JP2020011218A - Soil purification system - Google Patents

Abstract

To provide a simple and low-cost soil purification system capable of wet-classifying soil into gravel, sand, and fine particles and removing toxic metals and the like adsorbed on the fine particles.SOLUTION: A soil purification system includes: a soil classification portion that crushes soil contaminated with toxic metals while washing it with washing water and classifies the soil into gravel, sand, and fine particles; a pretreatment portion that reduces the toxic metals and the like by magnetically removing iron-based fine particles from sludge comprising the fine particles and the washing water separated in the soil classification portion; and a post-treatment portion that chemically treats the sludge discharged from the pretreatment portion to remove the toxic metals and the like. The pretreatment portion has an iron removing device 12 comprising a magnetic sphere-filled tank 21 filled with magnetic spheres 20 for magnetically adsorbing the iron-based fine particles in the sludge, a centrifuge 22 for removing the iron-based fine particles from the magnetic spheres 20 discharged from the magnetic sphere-filled tank 21, and a magnetic sphere returning device 23 for returning the magnetic spheres 20 discharged from the centrifuge 22 to the magnetic sphere-filled tank 21.SELECTED DRAWING: Figure 2

Description

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

  In recent years, for example, harmful metals such as chromium, lead, cadmium, selenium, and mercury and / or compounds thereof (hereinafter, these are collectively referred to as “harmful metals, etc.”) as a raw material or a site of a production facility or a nearby area thereof Soil pollution due to illegal soiling of industrial waste containing harmful metals and the like has occurred 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 present applicant has already classified the harmful metal-contaminated soil with washing water and classified it into gravel, sand, and fine particles, and then contained a chelating agent containing a chelating agent and water for the fine particles. 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 performing a washing process (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, this type of soil purification facility by a contaminated soil treatment company usually purifies a large amount of contaminated soil (for example, 2,000 tons per day), and thus generates a large amount of fine particles (for example, on a dry basis). 500-600 tons per day). 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 in such a soil purification facility increases as the content of harmful metals and the like in the fine particles increases. The same problem occurs when the fine particles are washed with a chemical other than the chelating agent to remove harmful metals and the like. A similar problem occurs when harmful metals or the like are removed by physicochemically using activated carbon or the like.

  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. Provided is a simple and low-cost soil purification system that can be classified into fine particles and can remove harmful metals and the like adsorbed or adhered to the separated fine particles. Issues to be solved.

  The present invention has been made to solve the above-mentioned problem, and has the object of the present invention. Soil purification for purifying soil contaminated with harmful metals and the like (harmful metals and / or compounds thereof) or their ions containing gravel, sand and fine particles. The system includes a soil classification unit, a pre-treatment unit, and a post-treatment unit. The soil classification unit crushes the gravel and sand while washing the soil with washing water, and then classifies the soil into gravel, sand, and fine particles. The pretreatment unit is configured to remove iron and / or iron oxide (hereinafter collectively referred to as “iron etc.”) from sludge containing the fine particles separated in the soil classification unit and the washing water to such an extent that it can be magnetically adsorbed. The content of harmful metals and the like in the sludge is reduced by removing the iron-based fine particles contained therein by magnetic attraction. The post-treatment section performs a chemical treatment or a physico-chemical treatment (for example, an adsorption treatment) on the sludge discharged from the pre-treatment section, and adsorbs or adheres to the surface of the fine particles in the sludge. Etc. are removed.

  The pretreatment unit includes an iron removing device having a magnetic sphere filling tank, a centrifugal separator, and a magnetic sphere returning device. The magnetic sphere filling tank has a plurality of magnetic spheres in which a plurality of permanent magnets are mounted in a hollow portion of a hollow sphere so that magnetic poles (N pole or S pole) of the same magnet face outward in the radial direction of the sphere. While being filled, the sludge discharged from the thickener is received and allowed to flow downward through the gap between the magnetic spheres, and the iron-based fine particles in the sludge are adsorbed (attached) to the magnetic spheres by magnetic force. The centrifugal separator intermittently accepts the magnetic spheres adsorbing the iron-based fine particles in the magnetic sphere filling tank 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 magnetic sphere filling tank.

  In the soil purification system according to the present invention, it is preferable that the magnetic sphere returning device includes an upright belt conveyor, magnetic sphere transport means, and magnetic sphere supply means. In this case, the upright belt conveyor includes a driving roller disposed at a position lower than the lower end of the centrifuge, a driven roller disposed at a position higher than the upper end of the magnetic sphere filling tank above the driving roller, and a driving roller. An endless metal belt made of a ferromagnetic metal wound around a roller and a driven roller, and a descent of a magnetic sphere attached to an outer surface of the endless metal belt and adsorbed on the endless metal belt when traveling above the endless metal belt. And a magnetic ball locking member for locking. 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 makes the magnetic spheres attract (adhere) 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 (moves) them to the magnetic sphere filling tank.

  In the soil purification system according to the present invention, the post-treatment unit has a fine particle fraction washing device, a filtration device, a reverse osmosis membrane separation device, a chelating agent regeneration device, and a permeated water transfer means. preferable. In this case, the fine-grain cleaning device mixes the sludge discharged from the iron-removing device with a chelating cleaning solution containing a chelating agent and water to generate a fine-grain slurry, and the fine-grain slurry is set in advance. The harmful metals and the like adhering to the fine particles are trapped by the chelating agent by causing the fluid to flow so as to secure the remaining residence time. The filtration device filters the fine-grain slurry discharged from the fine-grain washing device to generate a filtrate and a filter cake. The reverse osmosis membrane separation device separates the filtrate discharged from the filtration device into concentrated water in which the chelating agent is concentrated and permeated water containing no chelating agent by the reverse osmosis membrane. The chelating agent regenerating device receives the concentrated water discharged from the reverse osmosis membrane separation device, has a higher complexing power than the chelating agent, and adsorbs harmful metals and the like in the concentrated water when contacted with the concentrated water. Thus, harmful metals and the like are removed from the chelating agent in the concentrated water, and the concentrated liquid is supplied to the fine particle fraction cleaning device as a chelate cleaning liquid. The permeated water transfer means transfers (returns) the permeated water discharged from the reverse osmosis membrane separation device to the thickener.

  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.

  Then, according to the soil purification system according to the present invention, fine particles are generated by crushing the gravel and / or sand by the wet crusher, and among these fine particles, the fine particles are unevenly distributed in the gravel or sand. Fine particles containing many fine lumps of iron and the like that were scattered are iron-based fine particles, and the iron and the like exposed on the surface of these iron-based fine particles are 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 removing device as a pretreatment unit, 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 in the magnetic sphere filling tank, so that the harmful metals and the like of the sludge are removed. The content or the holding ratio can be reduced. Therefore, it is possible to reduce the load of the harmful metal or the like on the post-processing unit that performs the chemical treatment or the physicochemical treatment on the sludge discharged from the iron removal device. This makes it possible to reduce the required or used amount of a treating agent such as a chemical agent or an adsorbent, and to reduce the cost of treating the soil. 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. Therefore, when the magnetic spheres are supplied to the magnetic sphere-filling tank or when the magnetic spheres are discharged from the magnetic sphere-filling tank, the magnetic spheres do not adsorb to each other and form a lump (grape tuft). The magnetic sphere can move smoothly while repelling each other.

It is a block diagram showing the schematic structure of the soil purification system concerning the present invention. It is a typical elevation view of the iron removal apparatus (pre-processing part) which comprises a 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. (A) is a schematic plan view of the fine-grain cleaning device (part of the post-processing unit), (b) is a cross-sectional view of the fine-grain cleaning device shown in (a), taken along the line AA, (C) is an elevational sectional view of one slurry passage of the fine-grain cleaning device. FIG. 3 is a schematic elevation view of a chelating agent regenerating apparatus (a part of a post-processing unit).

  As shown in FIG. 1, in the soil purification system S according to the embodiment of the present invention, harmful metals and the like (hazardous metals and / or compounds thereof) or soil collected by excavation of the ground contaminated with these ions and the like. (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. 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 includes gravel (for example, particle size of 2 to 75 mm), sand (for example, particle size of 0.075 to 2 mm), and fine particles (for example, particle size of 0.075 mm or less). Some also include stones (eg, 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 minute clumps of iron or the like (iron and / or iron oxide) unevenly 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, harmful metals and the like or some of these ions present in the washing water are adsorbed or adhered to the exposed surface of the iron-based fine particles such as iron. 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. A method for treating harmful metals or the like in which harmful metals or the like are adsorbed to minute lump of iron or the like (iron-based fine particles) which has been exposed has not yet been proposed by anyone other than the applicant or the inventor of the present application. .

  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 (mesh) 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 separated into water are hardly adsorbed or attached to gravel and sand, so that the gravel separated by the trommel 4 is almost clean, for example, as aggregate for concrete or the like. Can be used. 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 sand and fine particles and washing water, stored 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 sand 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 (PAC) aqueous solution, 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 (including flocs) in the coagulation tank 7 is introduced into a thickener 8 (gravity settling tank). 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. 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 settled or retained in the lower part of the thickener 8 is transferred to the intermediate tank 9 and 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 as a pretreatment unit (the transfer is appropriately stopped for a short time). 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 sludge discharged from the iron removing device 12 is treated by a fine particle fraction washing device 13, a filtering device 14, a clarifying filter 15, a reverse osmosis membrane separating device 16, and a chelating agent regenerating device 17 to remove harmful metals. Almost clean fine particles containing almost no or the like, and a chelate cleaning liquid are produced. Note that these devices 13 to 17 are components of the post-processing unit of the soil purification system S, and the specific configuration and function will be described later in detail.

Hereinafter, the specific configuration and function of the iron removal device 12 as a pretreatment unit will be described with reference to FIGS. 2 to 5.
As shown in FIG. 2, the iron removing device 12 includes, as its main components, a magnetic sphere filling tank 21 filled with a large number of magnetic spheres 20, and an iron-based fine particle adsorbed on the magnetic spheres 20 by magnetic force. And a magnetic sphere returning device 23 for returning the magnetic spheres 20 discharged from the centrifugal separator 22 to the magnetic sphere filling tank 21. Further, the iron removing device 12 includes first to third magnetic sphere storage containers 24 to 26 for temporarily storing the magnetic spheres 20 supplied to the magnetic sphere filling tank 21, the centrifugal separator 22, or the magnetic sphere returning device 23, respectively. It has. In addition, the iron removing device 12 includes a sludge storage tank 27 for temporarily storing sludge discharged from the magnetic ball filling tank 21.

  As shown in FIG. 3, the magnetic sphere 20 is generally obtained by mounting a plurality of permanent magnets 30 in a hollow portion of a hollow spherical body 29 such that each N pole faces outward in the spherical body radial direction. It is. 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. That is, 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 transverse area decreases toward the center of the magnetic sphere, and the permanent magnet 30 is formed in a shape that fits or matches the magnet holding hole 32. ing. 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. It is preferable that the shape of the end face of the permanent magnet 30 located on the radially outer side in a state where the permanent magnet 30 is mounted on the magnet holding member 31 be a curved 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. 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, is used to reduce the weight of the magnetic sphere 20 as much as possible without floating in the sludge. , 1.2 to 1.5 g / cm ³ is practical. 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. Can easily be adjusted to an apparent density of 1.2 to 1.5 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 large number of magnetic spheres 20 are accommodated or filled in the magnetic sphere filling tank 21. Sludge is basically continuously supplied from the intermediate tank 9 (see FIG. 1) to the magnetic sphere filling tank 21, and the sludge flows down the gap between the magnetic spheres 20 in the magnetic sphere filling tank 21. At this time, the iron-based fine particles adsorbing the harmful metal or the like in the sludge or adsorbing the harmful metal or the like are adsorbed on the outer peripheral surface of the magnetic sphere 20 by magnetic force and accompany the magnetic sphere 20 as described later. Then, it is removed from the magnetic sphere filling tank 21. Thereby, the content of harmful metals and the like in the sludge is reduced.

  At the lower end (bottom) of the magnetic sphere filling tank 21, an opening / closing door 21a for discharging the magnetic spheres 20 in the magnetic sphere filling tank 21 downward at any time is provided. When the opening / closing door 21a is closed, the falling of the magnetic sphere 20 in the magnetic sphere filling tank 21 is locked by the opening / closing door 21a, and the sludge is prevented from flowing down. Further, at the lower end of the magnetic sphere filling tank 21 or in the vicinity thereof, when the opening / closing door 21a is closed, the iron-based fine particles fall down through the gap between the magnetic spheres 20 in the magnetic sphere filling tank 21. A sludge discharge pipe 33 for discharging the removed sludge to the sludge storage tank 27 is connected. The iron removing device 12 is provided with a sludge pump 34 for transporting the sludge in the sludge storage tank 27 to the fine particle cleaning device 13 (see FIG. 1).

  A first magnetic sphere storage container 24 is disposed above the magnetic sphere filling tank 21, and the magnetic spheres 20 stored therein are dropped at the lower end (bottom) of the first magnetic sphere storage container 24 as needed. An opening / closing door 24a for supplying the magnetic ball-filled tank 21 to the tank 21 is provided. When the door 24a is closed, the magnetic ball 20 in the first magnetic sphere storage container 24 is locked from falling downward by the door 24a.

  A second magnetic sphere storage container 25 is disposed below the magnetic sphere filling tank 21. When the door 21a of the magnetic sphere filling tank 21 is opened, the magnetic spheres 20 in the magnetic sphere filling tank 21 fall by gravity. Are stored in the second magnetic sphere storage container 25. At this time, the magnetic spheres repel each other due to magnetic force (repulsive force), so that the magnetic spheres 20 do not clump or grape-like and do not block the opening / closing door 21a, and the second magnetic sphere storage container smoothly and quickly. 25 (the same applies to other cases where the magnetic sphere 20 drops from one container or the like to another container or the like). In this case, the opening / closing door 21a temporarily stops the supply of the sludge to the magnetic sphere filling tank 21, and the sludge in the magnetic sphere filling tank 21 is discharged to the sludge storage tank 27 via the sludge discharge pipe 33. Will be opened later.

  A centrifuge 22 is disposed below the second magnetic sphere storage container 25. The centrifugal separator 22 intermittently receives the magnetic spheres 20 discharged from the magnetic sphere filling tank 21 and temporarily stored in the second magnetic sphere storage container 25 in a batch type (batch type), and receives the magnetic spheres by centrifugal force. The iron-based fine particles are separated from the sphere 20. 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.

  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.

  Here, the magnetic sphere 20 attached to and moving on the metal belt 45 traveling in a counterclockwise direction in the positional relationship in FIG. 2 collides with or contacts the end of the guide member 48 near the driven roller 44a. I do. 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 magnetic sphere filling tank 21, the second magnetic sphere storage container 25, the centrifuge 22, and the third magnetic sphere storage container 26. And the magnetic ball returning device 23 (the horizontal belt conveyor 41, the upright belt conveyor 42, and the guide member 48). Two broken arrows in FIG. 2 indicate the moving direction of the magnetic sphere 20. The magnetic spheres 20 move intermittently in a batch operation from the first magnetic sphere storage container 24 to the third magnetic sphere storage container 26, and move from the third magnetic sphere storage container 26 to the first magnetic sphere storage container 24. , Continuously moved by the magnetic ball returning device 23.

  Hereinafter, an example of an operation method of the iron removing device 12 will be described. The magnetic sphere filling tank 21 filled or accommodated with a large number of magnetic spheres 20 contains substantially fine particles (ferrous fine particles and non-ferrous fine particles) from the intermediate tank 9 (see FIG. 1). Sludge consisting of water is continuously supplied. This sludge flows through the gap between the many magnetic spheres 20 in the magnetic sphere filling tank 21 substantially downward, and then is discharged from the vicinity of the lower end of the magnetic sphere filling tank 21 to the sludge storage tank 27 via the sludge discharge pipe 33. Is done. Here, when the sludge flows through the gap between the magnetic spheres 20, the iron-based fine particles in the sludge are attracted to the outer peripheral surface of the magnetic sphere 20 by magnetic force.

  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 magnetic ball filling tank 21 are composed of 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) small amount of adsorption.

  As described above, the iron-based fine particles are removed from the sludge in the magnetic sphere filling tank 21. Therefore, the fine particles contained in the sludge discharged from the magnetic sphere filling tank 21 have an adsorbed amount of harmful metals and the like. Relatively (or considerably) less non-ferrous fines are predominant. Therefore, a part or a considerable part of the harmful metal and the like contained in the contaminated soil introduced into the soil purification system S is removed by the magnetic ball filling tank 21.

  As will be described later in detail, the sludge or fine particles discharged from the magnetic ball filling tank 21 is subjected to a chelate cleaning treatment with a chelating agent by a fine particle fraction cleaning device 13 (see FIG. 1), and The chelating agent is regenerated by the solid phase adsorbent in the agent regenerating device 17 (see FIG. 1). However, as described above, harmful metals and the like in the sludge are reduced in the magnetic sphere filling tank 21, so that the fine particles ( The load of toxic metals and the like on the chelate washing treatment of the 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 magnetic sphere filling tank 21 (iron removing device 12) functions as a pre-processing device or a pre-processing device for reducing the load of the harmful metal or the like on the fine particle cleaning device 13 or the chelating agent regenerating device 17.

  The operation of the magnetic sphere filling tank 21 is temporarily stopped when a predetermined amount of iron-based fine particles (for example, a thickness of 2 to 3 mm) is adsorbed on the outer peripheral surface of the magnetic sphere 20. At this time, the supply of the sludge to the magnetic sphere filling tank 21 is temporarily stopped, and the sludge remaining in the magnetic sphere filling tank 21 is discharged to the sludge storage tank 27. Thereafter, the opening / closing door 21a is opened, and the magnetic spheres 20 adsorbing the iron-based fine particles in the magnetic sphere filling tank 21 fall into the second magnetic sphere storage container 25 by gravity. Then, the opening / closing door 21a is closed, a predetermined amount (one-time filling amount) of the magnetic spheres 20 is supplied from the first magnetic sphere storage container 24 to the magnetic sphere filling tank 21, and the supply of the sludge to the magnetic sphere filling tank 21 is performed. Will be resumed. A plurality of magnetic sphere filling tanks 21 may be arranged in parallel, and these may be operated alternately or alternately so that sludge treatment is performed without interruption.

  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. It is adjusted so as to be equal to or less than the maximum transport amount of the conveyor 42.

  As shown in FIG. 1 again, the sludge discharged from the iron removing device 12 (sludge storage tank 27 in FIG. 2) is introduced into the fine particle cleaning device 13. Fine particle cleaning device 13 includes sludge containing non-ferrous fine particles discharged from iron removing device 12 and cleaning water, and a chelating agent and water supplied from a chelating agent regenerating device 17 described later. The chelate washing liquid is received, mixed and stirred to produce a fine-grained slurry, and generally in a plug flow so as to secure a preset residence time (for example, 0.5 to 2 hours). By continuously flowing, the harmful metals and the like adhering (adsorbed) to the fine particles or their ions are captured by the chelating agent. This removes harmful metals and the like adsorbed (adhered) to the surface of the fine particles in the fine particle slurry. The ratio between the flow rate of the sludge supplied to the fine particle cleaning device 13 and the flow rate of the chelate cleaning liquid is set to, for example, 1: 1.

  Examples of the chelating agent used in the chelate washing solution include EDTA (ethylenediaminetetraacetic acid), HIDS (3-hydroxy-2,2'-iminodisuccinic acid), IDS (2,2'-iminodisuccinic acid), and MGDA (methylglycine). Acetic acid), EDDS (ethylenediaminediacetic acid), or sodium salt of GLDA (L-glutamic acid diacetic 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.

  Hereinafter, the specific configuration and function of the fine-grain cleaning device 13 will be described with reference to FIGS. The fine-grain cleaning device 13 has a storage tank 50 provided with five elongated rectangular parallelepiped or prismatic slurry passages 55 to 59 formed by partitioning by four flat partition walls 51 to 54. are doing. The storage tank 50 may be, for example, an iron rectangular parallelepiped tank installed on the ground, or may be a concrete rectangular pit. Further, the partition walls 51 to 54 may be formed by, for example, connecting a plurality of iron plates or plastic plates in the direction in which the slurry passage extends.

  Two slurry passages adjacent to each other in the slurry passages 55 to 59 are connected to one end of a communicating portion (four curved lines in FIG. 6A) in the longitudinal direction of the slurry passage (the left-right direction in the positional relationship in FIGS. 6A and 6B). (A site indicated by a cross-shaped arrow). That is, the partition walls 51 to 54 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 55 to 59, there are provided air discharge tubes 61 to 65 for discharging air into the fine-grain slurry and agitating the fine-grain slurry. Each of the air discharge tubes 61 to 65 is a perforated tube which extends in the slurry passage longitudinal direction and has a plurality of air discharge holes formed in the bottom (lower side) of the peripheral wall and arranged 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 61 to 65, the air is released from the air discharge holes as bubbles into the fine-grain slurry and floats, and the fine-grain slurry is stirred by the bubbles. Is done.

  FIG. 6C shows a cross section of the slurry passage 55 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. 6A). . As is clear from FIG. 6C, the air discharge pipe 61 is disposed near one side of the slurry passage 55 and near the bottom of the slurry passage. For this reason, the bubbles released from the air discharge pipe 61 rise near this side surface. As a result, a circulating flow is formed in the slurry passage 55 in the direction indicated by the arrow P in a plane perpendicular to the longitudinal direction of the slurry passage, and the slurry for fine particles is stirred. The shape, size, volume, and the like of the storage tank 50 and each of the slurry passages 55 to 59, and the supply amount of pressurized air to the air discharge pipes 61 to 65, etc. 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.

  As apparent from FIG. 1, the fine-grain slurry discharged from the fine-grain cleaning device 13 is transferred to the filtration device 14. The filtration device 14 filters the fine-grain slurry to produce a filter cake and a filtrate having a water content of 30 to 40%. In addition, as the filtering device 14, a filter press, a vacuum filter, or the like can be used. Since the filter cake (the fine-grain fraction) discharged from the filter device 14 hardly contains harmful metals and the like, it is used, for example, as cultivation soil for agriculture or disposed of by landfilling.

  The filtrate, that is, the chelate washing solution discharged from the filtration device 14 is transferred to a reverse osmosis membrane separation device 16 after a suspended substance or a suspended substance (SS) is removed by a clarifying filter 15 (for example, a sand filter). . Although not shown in detail, the reverse osmosis membrane separator 16 receives the chelate washing solution discharged from the clarification filter 15, pressurizes the solution with a high-pressure pump, and concentrates the chelating agent by the reverse osmosis membrane. Separate into water and permeate without chelating agent. Then, the concentrated water is supplied to the chelating agent regenerating device 17, and the permeated water containing no chelating agent is returned to the thickener 8 by a permeated water transferring means (for example, a pump and a pipe).

  As the reverse osmosis membrane of the reverse osmosis membrane separation device 16, for example, a three-layer structure in which a polysulfone support layer and a dense crosslinked aromatic polyamide layer are laminated on a 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 16 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 16 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, the concentration ratio of the chelating agent in the concentrated water, and the like It is set appropriately according to the amount of the chelate cleaning liquid to be supplied to the cleaning device 13 and the concentration of the chelating agent. For example, the ratio between the flow rate of the sludge supplied to the fine particle cleaning device 13 and 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 13 is set to 1% by mass. In this case, the reverse osmosis membrane separation device 16 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 Therefore, in the fine-grain cleaning device 13, the sludge containing no chelating agent and the chelating 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 16, that is, the chelate washing liquid, is introduced into the chelating agent regeneration device 17 and is regenerated. The chelating agent regenerating device 17 is a solid-state adsorbent or a small piece on which the solid-state adsorbent is fixed, which has a higher complexing power than the chelating agent and adsorbs or extracts harmful metals and the like in the chelating cleaning solution when it comes into contact with the chelating cleaning solution. Or a particulate material, and removes harmful metals and the like from the chelating agent in the chelate cleaning solution to regenerate the chelate cleaning solution.

  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 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.

  Hereinafter, the specific configuration and function of the chelating agent regeneration device 17 will be described with reference to FIG. The chelating agent regenerating apparatus 17 is provided with a packed tower 70 in which solid phase adsorbent particles or a packing (packing) in which the solid phase adsorbent is fixed are packed. The chelating agent regenerating apparatus 17 includes an intermediate storage tank 71 for storing a chelate cleaning liquid (concentrated water) to be regenerated, a cleaning liquid storage tank 72 for storing a regenerated chelate cleaning liquid, and an acid liquid storage tank 73 for storing an acid liquid. And a water storage tank 74 for storing water.

  In the intermediate storage tank 71, the concentrated water discharged from the reverse osmosis membrane separation device 16 (see FIG. 1), that is, the chelate cleaning liquid, is temporarily stored. When the chelate cleaning liquid is regenerated, the chelate cleaning liquid stored in the intermediate storage tank 71 is transferred to the packed tower 70, while the chelate cleaning liquid regenerated in the packed tower 70 is transferred to the cleaning liquid storage tank 72 and a series of pumps 76. Pipelines 77 to 80 are provided. In addition, a pump 81 and a pipe 82 are provided for supplying the chelate cleaning liquid stored in the cleaning liquid storage tank 72 to the fine-grain cleaning device 13 (see FIG. 1).

  Further, the chelating agent regenerating device 17 transfers the acid solution stored in the acid solution storage tank 73 to the packed tower 70 and regenerates the acid solution discharged from the packed tower 70 when regenerating the solid phase adsorbent. A pump 83 for returning to the liquid storage tank 73 and a plurality of conduits 84 and 85 are provided. In addition, when the solid-phase adsorbent regenerated with the acid solution is washed with water, the chelating agent regenerating device 17 transfers the water stored in the water storage tank 74 to the packed tower 70 and discharges the water from the packed tower 70. A pump 86 for returning water to the water storage tank 74 and a plurality of conduits 87 and 88 are provided.

  Valves 91, 92, 93, 94 for opening and closing the corresponding pipes are provided in the pipes 77, 78, 84, 87 for transferring the chelate washing liquid, acid solution or water to the packed tower 70, respectively. I have. On the other hand, pipes 79, 80, 85, and 88 for discharging the chelate washing liquid, the acid solution, or the water from the packed tower 70 are provided with valves 95, 96, 97, and 98 for opening and closing the corresponding pipes, respectively. Have been. By switching between the open and closed states of these valves 91 to 98, any one of the chelate washing liquid, the acid liquid, and the water can be supplied to and discharged from the packed tower 70. The opening and closing of these valves 91 to 98 are automatically controlled by a controller (not shown).

  Hereinafter, an example of an operation method of the chelating agent regeneration device 17 will be described. When regenerating the chelate washing liquid (chelating agent), the valves 91, 92, 95, 96 provided in the pipes 77 to 80 are opened, while the other valves 93, 94, 97, 98 are closed, The pump 76 is operated. Thereby, the chelate cleaning liquid in the intermediate storage tank 71 flows through the packed tower 70 and is transferred to the cleaning liquid storage tank 72.

  In the packed tower 70, a chelate washing liquid containing a chelating agent capturing a harmful metal or the like is brought into contact with a solid phase adsorbent (solid phase adsorbent particles). As a result, 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 solution, and the chelating agent is again in a state capable of capturing the harmful metals and the like, and the chelate cleaning solution is regenerated.

  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 the adsorption capacity of the solid phase adsorbent has an upper limit. Therefore, 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. That is, an acid solution is flown into the packed tower 70 in a state where the chelate cleaning liquid has been removed, and harmful metals and the like adsorbed on the solid phase adsorbent are removed by the acid solution to regenerate the solid phase adsorbent. Thus, while the harmful metals and the like are recovered by the acid solution, the solid phase adsorbent is regenerated and becomes a state where the harmful metals and the like or these ions can be adsorbed or extracted again.

  When the solid-phase adsorbent in the packed tower 70 is regenerated with an acid solution, the valves 93, 92, 95, 97 provided in the pipes 84, 78, 79, 85 are opened, while the other valves 91, 92 are opened. , 94, 96, 98 are closed and the pump 83 is operated. Thus, the acid solution in the acid solution storage tank 73 flows through the packed tower 70 and returns to the acid solution storage tank 73. Whether or not the harmful metal adsorption amount of the solid phase adsorbent has reached a saturated state or its vicinity can be determined by detecting the content of harmful metals and the like in the chelate washing liquid discharged from the packed tower 70. .

  When the solid phase adsorbent is washed with water after the regeneration of the solid phase adsorbent with the acid solution, the valves 94, 92, 95, 98 provided in the pipes 87, 78, 79, 88 are opened. , The other valves 91, 93, 96, 97 are closed and the pump 86 is operated. Thereby, the water in the water storage tank 74 flows through the packed tower 70 and returns to the water storage tank 74. The water circulates and flows between the water storage tank 74 and the packed tower 70. At that time, the solid phase adsorbent in the packed tower 70 comes into contact with water, and the acid solution adhering to the solid phase adsorbent is washed. Thereafter, regeneration of the chelate cleaning liquid is restarted.

  The chelate cleaning liquid thus regenerated is temporarily stored in the cleaning liquid storage tank 72 and then supplied to the fine particle cleaning apparatus 13 (see FIG. 1). That is, the chelate cleaning liquid circulates while repeatedly purifying fine particles and regenerating the chelating agent. The reduced amount of the chelating agent is appropriately replenished.

  As described above, according to the soil purification system S according to the present invention, clean and reusable gravel, sand, and fine particles can be obtained. In addition, since the content of harmful metals and the like in the sludge discharged from the iron removing device 12 can be reduced, the load of harmful metals and the like on the fine particle fraction cleaning device 13 and the harmful metal and the like on the chelating agent regeneration device 17 can be reduced. The load can be reduced, the necessary or used amount of the chelating agent and the solid phase adsorbent can be reduced, and the cost for treating the soil can be reduced.

  S Soil purification system, 1 input hopper, 2 mixer, 3 mill breaker (wet crusher), 4 trommel, 5 cyclone, 6 PH adjustment tank, 7 coagulation tank, 8 thickener, 9 intermediate tank, 10 washing water tank, 11 reserve Water tank, 12 iron removal device, 13 fine particle washing device, 14 filtration device, 15 clarification filter, 16 reverse osmosis membrane separation device, 17 chelating agent regeneration device, 20 magnetic sphere, 21 magnetic sphere filling tank, 21a opening and closing door, Reference Signs List 22 centrifuge, 23 magnetic ball return 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 Vessel, 29 hollow spherical body, 30 permanent magnet, 31 magnet holding member, 32 magnet holding hole, 33 sludge discharge pipe, 34 sludge pump, 35 Housing, 36 bearing device, 37 rotating cylinder, 37a upper opening / closing door, 37b lower opening / closing door, 38 gear mechanism, 39 motor, 40 baffle, 41 horizontal conveyor, 41a belt, 42 upright conveyor, 43a drive roller, 43b drive Rollers, 44a driven rollers, 44b driven rollers, 45 metal belts, 46 idle rollers, 47 magnetic ball locking members, 48 guide members, 50 storage tanks, 51 to 54 partition walls, 55 to 59 slurry passages, 61 to 65 air discharge tubes , 70 packed tower, 71 intermediate storage tank, 72 washing liquid storage tank, 73 acid liquid storage tank, 74 water storage tank, 76 pump, 77-80 pipe, 81 pump, 82 pipe, 83 pump, 84 pipe, 85 pipe, 86 Pump, 87 lines, 88 lines, 91-98 valves.

Claims (3)

A soil purification system for purifying soil contaminated with harmful metals or compounds containing gravel, sand, and fine particles,
The soil purification system
After crushing the gravel and sand while washing the soil with washing water, a soil classification unit for classifying the soil into gravel, sand, and fine particles,
From the sludge containing the fine particles separated in the soil classification unit and the washing water, by removing the iron-based fine particles containing iron or iron oxide to a degree that can be magnetically adsorbed and removed by magnetic force, A pretreatment unit for reducing the content of harmful metals or compounds thereof in the sludge,
A post-treatment unit for subjecting the sludge discharged from the pre-treatment unit to a chemical treatment or a physico-chemical treatment to remove harmful metals or compounds thereof adsorbed or adhered to the surface of the fine particles in the sludge. With
The pre-processing unit,
While the hollow portion of the hollow spherical body is filled with a plurality of magnetic spheres in which a plurality of permanent magnets are mounted so that magnetic poles of the same magnet face radially outward, sludge discharged from the thickener is filled. A magnetic sphere filling tank that receives and circulates the gap between the magnetic spheres downward, and adsorbs the iron-based fine particles in the sludge to the magnetic spheres by magnetic force,
A centrifugal separator that intermittently receives the magnetic spheres adsorbing the iron-based fine particles in the magnetic sphere filling tank in a batchwise manner and separates the iron-based fine particles from the magnetic spheres by centrifugal force,
A soil purification system, comprising: an iron removing device having a magnetic sphere returning device for returning magnetic spheres discharged from the centrifuge to the magnetic sphere filling tank. The magnetic ball returning device,
A driving roller disposed at a position lower than a lower end of the centrifuge; a driven roller disposed above the driving roller at a position higher than an upper end of the magnetic sphere filling tank; the driving roller and the driven roller And an endless metal belt made of a ferromagnetic metal wound around the endless metal belt, and a magnetic sphere attached to the outer surface of the endless metal belt and adsorbed by the endless metal belt when traveling upward. An upright belt conveyor having a magnetic ball locking member for locking the
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,
2. The soil purification system according to claim 1, further comprising: a magnetic sphere supply unit configured to separate magnetic spheres from the endless metal belt at an upper end of the upright belt conveyor and supply the magnetic spheres to the magnetic sphere filling tank. 3. . The post-processing unit includes:
The sludge discharged from the iron removing device is mixed with a chelating cleaning solution containing a chelating agent and water to generate a fine-grain slurry, and the fine-grain slurry flows so as to secure a preset residence time. By doing so, a fine particle fraction cleaning device that captures the harmful metal or its compound attached to the fine particle content in the chelating agent,
A filtration device that filters the fine-grained slurry discharged from the fine-grained washing device to generate a filtrate and a filter cake;
The filtrate discharged from the filtration device, a reverse osmosis membrane, a reverse osmosis membrane separation device for separating the concentrated water in which the chelating agent is concentrated and permeated water containing no chelating agent,
The concentrated water discharged from the reverse osmosis membrane separation device is received, and has a complexing power higher than that of a chelating agent. A chelating agent regenerating device that removes harmful metals or compounds thereof from the chelating agent in water and supplies the concentrated solution as a chelating cleaning solution to the fine-grain cleaning device;
3. The soil purification system according to claim 1, further comprising: a permeated water transfer unit configured to transfer permeated water discharged from the reverse osmosis membrane separation device to the thickener. 4.

Images