Waste incineration equipment

Abstract

A waste incineration facility (1) is provided with: a recirculated exhaust gas line (6) for taking out a part of exhaust gas flowing through an exhaust gas flow path (4) as recirculated exhaust gas and supplying the recirculated exhaust gas into an incinerator (3); an oxygen mixing unit (5) for mixing high-concentration oxygen having a higher oxygen concentration than air with the recirculated exhaust gas flowing through the recirculated exhaust gas line (6); mixing ratio changing units (81-83) for changing the mixing ratio of the recirculated exhaust gas supplied into the incinerator (3) from a predetermined gas supply position in the incinerator (3) and the high-concentration oxygen gas; an amount of interest measurement unit (36-38) that measures, as an amount of interest, at least one of the amount of steam generated by the heat of the exhaust gas, the temperature inside the incinerator (3), and the oxygen concentration at the outlet of the incinerator (3); and a control unit (10) that controls the mixing ratio changing units (81-83) so that the measured value of the amount of interest approaches a predetermined target value. The main gas of the combustion gas supplied into the incinerator (3) via the gas pipe is a recirculated exhaust gas in which high-concentration oxygen is mixed.

Description

Technical Field

[0001] The invention relates to a waste incineration device.

[0002] [Reference to related applications]

[0003] This application claims the benefit of priority from Japanese patent application JP2022-80978 filed on May 17, 2022, and all disclosed contents of the application are incorporated into this application. Background Art

[0004] Previously, in waste incineration equipment, a portion of the exhaust gas flowing in the exhaust gas flow path was taken out as recycled exhaust gas and supplied to the incinerator. By utilizing the recycled exhaust gas, the amount of exhaust gas from the waste incineration equipment can be reduced. In the incineration facility of Japanese Patent Laid-Open No. 2021-71238 (Document 1), a combustion adjustment gas wind box is provided below the combustion stoker in the slow combustion area, and a low oxygen gas supply pipe for supplying low oxygen gas and a high oxygen gas supply pipe for supplying high oxygen gas are connected to the combustion adjustment gas wind box. The exhaust gas reflow system is used as a low oxygen gas source, and the oxygen concentration of the high oxygen gas is 21% to 30% by volume. When the main steam volume is lower than the target steam volume, the gas containing the high oxygen gas is supplied to the combustion adjustment gas wind box. When the main steam volume reaches or exceeds the target steam volume, the low oxygen gas is supplied to the combustion adjustment gas wind box.

[0005] Japanese Patent Gazette No. 4359536 (Document 2) discloses a combustion device that incinerates a fuel layer on a stoker using primary combustion air from the lower portion of the fuel layer. The device is provided with: a recirculating exhaust gas supply path that recirculates exhaust gas from an incinerator in the incinerator; an oxygen supply device; a first oxygen supply path that supplies oxygen from the oxygen supply device to the primary combustion air; a third oxygen supply path that supplies oxygen from the oxygen supply device to the recirculating exhaust gas; a switching device that switches the supply of oxygen from the oxygen supply device between the first oxygen supply path and the third oxygen supply path; and a control device that controls the switching device based on the measurement results of the temperature of the incinerator and / or the oxygen concentration at the outlet of the incinerator.

[0006] As described above, in Documents 1 and 2, the steam volume, the temperature of the incinerator, or the oxygen concentration at the outlet of the incinerator is used as the quantity of interest, and control is performed to bring the quantity of interest close to the target value. However, since the primary combustion air is supplied to the incinerator, that is, the main gas of the combustion gas supplied to the incinerator is air, there is a limit to the reduction of the exhaust gas volume. Therefore, a method is required to bring the quantity of interest close to the target value while significantly reducing the exhaust gas volume. Summary of the invention

[0007] The present invention is directed to waste incineration equipment, and its purpose is to significantly reduce the amount of exhaust gas while bringing the amount of interest close to a target value.

[0008] Embodiment 1 of the present invention is a waste incineration equipment, comprising: an incinerator for incinerating waste; an exhaust gas flow path for circulating exhaust gas discharged from the incinerator; a dust collector arranged in the exhaust gas flow path; a recirculating exhaust gas line connected to a take-out position on the downstream side of the dust collector in the exhaust gas flow path, taking out a part of the exhaust gas flowing in the exhaust gas flow path as recirculating exhaust gas and supplying it to the incinerator; an oxygen mixing unit for mixing high-concentration oxygen having an oxygen concentration higher than that of air with the recirculating exhaust gas flowing in the recirculating exhaust gas line; and a mixing ratio changing unit for changing the mixing ratio. a mixing ratio of the recirculated exhaust gas and the high-concentration oxygen supplied to the incinerator from a specified gas supply position in the incinerator; a quantity of interest measuring unit, which measures at least one of the amount of steam generated by the heat of the exhaust gas, the temperature in the incinerator and the oxygen concentration at the outlet of the incinerator as a quantity of interest; and a control unit, which controls the mixing ratio changing unit so that the measured value of the quantity of interest approaches a specified target value, and the main gas of the combustion gas supplied to the incinerator via the gas pipe is the recirculated exhaust gas mixed with the high-concentration oxygen.

[0009] According to the present invention, the exhaust gas volume can be significantly reduced while the amount of interest can be brought close to the target value.

[0010] Embodiment 2 of the present invention is a waste incineration device according to embodiment 1, further comprising: a waste pit for storing waste before being put into the incinerator; and an extracted gas line for extracting gas in the waste pit as extracted gas, wherein the oxygen mixing unit generates the high-concentration oxygen from the extracted gas and mixes it with the recirculating exhaust gas flowing in the recirculating exhaust gas line.

[0011] Embodiment 3 of the present invention is a waste incineration device according to Embodiment 1 (it may also be Embodiment 1 or Embodiment 2), further comprising: a carbon dioxide recovery device, which is arranged in the exhaust gas flow path on the downstream side of the extraction position, recovering carbon dioxide from the exhaust gas, and the oxygen mixing section generates the high-concentration oxygen from the exhaust gas passing through the carbon dioxide recovery device, and mixes it with the recycled exhaust gas flowing in the recycled exhaust gas line.

[0012] Embodiment 4 of the present invention is a waste incineration facility according to embodiment 1 (or any one of embodiments 1 to 3), wherein a flow rate of gas supplied from the gas supply position in the incinerator to the incinerator is substantially constant.

[0013] Embodiment 5 of the present invention is a waste incineration facility according to any one of embodiments 1 to 4, wherein the quantity of interest includes the steam quantity, and the gas supply position in the incinerator is set below a fire grate.

[0014] Embodiment 6 of the present invention is a waste incineration device according to any one of Embodiments 1 to 4 (or any one of Embodiments 1 to 5), wherein the quantity of interest includes the temperature inside the incinerator, and the gas supply position in the incinerator is arranged at the top above a portion of the fire grate portion, the side wall portion surrounding the primary combustion chamber of the incinerator, or the side wall portion surrounding the secondary combustion chamber of the incinerator.

[0015] Embodiment 7 of the present invention is a waste incineration device according to any one of Embodiments 1 to 4 (or any one of Embodiments 1 to 6), wherein the quantity of interest includes the oxygen concentration at the outlet of the incinerator, and the gas supply position in the incinerator is arranged on the side wall portion of the secondary combustion chamber surrounding the incinerator.

[0016] The above-mentioned object and other objects, features, aspects and advantages will become more apparent from the following detailed description of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] [ Figure 1 ] is a block diagram showing the structure of the waste incineration equipment of the first embodiment.

[0018] [ Figure 2 ] is a diagram showing the structure of a sewage pit and an incinerator.

[0019] [ Figure 3 ] is a diagram showing another example of a structure for supplying primary combustion gas to the fire grid section.

[0020] [ Figure 4 ] is a block diagram showing the structure of the waste incineration equipment of the second embodiment.

[0021] [ Figure 5 ] is a block diagram showing another example of waste incineration equipment.

[0022] [ Figure 6 ] is a block diagram showing the structure of the waste incineration equipment of the third embodiment.

[0023] [ Figure 7 ] is a block diagram showing another example of waste incineration equipment.

[0024] [ Figure 8 ] is a block diagram showing the structure of the waste incineration equipment of the fourth embodiment. DETAILED DESCRIPTION

[0025] (First Embodiment)

[0026] Figure 1 1 is a block diagram showing the structure of a waste incineration plant 1 according to a first embodiment of the present invention. The waste incineration plant 1 is a waste incineration plant and includes a waste pit 2, an incinerator 3, an exhaust gas flow path 4, and a control unit 10 (see the following). Figure 2 The control unit 10 is a computer including a central processing unit (CPU), for example, and is responsible for overall control of the waste incineration equipment 1. The waste pit 2 is a waste pit that stores waste as waste. The incinerator 3 incinerates the waste introduced from the waste pit 2. The exhaust gas flow path 4 is a flue for the exhaust gas discharged from the incinerator 3 to flow. Figure 1 In the example of FIG. 4 , the exhaust gas flow path 4 is a flow path from the incinerator 3 to a chimney 47 described below. Figure 1 In the figure, only the arrow between the incinerator 3 and the boiler tube group 41 described below is marked with the symbol 4. The sewage pit 2 and the incinerator 3 will be described in detail below.

[0027] The waste incineration equipment 1 further includes a boiler tube group 41, a filter dust collector 42 (hereinafter referred to as "dust collector 42"), a wet smoke scrubber 43, a carbon dioxide recovery device 44, an exhaust gas reheater 45, an exhaust fan 46, and a chimney 47. The boiler tube group 41, the dust collector 42, the wet smoke scrubber 43, the carbon dioxide recovery device 44, the exhaust gas reheater 45, the exhaust fan 46, and the chimney 47 are arranged in the exhaust gas flow path 4, and are arranged in order from the upstream side to the downstream side in the flow direction of the exhaust gas (i.e., from the incinerator 3 to the chimney 47).

[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 filter bag that captures fly ash contained in the exhaust gas through a filter cloth. On the upstream side of the dust collector 42, a powdered exhaust gas treatment agent can be supplied to the exhaust gas, and the fly ash and the exhaust gas treatment agent are captured in the dust collector 42. The exhaust gas treatment agent can be 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 passing through the dust collector 42 flows into the wet scrubber 43.

[0029] The wet scrubber 43 sprays a liquid containing an alkaline agent such as caustic soda and water into the exhaust gas. This lowers the temperature of the exhaust gas to, for example, 30°C to 70°C, and removes sulfur oxides, hydrogen chloride, etc. contained in the exhaust gas. The wet scrubber 43 is a desulfurization unit that removes sulfur oxides in the exhaust gas, and is also a desalination unit that removes hydrogen chloride in the exhaust gas.

[0030] The carbon dioxide recovery device 44 recovers carbon dioxide from the exhaust gas passing through the wet scrubber 43. An example of the carbon dioxide recovery device 44 recovers carbon dioxide by a chemical absorption method, including an absorption tower and a regeneration tower. In the absorption tower, for example, a liquid containing amines and water is sprayed into the exhaust gas, and the carbon dioxide is absorbed by the liquid. That is, carbon dioxide is removed from the exhaust gas. The liquid that has absorbed carbon dioxide is sent to the regeneration tower and heated, and the carbon dioxide is taken out for recovery. The recovered carbon dioxide is used for the production of methane by methanation or stored underground (carbon dioxide capture, utilization and storage (CCUS)). In the waste incineration equipment 1 in which the recirculating exhaust gas line 6 described below is set, the carbon dioxide concentration in the exhaust gas becomes high, so CCUS can be easily performed. The carbon dioxide recovery device 44 can also recover carbon dioxide by methods other than chemical absorption.

[0031] As described above, the wet scrubber 43 and the carbon dioxide recovery device 44 supply liquid containing water to the exhaust gas passing through the dust collector 42 and remove predetermined components from the exhaust gas. The exhaust gas passing through the wet scrubber 43 and the carbon dioxide recovery device 44 is a gas containing a large amount of water, oxygen and nitrogen.

[0032] The exhaust gas reheater 45 heats the exhaust gas using, for example, steam from a boiler (boiler tube group 41) as a heat medium. The exhaust fan 46 forms an airflow of gas from the upstream side toward the downstream side in the exhaust gas flow path 4 (i.e., an airflow of gas from the incinerator 3 toward the chimney 47). The exhaust gas passing through the exhaust fan 46 is discharged to the outside from the chimney 47. In the waste incineration equipment 1, for example, a reducing agent supply unit that sprays a reducing agent such as ammonia water into the incinerator 3 can be provided to perform catalyst-free denitration (selective non-catalytic reduction (SNCR)).

[0033] The waste incineration equipment 1 further includes a recirculating exhaust gas line 6, a fan 66, a preheater 67, and an oxygen mixing unit 5. The recirculating exhaust gas line 6 is a flow path for the recirculating exhaust gas described below to flow, and one end of the recirculating exhaust gas line 6 is connected to the extraction position P1 on the downstream side of the dust collector 42 in the exhaust gas flow path 4. Figure 1In the example, the extraction position P1 is a position between the wet scrubber 43 and the carbon dioxide recovery device 44. A portion of the exhaust gas flowing in the exhaust gas flow path 4 is extracted as recycled exhaust gas through the recycled exhaust gas line 6. The carbon dioxide recovery device 44 described above is arranged on the downstream side of the extraction position P1 in the exhaust gas flow path 4, so the recycled exhaust gas extracted from the extraction position P1 has a high carbon dioxide concentration and a low oxygen concentration. The other end of the recycled exhaust gas line 6 is connected to the incinerator 3, and the recycled exhaust gas is supplied to the incinerator 3. In Figure 1 In the figure, only the arrow connected to the extraction position P1 is marked with the symbol 6. According to the design of the waste incineration equipment 1, the extraction position P1 can be set between the dust collector 42 and the wet scrubber 43, and can also be set on the downstream side of the carbon dioxide recovery device 44.

[0034] The fan 66 and the preheater 67 are provided in the recirculation exhaust gas line 6. In one example of the waste incineration equipment 1, the preheater 67 and the fan 66 are arranged in order from the upstream side of the airflow of the recirculation exhaust gas toward the downstream side (i.e., toward the direction away from the extraction position P1). Alternatively, two preheaters (a first preheater and a second preheater) may be used, and the first preheater, the fan 66, and the second preheater may be arranged in order from the upstream side toward the downstream side. The order of the fan 66 and the preheater 67 in the recirculation exhaust gas line 6 can be determined arbitrarily.

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

[0036] The oxygen mixing unit 5 is a device for generating high-concentration oxygen having an oxygen concentration (volume concentration) higher than that of air from air, for example, a pressure swing adsorption (PSA) type oxygen generating device. The oxygen mixing unit 5 is connected to the recirculating exhaust gas line 6 via an oxygen mixed gas line 50, and the high-concentration oxygen generated in the oxygen mixing unit 5 is mixed with the recirculating exhaust gas flowing in the recirculating exhaust gas line 6. In the example where a first preheater, a fan 66 and a second preheater are provided, high-concentration oxygen can be mixed between the fan 66 and the second preheater. The order of the first preheater, the fan 66 and the second preheater or the mixing position of the high-concentration oxygen can be determined arbitrarily. By mixing the high-concentration oxygen, a recirculating exhaust gas having an oxygen concentration higher than that of the exhaust gas at the extraction position P1 is obtained, and it is supplied to the incinerator 3. The oxygen concentration of the high-concentration oxygen is sufficiently higher than that of air, and the oxygen concentration is, for example, 50% by volume or more, preferably 65% ​​by volume or more, and more preferably 80% by volume or more. As described below, the high-concentration oxygen can also be generated by something other than air.

[0037] Figure 22 is a diagram showing the structure of the sewage pit 2 and the incinerator 3. As described above, the sewage pit 2 stores sewage before being put into the incinerator 3, forming a sewage sediment layer 91. In the preferred sewage incineration equipment 1, a double-layer door structure is provided on the platform 22 connected to the sewage pit 2. Specifically, in the platform 22 where the sewage collection vehicle is parked, an outer door 221 and an inner door 222 are provided between the sewage pit 2. When the sewage collection vehicle puts sewage into the sewage pit 2, the outer door 221 is opened while the inner door 222 is closed, and sewage is put in from the sewage collection vehicle. The sewage is temporarily held between the inner door 222 and the outer door 221. When the sewage collection vehicle finishes putting sewage, the outer door 221 is closed, and then the inner door 222 is opened. Thus, the sewage is put into the sewage pit 2. After the sewage is put into the sewage pit 2, the inner door 222 is closed. In the double door structure, the amount of air flowing into the dirt pit 2 can be reduced.

[0038] The incinerator 3 includes a feed hopper 31, a waste supply unit 32, a primary combustion chamber 33, and a secondary combustion chamber 34. Waste is fed from the waste pit 2 into the feed hopper 31 by a waste crane 23. The waste supply unit 32 includes a push rod or a screw feeder, and supplies waste from the bottom of the feed hopper 31 into the primary combustion chamber 33.

[0039] At the bottom of the primary combustion chamber 33, a drying fire grate 331, a combustion fire grate 332, a post-combustion fire grate 333, and a discharge port 334 are arranged in order in a direction away from the waste supply portion 32. In the drying fire grate 331, the combustion fire grate 332, and the post-combustion fire grate 333, waste is transported from the waste supply portion 32 side toward the discharge port 334 by a well-known transporting action. In each of the drying fire grate 331, the combustion fire grate 332, and the post-combustion fire grate 333, a primary combustion gas described below is ejected into the primary combustion chamber 33, so that waste in the process of transport is burned. The burned waste (mainly ash) is discharged to the outside of the primary combustion chamber 33 through the discharge port 334. At least one nozzle 336 is provided at the top 335 covering the post-combustion fire grate 333. The auxiliary gas described below is ejected into the primary combustion chamber 33 from the nozzle 336. The assist gas stirs the gas in the primary combustion chamber 33. In addition, the nozzle 336 may be provided on a side wall portion surrounding the primary combustion chamber 33 (including a rear wall near the discharge port 334).

[0040] The secondary combustion chamber 34 is a space surrounded by a side wall portion, and is directly continuous from the primary combustion chamber 33 to form a flow path for the exhaust gas discharged from the primary combustion chamber 33. Figure 2In the example, the secondary combustion chamber 34 is a space that faces upward and has a flow path area that is sufficiently smaller than the floor area of ​​the primary combustion chamber 33. 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. As a result, the unburned gas generated in the primary combustion chamber 33 is burned. The secondary combustion chamber 34 is a part of the incinerator 3, and the flow path from the outlet of the secondary combustion chamber 34 to the downstream side is the exhaust gas flow path 4 that has been described. Figure 2 In the figure, the region where the boiler tube group 41 is provided is denoted by reference numeral 41 .

[0041] exist Figure 2 In the example of , the recirculation exhaust gas line 6 is bifurcated into a first bifurcated line 61, a second bifurcated line 62, and a third bifurcated line 63. The first bifurcated line 61 is bifurcated into a plurality of lines, which are respectively connected to the wind boxes of the drying fire grid section 331, the combustion fire grid section 332, and the post-combustion fire grid section 333. The second bifurcated line 62 is bifurcated into a plurality of lines, which are respectively connected to a plurality of nozzles 341. The third bifurcated line 63 is connected to the nozzle 336 at the top 335. The first bifurcated line 61, the second bifurcated line 62, and the third bifurcated line 63 are respectively provided with dampers 811, 821, and 831. The dampers 811, 821, and 831 are electrically connected to the control unit 10. The flow rate of the recirculation exhaust gas flowing through each of the bifurcated lines 61 to 63 can be adjusted by the dampers 811, 821, and 831. In order to adjust the flow rate of the recirculation exhaust gas with high accuracy, a flow meter or the like may be provided (the same applies to the branch lines 51 to 53 described below).

[0042] The oxygen mixed gas line 50 is branched into a first branch line 51, a second branch line 52, and a third branch line 53. The first branch line 51, the second branch line 52, and the third branch line 53 are respectively connected to the first branch line 61, the second branch line 62, and the third branch line 63 of the recirculation exhaust gas line 6. The first branch line 51, the second branch line 52, and the third branch line 53 are respectively provided with a damper 812, a damper 822, and a damper 832. The damper 812, the damper 822, and the damper 832 are electrically connected to the control unit 10. The flow rate of the high-concentration oxygen flowing through each branch line 51 to 53 can be adjusted by the damper 812, the damper 822, and the damper 832.

[0043] The mixed gas of the recirculated exhaust gas flowing in the first branch line 61 and the high-concentration oxygen flowing in the first branch line 51 is supplied to the primary combustion chamber 33 as the primary combustion gas. The primary combustion gas is a gas containing oxygen and is used for the combustion of waste in the primary combustion chamber 33. The gas supply position of the primary combustion gas is below the drying fire grid section 331, the combustion fire grid section 332 and the post-combustion fire grid section 333 (hereinafter also collectively referred to as "fire grid section 331 to fire grid section 333"). The dampers 811 and 812 provided in the first branch line 51 and the first branch line 61 are the mixing ratio changing section 81 for changing the mixing ratio of the high-concentration oxygen in the primary combustion gas and the recirculated exhaust gas. In addition, in the first branch line 61, the damper 811 is provided on the upstream side of the connection position of the first branch line 51 (the damper 821 of the second branch line 62 and the damper 831 of the third branch line 63 are the same).

[0044] The mixed gas of the recirculated exhaust gas flowing in the second bifurcated line 62 and the high-concentration oxygen flowing in the second bifurcated line 52 is supplied as the secondary combustion gas to the secondary combustion chamber 34. The secondary combustion gas is a gas containing oxygen and is used for the combustion of the unburned gas in the secondary combustion chamber 34. The gas supply position of the secondary combustion gas is the nozzle 341 of the side wall. The dampers 821 and 822 provided on the second bifurcated line 52 and the second bifurcated line 62 are the mixing ratio changing section 82 for changing the mixing ratio of the high-concentration oxygen in the secondary combustion gas and the recirculated exhaust gas.

[0045] The mixed gas of the recirculated exhaust gas flowing through the third bifurcated line 63 and the high-concentration oxygen flowing through the third bifurcated line 53 is supplied as auxiliary gas to the primary combustion chamber 33. The auxiliary gas is a gas containing oxygen and is used to stir the gas in the primary combustion chamber 33 or to burn the unburned gas. Figure 2 In the example, the assist gas supply position is the nozzle 336 at the top 335. The dampers 831 and 832 provided at the third bifurcation line 53 and the third bifurcation line 63 are the mixing ratio changing unit 83 for changing the mixing ratio of the high-concentration oxygen in the assist gas and the recirculation exhaust gas.

[0046] The waste incineration equipment 1 further includes a steam quantity measuring unit 36, an oxygen concentration measuring unit 37 and a furnace temperature measuring unit 38. The steam quantity measuring unit 36 ​​measures the amount of steam discharged from the boiler pipe group 41 (hereinafter referred to as "boiler generated steam quantity"). The steam is used for power generation, etc. The oxygen concentration measuring unit 37 uses a sensor provided at the outlet of the secondary combustion chamber 34, that is, the outlet of the incinerator 3 to measure the oxygen concentration of the outlet (hereinafter referred to as "furnace outlet oxygen concentration"). The furnace temperature measuring unit 38 uses a sensor provided in the primary combustion chamber 33 to measure the temperature in the primary combustion chamber 33. As described below, the furnace temperature measuring unit 38 can also measure the temperature in the secondary combustion chamber 34. The steam quantity measuring unit 36, the oxygen concentration measuring unit 37 and the furnace temperature measuring unit 38 are electrically connected to the control unit 10.

[0047] In the control unit 10, the amount of steam generated by the boiler measured by the steam amount measuring unit 36, the oxygen concentration at the furnace outlet measured by the oxygen concentration measuring unit 37, or the temperature in the primary combustion chamber 33 (or the temperature in the secondary combustion chamber 34) measured by the furnace temperature measuring unit 38 are used as the amount of interest, and control is performed based on the measured values ​​of the amount of interest. The steam amount measuring unit 36, the oxygen concentration measuring unit 37, and the furnace temperature measuring unit 38 are the amount of interest measuring units that measure the amount of interest.

[0048] In the first control example of the control unit 10, a target value of the amount of steam generated by the boiler as the amount of interest is set, and the mixing ratio changing unit 81 provided on the first bifurcated line 51 and the first bifurcated line 61 is controlled so that the measured value of the amount of steam generated by the boiler obtained by the steam amount measuring unit 36 ​​is close to the target value. Specifically, when the measured value of the amount of steam generated by the boiler is lower than the target value, the opening degree of the damper 811 in the mixing ratio changing unit 81 becomes smaller (than the previous opening degree), and the opening degree of the damper 812 becomes larger. As a result, the ratio of high-concentration oxygen in the mixed gas of the recirculated exhaust gas and high-concentration oxygen becomes higher, and a primary combustion gas with a high oxygen concentration (than the previous oxygen concentration) is supplied to the primary combustion chamber 33 from the lower part of the fire grate 331 to the fire grate 333. As a result, the measured value of the amount of steam generated by the boiler becomes higher.

[0049] In addition, when the measured value of the amount of steam generated by the boiler is higher than the target value, the opening of the damper 811 in the mixing ratio changing unit 81 is increased, and the opening of the damper 812 is decreased. As a result, the ratio of high-concentration oxygen in the mixed gas is reduced, and the primary combustion gas with a low oxygen concentration is supplied from the lower part of the fire grate 331 to the fire grate 333 into the primary combustion chamber 33. As a result, the measured value of the amount of steam generated by the boiler is reduced.

[0050] As described above, the mixing ratio of the recirculated exhaust gas and the high-concentration oxygen in the mixed gas (i.e., the oxygen concentration of the primary combustion gas) is changed by the mixing ratio changing unit 81, and the amount of steam generated by the boiler is controlled to be approximately constant within the target value. The oxygen concentration of the primary combustion gas (as well as the secondary combustion gas and the auxiliary gas) is, for example, less than 30% by volume, and in a typical example, less than 25% by volume. The oxygen concentration is, for example, greater than 0% by volume, and preferably greater than 3% by volume. In the mixing ratio changing unit 81, the change in the mixing ratio of the recirculated exhaust gas and the high-concentration oxygen can also be achieved by structures other than the dampers 811 and 812 (such as a fan, etc.) (the same is true in the mixing ratio changing unit 82 and the mixing ratio changing unit 83).

[0051] Preferably, the flow rate of the mixed gas (gas for primary combustion) supplied from the lower part of the fire grate 331 to the incinerator 3 is approximately constant before and after the mixing ratio changing section 81 changes the mixing ratio of the recirculated exhaust gas and the high-concentration oxygen. When the flow rate of the mixed gas is maintained within the range of ±20% of its average value (for example, the average value of one day) before and after the mixing ratio is changed, the flow rate of the mixed gas can be said to be approximately constant. Before and after the mixing ratio is changed, the flow rate of the mixed gas is preferably maintained within the range of ±15% of its average value, and more preferably maintained within the range of ±10%. The same is true before and after the mixing ratio changing section 82 or the mixing ratio changing section 83 changes the mixing ratio.

[0052] In the second control example of the control unit 10, a target value of the oxygen concentration at the furnace outlet is set as the amount of interest, and the mixing ratio changing unit 82 provided on the second bifurcated line 52 and the second bifurcated line 62 is controlled so that the measured value of the oxygen concentration at the furnace outlet obtained by the oxygen concentration measuring unit 37 is close to the target value. Specifically, when the measured value of the oxygen concentration at the furnace outlet is lower than the target value, the opening of the damper 821 in the mixing ratio changing unit 82 becomes smaller, and the opening of the damper 822 becomes larger. As a result, the ratio of the high-concentration oxygen in the mixed gas of the recirculated exhaust gas and the high-concentration oxygen becomes higher, and the secondary combustion gas with a high oxygen concentration is supplied from the nozzle 341 to the secondary combustion chamber 34. As a result, the measured value of the oxygen concentration at the furnace outlet becomes higher.

[0053] In addition, when the measured value of the oxygen concentration at the furnace outlet is higher than the target value, the opening of the damper 821 in the mixing ratio changing section 82 becomes larger, and the opening of the damper 822 becomes smaller. As a result, the ratio of high-concentration oxygen in the mixed gas becomes lower, and secondary combustion gas with a low oxygen concentration is supplied from the nozzle 341 to the secondary combustion chamber 34. As a result, the measured value of the oxygen concentration at the furnace outlet becomes lower. As described above, the mixing ratio of the recycled exhaust gas and the high-concentration oxygen in the mixed gas (that is, the oxygen concentration of the secondary combustion gas) is changed by the mixing ratio changing section 82, and the oxygen concentration at the furnace outlet is controlled to be approximately constant within the target value. As has been described, in the preferred mixing ratio changing section 82, the flow rate of the secondary combustion gas supplied from the nozzle 341 to the incinerator 3 is approximately constant before and after the mixing ratio of the recycled exhaust gas and the high-concentration oxygen is changed.

[0054] In the third control example of the control unit 10, a target value of the temperature in the primary combustion chamber 33 as a quantity of interest is set, and the mixing ratio changing unit 83 provided on the third bifurcated line 53 and the third bifurcated line 63 is controlled so that the measured value of the temperature in the primary combustion chamber 33 obtained by the furnace temperature measuring unit 38 approaches the target value. Specifically, when the measured value of the temperature in the primary combustion chamber 33 is lower than the target value, the opening degree of the damper 831 in the mixing ratio changing unit 83 becomes smaller, and the opening degree of the damper 832 becomes larger. As a result, the ratio of high-concentration oxygen in the mixed gas of the recirculated exhaust gas and high-concentration oxygen becomes higher, and the auxiliary gas with a high oxygen concentration is supplied to the primary combustion chamber 33 from the nozzle 336. As a result, the measured value of the temperature in the primary combustion chamber 33 becomes higher.

[0055] In addition, when the measured value of the temperature in the primary combustion chamber 33 is higher than the target value, the opening of the damper 831 in the mixing ratio changing unit 83 becomes larger, and the opening of the damper 832 becomes smaller. As a result, the ratio of high-concentration oxygen in the mixed gas becomes lower, and the auxiliary gas with a low oxygen concentration is supplied from the nozzle 336 to the primary combustion chamber 33. As a result, the measured value of the temperature in the primary combustion chamber 33 becomes lower. As described above, the mixing ratio of the recirculating exhaust gas and the high-concentration oxygen in the mixed gas (that is, the oxygen concentration of the auxiliary gas) is changed by the mixing ratio changing unit 83, and the temperature in the primary combustion chamber 33 is controlled to be substantially constant within the target value. As described above, in the preferred mixing ratio changing unit 83, the flow rate of the auxiliary gas supplied from the nozzle 336 to the incinerator 3 is substantially constant before and after the mixing ratio of the recirculating exhaust gas and the high-concentration oxygen is changed. In addition, depending on the design of the waste incineration equipment 1, the nozzle 336 may not be provided in the primary combustion chamber 33. In such a case, the third control example is not performed.

[0056] The furnace temperature measuring unit 38 may also measure the temperature in the secondary combustion chamber 34 using a sensor provided in the secondary combustion chamber 34. In the above case, the control unit 10 sets a target value for the temperature in the secondary combustion chamber 34, and controls the mixing ratio changing unit 82 and the mixing ratio changing unit 83 so that the measured value of the temperature in the secondary combustion chamber 34 obtained by the furnace temperature measuring unit 38 approaches the target value. Specifically, when the measured value of the temperature in the secondary combustion chamber 34 is lower than the target value, a secondary combustion gas with a high oxygen concentration is supplied from the nozzle 341 to the secondary combustion chamber 34, and an auxiliary gas with a high oxygen concentration is supplied from the nozzle 336 to the primary combustion chamber 33. As a result, the measured value of the temperature in the secondary combustion chamber 34 becomes higher.

[0057] In addition, when the measured value of the temperature in the secondary combustion chamber 34 is higher than the target value, a secondary combustion gas with a low oxygen concentration is supplied from the nozzle 341 to the secondary combustion chamber 34, and an auxiliary gas with a low oxygen concentration is supplied from the nozzle 336 to the primary combustion chamber 33. As a result, the measured value of the temperature in the secondary combustion chamber 34 becomes lower. As described above, the oxygen concentration of the secondary combustion gas and the oxygen concentration of the auxiliary gas are changed by the mixing ratio changing section 82 and the mixing ratio changing section 83, and the temperature in the secondary combustion chamber 34 is controlled to be substantially constant within the target value. In addition, when the nozzle 336 is not provided in the primary combustion chamber 33, the temperature in the secondary combustion chamber 34 can also be controlled by only changing the oxygen concentration of the secondary combustion gas.

[0058] In the control of the amount of steam generated by the boiler (the first control example), in addition to changing the oxygen concentration of the primary combustion gas, the oxygen concentration of the secondary combustion gas or / and the oxygen concentration of the auxiliary gas may be additionally changed. In the control of the oxygen concentration at the furnace outlet (the second control example), in addition to changing the oxygen concentration of the secondary combustion gas, the oxygen concentration of the primary combustion gas or / and the oxygen concentration of the auxiliary gas may be additionally changed. In the control of the temperature in the incinerator (the third control example), the oxygen concentration of the primary combustion gas may also be changed.

[0059] In addition, two or more of the steam amount generated by the boiler, the oxygen concentration at the furnace outlet, and the temperature in the incinerator may be taken as the quantities of interest, and the two or more quantities of interest may be controlled at the same time. In the above case, in the control of the two or more quantities of interest, when the change object (oxygen concentration of the primary combustion gas, oxygen concentration of the secondary combustion gas, or oxygen concentration of the auxiliary gas) is repeated, for example, the weights set for the two or more quantities of interest may be considered to determine the change amount of the change object.

[0060] As described above, the waste incineration equipment 1 includes: a recirculation exhaust gas line 6 for taking out a part of the waste gas flowing in the waste gas flow path 4 as recirculation exhaust gas and supplying it to the incinerator 3; and an oxygen mixing unit 5 for mixing high-concentration oxygen having an oxygen concentration higher than that of air with the recirculation exhaust gas flowing in the recirculation exhaust gas line 6. In the waste incineration equipment 1, by mixing high-concentration oxygen with the recirculation exhaust gas and using it as a combustion gas in the incinerator 3, the amount of recirculation exhaust gas taken out from the waste gas flow path 4 can be increased compared with the case where air is mixed with the recirculation exhaust gas. As a result, the amount of waste gas flowing to the downstream side of the connection position (i.e., the taking-out position P1) of the recirculation exhaust gas line 6 in the waste gas flow path 4 can be easily reduced.

[0061] In addition, in the waste incineration equipment 1, except for the air brought into the incinerator 3 by the waste or the air flowing into the incinerator 3 through the input hopper 31, almost no air is supplied to the incinerator 3 from the outside. In detail, almost all of the combustion gas supplied to the incinerator 3 through the gas pipe is the recirculation exhaust gas supplied to the incinerator 3 from the recirculation exhaust gas line 6, that is, the recirculation exhaust gas mixed with high concentration oxygen. As a result, the amount of exhaust gas discharged from the chimney 47 in the waste incineration equipment 1 can be greatly reduced. In addition, during the initial operation, air can be supplied to the incinerator 3 from the outside.

[0062] Here, a waste incineration plant of a comparative example in which a gas with a constant oxygen concentration (e.g., air) is supplied as a primary combustion gas, a secondary combustion gas, and an auxiliary gas is described. In the waste incineration plant of the comparative example, the amount of steam generated by the boiler, the oxygen concentration at the furnace outlet, or the temperature in the incinerator is taken as a quantity of interest, and the flow rate of the primary combustion gas, the secondary combustion gas, or the auxiliary gas is increased or decreased so that the quantity of interest approaches a target value. In the above case, the amount of exhaust gas discharged from the incinerator 3 varies greatly, so the power consumption of the exhaust fan 46 increases.

[0063] In contrast, the waste incineration equipment 1 is provided with a mixing ratio changing unit 81 to a mixing ratio changing unit 83, which changes the mixing ratio of the recirculated exhaust gas supplied from a predetermined gas supply position in the incinerator 3 to the high-concentration oxygen. Then, at least one of the amount of steam generated by the exhaust gas heat, the temperature in the incinerator 3, and the oxygen concentration at the outlet of the incinerator 3 is measured as the amount of interest by the amount-of-interest measuring unit (the steam amount measuring unit 36, the oxygen concentration measuring unit 37, and the furnace temperature measuring unit 38 in the above-mentioned description), and the mixing ratio changing unit 81 to the mixing ratio changing unit 83 is controlled by the control unit 10 so that the measured value of the amount of interest approaches the predetermined target value. In this way, by changing the oxygen concentration of the mixed gas supplied from the gas supply position to the incinerator 3, the fluctuation of the exhaust gas amount discharged from the incinerator 3 can be suppressed. As a result, it is possible to easily make the amount of interest approach the target value while reducing the power consumption of the exhaust fan 46.

[0064] It is preferred that the flow rate of the mixed gas supplied from the gas supply position to the incinerator 3 is substantially constant. Thus, the fluctuation of the amount of exhaust gas discharged from the incinerator 3 can be further suppressed, and the power consumption of the exhaust fan 46 can be further reduced. Moreover, the pressure in the incinerator 3 is made substantially constant, and stable and safe operation can be achieved. Depending on the conditions for waste incineration, etc., the mixing ratio of the recirculated exhaust gas and the high-concentration oxygen can also be changed while changing the flow rate of the mixed gas.

[0065] Preferably, the amount of interest includes the steam amount, and the gas supply position in the incinerator 3 is set below the fire grid section 331 to the fire grid section 333. In this way, the steam amount can be easily approached to the target value. Moreover, even in the case where low-calorie waste is supplied to the incinerator 3, the low-calorie waste can be properly incinerated by increasing the oxygen concentration of the primary combustion gas. In other words, in the combustion of the low-calorie waste, there is no need to use combustion aids such as fossil fuels, so the operating cost can be reduced. Furthermore, the combustion temperature during such low-load operation can be maintained at high temperature, and low-calorie waste, flood waste, sludge, etc. can be flexibly dealt with. In addition, when low-calorie waste is supplied to the incinerator 3, the flow rate of the primary combustion gas can be reduced while the oxygen concentration of the primary combustion gas is increased, so that the low-calorie waste can be burned efficiently.

[0066] Preferably, the amount of interest includes the oxygen concentration at the outlet of the incinerator 3, and the gas supply position in the incinerator 3 is provided at the side wall portion of the secondary combustion chamber 34 surrounding the incinerator 3. This makes it easier for the oxygen concentration at the outlet of the incinerator 3 to approach the target value.

[0067] Furthermore, as in the waste incineration equipment of the comparative example, when the flow rate of the secondary combustion gas (secondary combustion air) is increased or decreased, when the oxygen concentration at the outlet of the incinerator 3 is high, the flow rate of the secondary combustion air is reduced. In the case described above, due to the reduction in the ejection speed of the secondary combustion air from the nozzle, the penetration force of the secondary combustion air is reduced, and the stirring in the secondary combustion chamber 34 becomes insufficient. As a result, incomplete combustion is likely to occur, and carbon monoxide (CO) is likely to be generated. In contrast, in the waste incineration equipment 1, when the oxygen concentration at the outlet of the incinerator 3 is high, since the secondary combustion gas with a low oxygen concentration is supplied, a certain penetration force can be maintained and the secondary combustion chamber 34 can be fully stirred, and the occurrence of incomplete combustion can be suppressed. Moreover, NOx can also be appropriately reduced.

[0068] Preferably, the amount of interest includes the temperature in the incinerator 3, and the gas supply position in the incinerator 3 is set at the top 335 above the fire grid portion 331 to a part of the fire grid portion 333, the side wall portion surrounding the primary combustion chamber 33 of the incinerator 3, or the side wall portion surrounding the secondary combustion chamber 34 of the incinerator 3. As a result, the temperature in the incinerator 3 can be easily approached to the target value, and the stable operation of the waste incineration equipment 1 can be achieved. Moreover, as in the waste incineration equipment of the comparative example, when the flow rate of the secondary combustion gas or the auxiliary gas is increased or decreased, when the flow rate becomes too low, incomplete combustion is likely to occur and carbon monoxide is likely to be generated. In contrast, in the waste incineration equipment 1 that changes the oxygen concentration of the secondary combustion gas or the auxiliary gas, as described above, the occurrence of incomplete combustion can be suppressed.

[0069] Figure 3 FIG. 2 is a diagram showing another example of a structure for supplying primary combustion gas to the fire grid sections 331 to 333. Figure 3 In the embodiment, the first branch line 61 of the recirculating exhaust gas line 6 is branched into a plurality of lines 61a, 61b, and 61c, which are respectively connected to the wind boxes of the drying fire grid section 331, the combustion fire grid section 332, and the post-combustion fire grid section 333. Moreover, the first branch line 51 of the oxygen mixed gas line 50 is also branched into a plurality of lines 51a, 51b, and 51c, which are respectively connected to the plurality of lines 61a, 61b, and 61c. The air dampers of the mixing ratio changing section 81a are provided on the lines 51a and 61a, which can change the mixing ratio of the recirculating exhaust gas and the high-concentration oxygen supplied from the bottom of the drying fire grid section 331 to the incinerator 3. The air dampers of the mixing ratio changing section 81b are provided on the lines 51b and 61b, which can change the mixing ratio of the recirculating exhaust gas and the high-concentration oxygen supplied from the bottom of the combustion fire grid section 332 to the incinerator 3. The dampers of the mixing ratio changing section 81c are provided on the lines 51c and 61c, and can change the mixing ratio of the recirculated exhaust gas and the high-concentration oxygen supplied from below the post-combustion fire grate section 333 into the incinerator 3.

[0070] exist Figure 3 In the example, the mixing ratio changing section 81a to the mixing ratio changing section 81c are also controlled by the control section 10 so that the measured value of the amount of interest (for example, the amount of steam generated by the boiler) is close to the specified target value. In this way, the amount of interest can be made close to the target value with good accuracy. It is preferred that the flow rate of the gas supplied to the incinerator 3 from the bottom of each fire grid section 331 to 333 is approximately constant. In this way, the variation in the amount of exhaust gas discharged from the incinerator 3 can be suppressed, and the power consumption of the exhaust fan 46 can be reduced. In addition, similarly to the fire grid section 331 to the fire grid section 333, a plurality of mixing ratio changing sections can be respectively provided for the plurality of nozzles 341 in the secondary combustion chamber 34, and the mixing ratio of the recirculated exhaust gas and the high-concentration oxygen supplied from each nozzle 341 to the incinerator 3 can be respectively changed. The same is true for the case where a plurality of nozzles 336 are provided in the primary combustion chamber 33.

[0071] (Second Embodiment)

[0072] Figure 4 FIG. 1 is a block diagram showing a waste incineration plant 1 according to a second embodiment of the present invention. Figure 4 In the waste incineration equipment 1, the waste pit 2 and the oxygen mixing unit 5 are connected by an extraction gas line 21 as a gas flow path. The gas in the waste pit 2 is extracted as the extraction gas and supplied to the oxygen mixing unit 5 via the extraction gas line 21. Figure 1 The same waste incineration plant 1 is the same as the waste incineration plant 1, and the same symbols are given to the same structures.

[0073] In the extracted gas line 21, a fan 212 and a deodorizing device 72 are provided in order from the sewage pit 2 toward the oxygen mixing section 5. The order of the fan 212 and the deodorizing device 72 may be reversed. The extracted gas deodorized by the activated carbon layer of the deodorizing device 72 is supplied to the oxygen mixing section 5, and oxygen is concentrated from the extracted gas, thereby generating high-concentration oxygen. The high-concentration oxygen is mixed with the recirculating exhaust gas flowing in the recirculating exhaust gas line 6 via the oxygen mixed gas line 50, and is supplied to the incinerator 3. The remaining gas (mainly nitrogen) after the oxygen is concentrated in the oxygen mixing section 5 is discharged to the outside of the sewage incineration equipment 1. In the oxygen mixing section 5, in the case where the required amount of high-concentration oxygen cannot be generated by the extracted gas alone, the surrounding air may be introduced as needed.

[0074] As mentioned above, in Figure 4In the oxygen mixing section 5, an extraction gas line 21 for extracting the gas in the sewage pit 2 as an extraction gas is provided, and the negative pressure in the sewage pit 2 is appropriately maintained. Thus, it is possible to suppress the odor in the sewage pit 2 from leaking to the outside. In addition, high-concentration oxygen is generated from the extraction gas, and is mixed with the recycled exhaust gas to be used as combustion gas in the incinerator 3. Thus, the amount of recycled exhaust gas taken out from the exhaust gas flow path 4 can be increased, thereby reducing the amount of exhaust gas discharged from the chimney 47.

[0075] Moreover, almost all of the combustion gas supplied to the incinerator 3 through the gas pipe is the recirculated exhaust gas mixed with high-concentration oxygen, thereby significantly reducing the amount of exhaust gas discharged from the chimney 47. Furthermore, the control unit 10 controls the mixing ratio changing unit 81 to the mixing ratio changing unit 83 so that the measured value of the amount of interest approaches a predetermined target value (see Figure 2 ). Thus, the fluctuation of the exhaust gas amount discharged from the incinerator 3 can be suppressed, and as a result, the amount of interest can be easily brought close to the target value while reducing the power consumption of the exhaust fan 46. The same is true for the waste incineration equipment 1 of the third and fourth embodiments described below.

[0076] The deodorizing device 72 is not necessarily provided in the extracted gas line 21, but may also be provided in a Figure 5 As shown, it is arranged on the discharge path from the oxygen mixing section 5 to the outside. Figure 5 In the oxygen mixing section 5, the oxygen contained in the extracted gas (and air) is concentrated to generate high-concentration oxygen, which is mixed with the recirculated exhaust gas. On the other hand, the remaining gas of the extracted gas, that is, the remaining gas after oxygen concentration, is discharged to the outside through the deodorizing device 72. Figure 5 In the structure of Figure 4 Thus, a small deodorizing device 72 can be used, and the manufacturing cost of the waste incineration equipment 1 can be reduced.

[0077] (Third Embodiment)

[0078] Figure 6 FIG. 1 is a block diagram showing a waste incineration plant 1 according to a third embodiment of the present invention. Figure 6 In the waste incineration equipment 1, an oxygen enrichment device 5a is provided to replace Figure 1 The oxygen mixing unit 5 in the waste incineration equipment 1. The oxygen enrichment device 5a is arranged between the carbon dioxide recovery device 44 and the waste gas reheater 45 in the waste gas flow path 4. The oxygen enrichment device 5a is connected to the recirculation waste gas line 6 via the oxygen mixed gas line 50. The extracted gas line 21 is further connected to the oxygen enrichment device 5a. A gas-to-gas heat exchanger 71 is provided in the waste gas flow path 4 and the recirculation waste gas line 6. Other structures and Figure 1 The same symbols are used to mark the same structures.

[0079] In the gas-to-gas heat exchanger 71, heat exchange is performed between the exhaust gas flowing from the dust collector 42 toward the wet scrubber 43 in the exhaust gas flow path 4 and the recirculating exhaust gas flowing in the recirculating exhaust gas line 6. Thus, in the waste incineration equipment 1 having the take-out position P1 provided on the downstream side of the wet scrubber 43, the recirculating exhaust gas whose temperature has been reduced can be efficiently heated by the wet scrubber 43. The gas-to-gas heat exchanger 71 can also be used in other waste incineration equipment 1. Figure 6 In the example of , the preheater in the recirculation exhaust gas line 6 is omitted, but a preheater may be provided as needed. Moreover, a preheater may be provided instead of the gas-to-gas heat exchanger 71. In the case where the gas-to-gas heat exchanger 71 is not provided, the take-out position P1 may be provided between the dust collector 42 and the wet scrubber 43.

[0080] Towards Figure 6 The exhaust gas passing through the carbon dioxide recovery device 44 is supplied to the oxygen enrichment device 5a. In the extracted gas line 21, the extracted gas is extracted from the sewage pit 2 by the fan 212 and supplied to the oxygen enrichment device 5a via the deodorization device 72. Air from the outside can be supplied to the oxygen enrichment device 5a as needed. The oxygen enrichment device 5a is a device that generates high-concentration oxygen with a high oxygen concentration from these gases, for example, a PSA-type device like the above-mentioned oxygen mixing unit 5. In the present embodiment, the oxygen enrichment device 5a extracts nitrogen (N 2 ) is adsorbed and separated and directed to the exhaust gas reheater 45. In addition, the remaining gas (mainly oxygen (O 2 ) and carbon dioxide (CO 2 ) gas) is guided to the recirculation exhaust gas line 6 via the oxygen mixed gas line 50 and mixed in the recirculation exhaust gas. The gas mixed in the recirculation exhaust gas is high-concentration oxygen having an oxygen concentration higher than that of air, and can be used as a combustion gas (combustion oxidant) in the incinerator 3. The gas (mainly nitrogen) guided to the exhaust gas reheater 45 is guided to the chimney 47 via the exhaust fan 46 and released into the atmosphere. In addition, an adsorbent that adsorbs oxygen can also be used in the oxygen enrichment device 5a. The same is true in the above-mentioned oxygen mixing section 5.

[0081] As mentioned above, in Figure 6 In the waste incineration equipment 1, the oxygen enrichment device 5a is provided in the exhaust gas flow path 4. The oxygen enrichment device 5a is an oxygen mixing unit, which generates high-concentration oxygen with a high oxygen concentration from the exhaust gas passing through the carbon dioxide recovery device 44 and the extracted gas from the waste pit 2, and mixes it with the remaining carbon dioxide into the recirculating exhaust gas flowing in the recirculating exhaust gas line 6. As a result, the emission amount of carbon dioxide contained in the exhaust gas passing through the carbon dioxide recovery device 44 can be reduced.

[0082] Furthermore, an extraction gas line 21 for extracting the gas in the sewage pit 2 as extraction gas is provided, and the negative pressure in the sewage pit 2 is appropriately maintained. Then, the oxygen enrichment device 5a generates high-concentration oxygen from the extraction gas, and mixes it with the recirculation exhaust gas flowing in the recirculation exhaust gas line 6. Thus, compared with the case where the extraction gas is directly mixed with the recirculation exhaust gas or directly supplied to the incinerator 3, the amount of the recirculation exhaust gas taken out from the exhaust gas flow path 4 can be increased.

[0083] In the waste incineration equipment 1, a wet scrubber 43 is provided between a dust collector 42 and a take-out position P1 of the recirculated exhaust gas in the exhaust gas flow path 4. In the gas-to-gas heat exchanger 71, the recirculated exhaust gas is heated by heat exchange between the exhaust gas on the upstream side of the wet scrubber 43 in the exhaust gas flow path 4 and the recirculated exhaust gas flowing in the recirculated exhaust gas line 6. As described above, by heating the recirculated exhaust gas (i.e., the gas having a smaller flow rate than the exhaust gas in the exhaust gas flow path 4) of a part of the taken-out exhaust gas using the high-temperature exhaust gas flowing in the exhaust gas flow path 4, the temperature of the recirculated exhaust gas can be efficiently increased.

[0084] exist Figure 6 In the waste incineration equipment 1, the waste gas passing through the carbon dioxide recovery device 44 may not be supplied to the oxygen enrichment device 5a, depending on the oxygen content of the waste gas, etc. In the case, in the oxygen enrichment device 5a, high-concentration oxygen is taken out from the extracted gas from the waste pit 2 and the external air, and mixed with the recirculated waste gas. On the other hand, gases other than high-concentration oxygen (mainly nitrogen) are discharged to the waste gas reheater 45. Moreover, the waste gas passing through the carbon dioxide recovery device 44, for example, does not pass through the oxygen enrichment device 5a, but is guided to the downstream side of the oxygen enrichment device 5a and mixed with the gas (nitrogen, etc.) discharged from the oxygen enrichment device 5a.

[0085] like Figure 7 As shown, the deodorizing device 72 may be disposed between the oxygen enriching device 5a and the exhaust gas reheater 45. In the case described above, the residual gas after oxygen concentration in the oxygen enriching device 5a is discharged to the outside from the chimney 47 after passing through the deodorizing device 72. Moreover, the exhaust gas passing through the carbon dioxide recovery device 44 may be directed to the downstream side of the deodorizing device 72, for example, without passing through the oxygen enriching device 5a and the deodorizing device 72, and may be mixed with the gas (nitrogen, etc.) discharged from the deodorizing device 72. In addition, depending on the structure of the waste incineration equipment 1, the deodorizing device 72 may be omitted. Moreover, the extracted gas may not be supplied to the oxygen enriching device 5a.

[0086] (Fourth Embodiment)

[0087] Figure 8 FIG. 4 is a block diagram showing a waste incineration plant 1 according to a fourth embodiment of the present invention. Figure 8In the waste incineration equipment 1, a carbon dioxide utilization device 44a is provided instead of Figure 1 The carbon dioxide recovery device 44 in the waste incineration equipment 1 is omitted, and the exhaust gas reheater 45, the exhaust fan 46 and the chimney 47 are omitted. Figure 1 The same as the waste incineration plant 1.

[0088] like Figure 8 As shown, the carbon dioxide utilization device 44a is disposed in the exhaust gas flow path 4 on the downstream side of the extraction position P1. The carbon dioxide utilization device 44a is a device that utilizes exhaust gas to generate a specified product. In one example, methane gas and the like are generated from the exhaust gas by methanation. In other examples, solid carbonates are generated from the exhaust gas by mineralization (mineralization). In addition, components other than carbon dioxide contained in the exhaust gas may also be included in the product. In the waste incineration equipment 1 provided with the carbon dioxide utilization device 44a, the discharge of exhaust gas into the atmosphere can be greatly reduced. In other waste incineration equipment 1, Figure 8 Likewise, a carbon dioxide utilization device 44a may be provided in place of the carbon dioxide recovery device 44. Furthermore, both the carbon dioxide recovery device 44 and the carbon dioxide utilization device 44a may be provided. In such a case, for example, the carbon dioxide recovered by the carbon dioxide recovery device 44 is used to generate a predetermined product by the carbon dioxide utilization device 44a.

[0089] Various modifications are possible in the waste incineration plant 1 described.

[0090] In the embodiment, air is hardly supplied to the incinerator 3 from the outside, but according to the design of the waste incineration equipment 1, air can also be supplied to the incinerator 3 via a gas pipe as a part of the combustion gas (gas containing oxygen). In the case, in order to sufficiently reduce the amount of exhaust gas, it is preferred that the main gas of the combustion gas supplied to the incinerator 3 via the gas pipe is a recycled exhaust gas mixed with a high concentration of oxygen. The so-called main gas of the combustion gas is, for example, a gas that accounts for 50% or more of the volume of the combustion gas. As described above, in the case where air is supplied to the incinerator 3 via a gas pipe as a part of the combustion gas, the air is also preferably less than 50% by volume of the combustion gas. The air is more preferably less than 35% by volume, and further preferably less than 20% by volume.

[0091] In the embodiment, the recycled exhaust gas line 6 is connected to the primary combustion chamber 33 and the secondary combustion chamber 34 of the incinerator 3, and the recycled exhaust gas mixed with high concentration oxygen is used as the primary combustion gas and the secondary combustion gas. The recycled exhaust gas line 6 can be connected only to the primary combustion chamber 33 or the secondary combustion chamber 34.

[0092] When the oxygen concentration of the exhaust gas passing through the carbon dioxide recovery device 44 is sufficiently higher than that of air, the exhaust gas can be mixed in the recirculated exhaust gas as high-concentration oxygen. In this case, the carbon dioxide recovery device 44 is understood as an oxygen mixing unit.

[0093] The incinerator 3 may be an incinerator other than a stoker type incinerator (for example, a fluidized bed furnace, a kiln, etc.). The waste incineration facility 1 may also be used as a waste incineration facility for incinerating general waste or industrial waste other than waste.

[0094] The configurations in the above-described embodiment and various modifications may be appropriately combined unless they are contradictory to each other.

[0095] While the invention has been described and illustrated in detail, the descriptions described are for illustrative purposes only and are not intended to be limiting. Therefore, it is contemplated that many modifications and variations may be implemented without departing from the scope of the invention.

[0096] Explanation of symbols

[0097] 1: Waste incineration equipment

[0098] 2: Dirt Pit

[0099] 3: Incinerator

[0100] 4: Exhaust gas flow path

[0101] 5: Oxygen mixing unit

[0102] 5a: Oxygen enrichment device

[0103] 6: Recirculation exhaust gas line

[0104] 10: Control Department

[0105] 21: Extract gas line

[0106] 33: Primary combustion chamber

[0107] 34: Secondary combustion chamber

[0108] 36: Steam volume measurement unit

[0109] 37: Oxygen concentration measurement unit

[0110] 38: Furnace temperature measurement unit

[0111] 42: Dust collector

[0112] 44: Carbon dioxide recovery device

[0113] 81 to 83, 81a to 81c: Mixing ratio changing unit

[0114] 331-333: Fire Grid

[0115] 335: Top

[0116] 336, 341: Nozzle

[0117] P1: Take out position

Claims

1. A waste incineration device, comprising: Incinerators, to burn waste; An exhaust gas flow path for the exhaust gas discharged from the incinerator to flow; A dust collector is arranged in the exhaust gas flow path; a recirculating exhaust gas line connected to a take-out position on the downstream side of the dust collector in the exhaust gas flow path, taking out a portion of the exhaust gas flowing in the exhaust gas flow path as recirculating exhaust gas and supplying it to the incinerator; an oxygen mixing unit for mixing high-concentration oxygen having an oxygen concentration higher than that of air with the recirculation exhaust gas flowing through the recirculation exhaust gas line; a mixing ratio changing unit for changing a mixing ratio of the recirculated exhaust gas and the high-concentration oxygen supplied into the incinerator from a predetermined gas supply position in the incinerator; a quantity-of-interest measuring unit that measures at least one of a quantity of steam generated by heat of the exhaust gas, a temperature in the incinerator, and an oxygen concentration at an outlet of the incinerator as a quantity-of-interest; and a control unit that controls the mixing ratio changing unit so that the measured value of the amount of interest approaches a predetermined target value, The main gas of the combustion gas supplied to the incinerator through the gas pipe is the recirculation exhaust gas mixed with the high-concentration oxygen.

2. The waste incineration equipment according to claim 1, further comprising: A waste pit for storing waste before it is put into the incinerator; and A gas extraction line is used to extract the gas in the waste pit as the extracted gas. The oxygen mixing unit generates the high-concentration oxygen from the extracted gas and mixes the high-concentration oxygen with the recirculation exhaust gas flowing through the recirculation exhaust gas line.

3. The waste incineration equipment according to claim 1, further comprising: a carbon dioxide recovery device, which is disposed in the exhaust gas flow path at the downstream side of the extraction position and recovers carbon dioxide from the exhaust gas; The oxygen mixing unit generates the high-concentration oxygen from the exhaust gas that has passed through the carbon dioxide recovery device, and mixes the high-concentration oxygen with the recirculation exhaust gas that flows through the recirculation exhaust gas line.

4. The waste incineration equipment according to claim 1, wherein: The flow rate of the gas supplied from the gas supply position in the incinerator into the incinerator is substantially constant.

5. The waste incineration plant according to any one of claims 1 to 4, wherein: The quantity of interest includes the steam quantity, The gas supply position in the incinerator is provided below the fire grate portion.

6. The waste incineration plant according to any one of claims 1 to 4, wherein: The quantities of interest include the temperature within the incinerator, The gas supply position in the incinerator is provided at a top portion covering an upper portion of a part of a fire grate, a side wall portion surrounding a primary combustion chamber of the incinerator, or a side wall portion surrounding a secondary combustion chamber of the incinerator.

7. The waste incineration plant according to any one of claims 1 to 4, wherein: The quantities of interest include the oxygen concentration at the outlet of the incinerator, The gas supply position in the incinerator is provided at a side wall portion surrounding a secondary combustion chamber of the incinerator.

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