JP7699614B2 - How to separate and collect refractories - Google Patents

Description

The present invention relates to a method for separating and recovering refractories after use in a converter.

The converter refractories installed in converters are made of electrofused magnesia and high-purity graphite, and many of them use high-quality raw materials. In particular, the work refractories are generally graphite-containing refractories, which are less susceptible to slag infiltration and are less likely to deteriorate in quality due to slag after use, making them suitable for recycling. However, the load on the refractories varies depending on the part of the converter, such as the furnace bottom, furnace wall, and slag line. Therefore, in order to achieve both economical efficiency and long life, converter refractories of different grades are often used depending on the load at the location where they are installed. For example, in low-load areas, the purity of the electrofused magnesia and graphite raw materials may be changed, or cheaper sintered magnesia may be used instead of electrofused magnesia.

As a result, the scraps from dismantled refractories after use contain a mixture of refractories of various grades, and when they are recycled, they have no choice but to be used as low-grade raw materials. The grade of the refractories that are recovered is treated as the lowest grade refractory contained in the recovered material.

For example, Patent Document 1 considers a method for recycling used refractories. Patent Documents 2 and 3 also propose a method for separating and recovering used refractories after dismantling them by marking the back of the refractory that remains even after use, or painting the working surface before dismantling.

Japanese Patent Application Publication No. 05-339615 Japanese Patent Application Publication No. 09-328377 JP 2013-212481 A

However, the conventional technology has the following problems.
Converters use a large amount of refractories, and a large amount of used refractories is generated at one time. Therefore, even if the used refractories can be identified by symbols, sorting through a large amount of used refractories manually is heavy work and a large burden in terms of cost. In the case of converters, it is particularly difficult to separate refractories by grade, since refractories of various grades must be strictly used according to the part, compared to other vessels such as molten iron vessels.

The present invention was made in consideration of the above circumstances, and aims to provide a method for more easily separating and recovering refractories after use of a converter.

The method for separating and recovering refractories according to the present invention, which advantageously solves the above problem, is a method for separating and recovering refractories after use in a converter in which refractories of different qualities are installed in different parts, and is characterized by repeating the process of dismantling and recovering the refractories after use in parts.

The method for separating and recovering refractories according to the present invention includes the steps of:
(a) in the converter, the refractories are arranged in a plurality of stages in a height direction and the portions are divided in the height direction, and in the step, the refractories are dismantled and collected for each stage of the same quality;
(b) a boundary partition is provided at the boundary between the adjacent regions;
(c) the boundary partition is formed of a buffer material that absorbs the expansion of the refractory material;
(d) the boundary partition is formed by a different color portion having a different color from adjacent portions;
(e) the boundary partition is formed of a refractory material having a different shape from adjacent portions;
This is thought to be a more preferable solution.

According to the present invention, when converter refractories are dismantled, the refractories can be dismantled and collected by parts, allowing the refractories to be separated during dismantling. This eliminates the need for manual sorting of the dismantled waste or prior work such as marking the refractories for identification purposes, reducing the burden of sorting work for recycling. This also has economic benefits, as it allows recycling at low processing costs and by grade.

FIG. 1 is a schematic vertical cross-sectional view showing a configuration of a converter suitable for use in one embodiment of the present invention. FIG. 2 is a partially enlarged perspective view of the vicinity of a boundary partition portion according to the embodiment. 1A is a development view of brickwork using cushioning material in the boundary partition section in the above embodiment, FIG. 1B is a development view of brickwork using different colored sections, and FIG. 1C is a development view of brickwork using deformed materials.

The following is a detailed description of the embodiments of the present invention. Note that the drawings are schematic and may differ from the actual product. The following embodiments are illustrative 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.

(Configuration of converter)
Fig. 1 is a schematic vertical cross-sectional view of a converter suitable for use in the method for separating and recovering refractories according to this embodiment. As shown in Fig. 1, in this embodiment, a refractory (converter refractory) is applied to a converter 1. The converter 1 is configured, from the outer surface, of a shell 2, a permanent refractory layer 3, and a workpiece refractory layer 4 in that order, and the refractory of the permanent refractory layer 3 and the refractory of the workpiece refractory layer 4 are arranged in a plurality of stages in the height direction on the inner surface of the converter 1.

The refractories in the converter 1 are constructed with refractories of various grades depending on the load on the refractory and the purpose of the refractory. In other words, the grade of the refractory constructed varies depending on the part of the converter 1. In this embodiment, the work refractory layer 4 is divided into each part in the height direction of the converter 1, and the refractories of the work refractory layer 4 are divided (attached) in the height direction of the converter 1, that is, for each stage, so that they are classified according to material, or at least grade when recycled. In the example of FIG. 1, the heat load is small near the uppermost furnace mouth, so low-grade refractory 41 is used as the refractory of the work refractory layer 4. The slag line of the furnace wall has the highest heat load, so high-grade refractory 43 is used as the refractory of the work refractory layer 4, and the remaining furnace wall and furnace bottom use medium-grade refractory 42 as the refractory of the work refractory layer 4.

In this embodiment, as shown in the enlarged perspective view of the inner wall of the converter in FIG. 2, the boundary between each part of the work refractory layer 4, i.e., the dividing part between the refractories 42 and 43 of different grades (the boundary stage where the refractories of different grades are in contact), is provided with a boundary partition 5 to enhance the visibility of the boundary during dismantling. The boundary partition 5 is formed by a buffer material 51 provided between the stages of the refractories of different grades, as shown in FIG. 3(a), for example. This buffer material 51 is made of cardboard or non-combustible mineral fiber that can absorb the expansion of the refractory (is compressed by the expansion of the refractory). It is preferable that the buffer material 51 leaves traces even after the converter is used so that they can be seen during dismantling. In the example shown in FIG. 3(a), the height of the buffer material 51 is drawn higher than the actual height in order to emphasize the boundary partition 5, but the actual height of the buffer material 51 is about 2 mm.

As shown in FIG. 3(b), the refractory (brick) of the step at the material boundary portion may be colored to provide a different color portion 52 that is a different color from the other refractories (e.g., black), forming the boundary partition portion 5. In this case, when the refractory is installed, it is preferable to color at least the upper surface of the refractory (other than the working surface A shown in FIG. 2) in advance with a paint of a color that does not discolor due to heat, such as a chrome-based paint, and that is visible against the black color of the adjacent refractory. This makes it easier to see the boundary partition portion 5 when the refractory is dismantled from above.

In addition, the refractory (brick) of the step corresponding to the boundary partition 5 may be a different shape from the adjacent refractory, for example, a deformed material 53 with a different size (height) as shown in FIG. 3(c). As the boundary partition 5 having a different shape from the adjacent refractory, for example, an existing deformed part (a part where the shape of the brick changes) such as the boundary where the narrowing from the straight body part of the converter 1 to the furnace mouth begins or the angle change part connecting the furnace bottom to the straight body can be used as the boundary partition 5. In addition, the above configurations may be combined, such as by coloring the deformed material 53 or coloring the buffer material 51. By making the boundary partition 5 visible, it becomes easier to separate the grade of the refractory during dismantling. In addition, in FIG. 3(b) and (c), the bottommost step of the upper part is the boundary partition 5, but the topmost step of the lower part may be the boundary partition 5. It is preferable to use the bottommost step of the upper part as the boundary partition 5, and when the topmost step of the lower part is the boundary partition 5, it is preferable to make the boundary of the material visible on its upper surface. This prevents refractory materials of different grades from being mixed together when dismantling them from above.

(Disassembly method)
Next, a method for dismantling the refractory of the converter 1 and recovering it separately will be described. First, when the refractory is applied, a boundary partition 5 is formed in advance at the material boundary portion of the work refractory layer 4. Then, when repairing and dismantling the converter 1, the converter 1 is rotated and fixed at the refractory dismantling position, and the refractory is dismantled into the converter 1, layer by layer, starting from the top. When the refractory is dismantled up to the boundary partition 5 (material boundary), the converter 1 is turned upside down, and the dismantled refractory is carried out and recovered.

Then, the converter 1 is rotated and fixed again at the refractory dismantling position, and the refractory below the boundary partition 5 is dismantled into the converter 1 layer by layer. When the refractory has been dismantled down to the next boundary partition 5 (material boundary), the converter is again turned upside down and the dismantled refractory is removed and collected. In this way, by managing the number of layers to be dismantled when dismantling the converter, and repeating the process of removing and collecting the refractory each time the number of layers is dismantled to the extent that refractory of the same quality has been installed, it is possible to easily collect refractory by grade without prolonging the construction period.

In the above embodiment, the boundary partition 5 is provided to make the material boundary visible. Instead of or in addition to the boundary partition 5, the number of stages may be counted from the top or bottom during converter dismantling, or the dismantling height may be grasped using a laser range finder or the like, so that the stages in which the same-grade refractory material exists can be identified during dismantling.

As shown in Figure 1, refractories of different grades were lined in an actual converter, and attempts were made to separate, dismantle, and recover the refractories.
Commercially available magnesia carbon bricks were used as refractories of different grades. A low-grade refractory 41 using electrofused magnesia of 97% purity was arranged from the converter furnace mouth, which had the lowest load, to above the straight body. A medium-grade refractory 42 using electrofused magnesia of 98% purity was arranged from the upper part of the straight body to above the slag line in contact with the slag, and below the slag line. Furthermore, a high-grade refractory 43 using the highest grade electrofused magnesia of 98.5% purity was arranged in the slag line, which had the highest load and was in contact with the slag. In addition, cardboard was concentrated in the steps corresponding to the boundaries between these grades as boundary partitions 5, and was used in actual operation.

Due to the wear and tear of the refractory, it was dismantled in order to transfer the converter refractory. Prior to the dismantling, the refractory was removed from the furnace body, including slag and metal, and then the furnace mouth metal fittings were removed. After removing these items that had been dropped below the furnace, the dismantling of the refractory began.

To dismantle the refractory, a converter dismantling machine equipped with an air breaker powered by compressed air was used, and the converter was placed on its side. Dismantling began when the surface temperature of the converter refractory dropped below 500°C.

Dismantling began from the topmost layer of the converter refractory, and the refractory that made up the sideways converter ceiling was dismantled into the converter up to the same layer as the tap hole, which was the application range of low-grade refractory 41. The furnace was then turned upside down, and the refractory up to the dismantled layer was dropped below the furnace. The dropped refractory was removed from under the furnace using a wireless heavy machine, and then transported to a temporary storage area and managed as low-grade refractory scrap.

The converter was again turned on its side, and the tap hole refractory was dismantled. The medium-grade refractory 42 up to the top of the slag line was then similarly dismantled and dropped under the furnace. It was then transported to a temporary storage area, just like the low-grade refractory 41, and managed as medium-grade refractory scrap.

In the same manner, only the slag line portion, which is high-grade refractory 43, was dismantled and managed as high-grade refractory waste.

After the refractory material in the slag line section was dismantled, dropped and recovered, all that remained was medium-grade refractory material 42, which was dismantled down to the bottom of the furnace, dropped under the furnace and managed together with the medium-grade refractory scraps that had been recovered earlier.

Refractory waste managed by grade was crushed, magnetically separated, and then pulverized to the raw material particle size to produce recycled refractory materials. Magnesia carbon bricks (refractories) were prototyped and evaluated using a high-density brick manufacturing method that uses a low-viscosity binder, with 30% of the resulting recycled refractory materials. Test Nos. 3 to 5 are shown in Table 1.

As a comparative example, a prototype refractory (Test No. 2) was produced using refractory scraps (conventional scraps) obtained by a conventional dismantling method, in which the scraps were not broken down by grade, as a raw material for recycled refractories. As reference examples, a high-grade refractory (Test No. 1) was produced using the highest quality electrofused magnesia with a purity of 98.5%, which is the raw material for high-grade refractories, without using recycled raw materials; a commercially available low-grade refractory (Test No. 6) using electrofused magnesia with a purity of 97%; and a commercially available medium-grade refractory (Test No. 7) using electrofused magnesia with a purity of 98% were also prepared and evaluated.

The corrosion resistance was evaluated by performing a rotating drum corrosion test at 1700°C 10 times on slag adjusted to a basicity C/S of 3, and comparing the corrosion resistance index with the wear amount of test No. 1 set to 100. The lower the corrosion resistance index, the higher the corrosion resistance. The basicity C/S is the ratio of CaO to _SiO2 in the slag on a mass basis. The results of a series of experiments are shown in Table 1.

Comparing Test No. 1 with Test Nos. 3 to 5, it can be seen that the corrosion resistance index increases when recycled materials are used, but the extent of this increase, i.e., the degree of deterioration in corrosion resistance, varies depending on the grade of the recycled materials; the higher the grade of the recycled materials, the lower the degree of deterioration.

Test No. 2 and Test No. 3 had almost the same maximum corrosion resistance index value, and it can be seen that the presence of low-grade scrap determines the maximum corrosion resistance index value. In addition, in Test No. 3 to 5, the range of corrosion resistance index is the widest in Test No. 3, where low-grade refractory scrap was used. This is thought to be because medium-grade refractory was installed around the tap hole and was mixed and collected during dismantling. Since medium-grade refractory scrap and high-grade refractory scrap are not mixed with refractories of other grades, the variation in corrosion resistance index is small and the quality is stable.

Tests No. 3 to 5 all had lower corrosion resistance indices than the low-grade refractory (Test No. 6) used as a reference example, which shows that there is no problem with using recycled material blended bricks at least in the low-grade refractory construction range. Tests No. 4 and 5 had slightly higher corrosion resistance indices than the medium-grade refractory (Test No. 7), but roughly the same corrosion resistance indices were obtained, and recycled material blended bricks using medium-grade refractory waste and high-grade refractory waste can be applied to the medium-grade refractory construction range.

The above describes an embodiment of the invention made by the inventors, but the present invention is not limited by the description that forms part of the disclosure of the present invention according to this embodiment. In addition, the refractories have been described here as being divided into three grades, low grade, medium grade, and high grade, but the same effect can be obtained even if the number of grade categories is increased or decreased, so everything other than those listed in the above examples is included in the scope of the present invention. Furthermore, all other embodiments, examples, and operational techniques made by those skilled in the art based on this embodiment are included in the scope of the present invention.

The method for separating and recovering refractories of the present invention not only reduces the dismantling load, but also allows the separation and recovery of refractories according to grade, making them industrially useful as they can be recycled and used as converter refractories, thus providing economic benefits. It can also be applied to facilities and equipment that separate and install refractories of different grades.

Reference Signs List 1 Converter 2 Steel shell 3 Permanent refractory layer 4 Work refractory layer 41 Low-grade refractory 42 Medium-grade refractory 43 High-grade refractory 5 Boundary partition 51 Cushioning material 52 Different color portion 53 Shaped material A Working surface

Claims (5)

A method for separating and recovering used refractories in a converter in which refractories of different qualities are installed in different parts, the method comprising the steps of dismantling and recovering the used refractories in parts ,
A method for separating and recovering refractories, characterized in that a boundary partition is provided at the boundary between the portions . In the converter, the refractories are arranged in a plurality of stages in a height direction and the converter is divided into the portions in a height direction,
The method for separating and recovering refractory material according to claim 1 , wherein in the step, the refractory material is disassembled and recovered in stages of the same quality. 3. The method for separating and recovering refractory material according to claim 1 , wherein the boundary partition is formed by a buffer material that absorbs expansion of the refractory material. The method for separating and recovering refractories according to claim 1 or 2 , wherein the boundary partition portion is formed by a portion of a different color that is different from an adjacent portion. The method for separating and recovering refractory material according to claim 1 or 2 , wherein the boundary compartment is formed of a refractory material having a shape different from that of an adjacent portion.

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