JP2000093924A - Method for treating incineration residue of waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the elution of harmful heavy metals from generated molten slag and to recycle the slag easily by removing magnetic components from treated substances after a substance containing zirconium being added to the incineration residue of waste and subjected to high temperature melting/ solidification treatment. SOLUTION: As a zirconium compound, which is not limited in particular, zirconium, zirconium oxide, zirconium carbonate, and others are named, the amount of a substance containing zirconium to be added is, for example, 0.5-10% in oxide equivalent of the total weight. As a method for melting the incineration residue of the waste added with the substance containing zirconium, a melting method with the use of an auxiliary fuel such as heavy oil and others are named. Moreover, although a melting temperature is not limited in particular in so far as the incineration residue is melted, the temperature is preferably 1100-1500 deg.C, and a melting time is selected corresponding to a melting method and is usually between 10 min and 10 hr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting incineration residues such as incineration ash and fly ash generated during incineration of waste, and more particularly, to a method for removing harmful heavy metals from generated slag. The present invention relates to a method for melting incineration residues of wastes that hardly elute.

[0002]

2. Description of the Related Art In Japan, incineration is generally adopted for waste disposal because it is difficult to secure a landfill site. Landfill disposal is performed after reducing the volume of waste by incineration. ing. In addition, due to an increase in efforts for environmental issues on a global scale, thermal recycling for burning waste and recovering generated energy has been performed as one of recycling methods. By incinerating the waste, combustibles in the waste are gasified, and non-combustibles, that is, ash are discharged as residues.
These residues contain harmful heavy metals and dioxins.
There is a problem that harmful substances elute. Therefore, as a method of solving these problems and further reducing the amount of the residue, a method of melting and solidifying the residue to obtain a molten slag has been proposed. Furthermore, the generated molten slag is used for roadbed material,
It has been proposed to reuse it for concrete aggregate, backfill material, concrete secondary products, etc., and in some areas it has already begun to be used for roadbed materials.

[0003]

However, although dioxins are decomposed by the melt-solidification treatment, harmful substances are eluted from secondary products using the molten slag because heavy metals are contained in the molten slag as it is. It is necessary to completely suppress the elution of harmful substances from the molten slag. Furthermore, in April 1998, a guideline value regarding the reuse of molten slag was notified to local governments, and the elution of harmful substances including lead began to be regulated.

[0004] As a melting aid to be added when the incineration residue of wastes is melted and solidified at a high temperature, Japanese Unexamined Patent Publication (Kokai) No. 61-238387 is used.
Japanese Patent Application Laid-Open No. 4-321439 and Japanese Patent Application Laid-Open No. 4-321538 disclose that the melt flow point of molten slag can be lowered by adjusting the basicity and the sodium content, so that the energy required for melt solidification can be reduced. 61-15934 and JP-A-8-89923 propose that a silicon source or a metal can reduce a specific element from a slag layer or a metal layer. None of them aimed at suppressing elution of harmful substances from molten slag. An object of the present invention is to provide a method for treating incineration residues of wastes in which heavy metals are hardly eluted from generated molten slag.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve such problems, and as a result, added a zirconium-containing substance to the incineration residue of waste, solidified it at a high temperature, and then removed the magnetic component. By doing, we found that heavy metals hardly eluted from the generated molten slag,
The present invention has been reached.

That is, the gist of the present invention is a method for melting incineration residues, which comprises adding a zirconium-containing substance to a waste incineration residue, subjecting it to a solidification treatment, and then removing a magnetic component from the treated material. It is.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The waste incineration residue in the present invention means all components other than gas generated in the incineration process, such as incineration ash generated by incineration of general waste, industrial waste, sewage sludge, and fly ash collected from exhaust gas by a dust collector. It is. Further, the present invention can also be applied to a case where an incineration residue in an incineration process is melted and solidified without being taken out once, such as a gasification melting furnace or a direct melting furnace.

In the present invention, first, a zirconium-containing substance is added to the incineration residue of waste. The zirconium compound to be added is not particularly limited, and zirconium, zirconium oxide, zirconium carbide, zirconium oxychloride, zirconium alkoxide, zirconium nitride, zirconium silicate, zirconium chloride, zirconium hydride, zirconium nitrate, zirconium boride And so on. The amount of the zirconium-containing material added is 0.5 to 1 of the total weight in terms of oxide.
0%, preferably 1 to 5%. If the amount of the zirconium-containing material is less than the above range, the effect of preventing the elution of heavy metals decreases, and if it is more than the above range, only a large amount of addition does not provide a significant effect, so that it is not preferable.

Next, the incineration residue of the waste to which the zirconium-containing substance has been added is subjected to a melting treatment and then solidified by water granulation or air cooling. Methods for melting incineration residues include heavy oil, kerosene, gas,
Melting method using auxiliary fuel such as coke, melting method using electricity as heat source such as arc type, plasma type, electric resistance type, low frequency induction type, and direct melting such as pyrolysis melting or coke bed method Method. The melting temperature is not particularly limited as long as it is a temperature at which the incineration residue is melted.
It is preferable to melt at about ℃, as the melting time,
It is preferable to appropriately select according to the melting method.
It may be melted for 0 minutes to 10 hours.

Next, since the treated material prepared by such a method contains molten slag and metal, the metal is removed by removing the magnetic component. Separation of the magnetic component may be performed after crushing the processed material as necessary. As a method for removing the magnetic component, a permanent magnet or an electromagnet can be performed using a magnetic separator such as a cross belt type or a rotating drum type. In the present invention, when melting and solidifying the incineration residue in the presence of zirconium, heavy metals, particularly lead, from the molten slag migrate into the metal,
It is considered that the concentration of heavy metals in the molten slag decreases.

FIG. 1 shows the contents of lead in molten slag prepared under various conditions and measured by the method specified in "Environmental Standards for Soil Contamination" (Notification No. 46 of the Environment Agency, 1991). It is a figure which shows the relationship with the elution concentration of lead from a molten slag. From this figure, it can be seen that there is an approximately positive correlation between the content of lead in the molten slag and the amount of lead eluted from the molten slag. Therefore, in the present invention,
Since the content of heavy metals in the generated molten slag is reduced, heavy metals are hardly eluted from the molten slag. And, "About environmental standards related to soil pollution"
The elution concentration of each heavy metal from the molten slag in the case of performing the elution test according to the method specified in (Environment Agency Notification No. 46, 1991) can be set to the value shown in Table 1 below.

[0012]

[Table 1]

As described above, the molten slag generated by the method of the present invention prevents heavy metals, particularly lead, which is likely to be eluted from the molten slag, from being eluted, so that it can be reused for various uses. It is possible.

[0014]

Next, the present invention will be described in detail with reference to examples. Example 1 An incineration residue obtained by mixing incineration ash and fly ash generated from a stoker type incineration plant having the composition shown in Table 2 (PbO was added in an amount of 0.3% by weight to the incineration residue to increase the Pb content. 2.5 g of zirconium oxide was added to 250 g and mixed. Put the crucible in a small electric furnace and raise the temperature to 1
The temperature was maintained at 350 ° C., and the prepared incineration residue was charged.
Melt for 10 minutes, pour the melted product into 10 liters of water,
Granulated slag was used. The granulated slag was dried at 105 ° C. for 24 hours and then pulverized to remove magnetic components using a permanent magnet.

[0015]

[Table 2]

As a result of measuring the lead content of the molten slag (granulated slag from which the magnetic components were removed) by ICP (high frequency inductively coupled plasma) emission spectrometry, 0.07 mg / g of lead was found in the molten slag. Was contained only. Also, the amount of lead eluted from the molten slag was determined by the Environment Agency Notification 46.
As a result of measurement based on the signal method, the elution of lead was below the detection limit (<0.005 mg / l).

Comparative Example 1 A molten slag was prepared in the same manner as in Example 1 except that zirconium oxide was not added, and the lead content of the molten slag and the amount of lead eluted from the molten slag were measured. As a result of measurement in the same manner as in Example 1, 1.5 was found in the molten slag.
mg / g of lead, and the eluate contained 0.025
Elution of lead of mg / l was observed.

[0018]

According to the present invention, since the heavy metals are hardly eluted from the molten slag generated by melting and solidifying the incineration residue, the generated molten slag can be easily reused.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the content of lead in molten slag and the concentration of lead eluted from molten slag.

Claims (1)

[Claims] 1. A method for treating incineration residues, comprising adding a zirconium-containing substance to a waste incineration residue, subjecting it to a solidification treatment, and then removing a magnetic component from the treated product.