JPH06226236A - Melting and circulating treatment of solid containing heavy metal - Google Patents

Abstract

PURPOSE:To provide treating means for recycling ash-like waste to resources capable of establishing a circulation system without requiring ancillary equipment and treatment. CONSTITUTION:This treatment method for waste ashes consists in subjecting the waste ashes from a melting furnace to a washing or ash ferritization treatment and subjecting the solid-contents after removal of water-soluble components therefrom by washing to a drying treatment, then charging the ashes into the melting furnace. The circulation treatment system of subjecting the ashes generated from the melting furnace to the washing treatment or the ash ferritization treatment and returning the solid-contents after the removal of the water-soluble components therefrom by washing to the melting furnace is economically formed by applying the method to a waste treatment furnace of a melting type. Consequently, the recycling of the waste ashes to resources as slag and heavy metal resources is possible while these waste ashes are heretofore required to be used for reclamation after the non-pollution treatment. The need for a reclamation land is thus eliminated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to various kinds of waste, incineration ash from a waste incinerator, boiler ash, bottom ash, fly ash, etc. Fly ash and bottom generated from a waste melting furnace, a melting furnace for metallurgy, etc. It relates to the detoxification and recycling of solid materials such as ash.

[0002]

2. Description of the Related Art Solid substances such as incineration ash and fly ash generated from general refuse incinerators and fly ash generated from melting equipment are low boiling point substances such as Pb and Zn, and valuable substances such as NaCl and K.
Water-soluble components such as Cl, SiO ₂ and A as high-boiling substances
Cd, C along with slag forming components such as l ₂ O ₃
Contains harmful heavy metals such as r ⁶⁺ and As. In the treatment of the low boiling point solid matter generated when the solid matter containing such a heavy metal is melt-treated, an expensive heavy metal elution prevention treatment such as a chelation treatment is required, and a final disposal site is also required. .

As an alternative to this chelation treatment,
In Japanese Examined Patent Publication No. 61-47154, an alkali is added and mixed in the presence of an iron salt, and then the mixture is maintained at 300 ° C. or lower. In Japanese Examined Patent Publication No. 63-52552, the waste is finely pulverized. As a method for treating a product, it is disclosed that an alkali is added in the presence of an iron salt to form a slurry, which is then immersed in water and then filtered to solidify the residue. A place is needed.

Further, depending on the concentration of the water-soluble components (NaCl, KCl, etc.) in the solid substance to be treated, the life of the refractory material in the melting stage may be shortened, or the slag layer may have the high-boiling substance layer and the water-soluble components. In some cases, the slag cannot be effectively used because the slag cannot be separated into layers and homogeneous slag cannot be formed.

[0005]

The object of the present invention is to efficiently process the solid matter produced in the solid material melting treatment furnace, such as fly ash and bottom ash, and to convert the high melting point material into slag, The low boiling point substances are to be concentrated and recovered to a concentration that can be recycled, and to provide means for eliminating the need for a final disposal site.

At the same time, it is to provide measures for extending the life of the refractory material and improving the operational stability of the equipment.

[0007]

In order to achieve the above object, the present invention provides a method for treating a solid material containing heavy metals in a melting furnace, such as fly ash and bottom ash generated from the melting furnace. Repeating the step of returning the produced solids to the melting furnace, the high-boiling substances are detoxified and discharged as slag to reduce the volume, while the low-boiling substances are concentrated to a specified concentration by repeating the steps, and as valuable resources. It is characterized by collecting.

Here, the low-boiling substance is concentrated to a specified concentration by repeating the above steps, and then washed with water or ash-ferritized and washed with water to remove water-soluble components and increase the concentration of valuable substances. You may make it collect | recover as a thing.

Further, when a large amount of water-soluble components are concentrated in the produced solid matter such as fly ash and bottom ash generated from the melting furnace, the life of the refractory of the melting furnace and the heterogeneity of the slag occur, the generated solid matter is generated. Before returning the product to the melting furnace, washing treatment or ash-ferritization treatment and washing treatment may be performed.

Further, before the solid material containing the heavy metal is put into the melting furnace, a water washing treatment or an ash-ferritization treatment and a water washing treatment may be performed in advance.

Whether or not the ash-ferritization treatment is carried out depends on whether or not harmful heavy metals are eluted in the washing wastewater and whether there is a wastewater treatment facility containing heavy metals in the factory. It is more economical to judge.

[0012]

As shown in FIG. 1, by repeatedly charging the solid product produced in the melting furnace into the melting furnace, Zn, Pb, etc., which are low-boiling substances in the produced solid product, become concentrated valuables,
Collected by capturing with a dust collector.

On the other hand, Si which is a high boiling point substance in the produced solid
O ₂ , Al ₂ O _{3 and the} like are slagged each time they are charged in the melting furnace and discharged to the outside of the system. Therefore, it is not concentrated.

Further, as shown in FIG. 2, the concentrated Z
Before recovering valuable materials such as n, Pb, etc., by carrying out ash ferrite treatment and water washing treatment, harmful heavy metals such as Cd, Cr ⁶⁺ , As contained in the produced solid matter and Na
With respect to water-soluble components such as Cl and KCl, it is possible to prevent the harmful heavy metals from being eluted during the water washing treatment, and also to remove the water-soluble components.

Therefore, the concentration of the valuable material to be recovered becomes high.

These two methods are applied when the solid content of the water-soluble component is small.

Further, when the produced solid contains a large amount of water-soluble components, in order to prevent the life of the refractory material from being shortened, as shown in FIG. 3, the ash-ferritization treatment and the water-washing treatment are repeated and then repeated. By pouring it into the melting furnace, the harmful heavy metals in the produced solid matter are prevented from being eluted, and at the same time, the water-soluble components are removed and the produced solid matter is concentrated, so that the concentration of recovery of valuables is improved.

If the amount of water-soluble components in the solid containing heavy metals to be charged into the melting furnace is large, not only the life of the refractory material will be shortened but also the treatment cost will be high, which will cause a clogging trouble in the exhaust gas system. Therefore, it is not preferable. Therefore, FIG.
As shown in, after subjecting the solid material containing heavy metal to ash ferrite treatment and water washing treatment, by adding to the melt, it is possible to prolong the life of the equipment and to concentrate valuable resources,
Resources can be recycled.

In each of the above methods, if there is a wastewater treatment facility containing heavy metals in or near the factory, and if it is more economical to perform comprehensive treatment with this facility, the ash-ferritization treatment is excluded. May be.

In addition, it is more preferable that a solidified product after washing with water is subjected to a drying process in order to improve the energy efficiency of the melting furnace, extend the life of the refractory material, and reduce the amount of exhaust gas. Also, when a high concentration concentration is required, in order to prevent re-fly ash in the gas of the slag-forming component,
It is desirable to granulate and put into a melting furnace.

When the exhaust gas of the melting furnace contains harmful acid gas, it is preferable to blow an alkali into the gas for purification of the exhaust gas.

Further, when a solid substance containing heavy metals has a combustible content and a combustible gas such as CO gas is generated in the melting furnace, it is preferable to dispose the combustion chamber afterward. Further, when the bottom ash has a small amount of water-soluble components, it is not necessary to wash with water.

Ferrite is represented by MFe ₂ O ₄ in the chemical formula when M is represented as a heavy metal, and the ash-ferritization treatment in the present invention is an iron oxide in which divalent iron in the mixture is called ferrite. In the process of forming the crystal lattice of, the heavy metal is taken in instead of iron and fixed at the position where the iron atom should occupy.

The reaction formula is expressed as follows.

Neutralization reaction: M ²⁺ + 2Fe ²⁺ + 6OH ⁻ → MFe ²⁺ (OH) ₆ (1) Oxidation reaction: MFe ₂ (OH) ₆ + 1 / 2O ₂ → MFe ₂ O ₄ + 3H ₂ O (2) In the above reaction formula, if the pH is lower than 7.0,
OH ⁻ in the reaction of the formula (1) is insufficient, and the ferrite formation reaction does not proceed. Further, when the pH exceeds 11.5, heavy metals such as lead take the form of HPbO ₂ ^— and are not incorporated in the ferrite formation reaction. Further, when there is no oxygen or when there is no contact with oxygen, for example, when the mixture is not agitated such as standing, O _{2 in the} formula (2) is insufficient and the reaction does not proceed.

The above-mentioned ferrite formation reaction is carried out by adjusting the pH of the mixture.
Is preferably adjusted to 7.0 to 11.5 and then the temperature is preferably maintained at 30 to 99 ° C. This is because heating is effective in promoting the above-mentioned oxidation reaction (2) in the ferritization reaction, and the upper limit is almost zero when the solubility of oxygen in water in the oxidation reaction (2) is 100 ° C. or higher, and the oxidation reaction is almost zero. Does not progress, so it must be below 100 ° C.

As a result, the divalent iron in the mixture gradually crystallizes and turns into ferrite.

Therefore, in the ash-ferritization treatment of the present invention, the presence of divalent iron, the adjustment of pH 7.0 to 11.5 by the addition of an alkali or an acid, and the active presence of oxygen are essential.

[0029]

EXAMPLE The method of claim 3 of the present invention is applied to the treatment of fly ash and bottom ash from a melting treatment furnace for waste, and an example of treatment accompanied by ash-ferritization treatment and water washing treatment will be shown.

FIG. 3 is a diagram showing a system for processing.

In the figure, solid matter such as industrial waste is melted and processed in a known melting furnace. In the melting furnace, combustibles are combusted or gasified by the input fuel, combustible gas containing fly ash is generated, and slag is generated from the furnace bottom. The generated gas is burnt in the combustion chamber, and the exhaust gas is released from the chimney into the atmosphere through the gas cooler, the dust collector, and the exhaust fan. On the other hand, the bottom ash generated in the combustion chamber and the gas cooler, the produced solid matter such as fly ash collected in the dust collector are subjected to ash ferrite treatment in the reactor, and then washed with water to elute the water-soluble components to remove the residue. After drying, put into a melting furnace. In this step, an economical circulation treatment system for the produced solid indicated by a double line is formed.

The results of treatment of the solid product treated by the system shown in FIG. 1 are shown in the table.

[0033]

[Table 1]

[Table 2]

[Table 3]

[Table 4] In each of the above tables, Table 1 shows the values of solid components produced after ash-ferritization, Table 2 shows the results of washing the ash-ferritized ash with water for 5 minutes, and Table 3 shows the solid residue after washing with water. Is a solid product produced when the number of circulations is 5 in a melting furnace at 1300 ° C to 1500 ° C.

As a result, as shown in Table 3, 33
%, And the concentration of Pb was 18%, which is a concentration commensurate with the economical efficiency of recovery.

Table 4 shows the results of the dissolution test of the treated product solids in comparison with those obtained by other methods.

From the same table, it is shown that the immobilization of the heavy metal of the ash-ferritized ash according to the present invention is almost complete, and detoxification can be achieved.

Therefore, the waste water obtained by washing the produced solid matter with water can be discharged only by adjusting the pH, and the waste water treatment can be simplified.

The above examples have been described with respect to the case where the ash-ferritization treatment and the water-washing treatment are followed by circulation.
Even if the ash-ferritization step and the water washing step are omitted, the life of the refractory material is not so affected, and it is possible to obtain a highly concentrated valuable component.

Further, as shown in FIG. 2, the same effect can be obtained even if the water washing step is removed from the circulation line and provided on the heavy metal recovery line.

As in the case of solid ash to be put into the melting furnace, such as incineration ash and bottom ash of a general refuse incinerator and bottom ash and fly ash generated when the volume of fly ash is reduced by a plasma melting furnace, Water-soluble components (NaCl, KC)
FIG. 4 shows an example in which 1) is abundant and water-soluble heavy metals are abundant.

This system has the same effect of concentrating Zn and Pb, but since the water-soluble components are not in the melting furnace,
The slag layer became a uniform and uniform slag, and it was easy to make it into a resource, and the wear of the refractory material inside the furnace was reduced, and the life could be extended about three times.

[0042]

According to the present invention, the following effects can be obtained.

(1) The elution of heavy metals from the produced solid can be completely prevented, and the heavy metal treatment of the wash discharge water can be eliminated.

(2) Since the circulation system system for solid matter treatment is completed, the efficiency of treatment and the concentration of the recovered matter can be achieved, and the valuable resource can be recycled.

(3) The slag quality can be homogenized and can be recycled as a roadbed material or fine aggregate.

(4) The wear of the refractory material of the melting furnace, the combustion chamber and the gas cooler can be reduced and the clogging trouble can be prevented.

[Brief description of drawings]

FIG. 1 shows a processing system according to a first embodiment of the present invention.

FIG. 2 shows a processing system according to a second embodiment of the present invention.

FIG. 3 shows a processing system according to a third embodiment of the present invention.

FIG. 4 shows a processing system according to a fourth embodiment of the present invention.

Claims (4)

[Claims] 1. A method of treating a solid containing heavy metals in a melting furnace, wherein a step of returning the produced solid such as fly ash or bottom ash generated from the melting furnace to the melting furnace is repeated, , Detoxify, reduce volume, and discharge as slag,
On the other hand, the low boiling point substance is concentrated to a specified concentration by repeating the above steps and is recovered as a valuable substance, a method for melting and circulating a solid substance containing a heavy metal. 2. A method of treating a solid containing heavy metal in a melting furnace, wherein a step of returning the produced solid such as fly ash or bottom ash generated from the melting furnace to the melting furnace is repeated, , Detoxify, reduce volume, and discharge as slag,
On the other hand, low-boiling substances are characterized by being collected as valuables by washing with water or ash-ferritization and washing with water after concentration to a specified concentration by repeating the above steps, and melting / circulation of heavy metals. Processing method. 3. A method of treating a solid substance containing heavy metals in a melting furnace, wherein the produced solid matter such as fly ash and bottom ash generated from the melting furnace is washed with water or ash-ferritized and washed with water. After that, the process of returning to the melting furnace is repeated, and the high-boiling substance is detoxified and reduced in volume and discharged as slag, while the low-boiling substance is concentrated to a specified concentration by repeating the process and recovered as a valuable resource. A method for melting and circulating a solid material containing a heavy metal, comprising: 4. A solid material containing a heavy metal is preliminarily washed with water or ash-ferritized and washed with water, and then charged into a melting furnace to perform any one of the operations described in claims 1, 2 and 3. And a method for melting and circulating solid matter containing heavy metals.