JP2004025152A - Treatment method of incineration ash - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method of incineration ash capable of reducing the amount of harmful substances such as heavy metals in incineration ash by a small number of processes by removing ash adhering to the surfaces of particles of incineration ash in a closed apparatus generating no dust. <P>SOLUTION: The treatment method of incineration ash (1) is characterized by supplying incineration ash of urban waste refuse and/or industrial waste to the fluidized bed of a fluidized bed furnace and grinding ash adhering to particles of incineration ash by a fluidizing medium in the fluidized bed to remove the same. In a process (2), the incineration ash of urban waste refuse and/or industrial waste is supplied to the fluidized bed of the fluidized bed furnace and heated in the fluidized bed to be dried and the ash adhering to the surfaces of the particles of the incineration ash is ground by the fluidized medium to be removed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technical field related to a method of treating incinerated ash, and more particularly to a method of treating incinerated ash of municipal solid waste and / or industrial waste, and particularly to municipal solid waste and / or industrial waste using a stoker-type incinerator. So-called main ash discharged from the bottom of the incinerator after incineration of the material (incinerator ash under the furnace), or so-called dust obtained by mixing the dust and the ash collected by a dust collector at the latter stage of the incinerator with the main ash The present invention belongs to the technical field related to a method for treating mixed ash.
[0002]
[Prior art]
The main components of incineration ash (main ash or a mixture of main ash and dust ash) discharged from stoker-type incinerators are silicon oxide, calcium oxide and alumina, which are almost the same as natural rock and earth and sand. Similar components. In order to form a so-called resource recycling society, it is strongly desired to use these resources as materials for construction and civil engineering work.
[0003]
These incinerated ash contain metals such as iron, copper, and aluminum, which must be removed.
[0004]
Further, these incinerated ash contain a high content of harmful substances (such as heavy metals) contained in the original waste. Therefore, if these incinerated ash are reused as they are as construction materials, heavy metals and the like may elute into rainwater in the future, causing further environmental pollution. Therefore, there is a demand for a technique that removes a substance that may dissolve harmful heavy metals from the incinerated ash by a simple method and puts it in a state where it can be recycled.
[0005]
These incinerated ash are generally dropped from an incinerator into a water tank, which is then scraped and discharged. In this case, the incinerated ash changes from dry ash to wet ash (wet ash). Even when metal components are separated by magnetic separation or the like, such wet ash causes ash to adhere to each other, making it difficult to perform high-efficiency separation.
[0006]
In addition, although it is incinerated ash, it contains a certain amount of unburned matter, and there is a problem from the viewpoint of long-term stability. It is desired to remove these unburned substances (unburned organic substances) in order to make them into materials for civil engineering and construction.
[0007]
Furthermore, some incinerator facilities have a configuration in which main ash and fly ash are mixed and discharged when the ash is discharged.Because fly ash contains a relatively large amount of harmful substances, such Removal had to be performed.
[0008]
Further, if a belt conveyor or a sieve is frequently used, the generation of dust in the processing system cannot be ignored. Therefore, there has been a demand for a treatment using a closed system that does not generate dust.
[0009]
Various methods for recycling incinerated ash have been proposed so far, and typical ones are disclosed in Japanese Patent No. 2670417 and Japanese Patent Application Laid-Open No. 10-212484. ing.
[0010]
Among these methods, in the method described in Japanese Patent No. 2670417, after removing ingots such as metal pieces and clinker from incineration ash mechanically, the incineration ash is washed in a washing tank containing acid and chemicals. This is a method in which harmful substances such as heavy metals are removed, and after a dehydration / drying step, iron is removed, non-ferrous metals are removed, and then the particle size is adjusted.
[0011]
In this method, it is necessary to use washing water, and it is necessary to discharge a certain amount of washing water out of the system. However, wastewater treatment plants often do not allow off-site drainage, and improvement is desired. In addition, the processing system is complicated, and much maintenance and management is required.
[0012]
On the other hand, the method described in Japanese Patent Application Laid-Open No. Hei 10-212484 is a method of pulverizing incinerated ash using a fluidized-dry pulverizer after a first step of magnetically selecting and classifying the incinerated ash by vibrating sieve or the like. However, in this method, the wet ash is subjected to magnetic separation and classification as it is, and its separation efficiency is not high, and harmful substances such as heavy metals contained in the incinerated ash cannot be removed. There is a concern about harm when used.
[0013]
[Problems to be solved by the invention]
When the particles of the incinerated ash are observed closely, the structure is as shown in FIG. That is, the structure is such that the fine particles 81 adhere to the surface of the ash particles 80 containing a large amount of silicon oxide, aluminum oxide and the like. That is, the structure is such that the attached ash 81 is present on the surface of the incinerated ash particles 80. Such a structure is conspicuous in wet ash among incineration ash, and has a structure in which fine particles kneaded and hardened by moisture or the like are attached to the particle surface of the incineration ash. Further, among the wet ash, the mixed ash is more prominent, and fly ash is attached to the ash particles. That is, fly ash exists as ash on the ash particle surface.
[0014]
Among harmful substances such as heavy metals, those that cause elution are mainly contained in these attached ash. Therefore, by substantially removing the attached ash on the particle surface of the incinerated ash, only the portion suitable for recycling can be taken out.
[0015]
It is desired that such processing be performed in a closed apparatus with a small number of steps and no generation of dust.
[0016]
The present invention has been made in view of such circumstances, and has as its object to remove incinerated ash on the particle surface of incinerated ash by using a closed apparatus with a small number of steps and no generation of dust. An object of the present invention is to provide a method for treating incinerated ash that can reduce the amount of harmful substances such as heavy metals in ash.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, a method for treating incinerated ash according to the present invention is a method for treating incinerated ash according to claims 1 to 7 (a method for treating incinerated ash according to first to seventh inventions). It has the following configuration.
[0018]
That is, the method for treating incinerated ash according to claim 1 supplies incinerated ash of municipal solid waste and / or industrial waste to a fluidized bed of a fluidized-bed furnace, and in this fluidized bed, removes attached ash on the particle surface of the incinerated ash. This is a method for treating incinerated ash, which is characterized by being removed by polishing with a fluid medium (first invention).
[0019]
In the method for treating incinerated ash according to claim 2, incinerated ash of municipal solid waste and / or industrial waste is supplied to a fluidized bed of a fluidized-bed furnace, and the incinerated ash is heated and dried in the fluidized bed, and the incineration is performed. This is a method for treating incinerated ash, wherein the attached ash on the surface of the ash particles is removed by polishing with a flowing medium (second invention).
[0020]
The method for treating incinerated ash according to claim 3 is the method for treating incinerated ash according to claim 2, wherein the fluidized gas is preheated and then supplied to the fluidized bed (third invention). The method for treating incinerated ash according to claim 4 is the method for treating incinerated ash according to claim 2 or 3, wherein fuel is supplied to the fluidized bed.
[0021]
In the method for treating incinerated ash according to claim 5, after separating a fluidized medium containing incinerated ash discharged from the fluidized bed into incinerated ash and a fluidized medium, the separated fluidized medium is supplied to the fluidized bed. A method for treating incinerated ash according to any one of claims 1 to 4 (fifth invention).
[0022]
In the method for treating incineration ash according to claim 6, the cross-sectional area of the fluidized-bed furnace differs between the fluidized-bed section and the freeboard section above the fluidized-bed section, and the cross-sectional area of the latter freeboard section is smaller. A method for treating incinerated ash according to any one of the fifth to fifth aspects (sixth invention).
[0023]
The method for treating incinerated ash according to claim 7 is the method for treating incinerated ash according to any one of claims 1 to 6, wherein combustibles are supplied to the fluidized bed (seventh invention).
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is implemented, for example, as follows.
Supplying incinerated ash from municipal solid waste and / or industrial waste to a fluidized bed of a fluidized-bed furnace (hereinafter also referred to as a fluidized bed), and polishing the attached ash on the particle surface of the incinerated ash with a fluidized medium in the fluidized bed. To remove. Alternatively, the incineration ash is heated and dried in a fluidized bed. That is, incinerated ash of municipal solid waste and / or industrial waste is supplied to a fluidized bed of a fluidized-bed furnace, and the incinerated ash is heated and dried in the fluidized bed. And removed by polishing. The degree of removal of attached ash by the method of the present invention may be such that the amount of harmful substances such as heavy metals in incinerated ash can be significantly reduced.
[0025]
The attached ash removed by the polishing rises in the furnace together with the fluidized gas in the fluidized-bed furnace and is discharged out of the furnace from the upper part of the fluidized-bed furnace. On the other hand, the particles of the incinerated ash from which the attached ash has been removed by the polishing are extracted from the bottom (furnace bottom) of the fluidized bed furnace together with the fluidized medium. Thereafter, if necessary (for example, when the fluidized medium is reused in a fluidized-bed furnace), it is separated into incinerated ash particles and a fluidized medium.
[0026]
The present invention is implemented in such a form. Hereinafter, the operation and effect of the present invention will be mainly described.
[0027]
As described above, the method for treating incinerated ash according to the present invention supplies incinerated ash of municipal solid waste and / or industrial waste to a fluidized bed of a fluidized-bed furnace, and in this fluidized bed, adhering ash on particle surfaces of the incinerated ash. Is removed by polishing with a fluid medium (first invention).
[0028]
Since the adhered ash removed by this polishing has a small particle size, the ash rides with the fluidized gas flow in the fluidized bed furnace and rises inside the furnace together with the fluidized gas, and is discharged from the upper part of the fluidized bed furnace to the outside of the furnace. Can be. On the other hand, the particles of the incinerated ash from which the attached ash has been removed by this polishing can be extracted from the bottom (furnace bottom) of the fluidized bed furnace together with the fluidized medium.
[0029]
As described above, harmful substances such as heavy metals in incinerated ash are mainly contained in the attached ash on the ash particle surface. Therefore, the incinerated ash particles extracted from the furnace bottom together with the fluidized medium as described above have an extremely small amount of harmful substances such as heavy metals.
[0030]
Therefore, according to the method for treating incinerated ash according to the present invention, the amount of harmful substances such as heavy metals in the incinerated ash can be greatly reduced by removing the attached ash on the particle surface of the incinerated ash.
[0031]
The particles of the incinerated ash extracted from the furnace bottom as described above are mixed with the fluidized medium, and both are a mixture. As described later, the fluidized medium is, for example, natural sand or silica sand. Granular substances such as alumina powder can be used.Since these are granular substances that can be used as materials for civil engineering and construction, when such a granular substance is used as a fluid medium, the mixture is not separated. Can also be used without difficulty as a material for civil engineering or construction. The mixture may be separated into the particles of the incinerated ash and the fluidized medium as needed (for example, when the fluidized medium is reused in a fluidized-bed furnace), and there is no necessity for the separation.
[0032]
In the method for treating incineration ash according to the present invention, the steps are performed using a fluidized bed furnace. Outside of the furnace, only the incineration ash particles and the fluidized medium are separated as needed. Therefore, it can be performed in a closed apparatus with a small number of steps and no generation of dust.
[0033]
As described above, according to the method for treating incinerated ash according to the present invention, the number of steps is reduced and the attached ash on the particle surface of the incinerated ash is removed by a closed device that does not generate dust, and harmful substances such as heavy metals in the incinerated ash are removed. It can be said that the amount of the substance can be reduced.
[0034]
Further, as described above, the method for treating incinerated ash according to the present invention supplies incinerated ash of municipal solid waste and / or industrial waste to a fluidized bed of a fluidized-bed furnace, and heats the incinerated ash in the fluidized bed. After drying, the incinerated ash on the particle surface of the incinerated ash is removed by polishing with a fluid medium (second invention).
[0035]
In this method, the incinerated ash is also heated and dried in a fluidized bed of a fluidized bed furnace, as compared with the above-described method (the method for treating incinerated ash according to the first invention). This method is particularly effective when the incinerated ash supplied to the fluidized bed of the fluidized bed furnace is wet ash, and can easily remove the incinerated ash attached to the particle surface of the incinerated ash by polishing. That is, when the incinerated ash is wet ash, it tends to be more difficult to remove the attached ash on the particle surface of the incinerated ash by polishing than in the case of dry ash. Is heated and dried, and as in the case of dry ash, removal of the attached ash on the particle surface of the incinerated ash can be facilitated by polishing.
[0036]
The present invention has been made based on the knowledge obtained as a result of intensive studies to achieve the above-mentioned object of the present invention. That is, incinerated ash of municipal solid waste and / or industrial waste is supplied to a fluidized bed (fluidized bed) of a fluidized-bed furnace, and the adhered ash on the particle surface of the incinerated ash is polished with a fluidized medium in the fluidized bed. It has been found that the ash can be removed from the particles of the incineration ash, and therefore, the amount of harmful substances such as heavy metals in the incineration ash can be reduced. In addition, when incineration ash is heated and dried in the fluidized bed of the fluidized bed furnace, the same as in the case of dry ash, even when the incineration ash supplied to the fluidized bed of the fluidized bed furnace is wet ash. In addition, the present inventors have found that it is possible to easily remove the attached ash on the particle surface of the incinerated ash by polishing. The present invention has been completed based on such findings.
[0037]
In the present invention, when the incinerated ash is heated and dried in a fluidized bed of a fluidized bed furnace, the method is not particularly limited, but a fluidized gas for forming a fluidized bed is introduced (supplied) into the fluidized bed furnace. Preheating it, and then supplying the preheated fluidized gas to the fluidized-bed furnace, which heats the incinerated ash in the fluidized bed of the fluidized-bed furnace to dry it. Yes (third invention).
[0038]
When the fuel is supplied to the fluidized bed of the fluidized bed furnace, the fuel burns in the fluidized bed, and the heat generated by the fuel can heat and dry the incinerated ash (the fourth invention). When this fuel is supplied together with the supply of the preheated fluidized gas to the fluidized-bed furnace, the incineration ash can be heated and dried more easily.
[0039]
The particles of the incineration ash extracted from the furnace bottom together with the above-mentioned fluidized medium, that is, the fluidized medium containing the incinerated ash discharged from the fluidized bed of the fluidized-bed furnace, is separated into incinerated ash and the fluidized medium. When the fluidized medium supplied to the fluidized bed is supplied to the fluidized bed furnace, it can be reused in the fluidized bed furnace, and the operation (treatment of incinerated ash) can be performed with almost no need for replenishing the fluidized bed furnace with the fluidized medium. It can be continued (fifth invention).
[0040]
If the cross-sectional area of the fluidized-bed furnace is different between the fluidized-bed section and the freeboard section above the fluidized-bed furnace, and the cross-sectional area of the latter freeboard section is smaller, the fluidized-bed The flow velocity of the fluidizing gas in the freeboard section is larger than the flow velocity of the fluidizing gas just above the bed, and therefore, the particles of the attached ash once trapped in the gas flow of the fluidizing gas are more reliably exhausted. It can be further discharged outside the furnace (sixth invention).
[0041]
When the combustibles are supplied to the fluidized bed of the fluidized bed furnace, part or all of the heat required for drying the incinerated ash can be supplemented by the heat of combustion of the combustibles. According to this method, the advantage of saving fuel described in the fourth invention can be obtained (seventh invention).
[0042]
In the present invention, the fluid medium is not particularly limited as long as it can remove the attached ash on the particle surface of the incineration ash in the fluidized bed by the fluid medium. For example, natural sand, silica sand, alumina powder, or the like can be used. Since these exemplified fluid media are granular materials that can be used as materials for civil engineering and construction, when such granular materials are used as fluid media, fluid media extracted from the furnace bottom together with incinerated ash particles are Even if it is not separated, it can be used as a material for civil engineering or construction without any problems in the form of a mixture. From such a point, it is desirable to use a granular material that can be used as a material as the fluid medium.
[0043]
The type of fluidizing gas for the fluidized bed furnace is not particularly limited, and various types can be used. For example, air, combustion exhaust gas, or a mixed gas of both can be used. The oxygen concentration in the fluidized gas is desirably 5 to 21% in order to reliably burn unburned substances in the incineration ash supplied to the fluidized bed furnace.
[0044]
When heating and drying incinerated ash in a fluidized bed (fluidized bed) of a fluidized bed furnace, if the temperature of the fluidized bed is too low, drying of the incinerated ash will not be performed sufficiently. Causes clinker formation. In addition, in order to burn unburned matter in the ash, it is desired that the temperature be set to a temperature that is sufficient to burn the unburned matter. From these points, the temperature of the fluidized bed is desirably 250 to 700 ° C, and more desirably 500 to 700 ° C.
[0045]
As described above, the attached ash removed by polishing has a small particle size, so it rises in the furnace together with the fluidized gas along with the fluidized gas flow of the fluidized bed furnace, and moves out of the furnace from the upper part of the fluidized bed furnace. Can be discharged. If the air flow velocity (flow velocity of the fluidizing gas) at this time is too low, the stirring of the fluidized medium is not sufficient, and the discharge of the adhered ash to the outside of the furnace does not proceed. On the other hand, if the temperature is too high, not only the energy consumption of the blower is increased, but also the fluid medium is blown out of the furnace. From this point, the airflow velocity at this time is desirably 0.3 to 3 m / sec, and more desirably 0.5 to 2 m / sec.
[0046]
When separating the fluidized medium extracted from the furnace bottom together with the incinerated ash particles into the incinerated ash particles and the fluidized medium, the type of the device for the separation is not particularly limited, and various types are used. For example, a vibrating sieve, trommel, or the like can be used.
[0047]
When the fuel is supplied to the fluidized bed of the fluidized bed furnace, the kind of the fuel is not particularly limited, and various fuels can be used.For example, a gas such as city gas, propane, butane, or the like is used. Alternatively, a liquid such as kerosene or heavy oil may be used.
[0048]
When supplying combustibles to the fluidized bed of the fluidized bed furnace, the types of combustibles are not particularly limited, and various types can be used.For example, waste plastics, wood chips, and the like can be used. it can.
[0049]
The degree of removal of attached ash by the method of the present invention may be such that the amount of harmful substances such as heavy metals in incinerated ash can be significantly reduced. That is, it is sufficient that the attached ash can be substantially removed to the extent that the incinerated ash can be turned into a resource or a material.
[0050]
The incinerated ash from which the attached ash has been removed by the method for treating incinerated ash according to the present invention has very little heavy metal elution and can be used as a material for civil engineering and construction. The incineration ash may include metals such as iron, aluminum, and copper, which can be easily separated by a magnetic separator, a non-ferrous metal separator, or the like. In this case, if the ash is in a dried state, the ash particles do not adhere to each other, and the separation efficiency is high.
[0051]
【Example】
An embodiment of the present invention will be described below. Note that the present invention is not limited to this embodiment.
[0052]
[Example 1]
FIG. 2 shows a specific example of an apparatus for performing the incineration ash treatment method according to the present invention. A configuration and an example of usage of this device will be described below. The lower portion of the fluidized bed furnace 1 is filled with a fluidized medium 11 and supported by a dispersion plate 12. A number of nozzles 13 are attached to the dispersion plate 12 and are connected to a wind box 14. The fluidized-bed furnace 1 is provided with an exhaust port 15 and an incineration ash inlet 16. As the fluid medium 11, for example, natural sand, silica sand, alumina powder, or the like can be used.
[0053]
The fluidized gas 2 is pressurized by the blower 21, heated by the heat source 23 through the heat exchanger 22, blown into the furnace from the wind box 14 of the fluidized bed furnace through the nozzle 13, and fluidized the fluidized medium 11. Later, it rises inside the furnace and is discharged from the furnace through the exhaust port 15. After that, it is discharged outside the system via the exhaust gas treatment device 25. In addition, as the fluidizing gas 2, for example, air, combustion exhaust gas, or a mixed gas of both can be used. The oxygen concentration in the fluidized gas is preferably in the range of 5 to 21% in consideration of reliably burning unburned substances in the incineration ash.
[0054]
The incineration ash 3 is temporarily stored in an incineration ash hopper 31, is appropriately cut out by a cutting device 32, and is put into the furnace through the incineration ash input port 16. The added incineration ash 33 is dried by the high temperature in the fluidized bed, and the surface is polished by the fluidized medium 11 to remove the attached ash. Most of the removed adhered ash has a very small particle size, rises inside the furnace together with the fluidizing gas 2, and is discharged outside the furnace. In order to sufficiently dry the incinerated ash 33 and burn unburned substances in the incinerated ash 33, the temperature of the fluidized bed (fluidized bed) of the fluidized-bed furnace 1 is desirably 250 ° C. or more. Is preferably 500 ° C. or higher, while the temperature of the fluidized bed is preferably 700 ° C. or lower, and more preferably 500 ° C. or lower, in order to prevent clinker formation above the furnace. desirable. Further, in order to sufficiently stir the fluidized medium 11 and to proceed to discharge the adhered ash to the outside of the furnace and to prevent the adhered ash from being taken in the fluidized bed again, the gas flow velocity of the fluidized gas 2 is set to 0 / sec. 0.3 m or more, more preferably 0.5 m / s or more. On the other hand, in order to suppress the increase in energy consumption of the blower and to prevent the fluid medium from being blown out of the furnace. The flow velocity of the fluidized gas 2 is desirably 3 m or less per second, and more desirably 2 m or less per second.
[0055]
Further, the incinerated ash and the fluidized medium after removing the attached ash are extracted from the bottom of the fluidized bed furnace 1 by the continuous discharge device 4. After that, it can be separated into the incineration ash 42 and the flowing medium 43 by the separating device 41. As the separation device 41, for example, a vibration sieve, a trommel, or the like can be used.
[0056]
Using the above apparatus, incineration ash according to Example 1 of the present invention was treated. At this time, silica sand was used as the fluid medium 11 and air was used as the fluidizing gas 2. The temperature of the fluidized bed of the fluidized bed furnace 1 was 550 ° C. The gas flow velocity of the fluidizing gas 2 was 1 m per second. As the separation device 41, a vibration sieve was used.
[0057]
Wet ash was used as incineration ash supplied to the fluidized bed of the fluidized bed furnace 1. This wet ash is incinerated ash from municipal waste in a stoker-type incinerator, which is collected after being dropped into a water tank and collected by a dust collector at the latter stage of the incinerator. Is a so-called mixed ash.
[0058]
The heavy metal content in this incinerated ash (wet ash) is 1.4 mg / kg of mercury, 2400 mg / kg of lead, 8400 mg / kg of zinc, and the content of dioxins is 0.045 ng-. TEQ / g.
[0059]
The incinerated ash (wet ash) is supplied to the fluidized bed of the fluidized-bed furnace 1, the incinerated ash is heated and dried in the fluidized bed, and the attached ash on the particle surface of the incinerated ash is polished with a fluidized medium. Removal processing was performed. After the incinerated ash after this treatment was extracted from the bottom of the fluidized-bed furnace 1 together with the fluidized medium, the incinerated ash 42 and the fluidized medium 43 were separated by the separator 41. The incineration ash 42 having a particle size of 5 to 25 mm was measured for heavy metal content and dioxin content, and a test for elution resistance, which is important for resource recycling.
[0060]
As a result, the heavy metal content in the incinerated ash after the above treatment was as follows: mercury: less than 0.01 mg / kg, lead: 1200 mg / kg, zinc: 3700 mg / kg, etc., all of which were significantly reduced. The dioxin content was 0.0008 ng-TEQ / g, which was also significantly reduced. In the elution resistance test, the elution amounts were hexavalent chromium: less than 0.02 mg / liter (hereinafter, L), lead: less than 0.001 mg / L, cadmium: less than 0.001 mg / L, and mercury: 0.0005 mg. / L, arsenic: less than 0.001 mg / L, selenium: less than 0.001 mg / L, all of which were below the soil environmental standards.
[0061]
As described above, according to the incineration ash treatment method according to the first embodiment of the present invention, it is possible to reduce the amount of harmful substances such as heavy metals in the incineration ash by removing the attached ash on the particle surface of the incineration ash. It supports what you can do.
[0062]
The incinerated ash (recycled incinerated ash) obtained by the above-mentioned treatment is dried and has a very small amount of heavy metal dissolved therein, and can be used as a material for civil engineering and construction. In addition, depending on the wet ash before treatment, metals such as iron, aluminum, and copper may be contained in the incinerated ash that has been recycled, but these are easily separated by a magnetic separation device or a non-ferrous metal separation device. be able to. Also at this time, since the ash is in a dried state, the ash particles do not adhere to each other and the efficiency of separation is high.
[0063]
In the first embodiment, silica sand was used as the fluid medium 11, but the same result as in the first embodiment can be obtained when natural sand or alumina powder is used instead. Was. In the case of the first embodiment, air is used as the fluidizing gas 2. However, instead of this, the case of using a combustion exhaust gas or a mixed gas of air and combustion exhaust gas is the same as in the case of the first embodiment. Was obtained.
[0064]
Further, in the case of the first embodiment, wet ash was used as incineration ash to be supplied to the fluidized bed of the fluidized-bed furnace 1, but when dry ash was used instead, the case of the first embodiment was different from that of the first embodiment. Similar results were obtained. When this dry ash was used, the fluidized gas 2 was blown into the furnace through the nozzle 13 without raising the temperature (while still at room temperature). The same result as in the case of was obtained.
[0065]
[Example 2]
FIG. 3 shows another specific example of the apparatus for performing the incineration ash treatment method according to the present invention, which is different from the above-described apparatus. A configuration and an example of usage of this device will be described below. The lower part of the fluidized-bed furnace 1 is filled with a fluidized medium 11, and an air diffuser 17 is charged in the fluidized medium. Further, the fluidized bed furnace 1 is provided with an exhaust port 15 and an incineration ash input port 16, and further provided with a fluid medium return port 18 for returning the fluid medium 11 extracted from the furnace bottom into the furnace. .
[0066]
The fluidized gas 2 is pressurized by the blower 21, is heated by the heat source 23 through the heat exchanger 22, is blown into the furnace by the diffuser 17 through the header tube 24, and after fluidizing the fluid medium 11, And is discharged out of the furnace through the exhaust port 15. After that, it is discharged outside the system via the exhaust gas treatment device 25. In addition, as the fluidizing gas 2, for example, air, combustion exhaust gas, or a mixed gas of both can be used.
[0067]
The incineration ash 3 is temporarily stored in an incineration ash hopper 31, is appropriately cut out by a cutting device 32, and is put into the furnace through the incineration ash input port 16. The added incineration ash 33 is dried by the high temperature in the fluidized bed, and the surface is polished by the fluidized medium 11 to remove the attached ash. Most of the removed adhered ash has a very small particle size, rises inside the furnace together with the fluidizing gas 2, and is discharged outside the furnace.
[0068]
Further, the incinerated ash and the fluidized medium after removing the attached ash are extracted from the bottom of the fluidized bed furnace 1 by the continuous discharge device 4. After that, it can be separated into the incineration ash 42 and the flowing medium 43 by the separating device 41. As the separation device 41, for example, a vibration sieve, a trommel, or the like can be used. The separated fluid medium 11 can be transported by the conveyor 44 and returned to the fluidized bed furnace from the fluid medium return port 18. Then, the operation can be continued with almost no new replenishment of the fluid medium 11 required.
[0069]
The fuel 5 can be blown in by the fuel gun 51 to maintain the temperature of the fluidized bed. The fuel 5 may be a gas such as city gas, propane or butane, or a liquid such as kerosene or heavy oil. The fuel 5 is burned by oxygen in the fluidized gas, and its heat generation contributes to the maintenance of the temperature of the fluidized bed, thereby drying the incinerated ash.
[0070]
The cross-sectional area of the fluidized-bed furnace is such that the cross-sectional area 62 at a so-called freeboard portion above the fluidized-medium portion (fluidized-bed portion) is smaller than the cross-sectional area 61 at the upper portion thereof. This is because the flow velocity of the fluidizing gas in the free board part is made larger than the flow velocity of the fluidizing gas just above the fluid medium part, and the particles of the attached ash once trapped in the gas flow are reliably discharged from the exhaust port 15 to the furnace. Contributes to discharge to the outside.
[0071]
The combustibles 7 can be introduced into the fluidized bed furnace. As the combustibles, for example, waste plastics, wood chips and the like can be used. In the apparatus shown in FIG. 3, the combustibles are temporarily stored in a combustibles hopper 71, are appropriately cut out by a combustibles cutout device 72, and are charged into a furnace. The incineration ash and the combustibles may be mixed in advance at a fixed ratio, and may be charged from the incineration ash hopper.
[0072]
The incineration ash according to Example 2 of the present invention was treated using the above apparatus. At this time, silica sand was used as the fluid medium 11 and air was used as the fluidizing gas 2. The temperature of the fluidized bed of the fluidized bed furnace 1 was 550 ° C. The gas flow velocity of the fluidizing gas 2 was 0.5 m / sec. As the separation device 41, a vibration sieve was used.
[0073]
Wet ash was used as incineration ash supplied to the fluidized bed of the fluidized bed furnace 1. This wet ash is incinerator ash of municipal solid waste and industrial waste from a stoker-type incinerator, which is collected after being dropped into a water tank and collected by a dust collector at the latter stage of the incinerator. This is a so-called mixed ash obtained by mixing fly ash.
[0074]
The heavy metal content in this incinerated ash (wet ash) is 1.4 mg / kg of mercury, 2400 mg / kg of lead, 8400 mg / kg of zinc, and the content of dioxins is 0.045 ng-. TEQ / g.
[0075]
The incinerated ash (wet ash) is supplied to the fluidized bed of the fluidized-bed furnace 1, the incinerated ash is heated and dried in the fluidized bed, and the attached ash on the particle surface of the incinerated ash is polished with a fluidized medium. Removal processing was performed. After the incinerated ash after this treatment was extracted from the bottom of the fluidized-bed furnace 1 together with the fluidized medium, the incinerated ash 42 and the fluidized medium 43 were separated by the separator 41. The incineration ash 42 having a particle size of 5 to 25 mm was measured for heavy metal content and dioxin content, and a test for elution resistance, which is important for resource recycling.
[0076]
As a result, the heavy metal content in the incinerated ash after the above treatment was less than 0.01 mg / kg of mercury, 800 mg / kg of lead, 4200 mg / kg of zinc, etc., all of which were significantly reduced. The dioxin content was 0.0006 ng-TEQ / g, which was also significantly reduced. In the elution resistance test, the elution amount was hexavalent chromium: less than 0.02 mg / L, lead: less than 0.001 mg / L, cadmium: less than 0.001 mg / L, mercury: less than 0.0005 mg / L, arsenic : Less than 0.001 mg / L, selenium: less than 0.001 mg / L, all of which were below the soil environmental standard.
[0077]
As described above, according to the incineration ash processing method according to the second embodiment of the present invention, it is possible to reduce the amount of harmful substances such as heavy metals in the incineration ash by removing the attached ash on the particle surface of the incineration ash. It supports what you can do.
[0078]
In the second embodiment, when the fluidized medium 11 separated by the separation device 41 is transported by the conveyor 44 and returned into the fluidized-bed furnace from the fluidized medium return port 18, almost no new replenishment of the fluidized medium 11 is performed. I was able to continue driving without need.
[0079]
When the fuel 5 was blown by the fuel gun 51, the temperature of the fluidized bed was easily maintained at a predetermined temperature (550 ° C.) due to the heat generated by the combustion of the fuel 5.
[0080]
When the combustibles 7 were charged into the fluidized-bed furnace, the amount of the fuel 5 blown from the fuel gun 51 could be reduced.
[0081]
【The invention's effect】
According to the method for treating incinerated ash according to the present invention, the amount of harmful substances such as heavy metals in the incinerated ash is eliminated by removing the attached ash on the particle surface of the incinerated ash by using a closed apparatus with a small number of steps and no dust generation. Can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a cross-sectional structure of incinerated ash particles.
FIG. 2 is a schematic view showing an example of an apparatus for performing the method for treating incineration ash according to the present invention.
FIG. 3 is a schematic view showing an example of an apparatus for performing the method for treating incineration ash according to the present invention.
[Explanation of symbols]
1: fluidized bed furnace, 11: fluidized medium, 12: dispersion plate, 13: nozzle, 14: wind box, 15: exhaust port, 16: incineration ash inlet, 2: fluidized gas, 21: blower, 22: heat Exchanger, 23: heat source, 24: header, 25: exhaust gas treatment device, 3: incineration ash, 31: incineration ash hopper, 32: incineration ash cutting device, 33: incineration ash put into the furnace, 4: continuous discharge Apparatus, 41: Separator, 42: Incineration ash, 43: Fluid medium, 5: Fuel, 51: Fuel gun, 61: Cross-sectional area in the furnace of the fluidized bed, 62: Cross-sectional area in the furnace of the freeboard section, 7: Combustible material, 71: Combustible material hopper, 72: Combustible material cutting device. 80: particles of incinerated ash, 81: attached ash.

Claims (7)

The incineration ash of municipal solid waste and / or industrial waste is supplied to a fluidized bed of a fluidized-bed furnace, and in this fluidized bed, attached ash on the particle surface of the incinerated ash is removed by polishing with a fluidized medium. How to treat incinerated ash. The incinerated ash of municipal solid waste and / or industrial waste is supplied to a fluidized bed of a fluidized-bed furnace, the incinerated ash is heated and dried in the fluidized bed, and the ash attached to the particle surface of the incinerated ash is polished with a fluidized medium. A method for treating incinerated ash, characterized in that the incinerated ash is removed by carrying out. The method for treating incinerated ash according to claim 2, wherein the fluidized gas is preheated and then supplied to the fluidized bed. The method according to claim 2 or 3, wherein a fuel is supplied to the fluidized bed. The incineration according to any one of claims 1 to 4, wherein the fluidized medium containing incinerated ash discharged from the fluidized bed is separated into incinerated ash and a fluidized medium, and then the separated fluidized medium is supplied to the fluidized bed. Ash treatment method. The method for treating incineration ash according to any one of claims 1 to 5, wherein a cross-sectional area of the fluidized-bed furnace is different between a fluidized-bed portion and a freeboard portion above the fluidized-bed portion, and a cross-sectional area of the latter freeboard portion is smaller. . The method for treating incinerated ash according to claim 1, wherein a combustible material is supplied to the fluidized bed.

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