JP6434201B2 - Method and system for cleaning contaminated soil - Google Patents

Description

  The present invention relates to a cleaning method and a cleaning system for contaminated soil contaminated with harmful substances such as radioactive substances and heavy metals.

In soil contaminated with radioactive substances, hazardous substances such as heavy metals, harmful substances are difficult to penetrate into the soil particles, and are therefore mainly attached or adsorbed near the surface of the soil particles. Therefore, when comparing the contamination concentration of soil contaminated with toxic substances according to the particle size of the soil particles of its constituent elements, the finer particle portion with a larger specific surface area has a higher concentration, and the coarser particle component with a smaller specific surface area has a lower concentration. Become. Therefore, when washing contaminated soil, it is usually crushed by adding water to the original soil (that is, lump of fine particles contained in the original soil is broken up and adhered to the coarse particles. The fine particles are peeled off to separate the soil particles), and only the coarse particles are taken out by classification. The turbid water after removing the coarse particles contains the fine particles of the original soil, and since the pollution concentration is high, the turbid water treatment facility collects the fine particles as sludge, and after dehydration, Dispose as concentrated contaminants and recycle the treated water after removing fine particles. In such a method, a water jet device, a drum washer, or the like is often used as the crushing equipment, a horizontal bucket classifier, a spiral classifier, or a cyclone classifier is used as the classification equipment, and a coagulation sedimentation equipment is used as the turbid water treatment equipment. For example, Patent Document 1 proposes a technique related to this type of contaminated soil cleaning method.
In addition, the coarse particles extracted by this method usually have a contamination concentration below the target value and become washed soil. Depending on the concentration of the original contaminated soil and the type of harmful substances, the concentration may be below the target value. It may not be. In such a case, the contaminated soil is often excluded from the cleaning target because it is unsuitable for cleaning. However, on the other hand, attempts are being made to somehow increase the decontamination effect and lower the concentration to below the target value. In this case, since the concentration of only the coarse particles does not become the target value or less, the surface of the coarse particles adhering and adsorbing a lot of harmful substances is scraped to further reduce the concentration. To grind the surface of coarse particles, for example, a special grinding machine called hurricane under the trade name, a cavitation jet, etc. are used, and a chemical for promoting surface cutting is also used in combination. Yes.

JP 2005-28290 A

  However, in such a conventional method for cleaning contaminated soil, the soil cleaning plant used in this method requires large-scale equipment such as crushing equipment, classification equipment, turbid water treatment equipment, even if only a basic configuration is used. In addition, when equipment for surface cutting related to coarse particles is prepared, there is a problem that it becomes an extremely large-scale plant, and both initial cost and running cost increase, resulting in poor practicality. .

  The present invention solves such conventional problems, and in the cleaning of this type of contaminated soil, as in the past, special grinding machines, chemicals, etc., use equipment and equipment related to surface cutting of coarse particles. Without the need to do so, it is possible to cut the surface of coarse particles with extremely simple equipment using only general-purpose and inexpensive equipment and equipment, and to improve the cleaning effect. It aims at providing the washing | cleaning method and washing | cleaning system of the contaminated soil which can contribute to reduction.

In order to achieve the above object, the contaminated soil cleaning method of the present invention is a container in which a pump capable of sucking and transporting sand to the bottom is installed on the bottom surface, and the lower side of the peripheral surface is tapered and inclined toward the pump side. , is entering the slurry mixed with contaminated with harmful substances soil and water, the slurry in the container was sucked by the pump in the container, connect one end from the pump to the discharge port of the pump the The slurry in the container is circulated between the container, the pump, and the transport pipe by being conveyed via a transport pipe installed on the container and returned to the container, and the circulation of the slurry is performed by the pump. by the repeating Succoth by continuous operation, the stirring in the pump inside the coarse fraction in the slurry, the collision of the coarse fraction the pump interior and wall of the transport pipe, rubbing between the coarse fraction Including fit Each action is generated, removed coarse fraction of soil by classification from the slurry after a predetermined time circulated, to obtain a coarse fraction becomes low concentration than the concentration of harmful substances in the original soil, that The gist.

In addition, the cleaning system of the present invention has a taper shape inclined to the pump side installed on the bottom surface on the lower side of the peripheral surface, and is used for putting slurry mixed with soil and water contaminated with harmful substances. A container, a pump installed on the bottom surface of the container, capable of sucking and conveying the slurry in the container to the sand , and one end is connected to the discharge port of the pump, and the other end is discharged therefrom The slurry is disposed so as to return to the inside of the container, and is provided on the container, and includes a transport pipe for transporting the slurry sent out from the pump, and the slurry put in the container is the continuous operation of the pump, the container, the pump, by repeatedly circulating between the transportation pipeline, stirring at the pump inside the coarse fraction of the slurry, the pump interior of the coarse fraction Fine the collision on the wall of the transportation pipeline, to generate respective effects including rubbing between the coarse fraction, it is summarized in that.

According to the cleaning method of the contaminated soil of the present invention, placed in the slurry in a container having a tapered shape which is inclined to the pump side that is installed on the bottom on the lower side of the peripheral surface, the slurry in the vessel was placed in a container the sand By sucking with a pump capable of sucking and conveying up to a minute , transporting it via a transport pipe installed on the container connected to the pump, and returning it into a container having a tapered shape inclined toward the pump side on the lower side of the peripheral surface the slurry container, a pump to circulate between the transportation pipeline, for generating the circulation of the slurry in the repeating Succoth by continuous operation of the pump, stir at the pump inside the coarse fraction in the slurry, coarse fraction The high-concentrated layer near the coarse particle surface in the slurry is cut by the action including collisions inside the pump and the wall of the transport pipe and rubbing of the coarse particles, and the soil is crushed. Advance the lump of fines Construed, the fine fraction to firmly adhere to the coarse fraction is peeled, removed coarse fraction of soil by classification from the slurry after this manner by a predetermined time circulation, the concentration of harmful substances in the original soil Compared to the conventional method of cleaning the contaminated soil, special grinders and chemicals, etc., do not use equipment or equipment related to surface cutting of coarse particles. It is possible to cut the surface of coarse particles with an extremely simple equipment using only general-purpose and inexpensive equipment and equipment, and can improve the cleaning effect, contributing to the downsizing of the cleaning plant and the reduction of cleaning costs. can do.
Further, according to the cleaning system of the present invention, a container for containing a slurry having a tapered shape inclined to the pump side installed on the bottom surface on the lower side of the peripheral surface, and can be sucked and conveyed to the sand installed in the container A pump connected to the pump and installed on the container, and the slurry placed in the container is repeatedly circulated between the container, the pump and the transport pipe by the continuous operation of the pump, thereby roughening the slurry in the slurry. Since each action including agitation inside the pump of the granule, collision of the coarse granule inside the pump and the wall of the transportation pipe, and rubbing of the coarse particles , the above-described method for cleaning contaminated soil is realized, The effect based on the said washing | cleaning method can be show | played.
In particular, in this method and system for cleaning contaminated soil, during the circulation of the slurry, the coarse particles in the slurry settle at the bottom of the container. The particles can be circulated without any problems, and the lower part of the peripheral surface of the container is tapered and inclined to the pump side, so that coarse particles settled in the container are likely to gather near the pump. The coarse particles can also be circulated smoothly. In this way, the coarse particles in the slurry pass through the pump and the transportation pipe many times, and during this passage, strong stirring by the blades inside the pump, collision with the wall inside the pump and the transportation pipe, It is possible to cut a highly contaminated layer near the surface of the coarse particle by the action of rubbing between the particles, etc., and to promote the pulverization of the soil and to break up the lump of fine particles The fine particles strongly adhered to the coarse particles can be peeled off.

The figure which shows the washing | cleaning method of the contaminated soil in one embodiment of this invention The figure which shows the structure of the washing | cleaning system used for the washing | cleaning method of the contaminated soil

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows a method for cleaning contaminated soil.
As shown in FIG. 1, in this cleaning method, a container (circulation container) 1, a pump 2, and a transport pipe 3 are used. The container 1 is made of a material, size and shape suitable for circulating a predetermined amount of slurry mixed with soil contaminated with radioactive substances, heavy metals and other harmful substances (hereinafter simply referred to as contaminated soil) and water. What is necessary is just to have. In this case, the lower side of the peripheral surface of the container 1 is formed in a taper shape, and is inclined toward the suction port side of the pump 2 installed near the center of the bottom of the container 1. The particles are easily collected near the pump 2. The inclination of the container 1 is not essential and may be omitted. The pump 2 is a pump such as a so-called sand pump, and may be a submersible pump of the type installed in the water in the container 1 as long as it is capable of sucking and transporting up to the sand content. A pump etc. may be sufficient and a format will not be ask | required in particular. In this case, the pump 2 is installed near the center of the bottom of the container 1 as described above. The transport pipe 3 only needs to have a material, a diameter, and a length suitable for circulating and conveying a slurry in which contaminated soil and water are mixed. In this case, a hose 31 is attached to the front end of the transport pipe 3, and the discharge destination of the slurry is switched by changing the direction of the hose 31, and the discharge destination of the slurry is the container 1 or a classifier close to the container 1. The charging hopper 4 is switched to. Here, the discharge destination of the slurry is switched from the container 1 to the input hopper 4 or vice versa by the hose 31 at the tip of the transport pipe 3, but the slurry can be discharged from the transport pipe to both the container and the input hopper. As described above, the transportation piping may be previously connected to both the container and the charging hopper via the valve, and the slurry discharge destination may be switched by operating the valve. Here, one end of the transport pipe 3 is connected to the discharge port of the pump 2 and installed on the container 1, and the hose 31 at the other end is disposed in the container 1 toward the bottom of the container 1.

As shown in FIG. 1, in this cleaning method, first, a slurry a in which contaminated soil and water are mixed is put in a container 1, and the slurry a in the container 1 is sucked by a pump 2, and transported from the pump 2 to a transportation pipe. 3, the slurry a in the container 1 is circulated between the container 1, the pump 2, and the transport pipe 3 by discharging from the tip of the transport pipe 3 in the container 1 and returning to the original state. The circulation of the slurry a is repeated by continuous operation of the pump 2.
In this case, a predetermined amount of water is injected into the container 1, and the contaminated soil may be sequentially added while operating the pump 2 to circulate the water. In addition, when there are many large-diameter gravel and large foreign matter that cannot pass through the pump 2 in the contaminated soil, these gravel and foreign matter are removed using a screen or the like. Thus, the contaminated soil thrown into the container 1 is immediately stirred with water by the water circulation action of the pump 2 to become slurry a. When charging of a predetermined amount of contaminated soil into the container 1 is completed, the operation of the pump 2 is continued as it is, and the slurry a is repeatedly circulated between the container 1, the pump 2, and the transport pipe 3. During the circulation of the slurry a, the coarse fraction b in the slurry a settles in the lower part of the container 1 as shown in the figure, but this sedimentation is achieved by using a pump 2 that can suck and convey to the sand, such as a sand pump. The coarse particle fraction b can be circulated without any problem. Further, since the lower part of the peripheral surface of the container 1 is tapered and inclined toward the pump 2 side, the coarse particles b that have settled in the container 1 are likely to gather near the pump 2, and the coarse particles b are also smooth. Can be circulated. In this way, the coarse fraction b in the slurry a passes through the pump 2 and the transport pipe 3 many times, and during this passage, strong stirring by the blades of the pump 2, the inside of the pump 2 and the transport pipe 3 Due to the action of collision with the wall surface, rubbing of the coarse particles b, etc., the highly contaminated layer near the surface of the coarse particles b is cut, and the soil is crushed and the fine particles lump. As a result, the fine particles firmly adhered to the coarse particles are peeled off.
And the coarse-grained part b of a soil is taken out from the slurry a after circulating for a fixed time by classification, and the coarse-grained part b from which the density | concentration of the harmful | toxic substance became low compared with the original soil is obtained.
In this case, when circulation for a certain time is completed, as shown by a broken line in FIG. 1, the direction of the hose 31 at the tip of the transport pipe 3 is changed, and the charging hopper of the classifier installed with the opening of the hose 31 in the vicinity of the container 1 The slurry b is discharged toward the charging hopper 4 of the classifier.
Thereafter, when the coarse particle portion b is taken out from the slurry a after being circulated for a predetermined time by a classifier, the extracted coarse particle portion b is a coarse particle in which cutting of the surface or separation of fine particles attached to the surface has progressed. The concentration of harmful substances is a low-concentration coarse particle b compared to the original soil.

  As described above, according to the method for cleaning contaminated soil, the slurry a put in the container 1 is repeatedly circulated between the container 1, the pump 2 and the transport pipe 3 by the continuous operation of the pump 2, and is kept constant. Since the coarse-grained portion b of the soil is extracted from the slurry a after being circulated by classification, the coarse-grained portion b in which the concentration of harmful substances is lower than that of the original soil is obtained. For cleaning, it is possible to use rough and simple equipment using only general-purpose and inexpensive equipment and equipment without using special grinding machines and chemicals, etc. The surface cutting of the grain can be performed, the cleaning effect can be enhanced, and the cleaning plant can be reduced in size and the cleaning cost can be reduced.

FIG. 2 shows only the cleaning system used in the cleaning method of FIG.
As shown in FIG. 2, this cleaning system S includes a container 1 for containing a slurry in which contaminated soil and water are mixed, a pump 2 for sucking and sending the slurry in the container 1, and one end at the pump 2. Connected, the other end is arranged so that the slurry discharged therefrom returns to the inside of the container 1, and includes a transport pipe 3 for transporting the slurry sent out from the pump 2. A classifier (not shown) is installed in the vicinity of the cleaning system S, and a classifier charging hopper 4 is disposed adjacent to the container 1. In this case, the type of the classification device is not limited.
The container 1 should just have a material, a magnitude | size, and a shape suitable for circulating the slurry which mixed contaminated soil and water. In the case of the container 1, the lower side of the peripheral surface of the container 1 is formed in a tapered shape, and the lower side of the container 1 is inclined toward the suction port of the pump 2 installed near the center of the bottom of the container 1. The coarse particles settled in the container 1 are easily collected in the vicinity of the pump 2.
The pump 2 is a pump such as a sand pump, and may be a submersible pump of the type installed in the water in the container 1 as long as it is capable of sucking and conveying to the sand, and a suction pump of a type in which the pump body is placed separately from the container 1 The format is not particularly limited. As described above, the pump 2 is installed near the center of the bottom of the container 1.
The transport pipe 3 only needs to have a material, a diameter, and a length suitable for circulating and conveying a slurry in which contaminated soil and water are mixed. In this case, a hose 31 is attached to the tip of the transport pipe 3 and the discharge destination of the slurry is switched by changing the direction of the hose 31. In this case, the discharge destination of the slurry is placed in the container 1 or the container 1. It switches to the input hopper 4 of an adjacent classifier. Instead of the hose 31 at the tip of the transport pipe 3, the transport pipe may be previously connected to both the container and the charging hopper via a valve, and the slurry discharge destination may be switched by operating the valve. Further, a separate slurry return channel or the like may be provided in the container 1 so that the slurry discharged from the slurry discharge end of the transport pipe 3 returns to the container 1. In this case, it is not necessary to dispose the slurry discharge end of the transport pipe 3 in the container 1, and it may be disposed so that the slurry can be discharged to the return water channel or the like. Here, one end of the transport pipe 3 is connected to the discharge port of the pump 2 and installed on the container 1, and the other end can be selected as the slurry discharge destination in the container 1 or the input hopper 4 of the classifier as described above. Is arranged.
The cleaning system S has such a configuration, and the slurry placed in the container 1 is repeatedly circulated between the container 1, the pump 2, and the transport pipe 3 by the continuous operation of the pump 2. With this cleaning system S, the above-described contaminated soil cleaning method can be realized.

(Cleaning experiment for radioactively contaminated soil)
The inventors of the present application are: A: effect of conventional cleaning method using only pulverization and classification, B: effect of conventional cleaning method in which surface cutting of coarse particles by a grinder is added to pulverization and classification. C: In order to confirm the effect of the cleaning method of performing classification after performing crushing, soil particle surface cutting, and the like by the pump circulation method of the present invention, a cleaning experiment by each method was performed. In this experiment, three types of grinders were used for B. For C, the circulation time was 15 minutes and 30 minutes.
As a result, the following radioactivity concentration removal rate was obtained, and it was confirmed that the pump circulation method of the present invention had substantially the same effect as the conventional cleaning method in which surface cutting of coarse particles by a grinder was added. .
A: Removal rate of the conventional cleaning method using only crushing and classification 82.7%
B1: Removal rate of the conventional cleaning method with 2 hours of surface cutting by the grinding machine shell 87.7%
B2: Removal rate of the conventional cleaning method with surface grinding by a grinder B for 30 minutes 89.1%
B3: Removal rate of the conventional cleaning method with 4 times surface cutting with a grinder 89.9%
C1: Removal rate of the cleaning method of classifying after pump circulation (15 minutes) of the present invention 87.1%
C2: Removal rate of the cleaning method of classifying after pump circulation (30 minutes) of the present invention 89.3%

Moreover, in order to compare the equipment configuration of the soil washing plant using this washing system S with the equipment configuration of the conventional soil washing plant, conventional grinding and classification only without surface cutting of coarsely divided soil particles are performed. The equipment configuration of the soil washing plant is A. The equipment configuration of the conventional soil washing plant, which is obtained by adding the surface cutting of coarse particles with a grinder to the pulverization and classification, is B. The soil is crushed by the pump circulation method of the present invention. C shows the equipment configuration of the soil washing plant in the method of cutting the surface of the soil particles. In addition, when gravel and foreign matter are mixed in the original contaminated soil, a screen for removing them is required in advance, but this is necessary in any of A, B, and C. It is omitted in the device configuration.
A: Crushing device (water jet device, drum washer, etc.)
Classifier (horizontal bucket classifier, spiral classifier, cyclone classifier, etc.)
Turbid water treatment equipment (coagulation sedimentation equipment, etc.)
B: Crushing device (water jet device, drum washer, etc.)
Classifier (horizontal bucket classifier, spiral classifier, cyclone classifier, etc.)
Coarse soil particle surface cutting equipment (special grinder hurricane, cavitation jet equipment, etc.)
Turbid water treatment equipment (coagulation sedimentation equipment, etc.)
C: The proposed pump circulation coarse grain particle surface cutting device (consisting of a circulation vessel, pump, and transport piping)
Classifier (horizontal bucket classifier, spiral classifier, cyclone classifier, etc.)
Turbid water treatment equipment (coagulation sedimentation equipment, etc.)
As is clear from these A, B, and C device configurations, the C device configuration uses a circulation container, a pump, and a transport pipe (hereinafter referred to as the “usage device”). Compared to the B equipment configuration with performance, it is possible to eliminate the crushing equipment (water jet equipment, drum washer, etc.) and the coarse grained soil particle surface cutting equipment (special grinder hurricane, cavitation jet, etc.) The effect of was obtained.
(1) Since the proposed equipment is much cheaper than crushing equipment and coarse soil particle surface cutting equipment, the construction cost of the washing plant can be greatly reduced, and therefore the washing cost is greatly increased. Reduction can be achieved.
(2) Since the circulation device composed of the proposed device can be made much more compact than the crushing device and the coarse grain particle surface cutting device, the washing plant can be made compact.
(3) Since the proposed equipment is a general-purpose equipment and equipment, it is much easier to obtain than the crushing equipment and the coarse-grained soil particle surface cutting equipment, and the plant construction can be started immediately. It is easy to handle repairs.
In addition, compared with the conventional soil washing plant which does not perform until the surface cutting of said A, although any effect of said (1)-(3) is not acquired in the apparatus structure of A, this plan is the effect of said (2) However, it is difficult to say that the above effects (1) and (3) are obtained, and the effect of reducing the concentration by cutting the surface of coarse particles is sufficient. This is a method for cleaning contaminated soil with merit.

  In this embodiment, the case where the contaminated soil is directly cleaned by the contaminated soil cleaning method and the cleaning system of the present invention has been described. However, the cleaning method and system is used for the rough soil after the contaminated soil is cut by a cutting machine. It can also be used for cleaning to remove the cutting powder adhering to the granule. In particular, in the case of radioactively contaminated soil, the degree and degree of removal of the cutting powder from the coarse particles after cutting greatly affects the removal rate. Therefore, the method and system of the present plan that can efficiently remove the cutting powder with simple equipment. Is extremely effective.

S Cleaning system 1 Container (circulation container)
2 Pump 3 Transport piping 31 Hose 4 Input hopper a Slurry b Coarse fraction

Claims (2)

Bottom to set up a suction transportable pump to sand fraction, the lower side of the peripheral surface in a container with a slope to the pump side tapered, is entering the slurry mixed with contaminated with harmful substances soil and water Then, the slurry in the container is sucked by the pump in the container, and one end of the slurry is connected to the discharge port of the pump via a transport pipe installed on the container, by returning the vessel a slurry of said container, said pump, to circulate between the transportation pipeline, by repeating Succoth by continuous operation of the pump the circulation of the slurry, the slurry coarse fraction The slurry after generating each action including stirring inside the pump, collision of the coarse particles into the pump and the wall of the transport pipe, and rubbing of the coarse particles, and circulating for a certain period of time. Or Removed coarse fraction of soil by classification to obtain a coarse fraction becomes low concentration than the concentration of harmful substances in the original soil,
A method for cleaning contaminated soil. A container for containing a slurry mixed with soil and water contaminated with harmful substances, having a tapered shape inclined to the pump side installed on the bottom surface on the lower side of the peripheral surface ,
A pump installed on the bottom surface in the container and capable of sucking and transporting to the sand for sucking and feeding the slurry in the container;
One end is connected to the discharge port of the pump, and the other end is arranged so that the slurry discharged from the pump returns into the container, and is installed on the container to convey the slurry sent out from the pump Transportation piping,
With
The slurry was placed in the container, by continuous operation of the pump, the container, the pump, by repeatedly circulating between the transportation pipeline, stirring at the pump inside the coarse fraction of the slurry, the Collisions on the inside of the pump of coarse particles and the wall surface of the transport pipe, each action including friction between the coarse particles is generated,
Contaminated soil cleaning system characterized by that.

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