JPH08257530A - Incineration ash treatment method - Google Patents

Abstract

PURPOSE: To implement stabilization treatment to the inside of smoke dust particles of incineration ash etc., and to stabilize the effect for preventing harmful metal elution by kneading a mixture in which incineration fly ash is mixed with a heavy metal stabilizing agent and a surfactant. CONSTITUTION: In treating incineration ash and smoke dust of city waste etc., containing harmful heavy metals, a mixture is kneaded in which incineration ash etc., containing harmful heavy metals are mixed with a heavy metal stabilizing agent and a surfactant. In this process, the heavy metal stabilizing agent and a coagulant can be added. Heavy metals in incineration ash etc., containing harmful heavy metals are stabilized by the heavy metal stabilizing agent to decrease the solubility. When the surfactant is added into this, hydrophobic treatment reaches the pore inner wall of fly ash to hinder the elution of heavy metals from the pore inner wall. When the coagulant is added to the fly ash in which heavy metals are stabilized by the heavy metal stabilizing agent, the stabilized heavy metals are coagulated to further decrease the elution concentration.

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 (fly ash and bottom ash) and soot dust containing harmful heavy metals such as municipal waste, and in particular, complete elution of harmful heavy metals from incinerated ash and soot dust. The present invention relates to a method for suppressing it.

[0002]

2. Description of the Related Art In the case of landfilling incineration ash or soot containing the above-mentioned harmful heavy metals (hereinafter referred to as incineration ash etc.), the elution amount of heavy metals from this incineration ash must be suppressed to 0.1 ppm or less, 0.0 when used as valuables
It is mandatory to keep it below 1 ppm.

[0003] Conventionally, as a treatment method for detoxifying and stabilizing wastes including these incinerated ash, methods such as melting and solidifying, cement solidifying, chemical treatment, and acid extraction have been used.

[0004]

DISCLOSURE OF THE INVENTION In the above treatment method, particularly in the method of chemically reacting harmful metals with chemicals such as chemical treatment or acid extraction, the dissolution test is conducted several times after the treatment. There was a problem that the numbers fluctuated.

When the inventor of the present application carried out an electron microscope observation of soot dust, which is particularly strict in incineration ash and the like, it was found that primary particles having a diameter of 1 to 2 μm were aggregated.
Particles of ˜50 μm could be observed. And we could observe that there are many pores between these particles.

For this reason, when this is subjected to chemical treatment such as chemical treatment or acid extraction, the chemical treatment does not reach the inside of the pores and only the surface is treated. Occasionally, there may or may not be. Based on the above, it is considered that the elution concentration varies with each elution test.

The present invention has been conceived in view of the above, and it is possible to prevent elution of harmful heavy metals by subjecting incineration ash or the like to a stabilization treatment, especially inside fine dust particles. Moreover, it is an object of the present invention to provide a method for treating incineration ash containing harmful heavy metals, which is capable of stabilizing the elution preventing effect for a long period of time.

[0008]

In order to achieve the above object, a method for treating incinerated ash or the like according to the present invention is a kneading method in which a heavy metal stabilizer and a surfactant are added to incinerated ash or the like containing harmful heavy metals. I am trying to do it. A heavy metal stabilizer and a flocculant are added and kneaded.

[0009]

[Operation] Heavy metals in incineration ash, etc. containing harmful heavy metals are stabilized by heavy metal stabilizers, resulting in a marked decrease in solubility. Then, by adding a surfactant to this, the inner wall of the pores of the incinerated ash is made to be phobic and the heavy metal is not eluted from the inner wall of the pores, and a stable elution test is performed.

Further, by adding a coagulant to incineration ash or the like in which the heavy metal is stabilized by the heavy metal stabilizer, the stabilized heavy metal is agglomerated and the elution concentration thereof is further lowered.

[0011]

EXAMPLES Examples of the present invention will be described below. As samples, soot (fly ash) discharged from the municipal waste incinerator was used to perform various treatments (1) to (6) described below, and then Pb, Cd, Hg, Cr, and As were eluted from heavy metals, respectively. The test was conducted. Table 1 shows the content and elution amount of each metal before treatment of each sample, and the elution amount of each metal.
Shown in

[0012]

[Table 1]

Preparation of a sample before treatment was carried out as follows. Soot dust in which the content of each heavy metal was measured in advance, and 10 wt% Portland cement and 50w with respect to this soot dust
The mixture was kneaded with t% water, put into a mold, left to stand for 24 hours, solidified, then taken out from the mold, and allowed to stand in a room for 6 days for curing. After that, it was crushed, and particles having a particle size of 0.5 to 5 mm were taken out and used as a sample.

Water was added to the above sample in a weight ratio of 10 times,
Adjust initial PH to 5.8-6.3, shake for 6 hours 4
cm, 200 r. p. After shaking at m, filtration was performed to measure the concentration of each heavy metal in this filtrate, and the elution amount of each heavy metal was detected from this.

Preparation of the sample after the treatment was carried out by using 10 wt% of Portland cement and 50% by weight in the step of preparing the sample before the treatment.
At the time of kneading with wt% of water, the chemicals shown in the following respective treatments (1) to (6) were added and kneading was performed, and then the sample was prepared in the same manner as the sample before the treatment.

Treatment (1) An aqueous NaSH solution is added as a heavy metal stabilizer so that the amount of NaSH is 1 wt% with respect to the dust. This process (1)
According to The chemical reaction shown in is performed.

That is, the solubility of sodium hydrosulfide is reduced from about 1.07 ppm to 0.01 ppm by reacting with lead oxide contained in soot dust to form lead sulfide. Therefore, as shown in Table 1, the elution amount of heavy metals in the sample subjected to this treatment (1) was 170 → 1.0 ppm for lead.
Decreased to.

However, the above-mentioned elution amount of 1.0 ppm is an average value of 3 times excluding the maximum value and the minimum value out of 5 times of the test, and the maximum value reaches 3 times the average value. There were variations in the measurement results. Although the solubility of PbS produced is small, the molecules are very small, so if it remains as it is, it tends to come out from the pores between the dust particles, and PbS comes out to the outside of the extra pores and is contained in the filtrate of the elution test. May be detected as.

Treatment (2) NaSH added as a heavy metal fixing agent in the above treatment (1)
In addition to the above, sulfur powder was added as a coagulant so as to be 5 wt% with respect to the soot and dust, and the same treatment as the treatment (1) was performed.

In this treatment (2), lead sulfide produced by the equation (1) is agglomerated. That is, (2)
As shown in the formula, the formation of the ring is broken in the aqueous solution of sulfur,
It has a chain structure.

[0021]

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When lead sulfide is present here, as shown in the equation (3), sulfur is aggregated so as to surround it. Here, when alkyl polythiol is used instead of sulfur,
A reaction as shown in formula 4 occurs and is stabilized, and the same effect can be expected.

[0023]

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[0024]

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As a result of these reactions, PbS once formed
Can not come out from the pores between the soot and dust, and therefore the elution concentration with lead is 0.08 mg / l by the 100-fold concentration method, whereas the treatment (1) is 1.0. Met.

Treatment (3) In addition to NaSH and S added to the treatments (1) and (2),
As the surfactant, a nonionic type of fluorine type was added so as to be 3 wt% with respect to the dust. All other conditions were the same as in the treatment (1).

According to this treatment (3), since the hydrophobic group having a small polarity is oriented on the inner wall surface of the pore and the hydrophilic group is oriented in contact with water, water easily permeates into the inside of the pore. Along with this, the liquid processing agent also enters the inside of the pores.

After that, when water inside the pores disappears due to drying and air fills the inside of the pores, the hydrophilic groups invert to the highly polar wall surfaces, the hydrophobic groups come into contact with the air, and then the water becomes fine. It cannot enter the hole. Therefore, the dissolution test result of treatment (3) is 1/4 of that of treatment (2).
It was found that the elution amount was ˜1 / 10, indicating that the chemical treatment reaction was sufficiently performed.

Treatments (4) and (5) Treatment (4) was performed by stirring the treatment (3) using a roll kneader, and in treatment (5), stirring the treatment (3) was performed using a ball mill. The amount was further reduced to about 1/7 and 1/4 in the case of the treatment (3) with lead. Also, kneading with a ball mill is carried out when 20 kg of a material to be kneaded (mixture of cement, water, chemicals and dust) is put in a container of about 100 liters, 5 iron balls of 3 to 5 kg, 200 to 500
This was done using 100 balls of g. It is considered that this is because the treatment chemical was forced to enter the pores of the dust particles by the powerful kneading method using the roll kneader and the ball mill, and the reaction was sufficiently performed.

[0030]

EFFECTS OF THE INVENTION According to the present invention, the stabilizing treatment is carried out to the inside of particles such as incineration pressure containing fine particles such as soot dust, so that harmful heavy metals are eluted from the incinerated ash and the like. And the effect of preventing this elution can be stabilized over a long period of time. Therefore, it is safe to use the incinerated ash treated by the method of the present invention as a recycled product or as a landfill material.

Claims (2)

[Claims] 1. A method for treating incinerated ash, comprising adding a heavy metal stabilizer and a surfactant to kneaded ash containing harmful heavy metals and kneading the ash. 2. A method for treating incinerated ash, which comprises adding a heavy metal stabilizer and a coagulant to an incinerator ash containing harmful heavy metals and kneading the ash.