JP2000308868A - Method and apparatus for treating fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for treating fly ash capable of making the fly ash containing organohalogen compounds harmless at a low cost and at a high level. SOLUTION: This fly ash treating method comprises a step to generate the gas containing organohalogen compounds which are vaporized by adding 0.1-1.0 wt.% sodium hydroxide and 1-30 wt.% water to the fly ash containing organohalogen compounds and heating the fly ash thus prepared to 400-500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fly ash treatment method and a fly ash treatment apparatus, and more particularly to a fly ash treatment method and a treatment apparatus containing an organic halogen compound.

[0002]

2. Description of the Related Art Exhaust gas generated in the process of incinerating municipal solid waste or industrial waste and exhaust gas discharged when preheating and melting scrap containing flammable deposits in a metal smelting plant are various. It contains dust, ie fly ash, as well as harmful components. This fly ash is usually composed of highly toxic organic halogen compounds such as dioxins, dioxin precursors such as chlorobenzene and chlorophenol,
Furthermore, it contains harmful heavy metals such as mercury, and is collected by dust collectors in municipal waste incineration facilities and flammable waste treatment facilities.

[0003] As a method for detoxifying an organic halogen compound in fly ash, there are known an incineration method, a melting method, an oxidative decomposition method using a chemical, a heat decomposition method, and the like. For example, Japanese Patent Publication No. Hei 6-38863 discloses that a fly ash does not pass through a fly ash system at 200 to 550 ° C. in an oxygen-deficient state.
To decompose organic halogen compounds such as dioxins by heating. Also, Japanese Patent Application Laid-Open No. 2-784
No. 79 discloses a method of decomposing dioxins by providing a heating means in a stagnant portion filled with fly ash and heating to 300 ° C. or more.

However, these conventional methods have the following problems. That is, according to the incineration method, fly ash is generally removed by kiln or fluidized bed method.
Dioxins are decomposed by heating at a temperature between 00 and 1200 ° C. However, fly ash has a low combustible content and cannot be self-combusted, requiring an extremely large amount of external energy. Further, according to the incineration combustion method, the process of combustion exhaust gas including NO _x is required separately.

According to the melting treatment method, dioxins are decomposed by heating fly ash to 1300 ° C. or higher. That is, in the melting treatment method, the treatment is performed at a higher temperature than in the incineration treatment method, and therefore, more external energy is required. Furthermore, according to the melting treatment method, heavy metals such as Cd and Pb are volatilized, so that a separate treatment of the molten exhaust gas is required.

[0006] The oxidative decomposition treatment using a chemical is expensive because the chemical is generally expensive. In addition, a sufficiently high dioxin decomposition rate has not yet been realized by this method.

A heat treatment method, for example, the above-mentioned Japanese Patent Publication No. 6-38
According to the method disclosed in Japanese Patent No. 863, dioxins can be decomposed without requiring extremely high temperatures or expensive chemicals. However, on the other hand, there is a problem that a large amount of nitrogen gas or the like is required to form an oxygen-deficient state. According to this method, the heat treatment is performed at 200 to 550 ° C.
It has been found that dioxins are resynthesized at 200 to 350 ° C. Therefore, it is difficult to reliably remove dioxins according to the above method.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a fly ash treatment method and a fly ash treatment method capable of detoxifying fly ash containing an organic halogen compound at low cost. It is an object to provide a fly ash treatment device.

Another object of the present invention is to provide a fly ash treatment method and a fly ash treatment apparatus capable of detoxifying fly ash containing an organic halogen compound at a high level.

[0010]

In order to solve the above problems, the present invention provides a fly ash containing an organic halogen compound,
400% with 0.1 to 1.0% by weight of sodium hydroxide for fly ash and 1 to 30% by weight of water for fly ash
A fly ash treatment method comprising a step of heating to 500 ° C. to volatilize an organic halogen compound from the fly ash and generating a gas containing the volatilized organic halogen compound.

[0011] The present invention also provides a method of heating fly ash containing an organic halogen compound together with sodium hydroxide and water to volatilize the organic halogen compound from the fly ash and generate a gas containing the volatile organic halogen compound. Provided is a fly ash treatment device comprising a heating means and a detoxification treatment means for detoxifying the gas.

The organic halogen compounds referred to in the present invention include dioxins, dioxin precursors, chlorobenzene, chlorophenol, and so on, which are designated by the Ministry of Health and Welfare as guidelines for garbage treatment plants based on toxic conversion values. And PCBs, and those obtained by substituting chlorine atoms of these chemical substances with other halogen atoms. Further, dioxins are a general term for polydibenzoparadioxin and polydibenzofuran, which are usually evaluated based on the concentration in terms of toxicity.

[0013] The present inventors have investigated fly ash containing organic halogen compounds, particularly dioxins.
When fly ash is heat-treated in a temperature range of 350 to 500 ° C,
Some of the dioxins contained in the fly ash are volatilized without being decomposed, and the rest are thermally decomposed and dechlorinated or reduced in molecular weight. It has been found that the dioxin exists as a dioxin precursor which is easily converted into dioxins, and that the molecular weight is not further reduced. Such a fact indicates that when the heat treatment is performed in a non-through flow system (closed system), even if the heating temperature is set to 350 to 500 ° C. where resynthesis of dioxins hardly occurs, volatile dioxins or dioxins are not used. This indicates that it is difficult to remove dioxins at a high level because the precursors are re-adsorbed to fly ash.

Further, for example, if the heating temperature is 350 to 500
Even in the case of ℃, it is inevitable to pass through a temperature range of 200 to 350 ° C., which is considered to cause resynthesis of dioxins in the process of raising and cooling fly ash. Therefore, fly ash should be collected in a closed system.
In the case of heating to 50 to 500 ° C., in the heating / heating process, the concentration of dioxin temporarily increases, causing a problem that the heat treatment requires a long time. Further, as described above, according to such a method, the dioxin precursor cannot be completely removed from the fly ash, so that the dioxins are resynthesized in the cooling process.

On the other hand, according to the present invention, fly ash is heated to 400 to 500 ° C. together with sodium hydroxide and water. As described above, when fly ash is heated to 350 ° C. or more, it is inevitable that the fly ash will pass through a temperature range of 200 to 350 ° C. However, according to the present invention, since sodium hydroxide reacts with chlorine and water turns into steam to prevent contact between fly ash and oxygen, resynthesis of dioxins is suppressed.

Further, sodium hydroxide promotes dechlorination of dioxins. Since dioxins are dechlorinated to lower their boiling points, sodium hydroxide is added to volatilize dioxins more easily, that is, remove dioxins from fly ash at a high level. It becomes possible.

In the present invention, dioxins are volatilized from fly ash by heating the fly ash to 400 to 500 ° C. When the heating temperature is 200 ° C. or lower, dioxins and their precursors, such as chlorobenzene, can hardly be volatilized from fly ash. When the heating temperature is 350 ° C. or higher, dioxins and their precursors can be volatilized, but cannot be volatilized with sufficient efficiency. Further, as described above, the resynthesis of dioxins can be prevented by setting the heating temperature to 350 ° C. or higher, but in a practical apparatus, a temperature distribution is formed in the apparatus. Therefore, even if the heating temperature is set to 350 ° C. or higher, the local
When the temperature becomes lower than 50 ° C., dioxins may be resynthesized.

On the other hand, when the heating temperature is set to 400 ° C. or higher, dioxins can be volatilized with sufficient efficiency, and even in a practical apparatus, 350 ° C.
It does not become less than. Therefore, by performing the heat treatment while removing the gas containing the volatile organic halogen compounds from the fly ash, not only can the dioxins be efficiently removed from the fly ash, but also the resynthesis of dioxins can be achieved. It becomes possible to suppress.

When the heating temperature is excessively high, the inorganic low melting point compound contained in the fly ash is melted, and the fly ash is fixed in the apparatus. In such a case, there arises a problem that the transport of fly ash becomes difficult or more energy is required for heating. On the other hand, when the heating temperature is 500 ° C. or lower, the low melting point compound contained in the fly ash hardly melts. Therefore, it is possible to prevent the above-described problem from occurring.

As described above, according to the present invention, dioxins and dioxin precursors are removed at an extremely high level in the heating / heating process, so that dioxins are hardly resynthesized in the cooling process. That is, according to the present invention, it is possible to detoxify fly ash at a high level.

The heating of fly ash in the present invention is 400
Since the operation is performed at a relatively low temperature of about 500 ° C., a large amount of energy is not required. Further, the chemicals used for this detoxification treatment are inexpensive and small amounts are sufficient.
Further, since the amount of the organic halogen compound volatilized from the fly ash is small, a large-scale facility is not required to detoxify the gas containing the volatile organic halogen compound. Therefore, according to the present invention, it is possible to detoxify fly ash at low cost.

In the present invention, the fly ash is preferably heated by indirect heating using an electric heater or the like. According to the direct heating using hot air or the like, a hot air generator is required, and fly ash having a small particle diameter may fly and be exhausted together with the gas.

In the method of the present invention, the added amount of sodium hydroxide is 0.1 to 1.0% by weight based on fly ash. If the amount of sodium hydroxide added is less than 0.1% by weight, the effect of adding sodium hydroxide may hardly be obtained. The effect of adding sodium hydroxide is saturated at about 1.0% by weight. Therefore, when the amount of sodium hydroxide added is 0.1 to 1.0% by weight, a sufficient effect can be obtained with a relatively small amount of sodium hydroxide consumed.

In the method of the present invention, the amount of water to be added is 1 to 30% by weight based on fly ash. If the amount of water added is less than 1% by weight, it is difficult for the water vapor to uniformly spread over the fly ash, and the effect of preventing contact between the fly ash and oxygen may be insufficient. The effect of adding water saturates at about 30% by weight. Since the energy required for heating increases as the added amount of water increases, a sufficient effect can be obtained with a relatively low energy consumption when the added amount of water is 1 to 30% by weight.

It is preferable to add the above-mentioned sodium hydroxide and water to the fly ash as an aqueous sodium hydroxide solution. In this case, sodium hydroxide and water are not unevenly distributed in the fly ash. Therefore, the above-described effects can be obtained more reliably. The addition of sodium hydroxide and water to the fly ash may be performed simultaneously with the heating of the fly ash, or may be performed prior to the heating of the fly ash. When sodium hydroxide and water are added to the fly ash prior to the heating of the fly ash, they can be uniformly mixed.

In the present invention, it is preferable to flow a volatilization promoting gas when heating fly ash and the like. When the volatilization promoting gas is allowed to flow, it is possible to prevent the organic halogen compound such as dioxin volatilized from the fly ash by the heat treatment from remaining in the heating means such as a heater and being adsorbed to the fly ash again. Further, the volatile organic halogen compound can be quickly separated from the fly ash, and the evacuation from the heating means to the detoxification processing means can be promoted.

As the volatilization promoting gas, it is preferable to use a gas containing no chlorine or chlorine compound. When a combustion exhaust gas containing, for example, HCl is used as the volatilization promoting gas, re-synthesis of dioxins or synthesis of a dioxin precursor may occur by a chlorination reaction in the heating means. On the other hand, when a gas containing no chlorine or chlorine compound is used as the volatilization promoting gas, the above-described effects can be obtained without resynthesizing dioxins or synthesizing a dioxin precursor.

As the volatilization promoting gas containing no chlorine or chlorine compound, for example, nitrogen, air, water vapor and the like can be mentioned. In addition, since air contains oxygen, it is considered that dechlorination of dioxins is hindered. However, usually, the volatilization promoting gas is circulated to the upper layer of the fly ash, and since the water heated together with the fly ash stays near the surface of the fly ash as water vapor, the direct contact between the fly ash and oxygen hardly occurs. Absent. Therefore, even when air is used as the volatilization promoting gas, the dechlorination of dioxins is hardly hindered.

The gas containing the volatile organic halogen compound, that is, the tail gas, may be exhausted from the heating means together with fly ash having a small particle diameter. In such a case,
Prior to the detoxification treatment, it is preferable to remove solids from the tail gas by a dust collecting means such as a dust collector. According to the dust collector using an appropriate bag filter, not only solids but also dioxins can be removed from the tail gas. The removal of solids from the tail gas may be performed by a dust collector of ancillary equipment for processing waste or the like, or may be performed by a separately provided dust collector.

The detoxification treatment of the organic halogen compound contained in the tail gas can be performed by using a combustion means, a catalyst decomposition means and the like. For example, when using a combustion means, the tail gas can be supplied to a combustion means such as an incinerator and thermally decomposed at a temperature of 800 ° C. or more to easily detoxify the gas.

The detoxification of the tail gas may be performed by a combination of the combustion means and the catalytic decomposition means. In other words, after the tail gas is subjected to catalytic decomposition treatment to decompose and remove the organic halogen compound, combustion treatment may be performed. When the incinerator of ancillary equipment, for example, an incinerator that burns waste and generates fly ash, is used for the combustion of tail gas, the burden on the incinerator is increased by performing catalytic decomposition prior to tail gas combustion. Can be reduced, and the concentration of the organic halogen compound can be prevented from increasing due to the circulation of the organic halogen compound between the incinerator and the heater.

The above-mentioned tail gas may contain mercury as well as organic halogen compounds and fly ash having a small particle size. In such a case, it is preferable that the mercury is removed from the tail gas by the mercury removing means, and then the volatilized organic halogen compound is detoxified. For example, when the incinerator of ancillary equipment is shared for the combustion process, or when the dust collector of the ancillary equipment is shared for removing solids from the tail gas, mercury is removed from the tail gas in advance, so that the mercury and the heater are removed. It is possible to prevent the mercury concentration from circulating between and increasing.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. In each of the drawings, common members and the like are denoted by the same reference numerals, and redundant description will be omitted. FIGS. 1 to 4 are diagrams schematically showing fly ash treatment apparatuses according to first to fourth embodiments of the present invention, respectively. FIG. 5 is a diagram schematically showing a general waste incineration facility. Before describing the fly ash treatment apparatus according to the embodiment of the present invention, first, a waste incineration facility shown in FIG. 5 will be described.

According to the refuse incineration equipment shown in FIG. 5, refuse incineration is performed in the incinerator 21. From incinerator 21,
Exhaust gas having a high temperature of 800 ° C. or more is exhausted to the boiler 22, where heat recovery of the exhaust gas is performed. The exhaust gas heat recovered by the boiler 22 is cooled to a predetermined temperature in a cooling tower 23 and then supplied to a bag filter 24.

The exhaust gas from the cooling tower 23 contains nitrogen oxides and
HCl and SO in addition to dust and fly ash _xAcidic components like
It contains. According to the waste incineration equipment shown in FIG.
When supplying gas to the bag filter 24, the slaked lime supply device
Neutralization of acidic components by spraying slaked lime from storage 26
Is performed. In addition, fly ash in the exhaust gas
And the nitrogen oxides are removed as required by the catalytic denitration tower 25.
Is removed by

The fly ash collected by the bag filter 24 is transported to the fly ash silo 1 by a fly ash discharge conveyor (not shown) and is temporarily stored. The fly ash contains organic halogen compounds such as highly toxic dioxins, dioxin precursors such as chlorobenzene and chlorophenol, and harmful heavy metals such as mercury.

According to the fly ash processing apparatus shown in FIGS.
Such fly ash detoxification processing is performed. First, a fly ash processing method according to a first embodiment of the present invention will be described with reference to FIG.

The fly ash temporarily stored in the fly ash silo 1 is conveyed to the addition kneader 2. The addition kneader 2 serves both as an addition unit for adding a predetermined amount of an aqueous solution of caustic soda (NaOH) to fly ash and as a kneading unit for kneading them. The addition of the aqueous caustic soda solution to the fly ash may be performed, for example, by atomizing the aqueous caustic soda solution using a spray nozzle and spraying the fly ash, or may be performed by spraying the aqueous caustic soda solution in a liquid state. Good. The kneading of the fly ash and the aqueous solution of caustic soda can be performed using a known mechanical kneader such as a stirrer having a rotating blade or a kiln type kneader.

Next, the kneaded mixture of the aqueous solution of caustic soda and fly ash is conveyed to the heater 3 as a heating means, and is heated to a temperature of 400 to 500 ° C. by an external indirect heating means such as an electric heater. The heating method of the heater 3 is not particularly limited, but fly ash may be scattered by direct heating using hot air. Therefore, it is desirable to adopt an external heating method using an electric heater, an indirect heating method using heat exchange, or the like. The heater 3 desirably has a conveying means such as a screw type, a rotary type, and a bucket type.

The supply of the fly ash and the aqueous solution of caustic soda to the heater 3 may be a continuous type or a batch type as long as the fly ash can be heated to 400 to 500 ° C. The time required for heating depends on the heating method, the shape of the heater 3, the specific heat of fly ash, the thermal conductivity of the heat medium, and the like, and is appropriately determined in consideration of these factors. Usually, by setting the residence time at a temperature of 400 to 500 ° C. to be 5 minutes or more,
The organic halogen compound can be sufficiently volatilized.

By the heat treatment in the heater 3, an organic halogen compound such as dioxins volatilizes together with other volatile substances from the kneaded material. Exhausted from 3 The induction fan 6 is a separating unit that separates tail gas from fly ash.

As described above, fly ash is heated to 400 to 500 ° C.
In the process of heating to 200 ° C., it is inevitable to pass through a temperature range of 200 ° C. to 350 ° C. where resynthesis of dioxins occurs. However, according to the above method, fly ash is kneaded with an aqueous solution of caustic soda, so that caustic soda reacts with chlorine, and water becomes water vapor to prevent contact between the fly ash and oxygen. Is suppressed.
Further, since caustic soda promotes the dechlorination of dioxins, the above method makes it possible to volatilize dioxins more easily, that is, to remove dioxins from fly ash at a high level.

A small amount of tail gas exhausted from the heater 3 is exhausted to the outside A through, for example, a detoxification processing device 5 as detoxification processing means. Known devices such as a dust collector, a cooling device, an exhaust gas cleaning device, a mercury recovery device, a catalytic decomposition device, and an activated carbon moving bed,
And combinations of these devices. Since the amount of tail gas exhausted from the heater 3 is very small, a small-sized detoxifying apparatus 5 is sufficient.

It is not always necessary to provide the detoxifying device 5. When the fly ash treatment apparatus shown in FIG. 1 is installed in a refuse incineration facility or the like, for example, as shown as A1 in FIG. 5, a tail gas from the heater 3 may be supplied to the incinerator 21. In this case, the incinerator 21 and the bag filter 24
Are used as detoxifying means. Also, FIG.
, The tail gas from the heater 3 may be merged into the flue upstream of the bag filter 24. In this case, the bag filter 24 is used as detoxification processing means.

On the other hand, fly ash from which organic halogen compounds and other volatile substances have been removed is stored in a fly ash bunker 7. The fly ash stored in the fly ash bunker 7 is usually landfilled or subjected to a known treatment such as a heavy metal stabilization treatment as necessary.

The fly ash from which the organic halogen compounds and the like have been removed may be cooled by a cooling means or a waste heat recovery means while being transported from the heater 3 to the fly ash bunker 7. Alternatively, the ash may be allowed to cool naturally in the fly ash bunker 7 without cooling during the transportation. That is, cooling of fly ash may be either rapid cooling or slow cooling. This is because, as described above, fly ash discharged from the heater 3 is free of organic halogen compounds and other volatile substances, so that resynthesis of dioxins occurs in the process of cooling the fly ash. This is because the dioxins are not resynthesized even after passing through a temperature range of 200 to 350 ° C.

Next, a method for treating fly ash according to a second embodiment of the present invention will be described with reference to FIG. The fly ash treatment apparatus shown in FIG. 2 is different from FIG. 1 in that an addition kneading and heating device 4 is provided instead of the addition kneading device 2 and the heating device 3.
Is different from the fly ash treatment device shown in the figure. That is, in the fly ash treatment apparatus shown in FIG.
And an additive kneading and heating device 4 in which the components are integrated. In order to integrate the addition kneader 2 and the heater 3, for example, an electric heater may be provided in the addition kneader 2 or the addition kneading mechanism may be provided in the heater 3.

When the addition, kneading, and heating can be performed by a single apparatus, even if a sufficient installation space cannot be obtained, the same processing capacity as the fly ash processing apparatus shown in FIG. 1 is realized. be able to.

Next, a method for treating fly ash according to a third embodiment of the present invention will be described with reference to FIG. The fly ash treatment device shown in FIG. 3 is different from the detoxification treatment device 5 in that a dust collector 8 and a catalyst decomposition device 9 are provided instead of the detoxification treatment device 5.
Is different from the fly ash treatment device shown in the figure. That is, the fly ash treatment device shown in FIG. 3 has a structure in which a catalytic decomposition device 9 and a dust collector 8 are provided as detoxification treatment means.

According to the fly ash processing apparatus shown in FIG. 3, the tail gas exhausted from the heater 3 is removed by the dust collector 8 in a very small amount. The tail gas from which fly ash has been removed
Next, it is supplied to the catalytic decomposition device 9. Catalytic cracker 9
In this process, decomposition and removal of organic halogen compounds such as dioxins contained in tail gas are performed. In addition, as the catalyst decomposition device 9, a known device that contains an oxidation catalyst or the like containing a metal such as platinum or titanium can be used.

The tail gas from which the organic halogen compound has been decomposed and removed by the catalytic decomposition device 9 is supplied to the incinerator 2 as shown in A1 of FIG. 5 in the same manner as described in the first embodiment.
1 or merged into the flue upstream of the bag filter 24, as shown at A2 in FIG. 5, or diffused into the atmosphere.

As described above, when the tail gas exhausted from the heater 3 is supplied to the incinerator 21 or the bag filter 24 via the catalytic decomposition device 9, the tail gas exhausted from the heater 3 is supplied to the incinerator 21 or the bag filter 24. The incinerator 21 and the bag filter 2
4 can be reduced. Further, in this case, it is possible to prevent dioxins from circulating between the incineration equipment and the fly ash treatment device, thereby preventing the dioxin concentration from increasing.

Such an effect can be obtained similarly when a mercury recovery device (not shown) is provided instead of the catalytic decomposition device 9. That is, when the tail gas exhausted from the heater 3 is supplied to the incinerator 21 or the bag filter 24 via the mercury recovery device, mercury circulates between the incinerator and the fly ash treatment device, and the mercury concentration increases. Can be prevented. In addition, as the mercury recovery device, a known device such as a cooling and condensing method can be used.

When tail gas is released into the atmosphere without being supplied to the incinerator 21 or the bag filter 24, not only the catalytic decomposition device 9 but also other detoxifying devices such as a mercury recovery device and an exhaust gas cleaning device are installed. Is preferred. By providing these devices together, it is possible to more effectively prevent the release of harmful substances into the atmosphere.

Next, a method for treating fly ash according to a fourth embodiment of the present invention will be described with reference to FIG. The fly ash treatment apparatus shown in FIG. 4 has a mechanism for supplying a volatilization promoting gas to the heater 3 as a gas distribution means.
Is different from the fly ash treatment device shown in the figure. As mentioned above,
When the volatilization promoting gas is passed through the heater 3, it is possible to prevent the organic halogen compounds such as dioxins volatilized from the fly ash by the heat treatment from remaining in the heater 3 and being adsorbed to the fly ash again. it can. Further, the volatile organic halogen compound can be quickly separated from the fly ash, and the exhaust from the heater 3 can be promoted. Further, when a gas containing no chlorine or chlorine compound is used as the volatilization promoting gas, the above-described effects can be obtained without resynthesizing dioxins or synthesizing a dioxin precursor.

The supply of the volatilization promoting gas to the heater 3 is performed, for example, by installing an inlet or a nozzle above the heater 3 or near the fly ash supply unit and introducing the volatilization promoting gas using a cylinder or a blower. This is done by: When air is used as the volatilization-promoting gas, it is only necessary to form an opening above the heater or near the fly ash supply unit.

In the first to fourth embodiments described above, the detoxification processing device 5, the dust collector 8, and the catalyst decomposition device 9 shown as the detoxification processing means are limited to the configurations shown in FIGS. Instead, any type may be used as long as the tail gas can be rendered harmless. The detoxifying means may be any of known devices such as a dust collector, a cooling device, an exhaust gas cleaning device, a mercury recovery device, a catalytic decomposition device, and an activated carbon moving bed, and a combination thereof.

In the first to fourth embodiments, the entire amount of the tail gas from the heater 3 is supplied to the detoxification processing device 5,
Catalytic cracker 9, incinerator 21, or bag filter 24
However, a part may be supplied to the detoxification processing apparatus 5 or the catalytic decomposition apparatus 9, and the remaining part may be supplied to the incinerator 21 or the bag filter 24. The tail gas detoxification method is appropriately selected according to the type of detoxification means, the treatment dose, the target detoxification level, and the like.

It should be noted that the amount of tail gas generated is at least 1/100 as compared with the amount of exhaust gas treated in the incinerator shown in FIG.
It is a very small amount of 100 or less. Therefore, a simple device or a small device can be used for the detoxification treatment device used for the fly ash treatment device, and the installation and operation can be performed at a small cost.

When the fly ash treatment apparatus shown in FIGS. 1 to 4 is installed in an incineration facility, the fly ash silo 1 does not always need to be provided. For example, when the fly ash processing apparatus shown in FIGS. 1 to 4 is installed in the incineration facility shown in FIG. 5, the fly ash collected by the bag filter 24 is directly supplied to the addition kneader 2 or the addition kneading and heating device 4. Can be.

In the first to fourth embodiments,
We have described the detoxification of fly ash discharged from refuse incineration facilities.However, fly ash discharged from industrial waste treatment facilities and other combustion facilities, and contaminated soil containing organic halogen compounds such as dioxin. The same effect can be obtained when applied to a solid substance such as.

[0062]

Embodiments of the present invention will be described below.

The fly ash collected from the refuse incineration equipment shown in FIG. 5 was detoxified using the fly ash treatment apparatus shown in FIG. The fly ash after the heat treatment was allowed to cool naturally. The following table shows the detoxification treatment conditions and the dioxin concentration in fly ash before and after the treatment.

[0064]

[Table 1]

As shown in the above table, when fly ash was treated under the conditions (1) to (3) according to the embodiment of the present invention, 0.1 n
A dioxin concentration much lower than g / g could be realized. That is, dioxins could be sufficiently removed from fly ash.

On the other hand, when the fly ash was treated under the condition (4) according to the comparative example, the dioxin concentration was set to 0.1 ng / g or less, even though the heating temperature was sufficiently high at 450 ° C. could not. This is considered to be because heating without adding NaOH and water caused resynthesis of dioxins.

When fly ash was treated under the condition (5) according to the comparative example, the dioxin concentration was reduced from the initial value, but was significantly higher than 0.1 ng / g. That is, dioxins could not be sufficiently removed from fly ash. This result indicates that even if a predetermined amount of NaOH and water are added, dioxins cannot be sufficiently removed from fly ash unless the heating temperature is set to 400 ° C. or higher.

The tail gas generated during the processing of fly ash under the conditions (1) to (3) contained dioxins, but it must be sufficiently rendered harmless by using a catalytic decomposition apparatus. Was completed. Although not described in the above table, almost the same results as in the condition (2) are obtained when the amount of NaOH is 2% by weight. When the amount of NaOH is 0.05% by weight. It was confirmed that dioxins could not be sufficiently removed from fly ash, and that the dioxin concentration in fly ash could be reduced to about 0.1 ng / g when the amount of NaOH added was 0.1% by weight. did.

Furthermore, when the fly ash after the heat treatment was quenched rather than spontaneously cooled, the level of removal of dioxins did not increase significantly. That is, in the method of the present invention, it was confirmed that it was not essential to rapidly cool the fly ash after the heat treatment.

[0070]

As described above, according to the present invention,
Removal of the organic halogen compound from the fly ash is performed by heating the fly ash to a predetermined temperature together with a predetermined amount of sodium hydroxide and water. Therefore, the organic halogen compound can be sufficiently volatilized from the fly ash, and the resynthesis of dioxins can be prevented.
Therefore, according to the present invention, a fly ash treatment method and a fly ash treatment device capable of detoxifying fly ash containing an organic halogen compound at a high level are provided.

Further, according to the present invention, the fly ash detoxification process is performed at a relatively low temperature, so that a large amount of energy is not required. Further, the chemicals used for this detoxification treatment are inexpensive and small amounts are sufficient. further,
Since the amount of the organic halogen compound volatilized from the fly ash is small, a large-scale facility is not required to detoxify the gas containing the volatile organic halogen compound. Therefore, according to the present invention, a fly ash treatment method and a fly ash treatment apparatus capable of detoxifying fly ash containing an organic halogen compound at low cost are provided.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a fly ash processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a fly ash processing device according to a second embodiment of the present invention.

FIG. 3 is a view schematically showing a fly ash processing apparatus according to a third embodiment of the present invention.

FIG. 4 is a diagram schematically showing a fly ash processing device according to a fourth embodiment of the present invention.

FIG. 5 is a diagram schematically showing a general waste incineration facility.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fly ash silo 2 ... Addition kneader 3 ... Heater 4 ... Addition kneading and heating device 5 ... Detoxification processing apparatus 6 ... Attraction fan 7 ... Fly ash bunker 8 ... Dust collector 9 ... Catalyst decomposer 21 ... Incinerator 22 ... Boiler 23 ... Cooling tower 24 ... Bag filter 25 ... Catalyst denitration tower 26 ... Slaked lime supply device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toru Shioman 1-2-1 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 3K061 NA01 NA02 NA11 NA13 NA19 4D004 AA37 AB05 AB07 AC05 CA22 CA28 CC03 CC09 CC12 DA03 DA06 DA10

Claims (10)

[Claims] 1. A fly ash containing an organic halogen compound,
The fly ash is heated to 400 to 500 ° C. together with 0.1 to 1.0% by weight of sodium hydroxide and 1 to 30% by weight of water with respect to the fly ash to produce the organic halogen compound from the fly ash. A fly ash treatment method comprising a step of volatilizing the gas and generating a gas containing the volatilized organic halogen compound. 2. The fly ash treatment method according to claim 1, wherein an aqueous solution of sodium hydroxide is used as the sodium hydroxide and water to be heated together with the fly ash. 3. The fly ash processing method according to claim 1, wherein the step of generating the gas is performed while removing the generated gas from the fly ash. 4. The fly ash treatment method according to claim 1, wherein the step of generating the gas is performed under a flow of a volatilization promoting gas. 5. The fly ash treatment method according to claim 1, further comprising a step of removing mercury from the gas containing the volatile organic halogen compound. 6. The fly ash treatment method according to claim 1, further comprising a step of removing a solid content from the gas containing the volatile organic halogen compound. 7. The method according to claim 1, further comprising a step of subjecting the gas containing the volatile organic halogen compound to at least one of a combustion treatment and a catalytic decomposition treatment. Fly ash treatment method described in 1. 8. A fly ash containing an organic halogen compound,
A heating means for heating together with sodium hydroxide and water to volatilize the organic halogen compound from the fly ash and generate a gas containing the volatilized organic halogen compound, and a detoxifying means for detoxifying the gas. A fly ash treatment device characterized by the above-mentioned. 9. The fly ash processing method according to claim 8, wherein the heating means includes a gas distribution means for flowing a volatilization promoting gas above the fly ash. 10. The detoxification processing means includes: a first processing unit that performs at least one of removal of mercury from the gas and catalytic decomposition of the organic halogen compound; and a gas that has been processed in the first processing unit. The fly ash processing device according to claim 8 or 9, further comprising a second processing unit for performing a combustion process.