JPH10235140A - Exhaust gas treatment equipment in waste refuse incineration facility and treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To almost perfectly decompose and remove dioxin in fly ash and to also conserve required chemical cost and ash treatment cost. SOLUTION: This treatment equipment constituted so that exhaust gas discharged from a waste refuse incinerator 1 is introduced into a re-combustion chamber 1 to be re-burned to be guided to a bag filter 51 through appropriate cooling means 3, 4 and soot and acidic harmful gas in the exhaust gas are removed by the harmful gas neutralizing chemical agent supplied to the bag filter 51, is provided with a collected ash circulating apparatus 8 capable of introducing the collected ash 86 shaken off by the bag filter 51 into the re- combustion chamber 2 and a re-burnt ash treatment apparatus 9 introducing the re-burnt ash 94 accumulated on the bottom part of the re-combustion chamber 2 into the inlet of the bag filter 51. An activated carbon storage tank 55 supplying activated carbon 54 adsorbing dioxin is connected to the inlet of the bag filter 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment facility in a refuse incineration facility for incinerating refuse such as general waste and industrial waste, and a method for treating the same.

[0002]

2. Description of the Related Art Exhaust gas discharged from refuse incineration facilities contains toxic dioxins in addition to soot and dust, and various kinds of dioxins are required to decompose and remove these dioxins. Measures have been taken.

FIG. 5 is a schematic diagram showing the configuration of a conventional refuse incineration facility disclosed in Japanese Patent Application Laid-Open No. 5-23539.

In FIG. 5, reference numeral a denotes a combustion furnace, and a boiler c is continuously provided through a gas mixing chamber b provided at an outlet side of the combustion furnace a, and the temperature of the exhaust gas drops to 600 to 700 ° C. , A high-temperature dust collector d is installed.

A reaction tower f having a sprayer e at the head and a bag filter h having a screw conveyor g at the bottom are connected on the exhaust side of the boiler c. And is released into the atmosphere from the chimney j.

On the other hand, a chute pipe k, a conveyor m, and a bucket elevator n are connected to the discharge side of the screw conveyor g, and collected ash removed from the bag filter h is collected by the chute pipe k, the conveyor m. ,
It is sent through a bucket elevator n to a chute p installed above the combustion furnace a.

Next, a description will be given of a process of treating exhaust gas, fly ash, and the like in the refuse incineration facility configured as described above.

[0008] The flue gas of about 800 ° C containing fly ash composed of incombustibles and unburned matter generated from the combustion furnace a and acidic toxic gas and dioxins is reburned in the gas mixing chamber b. After that, it is introduced into the boiler c and cools down.
The fly ash contained is filtered and removed by the high-temperature dust collector d in the high-temperature zone of 00 ° C. or higher, and even a small amount of organochlorine compounds attached to the fly ash generate dioxins.
Most are designed to be pyrolyzed.

Next, the exhaust gas subjected to the primary treatment is introduced into the reaction tower f, and the contained acidic harmful gas is neutralized by an alkali agent such as slaked lime slurry sprayed from the sprayer e.

The bag filter h in the next step filters and removes fly ash, organochlorine compounds, neutralization reaction products, and unreacted chemicals that could not be removed by the high-temperature dust collector d, and purifies the exhaust gas. The gas is sucked by the induction ventilator i and released into the atmosphere from the chimney j.

The above collected ash collected by the bag filter h is removed as appropriate, and then the screw conveyor g, the chute pipe k, the transport conveyor m, the bucket elevator n
Through the chute p into the combustion furnace a,
The organic chlorine compound, the neutralization reaction product and the unreacted chemical are decomposed by heating in the gas mixing chamber b at ℃, and the remaining trapped ash is collected from the recovery ports q and r provided at the bottom of the combustion furnace a and the boiler c. It is discharged outside.

[0012]

However, in the above-mentioned conventional refuse incineration facility, Ca, which is a harmful gas neutralizing agent sprayed in the reaction tower f and recovered in the bag filter h, is recovered from the recovery ports q and r. Because it is discharged outside the facility, it is not reused, so that it is not possible to save the consumption of expensive chemicals, but also the amount of collected ash (discharged ash), which is a specially managed waste, is not reduced, thus reducing post-processing costs. Was also impossible.

[0013] In the high tropics of 800 ° C or higher, quick lime [CaO] is generated by thermally decomposing the reaction product [CaCl ₂ ] and the unreacted drug [Ca (OH) ₂ ]. Residual CaO, which cannot be completely combined with chlorine in exhaust gas due to solid-gas contact, is discharged as it is, which is dangerous because it reacts with moisture in the surroundings or atmosphere and generates high heat.

Further, the organic chlorine compound thermally decomposed almost completely in the reburning chamber b is then resynthesized from the reaction tower f between the bag filters h to form dioxins. There was a problem that the collection was incomplete.

On the other hand, in the activated carbon adsorption method for removing dioxins, which is generally performed in addition to the above-mentioned conventional one, the activated carbon having adsorbed dioxins is discharged to the outside as it is, so that the amount of ash discharged increases. In addition, there is a problem that post-processing costs are further increased.

[0016]

An exhaust gas treatment facility in a refuse incineration facility according to claim 1 of the present invention is provided in a refuse incineration facility for incinerating refuse such as general waste and industrial waste, and is provided from a refuse incinerator. After the discharged exhaust gas is introduced into the reburning chamber and reburned, the exhaust gas is guided from the reburning chamber to the bag filter via an appropriate cooling means, and the exhaust gas is discharged by the harmful gas neutralizing agent supplied to the bag filter. In an exhaust gas treatment facility configured to remove dust and acidic harmful gas contained therein, a collection ash circulating device capable of introducing collected ash removed by the bag filter to the reburning chamber is provided. And a reburn ash treatment device for introducing reburn ash deposited at the bottom of the reburn chamber to the inlet side of the bag filter.

According to a second aspect of the present invention, there is provided an exhaust gas treatment system in a refuse incineration plant, wherein an activated carbon supply device for supplying activated carbon for adsorbing dioxins is connected to the inlet side of the bag filter.

According to a third aspect of the present invention, there is provided a method for treating exhaust gas in a refuse incineration facility, wherein the exhaust gas discharged from the refuse incinerator is introduced into a reburning chamber for reburning, and then an appropriate cooling means is provided from the reburning chamber. Exhaust gas to a bag filter through the filter, and removes soot and acid harmful gas contained in the exhaust gas by a harmful gas neutralizing agent supplied to the bag filter, the exhaust gas treatment method in a garbage incineration facility, wherein the inlet of the bag filter Activated carbon is introduced to the side, dioxins are adsorbed by the activated carbon, and the collected ash containing the activated carbon that is removed by the bag filter is introduced into the reburning chamber,
While pyrolyzing chlorine compounds such as calcium chloride and dioxins in the collected ash, and burning the activated carbon, lime is deposited by injecting reburn ash deposited at the bottom of the reburn chamber toward the inlet side of the bag filter. Reuse.

According to a fourth aspect of the present invention, in the exhaust gas treatment method for a refuse incineration plant, the bag filter uses a harmful gas neutralizing agent and activated carbon on the surface of the filter cloth of the bag filter before starting the filtering operation. A precoat layer is formed.

[0020]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram centering on an exhaust gas treatment facility in a refuse incineration plant according to claim 1 or 2 of the present invention.

In FIG. 1, reference numeral 1 denotes a refuse incinerator for incinerating refuse such as general waste or industrial waste.
By 1, the incinerator 1 and the separately installed reburning chamber 2 are connected to each other, and connected to a chimney 62 via a gas cooling device 3, a residual heat utilization device 4, a bag filter 51, and an induction ventilator 61.

Here, the reburn chamber 2 includes a reburn chamber main body 21 made of a refractory or the like, and a reburn burner 22 provided upstream of the reburn chamber main body 21 for reburning the combustion gas 71.
A collecting ash supply mechanism 23 attached to the upper side wall of the reburning chamber main body 21; a hopper 24 provided at the bottom of the reburning chamber main body 21 to deposit ash in the reburning chamber main body 21;
Ash discharge mechanism 25 provided at the discharge port 4 and hopper 24
And an outlet duct 26 connected above.

The residual heat utilization device 4 is mainly composed of an air preheater 41 and other heat exchangers 42, cools the gas flowing therethrough, heats the air supplied from the forced air blower 43, and incinerates the refuse. This is a device for supplying necessary parts such as a furnace 1, a reburning chamber 2, a reburning ash treatment device described later, hot water supply / heating means (not shown) and the like.

The bag filter 51 is composed of a plurality of unit dust collecting mechanisms and accessories, and an exhaust gas duct 44 connected to the inlet side of the bag filter 51 is provided for neutralizing an acidic harmful gas such as slaked lime. A neutralizing medicine storage tank 53 for storing the medicine 52 and an activated carbon storage tank 55 for storing the powdered activated carbon 54 are connected to each other via a discharge mechanism. And, these neutralizing agent storage tank 53 and activated carbon storage tank 55
Each of the medicines discharged from the above is configured to be pressure-fed to the exhaust gas duct 44 by the medicine injection means 56 for branching and sucking a part of the clean gas 75.

The bag filter 51 and the neutralizing chemical storage tank 5
3. The harmful gas removing device 5 is constituted by the activated carbon storage tank 55 and the chemical injection means 56.

Below the plurality of discharge mechanisms at the bottom of the bag filter 51, a screw conveyor 81 is provided over each discharge mechanism.
Is disposed, and a collecting ash storage tank 82 is connected to the discharge end of the screw conveyor 81.

A reversible conveyor 83 is connected to the lower end of the collected ash storage tank 82. At one end of the reversible conveyor 83, a collecting ash transfer means 84 including a transport conveyor 841, a bucket elevator 842 and the like is continuously provided, and at the other end of the reversible conveyor 83, a discharge hopper 85 is provided. The collected ash discharged from the lower end of the collected ash storage tank 82 can be selectively transported to the collected ash transfer means 84 and the off-site unloading hopper 85 by switching the transport direction of the reversible conveyor 83. It is configured.

The screw conveyor 81, the collected ash storage tank 82, the reversible conveyor (conveyance to the collected ash transferring means 84) 83 and the collected ash transferring means 84 constitute a collected ash circulating device 8.

Below the ash discharging mechanism 25, a reburn ash storage tank 91 is provided. The discharge end of the reburn ash storage tank 91 is connected to the exhaust gas duct 44 by an air supply pipe 93 provided with an air supply amount adjusting valve 92. These reburn ash storage tanks 9
1. The refueling ash treatment device 9 is constituted by the air supply amount adjusting valve 92 and the empty feed pipe 93.

Note that a heat insulation work is performed outside each of the above devices.

Next, a method of treating harmful gases, pyrolyzing dioxins and recycling Ca (calcium) content by the exhaust gas treatment equipment constructed as described above is shown in FIGS.
This will be described with reference to FIG.

The combustion gas 71 generated in the refuse incinerator 1, whose temperature tends to fluctuate, is introduced into the reburning chamber 2, and is heated to a temperature of 800 ° C. or more by the flame of the reburning burner 22 and the reburning air 45. As a result, unburned carbons, which are precursors of dioxin generation, and unburned gases that cause malodor are completely incinerated.

At the same time, the dioxins contained therein are also thermally decomposed and then sent to the gas cooling device 3 as reburn gas 72.

At this time, non-combustible substances having a high specific gravity accompanying the reversal of the gas flow at the lower portion of the reburning chamber main body 21 are separated from the reburning gas 72 by centrifugal force and deposited on the bottom of the hopper 24.

The reburned gas 72 from which incombustible substances and the like have been separated is cooled in the gas cooling device 3 and then further cooled by the following heat exchange in the residual heat utilization device 4 to become exhaust gas 74, and passes through the exhaust gas duct 44. , And enters the bag filter 51.

On the other hand, the room-temperature air blown to the air preheater 41 by the push-in blower 43 exchanges heat with the high-temperature gas passing through the air preheater 41 to become high-temperature air. Combustion air 46 of furnace 1
In addition, it is used for the later-mentioned re-burning of ash.

Here, as shown in FIG. 3, a primary adhesion layer 512 made of slaked lime or the like is formed on the surface of the filter cloth 511 in the bag filter 51 in advance.

Then, in this state, the neutralizing agent 52 such as slaked lime is fed from the neutralizing agent storage tank 53 through the exhaust gas duct 44 by the chemical injection means 56, and the primary adhesion layer 5 is removed.
A drug layer 513 is formed on the substrate 12 (see FIG. 3).

Subsequently, the activated carbon 54 is similarly fed from the activated carbon storage tank 55 by air to form an activated carbon layer 514 on the drug layer 513, and a two-stage precoat layer is formed in combination with the drug layer 513 (see FIG. 3).

After the pre-coat layer is formed in this manner, the operation proceeds to the filtering operation in the bag filter 51, and the acidic harmful gas in the exhaust gas 74 introduced into the bag filter 51 is neutralized by the chemical layer 513, and The dioxins that cannot be completely decomposed by thermal decomposition in the reburning chamber 2 or are regenerated from the gas cooling device 3 to the residual heat utilization device 4 are adsorbed on the activated carbon layer 514.

On the other hand, the soot and dust that continues to fly along with the exhaust gas 74 is filtered and deposited on the surface of the precoat layer to form a dust layer 515, and the exhaust gas 74 is discharged as a completely harmless clean gas 75 (FIG. 3).

If the neutralization / adsorption / filtration operation using the precoat layer is continued and the pressure difference between the inside and outside of the filter cloth portion or the concentration of the harmful gas in the clean gas 75 exceeds a specified value, a cleaning means (not shown) As a result, the pre-coat layers 513 and 514 and the dust layer 515 adhering to the surface of the primary adhesion layer 512 are removed to form the collected ash 86, and then the pre-coat layer 51 is again applied to the surface of the primary adhesion layer 512 in the same manner as described above.
3, 514 and return to the filtration operation described above.

The components of the collected ash 86 include incombustible substances such as ash, activated carbon adsorbing dioxins and mercury, and HC.
l (hydrochloric acid), such as CaCl ₂ (calcium chloride), unreacted drug Ca (OH) ₂ (slaked lime), and Ca such as CaCO ₃ (calcium carbonate) reacted with CO ₂ (carbon dioxide). The collected ash 86 is stored in a collected ash storage tank 82 via a screw conveyor 81 from the bottom of the bag filter 51.

The collected ash 8 continuously stored in the collected ash storage tank 82
6 is discharged only for a short period of time, for example, 2 hours out of 24 hours in the stable period of the combustion state, and is passed through the reversible conveyor 83 and the collected ash transfer means 84, and is collected in the reburning chamber main body 21 by the collected ash supply mechanism 23. Supplied in batches.

As described above, the reburning chamber main body 21 is maintained at a reburning atmosphere of 800 ° C. or more by the high temperature of the combustion gas 71, the heating by the reburning burner 22, and the supply of the reburning air 45. Ash 8 supplied for
The activated carbon 54 and the unburned matter in 6 are completely incinerated into carbon dioxide gas, and the dioxins adsorbed on the activated carbon 54 are thermally decomposed into inorganic chlorine gas or inorganic chlorine compounds.

The above-mentioned respective Ca components are thermally decomposed to form CaO.
(Quick lime), is centrifuged out of the reburning gas 72 together with non-combustible substances, and is deposited on the hopper 24 to form reburning ash 94.
The ash is discharged from the ash discharging mechanism 25 to the reburnable ash storage tank 91 in a timely manner.

Further, quicklime, which is a thermal decomposition product of the collected ash, becomes stable calcium chloride in the bag filter, so that there is no danger in operation.

The Ca stored in the reburn ash storage tank 91
A predetermined amount of the reburned ash 94 containing O is continuously supplied to the exhaust gas duct 44 via the air supply pipe 93 by the return air 47 supplied from the air supply amount adjustment valve 92, and Ca content is contained in the dust tank 515. It has been made to add. Thus, C
The portion a is circulated and reused except for a part of the amount to be described later, so that the amount of the neutralizing agent 52 for forming the agent layer 513 can be greatly reduced.

That is, due to the recirculation of the reburn ash 94 described above, the Ca component and the incombustibles constituting the reburn ash 94 circulate in the bag filter 51, the collection ash circulating device 8, the reburn chamber 2, and the reburn ash treatment device 9. .

HCl separated from CaCl _{2 in the} reburning chamber 2 is circulated through the gas cooling device 3, the residual heat utilization device 4, the bag filter 51, the trapping ash treatment device 8, and the inside of the reburning chamber 2. The incombustibles ratio and the HCl content gradually increase.

Therefore, when the level detector 87 (see FIG. 1) provided in the collected ash storage tank 82 detects that the collected ash 86 has been stored more than a specified amount, the reversible conveyor 83 is reversed to rotate the reversible conveyor 83 by a predetermined amount. Is discharged to the outside transport hopper 85 to cope with the above-described increase / concentration phenomenon.

This partial discharge operation may be performed on a fixed time schedule according to a command from a control panel (not shown) for controlling and monitoring the entire operation cycle. Also, the operation of transferring the collected ash 86 to the reburning chamber 2 may be a batch operation in which the control panel disassembles the collected ash 86 three to four times a day.

Although the precoat layer has been described as having a two-layer structure of the drug layer 513 and the activated carbon layer 514, as shown in FIG. 4, after forming the precoat layer with the drug layer 513, the activated carbon 54 is filtered during the filtering operation. A continuous mixing system entrained in the exhaust gas 74 or a neutralizing agent 52 and activated carbon 5 (not shown) may be used.
4 and a mixed precoat layer forming method.

The method of continuously injecting the reburn ash 94 into the exhaust gas 74 during the filtering operation has been described. However, in order to improve the releasability, the reburn ash 94 is used as a base layer of the precoat layer, and each of the above-mentioned precoat layers is used as a surface layer. After forming the pre-coat layer, a filtration operation may be started.

Further, a method has been described in which a clean gas 75 is used for emptying the neutralizing agent 52 and the activated carbon 54, and high-temperature air heated by the air preheater 41 is used for the reburning air 45 and the returning air 47. However, each fluid supply source is not limited, and each drug and ash transportation means may be a method other than the description.

[0057]

As described above, according to the present invention, the collected ash removed by the bag filter is introduced into the reburning chamber, and the calcium ash in the collected ash neutralized with the acidic harmful gas is removed. Pyrolysis is generated by pyrolysis, and is introduced into the bag filter from the bottom of the reburning chamber as reburning ash, so that quicklime contained in the reburning ash can be reused as a neutralizing reactant. The use amount can be greatly reduced.

Activated carbon is fed into the bag filter, dioxins are adsorbed by the activated carbon, and the activated carbon adsorbed with the dioxins is collected as ash to be incinerated in a reburning chamber to form carbon dioxide gas. Can be pyrolyzed,
Detoxification of dioxins can be reliably achieved.

Therefore, the collected ash which is a special management waste is also:
Emissions are reduced by the amount of the activated carbon that has been vaporized and the amount of the drug that has been saved, thereby reducing the cost of post-treatment.

Further, by forming a precoat layer of a harmful gas neutralizing agent and activated carbon on the surface of the filter cloth of the bag filter, it is possible to more reliably perform the detoxification treatment of dioxins.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of an exhaust gas treatment facility in a refuse incineration facility according to the present invention.

FIG. 2 is a schematic flowchart illustrating an exhaust gas treatment method according to the present invention.

FIG. 3 is a cross-sectional view showing a state of deposition on the surface of a filter cloth.

FIG. 4 is a cross-sectional view showing another deposition state of the filter cloth surface.

FIG. 5 is a schematic configuration diagram showing a configuration of a conventional refuse incineration facility.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 refuse incinerator 2 reburn chamber 3 gas cooling device 4 residual heat utilization device 51 bag filter 52 neutralizing agent 54 activated carbon 55 activated carbon storage tank 8 collecting ash circulation device 86 collecting ash 9 reburn ash treatment device 94 reburn ash

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[Procedure amendment]

[Submission date] March 10, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FIF23G 5/14 ZAB B01D 53/34 134E

Claims (4)

[Claims] 1. A waste incineration facility for incinerating waste such as municipal waste and industrial waste is provided, and exhaust gas discharged from a waste incinerator is introduced into a reburning chamber and recombusted, and then reburned. In an exhaust gas treatment facility configured to guide exhaust gas to a bag filter through an appropriate cooling means and remove soot and acidic harmful gas contained in the exhaust gas by a toxic gas neutralizing agent supplied to the bag filter. A collecting ash circulating device capable of introducing collected ash removed by the bag filter into the reburn chamber is provided, and reburn ash deposited at the bottom of the reburn chamber is introduced to an inlet side of the bag filter. An exhaust gas treatment facility in a refuse incineration plant, which is provided with a reburning ash treatment device. 2. An exhaust gas treatment facility in a refuse incineration plant according to claim 1, wherein an activated carbon supply device for supplying activated carbon for adsorbing dioxins is connected to an inlet side of said bag filter. 3. After the exhaust gas discharged from the refuse incinerator is introduced into the reburning chamber and reburned, the exhaust gas is guided from the reburning chamber to the bag filter via an appropriate cooling means and supplied to the bag filter. In an exhaust gas treatment method in a refuse incineration facility for removing soot and acid harmful gas contained in exhaust gas with a harmful gas neutralizing agent, activated carbon is introduced into the inlet side of the bag filter, and dioxins are adsorbed by the activated carbon. The collected ash containing the activated carbon removed by the bag filter is introduced into the reburning chamber to thermally decompose chlorine compounds such as calcium chloride and dioxins in the collected ash while burning the activated carbon. The refuse incineration facility is characterized in that lime is reused by injecting reburn ash deposited on the bottom of the reburn chamber into the inlet side of the bag filter. Exhaust gas processing method that. 4. The bag filter according to claim 3, wherein a pre-coat layer is formed on the surface of the filter cloth of the bag filter using a harmful gas neutralizing agent and activated carbon before starting the filtering operation. Exhaust gas treatment method at refuse incineration facilities.