Fluidized bed furnace and bed material recovery method

Abstract

To provide a fluid bed furnace which can efficiently recover valuable metal from a fluid medium stored in a furnace body, and to provide a fluid medium recovery method.SOLUTION: A fluid bed furnace incinerates or gasifies a processed object including valuable metal and includes: a furnace body in which a fluid medium 13 is stored; and an air diffusing mechanism A which sprays fluidizing gas to the fluid medium 13. The furnace body has: a furnace bottom plate 16 for supporting the fluid medium 13; and a discharge port 16a which is provided adjacent to the furnace bottom plate 16 and may discharge the fluid medium 13. The air diffusing mechanism A includes multiple air diffusing pipes 19 protruding from a surface 16c of the furnace bottom plate 16. A height H with respect to the surface 16c of the furnace bottom plate 16 in at least one of the air diffusing pipes 19 is different from a height H in the other air diffusing pipes 19.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fluidized bed furnace and a method for recovering a fluidized bed material in a fluidized bed furnace. [Background technology]

[0002] As described in Patent Document 1, known fluidized bed furnaces include fluidized bed incinerators that incinerate various types of waste with a fluidizing medium such as sand in a fluidized state, and fluidized bed gasifiers that gasify the waste. These fluidized bed furnaces are equipped with a circulation mechanism that extracts the fluidizing medium from the bottom of the furnace, separates non-combustible materials from the fluidizing medium, and then returns the fluidized medium to the furnace body.

[0003] The fluidized bed furnace described in Patent Document 1 is configured to recover a fluidized bed material by withdrawing it from a discharge port (referred to as an "extraction port" in the document) provided at the bottom of the furnace. Waste to be incinerated or otherwise treated in a fluidized bed furnace contains trace amounts of valuable metals, such as precious metals such as gold and silver, or heavy metals such as lead and zinc. It is known that, among the fluidized bed materials contained in a fluidized bed furnace, the fluidized bed material remaining on the hearth plate without being withdrawn from the discharge port contains high concentrations of valuable metals derived from the waste. Therefore, in a fluidized bed furnace, the hearth plate is tilted toward the discharge port, and the fluidized bed material is discharged from the discharge port by gravity, and then the valuable metals are recovered from the fluidized bed material remaining on the hearth plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-25699 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, in the fluidized bed furnace described in Patent Document 1, in order to recover a large amount of valuable metals from the fluidized bed material, it is necessary to leave a certain amount of the fluidized bed material on the hearth plate. Therefore, there is room for improvement in terms of efficiently recovering valuable metals from the fluidized bed material remaining on the hearth plate.

[0006] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a fluidized bed furnace and a fluidized bed recovery method that can efficiently recover valuable metals from a fluidized bed contained in the furnace body. [Means for solving the problem]

[0007] A characteristic configuration of the fluidized bed furnace according to the present invention is a fluidized bed furnace for incinerating or gasifying a treatment target containing valuable metals, comprising a furnace body for accommodating a bed material, and an aeration mechanism for spraying a fluidizing gas toward the bed material, wherein the furnace body has a furnace bottom plate for supporting the bed material, and an outlet provided adjacent to the furnace bottom plate and capable of discharging the bed material, and the aeration mechanism includes a plurality of aeration tubes protruding from the surface of the furnace bottom plate, and the height of at least one of the plurality of aeration tubes relative to the surface is different from the heights of the other aeration tubes.

[0008] According to this configuration, the multiple diffuser tubes included in the diffusion mechanism protrude from the surface of the hearth plate, and the height of at least one of the diffuser tubes relative to the surface of the hearth plate is different from the height of the other diffuser tubes. Therefore, when the bed material filled in the furnace body is discharged from the furnace body through the discharge port, the bed material on the hearth plate is prevented from flowing into the discharge port by the diffuser tubes with a higher height, resulting in a large amount of bed material accumulating around the diffuser tubes with a higher height. This allows the bed material containing non-combustibles to be discharged through the discharge port while leaving a large amount of bed material on the hearth plate. Furthermore, because the height of at least one of the diffuser tubes relative to the surface of the hearth plate is simply set differently from the height of the other diffuser tubes, no additional components are required for the fluidized bed furnace. As a result, valuable metals can be efficiently recovered from the bed material remaining on the hearth plate.

[0009] Another characteristic configuration is that the plurality of aeration tubes are arranged side by side on the furnace bottom plate in a direction away from the discharge port, and the altitude of the aeration tube closest to the discharge port among the plurality of aeration tubes arranged side by side in the direction away from the discharge port is configured to be higher than the altitudes of the other aeration tubes.

[0010] According to this configuration, among the plurality of diffuser tubes arranged in a row away from the discharge port, the diffuser tube closest to the discharge port is located at a higher elevation than the other diffuser tubes. This prevents the bed material from flowing into the discharge port, making it easier to deposit the bed material on the hearth plate. As a result, the bed material deposited on the hearth plate acts as a resistance to the bed material moving along the surface of the hearth plate toward the discharge port, allowing a large amount of bed material to be deposited on the hearth plate. As a result, valuable metals can be efficiently recovered from the bed material remaining on the hearth plate.

[0011] Another characteristic feature is that the furnace bottom plate is provided with a damming member for preventing the fluidized medium from flowing into the discharge port, and the damming member is configured to include the air diffuser pipe.

[0012] According to this configuration, the damming member of the hearth plate includes an air diffuser, which prevents the bed material from flowing into the discharge port due to gravity. This allows the bed material blocked by the damming member to act as a resistance to the bed material moving along the surface of the hearth plate toward the discharge port, allowing a large amount of bed material to be deposited on the hearth plate. As a result, valuable metals can be efficiently recovered from the bed material remaining and deposited on the hearth plate. Furthermore, since the damming member includes an air diffuser, the air diffuser can be effectively used as a bed material.

[0013] Another characteristic feature is that the whole or a part of the hearth plate is inclined at an angle smaller than the angle of repose of the fluidized medium.

[0014] According to this configuration, the entire or part of the hearth bottom plate is inclined at an angle smaller than the angle of repose of the bed material. Therefore, when the bed material supported on the hearth bottom plate flows into the discharge outlet by gravity and is extracted, not all of the bed material filled in the furnace body is extracted outside the furnace, and some of the bed material can be reliably left on the hearth bottom plate.

[0015] The feature of the bed material recovery method of the present invention is that it is a bed material recovery method for stopping the above-described fluidized bed furnace and recovering the bed material, and includes an extraction step of causing the bed material supported on the furnace bottom plate to flow into the discharge outlet and be extracted, and a recovery step of recovering the bed material remaining on the furnace bottom plate after the extraction step.

[0016] According to this method, after the fluidized bed furnace is stopped, the bed material filled in the furnace body is first discharged through the discharge port and then extracted from the furnace body (extraction process). During the extraction process, the air diffuser can prevent the bed material from flowing into the discharge port, so a large amount of bed material remains on the furnace bottom plate. This allows a large amount of bed material remaining on the furnace bottom plate to be recovered (recovery process). As a result, valuable metals can be efficiently recovered from the bed material remaining on the furnace bottom plate.

[0017] Another characteristic feature is that the recovery step includes an air diffusion tube adjusting step of changing the height of the air diffusion tube in accordance with the accumulation state of the bed material.

[0018] According to this configuration, by changing the height of the air diffuser tube in the air diffuser tube adjusting step, the deposition state of the bed material on the hearth plate can be easily adjusted. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram schematically illustrating the configuration of a fluidized bed furnace facility according to a first embodiment. [Figure 2] FIG. 2 is a partial cross-sectional view showing the configuration of a hearth plate in a fluidized bed furnace. [Figure 3] FIG. 2 is a partial plan view showing the configuration of an air diffuser in a fluidized bed furnace. [Figure 4] FIG. 1 is a cross-sectional view of a fluidized bed furnace in a state where a fluidized bed material remains on the hearth plate. [Figure 5] FIG. 6 is a partial cross-sectional view showing the configuration of a hearth plate in a fluidized bed furnace according to a second embodiment. [Figure 6] FIG. 10 is a partial plan view showing the configuration of a hearth plate in a fluidized-bed furnace according to a second embodiment. [Figure 7] FIG. 10 is a partial cross-sectional view showing the configuration of a hearth plate in a fluidized-bed furnace according to a third embodiment. [Figure 8] FIG. 10 is a plan view of a fluidized bed furnace according to another embodiment. [Figure 9] FIG. 10 is a cross-sectional view of a fluidized bed furnace in a state where a fluidized medium remains on the hearth plate in another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, a fluidized bed furnace and a method for recovering a fluidized material in a fluidized bed furnace according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below are merely examples for explaining the present invention, and the present invention is not limited to these embodiments. Therefore, the present invention can be embodied in various forms without departing from the spirit and scope of the present invention.

[0021] [First embodiment] (Configuration of fluidized bed furnace equipment) The configuration of a fluidized bed furnace facility 1 will be described with reference to Figures 1 to 4. As shown in Figure 1, the fluidized bed furnace facility 1 mainly comprises a fluidized bed gasification furnace 10 (an example of a fluidized bed furnace, hereinafter abbreviated as "fluidized bed furnace 10"), a swirling flow melting furnace 20, and a duct 30. Each of these components will be described below.

[0022] The fluidized-bed furnace 10 is a facility for thermally decomposing various waste materials, such as municipal solid waste, sewage sludge, automobile shredder residue (ASR), and discarded home appliances, as well as combustible materials, such as home appliances containing valuable metals, into combustible gases (carbon monoxide, hydrogen, hydrocarbons, etc.), unburned materials (char), and ash. The materials to be treated include valuable metals, and the fluidized-bed furnace 10 incinerates or gasifies them. As shown in FIG. 1 , the fluidized-bed furnace 10 includes a furnace body 12 that accommodates a bed material 13. The furnace body 12 (fluidized-bed furnace 10) includes a hearth plate 16 that supports the bed material 13 and a discharge port 16a that is located adjacent to the hearth plate 16 and through which the bed material 13 can be discharged. In this embodiment, a circular opening is formed in the center of the hearth plate 16, and the discharge port 16a is configured by this opening. Furthermore, an exhaust pipe 15 extending below the furnace bottom plate 16 is connected to the exhaust port 16a of the furnace bottom plate 16. Furthermore, the fluidized-bed furnace 10 is equipped with an air diffusion mechanism A that blows fluidizing gas toward the bed material 13 from below the furnace bottom plate 16 of the furnace body 12. In this embodiment, the air diffusion mechanism A is configured to blow the fluidizing gas from below the furnace bottom plate 16. Although not shown, the air diffusion mechanism A may be configured to blow the fluidizing gas from above the furnace bottom plate 16 and from the side of the furnace body 12.

[0023] The furnace body 12 has, for example, a cylindrical shape extending in the vertical direction. The furnace body 12 is provided with a supply port 14, an outlet 11, and an inlet 17. The material to be treated is supplied into the furnace body 12 through the supply port 14. Combustible gas generated in the furnace body 12 is discharged outside the furnace through the outlet 11. As an aeration mechanism A, a wind box 18 is provided in the space below the furnace bottom plate 16 within the furnace body 12, and a fluidizing gas (e.g., air) for fluidizing the bed material 13 is introduced into the wind box 18 through the inlet 17. As shown in FIG. 1, the supply port 14 is provided in a side portion of the furnace body 12 above the furnace bottom plate 16. The outlet 11 is provided at the top of the furnace body 12. The inlet 17 is provided in a side portion of the furnace body 12 below the furnace bottom plate 16.

[0024] The hearth plate 16 is disposed at the bottom of the furnace body 12. A discharge port 16a for the bed material 13 is formed on the inner periphery of the hearth plate 16. A number of air diffusers 19 penetrate the hearth plate 16. As shown in FIG. 1, the hearth plate 16 is inclined downward toward the discharge port 16a on the inner periphery, with the inclination angle being smaller than the angle of repose of the bed material 13. Specifically, the angle of repose of the bed material 13 is preferably 30 to 40 degrees, while the angle of repose of the hearth plate 16 is 10 to 30 degrees. In FIG. 4, the inclination angle (angle θ) of the hearth plate 16 is shown as the angle between the horizontal direction (dotted line Y in FIG. 4) and the surface 16c of the hearth plate 16. In this embodiment, the entire hearth plate 16 is inclined at an angle smaller than the angle of repose of the bed material 13; however, the hearth plate 16 may be configured such that only a portion of the hearth plate 16 is inclined at an angle smaller than the angle of repose of the bed material 13.

[0025] The bed material 13 is fluidized sand such as silica sand or olivine sand, and is packed onto the hearth plate 16. As a result, a fluidized bed (sand layer) having a predetermined thickness is formed on the hearth plate 16, as shown in Fig. 1. The fluidized bed gasifier 10 processes a treatment target containing valuable metals (e.g., gold, silver, copper, lead, or zinc) while the bed material 13 is fluidized.

[0026] The discharge pipe 15 is used to discharge the bed material 13 together with the non-combustible material to the outside of the furnace body 12. As shown in Fig. 1, the discharge pipe 15 has an upper end connected to the discharge port 16a of the furnace bottom plate 16 and a lower end located outside the furnace body 12, and extends vertically from the upper end to the lower end, penetrating the bottom wall of the furnace body 12.

[0027] The air diffusion mechanism A is composed of an inlet 17, a wind box 18, and a plurality of air diffusion pipes 19. As shown in FIGS. 2 and 3, each air diffusion pipe 19 has a straight pipe section 19a that penetrates the furnace bottom plate 16 in the thickness direction and a U-shaped pipe section 19b connected to the upper end of the straight pipe section 19a. As shown in FIG. 1, in order to fluidize the bed material 13, the air diffusion mechanism A causes the fluidizing gas introduced into the wind box 18 from the inlet 17 to flow through the air diffusion pipes 19, and sprays the fluidizing gas toward the bed material 13 from below the furnace bottom plate 16 of the furnace body 12. The fluidizing gas introduced into the wind box 18 from the inlet 17 rises within the straight pipe section 19a and is then sent out toward the bed material 13 from the opening of the U-shaped pipe section 19b (arrow in FIG. 3).

[0028] As shown in FIG. 2, the air diffusion mechanism A includes a plurality of air diffuser pipes 19 protruding from the surface 16c of the hearth plate 16, and at least one of the plurality of air diffuser pipes 19 has a different height H from the surface 16c. Here, the height H refers to the length of the air diffuser pipe 19 protruding vertically from the portion of the air diffuser pipe 19 that contacts the surface 16c of the hearth plate 16. More specifically, the height H refers to the distance from the lowest point of the straight pipe portion 19a of the air diffuser pipe 19 that contacts the surface 16c of the hearth plate 16 to the highest point of the U-shaped pipe portion 19b of the air diffuser pipe 19 in the direction perpendicular to the installation surface (ground) of the fluidized-bed furnace 10. As shown in FIGS. 2 and 3, the plurality of air diffuser pipes 19 are arranged on a plurality of concentric circles surrounding the discharge port 16a and are arranged side by side in a direction away from the discharge port 16a (in a direction facing radially outward from the hearth plate 16). As shown in Fig. 3, the plurality of diffuser pipes 19 arranged in a row in a direction away from the discharge port 16a are arranged so that, from the side of the discharge port 16a, the diffuser pipe group 19A1, the diffuser pipe group 19A2, the diffuser pipe group 19A3, and the diffuser pipe group 19A4 are formed in this order. Of the diffuser pipes 19 of the diffuser pipe groups 19A1 to 19A4 arranged in a row in a direction away from the discharge port 16a, the height H1 of the diffuser pipe 19 of the diffuser pipe group 19A1 closest to the discharge port 16a is configured to be higher than the heights H2 to H4 of the other diffuser pipes 19 (the diffuser pipes 19 of the diffuser pipe groups 19A2 to 19A4). In the example shown in Fig. 2, the heights H1 to H4 of the diffuser pipes 19 of the diffuser pipe groups 19A1 to 19A4 are set so that H1 > H2 > H3 > H4. Although not shown, the air diffusion pipes 19 of the air diffusion pipe groups 19A1-19A4 may be set so that one of the altitudes H2-H4 is the highest among the altitudes H1-H4, or the altitudes H1-H4 may be varied irregularly. Furthermore, in each of the air diffusion pipe groups 19A1-19A4, the altitudes H of the multiple air diffusion pipes 19 included in the air diffusion pipe groups 19A1-19A4 do not necessarily all have to be the same, and the air diffusion pipes 19 having different altitudes H may be included.

[0029] As shown in Figure 1, the swirling flow melting furnace 20 is a furnace that completely combusts combustible gas and unburned materials while forming a swirling flow 100 of combustible gas generated in the fluidized bed furnace 10, and melts the ash entrained in the combustible gas. The swirling flow melting furnace 20 has a melting furnace body 23. The melting furnace body 23 is provided with an inlet 21 for combustible gas and a slag outlet 22 for discharging molten slag outside the furnace. The molten slag is formed by melting the ash of the combustible gas that flows into the melting furnace body 23 from the inlet 21.

[0030] The inlet 21 is provided in a position near the top of a side of the melting furnace body 23. The inlet 21 is connected to the outlet 11 of the fluidized-bed gasification furnace 10 by a duct 30. The slag outlet 22 is provided in the bottom of the melting furnace body 23. The exhaust gas generated by the combustion of combustible gas in the swirling-flow melting furnace 20 passes through various equipment (boiler, cooling tower, bag filter, catalytic reaction tower, etc.) located downstream of the swirling-flow melting furnace 20, and then is released into the atmosphere from a chimney (not shown).

[0031] The fluidized bed furnace 10 has a circulation path 40. The circulation path 40 separates the bed material 13 discharged outside the furnace body 12 from non-combustible materials and then returns the bed material 13 to the furnace body 12. The circulation path 40 has an extraction screw 41, a classifier 42, a circulation elevator 43, a storage tank 44, a first conveying path 45, a second conveying path 46, and a third conveying path 47.

[0032] The discharge screw 41, which is driven to rotate, discharges the bed material 13 together with the non-combustible material from the bottom of the furnace body 12 and is provided at the lower end of the discharge pipe 15. The classifier 42 is provided at the downstream end of the discharge screw 41 and separates the bed material 13 from the non-combustible material using a sieve. The non-combustible material separated from the bed material 13 is pulverized and then slag-formed in the swirling flow melting furnace 20 or transported outside the system.

[0033] The circulation elevator 43 transports the bed material 13 from which non-combustible materials have been removed by the classifier 42 to a predetermined height. As shown in Fig. 1, an inlet 43A for the bed material 13 is provided at the bottom of the circulation elevator 43, and this inlet 43A is connected to an outlet 42A of the classifier 42 (the outlet for the bed material 13) by a first transport path 45. In addition, an outlet 43B for the bed material 13 is provided at the top of the circulation elevator 43.

[0034] The storage tank 44 stores the bed material 13 transported upward by the circulation elevator 43. The second transport path 46 is provided from the outlet 43B of the circulation elevator 43 to the inlet 43A, with the storage tank 44 located midway along the second transport path 46. This allows the bed material 13 transported upward by the circulation elevator 43 to fall into the storage tank 44 via the second transport path 46 and be stored in the storage tank 44.

[0035] One end of the third transport path 47 is connected to a portion of the second transport path 46 above the storage tank 44, and the other end is connected to a side of the furnace body 12. This allows the bed material 13 discharged from the outlet 43B of the circulation elevator 43 to be returned to the furnace body 12 via the third transport path 47. Although not shown in the figures, the circulation path 40 may further have a switching unit (such as a valve) that switches whether the bed material 13 discharged from the outlet 43B of the circulation elevator 43 is guided to the storage tank 44 or to the furnace body 12.

[0036] <Method for recovering bed material in a fluidized bed furnace> A method for recovering the bed material 13 in the fluidized-bed furnace 10 according to this embodiment will be described. This recovery method is a method for recovering the bed material 13 from the furnace body 12 when the fluidized-bed furnace 10 is stopped, for example, during maintenance of the fluidized-bed furnace 10. The bed material recovery method is a method for recovering the bed material 13 by stopping the fluidized-bed furnace 10 (aeration mechanism A), and includes an extraction step of causing the bed material 13 supported on the furnace bottom plate 16 to flow into the discharge port 16a and being extracted, and a recovery step of recovering the bed material 13 remaining on the furnace bottom plate 16 after the extraction step.

[0037] As shown in Fig. 1, before maintenance of the fluidized-bed furnace 10, i.e., during steady-state operation of the fluidized-bed furnace 10, the bed material 13 is fluidized by a fluidizing gas (e.g., air) fed through an air diffuser 19, and the material to be treated is supplied into the furnace body 12 from a supply port 14. The material to be treated is heated by the bed material 13 in the furnace body 12 and thermally decomposed into combustible gas, unburned matter, and ash. The material to be treated contains considerable amounts of valuable metals, such as precious metals (gold, silver, copper, etc.) and heavy metals (lead, zinc, etc.).

[0038] The combustible gas generated in the fluidized bed furnace 10 flows into the swirling flow melting furnace 20 through the duct 30 together with unburned material and ash. In this swirling flow melting furnace 20, the combustible gas and unburned material are completely combusted and the ash is melted. During this steady operation, by operating the circulation path 40, the bed material 13 filled in the furnace body 12 can be discharged outside the furnace together with the unburned material, and the bed material 13 from which the unburned material has been removed can be returned to the furnace body 12.

[0039] Next, when the time for maintenance of the fluidized-bed furnace 10 arrives, first, the supply of the material to be treated to the furnace body 12 is stopped. Next, the supply of fluidizing gas to the wind box 18 is stopped. In other words, the air diffuser A is stopped. After that, an extraction process is performed in which the bed material 13 filled in the furnace body 12 is extracted to the outside of the furnace body 12.

[0040] In the extraction process, the bed material 13 filled in the furnace body 12 is caused to flow into the discharge port 16a and extracted to the outside of the furnace body 12. Specifically, by rotating the extraction screw 41, the bed material 13 filled in the furnace body 12 is extracted to the outside of the furnace body 12 through the discharge port 16a and the discharge pipe 15 communicating with the discharge port 16a.

[0041] The bed material 13 extracted to the outside of the furnace is separated from non-combustible materials by a classifier 42, transported upward by a circulation elevator 43, and then stored in a storage tank 44. In other words, in the extraction process, the bed material 13 extracted from the furnace body 12 is not returned to the furnace body 12, but is all stored in the storage tank 44.

[0042] 4 is a schematic diagram showing the state inside the furnace body 12 (the state near the furnace bottom plate 16) after the unloading step. As described above, the furnace bottom plate 16 is inclined downward toward the discharge port 16a at an angle θ smaller than the angle of repose of the bed material 13. Therefore, not all of the bed material 13 inside the furnace body 12 is unloaded to the outside of the furnace during the unloading step, and some of the bed material 13 is deposited on the furnace bottom plate 16 after the unloading step to form a deposit layer 13a and remain.

[0043] In this embodiment, as shown in FIG. 2 , a plurality of diffuser tubes 19 included in the diffusion mechanism A protrude from the surface 16c of the furnace bottom plate 16, and the height H of at least one of the diffuser tubes 19 relative to the surface 16c of the furnace bottom plate 16 is different from the height H of the other diffuser tubes 19. Therefore, when the bed material 13 filled in the furnace body 12 is discharged to the outside of the furnace body 12 through the discharge port 16a, the bed material 13 on the furnace bottom plate 16 is prevented from flowing into the discharge port 16a by the diffuser tube 19 with a relatively high height H, and a large amount of the bed material 13 accumulates around the diffuser tube 19 with a relatively high height H. This allows a predetermined amount of the bed material 13 to remain on the furnace bottom plate 16 while the bed material 13 containing incombustibles is discharged through the discharge port 16a. As a result, valuable metals can be efficiently recovered from the bed material 13 remaining on the furnace bottom plate 16. Furthermore, since the height H1 of the diffuser pipe 19 of the diffuser pipe group 19A1 closest to the discharge port 16a among the plurality of diffuser pipes 19 arranged in a row in a direction away from the discharge port 16a is higher than the heights H2 to H4 of the other diffuser pipes 19, the diffuser pipe 19 can prevent the bed material 13 from flowing into the discharge port 16a, making it easier to deposit the bed material 13 on the furnace bottom plate 16. As a result, the bed material 13 deposited on the furnace bottom plate 16 acts as a resistance to the bed material 13 moving along the surface 16c of the furnace bottom plate 16 toward the discharge port 16a, making it possible to deposit a large amount of bed material 13 on the furnace bottom plate 16.

[0044] In this way, most (for example, 90% or more) of the bed material 13 contained in the furnace body 12 is sent to the storage tank 44 in the withdrawal process, and the remainder remains inside the furnace body 12. It is known that in the fluidized bed furnace 10, the bed material 13 remaining in the furnace body 12 after the withdrawal process contains high concentrations of valuable metals (gold, silver, copper, lead, zinc, etc.) derived from the object to be treated.

[0045] Therefore, in the recovery process following the extraction process, the bed material 13 remaining in the furnace body 12 is recovered separately from the bed material 13 extracted from the furnace body 12 in the extraction process (the bed material 13 stored in the storage tank 44). Specifically, after the extraction process is completed, an operator enters the inside of the furnace body 12 and collects the bed material 13 remaining on the furnace bottom plate 16, thereby directly recovering the bed material 13 from inside the furnace body 12.

[0046] Thereafter, the worker performs maintenance work such as cleaning and inspection inside the furnace body 12. Note that cleaning and inspection inside the furnace may be performed before recovering the hearth medium, or recovery of the bed material 13 remaining on the furnace bottom plate 16 and maintenance work inside the furnace body 12 may be performed in parallel. In other words, the recovery process may be performed after stopping the aeration mechanism A.

[0047] In this way, in the recovery method according to the present embodiment, the fluidized bed furnace 10 is maintained at the timing to recover the fluidized bed material 13 containing a high concentration of valuable metals derived from the object to be treated.

[0048] Finally, valuable metals are separated from the bed material 13 recovered in the recovery step. Specifically, the valuable metals contained in the bed material 13 are separated from the bed material 13 by a method such as heat treatment, chemical treatment, or physical separation. Examples of heat treatment include melting (smelting), calcination, and chlorination volatilization. Examples of chemical treatment include solvent extraction using acids, etc. Examples of physical separation include air separation, magnetic separation, vibration separation, eddy current separation, electrostatic separation, and gravity separation.

[0049] Second Embodiment A fluidized bed furnace 10 according to a second embodiment will be described with reference to Figures 5 and 6. Only the differences from the first embodiment will be described below. The method for recovering the bed material 13 in the fluidized bed furnace 10 according to the second embodiment is basically the same as the method for recovering the bed material 13 in the fluidized bed furnace 10 according to the first embodiment.

[0050] 5 and 6, in the fluidized-bed furnace 10 according to the second embodiment, a damming member 51 is provided on the hearth plate 16 to prevent the bed material 13 from flowing into the discharge port 16a, and the damming member 51 includes a diffuser tube 19. In this embodiment, the damming member 51 includes the diffuser tube 19 (a diffuser tube group 19A1) that is closest to the discharge port 16a of the hearth plate 16 among the plurality of diffuser tubes 19 arranged in a row in a direction away from the discharge port 16a. In FIG. 6, the damming member 51 is provided continuously over the plurality of diffuser tubes 19 (a diffuser tube group 19A1). As a result, the bed material 13 blocked by the damming member 51 acts as a resistance to the bed material 13 moving along the surface 16c of the hearth plate 16 toward the discharge port 16a, allowing a large amount of bed material 13 to be deposited on the hearth plate 16 as a sediment layer 13a. As a result, valuable metals can be efficiently recovered from the bed material 13 remaining and accumulated on the furnace bottom plate 16. Furthermore, since the damming member 51 includes the diffuser pipe 19, the diffuser pipe 19 can be effectively utilized as the damming member 51. The damming member 51 may include the diffuser pipes 19 of the other diffuser pipe groups 19A2 to A4, or may be provided discontinuously between a plurality of diffuser pipes 19 (for example, the diffuser pipes 19 of the diffuser pipe group 19A1).

[0051] Third Embodiment A fluidized bed furnace 10 according to a third embodiment will be described with reference to Figure 7. Only the differences from the first embodiment will be described below. The method for recovering the bed material 13 in the fluidized bed furnace 10 according to the third embodiment is basically the same as the method for recovering the bed material 13 in the fluidized bed furnace 10 according to the first embodiment.

[0052] As shown in FIG. 7, in the fluidized-bed furnace 10 of the third embodiment, the aeration mechanism A includes a plurality of aeration pipes 19 (aeration pipe groups 19A1-19A4) protruding from the surface 16c of the hearth plate 16. The protruding length (heights H1-H4) of the plurality of aeration pipes 19 from the surface 16c of the hearth plate 16 is preferably, for example, 60 mm or more and 100 mm or less. When the protruding length of the plurality of aeration pipes 19 is 60 mm or more and 100 mm or less, the plurality of aeration pipes 19 protruding from the hearth plate 16 appropriately acts as a resistance, preventing the bed material 13 from flowing into the discharge port 16a. As a result, valuable metals can be efficiently recovered from the bed material 13 remaining and accumulated on the hearth plate 16.

[0053] [Another embodiment] (1) In the above embodiment, an example was shown in which, in the recovery step, an operator enters the furnace body 12 and collects the bed material 13 remaining on the furnace bottom plate 16, thereby directly recovering the bed material 13 from within the furnace body 12. Alternatively, in the recovery step, the bed material 13 remaining on the furnace bottom plate 16 may be recovered midway along the first transport path 45. For example, an operator may enter the furnace body 12, drop the bed material 13 remaining on the furnace bottom plate 16 into the discharge pipe 15 from the discharge port 16a, and then rotate the extraction screw 41 to recover the bed material 13.

[0054] As a result, the bed material 13 remaining on the hearth plate 16 after the unloading step can be discharged outside the furnace body 12 and then recovered at a location (on the way of the first transport path 45) different from the storage tank 44. As a result, the bed material 13 remaining on the hearth plate 16 can be recovered separately from the bed material 13 stored in the storage tank 44 in the unloading step.

[0055] Alternatively, a recovery port for the bed material 13 remaining on the furnace bottom plate 16 may be provided at another location in the circulation path 40 (for example, the circulation elevator 43, etc.).

[0056] (2) In the recovery process, when an operator drops the bed material 13 remaining on the furnace bottom plate 16 into the discharge pipe 15, the bed material 13 remaining on the furnace bottom plate 16 may be dropped into the discharge pipe 15 by supplying fluidizing gas from the air diffuser 19.

[0057] (3) The air diffusion mechanism A may be configured to change the height of the air diffuser pipe 19 protruding from the surface 16c of the hearth plate 16. If the height of the air diffuser pipe 19 is changeable, the recovery step may include an air diffuser pipe adjustment step of changing the height of the air diffuser pipe 19 depending on the deposition state of the bed material 13. By changing the height of the air diffuser pipe 19 in the air diffuser pipe adjustment step, the deposition state of the bed material 13 on the hearth plate 16 can be easily adjusted.

[0058] (4) In the above embodiment, the discharge port 16a is located on the center side of the furnace body 12 in a plan view, i.e., on the inner periphery side of the hearth plate 16. However, as shown in Figures 8 and 9, the fluidized bed furnace 10 may have the discharge port 16a located on the outer periphery side of the hearth plate 16 in a plan view of the furnace body 12.

[0059] (5) In the above embodiment, an example was shown in which a fluidized bed gasification furnace 10 was used as the fluidized bed furnace 10 to gasify the object to be treated. However, a fluidized bed incinerator that incinerates the object to be treated can also be used as the fluidized bed furnace 10.

[0060] (6) In the above embodiment, the furnace body 12 of the fluidized bed furnace 10 is formed in a cylindrical shape. However, the furnace body 12 of the fluidized bed furnace 10 may be formed in a rectangular cylindrical shape. [Industrial Applicability]

[0061] INDUSTRIAL APPLICABILITY The present invention can be widely used in fluidized bed furnaces for incinerating or gasifying objects containing valuable metals, and in methods for recovering fluidized bed materials in fluidized bed furnaces. [Explanation of symbols]

[0062] 1:Fluidized bed furnace equipment 10: Fluidized bed gasifier (fluidized bed furnace) 12: Furnace body 13: Fluid medium 14: Supply port 15: Discharge pipe 16: Furnace bottom plate 16a: Outlet 16c: surface 19: Diffuser pipe 19A1, 19A2, 19A3, 19A4: Diffuser pipe group 19a: Straight pipe section 19b: U-shaped tube part 40: Circulation path 41: Extraction screw 42:Classifier 43: Circulation elevator 44: Reservoir 45: First transport route 46: Second transport route 47: Third transport route 51: Damming member A: Aeration mechanism H,H1,H2,H3,H4: Altitude θ: angle

Claims

1. A fluidized bed furnace for incinerating or gasifying a treatment target containing valuable metals, a furnace body that accommodates a fluidized medium; an air diffusion mechanism that blows a fluidizing gas toward the fluidized medium, The furnace body has a furnace bottom plate that supports the bed material, and a discharge port that is provided adjacent to the furnace bottom plate and can discharge the bed material, The air diffusion mechanism includes a plurality of air diffusion tubes protruding from the surface of the hearth plate, and the height of at least one of the plurality of air diffusion tubes relative to the surface is different from the heights of the other air diffusion tubes.

2. 2. The fluidized bed furnace according to claim 1, wherein the plurality of diffuser tubes are arranged in parallel in a direction away from the discharge port on the hearth plate, and the elevation of the diffuser tube closest to the discharge port among the plurality of diffuser tubes arranged in parallel in the direction away from the discharge port is higher than the elevations of the other diffuser tubes.

3. The furnace bottom plate is provided with a damming member that prevents the fluidized medium from flowing into the discharge port, 2. The fluidized bed furnace according to claim 1, wherein the damming member includes the air diffuser tube.

4. 4. The fluidized bed furnace according to claim 1, wherein the entire or a part of the hearth plate is inclined at an angle smaller than the angle of repose of the fluidized medium.

5. A method for recovering a fluidized bed material by stopping the fluidized bed furnace according to any one of claims 1 to 3, comprising: a discharge step of causing the bed material supported on the furnace bottom plate to flow into the discharge port and discharge the bed material; a recovery step of recovering the bed material remaining on the furnace bottom plate after the extraction step.

6. 6. The bed material recovery method according to claim 5, wherein the recovery step includes an aeration tube adjusting step of changing the height of the aeration tube in accordance with the accumulation state of the bed material.

Images