Hazardous waste treatment system and hazardous waste secondary combustion device

Abstract

A hazardous waste secondary combustion device and a hazardous waste treatment system. A hazardous waste secondary combustion device (3) which makes a thermal decomposition gas generated by thermal decomposition of solid waste containing hazardous waste to be secondary combustion includes a secondary combustion furnace (4) which forms a secondary combustion chamber (40), an introduction pipe (5) which extends upward from a ceiling wall (42) of (4), and a manifold (6) which forms an air chamber (60) which supplies secondary air for secondary combustion around (5). A plurality of nozzles (8) are arranged in nozzle rows consisting of nozzles arranged on the same circumference in a form of being arranged in multiple stages in the up-down direction. The odd-numbered stage nozzle row is configured so that the blowing direction from (8) is the direction of forming a first direction cyclone flow; the even-numbered stage nozzle row is configured so that the blowing direction from (8) is the direction of forming a second direction cyclone flow opposite to the first direction, and the second direction cyclone flow cancels out the first direction cyclone flow.

Description

TECHNICAL FIELD

[0001] The present application relates to a secondary combustion device for hazardous waste and a hazardous waste treatment system including the same. BACKGROUND

[0002] Conventionally, there is known a waste treatment system including a gasification furnace that generates a thermal decomposition gas by thermally decomposing solid waste such as household garbage and factory garbage, and a secondary combustion device that makes the thermal decomposition gas to be combusted. For example, a secondary combustion device (called "re-combustion furnace" in Japanese Patent Application Publication No. 2003-202106) used for such a waste treatment system is disclosed in Japanese Patent Application Publication No. 2003-202106.

[0003] Specifically, the secondary combustion device disclosed in Japanese Patent Application Publication No. 2003-202106 includes a longitudinal secondary combustion furnace that forms a secondary combustion chamber. In more detail, the secondary combustion furnace includes a cylindrical peripheral wall that extends in the vertical direction and an upper side opening of the peripheral wall, and a conical ceiling wall that has an opening in the center. A seat plate is embedded in the opening of the ceiling wall, and a duct for the thermal decomposition gas is connected to the seat plate.

[0004] A plurality of nozzles that blow secondary air for the secondary combustion are provided in the seat plate. These nozzles are inclined in a form to form a rotational flow at the inlet of the secondary combustion chamber. SUMMARY

[0005] Problem to be solved by the Invention:

[0006] In recent years, it is studied to gasify and treat hazardous waste such as medical waste and agricultural chemical waste by thermal decomposition as well as garbage. However, since the melting point of the ash contained in the thermal decomposition gas when the hazardous waste is gasified and treated is lower than the melting point of the ash contained in the thermal decomposition gas when the garbage is gasified and treated, when the thermal decomposition gas containing the ash is combusted in the secondary combustion chamber, the molten ash adheres to the inner peripheral surface of the peripheral wall after the rotational flow is formed at the inlet of the secondary combustion chamber. On the other hand, in the case where the secondary air is blown without forming the rotational flow, the secondary air and the thermal decomposition gas are not sufficiently mixed, and the combustion of the thermal decomposition gas in the secondary combustion chamber is not sufficient.

[0007] Therefore, an object of the present application is to provide a secondary combustion device for hazardous waste that can sufficiently combust the thermal decomposition gas in the secondary combustion chamber without forming a rotational flow at the inlet of the secondary combustion chamber. Also, an object of the present application is to provide a hazardous waste treatment system including the secondary combustion device.

[0008] To solve the problem, a hazardous waste secondary combustion device according to the present invention is characterized by being a hazardous waste secondary combustion device that makes a thermal decomposition gas generated by thermal decomposition of solid waste containing hazardous waste undergo secondary combustion, and includes: a secondary combustion furnace that forms a secondary combustion chamber and includes a circumferential wall that extends in a vertical direction and a ceiling wall that covers an upper opening of the circumferential wall; an introduction pipe for the thermal decomposition gas that extends upward from the ceiling wall; and a header that forms an air chamber that supplies secondary air for secondary combustion around the introduction pipe; a plurality of nozzles that blow out the secondary air from the air chamber into the inside of the introduction pipe are arranged in nozzle rows in which nozzles arranged on the same circumference are arranged in a plurality of stages in the vertical direction, and the nozzle rows are arranged in a manner in which a first odd-stage nozzle row from the top is configured so that the blowout directions of the nozzles that make up the nozzle row are directions in which rotational flow in a first direction is formed, and a first even-stage nozzle row from the top is configured so that the blowout directions of the nozzles that make up the nozzle row are directions in which rotational flow in a second direction opposite to the first direction is formed, and the rotational flow in the second direction cancels out the rotational flow in the first direction.

[0009] According to the above structure, the rotational flow in the first direction formed by the blowout of the nozzles that make up the first odd-stage nozzle row cancels out the rotational flow in the second direction formed by the blowout of the nozzles that make up the first even-stage nozzle row. Therefore, the rotational flow can be eliminated at the outlet of the introduction pipe, that is, the inlet of the secondary combustion chamber. Also, even if the final rotational flow is eliminated, the thermal decomposition gas and the secondary air are sufficiently mixed by the rotational flow formed by each nozzle row. Thus, the thermal decomposition gas can be sufficiently combusted in the secondary combustion chamber.

[0010] Further, a hazardous waste treatment system according to the present invention is characterized by including: a fluidized bed type gasification furnace that generates a thermal decomposition gas by thermal decomposition of solid waste containing hazardous waste; the hazardous waste secondary combustion device described above that makes the thermal decomposition gas discharged from the gasification furnace undergo secondary combustion; and a boiler that recovers heat from exhaust gas after secondary combustion of the thermal decomposition gas discharged from the secondary combustion device.

[0011] According to the above structure, hazardous waste can be treated by gasification by thermal decomposition, as with garbage. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a general configuration view of a hazardous waste treatment system according to an embodiment of the present invention.

[0013] Figure 2 is a cross-sectional view of a part of a hazardous waste secondary combustion device.

[0014] Figure 3 is a cross-sectional view along the III-III line of Figure 2

[0015] Figure 4 is a cross-sectional view along the IV-IV line of Figure 2 DETAILED DESCRIPTION

[0016] Figure 1 A hazardous waste treatment system 1 according to an embodiment of the present application is shown. In this system 1, hazardous waste is treated by gasification by thermal decomposition, as with garbage.

[0017] Specifically, the system 1 includes a gasification furnace 2, a secondary combustion device 3 for hazardous waste, and a boiler 13. The gasification furnace 2 and the secondary combustion device 3 are connected by a pipe 11, and the secondary combustion device 3 and the boiler 13 are connected by a pipe 12.

[0018] The gasification furnace 2 generates a thermal decomposition gas by thermal decomposition of solid waste including hazardous waste. The solid waste can be only hazardous waste, or a mixture of hazardous waste and garbage.

[0019] In this embodiment, the gasification furnace 2 is of the fluidized bed type, and a fluidized bed 21 is formed in the lower portion of the gasification furnace 2, and a freeboard 20 is formed in the upper portion. Solid waste is fed into the gasification furnace 2 from a feeding portion 23. However, the gasification furnace 2 is not necessarily of the fluidized bed type, and can be of the kiln type.

[0020] The fluidized bed 21 is filled with a fluid medium such as sand, and a plurality of air diffusers 22 are provided at the bottom of the fluidized bed 21. Primary air is supplied to the air diffusers 22, and the primary air is ejected from the air diffusers 22. As a result, the fluid medium flows, and the solid waste is thermally decomposed while being mixed with the fluid medium, and a thermal decomposition gas is generated. The thermal decomposition gas discharged from the fluidized bed 21 is supplied to the secondary combustion device 3 through the freeboard 20 and the pipe 11.

[0021] The secondary combustion device 3 causes the thermal decomposition gas discharged from the gasification furnace 2 to undergo secondary combustion. The secondary combustion device 3 includes a secondary combustion furnace 4 that forms a secondary combustion chamber 40; a thermal decomposition gas introduction pipe 5 that is interposed between the secondary combustion furnace 4 and the pipe 11; and a header 6 that surrounds the introduction pipe 5. Details of the secondary combustion device 3 are described later.

[0022] The boiler 13 recovers heat from exhaust gas discharged from the secondary combustion device 3 after secondary combustion of the thermal decomposition gas. Specifically, the boiler 13 converts the heat energy of the exhaust gas discharged from the secondary combustion device 3 into steam, and the steam is supplied to a turbine that is coupled to a generator.

[0023] Next, the operation of the system 1 will be described with reference to the flowchart of Fig. 2.​​Figures 2 to 4 The secondary combustion device 3 will be described in detail. Also, the secondary combustion of the thermal decomposition gas in the secondary combustion chamber 40 is performed, for example, at a combustion temperature of 1100°C or higher for 2 seconds or more.

[0024] The secondary combustion furnace 4 described above includes a cylindrical peripheral wall 41 extending in the vertical direction, and a substantially conical ceiling wall 42 covering the upper side opening of the peripheral wall 41. The peripheral wall 41 and the ceiling wall 42 are made of refractory bricks or the like.

[0025] The introduction pipe 5 described above extends upward from the ceiling wall 42. A circular opening is provided in the center of the ceiling wall 42, and the introduction pipe 5 is inserted into the opening. Also, the connection structure of the introduction pipe 5 and the ceiling wall 42 is not limited to this, and can be appropriately changed.

[0026] The upper end of the introduction pipe 5 is connected to the pipe 11 described above. The inner diameter of the introduction pipe 5 is larger than the inner diameter of the intermediate portion of the pipe 11.

[0027] The pipe 11 includes a flared portion 11a flared toward the introduction pipe 5. That is, the cross-sectional area of the inside of the flared portion 11a becomes larger as it gets closer to the introduction pipe 5 (in other words, as it goes downward). The angle between the inner peripheral surface of the introduction pipe 5, which extends upward, and the inner peripheral surface of the flared portion 11a is, for example, 15 to 60 degrees. In the present embodiment, the pipe 11 is bent laterally above the flared portion 11a.

[0028] A burner 7 is disposed in the center of the introduction pipe 5. The burner 7 penetrates the bent portion of the pipe 11. The burner 7 includes a fuel injection pipe 71 that injects fuel, and an air injection pipe 72 that injects air. A flame is formed downward from the lower end of the burner 7 by the combustion of the mixture of the fuel and the air.

[0029] A ring-shaped air chamber 60 that supplies secondary air is formed around the introduction pipe 5 by a header 6. The header 6 includes a cylindrical lateral cover 61 that is larger in diameter than the introduction pipe 5, and a ring-shaped upper cover 62 that connects the upper end of the lateral cover 61 and the upper end of the introduction pipe 5.

[0030] The introduction pipe 5 is provided with a plurality of nozzles 8 that blow out secondary air from the air chamber 60 into the inside of the introduction pipe 5. The nozzles 8 are provided in the form of nozzle rows 80 in which the nozzles 8 disposed on the same circumference are arranged in a plurality of stages in the vertical direction.

[0031] In the present embodiment, the number of stages of the nozzle rows 80 is four. However, the number of stages of the nozzle rows 80 can be two or three, or five or more.

[0032] As shown in FIG. 2, the first-stage nozzle row 80A and the third-stage nozzle row 80C are each configured in such a manner that the blowout directions of the nozzles 8 that constitute the nozzle row are in the first direction (the upward direction) and the second direction (the downward direction), respectively. Figure 3 Figure 3 ​the direction of the rotational flow is counterclockwise.

[0033] On the other hand, the nozzle row 80B of the second stage and the nozzle row 80D of the fourth stage are respectively configured as shown in FIG. 2B in the following manner: the directions of the rotational flows formed by the blowouts from the nozzles 8 constituting the nozzle rows are the directions of the rotational flows of the second direction (counterclockwise) opposite to the first direction. Figure 4 Figure 4 The rotational flow of the second direction formed by the blowouts from the nozzles 8 constituting the nozzle rows 80B and 80D of the second and fourth stages cancels out the rotational flow of the first direction formed by the blowouts from the nozzles 8 constituting the nozzle rows 80A and 80C of the first and third stages. In the present embodiment, since the number of stages of the nozzle rows 80 is even, the nozzle rows 80B and 80D are mirror-symmetrical to the nozzle rows 80A and 80C.

[0034] The rotational flow of the second direction formed by the blowouts from the nozzles 8 constituting the nozzle rows 80B and 80D of the second and fourth stages cancels out the rotational flow of the first direction formed by the blowouts from the nozzles 8 constituting the nozzle rows 80A and 80C of the first and third stages. In the present embodiment, since the number of stages of the nozzle rows 80 is even, the nozzle rows 80B and 80D are mirror-symmetrical to the nozzle rows 80A and 80C.

[0035] For example, the flow rate of the secondary air blown out from each nozzle 8 is 20 m / s or more. With this configuration, the thermal decomposition gas and the secondary air can be effectively mixed by the rotational flow formed in the introduction pipe 5.

[0036] It is desirable that the number of nozzles 8 constituting each nozzle row 80 is 8 to 32. In the case where the number of nozzles 8 constituting each nozzle row 80 is less than 8, the nozzle pitch (i.e., the distance between the nozzles 8) is too large, and in the case where the number of nozzles 8 constituting each nozzle row 80 exceeds 32, the amount of the secondary air blown out from each nozzle 8 becomes small.

[0037] Further, the peripheral wall 41 of the secondary combustion furnace 4 is provided with a plurality of nozzles 9 for blowing tertiary air for protecting the peripheral wall 41 in the substantially horizontal tangential direction of the peripheral wall 41. Although not shown, the nozzles 9 are arranged in the form of nozzle rows each composed of nozzles 9 arranged on the same circumference, in a plurality of stages in the vertical direction.

[0038] In the secondary combustion device 3 of the above-described configuration, the rotational flow of the first direction formed by the blowouts from the nozzles 8 constituting the nozzle rows 80A and 80C of the first and third stages cancels out the rotational flow of the second direction formed by the blowouts from the nozzles 8 constituting the nozzle rows 80B and 80D of the second and fourth stages. Therefore, the rotational flow can be eliminated at the outlet of the introduction pipe 5 (i.e., the inlet of the secondary combustion chamber 40). Further, even if the final rotational flow is eliminated, since the rotational flow is formed by each nozzle row, the thermal decomposition gas and the secondary air are sufficiently mixed by the rotational flow. Thus, the thermal decomposition gas can be sufficiently combusted in the secondary combustion chamber 40.

[0039] ​Further, in the present embodiment, the nozzles 9 are provided to the peripheral wall 41 of the secondary combustion furnace 4, and an air film is formed along the inner circumferential surface of the peripheral wall 41. Therefore, the molten ash can be prevented from adhering to the inner circumferential surface of the peripheral wall 41.

[0040] (Modified example).

[0041] The present application is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present application.

[0042] For example, a ring plate that covers the peripheral edge portion of the upper side opening of the introduction pipe 5 can be provided, and the ring plate is connected to the pipe 11. That is, the pipe 11 can have a certain cross-sectional area in the entire length range. However, as in the above-described embodiment, the pipe 11 includes the enlarged diameter portion 11a, and the velocity of the thermal decomposition gas can be reduced in the pipe 11 on the upstream side of the introduction pipe 5.

[0043] (Summary).

[0044] The present application is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present application.

[0045] According to the above-described structure, the first direction rotational flow formed by the blow from the nozzles constituting the odd-numbered nozzle row cancels the second direction rotational flow formed by the blow from the nozzles constituting the even-numbered nozzle row. Therefore, the rotational flow can be eliminated at the outlet of the introduction pipe (i.e., the inlet of the secondary combustion chamber). Further, even if the final rotational flow is eliminated, since the rotational flow is formed by each nozzle row, the thermal decomposition gas and the secondary air are sufficiently mixed by the rotational flow. Thus, the thermal decomposition gas can be sufficiently combusted in the secondary combustion chamber.

[0046] The flow rate of the secondary air blown from the plurality of nozzles can be 20 m / s or more. According to this structure, the thermal decomposition gas and the secondary air can be effectively mixed.

[0047] For example, the number of nozzles constituting the nozzle row of each section can be 8 to 32.

[0048] The upper end of the introduction pipe can be connected to a pipe including a diameter expansion portion that expands the diameter of the introduction pipe. According to this structure, the velocity of the thermal decomposition gas can be reduced in the pipe on the upstream side of the introduction pipe.

[0049] The peripheral wall is provided with a plurality of nozzles that blow tertiary air for peripheral wall protection in the tangential direction of the peripheral wall. According to this structure, since an air film is formed along the inner peripheral surface of the peripheral wall, the attachment of molten ash to the inner peripheral surface of the peripheral wall can be suppressed.

[0050] Further, the hazardous waste treatment system of the present application is characterized by comprising: a fluidized bed type gasification furnace that generates thermal decomposition gas by thermally decomposing solid waste containing hazardous waste; a hazardous waste secondary combustion device that causes the thermal decomposition gas discharged from the gasification furnace to undergo secondary combustion; and a boiler that recovers heat from exhaust gas after secondary combustion of the thermal decomposition gas discharged from the secondary combustion device.

[0051] According to the above structure, hazardous waste can be gasification-treated by thermal decomposition, similarly to garbage.

[0052] Symbol explanation:

[0053] 1 hazardous waste treatment system

[0054] 11, 12 pipe

[0055] 13 boiler

[0056] 2 gasification furnace

[0057] 3 hazardous waste secondary combustion device

[0058] 4 secondary combustion furnace

[0059] 40 secondary combustion chamber

[0060] 41 peripheral wall

[0061] 42 ceiling wall

[0062] 5 introduction pipe

[0063] 6 header

[0064] 8 nozzle

[0065] 80 nozzle row

[0066] 9 nozzle.

Claims

1. A secondary combustion device for hazardous waste, characterized in that, is a hazardous waste secondary combustion device that makes a thermal decomposition gas generated by thermal decomposition of solid waste containing hazardous waste secondary combustion, provided with a secondary combustion furnace that forms a secondary combustion chamber and includes a circumferential wall that extends in the vertical direction in a cylindrical shape and a ceiling wall that covers an upper opening of the circumferential wall; an introduction pipe for the thermal decomposition gas that extends upward from the ceiling wall; and a header that forms an air chamber that supplies secondary air for secondary combustion around the introduction pipe, a nozzle row consisting of nozzles arranged on the same circumference is provided in the introduction pipe in a form in which the nozzle rows are arranged in multiple stages in the vertical direction, the first odd-numbered stage nozzle row from the top in the nozzle row is configured such that the blowing direction from the nozzles constituting the nozzle row is the direction in which a rotational flow in a first direction is formed, the first even-numbered stage nozzle row from the top in the nozzle row is configured such that the blowing direction from the nozzles constituting the nozzle row is the direction in which a rotational flow in a second direction opposite to the first direction is formed, and the rotational flow in the second direction cancels out the rotational flow in the first direction.

2. The hazardous waste secondary combustion device according to claim 1, characterized by The flow rate of the secondary air blown from the plurality of nozzles is 20 m / s or more.

3. The hazardous waste secondary combustion device according to claim 1 or 2, characterized by The number of nozzles constituting the nozzle row of each stage is 8 to 32.

4. The hazardous waste secondary combustion device according to claim 1 or 2, characterized by The upper end of the introduction pipe is connected to a pipe, The pipe includes a diameter expansion portion that expands the diameter of the introduction pipe.

5. The hazardous waste secondary combustion device according to claim 1 or 2, characterized by The circumferential wall is provided with a plurality of nozzles that blow tertiary air for circumferential wall protection in the tangential direction of the circumferential wall.

6. A hazardous waste treatment system characterized by, provided with a fluidized bed type gasification furnace that generates a thermal decomposition gas by thermal decomposition of solid waste containing hazardous waste; the hazardous waste secondary combustion device according to any one of claims 1 to 5 that makes the thermal decomposition gas discharged from the gasification furnace secondary combustion; and a boiler that recovers heat from exhaust gas after secondary combustion of the thermal decomposition gas discharged from the secondary combustion device.

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