JP2019098312A - Soil remediation system - Google Patents

Abstract

To provide a simple and low-cost soil remediation system allowing soil to be washed with wash water and classified into gravel, sand and fine-grain fractions, while reducing the amount of toxic metal and the like adsorbed to the fine-grain fraction.SOLUTION: A soil remediation system S comprises soil classification units 1 to 8, and an iron removal device 12. The soil classification units 1 to 8 crush gravel and sand in soil by a mill breaker 3 while washing the soil with wash water, and then perform classification into gravel, sand and fine-grain fractions by a trommel 4, a cyclone 5 and a thickener 8. The iron removal device 12 uses a magnet-equipped drum to cause a ferrous fine-grain fraction containing iron and the like to be removed, by adsorption by magnetic force, from sludge containing the wash water and the fine-grain fraction separated by the thickener 8, thereby reducing the content of toxic metal and the like in the sludge.SELECTED DRAWING: Figure 1

Description

  TECHNICAL FIELD The present invention relates to a soil purification system for purifying a soil which contains straw, sand and fine particles and which is contaminated with harmful metals or compounds thereof.

  In recent years, for example, sites of production facilities using harmful metals such as chromium, lead, cadmium, selenium, mercury, etc. and / or compounds thereof or ions thereof (hereinafter collectively referred to as "harmful metals etc.") as raw materials or materials Or the soil pollution in the neighboring land due to soil pollution or illegal dumping of industrial waste containing harmful metals etc. occurs frequently. Then, soil contaminated with harmful metals (hereinafter referred to as “toxic metal-contaminated soil”) is present at a position (hereinafter referred to as “in-situ position”), for example, insolubilization of harmful metals or the like, containment or electrical repair It is rather difficult to clean up more effectively. For this reason, harmful metal-contaminated soil is generally removed from the in-situ site by drilling and purified at an external soil purification facility.

  As a method of purifying harmful metal-contaminated soil at such a soil purification facility outside the in-situ site, conventionally, a washing method of washing harmful metal-contaminated soil with washing water etc. to remove harmful metals etc. is widely used . Then, when the harmful metal-contaminated soil is washed with washing water, most of the harmful metals and the like that have been temporarily removed from the soil are adsorbed or adhered to the surface of the relatively small particle size fine particles, and the fine particles It is known to be concentrated on the surface of (see, for example, Non-Patent Document 1).

  Therefore, by classifying the harmful metal contaminated soil with washing water while classifying it into sand, sand and fine particles, the fine particles are subjected to a chemical treatment to remove harmful metals and the like. It is possible to obtain straw, sand and fine particles containing almost no harmful metals. Thus, the inventor of the present application has already classified the harmful metal-contaminated soil with washing water, classified it into gravel, sand and fine particles, and then washed the fine particles with a chelating cleaning solution containing a chelating agent. Various soil purification facilities (contaminated soil purification devices) have been proposed which are designed to remove harmful metals and the like from fine grains (see Patent Documents 1 and 2, for example).

Patent No. 5723054 gazette Patent No. 5723055 gazette Patent No. 4755159 gazette Patent No. 60071144 gazette

Ministry of the Environment Water and Atmosphere Environment Bureau Soil Environment Division "Technical notes on permission assessment etc. of contaminated soil treatment industry" page 21, published in 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/rpsj1954/23/3/23_3_190/_pdf)

  By the way, in this kind of soil remediation facility by a contaminated soil processor, a large amount of contaminated soil is usually cleaned (for example, 2000 tons per day), so a large amount of fine particles is generated (for example, , 500-600 tons per day on a dry basis). Therefore, when such a large amount of fine particles is washed with, for example, a chelate washing solution, a large amount of a relatively expensive chelating agent is required, resulting in a problem that the cost of treating contaminated soil increases. Of course, the necessary amount or use amount of the chelating agent is increased as the content of the fine particles of harmful metals and the like is increased. In addition, 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 present invention was made to solve the above-mentioned conventional problems, and comprises washing with soil and containing soil, sand and fine particles and contaminated with harmful metals and the like while washing the soil with washing water. It can be classified into fine particles, and harmful metals etc. adsorbed or attached to the separated fine particles can be removed, or at least the content of harmful metals etc. in fine particles etc. The problem to be solved is to provide a simpler, low-cost soil purification system that can reduce the rate.

  The soil remediation system according to the present invention, which has been made to solve the above-mentioned problems, comprises soil which is polluted with harmful metals and the like (hazardous metals and / or compounds thereof or ions thereof), which comprises straw, sand and fine particles. Purify. This soil remediation system includes a soil classification unit and an iron removal device. Here, the soil classification unit crushes soil and sand in the soil while washing the soil with washing water, and then classifies the soil into soil, sand and fine particles. On the other hand, the iron content removing device is generically referred to as iron and / or iron oxide (hereinafter referred to as "iron etc." to the extent that can be adsorbed by magnetic force from sludge containing fine particles separated in the soil classification portion and washing water. By removing the iron-based fine particles including Y) by magnetic attraction and reducing the content of the harmful metals and the like of the sludge (fine particles) or the retention rate.

  In the soil purification system according to the present invention, the soil classification unit has a mixer, a wet crusher, a trommel, a hydrocyclone, and a thickener. Here, the mixer mixes the soil introduced into the soil classification unit with the wash water. A wet crusher can magnetically absorb iron etc. that is unevenly distributed or scattered inside the gravel and sand by crushing the gravel and sand in the mixture containing the soil and wash water discharged from the mixer An iron-based fine particle is contained to a certain extent, and harmful metals and the like are adsorbed on iron and the like exposed on the surface of the iron-based fine particle. The trommel separates the straw from the mixture discharged from the wet crusher, which contains straw, sand, fines and wash water. A hydrocyclone separates sand from a mixture comprising sand, fines and wash water discharged from the trommel. The thickener separates the mixture containing the fines and the wash water discharged from the hydrocyclone into the supernatant water and the sludge containing the fines and the wash water by sedimentation.

  On the other hand, the iron content removing device has a sludge tank, a magnet mounting drum, and a drum rotating mechanism. Here, the sludge tank temporarily holds the sludge including the fine particles discharged from the thickener and the washing water. The magnet mounting drum is formed in a drum shape, and is disposed such that the central axis of the drum is directed in the horizontal direction and the lower portion of the drum is immersed in the sludge in the sludge tank. A plurality of permanent magnets are mounted (arranged) in the circumferential direction of the drum such that the magnetic poles are directed outward in the radial direction of the drum, inside the circumferential surface of the drum. The drum rotation mechanism rotates the magnet mounting drum. In addition, it is preferable that the iron content removal apparatus has a pH adjusting device which adjusts the hydrogen index of the sludge retained in the sludge tank within the 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 comprises a filter press and a filtrate return means, and more preferably comprises a chelate washing device. In this case, the filter press receives and filters the sludge containing fine particles (fine particles other than iron fine particles) and water from which iron fine particles have been removed by an iron removing device, Separate into filtrate and cake containing fines. The filtrate return 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 chelating cleaning solution containing a chelating agent and water, and the harmful metal remaining in the fine particles (fine particles other than iron-based fine particles) Remove the etc.

  Generally, in the process of washing and classification of contaminated soil using washing water, harmful metals and the like are hardly adsorbed (adhered) on the gravel and sand, but collected in fine particles and adsorbed (adhered) (for example, non-adhesion) Patent Document 1). The fine particle content is a relatively small amount of iron-based fine particle content containing iron etc. to an extent that can be adsorbed by magnetic force, and a relatively large amount of fine particle content that can not be adsorbed by magnetic force other than iron-based fine particle content (hereinafter Non-ferrous fine particles). On the other hand, since iron and the like have the property of adsorbing harmful metals and the like (see, for example, Non-patent Document 2), the amount of adsorbed harmful metals and the like of iron-based fine particles including iron and the like exposed on the surface (adhesion amount ) Is considerably larger than the adsorption amount (adhesion amount) of harmful metals and the like of non-ferrous fine particles.

  And, according to the soil remediation system according to the present invention, the gravel and sand are crushed by the wet crusher to generate the fine particle fraction, and among these fine particles, uneven distribution or spotting in the crucible or in the sand is made. The fine particles containing a large amount of iron and other fine particles are iron-based fine particles, and iron and the like exposed on the surface of these iron-based fine particles are a series of products from wet crusher to iron content removing device Adsorbs relatively large amounts of harmful metals etc. in the distribution process of Therefore, iron-based fine particles existing before crushing and iron-based fine particles generated by crushing are introduced into the iron-removing apparatus, and all of these iron-based fine particles are considerably large (non-ferrous It adsorbs harmful metals, etc.) compared to the system fines.

  Thus, in the iron removing apparatus, since 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 sludge or the remaining fine particles (non-ferrous fine particles) The content rate or retention rate of metals etc. can be significantly reduced, and the content rate or retention rate of harmful metals etc. can be reduced to the extent that dumping or landfill treatment is possible depending on the properties of the soil.

  Therefore, even if harmful metals and the like adsorbed on the remaining fine particles (non-ferrous fine particles) are removed using relatively expensive chemicals such as chelating agents, the necessary or used amount of chemical is The cost of treating the soil can be significantly reduced. The wet crusher and iron remover have a simple mechanical structure that physically processes, and do not use special chemicals to treat harmful metals etc., so their operating costs are very low. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows schematic structure of the soil purification system which concerns on Embodiment 1 of this invention. (A) is typical side surface sectional drawing of the iron content removal apparatus which is a component of a soil purification system, (b) is a schematic plan view of the iron content removal apparatus shown to (a). (A) is typical side surface sectional drawing of another iron content removal apparatus, (b) is a schematic plan view of the iron content removal apparatus shown to (a). It is a block diagram which shows schematic structure of the chelate washing apparatus which is a component of a soil purification system. It is a typical elevation view which shows the structure of the mixing and dispersing apparatus which makes a part of chelate washing | cleaning apparatus. (A) is a schematic plan view of the fine particle size washing apparatus which forms a part of the chelate washing apparatus, and (b) is a sectional view taken along line A-A of the fine particle size washing apparatus shown in (a), (C) is an elevational cross-sectional view of one slurry passage of the fine particle content washing device. It is a typical elevation view which shows the structure of the washing | cleaning-liquid reproduction | regeneration part which makes a part of chelate washing | cleaning apparatus. It is a block diagram which shows schematic structure of the soil purification system which concerns on Embodiment 2 of this invention.

(Embodiment 1)
As shown in FIG. 1, in the soil purification system S according to Embodiment 1 of the present invention, it was collected by excavating the ground contaminated with harmful metals and the like (toxic metals and / or compounds thereof or ions thereof) Soil (contaminated soil) is received in the input hopper 1. Examples of the harmful metals include chromium, lead, cadmium, selenium, mercury, metal arsenic and the like. Then, the soil in the charging hopper 1 is continuously or intermittently charged into the mixer 2 and mixed with the washing water continuously supplied to the mixer 2. Here, the soil includes a weir (for example, a particle size of 2 to 75 mm), sand (for example, a particle size of 0.075 to 2 mm), and a fine particle fraction (for example, a particle size of 0.075 mm or less) Some contain stones (eg, 75 mm or more in particle size).

  A mixture containing soil and wash water generated by the mixer 2 (hereinafter referred to as "soil / water mixture") is transferred to a mill breaker 3 which is a wet crusher. For example, a rod mill can be used as the mill breaker 3. Although not shown in detail, the rod mill is a crushing apparatus in which a plurality of rods (for example, 10 75 mmφ × 2 m steel rods) are disposed in a drum, and the rods rotate parallel to one another by rotation of the drum. Can move into line contact and break up gravel and sand (in some cases even stones) by their impact force, shear force, frictional force etc. to produce small diameter soil particles such as fines . A ball mill or the like can be used as the mill breaker 3 in addition to the rod mill. In addition, a part of the gravel and the sand become fine particles, and not all the fine particles.

  Thus, the mill breaker 3 crushes sand and sand (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 and the like adsorbed (adhered) or contained in the straw and sand are released into the water. At this time, basically (except for adsorption by iron and the like described later), harmful metals and the like released in water are hardly adsorbed or not attached to straw and sand, and collected into fine particles and adsorbed. Or attach (see, for example, Non-Patent Document 1).

  In addition, a large number of iron-based fine particles are generated in which the micro-mass of iron or the like (iron and / or iron oxide) present inside or unevenly distributed or scattered inside the straw and sand is exposed to the surface. On the other hand, iron and the like generally have the property of adsorbing harmful metals and the like. For this reason, part or most of the harmful metals and the like present in the wash water are adsorbed or attached to the exposed surface of the iron-based fine particles such as iron. As a result, the adsorption amount (adhesion amount) of harmful metals and the like of iron-based fine particles is considerably larger than the adsorption amount (adhesion amount) of harmful metals and the like of non-ferrous fine particles. That is, the fine particles discharged from the mill breaker 3 are iron-based fine particles having a large amount of adsorption (adhesion) of harmful metals etc. and non-ferrous fine particles having a small amount of adsorption (adhesion) of harmful metals etc. And consists of In addition, it is needless to say that iron-based fine particles existing before crushing also adsorb considerably more harmful metals and the like than non-ferrous-based fine particles.

  The iron-based fine particles that adsorb the harmful metals and the like in this manner 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 the property of adsorbing harmful metals and the like, and utilizing this property, iron powder or iron oxide is contained in sludge containing harmful metals and the like. Various "iron powder methods" have been proposed in which harmful metals and the like are removed from sludge by adding powder (see, for example, Patent Documents 3 to 4 and Non-Patent Document 2). However, as in the present invention, crushing iron and sand forms iron-based fine particles in which fine lumps such as fresh iron (which has not adsorbed harmful metals and the like yet) are exposed on the surface. There is no proposal for a method for treating harmful metals and the like in which harmful metals and the like are adsorbed on the exposed micro-mass (iron-based fine particles) such as iron.

  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 disposed to be inclined with respect to a horizontal surface, and the drum screen Is rotatable about its central axis (the central axis of the cylinder) by a motor. In addition, the washing water can be sprayed in the form of a spray into the drum screen.

  As the soil-water mixture flows inside the rotating drum screen of Trommel 4, soil particles finer than the mesh of the drum screen pass through the mesh of the drum screen together with the washing water and go out of the drum screen to the inside of the receiving tank to go into. On the other hand, since soil particles coarser than the mesh of the drum screen can not pass through the mesh of the drum screen, they are discharged out of the drum screen via the lower open end of the drum screen.

  In the trommel 4, the classification diameter (opening) of the mesh of the drum screen is set so that soil particles having a particle 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, a weir, which is a soil particle having a particle size of 2 mm or more (sometimes also a stone), is separated from the soil-water mixture. As mentioned above, since harmful metals and the like released in water are hardly adsorbed or attached to straw and sand, the straw separated by the trommel 4 is clean, and is used, for example, as an aggregate for concrete be able to. The mesh size (opening) of the drum screen of the trommel 4 is not limited to the above, and of course it can be set arbitrarily according to the particle size of the soil particles to be obtained. It is.

  Soil particles contained in the receiving tank of the trommel 4 and having a particle diameter of less than 2 mm, that is, a soil / water mixture containing sand and fine particles and washing water, are introduced into the cyclone 5 (hydrocyclone). Although not shown in detail, the cyclone 5 pumps the soil-water mixture into a generally conical cylinder that narrows downward to generate a swirling flow, and the centrifugal force generated thereby is used to A mixture of soil and water, a mixture of fine particles having a relatively small particle size (for example, particle size less than 0.075 mm) and water, sand having a relatively large particle size (for example, a particle size of 0.075 mm or more) and water Separated into a mixture of

  Then, a mixture of fine particles and water (hereinafter referred to as “fine-grain-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. Be done. Here, since 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, it is drained or dried and used as regenerated sand. On the other hand, the fine particle-containing water is transferred to the PH adjustment tank 6.

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

  The fine particle-containing water whose pH has been adjusted in the PH adjustment tank 6 is introduced into the aggregation tank 7. In the coagulation tank 7, a polyaluminum chloride solution (PAC), a polymer flocculant, and a pH adjuster (acidic solution or alkaline solution) are added to the fine particle-containing water. 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 aggregation tank 7.

  The water containing fine particles in the coagulation tank 7 is introduced into the thickener 8. The chicna 8 is not shown in detail, but the non-water-soluble floc or fines are caused to settle by gravity while the fines-containing water is almost stationary, and the sludge layer located at the lower part (for example, solid) (5 to 10%) and a supernatant (wash water) which is located on the top and contains almost no floc or fines. When floated oil floats on the surface of the supernatant water, the floated oil is removed by overflowing a small amount of supernatant water from the top of the thickener 8.

  Supernatant water in the chicna 8 is introduced into the washing water tank 10 and temporarily stored. When the washing water tank 10 is full, the spare water tank 11 is used. The washing water stored in the washing water layer 10 or the reserve water tank 11 is supplied to the mixer 2 and the trommel 4 as circulating water. In addition, when the wash water stored by the wash water tank 10 reduces by evaporation etc., tap water is replenished suitably. On the other hand, the sludge deposited under the thickener 8 is transferred to the intermediate tank 9 and temporarily stored. Then, the sludge in the intermediate tank 9 is continuously transferred to the iron removing device 12.

  As shown in FIGS. 2 (a) and 2 (b), the iron removal device 12 includes a sludge tank 16 and a magnet mounting drum 17. Here, the sludge tank 16 receives sludge consisting of fine particles (ferrous fine particles and non-ferrous fine particles) transferred from the intermediate tank 9 through the pipe line 18 and water, and temporarily Hold. Then, the sludge in the sludge tank 16 is transferred (pumped) to the filter press 13 (see FIG. 1) through the pipe line 19 after the iron-based fine particles are removed as described later. In addition, in the sludge tank 16, in order to prevent the precipitation to the bottom part of a fine particle, the stirrer 20 is provided.

  The magnet mounting drum 17 has a rotary shaft 21, a cylindrical drum main body 22 coaxially attached to the rotary shaft 21, and a circumferential portion (outer edge portion) of the drum main body 22 adjacent to each other in the drum circumferential direction. And a cylindrical cover 24 covering the outer peripheral surface of the annularly arranged permanent magnet group. Here, the drum main body 22 is disposed such that its central axis of rotation is directed in the horizontal direction and the lower portion of the drum is immersed in the sludge in the sludge tank 16.

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

  The rotary shaft 21 and thus the drum body 22 are rotationally driven by the motor 25 (electric motor) through the reduction gear 26, and in the positional relationship in FIG. Rotate at 0r.p.m.). 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 the outer peripheral surface of the cylindrical cover 24 by the magnetic force of the permanent magnet 23 and adsorbed. Thus, when the drum body 22 comes out of the sludge, an iron-based fine particle separation layer is formed on the outer peripheral surface of the cylindrical cover 24. The iron-based fine particle separation layer formed on the outer peripheral surface of the cylindrical cover 24 is scraped off by the scraper 27 and removed from the drum main body 22. The removed iron-based fine particles can be used, for example, as an iron-making material.

  The iron-based fine particles are those produced by crushing straw and sand with the mill breaker 3 (see FIG. 1), which is a wet crusher, or those which exist before crushing of the straw and sand, any of which Micro-mass such as iron is exposed on the surface, and a considerable amount of harmful metals and the like are adsorbed on the micro-mass such as iron which is exposed. In general, small pieces of iron or the like are unevenly distributed or scattered in a gutter and sand, and the proportion of such small pieces is about 2 to 5% by mass. For this reason, a part of the fine particles generated by crushing of the straw and sand becomes an iron-based fine particle in which fresh iron and the like are exposed on the surface.

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

In addition, the inventor of the present invention crushes gravel and sand with a mill breaker a plurality of times (ten times) in July 2017 at the contaminated soil treatment site of Yamazaki Co., Ltd., a gravel shop along the way in Otsu City, Shiga Prefecture. Of sludge (fine particle content 1 to 3% by mass), which is a mixture of fine particles and water produced, using a magnet-equipped drum with a diameter of about 1 m (using neodymium magnet as a permanent magnet) It was carried out adsorption experiment, the average ferrous fine fraction of 3.4kg per sludge 10 m ³ was taken.

  Micro-mass such as iron exposed on the surface of iron-based fine particles generated by crushing gravel and sand with the mill breaker 3 are harmful metals etc. which were unevenly distributed or scattered in the gravel or sand. It is generated from small pieces of fresh iron etc. not adsorbed, and is exposed to the surface after crushing to adsorb harmful metals etc. from the washing water around it. Thus, the fine particle fraction discharged from the mill breaker 3 and finally introduced into the iron removing device 12 is an iron-based fine particle fraction having a relatively large (or considerable) adsorption amount of harmful metals and the like, harmful metals and the like And the non-ferrous fine particles having a relatively (or considerably) low adsorption amount.

  Then, as described above, since the iron-based fine particles are removed from the sludge in the iron-removing device 12, the fine-grains contained in the sludge discharged from the iron-removing device 12 have a relatively high adsorption amount of harmful metals and the like. Most (or rather) non-ferrous fine particles are small. Therefore, the iron removal device 12 removes most or a substantial portion of harmful metals and the like contained in the contaminated soil introduced into the soil purification system S. 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 will be described later, when the sludge or fine particles discharged from the iron removing device 12 are subjected to the chelate washing treatment with the chelate washing solution, the chelate washing treatment is performed as compared with the case where the iron removing device 12 is not provided. Since the burden of harmful metals and the like in the above can be reduced, the processing cost in the chelate cleaning can be reduced. In this case, the iron removal device 12 can also be positioned as a pretreatment device that reduces the load in the chelate cleaning process. In the case where the sludge or fine particles discharged from the iron removing device 12 are subjected to chemical treatment other than the chelate washing treatment, it is possible to position the iron removing device 12 as a pretreatment device.

  As shown in FIG. 1 again, the sludge discharged from the iron removing device 12 is introduced into the filter press 13 and dewatered to form a filtrate and a cake (filter cake). The filtrate is then returned to the thickener 8. On the other hand, the cake is transferred to the chelate cleaning device 14 to remove harmful metals and the like remaining in the fine particles (non-ferrous fine particles). In addition, if the content rate of the harmful metal or the like contained in the cake is within the standard, the cake is disposed of in a landfill or the like without being transferred to the chelate cleaning device 14.

  Hereinafter, the configuration and function of another iron removal device 12A having a different configuration from the iron removal device 12 shown in FIGS. 2 (a) and 2 (b) will be described with reference to FIGS. 3 (a) and 3 (b). . However, most of the components of the iron removal device 12A shown in FIGS. 3 (a) and 3 (b) are the same as the components of the iron removal device 12 shown in FIGS. 2 (a) and 2 (b). In the following, differences from the iron removal device 12 will be mainly described in order to avoid duplication of In addition, in the component of iron content removal apparatus 12A shown to FIG. 3 (a), (b), the same reference is carried out to what is common in the component of iron content removal apparatus 12 shown to FIG. 2 (a), (b). It has a number.

  As shown in FIGS. 3A and 3B, in the iron removing device 12A, a cylindrical drive roller 28 is provided above the sludge tank 16 separately from the drum main body 17A, and this drive roller 28 is a drive shaft It is coaxially attached to 29. The drive roller 28 and the drive shaft 29 are disposed such that their central axes of rotation are parallel to the central axis of rotation of the drum main body 17A, and are rotationally driven by the motor 25 via the reduction gear 26. The driving roller 28 has a smaller diameter (e.g., 1/5 to 1/10) than the drum main body 17A.

  On the drum main body 17A, a plurality of permanent magnets 23 are mounted or disposed in the same specification as the iron content removing device 12 shown in FIG. 2 (a). The rotary 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) is extended over the drum main body 17A and the drive roller 28 in which a plurality of permanent magnets 23 are annularly attached or arranged Belt) is wound. The endless belt 30 may be formed of a diamagnetic metal material (for example, copper or aluminum or an alloy thereof).

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

  A permanent magnet group in which an endless belt 30 traveling in a clockwise direction in a positional relationship in FIG. 3A between the drive roller 28 and the drum main body 17A is annularly arranged on the circumferential surface of the drum main body 17A. The iron-based fine particles in the sludge are attracted to the outer surface of the endless belt 30 by the magnetic force of the permanent magnet 23 while being in contact with the outer peripheral surface of the belt and immersed in the sludge in the sludge tank 16. Thus, when the endless belt 30 comes out of the sludge, an iron-based fine particle separation layer is formed on the outer surface of the endless belt 30. The iron-based fine particle separation layer formed on the outer surface of the endless belt 30 is scraped off by the scraper 27 in the vicinity of the driving roller 28 and removed from the endless belt 30.

  Also in the iron content removing device 12A shown in FIGS. 3A and 3B, the iron-based fine particles are removed from the sludge as in the iron content removing device 12 shown in FIGS. 2A and 2B. The fine particle fraction contained in the sludge discharged from the iron content removing device 12A is mostly a non-ferrous fine particle fraction having a very small (or quite) small adsorption amount of harmful metals and the like. The sludge discharged from the iron removal device 12A is introduced into the filter press 13 and dehydrated to form a filtrate and a cake (filter cake). The filtrate is then returned to the thickener 8. On the other hand, the cake is transferred to the chelate cleaning device 14 to remove harmful metals and the like remaining in the fine particles (non-ferrous fine particles).

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

  First, the general configuration and function of the cleaning 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 washing solution containing the chelating agent in the washing solution 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 washing solution, and fine particles or small particles in the chelate washing solution (for example, the particle diameter is about several 0.1 to 0.5 mm, or 0.1 Particles of about 1 mm (approximately 1 mm in size) are dispersed almost uniformly (suspended) to form a fine particle slurry.

  The fine particle slurry generated by the mixing and dispersing device 31 is transferred to the fine particle washing device 32. The fine particle content washing device 32 flows the plug material (plug flow) roughly so as to secure a preset residence time (for example, 0.5 to 2 hours) while stirring the fine particle content slurry, The harmful metals and the like attached to the fine particles are released and captured by the chelating agent in the chelating solution. Thereby, harmful metals and the like adsorbed (adhered) on the surface of the fine particles in the fine particle slurry are removed.

  Here, as a chelating agent used for the chelating washing solution, for example, EDTA (ethylenediaminetetraacetic acid), or HIDS (3-hydroxy-2,2'-iminodisuccinic acid), IDS (2,2'-iminodisuccinic acid), MGDA (Methylglycinediacetic acid), EDDS (ethylenediaminediacetic acid) or sodium salt of GLDA (L-glutamic acid diacetic acid), and the like. Any of these chelating agents can effectively capture (chelate) harmful metals and the like contained in the fine particle slurry or fine particle fraction. Of course, a chelating agent suitable for the treatment is selected or plural kinds of chelating agents are used according to the type of harmful metal and the like contained in the fine particle fraction.

  The fine particle slurry discharged from the fine particle washing device 32 is transferred to the filtering device 33. The filtration unit 33 filters the fine particle slurry to produce a cake with a moisture content of 30 to 40 percent (filter cake) and a filtrate. In addition, as such a filter apparatus 33, a filter press, a vacuum filter, etc. can be used. The filter cake (fine particle content) discharged from the filter device 33 contains almost no harmful metals and the like.

  The filtrate discharged from the filter device 33, that is, the chelate washing solution is introduced into the washing solution regeneration unit 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 cleaning solution regenerating apparatus 35 has a complex forming power higher than that of the chelating agent, and when in contact with the chelating cleaning solution (filtrate) discharged from the filtering apparatus 33, solid phase adsorption which adsorbs or extracts harmful metals and the like in the chelating cleaning solution. It is an apparatus which has a material or a small piece or particle on which the solid phase adsorbent is immobilized, and removes harmful metals and the like from the chelating agent in the chelating washing solution to regenerate the chelating washing solution.

  In the cleaning solution regenerating apparatus 35, a chelating cleaning solution containing a chelating agent capturing harmful metals and the like is brought into contact with a solid phase adsorbent having higher complexing power than the chelating agent. The solid phase adsorbent is a carrier having a cyclic molecule supported on the carrier, a coordination with a chelate ligand modified to the cyclic molecule and multipoint interaction by hydrogen bond and selectively incorporating ions such as harmful metals. is there. Thereby, 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 recovered from the chelate washing liquid (chelating agent), and the chelate washing liquid (chelating agent) is in a state capable of capturing harmful metals and the like again.

  The chelate washing solution thus regenerated is temporarily stored in the washing solution storage tank 36, and then returned to the mixing and dispersing device 31 by a washing solution reflux mechanism (a pump 81, a conduit 82, etc. described later). That is, the chelate washing solution circulates in the chelate washing device 14 while repeating purification of fine particles and regeneration of the chelating agent. In addition, the loss of the chelating agent is replenished appropriately.

  Solid phase adsorbents having higher complexing power than chelating agents are in solid form such as, for example, a gel, and generally, when contacted with an aqueous solution containing a chelating agent capturing a metal, coordination bond with the chelating agent The metal ion has a strong avidity other than the degree of covalent bonding that can release the metal ion from the chelating agent and transfer it to the solid phase adsorbent. Such a solid phase adsorbent, for example, when using EDTA (ethylenediaminetetraacetic acid) as a chelating agent, has a strong binding ability to recover almost 100% of metal ions from an aqueous solution of EDTA having a concentration of 10 mM / l. It is possessed.

  As such a solid phase adsorbent, for example, a solid support of a cyclic molecule on a carrier such as silica gel or resin, and a modification of a chelate ligand to this cyclic molecule, and the like can be mentioned. When such a solid phase adsorbent is used, a plurality of various bonds and interactions such as coordination bonds and hydrogen bonds are caused by adjacent cyclic molecules and chelate ligands, resulting in multipoint interaction and metal ion On the other hand, stronger chemical bonds occur than chelating agents, and metal ions can be selectively incorporated by the nature of cyclic molecules.

  The amount of adsorption of harmful metals and the like in the solid phase adsorbent increases with time as the chelate washing solution is regenerated, but the amount of adsorption of harmful metals and the like in the solid phase adsorbent has an upper limit. For this reason, when the adsorption amount of harmful metals and the like in the solid phase adsorbent reaches a saturated state or in the vicinity thereof, the solid phase adsorbent has a solid phase adsorbent regeneration mechanism (acid solution storage tank 37, pump 83, pipe line described later) 84, 78, 79, 85, etc.). That is, in the solid phase adsorbent regeneration mechanism, the acid solution is flowed to the cleaning solution regeneration apparatus 35 in a state where the chelate washing solution is removed, and harmful metals and the like adsorbed on the solid phase adsorbent are removed by the acid solution To play. Thus, while harmful metals and the like are recovered by the acid solution, the solid phase adsorbent is regenerated to be in a state capable of adsorbing harmful metals and the like again. The solid phase adsorbent is regenerated with an acid solution and then washed with water by a water washing mechanism (water storage tank 38, pump 86, pipelines 87, 78, 79, 88, etc. described later) and adheres to the solid phase adsorbent 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 with the chelate washing solution to generate a fine particle slurry in which the fine particles are dispersed in the chelating washing solution. Specifically, the mixing and dispersing device 31 pre-mixes a crusher 41 for crushing the cake (fine particles) discharged from the filter press 13, cake pieces shredded by the crusher 41 and a chelate washing solution. The mixture produced by the premixing tank 42 and the premixing tank 42 is stirred to chelate cake fragments (for example, particles having a particle size of about several 0.1 to 0.5 mm, or about 0.1 to 1 mm). And a line mixer 43 for dispersing or suspending in the washing solution.

  Then, in the mixing and dispersing device 31, the cake discharged from the filter press 13 is supplied to the crusher 41, and the cake is rotated by the blade 41a rotating at a high speed, for example, a large number of particle sizes of several mm (for example, 1 to 5 mm). It is broken up into cake pieces. On the other hand, to the crusher 41, the chelate washing solution in the chelate washing solution storage tank 44 is supplied by the pump 45 through the conduit 46. The chelate cleaning liquid is appropriately supplied to the chelate cleaning liquid storage tank 44 from the cleaning liquid storage tank 36 (see FIG. 4). Although not shown in detail, the chelate washing solution is sprayed or supplied to a large number of cake pieces immediately after being broken down by the blade 41a to prevent the cake pieces from adhering to each other. In addition, as such a crusher 41, for example, "dehydrated cake crusher" related to Taiyo Kiko Co., Ltd. or "dehydrated cake recycling apparatus" related to Shoko Co., Ltd. can be used. In the case of using a commercially available crusher, it is necessary to provide a mechanism for injecting or supplying a chelate washing solution to a large number of cake pieces immediately after being crushed.

  The chelate solution and cake pieces in the crusher 41 are transferred to the premix tank 42. The chelate washing solution and the cake pieces in the premix tank 42 are stirred and premixed by a stirrer 47 which is rotationally driven by a motor. Then, the mixture of the chelate washing solution and the cake pieces in the premix tank 42 is transferred by the pump 48 to the line mixer 43 through the pipe 49. The line mixer 43 is a flow-through type mixer in which a blade rotationally driven at a very high speed by a motor is disposed in a horizontal-arranged substantially cylindrical stirring chamber, and very vigorously stirs the chelate washing solution and cake pieces. The cake or fine particles in the chelate washing solution (eg, particles having a particle size of about 0.1 to 0.5 mm, or about 0.1 to 1 mm) are almost uniformly dispersed (suspended). A fine particle size slurry is produced. The fine particle slurry is transferred to the fine particle washing device 32 (see FIG. 4). As such a line mixer 43, for example, a "Satake multi-line mixer" or the like according to Satake Chemical Engineering Co., Ltd. can be used.

  Next, with reference to FIGS. 6 (a) to 6 (c), the specific configuration and function of the fine particle content washing device 32 which is a component of the chelate washing device 14 will be described. The fine particle content washing device 32 adsorbs (adheres to the fine particle content by flowing the fine particle content slurry generated by the mixing and dispersing device 31 by plug flow so as to secure a preset residence time while stirring. And the like) are released from the fine particles and trapped by the chelating agent.

  The fine particle content cleaning device 32 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 dividing 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 a concrete rectangular pit. The partition walls 51 to 54 may be formed, for example, by connecting a plurality of iron plates or plastic plates in the extending direction of the slurry passage.

  The two slurry channels adjacent in the slurry channels 55 to 59 have four curves in one communicating portion (FIG. 6A) at one end of the slurry channel longitudinal direction (left and right direction in FIG. 6A and FIG. 6B). Communicate with each other at the portions shown by 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, air release pipes 61 to 65 for releasing air into the fine particle slurry and stirring the fine particle slurry are disposed. Each air discharge pipe 61 to 65 extends in the longitudinal direction of the slurry passage, and is a porous pipe in which a plurality of air discharge holes are formed in the bottom of the peripheral wall (lower side) aligned in the longitudinal direction of the slurry passage. Although not shown, it is connected to a compressor or blower that supplies compressed air. When pressurized air is supplied to the air release pipes 61 to 65, the air becomes air bubbles from the air release holes, is released into the fine particle slurry and floats up, and the air bubbles agitate the fine particle slurry by the air bubbles. Be done.

  FIG. 6C shows a cross section of the most upstream slurry passage 55 as viewed in the flow direction of the fine particle 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 in the vicinity of the slurry passage bottom in the vicinity of one side surface of the slurry passage 55. Therefore, the air bubbles discharged from the air discharge pipe 61 rise in the vicinity of 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 fine particle slurry is agitated. The shape, size, capacity and the like of the storage tank 50 and the respective slurry passages 55 to 59, and the supply amount of the pressurized air to the air release pipes 61 to 65, etc. The water content is preferably set corresponding to the water content, flow rate, residence time, flow rate, turbulent flow rate (eg, Reynolds number), and the like.

  Hereinafter, the specific configuration and function of the cleaning liquid regenerating unit 34 which is a component of the chelate cleaning device 14 will be described with reference to FIG. 7. As a means for regenerating the chelate washing solution or the chelating agent, the washing solution regenerating section 34 is a packed tower type washing solution filled with solid adsorbent particles or a packing (solid phase adsorbent) immobilized therein. A playback device 35 is provided. Further, in the cleaning liquid regenerating unit 34, an intermediate storage tank 72 for storing the chelate cleaning liquid to be regenerated, a cleaning liquid storage tank 36 for storing the regenerated chelate cleaning liquid, an acid liquid storage tank 37 for storing the acid liquid, and water are stored. A water reservoir 38 is provided.

  The intermediate storage tank 72 temporarily stores the filtrate, that is, the chelate washing solution discharged from the filtration device 33 (see FIG. 4). Then, when the chelate cleaning liquid is regenerated, the pump 76 for transferring the chelate cleaning liquid stored in the intermediate storage tank 72 to the cleaning liquid storage device 35 while transferring the chelate cleaning liquid regenerated by the cleaning liquid reproduction device 35 to the cleaning liquid storage tank 36. And a series of conduits 77-80 are provided. In addition, a pump 81 and a pipeline 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 and dispersing device 31 (see FIG. 5).

  Further, when the solid phase adsorbent is regenerated, the cleaning solution regenerating unit 34 transfers the acid solution stored in the acid solution storage tank 37 to the cleaning solution regeneration unit 35 while the acid solution discharged from the cleaning solution regeneration unit 35 is A pump 83 and a plurality of pipelines 84, 85 for returning to the acid solution storage tank 37 are provided. Further, when the solid phase adsorbent regenerated with the acid solution is washed with water, the cleaning fluid regenerating unit 34 transfers the water stored in the water storage tank 38 to the cleaning fluid regenerating apparatus 35 while discharging the water from the cleaning fluid regenerating apparatus 35 A pump 86 and a plurality of lines 87, 88 are provided to return the water to the water reservoir 38.

  In the conduits 77, 78, 84, 87 for transferring the chelating cleaning fluid, the acid solution or the water to the cleaning fluid regenerating apparatus 35, valves 91, 92, 93, 94 for opening and closing the corresponding conduits are interposed respectively ing. On the other hand, in the conduits 79, 80, 85, 88 for discharging the chelate cleaning liquid, the acid solution or the water from the cleaning liquid regenerating apparatus 35, valves 95, 96, 97, 98 for opening and closing the corresponding conduits are interposed respectively. It is set up. By switching the open / close states of these valves 91 to 98, it is possible to supply or discharge any of the chelate cleaning liquid, the acid liquid, and the water to the cleaning liquid regenerating apparatus 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 solution regenerating unit 34 will be described. The operation method described below is merely an example, and it goes without saying that the operation method of the cleaning solution regenerating unit 34 according to the present invention is not limited to the following. When the chelating cleaning solution (chelating agent) is regenerated, the valves 91, 92, 95, 96 provided in the conduits 77-80 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 inside of the cleaning liquid regenerating apparatus 35 and is transferred to the cleaning liquid storage tank 36.

  In the cleaning solution regenerating apparatus 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 (solid phase adsorbent particles) having a higher complexing power than the chelating agent. As a result, harmful metals and the like trapped in 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 recovered from the chelate washing solution, and the chelating agent becomes able to capture the harmful metals and the like again, and the chelate washing solution is regenerated. The chelate cleaning solution stored in the cleaning solution storage tank 36 is returned by the pump 81 through the conduit 82 to the chelate cleaning solution storage tank 44 and hence to the mixing and dispersing device 31 (see FIG. 5).

  Solid phase adsorbents having higher complexing power than chelating agents are in solid form such as, for example, a gel, and generally, when contacted with an aqueous solution containing a chelating agent capturing a metal, coordination bond with the chelating agent The metal ion has a strong avidity other than the degree of covalent bonding that can release the metal ion from the chelating agent and transfer it to the solid phase adsorbent. As such a solid phase adsorbent, for example, a solid support of a cyclic molecule on a carrier such as silica gel or resin, and a modification of a chelate ligand to this cyclic molecule, and the like can be mentioned. When such a solid phase adsorbent is used, a plurality of various bonds and interactions such as coordination bonds and hydrogen bonds are caused by adjacent cyclic molecules and chelate ligands, resulting in multipoint interaction and metal ion On the other hand, stronger chemical bonds occur than chelating agents, and metal ions can be selectively incorporated by the nature of cyclic molecules.

  The amount of adsorption of harmful metals and the like in the solid phase adsorbent increases with time as the chelate washing solution is regenerated, but as described above, the adsorption capacity of the solid phase adsorbent has an upper limit. For this reason, when the adsorption amount of harmful metals and the like in the solid phase adsorbent reaches a saturated state or in the vicinity thereof, the solid phase adsorbent is regenerated. That is, the acid solution is flowed into the cleaning solution regenerating apparatus 35 in a state where the chelate cleaning solution is 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 harmful metals and the like are recovered by the acid solution, the solid phase adsorbent is regenerated to be in a state capable of adsorbing or extracting the harmful metals and the like or these ions again. As described later, the solid phase adsorbent is regenerated by the acid solution and then washed with water to remove the acid liquid adhering to the solid phase adsorbent.

  When the amount of adsorption of harmful metals or the like of the solid phase adsorbent in the cleaning solution regenerator 35 reaches a saturated state or in the vicinity thereof and the solid phase adsorbent is regenerated with the acid solution, the conduits 84, 78, 79, 85 are used. While the valves 93, 92, 95, 97 provided are opened, the other valves 91, 94, 96, 98 are closed and the pump 83 is operated. As a result, the acid liquid in the acid liquid storage tank 37 flows in the cleaning liquid regenerating apparatus 35 and is returned to the acid liquid storage tank 37. Before starting the solid phase adsorbent regeneration operation, the chelate washing liquid in the washing liquid regeneration device 35 is eliminated. If a plurality of cleaning fluid regenerating devices 35 are arranged in parallel, the chelate cleaning fluid can be regenerated continuously even when the supply of the chelate cleaning fluid to some of the cleaning fluid regenerating devices 35 is stopped. Whether or not the harmful metal adsorption amount of the solid phase adsorbent has reached a saturated state or in the vicinity thereof can be determined by detecting the content of the harmful metal or the like in the chelate washing liquid discharged from the washing liquid regenerating apparatus 35 it can.

  The time for flowing the acid solution into the cleaning liquid regenerating apparatus 35 is preferably set according to the size or shape of the cleaning liquid regenerating apparatus 35, the size of the solid phase adsorbent particles, and the like. The acid liquid circulates and flows between the acid liquid storage tank 37 and the cleaning liquid regenerating apparatus 35. At this time, the solid phase adsorbent in the cleaning solution regenerator 35 contacts the acid solution, and harmful metals and the like adsorbed on the solid phase adsorbent are released into the acid solution. That is, harmful metals and the like are recovered by the acid solution, and the solid phase adsorbent is regenerated to be in a state capable of adsorbing the harmful metals and the like again.

  When the solid phase adsorbent is washed with water after the regeneration of the solid phase adsorbent by the acid solution is finished, the valves 94, 92, 95, 98 interposed in the conduits 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 circulates in the cleaning liquid regenerating apparatus 35 and is returned to the water storage tank 38. Before starting the water washing operation of such a solid phase adsorbent, the acid solution in the washing solution regenerating apparatus 35 is eliminated. Water circulates and flows between the water storage tank 38 and the cleaning liquid regenerating apparatus 35. At this time, the solid phase adsorbent in the cleaning liquid regenerating apparatus 35 contacts water, and the acid liquid adhering to the solid phase adsorbent is washed. After this, regeneration of the chelate washing solution is resumed.

  In the soil purification system S according to the first embodiment, harmful metals and the like are hardly adsorbed by the moss and sand during the washing and classification of the contaminated soil by the washing water, and are concentrated and adsorbed to the fine particles, It is possible to obtain clean and reusable straw and sand. Then, in the soil purification system S, the mill breaker 3 crushes the gravel and the sand to generate an iron-based fine particle fraction and a non-ferrous-based fine particle fraction. Therefore, the iron-based fine particle fraction existing before crushing and the iron-based fine particle fraction generated by crushing are introduced to the iron content removing device 12, and all of these iron-based fine particle fractions are considerably large ( In comparison with non-ferrous fine particles, it adsorbs harmful metals etc.).

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

  Thus, since the content rate of harmful metals and the like of the sludge discharged from the iron removing device 12 is significantly reduced, the cake discharged from the filter press 13 for filtering the sludge is chelate-cleaned by the chelate cleaning device 14 In some cases, the amount of use or necessary amount of chelating agent can be significantly reduced, and the cost of treating the soil can be reduced. The mill breaker 3 and the iron removal device 12 are of a simple mechanical structure that physically processes, and do not use special chemicals for treating harmful metals and the like, so their operating costs are very high. Low.

Second Embodiment
Hereinafter, the soil purification system SA according to Embodiment 2 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 respects. So, below, in order to avoid duplication of explanation, a difference with soil purification system S in soil purification system SA is mainly explained. In the components of the soil purification system SA according to the second embodiment, the same reference numerals as in the first embodiment are attached to the same components as the components of the soil purification system S according to the first embodiment.

  Although soil purification system SA which concerns on Embodiment 2 abbreviate | omits the description of the one part in FIG. 8, like soil purification system S which concerns on Embodiment 1, a series from input hopper 1 to the intermediate tank 9 The apparatus 1-9, the washing water storage tank 10, the spare water tank 11, and the iron removal apparatus 12 are provided. However, the soil purification system SA does not include the filter press 13 and the chelate cleaning device 14 in the first embodiment. And soil purification system SA is provided with the fine-grains washing apparatus 101, the filtration apparatus 102, the clear filter 103, the reverse osmosis membrane separation apparatus 104 (RO separation apparatus), and the chelating agent regenerating apparatus 105. .

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

  The fine particle slurry discharged from the fine particle washing device 101 is transferred to the filtering device 102. The filtration device 102 filters the fines slurry to produce a cake with a moisture content of 30 to 40 percent (filter cake) and a filtrate. In addition, as the filtration apparatus 102, a filter press, a vacuum filter, etc. can be used. The cake (fine particle content) discharged from the filtering device 102 hardly contains harmful metals and the like.

  The filtrate or chelate washing solution discharged from the filtration device 102 is pumped to the reverse osmosis membrane separation device 104 after suspended matter or suspended matter (SS) is removed by a clear filter 103 (for example, sand filter). . Although not shown in detail, the reverse osmosis membrane separation device 104 receives the chelate washing solution discharged from the clear filter 103, and the reverse osmosis membrane does not contain the concentrated water in which the chelating agent is concentrated and the chelating agent. Separates to permeate water.

  The reverse osmosis membrane of the reverse osmosis membrane separation device 104 has, for example, a three-layer structure in which a polysulfone supporting layer and a crosslinked aromatic polyamide dense layer are laminated on the surface of a polyester non-woven fabric (100 to 120 μm thick). It can be used. The cross-linked aromatic polyamide dense layer has a large number of pores with a pore diameter of approximately 0.5 to 1.5 nm, and is permeable to water but impermeable to the chelating agent (eg, 0.2 to 0.2 nm) 0.25 μm) semipermeable membrane. Also, the polysulfone support layer is a relatively thick (e.g., 40 to 50 [mu] m) porous membrane to support or protect a very thin crosslinked aromatic polyamide dense layer to prevent its failure.

The reverse osmosis membrane separation device 104 is a spiral type, and includes a plurality of reverse osmosis membrane elements in which a spirally wound reverse osmosis membrane is accommodated in a cylindrical container. For example, 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 the 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 Austentec Co., Ltd., Nakatsugawa City, Gifu Prefecture) is It is about 40 m ² . In the case of this reverse osmosis membrane element, when the chelating agent concentration of about 1% by mass is supplied at a pressure of about 1 MPa, the processing amount of the chelating agent is estimated to be about 1.5 m ³ / hr. Therefore, for example, in the case of processing a chelate washing solution at 60 m ^{3 /} h, 40 reverse osmosis membrane elements may be connected in parallel.

  The reverse osmosis membrane separation device 104 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 concentrated water and permeated water, and the chelating agent concentration ratio of concentrated water It is appropriately set in accordance with the amount of chelating cleaning fluid to be supplied to the cleaning apparatus 101 and the concentration of the chelating agent. For example, the ratio of the flow rate of sludge supplied to the fine particle washing apparatus 101 to the flow rate of the chelate washing solution is set to 1: 1, and the chelating agent concentration of the fine particle slurry in the fine particle washing apparatus 101 is set to 1% by mass If so, the reverse osmosis membrane separation device 104 generates about 50% of permeate water (chelating agent concentration 0) and about 50% concentrated water (chelating agent concentration about 2 mass%) of the supply amount of the chelate washing solution. Set to Therefore, in the fine particle content washing apparatus 101, the sludge containing no chelating agent and the chelate washing solution having a chelating agent concentration of about 2% by mass are mixed 1: 1, and the chelating agent concentration in the fine particle content washing apparatus 101 is 1 mass. It is maintained at about%.

  The concentrated water, that is, the chelate washing solution discharged from the reverse osmosis membrane separation device 104 is introduced into the chelating agent regeneration device 105 and regenerated. That is, harmful metals and the like are removed and recovered from the chelate washing liquid (chelating agent), and the chelate washing liquid (chelating agent) is in a state capable of capturing harmful metals and the like again. As such a chelating agent regenerating apparatus 105, for example, the cleaning fluid 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, similar to the soil purification system S according to the first embodiment, clean and reusable straw and sand can be obtained, and the sludge discharged from the iron removing device 12 The content of harmful metals etc. can be significantly reduced. Thus, since the content rate of harmful metals and the like of the sludge discharged from the iron removing device 12 is significantly reduced, the amount or use of the chelating agent is significantly reduced even when the sludge is subjected to the chelate cleaning. 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 aggregation Tank, 8 Thickener, 9 Intermediate Tank, 10 Wash Water Tank, 11 Spare Water Tank, 12 Iron Remover, 12A Iron Remover, 13 Filter Press, 14 Chelate Wash, 16 Sludge Tank, 17 Magnet Attached Drum, 17A Magnetic Attached Drum, 18 pipelines, 19 pipelines, 20 agitators, 21 rotating shafts, 22 drum bodies, 23 permanent magnets, 24 cylindrical covers, 25 motors, 26 speed reducers, 27 scrapers, 28 drive rollers, 29 drive shafts, 30 endless belts, 31 mixing and dispersing device, 32 fine particle size washing device, 33 filtration device, 34 washing Regeneration unit, 35 cleaning solution regenerating apparatus, 36 cleaning solution storage tank, 37 acid solution storage tank, 38 water storage tank, 41 crusher, 41a blade, 42 premixing tank, 43 line mixer, 44 chelate cleaning solution storage tank, 45 pump, 46 pipeline, 47 Stirrer, 48 pumps, 49 pipelines, 50 reservoirs, 51 to 54 partition walls, 55 to 59 slurry channels, 61 to 65 air discharge tubes, 72 intermediate reservoirs, 76 pumps, 77 to 80 pipelines, 81 pumps, 82 pipelines , 83 pumps, 84 pipelines, 85 pipelines, 86 pumps, 87 pipelines, 88 pipelines, 91 to 98 valves, 101 fine particle washing devices, 102 filtration devices, 103 clarification filters, 104 reverse osmosis separation devices, 105 Chelator regenerator.

Claims (3)

What is claimed is: 1. A soil remediation system for remediation of soil contaminated with harmful metals or their compounds, comprising gravel, sand and fine particles,
The soil remediation system
The soil classification part which classifies sand and sand and fine particles after crushing soil and washing with washing water.
By magnetically adsorbing and removing iron-based fine particles containing iron or iron oxide to the extent that can be absorbed by magnetic force, from sludge containing fine particles and wash water separated in the soil classification unit, And an iron removing device for reducing the content of harmful metals in sludge or their compounds,
The soil classification section
A mixer for mixing the soil introduced into the soil classification unit and the washing water;
Iron or iron oxide that is unevenly distributed or scattered in the inside of the gravel and sand can be absorbed by magnetic force by crushing the gravel and sand in the mixture containing the soil and the washing water discharged from the mixer A wet crusher that produces an iron-based fine particle content to a certain extent and adsorbs harmful metals or compounds thereof to iron or iron oxide exposed on the surface of the iron-based fine particle content;
A trommel that separates the straw from the mixture containing the straw, sand, fine particles and washing water, which is discharged from the wet crusher;
A hydrocyclone separating sand from a mixture comprising sand, fines and wash water discharged from the trommel;
It has a thickener which separates a mixture containing fine particles and wash water discharged from the hydrocyclone into supernatant water and sludge containing fine particles and wash water by sedimentation.
The iron removal device is
A sludge tank for retaining sludge containing fine particles and wash water discharged from the thickener;
The drum is formed in a drum shape, the drum central axis is directed in the horizontal direction, and the lower portion of the drum is disposed so as to be immersed in the sludge in the sludge tank, and a plurality of permanent magnets are radially outward in the drum circumferential surface. Magnet mounted drums, which are mounted side by side in the circumferential direction of the drum, with the magnetic poles facing
And a drum rotation mechanism for rotating the magnet mounting drum.   The soil purification system according to claim 1, wherein the iron removing device has a pH adjusting device which adjusts the hydrogen index of the sludge retained in the sludge tank to a range of pH 4 to 6. A filter press which receives fine sludge and water-containing sludge from which iron-based fine particles have been removed by the above-mentioned iron removal device, and which is pressure-filtered to separate it into fine cake-containing cake and filtrate;
A chelate washing device for washing the cake separated by the filter press with a chelate washing solution containing a chelating agent and water to remove harmful metals or compounds thereof remaining in fine particles;
The soil purification system according to claim 1 or 2, further comprising: a filtrate return means for returning the filtrate separated by the filter press to the thickener.

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