JPH08290146A - Treatment of incineration ash - Google Patents

Abstract

PURPOSE: To prevent the elution of metals in an incineration ash and to contrive reutilizing the incineration ash as a source in a form capable of preventing environmental pollution. CONSTITUTION: The treating method of the incineration ash is by molding and hardening the incineration ash with cement in the presence of a water soluble polymer compound. The incineration ash is compression-molded using the water soluble polymer compound having a carboxylic group or its Na salt as a molding binder in at least two steps by a compression molding machine.

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 incinerated ash, and more particularly to a method for treating incinerated ash by molding and curing the incinerated ash with cement.

[0002]

2. Description of the Related Art It is important to efficiently recycle incinerated ash as a resource in order to deal with the so-called dust problem in recent years.
By the way, since the incinerated ash contains heavy metals such as lead, cadmium, chromium, and arsenic, although in trace amounts,
It is necessary to prevent their elution.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to prevent the elution of metals in incinerated ash and prevent the secondary pollution of the incinerated ash. An object of the present invention is to provide a method for treating incinerated ash that can be used as a resource.

[0004]

That is, the gist of the present invention is a method for treating incinerated ash by molding and curing incinerated ash with cement in the presence of a water-soluble polymer compound, wherein a carboxyl group or its A treatment method for incinerated ash, which comprises using a water-soluble polymer compound having a Na salt and performing at least two stages of compression molding by a compression molding machine.

The present invention will be described in detail below. The incineration ash that is a target of the present invention mainly includes incineration ash that is generated when incinerating collected waste discharged from a general household. The incineration ash is discharged from the refuse incinerator in a wet state by spraying water after combustion, and usually contains 20 to 30% by weight of water. Then, after being pre-dried, in order to remove metallic foreign matters and adjust to a predetermined particle size (for example, 15 mm undersize), it is appropriately treated with a magnetic separator, a sieving machine or the like.

In the present invention, incinerator ash is molded and hardened with cement in the presence of a water-soluble polymer compound. The water-soluble polymer compound is used as a molding binder when the combustion ash is molded and hardened with cement, but also acts as a kind of chelating agent for heavy metals. The hardened cement insolubilizes heavy metals in the combustion ash.

In the present invention, it is important to use a water-soluble polymer compound having a carboxyl group or its Na salt. That is, as the water-soluble polymer compound, for example, many compounds such as polyacrylamide, a partially saponified product of polyacrylamide, a copolymer of acrylamide and another monomer, and starch are known. According to the findings, when polyacrylamide or the like is used, it is difficult to recycle the concrete molded product because cracks occur in the concrete molded product and the compressive strength decreases, while when starch or the like is used, When the concrete molded product comes into contact with water, starch and the like elute, so that the BOD in the waste water becomes high, which causes secondary pollution.

The reason why cracking occurs in the concrete molded product when polyacrylamide or the like is used is not always clear, but since the smell of ammonia is felt from the concrete molded product, the amide group is decomposed by the alkaline component in the concrete. As a result, ammonia is generated, and it is presumed that a crack is generated in the concrete molded product when the gas is generated. Further, for example, the reason why the starch is eluted from the concrete molded product when the starch is used is not always clear as in the above, but since the starch is not fixed to the concrete matrix by a chemical bond, the concrete molding It is presumed that starch elutes when an object comes into contact with water.

On the other hand, when the water-soluble polymer compound having a carboxyl group is used, decomposition of the water-soluble polymer compound by the alkali component in concrete does not occur,
In addition, since the carboxyl group is chemically bonded to the concrete matrix (alkali component), it is considered that the elution of the water-soluble polymer compound having the carboxyl group is prevented. When a water-soluble polymer compound having a sodium salt of a carboxyl group is used, the water-soluble polymer compound does not decompose in the same manner as described above, and the carboxyl group is decomposed by a metathesis reaction with the concrete matrix (alkali component). It is considered that groups are generated and chemically bond to the matrix (alkali component) of concrete.

Specific examples of the water-soluble polymer compound having a carboxyl group or its Na salt include polyacrylic acid, Na polyacrylate, and acrylic acid / Na acrylate.
Examples thereof include copolymers, methyl methacrylate / Na acrylate copolymers, carboxymethyl cellulose and the like.

Further, in the present invention, a chelating agent may be used in combination in order to further ensure the insolubilization of heavy metals. The chelating agent has a function of concealing a very small amount of dissolved metal from the molded and cured product of the combustion ash. The kind of the chelating agent is not particularly limited, and conventionally known chelating agents such as an iminodiacetic acid type chelating agent containing a tertiary amino group and a carboxylic acid group can be appropriately used. For example, Miyoshi Yushi Co., Ltd. products "Eporba", "NEW
The chelating agents commercially available in each series of "Eporba" are examples of suitable chelating agents.

The cement used in the present invention is usually a mixture with an aggregate or the like. The types of cement and aggregate are not particularly limited, and as the cement, ordinary Portland cement or the like is used, and as the aggregate, various coarse aggregates or fine aggregates such as sand and crushed stone are used. These types and sizes are appropriately determined in consideration of the size of a cement molded product obtained by molding and curing combustion ash.
In particular, if crushed stone having an average particle size of 1 to 10 mm, preferably around 5 mm (so-called No. 7 product) is used, the anisotropy of strength that occurs during compression molding is eliminated and the so-called lamination structure is small and the hardness is small. There is an advantage that a molded product of high quality can be obtained.
Examples of additive components other than the above include AE agents (air entraining agents), water reducing agents, and alkali resistant glass fibers.

In the present invention, a water-soluble polymer compound having a carboxyl group or its Na salt is used as a molding binder, and an incinerator ash and a cement mixture are molded by a compression molding machine (briquette machine). By using a compression molding machine, a pellet-shaped molded product having high hardness and excellent handleability can be obtained. In a briquette machine, two pressure rollers each having an appropriately shaped depression are arranged to face each other, and a molding raw material is supplied between the pressure rollers to face each other.
This is a device that pressurizes the molding raw material between individual depressions (pockets) and molds it. The shape of the pocket is usually pillow-like or almond-like.

In the present invention, a briquette machine in which each pressure roller has a diameter of 300 to 1000 mm is preferably used. The linear pressure of each pressure roller is not particularly limited, but is preferably selected from the range of 1 to 7 t / cm.
Then, for example, the size of the almond-shaped molded product is usually 10 to 70 mm in both length and width, and preferably 15 to 50 mm. The maximum thickness is usually 10 to 20 mm.

In the present invention, the molding and hardening of the incineration ash with the cement mixture is carried out, for example, by the following process. First, the above-mentioned incinerated ash is subjected to a volume reduction treatment (vacuum deaeration), if necessary, and mixed with a water-soluble polymer compound and, if necessary, a chelating agent by an appropriate mixer (for example, a paddle mixer). . In this case, water can be adjusted by supplying water as needed.

Next, the mixture of the incineration ash mixed and treated with the water-soluble polymer compound and the chelating agent is kneaded with the cement mixture and supplied to the compression molding machine to be molded. The water content of the mixture during molding is preferably in the range of 5 to 20% by weight, more preferably 10 to
It is adjusted to the range of 15% by weight.

In the present invention, the ratio of each of the above components to the incineration ash is not particularly limited, but the water-soluble polymer compound is usually contained in an amount of 1 to 20 parts by weight per 1000 parts by weight of the water-containing incineration ash. Preferably 5 to 15 parts by weight, the chelating agent is usually 0 to 10 parts by weight, preferably 0.5 to 5 parts by weight, the cement is usually 100 to 600 parts by weight, preferably 200 to 400 parts by weight, and the aggregate is It is usually 200 to 600 parts by weight, preferably 300 to 500 parts by weight. As the aggregate, it is preferable to use sand and crushed stone together, and the ratio thereof is usually 1: 1 to 5, preferably about 1: 3 as a weight ratio of sand: crushed stone.
It is said. One example of a typical cement mixture consists of 1000 parts by weight cement, 100 parts by weight sand, and 300 parts by weight crushed stone.

In the present invention, the order of mixing the water-soluble polymer compound, the chelating agent and the cement mixture with respect to the incineration ash is not particularly limited, and the water-soluble polymer compound and the chelating agent are mixed with each other after mixing the incineration ash and the cement mixture. Although a method of mixing may be used, as described above, a method of mixing the cement mixture with a mixture containing incinerated ash, a water-soluble polymer compound and, if necessary, a chelating agent is preferable.

The greatest feature of the present invention resides in that at least two stages of compression molding are performed by a compression molding machine. Such compression molding can be carried out in a non-circulating manner by using, for example, two or more compression molding machines and disposing a crusher if necessary between the compression molding machines. Is continuously molded by a compression molding machine, and burrs and / or crushed materials of the obtained molding are circulated to the compression molding machine to perform two-stage compression molding. That is, the burr of the molded product obtained from the compression molding machine is recovered, or at least a part of the molded product is crushed by an appropriate crushing machine, and the burr and / or the crushed product is circulated to the compression molding machine to incinerate ash. , A water-soluble polymer compound, a chelating agent and a cement mixture, and a compression molding. The burr can be collected by using, for example, a vibrating sieve having an appropriate opening, and the molded product can be crushed by, for example, a normal crusher having an impeller structure.

In the two-stage molding, the above-mentioned burr and / or crushed material becomes a core during compression molding. As a result, the strength anisotropy that occurs during compression molding is eliminated, as when using crushed stone.
It is possible to obtain a molded product (briquettes) having a so-called lamination structure and high hardness. The size of the burr and / or crushed material circulated in the compression molding machine is not particularly limited,
From the viewpoint of exerting a sufficient function as a core during compression molding, the upper limit is preferably adjusted to about 1/3 or less of the size of the molded product, and the lower limit is about 1/10 of the size of the molded product. To be done. The circulation amount of the burr and / or the crushed material is not particularly limited, and it is also possible to crush the entire amount of the molded product as well as the burr and circulate the entire amount. These are appropriately determined in consideration of the hardness and economical efficiency of the target molded product (briquette). A preferred range of the circulating amount is 15 to 200 parts by weight as a total part by weight of burr and / or crushed material and crushed stone with respect to 100 parts by weight of a forming raw material composed of incinerated ash, a water-soluble polymer compound, a chelating agent and a cement mixture. is there.

The final molded product obtained by the two-stage molding is usually cured because its reliable curing is completed in a short time. The curing method is not particularly limited, and normal temperature curing, steam curing and the like can be appropriately adopted. In the case of steam curing, a two-stage condition in which the initial 0.5 to 2 hours is 30 to 50 ° C. and the subsequent 1 to 4 hours is 55 to 80 ° C. is adopted.

The concrete molded product of incinerated ash obtained by the treatment method of the present invention can be effectively used, for example, as a landfill material during construction. Further, the pellet-shaped molded product has an advantage that it can be piled after being spread. In particular, an almond-shaped molded product is easy to be piled because the thin end portion is easily broken. Further, if a mixture of pellet-shaped molded products having different sizes is used as the landfill material, there is an advantage that the closest packing is possible.

[0023]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Examples 1 to 4 and Comparative Examples 1 to 5 Various water-soluble polymer compounds shown in Table 1 in 1000 kg of general waste incineration ash (water content: 25% by weight), which has been subjected to sieving treatment and whose particle size is adjusted to 5 mm or less. (Each has an average molecular weight of about 500
10,000 kg) was added and mixed, and then 400 kg of Portland cement and 300 kg of crushed stone (No. 7 product) were added and kneaded with a paddle mixer to prepare a forming raw material. The water content of the forming raw material is 15 in any of the examples.
Adjusted to wt%.

Next, the above-mentioned forming raw materials are continuously supplied to a hopper on a briquette machine in which each pressure roller has a diameter of 700 mm, and compression-molded under the condition of a linear pressure of 4.7 t / cm, and the length is 30 mm and the width is 30 mm. , And formed into an almond mold having a maximum thickness of 15 mm.

Then, the whole amount of the obtained molded product was supplied to an impeller type crusher and crushed into a lump having a diameter of about 5 mm, and the entire amount was continuously supplied to a hopper on a briquette machine to obtain the above-mentioned forming raw material. The mixture was mixed and subjected to the second stage compression molding.

Then, the final molded product obtained was aged at room temperature for 2 hours to obtain an almond-shaped (30 mm long, 30 mm wide, 15 mm maximum thickness) concrete molded product. A compression strength test and a dissolution test were performed on each concrete molded product, and the results shown in Table 2 were obtained. The compressive strength test was performed using a computer-controlled hydraulic servo type “Shimadzu Universal Testing Machine” (UH-50A) manufactured by Shimadzu Corporation.

The values of compressive strength in Table 2 are average values of the measured values of 100 concrete moldings sampled at random. Dissolution test is based on the Environmental Agency Notification No. 64, dissolution of heavy metals and dissolution of water-soluble polymer compounds (BOD)
Both were measured. The numerical value of each dissolution test in Table 2 is an average value of the measured values of 10 concrete molded articles sampled at random.

[0029]

[Table 1]

[0030]

[Table 2]

As is clear from the results shown in Table 2, according to Examples 1 to 4 in which the water-soluble polymer compound having a carboxyl group or its Na salt was used as the molding binder, the compressive strength was high, and A cocreate molded article in which the elution of heavy metals and water-soluble polymer compounds is sufficiently prevented is obtained. 20 kg of the obtained cocreate molded product
As a result of filling the plastic bag of No. 3, the opening was sealed, and opened one year later, no ammonia odor was confirmed. No cracks were found in the cocreate molded product.

On the other hand, in the case of Comparative Example 2 in which polyacrylamide was used as the molding binder, many cracks were generated in the cocreate molded product immediately after molding, and ammonia odor was confirmed. In the case of Comparative Example 2 in which the partially saponified polyacramide was used as the molding binder, no clear ammonia odor was confirmed, but cracks were found in the cocreate molded product immediately after molding. In particular, in the case of Comparative Example 5 in which starch is used as the molding binder, starch is leached out so much that the BOD of waste water may be increased and secondary pollution may be caused.

Examples 5 to 7 In Example 1 using 10 kg of polyacrylic acid soda as a molding binder, a product "NEW Epolva 800" of Miyoshi Yushi Co., Ltd. was used together as a chelating agent in an amount shown in Table 3 to make a final molding. As the subsequent curing condition, the initial 1
The same two-stage compression molding as in Example 1 was performed except that the two-stage steam curing was performed at 40 ° C. for 2 hours and 75 ° C. for the subsequent 2 hours to form an almond shape (length 30 mm, width 30 m).
m, the maximum thickness of 15 mm) was obtained.
Perform the compression strength test and elution test of the obtained molded product,
The results shown in Table 4 were obtained.

[0034]

[Table 3]

[0035]

[Table 4]

As is clear from the results shown in Table 4, Examples 5 to 7 in which a chelating agent was used in combination with Na polyacrylate
According to the method, a cocreate molded product in which elution of heavy metals is further prevented can be obtained. Further, the steam-curing improves the compressive strength of the cocrete molded product.

Comparative Examples 6 to 9 In each of Examples 1 to 4, molding and curing were performed in the same manner as in Examples 1 to 4 except that the crushing and circulation of the one-step molded product was stopped to perform the one-step molding. An almond-shaped (length 30 mm, width 30 mm, maximum thickness 15 mm) concrete molded product was obtained. The obtained molded product was subjected to a compression strength test and a dissolution test, and the results shown in Table 5 were obtained.

[0038]

[Table 5]

As is clear from the comparison of Tables 2 and 5, it is understood that the two-stage compression molding increases the compressive strength of the concrete molded product by about 20%.

[0040]

EFFECTS OF THE INVENTION According to the present invention described above, there is provided a method for treating incinerated ash which can prevent the elution of metals in the incinerated ash and prevent the secondary pollution from being recycled. Provided. Since the concrete molded product obtained by the method of the present invention has excellent compressive strength, it is less likely to be damaged during handling and can be effectively used, for example, as a landfill material during construction.

Claims (3)

[Claims] 1. A method for treating incinerated ash, which comprises molding and curing the incinerated ash with cement in the presence of a water-soluble polymer compound, wherein a carboxyl group or its N is used as a molding binder.
A method for treating incinerated ash, comprising using a water-soluble polymer compound having a salt, and performing compression molding in at least two stages by a compression molding machine. 2. The method for treating incinerated ash according to claim 1, wherein cement is mixed with a mixture containing incinerated ash, a water-soluble polymer compound and, if necessary, a chelating agent, and the mixture is molded and cured. 3. The method according to claim 1, wherein curing is performed after the final molding.
The method for treating incinerated ash described in.