Method for separating mixture containing electric conductor particles and electric insulator particles, and electrostatic separation device

Abstract

One aspect of the present invention relates to a separation method for separating electric conductor particles and electric insulator particles in a mixture containing the electric conductor particles and the electric insulator particles, the method comprising passing the mixture over a first electrode, imparting an electric charge to the mixture, attracting the uncharged electric insulator particles to the first electrode, and attracting the charged electric conductor particles to a second electrode. the density d1 of the electric conductor particles and the density d2 of the electric insulator particles satisfying 0.2 ≤ d1 / d2 ≤ 1.

Description

Method and apparatus for separating a mixture containing electrically conductive particles and electrically insulating particles

[0001] The present invention relates to a method and an apparatus for electrostatic separation of a mixture containing electrically conducting particles and electrically insulating particles.

[0002] Electrostatic separation techniques that utilize differences in the chargeability, conductivity, dielectric constant, etc. of substances are known as methods for separating mixtures of different particles.

[0003] An example of a mixture of different particles is coal ash generated at coal-fired power plants. Coal ash is usually disposed of as waste in landfills, but by removing the unburned carbon contained therein, it can be used as a concrete admixture. If coal ash containing unburned carbon is used as a concrete admixture, the resulting concrete will be black in color and will not have high strength. Therefore, it is desirable to remove as much unburned carbon as possible from the coal ash. For example, a separation device described in Patent Document 1 is known as an apparatus for separating a mixture of particulate matter such as coal ash containing unburned carbon.

[0004] The separation device described in Patent Document 1 has a chamber, a first electrode that attracts negatively charged particles within the chamber, and a second electrode that attracts positively charged particles within the chamber. By blowing particles to be separated into the chamber, the particles are separated into negatively charged particles that are attracted to the first electrode and positively charged particles that are attracted to the second electrode. For example, when coal ash containing unburned carbon is passed through the separation device, the coal ash (electrically insulating particles) itself becomes negatively charged particles and is attracted to the first electrode, while the unburned carbon (electrically conducting particles) becomes positively charged particles and is attracted to the second electrode, and each is collected separately.

[0005] On the other hand, when separating a mixture of different particles, it is assumed that the size of the particles to be separated varies. However, the technology described in Patent Document 1 does not take into account the balance between the attraction (adsorption) of the particles to be separated to each electrode due to their charge and the falling of the particles from each electrode due to their weight. Furthermore, the voltage to be charged is not taken into account in the separation. Therefore, the technology described in Patent Document 1 does not provide sufficient separation efficiency for electrically conductive particles and electrically insulator particles.

[0006] U.S. Pat. No. 5,938,041

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a separation method and an electrostatic separation device for separating electrical conductor particles and electrical insulator particles using an electrostatic separation method, which can increase the recovery rate of at least one of electrical conductor particles and electrical insulator particles from a mixture of electrical conductor particles and electrical insulator particles, and which has high efficiency in separating the electrical conductor particles and electrical insulator particles.

[0008] A separation method according to one embodiment of the present invention is a separation method for separating electrically conductive particles and electrically insulator particles in a mixture containing the electrically conductive particles and the electrically insulator particles, the separation method including passing the mixture over a first electrode, applying an electric charge to the mixture, attracting the uncharged electrically insulator particles to the first electrode, and attracting the charged electrically conductor particles to a second electrode, wherein a density d1 of the electrically conductor particles and a density d2 of the electrically insulator particles satisfy the relationship 0.2≦d1 / d2≦1.

[0009] Another aspect of the present invention provides an electrostatic separation device for separating electrically conductive particles and electrically insulator particles from a mixture containing the electrically conductive particles and the electrically insulator particles, the electrostatic separation device comprising: a supply means for supplying the mixture; a corona discharge device for imparting an electric charge to the mixture; a first electrode for attracting the uncharged electrically insulator particles; and a second electrode for attracting the charged electrically conductor particles, the corona discharge device being connected to a high voltage power supply and supplied with a voltage of 20 kV or less; and the density d1 of the electrically conductor particles and the density d2 of the electrically insulator particles satisfying the relationship 0.2≦d1 / d2≦1.

[0010] FIG. 1 is a schematic diagram of an electrostatic separation device according to an embodiment of the present invention.

[0011] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these.

[0012] [Separation Method] A separation method according to an embodiment of the present invention is a method for separating electrically conductive particles and electrically insulator particles from a mixture containing the electrically conductive particles and the electrically insulator particles. The separation method includes passing the mixture over a first electrode, applying an electric charge to the mixture, attracting the uncharged electrically insulator particles to the first electrode, and attracting the charged electrically conductor particles to a second electrode. The density d1 of the electrically conductor particles and the density d2 of the electrically insulator particles satisfy the relationship 0.2≦d1 / d2≦1.

[0013] With this configuration, it is possible to increase the recovery rate of at least one of the electrical conductor particles and the electrical insulator particles from a mixture of the electrical conductor particles and the electrical insulator particles, and further to provide a separation method for separating the electrical insulator particles and the electrical conductor particles using an electrostatic separation method, which has high efficiency in separating the electrical conductor particles and the electrical insulator particles.

[0014] First, the mixture to be separated in the separation method of this embodiment will be specifically described below.

[0015] The mixture contains electrically conductive particles and electrically insulator particles, and the density d1 of the electrically conductive particles and the density d2 of the electrically insulator particles satisfy the relationship 0.2≦d1 / d2≦1.

[0016] According to the separation method of this embodiment, the recovery rate and separation efficiency can be improved by controlling the density ratio of the density d1 of the electrical conductor particles to the density d2 of the electrical insulator particles to 0.2≦d1 / d2≦1. The reasons for this are thought to be as follows, although not limited thereto. Specifically, if d1 / d2 is too small, even if particles are attracted to each electrode (first electrode, second electrode) due to electrostatic charge, they are significantly affected by gravity when falling from each electrode, making it difficult to maintain separation accuracy. On the other hand, if d1 / d2 is too large, the electrical conductor particles tend to float, making it difficult to maintain separation accuracy. Therefore, by making the density d1 of the electrical conductor particles and the density d2 of the electrical insulator particles satisfy the relationship 0.2≦d1 / d2≦1, the recovery rate of at least one of the electrical conductor particles and the electrical insulator particles can be increased, and further, the separation efficiency between the electrical conductor particles and the electrical insulator particles can be improved. The density d1 of the electrical conductor particles and the density d2 of the electrical insulator particles preferably satisfy the relationship 0.22≦d1 / d2≦0.98, and more preferably 0.24≦d1 / d2≦0.96.

[0017] By making the density d1 of the electrical conductor particles and the density d2 of the electrical insulator particles satisfy 0.2≦d1 / d2≦1, the recovery rate of at least one of the electrical conductor particles and the electrical insulator particles can be increased, particularly when the average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles are both 200 μm or less, i.e., even when the particles to be separated are small, and further, the separation efficiency between the electrical conductor particles and the electrical insulator particles can be increased.

[0018] The density d1 of the electrical conductor particles is preferably 1.4 g / ml or more and 2.5 g / ml or less from the viewpoint of separating the electrical conductor particles from the electrical insulator particles, and more preferably 1.6 g / ml or more and 2.4 g / ml or less.

[0019] The density d2 of the electrical insulator particles is preferably 1.4 g / ml or more and 6 g / ml or less from the viewpoint of separating the electrical conductor particles from the electrical insulator particles, and more preferably 1.6 g / ml or more and 5.6 g / ml or less.

[0020] In this specification, the densities d1 and d2 of the electrical conductor particles and the electrical insulator particles can be calculated by measuring the true density of helium using an "Ultrapyc 1200e" manufactured by Quantachrome Co., Ltd., with helium as the substitution medium.

[0021] In the separation method according to this embodiment, it is preferable that the average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles satisfy the relationship 0.1≦r1 / r2≦10. When the ratio of the average diameter r1 of the electrical conductor particles to the average diameter r2 of the electrical insulator particles satisfies the relationship 0.1≦r1 / r2≦10, the separation method according to this embodiment achieves a good balance between the adsorption of particles to each electrode (first electrode, second electrode) due to their charge and the fall of particles from each electrode due to their weight, thereby more reliably improving the separation efficiency of the electrical insulator particles and the electrical conductor particles. In other words, when the average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles satisfy the relationship 0.1≦r1 / r2≦10, the recovery rate of at least one of the electrical conductor particles and the electrical insulator particles can be increased, and the separation efficiency of the electrical insulator particles and the electrical conductor particles can be further improved. Specifically, when r1 / r2 is 0.1 or more, the electrical conductor particles tend to fall to a predetermined position in the separation method of this embodiment, thereby increasing the recovery rate of the electrical conductor particles. Furthermore, when r1 / r2 is 10 or less, the electrical insulator particles tend to fall to a predetermined position, thereby increasing the recovery rate of the electrical insulator particles. It is more preferable that the average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles satisfy 0.2≦r1 / r2≦9, and even more preferably 0.4≦r1 / r2≦8.

[0022] By making the average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles satisfy 0.1≦r1 / r2≦10, it is possible to increase the recovery rate of at least one of the electrical conductor particles and the electrical insulator particles, particularly when the average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles are both 200 μm or less, i.e., even when the particles to be separated are small, and further to increase the separation efficiency between the electrical conductor particles and the electrical insulator particles.

[0023] The average diameter r1 of the electrical conductor particles is preferably 200 μm or less. According to the separation method of this embodiment, the recovery rate can be increased even when r1 is 200 μm or less. Furthermore, from the viewpoint of separating the electrical conductor particles and the electrical insulator particles, r1 is preferably 1 μm or more and 200 μm or less. The average diameter r1 is more preferably 1.5 μm or more and 120 μm or less, and even more preferably 2 μm or more and 80 μm or less.

[0024] The average diameter r2 of the electrical insulator particles is preferably 200 μm or less. According to the separation method of this embodiment, the recovery rate can be increased even when r2 is 200 μm or less. Furthermore, from the viewpoint of separating the electrical conductor particles and the electrical insulator particles, r2 is preferably 1 μm or more and 200 μm or less. The average diameter r2 is more preferably 1.5 μm or more and 120 μm or less, and even more preferably 2 μm or more and 80 μm or less.

[0025] In this specification, the average diameters r1 and r2 of the electrical conductor particles and the electrical insulator particles can be calculated, for example, by measuring the particle size distribution by a laser scattering method using a particle size / particle size distribution measuring device ("Microtrac MT3300EXII" manufactured by Microtrac-Bell Co., Ltd.).

[0026] The electrically conductive particles are not particularly limited, and examples thereof include particles mainly composed of carbon (carbon particles). The electrically conductive particles may be particles mainly composed of one type of carbon, or may be particles mainly composed of two or more types of carbon. Examples of the carbon particles include activated carbon, and the electrically conductive particles are preferably activated carbon. From the viewpoint of exhibiting conductivity when separating the electrically conductive particles from the electrically insulator particles, the carbon content in the electrically conductive particles is preferably 80% by weight or more, more preferably 85% by weight or more, and even more preferably 90% by weight or more.

[0027] The electrical insulator particles are not particularly limited, but examples thereof include particles made of metal oxides. Examples of constituent metals include Mg, Ca, Sr, Ba, B, Al, Ga, In, Si, Sn, Ge, P, Ti, Zr, V, Nb, Mo, and W. These may be composed of a single metal or multiple metals. Furthermore, they may be partially ion-exchanged with Na, K, Li, Cs, or the like. More specific examples of the electrical insulator particles include silica, alumina, titania, zirconia, silica-alumina, silica-titania, and stabilized zirconia. Furthermore, the electrical insulator particles may be particles made of one type of metal oxide, or may be particles made of two or more types of metal oxides.

[0028] The electrical conductor particles preferably have a moisture content of 10% by weight or less. Having a moisture content of 10% by weight or less makes it easier to maintain electrical conductivity when separating the electrical conductor particles from the electrical insulator particles, thereby improving separation efficiency. From this perspective, the moisture content of the electrical conductor particles is more preferably 8% by weight or less, and even more preferably 7% by weight or less. The lower limit of the moisture content of the electrical conductor particles is not particularly limited.

[0029] The electrical insulator particles preferably have a moisture content of 12% by weight or less. Having a moisture content of 12% by weight or less makes it easier to maintain electrical insulation when separating the electrical conductor particles and the electrical insulator particles, thereby improving separation efficiency. From this perspective, the moisture content of the electrical insulator particles is more preferably 10% by weight or less, and even more preferably 8% by weight or less. The lower limit of the moisture content of the electrical insulator particles is not particularly limited.

[0030] The moisture contents of the electrically conductive particles and the electrically insulator particles can be measured, for example, by the method described in the Examples. In the separation method of this embodiment, the moisture contents of the electrically conductive particles and the electrically insulator particles may be adjusted to a predetermined concentration before applying an electric charge to the mixture. When the mixture is separated using an electrostatic separation device described below, the moisture contents may be adjusted inside the electrostatic separation device, or may be adjusted before the mixture is fed into the electrostatic separation device.

[0031] The content of the electrical conductor particles is preferably 80% by weight or more and 99% by weight or less relative to 100% by weight of the mixture. By being in this range, the recovery rate of at least one of the electrical conductor particles and the electrical insulator particles can be more reliably increased, and further, the separation efficiency of the electrical conductor particles and the electrical insulator particles can be more reliably increased. From this perspective, the content of the electrical conductor particles is more preferably 82% by weight or more and 97% by weight or less, and even more preferably 85% by weight or more and 95% by weight or less relative to 100% by weight of the mixture.

[0032] The content of the electrical insulator particles is preferably 1% by weight or more and 20% by weight or less relative to 100% by weight of the mixture. By being in this range, the recovery rate of at least one of the electrical conductor particles and the electrical insulator particles can be more reliably increased, and further, the separation efficiency of the electrical conductor particles and the electrical insulator particles can be more reliably increased. From this perspective, the content of the electrical insulator particles is more preferably 3% by weight or more and 18% by weight or less, and even more preferably 5% by weight or more and 15% by weight or less relative to 100% by weight of the mixture.

[0033] The separation method of this embodiment is preferably applicable when the mixture to be separated is a mixture obtained by heat-treating activated carbon molded bodies, and can efficiently separate electrically conductive particles (activated carbon) and electrically insulator particles contained in the mixture obtained by heat-treating activated carbon molded bodies.

[0034] The activated carbon molded body is a molded body made by using activated carbon and a binder resin, etc. The activated carbon molded body is not particularly limited, and may be molded by either dry molding or wet molding.

[0035] The activated carbon used for the activated carbon molded body is not particularly limited as a raw material thereof, and the binder resin used for the activated carbon molded body is also not particularly limited.

[0036] The activated carbon molded bodies are usually incorporated into a filter for use. The mixture may be a mixture obtained by removing the activated carbon molded bodies from a used activated carbon filter and subjecting them to heat treatment, or may be a mixture obtained by subjecting a used activated carbon filter to heat treatment without decomposition.

[0037] The activated carbon filter is not particularly limited in other configuration as long as it contains the activated carbon molded body, but may be a cylindrical filter containing a packing and a core in addition to the activated carbon molded body. The core is not particularly limited as long as it is inserted into the hollow portion of the cylindrical filter and can reinforce the cylindrical filter, but is preferably, for example, a toric pipe, a netron pipe, or a ceramic filter. Furthermore, a nonwoven fabric or the like may be wrapped around the outer periphery of the core and / or the outer periphery of the molded body. The packing, core, and nonwoven fabric contained in the activated carbon filter may be subjected to heat treatment together with the activated carbon molded body.

[0038] The activated carbon molded body is preferably used for water purification. For example, the activated carbon filter incorporating the activated carbon molded body is generally filled into a housing and used as a cartridge, and such a cartridge is installed in a water purifier and used for water purification. The water flow method used may be a total filtration method in which the entire amount of raw water is filtered, or a circulating filtration method. When the housing (casing) is made of an organic material, the mixture may be obtained by heat-treating the cartridge in which the activated carbon filter is filled in the housing. Furthermore, the mixture may be obtained by heat-treating a cartridge containing known nonwoven fabric filters, various adsorbents, mineral additives, ceramic filter materials, etc.

[0039] The mixture may be obtained by heat-treating an activated carbon filter or a molded activated carbon body contained in an activated carbon filter after passing water through it for a certain period of time. The water passing conditions in a water purifier equipped with the activated carbon filter are not particularly limited, but may be, for example, 100 to 5000 hours so as not to cause excessive pressure loss. －１ The activated carbon molded bodies contained in the activated carbon filter of a water purifier that has been used for a predetermined time after passing water through it at a space velocity (SV) of 1000 mbar or the activated carbon filter are subjected to a heat treatment. During this water passing process, the activated carbon molded bodies adsorb free residual chlorine, trihalomethanes, other trace organic compounds, and organic chlorine compounds in the raw water and permeated water.

[0040] The mixture may be a mixture obtained by heat-treating an activated carbon molded body having at least one of the organic compound and the organic chlorine compound adsorbed thereon.

[0041] The heat treatment preferably includes heating the activated carbon molded body in an inert atmosphere, and can be carried out by placing the activated carbon molded body (or activated carbon filter or cartridge) directly into a reactor and heating (heat treatment).

[0042] The inert atmosphere refers to an atmosphere that has no activity (oxidizing effect) within the heat treatment temperature range of this embodiment. Specifically, it is preferable that the atmosphere is made of a gas having an oxygen content of 5% or less, preferably 2% or less, and more preferably 1% or less.

[0043] As such an inert atmosphere, inert gases such as nitrogen, argon, water vapor, combustion gas, carbon dioxide, carbon monoxide, etc. Among these, water vapor is preferably used.

[0044] The inert gas may be used alone or in combination. When multiple gases are mixed, the ratio is not particularly limited. For example, in the case of nitrogen and water vapor, the molar ratio is preferably in the range of 1:100 to 100:1, more preferably 2:98 to 99:1, and even more preferably 5:95 to 95:5. The inert atmosphere of this embodiment may contain gases other than the inert gas in trace amounts that do not exhibit oxidizing effects.

[0045] The flow rate of the inert gas (vapor) in the heat treatment is not particularly limited, since it depends on the amount of activated carbon molded bodies present in the reactor. Preferably, the flow rate is adjusted to a range of 0.01 L / min to 10,000 L / min, more preferably 0.1 L / min to 8,000 L / min, and even more preferably 0.4 L / min to 4,000 L / min, in order to facilitate heat transfer to the activated carbon molded bodies and facilitate scavenging of compounds generated by decomposition.

[0046] The heat treatment temperature is preferably 500°C to 1200°C. If the temperature is too low, the adsorbed substances cannot be volatilized or decomposed, and may remain, which is undesirable. If the temperature is too high, the pores of the regenerated activated carbon may be blocked by heat, which may reduce the adsorption power, which is undesirable. Therefore, heating is usually performed at 500°C to 1200°C, more preferably 520°C to 800°C, and even more preferably 550°C to 800°C.

[0047] The heating time (heat treatment time) of the activated carbon molded body is not particularly limited and can be determined appropriately depending on the size of the activated carbon molded body and the amount of adsorbent adsorbed, but is usually in the range of 1 minute to 300 minutes. If the heating time is too short, there is a risk that the adsorbate will not be sufficiently desorbed. On the other hand, if the heating time is too long, there is a risk that the pores of the regenerated activated carbon will be blocked by heat, resulting in a decrease in adsorption power, which is not preferable. Therefore, the heating time is usually in the range of 1 minute to 300 minutes, more preferably in the range of 5 minutes to 240 minutes, and even more preferably in the range of 10 minutes to 220 minutes.

[0048] The heat treatment decomposes and volatilizes the adsorbent attached to the activated carbon and organic substances such as the binder and nonwoven fabric used in the molded body and filter. During decomposition, some of the substances are oxidized and decomposed to carbon dioxide, but the volatiles also contain carbon monoxide, various organic substances, hydrogen chloride, etc. These substances cannot be released directly into the atmosphere, so they are detoxified as needed by absorbing acidic substances using an alkali scrubber, decomposing by flame combustion, decomposing by catalytic combustion, etc.

[0049] The heat treatment method is not particularly limited, and can be carried out in a batch or continuous manner. As a batch method, any of a box furnace, a muffle furnace, etc. can be used. As a continuous furnace, any of a mesh belt, a roller hearth kiln, a pusher furnace, etc. can be used as long as it can transport the molded body in a state.

[0050] The heat-treated activated carbon molded body can be removed after cooling. The temperature at the time of removal is preferably a temperature at which the molded body is not oxidized by oxygen in the air. Therefore, it is preferable to cool the activated carbon molded body in the reactor to 300°C or less, more preferably 200°C or less, and then expose it to the atmosphere.

[0051] The mixture obtained by the heat treatment may retain the shape of the molded product even after the heat treatment, but if necessary, it can be re-crushed into powdered activated carbon, granular activated carbon, and / or fibrous activated carbon using a means such as a belt press, and adjusted to a desired size.

[0052] The mixture obtained by heat-treating the activated carbon molded body contains, in addition to activated carbon, electrical insulator particles such as particles made of a metal oxide. Specific examples of the metal oxide include silica, alumina, titania, zirconia, silica-alumina, silica-titania, and stabilized zirconia. According to the separation method of this embodiment, it is possible to efficiently separate the electrically conductive particles (activated carbon) and the electrical insulator particles (particles made of a metal oxide, etc.) from the mixture obtained by heat-treating the activated carbon molded body.

[0053] Next, each step of the separation method for separating the above-mentioned mixture into electrically conductive particles and electrically insulator particles will be specifically explained, but the scope of the present invention is not limited to these steps.

[0054] In this embodiment, the separation method for separating electrically conductive particles and electrically insulator particles includes passing the mixture over a first electrode, applying an electric charge to the mixture, attracting the uncharged electrically insulator particles to the first electrode, and attracting the charged electrically conductive particles to a second electrode.

[0055] First, the mixture is passed over a first electrode. Specifically, for example, the mixture can be passed over the first electrode by continuously or intermittently supplying the mixture using a supply means. As the first electrode, for example, a conventionally known device such as a belt conveyor (orthogonal, alternating current, or parallel type), a rotating cylinder type, a rotating magnet type, or a frictional charging type can be used. The first electrode is preferably a horizontally mounted rotating drum having an electrically conductive surface. As the supply means, for example, a conventionally known device such as a vibrating feeder can be used.

[0056] Next, the mixture on the first electrode is charged. Specifically, the mixture can be charged using, for example, a corona discharge device. As the corona discharge device, for example, a conventionally known device such as a pin electrode can be used.

[0057] The uncharged electrical insulator particles are then attracted to the first electrode. Specifically, since the electrical insulator particles are uncharged, they are attracted to the oppositely charged charges on the first electrode, are transported while adhering to the first electrode, and fall from the first electrode to a predetermined position depending on their conductivity and density. The uncharged electrical insulator particles may be removed from the first electrode by a scraper, such as a brush or scraper bar, adjacent to the first electrode.

[0058] On the other hand, the charged electrically conductive particles are attracted to a second electrode. Specifically, the charged electrically conductive particles are discharged onto the electrically conductive surface of the first electrode, which has the opposite polarity, and the discharged electrically conductive particles are repelled from the electrically conductive surface. The repelled electrically conductive particles fall while being attracted to the second electrode. The second electrode may be, for example, a conventionally known electrode such as an oval electrode.

[0059] In this way, each particle contained in the mixture falls from the first electrode to a predetermined position according to its conductivity, and is appropriately separated for each falling position. Note that the above operation may be repeated, for example, by separating insufficiently separated particle groups again in the same manner to improve separation efficiency.

[0060] [Electrostatic Separation Apparatus] The electrostatic separation apparatus of this embodiment will be specifically described with reference to Fig. 1. Note that the description of the mixture to be separated is the same as the description of the mixture to be separated described in the above [Separation Method], and therefore will be partially omitted.

[0061] As shown in Figure 1, the electrostatic separation device 1 is an electrostatic separation device that separates electrically conductive particles 9 and electrically insulator particles 10 from a mixture containing electrically conductive particles 9 and electrically insulator particles 10. The electrostatic separation device 1 includes a supply means 2 for supplying the mixture, a corona discharge device 3 for imparting an electric charge to the mixture, a first electrode 4 for attracting uncharged electrically insulator particles 10, and a second electrode 5 for attracting charged electrically conductive particles 9. The corona discharge device 3 is connected to a high-voltage power supply and is supplied with a voltage of 20 kV or less. Furthermore, the density d1 of the electrically conductive particles 9 and the density d2 of the electrically insulator particles 10 satisfy the relationship 0.2 ≤ d1 / d2 ≤ 1.

[0062] According to this configuration, it is possible to provide an electrostatic separation device that can increase the recovery rate of at least one of the electrical conductor particles and the electrical insulator particles from a mixture of the electrical conductor particles and the electrical insulator particles, and that can efficiently separate the electrical conductor particles and the electrical insulator particles. In a preferred embodiment, it is desirable that the average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles satisfy the relationships 0.1≦r1 / r2≦10, and r1≦200 μm and r2≦200 μm.

[0063] The supply means 2 is provided for supplying the mixture onto the first electrode 4. As the supply means 2, a conventionally known means can be used, for example, a conveyor, preferably a screw feeder or a vibrating conveyor, which may be provided with another conveyor, and it is preferable that the supply amount is constant and that the target mixture does not become lumpy.

[0064] A corona discharge device 3 is provided for imparting an electric charge to the mixture, and preferably comprises a plurality of corona discharge devices 3, each configured as a support rod with a series of spaced apart corona discharge pins.

[0065] The corona discharge device 3 is connected to a high voltage power supply and is supplied with a voltage of 20 kV or less. A voltage of 5 to 20 kV is preferably supplied to the corona discharge device 3, and a voltage of 6 to 16 kV is more preferably supplied to the corona discharge device 3. When a voltage of 20 kV or less is supplied to the corona discharge device 3, the distance between the corona discharge pin and the first electrode 4 is preferably 100 to 200 mm.

[0066] Each corona discharge pin and support rod is preferably provided with insulating means such as a rubber insulating jacket. The length and shape of the corona discharge pins are preferably selected for maximum effectiveness.

[0067] The first electrode 4 can be, for example, a conventionally known device, such as a belt conveyor (orthogonal, AC, or parallel), a rotating cylinder, a rotary magnet, or a frictional charging device. The rotary magnet device is preferred due to its simple structure. The first electrode 4 is preferably a horizontally mounted rotating drum having an electrically conductive surface. The first electrode 4 is preferably connected to a high-voltage power supply and is supplied with a voltage in the range of 1 to 50 kV. The first electrode 4 is preferably substantially the same width as the supply means 2 or slightly wider than the supply means 2. When the first electrode 4 is a rotating drum, the rotation speed of the drum is preferably selected so that the electrically conductive particles 9 describe a flight curve. Since the rotation speed depends on the diameter of the drum used, it is difficult to set a specific value. However, for a large drum with a radius of about 10 to 15 cm, the rotation speed is preferably about 50 rpm or less.

[0068] The second electrode 5 may be, for example, a conventionally known electrode, such as an oval electrode, a rod-shaped electrode, a mesh electrode, or a yarn-shaped electrode. The second electrode 5 is located downstream of the first electrode 4 and is preferably a charged electrode plate. It is preferable that the repelled electrically conductive particles 9 do not come into contact with the charged electrode plate. The electrode plate is preferably inclined at an acute angle with respect to the lower surface. The inclination of the electrode plate can be changed as desired to promote separation of the electrically insulator particles 10 and the electrically conductive particles 9. The second electrode 5 is preferably connected to a high-voltage power supply and is applied with a voltage in the range of 1 to 20 kV. The second electrode 5 has the same polarity as the corona discharge device 3.

[0069] The geometrical characteristics of the second electrode 5 relative to the first electrode 4, the length of the corona discharge pin and its distance from the first electrode 4, and the voltage supplied to the corona discharge device 3 all work together to adjust the amount of separation of the electrically conducting particles 9 from the electrically insulating particles 10 to a desired value.

[0070] A scraper 6 such as a brush or scraper bar may be provided adjacent to the first electrode 4 in order to remove uncharged electrical insulator particles 10 from the first electrode 4. When the first electrode 4 is a rotating drum, the scraper 6 is preferably located below the side surface of the rotating drum, on the lower surface side.

[0071] A partition plate 7 may be provided to separate particles falling from the first electrode 4 .

[0072] A separation vessel 8 may be provided to collect the separated particles. Multiple separation vessels 8 may be provided depending on the degree of separation, and each section may be removable or may be configured to be connectable to the same or other electrostatic separation device for further particle passage.

[0073] Heating means (not shown) may be provided to dry the mixture being fed, thereby adjusting the moisture content of the separated particles and controlling their electrical properties. The heating means is preferably located at the feeding means.

[0074] The present apparatus may be configured in one stage, or in multiple stages (multi-stages) in which insufficiently separated particle groups are passed through the same apparatus again to increase separation efficiency.

[0075] The electrostatic separator 1 can be used, for example, to separate a mixture obtained by heat-treating an activated carbon molded body, as described above in the "Separation Method." However, the uses of the electrostatic separator 1 are not limited to the above, and the electrostatic separator 1 can also be used to separate various particles or powders, for example, to separate substances with different electrical conductivity or chargeability, such as separating metals from waste, removing mercury, or removing impurities from minerals or food.

[0076] As described above, this specification discloses various aspects of the technology, but the main technologies among them are summarized below.

[0077] A first aspect of the separation method is a method for separating electrical insulator particles and electrical conductor particles from a mixture containing electrical conductor particles and electrical insulator particles, the method comprising: passing the mixture over a first electrode; applying an electric charge to the mixture; attracting the uncharged electrical insulator particles to the first electrode; and attracting the charged electrical conductor particles to a second electrode, wherein a density d1 of the electrical conductor particles and a density d2 of the electrical insulator particles satisfy the relationship 0.2≦d1 / d2≦1.

[0078] In the second aspect, the separation method is the separation method of the first aspect, wherein the average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles satisfy the relationships 0.1≦r1 / r2≦10, r1≦200 μm, and r2≦200 μm.

[0079] A third aspect of the separation method is the separation method according to the first or second aspect, wherein the electrical insulator particles are made of a metal oxide.

[0080] A fourth aspect of the separation method is the separation method according to any one of the first to third aspects, wherein the electrical insulator particles have a moisture content of 12% by weight or less.

[0081] A fifth aspect of the separation method is the separation method according to any one of the first to fourth aspects, wherein the content of the electrical insulator particles is 20% by weight or less with respect to 100% by weight of the mixture.

[0082] A sixth aspect of the separation method is the separation method according to any one of the first to fifth aspects, wherein the electrically conductive particles are carbon particles.

[0083] A seventh aspect of the separation method is the separation method according to any one of the first to sixth aspects, wherein the electrically conductive particles have a moisture content of 10% by weight or less.

[0084] In an eighth aspect of the present invention, the separation method is the separation method according to any one of the first to seventh aspects, wherein the mixture is obtained by heat treating an activated carbon molded body.

[0085] A ninth aspect of the separation method is the eighth aspect of the separation method, wherein the activated carbon molded body is used for water purification.

[0086] In a tenth aspect, an electrostatic separation device is provided for separating electrically conductive particles from electrically insulator particles in a mixture containing electrically conductive particles and electrically insulator particles, the electrostatic separation device comprising: a supply means for supplying the mixture; a corona discharge device for imparting an electric charge to the mixture; a first electrode for attracting the uncharged electrically insulator particles; and a second electrode for attracting the charged electrically conductor particles, the corona discharge device being connected to a high voltage power supply and supplied with a voltage of 20 kV or less, and the density d1 of the electrically conductor particles and the density d2 of the electrically insulator particles satisfying 0.2≦d1 / d2≦1.

[0087] An electrostatic separation device in an eleventh aspect is the electrostatic separation device in the tenth aspect, wherein the average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles satisfy 0.1≦r1 / r2≦10, and r1≦200 μm, r2≦200 μm.

[0088] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0089] [Measurement Method] First, the method for measuring the density d1 of electrical conductor particles, the density d2 of electrical insulator particles, the average diameter r1 of electrical conductor particles, the average diameter r2 of electrical insulator particles, and the moisture content of the electrical conductor particles and electrical insulator particles in the mixture to be separated will be described below.

[0090] (Density) The density d1 of the electrical conductor particles and the density d2 of the electrical insulator particles in the mixture to be separated were calculated by measuring the true density of helium using an "Ultrapyc 1200e" manufactured by Quantachrome Co., Ltd., with helium as the substitution medium.

[0091] (Average diameter) The average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles in the mixture to be separated were calculated by measuring the particle size distribution by a laser scattering method using a particle size / particle size distribution measuring device (Microtrac MT3300EXII manufactured by Microtrac Bell Co., Ltd.).

[0092] (Moisture Content) One gram of a sample (electrically conductive particles or electrically insulating particles) was heated to 250°C using a Karl Fischer moisture meter CA-310 manufactured by Mitsubishi Chemical Analytech Co., Ltd., and the moisture content (wt%) was measured based on coulometric titration under a nitrogen gas flow.

[0093] Example 1 Using an electrostatic separator ESCI type (manufactured by Nippon Magnetics Co., Ltd.) as an electrostatic separation device, 330 g of a mixture of activated carbon PGWB (manufactured by Kuraray Co., Ltd., average diameter r1 = 100 μm, density d1 = 2.0 g / ml, moisture content: 8.9 wt%) as electrical conductor particles and titanosilicate-based lead removal agent ATS (manufactured by BASF AG, density d2 = 3.7 g / ml, average diameter r2 = 20 μm, moisture content: 11.2 wt%) as electrical insulator particles was separated at a ratio of 10:1, with the distance between the corona discharge pin and the first electrode being 180 mm, the first electrode rotation speed being 44 rpm, and the corona discharge voltage being 10 kV. The results are shown in Table 1.

[0094] [Example 2] Separation of the mixture was carried out in the same manner as in Example 1, except that the corona discharge voltage was set to 15 kV. The results are shown in Table 1.

[0095] Example 3 The mixture was separated in the same manner as in Example 1, except that 330 g of a mixture of activated carbon PGWB (manufactured by Kuraray Co., Ltd., average diameter r1 = 100 μm, density d1 = 2.0 g / ml, moisture content: 7.5 wt %) as electrical conductor particles and silica (manufactured by Nakarai Chemicals, Inc., density d2 = 2.2 g / ml, average diameter r2 = 80 μm, moisture content: 9.2 wt %) as electrical insulator particles was used in a ratio of 10:1. The results are shown in Table 1.

[0096] Example 4 The separation of the mixture was carried out in the same manner as in Example 1, except that 330 g of a mixture of undried activated carbon PGWB (manufactured by Kuraray Co., Ltd., density d1 = 2.0 g / ml, average diameter r1 = 100 μm, moisture content: 12.5 wt %) as electrical conductor particles and titanosilicate-based lead removal agent ATS (manufactured by BASF SE, density d2 = 3.7 g / ml, average diameter r2 = 20 μm, moisture content: 11.2 wt %) as electrical insulator particles was used. The results are shown in Table 1.

[0097] Comparative Example 1 A mixture was separated in the same manner as in Example 1, except that 330 g of a mixture of activated carbon PGWB (manufactured by Kuraray Co., Ltd., density d1 = 2.0 g / ml, average diameter r1 = 100 μm, moisture content: 8.9 wt %) as electrical conductor particles and polystyrene (manufactured by Wako Pure Chemical Industries, Ltd., density d2 = 1.0 g / ml, average diameter r2 = 15 μm, moisture content: 3.3 wt %) as electrical insulator particles was used as the separation target. As a result, the polystyrene particles scattered, making it impossible to carry out the test and separating the mixture.

[0098]

[0099] As is clear from the results in Table 1, the separation methods of Examples 1 to 4 enable efficient recovery and separation of electrical conductor particles and electrical insulator particles from a mixture of electrical conductor particles and electrical insulator particles.

[0100] This application is based on Japanese Patent Application No. 2024-87282 filed on May 29, 2024, the contents of which are incorporated herein by reference. In order to express the present invention, the present invention has been adequately and sufficiently described above through embodiments with reference to the drawings. However, it should be recognized that those skilled in the art could easily modify and / or improve the above-described embodiments. Therefore, unless modifications or improvements made by those skilled in the art deviate from the scope of the claims set forth in the claims, such modifications or improvements are construed as being encompassed within the scope of the claims.

[0101] According to the present invention, it is possible to increase the recovery rate of at least one of electrical conductor particles and electrical insulator particles from a mixture of electrical conductor particles and electrical insulator particles, and it is also possible to provide a separation method and an electrostatic separation device for separating electrical conductor particles and electrical insulator particles using an electrostatic separation method, which has high efficiency in separating electrical conductor particles and electrical insulator particles.

Claims

1. A method for separating electrically conductive particles and electrically insulator particles from a mixture containing the electrically conductive particles and the electrically insulator particles, the method comprising: passing the mixture over a first electrode; applying an electric charge to the mixture; attracting the uncharged electrically insulator particles to the first electrode; and attracting the charged electrically conductor particles to a second electrode, wherein the density d1 of the electrically conductor particles and the density d2 of the electrically insulator particles satisfy the relationship 0.2≦d1 / d2≦1.

2. The separation method according to claim 1, wherein the average diameter r1 of the electrical conductor particles and the average diameter r2 of the electrical insulator particles satisfy the conditions 0.1≦r1 / r2≦10, and r1≦200 μm and r2≦200 μm.

3. The separation method according to claim 1 or 2, wherein the electrical insulator particles are made of a metal oxide.

4. The separation method according to claim 1 or 2, wherein the electrical insulator particles have a moisture content of 12% by weight or less.

5. The separation method according to claim 1 or 2, wherein the content of the electrical insulator particles is 20% by weight or less relative to 100% by weight of the mixture.

6. The separation method according to claim 1 or 2, wherein the electrically conductive particles are carbon particles.

7. The separation method according to claim 1 or 2, wherein the electrically conductive particles have a moisture content of 10% by weight or less.

8. The separation method according to claim 1 or 2, wherein the mixture is obtained by heat-treating activated carbon moldings.

9. The separation method according to claim 8, wherein the activated carbon molded body is for water purification.

10. An electrostatic separation device for separating electrically conductive particles and electrically insulator particles from a mixture containing the electrically conductive particles and the electrically insulator particles, comprising: a supply means for supplying the mixture; a corona discharge device for imparting an electric charge to the mixture; a first electrode for attracting the uncharged electrically insulator particles; and a second electrode for attracting the charged electrically conductive particles, wherein the corona discharge device is connected to a high voltage power supply and is supplied with a voltage of 20 kV or less, and wherein the density d1 of the electrically conductive particles and the density d2 of the electrically insulator particles satisfy the relationship 0.2≦d1 / d2≦1.

11. The electrostatic separation device according to claim 10, wherein the average diameter r1 of the electrically conductive particles and the average diameter r2 of the electrically insulator particles satisfy the conditions 0.1≦r1 / r2≦10, and r1≦200 μm and r2≦200 μm.

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