Method of charging raw materials into a bell-less blast furnace

Abstract

This invention provides a method for charging raw materials into a bellless blast furnace that can achieve an appropriate gas flow distribution. [Solution] The raw material charging method comprises a storage step, a discharge step, and a charging step. The storage step involves transporting the raw material (M) toward the top bunker (2) and storing the raw material (M) in the top bunker (2). The discharge step involves discharging the raw material (M) stored in the top bunker (2) through a flow rate adjustment gate (4). The charging step involves charging the raw material (M) discharged from the top bunker (2) into the blast furnace (1) via a swirling chute (3). In this raw material charging method, during the storage step, a particle size analyzer (9) installed on the belt conveyor (6) that transports the raw material (M) is used to measure the particle size of the raw material (M) during transport. Then, during the discharge step, the opening of the flow rate adjustment gate (4) is adjusted based on the particle size of the raw material (M) measured by the particle size analyzer (9).

Description

Technical Field

[0001] This disclosure relates to a method for charging raw materials into a bell-less blast furnace.

Background Art

[0002] In the steel industry, a blast furnace is a core device for producing pig iron. In a blast furnace, the raw materials for producing pig iron are mainly ore as an iron source and coke as a reducing agent. During the operation of the blast furnace, these raw materials are charged into the blast furnace from the top of the blast furnace. Specifically, ore and coke are alternately charged into the blast furnace, and as a result, ore layers composed of ore and coke layers composed of coke are alternately formed in the blast furnace.

[0003] In the case of a bell-less blast furnace, a revolving chute is used to charge raw materials. The revolving chute is also referred to as a distributing chute. The revolving chute is provided so as to be rotatable around the central axis of the blast furnace extending in the vertical direction and is provided so as to be tiltable with respect to the central axis of the blast furnace. The blast furnace includes a top bunker, and the revolving chute is disposed below the top bunker. The raw materials are conveyed toward the top of the furnace by a belt conveyor and dropped into the top bunker. Thereby, the raw materials are once stored in the top bunker. The raw materials stored in the top bunker are discharged from the lower end of the top bunker. The raw materials discharged from the top bunker fall into the blast furnace through the revolving chute that revolves in an inclined state and accumulate in the blast furnace.

[0004] When charging raw materials by the revolving chute, each time the revolving chute rotates once or multiple times, the tilt angle of the revolving chute is changed. The raw materials discharged from the top bunker are distributed in the circumferential direction in the blast furnace by the rotation of the revolving chute and are distributed in the radial direction in the blast furnace by the change in the tilt angle of the revolving chute. That is, the revolving chute designates the falling position of the raw materials, that is, the deposition position, and the raw materials are distributed in the circumferential and radial directions in the blast furnace and deposited in layers. Thus, in the charging of raw materials into a bell-less blast furnace, by using a revolving chute, the deposition shape of each raw material layer (ore layer, coke layer) in the blast furnace can be controlled.

[0005] In blast furnaces, it is crucial to achieve an appropriate gas flow distribution within the furnace for stable operation. The main factor influencing the gas flow within the blast furnace is the deposition shape of the raw material layer, that is, the particle size distribution of the raw material. In the case of bellless blast furnaces, the deposition shape of the raw material layer depends on the inclination angle and rotation speed of the swirling chute, as well as the particle size of the raw material and its charging speed. In particular, the deposition shape of the raw material layer changes depending on the particle size of the raw material. For example, raw material with small particle sizes tends to remain at the point of impact upon falling within the blast furnace. On the other hand, raw material with large particle sizes tends to move from the point of impact and due to the angle of repose. Therefore, it is important to design an appropriate deposition shape of the raw material layer according to the particle size of the raw material.

[0006] Generally, simulations using mathematical models that simulate a blast furnace are used to design the appropriate deposition shape of the raw material layer. In this mathematical model, input conditions such as the particle size of the raw material, the raw material charging rate, the inclination angle of the swivel chute, and the swivel chute's swivel speed are input to the mathematical model, and the deposition shape of the raw material layer is calculated. Based on the deposition shape of the raw material layer calculated under various input conditions, the gas flow distribution inside the blast furnace can be calculated and evaluated. In the operation of a bellless blast furnace, the operation of the swivel chute is set based on the mathematical model so that an appropriate gas flow distribution is generated inside the blast furnace.

[0007] As mentioned above, the deposition shape of the raw material layer changes depending on the particle size of the raw material. Therefore, it is necessary to adjust the settings such as the operation of the swirling chute according to the particle size of the raw material.

[0008] Japanese Patent Publication No. 2020-94283 (Patent Document 1) discloses an operating method for a bellless blast furnace. In the operating method of Patent Document 1, the particle size of the raw material charged into the blast furnace is measured using an online particle size analyzer, and the measured particle size and the bellless pattern at that time (inclination angle and rotation speed of the swirling chute) are automatically incorporated into a mathematical model. The mathematical model then predicts the deposition shape of the raw material layer and the gas flow distribution inside the blast furnace, and if the gas flow distribution fluctuates due to changes in the particle size of the raw material, the inclination angle and rotation speed of the swirling chute are adjusted to suppress such fluctuations. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2020-094283 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, regarding the charging of raw materials into a bellless blast furnace, even if the inclination angle and rotation speed of the swirling chute are adjusted according to the particle size of the raw materials measured by an online particle size analyzer, as in the operating method described in Patent Document 1, the deposition shape of the raw material layer may not be the same as the appropriate shape calculated by the mathematical model. In this case, the gas flow distribution inside the blast furnace fluctuates. As a result, the coke ratio (CR) and reducing agent ratio (PAR) may increase, potentially leading to an increase in the amount of coke and reducing agent used.

[0011] The object of this disclosure is to provide a method for charging raw materials into a bellless blast furnace that can achieve an appropriate gas flow distribution. [Means for solving the problem]

[0012] The raw material charging method for a bellless blast furnace according to this disclosure comprises a storage step, a discharge step, and a charging step. The storage step involves transporting the raw material toward the top bunker and storing the raw material in the top bunker. The discharge step involves discharging the raw material stored in the top bunker through a flow control gate. The charging step involves charging the raw material discharged from the top bunker into the blast furnace via a swirling chute. In this raw material charging method, in the storage step, a particle size analyzer installed on the belt conveyor that transports the raw material is used to measure the particle size of the raw material during transport. Then, in the discharge step, the opening of the flow control gate is adjusted based on the particle size of the raw material measured by the particle size analyzer. [Effects of the Invention]

[0013] According to the raw material charging method for a bellless blast furnace described herein, an appropriate gas flow distribution can be achieved in the blast furnace. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 shows the relationship between the particle size of the raw material and the opening degree of the flow control gate (FCG). [Figure 2] Figure 2 is a schematic diagram showing an example of a bellless blast furnace and its surrounding equipment to which the raw material charging method according to this embodiment is applied. [Figure 3] Figure 3 shows the relationship between the rotation error and the amount of heat removed from the furnace body. [Figure 4] Figure 4 shows the relationship between the rotation error and the belly section KR. [Modes for carrying out the invention]

[0015] To solve the above problems, the inventors diligently investigated the reasons why the depositional shape of the raw material layer may not be the same as the appropriate shape calculated by the mathematical model. As a result, they obtained the following findings.

[0016] In the operating method described in Patent Document 1, the setting conditions adjusted according to the particle size of the raw material are the inclination angle and rotation speed of the swirling chute. Both the inclination angle and rotation speed of the swirling chute are elements that are involved in the operation of the swirling chute. On the other hand, the deposition shape of the raw material layer depends not only on the inclination angle and rotation speed of the swirling chute, but also on the raw material charging speed. However, the operating method described in Patent Document 1 does not focus on the raw material charging speed and does not adjust the raw material charging speed according to the particle size of the raw material. Therefore, it is presumed that one of the reasons why the deposition shape of the raw material layer does not match the appropriate shape calculated by the mathematical model is that the particle size of the raw material affects the raw material charging speed, and the raw material charging speed differs between the calculation and the actual situation.

[0017] In this specification, the charging rate of the raw material means the mass flow rate (or volume flow rate) of the raw material discharged from the top bunker to the swivel chute. The top bunker has a flow control gate in the discharge passage near the discharge port, and the adjustment of the charging rate of the raw material can be carried out by adjusting the opening degree of the flow control gate. In this specification, the flow control gate may be referred to as "FCG".

[0018] Based on the above speculation, the inventors conducted a raw material charging test to investigate the relationship between the particle size of the raw material and the charging rate of the raw material. Specifically, the raw material was stored in the top bunker, and the raw material charging operation of discharging the raw material to the swivel chute was carried out in multiple charges. In each raw material charging operation, the setting conditions such as the operation of the swivel chute were calculated by a mathematical model. Coke was used as the raw material, and the particle size of the raw material was measured by an online particle size analyzer before the raw material was stored in the top bunker. The charging amount of the raw material stored and discharged from the top bunker was set to 21 ± 0.2 (ton) per charge. That is, the charging amount of the raw material was kept constant.

[0019] The investigation results are shown in FIG. 1. FIG. 1 is a diagram showing the relationship between the particle size of the raw material and the opening degree of the flow control gate (FCG). In FIG. 1, the horizontal axis represents the particle size (mm) of the raw material, and the vertical axis represents the opening degree (°) of the FCG. The particle size of the raw material is the average particle size of the raw material measured by a particle size analyzer. This average particle size is calculated by Equation (1). Average particle size = Σ (average value of particle size in each particle size range × weight ratio of each range) / 100 (1)

[0020] The opening degree of the FCG corresponds to the charging rate of the raw material. That is, as the opening degree of the FCG increases, the discharge passage of the top bunker widens, and the charging rate of the raw material increases.

[0021] In Fig. 1, for the charges among the multiple charges for which the test was conducted, the results are shown for the charges where the error between the actual number of revolutions (hereinafter also referred to as "actual revolution number") and the set number of revolutions of the swivel chute set by the mathematical model (hereinafter also referred to as "set revolution number") is within the range of ±0.1 revolution. The set revolution number is expressed as "raw material charging amount / (raw material charging speed × swivel speed of the swivel chute)". The swivel speed of the swivel chute is the time per revolution. The actual revolution number can be calculated from the start time and end time of the discharge of the raw material discharged from the top bunker, and specifically, the actual revolution number is calculated as "raw material discharge time / swivel speed of the swivel chute".

[0022] The set revolution number is usually set as an integer. This is to make the circumferential distribution of the raw material uniform even at the last revolution of the swivel chute. Then, in actual raw material charging, if there is an error between the set revolution number and the actual revolution number, the circumferential distribution of the raw material by the last revolution of the swivel chute is non-uniform. However, if the error of the actual revolution number with respect to the set revolution number is within the range of ±0.1 revolution, the circumferential distribution of the raw material is substantially uniform. Therefore, in order to evaluate the case where the circumferential distribution of the raw material is substantially uniform, in Fig. 1, the results are shown for the charges where the error of the actual revolution number with respect to the set revolution number is within the range of ±0.1 revolution.

[0023] As shown in Figure 1, the FCG opening is positively correlated with the particle size of the raw material. That is, as the particle size of the raw material increases, the FCG opening increases. As mentioned above, the FCG opening corresponds to the raw material charging rate, and consequently, the raw material charging rate depends on the particle size of the raw material. In short, when the amount of raw material charged is kept constant between charges and the circumferential distribution of the raw material is made uniform, in reality, the particle size of the raw material affects the FCG opening, and consequently, the raw material charging rate. Therefore, when charging raw materials into a blast furnace, it is necessary to adjust the raw material charging rate according to the particle size of the raw material, and to do so, it is necessary to adjust the FCG opening. By adjusting the FCG opening according to the particle size of the raw material, the deposition shape of the raw material layer approaches the appropriate shape calculated by the mathematical model. Moreover, by adjusting the FCG opening so that the actual number of turns is the same as the set number of turns, the deposition shape of the raw material becomes an even more appropriate shape.

[0024] The coke dry fire extinguishing system according to the embodiment of this disclosure was completed based on the above findings.

[0025] A raw material charging method for a bellless blast furnace according to the embodiment of this disclosure comprises a storage step, a discharge step, and a charging step. The storage step involves transporting the raw material toward the top bunker and storing the raw material in the top bunker. The discharge step involves discharging the raw material stored in the top bunker through a flow control gate. The charging step involves charging the raw material discharged from the top bunker into the blast furnace via a swirling chute. In this raw material charging method, in the storage step, a particle size analyzer installed on the belt conveyor that transports the raw material is used to measure the particle size of the raw material during transport. Then, in the discharge step, the opening of the flow control gate is adjusted based on the particle size of the raw material measured by the particle size analyzer (first configuration).

[0026] In the first configuration of the bellless blast furnace raw material charging method, the raw material is deposited in layers within the blast furnace by sequentially going through a storage process, a discharge process, and a charging process. Specifically, the raw material is measured for particle size by a particle size analyzer on a belt conveyor and then stored in a top bunker. The raw material in the top bunker is discharged into a swirling chute through a flow control gate (FCG). The discharged raw material is then charged into the blast furnace via the swirling chute. At this time, in the discharge process in which the raw material in the top bunker is discharged into the swirling chute, the opening of the flow control gate (FCG) is adjusted based on the particle size of the raw material measured by the particle size analyzer. That is, the opening of the FCG is adjusted according to the particle size of the raw material, and as a result, the charging speed of the raw material is adjusted. This causes the deposition shape of the raw material layers in the blast furnace to approach an appropriate shape calculated by a mathematical model. Therefore, according to the first configuration of the raw material charging method, an appropriate gas flow distribution can be achieved in the blast furnace.

[0027] In the above raw material charging method, preferably, the opening of the flow rate adjustment gate is adjusted in the discharge step so that the charging of raw materials into the blast furnace is completed when the swirling chute has rotated an integer number of times in the charging step (second configuration).

[0028] In the second configuration of the bellless blast furnace raw material charging method, the actual number of rotations becomes the same as the set number of rotations by adjusting the opening of the FCG. As a result, the distribution of raw materials in the circumferential direction becomes uniform even during the final rotation of the rotating chute. Therefore, the deposition shape of the raw materials becomes more appropriate. Consequently, the raw material charging method of the second configuration makes it possible to achieve a more appropriate gas flow distribution in the blast furnace.

[0029] In the above raw material charging method, preferably, the particle size of the raw material measured by a particle size analyzer is the average particle size represented by formula (1) (third configuration). Average particle size = Σ(average particle size of each particle size category × weight percentage of each category) / 100 (1)

[0030] The following describes the method of charging raw materials into a bellless blast furnace according to the embodiments of this disclosure, with reference to the drawings. In each drawing, the same or equivalent components are denoted by the same reference numerals, and redundant explanations are avoided. In this specification, a bellless blast furnace is also simply referred to as a blast furnace.

[0031] [Configuration of the Berles blast furnace] Figure 2 is a schematic diagram showing an example of a bellless blast furnace and its surrounding equipment to which the raw material charging method according to this embodiment is applied. Referring to Figure 2, the bellless blast furnace 1 comprises two top bunkers 2 and a swivel chute 3. In the example shown in Figure 2, the two top bunkers 2 are arranged in parallel above the blast furnace 1. The swivel chute 3 is provided at the top of the blast furnace 1. The swivel chute 3 is located below the two top bunkers 2. The swivel chute 3 is rotatable around the central axis 1a of the blast furnace 1 which extends vertically (see arrow in Figure 2). The swivel chute 3 is further rotatable with respect to the central axis 1a of the blast furnace 1.

[0032] Each furnace top bunker 2 has a discharge port 2a at its lower end. Each furnace top bunker 2 is further equipped with a flow control gate (FCG) 4 in the discharge passage near the discharge port 2a. The flow control gate 4 is configured to allow adjustment of its opening. When the opening is increased, the discharge passage expands, and when the opening is decreased, the discharge passage contracts.

[0033] Raw materials M for producing pig iron in the blast furnace 1 are dropped into the furnace top bunker 2. Specifically, the raw materials M are stored in multiple surge hoppers 5. The raw materials M stored in the multiple surge hoppers 5 differ in type and particle size from one another. For example, ore is stored in one surge hopper 5, and coke is stored in another surge hopper 5. A belt conveyor 6 is provided between the surge hoppers 5 and the furnace top bunker 2. A predetermined amount of raw materials M is dispensed from the surge hoppers 5 onto the belt conveyor 6. The dispensed raw materials M are then transported above the furnace top bunker 2 by the belt conveyor 6. The raw materials M transported above the furnace top bunker 2 are then dispensed into one of the two furnace top bunkers 2 via a sorting chute 7. As a result, the raw materials M are temporarily stored in the furnace top bunker 2.

[0034] The raw material M stored in the top bunker 2 is released from the outlet 2a of the top bunker 2. The raw material M released from the top bunker 2 falls through the blast furnace 1 via the swirling chute 3 and accumulates inside the blast furnace 1. At this time, the raw material M released from the top bunker 2 is guided to the swirling chute 3 via a discharge hopper 8 shared by the two top bunkers 2. However, the discharge hopper 8 does not have to be installed. Because the swirling chute 3 rotates at an inclination, the raw material M is distributed in the circumferential direction within the blast furnace 1. Furthermore, the inclination angle of the swirling chute 3 changes each time it rotates once or multiple times. As a result, the raw material M is distributed in the radial direction within the blast furnace 1. In other words, the swirling chute 3 plays a role in specifying the drop position, i.e., the volume position, of the raw material M. As a result, the raw material M accumulates in layers within the blast furnace 1. This forms a raw material layer (not shown) composed of raw material M inside the blast furnace 1.

[0035] During the operation of blast furnace 1, this process of charging raw materials M is repeated. At that time, ore and coke are charged alternately as raw materials M. As a result, within blast furnace 1, ore and coke are deposited alternately in layers, and layers of ore composed of ore and layers of coke composed of coke are formed alternately.

[0036] In this embodiment, the blast furnace 1 is equipped with an online particle size analyzer 9. The particle size analyzer 9 is installed on a belt conveyor 6 that transports the raw material M. The particle size analyzer 9 measures the particle size of the raw material M as it is being transported by the belt conveyor 6. The raw material M whose particle size has been measured by the particle size analyzer 9 is dropped into the furnace top bunker 2 for storage. As the particle size analyzer 9, a well-known particle size analyzer used for online particle size measurement can be used. The particle size analyzer 9 is, for example, an optical particle size analyzer including a camera. In this case, the particle size analyzer 9 images the raw material M on the belt conveyor 6 and calculates the particle size distribution by image analysis. The average particle size is determined from the calculated particle size distribution using the above formula (1). The obtained average particle size can be used as the particle size of the raw material M.

[0037] The blast furnace 1 is equipped with a blast furnace control device (not shown) that controls the entire operation. The particle size analyzer 9 is connected to the blast furnace control device. An actuator that adjusts the opening of the flow rate adjustment gate 4, a motor that rotates the swivel chute 3, and a motor that tilts the swivel chute 3 are also connected to the blast furnace control device. The blast furnace control device acquires particle size data of the raw material M measured by the particle size analyzer 9 and, based on this particle size data, operates the actuator of the flow rate adjustment gate 4 when necessary. This adjusts the opening of the flow rate adjustment gate 4.

[0038] [Method for charging raw materials into a bellless blast furnace] Referring to Figure 2, the raw material charging method for the bellless blast furnace 1 according to this embodiment will be described. The raw material charging method for the bellless blast furnace 1 according to this embodiment comprises a storage step, a discharge step, and a charging step.

[0039] The storage process involves transporting the raw material M towards the furnace top bunker 2 and storing the raw material M in the furnace top bunker 2. In the storage process, the raw material M is transported by a belt conveyor 6. The raw material M is either ore or coke. In the storage process, the particle size of the raw material M being transported by the belt conveyor 6 is measured. A particle size analyzer 9 installed on the belt conveyor 6 that transports the raw material M is used to measure the particle size of the raw material M.

[0040] The discharge process involves releasing the raw material M stored in the top bunker 2 through the flow control gate (FCG) 4. During the discharge process, the raw material M is released from the discharge port 2a of the top bunker 2 and guided to the swirling chute 3. The charging process involves charging the raw material M released from the top bunker 2 into the blast furnace 1 via the swirling chute 3. This forms a raw material layer composed of the raw material M inside the blast furnace 1.

[0041] In this embodiment of the raw material charging method, which includes a storage process, a discharge process, and a charging process, the blast furnace control device sets conditions such as the operation of the swirling chute 3. Specifically, the blast furnace control device calculates and sets the inclination angle and rotation speed of the swirling chute 3 using a mathematical model based on the particle size of the raw material M measured by the particle size analyzer 9. As a result, during the charging process, the swirling chute 3 operates under the set conditions.

[0042] Furthermore, the blast furnace control system pre-sets the opening degree of the flow control gate 4 using a mathematical model. Then, the blast furnace control system calculates and readjusts the opening degree of the flow control gate 4 based on the particle size of the raw material M measured by the particle size analyzer 9. As a result, the opening degree of the flow control gate 4 is adjusted according to the particle size of the raw material M, and in the discharge process, the raw material M in the top bunker 2 is discharged through the adjusted flow control gate 4. The adjusted opening degree of the flow control gate 4 satisfies the relationship with the particle size of the raw material M as shown in Figure 1, for example. Here, if the opening degree of the flow control gate 4 corresponding to the particle size of the raw material M is reflected in the mathematical model in advance, then the adjusted opening degree of the flow control gate 4 is reflected in the mathematical model, and therefore, readjusting the opening degree of the flow control gate 4 becomes unnecessary.

[0043] Furthermore, in the discharge process, the opening of the flow rate adjustment gate 4 may be adjusted so that the charging of raw materials M into the blast furnace 1 is completed when the swivel chute 3 has rotated an integer number of times during the charging process.

[0044] [effect] In the raw material charging method for the bellless blast furnace 1 according to this embodiment, the raw material M is deposited in layers within the blast furnace 1 by sequentially going through a storage process, a discharge process, and a charging process. Specifically, the raw material M is measured for particle size by a particle size gauge 9 on a belt conveyor 6 and then stored in the top bunker 2. The raw material M in the top bunker 2 is discharged to the swirl chute 3 through a flow rate adjustment gate 4. The discharged raw material M is then charged into the blast furnace 1 via the swirl chute 3. At that time, in the discharge process in which the raw material M in the top bunker 2 is discharged to the swirl chute 3, the opening of the flow rate adjustment gate 4 is adjusted based on the particle size of the raw material M measured by the particle size gauge 9. That is, the opening of the flow rate adjustment gate 4 is adjusted according to the particle size of the raw material M, and as a result, the charging speed of the raw material M is adjusted. This causes the deposition shape of the raw material layers in the blast furnace 1 to approach an appropriate shape calculated by a mathematical model. Therefore, according to the raw material charging method of this embodiment, an appropriate gas flow distribution can be achieved in the bellless blast furnace 1. As a result, the coke ratio (CR) and reducing agent ratio (PAR) become stable, and the amount of coke and reducing agent used can be reduced.

[0045] Furthermore, in the raw material charging method of this embodiment, the opening of the flow rate adjustment gate 4 is adjusted in the discharge process so that the charging of raw material M into the blast furnace 1 is completed when the swirling chute 3 has rotated an integer number of times during the charging process. In this case, by adjusting the opening of the flow rate adjustment gate 4, the actual number of rotations of the swirling chute 3 becomes the same as the set number of rotations. As a result, even during the final rotation of the swirling chute 3, the distribution of raw material M in the circumferential direction becomes uniform. Therefore, the accumulation shape of raw material M becomes more appropriate. Consequently, a more appropriate gas flow distribution can be achieved in the bellless blast furnace 1. [Examples]

[0046] The present disclosure will be further described below with reference to examples. However, the present disclosure is not limited to the following examples.

[0047] Using the bellless blast furnace and its surrounding equipment shown in Figure 2, a test was conducted to produce pig iron by alternately charging ore and coke. During the test, when transporting coke to the top bunker, the particle size of the coke was measured using a particle size analyzer. In the inventive example, the opening of the FCG was adjusted according to the particle size of the coke, and the FCG opening calculated by the mathematical model was reset based on the particle size of the coke. In the comparative example, no adjustment of the FCG opening was made, and the FCG opening calculated by the mathematical model was maintained. Furthermore, in the inventive example, the FCG opening was adjusted so that the actual number of rotations of the swivel chute was the same as the set number of rotations.

[0048] Each time ore and coke were charged, the rotation error (in rotations), furnace heat removal amount (in kW), and burrito KR (in 1 / m) were investigated. The rotation error is the absolute value of the error between the actual rotation count and the set rotation count of the rotating chute. The furnace heat removal amount is the amount of heat removed from the furnace wall of the blast furnace and is calculated from the temperature difference between the inlet and outlet of the cooling water in the blast furnace staves. The burrito KR is the permeability index of the blast furnace burrito and is calculated from the value of the static pressure gauge installed on the furnace wall of the blast furnace.

[0049] Both the furnace body heat removal amount and the Berry section KR are indicators for evaluating the gas flow distribution within the blast furnace. If an appropriate gas flow distribution occurs within the blast furnace, the furnace body heat removal amount will be small and the Berry section KR will be small. Figures 3 and 4 show the results of the investigation.

[0050] Figure 3 shows the relationship between the rotation error and the amount of heat removed from the furnace body. Figure 4 shows the relationship between the rotation error and the belly section KR. In each figure, white circles indicate the inventive example, and black circles indicate the comparative example.

[0051] As shown in Figure 3, the amount of heat removed from the furnace decreases as the rotation error decreases. In particular, the amount of heat removed from the furnace in the inventive example is smaller than that of the comparative example. In the comparative example, the deposition shape of the raw material layer deviates from the appropriate shape, and as a result, the heat of the gas rising inside the blast furnace is not effectively utilized inside the blast furnace, causing the temperature of the furnace wall to rise. On the other hand, in the inventive example, the deposition shape of the raw material layer approaches the appropriate shape, and as a result, an appropriate gas flow distribution is created, and the temperature rise of the furnace wall is suppressed. Also, as shown in the results in Figure 3, when the rotation error increases by 0.1 times, the amount of heat removed from the furnace increases by about 4815.4 kW. This translates to an increase of 2.9 kg / t in the reducing agent ratio. In the inventive example, since the amount of heat removed from the furnace is smaller compared to the comparative example, the amount of reducing agent used can be reduced.

[0052] As shown in Figure 4, the belly section KR decreases as the rotation error decreases. In particular, the belly section KR of the inventive example is smaller than that of the comparative example. The belly section KR is an index of the airflow resistance derived from the deposition shape of the raw material layer, excluding the effect of airflow. In the case of the comparative example, the deposition shape of the raw material layer deviated from the appropriate shape, resulting in high airflow resistance. On the other hand, in the case of the inventive example, the deposition shape of the raw material layer approached the appropriate shape, resulting in an appropriate gas flow distribution and suppressed airflow resistance.

[0053] Although embodiments relating to this disclosure have been described above, this disclosure is not limited to the above embodiments, and various modifications are possible without departing from its spirit. For example, the raw material M for which the opening of the flow rate adjustment gate 4 needs to be adjusted may be both ore and coke, or either one of them. [Explanation of symbols]

[0054] 1: Blast furnace (Berless blast furnace) 2: Hearthtop Bunker 3: Swinging Shot 4: Flow control gate (FCG) 6: Belt conveyor 9: Particle size meter M: Raw material

Claims

1. A storage process involves transporting raw materials toward the furnace top bunker and storing the raw materials in the furnace top bunker. A discharge step in which the raw material stored in the furnace top bunker is released through a flow rate adjustment gate, The process includes a charging step of charging the raw material discharged from the furnace top bunker into the blast furnace via a swirling chute, In the storage process, a particle size analyzer installed on the belt conveyor that transports the raw material is used to measure the particle size of the raw material while it is being transported. In the discharge step, the opening of the flow rate adjustment gate is adjusted based on the particle size of the raw material measured by the particle size meter. Method of charging raw materials into a bell-less blast furnace.

2. A method for charging raw materials into a bellless blast furnace according to claim 1, A method for charging raw materials into a bellless blast furnace, comprising adjusting the opening of the flow rate adjustment gate in the discharge step so that the charging of raw materials into the blast furnace is completed when the swirling chute has rotated an integer number of times in the charging step.

3. A method for charging raw materials into a bellless blast furnace according to claim 1 or 2, A method for charging raw materials into a bellless blast furnace, wherein the particle size of the raw material measured by the particle size analyzer is the average particle size represented by formula (1). Average particle size = Σ (average particle size of each particle size category × weight percentage of each category) / 100 (1)

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