Injector

Abstract

To provide an injector capable of reducing wear from a carbon source.SOLUTION: A hardened coating 16 formed on the inner surface of an injector 10 for blowing a carbon source is a wear resistant film capable of reducing wear from the carbon source.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an injector for injecting powder material into a metallurgical furnace, the inner surface of which is hardened. [Background technology]

[0002] For example, in electric furnace steelmaking, where scrap metal is melted in an electric furnace to produce steel, oxygen is blown into the furnace to cut the scrap metal and increase production efficiency. In this case, the scrap oxidizes, reducing yield, so a carbon source is blown into the furnace to reduce the oxide. There are various types of carbon sources used, including CDQ (Coke Dry Quenching) coke, which has a particle size similar to sand, and pulverized coal, which has a fine particle size. In addition, with the recent rise in carbon neutrality, plant-derived biocoke and waste plastics are sometimes used as carbon sources.

[0003] The carbon source is injected into the electric furnace by inserting a metal lance pipe into the side wall or through a work port on the front. A fixed amount of carbon source is usually cut out using a dedicated supply device, and then pressure-transported with air or inert gas and injected into the furnace. Some of the carbon source injected into the furnace undergoes a catalytic reduction reaction with the oxidized scrap, but the majority does not burn or react in the furnace space and simply scatters within the furnace, being sucked into the dust collection system, so the efficiency of carbon source injection using a normal lance pipe is not good.

[0004] As a solution to this problem, there is a well-known technique of using a metal injector to protect the jet with a supersonic jet and reduce the scattering of the carbon source, thereby injecting it efficiently (see, for example, Patent Document 1). The injector consists of two parts. One is a chamber with an inlet for the powder material, an inlet for the gas, and an outlet for spraying the mixture of powder material and gas. The other is a nozzle connected to the outlet of the chamber. This nozzle has a flow path for the mixed jet of powder material and gas, and a gas inlet for forming a tubular supersonic jet around the jet to protect it. Use of the injector makes it possible to suppress the scattering of carbon source, and has been confirmed to improve injection efficiency by approximately 20% compared to conventional lance pipes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 7,641,849 Summary of the Invention [Problem to be solved by the invention]

[0006] The carbon source flow path of the injector gradually wears with use, which reduces the performance of the device and eventually leads to failure. For this reason, extending the device's lifespan is an issue from the perspective of reducing running and maintenance costs.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an injector that can reduce wear from a carbon source. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides the following means. [1] An injector for injecting a carbon source, characterized in that a hardened coating is formed on the inner surface of the injector, and the hardened coating is an abrasion-resistant coating that reduces abrasion from the carbon source. [2] The injector according to [1], wherein the hard coating is an iron-boride-based hard coating. [3] The injector according to [2], characterized in that the iron-boride-based hardening coating penetrates the entire injector using a molten salt bath as a medium, forming a uniform coating on the inner and outer surfaces of the injector. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an injector that can reduce wear from a carbon source. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of an injector. [Figure 2] 10 is a photograph substituted for a drawing showing an example of a coating applied to an injector. [Figure 3] 1 is a graph showing PQ diagrams before and after hardening treatment according to an example. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below based on preferred embodiments.

[0012] The injector 10 shown in Figure 1 includes a chamber 11 and a nozzle 12. The chamber 11 has a transport gas inlet 11a, a powder material inlet 11b, and an internal space 11c. The transport gas is not particularly limited, but may be air or an inert gas such as nitrogen.

[0013] A transport gas is introduced into the internal space 11c through the transport gas inlet 11a, and powder material is supplied to the internal space 11c through the powder material inlet 11b. The transport gas and the powder material are mixed in the internal space 11c to form a mixed jet, which is then ejected toward the nozzle 12. A mixed jet inlet 12a of the nozzle 12 is connected to the outlet of the chamber 11.

[0014] The nozzle 12 has an inner tube 13 that forms a mixed jet flow path 13c for flowing a mixed jet of powder material and transport gas. The mixed jet flow path 13c is formed in a straight line from the inner tube inlet 13a to the inner tube outlet 13b. The mixed jet flow path 13c is a space surrounded by the inner surface of the inner tube 13. In the injector 10 for injecting the carbon source, a carbon source such as carbon, bio-coke, or waste plastic is used as the powder material. The carbon source is transported through the inner tube 13.

[0015] An outer pipe 14, which forms a shroud gas flow path 14c, is disposed around the inner pipe 13. The outer pipe 14 is formed in a straight line from a shroud gas inlet 14a to a nozzle outlet 14b. The shroud gas flow path 14c is a space between the outer surface of the inner pipe 13 and the inner surface of the outer pipe 14. The shroud gas introduced into the shroud gas inlet 14a is supplied from a shroud gas inlet port 14e of a shroud gas introduction pipe 14d connected to the side of the outer pipe 14.

[0016] At the tip of the nozzle 12, a tip member 15 is disposed, which forms a slit 15a between the nozzle 12 and the inner pipe 13 to form a tubular supersonic jet from the shroud gas. The slit 15a is formed along the outer circumferential surface of the inner pipe 13 so as to have a cross-sectional area narrower than that of the shroud gas flow path 14c. The shroud gas is not particularly limited, but may be air or an inert gas such as nitrogen.

[0017] A hardened coating 16 is formed on the inner surface of the injector 10. The hardened coating 16 is an abrasion-resistant coating that reduces abrasion from a carbon source that is a transported product of the mixed jet.

[0018] The hardened coating 16 is preferably formed at least on the inner surface of the inner pipe 13 facing the mixed jet flow passage 13c. Although not particularly shown, the hardened coating 16 may also be formed in other regions of the injector 10. For example, the hardened coating 16 may be formed on the outer surface of the inner pipe 13 facing the shroud gas passage 14c or the inner surface of the outer pipe 14, the outer surface of the outer pipe 14, the inner or outer surface of the chamber 11, or the like.

[0019] The injector 10 is exposed to strong radiant heat from heat sources such as molten steel in its installation environment. The tip member 15 of the nozzle 12 of the injector 10 is made of copper for its heat dissipation efficiency, but it is subject to wear and deterioration over time due to the radiant heat from the molten steel. Because the melting point of copper is around 1100°C, the processing method must be stable enough to be used above this temperature.

[0020] As shown in Table 1, stainless steel, which is widely used as a material for machined parts from the perspective of workability and strength, has a Vickers hardness of around 200. In contrast, the inner tube that forms the carbon source flow path of the injector is made of a harder material, such as chromium-molybdenum steel, to reduce wear. Chromium-molybdenum steel (SCM440) has a Vickers hardness of around 750, so the hardening treatment that is carried out must have a strength even higher than this.

[0021] [Table 1]

[0022] The carbon source flow path of the injector shown in the figure has a straight pipe section with a length of about 300 to 500 mm and an inner diameter of about 25 mm. The hardening treatment method must be one that can treat this section uniformly.

[0023] One example of a hardening treatment that meets these conditions is an iron-boride-based hardening coating. One method for applying an iron-boride coating is to modify the surface by diffusing boron from the surface of the base metal (boriding), one example of which is immersion in a molten salt bath. As shown in Table 2, this coating maintains stable hardness even at high temperatures, and because the treatment method involves immersion in a molten salt bath, it is possible to treat every detail and form a stable coating. In Table 2, "Cr plating" refers to chromium, and "nitriding" refers to an iron nitride (Fe-N) coating.

[0024] [Table 2]

[0025] The iron-boride-based hardening coating penetrates the entire injector using the molten salt bath as a medium, forming a uniform coating on both the inner and outer surfaces of the injector. The agent used in the molten salt bath contains boron, which reacts with the base metal of transition metals such as iron or their alloys to form boride compounds (e.g., Fe-B). In the molten salt bath, the salts contained in the agent melt at high temperatures and become liquid.

[0026] The injector 10 may be immersed in the molten salt bath while it has the chamber 11 and the shroud gas introduction pipe 14d, or without the chamber 11 or the shroud gas introduction pipe 14d. The nozzle 12 may be immersed in the molten salt bath while the inner tube 13 and the outer tube 14 are integrated. It is also possible to immerse only the inner tube 13 of the nozzle 12 in the molten salt bath. The nozzle 12 may be immersed in the molten salt bath while it has the tip member 15, or without the tip member 15.

[0027] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and configuration changes, combinations, deletions, etc. are also included within the scope that does not deviate from the gist of the present invention.

[0028] In the above-described embodiment, a nozzle is shown in which an outer tube, through which a supersonic jet is delivered, is disposed around an inner tube, through which a jet containing a carbon source is delivered. However, the injector for injecting the carbon source may be provided with a nozzle consisting of a single tube. It is sufficient that the above-described hardened coating is formed at least on the inner surface of the tube through which the jet containing the carbon source is delivered. Other coatings may be used as the hardened coating, as long as they are harder than the material of the tube through which the jet containing the carbon source is delivered and have heat resistance suitable for the application of the nozzle. [Example]

[0029] The present invention will be specifically described below with reference to examples.

[0030] An iron-boride-based hardening coating was actually applied to an injector. The application method involved immersing the injector in a molten salt bath, then heat treating it at approximately 1000°C, forming an iron-boride coating on the base material surface. Table 3 shows the Vickers hardness measurement results and coating thickness of the injector piece. The hardness was confirmed to be about 1.5 times that of the base material.

[0031] [Table 3]

[0032] We also checked whether there was any effect on equipment performance before and after the hardening treatment. To check, we flowed nitrogen gas into the injector and measured the back pressure at each flow rate to see if there was any difference before and after the hardening treatment. As shown in Figure 3, there was no significant difference in the PQ diagram before and after the hardening treatment, which confirmed that the hardening treatment did not affect equipment performance.

[0033] With this technology, it was confirmed that the Vickers hardness (HV) of the injector base material increased from 750 to approximately 1150 by carrying out hardening treatment. It was also confirmed that there was no effect on the equipment performance before and after hardening treatment. [Industrial Applicability]

[0034] The present invention can extend the life of the equipment and improve maintainability by applying a hardening coating treatment to the carbon source passage of an injector used when injecting auxiliary materials, particularly a carbon source, in an electric furnace steelmaking process. [Explanation of symbols]

[0035] 10...injector, 11...chamber, 11a...transport gas inlet, 11b...powder material inlet, 11c...internal space, 12...nozzle, 12a...mixed jet inlet, 13...inner tube, 13a...inner tube inlet, 13b...inner tube outlet, 13c...mixed jet flow path, 14...outer tube, 14a...shroud gas inlet, 14b...nozzle outlet, 14c...shroud gas flow path, 14d...shroud gas introduction tube, 14e...shroud gas introduction port, 15...tip member, 15a...slit, 16...hardened coating.

Claims

1. 1. An injector for injecting a carbon source, the injector having an inner surface on which a hardened coating is formed, the hardened coating being an abrasion-resistant coating that reduces abrasion from the carbon source.

2. 2. The injector according to claim 1, wherein the hard coating is an iron-boride based hard coating.

3. 3. The injector according to claim 2, wherein the iron-boride-based hardening coating penetrates the entire injector using a molten salt bath as a medium, forming a uniform coating on the inner and outer surfaces of the injector.

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