JP2000301103A - Detoxification treatment of incineration ash or fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method for detoxifying incineration ash or fly ash by easily removing heavy metals therefrom with high efficiency. SOLUTION: In a chlorinating process, incineration ash or fly ash is kneaded in the presence of chlorine, a chlorine compd. or chlorine ions to convert heavy metals, a zinc compd. an/or a tin compd. contained in the incineration ash or fly ash to chlorides. In a succeeding heating and removing process, the kneaded mater of the incineration ash or fly ash is heated to 600-900 deg.C to volatilize and remove heavy metal chlorides along with zinc chloride and/or tin chloride.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment method for removing heavy metals from incinerated ash or fly ash to render them harmless, and more particularly, to a method for removing heavy metals from incinerated ash or fly ash easily and with high efficiency. It relates to a treatment method for detoxification.

[0002]

Of the industrial waste and waste from city life, combustibles are collected and then incinerated in an incinerator to be discarded in the form of incinerated ash or to be buried. ing. However, these incinerated ash contain harmful heavy metals such as lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), and arsenic (As). If it is not below a certain level in a dissolution test or the like, it cannot be dumped into soil or reused as a roadbed material. On the other hand, when such wastes are burned, low-boiling substances in various components are volatilized to form so-called fly ash, which is much more harmful heavy metals and the like than the incinerated ash. Because it contains, it cannot be landfilled like general waste, and it is collected in a bag filter carrying slaked lime to prevent it from diffusing into the external environment. Such fly ash requires strict management in terms of environmental hygiene, and cannot be discarded or used as a landfill material as it is, but heavy metals are insolubilized in water and buried as a concrete compact together with cement and the like. And so on.

However, in recent years, the amount of industrial waste and waste from general households has been increasing steadily, and it has become difficult to secure land for disposal sites due to saturation of existing disposal sites and problems of environmental pollution. It has been studied to reuse incinerated ash, fly ash, etc. as a concrete molded body as a basis for various civil engineering and construction works or as a roadbed material.

[0004] Further, the incineration ash and fly ash from the incinerator are melt-treated to reduce the volume and to thermally decompose dioxins. However, in the above-mentioned melting treatment, lead or ash having a high vapor pressure is used. Heavy metals such as cadmium volatilize in the furnace and enter the exhaust gas, and the heavy metals entering the exhaust gas are condensed in the exhaust gas treatment facility and become fly ash again.

[0005] As a treatment method for removing heavy metals from incinerated ash or fly ash, JP-A-7-163965 discloses a method of incinerating waste containing heavy metals and treating combustion exhaust gas with a bag filter. The waste before incineration was mixed with chlorides and incinerated.The heavy metals in the wastes were converted into metal chlorides and scattered in the flue gas. There is disclosed a method for treating waste, in which the heavy metal chloride is removed by a filter.

However, this waste disposal method is
Heavy metals in the waste are scattered as chlorides by mixing chlorides into the waste before incineration and incinerating it. There is a problem that a large amount of substances must be mixed. In addition, although the incineration process using heavy metals as metal chlorides is performed at 800 to 900 ° C., it is difficult to control the combustion of waste to such a temperature,
High and low temperatures occur, and incomplete combustion occurs at low temperatures.
In a high temperature region, there is a problem that lead reacts with silicon dioxide to form lead silicate which is difficult to remove, and heavy metals cannot be completely removed.

Japanese Patent Application Laid-Open No. 7-214029 discloses that incinerated ash or fly ash containing a heavy metal is subjected to a heat treatment in the presence of at least 2% by weight of chloride in terms of chlorine to remove the heavy metal component from the chloride. The first step of concentrating heavy metals in fly ash by volatilizing, and dissolving the obtained fly ash in an aqueous solution and further neutralizing to collect heavy metal components in a solid precipitate And a second step of performing solid-liquid separation and recovering heavy metals in the solid precipitates. A method of recycling heavy metals by detoxifying incinerated ash or fly ash is disclosed.

However, in this method for recycling heavy metals, heavy metals are heat-treated in the presence of chloride to form metal chlorides. These metal chlorides are generally used and are generally contained in fly ash. Since sodium and calcium chloride are used, the removal rate of heavy metals at a temperature of 800 to 900 ° C. is not always sufficient. This is because this conventional technique aims at treating a residue as a resource in a non-ferrous smelter. If the metal chloride can be efficiently volatilized at a lower temperature, it is desirable not only to suppress the reaction with silicon oxide such as silicon dioxide but also to improve the energy efficiency.

Further, Japanese Patent Application Laid-Open No. 8-35018 discloses that
A method for recovering metal from fly ash containing chlorine generated by burning waste as immobilized as CaCl ₂ ,
a) heating the fly ash in an oxidizing atmosphere while applying a shearing force to cause chlorine and hydrogen chloride generated by the decomposition of CaCl ₂ to react with the metal component contained in the fly ash; Disclosed is a method for recovering metals from fly ash, which comprises dissolving and recovering volatile metal chlorides by contacting with an absorbing solution, and c) separately recovering dissolved metals from the obtained recovered solution.

However, recovery of metal from the fly ash
The method is based on CaCl contained in fly ash. _TwoUsing this C
aCl_TwoSuch as chlorine and hydrogen chloride obtained by decomposing
The elementary gas reacts with the metal component.
aCl_TwoIs a stable chloride, usually 600 to 1
Does not decompose at 000 ° C and does not generate chlorine or hydrogen chloride
The effect of removing heavy metals is not so high
There is a point. This is because this method is called so-called chlorination roasting.
Roasted with chlorides in an oxidizing atmosphere
Each time even at a temperature of 600 to 1000 ° C.
Seed oxide and CaCl_TwoReacts with chlorine, hydrogen chloride, etc.
Occurs but heats up to higher temperatures under other conditions
CaCl if not_TwoDoes not decompose. Accordingly
Therefore, this method has a sufficient effect unless it is in an oxidizing atmosphere.
It is not expected. Also at lower temperatures metal
If chloride can be volatilized,
Reaction with silicon oxide such as iodine can be suppressed
Not only improve energy efficiency,
Desirable.

The present inventor has focused on calcium hydroxide contained in incinerated ash for the purpose of solving such a problem in volatilizing and removing such heavy metals as chlorides. Or a first step of kneading fly ash together with moisture, and heating the kneaded material to a temperature of 400 ° C. or less in the presence of a chloride which is decomposed at a temperature of 400 ° C. or less to incinerate ash or fly ash Detoxification treatment of incinerated ash or fly ash comprising a second step of converting heavy metals contained therein into metal chlorides and a third step of raising the temperature to 1100 ° C. to volatilize and recover the metal chlorides According to this method (Japanese Patent Application Laid-Open No. 10-20221), a heavy metal is converted into a hydroxyl compound and then reacted with chlorine to improve the chlorination rate and to produce a compound having a high boiling point such as silicon oxide. Curb as much as possible Heavy metals has become possible to efficiently evaporate and remove. However, in this method 85
Since the heavy metal chlorides are volatilized and removed by heating to 0 to 1100 ° C., it is desirable to be able to volatilize the heavy metal chlorides at a lower temperature in order to improve energy efficiency.

SUMMARY OF THE INVENTION The present invention has been made in view of these problems, and has as its object to provide a processing method for removing heavy metals from incinerated ash or fly ash easily and with high efficiency to render them harmless. .

[0013]

Means for Solving the Problems In view of the above objects, the present inventors have conducted intensive studies and as a result, the volatilization of chloride after converting heavy metals into chloride tends to be easily affected by other salts. , Lead chloride has a boiling point of about 950 ° C, and sodium chloride and calcium chloride have a high boiling point of 1400 ° C or more, but high boiling points such as sodium chloride and calcium chloride are contained in incineration ash or fly ash. It has been found that when a large amount of salts is contained, chlorides of heavy metals such as lead chloride do not volatilize sufficiently unless heated to a temperature range exceeding 950 ° C. due to the effect. On the other hand, tin chloride, zinc chloride, and the like have boiling points in a relatively low temperature range of 600 to 750 ° C, but when these low-boiling chlorides and heavy metal chlorides coexist, the low-boiling chlorides are When the temperature near the boiling point is reached and it begins to volatilize actively, the chlorides of heavy metals also begin to co-evaporate actively, and as a result, the chlorides of heavy metals complete volatilization at a temperature lower than the boiling point. I understood. Further, the present inventor studied the relationship between chlorides of heavy metals, high boiling salts such as sodium chloride and calcium chloride, and low boiling salts such as tin chloride and zinc chloride. In order to volatilize vigorously, it is desirable that high-boiling salts such as sodium chloride and calcium chloride do not exist.
It was found that the effect of lowering the boiling point of heavy metals could not be obtained, and therefore, when this was insufficient, it was sufficient to add them. Based on these, the present invention has been completed.

The detoxifying method for incinerated ash or fly ash according to claim 1 of the present invention is a detoxifying method for removing heavy metals from incinerated ash or fly ash, wherein the incinerated ash is chlorine,
A chlorination step of kneading in the presence of a chlorine compound or chloride ion to make heavy metals contained in the incinerated ash or fly ash and a zinc compound and / or a tin compound as chlorides, and a kneaded product of the incinerated ash Is heated to 600 to 900 ° C. to volatilize and remove chlorides of heavy metals together with zinc chloride and / or tin chloride.

Further, in the method for detoxifying incinerated ash or fly ash according to claim 2, the incinerated ash or fly ash contains an alkali metal compound and an alkaline earth metal compound according to claim 1. In the chlorination step, the alkali metal compound and the alkaline earth metal compound become alkali metal chlorides and alkaline earth metal chlorides, and the zinc chloride and / or tin chloride is at least 8% based on the total amount of these chlorides. Things.

According to a third aspect of the present invention, there is provided the method for detoxifying incinerated ash or fly ash according to the second aspect, wherein the zinc ash and / or tin chloride is added to the incinerated ash so as to be 8% or more (by weight). A zinc compound and / or a tin compound is added.

Further, the method for detoxifying incinerated ash or fly ash according to claim 4 is provided by any one of claims 1 to 3.
In the above item, the chlorination step is to knead the incinerated ash or fly ash by adding an aqueous solution of iron chloride.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the method for detoxifying incinerated ash or fly ash of the present invention will be described in detail. The incineration ash to be treated in the present invention is referred to as bottom ash remaining at the bottom of the incinerator, and has a lower content of harmful substances such as heavy metals than fly ash described later. This incineration ash is not limited to that generated at urban garbage incineration plants,
Includes all incinerated ash containing heavy metals such as incineration ash generated in groundwater treatment plants and sewage sludge treatment plants, and those generated from industrial waste treatment plants. In the present invention, fly ash means that low-boiling substances in various components of the garbage volatilize when the garbage is incinerated, and this is collected by a filter or the like. ), Mercury (H
g) and other harmful heavy metals. Since this fly ash is collected by a bag filter or the like carrying slaked lime, its components contain a large amount of slaked lime or a neutralizing agent such as calcium chloride. Such incinerated ash or fly ash contains, in addition to heavy metals (their compounds), alkali metal salts such as sodium chloride and alkaline earth metal salts, and transition metal elements such as tin, zinc and iron. are doing. The present invention relates to tin, zinc,
Ingredients such as iron are used as chlorides. Note that zinc is sometimes classified as a heavy metal. In the present specification, zinc is excluded from the heavy metals for convenience of explanation. However, in any case, there is no problem since this is also removed from incineration ash or fly ash.

In the present invention, in the chlorination step, incinerated ash or fly ash is first kneaded in the presence of chlorine, chlorine compound or chloride ion, and heavy metals contained in the incinerated ash or fly ash are mixed with zinc compound. And transition metal compounds such as tin compounds are chlorides.

In this chlorination step, as a pretreatment, water is added to incinerated ash or fly ash as it is, or when the amount of calcium hydroxide contained therein is insufficient such as incinerated ash, it is necessary. Kneading is performed after appropriately adding calcium hydroxide accordingly. It is not necessary to use pure water or clean water as the water, and it may be sewage or steam as long as it can wet incineration ash or fly ash. When the incinerated ash or fly ash is kneaded with water in the presence of calcium hydroxide in this way, the heavy metals, oxides and sulfides in the incinerated ash or fly ash react rapidly with calcium hydroxide. Thus, hydroxides and basic carbonates of heavy metals are formed. For example, the following reaction occurs between lead sulfate and calcium hydroxide.

PbSO ₄ + Ca (OH) ₂ → CaSO ₄ + Pb (OH) ₂ Other heavy metals also react with calcium hydroxide to form hydroxides by a similar reaction. Further, compounds of transition metals such as zinc and tin also become hydroxides. In addition, since all of these metal compounds easily react with a hydroxyl group, this reaction proceeds very efficiently.

The mixing ratio of incineration ash or fly ash and water in this pretreatment is not particularly limited as long as it can be kneaded.
3 to 100 moisture per 100 parts by weight of incinerated ash or fly ash
The weight may be used. If the water content is less than 3 parts by weight, sufficient kneading properties and the effect of hydroxylating heavy metals cannot be obtained.
If the amount is more than 00 parts by weight, the water content becomes too large, and the efficiency in the heating step described later decreases. In the case of wet ash (moist ash), it can be used as long as the ratio of moisture to incinerated ash or fly ash is within the above range. Should be performed.

Then, chloride or chlorine-based gas is supplied to the incinerated ash or fly ash which has been subjected to such a pretreatment as necessary, and is reacted with a heavy metal compound or a transition metal element compound. As the chloride, for example, iron chloride can be used. The iron chloride may be added as it is, but since it has high solubility in water, if it is dissolved in water and converted to chloride ions, it reacts with heavy metal compounds or transition metal compounds in incinerated ash or fly ash. The performance is improved. When this aqueous iron chloride solution is used, the above-described pretreatment and chlorination can be continuously performed in the same step.

Heavy metals, zinc, tin, and the like rapidly react with chloride ions from the aqueous solution of iron chloride and the like to form chlorides even at a low temperature. In particular, when the above-mentioned pretreatment is performed, the following reaction occurs between heavy metals and chloride ions.

M (OH) ₂ + (H ++ Cl ⁻ ) → MCl ₂ + 2H ₂ O (where M is a heavy metal such as Pb, Cd, As, and Cu, and Zn and Sn). It is also possible to use a chloride which decomposes at a temperature of 400 ° C. or lower so that a reaction between the compound and silicon oxide such as silicon dioxide does not occur. Examples of the chloride that decomposes at a temperature of 400 ° C. or lower include, for example, ammonium chloride, aluminum chloride,
Chlorinated paraffin, chlorinated polyethylene, vinyl chloride,
Vinylidene chloride or the like can be used. In the case of high-molecular chlorides such as chlorinated polyethylene, vinyl chloride, and vinylidene chloride, it is not necessary to use unused ones, and waste products may be used. This polymer chloride is
When performing the above-mentioned pretreatment, it may be added before or during kneading with water.

The above-mentioned chloride compounding ratio is 1 to 5 in terms of chlorine with respect to 100 parts by weight of incinerated ash or fly ash.
It is about parts by weight. If the amount of chloride is less than 1 part by weight, it will be difficult to sufficiently chlorinate a heavy metal compound or a transition metal compound as described later, while if it exceeds 5 parts by weight, no more effect will be obtained. However, it is not preferable because the amount of unreacted chlorine increases in the heat removal step described below.

Instead of heating the chloride to generate chlorine gas, a chlorine-based gas may be directly introduced. The chlorine-based gas is, for example, chlorine gas or hydrogen chloride gas, and may further contain other gaseous impurities. For example, exhaust gas from an incinerator contains a large amount of chlorine gas and hydrogen chloride gas. Therefore, this may be introduced. Also in this case, heating is performed to about 400 ° C. or less, preferably to about 200 to 400 ° C.

By kneading while heating in the presence of chloride as necessary in this way, a compound of a heavy metal or a compound of a transition metal can be converted to a chloride. In particular, when pretreatment is performed, the following reaction occurs between heavy metals and hydrogen chloride gas or chlorine gas.

M (OH) ₂ + 2HCl → MCl ₂ + 2H ₂ O 2M (OH) ₂ + 2Cl ₂ → 2MCl ₂ + 2H ₂ O + O ₂ As a result, heavy metal chlorination occurs during incineration ash or fly ash after the chlorination step. And chlorides of zinc and tin, which are transition metal elements. In addition, since calcium oxide and calcium hydroxide are also chlorinated to form calcium chloride, chlorides of alkaline earth metals such as calcium chloride also exist, and alkali metal chlorides such as sodium chloride also exist. Become. The boiling points of these three chlorides are as follows: (1) sodium chloride is 1
413 ° C., potassium chloride of 1500 ° C. and calcium chloride of 1500 ° C. or more, (2) heavy metals of about 900 to 1
000 ° C (eg, 950 ° C for lead chloride and 960 ° C for cadmium chloride), (3) 732 ° C for zinc chloride and 623 ° C for tin chloride. That is, these three types of chlorides are (1) those having a boiling point in a temperature range of about 1400 to 1500 ° C or higher, (2) those having a boiling point in a temperature range of about 900 to 1000 ° C, and (3) 600 to 600 ° C. 800 ° C
And those having a boiling point in the temperature range described above.

Next, in the heat removal step, the chlorinated incinerated ash or fly ash is heated to 600 ° C. to 900 ° C., preferably while gradually increasing the temperature from the chlorination step. Then, in this temperature range, zinc chloride (732
C) and tin chloride (623 ° C.) should volatilize actively. With the volatilization of these salts, other salts, especially chlorides of heavy metals, also start to volatilize actively. This volatilization continues until the salts of heavy metals disappear. In this way, heavy metals can be volatilized and removed at a temperature lower than the boiling point.

The reason for obtaining such an effect is that the vapor pressure drops due to the volatilization of zinc chloride and tin chloride, and that heavy metals and these salts form a complex salt, and this complex salt volatilizes at a low temperature. That is, it is presumed that salts having different boiling points are mutually related. Therefore, if an alkali metal salt or an alkaline earth metal salt is present, these are naturally involved. And since these salts have a very high boiling point, they act to counteract the effect of the lowering of the boiling point by zinc chloride and tin chloride, which may hinder the lowering of the boiling point of heavy metals. Therefore, it is concluded that it is desirable that no alkali metal salt or alkaline earth metal salt be present. However, the fly ash inevitably mixes in fly ash according to its collection method. Therefore, when an alkali metal salt or an alkaline earth metal salt is present, it is sufficient if zinc chloride and tin chloride are at least 8% by weight based on a total of 100% by weight of the incinerated ash or fly ash. The effect can be expected.

The amount of the alkali metal salt or alkaline earth metal salt in the incinerated ash or fly ash can be determined by analyzing the components of the incinerated ash or fly ash (raw ash) before the treatment and determining the amount of sodium and calcium contained therein. And the like are mostly chlorides, which can be determined by converting the total amount to chlorides. Further, the total amount of zinc chloride and tin chloride can also be determined by converting the total amount of zinc and tin contained in the raw ash to chloride. As a result, when the total amount of zinc chloride and tin chloride is less than 8% by weight, a zinc compound or a tin compound is added to the incinerated ash or fly ash before the chlorination treatment step, or the incineration before the volatilization removal step is performed. Zinc chloride and tin chloride may be added to ash or fly ash.

After removing heavy metals in this way,
Since the remaining incinerated ash or fly ash is rendered harmless, it can be used as a filler (fine aggregate) such as asphalt as it is. In addition, this incinerated ash or fly ash is
By heating to about 0 to 1600 ° C., a slag having a very low content of heavy metals can be obtained. For this reason, even if this incineration ash or fly ash or slag is mixed with Portland cement, sand, gravel, etc. to form a concrete block or a roadbed material, the outflow of harmful substances is small.

According to the method of the present invention as described above, heavy metals in incinerated ash or fly ash can be removed at a low temperature of 600 to 900 ° C., which is lower than that of the conventional method. Energy efficiency can be improved, and its removal is easy. In addition, since the heat removal step can be performed at a low temperature, a general-purpose material can be used, which is also excellent in this respect.

Although the method for detoxifying incinerated ash or fly ash of the present invention has been described above, the present invention is not limited to this, and various modifications can be made without departing from the spirit of the present invention. For example, if the incinerated ash or fly ash contains a large amount of alkali metal or alkaline earth metal, it may be converted into chloride and then eluted in water to reduce its content.

[0036]

The present invention will be described in more detail with reference to the following specific examples. Examples 1 to 3 An aqueous solution of ferric chloride having a concentration of 50% by weight (100 parts by weight of ferric chloride dissolved in 100 parts by weight of water) was dissolved in fly ash (raw ash) having the composition shown in Table 1. It was added until the pH became 2, and kneaded well. The components after heating this kneaded product at 850 ° C. for 1 hour under reduced pressure were measured (Example 1). The results are shown in Table 1. In addition, most of the calcium in the raw ash in Table 1 is calcium oxide, calcium chloride, and calcium hydroxide, and these are mostly calcium chloride in the chlorination step. The fly ash after this treatment was subjected to a dissolution test (measured by the method specified in Notification No. 46 of the Environment Agency). The results are shown in Table 1 together with the results for the raw ash.

The raw ash (100 g) to which 0.5 g of lead oxide and 50 ml of arsenic standard solution were added (Example 2), and the zinc oxide (0.5 g) added to Example 2 (Example 2) Table 3 shows the component compositions and the results of the dissolution tests after the same treatment as in Example 1 was performed for 3).

[0038]

[Table 1]

As is clear from Table 1, by applying the treatment of the present invention to fly ash, all of the contents of lead, arsenic, and cadmium in the treated fly ash and the amount of elution are greatly reduced. Was confirmed.

[0040]

The method for detoxifying incinerated ash or fly ash according to claim 1 of the present invention is a detoxifying method for removing heavy metals from incinerated ash or fly ash, wherein the incinerated ash is chlorine, A chlorination step of kneading in the presence of a chlorine compound or chloride ion to make heavy metals contained in the incinerated ash or fly ash and a zinc compound and / or a tin compound as chlorides, and a kneaded product of the incinerated ash Is heated to 600 to 900 ° C. to remove volatile salts of heavy metals together with zinc chloride and / or tin chloride by heating. Thus, heavy metals can be removed below its boiling point. Thereby, the improvement and simplification of the removal efficiency of heavy metals are achieved.

According to a second aspect of the present invention, there is provided the method for detoxifying incinerated ash or fly ash, wherein the incinerated ash or fly ash contains an alkali metal compound and an alkaline earth metal compound. In the chlorination step, the alkali metal compound and the alkaline earth metal compound become alkali metal chlorides and alkaline earth metal chlorides, and the zinc chloride and / or tin chloride is at least 8% based on the total amount of these chlorides. Therefore, volatilization and removal of heavy metals can be performed at lower temperature.

According to a third aspect of the present invention, there is provided the method for detoxifying incinerated ash or fly ash according to the second aspect, wherein the incinerated ash contains a zinc compound and / or tin so that the zinc chloride and / or tin chloride is 8% or more. Alternatively, since a tin compound is added, the heavy metals can be volatilized and removed at a low temperature even when the amount of alkali metal chloride and alkaline earth metal chloride is large.

Further, the method for detoxifying incinerated ash or fly ash according to claim 4 is provided by any one of claims 1 to 3.
In the above item, since the chlorination step involves adding and kneading an aqueous solution of iron chloride to incineration ash or fly ash, heavy metals can be efficiently converted to chlorides without heating.

Claims (4)

[Claims] 1. A detoxification method for removing heavy metals from incinerated ash or fly ash, wherein the incinerated ash or fly ash is kneaded in the presence of chlorine, a chlorine compound or chloride ions, and the incinerated ash or fly ash is kneaded. A chlorination step in which the heavy metals and zinc compound and / or tin compound contained in the fly ash are chlorides, and the kneaded incineration ash or fly ash is heated to 600 to 900 ° C. to produce zinc chloride and / or chloride. A heat removal step of volatilizing and removing chlorides of heavy metals together with tin. A method for detoxifying incinerated ash or fly ash. 2. The incinerated ash or fly ash contains an alkali metal compound and an alkaline earth metal compound, and in the chlorination step, the alkali metal compound and the alkaline earth metal compound are an alkali metal chloride and an alkaline earth metal. 2. A method for detoxifying incinerated ash or fly ash according to claim 1, wherein said zinc chloride and / or tin chloride is 8% or more of the total amount of said metal chlorides. 3. The zinc chloride and / or tin chloride is 8%
The method for detoxifying incinerated ash or fly ash according to claim 2, wherein a zinc compound and / or a tin compound are added to the incinerated ash as described above. 4. The chlorination step comprises adding an aqueous solution of iron chloride to incineration ash or fly ash and kneading the mixture.
4. The method for detoxifying incinerated ash or fly ash according to any one of claims 3 to 3.