JP2004074100A - Method of treating incineration ash - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of treating incineration ash capable of easily reforming an incineration ash into harmful materials which are low in elution property compared with that in a conventional method. <P>SOLUTION: (1) In the treating method for incineration ash, water is supplied to an incineration ash of city garbage and/or industrial waste and moisture content of the incineration ash is maintained at 12 mass% or more, and the incineration ash is exposed to the atmosphere of CO<SB>2</SB>containing gas. (2) In the treating method for the incineration ash, it is specified that the moisture content of the incineration ash to be maintained is at 15 mass% or more. (3) In the treating method for the incineration ash, it is specified that the incineration ash is piled and the CO<SB>2</SB>containing gas is blown into the piled incineration ash. (4) In the treating method for the incineration ash, it is specified that incineration flue gas of the city garbage and/or the industrial waste, and one or more sorts of melting exhaust gas of the incineration ash of the city garbage and/or the industrial waste are used as the CO<SB>2</SB>containing gas. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field related to a method for treating incinerated ash, and more particularly to a technical field related to a method for treating ash (incinerated ash) generated when municipal waste and / or industrial waste is incinerated. .
[0002]
[Prior art]
Incineration ash discharged from incinerators for municipal solid waste and industrial waste has been conventionally disposed of in landfills, but from the perspective of tight landfill sites and the formation of a resource-recycling society, resource recycling is required.
[0003]
The main components of the incinerated ash are silicon oxide, calcium oxide, and alumina, and have properties that can be effectively used as a substitute for soil and the like.
[0004]
However, it contains harmful heavy metals such as lead as trace components, which may elute, which is an obstacle to effective use.
[0005]
Various methods have been proposed so far to prevent the elution of harmful heavy metals and to effectively utilize incinerated ash, and typical methods are disclosed in JP-A-2000-233174 and JP-A-2001-233. No. 9412, JP-A-2001-17942, JP-A-2001-132930, and those disclosed in JP-A-2001-270969 are known.
[0006]
Among these methods, the method described in JP-A-2000-233174 classifies incinerated ash and separates it into coarse ash, medium ash, fine ash, and fine ash. And the fine ash is subjected to a heavy metal fixing treatment. As an effect of the present invention, it is stated that only the provision of a simple facility called a screen eliminates the need to fix and treat the entire amount of incinerated ash with heavy metals, thereby reducing facility costs and running costs. However, in order to classify incinerated ash into four types, at least three-stage screens are required, and complicated facilities are required, such as requiring separate conveyors to separately handle the classified ash. . In addition, as the method of the heavy metal fixing treatment, a method by a chemical treatment and a method by a melting treatment are mentioned.
[0007]
Both the method described in JP-A-2001-9412 and the method described in JP-A-2001-17942 stabilize heavy metals such as lead by hydrothermally treating incinerated ash. High-temperature / high-pressure equipment.
[0008]
In the method described in JP-A-2001-132930, a reducing agent is added to incinerated ash and roasting is performed at 500 to 1200 ° C. As this effect, prevention of elution of heavy metals from incineration ash and the like are mentioned. However, this method requires a roasting furnace capable of withstanding a high temperature of 500 ° C. or more, requires a fuel for heating, and increases equipment costs and running costs.
[0009]
The method described in Japanese Patent Application Laid-Open No. 2001-27069 is to add cement and water to incinerated ash. As this effect, prevention of elution of heavy metals from incineration ash and the like are mentioned. However, this method requires addition of cement and also requires equipment for kneading.
[0010]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and an object of the present invention is to easily convert incinerated ash into a material having a low leaching property of harmful heavy metals as compared with the conventional method. It is an object of the present invention to provide a method for treating incinerated ash.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a method for treating incinerated ash according to the present invention is a method for treating incinerated ash according to claims 1 to 4 (a method for treating incinerated ash according to first to fourth inventions). It has the following configuration.
[0012]
That is, in the method for treating incinerated ash according to claim 1, water is supplied to the incinerated ash of municipal solid waste and / or industrial waste, the moisture content of the incinerated ash is maintained at 12% by mass or more, and the incinerated ash is maintained. Is exposed to an atmosphere of a CO ₂ -containing gas (invention 1).
[0013]
The method for treating incinerated ash according to claim 2 is the method for treating incinerated ash according to claim 1, wherein the retained incinerated ash has a water content of 15% by mass or more (second invention).
[0014]
The method for treating incinerated ash according to claim 3 is the method for treating incinerated ash according to claim 1 or 2, wherein the incinerated ash is laminated, and a CO ₂ -containing gas is blown into the laminated incinerated ash. (Third invention).
[0015]
The method for treating incinerated ash according to claim 4, wherein the CO ₂ -containing gas is at least one of incinerated exhaust gas of municipal waste and / or industrial waste and molten exhaust gas of incinerated ash of municipal waste and / or industrial waste. A method for treating incinerated ash according to claim 3 (fourth invention).
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is implemented, for example, as follows.
The incineration ash of municipal waste and / or industrial waste water was supplied, it holds the water content of the ash over 12 mass%, subjecting the ash to the atmosphere of CO ₂ containing gas. That is, exposed to an atmosphere of CO ₂ containing gas while holding the water content of ash over 12 mass%. At this time, the water is supplied to the incineration ash by, for example, spraying water on the incineration ash. Air or the like is used as the atmosphere of the CO ₂ -containing gas. When air is used, a method of placing incinerated ash in the air or a method of blowing air into incinerated ash (in a laminated state) is adopted.
[0017]
The present invention is implemented in such a form.
[0018]
The present invention has been made based on the knowledge obtained as a result of intensive studies to achieve the above-mentioned object of the present invention. That is, water is supplied to the incineration ash of municipal solid waste and / or industrial waste, the moisture content of the incineration ash is maintained at 12% by mass (% by weight) or more, and the incineration ash is converted to an atmosphere of a CO ₂ containing gas. It has been found that this incineration ash can be modified into a substance having a low leaching property of harmful heavy metals. The present invention has been completed based on such findings.
[0019]
The method for treating incinerated ash according to the present invention completed in this way supplies water to the incinerated ash of municipal solid waste and / or industrial waste, while maintaining the moisture content of the incinerated ash at 12% by mass or more. , it is set to be the ash is a processing method of incineration ash, characterized in that exposure to an atmosphere of CO ₂ containing gas. According to the incineration ash processing method, the incineration ash can be modified into a substance having a low leaching property of harmful heavy metals.
[0020]
The reason why the incineration ash can be modified into a substance having a low leaching property of harmful heavy metals according to the incineration ash treatment method of the present invention is considered as follows.
[0021]
By supplying water to the incineration ash and maintaining the water content of the incineration ash at 12% by mass or more, the harmful heavy metals M in the incineration ash are dissolved, that is, ionized to M ²⁺ . By exposing the incinerated ash to an atmosphere of a CO ₂ -containing gas, CO ₃ ^2- is generated by a reaction between CO ₂ in the gas and water, and the CO ₃ ^2- and the M ²⁺ are reacted with the following reaction formula (1). ) To produce MCO ₃ . Since MCO ₃ is a metal carbonate and has low solubility, it has low dissolution and is stable. In this way, it is considered that the harmful heavy metals in the incineration ash are converted into metal carbonates (MCO ₃ ) having low solubility, so that the incineration ash can be modified into one having a low elution property of the harmful heavy metals. Conceivable.
[0022]
M ^{2 +} + CO ₃ ^2- → MCO ₃ -----------Reaction formula (1)
[0023]
Here, if the moisture content of the incinerated ash is less than 12% by mass, the reforming of the incinerated ash becomes insufficient. That is, it becomes difficult to make the incineration ash sufficiently low in the leaching property of harmful heavy metals. This is because when the moisture content of the incinerated ash is less than 12% by mass, the amount of harmful heavy metals M in the incinerated ash, that is, the amount of ionization is reduced, and the heavy metals M still exist in the incinerated ash. It is thought that this is due to the increase.
[0024]
For this reason, in the incineration ash treatment method according to the present invention, the moisture content of the retained incineration ash is 12% by mass or more.
[0025]
At this time, if the moisture content of the retained incinerated ash is set to 15% by mass or more, the incinerated ash can be more reliably modified to one having low elution of harmful heavy metals, and the elution amount of harmful heavy metals can be further reduced. It can be set to a low level (second invention). This is because when the water content of the incinerated ash is 15% by mass or more, the amount of the harmful heavy metals M in the incinerated ash, that is, the amount of ionization increases, and the amount of the heavy metals M remaining in the incinerated ash remains small. It is thought to be because it becomes.
[0026]
The incinerated ash is laminated, and if the CO ₂ containing gas is blown into the laminated incinerated ash, the incinerated ash can be reformed in a shorter time to one having low elution of harmful heavy metals. . That is, it is possible to reduce the time required for reforming the incinerated ash into a material having low elution of harmful heavy metals (reforming time) (third invention).
[0027]
In the present invention, the CO ₂ containing gas, as long as it contains the CO _2, the kind is not particularly limited, and can be used various ones, for example, air, municipal waste and / or industrial Waste incineration exhaust gas, molten exhaust gas of municipal waste and / or incineration ash of industrial waste, and the like can be used. The same applies to the case where the CO ₂ -containing gas is blown into the incinerated ash stacked as described above (in the case of the third invention), but the same applies to the incineration exhaust gas of municipal waste and / or industrial waste, municipal waste and / or When one or more of the molten exhaust gas of incinerated ash of industrial waste is used, these exhaust gases have a higher CO ₂ concentration, and therefore, the time required for reforming (the incinerated ash has a higher elution property of harmful heavy metals than air). The time required for reforming to a low value can be reduced (fourth invention). In addition, the incineration exhaust gas of municipal waste and / or industrial waste refers to the exhaust gas generated when incinerating municipal waste and / or industrial waste. The molten exhaust gas of incinerated ash from municipal waste and / or industrial waste is an exhaust gas generated when ash (incinerated ash) generated by incineration of municipal waste and / or industrial waste is melted.
[0028]
The type of water to be supplied to the incineration ash is not particularly limited, and various types can be used. For example, tap water, industrial water, and the like can be used. The method for supplying water to the incineration ash is not particularly limited, and various types can be used. For example, a method of spraying water on the incineration ash or a method of immersing the incineration ash in water Etc. can be used.
[0029]
In the present invention, maintaining the water content of the incinerated ash at 12% by mass or more is not limited to continuously maintaining the water content at 12% by mass or more during the treatment period. Included. For example, even if the water content decreases to less than 12% by mass during the treatment period, the water content may be restored to 12% by mass or more by supplying water thereafter.
[0030]
The method for treating incinerated ash according to the present invention includes a screen required by the method described in JP-A-2000-233174, a screen required by the method described in JP-A-2001-9412, and a method required by the method described in JP-A-2001-17942. Hydrothermal treatment and high-temperature / high-pressure equipment, roasting treatment and roasting furnace required by the method described in JP-A-2001-132930, and cement addition and kneading equipment required by the method described in JP-A-2001-270699 are required. In addition, since it can be performed by a simple operation of supplying water to the incinerated ash and exposing the incinerated ash to an atmosphere of a CO ₂ -containing gas, it can be easily performed as compared with the method described in the above-mentioned publication.
[0031]
【Example】
Examples of the present invention and comparative examples will be described below. Note that the present invention is not limited to the present embodiment. The comparative example is an example for comparison with the example of the present invention, and is not limited to the example of the related art.
[0032]
[Example 1 and Comparative Example 1]
FIG. 1 shows the outline of the incineration ash processing status according to the example and the comparative example. As shown in FIG. 1, incineration ash 1 of municipal solid waste generated from a stoker-type incinerator is carried into a processing facility by a truck. The carried incineration ash 1 is stored in the yard 2 in a stacked state, and water is supplied to the incineration ash 1 by a water spray 3, and the water content of the incineration ash 1 is adjusted. The yard 2 is provided with a gas injection nozzle 4 so that air or incineration exhaust gas from municipal waste can be injected into the incineration ash layer as needed.
[0033]
The water content (% by mass) of the incinerated ash is usually defined by the following equation.
[0034]
Water content (% by mass) = [mass of total moisture contained in incinerated ash / (mass of total moisture contained in incinerated ash + mass of incinerated ash)] × 100
[0035]
The water content of the incinerated ash 1 to which water was supplied in the yard 2 was sampled from the surface layer portion, the middle portion, and the deepest portion in the depth direction of the incinerated ash 1 (incinerated ash layer) in a stacked state, It measured and these average values were used as a management index.
[0036]
After adjusting the water content of the ash 1 and the process of exposing the ash 1 atmosphere of CO ₂ containing gas (air). This treatment was performed by a method of placing the incinerated ash 1 as it is in the air (placed in the yard 2). At this time, the moisture content of the incineration ash 1 was changed as a parameter. The treatment period was 1 to 10 days. When the water content of the incinerated ash 1 was reduced during the treatment period, water was sprayed on the incinerated ash 1 with a water spray 3 as appropriate to keep the water content of the incinerated ash 1 at the initial value.
[0037]
Then, the incinerated ash 5 after each treatment period (the incinerated ash 1 after the treatment) was carried out of the facility, and a dissolution test of lead and the like was performed to confirm whether or not the effective use was possible. The test for dissolution of lead and the like was performed by a method according to the Environment Agency Notification No. 13. That is, the incinerated ash 5 (the incinerated ash 1 after the treatment) is immersed in 10 times (by mass) water for 6 hours, and the amount of lead or the like eluted in this water [mg / liter of water (hereinafter, L) )) Was determined by analysis.
[0038]
The result is shown in FIG. In FIG. 2, the abscissa plots the number of reforming days (treatment days), and the ordinate plots the amount of lead (mg / L of water) eluted into water from incineration ash 5 (incineration ash 1 after treatment), ie, And the elution concentration (mg / L) of lead from the incineration ash 5 are plotted.
[0039]
As can be seen from FIG. 2, incineration ash 1 before treatment (incineration ash 1 from municipal solid waste generated from a stoker-type incinerator) has a lead elution of about 1 mg / L, which is 0.1 mg / L as an effective use target standard. Was not clear. When water is supplied (sprayed) to the incinerated ash 1 to maintain the water content at 15% by weight (WT%) and expose it to an air atmosphere, the elution concentration of lead becomes longer as the treatment period (days) elapses. On the seventh day, it fell below the effective use target standard of 0.1 mg / L.
[0040]
When the moisture content of the incinerated ash 1 is changed to 10% by weight (WT%) instead of the above 15% by weight (WT%), the elution concentration of lead decreases with the lapse of the treatment period, but after 10 days, However, they did not meet the effective use target criteria.
[0041]
When the moisture content of the incinerated ash 1 was maintained at 5% by weight (WT%) instead of the above 15% by weight (WT%) and exposed to an atmosphere of air, the elution concentration of lead was hardly reduced. . This indicates that the presence of moisture is important for reforming the incinerated ash (reforming the incinerated ash to one having a low lead elution property).
[0042]
When the water content of the incinerated ash 1 was increased to more than 20% by weight instead of the above 15% by weight (WT%), the effect of the modification was the same as when the water content of the incinerated ash 1 was 15% by weight. Was. However, if the water content is more than 40% by weight, the incinerated ash becomes a slurry, so it is considered preferable that the water content be 40% by weight or less.
[0043]
If the moisture content of the incineration ash 1 is constantly higher than 12% during the treatment period, the incineration ash 1 is reformed in the treatment period of 7 days (lead elution amount: 0.1 mg based on the effective use target standard). / L less than incineration ash), but if the total number of days exceeding 12% exceeds 7 days even if the moisture content of the incineration ash 1 falls below 12% for several days during the treatment period, Incineration ash 1 was modified in the same manner as in 1.
[0044]
The above results are for the case where the harmful heavy metals in the incineration ash are lead. However, when the harmful heavy metals other than lead (cadmium, chromium, etc.) are used, the same results as above can be obtained.
[0045]
[Example 2 and Comparative Example 2]
The treatment of exposing the incinerated ash 1 after adjusting the moisture content to the atmosphere of the CO ₂ -containing gas is not performed by the method of placing the incinerated ash 1 in the above-mentioned Example 1 and Comparative Example 1 as it is in the air, but in a state of being stacked. CO ₂ containing gas in the incineration ash 1 (incineration ash layer) was carried out by method of blowing. Except for this point, the same processing and test as in Example 1 and Comparative Example 1 were performed.
[0046]
At this time, as the CO ₂ -containing gas, air or incineration exhaust gas (containing CO ₂ ) of municipal waste was used. The blowing of the CO ₂ -containing gas was performed using the gas blowing nozzle 4. The moisture content of all incineration ash 1 was 15% by weight (WT%).
[0047]
FIG. 3 shows the results of the above treatments and tests. FIG. 3 also shows the results of the process of exposing the incinerated ash 1 after adjusting the water content to an atmosphere of a CO ₂ -containing gas by a method of placing the incinerated ash 1 in the air (without blowing). I have.
[0048]
As can be seen from FIG. 3, incineration ash 1 before treatment (incineration ash 1 of municipal solid waste generated from a stoker-type incinerator) contains about 1 mg / L of lead in the same manner as in Example 1 and Comparative Example 1. There was elution, which did not clear the effective use target standard of 0.1 mg / L. Water is supplied (sprayed) to the incineration ash 1 to maintain the water content at 15% by weight (WT%), and the incineration exhaust gas (containing 8 vol% of CO ₂ ) of the municipal waste is blown, and the CO ₂ -containing gas is discharged. When exposed to the atmosphere, the lead elution concentration of the incinerated ash on the first day was lower than the effective use target standard of 0.1 mg / L. That is, the treatment period required for reducing the lead elution concentration of the incinerated ash to less than 0.1 mg / L (the number of days required for reforming) is based on the method of exposing to the atmosphere of a CO ₂ -containing gas in the air (without blowing). When performed, it took seven days. However, when performed by the above-described blowing method, the number of days required for reforming was reduced to one day.
[0049]
Even when air was blown in place of the incineration exhaust gas from the municipal solid waste, the lead elution concentration of the incineration ash on the third day was below the effective use target standard of 0.1 mg / L. This is considered to be because the contact efficiency between CO ₂ in the air and the incinerated ash was increased by forcibly blowing the air. In addition, when the incineration exhaust gas from municipal solid waste is blown, it is considered that, in addition to such an effect of increasing the contact efficiency, the high CO ₂ concentration has an effect, thereby further shortening the number of days required for reforming. .
[0050]
The above results are for the case where the harmful heavy metals in the incineration ash are lead, but the same tendency can be obtained when the harmful heavy metals other than lead are used.
[0051]
In the case of using the incineration exhaust gas of industrial waste or the incineration exhaust gas of municipal waste and industrial waste instead of the incineration exhaust gas of municipal waste, the same result as the case of using the incineration exhaust gas of municipal waste is obtained. Also, in the case of using the molten exhaust gas of incinerated ash of municipal waste and / or industrial waste, the same tendency as in the case of using the incinerated exhaust gas of municipal waste is obtained.
[0052]
【The invention's effect】
According to the method for treating incinerated ash according to the present invention, incinerated ash can be easily modified to one having a low leaching property of harmful heavy metals as compared with the conventional method.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an outline of a state of treatment of incinerated ash according to an example and a comparative example.
FIG. 2 is a graph showing the relationship between the number of modification days and the lead elution concentration according to Example 1 and Comparative Example 1.
FIG. 3 is a graph showing the relationship between the number of days of modification and the lead elution concentration according to Example 2 and Comparative Example 2.
[Explanation of symbols]
1 ... incineration ash, 2 ... yards, 3 ... water spray, 4 ... gas injection nozzle, 5 ... incineration ash after treatment.

Claims (4)

Ash to supply water municipal waste and / or industrial waste, holds the water content of the ash over 12 wt%, and wherein the exposing the ash into the atmosphere of the CO ₂ containing gas How to treat incinerated ash. The method for treating incinerated ash according to claim 1, wherein the moisture content of the retained incinerated ash is 15% by mass or more. The ash is laminated, the processing method of ash according to claim 1, wherein blowing of CO ₂ containing gas in the stacked ash. The CO ₂ containing gas, municipal waste and / or industrial incineration flue gas waste, municipal solid waste and / or treatment method of incineration ash of claim 3, wherein industrial waste is at least one of the melting exhaust gases incinerator ash.

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