JP2003010814A - Ash treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining a recyclable solid content by concentrating a heavy metal and by lowering the chloride ion concentration in the solid content of an exhaust gas generating from a melting furnace of fly ash. SOLUTION: The fly ash from an incineration furnace and/or the fly ash (a) from the melting furnace are continuously cleaned by washing the ashes with water, mechanically rubbing the surfaces of the ash a each other into slurry 1, and then subjecting the slurry 1 the solid/liquid separation process (2) to transfer salts to the water side (d) and remove the salts. The solid content (c) is melted at the melting furnace 4 into a molten solid content (g). The dust scattered in the exhaust gas (f) from the furnace 4 is captured 5 and mixed with water so that the dust is cleaned and makes into slurry 8. After that, the slurry (8) is subjected to the solid/liquid separation process 9 and the salts are transferred to the water side (m) and removed. Thus the solid content (p) enriched with the heavy metal is obtained and the exhaust gas (f) is captured by a dust collector after adding a neutralizing agent to the exhaust gas (f). The solid content is melted at the melting furnace 4, preferably in a reductive atmosphere.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating fly ash, and more particularly, to fly ash generated from an incinerator for general waste or industrial waste, or an ash melting furnace for melting the fly ash, and gasification. The present invention relates to a method for treating ash for treating molten fly ash generated from a melting furnace.

[0002]

2. Description of the Related Art Generally, municipal waste and industrial waste are incinerated so that the volume thereof is 1/20 to 1 as compared with that before incineration.
Although the volume can be reduced to / 30, the fly ash generated by incineration contains a large amount of heavy metals (particularly zinc, lead and copper). Therefore, as a detoxification measure, it is legally regulated to perform treatment by melt solidification, baking treatment, cement solidification, chemical treatment, acid, or other solvent extraction method. Of these treatments, the melting and solidification melts and solidifies the incineration ash and fly ash under high temperature conditions of 1200 ° C or higher, so the volume of dioxins is decomposed and the volume of ash is further reduced by about 1/2. ,
The molten solidified material can be effectively used as construction materials such as slag,
It can be said that this technology is suitable for creating a recycling-based society. But,
The heavy metal in the molten fly ash generated during melting needs to be further concentrated and detoxified. Currently, fly ash generated in the incinerator and molten fly ash generated in the melting furnace are disposed of at the final disposal site in most cases after detoxification treatment. Although relatively large amounts of heavy metals migrate to the fly ash and molten fly ash,
The concentration of this is low for Yamamoto reduction in a non-ferrous kneading company.

Table 1 shows an example of the composition of the main ash and fly ash of a general waste incinerator.

[Table 1]

Table 2 shows an example of the composition distribution of molten fly ash.

[Table 2] For the reduction of Yamamoto, it is desirable that the concentration of heavy metals be about several tens of percent, and unless the concentration of chloride ions in ash is reduced.
There may be problems such as corrosion of equipment on the Yamamoto reduction side.

[0005]

DISCLOSURE OF THE INVENTION In view of the above-mentioned prior art, the present invention reduces the concentration of chloride ions in the solid content of the exhaust gas discharged from the melting furnace for melting fly ash and increases the concentration of heavy metals to achieve non-ferrous kneading. It is an object to provide a method for treating ash that can be returned by Yamamoto at the company and collected.

[0006]

In order to solve the above problems, in the present invention, fly ash generated from an incinerator and / or molten fly ash generated from a melting furnace is mixed with water to mechanically remove ash. After continuous cleaning by rubbing the surface and making it into a slurry, solid-liquid separation is performed to remove salts by moving to the water side, and the solid content is melted in a melting furnace into a molten solid, which is then added to the exhaust gas of the melting furnace. The scattered dust is collected, mixed with water, washed and slurried in the same manner as described above, and then solid-liquid separated to move salts to the water side for removal, and solid contents enriched with heavy metals. The method of treating ash is characterized in that The washing at this time does not sufficiently dissolve the salts on the water side by simple stirring, and a large amount of water and a long stirring time are required for sufficient dissolution. Therefore, in the present invention, the slurry was mechanically rubbed against the ash surface and continuously treated to shorten the cleaning time and save water.

In the present invention, the fly ash generated from the incinerator and / or the molten fly ash generated from the melting furnace is mixed with water, and the ash surface is mechanically rubbed to continuously wash and slurry. , Solid-liquid separation to remove salts by moving to the water side, the solid content is melted in a melting furnace to a molten solid matter, and the dust in the exhaust gas generated from the melting furnace is captured by a bag filter to remove heavy metal content. A method for treating ash characterized by obtaining a solid content enriched with, and adding a neutralizing agent (slaked lime etc.) to the exhaust gas from the bag filter and capturing it with a dust collector (bug filter etc.) Is. In the method for treating ash, melting of solid matter in a melting furnace is preferably performed in a reducing atmosphere, and the fly ash or molten fly ash is a bag filter for dust in exhaust gas generated from an incinerator or a melting furnace. The exhaust gas that is captured and discharged from the bag filter can be further purified by a dust collector by adding a neutralizing agent.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in detail.
In the present invention, the fly ash generated from the incinerator and / or the molten fly ash generated from the melting furnace is mixed with water to be washed and slurried, and then solid-liquid separation is performed to move salts to the water side, Only the remaining solid content is targeted for melting. This allows
Chloride ions and alkali metals (sodium and potassium), which are high-concentration components in ash, can be eluted into water and the concentration of heavy metals can be relatively increased. The reduction of chloride ion concentration is also effective in preventing dust clogging due to salts generated during melting in the melting furnace. When the type of the melting furnace that melts solids is an electric resistance furnace, the alkali metal concentration is reduced by forming an alkali metal salt in the upper part of the furnace during the melting process. There are obstacles, but it is convenient for that.

Next, the solid content remaining after the solid-liquid separation is melted in a melting furnace. In the melting furnace, a carbon source is charged and an ash covering layer is formed on the molten slag layer in the furnace. It is preferable to melt in a furnace as a reducing atmosphere. In a reducing atmosphere, when heated to a high temperature, it is easily reduced, and zinc, lead, cadmium, etc., which have a relatively low boiling point, are converted into metal vapor and volatilized in the furnace, and are oxidized at the stage of leaving the furnace. This is the Welts method (in the Welts method, coke is used as a reducing agent)
It is a technology that has a proven track record as a reduction volatilization method found in. In particular, since a large amount of chloride ions are removed by slurry cleaning, heavy metals in the solid content are less likely to become chloride, which is disadvantageous in slurry cleaning in terms of promotion of volatilization by chlorination. Heavy metal scattering compensates for this disadvantage. Further, it is preferable that the melting furnace has a structure in which the amount of physically scattered matter is small, and the molten matter is slagged as much as possible.

Dust generated from the melting furnace is collected, further mixed with water, washed and slurried, and then solid-liquid separated to move salts to the water side. Thereby, the chloride ion concentration in the ash can be further reduced, and the heavy metal concentration can be relatively increased. Depending on the melting method and the properties of ash, acidic substances (HCl
Etc.) Suitable when the concentration can be kept low. For example, when the melting furnace is an electric resistance furnace, the concentration of acidic substances in the exhaust gas after trapping soot and dust with a bag filter tends to be suppressed, and this system is easily adopted in such equipment. If slaked lime is added, the unreacted component is difficult to dissolve in water and remains on the solid content side even if washed. On the smelting company side, when lead is separated, it is often the case that lead sulfate separates it as a solid content, and calcium in unreacted slaked lime also forms calcium sulfate, which is difficult to separate from lead sulfate, which is not preferable.

By a series of these operations, the concentration of chloride ions in the ash can be reduced, the concentration of heavy metals can be increased to several tens of percent, and a solid product that can be reduced to a non-ferrous smelting company can be obtained. Also, the purpose of washing and slurrying ash by adding water is to remove salts, so when melting solids, the soot and dust in the exhaust gas generated from the melting furnace is captured by the first-stage bag filter. Further, by adding a neutralizing agent to the discharged gas and neutralizing it to purify it with a dust collecting device, for example, a second stage bag filter, it is possible to substitute for ash slurry cleaning.

Next, the present invention will be described with reference to flow charts of the present invention shown in FIGS. In FIG. 1, the incineration ash and the ash a generated in the melting furnace are cleaned by the cleaning device 1. The structure of the cleaning device 1 is such that the protrusions on the rotor surface are rotated and the shell is rotated in the opposite direction to remove surface deposits of ash and promote elution of salts to the water side. Ash and water are mixed in the cleaning device 1 to form a slurry b, which is introduced into the dehydrator 2. The dehydrator 2 is generally a centrifugal separator and is divided into a solid content c and separated water d. The separated water d is purified by the coagulation washing method or the like in the water treatment device 6, and is discharged after purification. The solid content c is dried in the drying device 3 and then melted in the melting furnace 4. The exhaust gas f generated from the melting furnace 4 captures the soot and dust j in the dust collector 5.
The purified exhaust gas is released to the atmosphere i.

Soot and dust j is made into a slurry k in the cleaning device 8, and salts easily soluble in water are transferred to the separated water m side by the dehydrating device 9. Heavy metal is concentrated in the solid content p, and Yamamoto reduction is performed by a kneading company. In addition, the smelting company has a cleaning device 8,
It is also possible to install the dehydrator 9 and deliver it in the state of dust j. FIG. 2 is another flow configuration diagram of the processing method of the present invention. In FIG. 2, the dust collecting apparatus 5 of FIG. 1 includes a first stage bag filter 10 and a second stage bag filter 11. The soot and dust j captured by the first stage bug filter is
Yamamoto reduction can be carried out as it is at a smelting company without containing acidic substances and slaked lime for removing them. Neutralized ash R is generated from the second-stage bag filter.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 Table 3 shows the fly ash treatment test results obtained by treating the fly ash of the stoker furnace according to the flow diagram of FIG. The amount of water used in this treatment test was 5 times the fly ash mass in the cleaning device 1 and the dehydrating device 2 in FIG. 1, and 5 times the fly ash mass in the cleaning device 8 and the dehydrating device 9.
Double water was used. The melting furnace 4 is an electric resistance furnace.

[0015]

[Table 3] From Table 3, it was confirmed that the concentration of heavy metals (particularly Zn) was high, and that the concentration of chloride ions, which hindered the Yamamoto reduction, was significantly reduced.

[0016]

According to the present invention, useful heavy metals contained therein are concentrated and recovered without treating fly ash generated from an incinerator and molten fly ash generated from a melting furnace in a final treatment plant, It was possible to recycle it.

[Brief description of drawings]

FIG. 1 is a flow configuration diagram showing an example of a method for treating ash according to the present invention.

FIG. 2 is a flow configuration diagram showing another example of the method for treating ash according to the present invention.

[Explanation of symbols]

1: Washing device, 2: Dehydrating device, 3: Drying device, 4: Melting furnace, 5: Dust collector, 6: Water treatment device, 7: Slag manufacturing device, 8: Washing device, 9: Dehydrating device, 10: 1st stage bug filter, 11: 2nd stage bug filter,

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F27D 17/00 105 B09B 3/00 303L 5/00 N (72) Inventor Seiichi Tsuda Haneda, Ota-ku, Tokyo 11-1-1 Asahimachi F-term in EBARA CORPORATION (reference) 3K061 ND03 4D004 AA37 BA05 CA29 CA34 CA40 CC03 4D056 AB07 AC22 BA03 CA18 4K056 AA00 AA05 CA20 DB07 DB26 DB27

Claims (4)

[Claims] 1. Fly ash generated from an incinerator and / or molten fly ash generated from a melting furnace is mixed with water and mechanically rubbed on the ash surface to continuously wash and form a slurry, and then solid-liquid separation. Then, the salts are transferred to the water side to be removed, and the solid content is melted in a melting furnace to form a molten solid matter, and the dust scattered in the exhaust gas of the melting furnace is collected and mixed with water to mechanically Rubbing the ash surface continuously to make it into a slurry, and after making it into a slurry, solid-liquid separation is performed to remove salts by moving them to the water side, and ash treatment characterized by obtaining a solid content enriched in heavy metals. Method. 2. Fly ash generated from an incinerator and / or molten fly ash generated from a melting furnace are mixed with water and mechanically rubbed on the ash surface to continuously wash and form a slurry, and then solid-liquid separation. Then, the salts are transferred to the water side and removed, and the solid content is melted in a melting furnace to form a molten solid matter, and the dust in the exhaust gas generated from the melting furnace is captured by a bag filter to enrich the heavy metal content. A method for treating ash, which comprises obtaining a solid content and adding a neutralizing agent to the exhaust gas from the bag filter to capture the solid content with a dust collector. 3. The method for treating ash according to claim 1, wherein the solid material is melted in a melting furnace in a reducing atmosphere. 4. The fly ash or the molten fly ash is collected by a dust collector before the neutralizing agent is added to the exhaust gas generated from the incinerator or the melting furnace, and the collected matter is melt-treated. 4. The method for treating ash according to claim 1, 2 or 3.