JP2019103989A - Cleaning classification processing method of contaminated soil - Google Patents

Abstract

The present invention provides a method for cleaning and classifying contaminated soil, which can efficiently perform cleaning and classifying treatment of contaminated soil. First, water W1 is added to a contaminated soil 100, and a slurry-like earth and sand 101 separated by a wet sieve 11 classification process and separated into a coarse particle part 102 is further classified into a sand part 104 and a fine particle part 103. The step S1, the second step S2 for washing the sand 104 classified in the first step S1, the fine particles 103 classified in the first step S1 are agglomerated and precipitated, and the precipitated sludge 105 and the treated water W2 And a third step S3 for dewatering the precipitated sludge 105 to separate the concentrated residue 106 and the treated water W3. In the first step S1, a positive ion I is added to the contaminated soil 100. An ion addition step S12 is performed. [Selection] Figure 1

Description

  The present invention relates to a method for cleaning and classifying contaminated soil.

Radioactive substance contaminated soil (contaminated soil) collected from various places is carried into the receiving / separating treatment facility (pretreatment facility), pretreated and transported to the intermediate storage facility after storage and stored. In pretreatment facilities, it is necessary to secure high treatment capacity so that it can cope with a huge amount of contaminated soil. Therefore, in the pretreatment facility, each treatment facility is connected by a belt conveyor, and continuous treatment is performed while moving each treatment facility of the contaminated soil with the belt conveyor.
At the pre-treatment facility, a separation process is conducted to separate the contaminated soil according to particle size and concentration. In the separation step, the contaminated soil is sieved and separated according to particle size. Prior to the separation process, a modifier is added to the contaminated soil so that clogging of the sieve does not occur in the separation process.

Since the amount of contaminated soil stored in the intermediate storage facility is enormous, it is considered to reuse the contaminated soil having a radioactivity concentration of 8,000 Bq / kg or less. In addition, it is considered as one of the options to use contaminated soil with radioactivity concentration exceeding 8000 Bq / kg as soil with 8000 Bq / kg or less by purification by washing classification processing.
The flow of the washing classification process is disclosed, for example, in Patent Documents 1 to 4. In the washing and classification process, fine particles and non-contaminated sand are separated by adding water to the contaminated soil and using a centrifugal wet classifier or a precipitation classifier. The contaminated fine particles are coagulated and precipitated, and the coagulated and precipitated residue is dewatered by a dehydrator.

JP, 2013-092428, A JP, 2013-178147, A JP, 2013-178148, A JP, 2013-238484, A

The modifier introduced into the contaminated soil prior to the separation process at the pretreatment facility often contains a water-absorbing polymer. For this reason, when the contaminated soil to which the modifier has been added is subjected to water addition in the washing and classification treatment, the modifier has a large amount of water (a few dozen times to a few hundred times the weight of the water absorbing polymer in the modifier). Amount), and it is assumed that the washing classification process, in particular the dehydration step, is burdened.
Furthermore, if the function of the dewatering process is reduced, the amount of contaminated soil (residue) remaining as soil that could not be cleaned is increased, and there is a concern that the effect of volume reduction of the contaminated soil by the washing classification process is greatly reduced.
In addition, the water-absorbent polymeric polymer containing water behaves in the same manner as the fine particles in the contaminated soil, which may adversely affect each step.

  Then, an object of this invention is to provide the washing classification processing method of the contaminated soil which can perform washing | cleaning classification processing of contaminated soil efficiently.

  In order to achieve the above object, the method for washing and classifying contaminated soil according to the present invention comprises adding water to the contaminated soil and carrying out wet sieving classification to separate coarse particles from slurry-like sediment and sand and fine particles The first step of further classification treatment in the second step, the second step of washing treatment of the sand fraction classified in the first step, and the fine particle fraction classified in the first step are coagulated and precipitated to form precipitated sludge Separating the treated sludge into treated water and dewatering the sedimented sludge to separate it into concentrated residue and treated water; and adding cation to the contaminated soil in the first step. It is characterized by performing a process.

When the modifier containing the water absorbing polymer is added to the contaminated soil, when the volume of the water absorbing polymer increases due to water absorption, the increased water absorbing polymer behaves like fine particles. And move to the overflow side, which imposes a large burden on the subsequent steps.
On the other hand, in the present invention, since the cation addition step is carried out in the first classification step, the water absorbing function of the water absorbing polymer when the modifier containing the water absorbing polymer is added to the contaminated soil. Can be reduced to reduce the amount of water absorption of the water-absorbent polymer.
As a result, the burden on the subsequent steps can be reduced, and the subsequent steps can be performed efficiently. In particular, the load in the dehydration process of the third step can be reduced.

Further, in the method for washing and classifying contaminated soil according to the present invention, the cation addition step may add the cation together with the water to the contaminated soil.
By doing so, since the cation can inhibit the water absorption function of the water-absorbent polymer contained in the contaminated soil at an early stage, each step can be performed efficiently.

Further, in the method for washing and classifying contaminated soil according to the present invention, the cation addition step is carried out in the slurry-like soil after the coarse particle is separated by wet sieving classification of the contaminated soil. Cations may be added.
In this way, since cations are added to the slurry-like soil from which coarse particles have been separated rather than the entire contaminated soil, the amount of cations used is greater than when cations are added to the entire contaminated soil. It can be reduced. In addition, since cations can be reliably added to slurry-like earth and sand from which coarse particles have been separated, the load of processing for further classifying slurry-like earth and sand into fine particles and sand can be reduced. .

Further, in the method for washing and classifying contaminated soil according to the present invention, the cation addition step is carried out for the fine particles after being classified into the sand and the fine particles in the contaminated soil. Cations may be added.
By doing so, the amount of cations used can be reduced as compared to the case where cations are added to the entire contaminated soil, since cations are added only to the fine particles instead of the entire contaminated soil. In addition, since cations can be reliably added to the fine particles, the load in the dehydration treatment of the third step can be surely reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the washing classification process of contaminated soil can be performed efficiently.

It is a schematic diagram which shows an example of the washing classification processing method of the contaminated soil by embodiment of this invention.

Hereinafter, a method of washing and classifying contaminated soil according to an embodiment of the present invention will be described based on FIG.
As shown in FIG. 1, the method of the present invention for cleaning and classifying contaminated soil according to the present embodiment is a method of cleaning and classifying contaminated soil 100 contaminated with a radioactive substance such as cesium prior to storage in an intermediate storage facility.
In this embodiment, the contaminated soil 100 transported from various places is separated by particle size and concentration by the receiving and separating treatment facility (pretreatment facility) and then classified by washing and classification facility, and the radioactivity concentration is 8000 Bq / The soil of kg or less is recycled, and the contaminated soil 100 having a radioactivity concentration of more than 8000 Bq / kg is set to be stored at an intermediate storage facility.

  In the receiving / separating treatment facility, the contaminated soil 100 is sorted according to the particle size by a sieve. At this time, in order to prevent clogging of the sieve, a modifier including a water absorbing polymer is introduced into the contaminated soil 100. For this reason. The contaminated soil 100 to be washed and classified in the washing and classification facility contains a modifier containing a water absorbing polymer.

  In the method for washing and classifying contaminated soil according to the present embodiment, water W1 is added to the contaminated soil 100, and classification processing with a wet sieve 11 is performed to separate coarse particles 102 by separating slurry coarse sediments 101 into fine particles 103 and sand. The first step S1 of further classification to the portion 104, the second step S2 of washing the sand portion 104 classified in the first step S1, and the fine particle portion 103 classified in the first step S1 are aggregated and precipitated. And the third step S3 of separating the sedimented sludge 105 into the treated water W2 and dewatering the sedimented sludge 105 to separate it into the concentrated residue 106 and the treated water W3.

(First step S1)
The first step S1 includes a water adding step S11 in which water W1 is added to the contaminated soil 100, and a cation adding step S12 in which a cation I is added to the contaminated soil 100 simultaneously with or after the water adding step S11. After the water addition step S11 and the cation addition step S12, the coarse particle fraction 102 is separated from the contaminated soil 100 using the wet sieve 11 to make a slurry-like soil 101, and after the first classification step S13 There is a second classification step S14 in which the slurry-like sediment 101 is classified into the sand component 104 and the fine particle component 103 using the centrifugal wet type classifier 12.

In the water addition step S11, water W1 of an amount calculated according to the weight, particle size, radioactivity concentration and the like of the contaminated soil 100 is added to the contaminated soil 100.
In the cation addition step S12, the cation I in an amount calculated according to the amount of water W1 to be hydrolyzed in the water addition step S11 is added to the contaminated soil 100. The addition of the cation I to the contaminated soil 100 is performed, for example, by adding slaked lime or the like to the contaminated soil 100.

  In the first classification step S13, as the wet sieve 11, for example, a vibrating sieve is used. The wet sifter 11 is configured to sort foreign matter and classify it into coarse sand and coarse sand and slurry-like earth and sand 101 below it, and has a mesh surface inside. A well-known apparatus can be used for the wet sieve 11. In addition, the efficiency of surface treatment process S21, scrubbing process S22, and washing | cleaning process S23 can be improved by separating the coarse particle part 102 by the wet sieve 11. FIG.

  In the second classification step S14, the slurry-like sediment 101 excluding the coarse particle content 102 is classified into a sand content 104 and a fine particle content 103 using the centrifugal wet type classifier 12. At this time, the sand portion 104 and the fine particle portion 103 contain radioactive substances. In place of the centrifugal wet-type classifier 12, a sedimentation-type classifier may be used.

The centrifugal wet type classifier 12 is, for example, formed in a cylindrical shape, and is formed of a container whose bottom is formed in a conical shape, and is an upper inlet for introducing the slurry-like earth and sand 101 and a lower portion for taking out underflow. An outlet and an upper outlet for taking out the overflow are provided. The slurry-like earth and sand 101 which has entered from the upper inlet port is supplied at high speed in the circumferential direction of the cylindrical container to cause rotational movement to become a rotational flow and to advance toward the conical top. At this time, heavy particles having a specific gravity in the slurry-like soil 101 gather on the peripheral wall by centrifugal force, and gradually travel toward the underflow outlet (lower outlet), and are concentrated and discharged.
On the other hand, the liquid and light specific gravity particles rise in a swirling manner in the central portion of the cylindrical container and are discharged from the overflow outlet (upper outlet). In addition, as a centrifugal-type wet-type classifier 12, a well-known apparatus can be used. Then, since a large amount of radioactive substance adheres to and adsorbs to the fine particle portion 103, by classifying it with the centrifugal wet classifier 12, many radioactive substances can be removed from the treated soil. The number of classification processes is appropriately set, but is preferably performed once or more.

(2nd process S2)
The second step S2 includes a surface treatment step S21 for facilitating exfoliation of the radioactive substance adhering to the surface of the soil particles of the sand fraction 104 classified in the second classification step S14, and a sand fraction after the surface treatment step S21 In the scrubbing step S22 for peeling radioactive substances on the surface of the surface 104 and the fine particles containing radioactive substances peeled off from the surface of the sand portion 104 after the scrubbing step S22, the fine particles are removed from the sand portion 104 Radioactive substance extraction which extracts fine particles including radioactive substances remaining in the washed sand 107 taken out in the washing step S23 for taking out the washed treated sand 107 and the washed step S23 using the dehydration processing device And S24.

In the surface treatment step S21, the sand component 104 classified in the second classification step S14 is stored in the surface treatment tank 21 and a dispersant is added to the sand component 104 in the surface treatment tank 21, whereby the soil of the sand component 104 is obtained. The radioactive substance adhering to the surface of the particles is made easy to exfoliate with the fine particles.
In the scrubbing step S22, the fine particles containing the radioactive substance on the surface of the sand 104 surface-treated in the surface treatment step S21 are stirred off using a scrubber 22 so that the particles are peeled off and removed by rubbing. Thus, the fine particles containing radioactive substances adhering to the sand 104 are released.
In the washing step S23, the flotation device 23 is used to separate the sand components 104 introduced from the scrubber 22 into the flotation device 23 in the scrubbing step S22 (such as radioactive material and fine particles containing radioactive material) ) 108 is recovered by floss generated by flotation, and the washed sand 107 from which the separated material has been removed is taken out.
In the radioactive substance extraction step S24, the radioactive substance 110 remaining in the washed sand 107 taken out in the washing step S23 is extracted in the extraction tank 24 with, for example, a solution of a cesium-extracted drug, etc. The secondary cleaning treated sand (low density washed treated sand) 109 having a lower density is dewatered using this.

(Third step S3)
In the third step S3, a separation step S31 in which the fine particle fraction 103 classified in the second classification step S14 is separated into the treated water W2 and the settling sludge 105 by the coagulation settling apparatus 31, and the settling sludge separated in the separation step S31 And dewatering step S 32 for dewatering 105.
In the third step S3 of this embodiment, in addition to the fine particle fraction 103 classified in the second classification step S14, the floss in the washing step S23 in the washing step S23, and the treatment solution in the radioactive substance extraction step S24 is an aggregation and precipitation device It is configured to be sent to 31.

In the separation step S31, the flocculating agent is added to the suspension water containing the fine particle content 103 and stirred using the flocculating and settling apparatus 31 to precipitate fine suspended solids in the suspension water as large settling sludge 105, and settling sludge It separates into 105 and the clear treated water W2. At this time, the fine particle portion 103 adsorbs a radioactive substance (floss, treatment solution), and becomes coagulated sedimentation to form a sedimented sludge 105.
In the dewatering step S32, the precipitated sludge 105 is dewatered using the press dewatering device 32, and separated into the concentrated residue 106 and the treated water W3. The press dewatering device 32 is a known pressure type filtration device (belt press or filter press) or the like, and includes a filter made of a filter cloth or the like and a press.

  Next, the operation and effects of the method for the cleaning and classifying treatment method for the contaminated soil according to the embodiment of the present invention described above will be described using the drawings.

When the modifier containing the water absorbing polymer is added to the contaminated soil 100, when the volume of the water absorbing polymer increases due to water absorption, the increased water absorbing polymer behaves like fine particles. And move to the overflow side, which imposes a great burden on the subsequent steps.
On the other hand, in the method of the present invention for washing and classifying contaminated soil according to the present embodiment described above, since the cation addition step S12 is performed in the first classification step S13, a modifier containing a water absorbing polymer is added to the contaminated soil 100. If the water absorption property of the water absorbent polymer is reduced, the water absorption capacity of the water absorbent polymer can be reduced.
As a result, the burden on the subsequent steps can be reduced, and the subsequent steps can be performed efficiently. In particular, the load in the dehydration process of the third step S3 can be reduced.

  In addition, in the method for washing and classifying contaminated soil according to the present embodiment, the cation addition step S12 includes the cation I in the contaminated soil 100 by adding the cation I to the contaminated soil 100 together with the water W1. Each step can be performed efficiently because the water absorption function of the water-absorbent polymer can be inhibited at an early stage.

As mentioned above, although embodiment of the washing classification processing method of the contaminated soil by this invention was described, this invention is not limited to said embodiment, It can change suitably in the range which does not deviate from the meaning.
For example, in the above embodiment, the cation I is added to the contaminated soil 100 together with the water W1 in the cation addition step S12, but may be as follows.
For example, in the cation addition step S12, the cation I may be added to the slurry-like soil 101 after the first classification step S13.
In this way, cation I is added to the slurry-like soil 101 from which the coarse particle portion 102 has been separated instead of the whole contaminated soil 100, so compared to the case where cation I is added to the whole contaminated soil 100, The amount of cation I used can be reduced.

Also, for example, in the cation addition step S12, the cation I may be added to the fine particle fraction 103 after the second classification step S14.
By doing this, the amount of cation I used is reduced as compared with the case where cation I is added to the entire contaminated soil 100, since cations are added only to the fine particle portion 103 instead of the entire contaminated soil 100. be able to. Further, since cations can be reliably added to the fine particle portion 103, the load in the dehydration step S32 of the third step can be surely reduced.

100 Contaminated soil 102 Coarse particle content 101 Slurry-like sediment 103 Fine particle content 104 Sand content 105 Sedimented sludge 106 Concentrated residue I Cation W1 Water W2 Treated water W3 Treated water S1 First process S2 Second process S2 Second process S3 Third process S12 Ion addition process

Claims (4)

A first step of adding water to the contaminated soil and further classifying the slurry-like sediment from which coarse particles have been separated by wet sieve classification, into sand and fine particles;
A second step of washing the sand classified in the first step;
The fine particles fractionated in the first step are coagulated and precipitated to be separated into precipitated sludge and treated water, and the sedimented sludge is dewatered to be separated into concentrated residue and treated water, and the third step ,
In the first step, there is provided a cation addition step of adding a cation to the contaminated soil, and the method for washing and classifying contaminated soil.   The said cation addition process adds the said cation to the said contaminated soil with the said water, The washing classification processing method of the contaminated soil of Claim 1 characterized by the above-mentioned.   The said cation addition process adds the said cation to the said slurry-like earth and sand after the wet sieve classification process of the said contaminated soil and isolate | separating the said coarse particle part. Classification processing method.   The said cation addition process adds the said cation to the said fine particle fraction after the classification process to the said sand component and the said fine particle fraction of the said contaminated soil, The cleaning of the contaminated soil of Claim 1 characterized by the above-mentioned. Classification processing method.

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