JP2003094006A - Treating method for asbestos and the product thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating method for asbestos which makes the treated product recylable stably without dumping the treated material, consuming a great quantity of energy or producing the material which is easy to react with water such as forsterite having a posibility of recrystallization to chrysotile. SOLUTION: The material containing Si, Ca and/or Al is added to and mixed with a material to be treated containing asbestos conforming to the following condition, and the obtained mixture is heat-treated at 400 deg.C to 1,200 deg.C. Addition conditions: The mol ratio of Mg to Si in the material to be treated is adjusted to Mg/Si<=0.5, and the mole ratio of Ca to Si is adjusted to 0.5<=Ca/Si<=2.0. When the mole ratio is Ca/Si>=1.3, the material containing Al is added so as to make Al2 O3 mass percentage >= ((Ca/Si)×0.357-0.464)×100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating asbestos, and more specifically, it does not waste a substance to be treated and consumes a large amount of energy,
The present invention relates to a method for treating asbestos that does not generate a substance that easily reacts with water, such as forsterite that may be recrystallized into chrysotile, and that the treated product is stable and can be reused.

[0002]

2. Description of the Related Art In recent years, there has been a problem in the treatment of industrial waste, especially in the method of disposing of a large amount of construction waste. It also includes waste materials containing asbestos. Although the use of asbestos has been decreasing since its health effects were pointed out, it is still being used in large quantities in existing buildings, and it is expected that the problems related to its disposal will become even greater in the future. It

As a conventional method for treating asbestos, asbestos cement products such as asbestos slate are buried in the soil as they are. For sprayed asbestos and heat-insulating asbestos-containing materials, the asbestos is solidified with cement so that it does not scatter and then it is filled up. A method is adopted in which it is melted at a high temperature of 1500 ° C or higher, vitrified, and then discarded. However, these methods are expected to become difficult in the future due to the shortage of landfill due to the problems of the local environment. Therefore, there is a demand for a method of converting asbestos waste into non-asbestos and converting it into a substance harmless to the human body and effectively utilizing the treated product.

Until now, several methods for treating asbestos and recycling of treated products have been proposed. For example, in Japanese Patent Laid-Open No. 3-60789, SiO ₂ is added to natural asbestos.
A mixture of water treatment sludge with a higher CaO content than the basicity modifier, the mixture is molded, and the mixture is heated and melted by supplying it to a high-temperature hearth molded with a carbon-based combustible substance. Melt processing methods are disclosed. This is a method in which asbestos is melt-processed and discarded together with other wastes. JP-A-3-4980 discloses a basic inorganic solid mainly composed of asbestos and carbon-based solid fuel, and if necessary, these binders and / or oxidizers are added and, if desired, the asbestos is further lowered in melting point. Is added and mixed, the resulting mixture is granulated, the mixture is burned while feeding air to melt and sinter the needle-shaped asbestos, and a method for assembling and consolidating asbestos is disclosed. Has been done. Further, in Japanese Patent Laid-Open No. 3-21387, asbestos is treated with phosphoric acid and fired, and an alkaline agent such as calcium carbonate or calcium hydroxide is added to the asbestos to fire the waste asbestos. A detoxification treatment method is disclosed. According to this method, it is disclosed that asbestos waste such as asbestos packing can be made harmless and used as fertilizer or the like. As a firing method, in Japanese Patent Laid-Open No. 5-293457, asbestos cement products are heat-treated at 600 to 1450 ° C. for about 15 minutes to 2 hours to decompose asbestos into forsterite and detoxify it and obtain a hydraulic powder. An asbestos treatment method is disclosed.
Also JP The 6-134438 discloses MgO · 2CaO ·-product refining ash during aluminum refining waste asbestos material 5SiO ₂ · 5 / 3Al
Disclosed is a method for treating a waste asbestos material, which is characterized in that it is added so as to have a composition close to that of ₂ O ₃ and is baked at 800 ° C. or higher. Further, it is disclosed that chamotte can be added to the treated product to form a molded product, which can be dried and then baked at 1230 ° C. or higher to produce a ceramic product. Further, in JP-A-9-206726, a mixture of asbestos-containing material and municipal waste incineration ash is heated in a temperature range of 600 ° C. to 1700 ° C. to convert chrysotile into a solid solution containing gehrenite and / or akermanite, forsterite and cristobalite. A method for detoxifying waste asbestos characterized by detoxifying asbestos by changing it is disclosed. According to this method, it is disclosed that the obtained reaction-sintered body can be used as an adsorbent or a building material such as tile, brick, and cement filler.

[0005]

As described above, several methods have been implemented or proposed for asbestos treatment, but the conventional method of landfill has revealed a shortage of landfill sites due to the problem of the local environment. It is expected to become more difficult in the future. Further, the method of melting asbestos-containing material for processing generally requires processing at a high temperature of about 1500 ° C., which consumes a large amount of energy. Therefore, it is hard to say that it is appropriate from the viewpoint of energy saving. On the other hand, in the asbestos treatment method by the firing method at a relatively low temperature for the purpose of reuse, the inclusion of forsterite (Mg ₂ SiO ₄ ) is shown. Forsterite itself is one of the most commonly occurring minerals on earth and is harmless to the human body. However, it is known that forsterite and other minerals that are generally formed in nature at high temperature have a weak resistance to water due to their crystal structure and easily react with water. Chrysotile originally occupies most of asbestos
(Mg ₃ Si ₂ O ₅ (OH) ₄ ) is a forsterite-based peridotite that rises in the solid state from deep underground,
It is said that it reacts with surrounding water such as groundwater on the way and forms veins in the serpentinized rock body. Further MgO-SiO
_From the results of the synthesis experiment of the _2- H ₂ O system (NL Bowen and OF
Tuttle, Bull. Geol. Soc. Am., Vol.60, 439-460, (1
949), JJ Hemley, JW Montoya, DR Shaw, R.
W. Luce, Amer. J. Sci., Vol. 277, 358-383, (1977)), chrysotile was found to be formed at 500 ° C or lower, and 400 ° C in the reaction of forsterite and water.
Generate below. It has also been reported that chrysotile can be synthesized at 200 ° C (ET Carlson, RB P
eppler and LS Well, J. Res. Natl. Bur. Stand.,
Vol.51, 179-184, (1953)). Therefore, when the asbestos-treated product containing forsterite is reused in cement-based or calcium silicate-based building materials produced using water, forsterite is re-converted into chrysotile when autoclaving is performed to accelerate hardening. May crystallize.

[0006] Therefore, an object of the present invention is to produce a substance which easily reacts with water, such as forsterite, which may be recrystallized into chrysotile without discarding the substance to be treated and consuming a large amount of energy. Without
Another object of the present invention is to provide a method for treating asbestos in which the treated product is stable and can be reused.

[0007]

The present invention is directed to asbestos and / or
Alternatively, a treatment method for converting asbestos in the substance to be treated into a non-asbestos substance by heat-treating the substance to be treated containing asbestos-containing substance, wherein the substance to be treated contains a substance containing Si and Ca One or more substances selected from the group consisting of substances and substances containing Al are added and mixed so as to satisfy the following conditions, and the resulting mixture is heat-treated at 400 ° C to 1200 ° C. A method for treating asbestos is provided. Addition condition: The molar ratio of Mg and Si in the substance to be treated is Mg
/Si≦0.5 and the molar ratio of Ca and Si is 0.5 ≦ Ca / Si ≦ 2.0
Adjust to. However, at this time, the molar ratio is Ca / Si ≧ 1.
If 3, Al ₂ O ₃ mass% ≧ ((Ca / Si) × 0.357-0.464)
The substance containing Al is added so that the amount becomes × 100. The present invention provides the process product which has been treated by the method, MgO-SiO ₂ compound in the product, MgO and
There is provided the above-mentioned product, which is characterized by not containing Ca ₂ SiO ₄ . The present invention also provides a filler for building materials, which comprises the above products.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be further described below.
In the treatment method of the present invention, a substance to be treated composed of asbestos and / or an asbestos-containing substance is adjusted to have a chemical composition in a specific range and heat-treated under specific conditions to convert asbestos to a non-asbestos substance such as CaO- MgO-SiO _{2 compound, CaO-MgO-Al 2 O} 3
It is characterized by non-asbestos conversion to —SiO ₂ compounds. The chemical composition of the above specific range depends on the substance to be treated,
It is adjusted by adding one or more substances selected from the group consisting of a substance containing a, a substance containing Ca and a substance containing Al under the following addition conditions. That is, the addition condition is that the molar ratio of Mg and Si (Mg
/ Si molar ratio) to Mg / Si ≤ 0.5, and the molar ratio of Ca and Si (C
The a / Si molar ratio) is adjusted to 0.5 ≦ Ca / Si ≦ 2.0. However, at this time, the molar ratio of Ca / Si ≧ 1.3
If so, Al ₂ O ₃ mass% ≧ ((Ca / Si) × 0.357-0.464) ×
It is necessary to add the above-mentioned substance containing Al to 100.

Examples of the asbestos and / or asbestos-containing substance to be treated in the treatment method of the present invention include sprayed asbestos, asbestos-containing heat insulating material, asbestos slate, asbestos-containing pulp cement board, asbestos-cement products such as asbestos pipe, Joint sheet Asbestos cloth, asbestos rope, asbestos products such as friction materials, asbestos-organic composite waste such as vinyl asbestos tile, and the like. The chemical composition of these substances to be treated is asbestos products such as asbestos rope.
Since it contains almost no Ca and the Mg / Si molar ratio exceeds 0.5, asbestos changes to forsterite when heat-treated. Asbestos-cement products such as sprayed asbestos usually have an Mg / Si molar ratio of more than 0.5 due to the high content of asbestos, and when heat-treated, asbestos changes to forsterite. Also,
Asbestos cement products such as asbestos slate typically have a Mg / Si molar ratio of greater than 0.5 or a Ca / Si molar ratio of greater than 2.0.

Examples of the substance containing Si used in the treatment method of the present invention include amorphous precipitated silica silica stone, diatomaceous earth, waste glass, silica fume and the like. Examples of the substance containing Ca include quick lime, slaked lime, limestone, waste shell incineration ash and the like. Examples of the substance containing Al include aluminum oxide, aluminum hydroxide, bauxite and the like. In addition, waste incineration ash, sewage sludge incineration ash, tuff, shirasu, concrete waste material, raw consludge, fly ash, waste soil, waste tile, clay, calcium silicate product waste material, etc., including two or more of Si, Ca and Al Materials can be used as well. However, even if mixed and heated with the substance to be treated, the substance that exists stably at a temperature of 1200 ° C or lower is
At least one of Si, Ca and Al in its component
Even if the type is included, it does not correspond to any of the substance containing Si, the substance containing Ca, and the substance containing Al in the present invention.

The heating temperature in the heat treatment is as described above.
The temperature is 400 ° C to 1200 ° C, preferably 600 ° C to 1200 ° C, more preferably 600 ° C to 1000 ° C. When the heating temperature is lower than 400 ° C, asbestos remains without being completely dehydrated and decomposed even after long-term treatment. On the other hand, if the temperature is higher than 1200 ° C., not only the high temperature treatment but also the partial melting may cause the formation of an amorphous substance. Further, in order to reuse this, re-grinding is required, which is not preferable from the viewpoint of energy saving. The heat treatment must be carried out until the asbestos diffraction peak disappears by X-ray diffraction and the Ca-Mg silicate diffraction peak is observed. That is, if the processing temperature is high, the processing time is short, and if the processing temperature is low, the processing time must be long. For example, when the heat treatment temperature is 900 ℃ or 1000 ℃, and the heat treatment time is 1 hour, the X-ray diffraction peak of asbestos disappears.
The diffraction peak of a-Mg silicate appears, but when the heat treatment temperature is 600 ° C and the heat treatment time is 1 hour, the asbestos diffraction peak is not observed, but the diffraction peak of Ca-Mg silicate Since no peak is observed, it is necessary to continue the heat treatment. Before the heat treatment, it is preferable that the mixture be finely pulverized with a ball mill, a vibration mill, a jet mill, or the like so as to be easily reactive.

According to such a treatment method of the present invention, stones
Cotton is a water-unstable forsterite or enstata
Ito (MgSiO₃) Such as MgO-SiO₂Compounds, MgO, Ca₂SiO
_FourAnd stable amorphous Ca-Mg silicate
Converted to non-asbestos material. Note that stable Ca-Mg silicic acid
Salt is CaO-MgO-SiO.₂Compounds, CaO-MgO-Al₂O₃-S
iO₂Compounds such as diopside (CaMg
Si₂O₆), Wollastonite (CaSiO₃), Gehrenite (Ca₂A
l₂SiO₇) ― Akermanite (Ca₂MgSi₂O₇) Solid solution, Meru
Night (Ca₃MgSi₂O₈) Is mentioned. Of the above,
Which compound is converted depends on the Mg / Si mol of the substance to be treated.
Ratio and Ca / Si molar ratio. The molar ratio of Ca / Si
Free MgO and Ca in the treated product with a ratio of 1.3 or higher.₂S
iO _FourThere may be substances that easily react with water. So
When is Al₂O₃Mass% ≥ ((Ca / Si) x 0.357-0.464) x
Add a substance containing Al to 100 to treat,
Renite-Okermanite solid solution can be stabilized
Is.

When asbestos contains amosite containing a Fe ₂ O ₃ component, the above-mentioned Ca is contained in the treated product.
Besides diopside the -Mg silicate - F Denver Jai Doo (CaFeSi ₂ O ₆₎ solid solution and akermanite -Fe akermanite (Ca ₂ FeSi ₂ O ₇₎ solid solution is produced. These are also stabilized non-asbestos materials.

[0014]

The method of the present invention is effective for chrysotile asbestos and asbestos of amphibole type asbestos such as amosite and crocidolite, but is particularly effective for chrysotile. These asbestos are hydrous silicate minerals that have a fibrous shape, and their crystal structure is destroyed by heat treatment to change to other substances. For example, chrysotile, which accounts for the majority of asbestos in asbestos waste, is a hydrous Mg silicate, which starts dehydration decomposition at 400-600 ° C when it is heated, and at higher temperatures, it undergoes an amorphous phase to form forsterite and enstatite. It is well known that it decomposes into MgO-SiO ₂ compounds. However, as described above, when the MgO-SiO ₂ compound such as forsterite is contained in the heat-treated asbestos waste, when it is reused, for example, as a filler for cement products, it is autoclaved to accelerate curing. When cured, it may become rechrysotile due to reaction with water. Therefore, as a result of intensive studies, the present inventors have found that a substance to be treated composed of asbestos and / or an asbestos-containing substance contains Si, Ca, and Al.
One or more substances selected from the substances containing is added and mixed so as to meet the above conditions, and the resulting mixture is heated to 400 ° C.
It was found that the object of the present invention can be achieved by heat treatment at ~ 1200 ° C. The product treated by the treatment method of the present invention is a product obtained by converting a substance to be treated composed of asbestos and / or an asbestos-containing substance into a non-asbestos substance.
It does not contain O-SiO ₂ based compounds, MgO and Ca ₂ SiO _4, and can be used as a filler for building materials, specifically fiber reinforced cement boards.

[0015]

The present invention will be further described below with reference to Examples and Comparative Examples. (Example 1) An asbestos-cement board containing about 20% by mass of chrysotile was roughly crushed in an iron mortar to remove amorphous precipitated silica.
Dry mixing was performed so that the Mg / Si molar ratio was 0.23 and the Ca / Si molar ratio was 0.51. At this time, the content of Al ₂ O ₃ was 7.7% by mass. The mixture is further mixed with a planetary ball mill for 30
After mixing for 1 minute and pulverizing, the mixture was heat-treated at 1000 ° C. for 1 hour. When the constituent phase of the treated product was identified by X-ray diffraction, no chrysotile diffraction peak was observed and it was non-asbestos converted. The main constituent phases are diopside and wollastonite, which have no reactivity with water, and these can be reused as aggregates of fiber-reinforced cement boards, for example.

(Example 2) The same asbestos cement board as in Example 1 was coarsely crushed in an iron mortar and the amorphous precipitated silica was replaced with Mg.
Dry mixing was performed so that the / Si molar ratio was 0.48 and the Ca / Si molar ratio was 1.09. The mixture is further mixed with a planetary rotary ball mill.
After mixing and pulverizing for 30 minutes, heat treatment was performed at 1000 ° C. for 1 hour. When the constituent phase of the treated product was identified by X-ray diffraction, no chrysotile diffraction peak was observed and it was non-asbestos converted. The main constituent phase is aquermanite, which does not react with water, and these can be reused, for example, as an aggregate of fiber-reinforced cement board.

(Example 3) A commercially available asbestos cement plate of which asbestos content is unknown is roughly crushed with a jaw crusher, coarsely crushed with a hammer mill and a Nara type free crusher, and amorphous precipitated silica is Mg / Dry mixing was performed so that the Si molar ratio was 0.1 and the Ca / Si molar ratio was 1.06. At this time, the content of Al ₂ O ₃ was 6.7% by mass. The mixture was further mixed with a vibration mill for 30 minutes and pulverized, and then heat-treated at 900 ° C. for 1 hour. When the constituent phase of the treated product was identified by X-ray diffraction, no chrysotile diffraction peak was observed and it was non-asbestos converted. The main constituent phases were akermanite and wollastonite, which did not react with water. Next, for the above treated powder,
Add 5% by weight pulp, add water so that the water / powder weight ratio is 8, mix and stir, then radiate 80 mm x height 5 mm
It was molded with the press pressure of 12.1 MPa to the dimension of. The molded green sheet was aged in a humidity box (80 ° C) with a relative humidity of 100% for 20 hours, and then dried at 60 ° C for 24 hours. The obtained test piece was cut into a size of 40 × 130 × 5 mm and its physical properties were determined. The bulk density was 1.10 g / cm ³ and the bending strength was 0.9 N / mm ² . As described above, since the product of the present invention did not show strength development after curing, it was confirmed that the product has no hydraulic property and is a stable compound. The test piece prepared by the same method using ordinary Portland cement instead of the above treated powder has a bulk density of 1.77 g / cm ³ and a bending strength of 24.6 N / m.
It was m ² . Also, the treated powder was mixed at a ratio of 15% by mass and ordinary Portland cement at a ratio of 85% by mass, and a test body prepared by the same method had a bulk density of 1.61 g / cm ³ and a bending strength of 20.8 N / It was mm ² . In addition, the bulk density is 1.77 g / cm ³
Bending strength converted to density (conversion formula: Bending strength converted to density = 20.8 N / mm ² × (1.77 g / cm ³ ) ² /(1.61 g / cm ³ ) ² )
Was 25.1 N / mm ² , which was almost the same as when only ordinary Portland cement was used. This indicates that the bulk density of the treated powder is low and the bulk density of the test body can be reduced. Therefore, the product obtained by the treatment method of the present invention can be used as a filler for reducing the bulk density of a fiber-reinforced cement board.

(Example 4) A coarse asbestos-cement board crushed product similar to that in Example 3 and an amorphous precipitable silica were dry-mixed, and the composition of the whole system was Mg / Si molar ratio = 0.28, Ca / Si molar ratio. = 1.77
And However, at this time, since the Al ₂ O ₃ content was 3.9% by mass, aluminum hydroxide was further dry mixed to obtain Al 2.
_{The 2} O ₃ content was set to 27.8% by mass. The mixture was further mixed in a vibrating mill for 30 minutes and pulverized, and then 1
Heat treated for hours. When the constituent phase of the treated product was identified by X-ray diffraction, no chrysotile diffraction peak was observed and it was non-asbestos converted. The main constituent phase was gehlenite, which did not react with water.

(Example 5) An asbestos spraying product containing amosite and amorphous precipitable silica were dry-mixed, and the composition of the whole system was Mg / Si molar ratio = 0.13 and Ca / Si molar ratio = 0.63. At this time, the content of Al ₂ O ₃ was 2.5% by mass. The mixture was further mixed with a vibration mill for 30 minutes and pulverized, and then heat-treated at 1000 ° C. for 1 hour. When the constituent phase of the treated product was identified by X-ray diffraction, no diffraction peak of amosite was observed and it was non-asbestos. The main constituent phases were wollastonite, which did not react with water, and diopside-hedenbergite solid solution.

(Comparative Example 1) Composition analysis of asbestos-containing corrugated sheet waste revealed that Mg / Si molar ratio = 0.34 and Ca / Si molar ratio = 1.8.
It was 9. At this time, the content of Al ₂ O ₃ was 5.2% by mass. The mixture was further mixed with a vibration mill for 30 minutes and pulverized, and then heat-treated at 1000 ° C. for 1 hour. When the constituent phase of the treated product was identified by X-ray diffraction, no chrysotile diffraction peak was observed and it was non-asbestos converted. In addition to melwinite, MgO and β-Ca ₂ SiO ₄ that react with water were formed as the main constituent phase. These compounds recrystallize as chrysotile by autoclave curing.

Comparative Example 2 Amorphous precipitable silica was dry-mixed with an asbestos sprayed product containing chrysotile, and the composition of the entire system was set to a Mg / Si molar ratio = 0.65 and a Ca / Si molar ratio = 0.58. At this time, the content of Al ₂ O ₃ was 3.5% by mass. The mixture was further mixed with a vibration mill for 30 minutes and pulverized, and then heat-treated at 1000 ° C. for 1 hour. When the constituent phase of the treated product was identified by X-ray diffraction, no chrysotile diffraction peak was observed and it was non-asbestos converted. However, in addition to akermanite and diopside, forsterite that reacts with water was generated as the main constituent phase. When this product was used as an additive for a fiber-reinforced calcium silicate board and cured by autoclave at 200 ° C for 24 hours, the product was identified by X-ray diffraction, and formation of chrysotile was confirmed.

(Comparative Example 3) A coarse asbestos-cement board crushed product similar to that of Example 3 and amorphous precipitable silica were dry-mixed, and the composition of the entire system was Mg / Si molar ratio = 0.34, Ca / Si molar ratio. = 2.12
And Also, dry mix aluminum hydroxide to obtain Al ₂ O
₃ Content was 27.2 mass%. The mixture was further mixed with a vibration mill for 30 minutes and pulverized, and then heat-treated at 900 ° C. for 1 hour. When the constituent phase of the treated product was identified by X-ray diffraction, no chrysotile diffraction peak was observed and it was non-asbestos converted. As main constituent phases, MgO and β-Ca ₂ SiO ₄ , which react with water, were formed in addition to gehlenite. These compounds recrystallize as chrysotile by autoclave curing.

[0023]

EFFECTS OF THE INVENTION According to the present invention, a substance that easily reacts with water, such as forsterite that may be recrystallized into chrysotile, is produced without discarding the substance to be treated and consuming a large amount of energy. A process for treating asbestos is provided that does not require and that the treated product is stable and reusable.

Continued front page    (72) Inventor Noriyuki Yamazaki             2-12-10 Shiba Daimon, Minato-ku, Tokyo Stock market             Company A & A Material (72) Inventor Kohei Ota             2-12-10 Shiba Daimon, Minato-ku, Tokyo Stock market             Company A & A Material (72) Inventor Mitsuharu Osawa             2-12-10 Shiba Daimon, Minato-ku, Tokyo Stock market             Company A & A Material F-term (reference) 4D004 AA17 BA02 CA30 CA45 CC11                       CC12 CC13 DA03 DA06 DA10

Claims (3)

[Claims] 1. A treatment method for converting asbestos in a substance to be treated into a non-asbestos substance by subjecting a substance to be treated composed of asbestos and / or an asbestos-containing material to heat treatment, wherein the substance to be treated comprises: At least one substance selected from the group consisting of a substance containing Si, a substance containing Ca and a substance containing Al is added and mixed so as to satisfy the following conditions, and the obtained mixture is heated at 400 ° C to 1200 ° C. A method for treating asbestos, which comprises heat treatment. Addition condition: The molar ratio of Mg and Si in the substance to be treated is Mg
/Si≦0.5 and the molar ratio of Ca and Si is 0.5 ≦ Ca / Si ≦ 2.0
Adjust to. However, at this time, the molar ratio is Ca / Si ≧ 1.
If 3, Al ₂ O ₃ mass% ≧ ((Ca / Si) × 0.357-0.464)
The substance containing Al is added so that the amount becomes × 100. 2. A product treated by the treatment method according to claim 1, wherein the product does not contain a MgO—SiO ₂ compound, MgO and Ca ₂ SiO _4. Product. 3. Filling material for building materials, which comprises the product according to claim 2.