Waste incineration system and waste incineration method

Abstract

To reduce carbon monoxide included in exhaust gas discharged from a waste incinerator.SOLUTION: A waste incineration system includes: an incinerator having a combustion chamber for burning waste while conveying the waste in the combustion chamber with a fire grate and a secondary combustion chamber for burning combustion gas generated in the combustion chamber; dust removal means for removing dust from exhaust gas discharged from the incinerator; and mixed gas generation means for generating mixed gas by mixing at least oxygen, carbon dioxide from which dust has been removed by the dust removal means and that contains moisture and carbon dioxide from which dust has been removed by the dust removal means and from which water has been separated. The fire grate includes a drying fire grate, a combustion fire grate and a post-combustion fire grate in the conveyance direction of the waste. The mixed gas is supplied to at least the drying fire grate, the combustion fire grate and the secondary combustion chamber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a waste incineration system and a waste incineration method. [Background technology]

[0002] Conventionally, combustion technologies known as O2 / CO2 combustion, oxygen combustion, or oxy-fuel combustion have been proposed, and Patent Document 1 discloses a waste treatment device and a waste treatment method that apply this combustion technology. The waste treatment device described in Patent Document 1 first incinerates municipal waste using oxygen (O2) obtained by separating nitrogen (N2) from air. The waste treatment device then recovers heat from the exhaust gas generated by the incineration of the municipal waste, and then circulates a portion of the exhaust gas to the incinerator to control the incineration temperature. The waste treatment device also recovers water (H2O) and carbon dioxide (CO2) from the exhaust gas after heat recovery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-126324 Summary of the Invention [Problem to be solved by the invention]

[0004] The waste treatment device described in Patent Document 1 controls the temperature inside the incinerator to 800 to 1200°C by supplying oxygen obtained by separating nitrogen from air and a portion of the exhaust gas generated by incineration to the incinerator. However, the CO2 contained in the exhaust gas circulated to the incinerator is a radiative gas that easily absorbs heat and has a large heat capacity. Therefore, when the exhaust gas is circulated to the incinerator, the CO2 contained in the exhaust gas lowers the incinerator's combustion temperature, and the carbon monoxide (CO) content in the combustible gas generated by the incinerator does not decrease. Furthermore, circulating the exhaust gas to the combustion furnace increases the CO2 concentration in the incinerator, making it difficult for the combustible gas generated by the incinerator to oxidize, resulting in an increase in the carbon monoxide concentration.

[0005] The present invention has been made in view of the above, and has an object to reduce carbon monoxide contained in exhaust gas discharged from a waste incinerator. [Means for solving the problem]

[0006] A waste incineration system according to one aspect of the present invention comprises an incinerator having a combustion chamber having a grate in which waste is burned while being transported in the combustion chamber, and a secondary combustion chamber in which combustion gas generated in the combustion chamber is burned; a dust removal means for removing dust from exhaust gas discharged from the incinerator; and a mixed gas generation means for generating a mixed gas by mixing at least oxygen, carbon dioxide that has been removed by the dust removal means and contains moisture, and carbon dioxide that has been removed by the dust removal means and from which water has been separated, wherein the grate has a drying grate, a combustion grate, and a post-combustion grate along the direction in which the waste is transported, and the mixed gas is supplied to at least the drying grate, the combustion grate, and the secondary combustion chamber.

[0007] In the waste incineration system according to one aspect of the present invention, the mixed gas generated by the mixed gas generating means may further contain nitrogen.

[0008] In addition, in a waste incineration system according to one aspect of the present invention, the mixed gas may have an oxygen concentration of 30%, a carbon dioxide concentration of 35% or more, a water concentration of 28% or less, and a nitrogen concentration of 7% or less.

[0009] A waste incineration method according to one aspect of the present invention is a method of burning waste in an incinerator having a combustion chamber in which waste is burned while being transported in a combustion chamber having a grate, and a secondary combustion chamber in which combustion gas generated in the combustion chamber is burned, wherein the grate has a drying grate, a combustion grate, and a post-combustion grate along the direction in which the waste is transported, and exhaust gas discharged from the incinerator is removed by a dust removal means to generate a mixed gas containing at least oxygen, carbon dioxide that has been removed by the dust removal means and contains moisture, and carbon dioxide that has been removed by the dust removal means and from which water has been separated, and the mixed gas is supplied to at least the drying grate, the combustion grate, and the secondary combustion chamber. [Effects of the Invention]

[0010] According to the present invention, it is possible to reduce the carbon monoxide contained in the exhaust gas discharged from a waste incinerator. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the overall configuration of a waste incineration system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the state inside the combustion chamber of the waste incinerator according to the embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing the configuration of a waste incinerator according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below. In addition, in the description of the drawings, the same or corresponding elements are appropriately designated by the same reference numerals. Furthermore, it should be noted that the drawings are schematic, and the dimensional relationships between the elements may differ from the actual ones.

[0013] 1 is a diagram showing the configuration of a waste incineration system 1000 according to an embodiment of the present invention. The waste incineration system 1000 includes a waste incinerator 1 that employs a combustion technology known as O2 / CO2 combustion or Oxy-fuel combustion.

[0014] The waste incinerator 1 is, for example, a grate-type incinerator, and is equipped with a combustion chamber 2 and an inlet 3. The inlet 3 is an inlet for feeding waste W, such as industrial waste or household garbage, into the combustion chamber 2, and is provided above the combustion chamber 2 on the upstream side of the flow of the waste W within the combustion chamber 2. An extruder (not shown) is disposed below the inlet 3 to push the fed waste W into the combustion chamber 2, and the waste W fed into the inlet 3 is pushed into the combustion chamber 2 by the extruder.

[0015] A grate 5 is installed at the bottom of the combustion chamber 2 to burn the waste W as it moves. The grate 5 is composed of a drying grate 5a, a combustion grate 5b, and a post-combustion grate 5c, and is arranged in this order from the inlet 3 side in the direction of movement of the waste W. The drying grate 5a mainly dries, ignites, and initially burns the waste W. The combustion grate 5b mainly pyrolyzes and partially oxidizes the waste W. The combustion grate 5b also combusts the solids and pyrolysis gases generated by pyrolysis, including carbon monoxide and hydrocarbons. The post-combustion grate 5c performs post-combustion, completely burning the unburned waste W. This post-combustion forms a layer of incineration ash on the post-combustion grate 5c after complete combustion. This incineration ash is discharged from the combustion chamber 2 through a discharge section 6 located downstream of the post-combustion grate 5c in the flow of the waste W.

[0016] A boiler 4 is connected above the combustion chamber 2 on the downstream side in the flow direction of the waste W. Near the inlet of the boiler 4, a secondary combustion chamber 11 is formed, which burns unburned gas in the gas discharged from the combustion chamber 2. Secondary combustion gas is blown into the secondary combustion chamber 11 from an injection nozzle 40 by a supply line 31f equipped with a blower and damper (not shown). In the secondary combustion chamber 11, unburned components in the combustion gas generated in the combustion chamber 2 undergo secondary combustion, and the exhaust gas after secondary combustion is heat recovered by the boiler 4.

[0017] The boiler 4, which recovers heat from exhaust gas, is provided with two bends 12 and 13 that bend the flow path of the exhaust gas. These bends 12 and 13 form, from the upstream side along the flow direction of the exhaust gas, a first radiant chamber 14, a second radiant chamber 15, and a convective heat transfer chamber 16. The first radiant chamber 14, through which exhaust gas flows from the waste incinerator 1, has an upstream portion along the flow direction of the exhaust gas that serves as the secondary combustion chamber 11. The first radiant chamber 14 and the second radiant chamber 15 are connected via the bend 12, and the lower part of the second radiant chamber 15 and the lower part of the convective heat transfer chamber 16 are connected via the bend 13. The upper end of the convective heat transfer chamber 16 is connected via a flue 21 to a dust removal device 23 composed of a bag filter or the like.

[0018] The boiler 4 has an inner wall made of a refractory wall, and the first radiant chamber 14 and the second radiant chamber 15 have heat transfer tubes (not shown) formed of piping for circulating steam that are densely arranged outside the refractory wall that forms the inner wall. The heat transfer tubes arranged outside the refractory wall and through which water flows become a radiant heat transfer surface that receives radiant heat from the exhaust gas and generates steam, and function as an evaporator.

[0019] The convection heat transfer chamber 16 has heat transfer tubes (not shown) arranged in a flag shape at the most upstream portion in the direction of exhaust gas flow. The heat transfer tubes cool the exhaust gas flowing into the convection heat transfer chamber 16, solidifying gaseous or mist-like dust components and separating them as dust from the exhaust gas. The convection heat transfer chamber 16 also includes, from the upstream side in the direction of exhaust gas flow, three superheaters 16A and an economizer 16B. The superheater 16A includes a heat transfer tube group consisting of multiple heat transfer tubes arranged horizontally and arranged in multiple vertical stages, and the heat transfer tube group functions as a convection heat transfer surface. The superheater 16A further superheats the steam generated in the first radiation chamber 14 and the second radiation chamber 15 through heat exchange with the exhaust gas, producing high-temperature, high-pressure superheated steam.

[0020] The economizer 16B is provided downstream of the superheater 16A in the direction of exhaust gas flow, and is provided with heat transfer tubes (not shown). Steam generated in the boiler 4 and used to drive a steam turbine (not shown) is condensed in a condenser (not shown) and flows through the heat transfer tubes of the economizer 16B. The condensate flowing through the heat transfer tubes of the economizer 16B is heated by the heat retained in the exhaust gas after the steam is superheated by the superheater 16A, and the heated water is supplied to the heat transfer tubes of the first radiant chamber 14 and the second radiant chamber 15, which function as evaporators. The economizer 16B may be provided outside the boiler 4, downstream of the boiler 4 in the direction of exhaust gas flow, rather than within the convection heat transfer chamber 16. Alternatively, both an economizer inside the boiler 4 and an economizer outside the boiler 4 may be provided.

[0021] The exhaust gas from which heat has been recovered by the boiler 4 flows through a flue 21 to a dust removal device 23, which is, for example, a bag filter. In the flue 21, chemicals such as hydrated lime and activated carbon are injected into the exhaust gas together with CO2 from a chemical supply device 22. By injecting the chemicals into the exhaust gas, the chemicals bind to pollutants contained in the exhaust gas, such as hydrogen chloride and sulfur oxides.

[0022] Dust removal device 23, an example of a dust removal means, removes dust by capturing an agent to which dust and pollutants contained in the exhaust gas that has flowed through flue duct 21 are bound. An induced draft fan 24 is connected to dust removal device 23. The induced draft fan 24 draws the exhaust gas from which dust has been removed from dust removal device 23. The exhaust gas drawn from dust removal device 23 by induced draft fan 24 branches into second gas supply line 32 upstream of induced draft fan 24. In addition, the exhaust gas drawn from dust removal device 23 by induced draft fan 24 branches into cooling tower 51 and chimney 25 downstream of induced draft fan 24, and the exhaust gas that branches into chimney 25 is released into the atmosphere.

[0023] The cooling tower 51 separates moisture (H2O) from the branched exhaust gas and discharges it. The exhaust gas from which moisture has been separated in the cooling tower 51 is sent to the separator 52. The separator 52 separates carbon dioxide (CO2) from the exhaust gas from which moisture has been removed in the cooling tower 51, for example, by pressure swing adsorption (PSA). A portion of the exhaust gas (first exhaust gas) from which moisture has been removed and which contains carbon dioxide and which has been separated in the separator 52 is sent to the first gas supply line 30. Note that the separator 52 may separate nitrogen (N2) from the exhaust gas from which moisture has been removed by pressure swing adsorption, thereby increasing the CO2 concentration in the exhaust gas.

[0024] The first gas supply line 30 is connected to dampers 34a to 34c that adjust the flow rate of the first exhaust gas corresponding to the wind boxes 7a to 7c, respectively. The first gas supply line 30 is also connected to dampers 34d and 34e that adjust the flow rate of the first exhaust gas supplied to the combustion chamber 2, and damper 34f that adjusts the flow rate of the first exhaust gas supplied to the secondary combustion chamber 11.

[0025] Damper 34a is connected to wind box 7a via supply line 31a, damper 34b is connected to wind box 7b via supply line 31b, and damper 34c is connected to wind box 7c via supply line 31c. Damper 34d is connected to front-stage nozzle 41 via supply line 31d, damper 34e is connected to rear-stage nozzle 42 provided in combustion chamber 2 via supply line 31e, and damper 34f is connected to blowing nozzle 40 via supply line 31f. Dampers 34a to 34f are controlled by a control unit 70, which will be described later, to adjust the flow rate of the first exhaust gas.

[0026] The second gas supply line 32 is connected to dampers 39a, 39b, 39d to 39f that adjust the flow rate of exhaust gas (second exhaust gas) containing carbon dioxide and water vapor (H2O). Damper 39a is connected to wind box 7a via supply line 31a, and damper 39b is connected to wind box 7b via supply line 31b. Damper 39d is connected to front-stage nozzle 41 via supply line 31d, damper 39e is connected to rear-stage nozzle 42 via supply line 31d, and damper 39f is connected to blowing nozzle 40 via supply line 31f. Dampers 39a, 39b, 39d to 39f are controlled by control unit 70 to adjust the flow rate of the second exhaust gas.

[0027] The waste incineration system 1000 also includes a third gas supply line 35, a blower 36a, a fourth gas supply line 38, a blower 36b, and a gas supplier 60. The third gas supply line 35 is connected to the blower 36a, and the blower 36a is connected to the gas supplier 60. The fourth gas supply line 38 is connected to the blower 36b, and the blower 36b is connected to the gas supplier 60.

[0028] The gas supplier 60 separates oxygen from air using techniques such as cryogenic separation or PSA to generate gas (mainly O2 gas) with an O2 concentration of 50% or more and close to 100%. The gas supplier 60 also generates nitrogen gas from air with oxygen removed. The blower 36a sends the main O2 gas generated by the gas supplier 60 to the third gas supply line 35, and the blower 36b sends the nitrogen gas generated by the gas supplier 60 to the fourth gas supply line 38.

[0029] The third gas supply line 35 is connected to dampers 37a, 37b, 37d, and 37f that adjust the flow rate of the O2-based gas. Damper 37a is connected to wind box 7a via supply line 31a, and damper 37b is connected to wind box 7b via supply line 31b. Damper 37d is connected to front-stage nozzle 41 via supply line 31d, and damper 37f is connected to blowing nozzle 40 via supply line 31f. Dampers 37a, 37b, 37d, and 37f are controlled by control unit 70 to adjust the flow rate of the O2-based gas.

[0030] The fourth gas supply line 38 is connected to dampers 33a, 33b, 33d to 33f that adjust the flow rate of the nitrogen gas. Damper 33a is connected to wind box 7a via supply line 31a, and damper 33b is connected to wind box 7b via supply line 31b. Damper 33d is connected to front-stage nozzle 41 via supply line 31d, damper 33e is connected to rear-stage nozzle 42 via supply line 31e, and damper 33f is connected to blowing nozzle 40 via supply line 31f. Dampers 33a, 33b, 33d to 33f are controlled by control unit 70 to adjust the flow rate of the nitrogen gas.

[0031] In the supply line 31a, the first exhaust gas, the second exhaust gas, the O2-based gas, and the nitrogen gas are mixed, and this mixed gas is sent to the wind box 7a. In the supply line 31b, the first exhaust gas, the second exhaust gas, the O2-based gas, and the nitrogen gas are mixed, and this mixed gas is sent to the wind box 7b. In addition, the supply line 31c allows the first exhaust gas sent from the damper 34c to flow to the wind box 7c. In the supply line 31d, the first exhaust gas, the second exhaust gas, the O2-based gas, and the nitrogen gas are mixed, and this mixed gas is sent to the front-stage nozzle 41. In the supply line 31e, the first exhaust gas, the second exhaust gas, and the nitrogen gas are mixed, and this mixed gas is sent to the rear-stage nozzle 42. In addition, in the supply line 31f, the first exhaust gas, the second exhaust gas, the O2-based gas, and the nitrogen gas are mixed, and this mixed gas is sent to the blowing nozzle 40. The supply lines 31a, 31b, 31d to 31f are an example of a mixed gas generating means for generating a mixed gas by mixing a plurality of gases.

[0032] The wind boxes 7a to 7c are provided below the combustion chamber 2. Specifically, the wind box 7a is provided below the drying grate 5a, the wind box 7b is provided below the combustion grate 5b, and the wind box 7c is provided below the post-combustion grate 5c. The wind box 7a supplies the mixed gas supplied via the supply line 31a to the drying grate 5a, the wind box 7b supplies the mixed gas supplied via the supply line 31b to the combustion grate 5b, and the wind box 7c supplies the first flue gas supplied via the supply line 31c to the post-combustion grate 5c. Alternatively, the first flue gas, the second flue gas, the O2-based gas, and the nitrogen gas may be directly supplied to the wind boxes 7a and 7b, respectively, and mixed in the wind boxes 7a and 7b.

[0033] The combustion chamber 2 is provided with a front nozzle 41 and a rear nozzle 42. The front nozzle 41 and the rear nozzle 42 each function as a counterflow nozzle. The front nozzle 41 is provided above the gap between the drying grate 5a and the combustion grate 5b, for example, on the ceiling of the combustion chamber 2. A mixed gas containing the first exhaust gas, the second exhaust gas, an O2-based gas, and nitrogen gas is supplied to the front nozzle 41 from a supply line 31d. The rear nozzle 42 is provided above the gap between the combustion grate 5b and the rear combustion grate 5c, for example, on the ceiling of the combustion chamber 2. A mixed gas containing the first exhaust gas, the second exhaust gas, and nitrogen gas is supplied to the rear nozzle 42 from a supply line 31e.

[0034] An injection nozzle 40 is provided in the secondary combustion chamber 11 at the outlet portion of the combustion chamber 2. The injection nozzle 40 is connected to a supply line 31f. A mixed gas containing the first exhaust gas, the second exhaust gas, an O2-based gas, and nitrogen gas is supplied to the injection nozzle 40 from the supply line 31f.

[0035] A sensor group 71 is provided upstream in the combustion chamber 2 in the direction in which the waste W is transported. The sensor group 71 measures at least the temperature, O2 concentration, H2O concentration, CO2 concentration, and CO concentration (carbon monoxide concentration) at the installed position. The sensor group 71 transmits the measured values of the temperature, O2 concentration, H2O concentration, CO2 concentration, and CO concentration to the control unit 70. A sensor group 72 is provided downstream in the combustion chamber 2 in the direction in which the waste W is transported. The sensor group 72 measures at least the temperature, O2 concentration, H2O concentration, CO2 concentration, and CO concentration at the installed position. The sensor group 72 transmits the measured values of the temperature, O2 concentration, H2O concentration, CO2 concentration, and CO concentration to the control unit 70. A sensor group 73 is provided at the outlet of the combustion chamber 2. The sensor group 73 measures at least the temperature, O2 concentration, H2O concentration, CO2 concentration, and CO concentration at the installed position. The sensor group 73 transmits measured values such as the temperature, O2 concentration, H2O concentration, CO2 concentration, and CO concentration to the control unit 70.

[0036] Specifically, the control unit 70 includes a processor such as a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or an FPGA (Field-Programmable Gate Array), and a main memory such as a RAM (Random Access Memory) or a ROM (Read Only Memory) (none of which are shown). The control unit 70 may also be configured as an information processing device such as a computer equipped with a memory. In this case, the memory included in the control unit 70 includes a storage medium selected from volatile memory such as RAM, non-volatile memory such as ROM, erasable programmable read-only memory (EPROM), a hard disk drive (HDD), and removable media. The removable media may be, for example, a universal serial bus (USB) memory or a disc storage medium such as a compact disc (CD), a digital versatile disc (DVD), or a Blu-ray disc (BD). The storage may also be configured using a computer-readable storage medium such as an externally attachable memory card. Based on the measurement results of the sensor group 71 and the sensor group 72, the control unit 70 controls the dampers 33a, 33b, 33d, and 33f, the dampers 34a to 34f, the dampers 37a, 37b, 37d, and 37f, and the dampers 39a, 39b, and 39d to 39f.

[0037] In the waste incineration system 1000, the mixing ratios of the first flue gas, second flue gas, O2-based gas, H2O concentration, and nitrogen gas in the mixed gas supplied to the wind boxes 7a and 7b, the front nozzle 41, and the blowing nozzle 40, and the mixing ratios of the first flue gas, second flue gas, H2O concentration, and nitrogen gas in the mixed gas supplied to the rear nozzle 42 can be adjusted by the control unit 70 controlling the dampers. The mixed gas supplied to the wind boxes 7a and 7b, the front nozzle 41, and the blowing nozzle 40 preferably has an O2 concentration of 30%, a CO2 concentration of 35% or more, an H2O concentration of 28% or less, and an N2 concentration of 7% or less. The mixed gas supplied to the rear nozzle 42 preferably has a CO2 concentration of 50% or more, an H2O concentration of 40% or less, and an N2 concentration of 10% or less. By setting the O2 concentration, CO2 concentration, H2O concentration, and N2 concentration in the mixed gas supplied to the wind boxes 7a, 7b, the upstream nozzle 41, and the blowing nozzle 40 to the above-mentioned proportions, the CO2 concentration in the exhaust gas from which moisture has been separated in the cooling tower 51 becomes 80% or more, and CO2 can be efficiently separated in the separation device 52.

[0038] The above ratios of O2 concentration, CO2 concentration, H2O concentration, and N2 concentration in the mixed gas are merely examples, and are not limited to these concentrations and may be other ratios. For example, the O2 concentration may be 35%, the CO2 concentration may be 30.9% by reducing the amounts of the first and second exhaust gases mixed into the mixed gas, and the H2O concentration may be 26.9% and the N2 concentration may be 7.2% by controlling the mixing ratio of the first and second exhaust gases. Alternatively, for example, the O2 concentration may be 25%, the CO2 concentration may be 38.1%, the H2O concentration may be 24.4%, and the N2 concentration may be 12.5% by increasing the amount of nitrogen gas.

[0039] In addition, the ratios of CO2 concentration, H2O concentration, and N2 concentration in the mixed gas supplied to the rear nozzle 42 may be controlled so that the carbonation of the incineration ash is promoted, the combustible gas is easily oxidized, and the concentration of nitrogen oxides in the secondary combustion chamber 11 is reduced.

[0040] The control unit 70 acquires measured values of CO concentration from the sensor group 71 to 73. When the CO concentration acquired from the sensor group 71 exceeds a first threshold, the control unit 70 controls the dampers 37a and 37b to increase the O2 concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b, and controls the damper 34d to increase the O2 concentration in the mixed gas supplied to the front nozzle 41.

[0041] Furthermore, when the CO concentration acquired from the sensor group 71 exceeds a first threshold, the control unit 70 controls dampers 34a and 34b to decrease the CO concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b, controls dampers 39a and 39b to increase the HO concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b, and controls dampers 33a and 33b to increase the N concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b. Furthermore, when the CO concentration acquired from the sensor group 71 exceeds the first threshold, the control unit 70 controls damper 34d to decrease the CO concentration in the mixed gas supplied to the front nozzle 41, controls damper 39d to increase the HO concentration in the mixed gas supplied to the front nozzle 41, and controls damper 33d to increase the N concentration in the mixed gas supplied to the front nozzle 41.

[0042] When the CO concentration acquired from the sensor group 71 is less than a second threshold value that is smaller than the first threshold value, the control unit 70 controls the dampers 37a and 37b to decrease the O concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b, and controls the damper 34d to decrease the O concentration in the mixed gas supplied to the front nozzle 41. When the CO concentration acquired from the sensor group 71 is less than the second threshold value, the control unit 70 controls the dampers 34a and 34b to increase the CO concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b, controls the dampers 39a and 39b to decrease the H2O concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b, and controls the dampers 33a and 33b to decrease the N2 concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b. In addition, when the CO concentration obtained from the sensor group 71 becomes less than the second threshold value, the control unit 70 controls damper 34d to increase the CO2 concentration in the mixed gas supplied to the front-stage nozzle 41, controls damper 39d to decrease the H2O concentration in the mixed gas supplied to the front-stage nozzle 41, and controls damper 33d to decrease the N2 concentration in the mixed gas supplied to the front-stage nozzle 41.

[0043] When the CO concentration acquired from the sensor group 72 exceeds a first threshold, the control unit 70 controls damper 34e to decrease the CO2 concentration in the mixed gas supplied to the rear nozzle 42, controls damper 39e to increase the H2O concentration in the mixed gas supplied to the rear nozzle 42, and controls damper 33e to increase the N2 concentration in the mixed gas supplied to the rear nozzle 42. When the CO concentration acquired from the sensor group 72 is less than a second threshold, the control unit 70 controls damper 34e to increase the CO2 concentration in the mixed gas supplied to the rear nozzle 42, controls damper 39e to decrease the H2O concentration in the mixed gas supplied to the rear nozzle 42, and controls damper 33e to decrease the N2 concentration in the mixed gas supplied to the rear nozzle 42.

[0044] When the CO concentration acquired from the sensor group 73 exceeds a first threshold, the control unit 70 controls damper 37f to increase the O2 concentration in the mixed gas supplied to the blowing nozzle 40. When the CO concentration acquired from the sensor group 73 is less than a second threshold that is smaller than the first threshold, the control unit 70 controls damper 37f to decrease the O2 concentration in the mixed gas supplied to the blowing nozzle 40. When the CO concentration acquired from the sensor group 73 exceeds the first threshold, the control unit 70 controls damper 34f to decrease the CO2 concentration in the mixed gas supplied to the blowing nozzle 40, controls damper 39f to increase the H2O concentration in the mixed gas supplied to the blowing nozzle 40, and controls damper 33f to increase the N2 concentration in the mixed gas supplied to the blowing nozzle 40.

[0045] When the CO concentration acquired from the sensor group 73 is less than the second threshold, the control unit 70 controls damper 37f to reduce the O2 concentration in the mixed gas supplied to the blowing nozzle 40. Furthermore, when the CO concentration acquired from the sensor group 73 is less than the second threshold, the control unit 70 controls damper 34f to increase the CO2 concentration in the mixed gas supplied to the blowing nozzle 40, controls damper 39f to reduce the H2O concentration in the mixed gas supplied to the blowing nozzle 40, and controls damper 33f to reduce the N2 concentration in the mixed gas supplied to the blowing nozzle 40.

[0046] The incineration of waste W in the waste incineration system 1000 configured as described above will now be described. As shown in Figure 2, in the waste incinerator 1 according to this embodiment, a layer of waste W is formed on the drying grate 5a, the combustion grate 5b, and the post-combustion grate 5c. The waste W in the upstream range (front portion) of the drying grate 5a along the transport direction of the waste W is dried and ignited. In the downstream range (rear portion) of the drying grate 5a, initial combustion occurs, in which combustion of a portion of the waste W begins after drying, and pyrolysis and partial oxidation of the waste W begin. When the waste W is incinerated on the drying grate 5a, moisture evaporates from the waste W on the drying grate 5a, and then pyrolysis and partial oxidation reactions occur, producing pyrolysis gas.

[0047] Subsequently, after combustion of the waste W begins downstream of the drying grate 5a, pyrolysis and partial oxidation of the waste W generate pyrolysis gas, which burns a portion of the waste W. On the combustion grate 5b, the generated pyrolysis gas and the solid content of the waste W are combusted.

[0048] A mixed gas of the first exhaust gas, the second exhaust gas, the O2-based gas, and the nitrogen gas is supplied from a front-stage nozzle 41 above the drying grate 5a and the combustion grate 5b into the combustion chamber 2. Below the front-stage nozzle 41, a gas combustion zone S1 is formed by the mixed gas supplied from the front-stage nozzle 41 and the pyrolysis gas produced by the combustion of the waste W. The pyrolysis gas that is not combusted in the gas combustion zone S1 and becomes unburned gas flows downstream in the combustion chamber 2 in the direction in which the waste W is transported.

[0049] After the waste W is burned, unburned matter such as fixed carbon in the remaining waste W is completely burned on the post-combustion grate 5c. A mixed gas of the first exhaust gas, the second exhaust gas, and nitrogen gas is supplied from a post-stage nozzle 42 above the combustion grate 5b and the post-combustion grate 5c toward a burn-out point S3 on the combustion grate 5b or the post-combustion grate 5c. Downstream of the post-stage nozzle 42 in the direction of waste W transport, secondary combustion occurs in a secondary combustion zone S2 using the mixed gas supplied from the post-stage nozzle 42 and the pyrolysis gas of the unburned matter flowing from the gas combustion zone S1.

[0050] On the post-combustion grate 5c, the area downstream of the burnout point S3 in the direction of transport of the waste W becomes a post-combustion zone where solid unburned content (char) in the waste W is burned. A mixed gas of the first exhaust gas, the second exhaust gas, the O2-based gas, and the nitrogen gas is supplied from the post-combustion zone to the vicinity of the outlet of the combustion chamber 2 and the vicinity of the inlet of the secondary combustion chamber 11 from the injection nozzle 40. As described above, a layer of the waste W is formed mainly on the drying grate 5a and the combustion grate 5b, and an incineration ash layer is formed downstream of the post-combustion grate 5c.

[0051] In this embodiment, the second exhaust gas containing water vapor is supplied to the drying grate 5a, the combustion grate 5b, and the combustion chamber 2. This contributes to the reforming reaction of the combustible gas generated from the thermal decomposition of the waste material W, improving combustibility. Furthermore, in this embodiment, the first exhaust gas with a high CO2 concentration is supplied from the wind box 7c to the post-combustion grate 5c, promoting carbonation of the incineration ash. Furthermore, in this embodiment, the CO2 concentration in the combustion gas is lower than in the waste treatment device of Patent Document 1, making it easier for the combustible gas to oxidize in equilibrium. For example, if the O2 concentration in the mixed gas supplied to the wind boxes 7a, 7b, the upstream nozzle 41, and the injection nozzle 40 is 30% and the CO2 concentration is high at 70%, the CO2 concentration measured by the sensor group 73 would be 327 ppm. However, in this embodiment, the CO2 concentration is 161 ppm, improving combustibility and reducing the CO2 concentration. In addition, in this embodiment, the mixed gas supplied to the combustion chamber 2 and the secondary combustion chamber 11 contains nitrogen gas, so that it is possible to prevent the combustion temperature in the incinerator from decreasing and reduce the CO concentration.

[0052] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be implemented in various other forms. For example, the above-described embodiments may be modified as follows to implement the present invention. The above-described embodiments and the following modifications may be combined with each other. The present invention also includes configurations in which the components of the above-described embodiments and modifications are appropriately combined. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-described embodiments and modifications, and various modifications are possible.

[0053] In the embodiment described above, the combustion chamber 2 is provided with the front nozzle 41 and the rear nozzle 42, but the configuration may be such that these nozzles are not provided.

[0054] The waste incinerator according to the present invention may be an incinerator employing a double flow path. When the waste incinerator employs a double flow path, as shown in FIG. 3, a high-temperature air draft fan (HADF) 43 and a recirculated draft fan (RDF) 44 are provided in the combustion chamber 2. The high-temperature air blower 43 provided corresponding to the drying grate 5a is supplied with a mixed gas of the first flue gas, the second flue gas, an O2-based gas, and nitrogen gas from the supply line 31d. The high-temperature air blower 43 provided corresponding to the combustion grate 5b is supplied with a mixed gas of the first flue gas, the second flue gas, an O2-based gas, and nitrogen gas from the supply line 31d. The recirculation fan 44 provided corresponding to the post-combustion grate 5c is supplied with a mixed gas of the first flue gas, the second flue gas, and nitrogen gas from the supply line 31e.

[0055] In the above-described embodiment, water vapor may be supplied to the supply lines 31a, 31b, 31d, and 31e.

[0056] In the above-described embodiment, the fourth gas supply line 38 may not be provided, and the nitrogen gas generated by the gas supplier 60 may not be supplied to the combustion chamber 2. [Explanation of symbols]

[0057] 1. Waste incinerator 2. Combustion chamber 5a drying grate 5b Combustion grate 5c Post-combustion grate 21 Flue 22 Drug supply device 23 Dust removal equipment 24 Induced draft fan 40 blowing nozzle 41 Front nozzle 42 Rear nozzle 51 Cooling Tower 52 Separation device 60 Gas supply machine 70 Control Unit 1000 Waste Incineration System

Claims

1. an incinerator having a combustion chamber having a grate for burning waste while transporting the waste in the combustion chamber, and a secondary combustion chamber for burning combustion gas generated in the combustion chamber; a dust removal means for removing dust from the exhaust gas discharged from the incinerator; a mixed gas generating means for generating a mixed gas by mixing at least oxygen, carbon dioxide containing moisture after being dusted by the dust removing means, and carbon dioxide from which water has been separated after being dusted by the dust removing means; Equipped with The grate has a drying grate, a combustion grate, and a post-combustion grate along the waste transport direction; The mixed gas is supplied to at least the drying grate, the combustion grate, and the secondary combustion chamber. Waste incineration system.

2. The mixed gas generated by the mixed gas generating means further contains nitrogen.

2. The waste incineration system of claim 1.

3. The mixed gas has an oxygen concentration of 30%, a carbon dioxide concentration of 35% or more, a water concentration of 28% or less, and a nitrogen concentration of 7% or less.

2. The waste incineration system of claim 1.

4. A method for burning waste in an incinerator having a combustion chamber with a grate in which waste is burned while being transported in the combustion chamber, and a secondary combustion chamber in which combustion gas generated in the combustion chamber is burned, The grate has a drying grate, a combustion grate, and a post-combustion grate along the waste transport direction; Dust is removed from the exhaust gas discharged from the incinerator by dust removal means, generating a mixed gas by mixing at least oxygen, carbon dioxide having moisture removed by the dust removing means, and carbon dioxide having water separated by the dust removing means; The mixed gas is supplied to at least the drying grate, the combustion grate, and the secondary combustion chamber. Waste incineration methods.

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