JP2001348278A - Amorphous refractories and industrial waste incinerators - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prepared unshaped refractory which contains no chromium oxide and no alumina cement and shows corrosion resistance, or more specifically, excellent alkali resistance and excellent gaseous chlorine resistance. SOLUTION: This prepared unshaped refractory consists of 83-95% of refractory particles and 5-17% of a binder, wherein: the refractory particle component consists of 40-85% of mullite particles and 15-60% of spinel particles; and the binder component contains >=25% of hydraulic alumina.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous refractory containing neither chromium nor alumina cement and suitable for an industrial waste incinerator for incinerating industrial waste.

[0002]

2. Description of the Related Art In recent years, the amount of industrial waste generated has rapidly increased, and its disposal has become a major social problem. As a countermeasure, waste volume reduction, detoxification or recycling is desired, and incineration and melting treatment are attracting attention as one of the measures. Examples of industrial waste that can be incinerated or melted include cinder, sludge, waste oil, waste acid, waste alkali, waste plastic, waste tire, paper waste, wood waste, fiber waste, and the like. Refractories for industrial waste incinerators are required to have a service temperature of 1000 to 1400 ° C. and to have corrosion resistance such as alkali resistance and chlorine gas resistance. Alumina, silica-alumina, silicon carbide, or alumina-chromia amorphous refractories for incinerators that can withstand such processing conditions are used. It is not always sufficient in terms of properties and the like, and there is a problem in terms of corrosion resistance.

[0003] For example, alumina refractory and silica
Alumina amorphous refractories have good chlorine gas resistance, but form β-alumina against alkali,
Refractories are enormously collapsed due to formation of caryophyllite (K ₂ O.Al ₂ O ₃ .2SiO ₂ ) and the like. Silicon carbide amorphous refractories are used as amorphous refractories with good alkali resistance, but they require a metal water cooling wall due to their good thermal conductivity.
susceptible to degradation to generate the l _4. In addition, when an amorphous refractory containing chromium is used under alkaline atmosphere conditions, chromium oxide in the refractory changes into harmful hexavalent chromium, which is not preferable because it causes environmental pollution.

Further, any of the above-mentioned irregular shaped refractories is required.
Alumina cement is used as the binder
The CaO component in the nascent reacts with chlorine gas to produce Ca
Cl _TwoTo lose the coupling function during use.
There is a title.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an amorphous refractory which contains neither chromium nor alumina cement, has excellent alkali resistance and chlorine gas resistance, and is suitable for industrial waste incinerators and the like.

[0006]

According to the present invention, a refractory particle 8 is provided.
An amorphous refractory containing 3 to 95% by mass and 5 to 17% by mass of a binder, wherein 40% of mullite particles are contained in the refractory particles.
８５85% by mass, 15-60% by mass of spinel particles, and 25% by mass of hydraulic alumina in the binder
An irregular-shaped refractory characterized by including the above is provided. However, in the above description, the spinel particles are particles containing MgAl ₂ O ₄ crystals, and the MgO component is contained in the particles in an amount of 5 to 28%.
%, And the total amount of the MgO component and the Al ₂ O ₃ component is 9
5% by mass or more. The present invention also provides an industrial waste firing furnace in which an irregular refractory construction body formed from the irregular refractory is used for at least a part of a furnace wall.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present specification, an amorphous refractory refers to the whole powder before adding water, and a construction formed from the irregular refractory is referred to as an irregular refractory construction. That. The irregular refractory of the present invention (hereinafter, referred to as the irregular refractory) contains 83 to 95% by mass of refractory particles (hereinafter simply referred to as%) and 5 to 17% of a binder. The refractory particles are mainly composed of spinel particles and mullite particles.

Here, the spinel particles are MgAl ₂ O ₄
A particle containing crystals, wherein the MgO component is contained in the particle in an amount of 5-2.
8%, and the total amount of the MgO component and the Al ₂ O ₃ component is 95.
% Or more, and may be any of an electrofused (melted) spinel and a sintered spinel, or may be used in combination.

The spinel particles according to 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. The theoretical composition of spinel (MgAl ₂ O ₄ ) is as follows.
Although the l ₂ O ₃ component is 72%, various M
By using spinel particles having a gO: Al ₂ O ₃ component ratio properly, more excellent effects can be exhibited.

In the present specification, Mg in spinel particles
Those having an O component content of 5% or more and less than 28% are referred to as alumina-excess spinel particles, and those having an O content of 28% are referred to as theoretical composition spinel particles. Usually, corundum crystals are precipitated in the alumina-excess spinel particles.

The spinel particles in the present invention contain 5 to 28% of MgO component. If the MgO component exceeds 28%, free MgO will be present, making it easy to slake and easily eroded by chlorine gas. The mullite particles in the present invention are not particularly limited, but it is preferable that the SiO ₂ component has a theoretical composition or a composition lower than the theoretical composition in terms of alkali resistance.

In the amorphous refractory, the mullite particles and the spinel particles mainly constitute an aggregate portion, and are characterized by properties as a refractory. Therefore, in order to exhibit the characteristics of these particles, it is desirable that the content of these particles is as large as possible. Specifically, the total amount of mullite particles and spinel particles in the refractory particles is preferably set to 80% or more.

In the present invention, the refractory particles comprise 40 to 85% of mullite particles and 15 to 60% of spinel particles.
%, Respectively. If the content of spinel particles is less than 15%, the alkali resistance characteristic of spinel particles will not be exhibited, and if it exceeds 60%, the chlorine gas resistance will be poor. The refractory particles preferably contain 45 to 80% of mullite particles and 20 to 55% of spinel particles.

The refractory particles according to the present invention all or most constitute an aggregate portion as an amorphous refractory.
As the refractory particles, particles having various particle sizes can be usually used, but it is preferable to select an appropriate particle size within a range of 15 μm to 20 mm. In this specification, the coarse, medium and fine particles refer to the following. That is, coarse particles have a particle diameter of 1.19 mm or more and less than 5 mm, medium particles have a particle diameter of 0.105 mm or more and less than 1.19 mm, and fine particles have a particle diameter of less than 0.105 mm.

The refractory of the present invention comprises refractory particles 83 to 95.
% And the binder 5-17%. If the amount of the binder is less than 5%, the mechanical strength of the amorphous refractory decreases, and if it exceeds 17%, the spalling resistance decreases. Refractory particles 85-
Preferably, it contains 93% and 7-15% of binder. In the present irregular shaped refractory, the CaO component is more preferably less than 1%, particularly preferably less than 0.5%.

As a binder, hydraulic alumina is 25%
Use those that include the above. Thereby, the applied amorphous refractory can maintain sufficient dry strength, sufficient high temperature strength, and sufficient corrosion resistance. Preferably, the hydraulic alumina is at least 30%. Hydraulic alumina is substantially composed of ρ-alumina, has a property of causing a hydration reaction by reaction with water, and hardening at room temperature. Since it contains no CaO component, it has high corrosion resistance to chlorine gas. The hydraulic alumina preferably has an Al ₂ O ₃ purity of 95% or more, more preferably 99% or more.

As a binder, it is preferable to use an ultrafine oxide powder together with hydraulic alumina. When the oxide ultrafine powder is used together with the hydraulic alumina, the formed amorphous refractory construction body is densified, and the hot strength and the corrosion resistance can be improved. Examples of the oxide ultrafine powder include silica ultrafine powder and alumina ultrafine powder. The particle diameter of the oxide ultrafine powder is preferably 10 μm or less, particularly preferably 5 μm or less.

The amorphous refractory is used by adding a predetermined amount of water at the time of construction, but it is preferable to use a dispersant or a hardening modifier in combination in order to more effectively exhibit the function of the refractory particles. . The dispersant and the curing regulator are added in order to reduce the influence of the workability of the amorphous refractory and the influence of the working temperature, and any one can be used.

In the present invention, as the dispersant, sodium tripolyphosphate, polycarboxylic acid, citric acid and the like can be preferably used. It is preferable that the dispersant is contained in an outer amount of 0.02 to 0.2 part based on 100 parts by mass (hereinafter simply abbreviated as “part”) of the refractory particles and the binder.

The curing regulator includes a curing accelerator and a curing retarder. As the curing accelerator, lithium carbonate, quick lime and the like can be preferably used. Oxalic acid, boric acid and the like can be preferably used as the curing retarder. At a low temperature of 10 ° C. or less, the setting of the hydraulic alumina is slow, and at a temperature of 30 ° C. or more, the curing speed is fast. It is preferable that 0.05 to 0.2 part of the curing modifier is externally contained with respect to 100 parts of the total amount of the refractory particles and the binder. The dispersant and the curing regulator may be added to the mixture of the refractory particles and the binder in advance, or may be dissolved or suspended in water added during kneading.

In the industrial waste incinerator of the present invention, the irregular refractory construction body is used for at least a part of the furnace wall of the industrial waste incinerator. In particular, it is preferable to form the furnace wall of the portion in contact with the incineration material with the present irregular-shaped refractory construction body in terms of corrosion resistance and durability.

[0022]

In the following, Examples 1 to 8 are examples of the present invention, and Examples 9 to 15 are comparative examples. Table 1 and Table 2
Each raw material was weighed so that the raw material mixing ratio (unit: parts) shown in (1) was obtained, and water was added while mixing with a universal mixer to obtain a kneaded material. The kneaded material was cast into a 40 mm × 40 mm × 160 mm mold and various evaluation molds while being vibrated by a vibrator, cured for 24 hours, and demolded.
The specimen was dried at 0 ° C. for 24 hours.

The raw materials in Tables 1 and 2 are as follows. Particles M1: calcined mullite particles having a purity of 97%, coarse particles. Particles M2: calcined mullite particles having a purity of 97%, medium particles. Particles C1: 25% MgO component spinel particles, medium particles. Particle C2: spinel particles and fine particles having the same composition as particle C1. Particles D1: spinel particles of 10% MgO component, medium particles. Particle D2: spinel particles and fine particles having the same composition as particle D1. Table 3 shows the chemical compositions and crystal forms of the spinel particles C1, C2, D1, and D2.

Binder 1: average particle diameter 12 μm, purity 9
9.7% hydraulic alumina (ρ-alumina) particles. Binder 2: Ultrafine alumina powder having a particle diameter of 5 μm or less. Binder 3: Ultrafine silica powder having a particle diameter of 5 μm or less. Binder 4: 74% Al ₂ O ₃ component, 24.3% CaO component
And an alumina cement having a specific surface area of 5000 cm ² / g. Amorphous 1: Alumina cement used as binder, A
Alumina amorphous refractory containing 91% of l ₂ O ₃ component. Amorphous 2: Using alumina cement as binder, C
The r ₂ O ₃ component containing 5% alumina - chromia quality castable refractory. Dispersant 1: sodium tripolyphosphate. Dispersant 2: citric acid.

[Evaluation Results] Using the specimens obtained in Examples 1 to 15, the characteristics shown in Tables 1 and 2 were evaluated.
Evaluation items and measurement methods are as follows. Bulk density (g / cm ³ ): Refractory test method (JIS-R22)
05). Flexural strength A (MPa): 3-point flexural strength after heat treatment at 110 ° C. for 24 hours. Bending strength B (MPa): Three-point bending strength after heat treatment at 1200 ° C. for 3 hours.

Thermal shock resistance (times): A specimen fired at 1200 ° C. for 3 hours was placed in an electric furnace having a furnace temperature of 1200 ° C., held for 15 minutes, taken out of the furnace, and allowed to cool at room temperature for 15 minutes. This cycle was repeated, and the number of times until peeling 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, when there was no peeling at the time of repeating 25 times, it was represented as 25+ in the table.

Corrosion resistance index: 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. Next, oxygen propane flame was blown in the axial direction of the drum while rotating the drum, and heated to 1200 ° C. With the temperature maintained at 1200 ° C., synthetic slag (chemical composition is A
l ₂ O ₃ : 16%, CaO: 32%, SiO ₂ : 32%,
(K ₂ O + Na ₂ O: 20%) was charged into the drum and rotated for 6 hours. The synthetic alkaline slag was freshly injected every 30 minutes and tested. After cooling the rotating drum, the test piece was cut out and cut, and the amount of erosion (mm) was measured at each part of the test piece to obtain an average value. As for the corrosion resistance index, the ratio of the amount of erosion in each example when the amount of erosion in Example 14 was set to 100 was calculated as the corrosion resistance index. The smaller the corrosion resistance index, the better the corrosion resistance.

Mass loss rate (%) in chlorine gas resistance test: calcined at 1200 ° C. for 3 hours, 40 × 40 after calcining
The test specimen processed into a size of × 40 mm was inserted into a tubular electric furnace in which the inside of the furnace was kept at 1000 ° C., and a test was performed by flowing chlorine gas. The concentration of chlorine gas used in the test was 1 with nitrogen gas.
/ 20 was used and the flow rate was 5 ml / min. The mass loss after holding in the furnace for 48 hours was measured to determine the mass reduction rate (%). The smaller the value of the mass reduction rate, the higher the corrosion resistance to chlorine gas.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

The amorphous refractory contains a predetermined amount of mullite particles and spinel particles as refractory particles, and contains hydraulic alumina having excellent chlorine gas resistance as a binder. When used in a furnace, it exhibits excellent alkali resistance and chlorine gas resistance. Furthermore, since it does not contain chromium oxide, there is no possibility of causing a chromium contamination problem. Therefore, it is possible to provide a highly durable industrial waste incinerator without worrying about chromium contamination by the amorphous refractory.

Claims (4)

[Claims] (1) 83 to 95% by mass of refractory particles and a binder
An amorphous refractory containing 17% by mass of the refractory particles, wherein the refractory particles contain 40 to 85% by mass of mullite particles and 15 to 60% by mass of spinel particles, respectively, and have hydraulic alumina in the binder. An amorphous refractory containing 25% by mass or more. However, in the above, the spinel particles are
Particles containing MgAl ₂ O ₄ crystals, wherein MgO
5 to 28% by mass of a component, and MgO component and Al ₂ O ₃
Particles whose total amount of the components is 95% by mass or more. 2. The refractory according to claim 1, wherein the binder contains an ultrafine oxide powder having a particle diameter of 10 μm or less. 3. A dispersing agent comprising a total amount of refractory particles and a binder of 1
The amorphous refractory according to claim 1 or 2, comprising 0.02 to 0.2 parts by mass with respect to 00 parts by mass. 4. An industrial waste incinerator using an amorphous refractory construction formed from the amorphous refractory according to claim 1, 2 or 3 for at least a part of a furnace wall.