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JP-2026075530-A - Method and apparatus for recycling contaminated soil

JP2026075530AJP 2026075530 AJP2026075530 AJP 2026075530AJP-2026075530-A

Abstract

[Challenge] Based on a classification treatment method, the goal is to recover soil containing fine particles (for example, less than 75 μm) in a reusable state with low contamination levels. [Solution] The method includes a step of stirring and washing the contaminated soil with washing water, a step of classifying the soil after stirring and washing and recovering coarse particles of a predetermined particle size (for example, 75 μm) or larger, and a step of recovering the fine particles from the washing water containing the remaining fine particles (for example, less than 75 μm). Between the stirring and washing step and the fine particle recovery step, a plasma arc discharge treatment is performed at least once on the washing water containing the soil to separate radioactive materials such as cesium attached to the fine particles of soil and transfer them to the washing water. In the fine particle recovery step, the fine particles of soil and radioactive materials are separated and recovered from the washing water. [Selection Diagram] Figure 1

Inventors

  • 本間 勝人
  • ペトロフ スタニスラブ

Assignees

  • ＲＣＳＴ合同会社

Dates

Publication Date
20260508
Application Date
20241022

Claims (10)

  1. A stirring and washing process in which contaminated soil is washed by stirring it with washing water, The soil after the stirring and washing step is classified in the presence of the washing water to recover coarse-grained soil with a predetermined particle size or larger, and the remaining fine-grained soil after the recovery of the coarse-grained soil, along with the washing water, is supplied to the next step in a coarse-grain recovery step. A fine-grain recovery step is performed to recover the fine-grained soil from the washing water containing the fine-grained soil that remains after the recovery of the coarse-grained soil, After the stirring and washing step and before the fine particle recovery step, a plasma arc discharge treatment step is included in which a predetermined plasma arc discharge is performed at least once on the washing water containing soil. In the aforementioned plasma arc discharge process, In a plasma treatment tank in which the tips of a plurality of electrodes to which an AC voltage is applied are arranged with a predetermined interval between them, the cleaning water containing the soil is introduced so that at least the tip of each electrode is immersed in the cleaning water, and a working gas is injected into the cleaning water introduced between the tips of the electrodes to generate minute bubbles of the working gas dispersed in the cleaning water, thereby generating a plasma arc discharge between the electrodes and separating the radioactive material attached to the soil from the soil. In the aforementioned fine particle recovery process, From the washing water containing the fine-grained soil, the fine-grained soil and the radioactive material separated from the soil are separated and recovered. A method for recycling contaminated soil, characterized by the following features.
  2. In the aforementioned fine particle recovery process, By generating bubbles in the washing water, the radioactive material is made to adhere to the bubbles, float to the surface, and be recovered. The method for resource recovery of contaminated soil according to claim 1, characterized in that the fine-grained soil is recovered by settling in the washing water.
  3. The method for resource recovery of contaminated soil according to claim 1 or 2, further comprising a coarse particle recovery step for recovering coarse particles of a predetermined particle size or larger from the coarse-grained soil, following the aforementioned stirring and washing step.
  4. A washing water tank for storing the washing water and a recovery channel for introducing the washing water after the fine particle recovery process into the washing water tank are provided. The method for resource recovery of contaminated soil according to claim 1 or 2, characterized in that an auxiliary recovery step is provided in the recovery channel for recovering the fine-grained soil that remains in the washing water and is not recovered in the fine-grained soil recovery step.
  5. A washing water tank for storing the washing water and a recovery channel for introducing the washing water after the fine particle recovery process into the washing water tank are provided. The method for resource recovery of contaminated soil according to claim 3, characterized in that an auxiliary recovery step is provided in the recovery channel for recovering the fine soil particles that remain in the washing water and are not recovered in the fine particle recovery step.
  6. A stirring and washing device that washes contaminated soil by stirring it with washing water, A coarse particle recovery device that classifies the soil after it has been stirred and washed by the aforementioned stirring and washing device in the presence of the washing water, recovers the coarse particle portion of the soil with a predetermined particle size or larger, and supplies the remaining fine particle portion of the soil and the washing water to the next process, A fine-grain recovery device for recovering the fine-grained soil from the washing water containing the fine-grained soil remaining after the recovery of the coarse-grained soil, The system includes at least one plasma arc discharge apparatus that performs a predetermined plasma arc discharge on the washing water containing soil at any point after the stirring and washing apparatus and before the fine particle recovery apparatus, The plasma arc discharge processing apparatus, The plasma treatment tank is provided into which the cleaning water containing the soil is introduced, with the tips of the electrodes arranged at a predetermined interval between them; a gas introduction path is provided into which an operating gas is injected into and/or the cleaning water introduced into the plasma treatment tank to generate minute bubbles of the operating gas dispersed in the cleaning water; and a voltage source is provided to apply an AC voltage to each of the electrodes necessary to generate a plasma arc discharge between the tips of the electrodes under the generation of the bubbles, thereby separating radioactive material attached to the soil from the soil by the plasma arc discharge, The aforementioned fine particle recovery device A means for recovering the radioactive material separated from the soil, A contaminated soil resource recovery apparatus characterized by comprising a soil recovery means for recovering the fine-grained portion of the soil.
  7. The aforementioned fine particle recovery device A bubble generating device that generates bubbles in the aforementioned washing water, A storage tank for storing the washing water that has generated the bubbles, The radioactive material recovery means recovers the radioactive material that has adhered to the bubble and floated to the surface in the storage tank, The contaminated soil resource recovery apparatus according to claim 6, further comprising the soil recovery means for recovering the fine-grained soil that has settled in the storage tank.
  8. The contaminated soil volume reduction apparatus according to claim 6 or 7, further comprising a coarse particle recovery device arranged after the agitation and washing device, for recovering coarse particles of a predetermined particle size or larger from the coarse-grained soil.
  9. A washing water tank for storing the washing water and a recovery channel for introducing the washing water, after passing through the fine particle recovery device, into the washing water tank are provided. The contaminated soil resource recovery apparatus according to claim 6 or 7, characterized in that an auxiliary recovery device is provided in the recovery channel for recovering the fine soil particles that remain in the washing water and are not recovered by the fine particle recovery device.
  10. A washing water tank for storing the washing water and a recovery channel for introducing the washing water, after passing through the fine particle recovery device, into the washing water tank are provided. The contaminated soil resource recovery apparatus according to claim 8, characterized in that an auxiliary recovery device is provided in the recovery channel for recovering the fine soil particles that remain in the washing water and are not recovered by the fine particle recovery device.

Description

This invention aims to utilize contaminated soil as a resource. This technology relates to a method and apparatus for resource recovery of contaminated soil contaminated with radioactive materials, which generates reusable gravel, sand, silt, and clay from the contaminated soil. In Japan, the disposal of radioactive contaminated soil, which poses adverse health effects to humans, resulting from the Fukushima Daiichi nuclear power plant accident caused by the Great East Japan Earthquake, is a major issue. Therefore, radioactively contaminated soil is being collected and stored in large quantities at interim storage facilities and other locations. Generally, "classification treatment" is used to reduce the volume of radioactively contaminated soil. This "classification method" recognizes that radioactive materials such as cesium tend to adhere easily to the fine-grained components (silt and clay) of radioactively contaminated soil. Therefore, the soil is classified into coarse-grained components (gravel) with a particle size of 4 mm or more and components with a particle size of less than 4 mm (part of the fine gravel, sand, silt, and clay). The coarse-grained components (gravel), which are less likely to attract radioactive materials, are recovered as a recyclable resource, thereby reducing the volume of contaminated material sent to final disposal. In this specification, the terms "gravel," "sand," "silt," and "clay" are used to refer to particles contained in soil based on the particle size distribution shown in Table 1 below. In addition to the "classification method," other proposed methods for reducing the volume of contaminated soil include "chemical treatment" and "heat treatment." The "chemical treatment method" involves using strong acids or other solvents to elute cesium ions attached to the soil, adsorbing them onto an adsorbent, and then condensing the cesium adsorbed onto the adsorbent to recover it as a pollutant, thereby reducing the volume of the pollutant that needs to be sent for final disposal. Furthermore, the "heat treatment method" involves heating soil containing cesium to recover soil components as molten or calcined material, while simultaneously cooling the vaporized cesium-containing exhaust gas to condense the cesium. The condensed cesium is then collected and recovered using an exhaust gas filter before being sent for final disposal, thereby reducing the volume of contaminants that require final disposal. Furthermore, the above volume reduction methods may be used in combination. For example, after recovering coarse-grained material (gravel and sand) as a recyclable resource through classification, the remaining fine-grained material (silt and clay) may be further reduced in volume by applying chemical or heat treatment methods. Regarding the aforementioned "classification method," Patent Document 1, cited below, describes a method as shown in Figure 4, in which removed soil Sc is washed with water in a washing device WM, then classified in a classification device CM to recover soil components with a particle size of 75 μm or larger as regenerated soil Sp, and the washing water and remaining soil are introduced into a separation device DM such as a thickener to precipitate and recover the soil components, and then dewatered using a dewatering device DHM. This process allows for the volume reduction of contaminants by making the dewatered cake Sd, containing soil components with a particle size of less than 75 μm, the target of reprocessing or final disposal (Patent Document 1, [0058]-[0061], Figures 9 and 11). Furthermore, Patent Document 2, cited below, acknowledges that the aforementioned classification method may not reliably reduce the cesium concentration in coarse-grained soil (particle size 75 μm or larger) recovered as a recyclable resource to below the target value. Therefore, it is proposed to extract cesium from the coarse-grained soil by washing it with an extractant consisting of an alkaline salt after classification (see Claim 1 and Figure 1 of Patent Document 2). Although not targeting soil, Patent Document 3 (mentioned later) describes a water treatment method that targets conductive water containing impurities. This method solidifies inorganic substances such as heavy metals and radioactive materials dissolved in the water in an ionized state, making them extractable. It also includes gasification through the decomposition of organic matter, sterilization, washing, and activation. In this water treatment method, an operating gas such as air or carbon dioxide is injected into the water to be treated in a plasma treatment tank to generate a bubble jet, which is a two-phase gas-liquid flow composed of minute bubbles of the operating gas dispersed in the water and the water to be treated. This bubble jet is then introduced to the tip of an electrode to which an AC voltage is applied, generating a plasma arc discharge between the electrodes. This directly generates hi