JP2000093724A - Apparatus for collecting fly ash from flue gas of waste incinerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus capable of quickly collecting fly ash from a flue gas from combustion of wastes. SOLUTION: A cooling filter 3 having an agglomerate 12 of a cooling material with a high specific heat is installed in a first pipeline 4 communicating with a flue port 1a of a waste incinerator 1. A lower end opening part 13 and an upper end opening part 17 are formed in a cooling filter 3. A mesh conveyer 15 and a screw conveyer 16 for transporting the agglomerate 12 of the cooling material with a high specific heat from the lower end opening part 13 to the upper end opening part 17 are installed and a washing tank 14 is further installed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for quickly collecting and collecting fly ash contained in exhaust gas from a refuse incinerator.

[0002]

In recent years, industrial waste, general waste, or solid waste produced from these wastes has been developed.
Various harmful substances generated when incinerating (RDF) and the like have become a social problem. Of these harmful substances, heavy metals volatilize at low boiling points and become fly ash, which easily diffuses with the exhaust gas into the external environment such as the atmosphere and soil, and the fly ash particles become nuclei for catalytic reactions. Therefore, there is a problem that synthesis of harmful substances such as dioxin may be promoted.

[0003] Therefore, conventionally, the exhaust gas has been introduced into an alkaline solution or the like, and the heavy metals that have become fly ash have been dissolved or precipitated as alkali salts or the like, and collected. However, since such a recovery method directly introduces the exhaust gas into the water tank, it is difficult to provide the exhaust gas in the exhaust gas flow path of the incinerator, and the exhaust gas whose temperature has decreased to some extent cannot be treated. .

[0004] By the way, dioxin is generated in a waste incinerator because chlorine compounds such as vinyl chloride contained in the waste during combustion in the incinerator become precursors of chlorophenol, chlorobenzene and the like. The generation of dioxins in the temperature range of 250 to 400 ° C by the catalytic reaction on the ash, and the chlorinated aromatic compounds such as chlorophenol and chlorobenzene in the exhaust gas treatment process are reduced to a low temperature of 250 to 350 ° C. With unburned carbon,
It is known that there are two types, namely, so-called de novo synthesis, which is generated in the presence of air, moisture, inorganic chlorine and the like. Among these dioxins, the generation rate of the dioxins from the precursors during combustion is high, but only for a few seconds when the combustion gas passes through the temperature range of about 600 to 250 ° C. from the incinerator to the temperature control tower. While there is no reaction time, the residence time of fly ash in the exhaust gas treatment system where de novo synthesis occurs is very long, so in actual incinerators, it is thought that the latter reaction has more dioxins generated by the latter reaction Have been. And, of course, in addition to the above-mentioned temperature factors, chlorine, especially chlorine of 1% or more of the waste amount, is necessary for such a dioxin formation reaction,
A metal component to be a catalyst is also necessary, and among such metal components, it has become clear that fine particles of fly ash such as copper chloride and other heavy metals play an important role as a catalyst. I have. From these facts, dioxins are characteristic of chlorinated compounds under the condition of coexistence of oxygen, which is about 650 to 7 which is much higher than the decomposition / generation temperature.
Decomposition starts at about 50 ° C. and is expected to be almost decomposed at about 850 ° C. On the other hand, at 250 ° C. or lower, no synthesis is performed. In order to further suppress the synthesis, it is considered effective to remove chlorine (compound) as much as possible and to reduce chlorides of copper chloride and heavy metals having high catalytic activity.

[0005] That is, as for the timing for removing fly ash such as heavy metals, it is important to rapidly cool immediately after being discharged from an incinerator having a relatively high exhaust gas temperature.
As described above, in the conventional method in which the exhaust gas is directly introduced into the treated water tank, it is difficult to add the exhaust gas immediately after the incinerator.

The present invention has been made in view of these problems, and an object of the present invention is to provide an apparatus capable of quickly collecting fly ash from waste flue gas.

[0007]

Means for Solving the Problems As a result of intensive studies in view of the above-mentioned objects, the present inventor has found that, after an exhaust gas channel of a refuse incinerator, especially immediately after a smoke port, iron ingots, concrete ingots, ceramic granules, etc. If a cooling layer having a coolant having a large specific heat is arranged, the exhaust gas passing through the cooling layer can be rapidly cooled to about 300 ° C., whereby heavy metals and their compounds, and fly ash such as other inorganic salts are reduced. It has been found that this precipitates on the surface of the coolant having a large specific heat. If the coolant having a large specific heat in the cooling filter is once discharged from the cooling filter, washed, and then circulated, it is possible to collect heavy metals without directly cleaning the exhaust gas. The present inventors have found that fly ash can be efficiently collected from exhaust gas of the present invention, and have arrived at the present invention.

That is, the apparatus for collecting fly ash from the exhaust gas of a refuse incinerator according to claim 1 of the present invention is included in the exhaust gas discharged from a refuse incinerator having a waste inlet and a smoke inlet. A device for collecting fly ash, wherein a cooling filter having a coolant having a large specific heat is disposed in an exhaust gas passage communicating with a smoke port of the refuse incinerator, and the coolant having a large specific heat is provided in the cooling filter. And a transport device for transporting the coolant having a large specific heat from the discharge port to the supply port, and a washing tank for the coolant having a large specific heat.

Further, in the apparatus for collecting fly ash from the exhaust gas of a refuse incinerator according to the second aspect, in the apparatus according to the first aspect, the coolant having a large specific heat is made of ceramic, metal lump, concrete lump or the like. It is one or two or more selected.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a device for collecting fly ash from the exhaust gas of a refuse incinerator according to the present invention will be described in detail with reference to FIG. 1 and FIG.

FIG. 1 shows a device for collecting fly ash from the exhaust gas of a refuse incinerator according to a first embodiment of the present invention. 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 waste incinerator 1 at the top of the inlet 2 on the upper side of the waste incinerator 1, and a fixed amount of waste is supplied to the waste incinerator 1. ing. Reference numeral 3 denotes a cooling filter provided immediately after the chimney 1a of the refuse incinerator 1 by a first conduit 4, and a second conduit 4A is connected to an outlet of the cooling filter 3. Further, the first and second tubes 5 and 6 are provided in communication with the cooling filter 3 through the second conduit 4A.
The chlorine-based gas removal filter layers 5 and 6 are provided with a plurality of chlorine-based gas removal filters 5a, 5a, 6a and 6a, respectively. 4B is the first chlorine-based gas removal filter layer 5
And a third conduit connecting the second chlorine-based gas removal filter layer 6 to the second pipeline. The second chlorine-based gas removal filter layer 6 is connected to a fourth pipe 4C, which serves as a discharge path and serves as a dust removal device such as a bag filter or an electric dust collector.
(Not shown) and communicates with the external environment. In the present embodiment, an exhaust gas flow path is configured by the first pipeline 4, the second pipeline 4A, the third pipeline 4B, and the fourth pipeline 4C.

By the way, in this specification, wastes include not only general wastes and industrial wastes but also solid wastes (RDF). This refuse solid fuel is a fuel derived from waste (Refuse Derived).
Fuel) is a type of waste that does not contain metal chips, glass chips, or other removable inorganic substances and can be used as fuel as it is, especially after crushing garbage or combustible waste. 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 generation of harmful gas is suppressed. In this specification, fly ash basically refers to low-boiling heavy metals and their compounds contained in exhaust gas, but is contained in other exhaust gas such as low-boiling inorganic salts. Including those that are

In the above-described apparatus, as the coolant having a large specific heat used for the cooling filter 3, a metal having a large specific heat such as an iron-based material or a lump such as concrete or ceramic can be used. The mass of the coolant having a large specific heat is preferably increased in surface area by making it porous or roughened. As shown in FIG. 2, the cooling filter 3 has a structure in which a tubular body 11 is filled with a mass of coolant 12 having a large specific heat, and the lower end of the tubular body 11 is formed as a discharge port having a reduced diameter. A cleaning tank 14 is provided below the lower end opening 13. A mesh conveyor 15 as a transfer device is provided in the cleaning liquid tank 14, and a screw conveyor 16 is provided at the end of the mesh conveyor 15. The upper end of the screw conveyor 16 communicates with an upper opening 17 serving as a supply port of the tubular body 11. The cleaning tank 14 is filled with water or an alkaline cleaning liquid W, and may have an ultrasonic cleaning machine or a bubble cleaning machine as needed.

Further, chlorine-based gas removal filter layers 5 and 6
Can be used, for example, those filled with lime-based granules 7. Here, the lime-based granules 7 are basically granules and aggregates of quicklime or slaked lime, but in the present invention, quicklime may be used as it is, or Those obtained by two kinds of methods can also be used. First, 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
Is an alkali metal) can be arbitrarily selected in the range of ordinary commercial products, that is, in the 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 baking soda as described above is 5 to 20 parts per 100 parts by weight of calcium carbonate with respect to water glass (in terms of a 10% aqueous solution).
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

Further, a porous agent can be further added to the above-mentioned calcium carbonate, water glass and baking soda. 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 necessary are blended at predetermined ratios, and the mixture is sufficiently kneaded to form a gel composition. The calcium carbonate is denatured into quicklime by heating, preferably heating to about 900 ° C. and drying the gel composition.
It is possible to produce lime-based granules as quicklime granules having a size of about mm. 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.

In 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) per 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, and kneaded sufficiently to form a gel-like composition. The gelled composition is heated, preferably heated to 550 to 650 ° C., particularly about 600 ° C., and dried to transform slaked lime into quick lime.
It is possible to produce a lime-based granule as granules of quicklime having a size of about 30 mm. 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, quick lime (CaO), which accounts for the majority of the lime-based granulated product, reacts with chlorine gas (Cl ₂ ) to fix it on the surface thereof as calcium chloride (CaCl ₂ ). It exhibits the ability to remove chlorine-based gas in it. Further, NOx and the like can be removed by a similar reaction. And quicklime (Ca
O), if it sorbs calcium chloride to some extent, its catalytic activity decreases. However, if a small amount of water is supplied by steam or the like, quicklime rapidly breaks down and breaks down, mainly on its surface, and a new surface is obtained. Is exposed, so that the above-described sorption properties of corrosive gas can be reproduced. 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, in the method of producing a lime-based granule by heating and drying from a gel composition as exemplified in the first and second methods, another catalyst substance, such as denitration, is required before the heating and drying. It is possible to mix a powder such as a catalyst or a desulfurization catalyst, which has an effect that not only the function of removing the chlorine-based gas described above but also a further multifunctionality can be easily achieved.

Next, the operation of the apparatus for collecting fly ash from the exhaust gas of a refuse incinerator having the above-described configuration will be described. 1 and 2, the waste incinerator 1
Combustion of solid fuel by garbage can lead to high temperatures (about 600-70
Exhaust gas G (0 ° C.) reaches the cooling filter 3 from the chimney 1 a through the first conduit 4. Since the cooling filter 3 is filled with the mass 12 of the coolant having a large specific heat, the amount of heat of the exhaust gas G is absorbed by the specific heat of the mass 12. Therefore, by using a sufficient amount of the lumps 12 with respect to the flow rate of the exhaust gas G,
It can be quenched to below ℃. At this time, exhaust gas G
Since the temperature of the block 12 is lower than that of the block 12, fly ash such as heavy metals (including its compound) is deposited on the surface of the block 12. Subsequently, the exhaust gas G reaches the first chlorine-based gas removal filter layer 5 through the third conduit 4B, and the lime-based granules 7 can remove the chlorine-based gas in the exhaust gas G. Further, the chlorine-based gas is further removed from the second chlorine-based gas removal filter layer 6. As described above, in this embodiment, since the chlorine-based gas is removed after the exhaust gas G is rapidly cooled, not only fly ash is collected but also dioxin is hardly generated.

After being cooled in this way, the exhaust gas G is
The corrosive gas such as dust, chlorine-based gas and the like reaching the dust removing device (not shown) such as a bag filter and an electric dust collector from the fourth pipe 4C, and further, the ceramic and the like discharged from the cooling filter 3 Fine powder such as concrete and slaked lime or quick lime discharged from the first and second chlorine-based gas removal filters 5 and 6 are collected and released to the external environment.

On the other hand, in the cooling filter 3, the lump 12 falls from the lower end opening 13 little by little since the cylindrical body 11 is gradually reduced in diameter at the lower end side, and falls into the washing tank 14. On the mesh conveyor 15. Heavy metal components such as fly ash deposited on the surface of the lump 12 while moving on the mesh conveyor dissolve into the cleaning liquid W. At the same time, the mass 12 heated by the calorific value of the exhaust gas G is water-cooled. The lump 12 from which the fly ash deposited on the surface has been removed and cooled in this way is fed from the mesh conveyor 15 to the screw conveyor 16 and returned to the cylindrical body 11 from the upper end opening 17. By circulating the lump 12 in this manner, the fly ash is removed, and the ash is allowed to cool, and the exhaust gas G
Cooling and fly ash collection are possible. Further, by moving the lump 12 in the tubular body 11, it is possible to reduce the pressure loss during the flow of the exhaust gas G as compared with the case where the lump 12 is fixed. When the lump 12 becomes smaller due to abrasion or the like and becomes smaller than the mesh of the mesh conveyor 15, it falls through the mesh and is removed from the circulation system. What is necessary is just to replenish the lump 12 newly. Further, the washing liquid W may be replaced successively, and heavy metals and salts in fly ash may be precipitated and recovered by chemical treatment.

As described in detail above, the apparatus for collecting fly ash from the exhaust gas of the refuse incinerator according to the present embodiment uses the waste inlet 1a of the refuse incinerator 1 having the waste inlet 2 and the smoke outlet 1a. A cooling filter for collecting fly ash contained in the discharged exhaust gas G, and having a blockage 12 of a coolant having a large specific heat in a first conduit 4 which is an exhaust gas passage communicating with the above-mentioned chimney 1a. The cooling filter 3 is provided with a lower opening 13 serving as a discharge port and an upper opening 17 serving as a supply port of the coolant mass 12 having a large specific heat.
Since a mesh conveyor 15 and a screw conveyor 16 are provided as a transport device for transporting the bulk material 12 of the coolant having a large specific heat from 13 to the upper end opening portion 17, and a cleaning tank 14, the coolant having a large specific heat is provided. Exhaust gas G from the refuse incinerator 1 is separated by fly ash by the specific heat of
It can be cooled quickly to the following degree. In particular, fly ash is deposited on the coolant mass 12 having a large specific heat, and the fly ash is circulated from the lower end opening 13 toward the upper end opening 17, and fly ash is collected in the cleaning tank 14 during this time. Since the exhaust gas G is not directly passed through the cleaning tank 14,
The fly ash can be collected from the high temperature exhaust gas G immediately after a. In addition, since the coolant mass 12 having a large specific heat can be washed and allowed to cool in the washing tank 14, the exhaust gas G can be continuously and efficiently cooled, and fly ash can be stably compensated for a long period of time. Can be gathered.

Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the mesh conveyor 15 and the screw conveyor 16 are used as the transfer device of the cooling filter 3, but the transfer device is not limited to this, and may have various configurations.

[0028]

According to the present invention, the apparatus for collecting fly ash from the exhaust gas of a refuse incinerator according to claim 1 of the present invention is included in the exhaust gas discharged from a refuse incinerator having a waste inlet and a smoke inlet. A device for collecting fly ash, wherein a cooling filter having a coolant having a large specific heat is disposed in an exhaust gas passage communicating with a smoke port of the refuse incinerator, and the coolant having a large specific heat is provided in the cooling filter. And forming a discharge port and a supply port, and a transport device that transports the coolant having a large specific heat from the discharge port toward the supply port, and a cleaning tank for the coolant having a large specific heat are provided. Fly ash precipitates from the exhaust gas from the refuse incinerator due to the specific heat of the coolant having a large specific heat.
Cooling can be rapidly performed to about 0 ° C. or less, and fly ash can be precipitated on the surface of the coolant. By washing the coolant having a large specific heat in the washing tank, fly ash can be collected, so that it is not necessary to pass the exhaust gas directly through the washing tank, so that the fly ash is removed from the high-temperature exhaust gas immediately after the chimney. Can be collected.

Further, in the apparatus for collecting fly ash from the exhaust gas of a refuse incinerator according to claim 2, one or more kinds of the coolant having a large specific heat are selected from ceramics, metal lumps, concrete lumps and the like. Therefore, it is excellent both in economy and versatility.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a device for collecting fly ash from exhaust gas of a refuse incinerator according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a cooling filter used in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Garbage incinerator 1a Chimney 2 Inlet 3 Cooling filter 4 1st pipe (flow path) 4A 2nd pipe (flow path) 4B 3rd pipe (flow path) 4C 4th pipe ( Flow path) 11 Mass of coolant with large specific heat (coolant with large specific heat) 13 Lower end opening (discharge port) 14 Cleaning tank 15 Mesh conveyor (transfer device) 16 Screw conveyor (transport device) 17 Upper end opening (supply Mouth) G exhaust gas

Claims (2)

[Claims] An apparatus for collecting fly ash contained in exhaust gas discharged from a refuse incinerator having a waste inlet and a chimney, wherein the exhaust gas stream communicates with a chimney of the refuse incinerator. A cooling filter having a coolant having a large specific heat is disposed in the passage, and an outlet and a supply port of the coolant having a large specific heat are formed in the cooling filter, and the large specific heat is provided from the discharge port toward the supply port. A device for collecting fly ash from exhaust gas of a refuse incinerator, comprising a transport device for transporting a coolant and a washing tank for the coolant having a large specific heat. 2. The coolant having a large specific heat is ceramic,
The apparatus for collecting fly ash from exhaust gas of a refuse incinerator according to claim 1, wherein the apparatus is at least one selected from a metal lump, a concrete lump, and the like.