Waste incineration facility

Abstract

To easily reduce an exhaust gas amount in a waste incineration facility.SOLUTION: A waste incineration facility (1) comprises: an incinerator (3) that incinerates waste; an exhaust gas flow path (4) through which exhaust gas discharged from the incinerator (3) flows; a dust collector (42) provided in the exhaust gas flow path (4); a recirculation exhaust gas line (6) that is connected to an extraction position (P1) downstream of the dust collector (42) in the exhaust gas flow path (4), extracts a portion of the exhaust gas flowing through the exhaust gas flow path (4) as recirculation exhaust gas, and supplies it to the incinerator (3); and an oxygen mixing unit (68) that mixes high-concentration oxygen gas, which has a higher oxygen concentration than air, with the recirculation exhaust gas flowing through the recirculation exhaust gas line (6). This makes it easy to reduce an amount of exhaust gas.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a waste incineration plant. [Reference to Related Applications] This application claims the benefit of priority from Japanese patent application JP2021-202826, filed on December 14, 2021, and Japanese patent application JP2022-54107, filed on March 29, 2022, the entire disclosures of which are incorporated herein by reference. [Background technology]

[0002] Conventionally, in waste incineration facilities, a part of the exhaust gas flowing through the exhaust gas flow passage is extracted as recirculated exhaust gas and supplied to the incinerator. By using the recirculated exhaust gas, it is possible to reduce the amount of exhaust gas from the waste incineration facility. For example, Japanese Patent Application Laid-Open No. 2003-329228 discloses a waste incinerator in which air is mixed with the exhaust gas and the oxygen-enriched exhaust gas is blown into the combustion chamber. Japanese Patent Application Laid-Open No. 2001-241629 discloses a combustion device in which nozzles facing each other are provided in a secondary combustion chamber, and oxygen-enriched air is blown out from one nozzle and recirculated exhaust gas is blown out from the other nozzle. Japanese Patent Application No. 3949386 discloses a combustion method that combines a combustion method in which combustion gas in the upper space of a post-combustion stoker is extracted and recirculated into the furnace with localized oxygen-enriched combustion. Japanese Patent Application Laid-Open No. 10-9538 discloses an incineration facility in which urban waste fed into a first combustion furnace is combusted by supplying oxygen, and a portion of the exhaust gas that has passed through a boiler is circulated into the first combustion furnace.

[0003] In recent years, there has been a demand for further reduction in the amount of exhaust gas from waste incineration facilities. However, in order to ensure the amount of oxygen required for burning waste, a large amount of fresh air must be supplied from outside the system to the incinerator, and there is a limit to the amount of recirculated exhaust gas that can be used. Therefore, it is not easy to reduce the amount of exhaust gas. Summary of the Invention

[0004] The present invention is directed to a waste incineration facility and has an object to easily reduce the amount of exhaust gas in the waste incineration facility.

[0005] A first aspect of the present invention is a waste incineration facility comprising an incinerator for incinerating waste, an exhaust gas flow path through which exhaust gas discharged from the incinerator flows, a dust collector provided in the exhaust gas flow path, a recirculation exhaust gas line connected to an extraction position in the exhaust gas flow path downstream of the dust collector and extracting a portion of the exhaust gas flowing through the exhaust gas flow path as recirculated exhaust gas and supplying it to the incinerator, and an oxygen mixing section for mixing high-concentration oxygen gas, which has an oxygen concentration higher than that of air, with the recirculated exhaust gas flowing through the recirculation exhaust gas line.

[0006] According to the present invention, the amount of exhaust gas can be easily reduced in a waste incineration facility.

[0007] A second aspect of the present invention is a waste incineration facility according to the first aspect, in which the main combustion gas supplied to the incinerator through a gas pipe is the recirculated exhaust gas mixed with the high-concentration oxygen gas.

[0008] A third aspect of the present invention is a waste incineration facility according to the first aspect (which may be either the first or second aspect), in which the recirculated exhaust gas line is connected to the primary combustion chamber and / or the secondary combustion chamber of the incinerator, and the recirculated exhaust gas mixed with the high-concentration oxygen gas is used as the primary combustion gas and / or the secondary combustion gas.

[0009] A fourth aspect of the present invention is the waste incineration facility of the first aspect (which may be any one of the first to third aspects), further comprising a dehydration section provided in the recirculated exhaust gas line for removing water from the recirculated exhaust gas.

[0010] A fifth aspect of the present invention is the waste incineration facility of the first aspect (which may be any one of the first to fourth aspects), further comprising a preheater provided in the recirculated exhaust gas line for heating the recirculated exhaust gas.

[0011] A sixth aspect of the present invention is a waste incineration equipment according to any one of the first to fifth aspects, further comprising a wet smoke scrubber provided in the exhaust gas flow path between the dust collector and the extraction position, for supplying a water-containing liquid to the exhaust gas to remove predetermined components from the exhaust gas, and the recirculated exhaust gas is heated by heat exchange between the exhaust gas upstream of the wet smoke scrubber in the exhaust gas flow path and the recirculated exhaust gas flowing through the recirculated exhaust gas line.

[0012] A seventh aspect of the present invention is a waste incineration facility according to any one of aspects 1 to 5 (or any one of aspects 1 to 6), further comprising a waste pit for storing waste before it is fed into the incinerator, and an extracted gas line for extracting gas from within the waste pit as extracted gas, and the oxygen mixing section generates the high-concentration oxygen gas from at least a portion of the extracted gas and mixes it with the recirculated exhaust gas flowing through the recirculated exhaust gas line.

[0013] An eighth aspect of the present invention is the waste incineration equipment of the seventh aspect, wherein the oxygen mixing section concentrates the oxygen contained in the extracted gas to produce the high-concentration oxygen gas, and the remaining gas of the extracted gas is discharged to the outside via a deodorizing device.

[0014] A ninth aspect of the present invention is a waste incineration facility according to any one of aspects 1 to 5 (which may be any one of aspects 1 to 8), further comprising a carbon dioxide capture device provided in the exhaust gas flow path downstream of the extraction position for capturing carbon dioxide from the exhaust gas, and a treated gas line for mixing at least a portion of the exhaust gas that has passed through the carbon dioxide capture device with the recirculated exhaust gas flowing through the recirculated exhaust gas line.

[0015] A tenth aspect of the present invention is the waste incineration equipment of the ninth aspect, wherein the oxygen mixing section is provided in the treated gas line, and produces the high-concentration oxygen gas from the exhaust gas that has passed through the carbon dioxide recovery device, and mixes it with the recirculated exhaust gas flowing through the recirculated exhaust gas line.

[0016] An eleventh aspect of the present invention is a waste incineration facility according to any one of aspects 1 to 5 (or any one of aspects 1 to 10), further comprising a carbon dioxide utilization device located downstream of the extraction position in the exhaust gas flow path, which utilizes the exhaust gas to produce a predetermined product.

[0017] A twelfth aspect of the present invention is a waste incineration facility according to any one of aspects 1 to 5 (or any one of aspects 1 to 6), further comprising a waste pit for storing waste before it is fed into the incinerator, a carbon dioxide capture device provided in the exhaust gas flow path downstream of the extraction position for capturing carbon dioxide from the exhaust gas, and a treated gas line for supplying at least a portion of the exhaust gas that has passed through the carbon dioxide capture device as a treated gas to the waste pit and / or the incinerator.

[0018] A thirteenth aspect of the present invention is a waste incineration equipment of the twelfth aspect, further comprising: an extracted gas line through which the treated gas is supplied to the waste pit, the gas in the waste pit is extracted as extracted gas and supplied to the incinerator; and another oxygen mixing section which mixes the extracted gas flowing through the extracted gas line with a gas having a higher oxygen concentration than air.

[0019] A fourteenth aspect of the present invention is a waste incineration facility of the twelfth aspect, further comprising an extraction gas line for extracting the gas in the waste pit as an extraction gas, wherein the treated gas is supplied to the waste pit, and the extraction gas is mixed with the recirculation exhaust gas flowing through the recirculation exhaust gas line.

[0020] A fifteenth aspect of the present invention is a waste incineration equipment of the twelfth aspect, further comprising an extract gas line through which the treated gas is supplied to the waste pit and which extracts the gas in the waste pit as an extract gas, and the oxygen mixing section produces the high-concentration oxygen gas from at least a portion of the extract gas and mixes it with the recirculated exhaust gas flowing through the recirculated exhaust gas line.

[0021] A sixteenth aspect of the present invention is a waste incineration equipment of the twelfth aspect (which may be any one of the twelfth to fifteenth aspects), in which the treated gas is supplied from the treated gas line to the lower part of the waste pit, and the treated gas that has passed through a layer of waste in the waste pit is supplied into the incinerator.

[0022] A seventeenth aspect of the present invention is the waste incineration facility of the twelfth aspect (which may be any one of the twelfth to sixteenth aspects), wherein a double door structure is provided on a platform connected to the waste pit.

[0023] Aspect 18 of the present invention is a waste incineration equipment of any one of aspects 1 to 5, further comprising an exhaust gas treatment device located downstream of the dust collector in the exhaust gas flow path for supplying a water-containing liquid to the exhaust gas to remove specific components from the exhaust gas, and a separation membrane for removing water from the exhaust gas immediately after it has passed through the exhaust gas treatment device.

[0024] The above and other objects, features, aspects and advantages will become apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings. [Brief description of the drawings]

[0025] [Figure 1] 1 is a block diagram showing the configuration of a waste incineration facility according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing the configuration of a garbage pit and an incinerator. [Diagram 3] FIG. 11 is a diagram showing a part of a waste incineration facility according to a second embodiment. [Figure 4] FIG. 11 is a block diagram showing a waste incineration facility according to a third embodiment. [Diagram 5] FIG. 11 is a block diagram showing a waste incineration facility according to a fourth embodiment. [Figure 6] FIG. 11 is a block diagram showing a waste incineration facility according to a fifth embodiment. [Figure 7]FIG. 13 is a block diagram showing a waste incineration facility according to a sixth embodiment. [Figure 8] FIG. 13 is a block diagram showing a waste incineration facility according to a seventh embodiment. [Figure 9] FIG. 13 is a block diagram showing a waste incineration facility according to an eighth embodiment. [Figure 10] FIG. 13 is a block diagram showing another example of a waste incineration facility. [Figure 11] FIG. 13 is a block diagram showing a waste incineration facility according to a ninth embodiment. [Figure 12] FIG. 13 is a block diagram showing another example of a waste incineration facility. [Figure 13] FIG. 13 is a block diagram showing a waste incineration facility according to a tenth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] (First embodiment) FIG. 1 is a block diagram showing the configuration of a waste incineration facility 1 according to a first embodiment of the present invention. The waste incineration facility 1 is a waste incineration facility and includes a waste pit 2, an incinerator 3, an exhaust gas flow path 4, and a control unit (not shown). The control unit is, for example, a computer equipped with a CPU or the like, and is responsible for the overall control of the waste incineration facility 1. The waste pit 2 is a waste pit and stores waste, which is waste. The incinerator 3 incinerates the waste thrown from the waste pit 2. The exhaust gas flow path 4 is a flue through which the exhaust gas discharged from the incinerator 3 flows. In the example of FIG. 1, the exhaust gas flow path 4 is a flow path from the incinerator 3 to a carbon dioxide capture device 44 described later. In FIG. 1, only the arrow between the incinerator 3 and a boiler tube group 41 described later is marked with the symbol 4. Details of the waste pit 2 and the incinerator 3 will be described later.

[0027] The waste incineration facility 1 further includes a boiler tube group 41, a filter-type dust collector 42 (hereinafter simply referred to as the "dust collector 42"), a wet smoke scrubber 43, and a carbon dioxide capture device 44. The boiler tube group 41, the dust collector 42, the wet smoke scrubber 43, and the carbon dioxide capture device 44 are provided in the exhaust gas flow path 4, and are arranged in this order from the upstream side to the downstream side in the flow direction of the exhaust gas (i.e., in the direction away from the incinerator 3).

[0028] The boiler tube group 41 generates steam using the exhaust gas discharged from the incinerator 3 as a heat source. The dust collector 42 is a so-called bag filter, and collects fly ash contained in the exhaust gas with a filter cloth. A powdered exhaust gas treatment agent may be supplied to the exhaust gas upstream of the dust collector 42, and the exhaust gas treatment agent may be collected together with the fly ash in the dust collector 42. The exhaust gas treatment agent is used to remove sulfur oxides, hydrogen chloride, dioxins, mercury compounds, etc. The temperature of the exhaust gas at the outlet of the dust collector 42 is, for example, 150°C to 200°C. The exhaust gas that has passed through the dust collector 42 flows into the wet smoke scrubber 43.

[0029] The wet smoke scrubber 43 sprays a liquid containing an alkaline agent such as caustic soda and water into the flue gas. This lowers the temperature of the flue gas to, for example, 30°C to 70°C, and removes sulfur oxides, hydrogen chloride, and the like contained in the flue gas. In addition, the amount of water contained in the flue gas decreases with the decrease in the temperature of the flue gas. The wet smoke scrubber 43 is a desulfurization section that removes sulfur oxides from the flue gas, and is also a desalination section that removes hydrogen chloride from the flue gas. The carbon dioxide capture device 44 captures carbon dioxide from the flue gas that has passed through the wet smoke scrubber 43. One example of the carbon dioxide capture device 44 captures carbon dioxide by a chemical absorption method, and includes an absorption tower and a regeneration tower. In the absorption tower, for example, a liquid containing amine and water is sprayed into the flue gas, and carbon dioxide is absorbed by the liquid. That is, carbon dioxide is removed from the flue gas. The liquid that has absorbed the carbon dioxide is sent to the regeneration tower and heated, and the carbon dioxide is extracted and captured. The captured carbon dioxide is used for producing methane through methanation or is stored underground (CCUS (Carbon dioxide Capture, Utilization and Storage)). In the waste incineration facility 1 provided with the recirculation flue gas line 6 described below, the carbon dioxide concentration in the flue gas is high, so CCUS can be easily performed. The carbon dioxide capture device 44 may capture carbon dioxide by a method other than chemical absorption.

[0030] As described above, the wet smoke scrubber 43 and the carbon dioxide capture device 44 form an exhaust gas treatment device 45 that supplies a liquid containing water to the exhaust gas that has passed through the dust collector 42 to remove predetermined components from the exhaust gas. In the following description, the exhaust gas that has passed through the wet smoke scrubber 43 and the carbon dioxide capture device 44 (exhaust gas treatment device 45) is referred to as "treated gas." The treated gas in the waste incineration facility 1 is a gas that contains large amounts of water, oxygen, and nitrogen.

[0031] The waste incineration facility 1 further includes a treated gas line 5, an exhaust gas reheater 51, and an induced draft fan 52. The treated gas line 5 is a flow path through which the treated gas discharged from the carbon dioxide capture device 44 flows. The treated gas line 5 branches into two, one of which is connected to the waste pit 2 and the other of which is connected to a chimney 59. The exhaust gas reheater 51 and the induced draft fan 52 are provided in the treated gas line 5 and are arranged in order from the upstream side to the downstream side in the flow of the treated gas (i.e., in the direction away from the carbon dioxide capture device 44). In the example of FIG. 1, the branch point of the treated gas line 5 is provided downstream of the induced draft fan 52. In FIG. 1, only the arrow between the carbon dioxide capture device 44 and the exhaust gas reheater 51 is marked with the symbol 5.

[0032] The exhaust gas reheater 51 heats the treated gas using, for example, steam from a boiler (boiler tube group 41) as a heat medium. This suppresses condensation of moisture in the treated gas line 5. As a result, corrosion of the pipe wall of the treated gas line 5 caused by acid gases such as sulfur oxides and hydrogen chloride in the treated gas being dissolved in the condensed water is suppressed. The induced draft fan 52 forms a gas flow from the upstream side to the downstream side in the exhaust gas flow path 4 and the treated gas line 5 (i.e., a gas flow from the incinerator 3 to the garbage pit 2 and the chimney 59 via the dust collector 42, the carbon dioxide capture device 44, etc.). A part of the treated gas that has passed through the carbon dioxide capture device 44, the exhaust gas reheater 51, and the induced draft fan 52 is supplied to the garbage pit 2, and the remaining treated gas is discharged to the outside from the chimney 59. The branch point of the treated gas line 5 may be provided upstream of the induced draft fan 52. In this case, a fan is provided in the treated gas line 5 between the branch point and the waste pit 2. The waste incineration plant 1 may be provided with a reducing agent supply unit that sprays a reducing agent such as ammonia water into the incinerator 3, and non-catalytic denitrification (SNCR) may be performed. Since the exhaust gas that has passed through the carbon dioxide capture device 44 usually has a higher oxygen concentration than air, it may be discharged onto the roof of the facility in which the waste incineration plant 1 is installed, or into the soil. In addition, by returning the treated gas to the incinerator 3, the surplus oxygen contained in the treated gas that has passed through the carbon dioxide capture device 44 can be used again for combustion.

[0033] The waste incineration facility 1 further includes a recirculated flue gas line 6, a fan 66, a preheater 67, and an oxygen mixing unit 68. The recirculated flue gas line 6 is a flow path through which the recirculated flue gas described below flows, and one end of the recirculated flue gas line 6 is connected to an extraction position P1 downstream of the dust collector 42 in the flue gas flow path 4. In the example of FIG. 1, the extraction position P1 is a position between the wet smoke scrubber 43 and the carbon dioxide capture device 44. The recirculated flue gas line 6 extracts a part of the flue gas flowing through the flue gas flow path 4 as recirculated flue gas. The carbon dioxide capture device 44 described above is provided downstream of the extraction position P1 in the flue gas flow path 4, so that the recirculated flue gas extracted from the extraction position P1 has a high carbon dioxide concentration and a low oxygen concentration. The other end of the recirculated flue gas line 6 is connected to the incinerator 3, and the recirculated flue gas is supplied into the incinerator 3. In FIG. 1, only the arrow connected to the take-out position P1 is labeled with the reference symbol 6.

[0034] The fan 66 and the preheater 67 are provided in the recirculated exhaust gas line 6. In one example of the waste incineration facility 1, the preheater 67 and the fan 66 are arranged in this order from the upstream side to the downstream side in the flow of the recirculated exhaust gas (i.e., in the direction away from the take-out position P1). Two preheaters (first and second preheaters) may be used, and the first preheater, the fan 66 and the second preheater may be arranged in this order from the upstream side to the downstream side. The order of the fan 66 and the preheater 67 in the recirculated exhaust gas line 6 may be determined arbitrarily.

[0035] The fan 66 forms a flow of the recirculated exhaust gas from the upstream side to the downstream side of the recirculated exhaust gas line 6. The preheater 67 can heat the recirculated exhaust gas by using, for example, steam from a boiler (boiler tube group 41) as a heat medium. The preheater 67 may only heat the recirculated exhaust gas as necessary.

[0036] The oxygen mixing unit 68 is a device that generates gas having a higher oxygen concentration (volume concentration) than air (hereinafter simply referred to as "high-concentration oxygen gas") from air, and is, for example, a PSA-type oxygen gas generator. The high-concentration oxygen gas generated in the oxygen mixing unit 68 is mixed with the recirculated exhaust gas in the recirculated exhaust gas line 6. In an example in which the first preheater, the fan 66, and the second preheater are provided, the high-concentration oxygen gas is mixed between the fan 66 and the second preheater. By mixing the high-concentration oxygen gas, a recirculated exhaust gas having a higher oxygen concentration than the exhaust gas at the take-out position P1 is obtained and is supplied to the incinerator 3. The high-concentration oxygen gas has an oxygen concentration sufficiently higher than that of air, and the oxygen concentration is, for example, 50 vol% or more, preferably 65 vol% or more, more preferably 80 vol% or more, and even more preferably 100%. The high-concentration oxygen gas may be generated from something other than air. For example, the high-concentration oxygen gas may be generated by electrolysis of water.

[0037] FIG. 2 is a diagram showing the configuration of the garbage pit 2 and the incinerator 3. As described above, garbage is stored in the garbage pit 2, and a garbage accumulation layer 91 (hereinafter referred to as the "garbage accumulation layer 91"). The treated gas line 5 described above is connected to the lower part of the garbage pit 2. The lower part of the garbage pit 2 includes the side part below the platform 22 and the bottom part. In one example of the garbage pit 2, a treated gas outlet is provided on the side part. An outlet opening toward the bottom surface may be provided. The treated gas supplied from the treated gas line 5 into the garbage pit 2 passes through the garbage accumulation layer 91 in the garbage pit 2 and spreads upward. That is, the treated gas is dispersed into countless gaps between the garbage in the garbage accumulation layer 91, and reaches the upper part of the garbage accumulation layer 91. Therefore, the gas flow becomes gentle in the space above the garbage accumulation layer 91. In addition, acid gases and the like contained in the treated gas are dissolved in the moisture contained in the garbage and removed from the treated gas.

[0038] One end of the extracted gas line 21, which is a gas flow path, is connected to the upper part of the garbage pit 2. The upper part of the garbage pit 2 includes the side part above the inlet of the inlet hopper 31 described below in the incinerator 3, and the ceiling part. A fan (not shown) is provided in the extracted gas line 21. This allows gas in the garbage pit 2 to be extracted from the extracted gas line 21 as extracted gas. The gas in the garbage pit 2 includes treated gas that has passed through the garbage pile layer 91, and air that flows into the garbage pit 2 from the inlet door of the platform 22. In the garbage pit 2, the internal pressure is set to a negative pressure lower than atmospheric pressure, suppressing the leakage of odors from the garbage pit 2 to the outside.

[0039] As described above, acid gases and the like contained in the treated gas are removed in the garbage accumulation layer 91, so that even if moisture in the extracted gas is condensed in the extracted gas line 21, corrosion of the pipe wall of the extracted gas line 21 is suppressed. As will be described later, in the example of Fig. 2, the other end of the extracted gas line 21 is connected to the recirculated exhaust gas line 6. A preheater may be provided in the extracted gas line 21.

[0040] In a preferred waste incineration facility 1, a double door structure is provided on the platform 22 connected to the waste pit 2. Specifically, an outer door 221 and an inner door 222 are provided between the platform 22 where the waste collection truck stops and the waste pit 2. When the waste collection truck puts waste into the waste pit 2, the outer door 221 is opened with the inner door 222 closed, and the waste is put in from the waste collection truck. The waste is temporarily held between the inner door 222 and the outer door 221. When the waste collection truck has finished putting in the waste, the outer door 221 is closed, and then the inner door 222 is opened. This allows the waste to be put into the waste pit 2. After the waste has been put into the waste pit 2, the inner door 222 is closed. With the double door structure, it is possible to reduce the amount of air flowing into the waste pit 2.

[0041] The incinerator 3 comprises an input hopper 31, a waste supply section 32, a primary combustion chamber 33, and a secondary combustion chamber 34. Waste is input from the waste pit 2 into the input hopper 31 by the waste crane 23. The waste supply section 32 has a pusher or a screw feeder or the like, and supplies waste from the bottom of the input hopper 31 into the primary combustion chamber 33.

[0042] At the bottom of the primary combustion chamber 33, a drying grate section 331, a combustion grate section 332, a post-combustion grate section 333, and a discharge port 334 are arranged in this order in the direction away from the garbage supply section 32. In the drying grate section 331, the combustion grate section 332, and the post-combustion grate section 333, garbage is transported from the garbage supply section 32 side toward the discharge port 334 by a well-known transport operation. In each of the drying grate section 331, the combustion grate section 332, and the post-combustion grate section 333, primary combustion gas described below is ejected toward the inside of the primary combustion chamber 33, and the garbage is burned during transport. The burned garbage (mainly ash) is discharged to the outside of the primary combustion chamber 33 through the discharge port 334.

[0043] The secondary combustion chamber 34 is a space surrounded by the side wall, and directly continues from the primary combustion chamber 33 to form a flow path for exhaust gas discharged from the primary combustion chamber 33. In the example of FIG. 2, the secondary combustion chamber 34 is a space with a flow path area sufficiently smaller than the floor area of ​​the primary combustion chamber 33 and directed upward. A plurality of nozzles 341 are provided on the side wall of the secondary combustion chamber 34, and secondary combustion gas described below is ejected from the plurality of nozzles 341. This causes unburned gas generated in the primary combustion chamber 33 to burn. The secondary combustion chamber 34 is a part of the incinerator 3, and the flow path downstream from the outlet of the secondary combustion chamber 34 is the exhaust gas flow path 4 described above. In FIG. 2, the area in which the boiler tube group 41 is provided is indicated by the reference numeral 41.

[0044] 2, the recirculation exhaust gas line 6 branches into a primary combustion gas line 61 and a secondary combustion gas line 62 at a branch point P2 downstream (toward the incinerator 3) of the position where the high-concentration oxygen gas is mixed by the oxygen mixer 68. The primary combustion gas line 61 branches into a plurality of lines, which are connected to the wind boxes of the drying grate section 331, the combustion grate section 332, and the post-combustion grate section 333, respectively. The secondary combustion gas line 62 branches into a plurality of lines, which are connected to a plurality of nozzles 341, respectively.

[0045] The extracted gas line 21 is connected to the recirculation exhaust gas line 6 at a position upstream of the branch point P2. As a result, the extracted gas from the garbage pit 2 is further mixed with the recirculation exhaust gas mixed with the high-concentration oxygen gas. The mixed gas of the recirculation exhaust gas, the high-concentration oxygen gas, and the extracted gas flows into the primary combustion gas line 61 and the secondary combustion gas line 62. In the following description, the gas flowing through the primary combustion gas line 61 is referred to as the "primary combustion gas," and the gas flowing through the secondary combustion gas line 62 is referred to as the "secondary combustion gas." The primary combustion gas is supplied into the primary combustion chamber 33 from the drying grate section 331, the combustion grate section 332, and the post-combustion grate section 333. The secondary combustion gas is supplied into the secondary combustion chamber 34 from a plurality of nozzles 341.

[0046] The oxygen concentration of the primary combustion gas and the secondary combustion gas is, for example, 30 vol% or less, typically 25 vol% or less. The oxygen concentration is, for example, greater than 0 vol%, preferably 3 vol% or more. The oxygen concentration of the primary combustion gas and the secondary combustion gas in the example of FIG. 2 can be adjusted by changing the mixing ratio of the recirculated exhaust gas, the high-concentration oxygen gas, and the extracted gas, or by changing the oxygen concentration of the high-concentration oxygen gas. In addition, the oxygen concentrations of the primary combustion gas and the secondary combustion gas may be individually adjustable. In this case, for example, in each of the primary combustion gas line 61 and the secondary combustion gas line 62, the piping design is changed and a damper, a flow meter, etc. are provided so that the mixing ratio of the recirculated exhaust gas, the high-concentration oxygen gas, and the extracted gas can be individually changed. Furthermore, the oxygen concentration of the primary combustion gas in each of the drying grate section 331, the combustion grate section 332, and the post-combustion grate section 333 may be individually adjustable. Similarly, the oxygen concentration of the secondary combustion gas may be individually adjustable in each of the multiple nozzles 341. In the waste incineration facility 1, multiple mixing sections may be provided, and the mixing ratios of the recirculated exhaust gas, the high-concentration oxygen gas, and the extracted gas may be independently variable and supplied into the incinerator 3.

[0047] As described above, the preferred waste incineration system 1 includes the recirculation exhaust gas line 6 that extracts a part of the exhaust gas flowing through the exhaust gas flow passage 4 as recirculation exhaust gas and supplies it to the incinerator 3, and the oxygen mixing section 68 that mixes the recirculation exhaust gas flowing through the recirculation exhaust gas line 6 with a gas having a higher oxygen concentration than air (the above-mentioned high-concentration oxygen gas). In the waste incineration system 1, the recirculation exhaust gas is mixed with the high-concentration oxygen gas and used as a combustion gas in the incinerator 3, so that the amount of recirculation exhaust gas extracted from the exhaust gas flow passage 4 can be increased compared to the case where the recirculation exhaust gas is mixed with air. As a result, the amount of exhaust gas flowing downstream of the connection position of the recirculation exhaust gas line 6 (i.e., the extraction position P1) in the exhaust gas flow passage 4 can be easily reduced. In addition, by continuing the operation while minimizing the amount of air (especially nitrogen) supplied from outside the system to the incinerator 3, the amount of nitrogen contained in the exhaust gas gradually decreases, and the main components of the exhaust gas passing through the carbon dioxide capture device 44 can be carbon dioxide, water, and excess oxygen. When operating in this manner, the concentration of carbon dioxide contained in the exhaust gas increases, and therefore the carbon dioxide can be efficiently separated in the carbon dioxide capture unit 44. Furthermore, when operating in this manner, the amount of moisture contained in the exhaust gas also decreases in the wet smoke scrubber 43 as the temperature of the exhaust gas decreases, and therefore the moisture contained in the recirculated exhaust gas can also be removed.

[0048] Preferably, the recirculated exhaust gas line 6 is connected to the primary combustion chamber 33 and the secondary combustion chamber 34 of the incinerator 3, and the recirculated exhaust gas mixed with high-concentration oxygen gas is used as the primary combustion gas and the secondary combustion gas. This can more reliably increase the amount of recirculated exhaust gas used, and further reduce the amount of exhaust gas flowing downstream of the take-out position P1 in the exhaust gas flow path 4. In the waste incineration system 1, the recirculated exhaust gas line 6 may be connected only to the primary combustion chamber 33 or only to the secondary combustion chamber 34. In this case, too, it is possible to ensure a certain amount of use of the recirculated exhaust gas and reduce the amount of exhaust gas. As described above, in the waste incineration system 1, it is preferable that the recirculated exhaust gas line 6 is connected to the primary combustion chamber 33 or / and the secondary combustion chamber 34 of the incinerator, and the recirculated exhaust gas mixed with high-concentration oxygen gas is used as the primary combustion gas or / and the secondary combustion gas. In the waste incineration system 1, it is preferable to minimize the amount of air supplied to the incinerator 3 from outside the system. That is, during operation, it is preferable to eliminate air supplied from outside the system to the incinerator 3, other than air entering the incinerator 3 such as air flowing into the garbage pit 2 from the loading door of the platform 22, equipment purging air, equipment cooling air, and air brought in by garbage. Note that air may be supplied to the incinerator 3 from outside the system during initial operation.

[0049] Preferably, the waste incineration facility 1 includes a preheater 67 that is provided in the recirculated flue gas line 6 and heats the recirculated flue gas. This makes it possible to heat the recirculated flue gas to a temperature suitable for use as combustion gas.

[0050] Preferably, the waste incineration facility 1 comprises a waste pit 2 for storing waste before it is fed into the incinerator 3, a carbon dioxide capture device 44 that is provided downstream of the dust collector 42 in the exhaust gas flow path 4 and captures carbon dioxide from the exhaust gas, and a treated gas line 5 that supplies the exhaust gas that has passed through the carbon dioxide capture device 44 as treated gas to the waste pit 2. This makes it possible for the waste incineration facility 1 to reduce the amount of exhaust gas discharged to the outside from the chimney 59.

[0051] Preferably, the treated gas is supplied from the treated gas line 5 to the lower part of the garbage pit 2, and the treated gas that has passed through the garbage pile 91 in the garbage pit 2 is supplied to the incinerator 3. If the treated gas is ejected from a position above the garbage pile 91 in the garbage pit 2, a strong flow of gas occurs in the garbage pit 2, making it difficult to control the pressure to make the garbage pit 2 a constant negative pressure. In contrast, in the garbage incineration facility 1 that ejects the treated gas from the lower part of the garbage pit 2, the flow of the treated gas in the garbage pit 2 can be eased, making it easier to control the pressure to make the garbage pit 2 a negative pressure. In addition, acid gases and the like contained in the treated gas can be removed by the garbage pile 91, and corrosion can be suppressed in the line that extracts the gas in the garbage pit 2 (i.e., the extraction gas line 21).

[0052] Preferably, the waste incineration facility 1 is equipped with an extracted gas line 21 that is connected to the upper part of the waste pit 2 and extracts the gas in the waste pit 2 as extracted gas, and the extracted gas is mixed with the recirculated exhaust gas flowing through the recirculated exhaust gas line 6. This allows the treated gas filled in the waste pit 2 to be appropriately used as combustion gas in the incinerator 3.

[0053] Second embodiment Fig. 3 is a diagram showing a part of a waste incineration plant 1 according to a second embodiment of the present invention, and corresponds to Fig. 2. In the waste incineration plant 1 in Fig. 3, the configurations of the recirculated flue gas line 6 and the extracted gas line 21 are different from those in Fig. 1, and the recirculated flue gas and the extracted gas are supplied separately to the incinerator 3. The other configurations are the same as those in Fig. 1, and the same components are denoted by the same reference numerals.

[0054] The recirculated exhaust gas line 6 is connected to the wind boxes of the drying grate section 331, the combustion grate section 332, and the post-combustion grate section 333 as a primary combustion gas line. The recirculated exhaust gas mixed with high-concentration oxygen gas by the oxygen mixing section 68 is supplied into the primary combustion chamber 33 as a primary combustion gas. The extracted gas line 21 is connected to a plurality of nozzles 341 as a secondary combustion gas line. The waste incineration facility 1 is provided with an oxygen mixing section 211 similar to the oxygen mixing section 68 (indicated by a broken line block in FIG. 1), and the gas generated by the oxygen mixing section 211 and having a higher oxygen concentration than air (i.e., high-concentration oxygen gas) is mixed into the extracted gas flowing through the extracted gas line 21. As a result, the extracted gas having a higher oxygen concentration than the treated gas supplied to the waste pit 2 is supplied into the secondary combustion chamber 34 as a secondary combustion gas. In the waste incineration facility 1 of FIG. 3, it is easily possible to set the oxygen concentration of the primary combustion gas and the oxygen concentration of the secondary combustion gas separately (for example, to different values).

[0055] 3 is merely an example, and all or some of the drying grate section 331, the combustion grate section 332 and the post-combustion grate section 333 may be connected to the extracted gas line 21. Similarly, all or some of the multiple nozzles 341 may be connected to the recirculated exhaust gas line 6.

[0056] As described above, the waste incineration facility 1 in Fig. 3 is equipped with an extracted gas line 21 that is connected to the upper part of the waste pit 2 and extracts the gas in the waste pit 2 as extracted gas and supplies it to the incinerator 3, and an oxygen mixer 211 that mixes high-concentration oxygen gas, which has a higher oxygen concentration than air, with the extracted gas flowing through the extracted gas line 21. This allows the treated gas filled in the waste pit 2 to be appropriately used as combustion gas in the incinerator 3.

[0057] In the above-mentioned waste incineration facility 1, the exhaust gas from which carbon dioxide has been removed by the carbon dioxide capture device 44 is supplied as treated gas to the waste pit 2, but as shown by the broken line in FIG. 1, the treated gas line 5a may be connected to the incinerator 3, and the treated gas may be directly supplied to the incinerator 3. In this case, it is preferable that the treated gas is used as primary combustion gas or / and secondary combustion gas. The treated gas may be mixed with the recirculated exhaust gas, and the treated gas line 5a may be provided with an oxygen mixing section 211 that mixes high-concentration oxygen gas with the treated gas supplied to the incinerator 3. The treated gas may be distributed to the waste pit 2 and the incinerator 3. As described above, in the waste incineration facility 1, it is preferable that the treated gas line 5 is provided that supplies the exhaust gas that has passed through the carbon dioxide capture device 44 as treated gas to the waste pit 2 or / and the incinerator 3. This makes it possible to reduce the amount of exhaust gas discharged to the outside from the chimney 59.

[0058] Third embodiment FIG. 4 is a block diagram showing a waste incineration plant 1 according to a third embodiment of the present invention. In the waste incineration plant 1 of FIG. 4, the extracted gas line 21 is connected to the oxygen mixing section 68. The other configurations are the same as those in FIG. 1, and the same configurations are given the same reference numerals. In the waste incineration plant 1 of FIG. 4, the extracted gas extracted from the waste pit 2 is supplied to the oxygen mixing section 68 through the extracted gas line 21. In the oxygen mixing section 68, high-concentration oxygen gas is generated from all or a part of the extracted gas supplied. The high-concentration oxygen gas is mixed with the recirculated exhaust gas flowing through the recirculated exhaust gas line 6 and supplied to the incinerator 3. As described above, in the oxygen mixing section 68 of FIG. 4, high-concentration oxygen gas is generated from at least a part of the extracted gas. Then, the high-concentration oxygen gas is mixed with the recirculated exhaust gas and used as a combustion gas in the incinerator 3, so that the amount of exhaust gas discharged from the chimney 59 can be significantly reduced.

[0059] In the oxygen mixing section 68, high-concentration oxygen gas is generated from a portion of the extracted gas, and the high-concentration oxygen gas may be mixed with the remaining extracted gas flowing through the extracted gas line 21 and supplied to the incinerator 3 (see FIG. 3). In the oxygen mixing section 68, which is a PSA-type oxygen gas generator, gas adsorbed to the adsorbent during generation of high-concentration oxygen gas (i.e., gas other than oxygen, such as nitrogen gas) is deodorized in a deodorizing device provided with an activated carbon layer or the like, and then released into the atmosphere.

[0060] (Fourth embodiment) FIG. 5 is a block diagram showing a waste incineration plant 1 according to a fourth embodiment of the present invention. In the waste incineration plant 1 of FIG. 5, the treated gas line 5 is connected to the recirculated flue gas line 6. The other configurations are the same as those in FIG. 1, and the same configurations are given the same reference numerals. In the waste incineration plant 1 of FIG. 5, the treated gas discharged from the carbon dioxide capture device 44 is supplied to the recirculated flue gas line 6 through the treated gas line 5. That is, the treated gas is mixed with the recirculated flue gas flowing through the recirculated flue gas line 6 and is supplied to the incinerator 3 through the recirculated flue gas line 6. Similarly, in the example of FIG. 5, the amount of flue gas discharged to the outside from the chimney 59 can be reduced. As described above, the branch point of the treated gas line 5 may be provided upstream of the induced draft fan 52. In addition, the position to which the treated gas line 5 is connected in the recirculated flue gas line 6 may be determined arbitrarily. In the oxygen mixing section 68 of FIG. 5, high-concentration oxygen gas is generated from the air flowing into the waste pit 2.

[0061] Fifth embodiment Fig. 6 is a block diagram showing a waste incineration plant 1 according to a fifth embodiment of the present invention. In the waste incineration plant 1 of Fig. 6, a separation membrane 51a is provided in place of the exhaust gas reheater 51 in the treated gas line 5, and a separation membrane 65 is provided in the recirculation exhaust gas line 6. The other configurations are the same as those in Fig. 1, and the same components are denoted by the same reference numerals.

[0062] The separation membrane 51a is a dehydration membrane, for example, an amorphous silica membrane. The separation membrane 51a may be another type of dehydration membrane. The separation membrane 51a is disposed in the treated gas line 5 at a position immediately after the exhaust gas treatment unit 45. The separation membrane 51a removes water from the treated gas immediately after passing through the exhaust gas treatment unit 45. By lowering the humidity of the treated gas, condensation of water in the treated gas line 5 due to a decrease in the temperature of the treated gas is suppressed. As a result, corrosion of the pipe wall of the treated gas line 5 caused by acid gases such as sulfur oxides and hydrogen chloride in the treated gas being dissolved in the condensed water is suppressed. The separation membrane 51a may remove other components from the treated gas together with water.

[0063] The separation membrane 65 is a dehydration section, and is, for example, an amorphous silica membrane. The separation membrane 65 may be another type of dehydration membrane. The separation membrane 65 is provided at any position in the recirculated exhaust gas line 6. The separation membrane 65 removes water from the recirculated exhaust gas. This suppresses condensation of water and corrosion of the pipe wall in the recirculated exhaust gas line 6. The separation membrane 65 may remove other components, such as acid gases, from the recirculated exhaust gas together with water.

[0064] As described above, the waste incineration facility 1 in Fig. 6 is provided with an exhaust gas treatment unit 45 (in Fig. 6, a wet smoke scrubber 43 and a carbon dioxide capture device 44) that is provided downstream of the dust collector 42 in the exhaust gas flow path 4 and supplies a liquid containing water to the exhaust gas to remove predetermined components from the exhaust gas, and a separation membrane 51a that removes water from the exhaust gas immediately after passing through the exhaust gas treatment unit 45. This makes it possible to suppress corrosion caused by condensation of water downstream of the exhaust gas treatment unit 45 where wet treatment is performed. In addition, by reducing the humidity of the treated gas with the separation membrane 51a, it becomes possible to efficiently dry the waste in the waste pit 2 by the treated gas.

[0065] The waste incineration plant 1 is provided with a dehydration section (separation membrane 65 in FIG. 6) that is provided in the recirculated flue gas line 6 and removes water from the recirculated flue gas. This more reliably suppresses condensation of water in the recirculated flue gas, and suppresses corrosion in the recirculated flue gas line 6 that is caused by condensation of water. Depending on the design of the waste incineration plant 1, the dehydration section may be something other than the separation membrane 65. In the flue gas flow path 4, a wet smoke scrubber 43 is provided between the dust collector 42 and the take-out position P1 (just before the take-out position P1 in FIG. 6). In the wet smoke scrubber 43, in addition to suppressing the concentration of acid gases, it is possible to lower the absolute amount of moisture contained in the flue gas by lowering the flue gas temperature.

[0066] Sixth embodiment Fig. 7 is a block diagram showing a waste incineration plant 1 according to a sixth embodiment of the present invention. In the waste incineration plant 1 of Fig. 7, an extraction position P1 to which a recirculation flue gas line 6 is connected is provided between the dust collector 42 and the wet smoke scrubber 43 in the flue gas flow path 4. The other configuration is similar to that of Fig. 6, and the same components are denoted by the same reference numerals.

[0067] In the waste incineration plant 1 of FIG. 7, a part of the flue gas immediately after passing through the dust collector 42 in the flue gas flow path 4 is taken out as recirculated flue gas by the recirculated flue gas line 6. In the recirculated flue gas line 6, water is removed from the recirculated flue gas by the separation membrane 65, and the humidity of the recirculated flue gas is reduced. This prevents water from condensing in the recirculated flue gas line 6 due to a decrease in the temperature of the recirculated flue gas. As a result, corrosion of the pipe wall of the recirculated flue gas line 6 caused by acid gases such as sulfur oxides and hydrogen chloride in the recirculated flue gas being dissolved in the condensed water is prevented. In the separation membrane 65, other components may be removed from the recirculated flue gas together with the water.

[0068] As in the above-described waste incineration facility 1, the recirculated exhaust gas is mixed with high-concentration oxygen gas produced in the oxygen mixing section 68, and recirculated exhaust gas having a higher oxygen concentration than the exhaust gas at the discharge position P1 is obtained. The recirculated exhaust gas line 6 is connected to the primary combustion chamber 33 and / or secondary combustion chamber 34 of the incinerator 3, and the recirculated exhaust gas is used as primary combustion gas and / or secondary combustion gas.

[0069] As described above, in the waste incineration plant 1 of Fig. 7 as well, by mixing the recirculated flue gas with high-concentration oxygen gas and using it as combustion gas in the incinerator 3, it is possible to increase the amount of recirculated flue gas taken out from the flue gas flow path 4, compared to the case where air is mixed with the recirculated flue gas. As a result, it is possible to easily reduce the amount of flue gas flowing downstream of the connection position of the recirculated flue gas line 6 (i.e., the take-out position P1) in the flue gas flow path 4. In the waste incineration plant 1 of Figs. 1 to 5, the take-out position P1 may be provided between the dust collector 42 and the wet smoke scrubber 43.

[0070] Seventh embodiment FIG. 8 is a block diagram showing a waste incineration plant 1 according to a seventh embodiment of the present invention. In the waste incineration plant 1 of FIG. 8, all of the exhaust gas that has passed through the carbon dioxide capture device 44 is discharged from a chimney 59. In the waste incineration plant 1 of FIG. 8, as in FIG. 1, a part of the exhaust gas flowing through the exhaust gas flow passage 4 is taken out as a recirculated exhaust gas by the recirculated exhaust gas line 6 and supplied to the incinerator 3. In addition, in the oxygen mixing section 68, oxygen is concentrated from the surrounding air to generate a high-concentration oxygen gas having a higher oxygen concentration than air, which is mixed with the recirculated exhaust gas flowing through the recirculated exhaust gas line 6. As a result, the amount of recirculated exhaust gas taken out from the exhaust gas flow passage 4 can be increased compared to the case where air is mixed with the recirculated exhaust gas, and the amount of exhaust gas discharged from the chimney 59 can be easily reduced.

[0071] Eighth embodiment FIG. 9 is a block diagram showing a waste incineration plant 1 according to an eighth embodiment of the present invention. The waste incineration plant 1 of FIG. 9 is different from the waste incineration plant 1 of FIG. 8 in that the extracted gas extracted from the waste pit 2 is supplied to the oxygen mixing section 68 via the extracted gas line 21. The extracted gas line 21 is provided with a fan 212 and a deodorizing device 72 in this order from the waste pit 2 toward the oxygen mixing section 68. The extracted gas deodorized by the deodorizing device 72 is supplied to the oxygen mixing section 68, and high-concentration oxygen gas is generated by concentrating oxygen from at least a part of the extracted gas. The high-concentration oxygen gas is mixed with the recirculated flue gas flowing through the recirculated flue gas line 6 and supplied to the incinerator 3. The remaining gas (mainly nitrogen gas) after oxygen concentration in the oxygen mixing section 68 is discharged to the outside of the waste incineration plant 1. The oxygen mixing section 68 may take in ambient air as necessary, for example, when the required amount of high-concentration oxygen gas cannot be generated from the extracted gas alone.

[0072] As described above, in the oxygen mixing section 68 in Fig. 9, the extracted gas line 21 is provided to extract the gas in the garbage pit 2 as extracted gas, and the negative pressure in the garbage pit 2 is appropriately maintained. In addition, high-concentration oxygen gas is generated from at least a portion of the extracted gas, and is mixed with the recirculated exhaust gas to be used as combustion gas in the incinerator 3. This makes it possible to increase the amount of recirculated exhaust gas extracted from the exhaust gas flow path 4 and reduce the amount of exhaust gas discharged from the chimney 59.

[0073] The deodorizing device 72 does not necessarily have to be provided in the extracted gas line 21, and may be provided on the exhaust path leading from the oxygen mixing section 68 to the outside, as shown in FIG. 10. In the oxygen mixing section 68 in FIG. 10, the oxygen contained in the extracted gas (and air) is concentrated to generate high-concentration oxygen gas, which is mixed with the recirculated exhaust gas. Meanwhile, the remaining gas of the extracted gas, i.e., the remaining gas after oxygen concentration, is discharged to the outside via the deodorizing device 72. In the configuration of FIG. 10, the flow rate of gas flowing through the deodorizing device 72 is reduced. This allows the use of a small-sized deodorizing device 72, thereby reducing the manufacturing costs of the waste incineration facility 1.

[0074] Ninth embodiment FIG. 11 is a block diagram showing a waste incineration plant 1 according to a ninth embodiment of the present invention. In the waste incineration plant 1 of FIG. 11, an oxygen enrichment device 53 is provided between the carbon dioxide capture device 44 and the flue gas reheater 51 in the treated gas line 5. The treated gas line 5 branches into two at the oxygen enrichment device 53, one of which is connected to the recirculated flue gas line 6, and the other is connected to a chimney 59 via the flue gas reheater 51 and the like. The oxygen enrichment device 53 is further connected to an extracted gas line 21. A gas-gas heat exchanger 71 is provided in the flue gas flow path 4 and the recirculated flue gas line 6. The other configurations are the same as those in FIG. 1, and the same configurations are denoted by the same reference numerals.

[0075] In the gas-gas heat exchanger 71, heat is exchanged between the exhaust gas flowing from the dust collector 42 to the wet smoke scrubber 43 in the exhaust gas flow path 4 and the recirculated exhaust gas flowing through the recirculated exhaust gas line 6. This makes it possible to efficiently heat the recirculated exhaust gas whose temperature has been reduced in the wet smoke scrubber 43 in a waste incineration facility 1 in which the take-out position P1 is provided downstream of the wet smoke scrubber 43. The gas-gas heat exchanger 71 may be used in other waste incineration facilities 1. In the example of FIG. 11, the preheater in the recirculated exhaust gas line 6 is omitted, but a preheater may be provided as necessary. In addition, a preheater may be provided instead of the gas-gas heat exchanger 71. When the gas-gas heat exchanger 71 is not provided, the take-out position P1 may be provided between the dust collector 42 and the wet smoke scrubber 43, as in the example of FIG. 7.

[0076] Treated gas is supplied to the oxygen enrichment device 53 in FIG. 11 from the carbon dioxide recovery device 44. In the extracted gas line 21, extracted gas is extracted from the garbage pit 2 by the fan 212 and supplied to the oxygen enrichment device 53 via the deodorizing device 72. Air from the outside may be supplied to the oxygen enrichment device 53 as necessary. The oxygen enrichment device 53 is a device that produces high-concentration oxygen gas having a high oxygen concentration from these gases, and is, for example, a PSA type device similar to the above-mentioned oxygen mixing section 68. In this embodiment, the oxygen enrichment device 53 produces nitrogen (N2 ) gas is adsorbed and separated and led to the exhaust gas reheater 51, and the remaining gas (mainly oxygen (O 2 ) gas and carbon dioxide (CO 2 ) gas) is introduced to the recirculated exhaust gas line 6 and mixed with the recirculated exhaust gas. The gas mixed with the recirculated exhaust gas is a high-oxygen gas having a higher oxygen concentration than air, and is used as a combustion gas (combustion oxidizer) in the incinerator 3. The gas (mainly nitrogen gas) introduced to the exhaust gas reheater 51 is introduced to the chimney 59 via the induced draft fan 52 and released into the atmosphere. Note that an adsorbent that adsorbs oxygen may be used in the oxygen enrichment device 53. The same applies to the oxygen mixing section 68 described above.

[0077] As described above, in the waste incineration facility 1 in Fig. 11, the oxygen enrichment device 53 is provided in the treated gas line 5. The oxygen enrichment device 53 is an oxygen mixing section, which generates high-concentration oxygen gas having a high oxygen concentration from the exhaust gas that has passed through the carbon dioxide capture device 44, and mixes it with the recirculated exhaust gas flowing through the recirculated exhaust gas line 6. By generating high-concentration oxygen gas from the exhaust gas discharged from the incinerator 3 in this way, the amount of exhaust gas discharged to the outside from the chimney 59 can be further reduced.

[0078] Also, an extracted gas line 21 is provided to extract the gas in the garbage pit 2 as extracted gas, and the negative pressure in the garbage pit 2 is appropriately maintained. Then, an oxygen enrichment device 53 generates high-concentration oxygen gas from at least a portion of the extracted gas, and mixes it with the recirculated flue gas flowing through the recirculated flue gas line 6. This makes it possible to increase the amount of recirculated flue gas extracted from the flue gas flow path 4 compared to when the extracted gas is mixed directly with the recirculated flue gas or when it is supplied directly to the incinerator 3.

[0079] In the waste incineration plant 1, a wet smoke scrubber 43 is provided in the flue gas flow path 4 between the dust collector 42 and the extraction position P1 of the recirculated flue gas. In the gas-gas heat exchanger 71, the recirculated flue gas is heated by heat exchange between the flue gas upstream of the wet smoke scrubber 43 in the flue gas flow path 4 and the recirculated flue gas flowing in the recirculated flue gas line 6. In this way, the recirculated flue gas from which a portion of the flue gas has been extracted (i.e., gas with a lower flow rate than the flue gas in the flue gas flow path 4) is heated by the high-temperature flue gas flowing in the flue gas flow path 4, thereby making it possible to efficiently increase the temperature of the recirculated flue gas.

[0080] In the waste incineration facility 1 of FIG. 11, depending on the oxygen content of the exhaust gas that has passed through the carbon dioxide capture device 44, the exhaust gas may not be supplied to the oxygen enrichment device 53. In this case, in the oxygen enrichment device 53, high-concentration oxygen gas is extracted from the gas extracted from the waste pit 2 and the outside air, and mixed with the recirculated exhaust gas. Meanwhile, gases other than the high-concentration oxygen gas (mainly nitrogen gas) are discharged to the exhaust gas reheater 51. Also, the exhaust gas that has passed through the carbon dioxide capture device 44 is, for example, guided downstream of the oxygen enrichment device 53 without passing through the oxygen enrichment device 53, and mixed with the gas (nitrogen gas, etc.) discharged from the oxygen enrichment device 53. In such a configuration, the flow rate of the gas flowing through the oxygen enrichment device 53 is reduced, so that a small-sized oxygen enrichment device 53 can be used, and the manufacturing cost of the waste incineration facility 1 can be reduced.

[0081] As shown in FIG. 12, the deodorizer 72 may be disposed between the oxygen enrichment device 53 and the exhaust gas reheater 51. In this case, the remaining gas after oxygen concentration in the oxygen enrichment device 53 is discharged to the outside via the deodorizer 72. Also, the exhaust gas that has passed through the carbon dioxide capture device 44 may be, for example, guided downstream of the deodorizer 72 without passing through the oxygen enrichment device 53 and the deodorizer 72, and mixed with the gas (nitrogen gas, etc.) discharged from the deodorizer 72. In such a configuration, the flow rate of the gas flowing through the oxygen enrichment device 53 and the deodorizer 72 is reduced, so that a small oxygen enrichment device 53 and a small deodorizer 72 can be used, and the manufacturing cost of the waste incineration facility 1 can be reduced. Note that the deodorizer 72 may be omitted depending on the configuration of the waste incineration facility 1.

[0082] Tenth embodiment Fig. 13 is a block diagram showing a waste incineration plant 1 according to a tenth embodiment of the present invention. In the waste incineration plant 1 of Fig. 13, a carbon dioxide utilization device 44a is provided instead of the carbon dioxide capture device 44 in the waste incineration plant 1 of Fig. 8, and the flue gas reheater 51, induced draft fan 52, and chimney 59 are omitted. The other configurations are the same as those of the waste incineration plant 1 of Fig. 8.

[0083] As shown in FIG. 13, the carbon dioxide utilization device 44a is provided downstream of the extraction position P1 in the exhaust gas flow path 4. The carbon dioxide utilization device 44a is a device that uses the exhaust gas to generate a predetermined product. In one example, methane gas or the like is generated from the exhaust gas by methanation. In another example, solid carbonate is generated from the exhaust gas by mineralization. Note that components other than carbon dioxide contained in the exhaust gas may also be included in the product. In a waste incineration facility 1 provided with the carbon dioxide utilization device 44a, it is possible to significantly reduce the emission of exhaust gas into the atmosphere. In other waste incineration facilities 1, the carbon dioxide utilization device 44a may be provided instead of the carbon dioxide capture device 44 as in FIG. 13. In addition, both the carbon dioxide capture device 44 and the carbon dioxide utilization device 44a may be provided. In this case, for example, a predetermined product is generated in the carbon dioxide utilization device 44a by using the carbon dioxide captured in the carbon dioxide capture device 44.

[0084] The waste incineration plant 1 can be modified in various ways.

[0085] 1 to 7, all of the treated gas that has passed through the carbon dioxide capture device 44 is supplied to the garbage pit 2 and / or the incinerator 3, or the recirculation flue gas line 6, and the chimney 59 may be omitted. In order to reduce the amount of flue gas discharged to the outside in the garbage incineration plant 1, it is preferable to provide a treated gas line 5 that supplies at least a portion of the flue gas that has passed through the carbon dioxide capture device 44 (if a separation membrane 51a is provided, the flue gas that has passed through the carbon dioxide capture device 44 and the separation membrane 51a) as treated gas to the garbage pit 2 and / or the incinerator 3, or the recirculation flue gas line 6.

[0086] When the oxygen concentration of the treated gas (i.e., the exhaust gas that has passed through the carbon dioxide capture device 44) flowing through the treated gas line 5 is sufficiently higher than that of air, the treated gas line 5 may be connected to the recirculated exhaust gas line 6 as an oxygen mixing section. In this case, the recirculated exhaust gas mixed with the treated gas is supplied to the incinerator 3.

[0087] The extraction gas line 21 may be connected to any position in the garbage pit 2.

[0088] As described above, in the waste incineration facilities 1 of the first to tenth embodiments, almost no air is supplied from the outside to the incinerator 3, except for air brought into the incinerator 3 by the waste and air flowing into the incinerator 3 through the input hopper 31. In particular, in the waste incineration facilities 1 of Figs. 8 to 13, etc., almost all of the combustion gas supplied to the incinerator 3 through the gas pipe is the recirculated exhaust gas supplied to the incinerator 3 from the recirculated exhaust gas line 6, that is, the recirculated exhaust gas mixed with high-concentration oxygen gas. This makes it possible to significantly reduce the amount of exhaust gas discharged from the chimney 59 in the waste incineration facility 1. On the other hand, depending on the design of the waste incineration facility 1, air may be supplied to the incinerator 3 through the gas pipe as part of the combustion gas. In this case, in order to sufficiently reduce the amount of exhaust gas, it is preferable that the main gas of the combustion gas supplied to the incinerator 3 through the gas pipe is the recirculated exhaust gas mixed with high-concentration oxygen gas. The main gas of the combustion gas is, for example, a gas that is 50% or more by volume of the combustion gas. Thus, even when air is supplied as part of the combustion gas into the incinerator 3 through a gas pipe, the air is preferably less than 50% by volume of the combustion gas, more preferably less than 35% by volume, and even more preferably less than 20% by volume.

[0089] The incinerator 3 may be an incinerator other than a stoker type incinerator (for example, a fluidized bed furnace, a kiln furnace, etc.). The waste incineration facility 1 may be used as a waste incineration facility for incinerating general waste other than waste and industrial waste. The method of removing water from the recirculated exhaust gas using the dehydration section (separation membrane 65) and the method of removing water from the exhaust gas immediately after passing through the exhaust gas treatment unit 45 using the separation membrane 51a may be used independently.

[0090] The configurations in the above-described embodiment and each of the modified examples may be combined as appropriate as long as they are not mutually inconsistent.

[0091] Although the invention has been particularly illustrated and described, it is to be understood that the above description is illustrative and not restrictive, and therefore numerous modifications and variations are possible without departing from the scope of the invention. [Explanation of symbols]

[0092] 1. Waste incineration facility 2. Garbage Pit 3. Incinerator 4 Exhaust gas flow path 5,5a Treated Gas Line 6 Recirculation exhaust gas line 21 Extraction gas line 22 Platform 33 Primary Combustion Chamber 34 Secondary Combustion Chamber 42 Dust collector 43 Wet smoke washing tower 44 Carbon dioxide capture equipment 44a Carbon dioxide utilization device 45 Exhaust gas treatment unit 51a Separation membranes (for treated gas) 53 Oxygen enrichment device 65 Separation membrane (for recirculated exhaust gas) 67 Preheater 68 Oxygen mixing section (for recirculated exhaust gas) 72 Deodorizing equipment 91 Garbage deposits 211 Oxygen mixing section (for withdrawal gas) 221,222 Doors P1 Extraction position

Claims

[Claim 1] A waste incineration facility comprising: An incinerator for incinerating waste; An exhaust gas flow path through which exhaust gas discharged from the incinerator flows; A dust collector provided in the exhaust gas flow path; A recirculation exhaust gas line is connected to an extraction position downstream of the dust collector in the exhaust gas flow path, and extracts a portion of the exhaust gas flowing through the exhaust gas flow path as a recirculation exhaust gas and supplies it to the incinerator; an oxygen mixing section that mixes high-concentration oxygen gas having an oxygen concentration higher than that of air with the recirculation exhaust gas flowing through the recirculation exhaust gas line; A waste incineration facility equipped with:

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