Blast furnace operation method

Abstract

Disclosed is a new technique capable of changing a concentration distribution of reducing components inside a blast furnace while the blast furnace is in operation. A blast furnace operation method according to the present disclosure comprises supplying hot air to the inside of the blast furnace through a hot air flow path provided in a hot air tuyere, and supplying a reducing gas to the inside of the blast furnace through reducing gas outlets provided in the hot air tuyere. A plurality of the reducing gas outlets are provided in the hot air tuyere. The blast furnace operation method according to the present disclosure comprises changing a flow rate of the reducing gas blown out from at least one of the reducing gas outlets.

Description

Blast furnace operation method

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

[0002] CO in the steelmaking process ２ Reducing emissions has been studied. For example, when producing pig iron in a blast furnace, a reducing gas such as hydrogen gas may be used in place of a portion of the reducing material, such as coke. As a method for supplying reducing gas to a blast furnace, Patent Document 1 discloses a method in which a lance for injecting reducing gas is disposed in the hot blast flow path or wall surface of a hot blast tuyere, and reducing gas is injected through the lance. Although not intended to inject reducing gas, Patent Document 2 discloses a method in which a fuel injection lance is inserted into the wall surface of a hot blast tuyere, and pulverized coal as fuel is injected into the blast furnace through the fuel injection lance.

[0003] Patent No. 4997734 Patent No. 5840202

[0004] The present application discloses a new technology that makes it possible to change the concentration distribution of reducing components inside a blast furnace during operation of the blast furnace.

[0005] The present application discloses the following multiple aspects as means for solving the above-mentioned problems. <Aspect 1> A method for operating a blast furnace, comprising: supplying hot air into the interior of the blast furnace through a hot air flow path provided in a hot air tuyere, and supplying a reducing gas into the interior of the blast furnace through a reducing gas outlet provided in the hot air tuyere, wherein the hot air tuyere is provided with a plurality of the reducing gas outlets, and the method for operating a blast furnace comprises changing a flow rate of the reducing gas blown out of at least one of the reducing gas outlets. <Aspect 2> The method for operating a blast furnace according to Aspect 1, comprising: changing the flow rate of the reducing gas blown out of at least one of the reducing gas outlets in accordance with a concentration distribution of reducing components in a radial direction or a circumferential direction inside the blast furnace. <Aspect 3> The method of operating a blast furnace according to Aspect 1 or 2, comprising supplying reducing gas into the interior of the blast furnace through a plurality of reducing gas injection ports provided in the hot blast tuyere. <Aspect 4> The method of operating a blast furnace according to Aspect 1 or 2, comprising supplying reducing gas into the interior of the blast furnace through a plurality of reducing gas injection lances provided in the hot blast tuyere. <Aspect 5> The method of operating a blast furnace according to Aspect 1 or 2, comprising supplying reducing gas into the interior of the blast furnace through at least one reducing gas injection port and at least one reducing gas injection lance provided in the hot blast tuyere.

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

[0007] 1 is a schematic diagram showing an example of the configuration of a blast furnace. Some components of the blast furnace are omitted from the illustration.

[0023] FIG. 1 is a schematic diagram showing an example of the configuration of one of a plurality of reducing gas outlets provided in a hot air tuyere.

[0024] FIG. 1 is a schematic diagram showing an example of the configuration of one of a plurality of reducing gas outlets provided in a hot air tuyere.

[0025] FIG. 1 is a schematic diagram showing an example of the configuration of one of a plurality of reducing gas outlets provided in a hot air tuyere.

[0026] FIG. 1 is a schematic diagram showing an example of the configuration of one of a plurality of reducing gas outlets provided in a hot air tuyere.

[0027] FIG. 1 is a schematic diagram showing an example of the configuration of one of a plurality of reducing gas outlets provided in a hot air tuyere.

[0028] FIG. 1 is a schematic diagram showing an example of the configuration of one of a plurality of reducing gas outlets provided in a hot air tuyere.

[0029] FIG. 1 is a schematic diagram showing an example of the configuration of a plurality of reducing gas outlets in a hot air tuyere.

[0029] FIG. 1 is a schematic diagram showing an example of the configuration of a plurality of reducing gas outlets in a hot air tuyere. 1 shows an example of a flow when the concentration distribution of reducing components is changed inside a blast furnace. 2 shows an example of a flow when the concentration distribution of reducing components is changed inside a blast furnace. 3 shows an example of a flow when the concentration distribution of reducing components is changed inside a blast furnace. 4 shows a concentration distribution of hydrogen molecules based on simulation results. 5 shows a concentration distribution of hydrogen molecules based on simulation results. 6 shows a concentration distribution of hydrogen molecules based on simulation results. 7 shows a concentration distribution of hydrogen molecules based on simulation results. 8 shows a concentration distribution of hydrogen molecules based on simulation results. 9 shows a concentration distribution of hydrogen molecules based on simulation results. 10 shows a concentration distribution of hydrogen molecules based on simulation results.

[0008] Hereinafter, one embodiment of the blast furnace operation method of the present disclosure will be described. However, the blast furnace operation method of the present disclosure is not limited to the following embodiment.

[0009] 1. Blast Furnace Operating Method As shown in Figures 1 to 7 and 8A to 8C, a method for operating a blast furnace 100 according to one embodiment includes supplying hot air into the interior of the blast furnace 100 through a hot air flow path 12 provided in a hot air tuyere 10, and supplying reducing gas into the interior of the blast furnace 100 through a reducing gas outlet 13x provided in the hot air tuyere 10. Here, the hot air tuyere 10 is provided with a plurality of the reducing gas outlets 13x. The method for operating a blast furnace 100 according to one embodiment also 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 Blast Tuyere As shown in FIG. 1 , the hot blast tuyere 10 is provided, for example, below the shaft lower end 101ax of the blast furnace 100 and above the tap hole 102. The "shaft lower end" refers to the boundary between the shaft 101a and the belly 101b. The "shaft" refers to the portion above the belly 101b, where the furnace diameter typically increases from top to bottom. The "belly" refers to the portion below the shaft and above the bosch 101c, where the furnace diameter typically is greatest. The furnace diameter (diameter) of the belly 101b may be, for example, 5 m or more and 20 m or less, or 10 m or more and 18 m or less. The "tap hole" refers to a molten iron tap port provided at the bottom of the blast furnace 100. The "hot blast tuyere" refers to a nozzle for supplying hot air to the blast furnace. The blast furnace 100 may have a hot air tuyere 10 below the belly lower end 101bx and above the tap hole 102, or may have a hot air tuyere 10 below the morning glory lower end 101cx and above the tap hole 102.

[0011] The number of hot air tuyere 10 provided in the blast furnace 100 is not particularly limited and can be determined according to the internal volume of the blast furnace. The blast furnace 100 may have a plurality of hot air tuyere 10 arranged in the circumferential direction of the blast furnace 100. In other words, the blast furnace 100 may have a plurality of hot air tuyere 10 arranged in the circumferential direction when viewed from above. Usually, the height positions of the centers of the plurality of hot air tuyere 10 are the same.

[0012] 1.1.1 Hot Air Flow Channel The hot air tuyere 10 has a hollow tuyere body 11. The hot air flow channel 12 is defined by an inner wall 11a of the tuyere body 11. The upstream side of the hot air flow channel 12 (the side 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 flow channel 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 facing the interior of the blast furnace 100, and the opening 12x serves as the outlet of the hot air flow channel 12. The tuyere body 11 can be connected to a hot air stove outside the blast furnace 100 via a hot air pipe, a blowpipe, or the like. In other words, the blast furnace 100 can be configured so that hot air is supplied from the hot air stove to the inside of the blast furnace 100 via the hot air pipe, the blowpipe, and the tuyere body 11. The opening diameter of the outlet of the hot air flow path 12 of the tuyere body 11 (the circle equivalent 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 tuyere body 11 has, for example, an inner wall 11a that defines the hot air flow path 12, an outer wall 11b facing the inside of the blast furnace 100, and a tip 11x. The tuyere body 11 may have a cooling water flow path inside the wall. This makes it possible to cool the tuyere body 11 and its surroundings during operation of the blast furnace 100 and suppress thermal damage, etc. The shape of the cooling water flow path is not particularly limited. The tuyere body 11 is made of a known material, for example, copper.

[0014] 1.1.2 Reducing Gas Outlet The hot blast tuyere 10 has a plurality of 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 Position of the Reducing Gas Outlet As shown in FIGS. 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 FIGS. 4 and 5, at least one of the multiple reducing gas outlets 13x may be disposed inside the hot air flow path 12. In the case of the reducing gas outlets 13x shown in FIGS. 2 to 5, the reducing gas outlet 13x faces the hot air flow path 12, and reducing gas can be supplied to the hot air flow path 12 through the reducing gas outlet 13x. Alternatively, as shown in FIGS. 6 and 7, at least one of the multiple reducing gas outlets 13x may be provided at the tip 11x of the tuyere body 11. In the case of the reducing gas outlets 13x shown in FIGS. 6 and 7, the reducing gas outlet 13x does not face the hot air flow path 12, and reducing gas can be supplied from the tip 11x of the tuyere body 11 into the interior of the blast furnace 100 without merging into the hot air flow path 12.

[0016] 1.1.2.2 Configuration of the reducing gas passage The reducing gas outlet 13x is an outlet provided downstream of the reducing gas passage 13. In the blast furnace 100, the reducing gas passage 13 may be provided as a reducing gas injection port or as a reducing gas injection lance. In the present application, the term "port" refers to a gas passage provided so as to penetrate the wall of the tuyere body 11, and the term "lance" refers to a gas passage having an outlet in the hot air passage 12 without penetrating the wall of the tuyere body 11.

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

[0018] 4 and 5 , the reducing gas injection lance serving as the reducing gas flow path 13 is disposed in the hot blast flow path 12 without penetrating the wall of the tuyere body 11. The length, longitudinal shape, opening shape, etc. of the reducing gas injection lance can be determined appropriately in consideration of the shape of the hot blast flow path 12. Like the reducing gas injection port, the reducing gas injection lance can be connected to a reducing gas supply source outside the blast furnace 100 via piping, etc. 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 blast flow path 12. There are no particular limitations on the reducing gas supply source or the shape of the piping.

[0019] In the method according to the present embodiment, the above-described reducing gas injection ports and reducing gas injection lances may be combined in any desired manner. For example, as shown in FIG. 8A , the method according to the present embodiment may include supplying reducing gas into the interior of the blast furnace 100 through a plurality of reducing gas injection ports provided in the hot blast tuyere 10. Alternatively, as shown in FIG. 8B , the method according to the present embodiment may include supplying reducing gas into the interior of the blast furnace 100 through a plurality of reducing gas injection lances provided in the hot blast tuyere 10. Alternatively, as shown in FIG. 8C , the method according to the present embodiment may include supplying reducing gas into the interior of the blast furnace 100 through at least one reducing gas injection port and at least one reducing gas injection lance provided in the hot blast 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 sources connected to the other reducing gas flow paths 13 may be the same as or different from each other. That is, the reducing gas may be supplied from one reducing gas supply source to each reducing gas flow path 13 via branch paths, or the reducing gas may be supplied from one reducing gas supply source to one reducing gas flow path 13 and from another reducing gas supply source to the other reducing gas flow paths 13.

[0021] 1.1.2.3 Relationship between the Position 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 serving as the outlet of the hot air channel 12 of the tuyere body 11. Furthermore, the 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 serving as the outlet of the hot air channel 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 serving as the outlet of the hot air channel 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 the 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 serving as an outlet of the hot air flow channel 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 serving as an outlet of the hot air flow channel 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, it can be said that the concentration distribution of the 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 located at different heights.

[0023] For example, increasing the amount of reducing gas supplied to the interior of the blast furnace 100 through the reducing gas outlet 13x located at height (1) (including when supply is started) tends to increase the concentration of reducing components on the furnace wall side of the interior of the blast furnace 100, while decreasing the amount of reducing gas supplied to the interior of the blast furnace 100 (including when supply is stopped) tends to decrease the concentration of reducing components on the furnace wall side of the interior of the blast furnace 100. Therefore, when the concentration of reducing components on the furnace wall side of the interior of the blast furnace 100 is lower than a target value, for example, by increasing the amount of reducing gas supplied to the interior of the blast furnace 100 through the reducing gas outlet 13x located at height (1), the concentration of reducing components on the furnace wall side of the interior of the blast furnace 100 can be brought closer to the target value. Similarly, when the concentration of reducing components on the furnace wall side of the interior of the blast furnace 100 is higher than the target value, for example, by decreasing the amount of reducing gas supplied to the interior of the blast furnace 100 through the reducing gas outlet 13x located at height (1), the concentration of reducing components on the furnace wall side of the interior of the blast furnace 100 can be brought closer to the target value.

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

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

[0026] For example, if the concentration of reducing components in the intermediate portion of the interior of the blast furnace 100 (between the furnace wall and the furnace center) is lower than the target value, the amount of reducing gas supplied to the interior of the blast furnace 100 via the reducing gas injection lance can be increased to bring the concentration of reducing components in the intermediate portion of the interior of the blast furnace 100 closer to the target value. Similarly, if the concentration of reducing components in the intermediate portion of the interior of the blast furnace 100 is higher than the target value, the amount of reducing gas supplied to the interior of the blast furnace 100 via the reducing gas injection lance (5), for example, can be decreased to bring the concentration of reducing components in the intermediate portion of the interior of the blast furnace 100 closer to the target value.

[0027] Furthermore, according to the inventor's new findings, (6) the concentration distribution of the 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 more likely the concentration of the reducing components on the furnace wall side inside the blast furnace 100 becomes high. In other words, when one reducing gas outlet 13x provided in the hot air tuyere 12 is provided closer to the tip 11x of the tuyere body 11 than the other reducing gas outlets 13x, it can be said that the concentration distribution of the 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.

[0028] For example, when the concentration of the reducing components on the furnace wall side inside the blast furnace 100 is lower than the target value, the concentration of the reducing components on the furnace wall side inside the blast furnace 100 can be brought closer to the target value by increasing the amount of reducing gas supplied into the blast furnace 100 through the reducing gas outlet 13x provided on the tip 11x side of the tuyere body 11, among the multiple reducing gas outlets 13x provided on the hot air tuyere 12. Similarly, when the concentration of the reducing components on the furnace wall side inside the blast furnace 100 is higher than the target value, the concentration of the reducing components on the furnace wall side inside the blast furnace 100 can be brought closer to the target value by decreasing the amount of reducing gas supplied into the blast furnace 100 through the reducing gas outlet 13x provided on the tip 11x side of the tuyere body 11, among the multiple reducing gas outlets 13x provided on the hot air tuyere 12.

[0029] The above has exemplified a method of changing the flow rate of the reducing gas while selecting the height position of the reducing gas outlet 13x, the type of the reducing gas flow path 13, or the distance from the tip 11x of the tuyere body 11 to the reducing gas outlet 13x, as a method of changing the concentration distribution of the reducing component inside the blast furnace 100. In particular, when the flow rate of the reducing gas is changed while selecting the height position of the reducing gas outlet 13x as in (1) and (2) above, it is possible to more easily change the flow rate of the reducing gas in accordance with the operating status of the blast furnace 100.

[0030] In this way, the concentration distribution of the reducing components inside the blast furnace 100 changes depending on the position of the reducing gas outlet 13x. In this embodiment, a plurality of reducing gas outlets 13x are provided for the hot blast tuyere 10, and reducing gas is supplied into the inside of the blast furnace 100 through each of the plurality of reducing gas outlets 13x. By changing the flow rate of the reducing gas blown out from at least one of the plurality of reducing gas outlets 13x, it is possible to change the concentration distribution of the reducing components inside the blast furnace 100 to various states while maintaining the amount of reducing gas supplied to the inside of the blast furnace 100.

[0031] In the present embodiment, how to change the flow rate of the reducing gas blown out from the reducing gas outlet 13x can be determined appropriately depending on the operating status of the blast furnace 100. Furthermore, the timing for changing the flow rate of the reducing gas blown out from the reducing gas outlet 13x can also be determined appropriately depending on the operating status of the blast furnace 100. For example, the method according to the present embodiment may include changing the flow rate of the reducing gas blown out from at least one reducing gas outlet 13x depending on the concentration distribution of the reducing component in the radial direction or the circumferential direction inside the blast furnace 100. More specifically, as shown in FIGS. 9A and 9B , a method according to one embodiment may include confirming the concentration distribution of the reducing component in the radial direction or the circumferential direction inside the blast furnace 100 (S1), determining whether the concentration distribution is appropriate (S2), and, if it is determined that the concentration distribution is inappropriate, changing the flow rate of the reducing gas blown out from at least one reducing gas outlet 13x to change the concentration distribution (S3). Also, as shown in FIG. 9B , in the method according to one embodiment, the above steps S1 to S3 may be repeated until the concentration distribution of the reducing component in the radial direction or circumferential direction inside the blast furnace 100 becomes appropriate.

[0032] In S1, the concentration distribution of the reducing components inside the blast furnace 100 may be confirmed by estimating the concentration distribution of the reducing components inside the blast furnace 100 through simulation or the like, by understanding or estimating the concentration distribution of the 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 the reducing components inside the blast furnace 100 using measuring equipment installed in the blast furnace 100.

[0033] In S1, the presence or absence of a 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 determine the presence or absence of a 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 determine the consumption rate of the reducing gas supplied to the blast furnace 100, and the presence or absence of a bias in the concentration distribution of reducing components inside the blast furnace 100 may be estimated based on the consumption rate. Alternatively, the presence or absence of a bias in the concentration distribution of reducing components inside the blast furnace 100 may be determined comprehensively from the analysis results of an analyzer (gas concentration analyzer, thermometer, etc.) installed at the top of the blast furnace 100, the molten iron temperature, and the air permeability resistance index. For example, the excess or deficiency of reducing components in the radial 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 the reducing components in the radial or circumferential direction inside the blast furnace 100 is determined depending on the operating conditions of the blast furnace 100. For example, if there is a bias in the concentration distribution of the reducing components in the radial or circumferential direction inside the blast furnace 100, it may be determined that the concentration distribution of the reducing components in the radial or 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, it may be determined depending on the target operating conditions whether there is a bias in the concentration distribution of the reducing components in the radial or circumferential direction inside the blast furnace 100. For example, if the average concentration C ａｖｅ The maximum concentration C in the concentration distribution in the radial or circumferential direction inside the blast furnace is identified. ｍａｘ and minimum concentration C ｍｉｎ Difference C ｍａｘ -C ｍｉｎ Identify the difference C ｍａｘ -C ｍｉｎ and the average concentration C ａｖｅ The ratio of (C ｍａｘ -C ｍｉｎ ) / C ａｖｅis equal to or greater than a threshold value, it may be determined that there is a bias in the concentration distribution of the reducing components in the radial or circumferential direction inside the blast furnace 100. The threshold value may be, for example, an arbitrary value equal to or greater than 0.08.

[0035] Alternatively, in the event of a malfunction in the operation of the blast furnace 100, the flow rate of the reducing gas blown out from at least one reducing gas blowout port 13x may be changed to temporarily cause a bias in the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace 100, thereby making it possible to resolve the malfunction in the operation of 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, uniforming the concentration distribution of reducing components in the radial or circumferential direction inside the furnace is considered to result in a constant reduction rate in the radial or circumferential direction, thereby making the blast furnace in a favorable operating state. On the other hand, there are also cases where 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 differs in the radial direction inside the furnace. For example, when the furnace is operated so 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 position 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 reducing components are preferentially supplied to the position where the reduction deficiency occurs. In other words, in S2, if there is no bias in the concentration distribution of reducing components in the radial or circumferential direction within the blast furnace 100, it can be determined that the concentration distribution of reducing components in the radial or circumferential direction within 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 outlet 13x can be changed to cause the 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 positions within the blast furnace 100 where the amount of reducing components is sufficient to positions where the amount is insufficient.

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

[0037] 9C , a method according to one embodiment includes: determining, before or during operation of the blast furnace 100, a relationship between positions of a plurality of reducing gas outlets 13x provided in a hot blast tuyere 10, a flow rate of reducing gas supplied from the reducing gas outlets 13x into the interior of the blast furnace 100, and a concentration distribution of reducing components generated in a radial direction or a circumferential direction inside the blast furnace 100 when reducing gas is supplied from the reducing gas outlets 13x into the interior of the blast furnace 100 (S0); checking, during operation of the blast furnace 100, the concentration distribution of reducing components in the radial direction or the circumferential direction inside the blast furnace 100 (S1); determining, during operation of the blast furnace 100, whether the concentration distribution of reducing components in the radial direction or the circumferential direction inside the blast furnace 100 is appropriate (S2); and, when it is determined that the concentration distribution is inappropriate, changing the flow rate of reducing gas blown out from at least one reducing gas outlet 13x to change the concentration distribution (S3); The reducing gas outlet 13x that changes the flow rate of the reducing gas and the flow rate after the change may be determined based on the relationship. In this way, by specifying in advance 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 the relationship, the concentration distribution of the reducing component in the radial or circumferential direction inside the blast furnace 100 can be more easily changed to a target concentration distribution, and the number of repetitions as shown in Figure 9B can be reduced or the repetition can be omitted.

[0038] 1.1.2.3 Other Matters The diameter (diameter of a circle equivalent to an area) 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 serving as the outlet of the hot air flow path 12 of the tuyere body 11. When the reducing gas outlet 13x has such a diameter, it is easier to control the flow rate of the reducing gas.

[0039] The number of reducing gas outlets 13x provided in the hot air tuyere 10 may be more than one. The number of reducing gas outlets 13x provided in the hot air tuyere 10 may be two, or may be three or more. If the hot air tuyere 10 has only one reducing gas outlet 13x, changing the flow rate of the reducing gas blown out from the outlet 13x will change the overall flow rate of the reducing gas blown out from the hot air tuyere 10. In operation of the blast furnace 100, it may be preferable to keep the total flow rate of the reducing gas blown out from the hot air tuyere 10 constant. If the hot air tuyere 10 has multiple reducing gas outlets 13x, the flow rate of the reducing gas blown out from one reducing gas outlet 13x can be reduced while increasing the flow rates of the reducing gas blown out from the other reducing gas outlets 13x, thereby changing the concentration distribution of the reducing components inside the blast furnace 100 while keeping the total flow rate of the reducing gas blown out from the hot air tuyere 10 constant. In this embodiment, when the flow rate of the reducing gas blown out 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 the reducing gas blown out from some of the other outlets, thereby keeping the fluctuation in the total flow rate of the reducing gas blown out from that one hot air tuyere 10 within ±0.5%.

[0040] 1.2 Hot Air The hot air supplied from the hot air tuyere 10 into the blast furnace 100 may be, 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 1000°C or higher and 2000°C or lower, 1000°C or higher and 1700°C or lower, 1000°C or higher and 1500°C or lower, or 1000°C or higher and 1300°C or lower. The flow velocity of the hot air at the opening 12x serving as the outlet of the hot air channel 12 may be appropriately adjusted depending on the operating conditions of the blast furnace 100, and may be, for example, 100 m / s or higher and 300 m / s or lower, or 200 m / s or higher and 250 m / s or lower.

[0041] 1.3 Reducing Gas "Reducing gas" is a gas that functions as a reducing agent inside the blast furnace 100. In other words, even if a gas does not function as a reducing agent before being supplied to the blast furnace 100, as long as it can generate reducing components as reducing agents by, for example, thermal decomposition inside the blast furnace 100, it is included in the "reducing gas" referred to in the present application. In the present application, "reducing gas" and "reducing component" are used with different meanings. When molecules contained in the reducing gas function as reducing agents inside the blast furnace 100, the molecules contained in the reducing gas themselves are "reducing components." On the other hand, when the reducing gas decomposes inside the blast furnace 100 to generate a reducing agent, the reducing material generated by the decomposition is the "reducing component." For example, when the reducing gas contains hydrogen gas, the hydrogen molecules constituting the hydrogen gas can be the "reducing component." Furthermore, when the reducing gas contains ammonia gas, the hydrogen molecules generated by the decomposition of the ammonia gas can be the "reducing component."

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

[0043] 2. Supplementary Information In the operation of the blast furnace 100, for example, iron ore (iron oxide), coke, etc. may be charged into the blast furnace 100 from the top thereof. Hot air may be supplied from a hot stove outside the blast furnace 100 to the interior of the blast furnace 100 via a hot blast pipe and hot blast tuyere 10. Reducing gas may be supplied from a reducing gas supply source outside the blast furnace 100 to the interior of the blast furnace 100 via a reducing gas flow path 13 and a reducing gas outlet 13x. The coke, etc. supplied into the blast furnace 100 is combusted to generate reducing gas. The reducing gas generated by the combustion of the coke, etc., or the reducing gas supplied through the reducing gas outlet 13x reduces and melts iron oxide to obtain molten iron. The molten iron is tapped from a tap hole 102 provided at the bottom of the blast furnace 100. In this embodiment, the reducing gas is supplied to the inside of the blast furnace 100 through the reducing gas outlet 13x, and therefore the amount of solid reducing material containing carbon, such as coke, used can be reduced accordingly. ２ The amount of generated carbon dioxide can be reduced. The blast furnace 100 can have various configurations as long as it is capable of producing pig iron as described above. For example, the blast furnace 100 may have other tuyere(s), port(s), or lance(s) in addition to the above-described hot blast tuyere(s) 10. Furthermore, the above-described hot blast tuyere(s) 10 may have other ports, lances, etc. in addition to the above-described hot blast flow path 12, reducing gas flow path 13, and solid reducing material supply path 14. For example, the hot blast tuyere(s) 10 may have a solid reducing material injection lance, etc. The configuration of the blast furnace 100 other than the hot blast tuyere(s) 10 is known in the art, and therefore will not be described in detail 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 operation of the blast furnace.

[0045] The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. The present invention allows for various conditions to be adopted as long as the object is achieved without departing from the gist of the present invention. In the following examples, a case where a reducing gas consisting of only hydrogen gas is used is illustrated, but the type of reducing gas is not limited to this. In the examples shown below, the concentration of hydrogen molecules inside a blast furnace was evaluated by performing a simulation taking into account gas flow, heat transfer, and chemical reactions using the general-purpose thermal fluid analysis software FLUENT. In this simulation, the raceway region near the tuyere was treated as a cavity where no coke exists, and the coke-packed bed region in the blast furnace away from the raceway was treated as a porous medium. A standard k-ε model was used for turbulence analysis, a vortex dissipation model for gas combustion, and an O model for coke combustion. ２ , CO ２ , H ２ Field's model was used for the gasification reaction of O. In this example, the "concentration of hydrogen molecules" inside the blast furnace means the volume ratio of hydrogen molecules to the total volume of hydrogen molecules, carbon monoxide molecules, and nitrogen molecules inside the blast furnace, that is, [concentration of hydrogen molecules] = H ２ fraction / (CO fraction+N ２ Fraction + H ２ It is calculated as a fraction of the

[0046] Using simulations, the following cases were found: (1) when hydrogen gas was supplied into the hot air flow path from a hydrogen injection port that penetrates the upper wall of the tuyere body; (2) when hydrogen gas was supplied into the hot air flow path from a hydrogen injection port that penetrates the lower wall of the tuyere body; (3) when hydrogen gas was supplied into the blast furnace from a hydrogen injection port that penetrates the upper wall of the tuyere body at the tip of the tuyere body; (4) when hydrogen gas was supplied into the blast furnace from a 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 was arranged in the hot air flow path of the tuyere body and hydrogen gas was supplied from here into the hot air flow path; (6) when hydrogen gas was supplied into the blast furnace from a 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 in (1) to (5) above; (7) when the flow rate of hydrogen gas was reduced in the case of (1) above; (8) when the flow rate of hydrogen gas was reduced in the case of (5) above. (9) When hydrogen gas was supplied into the hot blast flow path from the hydrogen injection port penetrating the upper wall of the tuyere body, and when hydrogen gas was supplied into the hot blast flow path from the outlet of the hydrogen injection lance in the tuyere body (i.e., when the above (7) and (8) were combined), the concentration distribution of hydrogen molecules in the furnace radial direction at a height of 12 m from the center of the tuyere in the blast furnace was confirmed. In the above (1) to (5), the flow rate of hydrogen gas supplied from the port / lance was 2615 Nm ３ In addition, in the above (6), the flow rate of hydrogen gas supplied from the hydrogen injection port was 523 Nm ３ In the above (7), the flow rate of hydrogen gas supplied from the hydrogen injection port was 1389 Nm ３ / hr, and in the above (8), the flow rate of hydrogen gas supplied from the hydrogen injection lance is 1226 Nm ３ / hr, and in the above (9), the flow rate of hydrogen gas supplied from the hydrogen injection port is 1389 Nm ３ / hr, and the flow rate of hydrogen gas supplied from the hydrogen injection lance was 1226 Nm ３ / hr.

[0047] Fig. 10A shows the concentration distribution of hydrogen molecules in the case of (1) above, Fig. 10B shows the concentration distribution of hydrogen molecules in the case of (2) above, Fig. 10C shows the concentration distribution of hydrogen molecules in the case of (3) above, Fig. 10D shows the concentration distribution of hydrogen molecules in the case of (4) above, Fig. 10E shows the concentration distribution of hydrogen molecules in the case of (5) above, Fig. 10F shows the concentration distribution of hydrogen molecules in the case of (6) above, Fig. 10G shows the concentration distribution of hydrogen molecules in the case of (7) above, Fig. 10H shows the concentration distribution of hydrogen molecules in the case of (8) above, and Fig. 10I shows the concentration distribution of hydrogen molecules in the case of (9) above. In this example, the "molar fraction of hydrogen molecules / average molar fraction of hydrogen molecules" shown on the vertical axis of Figs. 10A to 10I means the molar fraction of hydrogen molecules at a certain position in the radial direction of the blast furnace relative to the average molar fraction of hydrogen molecules in the radial direction of the blast furnace. In this example, when the difference between the maximum and minimum values ​​of "molar fraction of hydrogen molecules / average molar fraction of hydrogen molecules" is 0.08 or more (the ratio (C ｍａｘ -C ｍｉｎ ) / C ａｖｅ When the difference is 0.08 or more, 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 has occurred), and when 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 has occurred). Here, when the difference between the maximum and minimum values ​​of "molar fraction of hydrogen molecules / average molar fraction of hydrogen molecules" is 0.08 or more, it corresponds to when the difference between the maximum and minimum concentrations of hydrogen molecules in the radial direction inside the blast furnace is 3% by volume or more.

[0048] 10A to 10F, it can be seen that the bias in the concentration distribution of hydrogen molecules within the furnace varies depending on the means and position of hydrogen gas supply. Furthermore, as shown in Figures 10G and 10H, it can be seen that the concentration distribution of hydrogen molecules within the furnace also changes depending on the flow rate of hydrogen gas supplied into the furnace. In other words, in a hot blast tuyere having multiple outlets of different types and / or different outlet positions, by changing the flow rate of hydrogen gas blown from each outlet, it is possible to arbitrarily change the concentration distribution of hydrogen molecules within the blast furnace, and it is thought that, for example, it is possible to average and homogenize the distribution of hydrogen molecules in the radial or circumferential direction within the blast furnace.

[0049] For example, when the flow rate of hydrogen gas is reduced as in (7) in the injection mode (1) above, the concentration distribution of hydrogen molecules inside the blast furnace changes from the concentration distribution shown in FIG. 10A to the concentration distribution shown in FIG. 10G. Furthermore, when the flow rate of hydrogen gas is reduced as in (8) in the injection mode (5) above, the concentration distribution of hydrogen molecules inside the blast furnace changes from the concentration distribution shown in FIG. 10E to the concentration distribution shown in FIG. 10H. Here, the shape of the concentration peak shown in FIG. 10G is upwardly convex in the middle of the furnace, while the shape of the concentration peak shown in FIG. 10H is downwardly convex in the middle of the furnace. That is, the shapes of the concentration peaks in FIG. 10G and FIG. 10H are out of phase with each other. Therefore, by combining the injection mode (7) above with the injection mode (8) above, the concentration peaks in FIG. 10G and FIG. 10H are combined, which is thought to result in the peaks canceling each other out and becoming smaller. In fact, by combining the blowing form of (7) above with the blowing form of (8) above, as in (9) above, the hydrogen gas concentration peak becomes flat as shown in Fig. 10I. As described above, by providing a plurality of reducing gas outlets in the hot blast tuyere and increasing or decreasing the flow rate of the reducing gas supplied from each reducing gas outlet, it can be said that, for example, the concentration distribution of the reducing components inside the blast furnace can be changed while maintaining the total flow rate of the reducing gas supplied inside the blast furnace.

[0050] Note that eliminating the bias in the concentration distribution of reducing components in the radial direction of the blast furnace is merely one preferred embodiment of the technology disclosed herein. It is also possible to locally increase the concentration of reducing components in a predetermined portion of the furnace in the radial direction by supplying reducing gas into the blast furnace from multiple reducing gas outlets and changing the flow rate of the reducing gas supplied from each reducing gas outlet. Furthermore, while the above example illustrates an embodiment in which the concentration distribution of reducing components in the radial direction of the blast furnace is changed, the technology disclosed herein is not limited thereto. For example, the concentration of reducing components in the circumferential direction of the blast furnace may be changed.

[0051] 100 Blast furnace 10 Hot blast tuyere 11 Tuyere body 11a Inner wall 11b Outer wall 11x Tip 12 Hot blast passage 12x Opening 13 Reducing gas passage 13x Reducing gas outlet

Claims

1. A method for operating a blast furnace, comprising: supplying hot air into the interior of the blast furnace through a hot air flow path provided in a hot air tuyere, and supplying reducing gas into the interior of the blast furnace through a reducing gas outlet provided in the hot air tuyere, wherein a plurality of the reducing gas outlets are provided in the hot air tuyere, and the method for operating a blast furnace comprises changing the flow rate of the reducing gas blown out from at least one of the reducing gas outlets.

2. A method for operating a blast furnace as set forth in claim 1, comprising: varying the flow rate of the reducing gas blown out from at least one of the reducing gas blowout ports in accordance with the concentration distribution of reducing components in the radial or circumferential direction inside the blast furnace.

3. A method for operating a blast furnace according to claim 1 or 2, comprising supplying reducing gas into the interior of the blast furnace through a plurality of reducing gas injection ports provided in the hot blast tuyere.

4. A method for operating a blast furnace according to claim 1 or 2, comprising supplying reducing gas into the interior of the blast furnace through a plurality of reducing gas injection lances provided in the hot blast tuyere.

5. A method for operating a blast furnace according to claim 1 or 2, comprising supplying reducing gas into the interior of the blast furnace through at least one reducing gas injection port and at least one reducing gas injection lance provided in the hot blast tuyere.

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