Blast furnace operation method

Abstract

To provide a blast furnace operating method capable of quickly and accurately making decision for opening a tuyere at start-up operation after a long period of blowing-stop or the like of a blast furnace.SOLUTION: A blast furnace operating method in which decision is made for opening a tuyere having been closed at a start-up operation after a long period of a blowing-stop or suspended operation of a blast furnace includes a blowing restart step of restarting blowing by opening some of the plurality of tuyeres, a temperature measurement step of measuring a temperature of the tuyeres other than the opened tuyeres, and a determination step of determining whether or not adjacent tuyeres can be opened by comparing the temperature of the tuyeres adjacent to the opened tuyeres with the temperature of the closed tuyeres other than the adjacent tuyeres.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a blast furnace operation method for determining whether to open closed tuyere holes in order to resume normal operation after a long-term shutdown or halt of the blast furnace. [Background technology]

[0002] A blast furnace is a pig iron manufacturing facility that heats up, reduces, and melts the charge (iron ore, etc.) using high-temperature reducing gas generated by the reaction of high-temperature air and oxygen blown into the furnace through a blast hole called a tuyere with the coke and pulverized coal inside the furnace, and discharges the molten iron and molten slag from the tap hole at the bottom of the tuyere. During normal operation of a blast furnace, the reaction heat inside the furnace and the heat supply from the tuyere are balanced, allowing for stable operation of the blast furnace.

[0003] When the blast furnace is shut down or stopped for a long period of time, the heat supply to the blast furnace is stopped. Meanwhile, heat radiation continues due to the temperature difference between the inside of the blast furnace and the atmosphere, so the inside of the furnace cools down and some of the molten material solidifies. Therefore, when the blast furnace is restarted, that is, when the blast furnace is restarted, it is necessary to melt the solidified layer in the furnace and heat the coke packed layer through which the solidified material passes until the molten material can pass through.

[0004] Therefore, when the blast furnace is shut down for a long period of time or when it is expected to be restarted, the coke ratio in the furnace is increased to shut down the furnace, and thermal compensation is performed until the injection of pulverized coal can be started after the blowing, and all but one or two tuyere holes on the tap hole are blocked with refractories or the like to limit the amount of molten iron and slag generated with the blowing, and a cycle of smooth discharge of a small amount of molten material is established, and then adjacent tuyere holes are opened in sequence, and the number of tuyere holes is gradually increased to restore normal operation. As another method, for example, as shown in Patent Document 1, a method has been proposed in which oxygen or oxygen and combustible gas are blown into the furnace by a hearth heating burner to burn the coke remaining in the furnace and reduce the volume of the residue in the furnace. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6947345 Summary of the Invention [Problem to be solved by the invention]

[0006] The decision to open the adjacent tuyere as described above is made based on the temperature, fluidity, composition, etc. of the molten iron and slag discharged from the tap hole below the open tuyere. However, when making a decision to open a tuyere using the above-mentioned judgment method, the molten iron and slag must be discharged to a state where sampling for temperature measurement, fluidity observation, composition analysis, etc. is possible. Even if a certain amount of molten iron and slag is discharged, there is always a lead time until the sample is taken and the analysis results are obtained. For this reason, if the above-mentioned judgment method is continued until the tuyere of the blast furnace is fully opened, the lead time for judgment materials will unnecessarily prolong the blast furnace startup period.

[0007] An object of the present invention is to propose a method of operating a blast furnace which solves the above problems and enables quick and accurate judgment as to whether to open tuyere holes when restarting the blast furnace after a long period of shutdown or the like. [Means for solving the problem]

[0008] 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 to open closed tuyere in order to resume operation after a long-term blast furnace shutdown or pause, the method comprising the following steps: a blast restart step for opening some of a plurality of tuyere to resume blast; a temperature measurement step for measuring the temperature of tuyere other than the open tuyere; and a determination step for determining whether or not to open the adjacent tuyere by comparing the temperature of the tuyere adjacent to the open tuyere with the temperature of a closed tuyere other than the adjacent tuyere.

[0009] 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 judgment step, at least one of whether (the body temperature of the adjacent tuyere / the body temperature of the blocked tuyere) is equal to or higher than a first threshold and whether (the temperature of the cooling water flowing in the adjacent tuyere / the temperature of the cooling water flowing in the blocked tuyere) is equal to or higher than a second threshold is judged, and when at least one of the first threshold and the second threshold is exceeded, it is judged that the adjacent tuyere can be opened. (3) the first threshold is 1.5 and the second threshold is 1.01; (4) in the judgment step, it is further determined whether or not an amount of iron and slag discharged from the blast furnace relative to an amount of iron and slag made in the blast furnace is equal to or greater than a predetermined ratio, and when the amount is equal to or greater than the predetermined ratio, it is determined that the adjacent tuyere can be opened; This is believed to be a more preferable solution. Effect of the Invention

[0010] According to the blast furnace operation method of the present invention, when determining whether to open the closed tuyere in order to resume operation after the blast furnace has been shut down or shut down for an extended period of time, the opening of the tuyere can be determined accurately and quickly, thereby shortening the start-up period and enabling the blast furnace to be restored as quickly as possible. [Brief description of the drawings]

[0011] [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] FIG. 2 is a schematic plan view illustrating an embodiment of a relationship between a tuyere and a tap hole in a blast furnace. [Diagram 3] FIG. 2 is a schematic diagram for explaining one embodiment of a method for measuring the tuyere temperature by the body temperature of the tuyere. [Figure 4] FIG. 2 is a schematic diagram for explaining one embodiment of a method for measuring the tuyere temperature by the temperature of cooling water flowing through the tuyere. [Diagram 5]4 is a graph for explaining an embodiment of opening a shutoff opening based on a body temperature of a tuyere according to a blast furnace operation method according to the present invention. [Figure 6] 4 is a graph for explaining an embodiment in which a shutoff opening is opened based on the temperature of cooling water flowing in a tuyere according to a blast furnace operation method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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.

[0013] 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 shut down 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 shut down the blast furnace. After that, hot air is gradually blown from the tuyere to return the blast furnace to normal operation. One embodiment of the present invention is directed to the process of gradually blowing hot air from the tuyere to return the blast furnace to normal operation.

[0014] In the blast furnace operation method according to one embodiment of the present invention, the following steps are sequentially performed: a restarting step of opening some of the multiple tuyere to restart the blast, a temperature measuring step of measuring the temperature of the tuyere other than the opened tuyere, and a judgment step of judging whether the adjacent tuyere can be opened by comparing the temperature of the tuyere adjacent to the opened tuyere with the temperature of the blocked tuyere other than the adjacent tuyere. In addition to the judgment step, it is preferable to perform an additional judgment step of judging whether the amount of slag discharged from the blast furnace relative to the amount of slag made in the blast furnace is equal to or greater than a predetermined ratio, and judging that the adjacent tuyere can be opened if the amount is equal to or greater than the predetermined ratio. The restarting step, the temperature measuring step, the judgment step, and the additional judgment step will be described in detail below, and the subsequent steps when it is judged possible to open the adjacent tuyere according to the present invention will also be described.

[0015] <About the airflow restart process> Fig. 2 is a schematic plan view for explaining one embodiment of the relationship between tuyere and tap hole in a blast furnace. In the embodiment shown in Fig. 2, tuyere Nos. 1 to 41 are provided in the circumferential direction of the blast furnace. And, tap holes 1 to 4 are provided below the tuyere and at the positions shown in Fig. 2 relative to tuyere Nos. 1 to 41.

[0016] In one embodiment of the air blowing restart step according to the blast furnace operation method of the present invention, in the relationship between the tuyere and the tap hole shown in Fig. 2, all of the tuyere are closed, and then some (for example, four) tuyere Nos. 1 to 4 are opened to restart the air blowing into the furnace. The tuyere that is opened first is preferably the tuyere (here, tuyere Nos. 1 to 4) located above the tap hole (here, tap hole 1) as shown in Fig. 2.

[0017] <About the temperature measurement process> In one embodiment of the temperature measurement process related to the blast furnace operation method of the present invention, following the above-mentioned air blowing resumption process, the temperatures of the tuyere other than the tuyere opened in the above-mentioned air blowing resumption process (all tuyere other than tuyere Nos. 1 to 4) are measured (monitored).

[0018] 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.

[0019] <About the evaluation process> In the judgment step according to one embodiment of the blast furnace operation method of the present invention, following the temperature measurement step, the temperature (at least one of the tuyere body temperature and the cooling water temperature) of a tuyere adjacent to the open tuyere (here, the fifth tuyere No. 5) is compared with the temperature (at least one of the tuyere body temperature and the cooling water temperature) of a blocked tuyere other than the adjacent tuyere to judge whether it is equal to or higher than a threshold value. Hereinafter, a detailed description of one embodiment of the judgment step according to the blast furnace operation method of the present invention and a specific example of the threshold value will be given.

[0020] During a long period of time when the blast furnace is not blowing air or is shut down, the inside of the furnace cools down and the coke near the tip of the tuyere solidifies. In this case, even if the tuyere is opened and blowing air is resumed, the coke inside the furnace does not move, so the blowing air does not pass through, and only the solidified material near the tuyere melts, which may cause the tuyere to melt.

[0021] In this embodiment, by opening some of the tuyere (tuyere Nos. 1 to 4) in the above-mentioned air blowing restart step to restart the air blowing into the furnace, the temperature in the furnace rises in sequence from the periphery of some of the open tuyere. Then, the temperature of the tuyere adjacent to the open tuyere, i.e., the opening judgment tuyere (the fifth tuyere No. 5) which judges whether to open in this embodiment, gradually rises due to heat transfer from the adjacent tuyere (tuyere No. 4). Note that here, for the sake of simplicity, only tuyere No. 5 is used as the opening judgment tuyere, but tuyere No. 41 adjacent to the open tuyere No. 1 can also be judged in the same way.

[0022] On the other hand, the temperature of blocked tuyere other than the adjacent tuyere (blocked tuyere Nos. 6 to 40: tuyere No. 41 is the same as the opening judgment tuyere (tuyere No. 5)) is not affected by heat transfer and hardly rises. Therefore, by comparing the temperature (at least one of the tuyere body temperature and the cooling water temperature) of the adjacent tuyere (the fifth tuyere No. 5) with the temperature (at least one of the tuyere body temperature and the cooling water temperature) of the blocked tuyere other than the adjacent tuyere, it is possible to determine whether or not to open the adjacent tuyere (here, tuyere No. 5).

[0023] Here, "the temperature of blocked tuyere other than adjacent tuyere" refers to the average temperature of the temperatures of the open tuyere (tuyere Nos. 1 to 4 here) and the multiple blocked tuyere (here tuyere Nos. 6 to 40) other than the adjacent tuyere (tuyere Nos. 5 and 41 here).While it is possible to determine whether or not a tuyere can be opened by comparing at least one of the tuyere body temperature and the cooling water temperature, it is possible to more accurately determine whether or not a tuyere can be opened by comparing both.

[0024] An example of the relationship between the tuyere body temperature (embedding temperature) and the cooling water temperature (discharge temperature) actually recorded in the temperature measurement process is shown below. FIG. 5 is a graph showing the change in (opening judgment tuyere embedding temperature (A) / blocked tuyere embedding temperature other than the relevant tuyere (B)) when determining whether to open each of the tuyere Nos. 5 to 8. FIG. 6 is a graph showing the change in (opening judgment tuyere cooling water discharge temperature (C) / blocked tuyere cooling water discharge temperature other than the relevant tuyere (D)) when determining whether to open each of the tuyere Nos. 5 to 8. In the graphs shown in FIG. 5 and FIG. 6, each of the tuyere Nos. 5 to 8 is opened at the time when A / B and C / D rise sharply. In other words, adjacent tuyere Nos. 5, 6, 7, and 8 are opened in sequence.

[0025] When A / B and C / D are equal to or greater than a predetermined first threshold and a predetermined second threshold, respectively, it can be determined that the inside of the blast furnace of the opening judgment tuyere (here, tuyere No. 5 to 8) is in a healthy state, i.e., the solidified material has melted, the coke can move, and air can pass through the tuyere, and it can be determined that the tuyere can be opened.

[0026] From the graphs of FIG. 5 and FIG. 6, it can be seen that when the value of A / B is less than 1.5 and the value of C / D is less than 1.01, the temperature rise of the opening judgment tuyere is not sufficient. Therefore, for example, it is preferable to set the threshold value to 1.5 (first threshold value) for A / B and 1.01 (second threshold value) for C / D. Note that it is sufficient to exceed the above threshold value (first threshold value and second threshold value) even once, and it is judged that "the opening of the tuyere is possible" even if it falls below the threshold value after exceeding the threshold value. In this embodiment, if at least one of the following is satisfied: the opening judgment tuyere embedding temperature A is 1.5 times or more the blocked tuyere embedding temperature B, and the opening judgment tuyere cooling water drainage temperature C is 1.01 times or more the blocked tuyere cooling water drainage temperature D, it is possible to judge that the melting of the solidified matter inside the tuyere is sufficient.

[0027] <Additional Judgment Process> In one embodiment of the additional judgment process related to the blast furnace operation method of the present invention, a process that is preferably added to the above judgment process is to check the discharge state of molten metal and slag from the blast furnace when the tuyere temperature is judged to be above a threshold value in the above judgment process, and to judge whether the ratio of the amount of molten metal and slag made in the blast furnace to the amount of metal and slag tapped from the blast furnace is above a predetermined ratio, and if it is above the predetermined ratio, to open an adjacent tuyere.

[0028] When the number of tuyere openings is increased, the amount of air blown into the blast furnace also increases, and the amount of molten iron and slag produced in the blast furnace increases. In this case, if the molten material tends to accumulate in the blast furnace, the molten material will continue to accumulate in the blast furnace. Therefore, if the opening of the tuyere is determined in the above-mentioned judgment process based only on the state of the tuyere tip, there is a possibility that the molten material will continue to accumulate in the blast furnace. For this reason, in this embodiment, when the temperature of the tuyere is determined to be equal to or higher than the threshold value in the above-mentioned judgment process, it is preferable to further check the discharge state of the molten iron and slag from the blast furnace.

[0029] Specifically, in one embodiment of this additional judgment step, the ratio of the "amount of tapped slag" which is the amount of molten metal and slag discharged outside the blast furnace to the "amount of slag produced in the blast furnace" is calculated, and it is judged whether or not the ratio is equal to or greater than a predetermined ratio. Here, if the ratio of the amount of tapped slag to the amount of slag produced is, for example, less than 50%, the amount of molten material discharged is too small, so the "predetermined ratio" is preferably 50%, and more preferably 80%. Note that in this embodiment, it is judged that the tuyere can be opened when the ratio of the amount of tapped slag to the amount of slag produced exceeds 100%. The above judgment is preferably performed for each tapping operation.

[0030] When calculating the ratio, the "amount of iron and slag produced" can be calculated from operating conditions such as the blast flow rate and coke ratio, and the "amount of iron and slag discharged" can be determined by measuring the amount of iron and slag discharged, for example, using a sensor installed downstream of the tap hole.

[0031] <About the process after that> The above-mentioned air flow resumption process, temperature measurement process, judgment process, preferably the additional judgment process are performed, and after tuyere No. 5 has been opened, the temperature measurement process, judgment process, preferably the additional judgment process are repeatedly performed for the sixth (tuyere No. 6) and subsequent blocked tuyere(s), opening them in order, until finally all tuyere(s) are opened. [Explanation of symbols]

[0032] 11 Tuyere 12 Tip embedded thermometer 13 Tuyere cooling water 14 Water supply header 15 Feed water thermometer 16 Drainage thermometer 17 Drainage trough

Claims

1. A blast furnace operation method for determining whether to open a closed tuyere in order to resume operation after a long-term shutdown or halt of the blast furnace, comprising: a blowing restart process of opening some of the multiple tuyere openings to restart blowing; a temperature measuring step of measuring the temperature of the tuyere other than the opened tuyere; a determining step of determining whether or not the adjacent tuyere is opened by comparing a temperature of the tuyere adjacent to the opened tuyere with a temperature of a blocked tuyere other than the adjacent tuyere; having 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, In the judgment step, at least one of whether (the body temperature of the adjacent tuyere / the body temperature of the blocked tuyere) is equal to or higher than a first threshold value and whether (the temperature of the cooling water flowing in the adjacent tuyere / the temperature of the cooling water flowing in the blocked tuyere) is equal to or higher than a second threshold value is judged, and when at least one of the first threshold value and the second threshold value is exceeded, it is judged that the adjacent tuyere can be opened; The first threshold is 1.5 and the second threshold is 1.

01. Blast furnace operating methods.

2. 2. The blast furnace operating method according to claim 1, wherein the determination step further comprises determining whether an amount of slag tapped from the blast furnace relative to an amount of slag made in the blast furnace is equal to or greater than a predetermined ratio, and determining that the adjacent tuyere can be opened if the amount is equal to or greater than the predetermined ratio.

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