JPH09110514A - Sintered compact as raw material of asbestos and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To render industrial wastes, which includes asbestos controlled as a toxic matter against environment, harmless and enable the production of a sintered compact of a valuable industrial product from the wastes. SOLUTION: This sintered compact is produced by adding sodium silicate or potassium silicate at the content of 3-15% to a raw material composition mainly containing wastes consisting of asbestos, in which the weight ratio of asbestos is >=60%. The compound is baked and sintered preferably at 1,000-1,200 deg.C to produce the objective sintered compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered body containing asbestos-containing waste as a main material and a method for producing the same. More specifically, the present invention detoxifies industrial waste containing asbestos, which is regulated as a harmful substance to the environment, and further makes it possible to effectively utilize the asbestos raw material sintered body and its production. It is about the method.

[0002]

2. Description of the Related Art Conventionally, asbestos contained in building materials, vehicle brakes, etc. is harmful to the human body. Therefore, there are many methods for detoxifying industrial waste containing such asbestos. Is being devised. As a method for detoxifying such industrial waste containing asbestos, for example, a) a treatment method in which asbestos, which is a basic mineral, is treated with hydrochloric acid or sulfuric acid to dissolve asbestos, or a) an aqueous solution of sodium silicate or A method of coating the asbestos fiber surface with a synthetic resin emulsion to close the micropores, c)
A treatment method of adding hydraulic cements to asbestos and solidifying them has been known so far.

However, although such a conventional method of detoxifying asbestos has achieved certain results only in terms of detoxifying asbestos, it is effective in treating substances after detoxifying the asbestos. As far as utilization is concerned, there have been almost no effective measures to date, and as a result, the asbestos-detoxifying treatment methods used up to now have had to be very expensive treatment techniques.

Therefore, taking into consideration such problems of the asbestos-detoxifying treatment method, only recently has been proposed a technique for effectively utilizing the asbestos-detoxifying treatment substance to reduce the treatment cost. Has been done. This method is a method of adding low-melting glass to asbestos and melting it at a temperature of 1400 ° C to 1500 ° C to obtain a glassy slag, and the generated glassy slag is effectively used as a construction or industrial material. It has become possible.

However, in this method, asbestos is melted at a very high temperature, so that a very large energy cost is required, and even if a treated substance which detoxifies asbestos can be effectively used, it is economically advantageous. The current situation is that it has not spread. The present invention has been made in view of the above circumstances, eliminates the drawbacks of the prior art, detoxifies industrial waste containing asbestos that is regulated as a harmful substance to the environment, and detoxifies the industrial waste. It is an object of the present invention to provide a completely new asbestos raw material sintered body and a method for producing the same, which makes it possible to reuse the asbestos at low cost.

[0006]

In order to solve the above problems, the present invention uses waste containing asbestos as a main raw material, and the weight ratio of asbestos in the mixed composition of the raw materials is 60% or more. The asbestos raw material sintered body (claim 1) is obtained by firing and sintering a blended composition containing 3% to 15% of sodium silicate or potassium silicate.

In the present invention, waste containing asbestos is used as a main raw material, and the weight ratio of asbestos in the composition of the raw material is 40% or more, and the hydraulic cement is 10% to 3%.
Also provided is an asbestos raw material sintered body (claim 2), which is obtained by firing and sintering a compounded composition containing 0%.
Further, in the present invention, the asbestos weight ratio is 60% or more, and further 85% to 97%, relative to the dry asbestos raw material from which impurities such as asbestos are crushed and crushed to remove impurities such as metals. Add 3 to 15% of sodium silicate or potassium silicate as an aqueous solution in terms of solid matter weight ratio, and divide water by 3
0% to 35% of dough is made into a dough, and the dough material is heated to 150 °
After heating at an ambient temperature of ~ 200 ° C for 10 to 15 minutes,
Dry at 100-150 ℃, then 1000 ℃
A method of manufacturing an asbestos raw material sintered body, which comprises firing and sintering in a temperature range of 1 to 1200 ° C.
Waste material containing asbestos is crushed and crushed, and raw materials from which impurities such as metals have been removed are treated with an aqueous solution of hydrochloric acid or sulfuric acid and then dehydrated and dried. Add 40% to 80% of hydraulic cement to 1
The composition of 1% or more of 0% to 30%, clay, coal ash, and blast furnace water slag is adjusted to 10 to 30%, dried, and then fired in a temperature range of 1000 ° C to 1200 ° C.
There is also provided a method for producing a sintered body of asbestos raw material characterized by sintering (claims 5 and 6).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention described above, the structure of asbestos is destroyed and modified by a chemical reaction and a high temperature sintering reaction to obtain a harmless ceramic sinter.
The temperature during the high temperature sintering reaction is 1200 ° C. at most, and the treatment temperature of 140 in the case of the method of adding the low-melting glassy substance to asbestos to generate the glassy slag as in the conventional method.
Compared with 0 ° C to 1500 ° C, the treatment at a much lower temperature becomes possible.

The method of the present invention that enables such a thing is based on the following findings. That is,
First, the harmfulness of asbestos to the human body is generally due to that the asbestos mineral has micropores having a tunnel structure of several angstroms, and the micropores adsorb to the human body. In other words, asbestos owns 12% of crystal water
In addition to ~ 13%, it is a porous body that absorbs nearly 40% to 50% of free water. As a result, asbestos has a very high adsorption function, and this adsorption function causes the adverse effect on the human body. ..

In the present invention, for example, when an aqueous sodium silicate solution or an aqueous potassium silicate solution is adsorbed on asbestos, sodium ions in the aqueous sodium silicate solution or potassium ions in the aqueous potassium silicate solution are adsorbed on the asbestos surface. In other words, the sodium ions or ions with a large ionic radius such as potassium ions cannot easily enter the micropores of the asbestos structure, so they are strongly adsorbed on the fiber surface of the asbestos. However, as a result, attention is paid to the fact that the fiber surface layer of asbestos is in a state of being coated with the alkali silicate gel.

Therefore, in the present invention, the high adsorption property peculiar to asbestos is avoided by this coating effect. Generally, there are six types of asbestos minerals, but one widely used for industrial purposes is Mg ₆ Si ₄ O ₁₀ (O
H) ₆ is a chrysotile (warm asbestos, white asbestos) having a chemical structural formula. Since this chrysotile is an alkali silicate, it is highly reactive with hydrochloric acid and sulfuric acid, and therefore, asbestos can be obtained by acid treatment. The fibrous morphology of is easily destroyed.

Therefore, in the present invention, acid treatment may be performed as the primary treatment to destroy the structure of asbestos,
As a result, the asbestos can be rendered harmless, and the harmfulness of dust to the worker in the manufacturing process of the sintered body of the present invention can be prevented. Furthermore, asbestos minerals generally release water of crystallization at about 600 ° C. when heated,

[0013]

Embedded image

The dehydroxylation reaction shown in
When the reaction product was heated to 900 ° C., the structure
Change, MgOSiO_TwoWith (clinoenstatite)
SiO _Two(Cristobalite) was transformed into a foreign object
Becomes These MgOSiO_Two(Clino Enstatai
G) and SiO_Two(Cristobalite) has high fire resistance
It cannot be melted unless heated to about 1500 ° C.

However, in the present invention, the micropores, which are the structural characteristics of asbestos, are hydrated so as to be sufficiently saturated, and a gel layer of alkali silicate is formed on the surface of the asbestos fiber to form a molded product in which water is enclosed. After forming the body, the formed body is placed in a heating furnace or the like heated to an atmosphere of 150 ° C. to 200 ° C., and water in the formed body is evaporated and moved to the forming surface layer.

In this process, the added sodium ion or potassium ion is concentrated in the surface layer together with water to form a dry film to prevent evaporation of internal moisture and increase the vapor pressure in the molded body to increase the size of the molded body. Foam. Such a foam can be effectively used as a building material. Further, in the present invention, the foaming treatment time is appropriately 15 to 20 minutes, and if the foaming time is too long, the coating film is broken. Then, it is preferable that the foamed molded body is dehydrated and dried in a dryer and then fired.

In the firing step, for example, when the content of the alkali silicate is 15% or more, the alkali silicate is concentrated on the surface layer of the molded body, the temperature is 1000 ° C. or higher, and the molded body is vitrified. As a result, the respective molded bodies are welded to each other, and a good quality sintered body cannot be obtained. Also, the content of alkali silicate is 15
When it is at least%, the size of the bubbles in the formed compact is not constant, and therefore, also in this respect, a good quality sintered body cannot be obtained.

On the other hand, if the content of alkali silicate is 3% or less, sintering is impossible. Further, the sintered body according to the present invention provides not only foams but also ceramic products used for general construction. That is, as described above, 9
At around 00 ° C, asbestos decomposes into MgO · SiO ₂ and SiO ₂ , but if CaO is present, first, the released Si is released.
O ₂ reacts with CaO and CaOSi near 1150 ° C
O ₂ (Wollastonite) is produced.

For example, when the CaO component in the molded body is obtained from hydraulic cements, β-C is obtained by a high temperature hydrothermal reaction.
aOSiO ₂ is generated, CaOSiO ₂ · MgOSiO
It becomes a strong crystal with a main crystal phase of ₂ (diobsite). In the present invention, the content of hydraulic cement is appropriately in the range of 10% to 30%, and if the content exceeds 30%, cracks or explosions may occur during firing of the molded body. There is. When the content of hydraulic cement is 10% or less, it becomes impossible to sufficiently maintain the strength of the molded body.

Further, according to the present invention, asbestos, which is the main raw material,
In addition to cement, which is a molding material, if it is necessary to correct the amount of CaO, a blast furnace slag can be used, and if it is necessary to correct the amount of SiO ₂ , clay can be used. And coal ash can be used. The higher the sintering temperature is, the more the strength characteristics are improved. However, it is desirable that the sintering temperature is 1200 ° C. or lower, and if the sintering temperature is 1200 ° C. or higher, the energy cost becomes very large, which is not preferable in terms of economy. Absent.

Examples will be shown below to describe the embodiments of the present invention in more detail.

[0022]

Example 1 Asbestos used as a raw material was a cotton-like product obtained by crushing vehicle brake waste, removing metal fibers contained therein, and drying the remaining asbestos. Also, sodium silicate is Na
No. 3 sodium silicate containing 10% of ₂ O was used. (A) Compounding process As a compounding ratio, 1000 g of asbestos, No. 3 sodium silicate 33
A mixture of 0 g and 200 g of water was mixed. (B) Mixing and kneading and molding step After the above compounds were mixed and kneaded, they were cured for 35 minutes. Then, the training product is made into a granular shape with a pan type pelletizer,
A granular material having a diameter of 10 m / m to 20 m / m was molded. (C) Foaming treatment and drying process Wavelength 10μ with ambient temperature adjusted in advance to 200 ° C
In a far infrared furnace of m to 30 μm, put the above-mentioned granular material,
It was treated for 10 minutes to obtain a molded product having a volume expanded to about twice. Then, the molded body was dried in a dryer at 120 ° C. for 1 hour. (D) Firing Step The above-mentioned compacts were arranged on a refractory tray and fired / sintered at 1050 ° C. using a roller hearth kiln. (E) Measurement of physical properties When the physical properties of the above sintered body were measured, the bulk specific gravity was 0.
The foam was 38 gr / cm ³ , the water absorption rate was 5.2%, the porosity was 78%, and the maximum porosity was 3 m / m or less.

Further, as a result of X-ray diffraction of the sintered body, no asbestos mineral was present in the sintered body. Example 2 Asbestos used as a raw material was asbestos waste mixed with a building fireproof spraying material and a gasket material. This asbestos waste was reacted in a 1N aqueous hydrochloric acid solution for 1 hour and then dehydrated and dried. (A) Blending step As the blending rate, as shown in Table 1, three different blending rates were used.

[0024]

[Table 1]

(B) Molding and Curing Steps A, B, and C compounds shown in Table 1 have a water content of 30% to 50%.
Was added to form a soft slushy cement mortar, and the soft slushy cement mortar was poured into a plate mold having a size of 30 cm × 30 cm × 30 cm, cured for about 24 hours, and then demolded. (C) Drying and Baking Step After drying the above-mentioned cured product in a dryer at 120 ° C. for 3 hours, 1150 A was applied using a roller hearth kiln.
C., B was fired at 1180.degree. C., and C was fired at 1200.degree. (D) Measurement of Physical Properties of Sintered Body Table 2 shows the physical properties of the sintered body produced in the step (c).

[0026]

[Table 2]

Considering the physical characteristics of the sintered body from Table 2, the sintered body of the present invention has extremely high specific strength (flexural strength / bulk specific gravity) as compared with general building tiles. . Ceramic tiles for building exterior, which are generally widely used, have a bulk specific gravity of 2.15 to 2.2 gr / c.
m ³ , bending strength is 200 to 250 kg / cm ² , and specific strength is 91 kg to 116 kg. In the sintered body produced in this example, A = 147 kg, B = 131 k
Since g and C = 120 kg, it can be seen that it is lightweight and has extremely high strength.

Further, the firing shrinkage of the sintered body of the present invention is extremely low, and the sintered body is sintered by a solid phase reaction.
It has a composition in which fine pores are uniformly dispersed.

[0029]

Industrial Applicability As described in detail above, the present invention makes it possible to detoxify industrial wastes containing asbestos, which are regulated as harmful substances to the environment, and further, valuable industrial products from the industrial wastes. It is also possible to produce a sintered body that is Further, the sintered body of the present invention is a foamed product, has a high porosity as a porous granular body, and can be used as a water treatment agent or the like which makes use of porous characteristics such as a bacterial carrier. Furthermore, this sintered body can be used as a lightweight and high-strength ceramic product for construction civil engineering.

Claims (6)

[Claims] 1. A mixture comprising asbestos-containing waste as a main raw material and containing 3% to 15% of sodium silicate or potassium silicate with respect to a weight ratio of asbestos in a mixed composition of the raw materials of 60% or more. A sintered asbestos material sintered body obtained by firing and sintering a composition. 2. A compounding composition comprising wastes containing asbestos as a main raw material and containing 10% to 30% of hydraulic cements with respect to a weight ratio of asbestos in the mixed composition of the raw materials of 40% or more. An asbestos raw material sintered body obtained by firing and sintering a product. 3. An asbestos weight ratio of 6 to a raw material obtained by crushing and crushing waste containing asbestos to remove impurities such as metals.
To 0% or more, 3-15% sodium silicate or potassium silicate as an aqueous solution is added as an aqueous solution in a solid conversion weight ratio to prepare a kneaded material having a water division amount of 30% -35%.
After heating for 10 to 15 minutes at an ambient temperature of ℃ to 200 ℃, it is dried at 100 to 150 ℃, then 100
A method for producing an asbestos raw material sintered body, which comprises firing and sintering in a temperature range of 0 ° C to 1200 ° C. 4. The method according to claim 3, wherein the weight ratio of asbestos from the raw material is 85 to 97%. 5. A waste material containing asbestos is crushed and crushed, and a raw material from which impurities such as metals are removed is treated with an aqueous solution of hydrochloric acid or sulfuric acid and then dehydrated and dried. % To more than 30% hydraulic cements
%, Clay, coal ash, and one or more of blast furnace water slag are adjusted to have a composition of 10 to 30%, and after drying,
A method for producing an asbestos raw material sintered body, which comprises firing and sintering in a temperature range of 1000 ° C to 1200 ° C. 6. The method according to claim 5, wherein the weight ratio of asbestos from the raw material is 40 to 80%.