JP2011012202A - Method for treating sedimented soil at bottom of water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for efficiently produce a granulated product with high mechanical strength and good stability from sedimented soil at the bottom of the water.SOLUTION: The granulated product can be efficiently produced from sedimented soil at the bottom of the water by using, in combination, paper sludge-incinerated ash and a calcium-containing solidifying auxiliary. The granulated product thus produced has moderate mechanical strength and size and maintains the mechanical strength underwater, therefore can be suitably used in applications including developing artificial dry beaches, shore protections, and inhibiting soil outflows.

Description

  The present invention relates to a soil improvement technique, and more particularly to a technique for solidifying and granulating sediment sediment on the bottom of water.

  In order to solidify sludge, sludge and other soft mud, soil that tends to flow out, and soil on soft ground to suppress soil outflow, various solidifying agents have been conventionally added to soft mud and sludge for treatment. It has been broken. As a solidifying agent at that time, a cement-based solidifying agent is generally used for inorganic soil, and a lime-based solidifying agent is generally used for organic sludge such as manure sludge.

  However, the cement-based solidifying agent solidifies the soil using the hydration hardening reaction of cement, and the hardening reaction of cement is inhibited by organic substances. Therefore, it is not effective to use a cement-based solidifying agent for a treatment target containing an organic substance such as dredged sand obtained from the bottom of the water, and a solidified product having sufficient strength cannot be obtained. Further, the lime-based solidifying agent has a problem that alkali is eluted after the solidification treatment, and from the viewpoint of environmental conservation, the lime-based solidifying agent is not suitable for uses such as soil outflow suppression, land reclamation, and revetment. Furthermore, dredged soil obtained from the bottom of the water contains a large amount of salt derived from seawater and has a high water content, and therefore, a general soil solidifying agent is often not effective for sediment at the bottom of the water.

  Therefore, various studies have been conducted to develop a solidification technique suitable for sediments on the bottom of the water. For example, the following techniques have been reported. That is, Patent Documents 1 to 6 describe a technique for solidifying dredged sand using polyvinyl alcohol. Patent Document 7 describes a technique for solidifying seabed sludge using ferrous sulfate. Furthermore, Patent Document 8 describes a technique for manufacturing a fish reef block from dredged soil.

JP 2008-253163 A JP 2007-167790 A JP 2007-007587 A JP 2006-325514 A JP 2006-325515 A JP 2005-131595 A JP 2005-334730 A JP 2008-182898 A

  However, the conventional technology related to the solidification of the bottom sediment is not technically or economically practical because it requires special treatment or expensive treatment agent, or uses a large amount of treatment agent. It was highly desired to develop an excellent method for treating bottom sediments.

  Then, the subject of this invention is providing the technique which obtains a granulated material simply and economically from the bottom sediment with high moisture content.

  The present inventor has eagerly studied to solve the above-mentioned problems, and by using incinerated ash of paper sludge and a solidification aid containing calcium together, the bottom sediment can be effectively solidified to obtain a granulated product. As a result, the present invention has been completed.

  In one embodiment, the present invention is a soil conditioner, in particular, a bottom sediment soil solidifying agent comprising paper sludge incineration ash and a solidification aid containing calcium. In another aspect, the present invention relates to a method for producing a granulated product, and more particularly to a method for producing a granulated product from bottom sediment and paper sludge incineration ash. In yet another aspect, the present invention relates to a soil improvement method, and more particularly, to a method for suppressing sediment discharge and improving soil by using a granulated product produced from paper bottom sediment using paper sludge incineration ash or the like.

Although this invention is not limited to the following, the following invention is included.
(1) A solidifying agent for bottom sediment, comprising paper sludge incinerated ash and a solidification aid containing calcium.
(2) A method for producing a granulated material from bottom sediment, including adding paper sludge incinerated ash and a solidification aid containing calcium to the bottom sediment.
(3) The method according to (2), wherein the paper sludge incineration ash comprises 20% by weight or more of calcium in terms of CaO.
(4) The method according to (2) or (3), wherein the solidification aid containing calcium is one or more selected from the group consisting of quicklime, calcium sulfate, and calcium hydroxide.
(5) The addition amount of the solidification aid containing calcium is 3 to 15% by weight with respect to the total weight of the bottom sediment and the paper sludge incineration ash, according to any one of (2) to (4) the method of.
(6) The method according to any one of (2) to (5), wherein the added amount of the paper sludge incineration ash is 100 to 400% by weight with respect to the solid weight of the bottom sediment.
(7) The method according to any one of (2) to (6), wherein the granulated product contains 40% by weight or more of particles having a diameter of 2 mm or more.
(8) A soil improvement method comprising introducing the granulated product obtained by the method according to any one of (2) to (7) into water.

  According to the present invention, a granulated material can be efficiently obtained from bottom sediment. In addition, the granulated product of the present invention has a certain level of strength, and since it has the property of increasing strength in water, it can be suitably used for land reclamation, revetment, creation of artificial tidal flats, etc. It is also useful for environmental conservation, such as suppression of environmental problems. Furthermore, since the present invention obtains a granulated material using waste such as bottom sediment and incineration ash of paper sludge, it is extremely superior in cost and advantageous from the viewpoint of waste reduction.

1 is an X-ray diffraction chart of dredged sand used in Example 1. FIG. FIG. 2 is an X-ray diffraction chart of the paper sludge incineration ash used in Example 1. FIG. 3 is an X-ray diffraction chart of the granulated product obtained in Example 1.

  In one aspect, the present invention relates to a submerged sediment soil solidifying agent comprising paper sludge incineration ash and a solidification aid containing calcium. In another aspect, the present invention relates to a method for producing a granulated product from bottom sediment, which comprises adding paper sludge incinerated ash and calcium-containing solidification aid to the bottom sediment and granulating it. In this invention, the granulated material which has moderate intensity | strength can be obtained from the bottom sediment soil which is soft mud by using the incineration ash of paper sludge and the solidification adjuvant containing calcium together.

Water bottom sediment present invention relates to granulation technique Subaqueous soil, the water bottom sediment in the present invention refers to the sediment deposited on the bottom of the water such as sea or lakes, rivers. The technique of the present invention may be applied as it is at the site such as the bottom of the water to granulate the bottom sediment, or may be granulated by applying the present invention to the soil dredged from the bottom of the water. The bottom sediment in the present invention may be a sediment in a freshwater environment such as a lake or a river, or a bottom sediment in a seawater environment such as a sea or a harbor. The dredged material used in the present invention refers to the material that is dredged from the bottom of the water for the purpose of channel dredging and sludge purification. In general, dredged soil is obtained when removing sludge in lakes and bays for environmental conservation, or when removing sediment accumulated in the channel, and transported to eroded beaches, etc. for land reclamation and revetment work in coastal areas. It may be used for such purposes.

  In the present invention, the bottom sediment can be used in any state such as a soft mud state or a cake state after dewatering. In a preferred embodiment, the water content of the bottom sediment when treated with paper sludge incineration ash is 10 to 65% by weight, more preferably 30 to 60% by weight. If it is a bottom sediment with such a water content, the concentration of the bottom sediment is high, so that a solidified product can be obtained efficiently, and since it has an appropriate fluidity, it is suitable for transportation and granulation treatment. .

  When dredged soil is used as the bottom sediment in the present invention, it can be obtained from the bottom by a known dredging method. For example, dredged sand can be obtained by a grab dredge or a pump dredge. Here, the grab dredging is to dig up the bottom sediment with a grab suspended from a dredger or the like, and is generally used for small dredging. Pump dredging is the use of a pump to dig up the sediment at the bottom of the water. Since the sediment can be continuously sucked in, the mud can be dredged widely and thinly (thin layer dredging), enabling large-scale and uniform dredging. It is. In the present invention, the dredging method for obtaining dredged soil is not particularly limited, for example, when dredging sludge on the bottom of the water, while the accumulation height of sludge is about several tens of cm, while suppressing sludge soaring, A method for thinning the sludge layer may be selected.

Paper sludge incineration ash The present invention uses paper sludge incineration ash. In the present invention, paper sludge (PS) refers to waste recovered from the papermaking process, and includes, for example, waste generated from a used paper recycling process (DIP manufacturing process), a pulp manufacturing process, a paper manufacturing process, and the like. . Accordingly, the paper sludge is configured to include pulp fibers, inorganic substances derived from fillers and pigments (kaolin, talc, calcium carbonate, etc.), inks, inks, adhesives, and the like. The paper sludge that is the raw material for the incinerated ash is particularly preferably paper sludge generated from the used paper recycling process from the viewpoint of calcium content and the like. In general, paper sludge is discharged in large quantities from a paper mill or the like, and paper sludge incineration ash is easily available. Therefore, the water bottom sedimentation solidifying agent of the present invention is particularly advantageous from the viewpoints of waste reduction, availability, economy, and the like.

  The paper sludge incineration ash (PS ash) used in the present invention is an incineration residue obtained by burning paper sludge, and contains an inorganic substance derived from calcium carbonate, cinnabar, talc, kaolin and the like as a main component. The paper sludge incineration ash of the present invention may contain fly ash (fly ash) or furnace bottom ash captured by a dust collector or the like as long as it is an incineration residue of paper sludge. Paper sludge can be incinerated at a temperature of about 700 to 1500 ° C., for example. Moreover, paper sludge can be incinerated using a well-known incinerator, Specifically, a fluidized bed incinerator etc. can be mentioned.

In general, since calcium such as calcium carbonate is added to paper as a pigment or filler, incineration ash made from paper sludge has a high calcium content compared to incineration ash from trash and blast furnace slag. Have In a preferred embodiment of the present invention, when the paper sludge incinerated ash of the present invention is subjected to elemental analysis, the CaO ratio in terms of CaO is preferably 20% by weight or more, and more preferably 30% by weight or more. The upper limit of the CaO ratio is not particularly limited, but is generally 60% by weight or less. Further, the paper sludge incineration ash of the present invention also has a relatively high ratio of calcium to aluminum, and the ratio of Al ₂ O ₃ and CaO is preferably about 1: 0.5 to 1: 3. More preferably, it is about 1 to 1: 2.5.

Paper sludge incineration ash in the present invention, when added to high water ooze like water bottom sediment, and water and the hydration reaction in soil, ettringite _{(3CaO · Al 2 O 3 ·} 3CaSO 4 · 32H 2 O) It is thought that the bottom sediments are agglomerated and solidified while producing hydrates and calcium silicate hydrates. Although the details of the reason why a granulated product having an appropriate strength can be obtained from the bottom sediment when using the paper sludge incineration ash of the present invention are not clear, aluminum and calcium contained in the paper sludge incineration ash of the present invention is the bottom sediment. It is thought that it is because it is suitable for self-hardening by reacting with the moisture in it.

  In the present invention, the amount of the paper sludge incinerated ash added is not particularly limited, but in a preferred embodiment, more paper sludge incinerated ash is used than the bottom sediment, for example, 100 to 100% of the solid weight of the bottom sediment. It is preferable to add 400% by weight of paper sludge incineration ash. That is, when a large amount of paper sludge incineration ash is blended with the bottom sediment, the strength of the granulated product is increased, and a stable granulated product can be obtained in the long term.

The solidification aid or the present invention uses a solidification aid containing calcium together with the paper sludge incineration ash in order to obtain a granulated product from the bottom sediment. By using such a solidification aid in combination, a granulated product having a high strength and a long-term stability can be obtained from the bottom sediment, which is soft mud. The solidification aid used in the present invention only needs to contain calcium. For example, natural minerals containing calcium such as quick lime, calcium sulfate, calcium hydroxide, and montmorillonite can be suitably used. Calcium and calcium hydroxide can be used more preferably, and quicklime can be used particularly preferably. Further, the solidification aid may be added to the bottom sediment with the paper sludge incineration ash, or may be added to the bottom sediment without being separated from the paper sludge incineration ash.

  The addition amount of the solidification aid is preferably 2 to 20% by weight and more preferably 3 to 15% by weight with respect to the total weight of the bottom sediment and the paper sludge incineration ash. Within such a range, a granulated product having high strength and a certain particle size can be efficiently produced.

  In the present invention, a paper sludge incineration ash and a solidification aid containing calcium are added to the bottom sediment, and a granulated product is produced. However, the bottom sediment and the additive are sufficiently mixed. For example, the mode of addition is not particularly limited.

Granulated product The shape of the granulated product obtained by the present invention is not limited as long as it is granular. The particle size of the granulated product means a diameter, but when there is a major axis or a minor axis, it indicates the average and can be determined by laser diffraction, microscopic observation or the like. The granulated product of the present invention preferably contains 40% by weight or more of particles having a diameter of 2 mm or more. Such a granulated product is particularly useful because it has a certain size and is not easily exposed to waves even when used in the sea, for example, and can suppress soil runoff in the natural environment. The granulated product of the present invention preferably has an average particle diameter of 1 mm or more, more preferably 2 mm or more. The particle size of the granulated product can be adjusted as appropriate depending on, for example, the amount of the solidifying agent added and the granulation time, and the granulated product has a fixed particle size by a sieving method such as a vibration type or a rotary type. Granules may be obtained.

  When manufacturing a granulated material, a normal granulation technique can be used. The granulation can be performed by a known method, and for example, a granulation method such as a reverse flow method, a rolling method, a stirring method, an extrusion method, or a crushing method can be employed. Specific examples of the apparatus include an intensive mixer (reverse flow type) manufactured by Japan Eirich, and a stand mixer (stirring system) manufactured by Kitchen Aid. It is possible to mix and granulate paper sludge incineration ash, etc. to the bottom sediment, and to use the reverse flow mixer and the mixer of the stirring method suitably because it is easy to adjust the porosity and strength of the granulated product. be able to. There is no restriction | limiting in particular in granulation time, When the granulation time is lengthened, there exists a tendency for the particle diameter of a granulated material to become large, but it does not grow more than fixed size. In the case of using a stirring type mixer, the granulation time is 1 to 5 minutes, preferably 2 to 4 minutes.

  The granulated product thus obtained can be suitably used for purposes such as creation, landfill, revetment, prevention of sediment discharge in the sea, harbor, lake, river, swamp, tidal flat and the like. In particular, when the granulated product of the present invention is placed in an environment such as seawater, the strength of the granulated product increases with time. Although the details of the reason why the strength of the granulated product of the present invention is improved in seawater are not clear, it is assumed that the granulated product is more agglomerated due to the hardening reaction of the granulated product progressed by the salt contained in the seawater. Is done. Since the granulated product of the present invention has sufficient strength in seawater and has the property of improving strength in seawater, the granulated product obtained by solidifying and granulating the bottom sediment is used again in seawater. Is particularly suitable. Furthermore, since such submarine sediments usually contain about 15-16% organic nutrients, granulated products produced from submarine sediments can be placed in the sea as artificial tidal flats, algae reefs, fish reefs, etc. It can be a source of nutrients for living organisms and can greatly contribute to the restoration of the environment in the sea area. From the above points, the granulated product obtained by the present invention is suitable for reclamation and creation of artificial tidal flats.

  Hereinafter, the content of the present invention will be described in detail with reference to examples of the present invention, but the present invention is not limited to the following examples. In the present specification, unless otherwise specified, parts and% are based on weight, and numerical ranges are described as including the end points.

Example 1
(1) Submarine sediment The dredged soil obtained from the sea floor of Shinko, Kumamoto City, Kumamoto Prefecture was used as the bottom sediment. The water content of the dredged sand when mixed with the solidifying agent described later was 60% by weight (solid content 40%). Table 1 below shows the results of elemental analysis (fluorescence X-ray analysis) of this dredged soil. As is apparent from Table 1, this dredged sand was mainly composed of Si and Al. Further, when the dredged sand was analyzed by X-ray diffraction, anorthite (CaAl ₂ Si ₂ O ₈ ), augite, SiO _{2 and the} like were confirmed (FIG. 1).

(2) Paper sludge incineration ash (PS incineration ash)
The incineration residue (incineration ash) obtained by incinerating paper sludge collected from the pulp manufacturing process and papermaking process of a paper mill was used. Paper sludge was incinerated at 800-900 ° C. in a fluidized bed incinerator. Table 2 shows the results of elemental analysis of the obtained paper sludge incineration ash. As is apparent from Table 2, this paper sludge incineration ash was composed mainly of Si, Al, and Ca. From the results of X-ray diffraction, SiO ₂ , gehlenite (CaAl ₂ SiO ₂ ), calcium carbonate, quicklime, etc. were confirmed (FIG. 2).

(3) Mixture of bottom sediment and PS incinerated ash Table 3 shows the results of elemental analysis of the 50:50 mixture of bottom sediment and PS incinerated ash, and FIG. 3 shows an X-ray diffraction chart.

(4) Granulation treatment of bottom sediment soil To 450 g of the above dredged sand (solid content: 180 g), 220 g of paper sludge incineration ash (PS ash), 20 g of quick lime (CaO), and 10 g of water are added to reduce the water content of the mixture to 40 g. %, And a granulated product was produced by treating for 3 minutes using a stand mixer (KSM50P, manufactured by Kitchen Aid) (Table 3: Sample 1). Moreover, the granulated material was manufactured like the above with the composition shown in Table 3 (Table 3: Samples 2 to 10). At this time, water was added so that the water content after mixing was 40%.

  In order to evaluate the particle size distribution of the obtained granulated product, the ratio of the granulated product having a diameter of 2 mm or more was measured using a sieve. The compressive strength of the granulated product was measured using a ring crush tester (manufactured by Nippon TMC) under the condition that the compression plate descended at a rate of 12.5 mm / min. . The compression strength was measured using a granulated product having a particle size of 2 mm.

  As is clear from Table 4, when the amount of quicklime, which is a solidification aid, is increased, the particle size of the resulting granulated product is increased, and the tendency for the compressed product to increase in compressive strength is confirmed (sample). 5-10). Moreover, when the addition amount of paper sludge incineration ash was increased, the granulated material of 2 mm or more decreased, and there existed a tendency for the compressive strength of a granulated material to become high (samples 1-4).

Example 2
A granulated material was produced in the same manner as Sample 1 of Example 1, and allowed to stand for 4 days. The granulated product was allowed to stand in seawater, and the change over time of the granulated product was followed.

  Table 5 shows the results of elemental analysis and measurement of compressive strength. As can be seen from Table 5, the compression strength of the granulated material has improved to about 1.5 times after 7 days from the production of the granulated material. It was confirmed that the strength was improved.

Claims (8)

  A solidifying agent for bottom sediment, comprising paper sludge incineration ash and a solidification aid containing calcium.   A method for producing a granulated product from bottom sediment, comprising adding paper sludge incinerated ash and a solidification aid containing calcium to the bottom sediment.   The method according to claim 2, wherein the paper sludge incineration ash comprises 20% by weight or more of calcium in terms of CaO.   The method according to claim 2 or 3, wherein the solidification aid containing calcium is one or more selected from the group consisting of quicklime, calcium sulfate, and calcium hydroxide.   The method of any one of Claims 2-4 whose addition amount of the solidification adjuvant containing calcium is 3 to 15 weight% with respect to the total weight of bottom sediment soil and paper sludge incineration ash.   The method of any one of Claims 2-5 that the addition amount of paper sludge incineration ash is 100 to 400 weight% with respect to the solid content weight of bottom sediment.   The method according to any one of claims 2 to 6, wherein the granulated product contains 40% by weight or more of particles having a diameter of 2 mm or more.   The soil improvement method including throwing in the water the granulated material obtained by the method of any one of Claims 2-7.

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