Hot dry spray material and hot dry spray construction method
Technical field
[0001]
　The present invention particularly relates to a hot dry spray material (amorphous refractory) and a construction method thereof, which are suitably used for hot repair of industrial kilns such as molten steel pots and furnace bodies (furnace walls) of electric furnaces.
　The term "hot" refers to an environment in which the temperature of the surface to be constructed is approximately 600 ° C. or higher.
Background technology
[0002]
　The construction method for amorphous refractories differs depending on the intended use. For example, when an amorphous refractory material is used as a castable material for the lining of an industrial kiln, the construction is carried out through a kneading process, a pouring process, a curing process, and a drying process of the refractory material and water.
[0003]
　On the other hand, amorphous refractories may be used as spraying materials for the construction or repair of industrial kilns. In this case, the construction method is roughly classified into a wet spray construction method and a dry spray construction method. In the wet spraying construction method, the spray material and water are sufficiently kneaded in advance by a mechanical kneading mechanism such as a mixer, and the kneaded material is pumped toward the spray nozzle and the tip of the spray nozzle is pumped. This is a construction method in which air and a quick-setting admixture are introduced and sprayed. The dry spraying construction method is a construction method in which water is added to a dry powder spraying material at the tip of a spraying nozzle and sprayed without using a mechanical kneading mechanism.
[0004]
　In general, spraying work using a spraying material is performed in both hot and cold environments, and the dry spraying method is applied in both environments. However, the wet spraying method is generally not applied in a hot environment. This is because in the case of the wet spraying method, since the kneading work is required in advance, the cleaning work such as the cleaning work of the transport hose used when pumping with the kneader or the pump is required after the work. Therefore, the wet construction method is not suitable for spraying in a hot environment, and the dry spraying method, which is a simple construction method, is often applied.
[0005]
　As a spraying material (amorphous refractory for dry spraying) used in this dry spraying construction method, a spraying material containing bitter limestone is disclosed in Patent Document 1. However, when the present inventors performed hot spraying using a spraying material containing calcium carbonate, it was found that there is room for improvement in corrosion resistance in particular.
Prior art literature
Patent documents
[0006]
Patent Document 1: Japanese Unexamined Patent Publication No. 58-145660
Outline of the invention
Problems to be solved by the invention
[0007]
　An object to be solved by the present invention is to improve corrosion resistance in a hot dry spray material and a hot dry spray construction method.
Means to solve problems
[0008]
　The present inventors have conducted repeated studies focusing on slag permeability in order to improve corrosion resistance in hot dry spray materials and hot dry spray construction methods, and as a result, the particle size is 0.075 mm or more and less than 1 mm. It was found that the bitter limestone of No. 1 contributes greatly to the improvement of slag permeability, and the present invention has been completed.
[0009]
　That is, according to one aspect of the present invention, the following hot dry spray material is provided.
　It is a hot dry spray material containing a refractory raw material and a binder, and in a
　total amount of 100% by mass of the refractory material and the binder, 10% by mass or more of bitter limestone having a particle size of 0.075 mm or more and less than 1 mm comprising less mass%,
　in the refractory raw material and the total content in 100% by mass of the binder, which is the content of magnesia limestone having a particle size of less than 0.075mm is 35 mass% or less (including 0.), dry for hot Spray material.
[0010]
　Further, according to another aspect of the present invention, the following hot-dry spraying method is provided.
　In a hot-dry spraying method in which a compound containing a refractory material and a binder is pumped toward a spray nozzle through a pipe, water is added at the tip of the spray nozzle, and the
　mixture is hot-sprayed. In 100% by mass of the total amount of the refractory material and the binder, 10% by mass or more and 50% by mass or less of bitter limestone having a particle size of 0.075 mm or more and less than 1 mm is contained,
　and in 100% by mass of the total amount of the refractory raw material and the binder. A hot-dry spraying method in which the content of refractory limestone having a particle size of less than 0.075 mm is 35% by mass or less (including 0).
[0011]
　The grain size referred to in the present invention is the size of the sieve mesh when the fire-resistant material particles are sieved and separated. For example, a clay limestone having a particle size of less than 0.075 mm is a sieve mesh. Is a limestone that passes through a sieve of 0.075 mm, and a limestone having a particle size of 0.075 mm or more is a limestone that does not pass through a sieve having a sieve size of 0.075 mm.
Effect of the invention
[0012]
　According to the present invention, the slag permeability is improved by setting the content of the hard soil limestone having a particle size of 0.075 mm or more and less than 1 mm in a specific range, and as a result, the corrosion resistance is improved.
A brief description of the drawing
[0013]
[Fig. 1] Fig. 1 is an explanatory diagram showing a method for evaluating adhesiveness.
Mode for carrying out the invention
[0014]
　The hot dry spray material of the present invention is a hard soil limestone having a particle size of 0.075 mm or more and less than 1 mm in 100% by mass of the total amount of the refractory material and the binder (hereinafter referred to as “total amount”) (hereinafter referred to as “medium grain”). "Binder limestone") is contained in an amount of 10% by mass or more and 50% by mass or less.
[0015]
　This medium-grained magnesium limestone (CaCO 3 , MgCO 3 ) creates voids inside by the degassing reaction (CaCO 3 , MgCO 3 → CaO, MgO + 2CO 2 ) during operation heat reception , and is highly reactive. To produce free CaO. Then, the slag that permeates from the moving surface is trapped in the generated voids and further reacts with the free CaO to produce the high melting point composition 2CaO · SiO 2 (melting point 2130 ° C.), which suppresses the permeation of the slag. ..
　If the content of medium-grain bitter limestone is less than 10% by mass, the slag penetration suppressing effect (slag permeability improving effect) is not sufficiently exhibited, and a sufficient corrosion resistance improving effect cannot be obtained. On the other hand, when the content of bitter limestone exceeds 50% by mass, voids (open pores) are excessively generated by the degassing reaction, and as a result, slag penetration is promoted and corrosion resistance is lowered.
　The content of medium-grained clay limestone is preferably 20% by mass or more and 40% by mass or less in a total amount of 100% by mass.
[0016]
　The hot dry spray material of the present invention may contain limestone with a particle size of less than 0.075 mm (hereinafter referred to as "fine-grained limestone").
　Here, fine-grained bitter limestone also produces CaO by the above-mentioned degassing reaction, but since this CaO is formed from fine-grained bitter limestone having a large contact area with water, a hydration reaction (CaO + 2H 2 O → Ca 2+ + 2OH − ) is likely to occur, and it is considered that Ca 2+ generated by this hydration reaction reacts with a binder or the like to contribute to strengthening the bond (increasing strength) of the matrix portion of the sprayed body, and the above-mentioned high melting point composition. It is considered that it does not contribute to product formation.
　However, when a large amount of fine-grained calcium carbonate is contained, the effect of the degassing reaction (effect of void formation) described above becomes stronger than the effect of strengthening the bond (strengthening) of the matrix portion described above, and voids are formed in the matrix portion. Is excessively generated, and as a result, the strength of the sprayed body is significantly reduced and the corrosion resistance is also lowered. Therefore, the content of fine-grained bitter limestone is 35% by mass or less (including 0) in 100% by mass of the total amount.
[0017]
　On the other hand, since the fine-grained bitter limestone exerts the bond strengthening (strengthening) action of the matrix portion as described above, the bond strengthening (strengthening) action of the matrix portion is positively utilized to provide adhesiveness (adhesiveness). From the viewpoint of improving the adhesiveness between the sprayed material and the surface to be constructed after the industrial kiln is operated after spraying, the content of fine-grained bitter limestone is 5% by mass or more in 100% by mass of the total amount 35. It is preferably 5% by mass or less, more preferably 5% by mass or more and 25% by mass or less.
[0018]
　The hot dry spray material of the present invention may also contain limestone with a particle size of 1 mm or more (hereinafter referred to as "coarse-grained limestone"). However, since coarse-grained bitter limestone produces large voids by the above-mentioned degassing reaction, if a large amount of coarse-grained bitter limestone is contained, slag permeates easily and corrosion resistance tends to decrease. Therefore, the content of coarse-grained hard soil limestone is preferably less than 50% by mass (including 0) in 100% by mass of the total amount.
[0019]
　As described above, the above-mentioned slag penetration suppressing effect (slag permeability improving effect) according to the present invention can be obtained by setting the content of medium-grained soil limestone in a specific range among the soil limestones of each particle size. ..
[0020]
　The hot dry spraying material of the present invention may include various refractory materials generally used for spraying materials as refractory materials other than olivine, but the main component thereof is consideration of compatibility with olivine. It is preferable to use a basic refractory material (basic oxide) such as magnesia, olivine, and used magnesia carbonaceous waste. The refractory material other than the basic refractory material may include alumina and the like.
[0021]
　As the binder, those generally used for dry spraying materials can be used as the binder, and examples thereof include phosphates, silicates, pitches, powdered resins, alumina cements, etc., but phosphorus is typically used. Use one containing at least one selected from phosphates and silicates. Examples of the phosphate include sodium phosphate, potassium phosphate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum phosphate and the like, and silicates include sodium silicate, potassium silicate and calcium silicate. Further, the amount (content) of the binder used may be the same as that of a general dry spray material, and is, for example, 1% by mass or more and 10% by mass or less in a total amount of 100% by mass.
　An additive may be used as the binder. As the additive, various additives such as a curing agent, a dispersant, and a thickener can be used. For example, slaked lime can be used as the curing agent, phosphate can be used as the dispersant, and clay can be used as the thickener.
[0022]
　In the hot dry spray material of the present invention as described above, the above-mentioned compound containing the refractory material and the binder is pressure-fed toward the spray nozzle through a pipe, and water is added at the tip of the spray nozzle. It is used in the hot dry spraying method of spraying hot.
　The amount of water added may be the same as that of a general hot-dry spraying method. For example, the amount of water added is 10% by mass or more and 40% by mass or less in the outer cover with respect to 100% by mass of the total amount.
Example
[0023]
　Table 1 shows the material composition and evaluation results of the examples and comparative examples of the hot dry spray material of the present invention. In Table 1, "others" of the binder are clay, slaked lime, dispersant and the like.
　The evaluation items and evaluation methods are as follows.
[0024]

　The hot dry spray material of each example was sprayed from the spray nozzle at a spray rate of 15 kg / min toward the surface of magnesia brick heated to 1000 ° C. as the surface to be constructed for 1 minute. At this time, the amount of water added at the tip of the spray nozzle was set to 20% by mass with respect to 100% by mass of the total amount.
　By performing the spraying for 1 minute, a sprayed construction body including a construction body of a spraying material having a thickness of about 50 mm was obtained. A sample of a predetermined size cut out from the sprayed body was eroded at 1650 to 1700 ° C. for 3 hours using a rotary erosion tester and using synthetic slag with C / S = 1.0 as an erosion agent. The maximum amount of erosion of each example was measured, and the relative amount was determined with the maximum amount of erosion of Example 1 as 100. The smaller the relative amount, the higher the corrosion resistance (slag permeability). In the evaluation of corrosion resistance, the case where the relative amount was 100 or less was evaluated as ⊚ (good), the case where the relative amount was more than 100 and 110 or less was evaluated as ◯ (possible), and the case where the relative amount was more than 110 was evaluated as × (impossible).
[0025]

　For a sample of a predetermined size cut out from the sprayed construction body of each example obtained in the above-mentioned procedure, the compressive strength at room temperature was measured according to JIS R2575, and the relative value with the compressive strength of Example 1 as 100. Asked. The larger this relative value is, the higher the strength of the sprayed body is. In the evaluation of the sprayed body strength, the case where the relative value was 80 or more was evaluated as ⊚ (good), the case where the relative value was 70 or more and less than 80 was evaluated as ○ (possible), and the case where the relative value was less than 70 was evaluated as × (impossible).
[0026]
As
　shown in the upper part of FIG. 1, a space of 15 mm is provided in the center of the yokan-shaped magnesia brick, and water (20 mass by externally applied to 100 mass% of the total amount) is applied to the spray material of each example during the interval. %) Is added, kneaded, cured, dried, and then fired at 1400 ° C. for 3 hours with a load of 0.25 MPa applied from the tip of yokan as shown in the lower part of FIG. Obtained. The bending strength of the adhesive surface of the test piece of each example was measured by a three-point bending test, and a relative value was obtained with the bending strength of Example 1 as 100. The larger the relative value, the higher the adhesiveness. In the evaluation of adhesiveness, the case where the relative value was 100 or more was evaluated as ⊚ (good), and the case where the relative value was more than 60 and less than 100 was evaluated as ◯ (possible).
　This evaluation of adhesiveness is an index showing the adhesive strength between the sprayed material and the surface to be constructed after the industrial kiln is operated after the spraying in the actual spraying work.
[0027]
In
　each of the above evaluations, if all are ◎, it is ◎ (good), if there is no x and there is ○ in one of them, it is ○ (possible), and if any one is ×, it is × (impossible). did. This comprehensive evaluation is an index showing the durability of the actual sprayed construction body.
[0028]
[table 1]
[0029]
　Examples 1 to 9 are hot dry spraying materials within the scope of the present invention. In each case, the overall evaluation was ◎ (good) or ○ (acceptable), and good results were obtained.
[0030]
　Comparative Example 1 is an example in which the content of medium-grained clay limestone is low. The slag penetration suppressing effect (slag permeability improving effect) was not sufficiently obtained, and the evaluation of corrosion resistance was × (impossible).
　Comparative Example 2 is an example in which the content of medium-grained hard soil limestone is high. Due to the above-mentioned degassing reaction, voids (open pores) were excessively generated to promote slag penetration, and as a result, the evaluation of corrosion resistance became × (impossible).
　Comparative Example 3 is an example in which the content of fine-grained bitter limestone is high. Due to the influence of the degassing reaction described above, voids were excessively generated in the matrix portion, and as a result, the evaluation of corrosion resistance and sprayed body strength became × (impossible).
The scope of the claims
[Claim 1]
　It is a hot dry spray material containing a refractory raw material and a binder, and in a
　total amount of 100% by mass of the refractory material and the binder, 10% by mass or more of bitter limestone having a particle size of 0.075 mm or more and less than 1 mm comprising less mass%,
　in the refractory raw material and the total content in 100% by mass of the binder, which is the content of magnesia limestone having a particle size of less than 0.075mm is 35 mass% or less (including 0.), dry for hot Spray material.
[Claim 2]
　The hot dry spray material according to claim 1, wherein the binder contains at least one selected from phosphates and silicates.
[Claim 3]
　The hot dry spray material according to claim 1 or 2, wherein the content of the hard soil limestone having a particle size of less than 0.075 mm is 5% by mass or more and 35% by mass or less.
[Claim 4]
　In a hot-dry spraying method in which a compound containing a refractory material and a binder is pumped toward a spray nozzle through a pipe, water is added at the tip of the spray nozzle, and the
　mixture is hot-sprayed. In 100% by mass of the total amount of the refractory material and the binder, 10% by mass or more and 50% by mass or less of bitter limestone having a particle size of 0.075 mm or more and less than 1 mm is contained,
　and in 100% by mass of the total amount of the refractory raw material and the binder. A hot-dry spraying method in which the content of refractory limestone having a particle size of less than 0.075 mm is 35% by mass or less (including 0).