JP4795015B2 - Fly ash detoxification method and apparatus - Google Patents

Description

  The present invention relates to the treatment of fly ash collected from exhaust gas generated when incinerating general waste or industrial waste, and in particular, reducing heavy metals, salts and dioxins contained in fly ash, The present invention relates to a method and an apparatus for detoxifying an object.

Conventionally, general waste such as municipal waste and sewage sludge or industrial waste discharged from various factories has been treated by incineration for volume reduction and detoxification.
Exhaust gas generated in an incinerator, which is an incineration facility, is cooled to 200 ° C. or less in a temperature reducing tower, and is then processed by removing dust from the dust with a dust removing device and decomposing and removing it from the chimney. In addition, fly ash accompanying the exhaust gas is present in the exhaust gas. Since the fly ash contains heavy metals, salts, dioxins, etc., the fly ash is collected and detoxified. There is a need to.

As a method for treating the collected fly ash, there are a method in which the collected fly ash is indirectly heated at a high temperature of 400 to 600 ° C., and a method in which the catalyst is brought into contact with the catalyst at a high temperature (200 to 550 ° C.) to decompose and remove dioxins. It has been done conventionally. However, the method of indirect heating has a problem that the heat exchange rate is low and the apparatus becomes large. The catalytic treatment in the catalytic cracking method requires a large amount of catalyst because of its low catalytic activity, and the processing cost is high. There was a problem of becoming.
Therefore, Patent Document 1 and Patent Document 2 disclose a method for cleaning collected fly ash and re-injecting the cleaned fly ash into an incinerator to render it harmless. The methods disclosed in Patent Literature 1 and Patent Literature 2 can remove heavy metals and salts that are likely to be eluted by washing by moving them to the liquid side, and thermally decompose dioxins by burning them in an incinerator. Therefore, fly ash can be rendered harmless.

However, in both methods disclosed in Patent Document 1 and Patent Document 2, dehydrated fly ash obtained by washing and dehydrating fly ash, that is, fly ash re-introduced into the incinerator contains combustible components. Therefore, there is a problem that when the fly ash passes through a low temperature region in the incinerator, the fly ash is not sufficiently heated, so that the thermal decomposition of dioxins may not be sufficiently performed. Since dehydrated fly ash has a higher specific gravity than the waste normally incinerated in an incinerator, it tends to move to the lower part of the waste layer by stirring with a grate in the furnace. For example, in a stoker type incinerator, combustion air is supplied to the lower part of the waste layer, but the temperature of the combustion air is as low as about 100 to 200 ° C., and a low temperature region is easily formed in the lower part of the waste layer. Therefore, the dehydrated fly ash containing no combustible material is in a state of being easily moved to the lower part of the waste layer in a low temperature region, and there is a high possibility that the dioxins are not sufficiently thermally decomposed.
Furthermore, when the dried dehydrated fly ash is agitated in the waste layer part, there is a possibility that it will re-scatter as fly ash, and when re-scattered, the amount of fly ash in the system increases more than expected, for example It may exceed the capacity of fly ash treatment such as fly ash cleaning, impede the operation of incinerators and fly ash treatment systems, and may accumulate harmful substances in the furnace.

  Conventionally, as a method of treating sludge such as sewage sludge, methane fermentation sludge, and papermaking sludge, a method of co-firing waste and sludge has been implemented. For example, Patent Document 3 and Patent Document 4 include waste and sludge. A method of mixing and charging into an incinerator and co-firing is disclosed. However, fly ash generated by co-firing contains a lot of heavy metals and dioxins, and thus requires a detoxifying process, which causes a problem of processing costs.

Japanese Patent No. 3492191 JP 2000-227214 A JP 54-84377 A Japanese Patent Laid-Open No. 61-208421

In this way, it is necessary to remove heavy metals, salts and dioxins contained in fly ash and detoxify the fly ash, but the conventional techniques described above increase the size of the equipment, increase the processing cost, The problem of sufficient thermal decomposition of dioxins remained.
Therefore, in view of the above-mentioned problems of the prior art, the present invention eliminates the need for an increase in the size of processing equipment and an increase in processing costs, and a method and apparatus for efficiently thermally decomposing dioxins and making fly ash harmless. The purpose is to provide.

Therefore, in order to solve this problem, the present invention provides:
In the fly ash detoxification method, the fly ash collected from the exhaust gas of the incinerator that incinerates the waste is reintroduced into the incinerator and burned to make it harmless.
The fly ash collected from the exhaust gas and non-dehydrated sludge introduced from the outside are mixed and dehydrated, and the dehydrated cake obtained by dehydration is re-introduced into the incinerator.
The sludge has only to have a high moisture content and a uniform composition. For example, sewage sludge, methane fermentation sludge, papermaking sludge and the like can be used.

According to the present invention, fly ash is mixed with sludge having a high water content so that the fly ash is washed with water contained in the sludge, and heavy metals and salts in the fly ash are transferred to the liquid side and treated as waste water. Is done.
Moreover, since dioxins in fly ash are hardly soluble in water and do not migrate to the liquid side, they are not treated as wastewater and remain in the dewatered cake. The sludge component contained in the dehydrated cake contains combustible materials and burns in the furnace that has been re-introduced, so the fly ash temperature rises as the sludge component burns, and the dioxins can be sufficiently pyrolyzed, Ashes can be detoxified.
Moreover, since a part of fly ash is melted by the char combustion of sludge, an ash lump is formed, and the possibility of re-scattering as fly ash is reduced. Furthermore, the dehydrated cake is difficult to re-scatter even after drying, is excellent in handling, and can be easily processed and deformed. Furthermore, the concentration of heavy metals such as Pb and salts in the discharged fly ash is also reduced.
Moreover, since fly ash and undehydrated sludge are mixed and dehydrated, the dehydration process is not required for each of the fly ash and sludge, and only one process is required. Since sludge having a high water content is mixed as it is, it is liquid and easy to mix.

In addition, in the fly ash detoxification method, the fly ash collected from the exhaust gas of the incinerator that incinerates waste is re-introduced into the incinerator and burned to make the fly ash harmless.
The fly ash collected from the exhaust gas is washed, mixed with non-dehydrated sludge introduced from the outside, dehydrated, and the dehydrated cake obtained by dehydration is reintroduced into the incinerator.
By washing the fly ash, heavy metals and salts in the fly ash move to the liquid side and are treated as waste water. Moreover, dioxins in fly ash remain in the dehydrated cake because they are hardly soluble in water and do not migrate to the liquid side. The sludge component contained in the dehydrated cake contains combustible materials and burns in the furnace that has been re-introduced, so the fly ash temperature rises as the sludge component burns, and the dioxins can be sufficiently pyrolyzed, Ashes can be detoxified.
Also, since the washed fly ash and undehydrated sludge are mixed and dehydrated, the dehydration process is not required for each of the fly ash and sludge, and only one process is required, and the washed fly ash and sludge with a high water content are mixed. Therefore, it is liquid and easy to mix.

In addition, in the fly ash detoxification method, the fly ash collected from the exhaust gas of the incinerator that incinerates waste is re-introduced into the incinerator and burned to make the fly ash harmless.
The fly ash collected from the exhaust gas is washed, mixed with dewatered sludge introduced from the outside, dehydrated, and the dehydrated cake obtained by dehydration is reintroduced into the incinerator.
The fly ash can be rendered harmless by washing the fly ash to remove heavy metals and salts and by thermally decomposing the dioxins by burning the dehydrated cake in a combustion furnace.
Moreover, since it is before dehydration and the fly ash after washing | cleaning and the sludge after dehydration are mixed, it is liquid and easy to mix.

In addition, in the fly ash detoxification method, the fly ash collected from the exhaust gas of the incinerator that incinerates waste is re-introduced into the incinerator and burned to make the fly ash harmless.
The fly ash collected from the exhaust gas is washed, further dehydrated, mixed with non-dehydrated sludge introduced from the outside, dehydrated, and dehydrated cake obtained by dehydration is re-injected into the incinerator. Features.
The fly ash can be rendered harmless by washing the fly ash to remove heavy metals and salts and by thermally decomposing the dioxins by burning the dehydrated cake in a combustion furnace.
Moreover, since the fly ash after washing and dehydration and the sludge before dehydration are mixed, it is liquid and easy to mix.
Furthermore, since fly ash is mixed with sludge after washing and dehydration, the fly ash has good properties. This is because inorganic fly ash is easier to dehydrate than organic sludge, and the moisture of the dewatered cake as adhering water can be made lower than dehydrated after mixing fly ash and sludge.

In addition, in the fly ash detoxification method, the fly ash collected from the exhaust gas of the incinerator that incinerates waste is re-introduced into the incinerator and burned to make the fly ash harmless.
The fly ash collected from the exhaust gas is washed, further dehydrated, and then dehydrated cake obtained by mixing with dewatered sludge introduced from the outside is re-introduced into the incinerator.
The fly ash can be rendered harmless by washing the fly ash to remove heavy metals and salts and by thermally decomposing the dioxins by burning the dehydrated cake in a combustion furnace.
Moreover, since fly ash is mixed with sludge after washing and dehydration, the properties of fly ash are good.

Any of the above five methods can achieve detoxification of fly ash.
In any method, when a dehydrated cake containing a fly ash component and a sludge component is charged into the furnace, the surface of the dehydrated cake is first heated to cause moisture evaporation and thermal decomposition. Thereafter, moisture evaporation and thermal decomposition proceed toward the center of the dehydrated cake while shrinking leaving ash, and eventually char combustion occurs in the center. Since char combustion is a strong exothermic reaction, the fly ash is heated strongly and a part of the fly ash is melted, so that a mass of ash is formed and the possibility of re-scattering as fly ash is reduced.
In addition, dehydrated cakes are difficult to re-scatter even after drying, are excellent in handling, and can be easily processed and deformed. For example, they can be processed into a plate shape to make it difficult to descend in the waste layer. By keeping the distance away, the possibility of dioxins being discharged without being thermally decomposed can be further reduced.
Furthermore, in addition to the thermal decomposition of dioxins due to exposure of fly ash to high temperatures, the concentration of heavy metals such as Pb, heavy metals such as Pb in the fly ash discharged due to volatilization of salts, and salts Becomes smaller.

Further, the dehydrated cake is directly fed into a combustion region in the furnace from a dehydrated cake charging means provided independently of the waste charging hopper of the incinerator.
When the dehydrated cake is fed into the furnace from the waste charging hopper, when the dehydrated cake passes through the lower part of the waste layer, it is cooled by the combustion air introduced from the lower part of the furnace, and is not heated sufficiently. However, according to the present invention, since the dehydrated cake is directly put into the main combustion zone in the furnace, more effective evaporation of heavy metals and salts can be realized.

Moreover, a sodium-based neutralizing agent is supplied to the exhaust gas upstream of the dust removing device that collects the fly ash.
Thus, by using a sodium-based neutralizing agent as the acidic gas neutralizing agent, hardly soluble CaSO ₄ is produced, and easily soluble Na ₂ SO ₄ is produced. It moves to the liquid side and does not remain in the dehydrated cake. As a result, the amount of dehydrated cake is reduced, the temperature in the furnace is reduced, and SO _x is not generated even when heated, so that the amount of exhaust gas neutralizer used can be reduced.

Furthermore, it has a main ash water washing step of washing main ash remaining after incineration of waste in an incinerator, and at least a part of the wastewater generated by the main ash water washing device in the main ash water washing step is the fly ash Is used as water for washing.
Thus, the amount of wastewater generated can be greatly reduced by reusing the wastewater used for washing the main ash for washing the fly ash.
In general, the salt content in the main ash is 0.5 to 1.5%, while the salt content in the fly ash is as high as 7 to 15%. Therefore, in the present invention, a flow of drainage from the main ash water washing device to the fly ash water washing device is formed, and in the main ash water washing device, the main ash is washed with washing water that does not contain salts, so that the salts in the main ash Desalinate the concentration to a very low value to make it suitable for reuse of cement and concrete raw materials. On the other hand, the fly ash water washing apparatus is configured to wash the fly ash using the waste water after washing the main ash water, but the fly ash is re-introduced into the furnace, so there is no problem even if some salt remains. The fly ash containing a concentration of salts is roughly washed.

Further, the exhaust gas after removing the fly ash with a dust removing device is introduced into the main ash water washing device.
Thus, by introducing the exhaust gas into the main ash water washing apparatus, it is possible to expect the elution amount suppression by carbonation of heavy metals. In addition, elution of Friedel's salt, which is a poorly soluble chlorine compound, can be expected.

In the fly ash detoxification device that detoxifies fly ash by re-injecting fly ash collected from the exhaust gas of the incinerator that incinerates waste into the incinerator by the return circuit and burning in the incinerator,
A dehydrating means for mixing and dewatering fly ash collected from the exhaust gas and non-dehydrated sludge introduced from the outside on the return circuit, and a dehydrated cake obtained by the dehydrating means are put into an incinerator. And a dehydrating cake returning means.

In addition, in the fly ash detoxification device that detoxifies fly ash by re-injecting fly ash collected from the exhaust gas of the incinerator that incinerates waste into the incinerator by a return circuit and burning in the incinerator,
On the return circuit, the fly ash washing means for washing the fly ash collected from the exhaust gas, the fly ash washed by the fly ash washing means and the non-dehydrated sludge introduced from the outside are mixed and dehydrated. A dehydrating means and a dehydrated cake returning means for feeding the dehydrated cake obtained by the dehydrating means into an incinerator are provided.

In addition, in the fly ash detoxification device that detoxifies fly ash by re-injecting fly ash collected from the exhaust gas of the incinerator that incinerates waste into the incinerator by a return circuit and burning in the incinerator,
On the return circuit, the fly ash washing means for washing the fly ash collected from the exhaust gas, the fly ash washed by the fly ash washing means and the dewatered sludge introduced from outside are mixed and dehydrated. A dehydrating means and a dehydrated cake returning means for feeding the dehydrated cake obtained by the dehydrating means into an incinerator are provided.

In addition, in the fly ash detoxification device that detoxifies fly ash by re-injecting fly ash collected from the exhaust gas of the incinerator that incinerates waste into the incinerator by a return circuit and burning in the incinerator,
On the return circuit, a fly ash cleaning means for cleaning fly ash collected from the exhaust gas, a fly ash dewatering means for dewatering the fly ash washed by the fly ash cleaning means, and the fly ash dewatering means A dehydrating means for mixing dehydrated fly ash and non-dehydrated sludge introduced from the outside to dehydrate, and a dehydrated cake returning means for putting the dehydrated cake obtained by the dehydrating means into an incinerator. Features.

In addition, in the fly ash detoxification device that detoxifies fly ash by re-injecting fly ash collected from the exhaust gas of the incinerator that incinerates waste into the incinerator by a return circuit and burning in the incinerator,
On the return circuit, a fly ash cleaning means for cleaning fly ash collected from the exhaust gas, a fly ash dewatering means for dewatering the fly ash washed by the fly ash cleaning means, and the fly ash dewatering means A mixing means for mixing dehydrated fly ash and sludge after dehydration introduced from the outside, and a dehydrated cake returning means for charging the dehydrated cake obtained by the mixing means into an incinerator .

  Furthermore, a dewatering cake charging means for directly charging the dewatering cake from the dewatering cake returning means into the combustion region in the furnace is provided independently of the waste charging hopper of the incinerator.

Further, the fly ash recovery circuit for collecting the fly ash, the boiler for heat recovery, the temperature reducing tower for reducing the temperature of the exhaust gas after the heat recovery, and the dust removing device for collecting the fly ash from the temperature reduced exhaust gas And consisting of
Means is provided for supplying a sodium-based neutralizing agent to the exhaust gas upstream of the dust remover on the fly ash recovery circuit.
In addition, fly ash shall be collect | recovered from a boiler, a temperature reduction tower, and a dust removal apparatus.

Furthermore, it has a main ash water washing means for washing main ash remaining after incineration of waste in the incinerator, and provided with means for putting waste water generated by the main ash water washing means into the fly ash washing means. Features.
At this time, at least one of a pulverizer that crushes the main ash and a sorting device that sorts and removes metal such as iron and aluminum from the main ash is provided in the previous stage of the main ash washing apparatus. good.

Further, the fly ash recovery circuit for collecting the fly ash, the boiler for heat recovery, the temperature reducing tower for reducing the temperature of the exhaust gas after the heat recovery, and the dust removing device for collecting the fly ash from the temperature reduced exhaust gas And consisting of
Means is provided for introducing the exhaust gas after the fly ash is removed by the dust removing device on the fly ash recovery circuit to the main ash water washing device.

As described above, according to the present invention, heavy metals and salts in the fly ash are transferred to the liquid side by washing the fly ash and are treated as waste water. Dioxins in fly ash are hardly soluble in water and do not move to the liquid side, so they remain in the fly ash and are mixed with sludge in an incinerator. The sludge component contains combustible materials and burns in the furnace that has been re-introduced. As the sludge component burns, the temperature of the fly ash rises and the dioxins can be fully pyrolyzed, making the fly ash harmless. be able to.
Therefore, it is not necessary to increase the size of processing equipment and increase the processing cost, and it is possible to provide a method and apparatus for efficiently thermally decomposing dioxins and making fly ash harmless.
In addition, the structure in which the dehydrated cake is directly put into the furnace enables stable heating of the dehydrated cake, and more effective evaporation of heavy metals and salts is realized.
Furthermore, by using a Na-based neutralizing agent as the exhaust gas neutralizing agent, hardly soluble CaSO ₄ is not generated, and sulfur components do not accumulate in the system.
Furthermore, the amount of wastewater generated can be significantly reduced by reusing the wastewater used for washing main ash for washing fly ash.
Moreover, by introducing the exhaust gas from the incinerator into the main ash water washing apparatus, it is possible to suppress elution of heavy metals by carbonation and elution of Friedel's salt which is a poorly soluble Cl compound.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is an overall configuration diagram of the ash treatment according to the first embodiment. Waste 31 such as municipal waste, sludge, and industrial waste is incinerated in the stoker-type incinerator 10. The stoker-type incinerator 10 includes a waste charging hopper 11, a grate 12 that moves the waste 31 that has been charged from the waste charging hopper 11 through the furnace while stirring, and combustion air (from below the grate 12 ( A primary air inlet 13 for introducing a primary air 15, a primary combustion chamber 16 formed on a grate, a main ash outlet 14 for discharging main ash after combustion, and above the primary combustion chamber 16. A secondary combustion chamber 18 that is formed and completely combusts unburned gas in the gas by introducing the secondary air 17 and an ash cooling device 27 that cools the main ash discharged from the main ash discharge port 14 are provided. In the present embodiment, the stoker type incinerator 10 is described as an example, but the present invention is not limited to this, and other incinerators such as a fluidized bed incinerator and a rotary kiln type incinerator may be used.

A boiler 20 is disposed downstream of the stoker-type incinerator 10, and exhaust gas from the incinerator 10 is heat-recovered by the boiler 20 and then introduced into the temperature reducing tower 21. In the temperature reducing tower 21, the exhaust gas is cooled by spraying cooling water. The exhaust gas cooled in the temperature reducing tower 21 is introduced into the dust removing device 22. As the dust removing device 22, a bag filter, a cyclone type dust collector, an electric dust collector or the like is used, and a bag filter is preferably used. At this time, the exhaust gas neutralizing agent 32 is sprayed in the exhaust gas pipe line on the upstream side of the dust removing device 22 or the temperature reducing tower 21. The neutralizing agent 32 is a chemical that removes acidic gases such as HCl and SO _x in the exhaust gas by a neutralization reaction. For example, slaked lime (Ca (OH) ₂ ), caustic soda (NaOH), or sodium bicarbonate (NaHCO ₃ ). Alkali neutralizing agents such as Na-based neutralizing agents are used alone or in combination. The exhaust gas from which the fly ash 33 has been removed by the dust removing device 22 is discharged from the chimney 23 to the outside of the system. In addition, a catalytic reaction tower may be installed after the dust removing device.

  The fly ash 33 is washed by the fly ash water washing device 24. The fly ash water washing device 24 is a device that performs the washing treatment of the fly ash 33 with the washing water supplied into the water tank. At this time, if necessary, a stirring means may be provided and washed with water while stirring. As for L / S (liquid / solid ratio) at the time of water washing, about 3-7 are preferable. The fly ash water washing device 24 can use either a batch type or a continuous type, but a batch type water washing device is preferred in this embodiment. In the batch type water washing apparatus, more effective washing is possible by performing washing a plurality of times, and the cost is reduced. Desirably, L / S is made small in the first water washing, and L / S is made equal to or more than the first time in the second and subsequent times. This is because almost 100% of the salt dissolves in water, but remains in the adhering water of the dehydrated cake, so that the adhering water is removed after the second time after being dissolved and dehydrated in the first time. . A plurality of cleanings may be performed with one apparatus, or a plurality of apparatuses may be arranged in series. Moreover, in the case of a batch-type washing apparatus, it is preferable to operate by alternately providing a plurality of washing water tanks.

As a characteristic configuration of the present embodiment, after the fly ash washing by the fly ash washing apparatus 24, the sludge 34 is put into the fly ash washing apparatus. The sludge has only to have a high moisture content and a uniform composition. For example, sewage sludge, methane fermentation sludge, paper sludge and the like can be used. It is preferable that the fly ash water washing device 24 is provided with a stirring means and stirred after the sludge 34 is added because the fly ash and the sludge after the water washing are uniformly mixed.
In this example, the washed fly ash and undehydrated sludge were mixed, but the unwashed fly ash and undehydrated sludge were mixed, the washed fly ash and the dehydrated sludge mixed, and washed. It is also possible to carry out a mixing method such as mixing fly ash after dehydration and undehydrated sludge, or mixing sludge after washing and dehydration after dehydration.

  The fly ash water washing device 24 simultaneously removes heavy metals contained in the fly ash and heavy metals and salts that are easily eluted in water. As a result, heavy metals and salts move to the liquid side, are separated into solid and liquid by the dehydrator 25, are contained in the waste water, and are fed to the waste water treatment facility 26. At this time, according to the experiment, about 90 to 100% of Cl and about 20 to 50% of Pb contained in the fly ash were transferred to the liquid side. The waste water treatment facility 26 is mainly composed of a device for removing heavy metals. For example, chelate treatment, coagulation sedimentation treatment, and advanced water treatment are performed. Wastewater after wastewater treatment is discharged.

In the dehydrator 25, dioxins in the fly ash are hardly soluble in water, and therefore remain on the solid side.
The solid matter separated by solid-liquid separation by the dehydrator 25, that is, the dehydrated cake 36, is guided to the waste pit of the incinerator 10 or the charging hopper 11 at the subsequent stage, and is re-introduced into the furnace together with the waste. In the dehydrated cake 35, dioxins are thermally decomposed by recharging into the furnace, and the remaining heavy metals such as Pb and salts are volatilized and move to the exhaust gas side.
At this time, in addition to the components derived from the fly ash 33, the dehydrated cake 36 also includes components derived from the sludge 34 mixed by the fly ash water washing device 24. Although the component derived from the fly ash 33 does not include a combustible material, the component derived from the sludge 34 includes the combustible material and burns in the combustion furnace. Therefore, the temperature of the fly ash component mixed with the sludge component is burned together with the combustion of the sludge component. Rises and can fully pyrolyze dioxins and make fly ash harmless.
FIG. 6 shows the combustion state in the air stream of sludge alone. The vertical axis is the dimensionless weight of the sludge, and is the relative weight with 1.0 as the weight before combustion. The vertical axis is the sludge center temperature (° C.), and the horizontal axis is the combustion time (s). From FIG. 6, when the sludge starts burning, the surface is first heated to cause moisture evaporation and thermal decomposition, and then the moisture evaporation and thermal decomposition proceeds toward the center of the sludge while shrinking. It can be seen that char combustion is occurring in the part. Therefore, by burning the dewatered cake 35 containing sludge, the sludge burns as described above, and finally char combustion occurs in the center. Since char combustion is a strong exothermic reaction, the fly ash is heated strongly and a part of the fly ash is melted, so that a mass of ash is formed and the possibility of re-scattering as fly ash is reduced.
In addition, the dehydrated cake 35 is not easily re-scattered even when dried, is excellent in handling, and can be easily processed and deformed. For example, it is processed into a plate shape to make it difficult to descend in the waste layer, so By moving away the ash, the possibility of dioxins being discharged without being thermally decomposed can be further reduced.
Further, when fly ash is exposed to high temperatures, in addition to thermal decomposition of dioxins, heavy metals such as Pb, volatilization of salts, and migration to the exhaust gas side are promoted, and heavy metals and salts in fly ash are promoted. The concentration is also reduced.

FIG. 2 is an overall configuration diagram of the ash treatment according to the second embodiment. The dehydrated cake 36 was configured in the same manner as in Example 1 except that the dehydrated cake 36 was directly charged into a combustion region in the furnace from a dehydrated cake charging means (not shown) provided separately from the waste charging hopper 11 of the incinerator 10.
As a result, in addition to the results obtained in Example 1, the volatilization of heavy metals and salts in the incinerator 10 and the shift to the exhaust gas side are further promoted. This is because when the dehydrated cake 36 is supplied from the waste charging hopper 11 into the furnace, when the dehydrated cake 36 passes through the lower part of the waste layer, the temperature of the combustion air 15 is lower than that in the furnace introduced from the lower part of the furnace. However, due to the fact that heavy metals and salts may remain in the dehydrated cake, the dehydrated cake is directly put into the combustion region in the furnace according to this embodiment. This is because more effective evaporation of heavy metals and salts is realized.

FIG. 3 is an overall configuration diagram of the ash treatment according to the third embodiment. The configuration was the same as in Example 1 except that an Na-based neutralizer was used as the exhaust gas neutralizer.
As a result, in addition to the results obtained in Example 1, it is possible to moderate the temperature drop in the incinerator and reduce the amount of exhaust gas neutralizer used. This is because the use of a sodium-based neutralizer as the acid gas neutralizer does not produce poorly soluble CaSO _4, but produces readily soluble Na ₂ SO ₄ . It moves to the liquid side and does not remain in the dehydrated cake. This is because the amount of dehydrated cake is reduced, the temperature inside the furnace is reduced, and SO _x is not generated even when heated, so that the amount of exhaust gas neutralizer used can be reduced.
As the Na-based neutralizing agent, weakly basic baking soda (NaHCO ₃ ) is suitable for use, but since sodium bicarbonate is expensive, it is particularly preferable to use sodium bicarbonate and strongly basic caustic soda (NaOH) together. desirable.

FIG. 4 is an overall configuration diagram of the ash treatment according to the fourth embodiment. The main ash washing device 30 for washing the main ash 37 discharged from the incinerator 10, the sorting device 28 for pre-treating the main ash for washing with the main ash washing device 30, and the pulverizer 29, The configuration is the same as in Example 1 except that the waste water 40 generated at 30 can be introduced into the fly ash water washing device 24.
The main ash 37 discharged from the incinerator 10 is subjected to sorting of metal components such as iron and aluminum by the sorting device 28, pulverized by the pulverizer 29, and put into the main ash water washing device 30. Unlike the fly ash 33, the main ash 37 has a large particle size and a small surface area, so that it is preferable to grind the ash to about 2 to 5 mm. The sorting apparatus 28 and the pulverizer 29 are most preferably configured as described in the present embodiment, but these are appropriately installed, and the arrangement configuration is not particularly limited. The main ash water washing apparatus 30 has a configuration substantially similar to the above-described fly ash water washing apparatus 24. Thus, by washing the main ash 37 with the main ash water washing apparatus 30, the salt concentration in the main ash is reduced to an extremely low value, and is suitable for use as a raw material 39 for civil engineering materials such as cement and concrete products. It can be.

Further, as a characteristic feature of the present embodiment, the waste water 40 supplied to the main ash water washing device 30 and used for washing is introduced into the fly ash water washing device 24 and reused for washing the fly ash 33. At this time, at least a part of the waste water 40 is reused, but preferably the entire amount is reused. Moreover, in addition to the waste water 40, water supply 35 from the outside may be used for water washing in the fly ash water washing device 24.
As a result, in addition to the results obtained in Example 1, the amount of generated wastewater can be greatly reduced.
In general, the salt content in the main ash 37 is 0.5 to 1.5%, while the salt content in the fly ash is as high as 7 to 15%. Therefore, in the main ash water washing apparatus 30, the main ash 37 is washed by supplying 38 cleaning water that does not contain salt, so that the salt removal rate of the main ash 37 can be made extremely high. It is possible to make the property suitable for recycling. On the other hand, the fly ash water washing device 24 is configured to wash the fly ash 33 using the waste water after washing with the main ash water. However, since the fly ash 33 is re-introduced into the furnace, there is no problem even if some salt remains. First, the fly ash 33 containing high-concentration salts is roughly washed.

FIG. 5 is an overall configuration diagram of the ash treatment according to the fifth embodiment. The configuration was the same as that of Example 4 except that the exhaust gas 41 from which the fly ash 33 was removed by the dust removing device 22 could be introduced into the main ash water washing device 30. The exhaust gas 41 is preferably returned to the upstream side of the dust removing device 22 after being introduced into the main ash water washing device 30.
As a result, in addition to the results obtained in Example 4, by introducing the exhaust gas into the main ash water washing apparatus, it is possible to suppress the elution amount due to carbonation of heavy metals. In addition, elution of Friedel's salt, which is a poorly soluble Cl compound, can be expected.
In the main ash washing apparatus 30, it is necessary to reduce the salt in order to reuse the main ash 37 as a raw material for cement and concrete products 39, but the salt is contained in the form of a hardly soluble Friedel salt. For this reason, it is difficult to reduce the ash to a sufficient level for reuse of ash only by washing with water. Therefore, exhaust gas is introduced into the washing suspension of ash dust, and elution of chlorine ions can be promoted and heavy metals can be fixed by carbon dioxide contained in the exhaust gas.

  The present invention is suitable for the treatment of fly ash because there is no need to increase the size of the treatment equipment and increase the treatment cost, and it can efficiently thermally decompose dioxins and render fly ash harmless. .

1 is an overall configuration diagram of ash treatment according to a first embodiment. It is a whole block diagram of the ash process which concerns on the present Example 2. FIG. It is a whole block diagram of the ash processing which concerns on the present Example 3. It is a whole block diagram of the ash processing which concerns on the present Example 4. It is a whole block diagram of the ash processing which concerns on the present Example 5. It is the figure which showed the combustion state in the airflow only by sludge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stoker type incinerator 11 Garbage hopper 20 Boiler 21 Temperature reduction tower 22 Dust removal device 24 Fly ash water washing device 25 Dehydrator 30 Main ash water washing device 32 Neutralizer 32a Na-based neutralizer 33 Fly ash 34 Sludge 36 Dehydrated cake 40 Wastewater 41 Exhaust gas

Claims (18)

In the fly ash detoxification method, the fly ash collected from the exhaust gas of the incinerator that incinerates the waste is reintroduced into the incinerator and burned to make it harmless.
Fly ash detoxification method comprising mixing fly ash collected from the exhaust gas and non-dehydrated sludge introduced from the outside, dehydrating, and re-injecting the dehydrated cake obtained by dehydration into the incinerator . In the fly ash detoxification method, the fly ash collected from the exhaust gas of the incinerator that incinerates the waste is reintroduced into the incinerator and burned to make it harmless.
The fly ash collected from the exhaust gas is washed, mixed with non-dehydrated sludge introduced from the outside, dehydrated, and the dehydrated cake obtained by dehydration is reintroduced into the incinerator. Ash detoxification method. In the fly ash detoxification method, the fly ash collected from the exhaust gas of the incinerator that incinerates the waste is reintroduced into the incinerator and burned to make it harmless.
The fly ash collected from the exhaust gas is washed, mixed with dehydrated sludge introduced from the outside, dehydrated, and the dehydrated cake obtained by dehydration is reintroduced into the incinerator. Ash detoxification method. In the fly ash detoxification method, the fly ash collected from the exhaust gas of the incinerator that incinerates the waste is reintroduced into the incinerator and burned to make it harmless.
The fly ash collected from the exhaust gas is washed, further dehydrated, mixed with non-dehydrated sludge introduced from the outside, dehydrated, and dehydrated cake obtained by dehydration is re-injected into the incinerator. A characteristic of fly ash detoxification. In the fly ash detoxification method, the fly ash collected from the exhaust gas of the incinerator that incinerates the waste is reintroduced into the incinerator and burned to make it harmless.
Washing fly ash collected from the exhaust gas, further dehydrating, and then re-injecting dehydrated cake obtained by mixing with dewatered sludge introduced from outside into the incinerator Method.   6. The fly ash detoxification according to claim 1, wherein the dehydrated cake is directly fed into a combustion region in the furnace from a dehydrated cake charging means provided independently of a waste charging hopper of the incinerator. Method.   The fly ash detoxification method according to any one of claims 1 to 5, wherein a sodium-based neutralizing agent is supplied to an exhaust gas upstream of a dust removing device that collects the fly ash.   It has a main ash rinsing process for rinsing main ash remaining after incineration of waste in an incinerator, and at least a part of the wastewater generated by the main ash rinsing apparatus in the main ash rinsing process is washed for the fly ash The fly ash detoxification method according to claim 2, wherein the fly ash is detoxified.   9. The fly ash detoxification method according to claim 8, wherein the exhaust gas after the fly ash is removed by a dust removing device is introduced into the main ash water washing device. In the fly ash detoxification device that detoxifies fly ash by re-injecting fly ash collected from the exhaust gas of the incinerator that incinerates waste into the incinerator by the return circuit and burning in the incinerator,
A dehydrating means for mixing and dewatering fly ash collected from the exhaust gas and non-dehydrated sludge introduced from the outside on the return circuit, and a dehydrated cake obtained by the dehydrating means are put into an incinerator. A fly ash detoxification device comprising dewatered cake return means. In the fly ash detoxification device that detoxifies fly ash by re-injecting fly ash collected from the exhaust gas of the incinerator that incinerates waste into the incinerator by the return circuit and burning in the incinerator,
On the return circuit, the fly ash washing means for washing the fly ash collected from the exhaust gas, the fly ash washed by the fly ash washing means and the non-dehydrated sludge introduced from the outside are mixed and dehydrated. A fly ash detoxification device comprising dehydrating means and dehydrated cake returning means for charging the dehydrated cake obtained by the dehydrating means into an incinerator. In the fly ash detoxification device that detoxifies fly ash by re-injecting fly ash collected from the exhaust gas of the incinerator that incinerates waste into the incinerator by the return circuit and burning in the incinerator,
On the return circuit, the fly ash washing means for washing the fly ash collected from the exhaust gas, the fly ash washed by the fly ash washing means and the dewatered sludge introduced from outside are mixed and dehydrated. A fly ash detoxification device comprising dehydrating means and dehydrated cake returning means for charging the dehydrated cake obtained by the dehydrating means into an incinerator. In the fly ash detoxification device that detoxifies fly ash by re-injecting fly ash collected from the exhaust gas of the incinerator that incinerates waste into the incinerator by the return circuit and burning in the incinerator,
On the return circuit, a fly ash cleaning means for cleaning fly ash collected from the exhaust gas, a fly ash dewatering means for dewatering the fly ash washed by the fly ash cleaning means, and the fly ash dewatering means A dehydrating means for mixing dehydrated fly ash and non-dehydrated sludge introduced from the outside to dehydrate, and a dehydrated cake returning means for putting the dehydrated cake obtained by the dehydrating means into an incinerator. Featuring fly ash detoxification equipment. In the fly ash detoxification device that detoxifies fly ash by re-injecting fly ash collected from the exhaust gas of the incinerator that incinerates waste into the incinerator by the return circuit and burning in the incinerator,
On the return circuit, a fly ash cleaning means for cleaning fly ash collected from the exhaust gas, a fly ash dewatering means for dewatering the fly ash washed by the fly ash cleaning means, and the fly ash dewatering means A mixing means for mixing dehydrated fly ash and sludge after dehydration introduced from the outside, and a dehydrated cake returning means for charging the dehydrated cake obtained by the mixing means into an incinerator Fly ash detoxification equipment.   The dewatered cake charging means for directly charging the dehydrated cake from the dehydrated cake returning means into the combustion region in the furnace is provided independently of the waste charging hopper of the incinerator. The fly ash detoxification device according to any one of the above. A fly ash recovery circuit for collecting the fly ash, a boiler for heat recovery, a temperature reducing tower for reducing the temperature of the exhaust gas after the heat recovery, and a dust removing device for collecting the fly ash from the reduced temperature exhaust gas Configure
The fly ash detoxification device according to any one of claims 10 to 14, further comprising means for supplying a sodium-based neutralizer to the exhaust gas upstream of the dust removal device on the fly ash recovery circuit.   It has a main ash water washing means for washing main ash remaining after incineration of waste in the incinerator, and provided with means for putting waste water generated by the main ash water washing means into the fly ash washing means. The fly ash detoxification device according to any one of claims 11 to 14. A fly ash recovery circuit for collecting the fly ash, a boiler for heat recovery, a temperature reducing tower for reducing the temperature of the exhaust gas after the heat recovery, and a dust removing device for collecting the fly ash from the reduced temperature exhaust gas Configure
18. The fly ash detoxifying device according to claim 17, further comprising means for introducing the exhaust gas after the fly ash has been removed by a dust removing device on the fly ash recovery circuit into the main ash washing device.

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