JP7810124B2 - converter - Google Patents

Description

The present invention relates to a converter that is suitable for use in the separate recovery of refractories after use.

Converter refractories installed in converters are made from electrofused magnesia and high-purity graphite, and often use high-quality raw materials. Work refractories, in particular, are generally graphite-containing refractories, which are less susceptible to slag infiltration and less degradation of refractory quality due to slag after use, making them suitable for recycling. However, the load on refractories varies depending on the part of the converter, such as the hearth, furnace wall, and slag line. Therefore, 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 recycled, they have no choice but to be used as low-grade raw materials. The grade of the recovered refractories is treated as the lowest-grade refractory contained in the recovered materials.

For example, Patent Document 1 considers a method for recycling used refractories. Furthermore, Patent Documents 2 and 3 propose methods for separating and recovering used refractories after dismantling, such as 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 huge amount of refractories, and a large amount of used refractories is generated at once. Therefore, even if the used refractories can be identified by symbols or other means, manually sorting through a large amount of used refractories is labor-intensive and also a significant burden in terms of cost. In the case of converters, compared to other vessels such as molten iron vessels, it is necessary to strictly select refractories of various grades depending on the part, making it particularly difficult to separate the refractories by grade.

The present invention was made in consideration of the above circumstances, and aims to provide a converter that can be suitably used when separating and recovering refractories after use.

The converter of the present invention, which advantageously solves the above problem, is a converter in which refractories of different qualities are installed in different sections, and is characterized by the provision of boundary partitions at the boundaries between these sections.

The converter according to the present invention is
(a) the refractories are arranged in a plurality of stages in the height direction, and the portions are divided in the height direction by boundary partition portions;
(b) the boundary partition is formed by one or a combination of two or more selected from (1) a buffer material that absorbs the expansion of the refractory material, (2) a different color portion that is different in color from adjacent portions, and (3) a refractory material that has a different shape from adjacent portions;
(c) a part of the refractories contains refractory scraps separated and recovered according to grade as part of its raw materials;
This is thought to be a more preferable solution.

According to the present invention, when converter refractories are dismantled, they can be dismantled and recovered in sections, allowing the refractories to be separated during dismantling. This eliminates the need for manual sorting of dismantled debris or preliminary work such as marking refractories for identification. This not only reduces the burden of sorting work for recycling, but also provides economic benefits by lowering processing costs and enabling recycling by grade.

1 is a vertical cross-sectional view showing a configuration of a converter according to one embodiment of the present invention. FIG. FIG. 2 is a partially enlarged perspective view of the vicinity of a boundary partition according to the embodiment. (a) is a development view of brickwork using cushioning material in the boundary partition section in the above embodiment, (b) is a development view of brickwork using different colored sections in the same manner, and (c) is a development view of brickwork using profiled materials in the same manner.

The following describes in detail the embodiments of the present invention. Note that the drawings are schematic and may differ from the actual product. Furthermore, the following embodiments exemplify devices and methods that embody the technical concepts of the present invention, and are not intended to limit the configuration to those described below. In other words, the technical concepts of the present invention can be modified in various ways within the technical scope set forth in the claims.

(Configuration of converter)
Fig. 1 is a schematic vertical cross-sectional view of a converter according to this embodiment. As shown in Fig. 1, this embodiment provides a converter in which refractories can be separately recovered after use. Refractories (converter refractories) are installed in a converter 1. The converter 1 is configured, from the outer surface, with a shell 2, a permanent refractory layer 3, and a workpiece refractory layer 4, in that order. The refractories of the permanent refractory layer 3 and the refractories of the workpiece refractory layer 4 are arranged in multiple tiers in the height direction on the inner surface of the converter 1.

Refractories of various grades are installed in the converter 1 depending on the load on the refractory and its purpose. In other words, the grade of refractory installed varies depending on the part of the converter 1. In this embodiment, the work refractory layer 4 is divided into various parts along the height of the converter 1, and the refractories of the work refractory layer 4 are divided (attached) along the height of the converter 1, i.e., by stage, so as to be classified by material, or at least by grade for recycling. In the example of Figure 1, the heat load near the top throat is low, so low-grade refractory 41 is used as the refractory of the work refractory layer 4. The slag line of the furnace wall experiences the greatest heat load, so high-grade refractory 43 is used as the refractory of the work refractory layer 4, and medium-grade refractory 42 is used as the refractory of the work refractory layer 4 for the remaining furnace wall and furnace bottom.

In this embodiment, as shown in the enlarged perspective view of the converter inner wall portion in Figure 2, boundary sections 5 are provided at the boundaries between sections of the workpiece refractory layer 4, i.e., at the dividing points between different-grade refractories 42, 43 (the boundary sections where different-grade refractories meet), to enhance the visibility of the boundaries during dismantling. As shown in Figure 3(a), the boundary sections 5 are formed by buffer material 51 provided between the different-grade refractory sections. This buffer material 51 is made of, for example, cardboard or non-combustible mineral fiber, which can absorb the expansion of the refractory (it is compressed by the expansion of the refractory). It is preferable that the buffer material 51 leave traces even after the converter is used, so that they can be seen during dismantling. In the example shown in Figure 3(a), the buffer material 51 is drawn taller than it actually is to emphasize the boundary section 5; however, the actual height of the buffer material 51 is approximately 2 mm.

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

In addition, the refractory (brick) in the row corresponding to the boundary partition 5 may have a different shape from the adjacent refractory, such as a deformed material 53 with a different size (height) as shown in Figure 3(c). The boundary partition 5, which differs in shape from the adjacent refractory, can be, for example, an existing deformed portion (a portion where the brick shape changes), such as the boundary where the narrowing from the straight body section of the converter 1 begins to the throat or the angle change section connecting the hearth to the straight body. Furthermore, the above configurations may be combined, such as by coloring the deformed material 53 or coloring the buffer material 51. Making the boundary partition 5 visible facilitates the quality classification of the refractory during dismantling. While Figures 3(b) and (c) show the bottommost row in the upper section as the boundary partition 5, the topmost row in the lower section may also be the boundary partition 5. It is preferable to use the bottommost row in the upper section as the boundary partition 5. If the topmost row in the lower section is used as the boundary partition 5, it is preferable to make the boundary between the materials visible on its top surface. This prevents refractory materials of different grades from being mixed in when dismantling them from above.

(Disassembly method)
Next, a method for dismantling the refractories of the converter 1 and separating and recovering them will be described. First, when the refractories are installed, 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 refractories are dismantled into the converter 1, row by row, starting from the top. Once the refractories have been dismantled down to the boundary partition 5 (material boundary), the converter 1 is turned upside down, and the dismantled refractories are removed and recovered.

The converter 1 is then rotated and fixed back into the refractory dismantling position, and the refractory below the boundary compartment 5 is dismantled row by row into the converter 1. Once the refractory has been dismantled down to the next boundary compartment 5 (material boundary), the converter is again turned upside down and the dismantled refractory is removed and recovered. In this way, by managing the number of rows to be dismantled during converter dismantling and repeating the process of removing and recovering the refractory each time the number of rows dismantled reaches the range in which refractory of the same quality has been installed, it is possible to easily recover refractory by grade without prolonging the construction period.

In the above embodiment, a boundary partition 5 is provided to make the material boundary visible. Instead of or in addition to the boundary partition 5, the number of layers may be counted from the top or bottom when the converter is dismantled, or the dismantling height may be determined using a laser rangefinder or similar device, so that layers containing the same-grade refractory material can be identified during dismantling.

(recycled refractories)
The separated and collected refractory waste is crushed and magnetically separated according to its grade, and then pulverized to a particle size suitable for use as raw material. The resulting recycled refractory raw material can be used in part to produce magnesia-carbon bricks as recycled refractories, for example, by a high-density brick manufacturing method using a low-viscosity binder. The recycled refractories can then be reused as refractories of a specified grade for use in converters after their properties have been evaluated in advance.

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 materials.
Commercially available magnesia-carbon bricks were used for the refractories of different grades. Low-grade refractories 41 using electrofused magnesia with a purity of 97% were arranged from the converter furnace throat, which had the lowest load, to above the straight body. Medium-grade refractories 42 using electrofused magnesia with a purity of 98% were arranged from the upper part of the straight body to above the slag line, which contacts the molten slag, and throughout the entire area below the slag line. Furthermore, high-grade refractories 43 using the highest-grade electrofused magnesia with a purity of 98.5% were arranged in the slag line, which is the highest load and contacts the molten slag. Additionally, cardboard was concentrated in the rows corresponding to the boundaries between these grades as boundary partitions 5, which were used in actual operation.

Due to wear and tear on the refractory, it was dismantled in order to replace the converter refractory. Prior to the dismantling, slag, metal, and other materials attached to the furnace body were removed, the furnace mouth metal fittings were removed, and these items that had been dropped below the furnace were then removed before 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. The converter was placed on its side, and dismantling began when the surface temperature of the converter refractory dropped below 500°C.

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

The converter was then turned onto its side again, and the tap hole refractory was further dismantled. Then, the medium-grade refractory 42 up to the top of the slag line was similarly dismantled and dropped below the furnace. Like the low-grade refractory 41, it was transported to a temporary storage area and then 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 scrap.

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 scrap 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 raw materials. Magnesia carbon bricks (refractories) were prototyped and evaluated using a high-density brick manufacturing method that uses a low-viscosity binder and blended at 30% of the resulting recycled refractory raw materials. The results are shown in Table 1 as Test Nos. 3 to 5.

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

To evaluate corrosion resistance, a rotating drum corrosion test was performed 10 times at 1700°C on slag adjusted to a basicity C/S of 3, and the results were compared using a corrosion resistance index, where the amount of wear in Test No. 1 was 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 by mass. The results of this series of experiments are shown in Table 1.

Comparing Test No. 1 with Test Nos. 3 to 5, it is clear that the corrosion resistance index increases when recycled materials are added, but the extent of this increase, or the degree of deterioration in corrosion resistance, varies depending on the quality of the recycled materials; the higher the quality of the recycled materials, the lower the degree of deterioration.

Test No. 2 and Test No. 3 had nearly the same maximum corrosion resistance index value, indicating that the presence of low-grade scrap determines the maximum corrosion resistance index value. Furthermore, in Test Nos. 3 to 5, the range of corrosion resistance indices was 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 in and recovered during demolition. Since the medium-grade and high-grade refractory scrap were not mixed with refractory of other grades, the corrosion resistance index showed little variation and was of stable quality.

Tests No. 3 to 5 all had lower corrosion resistance indices than the low-grade refractory used as a reference example (Test No. 6), demonstrating that there are no problems 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 achieved roughly the same corrosion resistance indices, indicating that recycled material blended bricks made from medium-grade refractory waste and high-grade refractory waste can be used in the medium-grade refractory construction range.

The above describes an embodiment applying the invention made by the inventors, but the present invention is not limited by the description that forms part of the disclosure of this embodiment. Furthermore, while the refractories have been described here as being divided into three grades - low, medium, and high - the same effect can be achieved whether the number of grade classifications is increased or decreased, and therefore all other embodiments other than those listed in the above examples are included in the scope of the present invention. Furthermore, all other embodiments, examples, operational techniques, etc. made by those skilled in the art based on this embodiment are included in the scope of the present invention.

The converter of the present invention not only reduces the burden of dismantling, but also allows refractories to be separated and recovered by grade, allowing them to be recycled and used as converter refractories, resulting in economic benefits and making it industrially useful. It can also be applied to facilities and equipment that separate and install refractories of different grades.

REFRACTORY OF SYMBOLS 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 Buffer material 52 Different color portion 53 Profile material A Working surface

Claims (2)

A converter in which refractories of different grades are installed in different parts,
A boundary partition is provided at the boundary between the sections,
The boundary partition is formed by one or a combination of two or more selected from (1) a buffer material that absorbs expansion of the refractory material, (2) a different color portion that is different in color from adjacent portions, and (3) a refractory material that has a different shape from adjacent portions. A converter as described in claim 1, wherein the refractories are arranged in multiple stages in the vertical direction, and the sections are divided in the vertical direction by boundary partitions.