Patent Application
20170205144
Field of the Invention
The present invention relates to a fired precast block to be used as part of an inner lining layer of a blast furnace runner, a blast furnace, etc.
Description of the Related Art
Blast furnace runners are equipment for separating hot liquid (molten metal and slag) drained from a tap hole of a blast furnace and having high temperatures of 1,450 to 1,550 deg. C into molten metal and molten slag by utilizing a difference in specific gravity, and transporting the molten metal and the molten slag to subsequent transport vessels or other facilities, respectively. A refractory material (a wear lining) of portions of a blast furnace runner to contact the molten metal or slag is easily worn away by molten slag. Therefore, it is demanded that the wear lining has high heat resistance and corrosion resistance.
In general, a blast furnace runner is produced by pouring an unshaped material (a castable) comprising alumina, magnesium spinel, silicon carbide, etc. as aggregate in formwork and thus forming a passage for molten metal or slag. A wear lining of the blast furnace runner is supported by an iron shell constituting an outer frame by way of refractories such as alumina-silicon carbide bricks and a heat-insulating castable.
Of the hot liquid, molten metal is metal in a liquid state having iron as a main component, and molten slag is oxides such as SiO2, Al2O3 and CaO in a liquid state. The molten metal and the molten slag are different in specific gravity and the molten metal has a greater specific gravity than the molten slag. Therefore, the molten metal descends to and flows at a bottom of a blast furnace runner, while the molten slag floats on top of the molten metal. It should be noted that an interface between the molten metal and the molten slag is called metal line and an interface between the molten slag and the air is called slag line. A portion of a side wall of a blast furnace runner to contact the metal line is called a metal line portion, and a portion of a side wall of a blast furnace runner to contact the slag line is called a slag line portion.
A wear lining is susceptible to cracking and local damages because the wear lining is brought in contact with high-temperature molten metal or slag and subjected to repetition of heating and cooling. Particularly severe wear is observed on the wear lining at a portion of a side wall to contact a boundary surface of molten slag or metal, such as the abovementioned slag line portion and the abovementioned metal line portion, because local flows of the molten slag or metal occur. If wear of the wear lining increases and thus thickness of the remaining side wall decreases, there arises a risk that molten metal or slag may leak out. Leak of molten metal or slag not only causes trouble to attached facilities of the blast furnace but also exerts adverse effect on operation safety and surrounding environment. Therefore, the wear lining of the side wall needs to be repaired at regular intervals.
However, wear of the wear lining is particularly severe at the slag line portion and the metal line portion as mentioned above. That is to say, wear occurs not uniformly over the entire wear lining but locally. If the wear lining at other portions of side walls is in good condition but the wear lining remaining at the slag line portion or the metal line portion locally decreases in thickness, repair is needed in order to prevent molten metal or slag from leaking out. Therefore, careful inspection and repair of the wear lining are frequently executed in practical operation.
In view of these circumstances, Patent Document 1 discloses that in a blast furnace runner having an inner lining layer formed by casting or spraying an unshaped refractory material, a plurality of precast refractory blocks are combined and placed at a portion of a side wall to be heavily attacked by molten metal or slag flows from a tap hole and thus need to have high fire resistance. This technique aims to reduce wear of a very vulnerable portion of the inner lining layer of the blast furnace runner and allow the entire blast furnace runner to be uniformly worn away, and thus improve durability of the blast furnace runner.
However, since a plurality of precast refractory blocks are combined and placed, the technique of Patent Document 1 requires precast refractory blocks of a plurality of kinds of shapes. In addition, the technique of Patent Document 1 has a risk that the precast refractory blocks may drop off early due to wear of the unshaped refractory material covering peripheries of the combined and placed precast refractory blocks. Therefore, the technique of Patent Document 1 does not fully solve problems such as an increase in production costs caused by the need of precast refractory blocks of a plurality of kinds of shapes and a decrease in service life caused by early drop off of the precast refractory blocks.
[PTL 1] Japanese Unexamined Patent Application Publication No. H09-95708
The present invention has been made in view of the above circumstances. It is an object of the present invention to provide a fired precast block capable of preventing itself from dropping off early due to corrosion by molten metal or slag, increasing service life of a blast furnace runner, etc. and reducing production costs.
In order to solve the abovementioned problems, a fired precast block of the present invention comprises an upper surface to contact molten metal or slag, a lower surface opposing the upper surface, and a plurality of side surfaces and is used by being embedded in a castable in such a manner that the upper surface is exposed from the castable and the lower surface and the plurality of side surfaces contact the castable, wherein each side surface of at least one opposing pair of of the plurality of side surfaces includes a planar portion and an uneven portion, and the uneven portion has at least one groove-shaped concave portion.
In the present invention, each side surface of at least one opposing pair of side surfaces has an uneven portion, and the uneven portion has at least one groove-shaped concave portion. When the fired precast block of the present invention is applied, for example, to a side wall of a blast furnace runner, the fired precast block is placed in such a manner that an upper surface is located on a molten metal or slag side and a lower surface is located on an iron shell side, and side surfaces and the lower surface are buried in a wear lining.
Even if the wear lining covering peripheries of side surfaces of the fired precast block is worn away early in such a case, the groove-shaped concave portion of the present invention can grasp the remaining wear lining. Therefore, the fired precast block of the present invention can suppress itself from dropping off.
Besides, since the present invention is a fired precast block, its resistance to fire is good. Owing to being fired beforehand, microstructure of the precast block increases in strength and is hardly affected by temperature of molten metal or slag. Therefore, the fired precast block of the present invention improves in resistance to attacks of molten metal and slag and thermal shock in receiving the tapped molten metal and slag. Furthermore, precast blocks are much more inexpensive than refractory bricks, and have higher degree of freedom in shape.
As mentioned above, the fired precast block of the present invention can effectively protect a very vulnerable metal line or slag line portion of a side wall of a blast furnace runner, etc. from being worn away. In addition, owing to having means for preventing drop off on at least one opposing pair of side surfaces thereof, the fired precast block of the present invention can prevent itself from dropping off early due to corrosion. Furthermore, since the present invention is a fired precast block, the present invention is more inexpensive than a refractory brick.
Thus, the fired precast block of the present invention can prevent itself from dropping off early, increase service life of a blast furnace runner, etc. and reduce production costs.
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In these drawings, the same numerals and letters of reference denote the same parts. Material, shape, and relative arrangement of component parts found in the following description of the preferred embodiments are illustrative only and are not intended to limit the scope of the present invention. Left, right, up, down, forward, and backward in the description of the present invention indicate those shown in
A fired precast block 1 of Example 1 will be discussed with reference to
The fired precast block 1 of Example 1 is employed, for example, in a side wall of a molten metal and slag passage of a blast furnace runner, and used by being embedded in a castable constituting part of the side wall. Specifically, the fired precast block 1 is embedded in the castable in such a manner that the upper surface 2 is exposed from the castable and the lower surface 3 and the four side surfaces contact the castable. That is to say, the fired precast block 1 is used in a side wall of a blast furnace runner in such a manner that the upper surface 2 serves as a surface to contact molten metal or slag.
The four side surfaces comprise a first side surface 4, a second side surface 5, a third side surface 6 and a fourth side surface 7. The first side surface 4 and the third side surface 6 oppose each other and the second side surface 5 and the fourth side surface 7 oppose each other. In Example 1, the first side surface 4 and the third side surface 6 have the same shape, and the second side surface 5 and the fourth side surface 7 have the same shape.
As shown in
In the fourth side surface 7, as shown in
As shown in
The convex portion 84 protrudes from the planar portion 70 in the left direction, and is located between the upper concave portion 8a and the lower concave portion 8b. The convex portion 84 has a peak portion 85 which protrudes most in the left direction.
As shown in
Position and shape of the concave portions 8 will be discussed.
As shown in
As shown in
More specifically, in Example 1, W2 is a length from the upper surface side 21 to a boundary between the vertical side 7a1 and the upper arcuate side 8a1, W1 is a length from the boundary between the vertical side 7a1 and the upper arcuate side 8a1 to a peak portion 85, and W3 is a length from the peak portion 85 to the lower surface side 31.
Method for producing the fired precast block 1 of Example 1 is not particularly limited, and an example of the production method is shown below. One or more refractory raw materials selected from silica-alumina, alumina, magnesia, magnesia-calcia, spinel, zircon, zirconia, etc. are used as main aggregate. One or more kinds of materials selected from carbon, carbides, nitrides, borides, chromium oxide, silicon carbide, ultrafine alumina powder, clay, ultrafine refractory powder, fibers, metal powder, etc. are mixed with the main aggregate, if necessary. A binder, a dispersant, and water are added and those are well kneaded and cast in a mold.
After being cast, a molding is cured and dried. Although method for producing a conventional precast block finishes with this step, a step of firing the molding is carried out in Example 1. Desired firing temperature is 800 to 1,600 deg. C.
The binder and the dispersant used in Example 1 are the same as those used for production of conventional precast blocks. Desired examples of the binder are one or more selected from colloidal silica, alumina sol, alumina cement, portland cement, light buried magnesia, hydraulic alumina, sodium phosphate, phosphate glass, sodium silicate, orthophosphoric acid, phenol resin, pitch, etc. Desired examples of the dispersant are one or more materials selected from alkali metal phosphates, alkali metal polyphosphates, alkali metal polyphosphoric acid and alkali metal carboxylate.
Although not limited to the above-mentioned, the main aggregate of the fired precast block is desirably a combination of alumina and spinel or a combination of alumina and zircon. It is also desired that the raw material mixture has a high content of silicon carbide. An alumina-spinel precast block has a high corrosion resistance because slag components such as FeO and MnO2 form a solid solution with spinel and slag are thus prevented from penetration. An alumina-zircon precast block has an improved corrosion resistance because SiO2 generated by dissociation of zircon is present in a high-viscosity liquid phase and prevents slag from penetration. Furthermore, silicon carbide hardly gets wet with molten slag and has good fire resistance and volume stability, and is more inexpensive than other carbides, so addition of silicon carbide is efficient in reduction of production costs.
Moreover, a fired precast block is employed in Example 1. In general, a refractory brick is produced by preparing a powdery material and filling and compressing the powdery material in a mold under high pressure, and then firing an obtained green compact at elevated temperatures to sinter the green compact. The mold for forming a green compact is very expensive because high pressure is applied to the hard powdery material. In addition, the firing at elevated temperatures requires much cost. However, the refractory brick has a high density and exhibits high performance such as high corrosion resistance. Therefore, such refractory bricks are often used in a portion which particularly requires heat resistance and corrosion resistance.
On the other hand, a castable, which is an unshaped refractory, is suitably used in a portion where bricks are hard to be laid or a portion which needs some measures for heat insulation or corrosion resistance. Generally, a castable is applied by kneading raw materials of the castable with water and casting the kneaded material or spraying raw materials of the castable with water on a site. The castable is fired into a dense layer at high temperatures under actual operating environment.
In contrast to this, fired precast blocks are produced by kneading raw materials with water, casting the kneaded material in a mold and firing an obtained molding in a factory. In a case of on-site production, the amount of water to be added and a process for kneading raw materials of the castable need to be subtly adjusted to temperature and humidity and these adjustments often need to be done based on experience and professional intuition of workers. In some cases, a variation is generated in accuracy in construction. In a factory, however, production of fired precast blocks are carried out under controlled temperature and humidity. Therefore, products can fully exhibit material characteristics and have little variation in performance. Formwork for fired precast blocks is inexpensive because the formwork does not need high pressure application unlike those for refractory bricks, and has a high degree of freedom in shape. Therefore, fire precast blocks can be produced at much lower costs than refractory bricks.
Advantageous effects of the fired precast block 1 of Example 1 will be hereinafter described. As mentioned before, the second side surface 5 and the fourth side surface 7 have the same shape in Example 1. Therefore, the fourth side surface 7 will be discussed as an example but the second side surface 5 exhibits similar advantageous effects.
The fired precast block 1 of Example 1 is used by being embedded in a castable such as a wear lining of a blast furnace runner. In this case, the castable, which has a lower fire resistance to the fired precast block 1 of Example 1, is worn away by molten metal or slag earlier than the fired precast block 1 of Example 1. Therefore, there is a risk that the fired precast block 1 may drop off due to corrosion of the castable surrounding the fired precast block 1. However, the fourth side surface 7 of the fired precast block 1 of Example 1 has two groove-shaped concave portions 8 (the upper concave portion 8a and the lower concave portion 8b). The groove-shaped concave portions 8 grasp the remaining castable and suppresses the fired precast block 1 from dropping off.
As shown in
Upon putting the ratio of the uneven portion 80 in the fourth side surface 7 within the abovementioned range, the concave portions (the upper concave portion 8a and the lower concave portion 8b) can more effectively grasp the remaining castable. That is to say, upon used in a side wall of a blast furnace runner, etc., the fired precast block 1 of Example 1 contributes to an increase in service life of the blast furnace runner, etc.
Moreover, when A is a length from a two-dot chain line h extended from the vertical side 7a1 toward the lower surface side 31 to a deepest portion 83 of the upper arcuate side 8a1, and B is a length from the two-dot chain line h to the peak portion 85 of the convex portion 84 as shown in
Long use of a blast furnace runner may increase wear of the wear lining which forms a molten metal or slag passage and cause molten metal or slag to penetrate into the castable surrounding the convex portion 84 of the fired precast block 1 embedded in the wear lining. In this case, a portion of the castable located above the convex portion 84 is worn away by the molten metal or slag and not left at all. Therefore, the upper concave portion 8a cannot effectively grasp the castable, and the convex portion 84 cannot exert the anchoring effect.
However, the fired precast block 1 of Example 1 has the lower concave portion 8b. That is to say, there is at least one groove-shaped concave portion which is more distant from the upper surface 2 than the convex portion 84. Accordingly, even if the fired precast block 1 falls in the abovementioned situation, the lower concave portion 8b can grasp the remaining castable and the fired precast block 1 suppresses itself from dropping off from the wear lining.
Moreover, when L1 is a straight-line length of the lower surface side 31 and L2 is a straight-line length from the peak portion 85 of the convex portion 84 provided on the second side surface 5 to the peak portion 85 of the convex portion 84 provided on the fourth side surface 7 as shown in
Owing to the abovementioned structure, the convex portion 84 prevents penetration of molten metal or slag. That is to say, because the convex portion 84 provided on the uneven portion 80 protrudes in the right or left direction from the planar portion 70, the castable located below the convex portions 80 is less likely to be worn away by molten metal or slag. Therefore, the lower concave portion 8b can more effectively grasp the remaining castable and suppress the fired precast block 1 from dropping off. Hence, use of the fired precast block 1 of Example 1 in a blast furnace runner, etc. contributes to an increase in service life of the blast furnace runner, etc.
Example 2 is an example of a plurality of fired precast blocks of the present invention applied to a blast furnace runner. Example 2 will be discussed with reference to
A blast furnace runner 9 shown in
In the blast furnace runner 9, as shown in
As shown in
Upon placed in the wear lining 10 which constitutes part of side walls of a molten metal and slag passage of the blast furnace runner 9, the fired precast blocks 1 of Example 2 can protect the particularly vulnerable slag line portions 14 and metal line portions 15 from being worn away by molten metal or slag and increase service life of the blast furnace runner 9.
However, portions of the wear lining 10 located between the fired precast blocks 1 of Example 2 may be worn away early. In such a case, there is a possibility that the molten metal or slag may enter from a worn portion of the wear lining 10 and the fired precast blocks 1 may drop off early from normal position.
In the fired precast blocks 1 of Example 2, each of side surfaces perpendicular to the flow direction of the molten metal and slag 13 (a second side surface 5 and a fourth side surface 8) has groove-shaped concave portions 8 (an upper concave portion 8a and a lower concave portion 8b) as means for preventing drop off. Therefore, even if portions of the wear lining 10 surrounding the fired precast blocks 1 are worn away by the molten metal and slag 13, the concave portions 8 (the upper concave portion 8a and the lower concave portion 8b) can grasp the remaining wear lining 10 and thus effectively prevent the fired precast blocks 1 from dropping off early. In addition, the fired precast blocks 1 of Example 2 exhibit similar advantageous effects to those of Example 1 described above.
Furthermore, although the uneven portion 80 of each side surface of the opposing pair of side surfaces of the fired precast block 1 of Example 1 comprises two concave portions 8, the number of concave portions 8 can be one or three or more in another example of the present invention.
Moreover, although the uneven portion 80 is provided on one opposing pair of side surfaces of the fired precast block 1 of Example 1, an uneven portion 80 can be provided on one or more of the other side surfaces.
In addition, although the side surfaces having the uneven portions 80 are placed in a perpendicular direction to the flow direction of molten metal and slag in each of the fired precast blocks 1 of Example 2, instead of these side surfaces, side surfaces having uneven portions 80 can be placed in parallel to the flow direction of molten metal and slag. Such a fired precast block can also exhibit the advantageous effects of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-007069 | Jan 2016 | JP | national |
