JP2000211963A - Production of refractory material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production process for a refractory material that has excellent refractoriness, corrosion resistance, can be used as a furnace wall material for refuse incinerators and has high freeness in its shape and size by using the molten product that is molten via the thermit reaction as a main material to mold the main material, as a cold curable resin is used as a binder. SOLUTION: This production process comprises the melting step wherein the ash is molten by the thermit reaction, the gradually cooling step wherein the molten product is gradually cooled, the grinding step wherein the cooled slag is ground, the deironization step wherein the ground slag is deironized by the electromagnetic separation, the kneading step wherein the ground and deironized slag is kneaded together with a binder and water, the casing step wherein the kneaded mixture is cast into a mold and the cast mixture is hardened and the drying step wherein the hardened product in the casting step is dried.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a refractory. More specifically, the present invention relates to a method for producing a refractory using slag obtained as a main raw material by melting ash such as garbage and industrial waste by a thermite reaction.

[0002]

2. Description of the Related Art Disposal of incinerated ash produced by incinerating household garbage, city garbage and the like, and dust ash collected by dust collectors in factories and the like have become problems. In particular, since these ashes are enormous in volume and harmful substances such as heavy metals and dioxins are mixed in the ash, burying and treating them as they are has a great effect on the environment. Therefore, various methods for melting ash at a high temperature, confining heavy metals in the melt, and thermally decomposing harmful substances such as dioxin have been studied. As such melting equipment, an electric melting furnace, a burner melting furnace, a plasma melting furnace, an arc melting furnace, and the like are known. However, each of them has a problem that a large amount of energy is required and the apparatus is enlarged. In recent years, as an alternative to the conventional melting equipment, when a metal oxide such as aluminum and iron oxide is ignited at 1100 ° C. or higher, a chemical reaction known as a thermite reaction represented by 8Al + 3Fe ₃ O ₄ → 9Fe + 4Al ₂ O ₃ occurs, Attention has been focused on a method of melting ash utilizing the fact that a high temperature of 2750 ° C. or higher can be obtained. For example, JP-A-9-
Nos. 60844, 9-101014, 10
Nos. 43717 and 10-46164 disclose similar melting methods.

[0003]

However, ash generated in a garbage incinerator or the like contains, for example, about 30 wt% of Si.
Although it contains O ₂ , about 20 wt% Al ₂ O ₃ , about 20 wt% CaO, etc., its composition is not constant, and trace components mainly composed of various metal oxides remain. However, the molten slag obtained by melting has a problem that it is easily formed into an amorphous, low-melting glass, and it is difficult to form a refractory having excellent hot strength. In particular, when using refractories for furnace walls of garbage incinerators, etc.,
During the incineration, an ash containing a large amount of alkali is generated, which breaks the Al ₂ O ₃ —SiO ₂ bond in the refractory or further reacts with the SiO ₂ to produce a low-melting glassy material, thereby reducing fire resistance. There is a problem that spalling is likely to occur due to expansion and expansion. The clinker generated in the incinerator adheres to the refractory on the furnace wall, so that there is a problem that the above erosion further proceeds. When garbage is incinerated, acid gases such as sulfuric acid, metaphosphoric acid, carbonic acid, sulfurous acid, nitric acid and nitrous acid are generated, causing a chemical reaction with the refractory, and the surface of the furnace wall peels and swells, and further gas leakage to the outside. There was a problem that it occurred. Conventional refractories for incinerator walls are generally made of relatively small, regular bricks.However, since there are many joints, if some joints are damaged, load separation occurs, and the adjacent regular bricks are used. There was a problem that it affected the brick portion and peeled off continuously. In order to repair this, the same number of parallel bricks had to be bonded with a joint material, so that there was a problem that the number of work steps was large and workability was lacking.

The present invention has been made to solve the above-mentioned conventional problems, and is excellent in fire resistance and erosion resistance by forming a molten material melted by a thermite reaction as a main raw material and molding using a room temperature curing type binder. It is an object of the present invention to provide a method of manufacturing a refractory which can be used for a furnace wall of a refuse incinerator and has a high degree of freedom in shape and size.

[0005]

In order to solve the above-mentioned conventional problems, a method for producing a refractory according to the present invention comprises: a melting step of melting ash by a thermite reaction; and a melting step obtained by the melting step. A slow cooling step of cooling, a crushing step of crushing the slag cooled in the slow cooling step, a deironing step of removing iron from the crushed slag crushed in the crushing step by magnetic separation, A kneading step of adding a binder and water to the ironed pulverized slag and kneading, a casting step of pouring and hardening the mixture kneaded in the kneading step into a mold, and a drying step of drying the cured product obtained in the casting step ,
Is provided. With this configuration, it has excellent fire resistance and erosion resistance and can be used for the walls of refuse incinerators, etc.
It is possible to obtain a refractory which has a high degree of freedom in shape and size and is excellent in workability when repairing a furnace wall.

[0006]

DETAILED DESCRIPTION OF THE INVENTION A method for producing a refractory according to claim 1 includes a melting step of melting ash by a thermite reaction;
A slow cooling step of gradually cooling the melt obtained in the melting step,
A crushing step of crushing the slag cooled in the slow cooling step, a de-ironing step of removing iron by magnetic separation from the crushed slag crushed in the crushing step, and a binder for the crushed slag de-ironed in the de-ironing step. And a kneading step of kneading by adding water and water, a casting step of pouring the mixture kneaded in the kneading step into a mold and curing, and a drying step of drying the cured product obtained in the casting step. are doing.
With this configuration, the ash melted by the thermite reaction is gradually cooled to obtain a mullite (3Al ₂ O ₃ .2SiO ₂
~ 2Al ₂ O ₃ · SiO ₂ ) or alumina (Al
₂ O ₃ ) crystalline high-melting point CaO-SiO _2-
Since an Al ₂ O ₃ -based eutectic can be obtained, it has an effect that a refractory having excellent fire resistance can be obtained. Since iron is removed by magnetic separation in the iron removal process,
The recovered iron can be used as a raw material for steelmaking, and a refractory can be formed without the iron having a large coefficient of thermal expansion, so that spalling of the refractory can be prevented and the hot strength can be increased. . In addition, since the aluminum oxide during the thermite reaction becomes insufficient or the iron oxide remaining when the iron oxide is excessively used can be completely removed, the strength of the refractory due to the thermal expansion of the iron can be prevented from lowering. It has the action of: Since it is hardened at substantially normal temperature in the casting step and is not fired at a high temperature, it has excellent energy saving properties, and has a function of obtaining a product with high dimensional accuracy since it has a low cure shrinkage.
By appropriately manufacturing molds and wooden molds, it is possible to easily form complicated shapes such as the upper arch and various nozzles of the garbage input section of the incinerator and large blocks, etc. Can be enlarged. When molded into a large size, it has the effect of reducing the number of work steps required for repairing when the furnace wall of the incinerator is damaged or the like and shortening the construction period. In addition, when a large-sized block is used, the joint portion is reduced, so that there is an effect that troubles such as load separation due to damage to the joint and a decrease in self-standing strength can be reduced. Compared to conventional refractory bricks using silicon carbide as a main material, they can be manufactured at extremely low cost, and have an effect of being excellent in economic efficiency.

Here, the thermite reaction includes (1)
Add aluminum and metal oxide respectively to the ash.
(2) A mixture of aluminum and a metal oxide in advance is added to the ash. (3) A mixture of aluminum and metal oxide is formed and processed into fuel rods, pellets and the like. Etc. can be used. As aluminum, slag generated in an aluminum remelting plant, small pieces of powdered aluminum can for soft drinks, powdery materials, and the like are used. As the metal oxide, iron oxide, copper oxide and the like are preferably used. Among them, iron oxide is particularly preferable because it can be used at low cost because it can utilize industrial waste and slag of a steel mill when producing titanium oxide (TiO ₂ ) from natural ilmenite ore. When the ash contains a large amount of metal oxides such as iron oxide,
The amount of metal oxide for thermite reaction may be reduced or even omitted in some cases. When the composition of the components in the ash is known in advance, alumina (corundum), high alumina, mullite, spinel, chamotte, and the like are used to adjust the composition so as to obtain the predetermined fire resistance and erosion resistance. Among other refractory materials such as chromite, zirconia, dolomite, magnesia, silica, etc. 1
Seeds or more may be added. For example, those containing a large amount of alumina can further improve the fire resistance of the refractory. Further, when dolomite or magnesia is added to increase the MgO content, eutecticity increases, so that hot strength can be improved. In the slow cooling step, in particular, 1800 to 8
By setting the cooling rate when passing through the range of 50 ° C. to 8 to 1 ° C./min, the melt changes from non-crystalline (glassy) to crystalline. Strength can also be increased. Here, when the cooling rate is higher than 8 ° C./min, the amorphous portion tends to increase,
In addition, since the cooling time becomes too long as the temperature becomes lower than 1 ° C./min, there is a tendency that it is difficult to continuously perform the operation. Here, in order to extend the cooling time in the temperature range, it is preferable to perform air cooling in a highly heat-insulating container or the like. As the grinding process,
Coarse pulverization with a jaw crusher, roll crusher, impeller breaker, etc., fine pulverization with a roller mill, edge runner mill, etc. It may be ground. Here, in order to adjust the porosity or the like of the product, it is preferable to adjust the product to a predetermined particle size distribution by sieving or the like. As the de-ironing process,
Dry or wet drum type or belt type magnetic separators are used. In the molten state immediately after the thermite reaction, the molten iron has a large specific gravity and is separated into two layers with other molten materials. Therefore, it is possible to remove iron to some extent by utilizing the specific gravity difference. Magnetic separation can be carried out as it is. High alumina castable material as binder,
Clay castable materials, sodium silicate, phosphate, clay, alumina cement, Portland cement, etc. are used.Alumina cement or high-alumina castable materials with high curing strength at room temperature, excellent strength and fire resistance, and clay High quality castable materials are particularly preferably used. Slag,
The mixing ratio of the binder and water is 5 to 70 parts by weight, preferably 1 to 100 parts by weight of the slag.
0 to 50 parts by weight, and water is used in an amount of 3 to 30 parts by weight, preferably 5 to 25 parts by weight based on 100 parts by weight of the binder. Here, as the amount of the binder becomes less than 10 parts by weight, it is difficult to obtain a predetermined bonding force, and therefore, it tends to be difficult to obtain a refractory having a sufficient strength. It is not preferable because the improvement tends to level off. If the amount is less than 5 parts by weight or more than 70 parts by weight, the above tendency becomes remarkable, so that it is further undesirable. As the amount of water becomes less than 5 parts by weight, depending on the type and amount of the binder, it tends to be difficult to knead or cause uneven mixing. As the amount of water becomes more than 25 parts by weight, the curing becomes slower and the curing becomes harder. It is not preferable because the compressive strength tends to decrease. If the amount is less than 3 parts by weight or more than 30 parts by weight, the above-mentioned tendency becomes remarkable, so that it is further undesirable. As the kneading step, a ball mill, a concrete mixer, a ribbon mixer, or the like is used. In the pouring step, a mold or a wooden mold is used, and the kneaded material obtained in the kneading step is poured and molded into a predetermined shape. Here, if the density of the kneaded material poured into a mold or a wooden mold is increased by applying vibration or pressure or reducing the pressure so as not to incorporate voids or bubbles, the porosity is reduced and the strength is improved. This is preferable because it is possible to prevent a decrease in strength due to penetration of an erosive gas and the like. The curing temperature is set according to the type of the binder and the like, but it is particularly preferable to use a binder which normally cures at about room temperature from the viewpoint of energy efficiency. In the pouring step, if necessary, a metal fitting made of stainless steel or the like for locking the outer wall of the incinerator is buried and the locking portion is projected, so that the furnace construction work can be performed more efficiently. At the same time, a stable furnace wall can be formed.

[0008] The method for producing a refractory according to claim 2 has a structure in which the particle size of the pulverized slag is adjusted to a range of 100 µm to 10 mm, preferably 2 to 6 mm in the pulverizing step. ing. With this configuration, the filling density can be increased during the casting process, so that the porosity of the product can be reduced, and extremely strong resistance to slag, ash, clinker, harmful gas, etc. generated in an incinerator or the like. It has the effect that a force can be applied. Here, as the particle size becomes smaller than 2 mm, multi-step pulverization is required and handling of the pulverized slag may be difficult. In addition, depending on the type of the binder, etc., 6 m
When the value is larger than m, the amount of the binder used tends to be increased in order to lower the porosity, which is not preferable. If the diameter is smaller than 100 μm or larger than 10 mm, the above tendency becomes remarkable, and therefore, it is further undesirable.

According to a third aspect of the present invention, in the method for producing a refractory according to the first or second aspect, the binder contains at least one of a high alumina castable material, a clay castable material, and an alumina cement. Configuration. With this configuration, it is possible to obtain a refractory having excellent heat resistance, and also to enhance the corrosion resistance to alkali in the combustion furnace and the spalling resistance.

[0010] According to a fourth aspect of the present invention, in the method for producing a refractory according to any one of the first to third aspects, the kneading step includes any one of silicon carbide, silicon nitride, and silica flour.
It has a configuration in which more than one kind of filler is added. With this configuration, when silicon carbide or silicon nitride is added, adhesion of the clinker to the refractory can be prevented, and thus the effect of improving durability can be obtained. Among them, silicon carbide is particularly preferably used because it has a high effect of preventing clinker adhesion. Further, when silica flour, silicon carbide, or silicon nitride having a small particle size (100 mesh or less) is used, the amount of binder can be reduced, and the amount of water at the time of kneading can be reduced. It has the effect of being able to increase. Here, as the shape of the filler, fine powder, fiber or whisker having a particle size of 100 mesh or less is used. The filler is used in an amount of 5 to 100 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the pulverized and deironed slag. When the amount is less than 10 parts by weight, the effect of preventing clinker adhesion tends to be low, and when the amount is more than 50 parts by weight, the effect corresponding to the increase in the amount of addition tends not to be obtained. Absent. If the amount is less than 5 parts by weight or more than 100 parts by weight, the above tendency becomes remarkable, so that it is even more undesirable.

According to a fifth aspect of the present invention, in the method for manufacturing a refractory according to any one of the first to fourth aspects, the drying step is performed by gradually heating the room temperature to a temperature of from 350 ° C. to 350 ° C., preferably 320 ° C. It has a configuration. With this configuration, the water content in the refractory can be significantly reduced, so that it does not peel or crack even if the temperature rises rapidly after construction at the site of use, and is used for repair parts of various furnaces, burner tiles, etc. Also has the effect that it can be widely used. Here, when the drying temperature is higher than 320 ° C., it is not preferable because a predetermined drying rate is reached and further drying cannot be expected, and a tendency to lack energy saving is seen. When the drying temperature is higher than 350 ° C., the above tendency becomes remarkable. More undesirable.

Hereinafter, the present invention will be described in more detail with reference to examples.

EXAMPLES (Example 1) As ash, three kinds of municipal waste, sewage sludge, and industrial waste were used. These main _{composition, SiO 2: 25~37wt%, Al} 2 O 3: 18~
_{28wt%, Fe 3 O 4:} 1.3~3.6wt%, Ca
O: 10 to 24 wt%. Another composition is M
Oxides of g, P, Na, and K were observed. In this ashes,
A powder obtained by pulverizing an aluminum can and a pulverized iron-made slag containing a large amount of iron oxide were respectively added and ignited to cause a thermite reaction and melt. This melt is
Slow cooling was performed so that the cooling rate in the range of ８850 ° C. was 1 ／ 5 ° C./min to obtain a slag highly containing a crystalline component.
This is crushed by a roll crusher, and the particle size is 2 to 6 m.
The particle size distribution was adjusted by sieving so as to be in the range of m.
As a deironing process, reduced iron and unreacted iron oxide were removed by passing through a drum type magnetic separator. Was observed The thus deferrisation slag obtained with an electron microscope, it was confirmed that the eutectic substance of CaO-Al ₂ O ₃ -SiO ₂ which highly contains mullite. The micro Vickers hardness was 803 at a load of 100 g and 494 at a load of 200 g, and it was confirmed that the hardness was extremely high. The main ingredients are
SiO ₂ : 20 to 31 wt%, Al ₂ O ₃ : 26 to 42
wt%, CaO: a 8~22wt%, Fe ₃ O ₄ was shown to have declined to 0.1~0.2wt%.
The dissolution property of heavy metals and the like from the obtained slag was determined by a dissolution test No. 13 notified by the Environment Agency on February 17, 1973, 1-1.
As a result of measurement at -a, no harmful metals, mercury, cadmium, lead, hexavalent chromium, arsenic, cyanide, copper, zinc, and tin were not detected, confirming that the safety was extremely high.

Example 2 A refractory was manufactured from the deironed crushed slag in the following steps. As a kneading step, alumina cement having a particle size of 100 mesh or less is used as a binder with respect to 100 parts by weight of the deferred pulverized slag.
3 to 30 parts by weight of water was added to 100 parts by weight of alumina cement as a binder, and the mixture was kneaded with a concrete mixer. As a pouring process, it is poured into a mold set on a vibrating table, filled with a trowel-type vibrator, left to cure at room temperature for one day, and has a length of 230 m for four regular bricks.
A block molded to mx 230 mm x 132 mm was obtained. As a drying step, 50 ° C. for 1 day, 100 ° C. for 1 day,
It was dried at 300 ° C. for 3 days and gradually cooled. The block obtained in this way has a compression strength of 42.0 MPa, 1000
The linear thermal expansion coefficient at 1.degree.
521%, residual expansion / shrinkage at 1000 ° C. is +0.47
4%, and the thermal conductivity (hot-wire method) was 1.94 W / m · K, indicating that it had excellent physical properties. The softening point under load measured with a separately prepared sample was 1206 ° C., indicating that the fire resistance was equivalent to SK32 to SK33 and the fire resistance was excellent.

[0014]

As described above, according to the first aspect of the present invention, a. By gradually cooling the incinerated ash melted by thermite reaction, high melting point CaO-S rich in mullite and other crystalline materials is obtained.
it is possible to obtain a co-crystalline of iO ₂ -Al ₂ O ₃ system, it is possible to obtain a refractory having excellent heat resistance. b. By magnetic separation in the iron removal process, iron can be recovered and used as a raw material for steelmaking, and the iron oxide remaining when aluminum in the thermite reaction is insufficient or iron oxide is contained in excess of aluminum is completely removed. In this case, a refractory can be formed without iron having a large coefficient of thermal expansion, so that spalling due to thermal expansion can be prevented. c. Because the hot strength is large and the load deformation is extremely small,
It has excellent durability and can be particularly suitably used for furnace walls of incinerators. d. In the casting step, the product is hardened at substantially normal temperature and is not fired at a high temperature, so that it is excellent in energy saving and has a low curing shrinkage, so that a product with high dimensional accuracy can be obtained. e. By appropriately manufacturing molds and wooden molds, it can be easily formed into complicated shapes such as the upper arch and various nozzles of the garbage input section of the incinerator, and large blocks, etc.
The application scene of refractories can be expanded. f. In the case of molding into a large size, it is possible to reduce the number of man-hours at the time of repairing, for example, when the furnace wall of the incinerator is damaged, and to shorten the construction period. In addition, when a large-sized block is used, joints are reduced, so that troubles such as load separation due to damage to joints and reduction in self-standing strength can be reduced. g. Compared to conventional refractory bricks using silicon carbide as a main material, it can be manufactured at extremely low cost, so that it is economical.

According to the second aspect of the present invention,
In addition to the effects of the first aspect of the present invention, since the filling rate can be increased during the casting step, the porosity of the product can be reduced, and slag, ash, harmful gas, etc. generated in an incinerator or the like. , An extremely strong resistance can be provided.

According to the third aspect of the present invention,
In addition to the effects of the invention described in claim 1 or 2, it is possible to obtain a refractory excellent in heat resistance, to enhance corrosion resistance to alkali in a combustion furnace, and to increase spalling resistance. .

According to the invention described in claim 4 of the present invention,
In addition to the effects of the invention described in claims 1 to 3, a. When silicon carbide or silicon nitride is added, the adhesion of clinker to the refractory can be prevented, so that the durability can be improved. b. When silicon carbide is used, the effect of preventing clinker adhesion can be enhanced. c. When using silica flour, silicon carbide, or silicon nitride with a fine particle size (100 mesh or less), the amount of binder can be reduced and the amount of water during kneading can be reduced, so that the hardness after curing is increased. Can be.

According to the invention described in claim 5 of the present invention,
In addition to the effects of the invention according to claims 1 to 4, since the water content in the refractory can be significantly reduced, peeling and cracking does not occur even when the temperature is rapidly increased after construction at the use site,
It can be widely used for repair parts of various furnaces and burner tiles.

Claims (5)

[Claims] 1. A melting step of melting ash by a thermite reaction, a slow cooling step of gradually cooling a melt obtained in the melting step, and a grinding step of grinding slag cooled in the slow cooling step, A de-ironing step of de-ironing from the crushed slag crushed in the crushing step by magnetic separation, a kneading step of adding a binder and water to the crushed slag de-ironed in the de-ironing step, and kneading, and the kneading step is performed. A casting step of pouring the mixture into a mold and curing the mixture, and a drying step of drying the cured product obtained in the casting step. 2. In the pulverizing step, the particle size of the pulverized slag is 1
The method for producing a refractory according to claim 1, wherein the refractory is adjusted to a range of from 00 µm to 10 mm, preferably from 2 to 6 mm. 3. The refractory according to claim 1, wherein the binder contains at least one of a high alumina castable material, a clay castable material, and an alumina cement. Method. 4. In the kneading step, silicon carbide, silicon nitride,
The method for producing a refractory according to any one of claims 1 to 3, wherein at least one filler is added to the silica flour. 5. The method for producing a refractory according to claim 1, wherein the drying step is carried out by gradually heating from room temperature to 350 ° C., preferably 320 ° C. .