JP7075860B2 - Fly ash processing equipment and processing method - Google Patents

Description

The present invention relates to a fly ash treatment apparatus and a treatment method, and in particular, fly ash containing alkaline earth metal components such as calcium generated in waste treatment and heavy metals such as mercury, zinc, lead and cadmium. Regarding the processing device and processing method.

Various fuels, waste, incinerated ash such as sludge, incinerated fly ash, molten fly ash, etc. may contain harmful heavy metals such as mercury, zinc, lead, and cadmium, and these harmful substances are included. It is not environmentally preferable to bury fly ash as it is, and even when burying it, it is required to detoxify it. Specifically, when disposing of incinerator fly ash, heavy metal elution suppression treatment such as chemical treatment and melting treatment is performed in advance on the object to be treated containing fly ash generated from the waste incinerator.

Generally, as one of such treatment methods, a kneading treatment using a heavy metal fixative such as a chelate is used. However, in the kneading process,
(I) The entire exhaust gas generated from the waste incinerator is uniformly fixed with a heavy metal fixing agent such as chelate in a state containing various fly ash. Such heavy metal fixatives are expensive, and reducing the amount used has been a major issue in the detoxification treatment of the object to be treated.

Further, in the waste treatment, the amount of landfill disposal of soot dust can be reduced, and soot dust containing no reaction product of an alkaline chemical is melt-treated to make the structure compact, as illustrated in FIG. , A waste treatment apparatus 1 has been proposed (see, for example, Patent Document 1). Specifically, an alkaline chemical is applied to the exhaust gas from the gasification melting furnace 2 between the gasification melting furnace 2 that thermally decomposes the waste and melts the residue, and the gasification melting furnace 2 and the dust collecting device 4. The alkaline chemical supply device 3 that blows in the alkaline chemical to generate the reaction product between the acidic substance contained in the exhaust gas and the alkaline chemical, and the dust collecting device 4 coarsely dusts the soot containing the reaction product. It is provided with a classification device 5 for classifying into fine dust and fine dust and separating the reaction product to the fine dust side, and a coarse dust return means 6 for returning the coarse dust to the gasification melting furnace 2.

However, the conventional method including such a waste treatment device has the following problems.
(Ii) In the waste treatment apparatus exemplified in FIG. 7, coarse-grained dust is finally treated as slag while periodically repeating melting treatment and alkali treatment. At this time, some heavy metals contained in the coarse-grained dust may remain in the slag. These heavy metals are contained in the slag without being fixed or removed, and when the slag is reused or disposed of, a secondary treatment for detoxification may be required.
(Iii) Conventionally, the object to be treated generated from the waste incinerator may contain a large amount of various acidic substances, and the object to be treated is subjected to alkaline treatment by adding an alkaline chemical as the primary treatment. The fly ash is dust-collected together with the reaction product. On the other hand, heavy metals contain a higher concentration of fine-grained dust than that of coarse-grained dust. At this time, as in the waste treatment apparatus exemplified in FIG. 7, the classification point set in the case of performing the classification treatment often depends on the particle size of the alkaline chemical to be charged, and the classified coarse particles are classified. The dust may contain a large amount of heavy metals, and the heavy metals may not be sufficiently treated on the object to be treated.
(Iv) If the object to be treated generated from the waste incineration facility contains a large amount of alkaline earth metal compounds such as calcium (Ca), or if an alkaline chemical is added as the primary treatment, the treatment is to be performed. Since the substance is a basic substance, it is necessary to prevent the elution of heavy metals and ensure safety for the final treated substance to be disposed of by landfill. Previously, as a treatment for ensuring such safety, a neutralization treatment or an immobilization treatment was performed on the entire object to be treated, and a large amount of treatment agent or the like was required.
(V) Further, when the object to be treated after the neutralization treatment contains heavy metals such as lead, the acid / basic characteristics (pH) of the object to be treated due to deterioration of the landfill soil or rainfall are long-term. Changes may occur, and if they are changed to basic, they may lead to elution of heavy metals.

Japanese Unexamined Patent Publication No. 2011-127861

Therefore, an object of the present invention is to provide an effective means for preventing the elution of harmful heavy metals such as lead contained in incinerated fly ash and the like generated in waste treatment, and to prevent such elution. It is an object of the present invention to provide a fly ash treatment apparatus and a treatment method capable of reducing the amount of a treatment agent such as a pH adjuster and a stabilizer required for the above.

As a result of diligent research, the present inventors have found that the above object can be achieved by the following fly ash treatment apparatus and treatment method, and have completed the present invention.

The fly ash processing apparatus according to the present invention is
For the fluid A to be treated, which contains powdery or crushed fly ash generated from a waste incinerator.
The fluid A to be treated is introduced, and the fly ash is classified as fine powder ash for fly ash below the classification point and coarse powder ash for fly ash above the classification point based on a predetermined classification point set in advance. Classification device,
An aqueous solution containing a chelating agent and a pH adjusting treatment with an aqueous solution containing the pH adjusting agent, which has a pH adjusting agent introducing part and a chelating agent introducing part, with respect to the fluid B to be treated containing the fine powder ash supplied from the classifying device. First treatment tank, which is chelated by
A second treatment tank, which has a chelating agent-introducing portion and is subjected to chelation treatment with an aqueous solution containing the chelating agent, with respect to the fluid C to be treated containing coarse powder ash supplied from the classification device.
A control device for controlling the supply amounts of the pH adjuster and the chelating agent supplied to the first treatment tank and the second treatment tank is provided.
It is characterized in that the supply amount of the pH adjuster and the chelating agent is adjusted according to the introduction amount of the fluid A to be treated and the classification point.
Further, the present invention is a method for treating fly ash.
For the fluid A to be treated, which contains powdery or crushed fly ash generated from a waste incinerator.
A classification treatment step in which the fly ash is classified as fine powder ash for fly ash below the classification point and coarse powder ash for fly ash above the classification point based on a predetermined classification point set in advance.
A fine powder ash treatment step in which the classified fluid B containing the fine powder ash is subjected to a pH adjustment treatment with an aqueous solution containing a pH adjuster and a chelate treatment with an aqueous solution containing a chelating agent.
A crude powder ash treatment step in which the fluid C to be treated containing the classified coarse powder ash is chelated with an aqueous solution containing a chelating agent.
The pH adjuster and the chelating agent are controlled and adjusted according to the amount of the fluid A to be introduced and the classification point.

In the process of treating incinerator fly ash and the like generated in waste treatment, efficient elution prevention treatment of heavy metals and reduction of treatment agents are important issues as described above. The present inventor has solved these problems as a result of various verifications.
(A) The smaller the particle size of fly ash (fine powder ash), the higher the concentration of heavy metals (compared to the same weight). In other words, not only the surface area per unit weight is larger than that of fine powder ash, but also the difference in particle size due to the difference in the content concentration of heavy metals between the vicinity of the particle surface of the fly ash and the inside in the formation of fly ash during combustion. It may be mentioned that there is a difference in the content concentration of heavy metals due to the above.
(B) The smaller the particle size of fly ash, the lower the acidity (pH). That is, in the formation of flying ash during combustion, the acidity of flying ash is accompanied by the formation of oxygen compounds under high temperature conditions (for example, alkali metal oxides and alkaline earth metal oxides form flying ash which is a basic substance). The degree decreases, and the tendency is higher for fine powder ash with a larger surface area per unit weight, and oxygen due to the difference in particle size due to the difference in the amount of oxygen compounds produced near and inside the particles of flying ash. Differences in the content concentration of the compounds may occur.
(C) By adjusting the pH of fly ash, it is possible to prevent the elution of heavy metals. Specifically, as shown in the verification results described later, the treatment target is further based on the findings that "the amount of elution of heavy metals affects the acidity of the fly ash" and "the tendency differs depending on the type of heavy metals". It was found that the elution of heavy metals can be effectively prevented by adjusting the pH of the fly ash according to the type of heavy metals in the fly ash. For example, by adjusting the pH of fly ash to more than 9 to less than 11, the amount of lead elution can be reduced below the legal standard, and by adjusting the pH of fly ash to 6 or more, elution of cadmiums can be achieved. The amount can be reduced below the statutory standard.
(D) In order to prevent the immobilization and elution of heavy metals in fly ash, chelation treatment corresponding to the particle size of fly ash and chelation treatment at the same time as pH adjustment treatment corresponding to the particle size of fly ash can be performed. It is effective.
(D-1) Based on the findings of (a) above, after the classification treatment, the fine powder ash with a high concentration of heavy metals and a small surface area is chelated to uniformly chelate the entire fly ash. The amount of chelate used can be significantly reduced as compared with the above.
(D-2) Further, based on the findings of (a) to (d-1) above, by performing a combination treatment of pH adjustment treatment and chelation treatment on fine powder ash, both treatment functions can be synergistically exerted. Can be done. That is, by performing a pH adjustment treatment on the classified fine powder ash, it is possible to perform an efficient pH adjustment treatment to prevent the elution of heavy metals, and at the same time, elution of heavy metals to a predetermined amount of fly ash. The amount of chelate used for prevention can be greatly reduced. Further, even when it is difficult to prevent long-term elution of heavy metals only by the pH adjustment treatment, a more stable elution prevention treatment function can be ensured by performing the chelate treatment.
I got the knowledge.
Based on these findings, the present invention has developed the optimum treatment of fly ash using the minimum amount of treatment agent.
Specifically, in the first stage treatment, a classification point is set, and the fly ash above the classification point is regarded as fine powder ash, and the fly ash above the classification point is treated as coarse powder ash. Next, in the second stage treatment, a chelate treatment is performed on the coarse powder ash having a low heavy metal content, and a pH adjustment treatment and a chelate treatment are performed on the fine powder ash having a high heavy metal content. The former (classification treatment) reveals the optimum treatment conditions for preventing the elution of heavy metals based on the above findings (a) and (b), and the latter reveals the chelating agent used for the chelating treatment of the coarse powder ash. The amount of ash can be reduced to more than the yield of fine ash, and the pH adjuster and chelating agent used for fine ash can be reduced to more than the yield of fine powder ash. Further, regarding the latter treatment for fine powder ash, the following technical effects can be obtained. That is, when the detoxified treated product is actually landfilled at a disposal site for a long period of time, the pH of the treated product may change due to rainfall, infiltration from geology, or the like. In the treatment process of the present application, such risks are eliminated in advance by performing pH adjustment treatment on fine powder ash having a particularly high concentration of heavy metals and further immobilization treatment using a chelating agent, and more stable and harmless. Can be processed. Therefore, the fly ash treatment apparatus and treatment method according to the present invention can reliably prevent the elution of heavy metals, and can significantly reduce the total amount of the chelating agent and pH adjuster used as the treatment agent. became.

The present invention is the fly ash treatment apparatus, and is characterized in that the fluid A to be treated is previously treated with a calcium-based agent to remove acidic harmful components.
Incinerator fly ash may contain alkaline earth metals and the like in addition to heavy metals, and some of these substances irreversibly form stable compounds by acid treatment or base treatment. In addition, the exhaust gas from the incinerator may be first detoxified with slaked lime or the like. As a result of the verification of the present invention including such conditions, the following new findings were obtained.
(B-1) When a treatment for removing acidic harmful components with a calcium-based chemical (hereinafter sometimes referred to as "Ca-based pretreatment") is performed in advance, the fly ash after the treatment is acidic due to the difference in particle size. It was found that there was almost no change in the degree (see "Verification Results" and FIG. 4 described later), and that the chemical stability of fly ash could be improved. In other words, by performing Ca-based pretreatment to prevent the elution of heavy metals due to changes in acidity during long-term storage, pH is the main treatment agent required for the elution prevention treatment of heavy metals for fine powder ash. By using the adjusting agent, it is possible to reduce the amount of the expensive chelating agent used, and it is possible to obtain a function of reducing the load of the pH adjusting treatment on the fine powder ash and reducing the amount of the pH adjusting agent used. ..
(B-2) By the classification treatment, the amount of the calcium-based drug used for the Ca-based pretreatment can be reduced. In other words, since it was found that the classified fine powder ash tends to contain not only heavy metals but also alkaline earth metal compounds, the calcium-based chemicals required for the Ca-based pretreatment are used. The amount used can be reduced in an amount corresponding to the content of the alkaline earth metal compound in the fine ash, as compared with the case where there is no classification treatment after the previous Ca-based pretreatment. Therefore, it is possible to make the Ca-based pretreatment function effectively by the classification treatment and to reduce the amount of the calcium-based drug used in the Ca-based pretreatment.

The present invention is the fly ash processing apparatus, characterized in that carbon dioxide is used as the pH adjuster.
As described above, incinerator fly ash may contain alkaline earth metals and the like, and some of these substances irreversibly form stable compounds by acid treatment or base treatment. Further, the classified fine powder ash contains not only heavy metals but also a large amount of such alkaline earth metals and the like. That is, by using a reagent such as an alkaline earth metal that is immobilized by reacting with calcium, for example, as a pH adjusting agent, not only the pH adjusting treatment but also the function of preventing the elution of heavy metals by such the immobilization treatment is increased. Is possible. Specifically, in this verification process,
(C-1) Carbon dioxide reacts with heavy metals such as lead to form a charcoal oxide (or bicarbonate) that is immobilized and difficult to elute, so that a higher elution prevention effect can be obtained. In addition, carbon dioxide is generated in the combustion process and is easily available, and when used as such a treatment agent, it can also contribute to the reduction of greenhouse gases in waste treatment.
(C-2) When the classified fine powder ash contains a large amount of alkaline earth metals (including cases where it has been treated with a calcium-based chemical in advance), carbon dioxide is not only heavy metals but also alkaline earth metals. By reacting with the above to form a carbon oxide (or hydride) that is immobilized and difficult to elute, it is possible to form a treated product that is chemically stable for a long period of time and whose acidity hardly changes.
I got the knowledge.

Further, the fly ash processing apparatus according to the present invention is
For the fluid A to be treated, which contains powdery or shattered fly ash generated from a waste incinerator.
The fluid A to be treated is introduced, and the fly ash is classified as fine powder ash for fly ash below the classification point and coarse powder ash for fly ash above the classification point based on a predetermined classification point set in advance. Classification device,
The first storage tank in which the fluid B to be treated containing the fine powder ash delivered from the classification device is stored,
A second storage tank in which the fluid C to be treated containing the coarse powder ash supplied from the classification device is stored.
A switching unit in which the delivery of the fluid B to be processed from the first storage tank and the delivery of the fluid C to be processed from the second storage tank are switched.
The fluid B to be treated, which has a pH adjusting agent introducing section and a chelating agent introducing section and is introduced via the switching section, is subjected to pH adjusting treatment with an aqueous solution containing a pH adjusting agent and chelating treatment with an aqueous solution containing a chelating agent. The third treatment tank, which is subjected to chelation treatment with an aqueous solution containing a chelating agent, with respect to the fluid C to be treated, which is subjected to or introduced through the switching portion.
A control device that controls the supply amounts of the pH adjuster and the chelating agent supplied to the third treatment tank.
Equipped with
It is characterized in that the supply amount of the pH adjuster and the chelating agent is adjusted according to the introduction amount of the fluid A to be treated and the classification point.
In the above-mentioned fly ash treatment apparatus, the fluid A to be treated is classified, and the fluids B and C to be treated after classification are individually and independently subjected to pH adjustment treatment and chelation treatment. It is based on a device that can be used. However, in the treatment of incinerator fly ash or the like, the content concentration of heavy metals in the fluid A to be treated may change significantly and continuous treatment may be difficult. Further, when the change in the treatment amount of the fluid A to be treated is large, it is necessary to use a treatment tank having a large capacity assuming the maximum treatment amount, which requires a large-scale equipment installation and an excess of the treatment agent for a small treatment amount. It may be necessary to have a function to prevent the occurrence of unprocessed products due to excessive processing such as input or sudden increase in processing amount. Further, there is a case where it is desired to add the component of the present invention to the existing fly ash processing apparatus to secure the function of the present invention. The present invention can respond to such a request by storing the fine powder ash and the coarse powder ash after the classification treatment in a predetermined amount or for a predetermined time, respectively, and switching between them and treating them in batches. In addition, it is possible to perform processing under optimum conditions corresponding to the processing amount of the fluid B or the fluid C to be processed before the treatment detected or estimated in advance and the content concentration of heavy metals.

The whole block diagram which shows the 1st (second) structural example of the fly ash processing apparatus which concerns on this invention. The whole block diagram which shows the 3rd structural example of the fly ash processing apparatus which concerns on this invention. Explanatory drawing which illustrates the verification result (a) of the fly ash treatment which concerns on this invention. Explanatory drawing which illustrates the verification result (b) of the fly ash treatment which concerns on this invention. Explanatory drawing which illustrates the verification result (c) of the fly ash treatment which concerns on this invention. Explanatory drawing which illustrates the verification result (d) of the fly ash treatment which concerns on this invention. An overall configuration diagram illustrating a waste treatment apparatus according to the background technique.

The flying ash processing device (hereinafter referred to as “the device”) according to the present invention includes a classification device, a first treatment tank, a second treatment tank, and a control device, and is powdered or crushed from a waste incineration facility. The fluid A to be treated is introduced into the classification device for the fluid A to be treated containing the flying ash, and the flying ash contained therein is equal to or lower than the classification point based on a predetermined classification point set in advance. The flying ash is classified as fine powder ash, and the flying ash above the classification point is classified as coarse powder ash. In the first treatment tank having the pH adjusting treatment, the pH adjusting treatment with the aqueous solution containing the pH adjusting agent and the chelating treatment with the aqueous solution containing the chelating agent are performed, and the treated fluid C containing the coarse powder ash supplied from the classifier is chelated. In the second treatment tank having the agent introduction unit, the chelating treatment is performed with an aqueous solution containing a chelating agent, and in the control device, the supply amount of the pH adjuster and the chelating agent supplied to the first treatment tank and the second treatment tank is increased. It is characterized in that the supply amount of the pH adjuster and the chelating agent is controlled and adjusted according to the introduction amount and the classification point of the fluid A to be treated.
With such a configuration, it is possible to surely prevent the elution of heavy metals, and it is possible to greatly reduce the total amount of the chelating agent and the pH adjusting agent used as the treatment agent. In particular, the effect of preventing the elution of heavy metals due to changes in the pH of the treated material due to rainfall or infiltration from the geology, such as when the detoxified processed material is landfilled at a disposal site for a long period of time. Is excellent in that In addition, even when the type (composition) of fly ash to be treated and the amount to be treated fluctuate greatly, the detoxification treatment was insufficient by performing a chelate treatment on a predetermined amount of heavy metals in advance. It is possible to prevent the elution of heavy metals that may occur.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Configuration example of this device>
As an embodiment of the present apparatus, a basic schematic overall configuration is illustrated in FIG. 1 (first configuration example).
This device targets the fluid A to be treated containing the flying ash Aa, and is to be treated containing the classification device 1 in which the fluid A to be treated is introduced and the flying ash Aa is classified, and the fine powder ash Ba supplied from the classification device 1. A fluid to be treated containing coarse powder ash Ca supplied from a first treatment tank 2 and a classification device 1 in which a pH adjusting agent Pa and an aqueous solution Wa containing a chelating agent Ka are used to perform a pH adjusting treatment and a chelating treatment on the fluid B. The pH adjuster Pa supplied to the second treatment tank 3 and the first treatment tank 2 and the chelating agent Kb supplied to the second treatment tank 3 are subjected to the chelating treatment with the aqueous solution Wb containing the chelating agent Kb with respect to C. A control device (not shown) for controlling the supply amount of the pH adjuster Pa and the chelating agents Ka and Kb are adjusted according to the introduction amount and the classification point of the fluid A to be treated. The solid-liquid mixture D treated and generated in the first treatment tank 2 and the solid-liquid mixture E treated and generated in the first treatment tank 2 are delivered as a treated product such as a landfill treated product.

[Fly ash]
In this device, the object to be treated is the fluid A to be treated, which contains powdery or crushed fly ash Aa generated from a waste incinerator, and was crushed in advance using a crusher as a pretreatment of this device. Also includes fly ash. Fly ash includes various industrial wastes including construction waste, incinerated ash such as sludge, incinerated fly ash, molten fly ash, and various other wastes that may contain alkaline earth metal components such as calcium. be able to. It includes not only heat-treated waste such as combustion treatment, but also chemically treated waste such as chelate treatment and cement solidification treatment. The fluid A to be treated is generally a gas containing solid fly ash Aa, but also includes a liquid containing muddy fly ash Aa when a cleaning step is widely performed as a pretreatment of the present apparatus. Further, as will be described later, when the exhaust gas generated from the waste incinerator is previously treated with a calcium-based chemical to remove acidic harmful components, the fluid A to be treated contains the chemical.

Fly ash Aa is treated as it is when fine powder ash and coarse powder ash are mixed in a predetermined ratio, such as incinerated fly ash and molten fly ash. However, if the solid matter has a particle size of several cm to several tens of centimeters or more due to flying ash that has been coagulated in advance, incinerated ash that has been cement-solidified, etc., a predetermined crusher is used as a pretreatment. It is preferable to have a pulverization step of pulverizing into a powdery substance having a particle size or less (for example, an average particle size of 200 μm or less). By forming the fluid A to be treated in which fine powder ash Ba and coarse powder ash Ca are mixed at a predetermined ratio, stable classification efficiency is ensured, the surface area is increased by crushing, and fine powder ash Ba having pores is formed. By forming the above, high pH treatment efficiency (chelate treatment efficiency, which will be described later) can be ensured. For chemically active flying ash and chemically unstable flying ash, acid treatment (for example, with hydrochloric acid or nitric acid) or base treatment (for example, sodium hydroxide or potassium hydroxide) is used as pretreatment. Etc.) or a treatment for removing acidic harmful components with a calcium-based chemical is preferable. It is possible to stably perform classification processing and stabilization processing. Further, in the case of a sludge-like body having a large variation in particle size and difficult to clean, such as main ash, it is preferable to perform acid treatment together with pulverization treatment.

[Classification device]
The fluid A to be treated, in which fine powder ash and coarse powder ash are mixed at a predetermined ratio, is first introduced into the classification device 1. In the classification device 1, with respect to the fly ash Aa contained in the fluid A to be treated, the fly ash below the classification point is fine powder ash Ba and the fly ash above the classification point is coarse powder ash based on the preset classification point. Classified as Ca. The setting value of the classification point differs depending on various requirements such as the type and properties of fly ash As or the fluid A to be treated, and the presence / absence and content of pretreatment. For example, in the case of incinerator ash of general waste without pretreatment, when the classification point is set to 7 to 10 μm, the fine powder ash Ba and coarse powder ash Ca are classified into the average particle size and yield exemplified in Table 1 below. An example is given.

In this device, the classification device 1 can use various classification means such as a cyclone type, an air flow centrifugal type (wind type), a sieve type (including a vibration sieve), and a filter type, but the cyclone type is more suitable. preferable. A classification means having excellent operability is preferable because there is no possibility of clogging of the sieve or filter without using a separate fluid such as classification air. Further, it is also preferable to use a plurality of classification means in combination according to the characteristics of fly ash Aa, such as a combination of a cyclone type and a sieve type, as the classification device 1 to perform the classification treatment.

[PH adjustment process]
The fluid B to be treated containing one of the classified fine ash Bas is introduced into the first treatment tank 2, where the chelation treatment is performed together with the pH adjustment treatment with the aqueous solution Wa containing the pH adjuster Pa and the chelating agent Ka. .. At this time, more efficient pH treatment can be performed by performing the following pH treatment based on the above-mentioned findings.
(A) The smaller the particle size of flying ash, the higher the concentration of heavy metals (compared to the same weight). Therefore, by performing pH adjustment treatment on the fine powder ash with a high content of classified heavy metals, it is efficient. It is possible to prevent the elution of heavy metals. (B) The smaller the particle size of flying ash, the lower the acidity (pH). Was found to be low. Therefore, the pH adjuster used for the fine powder ash can be used in a small amount as compared with the amount used for the same amount of fly ash before classification. Elution of heavy metals can be efficiently prevented by pH adjustment treatment using a small amount of pH adjuster. (C) Elution of heavy metals can be prevented by adjusting the pH of flying ash. Based on the findings that "the amount of heavy metals eluted affects the acidity of the flying ash" and "the tendency differs depending on the type of heavy metals", the flying ash according to the type of heavy metals to be treated By adjusting the pH of the ash, it is possible to effectively prevent the elution of heavy metals (see "Verification Results" described later and FIGS. 5 (A) and 5 (B)). For example, when fly ash contains a large amount of lead, heavy metals can be more efficiently adjusted by adjusting the pH to more than 9 to less than 11 with respect to the fluid B to be treated containing fine powder ash Ba having a high concentration of heavy metals. Elution prevention treatment can be performed. Further, when the fly ash contains a large amount of cadmium, the elution prevention treatment of heavy metals can be performed more efficiently by adjusting the pH of the fluid B to be treated to 6 or more. At this time, since the fine powder ash Ba has a lower pH characteristic, an appropriate pH adjustment can be performed by introducing a smaller amount of the pH adjuster Pa.
The "simultaneous treatment of pH adjustment treatment and chelation treatment" will be described later.

[PH regulator]
Since the components of fly ash Aa differ depending on the type of waste and the like, it is preferable to select the optimum pH adjuster Pa corresponding to the type and properties of fly ash Aa. Here, since the solid-liquid mixture D often contains heavy metals as an acidic substance, it is preferable to use a basic reagent as the pH adjuster Pa. Specifically, any one of sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), sodium bicarbonate (NaHCO ₃ ), sulfuric acid (H ₂ SO ₄ ) and phosphoric acid (H ₃ PO ₄ ). Alternatively, it is preferable to use some of these in combination. By using such a pH adjuster Pa, a calcium-containing water-insoluble compound can be produced even for calcium hydroxide (Ca (OH) ₂ ), calcium chloride (CaCl ₂ ) and the like as calcium-containing components. Further, for alkaline earth metal components such as magnesium (Mg) and barium (Ba) other than calcium, water-insoluble compounds can be similarly produced by using the pH adjusters Pa and Pb.

Further, gaseous carbon dioxide (CO ₂ ) can be used as the pH adjuster Pa. By bringing CO ₂ into contact with fly ash Ba, the pH adjustment process can be performed quickly and reliably. In particular, by injecting CO ₂ after adding water to the fine powder ash Ba with a kneader or the like, or by bubbling CO ₂ in an aqueous solution containing the fine powder ash Ba, the air-solid contact is activated, and the pH is more quickly and surely. Adjustment processing can be performed. In addition, CO ₂ is generated in the combustion process and is easily available, and by using it as a pH treatment agent Pa, it can also contribute to the reduction of greenhouse gases in waste treatment. Further, by using CO ₂ as the pH adjuster Pa, the following technical effects can be obtained.
(C-1) CO ₂ reacts with heavy metals such as lead to form a charcoal oxide (or hydride) that is immobilized and difficult to elute, so that a higher elution prevention effect can be obtained.
(C-2) Incinerator fly ash may contain alkaline earth metals and the like, and some of these substances irreversibly form stable compounds by acid treatment or base treatment. Further, the classified fine ash Ba contains not only heavy metals but also a large amount of such alkaline earth metals and the like. That is, when the classified fine powder ash Ba contains a large amount of alkaline earth metals (including the case where it has been treated with a calcium-based chemical in advance), by using CO ₂ as the pH adjuster Pa, only heavy metals can be used. By forming a carbon oxide (or hydride) that is fixed and difficult to elute by reacting with alkaline earth metals, etc., a treated product D that is chemically stable for a long period of time and whose acidity hardly changes is formed. Can be done.

[Chelating treatment]
The fluid B to be treated introduced into the first treatment tank 2 is subjected to a chelation treatment with an aqueous solution Wa containing a chelating agent Ka at the same time as the pH adjustment treatment. Further, the fluid C to be treated containing one of the classified coarse powder ash Ca is introduced into the second treatment tank 3, where the chelation treatment is performed with the aqueous solution Wb containing the chelating agent Kb. At this time, the following findings were obtained in the verification process according to the present invention.
(D-1) In order to prevent the immobilization and elution of heavy metals in fly ash, it is effective to perform a chelate treatment corresponding to the particle size of fly ash.
That is, rather than uniformly adding a chelating agent to unclassified fly ash, chelating is performed by intensively adding a large amount of chelating agent Ka to classified coarse powder ash Ca having a low concentration of heavy metals. It has become possible to reduce the amount of the agent used and prevent the elution of heavy metals more efficiently.
In addition, by performing chelation treatment on fine powder ash Ba, which has a high concentration of heavy metals and a small surface area, chelation treatment items are more efficient than uniformly adding a chelating agent to unclassified fly ash of the same weight. It became possible to reduce the amount of the chelating agent used and to prevent the elution of heavy metals more efficiently.
(D-2) Further, in order to prevent the immobilization / elution of heavy metals in the fine ash Ba, it is effective to perform the chelate treatment at the same time as the pH adjustment treatment.
That is, by performing the chelate treatment at the same time as the pH adjustment treatment having the function of preventing the elution of heavy metals from the fine ash Ba, the load of the chelate treatment is reduced, the amount of the chelating agent used is reduced, and the heavy metals are more efficiently used. It has become possible to prevent the elution of.
Further functions and effects of "simultaneous treatment of pH adjustment treatment and chelation treatment" will be described later.

[Chelating agent]
Examples of the chelating agent Kb (Ka) capable of efficiently preventing the elution of heavy metals include piperazine-based chelating agents, diethylamine-based chelating agents, dithiocarbamic acid-based chelating agents, and the like.

[Simultaneous treatment of pH adjustment treatment and chelation treatment]
As described above, it is preferable to carry out a chelate treatment at the same time as the pH adjustment treatment for the fine powder ash Ba. In other words, the following findings were obtained during the verification process.
(D) In order to prevent the immobilization and elution of heavy metals in fly ash, chelation treatment corresponding to the particle size of fly ash and chelation treatment at the same time as pH adjustment treatment corresponding to the particle size of fly ash can be performed. It is effective.
In other words, there is a possibility of elution due to changes in the pH of the treated product due to changes in soil quality (pH) due to external factors such as rainfall. At this time, heavy metals chelated by performing chelation treatment at the same time as pH adjustment treatment. It is possible to reduce the fluctuation amount of the pH of the processed product containing the same kind, and it is possible to maintain the elution prevention function by adjusting the pH for a long period of time. Further, by performing both treatments at the same time, the strict optimum setting range of pH in the pH adjustment treatment can be relaxed and the amount of the pH adjuster Pa can be reduced.
(D-1) It is more necessary than performing a uniform chelate treatment on the entire fly ash Aa by chelating the fine powder ash Ba having a high concentration of heavy metals and a small surface area after the classification treatment. The amount of chelate used can be greatly reduced.
(D-2) By performing a combination treatment of the pH adjustment treatment and the chelation treatment on the fine powder ash Ba, both treatment functions can be synergistically exerted. That is, by performing a pH adjustment treatment on the classified fine powder ash, it is possible to perform an efficient pH adjustment treatment to prevent the elution of heavy metals, and at the same time, elution of heavy metals to a predetermined amount of fly ash. The amount of chelate used for prevention can be greatly reduced. Further, even when it is difficult to prevent long-term elution of heavy metals only by the pH adjustment treatment, a more stable elution prevention treatment function can be ensured by performing the chelate treatment.
Further, by performing the pH adjusting treatment at the same time as the chelating treatment and using CO ₂ as the pH adjusting agent Pa, the solid phase fine powder ash Ba and the liquid phase chelating agent and the gas phase CO ₂ ensure reliable gas-liquid-solid. It is possible to make contact.

[Removal of acidic harmful components with calcium-based chemicals (Ca-based pretreatment)]
Incinerator fly ash may contain alkaline earth metals and the like in addition to heavy metals, and some of these substances irreversibly form stable compounds by acid treatment or base treatment. In addition, the exhaust gas from the incinerator may be first detoxified with slaked lime or the like. As a result of the verification of the present invention including such conditions, the following new findings were obtained.
(B-1) When Ca-based pretreatment is applied in advance, the acidity of the fly ash after the treatment hardly changes due to the difference in particle size, and the chemical stability of the fly ash is enhanced. (See "Verification Results" and Figure 4 below). In other words, by performing Ca-based pretreatment to prevent the elution of heavy metals due to changes in acidity during long-term storage, pH is the main treatment agent required for the elution prevention treatment of heavy metals for fine powder ash. By using the adjusting agent, it is possible to reduce the amount of the expensive chelating agent used, and it is possible to obtain a function of reducing the load of the pH adjusting treatment on the fine powder ash and reducing the amount of the pH adjusting agent used. ..
(B-2) The classified fine ash tends to contain not only heavy metals but also alkaline earth metal compounds in large quantities. Therefore, in the Ca-based pretreatment, the amount of the calcium-based agent required can be reduced to the amount corresponding to the content of the alkaline earth metal compound in the fine powder ash. That is, it is possible to reduce the amount of the treatment agent used in the pre-detoxification treatment with slaked lime or the like by the classification treatment.

<Other configuration examples of this device>
FIG. 2 shows another configuration example of the present device. The fluid B to be treated containing the fine powder ash Ba supplied from the classification device 1 is stored in the first storage tank 4 for a predetermined time, and similarly, the fluid C to be treated containing the coarse powder ash Ca is stored in the second storage tank 5. At the same time, the delivery of the fluid B to be treated from the first storage tank 4 and the delivery of the fluid C to be treated from the second storage tank 5 are periodically or at any time switched to the third treatment tank 6 for the fluid B to be treated or the treatment fluid C. The treatment fluid C is supplied, and one of them is subjected to pH adjustment treatment and chelating treatment with an aqueous solution Wa containing a pH adjusting agent Pa and a chelating agent Ka, or chelating treatment with an aqueous solution Wb containing a chelating agent Kb. It is characterized by. The supply amounts of the pH adjuster Pa and the chelating agent Ka or the chelating agent Kb supplied to the third treatment tank 6 are controlled and adjusted by the control device according to the classification point of the fly ash. Due to such a configuration, even when the concentration of heavy metals in the fluid A to be treated changes significantly or the amount of the fluid A to be treated changes significantly, excessive treatment such as installation of excessive equipment or excessive injection of treatment agent is performed. It is possible to prevent the occurrence of unprocessed products due to a sudden increase in the amount of processing.

Specifically, the fine powder ash Ba and the coarse powder ash Ca after the classification treatment for the fluid A to be treated are stored in the first storage tank 4 and the second storage tank 5 for a predetermined amount or a predetermined time, respectively, and then the first The delivery of the fluid to be treated B from the storage tank 4 and the delivery of the fluid to be treated C from the second storage tank 5 are switched alternately or at any time to supply each fluid to be treated to the third treatment tank 6. The third treatment tank 6 contains an aqueous solution Wa containing a pH adjuster and a chelating agent Ka, or a chelating agent Kb (or a common chelating agent K may be used) so as to correspond to the classification point of flying ash. An aqueous solution Wb (a common aqueous solution W can be used when a common chelating agent K is used) is supplied, and by performing a batch chelate treatment, a pre-detected or estimated pre-processed fluid B or a surface to be treated is applied. The pH adjustment treatment and the chelate treatment can be performed under the optimum conditions corresponding to the treatment amount of the treatment fluid C and the content concentration of heavy metals. The solid-liquid mixture D treated and generated in the third treatment tank 6 is delivered as a treated product such as a landfill treated product.

<Fly ash treatment method>
The method for treating fly ash using the present device (hereinafter referred to as "the method") is applied to the fluid A to be treated containing fly ash.
(1) A classification treatment step in which fly ash is classified as fine powder ash for fly ash below the classification point and coarse powder ash for fly ash above the classification point based on a predetermined classification point set in advance.
(2) A fine ash treatment step in which the classified fluid B containing the fine powder ash is subjected to a pH adjustment treatment with an aqueous solution containing a pH adjuster and a chelate treatment with an aqueous solution containing a chelating agent.
(3) A crude powder ash treatment step in which the fluid C to be treated containing the classified coarse powder ash is chelated with an aqueous solution containing a chelating agent.
The pH adjuster and the chelating agent are controlled and adjusted according to the amount of the fluid A to be introduced and the classification point.

(1) Classification treatment process The fluid A to be treated, which is generated from a waste incinerator and contains fly ash Aa to be treated by this method, is supplied to a classification device and is classified into fine powder ash Ba and coarse powder ash Ca. To. With respect to the fly ash Aa contained in the fluid A to be treated, the fly ash below the classification point is classified as fine powder ash Ba and the fly ash above the classification point is classified as coarse powder ash Ca based on the preset classification point. .. The setting value of the classification point differs depending on various requirements such as the type and properties of fly ash As or the fluid A to be treated, and the presence / absence and content of pretreatment. As the classification means, it is preferable to use the classification device 1 described above (first to third configuration examples), and when fly ash such as cement-solidified incinerator ash, which is difficult to classify as it is, is contained, the treatment fluid A is used. Therefore, it is preferable to perform a treatment such as pulverization or acid treatment in advance as a pretreatment for the classification treatment. Further, the classification processing step can be made into a plurality of stages by using a combination of a plurality of classification means. In this case, by providing the pretreatment in the middle of the plurality of classification processes, the classification process in the subsequent stage can be efficiently performed.

(2) Fine ash treatment step The classified fluid B containing the fine ash Ba is subjected to pH adjustment treatment and chelation treatment with an aqueous solution Wa containing a chelating agent Ka in addition to the pH adjusting agent Pa. In the method, by simultaneously performing the pH adjustment treatment and the chelate treatment on the fine powder ash Ba containing more heavy metals, a small amount of the pH adjuster or a chelate treatment is performed as compared with the case where only the pH adjustment treatment or the chelation treatment is performed. By supplying a chelating agent, efficient pH adjustment treatment and chelating treatment can be performed, and even when landfilled at a disposal site for a long period of time, elution of heavy metals can be reliably prevented. .. At this time, the pH of the processed product is adjusted to a predetermined range (for example, pH 9 to less than 11 when a large amount of lead is contained as a heavy metal, and pH 6 or more when a large amount of cadmium is contained). By doing this, it is possible to effectively prevent the elution of heavy metals.

(3) Coarse powder ash treatment step The classified fluid C containing coarse powder ash Ca is chelated with an aqueous solution Wb containing a chelating agent Kb. In this method, based on the finding that the classified coarse powder ash Ca contains a trace amount of heavy metals, the crude powder ash Ca is chelated by supplying a chelating agent Kb. Elution of heavy metals can be efficiently prevented by using a small amount of the chelating agent Kb.

In this method, it is preferable that (4) the fluid A to be treated is further subjected to a treatment for removing acidic harmful components (Ca-based pretreatment) with a calcium-based agent in advance.
By performing Ca-based pretreatment to prevent the elution of heavy metals due to changes in acidity during long-term storage, pH adjustment is the main treatment agent required for the elution prevention treatment of heavy metals for fine ash Ba. By using the agent, the amount of the expensive chelating agent Ka can be reduced, and the load of the pH adjusting treatment in the fine powder ash Ba can be reduced to reduce the amount of the pH adjusting agent Pa used. At this time, when the flying ash contains an alkaline earth metal compound, the alkaline earth metal compound having a higher concentration is contained in the fine ash Ba by having the (1) classification treatment step in this method. Therefore, the amount corresponding to the content of the alkaline earth metal compound in the fine ash Ba and the amount of the calcium-based drug used should be reduced as compared with the case where the Ca-based pretreatment step and the post-classification treatment step are not provided. Can be done.

Further, in this method, it is preferable to use carbon dioxide as the pH adjuster Pa. By reacting with heavy metals such as lead to form a carbon oxide (or hydride) that is immobilized and difficult to elute, a higher elution prevention effect can be obtained, and an alkaline earth metal in the classified fine powder ash Ba. A charcoal oxide (or hydride) that reacts with not only heavy metals but also alkaline earth metals containing calcium and is immobilized and difficult to elute when it contains a large amount of By forming the above, it is possible to form a treated product that is chemically stable for a long period of time and whose acidity hardly changes.

<Verification of this device>
Regarding the elution prevention function of heavy metals and the amount of treatment agent used in this device, the following items were verified, and the above findings (a) to (d) could be obtained.
(A) Correlation between the particle size of the flying ash and the content concentration of heavy metals in the flying ash (b) Correlation between the particle size of the flying ash and the acidity (pH) of the flying ash (c) The acidity (pH) of the flying ash Correlation between the amount of heavy metals eluted into the aqueous solution (d) Correlation between the amount of chelating agent used in the chelating treatment and the amount of heavy metals eluted

〔inspection result〕
(A) Regarding the correlation between the particle size of fly ash and the concentration of heavy metals contained in fly ash, the results shown in Table 2 below were obtained. Further, as shown in FIG. 3, there was a tendency that "the smaller the particle size of fly ash, the higher the concentration of heavy metals (compared to the same weight)". That is, a very efficient elution prevention treatment is performed by applying a treatment method corresponding to the content concentration of heavy metals with a predetermined particle size (for example, about 10 μm as shown in FIG. 3) as a critical point. It was found that this is possible.

(B) The results shown in Table 3 below were obtained for the correlation between the particle size of fly ash and the acidity (pH) of fly ash. When the exhaust gas from the incinerator containing fly ash was classified, the acidity (pH) of the fly ash corresponding to the particle size was detected, and the correlation was verified, the "particle size" was shown in the solid line in FIG. The smaller the fly ash, the lower the acidity (pH). " In addition, when a treatment for removing acidic harmful components with a calcium-based agent (for example, slaked lime was used in this verification) was performed as a pretreatment before classification, as shown by the chain line in FIG. 4, "acidity of fly ash". The degree (pH) hardly depends on the particle size of fly ash. "

(C) Regarding the correlation between the acidity (pH) of fly ash and the elution amount of heavy metals (followed for lead and cadmium in this verification) into the aqueous solution, as shown in FIG. 5 (A), "fly ash" When the pH is more than 9 to less than 11, the amount of lead elution is equal to or less than the predetermined value. " Further, as shown in FIG. 5 (B), the result was obtained that "the elution amount of cadmiums is equal to or less than a predetermined value when the pH of fly ash is 6 or less". That is, the elution prevention treatment can be performed by adjusting the pH of the fly ash within the range according to the type of heavy metal contained in the fly ash. Further, at this time, from the correlation between the particle size of fly ash and the acidity (pH) of fly ash, the treatment method corresponding to the pH is applied with a predetermined particle size as a critical point. It was found that efficient elution prevention treatment can be performed.

(D) Regarding the correlation between the amount of the treatment agent used in the chelate treatment and the elution amount of heavy metals, as shown in FIG. 6, the result that "the chelate treatment is effective in preventing the elution of heavy metals" was obtained. rice field. Here, the solid line in FIG. 6 shows the case where the entire fly ash to be treated is chelated (Ko). Further, the case where the fine powder ash after the classification treatment is chelated (K1) by utilizing the above-mentioned finding (a) that the content of heavy metals is higher in the fine powder ash is shown by the broken line in FIG. It was found that the amount of chelating agent used for the treatment of the entire fly ash can be significantly reduced by performing the chelate treatment on the fine powder ash having a high content concentration and a small surface area. Furthermore, using the above findings (a) to (c), the pH of fine powder ash is adjusted with a predetermined particle size as a critical point based on the correlation between the particle size of the flying ash and the acidity (pH) of the flying ash. The case where the chelating treatment is performed in combination with the treatment and the crude powder ash is subjected to the chelating treatment (K2) is shown by the chain line in FIG. It was found that a very efficient elution prevention treatment can be performed by performing a chelate treatment corresponding to the particle size of fly ash and the acidity of fly ash. As a proof result, when the amount of the chelating agent used in the case of (Ko) is 100, the result can be about 70 in the case of (K1) and about 58 in the case of (K2).

1 Classification device 2 1st treatment tank 3 2nd treatment tank A, B, C Processed fluid Aa Fly ash Ba Fine powder ash Ca Coarse powder ash D, E Processed product Solid-liquid mixture Ka, Kb Chelating agent Pa pH adjuster Wa, Wb aqueous solution

Claims (5)

For the fluid A to be treated, which contains powdery or shattered fly ash generated from a waste incinerator.
The fluid A to be treated is introduced, and the fly ash is classified as fine powder ash for fly ash below the classification point and coarse powder ash for fly ash above the classification point based on a predetermined classification point set in advance. Classification device,
An aqueous solution containing a chelating agent and a pH adjusting treatment with an aqueous solution containing the pH adjusting agent, which has a pH adjusting agent introducing part and a chelating agent introducing part, with respect to the fluid B to be treated containing the fine powder ash supplied from the classifying device. First treatment tank, which is chelated by
A second treatment tank, which has a chelating agent-introducing portion and is subjected to chelation treatment with an aqueous solution containing the chelating agent, with respect to the fluid C to be treated containing coarse powder ash supplied from the classification device.
A control device for controlling the supply amounts of the pH adjuster and the chelating agent supplied to the first treatment tank and the second treatment tank is provided.
A fly ash processing apparatus, characterized in that the supply amounts of a pH adjuster and a chelating agent are adjusted according to the amount of the fluid A to be introduced and the classification point. The fly ash treatment apparatus according to claim 1, wherein the fluid A to be treated is previously treated with a calcium-based chemical to remove acidic harmful components. The fly ash processing apparatus according to claim 1 or 2, wherein carbon dioxide is used as the pH adjuster. For the fluid A to be treated, which contains powdery or crushed fly ash generated from a waste incinerator.
The fluid A to be treated is introduced, and the fly ash is classified as fine powder ash for fly ash below the classification point and coarse powder ash for fly ash above the classification point based on a predetermined classification point set in advance. Classification device,
The first storage tank in which the fluid B to be treated containing the fine powder ash supplied from the classification device is stored,
A second storage tank in which the fluid C to be treated containing the coarse powder ash supplied from the classification device is stored.
A switching unit in which the delivery of the fluid B to be processed from the first storage tank and the delivery of the fluid C to be processed from the second storage tank are switched.
The fluid B to be treated, which has a pH adjusting agent introducing section and a chelating agent introducing section and is introduced via the switching section, is subjected to pH adjusting treatment with an aqueous solution containing a pH adjusting agent and chelating treatment with an aqueous solution containing a chelating agent. The third treatment tank, which is subjected to chelation treatment with an aqueous solution containing a chelating agent, with respect to the fluid C to be treated, which is subjected to or introduced through the switching portion.
A control device that controls the supply amounts of the pH adjuster and the chelating agent supplied to the third treatment tank.
Equipped with
A fly ash processing apparatus, characterized in that the supply amounts of a pH adjuster and a chelating agent are adjusted according to the amount of the fluid A to be introduced and the classification point. For the fluid A to be treated, which contains powdery or crushed fly ash generated from a waste incinerator.
A classification treatment step in which the fly ash is classified as fine powder ash for fly ash below the classification point and coarse powder ash for fly ash above the classification point based on a predetermined classification point set in advance.
A fine powder ash treatment step in which the classified fluid B containing the fine powder ash is subjected to a pH adjustment treatment with an aqueous solution containing a pH adjuster and a chelate treatment with an aqueous solution containing a chelating agent.
A crude powder ash treatment step in which the fluid C to be treated containing the classified coarse powder ash is chelated with an aqueous solution containing a chelating agent.
A method for treating fly ash, which comprises controlling and adjusting the supply amount of a pH adjuster and a chelating agent according to the introduction amount of the fluid A to be treated and the classification point.

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