Waste incineration device, and waste incineration method

Abstract

To accelerate carbonation of incineration ash and solidification of heavy metal in a waste incineration furnace.SOLUTION: The waste incineration furnace comprises a combustion chamber combusting waste, recirculation exhaust supply means of branching at least a portion of exhaust present in the incineration furnace to supply the same to the combustion chamber as recirculation exhaust, water separation means of dehydrating the recirculation exhaust, oxygen supply means of supplying oxygen gas to the combustion chamber, and gas mixing means of forming mixed gas of recirculation exhaust and oxygen gas. The combustion chamber comprises a drying fire grate, a combustion fire grate and a post-combustion fire grate along the waste transfer direction, a recirculation gas branching unit is disposed upstream of the water separation means, with one of branched recirculation exhaust branched by the branching unit being dehydrated by the water separation means, one of the dehydrated recirculation exhaust being supplied to the post-combustion fire grate, and mixed gas formed by mixing the other of the recirculation exhaust and oxygen gas by the gas mixing means being supplied to the drying fire grate and the combustion fire grate.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, a combustion technology called O2 / CO2 combustion, oxygen combustion, or Oxy-fuel combustion has been proposed (see Patent Document 1). Patent Document 1 discloses a method for incinerating municipal waste using O2 / CO2 combustion. In the technology described in Patent Document 1, municipal waste is first incinerated using oxygen (O2) obtained by separating nitrogen (N2) from air. After recovering heat from the exhaust gas generated by the incineration of this municipal waste, a portion 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).

[0004] In addition, various techniques have been studied for suppressing the elution of lead (Pb), a heavy metal contained in incineration ash, and for immobilizing it. Lead (Pb), which is a heavy metal contained in incineration ash at a high content rate, is an amphoteric metal, so the amount of lead (Pb) eluted can be reduced by subjecting the incineration ash, which shows strong alkalinity, to a treatment to lower the pH and make it into a poorly soluble region. The technology described in Patent Document 2 is known as a method for rendering incineration ash harmless.

[0005] Patent Document 2 discloses a method for making incineration ash harmless, in which exhaust gas discharged from a waste incinerator is heated and aerated through the incineration ash discharged from the waste incinerator to carbonize the ash and promote the immobilization of lead (Pb). In the technology described in Patent Document 2, the reaction sites for carbonating the incineration ash include the following four locations: first, a reaction tower below the incineration ash discharge chute; second, an incineration ash storage tank that stores the incineration ash extracted from the incineration ash extraction device below the waste incineration chute; third, an incineration ash storage tank that stores the incineration ash extracted from the wet ash extraction device below the incineration ash discharge chute; and fourth, on the post-combustion grate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-126324 [Patent Document 2] JP 2003-340397 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the above-mentioned conventional technology, the carbon dioxide (CO2) concentration of the exhaust gas discharged from the waste incinerator is low, on the order of about 10%. Therefore, in the technology described in Patent Document 2, in order to sufficiently promote the carbonation of the incineration ash and promote the immobilization of heavy metals such as lead, a long residence time and an increase in the equipment capacity are required. Therefore, there has been a demand for a technology that can further promote the carbonation of the incineration ash and the immobilization of heavy metals in waste incinerators.

[0008] The present invention has been made in consideration of the above, and its object is to provide a waste incineration apparatus and a waste incineration method that can promote the carbonation of incineration ash and the fixation of heavy metals in a waste incinerator. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, a waste incineration apparatus according to one aspect of the present invention is an incineration apparatus having an incinerator that combusts waste and discharges it as incineration ash, and is equipped with a combustion chamber for combusting the waste, a recirculated exhaust gas supplying 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 combustion chamber, a water separating means configured to be able to dehydrate the recirculated exhaust gas, an oxygen supplying means configured to be able to supply a gas containing oxygen as a main component to the combustion chamber, and a gas mixing means for mixing the recirculated exhaust gas supplied by the recirculated exhaust gas supplying means with the gas containing oxygen as a main component supplied by the oxygen supplying means to generate a mixed gas, and the combustion chamber is arranged such that the recirculated exhaust gas is supplied to the combustion chamber along a transport direction of the waste. The incineration system has a drying grate in which initial combustion takes place after the waste is dried, a combustion grate in which solid matter in the waste and the generated combustible gas are burned, and a post-combustion grate in which unburned matter in the waste is burned to produce the incineration ash, and a branching section that further branches the recirculated exhaust gas upstream of the water separation means along the flow direction of the recirculated exhaust gas is provided, and one of the recirculated exhaust gases branched at the branching section is supplied to the water separation means so as to be dehydrated, and one of the recirculated exhaust gases dehydrated by the water separation means is capable of being supplied to the post-combustion grate, and the other recirculated exhaust gas is mixed with a gas containing oxygen as a main component by the gas mixing means to produce a mixed gas that can be supplied to the drying grate and the combustion grate.

[0010] A waste incineration apparatus according to one embodiment of the present invention is provided with a control unit configured to control the flow rate of the recirculated exhaust gas, and the control unit controls the flow rate ratio of one of the recirculated exhaust gases to 15% or more and 25% or less, and controls the flow rate ratio of the other recirculated exhaust gas to 75% or more and 85% or less, based on the flow rate upstream of the branch section in the flow direction of the recirculated exhaust gas.

[0011] A waste incineration apparatus according to one embodiment of the present invention is configured as described above, with an ash carbonation grate downstream of the post-combustion grate in the direction of transport of the waste, in which the incineration ash is carbonated, and one of the recirculated exhaust gases dehydrated by the water separation means can be supplied to the post-combustion grate and the ash carbonation grate.

[0012] In the waste incineration apparatus according to one aspect of the present invention, the ash carbonation grate is disposed at a lower position than the post-combustion grate, separated by a step.

[0013] The waste incineration apparatus according to one aspect of the present invention is configured so that the temperature in the post-combustion grate can be adjusted to 400°C or higher and 600°C or lower in the above-mentioned invention.

[0014] The waste incineration apparatus according to one aspect of the present invention, in the above invention, further comprises carbon dioxide separation means for separating and removing a portion of the carbon dioxide contained in the one of the recirculated exhaust gases dehydrated by the water separation means.

[0015] A waste incineration method according to one aspect of the present invention is a waste incineration method in which waste is incinerated by an incinerator that burns the waste and discharges it as incineration ash, the incinerator having a combustion chamber for burning the waste, the combustion chamber having an initial combustion area in which initial combustion is performed after the waste is dried, a main combustion area in which solids in the waste and generated combustible gas are burned, and a post-combustion area in which unburned parts of the waste are burned to produce the incineration ash, along the direction in which the waste is transported, and after at least a portion of the exhaust gas from the incinerator is branched as a recirculated exhaust gas by a recirculated exhaust gas supply means, the recirculated exhaust gas is further branched into one recirculated exhaust gas and the other recirculated exhaust gas, the one recirculated exhaust gas is dehydrated and then supplied to the post-combustion area in the combustion chamber, and the other recirculated exhaust gas is mixed with a gas containing oxygen as a main component by an oxygen supply means to generate a mixed gas, and the mixed gas is supplied to the initial combustion area and the main combustion area in the combustion chamber.

[0016] In one embodiment of the waste incineration method of the present invention, a control unit configured to control the flow rate of the recirculated exhaust gas controls the flow rate ratio of one of the recirculated exhaust gases to 15% or more and 25% or less, and controls the flow rate ratio of the other recirculated exhaust gas to 75% or more and 85% or less, based on the flow rate upstream of the branch section in the flow direction of the recirculated exhaust gas.

[0017] A waste incineration method according to one embodiment of the present invention is the above-mentioned invention, further comprising an ash carbonation zone downstream of the post-combustion zone in the direction of transport of the waste, where the incineration ash is carbonated, and the dehydrated recirculated exhaust gas is supplied to the post-combustion zone and the ash carbonation zone.

[0018] In the waste incineration method according to one aspect of the present invention, in the above-mentioned invention, the ash carbonation zone is provided at a position lower than the post-combustion zone.

[0019] In the waste incineration method according to one aspect of the present invention, in the above-mentioned invention, the temperature in the post-combustion zone is adjusted to 400°C or higher and 600°C or lower.

[0020] In the waste incineration method according to one aspect of the present invention, in the above-mentioned invention, a part of carbon dioxide contained in the one of the dehydrated recirculated exhaust gases is separated and removed. Effect of the Invention

[0021] According to the waste incineration apparatus and waste incineration method of the present invention, it is possible to promote the carbonation of incineration ash and the fixation of heavy metals in a waste incinerator. [Brief description of the drawings]

[0022] [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 the configuration of a fire grate portion of a waste incineration apparatus according to a modified embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 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.

[0024] In describing the embodiment of the present invention, the inventor conducted intensive studies. First, the inventor conducted studies on the problems associated with the prior art. That is, according to the knowledge of the inventor, in the waste incinerator of the conventional waste incineration apparatus described in Patent Document 2 and the like, the carbon dioxide (CO2) contained in the exhaust gas discharged is low, at about 10% order. Even if such exhaust gas with a low CO2 concentration is circulated to carbonate the incineration ash, a long residence time is required to promote sufficient carbonation, so that the facility capacity needs to be increased. Therefore, the inventor conducted studies and came to the conclusion that it is preferable to increase the CO2 concentration in order to promote the carbonation of the incineration ash in the waste incinerator and the fixation of heavy metals such as lead.

[0025] Furthermore, the inventors have investigated methods for increasing the CO2 concentration in waste incinerators, and have devised a method of producing a mixture of O2 gas and CO2 gas (hereinafter, O2 / CO2 mixed gas) as a combustion-supporting gas by recirculating a portion of the combustion exhaust gas and mixing it with a gas containing oxygen (O2) as its main component (hereinafter, also referred to as O2 gas).

[0026] That is, CO2 contributes greatly to the carbonation of incineration ash and the fixation of lead as a heavy metal. If CO2 gas with a high CO2 concentration can be supplied to the area where incineration ash exists, the carbonation of incineration ash and the fixation of heavy metals can be promoted. That is, the present inventor devised a method of changing the CO2 concentration in the O2 / CO2 mixed gas depending on the place where it is blown in. In addition, the present inventor conducted various experiments and studies on a method of promoting the carbonation of incineration ash and the fixation of heavy metals by changing the CO2 concentration in the O2 / CO2 mixed gas supplied to the waste in a stoker-type waste incinerator. As a result of intensive studies, the present inventor devised the following method as a specific method for changing the CO2 concentration in the O2 / CO2 mixed gas.

[0027] That is, the present inventor mixed at least a part of the recirculated exhaust gas discharged from the waste incinerator with O2 gas while recirculating it, generated an O2 / CO2 mixed gas, and supplied it to the waste incinerator. As a result, the present inventor found that it is possible to reduce the concentration of N2 (N2 concentration) contained in the exhaust gas and increase the concentration of CO2 (CO2 concentration) contained in the exhaust gas to 50% or more. By generating such a combustion-supporting gas and supplying it to the waste incinerator, the nitrogen (N2) contained in the supplied combustion-supporting gas is significantly reduced compared to the conventional case in which air is supplied to the waste incinerator as a combustion-supporting gas, so that it is possible to increase the concentration of CO2 contained in the combustion exhaust gas to 50% or more. This can promote the carbonation of the incineration ash and promote the fixation of heavy metals, especially lead (Pb). In addition, by supplying an O2 / CO2 mixed gas as a combustion-supporting gas into the waste incinerator, it is also possible to promote the combustion of waste in the waste incinerator.

[0028] Here, in a stoker-type waste incinerator, a plurality of grates are provided 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 direction of waste transport. Therefore, the present inventor further studied and devised a method of branching the circulation system of the recirculated exhaust gas (hereinafter, recirculated exhaust gas) into two systems at the front stage along the flow direction of the recirculated exhaust gas relative to the moisture separation means when the combustion exhaust gas is recirculated into the waste incinerator in a state where the CO2 concentration is high at about 50%. In this case, as one circulation system, the recirculated exhaust gas from which moisture (H2O) such as water vapor has been removed by the moisture separation means is supplied to the post-combustion grate, and as the other circulation system, the recirculated exhaust gas from which moisture has not been removed is mixed with oxygen (O2) gas and supplied to the drying grate and the combustion grate. As a result, the CO2 concentration in the recirculated exhaust gas from which moisture has been removed is further improved, making it possible to further promote the carbonation of the incineration ash on the post-combustion grate and the fixation of heavy metals. On the other hand, by mixing the recirculated exhaust gas containing moisture with oxygen (O2) gas and supplying it to the drying grate and the combustion grate, the water vapor contributes to the reforming reaction of the combustible gas generated from the waste pyrolysis, thereby improving complete combustion.

[0029] Based on the above, the present inventors have further studied a method of providing an ash carbonation region (also called an ash carbonation stage) in a combustion chamber for carbonating incineration ash. By providing an ash carbonation region in a combustion chamber of a waste incinerator, the carbonation of incineration ash and the fixation of heavy metals such as lead are less susceptible to the effects of radiation from combustion occurring in the incinerator. By providing an ash carbonation region, an ash carbonation region in which carbonation of incineration ash is performed can be formed, and the temperature in the ash carbonation region can be easily controlled.

[0030] Furthermore, the inventor conducted detailed experiments and studies on the proposed ash carbonation region. Here, the inventor also came up with a method in which, when the waste incinerator is a stoker-type incinerator, the ash carbonation region is disposed at the rear of the post-combustion region of the incinerator, and the recirculated exhaust gas to be supplied to the ash carbonation region is supplied independently from other regions in the combustion chamber. This allows gas mainly composed of carbon dioxide (CO2) with a CO2 concentration of 50% or more to be efficiently supplied to the ash carbonation region at the last stage in the combustion chamber. Since the waste on the ash carbonation region is incineration ash from which combustion has been completed, the incineration ash on the ash carbonation region can be efficiently carbonated, and the fixation of heavy metals such as lead (Pb) can be promoted. Furthermore, in order to further suppress radiation due to combustion on the incineration ash, the inventor also devised a configuration in which the ash carbonation region is provided at a low position with a predetermined step with respect to the upper surface of the post-combustion grate constituting the post-combustion region in the stoker-type incinerator.

[0031] The present inventor also came up with a configuration in which a temperature sensor is provided in the ash carbonation area, and the flow rate of the recirculated exhaust gas is adjusted based on the measurement by the temperature sensor. That is, according to the knowledge of the present inventor, the higher the temperature, the more the carbonation reaction in which calcium oxide (CaO) or calcium hydroxide (Ca(OH)2) contained in the incineration ash reacts with CO2 to generate calcium carbonate (CaCO3) is promoted. Therefore, a high temperature is preferable for the temperature around the incineration ash, but if the temperature exceeds 600°C, the decomposition reaction of the generated CaCO3 may start. Therefore, it is preferable to adjust the temperature around the incineration ash to 400°C or higher and 600°C or lower by adjusting the flow rate of the combustion exhaust gas. This allows the temperature of the incineration ash on the ash carbonation area to be adjusted, and the carbonation of the incineration ash and the fixation of heavy metals can be further promoted. Note that the temperature of the ash carbonation area is not limited to a temperature of 400°C or higher and 600°C or lower. One embodiment of the present invention described below was devised by the present inventor through the above-mentioned intensive studies.

[0032] (Waste incineration equipment) FIG. 1 is a diagram showing the overall configuration of a waste incineration apparatus according to one embodiment of the present invention. The waste incineration apparatus according to this embodiment includes a waste incinerator 1. 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) along the flow direction of the waste W in 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 above the downstream side (right side in FIG. 1) along the flow direction of the waste W of the combustion chamber 2.

[0033] At the bottom of the combustion chamber 2, a grate (stoker) 5 is provided for burning the waste W while moving it. The grates 5 are provided with a drying grate 5a, a combustion grate 5b, and a post-combustion grate 5c in that order from the side closer to the waste inlet 3, i.e., from the upstream side along the transport direction of the waste W. An ash carbonation grate 5d may be further provided on the side farther from the waste inlet 3 than the post-combustion grate 5c, i.e., on the downstream side along the transport direction of the waste W.

[0034] In the waste incinerator 1 according to the present embodiment, a layer of waste W is formed on the drying grate 5a, the combustion grate 5b, and the post-combustion grate 5c. When the ash carbonation grate 5d is provided, a layer of waste W is also formed on the ash carbonation grate 5d. By the combustion of the waste W, a plurality of combustion regions are formed in the space within the combustion chamber 2 in the waste W on each of the drying grate 5a, the combustion grate 5b, and the post-combustion grate 5c.

[0035] In the drying grate 5a, the waste W is mainly dried and initially combusted. Specifically, the waste W in the upstream range (front) of the drying grate 5a in the waste flow direction, which is located directly above the drying grate 5a and corresponds to the lower part of the waste inlet 3, is dried and ignited, and combustion begins. Above the downstream range (rear) of the drying grate 5a, an initial combustion region is formed where initial combustion occurs, in which the waste W is dried and partly combusted, and pyrolysis and partial oxidation of the waste W begins. That is, the waste W on the drying grate 5a is dried and ignited in the upstream range on the drying grate 5a, and combustion begins in the downstream range, and initial combustion occurs, forming an initial combustion region for the waste W. The initial combustion region is a region where, after combustion of the waste W begins in the downstream part of the drying grate 5a, combustible gas begins to be generated by pyrolysis and partial oxidation of the waste W, and part of the waste W is combusted.

[0036] In the combustion grate 5b, the waste W is mainly pyrolyzed and partially oxidized. On the combustion grate 5b, carbon monoxide (CO) generated by pyrolysis, combustible gases including hydrocarbons, and solids (fixed carbon) are mainly burned. Specifically, when the waste W is incinerated on the combustion grate 5b, water evaporates, followed by pyrolysis and partial oxidation reactions to generate combustible gas. The generated combustible gas and the solids of the waste W are burned on the combustion grate 5b. On the combustion grate 5b, the waste W is substantially almost burned, and a main combustion region of the waste W is formed. The main combustion region is a combustion region where the pyrolysis and partial oxidation of the waste W are actively carried out on the combustion grate 5b, the generated combustible gas is burned with a flame, and the solids of the waste W are burned, and is a region up to the point where the combustion with a flame is completed (burnout point).

[0037] On the post-combustion grate 5c, the remaining unburned matter in the waste is completely burned as post-combustion. Specifically, the area on the post-combustion grate 5c behind the burnout point is the post-combustion area where the solid unburned matter (char) in the waste W is burned. After the waste W is burned, the unburned matter such as fixed carbon in the remaining waste W is completely burned on the post-combustion grate 5c. The post-combustion area is formed by the waste W on the post-combustion grate 5c. The post-combustion area is the area where the unburned matter of the waste W is burned on the post-combustion grate 5c and the waste W is turned into incineration ash.

[0038] After the waste W is turned into incineration ash on the post-combustion grate 5c, carbonation treatment is performed. Specifically, the downstream side of the post-combustion grate 5c is an ash carbonation area where carbonation treatment is performed using carbon dioxide (CO2) contained in the combustion exhaust gas discharged from the waste incinerator 1, for example, the recirculated exhaust gas discharged from the dust collector 18 described later. The ash carbonation area is an area where carbonation treatment is performed on the incineration ash. When the ash carbonation grate 5d is provided, the above-mentioned carbonation treatment is performed on the ash carbonation grate 5d, forming the ash carbonation area.

[0039] In the ash carbonation area, CO2 reacts with heavy metals contained in the incineration ash, mainly lead (Pb), and Pb is converted into a carbonate and becomes insoluble. This suppresses the elution of Pb from the incineration ash. In the ash carbonation area, calcium carbonate (CaCO3) is generated by reacting CO2 contained in the recirculated exhaust gas with calcium oxide (CaO) contained in the incineration ash. This lowers the pH of the incineration ash, making it a difficult-to-dissolve area in which Pb is insoluble, further suppressing the elution of Pb from the incineration ash. The incineration ash after the carbonation process is dropped and discharged from the incineration ash discharge section 6.

[0040] As described above, a waste layer 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, where carbonation is carried out. If the ash carbonation grate 5d is provided, carbonation is carried out on the ash carbonation grate 5d.

[0041] A wind box 7 is provided at the bottom of the combustion chamber 2. Specifically, wind boxes 7a, 7b, and 7c are provided at the bottom of the drying grate 5a, the combustion grate 5b, and the post-combustion grate 5c in the combustion chamber 2, respectively. When the ash carbonation grate 5d is provided, the wind box 7c may be provided in common with the post-combustion grate 5c, or may be provided independently at the bottom of the ash carbonation grate 5d. The wind boxes 7a and 7b of the wind box 7 can function as part of a gas mixing means for mixing a plurality of gases, and in this embodiment, can function as a gas mixing means for mixing the recirculated exhaust gas and a gas mainly composed of O2.

[0042] 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 combustion chamber 2 downstream in the direction of waste flow (right side in FIG. 1). 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 combustible 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 heat recovered by the boiler 4.

[0043] 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.

[0044] 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. In the convection heat transfer chamber 16, a heat transfer tube (not shown) is provided in the internal space through which the exhaust gas flows.

[0045] The boiler 4 configures an evaporator by the first radiation chamber 14 and the second radiation chamber 15. A plurality of, for example, three superheaters 16A are formed by a part of the convection heat transfer chamber 16. In the first radiation chamber 14 and the second radiation chamber 15, a heat transfer tube arranged on the outside of the refractory wall and through which water flows is configured as a radiation heat transfer surface that receives radiant heat from the exhaust gas and generates steam.

[0046] The convection heat transfer chamber 16 includes a superheater 16A and an economizer 16B from the upstream side (lower side) along the flow direction of the exhaust gas. 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 is configured as a convection heat transfer surface. The superheater 16A further superheats the steam generated in the evaporator by heat exchange with the exhaust gas to produce high-temperature and high-pressure superheated steam. The economizer 16B is provided downstream (upper side) of the superheater 16A and has heat transfer tubes arranged therein. The economizer 16B 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 it with the heat remaining in the exhaust gas after the steam is superheated in the superheater 16A, thereby heating the water by heat exchange with the exhaust gas, generating heated water, which is then supplied to the evaporator.

[0047] Note that the economizer 16B may not be provided inside the convection heat transfer chamber 16, but may be provided outside the boiler 4 on the downstream side of the boiler 4 as a separate economizer, or both an in-boiler economizer and a separate economizer may be provided. A screen tube (not shown) is provided in 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 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] In this embodiment, the recirculated exhaust gas supply line 30 is branched into at least two recirculated exhaust gas branch lines 30A, 30C at the rear of the induced draft blower 19. The branched portions of the recirculated exhaust gas branch lines 30A, 30C constitute a branching section. One of the recirculated exhaust gas branch lines 30C is provided with a cooling tower 31 as a water separation means. That is, the recirculated exhaust gas supply line 30 is branched into at least two recirculated exhaust gas branch lines 30A, 30C at the front stage along the flow direction of the recirculated exhaust gas in the cooling tower 31. Here, the flow rate ratio of the recirculated exhaust gas in the two recirculated exhaust gas branch lines 30A, 30C is preferably selected from the range of 75% to 85% in the recirculated exhaust gas branch line 30A and 15% to 25% in the recirculated exhaust gas branch line 30C, assuming that the sum is 100%. It is also possible to adjust the flow rate ratio of the recirculated exhaust gas in the two recirculated exhaust gas branch lines 30A, 30C based on the partial pressure ratio of the O2 concentration and the CO2 concentration in the recirculated exhaust gas supplied to the wind boxes 7a, 7b, i.e., the recirculated exhaust gas supplied to the drying grate 5a and the combustion grate 5b.

[0052] The cooling tower 31 provided in the recirculated flue gas branch line 30C separates and discharges moisture (H2O) from the recirculated flue gas. As a result, the recirculated flue gas flowing through the recirculated flue gas branch line 30C is supplied to the wind box 7c as dehydrated recirculated flue gas (hereinafter, dehydrated recirculated flue gas).

[0053] In addition, the recirculated flue gas branch line 30C is provided with a PSA section 32 as a carbon dioxide separation means or a carbon dioxide capture means. The PSA section 32 separates a portion of carbon dioxide (CO2) from the dehydrated recirculated flue gas, for example, by pressure swing adsorption (PSA), and then exhausts or captures the separated CO2. Note that a nitrogen PSA section may be separately provided that separates and exhausts nitrogen (N2) from the dehydrated recirculated flue gas to increase the CO2 concentration in the dehydrated recirculated flue gas.

[0054] Furthermore, the recirculation exhaust gas branch line 30C is provided with a recirculation exhaust gas flow rate adjustment unit 34c, which is made of, for example, a damper or a valve, for adjusting the flow rate, corresponding to the wind box 7c. The recirculation exhaust gas flow rate adjustment unit 34c adjusts the flow rate of the recirculation exhaust gas supplied to the wind box 7c. With the above configuration, the recirculation exhaust gas branch line 30C branched off at the front stage of the cooling tower 31 supplies the dehydrated recirculation exhaust gas to the wind box 7c and the post-combustion grate 5c while the flow rate is adjusted by the recirculation exhaust gas flow rate adjustment unit 34c. In addition, when the ash carbonation grate 5d is provided, the dehydrated recirculation exhaust gas is also supplied to the ash carbonation grate 5d.

[0055] On the other hand, the recirculation exhaust gas branch line 30A has branch lines 30a and 30b which are further branched in correspondence with the wind boxes 7a and 7b, respectively. Recirculation exhaust gas flow rate adjustment units 34a and 34b, which are formed of, for example, dampers or valves, are provided in correspondence with the branch lines 30a and 30b, respectively. The recirculation exhaust gas flow rate adjustment units 34a, 34b, and 34c described above constitute the recirculation exhaust gas flow rate adjustment unit 34 as a recirculation exhaust gas flow rate adjustment means for adjusting the flow rate.

[0056] An oxygen supply line 35 capable of supplying gas containing oxygen (O2) as a main component, i.e., gas with an O2 concentration of 50% or more (hereinafter, O2 gas), is connected to the branch lines 30a and 30b of the recirculation exhaust gas branch line 30A. A blower 36 is provided in the oxygen supply line 35. The oxygen supply line 35 has branch lines 35a and 35b that are branched to be able to supply O2 gas corresponding to the respective wind boxes 7a and 7b.

[0057] The branch lines 35a and 35b are connected to the branch lines 30a and 30b, respectively. The oxygen supply line 35 constituting the oxygen supply means is configured to be able to supply oxygen (O2) to each of the branch lines 30a and 30b. As a result, the recirculated exhaust gas and O2 gas are mixed by the branch lines 30a and 30b and the branch lines 35a and 35b. In this case, the recirculated exhaust gas branch line 30A and the oxygen supply line 35 constitute the gas mixing means. The branch lines 35a and 35b of the oxygen supply line 35 may be directly connected to the wind boxes 7a and 7b, respectively, to mix the recirculated exhaust gas and O2 gas in the wind boxes 7a and 7b. In this case, the wind boxes 7 (7a and 7b), the recirculated exhaust gas branch line 30A, and the oxygen supply line 35 constitute the gas mixing means.

[0058] In addition, the oxygen supply line 35 is provided with an oxygen flow rate regulator 37, which is an oxygen flow rate regulator consisting of, for example, a damper or a valve, for regulating the flow rate. The oxygen flow rate regulator 37 is composed of oxygen flow rate regulators 37a and 37b. The oxygen flow rate regulators 37a and 37b are provided on the branch lines 35a and 35b of the oxygen supply line 35, respectively.

[0059] The mixture ratio of the recirculated exhaust gas supplied through the recirculated exhaust gas branch line 30A and the O2 gas supplied through the oxygen supply line 35 can be controlled by adjusting the flow rate by the recirculated exhaust gas flow rate adjusting units 34a and 34b and by adjusting the flow rate by the oxygen flow rate adjusting unit 37. The recirculated exhaust gas flow rate adjusting unit 34 and the oxygen flow rate adjusting unit 37 constitute a carbon dioxide concentration adjusting means for adjusting the CO2 concentration in the O2 / CO2 mixed gas, which is a mixed gas of the recirculated exhaust gas and oxygen (O2). In this embodiment, the carbon dioxide concentration adjusting means can adjust the CO2 concentration of the O2 / CO2 mixed gas supplied to each of the drying grate 5a, the combustion grate 5b, and the post-combustion grate 5c to typically 50% or more, preferably 60% or more, and more preferably 80% or more.

[0060] With the above-mentioned configuration, the gas mainly composed of O2 and the recirculated exhaust gas with high concentration of CO2 are mixed in the branch lines 30a, 30b, 35a, 35b below the grate 5, respectively, and are selectively supplied to the drying grate 5a and the combustion grate 5b, respectively, as an O2 / CO2 mixed gas, which is a combustion-supporting gas. Note that the gas mainly composed of O2 and the recirculated exhaust gas with high concentration of CO2 may be mixed in the wind boxes 7a, 7b to generate an O2 / CO2 mixed gas, which is a combustion-supporting gas.

[0061] A temperature sensor 38 is provided as a temperature measuring means capable of measuring the temperature of the ash carbonation region above the post-combustion grate 5c or the ash carbonation grate 5d on the downstream side along the transport direction of the waste W in the combustion chamber 2. The temperature sensor 38 is configured to be capable of measuring the temperature inside the furnace at the position where it is installed. The temperature sensor 38 transmits the measured sensor value such as the furnace temperature to the control unit 50.

[0062] Specifically, the control unit 50 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 50 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 50 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.

[0063] (Waste incineration method) Next, the waste incineration method in the waste incineration apparatus according to this embodiment, particularly the case where dehydrated recirculation exhaust gas is supplied from the wind box 7c below the post-combustion grate 5c, will be described. Note that in the following description, in the case where the ash carbonation grate 5d is further provided, the post-combustion grate 5c and the corresponding parts can be replaced with the ash carbonation grate 5d and the corresponding parts to the extent possible. In other words, the "post-combustion grate 5c" can be replaced with "post-combustion grate 5c and ash carbonation grate 5d", etc.

[0064] That is, first, when the waste W is fed into the waste inlet 3, the waste W is extruded by an extruder (not shown) and fed to the drying grate 5a. The waste W moves from the drying grate 5a to the combustion grate 5b and then to the post-combustion grate 5c by the operation of the drying grate 5a, the combustion grate 5b, and the post-combustion grate 5c, successively, forming a layer of the waste W on the grate 5.

[0065] The drying grate 5a and the combustion grate 5b are respectively supplied with O2 / CO2 mixed gas as a combustion supporting gas through the branch lines 30a, 35a, 30b, and 35b. Note that primary air may be further supplied from the primary air supply line (not shown) during start-up and other times. The post-combustion grate 5c is supplied with CO2 dehydrated gas, which is the dehydrated recirculated exhaust gas and contains CO2 as a main component, through the recirculated exhaust gas branch line 30C. As a result, the waste W is dried and burned on the drying grate 5a and the combustion grate 5b, and is post-combusted in the post-combustion grate 5c to become incineration ash, which is then carbonized and discharged from the incineration ash discharge section 6.

[0066] In this embodiment, the dehydrated recirculated exhaust gas is supplied from below the post-combustion grate 5c, and the non-dehydrated recirculated exhaust gas (hereinafter, referred to as the wet recirculated exhaust gas as necessary) is supplied from below the drying grate 5a and the combustion grate 5b. Here, the recirculated exhaust gas is dehydrated to remove water vapor, and the CO2 concentration in the recirculated exhaust gas increases. Since the dehydrated recirculated exhaust gas, which has been dried and has an increased CO2 concentration, can be supplied to the incineration ash layer on the post-combustion grate 5c, the carbonation of the incineration ash and the fixation of lead (Pb) on the post-combustion grate 5c can be promoted. On the other hand, the non-dehydrated wet recirculated exhaust gas is supplied to the drying grate 5a and the combustion grate 5b. Since the wet recirculated exhaust gas can be supplied to the burning waste W in this way, the moisture (water vapor) contained in the wet recirculated exhaust gas can promote the reforming of the pyrolysis gas in the waste W on the drying grate 5a and the combustion grate 5b, and the complete combustion can be improved.

[0067] (Adjustment of the temperature of the incineration ash in the ash carbonation area) In addition, the control unit 50 can adjust the temperature of the ash carbonation region by controlling the recirculation exhaust gas flow rate adjustment unit 34c to adjust the flow rate of the recirculation exhaust gas based on the sensor value (temperature measurement value) input from the temperature sensor 38. It is preferable to adjust the temperature in the ash carbonation region to, for example, 400°C or more and 600°C or less by controlling the recirculation exhaust gas flow rate adjustment unit 34c by the control unit 50. By controlling the temperature of the incineration ash layer on the post-combustion grate 5c or the ash carbonation grate 5d to a range of 400 to 600°C, the reaction in which CaO or Ca(OH)2 contained in the incineration ash reacts with the high concentration of CO2 in the recirculation exhaust gas to generate CaCO3 is promoted, and the process of changing the pH of the incineration ash to a low pH range in which lead is sparingly soluble can be promoted. Therefore, it is more preferable to set the temperature of the incineration ash layer in the ash carbonation region to a range of 400 to 600°C, because the reaction to generate CaCO3 proceeds with high efficiency.

[0068] (Modification) Next, a modified example of the waste incineration apparatus according to the present embodiment will be described. Fig. 2 is a diagram showing the configuration of the grate portion of the waste incineration apparatus according to the modified example of the present embodiment. As shown in Fig. 2, in the waste incineration apparatus according to the modified example, ash carbonation grates 5d and 5e are provided on the downstream side of the post-combustion grate 5c along the direction of transport of the waste W in the grate 5 in the waste incineration apparatus according to the above-mentioned embodiment.

[0069] A wind box 7d, which is different from the wind boxes 7a, 7b, and 7c, is provided below the ash carbonation grate 5d. A branch line 30d, which is further branched from the recirculation flue gas branch line 30C, is connected to the wind box 7d, and CO2 dehydrated gas, which is dehydrated recirculation flue gas, is supplied to the wind box 7d. A recirculation flue gas flow rate regulator (not shown) is provided in the branch line 30d, and the flow rate of the dehydrated recirculation flue gas supplied to the ash carbonation grate 5d through the wind box 7d can be adjusted. The dehydrated recirculation flue gas is a CO2 dehydrated gas that has been dehydrated and has an improved CO2 concentration. In this case, the recirculation flue gas flow rate regulator provided in the branch line 30d constitutes a carbon dioxide flow rate regulator that regulates the flow rate of CO2 in the recirculation flue gas supplied to the ash carbonation grate 5d. The area above the ash carbonation grate 5d becomes an ash carbonation area where carbonation processing is performed after the waste W is turned into incineration ash.

[0070] In addition, it is also possible to install an ash carbonation grate 5e, which is configured in the same manner as the above-mentioned ash carbonation grate 5d, at a lower position, separated by a predetermined step, for example a step of about 1 m, from at least the preceding post-combustion grate 5c.

[0071] As described above, by providing the ash carbonation grates 5d, 5e in the combustion chamber 2 and forming a carbonation region, the incineration ash on the ash carbonation grates 5d, 5e can be sufficiently detoxified downstream of the post-combustion grate 5c. Therefore, there is no need to perform another detoxification process after discharging the incineration ash, and the processing cost can be reduced. In addition, by providing an ash carbonation region on the post-combustion grate 5c or the ash carbonation grates 5d, 5e in the combustion chamber 2, the carbonation of the incineration ash and the fixation of heavy metals such as Pb are less susceptible to the influence of radiation caused by combustion occurring in the drying grate 5a and the combustion grate 5b.

[0072] According to the embodiment described above, in the front stage along the flow direction of the recirculated exhaust gas, the recirculated exhaust gas is branched into at least two systems, and the recirculated exhaust gas flowing through one system is dehydrated by a water separation means and then supplied to the post-combustion grate 5c and the ash carbonation grate 5d, 5e, so that the CO2 concentration of the dehydrated recirculated exhaust gas can be improved, and in the carbonation treatment performed on the incineration ash on the post-combustion grate 5c and the ash carbonation grate 5d, 5e, the CO2 contained in the recirculated exhaust gas at high concentrations reacts with the Pb contained in the incineration ash to form a carbon oxide, thereby promoting the insolubility of the ash, and the detoxification treatment of the incineration ash can be efficiently promoted in the combustion chamber 2 of the waste incinerator 1. Therefore, the carbonation of the incineration ash and the fixation of heavy metals such as Pb can be promoted in the waste incinerator 1, and since it is not necessary to perform another detoxification treatment after discharging the incineration ash, the treatment cost can be reduced.

[0073] 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.

[0074] For example, in the above-mentioned embodiment, an incinerator employing a counterflow furnace as the waste incinerator 1 has been described as an example, but an incinerator employing a double-flow furnace may also be used.

[0075] For example, a dehydrated O2 / CO2 mixed gas from which moisture has been removed and a moist O2 / CO2 mixed gas from which moisture has not been actively removed may be further mixed to produce an O2 / CO2 mixed gas with an adjusted moisture concentration, and the O2 / CO2 mixed gas may be recirculated into the furnace.

[0076] For example, a carbon dioxide concentration measuring means for measuring the CO2 concentration of the dehydrated recirculated exhaust gas may be provided in the space below the post-combustion grate 5c or above the post-combustion grate 5c, and the control unit 50 may control the recirculated exhaust gas flow rate adjustment means based on the measured CO2 concentration value so that the carbon dioxide concentration of the dehydrated recirculated exhaust gas is within a predetermined range. [Explanation of symbols]

[0077] 1 Waste incinerator 2. Combustion chamber 3 Waste input port 4. Boiler 4A Exhaust section 5. Grate 5a drying grate 5b Combustion grate 5c Post-combustion grate 5d,5e Ash carbonation grate 6. Ash discharge section 7,7a,7b,7c,7d 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 30A, 30C Recirculation exhaust gas branch line 30a, 30b, 30d, 35a, 35b Branch lines 31 Cooling Tower 32 PSA Department 34,34a,34b,34c Recirculation exhaust gas flow rate adjustment section 35 Oxygen supply line 36 Blower 37,37a,37b Oxygen flow rate adjustment section 38 Temperature Sensor 50 Control section

Claims

1. A waste incineration apparatus having an incinerator that burns waste and discharges it as incineration ash, a combustion chamber for burning the waste; 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 combustion chamber; A water separation means configured to dehydrate the recirculated exhaust gas; An oxygen supply means configured to be able to supply a gas containing oxygen as a main component to the combustion chamber; 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 combustion chamber has, along a transport direction of the waste, a drying grate in which initial combustion is performed after the waste is dried, a combustion grate in which solid matter in the waste and generated flammable gas are burned, and a post-combustion grate in which unburned matter in the waste is burned to produce the incineration ash, a branching portion for further branching the recirculated exhaust gas is provided on the upstream side of the water separating means along a flow direction of the recirculated exhaust gas, One of the recirculated exhaust gases branched at the branching section is supplied to the water separation means so as to be dehydrated, The one of the recirculated exhaust gases dehydrated by the water separation means is configured to be able to be supplied to the post-combustion grate, and the other of the recirculated exhaust gases is mixed with the gas containing oxygen as a main component by the gas mixing means to generate a mixed gas, which is then configured to be able to be supplied to the drying grate and the combustion grate. Waste incineration equipment.

2. A control unit configured to be able to control the flow rate of the recirculated exhaust gas, The control unit is Based on a flow rate on the upstream side of the branch portion along the flow direction of the recirculated exhaust gas, the flow rate ratio of the one recirculated exhaust gas is controlled to 15% or more and 25% or less, and the flow rate ratio of the other recirculated exhaust gas is controlled to 75% or more and 85% or less.

2. A waste incineration apparatus according to claim 1.

3. An ash carbonation grate is provided downstream of the post-combustion grate in the waste transport direction, in which the incineration ash is carbonated; The one of the recirculated exhaust gases dehydrated by the water separation means is configured to be able to be supplied to the post-combustion grate and the ash carbonation grate.

2. A waste incineration apparatus according to claim 1.

4. The ash carbonation grate is disposed at a lower position than the post-combustion grate across a step.

4. A waste incineration apparatus according to claim 3.

5. The temperature in the post-combustion grate is adjustable to 400° C. or higher and 600° C. or lower.

2. A waste incineration apparatus according to claim 1.

6. The water separator further comprises a carbon dioxide separator for separating and removing a part of the carbon dioxide contained in the one of the recirculated exhaust gases dehydrated by the water separator.

2. A waste incineration apparatus according to claim 1.

7. A waste incineration method for incinerating waste using an incinerator that burns waste and discharges it as incineration ash, comprising: The incinerator comprises a combustion chamber for burning the waste, The combustion chamber has, along a transport direction of the waste, an initial combustion region in which initial combustion is carried out after the waste is dried, a main combustion region in which solid matter in the waste and generated flammable gas are burned, and a post-combustion region in which unburned matter in the waste is burned to produce the incineration ash, After at least a portion of the exhaust gas from the incinerator is branched off as a recirculated exhaust gas by a recirculated exhaust gas supply means, the recirculated exhaust gas is further branched off into one recirculated exhaust gas and the other recirculated exhaust gas, One of the recirculated exhaust gases is dehydrated and then supplied to the post-combustion zone in the combustion chamber, while the other recirculated exhaust gas is mixed with a gas containing oxygen as a main component by an oxygen supply means to generate a mixed gas, and the mixed gas is supplied to the initial combustion zone and the main combustion zone in the combustion chamber. Waste incineration methods.

8. A control unit configured to be able to control the flow rate of the recirculated exhaust gas, Based on a flow rate on the upstream side of the branch portion along the flow direction of the recirculated exhaust gas, the flow rate ratio of the one recirculated exhaust gas is controlled to 15% or more and 25% or less, and the flow rate ratio of the other recirculated exhaust gas is controlled to 75% or more and 85% or less.

8. The waste incineration method according to claim 7.

9. An ash carbonation zone in which the incineration ash is carbonated is provided downstream of the post-combustion zone along the direction of transport of the waste, The dehydrated recirculated exhaust gas is supplied to the post-combustion zone and the ash carbonation zone.

8. The waste incineration method according to claim 7.

10. The ash carbonation zone is located at a lower position than the post-combustion zone.

10. The waste incineration method according to claim 9.

11. The temperature in the post-combustion zone is adjusted to 400° C. or higher and 600° C. or lower.

8. The waste incineration method according to claim 7.

12. A part of the carbon dioxide contained in the dehydrated recirculated exhaust gas is separated and removed.

8. The waste incineration method according to claim 7.

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