Converter slag removing method and protective device used therefor

Abstract

To prevent the outflow of slag to a working floor in front of a furnace from a gap between a charging door in the closed state and a side protective wall during intermediate slag discharge in converter refining.SOLUTION: Provided are a converter slag removing method and a protective device used therefor in which intermediate slag removal is performed in a converter 4 having a side protective wall 6 and a charging door 2, wherein a shielding plate 1 covering a gap 3 between the charging door 2 and the side protective wall 6 is provided at both side ends of the charging door 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a converter slag removal method and a protective device used therein, which prevent slag from flowing out onto a furnace front work floor through gaps between both side ends of a closed charging door and side protective walls when removing slag from a converter in the converter refining process of steelmaking. [Background technology]

[0002] In general, in a converter facility for steelmaking, in converter refining performed at a high temperature of 1600 to 1800°C, a side protection wall 6 and a charging door 2 are provided to improve the operating environment (see Figs. 3 and 4). The side protection wall 6 is a fixed wall that protects incidental equipment (not shown) on both sides of the converter 4 from heat. The charging door 2 is a pair of left-right openable movable doors that are supported by a cart 9 and are opened and closed to the left and right by the movement of the cart 9 to protect the front work floor 5 from heat and discharged slag toward the front of the converter 4. The left-right opening and closing direction of the charging door 2 is set to be approximately parallel to the axial direction of the tilting axis 10 of the converter 4. The charging door 2 is opened to secure a working space when molten iron or scrap iron source is charged into the converter 4, and is closed during refining operation and slag discharge.

[0003] A gap 3 (FIG. 3) is provided between the charging door 2 and the side protection wall 6 so that smooth opening and closing of the charging door 2 is not hindered by contact between the charging door 2 and the side protection wall 6.

[0004] Meanwhile, in converter refining, when desiliconization refining and dephosphorization refining are performed consecutively in the same converter 4, the converter 4 is tilted toward the front of the furnace on the tilting shaft 10 between each refining, and the slag 7 on the molten pig iron 8 is removed while leaving the molten pig iron 8 in the converter 4, which is called "intermediate slag removal." In this case, the more slag removed in the desiliconization refining, the less limestone is used in the next dephosphorization refining process, which leads to a reduction in refining costs. Therefore, the converter 4 is tilted vigorously to increase the flow rate of the slag 7 and remove the slag. The removed slag 7 is collected in a ladle 60 (Figure 5).

[0005] At this time, the high-temperature slag 7, whose flow rate has increased, collides with the front faces of the left and right doors of the closed charging door 2. Repeated collisions cause the slag 7 to adhere and solidify on the opposing end faces where the left and right doors meet, creating a gap 42 at the joint of the closed position 40 of the charging door 2 when closed, and the slag may flow out from this gap 42 onto the front furnace work floor 5. If the slag flows out onto the front furnace work floor 5, it may cause a deterioration in the operating environment or a disaster such as a fire.

[0006] In order to prevent such slag from flowing out to the furnace front working floor 5, a technique has been proposed in which the closed position 40 of the charging door 2 is shifted by an amount d from the position directly facing the center of the tilting axis 10 of the converter 4, as shown in Fig. 6 (see Patent Document 1). Also, as shown in Fig. 7, a technique has been proposed in which a front protective wall 31 is provided in the front part of the furnace where slag scatters, so as to cover a gap 42 at the joint between the left and right doors when closed (see Patent Document 2). Furthermore, as shown in Fig. 8, a technique has been proposed which includes a step of installing a transportable protective device 32, which is provided with a front protective wall 31 that covers the gap 42 and is used when discharging slag from the converter, on the carriage 9 of the charging door 2 and a step of removing it from the carriage 9 (see Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2017-057496 A [Patent Document 2] JP 2017-066500 A [Patent Document 3] Patent Publication No. 2021-102795 Summary of the Invention [Problem to be solved by the invention]

[0008] The above technology is a technology to prevent slag 7 from flowing out from the gap 42 at the joint of the charging door 2 when it is closed to the furnace front work floor 5. However, in intermediate slag discharge with the charging door 2 closed, slag 7 may flow out from the above-mentioned gap 3 on the side surface (see Figures 3 and 6) to the furnace front work floor 5. The above technology has a problem in that it cannot prevent slag from flowing out from this gap 3.

[0009] In view of the above technical problems, the present invention aims to provide a converter slag removal method and a protective device used therein, which prevent slag from flowing out onto the furnace front work floor through the gap between the charging door and the side protective wall when closed, during intermediate slag removal in converter refining. [Means for solving the problem]

[0010] The inventors of the present invention have conducted extensive research to solve the above problems, and as a result, have found that by covering the gap between the charging door and the side protection wall when the door is closed with a shielding plate specially provided at the side end of the charging door, it is possible to prevent slag from flowing out of the gap onto the furnace front work floor. The present invention has been completed based on this knowledge and further research, and the gist of the present invention is as follows. [1] A converter slag removal method in a converter refining process in which intermediate slag removal is performed in a converter having a side protective wall and a charging door, the method being characterized in that a shielding plate covering the gap between the charging door and the side protective wall is provided on both side ends of the charging door. [2] The converter slag removal method according to [1], characterized in that the shielding plate is arranged so as to cover the outer surface of the furnace front end of the side protective wall. [3] The converter slag removal method according to [1] or [2], characterized in that the width of the shielding plate is 150 mm or more and / or the height of the shielding plate is 1 / 3 or more of the height of the charging door and / or the thickness of the shielding plate is 9 mm or more. [4] A converter slag removal method according to any one of the above [1] to [3], comprising any one of the following steps A to C: A: A step of shifting the closing position of the charging door from a position directly facing the center of the tilting axis of the converter. B: A process of providing a front protective wall to cover the gap between the left and right doors when the charging door is closed. C: A step of installing a protection device having a front protection wall that covers the gap between the left and right doors when the charging door is closed on the cart of the charging door, and a step of removing the protection device from the cart. [5] The converter slag removal method according to any one of the above [1] to [4], characterized in that the time for carrying out the intermediate slag removal is 5 minutes or less. [6] A protective device for preventing slag from flowing out onto a furnace front work floor during intermediate slag discharge in a converter having a side protective wall and a charging door, the protective device comprising a shielding plate for covering the gap between the charging door and the side protective wall, and a connecting means for fixing the shielding plate to both side end portions of the charging door. [7] The protective device according to [6], characterized in that the shielding plate covers the end of the side protective wall. [8] The protective device according to [6] or [7], characterized in that the width of the shielding plate is 150 mm or more and / or the height of the shielding plate is 1 / 3 or more of the height of the charging door and / or the thickness of the shielding plate is 9 mm or more. [9] The protective device according to any one of the above [6] to [8], characterized in that the shielding plate is made of at least one of a steel plate, a casting, and a refractory ceramic.

[10] The protective device according to any one of [6] to [9], wherein the connecting means is a welded joint and / or a bolted joint. Effect of the Invention

[0011] According to the present invention, the shielding plate prevents slag from flowing out from the gap between the charging door and the side protection wall to the furnace front work floor during slag discharge. As a result, there is no need to limit the slag flow rate during intermediate slag discharge, and intermediate slag discharge can be performed with high work efficiency, allowing dephosphorization refining with an appropriate amount of lime. This further reduces the refining cost compared to the conventional method. In addition, according to [4] of the present invention, slag can also be prevented from flowing out from the front of the charging door. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic top view illustrating an example of an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic top view showing another example of an embodiment of the present invention. [Diagram 3] FIG. 1 is a schematic top view showing an example of a general steelmaking converter facility. [Figure 4] FIG. 4 is a view taken along the line AA in FIG. [Diagram 5] FIG. 2 is a schematic side view showing how the discharged slag is collected. [Figure 6] FIG. 13 is a schematic top view illustrating a technique for shifting the closed position of the charging door from a position directly facing the center of the tilting axis of the converter. [Figure 7] 1 is a schematic side view showing a technique for providing a front protective wall to cover the gap between the joints of the left and right doors when closed. [Figure 8] FIG. 1 is a schematic side view showing a technique for installing or removing a transportable protection device having a front protective wall for use during converter slag removal from a charging door carriage. [Figure 9] FIG. 2 is a schematic top view showing another example of an embodiment of the present invention. [Figure 10] FIG. 2 is a top schematic view showing an example of a coupling means of the device of the present invention. [Figure 11] 1 is a top view schematic diagram showing an example in which a shielding plate is provided at the front end of a side protective wall. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts as those in the previous drawings are given the same reference numerals, and the description thereof will be omitted.

[0014] The present invention includes both a converter slag removal method (hereinafter also referred to as the "invention method") and a protection device used therein (hereinafter also referred to as the "invention device"). Fig. 1 is a top schematic view showing an example of an embodiment of the present invention.

[0015] As shown in Fig. 1, the method of the present invention is a method for converter refining in which intermediate slag removal is performed in a converter 4 having a side protective wall 6 and a charging door 2, using an apparatus equipped with a shield plate 1 covering a gap 3 between the charging door 2 and the side protective wall 6 at both end portions of the charging door 2. The apparatus of the present invention also includes the shield plate 1 and a connecting means 35 for fixing the shield plate 1 to both end portions of the charging door 2. The connecting means 35 can be composed of, for example, a welded connection portion 37 and / or a bolt fastening portion 39 (Fig. 10).

[0016] [Converter] The converter 4 is a steelmaking converter, and preferably has a molten iron processing capacity of 200 to 350 tons per refining.

[0017] [Side protection wall] The side protective wall 6 is made of steel and has dimensions within normal ranges, for example, the top height position of the side protective wall 6 is 0 to 2000 mm higher than the throat height position of the converter 4 in the upright state. The distance between the inner surface of the side protective wall 6 and the converter 4 is 1000 to 2000 mm, and the distance between the outer surface is 10000 to 20000 mm.

[0018] [Charging door] The pair of doors (hereinafter, simply referred to as "doors") forming the charging door 2 are made of steel, and the dimensions are within normal ranges, for example, door thickness: 19 to 36 mm, door height position: within ±500 mm of the top height position of the side protective wall 6. Regarding the door width, when the shift amount d (FIG. 6) is 0 mm, the left-right symmetrical door width is "(the outer surface distance W of the side protective walls 6, 6) / 2+(0 to 100) mm." When d is more than 0 mm, the left-right asymmetrical door width is "the left-right symmetrical door width + d" for one of the left and right doors, and "the left-right symmetrical door width - d" for the other.

[0019] [Intermediate slag removal] The time for intermediate slag discharge (hereinafter also referred to as "intermediate slag discharge time") is preferably within 5 minutes. If the intermediate slag discharge time exceeds 5 minutes, it is within the time limit in the absence of the shielding plate 1, and it is difficult to obtain the effect of improving the work efficiency of intermediate slag discharge according to the present invention. More preferably, it is within 4 minutes.

[0020] [Shielding plate] The shielding plates 1 are provided on both end portions of the charging door 2. The reason for this will be explained below.

[0021] In the case where the shielding plate 1 is provided at the furnace front end 6E of the side protection wall 6 in addition to both ends of the charging door 2 (FIG. 11), the following problem occurs. That is, the shielding plate 1 provided at the furnace front end 6E of the side protection wall 6 is in constant contact with the door of the charging door 2 to cover the gap 3, and slides and wears when the door is opened and closed. In addition, if the gap 3 expands from the initial installation due to thermal deformation of the door, it will not be able to cover the expanded gap 3. Therefore, an additional process is required to cover the expanded gap 3, which causes a problem of decreasing the productivity of the converter refining. If the shielding plate 1 is made movable so that it comes into contact with the door only when the door is closed, the above-mentioned sliding and wear can be avoided, but the installation structure of the shielding plate 1 becomes complicated and the equipment cost increases.

[0022] In contrast, when the shielding plate 1 is provided on both end portions of the charging door 2 (Fig. 1), the shielding plate 1, which moves in conjunction with the door when it is opened and closed, moves close to and away from the outer surface of the side protective wall 6 in a direction perpendicular to the outer surface, so there is no sliding and no wear. Furthermore, even if the gap 3 expands due to thermal deformation of the door, by setting the width of the shielding plate 1 to be larger than the actual maximum width of the gap 3 after expansion, no additional process is required to cover the expanded portion of the gap 3. Therefore, the shielding plate 1 is provided on both end portions of the charging door 2.

[0023] (The shielding plate covers the outer surface of the front end of the side protection wall) If the shielding plate 1 does not cover the outer surface of the furnace front end 6E of the side protective wall 6, it may not be possible to cover the expansion of the gap 3 caused by thermal deformation of the door. Therefore, it is preferable for the shielding plate 1 to cover the outer surface of the furnace front end 6E of the side protective wall 6. In this case, the overlap width X (FIG. 1) between the shielding plate 1 and the side protective wall 6 is determined taking into consideration the track record of the expansion of the gap 3 caused by thermal deformation of the door, and may be, for example, X=100 to 300 mm.

[0024] Furthermore, it is more preferable to dispose the shielding plate 1 so that it comes into contact with the outer surface of the side protective wall 6 when the door is closed. This state of contact may be either line contact or surface contact. This blocks the outflow path of slag that passes through the gap 3 between the shielding plate 1 and the side protective wall 6 to the outer surface of the side protective wall 6. As described above, the shielding plate 1 moves in a direction perpendicular to the outer surface of the side protective wall 6 in conjunction with the opening and closing of the door, so it does not slide and is not subject to wear.

[0025] When the shielding plate 1 is brought into contact with the outer surface of the side protective wall 6, it is preferable to incline the shielding plate 1 with an inclination means 50 so that the mutual distance between the pair of shielding plates 1, 1 narrows at the tip side (FIG. 2). Furthermore, it is even more preferable to have the reaction force from the side protective wall 6 elastically received by a spring (not shown) or the like. This makes it possible to maintain contact between the shielding plate 1 and the outer surface of the side protective wall 6 even if the door and / or the shielding plate 1 is thermally deformed.

[0026] (Shielding plate dimensions) If the width of the shielding plate 1 is less than 150 mm, it may be difficult to cover the gap 3 in preparation for the side edge of the door, so it is preferable that the width is 150 mm or more. However, if it exceeds 350 mm, it may result in excessive use of material, so the width of the shielding plate 1 is more preferably 150 to 350 mm. It is even more preferably 250 to 300 mm.

[0027] If the height of the shielding plate 1 is less than 1 / 3 of the door height, which is the height of the charging door 2, the scattered slag may climb over the shielding plate 1 and fall onto the furnace front working floor 5, so it is preferable that the height of the shielding plate 1 is 1 / 3 or more of the door height. However, if the height of the shielding plate 1 is more than 1 time the door height, excessive use of materials may occur, so the height of the shielding plate 1 is more preferably 1 / 3 to 1 time the door height. It is even more preferably 1 / 2 to 1 time the door height.

[0028] The thickness of the shielding plate 1 is preferably 9 mm or more, since a thickness less than 9 mm may result in insufficient rigidity. However, a thickness exceeding 25 mm may result in excessive use of material, so the thickness of the shielding plate 1 is more preferably 9 to 25 mm, and even more preferably 12 to 19 mm.

[0029] (Construction material of shielding plate) Since the shielding plate 1 comes into contact with the scattered high-temperature slag multiple times, it is preferable that the shielding plate 1 is made of a material that is fire-resistant and heat-resistant and easy to assemble. Examples of such materials include steel plate, castings, and fire-resistant ceramics. By making the shielding plate 1 out of one or a combination of two or more of these materials, the service life of the shielding plate 1 can be extended and the maintenance burden can be reduced.

[0030] [Prevention of slag leakage from the front side of the charging door] In the method of the present invention, in order to simultaneously prevent the outflow of slag from gap 3 and from gap 42 on the front side of charging door 2, it is preferable to include any one of the following steps A to C.

[0031] Step A is a step of shifting the closed position 40 of the charging door 2 by a shift amount d (mm) exceeding 0 mm from the position directly facing the center of the tilting shaft 10 of the converter 4 (FIG. 6). Here, it is preferable that the shift amount d satisfies the following formula (1). d / r≧1-3L / H ‥‥(1) r: radius of the converter 4 throat (mm), L: distance from the throat of the converter 4 tilted 90° from the upright state to the slag discharge side to the furnace front work floor 5 (mm), H: height from the center of the tilting axis 10 to the throat (mm) Step B is a step of providing a front protective wall 31 that covers the gap 42 at the joint between the left and right doors when the charging door 2 is closed (FIG. 7).

[0032] Step C is a step of installing a protection device 32 equipped with a front protection wall 31 that covers the gap 42 at the joint between the left and right doors when the charging door 2 is closed, on the dolly 9 of the charging door 2, and a step of removing it from the dolly 9 (FIG. 8). A forklift (not shown) can be preferably used for the installation and removal of the protection device 32. EXAMPLES

[0033] Hereinafter, the embodiments of the present invention will be described in more detail with reference to examples.

[0034] [Example 1] Example 1 includes Example 1 of the present invention and Conventional Example 1. Example 1 of the present invention (FIG. 1) and Conventional Example 1 (FIG. 3) differ in the presence or absence of a shielding plate 1, but otherwise were set under the same setting conditions.

[0035] The converter 4 has a molten iron processing capacity of 330 tons per refining run, and r in formula (1) is 1920 mm, L is 2425 mm, and H is 5375 mm. The side protection wall 6 has a top height position 500 mm higher than the throat height position of the converter 4 in the upright state, and a height of 7000 mm from the floor surface of the furnace front work floor 5. The distance D between the inner surface of the side protection wall 6 and the converter 4 is 1815 mm, and the distance W between the outer surface is 13000 mm. The charging door 2 has a door thickness of 25 mm, a door height of 8850 mm, a shift amount d of 0 mm, and a door width of 6500 mm on both the left and right sides. The distance S between the closed position 40 and the center line of the tilting axis 10 is 7800 mm.

[0036] The gap 3 was 150 mm when the charging door 2 was first installed, before it had been deformed by the heat of the slug 7, and increased to a maximum of 155 mm after deformation due to heat.

[0037] In addition, the intermediate slag discharge time for the slag 7 was set to 5 minutes in order to prevent production loss in the converter refining process. To complete the slag discharge in 5 minutes, a process is required to discharge the slag 7, whose molten metal surface has risen due to the foaming phenomenon in the converter 4, to the front of the converter. When this happens, the discharged slag 7 collides with the charging door 2 to a maximum height of 2000 mm, and spreads toward the side end of the door due to the force of the collision. As a result, in the conventional example 1, the slag 7 flows out from the gap 3 to the front of the converter work floor 5.

[0038] In contrast, in Example 1 of the present invention, the gap 3 was covered with a shielding plate 1. A steel plate having a thickness of 19 mm, a width of 250 mm, and a length of 4000 mm was used for the shielding plate 1. The steel plate was welded to both side ends of the charging door 2 so that the length and width of the steel plate were equal to the height and width of the shielding plate 1, respectively. The overlap width X between the shielding plate 1 and the side protective wall 6 was 100 mm.

[0039] As a result, like Conventional Example 1, slag removal was completed in 5 minutes, and even if the slag 7 reached the gap 3, it was blocked by the shielding plate 1, completely preventing the slag from flowing out onto the furnace front work floor 5.

[0040] In Example 1, the gap 42 at the joint between the left and right sides of the charging door 2 was still very small, and no slag flowed out from the gap 42 onto the furnace front working floor 5.

[0041] [Example 2] Example 2 includes Example 2 of the present invention and Example 2 of the prior art. Example 2 of the present invention (FIG. 9) and Example 2 of the prior art (FIG. 6) differ in the presence or absence of the shielding plate 1, and the other conditions are the same. Also, Example 2 of the prior art adds the above-mentioned step A to Example 1 of the prior art. Specifically, the shift amount d is changed from 0 mm to 1300 mm, and accordingly, one of the left and right door widths is changed to 5200 mm and the other to 7800 mm, and the other conditions are the same as those of Example 1 of the prior art. This is because the gap 42 in Example 2 of the prior art is larger than that in Example 1 of the prior art, and this is to prevent slag from flowing out from the gap 42, which may occur if d=0 mm is used.

[0042] As a result, in Conventional Example 2, no slag flowed out from the front side of the charging door 2 to the furnace front working floor 5, but slag flowed out from the gap 3 to the furnace front working floor 5.

[0043] In contrast, in the present invention example 2, the slag 7 did not flow out onto the furnace front working floor 5 from either the gap 3 or the front side of the charging door 2.

[0044] Thus, according to the present invention, it is possible to completely prevent slag from flowing out onto the furnace front work floor during intermediate slag removal, thereby improving the operating environment and improving production efficiency by shortening the slag removal time. [Explanation of symbols]

[0045] 1 Shielding plate 2 Charging door 3 Gap between side protection wall and charging door 4. Converter 5 Furnace front work floor 6 Side protection wall 6E Front end of side protection wall 7. Slug 8. Molten Iron 9 Trolley 10 Tilt axis 31 Front protection wall 32 Protective devices 35 Coupling means 37 Welded joints 39 Bolt fastening 40 Closed position 42 void 50 Inclination means 60 Pot

Claims

1. A converter slag removal method in a converter refining process in which intermediate slag removal is performed in a converter having a side protective wall and a charging door, characterized in that a shielding plate covering the gap between the charging door and the side protective wall is disposed on both side ends of the charging door.

2. 2. The converter slag removal method according to claim 1, wherein the shielding plate is arranged so as to cover an outer surface of the front end of the side protection wall.

3. 3. A converter slag removal method as claimed in claim 1 or 2, characterized in that the width of the shielding plate is 150 mm or more and / or the height of the shielding plate is 1 / 3 or more of the height of the charging door and / or the thickness of the shielding plate is 9 mm or more.

4. 3. The converter slag removal method according to claim 1, further comprising at least one of the following steps A, B, and C: A: A step of shifting the closed position of the charging door from a position directly facing the center of the tilting axis of the converter. B: A process of providing a front protective wall to cover the gap between the left and right door joints when the charging door is closed. C: A step of installing a protection device having a front protection wall that covers the gap between the left and right door joints when the charging door is closed on the cart of the charging door, and a step of removing the protection device from the cart.

5. The converter slag removal method according to claim 3, characterized in that it comprises at least one of the following steps A, B, and C. A: A step of shifting the closed position of the charging door from a position directly facing the center of the tilting axis of the converter. B: A process of providing a front protective wall to cover the gap between the left and right door joints when the charging door is closed. C: A step of installing a protection device having a front protection wall that covers the gap between the left and right door joints when the charging door is closed on the cart of the charging door, and a step of removing the protection device from the cart.

6. 3. The converter slag removal method according to claim 1, wherein the intermediate slag removal is carried out for a period of 5 minutes or less.

7. 4. The converter slag removal method according to claim 3, wherein the intermediate slag removal is carried out for a period of 5 minutes or less.

8. 5. The converter slag removal method according to claim 4, wherein the intermediate slag removal is carried out for a period of 5 minutes or less.

9. 6. The converter slag removal method according to claim 5, wherein the time for carrying out the intermediate slag removal is set to 5 minutes or less.

10. A protective device for preventing slag from flowing out onto a furnace front work floor when intermediate slag discharge is performed in a converter having a side protective wall and a charging door, characterized in that the protective device comprises a shielding plate that covers the gap between the charging door and the side protective wall, and a connecting means for fixing the shielding plate to both side end portions of the charging door.

11. The protection device used during slag removal in a converter according to claim 10, characterized in that the shielding plate covers an end portion of the side protection wall.

12. A protective device as described in claim 10 or 11, characterized in that the width of the shielding plate is 150 mm or more and / or the height of the shielding plate is 1 / 3 or more of the height of the charging door and / or the thickness of the shielding plate is 9 mm or more.

13. 12. The protective device according to claim 10 or 11, wherein the shielding plate is made of at least one of a steel plate, a casting, and a refractory ceramic.

14. 13. The protective device according to claim 12, wherein the shielding plate is made of at least one of a steel plate, a casting, and a refractory ceramic.

15. 12. A protection device according to claim 10 or 11, characterized in that the connection means are welded connections and / or bolted connections.

16. 13. A protection device according to claim 12, characterized in that the connection means are welded connections and / or bolted connections.

17. 14. A protection device according to claim 13, characterized in that the connection means are welded connections and / or bolted connections.

18. 15. A protection device according to claim 14, characterized in that the connection means are welded connections and / or bolted connections.

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