Mud material for blast furnace tap hole filling

Abstract

To provide a resin-based mud material capable of preventing clogging during charging into a blast furnace tap hole.SOLUTION: A mud material for blast furnace tap hole filling is obtained by kneading a novolac-type phenol resin, a solvent, and a refractory raw material mixture, wherein the novolac-type phenol resin has a weight-average molecular weight of 300 to 1500, the addition rate of a curing agent that promotes curing of the novolac-type phenol resin is 0.08 mass% or less (including 0) relative to 100 mass% of the phenol novolac resin, and the refractory raw material mixture contains 2 to 20 mass% of carbon black.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a mud material for filling a blast furnace taphole. In this specification, the "mud material for filling a blast furnace taphole" is also simply referred to as "mud material." [Background technology]

[0002] In blast furnace operation, after the completion of tapping, mud material is forced into the taphole using a mud gun and then plugged. Then, when the tapping is completed after a predetermined time (usually 2 to 5 hours), the mud material that has been baked by the furnace heat up until that time is drilled to form a runner. The basic composition of mud is a clay-like refractory material made by adding a binder to a refractory raw material compound and kneading it. Known types of mud include tar-based mud, which uses coal tars (hereinafter referred to as "tars") with adjusted composition as the binder, and resin-based mud, which uses a resin (usually a resin solution) as the binder. Of these, tar-based mud has advantages such as high plasticity (filling ability) and a large amount of residual carbon after firing, which effectively forms carbon bonds, thereby contributing to improved strength and reduced porosity. However, due to concerns about the working environment, mud is gradually being replaced by resin-based mud. However, resin-based mud materials have the problem of low plasticity (fillability), such as being prone to clogging during filling, because the resin itself, which is one component of the binder, has a lower hardening temperature than tar-based materials and tends to harden at low temperatures. Furthermore, resin-based mud materials tend to crack more easily than tar-based materials after filling, and to prevent this, a hardener is generally used to improve strength, but adding a hardener to resin-based mud reduces the thermal stability of the mud material, making it more prone to clogging during filling, creating a technical contradiction.

[0003] On the other hand, Patent Document 1 discloses a resin-based mud material that uses a novolac phenolic resin with a number average molecular weight of 601 to 700 as a resin, which is one component of the binder, and adds hexamethylenetetramine (hexamine) as a curing agent at an outer percent addition rate of 0.1 to 3 wt % relative to the novolac phenolic resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3938953 Summary of the Invention [Problem to be solved by the invention]

[0005] As in Patent Document 1, the use of a novolac phenolic resin with a low number-average molecular weight improves the plasticity (filling ability) of the mud material. However, it has been found that even when such a novolac phenolic resin with a low number-average molecular weight is used, clogging may occur during filling depending on the filling method and filling conditions of the mud material. Specifically, there are methods for filling the mud material, such as slowing down the filling speed midway through filling the mud material or temporarily suspending filling during filling (hereinafter collectively referred to as the "two-stage filling method"). It has been found that clogging is particularly likely to occur when using such two-stage filling methods.

[0006] Therefore, the problem to be solved by the present invention is to provide a resin-based mud material that is less likely to clog during filling into a blast furnace taphole. [Means for solving the problem]

[0007] In order to solve this problem, the inventors used a novolac-type phenolic resin with a low number average molecular weight, as in Patent Document 1, but did not add the hardener added in Patent Document 1, or added only in an extremely small amount.Furthermore, based on the technical idea of ​​using carbon black to obtain the strength development effect after filling achieved by the conventional hardener, the inventors conducted extensive testing and research on the specific configuration of a resin-based mud material, while also taking into consideration the basic properties required of a mud material, and as a result, they came up with the present invention.

[0008] That is, according to one aspect of the present invention, there is provided the following mud material for filling a taphole of a blast furnace. A blast furnace taphole filling mud material obtained by kneading a novolac phenolic resin, a solvent, and a refractory raw material blend, The novolac phenolic resin has a weight average molecular weight of 300 to 1500, the addition rate of the curing agent that promotes the curing of the novolac phenolic resin is 0.08% by mass or less (including 0) relative to 100% by mass of the phenolic novolac resin; The refractory raw material blend is a mud material for filling a taphole of a blast furnace, which contains 2 to 20 mass % of carbon black. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a resin-based mud material that is less likely to clog during filling into a blast furnace taphole. [Brief explanation of the drawings]

[0010] [Figure 1] Schematic diagram showing an overview of the hot indentation test. DETAILED DESCRIPTION OF THE INVENTION

[0011] The mud material of the present invention is a mud material for filling a taphole of a blast furnace, which is obtained by kneading a novolac phenolic resin, a solvent, and a refractory raw material blend.

[0012] The novolac phenolic resin used in the present invention has a weight-average molecular weight of 300 to 1500. If the weight-average molecular weight of the novolac phenolic resin is less than 300, the strength after firing, which is one of the basic properties required for a mud material, will be insufficient, and the apparent porosity after firing will be high, resulting in insufficient corrosion resistance. On the other hand, if the weight-average molecular weight of the novolac phenolic resin exceeds 1500, clogging will easily occur during filling into the blast furnace taphole. The weight-average molecular weight of the novolac phenolic resin is preferably 300 to 1000. The weight-average molecular weight specified in the present invention is determined by gel permeation chromatography.

[0013] The amount of novolac phenolic resin used can be approximately the same as the amount of resin used in general resin-based mud materials, for example, 8 to 14 mass% based on 100 mass% of the refractory raw material blend. In the present invention, the novolac phenolic resin may be dissolved in a solvent before use. Known solvents can be used to dissolve the novolac phenolic resin, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, furfural, glycerin, polyglycerin, diglycerin, n-decanol, sec-undecyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, butylene glycol, 2-methyl-2,4-pentanediol, hexanediol-2,5, heptanediol-2,4, dipropylene glycol, dibutyl phthalate, di-2-ethylhexyl phthalate, diethyl phthalate, diheptyl phthalate, propylene carbonate, organic acid esters, castor oil, etc. Such solvents can be used, for example, in an amount of 2 to 10% based on 100% by mass of the refractory raw material composition.

[0014] As described above, in the present invention, the hardener added in Patent Document 1 is not added, or if added, it is added in an extremely small amount. That is, in the mud material of the present invention, the addition rate of the hardener, such as hexamine, which promotes the hardening of the novolac phenolic resin, is set to 0.08 mass% or less (including 0) relative to 100 mass% of the novolac phenolic resin. Therefore, clogging is less likely to occur during filling into the blast furnace taphole.

[0015] On the other hand, in the present invention, carbon black is used in the refractory raw material blend. Carbon black not only improves the plasticity (filling ability) of the mud material, but also provides the strength development effect after filling, which is achieved by conventional curing agents. That is, in the present invention, carbon black prevents clogging of the mud material while it is being filled into the blast furnace taphole, and improves its strength after filling. Therefore, even if the curing agent addition rate is kept to 0.08% by mass or less (including 0), the strength after firing can be ensured. That is, carbon black is composed of nano-sized carbon particles, and it is believed that it not only mechanically improves the plasticity of the mud material, which is mainly composed of refractory raw materials with various particle shapes and particle size distributions, but also improves the thermal stability of the novolac phenolic resin by capturing radical components generated in the novolac phenolic resin during heating. Furthermore, when the novolac phenolic resin volatilizes and quasi-carbonizes (up to about 800°C) due to heating, it acts as a filler to promote the development of strength in the mud material, and at higher temperatures (about 1200°C), it reacts with ferrosilicon produced by the thermal decomposition of silicon nitride iron and other compounds in the mud material to produce silicon carbide, which is thought to further improve the strength of the mud material.

[0016] In the mud material of the present invention, the carbon black content in the refractory raw material blend is 2 to 20% by mass. If the carbon black content is 2% by mass, clogging is likely to occur during filling into the blast furnace taphole, and the strength after filling (after firing) is insufficient. On the other hand, if the carbon black content exceeds 20% by mass, the dispersibility of the refractory raw material blend, which is the raw material for the mud material, decreases. As a result, the apparent porosity of the mud material after firing increases, resulting in insufficient corrosion resistance. The carbon black content is preferably 4 to 10% by mass. Note that carbon black generally used as a refractory raw material for mud materials can be used.

[0017] The refractory raw material composition of the present invention contains carbon black as described above, but the remainder, similar to conventional mud compositions, is primarily composed of one or more materials selected from aluminous raw materials and siliceous raw materials. Here, aluminous raw materials refer to refractory raw materials containing more than 50% by mass of Al2O3 as a chemical component, such as alumina and bauxite. Siliceous raw materials refer to refractory raw materials containing more than 50% by mass of SiO2 as a chemical component, such as silica and pyrophyllite. The remainder of the refractory raw material composition of the present invention primarily contains one or more materials selected from these aluminous raw materials and siliceous raw materials. Specifically, when the remainder of the refractory raw material composition is taken as 100% by mass, the remainder of the refractory raw material composition contains more than 50% by mass of aluminous raw materials and siliceous raw materials. The remainder of the refractory raw material composition of the present invention may contain other refractory raw materials, such as coke, clay, silicon nitride, silicon carbide, and metallic silicon, as appropriate, similar to conventional mud compositions. In the mud material of the present invention, the particle size composition of the remaining refractory raw material blend can be appropriately adjusted within the particle size range of 3 mm or less, similar to conventional mud materials.

[0018] The mud material of the present invention can be obtained by adding the novolac phenolic resin and solvent as a binder to the refractory raw material composition and kneading them together. The ratios of the novolac phenolic resin and solvent are appropriately adjusted so that the ratio of the novolac phenolic resin is in the range of 8 to 14% by mass relative to 100% by mass of the refractory raw material composition, while also taking into consideration the workability during filling. [Example]

[0019] Table 1 shows the carbon black content in the refractory raw material blends used in the mud materials according to the examples of the present invention and the comparative examples, as well as the composition of the resin and solvent, and also shows the evaluation results of the properties of the resulting mud materials. The evaluation items and evaluation methods are as follows:

[0020] [Table 1]

[0021] <Compressive strength and apparent porosity after firing> Each mud material was molded into a 40 x 40 x 160 mm columnar shape using a metal frame and a hydraulic molding machine at a molding pressure of approximately 11 MPa. The temperature of the mud material was 65°C ± 5°C. The molded mud material was constrained in a metal frame and degreased at 500°C. It was then packed in coke and fired at 1200°C for 3 hours. The fired mud material was measured for compressive strength according to JIS R2553 and apparent porosity according to JIS R2205. Low compressive strength increases the risk of "hole breakage." On the other hand, excessively high compressive strength reduces pore openness. Therefore, a compressive strength of 10 MPa or higher was considered acceptable, with a higher value being preferable, with an upper limit of 30 MPa. Furthermore, high apparent porosity reduces corrosion resistance. Therefore, an apparent porosity of less than 30% was considered acceptable.

[0022] <Maximum filling pressure during hot press-fit testing> The maximum charging pressure during a hot injection test was measured as an indicator of the likelihood of clogging during charging into a blast furnace taphole. Figure 1 shows a schematic overview of the hot injection test. This hot injection test simulates the evaluation area of ​​a blast furnace taphole shown in the upper part of Figure 1. In the hot injection test, a silicon carbide sleeve 2 with a cavity 100 mm in diameter and 900 mm deep was placed in a furnace 1 maintained at 1200°C. Mud material A was forced into the sleeve 2 using a pump 3 and cylinder 4 simulating a mud gun. The charging method was the two-stage charging method described above. Specifically, the mud was first charged to half its depth, and after a predetermined waiting time, the remaining mud material was charged. The charging pressure was then measured using a hydraulic pressure gauge 31 attached to the pump 3 to determine the maximum charging pressure. Note that all maximum charging pressures were measured in the second stage. A high maximum charging pressure increases the likelihood of clogging during charging into a blast furnace taphole. Therefore, a maximum filling pressure of 10 MPa or less was deemed acceptable.

[0023] <Crack area ratio of the filler cross section after hot indentation test> After filling the mud material using the hot press-fit test described above, the material was fired by holding it at an ambient temperature of 1200°C for three hours, then allowed to cool naturally to room temperature. The center of the filled material was then cut to observe the state of filling of the mud material. The cross section of the cut-off filled material was photographed with a camera to obtain image data, which was then analyzed using the image analysis software Image J. The area ratio of cracks within the analyzed region was calculated as the crack area ratio. A high crack area ratio indicates poor filling of the mud material, making it more susceptible to so-called "hole breakage." Therefore, a crack area ratio of less than 5% was considered acceptable.

[0024] <Difference in extrusion resistance after storage at 80°C for 1 day> For each example, a mud sample of 1 kg ± 50 g was wrapped in aluminum foil and heated at an ambient temperature of 80°C for one day. After cooling to 60°C, the extrusion resistance was measured when the sample was extruded from a metal frame. The difference between the extrusion resistance measured at 60°C after mixing was calculated. The extrusion resistance was measured using the extrusion test device described in the "Refractories Handbook, Revised 12th Edition, Japan, Refractories Technology Association, August 31, 2015, p. 229." The temperatures of the mud material and metal frame during measurement were kept within a range of 60°C ± 2°C. If the difference in extrusion resistance is large, clogging is likely to occur when the blast furnace taphole is filled. Therefore, the extrusion resistance difference should be 10 kg / cm. 2 The smaller the difference in extrusion resistance value, the more preferable it is.

[0025] <Overall rating> When all the above evaluation results were passed, it was marked as ◯ (pass), and when any of the evaluation results were failed, it was marked as × (fail).

[0026] In Table 1, Examples 1 to 3 are examples in which the weight-average molecular weight of the novolac phenolic resin differs, but all are within the range of the present invention, and all of the above-mentioned evaluation results were acceptable. It can be seen from Examples 1 to 3 that as the weight-average molecular weight of the novolac phenolic resin increases, the maximum charging pressure and the difference in extrusion resistance during the hot injection test tend to increase. From this, it was determined that, from the viewpoint of preventing clogging during charging into the blast furnace taphole, it is preferable for the weight-average molecular weight of the novolac phenolic resin to be small within the range of the present invention, specifically, 300 to 1000. Comparative Example 1 is an example in which the weight-average molecular weight of the novolac phenolic resin is below the lower limit of the present invention, and the evaluation results other than the maximum filling pressure during the hot indentation test were unsatisfactory. On the other hand, Comparative Example 2 is an example in which the weight-average molecular weight of the novolac phenolic resin is above the upper limit of the present invention, and the maximum filling pressure during the hot indentation test exceeded 10 MPa, resulting in a failure. Note that for the mud material in Comparative Example 2 in which the maximum filling pressure during the hot indentation test exceeded 10 MPa, no filling body was obtained, and therefore the crack area ratio was not evaluated by cross-sectional observation.

[0027] Although Examples 4 to 8 have different carbon black contents, all of them are within the range of the present invention and passed all of the above-mentioned evaluation results. In particular, Examples 5 to 7, which have carbon black contents within the preferred range, were able to increase the compressive strength while suppressing increases in the maximum filling pressure and extrusion resistance difference during the hot indentation test. Comparative Example 3 is an example in which the carbon black content is below the lower limit of the present invention, and the plasticity of the mud material is reduced, resulting in a maximum filling pressure of more than 10 MPa during the hot indentation test, resulting in failure. On the other hand, Comparative Example 4 is an example in which the carbon black content is above the upper limit of the present invention, and the dispersibility of the refractory raw material blend is reduced, resulting in an increase in the apparent porosity after firing and the crack area ratio of the filler cross section, resulting in failure.

[0028] Example 9 is an example in which a curing agent (hexamine) was added at an addition rate of 0.08% by mass relative to 100% by mass of the phenol novolac resin, based on Example 6. Although there was a tendency for the maximum filling pressure, crack area ratio, and extrusion resistance value difference during the hot pressing test to increase, all evaluation results were at an acceptable level. In contrast, Comparative Example 5 is an example in which, based on Example 6, a curing agent (hexamine) was added at an addition rate of 0.1 mass% relative to 100 mass% of phenol novolac resin. The difference in the pressing resistance value was large, and the plasticity of the mud material decreased during hot filling, resulting in a maximum filling pressure of over 10 MPa during the hot pressing test, resulting in a failure. From the above, it can be said that in the present invention, it is most preferable that the addition rate of the curing agent is 0 mass %, that is, that no curing agent is contained. [Explanation of symbols]

[0029] 1 furnace 2 sleeves 3. Pump 31 Oil Pressure Gauge 4 cylinders A Mud material

Claims

1. A blast furnace taphole filling mud material obtained by kneading a novolac phenolic resin, a solvent, and a refractory raw material blend, The novolac phenolic resin has a weight average molecular weight of 300 to 1500, the addition rate of the curing agent that promotes the curing of the novolac phenolic resin is 0.08% by mass or less (including 0) relative to 100% by mass of the novolac phenolic resin; The refractory raw material blend is a mud material for filling a taphole of a blast furnace, and contains 2 to 20 mass % of carbon black.

2. The blast furnace taphole filling mud material according to claim 1, wherein the weight average molecular weight of the novolac phenolic resin is 300 to 1000.

3. The blast furnace taphole filling mud material according to claim 1 or 2, wherein the carbon black content in the refractory raw material blend is 4 to 10 mass%.

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