JP2009291730A - Method for detoxifying solid waste containing asbestos - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detoxifying method that keeps an energy cost low and supplies energy with high safety in a heat-treatment process in a method for detoxifying a waste containing asbestos. <P>SOLUTION: Provided is a method wherein the solid waste containing asbestos is mixed with the alkali silicate in a solid state, followed by heating. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for detoxifying solid waste containing asbestos.

  Asbestos is a naturally occurring fibrous crystal mineral that has excellent acid resistance, alkali resistance, heat resistance and mechanical strength, and has been used for many years as a building material, electrical product, automobile and household product. Have been used in a wide range of fields.

  However, it has become harmful to the human body, causing lung cancer and malignant mesothelioma, and in recent years its use has been completely banned. Accordingly, a large amount of waste containing asbestos (hereinafter also referred to as “asbestos-containing waste”) is generated, and how to treat such waste is a big problem.

  The handling of this asbestos-containing waste is strictly controlled by the “Act on Waste Disposal and Cleaning”, and the disposal methods for asbestos-containing waste are roughly divided into managed final disposal and melting treatment. . In the past, asbestos-containing waste was mostly subjected to controlled final disposal, but it has become difficult to secure a new final disposal site. Yes.

  However, in this melting process, waste containing asbestos is processed and melted at a high temperature of 1,500 ° C or higher, and the processing temperature is very high. For example, it is necessary to use a special heat-resistant material in the processing furnace. Therefore, the construction of such melt processing equipment requires a large amount of money. And even if such a facility for high-temperature processing is constructed, there is also a problem that the processing facility is remarkably deteriorated in a short period of time. Furthermore, in order to maintain such a high temperature, enormous energy is required, so the fuel cost is not negligible. The amount of carbon dioxide generated directly or indirectly during the heat treatment is also enormous. is there. Therefore, a disposal method that can change asbestos-containing waste to a safer form at a lower temperature is required.

Various methods have been proposed as countermeasures. For example, Patent Document 1 describes a method of adding aluminum oxide to asbestos-containing waste and baking it. In this method, baking is performed at a temperature of about 1280 ° C. Further, Patent Document 2 describes a method of reacting and sintering a mixture of asbestos-containing waste and municipal waste incineration ash. In this case, incineration ash is waste generated by incineration processing of municipal waste. The main component is Ca, Si, Al, Mg, Na, K, P inorganic components. Further, Patent Document 3 describes a method in which an aqueous solution of sodium silicate or potassium silicate is added to asbestos-containing waste to form a dough, which is dried once, and then fired and sintered.
Japanese Patent Laid-Open No. 5-138147 JP-A-9-206726 JP-A-9-110514

  An object of the present invention is to provide a detoxification method for detoxifying asbestos-containing waste, which suppresses energy costs in the heat treatment process and provides high safety.

  Yet another object of the present invention is a method for detoxifying waste containing asbestos, and provides a detoxification method with less attack on furnace materials in heat treatment equipment while maintaining low energy cost and high safety. It is to be.

  Yet another object of the present invention is to provide a method for detoxifying waste containing asbestos, which allows for a higher degree of detoxification while maintaining low energy costs and high safety. .

  As a result of intensive studies to achieve the above-mentioned object, the present inventors, when treating asbestos-containing waste, by mixing and heating alkali silicate as a treating agent in a solid state with asbestos-containing waste, It has been found that the above problems can be achieved.

  Therefore, this invention relates to the processing method of the waste containing asbestos including mixing the waste containing asbestos with a solid alkali silicate, and heating.

Furthermore, the present invention is a method for treating asbestos-containing waste by mixing and heating waste containing asbestos with solid alkali silicate, wherein the SiO ₂ / M ₂ O molar ratio (M Represents an alkali metal).

  The present invention also relates to an asbestos-containing waste detoxifying treatment agent comprising a solid alkali silicate.

  The present invention further relates to a silicate fertilizer produced by mixing and heating a waste material containing asbestos and a solid alkali silicate.

  The present invention also relates to a construction material produced by mixing and heating waste containing asbestos and solid alkali silicate.

  The “waste containing asbestos” treated in the present invention is not particularly limited as long as it is a waste containing asbestos, and the above-mentioned “Act on Waste Disposal and Cleaning” and its government are not limited. “Waste asbestos, etc.”, “waste containing asbestos” and “industrial waste containing asbestos” defined in the ministerial ordinance etc. are also included in “waste containing asbestos” of the present invention. Generally, the above-mentioned “waste containing asbestos” is applied to the method of the present invention in a solid form, that is, “solid waste containing asbestos (in this specification,“ asbestos-containing solids ”). Also called “waste”).

  The asbestos-containing solid waste may contain any component that is normally classified as asbestos, for example, any component such as chrysotile, amosite, or clothidite.

  Here, the components other than asbestos in this asbestos-containing solid waste are not particularly limited. For example, if it is building waste, concrete, mortar, various bricks, asphalt, wood, resin, etc. are mixed. However, even if such a component is present, it can be subjected to the detoxification treatment of the present invention without any problem.

  The asbestos-containing solid waste treated in the present invention is not particularly limited. For example, asbestos-made asbestos cloth (cloth), asbestos yarn (strings), asbestos ribbon, asbestos tape, asbestos yarn, asbestos board, asbestos Clothing, joint sheets, sealing materials, clay binders in glass melting furnaces of asbestos powder, porous materials in molten acetylene gas cylinders, asbestos cement cylinders, extruded cement boards, decorative slate for residential roofs, fiber reinforced cement boards, ceramic siding Waste including clutch facings, clutch linings, brake pads, brake linings, adhesives and the like.

  In addition, the asbestos-containing solid waste in the present invention can be collected by any method from the site where the asbestos-containing material was installed, for example, by spraying to prevent asbestos scattering The material may be collected and dismantled by wetting water or the like, and there is no particular limitation on the method for collecting and disassembling asbestos-containing solid waste.

  In carrying out the present invention, it is preferable to pulverize the asbestos-containing solid waste in advance in order to facilitate mixing with the alkali silicate. The smaller the size after pulverization, the higher the efficiency of the treatment with the alkali silicate. However, the pulverization cost and the like increase accordingly, and the generation of dust tends to occur. In general, it is generally sufficient to grind to a size that can pass through a sieve with an opening of 5 cm, but in order to achieve a more uniform mixing state, the size is enough to pass through a sieve with an opening of 1 cm. It is preferable to grind to a size that passes through a sieve having a mesh size of 5.6 mm (3.5 mesh). Usually, it is not necessary to grind until the entire amount passes through a sieve having an opening of 0.1 mm (149 mesh), and there is almost no need to grind the sieve having an opening of 0.5 mm (50 mesh) until the entire amount passes.

  The asbestos-containing solid waste can be pulverized using any known pulverizer such as a mill or a crusher. Further, at the time of pulverization, in order to suppress the generation of dust, it can be moistened with water or the like.

  In the present invention, a solid alkali silicate is used as a treatment agent for detoxifying solid waste containing asbestos. Here, “solid” means that solid alkali silicate that is solid at room temperature and normal pressure is used in the form of a solid without changing it into a solution or other phase state, that is, asbestos-containing solid waste is treated. means.

  As the alkali silicate in the present invention, it is possible to use either a crystalline alkali silicate or an amorphous alkali silicate, but the crystalline alkali silicate is an anhydride or has a water content of about 60% by weight. The amorphous alkali silicate is present in solid form at room temperature and normal pressure when it is anhydrous or has a water content of about 25% by weight or less. Amorphous silicate alkalis and crystalline alkali silicates can be used in appropriate mixture.

  In the present invention, the detoxification of asbestos-containing waste is promoted using a solid alkali silicate, and since the alkali silicate has a relatively low melting point, the covering effect by the alkali silicate can be obtained even at a lower temperature. Compared with the detoxification treatment simply by heating the asbestos-containing waste or the detoxification treatment using aluminum oxide, the heating temperature can be considerably reduced, and thereby the energy cost can be greatly reduced. Furthermore, it is necessary to volatilize and remove water by mixing asbestos-containing solid waste with such a solid alkali silicate, heating and treating it, as compared with the case where the alkali silicate is used as an aqueous solution containing it. Therefore, the energy cost can be kept low, and the processing operation can be performed safely because there is no fear of a volume increase due to foaming during the heat treatment. Further, by using a solid alkali silicate, it is possible to expect an improvement in storage stability related to the alkali silicate, and a reduction in storage cost and transportation cost.

  Various alkali silicates have been conventionally known. In the present invention, any solid alkali silicate can be used without particular limitation, and examples thereof include the following.

A phyllosilicate represented by the formula NaMSi _x O _{2x + 1} · yH ₂ O:
Where M is sodium or hydrogen, x is a number from 1.9 to 4, y is a number from 0 to 20, and preferred values for x are 2, 3 or 4.

Such phyllosilicates are disclosed in EP-B 0 164 514. Preferred phyllosilicates are those wherein M is sodium and x is a value of 2 or 3. In particular, beta - and delta - Two both sodium silicate _{Na 2 Si 2 O 5 · H} 2 O are preferred, wherein, beta - sodium disilicate, for example, a method described in International Patent Application Publication No. 91/08171 Can be obtained by: Beta-sodium disilicate is commercially available under the name ^TM SKS-7, and delta-sodium disilicate is commercially available under the name ^TM SKS-6 (product of Clariant GmbH).

Fine crystalline layered sodium disilicate represented by the formula NaMSi _x O _{2x + 1} · yH ₂ O:
Where M is sodium or hydrogen, x is a number from 1.9 to 4, and y is a number from 0 to 20, and alpha-disodium disodium is added in a proportion of 0 to 40% by weight, Contains disodium disilicate 0-40% by weight, delta-disodium disodium 40-40% by weight and amorphous fraction 0-40% by weight, less than 60% Has net residue and no sodium metasilicate. Silicates of this kind are described in German Offenlegungsschrift DE-A 198 30 591.

-Crystalline sodium phyllosilicate represented by the formula xNa ₂ O * ySiO ₂ * zP ₂ O ₅ :
Where the x: y ratio is 0.35-0.6, the x: z ratio is 1.75-1200, and the y: z ratio is 4-2800. This type of sodium silicate is described in German Offenlegungsschrift DE-A 196 01 063. These phosphorus-containing phyllosilicates having a high crystallinity and a very high calcium binding ability can also be preferably used in the present invention.

A crystalline alkali metal phyllosilicate represented by the formula aM ^I ₂ O, bEO ₂ , cX ₂ O ₅ , dZO ₃ , SiO ₂ , eH ₂ O:
Where M ^I is an alkali metal, E is an element of the 4th main group of the periodic table, X is an element of the 5th main group and Z is an element of the 6th main group, and Fits to:
0.25 ≦ a ≦ 6.25
2.5 ・ 10 ^-4 ≦ b ≦ 5.63
0 ≦ c ≦ 2.81
0 ≦ d ≦ 5.63
0 ≦ e ≦ 15.3.

Here, a preferable crystalline alkali metal phyllosilicate contains a certain amount of phosphorus, sulfur and / or carbon.
Highly alkaline crystalline sodium silicate represented by the formula Na ₂ O * xSiO ₂ * yH ₂ O:
Where x is a number from 1.2 to 2.1 and y is a number from 0 to 20. This highly alkaline crystalline sodium silicate is composed of 70-98% by weight layered disodium disilicate and 2-30% by weight
Na ₂ O * vSiO ₂ * wH ₂ O
[Wherein v is a number from 0.05 to 2 and w is a number from 0 to 20], and can be composed of non-phyllosilicate sodium silicate.

A sparingly soluble alkali metal silicate comprising an alkali metal phyllosilicate in a finely distributed form in the environment of a non-phyllosilicate alkali metal silicate represented by the formula xM ^I ₂ O · ySiO ₂ :
Where M ^l is an alkali metal and y / x is (1.9-500): 1. This alkali metal silicate has the following formula as a whole:
aM ^I ₂ O ・ bM ^II O ・ cX ₂ O ₃・ dZ ₂ O ₅・ eSiO ₂・ fH ₂ O
[Wherein M ^I is an alkali metal, M ^II is an alkaline earth metal, X is an element of the third main group of the Periodic Table of Elements and Z is an element of the fifth main group, and Fits to:
0.5 ≦ a ≦ 1;
0 ≦ b ≦ 0.5;
0 ≦ c / e ≦ 0.05;
0 ≦ d / e ≦ 0.25;
1.9 ≦ e ≦ 4;
0 ≦ f ≦ 20]
It corresponds to.

  However, in the present invention, an alkali silicate represented by the following formula is used among others.

aM ₂ O ・ bSiO ₂・ nH ₂ O
Where M is an alkali metal, preferably sodium and / or potassium, a is a real number from 0.5 to 2, b is a real number from 0.5 to 3, and a and b are 0.5 ≦ b / a ≦ 5, Preferably 1 ≦ b / a ≦ 3.5, particularly preferably 1.5 ≦ b / a ≦ 2.5, and n maintains a solid at room temperature and normal pressure in the alkali silicate determined by a, b and M above It is a real number that is less than or equal to the upper limit. In general, n is a real number from 0 to 9. Here, b / a in the above formula represents the molar ratio of SiO ₂ to M ₂ O, that is, the SiO ₂ / M ₂ O molar ratio (M represents an alkali metal).

  In general, sodium silicate and potassium silicate, which are common alkali silicates, often contain impurities derived from raw materials and production equipment, but in the present invention, commercially available sodium silicate (for example, Japanese silicate) Any sodium silicate or potassium silicate containing the same level of impurities as Koso Pure Chemical Industries, Ltd. (sodium metasilicate) can be used without any problem. Specifically, regardless of whether sodium silicate or potassium silicate is used, it is preferable that components contained in addition to sodium silicate or potassium silicate are 3% by weight or less on a dry basis.

  Examples of such alkali silicates include sodium orthosilicate n-hydrate (molar ratio = 0.5) manufactured by Wako Pure Chemical Industries, Ltd., anhydrous sodium metasilicate (molar ratio = 1) manufactured by Kanto Chemical Co., Inc., Tokuyamasil Co., Ltd. Technically, crystalline layered sodium silicate (trade name: Ecolayer) (molar ratio = 2), medium molar cullet (molar ratio = 3) manufactured by Tokuyama Co., Ltd., and the like can be obtained commercially.

Furthermore, the present inventors further investigated the relationship between the erosion of the furnace material generated during the heat treatment and the asbestos detoxifying action of the alkali silicate, and the SiO ₂ / M ₂ O molar ratio of the alkali silicate was If it is less than 1, the effect of alkali erosion on the furnace material starts to appear, and on the other hand, if the SiO ₂ / M ₂ O molar ratio exceeds 3.5, the alkali content decreases due to the decrease in alkali content, and asbestos is rendered harmless. I found out that it tends to be insufficient. Therefore, the SiO ₂ / M ₂ O molar ratio of the alkali silicate is preferably 1 to 3.5.

Furthermore, at a SiO ₂ / M ₂ O molar ratio of 1 to 3, preferably 1.5 to 2.5, especially 2, the melting point of the alkali silicate is the lowest, and the coating with the molten alkali silicate proceeds from the initial stage of the heating process. . Therefore, the SiO ₂ / M ₂ O ratio is most preferably 1.5 to 2.5, especially 2, considering the ability to treat asbestos-containing waste, the coating effect of alkali silicate, and the influence on the heating furnace.

  As a solid alkali silicate in this invention, a powdery thing, a granular form, or a pellet form can be used, for example. From the viewpoint of easy mixing, it is preferable to use a powdery or granular material.

  Here, “powder” means particles having an average particle diameter in the range of 1 μm to 1 mm, and “granular” means particles having an average particle diameter of more than 1 mm and less than 50 mm. However, in any case, the shape is not particularly limited as long as it has a diameter within the above range.

  When powdered or granular alkali silicate is used, the average particle size is preferably 10 μm to 20 mm. For powdered or granular alkali silicates, larger particles may be easier to handle, but in order to mix more uniformly, those with a smaller average particle size are advantageous, and therefore an average of 10 μm to 5 mm. Those having a particle size, for example, those having an average particle size of 10 μm to 1 mm are more preferred.

  However, when a powdery alkali silicate having an average particle size of 10 μm to 1 mm is used, the mixing unevenness confirmed after the heat treatment is reduced, and the average particle size is 10 μm to 200 μm, particularly 10 μm to 150 μm. When powdered alkali silicate is used, the asbestos-containing waste and alkali silicate react very uniformly, so no mixing unevenness is observed after the heat treatment, and the structure loss degree of asbestos also increases. There was found. Accordingly, it is particularly preferable to use a powdery alkali silicate having an average particle diameter of 10 μm to 1 mm, preferably 10 μm to 200 μm, particularly preferably 10 μm to 150 μm.

  The average particle size of the powdery or granular alkali silicate can be measured by a particle size measuring method using an analytical sieve. The particle size measurement using an analytical sieve can be performed according to the sieving test method for chemical products of JIS K0069. Specifically, several sieves are stacked so that the sieve with a large mesh is in the upper stage, and the powder or granules are put into the uppermost stage sieve and vibrated manually or by a machine. After that, the weight of powder or granules remaining on each sieve is measured to calculate the weight distribution, and the particle diameter when the integrated value of weight% is 50% is expressed as the average particle diameter (μm or mm). .

  Further, in the present invention, a hydrate or anhydride as the alkali silicate (in this specification, an alkali silicate having a moisture content of 1 wt% or less is referred to as “anhydride” and a silicate having a moisture content greater than 1 wt%. Any of the alkalis can be used. It is also confirmed in the present invention that the higher the water content of the alkali silicate used, the more remarkable the melting of asbestos fibers and the accompanying fusion of asbestos fibers, and the further reduction of the harmfulness of waste after heat treatment. It was done.

  As described above, the alkali silicate cannot maintain a solid state if its water content becomes too high, but in the case of a crystalline alkali silicate, usually up to about 60% by weight depending on its chemical composition. In the case of an amorphous alkali silicate, it changes from a solid to a viscous liquid as the water content increases, but usually maintains a solid form up to about 25% by weight.

  However, even when the solid state is maintained at a high water content such as crystalline alkali silicate, if the water content is too high, energy loss may occur when processing asbestos-containing waste. In addition, since the alkali silicate particles are easily consolidated, there is a concern that the asbestos-containing waste and the alkali silicate may be easily and uniformly mixed.

  Therefore, it is also preferable to use an alkali silicate having a moisture content of 10 to 25% by weight, for example, a moisture content of 15 to 25% by weight, from the viewpoints of energy cost and easy and uniform mixing.

  Moreover, when using a hydrated substance as an alkali silicate, it is preferable to use a crystalline alkali silicate at the point that it is hard to solidify particles even if it is the same moisture content, and is excellent in handleability. Of course, an amorphous alkali silicate and a crystalline alkali silicate may be appropriately mixed and used.

  Here, “moisture content” means the ratio of the moisture desorbed by igniting a solid alkali silicate (720 ° C.) to the weight of the silicate alkali (including moisture and contaminants) before ignition. Say. The amount of desorbed water can be determined by measurement by the Karl Fischer measurement method using the water vaporization method defined in the method for measuring moisture of JIS K0068 chemical products. In addition, since ordinary alkali silicates often contain only moisture as a component that is desorbed under the above-mentioned ignition conditions, in such solid alkali silicates, even if the moisture content is not determined by the Karl Fischer method, The water content can be calculated substantially and simply by measuring the weight change before and after.

  The measurement method will be described more specifically. When the moisture content is measured by the Karl Fischer measurement method, an apparatus specified in JIS K0068 is used. A sample (generally about 1 g) is precisely weighed, and the sample is introduced into a heating furnace (720 ° C.) in which an inert gas containing no moisture (eg, nitrogen, argon, etc.) is flowed at 100 ml / min. Titration is started after 3 minutes, and the water content is calculated from the titration result.

  When adopting the simplified method based on weight change, a sample (generally about 10 g) is precisely weighed in an empty-baked crucible and heated in a heating furnace at 720 degrees for 10 minutes. The weight of the sample after heating is measured to determine the amount of weight loss after heating, and the water content may be determined assuming that all of this weight loss is due to moisture desorption.

  Examples of the hydrated alkali silicate include powdered sodium silicate JIS-1 (moisture content = 20% by weight, amorphous) and the above-mentioned sodium metasilicate n-hydrate (manufactured by Wako Pure Chemical Industries, Ltd.). An integer of 9, water content = 13 to 60% by weight, crystalline) can be obtained commercially.

  In the present invention, the asbestos-containing solid waste and the alkali silicate can be mixed by any conventionally known method related to the mixing of the solids. For example, when the alkali silicate is powdered or granular, mixing the asbestos-containing solid waste and the alkali silicate powder or granule by rotating the mixing container, rotating the rotating blades of paddles, ribbons, etc. The whole powder or granule can be mixed. Specifically, rotary cylinder type mixer, V type mixer, rocking rotary type mixer, ribbon type mixer, paddle type mixer, rotary saddle type mixer, conical screw type mixer, biaxial planetary stirring type Mixing can be performed using a mixer, a rotating container mixer with a roller, a rotating container mixer with stirring, a rotating disk mixer, or the like.

  The mixing ratio in mixing the asbestos-containing solid waste and the alkali silicate is appropriately adjusted. Here, when the asbestos-containing solid waste contains components other than asbestos, the asbestos-containing solid waste can exhibit any of acidic, neutral or basic depending on components other than the asbestos. When the asbestos-containing solid waste is neutral or basic, the mixing ratio is 0.1 to 10 in terms of weight ratio (asbestos-containing solid waste: alkali silicate = 1) from the viewpoint of detoxification efficiency. The mixing ratio is preferably 0.1 to 10), and a mixing ratio of 0.2 to 5 is preferable in consideration of an economical viewpoint. In addition, when the asbestos-containing solid waste is acidic, the alkali silicate reacts with the acid to produce silica, which does not contribute to the melting of the asbestos, so that a larger amount of alkali silicate is required. . Therefore, when the asbestos-containing solid waste is acidic, a mixing ratio of 0.5 to 200 by weight ratio (asbestos-containing solid waste: alkali silicate = 1: 0.5 to 200) depending on the acidity and acid amount. The mixing ratio is preferably 1 to 20, considering an economical viewpoint.

  In the method of the present invention, a mixture of asbestos-containing solid waste and solid alkali silicate is heated, and at this time, the heating temperature is preferably at least 750 ° C. or higher. This is because if the heating temperature is lower than 750 ° C., the progress of the reaction may be reduced. On the other hand, the upper limit of the heating temperature depends only on the upper limit of the allowable temperature of the heating furnace to be used, and is not particularly limited. Since there is concern about an increase in cost and the like, it is generally sufficient to perform at a temperature of, for example, 750 ° C. to 1500 ° C.

  However, in the present invention, detoxification of asbestos-containing waste is promoted by alkali silicate, and since alkali silicate has a relatively low melting point, a coating effect by alkali silicate can be obtained even at a lower temperature. A sufficient detoxification effect can also be achieved by heat treatment at a temperature of ° C., for example, 750 ° C. to 1100 ° C.

  And considering the reaction efficiency, the covering effect by the alkali silicate and the influence on the heating furnace, the heat treatment is preferably performed at a temperature of 800 ° C. to 1000 ° C., preferably at a temperature of 850 ° C. to 950 ° C. Particularly preferred. By performing the heat treatment at such a low temperature, it is possible to achieve sufficient detoxification of the asbestos-containing waste while further reducing the equipment cost and energy cost.

  The heating time depends on the heating temperature, the type of the heating furnace used, etc., but in general, sufficient detoxification is achieved by performing a heat treatment for 1 minute to 100 hours. In many cases, the heat treatment is for about 10 minutes to 10 hours.

  The mixture of the asbestos-containing solid waste and the alkali silicate is preferably heated in a heating furnace maintained at a high temperature. Either a direct type or an indirect type can be used as the heating method of the heating furnace, and either fuel or electricity can be used as the heat source. Examples of these heating furnaces include hand furnaces, stalker furnaces, fluidized bed furnaces, kiln furnaces, muffle furnaces, solid melting furnaces, and the like.

  In addition, it is naturally possible to heat while mixing by using a device such as a rotary kiln.

  Whether or not the asbestos-containing solid waste has been rendered harmless after the treatment according to the present invention can be confirmed by observing the mixture after the heat treatment with a scanning electron microscope (hereinafter also referred to as “SEM”).

  In SEM observation, when the asbestos-specific needle-like fiber structure is not confirmed, that is, when the asbestos component fiber structure is lost, it is determined that the asbestos-containing solid waste has been rendered harmless (for example, FIG. 1 -(c)). In addition, the loss of the fiber structure alone is sufficient for detoxification, but not only the loss of the fiber structure but also the asbestos components that have lost the fiber structure are fused to each other. Scattering is further suppressed, and the harmfulness is further reduced (for example, FIG. 5-A (b)).

  The waste detoxified by the method of the present invention can be subjected to post-treatment and disposal methods similar to general slag not containing heavy metals. Moreover, since the main component is a silicate, the application to a silicate fertilizer is also considered.

  By using the method of the present invention, the molten alkali silicate coats the waste containing asbestos, and at the same time, the alkali in the alkali silicate attacks the asbestos, so that the needle-like fiber structure of asbestos harmful to the human body is lost. The detoxification of the waste is achieved.

  In the method of the present invention, since a solid alkali silicate is used (that is, it is not necessary to use water), there is no energy loss for volatilization / removal of water, and further during heating. Rapid heating is possible because there is no foaming. Therefore, when the method of the present invention is used, the asbestos-containing waste can be detoxified safely and inexpensively.

  Although it depends on the composition of the asbestos-containing waste to be treated, the detoxified components are composed mainly of asbestos and sodium silicate, so they are highly safe and can be safely disposed of. Or, depending on circumstances, it can be effectively used again for construction materials and the like.

  In the following, a plurality of examples, comparative examples and reference examples of the present invention including Example 1 are shown, but the present invention is not limited in any way by these examples and is specified by the claims. Needless to say, it is something.

  In the following Examples and the like, a low vacuum scanning electron microscope (model: JSM-5600LV) manufactured by JEOL Datum was used as a scanning electron microscope. In each Example, sodium silicate described in Table 1 below was used as a solid alkali silicate.

Example 1
Asbestos yarn 0.5 g and sodium orthosilicate n-hydrate (SiO ₂ / M ₂ O molar ratio = 0.5) 0.5 g were put into a crucible with a capacity of 50 ml, and stirred for about 10 seconds in a kettle. Then, the crucible was covered and charged in an electric heating furnace (Electric furnace KBF-894N manufactured by Koyo Lindberg Co., Ltd.), and heated in the electric furnace at 900 ° C. for 1 hour. Thereafter, the mixture was allowed to cool to room temperature, and the contents were taken out and observed with a scanning electron microscope.

  As a result, asbestos lost the needle-like fiber structure (Fig. 1- (a)).

Example 2
The same operation as in Example 1 was performed, except that 0.5 g of anhydrous sodium metasilicate (SiO ₂ / M ₂ O molar ratio = 1) was used as the sodium silicate.

  When the crucible contents after the heat treatment were observed with a scanning electron microscope, asbestos had lost the needle-like fiber structure (FIG. 1- (b)).

Example 3
The same operation as in Example 1 was carried out except that 0.5 g of Ecolayer powder (SiO ₂ / M ₂ O molar ratio = 2) was used as sodium silicate.

  When the contents of the crucible after the heat treatment were observed with a scanning electron microscope, asbestos had lost the needle-like fiber structure (FIG. 1- (c)).

Example 4
The same operation as in Example 1 was carried out, except that 0.5 g of medium molar cullet (SiO ₂ / M ₂ O molar ratio = 3) was used as sodium silicate.

  When the crucible contents after the heat treatment were observed with a scanning electron microscope, asbestos had lost the needle-like fiber structure (FIG. 1- (d)).

Examples 5 and 6
Except for heating at 750 ° C. (Example 5) or 1200 ° C. (Example 6) instead of heating at 900 ° C., the same operation as in Example 1 was performed (in the case of heating at 1200 ° C., We used Motoyama Co., Ltd. oxidation atmosphere ultra-high temperature electric furnace KB-2030D.

  When the inside of the crucible after the heat treatment was visually observed when heated at 1200 ° C., the contents of the crucible were completely melted (FIG. 3- (a)). The results of observation with a scanning electron microscope when heated at 750 ° C. are as shown in Table 2 below.

Examples 7-9
The same operation as in Example 2 was performed except that heating was performed at 600 ° C. (Example 7), 750 ° C. (Example 8), or 1200 ° C. (Example 9) instead of heating at 900 ° C. (1200 When heating at ℃, we used Motoyama Co., Ltd. oxidizing atmosphere ultra-high temperature electric furnace KB-2030D).

  The observation results by each electron microscope (Examples 7 and 8) or visually (Example 9) are as shown in Table 2 below.

Examples 10-13
Similar to Example 3 except heating at 600 ° C. (Example 10), 750 ° C. (Example 11), 1000 ° C. (Example 12) or 1200 ° C. (Example 13) instead of heating at 900 ° C. The operation was performed (in the case of heating at 1000 ° C. and 1200 ° C., an ultrahigh temperature electric furnace KB-2030D manufactured by Motoyama Co., Ltd. was used as the electric heating furnace).

  The observation results by each electron microscope (Examples 10, 11 and 12) or visually (Example 13) are as shown in Table 2 below.

Example 14
The same operation as in Example 4 was performed except that heating was performed at 1200 ° C. (Example 14) instead of heating at 900 ° C. (In addition, as an electric heating furnace, an ultra-high temperature electric furnace KB-2030D manufactured by Motoyama Co., Ltd.) It was used).

  When the inside of the crucible after the heat treatment was visually observed, the crucible contents were almost melted, but a part of the unmelted portion was observed (FIG. 3- (d)).

Comparative Example 0
Untreated asbestos yarn was observed with a scanning electron microscope. Asbestos has a needle-like fiber structure (Figure 4-A).

Comparative Example 1
Asbestos yarn 0.5 g used in Example 1 was put in a crucible having a capacity of 50 ml, and the crucible was covered and charged in an electric heating furnace (electric furnace KBF-894N manufactured by Koyo Lindberg Co., Ltd.). At 900 ° C. for 1 hour. Then, it stood to cool to room temperature and observed the inside of a crucible visually. As a result, the asbestos yarn in the crucible was slightly shrunk and was in a stiff state. When the crucible contents after the heat treatment were taken out and observed with a scanning electron microscope, the needle-like fiber structure was not lost (FIG. 4-B (c)).

Comparative Example 2
The same operation as in Example 1 was performed except that 1.66 g of an aqueous solution containing 30% sodium silicate having a SiO ₂ / M ₂ O molar ratio of 2 was used as sodium silicate. When the crucible was charged in an electric furnace and heated, foaming occurred rapidly and the contents overflowed from the crucible, so the test was stopped.

Comparative Example 3
The same operation as in Example 1 was carried out except that 0.5 g of anhydrous silicic acid (SiO ₂ / M ₂ O molar ratio was equivalent to infinity) was used as sodium silicate. As in Comparative Example 1, the asbestos yarn in the crucible was slightly shrunk and was in a stiff state. When the asbestos ribbon after the heat treatment was observed with a scanning electron microscope, the needle-like fiber structure was not lost.

Comparative Examples 4-7
Similar to Comparative Example 1 except heating at 600 ° C (Comparative Example 4), 750 ° C (Comparative Example 5), 1000 ° C (Comparative Example 6) or 1200 ° C (Comparative Example 7) instead of heating at 900 ° C The operation was performed (in the case of heating at 1000 ° C. and 1200 ° C., an ultrahigh temperature electric furnace KB-2030D manufactured by Motoyama Co., Ltd. was used as the electric heating furnace).

  The observation results by each electron microscope (Comparative Examples 4, 5 and 6) or visually (Comparative Example 7) are as shown in Table 2 below.

  Table 2 below summarizes the state of asbestos after heat treatment when heat treatment was performed at various temperatures using various alkali silicates.

実施例15
珪酸ナトリウムとして0.5 gの粉末珪酸ナトリウムJIS-1号（水ガラスを乾燥させた粉末で20重量%の含水率を有する）を使用すること以外、実施例1と同様の操作を行った。

Example 15
The same operation as in Example 1 was carried out except that 0.5 g of powdered sodium silicate JIS-1 (powder obtained by drying water glass and having a water content of 20% by weight) was used as sodium silicate.

  When the crucible contents after the heat treatment were observed with a scanning electron microscope, the asbestos had lost the needle-like fiber structure, and as a result of the asbestos fibers melting during the heat treatment, the asbestos fibers had a fused structure. (Fig. 5-A (b)).

Example 16
The same operation as in Example 1 was performed except that 0.5 g of sodium metasilicate.9 hydrate (water content: 57% by weight) was used as sodium silicate.

Examples 17 and 18
Except for heating at 750 ° C. (Example 17) or 1200 ° C. (Example 18) instead of heating at 900 ° C., the same operation as in Example 15 was performed (in the case of heating at 1200 ° C., We used Motoyama Co., Ltd. oxidation atmosphere ultra-high temperature electric furnace KB-2030D.

  Table 3 below collectively shows the state of asbestos after heating (electron microscope or visual observation results) when heat treatment was performed at various temperatures using alkali silicates having different moisture contents. Examples 3, 11, and 13 have already been described in Table 2, but are also described in Table 3 for easy comparison between the moisture contents.

表3の結果からは、含水率が高くなる程、石綿繊維同士の融着が顕著になり、それに伴って石綿の構造喪失度が高くなる傾向が認められる。

From the results shown in Table 3, it can be seen that as the moisture content increases, the asbestos fibers are more likely to be fused with each other, and the degree of asbestos structure loss tends to increase accordingly.

  This is thought to be because the hydrous sodium silicate once melted into a glass before the water contained therein evaporated, thereby increasing the reactivity to asbestos.

Examples 19 and 20
The same operation as in Example 1 was carried out except that 0.5 g of Ecolayer granules (average particle size 700 μm) (Example 19) or Ecolayer coarse particles (average particle size 3.4 mm) (Example 20) were used as sodium silicate. It was.

  In Table 4 below, the states of asbestos after heat treatment (observation results by an electron microscope) when heat treatment is performed using alkali silicates having different average particle diameters are collectively described. Note that Example 3 has already been described in Table 2, but is also described in Table 4 in order to facilitate comparison between the average particle diameters.

表4の結果からは、平均粒子径が低い程、加熱処理後の石綿の構造喪失度が高くなる傾向が認められる。

From the results in Table 4, it can be seen that the lower the average particle diameter, the higher the degree of structural loss of asbestos after heat treatment.

  This is presumably because the lower the average particle size of the alkali silicate, the more uniformly the alkali silicate can be in contact with asbestos over a wide area.

Reference example 1
Put 5 g of refractory bricks (chamotte bricks) (diameter of about 2-10 mm) and 5 g of sodium orthosilicate n-hydrate (SiO ₂ / M ₂ O molar ratio = 0.5) in a 50 ml crucible Stir for about 10 seconds. Then, the crucible was covered and charged in an electric heating furnace (Electric furnace KBF-894N manufactured by Koyo Lindberg Co., Ltd.), and heated in the electric furnace at 900 ° C. for 1 hour. Then, it stood to cool to room temperature and observed the state in a crucible visually.

  As a result, discoloration and melting were observed in some of the refractory bricks.

Reference example 2
Same as Reference Example 1 except that 5 g of anhydrous sodium metasilicate (SiO ₂ / M ₂ O molar ratio = 1) was used as sodium silicate and heated at 1100 ° C for 5 hours instead of heating at 900 ° C for 1 hour Was performed. As an electric heating furnace, an ultra-high temperature electric furnace KB-2030D manufactured by Motoyama Co., Ltd. was used.

  There were no signs of discoloration or component elution on the refractory bricks.

Reference example 3
The same operation as in Reference Example 2 was performed except that 5 g of Ecolayer powder (SiO ₂ / M ₂ O molar ratio = 2) was used as sodium silicate.

  There were no signs of discoloration or component elution on the refractory bricks.

Reference example 4
The same operation as in Reference Example 2 was carried out except that 5 g of a medium molar cullet glass cullet (SiO ₂ / M ₂ O molar ratio = 3.0) was used as sodium silicate.

  There were no signs of discoloration or component elution on the refractory bricks.

Reference Example 5
Place 5 g of refractory brick (chamotte brick) (diameter 2-10 mm) in a 50 ml crucible, cover the crucible and place it in an electric heating furnace (Motoyama oxidizing atmosphere ultra high temperature electric furnace KB-2030D) And heated in the electric furnace at 1200 ° C. for 7 hours. Then, it stood to cool to room temperature and observed the state in a crucible visually.

  As a result, the refractory bricks showed no discoloration or signs of component elution, and no change was observed (Figure 7-A).

Reference Example 6
5 g of sodium orthosilicate n hydrate (SiO ₂ / M ₂ O molar ratio = 0.5) is put in a 50 ml capacity crucible, the crucible is covered with an electric heating furnace (Motoyama oxidizing atmosphere ultra high temperature electric furnace KB- 2030D) and heated in the electric furnace at 1200 ° C. for 7 hours. Then, it stood to cool to room temperature and observed the state in a crucible visually.

  Melting of sodium silicate was observed.

Reference Example 7
Put 5 g of refractory brick (chamotte brick) pieces (diameter 2-10 mm) and 5 g of sodium orthosilicate n hydrate (SiO ₂ / M ₂ O molar ratio = 0.5) in a 50 ml crucible, The lid was put in an electric heating furnace (oxidizing atmosphere ultra-high temperature electric furnace KB-2030D manufactured by Motoyama) and heated in the electric furnace at 1200 ° C. for 7 hours. Then, it stood to cool to room temperature and observed the state in a crucible visually.

  Melting of sodium silicate was observed, and the melt was colored yellow.

Reference examples 8, 10 and 12
As sodium silicate, 5 g of anhydrous sodium metasilicate (SiO ₂ / M ₂ O molar ratio = 1) (Reference Example 8), 5 g of Eco-layer powder (SiO ₂ / M ₂ O molar ratio = 2) (Reference Example 10) Alternatively, the same operation as in Reference Example 6 was carried out except that 5 g of medium molculet (SiO ₂ / M ₂ O molar ratio = 3.0) (Reference Example 12) was used.

  The respective visual observation results are as shown in Table 5 below.

Reference examples 9, 11 and 13
As sodium silicate, 5 g of anhydrous sodium metasilicate (SiO ₂ / M ₂ O molar ratio = 1) (Reference Example 9), 5 g of Eco-layer powder (SiO ₂ / M ₂ O molar ratio = 2) (Reference Example 11) Alternatively, the same operation as in Reference Example 7 was carried out except that 5 g of medium molculet (SiO ₂ / M ₂ O molar ratio = 3.0) (Reference Example 13) was used.

  The respective visual observation results are as shown in Table 5 below.

  Table 5 below summarizes the visual observation results in the crucibles in Reference Examples 1 to 13.

表5の結果からは、モル比が小さい珪酸ナトリウムを用いた場合に、溶融（冷却後固化）した珪酸ナトリウムが黄色に着色していることがわかる。これは珪酸ナトリウムにより耐火レンガが攻撃され、その成分が溶出したためと考えられる。

From the results in Table 5, it can be seen that when sodium silicate having a small molar ratio is used, the molten (solidified after cooling) sodium silicate is colored yellow. This is thought to be due to the fire brick being attacked by sodium silicate and its components eluting.

An electron micrograph (magnification: 500 times) of the mixture after asbestos yarn is mixed with sodium silicate having a molar ratio of 0.5, 1, 2 or 3 and heated in a crucible at 900 ° C. for 1 hour is shown. (A) Sodium silicate with SiO ₂ / Na ₂ O molar ratio 0.5, (b) Sodium silicate with SiO ₂ / Na ₂ O molar ratio 1, (c) Sodium silicate with SiO ₂ / Na ₂ O molar ratio 2, (d ) Sodium silicate with a SiO ₂ / Na ₂ O molar ratio of 3. An electron micrograph (magnification: 500 times) of the mixture after mixing asbestos yarn with sodium silicate having a molar ratio of 0.5, 1 or 2 and heating in a crucible at 600 ° C, 750 ° C or 1000 ° C for 1 hour Show. A: Sodium silicate with a SiO ₂ / Na ₂ O molar ratio of 0.5—heating temperature 750 ° C., B: (b) Sodium silicate with a SiO ₂ / Na ₂ O molar ratio of 1—heating temperature 600 ° C., (c) SiO ₂ / Na ₂ O molar ratio 1 sodium silicate-heating temperature 750 ° C, C: (d) SiO ₂ / Na ₂ O molar ratio 2 sodium silicate-heating temperature 600 ° C, (e) SiO ₂ / Na ₂ O molar ratio 2 Sodium silicate—heating temperature 750 ° C., (f) SiO ₂ / Na ₂ O molar ratio 2 sodium silicate—heating temperature 1000 ° C. The photograph which image | photographed the inside of a crucible after mixing an asbestos yarn with the sodium silicate which has a molar ratio of 0.5, 1, 2, or 3 and heating in a crucible at 1200 degreeC for 1 hour is shown. (A) Sodium silicate with SiO ₂ / Na ₂ O molar ratio 0.5, (b) Sodium silicate with SiO ₂ / Na ₂ O molar ratio 1, (c) Sodium silicate with SiO ₂ / Na ₂ O molar ratio 2, (d ) Sodium silicate with a SiO ₂ / Na ₂ O molar ratio of 3. A: An electron micrograph (magnification: 500 times) of an asbestos yarn not subjected to any treatment. B: shows an electron micrograph (magnification: 500 times) of an asbestos yarn that has been heat-treated without adding sodium silicate ((a): 600 ° C, (b): 750 ° C, (c): 900 ° C, (D): 1000 ° C.), C: Photograph showing the inside of the crucible after heating the asbestos yarn at 1200 ° C. for 1 hour in the crucible. A: Electron microscope of the mixture after mixing asbestos yarn with sodium silicate having a water content of 20% by weight (SiO ₂ / Na ₂ O molar ratio 2) and heating in a crucible at 750 ° C. or 900 ° C. for 1 hour A photograph (magnification: 500 times) is shown ((a) 750 ° C, (b) 900 ° C). B: Electron micrograph of the mixture after mixing asbestos yarn with sodium silicate having a water content of 57% by weight (SiO ₂ / Na ₂ O molar ratio 2) and heating in a crucible at 900 ° C. for 1 hour : 500 times). C: Photograph showing the inside of a crucible after mixing asbestos yarn with sodium silicate having a water content of 20% by weight (SiO ₂ / Na ₂ O molar ratio 2) and heating in a crucible at 1200 ° C. for 1 hour. . Electron microscope of the mixture after mixing asbestos yarn with sodium silicate having an average particle diameter of 700 μm or 3.4 mm (SiO ₂ / Na ₂ O molar ratio is 2) and heating at 900 ° C. for 1 hour in a crucible A photograph (magnification: 500 times) is shown. A: Average particle diameter 700 μm, B: Average particle diameter 3.4 mm. Photograph (A) of the inside of the crucible after 5 g of refractory bricks were heated at 1200 ° C in a crucible for 7 hours, 5 g of various sodium silicates and 5 g of refractory bricks were heated together at 1200 ° C for 7 hours. After the photo taken inside the crucible (B- (b), (d), (f) or (h)), and 5 g of various sodium silicates alone in a crucible at 1200 ° C for 7 hours A photograph (B- (a), (c), (e) or (g)) taken inside the crucible is shown.

Claims (4)

  A method for treating asbestos-containing waste, comprising mixing and heating solid waste containing asbestos with solid alkali silicate. _2. The processing method according to claim 1, wherein the alkali silicate has a SiO ₂ / M ₂ O molar ratio (M represents an alkali metal) of 1 to 3.5.   3. The processing method according to claim 1, wherein the alkali silicate is powdery or granular.   The processing method according to any one of claims 1 to 3, wherein the mixture is heated at a temperature of 750C to 1200C.

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