JP7277773B2 - Manufacturing method of castable refractories - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a castable refractory used as a lining furnace material for kiln equipment for ironmaking.

Castable refractories are kneaded with water using a mixer at the furnace construction site, and the resulting kneaded material is simply poured into the furnace construction site while applying vibration. can be built. Therefore, the castable refractory is positioned as a very important refractory in order to improve the efficiency of furnace construction work and save labor.

In this way, the castable refractory built as the lining furnace material of the kiln equipment for ironmaking contains water, so before use, the water in the castable refractory is evaporated by heating with a gas burner or microwave. should be allowed to dry.

However, when rapid heating and drying occurs, the amount of water vapor generated inside the castable refractory increases, and the increased pressure of the water vapor may cause the castable refractory to explode. Recently, with the widespread use of dense castable refractory materials such as low-cement castables, the importance of this problem is increasing.

In order to eliminate the explosion during heating and drying of castable refractory containing water, in Patent Document 1, 0.01 to 1.0% by mass of organic fibers having a diameter of 1 to 100 μm and a length of 1 to 15 mm are added to the castable refractory. A method of adding is disclosed. The action of the organic fiber is that in the process of evaporating and diffusing the water contained in the refractory by heating and drying, the organic fiber melts or decomposes to create a three-dimensional diffusion path for water vapor inside the refractory. Another object of the present invention is to facilitate the diffusion of water vapor to the outside of the refractory system to reduce the pressure of water vapor generated inside the refractory.

Patent Literature 2 discloses a technique for preventing agglomeration of organic fibers added to a castable refractory during kneading. Further, Patent Literatures 3 and 4 disclose techniques for making it easier to form vent holes that serve as diffusion paths for water vapor during the heating and drying process of water-containing castable refractories.

JP-A-61-10079 Japanese Patent No. 2849154 Japanese Patent No. 5676207 Japanese Patent No. 5676343

By using the methods described in Patent Documents 1 to 4, it has become possible to eliminate the explosion during heat drying of water-containing castable refractories. On the other hand, when observing the structure of the castable refractories to which organic fibers are added described in Patent Documents 1 to 4 after heating and drying, it is found that huge vent holes having a length of about 300 μm and a width of about 20 μm are formed. It could be confirmed.
The formation of such huge air holes lowers the corrosion resistance and tensile strength of the castable refractory, and thus contributes to the deterioration of the durability of the castable refractory.

It is effective to use fine organic fibers with a fiber diameter of less than 1 μm in order to prevent the formation of giant air holes observed after heat-drying castable refractories to which organic fibers have been added in the prior art.
However, since the organic fibers having a fiber diameter of less than 1 μm are fine, they have a strong cohesive force and are easily agglomerated during kneading.

The present inventor adds an alkaline aqueous solution in which organic fibers having a fiber diameter of less than 1 μm are dispersed to alumina cement and a refractory material composed of refractory powder particles having a maximum particle diameter of 30 mm or less and kneads them. By doing so, the inventors have found that the problem can be solved, and have completed the present invention.

The gist of the present invention is as follows.
(1) preparing an alkaline organic fiber suspension containing organic fibers having a fiber diameter of less than 1 μm, a dispersant, and an antifoaming agent;
A method for producing a castable refractory, characterized by adding the organic fiber suspension to a refractory material composed of alumina cement and refractory granules and kneading them.
(2) According to (1), the amount of the organic fiber added to the fire-resistant material is 0.01 to 0.50% by mass with respect to 100% by mass of the fire-resistant material. A method for manufacturing a castable refractory.
(3) The method for producing a castable refractory according to (1) or (2), wherein the organic fiber suspension has a pH of 8 or more and 13 or less.

According to the present invention, the castable refractory can be used to prevent explosion during the heating and drying process, and to produce a densely-constructed body. As a result, the life of the kiln equipment for ironmaking can be extended, resulting in improved productivity.

In the present invention, there are two reasons why organic fibers having a fiber diameter of less than 1 μm are used.
The first point is that in the process of evaporating and diffusing the water contained in the refractory by heating and drying, the organic fiber melts and disappears, thereby generating a three-dimensional diffusion path for water vapor inside the refractory, and the water vapor. The purpose is to reduce the pressure of water vapor generated inside the refractory by facilitating its diffusion to the outside of the refractory system.
The second point is to prevent formation of huge vent holes after drying the castable refractory by heating.

Examples of organic fibers having a fiber diameter of less than 1 μm used in the present invention include polyester nanofibers having a fiber diameter of 700 nm and cellulose nanofibers having a fiber diameter of 20 nm, and at least one of these can be used.

In the present invention, the amount of organic fiber added with a fiber diameter of less than 1 μm is 0.01 to 0.50 mass in terms of external weight with respect to 100 mass% of the refractory material composed of alumina cement and refractory granules. % range is preferred. If the amount of organic fibers having a fiber diameter of less than 1 μm is less than 0.01% by mass, the number of ventilation holes that serve as diffusion paths for water vapor generated during the heating and drying process is small, so water vapor does not flow out of the refractory system. This is because the diffusion does not proceed easily, and the pressure of the water vapor generated inside the refractory rises, causing the refractory to explode. If the amount of organic fibers having a fiber diameter of less than 1 μm exceeds 0.50% by mass, the number of air holes formed after drying by heating increases and the porosity increases, resulting in a decrease in corrosion resistance.

In the present invention, the method for preparing the alkaline organic fiber suspension is not particularly limited. For example, an alkaline organic fiber suspension is prepared by dispersing organic fibers having a fiber diameter of less than 1 μm in an alkaline aqueous solution, or by adjusting the alkaline aqueous solution in which the organic fibers are dispersed. can be Alternatively, while the organic fibers are dispersed in water, the organic fibers, the dispersant, and the antifoaming agent are added to prepare a suspension in which the organic fibers are dispersed so that the pH becomes alkaline. good.

The reason why the suspension in which the organic fibers having a fiber diameter of less than 1 μm are dispersed is alkaline is that when kneading with alumina cement and a refractory material composed of refractory powder, aggregation of the organic fibers is prevented. This is to prevent When the suspension is alkaline, OH groups are adsorbed on the surfaces of the organic fibers, and the organic fibers are apparently negatively charged.

In the kneading process with refractory materials, alumina cement particles become negatively charged when they come into contact with water, but since organic fibers are negatively charged, they repel alumina cement particles. Aggregation due to coalescence can be prevented.

On the other hand, if the suspension in which organic fibers having a fiber diameter of less than 1 μm are dispersed is neutral or acidic, the organic fibers are apparently uncharged or positively charged. When the organic fibers in such a charged state collide with the negatively charged alumina cement particles during the kneading process, they are combined with the alumina cement particles and agglomerate.

To adjust the pH of the suspension in which organic fibers having a fiber diameter of less than 1 μm are dispersed, an aqueous solution in which phosphoric acid is dissolved and an aqueous solution in which sodium hydroxide is dissolved are used. This can be done by adding a different mixed aqueous solution to the suspension.
Specifically, the pH of the organic fiber suspension can be adjusted by changing the mixing ratio of the aqueous solution in which phosphoric acid is dissolved and the aqueous solution in which sodium hydroxide is dissolved.

Depending on the dispersant and antifoaming agent coexisting with the organic fibers, it may not be possible to adjust the pH to a specific value, but if the pH of the organic fiber suspension can be adjusted to 8 or higher, the organic fibers having a fiber diameter of less than 1 μm can be sufficiently dispersed. be able to. Further, if the pH is 13 or less, the corrosion resistance is not lowered even if Na is mixed.

The reason for dissolving the dispersant in the solvent of the organic fiber suspension to be kneaded with the refractory material composed of alumina cement and refractory granules is as follows.
The first point is to uniformly disperse the organic fibers having a fiber diameter of less than 1 μm in the solvent. The second point is to uniformly disperse the powder having a maximum particle size of 10 μm or less contained in the refractory powder during the kneading process. The solvent for the suspension is an aqueous solution or water for dispersing the organic fibers having a fiber diameter of less than 1 μm.

When the solvent of the organic fiber suspension does not contain a dispersant in advance, for example, when water and a dispersant are simultaneously added to alumina cement and refractory granules having a maximum particle size of 8 mm or less and kneaded is that the dispersant is dissolved in water, the dissolved dispersant is adsorbed on the surface of powder having a maximum particle size of 10 μm or less, and the powder collides with each other and aggregates before the powder disperses. Because it does.

Alkali metal phosphates, polycarboxylates, polyacrylates, alkylsulfonates, aromatic sulfonates and the like can be used as dispersants, and one or more of these can be used. The amount of the dispersant added is 0.1 to 0.6% by mass with respect to 100% by mass of the refractory material composed of alumina cement and refractory granules having a maximum particle size of 30 mm or less. A range is preferred. The dispersant may be used in either powder form or liquid form.

The reason for dissolving the antifoaming agent in addition to the dispersant in the water to be kneaded with the refractory material composed of the alumina cement and the refractory powder is as follows.
During the process of adding water in which a dispersant is dissolved to alumina cement and refractory granules and kneading them, bubbles are generated in the kneaded material. Since these bubbles do not disappear during the kneading process, they remain as voids inside the castable refractory constructed after kneading. Voids remaining inside the castable refractory lead to an increase in porosity, resulting in a decrease in corrosion resistance. Based on the above, antifoaming agents are used to eliminate foam generated during the kneading process.

Alcohols, fatty acid esters, amines, ethers, phosphate esters, silicones, etc. can be used as antifoaming agents, and at least one of these can be used. Antifoaming agents may be liquid, solid, or semi-solid, and any state can be used. The amount of antifoaming agent added is 0.003 to 0.010% by mass with respect to 100% by mass of the refractory material composed of alumina cement and refractory granules having a maximum particle size of 30 mm or less. A range is preferred.

In order to prepare an aqueous solution in which organic fibers with a fiber diameter of less than 1 μm, a dispersant, and an antifoaming agent are dispersed and dissolved, in addition to manual stirring, a rotating stirrer that rotates a stirrer, and a container that rotates or vibrates. A device that oscillates or the like may be used, or a device that can collide the aqueous solution discharged from a nozzle and stir it with the collision energy may be used.

As the alumina cement used in the present invention, an alumina cement containing CaO.Al ₂ O ₃ can be used. The blending ratio of alumina cement is within the range of 2 to 6% by mass with respect to 100% by mass of the refractory material composed of alumina cement and refractory granules having a maximum particle size of 30 mm or less. is preferred.

Raw materials for the refractory powder of the present invention include electrofused alumina, sintered alumina, electrofused magnesia, sintered magnesia, electrofused spinel, sintered spinel, zirconia, zircon, fused silica, silica, chamotte, feldspar, Using cordierite, mullite, silicon _carbide , graphite, silica fume, titania, yttria, mullite, cordierite, SiC, _Si3N4 , AlN, _B4C , BN, _ZrB2 , carbon can be done.

In the refractory material used in the present invention, the refractory granules having a particle size of more than 10 μm and 30 mm or less are preferably 80 to 95 mass by mass with respect to 100% by mass of the refractory material, and the maximum particle size is 10 μm or less. The refractory powder is preferably 5 to 20% by mass with respect to 100% by mass of the refractory material.

Used when adding an aqueous solution in which organic fibers with a fiber diameter of less than 1 μm, a dispersant, and an antifoaming agent are dispersed and dissolved into alumina cement and a refractory material composed of refractory granules and kneading. Any of vortex mixers, turbo mixers, twin-screw mixers, high-speed mixers, and ball mills can be used as mixers.

In addition, hardening modifiers known as additives for castable refractories, short metal fibers (for example, stainless steel fibers), ceramic fibers, chromium ore, and the like may be added.

In the construction of the castable refractory of the present invention, the organic fiber is added to the refractory material so that the solvent of the organic fiber suspension is 4 to 6% by mass with respect to the entire refractory material. It can be carried out by adding a suspension and pouring the kneaded product obtained by kneading with a mixer into a mold for construction. In order to improve the filling performance during construction, a vibrator is attached to the formwork, or a rod-shaped vibrator is inserted into the refractory to vibrate it.

Examples of the present invention and comparative examples are shown below.

[Production of Examples 1 to 4]
In Examples 1 to 4, the organic fibers having a fiber diameter of less than 1 μm, the dispersant, and the antifoaming agent were dispersed and dissolved in water using a ball mill. The pH was 4 to 8 immediately after the organic fibers having a fiber diameter of less than 1 μm and various additives used in the present invention were mixed with water. The pH of the aqueous solution is adjusted by using an aqueous solution in which phosphoric acid is dissolved and an aqueous solution in which sodium hydroxide is dissolved, and adding a mixed aqueous solution in which the mixing ratio of the two aqueous solutions is changed to the water. rice field. The pH of the aqueous solution was measured with a commercially available pH meter.

Example 3 will be specifically described as an example. 40 cc of the aqueous solution was used for kneading with respect to 1 kg of the refractory material. 1 g of organic fiber, 6 g of dispersant, 0.1 g of antifoaming agent, 8 cc of phosphoric acid with a concentration of 0.02 mol/L, 16.6 cc of sodium hydroxide with a concentration of 0.02 mol/L, and 15.4 cc of water in a ball mill. It was done by loading and mixing for 3 hours.

Examples 1 to 4 are invention examples in which an organic fiber, a dispersant, and an antifoaming agent were previously dispersed and dissolved in water to be added to the refractory material during kneading. In Examples 1 to 4, an organic fiber having a fiber diameter of less than 1 μm, a dispersing agent, and an antifoaming agent are dispersed and dissolved in a refractory material composed of alumina cement and refractory granules to make it alkaline. The prepared aqueous solution was added and kneaded using a vortex mixer.

As organic fibers, Nanofront (diameter: 700 nm) manufactured by Teijin and Vinfis (diameter: 20 nm) manufactured by Sugino Machine Co., Ltd. were used. Also, as the refractory material, raw materials used for typical monolithic refractories used as lining furnace materials for iron-making kiln equipment were used.

[Production of Comparative Examples 1 to 4]
Comparative Examples 1 and 2 are lining furnace materials for a blast furnace gutter, Comparative Example 3 is a lining furnace material for a steel ladle, and Comparative Example 4 is a lining furnace material for a tundish.

As shown in Tables 1-1 and 1-2, Comparative Examples 1 and 5 are Example 1, Comparative Example 2 is Example 2, Comparative Example 3 is Example 3, and Comparative Example 4 is Example. 4 corresponds to each raw material composition. The refractory granules used in Comparative Examples 1-4 and Examples 1-5 are as follows.
Refractory granules of Example 1, Comparative Example 1 and Comparative Example 5: 54% by mass of spinel, 41% by mass of alumina, 2% by mass of silica, 3% by mass of carbon
Refractory granules of Example 2 and Comparative Example 2: 33% by mass of alumina, 62% by mass of SiC, 1.5% by mass of silica,
Carbon 3% by mass, B ₄ C 0.5% by mass
Refractory granules of Example 3 and Comparative Example 3: 92% by mass of alumina, 7% by mass of magnesia, 1% by mass of silica
Refractory granules of Example 4 and Comparative Example 4: 67% by mass of alumina, 30% by mass of chamotte, 3% by mass of silica

However, Comparative Examples 1 to 4 were manufactured by adding water to a refractory powder containing organic fiber, a dispersant, an antifoaming agent, and alumina cement, and kneading all the components at once using a vortex mixer. It differs from Examples 1 to 4 in that Comparative Example 5 is an example in which an aqueous solution in which an organic fiber, a dispersant, and an antifoaming agent are dispersed and dissolved is prepared in advance, added to a refractory material, and kneaded using a vortex mixer. It differs from Example 1 in that the pH of is acidic.

Table 1-1 shows the raw material composition of Examples 1 to 4, and Table 1-2 shows the composition of castable refractories of Comparative Examples 1 to 5, respectively. The dispersant used in Examples 1 to 4 and Comparative Examples 1 to 5 was sodium polycarboxylate, the antifoaming agent was silicon, and the alumina cement was alumina cement (CaO·Al ₂ O ₃ , 12CaO·7Al ₂ O ₃ , CaO.2Al ₂ O ₃ mixture). As organic fibers, polypropylene fibers were used in Comparative Examples 1, 2 and 5, and vinylon fibers were used in Comparative Examples 3 and 4.

In Tables 1-1 and 1-2, the numerical value of "mixing amount (% by mass)" in the item "8 mm" to "10 μm or less" in the item "Particle size range of refractory powder" Shows the percentage by mass of the inner covering with respect to 100% by mass of the raw material. In Tables 1-1 and 1-2, the numerical values in the item "Aluminum cement compounding amount (mass%)" indicate the mass% of the inner coating with respect to 100 mass% of the refractory material. Other items (the amount of water added to the refractory material in the outer coating, the amount of organic fiber added, the amount of dispersant added, and the amount of defoaming agent added) are all Shows the mass% of.

[Evaluation of Examples and Comparative Examples]
Examples 1 to 4 and Comparative Examples 1 to 5 were evaluated by measuring the apparent porosity after drying at 300°C, air permeability after drying at 300°C, explosiveness, and corrosion resistance.

Apparent porosity and air permeability were measured by the following methods. The kneaded product was poured into a frame having a shape of φ50 mm×50 mm in height while being vibrated. Then, after curing at room temperature for 24 hours, the frame was removed and dried at 300° C. for 24 hours to prepare a measurement sample. The apparent porosity was measured according to JIS-R2205, and the air permeability was measured according to JIS-R-2115.

Evaluation of explosiveness was performed by the following method. The kneaded product was poured into a frame having a shape of φ100 mm×100 mm in height while being vibrated. Then, after curing at room temperature for 24 hours, the frame was removed to prepare a sample for evaluation. Explosibility is evaluated by placing the sample in an electric furnace preheated to 800°C, holding it for 30 minutes, removing it from the electric furnace, and visually observing the presence or absence of cracks on the sample surface and the presence or absence of blistering of the sample. Evaluated by Samples with no blisters and no cracks on the sample surface were judged to be excellent in explosion resistance.

Corrosion resistance was evaluated by the rotary erosion furnace method using blast furnace slag as the erosion material. The corrosion resistance evaluation sample was prepared by pouring the kneaded material into a metal frame of a predetermined size while applying vibration, curing at room temperature for 24 hours, drying at 110 ° C. for 24 hours, and firing at 1000 ° C. for 6 hours in the atmosphere. made.

In the rotary erosion furnace method, the evaluation sample is lined in the rotary erosion furnace, and when the surface temperature of the evaluation sample reaches 1600 ° C., slag is put into the furnace, and after 30 minutes, the molten slag is discharged. The test was carried out by repeating the operation of adding new slag four times. After the test, the samples were cut and corrosion resistance was evaluated by measuring the maximum corrosion depth on the cut surface. Corrosion resistance is an example in which the maximum corrosion depth of the samples of Comparative Examples 1, 2, 3, and 4 is set to 100% of the length, and the refractory material has the same composition as the comparative example. 1, Example 2, Example 3, and Example 4 were evaluated relative to each other. A smaller value means better corrosion resistance.

Tables 1-1 and 1-2 show the measurement results of the apparent porosity, air permeability, explosiveness, and corrosion resistance of Examples 1-4 and Comparative Examples 1-5.
When Examples 1 to 4 are compared with Comparative Examples 1 to 4, the apparent porosity after drying at 300 ° C. is lower than that of Comparative Examples, and in addition to being excellent in corrosion resistance, explosion resistance is better than that of Comparative Examples. It has been confirmed to be as good as

In Comparative Example 5, organic fibers having a fiber diameter of less than 1 μm, a dispersant, and an antifoaming agent were dispersed and dissolved, and the aqueous solution had a pH of 5, which was acidic. It has high hanging porosity and excellent explosion resistance, but has poor corrosion resistance.

INDUSTRIAL APPLICABILITY According to the present invention, a castable refractory can be used to prevent explosion during the heating and drying process, and it is possible to manufacture a lining furnace material for ironmaking kiln equipment that has a dense structure and is extremely durable. As a result, the life of the kiln equipment for ironmaking can be significantly extended.

Claims (3)

preparing an alkaline organic fiber suspension containing organic fibers with a fiber diameter of less than 1 μm, a dispersant, and an antifoaming agent;
A method for producing a castable refractory, characterized by adding the organic fiber suspension to a refractory material composed of alumina cement and refractory granules and kneading them. The castable refractory according to claim 1, wherein the amount of the organic fiber added to the refractory material is 0.01 to 0.50% by mass with respect to 100% by mass of the refractory material. A method of making things. 3. The method for producing a castable refractory according to claim 1, wherein the organic fiber suspension has a pH of 8 or more and 13 or less.