JP2020082057A - Soil remediation system - Google Patents

Abstract

To provide a simple and low-cost soil remediation system allowing wet classification of soil into gravel, sand and fine-grained fractions, while removing toxic metal and the like adsorbed to the fine-grained fraction.SOLUTION: A soil remediation system S allows soil to be washed with wash water and classified into gravel, sand and fine-grained fractions by a mill breaker 3, a trommel 4, a liquid cyclone 5 and a thickener 8. An iron removal device 12 causes a ferrous fine-grained fraction to be removed, by adsorption by magnetic force, from sludge discharged from the thickener 8, thereby reducing the content of toxic metal and the like in the sludge. A fine-grained fraction washing device 13 washes the sludge discharged from the iron removal device 12 with a chelating wash liquid to remove toxic metal and the like from the fine-grained fraction. A filter device 14 filters the sludge discharged from the iron removal device 12. A reverse osmosis membrane separation device 16 separates the filtrate of the filter device 14 into a permeate and a concentrate. A chelating agent recycle device 17 removes the toxic metal and the like from the concentrate and supplies it to the fine-grained fraction washing device 13 as the chelating wash liquid.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 and/or compounds thereof.

In recent years, for example, a site of a production facility using a harmful metal such as chromium, lead, cadmium, selenium, or mercury and/or its compound (hereinafter, these are collectively referred to as “toxic metal etc.”) or a neighboring area thereof. Soil pollution is frequently occurring in Sri Lanka or due to illegal dumping of industrial waste containing harmful metals. 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 applicant of the present application has already classified the gravel, the sand, and the fine particles while washing the harmful metal-contaminated soil with the cleaning water, and then contains the chelating agent and water for the fine particles. There have been proposed various soil purification facilities (polluted soil purification devices) in which harmful metals and the like are removed from fine particles by performing a cleaning treatment in (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), and thus a large amount of fine particles are generated (for example, on a dry basis). 500-600 tons per day). 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. The required amount or use amount of the chelating agent in such a soil remediation facility increases as the content of harmful metals and the like in the fine particles increases. The same problem occurs when the fine particles are washed with a chemical other than the chelating agent to remove harmful metals and the like. The same problem also occurs when the harmful metals and the like are physically and chemically removed using activated carbon and the like.

The present invention has been made to solve the above-mentioned conventional problems, and includes gravel and sand while washing the soil containing gravel, sand, and fine particles and contaminated with harmful metals and the like with washing water. It is possible to provide a simple soil purification system with low treatment cost, which can classify fine particles into fine particles and can remove harmful metals adsorbed or attached to the separated fine particles. It is a problem to be solved.

Soil purification for purifying soil contaminated with harmful metals and the like (harmful metals and/or compounds thereof) or these ions containing gravel, sand and fine particles according to the present invention made to solve the above problems The system consists of a mixer, a wet crusher, a trommel, a hydrocyclone, a thickener, an iron removal device, a fine particle cleaning device, a filtration device, a reverse osmosis membrane separation device, and a chelating agent regeneration device. And a means for transferring permeate.

Here, the mixer mixes the soil introduced into the soil purification system and the wash water. The wet crusher crushes gravel and/or sand in a mixture containing soil and wash water discharged from a mixer, so that iron and/or sand which are unevenly distributed or scattered inside the gravel and/or sand are crushed. Or, iron oxides (generally referred to as “iron etc.”) generate iron-based fine particles exposed on the surface, and iron, etc. exposed on the surface of iron-based fine particles cause harmful metals in washing water, etc. Is adsorbed (attached). 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 iron removing device 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 discharged from the thickener. The iron-based fine particles contain iron and the like to the extent that they can be attracted by magnetic force. The fine particle content cleaning device mixes the sludge discharged from the iron content removing device with a chelate cleaning liquid containing a chelating agent and water to produce a fine particle content slurry, and the fine particle content slurry has a preset residence time. By causing the chelating agent to flow, the harmful metal or the like attached to (adsorbing) the fine particles or these ions are captured by the chelating agent. The filter device filters the fine particle slurry discharged from the fine particle cleaning device to generate a filtrate and a filter cake.

The reverse osmosis membrane separation device separates the filtrate discharged from the filtration device into concentrated water in which the chelating agent is concentrated and permeated water containing no chelating agent by the reverse osmosis membrane. The chelating agent regenerator receives the concentrated water discharged from the reverse osmosis membrane separator and has a higher complexing power than the chelating agent and adsorbs harmful metals or the like in the concentrated water when contacting the concentrated water. The solid phase adsorbent removes harmful metals and the like from the chelating agent in the concentrated water and supplies the concentrated liquid as a chelate cleaning liquid to the fine particle cleaning device. The permeated water transfer means transfers (returns) the permeated water discharged from the reverse osmosis membrane separation device to the thickener.

The iron removal device has an iron-based fine particle adsorption device, a screen device, a centrifuge, and a magnetic sphere return 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. ) Magnetic sphere and sludge discharged from thickener are received in the upper part of a gutter-shaped or groove-shaped air passage that descends in a zigzag manner, and the mixture of magnetic sphere and sludge is moved downward by gravity in the air passage. Then, the iron-based fine particles in the sludge are attracted to the magnetic spheres by magnetic force during the movement. The screen device receives the 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 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, the air passage of the iron-based fine particle adsorption device is composed of a plurality of linear channel members arranged so as to be inclined downward so as to connect in a zigzag shape. preferable.

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. Here, the upright belt conveyor is a drive roller arranged at a position lower than the lower end of the centrifuge, and a driven roller arranged above the drive roller 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 wound around a driving roller and a driven roller, and attached to the outer surface of the endless metal belt and adsorbed to the endless metal belt when traveling above the endless metal belt. It is preferable to have a magnetic ball locking member for locking the descending of the magnetic ball. In this case, the magnetic sphere conveying means conveys the magnetic spheres discharged from the centrifuge to the lower end portion of the upright belt conveyor or in the vicinity thereof so as to be attracted to the endless metal belt by magnetic force. Further, the magnetic sphere supply means separates the magnetic spheres from the endless metal belt at the upper end of the upright belt conveyor or in the vicinity thereof and supplies (moves) the magnetic spheres to the iron-based fine particle adsorption device.

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, according to the soil purification system of the present invention, gravel and/or sand is crushed by a wet crusher to generate fine particles, but among these fine particles, uneven distribution in gravel or sand or Fine particles containing a large amount of scattered iron and other small lumps are iron-based fine particles, and iron exposed on the surface of these iron-based fine particles is transferred from the wet crusher to the iron removal device. A relatively large amount of harmful metals and the like are adsorbed in the entire distribution process. 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-based fine particle adsorption device of the iron removal device, when a mixture of magnetic spheres and sludge is moved downward by a gravity in a trough-shaped or groove-shaped air passage that descends in a zigzag manner, The iron-based fine particles inside are attracted to the magnetic spheres by magnetic force. As described above, the iron-based fine particles in the sludge having a large amount of adsorbed harmful metals are adsorbed by the magnetic spheres and removed from the sludge, so that the content or retention rate of the harmful metals in the sludge can be reduced. it can. Therefore, the load of harmful metals and the like on the fine particle cleaning device that purifies the sludge discharged from the iron removal device (iron-based fine particle adsorption device) with the chelate cleaning liquid, and the chelating agent regeneration that removes the harmful metal and the like from the chelating agent It is possible to reduce the load of harmful metals and the like on the device, reduce the required amount or use amount of the chelating agent and the solid phase adsorbent, and reduce the soil treatment cost. The wet crusher and the iron removal device have a mechanical structure for performing a physical treatment and do not use any special chemicals, so the operating cost thereof 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 repulsing each other, they can move smoothly while being appropriately separated.

It is a block diagram showing the schematic structure of the soil purification system concerning the present invention. It is a typical elevational view of the iron removal apparatus which comprises a soil purification system. FIG. 3 is a schematic elevational cross-sectional view of an iron-based fine particle content adsorption device that constitutes the iron content removal device. 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. (A) is a schematic plan view of a fine particle cleaning device, (b) is a sectional view taken along line AA of the fine particle cleaning device shown in (a), and (c) is a fine particle cleaning device. FIG. 3 is an elevational cross-sectional view of one slurry passage of the device. It is a typical elevation view of a chelating agent regeneration device.

As shown in FIG. 1, in the soil purification system S according to the embodiment of the present invention, harmful metals and the like (toxic metals and/or their compounds) or soil collected by excavation of the ground contaminated with these ions are used. (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). Some include stones (for example, 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 generated 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. On the other hand, iron or the like generally has a property of adsorbing harmful metals or the like. Therefore, harmful metals and the like existing in the washing water or a part of these ions are adsorbed or adhered to the exposed surface of iron or the like of the iron-based fine particles. 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, A method of treating harmful metals or the like by adsorbing harmful metals or the like to exposed iron microparticles (fine iron-based particles) has not 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 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 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 released in the water are hardly adsorbed on or adhered to the gravel and sand, so the gravel separated by the trommel 4 is almost clean, for example, as an aggregate for concrete. Can be used. 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.

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, which are accommodated in the receiving tank of the trommel 4, is 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 sand 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 and 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 (PAC) aqueous solution, a polymer aggregating agent, and a pH adjusting agent (acidic liquid or alkaline liquid) are added to the water containing fine particles. As a result, a large number of flocs in which the water-insoluble metal hydroxide and the fine particles are mixed are generated in the flocculation tank 7.

The water containing fine particles (including flocs) in the flocculation tank 7 is introduced into the thickener 8 (gravity settling tank). 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 temporarily stored. 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 that has settled or accumulated in the lower part of the thickener 8 is transferred to the intermediate tank 9 and temporarily stored. 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. 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. The sludge discharged from the iron removing device 12 is treated by the fine particle cleaning device 13, the filtering device 14, the clarification filter 15, the reverse osmosis membrane separating device 16 and the chelating agent regenerating device 17 to remove harmful metals. Almost clean fine particles containing almost no etc. and a chelate cleaning liquid are produced. The specific configurations and functions of these devices 13 to 17 will be described in detail later.

Hereinafter, the specific configuration and function of the iron content removing device 12 will be described with reference to FIGS. 2 to 6.
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. 4).

As shown in FIG. 3, the iron-based fine particle adsorption device 18 is arranged in the air at a position where they are substantially overlapped with each other or in the same position in a plan view, and they are arranged linearly in the vertical direction from the upper side to the lower side. The first to fourth channel members 100 to 103 extending in the direction of the arrow are provided. Note that, in the following, for the sake of simplicity, the positional relationship within the iron-based fine particle adsorption device 18 will be described. (The left side in FIG. 3) is referred to as “left”, and the opposite side, that is, the side where the first magnetic sphere storage container 24 is located (right side in FIG. 3) is referred to as “right” (see FIG. 2). ..

Although not shown in detail, each of the channel members 100 to 103 is a trough-shaped or groove-shaped member having an open upper portion, and a passage formed by the bottom surface and both side surfaces of the channel member 100 to 103 is a mixture of the magnetic spheres 20 and the sludge. However, it is possible to move (roll or flow) without deviating to the side or falling off. The first channel member 100 located on the uppermost side is arranged so as to descend and incline toward the left, and a mixture of the magnetic spheres 20 and sludge that has moved leftward in the first channel member 100 is provided at the left end portion thereof. An opening 100a is provided for free fall. Since the opening 100a is located slightly to the right of the left end of the second channel member 101 immediately below the opening 100a, the mixture of the magnetic spheres 20 and the sludge discharged from the opening 100a enters the second channel member 101. It falls or flows down.

The second channel member 101 is arranged so as to be inclined downward to the right, and an opening portion 101a is provided at the right end portion thereof similarly to the first channel member 100. Since the opening 101a is located slightly to the left of the right end of the third channel member 101 immediately below the opening 101a, the mixture of the magnetic spheres 20 and the sludge discharged from the opening 101a enters the third channel member 102. It falls or flows down. The third channel member 102 is arranged so as to descend and incline toward the left, and an opening 102a is provided at the left end thereof, like the first channel member 100. Since the opening 102a is located slightly to the right of the left end of the fourth channel member 103 immediately below the opening 102a, the mixture of the magnetic spheres 20 and the sludge discharged from the opening 102a enters the fourth channel member 103. It falls or flows down.

The fourth channel member 103 is arranged so as to be inclined downward to the right, and an opening portion 103a is provided at the right end portion thereof similarly to the first channel member 100. Since the opening 103a is located slightly to the left of the right end of the screen device 19 located therebelow, the mixture of the magnetic spheres 20 and sludge discharged from the opening 103a falls on the screen of the screen device 19. (See Figure 2). As described above, since the first to fourth linear channel members 100 to 103 are arranged so as to be inclined downward so as to be connected in a zigzag shape, the iron-based fine particle adsorption device 18 is provided with magnetic spheres. A zigzag descending air passage for moving the mixture of 20 and sludge is formed. The first to fourth channel members 100 to 103 are made of a non-magnetic material or a diamagnetic material so that the magnetic spheres 20 will not be attracted.

Thus, the large number of magnetic spheres 20 discharged from the first magnetic sphere storage container 24 (see FIG. 2) and the sludge discharged from the thickener 8 (see FIG. 1) are supplied to the vicinity of the right end portion of the first channel member 100. Then, the mixture of the magnetic spheres 20 and the sludge sequentially moves (rolls or flows) by gravity in the zigzag downward air passage formed by the first to fourth channel members 100 to 103. At this time, iron-based fine particles adsorbing harmful metals or the like in the sludge or adhering harmful metals or the like are adsorbed to the outer peripheral surface of the magnetic sphere 20 by magnetic force. As a result, the content of harmful metals and the like in the sludge is reduced.

As shown in FIG. 4, in the magnetic sphere 20, a plurality of permanent magnets 30 are roughly mounted in the hollow portion of the hollow spherical body 29 such 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 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 is a mesh-like or lattice-like screen below the iron-based fine particle adsorbing device 18 and extending obliquely while descending toward the second magnetic sphere storage container 25. Have. 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 fine particle cleaning device 13 (see FIG. 1).

The first magnetic sphere storage container 24 is arranged above the iron-based fine particle adsorption device 18, and the opening degree of the first magnetic sphere storage container 24 can be freely adjusted at the lower end portion (bottom portion) thereof. An opening/closing door 24a 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. It can be supplied to the first channel member 100 of the device 18.

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. 5, the centrifuge 22 has a housing 35, which is a substantially cylindrical container, and a bearing device 36 that is arranged coaxially with the housing 35 in the housing 35 and is 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 clear 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. 5) is opened when the rotary cylinder 37 is stopped, the third magnetic sphere storage container 26 is rotated. 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. 6) are provided 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. 4) of the magnetic sphere 20 is such that when the metal belt 45 extends in the horizontal direction, the magnetic sphere 20 is positioned below the metal belt 45 at an appropriate interval (for example, 5). It is set so that the magnetic 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. 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 of the metal belt 45 (traveling direction). 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. Here, the magnetic spheres 20 continuously move 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 sphere storage container 26 to the first magnetic sphere storage container 24.

Hereinafter, an example of the operation method of the iron removal device 12 will be described. To the first channel member 100 (see FIG. 3) of the iron-based fine particle adsorption device 18, a large number of magnetic spheres 20 from which the iron-based fine particle content is not substantially adsorbed are continuously provided from the first magnetic sphere storage container 24. On the other hand, the sludge substantially consisting of fine grains (ferrous fine grains and non-ferrous fine grains) and water is continuously fed from the intermediate tank 9 (see FIG. 1). Then, in the first to fourth channel members 100 to 103, the mixture in which the magnetic spheres 20 and the sludge are mixed moves (rolls or flows) by gravity in the air passage descending and inclined in a zigzag shape. At this time, iron-based fine particles adsorbing harmful metals or the like in the sludge or adhering harmful metals or the like are adsorbed to the outer peripheral surface of the magnetic sphere 20 by magnetic force. As a result, the content of harmful metals and the like in the sludge is reduced.

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. 4) 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 the sludge discharged downward from 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 are separated. Separated into the removed sludge. 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.

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 process is carried out by the chelating agent, and the chelating agent regenerating device 17 (see FIG. 1) regenerates the chelating agent by the solid phase adsorbent. Since the harmful metals and the like are reduced, the load of the harmful metals and the like on the chelate cleaning treatment of fine particles (sludge) and the regenerating treatment of the chelating agent is reduced. Therefore, the necessary 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.

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.

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 particle cleaning device 13 includes sludge containing non-ferrous fine particles discharged from the iron removing device 12 and cleaning water, and a chelating agent and water supplied from a chelating agent regenerating device 17 described later. Accept the chelate cleaning solution, mix and stir these to generate a fine-grained slurry, and generally use a plug flow to ensure a preset residence time (for example, 0.5 to 2 hours). By causing the chelating agent to continuously flow, harmful metals or the like adhering (adsorbing) to the fine particles are captured by the chelating agent. 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. The ratio of the flow rate of 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 cleaning solution include EDTA (ethylenediaminetetraacetic acid), HIDS (3-hydroxy-2,2′-iminodisuccinic acid), IDS (2,2′-iminodisuccinic acid), MGDA (methylglycine). Diacetic acid), EDDS (ethylenediamine diacetic 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.

Hereinafter, the specific configuration and function of the fine particle content cleaning device 13 will be described with reference to FIGS. The fine grain fraction cleaning device 13 has a storage tank 50 provided with five elongated rectangular parallelepiped or prismatic slurry passages 55 to 59 extending in parallel with each other and formed by partitioning with four plate-shaped partition walls 51 to 54. is doing. The storage tank 50 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 51 to 54 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 55 to 59 have four curves in the communicating portion (FIG. 7A) at one end in the slurry passage longitudinal direction (the horizontal direction in the positional relationship in FIGS. 7A and 7B). (The part indicated by the arrow) is communicating with each other. That is, the partition walls 51 to 54 do not exist in these communicating portions, and the adjacent slurry passages communicate with each other.

At the bottom of each slurry passage 55-59, air discharge pipes 61-65 for discharging air into the fine particle slurry and agitating the fine particle slurry are arranged, respectively. Each of the air discharge pipes 61 to 65 is a perforated pipe that extends in the slurry passage lengthwise direction and has a plurality of air discharge holes arranged in the slurry passage lengthwise 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 pressurized air is supplied to the air discharge pipes 61 to 65, the air becomes bubbles from the air discharge holes and is discharged into the fine particle slurry and floats up, and the bubbles agitate the fine particle slurry. To be done.

FIG. 7C shows a cross section of the slurry passage 55 on the most upstream side in the flow direction of the fine-grained slurry (directions indicated by curved arrows and linear arrows in FIG. 7A). .. As is clear from FIG. 7C, the air discharge pipe 61 is arranged near one bottom surface of the slurry passage 55 and near the bottom of the slurry passage. Therefore, the bubbles discharged from the air discharge pipe 61 rise in the vicinity of this side surface. As a result, in the slurry passage 55, a circulation 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-grained slurry is agitated. The shape, size, capacity, etc. of the storage tank 50 and each of the slurry passages 55-59, and the supply amount of the pressurized air to the air discharge pipes 61-65, etc. are set in advance in the fine particle content cleaning device 13. Of water content, flow rate, residence time, flow velocity, flow turbulence (eg Reynolds number), etc.

As is clear from FIG. 1, the fine particle slurry discharged from the fine particle cleaning device 13 is transferred to the filtering device 14. The filter device 14 filters the fine-grained slurry to produce a 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 14. Since the filter cake (fine particles) discharged from the filter device 14 contains almost no harmful metals and the like, it is used as, for example, agricultural soil, or is disposed by landfill.

The filtrate discharged from the filtration device 14, that is, the chelate cleaning liquid, is transferred to the reverse osmosis membrane separation device 16 after the suspended substance or suspended substance (SS) is removed by the clarification filter 15 (for example, sand filter). .. Although not shown in detail, the reverse osmosis membrane separation device 16 receives the chelate washing liquid discharged from the clarification filter 15, pressurizes it with a high-pressure pump, and then concentrates the chelating agent by the reverse osmosis membrane. Separate into water and permeate containing no chelating agent. Then, the concentrated water is supplied to the chelating agent regenerator 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 pipe).

As the reverse osmosis membrane of the reverse osmosis membrane separation device 16, 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) 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 16 is 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 16 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 13 and the concentration of the chelating agent. For example, the ratio of the flow rate of sludge supplied to the fine particle 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 particle cleaning device 13 is set to 1% by mass. In this case, the reverse osmosis membrane separation device 16 produces permeated water (concentration of chelating agent 0) of about 50% and concentrated water (concentration of chelating agent of about 2% by mass) of about 50% of the supply amount of the chelate cleaning liquid. Is set to. Therefore, in the fine particle cleaning device 13, the sludge containing no chelating agent and the chelate cleaning liquid having a chelating agent concentration of about 2% by mass are mixed at a ratio of 1:1 and the chelating agent concentration in the fine particle cleaning device 13 is 1 mass. % Is maintained.

The concentrated water discharged from the reverse osmosis membrane separation device 16, that is, the chelate cleaning liquid, is introduced into the chelating agent regenerating device 17 and regenerated. The chelating agent regenerator 17 has a complex formation power higher than that of the chelating agent, and a solid phase adsorbent that adsorbs or extracts harmful metals or the like in the chelate cleaning solution when contacted with the chelate cleaning solution or a small piece to which the solid phase adsorbent is fixed Or, it has a granular substance and removes harmful metals and the like from the chelating agent in the chelate cleaning liquid to regenerate the chelate cleaning liquid.

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.

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.

Hereinafter, the specific configuration and function of the chelating agent regenerator 17 will be described with reference to FIG. The chelating agent regenerator 17 is provided with a packed tower 70 filled with solid phase adsorbent particles or a packing (fixing) to which the solid phase adsorbent is fixed. In the chelating agent regenerator 17, 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.

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

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

The pipes 77, 78, 84, 87 for transferring the chelate cleaning liquid, the acid liquid or the water to the packed tower 70 are provided with valves 91, 92, 93, 94 for opening and closing the corresponding pipes, respectively. There is. On the other hand, the pipes 79, 80, 85, 88 for discharging the chelate cleaning liquid, the acid liquid or the water from the packed tower 70 are provided with valves 95, 96, 97, 98 for opening and closing the corresponding pipes, respectively. Has been done. By switching the open/closed states of these valves 91 to 98, it is possible to supply/discharge either the chelate cleaning liquid, the acid liquid, or the water to/from the packed tower 70. The opening and closing of these valves 91 to 98 are automatically controlled by a controller (not shown).

Hereinafter, an example of the operation method of the chelating agent regeneration device 17 will be described. When regenerating the chelate cleaning liquid (chelating agent), the valves 91, 92, 95, 96 provided in the conduits 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 packed tower 70 and is transferred to the cleaning liquid storage tank 72.

In the packed tower 70, a chelate cleaning liquid containing a chelating agent that traps 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 captured by the chelating agent are released from the chelating agent and are adsorbed or extracted by the solid phase adsorbent. As a result, harmful metals and the like are removed and collected from the chelate cleaning liquid, and the chelating agent can capture the harmful metals and the like again, and the chelate cleaning liquid is regenerated.

As the chelate cleaning liquid is regenerated, the adsorption amount of harmful metals and the like on the solid-phase adsorbent increases with time, but the adsorption capacity of the solid-phase adsorbent has an upper limit. Therefore, the solid phase adsorbent is regenerated when the amount of adsorbed harmful metals or the like in the solid phase adsorbent reaches a saturation state or a vicinity thereof. That is, the acid solution is allowed to flow into the packed tower 70 in a state where the chelate cleaning liquid is removed, and the harmful metal or the like adsorbed by the solid phase adsorbent is 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 to be in a state capable of again adsorbing or extracting the harmful metals and the like or these ions.

When the solid phase adsorbent in the packed tower 70 is regenerated with an acid solution, the valves 93, 92, 95, 97 provided in the pipe lines 84, 78, 79, 85 are opened, while the other valves 91 are opened. , 94, 96, 98 are closed and the pump 83 is operated. As a result, the acid liquid in the acid liquid storage tank 73 flows through the packed tower 70 and returns to the acid liquid storage tank 73. Whether or not the adsorbed amount of harmful metal of the solid phase adsorbent has reached a 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 packed tower 70. ..

When the solid phase adsorbent is rinsed with water after the regeneration of the solid phase adsorbent with the acid solution is completed, the valves 94, 92, 95, 98 provided in the pipelines 87, 78, 79, 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 circulates in the packed tower 70 and returns to the water storage tank 74. Water circulates between the water storage tank 74 and the packed tower 70 and flows. At that time, the solid phase adsorbent in the packed tower 70 comes into contact with water, and the acid liquid adhering to the solid phase adsorbent is washed. After that, the regeneration of the chelate cleaning solution is restarted.

The chelate cleaning liquid thus regenerated is temporarily stored in the cleaning liquid storage tank 72 and then supplied to the fine particle cleaning device 13 (see FIG. 1). That is, the chelate cleaning liquid circulates while repeating purification of fine particles and regeneration of the chelating agent. The depletion amount of the chelating agent is appropriately replenished.

As described above, according to the soil purification system S of the present invention, it is possible to obtain clean and reusable gravel, sand, and fine particles. Further, since the content of harmful metals or the like in the sludge discharged from the iron removal device 12 can be reduced, the load of harmful metals or the like on the fine particle content cleaning device 13 and the harmful metals or the like on the chelating agent regeneration 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 used can be reduced, and the soil treatment cost can be reduced.

S Soil cleaning system, 1 input hopper, 2 mixer, 3 mil breaker (wet crusher), 4 trommel, 5 cyclone, 6 PH adjusting tank, 7 flocculating tank, 8 thickener, 9 intermediate tank, 10 washing water tank, 11 preliminary Water tank, 12 Iron removal device, 13 Fine particle washing device, 14 Filtration device, 15 Clarifying filter, 16 Reverse osmosis membrane separation device, 17 Chelating agent regenerating device, 18 Iron-based fine particle adsorption device, 19 Screen device, 20 Magnetic sphere, 21 main body, 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 open/close door, 27 sludge storage tank, 29 hollow spherical body, 30 permanent magnet, 31 magnet holding member, 32 magnet holding hole, 34 sludge pump, 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 rollers, 47 magnetic ball locking members, 48 guide members, 50 storage tanks, 51-54 partition walls, 55-59 slurry passages, 61-65 air discharge pipes, 70 packed towers, 71 intermediate storage tanks, 72 cleaning liquid storage tanks, 73 acid liquid storage tank, 74 water storage tank, 76 pump, 77-80 pipeline, 81 pump, 82 pipeline, 83 pump, 84 pipeline, 85 pipeline, 86 pump, 87 pipeline, 88 pipeline, 91-98 Valve, 100 first channel member, 101 second channel member, 102 third channel member, 103 fourth channel member.

Claims (3)

A soil purification system for purifying soil contaminated with harmful metals or compounds containing gravel, sand, and fine particles,
A mixer for mixing the soil and the wash water introduced into the soil purification system,
By crushing gravel and sand in a mixture containing soil and wash water discharged from the mixer, iron or iron oxides unevenly distributed or scattered inside the gravel and sand are exposed on the surface. A wet crusher that produces fine particles of a system and adsorbs or attaches a harmful metal or a compound thereof in the washing water to iron or iron oxide exposed on the surface of the fine particles of an iron,
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, a thickener for separating supernatant liquid by sedimentation separation into sludge containing fine particles and washing water,
From the sludge discharged from the thickener, by removing the iron-based fine particles by adsorbing with a magnetic force, an iron removal device for reducing the content of harmful metals or compounds thereof in the sludge,
The sludge discharged from the iron removing device is mixed with a chelate cleaning liquid containing a chelating agent and water to produce a fine particle slurry, and the fine particle slurry is flowed so as to secure a preset residence time. By doing so, a fine particle cleaning device for trapping a harmful metal or its compound attached to the fine particles in a chelating agent,
A filtering device for filtering the fine particle slurry discharged from the fine particle cleaning device to generate a filtrate and a filter cake,
The filtrate discharged from the filtration device, by a reverse osmosis membrane, a reverse osmosis membrane separation device for separating the concentrated water in which the chelating agent is concentrated and the permeated water containing no chelating agent,
The concentrated water discharged from the reverse osmosis membrane separator is received and concentrated by a solid-phase adsorbent that has a complexing power higher than that of a chelating agent and adsorbs harmful metals or compounds thereof in the concentrated water A chelating agent regenerator for removing harmful metals or compounds thereof from a chelating agent in water and supplying the concentrated solution as a chelating cleaning solution to the fine particle content cleaning apparatus,
And a permeated water transfer means for transferring permeated water discharged from the reverse osmosis membrane separation device to the thickener,
The iron removal device,
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 are zigzag-shaped. It is received in the upper part of the descending trough-shaped or groove-shaped air passage, and the mixture of magnetic spheres and sludge is moved downward by gravity in the air passage. An iron-based fine particle adsorption device for adsorbing to
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 the magnetic spheres and sludge into a sludge,
A centrifugal separator that intermittently receives the magnetic spheres adsorbing the iron-based fine particles discharged from the screen device in a batch system and separates the iron-based fine particles from the magnetic spheres by a centrifugal force,
And a magnetic sphere returning device for returning the magnetic spheres discharged from the centrifuge to the iron-based fine particle adsorption device. The soil purification system according to claim 1, wherein the aerial passage is composed of a plurality of linear channel members arranged so as to be inclined downward so as to be connected in a zigzag shape. 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 the endless metal belt travels above. 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 means 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 according to 2.

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