JP2011235213A - Pretreatment method for soil polluted by pcb - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for effectively pretreating an excavated polluted soil containing PCB by flexibly corresponding to the pollution condition to obtain a pretreated soil conforming to various accession standards relating to a device used for the method.SOLUTION: The pretreatment method includes: a primary separation step (S100) of separating and removing large-size contaminants having the major axis of 100 mm or more from the excavated polluted soil; a drying step (S101) of drying the polluted soil from which the large-size contaminants are removed in the primary separation step; a secondary separation step (S102) of separating and removing middle-size contaminants having the major axis of at least 40 mm from the polluted soil passed through the drying step; a tertiary separation step (S103) of removing small-size contaminants such as waste materials of harmful matter-containing components, having the major axis of at least 5 mm from the polluted soil separated through the secondary drying step; and a conditioning sand-blending step (S105) of blending the soil passed through the sieve in the tertiary separation step and a conditioning sand 10 to control the PCB concentration to the level of the accession standard value or less.

Description

  The present invention relates to a pretreatment method for contaminated soil for detoxifying contaminated soil containing excavated PCB with the present treatment apparatus.

  Conventionally, soil contaminated with organochlorine compounds represented by PCB (polychlorinated biphenyl) or the like is present in the ground such as a factory site almost without being decomposed. The contaminated soil is excavated from the ground for detoxification and stored in containers such as drums, storage yards, and the like. In particular, the excavated contaminated soil is stored in large quantities without being detoxified, and the detoxification treatment is urgently needed.

  As a method for detoxifying contaminated soil, for example, a thermal decomposition method, an iron powder method, an alkali catalyst chemical decomposition method, a melt solidification method, an iron powder method, and the like are known. In the various detoxification treatment methods, the excavated contaminated soil is pretreated in a pretreatment step (apparatus) integrated with the treatment apparatus, and then transported to the treatment apparatus to perform the detoxification treatment. is there. Conventionally, the following is known as a typical detoxification method for these contaminated soils.

  Contaminated soil is provided with a pretreatment device that adjusts the moisture content in the contaminated soil (lowers the water content) by mixing the moisture content in the contaminated soil with the contaminated soil to be introduced into this treatment device. This is a contaminated soil treatment system that promotes dechlorination with this treatment device that decomposes pollutants in the soil by adding, stirring and heating chemicals that promote dechlorination (for example, patents) Reference 1).

  In addition, the moisture content adjusting means is charged with and mixed with the water treated material (contaminated soil) and a part of the processed material (carbide) that has been heat-treated and reduced in volume by the heat treatment means of this treatment apparatus. After reducing the moisture content of the processed material and adding a treatment agent thereto, heat treatment is performed by heat treatment means. (For example, refer to Patent Document 2).

JP 2004-97913 A JP 2001-246400 A

  However, since the thing of above-mentioned patent document 1 mixes the quick lime which carries out an exothermic reaction with water with the moisture control agent in a contaminated soil, this quick lime has various bad influences on this processing apparatus. In particular, since an exothermic reaction occurs, it is difficult to set a wide range of mixing amounts to contaminated soil, and there are also problems in terms of safety management.

  Moreover, since the thing of above-mentioned patent document 2 throws in the contaminated soil and mixes the heat-processed thing detoxified with this processing apparatus, always including the time of the start of detoxification processing with this processing apparatus, etc. There is a problem in adjusting the moisture content stably.

  Further, those described in Patent Documents 1 and 2 are pretreatment methods for contaminated soil specialized in the respective detoxification treatment methods of the present treatment apparatus, and are not versatile. Also, excavated contaminated soil may contain transformers, ballasts, low voltage transformers such as paper capacitors for household appliances, and PCB-containing articles such as capacitors, which can be removed to prevent damage. It is required to detoxify with this treatment equipment as contaminated soil.

  In recent years, acceptance standards for contaminated soil to be detoxified by this treatment apparatus have been set. For example, it is a condition that wastes should not be included, and the moisture content, PCB concentration, particle size, etc. should be below the acceptance standard value. ing. Furthermore, there are various treatment methods for this treatment apparatus, and there is a wide range of moisture content, PCB concentration, particle size, etc. as acceptance reference values, and flexible measures are required. There is a need for a pretreatment method for PCB contaminated soil that meets the various requirements of this acceptance standard.

  The present invention solves the above-mentioned conventional problems, pre-processes effectively and flexibly responds to the situation of contaminated soil containing excavated PCB, and conforms to various acceptance standards of this processing apparatus. The purpose is to obtain soil.

In order to achieve the above-mentioned object, the pretreatment method for PCB-contaminated soil according to the present invention is a pretreatment method for contaminated soil for conforming to the acceptance standard of the present processing apparatus for detoxifying contaminated soil containing excavated PCB. Because
A primary separation step of separating and removing at least 100 millimeters or more of large contaminants such as stone, glass, waste, etc. from the contaminated soil mainly composed of excavated sand and gravel soil, and stones and glass in the primary separation step. Separating the contaminated soil from which large contaminants such as waste have been removed, and separating medium-sized contaminants such as pebbles, glass, waste, etc. from the contaminated soil after the drying step. And a secondary separation step for removing at least 5 millimeters of small contaminants such as pebbles and hazardous substance-containing parts from the contaminated soil separated in the secondary separation step, If the PCB concentration in the contaminated soil that has passed through the sieve in the next separation step is higher than the acceptance standard value, the adjusted sand is mixed to make the PCB concentration below the acceptance standard value. It is characterized in that to obtain a pre-processing contaminated soil meet the acceptance criteria of the present processing apparatus provided with adjustment sand mixing step of settling.

  ADVANTAGE OF THE INVENTION According to this invention, it can pre-process effectively according to the condition of the contaminated soil containing excavated PCB flexibly, and can obtain the pre-treatment soil which adapted to various acceptance criteria of this processing apparatus.

The flowchart which shows the processing step of one embodiment of this invention 1 is a block diagram showing a typical preprocessing example in FIG.

The first invention is a pretreatment method for contaminated soil for conforming to the acceptance standard of the present processing apparatus for detoxifying contaminated soil containing excavated PCB,
A primary separation step of separating and removing at least 100 millimeters or more of large contaminants such as stone, glass, waste, etc. from the contaminated soil mainly composed of excavated sand and gravel soil, and stones and glass in the primary separation step. Separating the contaminated soil from which large contaminants such as waste have been removed, and separating medium-sized contaminants such as pebbles, glass, waste, etc. from the contaminated soil after the drying step. And a secondary separation step for removing at least 5 millimeters of small contaminants such as pebbles and hazardous substance-containing parts from the contaminated soil separated in the secondary separation step, If the PCB concentration in the contaminated soil that has passed through the sieve in the next separation step is higher than the acceptance standard value, the adjusted sand is mixed to make the PCB concentration below the acceptance standard value. And an adjusting sand mixing step of settling is obtained by the pretreatment method for PCB contaminated soil, characterized in that to obtain a pre-processing contaminated soil meet the acceptance criteria of the present processor.

  As a result, the contaminated soil containing the excavated PCB can be effectively pretreated, and pretreated soil that meets various acceptance standards of the present treatment apparatus can be obtained.

  According to a second invention, in the first invention, the drying step is a pretreatment method for PCB-contaminated soil, characterized in that the contaminated soil is dried by heating at or below the PCB volatilization suppression temperature with a rotary kiln. is there.

  This eliminates the need for volatile component treatment equipment by heating the PCB without volatilizing it, and also ensures the separation in the separation step by crushing the contaminated soil agglomerated by rotation and heating action of the rotary kiln. In addition, the PCB-containing article can be exposed from the agglomerated contaminated soil to facilitate removal.

  A third invention is a pretreatment method for PCB-contaminated soil, characterized in that, in the first invention, dredged sand is mixed as adjusted sand.

  As a result, the entire components of the silica sand containing quartz as a main component are constant, and the stability during processing by this processing apparatus can be further increased.

  A fourth invention is a pretreatment method for PCB-contaminated soil, characterized in that, in the first invention, pretreated soil having a low PCB concentration is mixed as adjusted sand.

  As a result, the pretreated soil can be effectively utilized.

  Hereinafter, a pretreatment method for PCB-contaminated soil according to an embodiment of the present invention will be described with reference to FIGS.

(Embodiment 1)
FIG. 1 is a flowchart showing processing steps according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a typical preprocessing example in FIG.

  In particular, the contaminated soil in the storage container 1 excavated mainly with sand and gravelly soil is transported to the vibration sieve device 2 serving as the primary separation step (S100). In the vibration sieve device 2, the mesh of the vibration sieve is set to, for example, about 1000 mm, and a large-scale mixture of relatively large size stones, glass, various wastes, etc. mixed in the contaminated soil on the vibration sieve. Items remain and are stored in the storage container 3 for storage and management. Contaminated soil mixed with harmful substance-containing parts such as PCB that have passed through the vibrating screen and shaken down is accommodated in a vessel (not shown).

  Next, the contaminated soil in the vessel from which large contaminants such as stone, glass, and waste are removed in the primary separation step is transported to the rotary kiln (drying device) 4 in the drying step (S101).

  Contaminated soil has a tendency to be easily agglomerated (aggregated) due to the combination of soil particles. Although the agglomerated contaminated soil is originally in the range of the particle size that can be processed by the present processing apparatus, it may be removed by the sieve of the separation step.

  Therefore, the contaminated soil is heated in a horizontal heating cylinder rotated by the rotary kiln 4. Thereby, it can be dried from the surface of the agglomerated soil to cause cracking, and can be crushed sequentially from the surface part by rubbing and impact during rotation of the agglomerated soil. Therefore, the contaminated soil to be treated by the present treatment apparatus can be effectively taken out from the excavated contaminated soil.

  In addition, by crushing the contaminated soil, separation in the next secondary and tertiary separation steps can be reliably performed, and the PCB-containing article can be exposed from the agglomerated contaminated soil to be more easily removed.

  In the drying step (S101), the rotary kiln 4 is used, and the contaminated soil is heated by heating below the PCB volatilization suppression temperature (for example, 180 ° C.) to dry the contaminated soil. This makes it possible to heat the PCB without volatilizing it and to eliminate the need for volatile component processing equipment.

  In addition, the agglomerated soil is crushed by drying the contaminated soil with the rotary kiln 4, and the moisture in the contaminated soil is evaporated to reduce the moisture content. As a result, it is possible to adjust the moisture content below the acceptance standard.

  In addition, the drying step (S101) is performed after removing large contaminants such as stone, glass, and waste in the primary separation step (S100). As a result, the rotary kiln can be prevented from being damaged due to the rotation of large contaminants such as stones, glass, and waste, and durability can be improved.

  Next, the contaminated soil treated in the drying step (S101) is conveyed to the vibration sieve device 5 serving as the secondary separation step (S102). In the vibration sieve device 5, the mesh of the vibration sieve is set to about 40 mm, for example, and medium size stones, glass, various wastes mixed in the contaminated soil are mixed on the vibration sieve. Items remain and are stored in the storage container 6 for storage and management. Contaminated soil containing harmful substance-containing parts that have been shaken down after passing through the vibrating screen is accommodated in a vessel (not shown).

  Next, the contaminated soil in the vessel from which medium-sized contaminants such as stone, glass, and various wastes have been removed is transported to the vibration sieve device 7 serving as a tertiary separation step (S103). The vibration sieve device 7 has a mesh size of, for example, about 5 mm, and a relatively small size of stone, glass, harmful substance-containing components mixed in the contaminated soil on the vibration sieve. Small contaminants such as waste remain, and these are stored in the storage container 8 for storage and management. The contaminated soil passed through the vibrating screen and shaken down is accommodated as pretreated contaminated soil in a vessel (not shown).

  By setting the mesh of the vibration sieve of the vibration sieve device 7 which is the above-described multiple-stage separation step and further the tertiary separation step (S103) to about 5 mm, for example, parts containing hazardous substances such as PCBs such as capacitors from contaminated soil In addition, it is possible to obtain a pretreated contaminated soil having a particle size stabilized while reliably removing other wastes.

  In addition, the vibration sieve apparatus used for each separation step may use a jumping screen that wave-moves the screen mat surface, or a multilayer screen that gradually becomes finer. Alternatively, a means for fixing the sieve and moving the contaminated soil on the sieve may be used.

  Examples of acceptance criteria for contaminated soil in this treatment apparatus include the following. (1) No waste, (2) Particle size of 100 mm or less, (3) Moisture content of 25% or less, and (4) PCB concentration of 10,000 mg / Kg or less. This will be described below as an example.

  Before satisfying (1) not including waste, (2) particle size of 100 mm or less, and (3) moisture content of 25% or less, according to the above-described plurality of separation steps and drying steps. Treated soil can be obtained.

  In contrast to the acceptance reference value in which the particle size is 100 mm or less, in the present embodiment, the particle size is set to 5 mm or less in the tertiary separation step (S103). This is to remove the waste that is a harmful substance-containing component mixed in the contaminated soil as described above, and further, by setting the particle size with a margin with respect to the acceptance standard value, It enables more stable detoxification treatment of contaminated soil in Japan.

  Next, the adjustment sand mixing step (S105) for adjusting the PCB concentration based on the PCB concentration measured in the PCB concentration measurement step (S104) will be described. The PCB concentration measurement step (S104) and the adjustment sand mixing step (S105) are performed on the contaminated soil that has passed through the sieve of the vibration sieve device 7 in the tertiary separation step (S103). The adjustment sand will be described below as a concept including dredged sand.

  These steps are for adapting (4) PCB concentration to 10000 mg / Kg or less among the acceptance standards of contaminated soil in this processing apparatus.

  In the adjusted sand mixing step (S105), when the PCB concentration of the contaminated soil measured in the PCB concentration measuring step (S104) is higher than the acceptance reference value, the PCB is added to the contaminated soil that has passed through the sieve in the tertiary separation step (S103). Adjusting sand 10 necessary for adjusting the concentration is mixed by the mixing device 9 so that the PCB concentration is adjusted to the acceptance reference value or less. The pretreated soil is stored in the storage container 11. When the PCB concentration of the contaminated soil is lower than the acceptance reference value, the pretreated soil that has passed through the sieve in the tertiary separation step (S103) is stored in the storage container 11 without performing the adjusted sand mixing step (S105). .

  In addition, among the acceptance standards for contaminated soil in this treatment apparatus, (3) the moisture content was 25% or less, and (4) the PCB concentration was 10,000 mg / Kg or less. Even if it is required as a lower one, it can be dealt with arbitrarily by adjusting the mixing amount of the adjustment sand 10.

  In the adjusted sand mixing step (S105), the amount of the adjusted sand 10 required to bring the PCB concentration of the contaminated soil below the acceptance reference value is the value necessary for making the PCB concentration value and the acceptance reference value or less. The correlation of the amount of sand 10 is grasped in advance, and the amount of adjusted sand 10 necessary to make it equal to or less than the acceptance reference value is set based on the value measured in the PCB concentration measurement step (S104).

  The PCB concentration measurement step (S104) is performed on the contaminated soil that has passed through the sieve of the vibration sieving device 7 in the tertiary separation step (S103), but the PCB concentration of the excavated contaminated soil is measured, You may set the required amount of the adjustment sand mixed based on this.

  Moreover, the adjustment sand 10 uses what dried the general purpose sand, for example. This is a low moisture content and does not contain PCB, so the required amount of conditioned sand 10 can be minimized. Furthermore, there is no stickiness and re-agglomeration (aggregation) of contaminated soil can be prevented, and the PCB concentration can be adjusted to the acceptance standard value or less with higher accuracy. The average particle diameter of the adjusted sand 10 is 0.1 to 0.2 mm.

  Moreover, it is preferable to use dredged sand as the adjustment sand 10. The overall composition of the silica sand containing quartz as a main component is constant, and the stability during processing by this processing apparatus can be further increased. In addition, the lower moisture content minimizes the required amount of dredged sand, prevents re-agglomeration (aggregation) of contaminated soil without stickiness, and makes the PCB concentration less than the acceptance standard value with higher accuracy. Can be adjusted. Furthermore, it can obtain stably.

  Moreover, by using the cinnabar having an average particle diameter of 0.1 to 0.2 mm, it can be uniformly mixed with the contaminated soil that has passed through the sieve of the third separation step. The silica sand having an average particle size of 0.1 to 0.2 mm corresponds to the silica sands for casting Nos. 8 to 7 defined in JIS G5901.

  Further, pretreated soil having a low PCB concentration may be mixed as the adjustment sand 10. As a result, the pretreated soil can be effectively utilized.

  Note that the acceptance criteria of the processing apparatus described in the present embodiment is an example, and the present invention is not limited to this.

  Moreover, the setting of the number of stages of the sieve in the separation step is an example, and the present invention is not limited to this. The separation step may be further performed in multiple stages.

  According to the pretreatment method of contaminated soil of the present invention, the separation step and the drying step of a plurality of stages using a sieve for obtaining contaminated soil having a particle size not larger than the acceptance standard value not including waste from excavated contaminated soil, It is possible to use pretreated contaminated soil that does not include waste, which is the acceptance standard of the treatment apparatus, and has a particle size equal to or smaller than the reference value.

  In addition, the contaminated soil agglomerated in the drying step is crushed, the hazardous substance-containing parts are removed from the excavated contaminated soil, and the pretreatment of the particle size and moisture content not including these wastes and below the acceptance standard value It can be contaminated soil.

  Further, the PCB concentration can be arbitrarily adjusted in the adjusted sand mixing step based on the PCB concentration of the contaminated soil.

  As a result, pretreatment of contaminated soil is effectively carried out in response to various conditions of the contaminated soil containing the excavated PCB and various acceptance standards of this treatment apparatus, and the pretreated contaminated soil conforming to the acceptance standards. Can be obtained.

  It can be applied to a wide range of uses as a pretreatment method for contaminated soil to be supplied to the present treatment apparatus for detoxifying the contaminated soil.

DESCRIPTION OF SYMBOLS 1 Storage container 2 Vibrating sieve apparatus 3 Storage container 4 Rotary kiln (drying apparatus)
5 Vibrating sieve device 6 Storage container 7 Vibrating sieve device 8 Storage container 9 Mixing device 10 Adjusting sand 11 Storage container

Claims (4)

A pretreatment method for contaminated soil to conform to the acceptance standard of the present processing apparatus for detoxifying contaminated soil containing excavated PCB,
A primary separation step of separating and removing at least 100 millimeters or more of large contaminants such as stone, glass, waste, etc. from the contaminated soil mainly composed of excavated sand and gravel soil, and stones and glass in the primary separation step. Separating the contaminated soil from which large contaminants such as waste have been removed, and separating medium-sized contaminants such as pebbles, glass, waste, etc. from the contaminated soil after the drying step. And a secondary separation step for removing at least 5 millimeters of small contaminants such as pebbles and hazardous substance-containing parts from the contaminated soil separated in the secondary separation step,
When the PCB concentration of the contaminated soil that has passed through the sieve of the tertiary separation step is higher than the acceptance reference value, an adjustment sand mixing step is provided for mixing the adjustment sand to adjust the PCB concentration to be equal to or less than the acceptance reference value. A pretreatment method for PCB-contaminated soil, characterized by obtaining pretreatment-contaminated soil that conforms to the acceptance criteria of the apparatus. 2. The pretreatment method for PCB-contaminated soil according to claim 1, wherein the drying step comprises drying the contaminated soil by heating at a temperature lower than the volatilization suppression temperature of the PCB with a rotary kiln. The pretreatment method for PCB-contaminated soil according to claim 1, wherein dredged sand is mixed as the adjustment sand. The pretreatment method for PCB-contaminated soil according to claim 1, wherein pretreated soil having a low PCB concentration is mixed as the adjusted sand.

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