JP2000093743A - Method for treating exhaust gas from refuse incinerator and treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly cool a combustion exhaust gas to control the generation of dioxin and at the same time, reuse the quantity of heat absorbed through cooling by first causing a waste to be burned and a generated high temperature exhaust gas to be circulated through a removing filter for a chlorine gas and then causing the exhaust gas to flow through a cooling filter composed of a Group II metal hydroxide. SOLUTION: When a refuse solid fuel is burned in a refuse incinerator 1, first a high temperature exhaust gas G reaches a chlorine gas removing filter 3 and a corrosive gas such as chlorine is removed by the chemical reaction of a lime granulated product 11. Next the exhaust gas G reaches a cooling filter layer 5 and a slaked lime is converted to calcium oxide through a dehydration and endothermic reaction because a mixture of the slaked lime and octahydrate of barium hydroxide is uses as a Group II metal hydroxide 24 in this filter 5a. The octahydrate of barium hydroxide is also converted to barium oxide. Since these chemical reactions are endothermic reactions, the quantity of heat of the exhaust gas G is absorbed to be rapidly cooled. Finally the exhaust gas G arrives at another cooling filter layer 6 to be again cooled likewise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method for rapidly cooling exhaust gas from a refuse incinerator and an apparatus therefor, and more particularly to an exhaust gas for a refuse incinerator in which the calorific value of the exhaust gas absorbed by cooling can be reused. The present invention relates to a processing method and a processing apparatus.

[0002]

In recent years, industrial waste, general waste, or solid waste produced from these wastes has been developed.
Dioxins generated when incinerating (RDF) and the like have become a social problem. The main cause of dioxins generated by burning waste is that chlorine-based compounds such as vinyl chloride contained in waste during combustion in incinerators become precursors to chlorophenol and chlorobenzene. 250-400 by catalytic reaction on fly ash
In the exhaust gas treatment process, chlorinated aromatic compounds such as chlorophenol and chlorobenzene form unburned carbon, air, moisture, and inorganic materials at low temperatures of 250 to 350 ° C. It is known that there are two types, namely, so-called de novo synthesis generated in the presence of chlorine and the like. Of these dioxins, the synthesis rate of the dioxins from the precursor during combustion is high, but the combustion exhaust gas generates 600 to 25 from the incinerator to the temperature control tower.
While there is only a reaction time of about several seconds flowing through a temperature range of about 0 ° C, the residence time of fly ash in an exhaust gas treatment system where de novo synthesis occurs is very long, so the actual incinerator uses the latter. It is thought that there are more dioxins produced by the reaction. Such a dioxin formation reaction requires not only the above-mentioned temperature factors but also chlorine, particularly chlorine of 1% or more of the amount of waste, and also a metal component as a catalyst. Among such metal components, it has become clear that fine particles such as copper chloride or fly ash plays an important role as a catalyst.

[0003] That is, from these facts, under the condition that dioxins are present in the presence of oxygen, dioxins are characteristic of chlorine-based compounds and have a temperature much higher than the decomposition / generation temperature of about 650-7.
Decomposition starts at about 50 ° C. and is expected to be almost decomposed at about 850 ° C. On the other hand, it is apparent that synthesis is not carried out at 250 ° C. or lower. In order to further suppress the synthesis, it is considered effective to remove chlorine (the compound) as much as possible and to reduce copper chloride having a large catalytic activity.

[0004] Therefore, as measures against such dioxins, the present situation is to raise the combustion temperature of the refuse incinerator itself and to remove chlorine in the refuse incinerator. However, raising the combustion temperature of the refuse incinerator itself or removing chlorine from the refuse incinerator basically suppresses the generation of dioxin inside the incinerator, and waste The flue gas contains chlorine-based gases such as hydrogen chloride gas and chlorine gas, NOx, S
Because it contains a large amount of corrosive gas such as Ox,
The fact that de novo synthesis has occurred in this exhaust gas treatment step is as described above. Therefore, in the exhaust gas treatment process, slaked lime is carried on a bag filter to collect and remove corrosive gas. However, this bag filter generally has a high service temperature of about 200 ° C., and thus has a high temperature. It cannot be used immediately after the exit of a refuse incinerator, and the pressure loss of exhaust gas is large.
For this reason, conventionally, a temperature control tower is provided in the exhaust gas flow path, and the temperature of the exhaust gas flowing through the temperature control tower is reduced by spraying water vapor with a scrubber or the like, and then the gas is circulated through a bag filter. However, the exhaust gas immediately after being discharged from the stack of the refuse incinerator is about 700 ° C., and the cooling rate of the exhaust gas is not rapid in the temperature control tower of the above-described type of spraying steam. Since the exhaust gas stays in a certain temperature range of 250 to 600 ° C. for a long time, dioxins may be generated in the exhaust gas channel. As a countermeasure, it is conceivable to rapidly cool the exhaust gas by increasing the supply amount of water vapor.However, to rapidly cool the exhaust gas requires a very large amount of water vapor, and the amount of gas flowing through the exhaust gas passage is large. In addition to this, the amount of gas flowing through the bag filter also increases, so that it is not practical, such as an extremely large-scale device, and the load on the bag filter also increases. Furthermore, it would be desirable if chlorine-based gas and the like could be removed while cooling quickly in the cooling device, because the generation of dioxins in the exhaust gas passage could be further suppressed. In addition, if such heat of the exhaust gas can be absorbed and used as a heat source, it is desirable from the viewpoint of energy efficiency and contribution to the spread of incinerator facilities.

SUMMARY OF THE INVENTION The present invention has been made in view of these problems, and a method for treating an exhaust gas of a refuse incinerator capable of rapidly cooling waste flue gas and suppressing generation of dioxins as much as possible. An object is to provide a device for that. Another object of the present invention is to provide an exhaust gas treatment method for an incinerator and a device therefor that can reuse the heat absorbed by cooling the combustion exhaust gas.

[0006]

According to a first aspect of the present invention, there is provided a method for treating waste gas in a refuse incinerator, comprising: burning waste in a refuse incinerator; And then a cooling filter using a Group II metal hydroxide. This allows
By first removing corrosive chlorine-based gas from the flue gas discharged from the refuse incinerator, and then passing a cooling filter made of Group II metal hydroxide at a stage where the temperature of the flue gas is still high, particularly at a temperature of 600 ° C. or higher. As the group II metal hydroxide is decomposed into a group II metal oxide, the calorific value of the exhaust gas is deprived, and the exhaust gas flowing therethrough can be quickly cooled to a temperature of 250 ° C. or less where no dioxins are generated. it can.

According to a second aspect of the present invention, in the exhaust gas treatment method for a refuse incinerator, the cooling filter according to the first aspect includes a group II metal hydroxide layer and an exhaust gas flow pipe penetrating the group II metal hydroxide layer. And the exhaust gas is in a non-contact state with the Group II metal hydroxide layer by flowing through the exhaust gas flow pipe. For this reason, the group II metal hydroxide becomes a group II metal oxide by removing heat from the exhaust gas.
When the group II metal oxide reacts with water, the group II metal oxide is restored to the group II metal hydroxide, and at this time, heat is released, so that the heat of the exhaust gas can be reused. At this time, the Group II metal hydroxide is deprived of heat only in a non-contact state with the exhaust gas, so that the Group II metal hydroxide is not contaminated by the exhaust gas and is suitable for reuse.

[0008] Further, in the method for treating exhaust gas of a refuse incinerator according to claim 3, in claim 1 or 2, the Group II metal hydroxide is selected from calcium, magnesium, barium and strontium. These are hydroxides or hydrates of the above metals. Therefore, it is suitable for cooling the exhaust gas at 600 ° C. or higher by its dehydration endothermic reaction.

Further, according to a fourth aspect of the present invention, there is provided an exhaust gas treatment apparatus for a refuse incinerator, which removes chlorine-based gas in an exhaust gas passage communicating with a chimney of the refuse incinerator having a waste inlet and a chimney. A filter and a cooling filter using a Group II metal hydroxide are provided. By adopting such a configuration, by providing a cooling filter made of a Group II metal hydroxide immediately after the exhaust gas channel of the refuse incinerator, particularly immediately after the smoke outlet of the incinerator where the exhaust gas temperature is 600 ° C. or higher, After removing the chlorine gas that causes dioxin, the heat of the exhaust gas is deprived of the decomposition of the Group II metal hydroxide to the Group II metal oxide. It can be cooled quickly to a temperature that does not produce.

According to a fifth aspect of the present invention, in the exhaust gas treatment apparatus for a refuse incinerator according to the fourth aspect, the cooling filter includes a casing for filling a Group II metal hydroxide, and the exhaust gas flow passing through the casing. An exhaust gas flow pipe communicating with the road, and a ventilation hole is formed in the casing. For this reason, the group II metal hydroxide becomes a group II metal oxide by removing heat from the exhaust gas.
When the group metal oxide reacts with water, it releases heat as it is restored to the group II metal hydroxide, so that the heat of the exhaust gas can be reused. At this time, the Group II metal hydroxide is deprived of heat only in a non-contact state with the exhaust gas, so that the Group II metal hydroxide is not contaminated by the exhaust gas and is suitable for reuse. Further, by attaching and detaching the cooling filter in units of the casing, it is easier to reuse the cooling filter.

According to a sixth aspect of the present invention, there is provided an exhaust gas treatment apparatus for a refuse incinerator, wherein the Group II metal hydroxide is one or more metals selected from the group consisting of calcium, magnesium, barium and strontium. Or a hydrate thereof. Therefore, 600
It is suitable for cooling an exhaust gas at a temperature of at least ° C by its dehydration endothermic reaction.

Further, in the exhaust gas treatment apparatus for a refuse incinerator according to claim 7, according to claim 5 or 6, the cooling filter supplies water from the vent hole after being removed from the exhaust gas channel. It can be used repeatedly by reacting with the water. Therefore, the cost required for the cooling filter can be reduced.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an exhaust gas treatment method for a refuse incinerator according to the present invention will be described in detail using an apparatus shown in FIGS. 1 to 3 as an example.

FIG. 1 shows an example of an exhaust gas treatment apparatus of a refuse incinerator to which the method of the present invention can be applied. In FIG. 1, reference numeral 1 denotes a heat-resistant refuse incinerator made of metal or ceramic. A waste stocker (not shown) communicates with the end of the inlet 2 on the upper side of 1 so that a fixed amount of waste is supplied to the refuse incinerator 1. Reference numeral 3 denotes a chlorine gas removal filter made of lime-based granules, which is provided immediately after the chimney 1a of the refuse incinerator 1. After the chlorine gas removal filter 3, the filter 3 passes through a pipe 4. A first cooling filter layer 5 is provided. In the first cooling filter layer 5, a plurality of first cooling filters 5a made of a hydroxide of a Group II metal are provided. Further, on the downstream side of the first cooling filter layer 5, a second cooling filter layer 6 is disposed via a pipe 4A, and a group II metal hydroxide is also provided in the second cooling filter layer 6. A plurality of second filters 6a are provided. Further, the pipe 4B serves as a discharge path after the second cooling filter layer 6 and communicates with an external environment or the like via a dust removing device (not shown) such as fly ash such as a bag filter or an electric dust collector. I have. In this embodiment, the pipes 4, 4
Exhaust gas channels are constituted by A and 4B.

By the way, in this embodiment, the waste includes not only general waste and industrial waste but also solid waste (RDF). This refuse solid fuel is a fuel obtained from waste (Refuse Derived F
uel), which is a waste form that does not contain metal pieces, glass pieces, or other removable inorganic substances and can be used as fuel as it is, especially after crushing garbage and combustible garbage It is dried to improve the calorific value and preservability, and it is compressed and molded into pellets to improve the preservability and transportability.Deodorization is preferably performed by adding slaked lime or quick lime before drying. And the generation of harmful gases.

In the apparatus as described above, the lime-based granules used for the chlorine-based gas removal filter 3 are basically quicklime granules, lumps, limestone and the like. In this method, quick lime or limestone may be crushed or used as it is, or one obtained by the following two methods may be used.

In the first method, calcium carbonate, water glass and baking soda are used. As the calcium carbonate used in the present invention, any of natural calcium carbonate and synthetic calcium carbonate can be used. As the natural calcium carbonate, shells, limestone, calcite, marble and the like can be used. The specific surface area and the like are not particularly limited. Further, the water glass used in the present invention is for mixing with the calcium carbonate to form a gel, and contributes to stabilization of heavy metals. Examples of the water glass include general-purpose water-soluble silicates such as sodium silicate and potassium silicate. Its molar ratio (SiO ₂
/ M ₂ O: M alkali metal) is, may be selected usually within a range of commercial products, that is, arbitrarily within a range of 0.5 to 4.2. As such a water glass, sodium silicate is particularly preferable, and an aqueous solution having a concentration of about 2 to 30% is used, and if necessary, an equivalent to about 10 times the amount of water is added to the water glass to obtain calcium carbonate. Can be adjusted. However, if the concentration of the water glass is too low, it cannot be formed into granules. In addition, baking soda (sodium bicarbonate) is added. This baking soda is necessary to gel the mixture of calcium carbonate and water glass.

The mixing ratio of calcium carbonate, water glass, and sodium bicarbonate as described above is 5 to 20 parts by weight of water glass (in terms of a 10% aqueous solution) with respect to 100 parts by weight of calcium carbonate.
It is preferred to use parts by weight. If the amount of water glass is less than 5 parts by weight, it is difficult to form a gel with calcium carbonate. On the other hand, if the amount of water glass exceeds 20 parts by weight, it takes a long time for drying, which is not preferable. Further, the mixing ratio of baking soda is preferably about 1 to 5 parts by weight based on 100 parts by weight of calcium carbonate. If the amount of baking soda is less than 1 part by weight, it is difficult to form a gel with calcium carbonate. On the other hand, if it exceeds 5 parts by weight, it is not meaningful, but the gelation is too fast and granulation is difficult. Becomes

The gelled product composed of each component as described above becomes porous by evaporating the water content. In the present invention, further, a porous agent is further added to the above-described calcium carbonate, water glass and baking soda. Can be blended. This porous agent is a solid at normal temperature, but when heated to a predetermined temperature or higher, the volume is greatly reduced due to carbonization and vaporization to form voids, and the obtained calcium carbonate granules are porous. And organic powder, low boiling point solid, or the like can be used. Specifically, wastes such as wood meal, coffee, corn starch, and soybeans such as soybeans can be used. The mixing ratio of the above-mentioned porosity agent may be about 5 to 20 parts by weight based on 100 parts by weight of calcium carbonate.

In the first method, the above-mentioned calcium carbonate, water glass, and baking soda, and a porosifying agent added as needed are blended at a predetermined ratio, and the mixture is sufficiently kneaded to form a gel composition. By adjusting the product and heating and drying the gel composition, the calcium carbonate remains 2 to 2 as calcium carbonate.
Although it can be used as a removing agent as a granular material having a size of about 30 mm, it is preferably heated to about 900 ° C. and dried to transform calcium carbonate into quicklime and used as the removing agent. Alternatively, the gel composition may be formed into a stick by shaping the gel composition into a stick shape, cutting the gel composition, and then drying by heating. Further, depending on the viscosity of the gel composition, the gel composition may be dried as it is without molding, and may be pulverized lightly.

As a second method for producing lime-based granules, slaked lime and water glass are used. As the slaked lime used in the present invention, JIS special lime slaked lime, which is generally used, or other commercially available products can be used, and the specific surface area and the like are not particularly limited. Further, as the water glass used in the present invention, the same one as in the first method described above can be used.

The mixing ratio of calcium carbonate and water glass as described above is preferably 5 to 20 parts by weight of water glass (in terms of a 10% aqueous solution) based on 100 parts by weight of calcium carbonate. If the water glass content is less than 5 parts by weight, it becomes difficult to gel calcium carbonate.
Exceeding the weight part is not preferable because it takes a long time for drying.

Further, in the second method, a porosifying agent can be blended. As the porosifying agent, the same one as in the first method described above can be used, and the compounding amount may be the same.

In the second method, the above-mentioned slaked lime and water glass, and a porosifying agent added as required, are blended at predetermined ratios, respectively, and sufficiently kneaded to form a gel-like composition. By adjusting and heating and drying this gel-like composition, slaked lime can be used as a remover as a granular material having a size of about 2 to 30 mm as it is, preferably about 550 to 650 ° C., particularly about 550 to 650 ° C. By heating to 600 ° C. and drying, slaked lime is transformed into quicklime and used as a remover. Alternatively, the gel composition may be formed into a stick by shaping the gel composition into a stick shape, cutting the gel composition, and then drying by heating.

In such a lime-based granulated product, for example, quicklime (CaO), which accounts for the majority of the lime-based granulated product, is 400 to 400%.
When it comes in contact with corrosive gas such as chlorine gas at a high temperature of 700 ° C., it reacts with chlorine gas (Cl ₂ ) to fix it on its surface as calcium chloride (CaCl ₂ ). It demonstrates the performance of removing. Further, NOx and the like can be removed by a similar reaction. In addition, these lime-based granules also exert the effect of converting fine particles and fly ash of copper chloride into copper oxide. Then, if quick lime (CaO) sorbs calcium chloride to some extent, its catalytic activity decreases. However, if a small amount of water is supplied by steam or the like, quick lime rapidly becomes embrittled mainly at the surface portion and collapses. Since the proper surface is exposed, it is possible to reproduce the sorption property of the corrosive gas described above. By repeating this, the particle size of the lime-based granulated material becomes small. When the particle size becomes smaller than a predetermined size, for example, less than 2 mm, the lime-based granulated material may be sieved and a new lime-based granulated product may be added little by little.

In particular, as described in the first and second methods, in the method for producing a lime-based granule by heating and drying from a gel composition, another catalyst substance, such as denitration, is required before the heating and drying. It is possible to mix a powder of a catalyst, a desulfurization catalyst, or the like, and there is also an effect that the performance of a lime-based granulated product as a catalyst can be easily improved and multifunctionalized.

The chlorine-based gas removal filter 3 having lime-based granules as described above, for example, as shown in FIG.
The lime-based granules 11, 11... In the form of granules or pellets are provided in the pipe 4 with two metal mesh plates 12, 12 having a finer grain size than the lime-based granules 11, 11. It can be formed by joining at predetermined intervals by the provided cylindrical body 13 and filling the space S formed between the two metal mesh plates 12. The particle size of the lime-based granule 11 may be appropriately set in consideration of the pressure loss of the exhaust gas and the efficiency of removing corrosive gas in the exhaust gas.
By using a material having a large particle size and a large surface area by making it porous, etc., it is possible to suppress the pressure loss of the exhaust gas, and it is possible to minimize the decrease in the exhaust gas temperature here. Desirable. Also, the interval between the mesh plates 12 and 12, which is the thickness of the catalyst layer, may be appropriately set in consideration of the pressure loss of the exhaust gas and the efficiency of removing the corrosive gas in the exhaust gas. Since the temperature of the exhaust gas decreases slowly and the exhaust gas is rapidly cooled by the cooling filters 5 and 6, the effect of preventing the generation of dioxin cannot be sufficiently obtained.

Also, the first and second cooling filter layers 5,
The group II metal hydroxide used for the cooling filters 5a and 6a constituting the element 6 is basically an alkaline earth metal having two hydroxyl groups bonded to each other, for example, an alkaline earth metal oxide. It is produced with exotherm by hydration reaction. As the group II metal hydroxide as described above, calcium hydroxide, magnesium hydroxide, barium hydroxide (octahydrate), strontium hydroxide (octahydrate) and the like can be used. Calcium hydroxide has a decomposition temperature in the range of about 400-500 ° C, magnesium hydroxide has a decomposition temperature in the range of about 670-420 ° C, and barium hydroxide (octahydrate) has a decomposition temperature in the range of about 670-420 ° C. 80-170 ° C
Strontium hydroxide (octahydrate) has a dehydration temperature in the range of
It has been experimentally confirmed to have a dehydration temperature of 0-150 ° C and a decomposition temperature of about 475-575 ° C. These Group II metal hydroxides can be used in the form of granules or aggregates, and in some cases, powders.

At a temperature higher than the decomposition temperature, such a Group II metal hydroxide absorbs heat as it releases water to convert to an oxide, contrary to the hydration reaction. Therefore, when it comes into contact with exhaust gas at a high temperature (more than its decomposition temperature), a decomposition reaction or the like is caused to absorb the heat. That is, when a group II metal such as calcium, magnesium, barium, and strontium is M, a dehydration / endothermic reaction of 2M (OH) ₂ → 2MO + 2H ₂ O− (calorific value) occurs. For example, in the case of calcium, as slaked lime (Ca (OH) ₂ ) is converted into quicklime (CaO), heat is absorbed from the surroundings. In addition, group II metal hydroxides such as barium hydroxide and strontium hydroxide
In the case of a hydrate, a dehydration reaction occurs due to the drying of the crystal water added before the dehydration endothermic reaction described above.
This also absorbs heat. Such a cooling filter 5
Although the amount of the Group II metal hydroxide used for a and 6a depends on the surface area per unit weight, it is preferable to use about 200 g to 1 kg per 1 m ³ of the flow rate of the exhaust gas G at 600 ° C. The reaction is preferably performed for a long period of time by using a sufficient amount of Group II metal hydroxide because the reaction rate is low.

Particularly, in the present embodiment, the cooling filter 5
It is preferable to use a and a as shown in FIG. This cooling filter 5a (6a)
And an opening cylindrical portion 22 formed on the upper side of the casing 21.
And an opening concave portion 23 formed on the lower side. A fine wire mesh 22A is stretched over the opening cylindrical portion 22 and the opening concave portion 23 serving as ventilation holes. The group II metal hydroxide granules 24 are filled to form a group II metal hydroxide layer. A plurality of exhaust gas distribution pipes 25, 25,... Are provided through the casing 21, and the exhaust gas distribution pipes 25, 25,.

Next, the operation of the exhaust gas treatment method according to the present embodiment using the exhaust gas treatment apparatus for a refuse incinerator having the chlorine-based gas removal filter 3 and the first and second cooling filter layers 5 and 6 as described above. The following describes an example in which a mixture of slaked lime and barium hydroxide octahydrate is used for the cooling filters 5a and 6a.

First, in the apparatus shown in FIGS. 1 to 3,
When the refuse incinerator 1 is used to burn refuse solid fuel, high-temperature (about 600 to 700 ° C.) exhaust gas G is discharged from the stack 1 a to the pipeline 4.
And reaches the chlorine-based gas removal filter 3. Here, corrosive gas such as chlorine is quickly removed by the reaction of the lime-based granules 11 described above. In addition, these lime-based granules 11 also exert an effect of converting copper chloride, which functions as a catalyst for the production of fine particles and fly ash as dioxin, into copper oxide.

Subsequently, the exhaust gas G reaches the first cooling filter layer 5. Since the filter 5a of the first cooling filter layer 5 uses a mixture of slaked lime and barium hydroxide octahydrate as the Group II metal hydroxide 24, the exhaust gas G flowing through the exhaust gas flow pipe 25 is used. If the temperature is higher than the decomposition starting temperature of about 400 to 500 ° C., a dehydration endothermic reaction occurs, slaked lime is converted to quicklime, and barium hydroxide octahydrate is dehydrated after the water of crystallization is dehydrated. Cause a reaction to be converted to Since these reactions are endothermic reactions as described above, the calories of the exhaust gas G are absorbed and quickly cooled. Then, water (steam) generated at this time is discharged from the opening cylindrical portion 22. In the initial stage,
The calorific value of the specific heat of slaked lime and barium hydroxide octahydrate itself is also absorbed. Moreover, in the present embodiment, the exhaust gas G flows through the exhaust gas flow pipe 25 without contacting the Group II metal hydroxide, so that the pressure loss is small, and
The group II metal hydroxide 24 is not contaminated by the exhaust gas G. Moreover, since the corrosive gas of the exhaust gas G is significantly reduced by the chlorine-based gas removing filter 3 before reaching the exhaust gas distribution pipe 25, the corrosion of the exhaust gas distribution pipe 25 and the pipes 4A and 4B is reduced. Is also suppressed.

Subsequently, the exhaust gas G proceeds further along the pipe 4A and reaches the second cooling filter layer 6. In the second cooling filter layer 6, the temperature of the exhaust gas G is about 400 to 5
If the temperature is higher than 00 ° C., the dehydrated endothermic reaction between slaked lime and barium hydroxide octahydrate occurs again, and the exhaust gas G is further cooled. On the other hand, in the first cooling filter layer 5, the exhaust gas G
Even if the temperature has already fallen below 400 ° C., if it is higher than about 80-170 ° C., barium hydroxide 8
The exhaust gas G is further cooled by a dehydration reaction by drying the hydrate. Therefore, in the second cooling filter layer 6,
Group II metal hydroxide 24 constituting second cooling filter 6a
It is desirable that the ratio of barium hydroxide octahydrate be higher than that of the first cooling filter 5a.

Such first and second cooling filters 5
By using a sufficient amount of Group II metal hydroxide 24 for exhaust gas G for a and 6a, it is possible to quickly cool exhaust gas G to 250 ° C. or less, and the chlorine gas contained in exhaust gas G Dioxins can be prevented from reacting and being synthesized via chlorophenol, chlorobenzene and the like.

After the exhaust gas G has been cooled in this manner, the exhaust gas G is further circulated through a pipe 4B and is removed by a dust removing device (not shown) such as a bag filter or an electric dust collector. The fine powder of the lime-based granules discharged from the chlorine-based gas removal filter 3 is collected and released to the external environment.

The first and second cooling filters 5, 6
When the calcium hydroxide (slaked lime) or barium hydroxide octahydrate, which is the Group II metal hydroxide 24, is sufficiently converted into calcium oxide or barium oxide by endothermic heat, the cooling efficiency of the exhaust gas G is reduced. , 6a to be taken out and replaced with a new one. The calcium oxide and barium oxide in the used filters 5a and 6a are
Due to the repetition of the hydration reaction, it easily reacts by supplying water such as steam to release the heat taken from the exhaust gas G and return to slaked lime and barium hydroxide octahydrate, so it can be reused as a filter can do. On this occasion,
It is desirable from the viewpoint of energy to reuse the heat generated by the hydration reaction as a heat source.

As a method of using the cooling filter 5a as a heat source, for example, as shown in FIG. 4, an evaporator 32 filled with water in a sealed reaction vessel 31 is connected to a pipe having a valve 33.
A device connected by a vacuum pump 35 is used for the reaction vessel 31. Then, the cooling filter 5a is housed in the reaction vessel 31 with the valve 33 closed, and the vacuum pump 35 is operated to reduce the pressure inside the reaction vessel 31 so that the valve 33 is opened. Evaporates and moves to the reaction vessel 31. At this time, the cooling filter 5a is
The hydration reaction of calcium oxide and barium oxide in the inside occurs, and heat of 300 ° C. level is generated. This heat can be reused as various heat sources by heating the water with a heat exchange pipe (not shown) or the like. If such a simple device as described above is provided by such a recycling method, it can be used as a heat source simply by removing only the cooling filter 5a and setting it in this device. In addition, by storing the cooling filter 5a in a dry state, it can be stored as a heat source for a long time.

In particular, according to the exhaust gas treatment apparatus of the present embodiment, the exhaust gas G is passed through the exhaust gas flow pipe 25 to directly contact the group II metal hydroxide 24 of the first and second cooling filters 5a and 6a. Since there is no contact, impurities and contaminants in the exhaust gas G do not adhere to the Group II metal hydroxide 24, so that it can be maintained in a clean state. It is public for use in a wide range of applications such as consumer heat sources.

As described in detail above, in the method for treating exhaust gas from a refuse incinerator according to the present embodiment, waste is burned in the refuse incinerator 1, and the high-temperature exhaust gas G generated at this time is filtered by the chlorine-based gas removal filter 3. After the circulation, the first and second cooling filters 5 and 6 using the Group II metal hydroxide are caused to flow, so that the corrosive chlorine-based gas which is a raw material of dioxin is first removed from the exhaust gas G. After that, the cooling filters 5a and 6a made of the Group II metal hydroxide 24 are allowed to flow while the exhaust gas temperature is still high, particularly 600 ° C. or more,
Since the calorific value of the exhaust gas G is deprived as the group II metal hydroxide is decomposed into the group II metal oxide, the exhaust gas G can be quickly cooled to a temperature of 250 ° C. or less where no dioxins are generated. This makes it possible to significantly suppress the generation of dioxin. In particular, since the cooling filters 5a and 6a have a casing 21 filled with a group II metal hydroxide 24 to form a group II metal hydroxide layer, and have an exhaust gas flow pipe 25 penetrating the casing 21. Since the exhaust gas G flows through the layer of the group II metal hydroxide 24 in a non-contact state, the exhaust gas G in the cooling filters 5a and 6a
The Group II metal hydroxide 24 is not contaminated by the exhaust gas G, and is suitable for reuse. This II
Group metal hydroxides include calcium, magnesium,
A hydroxide of one or more metals selected from barium and strontium, or a hydrate thereof can be used, which is suitable for cooling an exhaust gas at 600 ° C. or higher by its dehydration endothermic reaction. Has become.

The exhaust gas treatment apparatus for a refuse incinerator according to the present embodiment has a chlorinated gas flowing through an exhaust gas passage 4 communicating with a waste inlet 1a of the waste incinerator 1 having a waste inlet 2 and a smoke outlet 1a. Since the removal filter 3 and the cooling filters 5a and 6a using the group II metal hydroxide 24 are provided, first, the corrosive chlorine-based gas which is a raw material of dioxin is removed from the exhaust gas G, and then the exhaust gas temperature is reduced. Cooling filter 5a made of Group II metal hydroxide 24 at a still high temperature, especially at a temperature of 600 ° C. or higher.
By flowing the 6a, the heat of the exhaust gas G is deprived as the group II metal hydroxide is decomposed into the group II metal oxide, and the exhaust gas G flowing therethrough is heated to 250 ° C. or lower where no dioxins are generated. It can be cooled quickly to temperature. This makes it possible to significantly suppress the generation of dioxin. In particular, the cooling filters 5a and 6a
A casing 21 for filling a group II metal hydroxide 24,
Since the exhaust gas flow pipe 25 communicates with the exhaust gas flow path 4 penetrating through the casing 21, the exhaust gas G
Since the layer of the group II metal hydroxide 24 flows in a non-contact state, the group II metal hydroxide 24 is not contaminated by the exhaust gas G and is suitable for reuse. Also the casing
Since an opening cylindrical portion 22 as an air hole and an opening recess 23 are formed in the cooling filter 21, when the group II metal hydroxide 24 in the cooling filters 5 a and 6 a is consumed, it is removed from the exhaust gas channel 4 and opened. By supplying water from 23, it reacts with the water to restore to a Group II metal hydroxide, so that it can be used repeatedly.

Next, a second embodiment of the present invention will be described in detail with reference to FIG. The exhaust gas treatment device of the refuse incinerator of the second embodiment basically has the same configuration as that of the above-described first embodiment, and thus the same components are denoted by the same reference numerals and detailed description thereof will be omitted. .

In this embodiment, the pipe 4 is provided with the
The main flow path 41 formed immediately after, the annular flow path 42, and the discharge path
43, two openings 4 formed in the main channel 41.
An annular flow path 42 is connected to the main flow path 41 and 44A.
A chlorine-based gas removal filter 3 is provided on the base end (smoke vent 1a) side, and a first cooling filter layer 5 and a second cooling filter layer 6 are provided in an annular flow path 42. The main flow path 41 has first and second opening / closing valves 45, 45 serving as opening / closing mechanisms from the openings 44, 44A to the smoke port 1a side.
A, and first and second discharge valves 46, 46A are provided at both ends of the main flow path 41,
Thereafter, they merge to form a discharge path 43, which communicates with an external environment and the like via a dust filter (not shown) for removing fly ash such as a bag filter or an electric dust collector.

Next, with regard to the exhaust gas treatment apparatus of the refuse incinerator of the second embodiment as described above, the cooling filters 5a, 6a
An example in which a mixture of slaked lime and barium hydroxide octahydrate is used will be described. In the apparatus shown in FIG. 5, first, the first on-off valve 45 is opened, and the second on-off valve 45A is closed. Further, the first discharge valve 46 is closed, and the second discharge valve 46A is opened. When the refuse incinerator 1 burns the refuse solid fuel, the exhaust gas G having a high temperature (about 600 to 700 ° C.) flows into the main flow path 41 from the chimney 1a. The system gas is removed. In the main flow path 41, the first on-off valve 45 is opened, the second on-off valve 45A is closed, and the first discharge valve 46 is closed. It flows into the flow path 42, reaches the first cooling filter layer 5, and
As in the case of the above-described first embodiment, the heat of the exhaust gas G is absorbed and quickly cooled. Subsequently, in the filter 6a of the second cooling filter layer 6, the temperature of the exhaust gas G becomes about 400
If the temperature is higher than 500 ° C., the exhaust gas G is further cooled by a dehydration reaction of slaked lime and barium hydroxide octahydrate by a dehydration endothermic reaction. Even if the temperature of the exhaust gas G is lowered to 400 ° C. or lower, if the temperature is higher than about 80 to 170 ° C., the exhaust gas G is further cooled by a dehydration reaction by drying barium hydroxide octahydrate.

The exhaust gas G thus cooled returns to the main flow path 41 from the opening 44A. However, since the second on-off valve 45A is closed, the exhaust gas G is discharged from one end of the main flow path 41 to the discharge path 43. Through a dust filter (not shown) such as a bag filter or an electric dust collector, and is discharged from various corrosive gases such as dust and chlorine-based gas, and further from the first and second cooling filters 5 and 6. Fine powder of Group II metal hydroxide such as slaked lime is collected and released to the outside environment.

The first and second cooling filters 5, 6
Calcium hydroxide (hydrated lime) and barium hydroxide octahydrate, which are the Group II metal hydroxides 24, are gradually converted to calcium oxide (quick lime) and barium oxide by endotherm.
Naturally, the group II metal hydroxide in the first filter 6, which cools the exhaust gas G by the endothermic reaction first, is more consumed.
In such a case, as shown by a broken line in FIG. 5, the second on-off valve 45A is opened and the first on-off valve 45 is closed, while the first discharge valve 46 is opened and the second discharge valve is opened. Valve 46A closes. Then, the exhaust gas G flows through the annular flow path 42 in the reverse direction. That is, after flowing in from the opening 44A and sequentially flowing through the second cooling filter 6 and the first cooling filter 5, the air returns to the main flow path 41 from the opening 44 and flows through the discharge path 43 from the other end. Then, the second cooling filter layer 6
When the Group II metal hydroxide 24 of the above is also consumed, the on-off valves 45, 45
A and the discharge valves 46, 46A are switched, only the first cooling filter 5a is replaced with a new one, and the first cooling filter 5a is used in the same flow direction as the first, and the next on-off valves 45, 45A and the discharge valves 46, 46
The second cooling filter 6a may be replaced when A is switched. In this way, the number of replacements of the cooling filters 5a and 6a can be reduced.

Then, the used cooling filters 5a, 6a
Can be reused in the same manner as in the first embodiment.

As described in detail above, the annular filter 42 is formed in the pipe 4 as in this embodiment, and the flow direction of the exhaust gas in the annular channel 42 can be reversed so that the cooling filter 5
a and 6a can be used more efficiently and effectively.

Although the present invention has been described based on the above embodiment, the present invention is not limited to the first and second embodiments, and various modifications can be made. For example, in each of the above embodiments, the first cooling filter 5a
Although two cooling filters are provided as the second cooling filter 6a, three or more cooling filters may be provided. In particular, from the viewpoint of convenience in reuse, it is preferable to connect a large number of small ones.

[0050]

According to the method for treating exhaust gas of a refuse incinerator according to the first aspect of the present invention, waste is burned in a refuse incinerator, and high-temperature exhaust gas generated at this time is passed through a chlorine-based gas removal filter. After that, since the cooling filter using a Group II metal hydroxide is passed, after removing corrosive chlorine-based gas from the combustion exhaust gas discharged from the refuse incinerator, the exhaust gas temperature is still high, especially At a temperature of 600 ° C or higher
By circulating a cooling filter made of a Group II metal hydroxide, the exhaust gas can be quickly cooled to a temperature of 250 ° C. or less at which dioxins are not generated.

According to a second aspect of the present invention, there is provided the exhaust gas treatment method for a refuse incinerator according to the first aspect, wherein the cooling filter comprises a group II metal hydroxide layer and an exhaust gas flow pipe penetrating the group II metal hydroxide layer. Since the exhaust gas is in a non-contact state with the group II metal hydroxide layer by flowing through the exhaust gas flow pipe, the group II metal hydroxide deprives the calorific value in a non-contact state with the exhaust gas. Therefore, the Group II metal hydroxide is not contaminated by the exhaust gas, and is suitable for reuse.

Furthermore, in the method for treating exhaust gas of a refuse incinerator according to claim 3, the group II metal hydroxide is selected from the group consisting of calcium, magnesium, barium and strontium. Since it is a hydroxide or a hydrate of the above metal,
It is suitable for cooling the exhaust gas of 00 ° C. or higher by its dehydration endothermic reaction.

Further, according to a fourth aspect of the present invention, there is provided an exhaust gas treatment apparatus for a refuse incinerator, which removes chlorine-based gas in an exhaust gas passage communicating with a chimney of the refuse incinerator having a waste inlet and a chimney. Since it is provided with a filter and a cooling filter using a Group II metal hydroxide, the Group II is disposed immediately after the exhaust gas flow path of the refuse incinerator, particularly immediately after the smoke outlet of the incinerator where the exhaust gas temperature is 600 ° C or higher. By providing a cooling filter made of a metal hydroxide, after removing chlorine gas which causes dioxin, the exhaust gas can be quickly cooled to a temperature of 250 ° C. or less where dioxins are not generated.

According to a fifth aspect of the present invention, in the exhaust gas treatment apparatus for a refuse incinerator according to the fourth aspect, the cooling filter includes a casing for filling a Group II metal hydroxide, and the exhaust gas flow passing through the casing. An exhaust gas flow pipe communicating with the passage, and the casing is provided with a vent hole, so that the Group II metal hydroxide deprives the exhaust gas only of heat in a non-contact state. The group metal hydroxide is not contaminated by the exhaust gas, and is suitable for reuse. Further, by removing the casing unit, it is easier to reuse.

According to a sixth aspect of the present invention, there is provided the exhaust gas treatment apparatus for a refuse incinerator according to the fourth or fifth aspect, wherein the Group II metal hydroxide is one or more metals selected from calcium, magnesium, barium, and strontium. Since it is a hydroxide or a hydrate thereof, it is suitable for cooling exhaust gas at 600 ° C. or higher by its dehydration endothermic reaction.

Further, the exhaust gas treatment device for a refuse incinerator according to claim 7 is characterized in that, in claim 5 or 6, the cooling filter supplies water from the vent hole after being removed from the exhaust gas channel. Since it can be used repeatedly by reacting with the water, the cost required for the cooling filter can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an exhaust gas treatment device of a refuse incinerator according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a chlorine-based gas removal filter used in the embodiment.

FIG. 3 is a partially cutaway perspective view showing a cooling filter used in the embodiment.

FIG. 4 is a cross-sectional view showing an apparatus that uses a used cooling filter as a heat source.

FIG. 5 is a schematic view illustrating an exhaust gas treatment device of a refuse incinerator according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Garbage incinerator 1a Chimney 2 Inlet 3 Chlorine gas removal filter 4 Pipe line 5 First cooling filter layer 5a First cooling filter 6 Second cooling filter layer 6a Second cooling filter 11 Lime granulation Object 21 Casing 22 Open cylinder (vent) 23 Open recess (vent) 24 Group II metal hydroxide 25 Exhaust gas flow pipe

Claims (7)

[Claims] Claims: 1. Combustion of waste in a refuse incinerator, high-temperature exhaust gas generated at this time is passed through a chlorine-based gas removal filter, and then is passed through a cooling filter using a Group II metal hydroxide. An exhaust gas treatment method for a refuse incinerator. 2. The cooling filter has a Group II metal hydroxide layer and an exhaust gas flow pipe penetrating the Group II metal hydroxide layer. The exhaust gas treatment method for a refuse incinerator according to claim 1, wherein the exhaust gas treatment is in a non-contact state with the group-III metal hydroxide layer. 3. The group II metal hydroxide is a hydroxide of one or more metals selected from calcium, magnesium, barium and strontium, or a hydrate thereof. Item 3. An exhaust gas treatment method for a refuse incinerator according to item 1 or 2. 4. A filter for removing chlorine-based gas and a cooling filter using a Group II metal hydroxide are provided in an exhaust gas passage communicating with a chimney of a refuse incinerator having a waste inlet and a chimney. An exhaust gas treatment device for a refuse incinerator. 5. The cooling filter has a casing for filling a Group II metal hydroxide, and an exhaust gas flow pipe communicating with the exhaust gas passage penetrating the casing. The exhaust gas treatment device for a refuse incinerator according to claim 4, wherein pores are formed. 6. The group II metal hydroxide is a hydroxide of one or more metals selected from calcium, magnesium, barium and strontium, or a hydrate thereof. Item 6. An exhaust gas treatment device for a refuse incinerator according to item 4 or 5. 7. The cooling filter according to claim 5, wherein the cooling filter supplies water through the vent after being removed from the exhaust gas flow path, so that the cooling filter reacts with the water and can be used repeatedly. An exhaust gas treatment device for a refuse incinerator according to item 1.