Raw material charging device and raw material charging method

Abstract

A raw material charging device according to one embodiment of the present invention for charging an iron oxide raw material into a shaft furnace body, the raw material charging device being characterized by comprising: a plurality of charging hoppers for storing an iron oxide raw material to be charged into the shaft furnace body; a central raw material dispersion pipe, one end of which is connected to at least one charging hopper among the plurality of charging hoppers, and the other end of which is disposed at a position including the center, in a plan view, of the internal space of the shaft furnace body; and a plurality of peripheral raw material dispersion pipes, one end of which is connected to another charging hopper among the plurality of charging hoppers, and the other end of which is disposed at the periphery of the other end of the central raw material dispersion pipe.

Description

TITLE OF INVENTION: RAW MATERIAL CHARGING DEVICE AND RAW MATERIAL CHARGING METHOD TECHNICAL FIELD

[0001] The present invention relates to a raw material charging device and a raw material charging method. Priority is claimed on Japanese Patent Application No. 2024-059749, filed on April 2, 2024, the content of which is incorporated herein by reference. BACKGROUND ART

[0002] A method of producing reduced iron using a shaft furnace (shaft furnace operation) is a representative of a direct reduction process of producing reduced iron from an iron oxide raw material, and is widespread mainly in regions (oil-producing countries) where natural gas is available at low cost. Here, an outline of the method of producing reduced iron using a shaft furnace will be described. First, an iron oxide raw material (for example, iron oxide pellets) is charged from an upper part of the shaft furnace, and a reducing gas is blown in from a lower part of the shaft furnace. Here, the reducing gas is heated to a predetermined temperature (for example, about 900°C to 950°C) and then blown into the shaft furnace. The reducing gas blown into the shaft furnace reduces the iron oxide raw material in the shaft furnace. Reduced iron is produced by such a direct reduction process. The reduced iron is discharged from the lower part of the shaft furnace and cooled. From a top of the shaft furnace, a top gas (exhaust gas) containing hydrogen gas, CO gas, water vapor, and CO2 gas is discharged. After water vapor is removed from the top gas, hydrogen gas and CO gas in the top gas are reused as part of a feed gas. In addition, CO2 gas may be removed after water vapor has been removed from the top gas.

[0003] The reducing gas used in the shaft furnace is obtained by reforming a carbon-containing feed gas (for example, natural gas or coke oven gas) using water vapor, CO2 gas, oxygen gas, or the like. Alternatively, the feed gas is used as the reducing gas in the shaft furnace as it is without being reformed. Main components of the reducing gas are hydrogen gas (H2), CO gas (CO), and methane gas (CH4).

[0004] Incidentally, the iron oxide raw material is charged into the shaft furnace through a dispersion pipe from a charging hopper provided at the top of the furnace. End portions (opening parts) of the dispersion pipe in the shaft furnace are arranged at equal intervals in a circumferential direction such that dispersion of the iron oxide raw material into the shaft furnace becomes uniform, particularly, becomes uniform in the circumferential direction in a plan view (here, the plan refers to a plane in a direction perpendicular to a height direction of the shaft furnace; the same applies hereinafter) (Patent Documents 1 and 2).

[0005] However, since the reducing gas is blown in from a side surface of the shaft furnace, a reducing gas flow rate in the shaft furnace is not necessarily uniform. Specifically, the reducing gas flow rate at the center and its vicinity in the plan view of the shaft furnace is smaller than the reducing gas flow rate in the vicinity of a wall surface of the shaft furnace. Therefore, as disclosed in Patent Document 3, a technique for imparting a bias in a particle size distribution of the iron oxide raw material in the plan view has been proposed. In the technique disclosed in Patent Document 3, a particle size of the iron oxide raw material charged into the center and its vicinity in the plan view of the shaft furnace is made larger than a particle size of the iron oxide raw material charged near the wall surface of the shaft furnace. This facilitates a flow of the reducing gas at the center and its vicinity in the plan view of the shaft furnace, thereby making a distribution of the reducing gas flow rate in the shaft furnace uniform. Therefore, it is possible to reduce variation between the quality of reduced iron discharged from the center and its vicinity in the plan view of the shaft furnace and the quality of reduced iron discharged from the vicinity of the wall surface. Citation List Patent Documents

[0006] Patent Document 1: Japanese Unexamined Utility Model Application, First Publication No. S53-96004 Patent Document 2: Japanese Unexamined Patent Application, First Publication No. S55-69210 Patent Document 3: Japanese Unexamined Patent Application, First Publication No. H07-146080 SUMMARY OF INVENTION Technical Problem

[0007] The technique disclosed in Patent Document 3 is beneficial in that it can impart a bias in the particle size distribution of the iron oxide raw material in the plan view. However, as a result of detailed examination of the technique by the present inventor, it was found that there is room for further improvement. In addition, the present inventor has considered that a technique capable of varying a distribution of characteristics of the iron oxide raw material in the plan view is necessary in order to further increase a degree of freedom in the shaft furnace operation. It has been considered that, in a case where the distribution of characteristics in the plan view can be varied, the metallization rate of the iron oxide raw material can be improved.

[0008] Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel and improved raw material charging device and raw material charging method capable of varying a distribution of characteristics of an iron oxide raw material in a plan view, particularly increasing the metallization rate of the iron oxide raw material at a central part of a shaft furnace body, thereby improving the metallization rate of the iron oxide raw material as a whole. Solution to Problem

[0009] The gist of the present invention is as follows. (1) According to one aspect of the present invention, there is provided a raw material charging device that charges an iron oxide raw material into a shaft furnace body, the raw material charging device including: a plurality of charging hoppers configured to store an iron oxide raw material to be charged into the shaft furnace body; a central raw-material dispersion pipe having one end portion connected to at least one charging hopper among the plurality of charging hoppers and the other end portion disposed at a position including a center in a plan view within an internal space of the shaft furnace body; and a plurality of peripheral raw-material dispersion pipes each having one end portion connected to another charging hopper among the plurality of charging hoppers and the other end portion disposed at a periphery of the other end portion of the central raw-material dispersion pipe. (2) The raw material charging device according to (1) may further include: a cylindrical member provided inside the shaft furnace body, in which the other end portion of the central raw-material dispersion pipe may be disposed inside the cylindrical member in the plan view, and the other end portion of each of the plurality of peripheral raw-material dispersion pipes may be disposed outside the cylindrical member in the plan view. (3) According to another aspect of the present invention, there is provided a raw material charging method including: charging an iron oxide raw material into a central part and a peripheral part of a shaft furnace body; and making a charging surface of the iron oxide raw material charged into the central part lower than a charging surface of the iron oxide raw material charged into the peripheral part. (4) In the raw material charging method according to (3), the iron oxide raw material may be charged into an inside and an outside of a cylindrical member provided inside the shaft furnace body, a charging surface of the iron oxide raw material inside the cylindrical member may be used as the charging surface of the iron oxide raw material charged into the central part, and a charging surface of the iron oxide raw material outside the cylindrical member may be used as the charging surface of the iron oxide raw material charged into the peripheral part. (5) In the raw material charging method according to (3) or (4), the iron oxide raw material may be charged into the central part and the peripheral part of the shaft furnace body, and an iron oxide raw material having a particle size larger than a particle size of the iron oxide raw material charged into the peripheral part may be charged into the central part. (6) In the raw material charging method according to any one of (3) to (5), the iron oxide raw material may be charged into the central part and the peripheral part of the shaft furnace body, and an iron oxide raw material having a temperature higher than a temperature of the iron oxide raw material charged into the peripheral part may be charged into the central part. Advantageous Effects of Invention

[0010] According to the present invention, by varying a distribution of characteristics of an iron oxide raw material in a plan view, it is possible to increase the metallization rate of the iron oxide raw material at a central part of a shaft furnace body and to improve the metallization rate of the iron oxide raw material as a whole. BRIEF DESCRIPTION OF DRAWINGS

[0011] [FIG. 1] A side cross-sectional view schematically showing an example of a raw material charging device according to a first embodiment of the present invention. [FIG. 2] A cross-sectional view taken along line A-A in FIG. 1. [FIG. 3] A side cross-sectional view schematically showing an example of a raw material charging device according to a second embodiment of the present invention. [FIG. 4] A side cross-sectional view schematically showing an example of a raw material charging device according to a third embodiment of the present invention. [FIG. 5] A cross-sectional view taken along line B-B in FIG. 4. DESCRIPTION OF EMBODIMENTS

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. <1. First Embodiment (1-1. Raw Material Charging Device) First, a configuration of a raw material charging device 1A according to a first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a side crosssectional view schematically showing an example of the raw material charging device 1A according to the first embodiment. FIG. 2 is a cross-sectional view (plan cross-sectional view) taken along line A-A in FIG. 1.

[0014] The raw material charging device 1A is provided at an upper end of a shaft furnace body 10. The shaft furnace body 10 is known.

[0015] The raw material charging device 1A includes raw material tanks 100 and 110, a raw material conveying device 120, a plurality of charging hoppers 20a and 20b, a central raw-material dispersion pipe 30, a plurality of peripheral raw-material dispersion pipes 40, a diverter damper 130, and a plurality of pressure equalizing hoppers 140.

[0016] An iron oxide raw material 50a is stored in the raw material tank 100, and an iron oxide raw material 50b is stored in the raw material tank 110. The iron oxide raw materials 50a and 50b are known iron oxide raw materials, and are, for example, iron oxide pellets. The iron oxide raw materials 50a and 50b have different characteristics. In the first embodiment, the iron oxide raw materials 50a and 50b have different particle sizes. More specifically, the particle size of the iron oxide raw material 50a is larger than the particle size of the iron oxide raw material 50b. In other words, the raw material tank 100 and the raw material tank 110 have different particle sizes of the stored iron oxide raw materials, the particle size of the iron oxide raw material 50a being larger than the particle size of the iron oxide raw material 50b.

[0017] In this case, for example, the iron oxide raw material may be classified using a sieve having a predetermined mesh size (for example, 18 mm), the iron oxide raw material remaining on the sieve may be used as the iron oxide raw material 50a, and the iron oxide raw material that falls through the sieve may be used as the iron oxide raw material 50b. Further, an upper limit of the particle size of the iron oxide raw material 50a may be determined. For example, the iron oxide raw material 50a may be classified using a sieve having a predetermined mesh size (for example, 20 mm), and the iron oxide raw material 50a that falls through the sieve may be used. Similarly, a lower limit of the particle size of the iron oxide raw material 50b may be determined. For example, the iron oxide raw material 50b may be classified using a sieve having a predetermined mesh size (for example, 16 mm), and the iron oxide raw material 50b remaining on the sieve may be used. In this case, the particle size of the iron oxide raw material 50a is 18 mm or more and less than 20 mm, and the particle size of the iron oxide raw material 50b is 16 mm or more and less than 18 mm.

[0018] The raw material conveying device 120 conveys the iron oxide raw material 50a or the iron oxide raw material 50b to the diverter damper 130. The diverter damper 130 distributes the iron oxide raw material 50a or the iron oxide raw material 50b conveyed from the raw material conveying device 120 to the charging hopper 20a or the charging hopper 20b. Specifically, the diverter damper 130 distributes the iron oxide raw material 50a to the charging hopper 20a and distributes the iron oxide raw material 50b to the charging hopper 20b. The iron oxide raw material 50a and the iron oxide raw material 50b are placed on the raw material conveying device 120 at different timings and conveyed to the diverter damper 130. The iron oxide raw material 50a is charged into the charging hopper 20a when its flow direction is switched to a direction of the charging hopper 20a by the diverter damper 130. The iron oxide raw material 50b is charged into the charging hopper 20b when its flow direction is switched to a direction of the charging hopper 20b by the diverter damper 130.

[0019] The charging hopper 20a is disposed on the same axis as a central axis 11 (see FIG. 2) of the shaft furnace body 10. The charging hopper 20a stores the iron oxide raw material 50a. Four charging hoppers 20b are provided around the charging hopper 20a at equal intervals (90-degree intervals in a plan view). The charging hopper 20b stores the iron oxide raw material 50b.

[0020] The central raw-material dispersion pipe 30 is provided between the shaft furnace body 10 and the charging hopper 20a. One end portion 30a of the central rawmaterial dispersion pipe 30 is connected to the charging hopper 20a (one charging hopper), and the other end portion 30b is disposed at a position including a center 11 in a plan view within an internal space of the shaft furnace body 10 (see FIG. 2). The other end portion 30b being disposed at the position including the center 11 in the plan view within the internal space of the shaft furnace body 10 means that the other end portion 30b is disposed such that a central axis of the shaft furnace body 10 in a height direction is included inside the end portion 30b in the plan view. In the present embodiment, a central axis of the central raw-material dispersion pipe 30 in a length direction substantially coincides with the central axis of the shaft furnace body 10 in the height direction. The central raw-material dispersion pipe 30 charges the iron oxide raw material 50a stored in the charging hopper 20a into the center 11 and its vicinity in the plan view of the shaft furnace body 10.

[0021] The peripheral raw-material dispersion pipe 40 is provided between the internal space of the shaft furnace body 10 and each charging hopper 20b. One end portion 40a of the peripheral raw-material dispersion pipe 40 is connected to the charging hopper 20b, and the other end portion 40b is disposed around the other end portion 30b of the central raw-material dispersion pipe 30 (see FIG. 2). As shown in FIG. 2, the other end portions 40b of the peripheral raw-material dispersion pipes 40 are disposed at equal intervals (90-degree intervals) along a circumferential direction. The position of the end portion 40b of the peripheral raw-material dispersion pipe 40 in the plan view need only be determined in advance by an experiment, a calculation, or the like such that a desired distribution of characteristics in the plan view is obtained according to the characteristics of the iron oxide raw material 50a and the characteristics of the iron oxide raw material 50b. Note that the characteristics referred to here are gas flow resistances. For example, by changing the gas flow resistance in a radial direction of the shaft furnace body 10, a distribution of gas in the radial direction can be changed, and the amount of gas in the central part, where gas has conventionally been less distributed, can be increased. Since the distribution of the characteristics of the iron oxide raw material in the plan view can be varied, it becomes possible to improve the gas utilization efficiency, suppress reduction disintegration of the iron oxide raw materials 50a and 50b, and suppress stacking. In addition, it becomes possible to improve the metallization rate.

[0022] The peripheral raw-material dispersion pipe 40 charges the iron oxide raw material 50b into a peripheral portion (a peripheral portion of the iron oxide raw material 50a) in the plan view of the shaft furnace body 10. Therefore, the iron oxide raw material 50a is charged into the center 11 and its vicinity in the plan view of the shaft furnace body 10, and the iron oxide raw material 50b is charged into the periphery of the iron oxide raw material 50a.

[0023] In the first embodiment, four sets of the charging hopper 20b and the peripheral raw-material dispersion pipe 40 are provided around the set of the charging hopper 20a and the central raw-material dispersion pipe 30 at 90-degree intervals; however, the present invention is not limited to this example. For example, four peripheral rawmaterial dispersion pipes 40 may be extended from one charging hopper 20b. Alternatively, two peripheral raw-material dispersion pipes 40 may be extended from each of two charging hoppers 20b. In any case, it is preferable that the plurality of peripheral raw-material dispersion pipes 40 be disposed at equal intervals in the circumferential direction in the plan view.

[0024] The pressure equalizing hoppers 140 are provided in the central raw-material dispersion pipe 30 and the peripheral raw-material dispersion pipe 40, and maintain the internal pressure of these dispersion pipes equal.

[0025] As described above, with the raw material charging device 1A according to the present embodiment, the iron oxide raw material 50a stored in the charging hopper 20a is charged, via the central raw-material dispersion pipe 30, into the center 11 and its vicinity in the plan view of the shaft furnace body 10, and the iron oxide raw material 50b stored in the charging hopper 20b is charged, via the peripheral raw-material dispersion pipe 40, into the periphery of the iron oxide raw material 50a in the plan view of the shaft furnace body 10. Here, the distribution of the characteristics of the iron oxide raw materials 50a and 50b in the plan view can be varied only by changing the characteristics of the iron oxide raw material 50a stored in the charging hopper 20a and the characteristics of the iron oxide raw material 50b stored in the charging hopper 20b. Here, examples of the characteristics of the iron oxide raw materials 50a and 50b include a particle size, a temperature described below, and the like. Examples of other characteristics include components, brands, and the like of the iron oxide raw materials 50a and 50b. Therefore, the distribution of the characteristics of the iron oxide raw materials 50a and 50b in the plan view can be varied.

[0026] <1-2. Raw Material Charging Method> Next, an example of a raw material charging method using the raw material charging device 1A described above will be described. In the present raw material charging method, the particle size of the iron oxide raw material 50a charged into the shaft furnace body 10 from the central raw-material dispersion pipe 30 is made larger than the particle size of the iron oxide raw material 50b charged into the shaft furnace body 10 from the plurality of peripheral raw-material dispersion pipes 40. That is, the particle size of the iron oxide raw material 50a stored in the raw material tank 100 is made larger than the particle size of the iron oxide raw material 50b stored in the raw material tank 110. Then, when the iron oxide raw material 50a is conveyed from the raw material tank 100 to the diverter damper 130, the diverter damper 130 distributes the iron oxide raw material 50a to the charging hopper 20a. When the iron oxide raw material 50b is conveyed from the raw material tank 110 to the diverter damper 130, the diverter damper 130 distributes the iron oxide raw material 50b to the charging hopper 20b. As a result, the particle size of the iron oxide raw material 50a charged into the shaft furnace body 10 from the central raw-material dispersion pipe 30 is made larger than the particle size of the iron oxide raw material 50b charged into the shaft furnace body 10 from the plurality of peripheral raw-material dispersion pipes 40. In other words, in the present raw material charging method, the iron oxide raw material is charged into the central part and the peripheral part of the shaft furnace body 10, and the iron oxide raw material 50a having a particle size larger than the particle size of the iron oxide raw material 50b charged into the peripheral part is charged into the central part. That is, the particle size of the iron oxide raw material 50a in the center 11 and its vicinity in the plan view of the shaft furnace body 10 is made larger than the particle size of the iron oxide raw material 50b charged into the periphery of the iron oxide raw material 50a. The method of adjusting the particle size is as described above. The magnitude of the difference in particle size is not particularly limited, and need only be set such that the effect (reduction in variation in quality of reduced iron) described below is increased. The central part referred to herein is a portion including the central axis of the shaft furnace body 10 in the height direction in the plan view, and the peripheral part is a portion outside the central part in the shaft furnace body 10. The ratio of the central part to the peripheral part in the plan view is not particularly limited as long as the desired characteristics of the iron oxide raw material in the plan view are obtained.

[0027] As described above, the reducing gas is blown in from a side surface of the shaft furnace body 10. Therefore, when the particle size distribution of the iron oxide raw material in the plan view is uniform, the reducing gas flow rate at the center 11 and its vicinity in the plan view of the shaft furnace body 10 is smaller than the reducing gas flow rate in the vicinity of a wall surface of the shaft furnace body 10. Therefore, in the present embodiment, the particle size of the iron oxide raw material 50a in the center 11 and its vicinity in the plan view of the shaft furnace body 10 is made larger than the particle size of the iron oxide raw material 50b charged into the periphery of the iron oxide raw material 50a. This facilitates a flow of the reducing gas at the center 11 and its vicinity in the plan view of the shaft furnace body 10, thereby making the distribution of the reducing gas flow rate in the shaft furnace uniform. Therefore, it is possible to reduce the variation between the quality of the reduced iron discharged from the center 11 and its vicinity in the plan view of the shaft furnace body 10 and the quality of the reduced iron discharged from the vicinity of the wall surface, and consequently, to improve the quality of the reduced iron.

[0028] <2. Second Embodiment (2-1. Raw Material Charging Device) Next, a configuration of a raw material charging device IB according to a second embodiment will be described with reference to FIG. 3. FIG. 3 is a side crosssectional view schematically showing an example of the raw material charging device IB according to the second embodiment. The raw material charging device IB according to the second embodiment further includes a raw material preheating device 115 in addition to the configuration of the raw material charging device 1A according to the first embodiment.

[0029] The raw material preheating device 115 is provided below the raw material tank 100, and preheats the iron oxide raw material 50a discharged from the raw material tank 100 and then places the iron oxide raw material 50a on the raw material conveying device 120. The heating temperature by the raw material preheating device 115 need only be measured by, for example, installing a thermometer such as a thermocouple in the raw material preheating device 115 and using this thermometer. The operation of other devices in the raw material charging device IB is the same as that of the raw material charging device 1 A. Therefore, the temperature (surface temperature) of the iron oxide raw material 50a is higher than the temperature (surface temperature) of the iron oxide raw material 50b. In the second embodiment, the iron oxide raw material 50a is heated before being stored in the charging hopper 20a, but the iron oxide raw material 50a may be heated in the charging hopper 20a, or the iron oxide raw material 50a may be heated as it passes through the central raw-material dispersion pipe 30. The means for heating the iron oxide raw material 50a is not particularly limited, and may be, for example, an electric heater or the like. In the second embodiment, the iron oxide raw material 50a has a different characteristic from the iron oxide raw material 50b, namely a different temperature. In other words, the raw material tank 100 and the raw material tank 110 have different temperatures of the stored iron oxide raw materials, the temperature of the iron oxide raw material 50a being higher than the temperature of the iron oxide raw material 50b. The iron oxide raw material 50a is preheated to, for example, 600°C to 800°C. The temperature of the iron oxide raw material 50b is room temperature, for example, 0°C to 50°C.

[0030] (2-2. Raw Material Charging Method> Next, an example of a raw material charging method using the raw material charging device IB described above will be described. In the present raw material charging method, the temperature of the iron oxide raw material 50a charged into the shaft furnace body 10 from the central raw-material dispersion pipe 30 is made higher than the temperature of the iron oxide raw material 50b charged into the shaft furnace body 10 from the plurality of peripheral raw-material dispersion pipes 40. That is, the iron oxide raw material 50a stored in the raw material tank 100 is first preheated by the raw material preheating device 115. Then, when the iron oxide raw material 50a is conveyed from the raw material tank 100 to the diverter damper 130, the diverter damper 130 distributes the iron oxide raw material 50a to the charging hopper 20a. When the iron oxide raw material 50b is conveyed from the raw material tank 110 to the diverter damper 130, the diverter damper 130 distributes the iron oxide raw material 50b to the charging hopper 20b. As a result, the temperature of the iron oxide raw material 50a charged into the shaft furnace body 10 from the central raw-material dispersion pipe 30 is made higher than the temperature of the iron oxide raw material 50b charged into the shaft furnace body 10 from the plurality of peripheral raw-material dispersion pipes 40. In other words, in the present raw material charging method, the iron oxide raw material is charged into the central part and the peripheral part of the shaft furnace body 10, and the iron oxide raw material 50a having a temperature higher than the temperature of the iron oxide raw material 50b charged into the peripheral part is charged into the central part. That is, the temperature of the iron oxide raw material 50a in the center 11 and its vicinity in the plan view of the shaft furnace body 10 is made higher than the temperature of the iron oxide raw material 50b charged into the periphery of the iron oxide raw material 50a. The method of preheating the iron oxide raw material 50a is as described above. The magnitude of the preheating temperature is not particularly limited, and need only be set such that the effect (reduction in variation in quality of reduced iron) described below is increased. The iron oxide raw material 50a is heated to, for example, 600°C to 800°C.

[0031] As described above, the reducing gas is blown in from a side surface of the shaft furnace body 10. Therefore, when the particle size distribution of the iron oxide raw material in the plan view is uniform, the reducing gas flow rate at the center 11 and its vicinity in the plan view of the shaft furnace body 10 is smaller than the reducing gas flow rate in the vicinity of a wall surface of the shaft furnace body 10. That is, the iron oxide raw material charged into the center 11 and its vicinity in the plan view of the shaft furnace body 10 is less susceptible to heating.

[0032] Therefore, in the present embodiment, the temperature of the iron oxide raw material 50a in the center 11 and its vicinity in the plan view of the shaft furnace body 10 is made higher than the temperature of the iron oxide raw material 50b charged into the periphery of the iron oxide raw material 50a. As a result, the temperature distribution of the iron oxide raw materials 50a and 50b in the shaft furnace can be made uniform. Therefore, it is possible to reduce the variation between the quality of the reduced iron discharged from the center 11 and its vicinity in the plan view of the shaft furnace body 10 and the quality of the reduced iron discharged from the vicinity of the wall surface, and consequently, to improve the quality of the reduced iron.

[0033] The raw material charging method according to the first embodiment and the raw material charging method according to the second embodiment may be combined. That is, the particle size of the iron oxide raw material 50a may be made larger than the particle size of the iron oxide raw material 50b, and then the iron oxide raw material 50a may be preheated. As a result, it is possible to more effectively obtain the abovedescribed effects.

[0034] <3. Third Embodiment> (3-1. Raw Material Charging Device) Next, a configuration of a raw material charging device IC according to a third embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 is a side crosssectional view schematically showing an example of the raw material charging device IC according to the third embodiment. FIG. 5 is a cross-sectional view (plan crosssectional view) taken along line B-B in FIG. 4. In addition, FIG. 5 also shows a diagram in which the other end portion 40b of the peripheral raw-material dispersion pipe 40 is projected onto the B-B cross section. The raw material charging device IC according to the third embodiment further includes a cylindrical member 60 in addition to the configuration of the raw material charging device 1A according to the first embodiment.

[0035] As shown in FIG. 4, the raw material charging device IC is different from the raw material charging device 1A in that the cylindrical member 60 is provided. The cylindrical member 60 is provided inside the shaft furnace body 10, and, as shown in FIG. 5, it is preferable that a position of a central axis in a plan view coincide with the center 11 in the plan view of the shaft furnace body 10. The fact that the position of the central axis in the plan view coincides with the center 11 in the plan view of the shaft furnace body 10 means that the center 11 of the shaft furnace body 10 in the height direction is disposed inside the cylindrical member 60 in the plan view. The cylindrical member 60 has a function of preventing the iron oxide raw material 50b from flowing into the central part due to collapse of a loading state of the iron oxide raw material 50b at the peripheral part. The shape of the cross section perpendicular to the central axis of the cylindrical member 60 is not particularly limited, and may be a circular shape, an elliptical shape, a polygonal shape, or the like. Note that, in order to charge the iron oxide raw materials 50a and 50b symmetrically with respect to the center of the shaft furnace body 10 in a horizontal cross section, the shape of the cross section perpendicular to the central axis of the cylindrical member 60 is preferably a circular shape or a regular polygonal shape. As described above, the shape of the cross section perpendicular to the central axis of the cylindrical member 60 may be various shapes. Therefore, the central axis of the cylindrical member 60 refers to a geometric central axis.

[0036] Further, the other end portion 30b of the central raw-material dispersion pipe 30 is disposed inside the cylindrical member 60 in a side view and a plan view, and the other end portion 40b of each of the plurality of peripheral raw-material dispersion pipes 40 is disposed outside the cylindrical member 60 in the side view and the plan view. Therefore, the iron oxide raw material 50a discharged from the central raw-material dispersion pipe 30 is charged into the inside of the cylindrical member 60, and the iron oxide raw material 50b discharged from the peripheral raw-material dispersion pipe 40 is charged into the outside of the cylindrical member 60. The cylindrical member 60 can suppress the mixing of the iron oxide raw material 50a and the iron oxide raw material 50b. The position of the other end portion 30b of the central raw-material dispersion pipe 30 in the height direction and the position of the other end portion 40b of the peripheral raw-material dispersion pipe 40 in the height direction may be the same position. However, it is preferable that the position of the other end portion 30b of the central raw-material dispersion pipe 30 in the height direction be lower than the position of the other end portion 40b of the peripheral raw-material dispersion pipe 40 in the height direction. In this case, a charging surface 51a of the iron oxide raw material 50a charged into the shaft furnace body 10 from the central raw-material dispersion pipe 30 is lower than a charging surface 51b of the iron oxide raw material 50b charged into the shaft furnace body 10 from the plurality of peripheral raw-material dispersion pipes 40. For example, a position of an apex (a portion directly below the other end portion 30b of the central raw-material dispersion pipe 30) of the charging surface 51a of the iron oxide raw material 50a is lower than a position of an apex (a portion directly below the other end portion 40b of the peripheral raw-material dispersion pipe 40) of the charging surface 51b of the iron oxide raw material 50b. In other words, the height from the charging surface 51a of the iron oxide raw material 50a to a reducing gas inlet 12 can be made lower than the height from the charging surface 51b of the iron oxide raw material 50b to the reducing gas inlet 12. Here, the charging surface 51a of the iron oxide raw material 50a is an upper end surface of a stacked body of the iron oxide raw material 50a formed in the shaft furnace body 10, and the charging surface 51b of the iron oxide raw material 50b is an upper end surface of a stacked body of the iron oxide raw material 50b formed in the shaft furnace body 10. The charging surfaces 51a and 51b can be measured by, for example, sounding, an ultrasonic distance meter, or the like. Both the charging surfaces 51a and 51b are mountain-shaped surfaces. Therefore, a boundary between the charging surface 51a and the charging surface 51b and a boundary between one charging surface 51b and another charging surface 51b are valley-shaped portions between adjacent mountain-shaped surfaces. As a result, each of the charging surfaces 51a and 51b can be distinguished.

[0037] This facilitates a flow of the reducing gas at the center 11 and its vicinity in the plan view of the shaft furnace body 10, thereby making the distribution of the reducing gas flow rate in the shaft furnace uniform. Therefore, it is possible to reduce variation between the quality of reduced iron discharged from the center 11 and its vicinity in the plan view of the shaft furnace body 10 and the quality of reduced iron discharged from the vicinity of the wall surface.

[0038] An appropriate height from the apex of the charging surface 51a of the iron oxide raw material 50a to the reducing gas inlet 12 is preferably about 5% to 20% lower than a height from the apex of the charging surface 51b of the iron oxide raw material 50b to the reducing gas inlet 12, although the height varies depending on the shape of the shaft furnace, the gas amount, and the like. As a result, it is possible to obtain the above-described effects.

[0039] (3-2. Raw Material Charging Method) Next, an example of a raw material charging method using the raw material charging device IC described above will be described. In the present raw material charging method, the position of the other end portion 30b of the central raw-material dispersion pipe 30 in the height direction is made lower than the position of the other end portion 40b of the peripheral raw-material dispersion pipe 40 in the height direction. Further, the other end portion 30b of the central raw-material dispersion pipe 30 is disposed inside the cylindrical member 60 in the side view and the plan view. Further, the other end portion 40b of the peripheral raw-material dispersion pipe 40 is disposed outside the cylindrical member 60 in the side view and the plan view. In this state, the iron oxide raw material 50a is charged into the shaft furnace body 10 from the central raw-material dispersion pipe 30, and the iron oxide raw material 50b is charged into the shaft furnace body 10 from the peripheral raw-material dispersion pipe 40. This makes the charging surface 51a of the iron oxide raw material 50a charged into the shaft furnace body 10 from the central raw-material dispersion pipe 30 lower than the charging surface 51b of the iron oxide raw material 50b charged into the shaft furnace body 10 from the plurality of peripheral raw-material dispersion pipes 40. In other words, in the raw material charging method, the iron oxide raw material is charged into the central part and the peripheral part of the shaft furnace body 10, and the charging surface of the iron oxide raw material 50a charged into the central part is made lower than the charging surface of the iron oxide raw material 50b charged into the peripheral part.

[0040] This facilitates a flow of the reducing gas at the center 11 and its vicinity in the plan view of the shaft furnace body 10, thereby making the distribution of the reducing gas flow rate in the shaft furnace uniform. Therefore, it is possible to reduce variation between the quality of reduced iron discharged from the center 11 and its vicinity in the plan view of the shaft furnace body 10 and the quality of reduced iron discharged from the vicinity of the wall surface.

[0041] The third embodiment and the first or second embodiment may be combined. In this case, it is possible to more effectively obtain the above-described effects. In a case where the third embodiment and the first or second embodiment are combined, the position in the height direction of the charging surface 51a of the iron oxide raw material 50a charged into the shaft furnace body 10 from the central raw-material dispersion pipe 30 may be aligned with the position in the height direction of the charging surface 51b of the iron oxide raw material 50b charged into the shaft furnace body 10 from the plurality of peripheral raw-material dispersion pipes 40. In this case, the cylindrical member 60 makes the raw materials at each charging position less susceptible to mixing, and an improvement in the effect can be expected.

[0042] In the above-described embodiment, four charging hoppers 20b are provided around the charging hopper 20a at equal intervals (90-degree intervals in the plan view), but the disposition of the charging hoppers 20b is not limited to this. Three or more charging hoppers 20b may be disposed. In addition, as long as the end portions 40b of the peripheral raw-material dispersion pipes 40 connected to the charging hoppers 20b are disposed at equal intervals (90-degree intervals) along the circumferential direction, the peripheral raw-material dispersion pipes 40 may be bent or inclined, and the position of the charging hopper 20b connected to the end portion 40a of the peripheral rawmaterial dispersion pipe 40 may be set at any position. The position of the charging hopper 20b and the shape of the peripheral raw-material dispersion pipe 40 can be determined experimentally. Regarding the disposition of the charging hopper 20a, similarly to the disposition of the charging hopper 20b, as long as the end portion 30b of the central raw-material dispersion pipe 30 is disposed at a position including the center 11 in the plan view within the internal space of the shaft furnace body 10, the central raw-material dispersion pipe 30 may be bent or inclined, and the position of the charging hopper 20a connected to the end portion 30a of the central raw-material dispersion pipe 30 may be set at any position. Examples

[0043] <1. Comparative Example> In the raw material charging device 1A according to the first embodiment, a shaft furnace having a diameter of about 7 m was assumed in which the iron oxide raw material 50b was charged into the shaft furnace body 10 only from the peripheral rawmaterial dispersion pipe 40. Hydrogen was used as a reducing gas, and a blowing temperature was set to 950°C. A furnace top pressure was set to about 50 KPa, and an average particle size of the iron oxide raw material 50b was set to 13 mm. As a result of performing numerical analysis using a numerical two-dimensional model, the metallization rate of reduced iron was 94.7%.

[0044] <2. Example 1> In the raw material charging device 1A according to the first embodiment, the iron oxide raw materials 50a and 50b were charged into the shaft furnace body 10 from the central raw-material dispersion pipe 30 and the peripheral raw-material dispersion pipe 40. An average particle size of the iron oxide raw material 50a was set to less than 16 mm. Other conditions were the same as those in Comparative Example 1. Asa result of performing two-dimensional model analysis, the metallization rate of reduced iron was 97.1%, and the metallization rate was improved as compared with Comparative Example 1. This is considered to be because the quality of the reduced iron discharged from the center 11 and its vicinity in the plan view of the shaft furnace body 10 was improved, and the variation in the quality of the reduced iron was reduced.

[0045] <3. Example 2> In the raw material charging device IB according to the second embodiment, the iron oxide raw materials 50a and 50b were charged into the shaft furnace body 10 from the central raw-material dispersion pipe 30 and the peripheral raw-material dispersion pipe 40. A preheating temperature of the iron oxide raw material 50a was set to 800°C. The iron oxide raw material 50b was set to room temperature. Other conditions were the same as those in Example 1. Asa result of performing two-dimensional model analysis, the metallization rate of reduced iron was 97.7%, and the metallization rate was improved as compared with Example 1. This is considered to be because the quality of the reduced iron discharged from the center 11 and its vicinity in the plan view of the 25 shaft furnace body 10 was improved, and the variation in the quality of the reduced iron was reduced.

[0046] The preferred embodiment of the present invention has been described in detail above; however, the present invention is not limited to the embodiment. It is clear that any person with ordinary skill in the art to which the present invention belongs is able to conceive various modifications or alterations within the scope of the technical idea described in the claims, and these are also understood to naturally fall within the technical scope of the present invention. REFERENCE SIGNS LIST

[0047] 1A, IB, IC Raw material charging device 10 Shaft furnace body 20a, 20b Charging hopper 30 Central raw-material dispersion pipe 40 Peripheral raw-material dispersion pipe 50a, 50b Iron oxide raw material 51a, 51b Charging surface 60 Cylindrical member

Claims

1. A raw material charging device that charges an iron oxide raw material into a shaft furnace body, the raw material charging device comprising:a plurality of charging hoppers configured to store an iron oxide raw material to be charged into the shaft furnace body;a central raw-material dispersion pipe having one end portion connected to at least one charging hopper among the plurality of charging hoppers and the other end portion disposed at a position including a center in a plan view within an internal space of the shaft furnace body; anda plurality of peripheral raw-material dispersion pipes each having one end portion connected to another charging hopper among the plurality of charging hoppers and the other end portion disposed at a periphery of the other end portion of the central raw-material dispersion pipe.

2. The raw material charging device according to Claim 1, further comprising:a cylindrical member provided inside the shaft furnace body,wherein the other end portion of the central raw-material dispersion pipe is disposed inside the cylindrical member in the plan view, andthe other end portion of each of the plurality of peripheral raw-material dispersion pipes is disposed outside the cylindrical member in the plan view.

3. A raw material charging method comprising:charging an iron oxide raw material into a central part and a peripheral part of a shaft furnace body; andmaking a charging surface of the iron oxide raw material charged into the central part lower than a charging surface of the iron oxide raw material charged into theperipheral part.

4. The raw material charging method according to Claim 3,wherein the iron oxide raw material is charged into an inside and an outside of a cylindrical member provided inside the shaft furnace body, a charging surface of the iron oxide raw material inside the cylindrical member is used as the charging surface of the5 iron oxide raw material charged into the central part, and a charging surface of the iron oxide raw material outside the cylindrical member is used as the charging surface of the iron oxide raw material charged into the peripheral part.

5. The raw material charging method according to Claim 3 or 4,wherein an iron oxide raw material having a particle size larger than a particle10 size of the iron oxide raw material charged into the peripheral part is charged into the central part.

6. The raw material charging method according to Claim 3 or 4,wherein an iron oxide raw material having a temperature higher than atemperature of the iron oxide raw material charged into the peripheral part is charged into 15 the central part.

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