JP2004097873A - Classification method for dredged earth and sand - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To take out a sand component in dredged earth and sand efficiently by reduced energy to obtain the high quality sand component at a high recovery rate. <P>SOLUTION: A rough classification means 21, which separates dredged muddy water wherein dredged earth and sand containing the sand component and water are mixed into coarse particles and fine particles, is provided to a mud feed pipeline through which the muddy water is transported by a pump, and the muddy water stream in the pipeline is separated into muddy water low in sand content and muddy water high in sand content by the classification means. The separated muddy water low in sand content is sent to a sedimentation treatment basin 27 as it is while the muddy water high in sand content is sent in a classification treatment pipeline separate from the pipeline of the muddy water low in sand content, and a diluting water mixing means 23 is provided on the way of the pipeline. The mud feed pressure of the muddy water high in sand content is utilized by the means 23 to suck diluting water into the pipeline to mix the same with the muddy water, and the diluted muddy water high in sand content is sent to a sedimentation classification tank 22. The coarse particles are sedimented in the sedimentation classification tank 22 while the fine particles are allowed to flow along with water to separate the sand component. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for classifying a dredged soil to mainly extract sand from dredged sand containing sand in a river, a port, or the like and to make it usable as a resource.
[0002]
[Prior art]
Conventionally, dredged soil treatment has often been used for land reclamation in coastal areas, but in recent years, as interest in environmental changes and industrial structure changes has increased, the demand for land reclamation has decreased. It is becoming difficult to secure a stable treatment plant.
[0003]
On the other hand, the amount of construction materials such as sand and gravel to be collected is decreasing, and there is a need for a method capable of stably securing these construction materials with consideration for the environment.
[0004]
Therefore, a method for treating dredged soil has been proposed for the purpose of reducing the volume of the dredged soil and classifying and reusing construction materials such as sand and gravel from the dredged soil.
[0005]
In this method for treating dredged soil, as shown in FIGS. 7 and 8, dredging mud mixed with dredged soil and water is sent from a dredging means 1 to a mixing tank 2 having a stirrer 2a. The muddy water is stirred well to make the muddy water concentration uniform, and the muddy water in which the coarse mud mainly composed of sand and water are mixed is sent to the classifying means 4 by the pump 3, and the muddy water is Is classified into sand such as sand and gravel, and other components such as silt. The sand is taken out in a reusable state, and the other components are sent to the sedimentation treatment tank 5. As the classifying means 4, a vibrating sieve with a cyclone as shown in FIG. 7 and a means for sedimenting sand using a sedimentation tank (or sedimentation channel) as shown in FIG. 8 are known.
[0006]
Also, a method of classifying dredged muddy water into coarse particles such as sand and fine particles such as silt using a classifying apparatus 10 as shown in FIG. 9 to treat dredged soil (Japanese Patent Publication No. 5-58778). Gazette) has also been proposed.
[0007]
The classifying device 10 is provided with a plurality of classifying paths 11a, 11b,... Dividing the inside of a transport pipe connected to the dredging means into a plurality of upper and lower sections, and by setting the downstream sides of the respective classifying paths to different different flow paths. Fine particles such as silt and clay flow through the upper classifiers 11a and 11b, and most of the coarse particles such as sand flow through the lower classifier 11c. Therefore, the dredged mud sent by pumping in the pipeline is automatically classified by passing through the classifier 10, and divided into fine particles such as silt and coarse particles such as sand. It can handle dredged soil.
[0008]
[Problems to be solved by the invention]
However, in the conventional technology as described above, sand in dredged soil, a device that requires a power source such as a cyclone to extract sand such as gravel, and many pumps and the like are used to transport muddy water Therefore, there is a problem that a large amount of energy is consumed to operate these devices and pumps.
[0009]
In addition, in order to reuse the sand obtained from the dredged soil as aggregate for concrete and the like, a high-purity one containing no clay is desired. In the classification method and the like, there is a problem that the quality is deteriorated when the classification recovery rate is increased with respect to the ratio of the dredged soil to be processed, and the recovery rate is reduced when the quality is improved.
[0010]
The present invention has been made in view of such a state of the art, and it is possible to efficiently extract sand in dredged soil with little energy and obtain a high-quality sand at a high recovery rate. The purpose is to provide a classification method.
[0011]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION In order to solve the conventional problems as described above and to achieve the intended purpose, the invention of claim 1 is directed to a mud feeding pipeline in which dredged mud mixed with dredged earth and sand containing sand is pumped. In the middle of the process, a coarse classification means for separating into coarse and fine particles is provided, and the dredged mud flow in the mud pipe is divided into a low and a high mud containing mud by the coarse classification means. The low sand-bearing mud water sent to the sedimentation treatment pond as it is, the high sand-bearing mud water is sent to a separate pipe for classification treatment from the low sand-bearing mud water, and a dilution water mixing means is provided in the middle of the pipeline. The dilution water mixing means draws dilution water into the pipeline by using the mud pressure of the high sand content muddy water and mixes it with the high sand content muddy water. To separate the sand content by precipitating coarse-grained components and passing fine-grained components together with water in the sedimentation classification tank. And characterized in that.
[0012]
With this configuration, the high-sand content mud with a high sand content is diluted to promote the sedimentation of the sand content, so that high-quality sand content can be taken out at a high recovery rate. By sucking dilution water into the pipeline using the muddy water sending pressure, sand can be efficiently extracted with little energy.
[0013]
According to a second aspect of the present invention, in addition to the configuration of the first aspect, the dilution water mixing means includes an ejection nozzle that narrows the downstream side of the classification processing pipe, and a dilution water supply unit that supplies dilution water around the ejection nozzle. And an eductor having a narrowed neck on the downstream side of the dilution water supply unit and a tapered portion that is expanded on the downstream side of the neck, and the high sand content muddy water on the upstream side of the classification pipe is used. It is characterized in that the dilution water is sucked by the negative pressure generated at the time of discharge from the ejection nozzle, and the dilution water is mixed and diffused into the high sand-containing muddy water by diffusion in the tapered portion.
[0014]
With this configuration, the diluting water is sucked without using a pump device that requires a power source by the ejector effect of the diluting water mixing means, that is, the pumping effect by jetting high sand content muddy water from the jet nozzle. The dilution of the high sand content mud can be performed automatically and continuously, and the classification process can be performed efficiently. Further, since the effect of diluting and washing the high-sand content muddy water is obtained, higher quality sand can be obtained.
[0015]
The invention of claim 3 is characterized in that, in addition to the structure of claim 1 or 2, the dilution water uses surface water of a sedimentation treatment pond into which low-sand content muddy water is fed.
[0016]
With this configuration, it is not necessary to provide a facility for storing the dilution water, and the processing can be performed at low cost.
[0017]
In the invention of claim 4, in addition to the constitution of claim 1, 2 or 3, the coarse classification means comprises a plurality of stages by vertically dividing the mud feeding pipe in the middle of the mud feeding pipe for transporting the dredged muddy water. A classification path is provided, and the downstream side of the lower classification path is communicated with a classification processing pipeline.
[0018]
With this configuration, it is possible to reduce only the amount of water without reducing the amount of sand in the dredged soil, and since the sand is not washed away with the silt, the loss of sand in the classification operation is reduced. Sand and the like can be taken out at a low and high recovery rate.
[0019]
The invention of claim 5 is, in addition to the configuration of claims 1 to 3 or 4, wherein the sedimentation classification tank includes a sand sedimentation section on the upstream side where the high-sand content muddy water diluted by the diluting water mixing means flows. At the downstream end of the sand sedimentation section, a submerged weir that separates the sedimentation classification tank into an upstream side and a downstream side is movable upstream and downstream.
[0020]
With this configuration, the sand having the required particle size can be efficiently collected, and the submerged weir can be moved to adjust the particle size of the sand deposited in the sedimentation classification tank. can do.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 shows an outline of a device for classifying sediment.
[0023]
The dredged sediment classification apparatus includes a dredging means 20 for supplying dredged mud mixed with dredged sediment and water, and a mud feed pipe through which the dredged mud is transported by pumping. A coarse classification means 21 and a sedimentation classification tank 22 are provided on the way to perform classification step by step, and finally, sand contained in the dredged soil is taken out in a reusable state.
[0024]
Further, in this dredged sediment classification apparatus, a diluting water mixing means 23 is provided between the coarse classification means 21 and the sedimentation classification tank 22, and the high sand content muddy water mainly composed of the sand classified by the coarse classification means 21. And the diluting water is mixed into the sedimentation tank 22 so that the sand contained in the high-sand-containing muddy water is easily precipitated.
[0025]
The dredging means 20 takes in dredged soil in a state of being mixed with water, like a pump dredge, and sends the dredged mud mixed with the dredged sediment and water as it is to the mud line by the pump 20a, or The dredged earth and sand is transported to the classifying site by a soil carrier, etc. without adding water as in the case of grab dredging, etc. It is designed to be pumped.
[0026]
The coarse classification means 21 is provided with a classification branch pipe 24 in the middle of a mud feeding pipe for transporting dredged soil, thereby dividing the mud feeding pipe up and down to provide upper and lower classifiers 25 and 26, and an upper classifier 25. Is connected to the sedimentation treatment tank 27, and the downstream side of the lower classification passage 26 is connected to the classification treatment pipeline.
[0027]
As shown in FIGS. 2 to 4, the classifying branch pipe 24 communicates with a cylindrical main body 28, a partition plate 29 for vertically dividing the inside of the main body 28, and a partition plate lower flow path 30 b of the main body 28. And a guide plate 32 for closing the downstream opening of the partition plate lower flow path 30b of the main body.
[0028]
In the classifying branch pipe 24, since the inside of the main body is vertically divided by the partition plate 29, low sand-containing muddy water mainly composed of silt or clay flows through the partition plate upper flow path 30a, and high water mainly composed of sand. Since the sand-containing muddy water flows through the partition plate lower flow path 30b, and the induction plate 32 closes the downstream side of the partition plate lower flow path 30b of the main body 28, the high sand-containing muddy water is removed. It flows to the branch cylinder 31 side, that is, to the classification processing pipeline, and is sent to the dilution water mixing means 23 through the pipeline.
[0029]
Reference numerals 33, 33 ... in the figure denote rectifying strips. The rectifying strips 33, 33 ... partition the upstream opening of the partition plate lower flow path 30b, so that the partition plate lower pipe line 30b is separated by gravel or the like. Is prevented from being blocked.
[0030]
As shown in FIG. 5, an eductor is used for the dilution water mixing means 23. The eductor includes an ejection nozzle 34 that narrows the downstream side of the classification processing pipeline, and a dilution water that supplies dilution water around the ejection nozzle. It has a supply section 35 and a tapered section 36 in which the downstream side of the dilution water supply section 35 is a narrowed neck and the downstream side of the neck is expanded.
[0031]
This eductor discharges the high sand content mud fed from the coarse classification means 21 from the jet nozzle 34 by the pressure of the mud, so that the pressure in the dilution water supply unit 35 is reduced by the negative pressure generated at the time of discharge, and the dilution is performed. The diluting water is sucked into the water supply unit, and the high sand content muddy water spouted from the spouting nozzle 34 and the sucked dilution water are mixed and diffused by the diffusion in the taper portion 36. The diluted high sand content muddy water flows toward the downstream side, that is, the sedimentation classification tank 22 side, because the downstream side of the tapered portion 36 is expanded in a tapered shape.
[0032]
In the dilution water mixing means 23, the dilution water supply unit 36 is communicated with the upper part of the sedimentation treatment pond 27 into which the low sand content muddy water has been sent, and the surface water of the sedimentation treatment pond 27 is sucked as dilution water. You may.
[0033]
The sedimentation classification tank 22 is provided with a sand sedimentation part 37 on the upstream side where the high sand content muddy water diluted by the dilution water mixing means 23 flows, and the sedimentation classification tank 22 is provided on the downstream end of the sand sedimentation part 37. A submerged weir 38 that divides into an upstream side and a downstream side is provided so as to be movable up and down.
[0034]
In the sedimentation classification tank 22, sand such as sand and gravels, which are coarse components of the high sand content mud, is settled in the sand sedimentation section 37 on the upstream side, and fine particles of the high sand content mud are downstream. The components are separated from the sand by flowing the components together with the water over the submerged weir 38 to the sedimentation treatment pond 27.
[0035]
The sand accumulated in the sand sedimentation section 37 is taken out by sand collecting means 39 such as a backhoe and sent to a sand stock yard 40. In addition, an on-off valve 41 is provided in a pipeline before the sedimentation classification tank 22, the on-off valve 41 is closed, and the inflow of high sand-containing muddy water into the sedimentation classification tank 22 is stopped to collect sand. You may do so.
[0036]
Reference numeral 42 in the figure denotes a γ-ray density meter, and reference numerals 43, 43 denote electromagnetic flowmeters, and the dilution concentration and the like of the high sand content muddy water can be adjusted based on data obtained from these meters. ing.
[0037]
Next, a method of classifying dredged soil using the above-described classifying apparatus will be described.
[0038]
First, dredging mud mixed with dredged soil and water is sent from the dredging means 20 to a mud feeding pipeline by a pump 20a.
[0039]
The dredged muddy water pumped through the mud feeding pipe passes through a classification branch pipe 24 constituting a coarse classification means 21 provided in the middle of the mud feeding pipe. At this time, fine particles such as silt and clay flow over the entire step surface in the pipe at a substantially uniform concentration, whereas coarse particles such as sand concentrate on the lower side of the pipe and flow while rolling and sliding. , Low mud containing mainly silt, etc., to the upper classifying passage 25 through the upper partition passage 30a, and high mud containing mud mainly containing sand passes through the lower passage 30b of the partition plate for lower classification. It is sent to a passage 26, that is, a classification treatment pipeline. Accordingly, the low sand content muddy water is sent to the sedimentation treatment tank 27 through the upper classification path 25, and the high sand content muddy water is sent to the dilution water mixing means 23 through the lower classification path 26.
[0040]
The inside of the mud pipe constituting the lower classifying passage 26 is continuously pressurized by the high sand content, and the high sand content mud sent to the dilution water mixing means 23 is pressurized. Then, it is discharged from the ejection nozzle 34. At this time, the pressure around the ejection nozzle 34 is reduced by the negative pressure generated at the time of discharge, and the surface water is sucked as dilution water from the sedimentation basin 27 communicating with the dilution water supply unit 35, and the surface water is discharged from the ejection nozzle 34. The mixture is mixed and diffused by the highly sandy and muddy water discharged from 34 and the diffusion in the tapered portion 36.
[0041]
By diluting the high sand content mud in this way, as shown in FIG. 6 (the figure shows the case where the branching ratio of the classification branch pipe is 50%: 50%), the concentration of the sand content increases due to the classification. The viscosity coefficient μ of the mother liquor (ie, water containing silt) can be reduced, and the viscosity coefficient μ of the mother liquor decreases, as derived from the Stokes equation. It becomes large, and the sand can be easily classified.
[0042]
The Stokes equation is
v = 1/18 · g (ρ′−ρ) · d ² / μ
Where v is the terminal sedimentation velocity (cm / s), g is the gravitational acceleration (cm / s ² ), ρ ′ is the density of the particles (g / cm ³ ), and ρ is the density of the medium. (G / cm ³ ), d is the particle diameter (cm), and μ is the viscosity coefficient (g / cm · s) of the mother liquor.
[0043]
The diluted highly sandy mud is fed into the sedimentation and classification tank 22, where the coarse components such as sand and gravel are settled in the sand sedimentation section on the upstream side, and the fine-grained components are separated on the downstream side. Is discharged into the sedimentation basin 27 by overflow along with surface water.
[0044]
Finally, the sand separated from the other components is collected by a sand collecting means such as a backhoe and sent to a sand stock yard.
[0045]
Note that, in the above-described embodiment, an example in which surface water of the sedimentation treatment pond is used as the dilution water is described. However, the present invention is not limited to this.
[0046]
【The invention's effect】
As described above, the method for classifying dredged soil according to the present invention can efficiently obtain high-quality sand, sand and gravel at a high recovery rate with little energy.
[0047]
In addition, if the surface water of the sedimentation treatment pond is used as the dilution water, there is no need to discharge the surface water to the surrounding water area and the like. .
[0048]
Further, the dilution of the high sand content mud can be performed automatically and continuously without the need for a device requiring a power source other than the dredging means, and the energy efficiency is improved. Further, since the effect of diluting and washing the high-sand content muddy water is obtained, higher quality sand can be obtained.
[0049]
In addition, if a classification branch pipe is used, it is possible to reduce only the water content without reducing the sand content in the dredged soil, the sand loss in the classification work is small, and the sand content can be taken out at a high recovery rate. Thus, the amount of sand can be relatively increased as compared with the related art.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an outline of a method for classifying dredged soil according to the present invention.
FIG. 2 is a front view showing a classification branch pipe in FIG. 1;
FIG. 3 is a longitudinal sectional view of the same.
FIG. 4 is a sectional view taken along line AA in FIG.
FIG. 5 is a longitudinal sectional view showing a dilution water mixing means in FIG. 1;
FIG. 6 is a block diagram for explaining the principle of the above.
FIG. 7 is a flowchart showing an outline of an example of a conventional dredged soil classification method.
FIG. 8 is a flowchart schematically showing another example of the above.
FIG. 9A is a front view showing an example of a conventional classifier, and FIG. 9B is a longitudinal sectional view of the same.
[Explanation of symbols]
Reference Signs List 20 dredging means 20a pump 21 coarse classification means 22 sedimentation classification tank 23 dilution water mixing means 24 classification branch pipe 25 upper classification path 26 lower classification path 27 sedimentation treatment tank 28 main body 29 partition plate 30a partition plate upper channel 30b partition plate Lower flow path 31 Branch cylinder part 32 Guide plate 33 Straightening piece 34 Jet nozzle 35 Dilution water supply part 36 Taper part 37 Sand sedimentation part 38 Submerged weir 39 Sand collection means 40 Sand stock yard 41 Open / close valve 42 Gamma ray density meter 43 Electromagnetic flow meter

Claims (5)

In the middle of a mud feed pipe through which dredged muddy water mixed with dredged soil and sand containing sand is pumped, coarse classification means for separating into coarse particles and fine particles is provided, and the coarse classification means is provided. The dredged mud flow in the mud pipe is divided into low-sand muddy water and high-sand muddy water, and the divided low-sandy muddy water is sent to a sedimentation treatment pond as it is, and the high-sandy muddy water is mixed with the low-sandy muddy water. Is fed into another pipe line for classification treatment, and a dilution water mixing means is provided in the middle of the pipe line, and the dilution water mixing means dilutes into the pipe line by utilizing the feeding pressure of the high sand-containing muddy water. The water is sucked and mixed with the high sand content muddy water, and the diluted high sand content mud water is sent to the sedimentation classification tank, and the coarse component is precipitated in the sedimentation classification tank and the fine particle component is passed through with water. A method for classifying dredged earth and sand, comprising separating sand. The dilution water mixing means includes an ejection nozzle that narrows the downstream side of the classification processing pipeline, a dilution water supply unit that supplies dilution water around the ejection nozzle, and a neck that narrows the downstream side of the dilution water supply unit. Using an eductor having a tapered portion having a neck portion expanded at a downstream side thereof, and sucking dilution water by a negative pressure generated when the high sand content muddy water on the upstream side of the classification pipe is discharged from the jet nozzle. The method for classifying dredged soil according to claim 1, wherein the dilution water is mixed and diffused in the high sand content muddy water by diffusion in the tapered portion. 3. The method for classifying dredged soil according to claim 1, wherein the dilution water uses surface water of a sedimentation treatment pond into which low sand content muddy water has been fed. 4. The coarse classifying means is provided with a plurality of classifiers in the middle of a mud feeding pipe for transporting the dredged muddy water, by dividing the mud feeding pipe up and down, and providing a classifying treatment pipe downstream of the lower classifying pipe. The method for classifying dredged soil according to claim 1, 2 or 3, wherein the classification is performed. The sedimentation classification tank is provided with a sand sedimentation part on the upstream side where the high-sand content muddy water diluted by the dilution water mixing means flows, and a sedimentation classification tank is provided at the downstream end of the sand sedimentation part on the upstream and downstream sides. 5. The method for classifying dredged soil according to claim 1, wherein the submerged weir partitioning from the side is movable to the upstream and downstream sides.

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