JP2020075242A - 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 removing toxic metal and the like adsorbed to the fine-grain fraction.SOLUTION: A soil remediation system SA comprises soil classification units, a preprocessing unit being an iron removal device 12, and postprocessing units 101 to 105. The soil classification units crush gravel and sand in soil by a mill breaker while washing the soil with wash water, and then perform classification into gravel, sand and fine-grain fractions by a trommel, a cyclone 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. The postprocessing units 101 to 105 apply washing processing with a chelating agent to the sludge discharged from the iron removal device 12, thereby removing toxic metal and the like adsorbed to the surface of the fine-grain fraction in the sludge.SELECTED DRAWING: Figure 8

Description

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

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

  As a method for purifying harmful metal-contaminated soil in such an off-site soil purification facility, a cleaning method has conventionally been widely used for cleaning harmful metal-contaminated soil with cleaning water or the like to remove harmful metals. .. When the harmful metal-contaminated soil is washed with washing water, most of the harmful metals etc. that have once separated from the soil into the water are adsorbed or adhered to the surface of the fine particles having a relatively small particle size, It is known that they are aggregated on the surface of (see Non-Patent Document 1, for example).

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

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

Ministry of the Environment, Water and Air Environment Bureau, Soil Environment Section, "Technical considerations regarding permission examination of contaminated soil treatment business," page 21, published in August 2013 Katsura Tetsuo "Wastewater Treatment by Iron Powder Method" Flotation, vol. 23 (1976), no. 3, P190-198 (https://www.jstage.jst.go.jp/article/rpsj1954/23/3/23_3_190/_pdf)

  By the way, in this type of soil purification facility by a contaminated soil treatment company, a large amount of contaminated soil is usually purified (for example, 2000 tons per day), so a large amount of fine particles is generated (for example, , 500-600 tons per day on a dry basis). Therefore, when a large amount of fine particles are washed with, for example, a chelate washing liquid, a relatively expensive chelating agent is required in a large amount, so that there is a problem that the treatment cost of contaminated soil becomes high. Needless to say, the necessary amount or the amount of the chelating agent used increases as the content of harmful metal or the like in the fine particles increases. The same 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, including gravel and sand while washing soil contaminated with harmful metals and the like containing gravel, sand and fine particles with wash water. Fine particles can be classified, and harmful metals adsorbed or adhered to the separated fine particles can be removed, or at least the content rate of harmful metals or the like in fine particles or possession It is an issue to be solved to provide a soil purification system that can reduce the rate and is simpler and has a lower treatment cost.

  The soil purification system according to the present invention made in order to solve the above-mentioned problems includes soil containing gravel, sand, and fine particles, and soil contaminated with harmful metals and the like (toxic metals and / or their compounds or ions thereof). Purify. This soil purification system includes a soil classification unit and an iron content removal device. Here, the soil classification unit crushes 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-removing device is generically referred to as iron and / or iron oxide (hereinafter referred to as "iron etc.") to the extent that it can be adsorbed by magnetic force from sludge containing fine particles separated in the soil classification part and washing water. By removing the iron-based fine particles containing a) by magnetic attraction, the content rate or retention rate of harmful metals and the like in the sludge (fine particles) is reduced.

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

  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 containing the fine particles discharged from the thickener and the cleaning water. The magnet mounting drum is formed in a drum shape, and is arranged such that the drum central axis faces the horizontal direction and the drum lower part is immersed in the sludge in the sludge tank. Inside the drum circumferential surface of the magnet mounting drum, a plurality of permanent magnets are mounted side by side (arranged) in the drum circumferential direction so that the magnetic poles face outward in the drum radial direction. The drum rotation mechanism rotates the magnet mounting drum. The iron removing device preferably has a pH adjusting device that 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 filtrate returning means, and more preferably comprises a chelate cleaning device. In this case, the filter press receives the sludge containing fine particles (fine particles other than the iron fine particles) and water, from which the iron fine particles have been removed by the iron removing device, and pressure-filters the sludge. 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 liquid containing a chelating agent and water to remove harmful metals remaining in fine particles (fine particles other than iron-based fine particles). Etc. are removed.

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

  Then, according to the soil purification system according to the present invention, gravel and sand are crushed by a wet crusher to generate fine particles, but among these fine particles, uneven distribution or scattering in gravel or sand. The fine particles containing a large amount of iron and other small lumps are iron-based fine particles, and the iron, etc. exposed on the surface of these iron-based fine particles are fed from the wet crusher to the iron removal device. Adsorbs a relatively large amount of harmful metals and the like during the distribution process. Therefore, the iron-based fine particles that were present before the crushing and the iron-based fine particles that were generated by the crushing were introduced into the iron removal device. Adsorbs harmful metals, etc. (compared to fine particles).

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

  Therefore, even when removing harmful metals and the like adsorbed in the remaining fine particles (non-ferrous fine particles) using relatively expensive chemical agents such as chelating agents, the required amount or the amount of chemical agents used must be reduced. The cost of soil treatment can be significantly reduced. The wet crusher and iron removal device have a simple mechanical structure for physical treatment and do not use special chemicals for treating harmful metals, etc., so the operating cost is very low. ..

It is a block diagram showing a schematic structure of a soil purification system concerning Embodiment 1 of the present invention. (A) is a typical side surface sectional view of an iron removal device which is a component of a soil purification system, and (b) is a schematic plan view of the iron removal device shown in (a). (A) is a typical side surface sectional view of another iron content removing device, and (b) is a schematic plan view of the iron content removing device shown in (a). It is a block diagram which shows schematic structure of the chelate cleaning apparatus which is a component of a soil purification system. FIG. 3 is a schematic elevational view showing the configuration of a mixing and dispersing device that forms a part of the chelate cleaning device. (A) is a schematic plan view of a fine particle cleaning device forming a part of a chelate cleaning device, (b) is a cross-sectional view taken along line AA of the fine particle cleaning device shown in (a), (C) is an elevational sectional view of one slurry passage of the fine particle cleaning device. FIG. 3 is a schematic elevational view showing a configuration of a cleaning liquid regenerating unit which is a part of the chelate cleaning device. 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 the first embodiment of the present invention, the soil was collected by excavation of the ground contaminated with harmful metals and the like (toxic metals and / or their compounds or ions of these). The soil (contaminated soil) is received by the input hopper 1. Examples of harmful metals include chromium, lead, cadmium, selenium, mercury, and metal arsenic. Then, the soil in the input hopper 1 is continuously or intermittently charged into the mixer 2 and mixed with the wash water continuously supplied to the mixer 2. Here, the soil includes gravel (for example, a particle size of 2 to 75 mm), sand (for example, a particle size of 0.075 to 2 mm), and fine particles (for example, a particle size of 0.075 mm or less). Some include stones (for example, a particle size of 75 mm or more).

  The mixture containing the soil and the wash water (hereinafter referred to as “soil / water mixture”) generated by the mixer 2 is transferred to the mill breaker 3 which is a wet crusher. As the mill breaker 3, for example, a rod mill can be used. Although not shown in detail, the rod mill is a crushing device in which a plurality of rods (for example, 10 steel rods of 75 mmφ × 2 m) are arranged in a drum, and the rods are rotated in parallel with each other by the rotation of the drum. It moves and makes line contact, and the impact force, shearing force, frictional force, etc., can crush gravel and sand (and in some cases stones) to produce small-sized soil particles such as fine particles. .. As the mill breaker 3, a ball mill or the like can be used in addition to the rod mill. It should be noted that gravel and sand are partly fine-grained, not all.

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

  Further, a large number of iron-based fine particles are formed in which minute agglomerates of iron or the like (iron and / or iron oxide) that are present or unevenly distributed or scattered in the gravel and sand are exposed on the surface. On the other hand, iron or the like generally has a property of adsorbing harmful metals or the like. Therefore, a part or most of the harmful metals and the like existing in the wash water are adsorbed or adhered to the exposed surface of the iron-based fine particles, such as iron. As a result, the adsorption amount (adhesion amount) of the ferrous fine particles of the harmful metal or the like becomes considerably larger than the adsorption amount (adhesion amount) of the non-ferrous fine particles of the harmful metal or the like. In other words, the fine particles discharged from the mill breaker 3 include iron-based fine particles having a large adsorption amount (adhesion amount) of harmful metals and non-ferrous fine particles having a small adsorption amount (adhesion amount) of harmful metals. Composed of and. It is needless to say that the iron-based fine particles existing before the crushing also adsorb a considerable amount of harmful metals and the like as compared with the non-iron-based fine particles.

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

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

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

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

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

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

  In the pH adjusting tank 6, the pH of the water containing fine particles is adjusted to be substantially neutral by using an acid solution (for example, sulfuric acid, hydrochloric acid) and an alkaline solution (for example, sodium hydroxide aqueous solution). Although not shown, in the pH adjusting tank 6, the pH of the water containing fine particles is automatically adjusted by an automatic pH controller including a pH meter or the like.

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

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

  The supernatant water in the thickener 8 is introduced into the wash water tank 10 and temporarily stored. The spare water tank 11 is used when the cleaning water tank 10 is full. The wash water stored in the wash water layer 10 or the preliminary water tank 11 is supplied to the mixer 2 and the trommel 4 as circulating water. When the amount of cleaning water stored in the cleaning water tank 10 decreases due to evaporation or the like, tap water is appropriately replenished. On the other hand, the sludge accumulated under the thickener 8 is transferred to the intermediate tank 9 and temporarily stored therein. Then, the sludge in the intermediate tank 9 is continuously transferred to the iron content removing device 12.

  As shown in FIGS. 2A and 2B, the iron removal device 12 includes a sludge tank 16 and a magnet mounting drum 17. Here, the sludge tank 16 receives the sludge composed of fine particles (iron-based fine particles and non-ferrous-based fine particles) and water transferred from the intermediate tank 9 through the pipeline 18 and temporarily receives the sludge. Hold. Then, the sludge in the sludge tank 16 is transferred (pressure-fed) to the filter press 13 (see FIG. 1) via the conduit 19 after the iron-based fine particles are removed as described later. A stirrer 20 is provided in the sludge tank 16 to prevent the fine particles from settling on 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 a ring-shaped peripheral portion (outer edge) of the drum main body 22 adjacent to each other in the drum circumferential direction. And a cylindrical cover 24 that covers the outer peripheral surface of the permanent magnet group arranged in a ring shape. Here, the drum main body 22 is arranged such that the rotation center axis thereof is oriented in the horizontal direction and the lower portion of the drum is immersed in the sludge in the sludge tank 16.

  Each of the plurality of permanent magnets 23 is arranged so that the magnetic pole thereof faces outward in the radial direction of the drum (outward). The permanent magnets 23 may be arranged so that all N poles or S poles face outward, or may be arranged so 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 rotary shaft 21 and thus the drum main body 22 are rotationally driven by a motor 25 (electric motor) via a speed reducer 26, and in a positional relationship in FIG. Rotate at 0 r.p.m.). Then, 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. Thus, when the drum main body 22 comes out of the sludge, the iron-based fine grain separation layer is formed on the outer peripheral surface of the cylindrical cover 24. The iron-based fine particle sublayer 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 an iron-making raw material.

  The iron-based fine particles are those produced by crushing gravel and sand by a mill breaker 3 (see FIG. 1) which is a wet crusher, or those existing before crushing gravel and sand. A minute mass 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 mass of iron or the like. In general, small pieces of iron or the like are unevenly distributed or scattered in the gravel and sand, and the proportion of such small pieces is about 2 to 5% by mass. Therefore, a part of the fine particles generated by crushing the gravel and sand becomes iron-based fine particles having fresh iron or the like exposed on the surface.

Iron is a ferromagnetic material (soft magnetic material) and is adsorbed by a magnet. Further, the iron oxides existing in the soil are substantially triiron tetraoxide (Fe ₃ O ₄ ), γ-type diiron trioxide (γ-Fe ₂ O ₃ ), and α-type diiron trioxide ( α-Fe ₂ O ₃ ) and triiron tetroxide and γ-diiron trioxide are ferromagnetic materials (soft magnetic materials) and are adsorbed by the magnet. Note that α-type diiron trioxide is not magnetized and is not adsorbed by the magnet. Therefore, the iron-based fine particles in which minute lumps of iron or the like are exposed on the surface are attracted to the permanent magnet 23 by the ferromagnetism (soft magnetism) of iron, triiron tetraoxide or γ-type diiron trioxide, It is adsorbed to the outer peripheral surface of the cylindrical cover 24.

In addition, the inventor of the present application crushed gravel and sand with a mill breaker multiple times (10 times) in July 2017 at a contaminated soil treatment plant at a factory in Yamatsuzaki Co., Ltd. gravel store in Otsu City, Shiga Prefecture. The sludge (1 to 3% by mass of fine particles), which is a mixture of fine particles and water, produced by using a magnet-mounted drum (using a neodymium magnet as a permanent magnet) with a diameter of about 1 m, When an adsorption experiment was conducted, on average 3.4 kg of iron-based fine particles were collected per 10 m ³ of sludge.

  Fine lumps of iron and the like exposed on the surface of iron-based fine particles generated by crushing gravel and sand with a mill breaker 3 are harmful metals that are unevenly distributed or scattered in gravel or sand. It is generated from a small lump of fresh iron that does not adsorb, and is exposed on the surface after crushing and adsorbs harmful metals and the like from the cleaning water around it. Thus, the fine particles discharged from the mill breaker 3 and finally introduced into the iron removing device 12 include iron-based fine particles having a relatively large amount (or considerably large amount) of adsorbing harmful metals, and harmful metals. It is composed of non-ferrous fine particles that have a relatively (or considerably) small adsorption amount of.

  As described above, since the iron-based fine particles are removed from the sludge in the iron removal device 12, the fine particles contained in the sludge discharged from the iron removal device 12 have a relatively large adsorption amount of harmful metals and the like. Most (or quite) non-ferrous fines. Therefore, most or a considerable part of the harmful metals contained in the contaminated soil introduced into the soil purification system S is removed by the iron removing device 12. Therefore, 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 simply by dehydrating.

  Further, as will be described later, when the chelate cleaning treatment is performed on the sludge or fine particles discharged from the iron removing device 12, the chelate cleaning treatment is performed as compared with the case where the iron removing device 12 is not provided. Since the load of harmful metals and the like in the above is reduced, the treatment cost in the chelate cleaning treatment 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. When the sludge or fine particles discharged from the iron removing device 12 are subjected to a chemical treatment other than the chelate cleaning treatment, the iron removing device 12 can be positioned as a pretreatment device.

  As shown in FIG. 1 again, the sludge discharged from the iron removal 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 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). If the content ratio of harmful metal or the like in the fine particles contained in the cake is within the standard, the cake is disposed of by landfill or the like without being transferred to the chelate cleaning device 14.

  Hereinafter, with reference to FIGS. 3A and 3B, the configuration and function 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 constituent elements of the iron content removing apparatus 12A shown in FIGS. 3A and 3B are common to the constituent elements of the iron content removing apparatus 12 shown in FIGS. In order to avoid the duplication of the above, differences from the iron removal device 12 will be mainly described below. It should be noted that, in the constituent elements of the iron content removing device 12A shown in FIGS. 3A and 3B, those common to the constituent elements of the iron content removing device 12 shown in FIGS. Numbered.

  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 body 17A, and the drive roller 28 is a drive shaft. It is attached coaxially to 29. The drive roller 28 and the drive shaft 29 are arranged such that the rotation center axis thereof is parallel to the rotation center axis of the drum body 17A, and are rotationally driven by the motor 25 via the speed reducer 26. The drive roller 28 has a smaller diameter (for example, 1/5 to 1/10) than the drum body 17A.

  A plurality of permanent magnets 23 are attached to or disposed in the drum body 17A with the same specifications as the iron removal device 12 shown in FIG. 2 (a). The rotary shaft 21 of the drum body 17A is rotatably supported by bearings fixed to the sludge tank 16. An endless belt 30 (for example, steel) made of a soft magnetic metal material (for example, iron or an iron alloy) is provided across the drum body 17A in which a plurality of permanent magnets 23 are annularly mounted or arranged on the circumferential portion and the drive roller 28. Belt) is wrapped around. The endless belt 30 may be made of a diamagnetic metal material (for example, copper, aluminum, or an alloy thereof).

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

  An endless belt 30 that travels clockwise between the drive roller 28 and the drum body 17A in the positional relationship shown in FIG. 3A is arranged in a ring shape on the circumferential surface of the drum body 17A. When it is in contact with the outer peripheral surface of and is immersed in the sludge in the sludge tank 16, 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. Thus, when the endless belt 30 comes out of the sludge, the iron-based fine grain fraction layer is formed on the outer surface of the endless belt 30. The iron-based fine particle fraction 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.

  In the iron content removing device 12A shown in FIGS. 3A and 3B, as in the iron content removing device 12 shown in FIGS. 2A and 2B, the iron-based fine particles are removed from the 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 (or considerably) small amount of adsorbing harmful metals and the like. The sludge discharged from the iron removal device 12A 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 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).

  The configuration and function of the chelate cleaning device 14 will be described below. When the content of harmful metals or the like in the cake discharged from the filter press 13 is lower than a predetermined regulation value when the cake is disposed of by landfilling or reuse, it is not necessary to use or provide the chelate cleaning 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 the chelating agent in the cleaning liquid storage tank 36 are continuously supplied to the mixing and dispersing device 31. Then, the mixing / dispersing device 31 mixes the cake and the chelate cleaning liquid, and the fine particles or small pieces of the fine particles (for example, the particle diameter is about several 0.1 to 0.5 mm or 0.1) in the chelate cleaning liquid. A fine particle slurry is produced in which particles of about 1 mm are dispersed (suspended) almost uniformly.

  The fine particle content slurry generated by the mixing and dispersing device 31 is transferred to the fine particle content cleaning device 32. The fine particle content cleaning device 32 causes the fine particle content slurry to flow generally by 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 chelate cleaning liquid. As a result, harmful metals and the like adsorbed (adhered) on the surface of the fine particle component in the fine particle component slurry are removed.

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

  The fine particle slurry discharged from the fine particle cleaning device 32 is transferred to the filtering device 33. The filter device 33 filters the fine-grained slurry to produce a cake (filter cake) having a water content of 30 to 40 percent and a filtrate. A filter press, a vacuum filter, or the like can be used as the filtering device 33. The filter cake (fine particles) discharged from the filter device 33 contains almost no harmful metals.

  The filtrate discharged from the filtering device 33, that is, the chelate cleaning liquid is introduced into the cleaning liquid regenerating unit 34. The cleaning liquid regenerating unit 34 includes a cleaning liquid regenerating device 35, a cleaning liquid storage tank 36, an acid liquid storage tank 37, and a water storage tank 38. Here, the cleaning liquid regenerator 35 has a higher complexing power than the chelating agent, and when it comes into contact with the chelate cleaning liquid (filtrate) discharged from the filtering device 33, it adsorbs or extracts harmful metals and the like in the chelate cleaning liquid. It is an apparatus which has a small piece or a granular material to which the material or the solid phase adsorbent is fixed, and which removes harmful metals and the like from the chelating agent in the chelate cleaning liquid and regenerates the chelate cleaning liquid.

  In the cleaning liquid regenerator 35, a chelate cleaning liquid containing a chelating agent that traps harmful metals and the like is brought into contact with a solid phase adsorbent having a higher complexing power than the chelating agent. The solid-phase adsorbent is one that supports cyclic molecules on a carrier, has a multipoint interaction by coordination bonds and hydrogen bonds in which cyclic molecules are modified with chelate ligands, and selectively takes in ions such as harmful metals. is there. As a result, harmful metals and the like captured by the chelating agent are released from the chelating agent and adsorbed or extracted by the solid phase adsorbent. As a result, harmful metals and the like are removed and collected from the chelate cleaning liquid (chelating agent), and the chelate cleaning liquid (chelating agent) can capture the harmful metals and the like again.

  The chelate cleaning liquid thus regenerated is temporarily stored in the cleaning liquid storage tank 36, and then is recirculated to the mixing / dispersing device 31 by a cleaning liquid recirculation mechanism (a pump 81, a pipe line 82, etc. 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 depletion amount of the chelating agent is appropriately replenished.

  A solid-phase adsorbent having a higher complexing power than a chelating agent is, for example, a solid substance such as a gel, and generally, when brought into contact with an aqueous solution containing a chelating agent capturing a metal, the chelating agent and a coordinate bond are formed. It has a strong binding force other than the covalent bond to such an extent that the existing metal ions can be released from the chelating agent and moved to the solid phase adsorbent. When using EDTA (ethylenediaminetetraacetic acid) as a chelating agent, such a solid-phase adsorbent has a strong binding force capable of recovering almost 100% of metal ions from an EDTA aqueous solution having a concentration of 10 mM / l. I have.

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

  As the chelate cleaning liquid is regenerated, the amount of harmful metals adsorbed on the solid phase adsorbent increases with time, but the amount of adsorbed harmful metals etc. on the solid phase adsorbent has an upper limit. Therefore, when the adsorption amount of harmful metals or the like in the solid-phase adsorbent reaches a saturated state or in the vicinity thereof, the solid-phase adsorbent is regenerated by the solid-phase adsorbent regeneration mechanism (the acid solution storage tank 37, the pump 83, the pipe line described later). 84, 78, 79, 85 etc.). That is, the solid phase adsorbent regenerating mechanism causes the acid liquid to flow through the cleaning liquid regenerator 35 in a state where the chelate cleaning liquid is removed, and removes harmful metals and the like adsorbed on the solid phase adsorbent with the acid liquid 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 to be in a state capable of adsorbing the 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 (a water storage tank 38, a pump 86, pipe lines 87, 78, 79, 88, etc., described later) and attached to the solid phase adsorbent. The acid solution is removed.

The specific configuration and function of the chelate cleaning device 14 will be described below.
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 / 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 / dispersing device 31 pre-mixes a crusher 41 that crushes the cake (fine particles) discharged from the filter press 13, a cake small piece crushed by the crusher 41, and a chelate cleaning liquid. The premixing tank 42 and the mixture produced by the premixing tank 42 are stirred to chelate cake pieces (for example, particles having a particle size of several 0.1 to 0.5 mm or 0.1 to 1 mm). It has a line mixer 43 for dispersing or suspending in the cleaning liquid.

  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 processed by the blade 41a that rotates at a high speed into a large number of particles having a particle diameter of several mm (for example, 1 to 5 mm). It is broken into small pieces of cake. On the other hand, the chelate cleaning liquid in the chelate cleaning liquid storage tank 44 is supplied to the disintegrator 41 by the pump 45 via the pipe line 46. The chelate cleaning liquid storage tank 44 is appropriately supplied with the chelate cleaning liquid from the cleaning liquid storage tank 36 (see FIG. 4). 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 sticking to each other. As such a crusher 41, for example, a "dehydrated cake crusher" according to Taiheiyo Kiko Co., Ltd. or a "dehydrated cake recycling device" according to Kiko Co., Ltd. can be used. When using a commercially available crusher, it is necessary to attach a mechanism for injecting or supplying the chelate cleaning liquid to a large number of cake pieces immediately after crushing.

  The chelate purified solution and cake pieces in the crusher 41 are transferred to the premixing tank 42. The chelate cleaning liquid and the cake pieces in the premixing tank 42 are agitated and premixed by an agitator 47 which is rotationally driven by a motor. Then, the mixture of the chelate cleaning 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 rotationally driven at a very high speed by a motor is arranged in a horizontal type substantially cylindrical stirring chamber, and the chelate cleaning liquid and the cake pieces are stirred very violently. However, cakes or fine particles of fine particles (for example, particles having a particle size of several 0.1 to 0.5 mm or 0.1 to 1 mm) are almost uniformly dispersed (suspended) in the chelate cleaning liquid. To produce a fine particle slurry. The fine particle content slurry is transferred to the fine particle content cleaning device 32 (see FIG. 4). As such a line mixer 43, for example, "Satake multi-line mixer" of Satake Chemical Machinery Co., Ltd. or the like can be used.

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

  The fine grain fraction 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 partitioning with four flat partition walls 51 to 54. is doing. The storage tank 50 may be, for example, an iron rectangular parallelepiped rectangular tank installed on the ground, or may be a concrete rectangular parallelepiped pit. Further, the partition walls 51 to 54 may be formed by connecting, for example, a plurality of iron plates or plastic plates in the extending direction of the slurry passage.

  Two adjacent slurry passages in the slurry passages 55 to 59 have four curved lines in the communicating portion (FIG. 6A) at one end in the slurry passage longitudinal direction (the horizontal direction in the positional relationship in FIGS. 6A and 6B). (The part indicated by the arrow) is communicating with each other. That is, the partition walls 51 to 54 do not exist in these communicating portions, and the adjacent slurry passages communicate with each other.

  At the bottom of each slurry passage 55-59, air discharge pipes 61-65 for discharging air into the fine particle slurry and agitating the fine particle slurry are arranged, respectively. Each of the air discharge pipes 61 to 65 is a perforated pipe that extends in the slurry passage lengthwise direction and has a plurality of air discharge holes arranged in the slurry passage lengthwise direction at the bottom portion (lower side) of the peripheral wall. Although not shown, it is connected to a compressor or blower that supplies compressed air. When pressurized air is supplied to the air discharge pipes 61 to 65, the air becomes bubbles from the air discharge holes and is discharged into the fine particle slurry and floats up, and the bubbles agitate the fine particle slurry. To be done.

  FIG. 6C shows a cross section of the slurry passage 55 on the most upstream side as viewed in the flow direction of the fine-grained slurry (directions indicated by curved arrows and linear arrows in FIG. 6A). .. As is clear from FIG. 6C, the air discharge pipe 61 is arranged near the bottom of the slurry passage 55 near one side surface of the slurry passage 55. Therefore, the bubbles discharged from the air discharge pipe 61 rise in the vicinity of this side surface. As a result, in the slurry passage 55, a circulation flow that flows in the direction indicated by the arrow P in a plane perpendicular to the longitudinal direction of the slurry passage is formed, and the fine-grained slurry is agitated. The shape, size, capacity, etc. of the storage tank 50 and each of the slurry passages 55-59, and the supply amount of the pressurized air to the air discharge pipes 61-65, etc. are set in advance in the fine particle content cleaning device 32. Of water content, flow rate, residence time, flow velocity, flow turbulence (eg Reynolds number), etc.

  Hereinafter, the specific configuration and function of the cleaning liquid regenerating unit 34, which is a component of the chelate cleaning apparatus 14, will be described with reference to FIG. 7. In the cleaning liquid regenerating section 34, as a means for regenerating a chelate cleaning liquid or a chelating agent, a cleaning liquid of a packed tower type, in which solid phase adsorbent particles or packing in which the solid phase adsorbent is fixed, is packed. A playback device 35 is provided. In the cleaning liquid regenerator 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 storage tank 38 is provided.

  The intermediate storage tank 72 temporarily stores the filtrate discharged from the filtering device 33 (see FIG. 4), that is, the chelate cleaning liquid. Then, when regenerating the chelate cleaning liquid, the chelate cleaning liquid stored in the intermediate storage tank 72 is transferred to the cleaning liquid regenerator 35, while the chelate cleaning liquid regenerated by the cleaning liquid regenerator 35 is transferred to the cleaning liquid storage tank 36. And a series of conduits 77-80. Further, a pump 81 and a pipe line 82 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) are provided.

  Further, the cleaning liquid regenerator 34 transfers the acid liquid stored in the acid liquid storage tank 37 to the cleaning liquid regenerator 35 and regenerates the acid liquid discharged from the cleaning liquid regenerator 35 when regenerating the solid phase adsorbent. A pump 83 for returning to the acid liquid storage tank 37 and a plurality of conduits 84, 85 are provided. Further, in the cleaning liquid regenerating unit 34, when the solid phase adsorbent regenerated with the acid liquid is washed with water, the water stored in the water storage tank 38 is transferred to the cleaning liquid regenerating device 35, and is discharged from the cleaning liquid regenerating device 35. A pump 86 and a plurality of conduits 87, 88 for returning the collected water to the water storage tank 38 are provided.

  The pipes 77, 78, 84, 87 for transferring the chelate cleaning liquid, the acid liquid or the water to the cleaning liquid regenerator 35 are provided with valves 91, 92, 93, 94 for opening and closing the corresponding pipes, respectively. ing. On the other hand, the conduits 79, 80, 85, 88 for discharging the chelate cleaning liquid, the acid liquid or the water from the cleaning liquid regenerator 35 are provided with valves 95, 96, 97, 98 for opening and closing the corresponding conduits, respectively. It is set up. By switching the open / closed states of these valves 91 to 98, it is possible to supply / discharge either the chelate cleaning liquid, the acid liquid, or the water to / from the 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 a method of operating the cleaning liquid 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 liquid regenerating unit 34 according to the present invention is not limited to the following operation method. When regenerating the chelate cleaning liquid (chelating agent), the valves 91, 92, 95, 96 provided in the conduits 77 to 80 are opened, while the other valves 93, 94, 97, 98 are closed, The pump 76 is operated. As a result, the chelate cleaning liquid in the intermediate storage tank 72 flows through the cleaning liquid regenerator 35 and is transferred to the cleaning liquid storage tank 36.

  In the cleaning liquid regenerator 35, a chelate cleaning liquid containing a chelating agent that traps harmful metals and 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 captured by the chelating agent are released from the chelating agent and are adsorbed or extracted by the solid phase adsorbent. As a result, harmful metals and the like are removed and collected from the chelate cleaning liquid, and the chelating agent can capture the harmful metals and the like again, and the chelate cleaning liquid is regenerated. 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 conduit 82.

  A solid-phase adsorbent having a higher complexing power than a chelating agent is, for example, a solid substance such as a gel, and generally, when brought into contact with an aqueous solution containing a chelating agent capturing a metal, the chelating agent and a coordinate bond are formed. It has a strong binding force other than the covalent bond to such an extent that the existing metal ions can be released from the chelating agent and moved to the solid phase adsorbent. Examples of such solid phase adsorbents include those in which a cyclic molecule is densely supported on a carrier such as silica gel or resin, and the cyclic molecule is modified with a chelate ligand. When such a solid-phase adsorbent is used, a plurality of various bonds and interactions such as coordination bond and hydrogen bond are generated by the adjacent cyclic molecule and chelate ligand, and multi-point interaction occurs, resulting in metal ion. On the other hand, a stronger chemical bond than that of the chelating agent occurs, and the metal ion can be selectively taken in due to the property of the cyclic molecule.

  As the chelate cleaning liquid is regenerated, the adsorption amount of harmful metals and the like 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, the solid phase adsorbent is regenerated when the amount of adsorbed harmful metals or the like in the solid phase adsorbent reaches a saturation state or a vicinity thereof. That is, the acid solution is allowed to flow into the cleaning solution regenerator 35 with the chelate cleaning solution removed, and the harmful metal adsorbed on the solid phase adsorbent is removed by the acid solution to regenerate the solid phase adsorbent. Thus, while the harmful metals and the like are recovered by the acid solution, the solid phase adsorbent is regenerated to be in a state in which the harmful metals and the like or these ions can be adsorbed or extracted again. As will be described later, the solid phase adsorbent is regenerated with an acid solution and then washed with water to remove the acid solution adhering to the solid phase adsorbent.

  When the amount of adsorbed harmful metal or the like of the solid phase adsorbent in the cleaning liquid regenerator 35 reaches the saturated state or the vicinity thereof and the solid phase adsorbent is regenerated with the acid liquid, the lines 84, 78, 79, 85 are used. 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. As a result, the acid solution in the acid solution storage tank 37 flows through the cleaning solution regenerator 35 and returns to the acid solution storage tank 37. Before starting the regeneration operation of the solid phase adsorbent, the chelate cleaning liquid in the cleaning liquid regeneration device 35 is removed. If a plurality of cleaning liquid regenerators 35 are arranged in parallel, the chelate cleaning liquid can be continuously regenerated even when the supply of the chelate cleaning liquid to some cleaning liquid regenerators 35 is stopped. Whether or not the adsorbed amount of harmful metals of the solid phase adsorbent has reached a saturated state or in the vicinity thereof can be determined by detecting the content of harmful metals or the like in the chelate cleaning liquid discharged from the cleaning liquid regeneration device 35. it can.

  The time for flowing the acid solution into the cleaning liquid regenerator 35 is preferably set according to the size or shape of the cleaning liquid regenerator 35, the size of the solid phase adsorbent particles, and the like. The acid solution circulates between the acid solution storage tank 37 and the cleaning solution regenerator 35 and flows. At that time, the solid phase adsorbent in the cleaning liquid regenerator 35 comes into contact with the acid solution, and the harmful metals and the like adsorbed by 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 so that the harmful metals and the like can be adsorbed again.

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

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

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

  Since the content of harmful metals and the like in the sludge discharged from the iron removal device 12 is greatly reduced in this way, the cake discharged from the filter press 13 that filters this sludge is chelated by the chelate cleaning device 14. Even in this case, the amount of the chelating agent used or the amount required can be significantly reduced, and the treatment cost of soil can be reduced. The mill breaker 3 and the iron removal device 12 have a simple mechanical structure for physically performing treatment, and do not use any special chemicals for treating harmful metals and the like, so the operating cost thereof 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 order to avoid duplication of description, differences between the soil purification system SA and the soil purification system S will be mainly described below. In the constituent elements of the soil purification system SA according to the second embodiment, those common to the constituent elements of the soil purification system S according to the first embodiment are denoted by the same reference numerals as 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, the series from the input hopper 1 to the intermediate tank 9 is connected. 1 to 9, a wash water storage tank 10, a preliminary water tank 11, and an iron removal 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 cleaning 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 the non-ferrous fine particles discharged from the iron removing device 12 and cleaning water, and a chelate cleaning liquid containing a chelating agent and water. , These are mixed and stirred to form a fine particle slurry, which is continuously adsorbed (adhered) to the non-ferrous fine particles by continuously flowing so as to secure a preset residence time. The harmful metal or the like is released and captured by the chelating agent, or the harmful metal or the like present in water is captured by the chelating agent. As such a fine particle cleaning device 101, for example, the fine particle cleaning device 32 in Embodiment 1 (see FIGS. 6A to 6C) can be used. The ratio of the flow rate of sludge to the fine particle cleaning apparatus 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 content slurry discharged from the fine particle content cleaning device 101 is transferred to the filtration device 102. The filtering device 102 filters the fine-grained slurry to produce a cake having a water content of 30 to 40 percent (filter cake) and a filtrate. A filter press, a vacuum filter, or the like can be used as the filtering device 102. The cake (fine particles) discharged from the filtration device 102 contains almost no harmful metals.

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

  The reverse osmosis membrane of the reverse osmosis membrane separation device 104 has, for example, a three-layer structure in which a polysulfone support layer and a crosslinked aromatic polyamide dense layer are laminated on the surface of a polyester nonwoven fabric (thickness 100 to 120 μm). Can be used. The crosslinked aromatic polyamide dense layer has a large number of pores having a pore size of about 0.5 to 1.5 nm, and is very thin (for example, 0.2 to 0.25 μm) Semi-permeable membrane. The polysulfone support layer is a relatively thick (for example, 40 to 50 μm) porous membrane that supports or protects the very thin crosslinked aromatic polyamide dense layer to prevent its damage.

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

  The reverse osmosis membrane separation device 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 the concentrated water and the permeated water, and the concentration ratio of the chelating agent of the concentrated water are fine particle fractions. It is appropriately set according to the amount of chelate cleaning liquid to be supplied to the cleaning apparatus 101 and the concentration of the chelating agent. For example, the ratio of the flow rate of 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 chelating agent concentration of the fine particle cleaning device 101 is set to 1% by mass. In such a case, the reverse osmosis membrane separation device 104 produces permeated water (concentration of chelating agent 0) of about 50% of the supply amount of the chelate cleaning liquid and concentrated water (concentration of chelating agent of about 2% by mass) of about 50%. Is set to. Therefore, in the fine particle cleaning device 101, the sludge containing no chelating agent and the chelate cleaning liquid having a chelating agent concentration of about 2% by mass are mixed at a ratio of 1: 1, and the chelating agent concentration in the fine particle cleaning device 101 is 1 mass. % Is maintained.

  The concentrated water discharged from the reverse osmosis membrane separation device 104, that is, the chelate cleaning liquid is introduced into the chelating agent regenerating device 105 and regenerated. That is, harmful metals and the like are removed and collected from the chelate cleaning liquid (chelating agent), and the chelate cleaning liquid (chelating agent) is in a state of being able to capture the harmful metals and the like again. As such a chelating agent 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 of the second embodiment, as in the soil purification system S of the first embodiment, clean and reusable gravel and sand can be obtained, and sludge discharged from the iron removal device 12 is obtained. It is possible to significantly reduce the content rate of harmful metals and the like. In this way, the content of harmful metals and the like in the sludge discharged from the iron removal device 12 is greatly reduced, so that even when the sludge is washed with a chelate, the amount of chelating agent used or the amount required is greatly reduced. It is possible to reduce the soil treatment cost.

  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 adjusting tank, 7 flocculation Tank, 8 thickener, 9 intermediate tank, 10 washing water tank, 11 preliminary water tank, 12 iron removing device, 12A iron removing device, 13 filter press, 14 chelate washing device, 16 sludge tank, 17 magnet mounting drum, 17A magnet mounting drum, 18 pipe lines, 19 pipe lines, 20 stirrer, 21 rotating shaft, 22 drum 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 Grain Cleaning Device, 33 Filtration Device, 34 Cleaning Liquid Regenerating Unit, 35 Cleaning Liquid Regenerating 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 chelate cleaning liquid storage tank, 45 pump, 46 pipeline, 47 stirrer, 48 pump, 49 pipeline, 50 storage tank, 51-54 partition wall, 55-59 slurry passage, 61-65 air discharge pipe, 72 Intermediate storage tank, 76 pumps, 77-80 pipelines, 81 pumps, 82 pipelines, 83 pumps, 84 pipelines, 85 pipelines, 86 pumps, 87 pipelines, 88 pipelines, 91-98 valves, 101 fine granules Washing device, 102 filtration device, 103 clarification filter device, 104 reverse osmosis separation device, 105 chelating agent regeneration device.

Claims (3)

A soil purification system that includes a soil classification unit that classifies soil that contains gravel, sand, and fine particles and is contaminated with harmful metals or its compounds into gravel, sand, and fine particles while washing with wash water. There
The soil classification section,
A mixer for mixing the soil introduced into the soil classification section and the wash water,
By crushing gravel and sand in a mixture containing soil and wash water discharged from the mixer, it is possible to magnetically adsorb iron or iron oxides that are unevenly distributed or scattered inside the gravel and sand. A wet crusher that produces iron-based fine particles containing a certain amount and adsorbs a harmful metal or a compound thereof to iron or iron oxide exposed on the surface of the iron-based fine particles.
Trommel discharged from the wet crusher, for separating gravel from a mixture containing gravel, sand, fine particles, and washing water,
A liquid cyclone for separating sand from a mixture containing sand, fine particles and washing water discharged from the trommel,
A mixture containing fine particles and washing water discharged from the liquid cyclone, having a thickener for separating supernatant liquid by sedimentation separation into sludge containing fine particles and washing water,
From sludge containing fine particles discharged from the thickener and washing water, iron-based fine particles containing iron or iron oxide to the extent that they can be adsorbed by magnetic force are adsorbed and removed by magnetic force to remove sludge. A soil purification system comprising an iron removal device for reducing the content of harmful metals or compounds thereof.   The sludge discharged from the iron removal device is washed with a chelate washing liquid containing a chelating agent and water to remove a harmful metal or its compound adsorbed on or attached to the surface of fine particles in the sludge. The soil purification system according to claim 1, wherein a part is provided. The chelate processing unit,
The sludge discharged from the iron removal device and the chelate cleaning liquid are mixed to produce a fine particle slurry, and the fine particle slurry is fluidized so as to secure a preset residence time. A fine particle cleaning device for capturing a harmful metal or its compound adhering to the chelating agent,
A filtering device for filtering the fine particle slurry discharged from the fine particle cleaning device to produce a filtrate and a cake containing the fine particle component;
The filtrate discharged from the filtration device, by a reverse osmosis membrane, a reverse osmosis membrane separation device for separating the concentrated water in which the chelating agent is concentrated and the permeated water containing no chelating agent,
The concentrated water discharged from the reverse osmosis membrane separator is received and concentrated by a solid-phase adsorbent that has a complexing power higher than that of a chelating agent and adsorbs harmful metal or its compound in the concentrated water when contacted with the concentrated water. The soil according to claim 2, further comprising: a chelating agent regenerating device that removes harmful metals or compounds thereof from a chelating agent in water and supplies the concentrated liquid as a chelating cleaning liquid to the fine particle cleaning device. Purification system.

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