JP7625478B2 - Method for recovering valuable metals from valuable metal-containing waste - Google Patents

Description

The present invention relates to a method for recovering valuable metals from valuable metal-containing waste.

Attempts are being made to effectively use waste materials such as municipal waste incineration ash, waste plastics, and shredder dust as cement raw materials. These waste materials contain valuable metals such as gold, silver, copper, and aluminum, and from the perspective of preserving scarce resources, there is a need to recover these valuable metals before they are used as cement raw materials. However, the shape and percentage of valuable metals vary depending on the type of waste, and while there are cases where individual waste materials have been treated, there are cases where mixed waste materials that contain multiple types of waste materials have not been treated. As a result, it is necessary to determine the optimal sorting conditions for recovering valuable metals for each type of waste by trial and error.

A method has been proposed that can efficiently recover valuable metals from waste that has never been treated before without the need for trial and error, for example by measuring the chemical composition and physical properties of the waste, and selecting one or more processes from a heating process, a particle size adjustment process, a magnetic sorting process, a wind sorting process, an eddy current sorting process, a dry specific gravity sorting process, and a water washing process based on the results of these measurements (Patent Document 1).

JP 2018-167181 A

However, when sorting metals using eddy current sorting, it is necessary to set sorting conditions according to the shape of the waste and the content of valuable metals. In particular, since there is a large variation in the shape and content of valuable metals in mixed waste, it is difficult to set sorting conditions, and the recovery efficiency of valuable metals may decrease.
An object of the present invention is to provide a method capable of efficiently recovering valuable metals from waste.

The inventors have discovered that when recovering valuable metals from waste by eddy current sorting, by checking the trajectory of the waste falling from the conveyor belt of the eddy current sorter before eddy current sorting and determining the installation position of the partition plate based on the confirmed falling trajectory, valuable metals can be efficiently recovered from waste regardless of the shape of the waste or the percentage of valuable metals contained therein.

That is, the present invention provides the following [1] to [4].
[1] A method for recovering valuable metals from valuable metal-containing waste, comprising an eddy current sorting step of separating size-adjusted valuable metal-containing waste into non-magnetic metals and non-metals,
a trajectory confirmation step of confirming a trajectory along which the waste falls from the conveyor belt of the eddy current separator before the eddy current separation and determining an installation position of a partition plate based on the confirmed trajectory;
In the eddy current sorting process, non-magnetic metals and non-metals are separated using a partition plate installed based on the track confirmation process, and the non-magnetic metals, which are valuable metals, are recovered.
A method for recovering valuable metals from valuable metal-containing waste (hereinafter, also referred to simply as the "valuable metal recovery method").
[2] The valuable metal recovery method described in [1], wherein in the trajectory confirmation process, the falling trajectory of the waste is photographed by an imaging device, and the image of the falling trajectory obtained is analyzed to determine the installation position of the partition plate.
[3] The valuable metal recovery method described in [1] or [2], in the trajectory confirmation process, two images of the fall trajectory, a first fall trajectory closest to the conveyor belt and a second fall trajectory farthest from the conveyor belt, are selected from the images of the fall trajectory, and the intersection point between a virtual intermediate fall trajectory passing through the horizontal midpoint of the fall trajectories of both images and the trajectory when rotated around the axis of the partition plate is used as a reference point, and the installation position of the partition plate is determined by setting a position on a perpendicular to the virtual intermediate fall trajectory passing through the reference point and L mm (where L satisfies the relationship shown in the following formula (2)) away from the reference point in the direction of the second fall trajectory as the upper end of the partition plate.
r < L < 2r (2)
(In the formula, r represents the D50 of the valuable metal-containing waste whose particle size has been adjusted.)
[4] The valuable metal recovery method according to any one of [1] to [3], wherein the particle size of the valuable metal-containing waste is adjusted to satisfy the relationship of the following formula (1).
M / m ≦ 4 (1)
(In the formula, M represents the maximum diameter of the size-adjusted valuable metal-containing waste, and m represents the minimum diameter of the size-adjusted valuable metal-containing waste.)

According to the present invention, valuable metals can be efficiently recovered from waste, regardless of the shape of the waste or the percentage of valuable metals contained therein.

1 is a flowchart showing an example of a valuable metal recovery method of the present invention. 1 is a flowchart showing an example of a valuable metal recovery method of the present invention. 1 is a schematic diagram showing an overview of a valuable metal recovery method of the present invention. FIG. FIG. 2 is a schematic diagram showing an example of a trajectory confirmation step in the valuable metal recovery method of the present invention. FIG. 2 is a schematic diagram showing an example of a trajectory confirmation step in the valuable metal recovery method of the present invention. FIG. 2 is a schematic diagram showing an example of a trajectory confirmation step in the valuable metal recovery method of the present invention.

The valuable metal recovery method of the present invention will now be described in detail.
The valuable metal recovery method of the present invention is characterized in that valuable metal-containing waste (hereinafter also simply referred to as "waste") is subjected to a process including an eddy current sorting process to recover valuable metals from the waste, and a trajectory confirmation process is performed before the eddy current sorting. A flow chart of an example of the valuable metal recovery method of the present invention is shown in Figure 1.

Examples of waste materials include incineration ash, construction waste soil, and shredder dust generated by crushing scrapped automobiles and scrapped home appliances. Examples of incineration ash include ash obtained by incinerating urban waste and industrial waste, and specifically, in addition to industrial waste such as sludge, waste plastic, metal scraps, glass scraps, concrete scraps, ceramic scraps, slag, and rubble, shredder dust and ash obtained by incinerating general waste can be used. Examples of construction waste soil include soil and sludge generated secondarily from construction and civil engineering works.
The waste used in the present invention may be a single type of waste or a mixed waste in which a plurality of types of waste are mixed.

[Particle size adjustment process]
As shown in FIG. 1, the valuable metal recovery method of the present invention first carries out a particle size adjustment step to obtain valuable metal-containing waste having a particle size adjusted.
In the present invention, prior to the particle size adjustment step, the moisture content may be adjusted in a drying step according to the properties of the waste. The moisture content in the drying step can be adjusted by heating in a dryer or by mixing a moisture content adjuster such as quicklime. A commercially available dryer can be used. From the viewpoint of improving handleability, the moisture content of the waste after drying is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

In the particle size adjustment process, for example, as shown in FIG. 2, the waste may be subjected to one or more processes selected from magnetic separation, sieving, and crushing. Note that these processes may be performed two or more times to obtain waste of the desired particle size.

A magnetic separator can be used for magnetic separation. This makes it possible to remove coarse metal debris from the waste. The magnetic separator can be a commercially available device, and may be any of the drum, pulley, and hanging types, with no particular limitations. From the viewpoint of removing magnetic material, the surface magnetic flux density of the magnetic separator is preferably 700 to 10,000 gauss, more preferably 1,000 to 7,500 gauss, and even more preferably 1,500 to 5,000 gauss.

Sieving may be performed alone or in combination with crushing. For sieving, for example, a vibrating, in-plane motion, rotary, or fixed type sieving machine may be used, and the desired sieve size may be installed.
Crushing can be performed using a crusher. Examples of crushers include jaw crushers, impact crushers, hammer crushers, roll crushers, and rotary crushers. The crusher can be equipped with a screen of desired mesh size for the purpose of adjusting particle size, and when no screen is installed, the fixed teeth, rotating teeth, inner wall, etc. may be adjusted to a desired clearance.

In addition, in the particle size adjustment process, it is preferable to adjust the particle size of the waste material to satisfy the relationship of the following formula (1) from the viewpoints of work efficiency and high-quality valuable metal recovery.

M/m≦4 (1)

[In the formula, M represents the maximum diameter of the size-adjusted valuable metal-containing waste, and m represents the minimum diameter of the size-adjusted valuable metal-containing waste.]

From the viewpoints of work efficiency and high-quality valuable metal recovery, M/m in the above formula (1) is preferably 3.5 or less, more preferably 3 or less, and even more preferably 2.5 or less.

The maximum diameter (M) of the waste is usually less than 100 mm, but from the viewpoints of work efficiency and high-quality valuable metal recovery, it is preferably less than 15 mm, more preferably less than 10 mm. The minimum diameter (m) of the waste is usually 0.5 mm or more, but from the viewpoints of work efficiency and high-quality valuable metal recovery, it is preferably 1 mm or more, more preferably 1.5 mm or more.
In addition, from the viewpoint of improving the sorting efficiency, the particles may be separated into three or more particle groups by sieving, and the particle groups other than the particle group with the smallest diameter may be subjected to the orbit confirmation process described below for each particle group, and eddy current sorting may be performed.

[Trajectory confirmation process]
This process involves confirming the trajectory along which the size-adjusted waste falls from the conveyor belt of the eddy current separator, and determining the installation positions of the partition plates based on the confirmed falling trajectory.
A schematic diagram showing an overview of the valuable metal recovery method of the present invention is shown in Figure 3. In the drawings of this specification, the same elements are given the same symbols, and for convenience of illustration, the dimensional ratios of the drawings do not necessarily match those in the description.
In this process, as shown in Fig. 3, for example, a conveyor belt 2b having the same specifications as the conveyor belt 2a of the eddy current sorter is used, and the trajectory of the waste 1 falling from the conveyor belt 2b stretched around the head pulley 3 is photographed by the imaging device 4, and the image of the falling trajectory is analyzed to estimate the falling trajectory of the particles containing non-magnetic metals, and the installation position of the partition plate 5 can be determined. In this case, in the eddy current sorting, the particles containing non-magnetic metals are sorted to the back side of the partition plate due to the repulsive force caused by the eddy current, as shown in Fig. 3, so it is preferable to install the partition plate at a position away from the conveyor belt. For example, a digital camera can be used as the imaging device. In addition, for image analysis, for example, a personal computer and image processing software can be used. It is not necessary to generate an eddy current in the conveyor belt 2b.

Hereinafter, an example of a method for determining the installation position of the partition plate will be specifically described with reference to FIGS.
When waste falls from the conveyor belt, the speed and angle of radiation of the waste differ depending on the size and properties of the waste. As shown in FIG. 4(a), first, from among images of the fall trajectory of the waste 1 captured by an imaging device, two images are selected: a first fall trajectory 7 closest to the conveyor belt 2b, and a second fall trajectory 8 furthest from the conveyor belt. Next, as shown in FIG. 4(b), the horizontal midpoints of the first fall trajectory 7 and the second fall trajectory 8 are plotted. Note that in FIG. 4(b), four midpoints, m1 to m4, are shown, but n (n is an integer) can be plotted depending on the shape of the fall trajectory. Next, as shown in FIG. 5(a), the n midpoints are connected to create a virtual intermediate fall trajectory 9. Next, as shown in FIG. 5(b), the intersection of the trajectory when rotated around the axis 5a of the partition plate 5 and the virtual intermediate fall trajectory 9 is set as a reference point P. Next, as shown in Fig. 6(a), a perpendicular line v is drawn to the imaginary intermediate drop trajectory that passes through the reference point P. Then, as shown in Fig. 6(b), a partition plate 5 is installed so that its upper end portion contacts the perpendicular line v at a position L mm (where L satisfies the relationship shown in the following formula (2)) away from the reference point P in the direction of the second drop trajectory.

r < L < 2r (2)

[In the formula, r represents the D50 of the size-adjusted valuable metal-containing waste.]

In this specification, "D50 of size-adjusted valuable metal-containing waste" refers to the intermediate diameter between the maximum and minimum diameters of the size-adjusted valuable metal-containing waste.

[Eddy current sorting process]
This process involves eddy current sorting of the waste, separating it into non-magnetic metals and non-metallic matter using partition plates installed based on the track confirmation process, and recovering the non-magnetic metals, which are valuable metals.
In eddy current sorting, for example, eddy currents are generated in non-magnetic metals contained in waste by the electromagnetic induction effect of the moving magnetic field of a rotating magnet body installed at the tip of the conveyor belt, and a horizontal repulsive force acts on the metals, causing them to bounce from the tip of the conveyor belt and fall to the back of the partition plate, and valuable metals such as gold, silver, copper, and aluminum are recovered. Note that non-metals fall almost vertically from the tip of the conveyor belt, so they are separated from valuable metals by the partition plate.
As the eddy current separator, a known eddy current separator can be used, and although there is no particular limitation, examples thereof include a rotating magnet type, a cross-belt conveyor type, and a rotating cylinder type.
From the viewpoint of recovering high-quality valuable metals, the rotation speed of the rotating magnet body is preferably 1500 rpm or more, more preferably 3000 rpm or more, and even more preferably 4000 rpm or more.

The following examples are provided to further explain the embodiments of the present invention. However, the present invention is not limited to the following examples.

1. Raw materials used (1) Type: incineration bottom ash (2) Pretreatment: After drying the incineration bottom ash, the coarse metal scraps were removed using a magnetic separator. Next, the incineration bottom ash after magnetic separation was crushed to 20 mm or less using an impact crusher, sieved, and the particle size was adjusted to D50 of 3 mm and 6 mm, and then processed using a 3000G magnetic separator to remove magnetic materials.

2. Equipment used in the track confirmation process (1) Digital camera (imaging device)
(2) Conveyor for checking track A conveyor belt with the same specifications as the eddy current separator (which does not generate eddy currents) was used.

3. Equipment used in the eddy current sorting process Eddy current sorting machine (magnetic drum rotation speed set to 4000 rpm)

4. Analysis of Cu, Ag, and Al Analysis of Cu, Ag, and Al was performed by the method shown in Table 1 on the specimens to be analyzed that had been pretreated by matte fusion and then pulverized to a size of 100 μm or less.

Example 1
Using incineration bottom ash with a D50 of 3 mm, the track confirmation process was carried out according to the procedure shown in Figures 4 to 6, the partition plate installation position was set to L = 5 mm (within the range of r < L < 2r), and eddy current sorting was carried out. The sorted non-magnetic metals were recovered and analyzed for valuable metals such as copper, silver, and aluminum. The results are shown in Table 2.

Example 2
Using incineration bottom ash with a D50 of 6 mm, the track confirmation process was carried out according to the procedure shown in Figures 4 to 6, the partition plate was set at a position L = 10 mm (within the range of r < L < 2r), and eddy current sorting was carried out. The sorted non-magnetic metals were recovered and analyzed for valuable metals such as copper, silver, and aluminum. The results are shown in Table 2.

Comparative Example 1
Eddy current sorting was performed on the incineration bottom ash used in Example 2, with the partition plate installed at a position L = 5 mm. The sorted non-magnetic metals were recovered and analyzed for valuable metals such as copper, silver, and aluminum. The results are shown in Table 2.

Comparative Example 2
Eddy current sorting was performed on the incineration bottom ash used in Example 2, with the partition plate installed at a position L = 0 mm. The sorted non-magnetic metals were recovered and analyzed for valuable metals such as copper, silver, and aluminum. The results are shown in Table 2.

Comparative Example 3
Eddy current sorting was performed on the incineration bottom ash used in Example 2, with the partition plate installed at a position L of 30 mm. The sorted non-magnetic metals were recovered and analyzed for valuable metals such as copper, silver, and aluminum. The results are shown in Table 2.

From Table 2, it can be seen that by carrying out a trajectory confirmation process before the eddy current sorting process, in which the trajectory of the falling waste is predicted and the installation position of the partition plate is determined, valuable metals from valuable metal-containing waste can be recovered efficiently and at a high quality.

REFERENCE SIGNS LIST 1: Grain-size-adjusted valuable metal-containing waste 2a, 2b: Conveyor belt 3: Head pulley 4: Imaging device 5: Partition plate 5a: Partition plate axis 6: Tray 7: First drop trajectory 8: Second drop trajectory 9: Virtual intermediate drop trajectory m1 to m4: Midpoint P: Reference point v: Perpendicular line to the virtual intermediate drop trajectory passing through reference point P

Claims (1)

A method for recovering valuable metals from valuable metal-containing waste, comprising an eddy current sorting step of separating size-adjusted valuable metal-containing waste into non-magnetic metals and non-metals,
a particle size adjustment step of adjusting the particle size of the valuable metal-containing waste before the eddy current sorting so that the particle size satisfies the following formula (1);
M / m ≦ 4 (1)
(In the formula, M represents the maximum diameter of the size-adjusted valuable metal-containing waste, and m represents the minimum diameter of the size-adjusted valuable metal-containing waste.)
a trajectory confirmation step of photographing the trajectory of the waste falling from the conveyor belt of the eddy current sorter by an imaging device, selecting two images from the images of the trajectories, a first trajectory closest to the conveyor belt and a second trajectory furthest from the conveyor belt, setting a reference point as an intersection between a virtual midpoint trajectory passing through the horizontal midpoint of the trajectories of the two images and a trajectory when rotated around the axis of a partition plate, and determining an installation position of the partition plate as a position on a perpendicular line to the virtual midpoint trajectory passing through the reference point and spaced L mm (where L satisfies the relationship shown in the following formula (2)) from the reference point in the direction of the second trajectory as the upper end of the partition plate ,
r < L < 2r (2)
(In the formula, r represents the D50 of the valuable metal-containing waste whose particle size has been adjusted.)
In the eddy current sorting process, non-magnetic metals and non-metals are separated using a partition plate installed based on the track confirmation process, and the non-magnetic metals, which are valuable metals, are recovered.
A method for recovering valuable metals from valuable metal-containing waste.