Blast furnace operation method

Abstract

To provide a blast furnace operation method capable of accurately determining a long-time wind rest of a blast furnace and leakage of wind from a closed tuyere during the rest before starting the blast furnace.SOLUTION: A blast furnace operation method for determining leakage of a blocked tuyere while the blast furnace is in a long-term wind rest or in a state of rest comprises: a blast restart preparation step in which hot air is introduced into a blast branch pipe while the tuyere is blocked; a temperature measurement step in which the temperature of the tuyere is measured; and a wind leakage determination step in which the presence / absence of wind leakage of the tuyere is determined based on the measured temperature of the tuyere. Preferably, the temperature of the tuyere is at least one of the body temperature of the tuyere and the temperature of the cooling water flowing through the tuyere.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a blast furnace operation method for determining air leakage from a blocked tuyere during a long-term shutdown or halt of the blast furnace. [Background technology]

[0002] In blast furnace operations, short blast shutdowns are scheduled periodically to allow for equipment repairs. However, when major equipment repairs are required due to a problem, or when the blast furnace is in poor condition and the molten iron temperature drops significantly, causing the blast furnace to cool down, a long-term blast shutdown may be necessary. In addition, long-term shutdowns may be unavoidable in order to adjust the blast furnace's iron output.

[0003] After a regularly scheduled short-term shutdown, all blast tuyeres are opened to start up the blast furnace. In contrast, during a long shutdown or halt, the flow path of the molten pig iron and slag connecting each blast tuyeres and the tap hole may not be secured due to solidification of the molten pig iron and slag caused by a drop in temperature. In such a case, if all blast tuyeres are fully opened to blow in hot air and generate molten pig iron and slag in front of each blast tuyeres, the generated molten pig iron and slag will not flow down to the tap hole but will remain below the front of the blast tuyeres, and the blast tuyeres themselves will come into direct contact with the molten pig iron and slag. Each blast tuyeres is usually cooled by a high-speed water flow, but if they come into direct contact with the molten pig iron and slag, they may melt.

[0004] For this reason, during long periods of blasting or shutdown, it is necessary to suppress the generation of large amounts of molten iron and slag due to the blowing of hot air from the many blast tuyeres. For this reason, except for the 3-4 blast tuyeres directly above the tap hole, the remaining blast tuyeres are filled with refractory material to shield them, and the blowing of hot air from all but the 3-4 blast tuyeres directly above the tap hole is stopped, suppressing the generation of large amounts of molten iron and slag while starting up the blast furnace.

[0005] If the shielding by the refractory in the tuyere during a long time of shutdown or halt is insufficient, air leakage into the furnace occurs after the blast furnace is started up, the tuyere comes into contact with the molten material, the tuyere is damaged, and a shutdown is required to replace the tuyere. Therefore, it is necessary to reliably detect air leakage between the tuyere and the blocking refractory during a long time of shutdown or halt before starting up the blast furnace. As an example of a technology for determining air leakage from a blocked tuyere during a blast furnace shutdown, Patent Document 1 discloses a technology for detecting air leakage between the joint between the blower branch pipe and the tuyere. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2001-262210 A Summary of the Invention [Problem to be solved by the invention]

[0007] The technology described in Patent Document 1, which detects air leakage between the joint between the blower branch pipe and the tuyere, can detect air leakage from the tuyere to some extent. However, it cannot detect air leakage between the tuyere and the blocking refractory, and therefore it is not possible to accurately judge air leakage from the tuyere.

[0008] An object of the present invention is to solve the above problems and to propose a blast furnace operation method that can accurately determine air leakage from blocked tuyere during a long period of blast furnace shutdown or shutdown before starting up the blast furnace. [Means for solving the problem]

[0009] The blast furnace operation method of the present invention was developed to solve the above-mentioned problems, and is a blast furnace operation method for determining whether there is air leakage from a blocked tuyere when the blast furnace is shut down or down for a long period of time, and includes the following steps: a blast resumption preparation step for introducing hot air into the blast branch pipe while keeping the tuyere blocked; a temperature measurement step for measuring the temperature of the tuyere; and an air leakage determination step for determining whether or not there is air leakage from the tuyere based on the measured tuyere temperature.

[0010] In the blast furnace operation method according to the present invention configured as described above, (1) The temperature of the tuyere is at least one of the temperature of the main body of the tuyere and the temperature of the cooling water flowing through the tuyere; (2) In the air leakage determination step, when the tuyere temperature measured at a predetermined time interval is higher than the previous tuyere temperature or the tuyere temperature before the air blowing restart preparation step by a certain temperature range or more, the tuyere is determined to have air leakage; (3) in the air leakage determination step, when the tuyere temperature measured at a predetermined time interval is higher than the average temperature of the other tuyere by a certain temperature range or more, the tuyere is determined to have air leakage; (4) the air leakage determination step includes a step of comparing the temperatures of at least two tuyere to identify a tuyere that is not leaking air, and a step of determining the presence or absence of air leakage from the one tuyere by comparing the temperature of the identified tuyere with the temperature of any one tuyere other than the identified tuyere; (5) In the identifying step, when the ratios of the temperatures A and B of the two tuyere, A / B and B / A, are both 0.90 to 1.1, both tuyere are identified as tuyere without air leakage; (6) the judgment step judges at least one of whether (the body temperature of the one arbitrary tuyere / the average value of the body temperatures of the identified tuyere) is equal to or higher than a first threshold value and whether (the temperature of the cooling water flowing in the one arbitrary tuyere / the average value of the temperature of the cooling water flowing in the identified tuyere) is equal to or higher than a second threshold value, and judges that the one arbitrary blocked tuyere has leaked air when at least one of the first threshold value and the second threshold value is exceeded; (7) in the determination step, the first threshold value is set to 1.10 and the second threshold value is set to 1.010; (8) the judgment step judges at least one of whether (the body temperature of the one arbitrary tuyere - the average value of the body temperatures of the identified tuyere) is equal to or higher than a third threshold value, and whether (the temperature of the cooling water flowing in the one arbitrary tuyere - the average value of the temperature of the cooling water flowing in the identified tuyere) is equal to or higher than a fourth threshold value, and judges that the one arbitrary blocked tuyere has leaked air when at least one of the third threshold value and the fourth threshold value is exceeded; (9) in the determination step, the third threshold value is set to 3°C and the fourth threshold value is set to 0.3°C; This is believed to be a more preferable solution. Effect of the Invention

[0011] According to the blast furnace operation method of the present invention, air leakage from blocked tuyere during a long period of blast furnace shutdown or outage can be accurately detected before the blast furnace is started up. Tuyere where air leakage has been confirmed can be blocked by filling it with new refractory material, thereby improving the blocking ability of the tuyere. As a result, the blocking ability of blocked tuyere other than the open tuyere is ensured at the time of blast furnace startup, so that the blast furnace can be started up smoothly without melting the tuyere. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic vertical cross-sectional view showing a part of a cross section of a furnace body of a blast furnace. [Diagram 2] 13(a) to 13(d) are schematic diagrams illustrating the air blowing restart preparation step. [Diagram 3] FIG. 4 is a schematic diagram showing the temperature of the main body of the tuyere in the temperature measurement process. [Figure 4] FIG. 4 is a schematic diagram showing the cooling water temperature of the tuyere in the temperature measurement process. [Diagram 5] 1(a) to 1(d) are diagrams for explaining a first embodiment of an air leakage determination step. [Figure 6] 13(a) and 13(b) are diagrams for explaining a second embodiment of the air leakage determination step. [Figure 7] FIG. 11 is a diagram showing a transition of hot air temperature from a hot air stove in a third embodiment of the air leakage determination process. [Figure 8] FIG. 13 is a diagram showing that a tuyere without air leakage has been identified in the third embodiment of the air leakage determination step. [Figure 9] FIG. 13 is a diagram showing that air leakage from a tuyere has been determined in a third embodiment of the air leakage determination step. [Figure 10]FIG. 11 is a diagram showing a transition of hot air temperature from a hot air stove in a third embodiment of the air leakage determination process. [Figure 11] FIG. 13 is a diagram showing that a tuyere without air leakage has been identified in the third embodiment of the air leakage determination step. [Figure 12] FIG. 13 is a diagram showing that air leakage from a tuyere has been determined in a third embodiment of the air leakage determination step. [Figure 13] 13(a) and 13(b) are diagrams showing that air leakage from a tuyere has been determined in a fourth embodiment of the air leakage determination step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments of the present invention will be described in detail. Note that the following embodiments are merely examples of devices and methods for embodying the technical ideas of the present invention, and are not intended to limit the configuration to those described below. In other words, the technical ideas of the present invention can be modified in various ways within the technical scope described in the claims.

[0014] FIG. 1 is a schematic vertical cross-sectional view showing a part of the cross section of the furnace body of a blast furnace. In the embodiment shown in FIG. 1, when the blast furnace is suspended for a long period of time, the height of the surface of the raw material (coke packed layer) filled directly above the tuyere in the blast furnace is reduced below the upper end of the morning glory part of the blast furnace to suspend the blast. During the suspension of the blast, all tuyere in the blast furnace are filled with blocking refractory material to block the tuyere. After that, hot air is introduced into the blast branch pipe while all tuyere are blocked, and preparations are made to resume blast. After that, hot air is gradually blown from a specified tuyere to return the blast furnace to normal operation. One embodiment of the present invention is directed to a process of introducing hot air into the blast branch pipe while blocking the tuyere, and preparing to resume blast.

[0015] In a blast furnace operation method according to one embodiment of the present invention, a preparation process for resuming airflow is carried out in which hot air is introduced into the air blow branch pipe while the tuyere is kept blocked, a temperature measurement process in which the temperature of the tuyere is measured, and an air leakage determination process in which the presence or absence of air leakage from the tuyere is determined based on the measured tuyere temperature.

[0016] By applying the above-mentioned leakage determination process to all tuyere, it is possible to identify the tuyere that is leaking before re-blowing the blast furnace. For the tuyere where leakage has been confirmed, additional blocking refractory is added or the blocking refractory is removed and then newly filled with blocking refractory to improve the blocking performance, and then the blast furnace is re-blowing. The blowing restart preparation process, temperature measurement process, and leakage determination process are described below.

[0017] <About the preparation process for restarting ventilation> 2(a)-(d) are schematic diagrams for explaining the preparation process for restarting blasting. In the diagrams, 21 is a sight glass provided at the rear end of the blast branch pipe 5. FIG. 2(a) shows the flow of hot air during normal operation, not during blasting suspension, and hot air from a hot stove (not shown) is supplied to the inside of the blast furnace from the tuyere 3 through the annular pipe 6 and the blast branch pipe 5. When blasting suspension is performed in the blast furnace, first, as shown in FIG. 2(b), the tuyere 3 is blocked with an unshaped refractory material 22 (e.g., castable). Next, as shown in FIG. 2(c), the sight glass 21 provided at the rear end of the blast branch pipe 5 is opened. Next, with the sight glass 21 open as shown in FIG. 2(c), hot air from the hot stove is supplied to the annular pipe 6 and the blast branch pipe 5 as shown in FIG. 2(d). The temperature of the hot stove is adjusted to 100°C or higher and 900°C or lower.

[0018] 2(d) described above, the tuyere 3 is blocked with the monolithic refractory 22 and the sight window 21 provided at the rear end of the blast branch pipe 5 is in an open state, so that the supplied hot air is discharged outside the furnace through the sight window 21 of the blast branch pipe 5. Note that, although air is discharged from the sight window 21 at the rear end of the blast branch pipe 5 here, this is not limiting, and a valve may be provided in the piping system at a position close to the blast furnace to enable air discharge, or a piping route through which air can be discharged may be newly installed.

[0019] <About the temperature measurement process> In one embodiment of the temperature measuring step according to the blast furnace operation method of the present invention, following the above-mentioned air blow resumption preparation step, the temperatures of all the blocked tuyere are measured (monitored).

[0020] In this embodiment, as the "tuyere temperature", both the "tuyere body temperature (embedded temperature)" and the "temperature of cooling water flowing in the tuyere" are measured (monitored). As for the body temperature of the tuyere 11, as shown in FIG. 3, the body temperature of each tuyere 11 is measured by a tip-embedded thermometer 12 provided at the tip (inside the furnace) of each tuyere 11. As for the temperature of the tuyere cooling water 13 flowing in the tuyere 11, as shown in FIG. 4, the temperature of the tuyere cooling water (drainage) 13 after flowing in the tuyere 11 is measured by a drainage thermometer 16 provided outside the blast furnace for measuring the temperature of the tuyere cooling water 13. The measured body temperature of the tuyere 11 and the cooling water temperature are recorded as time-series data in a recording device outside the blast furnace. In FIG. 4, 14 is a feedwater header, 15 is a feedwater thermometer, and 17 is a drainage trough.

[0021] <About the air leak determination process> In the air leakage determination step according to the blast furnace operation method of the present invention, the presence or absence of air leakage from the tuyere is determined based on the temperature of the tuyere obtained in the temperature measurement step. Hereinafter, first to fourth embodiments of the air leakage determination step will be described separately.

[0022] <First embodiment of air leakage determination process> 5(a) to 5(d) are diagrams for explaining a first embodiment of the air leakage determination step. In the first embodiment of the air leakage determination step, following the temperature determination step, if the tuyere temperature measured at a predetermined time interval is higher than the previous tuyere temperature by a certain temperature range or more, or if the tuyere temperature measured at a predetermined time interval is higher than the tuyere temperature before the start of hot air supply from the hot stove by a certain temperature range or more, the tuyere is determined to have air leakage.

[0023] Specifically, for each tuyere, based on the tuyere temperature Ttr measured at a specified time interval T, if the measured Ttr is less than a certain temperature range ΔT above the previously measured Ttp (as in Fig. 5(a)), that tuyere is judged to have "no air leakage." For each tuyere, based on the tuyere temperature Ttr measured at a specified time interval T, if the measured Ttr is more than a certain temperature range ΔT above the previously measured Ttp (as in Fig. 5(b)), that tuyere is judged to have "air leakage" at that point in time.

[0024] For example, the change in the body temperature Ttr of each tuyere is monitored every 15 minutes from the start of hot air supply from the hot stove, and if Ttr becomes 3°C or more higher than the previous Ttp, that tuyere is judged to have "an air leak" at that point. Also, the change in the cooling water temperature Ttr of each tuyere is monitored every 15 minutes from the start of hot air supply from the hot stove, and if Ttr becomes 0.3°C or more higher than the previous Ttp, that tuyere is judged to have "an air leak" at that point.

[0025] Alternatively, for each tuyere, based on the tuyere temperature Ttr measured at a specified time interval T, if the measured Ttr is less than a certain temperature range ΔT above the tuyere temperature Tti before the start of hot air supply from the hot stove (as in Figure 5(c)), that tuyere is judged to have "air leakage" at that time. For each tuyere, based on the tuyere temperature Ttr measured at a specified time interval T, if the measured Ttr is more than a certain temperature range ΔT above the tuyere temperature Tti before the start of hot air supply from the hot stove (as in Figure 5(d)), that tuyere is judged to have "air leakage" at that time.

[0026] For example, the change in the body temperature Ttr of each tuyere is monitored every minute from the start of hot air supply from the hot stove, and if Ttr becomes 10°C or more higher than the body temperature Tti of the tuyere before the start of hot air supply from the hot stove, that tuyere is judged to have "air leakage" at that point. Also, the change in the cooling water temperature Ttr of each tuyere is monitored every minute from the start of hot air supply from the hot stove, and if Ttr becomes 3°C or more higher than the body temperature Tti of the tuyere before the start of hot air supply, that tuyere is judged to have "air leakage" at that point.

[0027] <Second embodiment of air leakage determination process> 6(a) and 6(b) are diagrams for explaining a second embodiment of the air leakage judgment process. In the second embodiment of the air leakage judgment process, following the temperature judgment process, when the tuyere temperature measured at a predetermined time interval is higher than the average temperature of the other tuyere by a certain temperature range or more, the tuyere is judged to have air leakage. Specifically, when the measured Ttr is less than a certain temperature range ΔT higher than the average temperature Tta of the other tuyere based on the tuyere temperature Ttr measured at a predetermined time interval T (as in FIG. 6(a)), the tuyere is judged to have "no air leakage". When the measured Ttr is more than a certain temperature range ΔT higher than the average temperature Tta of the other tuyere based on the tuyere temperature Ttr measured at a predetermined time interval T (as in FIG. 6(b)), the tuyere is judged to have "air leakage" at that time.

[0028] For example, the change in the body temperature Ttr of each tuyere is monitored at one-minute intervals from the start of hot air supply from the hot stove, and if Ttr becomes 3°C or more higher than the average temperature Tta of the other tuyere, that tuyere is judged to have "an air leak" at that point. Also, the change in the cooling water temperature Ttr of each tuyere is monitored every minute from the start of hot air supply from the hot stove, and if Ttr becomes 0.3°C or more higher than the average temperature Tta of the other tuyere, that tuyere is judged to have "an air leak" at that point.

[0029] <Third embodiment of the air leakage determination process> In a third embodiment of the air leakage determination process, following the temperature measurement process, the following identification process and determination process are carried out based on the obtained tuyere temperature. First, in the identification process, the temperatures of at least two tuyere are compared to identify tuyere with "no air leakage". Next, in the determination process, the temperature of any tuyere other than the identified tuyere is compared using a value obtained by dividing the temperature of the identified tuyere by the average temperature, and it is determined whether the divided value is equal to or greater than a threshold value. This determines whether the tuyere has "no air leakage" or "air leakage".

[0030] The identification process and the judgment process using the tuyere body temperature are described below. When there is no air leakage from the tuyere, the effect of the hot air temperature from the hot stove on the tuyere body temperature is limited to the effect of heat transfer from the piping and the refractory material blocking the tuyere. Therefore, when there is no air leakage from the tuyere, the temperature change of the tuyere body after the start of hot air supply from the hot stove is a limited fluctuation. Therefore, the inventors selected any two tuyere out of the tuyere in which no air leakage was confirmed, and investigated the transition of the ratio of the tuyere body temperature after the start of hot air supply from the hot stove, and found that it was within the range of 0.90 to 1.10.

[0031] On the other hand, when there is air leakage from the tuyere, the body temperature of the tuyere is significantly affected by the hot air temperature from the hot stove. The inventors investigated the change in the body temperature of a tuyere where air leakage was confirmed divided by the body temperature of a tuyere where no air leakage was confirmed after the start of hot air supply from the hot stove and found that the value exceeded 1.10.

[0032] As an example, Figures 7 and 8 show the change in the hot air temperature from the hot stove and the change in the ratio of the body temperatures of tuyere A and tuyere B, respectively. The change in the ratio of the body temperatures of tuyere A and tuyere B was between 0.90 and 1.10, and tuyere A and tuyere B were identified as tuyere without air leakage.

[0033] Meanwhile, Figure 9 shows the trend in the value obtained by dividing the body temperature of tuyere C, D, and E by the average body temperature of tuyere A and B, where no air leakage was confirmed. The value obtained by dividing the body temperature of tuyere C, D, and E by the average body temperature of tuyere A and B changes in accordance with the rise in the hot air temperature from the hot stove, and as it exceeded the first threshold value TH1 of 1.10, it was found that air was leaking from tuyere C, D, and E. As a result, tuyere C, D, and E were determined to be tuyere with "air leakage."

[0034] The identification step and the determination step using the tuyere cooling water temperature are described below. When there is no air leakage from the tuyere, the effect of the hot air temperature from the hot stove on the tuyere cooling water temperature is limited to the effect of heat transfer from the piping and the refractory material blocking the tuyere. Therefore, when there is no air leakage from the tuyere, the change in the tuyere cooling water temperature after the start of hot air supply from the hot stove is a limited fluctuation. Therefore, the inventors selected any two tuyere out of the tuyere in which no air leakage was confirmed, and investigated the transition of the ratio of the tuyere cooling water temperature after the start of hot air supply from the hot stove, and found that it was within the range of 0.990 to 1.010.

[0035] On the other hand, when there is air leakage from the tuyere, the temperature of the cooling water at the tuyere is significantly affected by the temperature of the hot air from the hot stove. The inventors investigated the transition of the body temperature of a tuyere where air leakage was confirmed divided by the cooling water temperature of a tuyere where no air leakage was confirmed after the start of hot air supply from the hot stove and found that the value exceeded 1.010.

[0036] As an example, the transition of the hot air temperature from the hot stove and the transition of the ratio of the cooling water temperatures of tuyere F and tuyere G are shown in Figures 10 and 11, respectively. The transition of the ratio of the cooling water temperatures of tuyere F and tuyere G was between 0.990 and 1.010, and tuyere F and tuyere G were identified as tuyere with no air leakage.

[0037] Meanwhile, Fig. 12 shows the transition of the cooling water temperature of tuyere H divided by the average value of the cooling water temperatures of tuyere F and G, where no air leakage was confirmed. Since it exceeded the second threshold value TH2 of 1.010, it was found that air was leaking from tuyere H. As a result, tuyere H was determined to be a tuyere with "air leakage."

[0038] <Fourth embodiment of the air leakage determination process> In a fourth embodiment of the air leakage determination process, following the temperature measurement process, the following identification process and determination process are carried out based on the obtained tuyere temperature. First, in the identification process, the temperatures of at least two tuyere are compared to identify a tuyere with "no air leakage". Next, in the determination process, the temperature of any tuyere other than the identified tuyere is compared with the difference between the average temperature of the identified tuyere, and it is determined whether the difference is equal to or greater than a threshold value. This determines whether the tuyere has "no air leakage" or "air leakage". The specific identification process and determination process in the fourth embodiment are the same as those in the third embodiment described above, except that the "divided value" used for comparison in the determination process is the "difference value".

[0039] Figure 13(a) shows the transition of the difference between the body temperature of tuyere C, D, E and the average body temperature of tuyere A and B where no air leakage was confirmed. The difference between the body temperature of tuyere C, D, E and the average body temperature of tuyere A and B transitions in accordance with the rise in the hot air temperature from the hot stove, and since it exceeds the third threshold value TH3 of 3°C, it is found that air is leaking from tuyere C, D, E. As a result, tuyere C, D, E are judged as tuyere with "air leakage". Figure 13(b) shows the transition of the difference between the cooling water temperature of tuyere H and the average cooling water temperature of tuyere F and G where no air leakage was confirmed. Since it exceeds the fourth threshold value TH4 of 0.3°C, it is found that air is leaking from tuyere H. As a result, tuyere H is judged as a tuyere with "air leakage".

[0040] <Subsequent process> The above-mentioned blast restart process, temperature measurement process, and leakage determination process are performed, and for any tuyere where leakage is confirmed, additional blocking refractory is packed into the tuyere, or the blocking refractory is removed and then the tuyere is blocked by newly packing the blocking refractory into the tuyere. Then, blast furnace blast is resumed. After the opening of the multiple tuyere directly above the tap hole, the adjacent tuyere is opened in sequence, until all tuyere are opened.

[0041] After the blast furnace is re-ventilated, the tuyere is monitored through the observation window, and if the refractory of the tuyere away from the open tuyere has disappeared, exposing the coke inside the furnace, the blast furnace is immediately stopped, and the tuyere is blocked by filling it with new refractory before being re-ventilated. [Explanation of symbols]

[0042] 3 Tuyere 5 Air branch pipe 6 Circular pipe 11 Tuyere 12 Tip embedded thermometer 13 Tuyere cooling water 14 Water supply header 15 Feed water thermometer 16 Drainage thermometer 17 Drainage trough 21 Peephole 22 Monolithic refractories

Claims

1. A blast furnace operation method for determining whether or not there is air leakage from a blocked tuyere when the blast furnace is shut down or suspended for an extended period of time, the method comprising: a blowing restart preparation step for introducing hot air into a blowing branch pipe while keeping the tuyere blocked; a temperature measurement step for measuring the temperature of the tuyere; and an air leakage determination step for determining whether or not there is air leakage from the tuyere based on the measured tuyere temperature, wherein in the air leakage determination step, if the tuyere temperature measured at a specified time interval for each tuyere is higher by a certain temperature range or more than the previous tuyere temperature or the tuyere temperature before the blowing restart preparation step, the tuyere is determined to have air leakage.

2. A blast furnace operation method for determining whether or not there is air leakage from a blocked tuyere when the blast furnace is shut down or down for an extended period of time, the method comprising: a preparation step for resuming air flow in which hot air is introduced into a blower branch pipe while the tuyere remains blocked; a temperature measurement step in which the temperature of the tuyere is measured; and an air leakage determination step in which the presence or absence of air leakage from the tuyere is determined based on the measured tuyere temperature, wherein in the air leakage determination step, if the tuyere temperature measured at a specified time interval for each tuyere is higher than the average temperature of the other tuyere by a certain temperature range or more, the blast furnace operation method determines that that tuyere has air leakage.

3. The blast furnace operating method according to claim 1 or 2, wherein the temperature of the tuyere is at least one of a body temperature of the tuyere and a temperature of cooling water flowing through the tuyere.

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