JPH11263673A - Lightweight castable and method for using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the weight and to considerably improve the adhesiveness of a castable by blending ceramic fibers, alumina, calcined gypsum and an org. sizing agent in a specified ratio. SOLUTION: This lightweight castable contains 5-50 wt.% ceramic fibers, 10-80 wt.% alumina, 5-30 wt.% calcined gypsum and 0.05-3 wt.% org. sizing agent based on an external rate. The ceramic fibers may be either of non- crystalline and crystalline ceramic fibers. Either of granular (curly) and bulky shapes may be used if >=30% Al2 O3 component is contained. The alumina preferably has <=10 μm particle diameter from the viewpoint of adhesiveness. The org. sizing agent is preferably at least one kind of sodium alginate, CMC or methylcellulose. The castable may further contain a 0.05-3 wt.% blowing agent based on an external rate. The blowing agent is preferably a commercially available detergent or sodium laurylsulfate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an industrial furnace such as a heating furnace, an incinerator for municipal solid waste and general waste, or a furnace for general kilns.
Alternatively, the present invention relates to a lightweight castable used for lining a continuous casting container such as a tundish or a ladle, and a method of using the same.

[0002]

2. Description of the Related Art Conventionally, a lightweight castable of this type has been made of ceramic fibers 1 to 4 as alumina aggregate.
0 wt%, alumina and / or mullite 20-60 wt% as refractory raw material, calcined gypsum 5-50 wt as binder
A lightweight refractory castable containing 0.5% to 10% by weight of at least one of clay, bentonite, and ultrafine silica powder as a workability aid is known (see JP-A-8-245271). The lightweight refractory castable is kneaded with water when used.

[0003]

However, in the conventional lightweight castable, calcined gypsum as a binder does not react with ceramic fibers as an alumina aggregate, and
Since it has a Mohs' hardness of 2 and functions as a soft lubricant, it does not impair the heat resistance of the alumina aggregate, and can improve the workability by improving the extensibility of the castables. Addition of clay, bentonite, and ultrafine silica powder, which have poor heat resistance as an auxiliary agent, necessitates an increase in the amount of alumina fine powder to cover heat resistance. There is a problem that cannot be improved. Further, in order to enhance the adhesiveness to the wall surface, it is required to be excellent in three properties of bulk specific gravity, linear change rate, and riband loss.
All three properties cannot be improved, and there is a problem that the adhesiveness is not good. On the other hand, water used for construction includes
Since there is no adhesiveness, improvement is required. Therefore, an object of the present invention is to provide a lightweight castable that can significantly improve weight reduction and adhesiveness, and a method of using the same.

[0004]

In order to solve the above-mentioned problems, a first lightweight castable according to the present invention comprises ceramic fibers of 5 to 50 wt%, alumina of 10 to 80 wt%,
5% to 30% by weight of plaster of Paris
-3 wt%. The organic paste is preferably at least one of sodium alginate, carboxymethylcellulose and methylcellulose. The second lightweight castable is characterized in that the first lightweight castable contains 0.05 to 3% by weight of a foaming agent in an outer ratio. The foaming agent is preferably at least one of a commercially available detergent and sodium lauryl sulfate.
On the other hand, the method of using the lightweight castable is characterized in that a silica sol aqueous solution is used as kneading water when the first or second lightweight castable is constructed.

[0005] When the content of the ceramic fiber as the alumina aggregate is less than 5 wt%, the heat insulating property is reduced, and the contraction rate of the construction after heating is increased. On the other hand, if it exceeds 50 wt%, the workability (adhesion) will be reduced, and it will be difficult to obtain a construction having excellent strength properties. As the ceramic fiber, any of an amorphous fiber and a crystalline fiber can be used. Al ₂ O ₃ component is also 3
If it is 0% or more, it can be used irrespective of the granular (curl) or bulk shape.

When the content of alumina as a refractory raw material is 1
When the amount is less than 0 wt%, heat resistance is poorly imparted.
If it exceeds 80 wt%, the thermal conductivity and the bulk specific gravity increase. Alumina having a particle size of 60 μm or less can be used, but it is preferable to use alumina having a particle size of 10 μm or less in consideration of adhesiveness and the like.

[0007] The content of calcined gypsum as a binder is 5 wt.
When the content is less than%, not only the mechanical strength properties of the lining construction body are lacking, but also the hardening time of the cast construction body is significantly prolonged, and it becomes difficult to obtain a construction body having excellent properties. On the other hand, if it exceeds 30 wt%, it causes a warpage or a crack in the construction body due to the setting and expanding properties of the plaster of Paris. The curing reaction of calcined gypsum (CaSO ₄ .0.5H ₂ O) with added water is represented by the following equation. CaSO ₄・
As the calcined gypsum of 0.5H ₂ O + 1.5H ₂ O → CaSO ₄ .2H ₂ O, those widely used for ceramic shapes are generally used, but depending on the situation, any gypsum may be used. It is also possible to use calcined gypsum. Further, calcined gypsum is known to have α and β types, but both can be used.

When the content of the organic paste as a workability aid is less than 0.05% by weight, the adhesiveness and water retention are lacking, and when it exceeds 3% by weight, the strength characteristics decrease due to an increase in kneading water. And the tackiness is extremely increased, resulting in a significant adverse effect on workability. The organic paste can be used in a mixture, but the effect of the mixture is not recognized.

When the content of the foaming agent is less than 0.05% by weight, the foaming property is lacking, and it is difficult to obtain a high heat insulating property.
If it exceeds 3 wt%, the strength characteristics of the construction body will be affected in terms of the amount of foaming.

The silica sol aqueous solution as the kneading water is used for further strengthening the adhesion to the wall surface, and its concentration is used as a commercially available solution having a silica content of 20 to 50 wt% (silica sol stock solution) itself. Is possible,
A solution obtained by diluting the solution with water to a concentration of 1/2 to 1/10 can also be used. The lightweight castable of the present invention has a kneading water addition amount of 40 to 150% by weight, so that the addition with a diluting liquid is preferable from the viewpoint of cost.

The lightweight castable of the present invention is mainly applied by spraying, but the kneaded soil kneaded with a mortar mixer can be applied by trowel coating and patching as well as ordinary castables. It can be used not only as a lining material in the industrial furnace field with excellent heat resistance and strength properties, but also as a veneering material constructed with ceramic fibers.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to specific examples and comparative examples. Examples 1 to 5 and Comparative Examples 1 to 3 First, 70% of Al ₂ O ₃ or A in the proportions shown in Tables 1 and 2
Table 1 and Table 2 show an organic glue (excluding Comparative Example 1) of sodium alginate, carboxymethylcellulose, or methylcellulose in a total of 100% by weight of ceramic fiber of 48% l ₂ O ₃ , 10 μm or less of sintered alumina and calcined gypsum. The mixture was added at the indicated ratios to obtain respective mixtures.
Next, kneading each mixture with a silica sol stock solution, a silica sol 50% solution (a silica stock solution diluted to 1/2 concentration with water) or a silica sol 10% solution (a silica sol stock solution diluted to 1/10 concentration with water). Water is added as an external ratio as shown in Table 1 to form a kneaded soil, which is cast into a mold, demolded after 24 hours, and each test piece (40 × 40 × 160 mm).
I got Next, each test piece was subjected to drying (110 ° C.) and heat treatment (1000 ° C., 1400 ° C.), and the bending strength, bulk specific gravity, and linear change rate after each of the above treatments were measured. As shown in FIG.
In addition, when a spray test was performed on each of the kneaded soils, the reband loss and adhesiveness were as shown in Tables 1 and 2.

[0013]

[Table 1]

[0014]

[Table 2]

Comparative Examples 4 and 5 First, 70% of Al ₂ O ₃ or Al ₂ O at a ratio shown in Table 2 was used.
_{3 At} least one of bentonite, silica fine powder and elutriated clay is added to 48% ceramic fiber, 10 μm or less sintered alumina and calcined gypsum in the ratio shown in Table 2,
A total of 100% by weight of the two mixtures was obtained. Next, kneading water was added to both mixtures in an external ratio as shown in Table 2, and the mixture was cast into a mold as kneaded soil, and after 24 hours, demolded to obtain both test pieces (40 × 40 × 160 mm). . Next, both test pieces were dried (110 ° C) and heat-treated (1000 ° C,
1400 ° C.), and the bending strength, bulk specific gravity and linear change rate after each of the above treatments were measured. The results are shown in Table 2. Further, when a spray test was performed on both kneaded soils, the rivand loss and the adhesiveness were as shown in Table 2.

From Tables 1 and 2, the lightweight castables of Examples 1 to 5 have good strength characteristics, bulk specific gravity and linear change rate characteristics for both dried and fired products, and have a reband loss due to a spray test. 0 to 5 wt% in the wall and 1 to 8 wt% in the ceiling. Spraying and detachment of the construction body were observed after half a year of spraying with a thickness of 50 mm to the ceiling of the heating furnace wall, although there were microcracks. It was found that the adhesiveness was good. On the other hand, although the lightweight castables of Comparative Examples 1 and 2 are good in characteristics, they have an operating surface layer of about 10
mm, the adhesiveness is lacking, and the lightweight castable of Comparative Example 3 has a good reband loss on both the wall and the ceiling, but has a linear change rate of 3.5 after the heat treatment at 1400 ° C. %, Which indicates that after the same spraying half year after the construction, the entire construction dropped out, which seems to be caused by the volume shrinkage of the construction, and it was found that the adhesiveness was lacking. Furthermore,
The light-weight castables of Comparative Examples 4 and 5 are good in characteristics, and after only half a year of spraying with a thickness of 50 mm to the wall of the heating furnace, only fine cracks are generated, and there is no falling off or delamination. However, about 60% of the former after half a year after similar spraying construction on the furnace wall ceiling,
In the latter case, about 40% peeling-off occurred, indicating that the adhesiveness was lacking.

Examples 6 to 10 and Comparative Examples 6 to 8 First, 70% of Al ₂ O ₃ or Al ₂ O in the proportions shown in Table 3
₃ A total of 100% by weight of 48% ceramic fiber, 10 μm or less of sintered alumina and calcined gypsum was added with an organic sizing agent of sodium alginate, carboxymethylcellulose or methylcellulose and a commercial detergent or a blowing agent of sodium lauryl sulfate in the proportions shown in Table 3. Each mixture was added at an external ratio to obtain each mixture. Next, kneading water was added to each mixture in an external ratio as shown in Table 3.
And kneaded soil as shown in Fig.
After time, remove the mold and test each test piece (40 × 40
× 160 mm). Next, each test piece was subjected to drying (110 ° C.) and heat treatment (1000 ° C., 1400 ° C.), and the bending strength, bulk specific gravity, and linear change rate after each of the above treatments were measured. It became so. Further, a spray test of each kneaded soil was carried out. As a result, the riband loss was as shown in Table 3.

[0018]

[Table 3]

From Table 3, it can be seen that the lightweight castables of Examples 6 to 10 can further increase the weight (heat insulation) by further reducing the bulk specific gravity than those of Examples 1 to 5, and obtain almost the same effects. It is understood that it is possible.

The light-weight castables of Examples 6 to 10 are not limited to the case where water is used as kneading water, and may be an aqueous solution of silica sol.
By doing so, the adhesiveness can be further enhanced.

[0021]

As described above, according to the first lightweight castable of the present invention, the organic glue contributes to the improvement of adhesion and water retention after construction, and the addition amount is small. In addition, since the heat resistance is not adversely affected, it is possible to increase the amount of the ceramic fiber added, and it is possible to reduce the weight and improve the heat insulating property as compared with the conventional case. In addition, since the three properties of bulk specific gravity, linear change rate, and reband loss are all excellent, the adhesiveness can be remarkably improved as compared with the related art. According to the second lightweight castable, since the bulk specific gravity can be further reduced in addition to the function and effect of the first lightweight castable, the weight reduction (insulation properties) can be further enhanced. On the other hand, according to the method of using the lightweight castable, the adhesion to the wall surface becomes stronger, so that the adhesiveness of the construction body can be drastically increased.

Claims (5)

[Claims] 1. A ceramic fiber of 5 to 50% by weight,
A lightweight castable comprising 10 to 80% by weight of alumina, 5 to 30% by weight of calcined gypsum, and 0.05 to 3% by weight of an organic glue. 2. A lightweight castable, wherein the organic paste is at least one of sodium alginate, carboxymethylcellulose and methylcellulose. 3. The lightweight castable according to claim 1, which further comprises 0.05 to 3% by weight of a foaming agent. 4. The lightweight castable according to claim 3, wherein the foaming agent is at least one of a commercially available detergent and sodium lauryl sulfate. 5. A method for using a lightweight castable according to claim 1, wherein a silica sol aqueous solution is used as kneading water when the lightweight castable according to claim 1, 2, 3, or 4.