How to start up a blast furnace after a period of blast shutdown.

Abstract

To provide a method for starting up a blast furnace after a wind break capable of determining an optimum tap hole as a tap hole to be opened in starting up after a wind break such as banking of a blast furnace.SOLUTION: In a method for starting up a blast furnace after a wind break, the temperature is measured by a temperature sensor provided in a hole opening bit of a hole opening machine during a hole opening operation in which the tap hole is opened by the hole opening machine, and it is determined whether the tap hole during the hole opening operation is opened as a tap hole for performing tapping at the time of starting up the blast furnace after a wind break, based on whether the measured temperature of the temperature sensor reaches a predetermined temperature.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for starting up a blast furnace after a stoppage of blowing such as banking.

Background Art

[0002] As a method for starting up a blast furnace after a stoppage of blowing, for example, in Patent Document 1, when heating and raising the temperature by blowing combustible gas and oxygen from the tapping hole into the charged materials and residues existing in a low-temperature state or a solidified state at the bottom of the blast furnace hearth, (a) the gas in the furnace is collected from the tuyere and the CO2 concentration is measured, and (b) according to the CO2 concentration, the blown gas is switched to either (b1) combustible gas and oxygen, or (b2) oxygen only, and blown in. A method for raising the temperature of the charged materials and residues at the bottom of the blast furnace is disclosed.

[0003] In Patent Document 2, for the furnace center angle θ of the tapping hole for blowing oxygen gas and gaseous fuel, in the regions of 30 to 90° respectively in the clockwise and counterclockwise directions, the temperature in front of the tuyere is measured, and the blowing into the blast furnace is started when the measured temperature in front of the tuyere exceeds 1000°C. A method is disclosed.

[0004] In Patent Document 3, a burner is inserted from the tapping hole and combustible gas and oxygen-containing gas, or oxygen-containing gas is blown into the furnace, and after burning the coke existing in the region between the tapping hole and the tuyere among the coke remaining in the furnace before the stoppage of blowing, a method for starting up the blast furnace from a stoppage of blowing by starting blowing from the tuyere is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0006] When the blast furnace is shut down for an extended period, such as during blast furnace banking, the heat input to the blast furnace is lost. As a result, the molten slag remaining in the hearth gradually cools, and a solidified layer forms from the periphery of the furnace bottom. Therefore, when restarting after a long period of shutdown, tapping is required while a solidified layer exists at the furnace bottom. Since the amount and state of the solidified layer vary depending on its location within the furnace, the opening of the tap port greatly affects whether or not good tapping can be achieved.

[0007] The tapping port to be opened is determined based on the experience of skilled operators, but if the wrong tapping port is selected, the molten iron may solidify without being tapped. Removing the resulting residue requires a great deal of work. Therefore, when starting up a blast furnace after a blast furnace shutdown, it is necessary to select the tapping port most suitable for tapping and perform the tapping efficiently. In the conventional technologies mentioned above, although the methods for starting up after a blast furnace shutdown are disclosed, how to determine which tapping port to open is not disclosed.

[0008] Therefore, the present invention aims to provide a method for starting up a blast furnace after a blast furnace shutdown, which can determine the optimal tapping port to be opened during startup after a blast furnace shutdown, such as during blast furnace banking. [Means for solving the problem]

[0009] This invention was made to solve the above-mentioned problems, and the gist of the invention is as follows.

[0010] (1) A method for starting up a blast furnace after a blast shutdown, characterized in that, during the opening operation in which a tapping port is opened with a hole opening machine, the temperature is measured by a temperature sensor provided on the opening bit of the hole opening machine, and based on whether or not the temperature measured by the temperature sensor reaches a predetermined temperature, it is decided whether or not to open the tapping port during the opening operation as a tapping port for tapping when starting up the blast furnace after a blast shutdown.

[0011] (2) The method for starting up a blast furnace after a blast furnace shutdown as described in (1) above, characterized in that when the measured temperature continues to rise until it reaches the predetermined temperature, the tapping port during the opening operation is opened and molten metal is tapped.

[0012] (3) The method for starting up a blast furnace after shutting down air, as described in (2) above, characterized in that the predetermined temperature is 1300°C.

[0013] (4) A method for starting up a blast furnace after a blast furnace shutdown as described in any one of (1) to (3) above, characterized in that if the measured temperature stagnates or decreases before reaching a second temperature which is lower than the first temperature which is the predetermined temperature, the operation is moved to opening a tapping port other than the tapping port currently being opened.

[0014] (5) The method for starting up a blast furnace after shutting down air, as described in (4) above, characterized in that the second temperature is 1250°C.

[0015] (6) The method for starting up a blast furnace after a blast furnace shutdown as described in (4) above, characterized in that if the measured temperature reaches the second temperature but stagnates or decreases before reaching the first temperature, the opening operation is continued by switching from the hole-opening machine to opening with an oxygen lance, or by moving on to opening a tap other than the tap that is currently being opened. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a method for starting up a blast furnace after a period of shutdown, such as blast furnace banking, which can determine the optimal tapping port to be opened during startup. [Brief explanation of the drawing]

[0017] [Figure 1] This graph shows the temperature distribution in the drilling direction, measured in a test example of hole-opening work. [Modes for carrying out the invention]

[0018] A method for starting up a blast furnace after a blow-off will be described. In the method for starting up a blast furnace after a blow-off in this embodiment, during the hole-opening operation of opening a plugged taphole with a hole-opening machine, the temperature is measured with a temperature sensor provided on the hole-opening bit of the hole-opening machine, and based on whether or not the measured temperature of the temperature sensor reaches a predetermined temperature, it is determined whether or not to open the taphole during the hole-opening operation as a taphole for performing tapping when starting up the blast furnace after the blow-off. Then, by opening a taphole that can perform optimal tapping as the first tapping during startup from among the plurality of tapholes arranged in the blast furnace according to the method of this embodiment, a good startup of the blast furnace can be achieved.

[0019] In this embodiment, "blow-off" means a long-term blow-off such as so-called banking of a blast furnace. The target blow-off is not limited to banking, and this method can also be applied to a blast furnace after a blow-off other than banking as long as the blast furnace is started up and tapped from a state where the blowing to the blast furnace is stopped, the molten iron on the hearth solidifies, and a solidified layer or semi-solidified layer is formed.

[0020] The hole-opening machine for performing the hole-opening operation in this embodiment will be described. The hole-opening machine may be composed of a known hydraulic hole-opening machine or the like. The hole-opening bit at the tip of the hole-opening rod provided in the hole-opening machine is rotated to excavate the mud or the like filled in the taphole to perform the hole-opening operation. And the hole-opening machine of this embodiment is provided with a temperature sensor such as a thermocouple in the hole-opening bit. With this temperature sensor, the temperature inside the taphole and the surrounding temperature inside the blast furnace can be measured during the hole-opening operation. The measured temperature is output to the outside via a communication unit and can be confirmed at a remote location such as an operator's room. The communication means by the communication unit may be wired or wireless.

[0021] Note that the boring bit is subject to vibration and impact during the excavation of the tapping hole, and as the excavation progresses, it is subject to the radiant heat of the hot metal in the furnace. Therefore, in order to protect the temperature sensor from these vibrations, impacts, and radiant heat, it is desirable that the boring bit have a structure with vibration resistance, impact resistance, and heat resistance (for example, refer to Japanese Patent Laid-Open No. 8-21768). Also, the temperature sensor only needs to have heat resistance sufficient to measure the temperature inside the tapping hole during the boring operation. For example, even if it contacts the hot metal and wears out and becomes unable to measure after penetrating through the tapping hole by the boring operation and reaching the hot metal discharge, it is acceptable.

[0022] Next, the method for starting up the blast furnace after the blast is stopped in this embodiment will be described. As described above, the method of this embodiment is a method of determining the optimal tapping hole that can achieve a good start-up from among a plurality of tapping holes as the tapping hole to be opened. What is determined by the method of this embodiment is the tapping hole to be opened for the first hot metal discharge when starting up the blast furnace after the blast is stopped.

[0023] First, based on the temperature situation inside the furnace in the blast furnace after banking, etc., select one tapping hole where good hot metal discharge can be expected, and start the boring operation (excavation of the tapping hole) with a boring machine. The temperature situation inside the furnace can be grasped by, for example, a thermometer embedded inside the hearth bricks. From that temperature situation, predict the thickness of the solidified layer, and the tapping hole predicted to have the thinnest solidified layer can be used as the tapping hole for the boring operation.

[0024] Next, while measuring the temperature during the boring operation with the temperature sensor provided on the boring bit of the boring machine, proceed with the boring. Then, based on whether the measured temperature of the temperature sensor reaches a predetermined temperature, determine whether to open the tapping hole during the boring operation as the tapping hole for the first hot metal discharge when starting up the blast furnace after the blast is stopped. Specifically, according to the change in the measured temperature, determine which of the following three types of patterns it corresponds to, and the tapping hole for the start-up after the blast is stopped can be determined.

[0025] (1) When the measured temperature reaches the first temperature If the measured temperature continues to rise during the hole-opening operation until it reaches the first temperature (predetermined temperature) of 1300°C, good molten metal can be expected from the tapping port during the hole-opening operation. In this case, the tapping port during the hole-opening operation is designated as the tapping port from which molten metal will be tapped when the blast furnace is started up after the blast furnace shutdown. Then, the hole-opening operation by the hole-opening machine is continued until that tapping port is completed and molten metal is tapped.

[0026] (2) If the rise stops before the measured temperature reaches the second temperature. If the measured temperature stagnates or decreases before reaching the second temperature of 1250°C, which is lower than the first temperature, and does not rise above 1250°C, then there is no prospect of good tapping from the tapping port being opened, and the tapping operation is moved to a different tapping port.

[0027] As for the alternative tapping port to transition to, one can select a tapping port from the remaining tapping ports that has the potential to produce good molten metal, based on the furnace temperature conditions which can be monitored by thermometers embedded in the furnace bottom bricks.

[0028] (3) When the measured temperature stops rising within the range of the second temperature or higher but less than the first temperature. If the measured temperature reaches the second temperature of 1250°C but stagnates or decreases before reaching the first temperature of 1300°C and does not rise above 1300°C, switch from the hole-drilling machine to the oxygen lance method and continue the drilling operation, or move on to drilling a tapping port other than the one being drilled. If the temperature rise stops between 1250°C and 1300°C, it may or may not result in good tapping, and it is difficult to judge based solely on the temperature measured by the temperature sensor of the drilling bit. Therefore, it is best to consider other information as well when deciding whether to continue drilling or move to another tapping port.

[0029] Other information includes, for example, empirical rules and temperature conditions measured by thermometers in the furnace bottom bricks as described above. Even if the drilling continues, the temperature has not yet reached 1300°C (the first temperature), so the solidified or semi-solidified layer may be thicker, or the molten iron temperature near the tapping port may be lower compared to when the temperature is above 1300°C. If the opening is not made quickly, solidification will progress, making tapping difficult. Therefore, it is preferable to switch from a drilling machine to oxygen drilling using an oxygen lance to perform the drilling operation in order to tap as quickly and reliably as possible.

[0030] According to this embodiment, by measuring the temperature inside the tapping port during the opening operation, the tapping port that should be opened first to produce good tapping can be determined more accurately by the above-mentioned discrimination. In other words, according to the method of this embodiment, when opening the tapping port during the startup of the blast furnace from banking, when tapping from the molten iron slag accumulation area at the bottom of the furnace including the solidified layer, it is possible to reliably select the tapping port in the direction where the temperature inside the furnace is highest and the solidified or semi-solidified layer is smallest, thereby reliably obtaining good tapping. Furthermore, since the opening operation can be performed efficiently, the working time can be shortened, working costs can be reduced, and working safety can be improved. Therefore, according to the method of this embodiment, smooth startup of the blast furnace after banking is possible.

[0031] Furthermore, according to the method of this embodiment, although the operator needs to decide whether to continue the hole-opening operation or move to another tapping port when the rise in the measured temperature stops within the range of the second temperature (1250°C) or higher and less than the first temperature (1300°C), if any other temperature change pattern (the patterns of (1) or (2) above) is met, the operator can immediately decide whether to continue the hole-opening operation or move to another tapping port. In other words, except when the measured temperature stagnates or drops within a range of only 50°C between 1250°C and 1300°C, it is possible to quickly decide whether to continue the hole-opening operation, thus enabling efficient hole-opening operations.

[0032] In contrast, conventional methods used thermometers embedded in the furnace bottom bricks to predict the erosion line of the refractory material inside the furnace and the thickness of the solidified layer, thereby determining the tapping port location for the first tapping after banking startup. However, this prediction was sometimes insufficient in accuracy, and even after determining the tapping port to be opened and starting the opening work, it was not possible to know whether the prediction was correct and whether good tapping would be obtained until the opening work was continued, the tapping port was penetrated, and tapping was performed. Furthermore, if the prediction was incorrect, the work would be prolonged, increasing costs and workload. Moreover, it took time to decide to switch to a different tapping port, allowing the molten iron to solidify further, making good tapping increasingly difficult. The method of this embodiment can efficiently identify a tapping port that will yield good tapping during startup from blast furnace banking, thus solving these conventional problems. [Examples]

[0033] An example of a blast furnace startup method after blast shutdown will be described in more detail with reference to an example. 3 After shutting down a small blast furnace for an extended period, drilling was performed using a drilling machine equipped with a temperature sensor, and the temperature distribution in the drilling direction was measured. The drilling machine was the same as that described in the above embodiment, and was equipped with a thermocouple in the drilling bit at the tip of the drilling rod, allowing for measurement of the ambient temperature during drilling.

[0034] The measurement results are shown in Figure 1. Figure 1 is a graph showing the temperature distribution in the drilling direction measured during drilling operations in the drilling operations of Test Examples 1 to 3. The vertical axis represents the temperature measured by a thermocouple placed on the drilling bit [°C], and the horizontal axis represents the drilling distance (depth inside the taphead) from the starting position of the drilling operation by the drilling machine [m].

[0035] In Test Example 1, the temperature began to rise from around 1.4m in excavation distance, and continued to rise, exceeding 1300°C at around 2.0m. It then exceeded 1360°C at around 2.2m, and tapping began at 2.6m. The molten iron discharge was satisfactory. Furthermore, the average molten iron temperature for the first five tappings was 1490°C.

[0036] In Test Example 2, the temperature rise started later than in Test Examples 1 and 3. The temperature began to rise after the drilling distance exceeded 1.5m, reaching 1250°C around 2.1m. However, the rate of rise then slowed, and the measured temperature stagnated without reaching 1300°C. Drilling continued to 2.7m, but no molten iron was tapped. Therefore, the drilling machine was moved back, and the method was switched to oxygen drilling using an oxygen lance. With oxygen drilling, good molten iron was tapped on the first drilling operation. The average molten iron temperature for the subsequent five tapping operations was 1476°C.

[0037] In Test Example 3, the temperature began to rise after the drilling distance exceeded 1.3m, reaching over 1200°C at approximately 2.3m, but tapping did not occur at this point. Subsequently, the measured temperature began to decrease before reaching 1250°C, suggesting that a large amount of solidified or semi-solidified molten metal was present at this tapping port. The drilling operation was stopped, and the drilling machine was moved backward. After switching to oxygen drilling, tapping was attempted again, and after five drilling attempts, tapping was achieved. The average molten metal temperature during the subsequent five tapping attempts was 1401°C.

[0038] Table 1 below summarizes the results of Test Examples 1-3.

[0039] [Table 1]

[0040] In Test Example 1, where the measured temperature rose to 1300°C, as described above, the opening process was continued, and the opening was successfully opened without switching to oxygen opening, resulting in good molten iron tapping. Therefore, it was confirmed that when the measured temperature exceeds 1300°C, molten iron can be efficiently tapped by continuing the opening process of the tapping port. Furthermore, the average molten iron temperature was the highest, confirming that the blast furnace startup was better than in the other test examples.

[0041] In Test Example 2, where the measured temperature reached 1250°C but stagnated before reaching 1300°C, it was confirmed that good molten iron tapping could be obtained by switching to oxygen venting. On the other hand, since the average molten iron temperature was lower than in Test Example 1, it was also confirmed that better molten iron tapping could be obtained when the temperature reached 1300°C.

[0042] In Test Example 3, where the measured temperature did not reach 1250°C, tapping was only achieved after five oxygen tapping operations in addition to the tapping machine operation, requiring a long working time. Furthermore, the average molten iron temperature at tapping was the lowest, and it cannot be said that the start-up was good compared to the other cases. Therefore, it was confirmed that if the measured temperature does not reach 1250°C, it is more efficient and a better result can be obtained by switching to another tapping port and performing the tapping operation there.

Claims

1. This is a method for starting up a blast furnace after a period of blast shutdown. During the drilling operation in which the tapping port is drilled with a drilling machine, the temperature is measured by a temperature sensor provided on the drilling bit of the drilling machine. A method for starting up a blast furnace after a blast furnace shutdown, characterized in that, based on whether or not the temperature measured by the temperature sensor reaches a predetermined temperature, it is determined whether or not to open the tapping port during the opening operation as a tapping port for tapping when starting up the blast furnace after a blast furnace shutdown.

2. The method for starting up a blast furnace after a blast furnace shutdown according to claim 1, characterized in that when the measured temperature continues to rise until it reaches the predetermined temperature, the tapping port during the opening operation is opened and molten metal is tapped.

3. The method for starting up a blast furnace after shutting down the airflow, as described in claim 2, characterized in that the predetermined temperature is 1300°C.

4. A method for starting up a blast furnace after a blast furnace shutdown, according to any one of claims 1 to 3, characterized in that if the measured temperature stagnates or decreases before reaching a second temperature lower than the first temperature which is the predetermined temperature, the process is moved to opening a tapping port other than the tapping port currently being opened.

5. The method for starting up a blast furnace after shutting down the airflow, as described in claim 4, characterized in that the second temperature is 1250°C.

6. The method for starting up a blast furnace after a blast furnace shutdown according to claim 4, characterized in that if the measured temperature reaches the second temperature but stagnates or decreases before reaching the first temperature, the opening operation is continued by switching from the hole-opening machine to oxygen opening with an oxygen lance, or by moving on to opening a taphead other than the taphead being opened.

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