JP2022091480A - Treatment method of burned residue - Google Patents

Abstract

To provide a treatment method of a main ash capable of reducing washing wastewater needing a wastewater treatment.SOLUTION: A treatment method of a burned residue includes: a washing step of feeding washing water to a main ash and washing the main ash; and an insolubilization step of adding an insolubilization agent and kneading water to a fly ash, followed by kneading for insolubilization of heavy metals included in the fly ash. The insolubilization step uses at least a part of washing wastewater discharged in the washing step and not having been through the wastewater treatment as the kneading water.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a method for treating an incinerator residue.

Incinerator residue is generated when waste is incinerated. The incinerator residue includes incinerator main ash (hereinafter referred to as main ash) and incinerator fly ash (hereinafter referred to as fly ash). This main ash contains metals such as iron, aluminum alloys and copper. In order to recover these resources (metals), treatments such as magnetic force sorting, grinding treatment, and sieving have been conventionally performed. Further, in the treatment of the main ash, grinding treatment or sieving may be carried out while supplying washing water to the main ash. According to this treatment, the washing wastewater discharged from the washing of the main ash contains ash particles and is a suspension. Here, the ash particles contain heavy metals, and the heavy metals are dissolved in the washing wastewater. Therefore, conventionally, after the washing wastewater is treated as wastewater, it is carried out of the system (outside the waste treatment facility) (see Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2016-32786

The amount of cleaning wastewater discharged from the cleaning of the main ash is large, and if all of the cleaning wastewater is treated as wastewater, a large amount of chemicals are required. Therefore, it is desired to utilize the washing wastewater for other purposes and reduce the washing wastewater that requires wastewater treatment.

The present disclosure has been made in view of the above, and an object of the present invention is to provide a method for treating an incinerator residue in which washing wastewater that requires wastewater treatment is used for the treatment of fly ash.

In order to achieve the above object, the method for treating the incineration residue according to one aspect of the present disclosure includes a washing step of supplying washing water to the main ash and washing the main ash, and adding an insolubilizer and kneading water to the fly ash. In addition, it includes an insolubilization treatment step of kneading to insolubilize the heavy metal contained in the fly ash. In the insolubilization treatment step, at least a part of the washing wastewater discharged in the washing step and not treated with wastewater is used as the kneading water.

As a desirable embodiment of the method for treating the incinerator residue, the liquid-solidification ratio of the fly ash to the kneaded water is 1.2 mL / g or less in the insolubilization treatment step.

As a desirable embodiment of the method for treating the incinerator residue, in the insolubilization treatment step, all of the washing wastewater discharged in the washing step is used as the kneading water. The liquid-solidity ratio of the main ash and the washing water in the washing step is 0.5 mL / g or less.

A preferred embodiment of the method for treating the incineration residue includes a sludge recovery step of recovering sludge from the washing wastewater, and the insolubilizing treatment step uses the washing wastewater from which the sludge has been removed in the sludge recovery step as the kneading water. do.

As a desirable embodiment of the method for treating the incinerator residue, the washing step grinds the lump contained in the main ash while supplying the washing water.

According to the method for treating the incinerator residue of the present disclosure, the washing wastewater is used as the kneading water. Therefore, the amount of washing wastewater that requires wastewater treatment is reduced. Then, by reducing the wastewater treatment, the scale of the wastewater treatment facility can be reduced or the wastewater treatment facility itself can be eliminated.

FIG. 1 is a schematic diagram schematically showing a waste treatment facility according to an embodiment. FIG. 2 is a graph showing the results of a dissolution test between the first example and the comparative example. FIG. 3 is a bar graph showing the results of elution tests of the first example, the second example, and the comparative example.

Hereinafter, the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the embodiment for carrying out the present disclosure (hereinafter referred to as the embodiment). Further, the components in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that are in a so-called equal range. Further, the components disclosed in the following embodiments can be appropriately combined.

(Embodiment)
FIG. 1 is a schematic diagram schematically showing a waste treatment facility according to an embodiment. The waste treatment facility 10 according to the embodiment includes an incinerator 11, a cleaning device 12, a slurry tank 13, a dehydration device 14, and an insolubilization device 15.

The incinerator 11 is a device for incinerating waste. When waste is incinerated, incinerator residue is generated. The incinerator residue contains main ash and fly ash. The main ash collects in the bottom of the incinerator 11. Fly ash is accompanied by exhaust gas generated during incineration and is collected by a dust collector (not shown). The main ash is recovered from the bottom of the incinerator 11, cooled by a cooler (not shown), and transferred to the cleaning device 12. The fly ash is conveyed from the dust collector to the insolubilizing treatment device 15. Further, in the present disclosure, the water content of the main ash is not particularly limited. That is, the present disclosure can be applied to either dry ash having a low water content (dry main ash) or wet ash having a high water content.

The cleaning device 12 is a device having a function of cleaning the main ash with a watering device 12a such as a sprinkler or a nozzle. Specific examples of the cleaning device 12 include a grinding and cleaning machine and a wet vibrating sieve. The grinding and washing machine is a device that grinds lumps contained in the main ash while supplying washing water. The wet vibrating sieve is for recovering metals having a predetermined particle size or larger contained in the main ash, and the main ash falls from the eyes of the sieve while supplying washing water to the main ash in the sieve. It keeps adding vibration automatically. Further, the cleaning device 12 also includes a device for cleaning for removing salts such as chlorine and alkali metals contained in the main ash.

The washing wastewater discharged from the washing device 12 contains ash particles collected by a grind washing machine and a wet vibrating sieve. The ash particles are suspended solids (hereinafter referred to as SS components), and the washing wastewater is a slurry (suspension). In addition, the ash particles contain heavy metals. Further, heavy metals are dissolved in the washing wastewater during washing. Therefore, wastewater treatment is required for cleaning wastewater.

The above-mentioned wastewater treatment of the washing wastewater is intended to reduce the elution component in order to drain the washing wastewater to the outside (outside the system) of the waste treatment facility 10, and is a standard for items corresponding to the wastewater standard and the like. Need to be cleared. Therefore, the eluted components are decomposed or removed from the waste water by a method such as coagulation precipitation, biological treatment, ion exchange, and adsorption. As elution components to be removed, calcium and chloride ions may also be applicable depending on the region, in addition to the items corresponding to the wastewater standards.

In the present embodiment, the cleaning wastewater discharged from the cleaning device 12 is supplied to the slurry tank 13 without going through the above-mentioned wastewater treatment. The cleaning water used in the cleaning device 12 may be fresh water such as tap water. Further, the cleaning device 12 has a cleaning water tank 12b for supplying cleaning water to the sprinkler device 12a.

The slurry tank 13 and the dehydration device 14 are devices for removing sludge from the washing wastewater. Specifically, the slurry tank 13 temporarily stores the washing wastewater. According to this, sludge contained in the washing wastewater is settled at the bottom of the slurry tank 13. Although a part of the SS content contained in the washing wastewater is settled at the bottom of the slurry tank 13 together with sludge, the supernatant liquid (washing wastewater) of the slurry tank 13 contains the SS content, and the SS content is completely removed from the washing wastewater. It is assumed that it will not be separated (removed). Then, the supernatant liquid (washing wastewater) of the slurry tank 13 is supplied to the insolubilizing treatment device 15. Further, the sludge collected on the bottom side of the slurry tank 13 is supplied to the dehydrating device 14.

The dehydrating device 14 dehydrates sludge. In this embodiment, centrifugation will be used as the dehydration method. According to this, dehydrated sludge and washing wastewater are collected. According to the dehydrating device 14, most of the SS contained in the sludge is contained in the dehydrated sludge, and a part of it is contained in the washing wastewater. Then, a part of the washing wastewater is supplied to the insolubilizing treatment device 15 and used for insolubilizing fly ash. The remaining washing wastewater is supplied to the washing water tank 12b and reused. On the other hand, since the dehydrated sludge contains chlorine and heavy metals, it is insolubilized and then transported to the outside of the waste treatment facility 10 for landfill treatment. The solid-liquid separation method using the dehydrator 14 of the present disclosure is not limited to centrifugal separation, and may be a pressure filtration method such as a filter press, and is not particularly limited.

The insolubilizing treatment device 15 is an apparatus for insolubilizing treatment. In detail, the insolubilization treatment is a treatment aimed at reducing heavy metals that dissolve in water, and it is difficult to combine with heavy metals derived from washing wastewater to coagulate and precipitate them to insolubilize them, or to make heavy metals in fly ash difficult. It is to dissolve it. The insolubilization treatment apparatus 15 of the present embodiment adds an insolubilizer and kneading water to fly ash and kneads the fly ash to insolubilize heavy metals contained in the fly ash. The insolubilizer is also called a fixing agent for fixing heavy metals contained in fly ash to fly ash. Specifically, as an organic chelating agent, mainly dithiocarbamic acid-based, piperazine-based, diethylamine-based, and phosphorus as an inorganic-based agent. , Iron, magnesium oxide and the like. As the kneading water, the washing drainage supplied from the slurry tank 13, the washing drainage supplied from the dehydrating device 14, and the washing drainage supplied from the slurry tank 13 and the washing drainage supplied from the dehydrating device 14 are mixed and washed. Use one of the three types of drainage. The liquid-solidification ratio of fly ash to kneaded water is preferably 1.2 mL / g or less. If the liquid-solidity ratio exceeds 1.2 mL / g, the water content will increase, which may cause problems such as leakage risk during transportation and a decrease in the ground strength of the landfill.

Next, a method for treating the incinerator residue according to the embodiment will be described. The method for treating the incineration residue includes a cleaning step, a sludge recovery step, and an insolubilization treatment step. In the washing step, the main ash is washed by the washing device 12. According to this, in the cleaning step, cleaning wastewater containing SS content and in which heavy metals are dissolved is generated as wastewater.

In the sludge recovery step, the sludge contained in the washing wastewater is recovered in the slurry tank 13 and the dehydrating device 14. In the insolubilization treatment step, an insolubilizer and kneading water are added to the fly ash and kneaded. For the kneaded water, wash wastewater that has undergone the sludge recovery process is used. According to this, the washing wastewater is absorbed by fly ash. Then, the metals (for example, Pb, Cr (VI), As, Se, Cd, Hg, dioxins) contained in the fly ash and the washing wastewater are insolubilized at once. That is, the heavy metals contained in the washing wastewater (heavy metals contained in the SS component and heavy metals dissolved in the washing wastewater) are insolubilized together with the fly ash. When the washing wastewater is used as the kneading water, the amount of heavy metals eluted from the insolubilized product is reduced due to the effect of adsorption of the main ash component and the like, as compared with the case where the fresh water is used as the kneading water. Therefore, the amount of insolubilizing agent required for the insolubilizing treatment is reduced.

As described above, the method for treating the incineration residue of the embodiment includes a washing step of supplying washing water to the main ash and washing the main ash, and adding an insolubilizer and kneading water to the fly ash and kneading the fly ash. It includes an insolubilization treatment step for insolubilizing heavy metals. In the insolubilization treatment step, at least a part of the washing wastewater discharged in the washing step and not treated with wastewater is used as the kneading water.

According to this treatment method, the washing wastewater of the main ash is used in the insolubilization treatment step of fly ash. Therefore, the amount of washing wastewater that requires wastewater treatment is reduced. In addition, the scale of the wastewater treatment facility can be reduced and the running cost can be suppressed.

Further, in the treatment method of the embodiment, all of the washing wastewater is finally used as the kneading water.

According to this treatment method, washing wastewater that requires wastewater treatment is not generated.

Further, in the insolubilization treatment step of the embodiment, the liquid-solidification ratio of the fly ash and the kneaded water in the insolubilization treatment step is 1.2 mL / g or less.

If the liquid-solidity ratio exceeds 1.2 mL / g, the water content will increase, which may cause problems such as leakage risk during transportation and a decrease in the ground strength of the landfill. It can be avoided.

Further, the method for treating the incineration residue of the embodiment includes a sludge recovery step of recovering sludge from the washing wastewater, and the insolubilizing treatment step includes the washing wastewater from which the sludge has been removed in the sludge recovery step and the kneaded water. Used as.

According to this treatment method, sludge is recovered in the sludge recovery step.

Further, in the washing step of the embodiment, the lump contained in the main ash may be ground while supplying the washing water.

According to this treatment method, many heavy metals can be recovered from the main ash.

Although the embodiment has been described above, the method for treating the incinerator residue according to the present disclosure is not limited to the example shown in the embodiment. For example, the cleaning device 12 includes a grinding cleaning machine and a wet vibrating sieve, but the cleaning apparatus 12 may be only a grinding cleaning machine or only a wet vibrating sieve, and is not particularly limited. Further, although the washing wastewater is supplied to the insolubilizing treatment device 15 from both the slurry tank 13 and the dehydrating device 14, all the washing wastewater generated by the dehydrating device 14 is directed to the washing water tank 12b of the washing device 12. It may be changed to supply to.

According to the embodiment, all of the washing wastewater is finally supplied to the insolubilizing treatment device 15, but a part of the washing wastewater generated by the dehydration device 14 is supplied to the wastewater treatment device (not shown). It may be supplied and treated as wastewater.

Further, in the embodiment, a part of the washing wastewater collected from the dehydrating device 14 is returned to the washing device 12 and reused as the washing water, but the method for treating the incineration residue of the present disclosure is recovered from the dehydrating device 14. All of the washed wastewater may be supplied to the insolubilizing device 15. According to this, it is possible to eliminate the need for a circulation device for returning the washing wastewater to the washing device 12.

Further, in the method for treating the incinerator residue according to the present disclosure, the washing wastewater that has not undergone the dehydration step may be supplied to the insolubilizing treatment apparatus 15 as it is. That is, all of the washing wastewater discharged in the washing step may be used as kneading water. This eliminates the need for the slurry tank 13 and the dehydrator 14. When all of the washing wastewater discharged in the washing step is used as kneading water, it is preferable to adjust the liquid-solidification ratio between the main ash and the washing water to be 0.5 mL / g or less in the washing step. .. By the way, the stoker furnace is actually the most installed type of incinerator 11. According to this stoker furnace, the ratio of main ash to fly ash is about 7: 3 with respect to the amount of incinerator residue generated. Assuming that an incineration residue is generated at a ratio of 70 g of main ash and 30 g of flying ash, and the liquid-solidity ratio of the main ash and the washing water is 0.5 mL / g, about 35 mL of washing wastewater is recovered in the washing step. .. When all of the 35 mL of the washing wastewater is supplied to the insolubilization treatment step as it is, the liquid-solidity ratio of the flying ash and the washing wastewater is 35 mL / 30 g, and the liquid-solidity ratio of the flying ash and the kneaded water described above is 1.2 mL /. It is possible to achieve g or less. Therefore, no extra cleaning wastewater is generated in the insolubilization treatment step, and the amount of cleaning wastewater is appropriate. The above example has been described with reference to an example in which all of the washing wastewater discharged in the washing step is directly supplied to the insolubilizing treatment device 15, but after the storage step of the slurry tank 13 and the dehydration step of the dehydration device 14 have been performed. , All of the washing wastewater may be supplied to the insolubilizing treatment apparatus 15. Next, an embodiment will be described.

(Example)
FIG. 2 is a graph showing the results of a dissolution test between the first example and the comparative example. FIG. 3 is a bar graph showing the results of elution tests of the first example, the second example, and the comparative example. As an example, two insolubilized products of the first embodiment and the second embodiment were prepared. The first embodiment is an insolubilized product using the washing wastewater recovered from the dehydrating device 14 as the kneading water. The second embodiment is an insolubilized product using the washing wastewater supplied from the slurry tank 13 as the kneading water. The SS content contained in the washing wastewater recovered from the dehydrator 14 is small, but the SS content contained in the washing wastewater recovered from the slurry tank 13 is relatively large. In addition, in order to confirm the effect of the examples, an insolubilized product using tap water as the kneading water was prepared as a comparative example. In all of the first example, the second example and the comparative example, the liquid-solidification ratio was set to 0.3 mL / g.

As shown in FIG. 2, for the first embodiment, an insolubilized product was produced when the addition amount (%) of the drug (insolubilizer) was 0%, 1%, 3%, and 5%. As shown in FIG. 3, for the second example, an insolubilized product was produced when the drug addition amount (%) was 0%, 1%, and 3%. As shown in FIG. 2, for the comparative example, an insolubilized product was produced when the drug addition amount (%) was 0%, 1%, 3%, and 5%. Then, the elution test was performed on each of the insolubilized products of the first example, the second example, and the comparative example, and the exudate was collected. Next, the Pb elution concentration (mg / L) contained in the leachate was calculated. The Pb elution concentration (mg / L) of the calculation result is shown in the graphs of FIGS. 2 and 3. The amount of the drug added (%) is the amount (kg) of the drug added to the fly ash per liter. In addition, an iron-based drug, which is an inorganic drug, was used as the drug.

As shown in FIGS. 2 and 3, when the drug addition amount (%) was 0%, the Pb elution concentration was 240 mg / L in each of the first example, the second example and the comparative example. When the drug addition amount (%) was 1%, the Pb elution concentration was 120 mg / L in each of the first example, the second example, and the comparative example. Therefore, when the drug addition amount (%) was less than 1%, there was no difference in the Pb elution concentration between the first example, the second example, and the comparative example.

On the other hand, when the drug addition amount (%) is 3%, as shown in FIG. 3, the Pb elution concentration of the first example is 0.18 mg / L and the Pb elution concentration of the second example is 0.09 mg / L. L, the Pb elution concentration of the comparative example was 6.5 mg / L. When the drug addition amount (%) is 5%, the Pb elution concentration of the first example is 0.004 mg / L and the Pb elution concentration of the comparative example is 0.019 mg / L, as shown in FIG. rice field. That is, the result was that the amount of Pb eluted in the first and second examples was smaller than that in the comparative example. From the above, when the drug addition amount (%) is 3% or more, the first embodiment and the second embodiment can suppress the elution amount of Pb to a low level even if the drug addition amount is smaller than that of the comparative example. Do you get it. Further, when the chemical addition amount (%) was 3%, the washing wastewater of the second embodiment (recovered from the slurry tank 13) was recovered from the washing wastewater of the first embodiment (washing wastewater recovered from the dehydrating device 14). The amount of Pb elution was suppressed to be lower in the wash wastewater).

10 Waste treatment facility 11 Incinerator 12 Cleaning equipment 13 Slurry tank 14 Dehydration equipment 15 Insolubilization equipment

Claims (5)

A cleaning process in which cleaning water is supplied to the main ash to clean the main ash,
An insolubilization treatment step for insolubilizing heavy metals contained in the fly ash by adding an insolubilizer and kneading water to the fly ash and kneading the fly ash.
Including
The insolubilization treatment step is a method for treating an incinerator residue in which at least a part of the washing wastewater discharged in the washing step and not treated with wastewater is used as the kneading water. The method for treating an incinerator residue according to claim 1, wherein in the insolubilization treatment step, the liquid-solidification ratio of the fly ash to the kneaded water is 1.2 mL / g or less. In the insolubilization treatment step, all of the washing wastewater discharged in the washing step is used as the kneading water.
The method for treating an incinerator residue according to claim 2, wherein the liquid-solidity ratio of the main ash to the washing water in the washing step is 0.5 mL / g or less. The sludge recovery step of recovering sludge from the washing wastewater is included.
The method for treating an incinerator residue according to any one of claims 1 to 3, wherein the insolubilization treatment step uses the washing wastewater from which the sludge has been removed in the sludge recovery step as the kneading water. The method for treating an incinerator residue according to any one of claims 1 to 4, wherein the washing step grinds a lump contained in the main ash while supplying the washing water.

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