Waste incineration method and waste incineration device

Abstract

To reduce a concentration of carbon monoxide contained in exhaust gas discharged from a waste incinerator.SOLUTION: In a waste incineration method, when incinerating waste in an incinerator having a combustion chamber in which waste is burned while being transported by a fire grate, recirculated exhaust gas supply means branches off at least a part of exhaust gas in the incinerator as recirculated exhaust gas, and oxygen supply means mixes oxygen-containing gas with the recirculated exhaust gas to generate mixed gas and supplies it to the combustion chamber, where a drying fire grate, a combustion fire grate, and a post-combustion fire grate are provided along a direction in which the waste is transported. The waste incineration method selectively supplies mixed gas having an oxygen concentration of more than 35% and mixed gas having an oxygen concentration of less than 5% to each of a plurality of divided drying division areas in the drying fire grate; and selectively supplies mixed gas having an oxygen concentration of 35% or more and mixed gas having an oxygen concentration of 35% or less to each of a plurality of divided combustion division areas in a combustion fire grate.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Conventionally, a combustion technology called O2 / CO2 combustion, oxygen combustion, or Oxy-fuel combustion has been proposed. Patent Document 1 discloses a waste treatment device and a waste treatment method that apply O2 / CO2 combustion. In the technology described in Patent Document 1, first, urban waste is incinerated with oxygen (O2) obtained by separating nitrogen (N2) from air. After recovering heat from the exhaust gas generated by the incineration of this urban waste, a part of the exhaust gas is supplied to the incineration process to control the incineration temperature. In addition to controlling the incineration temperature, water (H2O) and carbon dioxide (CO2) are recovered from the exhaust gas after heat recovery.

[0003] Specifically, the method for incinerating municipal waste described in Patent Document 1 is carried out as follows. That is, in order to control the temperature inside the incinerator to 800 to 1200°C, a part of the incineration flue gas (high concentration CO2) circulated in the system is circulated and supplied to the produced oxygen (O2) to mix it. The weight ratio of municipal waste to the circulated incineration flue gas is 1 to 12 times, preferably 4 to 8 times, the amount of incineration flue gas per unit of municipal waste. As a result, in the incinerator, waste such as municipal waste is incinerated mainly in an atmosphere of oxygen and incineration flue gas, that is, an atmosphere containing mainly carbon dioxide (CO2) and water vapor (H2O). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-126324 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses that the temperature inside the incinerator is controlled by adjusting the weight ratio of the circulated incineration exhaust gas to 1 to 12 times the amount of waste. However, the technology described in Patent Document 1 does not disclose any specific incineration method other than the above, and there was a problem as to whether or not combustibility in the incinerator was guaranteed. Therefore, in order to ensure combustibility in the incinerator, there was a need to develop a specific technology that completely combusts the waste and reduces the carbon monoxide (CO) contained in the exhaust gas.

[0006] The present invention has been made in consideration of the above, and its object is to provide a waste incineration method and a waste incineration apparatus that can reduce the carbon monoxide contained in the exhaust gas discharged from a waste incinerator. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, a waste incineration method according to one embodiment of the present invention is a waste incineration method in which, when incinerating waste in an incinerator having a combustion chamber in which waste is burned while being transported by a grate, at least a portion of the exhaust gas from the incinerator is branched off as recirculated exhaust gas by a recirculated exhaust gas supply means, and an oxygen supply means mixes a gas containing oxygen with the recirculated exhaust gas to generate a mixed gas and supplies it to the combustion chamber, wherein the grate is configured to have a drying grate, a combustion grate, and a post-combustion grate along the transport direction of the waste, and the mixed gas having an oxygen concentration of more than 35% and the mixed gas having an oxygen concentration of less than 5% are selectively supplied to each of the drying division regions divided into a plurality of regions in the drying grate, and the mixed gas having an oxygen concentration of more than 35% and the mixed gas having an oxygen concentration of less than 35% are selectively supplied to each of the combustion division regions divided into a plurality of regions in the combustion grate.

[0008] In one embodiment of the waste incineration method of the present invention, in the above invention, the oxygen concentration of the gas supplied to the vicinity of the outlet where exhaust gas is discharged from the combustion chamber is made less than the oxygen concentration of the mixed gas having the higher oxygen concentration supplied to the drying grate and the combustion grate.

[0009] In one embodiment of the waste incineration method of the present invention, in the above-mentioned invention, the gas supplied to the post-combustion grate is the recirculated exhaust gas, or the oxygen concentration of the gas supplied to the post-combustion grate is adjusted to less than 5%.

[0010] In one embodiment of the waste incineration method of the present invention, in the above invention, the mixed gas supplied to the drying grate is adjusted so that the oxygen concentration is higher than 35% in areas of the drying grate where the layer height of the waste piled up on the drying grate is higher than a predetermined height, and the oxygen concentration is adjusted to less than 5% in areas where the layer height of the waste piled up on the drying grate is less than the predetermined height, among the multiple divided areas of the drying grate.

[0011] In one embodiment of the waste incineration method of the present invention, in the above invention, the mixed gas supplied to the combustion grate is adjusted so that the oxygen concentration is higher than 35% in areas of the combustion grate where the layer height of the waste piled up on the combustion grate is higher than a predetermined height, and the oxygen concentration is adjusted to 35% or less in areas where the layer height of the waste piled up on the combustion grate is less than the predetermined height.

[0012] In one embodiment of the waste incineration method of the present invention, in the above invention, the oxygen concentration of the gas supplied into the combustion chamber from a front stage nozzle provided above the drying grate and the combustion grate, and a rear stage nozzle provided above the combustion grate and the rear combustion grate is adjusted to be higher than 35%.

[0013] In this configuration of a waste incineration method according to one embodiment of the present invention, the oxygen concentration of the gas supplied to the vicinity of the outlet where exhaust gas is discharged from the combustion chamber is made less than the oxygen concentration supplied to the combustion chamber from the front stage nozzle and the rear stage nozzle.

[0014] A waste incineration method according to one aspect of the present invention, in the above invention, measures the carbon monoxide concentration using a carbon monoxide measuring means configured to measure the carbon monoxide concentration and provided downstream in the waste transport direction within the combustion chamber, and adjusts the oxygen concentration of the mixed gas supplied into the combustion chamber based on the measured carbon monoxide concentration.

[0015] A waste incineration method according to one embodiment of the present invention, in the above invention, adjusts the oxygen concentration of the mixed gas supplied into the combustion chamber based on at least one measurement value of the furnace temperature, oxygen concentration, and carbon monoxide concentration measured by a first measuring means provided upstream in the combustion chamber along the waste transport direction and configured to be capable of measuring the furnace temperature, oxygen concentration, and carbon monoxide concentration, and a second measuring means provided near an outlet from which exhaust gas is discharged from the combustion chamber and configured to be capable of measuring the furnace temperature, oxygen concentration, and carbon monoxide concentration.

[0016] A waste incineration apparatus according to one aspect of the present invention is an incineration apparatus comprising: an incinerator having a combustion chamber in which waste is burned while being transported by a fire grate; a recirculated exhaust gas supply means configured to be able to branch off at least a portion of the exhaust gas from the incinerator as a recirculated exhaust gas and supply it to the incinerator; an oxygen supply means configured to be able to supply a gas containing oxygen as a main component to the incinerator; and a gas mixing means for mixing the recirculated exhaust gas supplied by the recirculated exhaust gas supply means with the gas containing oxygen as a main component supplied by the oxygen supply means to generate a mixed gas. The grate has a drying grate, a combustion grate, and a post-combustion grate along the waste transport direction, and is configured to be able to selectively supply the mixed gas having an oxygen concentration of more than 35% and the mixed gas having an oxygen concentration of less than 5% to each of the multiple divided drying division areas in the drying grate, and is configured to be able to selectively supply the mixed gas having an oxygen concentration of more than 35% and the mixed gas having an oxygen concentration of 35% or less to each of the multiple divided combustion division areas below the combustion grate.

[0017] In one embodiment of the waste incineration apparatus of the present invention, the oxygen concentration of the gas supplied to the vicinity of the outlet where exhaust gas is discharged from the combustion chamber is adjustable to be lower than the oxygen concentration of the mixed gas having the higher oxygen concentration supplied to the drying grate and the combustion grate.

[0018] A waste incineration apparatus according to one embodiment of the present invention is configured in the above-mentioned invention so that the gas supplied to the post-combustion grate is the recirculated exhaust gas, or the oxygen concentration of the gas supplied to the post-combustion grate can be adjusted to less than 5%.

[0019] In one embodiment of the waste incineration apparatus of the present invention, in the above invention, the oxygen concentration of the mixed gas supplied to the drying grate is configured to be adjustable to more than 35% in areas of the drying grate where the layer height of the waste piled up on the drying grate is higher than a predetermined height, and to less than 5% in areas of the drying grate where the layer height of the waste piled up on the drying grate is less than the predetermined height.

[0020] In one embodiment of the waste incineration apparatus of the present invention, in the above invention, the oxygen concentration of the mixed gas supplied to the combustion grate is configured to be adjustable to more than 35% in areas of the combustion grate where the layer height of the waste piled up on the combustion grate is higher than a predetermined height, and to be adjustable to 35% or less in areas of the combustion grate where the layer height of the waste piled up on the combustion grate is less than a predetermined height.

[0021] A waste incineration apparatus according to one embodiment of the present invention is configured in the above-mentioned invention so that the oxygen concentration of the gas supplied into the combustion chamber from the drying grate and a front stage nozzle provided above the combustion grate, and from the rear stage nozzle provided above the combustion grate and the rear combustion grate can be adjusted to be higher than 35%.

[0022] In this configuration of a waste incineration apparatus according to one embodiment of the present invention, the oxygen concentration of the gas supplied to the vicinity of the outlet where exhaust gas is discharged from the combustion chamber is adjustable to be less than the oxygen concentration supplied to the combustion chamber from the front stage nozzle and the rear stage nozzle.

[0023] A waste incineration apparatus according to one embodiment of the present invention, in the above invention, further comprises a carbon monoxide measuring means configured to be capable of measuring carbon monoxide concentration downstream in the waste transport direction within the combustion chamber, and is configured to be able to adjust the oxygen concentration of the mixed gas supplied into the combustion chamber based on the carbon monoxide concentration measured by the carbon monoxide measuring means.

[0024] A waste incineration apparatus according to one embodiment of the present invention, in the above invention, comprises a first measuring means provided upstream in the combustion chamber along the waste transport direction and configured to be capable of measuring the furnace temperature, oxygen concentration, and carbon monoxide concentration, and a second measuring means provided downstream in the combustion chamber along the waste transport direction and configured to be capable of measuring the furnace temperature, oxygen concentration, and carbon monoxide concentration, and is configured to be able to adjust the oxygen concentration of the mixed gas supplied into the combustion chamber based on at least one measurement value of the furnace temperature, oxygen concentration, and carbon monoxide concentration measured by the first measuring means and the second measuring means. Effect of the Invention

[0025] According to the waste incineration method and waste incineration apparatus of the present invention, it is possible to reduce the carbon monoxide contained in the exhaust gas discharged from the waste incinerator. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram showing the overall configuration of a waste incineration system according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing conditions within a combustion chamber of a waste incinerator according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing the state of the combustion chamber and the wind box taken along line III-III in FIG. [Figure 4] FIG. 4 is a top view of a fire grate in the combustion chamber of the waste incinerator in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all the drawings of the embodiment, the same or corresponding parts are denoted by the same reference numerals. Furthermore, the present invention is not limited to the embodiment described below.

[0028] In describing the embodiment of the present invention, the inventor conducted intensive research. First, the inventor conducted research on problems related to the conventional technology. According to the inventor's findings, in order to completely combust waste, it is necessary to thoroughly mix and stir the combustible gas from the waste and the oxygen (O2) in the oxidizer. By completely combusting the waste, the carbon monoxide concentration (CO concentration) in the exhaust gas can be reduced. In other words, it is considered that complete combustion of the waste can be ensured by controlling to reduce the CO concentration in the exhaust gas. Therefore, the inventor conducted research on a method for reducing the CO concentration in the exhaust gas in a stoker-type waste incinerator that applies the technology of O2 / CO2 combustion, oxygen combustion, or Oxy-fuel combustion. As a result of the inventor's intensive research, it was found that the CO concentration in the exhaust gas can be reduced by using a mixed gas of oxygen (O2) and recirculated exhaust gas circulated in the system as an oxidizer and changing the oxygen concentration of the oxidizer depending on the location where it is blown in.

[0029] The inventor also devised a method for changing the oxygen concentration as desired by controlling the mixing amount and mixing ratio of the recirculated exhaust gas to the oxygen using the recirculated exhaust gas as a diluent. Based on this, the inventor conducted various experiments and studies on a method for reducing the CO concentration in the exhaust gas by changing the oxygen concentration in the oxidizing agent supplied to the waste in a stoker-type waste incinerator. As a result of intensive studies, the inventor devised the following method as a specific method for changing the oxygen concentration in the oxidizing agent.

[0030] That is, in a stoker-type waste incinerator, a plurality of grates are provided in the combustion chamber according to the type of waste to be burned, specifically, a drying grate, a combustion grate, and a post-combustion grate are provided from the upstream side along the waste transport direction. Therefore, the present inventor has studied a method of independently controlling the gas supplied to the drying grate, the combustion grate, and the post-combustion grate. That is, the present inventor has studied a method of controlling the oxygen concentration of the gas supplied to the drying grate, the combustion grate, and the post-combustion grate, and in particular, of making the oxygen concentration of the gas supplied to the combustion grate different from that of the other grates, thereby reducing the CO concentration in the exhaust gas.

[0031] As a result, the inventor came up with a method of supplying gas to each of the drying grate and the combustion grate in order to completely combust the waste on the grate, in which the oxidizing agent is supplied from below to each of the drying grate and the combustion grate in a divided manner. Specifically, the inventor devised a method of selectively supplying one of a mixed gas (hereinafter, O2 low concentration gas) in which oxygen (O2) and recirculated exhaust gas are mixed to have an oxygen concentration of less than 5% and an O2 high concentration gas in which the oxygen concentration is higher than 35% to each divided region below the drying grate as the oxidizing agent to be supplied from below the drying grate. In addition, the inventor devised a method of selectively supplying one of a mixed gas (hereinafter, O2 medium concentration gas) in which oxygen (O2) and recirculated exhaust gas are mixed to have an oxygen concentration of more than 25% and less than 35% and an O2 high concentration gas in which the oxygen concentration is higher than 35% to each divided region below the combustion grate as the oxidizing agent to be supplied from below to each divided region below the combustion grate. The oxygen concentration of the O2-rich gas supplied from below the drying grate and the combustion grate is higher than 35%, typically 50% or more, and preferably 70% or more, but the oxygen concentration of the O2-rich gas may be 90% or more, and in particular, the O2-rich gas may be pure oxygen gas with an oxygen concentration of 99% or more. The O2-low concentration gas also includes the concept of recirculated exhaust gas with a 0% oxygen (O2) concentration.

[0032] As an example of this method, the inventors have come up with a method of supplying O2-rich gas to the central region along the direction perpendicular to the waste transport direction in the drying grate and the combustion grate (hereinafter, the width direction), and supplying a mixed gas of oxygen (O2) and recirculated exhaust gas to the left and right regions of the central region, so-called outer regions. Depending on the pile-up state of the waste on the grate, it is also possible to supply a mixed gas of oxygen (O2) and recirculated exhaust gas to the central region along the direction perpendicular to the waste transport direction, and supply O2-rich gas to at least one of the left and right regions of the central region, so-called outer regions. This allows the combustible gas generated from the waste and the oxygen (O2) contained in the oxidizer to be sufficiently mixed and stirred, so that the waste can be efficiently and completely combusted to reduce the CO concentration in the exhaust gas.

[0033] For the post-combustion grate that constitutes the post-combustion stage, since this is the area after the waste has been burned off, it is preferable that the gas supplied from below for ash carbonation of the incineration ash be only recirculated exhaust gas or a low-O2 concentration gas with an oxygen concentration of less than 5%.

[0034] Furthermore, the present inventor also studied the oxidizer supplied above the grate of the waste incinerator, i.e., into the combustion chamber. The present inventor came up with the idea of ​​making the oxygen concentration of the oxidizer supplied into the combustion chamber approximately the same as the oxygen concentration of the O2-rich gas supplied from below the drying grate and the combustion grate. That is, when the waste incinerator is, for example, a counterflow furnace, the oxygen concentration of the oxidizer supplied from, for example, a plurality of nozzles (ceiling nozzles) provided on the ceiling or a side wall is made to be approximately the same as the O2-rich gas supplied from below the grate. In other words, the inventor devised a method of making the oxidizer supplied from the ceiling nozzle or side wall into an O2-rich gas with an oxygen concentration exceeding 35%.

[0035] In addition, when the waste incinerator is a double-flow incinerator, O2-rich gas with an oxygen concentration of more than 35%, O2-medium gas with an oxygen concentration of more than 25% and less than 35%, or O2-low gas with an oxygen concentration of less than 5% is supplied from the forced draft fan (FDF) to the combustion chamber. In addition, the gas supplied from the high-temperature air draft fan (HADF) and the recirculated draft fan (RDF) to the combustion chamber is O2-rich gas with an oxygen concentration of more than 35%. In addition, O2-containing gas with an oxygen concentration adjusted to 5% to 35% or O2-rich gas with an oxygen concentration of more than 35% is supplied from the vicinity of the exit of the combustion chamber to the combustion chamber by the furnace cooling fan (CDF).

[0036] The inventors also found that, in order to further reduce the CO concentration in the exhaust gas, it is preferable to supply an oxidizing agent containing O2 to the downstream side along the waste transport direction, specifically, near the upper part of the post-combustion grate, for example, near the outlet of the combustion chamber, which is the secondary combustion region. Here, the inventors conducted further studies and found that it is preferable to set the oxygen concentration of the oxidizing agent supplied near the outlet where the exhaust gas is discharged from the combustion chamber to a lower concentration than the oxygen concentration of the oxidizing agent supplied from the side wall into the combustion chamber, or the oxygen concentration of the O2-rich gas among the oxidizing agents supplied from below the drying grate and combustion grate.

[0037] Furthermore, the present inventor has devised a method of providing sensors at at least two locations in the waste incinerator and adjusting the oxygen concentration of the oxidizer based on the measured values ​​by the sensors. More specifically, in the waste incinerator, sensors are provided at least at two locations, upstream (in front of the furnace) and downstream (in rear of the furnace) along the waste transport direction. These sensors measure the temperature inside the furnace, the oxygen concentration, and the carbon monoxide concentration. In this case, the relationship between the measured value of the carbon monoxide concentration and the oxygen concentration of the gas supplied to the drying grate is tabulated or constructed as a learning model by machine learning or the like, so that the oxygen concentration of the oxidizer can be controlled so that the carbon monoxide concentration is reduced. That is, the oxygen concentration in the oxidizer supplied from below and above the grate or near the outlet of the combustion chamber is controlled according to the temperature inside the furnace, the oxygen concentration, and the carbon monoxide concentration measured by the sensors. This ensures high (robust) complete combustion in the waste incinerator.

[0038] Based on the above studies, the present inventor has devised an incineration method capable of reducing CO in exhaust gas by adjusting the oxygen concentration according to the supply position of the oxidizing agent. One embodiment of the present invention described below was devised by the present inventor through the above diligent studies.

[0039] (Waste incineration system) 1 and 2 are diagrams showing the overall configuration of a waste incineration system according to an embodiment of the present invention and the state inside the combustion chamber of a waste incinerator, respectively. As shown in Fig. 1, the waste incineration system according to this embodiment includes a waste incinerator 1 to which O2 / CO2 combustion technology is applied.

[0040] The waste incinerator 1 is, for example, a grate-type waste incinerator, and includes a combustion chamber 2 and a waste inlet 3. The combustion chamber 2 burns waste, such as industrial waste and household garbage. The waste inlet 3 is disposed above the upstream side (left side in FIG. 1) in the direction of the flow of the waste W within the combustion chamber 2, and is configured so that the waste W can be input into the combustion chamber 2. A boiler 4 is connected to the upper part of the combustion chamber 2 on the downstream side (right side in FIG. 1) in the direction of the flow of the waste W.

[0041] As shown in FIG. 1 and FIG. 2, a grate (stoker) 5 is provided at the bottom of the combustion chamber 2 to burn the waste W while moving it. The grates 5 are provided in the order of a drying grate 51, a combustion grate 52, and a post-combustion grate 53 from the side closer to the waste inlet 3, i.e., from the upstream side. In the drying grate 51, mainly drying, ignition, and initial combustion of the waste W are performed. In the combustion grate 52, mainly pyrolysis and partial oxidation of the waste W are performed. On the combustion grate 52, carbon monoxide (CO) generated by pyrolysis, pyrolysis gas containing hydrocarbons, and solids (fixed carbon) are burned as the main combustion. On the post-combustion grate 53, the remaining unburned waste is completely burned as post-combustion. The combustion ash (incineration ash) after complete combustion is dropped and discharged from the incineration ash discharge section 6.

[0042] An air box 7 is provided below the combustion chamber 2. Specifically, air boxes 71, 72, and 73 are provided below the drying grate 51, the combustion grate 52, and the post-combustion grate 53 in the combustion chamber 2, respectively. The air boxes 7 (71, 72, and 73) can function as part of a gas mixing means for mixing gases supplied from multiple systems, and in this embodiment, can function as a gas mixing means for mixing the recirculated exhaust gas with a gas mainly composed of O2.

[0043] The area downstream of the combustion chamber 2 and near the inlet of the boiler 4 connected to the outlet of the combustion chamber 2 constitutes a secondary combustion chamber 11 that burns unburned gas in the gas discharged from the combustion chamber 2. The secondary combustion chamber 11 is connected to the upper part of the downstream side (right side in FIG. 1) of the combustion chamber 2 in the direction of waste flow. Secondary combustion gas is blown into the secondary combustion chamber 11 through a pipe line equipped with a blower and a damper (neither shown). In the secondary combustion chamber 11, unburned gas (unburned gas) in the combustion gas generated in the combustion chamber 2 is burned (secondary combustion), and the exhaust gas after secondary combustion has its heat recovered by the boiler 4.

[0044] The boiler 4, which recovers heat from exhaust gas, is divided into three sections by two deflection sections 12, 13 that bend the flow path of the exhaust gas. The boiler 4 includes a first radiation chamber 14, a second radiation chamber 15, and a convection heat transfer chamber 16, from the upstream side along the flow direction of the exhaust gas. The upstream part along the flow direction of the exhaust gas of the first radiation chamber 14, to which exhaust gas is supplied from the waste incinerator 1, becomes the secondary combustion chamber 11. The first radiation chamber 14 and the second radiation chamber 15 are connected to each other at their upper parts, and the lower part of the second radiation chamber 15 is connected to the lower part of the convection heat transfer chamber 16. The exhaust section 4A of the boiler 4 is connected to a dust collector 18 composed of a bag filter or the like via a flue 17.

[0045] The boiler 4 has an inner wall made of a refractory wall, and the first radiant chamber 14 and the second radiant chamber 15 are provided with heat transfer tubes (not shown) formed of piping for circulating steam, arranged in a dense manner on the outside of the refractory wall forming the inner wall. The convection heat transfer chamber 16 is provided with a heat transfer tube (not shown) in the internal space through which the exhaust gas flows. The boiler 4 is formed by the first radiant chamber 14 and the second radiant chamber 15 as an evaporator. A plurality of, for example, three superheaters 16A are formed by a part of the convection heat transfer chamber 16. In the first radiant chamber 14 and the second radiant chamber 15, the heat transfer tubes arranged on the outside of the refractory wall and through which water flows are configured as a radiant heat transfer surface that receives radiant heat from the exhaust gas and generates steam.

[0046] The convection heat transfer chamber 16 includes, from the upstream side (lower side) along the flow direction of the exhaust gas, a superheater 16A and an economizer 16B. The superheater 16A includes a group of heat transfer tubes in which a plurality of heat transfer tubes arranged horizontally are arranged in multiple stages in the height direction, and the group of heat transfer tubes constitutes a convection heat transfer surface. The superheater 16A further superheats the steam generated in the evaporator through heat exchange with the exhaust gas, turning it into high-temperature, high-pressure superheated steam.

[0047] The economizer 16B is provided downstream (above) of the superheater 16A. The economizer 16B is provided with heat transfer tubes, receives condensate obtained by condensing the steam generated in the boiler 4 and used to drive a steam turbine (not shown) in a condenser (not shown), and heats the water by the heat remaining in the exhaust gas after the steam is superheated by the superheater 16A. As a result, the water is heated by heat exchange with the exhaust gas, and heated water is generated and supplied to the evaporator. Note that the economizer 16B may not be provided in the convection heat transfer chamber 16, but may be provided outside the boiler 4 downstream as a separate economizer, or both an in-boiler economizer and a separate economizer may be provided. A screen tube (not shown) is provided at the most upstream portion (lower portion) of the convection heat transfer chamber 16 with heat transfer tubes arranged in a flag shape, and is configured to cool the exhaust gas introduced into the convection heat transfer chamber 16 and solidify the gaseous or mist-like dust components to be separated as dust from the exhaust gas. An evaporator may be provided upstream or downstream of the superheater 16A in the convection heat transfer chamber 16.

[0048] The exhaust gas from the waste incinerator 1 after secondary combustion in the secondary combustion chamber 11 is introduced into the boiler 4, and steam is generated by the evaporators in the first radiation chamber 14 and the second radiation chamber 15. The generated steam is then made into superheated steam by the superheater 16A in the convection heat transfer chamber 16.

[0049] The exhaust gas from which heat has been recovered by the boiler 4 is supplied to a dust collector 18, such as a bag filter, through a flue 17. In the flue 17, caustic soda, hydrated lime, activated carbon, and the like are added to the exhaust gas. The dust collector 18 collects and removes dust contained in the exhaust gas. An induced draft fan 19 is connected to the dust collector 18. The induced draft fan 19 induces exhaust gas from the waste incinerator 1 and supplies at least a portion of the induced exhaust gas to the wind box 7 for circulation to the waste incinerator 1. The non-circulated exhaust gas from the dust-removed exhaust gas is supplied to a chimney 20 and released into the atmosphere.

[0050] A recirculated exhaust gas supply line 30 is provided from the exhaust gas duct (flue) on the outlet side of the dust collector 18, as a recirculated exhaust gas supply means, which sends a portion of the exhaust gas after dust removal by the dust collector 18 as recirculated exhaust gas to the wind box 7 below the grate 5.

[0051] A cooling tower 31 as a water separation means and a PSA unit 32 as a carbon dioxide capture means are sequentially provided on the recirculated exhaust gas supply line 30. The cooling tower 31 separates water (H2O) from the recirculated exhaust gas and discharges it. The PSA unit 32 separates a portion of carbon dioxide (CO2) from the recirculated exhaust gas from which water has been removed, for example, by pressure swing adsorption (PSA), and then exhausts or captures the separated CO2. Note that a nitrogen PSA unit may be separately provided that separates and discharges nitrogen (N2) from the recirculated exhaust gas from which water has been removed, thereby increasing the CO2 concentration in the recirculated exhaust gas.

[0052] The recirculated exhaust gas supply line 30 has branch lines 301, 302, and 303 that are branched so as to be able to supply the recirculated exhaust gas corresponding to each of the wind boxes 71 to 73. The recirculated exhaust gas supply line 30 also has a branch line 304 for supplying the recirculated exhaust gas to the combustion chamber 2. The branch line 304 is connected to a branch line 354 of the oxygen supply line 35 that is connected to a blower 36 (described later) and to an injection nozzle 40 provided in the vicinity of the secondary combustion chamber 11.

[0053] The recirculated exhaust gas supply line 30 is provided with a recirculated exhaust gas flow rate adjustment unit 34 as a recirculated exhaust gas flow rate adjustment means for adjusting the flow rate, which is made of a damper, a valve, or the like. The recirculated exhaust gas flow rate adjustment unit 34 is composed of a plurality of recirculated exhaust gas flow rate adjustment units 341, 342, 343, and 344 corresponding to the branch lines 301 to 304, respectively. Fig. 3 is a diagram showing the state of the combustion chamber and the wind box taken along line III-III in Fig. 2, and Fig. 4 is a top view of the grate 5.

[0054] The recirculation exhaust gas flow rate adjusting units 341-343 are provided corresponding to the branch lines 301-303 of the recirculation exhaust gas supply line 30 and the wind boxes 71-73 communicating with the branch lines 301-303, respectively. More specifically, as shown in FIG. 3, the wind box 71 below the drying grate 51 is divided into a plurality of wind boxes 71a, 71b, 71c divided into, for example, three regions along the width direction of the drying grate 51. The wind boxes 71a-71c are provided corresponding to the drying divided regions divided into a plurality of regions in the drying grate 51, respectively. The recirculation exhaust gas flow rate adjusting unit 341 is composed of the recirculation exhaust gas flow rate adjusting units 341a, 341b, 341c corresponding to the respective wind boxes 71a, 71b, 71c.

[0055] Similarly, below the combustion grate 52, the wind box 72 is divided into a plurality of sections, for example, three sections, along the width direction of the combustion grate 52, and is composed of a plurality of wind boxes 72a, 72b, and 72c. The wind boxes 72a to 72c are provided corresponding to the plurality of combustion division sections divided in the combustion grate 52. The recirculation exhaust gas flow rate adjustment unit 342 is composed of recirculation exhaust gas flow rate adjustment units 342a, 342b, and 342c corresponding to the respective wind boxes 72a, 72b, and 72c.

[0056] The recirculated exhaust gas flow rate adjusting unit 343 is provided in a branch line 303 of the recirculated exhaust gas supply line 30 corresponding to the post-combustion grate 53. In addition, the recirculated exhaust gas flow rate adjusting unit 344 is provided corresponding to a branch line 304 of the recirculated exhaust gas supply line 30.

[0057] 1, an oxygen supply line 35 capable of supplying a gas containing oxygen (O2) as a main component (hereinafter, O2-main component gas), i.e., a gas having an O2 concentration of 50% or more, specifically, an oxygen gas having an O2 concentration of nearly 100% separated from air by a technique such as a cryogenic separation method or a PSA method, is connected to the branch lines 301, 302, 303, and 304 of the recirculation exhaust gas supply line 30. A blower 36 is connected to the oxygen supply line 35.

[0058] The oxygen supply line 35 has branch lines 351, 352, and 353 that are branched so as to be able to supply O2 gas to the respective wind boxes 71 to 73. The branch lines 351 to 353 correspond to the respective branch lines 301 to 303. More specifically, as shown in FIG. 3, the branch line 351 is composed of branch lines 351a, 351b, and 351c that correspond to the respective branch lines 301a, 301b, and 301c. The branch line 352 is composed of branch lines 352a, 352b, and 352c that are connected to the respective branch lines 302a, 302b, and 302c. Note that in FIG. 3, the lines are shown in a separated state for the sake of simplicity of explanation. The oxygen supply line 35 that constitutes the oxygen supply means is configured so as to be able to supply oxygen (O2) to the respective branch lines 301 to 303. As a result, the recirculated exhaust gas and the O2 gas are mixed by the branch lines 301 to 303 and the branch lines 351 to 353. In this case, the recirculated exhaust gas supply line 30 and the oxygen supply line 35 constitute a gas mixing means.

[0059] Alternatively, the branch lines 351 (351a to 351c), 352 (352a to 352c), and 353 of the oxygen supply line 35 may be directly connected to the wind boxes 71 (71a to 71c), 72 (72a to 72c), and 73, respectively, to mix the recirculated exhaust gas and O2 gas in the wind boxes 71 to 73. In this case, the wind box 7, the recirculated exhaust gas supply line 30, and the oxygen supply line 35 form a gas mixing means. The oxygen supply line 35 also has a branch line 354 that merges the O2-based gas with the branch line 304 in correspondence with the blowing nozzle 40.

[0060] 1, oxygen supply line 35 is provided with oxygen flow rate adjuster 37 as oxygen flow rate adjustment means for adjusting the flow rate, which is composed of a damper, a valve, or the like. Oxygen flow rate adjuster 37 is composed of oxygen flow rate adjusters 371, 372, 373, and 374. Oxygen flow rate adjuster 373 is provided in branch line 353 corresponding to post-combustion grate 53 and wind box 73. Oxygen flow rate adjuster 374 is provided in branch line 354 of oxygen supply line 35.

[0061] Further, the oxygen flow rate adjusters 371, 372 are provided corresponding to the branch lines 351, 352 of the oxygen supply line 35 and the wind boxes 71, 72 communicating with the branch lines 351, 352, respectively. As shown in more detail in FIG. 3, the oxygen flow rate adjuster 371 is composed of oxygen flow rate adjusters 371a, 371b, 371c corresponding to the multiple wind boxes 71a, 71b, 71c below the drying grate 51, respectively. Similarly, the oxygen flow rate adjuster 372 is composed of oxygen flow rate adjusters 372a, 372b, 372c corresponding to the multiple wind boxes 72a, 72b, 72c below the combustion grate 52, respectively.

[0062] The drying grate 51 corresponding to the wind box 71 is supplied with gas having an adjusted O2 concentration in each of the wind boxes 71a, 71b, and 71c. In the example shown in FIG. 3, the central wind box 71b is supplied with O2-rich gas adjusted to have an O2 concentration of more than 35%, and the left and right wind boxes 71a and 71c are supplied with O2-low-concentration gas having an O2 concentration of less than 5% and recirculated exhaust gas. As a result, O2-rich gas is supplied from below the drying grate 51 to the central part where the layer height (layer thickness) of the waste W is relatively large compared to the left and right, and O2-low-concentration gas and recirculated exhaust gas are supplied to the left and right where the layer height of the waste W is relatively small. That is, the wind box 71 is configured to selectively supply O2-rich gas and O2-low-concentration gas including the concept of recirculated exhaust gas with the O2 concentration appropriately adjusted to each of a plurality of regions along the width direction of the drying grate 51 from below the drying grate 51.

[0063] The gas with the O2 concentration adjusted is also supplied to the combustion grate 52 corresponding to the wind box 72 in each of the wind boxes 72a, 72b, and 72c of the wind box 72. In the example shown in FIG. 3, the central wind box 72b is supplied with O2-rich gas adjusted to have an O2 concentration of more than 35%, and the left and right wind boxes 72a and 72c are supplied with O2-medium concentration gas, which is a mixed gas with recirculated exhaust gas and has an O2 concentration of more than 25% and not more than 35%. As a result, the O2-rich gas is supplied from below the combustion grate 52 to the central part where the layer height of the waste W is relatively large compared to the left and right, and the O2-medium concentration gas is supplied to the left and right where the layer height of the waste W is relatively small. That is, the wind box 72 is configured to selectively supply the O2-rich gas and the O2-medium concentration gas mixed with the recirculated exhaust gas with the O2 concentration appropriately adjusted to each of a plurality of regions along the width direction of the combustion grate 52 from below the combustion grate 52.

[0064] The wind box 73 and the post-combustion grate 53 corresponding to the wind box 73 are supplied with low-O2 concentration gas, which is mainly composed of recirculated exhaust gas and has a relatively low O2 concentration, for example, with an O2 concentration adjusted to less than 5%, or with recirculated exhaust gas. That is, the wind box 73 is configured to be able to supply low-O2 concentration gas, which has a relatively low O2 concentration, or with recirculated exhaust gas from below to the post-combustion grate 53.

[0065] The combustion chamber 2 is provided with a front-stage nozzle 38 and a rear-stage nozzle 39. The front-stage nozzle 38 and the rear-stage nozzle 39 each function as a counterflow nozzle. From the front-stage nozzle 38 and the rear-stage nozzle 39, gas having approximately the same O2 concentration as the O2-rich gas supplied to the above-mentioned wind boxes 71, 72 is supplied. That is, from each of the front-stage nozzle 38 and the rear-stage nozzle 39, O2-rich gas adjusted to approximately the same O2 concentration as the O2-rich gas supplied to the wind boxes 71, 72 is supplied into the combustion chamber 2.

[0066] Specifically, the front-stage nozzle 38 is provided above the gap between the drying grate 51 and the combustion grate 52, for example, on the ceiling or side wall of the combustion chamber 2. An O2-rich gas having an O2 concentration adjusted to exceed 35%, for example, is supplied to the front-stage nozzle 38 as an oxidizer adjusted to have a high O2 concentration. In other words, the front-stage nozzle 38 is configured to be able to supply O2-rich gas having a high O2 concentration to the region between the drying grate 51 and the combustion grate 52 in the combustion chamber 2.

[0067] Similarly, the rear nozzle 39 is provided above between the combustion grate 52 and the rear combustion grate 53, for example, on the ceiling or side wall of the combustion chamber 2. An O2-rich gas adjusted to have an O2 concentration of, for example, more than 35% is supplied to the rear nozzle 39 as an oxidizing agent adjusted to have a high O2 concentration. That is, the rear nozzle 39 is configured to be able to supply O2-rich gas having a high O2 concentration to the region between the combustion grate 52 and the rear combustion grate 53 in the combustion chamber 2, for example, in the vicinity of the periphery of the burnout point of the waste.

[0068] The secondary combustion chamber 11 at the outlet of the combustion chamber 2 is provided with an injection nozzle 40. The injection nozzle 40 is connected to a branch line 304 of the recirculation exhaust gas supply line 30 and a branch line 354 of the oxygen supply line 35. The injection nozzle 40 can be supplied with, for example, an O2-rich gas adjusted to have an O2 concentration higher than 35% as an oxidizing agent adjusted to have a relatively high O2 concentration. The injection nozzle 40 can also be supplied with, for example, an O2-containing gas adjusted to have an O2 concentration higher than that of the O2-low concentration gas and lower than that of the O2-rich gas. That is, the injection nozzle 40 is configured to be able to supply an O2-rich gas with a high O2 concentration or an O2-containing gas with an O2 concentration of 5% to 35% to a region near the outlet of the combustion chamber 2 and at the inlet of the secondary combustion chamber 11. Here, it is preferable to adjust the O2 concentration of the O2-rich gas supplied from the blowing nozzle 40 to be lower than the O2 concentration of the O2-rich gas supplied from the front-stage nozzle 38 and the rear-stage nozzle 39 into the combustion chamber 2, i.e., lower than the O2 concentration of the O2-rich gas supplied to the wind boxes 71, 72. This makes it possible to further reduce the carbon monoxide concentration (CO concentration) in the exhaust gas while suppressing an excessive rise in the temperature of the exhaust gas near the outlet of the combustion chamber 2.

[0069] Specifically, the control unit 60 includes a processor such as a CPU (Central Processing Unit), a DSP (Digital Signal Processor), and an FPGA (Field-Programmable Gate Array), and a main storage unit such as a RAM (Random Access Memory) and a ROM (Read Only Memory) (none of which are shown). The control unit 60 may also be configured as an information processing device such as a computer equipped with a storage unit. In this case, the storage unit of the control unit 60 includes a storage medium selected from a volatile memory such as a RAM, a non-volatile memory such as a ROM, an EPROM (Erasable Programmable ROM), a hard disk drive (HDD, Hard Disk Drive), and a removable medium. The removable medium is, for example, a Universal Serial Bus (USB) memory, or a disk storage medium such as a Compact Disc (CD), a Digital Versatile Disc (DVD), or a Blu-ray (registered trademark) Disc (BD). The storage unit may also be configured using a computer-readable storage medium such as an externally mountable memory card.

[0070] A sensor group 61 serving as a first measuring means is provided upstream along the transport direction of the waste W in the combustion chamber 2. The sensor group 61 is configured to be able to measure at least the temperature, O2 concentration, and CO concentration at the installed position. The sensor group 61 transmits the measured sensor values ​​such as the temperature, O2 concentration, and CO concentration to the control unit 60.

[0071] Further, a sensor group 62 as a carbon monoxide measuring means or a second measuring means is provided on the downstream side along the transport direction of the waste W in the combustion chamber 2. The sensor group 62 measures at least the temperature, the O2 concentration, the CO concentration, and the nitrogen oxide concentration (NO x The sensor group 62 is configured to be able to measure the temperature, O2 concentration, CO concentration, and NO concentration. The sensor group 62 also includes an image sensor capable of capturing an image of the waste W in the combustion chamber 2. The sensor group 62 is configured to be able to measure the temperature, O2 concentration, CO concentration, and NO concentration.x The sensor values ​​such as the concentration and the imaging data are transmitted to the control unit 60. The control unit 60 can calculate the layer height of the waste layer based on the imaging data of the waste W.

[0072] (Waste incineration method) Incineration by the waste incineration system configured as above will be described. As shown in Fig. 2, in the waste incinerator 1 according to this embodiment, a layer of waste W is formed on the drying grate 51, the combustion grate 52, and the post-combustion grate 53. Specifically, the waste W in the upstream range (front portion) along the waste transport direction of the drying grate 51, which is located directly above the drying grate 51 and corresponds to the lower portion of the waste inlet 3, is dried and ignited, and combustion begins.

[0073] As shown in FIG. 2, in the downstream range (rear) of the drying grate 51, initial combustion is carried out in which a part of the waste W starts to burn after being dried, and pyrolysis and partial oxidation of the waste W begin. The region in which initial combustion takes place after the waste W is dried is called the combustion start region. The waste W on the drying grate 51 is dried and ignited in the upstream range on the drying grate 51, and combustion starts in the downstream range, and initial combustion takes place. Here, when the waste W is incinerated, moisture evaporates on the drying grate 51, and then pyrolysis and partial oxidation reactions occur, and pyrolysis gas begins to be generated.

[0074] Next, after the waste W starts to burn downstream of the drying grate 51, pyrolysis gas starts to be generated by pyrolysis and partial oxidation of the waste W, and a part of the waste W is burned. Here, the waste W on the combustion grate 52 is pyrolyzed and partially oxidized, and pyrolysis gas, which is a combustible gas, is generated. On the combustion grate 52, the generated pyrolysis gas and the solid content of the waste W are burned. On the combustion grate 52, the pyrolysis and partial oxidation of the waste W are actively performed, and the generated pyrolysis gas burns with a flame, and the solid content of the waste W is burned in the combustion region, and the region up to the point where the combustion with the flame is completed (burnout point) is defined as the main combustion region. On the combustion grate 52, the waste W is substantially almost burned.

[0075] Further, O2-rich gas is supplied into the combustion chamber 2 from the front nozzle 38 above the drying grate 51 and the combustion grate 52. In this case, a gas combustion region S1 is formed below the front nozzle 38 in the combustion chamber 2 by a mixed gas of the O2-rich gas supplied from the front nozzle 38 and the pyrolysis gas generated by the combustion of the waste W. The pyrolysis gas that is not combusted in the gas combustion region S1 and becomes unburned gas is transported downstream in the combustion chamber 2.

[0076] 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 53. From the post-stage nozzle 39 above the combustion grate 52 and the post-combustion grate 53, O2-rich gas is supplied toward the burnout point S3 on the combustion grate 52 or the post-combustion grate 53. In this case, downstream of the post-stage nozzle 39, secondary combustion is performed in the secondary combustion zone S2 by the O2-rich gas supplied from the post-stage nozzle 39 and the pyrolysis gas of the unburned matter transported from the gas combustion zone S1.

[0077] The area downstream of the burnout point S3 on the post-combustion grate 53 becomes a post-combustion area where the solid unburned matter (char) in the waste W is burned. From the post-combustion area, an O2-containing gas having an O2 concentration of 5% to 35% or a high O2 concentration gas having an O2 concentration of more than 35% is supplied from the injection nozzle 40 to the vicinity of the outlet of the combustion chamber 2 and the vicinity of the inlet of the secondary combustion chamber 11. As described above, a waste layer is formed mainly on the drying grate 51 and the combustion grate 52, and an incineration ash layer is formed downstream of the post-combustion grate 53. Note that the O2-containing gas is a broader concept than the medium O2 concentration gas.

[0078] As shown in FIG. 1, in the waste incineration system, the mixture ratio of the recirculated exhaust gas supplied through the recirculated exhaust gas supply line 30 and the O2-based gas supplied through the oxygen supply line 35 can be adjusted by adjusting the flow rate by the recirculated exhaust gas flow rate adjustment unit 34 and the oxygen flow rate adjustment unit 37. That is, the control unit 60 can control the flow rate of the recirculated exhaust gas by controlling the recirculated exhaust gas flow rate adjustment units 341-344, and can control the flow rate of the O2-based gas by controlling the oxygen flow rate adjustment units 371-374. In addition, the control unit 60 can control the O2 concentration of the O2-rich gas supplied to the front nozzle 38 and the rear nozzle 39. With the above configuration, the control unit 60 can individually and independently control the O2 concentration of the gas supplied to the wind box 7 (71-73), the grate 5 (51-53), the front nozzle 38, and the rear nozzle 39.

[0079] For example, as shown in FIG. 2, the O2-based gas and the recirculated exhaust gas with high CO2 concentration are mixed in the branch lines 301-303, 351-353 below the grate 5. As a result, by controlling the O2 concentration by the control unit 60, it is possible to selectively supply the O2-high concentration gas with an O2 concentration higher than 35%, the O2-medium concentration gas with an O2 concentration higher than 25% and lower than 35%, the O2-low concentration gas with an O2 concentration lower than 5%, and only the recirculated exhaust gas to the drying grate 51 and the combustion grate 52 independently for each divided region. In addition, by controlling the O2 concentration by the control unit 60, it is possible to selectively supply the O2-low concentration gas with an O2 concentration lower than 5% to the post-combustion grate 53. It is also possible to mix the O2-based gas and the recirculated exhaust gas in the wind boxes 71-73 to adjust and control the O2 concentration.

[0080] 3, in the drying grate 51, the flow rates of the recirculated exhaust gas supplied to the wind boxes 71a to 71c through the branch lines 301a to 301c branched off from the recirculated exhaust gas supply line 30 are adjusted by the recirculated exhaust gas flow rate adjustment units 341a to 341c. In the drying grate 51, the flow rates of the O2-based gas supplied to the wind boxes 71a to 71c through the branch lines 351a to 351c branched off from the oxygen supply line 35 are adjusted by the oxygen flow rate adjustment units 371a to 371c. The control unit 60 controls the recirculated exhaust gas flow rate adjustment units 341a to 341c and the oxygen flow rate adjustment units 371a to 371c, thereby adjusting the mixture ratio of the recirculated exhaust gas and the O2-based gas supplied to the wind boxes 71a to 71c. This allows the control unit 60 to individually and independently adjust the O2 concentration of the oxidizing agent supplied to each of the air boxes 71a to 71c.

[0081] Similarly, in the combustion grate 52, the flow rates of the recirculated exhaust gas supplied to the wind boxes 72a to 72c through the branch lines 302a to 302c branched from the recirculated exhaust gas supply line 30 are adjusted by the recirculated exhaust gas flow rate adjustment units 342a to 342c. In addition, in the combustion grate 52, the flow rates of the O2-based gas supplied to the wind boxes 72a to 72c through the branch lines 352a to 352c branched from the oxygen supply line 35 are adjusted by the oxygen flow rate adjustment units 372a to 372c. The control unit 60 can adjust the mixture ratio of the recirculated exhaust gas and the O2-based gas supplied to the wind boxes 72a to 72c by controlling the recirculated exhaust gas flow rate adjustment units 342a to 342c and the oxygen flow rate adjustment units 372a to 372c. This allows the control unit 60 to individually and independently adjust the O2 concentration of the oxidizer supplied to the wind boxes 72a to 72c.

[0082] Here, an example of a method for adjusting the O2 concentration in the wind boxes 71a to 71c by the control unit 60 will be described. First, the control unit 60 acquires imaging data of the waste W on the drying grate 51 from the sensor group 62. Based on the acquired imaging data, the control unit 60 derives the layer height of the waste W along the width direction on the drying grate 51. Based on the derived layer height distribution (height distribution) of the waste W, the control unit 60 adjusts the O2 concentration of the mixed gas in the wind boxes 71a to 71c below the region where the height of the waste W is equal to or higher than a predetermined height to 35% or more. In other words, O2-rich gas is supplied to the region of the drying grate 51 where the height of the waste W is equal to or higher than a predetermined height.

[0083] On the other hand, the control unit 60 adjusts the O2 concentration of the mixed gas in the wind boxes 71a-71c below the region where the height of the waste W is less than the predetermined height, for example, to less than 5%, based on the derived height distribution of the waste W. In other words, low O2 concentration gas is supplied to the region in the drying grate 51 where the height of the waste W is less than the predetermined height. It is also possible to supply high O2 concentration gas to two or more of the wind boxes 71a-71c, or all of the wind boxes 71a-71c as necessary. By such control, high O2 concentration gas can be supplied to the region in the drying grate 51 where the layer height of the waste W is large, and drying and combustion can be promoted.

[0084] The control unit 60 also acquires imaging data of the waste W on the combustion grate 52 from the sensor group 62. The control unit 60 derives the layer height of the waste W along the width direction on the combustion grate 52 based on the acquired imaging data. The control unit 60 adjusts the O2 concentration of the mixed gas supplied to the lower wind boxes 72a-72c in the region where the height of the waste W is equal to or higher than a predetermined height, to 35% or more, based on the derived height distribution of the waste W. In other words, O2-rich gas is supplied to the region of the combustion grate 52 where the height of the waste W is equal to or higher than a predetermined height.

[0085] On the other hand, the control unit 60 adjusts the O2 concentration of the mixed gas in the wind boxes 72a-72c below the region where the height of the waste W is less than the predetermined height, for example, to more than 25% and less than 35%, based on the derived height distribution of the waste W. In other words, a medium concentration O2 gas is supplied to the region in the combustion grate 52 where the height of the waste W is less than the predetermined height. It is also possible to supply high concentration O2 gas to two or more of the wind boxes 72a-72c, or all of the wind boxes 72a-72c as necessary. By such control, high concentration O2 gas can be supplied to the region in the combustion grate 52 where the layer height of the waste W is large, and complete combustion of the waste W on the combustion grate 52 can be promoted.

[0086] The control unit 60 also controls the recirculation exhaust gas flow rate adjustment unit 34 and the oxygen flow rate adjustment unit 37 based on various sensor values ​​such as temperature and concentration supplied from the sensor groups 61, 62. First, the control unit 60 acquires various measurement values ​​(sensor values) from the sensor groups 61, 62 in the waste incinerator 1 at all times or as needed.

[0087] Specifically, the control unit 60 acquires a measurement value of the CO concentration from the sensor group 62. When the acquired CO concentration exceeds a first predetermined value, the control unit 60 performs control to increase the O2 concentration of the O2-rich gas in the mixed gas supplied to the drying grate 51 and the combustion grate 52. It is also possible to simultaneously perform control to increase the O2 concentration of the mixed gas supplied to the post-combustion grate 53. Conversely, when the acquired CO concentration is less than a second predetermined value, the control unit 60 performs control to decrease the O2 concentration of the O2-rich gas in the mixed gas supplied to the drying grate 51 and the combustion grate 52. It is also possible to simultaneously perform control to decrease the O2 concentration of the mixed gas supplied to the post-combustion grate 53.

[0088] Furthermore, the control unit 60 can control the O2 concentration of each of the gases supplied to the front nozzle 38, the rear nozzle 39, and the blowing nozzle 40 so as to suppress the generation of carbon monoxide (CO) and reduce the CO concentration in the exhaust gas. That is, the control unit 60 adjusts the O2 concentration of the mixed gas supplied into the combustion chamber 2 based on the CO concentration measured by the sensor group 62. In this case, it is preferable that the O2 concentration of the gas supplied to the blowing nozzle 40 is lower than the O2 concentration of the gas supplied to the front nozzle 38 and the rear nozzle 39. This suppresses the amount of oxygen supplied to the vicinity of the exhaust port of the combustion chamber 2, suppressing the oxidation reaction, and making it possible to suppress a significant increase in the temperature of the exhaust gas discharged from the combustion chamber 2.

[0089] According to the embodiment described above, mixed gas having an O2 concentration of more than 35% and mixed gas having an O2 concentration of less than 5% are selectively supplied to each of the wind boxes 71a-71c corresponding to the drying division regions divided into a plurality of regions below the drying grate 51, and mixed gas having an O2 concentration of more than 35% and mixed gas having an O2 concentration of more than 25% and less than 35% are selectively supplied to each of the wind boxes 72a-72c corresponding to the combustion division regions divided into a plurality of regions in the combustion grate 52. This makes it possible to completely combust the waste W in the combustion chamber 2 and reduce the CO concentration in the exhaust gas discharged from the combustion chamber 2.

[0090] Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-mentioned embodiments, and various modifications based on the technical ideas of the present invention are possible. For example, the numerical values ​​given in the above-mentioned embodiments are merely examples, and numerical values ​​different from these may be used as necessary. The present invention also includes configurations in which the components of the above-mentioned embodiments and each modification are appropriately combined. Further effects and modifications can be easily derived by those skilled in the art. The broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Thus, various modifications are possible without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

[0091] For example, in the above-mentioned embodiment, an incinerator using a counterflow furnace has been described as an example of the waste incinerator 1, but an incinerator using a double-flow furnace may also be used. In this case, in the above-mentioned embodiment, the front nozzle 38 can be replaced with a high-temperature air blower (HADF), and the rear nozzle 39 can be replaced with a recirculation blower (RDF). [Explanation of symbols]

[0092] 1 Waste incinerator 2. Combustion chamber 3 Waste input port 4. Boiler 4A Exhaust section 5. Grate 6. Ash discharge section 7,71,71a,71b,71c,72,72a,72b,72c,73 Wind box 11 Secondary combustion chamber 12,13 Turning section 14 1st radiation room 15 Second radiation room 16 Convection Heat Transfer Chamber 16A superheater 16B Economizer 17 Flue 18 Dust collector 19 Induced draft fan 20 Chimney 30 Recirculated exhaust gas supply line 31 Cooling Tower 32 PSA Department 34,341,341a,341b,341c,342,342a,342b,342c,343,344 Recirculation exhaust gas flow rate adjustment section 35 Oxygen supply line 36 Blower 37,371,371a,371b,371c,372,372a,372b,372c,373,374 Oxygen flow rate adjustment section 38 Front stage nozzle 39 Rear nozzle 40 Blowing nozzle 51 Drying grate 52 Combustion grate 53 Post-combustion grate 60 Control section 61,62 Sensor Group 301, 301a, 301b, 301c, 302, 302a, 302b, 302c, 303, 304, 351, 351a, 351b, 351c, 352, 352a, 352b, 352c, 353, 354 Branch line

Claims

1. A method for incinerating waste in an incinerator having a combustion chamber in which waste is transported by a fire grate and combusted, comprising the steps of: branching at least a portion of the exhaust gas from the incinerator as recirculated exhaust gas by a recirculated exhaust gas supply means; and mixing an oxygen-containing gas with the recirculated exhaust gas by an oxygen supply means to generate a mixed gas, and supplying the mixed gas to the combustion chamber, comprising: The grate is configured to have a drying grate, a combustion grate, and a post-combustion grate along the waste transport direction; The mixed gas having an oxygen concentration of more than 35% and the mixed gas having an oxygen concentration of less than 5% are selectively supplied to each of the drying divided regions divided into a plurality of regions in the drying grate, The mixed gas having an oxygen concentration of more than 35% and the mixed gas having an oxygen concentration of 35% or less are selectively supplied to each of the combustion divided regions divided into a plurality of combustion divided regions in the combustion grate. Waste incineration methods.

2. The oxygen concentration of the gas supplied to the vicinity of the outlet where the exhaust gas is discharged from the combustion chamber is made lower than the oxygen concentration of the mixed gas supplied to the drying grate and the combustion grate, whichever has the higher oxygen concentration.

2. The waste incineration method according to claim 1.

3. The gas supplied to the post-combustion grate is the recirculated exhaust gas, or the oxygen concentration of the gas supplied to the post-combustion grate is adjusted to less than 5%.

2. The waste incineration method according to claim 1.

4. The mixed gas supplied to the drying grate is adjusted so that the oxygen concentration is higher than 35% in a region of the drying grate where the layer height of the waste piled up on the drying grate is higher than a predetermined height, and the oxygen concentration is adjusted to less than 5% in a region of the drying grate where the layer height of the waste piled up on the drying grate is less than the predetermined height.

2. The waste incineration method according to claim 1.

5. The mixed gas supplied to the combustion grate is adjusted so that the oxygen concentration is higher than 35% in a region of the combustion grate where the layer height of the waste piled up on the combustion grate is higher than a predetermined height, and the oxygen concentration is adjusted to 35% or less in a region where the layer height of the waste piled up on the combustion grate is less than the predetermined height, among the multiple divided regions of the combustion grate.

2. The waste incineration method according to claim 1.

6. The oxygen concentration of the gas supplied into the combustion chamber from a front stage nozzle provided above the drying grate and the combustion grate and a rear stage nozzle provided above the combustion grate and the rear combustion grate is adjusted to be higher than 35%.

2. The waste incineration method according to claim 1.

7. The oxygen concentration of the gas supplied to the vicinity of an outlet through which exhaust gas is discharged from the combustion chamber is made lower than the oxygen concentration supplied to the combustion chamber from the front stage nozzle and the rear stage nozzle.

7. The waste incineration method according to claim 6.

8. measuring a carbon monoxide concentration by a carbon monoxide measuring means configured to be capable of measuring a carbon monoxide concentration and provided downstream in the direction of transport of the waste in the combustion chamber; The oxygen concentration of the mixed gas to be supplied into the combustion chamber is adjusted based on the measured carbon monoxide concentration.

2. The waste incineration method according to claim 1.

9. The oxygen concentration of the mixed gas supplied into the combustion chamber is adjusted based on at least one of the measured values ​​of the furnace temperature, the oxygen concentration, and the carbon monoxide concentration measured by a first measuring means provided upstream in the combustion chamber along the direction in which the waste is transported and configured to be capable of measuring the furnace temperature, the oxygen concentration, and the carbon monoxide concentration, and a second measuring means provided near an outlet through which exhaust gas is discharged from the combustion chamber and configured to be capable of measuring the furnace temperature, the oxygen concentration, and the carbon monoxide concentration.

2. The waste incineration method according to claim 1.

10. An incinerator having a combustion chamber in which waste is transported by a fire grate and burned; A recirculated exhaust gas supply means configured to branch off at least a portion of the exhaust gas from the incinerator as a recirculated exhaust gas and supply it to the incinerator; An oxygen supply means configured to be able to supply a gas containing oxygen as a main component to the incinerator; A waste incineration apparatus comprising: a gas mixing means for mixing the recirculated exhaust gas supplied by the recirculated exhaust gas supply means with a gas containing oxygen as a main component supplied by the oxygen supply means to generate a mixed gas, The grate has a drying grate, a combustion grate, and a post-combustion grate along the waste transport direction; The mixed gas having an oxygen concentration of more than 35% and the mixed gas having an oxygen concentration of less than 5% can be selectively supplied to each of the drying divided regions divided into a plurality of regions in the drying grate, and the mixed gas having an oxygen concentration of more than 35% and the mixed gas having an oxygen concentration of 35% or less can be selectively supplied to each of the combustion divided regions divided into a plurality of regions below the combustion grate. Waste incineration equipment.

11. The oxygen concentration of the gas supplied to the vicinity of the outlet where the exhaust gas is discharged from the combustion chamber can be adjusted to be lower than the oxygen concentration of the mixed gas having a higher oxygen concentration supplied to the drying grate and the combustion grate.

11. A waste incineration apparatus according to claim 10.

12. The gas supplied to the post-combustion grate is the recirculated exhaust gas, or the oxygen concentration of the gas supplied to the post-combustion grate can be adjusted to less than 5%.

11. A waste incineration apparatus according to claim 10.

13. The oxygen concentration of the mixed gas supplied to the drying grate is adjustable to be higher than 35% in a region in which the layer height of the waste piled on the drying grate is higher than a predetermined height among the multiple divided regions of the drying grate, and is adjustable to be less than 5% in a region in which the layer height of the waste piled on the drying grate is less than the predetermined height.

11. A waste incineration apparatus according to claim 10.

14. The oxygen concentration of the mixed gas supplied to the combustion grate is configured to be adjustable to be higher than 35% in a region in which the layer height of the waste piled up on the combustion grate is higher than a predetermined height among a plurality of divided regions in the combustion grate, and is configured to be adjustable to be 35% or less in a region in which the layer height of the waste piled up on the combustion grate is less than the predetermined height.

11. A waste incineration apparatus according to claim 10.

15. The oxygen concentration of the gas supplied into the combustion chamber from a front nozzle provided above the drying grate and the combustion grate, and a rear nozzle provided above the combustion grate and the rear combustion grate can be adjusted to be higher than 35%.

11. A waste incineration apparatus according to claim 10.

16. The oxygen concentration of the gas supplied to the vicinity of an outlet where exhaust gas is discharged from the combustion chamber can be adjusted to be lower than the oxygen concentration supplied to the combustion chamber from the front stage nozzle and the rear stage nozzle.

16. A waste incineration apparatus according to claim 15.

17. A carbon monoxide measuring means configured to be capable of measuring a carbon monoxide concentration is further provided downstream in the direction of transport of the waste within the combustion chamber, The oxygen concentration of the mixed gas supplied into the combustion chamber can be adjusted based on the carbon monoxide concentration measured by the carbon monoxide measuring means.

11. A waste incineration apparatus according to claim 10.

18. A first measuring means is provided on an upstream side in the direction of transport of the waste in the combustion chamber and configured to be able to measure an in-furnace temperature, an oxygen concentration, and a carbon monoxide concentration; A second measuring means is provided downstream in the direction of transport of the waste in the combustion chamber and configured to be able to measure an in-furnace temperature, an oxygen concentration, and a carbon monoxide concentration; The oxygen concentration of the mixed gas supplied into the combustion chamber can be adjusted based on at least one of the measured values ​​of the furnace temperature, the oxygen concentration, and the carbon monoxide concentration measured by the first measuring means and the second measuring means.

11. A waste incineration apparatus according to claim 10.

Images