JPH10225671A - Treatment of making incineration residual ash harmless and treating agent for making harmless - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating method of effectively making incineration residual ash harmless in a cooling process usually performed without reprocessing of the incineration residual ash being needed as in a conventional method and also to provide a treating agent for making harmless which is solidified so that it is gradually eluted into cooling water in such treating method of making harmless. SOLUTION: When cooling incineration residual ash generated on trash incineration by cooling water, as the cooling water, that containing a treating agent for making heavy metals insoluble in water is used to make heavy metals insoluble in water simultaneously with cooling. In this way, the incineration residual ash is made harmless. The treating agent for making harmless is that used, contained in water added to the incineration residual ash and/or incineration fly ash generated on trash incineration, and is that which a material consisting essentially of hydrous or anhydrous phosphate is solidified by melting and cooling to form, and is that which anhydrous phosphate or phosphate enable to be hydrous is solidified as hydrous salt by adding water and coagulating it to form.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating heavy metals contained in residue ash generated during incineration of waste so as not to be eluted, that is, incineration residue generated in an incineration plant for general municipal waste and industrial waste. The present invention relates to a detoxification treatment method for water insolubilization treatment of heavy metals contained in ash, and a detoxification treatment agent.

[0002]

2. Description of the Related Art When general municipal waste is incinerated, heavy metals contained in the trash are usually sublimated by incineration and are collected as dust. As a result, heavy metals are contained in a large amount in fly ash. Therefore, strict regulations are imposed on the fly ash by law, but there is no such regulation on the incineration residue ash, and only the regulation based on the landfill standards of the Industrial Waste Management Law becomes a problem. However, it is a fact that heavy metals which do not completely sublime during the incineration of garbage remain in the incineration residue ash. As a result, some heavy metals may remain in such incineration residue ash and elute as a result, possibly exceeding the above criteria.

[0003] On the other hand, the properties of ash vary depending on the type of garbage to be incinerated. Ash is easily acidified when waste containing acidic substances is incinerated. However, when garbage or the like is ashed by incineration, calcium and magnesium contained therein are contained. Therefore, the incineration residue ash itself tends to be alkaline.

[0004] Generally, heavy metals dissolve in an acidic region and do not dissolve in an alkaline region. Among heavy metals, metals such as lead have the property of dissolving in an alkali having a certain pH or higher.
In particular, the property becomes remarkable when the pH becomes 12 or more.

[0005] Since the incineration residue ash from which heavy metals are eluted as described above cannot be landfilled unless the landfill standards are met by the industrial waste treatment method, the incinerated ash is collected and sufficiently insolubilized by the heavy metal insoluble treatment agent. Must be processed and landfilled.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the need to reprocess incinerated residue ash as in the conventional method, and to provide a treatment which can efficiently detoxify incinerated residue ash in a cooling step usually performed. It is to provide a method. Another object of the present invention is to provide a detoxifying agent solidified so as to be gradually eluted into cooling water in the detoxifying method.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that when cooling incineration residue ash generated during garbage incineration with cooling water, a treating agent for insolubilizing heavy metals with water. It has been found that the above object can be achieved by performing water insolubilization of heavy metals at the same time as cooling by using cooling water containing, and further advanced the studies and completed the present invention.

That is, the gist of the present invention is as follows: (1) When cooling incineration residue ash generated during incineration of refuse with cooling water, cooling water containing a treating agent for insolubilizing heavy metals is used, and at the same time cooling is performed. Detoxification method of incineration residue ash, characterized in that water is insolubilized, (2)
(1) The solidified treatment agent is disposed in a cooling water storage tank or in a portion of the water supply path that comes into contact with the cooling water, and the treatment agent is gradually eluted into the cooling water.
The detoxification treatment method described in (3), wherein the solidified treatment agent is
Water is insolubilized to heavy metals by salt formation, and pH 6 to
(4) a detoxification method according to the above (2), which is a solid pH buffer having a buffering capacity of 10; and (4) water contained in incineration residue ash and / or incineration fly ash generated during incineration of garbage. A detoxifying agent to be used, which is obtained by solidifying a substance containing water-containing or anhydrous phosphate as a main component by melting and cooling. (5) Incineration residues generated during incineration of garbage A detoxifying agent used by adding to the water added to ash and / or incinerated fly ash, which is obtained by solidifying an anhydrous or water-containing phosphate by adding water and coagulating to form a hydrated salt. (6) The detoxifying agent according to the above (5), wherein the detoxifying agent is prepared by further adding phosphoric acid at the time of adding water to exhibit a buffering ability at pH 6 to 10. Chemical treating agent.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The detoxification method of the present invention treats incineration residue ash generated during incineration of general municipal waste, industrial waste, combustible waste, and the like. Heavy metals remain in the incineration residue ash without completely sublimating when the garbage is incinerated, and the present invention detoxifies the heavy metals by insolubilizing them with water.

According to the detoxification method of the present invention, when such incineration residue ash is cooled with cooling water, water insolubilization of heavy metals is performed simultaneously with cooling using cooling water containing a treating agent for insolubilizing heavy metals. Is performed. In the present invention, instead of the conventional method of reprocessing incineration residue ash after it is generated, the ash can be processed in the cooling step immediately after the generation, so there is no need for reprocessing equipment, and furthermore, the ash and Because of the ash having heat, the reactivity of the inorganic treating agent is improved, and it is possible to treat efficiently.

Here, the cooling water containing the processing agent may be a liquid obtained by appropriately adding a liquid processing agent to water. However, the cooling water in the storage tank or a portion of the water supply path which comes into contact with the cooling water may be used. It is preferable to arrange a solidified treating agent in the cooling water and gradually dissolve the treating agent into the cooling water so that the treating agent is contained in the cooling water.

That is, in the method using the solidified processing agent, the dissolution of the processing agent is suitably maintained, so that there is no need to modify the equipment for supplying the liquid processing agent or other equipment. There is. Here, in the cooling water storage tank, in addition to the storage tank provided in a place different from the cooling place (including the one provided in the middle of the water supply path), cooling water is stored as a cooling place, and residual ash is stored. It may be a storage tank to be introduced (see FIG. 1). The portion of the water supply path that comes into contact with the cooling water may be any portion that contacts the cooling water other than the storage tank, such as the outlet of the water supply port and the inside of the water supply pipe.

Although the concentration of the treating agent dissolved in the cooling water depends on the heavy metal content in the object to be treated, it is generally about several tens to several tens of thousands ppm, and several hundreds to several thousand ppm.
Is preferred. This is because when the content is within this range, insolubilization of heavy metals and control of pH can be suitably performed. ADVANTAGE OF THE INVENTION According to this invention, the effect | action of forming the insoluble salt of a heavy metal, and the pH adjustment effect which makes the insoluble pH range of a heavy metal two effects make it possible to perform a process reliably even if the amount of drug addition is small compared with a normal drug process. Can be.

The treating agent to be used is not particularly limited as long as it makes the heavy metal insoluble in water, but it forms an insoluble compound (such as an insoluble salt or an insoluble complex) with the heavy metal, or controls the pH to an alkaline side. Any treating agent may be used as long as it is a treatment agent that makes heavy metals water insoluble by forming heavy metal hydroxides.

Specifically, in addition to phosphoric acid, phosphate, sulfurizing agent, chelating agent, etc., which are generally used for the water insolubilization treatment of heavy metals, phosphates whose pH can be controlled to an alkali side,
Acetate, alkali hydroxide and the like can be mentioned.

In the present invention, the solidified treating agent makes the heavy metal water-insoluble by salt formation, and has a pH of 6 to 10;
In particular, a solid pH buffer exhibiting a buffering ability at pH 7 to 9 is preferable.

As described above, by imparting a buffering property to the pH as a performance of the processing agent, the harmful effects due to excessive addition of the processing agent are eliminated, and the properties of lead and the like in heavy metals are soluble at pH 7 or lower and pH 12 or higher. Therefore, it is possible to avoid an acidic region or an excessively alkaline region and to automatically adjust the pH to a range in which heavy metals do not dissolve.

That is, it is a well-known fact that phosphoric acid has a pH buffering property by a reaction with a basic salt, but there is a pH range in which heavy metals do not dissolve in the treatment of incineration residue ash. By controlling the pH with, it is possible to produce an effect that does not elute.

The detoxifying agent of the present invention can be suitably used in the detoxifying method of the present invention as described above. In addition, incineration of general municipal garbage, industrial waste, flammable waste and the like can be used. It can also be used for detoxifying incinerated fly ash, which sometimes occurs and is collected by an electric dust collector, bag filter, or the like. Specifically, there is the following mode. A substance composed mainly of water-containing or anhydrous phosphate solidified by melting and cooling. A substance composed mainly of anhydrous or water-containing phosphate is solidified by adding water to solidify as a water-containing salt. And a substance containing an anhydrous or water-containing phosphate as a main component, and solidified as a hydrated salt by adding water and phosphoric acid.

Each of the above embodiments has the following advantages. In the embodiment, since the solidifying agent in a substantially anhydrous state can be obtained, the dissolution rate can be reduced and the amount of elution can be suppressed to a low level. In the embodiment, the solidifying agent can be obtained by a simple method. Can control the amount of elution,
In the embodiment, the solidification treating agent can be obtained by a simple method, can be prepared so as to exhibit a buffering ability at pH 6 to 10, and further, the amount ratio of acid and acid salt to alkali salt can be adjusted. By doing so, the buffer pH can be easily controlled.

That is, in the embodiment (1), the treatment agent is solidified by adding water to an anhydrous treatment agent, but an alkali phosphate anhydride or the like is used. An appropriate equivalent for adjusting the pH to the range of 6 to 10 with phosphoric acid can be blended to obtain a solidification treating agent having a controlled buffer pH.

As a specific compounding ratio, a neutralizing amount of an acid and an alkali for obtaining a target buffer pH is used.
The mixing ratio is a water addition amount for absorbing and solidifying water as needed.

Examples of the phosphate include alkali metal salts such as sodium and potassium, alkaline earth metal salts such as calcium and magnesium, ammonium salts, and double salts in which two or more cations are bonded. . Among them, alkali metal salts are preferred.

The method for producing the solidification treating agent is not particularly limited, and it can be appropriately produced using a commonly used melting furnace, heating device, or an appropriate mixing device. The shape of the solidification treatment agent is not particularly limited, and may be appropriately adjusted from a lump to a granular shape in consideration of the amount of cooling water used, the dissolution rate of the treatment agent, and the like. That is, the elution rate increases as the surface area per unit mass increases, as in the case of particles, whereas the elution rate decreases as the surface area decreases, as in the case of lumps.

The treating agent of the present invention has a buffering property as described above, which itself forms an insoluble salt with a heavy metal, or a compounding agent which forms an insoluble salt with a heavy metal, thereby blending the treating agent with a heavy metal. Elution treatment becomes possible.

Therefore, the major features of the treating agent of the present invention are that the heavy metal is made non-elutable by the drug component, and that the pH is controlled in the lead-insoluble region by pH buffering. It is also possible to suppress corrosion to the surface.

Hereinafter, a specific cooling operation of the processing method of the present invention will be described with reference to the drawings. Fig. 1 shows a cooling system for incinerators currently used in garbage incineration plants.
2 and a martin method shown in FIG. 2 are the main ones. The processing method of the present invention can be similarly applied to other cooling methods, but a case where a solidified processing agent is used will be described by taking these two methods as examples.

In the cooling by the water sealing method shown in FIG.
The cooling water supplied from the hopper is stored in the cooling water tank 4, but the ash dropped from the ash hopper 2 is cooled in the cooling water tank 4 and then conveyed by the scraping conveyor 3. then,
By placing (suspending) the solidified processing agent at the position of P1 to make contact with the supplied cooling water, or by placing (suspending) the solidified processing agent at the position of P2, the cooling water in the storage tank is brought into contact with the cooling water. The contact agent is allowed to gradually elute into the cooling water. In addition, ash scraping conveyor 3
The processing agent can be suspended by suspending the treating agent at the position of the upper part P5, dissolving it with tap water while pouring water, and passing the dissolved solution through a conveyor and into a cooling water tank.

In the cooling by the martin method shown in FIG. 2, the cooling water supplied from the water supply pipe 1 falls from the ash hopper 2 and is directly supplied to the ash conveyed by the ash extracting device 5 to be cooled. At this time, the cooling water in the service tank 6 may be brought into contact with the supplied cooling water by disposing (suspending) the solidification treating agent at the position P4, or by disposing the solidifying treatment agent at the position P3. , So that the treating agent can be gradually eluted into the cooling water.

In the above-mentioned cooling operation, when the treatment agent is a liquid, a tank or a pipe for the treatment agent is required, and a device for adding the liquid at an appropriate concentration is required, so that the process is troublesome. However, by solidifying the treating agent, it can be gradually melted out just by putting it into a tank for cooling water or by providing a dissolution layer in the cooling water pipe, and the effect can be maintained for a long time Become.

[0031]

EXAMPLES Hereinafter, the present invention will be described in more detail by reference examples and examples, but the present invention is not limited to these examples and the like.

REFERENCE EXAMPLE 1 Heat was generated by mixing 60 parts by weight of anhydrous tribasic sodium phosphate with a mixture of 30 parts by weight of 75% phosphoric acid and 10 parts by weight of water in a container serving as a solid material mold. And cooled to room temperature to obtain a solid. It has a pH of about 6.
5 has buffering capacity.

A 1% concentration solution of this solid was prepared, and 10 g of incineration residue ash having high alkalinity and containing a lot of heavy metals was stirred for 1 hour with 1000 ml of tap water. Was added in the amounts shown in Table 1. At that time, the pH and the amount of heavy metal eluted were measured. Table 1 shows the results.

[0034]

[Table 1]

With regard to this incineration residue ash, although the pH was not lowered by the high alkalinity and the buffering property of the dissolved salt was not remarkable, it was found that the pH was surely lowered, and a remarkable effect was observed on the amount of lead eluted. Obtained.

The lead content of this ash is 1980 ppm, and when the amount of the treating agent added is 0.1% (1000 ppm), considering the reaction equivalent of the treating agent for forming lead phosphate, it is practically considered. In order to make the heavy metal non-elutable, the amount should be equal to or less than the reaction equivalent. However, it can be said that the reason why the amount of lead elution is suppressed in spite of this is that it is combined with the action of pH adjustment.

In the actual treatment, since the ash immediately after incineration is cooled by cooling water containing a treating agent, the reaction proceeds at a high temperature, so that it is considered that the reaction proceeds preferentially with heavy metals.

Further, as the concentration of the treating agent increases, the concentrations of calcium and magnesium in the solution also decrease, indicating that these components form insoluble salts. This also makes it possible to reduce the scale failure in the cooling water circulation, the piping of the cooling water path, and the equipment.

Example 1 As in Reference Example 1, 15 parts by weight of 85% phosphoric acid and 10 parts by weight of water were mixed with 50 parts by weight of anhydrous tribasic sodium phosphate and 25 parts by weight of sodium hexametaphosphate. The mixture was slowly mixed to generate heat,
After cooling to room temperature, a solidified treating agent having a buffer capacity at about pH 7.2 was obtained.

At a municipal garbage incineration plant in a city A, a test was conducted by incorporating this treating agent into an actual ash cooling device.
In this incineration plant, ash is cooled in a so-called martin method (see Fig. 2), in which ash coming out of a hopper that stores incinerated ash is sprayed with water and cooled by cooling. . For this reason, in order to dissolve the solid processing agent by the water sprayed from the nozzle, a processing agent dissolving tank is provided upstream of the nozzle, and the processing agent is placed therein (P3 position in FIG. 2). The ash was cooled with the liquid passed through the tank.

The ash that had cooled and accumulated in the ash pits was sampled daily, and the state of the ash was confirmed for one week. To confirm the ash, the ash sampled in accordance with the law on waste treatment and cleaning was tested by the lead elution test method (JIS K-0102), and the concentration of lead, Ca + Mg, etc. in the eluate was measured. Table 2 shows the results.

[0042]

[Table 2]

According to the results, the pH was surely lowered by about 0.4 as compared to before the use of the treating agent, and the amount of lead eluted was stabilized below the reference value for landfill (0.3 ppm for lead). Turned out to be lower. Judging only by heavy metals, the ash after incineration included lead, mercury, and cadmium, and as shown in Table 3, the elution amount was lower than the standard value for landfill as shown in Table 3.

[0044]

[Table 3]

The plant has two furnaces capable of incinerating garbage by 90 tons per day, and one furnace generates about 10 to 15 tons of incineration residue ash. I use 2 tons of water a day. In this embodiment, the treatment agent is consumed at a rate of 750 g per day, and the concentration of the treatment agent in the cooling water is 375 pp.
At a concentration of m, ash is added at a concentration of 75 ppm.

It can be seen that the purpose of the treating agent is sufficiently exhibited at this added concentration, and that calcium and magnesium are surely reduced, and that the effect of suppressing the formation of scale is produced.

Example 2 A method was used in which the solid processing agent used in Example 1 was incorporated into cooling water at a certain B city incineration plant. This incineration plant employs a water ring method (see Fig. 1) for ash cooling. Since the ash is dropped directly from the hopper for incineration residue ash into the tank that holds water, it is cooled. A method of providing a dissolving portion of the treatment agent in the cooling water supply path, a method of charging a solid treatment agent into the cooling water storage tank, and the like can be considered. In the present embodiment, a conveyor for scraping out the ash dropped into the cooling tank and a conveyor for feeding the scraped ash to the ash bunker are interlocked. And dissolve the treatment agent in the cooling water tank (P in FIG. 1).
4 position).

[0048]

According to the present invention, there is no need to reprocess incineration residue ash unlike the conventional method, and the incineration residue ash can be detoxified in a cooling step usually performed. At this time, since the target ash has heat, the reactivity of the treatment agent is improved, and the treatment can be performed efficiently. In addition, when a solidified treatment agent is used, the dissolution of the treatment agent is continued, so that suitable treatment can be performed without the need for modification of equipment.
In addition, by imparting a pH buffering property to the treating agent, it is possible to prevent the dissolution of heavy metals in an acidic region by preventing the dissolving agent from becoming neutral or lower due to excessive dissolution of the treating agent, and to suppress corrosion to equipment. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a cooling device (water sealing method) to which the detoxification treatment method of the present invention can be applied.

FIG. 2 is a schematic cross-sectional view showing an example (martin system) of a cooling device to which the detoxification processing method of the present invention can be applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water supply pipe 2 Ash hopper 3 Scavenging conveyor 4 Cooling water tank 5 Ash scavenging device 6 Service tank

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FIF23J 1/00 B09B 3/00 ZAB

Claims (6)

[Claims] When cooling incineration residue ash generated during incineration of refuse with cooling water, water insolubilization of heavy metals is performed simultaneously with cooling using cooling water containing a treating agent for insolubilizing heavy metals. Detoxification method of incineration residue ash. 2. A solidified treatment agent is disposed in a cooling water storage tank or in a portion of the water supply path which comes into contact with the cooling water, and the treatment agent is gradually eluted into the cooling water. The detoxification processing method according to claim 1. 3. The detoxification treatment method according to claim 2, wherein the solidified treatment agent is a solid pH buffer agent that makes heavy metals water insoluble by salt formation and exhibits a buffering ability at pH 6 to 10. 4. Incineration residue ash generated during incineration of garbage and / or
Or a detoxifying agent used by adding it to the water added to the incineration fly ash, which is obtained by solidifying a substance containing water-containing or anhydrous phosphate as a main component by melting and cooling. Processing agent. 5. An incineration residue ash generated during incineration of garbage and / or
Or a detoxifying agent used by adding to the water added to the incineration fly ash, wherein the anhydrous or water-containing phosphate is solidified as a water-containing salt by coagulation by adding water. Processing agent. 6. The detoxifying agent according to claim 5, wherein the detoxifying agent is prepared by adding phosphoric acid at the time of adding water so as to exhibit a buffering ability at pH 6 to 10.