JP2015227853A - Classification device, contamination water treatment system, and classification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a classification device efficiently removing a radioactive material from a water bottom sediment without dispersing the radioactive material contained in the water bottom sediment, a contamination water treatment system, and the classification device.SOLUTION: A classification device includes: a casing 110 grounded to a water bottom and forming a closed region inside thereof; a jet nozzle 120 arranged below the casing 110 and floating the water bottom sediment inside the closed region; an underwater oscillation mixer 130 agitating the water bottom sediment floated inside the closed region; and an oscillation sieve 140 for classifying the water bottom sediment circulating inside the closed region into coarse particles equal to or more than classification boundary particles and fine particles equal to or less than the classification boundary particles.

Description

  The present invention relates to a classification device, a contaminated water treatment system, and a classification method, and in particular, a classification device that classifies fine particles in which radioactive substances are adsorbed from bottom sediment such as ponds, river areas, lakes, estuaries, and sea areas. The present invention relates to a contaminated water treatment system and a classification method.

  Contaminated soil contaminated with radioactive materials must be temporarily stored before final disposal, and the larger the amount of contaminated soil, the larger the storage space and disposal costs. Therefore, in order to reduce the disposal amount of contaminated soil, it is desired to reduce the volume of contaminated soil.

  Generally, a radioactive substance has a fine particle fraction (clay, silt) having a surface area (specific surface area) per gram larger than the coarse particle and less than 75 μm than a coarse particle (pebbles, sand) having a particle size of 75 μm or more. ). Therefore, in order to realize volume reduction of contaminated soil, it is known that particles of contaminated soil are classified according to the size of the particle size, and fine particles adsorbed with contaminants are selectively removed from the contaminated soil. It has been. In classifying the fine particles from the contaminated soil, for example, using an ultrasonic cleaning device described in Patent Document 1, coarse particles and fine particles are separated from the particles in the contaminated soil, Realized volume reduction.

Japanese Patent No. 5249474

  However, when removing radioactive materials contained in sediments such as ponds, river areas, lakes, estuaries, sea areas, etc. using the ultrasonic cleaning device described in Patent Document 1, the sediments are landed and installed on land. After putting the bottom sediment into the ultrasonic cleaning device and classifying it, it is necessary to return the coarse particles with a low degree of contamination to the bottom again, so the human burden and time burden required for construction are very heavy. was there.

  In addition, radioactive substances contained in the bottom sediment are concentrated on the surface layer of the bottom (for example, about 10 cm from the bottom of the water). From the viewpoint of work efficiency, the bottom sediment collects the surface layer. desirable. However, radioactive substances are easily diffused in the water as suspended solids suspended in water, and there is a possibility that the radioactive substances may be inadvertently diffused around when collecting the bottom sediment.

  Therefore, there is a technical problem to be solved in order to efficiently remove the radioactive substance from the bottom sediment without diffusing the radioactive substance contained in the bottom sediment, and the present invention solves this problem. With the goal.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 is a classification device for classifying fine particles to which radioactive substances have adhered from sediment on the bottom of the water, and is attached to the bottom of the water. A casing which is bottomed to form a closed area inside, a sediment floating means which is disposed below the casing and floats the bottom sediment in the closed area, and the bottom sediment which has floated in the closed area is closed. Stirring means for stirring in the region, and sorting means for classifying the bottom sediment circulated in the closed region into coarse particles having a classification boundary particle size or larger and fine particles having a particle size less than the classification boundary particle size. A classification device is provided.

  According to this configuration, the fine particles contained in the bottom sediment are classified in water without being landed on land, so that the fine particles can be classified efficiently and the diffusion of radioactive substances in the water can be achieved. Can be suppressed. The “classified boundary particle size” is the lower limit of the particle size of the coarse particles placed on the bottom of the water, and the specific surface area is obtained by classifying and collecting fine particles having a particle size less than the classified boundary particle size. The radioactive material adsorbed by the large fine particles is removed from the bottom sediment.

  A second aspect of the present invention provides the classification apparatus according to the first aspect of the present invention, further comprising a pumping means for sucking mud containing the fine particles floating in the closed region.

  According to this configuration, since the fine particles easily pass through the sorting means due to the suction force of the pumping means, the time required for classification can be shortened and the fine particles can be classified efficiently. Furthermore, when the casing is moved, settled, and pulled out, the pumping means keeps sucking the muddy water in the casing, so that floating substances around the casing are drawn into the casing, thereby suppressing the inadvertent diffusion of radioactive substances. can do.

  A third aspect of the present invention provides the classification apparatus according to the first or second aspect, wherein the earth and sand floating means floats a surface layer portion containing a radioactive substance in the bottom sediment in the closed region.

  According to this configuration, the sediment levitation means soars the surface layer of the bottom sediment that contains a lot of radioactive substances, so that the bottom sediment that circulates in the casing is reduced. Can be done.

  According to a fourth aspect of the present invention, there is provided the classification apparatus according to any one of the first to third aspects of the present invention, further comprising a cleaning means for separating the particles of the submarine sediment fixed to each other.

  According to this configuration, the cleaning means peels the fine particles adhered to each other, or the coarse particles and the fine particles adhered to each other, thereby separating the fine particles to which the radioactive substance is attached. Therefore, the time required for classification can be shortened, and classification of fine particles can be performed efficiently.

  A fifth aspect of the present invention provides the classifier according to the fourth aspect of the present invention, wherein the cleaning means is an ultrasonic wave transmitting element that irradiates ultrasonic waves and / or a cavitation nozzle that discharges a cavitation jet.

  According to this configuration, the ultrasonic wave emitted from the ultrasonic wave transmitting element or the cavitation jet discharged from the cavitation nozzle can eliminate the adhesion between the fine particles and the adhesion between the coarse particles and the fine particles. This makes it easy for the fine particles to which the radioactive substance is attached to pass through the sorting means, so that the fine particles can be classified efficiently.

  A sixth aspect of the present invention provides the classification apparatus according to any one of the first to fifth aspects, wherein the selecting means is a vibration sieve.

  According to this configuration, the vibration sieve can be used over a long period of time without clogging, so that the fine particles can be classified efficiently.

  A seventh aspect of the present invention provides the classification apparatus according to the sixth aspect of the present invention, wherein the mesh size of the vibrating screen can be arbitrarily changed according to the classification boundary particle size.

  According to this configuration, the particle size of the fine particles passing through the vibrating screen is arbitrarily changed according to the mesh size of the vibrating screen, so that it adheres to the fine particles according to the desired decontamination rate. Since the concentration of radioactive material removed from the bottom sediment can be adjusted, classification can be performed efficiently.

  According to an eighth aspect of the present invention, there is provided the classification apparatus according to any one of the first to seventh aspects, wherein the earth and sand floating means is a jet nozzle that discharges a jet water flow.

  According to this configuration, the bottom sediment can be easily raised by the jet water flow discharged from the jet nozzle.

  A ninth aspect of the present invention provides the classifier according to the eighth aspect of the present invention, wherein the jet water stream includes ozone.

  According to this configuration, the coarse particles that settle on the bottom after classification are aerobic, and the bottom environment can be improved.

  A tenth aspect of the invention includes a classification apparatus according to any one of the first to ninth aspects, a water treatment apparatus that separates the fine particles classified by the classification apparatus into a solid-liquid separation, and a solid-liquid separated fine section. There is provided a contaminated water treatment system device comprising a dewatering device for dewatering and recovering a granule.

  According to this configuration, since the classifier removes only fine particles from the bottom sediment, the volume of contaminated soil containing radioactive substances can be reduced.

  The invention according to claim 11 is a classification method for classifying fine particles to which radioactive substances are attached from the sediment at the bottom of the water, wherein a casing is attached to the bottom of the water to form a closed region in the casing; A step of floating the bottom sediment in the closed region using a sediment floating means; a step of stirring the bottom sediment in the closed region using a stirring means; and circulating in the closed region And a step of classifying the subsoil sediment into a coarse fraction having a classification boundary particle size or larger and a fine particle fraction having a classification boundary particle size or less.

  According to this configuration, since the coarse particles contained in the bottom sediment are classified in water without being landed on land, the fine particles can be classified efficiently and the radioactive material can be diffused in water. Can be suppressed.

  The present invention can efficiently remove radioactive substances from the bottom sediment without diffusing radioactive substances contained in the bottom sediment.

The figure which shows one Example of the contaminated water processing system which concerns on this invention. It is a figure which shows the classification apparatus shown in FIG. 1, (a) is a side view, (b) is a top view. The flowchart which shows the classification method. The figure which shows the particle size accumulation curve of the soil particle before and behind classification.

  In order to achieve the object of efficiently removing radioactive substances from the bottom sediment without diffusing the radioactive substances contained in the bottom sediment, the classifying apparatus according to the present invention is a fine substance to which radioactive substances have adhered from the bottom sediment. A classifying apparatus for classifying a grain fraction, a casing that is attached to the bottom of the water to form a closed region therein, a sediment floating means that is disposed below the casing and floats the bottom sediment in the closed region, and a closure Agitation means for agitating the subsoil floating in the region in the closed region, and subsoil circulated in the closed region into a coarse fraction greater than the classification boundary particle size and a fine fraction less than the classification boundary particle size. This is realized by having sorting means for classifying.

  Further, the classification method according to the present invention attaches radioactive substances from the bottom sediment to achieve the purpose of efficiently removing radioactive substances from the bottom sediment without diffusing radioactive substances contained in the bottom sediment. A classification method for classifying the fine particles, a step of bottoming the casing on the bottom of the water to form a closed region in the casing, a step of floating the bottom sediment in the closed region using earth and sand floating means, The step of stirring the bottom sediment that has floated in the closed region in the closed region using a stirring means, and the bottom sediment that circulates in the closed region are divided into coarse particles that are larger than the classification boundary particle size and fine particles that are smaller than the classification boundary particle size. And a step of classifying the particles into particles.

  Hereinafter, a contaminated water treatment system 1 according to an embodiment of the present invention will be described with reference to the drawings. In the following, the terms “upper” and “lower” correspond to the upper and lower parts in the vertical direction.

  As shown in FIG. 1, the contaminated water treatment system 1 according to the present embodiment classifies fine particles to which radioactive substances such as cesium are adhered from bottom sediment such as ponds, river areas, lakes, estuaries, sea areas, etc. In this way, the contaminated bottom sediment is washed. The contaminated water treatment system 1 includes a classification device 100, a water treatment device 10, and a dehydration treatment device 20.

  The classification device 100 is installed on the bottom b of a pond, a river area, a lake, an estuary area, a sea area, or the like. Specifically, the classifying device 100 is transported to a desired position by a small floater F (assembly boat) traveling on the water surface s and then lowered to the bottom of the water by a lifting device such as a crane. In addition, the classification apparatus 100 is not restricted to what is installed with the small floater F, For example, you may suspend it to a desired position with the crane arrange | positioned on land. Moreover, when classifying on a large pond or the sea, the contaminated water treatment system 1 may be constructed on the small floater F.

  The water treatment device 10 is connected to the classification device 100 via a raw water tank 11 that temporarily stores muddy water. The muddy water containing the fine particles classified by the classification device 100 is mixed with the flocculant in the water treatment device 10 and separated into solid and liquid. The muddy water containing the fine particles is sent to the muddy water tank 21 described later, and the muddy water from which the fine particles are separated is sent to the treated water tank 22.

  The dehydration apparatus 20 is connected to the water treatment apparatus 10 via the muddy water tank 21. The fine particles separated by solid-liquid separation in the water treatment device 10 are dehydrated in the dehydration treatment device 20 and then packed in a weatherproof soil bag sb and stored. Moreover, the muddy water (washing water) separated from the fine particles is discharged through the treated water tank 22 for storing the treated washing water.

  The high-pressure pump 30 supplies the cleaning water stored in the treated water tank 22 to the classification device 100.

Next, the classification device 100 will be described with reference to FIG.
As shown in FIG. 2, the classification device 100 includes a casing 110, a jet nozzle 120 as a sediment floating means, an underwater mixer 130 as a circulation means, a vibrating sieve 140 as a sorting means, and a drainage pump as a pumping means. 150. Reference numeral 160 denotes a basket that collects floating substances such as fallen leaves and the like having a predetermined size (for example, 100 μm) or more.

  The casing 110 includes a main body portion 111 formed in a hollow quadrangular prism shape and a base portion 112 on which the main body portion 111 is placed. The main body 111 is extended longer than the depth of the water bottom from the water surface s to the water bottom b. Accordingly, the closed region R is formed in the casing 111 by the lower opening 113 being installed on the bottom of the water facing downward and the upper opening 114 being positioned above the water surface. The base portion 112 is bottomed so as to be partially buried in the water bottom.

  The jet nozzle 120 is provided suspended from a rectangular frame 112 a installed in the base portion 112. The jet nozzle 120 is disposed at an angle with respect to the frame 112a such that the jet nozzle 120 is substantially horizontal to the water bottom b and the discharge port of the jet nozzle 120 faces inward. The jet nozzle 120 discharges the jet water flow supplied from the high-pressure pump 30 into the closed region R. The discharge flow rate of the jet nozzle 120 can be arbitrarily changed according to the amount of bottom sediment that floats in the closed region R. The jet water stream preferably contains ozone. Thereby, the coarse-grained part which settles to a water bottom after classification can be aerobic and environmental improvement can be aimed at.

  The underwater mixer 130 is disposed at the lower center of the main body 111. The underwater mixer 130 generates a stirring water flow that stirs the muddy water containing the radioactive substance in the casing 110. The stirring water flow generated by the underwater mixer 130 circulates in the casing 110 in the vertical direction.

  The vibrating screen 140 includes a mesh cage 141 formed in a bottomed cylindrical shape, a vibrating body 142 that vibrates the mesh cage 141, and a frame 143 that is attached to the mesh cage 141 and on which the vibrating body 142 is placed. I have. The vibration sieves 140 are arranged one by one at two diagonal corners of the four corners of the main body 111. When the vibrating body 142 vibrates, clogging of the mesh cage 141 is suppressed. Further, the frame 143 is connected to the main body 111 via a vibration-proof rubber (not shown) so that vibration is not transmitted to the main body 111 even if the vibrating body 141 oscillates. The vibrating screen 140 can arbitrarily change the mesh size according to the decontamination target of the radioactive substance, that is, the classification boundary particle size of the fine particles.

  The drainage pump 150 is disposed in the mesh car 141, sucks fine particles circulating in the casing 110, passes the mesh car 141, and sends the fine particles passed through the mesh car 141 to the raw water tank 11. The drainage pump 150 is fixed to a frame (not shown) that does not contact the mesh basket 141, and the vibration of the vibrating screen 140 is not transmitted to the drainage pump 150. The suction pressure of the drain pump 150 may be arbitrarily adjusted within a range in which fine particles circulating in the casing 110 can be sucked.

  Further, the classification device 100 includes an ultrasonic oscillation element 170 as a cleaning unit and a cavitation nozzle 180. The ultrasonic wave emitted from the ultrasonic oscillator 170 and the cavitation jet discharged from the cavitation nozzle 180 separate the fixed coarse particles and fine particles, and separate the fixed fine particles. This makes it easier for fine particles to pass through the vibrating screen 140. Note that it is not always necessary to provide both the ultrasonic oscillation element 170 and the cavitation nozzle 180, and only one of them may be provided as necessary.

  One ultrasonic oscillator 170 is attached to the side wall 111 a of the main body 111 in a state of being covered with the cover 171. The frequency of the ultrasonic wave irradiated from the ultrasonic oscillator 170 is preferably set between 18 and 50 kHz where a high cavitation effect can be expected. The number of ultrasonic oscillators 170 installed may be adjusted as appropriate in order to obtain a cavitation effect according to the decontamination target.

  Eight cavitation nozzles 180 are provided on the outer periphery of the underwater mixer 130. The cavitation nozzle 180 is connected to a cavitation jet pump (not shown), and discharges the cavitation jet upward.

Next, a classification method using the classification device 100 will be described with reference to FIG.
First, the casing 110 is settled on the water bottom, and a closed region R is formed in the casing 110 (S1). When the casing 110 is settled on the bottom of the water, the drainage pump 150 continues to suck the muddy water in the casing 110, so that the surface layer portion of the bottom of the water diffuses out of the casing 110 due to an impact when the casing 110 reaches the bottom. This can be suppressed. When the casing 110 is settled on the bottom of the water, the base portion 112 of the casing 110 is, for example, embedded in the bottom of the water b by 20 cm.

Next, the jet water flow discharged from the jet nozzle 120 raises the bottom sediment in the casing 110 into the closed region R (S2).
It is preferable that the jet water flow is set to have a discharge flow rate so that a surface layer portion stacked in a predetermined amount (for example, 10 cm from the water bottom) rises from the water bottom. Thereby, since classification is performed only for the surface layer portion containing a large amount of radioactive substance, the time required for classification can be shortened efficiently. However, the bottom sediment that the jet water stream soars is not limited to the surface layer portion, and a larger amount of the bottom sediment may be soared including the surface layer portion according to the decontamination target.

  Next, the stirring water flow of the underwater mixer 130 circulates the bottom sediment in the casing 110 (S3). The stirring water flow is formed so as to circulate in the casing 110 in the vertical direction, for example.

  Then, among the submarine soil floating in the casing 110, the fine particles pass through the mesh basket 141, and the coarse particles continue to circulate in the casing 110 (S4). By providing the drainage pump 150 in the mesh cage 141, fine particles floating near the mesh cage 141 are sucked and easily pass through the mesh cage 141, so that the time required for classification can be shortened.

  After the underwater mixer 130 is operated for a predetermined time, the fine particles that have passed through the vibrating screen 140 are collected, and the coarse particles that have not passed through the vibrating screen 140 are settled in the casing 110 and returned to the bottom of the water.

  Next, FIG. 4 shows a particle size accumulation curve when the simulated submarine sediment is classified using the classifier 100. The solid line in FIG. 4 is the particle size accumulation curve of the simulated bottom sediment before classification, the fine chain line is the particle size accumulation curve of the fine particle after classification, and the thick chain line is inside the casing 110 after classification. It is a particle size accumulation curve of the coarse grain which remained in. The A line in FIG. 4 indicates a particle size of 0.075 μm, and the B line indicates a particle size of 0.106 μm. The particle size was measured by sedimentation analysis for particles having a particle size of less than 0.075 mm and fluid analysis for particles having a particle size of 0.075 mm or more. Various conditions at the time of classification were set such that the capacity of the casing 110 was 25 m 3, the discharge amount of the jet water flow was 50 L / min, the mesh size of the vibrating sieve 140 was 0.3 mm, and the stirring time was 10 minutes.

  As shown in FIG. 4, the content of fine particles in the simulated bottom water sediment before classification is about 56%, whereas the content of silt and clay contained in the coarse particles after classification is about 4%. The fine particle content in the casing 110 is remarkably lowered from about 56% to about 4% before and after classification. Moreover, the silt content and the clay content contained in the fine granule after classification are about 90%, and the classification boundary particle size of the fine granule obtained under the above conditions using the classifier 100 is the A line. It can be seen that the region surrounded by the line B, that is, between 0.075 and 0.106 mm.

  Next, Table 1 shows the effect of classifying and cleaning cesium (Cs), which is a radioactive substance, using a jet water stream, ultrasonic waves, and a cavitation jet. Cases 1 to 4 in Table 1 are obtained by classifying four samples of homogeneous bottom mud by different methods, case 1 is a case where classification is performed only with jet water, and case 2 is This is a case where classification is performed with jet water and ultrasonic waves, case 3 is a case where classification is performed with jet water and a cavitation jet, and case 4 is classification with jet water, ultrasonic waves and a cavitation jet. This is the case.

  As shown in Table 1, the decontamination rate reaches 97.4% even when the classification is performed only with the jet water flow, and it can be seen that cesium can be sufficiently reduced. Further, it can be seen that the use of ultrasonic waves and a cavitation jet can further reduce Cs as compared with the case where classification cleaning is performed only with a jet water flow.

  In this way, the classification device 100 according to the present invention transports the bottom sediment to land or the like by grounding the casing 110 on the bottom of the water and classifying the fine particles within the closed region R in the casing. Therefore, the fine particles can be classified, so that the fine particles can be classified efficiently and the diffusion of the radioactive substance can be suppressed.

  Further, in the contaminated water treatment system 1 using the classification device 100, since the classification device removes only fine particles from the bottom sediment, the volume of removed soil can be reduced.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

DESCRIPTION OF SYMBOLS 1 ... Contaminated water treatment system 10 ... Water treatment apparatus 11 ... Raw water tank 20 ... Dehydration treatment apparatus 21 ... Muddy water tank 22 ... Treated water tank 30 ... High pressure pump 100 ... Classifier 110 ... Casing 111 ... Main body 111a ... (Body side) side wall 112 ... Base part 112a ... (Base part) frame 113 ... Lower opening 114 ... Upper opening 120 ... Jet nozzle 130 ... Submerged mixer 140 ... Vibrating sieve 141 ... Mesh basket 142 ... Vibrating body 143 ... (vibrating body) frame 150 ... Drain pump 160 ... Floating object collection basket 170 ... Ultrasonic transmission element 171 ... Cover 180 ... Cavitation nozzle

Claims (11)

A classification device for classifying fine particles to which radioactive substances have adhered from the bottom sediment,
A casing that is attached to the bottom of the water and forms a closed region therein;
A sediment surfacing means that is disposed below the casing and floats underwater sediment within the closed area;
Agitation means for agitating the submarine sediment floating in the closed area in the closed area;
Sorting means for classifying the bottom sediment circulating in the closed region into a coarse fraction having a classification boundary particle size or more and a fine fraction having a classification boundary particle size or less,
A classification device characterized by comprising:   The classification apparatus according to claim 1, further comprising pumping means for sucking mud containing the fine particles floating in the closed region.   The classification apparatus according to claim 1 or 2, wherein the earth and sand floating means floats a surface layer portion containing a radioactive substance in the bottom sediment in the closed region.   The classification apparatus according to any one of claims 1 to 3, further comprising a cleaning unit that separates the particles of the bottom sediment that are fixed to each other.   The classification device according to claim 4, wherein the cleaning means is an ultrasonic wave transmitting element that emits ultrasonic waves and / or a cavitation nozzle that discharges a cavitation jet.   The classification device according to any one of claims 1 to 5, wherein the selecting means is a vibration sieve.   The classification device according to claim 6, wherein the mesh size of the vibrating screen can be arbitrarily changed according to the classification boundary particle size.   The classification apparatus according to any one of claims 1 to 7, wherein the earth and sand floating means is a jet nozzle that discharges a jet water flow.   The classifier according to claim 8, wherein the jet water stream includes ozone. A classification device according to any one of claims 1 to 9,
A water treatment device for solid-liquid separation of fine particles classified by the classification device;
A dehydration processing device for dehydrating and recovering the fine-particle fraction separated by solid-liquid, and
A contaminated water treatment system characterized by comprising: A classification method for classifying fine particles to which radioactive substances are attached from the bottom sediment,
Forming a closed region in the casing by bottoming a casing on the water bottom;
Floating the bottom sediment in the closed area using sediment floating means;
Agitating the submarine soil floating in the closed area in the closed area using a stirring means;
Classifying the submarine sediment circulating in the closed region into a coarse fraction having a classification boundary particle diameter or more and a fine fraction having a classification boundary particle diameter of less than,
Classification method characterized by including.