JP2000037676A - Stabilization treatment of waste containing heavy metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely and inexpensively perform a stabilization treatment for heavy metal-containing waste such as incineration fly ash, molten fly ash or direct molten fly ash. SOLUTION: In the case of the stabilization treatment of waste such as incineration fly ash 1a, molten fly ash 1b or direct molten fly ash 1c, a powder with an average particle size of 150 μm or less comprising one of secondary refining slag 2a, molten iron pretreatment slag 2b and converter slag 2c or a combination of two or more kinds of them is added to the waste to be kneaded with water and the kneaded matter is heated to suppress the elution of heavy metals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces the volume of at least one of incinerated fly ash, incinerated ash and incinerated fly ash generated by incinerating waste such as municipal waste and industrial waste. Waste containing heavy metals, such as fly ash generated by melting in a melting furnace, and direct melt fly ash generated by directly melting waste with a direct melting furnace or gasification melting furnace The present invention relates to a method for stabilizing an object.

[0002]

2. Description of the Related Art For example, in the year 1991, the total amount of general waste discharged in Japan was about 140,000 tons per day, and reached 50.77 million tons per year. 72.7% of this municipal waste was incinerated at incineration facilities. At that time, 65
80,000 tons of incineration ash and incineration fly ash (hereinafter collectively referred to as “incineration residue”) were generated and landfilled at the final disposal site.

[0003] With the increase of incineration residues, the Waste Management Law was revised in 1992. That is, since harmful heavy metals are contained at a high concentration in the incineration residue, if the landfill is performed as it is, environmental pollution will inevitably occur. Therefore, the revised Waste Disposal and Public Cleansing Law requires incineration residues to be designated as specified management waste and requires stabilization before landfill disposal. Can no longer be reclaimed.

[0004] Stabilization methods for incineration residues are described in the Ministry of Health and Welfare Notification No. 194 No. 1 by cement solidification method, chemical treatment method,
It is classified as an acid extraction method and a melting method.

[0005] The cement solidification method is based on the principle that when the oxides in the cement combine with water to form a hydrate and harden, heavy metals are adsorbed on the surface of calcium silicate hydrate and solidified. Processing technology. Although this cement setting method is an established technology that has a simple processing apparatus, is easy to operate and control, and consumes little energy, it has a low tolerable heavy metal content. Therefore, a large amount of cement is required for stabilizing incinerated fly ash, and it cannot be applied to the treatment of incinerated fly ash having a high heavy metal content. further,
Since a large amount of cement is used, the amount of final waste increases, and the volume of waste cannot be reduced. Therefore, the cement solidification method is not suitable as a method for stabilizing incineration residues.

[0006] The chemical treatment method is a treatment technique for producing an insoluble heavy metal complex compound by adding water together with a small amount of a heavy metal collecting agent, a flocculant, an inhibitor and the like, and kneading the mixture. Since its operation is easy, it has been widely used. However, the chemical treatment method, the chemical cost increases, in particular, the chelating agent reacts with other metal ions other than heavy metals, depending on the composition of the incinerated ash, the amount of the required chemical increases and the chemical cost increases significantly, Furthermore, there is a problem that secondary phytotoxicity may occur. Therefore, the chemical treatment method is not suitable as a method for stabilizing incineration residues.

[0007] The acid extraction method is a treatment technique in which dust is dissolved in an aqueous solution, heavy metals contained in the dust are transferred to the aqueous solution side, and then hydroxides and sulfides are generated to stabilize and insolubilize and dehydrate. And has the feature that the stabilization process can be performed without selecting the type of dust. However, the number of processing facilities that actually perform the acid extraction method is small because the processing apparatus becomes large-sized and complicated, and the processing cost and equipment maintenance cost increase.

[0008] On the other hand, the melting method is a treatment technique in which harmful heavy metals contained in the incineration residue are stably confined in the vitrified slag by heating the incineration residue into a molten slag state. Compared to the cement solidification method, the chemical treatment method, and the acid extraction method, the melting method requires higher operating costs and equipment costs, but can completely detoxify incineration residues and significantly reduce the volume of incineration residues. Because of its ability to be incinerated, it has been widely used and has recently become the mainstream of incineration residue treatment technology in existing incineration facilities.

On the other hand, as a new technology developed from the melting method,
After using a direct melting furnace or a gasification melting furnace to generate flammable gas from waste in a pyrolysis zone at 300 to 1000 ° C, the flammable gas is used as a fuel to further raise the combustion temperature, resulting in waste. Techniques for directly melting materials have also been developed.

However, in these melting methods, the melting treatment is not performed.
Since it is necessary to perform at a high temperature of 1100 to 1500 ° C, substances with high vapor pressure are easily volatilized, and the dust collector collects molten fly ash containing harmful heavy metals at a higher concentration than the original incinerated ash Will be. In the above-described direct melting furnace and gasification melting furnace, fly ash generated when combustible gas is extracted from waste and fly ash generated during subsequent melting are discharged together (hereinafter referred to as `` direct melting furnace ''). Fly ash ”.), The concentration of harmful heavy metals becomes extremely high. Therefore, even if the same stabilization treatment as incineration fly ash is performed on molten fly ash or direct molten fly ash, harmful heavy metals contained in high concentrations in the molten fly ash or direct molten fly ash should be stabilized. Is impossible.

Therefore, Japanese Patent Application Laid-Open No. 6-154795 discloses that, as a substitute for cement, fine powder of amorphous granulated blast furnace slag is used as a main raw material of a solidified material to prevent elution of heavy metals from waste. Inventions have been proposed.

[0012]

However, Japanese Patent Laid-Open Publication No.
The invention proposed by No. 4795, according to confirmation experiments by the present inventors, because granulated blast furnace slag is amorphous, for example, using an alkali stimulant such as Ca (OH) ₂ and crystalline However, as minerals contained, akermanite (Ca ₂ Mg
Si ₂ O ₇ ) and Gehlenite (CaAl ₂ SiO ₇ and Ca ₂ Al ₂₆ Mg ₃ Si ₃ O ₆₈ )
The effect of preventing heavy metal from being dissolved into incinerated fly ash, molten fly ash, and even directly molten fly ash is small, and it is difficult to perform stabilization treatment of heavy metal.

Further, in the invention according to this proposal, since expensive granulated blast furnace slag is used, the processing cost is increased. Therefore, from the viewpoint of processing cost, there is a very low possibility that this method is used to stabilize incinerated fly ash, molten fly ash, or directly melt fly ash.

Here, an object of the present invention is to provide a stabilization method capable of reliably and stably treating waste containing heavy metals such as incinerated fly ash, molten fly ash and direct molten fly ash at low cost. It is to provide.

From another aspect, an object of the present invention is to provide an inexpensive and stabilizing treatment by using a small amount of a fixing agent. It is an object of the present invention to provide a stabilization treatment method capable of performing a stabilization treatment of molten fly ash and direct molten fly ash.

[0016]

Here, the gist of the present invention is to use a powder of a product in a steelmaking process containing one or both of calcium aluminate and calcium silicate as a fixing agent and to remove heavy metals. A method for stabilizing waste containing heavy metals, characterized by performing stabilization of waste containing waste.

In the present invention described above, the product is exemplified as steelmaking slag, and specifically, is one or a combination of secondary smelting slag, hot metal pretreatment slag, and converter slag. Is exemplified.

In the present invention, it is desirable that the average particle size of the powder is 150 μm or less in order to stably stabilize heavy metals.

According to the present invention, the waste is one of incineration fly ash generated by incineration of waste in an incinerator, incineration ash generated by incineration of waste in an incinerator, and incineration fly ash. Examples include a fly ash generated by melting at least one of the waste in a melting furnace and a direct fly ash generated by directly melting waste in a melting furnace.

According to the present invention, when the waste is incinerated fly ash, 10 to 50 parts by weight of powder is added to 100 parts by weight of incinerated fly ash, and the waste is melted fly ash or ash. In the case of direct molten fly ash, molten fly ash or direct molten fly ash
It is desirable to add 30 to 100 parts by weight of the powder to 100 parts by weight in order to surely stabilize the heavy metal and to suppress an increase in the processing cost.

In the present invention, the stabilization treatment is performed by (i) heating the incinerated fly ash and the powder to 60 ° C. or more in the presence of water, or performing autoclave treatment.
Heating and pressurizing to above ℃, or (ii) Heating and pressurizing to above 80 ° C by performing autoclave treatment or steam curing of molten fly ash or direct molten fly ash and powder in the presence of water Is exemplified by the following.

Further, in the present invention, it is desirable to use cement as a fixing agent together with the powder.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a method for stabilizing waste containing a heavy metal according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory view schematically showing the stabilization processing method in the present embodiment. As shown in the drawing, in the present embodiment, a powder 2 of a crystalline product containing one or both of calcium aluminate and calcium silicate and obtained in a steelmaking process is used as a fixing agent, and waste containing heavy metals is used. 1 is performed. Therefore, the waste 1, the fixing agent 2, and the stabilization process will be sequentially described.

[Waste 1] Waste 1 subjected to the stabilization treatment according to the present invention includes (1) incinerated fly ash 1a generated by incineration of waste such as municipal solid waste and industrial waste in an incinerator.
(2) Melt fly ash 1b generated by melting at least one of incinerated ash and incinerated fly ash 1a for volume reduction with a melting furnace, (3) Waste such as municipal solid waste and industrial waste Is directly melted by a direct melting furnace or a gasification melting furnace.

In the present invention, there is no limitation on the type of incinerator that generates the incineration fly ash 1a. In addition, neutral fly ash and alkali fly ash generated by blowing slaked lime into a flue for collecting chlorine gas are applicable.

In the present invention, the type of the melting furnace for generating the fly ash 1b is not limited at all. For example, a surface melting furnace using a rotary furnace or a fixed furnace, a coke bed furnace using coke heating, and the like can be used. Examples can be given. Also,
An electric melting furnace using arc heating, plasma heating, resistance heating, or high-frequency heating can also be used.

Further, the type of the melting furnace for directly generating the fly ash 1c is not limited at all, and examples thereof include a direct melting furnace and a gasification melting furnace. In this case, the generated acidic fly ash, neutral fly ash, and
Any alkaline fly ash obtained by blowing slaked lime into a flue for collecting chlorine gas is an object of the present invention.

Naturally, the composition of the waste fluctuates depending on various factors such as, for example, the generation area and generation time, and accordingly, the composition of the incinerated fly ash 1a, the molten fly ash 1b, and the direct molten fly ash 1c Also change respectively. However, incineration fly ash 1a
According to previous reports on the composition of molten fly ash 1b,
Both contain large amounts of chlorine, such as incinerated fly ash
2.9-27% by weight of chlorine is used for 1a, and 32-39% for molten fly ash 1b.
Wt.% Chlorine, and in direct melt fly ash 1c, contains 20-28 wt.% Chlorine. According to the thermodynamic calculation results, since the vapor pressure of heavy metal chloride at the incineration temperature and the melting temperature is high, heavy metals in the incineration fly ash 1a, molten fly ash 1b and direct molten fly ash 1c It exists stably as an object.

[Fixing agent] In the present invention, as a crystalline product powder 2 containing one or both of calcium aluminate and calcium silicate and obtained in a steelmaking process, a steelmaking slag powder, specifically 2 Powder 2 of one or more of powder 2a of secondary refining slag, powder 2b of hot metal pre-treatment slag and powder 2c of converter slag
Is used as a fixing agent.

In the present invention, "calcium aluminate"
“3CaO · Al ₂ O ₃ , 12CaO · 7Al ₂ O ₃ , or a hydrate thereof. 3CaO ・ Al ₂ O ₃ and 12CaO ・ 7Al ₂ O ₃
Are easily synthesized by a high-temperature calcination method, and various hydrates can be obtained by reacting with water. For example,
Minerals with 3CaO.Al ₂ O ₃ .6H ₂ O composition include Katoite and
Hydrogrossular is known. _{3CaO · Al 2 O 3, 12CaO} · 7Al 2 O 3, or by any of these hydrates, heavy metals present in the waste, can be easily and reliably fixed.

The term "calcium silicate" in the present invention means 2CaO.SiO ₂ or a hydrate thereof.
2CaO.SiO _{2 is} also easily synthesized by a high-temperature baking method, and a hydrate can be obtained by reacting with water. For example, 2CaO
Larnite is known as a mineral of SiO ₂ composition, and Hillebran is a mineral of 2CaO ・ SiO ₂・ H ₂ O composition.
dite (Hillebrandite) is known. 2CaO ・ SiO ₂
Alternatively, any of the hydrates can easily and reliably immobilize heavy metals present in the waste.

In the present invention, steelmaking slag powder 2 containing one or both of calcium aluminate and calcium silicate is used. For example, in the case of an amorphous product such as granulated blast furnace slag, the product is made crystalline using an alkali stimulant such as Ca (OH) ₂ , and the contained mineral is akermanite (Ca ₂ MgSi ₂ O ₇ ) Or Gehlenite (CaAl ₂ SiO ₇ or Ca ₂ A
l ₂₆ Mg ₃ Si ₃ O ₆₈ ), because it does not contain minerals such as calcium aluminate and calcium silicate, it lacks reactivity with waste and cannot sufficiently fix heavy metals. is there.

Here, the steelmaking slag means slag generated in the steelmaking process, and includes one or a combination of secondary smelting slag, hot metal pretreatment slag, and converter slag. . Note that granulated blast furnace slag is not included.

The secondary refining slag is a vacuum refining method,
This refers to the slag generated when secondary refining (out-of-pile refining) such as ladle refining or simple ladle refining is performed.

The hot metal pre-treatment slag is defined as dephosphorization or desulfurization of hot metal discharged from a blast furnace by means of a ladle, a mixed iron wheel, and, if necessary, degassing, decarburization, and dechromization. , Slag generated when vanadium removal, titanium removal, denitrification, denitration, and addition of silicon are performed. Furthermore, converter slag means slag generated in a steelmaking process using a converter.

The powder 2 composed of one or more of the powder 2a of the secondary refining slag, the powder 2b of the hot metal pre-treatment slag and the powder 2c of the converter slag used as a fixing agent in the present invention is subjected to, for example, an X-ray diffraction method. Identified by appropriate methods such as etc., the powder 2a of the secondary refining slag is 3CaO.Al ₂ O ₃ or 12C
aO.7Al ₂ O ₃ is the main mineral phase, and powder 2b of hot metal pretreatment slag and powder 2c of converter slag are both 2CaO
SiO ₂ is the main mineral phase.

In the present embodiment, if the average particle diameter of the powder 2 as a fixing agent exceeds 150 μm, the reaction interface area between the powder 2 and the incinerated fly ash 1a, the molten fly ash 1b or the direct molten fly ash 1c Incineration fly ash 1a, molten fly ash 1b or direct molten fly ash
An unreacted portion may remain in 1c and immobilization of heavy metals may be insufficient. Therefore, the average particle size of powder 2 is 150μ.
m or less, and from the same viewpoint, 30 μm
It is desirable that: From such a viewpoint, the lower limit of the average particle size of the powder 2 is not limited, but if the average particle size is less than 10 μm, handling of the powder 2 becomes troublesome.
It is desirable that the thickness be 10 μm or more.

When the amount of the powder 2 as the fixing agent is small, the area of the reaction interface between the powder 2 and the incinerated fly ash 1a, the molten fly ash 1b or the direct molten fly ash 1c is reduced, and the incinerated fly ash is reduced. 1a,
An unreacted portion may remain in the molten fly ash 1b or the direct molten fly ash 1c, and immobilization of heavy metals may be insufficient. This tendency is due to molten fly ash 1b, which has a higher concentration of heavy metals than incinerated fly ash 1a.
And in the direct molten fly ash 1c, it becomes even more remarkable. On the other hand, when the addition amount of the powder 2 is large, the stabilizing effect of the heavy metal is saturated, and the cost is increased to hinder volume reduction.

Therefore, when performing the stabilization treatment of the incinerated fly ash 1a, 5 to 5 parts of the powder 2 is added to 100 parts by weight of the incinerated fly ash 1a.
It is desirable to add 50 parts by weight, more preferably 20 to 50 parts by weight. When stabilizing the molten fly ash 1b or the direct molten fly ash 1c, 30 to 100 parts by weight of the powder 2 is added to 100 parts by weight of the molten fly ash 1b or the direct molten fly ash 1c. It is preferable to add 50 to 100 parts by weight.

[Stabilization Treatment] In the present invention, the powder 2
Incineration fly ash 1a, molten fly ash 1b or direct molten fly ash 1c
Is performed.

As the stabilization treatment, in the case of the incinerated fly ash 1a, an appropriate amount of water is added to the incinerated fly ash 1a and the powder 2, for example,
The incineration fly ash 1a and the powder 2 are kneaded by using a kneader, a granulator, or a machine 3 having both functions of kneading and granulation to obtain a granulated material 4 having a desired shape (for example, a cylindrical body). This is a process of fixing the heavy metals in the incineration fly ash by heating to 60 ° C. or higher. At this time, it is more desirable to heat and pressurize the mixture to 100 ° C. or higher using the autoclave 5 in order to promote the immobilization.

On the other hand, in the case of the molten fly ash 1b or the direct molten fly ash 1c, the stabilization treatment is carried out by adding an appropriate amount of water to the molten fly ash 1b or the direct molten fly ash 1c and the powder 2 and kneading them. Shape
After making the granules 4 (for example, cylindrical), the heavy metals in the molten fly ash 1b or the direct molten fly ash 1c are fixed by heating and pressurizing to 80 ° C or more by autoclaving or steam curing in the presence of water. This is the process of converting

In the stabilization treatment, the water which coexists with the powder 2 and the incinerated fly ash 1a, the molten fly ash 1b or the direct molten fly ash 1c is, in the present invention, tumbling granulation, stirring granulation and the like. Is used to form the granulated material 4 by causing the aggregation and granulation phenomenon. Therefore, an appropriate solvent may be used together with water depending on the strength, hardness, and the like required for the dried granules 4. Such solvents include, for example, dextrin,
Examples thereof include sodium alginate, lignin, and bentonite.

By such a stabilizing treatment, incinerated fly ash 1
a, the reason why the harmful heavy metal contained in the molten fly ash 1b or the direct molten fly ash 1c is fixed will be described. We have:
3CaO.Al ₂ O ₃ or 12CaO.7Al ₂ O ₃ is used as a main mineral phase for secondary refining slag powders with various heavy metal chlorides MCl ₂ (M = P
b, Zn, etc.) and kept at 120 ° C. for 3 to 12 hours in an autoclave, and the mineral phase after the reaction was identified by X-ray diffraction. As a result, it was confirmed that Friedel's salt (3CaO.Al ₂ O ₃ .CaCl ₂ .10H ₂ O) was newly present from the mineral phase, and the simple heavy metal chloride MCl ₂ had disappeared.

Further, Friedel's salt (3CaO.Al ₂ O _3.
CaCl ₂・ 10H ₂ O) powder is synthesized in advance, and various compacts of heavy metal chloride MCl ₂ are embedded in the compact, and then compacted, and then maintained at 120 ° C. in an autoclave. 3 to 12
Allowed to react for hours. And after the reaction, Friedel salt (3C
The vicinity of the interface between _{aO · Al 2 O 3 · CaCl} 2 · 10H 2 O) and heavy metal chlorides MCl ₂ was observed with an electron microscope, was quantified the composition of each part a minute portion X-ray analyzer. As a result, it was found that Ca and M of CaCl ₂ in the Friedel salt in the Friedel salt up to about 10 μm from the interface were replaced, and the heavy metal chloride MCl ₂ was stabilized by the Friedel salt.

The stabilization of such heavy metal chlorides by the secondary refining slag powder containing calcium aluminate is represented by the following formula.

3CaO · Al ₂ O ₃ (in slag) + xMCl ₂ (in fly ash) + (1−x) CaCl ₂ (in fly ash) + 10H ₂ O → 3CaO · Al ₂ O ₃ · (Ca _1-x M _x ) Cl ₂・ 10H ₂ O ・ ・ ・ ・ ・ 1/4 (12CaO ・ 7Al ₂ O ₃ (in slag) + xMCl ₂ (in fly ash) + (1−x) CaCl ₂ (in fly ash) + 49 / 4H ₂ O → 3CaO ・ Al ₂ O ₃・ (Ca _1-x M _x ) Cl ₂・ 10H ₂ O + 3/4 (Al ₂ O ₃・ 3H ₂ O ・ ・ ・ ・ 2CaO ・ SiO Hot metal pretreated slag powder containing ₂ as the main mineral phase is mixed with various heavy metal chlorides MCl ₂ and reacted in an autoclave at 120 ° C. for 3 to 12 hours, and the mineral phase after the reaction is subjected to X-ray diffraction. It was identified by. as a result, the hydrates of the newly 2CaO.SiO ₂ from mineral phase is observed, a single heavy metal chlorides MCl ₂ had disappeared.

[0049] Furthermore, previously synthesized hydrates of 2CaO.SiO _2, since the dust is embedded a cylindrical powder compact of various heavy metal chlorides MCl ₂ therein in an autoclave 120
The reaction was maintained at a temperature of 3 ° C. for 3 to 12 hours. And after the reaction
The vicinity of the interface between the hydrate of 2CaO.SiO ₂ and the heavy metal chloride was observed with an electron microscope, and the composition of each part was quantified with a micropart X-ray analyzer. As a result, 2CaO.SiO ₂
It was found that heavy metal chloride was stabilized by replacing Ca and O 2 of CaO site in M hydrate with M and Cl, respectively.

The stabilization of such heavy metal chlorides by the hot metal pretreatment slag containing calcium silicate is represented by the following equation.

2CaO · SiO ₂ (in slag) + x MCl ₂ (in fly ash) + m H ₂ O → 2 (Ca _{1 -x} M _x O _{1 -x} Cl _x ) · SiO ₂ · mH ₂ O + xCaO ··· According to the present invention, in this way, steelmaking slag containing calcium aluminate and / or calcium silicate, that is, from one or a combination of two or more of secondary smelting slag, hot metal pretreatment slag, and converter slag By using powder 2 as a fixing agent
Stabilization of 1a, molten fly ash 1b or direct molten fly ash 1c is performed.

In the stabilization treatment, cement 6
Is preferably added together with the powder 2. By adding the cement 6 together with the powder 2, a dense structure of the cement 6 can be generated around the immobilization phase of the heavy metal by the powder 2 in the granulated product 4, and the immobilization process can be further completed. can do. In order to ensure the denseness of the cement 6, the Blaine specific surface area value is 1000
It is desirable to add a particulate cement of not less than 40 cm ² / g of powder 2 to the powder 2.

The granules 4 'obtained in this manner sufficiently satisfy the standard of stabilization treatment required by the revised Waste Management Law, so that they can be disposed of at the final waste disposal site. It can be used effectively as a roadbed material, backfill material, etc. in civil engineering sites and the like.

As described above, according to the present invention, incinerated fly ash 1
a, wastes containing heavy metals, such as molten fly ash 1b and directly molten fly ash 1c, can be reliably stabilized. In addition, in this process, since the low cost steelmaking slag powder 2 is used, an increase in the processing cost can be surely suppressed.

Further, since the steelmaking slag powder 2 used reacts with the heavy metal contained in the waste efficiently and preferentially, an increase in the usage of the powder 2 is suppressed. Therefore, also from this aspect, an increase in processing cost is reliably suppressed.

Further, a new use for effectively utilizing steelmaking slag, which had conventionally only been used as a landfill material or a roadbed material, could be provided. Further, the present invention will be described more specifically with reference to examples.

[0057]

EXAMPLES (Example 1) Table 1 shows the chemical composition of alkaline incinerated fly ash collected by a bag filter type dust collector in a stoker type incineration facility in actual operation.

[0058]

[Table 1]

The incineration fly ash was subjected to a dissolution test specified in Notification No. 13 of the Environment Agency. Table 2 shows the elution amount of heavy metals and the regulated values for landfill disposal in comparison with Table 2.

[0060]

[Table 2]

From the results shown in Table 2, it was clear that the amount of lead eluted from the incinerated fly ash exceeds the regulation value, and thus it is necessary to perform a lead immobilization treatment. Particle size of 250 μm or less, 150 μm or less, or 32
50 parts by weight of secondary refining slag powder, hot metal pre-treated slag powder or converter slag powder of μm or less was added, kneaded with an appropriate amount of water to form a cylindrical body, and then cured at 60 ° C. for 48 hours.

Regarding the obtained processed product, the Environment Agency Notification No. 13
The dissolution test specified in No. was performed. FIG. 2 is a graph showing the relationship between the lead concentration in the eluate and the slag particle size. From the graph shown in FIG. 2, it can be seen that when the slag particle size is 150 μm or less, the lead concentration in the eluate is lower than the regulation value for landfill.

(Example 2) For 100 parts by weight of incinerated fly ash,
After adding 50 parts by weight of secondary refining slag powder, hot metal pre-treated slag powder or the above calcium aluminate powder having a particle size of 150 μm or less, kneading with an appropriate amount of water to form a cylinder, C. (in an air bath) for 48 hours or 120.degree. C. (in an autoclave) for 3 hours.

Regarding the obtained processed product, the Environment Agency Notification No. 13
The dissolution test specified in No. was performed. FIG. 3 is a graph showing the relationship between the lead concentration in the eluate and the curing temperature in the dissolution test.

It can be seen that when the curing temperature is 60 ° C. or higher, the lead concentration in the eluate is lower than the regulated value for landfill. The same tendency was observed when using converter slag powder and calcium silicate powder.

(Example 3) Secondary refined slag powder or molten iron pre-treated slag powder having a particle size of 32 µm or less was added to incinerated fly ash, and kneaded with an appropriate amount of water to form a cylindrical body.
Cured at 60 ° C for 48 hours. At this time, the slag weight / incinerated fly ash weight ratio was changed in the range of 0.1 to 1.0.

Regarding the obtained processed product, the Environment Agency Notification No. 13
The dissolution test specified in No. was performed. FIG. 4 is a graph showing the relationship between the lead concentration in the eluate and the slag weight / incinerated fly ash weight ratio in the dissolution test.

When the weight ratio of slag / incinerated fly ash is 0.5 or more, the effect of suppressing lead elution by the secondary refining slag and the hot metal pretreatment slag is saturated. The same tendency was observed when using converter slag powder and calcium aluminate powder.

(Example 4) Particle size was reduced to 100 parts by weight of incinerated fly ash.
Add 50 parts by weight of secondary refining slag powder or molten iron pre-treated slag powder of 32 μm or less, or secondary refining slag powder or molten iron pre-treated slag powder of 150 μm or less in particle size, and knead with an appropriate amount of water. After curing, the mixture was cured at 60 ° C.

Regarding the obtained processed product, the Environment Agency Notification No. 13
The dissolution test specified in No. was performed. FIG. 5 is a graph showing the relationship between the lead concentration in the eluate and the curing time in the dissolution test.

The effect of suppressing lead elution by the secondary refining slag and the hot metal pretreatment slag is saturated. Particle size 32μm
When the following secondary refining slag powder or hot metal pre-treatment slag powder is used, the effect of suppressing lead elution is saturated after curing for 48 hours. The same tendency was observed when converter slag powder, calcium aluminate powder, or calcium silicate powder was used.

According to the above Examples 1 to 4, one or more of secondary smelting slag, hot metal pre-treatment slag and converter slag are used as a fixing agent to reduce incineration fly ash. It can be seen that lead elution can be reliably suppressed.

(Example 5) Acid melt fly ash collected by a bag filter type dust collector in a rotating rotary surface melting furnace in operation, and immediately after being collected by a bag filter type dust collector in a gasification melting furnace. Table 3 shows the chemical composition of the molten fly ash.

[0074]

[Table 3]

Comparing Table 3 with Table 1, it is clear that the concentration of each heavy metal in the molten fly ash is higher than that of the incinerated ash, and that the fixing treatment is more difficult. In addition, since the fly ash directly melted is a mixture of fly ash generated when extracting combustible gas from waste and fly ash generated during subsequent melting, the incinerated ash in Table 1 and the molten ash in Table 3 are mixed. Although it has an intermediate composition of fly ash, it has a higher concentration of harmful heavy metals than incinerated ash. From Table 3, it can be seen that if heavy metals in the molten fly ash can be fixed, heavy metals can be directly fixed in the molten fly ash. Therefore, in the following examples, examples of molten fly ash which are more difficult to fix are shown.

Regarding the molten fly ash shown in Table 3, the Environment Agency Notification No. 13
The dissolution test specified in No. was performed. Table 4 shows the elution amount of heavy metals and the regulated value of landfill disposal for the melted fly ash subjected to the dissolution test as it is and for the sludge added with the slaked lime to increase the pH.

[0077]

[Table 4]

Referring to Table 4, the amount of lead and cadmium eluted from the molten fly ash exceeds the regulation value for landfill. There is no regulation value for zinc for landfill, but it is significantly higher than the criterion value of 5 mg / L for waste to be injected into the ocean. Even if slaked lime is added to raise the pH, the amount of lead eluted exceeds the regulation value for landfill. Also in the comparison between Table 4 and Table 2, it is expected that the elution amount of heavy metal from the molten fly ash is higher than that of the incinerated fly ash, and that the immobilization treatment of these heavy metals will be difficult.

Conventionally, molten fly ash was treated by a cement solidification method used for stabilizing incinerated fly ash and a chemical treatment method using a chelating resin K, and a dissolution test was conducted in accordance with Notification No. 13 of the Environment Agency. . Table 5 shows the results.

[0080]

[Table 5]

Here, in the cement solidification method, a fine particle cement having a Blaine specific surface area value of 1000 cm ² / g or more was kneaded with an appropriate amount of water and cured at room temperature for 7 days. In an experiment using chelating resin K, slaked lime was added to eluate.
The pH was raised.

In both the cement solidification method and the chemical treatment method, it is difficult to suppress the elution of lead. In particular, in the cement solidification method, increasing the amount of cement
Due to the increase in pH, the amount of lead eluted has increased.

(Example 6) Secondary refining slag powder or hot metal pre-treated slag powder which was effective against incineration fly ash was used for fixing heavy metals in molten fly ash.

The particle size is 150 with respect to 100 parts by weight of molten fly ash.
100 parts by weight of secondary refining slag powder of less than μm, hot metal pretreatment slag powder, converter slag powder, synthetic calcium aluminate powder, or synthetic calcium silicate powder were added and kneaded with an appropriate amount of water to form a cylinder. Later, 60
C. for 48 hours at 80.degree. C. (in an air bath), or 3 hours at 120.degree. C. (in an autoclave).

Regarding the obtained processed product, the Environment Agency Notification No. 13
The dissolution test specified in No. was performed. Table 6 shows the relationship between the lead, zinc, and cadmium concentrations in the eluate and the curing temperature in the dissolution test.

[0086]

[Table 6]

In any of the fixing agents, when the curing temperature was 80 ° C. or higher, the lead concentration in the eluate was lower than the regulation value for landfill.

(Example 7) Secondary refined slag powder, hot metal pre-treated slag powder, converter slag powder, synthetic calcium aluminate powder, or synthetic calcium silicate powder having a particle size of 150 µm or less was added to molten fly ash. After kneading with an appropriate amount of water to form a cylinder, the mixture was cured at 120 ° C. for 3 hours. At this time, the ratio of the weight of the fixing agent to the weight of the incinerated fly ash is 0.1 to 1.0.
Was changed within the range.

Regarding the obtained processed product, the Environment Agency Notification No. 13
The dissolution test specified in No. was performed. Table 7 shows the relationship between the concentration of heavy metal in the eluate and the ratio of the weight of the fixing agent to the weight of the incinerated fly ash in the dissolution test.

[0090]

[Table 7]

In any of the fixing agents, the weight ratio of slag to incinerated fly ash was 0.3 or more, and the lead concentration in the eluate was lower than the regulation value for landfill.

(Example 8) 100 parts by weight of molten fly ash
Secondary refining slag powder with a particle size of 150 μm or less, hot metal pre-treatment slag powder or converter slag powder, or particle size
100 parts by weight of calcium aluminate powder or calcium silicate powder of 150 μm or less was added, kneaded with an appropriate amount of water to form a cylinder, and then cured at 80 ° C. The obtained treated product was subjected to a dissolution test prescribed in the Environment Agency Notification No. 13. Table 8 shows the relationship between the lead concentration in the eluate and the curing time in the dissolution test.

[0093]

[Table 8]

At a curing temperature of 80 ° C., the particle size is 150 μm in 24 hours.
m or less, the effect of suppressing lead elution by the secondary refining slag powder, hot metal pre-treated slag powder or converter slag powder is almost saturated. In addition, as the particle size of the secondary refining slag powder is smaller, the effect of suppressing elution of heavy metals appears in a shorter time.

Example 9 100 parts by weight of molten fly ash had a particle size
After adding 50 parts by weight of secondary refining slag powder of 150 μm or less or hot metal pre-treated slag powder, and 5 to 30 parts by weight of fine-particle Portland cement having a specific surface area of 1000 cm ² / g or more, add an appropriate amount of water. The mixture was kneaded to form a cylindrical body, and then cured at 60 ° C. (in an air bath) for 48 hours.

[0096] Regarding the obtained processed product, the Environment Agency Notification No. 13
The dissolution test specified in No. was performed. Table 9 shows the relationship between the concentrations of lead, zinc, and cadmium in the eluate and the amount of cement added in the elution test.

[0097]

[Table 9]

By adding 10 parts by weight or more of cement, secondary refining slag powder, hot metal pre-treatment slag powder,
Alternatively, a dense structure of cement is generated around the heavy metal immobilized phase by the converter slag powder, and the lead concentration in the eluate is below the regulation value for landfill. In addition, since the effect of suppressing the elution of lead is saturated by adding up to 20 parts by weight of cement, the addition of cement beyond this level is not preferable for volume reduction.

Mixing cement with secondary refining slag powder, hot metal pre-treated slag powder, or converter slag powder is effective in stabilizing heavy metals in molten fly ash. It is also effective in stabilizing heavy metals.

From the results of Examples 5 to 9, the use of secondary refining slag powder, hot metal pre-treated slag powder, converter slag powder, calcium aluminate powder, or calcium silicate powder as a fixing agent makes It can be seen that heavy metal elution from the ash can be reliably suppressed.

Example 10 The particle size was reduced to 100 parts by weight of molten fly ash.
After adding secondary refining slag powder, hot metal pre-treatment slag powder or converter slag powder of 150 μm or less, kneading with an appropriate amount of water to form a cylinder, and curing at 80 ° C, sample 1 Invention Example) was obtained.

On the other hand, 100 parts by weight of the molten fly ash were mixed with granulated blast furnace slag having a brane specific surface area of 6000 cm ² / g or more.
A sample 2 (comparative example) was obtained by adding a part by weight, kneading with an appropriate amount of water to form a cylinder, and curing the mixture in an autoclave.

Further, 100 parts by weight of molten fly ash is added with 100 parts by weight of cement having a specific surface area of 1000 cm ² / g or more, kneaded with an appropriate amount of water to form a cylindrical body, and then cured at room temperature. As a result, a sample 3 (conventional example) was obtained.

With respect to these samples 1 to 3, the dissolution test specified in the Environment Agency Notification No. 13 was performed, and the dissolution amount of heavy metals in the dissolution test was measured. The results are summarized in Table 10.

[0105]

[Table 10]

From Table 10, it can be seen that according to the present invention, heavy metals contained in wastes can be reliably immobilized. On the other hand, sample 2 uses granulated blast furnace slag as a fixing agent, and therefore does not contain minerals such as calcium aluminate and calcium silicate. Therefore, immobilization of heavy metals is insufficient, and heavy metals are eluted. Was. In addition, since Sample 3 uses cement as a fixing agent, it is also found that immobilization of heavy metals is insufficient.

[0107]

As described in detail above, claims 1 to 5
According to the ninth aspect of the present invention, wastes containing heavy metals such as incinerated fly ash, molten fly ash, and direct molten fly ash can be stably treated. In addition, in this treatment, since the powder of the product from the low-cost steelmaking process is used, an increase in the treatment cost can be surely suppressed.

Further, since the powder of the product in the steel making process used reacts with the heavy metal contained in the waste efficiently and preferentially, the increase in the amount of powder used is suppressed. Therefore, also from this aspect, an increase in processing cost is reliably suppressed.

Further, it is possible to provide a new use for effectively utilizing steelmaking slag which has conventionally only been used as a landfill material or a roadbed material. The significance of the present invention having such an effect is extremely remarkable.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically showing a stabilization processing method according to an embodiment.

FIG. 2 is a graph showing the effect of slag particle size on the lead concentration in eluate when incinerated fly ash is stabilized with secondary smelting slag powder, hot metal pre-treated slag powder, or converter slag powder. .

FIG. 3 is a graph showing the effect of the curing temperature on the lead concentration in the eluate when incinerated fly ash is stabilized with secondary smelting slag powder, hot metal pre-treated slag powder, or calcium aluminate powder. .

FIG. 4 shows the relationship between the lead concentration in the eluate and the slag weight / incineration ash weight ratio when incinerated fly ash is stabilized with secondary refining slag powder, hot metal pre-treated slag powder, or calcium silicate powder. It is a graph shown.

FIG. 5 is a graph showing the relationship between the lead concentration in the eluate and the curing time when incinerated fly ash and secondary refining slag powder or molten iron pre-treated slag powder are kneaded and cured at 60 ° C.

[Explanation of symbols]

 1a Incineration fly ash 1b Melting fly ash 1c Direct melting fly ash 2 Steelmaking slag powder 2a Secondary refining slag powder 2b Hot metal pre-treatment slag powder 2c Converter slag powder 3 Machine with both functions of kneading and granulation 4,4 '' Granules 5 Autoclave 6 Cement

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazumi Yusa, 3 Oaza Hikari, Kashima City, Ibaraki Prefecture Sumitomo Metal Industries, Ltd. Kashima Works (72) Inventor Kenji Koda 4-5-33 Kitahama, Chuo-ku, Osaka City Sumitomo Gold (72) Inventor Ryo Inoue 4-29F, Minaminakayama 4-chome, Izumi-ku, Sendai-shi (Reference) 2E191 BA02 BB00 BC02

Claims (9)

[Claims] 1. A waste containing heavy metals, wherein a powder of a product from a steelmaking process containing calcium aluminate and / or calcium silicate is used as a fixing agent to stabilize a waste containing heavy metals. Stabilization method for objects. 2. The method according to claim 1, wherein the product is steelmaking slag. 3. The method according to claim 1, wherein the steelmaking slag is one or a combination of secondary smelting slag, hot metal pretreatment slag, and converter slag. Chemical treatment method. 4. The method for stabilizing waste containing a heavy metal according to claim 1, wherein the average particle diameter of the powder is 150 μm or less. 5. The incineration fly ash generated by incinerating the waste in an incinerator, at least one of the incineration ash generated when the waste is incinerated in an incinerator, and the incineration fly ash Is a fly ash generated by melting a slag in a melting furnace, or a direct fly ash generated by directly melting waste in a melting furnace. A method for stabilizing waste containing a heavy metal according to the above. 6. When the waste is the incinerated fly ash, the powder is added in an amount of 10 to 100 parts by weight of the incinerated fly ash.
When 50 parts by weight are added and the waste is the molten fly ash or the direct molten fly ash, the powder is mixed with 30 to 100 parts by weight based on 100 parts by weight of the molten fly ash or the direct molten fly ash.
The method for stabilizing waste containing a heavy metal according to claim 5, which is added in parts by weight. 7. The stabilization treatment comprises heating the incinerated fly ash and the powder to 60 ° C. or higher in the presence of water, or performing autoclaving to heat and pressurize the powder to 100 ° C. or higher. The method for stabilizing waste containing a heavy metal according to claim 5 or 6, wherein the method comprises the steps of: 8. The stabilizing treatment comprises heating and pressurizing the molten fly ash or the direct molten fly ash and the powder to 80 ° C. or higher by performing autoclave treatment or steam curing in the presence of water. The method for stabilizing waste containing a heavy metal according to claim 5 or 6, wherein the method comprises the steps of: 9. The method for stabilizing waste containing a heavy metal according to claim 1, further comprising using cement together with the powder as a fixing agent.