JPH1099813A - Treatment of incineration ash of waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste incineration ash treatment method capable of stabilizing a harmful substance such as a heavy metal contained in waste incineration ash such as industrial waste incineration ash or urban waste refuse incineration ash discharged from the water tank of a wet ash cooling apparatus without being accompanied by a practical problem such as stabilizing capacity, the corrosion of the apparatus or the generation of scum in the water tank. SOLUTION: A harmful substance treatment material based on a soluble silicate is injected into the cooling water (w) of a thrust rod incineration ash discharge apparatus having a thrust rod 3 delivering incineration ash (a) charged in the cooling water (w) in a water tank 1 from the water tank 1 and waste incineration ash (a) is charged in the cooling water (w) in the water tank l from an ash chuter 2 and the slurry like incineration ash (a) delivered from the cooling water (w) by the thrust rod 3 is stagnated within a cooling apparatus and aged in the state held to 40-70V by the heat generated from incineration ash (a) and cooling water (w) to be discarded to an ash pit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste incineration ash treatment method effective for stabilizing waste incineration ash containing harmful heavy metals and the like. The present invention relates to a method for treating waste incineration ash, which can stabilize harmful substances in incineration ash. The method of the present invention is effective for treating incineration ash in municipal solid waste incineration plants and industrial waste incineration plants, and particularly for stabilizing lead in incineration ash.

[0002]

2. Description of the Related Art Municipal solid waste has a bad smell, and it has been considered that the treatment will be completed if incinerated to reduce its volume and the incinerated ash is disposed of at a final disposal site. However, as the contents of the garbage changed, that aspect has changed. Plastics that are incinerated, paper that is color printed, and batteries that are intentionally discarded in garbage contain heavy metals such as cadmium (Cd), lead (Pb), chromium (Cr), and mercury (Hg).
When these are incinerated, heavy metals remain in the incineration ash.

[0003] Some heavy metals have biotoxicity such as carcinogenicity, mutagenicity and organ damage. For example, lead
It acts destructively on the kidneys with cadmium, mercury and chromium. Lead is known to have a heme synthesis inhibitory effect on blood components and an effect on the nervous system together with mercury. Cadmium is
It has been pointed out that there is a possibility of hypertension and a decrease in spermatogenesis ability. Therefore, municipal solid waste incineration ash is considered hazardous waste. In Japan, since April 1995, municipal solid waste has been
Sufficient control of heavy metal elution as a specially controlled general waste is required. For that purpose, various treatments such as treatment with cements, powder chemicals, liquid chemicals, and the like, and melting treatment are performed in order to suppress elution of heavy metals from incineration ash after incineration of refuse.

[0004] A wet ash cooling device, which is one of the municipal waste treatment devices, is also called an ash removal device, a clinker channel or the like. As shown in FIG. 1, for example, this apparatus includes a water tank 1 for storing cooling water w (generally referred to as equipment water) for cooling incineration ash a such as incineration ash or fly ash generated from an incinerator (not shown). And cooling water w in the water tank 1
An ash shooter 2 into which incineration ash a is charged, a push rod 3 for discharging cooled incineration ash a from the inside of the water tank 1, and the water tank 1
And an ash pit 4 for receiving incineration ash a discharged from the incinerator. The incineration ash a such as incineration main ash or fly ash discharged from the incinerator is supplied from the ash shooter 2 into the cooling water w in the water tank 1. This is a device which, after charging and cooling, discharges the ash from the inside of the water tank 1 to the ash pit 4 by the ash discharging push rod 3.

[0005] However, when an incineration ash a discharged from such a cooling device is subjected to an extraction test in accordance with the Environmental Agency Notification No. 13, lead may be detected as a harmful metal in excess of a regulated value. In such a case, the harmful substance treating material is injected into the cooling water w in the water tank 1 for stabilization. This is the cooling water w
This is because the harmful substance treatment material is likely to be uniformly mixed with the incineration ash a. That is, when the incinerated ash a is put into the cooling water w in the water tank 1, it is settled at the bottom of the water tank 1, but since the incinerated ash a has buoyancy, it is not compressed in the cooling water w. The harmful substance treating material charged into the cooling water w enters the gap between the particles and contacts the incineration ash a. Also, the incineration ash a is mixed with the push rod 3. Therefore, the harmful substance treatment material injected into the cooling water w in the water tank 1 uniformly contacts and reacts with the incineration ash a, thereby stabilizing the harmful substance in the incineration ash a. In addition, incineration ash “a” from the incinerator falls discontinuously into the water tank 1 because the amount of generation varies. Even with the incineration ash a whose generation amount fluctuates and falls into the water tank 1 discontinuously, if a certain concentration of harmful substance treatment material is added to the cooling water w, the irregular incineration ash a Harmful substances can be constantly stabilized irrespective of the generation time of the harmful substances.

In the above case, as a harmful substance treating material to be injected into the cooling water w in the water tank 1, an organic substance containing a dithiocarboxyl group in polyethyleneimine is generally frequently used.
However, since these liquid organic treatment materials are synthesized using mutagenic carbon disulfide as a raw material, they are decomposed in the treatment process, and the cooling water w and the ash pits 4 in the water tank 1 are decomposed.
There is a concern that carbon disulfide gas is generated from the gas. This is because the cooling water w in the water tank 1 has a high temperature of 50 ° C. or more in summer and the liquid organic processing material is unstable to heat and easily decomposes. From such a viewpoint, there is a problem in using an organic harmful substance treating material, and it is considered that it is preferable to inject an inorganic harmful substance treating material that does not generate harmful gas into the cooling water w.

As a method for treating such incinerated ash, as disclosed in Japanese Patent Application Laid-Open No. 5-305280, a soluble silicate is added to incinerated ash and the washing waste liquid obtained by washing the incinerated ash, and the silicate is added to the washing liquid. It is conceivable to make the eluted heavy metals insoluble.

[0008] However, in this method, it is described that stabilization of heavy metals in the washed incineration ash cannot be performed without additional treatment such as melting treatment. Therefore,
When sodium silicate is introduced into the cooling water w of the wet ash cooling device as described above, it is not clear whether the incinerated ash a after the washing can be stabilized. In addition, the method is described as having an effect of removing calcium and magnesium simultaneously with insolubilization of heavy metals. However, when a large amount of sodium silicate is introduced into the cooling water w of the wet ash cooling device to remove calcium and magnesium as described above, the cooling water w
The equilibrium relationship between the polyvalent metal salt concentrations in the medium is broken, and bubbles called scum are generated on the surface of the cooling water w, which is a problem. The reason why this scum is not preferable is that if it accumulates in the ash shooter 2, the incineration ash a thrown into the water tank 1 from the ash shooter 2 is prevented from settling below the water surface, and the incineration ash a is removed from the ash shooter 2. This is because they are jammed and cannot be incinerated. As described above, there is a problem in the use of the soluble silicate in performance and practically.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in treating incinerated ash such as municipal incinerated ash and industrial waste incinerated ash. It is an object of the present invention to provide a method for treating waste incineration ash that can reliably stabilize harmful substances, and to reduce harmful substances in incineration ash discharged from a wet ash cooling device in terms of performance and practical use as described above. An object of the present invention is to provide a method for treating waste incineration ash that can be stabilized without any problem.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above-mentioned object, and as a result, when a harmful substance treating material is added to cooling water in a wet ash cooling device, unexpectedly, We have found a method that can very easily stabilize harmful substances such as heavy metals in incinerated ash in the form of slurry containing water and that have no practical problems such as generation of scum in cooling water. In other words, if a hazardous substance treatment material containing soluble silicate is injected into the cooling water in the incineration ash cooling device called a wet ash cooling device or a gadget incineration ash discharging device, waste incineration ash is injected into this cooling water. Surprisingly, it was found that by discharging the cooling water, it was possible to stabilize heavy metals very easily, and that there was no practical problem such as generation of scum. The inventor found that the incinerated ash in the form of a stagnation was retained on the ash sloping slope in the apparatus and kept heat, and completed the present invention.

That is, in the method for treating waste incineration ash according to the present invention, waste incineration ash is put into cooling water into which a harmful substance treating material has been injected, and is discharged from the cooling water in the water tank in a state where it is not completely cooled. A method of treating waste incineration ash, characterized in that it is cured while being kept warm by heat generated from incineration ash and cooling water. Specifically, a so-called push rod having a water tank containing cooling water, an ash shooter for putting incineration ash into the cooling water in the water tank, and ash discharging means for discharging incineration ash in the cooling water from the water tank. Using an incineration ash discharge device, a harmful substance treatment material is injected into the cooling water in the water tank, and waste incineration ash is put into the cooling water,
The incinerated ash in the form of slurry discharged from the cooling water by the ash discharging means is retained in the cooling device, cured after being insulated by the heat generated from the incinerated ash and the cooling water, and then discarded. Is preferred. In this case, it is preferable that the waste incineration ash is kept at a temperature of 40 to 70 ° C. and cured.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present invention is to effectively utilize the heat radiation generated during the cooling process of waste incineration ash and to stabilize harmful substances. here,
The heat retention method of the incineration ash will be described with reference to the attached drawings. In the present invention, it is essential that the incinerated ash a in the form of slurry discharged from the cooling water w of the wet ash cooling device as shown in FIG. The incineration ash a that has fallen from the ash shooter 2 is cooled by the cooling water w in the contained water tank 1. In this case, the weight of the cooling water w is preferably smaller than the incinerated ash generation amount (tons) per day. Since the wet ash cooling device is intended to cool incinerated ash discharged from incinerators such as stalker furnaces, the scrap-type incinerated ash discharging device cools about 20 tons of incinerated ash a day to about 30 tons. Use water. In that case, the temperature of the cooling water is
It is 20 ° C in winter and close to 50 ° C in summer. On the other hand, in the gadget incineration ash discharge device, when cooling 8 tons of incineration ash a day, by using cooling water of about 1 to ³ m ³ , a high temperature of 35 ° C. in winter and nearly 60 ° C. in summer is used. Becomes When the volume of the cooling water w is reduced as described above, the incineration ash a that has fallen into the cooling water w is cooled to a certain extent, but is not completely cooled and remains at a high temperature.

In the grate incineration ash cooling device as shown in the figure, when the grate 3 in the water tank 1 is pushed out to the ash pit 4 side by the grate 3, the grate 3 operates once every 2 to 5 minutes. The incineration ash a gradually moves on the ash pit 4 of the water tank 1 toward the ash pit 4 and appears on the water surface on the ash hill 11, and is cooled by air. However, since this apparatus does not have a forced scraping device such as a scraper, the incinerated ash a becomes a slurry containing water, and the ash-out slope 11
Deposits on top, and in some cases a thickness of close to one meter. In such a case, the incineration ash a is kept at a high temperature of 40 to 70 ° C. for 4 to 12 hours without being completely cooled.

In the present processing method, it is more preferable to install a hood 5 as shown in the figure around the discharge port where the incinerated ash a falls from the ash extraction slope 11 to the ash pit 4 to avoid heat radiation outside the apparatus. . The structure of the hood 5 is preferably closed on the upper side, the front side, and the side where heat is dissipated, and the lower side is preferably open to throw incineration ash a into the ash pit 4. When this hood 5 is installed, the incineration ash a
Further, the release of steam and heat generated from the slurry-like incineration ash a to the outside is suppressed, and the incineration ash a is discharged in a state where the heat is kept.

As the harmful substance treating material used in the waste incineration ash treatment method according to the present invention as described above, powdery, liquid, or slurry-like materials can be used.
Further, fine particles such as activated carbon may be contained in the liquid. Examples of the composition of the harmful substance treating material usable in the present invention include soluble silicates such as sodium silicate and potassium silicate, sodium monohydrogen phosphate, sodium dihydrogen phosphate,
Contains at least one of soluble phosphates such as sodium phosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, etc., a mixture of soluble silicate and phosphate or carbonate, a sulfate band, and an aluminum phosphate solution. Liquids. Further, as the harmful substance treating material, a powdery material can be used. In that case, it may be mixed with water in advance and poured in a slurry form, or a feeder may be provided. Among these, the soluble silicates are
Most suitable for this processing method. This is because the soluble silicate has an improved ability to stabilize heavy metals at high temperatures. Further, it is more preferable to add a mixed liquid of a soluble silicate and potassium carbonate since the heavy metal can be further stabilized.

As long as the processing material can be injected into the cooling water w, even if it is the ash shooter 2 portion,
, That is, from a portion far from the ash pit 4.

The mechanism by which this treatment method is effective in stabilizing harmful substances such as heavy metals in waste incineration ash can be inferred as follows. In the method of the present invention, the incineration ash a on the ash-out slope 11 of the wet ash cooling device is maintained by the heat generated from the incineration ash a and the cooling water w.
In order to reach 0 to 70 ° C., the incinerated ash “a” is maintained in a high-temperature curing state before falling into the ash pit 4. At this time, the soluble silicate as a harmful substance treatment material directly reacts with the heavy metal in the incineration ash a to form a heavy metal silicate, and also forms a complex of calcium and silicate, in which the heavy metal is contained. It is considered to include In this mechanism of action, the formation of a complex of calcium and silicate is promoted by keeping the incinerated ash a heated and heated and cured as described above, thereby exhibiting a stabilizing effect for harmful substances such as heavy metals. It is thought that it is.

Further, in the method of the present invention, by combining a soluble silicate and a carbonate as the harmful substance treating material, the viscosity of the treated material is reduced when compared with the same solid content, and the handling becomes easy. Salts are preferred because they assist the action of soluble silicates and stabilize heavy metals in a short time. In this case, a preferable addition ratio of the soluble silicate and the carbonate is 95: 5 to 80:20 in terms of a solid content ratio. This can be expected to improve the performance by adding a carbonate, but causes a practical problem when added in a large amount. That is, since precipitation of carbonate occurs during transportation in winter, it is necessary to keep heat in the storage tank and the transport equipment of the processing material, and the processing material injection equipment and the processing material storage equipment become expensive, which is preferable in handling. Absent. Total solid content of the treated material, that is, Na ₂ O, S
The total sum of iO ₂ and K ₂ CO ₃ is preferably 43% by weight or less due to transportation and storage problems, and the viscosity is preferably lower than 1000 centipoise at room temperature (25 ° C.).

The incineration ash treatment method of the present invention as described above comprises:
Effective for waste incineration ash containing harmful inorganic substances such as lead, cadmium, mercury, selenium, histo, zinc and chromium. Such incineration ash includes incineration ash such as fly ash and main ash generated from municipal waste incineration ash and industrial waste incineration ash. Here, fly ash is obtained by collecting dust and dust generated by incineration and dust generated from a melting furnace, and includes EP ash collected by an electric dust collector. On the other hand, main ash is ash discharged from the lower part of the incinerator at incinerators for municipal solid waste and industrial waste, and includes harmful heavy metals. In a wet ash cooling device of a normal municipal solid waste incineration plant, main ash or a mixture of main ash and fly ash is to be treated. In particular, it is suitable for stabilizing lead generated from municipal waste incineration ash. Further, the treatment method of the present invention can also treat waste containing hazardous heavy metals such as incinerated ash of industrial waste and activated sludge.

[0020]

According to the waste incineration ash treatment method of the present invention, if incineration ash generated from industrial waste containing harmful substances or municipal waste incinerators and discharged from a wet ash cooling device is treated, Hazardous substances in incineration ash can be reliably stabilized. Moreover, in the present invention, although the harmful substance treatment material is injected into the cooling water, the reason is not clear,
There is no problem such as generation of scum due to the harmful substance treatment material, and even if the incineration ash is generated irregularly, the elution concentration of heavy metals can be stably reduced.

[0021]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

A stake incineration ash discharging device in the municipal waste incineration plant shown in FIG. 2 was used. The incineration ash (main ash here) generated by 8 tons per day falls from the ash shooter 2 to the cooling water w (facility water) in the water tank 1. Incineration ash a is a stick 3
Is discharged from the water tank 1. In this cooling device, the amount of the cooling water w was 1 ton. The harmful substance treating material was prepared by mixing liquid No. 3 water glass and potassium carbonate at a solid content of 90:10 so that the total solid content was 34% by weight. This harmful substance treating material is incinerated ash generated in one day from the rear of the ram 3 in the ram incineration ash discharge device shown in FIG. 2, that is, the rightmost position among the three injection positions shown in the figure. A was added to the cooling water w in the water tank 1 so as to be 1.2 to 2.6 parts by weight with respect to 100 parts by weight of a. The addition rate of the harmful substance treatment material was changed immediately after the sampling was completed, and the addition rate was not changed almost daily. Sampling was performed from the ash-out slope 11 of the water tank 1. Untreated incineration ash used for comparison was collected before the start of the experiment. For these incinerated ash, the lead elution concentration and the pH of the extract were measured by the Environment Agency Notification No. 13 method (Japan). Table 1 shows the results.

[0023]

[Table 1]

From the comparison between the untreated case shown in Table 1 and the case where the harmful substance treatment material was added, the treatment material addition amount was 1.2 parts by weight or more with respect to 100 parts by weight of incinerated ash. When the lead elution concentration falls below the regulation value (0.3 mg / L), a treatment material containing a soluble silicate aqueous solution as a main component is poured into cooling water, and the incinerated ash introduced into the cooling water is cooled while keeping heat. It is possible to stabilize the lead easily by wiping it out of the water and curing it by heating, thus demonstrating the effectiveness of the waste incineration ash treatment method of the present invention. No scum was observed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a general push rod incineration ash discharge device.

FIG. 2 is a schematic sectional view of a gadget incineration ash discharging device used in the present invention.

[Explanation of symbols]

1 aquarium, 2 ash shooter, 3 gadget, 4
Ash pit, 5 hoods, 11 Ashing slope, a
Incineration ash, w cooling water.

Claims (8)

[Claims] A waste incineration ash is poured into cooling water into which a harmful substance treatment material containing soluble silicate as a main component has been injected, and is discharged from the cooling water in a water tank in a state of not being completely cooled. A method for treating waste incineration ash, comprising curing while keeping heat from heat generated from cooling water. 2. A wet ash cooling device having a water tank containing cooling water, an ash shooter for charging incineration ash into the cooling water in the water tank, and ash discharging means for discharging incineration ash in the cooling water from the water tank. Injecting the harmful substance treatment material into the cooling water in the water tank, charging the waste incineration ash into the cooling water, retaining the slurry incineration ash discharged from the cooling water in the cooling device, The waste incineration ash treatment method according to claim 1, wherein the waste is insulated after being cured while being kept warm by heat generated from cooling water. 3. The waste incineration ash treatment method according to claim 1, wherein the waste incineration ash is cured while being kept at a temperature of 40 to 70 ° C. 4. The method according to claim 1, wherein the harmful substance treating material is a liquid containing a soluble silicate as a main component. 5. The method according to claim 4, wherein the soluble silicate is sodium silicate or potassium silicate. 6. The harmful substance treating material includes sodium or potassium silicate and potassium carbonate.
Waste incineration ash treatment method as described. 7. The waste incineration ash is lead, cadmium,
2. The composition according to claim 1, wherein the substance contains at least one harmful substance selected from the group consisting of mercury, selenium, histo, zinc and chromium.
7. The waste incineration ash treatment method according to any one of claims 6 to 6. 8. The waste incineration ash is incinerated fly ash, main ash,
The waste incineration ash treatment method according to claim 7, which is incineration ash of municipal waste such as molten fly ash, incineration ash of industrial waste, and incineration ash of waste containing harmful heavy metals such as activated sludge.