JP2007289866A - Treatment method of dredged soil from sea bottom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method of dredged soil from a sea bottom which can stably perform treatment processes for washing and dehydrating fine granular soil separated from the dredged soil from a sea bottom. <P>SOLUTION: Treated fine granular soil 7 capable of being used as a cement raw material is obtained by carrying out a wet storage process for supplying fine granular soil 6 obtained by classifying the dredged soil 5 from a sea bottom by a classification apparatus 2 to a storage tank 3 in which water of a volume capable of forming a water surface is made to exist, and a fine granular soil treatment process for taking out the fine granular soil from the storage tank 3 in the wet storage process, and dehydrating the fine granular soil by dehydration equipment 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel method for treating submarine dredged soil (hereinafter sometimes simply referred to as “dred”). Specifically, it is a method for treating submarine clay that can stably carry out a treatment process of washing and dewatering fine soil separated from the submarine clay.

  Dredging work to construct a new port, formation, expansion, and deepening of the route, and dredging work (maintenance dredging) to maintain the depth of the route and anchorage.

  In the past, the submarine dredged soil discharged by these dredging works has been used for land reclamation in the coastal area or treated by methods such as ocean dumping.

  In recent years, a review of past disposal methods has been demanded as industrial structures have changed and interest in environmental issues has increased.

  As a treatment method for effectively using such submarine clay as a resource, a method of cleaning the submarine clay and using the obtained washed material as a cement raw material has been proposed (see Patent Document 1). In this method, submarine dredged soil is separated into coarse-grained soil such as sand and gravel and fine-grained soil such as silt, the fine-grained soil is washed to reduce salinity, and the resulting washed product is used as a cement raw material. To do.

However, dredged by dredging is not occurring on average throughout the year, moreover, in the practice of dredging is mass in a short period of time, for example, also be the amount which can reach the number per 1 hour 100 m ³ is there. And the above-mentioned fine soil processing equipment, which has great merit for use as a cement raw material, requires a lot of time for washing and dehydration due to the small particles to be processed. A situation occurs where the field is left untreated for a long time.

  However, the above-mentioned fine soil often contains sludge, and not only environmental pollution due to odor is concerned, but the fine soil is scattered by the wind by drying or solidified to wash out the salt content. This causes a problem that the remarkably decreases.

  In order to solve the above problem, it is possible to increase the size of the processing device in accordance with the amount of dredged soil generated in large quantities in a short period of time. However, as mentioned above, dredged soil is generated on an average throughout the year. Therefore, in the next period when dredging work is interrupted, there are concerns that the capacity utilization rate will decrease and maintenance will be expensive.

JP-A-11-35350

  Accordingly, an object of the present invention is to provide a method for treating subsea dredged soil that can stably and reliably carry out a large amount, a process of washing and dewatering fine soil separated from the submarine dredged soil. There is to do.

  As a result of repeated research to solve the above problems, the present inventors have stored the fine soil as a means for storing fine soil obtained by classifying the submarine dredged soil without contact with the outside air. As a result, it was found that the problem of odor can be greatly solved. And based on such knowledge, as the storage tank for storing the fine soil, a water surface can be formed in a state in which the fine soil is stored, that is, a storage tank in which an amount of water in which the fine soil is submerged is used. By doing so, the problem of odor caused by finely divided soil is solved, and in the subsequent dewatering treatment step, even when the finely divided soil is stored for a long time, it is easy to wash and dewater, and it is found that all of the above problems can be solved. The present invention has been completed.

  That is, the present invention provides a wet storage process for supplying and storing fine soil obtained by classifying submarine dredged soil in a storage tank in which an amount of water capable of forming a water surface is present, and the wet storage process described above. It is the processing method of the submarine dredged soil which includes taking out the fine soil from the storage tank and dewatering the fine soil.

  In addition, the present invention provides a method for treating submarine dredged soil using the treated fine soil obtained from the fine soil treatment step as a cement raw material.

  Moreover, this invention provides the processing method of the submarine dredging which adjusts the salt concentration (NaCl conversion) in the storage tank in the said wet storage process to 5 g / L or less.

  Furthermore, this invention provides the processing method of the submarine dredging whose storage tank in the said wet storage process is an industrial sedimentation basin.

  According to the present invention, by providing a storage tank for finely divided soil obtained by separating from submarine dredged soil, a large amount of processing equipment is not required for the treatment of the finely divided soil, and the amount of treatment that averages the amount of annual treatment. Therefore, the processing equipment can be operated in a stable manner.

  In addition, even when untreated fine soil is stored for a long period of time by carrying out “wet storage” in which an amount of water that can form a water surface in the state in which fine soil is stored is present in the storage tank. The generation of odor is suppressed, and the fine soil is not solidified (dried) during storage, and can be washed efficiently even when it is washed.

  Furthermore, it is also possible to obtain a treated fine soil that can be used as a cement raw material by performing only dehydration substantially by adjusting the salinity of the water in the storage tank to a low level.

  Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the accompanying drawings.

  FIG. 1 is a schematic view showing one embodiment of a method for treating submarine clay of the present invention.

  In the present invention, the fine-grained soil obtained by classifying the clay does not have a strict range in size, but indicates the relative size of the coarse-grained soil to be classified.

  However, the effect of the present invention can be sufficiently exerted by a relatively large number of fine particles. The fine particle soil in which the present invention is effective is a coarse-grained soil having a particle size of 75 μm or more, preferably 30 wt% or less, preferably 20 It is classified so as to be less than wt%.

  In addition, the proportion of the fine soil in the clay is largely about 30 to 99% by weight, although it varies greatly depending on the type and location of the clay.

  In FIG. 1, the fine soil 6 is obtained by lifting the dredged soil 5 carried by the carrier 1 to the hopper 9 by the cargo handling equipment 8, and by the classifying equipment 2, the coarse grained soil (the unloading position is not shown) and the fine soil Classified. The classified fine soil is sent from the pipe 10 to the storage tank 3 in the wet storage process.

  In the above FIG. 1, the mode of landing and classifying dredged soil is illustrated, but classification may be performed at another place, for example, on the ocean at dredging, or on another land as necessary. Well, it is possible to carry only fine soil. Moreover, the carrying-in may be carried out by a transport ship or by land transportation such as a truck.

  Moreover, a well-known thing is used for the said classification equipment without a restriction | limiting in particular. For example, if necessary, a vibrating screen such as a trommel, vibro screen, or vibrating conveyor is used as a pretreatment device, a classifier for classifying fine soil, a classifier using centrifugal force, such as a liquid cyclone, etc. And a classifier using the difference in sedimentation properties of particles, for example, a decanter classifier.

  The method for treating submarine dredged soil according to the present invention includes a wet storage step of supplying and storing the finely divided soil obtained by classifying dredged soil to a storage tank 3 in which an amount of water capable of forming a water surface is present. Have.

  In addition, the fine particles after classification can be sent to the storage tank after dehydration, or by performing classification and dehydration at the same time, reducing the salt content brought into the storage tank, It is effective in improving the cleaning efficiency of the fine soil performed as necessary.

  The storage tank 3 is a container for storing the untreated fine soil 3 and, therefore, its capacity needs to be able to store the fine soil temporarily generated by dredging. The specific capacity is appropriately determined according to the scale of the dredging project to be implemented and the proportion of fine soil in the dredged soil.

  Moreover, since the storage tank 3 makes water exist, it has the function to store water. For example, a tank constituted by a non-permeable structural material, a pool constructed by excavating the ground and water-stopping the wall surface, an existing industrial sedimentation basin and the like can be mentioned. Among them, it is preferable to use an existing industrial sedimentation basin having a large capacity and requiring no capital investment.

In the wet storage process of the present invention, it is important to allow the storage tank 3 to have an amount of water that can form a water surface after the fine soil 6 is supplied in order to achieve the object of the present invention. That is, when the amount of water is insufficient, the odor generation from the fine soil exposed from the surface of the water is severe during long-term storage, and it is scattered by drying or the surface is solidified. Also decreases.
It is also effective to provide the storage tank 3 with an agitation function or a static stabilization function as necessary.

  The amount of the water is preferably 2 times or more, and preferably 3 times or more, by weight with respect to the fine soil, so that the fine soil is immersed in water and the water surface is reliably formed.

  The water is not particularly limited, such as industrial water, fresh water such as rainwater, industrial wastewater, seawater and the like. However, when using fine soil as a cement raw material, it is preferable to use water having a low salinity concentration in order to reduce or eliminate the washing load in the dehydration process described later. More preferably, the salt concentration in the aqueous phase of the storage tank 3 is adjusted to 5 g / L or less, preferably 1 g / L or less, with water having such a low salt concentration.

The processing method of the submarine dredged soil of this invention has a fine soil processing process following the said wet storage process. This fine soil treatment process is a process of taking out a part of the fine soil 6 from the storage tank 3 of the wet storage process and dehydrating the fine soil.
In FIG. 1, a mode in which the fine soil 6 is pumped up in a slurry state from the storage tank 3 by the pump 13 and is supplied to the dehydration equipment 4 through the pipe 11 is shown. Of course, the method of taking out the fine soil from the storage tank is not limited to the above method, and a known method using a general sand pump or the like is employed without any particular limitation.

  Moreover, the dehydration equipment 4 may have a function of washing with water as necessary, and a separate washing equipment may be provided in front of the dehydration equipment. Examples of the dehydration equipment include a filter press, a centrifuge, a belt press, and a screw press. Among them, devices such as a filter press and a centrifuge are preferable because they can add a washing function.

  In the present invention, the treated fine soil 7 treated in the fine soil treatment step can be suitably used as a cement raw material.

  In addition, as shown in FIG. 1, the waste water generated by dehydration or washing in the dehydration facility can be used by circulating in the storage tank 3 by providing a pipe 12. Moreover, although not shown in figure, the said waste_water | drain can also be used as classification water of the classifier 2. FIG.

  In the present invention, the coarse-grained soil obtained by the classification can be used as a building material by washing with a separate facility, or as a material for coastal regeneration without washing.

  In order to confirm the effect of the wet storage process of the present invention, the following experiment was conducted.

Example 1
After adding 1 L of industrial water to a 2 L beaker, after adding 100 g of wet fine soil with a particle size of 75 μm or more classified from the submarine dredged soil of Tokuyama Port to 10 wt% or less Stir with stirring. A water surface was formed in the beaker, and no fine soil was exposed.

  In the vicinity of the beaker, almost no odor was felt. Moreover, after performing said storage for 2 weeks, when the salt concentration of the beaker water phase was measured, it was 0.6 g / L.

  Next, the slurry containing fine soil was pumped from the bottom of the beaker, and washed and filtered on the filter paper set in the funnel. As a result, a treated fine soil having a salt concentration of 0.17% by weight was obtained.

  For comparison, the classified fine soil was put in an empty beaker in a wet state. As a result, odor was felt around the beaker. Moreover, when the storage in the above state was performed for 2 weeks, almost the whole was solidified by drying. As a result of performing water washing and filtration on the filter paper set in the funnel, work for repulping the solidified material occurred, and washing was difficult.

Schematic showing a typical embodiment of the method of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carrier ship 2 Classifying equipment 3 Reservoir 4 Dewatering equipment 5 Dredging 6 Fine soil 7 Treated fine soil 8 Handling equipment 9 Hopper

Claims (5)

A wet storage process in which fine soil obtained by classifying submarine dredged soil is supplied to and stored in a storage tank in which an amount of water that can form a water surface is present, and the fine soil from the storage tank in the wet storage process A method for treating submarine dredged soil, comprising a fine soil treatment step of taking out the fine soil and dehydrating the fine soil. The method for treating submarine dredged soil according to claim 1, wherein the fine-grained soil is 30 wt% or less of coarse-grained soil having a particle diameter of 75 µm or more. The processing method of the submarine dredged soil of Claim 1 or 2 which uses the processed fine soil obtained from the said fine soil processing process as a cement raw material. The processing method of the seabed dredged material in any one of Claims 1-3 which adjusts the salt concentration (NaCl conversion) in the water in the storage tank in the said wet storage process to 5 g / L or less. The storage method in the said wet storage process is an industrial sedimentation basin, The processing method of the submarine dredged material in any one of Claims 1-4.

Images