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 unburned gas in combustion gas generated in the combustion chamber; dust removal means for removing dust from exhaust gas discharged from the incinerator; mixed gas generation means for generating mixed gas by mixing at least oxygen and exhaust gas from which dust has been removed by the dust removal means and that contains carbon dioxide; blowing means for blowing the mixed gas into the secondary combustion chamber and capable of changing a direction of blowing the mixed gas; detection means for detecting a flowing direction of the combustion gas in the secondary combustion chamber; and control means for controlling the direction in which the blowing means blows the mixed gas, on the basis of the direction detected by the detection means.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] Patent Document 1 discloses a grate-type waste incinerator that performs secondary combustion of unburned gas in the exhaust gas by injecting exhaust gas containing carbon dioxide and air into a secondary combustion chamber. This waste incinerator has two stages for injecting air and exhaust gas into the secondary combustion chamber, with air being injected from the first stage and exhaust gas discharged from a waste heat boiler and circulated being injected from the second stage. The air and exhaust gas injected in these two stages agitate and mix the unburned gas, air, and exhaust gas in the secondary combustion chamber, reducing carbon monoxide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-191537 Summary of the Invention [Problem to be solved by the invention]

[0004] The direction of the unburned gas flowing from the primary combustion chamber to the secondary combustion chamber varies greatly depending on the state of the waste piled up on the grate, the amount of primary air supplied to the grate, and the state of the primary air flow. Therefore, even if air and exhaust gas are blown into the secondary combustion chamber in two stages, depending on the direction of the unburned gas flow, sufficient stirring and mixing may not occur, and carbon monoxide may not be reduced.

[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 in which waste is burned while being transported in a combustion chamber having a fire grate, and a secondary combustion chamber in which unburned gas in the combustion gas generated in the combustion chamber is burned; dust removal means for removing dust from exhaust gas discharged from the incinerator; mixed gas generation means for generating a mixed gas by mixing at least oxygen and exhaust gas that has been dust removed by the dust removal means and contains carbon dioxide; injection means for injecting the mixed gas into the secondary combustion chamber and capable of changing the direction in which the mixed gas is injected; detection means for detecting the direction of flow of the combustion gas in the secondary combustion chamber; and control means for controlling the direction in which the mixed gas is injected by the injection means based on the direction detected by the detection means.

[0007] In a waste incineration system according to one aspect of the present invention, the detection means may measure the temperatures at multiple locations in the secondary combustion chamber and detect the direction of flow of the combustion gas based on the measured temperatures at the multiple locations.

[0008] In addition, in a waste incineration system according to one aspect of the present invention, the detection means may measure the concentration distribution of carbon monoxide in the secondary combustion chamber and detect the direction of flow of the combustion gas based on the measured concentration distribution.

[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 unburned gas in the combustion gas generated in the combustion chamber is burned, wherein exhaust gas discharged from the incinerator is removed by a dust removal means, a mixed gas is generated by a mixed gas generation means which mixes at least oxygen and exhaust gas which has been removed by the dust removal means and contains carbon dioxide, the mixed gas is injected into the secondary combustion chamber by an injection means which is capable of changing the direction in which the mixed gas is injected, the flow direction of the combustion gas in the secondary combustion chamber is detected by a detection means, and a control means controls the injection means to change the direction in which the mixed gas is injected based on the direction detected by the detection means. [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. [Figure 2] FIG. 2 is a schematic cross-sectional view of the arrangement position of the blowing nozzle. [Figure 3] FIG. 3 is a diagram showing the state inside the combustion chamber according to the embodiment. [Figure 4] FIG. 4 is a schematic diagram of the gas flow in the secondary combustion chamber according to the embodiment. [Figure 5A] FIG. 5A is a schematic cross-sectional view of the arrangement position of a blowing nozzle according to a modified example. [Figure 5B] FIG. 5B is a schematic cross-sectional view of the arrangement position of the blowing nozzle according to the modified example. [Figure 5C] FIG. 5C is a schematic cross-sectional view of the arrangement position of the blowing nozzle according to the 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. A secondary combustion chamber 11 is formed near the inlet of the boiler 4, which burns unburned gas in the gas discharged from the combustion chamber 2. Gas for secondary combustion, supplied via a supply line 31f, is injected into the secondary combustion chamber 11 from injection nozzles 40a, 40b. In the secondary combustion chamber 11, unburned components in the combustion gas generated in the combustion chamber 2 undergo secondary combustion, and the boiler 4 recovers heat from the exhaust gas after secondary combustion.

[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 dust removal means, removes dust by capturing chemicals that combine with dust and pollutants contained in the exhaust gas that has flowed through flue 21. 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 is discharged from induced draft fan 24 and then branches off to cooling tower 51 and chimney 25, and the exhaust gas branched to 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 gas) from which moisture has been removed and which contains carbon dioxide 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 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 gas supplied to the combustion chamber 2, and damper 34f that adjusts the flow rate of the first 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 nozzles 40a and 40b 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 gas.

[0026] The waste incineration system 1000 also includes a second gas supply line 35, a blower 36, and a gas supplier 60. The second gas supply line 35 is connected to the blower 36, and the blower 36 is connected to the gas supplier 60.

[0027] The gas supplier 60 separates oxygen from air using techniques such as cryogenic separation or PSA to generate a gas (second gas) having an O2 concentration of 50% or more and close to 100%. The blower 36 sends the second gas generated by the gas supplier 60 to the second gas supply line 35.

[0028] The second gas supply line 35 is connected to dampers 37a, 37b, 37d, and 37f that adjust the flow rate of the second 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 nozzles 40a and 40b via supply line 31f. Dampers 37a, 37b, 37d, and 37f are controlled by control unit 70 to adjust the flow rate of the second gas.

[0029] In the supply line 31a, the first gas and the second gas are mixed, and the mixed gas is sent to the wind box 7a. In the supply line 31b, the first gas and the second gas are mixed, and the mixed gas is sent to the wind box 7b. In addition, the supply line 31c distributes the first gas sent from the damper 34c to the wind box 7c. In the supply line 31d, the first gas and the second gas are mixed, and the mixed gas is sent to the front nozzle 41. In the supply line 31e, the first gas sent from the damper 34e is distributed to the rear nozzle 42. In addition, in the supply line 31f, the first gas and the second gas are mixed, and the mixed gas is sent to the blowing nozzles 40a and 40b. The supply lines 31a, 31b, 31d, and 31f are an example of a mixed gas generating means for generating a mixed gas by mixing multiple gases.

[0030] The wind boxes 7a to 7c are provided in the lower part of 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 through the supply line 31a to the drying grate 5a, the wind box 7b supplies the mixed gas supplied through the supply line 31b to the combustion grate 5b, and the wind box 7c supplies the first gas supplied through the supply line 31c to the post-combustion grate 5c. The first gas and the second gas may be supplied directly to the wind boxes 7a and 7b, respectively, and mixed in the wind boxes 7a and 7b.

[0031] 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 obtained by mixing the first gas and the second 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 post-combustion grate 5c, for example, on the ceiling of the combustion chamber 2. The first gas is supplied to the rear nozzle 42 from a supply line 31e.

[0032] Injection nozzles 40a and 40b are provided in the secondary combustion chamber 11 at the outlet of the combustion chamber 2. The injection nozzles 40a and 40b, which are an example of injection means, are connected to a supply line 31f. A mixed gas obtained by mixing a first gas and a second gas is supplied to the injection nozzles 40a and 40b from the supply line 31f.

[0033] FIG. 2 is a schematic diagram of a cross section at the position where injection nozzle 40a is disposed. Injection nozzle 40a is disposed in recess 202 provided in furnace wall 201 of combustion chamber 2. Injection nozzle 40a is composed of nozzle 401 and support portion 402. Nozzle 401 is cylindrical and supported by support portion 402. A drive mechanism (not shown) provided in support portion 402 enables nozzle 401 to change its angle relative to support portion 402 around the end portion on the support portion 402 side. Support portion 402 can rotate in the directions of arrows C and D by a drive mechanism (not shown). The angle of nozzle 401 relative to support portion 402 and the rotation angle of support portion 402 are controlled by control unit 70. Supply line 403 is connected to support portion 402 and supply line 31f, and mixed gas is supplied from supply line 31f. The mixed gas supplied to the supply line 403 flows through the support part 402 and the nozzle 401 and is discharged from the nozzle 401 into the secondary combustion chamber 11 .

[0034] The direction in which the mixed gas is discharged from the blowing nozzle 40a can be changed by controlling the angle of the nozzle 401 relative to the support part 402 and the rotation angle of the support part 402. Assuming that the front side of the drawing in the direction perpendicular to the plane of FIG. 2 is the inlet 3 side and the back side is the outlet 6 side, for example, by tilting the nozzle 401 in the direction of arrow B from the state shown in FIG. 2 and then rotating the support part 402 in the direction of arrow C, the mixed gas can be discharged downward from the blowing nozzle 40a on the inlet 3 side of the blowing nozzle 40a. Furthermore, for example, by tilting the nozzle 401 in the direction of arrow A from the state shown in FIG. 2 and then rotating the support part 402 in the direction of arrow D, the mixed gas can be discharged upward from the blowing nozzle 40a on the inlet 3 side of the blowing nozzle 40a. Like the blowing nozzle 40a, the blowing nozzle 40b is also arranged on the furnace wall of the secondary combustion chamber 11, and the configuration of the blowing nozzle 40b is the same as that of the blowing nozzle 40a, so a description of the blowing nozzle 40b will be omitted.

[0035] 1, a sensor group 71 is provided on the upstream side of the combustion chamber 2 in the direction of transport of the waste W, and a sensor group 72 is provided on the downstream side of the combustion chamber 2 in the direction of transport of the waste W. The sensor groups 71 and 72 measure at least the temperature, O2 concentration, H2O concentration, CO2 concentration, and CO concentration (carbon monoxide concentration) at their installed positions. The sensor groups 71 and 72 transmit the measured values of the temperature, O2 concentration, H2O concentration, CO2 concentration, CO concentration, etc. to the control unit 70.

[0036] A sensor group 73 is provided on the furnace wall at the outlet of the combustion chamber 2. The sensor group 73 measures at least O2 concentration, H2O concentration, CO2 concentration, and CO concentration at the installed position. The sensor group 73 also has multiple thermocouples arranged from the upper upstream side to the lower downstream side in the transport direction of the waste W, and measures the temperature at the installed position. The sensor group 73 transmits the measured values of temperature, O2 concentration, H2O concentration, CO2 concentration, CO concentration, etc. to the control unit 70. Sensor groups 74 and 75 are provided on the furnace wall above the secondary combustion chamber 11. Each of the sensor groups 74 and 75 has multiple thermocouples arranged horizontally and measures the temperature at the installed position. The sensor groups 74 and 75 transmit the measured temperature values to the control unit 70.

[0037] The control unit 70, which is an example of a detection means and a control means, specifically 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 unit. In this case, the memory unit of the control unit 70 is configured as 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. Removable media is, 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 unit may also be configured using a computer-readable storage medium such as an externally attachable memory card. The control unit 70 controls the dampers 34a to 34f and the dampers 37a, 37b, 37d, and 37f based on the measurement results of the sensor group 71 and the sensor group 72. The control unit 70 also controls the blowing nozzles 40a and 40b based on the measurement results of the sensor groups 73 to 75.

[0038] In the waste incineration system 1000, the mixing ratio of the first gas and the second gas in the mixed gas supplied to the wind boxes 7a, 7b, the front nozzle 41, and the blowing nozzles 40a, 40b, and the first gas in the mixed gas supplied to the rear nozzle 42 can be adjusted by the control unit 70 controlling the damper.

[0039] Specifically, the control unit 70 acquires measured values of CO2 concentration from the sensor group 71 to 73. When the CO2 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. Furthermore, when the CO2 concentration acquired from the sensor group 71 exceeds the first threshold, the control unit 70 controls the dampers 34a and 34b to decrease the CO2 concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b, and controls the damper 34d to decrease the CO2 concentration in the mixed gas supplied to the front nozzle 41.

[0040] 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 O2 concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b, and controls the damper 34d to decrease the O2 concentration in the mixed gas supplied to the front nozzle 41. Furthermore, 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 CO2 concentration in the mixed gas supplied to the drying grate 5a and the combustion grate 5b, and controls the damper 34d to increase the CO2 concentration in the mixed gas supplied to the front nozzle 41.

[0041] When the CO concentration acquired from the sensor group 72 exceeds a first threshold, the control unit 70 controls the damper 34c to reduce the first gas supplied to the rear nozzle 42, and when the CO concentration acquired from the sensor group 72 becomes less than a second threshold, the control unit 70 controls the damper 34c to increase the first gas supplied to the rear nozzle 42.

[0042] When the CO concentration acquired from the sensor group 73 exceeds a first threshold, the control unit 70 controls the damper 37f to increase the O2 concentration in the mixed gas supplied to the blowing nozzles 40a, 40b, and controls the damper 34f to decrease the CO2 concentration in the mixed gas supplied to the blowing nozzles 40a, 40b. When the CO concentration acquired from the sensor group 73 falls below a second threshold, the control unit 70 controls the damper 37f to decrease the O2 concentration in the mixed gas supplied to the blowing nozzles 40a, 40b, and controls the damper 34f to increase the CO2 concentration in the mixed gas supplied to the blowing nozzles 40a, 40b.

[0043] Furthermore, the control unit 70 controls the direction in which the mixed gas is discharged from the blowing nozzles 40a and 40b based on the temperatures acquired from the group of sensors 73-75.

[0044] The incineration of waste W in the waste incineration system 1000 configured as described above will now be described. FIG. 3 is a diagram showing the state inside the combustion chamber 2. As shown in FIG. 3, in the waste incinerator 1 according to this embodiment, layers of waste W are 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 direction of transport 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 part 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.

[0045] 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.

[0046] A mixed gas of the first gas and the second gas is supplied into the combustion chamber 2 from a front nozzle 41 above the drying grate 5a and the combustion grate 5b. Below the front nozzle 41, a gas combustion zone S1 is formed by the mixed gas supplied from the front nozzle 41 and the pyrolysis gas produced by the combustion of the waste W. The pyrolysis gas (combustion 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.

[0047] 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 first gas is supplied from a post-stage nozzle 42 above the combustion grate 5b and the post-combustion grate 5c toward a burnout 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 first gas supplied from the post-stage nozzle 42 and pyrolysis gas of the unburned matter flowing from the gas combustion zone S1. A mixed gas of the first gas and the second gas is supplied from the injection nozzles 40a and 40b toward the secondary combustion zone S2.

[0048] The control unit 70 identifies the flow direction of the pyrolysis gas based on the position of the thermocouple that measured the highest temperature among the temperatures measured by the multiple thermocouples in the sensor group 73-75, and controls the discharge direction of the mixed gas based on the identified direction and angle. For example, when the temperature in areas S4 and S6 is high, the control unit 70 controls the angle of the nozzle 401 and the rotation angle of the support unit 402 so that the mixed gas flows from the blowing nozzles 40a and 40b in the direction of the angle of area S4. Also, when the temperature in areas S5 and S7 is high, the control unit 70 controls the angle of the nozzle 401 and the rotation angle of the support unit 402 so that the mixed gas flows from the blowing nozzles 40a and 40b in the direction of the angle of area S5.

[0049] Fig. 4 is a schematic diagram of the gas flow in the secondary combustion chamber 11. Note that the waste material W and the grate are not shown in Fig. 4. As shown in Fig. 4, in the combustion chamber 2, the first gas G1 is blown in from the post-combustion grate 5c and the post-stage nozzle 42, which are not shown. In addition, pyrolysis gas G3 containing unburned gas flows toward the secondary combustion chamber 11. The mixed gas is blown out from the blowing nozzles 40a and 40b, the angle of which is controlled in the nozzle 401, so as to collide with the high-temperature pyrolysis gas G3 flowing into the secondary combustion chamber 11, and therefore the pyrolysis gas is efficiently mixed with the mixed gas.

[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 area where the solid unburned content (char) in the waste W is burned. 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, a mixed gas of a first gas containing carbon dioxide and a second gas containing oxygen is injected from the injection nozzles 40a, 40b into the unburned gas flowing into the secondary combustion chamber 11 so as to collide with the unburned gas, thereby sufficiently stirring and mixing the unburned gas, oxygen and carbon dioxide, causing the unburned gas to burn and reducing carbon monoxide.

[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] In the above-described embodiment, the gas supplier 60 supplies a gas with a high oxygen concentration, but it may also be configured to supply air instead of the gas with a high oxygen concentration.

[0055] 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, the combustion chamber 2 is provided with a high-temperature air draft fan (HADF) (not shown) and a recirculated draft fan (RDF) (not shown). The high-temperature air blower provided corresponding to the drying grate 5a is supplied with a mixed gas of a first gas and a second gas from a supply line 31d, and the high-temperature air blower provided corresponding to the combustion grate 5b is supplied with a mixed gas of the first gas and the second gas from a supply line 31d. The recirculation blower provided corresponding to the post-combustion grate 5c is supplied with the first gas from a supply line 31e.

[0056] The configuration for changing the discharge direction of the mixed gas in the blowing nozzles 40a, 40b is not limited to that of the embodiment, and other configurations may be used. Figures 5A to 5C are schematic cross-sectional views of the arrangement position of blowing nozzle 40a according to a modified example. This blowing nozzle 40a is composed of multiple movable plates 404 and a support portion 402a. The movable plates 404 can change their angle with respect to the support portion 402a by a drive mechanism (not shown) provided in the support portion 402a. The support portion 402a can rotate in the directions of arrows C and D by a drive mechanism (not shown).

[0057] In the modified blowing nozzle 40a, the discharge direction of the mixed gas can be changed by controlling the angle of the movable plate 404 relative to the support portion 402a and the rotation angle of the support portion 402a. Assuming that the front side of the paper in the direction perpendicular to the paper surface of FIGS. 5A to 5C is the inlet 3 side and the back side is the outlet 6 side, for example, by tilting the movable plate 404 upward as shown in FIG. 5B and further rotating the support portion 402 in the direction of arrow D, the mixed gas can be made to flow upward from the blowing nozzle 40a on the inlet 3 side. Furthermore, for example, by tilting the movable plate 404 downward as shown in FIG. 5C and further rotating the support portion 402a in the direction of arrow C, the mixed gas can be made to flow downward from the blowing nozzle 40a on the inlet 3 side.

[0058] The blowing nozzles 40a and 40b may be configured to include a so-called deflection nozzle in order to change the discharge direction of the mixed gas.

[0059] In the present invention, the sensor group 73-75 may be configured to include a measuring device that uses laser light to measure the concentration distribution of O2 concentration, H2O concentration, CO2 concentration, and CO concentration. When the sensor group 73-75 measures the concentration distribution with laser light, for example, the blowing nozzles 40a, 40b may be controlled so that the mixed gas of the first gas and the second gas is blown into an area where the measured CO2 concentration is high.

[0060] The sensor group 75 may be provided not only on the wall surface in the width direction of the waste incinerator 1 but also on the wall surface on the upstream side in the direction of transport of the waste W and on the wall surface on the downstream side in the direction of transport. [Explanation of symbols]

[0061] 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 40a, 40b Blowing nozzle 41 Front nozzle 42 Rear nozzle 51 Cooling Tower 52 Separation device 60 Gas supply machine 70 Control Unit 71~75 Sensor group 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 unburned gas in the 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 and the exhaust gas that has been subjected to dust removal by the dust removing means and contains carbon dioxide; an injection means for injecting the mixed gas into the secondary combustion chamber and capable of changing the direction in which the mixed gas is injected; a detection means for detecting a flow direction of the combustion gas in the secondary combustion chamber; a control means for controlling the direction in which the blowing means blows the mixed gas based on the direction detected by the detection means; A waste incineration system comprising:

2. The detection means measures temperatures at a plurality of positions in the secondary combustion chamber and detects the direction of flow of the combustion gas based on the measured temperatures at the plurality of positions.

2. The waste incineration system of claim 1.

3. The detecting means measures the concentration distribution of carbon monoxide in the secondary combustion chamber and detects the flow direction of the combustion gas based on the measured concentration distribution.

2. The waste incineration system of claim 1.

4. A method for burning waste in 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 unburned gas in the combustion gas generated in the combustion chamber is burned, Dust is removed from the exhaust gas discharged from the incinerator by dust removal means, generating a mixed gas by a mixed gas generating means by mixing at least oxygen and the exhaust gas from which dust has been removed by the dust removing means and which contains carbon dioxide; Injecting the mixed gas into the secondary combustion chamber using an injection means capable of changing the direction in which the mixed gas is injected; detecting a flow direction of the combustion gas in the secondary combustion chamber with a detection means; Based on the direction detected by the detection means, the control means controls the blowing means to change the direction in which the mixed gas is blown. Waste incineration methods.

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