JP2003088726A - Wet exhaust gas treatment method and system therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sharply reduce the running cost in the wet exhaust gas treatment of incineration equipment and to prevent injury from salt in the downstream region of an incineration plant. SOLUTION: The acidic gas component of exhaust gas discharged from the incineration equipment is recovered as an NaCl solution by a dust collector 2, a smoke washing column 3, a solid removing means 4 and an impurity removing means 7, and an NaOH solution and an HCl solution are separated and extracted from the NaCl solution by a bipolar electrodialyzing tank 12 and the NaCl solution is converted to NaCl removed water. This NaCl removed water is discharged from the incineration plant and the separated and extracted NaOH solution is used in the neutralization of the washing liquid in the smoke washing column 3 or the backwashing of the system and the separated and extracted HCl solution is used in the pH adjustment or backwashing of the inside and outside of the system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and system for wet-treating exhaust gas in a refuse incineration facility (general waste or industrial waste incineration plant, etc.).

[0002]

2. Description of the Related Art Conventionally, in waste incineration facilities (general waste or industrial waste incineration plants, etc.), exhaust gas discharged from the waste incineration facilities contains acidic gas components such as HCl and SOx. As a method for deoxidizing the acidic gas components, washing those acidic gas components with water,
By neutralizing caustic soda and other alkaline agents, the pH is adjusted to 6
The method of changing to salt by adjusting to 9 is most commonly adopted.

This conventional method will be described with reference to the system configuration diagram shown in FIG. This conventional wet type exhaust gas treatment system 50 is configured to include a dust collector 51 and a smoke washing tower 52. Exhaust gas from a refuse incineration facility (not shown) is cleaned by the dust collector 51 and then the smoke washing tower 52 is removed. Was introduced in
The smoke washing tower 52 is washed with the washing water sprayed and circulated. As a result, the acidic gas components (HCl, SOx, etc.) in the exhaust gas introduced into the smoke washing tower 52 are absorbed by the wash water. The exhaust gas from which the acidic gas components have been removed in this way is released to the outside through the chimney. On the other hand, the cleaning water that has absorbed the acidic gas component has a p
Since H has a small value, an alkaline agent such as caustic soda is added to maintain the pH at 6-9. At this time, HC
Salt is generated by the neutralization reaction between 1 and NaOH, and the wash water containing the salt is withdrawn from the smoke washing tower 52.

The washing water drawn from the smoke washing tower 52 (hereinafter referred to as "smoke washing drainage") is a coagulation separation tank 53,
After passing through the filtration tank 54, the heavy metal collecting chelate tower 55, and the organic matter removing activated carbon adsorption tower 56, the salt water is discharged to the outside of the site such as a river. Here, in the coagulation / separation tank 53, the solid content coagulated and precipitated is removed. In addition, the filtration tank 54
At, solid components such as insoluble substances (SS) floating in the smoke washing wastewater are removed. In the heavy metal collecting chelate tower 55, heavy metals (lead, cadmium, mercury, etc.) are removed. Further, in the activated carbon adsorption tower 56 for removing organic substances, organic substances and dioxins are removed.

[0005]

However, in the conventional wet exhaust gas treatment system 50, the solid content and harmful substances in the smoke washing wastewater are removed, but the smoke washing wastewater is finally converted to salt water outside the river or the like. Therefore, there is a problem that salt damage may occur in the downstream area of the refuse incineration plant. Also, there is a problem that the running cost becomes high because it is necessary to always purchase caustic soda according to the amount of acid gas.

As a related prior art capable of solving such a problem, there is one disclosed in JP-A-11-10116. In this prior art, as shown in FIG. 4, the exhaust gas from the melting furnace is sent to a smoke scrubber 62 after the molten fly ash in the exhaust gas is removed by a dust collector 61, and the acidic gas components of the exhaust gas are discharged. Is neutralized with NaOH solution. The smoke washing wastewater generated by this neutralization is the neutralization tank 65.
Sent to. On the other hand, the molten fly ash collected by the dust collector 61 is put into an acid dissolution tank 63 filled with an acidic solution, and the heavy metals in the molten fly ash are dissolved in the acidic solution.
The acidic solution containing the heavy metals in a dissolved state is fed into the first coagulation / separation tank 64, and the first coagulation / separation tank 64 is supplied.
After the solid content is removed at, it is fed into the neutralization tank 65.
Then, in the neutralization tank 65, the acidic solution is neutralized by the residual NaOH in the smoke washing wastewater. The solution thus neutralized in the neutralization tank 65 is the second coagulation separation tank 66.
And the heavy metals are removed in the second coagulation / separation tank 66, and then sent to the electrodialysis tank 67. The solution sent to the electrodialysis tank 67 is a concentrated HCl solution and NaO.
Separated and extracted with H concentrated solution. Then, the separated and extracted HCl concentrated solution is sent to the acid dissolving tank 63 and is used again as an acidic solution. On the other hand, the separated and extracted Na
Part of the OH concentrated liquid is sent to the smoke scrubber 62 and used for neutralizing the acidic gas component, and the rest is sent to the neutralization tank 65 and used for neutralizing the acidic solution. On the other hand, the neutralized solution obtained by separating and extracting the HCl concentrated solution and the NaOH concentrated solution is
It is discharged as desalted water outside the river and other places. Therefore,
It is understood that the prior art can prevent the salt damage and reduce the running cost described above.

By the way, in the specification relating to the prior art, the electrodialysis tank 67 is provided with an electrode and a diaphragm (dialysis membrane), and the second coagulation is caused by an electric action (electrolysis). It is described that the solution sent from the separation tank 66 to the electrodialysis tank 67 is separated into an HCl concentrated solution and an NaOH concentrated solution. In this description, from the part related to the configuration and function of the electrodialysis tank 67, the electrodialysis tank 67 is understood to be an electrodialysis device having a known structure or an ion exchange membrane method soda electrolysis device having a known structure.

Here, an electrodialysis apparatus having a known structure will be described with reference to FIG. In an electrodialysis device having a well-known structure, a plurality of anion exchange membranes (A membranes) 73 and cation exchange membranes (C membranes) 74 are alternately arranged between an anode (anode) 71 and a cathode (cathode) 72. The cells are partitioned by the anion / cation exchange membranes 73 and 74. Then, by applying a DC voltage to the electrodes arranged at both ends, the cation Na ⁺ moves toward the cathode (− pole) 72 and the anion Cl ⁻ moves toward the anode (+ pole) 71 according to the potential gradient. try to. However, Na
⁺ Cannot pass through the anion exchange membrane 73. Also, Cl ⁻
Cannot pass through the cation exchange membrane 74. Therefore, diluted saline and concentrated saline are generated in every other cell. That is, in the electrodialysis device 70 having this well-known structure, N
It cannot be uniquely derived that the HCl concentrated solution and the NaOH concentrated solution are separated and extracted from the aCl solution.

Next, an ion exchange membrane method soda electrolysis device having a known structure will be described with reference to FIG. The ion-exchange membrane method soda electrolysis device having a well-known structure has an ion-exchange membrane 81.
The interior of the tank is divided into an anode chamber 82 and a cathode chamber 83 by means of which a NaCl solution and pure water are injected into the anode chamber 82 and the cathode chamber 82, respectively.
An anode (+ pole) 84 is arranged in the cathode chamber 83, and a cathode (− pole) 85 is arranged in the cathode chamber 83. When a DC voltage is applied to both electrodes, electricity is carried by Na ⁺ and the anode (+ pole) 84 Cl _{2 and} H ₂ from the cathode (−electrode) 85, respectively, and the anode chamber 8
The NaOH solution is generated in the cathode chamber 83 with the decrease in the concentration of the NaCl solution of 2. That is, in this ion exchange membrane method soda electrolysis device 80, a NaOH concentrated solution can be obtained, but an HCl concentrated solution cannot be obtained directly. In addition, Cl generated from the anode (+ electrode) 84
It is possible to obtain HCl concentrated solution by synthesizing HCl from H ₂ produced from the cathode ₂ and the cathode (−electrode) 85. However, such description or suggestion is not given in the specification of the prior art. Absent. However, the generated C
If a facility for synthesizing HCl from l ₂ and H ₂ to obtain an HCl concentrated solution is required, a large-scale facility must be introduced, and it is profitable to introduce such a large-scale facility in a waste treatment plant. It is actually impossible from the aspect of cost, cost, and management ability.

Therefore, in the electrodialysis tank 67 according to the prior art, the HCl concentrated solution and the NaOH concentrated solution are separated from the solution (NaCl solution) fed into the electrodialysis tank 67 from the second coagulation separation tank 66. The action effect of extracting cannot be derived.

Further, in the above-mentioned prior art, the solid content in the first coagulation / separation tank 64 is changed to the second coagulation / separation tank 65.
Although heavy metals are respectively removed in (1), removal of suspended solids (SS), soluble organic substances, and scale components (calcium, magnesium, silica, etc.) is not considered. Therefore, it is unlikely that the electrodialysis tank 67 operates stably and efficiently.

From the above description, the above-mentioned prior art cannot derive the action and effect described in the description of the prior art, and the above-mentioned problems have not yet been solved.

The present invention has been made in view of the above problems, and it is possible to significantly reduce the running cost in the wet exhaust gas treatment of a refuse incineration facility and prevent salt damage in the downstream region of the refuse incineration plant. An object of the present invention is to provide a wet exhaust gas treatment method and system capable of performing the same.

[0014]

In order to achieve the above object, the wet exhaust gas treatment method according to the first aspect of the present invention comprises a dust removal step of removing soot dust contained in the exhaust gas discharged from the refuse incinerator, While dissolving the acidic components of the exhaust gas from which the dust has been removed in the dust removal step in the cleaning liquid,
The exhaust gas cleaning step of neutralizing the cleaning liquid in which the acidic component is dissolved, the solid matter removing step of removing solid matter contained in the cleaning liquid neutralized in the exhaust gas cleaning step, and the neutralization in the exhaust gas cleaning step By the impurity removal step of removing impurities contained in the cleaning liquid, the acidic component of the exhaust gas is converted to N
In the wet exhaust gas treatment method of recovering as an aCl solution, the NaCl solution is electrodialyzed by a bipolar electrodialyzer to separate and extract a NaOH solution and an HCl solution from the NaCl solution.

In the present invention, the NaCl solution is electrodialyzed by a bipolar electrodialysis device,
A NaOH solution and an HCl solution are separated and extracted from the NaCl solution, and the NaCl solution is demineralized water. Usually, this desalinated water is discharged from the refuse incineration plant to the outside world such as a river. According to the invention said NaCl
It is possible to recover the valuable NaOH solution and HCl solution from the solution, and it is possible to prevent salt damage in the downstream region of the waste incineration plant because it is demineralized water that is discharged from the waste incineration plant to the outside.

In the first invention, before the NaCl solution is electrodialyzed by a bipolar electrodialyzer, its N
The aCl solution is preferably electrodialyzed with an electrodialyzer equipped with a cation exchange membrane and an anion exchange membrane (second
invention). In this way, the Na solution can be processed by the electrodialyzer equipped with the cation exchange membrane and the anion exchange membrane.
The concentrated NaCl solution and the diluted NaCl solution can be freely obtained from the Cl solution, in other words, the concentration of the NaCl solution can be freely adjusted, so that the electrodialysis in the bipolar electrodialyzer can be performed stably and efficiently. There is an effect that can be.

In the first invention or the second invention, it is preferable that the NaOH solution separated and extracted from the NaCl solution is used for neutralizing the cleaning solution in the exhaust gas cleaning step (third invention). By doing so, it is possible to reduce the amount of the alkaline agent added in the exhaust gas cleaning step, and thus it is possible to significantly reduce the running cost.

Next, the wet exhaust gas treatment system according to the fourth aspect of the present invention comprises a dust collector for removing soot and dust contained in the exhaust gas discharged from the refuse incinerator, and an acidic component of the exhaust gas from which soot and dust have been removed by the dust collector. An exhaust gas cleaning device for neutralizing the cleaning liquid in which this acidic component is dissolved, and a solid matter removing means for removing solids contained in the cleaning liquid neutralized by the exhaust gas cleaning device, and the exhaust gas. A wet exhaust gas treatment system, comprising: an impurity removing unit for removing impurities contained in a cleaning liquid neutralized by a cleaning device, and configured to recover an acidic component of the exhaust gas as a NaCl solution.
It is characterized in that a bipolar electrodialyzer for separating and extracting the H solution and the HCl solution is provided.

The present invention relates to a system for embodying the wet exhaust gas treatment method according to the first aspect of the invention, and has the same effects as the first aspect of the invention. In addition, the acidic components of the exhaust gas discharged from the refuse incineration facility are
For a wet exhaust gas treatment system that collects as an aCl solution,
Since the desired purpose can be achieved with a simple structure of providing the bipolar electrodialysis device, it can be easily attached not only to a new plant but also to an existing plant, and its operation and maintenance are relatively easy. It has the advantage of being easy.

In the fourth invention, an electrodialysis device for electrodialyzing the NaCl solution using a cation exchange membrane and an anion exchange membrane is preferably provided upstream of the bipolar electrodialysis device (fifth invention). . With this configuration, it is possible to achieve stable and efficient operation of the bipolar electrodialysis device due to the effects described in the second aspect of the invention.

In the fourth invention or the fifth invention, the N
It is preferable that the NaOH solution separated and extracted from the aCl solution is supplied to the exhaust gas cleaning device to neutralize the cleaning liquid in the exhaust gas cleaning device (sixth invention). By doing so, it is possible to reduce the amount of the alkaline agent added in the exhaust gas cleaning device, and thus it is possible to significantly reduce the running cost.

In the fourth invention to the sixth invention, the solid matter removing means includes an aggregating / separating device that removes solids contained in the cleaning liquid neutralized by the exhaust gas cleaning device by aggregating separation, and the exhaust gas cleaning device. And a filtering device that removes solids contained in the neutralized cleaning liquid by filtration, and the impurity removing means removes heavy metals contained in the cleaning liquid neutralized by the exhaust gas cleaning device. And a scale removing device for removing scale components contained in the cleaning liquid neutralized by the exhaust gas cleaning device (seventh invention). In this way, the solid content, heavy metals and scale components contained in the cleaning liquid neutralized by the exhaust gas cleaning device can be reliably removed, so that it is possible to remove an anisotropy in each device of the electrodialysis device and the bipolar electrodialysis device. It is possible to prevent the solid content, heavy metal, and scale components from depositing and depositing on the cation exchange membrane and the bipolar membrane, which contributes to stable operation and efficiency improvement of the electrodialysis device and the bipolar electrodialysis device.

In the fourth invention to the sixth invention, the solid matter removing means includes an aggregating / separating device that removes solids contained in the cleaning liquid neutralized by the exhaust gas cleaning device by aggregating separation, and the exhaust gas cleaning device. And a filtering device that removes solids contained in the neutralized cleaning liquid by filtration, and the impurity removing means removes heavy metals contained in the cleaning liquid neutralized by the exhaust gas cleaning device. And an organic matter removing device for removing organic matter contained in the cleaning liquid neutralized by the exhaust gas cleaning device, and a scale removing device for removing scale components contained in the cleaning liquid neutralized by the exhaust gas cleaning device. Is preferred (eighth invention). By doing so, the solid content, heavy metals and scale components contained in the cleaning liquid neutralized by the exhaust gas cleaning device are surely removed as in the seventh aspect of the invention, and the organic substances contained in the cleaning liquid are also ensured. Since it is removed, there is an effect that it contributes to stable operation and efficiency improvement of the electrodialysis device and the bipolar electrodialysis device.

In the fourth to eighth inventions, the Na
It is preferable that the NaOH solution separated and extracted from the Cl solution is configured to be used for backwashing a part or all of each device constituting the impurity removing means (9th embodiment).
invention). In this way, the amount of caustic soda that is newly added can be reduced, so that the running cost can be reduced.

In the seventh to ninth inventions, the Na
It is preferable that the HCl solution separated and extracted from the Cl solution is configured to be used for adjusting the pH of the aggregation and separation apparatus (the tenth invention). Further, in the fourth to tenth inventions, the HCl solution separated and extracted from the NaCl solution is used for backwashing a part or all of the respective devices constituting the impurity removing means. Is preferable (11th invention). In the fourth to eleventh inventions, the HC separated and extracted from the NaCl solution is used.
Preferably, the 1-solution is adapted to be used to neutralize plant effluent in a refuse incineration plant (twelfth invention). In any of the tenth invention to the twelfth invention, the amount of HCl solution newly introduced can be reduced, so that the running cost can be reduced.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Next, specific embodiments of a wet exhaust gas treatment method and system thereof according to the present invention will be described with reference to the drawings.

FIG. 1 is a system configuration diagram of a wet exhaust gas treatment system according to an embodiment of the present invention.

Wet exhaust gas treatment system 1 of the present embodiment
Includes a dust collector (corresponding to the dust collecting apparatus of the present invention) 2, a smoke washing tower (corresponding to the exhaust gas cleaning apparatus of the present invention) 3, a solid matter removing unit 4, and an impurity removing unit 7, which are not shown. Exhaust gas emitted from rugoly waste incineration equipment
Say. ) Is collected as an NaCl solution, and the acidic gas component (particularly HCl) of
An electrodialysis tank (corresponding to the electrodialysis apparatus of the present invention) 11 for adjusting the NaCl concentration of the Cl solution, and for separating and extracting the NaOH solution and the HCl solution from the NaCl solution whose concentration has been adjusted by the electrodialysis tank 11. And a bipolar electrodialysis tank 12 (corresponding to the bipolar electrodialysis apparatus of the present invention).

The dust collector 2 is used by appropriately selecting from a filter type dust collecting device, an electric type dust collecting device, a centrifugal force type dust collecting device, etc., and is adapted to remove the soot dust contained in the exhaust gas. Then, the exhaust gas from which dust is removed by the dust collector 2 is introduced into the smoke washing tower 3. Here, the filter-type dust collector is a system in which the exhaust gas containing soot and dust is entirely passed through a filter cloth or filter mainly composed of fibers and is filtered by a dust layer formed on the surface of the filter cloth. Further, the electric dust collector is a system in which the dust particles in the exhaust gas are charged by the static electricity from the discharge electrode due to the high DC voltage, and the charged dust particles are accumulated on the ground surface serving as a dust collecting electrode.
Further, the centrifugal force type dust collector is a method of separating the soot dust from the exhaust gas by swirling the exhaust gas containing the dust inside the device and collecting the soot dust on the wall surface of the dust collector by the centrifugal force to coagulate and compress it. Is.

The smoke washing tower 3 is a kind of an exhaust gas cleaning device, and introduces the exhaust gas from which the dust is removed by the dust collector 2 into the tower, and the cleaning liquid circulated in the tower with respect to the exhaust gas. By spraying from the spray nozzle, the acidic gas components (HCl, SOx, etc.) in the exhaust gas are absorbed in the cleaning liquid, and caustic soda is added to the cleaning liquid whose pH becomes a small value due to the absorption of the acidic gas components. The neutralization is carried out to maintain the pH of the cleaning liquid at 6-9. Then, the excess cleaning liquid in the smoke washing tower 3 is drawn out as smoke washing drainage. In addition, this smoke washing tower 3
Is not limited to the spray tower described above, and may be one of various other methods (such as a cyclone scrubber method, a venturi scrubber dehumidifying tower method, a tray method) such as a method in which a filling material such as Raschig ring is filled. .

The solid substance removing means 4 comprises a coagulation / separation tank (corresponding to the coagulation / separation apparatus of the present invention) 5 and a filtration tank (corresponding to the filtration apparatus of the present invention) 6. The coagulation / separation tank 5 coagulates and separates the smoke washing wastewater drawn out from the smoke washing tower 3 by a coagulation / separation action accompanying the addition of a coagulant, and the coagulated / precipitated solids It is designed to remove the minute. On the other hand, the filtration tank 6 is
A solid material (SS) which is an organic or inorganic substance suspended in the smoke washing waste water and which is not removed by a screen or the like is separated by a filter material.

The impurity removing means 7 includes a chelate tower for collecting heavy metals (corresponding to the heavy metal removing apparatus of the present invention) 8, an activated carbon adsorption tower for removing organic substances (corresponding to the organic substance removing apparatus of the present invention) 9, and scale removal. Chelating tower (corresponding to the scale removing device of the present invention) 10. The heavy metal collecting chelate tower 8 is configured to remove heavy metals (lead, cadmium, mercury, etc.) contained in the smoke washing wastewater by adding a chelating agent or adsorbing with a chelating resin. In addition, the activated carbon adsorption tower 9 for removing the organic matter
Is an adsorbent of activated carbon to remove organic substances and dioxins contained in the smoke washing wastewater. The scale removing chelate tower 10 is designed to remove scale components (calcium, magnesium, silica, etc.) contained in the smoke washing wastewater by adding a chelating agent or adsorbing with a chelating resin.
The arrangement of the chelate tower 8 for collecting heavy metals, the activated carbon adsorption 9 for removing organic substances, and the chelate tower 10 for scale removal is not limited to this, and can be freely rearranged. Also,
In each column constituting the impurity removing means 7, each component to be removed may be omitted if it does not affect the system and the regulation value.

Thus, the smoke washing wastewater (NaCl solution) from which solid matters, heavy metals, organic substances, scale components, etc. in the smoke washing wastewater have been sufficiently removed by the solid matter removing means 4 and the impurity removing means 7 is electrodialysis tank 11 By introducing the electrodialysis tank 11 and the bipolar electrodialysis tank 12 into the electrodialysis tank 11 and the bipolar electrodialysis tank 12, a metal is used for the ion exchange membrane and the bipolar membrane that compose the electrodialysis tank 11 and the bipolar electrodialysis tank 12. Oxides, alkaline earth metals, high molecular weight organic acids and the like are prevented from depositing and depositing, and stable and highly efficient operation of the electrodialysis tank 11 and the bipolar electrodialysis tank 12 is enabled.

The electrodialysis tank 11 has a well-known structure as shown in FIG. 5A, and as described above, an anion exchange membrane (A membrane) 73 is provided between the anode 71 and the cathode 72.
A plurality of cells and cation exchange membranes (C membranes) 74 are alternately arranged to form cells, and by applying a DC voltage to the electrodes arranged at both ends, diluted saline and concentrated saline are alternately placed. Is configured to be generated within the cell of. Thus, the smoke washing wastewater (NaC) introduced into the electrodialysis tank 11
(1 solution) can be adjusted to a concentration such that it can be concentrated to an operable concentration of the bipolar electrodialysis tank 12 disposed downstream, or can be maintained at an appropriate concentration for stable operation of the bipolar electrodialysis tank 12. Is being done. If a state where the concentration of NaCl in the smoke washing wastewater introduced into the electrodialysis tank 11 is as high as 5 wt% or more is always ensured, the electrodialysis tank 11 may be omitted. .

The bipolar electrodialysis tank 12 has a structure known per se as shown in FIG. 2, in which a bipolar membrane (B) 15 and an anion exchange membrane ( A) 16, cation exchange membrane (C) 17,
A plurality of each of the bipolar membranes (B) 15 are sequentially arranged to form a cell, and a DC voltage is applied to the electrodes arranged at both ends of the cell to form a bipolar membrane (B) 15 and an anion exchange membrane ( HCl solution from inside the cell partitioned with A) 16 and NaO from within the cell partitioned with bipolar membrane (B) 15 and cation exchange membrane (C) 17.
From the inside of the cell where the H solution is partitioned and formed by the anion exchange membrane (A) 16 and the cation exchange membrane (C) 17, NaCl is removed.
The water is configured to be separated and extracted.

Next, the exhaust gas treatment from the refuse incineration facility in the wet exhaust gas treatment system 1 of this embodiment will be described.

In the wet exhaust gas treatment system 1 of this embodiment, the exhaust gas introduced into the dust collector 2 is the dust collector 2
After the soot and dust are removed, it is introduced into the smoke washing tower 3. Then
The exhaust gas introduced into the smoke washing tower 3 is washed with the wash water sprayed and circulated in the smoke washing tower 3, and the acidic gas components (HCl, SOx, etc.) in the exhaust gas are absorbed in the wash water. The exhaust gas from which the acidic gas components have been removed in this way is released to the outside through the chimney. On the other hand, the cleaning water that has absorbed the acidic gas component has a p
Since H has a small value, an alkaline agent such as caustic soda is supplied to maintain the pH at 6-9. At this time, HC
Salt is generated by the neutralization reaction between 1 and NaOH, and the wash water containing the salt is withdrawn from the smoke washing tower 3.

The washing water drawn out from the smoke washing tower 3, that is, the smoke washing waste water, is subjected to the coagulation separation tank 5, the filtration tank 6, the heavy metal collecting chelate tower 8, the organic matter removing activated carbon adsorption tower 9 and the scale removing chelate. After passing through the tower 10, the solid content that has been aggregated and precipitated, the solid content such as the suspended insoluble substance (SS),
Heavy metals (lead, zinc, mercury, etc.), organic substances (including dioxins) and scale components (calcium, magnesium, silica, etc.) are removed.

The smoke washing waste water discharged from the scale removing chelate tower 10 is introduced into the electrodialysis tank 11 and the NaCl concentration is adjusted by the electrodialysis treatment. here,
When the smoke washing wastewater introduced into the electrodialysis tank 11 is a dilute NaCl solution, N
The aCl concentration is concentrated to 5 to 30 wt%. The smoke-washing wastewater thus adjusted to have a NaCl concentration of 5 to 30 wt% is introduced into the bipolar electrodialysis tank 12 and is subjected to electrodialysis treatment to remove NaCl water and 5 to 20 wt% of N 2.
The aOH solution and the 5 to 20 wt% HCl solution are separately extracted.

The NaCl-free water separated and extracted in the bipolar electrodialysis tank 12 is returned to the upstream of the electrodialysis tank 11 or discharged outside the plant site. On the other hand, the separated and extracted NaOH solution is used for neutralizing the acidic gas in the smoke washing tower 3 or the chelate tower 8 for collecting heavy metals.
It is also used for backwashing the activated carbon adsorption tower 9 for removing organic substances and the chelate tower 10 for removing scale. On the other hand, the separated and extracted HCl solution is used for adjusting the pH of the coagulation / separation tank 5, and for backwashing the heavy metal collecting chelate tower 8, the organic matter removing activated carbon adsorption tower 9, and the scale removing chelate tower 10. It is also used as a wastewater treatment plant, or for neutralizing plant wastewater in other waste incineration plants.

According to the present embodiment, the HCl solution and the NaOH solution as valuables can be recovered from the smoke washing wastewater, and the HCl solution and the NaOH solution are reused in the internal and external systems of the system, so that the running cost is greatly reduced. At the same time, it can play a part in building a resource recycling society. In addition, since it is the NaCl-free water separated and extracted in the bipolar electrodialysis tank 12 that is discharged outside the plant site, salt damage is not caused in the downstream region of the plant. Further, in the present embodiment, the conventional wet exhaust gas treatment system 50 shown in FIG. 3 can be used as it is, and the conventional wet exhaust gas treatment system 50 is provided with the scale removing chelate tower 10 and the electrodialysis tank 11 (may be omitted in some cases. ), Since the desired purpose can be achieved by adding the bipolar electrodialysis tank 12, the system can be easily changed even in the existing plant, and the system can be changed at low cost.

As described above, the wet exhaust gas treatment system 1 of the present embodiment surely removes solids, heavy metals, organic substances, scale components, etc. in the smoke washing waste water and adjusts the NaCl concentration in the electrodialysis tank 11. It is a system constructed from the viewpoint of operating the bipolar electrodialysis tank 12 stably and efficiently by sufficiently performing pretreatment such as adjusting to an appropriate concentration, and it can be said that the system is effective. .

In this embodiment, the example in which the present invention is applied to the wet treatment of the exhaust gas from the refuse incineration facility is shown, but according to the gist of the present invention, the present invention is applied to the wet treatment of the exhaust gas from the ash melting facility. It goes without saying that the invention can be applied.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a wet exhaust gas treatment system according to an embodiment of the present invention.

FIG. 2 is a structural explanatory view of a bipolar electrodialysis device.

FIG. 3 is a system configuration diagram of a conventional wet exhaust gas treatment system.

FIG. 4 is a system configuration diagram of a wet exhaust gas treatment system according to related art.

FIG. 5 is a structural explanatory diagram (a) of an electrodialysis device and a structural explanatory diagram (b) of an ion exchange membrane method soda electrolysis device.

[Explanation of symbols]

1 Wet exhaust gas treatment system 2 dust collector 3 smoke tower 4 Solids removal means 5 coagulation separation tank 6 filtration tanks 7 Impurity removing means 8 Chelating tower for heavy metal collection 9 Activated carbon adsorption tower for organic matter removal 10 Scale removing chelate tower 11 electrodialysis tank 12 Bipolar electrodialysis tank

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01D 61/44 520 C01B 7/01 H 61/46 500 C01D 1/04 Z 61/52 500 3/04 Z 61/58 C02F 1/42 H C01B 7/01 1/52 K C01D 1/04 5/00 610C 3/04 620B C02F 1/42 620C 1/469 1/00 L 1/52 B01D 53/34 134B 5 / 00 610 125C 620 ZAB C02F 1/46 103 // C02F 1/00 F term (reference) 4D002 AA02 AA19 AB01 AC04 BA02 CA01 DA35 EA07 EA13 FA04 4D006 GA17 KA01 KA52 KB12 KB13 KB14 MA13 MA14 MA15 PA02 PA05 P280880 PB27 P80 CA20 EA12 EA32 FA02 FA15 4D025 AA09 AB25 AB27 AB28 BA17 4D061 DA08 DB18 EA09 EB04 EB13 FA06

Claims (12)

[Claims] 1. A dust removal step of removing soot and dust contained in exhaust gas discharged from a refuse incineration facility, and an acidic component of exhaust gas from which soot dust has been removed in the dust removing step is dissolved in a cleaning liquid, and this acidic component is dissolved. An exhaust gas cleaning step of neutralizing the cleaning solution, a solid matter removing step of removing solid matter contained in the cleaning solution neutralized in the exhaust gas cleaning step, and impurities contained in the cleaning solution neutralized in the exhaust gas cleaning step. In the wet exhaust gas treatment method of recovering the acidic component of the exhaust gas as a NaCl solution by the impurity removing step to be removed, the NaCl solution is electrodialyzed with a bipolar electrodialysis device to obtain a NaOH solution and an HCl solution from the NaCl solution. A method for treating a wet exhaust gas, which comprises: 2. The wet method according to claim 1, wherein the NaCl solution is electrodialyzed by an electrodialyzer equipped with a cation exchange membrane and an anion exchange membrane before electrodialyzing the NaCl solution by a bipolar electrodialysis machine. Exhaust gas treatment method. 3. N separated and extracted from the NaCl solution
The wet exhaust gas treatment method according to claim 1, wherein the aOH solution is used for neutralizing the cleaning liquid in the exhaust gas cleaning step. 4. A dust collector for removing soot and dust contained in the exhaust gas discharged from the refuse incinerator, and an acidic component of the exhaust gas from which the soot and dust has been removed by the dust collector are dissolved in a cleaning liquid, and the acidic component is Included in the exhaust gas cleaning device for neutralizing the dissolved cleaning liquid, solid matter removing means for removing solids contained in the cleaning liquid neutralized by the exhaust gas cleaning device, and the cleaning liquid neutralized by the exhaust gas cleaning device A wet exhaust gas treatment system, comprising: an impurity removing means for removing impurities, configured to recover an acidic component of the exhaust gas as a NaCl solution, and a bipolar for separating and extracting a NaOH solution and an HCl solution from the NaCl solution. A wet exhaust gas treatment system comprising an electrodialysis device. 5. An upstream of the bipolar electrodialysis device,
The wet exhaust gas treatment system according to claim 4, further comprising an electrodialysis device for electrodialyzing the NaCl solution using a cation exchange membrane and an anion exchange membrane. 6. N separated and extracted from the NaCl solution
The wet exhaust gas treatment system according to claim 4 or 5, wherein an aOH solution is supplied to the exhaust gas cleaning device and is configured to neutralize a cleaning liquid in the exhaust gas cleaning device. 7. The solid matter removing means includes a coagulation / separation device for removing solids contained in the cleaning liquid neutralized by the exhaust gas cleaning device by coagulation separation, and a cleaning liquid neutralized by the exhaust gas cleaning device. And a filtering device for removing solid content by filtration, and the impurity removing means is a heavy metal removing device for removing heavy metals contained in the cleaning liquid neutralized by the exhaust gas cleaning device, and the exhaust gas cleaning device. The wet exhaust gas treatment system according to any one of claims 4 to 6, which comprises a scale removing device that removes scale components contained in the neutralized cleaning liquid. 8. The solid matter removing means includes a coagulation / separation device for removing solids contained in the cleaning liquid neutralized by the exhaust gas cleaning device by coagulation separation, and a cleaning liquid neutralized by the exhaust gas cleaning device. And a filtering device for removing solid content by filtration, and the impurity removing means is a heavy metal removing device for removing heavy metals contained in the cleaning liquid neutralized by the exhaust gas cleaning device, and the exhaust gas cleaning device. 7. An organic matter removing device for removing organic matter contained in the neutralized cleaning liquid, and a scale removing device for removing scale components contained in the cleaning liquid neutralized by the exhaust gas cleaning device. A wet exhaust gas treatment system according to claim 1. 9. N separated and extracted from the NaCl solution
The wet exhaust gas treatment system according to any one of claims 4 to 8, wherein the aOH solution is configured to be used for backwashing a part or all of each device constituting the impurity removing means. 10. The wet exhaust gas treatment system according to claim 7, wherein the HCl solution separated and extracted from the NaCl solution is configured to be used for adjusting the pH of the coagulation / separation device. 11. The method according to claim 4, wherein the HCl solution separated and extracted from the NaCl solution is used for backwashing a part or all of each device constituting the impurity removing means. A wet exhaust gas treatment system according to claim 1. 12. The HCl solution separated and extracted from the NaCl solution is configured to be used for neutralizing plant wastewater in a refuse incineration plant.
11. The wet exhaust gas treatment system according to any one of 11.