Reduced iron production system and reduced iron production method

Abstract

To provide a reduced iron production system with which the reduced iron can be produced in high yield.SOLUTION: A reduced iron production system 50 includes an electric furnace 10 for melting powdery reduced iron P, and a reduced iron charging device 20 for charging the reduced iron P into the electric furnace 10. The reduced iron charging device 20 has a powder introduction part for introducing the reduced iron, a gas introduction part for introducing carrier gas, and a powder spouting part for spouting the reduced iron accompanied with the carrier gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a system for producing reduced iron and a method for producing reduced iron. [Background technology]

[0002] CO2 emissions from the steel industry account for approximately half of the total CO2 emissions from the industry as a whole, and there is a need to reduce these emissions. Iron is mainly produced using the indirect reduction method, which uses blast furnaces. The indirect reduction method produces iron by melting and reducing the raw iron ore, but it is known as a manufacturing method that emits a large amount of CO2. Currently, iron produced using the indirect reduction method, which uses blast furnaces, accounts for the majority of iron production.

[0003] On the other hand, direct steelmaking is known as a steelmaking method with low CO2 emissions. Direct steelmaking is a method in which iron ore is reduced in its solid state using a reducing agent such as natural gas or coal to obtain reduced iron. The reduced iron obtained by the direct steelmaking method is then fed into, for example, an electric furnace and melted.

[0004] As an example of a method for producing reduced iron using a direct iron making process, Patent Document 1 describes a reduced iron production system including a reduction furnace (reduced iron production apparatus) that reduces an oxidized iron raw material using a reducing gas to produce reduced iron, and an arc-type reduction melting furnace (electric furnace), in which the reduced iron produced in the reduction furnace is fed into the arc-type reduction melting furnace and further reduced and melted to produce molten steel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-088912 Summary of the Invention [Problem to be solved by the invention]

[0006] In the reduced iron production system disclosed in Patent Document 1, reduced iron produced in a reduction furnace is directly introduced into an arc-type reduction melting furnace, but the interior of the arc-type reduction melting furnace is usually under positive pressure due to furnace gas generated from melted scrap, etc., and the furnace gas is ejected from the melting furnace to the outside. Therefore, when the reduced iron is fed from the reduction furnace into the arc-type reduction melting furnace, reduced iron particles with small particle diameters are not supplied to the molten steel in the arc-type reduction melting furnace, which may result in a decrease in the overall yield.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a reduced iron manufacturing system and a reduced iron manufacturing method that can obtain reduced iron with a high yield. [Means for solving the problem]

[0008] The present invention has the following configuration. [1] an electric furnace for melting powdered reduced iron; a reduced iron charging device that charges the reduced iron into the electric furnace, the reduced iron feeding device includes a powder introduction section that introduces the reduced iron, a gas introduction section that introduces a carrier gas, and a powder ejection section that ejects the reduced iron entrained in the carrier gas. [2] The reduced iron charging device is connected to the electric furnace, The reduced iron manufacturing system according to [1], wherein the powder ejection section is located inside the electric furnace. [3] The system for producing reduced iron according to [1] or [2], further comprising a carrier gas supply path connected to the gas inlet and supplying the carrier gas to the reduced iron charging device. [4] The reduced iron manufacturing system according to [3], further comprising a gas heating device located in the carrier gas supply path and configured to heat the carrier gas. [5] The system for producing reduced iron according to [4], wherein the gas heating device is a heat exchanger. [6] Further provided is an exhaust gas recovery path for recovering exhaust gas discharged from the electric furnace; The reduced iron manufacturing system according to [5], wherein the heat exchanger is provided between the carrier gas supply path and the exhaust gas recovery path. [7] A reduced iron manufacturing apparatus that reduces an iron oxide-containing raw material to produce the reduced iron; The system for producing reduced iron according to any one of [1] to [6], further comprising: a reduced iron supply path located between the reduced iron production apparatus and the powder introduction part, for supplying the reduced iron from the reduced iron production apparatus to the powder introduction part. [8] The system for producing reduced iron according to any one of [1] to [7], wherein the average particle size D50 of the reduced iron is 0.001 mm or more and 10 mm or less. [9] A method for producing reduced iron using an electric furnace, A method for producing reduced iron, comprising: spraying powdered reduced iron together with a carrier gas into the electric furnace; and introducing the reduced iron into molten steel in the electric furnace. [Effects of the Invention]

[0009] According to the reduced iron manufacturing system and the reduced iron manufacturing method of the present invention, reduced iron can be obtained with a high yield. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating an example of the configuration of a reduced iron production system according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating an example of a reduced iron charging device included in a reduced iron production system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings used in the following description, the dimensions of the components may be shown at different scales to make them easier to see, and the dimensional ratios of the components may not be the same as in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not necessarily limited to them, and can be implemented with appropriate changes within the scope of the present invention. The symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0012] [Reduced iron production system] First, a reduced iron production system 50 shown in FIG. 1 will be described as one embodiment of the present invention. FIG. 1 is a block diagram showing an example of the configuration of a reduced iron manufacturing system according to an embodiment of the present invention.

[0013] 1, a reduced iron manufacturing system (hereinafter simply referred to as "manufacturing system") 50 of this embodiment is generally configured to include an electric furnace 10 and a reduced iron charging device 20. Preferably, the manufacturing system 50 of this embodiment further includes a reduced iron manufacturing apparatus 30 and a gas heating device 40.

[0014] (electric furnace) The manufacturing system 50 of this embodiment includes an electric furnace 10 for melting reduced iron P in powder form. The electric furnace (also called an electric furnace) 10 melts raw materials such as iron scrap using discharge heat generated by arc discharge, removes impurities such as oxygen and nitrogen, and produces steel. The electric furnace 10 is not particularly limited, and a conventionally known structure can be used.

[0015] In one embodiment, the electric furnace 10 is generally configured to include a furnace body 11 and electrodes 12 that generate arcs. The electric furnace 10 melts the iron source (reduced iron P, other scrap, etc.) inside by the arc of the electrodes 12.

[0016] At least the lower part of the furnace body 11 is made of a refractory material 14. This allows the furnace body 11 to store iron (molten steel) 13 melted by the electrodes 12.

[0017] A reduced iron charging device 20 is provided above the furnace body 11 so as to penetrate the furnace body 11. The tip of the electrode 12 is provided so as to face the molten steel 13 in the space inside the furnace body 11.

[0018] An exhaust duct 15 is provided above the furnace body 11. This exhaust duct 15 allows the atmosphere inside the electric furnace 10 to be discharged to the outside of the furnace body 11 as electric furnace exhaust gas (exhaust gas).

[0019] An exhaust gas recovery path L4 is connected to the exhaust duct 15. This makes it possible to recover a portion of the gas from the atmosphere inside the electric furnace 10 or the electric furnace exhaust gas (exhaust gas) discharged from the electric furnace 10.

[0020] (reduced iron feeding device) The manufacturing system 50 of this embodiment includes a reduced iron charging device 20 that charges reduced iron P into the electric furnace 10.

[0021] As shown in FIG. 2, the reduced iron feeding device 20 has a powder introduction section 21 for introducing reduced iron, a gas introduction section 22 for introducing a carrier gas, and a powder ejection section 23 for ejecting reduced iron P entrained in the carrier gas.

[0022] The powder introduction section 21 is connected to a reduced iron supply path L2 for supplying reduced iron.

[0023] The reduced iron P is a powder having an average particle size D50 of 0.001 mm or more and 10 mm or less. Here, the average particle size is a value obtained from the particle diameter measured by dynamic light scattering (DLS). The reduced iron P may be obtained by a reduced iron manufacturing apparatus 30 described later, or may be obtained by other methods.

[0024] The gas inlet 22 is connected to a carrier gas supply path L3 that supplies a carrier gas to the reduced iron charging device 20.

[0025] The type of carrier gas is not particularly limited, and although general industrial gases such as oxygen, nitrogen, and argon can be used as the carrier gas, it is preferable to use an inert gas such as nitrogen or argon in order to suppress reoxidation of the reduced iron P while it is entrained.

[0026] According to the reduced iron charging device 20, the reduced iron P introduced into the device through the powder introduction section 21 merges with the carrier gas introduced into the device through the gas introduction section 22 inside the device, is entrained by the carrier gas, and is ejected from the powder ejection section 23.

[0027] The method for introducing reduced iron into the reduced iron charging device 20 is not particularly limited, and may be a method of suctioning reduced iron P with a carrier gas using an ejector system, or an appropriate method may be selected depending on the amount of reduced iron P to be introduced, the position where the reduced iron charging device 20 is installed in the electric furnace 10, etc.

[0028] 1 and 2 , the reduced iron feeding device 20 is connected to the electric furnace 10 so as to penetrate the upper surface of the furnace body 11. As a result, the powder jetting part 23 provided below the reduced iron feeding device 20 is located inside the electric furnace 10, and the powder jetting part 23 and the furnace body 11 are exposed to the space inside the furnace body 11. This allows the reduced iron P to be reliably supplied into the molten steel located inside the furnace body 11 when the reduced iron P entrained in the carrier gas is ejected from the reduced iron charging device 20 into the electric furnace 10.

[0029] (reduced iron manufacturing equipment) The manufacturing system 50 of this embodiment may include a reduced iron manufacturing apparatus 30 that produces reduced iron P by reducing the iron oxide-containing raw material.

[0030] The configuration of the reduced iron manufacturing apparatus 30 is not particularly limited as long as it can obtain reduced iron from an iron oxide-containing raw material. As such a reduced iron manufacturing apparatus 30, for example, a known reduction furnace such as a reduction furnace (WO 2023 / 162389) that utilizes a fluidized bed phenomenon to reduce fine iron ore raw material to produce reduced iron can be applied.

[0031] The reduced iron manufacturing apparatus 30 is connected to a raw material supply path L1 that supplies iron oxide-containing raw materials to the reduced iron manufacturing apparatus 30, a reduced iron supply path L2 that supplies the obtained reduced iron P to the reduced iron charging device 20, and an exhaust gas recovery path L5 that recovers the atmosphere within the reduced iron manufacturing apparatus 30 as exhaust gas.

[0032] The raw material supply path L1 is located between a supply source of the iron oxide-containing raw material (not shown) and the reduced iron manufacturing apparatus 30, and is a path for supplying the iron oxide-containing raw material from the supply source to the reduced iron manufacturing apparatus 30.

[0033] The iron oxide-containing raw material is a powder having an average particle size D50 of 0.001 to 10 mm, where the average particle size is a value measured by dynamic light scattering (DLS).

[0034] The reduced iron supply path L2 is located between the reduced iron manufacturing apparatus 30 and the reduced iron charging device 20, and is a path for supplying the reduced iron obtained in the reduced iron manufacturing apparatus 30 to the reduced iron charging device 20.

[0035] An exhaust gas recovery path L5 is connected to the reduced iron manufacturing apparatus 30. This makes it possible to recover a portion of gas from the atmosphere in the reduced iron manufacturing apparatus 30 or exhaust gas (exhaust gas) discharged from the reduced iron manufacturing apparatus 30.

[0036] (Gas heating device) The production system 50 of this embodiment may include a gas heating device 40 that heats the carrier gas to be supplied to the reduced iron feeding device 20.

[0037] As shown in FIG. 2, the gas heating device 40 is located in the carrier gas supply path L3. The gas heating device 40 is not particularly limited as long as it can heat the carrier gas supplied to the reduced iron charging device 20 .

[0038] In one embodiment, the gas heating device 40 is a heat exchanger provided between the carrier gas supply line L3 and the exhaust gas recovery line L4. This allows the latent heat and sensible heat of the exhaust gas recovered from the electric furnace 10 to be used to heat the carrier gas in the carrier gas supply line L3.

[0039] [Method of manufacturing reduced iron] Next, a method for producing reduced iron according to one embodiment of the present invention will be described using a reduced iron production system 50 shown in FIGS. 1 and 2 as an example. In the reduced iron manufacturing method of this embodiment (hereinafter simply referred to as the "manufacturing method"), powder reduced iron P is injected into the electric furnace together with a carrier gas, and the reduced iron P is introduced into molten steel in the electric furnace .

[0040] Specifically, first, iron oxide-containing raw materials are supplied from a supply source (not shown) via a raw material supply path L1 to the reduced iron manufacturing apparatus 30. In the reduced iron charging device 20, reduced iron P having an average particle size D50 of 0.001 mm or more and 10 mm or less is produced.

[0041] Next, the reduced iron P obtained by the reduced iron manufacturing apparatus 30 is supplied from the powder introduction section 21 to the reduced iron charging device 20 via the reduced iron supply path L2. Next, a carrier gas is supplied from the gas introduction section 22 to the reduced iron charging device 20 via the carrier gas supply path L3. At this time, the reduced iron P is sucked into the reduced iron charging device 20 by the ejector system.

[0042] Next, the reduced iron P entrained in the carrier gas is ejected from the powder ejection section 23 of the reduced iron charging device 20 into the electric furnace 10. As a result, the powder reduced iron P entrained in the gas flow is effectively injected into the molten steel in the electric furnace 10 without being collected by the exhaust duct 15 provided in the electric furnace 10. Therefore, the production method of this embodiment makes it possible to improve the yield when producing reduced iron.

[0043] In the manufacturing method of this embodiment, the exhaust heat of the exhaust gas recovered from the electric furnace 10 is utilized to heat (preheat) the carrier gas by the gas heating device 40, and the carrier gas is then supplied to the reduced iron feeding device 20, thereby suppressing the loss of thermal energy and enabling highly efficient operation.

[0044] As described above, according to the manufacturing system 50 and manufacturing method of this embodiment, the reduced iron P entrained in the carrier gas is ejected into the electric furnace 10, so that even reduced iron with a small particle size can be reliably introduced into molten steel without being collected as dust in the electric furnace 10. This makes it possible to improve the yield when manufacturing reduced iron.

[0045] Furthermore, according to the manufacturing system 50 and manufacturing method of this embodiment, a portion of the gas can be recovered from the atmosphere in the electric furnace 10 while it is operating and supplied to the gas heating device 40 as a heat source for heating the carrier gas. In this way, the exhaust gas (exhaust gas) in the electric furnace is recovered and heat exchanged with the carrier gas in the gas heating device 40, which is a heat exchanger, thereby recovering latent heat and sensible heat, resulting in excellent energy efficiency.

[0046] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0047] Specifically, in the manufacturing system 50 of the above-described embodiment, as shown in Figures 1 and 2, the gas heating device 40 is described as a heat exchanger installed across the carrier gas supply path L3 and the exhaust gas recovery path L4 as an example, but the present application is not limited to this.

[0048] 2, the gas heating device 40 may be a heat exchanger provided between the carrier gas supply path L3 and the exhaust gas recovery path L5. Alternatively, the gas heating device 40 may be a heat exchanger provided between the carrier gas supply path L3 and the exhaust gas recovery path L4 and the exhaust gas recovery path L5. [Example]

[0049] The effects of the present invention will be explained below using experimental examples, but the present invention is not limited to the following descriptions in any way.

[0050] As the reduced iron production system, a reduced iron production system 50 shown in FIGS. 1 and 2 was used. The feed yield of reduced iron with different average particle sizes was evaluated with and without a carrier gas. Argon was used as the carrier gas to prevent reoxidation of the reduced iron. Table 1 shows the conditions for charging reduced iron and the charging yield in each of the examples and comparative examples.

[0051] [Table 1]

[0052] As shown in Table 1, when the carrier gas flow rate is 0 Nm 3 In Comparative Examples 1 to 3, a decrease in the yield of reduced iron was observed, particularly in Comparative Example 1 and Comparative Example 2, where the average particle size D50 of reduced iron was small. This is thought to be because in both Comparative Examples 1 and 2, the particle size of the reduced iron charged into the electric furnace was small, causing the reduced iron to be collected by the exhaust duct installed in the electric furnace, resulting in a decrease in yield.

[0053] On the other hand, in Comparative Example 3, the particle size of the reduced iron charged into the electric furnace was relatively large, so the yield of reduced iron did not decrease significantly. This is thought to be because the particle size of the reduced iron was large, so a large amount of reduced iron was charged into the molten metal by free fall.

[0054] In contrast, the carrier gas flow rate is 50 Nm 3 In Examples 1 to 3, an improvement in yield was confirmed for all particle sizes of reduced iron compared to when no carrier gas was used. This is believed to be because the reduced iron was effectively injected into the molten steel by being entrained in the carrier gas and ejected into the electric furnace. [Explanation of symbols]

[0055] 10 Electric furnace 11 Furnace body 12 electrodes 13 Iron (molten steel) 14 Refractories 15 Exhaust duct 20 Reduced iron feeding device 21 Powder introduction section 22 Gas inlet 23 Powder spouting part 30 Reduced iron production equipment 40 Gas heating device (heat exchanger) 50 Reduced iron production system (production system) L1 Raw material supply route L2 Reduced iron supply route L3 Carrier gas supply route L4, L5 exhaust gas recovery route P reduced iron

Claims

1. an electric furnace for melting the powdered reduced iron; a reduced iron charging device that charges the reduced iron into the electric furnace, the reduced iron feeding device includes a powder introduction section that introduces the reduced iron, a gas introduction section that introduces a carrier gas, and a powder ejection section that ejects the reduced iron entrained in the carrier gas.

2. the reduced iron feeding device is connected to the electric furnace, The reduced iron manufacturing system according to claim 1 , wherein the powder ejection section is located inside the electric furnace.

3. The system for producing reduced iron according to claim 1 , further comprising: a carrier gas supply path connected to the gas inlet portion and supplying the carrier gas to the reduced iron charging device.

4. The system for producing reduced iron according to claim 3 , further comprising a gas heating device located in the carrier gas supply path and configured to heat the carrier gas.

5. The system for producing reduced iron according to claim 4, wherein the gas heating device is a heat exchanger.

6. Further, an exhaust gas recovery path is provided to recover exhaust gas discharged from the electric furnace. The reduced iron manufacturing system according to claim 5 , wherein the heat exchanger is provided between the carrier gas supply path and the exhaust gas recovery path.

7. a reduced iron manufacturing apparatus that reduces an iron oxide-containing raw material to manufacture the reduced iron; 2. The system for producing reduced iron according to claim 1, further comprising: a reduced iron supply path located between the reduced iron production apparatus and the powder introducing portion, the reduced iron being supplied from the reduced iron production apparatus to the powder introducing portion.

8. 2. The system for producing reduced iron according to claim 1, wherein the reduced iron has an average particle size D50 of 0.001 mm or more and 10 mm or less.

9. A method for producing reduced iron using an electric furnace, comprising: A method for producing reduced iron, comprising: spraying powdered reduced iron together with a carrier gas into the electric furnace; and introducing the reduced iron into molten steel in the electric furnace.

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