Valuable metal content estimation method and valuable metal recovery method

Abstract

To provide a valuable metal content estimation method and a valuable metal recovery method capable of efficiently recovering valuable metal.SOLUTION: A fluidized bed furnace 10 for incinerating or gasifying an object to be incinerated, has: a furnace body 12 that houses a bed material 13 and an aeration mechanism A that sprays fluidizing gas to fluidize the bed material 13. The furnace body 12 has a furnace bottom plate 16 that supports the bed material 13, and a discharge port 16a adjacent to the furnace bottom plate 16 through which the bed material 13 can be discharged. In the fluidized bed furnace, an amount of valuable metal contained in the bed material 13 remaining on the furnace bottom plate 16 is estimated based on pretreatment information for incineration of the object to be incinerated, with the aeration mechanism A stopped and at least a part of the bed material 13 removed from the discharge port 16a.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for estimating a content of valuable metals and a method for recovering valuable metals. [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 extract and recover a fluidized bed material through 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 like gold and silver, or heavy metals like 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 extracted through 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, after which 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] Efficient recovery of valuable metals is achieved by recovering a fluidized bed material with a high content of valuable metals, but the content of valuable metals in the fluidized bed material has been estimated empirically. Therefore, it is not possible to estimate the content of valuable metals in a fluidized bed furnace that has not yet recovered valuable metals, and there is room for improvement in terms of efficient recovery of valuable metals.

[0006] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a valuable metal content estimation method for estimating the amount of valuable metals contained in a bed material contained in a furnace body, and a valuable metal recovery method. [Means for solving the problem]

[0007] The characteristic configuration of the valuable metal content estimation method of the present invention is that in a fluidized bed furnace that incinerates or gasifies an object to be incinerated, the furnace body comprises a furnace body that accommodates a bed material and an aeration mechanism that sprays a fluidizing gas to fluidize the bed material, the furnace body having a furnace bottom plate that supports the bed material and an outlet that is located adjacent to the furnace bottom plate and through which the bed material can be discharged, the aeration mechanism is stopped and at least a portion of the bed material is extracted through the outlet, and the amount of valuable metals contained in the bed material remaining on the furnace bottom plate is estimated based on pretreatment information for the incineration of the object to be incinerated.

[0008] According to this configuration, the amount of valuable metals contained in the bed material stored in the furnace body of the fluidized bed furnace is estimated based on pretreatment information for the incineration of the incineration target. This makes it possible to easily estimate the amount of valuable metals contained in the bed material using existing pretreatment information, without having to investigate the type and amount of the incineration target actually placed in the incinerator.

[0009] Another feature of the configuration is that the pre-processing information includes sorting information of the waste to be incinerated.

[0010] According to this configuration, since the pretreatment information includes the separation information of the incineration target, the content of valuable metals in the bed material can be estimated based on the separation information. Because the type and amount of the incineration target input into the fluidized bed incinerator changes depending on the separation method of the incineration target, the accuracy of estimating the content of valuable metals in the bed material can be improved.

[0011] Another feature of the configuration is that the sorting information includes whether or not sorting has been performed and the type of sorting.

[0012] With this configuration, the sorting information includes whether or not sorting has been performed and the type of sorting, so the type of sorting performed by each local government can be reflected in the pretreatment information. Because the type and amount of materials to be incinerated fed into the fluidized bed furnace change depending on whether or not sorting has been performed and the type of sorting, it is possible to improve the accuracy of estimating the valuable metal content of the bed material.

[0013] Another configuration feature is that the incineration objects include small home appliances.

[0014] According to this configuration, small household appliances containing valuable metals such as gold, silver, copper, and rare metals are included in the items to be incinerated, so by estimating the valuable metal content of the bed material based on preprocessing information for these items, the accuracy of estimating the valuable metal content of the bed material can be improved.

[0015] Another feature of the configuration is that the amount of valuable metals is expressed by a correlation equation based on a correlation with a small appliance input point, which indicates the ease of input of the small appliance into the fluidized bed furnace, obtained from the pretreatment information.

[0016] According to this configuration, the amount of valuable metals contained in the bed material is estimated based on the correlation with the small appliance input point, which indicates the ease of input of small appliances into a fluidized bed incinerator, obtained from the pretreatment information. By quantifying the pretreatment information and using it as the small appliance input point, a correlation equation can be created, making it possible to estimate the amount of valuable metals contained in the bed material based on the correlation equation.

[0017] Another feature of the configuration is that the correlation equation is expressed using the small appliance input points for each type of small appliance.

[0018] The amount of valuable metals contained in the bed material varies depending on the type of small appliance. This configuration creates a correlation equation using the small appliance input point for each type of small appliance, thereby improving the accuracy of estimating the amount of valuable metals contained in the bed material.

[0019] Another feature of the present invention is that the valuable metal is gold.

[0020] According to this configuration, by estimating the gold content in the fluid medium, it is possible to determine whether or not gold recovery can be carried out based on the economic merit.

[0021] Furthermore, a characteristic feature of the valuable metal recovery method according to the present invention is that the frequency or method of recovering the valuable metal is changed depending on the value estimated by the valuable metal content estimation method.

[0022] According to this configuration, the frequency or method of recovering valuable metals is changed depending on the value estimated by the valuable metal content estimation method, which makes it possible to recover valuable metals at the timing or by the method that maximizes the recovery efficiency of valuable metals. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram schematically illustrating a configuration of a fluidized bed furnace facility according to an 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 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. 1 is a diagram showing the configuration of a valuable metal content estimation device. [Figure 6] FIG. 1 is a flow chart of a method for estimating the content of valuable metals. [Figure 7] FIG. 10 is a diagram illustrating an example of classifications of small home appliances and first coefficients. [Figure 8] FIG. 10 is a diagram illustrating an example of an estimation formula. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the valuable metal content estimation method and valuable metal recovery method according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications are possible within the scope of the present invention.

[0025] [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.

[0026] The fluidized bed furnace 10 is a facility for thermally decomposing materials to be incinerated, such as various waste materials such as municipal solid waste, sewage sludge, automobile shredder residue (ASR), and discarded home appliances, as well as home appliances containing valuable metals, into combustible gases (carbon monoxide, hydrogen, hydrocarbons, etc.), unburned materials (char), and ash. Home appliances may include small home appliances such as personal computers, mobile phones, and digital cameras. The materials to be incinerated contain valuable metals such as gold, silver, copper, and rare metals derived from the home appliances.

[0027] A fluidized-bed furnace 10 incinerates or gasifies materials to be incinerated. 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 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 formed by this opening. A discharge pipe 15 extending below the hearth plate 16 is connected to the discharge port 16a of the hearth plate 16. The fluidized-bed furnace 10 also includes an air diffusion mechanism A that blows fluidizing gas toward the bed material 13 from below the hearth plate 16 of the furnace body 12. In this embodiment, the air diffusion mechanism A is configured to blow fluidizing gas from below the hearth plate 16. Although not shown, the air diffusion mechanism A may be configured to spray the fluidizing gas from above the furnace bottom plate 16 and from the side of the furnace body 12.

[0028] 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 incinerated 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 air diffusion 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 portion of the side 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 portion of the side of the furnace body 12 below the furnace bottom plate 16.

[0029] 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.

[0030] 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 Figure 1. The fluidized bed furnace 10 processes incineration targets containing valuable metals (e.g., gold, silver, copper, lead, or zinc) while the bed material 13 is fluidized.

[0031] 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.

[0032] 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).

[0033] 2 to 4, the hearth plate 16 has a deposition mechanism B, which deposits the bed material 13 to form a deposition layer 13a when the bed material 13 is discharged from the discharge port 16a with the air diffusion mechanism A stopped, at a position different from the air diffusion mechanism A. The deposition mechanism B is composed of a damming member 16b provided on the hearth plate 16. In this embodiment, the damming member 16b is provided on the periphery of the opening, which is the end of the hearth plate 16 on the discharge port 16a side, and prevents the bed material 13 remaining on the hearth plate 16 from flowing into the discharge port 16a due to gravity.

[0034] 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.

[0035] The inlet 21 is provided in a position near the top of one side of the melting furnace body 23. The inlet 21 is connected to the outlet 11 of the fluidized-bed 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).

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] [Valuable metal content estimation method] Next, a valuable metal content estimation method for estimating the amount of valuable metals contained in the bed material 13 will be described with reference to Figures 5 and 6. In this embodiment, the valuable metal content is estimated based on pretreatment information for the incineration of the incineration object. Below, a valuable metal content estimation method will be described for the case where the incineration object, including small household appliances, is treated in the fluidized bed furnace 10. The valuable metal content is estimated, for example, by a valuable metal content estimation device 50.

[0042] The valuable metal content estimation device 50 acquires pretreatment information for an incineration target and estimates the valuable metal content based on the pretreatment information. As shown in FIG. 5, the valuable metal content estimation device 50 includes an acquisition unit 51 that acquires pretreatment information, an estimation equation creation unit 52 that creates an estimation equation for the valuable metal content (an example of a correlation equation), and an estimation unit 53 that estimates the valuable metal content. The acquisition unit 51, the estimation equation creation unit 52, and the estimation unit 53 are operated by a control unit 54. The control unit 54 has a processor and includes an ASIC, an FGPA, a CPU, or other hardware for executing applications stored in a storage unit (not shown). As shown in FIG. 6, the valuable metal content estimation method according to this embodiment includes the steps of acquiring pretreatment information and sorting information (S1), determining a first coefficient (S2), calculating small appliance input points (S3), creating an estimation equation (S4), and estimating the valuable metal content (S5).

[0043] The pretreatment information is information about whether the incineration target can be fed into the fluidized bed furnace 10, and includes, for example, sorting information about the incineration target. The sorting information is, for example, information about which type of waste the small household appliance to be incinerated falls into, such as combustible waste, non-combustible waste, or bulky waste. Because waste classification methods differ depending on the municipality, the sorting information should include information about the classification of each small household appliance in each municipality. In other words, the sorting information should include the type, number, or weight of the small household appliances to be treated as recyclables, combustible waste, non-combustible waste, or bulky waste.

[0044] The sorting information may also include whether or not each municipality sorts the waste to be incinerated and the type of sorting. Sorting may be, for example, mechanical sorting, such as magnetic separation, or manual sorting. The sorting information may also include the time it took to sort the waste to be incinerated and the amount of valuable metals recovered by sorting. The acquisition unit 51 acquires, for example, via a network (not shown), pretreatment information for the waste to be incinerated that is fed into the fluidized-bed furnace 10 in each municipality, and the actual amount of valuable metals recovered by recovering the bed material 13 (S1 in FIG. 6). If there are multiple actual recoveries, the actual amount of valuable metals recovered may be the average of the results. The pretreatment information may also be input directly to the valuable metal content estimation device 50.

[0045] The estimation formula creation unit 52 creates an estimation formula for the valuable metal content based on the pretreatment information acquired by the acquisition unit 51. First, the estimation formula creation unit 52 calculates a small appliance input point that indicates the ease of inputting small appliances into the fluidized bed furnace 10 for each fluidized bed furnace 10 in each municipality. The small appliance input point is calculated, for example, by multiplying the number of small appliances in each waste type by a first coefficient that indicates the ease of inputting small appliances into the fluidized bed furnace 10.

[0046] The estimation formula creation unit 52 sets the first coefficient based on the preprocessing information (S2 in FIG. 6). For example, small household appliances classified as recyclable waste are not fed into the fluidized bed furnace 10, so the estimation formula creation unit 52 sets the first coefficient for small household appliances classified as recyclable waste to 0. Similarly, small household appliances classified as combustible waste are fed into the fluidized bed furnace 10, so the first coefficient for small household appliances classified as combustible waste is set to 1. The estimation formula creation unit 52 may also calculate the first coefficient based on sorting information, including the presence or absence of sorting, such as mechanical sorting or manual sorting, and the type of sorting. Non-combustible waste and bulky waste are crushed and sorted before being fed into the fluidized bed furnace 10, but the degree of sorting varies depending on the municipality. For example, if the time required for manual sorting of non-combustible waste and bulky waste is long and most of the valuable metals contained in the small household appliances are recovered, the first coefficient can be set to 0. On the other hand, if the time required for manual sorting on a conveyor is short and some of the valuable metals are not recovered and the small household appliances are fed into the fluidized bed furnace 10, the first coefficient can be set to 0.3. Furthermore, since mechanical sorting is not considered to have as high a recovery rate of valuable metals as manual sorting, if only mechanical sorting is performed without manual sorting, the first coefficient can be set to 0.6. The first coefficient may also be set depending on the time required to sort small household appliances and the amount of valuable metals recovered by sorting.

[0047] For example, if there are 30 small household appliances classified as recyclable waste, the estimation formula creation unit 52 multiplies them by the first coefficient for recyclable waste, 0, to set the small household appliance input points to 0. If there are 5 small household appliances classified as combustible waste, the estimation formula creation unit 52 multiplies them by the first coefficient for combustible waste, 1, to set the small household appliance input points to 5. Similarly, if there are 20 small household appliances classified as non-combustible waste and the municipality only performs mechanical sorting, the estimation formula creation unit 52 multiplies them by the first coefficient for non-combustible waste, 0.6, to set the small household appliance input points to 12. If there are 10 small household appliances classified as bulky waste and the municipality performs manual sorting, the estimation formula creation unit 52 multiplies them by the first coefficient for bulky waste, 0.3, to set the small household appliance input points to 3. The estimation formula creation unit 52 then adds up the small household appliance input points for each waste type to calculate the small household appliance input points for the municipality in which the fluidized bed furnace 10 is installed (S3 in FIG. 6).

[0048] After calculating the small appliance drop-off points, the estimation formula creation unit 52 creates an estimation formula for the valuable metal content based on the small appliance drop-off points in each local government and the actual value of the amount of valuable metal recovered through the recovery of the bed material 13 (S4 in FIG. 6). The estimation formula may be created using simple regression or multiple regression. This makes it possible to estimate the valuable metal content in the bed material 13 based on the correlation with the small appliance drop-off points.

[0049] 7 and 8 are diagrams showing the small appliance input points calculated by the estimation formula creation unit 52 and an example of an estimation formula. FIG. 7 shows the number of small appliances corresponding to each waste type in municipalities a to d that have fluidized bed furnaces 10, the first coefficient determined for each municipality, and the small appliance input points calculated using the first coefficient. The estimation formula creation unit 52 determines the first coefficient based on preprocessing information for each municipality. FIG. 8 is a graph showing the correlation between the small appliance input points and the gold content contained in the bed material 13. It can be seen that the larger the small appliance input point, the more likely the small appliance is to be input into the fluidized bed furnace 10, and therefore the greater the valuable metal content.

[0050] In addition, the small appliance input points may be calculated by multiplying the weight of small appliances of each waste type by a first coefficient, or by multiplying the weight of each small appliance by the first coefficient and a second coefficient indicating the amount of valuable metals in the small appliance.

[0051] After the estimation formula creation unit 52 creates the estimation formula, the estimation unit 53 estimates the valuable metal content in the fluidized-bed furnace 10 for which the valuable metal content is to be estimated (S5 in FIG. 6 ). First, the estimation unit 53 calculates the small appliance input point in the fluidized-bed furnace 10 based on the classification information of the small appliances in the fluidized-bed furnace 10 related to the estimation of the valuable metal content acquired by the acquisition unit 51. Then, the estimation unit 53 estimates the valuable metal content in the fluidized-bed furnace 10 based on the small appliance input point and the estimation formula created by the estimation formula creation unit 52. The estimated value estimated by the estimation unit 53 may be displayed on a display unit (not shown) of the valuable metal content estimation device 50. Note that a trained model for estimating the valuable metal content of the fluidized material 13 may be generated by performing machine learning using the estimated amount estimated by the valuable metal content estimation device 50 and the actual amount of valuable metals contained in the fluidized material 13. This improves the accuracy of estimating the valuable metal content of the fluidized material 13.

[0052] [Method for recovering bed material in a fluidized bed furnace] Next, a method for recovering the bed material 13 in the fluidized-bed furnace 10 according to this embodiment will be described. This recovery method recovers the bed material 13 from the furnace body 12 when the fluidized-bed furnace 10 is stopped, for example, during maintenance. The bed material recovery method recovers the bed material 13 after stopping the fluidized-bed furnace 10 (aeration mechanism A). The method includes an extraction step in which the bed material 13 supported on the furnace bottom plate 16 is discharged through the discharge port 16a and extracted, and a recovery step in which the bed material 13 remaining on the furnace bottom plate 16 after the extraction step is recovered. In the extraction step, the bed material 13 is deposited on the furnace bottom plate 16 by the deposition mechanism B (damming member 16b). In this embodiment, the bed material 13 remaining on the furnace bottom plate 16 is deposited by the deposition mechanism B (damming member 16b) during the extraction step to form a deposition layer 13a. The bed material 13 is deposited such that the thickness of the deposition layer 13a is greater on the discharge port 16a side than on the central portion C in the radial direction from the center X of the furnace body 12 to the inner surface 12a of the furnace body 12 (see FIG. 4).

[0053] As shown in Figure 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) sent through an air diffuser 19, and the material to be incinerated is supplied into the furnace body 12 from a supply port 14. The material to be incinerated is heated by the bed material 13 within the furnace body 12 and thermally decomposed into combustible gas, unburned material, and ash. The material to be incinerated contains considerable amounts of valuable metals, such as precious metals (gold, silver, copper, etc.) and heavy metals (lead, zinc, etc.).

[0054] 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.

[0055] Next, when the time for maintenance of the fluidized-bed furnace 10 arrives, first, the supply of material to be incinerated 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.

[0056] 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.

[0057] The bed material 13 discharged 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. That is, in the discharge step, the bed material 13 discharged from the furnace body 12 is not returned to the furnace body 12, but is all stored in the storage tank 44. 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. For this reason, not all of the bed material 13 in the furnace body 12 is discharged to the outside of the furnace during the discharge step, and some of the bed material 13 is deposited on the furnace bottom plate 16 after the discharge step to form a sediment layer 13a and remain.

[0058] In this embodiment, the hearth plate 16 further includes a damming member 16b provided on the periphery of the opening, which is the end of the hearth plate 16 on the discharge port 16a side, as a deposition mechanism B for the bed material 13 (see FIGS. 2 to 4). Therefore, in the unloading process, the flow of the bed material 13 into the discharge port 16a is blocked by the damming member 16b, so that a large amount of the bed material 13 remains on the hearth plate 16 as a deposition layer 13a. In this embodiment, the bed material 13 is deposited so that the thickness of the deposition layer 13a of the bed material 13 remaining on the hearth plate 16 due to the deposition mechanism B (damming member 16b) is greater on the discharge port 16a side than on the central portion C in the radial direction from the center X of the region where the hearth plate 16 is located to the inner surface 12a of the furnace body 12, with the center X being the reference point in the plan view of the furnace body 12 (see FIGS. 2 and 4). Specifically, as shown in FIG. 2, the thickness of the sediment layer 13a on the discharge port 16a side is greater than the thicknesses T2 and T3 of the central portion C in the radial direction from the center X to the inner surface 12a of the furnace body 12. Furthermore, the sediment layer 13a on the discharge port 16a side acts as a resistance to the bed material 13 moving toward the discharge port 16a along the surface 16c of the furnace bottom plate 16, making it difficult for the bed material 13 to flow toward the discharge port 16a. This allows the furnace bottom plate 16 to retain a large amount of bed material 13 near the discharge port 16a. As a result, valuable metals can be efficiently recovered from the bed material 13 (sediment layer 13a) remaining on the furnace bottom plate 16.

[0059] In this embodiment, the damming member 16b is formed in a circular shape in a plan view at an end (opening edge) closer to the discharge port 16a than the innermost diffuser tube group among the concentrically arranged diffuser tube groups made up of a plurality of diffuser tubes 19. As shown in FIG. 2, the height of the damming member 16b relative to the surface 16c of the furnace bottom plate 16 is smaller than the height of the diffuser tubes 19. In particular, since the damming member 16b is located lower than the U-shaped pipe portion 19b of the diffuser tube 19, the deposition layer 13a can be efficiently formed by the deposition mechanism B without interfering with the air diffusion process of the diffusion mechanism A during operation. The damming member 16b may be configured to be movable between a state in which it protrudes from the surface 16c of the furnace bottom plate 16 and a state in which it does not protrude from the surface 16c of the furnace bottom plate 16.

[0060] 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 extraction 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 extraction process contains high concentrations of valuable metals (gold, silver, copper, lead, zinc, etc.) derived from the material to be incinerated.

[0061] 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.

[0062] 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.

[0063] In this way, in the recovery method according to the present embodiment, the timing of maintenance of the fluidized bed furnace 10 is utilized to recover the fluidized material 13 containing a high concentration of valuable metals derived from the object to be incinerated.

[0064] 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.

[0065] The frequency and method of valuable metal recovery described above may be changed depending on the estimated value obtained by the valuable metal content estimation method. For example, if the estimated value of the valuable metal content is low, the valuable metal recovery frequency may be reduced and performed at the next furnace shutdown, thereby enabling the valuable metals to be recovered efficiently. Furthermore, the height of the damming member 16b serving as the deposition mechanism B may be changed depending on the estimated value of the valuable metal content, or multiple steps or protrusions may be provided on the surface 16c of the furnace bottom plate 16. This allows the bed material 13 to remain in a region near the discharge port 16a, thereby increasing the amount of valuable metal recovered.

[0066] Other Embodiments (a) In the above embodiment, the valuable metal content of the bed material 13 was estimated based on pre-processing information of the incineration target, which includes small household appliances. However, the valuable metal content of the bed material 13 may also be estimated based on pre-processing information of materials other than small household appliances, such as urban waste or automobile shredder residue.

[0067] (b) The estimation formula creation unit 52 may update the estimation formula each time it acquires preprocessing information or classification information, or may use the same estimation formula for the same municipality. This allows for increased accuracy of the estimation formula.

[0068] (c) The estimation formula creation unit 52 may create an estimation formula for each type of small home appliance fed into the fluidized-bed furnace 10 or for each valuable metal recovered. This makes it possible to improve the accuracy of the estimation formula. [Industrial Applicability]

[0069] The present invention can be used in a valuable metal content estimation method and a valuable metal recovery method that estimate the amount of valuable metals contained in a bed material remaining on a furnace bottom plate based on pretreatment information for incineration of the incineration object. [Explanation of symbols]

[0070] 10:Fluidized bed furnace 12: Furnace body 13: Fluid medium 16: Furnace bottom plate 16a: discharge outlet A: Dissipation mechanism

Claims

1. A fluidized bed furnace for incinerating or gasifying an object to be incinerated, comprising: a furnace body for accommodating a fluidized medium; and an aeration mechanism for spraying a fluidizing gas to fluidize the fluidized medium, wherein the furnace body has a furnace bottom plate for supporting the fluidized medium; and a discharge port provided adjacent to the furnace bottom plate and capable of discharging the fluidized medium, A method for estimating the amount of valuable metals contained in the bed material remaining on the furnace bottom plate, based on pretreatment information for incineration of the object to be incinerated, with the aeration mechanism stopped and at least a portion of the bed material extracted from the discharge outlet.

2. The method for estimating a content of valuable metals according to claim 1 , wherein the pretreatment information includes separation information of the object to be incinerated.

3. The valuable metal content estimation method according to claim 2 , wherein the sorting information includes whether or not sorting has been performed and the type of sorting.

4. The method for estimating a content of valuable metals according to claim 2 , wherein the object to be incinerated includes small household appliances.

5. 5. The method for estimating a content of valuable metals according to claim 4, wherein the amount of valuable metals is expressed by a correlation equation based on a correlation with a small appliance input point that indicates the ease of input of the small appliance into the fluidized bed furnace, obtained from the pretreatment information.

6. The valuable metal content estimation method according to claim 5 , wherein the correlation equation is expressed using the small appliance input points for each type of small appliance.

7. The method for estimating a content of valuable metals according to claim 5, wherein the valuable metal is gold.

8. A valuable metal recovery method, which changes the recovery frequency or recovery method of the valuable metal depending on the estimated value estimated by the valuable metal content estimation method according to any one of claims 1 to 7.

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