JP7528391B1 - Valuable metal content estimation method and valuable metal recovery method - Google Patents

Abstract

The present invention provides a method for estimating a content of valuable metals and a method for recovering valuable metals, which are capable of efficiently recovering valuable metals.
[Solution] In a fluidized bed furnace (10) that incinerates or gasifies an object to be incinerated, the furnace body (12) comprises a furnace body (12) that contains a bed material (13), and an aeration mechanism (A) that sprays a 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 outlet (16a) provided adjacent to the furnace bottom plate (16) through which the bed material (13) can be discharged. In this state, with the aeration mechanism (A) stopped and at least a portion of the bed material (13) extracted from the discharge outlet (16a), the amount of valuable metals contained in the bed material (13) remaining on the furnace bottom plate (16) is estimated based on pretreatment information for the incineration of the object to be incinerated.
[Selected Figure] Figure 1

Description

The present invention relates to a method for estimating valuable metal content and a method for recovering valuable metals.

As described in Patent Document 1, known fluidized bed furnaces include fluidized bed incinerators that incinerate various waste materials while a fluidizing medium such as sand is in motion, and fluidized bed gasifiers that gasify the waste materials. 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 fluidizing medium to the furnace body.

The fluidized bed furnace described in Patent Document 1 is configured to extract and recover fluidized media from a discharge port (referred to as an "extraction port" in the document) provided at the bottom of the furnace. Waste that is incinerated or otherwise treated by a fluidized bed furnace contains trace amounts of valuable metals, such as precious metals such as gold and silver, and heavy metals such as lead and zinc. It is known that of the fluidized media contained in the fluidized bed furnace, the fluidized media that remains on the furnace bottom plate without being extracted from the discharge port contains high concentrations of valuable metals derived from the waste. Therefore, in the fluidized bed furnace, the furnace bottom plate is tilted toward the discharge port to discharge the fluidized media from the discharge port by gravity, and then the valuable metals are recovered from the fluidized media remaining on the furnace bottom plate.

JP 2021-25699 A

Efficient recovery of valuable metals is achieved by recovering a fluidized bed material with a high valuable metal content, but the valuable metal content of the fluidized bed material has been estimated empirically. As a result, it is not possible to estimate the valuable metal content in fluidized bed furnaces that have not yet recovered valuable metals, and there is room for improvement in the efficient recovery of valuable metals.

The present invention was made in consideration of the above problems, and its purpose is to provide a valuable metal content estimation method for estimating the amount of valuable metals contained in the fluidized medium contained in the furnace body, and a valuable metal recovery method.

The characteristic configuration of the valuable metal content estimation method according to the present invention is that in a fluidized bed furnace that incinerates or gasifies an object to be incinerated, the furnace body includes a furnace body that contains a fluidized medium, and an aeration mechanism that sprays a fluidizing gas to fluidize the fluidized medium, the furnace body having a furnace bottom plate that supports the fluidized medium, and an outlet that is adjacent to the furnace bottom plate and can discharge the fluidized medium, the amount of valuable metals contained in the fluidized medium remaining on the furnace bottom plate is estimated based on pretreatment information for the incineration of the object to be incinerated when the aeration mechanism is stopped and at least a portion of the fluidized medium is extracted from the outlet.

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

Another feature of the configuration is that the pre-processing information includes sorting information for the incineration object.

According to this configuration, the pretreatment information includes sorting information for the incineration target, so the valuable metal content of the fluidized medium can be estimated based on the sorting information. Since the type and amount of the incineration target fed into the fluidized bed incinerator changes depending on the sorting method for the incineration target, it is possible to improve the accuracy of estimating the valuable metal content of the fluidized medium.

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

According to this configuration, the sorting information includes whether or not sorting was performed and the type of sorting, so the type of sorting performed by each local government can be reflected in the pretreatment information. Since the type and amount of incineration material fed into the fluidized bed furnace changes depending on whether or not sorting was performed and the type of sorting, it is possible to improve the accuracy of estimating the valuable metal content of the fluidized medium.

Another feature of the configuration is that the items to be incinerated include small household appliances.

According to this configuration, small household appliances that contain 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 pretreatment information for incineration, it is possible to improve the accuracy of estimating the valuable metal content of the bed material.

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

According to this configuration, the amount of valuable metals contained in the fluidized medium is estimated based on a correlation with the small appliance input point, which indicates the ease of inputting 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 valuable metal content of the fluidized medium based on the correlation equation.

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

Small household appliances have different valuable metal content and pre-processing information depending on the type. With this configuration, a correlation equation is created using the small appliance input points for each type of small appliance, improving the accuracy of estimating the amount of valuable metals contained in the flow medium.

Another feature of the configuration is that the valuable metal is gold.

With 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.

The valuable metal recovery method according to the present invention is characterized in that the valuable metal recovery frequency or recovery method is changed depending on the value estimated by the valuable metal content estimation method.

According to this configuration, the valuable metal recovery frequency or recovery method is changed depending on the value estimated by the valuable metal content estimation method. This makes it possible to recover valuable metals at the timing or with the method that maximizes the valuable metal recovery efficiency.

FIG. 1 is a diagram illustrating a schematic configuration of a fluidized bed furnace facility according to an embodiment. FIG. 2 is a partial cross-sectional view showing the configuration of a hearth plate in a fluidized bed furnace. FIG. 2 is a plan view showing the configuration of an aeration pipe in a fluidized bed furnace. FIG. 2 is a cross-sectional view of a fluidized bed furnace with a fluidized medium remaining on the bottom plate. FIG. 1 is a diagram showing the configuration of a valuable metal content estimation device. FIG. 1 is a process diagram of a method for estimating the content of valuable metals. FIG. 11 is a diagram showing an example of classifications of small home appliances and first coefficients. FIG. 13 is a diagram illustrating an example of an estimation formula.

Below, an embodiment 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 embodiment, and various modifications are possible without departing from the spirit of the present invention.

[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.

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), discarded home appliances, and combustible materials, such 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 home appliances.

The fluidized bed furnace 10 incinerates or gasifies the incineration target. As shown in FIG. 1, the fluidized bed furnace 10 is provided with a furnace body 12 that accommodates the fluidized medium 13. The furnace body 12 (fluidized bed furnace 10) has a furnace bottom plate 16 that supports the fluidized medium 13, and a discharge port 16a that is provided adjacent to the furnace bottom plate 16 and can discharge the fluidized medium 13. In this embodiment, a circular opening is formed in the center of the furnace bottom plate 16, and the discharge port 16a is formed by this opening. In addition, the discharge port 16a of the furnace bottom plate 16 is connected to a discharge pipe 15 that extends below the furnace bottom plate 16. Furthermore, the fluidized bed furnace 10 is provided with an aeration mechanism A that blows fluidizing gas toward the fluidized medium 13 from below the furnace bottom plate 16 of the furnace body 12. In this embodiment, the aeration mechanism A is configured to blow fluidizing gas from below the furnace bottom plate 16. Although not shown, the air diffusion mechanism A may be configured to blow fluidizing gas from the side of the furnace body 12 above the furnace bottom plate 16.

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

The hearth plate 16 is disposed at the bottom side of the furnace body 12. The discharge port 16a of the bed material 13 is formed on the inner periphery side 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 side, and the inclination angle is smaller than the angle of repose of the bed material 13. Specifically, the angle of repose of the bed material 13 is preferably 30 degrees to 40 degrees, while the inclination angle of the hearth plate 16 is 10 degrees 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, but the hearth plate 16 may be configured so that only a portion of it is inclined at an angle smaller than the angle of repose of the bed material 13.

The fluidized bed furnace 10 processes the incineration target containing valuable metals (e.g., gold, silver, copper, lead, or zinc) while the fluidized bed furnace 10 is in a fluidized state with the fluidized bed medium 13 in fluidized state. The fluidized bed furnace 10 processes the incineration target containing valuable metals (e.g., gold, silver, copper, lead, or zinc) while the fluidized bed medium 13 is in fluidized state.

The discharge pipe 15 is for drawing out 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.

The air diffusion mechanism A is composed of an inlet 17, a wind box 18, and a number of air diffusion tubes 19. As shown in Figures 2 and 3, each air diffusion tube 19 has a straight tube section 19a that penetrates the furnace bottom plate 16 in the thickness direction, and a U-shaped tube section 19b connected to the upper end of the straight tube section 19a. As shown in Figure 1, in order to fluidize the bed material 13, the air diffusion mechanism A circulates the fluidizing gas introduced into the wind box 18 from the inlet 17 through the air diffusion tubes 19, and blows 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 inside the straight tube section 19a and is then sent out from the opening of the U-shaped tube section 19b toward the bed material 13 (arrow in Figure 3).

As shown in Figures 2 to 4, the furnace bottom plate 16 has a deposition mechanism B at a position different from the aeration mechanism A, which deposits the bed material 13 to form a deposition layer 13a when the aeration mechanism A is stopped and the bed material 13 is extracted from the discharge port 16a. The deposition mechanism B is composed of a damming member 16b provided on the furnace bottom plate 16. In this embodiment, the damming member 16b is provided on the opening periphery, which is the end of the furnace bottom plate 16 on the discharge port 16a side, and prevents the bed material 13 remaining on the furnace bottom plate 16 from flowing into the discharge port 16a due to gravity.

As shown in FIG. 1, the swirling flow melting furnace 20 is a furnace that completely combusts the combustible gas and unburned materials while forming a swirling flow 100 of the combustible gas generated in the fluidized bed furnace 10, and melts the ash entrained by 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 the combustible gas and a slag outlet 22 for discharging the 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.

The inlet 21 is provided at a portion near the top of the 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 at 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.) arranged downstream of the swirling flow melting furnace 20, and is then released into the atmosphere from a chimney (not shown).

The fluidized bed furnace 10 has a circulation path 40. The circulation path 40 separates the fluidized medium 13 discharged outside the furnace body 12 from the non-combustible materials and then returns it 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.

The extraction screw 41 is provided at the lower end of the discharge pipe 15 and is used to extract the bed material 13 together with the non-combustible material from the bottom of the furnace body 12 by rotational drive. The classification device 42 is provided at the downstream end of the extraction 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 crushed and then turned into slag in the swirling flow melting furnace 20 or transported outside the system.

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

The storage tank 44 stores the fluid medium 13 transported upward by the circulation elevator 43. The second transport path 46 is provided from the outlet 43B to the inlet 43A of the circulation elevator 43, with the storage tank 44 located midway along the path. This allows the fluid medium 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.

One end of the third conveying path 47 is connected to a portion of the second conveying path 46 above the storage tank 44, and the other end is connected to the 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 conveying path 47. Although not shown, the circulation path 40 may further have a switching unit (valve, etc.) that switches whether the bed material 13 discharged from the outlet 43B of the circulation elevator 43 is led to the storage tank 44 or to the furnace body 12.

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

The valuable metal content estimation device 50 acquires pretreatment information of the 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 has an acquisition unit 51 that acquires pretreatment information, an estimation equation creation unit 52 that creates an estimation equation (an example of a correlation equation) for the valuable metal content, 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 FPGA, 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 has the steps of acquiring pretreatment information and sorting information (S1), determining a first coefficient (S2), calculating small home appliance input points (S3), creating an estimation equation (S4), and estimating the valuable metal content (S5).

The pretreatment information is information about whether the items to be incinerated can be fed into the fluidized bed furnace 10, and includes, for example, sorting information about the items to be incinerated. The sorting information is, for example, information about which type of waste the small home appliances to be incinerated fall into, such as burnable waste, non-burnable waste, or bulky waste. Since waste classification methods differ depending on the municipality, the sorting information should include information about the classification of each small home appliance in each municipality. In other words, the sorting information should include the type, number, or weight of the small home appliances to be treated as recyclable items, burnable waste, non-burnable waste, or bulky waste.

In addition, the sorting information may include whether or not the incineration targets are sorted in each municipality 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 takes to sort the incineration targets and the amount of valuable metals recovered by sorting. The acquisition unit 51 acquires, for example, pretreatment information for the incineration targets input to the fluidized bed furnace 10 in each municipality via a network (not shown) or the like, and the actual value of the amount of valuable metals recovered by the recovery of the fluidized medium 13 (S1 in FIG. 6). If there are multiple recovery results, the actual value of the amount of valuable metals recovered may be the average value. The pretreatment information may be input directly to the valuable metal content estimation device 50.

The estimation formula creation unit 52 creates an estimation formula for the valuable metal content based on the preprocessing information acquired by the acquisition unit 51. First, the estimation formula creation unit 52 calculates a small appliance input point indicating 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 indicating the ease of inputting into the fluidized bed furnace 10.

The estimation formula creation unit 52 sets the first coefficient based on the pre-processing information (S2 in FIG. 6). For example, small household appliances whose waste type is a recyclable item are not fed into the fluidized bed furnace 10, so the estimation formula creation unit 52 sets the first coefficient of small household appliances that correspond to recyclable items to 0. Similarly, combustible waste is fed into the fluidized bed furnace 10, so the first coefficient of small household appliances that correspond to 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-burnable waste and bulky waste is long and most of the valuable metals contained in small household appliances are recovered, the first coefficient can be set to 0. If the time required for manual sorting on a conveyor is short and some of the valuable metals are not recovered and are fed into the fluidized bed furnace 10, the first coefficient can be set to 0.3. In addition, since mechanical sorting is not considered to have as high a recovery rate of valuable metals as manual sorting, the first coefficient can be set to 0.6 when only mechanical sorting is performed without manual sorting. The first coefficient may be set according to the time required for sorting small household appliances and the amount of valuable metals recovered by sorting.

For example, if there are 30 small household appliances whose waste type is recyclable, the estimation formula creation unit 52 multiplies them by the first coefficient 0 for recyclables to set the small household appliance input points to 0, and if there are 5 small household appliances whose waste type is combustible, the estimation formula creation unit 52 multiplies them by the first coefficient 1 for combustible, to set the small household appliance input points to 5. Similarly, if there are 20 small household appliances whose waste type is non-burnable and the municipality only performs mechanical sorting, the estimation formula creation unit 52 multiplies them by the first coefficient 0.6 for non-burnable, to set the small household appliance input points to 12, and if there are 10 small household appliances whose waste type is bulky and the municipality performs manual sorting, the estimation formula creation unit 52 multiplies them by the first coefficient 0.3 for bulky 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).

After calculating the small appliance input points, the estimation formula creation unit 52 creates an estimation formula for the valuable metal content based on the small appliance input points in each local government and the actual value of the valuable metal recovery amount from the recovery of the bed material 13 (S4 in FIG. 6). The estimation formula may be created by 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 input points.

Figures 7 and 8 show the small appliance input points calculated by the estimation formula creation unit 52 and an example of an estimation formula. Figure 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 pre-processing information for each municipality. Figure 8 is a graph showing the correlation between the small appliance input points and the gold content contained in the fluidized medium 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.

The small appliance input points may be calculated by multiplying the weight of each small appliance for each waste type by the 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.

After the estimation formula is created by the estimation formula creation unit 52, 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 home appliance input point in the fluidized bed furnace 10 from the classification information of the small home appliances in the fluidized bed furnace 10 related to the estimation of the valuable metal content acquired by the acquisition unit 51. Then, the valuable metal content in the fluidized bed furnace 10 is estimated from the small home 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. In addition, a trained model for estimating the valuable metal content of the fluidized medium 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 actually contained in the fluidized medium 13. This makes it possible to improve the estimation accuracy of the valuable metal content of the fluidized medium 13.

[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 the present 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 in which the bed material 13 supported on the furnace bottom plate 16 is caused to flow into 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 addition, 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, in the extraction step, the bed material 13 remaining on the furnace bottom plate 16 is deposited by the deposition mechanism B (damming member 16b) to form a deposition layer 13a. In addition, the bed material 13 is deposited such that the thickness of the deposition layer 13a is greater on the discharge outlet 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 Figure 4).

As shown in FIG. 1, before maintenance of the fluidized bed furnace 10, i.e., during normal operation of the fluidized bed furnace 10, the fluidized medium 13 is fluidized by the fluidizing gas (e.g., air) sent through the air diffuser 19, and the material to be incinerated is supplied into the furnace body 12 from the supply port 14. The material to be incinerated is heated by the fluidized medium 13 in the furnace body 12 and pyrolyzed into combustible gas, unburned material, and ash. The material to be incinerated contains a considerable amount of valuable metals such as precious metals (gold, silver, copper, etc.) and heavy metals (lead, zinc, etc.).

The combustible gas generated in the fluidized bed furnace 10 flows into the swirling flow melting furnace 20 through the duct 30 together with the unburned material and ash. In the swirling flow melting furnace 20, the combustible gas and unburned material are completely combusted and the ash melts. During this steady operation, the circulation path 40 is operated to extract the fluidized medium 13 filled in the furnace body 12 together with the non-combustible material to the outside of the furnace, and to return the fluidized medium 13 from which the non-combustible material has been removed to the furnace body 12.

Next, when the time for maintenance of the fluidized bed furnace 10 arrives, first the supply of the 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 aeration mechanism A is stopped. After that, an extraction process is performed in which the fluidized medium 13 filled in the furnace body 12 is extracted to the outside of the furnace body 12.

In the extraction process, the bed material 13 filled in the furnace body 12 is made to flow into the discharge port 16a and extracted to the outside of the furnace body 12. Specifically, the extraction screw 41 is rotated to extract the bed material 13 filled in the furnace body 12 to the outside of the furnace body 12 via the discharge port 16a and the discharge pipe 15 connected to the discharge port 16a.

The bed material 13 discharged outside 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 discharge process, 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. Therefore, not all of the bed material 13 in the furnace body 12 is discharged outside the furnace in the discharge process, and some of the bed material 13 is deposited on the furnace bottom plate 16 after the discharge process to form a deposit layer 13a and remain.

In this embodiment, the furnace bottom plate 16 further has a damming member 16b provided on the opening periphery, which is the end of the furnace bottom plate 16 on the discharge port 16a side, as a deposition mechanism B for the bed material 13 (see Figures 2 to 4). Therefore, in the extraction process, the bed material 13 is prevented from flowing into the discharge port 16a by the damming member 16b, so that a large amount of bed material 13 remains on the furnace bottom plate 16 as a deposition layer 13a. In addition, 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 furnace bottom plate 16 by the deposition mechanism B (damming member 16b) is larger on the discharge port 16a side than in the central portion C in the radial direction from the center X to the inner surface 12a of the furnace body 12, with the center X being the reference in the area where the furnace bottom plate 16 is located in a plan view of the furnace body 12 (see Figures 2 and 4). Specifically, as shown in FIG. 2, the thickness of the sediment layer 13a is greater on the discharge port 16a side 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. In addition, 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 leave a large amount of bed material 13 in the area 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.

In this embodiment, the damming member 16b is formed in a circular shape in a plan view at the end (opening edge) of the diffuser tube group located at the innermost side of the diffuser tube group arranged in a concentric circle composed of a plurality of diffuser tubes 19, which is closer to the discharge port 16a. As shown in FIG. 2, the height of this damming member 16b based on the surface 16c of the furnace bottom plate 16 is smaller than the height of the diffuser tube 19. In particular, since the damming member 16b is located at a position lower than the U-shaped tube portion 19b of the diffuser tube 19, the deposition layer 13a can be efficiently formed by the deposition mechanism B without hindering the diffusion process of the diffusion mechanism A during operation. The damming member 16b may be configured to be freely moved between a state where it protrudes from the surface 16c of the furnace bottom plate 16 and a state where it does not protrude from the surface 16c of the furnace bottom plate 16.

In this way, most (e.g., 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 a 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.

For this reason, 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 (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 recovering the bed material 13 directly from inside the furnace body 12.

Then, 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 furnace bottom 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 can be performed after stopping the aeration mechanism A.

In this way, the recovery method according to this embodiment utilizes the timing of maintenance of the fluidized bed furnace 10 to recover the fluidized medium 13 that contains a high concentration of valuable metals derived from the incineration target.

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

The frequency and method of valuable metal recovery described above may be changed depending on the estimated value estimated 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 timing, thereby allowing the valuable metals to be recovered efficiently. In addition, the height of the damming member 16b as the accumulation 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 portion near the discharge port 16a, thereby increasing the amount of valuable metals recovered.

Other embodiments
(a) In the above embodiment, the valuable metal content of the bed material 13 was estimated based on pretreatment information of the incineration target, which included small household appliances. However, the valuable metal content of the bed material 13 may be estimated based on pretreatment information of targets other than small household appliances, for example, urban waste, automobile crushing residues, etc.

(b) The estimation formula creation unit 52 may update the estimation formula each time preprocessing information or sorting information is acquired, or may use the same estimation formula for the same municipality. This makes it possible to improve the accuracy of the estimation formula.

(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 and for each valuable metal recovered. This makes it possible to improve the accuracy of the estimation formula.

The present invention can be used in a valuable metal content estimation method that estimates the amount of valuable metals contained in the bed material remaining in the furnace bottom plate based on pretreatment information for the incineration of the object to be incinerated, and in a valuable metal recovery method.

10: Fluidized bed furnace 12: Furnace body 13: Fluidized medium 16: Furnace bottom plate 16a: Discharge port A: Diffusion mechanism

Claims (8)

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 blowing a fluidizing gas to fluidize the fluidized medium, the furnace body having 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 a valuable metal content, which estimates the amount of valuable metals contained in the bed material remaining in 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. The method for estimating the amount of valuable metals according to claim 1, wherein the pretreatment information includes sorting information for the incineration target. 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. The method for estimating the amount of valuable metals according to claim 2, wherein the incineration target includes small household appliances. The method for estimating the amount 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 indicating the ease of inputting the small appliance into the fluidized bed furnace, obtained from the pretreatment information. 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. The method for estimating valuable metal content according to claim 5, wherein the valuable metal is gold. A method for recovering valuable metals, comprising changing a recovery frequency or a recovery method of the valuable metals according to an estimated value estimated by the valuable metal content estimation method according to any one of claims 1 to 7.

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