JP2002128573A - Amorphous refractory and waste melting furnace - Google Patents

Abstract

(57) [Summary] [Problem] To provide an amorphous refractory which does not contain chromium, has excellent corrosion resistance, slag penetration resistance, and thermal shock resistance, and is suitable for a waste melting furnace. SOLUTION: Refractory particles 91 to 99% by mass and a binder 1
An amorphous refractory comprising the refractory particles, wherein the content of the spinel particles in the refractory particles is 95% by mass or more. However, in the above, the spinel particles are M
gAl ₂ O ₄ crystals, and MgO component in particles is 23-6.
Particles containing 0% by mass and having a total amount of 95% by mass or more of the MgO component and the Al ₂ O ₃ component.

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 to 45% by mass (hereinafter simply referred to as%), Al ₂ O ₃ : 1
0~20%, CaO: 5~45%, Na 2 O: 1~15
%. In addition, incineration ash and fly ash include Cd, Pb, Z
Many harmful metals such as n, Cu, As, Cr, and Hg are also contained. Sewage sludge contains ₅ to 15% of P ₂ O ₅ , although the amount of metal is small. S and C as volatile components
The compound 1 is also included in a large amount. 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.

As unfired refractories containing no chromium, there are magnesia-carbon type, alumina-silicon carbide-carbon type, alumina type and the like. 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, has excellent corrosion resistance, thermal shock resistance and workability, and is suitable for a waste melting furnace.

[0007]

According to the present invention, a refractory particle 9 is provided.
An amorphous refractory comprising 1 to 99% and a binder 1 to 9%, wherein the content of spinel particles in the refractory particles is 95% or more. However, in the above, the spinel particles include MgAl ₂ O ₄ crystals, 23 to 60% of the MgO component in the particles, and the MgO component and A
Particles having a total amount of l ₂ O ₃ components of 95% or more. Further, the present invention provides a waste melting furnace using an irregular refractory construction body formed from the above irregular refractory on at least a part of a furnace wall.

[0008]

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 91 to 99% of refractory particles and 1 to 9% of a binder. The refractory particles are mainly composed of spinel particles.

Here, the spinel particles are MgAl ₂ O ₄
Containing crystals, containing 23-60% of MgO component in the particles,
In addition, it refers to particles having a total amount of the MgO component and the Al ₂ O ₃ component of 95% or more. The spinel particles may be either electrofused (fused) spinel particles or sintered spinel particles, or may be used in combination.

These spinel particles comprise magnesia of seawater and alumina of 23 to 60% of MgO and 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 about 77% is baked 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.

The spinel particles in the present invention 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:
By using spinel particles having an Al ₂ O ₃ component ratio properly, an even more excellent effect is exhibited.

In the present specification, Mg in spinel particles
Those having an O component content of 23% or more and less than 33% are referred to as substantially theoretical composition spinel particles, and those having an O component content of 33% or more and 60% or less are referred to as magnesia-excess spinel particles. The stoichiometric composition spinel particles comprise MgAl ₂ O ₄ crystal, the magnesia excess spinel particles typically, MgAl ₂ O ₄ crystal and periclase crystals are precipitated.

The spinel particles according to the present invention contain 23-60% of MgO component. If the MgO content exceeds 60%, corrosion resistance is obtained but slag penetration resistance is reduced, and systematic spalling is likely to occur. If the MgO component is less than 23%, the corrosion resistance is reduced. MgO component in spinel particles is 2
More preferably, it is 3 to 55%.

The refractory particles of the present invention contain 95% or more of spinel particles. If the spinel particle content is less than 95%, the corrosion resistance and the thermal shock resistance deteriorate. Preferably, spinel particles in the refractory particles are 98% by mass or more. In addition, in the spinel particles, 2 magnesia-excess spinel particles
A content of 0 to 95% is preferable because it has slag penetration resistance as well as corrosion resistance.

The refractory particles of the present invention preferably have a particle diameter of 10 μm to 20 mm. In the present specification, a coarse particle means a particle having a particle diameter of 1.19 mm or more and less than 5 mm, and a medium particle has a particle diameter of 0.105 mm or more and 1.1 mm or less.
Particles smaller than 9 mm mean fine particles having a particle diameter of 0.105.
Refers to particles smaller than mm.

As spinel particles, it is preferable to use particles having different particle diameters depending on the composition. In the present invention, the spinel particles having a substantially theoretical composition are preferably used for coarse particles or medium particles for densification of an amorphous refractory,
It is preferable that the magnesia-excess spinel particles be used in the form of medium or fine particles because the corrosion resistance is improved.

The present refractory contains 1 to 9% 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 9%, the heat resistance and the corrosion resistance decrease.
Those containing 94 to 98% of refractory particles and 2 to 6% of binder are particularly preferred.

The binder may be any one that causes a hydration reaction in the coexistence of water to give a hardening effect. It is more preferable that the binder contains 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, the binder preferably contains aluminum lactate. As aluminum lactate, aluminum lactate normal salt Al (OCOCH (O
H) CH ₃ ) ₃ , slightly basic aluminum lactate Al (OH)
(OCOCH (OH) CH ₃ ) ₂ , Al (OH) ₂ (OC
OCH (OH) CH ₃ ) and hydrates thereof. By replacing a part of the alumina cement with aluminum lactate, the irregular-shaped refractory construction can be made denser, and the hot strength and corrosion resistance can be 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 also has an anti-digestion property and improves digestion resistance of magnesia-excess spinel particles. Such composite salt, for example the chemical composition 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 a binder, particle diameter 5μ
m or less, and those which cause a hydration reaction, such as silica flour and ultrafine alumina, can also be used.

When a predetermined amount of water is added to the amorphous refractory for application, it is preferable to use a dispersant or a hardening modifier in order 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 a 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 regulator 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 are preferable. Can be 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, the curing modifier is 0.05 to 0.2% in the amorphous refractory.
Preferably it is included. In addition, the dispersant and the curing modifier are
The mixture may be previously mixed with the mixture of the refractory particles and the binder, or may be dissolved or suspended in water added at the time of kneading.

The amorphous refractory is excellent in workability, and an amorphous refractory construction formed from the amorphous refractory (hereinafter referred to as the amorphous refractory construction) is also dense. In addition, since this amorphous refractory contains spinel particles dispersed uniformly,
Excellent corrosion resistance, low penetration of molten slag, and low occurrence of systematic spalling.

In the waste melting furnace according to the present invention, the amorphous refractory construction body is used for at least a part of a 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 the molten slag such as incineration ash react with the spinel particles, but the reactant with the spinel particles has a high viscosity. Since it becomes a substance, the furnace wall composed of the 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 has excellent 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.

[0027]

EXAMPLES Examples of the present invention (Examples 1 to 10) and comparative examples (Examples 11 to 14) will be described below. Table 1, Table 2,
Each raw material was weighed so that the raw material mixing ratio (unit: parts by mass) shown in Table 3 was obtained, and water (outer surface,% 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 was cast into a m-type mold while being vibrated with a vibrator, cured for a predetermined time, demolded, and dried at 110 ° C. for 24 hours to obtain a test 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). Particle C3: Fine particles of spinel particles (sintered product) having a substantially theoretical composition. Particle D1: coarse particles of magnesia-excess spinel particles (sintered product). Particles D2: Medium particles of magnesia-excess spinel particles (sintered product). Particle D3: Fine particles of magnesia-excess spinel particles (sintered product). 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 C3, Particle D
Table 1 shows the chemical compositions and crystal forms of 1, D2 and D3. In Examples 13 and 14, in addition to alumina cement, alumina particles having a particle diameter of 5 μm or less were also blended.

[Evaluation Results] The characteristics of the test specimens obtained in Examples 1 to 14 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 sample 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 rapidly cooled, and a cycle of repeated peeling was performed. 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 14 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.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

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

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F23G 5/44 ZAB F23G 5/44 ZABD F27D 1/00 F27D 1/00 N

Claims (5)

[Claims] 1. The composition according to claim 1, wherein the content of the refractory particles is 91 to 99% by mass and
An amorphous refractory containing 9% by mass, wherein the content of spinel particles in the refractory particles is 95% by mass or more. However, in the above, the spinel particles are Mg
It contains Al ₂ O ₄ crystals, and the MgO component is 23-60 in the particles.
% By mass and refers to particles having a total amount of 95% by mass or more of the MgO component and the Al ₂ O ₃ component. 2. The method according to claim 1, wherein the content of alumina cement in the binder is 5%.
The amorphous refractory according to claim 1, which is 0% by mass or more. 3. The refractory according to claim 1, wherein the binder contains aluminum lactate. 4. A method for dispersing a dispersant in an amorphous refractory in an amount of from 0.02 to 0.
4. The amorphous refractory according to claim 1, containing 3% by mass. 5. A waste melting furnace in which an irregular refractory construction body formed from the irregular refractory according to claim 1, 2, 3 or 4 is used for at least a part of a furnace wall.