JP6447856B1 - Soil purification system - Google Patents

Abstract

[PROBLEMS] To provide a simple and low-cost soil remediation system capable of classifying gravel, sand and fine particles while washing soil with washing water, while reducing harmful metals adsorbed on the fine particles. To do.
A soil purification system S includes soil classification units 1 to 8, an iron removal device 12 as a pretreatment unit, and a chelate cleaning device 14 as a posttreatment unit. The soil classification units 1 to 8 crush the gravel and sand in the soil with the mill breaker 3 while washing the soil with washing water, and then use the trummel 4, cyclone 5 and thickener 8 to remove the gravel, sand and fine particles. And classify. The iron removing device 12 uses magnetic balls to adsorb and remove iron-based fine particles from the sludge containing fine particles separated by thickener 8 and washing water by magnetic force. Reduce the rate. The chelate cleaning device 14 removes harmful metals and the like from sludge (fine particles) using a chelate cleaning liquid.
[Selection] Figure 1

Description

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

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

  As a method for purifying toxic metal-contaminated soil at such off-site soil purification facilities, conventionally, a cleaning method that removes toxic metal by washing toxic metal-contaminated soil with washing water or the like has been widely used. . When the toxic metal-contaminated soil is washed with washing water, most of the toxic metals once released from the soil into the water are adsorbed or adhered to the surface of the fine particles having a relatively small particle size. It is known that they are aggregated on the surface of the film (for example, see Non-Patent Document 1).

  Therefore, after washing the toxic metal contaminated soil with washing water and classifying it into gravel, sand and fine particles, by applying chemical treatment to remove toxic metals etc. on the fine particles, Gravel, sand, and fine particles that contain almost no harmful metals can be obtained. Thus, the present inventor has already washed the hazardous metal-contaminated soil with washing water, classified it into gravel, sand and fine particles, and then washed the fine particles with a chelate washing liquid containing a chelating agent. Various soil purification facilities (contaminated soil purification devices) that remove harmful metals and the like from fine particles have been proposed (for example, see Patent Documents 1 and 2).

Japanese Patent No. 5723054 Japanese Patent No. 5723055 Japanese Patent No. 4755159 Japanese Patent No. 6007144

Issued by the Ministry of the Environment, Water and Air Environment Bureau, Soil Environment Division, “Technical Considerations for Permitted Examination of Contaminated Soil Treatment Industry”, page 21, August 2013 Tetsuo Katsura “Wastewater Treatment by Iron Powder Method” flotation, vol. 23 (1976), no. 3. P190-198 (https://www.jstage.jst.go.jp/article/rpsj1954/23/3/23_3_190/_pdf)

  By the way, in this kind of soil remediation facility by a contaminated soil treatment company, usually a large amount of contaminated soil is purified (for example, 2000 tons per day), so a large amount of fine particles are produced (for example, , 500 to 600 tons per day on a dry basis). Therefore, when washing such a large amount of fine particles with, for example, a chelate washing solution, a large amount of a relatively expensive chelating agent is required, so that there is a problem that the cost for treating contaminated soil increases. The necessary amount or amount of the chelating agent increases as the content of harmful metals and the like in the fine particles increases. In addition, when the fine particles are washed with a cleaning solution containing chemicals other than chelating agents to remove harmful metals, etc. (chemical treatment), or adsorbents are used to remove harmful metals, etc. by physicochemical treatment. Similar problems arise in some cases.

  The present invention has been made to solve the above-mentioned conventional problems, and includes gravel and sand while washing soil containing gravel, sand and fine particles and contaminated with harmful metals with washing water. It can be classified into fine particles, and harmful metals adsorbed or adhered to the separated fine particles can be removed, or at least the content or possession of harmful metals etc. in the fine particles It is an object to be solved to provide a soil purification system with a lower processing cost that can reduce the rate.

  The present invention has been made to solve the above-mentioned problems, and is a soil purification method for purifying soil containing gravel, sand and fine particles and contaminated with harmful metals or the like (toxic metals and / or compounds thereof or ions thereof). The system includes a soil classification unit, a pretreatment unit, and a posttreatment unit. Here, the soil classification unit crushes gravel and sand while washing the soil with washing water, and then classifies the gravel into sand and fine particles. The pretreatment section contains iron or iron oxide (hereinafter collectively referred to as “iron etc.”) to an extent that can be adsorbed by magnetic force from the sludge containing fine particles separated by the soil classification section and the washing water. The content of harmful metals and the like in sludge (fine particles) is reduced by adsorbing and removing system fine particles by magnetic force. The post-treatment unit performs chemical treatment or physicochemical treatment on the sludge discharged from the pre-treatment unit, and removes harmful metals adsorbed or adhered to the surface of the fine particles in the sludge.

  In the soil purification system according to the present invention, the soil classification unit includes a mixer, a wet crusher, a trommel, a hydrocyclone, and a thickener. Here, the mixer mixes the soil introduced into the soil classification unit and the washing water. The wet crusher can adsorb iron or the like that is unevenly or scattered inside the gravel and sand by crushing the gravel and sand in the mixture containing soil and washing water discharged from the mixer. An iron-based fine particle content is generated to a certain extent, and a toxic metal or the like is adsorbed on iron or the like exposed on the surface of the iron-based fine particle content. Trommel separates gravel from a mixture of gravel, sand, fines and wash water discharged from a wet crusher. The hydrocyclone separates sand from a mixture containing sand, fines and wash water discharged from the 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 separation.

  The pretreatment unit includes an iron removing device having a magnetic sphere filling tank, a centrifuge, and a magnetic sphere return device. Here, the magnetic sphere filling tank is mounted in the hollow part of the hollow sphere so that a plurality of (many) permanent magnets have the same magnetic pole (N pole or S pole) outward in the radial direction of the sphere. While multiple (many) magnetic spheres are filled, the sludge discharged from the thickener is received and the gap between the magnetic spheres is circulated downward, and the iron-based fine particles in the sludge are adsorbed to the magnetic sphere by magnetic force. . The centrifuge accepts the magnetic spheres adsorbing the iron-based fine particles in the magnetic sphere filling tank intermittently (batch type) and detaches the iron-based fine particles from the magnetic spheres by centrifugal force. Let The magnetic sphere return device returns the magnetic sphere 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 iron content removing device as the pretreatment unit includes an upright belt conveyor, a magnetic ball transport unit, and a magnetic ball supply unit. 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 above the driving roller and higher than the upper end of the magnetic ball filling tank, An endless metal belt made of a ferromagnetic metal wound around a roller and a driven roller, and a magnetic ball attached to the outer surface of the endless metal belt and adsorbed to the endless metal belt when traveling above the endless metal belt And a magnetic ball locking member for locking the lowering of the ball. The magnetic sphere conveying means conveys the magnetic sphere discharged from the centrifuge to the lower end portion of the upright belt conveyor and attracts it to the endless metal belt with a magnetic force. The magnetic ball supply means separates the magnetic ball from the endless metal belt at the upper end of the upright belt conveyor and supplies the magnetic ball to the magnetic ball filling tank.

  In the soil purification system according to the present invention, the post-treatment unit is adsorbed or adhered to the surface of fine particles in the sludge by washing the sludge discharged from the pre-treatment unit with a chelate washing liquid containing a chelating agent and water. It is preferable to provide a chelate cleaning device that removes harmful metals and the like.

  In general, in the process of cleaning and classification of contaminated soil using washing water, toxic metals and the like are hardly adsorbed (attached) to gravel and sand, but are aggregated and adsorbed (attached) to fine particles (for example, non-adhesive) Patent Document 1). The fine particles are divided into 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 “ 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 adsorption of harmful metals and the like of iron-based fine particles including iron exposed on the surface (attachment amount) ) Is considerably larger than the adsorption amount (adhesion amount) of toxic metals and the like for non-ferrous fine particles.

  In the soil purification system according to the present invention, gravel and / or sand is crushed by a wet crusher to produce fine particles, and among these fine particles, uneven distribution or points in the gravel or sand. The fine particles containing a large amount of fine particles such as iron are iron-based fine particles, and the iron exposed on the surface of these iron-based fine particles reaches the iron removal device from the wet crusher. Adsorbs a relatively large amount of harmful metals in a series of distribution processes. Therefore, iron-based fine particles that existed before crushing and iron-based fine particles generated by crushing are introduced into the iron removal device, and both of these iron-based fine particles are considerably large (non-ferrous). (Compared with fine particles of the system)) Adsorbs harmful metals.

  Thus, in the iron content removing device, iron fine particles with 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. Can be reduced. Therefore, it is possible to reduce the load of harmful metals and the like on the post-treatment unit that applies chemical treatment or physicochemical treatment to the sludge discharged from the iron removing device (pre-treatment unit). Thereby, the required amount or usage-amount of processing agents, such as a chemical agent and an adsorption agent, can be reduced, and the processing cost of soil can be reduced. Since the wet crusher and the iron content removing device have a mechanical structure for performing physical treatment and do not use any special chemical or treatment agent, the operation cost is very low.

  In each magnetic sphere, a plurality of permanent magnets are mounted in the hollow part of the hollow sphere so that the same magnetic pole (for example, N pole) is directed outward in the spherical body radial direction. Repel each other. For this reason, at the time of supplying the magnetic sphere to the magnetic sphere filling tank or at the time of discharging the magnetic sphere from the magnetic sphere filling tank, the magnetic spheres are not adsorbed to each other and become a lump (grape bunch). The magnetic sphere can move smoothly while repelling each other.

It is a block diagram which shows schematic structure of the soil purification system which concerns on Embodiment 1 of this invention. It is a typical elevation view of the iron content removal device (pretreatment part) which constitutes a soil purification system. It is a typical sectional view of a magnetic sphere. It is a typical partial cross section elevation of a centrifuge. (A) is a schematic side view of a part of a magnetic ball conveyor and an upright belt conveyor, (b) is a schematic side view of a part of an upright belt conveyor, and (c) is upright. It is a typical front view of a part of type | mold belt conveyor. It is a block diagram which shows schematic structure of the chelate washing | cleaning apparatus (post-processing part) which is a component of a soil purification system. It is a typical elevation which shows the structure of the mixing and dispersing apparatus which makes a part of chelate washing | cleaning apparatus. (A) is a schematic plan view of a 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 particle cleaning device. It is a block diagram which shows schematic structure of the soil purification system which concerns on Embodiment 2 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
(Embodiment 1)
As shown in FIG. 1, in the soil purification system S according to Embodiment 1 of the present invention, the soil is collected by excavation of the ground contaminated with harmful metals or the like (hazardous metals and / or compounds thereof, or ions thereof). Soil (contaminated soil) is received by the input hopper 1. Examples of harmful metals include chromium, lead, cadmium, selenium, mercury, and metal arsenic.

  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 includes gravel (for example, particles having a particle size of 2 to 75 mm), sand (for example, particles having a particle size of 0.075 to 2 mm), and fine particles (for example, particles having a particle size of 0.075 mm or less). ) And, in some cases, stones (for example, particles having a particle size of 75 mm or more).

  A mixture (hereinafter referred to as “soil / water mixture”) containing soil and washing water generated by the mixer 2 is transferred to a mill breaker 3 which 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 crushing device in which a plurality of rods (for example, ten 75 mmφ × 2 m steel rods) are arranged in a drum, and the rods rotate parallel to each other by the rotation of the drum. Moves and makes line contact, and can crush gravel and sand (and stone in some cases) by the impact force, shear force, friction force, etc. to generate 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. The gravel and sand are partly fine and not all fine.

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

  In addition, a large number of iron-based fine particles are produced in which minute masses of iron or the like (iron and / or iron oxide) that are present, unevenly distributed or scattered in 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 metal or the like present in the washing water is adsorbed or adhered to the exposed surface of iron or the like of the iron-based fine particles. As a result, the amount of adsorption (adhesion amount) of harmful metals and the like for iron-based fine particles is considerably larger than the amount of adsorption (adhesion amount) of harmful metals and the like for non-ferrous fine particles. In other words, the fine particles discharged from the mill breaker 3 are iron-based fine particles with a large amount of adsorption (adhesion amount) of toxic metals and non-ferrous fine particles with a small amount of adsorption (adhesion amount) of toxic metals. It consists of. Needless to say, iron-based fine particles existing before crushing also adsorb considerably more harmful metals and the like than non-ferrous fine particles.

  As described later, the iron-based fine particles adsorbing harmful metals and the like are removed by the iron content removing device 12. On the other hand, it is generally known that iron or the like (iron and / or iron oxide) has a property of adsorbing harmful metals and the like, and using this property, iron powder or iron oxide is added to sludge containing 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 (see, for example, Patent Documents 3 to 4 and Non-Patent Document 2). However, as in the present invention, by crushing gravel and sand, fine iron-based fine particles with exposed fine lumps of iron (not yet adsorbing harmful metals, etc.) are generated on the surface. There has been no proposal of a method for treating harmful metals or the like in which harmful metals or the like are adsorbed on a fine lump (iron-based fine particles) of exposed iron or the like.

  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 device having a receiving tank capable of storing water, and a substantially cylindrical drum screen arranged to be inclined with respect to a horizontal plane. Can be rotated around its central axis (cylindrical central axis) by a motor. Further, the washing water can be sprayed into the drum screen.

  When the soil / water mixture flows through the rotating drum screen of the trommel 4, the soil particles finer than the mesh of the drum screen pass through the mesh of the drum screen together with the washing water, and go out of the drum screen and into the receiving tank. to go into. On the other hand, the 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 so that soil particles having a particle diameter of less than 2 mm, that is, sand and fine particles, pass through the mesh of the drum screen. Therefore, in this trommel 4, gravel (soil in some cases) which is a soil particle having a particle size of 2 mm or more is separated from the soil / water mixture. As described above, toxic metals and the like that have separated into the water are hardly adsorbed or adhered to the gravel and sand. Therefore, the gravel separated by the trommel 4 is clean, and is used as an aggregate for concrete, for example. be able to. The mesh size (opening) of the drum screen of Trommel 4 is not limited to that described above, and can be arbitrarily set according to the particle size of the soil particles to be obtained. It is.

  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, contained in the trombone 4 receiving tank is introduced into a cyclone 5 (liquid cyclone). Although not shown in detail, the cyclone 5 pumps the soil / water mixture in a substantially conical cylinder that narrows downward to generate a swirling flow, and utilizes the centrifugal force generated thereby, A mixture of soil and water, a mixture of fine particles having a relatively small particle size (for example, a particle size of less than 0.075 mm) and water, sand having a relatively large particle size (for example, a particle size of 0.075 mm or more) and water Separated into a mixture of

  A mixture of fine particles and water (hereinafter referred to as “fine particle-containing water”) is discharged from the upper end of the cyclone 5, and a mixture of sand and water having a relatively large particle size is discharged from the lower end of the cyclone 5. Is done. Here, since the mixture of sand and water discharged from the lower end of the cyclone 5 does not contain any harmful metals or the like as described above, it is drained or dried and used as reclaimed sand. On the other hand, the water containing fine particles is transferred to the PH adjustment tank 6.

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

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

  The water containing fine particles in the coagulation tank 7 is introduced into the thickener 8. Although the thickener 8 is not shown in detail, the water-insoluble floc or fine particle is settled by gravity in a state where the fine particle-containing water is almost stationary, and a sludge layer (for example, solid And 5% to 10%), and supernatant water (wash water) which is located in the upper part and hardly contains flocs 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 temporarily stored as washing water. When the washing water tank 10 is full, the auxiliary water tank 11 is used. The washing water stored in the washing water layer 10 or the auxiliary water tank 11 is supplied to the mixer 2 and the trommel 4 as circulating water. In addition, when the wash water stored in the wash water tank 10 decreases due to evaporation or the like, tap water is appropriately replenished. On the other hand, the sludge accumulated in the lower part of the thickener 8 is transferred to the intermediate tank 9 and temporarily stored. A series of devices 1 to 9 from the charging hopper 1 to the intermediate tank 9 are components of the soil classification unit of the soil purification system S.

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

  The sludge discharged from the iron removing device 12 is introduced into the filter press 13 and dehydrated to produce a filtrate and cake. The filtrate is then returned to the thickener 8. On the other hand, the cake is transferred to the chelate cleaning device 14, and harmful metals remaining in the fine particles (non-ferrous fine particles) are removed. Here, if the content of harmful metals and the like of 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 cleaning device 14. In addition, it may replace with the filter press 13 and may use another filter, for example, a vacuum filter. The specific configuration and function of the chelate cleaning device 14 will be described in detail later.

Hereinafter, with reference to FIGS. 2 to 5, a specific configuration and function of the iron content removing device 12 as the preprocessing unit will be described.
As shown in FIG. 2, the iron content removing device 12 includes, as main components, a magnetic sphere filling tank 21 filled with a large number of magnetic spheres 20 and an iron-based fine particle fraction adsorbed on the magnetic spheres 20 by magnetic force. Are separated by a centrifugal force, and a magnetic ball return device 23 for returning the magnetic spheres 20 discharged from the centrifuge 22 to the magnetic sphere filling tank 21 is provided. Furthermore, the iron content removing device 12 includes first to third magnetic sphere storage containers 24 to 26 that temporarily store the magnetic spheres 20 supplied to the magnetic sphere filling tank 21, the centrifuge 22, or the magnetic sphere return device 23, respectively. It has. The iron content removing device 12 includes a sludge storage tank 27 that temporarily stores the sludge discharged from the magnetic ball filling tank 21.

  As shown in FIG. 3, the magnetic sphere 20 schematically includes a plurality of permanent magnets 30 mounted in a hollow portion of a hollow sphere 29 so that each N pole faces outward in the radial direction of the sphere. 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 into a magnet holding hole 32 formed in a hollow spherical magnet holding member 31. A magnet holding member 31 with a permanent magnet 30 is fitted in the hollow portion of the hollow spherical body 29. That is, the hollow spherical body 29 is 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 formed in a shape that fits or matches the magnet holding hole 32. ing. For this reason, 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 the outside of the magnet holding member 31. The shape of the end face of the permanent magnet 30 located on the radially outer side in the state of being mounted on the magnet holding member 31 is preferably a curved surface that matches the outer peripheral face of the magnet holding member 31. In this way, the outer peripheral surface of the assembly of the permanent magnet 30 and the magnet holding member 31 is spherical, and the assembly and the hollow sphere 29 can be brought into close contact with each other.

The diameter of the magnetic sphere 20 (that is, the outer diameter of the hollow sphere 29) is practically 3 to 5 cm, for example, in order to facilitate the transportation or 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 is to reduce the weight as much as possible without causing the magnetic sphere 20 to float in the sludge. The range of 1.2 to 1.5 g / cm ³ is practical. The apparent density of the magnetic spheres 20 can be adjusted or increased or decreased by appropriately setting the size of the permanent magnets 20 and the number of the permanent magnets 20, the volume of the magnet holding member 31 or the hollow portion thereof, etc. It is easy to adjust the apparent density to 1.2 to 1.5 g / cm ³ .

  The material of the hollow sphere 29 is not particularly limited as long as it has corrosion resistance against sludge and appropriate mechanical strength, but it is practical to use stainless steel or aluminum (or an alloy thereof). The thickness of the hollow sphere 29 is preferably about 0.2 to 0.5 mm, for example. If the hollow sphere 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 the hemisphere. If the match is canceled, the magnetic sphere 20 can be disassembled.

  The magnet holding member 31 can be manufactured, for example, by injection molding of a thermoplastic resin (for example, polyethylene, polypropylene, etc.). As the permanent magnet 20, a neodymium magnet having a tapered shape corresponding to the magnet holding hole 32, an end face on the large diameter side being an N pole, and an end face on the small diameter side being an S pole can be used. A neodymium magnet in which the end surface on the large diameter side is the S pole and the end surface on the small diameter side is the N pole may be used.

  As shown in FIG. 2 again, a large number of magnetic spheres 20 are accommodated or filled in the magnetic sphere filling tank 21. The sludge is basically supplied continuously from the intermediate tank 9 (see FIG. 1) to the magnetic sphere filling tank 21, and this sludge flows down the gap between the magnetic spheres 20 in the magnetic sphere filling tank 21. At that time, the iron-based fine particles adsorbing the toxic metal or the like in the sludge or adhering the toxic metal or the like are adsorbed by the magnetic force on the outer peripheral surface of the magnetic sphere 20 and are accompanied by the magnetic sphere 20 as described later. Then, it is removed from the magnetic sphere filling tank 21. Thereby, the content rate of the harmful metal etc. of sludge is reduced.

  At the lower end (bottom) of the magnetic sphere filling tank 21, an opening / closing door 21a for discharging the magnetic sphere 20 in the magnetic sphere filling tank 21 downward as needed is attached. When the open / close door 21a is closed, the downward opening of the magnetic sphere 20 in the magnetic sphere filling tank 21 is locked by the open / close door 21a, and the downward flow of sludge is prevented. Further, at the lower end portion of the magnetic sphere filling tank 21 or in the vicinity thereof, when the open / close door 21a is closed, the iron-based fine particle fraction flows down 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 filter press 13 (see FIG. 1).

  A first magnetic sphere storage container 24 is disposed above the magnetic sphere filling tank 21, and the magnetic sphere 20 stored in the first magnetic sphere storage container 24 is dropped at any time on the lower end (bottom) of the first magnetic sphere storage container 24. An opening / closing door 24 a for supplying the magnetic sphere filling tank 21 is provided. When the opening / closing door 24a is closed, the downward opening of the magnetic ball 20 in the first magnetic ball storage container 24 is locked by the opening / closing door 24a.

  A second magnetic sphere storage container 25 is disposed below the magnetic sphere filling tank 21. When the open / close door 21a of the magnetic sphere filling tank 21 is opened, the magnetic sphere 20 in the magnetic sphere filling tank 21 falls due to gravity. The second magnetic ball storage container 25 is accommodated. At this time, since the magnetic balls repel each other by magnetic force (repulsive force), the magnetic ball 20 does not block the opening / closing door 21a in the shape of a lump or a bunch of grapes, and smoothly and quickly the second magnetic ball storage container. (The same applies to other cases in which the magnetic ball 20 falls from one container or the like to another container or the like.) In this case, the open / close door 21 a temporarily stops the supply of 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 magnetically receives 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 sphere 20 stored therein and supplying it to the centrifuge 22 at any time is attached.

  As shown in FIG. 4, the centrifuge 22 includes a housing 35 that is a substantially cylindrical container, and a bearing device 36 that is coaxially disposed in the housing 35 and fixed to the housing 35. And a rotating cylinder 37 supported rotatably around the axis. An upper opening / closing door 37a and a lower opening / closing door 37b, which can be opened and closed at any time, are attached to the upper end portion and the lower end portion of the rotating cylinder 37, respectively. The circumferential portion (side portion) of the rotating cylinder 37 is formed of a cylindrical net-like member or a lattice-like member having a large number of openings with openings that the magnetic ball 20 cannot pass through. The rotary cylinder 37 is rotationally driven by a motor 39 via a gear mechanism 38. Instead of the gear mechanism 38, a belt / pulley mechanism may be used. In addition, a hollow frustum-shaped baffle 40 (an umbrella-shaped baffle plate) that receives and drops particles of an iron-based fine particle flying in the horizontal direction by centrifugal force from a rotating cylinder 37 that rotates at a high speed is provided in the housing 35. Has been placed.

  As apparent from FIG. 2, the third magnetic ball storage container 26 is disposed below the centrifuge 22, and when the lower opening / closing door 37 b (see FIG. 4) is opened when the rotating cylinder 37 is stopped, the third magnetic ball 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. An opening / closing door 26 a whose opening degree can be freely adjusted is attached to the lower end portion of the third magnetic ball storage container 26. 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) downward at a desired passing amount (flow rate).

  Below the third magnetic ball storage container 26, the magnetic balls 20 continuously discharged from the third magnetic ball storage container 26 are received on a belt 41a (endless belt) and transported horizontally by the belt 41a. A horizontal belt conveyor 41 that is supplied to the upright belt conveyor 42 is provided. The horizontal belt conveyor 41 has one end (upstream end with respect to the magnetic ball transport direction) positioned near the lower end of the third magnetic ball storage container 26 and the other end (downstream end with respect to the magnetic ball transport direction). Are arranged in the vicinity of 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 return device 23.

  The belt 41a is made of a flexible nonmagnetic material (for example, rubber). Further, side plates (not shown) are provided on both sides of the belt 41a so as to be close to the belt side portion and prevent the magnetic balls 20 on the belt from falling off the belt side portion. . In addition, the side plate may not be provided, and both sides of the belt 41a may have a moderate height (for example, 1 to 2 cm) and a bank-like or bank-like protrusion that extends in the belt extending direction may be integrally formed.

  The upright belt conveyor 42 is slightly higher than the upper end of the first magnetic ball storage container 24 immediately above the two driving rollers 43a and 43b and the driving rollers 43a and 43b disposed slightly above the horizontal belt conveyor 41. A ring-shaped (endless) made of a ferromagnetic material (for example, 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 rotationally driven in a counterclockwise direction by a motor (not shown). Along with this, the metal belt 45 runs 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 to assist the movement / adsorption of the magnetic ball 20 on the belt 41a to the metal belt 45. It is mounted so that it faces outward. When the permanent magnet 30 is mounted on the magnetic sphere 20 so that the south pole faces outward in the spherical body radial direction, the permanent magnet 49 is mounted so that the north pole faces outward in the roller radial direction. The The idle roller 46 abuts on the inner surface (rear surface) of the ring-shaped metal belt 45 and regulates the position or travel path of the metal belt 45 so that the metal belt 45 travels on a predetermined travel path.

  Since the metal belt 45 is formed of a ferromagnetic material, the magnetic sphere 20 can adhere to the metal belt 45 by magnetic force. The magnetic characteristics or magnetic strength of the permanent magnet 30 (see FIG. 3) of the magnetic sphere 20 is such that when the metal belt 45 extends in the horizontal direction, the magnetic sphere 20 is positioned below the metal belt 45 at an appropriate interval (for example, 5 It is set so that the magnetic sphere 20 can move upward against gravity and adhere to the lower surface of the metal belt with a magnetic force when arranged with a gap of ~ 15 mm.

  Further, the horizontal belt conveyor 41 has a magnetic force between the top of the magnetic ball 20 mounted on the belt 41a and the lower surface of the metal belt at the lower end of the upright belt conveyor 42. It arrange | positions so that the said moderate space | interval which can adhere can arise. Therefore, the magnetic balls 20 transported to the lower side of the upright belt conveyor 42 by the horizontal belt conveyor 41 are sequentially attached to the lower surface of the metal belt by magnetic force. The adhesion of the magnetic sphere 20 to the lower surface of the metal belt is assisted by a permanent magnet 49 (see FIG. 5).

  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 ball 20 in the direction in which the metal belt 45 extends (traveling direction). A plurality of (multiple) magnetic ball locking members 47 in the form of a prism or a rectangular bar 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.

  The magnetic ball locking member 47 is configured to move or move the magnetic ball 20 attached to the surface of the metal belt 45 by magnetic force downward when the metal belt 45 extends or moves upward in the vertical direction. Lock the rolling. The height or protrusion length of the magnetic ball locking member 47 from the metal belt surface is practically 1/8 to 1/4 of the diameter of the magnetic ball 20. Further, it is practical that the interval between the magnetic ball locking members 47 adjacent to each other in the extending direction (traveling direction) of the metal belt 45 is 1.2 to 1.5 times the diameter of the magnetic ball 20.

  Thus, the magnetic ball 20 transported by the horizontal belt conveyor 41 and attached to the metal belt 45 by the magnetic force at or near the lower end of the upright belt conveyor 42 is moved downward by the metal belt 45 traveling around counterclockwise. Are conveyed to the upper end of the upright belt conveyor 42 without moving or rolling.

  As is apparent from FIG. 2, in the vicinity of the upper end of the upright belt conveyor 42, the magnetic sphere 20 attached to the metal belt 45 by magnetic force is detached 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 upright belt conveyor side is positioned in the vicinity of the driven roller 44 a, while the end of the first magnetic ball storage container side is positioned in the vicinity of the upper end of the first magnetic ball storage container 24. . The guide member 48 is inclined downward from the upright belt conveyor side toward the first magnetic ball storage container side. The guide member 48 is made of a nonmagnetic material.

  Here, the magnetic ball 20 attached to and moving on the metal belt 45 that runs counterclockwise in the positional relationship in FIG. 2 collides with or contacts the end of the guide member 48 in the vicinity of the driven roller 44a. To do. As a result, the magnetic ball 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 ball storage container 24. That is, the magnetic spheres 20 continuously discharged downward from the third magnetic sphere storage container 26 are first magnetic spheres by the magnetic sphere return device 23 (horizontal belt conveyor 41, upright belt conveyor 42, guide member 48). It is continuously returned to the storage container 24.

  Thus, the magnetic spheres 20 are in order of 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. The magnetic ball returning device 23 (the horizontal belt conveyor 41, the upright belt conveyor 42, the guide member 48) is circulated and moved. The seven broken arrows in FIG. 2 indicate the moving direction of such a magnetic sphere 20. The magnetic sphere 20 moves intermittently by a batch operation from the first magnetic sphere storage container 24 to the third magnetic sphere storage container 26, and from the third magnetic sphere storage container 26 to the first magnetic sphere storage container 24. The magnetic ball returning device 23 moves continuously.

  Hereinafter, an example of the operation method of the iron content removal apparatus 12 is demonstrated. A magnetic sphere filling tank 21 in which a large number of magnetic spheres 20 are filled or accommodated is substantially divided into fine particles (iron fine particles and non-ferrous fine particles) from the intermediate tank 9 (see FIG. 1). Sludge composed of water is continuously supplied. The sludge flows through the gaps of 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 adsorbed on the outer peripheral surface of the magnetic sphere 20 by magnetic force.

  The iron-based fine particles are produced 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. On the surface, a fine lump such as iron is exposed, and harmful metals and the like are adsorbed on the exposed fine lump such as iron. In general, small blocks such as iron are unevenly distributed or scattered in gravel and sand, and the ratio of such small blocks is about 2 to 7% by mass. For this reason, at least a part of the fine particles generated by crushing gravel and sand is an iron-based fine particle portion in which fresh iron (that is, no toxic metal or the like is adsorbed) is exposed on the surface.

Iron is a ferromagnetic material (soft magnetic material) and is adsorbed by a magnet. In addition, iron oxides present in the soil are substantially composed of triiron tetroxide (Fe ₃ O ₄ ), γ-type ferric 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 materials (soft magnetic materials) and are adsorbed by a magnet. Note that α-type ferric trioxide is not magnetized and is not attracted to the magnet. For this reason, the iron-based fine particles having a surface exposed to a fine mass such as iron are permanent magnets in the magnetic sphere 20 due to 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 sphere 29) by magnetic force.

  Iron or other fine mass exposed on the surface of fine iron particles produced by crushing gravel and sand with a mill breaker 3 (see FIG. 1) is unevenly distributed or scattered in the gravel or sand. It originates from a small lump of fresh iron or the like that has not adsorbed the toxic metals that have been adsorbed, and is exposed to the surface after crushing and adsorbs toxic metals and / or these ions from the surrounding wash water. Thus, the fine particles discharged from the mill breaker 3 (see FIG. 1) and introduced into the magnetic sphere filling tank 21 are iron-based fine particles having a relatively large (or considerably) adsorption amount of harmful metals and the like, and harmful metals. And the like, and non-ferrous fine particles with a relatively small (or considerably) adsorption amount.

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

  As will be described in detail later, the sludge or fine particles discharged from the magnetic sphere filling tank 21 is subjected to chelate cleaning treatment with a chelating agent in the chelate cleaning device 14 (see FIG. 1), and the cleaning liquid regenerating device. 55 (see FIG. 6), the chelating agent is regenerated by the solid-phase adsorbent. As described above, the content of toxic metals and the like in the sludge is reduced in the magnetic sphere filling tank 21, so that the fine particles ( The burden of harmful metals and the like on the sludge chelate cleaning process and the cleaning liquid (chelating agent) regeneration process is reduced. For this reason, the required amount or usage-amount of the chelating agent and solid-phase adsorbent in the soil purification system S can be reduced, and the processing cost of soil can be reduced. That is, the magnetic sphere filling tank 21 (iron removal device 12) functions as a pretreatment device or a pretreatment device that reduces the load of harmful metals or the like on the chelate washing device 14 or the cleaning liquid regenerating device 55.

  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 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 sphere 20 adsorbing the iron-based fine particles in the magnetic sphere filling tank 21 falls into the second magnetic sphere storage container 25 by gravity. Then, the open / close door 21a is closed, and a predetermined amount (a single 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 sludge is supplied to the magnetic sphere filling tank 21. Resumed. A plurality of magnetic ball 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, the upper door 37a is opened, while the lower door 37b is closed, the door 25a is opened and processed once from the second magnetic ball storage container 25 into the rotary cylinder 37. Minute magnetic sphere 20 is supplied. For example, an amount of the magnetic sphere 20 that occupies 1/3 to 1/2 of the space in the rotary cylinder 37 is supplied.

  Thereafter, the upper opening / closing door 37a is closed, the motor 39 is started, and the rotating cylinder 37 is rotated at a high speed (for example, when the radius of the rotating cylinder 37 is 1 m, 100 to 500 rpm). As a result, the iron 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 on the peripheral wall of the rotating cylinder 37 Or jump out through the hole. Here, the rotational 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, etc. It is preferably set to be separated.

  The iron-based fine particles separated from the magnetic sphere 20 and jumping out of the rotating cylinder 37 collide with the baffle 40 and then fall and accumulate at the bottom of the housing 35. The iron-based fine particles in the housing 35 are appropriately discharged to the outside by hand. The removed iron-based fine particles can be used, for example, as a raw material for iron making. Then, after the elapse 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 rotating cylinder 37 are 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 transported to the vicinity of the lower end of the upright belt conveyor 42 by the belt 41a. Thereafter, the magnetic sphere 20 on the belt 41 a is transported to the upper end portion thereof by the upright belt conveyor 42 and introduced into the first magnetic sphere storage container 24 by the guide member 48. The supply amount (supply speed) of the magnetic balls 20 from the third magnetic ball storage container 26 to the horizontal belt conveyor 41 is changed by changing the opening degree of the opening / closing door 26a. The conveyor 42 is adjusted to be equal to or less than the maximum transport amount.

  Hereinafter, the configuration and function of the chelate cleaning device 14 as a post-processing unit will be described. In addition, when the content rate of harmful metals etc. of the cake discharged | emitted from the filter press 13 is lower than the predetermined regulation value in the case of disposing by landfill, reuse, etc., it is necessary to use the chelate washing apparatus 14 which is a post-processing part. It is not necessary to provide it.

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

  The fine particle slurry produced by the mixing and dispersing device 51 is transferred to the fine particle washing device 52. The fine particle washing device 52 flows the fine particle slurry in a generally plug flow (plug flow) so as to ensure a preset residence time (for example, 0.5 to 2 hours) while stirring. Harmful metals adhering to the fine particles are removed and captured by the chelating agent in the chelate cleaning solution. Thereby, the harmful metal adsorbed (attached) on the surface of the fine particles in the fine particle slurry is removed.

  Here, examples of the chelating agent used in the chelate cleaning solution include EDTA (ethylenediaminetetraacetic acid), HIDS (3-hydroxy-2,2′-iminodisuccinic acid), IDS (2,2′-iminodisuccinic acid), and MGDA. (Methyl glycine diacetic acid), EDDS (ethylenediamine diacetic acid) or GLDA (L-glutamic acid diacetic acid) sodium salt. Any of these chelating agents can effectively capture (chelate) the fine metal slurry or the harmful metals contained in the fine particle. Of course, a chelating agent suitable for the treatment is selected or a plurality of chelating agents are used depending on the type of harmful metal contained in the fine particles.

  The fine particle slurry discharged from the fine particle washing device 52 is transferred to the filtration device 53. The filtering device 53 filters the fine particle slurry to produce a cake (filter cake) having a water content of 30 to 40 percent and a filtrate. In addition, as such a filtration apparatus 53, a filter press, a vacuum filter machine, etc. can be used. The filter cake (fine particles) discharged from the filter device 53 contains almost no harmful metals.

  The filtrate discharged from the filtration device 53, that is, the chelate cleaning liquid is introduced into the cleaning liquid regeneration unit 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, the cleaning liquid regenerating device 55 is not shown in detail, but has a complexing power higher than that of the chelating agent and is in contact with the chelating cleaning solution (filtrate) discharged from the filtering device 53. A solid-phase adsorbent that adsorbs or extracts or a packing (small piece or granular material) to which the solid-phase adsorbent is fixed is held inside the chelating agent in the chelating cleaning solution that flows through the gap between the packings and harmful metals. Is a packed tower type device that regenerates the chelate cleaning liquid.

  In the cleaning liquid regenerating apparatus 55, a chelate cleaning liquid containing a chelating agent capturing toxic metals and 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 multipoint interaction by coordinating bonds and hydrogen bonds in which a cyclic molecule is supported on a carrier and a chelate ligand is modified on the cyclic molecule, and selectively incorporates ions such as harmful metals. is there. As a result, harmful metals and the like captured by the chelating agent are separated from the chelating agent and adsorbed or extracted by the solid phase adsorbent. As a result, harmful metals and the like are removed and collected from the chelate cleaning solution (chelating agent), and the chelate cleaning solution (chelating agent) is in a state where it can capture the harmful metals and the like again.

  The chelate cleaning liquid regenerated by the cleaning liquid regenerating device 55 in this manner is temporarily stored in the cleaning liquid storage tank 56 and then returned to the mixing and dispersing device 51 by a cleaning liquid recirculation 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. Note that the reduced amount of the chelating agent is appropriately supplemented.

  A solid-phase adsorbent having a higher complexing power than a chelating agent is a solid material such as a gel, and is generally coordinated with a chelating agent when contacted with an aqueous solution containing a chelating agent capturing a metal. It has a strong binding force other than a covalent bond to such an extent that the metal ions can be detached from the chelating agent and 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 EDTA aqueous solution having a concentration of 10 mM / l. It is what you have.

  Examples of such a solid-phase adsorbent include a material in which a cyclic molecule is densely supported on a carrier such as silica gel or a resin and a chelate ligand is modified on the cyclic molecule. When such a solid-phase adsorbent is used, a plurality of various bonds and interactions such as coordination bonds and hydrogen bonds occur due to adjacent cyclic molecules and chelate ligands, resulting in multipoint interactions, and metal ions In contrast to this, a chemical bond stronger than that of a chelating agent is generated, and metal ions can be selectively taken in by the properties of the cyclic molecule.

  As the chelate cleaning solution is regenerated, the amount of adsorption of harmful metals and the like on the solid-phase adsorbent increases with time, but the amount of adsorption of harmful metals and the like on the solid-phase adsorbent has an upper limit. For this reason, when the amount of adsorption of harmful metals or the like in the solid phase adsorbent reaches a saturated state or in the vicinity thereof, the solid phase adsorbent is regenerated by a solid phase adsorbent regeneration mechanism (not shown in detail). That is, the solid-phase adsorbent regeneration mechanism allows the acid solution in the acid solution storage tank 57 to flow into the cleaning solution regenerator 55 in a state where the chelate cleaning solution is removed, and removes harmful metals 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 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.

  The solid phase adsorbent in the cleaning liquid regenerator 55 is regenerated with an acid solution, and then 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 is circulated between the water storage tank 58 and the cleaning liquid regenerating device 55. The detailed configuration of the cleaning liquid regenerating unit 54 and the operation method thereof are disclosed in Japanese Patent No. 6264592 (see FIG. 3 and paragraphs [0035] to [0045]) and Japanese Patent No. 6264593. (See FIG. 3 and paragraphs [0035] to [0045]).

Hereinafter, a specific configuration and function of the chelate cleaning device 14 will be described.
First, a specific configuration and function of the mixing and dispersing device 51 that 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 the fine particles are dispersed in the chelate cleaning liquid. A slurry is produced. Specifically, the mixing and dispersing device 51 premixes the crusher 61 that crushes the cake (fine particles) discharged from the filter press 13, the cake pieces crushed by the crusher 61, and the chelate washing liquid. The premixing tank 62 and the mixture produced by the premixing tank 62 are agitated 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). And a line mixer 63 for dispersing or suspending in the cleaning liquid.

  In the mixing and dispersing device 51, the cake discharged from the filter press 13 is supplied to the crusher 61, and the cake is rotated by a blade 61a that rotates at a high speed, for example, a large number of particles having a particle diameter of several mm (for example, 1 to 5 mm). Breaked into small pieces of cake. On the other hand, the chelating cleaning liquid in the chelating cleaning liquid storage tank 64 is supplied to the crusher 61 by the pump 65 through the conduit 66. The chelate cleaning liquid storage tank 64 is appropriately supplied with the chelating cleaning liquid from the cleaning liquid storage tank 56 (see FIG. 6). Although not shown in detail, the chelate cleaning liquid is jetted or supplied to a large number of cake pieces immediately after being crushed by the blade 61a, thereby preventing the cake pieces from adhering to each other. As such a crusher 61, for example, a “dehydrated cake crusher” according to Taiheiyo Kiko Co., Ltd. or a “dehydrated cake recycling device” according to Shoko Co., Ltd. can be used. In the case of using a commercially available crusher, it is necessary to provide a mechanism for injecting or supplying the chelate cleaning liquid to a large number of cake pieces immediately after crushing.

  The chelate solution and 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 that is rotationally driven by a motor. Then, the mixture of the chelate cleaning solution and the cake pieces in the premixing tank 62 is transferred to the line mixer 63 by the pump 68 through the pipe 69. The line mixer 63 is a flow-type mixer in which a blade that is rotated at a very high speed by a motor is placed in a horizontal cylindrical stirring chamber. In the chelate cleaning solution, 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 dispersed (suspended) almost uniformly. To produce a fine particle slurry. This fine particle slurry is transferred to a fine particle 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, a specific configuration and function of the fine particle cleaning device 52 which is a component of the chelate cleaning device 14 will be described. The fine particle washing device 52 adsorbs (adheres) the fine particle slurry produced by the mixing and dispersing device 51 to the fine particle portion by flowing it with a plug flow so as to ensure a preset residence time while stirring. ) The toxic metal etc. that have been removed from the fine particles are captured by the chelating agent.

  The fine particle washing device 52 has a storage tank 70 having five elongated rectangular parallelepiped or prismatic slurry passages 75 to 79 formed by partitioning with four flat partition walls 71 to 74 and extending in parallel with each other. doing. The storage tank 70 may be, for example, an iron rectangular parallelepiped square tank installed on the ground, or a concrete rectangular parallelepiped pit. Moreover, the partition walls 71-74 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 75 to 79 have four curved lines in the communicating portion (FIG. 8A) at one end in the longitudinal direction of the slurry passage (left and right in the positional relationship in FIGS. 8A and 8B). Are communicated with each other at the site indicated by the arrows. That is, partition walls 71 to 74 do not exist in these communicating portions, and adjacent slurry passages communicate with each other.

  Air discharge pipes 81 to 85 for discharging air into the fine particle slurry and stirring the fine particle slurry are disposed at the bottoms of the slurry passages 75 to 79, respectively. Each of the air discharge pipes 81 to 85 is a porous pipe extending in the slurry passage longitudinal direction and having a plurality of air discharge holes arranged in the slurry passage longitudinal direction at the bottom (lower side) of the peripheral wall. Although not shown, it is connected to a compressor or a blower that supplies compressed air. When pressurized air is supplied to the air discharge pipes 81 to 85, the air is bubbled from the air discharge holes and released into the fine particle slurry, and the fine particle slurry is stirred by the bubbles. 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 particle 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 disposed near the bottom of the slurry passage in the vicinity of one side surface of the slurry passage 75. For this reason, the bubbles discharged from the air discharge pipe 81 rise in the vicinity of this 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 fine particle slurry is stirred. The shape, size, capacity and the like of the storage tank 70 and each of the slurry passages 75 to 79 and the amount of pressurized air supplied to the air discharge pipes 81 to 85 are set in advance in the fine particle washing device 52. The water content, flow rate, residence time, flow velocity, turbulence degree of flow (for example, Reynolds number) and the like are preferably set.

  In the soil purification system S according to Embodiment 1, in the process of cleaning and classification of contaminated soil with washing water, toxic metals and the like are hardly adsorbed on gravel and sand, but are concentrated and adsorbed on fine particles. Clean and recyclable gravel and sand can be obtained. And in the soil purification system S, gravel and sand are crushed with the mill breaker 3, and a ferrous fine particle part and a nonferrous fine particle part are produced | generated. Therefore, the iron-based fine particle content that existed before crushing and the iron-based fine particle content generated by crushing are introduced into the iron content removing device 12, and both of these iron-based fine particle content are considerably large ( (Compared with non-ferrous fine particles)) Adsorbs harmful metals.

  And in the iron content removal apparatus 12, since the iron type fine particle content with much adsorption amount of a harmful metal etc. is removed from sludge by the magnetic ball 20 in the magnetic ball filling tank 21, the content rate of the harmful metal etc. of this sludge Or the ownership rate can be reduced. Therefore, it is possible to reduce the load of harmful metals and the like on the chelate cleaning device 14 as a post-processing unit that performs a chelate cleaning process on the sludge discharged from the iron removing device 12 (pre-processing unit). Depending on the properties of the soil, the content of toxic metals and the like can be reduced to the extent that dumping or landfilling is possible.

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

(Embodiment 2)
Hereinafter, the soil purification system S ′ according to the second embodiment of the present invention will be described with reference to FIG. 9. However, the soil purification system S ′ according to the second embodiment and the soil purification system S according to the first embodiment shown in FIGS. 1 to 8 are common in many respects. Therefore, in order to avoid duplication of explanation, differences between the soil purification system S ′ and the soil purification system S will be mainly described below. In addition, in the component of soil purification system S 'which concerns on Embodiment 2, the same reference number as Embodiment 1 is attached | subjected to the component which is common in the component of soil purification system S which concerns on Embodiment 1. FIG.

  The soil purification system S ′ according to the second embodiment is omitted in FIG. 9, but the input from the input hopper 1 to the intermediate tank 9 is similar 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 preliminary 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 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. Yes.

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

  The fine particle slurry discharged from the fine particle washing device 91 is transferred to the filtration device 92. The filtering device 92 filters the fine particle slurry to produce a cake (filter cake) having a water content of 30 to 40 percent and a filtrate. As the filtering device 92, a filter press, a vacuum filter, or the like can be used. The cake (fine particles) discharged from the filtering device 92 contains almost no harmful metals.

  The filtrate discharged from the filtration device 92, that is, the chelate washing solution is pumped to the reverse osmosis membrane separation device 94 after the suspended matter or suspended matter (SS) is removed by the clarification filter 93 (for example, 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 contain the concentrated water in which the chelating agent is concentrated by the reverse osmosis membrane and the chelating agent. Separated into permeate.

  The reverse osmosis membrane of the reverse osmosis membrane separator 94 is, for example, a three-layer structure in which a polysulfone support layer and a crosslinked aromatic polyamide dense layer are laminated on the surface of a polyester nonwoven fabric (thickness: 100 to 120 μm). Can be used. The dense cross-linked aromatic polyamide layer has a large number of pores having a pore diameter of about 0.5 to 1.5 nm, and is very thin (for example, 0.2 to 0.25 μm) 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 breakage thereof.

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 Authentec Co., Ltd., Nakatsugawa, Gifu Prefecture) is About 40 m ² . In the case of this reverse osmosis membrane element, when the chelate cleaning solution having a chelating agent concentration of about 1% by mass is supplied at a pressure of about 1 MPa, the treatment amount of the chelate cleaning solution is estimated to be about 1.5 m ³ / hr. Therefore, for example, when processing a chelate washing solution of 60 m ^{3 /} h, 40 reverse osmosis membrane elements may be connected in parallel.

  The reverse osmosis membrane separation device 94 is a continuous type, and the operating conditions such as the supply amount and supply pressure (operation pressure) of the chelate washing liquid, the discharge amount of concentrated water and permeate, the chelating agent concentration ratio of concentrated water are as follows. It is set appropriately according to the amount of chelate cleaning liquid to be supplied to the cleaning device 91 and the chelating agent concentration. For example, the ratio of the flow rate of the sludge supplied to the fine particle cleaning device 91 and the flow rate of the chelate cleaning solution is set to 1: 1, and the chelating agent concentration 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 separator 94 generates permeated water (chelating agent concentration 0) of about 50% of the supply amount of the chelate washing liquid and concentrated water (chelating agent concentration of about 2 mass%) of about 50%. Set to Therefore, in the fine particle washing apparatus 91, the sludge not containing the chelating agent and the chelating washing liquid having a chelating agent concentration of about 2% by mass are mixed at a ratio of 1: 1, and the chelating agent concentration in the fine particle washing apparatus 91 is 1 mass. % Is maintained.

  The concentrated water, that is, the chelate washing liquid discharged from the reverse osmosis membrane separator 94 is introduced into the chelating agent regenerator 95 and regenerated. That is, harmful metals and the like are removed and collected from the chelate cleaning solution (chelating agent), and the chelate cleaning solution (chelating agent) is in a state where it can capture the harmful metals and the like again. As such a chelating agent regeneration device 95, for example, the cleaning liquid regeneration unit 54 (see FIG. 6) in the first embodiment can be used.

  According to the soil purification system S ′ according to the second embodiment, as in the soil purification system S according to the first embodiment, clean and reusable gravel and sand can be obtained and discharged from the iron removing device 12. The content of harmful metals, etc. in sludge can be reduced. Thus, since the content rate of the harmful metal etc. of the sludge discharged | emitted from the iron content removal apparatus 12 is reduced, the usage-amount or required amount of the chelating agent in the fine grain washing | cleaning apparatus 91 can be reduced, and The amount of use or necessary amount of the solid-phase adsorbent in the chelating agent regenerator 95 can be reduced, and the soil treatment cost can be reduced.

  S soil purification system (Embodiment 1), S 'soil purification system (Embodiment 2), 1 input hopper, 2 mixer, 3 mil breaker (wet crusher), 4 trommel, 5 cyclone, 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 washing device, 20 magnetic ball, 21 magnetic ball filling tank, 21a open / close door, 22 centrifuge , 23 Magnetic sphere return device, 24 First magnetic sphere storage container, 24a Open / close door, 25 Second magnetic sphere storage container, 25a Open / close door, 26 Third magnetic sphere storage container, 26a Open / close door, 27 Sludge storage tank, 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 door, 37b lower door, 38 gear mechanism, 39 motor, 40 baffle, 41 horizontal conveyor, 41a belt, 42 upright conveyor, 43a drive roller, 43b drive 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 Crusher, 61a Blade, 62 Premixing tank, 63 Line mixer, 64 Chelate cleaning liquid storage tank, 65 Pump, 66 Pipe line, 67 Stirrer, 68 pump, 69 pipeline, 70 storage tank, 71-74 Partition wall, 75 to 79 slurry passage, 81 to 85 air discharge pipe, 91 fine particle 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 containing gravel, sand and fine particles and contaminated with harmful metals or compounds thereof,
The soil purification system
A soil classification unit for classifying gravel and sand into fine particles after crushing gravel and sand while washing the soil with washing water,
From the sludge containing the fine particles separated in the soil classification part and the washing water, by removing the iron-based fine particles containing iron or iron oxide to the extent that can be adsorbed by magnetic force, A pretreatment section for reducing the content of harmful metals or compounds thereof in sludge;
A post-treatment unit that performs chemical treatment or physicochemical treatment on the sludge discharged from the pre-treatment unit to remove harmful metals adsorbed or adhered to the surface of fine particles in the sludge or a compound thereof; With
The soil classification part is
A mixer for mixing the soil introduced into the soil classifying unit and washing water;
By crushing gravel and sand in a mixture containing soil and washing water discharged from the mixer, iron or iron oxide that is unevenly distributed or scattered inside the gravel and sand can be adsorbed by magnetic force. A wet crusher that generates an iron-based fine particle content to a degree and adsorbs a harmful metal or a compound thereof to iron or iron oxide exposed on the surface of the iron-based fine particle;
Trommel for separating gravel from a mixture containing gravel, sand, fine particles and washing water discharged from the wet crusher;
A liquid cyclone for separating sand from a mixture containing sand, fine particles and washing water discharged from the trommel;
A thickener that separates the mixture containing fine particles discharged from the hydrocyclone and washing water into supernatant water and sludge containing fine particles and washing water by sedimentation separation;
The pre-processing unit is
The hollow part of the hollow sphere is filled with a plurality of magnetic spheres in which a plurality of permanent magnets are mounted so that the magnetic poles of the same magnet face outward in the spherical body radial direction, while sludge discharged from the thickener A magnetic sphere filling tank that receives and circulates the gaps 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 accepts the magnetic spheres adsorbing the iron-based fine particles in the magnetic sphere filling tank in a batch manner, and detaches the iron-based fine particles from the magnetic spheres by centrifugal force;
A soil remediation system comprising an iron removal device having a magnetic sphere return device for returning magnetic spheres discharged from the centrifuge to the magnetic sphere filling tank. The magnetic ball returning device is
A driving roller disposed at a position lower than a lower end portion of the centrifugal separator, a driven roller disposed above the driving roller and disposed at a position higher than an upper end portion of the magnetic ball filling tank, the driving roller and the driven roller And an endless metal belt made of ferromagnetic metal wound around the lower end of the endless metal belt and attached to the outer surface of the endless metal belt and descending the magnetic sphere adsorbed to the endless metal belt when traveling above the endless metal belt An upright belt conveyor having a magnetic ball locking member for locking
Magnetic sphere conveying means for conveying the magnetic sphere discharged from the centrifuge to the 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 that detaches the magnetic sphere from the endless metal belt at the upper end of the upright belt conveyor and supplies the magnetic sphere to the magnetic sphere filling tank. .   The post-treatment unit is configured to wash the sludge discharged from the pre-treatment unit with a chelate cleaning solution containing a chelating agent and water, or to remove the harmful metal adsorbed or adhered to the surface of the fine particles in the sludge or its The soil purification system according to claim 1, further comprising a chelate cleaning device that removes the compound.

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