxygen outlet holes 10a. These main oxygen outlet holes are evenly spaced along the front periphery 9a and have a trapezoidal shape, with the maximum width on one side of the annular wall 13a of the cap 12a. The total surface area of ​​the seven main oxygen outlet holes 10a is approximately 36% of the surface area of ​​the front periphery 9a of the front surface of the end portion 7a of the spray gun 1a.

[0035] The front periphery 9a further includes seven auxiliary oxygen outlet holes 15a, each located between two adjacent main oxygen outlet holes 10a on one side of the annular wall 13a of the cap 12a. Each auxiliary oxygen outlet hole 15a has a stadium shape. The total surface area of ​​the auxiliary oxygen outlet holes 15a is approximately 6% of the surface of the front periphery 9a of the front face 11a of the end portion 7a of the spray gun 1a.

[0036] The reducing agent outlet hole 8a extends beyond the periphery 9a of the front face and also extends beyond the free end edge 14a of the cap 12a. The outer extension of the inner tube 5 is 20 mm, so that the reducing agent outlet hole 8a extends beyond the free end edge 14a of the cap 12a by 4 mm.

[0037] Due to this configuration, the maximum temperature of the end portion 7a of the spray gun 1a is 1030°C, and the impact force of the airflow at the outlet is 384 N.

[0038] See Figure 4 Coal particles 2 will not be sucked into the cap 12a and will be ejected from the vent 4 without impacting the inner wall of the vent 4.

[0039] exist Figures 5 to 8 In the second embodiment of the spray gun according to the invention shown, the end portion 7b of the double-walled spray gun 1b has a front face 11b having a diameter D of 56.5 mm and including a circular reducing agent outlet orifice 8b forming the free end of the inner tube 5. The circular reducing agent outlet orifice 8b is surrounded by a periphery 9b of the front face located between the inner tube 5 and the outer tube 6. Figure 7 As shown, the end portion 7b of the spray gun 1b is slightly tilted to inject the reducing agent 2 and oxygen 3 into the gas 18 along the longitudinal axis XX' of the vent 4. Figure 1 ).

[0040] The end portion 7b further includes a cap 12b made of an annular wall 13a, which is a slightly truncated cone shape. Figure 7 The cap 12b extends from the front face 11b to the rounded free end edge 14b. The cap 12b has a length L of 16 mm, such that the length of the cap is 28.3% of the diameter D of the front face.

[0041] The front periphery 9b is arranged converging towards the opening end of the cap 12b and extends to the free end edge 14b of the cap 12b, such that the reducing agent outlet hole 8b is located in the same transverse plane as the free end edge 14b of the cap 12b. Figure 7 The convergence angle is 28°.

[0042] The front periphery 9b includes eight main oxygen outlet holes 10b, which are irregularly spaced along the front periphery 9b and have a trapezoidal shape, with the maximum width on one side of the annular wall 13b of the cap 12b. The total surface area of ​​the eight main oxygen outlet holes 10b is approximately 36% of the surface area of ​​the front surface 11b of the end portion 7b of the spray gun 1b.

[0043] The front periphery 9b further includes auxiliary oxygen outlet holes 15b located between the main oxygen outlet holes 10b. Each auxiliary oxygen outlet hole 15b has a circular shape. One, two, or three auxiliary oxygen outlet holes 15b are located between two adjacent main oxygen outlet holes 10b on one side of the annular wall 13b of the cap 12b, thereby causing the main oxygen outlet holes 10b to be arranged irregularly.

[0044] The total surface of the auxiliary oxygen outlet hole 15b is approximately 6% of the surface of the front surface periphery 9b of the front surface of the end portion 7b of the spray gun 1b.

[0045] Due to this configuration, the maximum temperature of the end portion 7b of the spray gun 1b is below 1100°C, and the impact force is 366N.

[0046] See Figure 8 Coal particles 2 will not be sucked into the cap 12b and will be ejected from the vent 4 without impacting the inner wall of the vent 4.

[0047] exist Figures 9 to 11 In the third embodiment of the spray gun according to the invention shown, the end portion 7c of the double-walled spray gun 1c has a front face 11c having a diameter D of 56.5 mm and including a circular reducing agent outlet hole 8c forming the free end of the inner tube 5. The circular reducing agent outlet hole 8c is surrounded by a periphery 9c of the front face located between the inner tube 5 and the outer tube 6. As in the first and second embodiments, the end portion 7c of the spray gun 1c is slightly inclined.

[0048] The end portion 7c further includes a cap 12c made of an annular wall 13c, which is a slightly truncated cone. The cap 12c extends from the front face 11c to the rounded free end edge 14c. The cap 12c has a length L of 16 mm, such that the length of the cap is 28.3% of the diameter D of the front face.

[0049] The front periphery 9c is arranged converging towards the opening end of the cap 12c and extends to the free end edge 14c of the cap 12c, such that the reducing agent outlet hole 8b is located in the same transverse plane as the free end edge 14c of the cap 12c. The convergence angle is 42°.

[0050] The front perimeter 9c includes seven main oxygen outlet holes 10c, which are evenly spaced along the front perimeter 9c and have a trapezoidal shape, with the maximum width on one side of the annular wall 13c of the cap 12c.

[0051] The front perimeter 9c further includes seven auxiliary oxygen outlet holes 15c, each located between two adjacent main oxygen outlet holes 10c on one side of the annular wall 13c of the cap 12c. Each auxiliary oxygen outlet hole 15c has a stadium shape.

[0052] In this embodiment, the surface area of ​​each main oxygen outlet orifice 10c is 87.94 mm. 2 Furthermore, the surface area of ​​each auxiliary oxygen outlet port 15c is 14.57 mm. 2Therefore, for the total surface area of ​​the front perimeter 9c (1688.80 mm²), the total surface area of ​​the seven main oxygen outlet holes 10c is 36.45% of the surface area of ​​the front perimeter 9c, and the total surface area of ​​the seven auxiliary oxygen outlet holes 15c is 6.04% of the surface area of ​​the front perimeter 9c. Thus, the total surface area of ​​the main oxygen outlet holes 10c and the auxiliary oxygen outlet holes 15c is 42.09% of the surface area of ​​the front perimeter 9c.

[0053] Due to this configuration, the maximum temperature of the end portion 7b of the spray gun 1b is below 1100°C, and the impact force is 366N.

[0054] See Figure 11 Coal particles 2 will not be sucked into the cap 12c and will be ejected from the vent 4 without impacting the inner wall of the vent 4.

[0055] A comparative example illustrating the effects of the features of the spray gun of the present invention will now be described.

[0056] Tables 1 and 2 show the results obtained using the spray gun according to the invention, compared to spray guns outside the scope of the invention.

[0057] These tables (the last three columns) present three results: the impact force in Newtons, the trajectory of the reducing agent particles in the nozzle, and whether there are hot spots at the tip of the spray gun.

[0058] For the trajectory of reducing agent particles, the symbol "--" indicates that the coal particles collide with the inner wall of the tuyer, while the symbol "++" indicates that the coal particles do not collide with the inner wall of the tuyer. The symbol "+" means that the trajectory of the particles is acceptable.

[0059] Regarding hot spots at the tip of the spray gun, the symbol "- -" indicates that the temperature at the tip of the spray gun is unacceptably higher than 1100°C, while the symbol "++" indicates that the temperature at the tip of the spray gun is lower than 1100°C. The symbol "+" indicates that the temperature at the tip of the spray gun is within the permissible range of approximately 1100°C but lower than 1100°C.

[0060] In Table 1, Examples A to E correspond to spray guns not according to the invention. In Tables 1 and 2, Examples 1 to 7 correspond to spray guns according to the invention. Examples 1 to 3 correspond to the preceding references respectively. Figures 2 to 11 Examples 1 to 3 are described. In all examples A to E and examples 1 to 7, the diameter of the front face is 56.5 mm.

[0061] According to Table 1, when the cap length is 12 mm (21.3% of the diameter of the front face), the temperature at the tip of the spray gun is unacceptable, while for a cap length of 13 mm (23.0% of the diameter of the front face), the temperature is within the permissible range of approximately 1100°C. Therefore, the cap length must be greater than 21.3% of the diameter of the front face, and thus must be greater than 12 mm, and more preferably at least 13 mm.

[0062] Table 1 illustrates the presence of the cap and the effect of its length. To achieve the permissible temperature at the tip of the spray gun, the cap length must be at least 23% of the diameter of the front face. In these examples, the cap length must be at least 13 mm. A length of 16 mm is preferred (according to Examples 1 to 3) to achieve temperatures below 1100°C.

[0063] Table 2 shows the results obtained from four examples of spray guns according to the invention, wherein the periphery of the front face is perpendicular to the wall of the cap. (See previous references.) Figures 2 to 4 Example 1, as described, gives the best result.

[0064]

[0065] Table 1: Examples showing a comparison of the effects of cap and cap length.

[0066] Table 2: Comparative examples of the vertical shapes for the periphery of the front face according to the present invention.

Claims

1. A double-walled lance (1) for injecting reducing agent (2) and oxygen (3) through a tuyer (4) of a blast furnace, said lance (1, 1a, 1b, 1c) comprising: a. Inner tube (5), which is used to inject reducing agent (2); b. Outer tube (6), which is used to inject oxygen (3), surrounds the inner tube (5); c. End portion (7, 7a, 7b, 7c), which is located at the end of the spray gun (1) and within the vent (4), the end portion (7, 7a, 7b, 7c) enclosing the spray gun (1) and having: - Front faces (11a, 11b, 11c), which have a diameter D and include: i. Reducing agent outlet holes (8a, 8b, 8c), which are located at the front of the inner tube (5) to allow the reducing agent (2) to leave; ii. Front perimeter (9a, 9b, 9c), which includes a plurality of main oxygen outlet holes (10a, 10b, 10c) located at the front of the outer tube (6) to allow oxygen (3) to leave. - A cap (12a, 12b, 12c) having an open end and an annular wall (13a, 13b, 13c) surrounding the end portion (7, 7a, 7b, 7c), the cap extending along a length L from the front face (11a, 11b, 11c) of the end portion (7, 7a, 7b, 7c) to the free end edge (14a, 14b, 14c). The length L of the cap (12a, 12b, 12c) is greater than 21.3% of the diameter D of the front face (11a, 11b, 11c).

2. The spray gun according to claim 1, wherein, The cap (12a, 12b, 12c) extends over a length L greater than 12 mm from the front face (11a, 11b, 11c) of the end portion (7, 7a, 7b, 7c) to the free end edge (14a, 14b, 14c).

3. The spray gun according to any one of claims 1 and 2, wherein, The cap (12a, 12b, 12c) extends over a length L of at least 13 mm from the front face (11a, 11b, 11c) of the end portion (7, 7a, 7b, 7c) to the free end edge (14a, 14b, 14c).

4. The spray gun according to any one of claims 1 or 2, wherein, The total surface area of ​​these main oxygen outlet holes (10a, 10b, 10c) is at least 30% of the surface area of ​​the front periphery (9a, 9b, 9c) of the front face of the end portion (7, 7a, 7b, 7c) of the spray gun (1, 1a, 1b, 1c).

5. The spray gun according to any one of claims 1 to 4, wherein, The wall of the inner tube (5) is made of solid material.

6. The spray gun according to any one of the preceding claims, wherein, These main oxygen outlet holes (10a, 10b, 10c) are spaced apart along the periphery of the front face (9a, 9b, 9c).

7. The spray gun according to any one of the preceding claims, wherein, The number of these main oxygen outlet holes (10a, 10b, 10c) is at least seven.

8. The spray gun according to any one of the preceding claims, wherein, These main oxygen outlet holes (10a, 10b, 10c) have a trapezoidal shape.

9. The spray gun according to any one of the preceding claims, wherein, The front surface periphery (9a, 9b, 9c) further includes auxiliary oxygen outlet holes (15a, 15b, 15c) located around the periphery of the front surface periphery (9a, 9b, 9c) between the main oxygen outlet holes (10a, 10b, 10c).

10. The spray gun according to claim 9, wherein, The total surface area of ​​these auxiliary oxygen outlet holes (15a, 15b, 15c) is at most 10% of the surface area of ​​the front periphery (9a, 9b, 9c) of the front face of the end portion (7, 7a, 7b, 7c) of the spray gun (1, 1a, 1b, 1c).

11. The spray gun according to claim 10, wherein, The reducing agent outlet holes (8a, 8b, 8c) are located in the same transverse plane as the free end edges (14a, 14b, 14c) of the cap (12a, 12b, 12c), or extend beyond the free end edges (14a, 14b, 14c) of the cap (12a, 12b, 12c).

12. The spray gun according to claim 11, wherein: - The periphery (9a) of the front surface is arranged perpendicular to the annular wall (13a) of the cap (12a). - The reducing agent outlet hole (8a) extends beyond the free end edge (14a) of the cap (12a). - The front perimeter (9a) includes seven main oxygen outlet ports (10a), and - These auxiliary oxygen outlet holes (15a) have a stadium shape.

13. The spray gun according to claim 11, wherein, The periphery (9b, 9c) of the front face is arranged converging toward the opening end of the cap (12b, 12c), and wherein the reducing agent outlet hole (8b, 8c) is located in the same transverse plane as the free end portion (14b, 14c) of the cap (12b, 12c).

14. The spray gun according to claim 13, wherein, The front perimeter (9b) includes eight main oxygen outlet holes (10b), wherein these auxiliary oxygen outlet holes (15b) have a circular shape.

15. The spray gun according to claim 13, wherein, The front perimeter (9c) includes seven main oxygen outlet holes (10c), and these auxiliary oxygen outlet holes (15c) have a stadium shape.

16. A method for injecting thermal reducing gas into a blast furnace through a tuyer (4), the method comprising: a. Inject the thermal reducing gas into the air vent (4); b. Inject the reducing agent (2) into the inner tube (5) of the double-walled spray gun (1, 1a, 1b, 1c) according to any one of the preceding claims, wherein the double-walled spray gun (1, 1a, 1b, 1c) is inserted into the air outlet (4); c. Inject the oxygen-carrying gas (3) into the outer tube (6) of the double-walled spray gun (1, 1a, 1b, 1c); and d. Contact the reducing agent (2) with the oxygen-carrying gas (3) before it is injected into the blast furnace.

17. The method according to claim 16, wherein, The thermal reducing gas includes the top gas from the recirculated blast furnace.

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