JP2020069463A - Soil cleaning system - Google Patents

Abstract

To provide a simple and low-cost soil cleaning system that classifies soil into small stones, sand, and fine particles while washing the soil with wash water, and reduces harmful metal or the like adsorbed on the fine particles.SOLUTION: A soil cleaning system S is equipped with soil classifying units 1-8, an iron removal device 12 as a pretreatment unit, and a chelate cleaning device 14 as a posttreatment unit. The soil classifying units 1-8 crush small stones and sand in the soil with a mill breaker 3 while washing the soil with wash water, and then classifies the soil into small stones, sand, and fine particles with a trommel 4, a cyclone 5, and a thickener 8. The iron removal device 12 removes iron-based fine particles by magnetic desorption using a magnetic ball from sludge containing the fine particles separated by the thickener 8 and wash water to lower the content of harmful metal or the like in the sludge. The chelate cleaning device 14 removes the harmful metal or the like from the sludge (fine particles) using a chelate cleaning fluid.SELECTED DRAWING: 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 their compounds.

  In recent years, the site of a production facility using a harmful metal such as chromium, lead, cadmium, selenium, or mercury and / or a compound thereof or an ion thereof (hereinafter collectively referred to as “toxic metal etc.”) as a raw material or material. Or, soil pollution frequently occurs in neighboring areas or due to illegal dumping of industrial waste containing harmful metals and the like. Then, the soil contaminated with harmful metals and the like (hereinafter referred to as “toxic metal-contaminated soil”) is used at the existing position (hereinafter referred to as “in-situ”), for example, insolubilization, containment or electrical restoration of harmful metals. It is quite difficult to purify effectively. For this reason, harmful metal-contaminated soil is generally removed from its original location by excavation and purified in an external soil purification facility.

  As a method for purifying harmful metal-contaminated soil in such an off-site soil purification facility, a cleaning method has conventionally been widely used for cleaning harmful metal-contaminated soil with cleaning water or the like to remove harmful metals. .. When the harmful metal-contaminated soil is washed with washing water, most of the harmful metals etc. that have once separated 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 (see Non-Patent Document 1, for example).

  Therefore, by classifying the gravel, sand, and fine particles while washing the harmful metal-contaminated soil with washing water, and then subjecting the fine particles to a chemical treatment for removing harmful metals and the like, It is possible to obtain gravel, sand, and fine particles containing almost no harmful metals. Thus, the present inventor has already classified the gravel, the sand and the fine particles while washing the harmful metal-contaminated soil with the washing water, and then performs the washing treatment with the chelate cleaning liquid containing the chelating agent for the fine particles. Various soil purification facilities (polluted soil purification devices) have been proposed in which harmful metals and the like are removed from fine particles by applying the above (see, for example, Patent Documents 1 and 2).

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

Ministry of the Environment, Water and Air Environment Bureau, Soil Environment Section, "Technical considerations regarding permission examination of contaminated soil treatment business," page 21, published in August 2013 Katsura Tetsuo "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 type of soil purification facility by a contaminated soil treatment company, a large amount of contaminated soil is usually purified (for example, 2000 tons per day), so a large amount of fine particles is generated (for example, , 500-600 tons per day on a dry basis). Therefore, when a large amount of fine particles are washed with, for example, a chelate washing liquid, a relatively expensive chelating agent is required in a large amount, so that there is a problem that the treatment cost of contaminated soil becomes high. In addition, the required amount or the amount of the chelating agent used increases as the content of the harmful metal or the like in the fine particles increases. Further, when the fine particles are washed with a washing liquid containing a chemical other than the chelating agent to remove harmful metals and the like (chemical treatment), or the adsorbent and the like are used to remove harmful metals and the like by physicochemical treatment. In this case, the same problem occurs.

  The present invention has been made in order to solve the above-mentioned conventional problems, including gravel and sand while washing soil contaminated with harmful metals and the like containing gravel, sand and fine particles with wash water. Fine particles can be classified, and harmful metals adsorbed or adhered to the separated fine particles can be removed, or at least the content or retention of harmful metals in fine particles It is an issue to be solved to provide a soil purification system which can reduce the rate and has a lower treatment cost.

  Soil purification for purifying soil contaminated with harmful metals and the like (harmful metals and / or compounds thereof or ions thereof) containing gravel, sand and fine particles according to the present invention made to solve the above problems 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, sand, and fine particles. The pretreatment part contains iron or iron oxides (hereinafter collectively referred to as “iron etc.”) from a sludge containing fine particles separated by the soil classification part and washing water to the extent that it can be adsorbed by magnetic force. By magnetically adsorbing and removing the fine particles of the system, the content of harmful metals and the like in the sludge (fine particles) is reduced. The post-treatment unit performs chemical treatment or physico-chemical treatment on the sludge discharged from the pre-treatment unit to remove harmful metals or the like adsorbed or attached to the surface of the fine particles in the sludge.

  In the soil purification system according to the present invention, the soil classification unit has a mixer, a wet crusher, a trommel, a hydrocyclone, and a thickener. Here, the mixer mixes the soil introduced into the soil classification unit with the wash water. The wet crusher can crush the gravel and sand in the mixture containing the soil and the wash water discharged from the mixer by magnetic force to adsorb iron or the like that is unevenly distributed or scattered inside the gravel and sand. Iron-based fine particles containing a certain amount are produced, and harmful metals and the like are adsorbed on iron and the like exposed on the surface of the iron-based fine particles. Trommel separates gravel from the mixture discharged from the wet crusher and containing gravel, sand, fines and wash water. A hydrocyclone separates sand from a mixture of sand, fines and wash water discharged from the trommel. Thickener separates a mixture containing fine particles discharged from a liquid cyclone and wash water into supernatant water and sludge containing fine particles and wash water by sedimentation separation.

  The pretreatment unit is provided with an iron content removing device having an iron-based fine particle content adsorbing device, a screen device, a centrifuge, and a magnetic sphere returning device. In the iron-based fine particle adsorption device, a plurality of magnets (a large number of permanent magnets are mounted in the hollow portion of the hollow spherical body so that magnetic poles (N pole or S pole) having the same magnetic force are directed outward in the radial direction of the spherical body. ) And the sludge discharged from the thickener are received in a movable container that can be swung or vibrated, and the mixture of magnetic balls and sludge is agitated by the shaking or vibrating of the movable container, and the iron in the sludge is mixed. The fine particles of the system are magnetically attracted to the magnetic spheres. The screen device receives the mixture of magnetic spheres and sludge discharged from the iron-based fine particle adsorption device, and separates (screens) the magnetic spheres and sludge. The centrifuge intermittently receives the magnetic spheres adsorbing the iron-based fine particles, which are discharged from the screen device, in a batch type and intermittently receives the iron-based fine particles from the magnetic spheres by centrifugal force. Let go. The magnetic sphere returning device returns the magnetic spheres discharged from the centrifuge, which have hardly adsorbed the iron-based fine particles, to the iron-based fine particles adsorption device.

  In the soil purification system according to the present invention, it is preferable that the magnetic sphere returning device includes an upright belt conveyor, a magnetic sphere conveying means, and a magnetic sphere supplying means. In this case, the upright belt conveyor includes a drive roller arranged at a position lower than the lower end of the centrifuge and a driven roller arranged above the drive roller and at a position higher than the upper end of the iron-based fine particle adsorption device. And an endless metal belt made of a ferromagnetic metal wrapped around a driving roller and a driven roller, and attached to the outer surface of the endless metal belt and adsorbed by the endless metal belt when traveling upward. And a magnetic ball locking member for locking the descending of the magnetic sphere. The magnetic sphere conveying means conveys the magnetic spheres discharged from the centrifuge to the lower end portion of the upright belt conveyor and magnetically attracts them to the endless metal belt. The magnetic sphere supply means separates the magnetic spheres from the endless metal belt at the upper end portion of the upright belt conveyor and supplies the magnetic spheres to the iron-based fine particle adsorption device.

  In the soil purification system according to the present invention, the post-treatment unit adsorbs or adheres to the surface of the 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 for removing harmful metals and the like.

  Generally, in the process of cleaning and classifying contaminated soil using cleaning water, harmful metals are hardly adsorbed (adhered) to gravel and sand, and are adsorbed (adhered) collectively in fine particles. See Patent Document 1). Fine particles include a relatively small amount of iron-based fine particles containing iron or the like to the extent that they can be adsorbed by magnetic force, and a relatively large amount of fine particles that cannot be adsorbed by magnetic force other than iron-based fine particles (hereinafter referred to as " Non-ferrous fine grains "). On the other hand, since iron and the like have a property of adsorbing harmful metals and the like (for example, refer to Non-Patent Document 2), the adsorption amount (adhesion amount) of the iron-based fine particles including iron and the like exposed on the surface ) Is much larger than the adsorption amount (adhesion amount) of non-ferrous fine particles such as harmful metals.

  Then, in the soil purification system according to the present invention, gravel and / or sand is crushed by a wet crusher to generate fine particles, but among these fine particles, uneven distribution or points in gravel or sand. The fine particles containing a large amount of fine particles such as iron that existed are iron-based fine particles, and the iron, etc. exposed on the surface of these iron-based fine particles are fed from the wet crusher to the iron removal device. A relatively large amount of harmful metals are adsorbed in a series of distribution processes. Therefore, the iron-based fine particles that were present before the crushing and the iron-based fine particles that were generated by the crushing were introduced into the iron removal device. Adsorbs harmful metals, etc. (compared to fine particles).

  Thus, in the iron removal device, the mixture of the magnetic spheres and sludge in the movable container is agitated by the swinging or vibration of the movable container, and the iron-based fine particles in the sludge are magnetically attracted to the magnetic spheres. Since it is removed from the sludge, the content rate or retention rate of the harmful metal or the like in the sludge can be reduced. Therefore, it is possible to reduce the load of harmful metals or the like on the post-treatment unit that chemically or physicochemically treats the sludge discharged from the iron removal device (pre-treatment unit). As a result, it is possible to reduce the required amount or the amount of the treatment agent such as the chemical agent or the adsorbent, and it is possible to reduce the soil treatment cost. 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 operating cost is very low.

  In each magnetic sphere, a plurality of permanent magnets are mounted in the hollow portion of the hollow sphere so that magnetic poles (for example, N poles) of the same magnetic are directed outward in the radial direction of the sphere. Repel each other. Therefore, in the iron-based fine particle adsorption device, on the screen device, or in other magnetic sphere moving paths, the magnetic spheres do not stick to each other to form lumps (bunches of grapes), and While repelling each other, they can move smoothly while being appropriately separated.

It is a block diagram showing a schematic structure of a soil purification system concerning Embodiment 1 of the present invention. It is a typical elevation view of the iron removal apparatus (pretreatment part) which comprises a soil purification system. (A) is a plan view of an iron-based fine-particles adsorption device that constitutes the iron-based removal device, (b) is a side cross-sectional view of the iron-based fine-particles adsorption device shown in (a), and (c) is a sectional view. It is a BB line sectional view (cross-sectional view) of the iron-based fine particle adsorption device shown in (b). (A) is a cross-sectional view of the movable container with the opening facing upward, and (b) is a movable container in a state rotated by a predetermined angle in the counterclockwise direction from the state shown in (a). It is a cross-sectional view of a container, (c) is a cross-sectional view of the movable container in the state rotated by a predetermined angle in the clockwise direction from the state shown in (a), (d) in (a) It is a transverse cross-sectional view of the movable container in a state rotated 180 ° from the state shown (inverted state). It is a typical sectional view of a magnetic sphere. It is a typical partial section elevation view of a centrifuge. (A) is a typical side view of a part of a magnetic sphere conveyance conveyor and an upright belt conveyor, (b) is a typical side view of a part of an upright belt conveyor, (c) is an upright. It is a typical front view of some mold belt conveyors. It is a block diagram which shows schematic structure of the chelate cleaning apparatus (post-processing part) which is a component of a soil purification system. FIG. 3 is a schematic elevational view showing the configuration of a mixing and dispersing device that forms a part of the chelate cleaning device. (A) is a schematic plan view of a fine particle cleaning device forming a part of a 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 specifically described with reference to the accompanying drawings.
(Embodiment 1)
As shown in FIG. 1, in the soil purification system S according to the first embodiment of the present invention, the soil is collected by excavation of the ground contaminated with harmful metals and the like (toxic metals and / or their compounds, or ions of these). The 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 input hopper 1 is continuously or intermittently charged into the mixer 2 and mixed with the wash water continuously supplied to the mixer 2. Here, the soil includes gravel (for example, a particle size of 2 to 75 mm), sand (for example, a particle size of 0.075 to 2 mm), and fine particles (for example, a particle size of 0.075 mm or less). ) And, in some cases, stone (for example, having a particle size of 75 mm or more).

  The mixture containing the soil and the wash water (hereinafter referred to as “soil / water mixture”) generated by the mixer 2 is transferred to the 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, 10 steel rods of 75 mmφ × 2 m) are arranged in a drum, and the rods are rotated in parallel with each other by the rotation of the drum. It moves and makes line contact, and the impact force, shearing force, frictional force, etc., can crush gravel and sand (and in some cases stones) to produce small-sized 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 gravel and sand are partly fine-grained, not all.

  Thus, the mill breaker 3 crushes gravel and sand (and in some cases 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 and the like that are adsorbed (adhered) 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 that have been released into the water are hardly adsorbed on the gravel and sand, or do not adhere to them, and are aggregated and adsorbed in the fine particles. Or attached (see, for example, Non-Patent Document 1).

  Further, a large number of iron-based fine particles are formed in which minute agglomerates of iron or the like (iron and / or iron oxide) that are present or unevenly distributed or scattered in the gravel and sand are exposed on the surface. On the other hand, iron or the like generally has a property of adsorbing harmful metals or the like. Therefore, a part or most of the harmful metals and the like existing in the wash 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 the ferrous fine particles of the harmful metal or the like becomes considerably larger than the adsorption amount (adhesion amount) of the non-ferrous fine particles of the harmful metal or the like. In other words, the fine particles discharged from the mill breaker 3 include iron-based fine particles having a large adsorption amount (adhesion amount) of harmful metals and non-ferrous fine particles having a small adsorption amount (adhesion amount) of harmful metals. Composed of and. It is needless to say that the iron-based fine particles existing before the crushing also adsorb a considerable amount of harmful metals and the like as compared with the non-iron-based 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) has a property of adsorbing harmful metals and the like, and by utilizing this property, sludge containing harmful metals and the like can be treated with iron powder or iron oxide. 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, iron-based fine particles in which fine lumps of fresh iron (which have not yet adsorbed harmful metals etc.) are exposed on the surface are generated, There has not been proposed a method for treating harmful metals or the like by adsorbing the harmful metals or the like to the exposed minute lumps of iron or the like (fine iron-based particles).

  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 the horizontal plane. Can be rotated about its central axis (the central axis of the cylinder) by a motor. Further, cleaning water can be sprayed in the drum screen.

  When the soil / water mixture flows inside the rotating drum screen of the Trommel 4, the soil particles smaller 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 to the inside of 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 to the outside of the drum screen via the opening end on the lower side of the drum screen.

  In this trommel 4, the classification diameter (opening) of the mesh of the drum screen is set so 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 this trommel 4, the gravel which is a soil particle with a particle size of 2 mm or more (and also stone in some cases) is separated from the soil-water mixture. As described above, the harmful metals and the like that have separated into the water are scarcely adsorbed or adhered to the gravel and sand, so the gravel separated by the trommel 4 is clean, and is used as an aggregate for concrete, for example. be able to. In addition, the mesh size (opening) of the drum screen of the Trommel 4 is not limited to the above-mentioned one, and can be set arbitrarily according to the particle size of the soil particles to be obtained. Is.

  Soil particles having a particle size of less than 2 mm, which are contained in the receiving tank of the trommel 4, that is, a soil / water mixture containing sand and fine particles and washing water are introduced into a cyclone 5 (a liquid cyclone). Although not shown in detail, the cyclone 5 pumps the soil-water mixture into a substantially conical cylinder that narrows downward to generate a swirling flow, and utilizes the centrifugal force generated by this to generate a swirling flow. The soil / water mixture is a mixture of fine particles having a relatively small particle size (for example, a particle size of less than 0.075 mm) and water, and sand having a relatively large particle size (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-containing 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. To be done. Here, since the mixture of sand and water discharged from the lower end of the cyclone 5 contains almost no harmful metals and the like as described above, 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 adjusting tank 6.

  In the pH adjusting tank 6, the pH (hydrogen index) of the water containing fine particles is made almost neutral by using an acid solution (eg, sulfuric acid, hydrochloric acid) and an alkaline solution (eg, sodium hydroxide aqueous solution). Adjusted. Although not shown, in the pH adjusting tank 6, the pH of the water containing fine particles is automatically adjusted by an automatic pH controller including 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 aggregating tank 7. In the aggregating tank 7, a polyaluminum chloride solution (PAC), a polymer aggregating agent, and a pH adjusting agent (acidic solution or alkaline solution) are added to the water containing fine particles. As a result, a large number of flocs in which the water-insoluble metal hydroxide and the fine particles are mixed are generated in the flocculation tank 7.

  The water containing fine particles in the flocculation tank 7 is introduced into the thickener 8. The thickener 8 is not shown in detail, but the water-insoluble flocs or fine particles are allowed to settle by gravity while the water containing fine particles is almost stationary, and the sludge layer (for example, solid matter) located at the bottom is Minute ratio of 5 to 10%) and supernatant water (washing water) located at the top and containing almost no flocs or fine particles. When floating oil floats on the surface of the supernatant water, this floating oil is removed by overflowing a small amount of the supernatant water from the upper portion of the thickener 8.

  The supernatant water in the thickener 8 is introduced into the wash water tank 10 and is temporarily stored as wash water. The spare water tank 11 is used when the cleaning water tank 10 is full. The wash water stored in the wash water layer 10 or the preliminary water tank 11 is supplied to the mixer 2 and the trommel 4 as circulating water. When the amount of cleaning water stored in the cleaning water tank 10 decreases due to evaporation or the like, tap water is appropriately replenished. On the other hand, the sludge accumulated under the thickener 8 is transferred to the intermediate tank 9 and temporarily stored therein. The series of devices 1 to 9 from the input 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 transferred to the iron removing device 12 by a sludge pump or the like (not shown). The iron removing device 12 reduces the content of harmful metals and the like in the sludge by magnetically adsorbing and removing the iron-based fine particles from the sludge. 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 manufacturing. A specific configuration and function of the iron removal device 12 will be described later in detail.

  The sludge discharged from the iron removal device 12 is introduced into the filter press 13 and dehydrated, and a filtrate and a cake are produced. Then, the filtrate is returned to Thickener 8. On the other hand, the cake is transferred to the chelate cleaning device 14 to remove harmful metals and the like remaining in the fine particles (non-ferrous fine particles). Here, if the content rate of the harmful metal or the like in the fine particles contained in the cake is within the standard, the cake is disposed of by landfill or the like without being transferred to the chelate cleaning device 14. Instead of the filter press 13, another filter, such as a vacuum filter, may be used. The specific configuration and function of the chelate cleaning device 14 will be described in detail later.

Hereinafter, the specific configuration and function of the iron removal device 12 as the pretreatment unit will be described with reference to FIGS. 2 to 7.
As shown in FIG. 2, the iron content removing device 12 has, as its main component, an iron-based fine particle content adsorption device that brings a plurality (a large number) of magnetic spheres 20 into contact with sludge discharged from the thickener 8 (see FIG. 1). Device 18, screen device 19 for separating a mixture (composite) of magnetic spheres 20 and sludge discharged from the iron-based fine particle adsorption device 18 into magnetic spheres 20 and sludge, and magnetic spheres received from the screen device 19. A centrifugal separator 22 for removing iron-based fine particles is provided from 20, and a magnetic sphere returning device 23 for returning the magnetic spheres 20 discharged from the centrifugal separator 22 to the iron-based fine particle adsorption device 18.

  Further, the iron removing device 12 temporarily stores the magnetic spheres 20 supplied to the iron-based fine particle adsorbing device 18, the centrifuge 22, or the magnetic sphere returning device 23, respectively. The containers 24 to 26 and a sludge storage tank 27 for temporarily storing the sludge flowing down from the screen device 19 are provided. As will be described later, in the magnetic sphere 20, a plurality of permanent magnets 30 have magnetic poles (N poles or S poles) of the same magnet in the hollow portion of the hollow spherical body 29 so as to face outward in the radial direction of the spherical body. It is mounted (see FIG. 5).

  The iron-based fine particle adsorption device 18 receives a plurality (a large number) of magnetic spheres 20 and sludge discharged from the thickener 8 (see FIG. 1) in a movable container 100 capable of swinging (moving), and magnetizing the sludge. The mixture of the spheres 20 and the sludge is agitated by rocking the movable container 100, and the iron-based fine particles in the sludge are magnetically attracted to the magnetic spheres 20. The specific structure and function of the iron-based fine particle adsorption device 18 will be described later with reference to FIGS. 3 and 4.

  The screen device 19 receives the mixture of the magnetic spheres 20 and the sludge discharged from the iron-based fine particle adsorption device 18, and separates (screens) the magnetic spheres 20 and the sludge. Although not shown in detail, the screen device 19 has a mesh-like or lattice-like screen below the movable container 100 and extending obliquely while descending toward the second magnetic sphere storage container 25. The openings (opening size) of the screen are such that the magnetic spheres 20 cannot pass through.

  When the mixture containing the magnetic spheres 20 and the sludge is dropped or flows from the iron-based fine particle adsorption device 18 onto the screen, the magnetic spheres 20 roll on the inclined screen and the second magnetic sphere storage container. Drop into 25. On the other hand, the sludge passes through the mesh or opening of the screen, flows down, and is stored in the sludge storage tank 27. The iron removing device 12 is provided with a sludge pump 34 for transporting the sludge in the sludge storage tank 27 to the filter press 13 (see FIG. 1).

  As shown in FIGS. 3 (a) to 3 (c), the movable container 100 of the iron-based fine particle adsorption device 18 basically has both end plates in the longitudinal direction (direction in which the movable container central axis extends). It has a generally cylindrical shape (drum shape) closed by 101 and 102, but its upper part is cut out and opened (for example, 90 to 120 ° at the central angle) to form a container shape. A rotary shaft 103 is fixed to the movable container 100 so as to extend in the direction in which the central axis of the cylinder extends and penetrate both end plates 101 and 102 to project to the outside of the cylindrical container. The rotary shaft 103 is firmly fixed to both end plates 101 and 102 by a plurality of flanges 104.

  The vicinity of both ends of the rotating shaft 103 is rotatably supported by the bases 107 and 108 via bearings 105 and 106, respectively. One end of the rotating shaft 103 is coaxially connected to the output shaft of the motor 109 with a reducer arranged on the one base 107. The motor with reduction gear 109 enables the output shaft (and thus the rotation shaft 103 and the movable container 100) to rotate at an arbitrary rotation angle within a range of 360 ° or less around the rotation shaft central axis. Is becoming

  FIGS. 4A to 4D show an example of an operation method of the movable container 100 when the iron-based fine-particles adsorbing device 18 causes the magnetic spheres 20 to adsorb the iron-based fine-particles in sludge by magnetic force. There is. In this operation, as shown in FIG. 4A, a large number of magnetic spheres 20 and an appropriate amount of sludge are supplied in the direction indicated by the arrow P1 with the opening of the movable container 100 facing upward. The depth of the mixture of the magnetic spheres 20 and the sludge housed in the movable container 100 is preferably equal to or less than the position of the rotating shaft 103 in order to prevent overflow of the rotating container 100 when the rotating container 100 is rocked. ..

  Next, as shown in FIG. 4B, the movable container 100 is rotated about the central axis of the rotation shaft in the counterclockwise direction (direction indicated by arrow P2) by a predetermined angle (for example, 30 to 45 °). After that, as shown in FIG. 4C, the movable container 100 is swung by a predetermined angle (for example, 30 to 45 °) in the clockwise direction (the direction indicated by the arrow P3) around the central axis of the turning shaft. The swinging operation or the rotating operation such as the operation is repeated a predetermined number of times (for example, 20 to 100 times). It should be noted that such swinging operation or rotating operation of the movable container 100 is performed by automatically controlling the rotation angle of the output shaft of the motor 109 with a speed reducer and thus the rotation shaft 103. At that time, the iron-based fine particles adsorbing harmful metals or the like in the sludge or adhering the harmful metals or the like are adsorbed to the outer peripheral surface of the magnetic spheres 20 by magnetic force. As a result, the content of harmful metals and the like in the sludge is reduced.

  After that, as shown in FIG. 4D, the motor 109 with a speed reducer rotates the movable container 100 so that the opening faces downward, and the mixture of the magnetic spheres 20 and the sludge is moved in a direction indicated by an arrow P4. It is discharged and dropped or dropped onto the screen device 19 (see FIG. 2). Such a series of operations shown in FIGS. 4A to 4D are repeated.

  As shown in FIG. 5, in the magnetic sphere 20, a plurality of permanent magnets 30 are roughly mounted in the hollow portion of the hollow spherical body 29 so that the N poles of the permanent magnets 30 are outward in the radial direction of the spherical body. It is a thing. The magnetic sphere 20 may be one in which each of the permanent magnets 30 is mounted so that the S pole thereof faces outward in the radial direction of the spherical body. 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 portion of the hollow spherical body 29. In other words, the hollow spherical body 29 is fitted onto 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 magnetic sphere center direction, and the permanent magnet 30 has a shape (complementary shape) that fits or aligns with the magnet holding hole 32. ) Is formed. Therefore, by inserting or inserting the permanent magnet 30 into the magnet holding hole 32 from the outside of the magnet holding member 31, the permanent magnet 30 can be easily attached to the magnet holding member 31. The shape of the end surface of the permanent magnet 30 located on the radially outer side when mounted on the magnet holding member 31 is preferably a curved surface (a part of the spherical surface) that matches the outer peripheral surface of the magnet holding member 31. By doing so, the outer peripheral surface of the assembly of the permanent magnets 30 and the magnet holding member 31 becomes spherical, and the assembly and the hollow spherical body 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 spherical body 29) is practically set to, for example, 3 to 5 cm in order to facilitate the transportation or transportation of the magnetic sphere 20. Further, the apparent density (or bulk density) of the magnetic spheres 20, that is, the value obtained by dividing the mass of the magnetic spheres 20 by the volume thereof is to reduce the weight as much as possible without levitating the magnetic spheres 20 in the sludge. , 1.1 to 1.3 g / cm ³ is practical. The apparent density of the magnetic spheres 20 can be adjusted or increased / decreased by appropriately setting the size of the permanent magnets 20, the number of the permanent magnets 20 mounted, the volume of the magnet holding member 31 or the hollow portion thereof, and the like. It is easy to adjust the apparent density of 1.1 to 1.3 to 1.3 g / cm ³ .

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

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

  As shown in FIG. 2 again, the first magnetic sphere storage container 24 is arranged above the iron-based fine particle adsorption device 18, and the opening degree is provided at the lower end (bottom) of the first magnetic sphere storage container 24. An opening / closing door 24a capable of freely adjusting is attached. By adjusting the opening degree of the opening / closing door 24a, the magnetic spheres 20 stored in the first magnetic sphere storage container 24 are discharged downward at a desired passage amount (flow rate) to adsorb iron-based fine particles. The movable container 100 of the device 18 can be supplied.

  The second magnetic sphere storage container 25 is arranged below the front end (lower end) of the screen device 19 which is inclined downward, and the magnetic sphere 20 rolled on the screen of the screen device 19 is the front end part of the screen. It falls by gravity and is accommodated in the second magnetic sphere storage container 25. Since the magnetic spheres repel each other by a magnetic force (repulsive force), the magnetic spheres 20 do not aggregate in a lump or a tuft of grapes during movement, and can move smoothly and quickly (the magnetic sphere 20). However, the same applies when moving within a device or container, or moving to another device or container).

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

  As shown in FIG. 6, the centrifuge 22 has a housing 35, which is a substantially cylindrical container, and a bearing device 36 which is arranged coaxially with the housing 35 in the housing 35 and fixed to the housing 35. The rotary cylinder 37 is rotatably supported around the axis. An upper opening / closing door 37a and a lower opening / closing door 37b that can be opened and closed at any time are attached to the upper end and the lower end of the rotary cylinder 37, respectively. The circumferential portion (side portion) of the rotary cylinder 37 is formed of a cylindrical mesh member or lattice member having a large number of openings with which the magnetic sphere 20 cannot pass. The rotary cylinder 37 is rotationally driven by a motor 39 via a gear mechanism 38. A belt / pulley mechanism may be used instead of the gear mechanism 38. Further, inside the housing 35, there is provided a hollow truncated cone-shaped baffle 40 (umbrella-shaped baffle plate) for receiving and dropping iron-based fine grain particles flying horizontally from a rotating cylinder 37 rotating at high speed by centrifugal force. It is arranged.

  As is apparent from FIG. 2, the third magnetic sphere storage container 26 is disposed below the centrifuge 22, and when the lower opening / closing door 37b (see FIG. 6) is opened when the rotating cylinder 37 is stopped, the rotation is prevented. The magnetic sphere 20 in the cylinder 37 falls by gravity and is housed 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) downward at a desired passage amount (flow rate).

  Below 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 horizontally by the belt 41a. A horizontal belt conveyor 41 that supplies the upright belt conveyor 42 to the upright belt conveyor 42 is provided. The horizontal belt conveyor 41 has one end portion (upstream end in the magnetic sphere transportation direction) located near the lower end portion of the third magnetic sphere storage container 26 and the other end portion (downstream end in the magnetic sphere transportation direction). Is arranged near the lower end of the upright belt conveyor 42. The horizontal belt conveyor 41 and the upright belt conveyor 42 are constituent elements of the magnetic ball returning device 23.

  The belt 41a is made of a flexible non-magnetic material (for example, rubber). Then, on both sides of the belt 41a, side plates (not shown) are provided which are arranged close to the belt side portions and prevent the magnetic balls 20 on the belt from falling off from the belt side portions. .. Alternatively, the side plate may not be provided, and 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, 43b arranged slightly above the horizontal belt conveyor 41, and a position just above the drive rollers 43a, 43b and slightly higher than the upper end of the first magnetic sphere storage container 24. A ring-shaped (endless) ring made of a ferromagnetic material (for example, steel, stainless steel, etc.) wound around the two driven rollers 44a and 44b, the drive rollers 43a and 43b, and the driven rollers 44a and 44b. A metal belt 45 and a plurality of idle rollers 46 are provided. Here, the drive rollers 43a and 43b are rotationally driven counterclockwise by a motor (not shown). Along with this, the metal belt 45 runs counterclockwise between the drive rollers 43a and 43b and the driven rollers 44a and 44b. Here, in the drive roller 43a, a plurality of permanent magnets 49 (see FIG. 7) are provided in the drive roller 43a in order to assist the movement / adsorption of the magnetic balls 20 on the belt 41a to the metal belt 45, and the S pole is in the roller radial direction. It is installed so that it faces outward. When the permanent magnet 30 is mounted on the magnetic ball 20 so that the S pole is outward in the radial direction of the spherical body, the permanent magnet 49 is installed so that the N pole is outward in the roller radial direction. It The idle roller 46 contacts the inner surface (back surface) of the ring-shaped metal belt 45, and regulates the position or running path of the metal belt 45 so that the metal belt 45 runs on a predetermined running path.

  Since the metal belt 45 is made of a ferromagnetic material, the magnetic spheres 20 can be magnetically attached to the metal belt 45. The magnetic characteristics or magnetic strength of the permanent magnet 30 (see FIG. 5) of the magnetic sphere 20 is such that the magnetic sphere 20 is below the metal belt 45 at an appropriate interval (for example, 5 when the metal belt 45 extends in the horizontal direction). It is set so that the magnetic spheres 20 can move upwards against the gravity and magnetically adhere to the lower surface of the metal belt when they are arranged apart from each other by about 15 mm).

  Further, in the horizontal belt conveyor 41, the magnetic balls 20 are magnetically applied to the lower surface of the metal belt between the top of the magnetic balls 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 so as to have the above-mentioned appropriate spacing which can be attached. Therefore, the magnetic balls 20 transported to the lower side of the upright belt conveyor 42 by the horizontal belt conveyor 41 sequentially adhere to the lower surface of the metal belt by magnetic force.

  As shown in FIGS. 7A to 7C, 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 (traveling direction) of the metal belt 45. A plurality (a large number) of magnetic sphere locking members 47 in the form of prisms or rods 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 removed from the metal belt 45 (for example, screwed) and has durability against a collision with the magnetic ball 20. For example, synthetic resin or aluminum alloy can be used.

  When the metal belt 45 extends in the vertical direction and travels or moves upward, the magnetic ball locking member 47 causes the magnetic balls 20 attached to the surface of the metal belt 45 by magnetic force to move downward due to gravity. Stop rolling. It is practical that the height or protrusion length of the magnetic ball locking member 47 from the surface of the metal belt is 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 balls 20.

  Thus, the magnetic spheres 20 transported by the horizontal belt conveyor 41 and magnetically attached to the metal belt 45 at or near the lower end portion of the upright belt conveyor 42 are moved downward by the metal belt 45 running in the counterclockwise direction. It is conveyed to the upper end of the upright belt conveyor 42 without moving or rolling.

  As is clear from FIG. 2, in the vicinity of 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 upright belt conveyor side is located near the driven roller 44a, while the end 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 side toward the first magnetic sphere storage container side. The guide member 48 is made of a non-magnetic material.

  In the positional relationship in FIG. 2, the magnetic sphere 20 attached to and moving on the metal belt 45 running in the counterclockwise direction makes collision or contact with the end of the guide member 48 in the vicinity of the driven roller 44a. As a result, the magnetic sphere 20 is separated from the metal belt 45 by the guide member 48, rolls on the upper surface of the guide member 48, and falls into the first magnetic sphere storage container 24. That is, the magnetic spheres 20 continuously discharged downward from the third magnetic sphere storage container 26 are supplied to the first magnetic spheres by the magnetic sphere returning 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, the first magnetic sphere storage container 24, the iron-based fine particle adsorption device 18, the screen device 19, the second magnetic sphere storage container 25, the centrifuge 22, The third magnetic sphere storage container 26 and the magnetic sphere returning device 23 (horizontal belt conveyor 41, upright belt conveyor 42, guide member 48) are circulated and moved. The seven broken line arrows in FIG. 2 indicate the moving direction of the magnetic sphere 20. The magnetic spheres 20 move intermittently or batchwise from the first magnetic sphere storage container 24 to the third magnetic sphere storage container 26, and continuously from the third magnetic sphere storage container 26 to the first magnetic sphere storage container 24. Move to.

  Hereinafter, an example of the operation method of the iron removal device 12 will be described. The movable container 100 of the iron-based fine particle adsorption device 18 is intermittently or batchwise supplied with a large number of magnetic spheres 20 from which the iron-based fine particle storage container 24 does not substantially adsorb iron-based fine particle components. On the other hand, from the intermediate tank 9 (see FIG. 1), sludge substantially consisting of fine grains (iron fine grains and non-ferrous fine grains) and water is intermittently or batchwise supplied. Then, in the movable container 100 of the iron-based fine particle adsorption device 18, the mixture of the magnetic spheres 20 and the sludge is agitated by rocking or rotating the movable container 100. At that time, the iron-based fine particles in the sludge are magnetically attracted to the outer peripheral surface of the magnetic sphere 20.

  The iron-based fine particles are produced by crushing gravel and sand with a mill breaker 3 (see FIG. 1) that is a wet crusher, or are present before crushing gravel and sand. A small lump of iron or the like is exposed on the surface, and a harmful metal or the like is adsorbed on the exposed small lump of iron or the like. Generally, small pieces of iron or the like are unevenly distributed or scattered in the gravel and sand, and the proportion of such small pieces is about 2 to 7% by mass. Therefore, at least a part of the fine particles generated by the crushing of the gravel and the sand becomes the iron-based fine particles in which the fresh iron (that is, the harmful metal or the like is not adsorbed) is exposed on the surface.

Iron is a ferromagnetic material (soft magnetic material) and is adsorbed by a magnet. Further, the iron oxides existing in the soil are substantially triiron tetraoxide (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-diiron trioxide are ferromagnetic materials (soft magnetic materials) and are adsorbed by the magnet. Note that α-type diiron trioxide is not magnetized and is not adsorbed by the magnet. Therefore, the iron-based fine particles in which minute lumps of iron or the like are exposed on the surface are permanent magnets in the magnetic sphere 20 due to the ferromagnetism (soft magnetism) of iron, triiron tetraoxide, or γ-type diiron trioxide. It is attracted to 30 (see FIG. 5) and is magnetically attracted to the outer peripheral surface of the magnetic sphere 20 (hollow sphere 29).

  Fine lumps of iron and the like exposed on the surface of iron-based fine particles generated by crushing gravel and sand with a mill breaker 3 (see FIG. 1) are unevenly distributed or scattered in gravel or sand. It is generated from a small lump of fresh iron or the like that has not adsorbed harmful metals and the like, and is exposed on the surface after crushing and adsorbs harmful metals and the like or ions thereof from the cleaning water around it. Thus, the fine particles discharged from the mill breaker 3 (see FIG. 1) and introduced into the iron-based fine particle adsorption device 18 are the iron-based fine particles having a relatively (or considerably) large adsorption amount of harmful metals and the like. , Non-ferrous fine particles that have a relatively (or considerably) small amount of adsorption of harmful metals and the like.

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

  The mixture of the magnetic spheres 20 and sludge discharged downward from the movable container 100 of the iron-based fine particle adsorption device 18 is introduced into the screen device 19, and the magnetic spheres 20 adsorbing the iron-based fine particle components and the iron-based fine particle components. Fine particles are separated into sludge that has been removed. The magnetic spheres 20 are stored in the second magnetic sphere storage container 25, and the sludge is stored in the sludge storage tank 27.

  Sludge (fine particles) discharged from the iron-based fine particle adsorption device 18 and separated by the screen device 19 is filtered by the filter press 13, and the chelate cleaning device 14 (FIG. 1) is applied to the filter cake. Although the chelate cleaning treatment with the chelating agent is performed in (1), the harmful metal and the like in the sludge is reduced by the iron-based fine particle adsorption device 18 as described above, and thus the chelate cleaning treatment of the fine particle (sludge) or The load of harmful metals and the like on the regeneration treatment of the chelating agent is reduced. Therefore, the necessary amount or the amount of the chelating agent used in the soil purification system S can be reduced, and the soil treatment cost can be reduced. That is, the iron-based fine particle adsorption device 18 (iron removal device 12) functions as a pretreatment device or a pretreatment device for reducing the load of harmful metals or the like on the chelate cleaning device 14.

  The magnetic spheres 20 adsorbing the iron-based fine particles in the second magnetic sphere storage container 25 are appropriately supplied to the rotary cylinder 37 of the centrifuge 22. Specifically, while the upper opening / closing door 37a is opened, the lower opening / closing door 37b is closed, the opening / closing door 25a is opened, and the second magnetic sphere storage container 25 is processed once into the rotary cylinder 37. A minute magnetic sphere 20 is supplied. For example, the amount of the magnetic spheres 20 occupying 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 activated, 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 attached 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 rotary cylinder 37 are formed. Or it goes through the hole and jumps out. Here, the rotation speed of the rotary cylinder 37 depends on the radius of the rotary cylinder 37, the magnetic force of the magnetic spheres 20, the magnetic characteristics of the iron-based fine particles, and most of the iron-based fine particles are released from the magnetic spheres 20. It is preferably set to be separated.

  The iron-based fine particles separated from the magnetic sphere 20 and jumping out of the rotary cylinder 37 collide with the baffle 40 and then fall to be accumulated in the bottom portion of the housing 35. The iron-based fine particles in the housing 35 are appropriately discharged to the outside manually. The removed iron-based fine particles can be used, for example, as an iron-making raw material. Then, after a lapse of a predetermined time (for example, 2 to 5 minutes), the rotation of the motor 39 and thus the rotary cylinder 37 is stopped. After that, the lower opening / closing door 37b is opened, and the magnetic spheres 20 from which the iron-based fine particles in the rotary cylinder 37 are substantially removed fall 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 to the vicinity of the lower end of the upright belt conveyor 42 by the belt 41a. After that, the magnetic balls 20 on the belt 41 a are transported to the upper end portion thereof by the upright belt conveyor 42 and introduced into the first magnetic ball 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 of the opening / closing door 26a. It is adjusted so as to be less than the maximum transport amount of the conveyor 42.

  Hereinafter, the configuration and function of the chelate cleaning device 14 as the post-processing unit will be described. When the content of harmful metals or the like in the cake discharged from the filter press 13 is lower than a predetermined regulation value when the cake is disposed of by landfilling or reuse, it is necessary to use the chelate cleaning device 14 which is the post-treatment section. Or need not be provided.

  First, with reference to FIG. 8, the general configuration and function of the cleansing device 14 will be described. In the chelate cleaning device 14, first, the cake (filter cake) discharged from the filter press 13 (see FIG. 1) and the chelate cleaning liquid containing the chelating agent in the cleaning liquid storage tank 56 are continuously supplied to the mixing and dispersing device 51. To be done. Then, the mixing / dispersing device 51 mixes the cake and the chelate cleaning liquid, and the fine particles or small pieces of the fine particles (for example, the particle size is about several 0.1 to 0.5 mm or 0.1) in the chelate cleaning liquid. A fine particle slurry is produced in which particles of about 1 mm are dispersed (suspended) almost uniformly.

  The fine particle content slurry produced by the mixing and dispersing device 51 is transferred to the fine particle content cleaning device 52. The fine particle cleaning device 52 causes the fine particle slurry to flow with a plug flow (plug flow) so as to ensure a preset residence time (for example, 0.5 to 2 hours) while stirring. The harmful metals and the like adhering to the fine particles are released and captured by the chelating agent in the chelate cleaning liquid. As a result, harmful metals and the like adsorbed (adhered) on the surface of the fine particle component in the fine particle component slurry are removed.

  Here, examples of the chelating agent used in the chelate cleaning liquid include EDTA (ethylenediaminetetraacetic acid), HIDS (3-hydroxy-2,2′-iminodisuccinic acid), IDS (2,2′-iminodisuccinic acid), and MGDA. (Methylglycinediacetic acid), EDDS (ethylenediaminediacetic acid), GLDA (L-glutamic acid diacetic acid) sodium salt, and the like. All of these chelating agents are capable of effectively capturing (chelating) harmful metal or the like contained in the fine particle slurry or fine particle. In addition, it goes without saying that a chelating agent suitable for the treatment is selected or a plurality of types of chelating agents are used according to the kind of harmful metal or the like contained in the fine particles.

  The fine particle slurry discharged from the fine particle cleaning device 52 is transferred to the filtering device 53. The filtering device 53 filters the fine-grained slurry to produce a cake (filter cake) having a water content of 30 to 40 percent and a filtrate. A filter press, a vacuum filter, or the like can be used as the filtering device 53. 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 regenerating unit 54. The cleaning liquid regenerating unit 54 includes a cleaning liquid regenerating device 55, a cleaning liquid storage tank 56, an acid liquid storage tank 57, and a water storage tank 58. Here, although not shown in detail, the cleaning liquid regenerating device 55 has a complexing power higher than that of the chelating agent, and when the cleaning liquid regenerating device 55 comes into contact with the chelate cleaning liquid (filtrate) discharged from the filtering device 53, the harmful metal in the chelate cleaning liquid, Holding a solid phase adsorbent for adsorbing or extracting or a packing (small pieces or particles) to which the solid phase adsorbing material is fixed, from the chelating agent in the chelate cleaning liquid flowing through the gap of the packing to harmful metals, etc. This is a packed tower type device that removes the above and regenerates the chelate cleaning liquid.

  In the cleaning liquid regenerator 55, a chelate cleaning liquid containing a chelating agent that traps harmful 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 is one that supports cyclic molecules on a carrier, has a multipoint interaction by coordination bonds and hydrogen bonds in which cyclic molecules are modified with chelate ligands, and selectively takes in ions such as harmful metals. is there. As a result, harmful metals and the like captured by the chelating agent are released 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 liquid (chelating agent), and the chelate cleaning liquid (chelating agent) can capture the harmful metals and the like again.

  The chelate cleaning liquid thus regenerated by the cleaning liquid regenerator 55 is temporarily stored in the cleaning liquid storage tank 56, and then recirculated to the mixing / 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. The depletion amount of the chelating agent is appropriately replenished.

  A solid-phase adsorbent having a higher complexing power than a chelating agent is, for example, a solid substance such as a gel, and generally, when brought into contact with an aqueous solution containing a chelating agent capturing a metal, the chelating agent and a coordinate bond are formed. It has a strong binding force other than the covalent bond to such an extent that the existing metal ions can be released from the chelating agent and moved to the solid phase adsorbent. When using EDTA (ethylenediaminetetraacetic acid) 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. I have.

  Examples of such solid-phase adsorbents include those in which a cyclic molecule is densely supported on a carrier such as silica gel or resin, and the cyclic molecule is modified with a chelate ligand. When such a solid-phase adsorbent is used, a plurality of various bonds and interactions such as coordination bond and hydrogen bond are generated by the adjacent cyclic molecule and chelate ligand, and multi-point interaction occurs, resulting in metal ion. On the other hand, a stronger chemical bond than that of the chelating agent is generated and the metal ion can be selectively taken in due to the property of the cyclic molecule.

  As the chelate cleaning liquid is regenerated, the amount of harmful metals adsorbed on the solid phase adsorbent increases with time, but the amount of adsorbed harmful metals etc. on the solid phase adsorbent has an upper limit. Therefore, when the amount of adsorbed 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 causes the acid solution in the acid solution storage tank 57 to flow to the cleaning solution regenerator 55 in a state where the chelate cleaning solution is removed, and the harmful metals and the like adsorbed on the solid phase adsorbent are removed 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 regenerator 55. Thus, while the harmful metals and the like are recovered by the acid solution, the solid phase adsorbent is regenerated to be in a state 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 cleaning mechanism (not shown in detail) to remove the acid solution adhering to the solid phase adsorbent. At this time, the water used for washing the solid phase adsorbent circulates between the water storage tank 58 and the cleaning liquid regenerator 55. The detailed configuration of the cleaning liquid regenerating unit 54 and its operation method are described in Japanese Patent No. 6264592 (see FIG. 3 and paragraphs [0035] to [0045]) and Japanese Patent No. 6264593, the patent owner of which is the present applicant. (See FIG. 3 and paragraphs [0035] to [0045]) and the like.

The specific configuration and function of the chelate cleaning device 14 will be described below.
First, with reference to FIG. 9, a specific configuration and function of the mixing / dispersing device 51, which is a component of the chelate cleaning device 14, will be described. 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 formed by dispersing the fine particles in the chelate cleaning liquid. Generate a slurry. Specifically, the mixing / dispersing device 51 pre-mixes a crusher 61 that crushes the cake (fine particles) discharged from the filter press 13, a cake small piece crushed by the crusher 61, and a chelate cleaning liquid. The premixing tank 62 and the mixture produced by the premixing tank 62 are stirred to chelate cake pieces (for example, particles having a particle size of several 0.1 to 0.5 mm or 0.1 to 1 mm). It has a line mixer 63 which is dispersed or suspended in the cleaning liquid.

  Then, in the mixing and dispersing device 51, the cake discharged from the filter press 13 is supplied to the disintegrator 61, and the cake is rotated by the blade 61a that rotates at a high speed, so that the cake has a large number of particles having a particle diameter of several mm (for example, 1 to 5 mm). It is broken into small pieces of cake. On the other hand, the chelate cleaning liquid in the chelate cleaning liquid storage tank 64 is supplied to the crusher 61 by the pump 65 via the pipe line 66. The chelate cleaning liquid storage tank 64 is appropriately supplied with the chelate cleaning liquid from the cleaning liquid storage tank 56 (see FIG. 8). Although not shown in detail, the chelate cleaning liquid is sprayed or supplied to a large number of cake pieces immediately after being crushed by the blade 61a to prevent the cake pieces from sticking to each other. As such a crusher 61, for example, a "dehydrated cake crusher" relating to Taiheiyo Kiko Co., Ltd. or a "dehydrated cake recycling device" relating to Kiko Co., Ltd. can be used. When using a commercially available crusher, it is necessary to attach a mechanism for injecting or supplying the chelate cleaning liquid to a large number of cake pieces immediately after crushing.

  The chelate cleaning 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 agitated and premixed by an agitator 67 which is rotationally driven by a motor. Then, the mixture of the chelate cleaning liquid and the cake pieces in the premixing tank 62 is transferred to the line mixer 63 by the pump 68 via the pipe 69. The line mixer 63 is a flow-type mixer in which a blade that is rotationally driven at a very high speed by a motor is arranged in a horizontal cylindrical stirring chamber, and the chelate cleaning liquid and cake pieces are stirred very violently. However, cakes or fine particles of fine particles (for example, particles having a particle size of several 0.1 to 0.5 mm or 0.1 to 1 mm) are almost uniformly dispersed (suspended) in the chelate cleaning liquid. To produce a fine particle slurry. This fine-grained slurry is transferred to the fine-grained cleaning device 52 (see FIG. 8). As such a line mixer 63, for example, "Satake multi-line mixer" of Satake Chemical Machinery Co., Ltd. or the like can be used.

  Hereinafter, with reference to FIGS. 10A to 10C, a specific configuration and function of the fine particle content cleaning device 52, which is a component of the chelate cleaning device 14, will be described. The fine particle cleaning device 52 adsorbs (adheres) to the fine particles by flowing the fine particle slurry generated by the mixing / dispersing device 51 by a plug flow so as to secure a preset residence time while stirring. ) The harmful metals and the like are removed from the fine particles and captured by the chelating agent.

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

  Two adjacent slurry passages in the slurry passages 75 to 79 have four curved lines in the communicating portion (FIG. 10A) at one end in the slurry passage longitudinal direction (the horizontal direction in the positional relationship in FIGS. 10A and 10B). (The part indicated by the arrow) is communicating with each other. That is, the partition walls 71 to 74 do not exist in these communication portions, and the adjacent slurry passages communicate with each other.

  At the bottom of each of the slurry passages 75 to 79, air discharge pipes 81 to 85 for discharging air into the fine particle slurry and agitating the fine particle slurry are provided. Each of the air discharge pipes 81 to 85 is a perforated pipe that extends in the slurry passage longitudinal direction and has a plurality of air discharge holes arranged in the slurry passage longitudinal direction at the bottom portion (lower side) of the peripheral wall. Although not shown, it is connected to a compressor or blower that supplies compressed air. When the pressurized air is supplied to the air discharge pipes 81 to 85, the air becomes bubbles from the air discharge holes and is discharged into the fine particle slurry and floats up, and the bubbles cause the fine particle slurry to stir. To be done.

  FIG. 10C shows a cross section of the slurry passage 75 on the most upstream side in the flow direction of the fine-grained slurry (the direction indicated by the curved arrow and the straight arrow in FIG. 10A). .. As is clear from FIG. 10C, the air discharge pipe 81 is arranged near the bottom of the slurry passage in the vicinity of one side surface of the slurry passage 75. Therefore, the bubbles discharged from the air discharge pipe 81 rise in the vicinity of this side surface. As a result, in the slurry passage 75, 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, and the fine particle slurry is stirred. The shapes, sizes, capacities, etc. of the storage tank 70 and the respective slurry passages 75 to 79, and the supply amount of the pressurized air to the air discharge pipes 81 to 85 are preset in the fine particle content cleaning device 52. Of water content, flow rate, residence time, flow velocity, flow turbulence (eg Reynolds number), etc.

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

  Then, in the iron removal device 12, the magnetic spheres 20 remove the iron-based fine particles having a large adsorption amount of harmful metals and the like from the sludge in the movable container 100 (see FIG. 3) of the iron-based fine particle adsorption device 18. Therefore, it is possible to reduce the content rate or the retention rate of harmful metals and the like in the sludge. Therefore, it is possible to reduce the load of harmful metals and the like on the chelate cleaning device 14 as a post-treatment part that performs the chelate cleaning treatment on the sludge discharged from the iron removal device 12 (pre-treatment part). Depending on the properties of the soil, the content of harmful metals and the like can be reduced to the extent that it can be dumped or landfilled.

  Since the content of harmful metals and the like in the sludge discharged from the iron removal device 12 is reduced in this way, when the cake discharged from the filter press 13 that filters this sludge is chelated by the chelate cleaning device 14, The use amount or required amount of the chelating agent and the solid phase adsorbent can be reduced, and the treatment cost of soil can be reduced. The mill breaker 3 and the iron removing device 12 have a mechanical structure for physically performing treatment, and do not use any special chemicals for treating harmful metals and the like, and therefore their operating costs are 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. 11. 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 10 are common in many points. Therefore, in order to avoid duplication of description, differences between the soil purification system S ′ and the soil purification system S will be mainly described below. In the constituent elements of the soil purification system S'according to the second embodiment, those common to the constituent elements of the soil purification system S according to the first embodiment are designated by the same reference numerals.

  Although a part of the soil purification system S ′ according to the second embodiment is omitted in FIG. 11, like the soil purification system S according to the first embodiment, from the input hopper 1 to the intermediate tank 9. A series of devices 1 to 9, a wash water storage tank 10, a preliminary water tank 11, and an iron removal 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 cleaning 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. There is.

  Although not shown in detail, the fine particle cleaning device 91 receives sludge containing the non-ferrous fine particles discharged from the iron removing device 12 and cleaning water, and a chelate cleaning liquid containing a chelating agent and water. , These are mixed and stirred to form a fine particle slurry, which is continuously adsorbed (adhered) to the non-ferrous fine particles by continuously flowing so as to secure a preset residence time. The harmful metal or the like is released and captured by the chelating agent, or the harmful metal or the like present in water is captured by the chelating agent. As such a fine particle cleaning device 91, for example, the fine particle cleaning device 52 in Embodiment 1 (see FIGS. 10A to 10C) can be used. The ratio of the flow rate of the sludge supplied to the fine particle cleaning device 91 to the flow rate of the chelate cleaning liquid is set to, for example, 1: 1. The chelating agent used is the same as in the first embodiment.

  The fine particle content slurry discharged from the fine particle content cleaning device 91 is transferred to the filtration device 92. The filter 92 filters the fine-grained slurry to produce a cake having a water content of 30 to 40 percent (filter cake) and a filtrate. A filter press, a vacuum filter, or the like can be used as the filtering device 92. 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 cleaning liquid, is subjected to pressure-feeding to the reverse osmosis membrane separation device 94 after the suspended substance or suspended substance (SS) is removed by a clarification filter 93 (for example, a sand filter). .. Although not shown in detail, the reverse osmosis membrane separation device 94 receives the chelate cleaning 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. Separate into permeate.

  As the reverse osmosis membrane of the reverse osmosis membrane separation device 94, for example, one having 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), etc. Can be used. The crosslinked aromatic polyamide dense layer has a large number of pores having a pore size of about 0.5 to 1.5 nm, and is very thin (for example, 0.2 to 0.25 μm) Semi-permeable membrane. The polysulfone support layer is a relatively thick (for example, 40 to 50 μm) porous membrane that supports or protects the very thin crosslinked aromatic polyamide dense layer to prevent its damage.

The reverse osmosis membrane separation device 94 is of a spiral type, and has a plurality of reverse osmosis membrane elements in which a spirally wound reverse osmosis membrane is housed in a cylindrical container. It is practical that each reverse osmosis membrane element has 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. in Nakatsugawa City, Gifu Prefecture) is It 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 throughput of the chelate cleaning solution is estimated to be about 1.5 m ³ / hr. Therefore, for example, when treating 60 m ³ of the chelate cleaning liquid per hour, 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 (operating pressure) of the chelate cleaning liquid, the discharge amount of the concentrated water and the permeated water, and the concentration ratio of the chelating agent of the concentrated water are fine particle fractions. It is appropriately set according to the amount of chelate cleaning liquid to be supplied to the cleaning device 91 and the concentration of the chelating agent. For example, the ratio of the flow rate of the sludge supplied to the fine particle cleaning device 91 to the flow rate of the chelate cleaning liquid is set to 1: 1 and the chelating agent concentration of the fine particle cleaning device 91 is set to 1% by mass. In such a case, the reverse osmosis membrane separation device 94 generates about 50% of permeated water (chelating agent concentration 0) and about 50% of concentrated water (chelating agent concentration about 2% by mass) of the supply amount of the chelating cleaning liquid. Is set to. Therefore, in the fine particle cleaning device 91, the sludge containing no chelating agent and the chelate cleaning liquid having a chelating agent concentration of about 2 mass% are mixed at a ratio of 1: 1 and the chelating agent concentration in the fine particle cleaning device 91 is 1 mass. % Is maintained.

  The concentrated water discharged from the reverse osmosis membrane separation device 94, that is, the chelate cleaning liquid, is introduced into the chelating agent regenerating device 95 and regenerated. That is, harmful metals and the like are removed and collected from the chelate cleaning liquid (chelating agent), and the chelate cleaning liquid (chelating agent) is in a state of being able to capture the harmful metals and the like again. As such a chelating agent regenerator 95, for example, the cleaning liquid regenerator 54 (see FIG. 8) in the first embodiment can be used.

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

  S soil purification system (Embodiment 1), S'soil purification system (Embodiment 2), 1 input hopper, 2 mixer, 3 mill breaker (wet crusher), 4 trommel, 5 cyclone, 6 PH adjusting tank, 7 Coagulation tank, 8 thickener, 9 intermediate tank, 10 washing water tank, 11 preliminary water tank, 12 iron removal device, 13 filter press, 14 chelate washing device, 18 iron-based fine particle adsorption device, 19 screen device, 20 magnetic spheres, 21 Body part, 21a inclined plate, 22 centrifuge, 23 magnetic sphere returning 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 Opening / closing door, 27 Sludge storage tank, 29 Hollow spherical body, 30 Permanent magnet, 31 Magnet holding member, 32 Magnet holding hole, 34 Sludge port 35 housing, 36 bearing device, 37 rotary 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 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 / dispersing device, 52 fine particle cleaning device, 53 filtration Equipment, 54 cleaning liquid regenerating unit, 55 cleaning liquid regenerating 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 Pipeline, 67 stirrer, 68 pump, 69 pipeline, 7 Storage tank, 71-74 partition wall, 75-79 slurry passage, 81-85 air discharge pipe, 91 fine particle cleaning device, 92 filtration device, 93 clarification filter, 94 reverse osmosis separation device, 95 chelating agent regeneration device, 100 Movable container, 101 end plate, 102 end plate, 103 rotating shaft, 104 flange, 105 bearing, 106 bearing, 107 base part, 108 base part, 109 motor with reduction gear.

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 is
After crushing the gravel and sand while washing the soil with washing water, a soil classification unit that classifies the gravel, sand, and fine particles,
From sludge containing fine particles and washing water separated in the soil classification section, by magnetically adsorbing and removing iron-based fine particles containing iron or iron oxide to the extent that they 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 for performing chemical treatment or physico-chemical treatment on the sludge discharged from the pre-treatment unit to remove harmful metals or compounds thereof adsorbed or adhering to the surface of fine particles in the sludge. Is equipped with
The soil classification section,
A mixer for mixing the soil introduced into the soil classification section and the wash water,
By crushing gravel and sand in a mixture containing soil and wash water discharged from the mixer, it is possible to magnetically adsorb iron or iron oxides that are unevenly distributed or scattered inside the gravel and sand. A wet crusher that produces iron-based fine particles containing a certain amount and adsorbs a harmful metal or a compound thereof to iron or iron oxide exposed on the surface of the iron-based fine particles.
Trommel discharged from the wet crusher, for separating gravel from a mixture containing gravel, sand, fine particles, and washing water,
A liquid cyclone for separating sand from a mixture containing sand, fine particles and washing water discharged from the trommel,
A mixture containing fine particles discharged from the liquid cyclone and washing water, by sedimentation separation, supernatant water, and a thickener for separating into sludge containing fine particles and washing water,
The pre-processing unit,
A plurality of magnetic spheres, in which a plurality of permanent magnets are mounted in the hollow portion of the hollow spherical body so that magnetic poles of the same magnet are directed outward in the radial direction of the spherical body, and sludge discharged from the thickener is swung or An iron-based fine particle fraction that is received in a movable container that can vibrate, agitates the mixture of magnetic spheres and sludge by shaking or vibration of the movable container, and causes the iron-based fine particle component in the sludge to be attracted to the magnetic sphere by magnetic force. Adsorption device,
A screen device that receives a mixture of magnetic spheres and sludge discharged from the iron-based fine particle adsorption device, and separates the mixture into magnetic spheres and sludge,
A centrifugal separator for intermittently receiving the magnetic spheres adsorbing the iron-based fine particles discharged from the screen device in a batch system, and separating the iron-based fine particles from the magnetic spheres by a centrifugal force,
A soil purification system comprising an iron removing device having a magnetic sphere returning device for returning the magnetic spheres discharged from the centrifuge to the iron-based fine particle adsorption device. The magnetic sphere returning device,
A drive roller arranged at a position lower than the lower end of the centrifuge, a driven roller arranged at a position higher than the upper end of the iron-based fine particle adsorption device above the drive roller, and the drive roller. An endless metal belt made of a ferromagnetic metal wrapped around the driven roller, and a magnetism that is attached to the outer surface of the endless metal belt and is attracted to the endless metal belt when traveling above the endless metal belt. An upright belt conveyor having a magnetic ball locking member for locking the descent of the ball,
Magnetic spheres ejected from the centrifuge, magnetic spheres conveying means for conveying to the lower end of the upright belt conveyor to attract the endless metal belt with magnetic force,
2. A magnetic sphere supply unit for separating magnetic spheres from the endless metal belt at the upper end of the upright belt conveyor and supplying the magnetic spheres to the iron-based fine particle adsorption device. The soil purification system described.   The post-treatment unit is a sludge discharged from the pre-treatment unit, a toxic metal adsorbed on or adhering to the surface of fine particles in the sludge by washing with a chelate cleaning liquid containing a chelating agent and water, or its The soil purification system according to claim 1 or 2, further comprising a chelate cleaning device for removing a compound.

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