Method for producing molten iron

Abstract

The present invention provides a method for efficiently producing molten iron using an arc-type electric furnace. The method for producing molten iron involves supplying a cold iron source to an arc-type electric furnace and melting the supplied cold iron source to produce molten iron, wherein the method satisfies a predetermined formula.

Description

[Technical Field]

[0001] The present invention relates to a method for producing molten iron. [Background Art]

[0002] With the global promotion of carbon neutrality, a shift from the blast furnace process to an electric arc furnace process for molten iron production is required in the steel industry. In the blast furnace process, lump ore, sintered ore, and coke are the main raw materials. Coke serves as a fuel for temperature rise, and at the same time, it is a raw material for reducing iron oxide in iron ore and obtaining low-melting point hot metal, that is, hot metal having a carbon concentration of about 4 mass% or more and 5 mass% or less. For this reason, a large amount of coke is charged into a blast furnace. Carbon in the hot metal produced in a blast furnace is removed in the converter process, and is eventually converted into carbon dioxide. As a result, approximately 2 tons of carbon dioxide is generated per ton of iron in crude steel production via the blast furnace and converter process.

[0003] In contrast, the electric arc furnace process produces crude steel by heating and melting raw materials such as scrap through electrical energy. In the electric arc furnace process, an already reduced iron source is used as a raw material, so no reduction energy is required, and the energy for heating the raw material is also supplied by electricity. Therefore, the amount of carbon dioxide generated is approximately 0.5 tons per ton of iron, which is lower than that of the method using a blast furnace and a converter.

[0004] Raw materials used in the electric arc furnace process include scrap and reduced iron. Although high-quality scrap suitable for producing high-grade steel exists, the volume of such scrap is limited, which may lead to competition for scrap between the company and other companies including other electric arc furnace steelmakers. As described above, even if the production of molten iron is simply shifted from the blast furnace process to the electric arc furnace process to promote carbon neutrality, it may still be difficult to newly secure a large stable supply of high-quality scrap for use in the electric arc furnace process.

[0005] Therefore, the use of reduced iron as a raw material for the electric furnace method has been considered. Reduced iron is metallic iron obtained by reducing iron ore. When the MIDREX method is used as a method for producing reduced iron, natural gas is used as a raw material, and a gas containing a large amount of hydrogen gas is used as a reducing agent. Therefore, compared with the blast furnace method, carbon dioxide can be reduced by the amount corresponding to the reduction by hydrogen gas. Further, a method for producing reduced iron that directly uses hydrogen gas as a reducing agent is under development, and if realized, completely zero-carbon ironmaking will be possible.

[0006] However, reduced iron may contain gangue components derived from ore, that is, impurities other than iron, in an amount of about 2 mass% or more and 10 mass% or less. Therefore, when melting reduced iron, extra energy is required for melting the gangue components and for melting the lime added to neutralize the gangue components. Therefore, when an arc electric furnace, which is an example of an electric furnace, is used, there has been a problem that as the proportion of reduced iron in the raw material increases, the power consumption per unit raw material (the amount of electric power used to produce 1 ton of iron) deteriorates, compared to a case where all the raw materials are scrap. In addition, since reduced iron is relatively difficult to melt, reduced iron particles aggregate with each other in the arc electric furnace and form large lumps (iceberg formation). This makes reduced iron even more difficult to melt in the arc electric furnace, leading to an extension of steelmaking time and a deterioration in power consumption per unit.

[0007] Various methods have been developed to reduce the power consumption per unit in arc electric furnaces and improve productivity. For example, methods such as preheating cold iron sources before melting and blowing coke as an auxiliary heat source have been adopted. As preheating furnaces for preheating scrap, for example, CONSTEEL has been developed for horizontal preheating furnaces, while ECOARC (registered trademark), Quantum, and SHARC have been developed for vertical preheating furnaces.

[0008] Further, studies have been conducted to improve the preheating efficiency of cold iron sources. For example, Patent Document 1 discloses that in an electric furnace provided with a preheating chamber, the apparent bulk density of iron-based scrap in the preheating chamber is set to 0.50 t / m 3 or more and 1.00 t / m 3A method for producing molten iron is disclosed, characterized by keeping the temperature below a certain level and keeping the height of the scrap filling in the preheating chamber within a predetermined range.

[0009] Patent Document 2 describes an electric furnace equipped with a preheating chamber, in which the apparent bulk density of scrap in the preheating chamber is 0.7 t / m³. 3 The above describes a method for dissolving scrap. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] International Publication No. 2021 / 049125 [Patent Document 2] Japanese Patent Publication No. 2012-180560 [Overview of the project] [Problems that the invention aims to solve]

[0011] The technologies described in Patent Documents 1 and 2 primarily aim to improve energy utilization efficiency by improving preheating efficiency. However, there is a need for technologies to further improve power consumption per unit of electricity by further improving dissolution efficiency. In addition, there is a need for methods to improve dissolution efficiency regardless of the apparent bulk density of the cold iron source.

[0012] This invention has been made in view of the above circumstances, and aims to provide a method for efficiently producing molten iron using an arc-type electric furnace. [Means for solving the problem]

[0013] As a result of diligent research, the inventors have found that the above objective can be achieved by adopting the following configuration.

[0014] 1. A method for producing molten iron, comprising supplying a cold iron source to an arc-type electric furnace and melting the supplied cold iron source to produce molten iron, A method for producing molten iron that satisfies the following formulas (1) and (2).

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[0015] 2. The method for producing molten iron according to paragraph 1, wherein the cold iron source comprises scrap and reduced iron.

[0016] 3. A method for producing molten iron as described in 1 or 2 above, The aforementioned arc-type electric furnace is equipped with a measuring device and a control device. The measuring device is used to measure at least one of the following: the temperature of the cold iron source, the temperature of the molten iron, and the bulk density of the cold iron source. A method for producing molten iron, comprising the control device controlling at least one of the input energy and the supply rate based on the measurement results from the measuring device. [Effects of the Invention]

[0017] According to the present invention, a method for efficiently producing molten iron using an arc-type electric furnace can be provided. [Brief explanation of the drawing]

[0018] [Figure 1] This is a diagram showing an example of an arc-type electric furnace. [Figure 2] This is a diagram showing an example of an arc-type electric furnace. [Figure 3] This is a diagram showing an example of an arc-type electric furnace. [Figure 4] This is a diagram showing an example of an arc-type electric furnace. [Figure 5] This graph shows the relationship between the temperature of the cold iron source and the dissolution time coefficient. [Figure 6] This graph shows the relationship between molten iron temperature and the dissolution time coefficient. [Figure 7] This graph shows the relationship between bulk density and the dissolution time coefficient. [Modes for carrying out the invention]

[0019] The present invention will be described in detail below. The following description is an example of a preferred embodiment of the present invention, and the present invention is not limited to the embodiments described below.

[0020] [Method for producing molten iron] In a method for producing molten iron according to one embodiment of the present invention, a cold iron source is supplied to an arc-type electric furnace, and the supplied cold iron source is melted to produce molten iron. The production method is characterized by satisfying the above formulas (1) and (2). If the supply rate of the cold iron source is too large relative to the melting rate in the electric furnace, the amount of unmelted cold iron source in the furnace increases, and the cold iron sources may fuse together to form a large mass of iron. Because the surface area ratio to the volume of the mass is small, the melting rate is low, and the formation of a mass of iron leads to a decrease in productivity and an increase in the amount of electricity required. If the physical properties of the supplied cold iron source, the supply rate of the cold iron source, etc., satisfy predetermined conditions, the cold iron source can be melted efficiently.

[0021] [Cold iron source] The cold iron source used in this embodiment is not particularly limited, and raw materials containing iron such as scrap, reduced iron, and pig iron can be used. The cold iron source may contain scrap and reduced iron, or may consist of scrap and reduced iron. As reduced iron, for example, briquette-formed reduced iron, such as HBI, can be used. As mentioned above, since reduced iron is relatively difficult to dissolve, the power consumption per unit tends to decrease as the proportion of reduced iron in the cold iron source increases. However, according to the present invention, molten iron can be efficiently produced even when the cold iron source contains scrap and reduced iron. Furthermore, the component composition of the cold iron source is not limited. Reduced iron may contain components other than Fe (typically impurities) in an amount of 2% to 10% by mass.

[0022] The mixing ratio of the cold iron source is not particularly limited, but it is preferable to set the scrap ratio in the range of 30% to 70% by mass. It is also preferable to set the reduced iron ratio in the range of 30% to 70% by mass. If the proportion of scrap is too high, the risk of impurity contamination increases, and if the proportion of reduced iron is too high, the dissolution efficiency may decrease, so the optimal ratio should be selected according to operating conditions, product quality, etc.

[0023] Furthermore, by adjusting the mixing ratio with scrap according to the physical properties of HBI used as reduced iron, such as particle size, bulk density, and metallization rate, it is possible to suppress aggregation and iceberg formation in the furnace and achieve stable dissolution behavior.

[0024] The mixing ratio of the cold iron source may be controlled in advance or adjusted during the operation of the arc-type electric furnace. Specific methods will be described later.

[0025] [Arc-type melting furnace] The arc-type electric furnace used in this embodiment will be described with reference to the figures. Figures 1 to 4 show suitable examples of arc-type electric furnaces.

[0026] The arc-type electric furnace 1a shown in Figure 1 is equipped with a melting chamber 2a. A cold iron source supply device 3 is provided on the top lid of the melting chamber 2a, and has an opening on the melting chamber side. The cold iron source x, which is the raw material, is supplied to the melting chamber 2a through the opening of the cold iron source supply device 3. The opening of the cold iron source supply device 3 is, for example, the opening of a supply bucket. The melting chamber 2a is equipped with electrodes 4 for generating an arc A and heating. The cold iron source x supplied to the melting chamber 2a melts due to the arc heat to become molten iron m and molten slag s. The obtained molten iron m can be tapped by any method.

[0027] The arc-type electric furnace 1b shown in Figure 2 is equipped with a melting chamber 2b and a preheating chamber 5b. The raw material, a cold iron source x, is loaded into a supply bucket 6 and transported via a traveling carriage 7 to above the desired cold iron source supply port 8. Next, the cold iron source supply port 8 is opened, and the cold iron source x is supplied from above into the preheating chamber 5b.

[0028] The cold iron source x supplied to the preheating chamber 5b is preheated by any method. For example, the production efficiency can be increased by preheating the cold iron source x by passing the high-temperature exhaust gas generated in the melting chamber 2b through to the preheating chamber 5b. Alternatively, the exhaust gas may be drawn in through the duct 9 and passed through the preheating chamber 5b, with any excess exhaust gas being exhausted through the duct 9.

[0029] The preheated cold iron source x is supplied to the melting chamber 2b. When the opening 10 is opened, the cold iron source x falls in and is supplied by the extruder 11.

[0030] The melting chamber 2b is partitioned by the furnace wall 12 and the furnace lid 13, and can be equipped with an electrode 4 for generating and heating an arc A, an oxygen injection lance 14 and a carbon material injection lance 15 for maintaining a desired high temperature, and a burner 16 for locally heating low-temperature areas. The carbon material injection lance 15 is a lance for injecting powdered carbon material into the furnace. However, the method of introducing carbon material is not limited to this, and lump coke, lump anthracite, etc., can be introduced from the top of the furnace. Any of these carbon materials functions as a heat source that supplements the arc heat, contributing to further improvement of melting efficiency and further reduction of power consumption per unit. Furthermore, by using a burner, the furnace temperature can be made uniform and melting can be accelerated. This makes it possible to stabilize the melting rate of the cold iron source and improve operational efficiency. To obtain this effect even further, it is preferable to use the burner in combination with the oxygen injection lance and the carbon material injection lance.

[0031] The cold iron source x supplied to the melting chamber 2b melts due to arc heat, becoming molten iron m and molten slag s. The obtained molten iron m can be tapped out through the tapping door 17 and tapping out through the tapping port 18. The molten slag s can be discharged through the slag outlet 20 by opening the slag removal door 19.

[0032] The arc-type electric furnace 1c shown in Figure 3 comprises a melting chamber 2c and a preheating chamber 5c. A cold iron source x is supplied to the preheating chamber 5c and preheated by any method. After preheating, the cold iron source x is supplied to the melting chamber 2c through the opening of the cold iron source supply device 3. The structure of the melting chamber 2c is the same as that of the melting chamber 2a.

[0033] The arc electric furnace 1d shown in Fig. 4 comprises a melting chamber 2d and a preheating chamber 5d. A cold iron source x is supplied into the preheating chamber 5d and preheated by any arbitrary method. For example, the cold iron source x is preheated by passing high-temperature exhaust gas generated in the melting chamber 2d (indicated by an arrow in the figure) through the preheating chamber 5d. The cold iron source x is placed on a conveyor 21 provided in the preheating chamber 5d and moved in the direction toward the melting chamber 2d (rightward in the figure). The cold iron source x is supplied into the melting chamber 2d through an opening 22 provided between the preheating chamber 5d and the melting chamber 2d. The melting chamber 2d is provided with an electrode 4 for generating an arc A to perform heating. The cold iron source x supplied into the melting chamber 2d is melted by arc heat into molten iron m and molten slag s. The obtained molten iron m can be tapped by any arbitrary method.

[0034] Arc electric furnaces 1a to 1d may be provided with, for example, a thermographic camera 23, a probe 24, and a distance meter 25 as measurement devices. The thermographic camera 23 is configured to measure the temperature T of the cold iron source ph and may be provided, for example, in the preheating chambers 5b to 5d or the cold iron source supply device 3. The probe 24 is configured to measure the molten iron temperature T m and may be provided in the melting chambers 2a to 2d. The distance meter 25 is configured to measure the bulk density ρ of the cold iron source, and may be provided, for example, in the preheating chambers 5b to 5d or the cold iron source supply device 3. Specifically, the volume of the cold iron source x in the preheating chamber can be obtained by the distance meter 25. Further, the weight of the cold iron source x can be obtained by providing a weight scale such as a load cell in the cold iron source supply device 3 and measuring the weight difference of the cold iron source x before and after supply using the weight scale. The bulk density ρ can be obtained based on the obtained volume and weight. Specifically, the bulk density ρ is calculated by dividing the weight of the cold iron source by the volume of the cold iron source. In the case where the cold iron source is continuously supplied using a conveyor or the like, the bulk density can also be calculated by measuring the weight of the cold iron source being conveyed in real time with a weight scale installed on the conveyor or the like, and using the measurement in combination with volume measurement performed by the distance meter.

[0035] [Supply and Melting of Cold Iron Source] In the molten iron production method according to this embodiment, a cold iron source is supplied to an arc-type electric furnace. Specifically, the cold iron source may be supplied to a melting chamber provided in the arc-type electric furnace. The method of supplying the cold iron source is not limited and can be done continuously or intermittently.

[0036] When supplying the cold iron source, the mixing ratio of the cold iron source may be adjusted. For example, the mixing ratio may be adjusted by pre-mixing in a supply bucket provided in the cold iron source supply device 3. Alternatively, the cold iron source supply device 3 may continuously control the mixing ratio simultaneously with the supply of the cold iron source. For example, an arc-type electric furnace may be equipped with a control device, and the control device may control the mixing ratio of the cold iron source in the cold iron source supply device based on measurement results from a measuring device. Specifically, the dissolution behavior can be monitored using measuring devices such as a thermal camera 23 and a probe 24, and control can be achieved by reducing the ratio of reduced iron if there is a large amount of undissolved material. Furthermore, a feedback mechanism can be implemented to control the mixing ratio of the cold iron source based on measurement results acquired in real time by the measuring device.

[0037] Furthermore, in the method for producing molten iron according to this embodiment, molten iron is produced by melting a cold iron source supplied to the melting chamber. The cold iron source is typically melted by arc heat.

[0038] [Equations (1) and (2)] The method for producing molten iron according to this embodiment satisfies the above formulas (1) and (2). The tests conducted to derive the above formulas (1) and (2) will be described below.

[0039] First, the temperature T of the cold iron source. ph (Unit: °C) Effect on dissolution time, molten iron temperature T m The effect of (unit: °C) on dissolution time, bulk density ρ (unit: t / m³) of the cold iron source. 3 Tests were conducted to investigate the effect of each on the dissolution time. The test results are shown in Figures 5-7. Reference conditions (temperature T of the cold iron source) ph :20℃ (no preheating), molten iron temperature T m :1580℃, bulk density ρ of cold iron source: 2.6 t / m³ 3When the dissolution rate at ) is set to 1, the following approximate formula holds for the dissolution rate (dissolution rate coefficient) y under each condition.

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[0040] Next, under the above standard conditions, the effect of the cold iron source supply rate on operation was investigated. While keeping the energy input to the arc-type electric furnace and the cold iron source supply rate constant, the cold iron source was intermittently supplied to the melting chamber and melted. As a result, the cold iron source supply rate (unit: t / min) was 6.8 × 10⁻⁶. -2 When the energy input to the arc-type electric furnace (in MW) exceeded P, the reduced iron aggregated and formed large clumps within the arc-type electric furnace. This made it difficult for the reduced iron to dissolve within the arc-type electric furnace. Furthermore, it became difficult to supply the cold iron source at a constant rate, extending the time until additional cold iron source could be supplied, ultimately leading to an extension of the steelmaking time. On the other hand, the supply rate of the cold iron source was 1.9 × 10⁻⁶ -2 When the value is less than P, the molten iron temperature rises, leading to increased heat loss due to radiant heat from the molten iron, which results in an extended steelmaking time. Therefore, under the above standard conditions, 1.9 × 10 -2 P≦v I ≤ 6.8 × 10 -2 It was found that molten iron could be produced efficiently by setting the condition P.

[0041] When the melting rate of the cold iron source changes, the upper and lower limits of the supply rate at which molten iron can be efficiently produced also change accordingly. Therefore, 1.9 × 10 -2 P≦v I ≤ 6.8 × 10 -2 By introducing a correction term based on the above approximation formula for the condition P, we obtained equations (1) and (2). By satisfying equations (1) and (2), molten iron can be produced efficiently.

[0042] In equations (1) and (2) above, the supply rate v of the cold iron source IThis is the ratio of the amount of cold iron supplied to the time required to supply the cold iron source. The temperature of the cold iron source is T. ph ρ is the temperature of the cold iron source when it is supplied to the melting chamber. If an arc-type electric furnace with a preheating chamber is used, it is the preheating temperature; if an arc-type electric furnace without a preheating chamber is used, it is usually room temperature. The bulk density ρ of the cold iron source is the ratio of the amount of cold iron source supplied to the volume of the cold iron source in air, including the voids between the particles constituting the cold iron source and the voids inside it.

[0043] Temperature T of the cold iron source ph The temperature is not particularly limited, but for example, it can be 20°C or higher. Preheating can further improve the supply rate of the cold iron source, so T ph The temperature may be 300°C or higher, or 700°C or higher. On the other hand, T ph For example, the temperature may be 1200°C or lower.

[0044] Molten iron temperature T m The temperature is not particularly limited, but for example, it can be 1550°C or higher. By increasing the temperature of the molten iron, the supply rate of the cold iron source can be further increased, so T m The temperature may be 1650°C or higher, or 1655°C or higher. On the other hand, T m For example, the temperature may be 1700°C or lower.

[0045] The bulk density ρ of the cold iron source is not particularly limited, but for example, 0.5 t / m³ 3 The above can be used. On the other hand, ρ is, for example, 4.0 t / m 3 The following may be true: 2.8 t / m 3 The following may also be true: 2.4 t / m 3 The following is also acceptable.

[0046] The energy P input to the arc-type electric furnace refers to the electricity supplied to the arc-type electric furnace. In addition to arc power, heating energy from the charcoal material and burner may also be supplied to the arc-type electric furnace. However, in this embodiment, the heating energy from the charcoal material and burner is not included in the energy P input to the arc-type electric furnace.

[0047] [Preheating of cold iron source] In the method for producing molten iron according to this embodiment, the cold iron source may be preheated prior to supplying it.

[0048] [Control of operating conditions] In the molten iron production method according to this embodiment, the supply rate of the cold iron source v I And at least one of the energy P input to the arc-type electric furnace may be controlled. That is, v I At least one of P and the cold iron source may be determined, and the cold iron source may be supplied and melted under the determined operating conditions.

[0049] The method for determining operating conditions is not limited, ph , T m And ρ may be obtained, and the operating conditions may be determined based on the obtained results. ph , T m The method for obtaining and ρ is not limited, but it is preferable to obtain them by measuring with a measuring device. For example, the current T ph It is possible to obtain the current T by a probe. m This can be obtained. For example, ρ can be obtained using a distance meter. In other words, in the method for producing molten iron according to this embodiment, at least one of the following can be measured by a measuring device: the temperature of the cold iron source, the temperature of the molten iron, and the bulk density of the cold iron source.

[0050] The method for determining operating conditions based on the acquired results is not particularly limited as long as the determined operating conditions satisfy the above formulas (1) and (2), and it is not necessarily required to perform the calculations using the above formulas (1) and (2). However, it is preferable to perform the calculations using the above formulas (1) and (2).

[0051] An example of performing calculations using the above formulas (1) and (2) is explained below. I If you decide, T ph , T m By obtaining ρ and P, and substituting the obtained parameters into equations (1) and (2) above, v IDetermine the numerical range. From the values ​​included in that numerical range, use any method to determine v I Determine the center value of the given numerical range. I It is also possible to use the central value of the relevant numerical range as a reference, and in accordance with predetermined operating policies, etc. I You may adjust it. Similarly, when determining P, T ph , T m ρ and v I Further data is obtained, and the numerical range of P is determined by substituting the obtained parameters into equations (1) and (2) above. P is determined by any method from among the values ​​included in the numerical range. Specifically, the value at the center of the numerical range may be used as P, or P may be adjusted based on the value at the center of the numerical range according to a predetermined operational policy. The numerical range of P can also be determined by the following equations (3) and (4), which are derived by rearranging equations (1) and (2) above.

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[0052] The number and frequency of determining operating conditions are not particularly limited. However, when the cold iron source is supplied intermittently, the amount of cold iron source supplied per instance relative to the period between the supply of cold iron source and the next supply can be defined as the cold iron source supply rate. Furthermore, it is preferable to determine at least one of the cold iron source supply rate and the energy input to the arc-type electric furnace for each supply of cold iron source (for example, for every supply of cold iron source). On the other hand, when the cold iron source is supplied continuously, it is preferable to determine at least one of the cold iron source supply rate and the energy input to the arc-type electric furnace at least once during a continuous one-minute interval.

[0053] The arc-type electric furnace according to this embodiment includes v I The device may also be provided to determine at least one of P. I The device may be equipped with an output (for example, output by display) of at least one of P and P. By checking the displayed output, the operator can operate the arc electric furnace to satisfy the above equations (1) and (2).

[0054] Also, v I and at least one, preferably both, of P may be automatically controlled. In other words, the arc-type electric furnace may be equipped with a control device, and the method for producing molten iron according to this embodiment is such that the control device controls v based on the measurement results from the measuring device. I and may include controlling P. Also, based on the measurement results acquired in real time by the measuring device, v I It can also be used as a feedback mechanism to control P. This allows for further optimization of operating conditions and further improvement of dissolution efficiency.

[0055] After supplying and melting the cold iron source under conditions that satisfy equations (1) and (2) above, the melting process may be terminated by setting P to 0. After the melting process is terminated, a step of tapping the molten iron from the melting chamber of the arc-type electric furnace may be provided. Alternatively, a step of removing the slag from the melting chamber of the arc-type electric furnace may be provided. [Examples]

[0056] Examples of actions taken to confirm the operation and effects of the present invention will be described below. In these examples, tests were conducted using an arc-type electric furnace having the configuration shown in Figure 1. For the example in which preheating was performed, an arc-type electric furnace having the configuration shown in Figure 3 was used.

[0057] As the cold iron source, we used a cold iron source consisting of shredded waste as scrap and HBI as reduced iron.

[0058] For the shredded waste, we used general iron-based scrap from among the scrap types specified in the Japan Iron and Steel Association's "Unified Standards for Inspection and Acceptance of Iron Scrap." Specifically, we used iron scrap that was primarily made from processed steel plates, shredded in a shredder, and then separated using a magnetic separator.

[0059] For reduced iron, briquette-formed reduced iron (HBI) was used. HBI has the following characteristics: T.Fe (total iron content) 88-94% by mass, M.Fe (metallic iron content) 83-88% by mass, metallization rate (M.Fe / T.Fe) 94%, C 1.0-1.5% by mass, and bulk density 2.0-3.0 t / m³. 3 The following was used. Furthermore, the thickness t of the HBI was 30mm, the width w was 50mm, and the length l was 110mm or less.

[0060] In this example, the amount of cold iron source supplied to the arc-type electric furnace was 100 tons. The amount of molten iron produced by melting the cold iron source was approximately 80 tons, the amount of residual molten iron (molten iron remaining in the furnace) was approximately 10 tons, and the amount of slag was approximately 10 tons. Here, the cold iron source was a mixture of scrap and reduced iron, and the supply amount was 50 tons at a time, supplied in two separate batches.

[0061] The table shows the production conditions for molten iron in each example. ph , T m and ρ were measured using a thermal camera, probe, and rangefinder, respectively, installed in the arc-type electric furnace. In some examples, preheating was performed to Tm The temperature was set to over 20°C. The input energy P remained constant throughout the operation. Also, the time interval between the first and second supply was the same as the time interval between the second supply and the end of the operation.

[0062] Table 1 shows the amount of electricity supplied to an arc-type electric furnace to produce 1 ton of iron, expressed as power consumption per unit. P, T ph , T m When comparing and ρ under the same conditions, molten iron produced under manufacturing conditions that satisfy equations (1) and (2) achieved a lower power consumption per unit of production than molten iron produced under manufacturing conditions that do not satisfy either equation (1) or (2).

[0063] [Table 1] [Explanation of Symbols]

[0064] 1a, 1b, 1c, 1d Arc-type electric furnace 2a, 2b, 2c, 2d Melting chamber 3 Cold iron source supply device 4 electrodes 5b, 5c, 5d Preheating chambers 6. Supply buckets 7. Running bogie 8 Cold iron source supply port 9 ducts 10 Opening / Closing 11. Extruder 12 Furnace wall 13 Hearth cover 14. Oxygen blowing lance 15. Charcoal material blowing lance 16 burners 17 Hot water outlet door 18 Hot water outlet 19. Door for waste disposal 20 Slag outlet 21 Conveyor 22 Opening 23 Thermal cameras 24 probes 25 Rangefinder x cold iron source m molten iron s molten slag A Ark

Claims

1. A method for producing molten iron, comprising supplying a cold iron source to an arc-type electric furnace and melting the supplied cold iron source to produce molten iron, A method for producing molten iron that satisfies the following formulas (1) and (2). [Math 1] [Math 2] Here, v Ｉ : Supply rate of the cold iron source (t / min) P: Energy input to the arc-type electric furnace (MW) T ｐｈ : Temperature of the cold iron source (°C) T ｍ : The temperature of the molten iron in the arc-type electric furnace (°C) ρ: Bulk density (t / m³) of the cold iron source ３ ) That is the case.

2. The method for producing molten iron according to claim 1, wherein the cold iron source comprises scrap and reduced iron.

3. A method for producing molten iron according to claim 1 or 2, The aforementioned arc-type electric furnace is equipped with a measuring device and a control device. The measuring device is used to measure at least one of the following: the temperature of the cold iron source, the temperature of the molten iron, and the bulk density of the cold iron source. A method for producing molten iron, comprising the control device controlling at least one of the input energy and the supply rate based on the measurement results from the measuring device.

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