Injector

Abstract

To provide an injector which can reduce wear from a carbon source.SOLUTION: Disclosed is an injector 10 for injecting a carbon source. A ceramic sleeve 16 is inserted into an inner tube 13 through which the carbon source is conveyed, and the ceramic sleeve 16 is a wear-resistant layer for 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 provided with a ceramic sleeve. [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 ceramic sleeve is inserted into an inner tube through which the carbon source is transported, and the ceramic sleeve is an abrasion-resistant layer that reduces abrasion from the carbon source. [2] The injector according to [1], characterized in that the ceramic sleeve is formed into a uniform shape, and a uniform wear-resistant layer is formed on the inner surface of the inner pipe 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. 2 is a schematic diagram illustrating an example of an injector. [Figure 2] FIG. 2 is a partial enlarged view illustrating the tip of the injector. 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 ceramic sleeve 16 is inserted into the inner tube 13 of the injector 10. The ceramic sleeve 16 is an abrasion-resistant layer that reduces abrasion from the carbon source that is the transported product of the mixed jet.

[0018] 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.

[0019] As shown in Table 1, stainless steel, which is widely used as a material for machined workpieces 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 chrome-molybdenum steel, to reduce wear. Because the Vickers hardness of chrome-molybdenum steel (SCM440) is around 750, the wear-resistant layer must have even higher wear resistance strength.

[0020] [Table 1]

[0021] 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 wear-resistant treatment method must be one that can uniformly treat this section as well.

[0022] One method of treatment that meets these conditions is to apply a ceramic sleeve lining to the inside of the injector. Alumina is one example of a ceramic that can be applied. As shown in Table 2, alumina is a material with excellent wear and heat resistance (HV: 1400-1600, melting point: 2000°C), and is widely used as a wear-resistant material. For example, alumina linings are used in parts of piping that are subject to severe wear in powder material transport lines, and have a proven track record. In Table 2, "Cr plating" refers to chromium, and "nitride" refers to an iron nitride (Fe-N) coating.

[0023] [Table 2]

[0024] It is preferable that the ceramic sleeve 16 is molded into a uniform shape, and that a uniform wear-resistant layer is formed on the inner surface of the injector 10. To fix the wear-resistant layer to the injector 10, the ceramic sleeve 16 may be fixed to the inner pipe 13 via a fixing material 17. The fixing material 17 is not particularly limited, but examples thereof include non-shrink mortar.

[0025] The ceramic sleeve 16 may be inserted into the injector 10 when it has the chamber 11 and the shroud gas inlet pipe 14d, or when it does not have the chamber 11 or the shroud gas inlet pipe 14d. The ceramic sleeve 16 may also be inserted into the nozzle 12 when the inner tube 13 and the outer tube 14 are integrated together. The ceramic sleeve 16 may also be inserted into the nozzle 12 when only the inner tube 13 is present. The ceramic sleeve 16 may be inserted into the nozzle 12 when it has the tip member 15, or when it does not have the tip member 15.

[0026] 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.

[0027] In the above-described embodiment, a nozzle in which an outer tube for delivering a supersonic jet is disposed around an inner tube for delivering a jet containing a carbon source is shown. However, the injector for injecting the carbon source may include a nozzle consisting of a single tube. It is sufficient that the above-described ceramic sleeve is inserted into at least the tube for delivering the jet containing the carbon source. [Example]

[0028] The present invention will be specifically described below with reference to examples.

[0029] Ceramic sleeves were actually installed in the injector. The installation method involved inserting the ceramic sleeve into the inner pipe of the injector and filling the space between the inner pipe and the ceramic with non-shrinkage mortar to fix the sleeve in place. Multiple sleeves were inserted, each 30 mm long. The conditions for the inserted ceramic sleeves are shown in Table 3.

[0030] [Table 3]

[0031] Since the thickness of the ceramic sleeve and mortar was 4 mm each, the outer and inner pipe diameters of the injector of the example were enlarged to a size that could accommodate the ceramic sleeve, compared to the comparative injector without a ceramic sleeve. When the outer diameter of the nozzle tip member of the comparative injector was 1D, the outer diameter of the nozzle tip member of the injector of the example was 1.26D.

[0032] After inserting the ceramic sleeve, the injector was used in an actual electric furnace. Some wear was observed on the ceramic sleeve, but no wear was observed on the injector itself. Injectors without a ceramic sleeve showed signs of wear after about 10 days. In comparison, wear was observed at the nozzle outlet and the inner surface of the inner tube, and in some cases wear at the thin nozzle wall near the inlet of the inner tube penetrated all the way to the outer tube.

[0033] However, in the example, it was confirmed that increasing the outer diameter of the injector accelerated wear at the tip. The wear at the tip is thought to be caused by the jet spreading inside the tip nozzle and the carbon source colliding with the inner surface. The jet spreading is thought to be caused by the distance between the central jet and the surrounding supersonic jets increasing. In the comparative example, the distance from the jet tip to the supersonic jet (thickness of the inner tube) is assumed to be 1L, whereas in the example, the distance was 3L, taking into account the thickness of the ceramic sleeve and mortar. This makes the central jet less susceptible to the convergence caused by the supersonic jet, which is thought to have resulted in the jet spreading inside the nozzle and wear.

[0034] Figure 2 is an enlarged partial view of the tip of the injector. When inserting a ceramic sleeve into the injector to suppress wear at the nozzle tip, it is desirable to set the inner diameter D2 of the inner pipe, which takes into account the thickness of the ceramic sleeve and mortar, relative to the actual central jet outlet diameter D1, to the value given by the following formula: D2=αD1 α=1.4~1.5 It is also desirable that the outer diameter D3 of the inner pipe relative to the inner diameter D2 of the inner pipe be within the following formula in order to reduce the wall thickness of the inner pipe. D3=βD2 β=1.1~1.2

[0035] In addition, in Figure 2, the tip position of the inner pipe 13 and the tip position of the tip member 15 are roughly the same, so the structure prevents the jet from spreading inside the nozzle. However, with this structure, the inner pipe outlet is closer to the molten steel than when the supersonic jet outlet protrudes from the inner pipe outlet as in Figure 1, and it is thought that the effects of radiant heat and dust / splash from inside the furnace will increase. For this reason, when installing and operating an injector inside the furnace, it is desirable to keep the fluid flowing from the supersonic jet outlet at all times, even when the carbon source is not being injected, from the perspective of promoting cooling and preventing clogging.

[0036] With this technology, it was confirmed that inserting an alumina sleeve into the injector increased the strength of the carbon source flow path from 750 to approximately 1400 Vickers hardness (HV). It was also confirmed that the lifespan of the equipment was extended in the example where an alumina sleeve was inserted compared to the control where no alumina sleeve was inserted. Regarding the problem of increasing the diameter of the injector body when inserting a ceramic sleeve, it was possible to reduce the diameter to the same size as the control by reviewing the injector structure. [Industrial Applicability]

[0037] The present invention provides an injector used in the electric furnace steelmaking process when injecting auxiliary raw materials, particularly a carbon source, by adding an abrasion-resistant layer to the carbon source flow path, thereby extending the equipment life and improving maintainability. [Explanation of symbols]

[0038] 10...injector, 11...chamber, 11a...transport gas inlet, 11b...powder material inlet, 11c...internal space, 12...nozzle, 12a...mixing jet inlet, 13...inner tube, 13a...inner tube inlet, 13b...inner tube outlet, 13c...mixing jet flow path, 14...outer tube, 14a...shroud gas inlet, 14b...nozzle outlet, 14c...shroud gas flow path, 14d...shroud gas introduction pipe, 14e...shroud gas introduction port, 15...tip member, 15a...slit, 16...ceramic sleeve, 17...fixing material.

Claims

1. 1. An injector for injecting a carbon source, the injector comprising an inner tube through which the carbon source is transported and a ceramic sleeve inserted therein, the ceramic sleeve being an abrasion-resistant layer that reduces abrasion from the carbon source.

2. 2. The injector according to claim 1, wherein the ceramic sleeve is formed into a uniform shape, and a uniform wear-resistant layer is formed on the inner surface of the inner pipe of the injector.

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