Incineration ash storage device

Abstract

To suppress elution of heavy metals by retaining water in incineration ash.SOLUTION: An incineration ash storage device according to the present invention is the incineration ash storage device which comprises a storage tank that stores incineration ash discharged from a waste incinerator, and in which the incineration ash is supplied into the storage tank from an upper part of the storage tank and the incineration ash is discharged from a lower part of the storage tank, the relative humidity inside the storage tank is maintained at a predetermined relative humidity or higher, and the incineration ash that has been stored in the storage tank for more than a predetermined number of days is discharged. Since the incineration ash is retained in the incineration ash storage device until the predetermined number of days elapses, sufficient reaction time between the water and the incineration ash is ensured, the water and the incineration ash are allowed to react with each other, and elution of heavy metals can be suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an incineration ash storage device. [Background technology]

[0002] An example of an invention that suppresses the elution of heavy metals contained in incineration ash discharged from an incinerator is the incineration ash treatment device disclosed in Patent Document 1. This incineration ash treatment device stores the incineration ash discharged from the incinerator in an ash discharge device and supplies the stored incineration ash to a belt conveyor. The incineration ash treatment device sprays water from a nozzle onto the incineration ash on the belt conveyor, and then blows in incineration exhaust gas onto the incineration ash that has been sprayed with water. The spraying of water suppresses the elution of heavy metals from the incineration ash, and the blowing of incineration exhaust gas causes it to be carbonated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-30121 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to prevent the elution of heavy metals from incineration ash, the incineration ash needs to retain water, but in the invention of Patent Document 1, water is sprayed onto the incineration ash on a belt conveyor, and then carbon dioxide is blown into the incineration ash to dry it, so the water is not retained for a sufficient period of time, and there is a risk that the elution of heavy metals cannot be prevented. Furthermore, the incineration ash to which water has been added is stored in an incineration ash storage facility, but in the incineration ash storage facility, the water evaporates from the incineration ash, causing it to dry, so the incineration ash cannot retain water and the elution of heavy metals cannot be prevented.

[0005] The present invention has been made in view of the above, and has as its object to retain water in incineration ash and suppress the elution of heavy metals. [Means for solving the problem]

[0006] An incineration ash storage device according to one aspect of the present invention is an incineration ash storage device that includes a storage tank for storing incineration ash discharged from a waste incinerator, wherein the incineration ash is supplied into the storage tank from the top of the storage tank and discharged from the bottom of the storage tank, the relative humidity inside the storage tank is maintained at or above a predetermined relative humidity, and the incineration ash that has been stored in the storage tank for more than a predetermined number of days is discharged.

[0007] The incineration ash storage device according to one aspect of the present invention may further include a water supply means for supplying water to the incineration ash.

[0008] In addition, the incineration ash storage device according to one aspect of the present invention may be provided with a measuring means for measuring a predetermined measurement object, and a control means for controlling the water supply means in accordance with the measurement results of the measuring means to control the amount of water supplied to the incineration ash.

[0009] In addition, in an incineration ash storage device according to one aspect of the present invention, the measuring means may measure the relative humidity in the storage tank, and the control means may control the water supply means so that the relative humidity is equal to or higher than a predetermined relative humidity.

[0010] In addition, the incineration ash storage device according to one aspect of the present invention may be configured so that the incineration ash to which water has been added is supplied from an upper portion of the storage tank to the inside of the storage tank.

[0011] The incineration ash storage device according to one aspect of the present invention may further include a discharge section for discharging water present in a lower portion of the storage tank.

[0012] Furthermore, the incineration ash storage device according to one aspect of the present invention may be provided with an agitating blade that agitates the incineration ash in the storage tank. [Effects of the Invention]

[0013] According to the present invention, water can be retained in the incineration ash, thereby suppressing the elution of heavy metals. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing the configuration of a waste incineration system. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below. In addition, in the description of the drawings, the same or corresponding elements are appropriately designated by the same reference numerals. Furthermore, it should be noted that the drawings are schematic, and the dimensional relationships between the elements may differ from the actual ones. There may also be parts in which the dimensional relationships and ratios between the elements differ from one another.

[0016] 1 is a diagram showing the configuration of a waste incineration system 1000 according to an embodiment of the present invention. The waste incinerator 1 is, for example, a grate-type incinerator, and is equipped with a combustion chamber 2 and an inlet 3. The inlet 3 is an inlet for feeding waste W, such as industrial waste or household garbage, into the combustion chamber 2, and is located above the combustion chamber 2 on the upstream side of the flow of the waste W within the combustion chamber 2. An extruder (not shown) is disposed below the inlet 3, which pushes the fed waste W into the combustion chamber 2, and the waste W fed into the inlet 3 is pushed into the combustion chamber 2 by the extruder.

[0017] A grate 5 is provided at the bottom of the combustion chamber 2 for burning the waste W as it moves. The grate 5 is composed of a drying grate 5a, a combustion grate 5b, and a post-combustion grate 5c, and is arranged in this order from the inlet 3 side in the direction of movement of the waste W. The drying grate 5a mainly dries, ignites, and initially combusts the waste W. The combustion grate 5b mainly pyrolyzes and partially oxidizes the waste W. The combustion grate 5b also combusts the solids and pyrolysis gases generated by pyrolysis, including carbon monoxide and hydrocarbons. The post-combustion grate 5c performs post-combustion, completely combusting the unburned waste W. This post-combustion forms a layer of incineration ash on the post-combustion grate 5c after complete combustion.

[0018] A boiler 4 is connected above the combustion chamber 2 on the downstream side in the flow direction of the waste W. Near the inlet of the boiler 4, a secondary combustion chamber 11 is formed which burns unburned gas in the gas discharged from the combustion chamber 2. Secondary combustion gas is blown into the secondary combustion chamber 11 by a nozzle (not shown). In the secondary combustion chamber 11, unburned components in the combustion gas generated in the combustion chamber 2 are secondarily combusted by the secondary combustion gas, and the exhaust gas after secondary combustion is heat recovered by the boiler 4.

[0019] The boiler 4, which recovers heat from exhaust gas, has two bends 12 and 13 that bend the flow path of the exhaust gas. These bends 12 and 13 form, from the upstream side along the flow direction of the exhaust gas, a first radiant chamber 14, a second radiant chamber 15, and a convective heat transfer chamber 16. The first radiant chamber 14, through which exhaust gas flows from the waste incinerator 1, has an upstream portion along the flow direction of the exhaust gas that serves as the secondary combustion chamber 11. The first radiant chamber 14 and the second radiant chamber 15 are connected via the bend 12, and the lower part of the second radiant chamber 15 and the lower part of the convective heat transfer chamber 16 are connected via the bend 13. The upper end of the convective heat transfer chamber 16 is connected via a flue 21 to a dust removal device 23 composed of a bag filter or the like.

[0020] The boiler 4 has an inner wall made of a refractory wall, and the first radiant chamber 14 and the second radiant chamber 15 have heat transfer tubes (not shown) formed of piping for circulating steam that are densely arranged outside the refractory wall that forms the inner wall. The heat transfer tubes arranged outside the refractory wall and through which water flows become a radiant heat transfer surface that receives radiant heat from the exhaust gas and generates steam, and function as an evaporator.

[0021] The convection heat transfer chamber 16 has heat transfer tubes (not shown) arranged in a flag shape at the most upstream portion in the direction of exhaust gas flow. The heat transfer tubes cool the exhaust gas flowing into the convection heat transfer chamber 16, solidifying gaseous or mist-like dust components and separating them as dust from the exhaust gas. The convection heat transfer chamber 16 also includes, from the upstream side in the direction of exhaust gas flow, three superheaters 16A and an economizer 16B. The superheater 16A includes a heat transfer tube group consisting of multiple heat transfer tubes arranged horizontally and arranged in multiple vertical stages, and the heat transfer tube group functions as a convection heat transfer surface. The superheater 16A further superheats the steam generated in the first radiation chamber 14 and the second radiation chamber 15 through heat exchange with the exhaust gas, producing high-temperature, high-pressure superheated steam.

[0022] The economizer 16B is provided downstream of the superheater 16A in the direction of exhaust gas flow, and is provided with heat transfer tubes (not shown). Steam generated in the boiler 4 and used to drive a steam turbine (not shown) is condensed in a condenser (not shown) and flows through the heat transfer tubes of the economizer 16B. The condensate flowing through the heat transfer tubes of the economizer 16B is heated by the heat retained in the exhaust gas after the steam is superheated by the superheater 16A, and the heated water is supplied to the heat transfer tubes of the first radiant chamber 14 and the second radiant chamber 15, which function as evaporators. The economizer 16B may be provided outside the boiler 4, downstream of the boiler 4 in the direction of exhaust gas flow, rather than within the convection heat transfer chamber 16. Alternatively, both an economizer inside the boiler 4 and an economizer outside the boiler 4 may be provided.

[0023] The exhaust gas from which heat has been recovered by the boiler 4 flows to a temperature reducing tower 17. The temperature reducing tower 17 sprays water onto the exhaust gas to reduce the temperature of the exhaust gas to 200°C or less. The exhaust gas whose temperature has been reduced in the temperature reducing tower 17 flows through a flue 21 to a dust removal device 23, which is, for example, a bag filter.

[0024] In the flue 21, chemicals such as hydrated lime and activated carbon are injected into the flue gas from a chemical supply device 22. By injecting the chemicals into the flue gas, the chemicals bind to pollutants such as hydrogen chloride and sulfur oxides contained in the flue gas.

[0025] The dust remover 23 removes dust by capturing chemicals that combine with dust and pollutants contained in the exhaust gas that has flowed through the flue 21. An induced draft fan 24 is connected to the dust remover 23. The induced draft fan 24 draws the exhaust gas from which dust has been removed from the dust remover 23. The exhaust gas drawn from the dust remover 23 by the induced draft fan 24 is sent to a chimney 25 and released into the atmosphere.

[0026] The wind boxes 7a to 7c are provided in the lower part of the combustion chamber 2. Specifically, the wind box 7a is provided below the drying grate 5a, the wind box 7b is provided below the combustion grate 5b, and the wind box 7c is provided below the post-combustion grate 5c. A supply line 31a for supplying primary air used in the combustion of the waste W is provided below the wind box 7a, a supply line 31b for supplying primary air is provided below the wind box 7b, and a supply line 31c for supplying primary air is provided below the wind box 7c. The wind box 7a supplies the primary air supplied through the supply line 31a to the drying grate 5a, the wind box 7b supplies the primary air supplied through the supply line 31b to the combustion grate 5b, and the wind box 7c supplies the primary air supplied through the supply line 31c to the post-combustion grate 5c.

[0027] Supply line 31a is provided with a damper 32a that adjusts the amount of primary air supplied to wind box 7a, and supply line 31b is provided with a damper 32b that adjusts the amount of primary air supplied to wind box 7b. Fan 34 is a device that sends primary air to supply lines 31a, 31b, and 31c. Heating device 33 is a device that heats the primary air discharged from fan 34. Heating device 33 is controlled by a control device (not shown) to control the temperature of the primary air. Damper 32c adjusts the amount of primary air sent to supply lines 31a, 31b, and 31c. Dampers 32a, 32b, and 32c are controlled by a control device (not shown), and the amount of primary air flowing through each damper can be adjusted independently.

[0028] Primary air supplied from the blower 34 passes through the heating device 33, the supply pipe 31 for supplying primary air, and the damper 32c before being branched. A portion of the branched primary air is supplied to the drying grate 5a via the damper 32a and the supply line 31a, and a portion of the branched primary air is supplied to the combustion grate 5b via the damper 32b and the supply line 31b. The remainder of the branched primary air is supplied to the post-combustion grate 5c via the supply line 31c. The primary air supplied from below the grate 5 is supplied to the combustion chamber 2 to dry, agitate, and burn the waste W, and also cools the grate 5.

[0029] The incineration ash AS obtained by combustion in the post-combustion grate 5c is sent from the post-combustion grate 5c to a discharge section 6 provided downstream of the flow of waste W. The discharge section 6 is provided with a flapper 6a that is driven to open and close by a drive device (not shown). When the flapper 6a is closed, the incineration ash AS accumulates on the flapper 6a, and when the flapper 6a is opened, the incineration ash AS accumulated on the flapper 6a is sent to the incineration ash treatment system 100.

[0030] The incineration ash treatment system 100 comprises a cooling device 40, a transport device 50, an ash storage tank 60, a supply device 70, a control device 80, and a sensor 81. The cooling device 40 comprises a water tank 41 in which cooling water is stored. The water tank 41 receives the incineration ash AS that falls from the discharge section 6, and by immersing the received incineration ash AS in the cooling water in the water tank 41, the incineration ash AS is hydrated and cooled. An ash outlet 42 is formed at one end of the water tank 41. An extrusion device (not shown) is provided at the other end of the water tank 41. The extrusion device pushes the incineration ash AS that has accumulated at the bottom of the water tank 41 toward the ash outlet 42.

[0031] The incineration ash AS pushed out from the ash outlet 42 is sent to the conveying device 50. The conveying device 50 is, for example, a belt conveyor, and conveys the incineration ash AS pushed out from the ash outlet 42 to the ash storage tank 60. The ash storage tank 60, which is an example of an incineration ash storage device, stores the incineration ash AS sent by the conveying device 50. The incineration ash AS is loaded into the ash storage tank 60 from the top, and the stored incineration ash AS is discharged from the bottom. The incineration ash AS discharged from the ash storage tank 60 is loaded onto the bed of a truck TR and transported by the truck TR to a final disposal site.

[0032] The supply device 70 and the nozzle 61 are an example of a water supply means for supplying water to the incineration ash AS in the ash storage tank 60. The water supplied by the supply device 70 is sprayed onto the incineration ash AS through the nozzle 61 installed in the ash storage tank 60. The nozzle 61 is installed, for example, at the upper end of the ash storage tank 60, near the upper end of the incineration ash AS stored in the ash storage tank 60, or near the vertical center of the incineration ash AS stored in the ash storage tank 60. However, a configuration in which at least one of three nozzles 61 is installed may also be used. Note that spraying water onto the incineration ash AS may result in an excess of water relative to the incineration ash AS. To deal with such cases, the ash storage tank 60 may be equipped with a discharge section for discharging water accumulated at the bottom. The ash storage tank 60 may also be equipped with a lid on its top to prevent the incineration ash AS from drying out.

[0033] The sensor 81, which is an example of a measuring means, is a sensor that measures the relative humidity in the air in the ash storage tank 60 and is installed in the ash storage tank 60. The relative humidity measurement results by the sensor 81 are sent to the control device 80. The control device 80, which is an example of a control means, is a device that controls the supply device 70. The control device 80 controls the supply device 70 in accordance with the measurement results of the sensor 81, and controls the injection of water onto the incineration ash AS. For example, the control device 80 controls the supply device 70 to inject water from the nozzle 61 so that the relative humidity becomes equal to or higher than a predetermined relative humidity.

[0034] The incineration ash AS stored in the ash storage tank 60 is stored inside the ash storage tank 60 for at least four days before being discharged onto the truck TR. For example, if the incineration ash AS is stored in the ash storage tank 60 in the following order from bottom to top: incineration ash AS that has been stored for four days, incineration ash AS that has been stored for three days, incineration ash AS that has been stored for two days, incineration ash AS that has been stored for one day, and incineration ash AS that has been stored for less than one day, the incineration ash AS that has been stored for four days will be discharged onto the truck TR, and the incineration ash AS that has been stored for three days will be discharged the following day.

[0035] According to this embodiment, water is sprayed onto the incineration ash AS inside the ash storage tank 60, and the incineration ash AS does not dry out, allowing the incineration ash AS to retain water and suppress the elution of heavy metals. Also, in this embodiment, the incineration ash AS at the bottom of the ash storage tank 60 that has been there for several days is less likely to dry out because there is incineration ash AS containing water above it, and this allows the water to be retained and the elution of heavy metals to be suppressed. Also, in this embodiment, the incineration ash AS is retained in the ash storage tank 60 for a predetermined number of days, ensuring sufficient time for the water and incineration ash AS to react, thereby suppressing the elution of heavy metals.

[0036] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be implemented in various other forms. For example, the above-described embodiments may be modified as follows to implement the present invention. The above-described embodiments and the following modifications may be combined with each other. The present invention also includes configurations in which the components of the above-described embodiments and modifications are appropriately combined. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-described embodiments and modifications, and various modifications are possible.

[0037] In the present invention, the moisture content of the incineration ash AS stored in the ash storage tank 60 may be measured by the sensor 81, and water may be injected into the incineration ash AS depending on the measurement results. In this case, when the moisture content of the ash falls below 15%, for example, the control device 80 controls the supply device 70 to inject water into the incineration ash AS.

[0038] In the present invention, by retaining water in the incineration ash AS, cement compounds such as calcium silicate hydrate are produced. Furthermore, since the incineration ash AS contains aluminum, when water comes into contact with the incineration ash AS, hydrogen is generated through the hydration reaction of the aluminum, resulting in the production of cement compounds such as calcium aluminate hydrate. These cement compounds capture the heavy metals contained in the incineration ash AS, thereby suppressing their leaching. Furthermore, in the present invention, the incineration ash AS is retained in the ash storage tank 60 for a predetermined number of days, ensuring sufficient reaction time for the production of cement compounds. This prevents the incineration ash AS from drying out and fully suppresses the leaching of heavy metals. In the present invention, the hydrogen concentration may be measured by a sensor 81, and water may be injected into the incineration ash AS based on the measurement results. In this case, when the hydrogen concentration falls below a predetermined threshold, for example, the control device 80 controls the supply device 70 to inject water into the incineration ash AS.

[0039] In addition, in the present invention, the incineration ash AS inside the ash storage tank 60 may be collected and measured using an X-ray diffraction device, and the control device 80 may control the supply device 70 based on the measurement results. In this case, when the amount of cement compounds falls below a predetermined threshold, for example, the control device 80 controls the supply device 70 to inject water into the incineration ash AS.

[0040] In the present invention, the ash storage tank 60 may be equipped with an agitating blade for agitating the incineration ash AS. The agitating blade is preferably installed, for example, so as to agitate the upper end of the incineration ash AS stored in the ash storage tank 60. According to this modification, by agitating the incineration ash AS, the incineration ash AS can be uniformly soaked in water. The agitating blade may be driven when the incineration ash AS is charged into the ash storage tank 60, or may be driven at a predetermined interval, for example, once every half day.

[0041] In the present invention, water may be sprayed onto the incineration ash AS in the transport device 50. Also, in the present invention, water vapor may be sprayed onto the incineration ash AS instead of water. Also, in the present invention, the incineration ash AS pushed out from the cooling device 40 contains water, and the incineration ash AS containing water is sequentially stored in the ash storage tank 60, so it is not necessary to spray water onto the incineration ash AS in the ash storage tank 60.

[0042] In FIG. 1, the ash storage tank 60 has a vertically long shape, but it is not limited to a vertically long shape and may have other shapes as long as the incineration ash AS is stacked one on top of the other. [Explanation of symbols]

[0043] 1. Waste incinerator 2. Combustion chamber 5. Grate 6 Discharge section 40 Cooling device 50 Conveyor 60 Ash storage tank 70 Feeding device 80 Control device 81 Sensors 100 Incineration ash treatment system 1000 Waste Incineration System

Claims

1. An incineration ash storage device having a storage tank for storing incineration ash discharged from a waste incinerator, The incineration ash is supplied into the storage tank from the upper part of the storage tank, and the incineration ash is discharged from the lower part of the storage tank, The relative humidity inside the storage tank is maintained at a predetermined relative humidity or higher, and the incineration ash that has been stored in the storage tank for more than the predetermined number of days is discharged. Incineration ash storage device.

2. A water supply means for supplying water to the incineration ash is provided. The incineration ash storage device according to claim 1.

3. a measuring means for measuring a predetermined measurement object; A control means for controlling the water supply means in accordance with the measurement result of the measuring means to control the amount of water supplied to the incineration ash; The incineration ash storage device according to claim 2, comprising:

4. the measuring means measures the relative humidity in the storage tank; The control means controls the water supply means so that the relative humidity is equal to or higher than a predetermined relative humidity. The incineration ash storage device according to claim 3.

5. The incineration ash to which water has been added is supplied from the top of the storage tank into the storage tank. The incineration ash storage device according to claim 1.

6. 2. The incineration ash storage device according to claim 1, further comprising a discharge section for discharging water present at a lower portion of the storage tank.

7. The incineration ash storage device according to claim 1, further comprising an agitating blade for agitating the incineration ash in the storage tank.

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