JPS6155427B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic separation device that uses differences in electrical properties of substances to be sorted and electrostatic Coulomb force to select and refine substances to be sorted.

Recently, the reuse of kitchen waste in municipal waste as compost has begun to be put to practical use. The method for this purpose is to first sort and separate metals, glass, rubble, sand, and plastics from the municipal waste brought into the waste treatment plant, and then finely crush the remaining garbage. The waste is then sent to a composting device and composted. In addition, in such a composting apparatus, food waste is converted into fully ripened compost through the processes of preliminary fermentation and post-fermentation, and then a compost product is obtained through a purification process using a vibrating sieve or the like. However, the compost that comes out after completing the post-ripening process is fine granular pure compost in which the raw organic matter has sufficiently decayed and decomposed and hardened into lumps of soil, components that have not sufficiently decayed and decomposed, and other raw materials. This is a mixture of foreign substances such as glass, plastic, and debris that have come into the environment. Of these, large lump components that have not fully decomposed or large-sized impurities can be classified and sorted using a vibrating sieve, but as with pure compost, impurities that have been finely ground to a few millimeters are passed through the sieve as is. It will pass through and be mixed into the compost. Although the amount of impurities mixed in the compost that has gone through the classification and sorting process is usually only a few percent, it is still undesirable for farmland and needs to be removed and purified as much as possible. Using the separate sorting method, it is extremely difficult to further refine the compost by removing only the finer impurities.

The present invention relates to an electrostatic sorting device whose main purpose is to improve the quality of compost by removing finer impurities from the compost after the classification and purification process as described above.

The principle of electrostatic separation is well known, and various types of electrostatic separation devices have been proposed and put into practical use in various industrial fields. Figure 1 shows the principle of a typical electrostatic separation device used for refining ores and food powders. In this device, a rotating drum 1 is used as one ground electrode, and a corona discharge electrode 2 for applying a high voltage is placed on the side of the rotating drum 1, and a supply is provided above the drum 1 for supplying the mixture M to be sorted to the drum 1. A feeder 3 with a hopper is disposed below the drum 1, and collection hoppers 4 and 5 are disposed, respectively. Note that 6 is a scraper like a brush that slides on the circumferential surface of the drum 1. The principle of operation of such a device is well known, and its operation will be briefly described here. First, let us take as an example the case where the mixture to be sorted is the above-mentioned compost.The mixture to be sorted M has electrical conductivity because it has insulating particles N of glass and plastics shown by white circles and a relatively high water content. It is a mixture with conductive particles O shown in black circles of compost. On the other hand, corona discharge electrode 2
A strong electric field exists in the space between the drum 1 and the drum 1, and a corona current flows toward the drum 1. Therefore, when the compost containing impurities supplied from the feeder 3 onto the drum 1 reaches the strong electric field area, it is exposed to an ion shower. In this process, the pure compost, which is conductive particles O, discharges its ionic charge by contact with the drum 1, and conversely becomes charged to the same polarity as the drum electrode due to electrostatic induction, and is transferred between the cylindrical drum 1 and the conductive particles O. It is repulsed by the applied Coulomb force and falls forward toward the compost collection hopper 5 as shown by arrow A. On the other hand, contaminants such as glass and plastic, which are insulating particles N, receive charges of the same polarity as the corona discharge electrode 2 and are charged, and move with the rotation of the drum 1 while being adsorbed to the surface of the drum 1, and eventually reach the final stage. When it reaches the vicinity of the lower level, it falls into the foreign matter recovery hopper 4 as shown by arrow B due to its own weight. Incidentally, objects whose own weight is light and remain adsorbed are forcibly scraped off by the scraper 6.

By the way, the above-mentioned conventional electrostatic sorting has the following practical difficulties when purifying a large amount of material to be sorted, for example, compost.

(1) The processing capacity is small. As mentioned earlier, in order to remove foreign matter by adsorption to the drum, it is necessary to charge the foreign matter with ions by corona discharge. To do this, limit the amount of compost supplied from the feeder,
It is necessary for the contaminants to form a layer on the drum and be exposed towards the corona discharge electrode. Therefore, in order to expose the foreign matter and distribute it on the drum, the amount of feeder must be sufficiently restricted so that the foreign matter and the compost do not overlap on the drum. Due to this point, the conventional apparatus described above has a small processing capacity per unit length in the axial direction of the rotating drum, and when put into practical use, the size of the apparatus becomes very large.

(2) There are restrictions on the size and shape of contaminants that can be treated.As shown in Figure 2, insulating contaminants N adhere to the drum 1 and move, but plastics. In a thin and light strip like a film, the separation distance d when the positive ions q ⁺ on the strip and the negative ions q ^- on the drum surface are attracted to each other is small, so a large Coulomb force acts, and even when they reach the bottom of the drum, It won't fall under its own weight. However, thick pieces such as glass have a large separation distance d, so the Coulomb force that attracts them is small, and their own weight is heavy, so they cannot stick to the drum and immediately slide off the drum. It falls into the hopper on the compost side,
It may end up getting mixed into the compost again. Regarding conventional electrostatic sorting equipment, furthermore,
The following is known as disclosed in the above publication.
That is, a high voltage is applied between the inclined upper electrode and the endless belt, and the mixed particles supplied from the hopper are controlled by the electric field between the upper electrode and the endless belt, the running up of the endless belt, and the mutual interference of the component particles. resulting agitation, suppression,
An endless strip run-up system that utilizes the effects of restraint, flight, and stacking to move each component particle down and up the slope and collect it, depending on the magnitude of the electric flying force specific to each component particle. This is an electrostatic ore beneficiation device. Since this device separates and collects the objects to be sorted at the top and bottom of the endless belt in the direction of movement, the collection line length is short, making it unsuitable for sorting objects such as compost, where the amount of processing per unit is an issue. be. Furthermore, when multiple hoppers are stacked vertically in order to increase throughput, the insulation distance in the vertical direction becomes excessive because the hopper has a high potential. The disadvantage was that it was inevitable that there would be an increase in

The present invention has been made in consideration of the above points, and eliminates the drawbacks of the conventional electrostatic sorting device described above.
It is an object of the present invention to provide an electrostatic sorting device that has a large processing capacity and a wide range of shapes and dimensions of contaminants that can be sorted.

Next, referring to FIGS. 3 and 4, the structure and operating principle of the embodiment of the present invention will be described. In each figure, 1
0 is a sorting stage corresponding to the rotating drum 1 in FIG. 1, and the sorting stage 10 has two partition fences 12 on the inner and outer peripheries along the circumferential direction at the center of the upper surface of the sorting plate 11, which is a ring-shaped disc. A trough-like channel 13 is formed between the partition fences, and is supported on a rotating shaft 14, which is a vertical shaft, in a plurality of vertical stages. The upper and lower sorting stages 10 are moved at a slow speed by an arrow C by a rotating shaft 14 and a drive motor 15 via a deceleration mechanism.
Rotation operation is performed in the direction. Furthermore, the sorting stage 1
0, a supply position and a sorting collection position of the mixture to be sorted are set on the circumference of the sorting plate 11, and a DC high voltage electrode 20 is installed above the sorting plate in the circumferential area between these two positions with the sorting stage 10 as a ground electrode. They are placed opposite each other. As clearly shown in FIG. 5, this high voltage electrode 20 is made up of a pair of a needle-like or thin wire-like corona discharge electrode 21 and a flat electrode 22, which are charged with the same polarity, and the sorting stage 10 One set or a plurality of sets of corona discharge electrodes 21 and flat plate electrodes 22 are arranged in a circular shape along the rotation direction C of the electrode. On the other hand, at the above-mentioned mixture supply position, the supply port 31 of the feeder 30 for supplying the mixture M to be sorted is opened facing the channel 13 from above. In addition, at the sorting and collection position, a suction pipe 41 connected to a hopper 40 for collection of insulating particles N is arranged with an opening toward the channel 13 from above,
On the sides of the inner and outer peripheries of the sorting plate 11, a conduit 51 connected to a hopper 50 for collecting conductive particles O is opened from below. Further, 60 is a scraper for scraping off the conductive particles O that have been transferred to the inner and outer peripheries of the sorting plate 11 toward the hopper 50 . Note that each component such as the high-voltage electrode 20 is installed facing each other in each of the upper and lower sorting stages. The assembly of the multistage sorting stage described above is housed in a cover case 70, and a bushing 71 attached to the cover case 70
A high voltage DC power supply 80 is connected to the high voltage electrode 20 via.

The arrangement of one stage of the above structure taken out and developed along the circumferential direction is shown in FIG. 5, and furthermore, when the cross sections of the parts indicated in FIG. Become.

Next, the sorting operation of the embodiment of the present invention will be described with reference to FIGS. 5 and 6. First, high voltage DC power supply 8
When a voltage is applied to the high voltage electrode 20 from 0, the corona discharge electrode 21
A corona discharge electric field region is formed directly below the plate electrode 22, and a strong electric field region is formed directly below the flat electrode 22.
In this state, the sorting stage 10 is rotated in the direction of arrow C, and the supply feeder 30 is
If the mixture M to be sorted, which is a mixture of the conductive particles O, which is pure compost, and the insulating particles N, which are impurities, is fed into the channel 13, as the sorting stage 10 rotates, the mixture will first be separated. M
When M enters the corona discharge electric field region, the mixture M is showered with a large amount of positive ions from the corona discharge electrode 21 and gains a positive charge q ⁺ . In this case, the insulating particles N (indicated by white circles) retain a positive charge for a long time, so they are attracted to the negative polarity sorting stage 10 and transported while being confined within the channel 13. On the other hand, the conductive particles O (indicated by black circles) discharge the positive charges acquired by being exposed to the ion shower to the sorting stage 10, and conversely are charged to negative polarity by electrostatic induction. Then, as the rotation progresses and enters the strong electric field region, the insulating particles N remain adsorbed within the channel, while the conductive particles O are repelled from the sorting stage by the Coulomb force acting along the electric field and fly away. It rises, attracts and collides with the flat electrode 22 of positive polarity, and further discharges due to contact with the electrode 22 and loses its charge, then falls downward and is charged to negative polarity again by electrostatic induction. The cycle of negative polarity charging → attraction to the flat electrode → discharge → falling is repeated, and as shown in FIG. This process is repeated, and the particles eventually climb over the partition fence 12 and jump out from the channel 13 to both the left and right sides, and gather toward the inner and outer peripheries of the sorting plate 11. At the same time, due to the vertical movement of the particles, the mixture M supplied in layers into the channel 13 is subjected to a stirring action. Therefore, the particles that were previously buried under the layer are exposed to the surface and are directly exposed to the electric field in the next corona discharge electric field area and strong electric field area, so that the entire particle is evenly subjected to the electrostatic sorting effect. become. In this way, when the rotation of the sorting stage 10 progresses and reaches the sorting and collection position, the insulating particles N remain in the channel 13, while the conductive particles O are distributed in the inner and outer circumferential regions outside the channel. becomes. Therefore, the conductive particles O are scraped off by the scraper 60 at the collection position and collected into the collection hopper 50, while the insulating particles N are sucked and collected at the collection position into the collection hopper 40 using, for example, a pug filter. . The above sorting operation is performed in parallel for each of the upper and lower sorting stages.

As a special case, if the insulating particles N mixed in the mixture M are only substances with a higher specific gravity than the conductive particles O, the corona discharge electrode 21 may be omitted and only the flat electrode 22 may be used. High voltage electrode 20
Even with this structure, the particles N having a large specific gravity do not escape from the channel due to the Coulomb force, so that sorting can be performed in the same way as in the previous embodiment.

As described above, the present invention has a method in which a high-voltage electrode is disposed facing above a sorting stage with a trough-like channel that is rotatably operated around a vertical axis, with the sorting stage as the other electrode, and In addition to supplying the mixture to be sorted into the channel,
At the sorting and collection position, collection hoppers for each particle are arranged so as to face the inside and outside of the trough-like channel, and only the conductive particles are collected by coulombization while the insulating particles of the mixture to be sorted are confined within the trough-like channel. By reciprocating motion between a force-based sorting stage and a high-voltage electrode, the particles are taken out of the trough-like channel and sorted. Therefore, due to the stirring effect of the mixture caused by the movement of the conductive particles, electrostatic separation acts evenly on the entire mixture to be sorted, which is supplied in layers, thereby improving processing capacity and sorting efficiency. In addition, since only the conductive particles in the mixture are repelled by Coulomb force and taken out to the outside of the channel for sorting, insulating impurities are not mixed in when used for the compost purification process mentioned above. Excellent effects such as being able to select and refine only pure compost can be obtained. In addition, in the present invention, by configuring the sorting stage in an upper and lower multistage manner as in the illustrated embodiment, there is an advantage that a narrow space can be effectively utilized and an apparatus with a large processing capacity can be made compact.

It goes without saying that the present invention can also be applied to various fields that handle granular materials such as minerals, foods, and medicines other than the field of compost refining described above.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of a typical conventional electrostatic separation device, Fig. 2 is an explanatory diagram of the adsorption effect of insulating particles in Fig. 1, and Figs. A side view and a plan view showing the configuration arrangement, and FIGS. 5 and 6 are explanatory diagrams of the sorting operation of the embodiment of the present invention, FIG. 5 is a developed view in the circumferential direction of the sorting stage, and FIG. FIG. 3 is a cross-sectional view showing the sorting operations in the respective parts indicated by the symbols . 10... Sorting stage, 11... Sorting board, 12
...Partition fence, 13...Gutter channel, 1
4... Vertical rotation axis, 20... DC high voltage electrode,
21... Corona discharge electrode, 22... Flat electrode,
30... Mixture supply feeder to be sorted, 40... Hopper for collecting insulating particles, 50... Hopper for collecting conductive particles, 60... Scraper, 80... High voltage DC power supply, C... Rotation direction of sorting stage, M...
Mixture to be sorted, N: insulating particles, O: conductive particles.

Claims (1)

[Scope of Claims] 1. A plurality of stages formed by forming a gutter-like channel along the circumferential direction at the center of the upper surface of a sorting plate that is rotated in a predetermined direction around a vertical axis and provided on the same axis in a plurality of upper and lower stages. The corona discharge is arranged oppositely above each sorting plate with the sorting stage as the other electrode in the circumferential region between the sorting stage and the supply position and sorting collection position of the mixture to be sorted, which are set on the circumference of each sorting plate. A multi-stage DC high-voltage electrode that combines electrodes and a flat plate electrode following a corona discharge electrode, a supply feeder for the mixture to be sorted that opens into the trough-like channel at the supply position, and a trough at the sorting and collection position. 1. An electrostatic sorting device comprising: a hopper for collecting insulating particles that is open toward a trough-like channel; and a hopper for collecting conductive particles that is open to the side of a disc outside the trough-like channel. 2. In the electrostatic sorting device according to claim 1, the sorting stage has two partition fences protruding along the circumferential direction from the center of the upper surface of the sorting plate as a ring-shaped disk, and the partition 1. An electrostatic sorting device characterized by forming a trough-like channel between fences.