Milling method at the bottom of the furnace

Abstract

To provide a furnace bottom tap method for early determining whether or not to reach tapping in performing a drilling operation, and improving efficiency in a furnace bottom tapping operation.SOLUTION: A furnace bottom tapping method performs tapping by drilling a furnace bottom in a blast furnace by a hole opening machine. The hole opening machine comprises a temperature sensor at a hole opening bit. The furnace bottom tapping method has: a first step of continuing drilling regardless of a detection temperature till a drilling distance reaches a first drilling distance; a second step of continuing drilling as long as the detection temperature increase after the drilling distance reaches the first drilling distance; a third step of stopping drilling when the detection temperature does not increase after the drilling distance reaches the first drilling distance; and a fourth step of determining whether to continue drilling on the basis of a length of a delay region when the delay region where the temperature increase is delayed after the execution of the second step.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for tapping molten iron from the bottom of a furnace.

Background Art

[0002] In a blast furnace, with long-term operation, the inner refractory lining, furnace body cooling equipment, etc. deteriorate, so these are regularly repaired and replaced. A particular problem during this blast furnace repair is that the molten iron remaining in the furnace after the blowdown operation solidifies at the bottom of the furnace and remains in large amounts as residual lumps. Since the removal operation of these residual lumps is very difficult, it prolongs the repair period and causes problems such as an increase in repair costs. As a countermeasure, a tapping opening for removing residual molten iron is provided below the tapping opening, and bottom tapping of the molten iron from this tapping opening for removing residual molten iron to discharge the molten iron outside the furnace may be carried out.

[0003] During the final operation period of the furnace lining until blowdown, from the aspect of protecting the bottom refractory of the furnace, due to reducing the tapping ratio from normal operation, the temperature at the bottom of the furnace decreases, so there is a problem that solidified deposits of molten iron grow at the bottom of the furnace. As a countermeasure, in Patent Document 1, when performing a blast furnace repair, at least from 4 months before blowdown, the operating conditions are controlled to maintain the tapping ratio at a high level and suppress the decrease in production volume, while suppressing the growth of solidified deposits at the bottom of the furnace. After that, the remaining molten iron is tapped from the bottom of the furnace at the time of blowdown to reduce the amount of solidified deposits at the bottom of the furnace. A technique is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Because the size and shape of solidified deposits vary depending on the excavation location, for example, if an area with a thick layer of solidified deposits is excavated, it may not result in pig iron production. In this case, it is necessary to temporarily remove the drilling bit from the furnace and restart the excavation work by changing the entry angle of the drilling bit. This can lead to a heavy workload, prolonged working time, and increased costs. Patent Document 1 does not address this issue at all.

[0006] The present invention aims to improve the efficiency of bottom-furnace tapping operations by enabling early determination of whether or not to tap the furnace during excavation work. [Means for solving the problem]

[0007] (1) In order to solve the above problems, the bottom tapping method of the present invention is characterized by (1) a bottom tapping method of a blast furnace in which molten iron is tapped by drilling the bottom of the blast furnace with a drilling machine, wherein the drilling machine is equipped with a temperature sensor on the drilling bit, and comprises: a first step of continuing drilling regardless of the detected temperature until the drilling distance reaches a first drilling distance; a second step of continuing drilling as long as the detected temperature is rising after the drilling distance reaches the first drilling distance; a third step of stopping drilling if the detected temperature does not rise after the drilling distance reaches the first drilling distance; and a fourth step of determining whether to continue drilling based on the length of the stagnation area if a stagnation area occurs after the execution of the second step in which the temperature rise stagnates.

[0008] (2) The bottom tapping method according to (1) above, characterized in that in the fourth step, if the maximum temperature, which is the highest value of the detected temperature, is not updated, and the drilling distance starting from the drilling position corresponding to the maximum temperature reaches a second drilling distance or more, drilling is stopped.

[0009] (3) The furnace bottom tapping method according to (1) or (2) above, characterized in that the first excavation distance is the design value of the thickness of the furnace bottom brick side wall in the excavation direction of the hole bit.

[0010] (4) The bottom tapping method according to any one of (1) to (3) above, characterized in that the second excavation distance is 0.3 m. [Effects of the Invention]

[0011] According to the present invention, it is possible to determine early on whether or not to tap the furnace during excavation work. This makes it possible to perform bottom-of-furnace tapping work efficiently. [Brief explanation of the drawing]

[0012] [Figure 1] This is a functional block diagram of the mouthpiece. [Figure 2] These are explanatory diagrams for patterns A through D. [Figure 3] This shows the temperature distribution in the drilling direction (example). [Figure 4] This is a magnified view of a portion of Figure 3. [Modes for carrying out the invention]

[0013] Figure 1 is a functional block diagram of the hole-opening machine for implementing the bottom-of-furnace tapping method of this embodiment, and the dotted arrows indicate the direction in which the signal flows. The drilling machine 1 includes a drilling bit (not shown), a temperature sensor 11, a bit drive motor 12, a motor control unit 13, and a communication unit 14. The drilling machine 1 may be hydraulic. The temperature sensor 11 is built into the drilling bit. The drilling bit rotates due to power transmitted from the bit drive motor 12, thereby excavating the side wall bricks of the furnace bottom. Here, the drilling bit is subjected to vibration and shock during excavation, and as excavation progresses, it receives radiant heat from the molten iron inside the furnace. Therefore, it is desirable to implement a protective structure (see, for example, Japanese Patent Application Publication No. 8-21768) on the drilling bit to protect the temperature sensor 11 from these vibrations, shocks, and radiant heat.

[0014] For example, a thermocouple that calculates temperature using the Seebeck effect can be used as the temperature sensor 11. When the opening bit is located within the bricks of the furnace bottom side wall, the temperature of the bricks is detected by the temperature sensor 11. When the opening bit advances and reaches the solidified deposits inside the furnace, the temperature of the solidified deposits is detected by the temperature sensor 11. When the opening bit advances further and reaches the furnace residue slag, the temperature of the furnace residue slag is detected by the temperature sensor 11.

[0015] The motor control unit 13 controls the drive of the bit drive motor 12 based on instruction information from the operator room 2, and calculates the travel distance of the drilling bit (in other words, the drilling distance) based on the rotational speed of the bit drive motor 12.

[0016] The temperature detected by the temperature sensor 11 can be transmitted to the operator room 2 via the communication unit 13. The drilling distance calculated by the motor control unit 13 can also be transmitted to the operator room 2 via the communication unit 13. These temperatures and drilling distances can be displayed, for example, on a monitor screen installed in the operator room 2. The operator can understand the relationship between these temperatures and drilling distances from the temperature and drilling distance displayed on the monitor screen. However, these temperatures and drilling distances may also be displayed on a display provided on the hole drilling machine 1. The communication means by the communication unit 13 may be wired or wireless.

[0017] The inventors performed bottom-of-furnace tapping operations using the drilling machine 1 described above and investigated the relationship between drilling distance and detected temperature. As a result, they discovered that these relationships can be categorized into patterns A to D, which are described below.

[0018] Figure 2 is an explanatory diagram (also called "excavation feasibility determination information") for explaining patterns A to D, with the horizontal and vertical axes representing excavation distance and detected temperature, respectively. Referring to this figure, it was found that in all patterns, there is a period 1 in which the temperature rise is gradual. In Pattern A, the temperature increased rapidly immediately after Period 1. Although there was a period during which the temperature increase became gradual thereafter, the temperature increase continued until tapping. In Pattern B, almost no temperature increase was observed after Period 1, and tapping did not occur. In Pattern C, the temperature increased rapidly immediately after Period 1, and then a stagnation region C where the temperature increase stagnated occurred. Thereafter, the temperature increased again and tapping occurred. Since the stagnation region C occurs in a temperature range of about 1200°C, it is presumed to be the solid-liquid mixed layer of the molten iron. In Pattern D, a stagnation region D corresponding to the stagnation region C of Pattern C continued for a long time, and tapping did not occur.

[0019] Based on the above investigation results, the inventor of the present invention has found an efficient tapping method for the furnace bottom consisting of the following Steps 1 to Step 4.

[0020] Step 1: Until the excavation distance reaches the first excavation distance, continue excavation regardless of the detected temperature. The first excavation distance may be the designed thickness value of the furnace bottom brick side wall in the excavation direction of the opening bit. That is, the designed thickness value corresponds to the excavation distance (or penetration distance) at which the tip of the opening bit excavates the furnace bottom side wall brick, and corresponds to Period 1 in FIG. 2. Therefore, when the opening bit enters perpendicularly to the outer surface of the furnace bottom side wall brick, the excavation distance within the furnace bottom side wall brick in the vertical direction corresponds to the first excavation distance. When the opening bit is moved in an inclined direction inclined with respect to the vertical direction, the excavation distance within the furnace bottom side wall brick in the inclined direction corresponds to the first excavation distance. Even if the excavation start position is the same, the first excavation distance can vary depending on the excavation direction. The operator can compare the excavation distance displayed on the monitor screen in the operator room 2 with the designed thickness value based on the design information, and can grasp that the excavation distance has reached the first excavation distance when they match.

[0021] In this embodiment, the first excavation distance was determined from the design thickness of the furnace bottom side wall bricks, but the present invention is not limited thereto. For example, the excavation distance may be determined by monitoring the torque value of the bit drive motor 12, which fluctuates before and after penetration of the furnace bottom side wall bricks.

[0022] Step 2: After the drilling distance reaches the first drilling distance, continue drilling as long as the detected temperature is rising. In this case, drilling is continued as pig iron can be expected to be produced according to pattern A or pattern C.

[0023] Step 3: If it is determined that the detected temperature does not rise after the drilling distance has reached the first drilling distance, drilling is stopped. In this case, it is classified as pattern B, and drilling is stopped because pig iron production cannot be expected. Here, it is desirable that the determination in step 3 be made at a predetermined position where drilling has progressed beyond the first drilling distance. This is because even in cases where pig iron production is achieved, the temperature does not necessarily rise immediately after reaching the first drilling distance, and there may be some delay. The predetermined position is preferably a position where drilling has progressed 0.75m or more beyond the first drilling distance. After stopping drilling, the drilling bit is temporarily moved out of the furnace, and new drilling operations (hereinafter also referred to as reopening operations) are carried out. Reopening operations can be performed by changing the entry angle of the drilling bit or changing the drilling position. By halting the excavation midway, it becomes possible to transition to reopening the borehole earlier, thereby improving the efficiency of bottom-of-furnace tapping operations.

[0024] Step 4: If a stagnation zone occurs after Step 2, the decision to continue drilling is made based on the size of the stagnation zone. Referring to Figure 2, if a stagnation zone occurs in the temperature range of approximately 1200°C, the situation will transition to either pattern C, where pig iron production can be expected, or pattern D, where pig iron production cannot be expected. The difference between pattern C and pattern D is the length of the stagnation zone. Therefore, if the stagnation zone is long In that case, the situation will transition to pattern D, where pig iron production cannot be expected, and the excavation will be stopped.

[0025] The length of the stagnation zone can be determined, for example, by whether the excavation distance from the excavation location where the highest temperature detected by the temperature sensor 11 was recorded (hereinafter also referred to as the non-updated excavation distance) has reached a second excavation distance or greater, without the highest temperature detected by the temperature sensor 11 being updated. If the non-updated excavation distance reaches a second excavation distance or greater, excavation is stopped. The second excavation distance is the distance at which further excavation is not expected to yield any further pig iron, and can be set appropriately based on empirical rules. The second excavation distance can be set to, for example, 0.3m.

[0026] In the above-described embodiment, the length of the stagnation zone was determined based on the non-updating distance at which the highest temperature was not updated, but the present invention is not limited thereto. For example, a first detection temperature, which is the temperature detected immediately after entering the stagnation zone, and a second detection temperature, which is the temperature detected at a position beyond a second drilling distance, may be compared, and if the second detection temperature is lower than the first detection temperature, it may be determined that the stagnation zone is long and drilling may be stopped.

[0027] According to this embodiment, it is possible to determine early whether or not pig iron can be expected to be tapped during drilling, and if pig iron is not expected to be tapped, the drilling process can be stopped midway. This allows for an early transition to the reopening of the hole, thereby improving the efficiency of bottom-of-furnace tapping operations.

[0028] (Examples) The present invention will be specifically described with reference to examples. 2903m 3After the blast furnace (hearth diameter: 9.6m, brick thickness: 1m) was opened, bottom tapping was performed using the drilling machine described in the embodiment, and the temperature distribution in the drilling direction was measured. The first drilling distance was set to the design thickness of the furnace bottom side wall bricks. In Examples 1 to 3, drilling was performed in the thickness direction of the furnace bottom side wall bricks, so the first drilling distance was the brick thickness (i.e., 1m). In Example 4, drilling was performed in an inclined direction relative to the thickness direction of the furnace bottom side wall bricks, so the first drilling distance was 1.5m. Figure 3 shows the measurement results, with the horizontal axis and vertical axis representing drilling distance and detected temperature, respectively. Figure 4 is an enlarged view of a part of the graph in Figure 3 (the rectangular area shown by the dotted line).

[0029] In Example 1, the excavation distance reached the first excavation distance (1m), and even after excavating an additional 0.8m, there was almost no temperature increase, and since pig iron production was not expected, excavation was stopped within 2m.

[0030] In Example 2, after the excavation distance reached the first excavation distance (1m), the temperature rose to around 1200°C at 2.2m, but no pig iron was tapped at this point. Subsequently, the maximum temperature Tmax (Example 2) was reached at approximately 2.3m, but the maximum temperature Tmax (Example 2) was not updated even after excavating to 2.75m. In other words, the stagnation region where the maximum temperature Tmax (Example 2) was not updated was at least 0.45m (450mm). In this case, it is presumed that a large amount of solidified deposits or semi-molten pig iron slag was present at this excavation location.

[0031] In Example 3, after the drilling distance reached the first drilling distance (1m), the temperature rose to around 1200°C at a point exceeding 2m, but no iron tapping was observed at this point. Subsequently, the maximum temperature Tmax (Example 3) was reached at approximately 2.2m, and the maximum temperature Tmax (Example 3) was updated at a point exceeding approximately 2.3m. In other words, there was a stagnant region of about 0.1m (100mm) where the maximum temperature Tmax (Example 3) was not updated. Furthermore, when drilling was continued, a hole was opened at 2.7m, and the tapping of high-viscosity molten iron slag at approximately 1350°C began. After that, the furnace residue slag could be discharged almost as planned. By comparing Examples 2 and 3, it was found that the feasibility of tapping can be determined by the length of the stagnation period in which the maximum temperature Tmax is not updated. From these examples, the second drilling distance can be determined to be 0.3m.

[0032] In Example 4, after the drilling distance reached the first drilling distance (1.5m), the temperature continued to rise consistently, and at approximately 2.4m of drilling distance, molten iron at a temperature of 1400°C was tapped. Although the thermocouple broke at the same time, the slag residue in the furnace was successfully discharged. This is an ideal example of bottom tapping operations.

[0033] The results of Examples 1 to 4 are summarized in Table 1. [Table 1] [Explanation of symbols]

[0034] 1 Drilling machine 2 Operator Room 11. Temperature sensor 12 Pit drive motor 13 Motor Control Unit 14 Communications Department

Claims

[Claim 1] A bottom blast furnace tapping method, which involves tapping molten metal by excavating the bottom of the blast furnace with a drilling machine, The aforementioned hole drilling machine is equipped with a temperature sensor on the hole drilling bit. The first step involves continuing drilling regardless of the detected temperature until the drilling distance reaches a first drilling distance, The second step involves continuing drilling as long as the detected temperature is rising after the drilling distance has reached the first drilling distance. A third step is to stop drilling if, after the drilling distance has reached the first drilling distance, the detected temperature does not rise at a position where the drilling has advanced 0.75 m or more beyond the first drilling distance. If a stagnation zone occurs after the execution of the second step, a fourth step is taken to determine whether or not to continue drilling based on the length of the stagnation zone. It has, In the fourth step, the length of the stagnation zone is determined by whether the maximum temperature, which is the highest value of the detected temperature, is not updated, and whether the drilling distance starting from the drilling position corresponding to the maximum temperature has reached or exceeds the second drilling distance. If the drilling distance has reached or exceeds the second drilling distance, drilling is stopped. The first excavation distance is the design value of the thickness of the furnace bottom brick side wall in the excavation direction of the hole bit. A method for bottom-fired pig iron, characterized in that the second excavation distance is 0.3 m.

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