JP2002193681A - Castable refractory and waste melting furnace utilizing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a castable refractory suitable for a waste melting furnace which does not contain chromium and has good corrosion resistance, slag infiltration resistance, thermal shock resistance and workability. SOLUTION: The castable refractory characteristically contains refractory particles of 92-99% and a binder of 1-8% and the refractory particles contain excess magnesia spinel particles 15-95% and a total of excess alumina spinel particles and/or alumina particles in the amount of 5-10% converted into the amount of corundum crystals while the balance materially consists of roughly theoretical composition of spinel particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention does not contain chromium,
The present invention relates to an amorphous refractory suitable for a waste melting furnace for melting waste such as incineration ash.

[0002]

2. Description of the Related Art In recent years, the amount of waste generated has increased rapidly.
The treatment has become a major social problem. As a countermeasure, it is desired to reduce the volume, detoxify or recycle the waste, and a melting method has been attracting attention as a measure. The melting method is a method in which inorganic substances in waste are taken out as molten slag and the volume is significantly reduced. There are two methods of melting waste: direct pyrolysis of solid waste (garbage, etc.) and melting, and primary incineration of waste in an incinerator, and secondary incineration ash, fly ash, and sewage sludge generated. There is a method of melting.

In any of the melting methods, the erosion of the refractory used in the melting furnace largely depends on the components of the melting slag such as incineration ash, fly ash, sewage sludge and the like and the melting temperature. . Although the components of the molten slag vary depending on the type of waste and the like, generally, the chemical composition of incinerated ash, fly ash, and dried solidified sewage sludge is SiO ₂ : 1
5-45% (a mass percentage, herein the _{same), Al 2 O 3: 10~20} %, CaO: 5~45%,
Na ₂ O: 1 to 15%. In addition, incinerated ash and fly ash contain many harmful metals such as Cd, Pb, Zn, Cu, As, Cr, and Hg. Sewage sludge contains ₅ to 15% of P ₂ O ₅ , although the amount of metal is small. Furthermore, many compounds such as S and Cl are contained as volatile components.
Further, the temperature inside the melting furnace must be as high as 1400 to 1650 ° C.

[0004] Therefore, refractories containing chromium oxide are currently used from the viewpoint of corrosion resistance. Refractories containing chromium oxide have higher corrosion resistance as the content of chromium oxide is higher, but chromium oxide in the refractory changes to harmful hexavalent chromium when used at high temperatures and in alkaline atmosphere. Therefore, there is a possibility that an environmental pollution problem may occur.

[0005] Examples of unfired refractories containing no chromium include magnesia-carbon type, alumina-silicon carbide-carbon type, alumina type, etc., but the same corrosion resistance and spalling resistance as those of fired refractories are secured. It is not enough as a refractory for waste melting furnaces. Further, there is no known chromium-free amorphous refractory which has excellent corrosion resistance, thermal shock resistance and workability and is suitable for use in a waste melting furnace.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an amorphous refractory which does not contain chromium, is excellent in corrosion resistance, slag penetration resistance, thermal shock resistance and workability, and is suitable for a waste melting furnace and the like. I do.

[0007]

According to the present invention, a refractory particle 9 is provided.
An amorphous refractory containing 2 to 99% and 1 to 8% of a binder, wherein the refractory particles include 1 magnesia-excess spinel particles.
5 to 95%, and contains alumina-excess spinel particles and / or alumina particles in a total amount of 5 to 10% in terms of corundum crystals, with the balance being substantially substantially theoretical composition spinel particles. Provide shaped refractories. However, in the above, the spinel particles are MgAl
Particles containing ₂ O ₄ crystals, containing 5-60% of MgO component in the particles, and having a total amount of 95% or more of MgO component and Al ₂ O ₃ component. Those having an MgO component content of 5% or more and less than 23% in the spinel particles are referred to as alumina-excess spinel particles, those having 23% or more and less than 33% are referred to as substantially theoretical composition spinel particles, and 33% or more. 6
Those having 0% or less are referred to as magnesia-excess spinel particles.

Further, the present invention provides a waste melting furnace in which an amorphous refractory construction body formed from the above-mentioned amorphous refractory is used for at least a part of a furnace wall.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present specification, an amorphous refractory refers to the entire powder before water is added, and a construction formed from the irregular refractory is referred to as an irregular refractory construction.
The refractory of the present invention (hereinafter referred to as the present refractory)
Contains 92 to 99% of refractory particles and 1 to 8% of a binder. The refractory particles in the present amorphous refractory contain 15 to 95% of magnesia-excess spinel particles and 5 to 10% of alumina-excess spinel particles and / or alumina particles in a total amount in terms of corundum crystals, with a remainder. In some cases, the composition is substantially a theoretical composition spinel.

However, in the present specification, spinel particles include MgAl ₂ O ₄ crystals, the particles contain 5 to 60% of an MgO component, and the total amount of the MgO component and the Al ₂ O ₃ component is 95%. The above particles are referred to. 60% MgO component
When it exceeds, although it has corrosion resistance, slag penetration resistance is reduced, and systematic spalling is likely to occur. MgO component is 5
%, The corrosion resistance decreases. M in spinel particles
It is more preferable that the gO component is 7 to 55%.

In the present invention, the spinel particles consist essentially of an MgO component and an Al ₂ O ₃ component, but may contain unavoidable impurities or other components that do not impair the object and effects of the present invention. Good. The total amount of the MgO component and the Al ₂ O ₃ component is preferably 97% or more. Spinel (Mg
Theoretical composition of Al ₂ O ₄₎ is, MgO component 28%, Al ₂ O ₃
Although the component is 72%, various MgO:
An excellent effect is exhibited by properly using spinel particles having an Al ₂ O ₃ component ratio.

When the content of the MgO component in the spinel particles is 5
% Or more and less than 23% are referred to as alumina-excess spinel particles, those having 23% or more and less than 33% are referred to as substantially theoretical composition spinel particles, and those having 33% or more and 60% or less are referred to as magnesia-excess spinel particles. Alumina-excess spinel particles usually include corundum crystals and MgAl ₂ O ₄
Crystals are precipitated, and the spinel particles having a substantially theoretical composition include M
It contains only gAl ₂ O ₄ crystals, and MgAl ₂ O ₄ crystals and periclase crystals are usually precipitated in the magnesia-excess spinel particles.

These spinel particles are composed of magnesia of seawater and alumina of 5 to 60% of MgO and 40 to 40% of Al ₂ O _3.
It is produced by a method in which a raw material mixture mixed so as to be in a range of 95% is burned by a rotary kiln, or a method in which the raw material mixture is melted by an electric melting method, cooled, pulverized, and then sized. A spinel obtained by firing is called a sintered spinel, and a spinel obtained by an electric melting method is called an electromelted (melted) spinel. The spinel particles in the present invention may be any of sintered spinel and electrofused (melted) spinel, or may be used in combination.

The refractory particles of the amorphous refractory contain 15 to 95% of magnesia-excess spinel particles. When the content of the magnesia-excess spinel particles is less than 15%, the amount of free periclase crystals is small, the volume expansion due to the reaction with corundum crystals (hereinafter, referred to as spinel expansion) becomes small, and the effect of densifying the amorphous refractory is reduced. small. On the other hand, when the content of the magnesia-excess spinel particles exceeds 95%, spinelization expansion becomes too large and the amorphous refractory becomes porous, which is not good.

A part of the magnesia-excess spinel particles may be replaced with magnesia particles and spinel particles having a substantially theoretical composition so that the amounts of MgAl ₂ O ₄ crystals and periclase crystals do not change. As the magnesia particles in this case, fired magnesia obtained by firing magnesium hydroxide obtained from seawater at a high temperature, electrofused magnesia obtained by melting and resolidifying the fired magnesia by electromelting and pulverizing, and the like can be preferably used.
The magnesia particles preferably have a purity of 95% or more,
More preferably, it is 98% or more.

In the present invention, the refractory particles contain not only magnesia-excess spinel particles but also alumina-excess spinel particles and / or alumina particles in a total amount of 5 to 10% in terms of corundum crystals. Here, conversion to corundum crystal means the content of corundum crystal. In the case of alumina particles, the total amount is corundum crystal, and in the case of alumina-excess spinel particles, the total amount is x total corundum crystal / (corundum crystal + MgAl ₂ O ₄ crystal).

In the refractory particles, when the content in terms of corundum crystal is less than 5%, the expansion of spinel due to the reaction with free periclase crystals is small, the effect of densifying the amorphous refractory is small, and the thermal shock resistance is also low. descend. On the other hand, when the corundum crystal equivalent content exceeds 10%,
The spinel expansion becomes too large, and the amorphous refractory becomes porous, and the corrosion resistance and the slag penetration resistance decrease. A more preferable content in terms of corundum crystal is 6 to 9%.

When alumina particles are used, the content of the alumina particles in the refractory particles is preferably 1 to 10%. When the alumina-excess spinel particles are used, the content of the alumina-excess spinel particles in the refractory particles is preferably 5 to 15%. The content of corundum crystals in the alumina-excess spinel particles is 7
0 to 80% is preferable in terms of availability and the like.

As the alumina particles in the present invention, calcined alumina, fused alumina and the like can be used. They are,
Generally, those manufactured by the Bayer method or the electrofusion method, crushed, and sized for refractory particles are used. The purity of the alumina particles is preferably at least 95%, more preferably at least 98%.

The refractory particles in the amorphous refractory may include, in addition to magnesia-excess spinel particles, alumina-excess spinel particles and / or alumina particles,
The remainder is substantially spinel particles having substantially the theoretical composition. Therefore, the crystals present in the refractory particles are substantially M
gAl ₂ O ₄ crystal, corundum crystal and periclase crystal.

[0021] In the refractory particles, each spinel particle mainly constitutes an aggregate portion, and is characterized by properties as a refractory.
Therefore, the total amount of each spinel particle in the refractory particles is 9
It is preferably at least 2%.

The refractory particles in the present invention preferably have a particle diameter of 10 μm to 20 mm. In this specification, coarse particles refer to particles having a particle diameter of 1.19 mm to less than 5 mm, medium particles refer to particles having a particle diameter of 0.105 mm to less than 1.19 mm, and fine particles refer to particles having a particle diameter of 0.15 mm to less than 1.19 mm.
Refers to particles smaller than 105 mm.

As spinel particles, it is preferable to use particles having different particle diameters depending on the composition. That is, it is preferable that the substantially theoretical composition spinel particles are mainly composed of coarse particles and medium particles in terms of corrosion resistance and volume stability. When the magnesia-excess spinel particles are mainly composed of coarse particles, medium particles, and fine particles, they are effective for densification of amorphous refractories due to corrosion resistance and spinel expansion. When the alumina-excess spinel particles are mainly composed of fine particles, they are more effective in densifying the irregular-shaped refractory due to spinel expansion. For the same reason, when using alumina particles, fine particles are preferred,
It is more preferable that the fine particles have a particle diameter of 5 μm or less (hereinafter, referred to as ultrafine powder). When using magnesia particles, ultrafine powder is also preferable.

The present refractory contains 1 to 8% of a binder.
If the amount of the binder is less than 1%, the mechanical strength of the amorphous refractory decreases, and if it exceeds 8%, the heat resistance and corrosion resistance decrease.
Those containing 93 to 98% of refractory particles and 2 to 7% of binder are more preferable.

The binder may be any one which causes a hydration reaction in the coexistence of water to give a hardening effect. It is more preferable that the binder is alumina cement in terms of corrosion resistance, heat resistance, mechanical strength and the like. . As the alumina cement, various alumina cements containing calcium aluminate as a main component (including similar hydraulic alumina compounds) can be generally used. The content of the alumina cement in the binder is preferably 50% or more.

Further, in the present amorphous refractory, it is preferable that the binder contains aluminum lactate. Aluminum lactate includes aluminum lactate normal salt Al (OCOC
_{H (OH) CH 3) 3} , or a basic aluminum lactate Al
(OH) (OCOCH (OH) CH ₃ ) ₂ , Al (OH)
₂ (OCOCH (OH) CH ₃ ) and hydrates thereof. By replacing a part of the alumina cement with aluminum lactate, the amorphous refractory construction body is densified, and the hot strength and corrosion resistance are further improved.

It is more preferable that the binder contains aluminum lactate and a SiO ₂ component because densification proceeds. For example, if the chemical composition is Al ₂ O ₃ : 24%, SiO ₂ : 11.5
%, Lactic acid: 31%, and the balance of water of crystallization is preferable because it produces α-alumina and a small amount of mullite at a high temperature. In the present invention, aluminum lactate is preferably contained in the amorphous refractory in an amount of 0.1 to 2%.

Further, it is preferable to include a complex salt of aluminum hydroxide, citric acid and lactic acid in the amorphous refractory, because it has an anti-digestion property and improves digestion resistance of magnesia-excess spinel particles. Examples of such a composite salt include those having a chemical composition of Al ₂ O ₃ : 17.5%, lactic acid: 46.5%,
Citric acid: 33% white powder. In the present invention,
The complex salt is preferably contained in the amorphous refractory in an amount of 0.1 to 2%. If it is less than 0.1%, the effect of preventing digestion is small, and if it exceeds 2%, the amorphous refractory construction body becomes porous, which is not preferable.

As the binder, those having a particle diameter of 5 μm or less (that is, ultrafine powder) and causing a hydration reaction, such as silica flour, can be used.

When adding a predetermined amount of water to the amorphous refractory and applying the same, it is preferable to use a dispersant or a curing modifier in combination to more effectively exhibit the function of the refractory particles. The dispersing agent and the curing modifier are added to reduce the influence of workability and construction temperature.

As the dispersant, sodium tripolyphosphate, β-naphthalene sulfonate and the like can be preferably used. The dispersant is preferably contained in the amorphous refractory in an amount of 0.02 to 0.3%.

The curing modifier includes a curing accelerator and a curing retarder. As the curing accelerator, quick lime, lithium carbonate and the like can be preferably used, and as the curing retarder, oxalic acid, boric acid and the like can be preferably used. At a low temperature of less than 15 ° C., the setting of the alumina cement is slow, and when the temperature exceeds 30 ° C., the setting is fast.
It is necessary to change according to the temperature at the time of construction. Generally, it is preferable that the curing modifier be contained in the amorphous refractory in an amount of 0.05 to 0.2%. The dispersant and the curing modifier may be previously mixed in the mixture of the refractory particles and the binder, or may be added by dissolving or suspending in water added at the time of kneading.

The refractory of the present invention is excellent in workability, and the refractory of the present invention (hereinafter, referred to as the refractory of the present invention) is also dense. In addition, the amorphous refractory contains various spinel particles uniformly dispersed.In use, the amorphous refractory becomes spinel by heating, and the amorphous refractory is densified. Hard to cause spalling.

In the waste melting furnace of the present invention, the amorphous refractory construction body is used for at least a part of the furnace wall of the waste melting furnace. In particular, it is preferable in terms of corrosion resistance, durability, and the like, to form the furnace wall in a portion that comes into contact with the molten slag with the present amorphous refractory construction body. In this case, components such as SiO ₂ , CaO, Al ₂ O ₃ , Fe ₂ O ₃ , and Na ₂ O contained in molten slag such as incinerated ash react with spinel particles and the like, but the reactant with spinel particles is Since it becomes a highly viscous substance, it is considered that the furnace wall composed of the present irregular-shaped refractory construction body has good slag penetration resistance, low corrosion resistance, and high thermal shock resistance.

As described above, the present refractory molded body is excellent in slag penetration resistance to molten slag and the like, and as a result, forms a highly durable furnace wall having high corrosion resistance and thermal shock resistance. In addition, the present amorphous refractory construction body is most suitable for a waste melting furnace, but is also preferably used for various furnaces and incinerators for steel, non-ferrous metal, cement and the like.

[0036]

The present invention will be described below with reference to Examples (Examples 1 to 12) and Comparative Examples (Examples 13 to 18). Table 1,
Each raw material was weighed so as to have a raw material mixing ratio (mass ratio) shown in Tables 2 and 3, and water (outer portion,% relative to the raw material) shown in the table was added while mixing with a universal mixer. A kneaded product was obtained. This kneaded material is sized 40 mm x 40 mm x 160 m
The mold of m was cast while being vibrated with a vibrator, cured for a predetermined time, demolded, and dried at 110 ° C. for 24 hours to obtain a specimen.

The raw materials in Tables 1, 2 and 3 are as follows. Particles C1: coarse particles of spinel particles (sintered product) having a substantially theoretical composition. Particle C2: Medium grain of approximately theoretical composition spinel particles (sintered product). Particles D1: coarse particles of magnesia-excess spinel particles (sintered product). 75% of periclase crystals in the particles, MgAl ₂ O ₄
25% of crystals. Particles D2: Medium particles of magnesia-excess spinel particles (sintered product). 75% of periclase crystals in the particles, MgAl ₂ O ₄
25% of crystals. Particle D3: Fine particles of magnesia-excess spinel particles (sintered product). 75% of periclase crystals in the particles, MgAl ₂ O ₄
25% of crystals. Particle E1: Fine particles of alumina-excess spinel particles (sintered product). In the particles, 75% of corundum crystals and 25% of MgAl ₂ O ₄ crystals. Particle F1: Ultra fine powder of alumina particles.

Amorphous 1: Alumina amorphous refractory containing 96% Al ₂ O ₃ . Amorphous 2: Alumina-chromia amorphous refractory containing 10% Cr ₂ O ₃ . Alumina Cement: Al ₂ O ₃ min 73%, CaO content 26%
Having a specific surface area of 6000 cm ² / g. Lactate: aluminum lactate (manufactured by Taki Kagaku Co., trade name: Taxelum M-2500). Lactic acid complex salt: a mixed salt composed of aluminum hydroxide, citric acid and lactic acid (trade name: Taxelam AS-300, manufactured by Taki Kagaku Co., Ltd.). Dispersant: sodium tripolyphosphate.

Particle C1, Particle C2, Particle D1, Particle D
Table 4 shows the chemical compositions and crystal forms of Particle 2, Particle D3, Particle E1, and Particle F1. In Examples 17 and 18, alumina particles having a particle diameter of 5 μm or less were also blended in addition to the alumina cement.

[Evaluation Results] The characteristics of the test specimens obtained in Examples 1 to 18 were measured and evaluated, and the results are shown in Tables 1, 2 and 3.
Evaluation items and measurement methods are as follows. Bulk density (g / cm ³ ): Refractory test method (JIS R22)
05). Flexural strength A (MPa): room temperature three-point flexural strength after heat treatment at 110 ° C. for 24 hours. Bending strength B (MPa): Three-point bending strength at room temperature after heat treatment at 1500 ° C. for 3 hours.

Thermal shock resistance (times): A specimen fired at 1300 ° C. for 3 hours was held in an electric furnace at 1300 ° C. for 15 minutes, then taken out of the furnace and quenched, and a cycle was repeated until peeling. The number was measured. The number of cycles was limited to 25 times. The thermal shock resistance is better when the number of times until peeling is larger. In addition, the thing which does not have peeling at the time of repeating 25 times was represented as "25+" in the table.

The corrosion resistance index and the slag penetration depth (m
m): A plurality of trapezoidal column-shaped test pieces were cut out from the specimen, polished to a predetermined size, and lined in a rotating drum. Then, while rotating the rotating drum, oxygen propane flame was blown 1600 in the axial direction of the rotating drum.
Heated to ° C. With the temperature maintained at 1600 ° C., a synthetic slag of incinerated ash and fly ash was charged into a rotating drum as an erosion material and rotated for 6 hours. The chemical composition of synthetic slag is A
l ₂ O ₃ : 16%, CaO: 32%, SiO ₂ : 32%,
Fe ₂ O ₃ : 8%, K ₂ O: 2%, Na ₂ O: 2%, Mg
_{O: 2%, P 2 O} 5: 6%. The synthetic slag was tested fresh every 30 minutes.

After cooling the rotating drum, the test piece was taken out and cut, and the erosion amount (mm) and the slag penetration depth (m
m) was measured at each part of the test piece, and the average value was determined.
The ratio of the amount of erosion in each example when the amount of erosion in Example 18 was 100 was calculated as the corrosion resistance index. A small corrosion resistance index indicates that the corrosion resistance is good.

Mass increase rate (%) in digestion resistance test:
Gakushin Method 7 "Drugite Clinker Digestibility Test Method"
The rate of mass increase (%) after holding at 134 ° C. in a 3 atm autoclave for 2 hours was measured. The digestion resistance is better as the mass increase rate is smaller.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[0048]

[Table 4]

[0049]

The refractory of the present invention is easy to construct, has excellent corrosion resistance to molten metal, molten slag, glass, etc., slag penetration resistance, thermal shock resistance, and durability after construction. Form a furnace wall. Further, since it does not contain chromium, there is no possibility of causing chromium contamination. Therefore, the present refractory can replace the chromium-based refractory used in the waste melting furnace and the like.

Claims (8)

[Claims] 1. A refractory particle of 92 to 99% and a binder of 1 to 8%.
Wherein the refractory particles comprise 15 to 9 magnesia-excess spinel particles.
5%, and a total amount of alumina-excess spinel particles and / or alumina particles of 5 to 5 in terms of corundum crystals.
An amorphous refractory comprising 10% by weight, with the balance being substantially theoretical composition spinel particles. However, in the above, the spinel particles include MgAl ₂ O ₄ crystals, the particles contain 5 to 60% of an MgO component, and the MgO component and Al ₂
Particles having a total amount of O ₃ component of 95% or more. The content of MgO component in the spinel particles is 5% or more and 2% or more.
Those having less than 3% are called alumina-excess spinel particles.
Those having 3% or more and less than 33% are referred to as substantially theoretical composition spinel particles, and those having 33% or more and 60% or less are referred to as magnesia-excess spinel particles. 2. The refractory particles contain 1 to 10% of alumina particles.
The refractory according to claim 1, comprising: 3. The alumina particle has a particle diameter of 0.105 mm.
3. The refractory according to claim 2, wherein the amount of the refractory is less than. 4. The refractory according to claim 1, wherein the refractory particles contain 5 to 15% of alumina-excess spinel particles. 5. The refractory according to claim 1, wherein the binder contains 50% or more of alumina cement. 6. The refractory according to claim 1, wherein the binder contains aluminum lactate. 7. A dispersant of 0.02 to 0.
The amorphous refractory according to any one of claims 1 to 6, containing 3%. 8. A waste melting furnace using an irregular refractory construction formed from the irregular refractory according to any one of claims 1 to 7 for at least a part of a furnace wall.