JPH0764558B2 - Alumina porous granular material and refractory material using the granular material as an aggregate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an alumina-based porous granular material excellent in pressure resistance and heat insulation and a refractory material using the granular material as an aggregate.

(Prior Art) A refractory used as a furnace wall building material for a kiln has been strongly required to have better heat insulating property in addition to mechanical strength at high temperature. This is because the improvement of the heat insulation of the furnace material contributes to the reduction of fuel consumption and the downsizing of the furnace body. Therefore, as a countermeasure, attempts have been made to replace a part of the aggregate, which is the main raw material of the refractory, with an alumina hollow particle (alumina bubble) having a high heat resistance.

(Problems to be Solved by the Invention) However, since the conventional porous inorganic particles such as the above-mentioned alumina bubbles have remarkably weak strength, they are useful for improving the heat insulating property, but difficult when molding a refractory. Come across.
That is, as a refractory molding method, a ramming method of compacting a powdered and granular compound raw material containing water into a molding die by using a tamping tool (rammer) and tightly filling it, a pressing method using a pressing machine, Alternatively, a casting method of injecting a slurry-form compounded raw material into a molding space, or a spray method of spraying an object to be coated with a spray gun is used. According to the ramming method, for example, a ping-pong ball is used. The shaped alumina bubbles are easily crushed by the rammer or the press pressure, and according to the casting method, these light-weight particles are floated and separated on the slurry, and according to the spray method, they also have the same high specific gravity. It is separated from the raw material and is skipped.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an aluminum porous granular material having good pressure resistance and heat insulating properties, and particularly suitable for refractory aggregates, and the granular material. In order to provide a refractory material having a good heat insulating property and a good moldability, which is compounded as an aggregate.

[Structure of the Invention] (Means for Solving the Problems) The alumina-based porous granular material according to the first invention has a structure in which the internal structure having a pore structure is covered with a substantially non-porous outer shell layer. The refractory material according to the second aspect of the present invention is characterized in that the alumina-based porous granular material having a structure in which an internal structure having a pore structure is covered with a substantially nonporous outer shell layer is blended as an aggregate. However, it has a feature.

(Function) The alumina-based porous granular material according to the first aspect of the present invention has a spherical shell structure because its internal structure has a pore structure and this internal structure is covered with a substantially non-porous outer shell layer. It has both excellent pressure resistance derived from it and good heat insulation due to the presence of air bubbles trapped in the outer shell.

Further, the refractory material according to the second invention is a bone material which substitutes at least a part of aggregate such as conventional non-porous alumina coarse particles in the raw material blending of the alumina porous granular material having such characteristics. By being blended as a material, it has both high heat insulating properties and good moldability such that the aggregate is not crushed, separated into a slurry, or blown off during molding.

In the second invention, the bulk specific gravity of the alumina porous granular material is most preferably in the range of 1.0 to 1.5.
When the bulk specific gravity is 1.5 or less, the effect of improving the heat insulating property of the refractory is most remarkable, but when the bulk specific gravity is 1.0 or less, it is easily crushed by the pressing force of the rammer or the press machine, and when the aggregate is floated during casting or sprayed. This is because scattering easily occurs.

(Example) Below, several examples which materialized each invention of this application are described.

At first, the outline of the alumina porous granular material is as follows.
A raw material composition containing ~ 5.0% by weight of silica is melted by heating it to 2000 ° C or higher using an Elu-type electric furnace having a single-phase or three-phase alternating current as a power source and having a capacity of 500 to 200 KVA. Then, the melt is used for 2 to 7 kg /
Place in a pressurized air stream of cm ² and inject into the atmosphere. As a result, the melt is entrained with air, contains numerous bubbles, and becomes spherical due to surface tension and solidifies. The silica mixing ratio in the raw material composition is closely related to the bulk specific gravity and the heat insulating property and the pressure resistance strength of the obtained porous granular material, and when the silica content is 0.3% by weight or less, the bulk density becomes too light and the pressure resistance is low. descend. On the other hand, if it is 5% or more, the bulk specific gravity becomes heavy, the heat insulating property deteriorates, and the fire resistance tends to deteriorate. On the other hand, since the temperature of the molten composition slightly affects the bulk specific gravity and the formation of the porous structure, the power per raw material of the melting furnace is controlled so that the desired bulk specific gravity and the porous structure can be obtained.

The alumina porous granular material thus produced has a pore structure containing a large number of closed cells inside, and the outer surface is covered with a substantially non-porous outer shell layer. .

Table 1 summarizes the data for the three types of alumina particulates. Further, FIGS. 1 to 3 are sectional views based on these three types of sectional micrographs.

The comparative example shown as Sample No. 3 (FIG. 3) among the three types of alumina-based particulates corresponds to a so-called alumina bubble in which the inside of the spherical outer shell layer 1 is hollow, and has a compressive strength. It is unsuitable as a refractory aggregate because it causes a problem in molding due to lack of the like. On the other hand, sample No. 1 (first
(Fig.) And No. 2 (Fig. 2) have a pore structure in which the internal structure has a large number of closed cells 2 and are covered with a substantially non-porous outer shell layer 1 having a spherical shape. It is an example according to the first invention of the present application. Among them, the sample No. 1 is
As shown in Table 1, the bulk specific gravity is 1.38, and the formability can be sufficiently maintained while significantly improving the heat insulating property of the refractory material. However, the sample No. 2 has a bulk specific gravity of 2.
Although it is as large as 11, it can be put to practical use when importance is attached to formability rather than heat insulation.

Next, Table 2 shows an example of the amorphous refractory of the second invention of the present application using the alumina porous granular material of Sample No. 1 as an aggregate, and the content rate of the alumina porous granular material is shown. 0 to 3
The raw material composition and characteristic values of a series of trial refractories manufactured by variously changing the range of 8.3% by weight are summarized. These refractory materials should be produced according to the conventional general refractory material manufacturing method, and in order to evaluate the pressure resistance during molding of the alumina porous granular material as an aggregate, The molding was performed by the ramming method. Further, as shown in Table 2, a plurality of types of refractory materials were manufactured by changing the firing temperature in the range of 1400 to 1600 ° C. for each formulation example.

As is clear from the data in Table 2, a part of the aggregate was replaced with the alumina porous particles as compared with the comparative example (conventional amorphous refractory material) containing no alumina porous particles. In Examples 1 to 5, the thermal conductivity was at least 10
% Or more.

Next, Table 3 shows some examples in which the second invention is applied to a standard refractory material. The alumina-based porous granular material used here is that of sample No. 1 shown in Table 1. Also,
Carboxymethyl cellulose (CMC) or the like is used as the organic binder. The raw material formulation in this example is based on the formulation of a normal alumina-based shaped refractory material,
A part of coarse granular high purity alumina is replaced by porous alumina spheres. And Examples 1-3 of this table
As can be seen in Fig. 2, the shaped refractory made by setting the content of the aluminum porous particles to the high-purity alumina in the range of 40 to 60% does not cause a decrease in hot bending strength at all, Compared with the usual alumina refractory (comparative example), the heat insulating property was remarkably improved, and the bulk specific gravity could be considerably reduced.

Since the alumina porous granular material according to the first invention of the present application also has a characteristic as a sound absorbing material or a sound insulating material due to its unique porous structure, its porosity and the thickness of the molten shell layer are By arbitrarily changing it according to the purpose of use, if it is used as a building material, for example, beyond the field of use as a refractory, its various characteristics such as light weight, strength, and sound absorption can be utilized at the same time.

[Effects of the Invention] As is clear from the above description, the alumina-based porous granular material according to the first invention is a shell layer having a pore structure in its internal structure and a substantially non-porous outer surface portion. Since it has a covered structure, it has unique properties such as high heat resistance, high strength, heat insulation, lightweight, sound absorption, and can be widely used for various refractories, heat insulating materials, building materials, etc. it can.

Further, according to the refractory material of the second invention using such an alumina porous granular material as an aggregate, good heat insulation is obtained, and since the aggregate has sufficient compressive strength, a ramming method or It is possible to withstand impact force exerted by a rammer or a press when molding with a press machine and prevent crushing of the aggregate, and in the case of the casting method, there is no possibility that the granular aggregate separates from the slurry-like raw material mixture and floats. Further, even in the case of using the spray method, there is an effect that the problem that only the granular aggregate is scattered does not occur.

[Brief description of drawings]

1 and 2 are cross-sectional views of an alumina porous granular material showing an embodiment of the first invention, and FIG. 3 is a cross-sectional view of a conventional alumina bubble having insufficient internal pore structure. In the figure, 1 is an outer shell layer and 2 is closed cells.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motohide Kitada 94, 812 Chuo, Mitake-cho, Kani-gun, Gifu Prefecture (56) References JP-A-51-64513 (JP, A) , B2) JP 59-19070 (JP, B2) JP 54-22800 (JP, B2)

Claims (3)

[Claims] 1. An alumina-based porous granular material having a structure in which an internal structure having a pore structure is covered with a substantially non-porous outer shell layer. 2. A refractory material characterized in that an alumina-based porous granular material having a structure in which an internal structure having a pore structure is covered with a substantially non-porous outer shell layer is blended as an aggregate. 3. The bulk specific gravity of the alumina porous granular material is 1.0.
The refractory material according to claim 2, characterized in that