Fly ash circulation device

Abstract

To circulate medicine-mixed fly ash discharged from a dust collection device to an upstream exhaust gas pathway of the dust collection device without using a separate conveyor-type or pneumatic transport device for lifting the medicine-mixed fly ash.SOLUTION: A fly ash circulation device 1 includes at least: a medicine supply device 3 which supplies a medicine to purify dust-containing exhaust gas to a first exhaust gas pathway 2 in which the dust-containing exhaust gas generated in a combustion furnace plant flows; a dust collection device 4 whose upstream side is connected to the first exhaust gas pathway and downstream side is connected a second exhaust gas pathway, and which discharges the exhaust gas after dust removal from which the dust-containing exhaust gas in the first exhaust gas pathway is removed to the second exhaust gas pathway 6; and a medicine-mixed fly ash supply device 5 which is connected to the lower part of the dust collection device 4 and supplies the medicine-mixed fly ash in which the medicine and fly ash that have fallen to the lower part in the dust collection device 4 due to dust removal are mixed to the first exhaust gas pathway 2 that passes immediate below itself or below the vicinity immediately below itself.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fly ash circulating device that reuses chemicals contained in fly ash for purifying exhaust gas. [Background technology]

[0002] In plants using combustion furnaces such as waste incinerators (hereinafter referred to as "combustion furnace plants"), exhaust gases (hereinafter referred to as "exhaust gases") generated by the combustion of fuels such as waste are purified by spraying them with chemicals such as slaked lime, and dust is removed using a dust collector (such as a bag filter device or an electrostatic precipitator).Then, the exhaust gases are released into the atmosphere through an exhaust device such as a chimney, i.e., outside the plant. The agent is generally supplied in the exhaust gas path from the combustion furnace to the chimney, downstream of the combustion furnace and upstream of the dust collector. The dust ash collected by the dust collector contains fly ash, reaction products of the chemical reaction, and chemicals that have not fully contributed to purifying the exhaust gas (unreacted or insufficiently reacted chemicals, hereinafter collectively referred to as "unreacted chemicals" for convenience). In order to effectively utilize these unreacted chemicals, a so-called "fly ash circulation" technology has been proposed (see Patent Document 1).

[0003] Fly ash circulation technology is a technology that reuses unreacted chemicals that have been supplied to the exhaust gas route without discarding them. In general, it is a technology that supplies fly ash mixed with unreacted chemicals that have been collected by a dust collector (hereinafter referred to as "chemical-mixed fly ash") back to the exhaust gas route upstream of the dust collector. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-58997 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a combustion furnace plant, particularly in a combustion furnace plant equipped with a power generation boiler, the boiler is generally large, for example, as high as the third or fourth floor of an office building, i.e., as high as an upper floor. The exhaust gas path that carries exhaust gas containing soot such as fly ash (hereinafter referred to as "dust-containing exhaust gas") is connected from the boiler, which is a high-rise structure, to a dust collector below. However, the drug-mixed fly ash stored in the dust collection device is discharged from the bottom of the dust collection device, and in order to supply the drug-mixed fly ash to the exhaust gas route, the drug-mixed fly ash removed from the bottom is lifted up to the exhaust gas route using a conveyor-type or air-transport type transport device. Therefore, depending on the frequency and duration of maintenance of the transport device, the operating rate of the combustion furnace plant may decrease.

[0006] Therefore, the present invention aims to provide a fly ash circulation device that can circulate chemical-mixed fly ash discharged from a dust collector to the exhaust gas path upstream of the dust collector without having to provide a separate conveyor-type or air-transport type transport device for lifting the chemical-mixed fly ash, thereby making effective use of unreacted chemicals. [Means for solving the problem]

[0007] The fly ash circulation system of the present invention comprises a chemical supplying device which supplies a chemical for purifying a dust-containing exhaust gas generated in a combustion furnace plant to a first exhaust gas path through which the dust-containing exhaust gas flows, a dust collecting device connected to the upstream side of the first exhaust gas path and to the downstream side of a second exhaust gas path, the dust collecting device discharging a post-dust removal exhaust gas from the first exhaust gas path into the second exhaust gas path, and a chemical-mixed fly ash supplying device connected below the dust collecting device for supplying chemical-mixed fly ash, which is a mixture of the chemical and fly ash that have fallen to the lower inside of the dust collecting device by the dust removal, to the first exhaust gas path, and the chemical-mixed fly ash supplying device supplies the chemical-mixed fly ash to the first exhaust gas path which passes directly below or below near the immediate vicinity of the chemical-mixed fly ash supplying device. Effect of the Invention

[0008] According to the fly ash circulation device of the present invention, the first exhaust gas path upstream of the dust collector passes directly below the chemical-mixed fly ash supply device arranged below the dust collector or below the area directly below the supply device. Therefore, the chemical-mixed fly ash that falls below the inside of the dust collector can be easily supplied to the first exhaust gas path passing below the chemical-mixed fly ash supply device, and the exhaust gas in which the chemical-mixed fly ash is dispersed is automatically lifted upward by the flow of the exhaust gas and introduced into the dust collector. Therefore, there is no need to provide a separate conveying device to lift the chemical-mixed fly ash to the exhaust gas path as in the conventional technology. Therefore, according to the fly ash circulation device of the present invention, without the need to separately install a conveyor-type or air-transporting device for lifting the fly ash mixed with chemicals, the fly ash mixed with chemicals discharged from the dust collector can be circulated to the first exhaust gas path upstream of the dust collector, and the unreacted chemicals can be effectively utilized. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a fly ash circulation device according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a first modified example of the fly ash circulating device shown in FIG. [Diagram 3] FIG. 2 is a schematic diagram showing a second modified example of the fly ash circulating device shown in FIG. [Figure 4] FIG. 2 is a schematic diagram showing a third modified example of the fly ash circulating device shown in FIG. [Diagram 5] FIG. 2 is a schematic diagram showing a fourth modified example of the fly ash circulating device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the fly ash circulation device of the embodiment of the present invention and its modified examples (first modified example to fourth modified example) will be described with reference to the drawings (FIGS. 1 to 5). The embodiment and each modified example are merely illustrative, and are not intended to exclude the application of various modifications and techniques not specifically described. The configurations of the embodiment and each modified example can be modified in various ways without departing from the spirit of the invention. Moreover, each of the configurations can be selected as necessary, or can be appropriately combined between the embodiment and each modified example, except for the configurations essential to the invention. 1 to 5, an orthogonal coordinate system consisting of an X-axis and a Y-axis will be used as appropriate for the explanation. The X-axis is horizontal, and the Y-axis is vertical. The arrow direction of the Y-axis is vertical and points upward.

[0011] [Embodiment of fly ash circulation device] A fly ash circulating apparatus 1 according to an embodiment will now be described with reference to Fig. 1. First, the outline of the overall configuration of the fly ash circulating apparatus 1 will be briefly described, and then each component of the fly ash circulating apparatus 1 will be described in detail. The fly ash circulation device 1 is connected to a first exhaust gas passage 2 through which exhaust gas containing soot and dust such as fly ash (hereinafter referred to as "dust-containing exhaust gas") flows from a combustion furnace (including an incinerator) in a combustion furnace plant such as a waste incineration plant or a biomass-fired power plant. The exhaust gas passage 2 is specifically a pipeline such as a duct or pipe connected between the combustion furnace and the fly ash circulation device 1. Note that hereinafter, when the term "pipe" is used simply, it means a pipeline such as a duct or pipe. The fly ash circulation system 1 includes at least a chemical supplying device 3 that supplies chemicals such as slaked lime and activated carbon to the first exhaust gas path 2 in order to purify the dust-containing exhaust gas flowing through the first exhaust gas path 2, a dust collector 4 connected to one end of the first exhaust gas path 2 in order to remove dust from the dust-containing exhaust gas, and a chemical-mixed fly ash supplying device 5 connected below the dust collector 4. The drug-mixed fly ash supplying device 5 supplies collected dust ash (hereinafter referred to as "drug-mixed fly ash") which is a mixture of drug and fly ash that has fallen to the bottom inside the dust collector 4 due to the removal of dust-containing exhaust gas, to the first exhaust gas path 2 located directly below it (the drug-mixed fly ash supplying device 5) or directly below and adjacent to it (in the -Y axis direction), and disperses and reacts the unreacted drug in the drug-mixed fly ash with the dust-containing exhaust gas in the first exhaust gas path 2. Since the fly ash circulation device 1 is configured as described above, the first exhaust gas path 2 passes below the drug-mixed fly ash supplying device 5 (-Y axis direction) and then bends upward (+Y axis direction), and then the above-mentioned one end of the first exhaust gas path 2 is connected to the dust collection device 4.

[0012] The exhaust gas from which dust has been removed by the dust collector 4 (hereinafter referred to as "exhaust gas after dust removal") is drawn in by a blower (first blower) 7 installed in a second exhaust gas passage 6 connected between the dust collector 4 and an exhaust device such as a chimney. The blower 7 is appropriately selected from, for example, a fan, a blower, or a compressor depending on the design. Note that the second exhaust gas passage 6 is a pipe such as a duct or pipe, similar to the first exhaust gas passage 2. In terms of the flow of exhaust gas, the first exhaust gas path 2 is connected to the upstream side of the dust collector 4, and the second exhaust gas path 6 is connected to the downstream side of the dust collector 4. Then, as a result of the above-mentioned induction by the blower 7, the dust-containing exhaust gas in the first exhaust gas path 2 flows from the combustion furnace toward the dust collector 4. Also, as a result of the above-mentioned induction by the blower 7, the dust-removed exhaust gas in the second exhaust gas path 6 flows from the dust collector 4 toward an exhaust device such as a chimney, and is discharged into the atmosphere.

[0013] Now, each component of the fly ash circulation device 1 will be described in detail. First, as described above, the drug supplying device 3 is a device that supplies a drug to the first exhaust gas path 2. The drug can be sprayed into the first exhaust gas path 2 by a blower (not shown), such as a high-pressure blower. The positional relationship between a specific location (hereinafter referred to as "location A") in the first exhaust gas path 2 to which the drug-mixed fly ash supplying device 5 supplies the drug-mixed fly ash and a specific location (hereinafter referred to as "location B") in the first exhaust gas path 2 to which the drug supplying device 3 supplies the drug may be such that location B is upstream of location A, or location B is downstream of location A. However, here, an example is shown in which location B is upstream of location A so that the reaction time of new drug can be longer than the reaction time of unreacted drug in the drug-mixed fly ash. The chemical supply device 3 may spray the chemical into the first exhaust gas path 2 using compressed air from a compressed air supply device (not shown) instead of the above-mentioned blower, or may cut out the chemical using a rotary valve or table feeder (not shown) and distribute it into the first exhaust gas path 2 by free fall due to gravity. Even in the case of free fall, the inside of the first exhaust gas path 2 is under negative pressure due to the blower 7, so that in addition to gravity, a suction force due to the negative pressure is applied to the first exhaust gas path 2, and the chemical supplied from the chemical supply device 3 is introduced into the first exhaust gas path 2 and dispersed in the dust-containing exhaust gas.

[0014] Next, the dust collector 4 may be a bag filter device or an electric dust collector. Here, as an example, the dust collector 4 will be described as a bag filter device having a plurality of bag filters 4a made of cylindrical, bag-shaped filter fabric. In the dust collector 4, the dust-containing exhaust gas flowing through the first exhaust gas passage 2, the chemical-mixed fly ash supplied at point A, and the chemical supplied at point B are removed from the outside of the bag-shaped filter cloth of the bag filter 4a, and the exhaust gas flows upward (in the +Y-axis direction) inside the filter cloth after removing the dust. Therefore, the second exhaust gas passage 6 is connected to the dust collector 4 above the inlet (inlet of the bag-shaped filter cloth) of the bag filter 4a when viewed in the Y-axis direction. The bottom of the dust collecting device 4 is a hopper 4b having an inclined wall surface that is larger at the top and smaller at the bottom, such as an inverted pyramid type, a ship bottom type, an inverted cone type, etc. The bottom may be a flat bottom type that does not have an inclined wall surface.

[0015] The dust collector 4 may be provided with a feeder 4c disposed inside the hopper 4b or below the hopper 4b (in the -Y-axis direction) for feeding the drug-mixed fly ash stored in the hopper 4b to the drug-mixed fly ash feeder 5. A conveying device such as a screw conveyor may be disposed at the bottom of the hopper 4b for conveying the stored drug-mixed fly ash toward the feeder 4c. The feed device 4c is, for example, a rotary valve or a table feeder. Although FIG. 1 shows an example in which the feed device 4c is directly connected to the bottom of the hopper 4b, the feed device 4c may be indirectly connected to the bottom via a pipe. The amount and timing of the chemical-mixed fly ash excavated by the excavation device 4c is controlled by a control device (not shown) according to the design.

[0016] Here, since the dust collector 4 is a bag filter device, by periodically performing so-called "backwashing", the chemical-mixed fly ash adhering to the outer surface of the bag filter 4a can be sifted into a hopper 4b. When the first exhaust gas passage 2 is connected to the dust collector 4, the one end of the first exhaust gas passage 2 may be connected to the dust collector 4 above the hopper 4b, or the one end may be connected to the hopper 4b. When the one end is connected to the hopper 4b, the pressure of the flow of the dust-containing exhaust gas ejected from the one end into the dust collector 4 can cause the chemical-mixed fly ash that has fallen into and been stored in the hopper 4b to fly up in the dust collector 4, and the unreacted chemical in the chemical-mixed fly ash can be used more effectively to purify the dust-containing exhaust gas.

[0017] Next, the chemical-mixed fly ash supplying device 5 will be described. The inlet of the drug-mixed fly ash supplying device 5, into which the drug-mixed fly ash supplied from the dust collector 4 is introduced, is connected to the lower side (-Y axis direction) of the dust collector 4. Therefore, the drug-mixed fly ash can be easily supplied from the dust collector 4 to the inlet of the drug-mixed fly ash supplying device 5 by free fall due to gravity. The chemical-mixed fly ash supplying device 5 has two outlets: a first outlet that is directly connected to point A of the first exhaust gas route 2 or indirectly connected via a pipeline, and a second outlet that discharges some of the chemical-mixed fly ash to the outside of the fly ash circulation device 1 for dust ash treatment such as treatment to prevent heavy metal leaching. The first exhaust gas path 2 is disposed directly below the first outlet or below its vicinity. Here, the "vicinity" means a position that is a predetermined distance away from "directly below" the first outlet so that the chemical-mixed fly ash discharged from the first outlet is appropriately introduced into the location A of the first exhaust gas path 2 by gravity or by the suction force to the first exhaust gas path 2 due to gravity and negative pressure. Therefore, the "nearby" corresponds to a vertically downward position at a position that is a predetermined distance away from the first outlet in the horizontal direction. The predetermined distance may vary depending on the design, but can be considered to be about 1 to 5 m. The chemical-mixed fly ash supplying device 5 includes at least a distributor 5a, and may include a sealing device 5b depending on the design. These will be described in detail below.

[0018] The distributor 5a distributes the chemical-mixed fly ash introduced from the inlet of the chemical-mixed fly ash supply device 5 to a first path 5aA connected to the first outlet by a pipeline and a second path 5aB connected to the second outlet by a pipeline. The first path 5aA and the second path 5aB are, for example, pipelines such as ducts and pipes. One end of the first path 5aA may be the first outlet. Also, one end of the second path 5aB may be the second outlet. The distributor 5a may be, for example, a screw conveyor with a rotating shaft arranged in the X-axis direction. When the distributor 5a is a screw conveyor, for example, when the rotating shaft is rotated forward, the drug-mixed fly ash is transported toward the first outlet via the first path 5aA, and when the rotating shaft is rotated in the reverse direction, the drug-mixed fly ash is transported toward the second outlet via the second path 5aB. That is, the distributor 5a selectively selects either the first path 5aA or the second path 5aB to distribute the drug-mixed fly ash.

[0019] The distributor 5a may be configured to include, in addition to the screw conveyor described above, a bifurcated chute that branches into two paths, a first path 5aA inclined diagonally downward and a second path 5aB inclined diagonally downward, and a damper (e.g., a double flap damper) disposed at the branching point of the chute. The damper closes one of the paths of the bifurcated chute, so that either the first path 5aA or the second path 5aB can be selected alternatively, and the drug-mixed fly ash can be distributed toward the first outlet or the second outlet. Furthermore, in this case, by adjusting the opening degree of the damper, the drug-mixed fly ash can be distributed simultaneously to both the first path 5aA and the second path 5aB at a predetermined ratio. Here, the distributor 5a may be provided with a device equivalent to the sealing device 5b described below, such as a rotary valve, a table feeder, or a double flap damper, at each outlet of the bifurcated chute.

[0020] In addition to the above-mentioned examples, the distribution device 5a may be configured such that, for example, an inlet dedicated to the first path 5aA and an inlet dedicated to the second path 5aB are separately connected to the bottom of the dust collection device 4, and the drug-mixed fly ash is introduced independently and separately into each inlet from an opening in the bottom. The control of the distribution device 5a, for example, the control of the rotation direction of the screw conveyor, the control of the operation of the damper, and the control of the operation of the rotary valve, etc. (the rotation speed in the case of a rotary valve or a table feeder) are performed by the above-mentioned control device according to the design or according to the operation of the operator.

[0021] Finally, the sealing device 5b is installed in a path connecting the first outlet connected to the first path 5aA and the point A of the first exhaust gas path 2. The path is, for example, a conduit such as a duct or a pipe. As described later, in the case where the sealing device 5b is not installed, the path may not be provided and the first outlet may be directly connected to the point A. The sealing device 5b is a device that separates the first exhaust gas path 2 from the first path 5aA because the internal pressure of the first path 5aA is different from the internal pressure of the first exhaust gas path 2 due to the above-mentioned induction by the blower 7. Furthermore, the sealing device 5b is a device that can separate the first path 5aA from the first exhaust gas path 2 without hindering the supply of the chemical-mixed fly ash from the first path 5aA to the first exhaust gas path 2 by the distributor 5a. If there is no need for such separation, the sealing device 5b does not need to be installed. The sealing device 5b may be, for example, a rotary valve, a table feeder, a double flap damper, etc. When the sealing device 5b supplies the chemical-mixed fly ash from the first path 5aA to the first exhaust gas path 2, the first path 5aA is substantially separated from the first exhaust gas path 2, whose internal air pressure is more negative than that of the first path 5aA. The operation of the sealing device 5b, such as the rotary valve, the table feeder, and the double flap damper, is controlled by the above-mentioned control device according to the design. In addition, in order to prevent clogging due to adhesion of the chemical-mixed fly ash, a vibration device such as a knocker or a vibrator may be installed in the path connecting the first path 5aA and the location A of the first exhaust gas path 2.

[0022] As described above, in the fly ash circulation system 1 of the embodiment of the present invention, the first exhaust gas path 2 upstream of the dust collector 4 passes directly below or below the chemical-mixed fly ash supplying device 5 located below the dust collector 4, then passes upward and is connected to the dust collector 4. Therefore, the drug-mixed fly ash supplying device 5 can easily supply the drug-mixed fly ash that has fallen to the inside and below the dust collector 4 to the first exhaust gas path 2 that passes below the drug-mixed fly ash supplying device 5 by gravity or by gravity and the suction force of the negative pressure first exhaust gas path 2. The drug-mixed fly ash is introduced into the first exhaust gas path 2 and dispersed, and is automatically lifted upward by the flow of the dust-containing exhaust gas and introduced again into the dust collector. In other words, the chemical-mixed fly ash stored in the dust collector 4 is re-supplied to the first exhaust gas path 2 upstream of the dust collector 4 and circulated, thereby making effective use of the unreacted chemicals in the chemical-mixed fly ash. In this way, the unreacted chemicals in the chemical-mixed fly ash can be effectively utilized, so the amount of new chemicals supplied from the chemical supply device 3 can be reduced. Therefore, the operating cost of the combustion furnace plant in which the fly ash circulation device 1 is installed can be reduced. Moreover, unlike the conventional technology, a conveyor-type or air-transporting device for lifting the chemical-mixed fly ash toward the exhaust gas piping above is not required, and the fly ash circulation device 1 can be manufactured at low cost. Furthermore, since the conveying device is not required, the maintenance frequency and maintenance period of the fly ash circulation device 1 can be reduced compared to conventional technology, and as a result, the operating rate of the combustion furnace plant in which the fly ash circulation device 1 is installed can be improved.

[0023] Now, the fly ash circulating apparatuses 1A, 1B, 1C, and 1D which are modifications of the embodiment will be described in order. The same components as those of the fly ash circulating apparatus 1 of the embodiment will be given the same reference numerals and the description thereof will be omitted.

[0024] [First modified fly ash circulation device] A fly ash circulation apparatus 1A of the first modified example will be described with reference to Fig. 2. The fly ash circulation apparatus 1A is significantly different from the fly ash circulation apparatus 1 of the embodiment in the chemical supply device 3A and a specific location (hereinafter referred to as "location B'") of the first exhaust gas path 2 to which the chemical supply device 3A supplies the chemical. The other configurations of the fly ash circulation apparatus 1A are similar to those of the fly ash circulation apparatus 1, and therefore will not be described. The chemical-mixed fly ash supplied from the chemical-mixed fly ash supplying device 5 to the point A of the first flue gas passage 2 may not be uniformly dispersed in the dust-containing flue gas flowing through the first flue gas passage 2. Therefore, in the fly ash circulation system 1A, the chemical supplying device 3A is equipped with a blower such as a high-pressure blower or a compressed air supplying device that supplies compressed air, and uses pressurized air (hereinafter referred to as "pressurized air") to spray and disperse a chemical toward the chemical-mixed fly ash supplied from point A by the chemical-mixed fly ash supplying device 5 from point B' of the first exhaust gas path 2, which is upstream of point A of the first exhaust gas path 2 and is at approximately the same position as point A in the X-axis direction. The chemical supplying device 3A may include a nozzle for spraying the chemical so that the chemical can be easily sprayed onto the chemical-mixed fly ash supplied from the location A. With the above-described configuration, the fly ash circulation device 1A applies pressure to the chemical-mixed fly ash supplied to location A to inject new chemicals from the chemical supply device 3A, thereby crushing relatively large particles and lumps in the chemical-mixed fly ash. This enables not only the new chemicals but also the unreacted chemicals in the chemical-mixed fly ash to be effectively dispersed into the dust-containing exhaust gas flowing through the first exhaust gas path 2. Therefore, the fly ash circulating apparatus 1A of the first modified example is superior to the fly ash circulating apparatus 1 of the embodiment in that the unreacted chemical in the chemical-mixed fly ash can be reacted with the dust-containing flue gas more effectively.

[0025] [Fly ash circulation device of the second modified example] A fly ash circulating apparatus 1B of the second modified example will be described with reference to Fig. 3. The fly ash circulating apparatus 1B is significantly different from the fly ash circulating apparatus 1 of the embodiment in that the fly ash circulating apparatus 1B is provided with a pressurized air supplying apparatus 8 that includes a blower such as a high-pressure blower and a compressed air supplying apparatus for supplying compressed air, and that injects and supplies the pressurized air to a specific location (hereinafter referred to as "location C") in the first exhaust gas passage 2. Other configurations of the fly ash circulating apparatus 1B are similar to those of the fly ash circulating apparatus 1, and therefore description thereof will be omitted. The pressurized air supplying device 8 injects pressurized air from a position C toward the chemical-mixed fly ash supplied to the position A by the chemical-mixed fly ash supplying device 5. The pressurized air supplying device 8 may be provided with a nozzle for pressurized air so that the pressurized air can be easily sprayed toward the chemical-mixed fly ash supplied from the location A. It is desirable that the point C be located upstream of the point A of the first exhaust gas passage 2 and at a position substantially the same as or close to the point A in the X-axis direction. With the above-described configuration, the fly ash circulation device 1B can apply pressure by injecting pressurized air to the chemical-mixed fly ash supplied to location A, thereby crushing relatively large particles and lumps in the chemical-mixed fly ash, thereby effectively dispersing unreacted chemicals in the chemical-mixed fly ash into the dust-containing exhaust gas flowing through the first exhaust gas path 2. Therefore, the fly ash circulating apparatus 1B of the second modified example is superior to the fly ash circulating apparatus 1 of the embodiment in that the unreacted chemical in the chemical-mixed fly ash can be reacted with the dust-containing flue gas more effectively. In addition, by adding the pressurized air supply device 8 of the fly ash circulation device 1B of the second modified example to the fly ash circulation device 1A of the first modified example, the unreacted chemicals in the chemical-mixed fly ash can be more effectively reacted with the dust-containing exhaust gas.

[0026] [Third modified fly ash circulation device] A third modified fly ash circulating apparatus 1C will be described with reference to Fig. 4. The fly ash circulating apparatus 1C is significantly different from the fly ash circulating apparatus 1 of the embodiment in that a circulating exhaust gas supply path 9 is connected between the point A of the first exhaust gas path 2 and the second exhaust gas path 6, and the first outlet connected to the point A of the chemical-mixed fly ash supplying apparatus 5 is directly connected to the circulating exhaust gas supply path 9, so that the chemical-mixed fly ash supplying apparatus 5 indirectly supplies the chemical-mixed fly ash to the point A of the first exhaust gas path 2. The circulating exhaust gas supply path 9 is disposed so as to pass directly below or below the vicinity of the chemical-mixed fly ash supply device 5 (in the -Y-axis direction). Therefore, the chemical-mixed fly ash supply device 5 can easily supply the chemical-mixed fly ash to the circulating exhaust gas supply path 9 by gravity, or by gravity and the suction force of the negative pressure of the circulating exhaust gas supply path 9. As a result, the chemical-mixed fly ash supply device 5 can supply the chemical-mixed fly ash to the point A of the first exhaust gas path 2 by entraining it in the flow of the post-dust removal exhaust gas that branches off from the second exhaust gas path 6 and flows through the circulating exhaust gas supply path 9. Like the first exhaust gas passage 2 and the second exhaust gas passage 6, the exhaust gas passage 2 is, for example, a pipe such as a duct or a pipe.

[0027] Here, a configuration in which a blower (second blower) 10 is installed between a portion of the circulating exhaust gas supply path 9 to which the first outlet of the chemical-mixed fly ash supply device 5 is connected and the second exhaust gas path 6 is shown as an example. The blower 10 is a device that pressurizes and sends a portion of the post-dust removal exhaust gas that has been removed by the dust collector 4 and flows through the second exhaust gas path 6 to a portion A of the first exhaust gas path 2. By disposing the blower 10, the post-dust removal exhaust gas that flows through the circulating exhaust gas supply path 9 can be pressurized and caused to flow, so that the chemical-mixed fly ash can be uniformly or effectively dispersed in the post-dust removal exhaust gas. The blower 10 is appropriately selected from, for example, a fan, a blower, a compressor, etc., depending on the design. When the circulating exhaust gas supply path 9 is connected between the second exhaust gas path 6 downstream of the first blower 7 and the location A of the first exhaust gas path 2, it may not be necessary to install the second blower 10. Other configurations of the fly ash circulating apparatus 1C are similar to those of the fly ash circulating apparatus 1, so the description will be omitted.

[0028] According to the configuration of the fly ash circulation apparatus 1C, unlike the fly ash circulation apparatus 1A of the first modified example and the fly ash circulation apparatus 1B of the second modified example, pressurized air is not injected into the first flue gas path 2, but a part of the flue gas after dust removal is used to effectively disperse the unreacted chemical in the chemical-mixed fly ash into the dust-containing flue gas flowing through the first flue gas path 2. Therefore, the ash circulation apparatus 1C of the third modified example is superior to the fly ash circulation apparatus 1A of the first modified example and the fly ash circulation apparatus 1B of the second modified example in that it does not increase the total amount of flue gas discharged from the combustion furnace plant.

[0029] In addition, in existing combustion furnace plants, for example, waste incineration plants, in order to reduce oxides (such as NOx) in the dust-containing exhaust gas, the post-dust removal exhaust gas may be returned to the incinerator and used for burning waste. The technology of returning the post-dust removal exhaust gas to the furnace of a combustion furnace such as an incinerator is called exhaust gas recirculation technology (Exhaust Gas Recirculation (EGR)). Therefore, a part of the post-dust removal exhaust gas flowing through the circulating exhaust gas supply path 9 may be branched off and blown into the combustion furnace. In addition, in the configuration of the fly ash circulation device 1B of the second modification, instead of the pressurized air supply device 8, a circulating exhaust gas supply path 9 may be arranged between the point C of the first exhaust gas path 2 and the second exhaust gas path 6 as in the fly ash circulation device 1C of the third modification, and the dust-removed exhaust gas may be sprayed to target the chemical-mixed fly ash supplied directly to the point A of the first exhaust gas path 2 from the chemical-mixed fly ash supply device 5. In this case, as described in the second modification, relatively large particles and lumps in the chemical-mixed fly ash can be crushed, so that the unreacted chemical in the chemical-mixed fly ash can be effectively dispersed in the dust-containing exhaust gas flowing through the first exhaust gas path 2. Furthermore, in the fly ash circulation apparatus 1C, the circulating exhaust gas supply path 9 is directly connected between the point A of the first exhaust gas path 2 and the second exhaust gas path 6, but in the configuration of the fly ash circulation apparatus 1A of the first modified example or the fly ash circulation apparatus 1B of the second modified example, the circulating exhaust gas supply path 9 may be disposed between the second exhaust gas path 6 and the middle of the path connecting the sealing device 5b and the point A. Even in this configuration, the unreacted chemical in the chemical-mixed fly ash can be effectively dispersed by the pressure of the exhaust gas flow after dust removal.

[0030] [Fourth modified fly ash circulation device] A fourth modified fly ash circulating apparatus 1D will be described with reference to Fig. 5. The fly ash circulating apparatus 1D is significantly different from the first modified fly ash circulating apparatus 1A in that a classifier 5c is disposed above (in the +Y-axis direction) the sealing device 5b in the path connecting the first path 5aA and the portion A of the first exhaust gas path 2. Fig. 5 shows an example in which the chemical-mixed fly ash supplying apparatus 5 is provided with the classifier 5c. Other configurations of the fly ash circulating apparatus 1D are similar to those of the fly ash circulating apparatus 1A, so the description will be omitted. The classifier 5c is a device that crushes the drug-mixed fly ash when the drug-mixed fly ash contains relatively large particles or lumps, uniforms the size of the particles or lumps overall, and scrapes off and removes the layer of reaction products formed on the surface of the drug in the drug-mixed fly ash to expose the unreacted drug. The classifier 5c can be, for example, a vibrating sieve or a trommel with a cylinder having a predetermined number of through holes. The classifier 5c allows the chemical-mixed fly ash to have an appropriate particle size and to be supplied to the first exhaust gas path 2, and also allows the chemical-mixed fly ash to be supplied with its unreacted surface exposed to the first exhaust gas path 2. Therefore, the fly ash circulation device 1D of the fourth modified example is superior to the fly ash circulation device 1A of the first modified example in that the unreacted chemical in the chemical-mixed fly ash can be more effectively dispersed and reacted with the dust-containing exhaust gas. The classifier 5c of the fly ash circulation apparatus 1D of the fourth modification may be installed in the fly ash circulation apparatus 1 of the embodiment, the fly ash circulation apparatus 1B of the second modification, and the fly ash circulation apparatus 1C of the third modification at the same position as that of the fly ash circulation apparatus 1D. That is, the classifier 5c of the fly ash circulation apparatus 1D may be installed above the sealing device 5b (in the +Y-axis direction) in the path connecting the first path 5aA of the fly ash circulation apparatus 1, the fly ash circulation apparatus 1B, and the fly ash circulation apparatus 1C to the portion A of the first exhaust gas path 2. When configured in this way, the same effects as those of the fly ash circulation apparatus 1D of the fourth modification can be obtained in these embodiments and modifications. [Explanation of symbols]

[0031] 1, 1A, 1B, 1C, 1D Fly ash circulation device 2. First exhaust gas route 3. 3A Drug Supply Device 4 Dust collector (4a bag filter, 4b hopper, 4c feeder) 5 Chemical-mixed fly ash supply device (5a distribution device (5aA first path, 5aB second path), 5b Sealing device 5c classifier) 6 Second exhaust gas route 7 Blower (first blower) 8. Compressed air supply device 9. Circulating exhaust gas supply route 10 Blower (second blower)

Claims

1. a chemical supplying device that supplies a chemical for purifying the dust-containing exhaust gas to a first exhaust gas passage through which the dust-containing exhaust gas generated in a combustion furnace plant flows; a dust collector connected to an upstream side of the first exhaust gas passage and a downstream side of the second exhaust gas passage, the dust collector removing the dust-containing exhaust gas from the first exhaust gas passage and discharging the removed exhaust gas to the second exhaust gas passage; A chemical-mixed fly ash supplying device is connected below the dust collector and supplies the chemical-mixed fly ash, which is a mixture of the chemical and the fly ash that has fallen to the inside lower portion of the dust collector by the dust removal, to the first exhaust gas path; The drug-mixed fly ash supplying device is a fly ash circulating device that supplies the drug-mixed fly ash to the first exhaust gas path that passes directly below or below near the drug-mixed fly ash supplying device.

2. The fly ash circulation device of claim 1, further comprising a dust ash distributor that selectively distributes the drug-mixed fly ash to either a first path for supplying the drug-mixed fly ash to the first exhaust gas path or a second path for discharging the drug-mixed fly ash for dust ash treatment, or simultaneously distributes the drug-mixed fly ash to both the first path and the second path.

3. The fly ash circulation device according to claim 2, further comprising a sealing device connected to the first passage and separating the first passage from the first exhaust gas passage without impeding the supply of the drug-mixed fly ash to the first exhaust gas passage.

4. The fly ash circulating apparatus according to claim 3 , further comprising a classifier disposed between the first path and the sealing device for classifying the chemical-mixed fly ash.

5. The fly ash circulation device according to any one of claims 1 to 4, wherein the chemical supply device disperses the chemical in pressurized air and supplies the chemical to the chemical-mixed fly ash supplied to the first exhaust gas path.

6. The fly ash circulating apparatus according to any one of claims 1 to 4, further comprising a pressurized air supplying device that supplies pressurized air toward the chemical-mixed fly ash supplied to the first exhaust gas path.

7. The fly ash circulation device according to any one of claims 1 to 4, further comprising a circulating exhaust gas supply path that disperses the drug-mixed fly ash supplied to the first exhaust gas path with the dust-removed exhaust gas of the second exhaust gas path.

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