Blast furnace operation methods

Abstract

A novel technology is disclosed that makes it possible to change the concentration distribution of reducing components inside a blast furnace during its operation. The method of operating a blast furnace according to this disclosure includes supplying hot air into the blast furnace through a hot air flow path provided in a hot air tuyere, and supplying reducing gas into the blast furnace through a reducing gas outlet provided in the hot air tuyere. Here, the hot air tuyere is provided with a plurality of reducing gas outlets. The method of operating a blast furnace according to this disclosure includes changing the flow rate of the reducing gas blown out from at least one of the reducing gas outlets.

Description

[Technical Field]

[0001] This application discloses a method for operating a blast furnace. [Background technology]

[0002] Reducing CO2 emissions in the steelmaking process is being considered. For example, when producing pig iron in a blast furnace, it is possible to use reducing gases such as hydrogen gas instead of some of the reducing agent such as coke. Patent Document 1 discloses a method of supplying reducing gas to a blast furnace in which a lance for injecting reducing gas is placed inside or inside the wall of the hot air passage of the hot air tuyer, and the reducing gas is injected through the lance. Although not intended for injecting reducing gas, Patent Document 2 discloses a method in which a fuel injection lance is inserted inside the wall of the hot air tuyer, and pulverized coal is injected into the blast furnace as fuel through the fuel injection lance. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 4997734 [Patent Document 2] Patent No. 5840202 [Overview of the project] [Problems that the invention aims to solve]

[0004] This invention discloses a novel technology that makes it possible to change the concentration distribution of reducing components inside a blast furnace during its operation. [Means for solving the problem]

[0005] This application discloses several embodiments as means for solving the above-mentioned problems. <Aspect 1> A method for operating a blast furnace, Hot air is supplied to the inside of the blast furnace through a hot air passage provided in the hot air tuyeres, and reducing gas is supplied to the inside of the blast furnace through a reducing gas outlet provided in the hot air tuyeres. Includes, The hot air nozzle is provided with multiple reducing gas outlets. The method of operating the blast furnace includes changing the flow rate of the reducing gas blown out from at least one of the reducing gas outlets. The operation method of a blast furnace. <Aspect 2> A method for operating a blast furnace according to Embodiment 1, The flow rate of the reducing gas blown out from at least one of the reducing gas outlets is changed according to the concentration distribution of the reducing component in the radial or circumferential direction inside the blast furnace. A method of operating a blast furnace, including [specific details omitted]. <Aspect 3> A method for operating a blast furnace according to embodiment 1 or 2, Reducing gas is supplied into the blast furnace through a plurality of reducing gas injection ports provided in the hot air tuyeres. A method of operating a blast furnace, including [specific details omitted]. <Aspect 4> A method for operating a blast furnace according to embodiment 1 or 2, Reducing gas is supplied into the blast furnace through a plurality of reducing gas injection lances provided in the hot air tuyeres. A method of operating a blast furnace, including [specific details omitted]. <Aspect 5> A method for operating a blast furnace according to embodiment 1 or 2, Reducing gas is supplied into the blast furnace through at least one reducing gas injection port and at least one reducing gas injection lance provided in the hot air tuyer. A method of operating a blast furnace, including [specific details omitted]. [Effects of the Invention]

[0006] According to the technology of this disclosure, it is possible to change the concentration distribution of reducing components inside a blast furnace during its operation. [Brief explanation of the drawing]

[0007] [Figure 1] An example of the structure of a blast furnace is schematically shown. Some of the structures provided in the blast furnace are shown in an omitted manner. [Figure 2] An example of the structure of one of the plurality of reducing gas outlets provided in the hot blast tuyere is schematically shown. [Figure 3] An example of the structure of one of the plurality of reducing gas outlets provided in the hot blast tuyere is schematically shown. [Figure 4] An example of the structure of one of the plurality of reducing gas outlets provided in the hot blast tuyere is schematically shown. [Figure 5] An example of the structure of one of the plurality of reducing gas outlets provided in the hot blast tuyere is schematically shown. [Figure 6] An example of the structure of one of the plurality of reducing gas outlets provided in the hot blast tuyere is schematically shown. [Figure 7] An example of the structure of one of the plurality of reducing gas outlets provided in the hot blast tuyere is schematically shown. [Figure 8A] An example of the structure of a plurality of reducing gas outlets in the hot blast tuyere is schematically shown. [Figure 8B] An example of the structure of a plurality of reducing gas outlets in the hot blast tuyere is schematically shown. [Figure 8C] An example of the structure of a plurality of reducing gas outlets in the hot blast tuyere is schematically shown. [Figure 9A] An example of the flow when changing the concentration distribution of reducing components inside the blast furnace is shown. [Figure 9B] An example of the flow when changing the concentration distribution of reducing components inside the blast furnace is shown. [Figure 9C] An example of the flow when changing the concentration distribution of reducing components inside the blast furnace is shown. [Figure 10A] The concentration distribution of hydrogen molecules based on the simulation results is shown. [Figure 10B] This shows the concentration distribution of hydrogen molecules based on the simulation results. [Figure 10C] This shows the concentration distribution of hydrogen molecules based on the simulation results. [Figure 10D] This shows the concentration distribution of hydrogen molecules based on the simulation results. [Figure 10E] This shows the concentration distribution of hydrogen molecules based on the simulation results. [Figure 10F] This shows the concentration distribution of hydrogen molecules based on the simulation results. [Figure 10G] This shows the concentration distribution of hydrogen molecules based on the simulation results. [Figure 10H] This shows the concentration distribution of hydrogen molecules based on the simulation results. [Figure 10I] This shows the concentration distribution of hydrogen molecules based on the simulation results. [Modes for carrying out the invention]

[0008] The following describes one embodiment of the blast furnace operation method of this disclosure. However, the blast furnace operation method of this disclosure is not limited to the following embodiment.

[0009] 1. Blast furnace operation method As shown in Figures 1-7 and 8A-8C, an operating method for a blast furnace 100 according to one embodiment includes supplying hot air into the blast furnace 100 via a hot air passage 12 provided in a hot air tuyere 10, and supplying reducing gas into the blast furnace 100 via a reducing gas outlet 13x provided in the hot air tuyere 10. Here, the hot air tuyere 10 is provided with a plurality of reducing gas outlets 13x. Furthermore, an operating method for a blast furnace 100 according to one embodiment includes changing the flow rate of the reducing gas blown out from at least one of the reducing gas outlets 13x.

[0010] 1.1 Hot air nozzle As shown in Figure 1, the hot air tuyeres 10 are located, for example, below the lower end 101ax of the shaft of the blast furnace 100 and above the tapping port 102. The "lower end of the shaft" refers to the boundary between the shaft 101a and the furnace belly (belly) 101b. The "shaft" refers to the part above the furnace belly 101b, where the furnace diameter usually increases from top to bottom. The "furnace belly" refers to the part below the shaft and above the bellows (bosch) 101c, where the furnace diameter is usually the largest. The furnace diameter (diameter) of the furnace belly 101b may be, for example, 5m to 20m or 10m to 18m. The "tapping port" refers to the molten iron tapping port located at the bottom of the blast furnace 100. The "hot air tuyeres" refer to nozzles for supplying hot air to the blast furnace. The blast furnace 100 may have hot air tuyeres 10 located below the lower end 101bx of the furnace belly and above the taphole 102, or it may have hot air tuyeres 10 located below the lower end 101cx of the bellows and above the taphole 102.

[0011] The number of hot air tuyeres 10 provided in the blast furnace 100 is not particularly limited and can be determined according to the internal volume of the blast furnace. Multiple hot air tuyeres 10 may be arranged in the circumferential direction of the blast furnace 100. In other words, in the blast furnace 100, multiple hot air tuyeres 10 may be arranged in the circumferential direction when viewed from above. Typically, the height position of the center of each of the multiple hot air tuyeres 10 is the same.

[0012] 1.1.1 Hot air channel The hot air tuyere 10 has a hollow tuyere body 11. The hot air passage 12 is defined by the inner wall 11a of the tuyere body 11. The upstream side of the hot air passage 12 (opposite the tip 11x of the tuyere body 11) of the tuyere body 11 is connected to a blowpipe (not shown), and the downstream side of the hot air passage 12 (the side of the tip 11x of the tuyere body 11) faces the inside of the blast furnace 100. The tuyere body 11 has an opening 12x that faces the inside of the blast furnace 100, and this opening 12x is the outlet of the hot air passage 12. The tuyere body 11 can be connected to a hot air furnace outside the blast furnace 100 via a hot air pipe, blowpipe, etc. In other words, the blast furnace 100 can be configured so that hot air is supplied to the inside of the blast furnace 100 from the hot air furnace via a hot air pipe, blowpipe, and tuyere body 11. The diameter of the outlet of the hot air passage 12 of the tuyeres body 11 (the circular diameter of the opening 12x facing the inside of the blast furnace 100, the nozzle diameter) may be, for example, 20 mm or more and 400 mm or less, or 40 mm or more and 300 mm or less.

[0013] The wall of the tuyeres body 11 has, for example, an inner wall 11a that defines the hot air passage 12, and an outer wall 11b and tip 11x that face the inside of the blast furnace 100. The tuyeres body 11 may have a cooling water passage inside the wall. This allows the tuyeres body 11 and its surroundings to be cooled during the operation of the blast furnace 100, thereby suppressing thermal damage. The shape of the cooling water passage is not particularly limited. The tuyeres body 11 is made of a known material, for example, copper.

[0014] 1.1.2 Reducing gas outlet The hot air tuyeres 10 have multiple reducing gas outlets 13x, and reducing gas is supplied to the inside of the blast furnace 100 through each of the reducing gas outlets 13x.

[0015] 1.1.2.1 Location of the reducing gas outlet As shown in Figures 2 and 3, at least one of the multiple reducing gas outlets 13x may be provided on the inner wall 11a of the tuyere body 11. Alternatively, as shown in Figures 4 and 5, at least one of the multiple reducing gas outlets 13x may be located inside the hot air passage 12. In the case of the reducing gas outlets 13x shown in Figures 2-5, the reducing gas outlets 13x face the hot air passage 12, and the reducing gas can be supplied to the hot air passage 12 via the reducing gas outlets 13x. Alternatively, as shown in Figures 6 and 7, at least one of the multiple reducing gas outlets 13x may be provided on the tip 11x of the tuyere body 11. In the case of the reducing gas outlets 13x shown in Figures 6 and 7, the reducing gas outlets 13x do not face the hot air passage 12, and the reducing gas can be supplied from the tip 11x of the tuyere body 11 to the inside of the blast furnace 100 without merging with the hot air passage 12.

[0016] 1.1.2.2 Morphology of the reducing gas flow path The reducing gas outlet 13x is an outlet provided on the downstream side of the reducing gas flow path 13. In the blast furnace 100, the reducing gas flow path 13 may be provided as a reducing gas injection port or as a reducing gas injection lance. In this application, "port" means a gas flow path provided so as to penetrate the wall of the tuyere body 11, and "lance" means having an outlet within the hot air flow path 12 without penetrating the wall of the tuyere body 11.

[0017] As shown in Figures 2, 3, 6, and 7, the reducing gas injection port, which serves as the reducing gas flow path 13, is provided so as to penetrate the wall of the tuyere body 11. For example, the reducing gas injection port has a reducing gas flow path 13 inside the wall of the tuyere body 11, and a reducing gas outlet 13x on the downstream side of the flow path. The length, longitudinal shape, and opening shape of the reducing gas injection port can be appropriately determined in consideration of the thickness of the wall of the tuyere body 11 and the water cooling structure inside the wall. The reducing gas injection port, which serves as the reducing gas flow path 13, can be connected to a reducing gas supply source outside the blast furnace 100 via piping or the like. In other words, the blast furnace 100 can be configured so that reducing gas is supplied to the inside of the blast furnace 100 from a reducing gas supply source via reducing gas supply piping, the reducing gas injection port, and the hot air flow path 12. There are no particular restrictions on the form of the reducing gas supply source or piping.

[0018] As shown in Figures 4 and 5, the reducing gas injection lance, which serves as the reducing gas flow path 13, is positioned in the hot air flow path 12 without penetrating the wall of the tuyere body 11. The length, longitudinal shape, and opening shape of the reducing gas injection lance can be appropriately determined in consideration of the shape of the hot air flow path 12. The reducing gas injection lance, like the reducing gas injection port, can be connected to a reducing gas supply source outside the blast furnace 100 via piping or the like. In other words, the blast furnace 100 can be configured so that reducing gas is supplied from the reducing gas supply source to the inside of the blast furnace 100 via the reducing gas supply piping, the reducing gas injection lance, and the hot air flow path 12. There are no particular restrictions on the form of the reducing gas supply source or piping.

[0019] In the method according to this embodiment, the reduction gas injection ports and reduction gas injection lances described above may be combined in any way. For example, as shown in Figure 8A, the method according to this embodiment may include supplying reduction gas to the inside of the blast furnace 100 through a plurality of reduction gas injection ports provided in the hot air tuyere 10. Alternatively, as shown in Figure 8B, the method according to this embodiment may include supplying reduction gas to the inside of the blast furnace 100 through a plurality of reduction gas injection lances provided in the hot air tuyere 10. Alternatively, as shown in Figure 8C, the method according to this embodiment may include supplying reduction gas to the inside of the blast furnace 100 through at least one reduction gas injection port and at least one reduction gas injection lance provided in the hot air tuyere 10.

[0020] In the method according to this embodiment, the reducing gas supply source connected to one reducing gas flow path 13 and the reducing gas supply source connected to the other reducing gas flow path 13 may be the same or different. That is, reducing gas may be supplied from one reducing gas supply source to each reducing gas flow path 13 via a branch flow path, or reducing gas may be supplied from one reducing gas supply source to one reducing gas flow path 13, and reducing gas may be supplied from a different reducing gas supply source to the other reducing gas flow path 13.

[0021] 1.1.2.3 Relationship between the location of the reducing gas outlet and the concentration of reducing components inside the blast furnace The height position of the reducing gas outlet 13x provided in the hot air tuyere 10 is not particularly limited. The height position of the center of the reducing gas outlet 13x may be above, below, or at the same height as the height position of the center of the opening 12x that serves as the outlet for the hot air flow path 12 of the tuyere body 11. Furthermore, multiple reducing gas outlets 13x may each be located at different height positions. For example, the height position of at least one of the multiple reducing gas outlets 13x may be above the height position of the center of the opening 12x that serves as the outlet for the hot air flow path 12 of the tuyere body 11, and the height position of at least one of the multiple reducing gas outlets 13x may be below the height position of the center of the opening 12x that serves as the outlet for the hot air flow path 12 of the tuyere body 11. The distance between the tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x is also not particularly limited.

[0022] According to the inventor's new findings, the concentration distribution of reducing components inside the blast furnace 100 changes depending on whether (1) the height position of the center of the reducing gas outlet 13x is above the height position of the center of the opening 12x that serves as the outlet of the hot air flow path 12, or (2) the height position of the center of the reducing gas outlet 13x is below the height position of the center of the opening 12x that serves as the outlet of the hot air flow path 12. In other words, when the height position of one reducing gas outlet 13x provided in the hot air tuyere 12 is different from the height positions of the other reducing gas outlets 13x, the concentration distribution of reducing components inside the blast furnace 100 can be changed by changing the flow rate of the reducing gas blown out from at least one of these reducing gas outlets 13x with different height positions.

[0023] For example, increasing the amount of reducing gas supplied to the inside of the blast furnace 100 via the reducing gas outlet 13x located at height (1) tends to increase the concentration of reducing components on the furnace wall side inside the blast furnace 100, while decreasing it (including stopping the supply) tends to decrease the concentration of reducing components on the furnace wall side inside the blast furnace 100. Therefore, if the concentration of reducing components on the furnace wall side inside the blast furnace 100 is lower than the target value, for example, increasing the amount of reducing gas supplied to the inside of the blast furnace 100 via the reducing gas outlet 13x located at height (1) can bring the concentration of reducing components on the furnace wall side inside the blast furnace 100 closer to the target value. Similarly, if the concentration of reducing components on the furnace wall side inside the blast furnace 100 is higher than the target value, for example, decreasing the amount of reducing gas supplied to the inside of the blast furnace 100 via the reducing gas outlet 13x located at height (1) can bring the concentration of reducing components on the furnace wall side inside the blast furnace 100 closer to the target value.

[0024] Furthermore, increasing the amount of reducing gas supplied to the inside of the blast furnace 100 via the reducing gas outlet 13x located at the height of (2) tends to increase the concentration of reducing components in the center of the blast furnace 100, while decreasing it (including stopping the supply) tends to decrease the concentration of reducing components in the center of the blast furnace 100. Therefore, if the concentration of reducing components in the center of the blast furnace 100 is lower than the target value, the concentration of reducing components in the center of the blast furnace 100 can be brought closer to the target value by, for example, increasing the amount of reducing gas supplied to the inside of the blast furnace 100 via the reducing gas outlet 13x located at the height of (2). Similarly, if the concentration of reducing components in the center of the blast furnace 100 is higher than the target value, the concentration of reducing components in the center of the blast furnace 100 can be brought closer to the target value by, for example, decreasing the amount of reducing gas supplied to the inside of the blast furnace 100 via the reducing gas outlet 13x located at the height of (2).

[0025] Furthermore, according to the inventor's new findings, the concentration distribution of reducing components inside the blast furnace 100 changes depending on whether (4) a reducing gas injection port is used as the reducing gas flow path 13 or (5) a reducing gas injection lance is used as the reducing gas flow path 13. In particular, when reducing gas is supplied to the inside of the blast furnace 100 via a reducing gas injection lance as in (5), the concentration of reducing components tends to increase in the middle part of the furnace (between the furnace wall and the furnace center) inside the blast furnace 100. In other words, when one reducing gas flow path 13 provided in the hot air tuyere 12 is a reducing gas injection port and the other reducing gas flow path 13 is a reducing gas injection lance, the concentration distribution of reducing components inside the blast furnace 100 can be changed by changing the flow rate of reducing gas blown out from one or both of these ports and lances.

[0026] For example, if the concentration of reducing components in the intermediate part of the blast furnace 100 (between the furnace wall and the furnace center) is lower than the target value, the concentration of reducing components in the intermediate part of the blast furnace 100 can be brought closer to the target value by increasing the amount of reducing gas supplied to the inside of the blast furnace 100 via the reducing gas injection lance. Similarly, if the concentration of reducing components in the intermediate part of the blast furnace 100 is higher than the target value, the concentration of reducing components in the intermediate part of the blast furnace 100 can be brought closer to the target value by decreasing the amount of reducing gas supplied to the inside of the blast furnace 100 via the reducing gas injection lance (5).

[0027] Furthermore, according to the inventor's new findings, (6) the concentration distribution of reducing components inside the blast furnace 100 can also change depending on the distance between the tip 11x of the tuyere body 11 and the center of the reducing gas outlet 13x. For example, the closer the reducing gas outlet 13x is to the tip 11x of the tuyere body 11, the higher the concentration of reducing components on the furnace wall side inside the blast furnace 100 tends to be. In other words, if one reducing gas outlet 13x provided in the hot air tuyere 12 is located closer to the tip 11x of the tuyere body 11 than the other reducing gas outlets 13x, the concentration distribution of reducing components inside the blast furnace 100 can be changed by changing the flow rate of reducing gas blown out from at least one of these reducing gas outlets 13x.

[0028] For example, if the concentration of reducing components on the furnace wall side inside the blast furnace 100 is lower than the target value, the amount of reducing gas supplied into the blast furnace 100 via the reducing gas outlet 13x located on the tip 11x side of the tuyere body 11, among the multiple reducing gas outlets 13x provided in the hot air tuyere 12, can be increased to bring the concentration of reducing components on the furnace wall side inside the blast furnace 100 closer to the target value. Similarly, if the concentration of reducing components on the furnace wall side inside the blast furnace 100 is higher than the target value, the amount of reducing gas supplied into the blast furnace 100 via the reducing gas outlet 13x located on the tip 11x side of the tuyere body 11, among the multiple reducing gas outlets 13x provided in the hot air tuyere 12, can be decreased to bring the concentration of reducing components on the furnace wall side inside the blast furnace 100 closer to the target value.

[0029] The above examples illustrate methods for changing the concentration distribution of reducing components inside the blast furnace 100, specifically by selecting the height of the reducing gas outlet 13x, the type of reducing gas flow path 13, or the distance from the tip 11x of the tuyeres body 11 to the reducing gas outlet 13x while changing the flow rate of the reducing gas. In particular, when changing the flow rate of the reducing gas while selecting the height of the reducing gas outlet 13x, as described in (1) and (2) above, it becomes easier to change the flow rate of the reducing gas according to the operating conditions of the blast furnace 100.

[0030] Thus, the concentration distribution of reducing components inside the blast furnace 100 changes depending on the position of the reducing gas outlet 13x. In this embodiment, multiple reducing gas outlets 13x are provided on the hot air tuyere 10, and reducing gas is supplied to the inside of the blast furnace 100 through each of the multiple reducing gas outlets 13x. By changing the flow rate of reducing gas blown out from at least one of the multiple reducing gas outlets 13x, the concentration distribution of reducing components inside the blast furnace 100 can be changed to various states while maintaining the amount of reducing gas supplied to the inside of the blast furnace 100.

[0031] In this embodiment, how the flow rate of the reducing gas blown out from the reducing gas outlet 13x is changed can be appropriately determined according to the operating conditions of the blast furnace 100. The timing of changing the flow rate of the reducing gas blown out from the reducing gas outlet 13x can also be appropriately determined according to the operating conditions of the blast furnace 100. For example, the method according to this embodiment may include changing the flow rate of the reducing gas blown out from at least one reducing gas outlet 13x according to the concentration distribution of the reducing component in the radial or circumferential direction inside the blast furnace 100. More specifically, as shown in Figures 9A and 9B, the method according to one embodiment may include checking the concentration distribution of the reducing component in the radial or circumferential direction inside the blast furnace 100 (S1), determining whether the concentration distribution is appropriate or not (S2), and, if the concentration distribution is determined to be inappropriate, changing the concentration distribution by changing the flow rate of the reducing gas blown out from at least one reducing gas outlet 13x (S3). Furthermore, as shown in Figure 9B, in one embodiment, steps S1 to S3 may be repeated until the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace 100 becomes appropriate.

[0032] In S1, the concentration distribution of reducing components inside the blast furnace 100 may be confirmed by estimating the concentration distribution of reducing components inside the blast furnace 100 through simulation or the like, by grasping or estimating the concentration distribution of reducing components inside the blast furnace 100 from the actual operating conditions of the blast furnace 100, or by directly measuring the concentration distribution of reducing components inside the blast furnace 100 using measuring instruments installed in the blast furnace 100.

[0033] In S1, the presence or absence of bias in the concentration distribution of reducing components inside the blast furnace 100 may be confirmed. For example, the gas composition inside the blast furnace 100 may be measured to grasp the presence or absence of bias in the concentration distribution of reducing components inside the blast furnace 100. Alternatively, the exhaust gas from the blast furnace 100 may be analyzed to obtain the consumption rate of the reducing gas supplied to the blast furnace 100, and based on the consumption rate, the presence or absence of bias in the concentration distribution of reducing components inside the blast furnace 100 may be inferred. Alternatively, the presence or absence of bias in the concentration distribution of reducing components inside the blast furnace 100 may be comprehensively determined from the analysis results by an analyzer (gas concentration analyzer, thermometer, etc.) provided at the upper part of the blast furnace 100, the hot metal temperature, and the ventilation resistance index. For example, the excess or deficiency of reducing components in the furnace diameter direction inside the blast furnace 100 can be determined from the gas concentration distribution measured by the analyzer.

[0034] In S2, the suitability of the concentration distribution of reducing components in the furnace diameter direction or the furnace circumferential direction inside the blast furnace 100 is determined according to the operating conditions of the blast furnace 100. For example, when there is a bias in the concentration distribution of reducing components in the furnace diameter direction or the furnace circumferential direction inside the blast furnace 100, it may be determined that the concentration distribution of reducing components in the furnace diameter direction or the furnace circumferential direction inside the blast furnace 100 is inappropriate. In this case, in S3, the flow rate of the reducing gas blown out from at least one reducing gas blowout port 13x may be changed to reduce the bias. In this case, whether or not there is a bias in the concentration distribution of reducing components in the furnace diameter direction or the furnace circumferential direction inside the blast furnace 100 may be determined according to the target operating conditions. For example, the average concentration C of reducing components in the furnace diameter direction or the furnace circumferential direction inside the blast furnace 100 ave is specified, and the maximum concentration C in the concentration distribution in the furnace diameter direction or the furnace circumferential direction inside the blast furnace max and the minimum concentration C min and the difference C max -C min are specified, and the ratio of the difference C max -C min to the average concentration C ave (C max -C min ) / C aveIf the value is above a threshold, it may be determined that there is a bias in the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace 100. The threshold may be any value greater than or equal to 0.08, for example.

[0035] Alternatively, in the event of a malfunction in the operation of the blast furnace 100, the malfunction can sometimes be resolved by changing the flow rate of reducing gas blown out from at least one reducing gas outlet 13x, thereby temporarily creating a bias in the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace 100. For example, assuming that the moisture content and particle size of the raw materials charged into the blast furnace 100 are constant, it is considered that making the concentration distribution of reducing components uniform in the radial or circumferential direction inside the furnace will result in a constant reduction rate in the radial or circumferential direction, thus creating a desirable operating state for the blast furnace. On the other hand, the moisture content and particle size of the raw materials charged into the blast furnace 100 are not constant, and the required concentration of reducing components may differ in the radial direction inside the furnace. For example, in a state where the furnace is being operated in such a way that the concentration distribution of reducing components in the radial or circumferential direction within the furnace is uniform, if a reduction deficiency occurs at a certain location in the radial or circumferential direction within the furnace, it can be determined that the concentration distribution of reducing components is inappropriate, and the flow rate of the reducing gas blown out from at least one reducing gas outlet 13x can be changed so that the reducing components are preferentially supplied to the location where the reduction deficiency occurs. In other words, in S2, even if there is no bias in the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace 100, it can be determined that the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace 100 is inappropriate, and in this case, in S3, the flow rate of the reducing gas blown out from at least one reducing gas outlet 13x can be changed to cause such bias. In this embodiment, as described above, by changing the flow rate of the reducing gas blown out from at least one reducing gas outlet 13x, the reducing components can be distributed from locations where the amount of reducing components inside the blast furnace 100 is sufficient to locations where it is insufficient.

[0036] Furthermore, for example, if there is a part inside the blast furnace 100 where the temperature is insufficient, there is a risk of insufficient reduction in that part. Insufficient reduction can lead to problems such as deterioration of airflow resistance and a decrease in the molten iron temperature due to unreduced ore dripping into the molten iron. To prevent this, it is advisable to preferentially supply reducing components to the part where reduction is insufficient to promote the reduction reaction. In other words, in this embodiment, in S2, if the concentration distribution in the radial or circumferential direction inside the blast furnace, as confirmed in S1, is not such that reducing components are preferentially supplied to the part where reduction is insufficient (the part where the temperature is insufficient), it may be determined that the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace is inappropriate. In this case, in S3, the insufficient reduction can be resolved by changing the flow rate of the reducing gas blown out from at least one reducing gas outlet 13x so that reducing components are preferentially supplied to the part inside the blast furnace where reduction is insufficient (the part inside the blast furnace where the temperature is insufficient). In other words, the method according to this embodiment may include determining whether the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace 100 is appropriate based on the temperature distribution in the radial or circumferential direction inside the blast furnace 100 (S2), and if it is determined that the concentration distribution is inappropriate, changing the concentration distribution by changing the flow rate of reducing gas blown out from at least one reducing gas outlet 13x (S3). The temperature distribution in the radial or circumferential direction inside the blast furnace 100 can be determined by a plurality of thermometers provided in the radial or circumferential direction inside the blast furnace 100.

[0037] Furthermore, the method according to one embodiment is shown in Figure 9C, Before or during the operation of blast furnace 100, The positions of the multiple reducing gas outlets 13x provided in the hot air tuyere 10, The flow rate of the reducing gas supplied from the reducing gas outlet 13x to the inside of the blast furnace 100, When reducing gas is supplied from the reducing gas outlet 13x into the interior of the blast furnace 100, the concentration distribution of the reducing component generated in the radial or circumferential direction inside the blast furnace 100 is as follows: Identifying the relationship (S0), During the operation of the blast furnace 100, the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace 100 is confirmed (S1). During the operation of the blast furnace 100, it is necessary to determine whether the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace 100 is appropriate (S2), and If the aforementioned concentration distribution is determined to be inappropriate, the concentration distribution is changed by changing the flow rate of the reducing gas blown out from at least one reducing gas outlet 13x (S3), and, The reducing gas outlet 13x that changes the flow rate of the reducing gas and the changed flow rate are determined based on the above relationship. It may also be an object. In this way, by pre-determining the relationship between the position of the reducing gas outlet 13x, the flow rate of the reducing gas, and the concentration distribution of the reducing component in the radial or circumferential direction inside the blast furnace 100, and determining the flow rate of the reducing gas from the reducing gas outlet 13x based on this, the concentration distribution of the reducing component in the radial or circumferential direction inside the blast furnace 100 can be changed to the desired concentration distribution, and the number of repetitions shown in Figure 9B can be reduced or even omitted.

[0038] 1.1.2.3 Other Matters The diameter (equivalent area of ​​a circular diameter) of the reducing gas outlet 13x may be, for example, 10 mm to 50 mm, or 20 mm to 30 mm. Alternatively, the diameter of the reducing gas outlet 13x may be 10% to 50% or 15% to 30% of the diameter of the opening 12x that serves as the outlet for the hot air passage 12 of the tuyere body 11. When the reducing gas outlet 13x has such a diameter, the flow rate of the reducing gas is easier to control.

[0039] The number of reducing gas outlets 13x provided in the hot air tuyere 10 may be multiple. The number of reducing gas outlets 13x provided in the hot air tuyere 10 may be two, three or more. However, if there is only one reducing gas outlet 13x provided in the hot air tuyere 10, changing the flow rate of reducing gas blown out from that outlet 13x will change the overall flow rate of reducing gas blown in from the hot air tuyere 10. In the operation of the blast furnace 100, it may be desirable to keep the total flow rate of reducing gas blown in from the hot air tuyere 10 constant. By providing multiple reducing gas outlets 13x in the hot air tuyere 10, it is possible to change the concentration distribution of reducing components inside the blast furnace 100 while keeping the total flow rate of reducing gas blown out from the hot air tuyere 10 constant by decreasing the flow rate of reducing gas blown out from one reducing gas outlet 13x while increasing the flow rate of reducing gas blown out from other reducing gas outlets 13x. In this embodiment, when the flow rate of reducing gas discharged from some of the multiple reducing gas outlets 13x provided in one hot air tuyere 10 is reduced, it is preferable to increase the flow rate of reducing gas discharged from the other outlets so that the fluctuation in the total flow rate of reducing gas discharged from the one hot air tuyere 10 is kept within ±0.5%.

[0040] 1.2 Hot air The hot air supplied from the hot air tuyeres 10 into the blast furnace 100 may consist of, for example, air, or oxygen-enriched air. The temperature of the hot air is, for example, 1000°C or higher. The temperature of the hot air may be between 1000°C and 2000°C, between 1000°C and 1700°C, between 1000°C and 1500°C, or between 1000°C and 1300°C. The flow velocity of the hot air at the opening 12x, which serves as the outlet of the hot air flow path 12, may be adjusted as appropriate according to the operating conditions of the blast furnace 100, for example, between 100 m / s and 300 m / s, or between 200 m / s and 250 m / s.

[0041] 1.3 Reducing gas "Reducing gas" refers to a gas that functions as a reducing agent inside the blast furnace 100. That is, even if a gas does not function as a reducing agent before being supplied to the blast furnace 100, if it can generate reducing components that function as a reducing agent by thermal decomposition inside the blast furnace 100, it is included in the definition of "reducing gas" as used in this application. In this application, "reducing gas" and "reducing components" are used with different meanings. If the molecules contained in the reducing gas function as a reducing agent directly inside the blast furnace 100, then the molecules contained in the reducing gas themselves are the "reducing components." On the other hand, if the reducing gas decomposes inside the blast furnace 100 to produce a reducing agent, then the reducing agent produced by the decomposition is the "reducing component." For example, if the reducing gas contains hydrogen gas, then the hydrogen molecules that make up the hydrogen gas can be the "reducing components." Also, if the reducing gas contains ammonia gas, then the hydrogen molecules produced by the decomposition of the ammonia gas can be the "reducing components."

[0042] In this embodiment, the reducing gas may include hydrogen gas. The proportion of hydrogen gas in the reducing gas may be, for example, 30% to 100% by volume, 40% to 100% by volume, 50% to 100% by volume, 60% to 100% by volume, 70% to 100% by volume, 80% to 100% by volume, or 90% to 100% by volume. Examples of reducing gases other than hydrogen gas include at least one selected from hydrocarbon gases (e.g., methane gas), carbon monoxide gas, ammonia gas, and alcohol gases (e.g., methanol gas or ethanol gas). In this embodiment, at least one selected from coke oven gas (COG), converter gas (LDG), blast furnace gas (BFG), natural gas (NG), and synthesis gas (Syngas) may be used as the reducing gas. These reducing gases may be used individually or in combination of two or more types. The temperature of the reducing gas supplied from the reducing gas outlet 13x to the hot air flow path 12 may be, for example, 0°C to 2000°C or 25°C to 1500°C. In this embodiment, the flow velocity of the reducing gas at the reducing gas outlet 13x may be, for example, less than or equal to the speed of sound at the operating temperature of each reducing gas. Other gases may be supplied from the reducing gas outlet 13x along with the reducing gases. Examples of other gases include inert gases such as nitrogen gas.

[0043] 2. Supplement In the operation of the blast furnace 100, for example, iron ore (iron oxide) or coke can be charged into the blast furnace 100 from the top. Hot air can also be supplied into the blast furnace 100 from a hot blast furnace outside the blast furnace 100 via hot air pipes and hot air tuyeres 10. Reducing gas can also be supplied into the blast furnace 100 from a reducing gas supply source outside the blast furnace 100 via a reducing gas flow path 13 and a reducing gas outlet 13x. The coke supplied into the blast furnace 100 burns to generate reducing gas. The reducing gas produced by the combustion of the coke, etc., and the reducing gas supplied through the reducing gas outlet 13x reduce and dissolve the iron oxide to obtain molten iron. This molten iron is tapped out from a tapping port 102 located at the bottom of the blast furnace 100. In this embodiment, reducing gas is supplied to the inside of the blast furnace 100 via the reducing gas outlet 13x, thereby reducing the amount of carbon-containing solid reducing material used, such as coke. As a result, CO2 emissions can be reduced. The blast furnace 100 can take various configurations as long as it is capable of producing pig iron as described above. For example, the blast furnace 100 may have other tuyeres, ports, or lances in addition to the hot air tuyere 10 described above. Furthermore, the hot air tuyere 10 may be equipped with other ports, lances, etc., in addition to the hot air flow path 12, reducing gas flow path 13, and solid reducing material supply path 14 described above. For example, the hot air tuyere 10 may be equipped with a solid reducing material injection lance, etc. As the configuration of the blast furnace 100 other than the hot air tuyere 10 is known in the art, a detailed explanation is omitted here.

[0044] 3. Effects As described above, according to this embodiment, it is possible to change the concentration distribution of reducing components inside the blast furnace during blast furnace operation. [Examples]

[0045] The present invention will be further described below with reference to examples, but the present invention is not limited to the following examples. The present invention allows for the adoption of various conditions without departing from its gist and insofar as it achieves its objective. In the following examples, the case in which a reducing gas consisting only of hydrogen gas is used is illustrated, but the type of reducing gas is not limited thereto. In the examples shown below, the concentration of hydrogen molecules inside the blast furnace was evaluated by performing simulations that considered gas flow, heat transfer, and chemical reactions using the general-purpose thermal fluid analysis software FLUENT. At this time, the raceway region near the tuyeres was treated as a cavity without coke, and the coke-packed bed region inside the blast furnace away from the raceway was treated as a porous medium. A standard k-ε model was used for turbulence analysis, an eddy dissipation model for gas combustion, and Field's model for the gasification reactions of O2, CO2, and H2O in coke. In this embodiment, the "concentration of hydrogen molecules" inside the blast furnace refers to the volume ratio of hydrogen molecules to the total amount of hydrogen molecules, carbon monoxide molecules, and nitrogen molecules inside the blast furnace, and is calculated as follows: [concentration of hydrogen molecules] = H2 fraction / (CO fraction + N2 fraction + H2 fraction).

[0046] Using simulation, (1) When hydrogen gas is supplied into the hot air passage from the hydrogen injection port that penetrates the upper wall of the tuyere body. (2) When hydrogen gas is supplied into the hot air passage from the hydrogen injection port that penetrates the lower wall of the tuyere body. (3) When hydrogen gas is supplied into the blast furnace from the hydrogen injection port that penetrates the upper wall of the tuyere body at the tip of the tuyere body. (4) When hydrogen gas is supplied into the blast furnace from the hydrogen injection port that penetrates the lower wall of the tuyere body at the tip of the tuyere body. (5) When the outlet of the hydrogen injection lance is placed inside the hot air passage of the tuyere body and hydrogen gas is supplied into the hot air passage from there. (6) When hydrogen gas is supplied to the blast furnace from the hydrogen injection port that penetrates the upper wall of the tuyere body at the tip of the tuyere body at a flow rate different from that of (1) to (5) above. (7) In the case of (1) above, if the flow rate of hydrogen gas is reduced (8) In the case of (5) above, if the flow rate of hydrogen gas is reduced (9) When hydrogen gas is supplied into the hot air passage from a hydrogen injection port that penetrates the upper wall of the tuyere body, and hydrogen gas is also supplied into the hot air passage of the tuyere body from the outlet of the hydrogen injection lance (i.e., when (7) and (8) above are combined) For each of these, the concentration distribution of hydrogen molecules in the radial direction of the furnace was confirmed at a height of 12 m from the center of the tuyere inside the blast furnace. In (1) to (5) above, the flow rate of hydrogen gas supplied from the port / lance was 2615 Nm³. 3 The rate was set to / hr. Also, in (6) above, the flow rate of hydrogen gas supplied from the hydrogen injection port was 523 Nm³. 3 The value was set to / hr. In addition, in (7) above, the flow rate of hydrogen gas supplied from the hydrogen injection port was 1389 Nm³. 3 Let / hr be used, and in (8) above, the flow rate of hydrogen gas supplied from the hydrogen injection lance is 1226 Nm³. 3 Let / hr be used, and in (9) above, the flow rate of hydrogen gas supplied from the hydrogen injection port is 1389 Nm³ 3 The flow rate of hydrogen gas supplied from the hydrogen injection lance is set to / hr, and the flow rate is 1226 Nm³. 3 I set it to / hr.

[0047] Figure 10A shows the concentration distribution of hydrogen molecules in case (1) above, Figure 10B shows the concentration distribution of hydrogen molecules in case (2) above, Figure 10C shows the concentration distribution of hydrogen molecules in case (3) above, Figure 10D shows the concentration distribution of hydrogen molecules in case (4) above, Figure 10E shows the concentration distribution of hydrogen molecules in case (5) above, Figure 10F shows the concentration distribution of hydrogen molecules in case (6) above, Figure 10G shows the concentration distribution of hydrogen molecules in case (7) above, Figure 10H shows the concentration distribution of hydrogen molecules in case (8) above, and Figure 10I shows the concentration distribution of hydrogen molecules in case (9) above. In this embodiment, the "mole fraction of hydrogen molecules / average mole fraction of hydrogen molecules" shown on the vertical axis of Figures 10A to 10I means the mole fraction of hydrogen molecules at a certain position in the radial direction inside the blast furnace relative to the average mole fraction of hydrogen molecules in the radial direction inside the blast furnace. In this embodiment, when the difference between the maximum and minimum values ​​of "mole fraction of hydrogen molecules / average mole fraction of hydrogen molecules" is 0.08 or more (the ratio described in the embodiment of this specification (C) max -C min ) / C ave If the difference is 0.08 or greater, it is considered that there is a bias in the concentration distribution of hydrogen molecules in the radial direction inside the blast furnace (a concentration peak is present), and if the difference is less than 0.08, it is considered that there is no bias in the concentration distribution of hydrogen molecules in the radial direction inside the blast furnace (no concentration peak is present). Here, a difference of 0.08 or greater between the maximum and minimum values ​​of "mole fraction of hydrogen molecules / average mole fraction of hydrogen molecules" corresponds to a difference of 3 volume% or more between the maximum and minimum concentrations of hydrogen molecules in the radial direction inside the blast furnace.

[0048] As shown in Figures 10A to 10F, it can be seen that the distribution of hydrogen molecules in the furnace differs depending on the means and location of hydrogen gas supply. Furthermore, as shown in Figures 10G and H, it can be seen that the concentration distribution of hydrogen molecules in the furnace also changes depending on the flow rate of hydrogen gas supplied into the furnace. In other words, in a hot air tuyeres having multiple outlets of different types and / or outlet locations, the concentration distribution of hydrogen molecules inside the blast furnace can be arbitrarily changed by changing the flow rate of hydrogen gas blown in from each outlet, and it is thought that the distribution of hydrogen molecules in the radial or circumferential direction inside the blast furnace can be averaged and made uniform.

[0049] For example, if the hydrogen gas flow rate is reduced as shown in (7) above in the injection configuration described in (1) above, the concentration distribution of hydrogen molecules inside the blast furnace changes from the concentration distribution shown in Figure 10A to the concentration distribution shown in Figure 10G. Also, if the hydrogen gas flow rate is reduced as shown in (8) above in the injection configuration described in (5) above, the concentration distribution of hydrogen molecules inside the blast furnace changes from the concentration distribution shown in Figure 10E to the concentration distribution shown in Figure 10H. Here, the shape of the concentration peak shown in Figure 10G is convex upward in the middle of the furnace, while the shape of the concentration peak shown in Figure 10H is convex downward in the middle of the furnace. In other words, the shapes of the concentration peaks in Figure 10G and Figure 10H are in opposite phases to each other. Therefore, by combining the injection configuration described in (7) above and the injection configuration described in (8) above, the concentration peaks in Figure 10G and Figure 10H are combined, resulting in the peaks canceling each other out and becoming smaller. In fact, as shown in (9) above, by combining the injection method described in (7) and the injection method described in (8) above, the hydrogen gas concentration peak becomes flat as shown in Figure 10I. As described above, by providing multiple reducing gas outlets in the hot air tuyer and increasing or decreasing the flow rate of reducing gas supplied from each reducing gas outlet, it is possible to change the concentration distribution of reducing components inside the blast furnace while maintaining the total flow rate of reducing gas supplied inside the blast furnace.

[0050] Furthermore, eliminating the bias in the concentration distribution of reducing components in the radial direction inside the blast furnace is merely one preferred embodiment of the technology of this disclosure. It is also possible to locally increase the concentration of reducing components in a predetermined part in the radial direction inside the furnace by supplying reducing gas to the inside of the blast furnace from multiple reducing gas outlets and changing the flow rate of reducing gas supplied from each reducing gas outlet. In addition, although the above embodiment exemplifies a form of changing the concentration distribution of reducing components in the radial direction inside the blast furnace, the technology of this disclosure is not limited thereto. For example, the concentration of reducing components in the circumferential direction inside the blast furnace may also be changed. [Explanation of Symbols]

[0051] 100 blast furnace 10 Hot air nozzles 11 Tuyere body 11a Inner wall 11b Exterior wall 11x tip 12 Hot air channel 12x aperture 13. Reducing gas flow path 13x Reducing Gas Outlet

Claims

1. A method for operating a blast furnace, Hot air is supplied to the inside of the blast furnace through a hot air passage provided in the hot air tuyeres, and reducing gas is supplied to the inside of the blast furnace through a reducing gas outlet provided in the hot air tuyeres. Includes, The hot air nozzle is provided with multiple reducing gas outlets. The method of operating the blast furnace includes changing the flow rate of the reducing gas blown out from at least one of the reducing gas outlets, By reducing the flow rate of the reducing gas blown out from at least one of the plurality of reducing gas outlets while increasing the flow rate of the reducing gas blown out from at least one other reducing gas outlet, the fluctuation in the total flow rate of the reducing gas blown out from the hot air tuyere can be kept within ±0.5%. The operation method of a blast furnace.

2. A method for operating a blast furnace according to claim 1, The flow rate of the reducing gas blown out from at least one of the reducing gas outlets is changed according to the concentration distribution of the reducing component in the radial or circumferential direction inside the blast furnace. A method of operating a blast furnace, including [specific details omitted].

3. A method for operating a blast furnace according to Claim 2, Of the multiple reducing gas outlets, one reducing gas outlet is located closer to the tip of the tuyere body of the hot air tuyere than the other reducing gas outlets. Depending on the concentration distribution of reducing components in the radial direction inside the blast furnace, at least one of the following (1) and (2) is performed: Blast furnace operation methods: (1) If the concentration of reducing components on the furnace wall side inside the blast furnace is lower than the target value, the amount of reducing gas supplied into the blast furnace via the reducing gas outlet provided on the tip side of the tuyere body of the hot air tuyere will be increased to bring the concentration of reducing components on the furnace wall side inside the blast furnace closer to the target value; (2) If the concentration of reducing components on the furnace wall side inside the blast furnace is higher than the target value, the amount of reducing gas supplied into the blast furnace through the reducing gas outlet provided on the tip side of the tuyere body of the hot air tuyere will be reduced to bring the concentration of reducing components on the furnace wall side inside the blast furnace closer to the target value.

4. A method for operating a blast furnace according to Claim 2, The height position of at least one of the plurality of reducing gas outlets is above the height position of the center of the opening that serves as the outlet for the hot air passage of the tuyere body of the hot air tuyere, and the height position of at least one of the plurality of reducing gas outlets is below the height position of the center of the opening that serves as the outlet for the hot air passage of the tuyere body of the hot air tuyere. Depending on the concentration distribution of reducing components in the radial direction inside the blast furnace, at least one of the following (3) to (6) is performed: Blast furnace operation methods: (3) If the concentration of reducing components on the furnace wall side inside the blast furnace is lower than the target value, the amount of reducing gas supplied into the blast furnace through the reducing gas outlet located at the upper height position is increased to bring the concentration of reducing components on the furnace wall side inside the blast furnace closer to the target value; (4) If the concentration of reducing components on the furnace wall side inside the blast furnace is higher than the target value, the amount of reducing gas supplied into the blast furnace through the reducing gas outlet located at the upper height position is reduced to bring the concentration of reducing components on the furnace wall side inside the blast furnace closer to the target value; (5) If the concentration of reducing components in the center of the blast furnace is lower than the target value, increase the amount of reducing gas supplied into the blast furnace through the reducing gas outlet located at the lower height position to bring the concentration of reducing components in the center of the blast furnace closer to the target value: (6) If the concentration of reducing components in the center of the blast furnace is higher than the target value, the amount of reducing gas supplied into the blast furnace via the reducing gas outlet located at the lower height position is reduced to bring the concentration of reducing components in the center of the blast furnace closer to the target value.

5. A method for operating a blast furnace according to any one of claims 1 to 4, Reducing gas is supplied into the blast furnace through a plurality of reducing gas injection ports provided in the hot air tuyeres. A method of operating a blast furnace, including [specific details omitted].

6. A method for operating a blast furnace according to any one of claims 1 to 4, Reducing gas is supplied into the blast furnace through a plurality of reducing gas injection lances provided in the hot air tuyeres. A method of operating a blast furnace, including [specific details omitted].

7. A method for operating a blast furnace according to any one of claims 1 to 4, Reducing gas is supplied into the blast furnace through at least one reducing gas injection port and at least one reducing gas injection lance provided in the hot air tuyer. A method of operating a blast furnace, including [specific details omitted].

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