JPH1192211A - Production of ceramic composition and ceramic sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dry molded form in a short time, without the need of undergoing processes such as drying, by self-exothermic hardening of aluminum dross produced during metallic aluminum melting. SOLUTION: This method for producing a ceramic sintered compact comprises the following processes: first, a composition is prepared by blending aluminum dross containing >=5 wt.% of metallic aluminum with at least one stock selected from quicklime, slaked lime, light burned magnesia, magnesium hydroxide, silica sand and gypsum so as to comprise 3CaO.Al2 O3 , 2MgO.2Al2 O. 5SiO2 3Al2 O3 2 SiO2 , MgO.Al2 O3 , 3CaO.Al2 O3 , and 3CaSO4 followed by agitation in a state of fine powder and then adding an aqueous solution of an alkali salt including sodium hydroxide, sodium carbonate and sodium aluminate (>=pH12) to the mixture, and the resulting system is put into a heat resistant vessel to carry out a hydrothermal synthesis at >=100 deg.C to afford a ceramic composition; subsequently, this ceramic composition is molded and then sintered at a temp. of 1,000-1,500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION Aluminum dross is residual ash generated when aluminum is melted.
1. When aluminum nitride, aluminum carbide, etc. get wet with water, they gradually generate harmful gases such as hydrogen, methane, ammonia, etc., causing great environmental pollution.
The treatment of the above-mentioned residual ash of not less than 10,000 [ton] is a problem. Therefore, treatment methods for detoxifying these aluminum dross as waste have been proposed in various countries around the world, but all of these methods have a large economical burden and can be widely used.
There is no permanent technology that can be implemented. The present invention
In addition to the proposal of an economical method for detoxifying aluminum dross, the method further advanced, but rather utilized the effective use of intense heat energy generated during the oxidation of metallic aluminum, and generated gas and foaming properties. The present invention relates to a novel technology for producing a high value-added ceramic composition or product.

[0002]

2. Description of the Related Art About half of the amount of aluminum dross generated is used as a cement raw material for deoxidizing steel, but it is a treatment for fine dross of fine powder. In Europe and the United States, N
The metal pieces in the dross are collected as molten salt together with aCl and KCl, but the metal recovery rate is high,
There is a problem because the cost of treating a large amount of molten salt residue is very high, and it has not been adopted in Japan. Many patents or research papers on the treatment of these aluminum dross have been published. Japanese Patent Application Laid-Open No. Hei 4-7390 proposes a method in which a large amount of water is added to an aluminum dross and treated at 80 ° C. or higher for 3 hours to remove ammonia gas. Also, in the 92nd Spring Meeting of the Japan Institute of Light Metals (1997) In a paper from Himeji Institute of Technology regarding the reaction of aluminum nitride and aluminum dross with water, in the reaction of PH2 with HCl and PH10 with NaOH, NaOH acts as a catalyst at the time of hydrolysis, and is used for about 20 hours at 80 [° C.] It has been reported that when the treatment is carried out at １００100 [° C.], almost the reaction becomes AlOOH. However, a reaction system having a pH of 10 or more and a pollution-free treatment method have not yet been disclosed.

Further, Japanese Patent Publication No. 26-1124 and Japanese Patent Publication No. 56
-5701, JP-A-51-124117, JP-A-52-1.
No. 152928, Japanese Patent Application Laid-Open No. 56-78461 and the like using a dross alumina component as a cement raw material, and Japanese Patent Application Laid-Open Nos. 47-34517 and 48-64108 disclose lime using hydrogen gas that generates aluminum dross. ,
There is known a method of producing cellular concrete by reacting with an alkali component such as cement and foaming, and curing with an autoclave. This is because the oxidation reaction of metallic aluminum is performed by an autoclave treatment at a hydrothermal temperature of 150 ° C. or higher. Although the foaming is accelerated, the problem in this case has not been put into practical use due to a problem in the treatment of ammonia gas generated during the autoclave treatment.

Japanese Patent Application Laid-Open No. 5-51608 discloses a method of producing α-alumina by firing aluminum dross to 1800 ° C. to 2100 ° C., and a presentation at the 92nd Spring Meeting of the Japan Institute of Light Metals (Kobe Steel, Tokyo Electric Power Company) In the above, regarding the oxidative decomposition of aluminum nitride in aluminum dross, MgO and Fe ₂
A small amount of O ₃ is added and oxidized at about 1300 [° C.].
A method for obtaining l ₂ O ₃ has been announced. The present inventors also conducted an experiment for confirmation of the present invention, but continued research and experiments on the decomposition and oxidation of metal aluminum and aluminum nitride in aluminum dross. After a few days, it is exposed to air and covered with a stable oxide film, and does not easily react with water or hot water. In addition, as described in JP-A-47-3457, even in the case of lime alkali, foaming and gas release occur at the beginning of the reaction. However, it was confirmed that the solution was almost impractical because it immediately became passive and no continuous oxidation reaction occurred.

[0005]

SUMMARY OF THE INVENTION The present invention eliminates many of the disadvantages of the prior art, compensates for the shortcomings, and, by a theoretical method, pollutes the waste. The purpose of the present invention is to establish and provide a method for producing a ceramic composition and a method for producing a ceramic sintered body for converting existing aluminum dross-based waste into a useful new material, a foamed compact, and the like. And

[0006]

According to the present invention, the following theory and means have been developed to achieve the above object. That is, the chemical theory of the reaction system related to aluminum dross (inorganic chemistry, written by Toshizo Chitani) is Al (OH) ₃ + OH ⁻ =
[Al (OH) _4] ^- occurs complex ions by alkali as, Al (OH) ₃ was dissolved, to produce a hydroxo aluminate, gist be aluminum metahydroxide AlO (OH) by heating It is. The present invention is based on the above theory. In particular, since an intense exothermic reaction during oxidation of metallic aluminum is controlled as thermal energy, the reaction is completed in a short time under hydrothermal conditions of 100 ° C. or more. In addition, it is an object of the present invention to produce a multi-cellular molded body by using hydrogen, methane, and ammonia generated by these reactions to react using volatile gas.

To explain this as a requirement, a first feature of the present invention is that aluminum dross containing 5% by weight or more of metallic aluminum is preferably PH11 or more containing sodium salt of sodium hydroxide, sodium carbonate or sodium aluminate. Is PH
12 or more aqueous solutions of alkali salts are added in a range of 10 times or more and 20 times or less by weight relative to the total amount of metal aluminum and aluminum nitride contained in the aluminum dross, and after uniform mixing, in a heat-resistant container. , Hydrothermal temperature 100
This is a method for producing a ceramic composition in which a composition comprising aluminum metahydroxide as a main component is formed through heat generation, foaming, and gas releasing processes at a temperature of [° C.] or more, and then dried by self-heating.

[0008] A second feature of the present invention is that aluminum dross containing 5% by weight or more of metallic aluminum is converted into at least one selected from quicklime, slaked lime, light-burned magnesia, magnesium hydroxide, silica sand, and gypsum. Depending on the raw material, the main component is
3CaO. Al ₂ O ₃ , 2MgO ₂ Al ₂ O ₃ 5SiO
_{2 3Al 2 O 3 2SiO 2,} MgOAl 2 O 3, 3Ca
O. The composition was adjusted to be Al ₂ O ₃ and 3CaSO ₄ , mixed in the form of fine powder, and mixed with sodium hydroxide, sodium carbonate, and sodium aluminate.
Two or more aqueous solutions of alkali salts were added, and a ceramic composition synthesized hydrothermally at a hydrothermal temperature of 100 ° C. or higher was molded in a heat-resistant container, and then fired at a temperature of 1000 to 1500 ° C. This is a method for producing a ceramic sintered body.

A third feature of the present invention is that it is selected from natural ceramic raw materials widely used in refractories, ceramics, and / or artificially produced glass, glassy slag, fly ash, and cement. The prepared raw material is mixed and pulverized to obtain a powdered material having a particle size of 0.5 [mm] or less in a range of 60 to 95 [wt%], and aluminum dross in a range of 5 to 40 [wt%]. The mixture was mixed with water, and an aqueous solution adjusted to a pH of 12 or more with sodium aluminate was added to form a soft mud. After pouring into a predetermined mold, a porous molded body cured through a foaming heat generation process was subjected to 1000 or more. This is a method for producing a fired ceramic body fired at a temperature of 1350 or less [° C.].

The operation of the present invention will be described first.
In the process of dissolving an inert film such as an oxide film or aluminum hydroxide formed on the surface of particles such as aluminum metal, aluminum nitride, aluminum carbide, etc., contained in aluminum oxide with a trace amount of caustic to form hydroxyaluminate The first point is to select an economical alkali component. Next, the second point is the effective use of the heat of formation in these reactions. By synthesizing a characteristic alumina compound together with various component raw materials under hydrothermal conditions of at least 100 [° C.]. is there. The third point is that a gas component which is generated by hydrothermal treatment is appropriately sealed, and a foamed article dehydrated and dried by self-heating is manufactured in a short time.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Aluminum dross, particularly fine dross, has different chemical components depending on the treatment method, but the subject of the present invention is the following range and is shown in Table 1.

[0012]

[Table 1]

These are oxidized by firing or the like to obtain α-Al ₂ O ₃ 50 [%] to 60 [%] MgOA.
About 30% of spinel analogs such as l ₂ O ₃ , Si
X-ray diffraction revealed that O ₂ and these compounds were 10 [%] to 20 [%]. The volatile matter generated by the dross treatment is 12 [m ³ ] to 15 [m ³ ] per 1000 [kg] of dross, of which 50 is hydrogen.
[%] To 60%, methane 25% to 30%,
Ammonia is 4 [%] to 5 [%]. If only water is added or heated, the smell of ammonia remains even after 10 hours, but a 2 [%] solution of caustic soda is added. After 5 minutes, it is in a state of boiling with intense heat generation and generates a large amount of gas.
[%] The added water was evaporated to a completely dehydrated product.

The reaction of these aqueous solutions is accelerated with an increase in pH, but when the pH is 10 or less, they are not suitable for processing in a short time as the object of the present invention.

Various attempts have been made to determine the effects of these alkalis. Among them, those in which the reaction is completed within at least one hour are sodium hydroxide, sodium carbonate, sodium aluminate, and PH.
Twelve or more conditions were suitable, and sodium silicate, sodium phosphate, lime and the like were tried, but were not in the selected range.

The exothermic reaction due to oxidation of metal Al is the largest of all metals, and Al + 3 / 4O ₂
= 1/2 Al ₂ O ₃ +199 kcal, and Al 1
It is about 7 [kcal] to 8 [kcal] per [g].

Al + 3H ₂ O = Al (OH) ₃ +
The heat of formation in the 3 / 2H ₂ reaction is close to these values, and aluminum dross containing 10% Al is 700%.
Thermal energy of [kcal / kg] to 800 [kcal / kg] can be obtained.

[0018]

EXAMPLE 1 An experiment was conducted based on these theories. As a result, dross containing 12% of Al was added to NaOH 2%
When the liquid (PH12.6) was mixed at a weight ratio of 1: 1, heat generation, foaming and gas release started within a few minutes immediately after the mixing, and after 5 minutes, it became a boiling state, and the plastic container was deformed. After 10 minutes, it was almost dehydrated.

It has also been found that when the gas released during these reaction processes is ignited, a flame is emitted to burn it.

The high heat of reaction of Al is cooled by the latent heat of vaporization of the added water.
Although it is 00 [° C.], it is estimated from calculation that the reaction temperature changes from 250 [° C.] to 300 [° C.] in a hydrothermal state even when the water ratio is 1: 1. It was confirmed that if the internal pressure was kept high, a higher temperature hydrothermal state could be maintained.

The hydrothermal temperature is controlled by calculating the amount of water in the range of 10 times or more that of Al and aluminum nitride in the treated dross. That is, in the prior art, a major feature of the prior art is that no invention or research has been made on high-temperature water conditions as in the present invention. This is a new technology disclosed in No. 1.

[0022]

[Embodiment 2] Next, in claim 2, under these hydrothermal conditions, a refractory or cement-based ceramic composition containing alumina is synthesized, and a ceramic sintered body is produced therefrom. Raw materials include CaO, MgO, SiO
Although fine powder containing ₂ of interest, particularly CaO, quicklime, slaked lime, MgO is dried magnesia, SiO ₂ is
A substance having a higher reaction activity such as silica fume is more preferable.
It is a feature of the present invention that metal Al and aluminum nitride in the dross are efficiently bonded at the time of oxidization, and the synthesized alumina compound can be used as it is as a ceramic raw material.
Those sintered at a temperature of [° C.] or more can also be used. 3CaOAl ₂ O ₃ 3CaSO _{4 with} gypsum is
A composition of ettringite, which is a cement compound, which is fired at 1300 [° C.] is used as an additive for expansive cement.

X-ray diffraction of these hydrothermally synthesized products showed that although the degree of bonding was weak, crystals of the desired compositions were deposited.

[0024]

[Embodiment 3] A third aspect of the present invention is to produce a foamed article using a gas such as hydrogen generated from metal Al in aluminum dross. The foamed molded product is described in A.I. L. C. As described above, a method of generating hydrogen by metal Al and CaO alkali from cement and lime is known, but as disclosed in JP-A-48-64108, when Al is removed from dross, it is subjected to an autoclave treatment of at least 150 ° C. It is possible, at room temperature like fresh metal Al powder,
A foam is not easily obtained.

[0025] The polyfoam to be intended in the present invention is, in particular, a large-sized plate-like material, which is made of a sound absorbing material, a heat insulating material, a filtering material, etc. as a commercial product. It has sufficient strength and has a bulk specific gravity of 0.4
[G / cc] to 1.0 [g / cc], bending strength 30 [k]
g / cm ³ ] to 100 [kg / cm ³ ] The main raw materials for producing rigid plate-like products are refractory raw materials, minerals and clays as ceramic raw materials, bottle glass, plate glass cullet and the like. , Glass or municipal waste melting slag,
Slags such as iron and steel slags, fly ash, and the like are used as compositions suitable for the firing sintering temperature and physical properties, but aluminum dross is partially used in a range of 5% to 40%. Replace. When the dross is 5% or less, the foaming condition is satisfied, but the self-heating value is small and the drying and dehydrating time is long, which is not suitable in terms of productivity. Dross 40
[%] Or more, foaming occurs too rapidly and the pore size varies greatly. As an alkali salt, sodium aluminate has the strongest effect of developing strength, and PH1
When the amount is 2 or more and the amount of sodium aluminate added is in the range of 10% to 40% with respect to the weight of dross, a molded article having extremely high strength can be obtained. In addition, the polyfoam of the present invention can be applied not only to large-sized plate-shaped ones but also small-sized ones as long as it is based on this novel production method.

These compositions need to be molded in a state in which a required amount of generated gas is sealed in a molded body, and the raw materials are preferably in the form of fine powder having a particle size of 0.5 [mm] or less. Can also adjust the filling amount. Furthermore, if the reaction between dross and alkali is too rapid, the cell size becomes non-uniform, and it has been found that the foaming rate can be controlled by adding a small amount of hydraulic cement or gypsum to stabilize the cells. .

[0027]

Example 4 Reaction of Almidros with Alkaline Salt Aqueous Solution Almidros differ in the metal Al content depending on the particle size, and coarse dross has a large metal Al content. Chemical analysis values of dross using a sieve of 74 [μm] are as follows and are shown in Table 2.

[0028]

[Table 2]

To 100 g of dross, 440 g of an aqueous solution of an alkali salt (20 times the amount of metallic aluminum) was added, and the time required for foaming, heat generation, and gas release was measured. Table 3 shows the results.

[0030]

[Table 3]

As described above, sodium hydroxide, sodium carbonate,
Sodium aluminate completes the reaction in about 10 minutes in a 2% solution, but sodium silicate and quicklime rapidly foam,
There was outgassing, but after about 5 minutes, with a near-passive state, the visible reaction was dormant. Also, 1,
In the case of 2, 3, after 5 minutes, it became a boiling state, and after 10 minutes, it became almost dehydrated. That is, according to the method of the present invention, it is economical that the treated product can be taken out in a substantially dry state by adjusting an appropriate amount of water.

Example 2 2MgO · 2A according to claim 2
An example will be described for the synthesis of l ₂ O ₃ .5SiO ₂ (cordylite).

2MgO.2Al ₂ O ₃ .5SiO ₂ is
A typical example of a refractory having low thermal expansion is MgO14.
[%], Al ₂ O ₃ 35 [%], MgO 16 [%], A
l ₂ O ₃ 67% and SiO ₂ 17%.

Raw material composition, dross 52%, lightly burned MgO
500 [g] was adjusted by the mixing ratio of 6 [%] and silica sand (320 mesh or less) 42 [%], and 1150 [g] as water of 20 times the amount of metal Al in dross and caustic soda 23 were used.
An alkali aqueous solution containing [g] was added, and the mixture was subjected to hydrothermal treatment for 1 hour in a 5 [〓] metal container. These composites were molded as a dry powder at a pressure of 200 [kg / cm ² ],
A sample of 00 [mm] × 50 [mm] × 10 [mm] was prepared and fired at 1200 [° C.].

According to X-ray diffraction, the main phase of the synthesized product was a cordierite crystal and a small amount of MgOAl ₂ O ₃ α-Al
It was ₂ O ₃ and the coefficient of thermal expansion was measured.
× 10 ⁻⁷ [° C.], a low expansion characteristic of cordierite.

Example 3 A porous sintered body was blended, molded and fired according to Table 4, and a physical property test was conducted.

[0037]

[Table 4]

The above weight ratio composition was mixed with sodium aluminate 1
An aqueous solution of 0% (30%) was added to make a slurry,
It was injection-molded into a mold of [mm] × 300 [mm] × 50 [mm].

Next, the foam hardening process will be described. After 5 minutes from the injection of the mold, the foaming action is started, and after 20 minutes, the volume is almost doubled. However, the temperature inside the molded body became 80 [° C.] to 90 [° C.], and the water that had been added was evaporated and cured. After foaming for 1 hour, the cured body had sufficient strength and was demolded.

By the above manufacturing method, a dehydrated, cured and dried molded article was obtained without performing any heat drying treatment by self-heating and curing of aluminum dross, which is one feature of the present invention. The physical properties of the porous sintered bodies obtained by firing these molded bodies at a temperature of 1160 [° C.] are as shown in Table 5.

[0041]

[Table 5]

[0042]

【The invention's effect】

1) According to the present invention, conventionally, at a waste disposal site,
The aluminum dross, which has generated harmful gas and caused pollution, can be made pollution-free by controlling the gas emission by a series of treatments by adding an aqueous alkali salt solution by the treatment method of the present invention. 2) According to the present invention, lime, silica sand, and other raw materials are added to aluminum dross and hydrothermally synthesized in a heat-resistant container, whereby the aluminum dross can be converted into a raw material for producing a useful material. 3) According to the present invention, various types of natural ceramics raw materials and / or artificial materials are further added to the raw material in addition to the pollution-free method, and the raw material is pulverized into ooze, and injected into a mold to generate self-heating. By doing so, a foam molded article with high added value can be obtained. 4) According to the present invention, in addition to the above effects, by firing the molded body, it is possible to manufacture a fired ceramic product of higher quality. 5) According to the present invention, the above-mentioned original technology can eliminate the pollution and economical negative effects brought about by aluminum dross and can produce high quality ceramic products. Has a remarkable effect.

Continued on the front page (72) Inventor Hideo Inoue 2-14-14, Koyodai, Takanezawa-machi, Shioya-gun, Tochigi Prefecture (72) Inventor Joh 2-14-14, Koyodai, Takanezawa-cho, Shioya-gun, Tochigi

Claims (3)

[Claims] 1. An aluminum dross containing 5% by weight or more of metallic aluminum, containing PH11 or more, preferably P11 or more, containing sodium salt of caustic soda, sodium carbonate, and sodium aluminate.
An aqueous solution of an alkali salt of H12 or more is added in a range of 10 times or more and 20 times or less by weight with respect to the total amount of metal aluminum and aluminum nitride contained in the aluminum dross, and after uniform mixing, in a heat-resistant container. , Hydrothermal temperature 100
A method of producing a ceramic composition, wherein a composition comprising aluminum metahydroxide as a main component is formed through heat generation, foaming, and gas release at [° C.] or higher, and then dried by self-heating. . 2. An aluminum dross containing 5% by weight or more of metallic aluminum, which is prepared from quick lime, slaked lime, light-burned magnesia
One or more raw materials selected from magnesium hydroxide, silica sand, and gypsum make the main component 3CaO. Al ₂ O
_{3, 2MgO2Al 2 O 3 5SiO 2} 3Al 2 O 3 2S
iO ₂ , MgOAl ₂ O ₃ , 3CaO. Al ₂ O ₃ , 3
The composition was adjusted to CaSO ₄ and mixed and mixed in the form of fine powder, and then an aqueous solution of an alkali salt having a pH of 12 or more containing sodium hydroxide, sodium carbonate, and sodium aluminate was added. A ceramic composition synthesized hydrothermally at a hydrothermal temperature of 100 ° C. or higher is molded,
A method for producing a ceramic sintered body, characterized by firing at a temperature of from 000 [° C] to 1500 [° C]. 3. A mixture of natural ceramic raw materials widely used in refractories and ceramics and / or artificial materials selected from artificially generated glass, vitreous slag, fly ash and cement. Crushed, particle size 0.5 [m
m] or less in a powdered state of 60 to 95 [% by weight], and aluminum dross in a range of 5 to 40 [% by weight], and then mixed with sodium aluminate to adjust the pH to 12 or more. The obtained aqueous solution is added to form a soft mud, injected into a predetermined mold, and then fired at a temperature of 1000 to 1350 [° C.] of a porous molded body cured through a foaming heat generation process. A method for producing a ceramic fired body.