JP2020011225A - Soil purification system - Google Patents

Abstract

To provide a simple and low-cost soil purification system capable of classifying soil into gravel, sand, and fine particles while washing the soil with washing water, and reducing or removing toxic metals and the like adsorbed on the fine particles.SOLUTION: A soil purification system S crushes gravel and sand in soil containing gravel, sand, and fine particles by a mill breaker 3, and then classifies the soil into gravel, sand, and fine particles by a trommel 4, a liquid cyclone 5, and a thickener 8 while washing the soil with washing water. An iron removing device 12 uses magnetic spheres to magnetically adsorb and remove iron-based fine particles from sludge containing the fine particles and the washing water separated by the thickener 8 to reduce the content of toxic metals and the like in the sludge. A chelate washing device 14 uses a chelate washing liquid to remove the toxic metals and the like from the sludge (fine particles) from which the iron-based fine particles have been removed.SELECTED DRAWING: Figure 1

Description

  TECHNICAL FIELD The present invention relates to a soil purification system for purifying soil contaminated with harmful metals or compounds containing gravels, sand, and fine particles.

  In recent years, premises of production facilities that use harmful metals such as chromium, lead, cadmium, selenium, and mercury and / or their compounds or their ions (hereinafter collectively referred to as “harmful metals, etc.”) as raw materials or materials. In addition, soil pollution due to soil pollution in nearby areas or illegal dumping of industrial waste containing harmful metals and the like occurs frequently. Then, the soil contaminated with harmful metals and the like (hereinafter referred to as “hazardous metal contaminated soil”) is used at the existing position (hereinafter referred to as “in-situ”), for example, to insolubilize harmful metals, containment, or electrical restoration. It is quite difficult to purify more effectively. For this reason, the toxic metal-contaminated soil is generally removed from the original site by excavation and purified by an external soil purification facility.

  Conventionally, as a method of purifying toxic metal-contaminated soil in such an off-site soil purification facility, a cleaning method of removing harmful metals and the like by cleaning harmful metal-contaminated soil with washing water or the like has been widely used. . When the harmful metal-contaminated soil is washed with washing water, most of the harmful metals and the like once separated from the soil into the water are adsorbed or adhered to the surface of fine particles having a relatively small particle size, and (See, for example, Non-Patent Document 1).

  Therefore, by washing harmful metal contaminated soil with washing water and classifying it into gravel, sand, and fine particles, and then subjecting the fine particles to a chemical treatment to remove harmful metals, etc., It is possible to obtain gravel, sand, and fine particles containing almost no harmful metals. Thus, the inventor of the present application has already classified harmful metal-contaminated soil with washing water, classified it into gravel, sand, and fine particles, and then performed a cleaning treatment on the fine particles with a chelating cleaning solution containing a chelating agent. Various types of soil remediation facilities (contaminated soil remediation devices) have been proposed in which harmful metals and the like are removed from fine particles by applying the method (see, for example, Patent Documents 1 and 2).

Japanese Patent No. 5723054 Japanese Patent No. 5723055 Japanese Patent No. 4755159 Japanese Patent No. 607144

Ministry of the Environment, Water and Atmospheric Environment Bureau, Soil Environment Section, “Technical Considerations on Permission Examinations for Contaminated Soil Treatment Business”, page 21, published August 2013 Tetsuo Katsura “Drainage treatment by iron powder method” flotation, vol. 23 (1976), no. 3, P190-198 (https://www.jstage.jst.go.jp/article/rpsj1954/23/3/3/23_3_190/_pdf)

  By the way, in a soil purification facility of this kind by a contaminated soil treatment company, a large amount of contaminated soil is usually purified (for example, 2,000 tons per day), so that a large amount of fine particles is generated (for example, 500-600 tons per day on a dry basis). Therefore, when such a large amount of fine particles is washed with, for example, a chelate washing solution, a relatively expensive chelating agent is required in a large amount, and there is a problem that the treatment cost of contaminated soil is increased. The necessary or used amount of the chelating agent increases as the content of the harmful metal or the like in the fine particles increases. When the fine particles are washed with a cleaning solution containing a chemical other than the chelating agent to remove harmful metals (chemical treatment), or by removing the harmful metals by physicochemical treatment using an adsorbent or the like. In such a case, a similar problem may occur.

  The present invention has been made in order to solve the above-mentioned conventional problems, and it is intended to wash gravels, sand, and soil containing gravels, sand, and fine particles and contaminated with harmful metals and the like with washing water. It can be classified as fine particles and can remove harmful metals and the like adsorbed or adhered to the separated fine particles, or at least contain or hold the harmful metals and the like in the fine particles An object of the present invention is to provide a soil purification system that can lower the rate and has a lower treatment cost.

  Soil for purifying soil contaminated with harmful metals and the like (harmful metals and / or compounds thereof) or ions thereof, including gravel, sand and fine particles according to the present invention made to solve the above-mentioned problem. The purification system includes a mixer, a wet crusher, a trommel, a hydrocyclone, a thickener, an iron removing device, a filter, a chelate washing device, and a filtrate returning means.

  Here, the mixer mixes the soil introduced into the soil purification system with the washing water. A wet crusher crushes gravels and sand in a mixture containing soil and washing water discharged from a mixer, thereby forming iron or iron oxides (hereinafter referred to as “iron or iron oxides”) unevenly or scattered inside the gravels and sand. The iron-based fine particles exposed on the surface generate iron-based fine particles, and the harmful metals and the like in the washing water are adsorbed or adhered to the iron and the like exposed on the surface of the iron-based fine particles. Trommel separates gravel from a mixture of gravel, sand, fines and wash water discharged from the wet crusher. The hydrocyclone separates sand from a mixture containing sand, fines and wash water discharged from trommel. The thickener separates a mixture containing fine particles discharged from the hydrocyclone and washing water into supernatant water and sludge containing fine particles and washing water by sedimentation. The iron removing device reduces the content of harmful metals and the like in the sludge (fine particles) by magnetically absorbing and removing iron-based fine particles from the sludge discharged from the thickener. The filter receives and filters sludge containing fine particles and water, from which iron-based fine particles have been removed by the iron removing device, and separates the filtrate into a filter cake containing fine particles and a filtrate. The chelate cleaning device cleans the filter cake separated by the filter with a chelate cleaning liquid containing a chelating agent and water to remove harmful metals and the like remaining in fine particles. The filtrate returning means returns the filtrate separated by the filter to the thickener.

  In the soil purification system according to the present invention, the iron removing device includes an iron-based fine particle adsorption device, a screen device, a centrifugal separator, and a magnetic sphere returning device. Here, in the iron-based fine particle adsorption device, a plurality (many) of permanent magnets are mounted in the hollow portion of the hollow sphere such that magnetic poles (N pole or S pole) of the same magnet face outward in the sphere radial direction. It receives a plurality (many) of magnetic spheres and sludge discharged from a thickener, and moves a fluid in which the magnetic spheres and the sludge are mixed downward by a gravity in a zigzag-like path. The iron-based fine particles are adsorbed on the magnetic spheres by magnetic force. The screen device receives the fluid discharged from the iron-based fine particle adsorption device and separates it into magnetic spheres and sludge. The centrifugal separator intermittently receives the magnetic spheres adsorbing the iron-based fine particles discharged from the screen device in a batch type (batch type), and separates the iron-based fine particles from the magnetic spheres by centrifugal force. Let it. The magnetic sphere returning device returns the magnetic spheres discharged from the centrifuge to the iron-based fine particle adsorption device.

  In the soil purification system according to the present invention, the magnetic sphere returning device preferably includes an upright belt conveyor, magnetic sphere transport means, and magnetic sphere supply means. In this case, the upright belt conveyor has a driving roller disposed at a position lower than the lower end of the centrifugal separator, and a driven roller disposed at a position higher than the upper end of the iron-based fine particle adsorption device above the driving roller. And an endless metal belt made of a ferromagnetic metal wound around a driving roller and a driven roller, and attached to the outer surface of the endless metal belt and adsorbed to the endless metal belt when traveling upward. A magnetic ball locking member for locking the magnetic ball from descending. The magnetic sphere conveying means conveys the magnetic spheres discharged from the centrifugal separator to a lower end portion of the upright belt conveyor, and causes the magnetic sphere to be attracted to the endless metal belt. The magnetic sphere supply means separates the magnetic spheres from the endless metal belt at the upper end of the upright belt conveyor and supplies the magnetic spheres to the iron-based fine particle adsorption device.

  In the soil purification system according to the present invention, the chelate cleaning device preferably includes a mixing / dispersion device, a fine particle fraction cleaning device, a filtration device, a cleaning solution regenerating device, and a cleaning solution recirculation mechanism. In this case, the mixing and dispersing device mixes the filter cake separated by the filter and the chelate cleaning liquid, and generates a fine particle fraction slurry in which fine particles are dispersed in the chelate cleaning liquid. The fine particle cleaning device is configured to remove the harmful particles attached to the fine particles by flowing the fine particle slurry generated by the mixing and dispersing device in a plug flow so as to secure a preset residence time while stirring. The metal or the like or its ions are released from the fine particles to be captured by the chelating agent. The filtering device filters the fine particle slurry discharged from the fine particle washing device. The washing liquid regenerating device has a solid-phase adsorbent that has a higher complexing power than the chelating agent and adsorbs harmful metals or the like or ions thereof in the filtrate when coming into contact with the filtrate discharged from the filtering device. The filtrate is regenerated as a chelate washing solution by removing harmful metals and the like from the chelating agent. The washing liquid reflux mechanism causes the chelating washing liquid discharged from the washing liquid regenerating device to be refluxed to the mixing / dispersing device.

  Generally, in the process of washing and classifying contaminated soil using washing water, harmful metals and the like are hardly adsorbed (adhered) to gravel and sand, but are adsorbed (adhered) to fine particles (for example, non-adhered). Patent Document 1). The fine particles are composed of a relatively small amount of iron-based fine particles containing iron or the like that can be adsorbed by a magnetic force, and a relatively large amount of fine particles that cannot be adsorbed by a magnetic force other than the iron-based fine particles (hereinafter referred to as “fine particles”). Non-ferrous fine particles ”). On the other hand, since iron and the like have the property of adsorbing harmful metals and the like (see, for example, Non-Patent Document 2), the amount of harmful metal and the like adsorbed on iron-based fine particles including iron and the like exposed on the surface (the amount of adhesion ) Is considerably larger than the adsorption amount (adhesion amount) of harmful metals and the like in the non-ferrous fine particles.

  In the soil purification system according to the present invention, the gravel and / or the sand are crushed by the wet crusher to generate fine particles. The fine particles containing a large amount of iron and other fine lump were iron-based fine particles, and the iron etc. exposed on the surface of these iron-based fine particles was transferred from the wet crusher to the iron removal device. Adsorbs a relatively large amount of harmful metals and the like in a series of distribution processes. Therefore, the iron-based fine particles existing before the crushing and the iron-based fine particles generated by the crushing are introduced into the iron removing device, and both of these iron-based fine particles are considerably large (non-ferrous particles). (Compared to the fine particles).

  Thus, in the iron removal device, when the fluid (mixture) in which the magnetic spheres and the sludge are mixed moves downward in the zigzag path in the iron-based fine particle adsorption device, the adsorption amount of harmful metals and the like is large. Since the iron-based fine particles in the sludge are magnetically adsorbed by the magnetic spheres and are removed from the sludge, the content or the holding ratio of harmful metals and the like in the sludge can be reduced. Therefore, when the sludge discharged from the iron removing device is subjected to the chemical treatment by the chelate cleaning device, the load of the toxic metal or the like on the chelate cleaning device can be reduced. As a result, the required or used amount of a chemical such as a chelating agent can be reduced, and the cost of treating soil can be reduced. Since the wet crusher and the iron removing device have a mechanical structure for performing physical treatment and do not use any special chemicals or treating agents, their operation costs are very low.

  In each magnetic sphere, a plurality of permanent magnets are mounted in the hollow portion of the hollow sphere such that the magnetic poles (for example, N poles) of the same magnet face outward in the sphere radial direction. Repel each other. For this reason, in the iron-based fine particle adsorption device, on the screen device, or in another magnetic sphere moving path, the magnetic spheres do not adsorb to each other and form a mass (tuft of grapes). Can move smoothly with a suitable distance while repelling each other.

It is a block diagram showing the schematic structure of the soil purification system concerning Embodiment 1 of the present invention. It is a typical elevation view of the iron removal device which comprises the soil purification system. FIG. 3 is a schematic sectional view of a magnetic sphere. It is a typical partial section elevation view of a centrifuge. (A) is a schematic side view of a part of a magnetic sphere conveyor and an upright belt conveyor, (b) is a schematic side view of a part of an upright belt conveyor, and (c) is an upright. It is a typical front view of a part of type | mold belt conveyor. It is a block diagram showing a schematic structure of a chelate washing device which is a component of a soil purification system. FIG. 2 is a schematic elevation view showing a configuration of a mixing and dispersing device forming a part of the chelate washing device. (A) is a schematic plan view of the fine particle cleaning device forming a part of the chelate cleaning device, (b) is a cross-sectional view taken along line AA of the fine particle cleaning device shown in (a), (C) is an elevational sectional view of one slurry passage of the fine-grain cleaning device. It is a block diagram showing the schematic structure of the soil purification system concerning Embodiment 2 of the present invention.

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.
(Embodiment 1)
As shown in FIG. 1, in the soil purification system S according to the first embodiment of the present invention, the soil is collected by excavating the ground contaminated with harmful metals and the like (hazardous metals and / or compounds thereof, or ions thereof). The waste soil (contaminated soil) is received by the input hopper 1. The harmful metal includes, for example, chromium, lead, cadmium, selenium, mercury, metal arsenic, and the like.

  Then, the soil in the charging hopper 1 is continuously or intermittently charged into the mixer 2 and mixed with the washing water continuously supplied to the mixer 2. Here, the soil is gravel (for example, having a particle size of 2 to 75 mm), sand (for example, having a particle size of 0.075 to 2 mm), and fine particles (for example, having a particle size of 0.075 mm or less). ), And in some cases, a stone (for example, one having a particle size of 75 mm or more).

  A mixture containing the soil and the washing water generated in the mixer 2 (hereinafter, referred to as “soil-water mixture”) is transferred to a mill breaker 3 that is a wet crusher. As the mill breaker 3, for example, a rod mill can be used. Although not shown in detail, the rod mill is a crusher in which a plurality of rods (for example, ten 75 mmφ × 2 m steel rods) are arranged in a drum, and the rods are rotated in parallel with each other by rotation of the drum. It moves and makes line contact, and can crush gravels and sand (and, in some cases, stones) by the impact force, shearing force, frictional force, etc., and produce small-diameter soil particles such as fine particles. . As the mill breaker 3, a ball mill or the like can be used in addition to the rod mill. It should be noted that some of the gravel and sand are fine particles, and not all of them are fine particles.

  Thus, the mill breaker 3 crushes the gravels and sand (and, in some cases, stones) in the soil / water mixture discharged from the mixer 2 to generate small-diameter soil particles such as fine particles. As a result, harmful metals or the like adsorbed (attached) to or contained in the gravel and sand are released into the water. At this time, basically (aside from the adsorption by iron etc. described later), the harmful metals released into the water are hardly adsorbed on the gravel and sand, or do not adhere, and are collected and adsorbed on the fine particles. Or adheres (for example, see Non-Patent Document 1).

  In addition, a large number of iron-based fine particles are generated in which fine clumps of iron or the like (iron and / or iron oxide) existing, unevenly distributed, or scattered inside the gravel and sand are exposed on the surface. On the other hand, iron and the like generally have a property of adsorbing harmful metals and the like. For this reason, a part or most of the harmful metals and the like present in the washing water are adsorbed or adhered to the exposed surface of the iron and the like of the iron-based fine particles. As a result, the adsorption amount (adhesion amount) of harmful metals and the like in the iron-based fine particles is considerably larger than the adsorption amount (adhesion amount) of harmful metals and the like in the non-ferrous fine particles. In other words, the fine particles discharged from the mill breaker 3 are divided into an iron-based fine particle having a large adsorption amount (adhesion amount) of harmful metals and a non-ferrous fine particle having a small adsorption amount (adhesion amount) of harmful metals and the like. It is composed of It should be noted that the iron-based fine particles existing before the crushing also adsorb considerably more harmful metals and the like than the non-ferrous fine particles.

  The iron-based fine particles adsorbing the harmful metals and the like are removed by the iron removing device 12 as described later. On the other hand, it is generally known that iron and the like (iron and / or iron oxide) have a property of adsorbing harmful metals and the like. Various “iron powder methods” have been proposed in which harmful metals and the like are removed from sludge by adding powder (for example, see Patent Documents 3 and 4 and Non-Patent Document 2). However, as in the present invention, by crushing gravels and sand, iron-based fine particles having fine lumps such as fresh iron (not yet adsorbing harmful metals and the like) exposed on the surface are generated. There is no proposal for a method for treating harmful metals or the like in which harmful metals or the like are adsorbed to the minute lump of iron or the like (the iron-based fine-grain portion).

  The soil / water mixture discharged from the mill breaker 3 is introduced into the trommel 4. Although not shown in detail, the trommel 4 is a sieving apparatus that includes a receiving tank that can store water and a substantially cylindrical drum screen that is arranged to be inclined with respect to a horizontal plane. Can be rotated around its central axis (the central axis of the cylinder) by a motor. Further, cleaning water can be sprayed into the drum screen.

  When the soil / water mixture flows inside the rotating drum screen of the trommel 4, fine soil particles finer than the mesh of the drum screen pass through the mesh of the drum screen together with the washing water, exit the drum screen, and enter the receiving tank. to go into. On the other hand, soil particles coarser than the mesh of the drum screen cannot pass through the mesh of the drum screen, and are discharged out of the drum screen via the lower open end of the drum screen.

  In the trommel 4, the classification diameter (opening) of the mesh of the drum screen is set such that soil particles having a particle size of less than 2 mm, that is, sand and fine particles, pass through the mesh of the drum screen. Therefore, in the trommel 4, the gravels (in some cases, stones), which are soil particles having a particle size of 2 mm or more, are separated from the soil / water mixture. As described above, harmful metals and the like that have been separated into water are hardly adsorbed or adhered to gravel and sand, so that the gravel separated by the trommel 4 is clean and used as, for example, aggregate for concrete. be able to. Note that the mesh size (mesh size) of the drum screen of the trommel 4 is not limited to the above-described one, but can be arbitrarily set according to the particle size of the soil particles to be obtained. It is.

  The soil particles having a particle diameter of less than 2 mm, that is, a soil / water mixture containing fine particles and washing water, contained in the receiving tank of the trommel 4 are introduced into the cyclone 5 (liquid cyclone). The cyclone 5, which is not shown in detail, pumps the soil / water mixture into a substantially conical cylinder that narrows downward to generate a swirling flow, and utilizes the centrifugal force generated thereby, The soil / water mixture is made up of a mixture of water having a relatively small particle size (for example, a particle size of less than 0.075 mm) and water, a relatively large particle size of sand (for example, a particle size of 0.075 mm or more) and water. And a mixture of

  A mixture of fine particles and water (hereinafter referred to as “fine particle content water”) is discharged from the upper end of the cyclone 5, and a mixture of sand and water having a relatively large particle diameter is discharged from the lower end of the cyclone 5. Is done. Here, the mixture of sand and water discharged from the lower end of the cyclone 5 hardly contains harmful metals and the like as described above, so that it is drained or dried to be used as recycled sand. On the other hand, the water containing fine particles is transferred to the PH adjustment tank 6.

  In the pH adjusting tank 6, the pH (hydrogen index) of the fine-particle-containing water is made substantially neutral using an acid solution (for example, sulfuric acid or hydrochloric acid) and an alkali solution (for example, aqueous sodium hydroxide solution). Adjusted. Although not shown, in the pH adjusting tank 6, the pH of the fine-particle-containing water is automatically adjusted by a pH automatic control device equipped with a pH meter and the like.

  The water containing fine particles whose pH has been adjusted in the pH adjusting tank 6 is introduced into the coagulation tank 7. In the coagulation tank 7, a polyaluminum chloride liquid (PAC), a polymer coagulant, and a pH adjuster (acidic or alkaline liquid) are added to the water containing fine particles. Thereby, a large number of flocs in which the water-insoluble metal hydroxide and the fine particles are mixed in the flocculation tank 7 are generated.

  The water containing fine particles in the coagulation tank 7 is introduced into the thickener 8. Although not shown in detail, the thickener 8 sediments the water-insoluble floc or fine particles by gravity in a state where the fine particle-containing water is almost stationary, and forms a sludge layer (for example, solid And the supernatant water (washing water) which is located at the upper portion and contains almost no floc or fine particles. When the floating oil is floating on the surface of the supernatant water, the floating oil is removed by overflowing a small amount of the supernatant water from the upper part of the thickener 8.

  The supernatant water in the thickener 8 is introduced into the washing water tank 10 and is temporarily stored as washing water. When the washing water tank 10 becomes full, the spare water tank 11 is used. The washing water stored in the washing water layer 10 or the preliminary water tank 11 is supplied to the mixer 2 and the trommel 4 as circulating water. In addition, when the washing water stored in the washing water tank 10 decreases due to evaporation or the like, tap water is appropriately supplied. On the other hand, the sludge deposited at the lower part of the thickener 8 is transferred to the intermediate tank 9 and is temporarily stored. Note that a series of devices 1 to 9 from the charging hopper 1 to the intermediate tank 9 are components of a soil classification unit of the soil purification system S.

  The sludge in the intermediate tank 9 is basically continuously transferred to the iron removing device 12 by a sludge pump or the like (not shown). The iron removing device 12 reduces the content of harmful metals and the like in the sludge by adsorbing and removing iron-based fine particles from the sludge by magnetic force. The iron-based fine particles discharged from the iron removing device 12 are supplied to, for example, an iron making company or the like, and are used as a raw material for iron making. The specific configuration and function of the iron removing device 12 will be described later in detail.

  The sludge discharged from the iron removing device 12 is introduced into the filter press 13 and dewatered, and a filtrate and a cake are generated. Then, the filtrate is returned to the thickener 8. On the other hand, the cake is transferred to the chelate washing device 14 to remove harmful metals and the like remaining in the fine particles (non-ferrous fine particles). Here, if the content of the harmful metal or the like in the fine particles contained in the cake is within the standard, the cake is disposed of by landfill or the like without being transferred to the chelate washing device 14. Note that another filter, for example, a vacuum filter may be used instead of the filter press 13. The specific configuration and function of the chelate cleaning device 14 will be described later in detail.

Hereinafter, the specific configuration and function of the iron removing device 12 will be described with reference to FIGS.
As shown in FIG. 2, the iron removal device 12 has, as its main components, iron-based fine particle adsorption for bringing a plurality (many) of magnetic spheres 20 into contact with sludge discharged from the thickener 8 (see FIG. 1). The device 18, a screen device 19 for separating the mixture discharged from the iron-based fine particle adsorption device 18 into magnetic spheres 20 and sludge, and the iron-based fine particles are removed from the magnetic spheres 20 received from the screen device 19. A centrifugal separator 22 and a magnetic sphere returning device 23 for returning the magnetic spheres 20 discharged from the centrifugal separator 22 to the iron-based fine particle adsorption device 18 are provided. Further, the iron content removing device 12 temporarily stores the magnetic spheres 20 supplied to the iron-based fine particle content adsorption device 18, the centrifugal separator 22, or the magnetic sphere returning device 23, respectively. The container is provided with containers 24 to 26 and a sludge storage tank 27 for temporarily storing sludge flowing down from the screen device 19.

  The iron-based fine particle adsorption device 18 receives a plurality (many) of magnetic spheres 20 and sludge discharged from the thickener 8 (see FIG. 1), and receives a fluid (mixture) in which the magnetic spheres 20 and sludge are mixed. ) Is moved downward in a zigzag path by gravity, and the iron-based fine particles in the sludge are attracted to the magnetic spheres 20 by magnetic force during the movement. Specifically, the iron-based fine particle adsorption device 18 has a hollow cylindrical (cylindrical) or hollow quadrangular prism (duct-shaped) main body 21 (housing). Is attached. As for these inclined plates 21a, the odd-numbered inclined plate 21a and the even-numbered inclined plate 21a are located on the opposite side (to face each other) from the upper side to the lower side (part of the entire circumference). It is arranged so as to extend downward from the center toward the center.

  For example, according to the positional relationship in FIG. 2, the odd-numbered (left-side) inclined plate 21a as viewed from above is descending from the inner peripheral portion on the left (part of the entire periphery) to the right. The even-numbered (right-side) inclined plate 21a extends from the right inner peripheral portion (a part of the entire periphery) while descending to the left. Here, the odd-numbered inclined plate 21a and the even-numbered inclined plate 21a overlap each other at a central portion in plan view. Therefore, the magnetic spheres 20 and sludge that have moved or flowed on one inclined plate 21a fall or flow down on the lower inclined plate 21a. As a result, the magnetic spheres 20 and the sludge introduced into the upper part of the iron-based fine particle adsorption device 18 move or flow along the zigzag path in order on the upper surfaces of the plurality of inclined plates 21a arranged from the upper side to the lower side. I do. At this time, the iron-based fine particles adsorbing the harmful metal or the like in the sludge or adhering the harmful metal or the like are adsorbed to the outer peripheral surface of the magnetic sphere 20 by magnetic force. Thereby, the content of harmful metals and the like in the sludge is reduced.

  The screen device 19 receives the fluid (mixture) discharged from the iron-based fine particle adsorption device 18 and separates (screens) it into magnetic balls 20 and sludge. Although not shown in detail, the screen device 19 has a mesh-like or grid-like screen that extends from the lower position of the iron-based fine particle adsorption device 18 to the side while being inclined and inclined. The opening (opening size) of the screen is a size that the magnetic sphere 20 cannot pass through. When a fluid (mixture) in which the magnetic spheres 20 and sludge are mixed on the screen falls or falls, the magnetic spheres 20 roll on the inclined screen and fall into the second magnetic sphere storage container 25. . On the other hand, the sludge flows downward through meshes or openings of the screen and is stored in the sludge storage tank 27. The iron removing device 12 is provided with a sludge pump 34 for transporting the sludge in the sludge storage tank 27 to the filter press 13 (see FIG. 1).

  As shown in FIG. 3, in the magnetic sphere 20, a plurality of permanent magnets 30 are roughly mounted in a hollow portion of a hollow spherical body 29 such that respective N poles face outward in the spherical body radial direction. Things. In addition, the magnetic sphere 20 may be one in which each permanent magnet 30 is mounted such that each S pole faces outward in the spherical body radial direction. Specifically, each permanent magnet 30 is fitted in a magnet holding hole 32 formed in a hollow spherical magnet holding member 31. The magnet holding member 31 with the permanent magnet 30 is fitted in the hollow part of the hollow spherical body 29. In other words, the hollow spherical body 29 is externally fitted on the peripheral surface of the magnet holding member 31, or the peripheral surface of the magnet holding member 31 is covered with the hollow spherical body 29.

  The magnet holding hole 32 formed in the magnet holding member 31 is a tapered hole whose cross-sectional area decreases toward the center of the magnetic sphere, and the permanent magnet 30 is fitted or aligned with the magnet holding hole 32 (complementary type). ) Is formed. Therefore, the permanent magnet 30 can be easily attached to the magnet holding member 31 by fitting or inserting the permanent magnet 30 into the magnet holding hole 32 from outside the magnet holding member 31. The shape of the end face of the permanent magnet 30 located on the radially outer side when mounted on the magnet holding member 31 is preferably a curved surface (part of a spherical surface) that matches the outer peripheral surface of the magnet holding member 31. By doing so, the outer peripheral surface of the aggregate of the permanent magnet 30 and the magnet holding member 31 becomes spherical, and the aggregate and the hollow spherical body 29 can be brought into close contact.

It is practical that the diameter of the magnetic sphere 20 (that is, the outer diameter of the hollow spherical body 29) is, for example, 3 to 5 cm in order to facilitate the transportation of the magnetic sphere 20. Further, the apparent density (or bulk density) of the magnetic sphere 20, that is, the value obtained by dividing the mass of the magnetic sphere 20 by its volume, aims to reduce the weight as much as possible without causing the magnetic sphere 20 to float in the sludge at the time of flowing. Therefore, it is practical to set it in the range of 1.1 to 1.3 g / cm ³ . The apparent density of the magnetic sphere 20 can be adjusted or increased or decreased by appropriately setting the size and number of the permanent magnets 20 and the number of the permanent magnets 20 and the volume of the magnet holding member 31 or the hollow portion thereof. It is easy to adjust the apparent density of 1.1 to 1.3 g / cm ³ .

  The material of the hollow spherical body 29 is not particularly limited as long as it has corrosion resistance to sludge and appropriate mechanical strength, but it is practical to use stainless steel or aluminum (or an alloy thereof). The thickness of the hollow spherical body 29 is preferably, for example, about 0.2 to 0.5 mm. If the hollow spherical body 29 is formed of a pair of hollow hemispheres that can be screwed together, the magnetic sphere 20 can be easily manufactured. In this case, the magnetic ball 20 can be easily assembled by inserting the magnet holding member 31 with the permanent magnet 30 into one hemisphere and screwing the other hemisphere into this hemisphere. When the combination is released, the magnetic sphere 20 can be dismantled.

  The magnet holding member 31 can be manufactured by injection molding of, for example, a thermoplastic resin (eg, polyethylene, polypropylene, or the like). As the permanent magnet 20, it is possible to use a neodymium magnet having a tapered shape corresponding to the magnet holding hole 32, a large-diameter end face having N poles, and a small-diameter end face having S poles. It is to be noted that a neodymium magnet may be used in which the end face on the large diameter side is an S pole and the end face on the small diameter side is an N pole.

  As shown in FIG. 2 again, a first magnetic sphere storage container 24 is disposed above the iron-based fine particle adsorption device 18, and a lower end (bottom) of the first magnetic sphere storage container 24 has an opening degree thereof. An opening / closing door 24a that can freely adjust is provided. By adjusting the opening of the opening / closing door 24a, the magnetic spheres 20 stored in the first magnetic sphere storage container 24 are continuously discharged downward at a desired flow rate (flow rate), and the iron-based fine spheres are discharged. It can be supplied to the upper part of the particle adsorption device 18.

  A second magnetic sphere storage container 25 is disposed below the tip of the screen device 19 (the end farther from the iron-based fine particle adsorbing device 18), and the magnetic sphere 20 rolled on the screen of the screen device 19. Are dropped by the gravity from the tip of the screen device 19 and accommodated in the second magnetic sphere storage container 25. Since the magnetic spheres repel each other due to a magnetic force (repulsive force), the magnetic spheres 20 can move smoothly and quickly without moving into clusters or clusters of grapes when moving. However, the same applies to a case in which the object moves in a certain device or container, or moves to another device or container.)

  A centrifuge 22 is disposed below the second magnetic sphere storage container 25. The centrifugal separator 22 intermittently batches the magnetic spheres 20 discharged from the iron-based fine particle adsorption device 18 and temporarily stored in the second magnetic sphere storage container 25 via the screen device 19 into a batch type (batch type). And the iron-based fine particles are separated from the magnetic sphere 20 by centrifugal force. At the lower end (bottom) of the second magnetic sphere storage container 25, an opening / closing door 25a for dropping the magnetic spheres 20 stored therein at any time and supplying the same to the centrifuge 22 is provided.

  As shown in FIG. 4, the centrifugal separator 22 includes a housing 35, which is a substantially cylindrical container, and a coaxial arrangement with the housing 35 in the housing 35, and a bearing device 36 fixed to the housing 35. A rotating cylinder 37 rotatably supported around an axis. The upper and lower ends of the rotating cylinder 37 are respectively provided with an upper opening / closing door 37a and a lower opening / closing door 37b that can be opened and closed at any time. The circumferential portion (side portion) of the rotary cylinder 37 is formed of a cylindrical net-like member or a lattice-like member having a large number of openings with openings through which the magnetic sphere 20 cannot pass. The rotary cylinder 37 is driven to rotate by a motor 39 via a gear mechanism 38. Note that a belt pulley mechanism may be used instead of the gear mechanism 38. In the housing 35, a frustoconical baffle 40 (an umbrella-shaped baffle plate) for receiving and dropping particles of iron-based fine particles flying horizontally by centrifugal force from a rotating cylinder 37 rotating at a high speed and dropping the same. Are located.

  As is clear from FIG. 2, the third magnetic sphere storage container 26 is disposed below the centrifugal separator 22. When the lower opening / closing door 37 b (see FIG. 4) is opened when the rotary cylinder 37 is stopped, the third magnetic sphere storage container 26 rotates. The magnetic sphere 20 in the cylinder 37 falls by gravity and is stored in the third magnetic sphere storage container 26. At the lower end of the third magnetic sphere storage container 26, an opening / closing door 26a whose opening can be freely adjusted is attached. By adjusting the opening degree of the opening / closing door 26a, the magnetic spheres 20 in the third magnetic sphere storage container 26 can be continuously discharged (dropped) at a desired passage amount (flow rate).

  Under the third magnetic sphere storage container 26, the magnetic spheres 20 continuously discharged from the third magnetic sphere storage container 26 are received on a belt 41a (endless belt) and transported in a horizontal direction by the belt 41a. There is provided a horizontal belt conveyor 41 for feeding to an upright belt conveyor. The horizontal belt conveyor 41 has one end (upstream end in the magnetic sphere transport direction) located near the lower end of the third magnetic sphere storage container 26 and the other end (downstream end in the magnetic sphere transport direction). Are arranged near the lower end of the upright belt conveyor 42. The horizontal belt conveyor 41 and the upright belt conveyor 42 are components of the magnetic ball returning device 23.

  The belt 41a is formed of a flexible non-magnetic material (for example, rubber). Further, on both sides of the belt 41a, side plates (not shown) for preventing the magnetic spheres 20 on the belt from dropping off from the belt side portion are provided on both sides of the belt 41a. . Note that, without the side plate, a bank-shaped or bank-shaped protrusion having an appropriate height (for example, 1 to 2 cm) and extending in the belt extension direction may be integrally formed on both sides of the belt 41a.

  The upright belt conveyor 42 has two drive rollers 43a and 43b arranged slightly above the horizontal belt conveyor 41, and a position slightly higher than the upper end of the first magnetic sphere storage container 24 just above the drive rollers 43a and 43b. (Endless) made of a ferromagnetic material (eg, steel, stainless steel, etc.) wound around two driven rollers 44a, 44b, and driving rollers 43a, 43b and driven rollers 44a, 44b. A metal belt 45 and a plurality of idle rollers 46 are provided. Here, the drive rollers 43a and 43b are driven to rotate counterclockwise by a motor (not shown). Accordingly, the metal belt 45 travels in a counterclockwise direction between the driving rollers 43a and 43b and the driven rollers 44a and 44b. Here, a plurality of permanent magnets 49 (see FIG. 5) are provided in the drive roller 43a in order to assist the magnetic ball 20 on the belt 41a to move and attract to the metal belt 45. It is mounted so that it faces outward. In the case where the permanent magnet 30 of the magnetic sphere 20 is mounted such that the S pole faces outward in the radial direction of the spherical body, the permanent magnet 49 is mounted such that the N pole faces outward in the roller radial direction. You. The idle roller 46 abuts on the inner surface (rear surface) of the ring-shaped metal belt 45 and regulates the position or the traveling path of the metal belt 45 so that the metal belt 45 travels on a predetermined traveling track.

  Since the metal belt 45 is formed of a ferromagnetic material, the magnetic spheres 20 can adhere to the metal belt 45 by magnetic force. The magnetic properties or the magnetic strength of the permanent magnet 30 (see FIG. 3) of the magnetic sphere 20 are such that the magnetic sphere 20 is positioned below the metal belt 45 at an appropriate distance (for example, 5) in a state where the metal belt 45 extends in the horizontal direction. When the magnetic spheres 20 are arranged at an interval of about 15 mm, the magnetic spheres 20 are set to move upward against the gravity and adhere to the lower surface of the metal belt by magnetic force. The attachment of the magnetic sphere 20 to the lower surface of the metal belt is assisted by the permanent magnet 49 (see FIG. 5).

  Further, the horizontal belt conveyor 41 is arranged such that the magnetic sphere 20 is magnetically attached to the lower surface of the metal belt between the top of the magnetic sphere 20 placed on the belt 41a and the lower surface of the metal belt at the lower end of the upright belt conveyor 42. It is arranged in such a way that the above-mentioned suitable spacing to which it can adhere is created. Therefore, the magnetic spheres 20 transported by the horizontal belt conveyor 41 to the lower side of the upright belt conveyor 42 sequentially adhere to the lower surface of the metal belt by magnetic force.

  As shown in FIGS. 5A to 5C, the outer surface of the metal belt 45 of the upright belt conveyor 42 is slightly longer than the diameter of the magnetic sphere 20 in the extending direction (running direction) of the metal belt 45. A plurality of (many) prismatic or square rod-shaped magnetic ball locking members 47 extending linearly in the belt width direction are attached at intervals. The material of the magnetic ball locking member 47 is not particularly limited as long as it can be easily attached to and detached from the metal belt 45 (for example, screwed) and has durability against collision with the magnetic ball 20. For example, a synthetic resin or an aluminum alloy can be used.

  When the metal belt 45 extends vertically and travels or moves upward, the magnetic ball locking member 47 causes the magnetic sphere 20 attached to the surface of the metal belt 45 by magnetic force to move downward or move by gravity. Lock rolling. It is practical that the height or the protruding length of the magnetic ball locking member 47 from the surface of the metal belt is １ ／ to ４ of the diameter of the magnetic sphere 20. Further, it is practical that the distance between the magnetic ball locking members 47 adjacent in the extending direction (running direction) of the metal belt 45 is 1.2 to 1.5 times the diameter of the magnetic ball 20.

  Thus, the magnetic spheres 20 transported by the horizontal belt conveyor 41 and adhered to the metal belt 45 by magnetic force at or near the lower end portion of the upright belt conveyor 42 are moved downward by the metal belt 45 circling counterclockwise. The belt is conveyed to the upper end of the upright belt conveyor without moving or rolling.

  As is clear from FIG. 2, near the upper end of the upright belt conveyor 42, the magnetic spheres 20 attached to the metal belt 45 by magnetic force are separated from the metal belt 45 and guided to the first magnetic sphere storage container 24. A guide member 48 is provided. The end of the guide member 48 on the side of the upright belt conveyor is located near the driven roller 44a, while the end on the side of the first magnetic sphere storage container is located near the upper end of the first magnetic sphere storage container 24. . The guide member 48 is inclined downward from the upright belt conveyor toward the first magnetic sphere storage container. Note that the guide member 48 is formed of a non-magnetic material.

  In the positional relationship in FIG. 2, the magnetic sphere 20 attached to and moving on the metal belt 45 traveling around in the counterclockwise direction collides with or contacts the end of the guide member 48 near the driven roller 44a. As a result, the magnetic sphere 20 is separated from the metal belt 45 by the guide member 48, rolls on the upper surface of the guide member 48, and falls into the first magnetic sphere storage container 24. That is, the magnetic spheres 20 continuously discharged downward from the third magnetic sphere storage container 26 are returned to the first magnetic spheres by the magnetic sphere returning device 23 (the horizontal belt conveyor 41, the upright belt conveyor 42, and the guide member 48). It is continuously returned to the storage container 24.

  As described above, the magnetic spheres 20 include, in order, the first magnetic sphere storage container 24, the iron-based fine particle adsorption device 18, the screen device 19, the second magnetic sphere storage container 25, the centrifugal separator 22, The third magnetic sphere storage container 26 and the magnetic sphere returning device 23 (the horizontal belt conveyor 41, the upright belt conveyor 42, and the guide member 48) circulate and move. Two broken arrows in FIG. 2 indicate the moving direction of the magnetic sphere 20. The magnetic spheres 20 move continuously from the first magnetic sphere storage container 24 to the second magnetic sphere storage container 25, and intermittently or batchwise from the second magnetic sphere storage container 25 to the third magnetic sphere storage container 26. And moves continuously from the third magnetic sphere storage container 26 to the first magnetic sphere storage container 24.

  Hereinafter, an example of an operation method of the iron removing device 12 will be described. A large number of magnetic spheres 20 that do not substantially adsorb the iron-based fine particles are continuously supplied from the first magnetic sphere storage container 24 to the upper part of the iron-based fine particle adsorption device 18, while the intermediate tank From 9 (see FIG. 1), sludge substantially consisting of fine particles (ferrous fine particles and non-ferrous fine particles) and water is continuously supplied. Then, in the iron-based fine particle adsorption device 18, a fluid or mixture obtained by mixing the magnetic spheres 20 and sludge moves or moves downward along a zigzag path formed by the plurality of inclined plates 21 a. Flow. At this time, the iron-based fine particles in the sludge are magnetically attracted to the outer peripheral surface of the magnetic sphere 20.

  The iron-based fine fraction is generated by crushing gravel and sand with a mill breaker 3 (see FIG. 1), which is a wet crusher, or existing before crushing of gravel and sand. A minute lump of iron or the like is exposed on the surface, and the harmful metal or the like is adsorbed on the minute lump of iron or the like that is exposed. Generally, small lumps such as iron are unevenly scattered or scattered in gravel and sand, and the ratio of such small lumps is about 2 to 7% by mass. For this reason, at least a part of the fine particles generated by the crushing of the gravels and sand becomes iron-based fine particles in which fresh iron (ie, no harmful metal or the like is adsorbed) is exposed on the surface.

Iron is a ferromagnetic material (soft magnetic material) and is attracted to a magnet. The iron oxides present in the soil are substantially triiron tetroxide (Fe ₃ O ₄ ), γ-type diiron trioxide (γ-Fe ₂ O ₃ ), and α-type diiron trioxide ( α-Fe ₂ O ₃ ), and triiron tetroxide and γ-type diiron trioxide are ferromagnetic substances (soft magnetic substances) and are adsorbed by magnets. The α-type diiron trioxide is not magnetized and is not adsorbed by the magnet. For this reason, the iron-based fine particles, on the surface of which a fine lump of iron or the like is exposed, are made of a permanent magnet in the magnetic sphere 20 due to the ferromagnetism (soft magnetism) of iron, triiron tetroxide or γ-type diiron trioxide. 30 (see FIG. 3) and is attracted to the outer peripheral surface of the magnetic sphere 20 (hollow spherical body 29) by magnetic force.

  The fine lump such as iron exposed on the surface of the iron-based fine particles generated by crushing the gravel and sand with the mill breaker 3 (see FIG. 1) is unevenly distributed or dotted in the gravel or sand. It is generated from a small lump of fresh iron or the like that does not adsorb the harmful metals and the like, and is exposed to the surface after crushing and adsorbs harmful metals and the like or ions thereof from the surrounding washing water. Thus, the fine particles discharged from the mill breaker 3 (see FIG. 1) and introduced into the iron-based fine particle adsorption device 18 are combined with the iron-based fine particles having a relatively (or considerably) large amount of adsorption of harmful metals and the like. And non-ferrous fine particles having a relatively (or considerably) less adsorption amount of harmful metals and the like.

  As described above, since the iron-based fine particles are removed from the sludge in the iron-based fine particles adsorption device 18, the fine particles contained in the sludge discharged from the iron-based fine particles adsorption device 18 are: Most of the non-ferrous fine particles have a relatively (or considerably) small amount of adsorbed harmful metals. Therefore, a part or a considerable part of the harmful metals and the like contained in the contaminated soil introduced into the soil purification system S is removed in the iron-based fine particle adsorption device 18.

  The mixture of the magnetic spheres 20 and the sludge discharged downward from the lower end portion of the iron-based fine particle adsorption device 18 is introduced into the screen device 19, and the magnetic spheres 20 adsorbing the iron-based fine particles and the iron-based fine particles The particles are separated into sludge from which the particles have been removed. Then, the magnetic sphere 20 is stored in the second magnetic sphere storage container 25, and the sludge is stored in the sludge storage tank 27.

  As will be described later in detail, sludge (fine particles) discharged from the iron-based fine particle adsorption device 18 and separated by the screen device 19 is chelated by a chelating agent 14 (see FIG. 1) using a chelating agent. The washing process is performed, and the chelating agent is regenerated by the solid-phase adsorbent in the cleaning liquid regenerating section 54 (see FIG. 6). Is reduced, the load of harmful metals and the like on the chelate washing treatment of the fine particles (sludge) and the regeneration treatment of the chelating agent is reduced. For this reason, the necessary amount or use amount of the chelating agent and the solid phase adsorbent in the soil purification system S can be reduced, and the cost for treating the soil can be reduced. In other words, the iron-based fine particle adsorption device 18 (iron removal device 12) functions as a pretreatment device or a pretreatment device for reducing the load of harmful metals or the like on the chelate cleaning device 14 or the cleaning liquid regenerating section 54. .

  The magnetic spheres 20 adsorbing the iron-based fine particles in the second magnetic sphere storage container 25 are appropriately supplied to the rotating cylinder 37 of the centrifuge 22. Specifically, in a state where the upper opening / closing door 37a is opened and the lower opening / closing door 37b is closed, the opening / closing door 25a is opened, and the processing is performed once from the second magnetic sphere storage container 25 into the rotating cylinder 37. The minute magnetic sphere 20 is supplied. For example, the magnetic spheres 20 are supplied in an amount that occupies 1/3 to 1/2 of the space in the rotating cylinder 37.

  Thereafter, the upper opening / closing door 37a is closed, the motor 39 is started, and the rotary cylinder 37 is rotated at a high speed (for example, when the radius of the rotary cylinder 37 is 1 m, 100 to 500 rpm). As a result, the iron-based fine particles adsorbed or adhered to the outer peripheral surface of the magnetic sphere 20 are separated from the magnetic sphere 20 by a strong centrifugal force (for example, 10 to 100 G), and a large number of meshes of the peripheral wall of the rotating cylinder 37 are formed. Or it jumps out through a hole. Here, the rotation speed of the rotating cylinder 37 depends on the radius of the rotating cylinder 37, the magnetic force of the magnetic sphere 20, the magnetic characteristics of the iron-based fine particles, and the like. Preferably, they are set apart.

  The iron-based fine particles that have separated from the magnetic sphere 20 and jumped out of the rotary cylinder 37 collide with the baffle 40, fall, and accumulate at the bottom of the housing 35. The iron-based fine particles in the housing 35 are appropriately and manually discharged to the outside. The removed iron-based fine particles can be used, for example, as a raw material for ironmaking. Then, after a lapse of a predetermined time (for example, 2 to 5 minutes), the rotation of the motor 39 and thus the rotating cylinder 37 is stopped. Thereafter, the lower opening / closing door 37b is opened, and the magnetic sphere 20 from which the iron-based fine particles in the rotary cylinder 37 have been almost removed falls into the third magnetic sphere storage container 26 by gravity.

  The magnetic spheres 20 in the third magnetic sphere storage container 26 are continuously supplied onto the belt 41a of the horizontal belt conveyor 41, and are transported by the belt 41a to the vicinity of the lower end of the upright belt conveyor 42. Thereafter, the magnetic spheres 20 on the belt 41a are transported to the upper end by the upright belt conveyor 42, and are introduced into the first magnetic sphere storage container 24 by the guide member 48. The supply amount (supply speed) of the magnetic spheres 20 from the third magnetic sphere storage container 26 to the horizontal belt conveyor 41 can be changed by changing the opening degree of the opening / closing door 26a. Adjusted to be less than or equal to the maximum transport amount of the conveyor 42

  Hereinafter, the configuration and function of the chelate cleaning device 14 will be described. When the content of harmful metals and the like in the cake discharged from the filter press 13 is lower than a predetermined regulation value in the case of disposal by landfilling or reuse, it is necessary to use the chelating cleaning device 14 as a post-processing unit. No need to provide.

  First, the general configuration and function of the cleansing device 14 will be described with reference to FIG. In the chelate cleaning device 14, first, the cake (filter cake) discharged from the filter press 13 (see FIG. 1) and the chelate cleaning liquid containing a chelating agent in the cleaning liquid storage tank 56 are continuously supplied to the mixing and dispersing device 51. Is done. Then, the mixing and dispersing device 51 mixes the cake and the chelate cleaning liquid, and in the chelate cleaning liquid, fine particles or small pieces of fine particles (for example, having a particle size of about several 0.1 to 0.5 mm or 0.1 To about 1 mm) is almost uniformly dispersed (suspended) to produce a fine-grain slurry.

  The fine particle slurry generated by the mixing and dispersing device 51 is transferred to the fine particle cleaning device 52. The fine-grain-part washing device 52 allows the fine-grain-part slurry to flow through a plug flow (plug flow) so as to secure a preset residence time (for example, 0.5 to 2 hours) while stirring. The harmful metals and the like adhering to the fine particles are released and captured by the chelating agent in the chelating cleaning solution. This removes harmful metals and the like adsorbed (adhered) to the surface of the fine particles in the fine particle slurry.

  Here, as a chelating agent used in the chelate cleaning solution, for example, EDTA (ethylenediaminetetraacetic acid), HIDS (3-hydroxy-2,2′-iminodisuccinic acid), IDS (2,2′-iminodisuccinic acid), MGDA (Methylglycine diacetate), sodium salt of EDDS (ethylenediaminediacetate) or GLDA (L-glutamic aciddiacetic acid). Any of these chelating agents can effectively capture (chelate) harmful metals and the like contained in the fine-grain slurry or fine-grain. In addition, depending on the type of the harmful metal contained in the fine particles, a chelating agent suitable for the treatment is selected or a plurality of chelating agents are used.

  The fine-grain slurry discharged from the fine-grain cleaning device 52 is transferred to the filtration device 53. The filtration device 53 filters the fine-grain slurry to generate a cake (filter cake) having a water content of 30 to 40% and a filtrate. In addition, as such a filtration device 53, a filter press, a vacuum filtration machine, or the like can be used. The filter cake (fine particles) discharged from the filtering device 53 contains almost no harmful metal or the like.

  The filtrate, that is, the chelate cleaning liquid discharged from the filtration device 53 is introduced into the cleaning liquid regenerating section 54. The cleaning liquid regeneration unit 54 includes a cleaning liquid regeneration device 55, a cleaning liquid storage tank 56, an acid liquid storage tank 57, and a water storage tank 58. Here, although not shown in detail, the cleaning liquid regenerating device 55 has a higher complexing power than the chelating agent, and when the cleaning liquid regenerating device 55 comes into contact with the chelating cleaning liquid (filtrate) discharged from the filtering device 53, the harmful metals and the like in the chelating cleaning liquid. A solid-phase adsorbent for adsorbing or extracting water or a packing (small or granular material) to which the solid-phase adsorbing material is fixed is held inside the solid-phase adsorbent, and a harmful metal, etc. This is a packed tower type device that removes water and regenerates the chelate washing liquid.

  In the cleaning solution regenerating device 55, a chelate cleaning solution containing a chelating agent capturing a harmful metal or the like is brought into contact with a solid phase adsorbent having a higher complexing power than the chelating agent. The solid-phase adsorbent has a multi-point interaction through coordination bond and hydrogen bond, in which a carrier carries a cyclic molecule, and a cyclic molecule is modified with a chelating ligand, and selectively takes in ions such as harmful metals. is there. As a result, the harmful metals and the like captured by the chelating agent are separated from the chelating agent, and are adsorbed or extracted by the solid phase adsorbent. As a result, harmful metals and the like are removed and recovered from the chelate cleaning liquid (chelating agent), and the chelating cleaning liquid (chelating agent) is again in a state capable of capturing harmful metals and the like.

  The chelate cleaning liquid thus regenerated by the cleaning liquid regenerating device 55 is temporarily stored in the cleaning liquid storage tank 56 and then returned to the mixing / dispersing device 51 by a cleaning liquid recirculating mechanism (not shown in detail). That is, the chelate cleaning liquid circulates in the chelate cleaning device 14 while repeating purification of fine particles and regeneration of the chelating agent. The reduced amount of the chelating agent is appropriately replenished.

  The solid-phase adsorbent having a higher complexing power than the chelating agent is, for example, a solid such as a gel, and generally, when it comes into contact with an aqueous solution containing a chelating agent capturing a metal, the solid-state adsorbing material is coordinated with the chelating agent. It has a strong binding force other than a covalent bond to such an extent that the metal ions are released from the chelating agent and can be transferred to the solid phase adsorbent. For example, when EDTA (ethylenediaminetetraacetic acid) is used as a chelating agent, such a solid-phase adsorbent has a strong binding force capable of recovering almost 100% of metal ions from an aqueous solution of EDTA having a concentration of 10 mM / l. Have

  Examples of such a solid phase adsorbent include those in which a cyclic molecule is densely supported on a carrier such as silica gel or a resin and the cyclic molecule is modified with a chelating ligand. When such a solid-phase adsorbent is used, a plurality of various bonds and interactions such as a coordination bond and a hydrogen bond are generated by an adjacent cyclic molecule and a chelating ligand, and a multipoint interaction is generated, and a metal ion is formed. And a metal ion can be selectively taken in due to the properties of the cyclic molecule.

  As the chelate cleaning solution is regenerated, the amount of harmful metals and the like adsorbed on the solid phase adsorbent increases with time, but there is an upper limit to the amount of harmful metals and the like adsorbed on the solid phase adsorbent. For this reason, when the amount of harmful metals or the like adsorbed on the solid phase adsorbent reaches a saturated state or near the saturated state, the solid phase adsorbent is regenerated by a solid phase adsorbent regeneration mechanism (not shown in detail). That is, the solid-phase adsorbent regenerating mechanism allows the acid solution in the acid solution storage tank 57 to flow to the cleaning solution regenerating device 55 in a state where the chelate cleaning solution is removed, and removes harmful metals and the like adsorbed on the solid-phase adsorbent by the acid solution. Remove and regenerate the solid phase adsorbent. At this time, the acid solution circulates between the acid solution storage tank 57 and the cleaning solution regenerating device 55. Thus, while the harmful metals and the like are recovered by the acid solution, the solid phase adsorbent is regenerated and becomes capable of adsorbing the harmful metals and the like again.

  After the solid phase adsorbent in the cleaning liquid regenerating device 55 is regenerated with an acid solution, the solid phase adsorbent is washed with a water washing mechanism (not shown in detail) to remove the acid solution adhering to the solid phase adsorbent. At this time, the water used for washing the solid phase adsorbent circulates and flows between the water storage tank 58 and the washing liquid regenerating device 55. It should be noted that the detailed configuration of the cleaning liquid regenerating section 54 and the operation method thereof are described in Japanese Patent No. 6264592 (see FIG. 3 and paragraphs [0035] to [0045]) and Japanese Patent No. 6264593 in which the present applicant is the patentee. (See FIG. 3 and paragraphs [0035] to [0045]).

Hereinafter, the specific configuration and function of the chelate cleaning device 14 will be described.
First, the specific configuration and function of the mixing and dispersing device 51, which is a component of the chelate cleaning device 14, will be described with reference to FIG. The mixing and dispersing device 51 continuously mixes the cake (fine particles) discharged from the filter press 13 (see FIG. 1) and the chelate cleaning liquid, and disperses the fine particles in the chelate cleaning liquid. Produce a slurry. Specifically, the mixing / dispersing device 51 pre-mixes the crusher 61 for crushing the cake (the fine particles) discharged from the filter press 13 and the cake pieces crushed by the crusher 61 and the chelate washing liquid. The premixing tank 62 and the mixture generated by the premixing tank 62 are stirred to chelate cake pieces (for example, particles having a particle size of about 0.1 to 0.5 mm or about 0.1 to 1 mm). A line mixer 63 for dispersing or suspending in the washing liquid.

  In the mixing and dispersing device 51, the cake discharged from the filter press 13 is supplied to a crusher 61, and the cake is formed by a high-speed rotating blade 61a into a large number of particles having a particle size of several mm (for example, 1 to 5 mm). Crushed into cake pieces. On the other hand, the chelate cleaning liquid in the chelate cleaning liquid storage tank 64 is supplied to the crusher 61 via the pipe 66 by the pump 65. Note that the chelate cleaning liquid is appropriately supplied to the chelate cleaning liquid storage tank 64 from the cleaning liquid storage tank 56 (see FIG. 6). Although not shown in detail, the chelate cleaning liquid is sprayed or supplied to a large number of cake pieces immediately after being crushed by the blade 61a to prevent the cake pieces from adhering to each other. In addition, as such a crusher 61, for example, a "dewatered cake crusher" according to Taiyo Kiko Co., Ltd. or a "dewatered cake recycling device" according to Kiko Co., Ltd. can be used. When a commercially available crusher is used, it is necessary to provide a mechanism for injecting or supplying a chelate washing liquid to a large number of cake pieces immediately after crushing.

  The clean chelate and the cake pieces in the crusher 61 are transferred to the premixing tank 62. The chelate cleaning liquid and the cake pieces in the premixing tank 62 are stirred and premixed by a stirrer 67 driven by a motor. Then, the mixture of the chelate cleaning liquid and the cake pieces in the premixing tank 62 is transferred to the line mixer 63 via the pipe 69 by the pump 68. The line mixer 63 is a flow-type mixer in which a blade that is driven to rotate at a very high speed by a motor is disposed in a horizontal-type, substantially cylindrical stirring chamber, and stirs the chelating cleaning liquid and cake pieces very vigorously. Then, fine pieces of cake or fine particles (for example, particles having a particle size of about 0.1 to 0.5 mm or about 0.1 to 1 mm) are substantially uniformly dispersed (suspended) in the chelate cleaning liquid. To produce a fine-grain slurry. The fine-grain slurry is transferred to the fine-grain cleaning device 52 (see FIG. 6). As such a line mixer 63, for example, "Satake multi-line mixer" according to Satake Chemical Machinery Co., Ltd. can be used.

  Hereinafter, with reference to FIGS. 8A to 8C, the specific configuration and function of the fine particle fraction cleaning device 52 that is a component of the chelate cleaning device 14 will be described. The fine particle cleaning device 52 adsorbs (adheres) to the fine particles by flowing the fine particle slurry generated by the mixing and dispersing device 51 with a plug flow so as to secure a preset residence time while stirring. ) Is released from the fine particles and trapped by the chelating agent.

  The fine-particle cleaning device 52 has a storage tank 70 having five elongated rectangular parallelepiped or prismatic slurry passages 75 to 79 formed by partitioning by four flat partition walls 71 to 74 and extending in parallel with each other. are doing. The storage tank 70 may be, for example, an iron rectangular parallelepiped tank installed on the ground, or may be a concrete rectangular pit. Further, the partition walls 71 to 74 may be formed by, for example, connecting a plurality of iron plates or plastic plates in a direction in which the slurry passage extends.

  Two slurry passages adjacent to each other in the slurry passages 75 to 79 are connected to one end of a communicating portion at one end in the longitudinal direction of the slurry passage (the left and right direction in the positional relationship in FIGS. 8A and 8B) (four curves in FIG. 8A). (A site indicated by a cross-shaped arrow). That is, the partition walls 71 to 74 do not exist in these communicating portions, and the adjacent slurry passages communicate with each other.

  At the bottom of each of the slurry passages 75 to 79, there are provided air discharge tubes 81 to 85 for discharging air into the fine-grain slurry and stirring the fine-grain slurry. Each of the air discharge tubes 81 to 85 is a porous tube having a plurality of air discharge holes extending in the slurry passage longitudinal direction at the bottom (lower side) of the peripheral wall and extending in the slurry passage longitudinal direction. Although not shown, it is connected to a compressor or a blower that supplies compressed air. When the pressurized air is supplied to the air discharge pipes 81 to 85, the air becomes bubbles from the air discharge holes and is released into the fine-grain slurry, whereby the fine-grain slurry is stirred. Is done.

  FIG. 8C shows a cross section of the slurry passage 75 on the most upstream side when viewed in the flow direction of the fine-grain slurry (the direction indicated by the curved arrow and the straight arrow in FIG. 8A). . As is clear from FIG. 8C, the air discharge pipe 81 is arranged near one side of the slurry passage 75 and near the bottom of the slurry passage. For this reason, the bubbles released from the air discharge pipe 81 rise near the side surface. As a result, a circulating flow that flows in the direction indicated by the arrow P in a plane perpendicular to the longitudinal direction of the slurry passage is formed in the slurry passage 75, and the slurry for fine particles is stirred. The shape, size, volume, etc. of the storage tank 70 and each of the slurry passages 75 to 79, the supply amount of pressurized air to the air discharge pipes 81 to 85, and the like are determined in advance in the fine particle cleaning device 52. It is preferably set in accordance with the water content, flow rate, residence time, flow velocity, turbulence degree of the flow (for example, Reynolds number), and the like.

  In the soil purification system S according to the first embodiment, in the process of cleaning and classifying the contaminated soil with the wash water, harmful metals and the like are hardly adsorbed to gravel and sand, and are concentrated and adsorbed to fine particles. Clean and reusable gravel and sand can be obtained. Then, in the soil purification system S, the rubble and sand are crushed by the mill breaker 3 to generate iron-based fine particles and non-ferrous-based fine particles. Therefore, the iron-based fine particles existing before the crushing and the iron-based fine particles generated by the crushing are introduced into the iron-based removing device 12, and both of these iron-based fine particles are considerably large ( (Compared to non-ferrous fine particles).

  Then, in the iron removing device 12, since the iron-based fine particles having a large amount of adsorption of harmful metals and the like are removed from the sludge by the magnetic spheres 20 in the iron-based fine particles adsorption device 18, the harmful metals and the like of the sludge are removed. Can be reduced. Therefore, it is possible to reduce the load of toxic metals and the like on the chelate cleaning device 14 that performs the chelate cleaning process on the sludge discharged from the iron removing device 12. Depending on the properties of the soil, the content of harmful metals and the like can be reduced to such an extent that dumping or landfilling is possible.

  Since the content of harmful metals and the like in the sludge discharged from the iron removing device 12 is reduced in this manner, when the cake discharged from the filter press 13 that filters this sludge is subjected to chelate cleaning by the chelate cleaning device 14, The use or required amount of the chelating agent and the solid phase adsorbent can be reduced, and the cost for treating the soil can be reduced. The operation cost of the mill breaker 3 and the iron removing device 12 is very low because the mill breaker 3 and the iron removing device 12 have a mechanical structure for performing physical treatment and do not use any special chemicals for treating harmful metals and the like.

(Embodiment 2)
Hereinafter, the soil purification system S ′ according to the second embodiment of the present invention will be described with reference to FIG. However, the soil purification system S ′ according to the second embodiment and the soil purification system S according to the first embodiment illustrated in FIGS. 1 to 8 are common in many points. Therefore, in the following, in order to avoid repetition of the description, differences between the soil purification system S ′ and the soil purification system S will be mainly described. Note that among the components of the soil purification system S ′ according to the second embodiment, those that are common to the components of the soil purification system S according to the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  Although a part of the soil purification system S ′ according to the second embodiment is omitted in FIG. 9, the soil purification system S ′ extends from the charging hopper 1 to the intermediate tank 9 similarly to the soil purification system S according to the first embodiment. A series of devices 1 to 9, a washing water storage tank 10, a spare water tank 11, and an iron removing device 12 are provided. However, the soil purification system S 'does not include the filter press 13 and the chelate cleaning device 14 in the first embodiment. The soil purification system S ′ includes a fine particle fraction washing device 91, a filtration device 92, a clarification filter 93, a reverse osmosis membrane separation device 94 (RO separation device), and a chelating agent regeneration device 95. I have.

  Although not shown in detail, the fine particle cleaning device 91 receives sludge containing non-ferrous fine particles discharged from the iron removing device 12 and cleaning water, and a chelate cleaning liquid containing a chelating agent and water. These are mixed and stirred to produce a fine-grain slurry, which is continuously adsorbed (adhered) to the non-ferrous fine granules by continuously flowing so as to secure a preset residence time. The harmful metal or the like is released and captured by the chelating agent, or the harmful metal or the like existing in water is captured by the chelating agent. As such a fine particle cleaning device 91, for example, the fine particle cleaning device 52 in Embodiment 1 (see FIGS. 8A to 8C) can be used. The ratio between the flow rate of the sludge supplied to the fine particle cleaning device 91 and the flow rate of the chelate cleaning liquid is set to, for example, 1: 1. The chelating agent used is the same as in the first embodiment.

  The fine particle slurry discharged from the fine particle cleaning device 91 is transferred to the filtration device 92. The filtration device 92 filters the fine-grain slurry to produce a cake (filter cake) having a water content of 30 to 40% and a filtrate. In addition, as the filtering device 92, a filter press, a vacuum filter, or the like can be used. The cake (fines) discharged from the filtration device 92 contains almost no harmful metal or the like.

  The filtrate, that is, the chelate washing liquid, discharged from the filtration device 92 is sent to a reverse osmosis membrane separation device 94 after a suspended substance or a suspended substance (SS) is removed by a clarifying filter 93 (for example, a sand filter). . Although not shown in detail, the reverse osmosis membrane separation device 94 receives the chelate washing liquid discharged from the clarification filter 93, and does not include the concentrated water in which the chelating agent is concentrated by the reverse osmosis membrane and the chelating agent. Separate from permeate.

  As the reverse osmosis membrane of the reverse osmosis membrane separator 94, for example, a three-layer structure in which a polysulfone support layer and a dense crosslinked aromatic polyamide layer are laminated on the surface of a polyester nonwoven fabric (100 to 120 μm in thickness) is used. Can be used. The dense crosslinked aromatic polyamide layer has a large number of pores having a pore size of about 0.5 to 1.5 nm, and is very thin that allows water to permeate but does not allow the chelating agent to permeate (for example, 0.2 to 0.25 μm) It is a semipermeable membrane. The polysulfone support layer is a relatively thick (for example, 40 to 50 μm) porous membrane for supporting or protecting a very thin crosslinked aromatic polyamide dense layer to prevent its breakage.

The reverse osmosis membrane separation device 94 is of a spiral type, and has a plurality of reverse osmosis membrane elements in which a reverse osmosis membrane wound in a spiral shape is accommodated in a cylindrical container. It is practical that each reverse osmosis membrane element has, for example, a total length of about 1 to 2 m and an outer diameter of about 0.2 to 0.4 m. For example, the effective membrane area of a reverse osmosis membrane in a commercially available reverse osmosis membrane element of this type having a total length of about 1 m and an outer diameter of about 0.2 m (for example, manufactured by Osentech Co., Ltd. of Nakatsugawa City, Gifu Prefecture) is It is about 40 m ² . In the case of this reverse osmosis membrane element, when a chelate cleaning solution having a chelating agent concentration of about 1% by mass is supplied at a pressure of about 1 MPa, the processing amount of the chelate cleaning solution is estimated to be about 1.5 m ³ / hr. Therefore, for example, when processing a 60 m ^{3 /} hour chelate cleaning solution, 40 reverse osmosis membrane elements may be connected in parallel.

  The reverse osmosis membrane separator 94 is of a continuous type, and the operating conditions such as the supply amount and supply pressure (operating pressure) of the chelate washing liquid, the discharge amount of the concentrated water and the permeated water, and the concentration ratio of the chelating agent in the concentrated water are as follows. It is set appropriately according to the amount of the chelate cleaning liquid to be supplied to the cleaning device 91 and the concentration of the chelating agent. For example, the ratio of the flow rate of the sludge supplied to the fine particle cleaning device 91 to the flow rate of the chelate cleaning liquid is set to 1: 1 and the concentration of the chelating agent of the fine particle slurry in the fine particle cleaning device 91 is set to 1% by mass. In this case, the reverse osmosis membrane separation device 94 generates permeated water (chelating agent concentration 0) of about 50% and concentrated water (chelating agent concentration of about 2% by mass) of about 50% of the supply amount of the chelating washing liquid. Is set to Accordingly, in the fine-grain cleaning device 91, the sludge containing no chelating agent and the chelating-cleaning solution having a chelating agent concentration of about 2% by mass are mixed at a ratio of 1: 1. % Is maintained.

  The concentrated water discharged from the reverse osmosis membrane separation device 94, that is, the chelate washing liquid, is introduced into the chelating agent regenerating device 95 and is regenerated. That is, harmful metals and the like are removed and recovered from the chelate cleaning liquid (chelating agent), and the chelating cleaning liquid (chelating agent) is again in a state capable of capturing harmful metals and the like. As such a chelating agent regenerating device 95, for example, the cleaning liquid regenerating unit 54 (see FIG. 6) in the first embodiment can be used.

  According to the soil purification system S ′ according to the second embodiment, similarly to the soil purification system S according to the first embodiment, clean and reusable gravel and sand can be obtained, and discharged from the iron removal device 12. The sludge can reduce the content of harmful metals and the like. As described above, since the content of the harmful metals and the like in the sludge discharged from the iron removing device 12 is reduced, the use amount or the required amount of the chelating agent in the fine particle cleaning device 91 can be reduced, and The amount of use or required amount of the solid phase adsorbent in the chelating agent regeneration device 95 can be reduced, and the cost of treating the soil can be reduced.

  S soil purification system (Embodiment 1), S 'soil purification system (Embodiment 2), 1 input hopper, 2 mixer, 3 mill breaker (wet crusher), 4 trommel, 5 cyclones, 6 PH adjustment tank, 7 Coagulation tank, 8 thickener, 9 intermediate tank, 10 washing water tank, 11 spare water tank, 12 iron removal device, 13 filter press, 14 chelate cleaning device, 18 iron fine particle adsorption device, 19 screen device, 20 magnetic sphere, 21 Body part, 21a inclined plate, 22 centrifugal separator, 23 magnetic sphere returning device, 24 first magnetic sphere storage container, 24a opening / closing door, 25 second magnetic sphere storage container, 25a opening / closing door, 26 third magnetic sphere storage container, 26a Opening / closing door, 27 Sludge storage tank, 29 hollow spherical body, 30 permanent magnet, 31 magnet holding member, 32 magnet holding hole, 34 sludge port Pump, 35 housing, 36 bearing device, 37 rotating cylinder, 37a upper opening door, 37b lower opening door, 38 gear mechanism, 39 motor, 40 baffle, 41 horizontal conveyor, 41a belt, 42 upright conveyor, 43a drive roller , 43b driven roller, 44a driven roller, 44b driven roller, 45 metal belt, 46 idle roller, 47 magnetic ball locking member, 48 guide member, 49 permanent magnet, 51 mixing and dispersing device, 52 fine particle washing device, 53 filtration Device, 54 cleaning liquid regeneration unit, 55 cleaning liquid regeneration device, 56 cleaning liquid storage tank, 57 acid liquid storage tank, 58 water storage tank, 61 pulverizer, 61a blade, 62 premixing tank, 63 line mixer, 64 chelate cleaning liquid storage tank, 65 pump, 66 Pipeline, 67 stirrer, 68 pump, 69 pipeline, 7 0 storage tank, 71-74 partition wall, 75-79 slurry passage, 81-85 air discharge tube, 91 fine particle fraction washing device, 92 filtration device, 93 clarification filter, 94 reverse osmosis separation device, 95 chelating agent regeneration device.

Claims (3)

A soil purification system for purifying soil contaminated with harmful metals or compounds containing gravel, sand, and fine particles,
A mixer for mixing the soil and the washing water introduced into the soil purification system,
By crushing gravels and sand in a mixture containing soil and washing water discharged from the mixer, iron or iron oxide unevenly or scattered inside the gravels and sand is exposed on the surface. A wet crusher that generates system-based fines and adsorbs or attaches harmful metals or compounds thereof in the wash water to iron or iron oxide exposed on the surface of the iron-based fines,
A trommel that separates gravel from a mixture containing gravel, sand, fines, and washing water discharged from the wet crusher,
A liquid cyclone that separates sand from a mixture containing sand, fines, and washing water discharged from the trommel;
A mixture containing fine particles and washing water discharged from the hydrocyclone, by sedimentation separation, supernatant water, and a thickener for separating sludge containing fine particles and washing water,
From the sludge discharged from the thickener, by removing and removing the iron-based fine particles by magnetic force, an iron removal device that reduces the content of harmful metals or compounds thereof in the sludge,
The iron-based fine particles have been removed by the iron content removing device, a filter that receives and filters sludge containing fine particles and water, and separates the filtrate into a filter cake and a filtrate containing fine particles.
The filter cake separated by the filter machine is washed with a chelate washing solution containing a chelating agent and water, and a chelate washing device for removing harmful metals or compounds thereof remaining in fine particles,
Filtrate return means for returning the filtrate separated by the filter to the thickener,
The iron removal device,
A plurality of permanent magnets are mounted in the hollow portion of the hollow spherical body so that magnetic poles of the same magnetic polarity are directed outward in the radial direction of the spherical body, and sludge discharged from the thickener is received. And an iron-based fine particle adsorber that moves a fluid in which a mixture of sludge and sludge is moved downward in a zigzag path by gravity, and adsorbs the iron-based fine particles in the sludge to the magnetic spheres by magnetic force when moving.
A screen device that receives the fluid discharged from the iron-based fine particle adsorption device, and separates it into magnetic spheres and sludge,
A centrifugal separator that intermittently receives the magnetic spheres adsorbing the iron-based fine particles discharged from the screen device in a batchwise manner and separates the iron-based fine particles from the magnetic spheres by centrifugal force,
A magnetic sphere returning device for returning the magnetic spheres discharged from the centrifuge to the iron-based fine particle adsorption device. The magnetic ball returning device,
A drive roller disposed at a position lower than a lower end of the centrifugal separator; a driven roller disposed at a position higher than an upper end of the iron-based fine particle adsorption device above the drive roller; and the drive roller. An endless metal belt made of a ferromagnetic metal wound around the driven roller; and a magnetic member attached to an outer surface of the endless metal belt and adsorbed to the endless metal belt when traveling above the endless metal belt. An upright belt conveyor having a magnetic ball locking member that locks the downward movement of the ball,
Magnetic sphere transporting means for transporting the magnetic spheres discharged from the centrifugal separator to a lower end of the upright belt conveyor and attracting the endless metal belt with a magnetic force,
The magnetic sphere supply means, which separates magnetic spheres from the endless metal belt at an upper end portion of the upright belt conveyor and supplies the magnetic spheres to the iron-based fine particle adsorption device, wherein: A soil purification system as described. The chelate washing device,
A mixing and dispersing apparatus that mixes the filter cake and the chelate cleaning liquid separated by the filter, and generates a fine-grain fraction slurry in which the fine grains are dispersed in the chelate cleaning liquid,
The harmful metal or its compound adhering to the fine particles is finely dispersed by flowing the fine particle slurry generated by the mixing and dispersing device with a plug flow so as to secure a preset residence time while stirring. A fine-grain cleaning device that is separated from the granules and captured by the chelating agent,
A filtration device for filtering the fine particle slurry discharged from the fine particle washing device,
A solid phase adsorbent that has a higher complexing power than the chelating agent and adsorbs the harmful metal or its compound in the filtrate when coming into contact with the filtrate discharged from the filtration device, and removes the harmful metal from the chelating agent in the filtrate; Or a washing solution regenerating apparatus for removing the compound and regenerating the filtrate as a chelating washing solution,
3. The soil purification system according to claim 1, further comprising a cleaning liquid reflux mechanism configured to return the chelate cleaning liquid discharged from the cleaning liquid regeneration device to the mixing and dispersing device. 4.

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