JP6678353B2 - Soil purification system - Google Patents

Description

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

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

  Conventionally, as a method of purifying toxic metal-contaminated soil in such an off-site soil purification facility, a cleaning method of removing harmful metals and the like by cleaning harmful metal-contaminated soil with washing water or the like has been widely used. . When the harmful metal-contaminated soil is washed with washing water, most of the harmful metals and the like once separated from the soil into the water are adsorbed or adhered to the surface of fine particles having a relatively small particle size, and (See, for example, Non-Patent Document 1).

  Therefore, by washing harmful metal contaminated soil with washing water and classifying it into gravel, sand, and fine particles, and then subjecting the fine particles to a chemical treatment to remove harmful metals, etc., It is possible to obtain gravel, sand, and fine particles containing almost no harmful metals. Thus, the inventor of the present application has already classified harmful metal-contaminated soil with washing water, classified it into gravel, sand, and fine particles, and then performed a cleaning treatment on the fine particles with a chelating cleaning solution containing a chelating agent. Various types of soil remediation facilities (contaminated soil remediation devices) have been proposed in which harmful metals and the like are removed from fine particles by applying the method (see, for example, Patent Documents 1 and 2).

Japanese Patent No. 5723054 Japanese Patent No. 5723055 Japanese Patent No. 4755159 Japanese Patent No. 607144

Ministry of the Environment, Water and Atmospheric Environment Bureau, Soil Environment Section, “Technical Considerations on Permission Examinations for Contaminated Soil Treatment Business”, page 21, published August 2013 Tetsuo Katsura “Drainage treatment by iron powder method” flotation, vol. 23 (1976), no. 3, P190-198 (https://www.jstage.jst.go.jp/article/rpsj1954/23/3/3/23_3_190/_pdf)

  By the way, in a soil purification facility of this kind by a contaminated soil treatment company, a large amount of contaminated soil is usually purified (for example, 2,000 tons per day), so that a large amount of fine particles is generated (for example, 500-600 tons per day on a dry basis). Therefore, when such a large amount of fine particles is washed with, for example, a chelate washing solution, a relatively expensive chelating agent is required in a large amount, and there is a problem that the treatment cost of contaminated soil is increased. Needless to say, the necessary or used amount of the chelating agent increases as the content of the harmful metal or the like in the fine particles increases. A similar problem also occurs when the fine particles are washed with a chemical other than the chelating agent to remove harmful metals and the like.

  The present invention has been made in order to solve the above-mentioned conventional problems, and it is intended to wash gravel, sand, and soil that contain gravel, sand, and fine particles, and that are contaminated with harmful metals and the like, with washing water. It can be classified as fine particles and can remove harmful metals and the like adsorbed or adhered to the separated fine particles, or at least contain or hold the harmful metals and the like in the fine particles It is an object of the present invention to provide a simpler soil purification system that can lower the rate and has a lower treatment cost.

  The soil purification system according to the present invention which has been made to solve the above-mentioned problem is intended to remove soil contaminated with harmful metals and the like (harmful metals and / or compounds thereof or their ions), including gravel, sand and fine particles. Purify. This soil purification system includes a soil classification unit and an iron removal device. Here, the soil classification unit crushes the gravel and sand in the soil while washing the soil with washing water, and then classifies the soil into gravel, sand, and fine particles. On the other hand, the iron content removing device is collectively referred to as iron and / or iron oxide (hereinafter referred to as “iron etc.”) to the extent that it can be magnetically adsorbed from sludge containing fine particles separated in the soil classification part and washing water. ) Is removed by magnetic attraction to remove the iron-based fine particles containing), thereby reducing the content or holding ratio of harmful metals and the like in the sludge (fine particles).

  In the soil purification system according to the present invention, the soil classification unit includes a mixer, a wet crusher, a trommel, a liquid cyclone, and a thickener. Here, the mixer mixes the soil introduced into the soil classification section with the washing water. The wet crusher can adsorb iron, etc. unevenly or scattered inside the gravels and sand by crushing the gravels and sand in the mixture containing soil and washing water discharged from the mixer. An iron-based fine particle containing a certain amount is generated, and harmful metals and the like are adsorbed to iron and the like exposed on the surface of the iron-based fine particle. Trommel separates gravel from a mixture of gravel, sand, fines and wash water discharged from the wet crusher. The hydrocyclone separates sand from a mixture containing sand, fines and wash water discharged from trommel. The thickener separates a mixture containing fine particles discharged from the hydrocyclone and washing water into supernatant water and sludge containing fine particles and washing water by sedimentation.

  On the other hand, the iron removing device has a sludge tank, a magnet mounting drum, and a drum rotating mechanism. Here, the sludge tank temporarily holds sludge containing the fine particles discharged from the thickener and the washing water. The magnet mounting drum is formed in a drum shape, and is arranged such that the center axis of the drum faces in the horizontal direction and the lower part of the drum is immersed in sludge in a sludge tank. A plurality of permanent magnets are mounted (arranged) in the drum circumferential direction inside the drum circumferential surface of the magnet mounting drum so that the magnetic poles face outward in the drum radial direction. The drum rotation mechanism rotates the magnet mounting drum. In addition, it is preferable that the iron content removing device has a pH adjusting device that adjusts the hydrogen index of the sludge held in the sludge tank within a range of pH 4 to 6. In this case, it is more preferable that the iron removing device has a means (neutralizing device) for neutralizing the sludge discharged from the sludge tank.

  The soil purification system according to the present invention preferably includes a filter press and a filtrate returning means, and more preferably includes a chelate washing device. In this case, the filter press receives sludge containing fine particles (fine particles other than iron-based fine particles) and water from which iron-based fine particles have been removed by the iron-removing device, and performs pressure filtration. Separate into filtrate and cake containing fines. The filtrate returning means returns the filtrate separated by the filter press to the thickener. The chelate cleaning device cleans the cake separated by the filter press with a chelate cleaning solution containing a chelating agent and water, and removes harmful metals remaining in fine particles (fine particles other than iron-based fine particles). Etc. are removed.

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

  Then, according to the soil purification system according to the present invention, the gravel and sand are crushed by the wet crusher to generate fine particles, and among these fine particles, the fine particles are unevenly or scattered in the gravel or sand. The fine particles containing a large amount of fine lump such as iron were iron-based fine particles, and the iron and the like exposed on the surface of these iron-based fine particles were removed from the wet crusher to the iron removal device. Adsorbs a relatively large amount of harmful metals and the like during the distribution process. Therefore, the iron-based fine particles existing before the crushing and the iron-based fine particles generated by the crushing are introduced into the iron removing device, and both of these iron-based fine particles are considerably large (non-ferrous particles). (Compared to the fine particles).

  Thus, in the iron removing device, since the iron-based fine particles having a large amount of adsorption of these harmful metals and the like are removed from the sludge by the magnet mounting drum, the harmful effect of the sludge or the remaining fine particles (non-ferrous fine particles) is eliminated. The content or holding ratio of metals and the like can be significantly reduced, and depending on the properties of the soil, the content or holding ratio of harmful metals and the like can be reduced to such an extent that dumping or landfilling is possible.

  Therefore, even when harmful metals and the like adsorbed on the remaining fine particles (non-ferrous fine particles) are removed using a relatively expensive chemical such as a chelating agent, the necessary or used amount of the chemical is reduced. Thus, the cost for treating the soil can be significantly reduced. Since the wet crusher and the iron removing device have a simple mechanical structure for performing physical treatment and do not use any special chemicals for treating harmful metals, the operation cost is very low. .

It is a block diagram showing the schematic structure of the soil purification system concerning Embodiment 1 of the present invention. (A) is a typical side sectional view of the iron removing device which is a component of the soil purification system, and (b) is a schematic plan view of the iron removing device shown in (a). (A) is a schematic side sectional view of another iron removing device, and (b) is a schematic plan view of the iron removing device shown in (a). It is a block diagram showing a schematic structure of a chelate washing device which is a component of a soil purification system. FIG. 2 is a schematic elevation view showing a configuration of a mixing and dispersing device forming a part of the chelate washing device. (A) is a schematic plan view of the fine particle cleaning device forming a part of the chelate cleaning device, (b) is a cross-sectional view taken along line AA of the fine particle cleaning device shown in (a), (C) is an elevational sectional view of one slurry passage of the fine-grain cleaning device. FIG. 3 is a schematic elevation view illustrating a configuration of a cleaning liquid regenerating unit that forms a part of the chelate cleaning device. It is a block diagram showing the schematic structure of the soil purification system concerning Embodiment 2 of the present invention.

(Embodiment 1)
As shown in FIG. 1, in the soil purification system S according to the first embodiment of the present invention, the soil is collected by excavation of the ground contaminated with harmful metals and the like (hazardous metals and / or their compounds or their ions). The soil (contaminated soil) is received by the input hopper 1. The harmful metal includes, for example, chromium, lead, cadmium, selenium, mercury, metal arsenic, and the like. The soil in the charging hopper 1 is continuously or intermittently charged into the mixer 2 and mixed with the washing water continuously supplied to the mixer 2. Here, the soil includes gravel (for example, particle size of 2 to 75 mm), sand (for example, particle size of 0.075 to 2 mm), and fine particles (for example, particle size of 0.075 mm or less). Some include stone (for example, a particle diameter of 75 mm or more).

  A mixture containing the soil and the washing water generated in the mixer 2 (hereinafter, referred to as “soil-water mixture”) is transferred to a mill breaker 3 that is a wet crusher. As the mill breaker 3, for example, a rod mill can be used. Although not shown in detail, the rod mill is a crusher in which a plurality of rods (for example, ten 75 mmφ × 2 m steel rods) are arranged in a drum, and the rods are rotated in parallel with each other by rotation of the drum. It moves and makes line contact, and can crush gravels and sand (and, in some cases, stones) by the impact force, shearing force, frictional force, etc., and produce small-diameter soil particles such as fine particles. . As the mill breaker 3, a ball mill or the like can be used in addition to the rod mill. It should be noted that some of the gravel and sand are fine particles, and not all of them are fine particles.

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

  In addition, a large number of iron-based fine particles are generated in which fine clumps of iron or the like (iron and / or iron oxide) existing, unevenly distributed, or scattered inside the gravel and sand are exposed on the surface. On the other hand, iron and the like generally have a property of adsorbing harmful metals and the like. For this reason, a part or most of the harmful metals and the like present in the washing water are adsorbed or adhered to the exposed surface of the iron and the like of the iron-based fine particles. As a result, the adsorption amount (adhesion amount) of harmful metals and the like in the iron-based fine particles is considerably larger than the adsorption amount (adhesion amount) of harmful metals and the like in the non-ferrous fine particles. In other words, the fine particles discharged from the mill breaker 3 are divided into an iron-based fine particle having a large adsorption amount (adhesion amount) of harmful metals and a non-ferrous fine particle having a small adsorption amount (adhesion amount) of harmful metals and the like. It is composed of It should be noted that the iron-based fine particles existing before the crushing also adsorb considerably more harmful metals and the like than the non-ferrous fine particles.

  The iron-based fine particles adsorbing the harmful metals and the like are removed by the iron removing device 12 as described later. On the other hand, it is generally known that iron and the like (iron and / or iron oxide) have a property of adsorbing harmful metals and the like. Various “iron powder methods” have been proposed in which harmful metals and the like are removed from sludge by adding powder (for example, see Patent Documents 3 and 4 and Non-Patent Document 2). However, as in the present invention, by crushing gravels and sand, iron-based fine particles having fine lumps such as fresh iron (not yet adsorbing harmful metals and the like) exposed on the surface are generated. There is no proposal for a method for treating harmful metals or the like in which harmful metals or the like are adsorbed to the minute lump of iron or the like (the iron-based fine-grain portion).

  The soil / water mixture discharged from the mill breaker 3 is introduced into the trommel 4. Although not shown in detail, the trommel 4 is a sieving apparatus that includes a receiving tank that can store water and a substantially cylindrical drum screen that is arranged to be inclined with respect to a horizontal plane. Can be rotated around its central axis (the central axis of the cylinder) by a motor. Further, cleaning water can be sprayed into the drum screen.

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

  In the trommel 4, the classification diameter (opening) of the mesh of the drum screen is set such that soil particles having a particle size of less than 2 mm, that is, sand and fine particles, pass through the mesh of the drum screen. Therefore, in the trommel 4, the gravels (in some cases, stones), which are soil particles having a particle size of 2 mm or more, are separated from the soil / water mixture. As described above, harmful metals and the like that have been separated into water are hardly adsorbed or adhered to gravel and sand, so that the gravel separated by the trommel 4 is clean and used as, for example, aggregate for concrete. be able to. Note that the mesh size (mesh size) of the drum screen of the trommel 4 is not limited to the above-described one, but can be arbitrarily set according to the particle size of the soil particles to be obtained. It is.

  The soil particles having a particle diameter of less than 2 mm, that is, a soil / water mixture containing fine particles and washing water, contained in the receiving tank of the trommel 4 are introduced into the cyclone 5 (liquid cyclone). The cyclone 5, which is not shown in detail, pumps the soil / water mixture into a substantially conical cylinder that narrows downward to generate a swirling flow, and utilizes the centrifugal force generated thereby, The soil / water mixture is made up of a mixture of water having a relatively small particle size (for example, a particle size of less than 0.075 mm) and water, a relatively large particle size of sand (for example, a particle size of 0.075 mm or more) and water. And a mixture of

  A mixture of fine particles and water (hereinafter referred to as “fine particle content water”) is discharged from the upper end of the cyclone 5, and a mixture of sand and water having a relatively large particle diameter is discharged from the lower end of the cyclone 5. Is done. Here, the mixture of sand and water discharged from the lower end of the cyclone 5 hardly contains harmful metals and the like as described above, so that it is drained or dried to be used as recycled sand. On the other hand, the water containing fine particles is transferred to the PH adjustment tank 6.

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

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

  The water containing fine particles in the coagulation tank 7 is introduced into the thickener 8. Although not shown in detail, the thickener 8 sediments the water-insoluble floc or fine particles by gravity in a state where the fine particle-containing water is almost stationary, and forms a sludge layer (for example, solid And the supernatant water (washing water) which is located at the upper portion and contains almost no floc or fine particles. When the floating oil is floating on the surface of the supernatant water, the floating oil is removed by overflowing a small amount of the supernatant water from the upper part of the thickener 8.

  The supernatant water in the thickener 8 is introduced into the washing water tank 10 and is temporarily stored. When the washing water tank 10 becomes full, the spare water tank 11 is used. The washing water stored in the washing water layer 10 or the preliminary water tank 11 is supplied to the mixer 2 and the trommel 4 as circulating water. In addition, when the washing water stored in the washing water tank 10 decreases due to evaporation or the like, tap water is appropriately supplied. On the other hand, the sludge deposited at the lower part of the thickener 8 is transferred to the intermediate tank 9 and is temporarily stored. Then, the sludge in the intermediate tank 9 is continuously transferred to the iron removing device 12.

  As shown in FIGS. 2A and 2B, the iron removing device 12 includes a sludge tank 16 and a magnet mounting drum 17. Here, the sludge tank 16 temporarily receives sludge composed of fine particles (ferrous fine particles and non-ferrous fine particles) and water transferred from the intermediate tank 9 through the pipe 18 and temporarily receives the sludge. Hold. Then, the sludge in the sludge tank 16 is transferred (pressurized) to the filter press 13 (see FIG. 1) via the pipe 19 after the iron-based fine particles are removed as described later. Note that a stirrer 20 is provided in the sludge tank 16 in order to prevent fine particles from settling at the bottom.

  The magnet mounting drum 17 includes a rotating shaft 21, a cylindrical drum main body 22 coaxially attached to the rotating shaft 21, and an annular portion adjacent to a circumferential portion (outer edge portion) of the drum main body 22 in a drum circumferential direction. And a plurality of permanent magnets 23 mounted or arranged on the outer peripheral surface, and a cylindrical cover 24 for covering the outer peripheral surface of the group of permanent magnets arranged in a ring. Here, the drum main body 22 is arranged such that its rotation center axis is oriented in the horizontal direction and the lower part of the drum is immersed in the sludge in the sludge tank 16.

  The plurality of permanent magnets 23 are disposed (outward) such that the magnetic poles face outward in the drum radial direction. The permanent magnets 23 may be arranged such that all N poles or S poles face outward, or may be arranged such that N poles and S poles alternately face outward. The cylindrical cover 24 is preferably formed of a soft magnetic metal material (for example, iron or iron alloy) having a relatively small thickness (for example, 5 to 10 mm), but a diamagnetic metal material (for example, copper or aluminum or These alloys) may be used.

  The rotating shaft 21 and, consequently, the drum main body 22 are rotationally driven by a motor 25 (electric motor) via a speed reducer 26, and slowly rotate in a clockwise direction in the positional relationship in FIG. 0 rpm). When the drum body 22 is immersed in the sludge in the sludge tank 16, the iron-based fine particles in the sludge are attracted to and attracted to the outer peripheral surface of the cylindrical cover 24 by the magnetic force of the permanent magnet 23. Thus, when the drum body 22 comes out of the sludge, an iron-based fine-grained sublayer is formed on the outer peripheral surface of the cylindrical cover 24. The iron-based fine particle layer formed on the outer peripheral surface of the cylindrical cover 24 is scraped off by the scraper 27 and removed from the drum body 22. The removed iron-based fine particles can be used, for example, as a raw material for ironmaking.

  The iron-based fine fraction is produced by crushing gravel and sand with a mill breaker 3 (see FIG. 1), which is a wet crusher, or existing before crushing of gravel and sand. A minute lump of iron or the like is exposed on the surface, and a considerably large amount of harmful metal or the like is adsorbed on the exposed minute lump of iron or the like. 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 5% by mass. For this reason, a part of the fine particles generated by the crushing of the gravels and sand becomes iron-based fine particles in which fresh iron or the like is exposed on the surface.

Iron is a ferromagnetic material (soft magnetic material) and is attracted to a magnet. The iron oxides present in the soil are substantially triiron tetroxide (Fe ₃ O ₄ ), γ-type diiron trioxide (γ-Fe ₂ O ₃ ), and α-type diiron trioxide ( α-Fe ₂ O ₃ ), and triiron tetroxide and γ-type diiron trioxide are ferromagnetic substances (soft magnetic substances) and are adsorbed by magnets. The α-type diiron trioxide is not magnetized and is not adsorbed by the magnet. For this reason, the iron-based fine particles, on the surface of which fine lump such as iron is exposed, are attracted to the permanent magnet 23 by the ferromagnetism (soft magnetism) of iron, triiron tetroxide or γ-type diiron trioxide, It is adsorbed on the outer peripheral surface of the cylindrical cover 24.

The inventor of the present application crushed pebbles and sand with a mill breaker several times (10 times) in July 2017 at a contaminated soil treatment plant in Yamagatazaki Co., Ltd. Sludge (1 to 3% by mass of fine particles), which is a mixture of fine particles and water produced by the above method, is divided into iron-based fine particles using a magnet mounting drum (using a neodymium magnet as a permanent magnet) having a diameter of about 1 m. As a result of the adsorption experiment, 3.4 kg of iron-based fine particles were collected on average per 10 m ³ of sludge.

  Fine lump of iron and the like exposed on the surface of iron-based fine particles generated by crushing gravel and sand with mill breaker 3 is harmful metal or the like unevenly or dotted in the gravel or sand. It is generated from small lumps of fresh iron or the like not adsorbing harmful metals, and is exposed to the surface after crushing and adsorbs harmful metals and the like from the washing water around the crushing. Thus, the fine particles discharged from the mill breaker 3 and finally introduced into the iron removing device 12 include the iron-based fine particles having a relatively large (or considerable) adsorption amount of harmful metals and the like, Is relatively (or considerably) non-ferrous fine particles.

  As described above, since the iron-based fine particles are removed from the sludge in the iron removing device 12, the fine particles contained in the sludge discharged from the iron removing device 12 have a relatively low adsorption amount of harmful metals and the like. Most (or quite) less non-ferrous fines. Therefore, most or a considerable part of the harmful metals and the like contained in the contaminated soil introduced into the soil purification system S are removed by the iron removing device 12. For this reason, depending on the properties of the contaminated soil introduced into the soil purification system S, the sludge or fine particles discharged from the iron removing device 12 can be disposed of by landfilling or the like only by dewatering.

  Further, as described later, when the chelate cleaning treatment is performed on the sludge or fine particles discharged from the iron removal device 12 with the chelate cleaning solution, the chelate cleaning treatment is performed in comparison with the case where the iron removal device 12 is not provided. Since the load of harmful metals and the like is reduced, processing costs in the chelate cleaning processing can be reduced. In this case, the iron removal device 12 can be positioned as a pretreatment device that reduces the load in the chelate cleaning process. It should be noted that the iron removal device 12 can be positioned as a pretreatment device also when performing a chemical treatment other than the chelate cleaning process on the sludge or fine particles discharged from the iron removal device 12.

  As shown in FIG. 1 again, the sludge discharged from the iron removing device 12 is introduced into the filter press 13 and dehydrated, and a filtrate and a cake (filter cake) are generated. Then, the filtrate is returned to the thickener 8. On the other hand, the cake is transferred to the chelate washing device 14 to remove harmful metals and the like remaining in the fine particles (non-ferrous fine particles). If the content of the harmful metal in the fine particles contained in the cake is within the standard, the cake is disposed of by landfilling without being transferred to the chelate washing device 14.

  Hereinafter, with reference to FIGS. 3A and 3B, the configuration and functions of another iron removal device 12A having a different configuration from the iron removal device 12 shown in FIGS. 2A and 2B will be described. . However, most of the components of the iron removing device 12A shown in FIGS. 3A and 3B are common to the components of the iron removing device 12 shown in FIGS. In order to avoid duplication, the following mainly describes points different from the iron removing device 12. In the components of the iron removing device 12A shown in FIGS. 3A and 3B, the same reference numerals are used for components common to the components of the iron removing device 12 shown in FIGS. 2A and 2B. Numbered.

  As shown in FIGS. 3A and 3B, in the iron removing device 12A, a cylindrical driving roller 28 is provided above the sludge tank 16 separately from the drum main body 17A. 29 is coaxially mounted. The drive roller 28 and the drive shaft 29 are arranged so that their rotation center axes are parallel to the rotation center axis of the drum main body 17A, and are driven to rotate by a motor 25 via a speed reducer 26. The drive roller 28 has a smaller diameter (for example, 1/5 to 1/10) than the drum main body 17A.

  A plurality of permanent magnets 23 are mounted or arranged on the drum main body 17A in the same specification as the iron removing device 12 shown in FIG. The rotating shaft 21 of the drum main body 17A is rotatably supported by a bearing fixed to the sludge tank 16. Then, an endless belt 30 (for example, steel) made of a soft magnetic metal material (for example, iron or iron alloy) extends over the drum body 17A and the drive roller 28 in which a plurality of permanent magnets 23 are annularly mounted or arranged on the circumference. Belt). Note that the endless belt 30 may be formed of a diamagnetic metal material (for example, copper, aluminum, or an alloy thereof).

  When the drive roller 28 is driven to rotate clockwise by the motor 25 via the speed reducer 26 in the positional relationship in FIG. 3A, the drum body 17A is driven to rotate clockwise and the endless belt 30 is rotated. Travels clockwise between the drive roller 28 and the drum body 17A. The rotation speed of the motor 25 or the drive roller 28 is set such that the drum main body 17A rotates at a low speed (for example, 0.5 to 2.0 rpm).

  An endless belt 30 that runs in a clockwise direction between the driving roller 28 and the drum main body 17A in the clockwise direction in the positional relationship in FIG. 3A is a group of permanent magnets arranged in an annular shape on the circumferential surface of the drum main body 17A. When it is in contact with the outer peripheral surface of the endless belt and is immersed in the sludge in the sludge tank 16, the iron-based fine particles in the sludge are attracted to and attracted to the outer surface of the endless belt 30 by the magnetic force of the permanent magnet 23. Thus, when the endless belt 30 comes out of the sludge, an iron-based fine-grained layer is formed on the outer surface of the endless belt 30. The iron-based fine-grained layer formed on the outer surface of the endless belt 30 is scraped off by the scraper 27 near the driving roller 28 and removed from the endless belt 30.

  In the iron removing device 12A shown in FIGS. 3A and 3B, similarly to the iron removing device 12 shown in FIGS. 2A and 2B, iron-based fine particles are removed from sludge. Most of the fine particles contained in the sludge discharged from the iron removing device 12A are non-ferrous fine particles having a very small (or considerable) amount of adsorption of harmful metals and the like. The sludge discharged from the iron removing device 12A is introduced into the filter press 13 and dewatered, and a filtrate and a cake (filter cake) are generated. Then, the filtrate is returned to the thickener 8. On the other hand, the cake is transferred to the chelate washing device 14 to remove harmful metals and the like remaining in the fine particles (non-ferrous fine particles).

  Hereinafter, the configuration and function of the chelate cleaning device 14 will be described. When the content of harmful metals and the like in the cake discharged from the filter press 13 is lower than a predetermined regulation value in the case of disposal by landfill or reuse, it is not necessary to use or provide the chelate washing device 14. .

  First, the general configuration and function of the cleansing device 14 will be described with reference to FIG. In the chelate cleaning device 14, first, the cake (filter cake) discharged from the filter press 13 and the chelate cleaning liquid containing a chelating agent in the cleaning liquid storage tank 36 are continuously supplied to the mixing and dispersing device 31. Then, the mixing and dispersing device 31 mixes the cake and the chelate cleaning liquid, and in the chelate cleaning liquid, fine particles or small pieces of fine particles (for example, having a particle size of about several 0.1 to 0.5 mm, or 0.1 To about 1 mm) is almost uniformly dispersed (suspended) to produce a fine-grain slurry.

  The fine-grain slurry generated by the mixing and dispersing device 31 is transferred to the fine-grain cleaning device 32. The fine-grain cleaning device 32 is configured to allow the fine-grain slurry to flow through a plug flow (plug flow) so as to secure a preset residence time (for example, 0.5 to 2 hours) while stirring. The harmful metals and the like adhering to the fine particles are released and captured by the chelating agent in the chelating cleaning solution. This removes harmful metals and the like adsorbed (adhered) to the surface of the fine particles in the fine particle slurry.

  Here, as a chelating agent used in the chelate cleaning solution, for example, EDTA (ethylenediaminetetraacetic acid), HIDS (3-hydroxy-2,2′-iminodisuccinic acid), IDS (2,2′-iminodisuccinic acid), MGDA (Methylglycine diacetate), sodium salt of EDDS (ethylenediaminediacetate) or GLDA (L-glutamic aciddiacetic acid). Any of these chelating agents can effectively capture (chelate) harmful metals and the like contained in the fine-grain slurry or fine-grain. In addition, depending on the type of the harmful metal contained in the fine particles, a chelating agent suitable for the treatment is selected or a plurality of chelating agents are used.

  The fine particle slurry discharged from the fine particle cleaning device 32 is transferred to the filtration device 33. The filtering device 33 filters the fine-grain slurry to generate a cake (filter cake) having a water content of 30 to 40% and a filtrate. In addition, as such a filtering device 33, a filter press, a vacuum filter, or the like can be used. The filter cake (fine-grained portion) discharged from the filter device 33 contains almost no harmful metal or the like.

  The filtrate, that is, the chelate cleaning liquid discharged from the filtration device 33 is introduced into the cleaning liquid regenerating section 34. The cleaning liquid regeneration unit 34 includes a cleaning liquid regeneration device 35, a cleaning liquid storage tank 36, an acid liquid storage tank 37, and a water storage tank 38. Here, the washing liquid regenerating device 35 has a higher complexing power than the chelating agent, and solid-phase adsorption for adsorbing or extracting harmful metals and the like in the chelating washing solution when coming into contact with the chelating washing solution (filtrate) discharged from the filtering device 33. This is a device for regenerating a chelate cleaning liquid having a small piece or a granular material in which the material or the solid phase adsorbent is fixed, removing harmful metals and the like from the chelating agent in the chelate cleaning liquid.

  In the cleaning solution regenerating device 35, a chelating cleaning solution containing a chelating agent capturing a harmful metal or the like is brought into contact with a solid phase adsorbent having a higher complexing power than the chelating agent. The solid-phase adsorbent has a multi-point interaction through coordination bond and hydrogen bond, in which a carrier carries a cyclic molecule, and a cyclic molecule is modified with a chelating ligand, and selectively takes in ions such as harmful metals. is there. As a result, the harmful metals and the like captured by the chelating agent are separated from the chelating agent, and are adsorbed or extracted by the solid phase adsorbent. As a result, harmful metals and the like are removed and recovered from the chelate cleaning liquid (chelating agent), and the chelating cleaning liquid (chelating agent) is again in a state capable of capturing harmful metals and the like.

  The chelate cleaning liquid thus regenerated is temporarily stored in the cleaning liquid storage tank 36, and then returned to the mixing / dispersing device 31 by a cleaning liquid reflux mechanism (a pump 81, a pipe 82, and the like described later). That is, the chelate cleaning liquid circulates in the chelate cleaning device 14 while repeating purification of fine particles and regeneration of the chelating agent. The reduced amount of the chelating agent is appropriately replenished.

  The solid-phase adsorbent having a higher complexing power than the chelating agent is, for example, a solid such as a gel, and generally, when it comes into contact with an aqueous solution containing a chelating agent capturing a metal, the solid-state adsorbing material is coordinated with the chelating agent. It has a strong binding force other than a covalent bond to such an extent that the metal ions are released from the chelating agent and can be transferred to the solid phase adsorbent. For example, when EDTA (ethylenediaminetetraacetic acid) is used as a chelating agent, such a solid-phase adsorbent has a strong binding force capable of recovering almost 100% of metal ions from an aqueous solution of EDTA having a concentration of 10 mM / l. Have

  Examples of such a solid phase adsorbent include those in which a cyclic molecule is densely supported on a carrier such as silica gel or a resin and the cyclic molecule is modified with a chelating ligand. When such a solid-phase adsorbent is used, a plurality of various bonds and interactions such as a coordination bond and a hydrogen bond are generated by an adjacent cyclic molecule and a chelating ligand, and a multipoint interaction is generated, and a metal ion is formed. And a metal ion can be selectively taken in due to the properties of the cyclic molecule.

  As the chelate cleaning solution is regenerated, the amount of harmful metals and the like adsorbed on the solid phase adsorbent increases with time, but there is an upper limit to the amount of harmful metals and the like adsorbed on the solid phase adsorbent. For this reason, when the adsorption amount of harmful metals and the like in the solid phase adsorbent reaches a saturated state or near the saturated state, the solid phase adsorbent is driven by the solid phase adsorbent regeneration mechanism (the acid solution storage tank 37, the pump 83, the pipe 84, 78, 79, 85, etc.). That is, the solid-phase adsorbent regenerating mechanism supplies an acid solution to the cleaning solution regenerating device 35 in a state where the chelate cleaning solution has been removed, and removes harmful metals and the like adsorbed on the solid-phase adsorbent with the acid solution to remove the solid-phase adsorbent. To play. Thus, while the harmful metals and the like are recovered by the acid solution, the solid phase adsorbent is regenerated and becomes capable of adsorbing the harmful metals and the like again. After being regenerated with an acid solution, the solid-phase adsorbent is washed with a water-washing mechanism (a water storage tank 38, a pump 86, pipes 87, 78, 79, 88, etc.), and adheres to the solid-phase adsorbent. The acid solution is removed.

Hereinafter, the specific configuration and function of the chelate cleaning device 14 will be described.
First, the specific configuration and function of the mixing and dispersing device 31 which is a component of the chelate cleaning device 14 will be described with reference to FIG. The mixing and dispersing device 31 continuously mixes the cake (fine particles) discharged from the filter press 13 and the chelate cleaning liquid to generate a fine particle slurry in which the fine particles are dispersed in the chelate cleaning liquid. Specifically, the mixing and dispersing device 31 premixes the crusher 41 for crushing the cake (the fine particles) discharged from the filter press 13 and the cake pieces crushed by the crusher 41 and the chelate washing liquid. The premixing tank 42 and the mixture generated by the premixing tank 42 are stirred to chelate cake pieces (for example, particles having a particle size of about 0.1 to 0.5 mm or about 0.1 to 1 mm). A line mixer 43 for dispersing or suspending in the washing liquid.

  Then, in the mixing and dispersing device 31, the cake discharged from the filter press 13 is supplied to a crusher 41, and the cake is formed by a high-speed rotating blade 41a into a large number of particles having a particle size of several mm (for example, 1 to 5 mm). Crushed into cake pieces. On the other hand, the chelate cleaning liquid in the chelate cleaning liquid storage tank 44 is supplied to the crusher 41 via a pipe 46 by a pump 45. The chelate cleaning liquid is appropriately supplied from the cleaning liquid storage tank 36 (see FIG. 4) to the chelate cleaning liquid storage tank 44. Although not shown in detail, the chelate cleaning liquid is sprayed or supplied to a large number of cake pieces immediately after being crushed by the blade 41a to prevent the cake pieces from adhering to each other. In addition, as such a crusher 41, for example, a "dewatered cake crusher" according to Taiyo Kiko Co., Ltd. or a "dewatered cake recycling device" according to Kikosha can be used. When a commercially available crusher is used, it is necessary to provide a mechanism for injecting or supplying a chelate washing liquid to a large number of cake pieces immediately after crushing.

  The pure chelate solution and the cake pieces in the crusher 41 are transferred to the premixing tank 42. The chelate cleaning liquid and cake pieces in the premixing tank 42 are stirred and premixed by a stirrer 47 which is driven to rotate by a motor. Then, the mixture of the chelate washing liquid and the cake pieces in the premixing tank 42 is transferred to the line mixer 43 via the pipe 49 by the pump 48. The line mixer 43 is a flow-type mixer in which a blade that is driven to rotate at a very high speed by a motor is arranged in a horizontal-type substantially cylindrical stirring chamber, and stirs the chelate cleaning liquid and cake pieces very vigorously. Then, fine pieces of cake or fine particles (for example, particles having a particle size of about 0.1 to 0.5 mm or about 0.1 to 1 mm) are substantially uniformly dispersed (suspended) in the chelate cleaning liquid. To produce a fine-grain slurry. The fine-grain slurry is transferred to the fine-grain cleaning device 32 (see FIG. 4). As such a line mixer 43, for example, “Satake multi-line mixer” according to Satake Chemical Machinery Co., Ltd. can be used.

  Next, with reference to FIGS. 6A to 6C, the specific configuration and function of the fine-grain cleaning device 32 that is a component of the chelate cleaning device 14 will be described. The fine particle cleaning device 32 adsorbs (adheres) to the fine particles by causing the fine particle slurry generated by the mixing and dispersing device 31 to flow through a plug flow while securing a preset residence time while stirring. ) Is released from the fine particles and trapped by the chelating agent.

  The fine-grain cleaning device 32 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. doing. The storage tank 50 may be, for example, an iron rectangular parallelepiped tank installed on the ground, or may be a concrete rectangular pit. Further, the partition walls 51 to 54 may be formed by, for example, connecting a plurality of iron plates or plastic plates in the direction in which the slurry passage extends.

  Two slurry passages adjacent to each other in the slurry passages 55 to 59 are connected to one end of a communicating portion (four curved lines in FIG. 6A) in the longitudinal direction of the slurry passage (the left-right direction in the positional relationship in FIGS. 6A and 6B). (A site indicated by a cross-shaped arrow). That is, the partition walls 51 to 54 do not exist in these communicating portions, and the adjacent slurry passages communicate with each other.

  At the bottom of each of the slurry passages 55 to 59, there are provided air discharge tubes 61 to 65 for discharging air into the fine-grain slurry and agitating the fine-grain slurry. Each of the air discharge tubes 61 to 65 is a perforated tube which extends in the slurry passage longitudinal direction and has a plurality of air discharge holes formed in the bottom (lower side) of the peripheral wall and arranged in the slurry passage longitudinal direction. Although not shown, it is connected to a compressor or a blower that supplies compressed air. When the pressurized air is supplied to the air discharge pipes 61 to 65, the air is released from the air discharge holes as bubbles into the fine-grain slurry and floats, and the fine-grain slurry is stirred by the bubbles. Is done.

  FIG. 6C shows a cross section of the slurry passage 55 on the most upstream side when viewed in the flow direction of the fine-grain slurry (the direction indicated by the curved arrow and the straight arrow in FIG. 6A). . As is clear from FIG. 6C, the air discharge pipe 61 is disposed near one side of the slurry passage 55 and near the bottom of the slurry passage. For this reason, the bubbles released from the air discharge pipe 61 rise near this side surface. As a result, a circulating flow is formed in the slurry passage 55 in the direction indicated by the arrow P in a plane perpendicular to the longitudinal direction of the slurry passage, and the slurry for fine particles is stirred. The shape, size, volume, and the like of the storage tank 50 and each of the slurry passages 55 to 59, the supply amount of pressurized air to the air discharge pipes 61 to 65, and the like are determined in advance in the fine particle fraction washing device 32. It is preferably set in accordance with the water content, flow rate, residence time, flow velocity, turbulence degree of the flow (for example, Reynolds number), and the like.

  Hereinafter, the specific configuration and function of the cleaning liquid regeneration unit 34, which is a component of the chelate cleaning device 14, will be described with reference to FIG. The washing liquid regenerating section 34 is a packed tower type washing liquid in which solid phase adsorbent particles or a packing (packing) in which the solid phase adsorbent is fixed are filled as a means for regenerating a chelate washing liquid or a chelating agent. A playback device 35 is provided. The cleaning liquid regenerating section 34 stores an intermediate storage tank 72 for storing a chelate cleaning liquid to be regenerated, a cleaning liquid storage tank 36 for storing a regenerated chelate cleaning liquid, an acid liquid storage tank 37 for storing an acid liquid, and stores water. A water storage tank 38 is provided.

  In the intermediate storage tank 72, the filtrate discharged from the filtration device 33 (see FIG. 4), that is, the chelate cleaning liquid, is temporarily stored. When regenerating the chelate cleaning liquid, the pump 76 for transferring the chelate cleaning liquid stored in the intermediate storage tank 72 to the cleaning liquid regenerating device 35 and transferring the chelate cleaning liquid regenerated by the cleaning liquid regenerating device 35 to the cleaning liquid storage tank 36. And a series of conduits 77-80. In addition, a pump 81 and a pipe 82 are provided for supplying the chelate cleaning liquid stored in the cleaning liquid storage tank 36 to the chelate cleaning liquid storage tank 44 and further to the mixing / dispersing device 31 (see FIG. 5).

  Further, the cleaning solution regenerating section 34 transfers the acid solution stored in the acid solution storage tank 37 to the cleaning solution regenerating device 35 when regenerating the solid-phase adsorbent, and the acid solution discharged from the cleaning solution regenerating device 35. A pump 83 and a plurality of conduits 84 and 85 for returning to the acid solution storage tank 37 are provided. Further, the washing liquid regenerating section 34 transfers the water stored in the water storage tank 38 to the washing liquid regenerating device 35 and discharges the water from the washing liquid regenerating device 35 when washing the solid phase adsorbent regenerated with the acid solution. A pump 86 and a plurality of pipelines 87 and 88 for returning the drained water to the water storage tank 38 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 solution or the water to the cleaning liquid regenerating apparatus 35, respectively. ing. On the other hand, pipes 79, 80, 85, and 88 for discharging the chelate cleaning liquid, the acid solution, or the water from the cleaning liquid regenerating apparatus 35 are provided with valves 95, 96, 97, and 98 that open and close the corresponding pipes, respectively. Has been established. By switching between the open and closed states of these valves 91 to 98, any one of the chelating cleaning liquid, the acid liquid and the water can be supplied to and discharged from the cleaning liquid regenerating device 35. The opening and closing of these valves 91 to 98 are automatically controlled by a controller (not shown).

  Hereinafter, an example of an operation method of the cleaning liquid regeneration unit 34 will be described. The operation method described below is merely an example, and the operation method of the cleaning liquid regenerating unit 34 according to the present invention is not limited to the following method. When regenerating the chelate washing liquid (chelating agent), the valves 91, 92, 95, 96 provided in the pipes 77 to 80 are opened, while the other valves 93, 94, 97, 98 are closed, The pump 76 is operated. Thereby, the chelate cleaning liquid in the intermediate storage tank 72 flows through the cleaning liquid regenerating device 35 and is transferred to the cleaning liquid storage tank 36.

  In the cleaning liquid regenerating device 35, a chelate cleaning liquid containing a chelating agent capturing a harmful metal or the like is brought into contact with a solid-phase adsorbent (solid-state adsorbent particles) having a higher complexing power than the chelating agent. As a result, harmful metals and the like captured by the chelating agent are separated from the chelating agent, and are adsorbed or extracted by the solid phase adsorbent. As a result, harmful metals and the like are removed and recovered from the chelate cleaning solution, and the chelating agent is in a state capable of capturing the harmful metals and the like again, and the chelate cleaning solution is regenerated. The chelate cleaning liquid stored in the cleaning liquid storage tank 36 is returned by the pump 81 to the chelate cleaning liquid storage tank 44 and the mixing / dispersing device 31 (see FIG. 5) via the pipe 82.

  The solid-phase adsorbent having a higher complexing power than the chelating agent is, for example, a solid such as a gel, and generally, when it comes into contact with an aqueous solution containing a chelating agent capturing a metal, the solid-state adsorbing material is coordinated with the chelating agent. It has a strong binding force other than a covalent bond to such an extent that the metal ions are released from the chelating agent and can be transferred to the solid phase adsorbent. Examples of such a solid phase adsorbent include those in which a cyclic molecule is densely supported on a carrier such as silica gel or a resin and the cyclic molecule is modified with a chelating ligand. When such a solid-phase adsorbent is used, a plurality of various bonds and interactions such as a coordination bond and a hydrogen bond are generated by an adjacent cyclic molecule and a chelating ligand, and a multipoint interaction is generated, and a metal ion is formed. And a metal ion can be selectively taken in due to the properties of the cyclic molecule.

  As the chelate cleaning solution is regenerated, the amount of harmful metals and the like adsorbed on the solid phase adsorbent increases with time, but as described above, the adsorption capacity of the solid phase adsorbent has an upper limit. Therefore, when the amount of harmful metals or the like adsorbed on the solid phase adsorbent reaches a saturated state or near the saturated state, the solid phase adsorbent is regenerated. That is, an acid solution is flown into the cleaning solution regenerating device 35 in a state where the chelate cleaning solution has been removed, and harmful metals and the like adsorbed on the solid phase adsorbent are removed by the acid solution to regenerate the solid phase adsorbent. Thus, while the harmful metals and the like are recovered by the acid solution, the solid-phase adsorbent is regenerated to a state where the harmful metals and the like or these ions can be adsorbed or extracted again. As described later, the solid phase adsorbent is washed with water after being regenerated with an acid solution, and the acid solution adhering to the solid phase adsorbent is removed.

  When the adsorption amount of harmful metals and the like of the solid-phase adsorbent in the cleaning liquid regenerating device 35 reaches a saturated state or a vicinity thereof, and the solid-state adsorbent is regenerated with an acid solution, the pipes 84, 78, 79, and 85 are connected. The interposed valves 93, 92, 95, 97 are opened, while the other valves 91, 94, 96, 98 are closed, and the pump 83 is operated. Thereby, the acid solution in the acid solution storage tank 37 flows through the cleaning liquid regenerating device 35 and returns to the acid solution storage tank 37. Before the regeneration operation of the solid phase adsorbent is started, the chelate cleaning solution in the cleaning solution regeneration device 35 is removed. If a plurality of cleaning liquid regenerating devices 35 are arranged in parallel, the chelating cleaning liquid can be continuously regenerated even when the supply of the chelating cleaning liquid to some cleaning liquid regenerating devices 35 is stopped. Whether or not the harmful metal adsorption amount of the solid phase adsorbent has reached a saturated state or its vicinity can be determined by detecting the content of harmful metals and the like in the chelate cleaning liquid discharged from the cleaning liquid regenerating device 35. it can.

  The time during which the acid solution flows through the cleaning liquid regenerating device 35 is preferably set according to the size or shape of the cleaning liquid regenerating device 35, the size of the solid phase adsorbent particles, and the like. The acid solution circulates and flows between the acid solution storage tank 37 and the cleaning solution regenerating device 35. At this time, the solid phase adsorbent in the cleaning liquid regenerating device 35 comes into contact with the acid solution, and harmful metals and the like adsorbed by the solid phase adsorbent are released into the acid solution. That is, the harmful metals and the like are recovered by the acid solution, and the solid-phase adsorbent is regenerated so that the harmful metals and the like can be adsorbed again.

  When the solid phase adsorbent is washed with water after the regeneration of the solid phase adsorbent with the acid solution, the valves 94, 92, 95, 98 provided in the pipes 87, 78, 79, 88 are opened. , The other valves 91, 93, 96, 97 are closed and the pump 86 is operated. Thus, the water in the water storage tank 38 flows through the cleaning liquid regenerating device 35 and returns to the water storage tank 38. Before such a solid phase adsorbent washing operation is started, the acid solution in the washing liquid regenerating device 35 is removed. The water circulates and flows between the water storage tank 38 and the cleaning liquid regenerating device 35. At that time, the solid phase adsorbent in the cleaning liquid regenerating device 35 comes into contact with water, and the acid solution adhering to the solid phase adsorbent is washed. Thereafter, regeneration of the chelate cleaning liquid is restarted.

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

  Since the iron-based fine particles having a large amount of adsorption of harmful metals and the like are removed from the sludge by the magnet mounting drum 17 in the iron-removing device 12, the sludge or the remaining fine particles (non-ferrous fine particles) are harmful. The content of metals and the like can be significantly reduced, and depending on the properties of the soil, the content of harmful metals and the like can be reduced to such an extent that dumping or landfilling is possible.

  Since the content of harmful metals and the like in the sludge discharged from the iron removing device 12 is greatly reduced in this way, the cake discharged from the filter press 13 for filtering the sludge is subjected to chelate cleaning by the chelate cleaning device 14. Even in this case, the use amount or required amount of the chelating agent can be greatly reduced, and the cost for treating the soil can be reduced. Since the mill breaker 3 and the iron removing device 12 have a simple mechanical structure for performing a physical treatment and do not use any special chemicals for treating harmful metals and the like, the operation cost is very high. Low.

(Embodiment 2)
Hereinafter, the soil purification system SA according to the second embodiment of the present invention will be described with reference to FIG. However, the soil purification system SA according to the second embodiment and the soil purification system S according to the first embodiment shown in FIGS. 1 to 7 are common in many points. Therefore, in the following, in order to avoid repetition of the description, differences between the soil purification system SA and the soil purification system S will be mainly described. Note that among the components of the soil purification system SA according to the second embodiment, those that are common to the components of the soil purification system S according to the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  Although a part of the soil purification system SA according to the second embodiment is omitted in FIG. 8, like the soil purification system S according to the first embodiment, a series of steps from the charging hopper 1 to the intermediate tank 9 is performed. 1 to 9, a washing water storage tank 10, a spare water tank 11, and an iron removing device 12. However, the soil purification system SA does not include the filter press 13 and the chelate cleaning device 14 in the first embodiment. The soil purification system SA includes a fine particle fraction washing device 101, a filtration device 102, a clarification filter 103, a reverse osmosis membrane separation device 104 (RO separation device), and a chelating agent regeneration device 105. .

  Although not shown in detail, the fine particle cleaning device 101 receives sludge containing non-ferrous fine particles and cleaning water discharged from the iron removing device 12 and a chelate cleaning liquid containing a chelating agent and water. These are mixed and stirred to produce a fine-grain slurry, which is continuously adsorbed (adhered) to the non-ferrous fine granules by continuously flowing so as to secure a preset residence time. The harmful metal or the like is released and captured by the chelating agent, or the harmful metal or the like existing in water is captured by the chelating agent. As such a fine-grain cleaning device 101, for example, the fine-grain cleaning device 32 in Embodiment 1 (see FIGS. 6A to 6C) can be used. The ratio between the flow rate of the sludge supplied to the fine particle cleaning device 101 and the flow rate of the chelate cleaning liquid is set to, for example, 1: 1. The chelating agent used is the same as in the first embodiment.

  The fine particle slurry discharged from the fine particle cleaning device 101 is transferred to the filtration device 102. The filtration device 102 filters the fine-grain slurry to produce a cake (filter cake) having a water content of 30 to 40% and a filtrate. In addition, as the filtering device 102, a filter press, a vacuum filter, or the like can be used. The cake (fines) discharged from the filtration device 102 contains almost no harmful metal or the like.

  The filtrate discharged from the filtration device 102, that is, the chelate washing solution, is subjected to pressure removal to a reverse osmosis membrane separation device 104 after a suspended substance or a suspended substance (SS) is removed by a clarifying filter 103 (for example, a sand filter). . Although not shown in detail, the reverse osmosis membrane separation device 104 receives the chelate washing liquid discharged from the clarification filter 103, and does not include the concentrated water in which the chelating agent is concentrated by the reverse osmosis membrane and the chelating agent. Separate from permeate.

  As the reverse osmosis membrane of the reverse osmosis membrane separation device 104, for example, a three-layer structure in which a polysulfone support layer and a dense crosslinked aromatic polyamide layer are laminated on a surface of a polyester nonwoven fabric (100 to 120 μm in thickness) is used. Can be used. The dense crosslinked aromatic polyamide layer has a large number of pores having a pore size of about 0.5 to 1.5 nm, and is very thin that allows water to permeate but does not allow the chelating agent to permeate (for example, 0.2 to 0.25 μm) It is a semipermeable membrane. The polysulfone support layer is a relatively thick (for example, 40 to 50 μm) porous membrane for supporting or protecting a very thin crosslinked aromatic polyamide dense layer to prevent its breakage.

The reverse osmosis membrane separation device 104 is of a spiral type, and has a plurality of reverse osmosis membrane elements in which a reverse osmosis membrane wound in a spiral shape is accommodated in a cylindrical container. It is practical that each reverse osmosis membrane element has, for example, a total length of about 1 to 2 m and an outer diameter of about 0.2 to 0.4 m. For example, the effective membrane area of a reverse osmosis membrane in a commercially available reverse osmosis membrane element of this type having a total length of about 1 m and an outer diameter of about 0.2 m (for example, manufactured by Osentech Co., Ltd. of Nakatsugawa City, Gifu Prefecture) is It is about 40 m ² . In the case of this reverse osmosis membrane element, when a chelate cleaning solution having a chelating agent concentration of about 1% by mass is supplied at a pressure of about 1 MPa, the processing amount of the chelate cleaning solution is estimated to be about 1.5 m ³ / hr. Therefore, for example, when processing a 60 m ^{3 /} hour chelate cleaning solution, 40 reverse osmosis membrane elements may be connected in parallel.

  The reverse osmosis membrane separation device 104 is of a continuous type, and the operating conditions such as the supply amount and supply pressure (operating pressure) of the chelate washing liquid, the discharge amount of the concentrated water and the permeated water, and the concentration ratio of the chelating agent in the concentrated water are as follows. It is appropriately set according to the amount of the chelate cleaning liquid to be supplied to the cleaning device 101 and the concentration of the chelating agent. For example, the ratio of the flow rate of the sludge supplied to the fine particle cleaning device 101 to the flow rate of the chelate cleaning liquid is set to 1: 1 and the concentration of the chelating agent of the fine particle slurry in the fine particle cleaning device 101 is set to 1% by mass. In this case, the reverse osmosis membrane separation device 104 generates permeated water (chelating agent concentration 0) of about 50% of the supply amount of the chelating washing liquid and concentrated water (chelating agent concentration of about 2% by mass) of about 50%. Is set to Therefore, in the fine-grain cleaning device 101, the sludge containing no chelating agent and the chelating solution having a chelating agent concentration of about 2% by mass are mixed at a ratio of 1: 1. % Is maintained.

  The concentrated water discharged from the reverse osmosis membrane separation device 104, that is, the chelate washing liquid, is introduced into the chelating agent regenerating device 105 and is regenerated. That is, harmful metals and the like are removed and recovered from the chelate cleaning liquid (chelating agent), and the chelating cleaning liquid (chelating agent) is again in a state capable of capturing harmful metals and the like. As such a chelating agent regenerating device 105, for example, the cleaning liquid regenerating unit 34 (see FIG. 7) in the first embodiment can be used.

  According to the soil purification system SA according to the second embodiment, similarly to the soil purification system S according to the first embodiment, clean and reusable gravel and sand can be obtained, and the sludge discharged from the iron removal device 12 can be obtained. Can greatly reduce the content of harmful metals and the like. As described above, since the content of harmful metals and the like in the sludge discharged from the iron removing device 12 is greatly reduced, even when the sludge is chelated and washed, the amount of the chelating agent used or the required amount is greatly reduced. And the cost of treating the soil can be reduced.

  S soil purification system (Embodiment 1), SA soil purification system (Embodiment 2), 1 input hopper, 2 mixer, 3 mill breaker (wet crusher), 4 trommel, 5 cyclone, 6 PH adjustment tank, 7 coagulation Tank, 8 thickener, 9 intermediate tank, 10 washing water tank, 11 spare water tank, 12 iron removing device, 12A iron removing device, 13 filter press, 14 chelating washing device, 16 sludge tank, 17 magnet mounting drum, 17A magnet mounting drum, References 18 Pipeline, 19 Pipeline, 20 Stirrer, 21 Rotary Shaft, 22 Drum Main Body, 23 Permanent Magnet, 24 Cylindrical Cover, 25 Motor, 26 Reducer, 27 Scraper, 28 Drive Roller, 29 Drive Shaft, 30 Endless Belt, 31 mixing and dispersing device, 32 fine particle cleaning device, 33 filtration device, 34 cleaning Regeneration unit, 35 cleaning liquid regeneration device, 36 cleaning liquid storage tank, 37 acid liquid storage tank, 38 water storage tank, 41 crusher, 41a blade, 42 premixing tank, 43 line mixer, 44 chelating cleaning liquid storage tank, 45 pump, 46 pipe, 47 Stirrer, 48 pumps, 49 pipes, 50 storage tanks, 51-54 partition walls, 55-59 slurry passages, 61-65 air discharge pipes, 72 intermediate storage tanks, 76 pumps, 77-80 pipes, 81 pumps, 82 pipes , 83 pumps, 84 pipes, 85 pipes, 86 pumps, 87 pipes, 88 pipes, 91-98 valves, 101 fine particle washing device, 102 filtration device, 103 clarification filter, 104 reverse osmosis separation device, 105 Chelating agent regeneration device.

Claims (3)

A soil purification system equipped with a soil classification unit that classifies soil contaminated with harmful metals or its compounds containing gravels, sand, and fine particles into gravels, sand, and fine particles while washing with washing water. So,
The soil classification unit includes:
A mixer for mixing the soil and the washing water introduced into the soil classification unit,
By crushing the gravel and sand in the mixture containing the soil and the washing water discharged from the mixer, iron or iron oxide unevenly or scattered inside the gravel and sand can be magnetically adsorbed. A wet crusher that generates iron-based fine particles containing to a degree and adsorbs harmful metals or compounds thereof to iron or iron oxide exposed on the surface of the iron-based fine particles,
A trommel that separates gravel from a mixture containing gravel, sand, fines, and washing water discharged from the wet crusher,
A liquid cyclone that separates sand from a mixture containing sand, fines, and washing water discharged from the trommel;
A mixture containing the fine particles and the washing water discharged from the hydrocyclone, by sedimentation, supernatant water, and a thickener for separating sludge containing the fine particles and the washing water,
It has a filter press for producing a filter cake and a filtrate by filtering the sludge discharged from the thickener under pressure and producing a fine cake.
Between the thickener and the filter press, from the sludge containing the fine particles discharged from the thickener and the washing water, the iron-based fine particles containing iron or iron oxide to an extent that can be adsorbed by magnetic force are magnetically applied. An iron removal device is provided to reduce the content of harmful metals or compounds of sludge by adsorption and removal,
The filter cake discharged from the filter press is provided with a chelate washing device that removes harmful metals or compounds thereof adsorbed or adhered to the surface of fine particles by washing with a chelate washing solution containing a chelating agent and water. Sat壌浄system characterized by being. The iron removal device,
A sludge tank for holding sludge containing fine particles and washing water discharged from the thickener,
It is formed in the shape of a drum, the center axis of the drum is oriented in the horizontal direction, and the lower part of the drum is arranged so as to be immersed in the sludge in the sludge tank. A magnet mounting drum mounted side by side in the drum circumferential direction so that the magnetic poles face
The soil purification system according to claim 1, further comprising: a drum rotation mechanism configured to rotate the magnet mounting drum. The iron removal device,
A sludge tank for holding sludge containing fine particles and washing water discharged from the thickener,
It is formed in a drum shape, the center axis of the drum is oriented in the horizontal direction, and the lower part of the drum is rotatably attached to the sludge tank so as to be immersed in the sludge in the sludge tank. A magnet mounting drum in which permanent magnets are mounted side by side in the drum circumferential direction such that the magnetic poles face outward in the drum radial direction;
Above the sludge tank, a cylindrical drive roller smaller in diameter than the drum body of the magnet mounting drum, arranged so that the roller center axis is parallel to the drum center axis of the magnet mounting drum,
An endless belt made of a soft magnetic metal material or a diamagnetic metal material, wound around the drum body of the magnet mounting drum and the drive roller,
The soil purification system according to claim 1, further comprising a roller rotation mechanism configured to rotate the driving roller.

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