JP2012149863A - Lining structure of furnace bottom refractory of shaft furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lining structure of furnace bottom refractory of a shaft furnace effective in improvement of production efficiency of molten iron by reducing a wear speed of the lining refractory of a furnace bottom center part of the large-sized shaft furnace and achieving extension of a repair cycle.SOLUTION: In the lining structure of the furnace bottom refractory of the shaft furnace for manufacturing the molten iron for forming a stamp layer 3 of monolithic refractory on a furnace inside of a furnace base bottom brick layer 2, precast blocks 4 are constructed by replacing a part or all of the stamp layer 3, especially the stamp layer 3 on the center part of the furnace bottom surface.

Description

  The present invention relates to the lining structure of a bottom refractory in a vertical furnace such as a blast furnace or a shaft furnace, and more particularly, to the lining structure of a bottom refractory consisting of a brick and an amorphous refractory layer to be constructed thereon. It is a proposal.

Conventionally, in the field of the steel industry, as a hot metal production facility, a type of blast furnace that mainly reduces iron ore has been used. In addition, in recent years, a shaft furnace that melts iron scrap has also attracted attention for the purpose of reducing CO ₂ .

  Shaft furnace is a type of vertical melting furnace. It is charged with iron scrap as raw material and coke as solid fuel from the top, and burns the coke by sending air from the tuyere provided in the lower trunk circumference. By doing so, the steel scrap is melted and the hot metal and slag are discharged from the tap near the furnace bottom.

For example, alumina (Al ₂ O ₃ ) -silicon carbide (SiC) -carbon (C) refractory (hereinafter referred to as “ASC”) is generally used for the bottom of such a shaft furnace for the purpose of shortening repair time (drying time). It is usually stamped and constructed using a stamp material such as “abbreviated to“ system refractory ””.

  In the case of the shaft furnace bottom, damage is so severe that repair in a relatively short time is required. Therefore, a stamping method that only pressurizes and forms granular ASC refractories with a rammer is advantageous. It is. That is, as in the prior art, first, a method of forming a mold and pouring an amorphous refractory into the form, takes time for curing and drying, and prolongs the repair time. In this respect, the stamping method can be applied in a shorter time. In the case of this method, a lining refractory layer having a thickness of 50 to 200 mm is usually formed by one stamping, and a refractory layer having a thickness of 500 to 1000 mm is formed by repeating this multiple times.

In this regard, Patent Document 1 conventionally defines the wear rate of a refractory by changing from an ASC refractory to a refractory mainly composed of ZrO ₂ as a stamping material for a shaft furnace outlet. Techniques for reducing the frequency have been proposed.

  Patent Document 2 discloses a cupola bottom refractory structure, a first layer composed of a highly corrosion-resistant material on the surface side, a second layer composed of a highly heat-insulating material, and a bottom surface. A refractory structure comprising a mold sand layer on the side is disclosed.

JP 2009-263203 A JP 2002-147959 A

  However, in the case of the prior arts described in Patent Documents 1 and 2, the improvement in the refractory itself used around the taphole and the bottom of the furnace has been achieved. However, as the shaft furnace itself becomes larger as in recent years, in particular, the cooling at the center of the furnace bottom cannot catch up, and the wear rate of the refractory in this part becomes larger than expected. Therefore, there is a problem that the repair interval is extremely short and the operating rate of the furnace does not increase.

That is, in recent years, in order to improve hot metal productivity, large shaft furnaces having an inner diameter of the furnace bottom of 3.0 m or more have been manufactured. In the case of such a large furnace, the larger the furnace body, not only the cooling of the center of the furnace bottom becomes insufficient and the erosion becomes severe, but also the tapping speed exceeds 70 t / h. The refractory in the center tends to be easily damaged by hot metal flow. Therefore, even if the type of refractory around the outlet is changed as described above, the life of the furnace itself does not extend as much as expected due to the rate of damage at the center of the furnace bottom. For this reason, there was a problem that the operating rate of the furnace decreased. In addition, it is economically difficult to use a large amount of expensive ZrO ₂ as in Patent Document 1 as a furnace bottom refractory.

  In addition, as described in Patent Document 2, even if a highly corrosion-resistant material is used for the inside (surface side) of the furnace, it is particularly resistant to corrosion in stamping where rough and dense inevitably occur in the upper and lower layers. There was also a problem that the improvement effect could not be fully exhibited.

  As described above, in the case of a large shaft furnace, the refractory wear (erosion) speed at the center of the furnace bottom is fast, and at least this part (center of the furnace bottom) is reinforced to improve the furnace life. It turns out to be essential.

  Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to produce a hot metal such as a blast furnace and a shaft furnace, in particular, a furnace lining refractory for a large vertical furnace, especially a furnace bottom. This is to propose a lining structure for the bottom refractory of a vertical furnace that reduces the wear rate of the lining refractory at the center, extends the repair cycle, and is effective in improving the production efficiency of hot metal.

  By the way, when the inventors investigated the erosion situation of the bottom refractory of the shaft furnace, the refractory at the bottom of the furnace is most severely eroded at the center, and further, the erosion at the center of the eroded bottom is horizontal. It has been found that erosion is progressing hierarchically.

  As a result of intensive studies on the reason, as long as the construction method is a stamping method, the laminated structure of one stamp layer is a relatively dense (high density) layer in the upper layer, but the lower layer is Since the upper layer portion becomes a cushion, it is inevitable that the layer becomes a relatively rough (low density) layer. In other words, the furnace bottom refractory layer formed through a plurality of stampings always has a structure in which coarse and dense portions are alternately laminated.

  In addition, in the operation of a large vertical furnace having a furnace inner diameter of 3.0 m or more, if the stamp layer at the center of the furnace bottom is eroded as described above, only the erosion rate of the rough layer is increased. Therefore, this part is eroded in the horizontal direction (outside of the furnace) sequentially from the central part ahead of the other part (dense part), and further, the hot metal is in the eroded part (coarse part). It was found that by entering (metal), the dense refractory layer that was not eroded was peeled and floated, and erosion of the entire furnace refractory layer further progressed.

  Based on the above findings, the inventors have intensively studied a desirable lining structure for the bottom refractory of the vertical furnace, and as a result, formed an amorphous refractory stamp layer inside the furnace base brick layer. The bottom refractory lining structure of the vertical furnace in which a part or all of the stamp layer is replaced with a precast block is effective As a result, the present invention has been developed.

In the present invention,
(1) The construction range of the precast block is a portion where the refractory erosion rate is fast on the furnace bottom surface;
(2) The precast block has a construction range in the center of the furnace bottom, and has a pre-worked stamp layer under the precast block and a post-worked stamp layer on the outer periphery of the precast block. thing,
(3) The precast block has a concave portion on a side surface that contacts a joint surface between the blocks,
(4) The precast block has a convex portion on a side surface that hits a joint surface between the blocks,
(5) The vertical furnace is a large furnace with an inner diameter of the furnace bottom of 3.0 m or more,
Is a more preferable solution.

  According to the furnace bottom refractory lining structure according to the present invention configured as described above, since the precast block that has been dried in advance is used as the lining refractory only in the furnace bottom central part where the erosion of the furnace bottom part is severe. Compared to the case where the entire surface including the central portion is constructed with a stamp material as in the prior art, the construction time can be shortened. In addition, according to the present invention, the center of the furnace bottom is lined with a uniform and dense precast block over the entire thickness direction, and compared with the furnace bottom of the stamp material laminate structure, The wear rate can be significantly reduced. In particular, the use of a precast block eliminates the layered joint surface that is repeatedly rough and dense as seen during stamping work, reduces the amount of metal squeezed between the layers, and increases the bottom life of the furnace.

  Therefore, according to the present invention, the wear rate of the lining refractory layer used for the bottom of a vertical furnace such as a blast furnace or a shaft furnace, particularly the wear rate at the center of the bottom of the furnace is greatly reduced, and long-term continuous operation of the vertical furnace can be achieved. As a result, it becomes possible to improve productivity and reduce hot metal production cost by the amount that enables high operation rate operation.

It is a fragmentary sectional view of the vertical furnace bottom part concerning the present invention. It is a fragmentary sectional view of the furnace bottom part of the conventional vertical furnace. It is sectional drawing which shows the erosion situation at the time of precast block construction. It is sectional drawing which shows the erosion state in the prior art example which constructed only the stamp material. It is a perspective view which shows one Embodiment of a precast block.

  FIG. 1 is a diagram schematically showing a lower portion of a vertical furnace (cupola) for explaining an embodiment of the present invention. As shown in this figure, the furnace side wall is formed by laminating bricks 2 on the inner side of an unillustrated iron skin. At the bottom of the furnace side wall, a spout 1 for taking out hot metal and hot metal (slag) in a lump is formed.

  At the bottom of the furnace, the base brick layer 2 is built, and then the stamp layer 3 is formed by stamping the ASC stamp material. In the illustrated example, the precast block 4 is placed and installed only in the central part of the furnace floor where the erosion is severe, and then the stamp material is also stamped around the precast block 4 with a well-known rammer. By forming the stamp layer 3 so as to surround it, a lining structure at the bottom of the furnace is constructed.

  In the above stamping process, the layer thickness formed by one stamping is about 80 mm, and is usually divided into 5 to 10 layers, and the bottom stamp (in this case, the outer peripheral stamp layer around the precast) layer 3 Form.

  Unlike the stamp layer 3, the precast block 4 used in the present invention is a shaped refractory that is homogeneous in the thickness direction and excellent in corrosion resistance, because it is cast into a mold and molded and dried. The precast block 4 may have a simple shape such as a rectangular parallelepiped. However, as shown in FIG. 5, at least the corners of the upper outer peripheral edge are chamfered 6 or rounded, or at least the outer peripheral surface on the side in contact with the stamp layer. It is more preferable to form a concave portion 7 for preventing the rising of the stamp material into the bottom.

  Furthermore, it is preferable that the precast block 4 is subjected to grinding to adjust the shape after rough casting in a casting mold. When a plurality of the precast blocks 4 are arranged, the chamfer 6 is not necessary between the blocks facing each other, and only the outer peripheral portion may be chamfered as described above. This is because the chamfer 6 prevents the rammer from hitting the corners of the precast block 4 during stamping around the outer periphery. Further, the concave portion 7 can also be structured to have a concave portion 7 fitted to each other and a convex portion fitted to this with respect to the side surfaces of adjacent blocks, and in this case, the lifting prevention effect is further improved, The insertion of the metal 5 as in the prior art can be minimized.

  Next, the inventors conducted a comparative test of the characteristics of the precast block 4 and the stamp layer 3. This comparative test was performed by a conventional method of forming a stamp layer on the bottom of a vertical furnace, and first, a stamp layer consisting of two layers each having a thickness of 80 mm was formed. And about the stamp layer 3, 0-10mm part, 35-45mm part, 70-80mm part (0-10mm part from the lower part) was extract | collected from the upper part of the upper stamp layer, and each density was measured. The upper layer was larger and the lower layer was smaller.

  On the other hand, for the precast block 4, a block having a thickness of 80 mm was prepared with the pressing pressure at the time of forming the stamp layer 3, and the density was measured. And the wear characteristic of four types of refractories obtained in this way was evaluated. The results are shown in Table 1. The wear characteristics were evaluated by an induction furnace lining erosion test method. This test is a test in which a refractory is lined in the induction furnace, the shaft furnace molten iron is induction-melted therein, and the refractory is eroded. The wear rate of the locally damaged portion due to erosion is measured and evaluated. The test conditions were a heating condition of 1550 ° C. × 6 h and a non-atmospheric atmosphere with nitrogen gas of 40 liters / minute. For the evaluation, a shaft furnace hot metal containing about 4 mass% of C was used.

  As a result, it was found that even the stamp layer 3 applied at one time has a large difference in wear rate between the upper layer portion 3a and the lower layer portion 3b. On the other hand, it was found that in the case where the brecast block was applied, the wear rate was smaller and superior in corrosion resistance than the most excellent stamp layer.

In this example, when a precast block suitable for the present invention and a stamp layer, which is a conventional comparative example, were applied to the bottom of the shaft furnace, a comparative test was conducted on the corrosion resistance (furnace bottom wear rate) of the two. It explains the results. The shaft furnace used is a large vertical furnace with an inner diameter of 3.4 m. The precast block used is a rectangular parallelepiped shape (size: 1500 mm × 930 mm × 300 mm) having a chamfered concave portion and a material of 62 mass% Al ₂ O ₃ -32 mass% SiC-1.5 mass% C. is there. On the other hand, the material used for the stamp layer is 65 mass% Al ₂ O ₃ -23 mass% SiC-2 mass% C.

  In the actual test, first, as an example of the lining structure of the application example of the present invention, a stamp material is applied on the brick layer of the furnace base, and four layers of 80 mm thickness are applied. After that, the stamp layer was formed by filling around the precast block with four layers of stamp material.

In addition, as an example of a conventional lining structure for comparison, a stamp material of 65 mass% Al ₂ O ₃ -23 mass% SiC-2 mass% C is applied to the base of the furnace base brick layer with a thickness of 80 mm and 8 layers. Stamp layer 3.

  About both the example of this invention and the comparative example, after operating for 60 days at the tapping rate of 70 t / h, the erosion situation of the furnace lining refractory was confirmed. The erosion rate was as shown in Table 2 at the center of the furnace. That is, in the example of the present invention in which the precast block was applied, the erosion of the block was stopped at half (150 mm) or less of the thickness before the block application, but in the comparative example, erosion of about 300 mm was confirmed in the furnace center. Further, in the comparative example, the hot metal was inserted into the coarse layer as shown in FIG. 3, and lifting was observed in the stamp layer at the center as shown in FIG.

  The technology of the present invention can be applied not only as a lining structure of a furnace bottom refractory of a shaft furnace such as a blast furnace or a cupola, but also as a structure of the bottom part of another metallurgical furnace or a ladle.

DESCRIPTION OF SYMBOLS 1 Outlet 2 Base brick layer 3 Stamp layer 3a Upper layer part 3b Lower layer part 4 Precast block 5 Metal 6 Chamfering 7 Recessed part (preventing raising)

Claims (6)

In the lining structure of the bottom refractory of the vertical furnace for hot metal production, in which a stamp layer of irregular refractory is formed inside the furnace base brick layer, a part or all of the stamp layer is precast block The lining structure of the bottom refractory of the vertical furnace characterized by being replaced by 2. The furnace bottom refractory lining structure according to claim 1, wherein the construction range of the precast block is a portion of the furnace bottom surface where the refractory erosion rate is fast. The construction range of the precast block is in the center of the furnace bottom, and has a pre-worked stamp layer under the precast block and a post-worked stamp layer on the outer periphery of the precast block. The lining structure of the bottom refractory of the vertical furnace according to claim 1 or 2. The lining structure of a bottom refractory for a vertical furnace according to any one of claims 1 to 3, wherein the precast block has a concave portion on a side surface corresponding to a joint surface between the blocks. The lining structure of a bottom refractory for a vertical furnace according to any one of claims 1 to 4, wherein the precast block has a convex portion on a side surface corresponding to a joint surface between the blocks. The vertical furnace lining refractory lining structure according to any one of claims 1 to 5, wherein the vertical furnace is a large furnace having an inner diameter of the furnace bottom of 3.0 m or more.

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