JP5809820B2 - Processing method and processing system for dredged soil - Google Patents

Description

  The present invention relates to a method and a system for treating dredged soil. More specifically, the present invention relates to a processing method and a processing system for dredged soil. More specifically, the treated water generated in the final treatment process is effectively used in the process while reducing the treatment cost, and an unnecessary load is applied to the external environment. The present invention relates to a method and a system for treating dredged clay.

  Various treatment methods have been proposed for reducing dredged soil when dredging the bottom of seabeds, rivers, and lakes (for example, see Patent Document 1). In the invention of Patent Document 1, the clay is classified using a centrifuge, a vibration sieve, or the like, and the overflowed amount in the classification process is placed in a concentration tank and settled. The supernatant water of the concentration tank is then adjusted to pH if necessary and discharged into the original water area (paragraphs 0018 to 0020).

  However, even if it is the supernatant water, if it is released into the original water area, it may affect the ecosystem of the water area and place an unnecessary load on the environment. In order to eliminate the environmental load caused by the discharged water, it is necessary to perform strict treatment on the discharged water. Along with this, there arises a problem that the processing cost increases. Therefore, it is desirable not to discharge the water generated through the final treatment process of the clay as much as possible.

JP 2001-212600 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method and a system for treating clay so as to prevent unnecessary load from being applied to the external environment by effectively using the treated water generated in the final treatment process while suppressing the treatment cost. Is to provide.

In order to achieve the above object, the clay treatment method of the present invention uses a first vibration sieve from the clay to remove a component mainly composed of gravel, and a treatment after the first treatment step. Using the second vibration sieve and the centrifuge disposed above the second vibration sieve from the soil, the second treatment step for removing components mainly composed of sand, and the second treatment step from the treated soil after the second treatment step . using three vibration sieve and third vibration upwardly arranged centrifuge sieve, and a third processing step of removing the component mainly the silt, in a first process step, the first vibrating screen The first mud storage tank is located under the first mud storage tank, removes gravel that cannot pass through the screen of the first vibrating screen, and the components passed through are stored in the first mud reservoir, and then the first mud storage tank. In the slurry state as the treated soil by the mud pump installed in the second The second processing step is equipped with a second mud storage tank disposed below the second vibrating screen, and the treated soil sent from the first processing step is classified by the second vibrating screen, After removing the gravel that cannot pass through the screen on the lower screen of the second vibrating screen, the passed components are stored in the second mud reservoir, and then centrifuged by the mud pump installed in the second mud reservoir. It is sent to the inlet of the machine and classified by cyclone centrifuge, and the components discharged from the outlet of this centrifuge are classified by the second vibrating screen to remove sand and gravel that cannot pass through the eyes of the upper screen. The components that have been removed and passed through the upper screen and the lower screen are stored in the second mud reservoir, then repeatedly sent to the centrifuge by the mud pump, and the particles centrifuged by the centrifuge Small ingredients The soil is sent from the outlet to the third treatment step, and in the third treatment step, a third mud storage tank is provided below the third vibrating screen, and the treated soil sent from the second treatment step is the first. After being stored in the three mud tanks, the mud pump installed in the third mud tank is sent to the inlet of the centrifuge and classified by cyclone centrifuge, and discharged from the outlet of the centrifuge The components are classified by the third vibrating screen, the silt component that cannot pass through the screen of the third vibrating screen is removed, and the passed components are stored in the third mud reservoir and then repeatedly centrifuged by the mud pump. The small component of the particles centrifuged by the centrifuge was sent to the fourth mud storage tank from the outlet as treated water and obtained through the third treatment step stored in the fourth mud tank . Treated water consisting of soil and water It is characterized by adjusting and reducing the specific gravity of the treated soil sent to the second treatment step by sending it to the first mud storage tank of one treatment step and circulating it.

  Here, a part of the treated water to be circulated in the first treatment step is supplied to at least one of the second treatment step and the third treatment step, and the treatment soil on the screen of the vibration sieve installed in the treatment step Can also be sprayed on.

The dredged soil treatment system of the present invention is installed in the first treatment step, and a first vibrating screen that removes components mainly composed of gravel from the dredged soil and a first vibrating screen disposed below the first vibrating screen. Centrifugation placed above the second vibrating sieve and the second vibrating sieve, which is installed in the mud storage tank and the second treating process and removes components mainly composed of sand from the treated soil that has passed through the first treating process. The machine, the second mud storage tank disposed below the second vibrating screen, and the third processing step are installed in the third processing step to remove components mainly composed of silt from the treated soil after the second processing step. Treated water comprising a centrifugal separator disposed above the vibrating screen and the third vibrating screen, a third mud storage tank disposed below the third vibrating screen, and a soil and water that has undergone the third treatment step. The 4th mud storage tank that stores water and the treated water stored in the 4th mud tank And a degree of the first貯泥tank water circulation line for circulating, in a first process step, the gravel fraction can not pass through the eye of the screen of the first vibrating sieve is removed, component passed through the reservoir to the first貯泥layer After that, it is configured to send to the second treatment step in a slurry state as treated soil by a mud pump installed in the first mud storage tank. In the second treatment step, the treated soil sent from the first treatment step is Classifying with a two-vibration sieve removes gravel that cannot pass through the screen on the lower side of the second vibration sieve, and the components that have passed are stored in the second mud reservoir and then installed in the second mud reservoir. The mud pump is sent to the inlet of the centrifuge and classified by a cyclone centrifuge. The components discharged from the outlet of the centrifuge are classified by a second vibrating screen, and the upper screen is closed. Excludes sand and gravel that cannot pass The components that have passed through the upper screen and the lower screen are stored in the second mud reservoir, and then repeatedly sent to the centrifuge by the mud pump, and the particles that have been centrifuged by the centrifuge are small. Ingredients are sent as treated soil from the delivery port to the third treatment step. In the third treatment step, the treated soil sent from the second treatment step is stored in the third mud storage tank, and then the third mud storage tank. A mud pump installed in the centrifuge is sent to the inlet of the centrifuge and classified by cyclone centrifuge, and the components discharged from the outlet of the centrifuge are classified by a third vibrating sieve. The silt that cannot pass through the screen of the screen is removed, and the components that have passed are stored in the third mud reservoir, and then repeatedly sent to the centrifuge by the mud pump and centrifuged by the centrifuge. The small component of the particles is sent to the fourth mud storage tank from the outlet as treated water, and the specific gravity of the treated soil of the first mud tank containing the component that has passed through the eyes of the screen of the first vibrating sieve, It adjusts with the treated water of the 4th mud storage tank sent through the said water circulation line, It is characterized by the above-mentioned.

Here, a system provided with a water supply line for supplying the treated water to be circulated to the first treatment step onto at least one of the screens of the second or third vibrating sieve can be provided. A system having a variable structure in which the inclination angle of the second and third vibrating screens with respect to the horizontal of the screen can be adjusted can be provided. A system in which the tilt angle of the third vibrating screen with respect to the horizontal of the screen is set to be smaller than the tilt angle of the second vibrating screen with respect to the horizontal of the screen may be provided. A system in which the drive source for exciting the screens of the second and third vibrating screens is an inverter motor may be used.

  According to the present invention, the components contained in the clay are removed in the descending order of the particle content through the first treatment step, the second treatment step, and the third treatment step. After passing through the third treatment step as the final step, treated water composed of soil and water is obtained. And since this treated water is circulated to a 1st process process, without discharging | emitting outside, an unnecessary load is not applied to an external environment. Moreover, the circulated treated water is effectively used to adjust the specific gravity of the treated soil sent from the first treatment process to the second treatment process. As a result, the treated soil treated in the first treatment step can be easily made into a slurry having an appropriate specific gravity and sent to the second treatment step, which is advantageous in improving the treatment efficiency. Moreover, since it is not necessary to use a special agent such as a flocculant for the treatment, it is advantageous for suppressing the treatment cost.

1 is an overall schematic diagram of a clay processing system according to the present invention. It is explanatory drawing which illustrates the system of a 1st process process. It is explanatory drawing which illustrates the system of a 2nd process process. It is explanatory drawing which illustrates the system of a 3rd process process.

  Hereinafter, the clay processing method and processing system of the present invention will be described based on embodiments.

  As illustrated in FIG. 1, the processing system of the present invention includes a first processing step T1, a second processing step T2, and a third processing step T3. In the first treatment step T1, components mainly composed of gravel are removed from the clay S (for example, coarse gravel A). In the second treatment step T2, components mainly composed of sand B (for example, remaining gravel A1 and sand B) are removed from the treated soil S1 that has undergone the first treatment step T1. In the third treatment step T3, components mainly composed of the silt component C are removed from the treated soil S2 that has undergone the second treatment step T2. After passing through the third treatment step, treated water S3 composed of soil content D and water W is obtained.

  As illustrated in FIG. 2, the first processing step T <b> 1 includes a first vibrating screen 1. Below the first vibrating screen 1, a first mud storage tank 3 and a discharge container 3a are arranged. A screw feeder 3 d is disposed between the first vibrating screen 1 and the first mud storage tank 3.

  A mud pump 4 and a stirrer 3b are installed in the first mud storage tank 3, and a hydrometer 3c is provided. The line L1 connected to the mud pump 4 is extended toward the second treatment step T2.

  The first vibrating screen 1 includes a hopper 1b, a screen 2 disposed below the hopper 1b, and an inverter motor 1a that vibrates the screen 2. The screen 2 has a predetermined opening and is installed to be inclined downward toward the discharge container 3a at a predetermined inclination angle Ag1 with respect to the horizontal. The inclination angle Ag1 is set to 0 ° to 15 °, for example. Although it is possible to adopt a tilt angle fixing structure in which the tilt angle Ag1 is fixed to a specific angle, in this embodiment, a tilt angle variable structure that can adjust the tilt angle Ag1 is provided.

  The opening of the screen 2 is, for example, about 25 mm, and is not large enough for the gravel A to pass through. The coarse gravel A has a diameter equivalent to, for example, a size of about 25 mm to 75 mm.

  The flat screen 2 is vibrated back and forth in an obliquely upward direction toward the discharge container 3a by the inverter motor 1a. The excitation frequency is, for example, about 30 Hz to 60 Hz.

  As illustrated in FIG. 3, the second processing step T <b> 2 includes a second vibrating screen 5 and a centrifuge 9. Below the second vibrating screen 5, a second mud storage tank 7 and a discharge container 7a are arranged. A mud feed pump 8 is installed in the second mud storage tank 7.

  The second vibrating screen 5 includes an upper screen 6a and a lower screen 6b disposed below the centrifuge 9, and an inverter motor 5a that vibrates the screens 6a and 6b. The upper screen 6a and the lower screen 6b have predetermined openings and are installed so as to be inclined downward toward the discharge container 7a at a predetermined inclination angle Ag2 with respect to the horizontal. The inclination angle Ag2 is set to, for example, -5 ° to + 5 °. A negative value of the inclination angle Ag2 indicates that the inclination angle Ag2 is inclined upward toward the discharge container 7a.

  Although it is possible to adopt a tilt angle fixing structure in which the tilt angle Ag2 is fixed to a specific angle, in this embodiment, the tilt angle variable structure is such that the tilt angles Ag2 of the upper screen 6a and the lower screen 6b can be adjusted integrally. ing. The upper screen 6a and the lower screen 6b can be independently changed. Further, the inclination angle Ag2 of the upper screen 6a and the lower screen 6b can be set to different angles.

  The opening of the upper screen 6a is, for example, about 0.50 mm to 0.71 mm, and has a structure in which the sand component B cannot pass. The sand content B is equivalent to a diameter and is, for example, about 0.075 mm or more and less than 2 mm.

  The opening of the lower screen 6b is, for example, about 5 mm, and the size is such that the remaining gravel A1 (inner gravel, pebbles) cannot pass through. The gravel portion A1 is equivalent to a diameter and has a size of, for example, about 5 mm or more and less than 25 mm.

  The flat screens 6a and 6b are vibrated back and forth in an obliquely upward direction toward the discharge container 7a by the inverter motor 5a. The excitation frequency is, for example, about 30 Hz to 60 Hz.

  The upper screen 6a is arranged so as to be shifted back and forth with respect to the lower screen 6b. In the top view, the lower screen 6b can be directly viewed without being blocked by the upper screen 6a. And the front-end | tip of the line L1 is located above the lower screen 6b of the position which is not interrupted | blocked by the upper screen 6a.

  A line L2 extending from the mud pump 8 is connected to the inlet 9a of the centrifugal separator 9, and the outlet 9b faces the upper surface of the upper screen 6a. A line L2 extending toward the third processing step T3 is connected to the outlet 9c of the centrifuge 9.

  As illustrated in FIG. 4, the third processing step T <b> 3 includes a third vibrating screen 10 and a centrifuge 14. Below the third vibrating screen 10, a third mud storage tank 12 and a discharge container 12a are arranged. In the third mud storage tank 12, a mud pump 13 is installed.

  The third vibrating screen 10 includes a screen 11 disposed below the centrifuge 14 and an inverter motor 10a that vibrates the screen 11. The screen 11 has a predetermined opening, and is installed to be inclined downward toward the discharge container 12a at a predetermined inclination angle Ag3 with respect to the horizontal. The inclination angle Ag3 is set to, for example, −5 ° to + 5 °.

  Although it is possible to adopt a tilt angle fixing structure in which the tilt angle Ag3 is fixed to a specific angle, in this embodiment, the tilt angle Ag3 is adjustable so that the tilt angle Ag3 can be adjusted. The inclination angle Ag3 may be set smaller than the inclination angle Ag2 of the upper screen 6a and the lower screen 6b.

  The opening of the screen 11 is, for example, about 0.090 mm to 0.106 mm, and has a structure in which a part of the silt portion C cannot pass. The silt portion C is equivalent to a diameter and has a size of about 0.030 mm or more and less than 0.075 mm, for example.

  The flat screen 11 is reciprocally vibrated obliquely upward toward the discharge container 12a by the inverter motor 10a. The excitation frequency is, for example, about 30 Hz to 60 Hz.

  A line L3 extending from the mud pump 13 is connected to the inlet 14a of the centrifuge 14, and the outlet 14b faces the upper surface of the screen 11. A line L3 extending toward the fourth mud storage tank 15 is connected to the outlet 14c of the centrifuge 14. A mud pump 16 is installed in the fourth mud tank 15. A water circulation line 17 extending from the mud pump 16 is extended to above the first mud storage tank 3 in the first treatment step T1. Two water supply lines 18 a are branched in the middle of the water circulation line 17. Each of the water supply lines 18 a extends to above the upper screen 6 a of the second vibrating screen 5 and above the screen 11 of the third vibrating screen 10. A shower nozzle 18b is attached to the tip of each water supply line 18a.

  The water supply line 18a is provided as necessary. When the water supply line 18a is provided, the water supply line 18a is extended toward the screen of the vibrating screen installed in at least one of the second processing step T2 and the third processing step T3.

  Hereinafter, a method for treating clay using this processing system will be described.

  The clay S dredged from the seabed or the like is put into the hopper 1b in the first processing step T1. The introduced clay S is placed on the vibrating screen 2 and classified by the first vibrating screen 1. Here, the gravel A that cannot pass through the eyes of the screen 2 is discharged and removed into the discharge container 3a. The components that have passed through the eyes of the screen 2 are defrosted by the screw feeder 3d. Then, while being stored in the first mud storage tank 3 and being stirred by the stirrer 3b, it is sent to the second treatment step T2 through the line L1 by the mud pump 4 in the slurry state as the treated soil S1.

  In the 1st mud storage tank 3, although the specific gravity of the processing soil S1 sent to 2nd processing process T2 is adjusted, this is mentioned later.

  The treated soil S1 sent to the second treatment step T2 is classified by the second vibrating screen 5. The treated soil S1 is first placed on the vibrating lower screen 6b, and the remaining gravel A1 that cannot pass through the eyes of the lower screen 6b is discharged and removed into the discharge container 7a. The The component that has passed through the eyes of the lower screen 6 b is stored in the second mud storage tank 7.

  The components stored in the second mud storage tank 7 are sent to the inlet 9a of the centrifuge 9 through the line L2 by the mud pump 8. The components sent to the centrifuge 9 are classified by cyclone centrifugation. Here, large components of particles are discharged from the discharge port 9 b and classified by the second vibrating screen 5.

  The component discharged from the discharge port 9b is placed on the upper screen 6a being vibrated. Then, the sand B and gravel A1 (the remaining medium gravel and small gravel) that cannot pass through the eyes of the upper screen 6a are discharged and removed into the discharge container 7a. The component that has passed through the eyes of the upper screen 6 a passes through the eyes of the lower screen 6 b and is stored in the second mud storage tank 7.

  The components stored in the second mud storage tank 7 are sent again to the centrifuge 9 by the mud pump 8. That is, in the second processing step T2, classification by the second vibrating screen 5 and the centrifuge 9 is repeatedly performed.

  On the other hand, the small component (for example, particle | grains are less than 75 micrometers) of the particle | grains centrifuged by the centrifuge 9 is sent to the 3rd process process T3 through the line L2 from the delivery port 9c as process soil S2.

  The reason why the treated soil S1 is first classified by the lower screen 6b in the second treatment step T2 is that the cyclone centrifuge 9 does not function sufficiently if large components such as gravel fraction A1 are present. .

  The treated soil S2 sent to the third treatment step T3 is stored in the third mud storage tank 12. Then, it is sent to the inlet 14a of the centrifuge 14 through the line L3 by the mud pump 13. The components sent to the centrifuge 14 are classified by cyclone centrifugation. Here, a large component of particles is discharged from the discharge port 14b and classified by the third vibrating screen 10.

  The component discharged from the discharge port 14b is placed on the screen 11. Then, the silt component C that cannot pass through the eyes of the screen 11 being vibrated is discharged and removed into the discharge container 12a. The components that have passed through the eyes of the screen 11 are stored in the third mud storage tank 12.

  The components stored in the third mud storage tank 12 are sent again to the centrifugal separator 14 by the mud pump 13. That is, in the third processing step T3, classification by the third vibrating sieve 10 and the centrifugal separator 14 is repeatedly performed.

  On the other hand, the small component (for example, particle | grains are less than 30 micrometers) of the particle | grains centrifuged by the centrifuge 14 is sent to the 4th mud storage tank 15 through the line L3 from the delivery port 14c as the treated water S3, and is stored. . This treated water S3 is composed of a soil component D and water W. The soil content D is equivalent to the diameter and has a size of, for example, about 0.030 mm, specifically, the remaining silt content C, clay, and colloid.

  The treated water S3 stored in the fourth mud storage tank 15 is sent to the first mud storage tank 3 of the first treatment step T1 through the water circulation line 17 by the mud pump 16. In the first treatment step T1, by detecting the specific gravity of the treated soil S1 stored in the first mud storage tank 3 with the hydrometer 3b, by controlling the amount of treated water S3 sent by the mud pump 16, The specific gravity is reduced to about 1.5 (1.3 to 1.6).

  In this way, after removing the large components of the particles sequentially and passing through the third treatment step T3 as the final step, the treated water S3 composed of the soil content D and the water W is obtained. The treated water S3 is circulated to the first treatment step T1 without being discharged to the outside, so that no unnecessary load is applied to the external environment. Further, the circulated treated water S3 is effectively used to adjust the specific gravity of the treated soil S1 sent from the first treatment step T1 to the second treatment step T2.

  The clay S has a specific gravity of, for example, about 1.7 to 2.0, and the specific gravity is too high as it is, so that it cannot be efficiently fed by the mud pump 4 and cannot be classified well by the centrifugal separator 9. Therefore, the specific gravity of the treated soil S1 is reduced to about 1.5 using the circulated treated water S3. This is advantageous for improving the processing efficiency.

  In addition, since a special agent such as an aggregating agent is not used in the processing step, it is advantageous for suppressing the processing cost. Since no special drug is used, the burden on the external environment is further reduced.

  In addition, the density | concentration of the soil content D of the treated water S3 stored in the 4th mud storage tank 15 becomes high gradually by repeating circulation of the treated water S3. If the concentration of the soil content D increases to some extent, the classification efficiency in the process decreases. Therefore, a target concentration of the soil content D in the fourth mud storage tank 15 is set in advance, and when the target concentration is reached, the circulation of the treated water S3 is stopped and the soil is taken out from the fourth mud storage tank 15. Then, a solidifying material such as cement is added to the extracted treated water S3 and kneaded to make a landfill material.

  In the present invention, even when the landfill material is manufactured in this way, the amount of the solidifying material used is small because the concentration of the soil content D of the treated water S3 is high. This is also advantageous for reducing processing costs.

  In this embodiment, a part of the treated water S3 to be circulated is applied to components (treated soil) placed on the screens 6a and 6b of the vibrating screen 5 and the screen 11 of the vibrating screen 10 through the water supply line 18a. It sprays with the shower nozzle 18b. Therefore, clogging of the screens 6a, 6b, and 11 is suppressed. As a result, classification by the vibration sieves 5 and 10 can be performed quickly and accurately, and can be performed for a long time without maintenance. Similarly, the dispersion of the treated water S3 can be applied to the screen 16 of the fourth vibrating screen 15 or the screen 2 of the first vibrating screen 1.

  In this embodiment, at least the tilt angle Ag2 of the screens 6a and 6b and the tilt angle Ag3 of the screen 11 are adjustable so that the tilt angle can be adjusted appropriately according to the properties of the components to be processed. By setting, the processing efficiency can be improved. If the inclination angles Ag1 to Ag4 are excessive, the moisture content of the components to be discharged and removed increases, and if the inclination angles Ag1 to Ag4 are excessively small, the time required for the processing increases, so that it can be set appropriately according to the properties of the components to be processed. I need it. For example, by setting the inclination angle Ag3 of the screen 11 to be smaller than the inclination angle Ag2 of the screens 6a and 6b, the component mainly composed of the sand component B and the component mainly composed of the silt component C that require a relatively long time for classification. , Classification processing can be performed with high accuracy in a short time.

  In addition, by using the inverter motors 1a, 5a, 10a, and 15a as the drive sources for exciting the screens 2, 6a, 6b, 11, and 16, the vibration conditions such as frequency and amplitude can be controlled in detail with high precision. I can. Therefore, it is easy to carry out appropriate classification according to the properties of the components to be processed. In addition, an inverter motor can also be employed only for the vibrating screen 5 (screens 6a and 6b) installed in the second processing step T2 and the vibrating screen 10 (screen 11) installed in the third processing step T3.

  The gravel A, gravel A1, and sand B removed from the clay S are appropriately used as materials. Further, since the silt C is used or disposed through a predetermined process or the like, the volume of the clay S can be greatly reduced.

DESCRIPTION OF SYMBOLS 1 First vibration sieve 1a Inverter motor 2 Screen 3 First mud storage tank 3c Hydrometer 4 Mud pump 5 Second vibration sieve 5a Inverter motor 6a Upper screen 6b Lower screen 7 Second mud tank 8 Mud pump 9 Centrifugal Separator 10 Third vibrating screen 10a Inverter motor 11 Screen 12 Third mud tank 13 Mud pump 14 Centrifugal separator 15 Fourth mud tank 16 Mud pump 17 Water circulation line 18a Water supply line 18b Shower nozzle S Soil

Claims (7)

The first vibration process is used to remove components mainly composed of gravel using the first vibration sieve from the dredged soil, and the second vibration sieve and the second vibration sieve are disposed above the treated soil after the first treatment process. A second processing step for removing components mainly composed of sand using a centrifuge, and a centrifugal separator disposed above the third vibrating screen and the third vibrating screen from the treated soil after the second processing step. Using a machine, and having a third treatment step for removing components mainly composed of silt,
In the first treatment step, a first mud storage tank is provided below the first vibrating screen to remove gravel that cannot pass through the screen of the first vibrating screen. After being stored in the slurry, it is sent to the second treatment step in a slurry state as treated soil by a mud pump installed in the first mud storage tank,
In the second treatment step, a second mud storage tank is provided below the second vibration sieve, and the treated soil sent from the first treatment step is classified by the second vibration sieve, and the second vibration sieve Gravel that cannot pass through the eyes of the lower screen is removed, and the components that have passed are stored in the second mud reservoir, and then are fed to the inlet of the centrifuge by a mud pump installed in the second mud reservoir. Sent and classified by cyclone centrifuge, the components discharged from the outlet of this centrifuge are classified by the second vibrating screen to remove sand and gravel that cannot pass through the eyes of the upper screen, The components that have passed through the screen and the lower screen are stored in the second mud reservoir, and then repeatedly sent to the centrifuge by the mud pump, and the small components of the particles centrifuged by the centrifuge are treated soil. As that Feed from the outlet to the third process step,
In the third treatment step, a third mud storage tank is provided below the third vibrating screen, and after storing the treated soil sent from the second treatment step in the third mud storage tank, the third mud storage tank A mud pump installed in the centrifuge is sent to the inlet of the centrifuge and classified by cyclone centrifuge, and the components discharged from the outlet of the centrifuge are classified by a third vibrating sieve. The silt component that cannot pass through the screen of the screen is removed, and the components that have passed are stored in the third mud reservoir, and then repeatedly sent to the centrifuge by the mud pump and centrifuged by the centrifuge The small component is sent as treated water from its outlet to the fourth mud storage tank, and the treated water consisting of soil and water obtained through the third treatment process stored in the fourth mud tank is the first treatment process. To be sent to the first mud tank for circulation More, the processing method of the dredged soil, which comprises reducing by adjusting the specific gravity of the treated soil to be sent to the second processing step.   A part of the treated water to be circulated in the first treatment step is supplied to at least one of the second treatment step and the third treatment step, and is spread on the treatment soil on the screen of the vibration sieve installed in the treatment step. The method for treating clay according to claim 1. A first vibration sieve installed in the first treatment step to remove components mainly composed of gravel from dredged soil, a first mud storage tank disposed below the first vibration sieve,
A second vibration sieve installed in the second treatment step to remove components mainly composed of sand from the treated soil that has undergone the first treatment step, and a centrifuge disposed above the second vibration sieve; A second mud storage tank disposed below the vibrating screen;
A third vibration sieve installed in the third treatment step and removing a component mainly composed of silt from the treated soil that has undergone the second treatment step; and a centrifuge disposed above the third vibration sieve; A third mud storage tank located below the vibrating screen;
A fourth mud storage tank that stores treated water consisting of soil and water that has undergone the third treatment process, and the treated water stored in the fourth mud tank is circulated to the first mud tank of the first treatment process. A water circulation line
In the first treatment process, gravel that cannot pass through the screen of the first vibrating screen is removed, and the components that have passed are stored in the first mud reservoir, and then the mud pump installed in the first mud tank. It is configured to send to the second treatment process in the slurry state as the treatment soil,
In the second processing step, the treated soil sent from the first processing step is classified by the second vibrating screen to remove gravel that cannot pass through the eyes of the screen below the second vibrating screen, and the components that have passed Is stored in the second mud reservoir, then sent to the inlet of the centrifuge by a mud pump installed in the second mud tank, classified by cyclone centrifuge, and discharged from the outlet of the centrifuge The classified components are classified by the second vibrating screen to remove sand and gravel that cannot pass through the eyes of the upper screen, and the components that have passed through the upper and lower screens are stored in the second mud reservoir. Then, repeatedly sent to the centrifuge by the mud pump, a small component of the particles centrifuged by the centrifuge is configured to send to the third treatment step from its outlet as treated soil,
In the third treatment step, the treated soil sent from the second treatment step is stored in the third mud tank, and then sent to the inlet of the centrifuge by a mud pump installed in the third mud tank. Classification by cyclone centrifugation, components discharged from the outlet of this centrifuge are classified by a third vibrating screen, the silt component that cannot pass through the eyes of the screen of the third vibrating sieve is removed, After being stored in the three mud reservoirs, it is repeatedly sent to the centrifuge by the mud pump, and the small components of the particles centrifuged by the centrifuge are sent to the fourth mud tank from the outlet as treated water. With configuration,
The specific gravity of the treated soil of the first mud tank containing components that have passed through the screen of the first vibrating screen is adjusted to be smaller by adjusting the treated water of the fourth mud tank sent through the water circulation line. The dredged soil processing system.   The dredged soil treatment system according to claim 3, further comprising a water supply line for supplying the treated water to be circulated to the first treatment step onto at least one of the screens of the second or third vibrating sieve.   The clay processing system according to claim 3 or 4, wherein the second and third vibrating screens have a variable structure capable of adjusting an inclination angle of the screen with respect to the horizontal.   The clay processing system according to any one of claims 3 to 5, wherein an inclination angle of the screen of the third vibrating screen with respect to the horizontal is set smaller than an inclination angle of the screen of the second vibrating screen with respect to the horizontal.   The clay processing system according to any one of claims 3 to 6, wherein a drive source for exciting the screens of the second and third vibrating screens is an inverter motor.

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