JPH0777981B2 - High corrosion resistance silicon carbide / alumina brick - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention related to the high corrosion resistance of silicon carbide, alumina bricks, more particularly incinerator or incineration
Ru related to <br/> the high corrosion resistance of silicon carbide, alumina brick for ash melting furnace.

[0002]

2. Description of the Related Art Conventionally, refractory bricks containing silicon carbide have generally been of high purity with a SiC content of about 90%. This high-purity silicon carbide brick is extremely effective in preventing adhesion of molten metal or molten incineration ash, and preventing damage due to thermal spalling and the like.

However, such a high-purity silicon carbide brick is likely to undergo residual linear expansion / contraction volume change due to heating during use. This is considered to be due to the swelling and burning of SiC, and is particularly likely to occur at a high temperature of 1100 ° C. or higher. Further, since the high-purity silicon carbide brick has a high thermal conductivity as high as that of a metal, and since the surface of the brick outside the furnace is almost the same as the temperature inside the furnace, the amount of heat dissipated is large and the heat energy is lost. Further, since the SiC raw material is very expensive, the high-purity silicon carbide brick becomes very expensive as compared with the refractory bricks generally used.

As a solution to such a drawback of high-purity silicon carbide bricks, for example, in JP-A-62-283869, 15 to 70% by weight of SiC and substantially the balance of SiO 2 are disclosed.
_A refractory brick for a combustion furnace containing SiC, SiO ₂ , or Al ₂ O ₃ as a main component, which has a weight component ratio of ₂ / Al ₂ O ₃ of 1.5 or more is disclosed.

[0005]

However, the above-mentioned silicon carbide brick having a SiO ₂ -Al ₂ O ₃ type silicate bond is generally subjected to SiC oxidation by steam or oxygen up to 800 to 1100 ° C. There is an associated increase in volume and weight, leading to premature damage. Also, from around 1100 ° C, SiC
Oxidation reaction becomes remarkable, volume and weight decrease due to burning of SiC are recognized, and the characteristics of SiC brick are lost, so that it becomes difficult to withstand use at the actual operating temperature of the furnace, for example, 1300 ° C. In addition, the damage caused by the reaction with the molten incineration ash containing the molten metal and the alkali becomes large. For these reasons, the use of materials other than silicon carbide bricks, such as high alumina bricks, has been attempted, but dust or clinker adhesion may interfere with operation.

Therefore, the object of the present invention is to prevent the deterioration of the durability of silicon carbide bricks due to high temperature combustion in recent years in severe conditions of use of combustion furnaces, etc., for example, in a refuse combustion furnace to increase the calorie of the refuse quality. In addition, in the incinerator ash melting furnace,
Excellent corrosion resistance, spalling resistance, clinker adhesion resistance, and other required properties even at high temperatures above 00 ° C.
The purpose is to provide alumina bricks.

[0007]

That is, the incineration according to the present invention
High corrosion resistance silicon carbide / alumina brick for furnace or incinerator ash melting furnace , Al ₂ O ₃ content 99.
0% or more of high-purity fused alumina or sintered alumina 20
~ 60 wt%, Al ₂ O ₃ content of particle size 0.03 mm or less 9
A mixture containing 5 to 25% by weight of high-purity calcined alumina of 9.0% or more and 15 to 60% by weight of silicon carbide having a particle size of 0.01 mm or more , Si, Al, B ₄ C, borax, E
A molded product having an apparent porosity of less than 15%, which is obtained by molding a composition containing oxalic acid in an amount of less than 5% by weight and firing .
It is characterized by becoming

[0008]

The high-corrosion silicon carbide / alumina brick of the present invention contains high purity fused alumina or sintered alumina in an amount of 20-6.
Add 0% by weight. The Al ₂ O ₃ content of these raw materials is 9
It is preferably 9.0% by weight or more, and the particle size is preferably in the range of 5 to 0.044 mm. In addition,
If the content is less than 20% by weight, the corrosion resistance tends to be significantly inferior, and if the content of silicon carbide increases, the residual linear expansion of the brick increases due to the oxidation of SiC, which is not preferable. Further, if the content is more than 60% by weight, the elastic modulus becomes high, so that the spalling resistance is inferior, and at the same time, the content of silicon carbide is reduced and the clinker peeling property tends to be inferior, which is not preferable. On the other hand, if the particle size is out of the above range, the structure of the brick becomes poor, lamination (cracks) at the time of molding, uneven distribution of coarse particles and change in firing shrinkage are large, and the quality of the brick is inferior, which is not preferable.

Next, the brick of the present invention is compounded with 5 to 25% by weight of high-purity calcined alumina. By blending this calcined alumina, the formability becomes good, and the sintering is promoted by firing, so that alumina and silicon carbide can be closely bonded, and the porosity and air permeability of the resulting brick are remarkably increased. Can be lowered.

The Al ₂ O ₃ content of this calcined alumina is also 99.
It is preferably 0% by weight or more. The particle size of the high-purity calcined alumina is preferably 0.03 mm or less, and more preferably 0.004 mm or less as the main component in terms of formability and sinterability of the brick. If the blending amount is less than 5% by weight, moldability cannot be imparted, and
The dense brick structure cannot be obtained by firing. Also, 2
If it exceeds 5% by weight, lamination tends to occur at the time of molding, firing shrinkage is large, and a dense structure cannot be obtained.

Further, the brick of the present invention has a particle size of 0.01.
15 to 60% by weight of silicon carbide of mm or more is blended. If the blending amount is less than 15% by weight, the clinker is often attached and the effect of adding silicon carbide is deteriorated such as poor spalling resistance, which is not preferable. On the other hand, if it exceeds 60% by weight, the alumina content becomes low and the corrosion resistance becomes poor, which is not preferable.

The smaller the particle size of silicon carbide, the larger the surface area of silicon carbide and the more likely it is to cause an oxidation reaction. Therefore, the particle size is 0.
If a large amount of silicon carbide of less than 01 mm is included, the oxidation resistance is poor,
When the brick is used, the content of SiO ₂ in the brick increases and the corrosion resistance decreases. Further, residual linear expansion is likely to occur due to oxidation during use of brick, which is not preferable.

The brick of the present invention comprises the above-mentioned refractory raw materials .
For the purpose of further preventing oxidation and imparting strength to the resulting mixture , Si, Al, B ₄ C, borax, boric acid, etc. are externally applied to the mixture.
It is blended in an amount of less than wt% .

Further, in the preparation of the brick molding compound of the present invention, since there are few plastic raw materials, sodium naphthalene sulfonate, sodium hexametaphosphate, etc. can be used as the surfactant. Further, as the organic plasticizer, for example, CMC, PVA, molasses, pulp waste liquid or the like can be used to improve the moldability.

The molding can be easily carried out by a uniaxial pressure type press, but it is also possible to use a hydrostatic press.

The brick of the present invention is prepared by molding the above-mentioned compound into a predetermined shape and then according to a conventional method, 1400 to 1600 ° C.
It is obtained by firing in the temperature range of.

The brick obtained has an apparent porosity of 15
It is preferably less than%. When the apparent porosity exceeds 15%, the air permeability becomes large, oxygen in the furnace gas easily penetrates into the inside of the brick, some of the silicon carbide is oxidized, and the SiO ₂ content in the brick increases, It is not preferable because the corrosion resistance decreases. The SiO ₂ content in the brick is preferably less than 7% by weight.

Further, although the brick of the present invention has a problem of environment and the like, the corrosion resistance can be greatly improved by incorporating a chromium raw material such as chromium oxide.

[0019]

EXAMPLES Example 1 Blends were prepared in the blending ratios shown in Table 1 below, molded, dried, and fired at 1530 ° C. to obtain bricks of the present invention and comparative products. Table 1 also shows various properties of the obtained brick.

[0020]

[Table 1]

Use Example 1 Conventionally, goodwill of the comparative products E and F was used in the combustion section of the incinerator, but melt damage, spalling due to diversification of waste, increase in calorie, and severe usage conditions. , The durability was lower than in the past due to the excessive oxidation of SiC. As a result of using the product B of the present invention in the burning part of the incinerator, it was possible to extend the life of the bricks to about 4 years, although the durability was about 2 years, due to the improvement in corrosion resistance and oxidation resistance.

USE EXAMPLE 2 Inventive products A, B and C of Example 1 and comparative products D, E,
F, G, zirconia bricks, various furnaces material such as MgO-Cr ₂ O ₃ brick were tested at waste incineration ash melting furnace. As a result, the furnace materials other than the product of the present invention had many problems such as corrosion resistance and damage such as heat spalling. The product of the present invention has the effect of heat spalling property due to the addition effect of SiC, the clinker adhesion resistance and the infiltration resistance, and in combination with the effect of the corrosion resistance due to the addition of fused alumina, an extremely good result is obtained, and at present,
The product B of the present invention is continuously used in an actual furnace.

[0023]

The highly corrosive silicon carbide / alumina brick of the present invention has a low porosity and a low air permeability, and is excellent in oxidation resistance to oxygen or water vapor in a high temperature range. In addition, it is effective in suppressing the infiltration of foreign components, and has little erosion and reaction. Further, it is excellent in abrasion resistance, excellent in dust adhesion and clinker peeling property despite the low SiC content, and has low thermal expansion and high strength, so that it has high thermal shock resistance.

Claims (1)

[Claims] 1. A particle size 5~0.044mm Al ₂ O ₃ content of 99.0% or more purity fused alumina or sintered alumina 20-60% by weight of a particle size 0.03mm following Al ₂ O ₃
A mixture containing 5 to 25% by weight of high-purity calcined alumina having a content of 99.0% or more and 15 to 60% by weight of silicon carbide having a particle size of 0.01 mm or more is added to Si, Al, B ₄ C, and boro.
Molding with an apparent porosity of less than 15% obtained by molding a composition containing sand and boric acid in an amount of less than 5% by weight and firing.
Incinerator or incinerator ash melting furnace characterized by comprising a body
High corrosion resistance silicon carbide / alumina brick for use .