JPH0994548A - Solidifying agent for incineration residue and solidification method of incineration residue - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a solidifying material provided combinedly with strength for using incineration residues like incineration ash, soot and others as a recycle material and the preventive properties against the elution of heavy metals. SOLUTION: This solidifying agent is composed of components consisting of 0.1-29wt.% cement and a mixing material demonstrating latent hydraulic properties or pozzolan activities of 71-99.9wt.%, and the solidifying agent is mixed with incineration residues at a given blend ratio, and water of a required amount is added thereto, and the mixture thus formed is kneaded and molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solidifying agent for solidifying an incineration residue such as incineration ash and dust generated in an incinerator such as a waste incineration plant and a method for solidifying the incineration residue.

[0002]

2. Description of the Related Art Incineration ash generated when incinerating industrial waste and municipal waste, and incineration residues such as soot dust collected by an electric dust collector, etc. are harmful to cadmium (Cd) and lead (Pb). Heavy metals are often contained, and when they are landfilled, the law stipulates that the heavy metals contained must be treated so that they do not elute, such as solidifying with cement, before disposal.

As means for solidifying the incineration residue, agents such as chelates and various cement-based solidifying agents have been proposed, and various methods for solidifying the incineration residue by using the solidifying agent have been proposed.

On the other hand, at present, the above-mentioned incineration residue generated when incinerating industrial waste and municipal waste is landfilled in a managed final disposal site. However, the amount of incineration residue of general municipal waste alone is enormous. It is said that 5 to 6 million tons per year are nationwide, and the shortage of disposal sites has become a problem.
As one of the solutions, there is an increasing demand for solidifying the incineration residue with a solidifying agent and recycling it to civil engineering materials.

[0005]

A conventional technique as a method for solidifying such an incineration residue is disclosed in, for example, JP-A-61-161.
There are those disclosed in JP-A-133186, JP-A-5-309356 and JP-A-4-118087. In the conventional technique disclosed in Japanese Patent Laid-Open No. 61-133186, after the carbon content, starches, proteins and the like of the incinerated ash are gelled with a chemical agent such as polyaluminum chloride, a cement-based solidifying agent is used. I try to harden it with
In this conventional technique, the strength of the solidified product (8-day curing, uniaxial compression strength of 1.57 kg / cm ² ) is extremely low, and no data is provided on the effect of preventing the elution of harmful substances, and it is unknown.

Further, the conventional technique disclosed in Japanese Patent Laid-Open No. 5-309356 is a method for treating incinerated ash in which the incinerated ash is stabilized with sulfuric acid and then solidified with cement such as blast furnace cement. Since the purpose of the treatment is landfill disposal at the final disposal site, the strength of the solidified product and the elution preventive property of heavy metals (Pb elution amount 2 ppm) are extremely low.

Further, in the conventional technique disclosed in Japanese Patent Laid-Open No. 4-118087, the hydrothermally reactive powder component is hydrothermally bonded with the excessively hydrated lime due to the hydration of cement to bond with the pH value. Although this is a solidification method that utilizes the function of decreasing the amount of water, it mainly involves curing by a hot water reaction, and therefore requires heating and pressurization with steam in an autoclave as a curing process, which has the drawback of increasing manufacturing costs. Further, the ability to prevent heavy metal elution was low, and it was 0.02 ppm with respect to the soil environmental standard (less than 0.01 ppm in the case of Pb), which was insufficient.

On the other hand, conventionally, there is an example of using blast furnace cement mixed with blast furnace slag as a solidifying agent instead of cement because of its cost, heat of hydration, and low corrosion.

However, an admixture having latent hydraulicity and pozzolanic activity, such as blast furnace slag, reduces hydroxide ions in the solidified product at room temperature and pressure, and positively utilizes this action to control the pH. There has been no solidifying agent for improving the elution prevention effect and mechanical strength of amphoteric metals such as lead.

The conventional method for treating incinerated ash has the strength required for landfill disposal at the final disposal site (uniaxial compressive strength 10
For kg / cm ² or higher) and elution preventing property (landfill reference Pb are mostly intended 3ppm or less),
Even if the material was recycled as a civil engineering material, there was no solidifying agent capable of satisfying both the soil environmental standard (0.01 ppm in the case of Pb) and high strength (uniaxial compressive strength 50 to 100 kg / cm ² or more).

At present, a clear environmental standard for recycled waste products is not statutory, but in consideration of the environment, local governments have come to use the soil environmental standard as a standard for civil engineering materials. ing.

The inventors of the present invention have conducted various experiments to solidify incineration residues such as incineration ash and soot dust while achieving both mechanical strength and prevention of heavy metal elution, and a solidifying agent for the incineration residues. Invented a method for solidifying incineration residue, which is solidified by using.

[0013]

It is known that the elution amount of heavy metals such as Cd and Pb contained in the incineration residue such as incineration ash and dust is largely dependent on the pH of the solidified matter. FIG. 1 shows an example of the relationship between the pH of the solidified product in the solution and the solubility of the heavy metal. In the figure, a is Cd and b is Pb
The solubility of Pb in the pH range of 9.5 to 11.5 is small, but it is large before and after this, especially when the pH is above about 12. The solubility on the side is significantly increased.

When the incineration residue is solidified with a cement-based solidifying agent, the solidified solution generally shows a strong alkali.
Elution of amphoteric heavy metals such as Pb is mainly a problem, but if there is a solidifying agent that exhibits mechanical strength while keeping the pH low, both the above-mentioned mechanical strength and anti-elution properties can be achieved.

The present inventors have paid attention to the action of an admixture having latent hydraulic properties such as blast furnace slag, fly ash, and pozzolan, or having pozzolanic activity, to reduce hydroxide ions (OH ⁻ ) during curing by addition of water, Hydraulic cement and these admixtures are mixed at a certain ratio, an appropriate amount of water is added, and the mixture is kneaded and then molded at room temperature by a molding method such as extrusion molding or compression molding to elute Cd and Pb. It has been found that it is possible to obtain a solidified product that can be recycled and used as a civil engineering material or the like that has both preventability and mechanical strength.

That is, the solidifying agent for incineration residue according to the present invention is cement: 0.1-29 wt% latent hydraulic property, or admixture showing pozzolanic activity: 71
˜99.9 wt%, and the solidifying agent and the incineration residue are mixed in a predetermined mixing ratio, and water is added in a necessary amount to knead and mold.

In this solidifying agent, since the pH of the solidifying agent largely depends on the blending ratio of cement (Portland cements) showing a strong alkali, the elution amount of heavy metals is not so much influenced by the blending ratio of the incineration residue and the solidifying agent. Therefore, the breakdown of incineration residue and solidification agent can be considered independently.

As a content ratio of the solidifying agent, an admixture exhibiting latent hydraulicity or pozzolanic activity, such as blast furnace slag, does not exhibit curability by itself, and calcium hydroxide (Ca (Ca (Ca The presence of OH) ₂ ) makes it hardenable, so at least about 0.1 wt% cement or alkali such as calcium hydroxide,
A hardening stimulant such as sulfate is required.

Further, the cement has a higher mechanical strength as the compounding amount thereof increases, but at the same time, the pH also increases.
There is an upper limit to the blending ratio of this. According to various experiments conducted by the present inventors, it has been found that when the amount exceeds 29 wt%, the elution amount of heavy metals such as Pb increases in many cases and exceeds the environmental standard.

Further, when the cement containing the admixture having latent hydraulicity or pozzolanic activity such as blast furnace slag, fly ash, pozzolan, etc. is used as the cement in the above-mentioned solidifying agent, the mixing ratio in the solidifying agent is as follows. Become.

Mixing cement containing an admixture showing latent hydraulic property or pozzolanic activity: 0.1 to 97 wt% Admixture showing latent hydraulic property or pozzolanic activity: 3 to
It is 99.9 wt%, and this solidifying agent is mixed with the incineration residue in a predetermined mixing ratio, and a necessary amount of water is added to knead and mold.

Latent hydraulic property instead of cement in the solidifying agent,
Alternatively, when a mixed cement containing an admixture exhibiting pozzolanic activity is used, this cement, unlike Portland cements, already has latent hydraulic properties such as blast furnace slag,
Alternatively, since the admixture exhibiting pozzolanic activity is contained, the upper limit of the amount of this mixed cement becomes large as compared with the case where Portland cement is used, and on the contrary, the lower limit of the amount of the admixture becomes small. This is because the mixture ratio of the latent hydraulic property in the solidifying agent or the admixture showing pozzolanic activity is
The total amount of the admixture in the solidifying agent is a problem, and the amount of the admixture can be obtained by converting it based on the component ratio of the mixed cement to be used when the above Portland cement is used.

The following is a conversion example of the mixed cement and the admixture in the solidifying agent when blast furnace cement is used as the mixed cement. Blast furnace cement is a mixture of Portland cement and blast furnace slag, and the mixing ratio is JI.
It is determined by S as shown in Table 1.

[0024]

[Table 1]

(Conversion example 1) When the breakdown of the solidifying agent is 29% by weight of Portland cement and 71% by weight of blast furnace slag, the mixture of blast furnace cement and blast furnace slag when the above Portland cement is replaced with blast furnace cement (C type) The conversion of the ratio is shown below.

The blast furnace cement (C type) is, for example, a mixture of 30% by weight of Portland cement and 70% by weight of blast furnace slag. Therefore, the ratio of the blast furnace cement is adjusted so that the cement components contained in the blast furnace cement are the same. If so, an equivalent solidifying agent can be obtained.

That is, assuming that the blast furnace cement is X wt% and the added blast furnace slag is Y wt%, the cement content contained in the whole is X × (30/100) = 29 (wt%) The blast furnace slag content contained in the whole is Y + X X (70/100) = 71 (wt%), which can be converted into the blast furnace cement ratio X = 97 wt% and the blast furnace slag ratio Y = 3 wt%.

(Conversion example 2) When the breakdown of the solidifying agent is 0.1% by weight of Portland cement and 99.9% by weight of blast furnace slag, the above-mentioned Portland cement is replaced with blast furnace cement (class A). The conversion of the blending ratio of blast furnace slag is shown below.

The blast furnace cement (A type) is, for example, a mixture of 95% by weight of Portland cement and 5% by weight of blast furnace slag. Therefore, the ratio of the blast furnace cement is adjusted so that the cement components contained in the blast furnace cement are the same. If so, an equivalent solidifying agent can be obtained.

That is, assuming that the blast furnace cement is X wt% and the added blast furnace slag is Y wt%, the total cement content is X × (95/100) = 0.1 (wt%) The total blast furnace slag content is Is Y + X × (5/100) = 99.9 (wt%), which can be converted into the blast furnace cement ratio X = 0.11 wt% and the blast furnace slag ratio Y = 99.89 wt%.

(Conversion Example 3) Fly ash cement is a mixed cement of Portland cement and fly ash, and the mixing ratio thereof is determined by JIS as shown in Table 2.

[0032]

[Table 2]

Silica cement is a mixed cement of siliceous admixture such as Portland cement and pozzolan, and the mixing ratio thereof is similarly set as shown in the third.

[0034]

[Table 3]

The breakdown of the solidifying agent is Portland cement 2
In the case of 9 wt% and the siliceous admixture 71 wt%, the above-mentioned Portland cement was replaced with silica cement (C
The following is an example of conversion of the ratio of silica cement and siliceous admixture when replaced with (type).

Silica cement (C type) is, for example, 30% by weight of Portland cement and 70w of siliceous admixture.
Since it is a mixture of t%, the same solidifying agent can be obtained by adjusting the ratio of silica cement so that the cement content contained in the silica cement becomes the same.

That is, assuming that silica cement is X wt% and the siliceous admixture to be added is Y wt%, the total cement content is X × (30/100) = 29 (wt%) The quality admixture content is Y + X × (70/100) = 71 (wt%), and can be converted to silica cement ratio X = 96.7 wt% silicic admixture ratio Y = 3.3 wt%.

Further, the above incineration residue is subjected to uniaxial compressive strength of 50 to 100 kg / cm ² such as roadbed materials and various blocks.
When recycling to a civil engineering material that requires a certain degree of mechanical strength, use one of the above two types of solidifying agents and mix them with the incineration residue 30 to 90 wt% solidifying agent 10 to 70 wt%. Then, the required amount of water is added, and the mixture is kneaded and molded.

The solidified product thus molded has a uniaxial strength of 50 to 10 after 28 days of curing at room temperature and normal curing at normal temperature.
It is 0 kg / cm ² or more, and as a result of the dissolution test based on the Environmental Agency Notification No. 13, the Pb dissolution amount is 0.01 ppm.
It was less than (soil environmental standard).

As for the mixing ratio of the incineration residue and the solidifying agent, there is no problem in terms of mechanical strength and elution prevention due to the large proportion of the solidifying agent, but the recycling rate of the incineration residue as a raw material as a recycling material. However, the solidifying agent is generally considered to have an upper limit of about 70 wt% even in view of the decrease in the treatment cost and the increase in the processing cost.

Further, as the minimum mixing ratio of the solidifying agent,
When the solidifying agent is less than the incineration residue that is the raw material,
The mechanical strength of the solidified product decreases. According to various experiments conducted by the present inventors, when the content is 10 wt% or less, the uniaxial compression strength of 50 kg / cm ² , which is a standard of mechanical strength required for recycling civil engineering materials and the like, is often exceeded.

By solidifying the incineration residue as a recycled material by using the solidifying agent blended as described above, the incineration residue can be solidified with a heavy metal elution preventive property that clears the environmental standard.

By using the above solidifying agent and setting the mixing ratio of the solidifying agent and the incineration residue to 30 to 90% by weight of the incineration residue and 10 to 70% by weight of the solidifying agent, the strength that can be used as a recycle material for civil engineering materials, etc. Was obtained.

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a solidifying agent and a solidifying method according to the present invention will be described below based on some examples. Example 1 Incinerated ash 90 wt% Solidifying agent 10 wt% Breakdown: Portland cement 28 wt% Blast furnace slag 72 wt% An appropriate amount of water was added to the above composition and kneaded to obtain 100 kg.
When press-molded with a pressure of / cm ² applied, 28-day curing (normal curing at room temperature and normal pressure) uniaxial compressive strength 54 kg / cm ² Lead elution amount 0.008 ppm (elution test based on Environmental Agency Notification No. 13) ) Got

Example 2 Incinerated ash 92 wt% Solidifying agent 8 wt% Breakdown: Portland cement 30 wt% Blast furnace slag 70 wt% An appropriate amount of water was added to the above composition and kneaded to obtain 100 kg.
When press-molded under a pressure of / cm ^2, the pressure is 48 days after curing (normal curing at room temperature and normal pressure), uniaxial compressive strength 48 kg / cm ² Lead elution amount 0.011 ppm (Environment Agency Notification No. 13) ) Got

Example 3 Incinerated ash 70 wt% Solidifying agent 30 wt% Breakdown: Portland cement 1 wt% Blast furnace slag 99 wt% An appropriate amount of water was added to the above composition and kneaded to obtain 100 kg.
/ Pressured cm ² of press molded at 28 days curing dissolution test based on the unconfined compressive strength of 85 kg / cm ² lead elution amount 0.002 ppm (Environment Agency Notification No. 13 (room temperature, usually cured under normal pressure) ) Got

Example 4 Incinerated ash 80 wt% Solidifying agent 20 wt% Breakdown: Blast furnace cement (B type) 50 wt% Blast furnace slag 50 wt% An appropriate amount of water was added to the above composition and kneaded to obtain 100 kg.
When press-molded with a pressure of / cm ² applied, it is cured for 28 days (normal curing under normal temperature and pressure) Uniaxial compressive strength 117 kg / cm ² Lead elution amount 0.009 ppm (elution test based on Environmental Agency Notification No. 13) ) Got

Example 5 Incinerated ash 65 wt% Solidifying agent 35 wt% Breakdown: Silica cement (C type) 40 wt% Silica fume 60 wt% An appropriate amount of water was added to the above composition and kneaded to obtain 100 kg.
/ Pressured cm ² of press molded at 28 days curing dissolution test based on the unconfined compressive strength of 132 kg / cm ² lead elution amount 0.009Ppm (Environment Agency Notification No. 13 (room temperature, usually cured under normal pressure) ) Got

Example 6 Incinerated ash 60 wt% Dust 20 wt% Solidifying agent 20 wt% Breakdown: Portland cement 0.3 wt% Blast furnace slag 99.7 wt% An appropriate amount of water was added and kneaded to 100 kg.
/ Pressured cm ² of press molded at 28 days curing dissolution test based on the unconfined compressive strength of 121 kg / cm ² lead elution amount 0.009Ppm (Environment Agency Notification No. 13 (room temperature, usually cured under normal pressure) ) Got

In each of the above examples, the mixing ratio of the solidifying agent to the incinerated ash was set to 8 wt%, which is less than 10 wt%,
The mixing ratio of Portland cement in the solidifying agent is 30 wt.
%, The strength of the solidified product is 50 kg / cm.
There was a problem in strength without reaching ² . In addition, the lead elution preventive property slightly exceeded the standard.

However, in other experimental examples in which the mixing ratio of the solidifying agent was 10 wt% or more and the mixing ratio of the Portland cement component in the solidifying agent was 29 wt% or less, the mechanical strength of the solidified product was 50 kg / cm, respectively. ^The desired strength could be obtained over ² . The amount of lead (heavy metal) elution was below the environmental standard value, respectively, and the elution prevention property of heavy metal was confirmed.

In all of the above-mentioned examples, among the harmful substances regulated by the soil environmental standard, all substances other than Pb were below the standard value.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between pH and solubility of heavy metals.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideko Murai, 1200, Manda, Hiratsuka, Kanagawa Prefecture, Komatsu Ltd. (72) Inventor, Takehiko Iizuka, 1200, Manda, Hiratsuka, Kanagawa, Ltd., Komatsu Ltd.

Claims (3)

[Claims] 1. Cement: 0.1-29 wt%, latent hydraulic property, or admixture showing pozzolanic activity: 71-9
A solidifying agent for incineration residue, which is blended to 9.9 wt%. 2. A mixed cement containing an admixture having latent hydraulic property or pozzolanic activity: 0.1 to 97 wt%, an admixture having latent hydraulic property or pozzolanic activity: 3 to 9
A solidifying agent for incineration residue, which is blended to 9.9 wt%. 3. The incineration residue: 30 to 90 wt%, and the solidification agent for incineration residue: 10 to 70 according to claim 1 or 2.
A method for solidifying an incineration residue, which comprises blending wt% and adding a required amount of water to mold.