Incineration ash treatment system

Abstract

To suppress elution of heavy metals from incineration ashes at low cost and simply for a prolonged period.SOLUTION: An incineration ash treatment system includes: aluminum supply means for supplying aluminum to incineration ashes discharged from a waste incinerator; and water supply means for supplying water to the incineration ashes. By addition of aluminum and water to incineration ashes, a cement compound which is a compound of aluminum oxide and calcium oxide is formed, and lead is fixed to the cement compound, thus lead elution can be suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an incineration ash treatment system. [Background technology]

[0002] Patent Document 1 discloses, for example, a treatment method for suppressing the elution of heavy metals contained in incineration ash discharged from an incinerator. In this treatment method, water is supplied to the incineration ash to maintain the moisture content of the incineration ash at 12% by mass or higher. Furthermore, in this treatment method, the incineration ash with a moisture content of 12% by mass or higher is placed in the air or air is blown into the incineration ash, thereby bringing the incineration ash into contact with carbon dioxide in the air. Exposure of the incineration ash to water suppresses the elution of heavy metals contained in the incineration ash. Furthermore, exposure of the incineration ash to carbon dioxide converts the lead oxide contained in the incineration ash into lead carbonate, which reduces its solubility in water and makes it sparingly soluble. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-74100 Summary of the Invention [Problem to be solved by the invention]

[0004] The treatment method disclosed in Patent Document 1 requires equipment for injecting carbon dioxide into the incineration ash, which increases the cost of the equipment and makes the configuration complex. Furthermore, although the treatment method disclosed in Patent Document 1 suppresses the elution of heavy metals, its long-term stability is unknown, and there is a risk that heavy metals will be re-eluted if the acidity becomes high at the final disposal site.

[0005] The present invention has been made in view of the above, and aims to suppress the elution of heavy metals from incineration ash at low cost, simply, and for a long period of time. [Means for solving the problem]

[0006] An incineration ash treatment system according to one aspect of the present invention comprises an aluminum supply means for supplying aluminum to incineration ash discharged from a waste incinerator, and a water supply means for supplying water to the incineration ash.

[0007] In addition, the incineration ash treatment system according to one aspect of the present invention may be provided with a sensor that measures the concentration of hydrogen generated from the incineration ash to which the aluminum and water have been supplied, and a control means that controls the aluminum supply means in accordance with the concentration measured by the sensor to control the amount of aluminum supplied to the incineration ash.

[0008] In addition, the incineration ash treatment system according to one aspect of the present invention may be provided with a measuring means for measuring the amount of calcium oxide contained in the incineration ash, and a control means for controlling the amount of aluminum supplied to the incineration ash by controlling the aluminum supply means in accordance with the amount of calcium oxide measured by the measuring means.

[0009] In addition, the incineration ash treatment system according to one aspect of the present invention may be provided with a measuring means for measuring the amount of cement compounds contained in the incineration ash, and a control means for controlling the amount of aluminum supplied to the incineration ash by controlling the aluminum supply means in accordance with the amount of cement compounds measured by the measuring means. [Effects of the Invention]

[0010] According to the present invention, the elution of heavy metals from incineration ash can be suppressed at low cost, simply, and for a long period of time. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the configuration of a waste incineration system. DETAILED DESCRIPTION OF THE INVENTION

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

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] The incineration ash treatment system 100 comprises a cooling device 40, a transport device 50, an ash pit 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, which is an example of a water supply means, receives the incineration ash AS that falls from the discharge section 6 and immerses the received incineration ash AS in the cooling water in the water tank 41, thereby hydrating the incineration ash AS and cooling the incineration ash AS. 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 accumulated at the bottom of the water tank 41 toward the ash outlet 42.

[0028] 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 pit 60. The ash pit 60 stores the incineration ash AS sent by the conveying device 50. The incineration ash AS stored in the ash pit 60 is carried to the bed of a truck by a crane (not shown). The truck transports the incineration ash AS loaded on the bed to a final disposal site.

[0029] The supply device 70, an example of an aluminum supply means, is a device that supplies aluminum to the incineration ash AS. The supply device 70 supplies, for example, small pieces of aluminum foil to the incineration ash AS being transported by the transport device 50. The supply device 70 may supply aluminum to the incineration ash AS on the post-combustion grate 5c from above or from the side, or may supply aluminum to the incineration ash AS accumulated on the flapper 6a. The supply device 70 may also supply aluminum to the water tank 41 into which the incineration ash AS has been placed, or may supply aluminum to the incineration ash AS in the ash pit 60. The supply device 70 may also supply aluminum to the incineration ash AS accumulated on the flapper 6a and spray water thereon, or may supply aluminum to the incineration ash AS being transported by the transport device 50 and spray water thereon. The supply device 70 may also supply aluminum to the incineration ash AS in the ash pit 60 and spray water thereon. The supply device 70 may also supply aluminum to the incineration ash AS in the ash pit 60 and spray water thereon. The supply device 70 may also supply aluminum to aluminum powder, aluminum pellets, or an aqueous solution containing aluminum instead of aluminum foil. The supply device 70 may also supply aluminum to the incineration ash at multiple locations in the incineration ash treatment system 100.

[0030] The sensor 81 measures the hydrogen concentration in the air and is installed above the belt conveyor of the transport device 50. The sensor 81 measures the concentration of hydrogen generated from the incineration ash AS when it reacts with aluminum and water. The hydrogen concentration measurement results from the sensor 81 are sent to the control device 80. The sensor 81 may also be installed inside the cooling device 40 or the ash pit 60 to measure the concentration of hydrogen generated therein. The control device 80, which is an example of a control means, controls the supply device 70. The control device 80 controls the supply device 70 according to the measurement results of the sensor 81 to control the amount of aluminum supplied to the incineration ash AS. For example, the control device 80 controls the supply device 70 so that the amount of aluminum supplied decreases as the hydrogen concentration increases, and so that the amount of aluminum supplied increases as the hydrogen concentration decreases. The control device 80 preferably controls the amount of aluminum supplied to a maximum of 1% of the weight of the incineration ash AS.

[0031] Table 1 shows an example of the results of a lead elution test when the amount of aluminum supplied to the incineration ash AS was changed. Table 1 shows that adding aluminum and water to the incineration ash AS reduces the amount of lead eluted compared to when no aluminum and water are added. Table 1 also shows that adding aluminum and water to the incineration ash AS reduces the pH (hydrogen ion exponent) and alkaline content compared to when no aluminum and water are added.

[0032] [Table 1]

[0033] According to this embodiment, a cement compound, which is a compound of aluminum oxide and calcium oxide, is produced by the reaction of aluminum supplied from the supply device 70, calcium oxide in the incineration ash AS, and water contained in the incineration ash AS in the cooling device 40. The production of the cement compound fixes lead to the cement compound, making it possible to suppress lead elution. Furthermore, the production of the cement compound reduces calcium oxide from the incineration ash AS, making it possible to reduce the alkaline components in the incineration ash AS.

[0034] [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.

[0035] In the present invention, a lead elution test may be conducted on the incineration ash AS collected from the ash pit 60, the incineration ash AS collected from the transport device 50, or the incineration ash AS loaded onto a truck by a crane from the ash pit 60, and the control device 80 may control the supply device 70 according to the test results. In this modified example, the control device 80 controls the supply device 70 so that the amount of aluminum supplied increases as the amount of eluted lead increases, and so that the amount of aluminum supplied decreases as the amount of eluted lead decreases.

[0036] In addition, in the present invention, the incineration ash collected from the transport device 50, the incineration ash AS collected from the ash pit 60, or the incineration ash AS loaded onto a truck by a crane from the ash pit 60 may be measured with an X-ray diffraction device, and the control device 80 may control the supply device 70 based on the measurement results. In this modified example, the control device 80 controls the supply device 70 so that the amount of aluminum supplied decreases as the amount of cement compound increases, and so that the amount of aluminum supplied increases as the amount of cement compound decreases.

[0037] In addition, in the present invention, the incineration ash AS before the addition of aluminum and water may be collected from above the flapper 6a and measured with an X-ray diffraction device, and the control device 80 may control the supply device 70 based on the measurement results. In this modified example, the control device 80 controls the supply device 70 so that the amount of aluminum supplied increases as the amount of calcium oxide increases, and so that the amount of aluminum supplied decreases as the amount of calcium oxide decreases.

[0038] Furthermore, in the present invention, when measurements are made using an X-ray diffraction device, real-time measurements may be made in the incineration ash treatment system 100, and the measurement results may be sent to the control device 80 online. [Explanation of symbols]

[0039] 1. Waste incinerator 2. Combustion chamber 5. Grate 6 Discharge section 40 Cooling device 50 Conveyor 60 Ash Pit 70 Feeding device 80 Control device 81 Sensors 100 Incineration ash treatment system 1000 Waste Incineration System

Claims

1. an aluminum supply means for supplying aluminum to the incineration ash discharged from the waste incinerator; A water supply means for supplying water to the incineration ash; An incineration ash treatment system comprising:

2. a sensor for measuring the concentration of hydrogen generated from the incineration ash to which the aluminum and the water have been supplied; A control means for controlling the aluminum supply means in accordance with the concentration measured by the sensor to control the amount of aluminum supplied to the incineration ash; The incineration ash treatment system according to claim 1, comprising:

3. A measuring means for measuring the amount of calcium oxide contained in the incineration ash; a control means for controlling the aluminum supply means in accordance with the amount of calcium oxide measured by the measuring means to control the amount of aluminum to be supplied to the incineration ash; The incineration ash treatment system according to claim 1, comprising:

4. A measuring means for measuring the amount of cement compounds contained in the incineration ash; a control means for controlling the aluminum supply means in accordance with the amount of cement compound measured by the measuring means to control the amount of aluminum to be supplied to the incineration ash; The incineration ash treatment system according to claim 1, comprising:

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