JP6769589B2 - Soil purification system - Google Patents

Description

The present invention relates to a soil purification system that purifies soil contaminated with harmful metals and / or compounds thereof, including gravel, sand and fine particles.

In recent years, for example, the site of a production facility that uses harmful metals such as chromium, lead, cadmium, selenium, and mercury and / or their compounds (hereinafter, these are collectively referred to as "hazardous metals, etc.") as raw materials or raw materials or their neighboring areas Selenium pollution occurs frequently due to soil pollution in Japan or illegal dumping of industrial waste containing harmful metals. Then, the soil contaminated with harmful metal or the like (hereinafter referred to as "harmful metal contaminated soil") is placed at an existing position (hereinafter referred to as "in-situ"), for example, insolubilization, containment or electrical repair of harmful metal or the like. It is quite difficult to purify more effectively. For this reason, soil contaminated with harmful metals is generally removed from its original position by excavation and purified at an external soil purification facility.

As a method for purifying toxic metal-contaminated soil in such a soil purification facility outside the in-situ, a cleaning method for cleaning toxic metal-contaminated soil with washing water or the like to remove toxic metals or the like has been widely used. .. When the soil contaminated with harmful metals is washed with washing water, most of the harmful metals 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, and the fine particles It is known that it is concentrated on the surface of (see, for example, Non-Patent Document 1).

Therefore, the soil contaminated with harmful metals is washed with washing water, classified into gravel, sand, and fine particles, and then the fine particles are chemically treated to remove harmful metals and the like. It is possible to obtain gravel, sand and fine particles containing almost no harmful metals. Thus, the applicant of the present application has already washed the soil contaminated with harmful metals with washing water, classified it into gravel, sand and fine particles, and then contained a chelating agent and water for the fine particles. We have proposed various soil purification facilities (contaminated soil purification equipment) that remove harmful metals and the like from fine particles by performing a cleaning treatment in (see, for example, Patent Documents 1 and 2).

Japanese Patent No. 5723504 Japanese Patent No. 5723505 Japanese Patent No. 4755159 Japanese Patent No. 6007144

Ministry of the Environment, Water and Air Environment Bureau, Soil Environment Division, "Technical Precautions for Permit Examination, etc. of Contaminated Soil Treatment Industry", p. 21, published in August 2013 Tetsuo Katsura "Wastewater treatment by iron powder method" flotation, vol. 23 (1976), No. 3, P190-198 (https://www.jstage.jst.go.jp/article/rpsj1954/23/3/23_3_190/_pdf)

By the way, this type of soil purification facility by a contaminated soil treatment company usually purifies a large amount of contaminated soil (for example, 2000 tons per day), so that a large amount of fine particles are produced (for example, on a dry basis). 500-600 tons per day). Therefore, when such a large amount of fine particles are washed with, for example, a chelate washing solution, a large amount of a relatively expensive chelating agent is required, which causes a problem that the treatment cost of contaminated soil is high. The required amount or amount of chelating agent used in such a soil purification facility increases as the content of fine-grained harmful metals and the like increases. The same problem occurs when the fine particles are washed with a chemical other than a chelating agent to remove harmful metals and the like. Further, the same problem occurs when the harmful metal or the like is physically and chemically removed by using activated carbon or the like.

The present invention has been made to solve the above-mentioned conventional problems, and the soil containing gravel, sand and fine particles and contaminated with harmful metals or the like is washed with washing water while using gravel and sand. To provide a simple and low treatment cost soil purification system that can be classified into fine particles and can remove harmful metals and the like adsorbed or adhered to the separated fine particles. It is an issue to be solved.

Soil purification for purifying soil contaminated with harmful metals (harmful metals and / or compounds thereof) containing gravel, sand and fine particles, or soil contaminated with these ions, according to the present invention, which was made to solve the above problems. The system includes a soil classification unit, a pretreatment unit, and a posttreatment unit. The soil classification section crushes gravel and sand while washing the soil with washing water, and then classifies the soil into gravel, sand, and fine particles. The pretreatment section removes iron and / or iron oxide (hereinafter collectively referred to as "iron, etc.") to the extent that it can be attracted by magnetic force from sludge containing fine particles and washing water separated in the soil classification section. By magnetically adsorbing and removing the iron-based fine particles contained therein, the content of harmful metals and the like in sludge is reduced. In the post-treatment section, the sludge discharged from the pre-treatment section is subjected to chemical treatment (for example, chelation treatment, acid cleaning treatment, aggregation treatment, etc.) or physicochemical treatment (for example, activated carbon adsorption treatment, ion exchange treatment, etc.). Then, harmful metals and the like adsorbed or adhered to the surface of the fine particles in the sludge are removed.

The pretreatment unit includes an iron-based fine particle adsorption device, a screen device, a centrifuge, and an iron removal device having a magnetic ball return device. The iron-based fine-grained attracting device is composed of a plurality of permanent magnets mounted on a hollow portion of a hollow sphere so that magnetic poles (N pole or S pole) having the same magnetism face outward in the radial direction of the sphere (many). ) And the sludge discharged from the thickener are attached to the outer periphery of the support column arranged so that the central axis extends in the vertical direction, and spirally descends around the support column. It is received at the upper or upper end of the passage, and the mixture of magnetic sphere and sludge is moved downward by gravity in the spiral passage, and the iron-based fine particles in the sludge are attracted to the magnetic sphere by magnetic force during movement. The screen device accepts a mixture of magnetic spheres and sludge discharged from the lower part or the lower end of the iron-based fine particle adsorption device, and separates (screens) the magnetic spheres and sludge. The centrifuge intermittently accepts the magnetic spheres adsorbing the iron-based fine particles discharged from the screen device in a batch system, and uses centrifugal force to separate the iron-based fine particles from the magnetic spheres. Let go. The magnetic ball return device returns the magnetic balls discharged from the centrifuge, which hardly adsorb the iron-based fine particles, to the iron-based fine particle adsorption device.

In the soil purification system according to the present invention, the magnetic ball returning device preferably includes an upright belt conveyor, a magnetic ball transporting means, and a magnetic ball supplying means. Here, 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 higher than the upper end of the iron-based fine particle adsorption device. The endless metal belt made of ferromagnetic metal wound around the drive roller and the driven roller, and the endless metal belt attached to the outer surface of the endless metal belt and attracted to the endless metal belt when traveling upward. It is preferable to have a magnetic ball locking member that locks the descent of the magnetic ball. In this case, the magnetic ball transporting means transports the magnetic ball discharged from the centrifuge to the lower end of the upright belt conveyor or its vicinity, and magnetically attracts the magnetic ball to the endless metal belt. Further, the magnetic ball supply means separates the magnetic ball from the endless metal belt at or near the upper end of the upright belt conveyor and supplies (moves) the magnetic ball to the iron-based fine particle adsorption device.

In the soil purification system according to the present invention, the post-treatment unit includes a fine-grain cleaning device, a filtration device, a reverse osmosis membrane separation device, a chelating agent regeneration device, and a permeated water transfer means. preferable. In this case, the fine particle size cleaning device mixes the sludge discharged from the iron removal device with a chelate cleaning solution containing a chelating agent and water to generate a fine particle size slurry, and the fine particle size slurry is preset. The chelating agent captures harmful metals and the like adhering to the fine particles by flowing the slurry so as to secure the residence time. The filtration device filters the fine particle slurry discharged from the fine particle washing device to generate a filtrate and a filtration cake. The reverse osmosis membrane separator separates the filtrate discharged from the filtration device into concentrated water in which the chelating agent is concentrated and permeated water containing no chelating agent by the reverse osmosis membrane. The chelating agent regenerating device is a solid phase adsorbent that accepts the concentrated water discharged from the reverse osmosis membrane separation device and has a higher complexing power than the chelating agent and adsorbs harmful metals and the like in the concentrated water when it comes into contact with the concentrated water. Harmful metals and the like are removed from the chelating agent in the concentrated water, and the concentrated solution is supplied to the fine particle cleaning device as a chelate cleaning solution. The permeated water transfer means transfers (returns) the permeated water discharged from the reverse osmosis membrane separation device to the thickener.

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

Then, according to the soil purification system according to the present invention, gravel and / or sand is crushed by a wet crusher to generate fine particles, and among these fine particles, the fine particles are unevenly distributed in the gravel or sand. The fine particles containing a large amount of fine particles such as iron that were scattered are iron-based fine particles, and the iron and the like exposed on the surface of these iron-based fine particles are transferred from the wet crusher to the iron remover. Adsorbs a relatively large amount of harmful metals in a series of distribution processes. Therefore, the iron-based fine particles that existed before crushing and the iron-based fine particles generated by crushing are introduced into the iron removal device, and both of these iron-based fine particles are considerably large (non-ferrous). Adsorbs harmful metals (compared to fine particles).

Thus, in the iron removing device as the pretreatment unit, when the mixture of magnetic spheres and sludge moves downward by gravity in the gutter-shaped or groove-shaped spiral passage, the iron-based fine particles in the sludge are removed. It is attracted to the magnetic sphere by magnetic force. In this way, the iron-based fine particles in the sludge that adsorbs a large amount of harmful metals and the like are adsorbed by the magnetic spheres and removed from the sludge, so that the content or retention rate of the harmful metals and the like in the sludge can be reduced. it can. Therefore, it is possible to reduce the load of harmful metals and the like on the post-treatment section where the sludge discharged from the iron removing device is chemically or physicochemically treated. As a result, the required amount or amount of the treatment agent such as chemicals and adsorbents can be reduced, and the soil treatment cost can be reduced. Wet crushers and iron removers have a mechanical structure for physical treatment and do not use any special chemicals or treatment agents, so their operating costs are very low.

In each magnetic sphere, a plurality of permanent magnets are mounted in the hollow portion of the hollow sphere so that the magnetic poles (for example, N poles) of the same magnetism face 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 ball movement paths, the magnetic balls do not adsorb to each other and form a lump (grape tuft), and each magnetic ball. Can move smoothly apart from each other while repelling each other.

It is a block diagram which shows the schematic structure of the soil purification system which concerns on this invention. It is a schematic elevation view of the iron removal device (pretreatment part) which constitutes a soil purification system. It is a schematic perspective view of the iron-based fine particle adsorption device which constitutes an iron removal device. It is a schematic cross-sectional view of a magnetic sphere. It is a typical partial cross-sectional elevation view of a centrifuge. (A) is a schematic side view of a part of a magnetic ball transport conveyor and an upright belt conveyor, (b) is a schematic side view of a part of an upright belt conveyor, and (c) is an upright view. It is a schematic front view of a part of a type belt conveyor. (A) is a schematic plan view of a fine particle cleaning device (a part of a post-processing unit), and (b) is a sectional view taken along line AA of the fine particle cleaning device shown in (a). (C) is an elevation sectional view of one slurry passage of the fine particle cleaning apparatus. It is a schematic elevation view of a chelating agent regenerator (a part of a post-treatment part).

As shown in FIG. 1, in the soil purification system S according to the embodiment of the present invention, soil collected by excavation of harmful metals (harmful metals and / or compounds thereof) or the ground contaminated with these ions. (Contaminated soil) is accepted by the input hopper 1. Examples of harmful metals include chromium, lead, cadmium, selenium, mercury, and metallic arsenic. Then, the soil in the charging hopper 1 is continuously or intermittently charged into the mixer 2 and mixed with the washing water continuously supplied to the mixer 2. Here, the soil contains gravel (for example, particle size 2 to 75 mm), sand (for example, particle size 0.075 to 2 mm), and fine particles (for example, particle size 0.075 mm or less). Some stones (for example, having a particle size of 75 mm or more) are also included.

The mixture containing the soil and the washing water produced by the mixer 2 (hereinafter referred to as “soil / water mixture”) 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 75 mmφ × 2 m steel rods) are arranged in a drum, and the rods are rotated in parallel with each other by the rotation of the drum. It can move and make line contact, and crush gravel and sand (and stones in some cases) by its impact force, shearing force, frictional force, etc. to generate small-diameter soil particles such as fine particles. .. As the mill breaker 3, a ball mill or the like can be used in addition to the rod mill. It should be noted that some of the gravel and sand are in fine particles, and not all of them are in fine particles.

Thus, the mill breaker 3 crushes gravel and sand (and stones in some cases) in the soil / water mixture discharged from the mixer 2 to generate small-diameter soil particles such as fine particles. As a result, harmful metals adsorbed (attached) or contained in gravel and sand are separated into water. At this time, basically (aside from the adsorption by iron etc. described later), the harmful metals etc. that have escaped into the water are hardly adsorbed or adhered to the gravel and sand, and are aggregated and adsorbed into fine particles. Or adhere (see, for example, Non-Patent Document 1).

Further, a large number of iron-based fine particles in which minute lumps of iron or the like (iron and / or iron oxide) that are unevenly distributed or scattered inside the gravel and sand are exposed on the surface are generated. On the other hand, iron and the like generally have the property of adsorbing harmful metals and the like. Therefore, harmful metals or some of these ions existing in the washing water are adsorbed or adhered to the exposed surface of iron or the like of iron-based fine particles. As a result, the adsorption amount (adhesion amount) of the harmful metal and the like of the iron-based fine particles is considerably larger than the adsorption amount (adsorption amount) of the harmful metal and the like of the non-ferrous fine particles. That is, the fine particles discharged from the mill breaker 3 are iron-based fine particles having a large adsorption amount (adhesion amount) of harmful metals and the like, and non-ferrous fine particles having a small adsorption amount (adhesion amount) of harmful metals and the like. Consists of. Of course, the iron-based fine particles that have existed before crushing also adsorb a considerably larger amount of harmful metals and the like than the non-ferrous fine particles.

The iron-based fine particles adsorbing harmful metals and the like in this way are removed by the iron removing device 12 as will be described later. On the other hand, it is generally known that iron and the like (iron and / or iron oxide) have the property of adsorbing harmful metals and the like, and by utilizing this property, iron powder or iron oxide can be added to sludge containing harmful metals and the like. Various "iron powder methods" have been proposed in which harmful metals and the like are removed from sludge by adding powder (see, for example, Patent Documents 3 to 4 and Non-Patent Document 2). However, as in the present invention, by crushing gravel and sand, iron-based fine particles in which fresh (not yet adsorbing harmful metals and the like) minute lumps such as iron are exposed are generated on the surface. A method for treating harmful metals, etc., in which harmful metals, etc. are adsorbed on exposed fine lumps of iron, etc. (iron-based fine particles) has not yet been proposed by anyone other than the applicant or the inventor of the present application. ..

The soil / water mixture discharged from the mill breaker 3 is introduced into the trommel 4. Although not shown in detail, the trommel 4 is a sieving device having a receiving tank capable of storing water and a substantially cylindrical drum screen arranged at an angle with respect to a horizontal plane, and is a drum screen. Can be rotated around its central axis (the central axis of the cylinder) by a motor. In addition, the washing water can be sprayed into the drum screen.

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

In 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, gravel (or stone in some cases), which is a soil particle having a particle size of 2 mm or more, is separated from the soil / water mixture. As described above, harmful metals and the like separated into water are hardly adsorbed or adhered to gravel and sand, so that the gravel separated by Trommel 4 is almost clean, for example, as an aggregate for concrete. Can be used. The mesh size (opening) of the drum screen of Trommel 4 is not limited to the above, and can be arbitrarily set according to the particle size of the soil particles to be obtained. Is.

A soil / water mixture containing soil particles having a particle size of less than 2 mm, that is, sand and fine particles, and washing water contained in the receiving tank of the trommel 4 is introduced into the cyclone 5 (liquid cyclone). Although not shown in detail, the cyclone 5 pumps a 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. A soil / water mixture is a mixture of fine particles with a relatively small particle size (for example, a particle size of less than 0.075 mm) and water, and sand with a relatively large particle size (for example, a particle size of 0.075 mm or more) and water. Separate into a mixture of.

Then, the mixture of fine particles and water (hereinafter referred to as "water containing fine particles") is discharged from the upper end of the cyclone 5, and the mixture of sand and water having a relatively large particle size is discharged from the lower end of the cyclone 5. Will be done. Here, since the sand discharged from the lower end of the cyclone 5 contains almost no harmful metals or the like as described above, it is drained or dried and used as recycled sand. On the other hand, the fine particle-containing water is transferred to the PH adjusting tank 6.

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

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

The fine particle-containing water (including flocs) in the coagulation tank 7 is introduced into the thickener 8 (gravity settling tank). Although not shown in detail, the thickener 8 is a sludge layer (for example, solid) located at the lower part of the sludge layer (for example, solid) in which water-insoluble flocs or fine particles are settled by gravity while the fine particle-containing water is almost stationary. The ratio of the minutes is 5 to 10%), and the supernatant water (washing water) which is located at the upper part and contains almost no flocs or fine particles is formed. When floating oil is suspended on the surface of the supernatant water, this floating oil is removed by overflowing a small amount of the supernatant water from the upper part of the thickener 8.

The supernatant water in the thickener 8 is introduced into the washing water tank 10 and temporarily stored. When the washing water tank 10 is full, the reserve water tank 11 is used. The wash water stored in the wash water layer 10 or the reserve water tank 11 is supplied to the mixer 2 and the trommel 4 as circulating water. When the washing water stored in the washing water tank 10 decreases due to evaporation or the like, tap water is appropriately replenished. On the other hand, the sludge that has settled or accumulated in the lower part of the thickener 8 is transferred to the intermediate tank 9 and temporarily stored. A series of devices 1 to 9 from the 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 as a pretreatment unit. 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, an iron manufacturer or the like and used as a raw material for iron making. The sludge discharged from the iron removal device 12 is treated by the fine particle cleaning device 13, the filtration device 14, the clarification filter 15, the reverse osmosis membrane separation device 16, and the chelating agent regeneration device 17, and is a harmful metal. Almost clean fine particles containing almost no such substances and a chelate cleaning solution are produced. These devices 13 to 17 are components of the post-treatment section of the soil purification system S, and the specific configurations and functions thereof will be described in detail later.

Hereinafter, the specific configuration and function of the iron removing device 12 as the pretreatment unit will be described with reference to FIGS. 2 to 6.
As shown in FIG. 2, the iron removing device 12 attracts a plurality of (many) magnetic spheres 20 and sludge discharged from the thickener 8 (see FIG. 1) as its main component. The device 18, the screen device 19 that separates the mixture (mixture) of the magnetic sphere 20 and sludge discharged from the iron-based fine particle adsorption device 18 into the magnetic sphere 20 and sludge, and the magnetic sphere received from the screen device 19. It includes a centrifuge 22 that removes iron-based fine particles from 20 and a magnetic ball return device 23 that returns the magnetic spheres 20 discharged from the centrifuge 22 to the iron-based fine-grain adsorption device 18.

Further, the iron removing device 12 temporarily stores the magnetic balls 20 supplied to the iron-based fine particle adsorption device 18, the centrifuge 22, or the magnetic ball 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 the same magnetic magnetic poles (N pole or S pole) in the hollow portion of the hollow sphere 29 so that the magnetic poles (N pole or S pole) face outward in the radial direction of the sphere. It is attached (see FIG. 4).

As shown in FIG. 3, the iron-based fine-grained adsorption device 18 has a hollow columnar column 100 arranged so that the central axis extends in the vertical direction, and a column 100 attached to the outer peripheral portion of the column 100 around the column 100. It is provided with a gutter-shaped, duct-shaped, or groove-shaped spiral passage 101 that descends while curving in a spiral shape. It is practical that the diameter of the support column 100 is about 1 to 2 m and the width of the spiral passage 101 is about 0.5 to 1 m. The support column 100 may be a hollow prismatic (for example, a hollow square columnar shape), and the spiral passage 101 may be a path having an angular shape in a plan view, which is gradually lowered and inclined along the outer peripheral portion of the support column 100.

Thus, a large number of magnetic spheres 20 discharged from the first magnetic sphere storage container 24 and sludge discharged from the thickener 8 (see FIG. 1) are located at the upper or upper end of the spiral passage 101 of the iron-based fine particle adsorption device 18. When and is supplied, the mixture of the magnetic sphere 20 and the sludge moves (rolls) or flows by gravity in the spiral passage 101 that descends while curving in a spiral shape. At that time, harmful metals and the like in the sludge are adsorbed, or iron-based fine particles to which the harmful metals and the like are attached are magnetically attracted to the outer peripheral surface of the magnetic sphere 20. As a result, the content of harmful metals and the like in sludge is reduced.

As shown in FIG. 4, in the magnetic sphere 20, a plurality of permanent magnets 30 are generally mounted in the hollow portion of the hollow sphere 29 so that their respective north poles face outward in the radial direction of the sphere. It is a thing. The magnetic sphere 20 may be mounted so that each permanent magnet 30 has its S pole facing outward in the radial direction of the sphere. Specifically, each permanent magnet 30 is fitted into a magnet holding hole 32 formed in a hollow spherical magnet holding member 31. Then, the magnet holding member 31 with the permanent magnet 30 is fitted into the hollow portion of the hollow spherical body 29. In other words, the hollow spherical body 29 is externally fitted on the peripheral surface of the magnet holding member 31, or the peripheral surface of the magnet holding member 31 is covered with the hollow spherical body 29.

The magnet holding hole 32 formed in the magnet holding member 31 is a tapered hole whose cross-sectional area narrows toward the center of the magnetic sphere, and the permanent magnet 30 has a shape (complementary shape) that fits or matches the magnet holding hole 32. ) Is formed. Therefore, the permanent magnet 30 can be easily attached to the magnet holding member 31 by inserting or inserting the permanent magnet 30 into the magnet holding hole 32 from the outside of the magnet holding member 31. The shape of the end face of the permanent magnet 30 located on the outer side in the radial direction when mounted on the magnet holding member 31 is preferably a curved surface (a part of a spherical surface) that matches the outer peripheral surface of the magnet holding member 31. In this way, the outer peripheral surface of the aggregate of the permanent magnet 30 and the magnet holding member 31 becomes spherical, and the aggregate and the hollow sphere 29 can be brought into close contact with each other.

It is practical that the diameter of the magnetic sphere 20 (that is, the outer diameter of the hollow sphere 29) is, 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 sphere 20, that is, the value obtained by dividing the mass of the magnetic sphere 20 by its volume is used to reduce the weight of the magnetic sphere 20 as much as possible without floating it in the sludge. , 1.1 to 1.3 g / cm ³ is practical. The apparent density of the magnetic sphere 20 can be adjusted or increased or decreased by appropriately setting the size of the permanent magnet 20, the number of mounted permanent magnets 20, 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 the magnet to 1.1 to 1.3 g / cm ³ .

The material of the hollow spherical body 29 is not particularly limited as long as it has corrosion resistance against sludge and appropriate mechanical strength, but it is practical to use stainless steel or aluminum (or an alloy thereof). The thickness of the hollow spherical body 29 is preferably about 0.2 to 0.5 mm, for example. If the hollow spheres 29 are 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 fitting the magnet holding member 31 equipped with the permanent magnet 30 into one hemisphere and then screwing the other hemisphere into the hemisphere. The magnetic sphere 20 can be disassembled by releasing the combination.

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

As shown in FIG. 2 again, the screen device 19 receives the mixture of the magnetic spheres 20 and the sludge discharged from the iron-based fine particle adsorbing device 18 and separates (screens) the magnetic spheres 20 and the sludge. Although not shown in detail, the screen device 19 is a mesh-like or grid-like screen that extends downward and inclined toward the second magnetic ball storage container 25 under the iron-based fine particle adsorption device 18. Has. The opening (opening size) of the eyes of this screen is a size that the magnetic sphere 20 cannot pass through.

When a mixture of magnetic spheres 20 and sludge falls or flows down from the iron-based fine particle adsorption device 18 on the screen, the magnetic spheres 20 roll on the inclined screen and the second magnetic sphere storage container. It falls within 25. On the other hand, the sludge passes through the mesh or opening of the screen and flows downward, and is housed 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 fine particle cleaning device 13 (see FIG. 1).

The first magnetic ball storage container 24 is arranged above the iron-based fine particle adsorbing device 18, and the opening degree thereof can be freely adjusted at the lower end (bottom) of the first magnetic ball storage container 24. An opening / closing door 24a is attached. By adjusting the opening degree of the opening / closing door 24a, the magnetic sphere 20 stored in the first magnetic sphere storage container 24 is discharged downward at a desired passing amount (flow rate) to adsorb iron-based fine particles. It can be supplied to the spiral passage 101 of the device 18.

A second magnetic sphere storage container 25 is arranged below the tip (lower end) of the screen that is inclined downward of the screen device 19, and the magnetic sphere 20 that has rolled on the screen of the screen device 19 is the tip of the screen. It falls by gravity from the screen and is housed in the second magnetic ball storage container 25. Since the magnetic spheres repel each other by magnetic force (repulsive force), the magnetic spheres 20 do not gather in the form of lumps or tufts of grapes when moving, and can move smoothly and quickly (magnetic spheres 20). However, the same applies when moving within one device or container, or moving to another device or container).

A centrifuge 22 is arranged below the second magnetic ball storage container 25. The centrifuge 22 intermittently batches the magnetic spheres 20 discharged from the iron-based fine particle adsorption device 18 and temporarily stored in the second magnetic sphere storage container 25 via the screen device 19. (Equation), the iron-based fine particles are separated from the magnetic sphere 20 by centrifugal force. An opening / closing door 25a for dropping the magnetic sphere 20 stored in the second magnetic sphere storage container 25 at any time and supplying it to the centrifuge 22 is attached to the lower end portion (bottom portion) of the second magnetic sphere storage container 25.

As shown in FIG. 5, the centrifuge 22 is arranged coaxially with the housing 35, which is a substantially cylindrical container, and inside the housing 35, and is centered on the housing by a bearing device 36 fixed to the housing 35. A rotary cylinder 37 rotatably supported around the shaft is provided. An upper opening / closing door 37a and a lower opening / closing door 37b that can be opened / closed at any time are attached to the upper end portion and the lower end portion of the rotary cylinder 37, respectively. The circumferential portion (side portion) of the rotary cylinder 37 is formed of a cylindrical net-like member or a grid-like member having a large number of openings through 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, in the housing 35, a hollow truncated cone-shaped baffle 40 (umbrella-shaped obstruction plate) that receives and drops particles of iron-based fine particles flying in the horizontal direction by centrifugal force from a rotating cylinder 37 that rotates at high speed is provided. Have been placed.

As is clear from FIG. 2, a third magnetic ball storage container 26 is arranged below the centrifuge 22, and rotates when the lower opening / closing door 37b (see FIG. 5) is opened when the rotary cylinder 37 is stopped. The magnetic sphere 20 in the cylinder 37 falls due to gravity and is housed in the third magnetic sphere storage container 26. An opening / closing door 26a capable of freely adjusting the opening degree is attached to the lower end of the third magnetic ball storage container 26. By adjusting the opening degree of the opening / closing door 26a, the magnetic sphere 20 in the third magnetic sphere storage container 26 can be continuously discharged (dropped) downward at a desired passing amount (flow rate).

On the lower side of the third magnetic ball storage container 26, the magnetic balls 20 continuously discharged from the third magnetic ball storage container 26 are received on the belt 41a (endless belt) and transported horizontally by the belt 41a. A horizontal belt conveyor 41 for supplying the upright belt conveyor 42 is provided. One end of the horizontal belt conveyor 41 (upstream end in the magnetic ball transport direction) is located near the lower end of the third magnetic ball storage container 26, and the other end (downstream end in the magnetic ball transport direction). Is arranged so as to be located near the lower end of the upright belt conveyor 42. The horizontal belt conveyor 41 and the upright belt conveyor 42 are components of the magnetic ball return device 23.

The belt 41a is made of a flexible non-magnetic material (for example, rubber). On both sides of the belt 41a, side plates (not shown) are provided so as to be arranged close to the belt side portion and prevent the magnetic sphere 20 on the belt from falling off from the belt side portion. .. It should be noted that the side plates may not be provided, and embankment-shaped or bank-shaped protrusions having an appropriate height (for example, 1 to 2 cm) and extending in the belt extending direction may be integrally formed on both side portions of the belt 41a.

The upright belt conveyor 42 is located slightly above the upper ends of the first magnetic ball storage container 24 directly above the two drive rollers 43a and 43b and the drive rollers 43a and 43b arranged slightly above the horizontal belt conveyor 41. A ring-shaped (endless) material made of a ferromagnetic material (for example, steel, stainless steel, etc.) wound around the two driven rollers 44a, 44b, the driving rollers 43a, 43b, and the driven rollers 44a, 44b. It includes a metal belt 45 and a plurality of idle rollers 46.

Here, the drive rollers 43a and 43b are rotationally driven in the counterclockwise direction by a motor (not shown). Along with this, the metal belt 45 orbits between the driving rollers 43a and 43b and the driven rollers 44a and 44b in the counterclockwise direction. Here, in the drive roller 43a, in order to assist the movement / attraction of the magnetic ball 20 on the belt 41a to the metal belt 45, a plurality of permanent magnets 49 (see FIG. 6) have S poles in the roller radial direction. It is mounted so that it faces outward.

In the magnetic sphere 20, when the permanent magnet 30 is mounted so that the S pole faces outward in the radial direction of the sphere, the permanent magnet 49 is mounted so that the north pole faces outward in the radial direction of the roller. The radius. The idle roller 46 comes into contact with the inner surface (back surface) of the ring-shaped metal belt 45, and regulates the position or travel path of the metal belt 45 so that the metal belt 45 travels on a predetermined traveling track.

Since the metal belt 45 is made of a ferromagnetic material, the magnetic sphere 20 can be magnetically attached to the metal belt 45. The magnetic characteristics or magnetic strength of the permanent magnet 30 (see FIG. 4) of the magnetic sphere 20 is such that the magnetic sphere 20 is appropriately spaced below the metal belt 45 (for example, 5) when the metal belt 45 is extended in the horizontal direction. The magnetic sphere 20 is set so that it can move upward against gravity and adhere to the lower surface of the metal belt by magnetic force when it is arranged with an interval of ~ 15 mm).

Further, in the horizontal belt conveyor 41, the magnetic sphere 20 is magnetically applied to the lower surface of the metal belt between the top of the magnetic sphere 20 mounted on the belt 41a and the lower surface of the metal belt at the lower end of the upright belt conveyor 42. It is arranged so that the above-mentioned appropriate spacing that can be attached occurs. Therefore, the magnetic spheres 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. 6A to 6C, 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 (many) magnetic ball locking members 47 in the shape of a prismatic or square rod extending linearly in the width direction of the belt 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 collision with the magnetic ball 20. For example, a synthetic resin or an aluminum alloy can be used.

In the magnetic ball locking member 47, when the metal belt 45 extends in the vertical direction and travels or moves upward, the magnetic ball 20 adhered to the surface of the metal belt 45 by magnetic force moves downward or downward by gravity. Locks to roll. 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 distance between the magnetic ball locking members 47 adjacent to each other in the extension direction (traveling direction) of the metal belt 45 is 1.2 to 1.5 times the diameter of the magnetic ball 20.

Thus, the magnetic sphere 20 transported by the horizontal belt conveyor 41 and magnetically adhered to the metal belt 45 at or near the lower end of the upright belt conveyor 42 is lowered by the metal belt 45 orbiting 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 portion of the upright belt conveyor 42, the magnetic sphere 20 attached to the metal belt 45 by magnetic force is 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 on the first magnetic ball storage container side is located near the upper end of the first magnetic ball storage container 24. .. The guide member 48 is inclined downward from the upright belt conveyor side toward the first magnetic ball storage container side. The guide member 48 is made of a non-magnetic material.

The magnetic sphere 20 that is attached to and moving on the metal belt 45 that orbits in the counterclockwise direction in the positional relationship in FIG. 2 collides with or comes into 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 sphere 20 continuously discharged downward from the third magnetic sphere storage container 26 is the first magnetic sphere by the magnetic sphere return device 23 (horizontal belt conveyor 41, upright belt conveyor 42, guide member 48). It is continuously returned to the storage container 24.

As described above, 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 and the like. The third magnetic ball storage container 26 and the magnetic ball return device 23 (horizontal belt conveyor 41, upright belt conveyor 42, guide member 48) circulate and move. The seven dashed arrows in FIG. 2 indicate the moving direction of such a magnetic sphere 20. Here, the magnetic sphere 20 continuously moves from the first magnetic sphere storage container 24 to the second magnetic sphere storage container 25, and intermittently from the second magnetic sphere storage container 25 to the third magnetic sphere storage container 26. Or, it moves in batches, and continuously moves from the third magnetic ball storage container 26 to the first magnetic ball storage container 24.

Hereinafter, an example of the operation method of the iron removing device 12 will be described. A large number of magnetic spheres 20 that do not substantially adsorb iron-based fine particles from the first magnetic sphere storage container 24 continuously enter the spiral passage 101 (see FIG. 3) of the iron-based fine particle adsorbing device 18. While being supplied, sludge composed of substantially fine particles (iron-based fine particles and non-ferrous fine particles) and water is continuously supplied from the intermediate tank 9 (see FIG. 1). Then, the mixture formed by mixing the magnetic sphere 20 and the sludge moves (rolls) or flows by gravity in the spiral passage 101 that descends while inclining in a spiral shape. At that time, harmful metals and the like in the sludge are adsorbed, or iron-based fine particles to which the harmful metals and the like are attached are magnetically attracted to the outer peripheral surface of the magnetic sphere 20. As a result, the content of harmful metals and the like in sludge is reduced.

The iron-based fine granules are produced by crushing gravel and sand with a mill breaker 3 (see FIG. 1), which is a wet crusher, or exist before crushing gravel and sand. Microlumps such as iron are exposed on the surface, and harmful metals and the like are adsorbed on the exposed microlumps such as iron. Generally, small lumps such as iron are unevenly distributed or scattered in gravel and sand, and the ratio of such small lumps is about 2 to 7% by mass. For this reason, at least a part of the fine particles produced by crushing gravel and sand becomes iron-based fine particles in which fresh iron or the like (that is, harmful metals or the like is not adsorbed) is exposed on the surface.

Iron is a ferromagnet (soft magnetic material) and is attracted to magnets. In addition, the iron oxides present in the soil are substantially triiron tetroxide (Fe ₃ O ₄ ), γ-type diiron trioxide (γ-Fe ₂ O ₃ ), and α-type diiron trioxide (Fe ₃ O ₃ ). It is composed of α-Fe ₂ O ₃ ), and triiron tetroxide and γ-type diiron trioxide are ferromagnetic materials (soft magnetic materials) and are attracted to magnets. The α-type ferric trioxide is not magnetized and is not attracted to the magnet. Therefore, the iron-based fine particles in which minute lumps such as iron are exposed on the surface are permanent magnets in the magnetic sphere 20 due to the ferromagnetic (soft magnetism) of iron, triiron tetroxide or γ-type diiron trioxide. It is attracted to 30 (see FIG. 4) and magnetically attracted to the outer peripheral surface of the magnetic sphere 20 (hollow sphere 29).

Microlumps of iron or 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 the gravel or sand. It is generated from small lumps of fresh iron or the like that have not adsorbed the harmful metals or the like, and is exposed to the surface after crushing and adsorbs the harmful metals or these ions from the surrounding wash water. Thus, the fine particles discharged from the mill breaker 3 (see FIG. 1) and introduced into the iron-based fine particle adsorbing device 18 are the iron-based fine particles having a relatively (or considerably) large amount of adsorbed harmful metals and the like. , It is composed of non-ferrous fine particles with a relatively (or considerably) small amount of adsorbed harmful metals.

Then, as described above, since the iron-based fine particle 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 particle adsorbing device 18 are harmful. Most of them are non-ferrous fine particles with a relatively (or considerably) small amount of metal adsorbed. Therefore, a part or a considerable part of 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.

A mixture of the magnetic spheres 20 and sludge discharged downward from the iron-based fine particle adsorbing device 18 is introduced into the screen device 19, and the magnetic spheres 20 adsorbing the iron-based fine particles and the iron-based fine particles are separated. Separated from the removed sludge. Then, the magnetic sphere 20 is housed in the second magnetic sphere storage container 25, and the sludge is housed in the sludge storage tank 27.

As will be described in detail later, the sludge (fine particles) discharged from the iron-based fine particle adsorption device 18 and separated by the screen device 19 is chelated by the fine particle cleaning device 13 (see FIG. 1). The chelate cleaning treatment is carried out by the chelating agent regenerating device 17 (see FIG. 1), and the chelating agent is regenerated by the solid phase adsorbent. As described above, the iron-based fine particle adsorbing device 18 is in the sludge. Since harmful metals and the like are reduced, the load of harmful metals and the like on the chelate cleaning treatment of fine particles (sludge) and the regeneration treatment of the chelating agent is reduced. Therefore, the required amount or the amount of the chelating agent and the solid phase adsorbent 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 that reduces the load of harmful metals and the like on the fine particle cleaning device 13 or the chelating agent regeneration device 17. ..

The magnetic sphere 20 adsorbing the iron-based fine particles in the second magnetic sphere storage container 25 is appropriately supplied to the rotary cylinder 37 of the centrifuge 22. Specifically, while the upper opening / closing door 37a is opened, the opening / closing door 25a is opened with the lower opening / closing door 37b closed, and the second magnetic ball storage container 25 is processed once into the rotary cylinder 37. The magnetic sphere 20 for the minute is supplied. For example, an amount of magnetic spheres 20 that occupy 1/3 to 1/2 of the space in the rotating cylinder 37 is supplied.

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

The iron-based fine particles that have separated from the magnetic sphere 20 and jumped out of the rotating cylinder 37 collide with the baffle 40, then fall and accumulate at the bottom of the housing 35. The iron-based fine particles in the housing 35 are appropriately manually discharged to the outside. The removed iron-based fine particles can be used, for example, as a raw material for iron making. Then, after a predetermined time (for example, 2 to 5 minutes) has elapsed, 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 sphere 20 from which the iron-based fine particles in the rotary cylinder 37 have been removed is dropped into the third magnetic sphere storage container 26 by gravity.

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

As shown in FIG. 1 again, the sludge discharged from the iron removing device 12 (sludge storage tank 27 in FIG. 2) is introduced into the fine particle cleaning device 13. The fine-grain cleaning device 13 includes sludge containing non-ferrous fine-grains discharged from the iron removing device 12 and cleaning water, and a chelating agent and water supplied from the chelating agent regenerating device 17, which will be described later. Accepts the chelate cleaning solution, mixes and stirs them to generate a fine-grained slurry, and generally with a plug flow (plug flow) so as to secure a preset residence time (for example, 0.5 to 2 hours). By continuously flowing, harmful metals and the like adhering (adsorbing) to the fine particles or these ions are captured by the chelating agent. As a result, harmful metals and the like adsorbed (adhered) to the surface of the fine particles in the fine particle slurry are removed. The ratio of the flow rate of the sludge supplied to the fine particle cleaning device 13 to the flow rate of the chelate cleaning liquid is set to, for example, 1: 1.

Examples of the chelating agent used in the chelate washing solution include EDTA (ethylenediaminetetraacetic acid), HIDS (3-hydroxy-2,2'-iminodiacetic acid), IDS (2,2'-iminodiacetic acid), and MGDA (methylglycine). Diacetic acid), EDDS (ethylenediaminediamine) or GLDA (L-glutamate diacetic acid) sodium salt and the like. All of these chelating agents are capable of effectively capturing (chelating) harmful metals and the like contained in the fine particle slurry or the fine particles. It goes without saying that a chelating agent suitable for the treatment is selected or a plurality of types of chelating agents are used depending on the type of harmful metal and the like contained in the fine particles.

Hereinafter, the specific configuration and function of the fine particle size cleaning device 13 will be described with reference to FIGS. 7 (a) to 7 (c). The fine particle cleaning apparatus 13 has a storage tank 50 provided with five elongated rectangular parallelepiped or prismatic slurry passages 55 to 59 formed by partitioning by four flat partition walls 51 to 54 and extending in parallel with each other. are doing. The storage tank 50 may be, for example, an iron rectangular parallelepiped square tank installed on the ground, or may be a concrete rectangular parallelepiped pit. Further, the partition walls 51 to 54 may be formed by, for example, connecting a plurality of iron plates or plastic plates in the extending direction of the slurry passage.

Two adjacent slurry passages in the slurry passages 55 to 59 are connected to one end in the longitudinal direction of the slurry passage (the left-right direction in the positional relationship in FIGS. 7A and 7B) (four curves in FIG. 7A). The parts indicated by the arrow-shaped arrows) communicate with each other. That is, there are no partition walls 51 to 54 in these communication portions, and adjacent slurry passages communicate with each other.

At the bottom of each of the slurry passages 55 to 59, air discharge pipes 61 to 65 are arranged to release air into the fine particle slurry and stir the fine particle slurry, respectively. Each of the air discharge pipes 61 to 65 is a perforated pipe extending in the longitudinal direction of the slurry passage and having a plurality of air discharge holes arranged in the longitudinal direction of the slurry passage formed at the bottom (lower side) of the peripheral wall. Although not shown, it is connected to a compressor or blower that supplies compressed air. When pressurized air is supplied to the air discharge tubes 61 to 65, the air becomes bubbles from the air discharge holes and is released into the fine particle slurry to float, and the fine particle slurry is agitated by the bubbles. Will be done.

FIG. 7 (c) shows a cross section of the slurry passage 55 on the most upstream side in the flow direction of the fine-grained slurry (the direction indicated by the curved arrow and the linear arrow in FIG. 7 (a)). .. As is clear from FIG. 7C, the air discharge pipe 61 is arranged near the bottom of the slurry passage in the vicinity of one side surface of the slurry passage 55. Therefore, the bubbles discharged from the air discharge pipe 61 rise in the vicinity of this side surface. As a result, a circulating flow flowing in the direction indicated by the arrow P is formed in the slurry passage 55 in a plane perpendicular to the longitudinal direction of the slurry passage, and the fine-grained slurry is agitated. The shape, size, capacity, etc. of the storage tank 50 and each slurry passage 55-59, and the amount of pressurized air supplied to the air discharge pipes 61-65 are set in advance in the fine particle cleaning device 13. It is preferably set according to the water content, flow rate, residence time, flow velocity, turbulence degree of flow (for example, Reynolds number) and the like.

As is clear from FIG. 1, the fine particle slurry discharged from the fine particle cleaning device 13 is transferred to the filtration device 14. The filtration device 14 filters the fine particle slurry to produce a filtration cake and a filtrate having a water content of 30-40%. As the filtration device 14, a filter press, a vacuum filter, or the like can be used. Since the filtration cake (fine particles) discharged from the filtration device 14 contains almost no harmful metals or the like, it is used as, for example, agricultural soil for agriculture, or is disposed of by landfill or the like.

The filtrate or chelate washing liquid discharged from the filtration device 14 is transferred to the reverse osmosis membrane separation device 16 after the suspended solids or suspended solids (SS) are removed by the clarification filter 15 (for example, a sand filter). .. Although not shown in detail, the reverse osmosis membrane separator 16 receives the chelate cleaning solution discharged from the clarification filter 15, pressurizes it with a high-pressure pump, and then concentrates the chelate agent by the reverse osmosis membrane. Separate into water and permeated water containing no chelating agent. Then, the concentrated water is supplied to the chelating agent regenerating device 17, and the permeated water containing no chelating agent is returned to the thickener 8 by the permeated water transfer means (for example, a pump and a pipeline).

The reverse osmosis membrane of the reverse osmosis membrane separation device 16 includes, for example, a three-layer structure in which a polysulfone support layer and a crosslinked aromatic polyamide dense layer are laminated on the surface of a polyester non-woven fabric (thickness 100 to 120 μm). 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 0.2 to permeate), which allows water to permeate but does not allow the chelating agent to permeate. 0.25 μm) Semipermeable membrane. Further, the polysulfone support layer is a relatively thick (for example, 40 to 50 μm) porous film for supporting or protecting a very thin crosslinked aromatic polyamide dense layer to prevent its breakage.

The reverse osmosis membrane separation device 16 is of a spiral type, and has a plurality of reverse osmosis membrane elements in which a reverse osmosis membrane wound in a spiral shape is housed in a cylindrical container. It is practical that each reverse osmosis membrane element has, for example, a total length of about 1 to 2 m and an outer diameter of about 0.2 to 0.4 m. For example, the effective membrane area of a commercially available reverse osmosis membrane element (for example, manufactured by Authentec Co., Ltd. in Nakatsugawa City, Gifu Prefecture) having a total length of about 1 m and an outer diameter of about 0.2 m is It is about 40 m ² . In the case of this reverse osmosis membrane element, the processing amount of the chelate cleaning solution is estimated to be about 1.5 m ³ / hr when the chelate cleaning solution having a chelating agent concentration of about 1% by mass is supplied at a pressure of about 1 MPa. Thus, for example, when processing a chelating washing liquid per hour 60 m ³ may be connected to the reverse osmosis membrane elements in parallel forty.

The reverse osmosis membrane separator 16 is a continuous type, and the operating conditions such as the supply amount and supply pressure (operating pressure) of the chelate washing liquid, the discharge amount of the concentrated water and the permeated water, and the chelating agent concentration ratio of the concentrated water are fine particles. It is appropriately set according to the amount of the chelate cleaning solution to be supplied to the cleaning device 13 and the concentration of the chelating agent. For example, the ratio of the flow rate of sludge supplied to the fine-grain cleaning device 13 to the flow rate of the chelate cleaning liquid is set to 1: 1 and the chelating agent concentration of the fine-grain slurry in the fine-grain cleaning device 13 is set to 1% by mass. In this case, the back-penetrating membrane separator 16 produces about 50% of the permeated water (chelating agent concentration 0) and about 50% concentrated water (about 2% by mass of the chelating agent concentration) of the supply amount of the chelate washing liquid. Is set to. Therefore, in the fine-grain cleaning device 13, sludge containing no chelating agent and a chelating cleaning solution having a chelating agent concentration of about 2% by mass are mixed at a ratio of 1: 1 and the chelating agent concentration in the fine-grain cleaning device 13 is 1% by mass. It is maintained at about%.

The concentrated water, that is, the chelate washing liquid discharged from the reverse osmosis membrane separation device 16 is introduced into the chelate agent regenerating device 17 and regenerated. The chelating agent regenerating device 17 has a higher complexing power than the chelating agent and adsorbs or extracts harmful metals and the like in the chelate cleaning solution when it comes into contact with the chelating cleaning solution, or a small piece to which the solid phase adsorbent is fixed. It has particles or particles, and removes harmful metals and the like from the chelating agent in the chelate cleaning solution to regenerate the chelate cleaning solution.

The solid-state adsorbent has a cyclic molecule supported on a carrier, has a multipoint interaction by a coordinate bond and a hydrogen bond in which the cyclic molecule is modified with a chelate ligand, and selectively takes in ions such as harmful metals. is there. As a result, harmful metals and the like trapped in the chelating agent are separated from the chelating agent and adsorbed or extracted by the solid phase adsorbent. As a result, harmful metals and the like are removed and recovered from the chelate cleaning solution (chelating agent), and the chelating cleaning solution (chelating agent) is in a state where harmful metals and the like can be captured again.

Solid-state adsorbents, which have higher complex-forming power than chelating agents, are solid adsorbents such as gels, and generally, when they come into contact with an aqueous solution containing a chelating agent that traps a metal, they coordinate with the chelating agent. It has a strong binding force other than the covalent bond to the extent that the metal ions can be separated from the chelating agent and transferred to the solid phase adsorbent. When EDTA (ethylenediaminetetraacetic acid) is used as a chelating agent, such a solid phase adsorbent has a strong binding force capable of recovering almost 100% of metal ions from an aqueous solution of EDTA having a concentration of 10 mM / l. To have.

Examples of such a solid phase adsorbent include those in which cyclic molecules are densely supported on a carrier such as silica gel or resin, and the cyclic molecules are modified with a chelate ligand. When such a solid phase adsorbent is used, adjacent cyclic molecules and chelating ligands cause a plurality of various bonds and interactions such as coordination bonds and hydrogen bonds to cause multipoint interactions, resulting in metal ions. On the other hand, a stronger chemical bond is formed than the chelating agent, and metal ions can be selectively taken in depending on the properties of the cyclic molecule.

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

The concentrated water, that is, the chelate washing liquid discharged from the reverse osmosis membrane separation device 16 (see FIG. 1) is temporarily stored in the intermediate storage tank 71. Then, when the chelate cleaning liquid is regenerated, the chelate cleaning liquid stored in the intermediate storage tank 71 is transferred to the filling tower 70, while the pump 76 and a series for transferring the chelate cleaning liquid regenerated in the filling tower 70 to the cleaning liquid storage tank 72. The pipelines 77 to 80 are provided. Further, a pump 81 and a pipeline 82 for supplying the chelate cleaning liquid stored in the cleaning liquid storage tank 72 to the fine particle size cleaning device 13 (see FIG. 1) are provided.

Further, when the solid phase adsorbent is regenerated, the chelating agent regenerating device 17 transfers the acid solution stored in the acid solution storage tank 73 to the filling tower 70, while the acid solution discharged from the filling tower 70 is acidified. A pump 83 for returning to the liquid storage tank 73 and a plurality of pipelines 84 and 85 are provided. Further, in the chelating agent regenerating device 17, when the solid phase adsorbent regenerated with the acid solution was washed with water, the water stored in the water storage tank 74 was transferred to the filling tower 70, while being discharged from the filling tower 70. A pump 86 for returning water to the water storage tank 74 and a plurality of pipelines 87 and 88 are provided.

Valves 91, 92, 93, 94 for opening and closing the corresponding pipes are provided in the pipes 77, 78, 84, 87 for transferring the chelate cleaning liquid, the acid liquid, or water to the filling tower 70, respectively. There is. On the other hand, valves 95, 96, 97, 98 for opening and closing the corresponding pipes are provided in the pipes 79, 80, 85, 88 for discharging the chelate cleaning liquid, the acid liquid, or water from the filling tower 70, respectively. Has been done. By switching the open / closed state of these valves 91 to 98, any of the chelate cleaning liquid, the acid liquid and the water can be supplied and discharged to the filling tower 70. The opening and closing of these valves 91 to 98 is automatically controlled by a controller (not shown).

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

In the filling tower 70, a chelate cleaning solution containing a chelating agent that captures harmful metals and the like is brought into contact with the solid phase adsorbent (solid phase adsorbent particles). As a result, harmful metals and the like trapped in the chelating agent are separated from the chelating agent and adsorbed or extracted by the solid phase adsorbent. As a result, harmful metals and the like are removed and recovered from the chelate cleaning solution, and the chelating agent is in a state where the harmful metals and the like can be captured again, and the chelate cleaning solution is regenerated.

With the regeneration of the chelate cleaning solution, the amount of harmful metals adsorbed on the solid phase adsorbent increases with time, but the adsorption capacity of the solid phase adsorbent has an upper limit. Therefore, when the amount of harmful metals adsorbed on the solid phase adsorbent reaches the saturated state or its vicinity, the solid phase adsorbent is regenerated. That is, the acid solution is flowed into the filling tower 70 with the chelate cleaning solution removed, and the harmful metals and the like adsorbed on the solid phase adsorbent are removed by the acid solution to regenerate the solid phase adsorbent. Thus, while the harmful metals and the like are recovered by the acid solution, the solid phase adsorbent is regenerated so that the harmful metals and the like or these ions can be adsorbed or extracted again.

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

When the solid phase adsorbent is washed with water after the regeneration of the solid phase adsorbent by the acid solution is completed, the valves 94, 92, 95 and 98 interposed in the pipelines 87, 78, 79 and 88 are opened. , The other valves 91, 93, 96, 97 are closed and the pump 86 is operated. As a result, the water in the water storage tank 74 flows through the filling tower 70 and returns to the water storage tank 74. Water circulates and flows between the water storage tank 74 and the filling tower 70. At that time, the solid phase adsorbent in the filling tower 70 comes into contact with water, and the acid solution adhering to the solid phase adsorbent is washed. After this, the regeneration of the chelate washing solution is restarted.

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

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

S Soil purification system, 1 input hopper, 2 mixer, 3 mil breaker (wet crusher), 4 trommel, 5 cyclone, 6 PH adjustment tank, 7 coagulation tank, 8 thickener, 9 intermediate tank, 10 wash water tank, 11 spare Water tank, 12 Iron removal device, 13 Fine grain cleaning device, 14 Filter device, 15 Clarification filter, 16 Back osmotic membrane separation device, 17 Chelating agent regeneration device, 18 Iron-based fine grain adsorption device, 19 Screen device, 20 Magnetic ball, 21 Main body, 21a Inclined plate, 22 Centrifugal separator, 23 Magnetic ball return device, 24 1st magnetic ball storage container, 24a open / close door, 25 2nd magnetic ball storage container, 25a open / close door, 26 3rd magnetic Sphere storage container, 26a open / close door, 27 sludge storage tank, 29 hollow sphere, 30 permanent magnet, 31 magnet holding member, 32 magnet holding hole, 34 sludge pump, 35 housing, 36 bearing device, 37 rotating cylinder, 37a upper opening / closing Door, 37b lower opening / closing door, 38 gear mechanism, 39 motor, 40 baffle, 41 horizontal conveyor, 41a belt, 42 upright conveyor, 43a drive roller, 43b drive roller, 44a driven roller, 44b driven roller, 45 metal belt , 46 idle roller, 47 magnetic ball locking member, 48 guide member, 50 storage tank, 51-54 partition wall, 55-59 slurry passage, 61-65 air release pipe, 70 filling tower, 71 intermediate storage tank, 72 cleaning liquid storage tank, 73 Acid solution storage tank, 74 Water storage tank, 76 pump, 77-80 line, 81 pump, 82 line, 83 pump, 84 line, 85 line, 86 pump, 87 line, 88 line, 91-98 Valves, 100 stanchions, 101 spiral passages.

Claims (1)

A soil purification system that purifies soil contaminated with harmful metals or compounds containing gravel, sand, and fine particles.
The soil purification system
The soil is washed with washing water, crushed gravel and sand, and then classified into gravel, sand, and fine particles.
By magnetically adsorbing and removing iron-based fine particles containing iron or iron oxide to the extent that they can be attracted by magnetic force from the sludge containing the fine particles separated in the soil classification part and the washing water. A pretreatment section that reduces the content of harmful metals in sludge or its compounds, and
A post-treatment unit that removes harmful metals or compounds thereof adsorbed or adhered to the surface of fine particles in the sludge by subjecting the sludge discharged from the pretreatment unit to chemical treatment or physicochemical treatment. Is equipped with
The pretreatment unit
A plurality of permanent magnets are mounted on the hollow portion of the hollow sphere so that the magnetic poles of the same magnetism face outward in the radial direction of the sphere, and the magnets are discharged from the thickener, which is a component of the soil classification portion. The sludge is attached to the outer periphery of a strut whose central axis is arranged so as to extend in the vertical direction, and is received in the upper part of a girder-shaped or groove-shaped spiral passage that spirally descends around the strut. An iron-based fine particle adsorption device that moves a mixture of sludge downward by gravity in the spiral passage and magnetically attracts iron-based fine particles in the sludge to a magnetic sphere during movement.
A screen device that receives a mixture of magnetic spheres and sludge discharged from the lower part of the iron-based fine particle adsorption device and separates them into magnetic spheres and sludge.
A centrifuge that intermittently accepts magnetic spheres adsorbing iron-based fine particles discharged from the screen device in a batch manner and separates the iron-based fine particles from the magnetic spheres by centrifugal force.
A soil purification system comprising an iron removal device including a magnetic ball return device that returns the magnetic balls discharged from the centrifuge to the iron-based fine particle adsorption device.

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