JP2001327834A - Oxidative gas removing agent fo refuse incineration exhaust gas and material for treating refuse incineration fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acidic gas removing agent for refuse incineration exhaust gases which captures fly ash of the characteristic capable of stabilizing heavy metals simply by carrying out simple treatment and a method for treating refuse incineration fly ash which is capable of stabilizing the heavy metals with a simple device without using costly chemicals. SOLUTION: This acidic gas removing agent for the refuse incineration exhaust gaseous is a mixture composed of at least slaked lime powder and powder of sulfate-containing substance and is regulated in a molar ratio of SO4 to CaO quantitatively determined as an alkaline component to a range of CaO:CO4=1:0.008 to 0.4. The method for treating the refuse incineration fly ash consists in adding at least the sulfate-containing substance to the alkaline fly ash to regulate the molar ratio of SO4 to CaO quantitatively determined as the alkaline component to the range of CaO:CO4/CaO>=0.3, then adding water to the mixture, kneading the mixture and heating the kneaded matter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acid gas remover for waste incineration exhaust gas and a method for treating waste incineration fly ash.

[0002]

2. Description of the Related Art In a refuse incineration facility, fly ash that is scattered and collected together with exhaust gas from an incinerator is designated as a specially managed municipal waste, so the method specified by the Minister of Health and Welfare (the cement solidification method, Method, melt-solidification method, extraction method into acid or other solvent), stabilize heavy metals in fly ash, and landfill. Of the above four methods, a drug addition method is widely adopted, and a liquid chelating agent such as dithiocarbamic acid is often used as a drug. In this case, a process of adding a liquid chelating agent to the fly ash and kneading it to insolubilize heavy metals is performed.

[0003] In a refuse incineration plant, a treatment for removing acidic gases such as hydrogen chloride and sulfur oxides contained in exhaust gas generated from an incinerator is performed. One of the methods for removing this acidic gas is as follows. As a method, an acid gas remover is blown into an exhaust gas flow path on the upstream side of a dry dust collector to react with the acid gas, thereby removing the acid gas in the exhaust gas, and is widely used. At this time, slaked lime powder is used as an acid gas remover.

[0004] In a dust collector for exhaust gas treated by this method, reaction products of slaked lime and acid gas and unreacted slaked lime are collected together with fly ash scattered from the incinerator. Fly ash collected when slaked lime is blown into this exhaust gas channel (hereinafter, referred to as alkali fly ash) is also subjected to heavy metal stabilization according to the above-mentioned laws and regulations,
Landfill disposal.

[0005] In the following description, fly ash collected by a dust collector when slaked lime is not blown for removing acid gas from exhaust gas generated from an incinerator is referred to as neutral fly ash. . Therefore, when described as neutral fly ash, it means fly ash that does not contain slaked lime, and when it is described as alkaline fly ash, it is fly ash that contains slaked lime. And, when simply written as fly ash, it means that it is a generic name of both.

[0006]

However, there are several problems with the drug addition method using a liquid chelating agent such as dithiocarbamic acid. As one of the problems, when fly ash is treated by the chemical addition method using the above-mentioned liquid chelating agent, there is a problem that the processing cost is increased because the liquid chelating agent is an expensive chemical. In addition, during the process of adding and kneading a liquid chelating agent to fly ash, harmful gases such as carbon disulfide are generated. Therefore, equipment for improving the working environment must be provided.

Further, when the treatment of alkali fly ash is performed by the above-described method using a liquid chelating agent, there is a problem that the ability of the liquid chelating agent to capture heavy metals is reduced. This phenomenon is because alkali fly ash contains a large amount of unreacted slaked lime, so the pH of the eluate becomes extremely high, and the pH value is such that a liquid chelating agent such as dithiocarbamic acid efficiently removes heavy metals. It is caused by being out of the area that can be captured. For this reason, when treating alkali fly ash, an agent such as iron chloride is further added to lower the pH of the fly ash to an appropriate range. Therefore, the processing cost of fly ash is further increased.

Further, in a pH range of pH 12 or more, since amphoteric metals such as lead (Pb) are easily dissolved as hydroxide complex ions, it is difficult to suppress elution of heavy metals such as Pb, which is an amphoteric metal. Become.

In the case of processing fly ash by the melt-solidification method, a process of heating and melting the fly ash to a hundred thousand degrees by using a melting furnace such as an electric furnace or a coke bed type melting furnace. Must. For this reason, complicated processing equipment is required and a large amount of energy is consumed, so that the cost of processing fly ash is extremely high.

[0010] The present invention does not require the use of an acid gas remover for waste incineration exhaust gas from which fly ash having the property of being able to stabilize heavy metals by a simple treatment and an expensive chemical are used. It is another object of the present invention to provide a method for treating incineration fly ash that can stabilize heavy metals with a simple device.

[0011]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted various studies on an exhaust gas treatment technology for removing slaked lime into exhaust gas generated from a refuse incinerator to remove acidic gas. went. Then, in the course of the research, if sulfate-containing substances were added to slaked lime blown into the exhaust gas, the heavy metals contained in the fly ash collected by the dust collector were simply added by a simple process of adding and kneading the water. It has been found that the effect of stabilization and suppression of the elution can be obtained. Furthermore, it has been found that the addition of an aluminum-containing substance in addition to a sulfate-containing substance stabilizes heavy metals in fly ash and further enhances the effect of suppressing elution thereof. Also, to the incineration fly ash, slaked lime and quick lime, or one of them is added and a sulfate-containing substance is added, or after further adding an aluminum-containing substance, if water is added and kneaded, It has been found that heavy metals in fly ash are stabilized and their elution is suppressed.

The present invention has been made based on the above findings, and the above-mentioned problems are solved by the following invention.

The acid gas remover for waste incineration exhaust gas according to the first aspect of the present invention is a mixture comprising at least slaked lime powder and a powder of a sulfate-containing substance, and a molar ratio of SO ₄ to CaO, which is determined as an alkali component. Is CaO: SO
₄ = 1: characterized by being adjusted in the range of 0.008 to 0.4.

According to a second aspect of the present invention, in the first aspect of the present invention, the acid gas remover for waste incineration exhaust gas has a molar ratio of SO ₄ to CaO, which is determined as an alkali content, of Ca.
O: SO ₄ = 1: 0.02 to 0.08.

According to the third aspect of the present invention, the acidic gas remover for waste incineration exhaust gas according to the first or second aspect of the present invention is a mixture further containing a powder of an aluminum-containing substance, and is determined as an alkali component. A for CaO
The molar ratio of l ₂ O ₃ is CaO: Al ₂ O ₃ = 1: 0.00
It is characterized in that it is adjusted in the range of 3 to 0.133.

According to a fourth aspect of the present invention, in the third aspect of the present invention, there is provided the acid gas remover for waste incineration exhaust gas, wherein the molar ratio of Al ₂ O ₃ to CaO, which is determined as an alkali content, is CaO: Al ₂ O ₃ = 1: It is characterized in that it is adjusted in the range of 0.007 to 0.027.

According to a fifth aspect of the present invention, there is provided the acid gas remover for waste incineration exhaust gas according to any one of the first to fourth aspects, wherein the slaked lime powder has a specific surface area of 20 m ² / g or more. And

According to a sixth aspect of the present invention, there is provided a method for treating fly ash from refuse incineration, wherein a sulfate-containing substance is added to alkali fly ash collected when slaked lime is blown into refuse incineration exhaust gas to remove acid gas. C which is added and quantified as alkali
SO ₄ molar ratio of SO ₄ with respect to aO-/CaO≧0.3
And then kneading in the presence of water, and heating the kneaded material.

The method for treating refuse incineration fly ash according to the invention of claim 7 is characterized in that the alkali fly ash collected when slaked lime is blown into the refuse incineration exhaust gas to remove the acid gas contains a sulfate-containing substance. By adding an aluminum-containing substance, the molar ratio of the SO ₄ component to CaO determined as the alkali content is SO ₄ /CaO≧0.3, and the molar ratio of the Al ₂ O ₃ component to CaO determined as the alkali content is CaO. :
After each adjustment to the range of Al ₂ O ₃ = 3: 1 to 3,
It is characterized by kneading in the presence of water and heating the kneaded material.

[0020] The method for treating incineration fly ash according to the invention of claim 8 is characterized in that slaked lime and / or quick lime is added to alkali fly ash collected when slaked lime is blown into refuse incineration exhaust gas to remove acidic gas. Is added, and a sulfate-containing substance is further added so that the content of CaO quantified as an alkali content is 30 wt% or less, and the content of CaO quantified as an alkali
After adjusting each molar ratio of SO ₄ in the range of SO ₄ /CaO≧0.3 against, and kneaded in the presence of water, it is characterized by heating a kneaded mixture.

According to a ninth aspect of the present invention, there is provided a method for treating incineration fly ash, wherein slaked lime and / or quick lime is added to alkaline fly ash collected when slaked lime is blown into refuse incineration exhaust gas to remove acid gas. was added, further added sulfate containing material and an aluminum-containing substance, the following 30 wt% the content of CaO to be quantified as an alkali component, SO ₄ molar ratio of SO ₄ component to CaO which is quantified as alkali components /CaO≧0.3, the molar ratio of the Al ₂ O ₃ component to CaO, which is determined as the alkali content, is expressed as CaO: Al
It is characterized in that after adjusting each to the range of ₂ O ₃ = 3: 1 to 3, kneading is performed in the presence of water, and the kneaded material is heated.

According to a tenth aspect of the present invention, there is provided a method for treating fly ash from refuse incineration, wherein neutral fly ash collected when the acid gas removal treatment for blowing slaked lime into the waste gas from the refuse incineration is not carried out includes slaked lime and / or Quick lime is added, and a sulfate-containing substance is further added to reduce the content of CaO, which is determined as an alkali, to 30% by weight or less, and the content of CaO, which is determined as an alkali, is determined.
The molar ratio of the SO ₄ component to SO ₄ /CaO≧0.3
, And kneaded in the presence of water, and the kneaded material is heated.

According to the eleventh aspect of the present invention, there is provided a method for treating fly ash from refuse incineration, wherein neutral fly ash collected when the acid gas removal treatment for blowing slaked lime into the refuse incineration exhaust gas has not been performed is carried out by adding slaked lime and / or Quick lime is added, and a sulfate-containing substance and an aluminum-containing substance are further added to reduce the content of CaO, which is determined as an alkali content, to 30 wt% or less, and the molar ratio of SO ₄ component to CaO, which is determined as an alkali content, is SO ₄ / CaO ≧ 0.3, the molar ratio of the Al ₂ O ₃ component to CaO, which is determined as the alkali content, is expressed as CaO: Al
It is characterized in that after adjusting each to the range of ₂ O ₃ = 3: 1 to 3, kneading is performed in the presence of water, and the kneaded material is heated.

According to a twelfth aspect of the present invention, there is provided a method for treating fly ash from refuse incineration, wherein the acidic gas remover according to any one of the first to fifth aspects of the present invention is used to remove acid gas in waste gas from refuse incineration. Waste incineration fly ash collected during exhaust gas treatment,
It is characterized by kneading in the presence of water and heating the kneaded material.

According to a thirteenth aspect of the present invention, in the method for treating incineration fly ash according to any one of the sixth to twelfth aspects, the kneaded material is placed in a closed container, and the pressure is maintained at less than 2 atm. It is characterized by heating as follows.

In each of the above inventions, CaO quantified as an alkali (hereinafter referred to as CaO of the alkali)
Is CaO derived from alkali such as slaked lime or quicklime
And does not include calcium which forms salts or the like. In addition, CaO for alkali content
For example, MgO separately quantified from the alkali content obtained by the method specified in the Fertilizer Analysis Method 1992 Edition (Ministry of Agriculture, Forestry and Fisheries, Agricultural and Environmental Technology Research Institute, issued by the Japan Fertilizer Inspection Association in December 1992) Can be obtained by subtracting the value converted to.

In the case of removing acid gas in the waste gas from the incineration by injecting slaked lime, excess slaked lime is blown in than the amount that reacts with the acid gas in the exhaust gas, so that unreacted fly ash collected by the dust collector is unreacted. Contains slaked lime. Therefore, the alkali fly ash collected when the acid gas remover of the present invention is blown is a mixture of dust (fly ash), slaked lime, and a sulfate-containing substance scattered from the incinerator, or scattered from the incinerator. It is a mixture of fly ash, slaked lime, sulfate-containing material and aluminum-containing material. And
As described above, the alkali fly ash has a property that the heavy metal contained therein is stabilized and not eluted only by adding water and kneading.

Although the mechanism of stabilization of heavy metals expressed as described above is not necessarily clear, when water is added to the above-mentioned mixture of alkali fly ash, a reaction for generating stable minerals occurs, and heavy metals are removed. It is considered that it is taken into the stable mineral tissue and stabilized, or is adsorbed therein and stabilized.

That is, the acid gas treating agent of the present invention is blown.
When water is added to the alkaline fly ash collected when
CaO component of alkali contained in fly ash and sulfuric acid
Salts, aluminum compounds, silicate compounds in fly ash, etc.
React to produce the following stable minerals: Generate
As stable minerals, calcium silicate compounds, Ca
O ・ Al_Two O_Three ・ H_Two O, 3CaO · Al_Two O_Three ・ 6H
_Two O, 3CaO · Al _Two O_Three ・ 10-12H_Two Such as O
Calcium aluminate hydrate, ettringite (3Ca
O ・ Al_Two O_Three ・ 3CaSO_Four ・ 32H_Two O)
And a lithium aluminum sulfate compound.

The following effects are brought about by the occurrence of the reaction for producing a stable mineral as described above.
First, when the above-mentioned minerals are generated, heavy metals are taken into the minerals or adsorbed by the minerals, and the heavy metals in the fly ash are stabilized. Further, since CaO of the alkali is consumed, the collected alkali fly ash is prevented from becoming highly alkaline (high pH), and the amphoteric metal such as Pb is hardly eluted. Further, due to the generation of the mineral, the strength of the treated product when it is solidified increases.

It is necessary that at least a sulfate-containing substance be mixed in addition to slaked lime as a substance constituting the acid gas removing agent which can obtain the above-mentioned effects. If the aluminum-containing substance is further mixed, the effect can be further enhanced. In addition, since fly ash scattered from the incinerator contains a silicate-based compound, it is usually unnecessary to add a silica-containing substance, but when the content of the silica-containing substance in the fly ash is small, Add a silica-containing substance as needed.

As the sulfate-containing substance, gypsum, anhydrous gypsum, gypsum hemihydrate, alunite, sodium sulfate, aluminum sulfate and the like can be used. As the aluminum-containing substance, alunite, aluminum hydroxide, aluminum sulfate, aluminum chloride, kaolin and the like can be used. Further, as the silica-containing substance, silica stone, alunite, diatomaceous earth, kaolin, sodium silicate and the like can be used.

The acid gas remover of the present invention can be prepared by adding an appropriate amount of a sulfate-containing substance powder to slaked lime powder as a base material or further adding and mixing an appropriate amount of an aluminum-containing substance powder. Prepared. In this preparation, an appropriate amount of the powder of the sulfate-containing substance or the powder of the aluminum-containing substance is added to slaked lime as the base material. When the added substance is only a sulfate-containing substance, the molar ratio of SO _{4 to} CaO of the alkali derived from slaked lime is CaO: SO ₄ = 1: 0.008 to 0.4, preferably CaO: SO ₄ = 1. : The acid gas remover of the present invention can be obtained by adding the sulfate-containing substance so as to be 0.02 to 0.08. When the additive substances are a sulfate-containing substance and an aluminum-containing substance, the molar ratio of SO _{4 to} CaO of the alkali component derived from slaked lime is CaO:
SO ₄ = 1: 0.008 to 0.4, preferably CaO:
A sulfate-containing substance was added so that SO ₄ = 1: 0.02 to 0.08, and the molar ratio of Al ₂ O ₃ was CaO: Al ₂
O ₃ = 1: 0.003-0.133, preferably Ca
By adding the aluminum-containing substance so that O: Al ₂ O ₃ = 0.007 to 0.027, the acid gas remover of the present invention can be obtained.

The slaked lime powder, which is the base material of the acid gas removing agent, reacts with and absorbs the acid gas in the exhaust gas. And other components react with each other to produce a stable mineral. In any case, a material having good reactivity is desirable, and a material having a specific surface area as large as possible is desirable. The slaked lime powder used for the acid gas remover of the present invention has a specific surface area of 15 m ² / g or more, preferably 20 m ² / g or more. This is based on the results of the fly ash dissolution test in the examples described later. According to the dissolution test results, even when slaked lime having a specific surface area of 15 m ² / g is used, the dissolution of heavy metals is suppressed below the regulation value.
In order to stably reduce the elution amount of heavy metals, it is desirable to use slaked lime having a specific surface area of about 20 m ² / g or more.

The addition amount of the powder of the sulfate-containing substance or the powder of the aluminum-containing substance mixed in the acid gas removing agent of the present invention is determined based on the experimental results.
In the acid gas remover of the present invention, the alkaline content of CaO
If the molar ratio of SO ₄ to is less than 0.008, the elution of heavy metals cannot be sufficiently suppressed. In addition, even if the molar ratio of SO _{4 to} CaO in the alkali exceeds 0.4, the effect of suppressing the elution of heavy metals corresponding to the increase in the amount of the sulfate-containing substance is not observed. And Ca of alkali content
If the molar ratio of Al ₂ O ₃ to O is less than 0.003, the effect of further suppressing the elution of heavy metals by adding an aluminum-containing substance cannot be obtained. In addition, alkaline CaO
The molar ratio of Al ₂ O ₃ to
The effect of suppressing the elution of heavy metals corresponding to the increase in the amount of the aluminum-containing substance is not observed.

If an acid gas remover in which a sulfate-containing substance or an aluminum-containing substance is mixed with slaked lime is blown into the waste gas, the fly ash collected by the dust collector is a reactant that produces a stable mineral. Slaked lime, sulfate-containing substances, and aluminum-containing substances are taken out in a well-mixed state.When stabilizing fly ash, it is only necessary to add water and knead it, which simplifies the processing operation. You.

When the acid gas remover is prepared, it is desirable that the mixing ratio of slaked lime and other additives be determined for each incinerator into which the remover is injected. This is because the quality of the refuse charged into the incinerator does not vary so much within the same collection area, but there are regional differences, so the composition of fly ash scattered from the refuse incinerator may vary from area to area. Because there is. For this reason, the compounding ratio of the acid gas remover is determined based on the composition of the fly ash in the past and the equivalent ratio of slaked lime to the acid gas (blowing amount of slaked lime). If desired, further desirable effects can be obtained by adding a silica-containing substance.

Next, a treatment method for stabilizing heavy metals in refuse incineration fly ash will be described. The present invention can be applied to any treatment of alkali fly ash and neutral fly ash.
As described above, slaked lime and quick lime, or one of them, and a sulfate-containing substance are added to neutral fly ash, and the mixture is kneaded in the presence of water. It is stabilized and its elution is suppressed. If neutral ash is added with slaked lime and quick lime or any of them and a sulfate-containing substance, and then an aluminum-containing substance is added, the elution of heavy metals in the fly ash is further enhanced. Is suppressed. This heavy metal elution suppression, the added slaked lime or quicklime or both, sulfates, aluminum compounds, components such as silicic acid compounds in fly ash react, and various stable minerals as described above are generated, It is thought that when the mineral is produced, heavy metals are incorporated into the mineral or are absorbed by the mineral and stabilized to stabilize.

If a sulfate-containing substance is added to the alkali fly ash and kneaded in the presence of water, heavy metals in the fly ash are stabilized, and the elution of the heavy metal is suppressed. Alternatively, if an aluminum-containing substance is further added, elution of heavy metals in fly ash is further suppressed. In order to suppress the dissolution of heavy metals, components such as added sulfates and aluminum compounds, slaked lime in alkali fly ash, and silicic acid compounds in fly ash react to generate various stable minerals as described above. It is considered that heavy metals are stabilized. In the case of treating alkali fly ash, slaked lime is already contained, so that a predetermined component adjustment can be usually performed without newly adding slaked lime or quick lime. However, when the content of slaked lime in the alkali fly ash is small, slaked lime and / or quick lime are added to increase the amount of stable minerals produced.

In order to produce a mineral having the above effects, slaked lime and quick lime or any one of them is added to fly ash, and a sulfate-containing substance is added to the fly ash. It was added containing material, component ratio of the alkali content of CaO and SO _4, or the component ratio of the alkali content of CaO and SO ₄ and alkalinity CaO and Al
_It is necessary to adjust the component ratio of ₂ O ₃ to a predetermined range.

The component ratio of the above defined based on various experiments, the component ratio of SO ₄ with respect to CaO of alkalinity (SO ₄ / CaO) is preferably 0.3 or more. If SO ₄ / CaO is less than 0.3, the generation amount of the calcium aluminum sulfate compound is small, the fly ash becomes highly alkaline (high pH), and the elution amount of amphoteric metal such as Pb increases. In addition, CaO: A of alkali content
The molar ratio of l ₂ O ₃ is preferably from 1: 1 to 3: 1. When the molar ratio is CaO <Al ₂ O ₃ , the amount of stable minerals generated is reduced, and the degree of the effect of suppressing the elution of heavy metals is reduced. In addition, CaO in alkali content is changed to Al ₂ O
_{If the} molar ratio is more than three times as large as 3, the alkali content of CaO
Becomes excessive, and the pH of the processed product rises.

In the above-mentioned component adjustment, the content of CaO as an alkali component, which is a reference component when adjusting the component ratio, is as follows:
The content is adjusted to 30 wt% or less based on the total amount of the powder after the component adjustment. If the alkali content of CaO exceeds the upper limit of 30 wt%, the amount of the processed material increases, which is disadvantageous for landfill disposal.

In the above description of the fly ash treatment method, it is described that, after adding additive substances such as slaked lime, quicklime, a sulfate-containing substance, an aluminum-containing substance, and the like to the incinerated fly ash, kneading is performed in the presence of water. It is described that by doing so, the heavy metals in the fly ash are stabilized, but in the present invention, it is not always necessary to add each of the above-mentioned additives in powder form. Each of the above-mentioned additives may be a slurry prepared by adding water in advance. When the additive is added in the form of a slurry, part or all of the water required for kneading is supplied at the time of addition of the additive. Therefore, a shortage of water is supplied as needed during kneading. On this occasion,
It is not necessary to add all additives in a slurry.
Only specific additive substances may be used.

[0044]

Embodiments of the present invention will be described below. A. Test of acid gas remover (Preparation of acid gas remover)
The specific surface area is 43m^Two / G and 15m ^Two / G
Were used. Also, as a sulfate-containing substance
Uses two types of gypsum powder, anhydrous gypsum powder and dihydrate gypsum powder.
Was. Aluminum-containing substances include Izu alumite (composition
Is shown in Table 1). Raw materials of these things
And prepare various acid gas removers with different mixing ratios.
Was. The mixing ratio and component ratio of the prepared acid gas remover are shown in the table.
It is shown in FIG. Then, incinerate these acid gas removers
Used as an acid gas remover that blows into the furnace exhaust gas
Was.

[0045]

[Table 1]

[0046]

[Table 2]

Example 1 15 kg of anhydrous gypsum powder was added to 1000 kg of high surface area slaked lime having a specific surface area of 43 m ² / g (trade name: Tamacalc, manufactured by Okutama Industry Co., Ltd.)
, And mixed to prepare an acid gas remover. This acid gas remover was used to treat waste gas from a refuse incinerator having a treatment capacity of 95 tons / day of municipal waste and an exhaust gas amount of 28,800 Nm ³ / h.

In this treatment, an acid gas remover containing about 2 equivalents of slaked lime with respect to the amounts of HCl and SO ₂ in the exhaust gas was injected into the exhaust gas treatment tower. The concentration of exhaust gas at the exhaust gas flue inlet of the exhaust gas treatment tower was 583 ppm for HCl,
SO ₂ was 46.3ppm. The concentration of the exhaust gas after treatment at the outlet of the exhaust gas treatment tower was 16 pp.
m, SO ₂ was 8.2 ppm, and the removal rate was 9 ppm for HCl.
7% was SO ₂ 82%. At this time, the temperature of the exhaust gas was 170 to 180 ° C. Dust collection was good with a bag filter.

The composition of fly ash collected by the bag filter is as follows: 15% by weight of alkali CaO and 8% by weight of SO _4.
%, Al ₂ O ₃ was 12 wt%, and SiO 2 was 22 wt%. When heavy metals in fly ash were analyzed, lead was found to be 2%.
800 mg / kg, cadmium 50 mg / kg, arsenic 11 mg / kg, total chromium 83 mg / kg, total mercury 3.6 mg / kg.

Water was added to the fly ash and kneaded. The kneaded material was placed in a closed vessel, heated, and kept at a pressure of 1.9 atm (118 ° C.) for 2 hours. The treated product was subjected to an elution test based on the notification of the Environment Agency Notification No. 13, and the elution amount of heavy metal was less than 0.05 mg / liter of lead, which was below the legal standard value. Mercury, cadmium, arsenic, and chromium were not detected. The pH of the elution water was 11.8, which was a low value.
The results are shown in Table 3. In Table 3, ND described in the column of heavy metal elution amount indicates that the heavy metal elution amount is below the detection limit.

[0051]

[Table 3]

(Examples 2 to 32) The same waste gas incinerator exhaust gas treatment as in Example 1 was carried out under the same conditions as in Example 1 by using the acid gas remover compounded in the ratio shown in Table 2. I went in. The fly ash collected by the bag filter was subjected to a dissolution test under the same conditions as in Example 1. The results were as shown in Table 3.

According to Table 3, in the above embodiment, the amount of lead elution, which is particularly problematic, is determined by the regulation value (0.
3 mg / liter) or less, and good results have been obtained. In particular, when Izu alumite is added as an aluminum-containing substance in addition to gypsum added as a sulfate-containing substance, elution of heavy metals is further suppressed.

In the treatment of the collected fly ash, when the kneaded material was heated to a pressure of 1.9 atm, the amount of heavy metal eluted dropped below the regulation value in a short time. (Comparative Example 1 to Comparative Example 3) The same waste gas incinerator exhaust gas treatment as in Example 1 was performed under the same conditions as in Example 1 using a slaked lime-only acidic gas remover. For the fly ash collected by the bag filter, a dissolution test was performed under the same conditions as in the example. The results are shown in Table 3 together with the results of the examples.

According to Table 3, the dissolution of heavy metals in Comparative Example
The output is very large, far exceeding the regulated value.
Was. B Fly ash treatment test Alkali fly ash is combined with sulfate-containing substances or sulfate-containing substances.
Add aluminum-containing material, CaO for alkali,
SO_Four , And Al_Two O_Three The content of each component
After adjusting to within the range, water is added and kneaded, and this kneaded material is
Heating treatment was performed. In this test,
Alkali fly that already contains moderate slaked lime
Since it was ash, slaked lime was not added. (Example 33) Anhydroplaster 10 in 1000 g of alkali fly ash
0 g was added and mixed well. Set of fly ash mixed with gypsum
The composition is 20% by weight of alkaline CaO, SO_Four Is 11w
t%, Al_Two O_Three Is 7wt%, SiO_Two Is 19wt%
there were. From this composition, the component ratio (molar ratio) of the powder before kneading
, SO_Four /CaO=0.33, CaO: Al
_Two O_Three = 3: 0.6 and at least SO_Four / Ca
The value of O was within the range defined in the present invention.
The heavy metal content of alkali fly ash is 2100 mg of lead.
/ Kg, cadmium 58mg / kg, arsenic 8mg / kg
kg, total chromium 79mg / kg, total mercury 2.9mg
/ Kg.

Then, 450 g of water was added to the fly ash mixed with gypsum.
g, and kneaded, the kneaded material was placed in a closed container, heated, and kept at 1.9 atm for 2 hours while pressurizing (118 ° C.). Thereafter, a dissolution test was performed on the treated product based on the Notification of the Environment Agency No. 13.

As a result of the dissolution test, the amount of lead dissolved was 0.12.
mg / liter, which was below the legal standard. Mercury, cadmium, arsenic, and chromium were not detected. The pH of the elution water was 11.9. This pH value was a low value, while the pH in the case where the stabilization treatment was performed without adding any additive increased to about 12.5. The results are shown in Table 4. In Table 4, ND described in the column of heavy metal elution amount indicates that the heavy metal elution amount is below the detection limit.

[0058]

[Table 4]

(Examples 34 to 40) Gypsum (anhydrite or gypsum dihydrate) or gypsum and Izu alumite were mixed with fly ash at the ratios shown in Table 4 and the same method as in Example 33 was used. , And fly ash treatment. The results are shown in Table 4.

According to Table 4, in Examples 33 to 40, the elution amount of lead, which is particularly problematic, was all below the regulation value of the law, and good results were obtained.
In particular, when Izu alumite is added in addition to gypsum, elution of heavy metals is further suppressed.

According to this result, in order to make the elution amount of heavy metals in fly ash equal to or less than the regulation value, it is necessary to mix at least a sulfate-containing substance in addition to slaked lime. At this time, the amount of the sulfate-containing substance to be added is such that the molar ratio of SO _{4 to} CaO in the alkali portion is 0.3 or more. And if you want to further suppress the elution of heavy metals,
Further, it is necessary to add an aluminum-containing substance.

The treatment of fly ash was performed in a closed vessel, and 1.9a
When heating was performed to increase the pressure to tm, the elution amount of heavy metal was reduced below the regulation value in a short time, and the processing time was significantly shortened. (Comparative Example 4 and Comparative Example 5) After adding and mixing 500 g of water to 1000 g of alkali fly ash discharged from a dust collector of a refuse incineration plant, the kneaded material was left standing without heating, and under pressure. Two methods of heating treatment were performed. The results are shown in Table 4 together with the results of the examples.

According to Table 4, the elution amount of heavy metal in the comparative example was very large, far exceeding the regulation value. In the comparative example, the molar ratio of SO ₄ with respect to the alkali content of CaO in the fly ash to be processed SO ₄ / CaO = 0.
It was about 1. From these results, it was confirmed that the elution of heavy metals was suppressed by setting the component ratio of SO ₄ / CaO to a predetermined value or more.

[0064]

As described above, if the acid gas removing agent according to the present invention is used to remove the acid gas from the waste incineration exhaust gas, it is only necessary to add water to the fly ash collected by the dust collector and knead it. By simply carrying out the simple treatment described above, heavy metals in fly ash are stabilized and their elution is suppressed. For this reason, processing at the time of landfill disposal of fly ash is greatly simplified. This reduces processing costs. Furthermore, in the treatment of fly ash, slaked lime remaining in the fly ash is used as one component of a reactant that stabilizes heavy metals, so that resources are effectively used.

Further, since the collected fly ash can be processed by a simple device, the energy consumption is very small. In addition, since no chemical such as a liquid chelating agent is added, no harmful gas is generated during fly ash treatment.

According to the method for treating incineration fly ash of the present invention, heavy metals in fly ash are stabilized by adding inexpensive lime and inorganic substances such as sulfate-containing substances and aluminum-containing substances to fly ash. Since the elution is suppressed, the processing cost when landfilling fly ash is greatly reduced.

When alkali fly ash is treated by the method for treating incinerated fly ash according to the present invention, slaked lime remaining in the fly ash is one component of a reactant for stabilizing heavy metals. Therefore, the slaked lime residue used as an acid gas remover can be used as it is as a component for stabilizing heavy metals. For this reason, resources can be effectively used, and processing costs can be reduced.

Further, in the treatment of alkali fly ash,
Since the slaked lime in the fly ash reacts with the added inorganic substance to become a stable mineral, the slaked lime is consumed, and an increase in the pH of the fly ash is suppressed. For this reason, the pH of fly ash can be reduced to a region where heavy metal elution does not occur.

Since no chemical such as a liquid chelating agent is used, no harmful gas is generated. In addition, since only simple processing such as kneading and heating is required, the processing apparatus is simple and energy consumption is very small.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 20/08 B09B 3/00 304G B09B 3/00 F term (Reference) 4D002 AA02 AA19 AB01 AC04 BA03 CA01 DA05 DA08 DA11 DA14 GA01 GB08 4D004 AA37 AB03 CA15 CA22 CA34 CA47 CC03 CC11 CC12 DA03 DA07 DA10 4G066 AA16B AA20B AA22B AA47B AA66B AA78B BA26 CA07 CA23 CA31 DA02 FA03 FA20 FA21 FA37

Claims (13)

[Claims] 1. A mixture comprising at least slaked lime powder and a powder of a sulfate-containing substance, wherein the molar ratio of SO ₄ to CaO, which is determined as an alkali content, is CaO: SO _4.
= 1: An acid gas remover for refuse incineration exhaust gas, which is adjusted to a range of 0.008 to 0.4. 2. The molar ratio of SO ₄ to CaO, which is determined as an alkali content, is CaO: SO ₄ = 1: 0.02-
The acid gas remover for waste incineration exhaust gas according to claim 1, wherein the agent is adjusted to a range of 0.08. 3. The method according to claim 1, further comprising a powder of an aluminum-containing substance.
CaO which is determined as an alkali component
Al for_Two O_Three Is molar ratio of CaO: Al _Two O_Three =
1: Adjusted to the range of 0.003 to 0.133
Waste incineration according to claim 1 or claim 2, characterized in that:
Acid gas remover for exhaust gas. 4. The molar ratio of Al ₂ O ₃ to CaO, which is determined as an alkali content, is CaO: Al ₂ O ₃ = 1:
The acid gas remover for waste incineration exhaust gas according to claim 3, wherein the acid gas remover is adjusted to a range of 0.007 to 0.027. 5. The acid gas remover for waste incineration exhaust gas according to claim 1, wherein the specific surface area of the slaked lime powder is 20 m ² / g or more. 6. A sulfate-containing substance is added to alkali fly ash that is collected when slaked lime is blown into refuse incineration exhaust gas to remove acidic gas, and SO _{4 with} respect to CaO quantified as an alkali component is added. The molar ratio of SO ₄ / CaO
A method for treating garbage incineration fly ash, comprising adjusting the mixture to a range of ≧ 0.3, kneading in the presence of water, and heating the kneaded material. 7. A sulfate-containing substance and an aluminum-containing substance are added to alkali fly ash that is collected when slaked lime is blown into a waste incineration exhaust gas to remove an acid gas, and is determined as an alkali component. SO ₄ for CaO
After adjusting the molar ratio of the components to SO ₄ /CaO≧0.3 and the molar ratio of the Al ₂ O ₃ component to CaO quantified as the alkali content in the range of CaO: Al ₂ O ₃ = 3: 1 to 3, respectively. A method for treating incinerated fly ash, comprising kneading in the presence of water and heating the kneaded material. 8. A method in which slaked lime is blown into waste gas from incineration to generate acid.
Alkali fly ash collected during the removal of volatile gases
Slaked lime and / or quick lime are added to
CaO which is determined as an alkali content by adding a substance
Is determined as an alkali content of 30 wt% or less.
SO for CaO_Four The molar ratio of SO _Four / CaO ≧
After adjusting each to the range of 0.3, knead in the presence of water
Waste incineration by heating the kneaded material
Ash treatment method. 9. A slaked lime and / or quick lime is added to alkali fly ash collected when slaked lime is blown into a waste incineration exhaust gas to remove an acid gas, and a sulfate-containing substance and an aluminum-containing substance are further added. In addition, the content of CaO quantified as alkali content is 30 wt% or less, the molar ratio of the SO ₄ component to CaO quantified as alkali content is SO ₄ /CaO≧0.3, and the content of CaO quantified as alkali content is CaO. The molar ratio of the Al ₂ O ₃ component to Ca
_{O: Al 2 O 3 = 3} : After adjusting each 1-3 range, and kneaded in the presence of water, treatment method of waste incineration fly ash, which comprises heating the kneaded material. 10. A slaked lime and / or quick lime is added to neutral fly ash which is collected when an acid gas removal treatment is not performed by blowing slaked lime into a waste incineration exhaust gas, and a sulfate-containing substance is further added. , CaO quantified as alkali content
30 wt% of the content of the following, the molar ratio of SO ₄ component to CaO which is quantified as alkalinity SO ₄ / CaO
A method for treating incinerated fly ash, which comprises adjusting the mixture to ≧ 0.3, kneading the mixture in the presence of water, and heating the kneaded material. 11. A method for removing slaked lime and / or lime to neutral fly ash which is collected when an acid gas removal treatment for blowing slaked lime into a waste incineration exhaust gas is not performed, and further comprising a sulfate-containing substance and an aluminum-containing substance. Is added, the content of CaO quantified as an alkali is 30 wt% or less, the molar ratio of the SO ₄ component to CaO quantified as an alkali is SO ₄ /CaO≧0.3, and the content is quantified as an alkali. The molar ratio of the Al ₂ O ₃ component to CaO is Ca
_{O: Al 2 O 3 = 3} : After adjusting each 1-3 range, and kneaded in the presence of water, treatment method of waste incineration fly ash, which comprises heating the kneaded material. 12. Waste incineration fly ash collected during an exhaust gas treatment for removing an acidic gas in a waste incineration exhaust gas using the acid gas removing agent according to any one of claims 1 to 5. , In the presence of water, and heating the kneaded material. 13. The treatment of incinerated fly ash according to claim 6, wherein the kneaded material is placed in a closed container and heated so that the pressure is maintained at less than 2 atm. Method.