JP2017064605A - Treatment method of heavy metal polluted water in shield construction - Google Patents

Treatment method of heavy metal polluted water in shield construction Download PDF

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JP2017064605A
JP2017064605A JP2015191310A JP2015191310A JP2017064605A JP 2017064605 A JP2017064605 A JP 2017064605A JP 2015191310 A JP2015191310 A JP 2015191310A JP 2015191310 A JP2015191310 A JP 2015191310A JP 2017064605 A JP2017064605 A JP 2017064605A
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iron powder
mud
muddy water
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soil
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JP6599190B2 (en
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小林 修
Osamu Kobayashi
修 小林
卓人 中山
Takuto Nakayama
卓人 中山
市川 政美
Masami Ichikawa
政美 市川
広志 中島
Hiroshi Nakajima
広志 中島
田中 孝
Takashi Tanaka
孝 田中
田中 徹
Toru Tanaka
徹 田中
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戸田建設株式会社
Toda Constr Co Ltd
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PROBLEM TO BE SOLVED: To increase a ratio of clean soil in which heavy metals are not mixed as high as possible in a classification step for classifying concentrated muddy water in which iron powder is mixed into the clean soil in which iron powder is not mixed and the contaminated soil in which the iron powder is mixed as to a treatment of dug sand (excess sludge) containing heavy metals generated in the shield construction.SOLUTION: A treatment method of heavy metal sludge water generated in the shield construction includes a muddy water concentration step B for adjusting excess muddy water generated in the shield construction to concentrated muddy water having specific gravity of 1.4±5% by a concentration decanter 5, a mixing and stirring step C for making the iron powder absorb the heavy metals by stirring for from 10 to 60 minutes by mixing the iron powder for absorbing the heavy metals at a ratio of from 1 to 5% by weight to a sand weight in the concentrated muddy water, and a classification step D for classifying into clean soil in which the iron powder is not mixed and contaminated soil in which the iron powder is mixed by sending the concentrated muddy water in which the iron powder is mixed to a magnetic separator 9.SELECTED DRAWING: Figure 1

Description

本発明は、シールド工事で発生した重金属を含む掘削土砂(余剰泥水)の処理に係り、分級工程において重金属が混入していない浄化土の割合を可及的に高めたシールド工事における重金属汚泥水の処理方法に関する。   The present invention relates to the processing of excavated earth and sand (surplus mud water) containing heavy metal generated in shield construction, and heavy metal sludge water in shield construction in which the ratio of purified soil not containing heavy metals in the classification process is increased as much as possible. It relates to the processing method.
現在、首都圏では鉄道や道路整備を目的としたシールド工事での大深度・大断面施工が増加している。地質的にみると大深度となる地下40m以深では上総層群が多く堆積しており、この上総層群の固結シルト層からは環境基準値を超える砒素をはじめとする自然由来の重金属の溶出が確認されている。大断面シールド工事では、大量の掘削土砂(汚泥)が発生する。この土砂が重金属が混入した汚染土である場合、この土砂は管理型処分場で処分する必要があるが、その受け入れ量は限られているうえに、処理コストも甚大なものとなる。   Currently, in the Tokyo metropolitan area, large-depth and large-section construction is increasing for shield construction for the purpose of railway and road maintenance. Geologically, the Kazusa Group is deposited a lot deeper than 40m below the ground, and from the consolidated silt layer of this Kazusa Group, elution of naturally derived heavy metals including arsenic exceeding the environmental standard value Has been confirmed. Large-scale shield construction generates a large amount of excavated soil (sludge). When this earth and sand is contaminated earth mixed with heavy metals, it is necessary to dispose of this earth and sand at a controlled disposal site. However, the amount of the earth and sand received is limited, and the processing cost is enormous.
そこで、重金属が混入した汚染土の量を低減するために、汚染土を基地内で重金属が混入した汚染土と重金属が混入されていない浄化土とに分級処理する試みが研究・開発されている。   Therefore, in order to reduce the amount of contaminated soil mixed with heavy metals, an attempt to classify the contaminated soil into contaminated soil mixed with heavy metals and purified soil not mixed with heavy metals is being researched and developed. .
例えば、下記特許文献1では、重金属で汚染された土壌を浄化する方法であって、重金属で汚染された土壌に対し、水と鉄粉と重金属の移動を促す薬剤を加えて攪拌し、土壌中の重金属を鉄粉に担持させる第1工程と、次いで第1工程で重金属を担持した鉄粉を土壌から分離する第2工程からなる土壌の浄化方法が開示されている。   For example, Patent Document 1 below is a method for purifying soil contaminated with heavy metals, adding water, iron powder, and a chemical that promotes the movement of heavy metals to the soil contaminated with heavy metals, and stirring the soil. A soil purification method comprising a first step of supporting heavy metal on iron powder and a second step of separating the iron powder supporting heavy metal from the soil in the first step is disclosed.
下記特許文献2では、重金属を含有する汚染水から前記重金属を除去する重金属汚染水の処理方法であって、前記重金属を含有する汚染水に鉄を含有する鉄含有粒子を混合して、前記鉄含有粒子に前記重金属を付着させる混合工程と、前記混合工程において前記汚染水に混合された前記鉄含有粒子を前記汚染水から磁気により分離して回収する磁気分離工程と、前記磁気分離工程において回収された前記鉄含有粒子を、再度汚染水に混合するために返送する返送工程とを含む重金属汚染水の処理方法が開示されている。   In the following Patent Document 2, a method for treating heavy metal contaminated water that removes the heavy metal from contaminated water containing heavy metal, the iron containing particles containing iron mixed with the contaminated water containing heavy metal, the iron A mixing step of attaching the heavy metal to the contained particles, a magnetic separation step of separating and collecting the iron-containing particles mixed in the contaminated water in the mixing step by magnetism from the contaminated water, and a recovery in the magnetic separation step A method for treating heavy metal-contaminated water is disclosed, including a return step of returning the iron-containing particles that have been returned to mix again with the contaminated water.
更に下記特許文献3では、掘削工事で生じた重金属を含む掘削土に重金属吸着用の鉄粉を添加する鉄粉添加工程と、重金属を吸着した前記鉄粉を含んだ掘削土を遠心分離機に供給し、当該遠心分離機によって、前記掘削土から重金属を吸着した前記鉄粉を分離する鉄粉分離工程とを含む汚染土壌浄化方法が開示されている。   Further, in Patent Document 3 below, an iron powder addition step of adding iron powder for heavy metal adsorption to excavated soil containing heavy metal generated by excavation work, and excavated soil containing the iron powder adsorbed heavy metal to a centrifuge A method for purifying contaminated soil is disclosed, including an iron powder separation step of supplying and separating the iron powder having adsorbed heavy metal from the excavated soil by the centrifuge.
特開2000−51835号公報JP 2000-51835 A 特開2011−56483号公報JP 2011-56483 A 特開2014−188408号公報JP 2014-188408 A
前記特許文献1〜3による重金属の除去方法は、いずれも汚染土中に鉄粉を混入し、この鉄粉に重金属を吸着させた後、この鉄粉を分離・回収するものである。この処理方法による汚泥中に混入している重金属の回収率は、鉄粉の回収率に依存することになるが、前記特許文献2において磁気分離装置の場合は、鉄粉の回収率はほぼ100%近いことが記載されているとともに(段落[0030]参照)、既往の文献(非特許文献1)によっても、浄化土の重金属混入量は環境基準値をかなり下回る量まで低減できることが確認されている。   In all of the methods for removing heavy metals according to Patent Documents 1 to 3, iron powder is mixed into contaminated soil, and after the heavy metal is adsorbed to the iron powder, the iron powder is separated and recovered. The recovery rate of heavy metals mixed in the sludge by this treatment method depends on the recovery rate of iron powder. In the case of the magnetic separation device in Patent Document 2, the recovery rate of iron powder is almost 100. % (See paragraph [0030]), and past literature (Non-Patent Document 1) also confirmed that the amount of heavy metals mixed in the clarified soil can be reduced to an amount well below the environmental standard value. Yes.
しかしながら、鉄粉の回収に伴ってある程度の量の泥水も一緒に回収されることになり、この鉄粉が混入した泥水は管理型処分場で処分することになる。シールド工事で発生する重金属を含む掘削土砂(汚泥)は大量であり、重金属が混入していない浄化土の割合を可及的に高めるようにすれば、必然的に前記鉄粉の回収に伴って回収される泥水の量を最小限にでき、その分管理型処分場での処分コストを低減できることになる。   However, a certain amount of muddy water is also collected along with the recovery of the iron powder, and the muddy water mixed with this iron powder is to be disposed of at the managed disposal site. There is a large amount of excavated soil (sludge) containing heavy metals generated by shield construction. If the proportion of purified soil containing no heavy metals is increased as much as possible, it will inevitably accompany the recovery of the iron powder. The amount of muddy water collected can be minimized, and the disposal cost at the management-type disposal site can be reduced accordingly.
そこで本発明の主たる課題は、シールド工事で発生した重金属を含む掘削土砂(余剰汚泥)の処理に関して、鉄粉が混入された濃縮泥水を鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する分級工程において、重金属が混入していない浄化土の割合を可及的に高めるようにした重金属汚泥水の処理方法を提供することにある。   Therefore, the main problem of the present invention is that regarding the processing of excavated earth and sand (excess sludge) containing heavy metals generated in shield construction, the concentrated mud mixed with iron powder is mixed with purified soil without iron powder mixed with iron powder. Another object of the present invention is to provide a method for treating heavy metal sludge water in which the ratio of purified soil not containing heavy metals is increased as much as possible in the classification step of classifying the contaminated soil with the contaminated soil.
上記課題を解決するために請求項1に係る本発明として、シールド工事で発生した余剰泥水を濃縮デカンタにより比重1.4±5%の濃縮泥水に調整する泥水濃縮工程と、
前記濃縮泥水中の土砂重量に対して重金属を吸着するための鉄粉を1〜5重量%の割合で混入し、10〜60分の撹拌を行い、前記鉄粉に重金属を吸着させる鉄粉混入撹拌工程と、
前記鉄粉を混入した濃縮泥水を磁気選別機に送り、鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する分級工程とを備えることを特徴とするシールド工事における重金属汚泥水の処理方法が提供される。
In order to solve the above-mentioned problems, as the present invention according to claim 1, a muddy water concentration step of adjusting surplus muddy water generated in shield construction to a concentrated muddy water having a specific gravity of 1.4 ± 5% by a concentrated decanter;
Mixing iron powder for adsorbing heavy metals at a ratio of 1 to 5% by weight with respect to the weight of earth and sand in the concentrated mud water, stirring for 10 to 60 minutes, and mixing iron powder to adsorb heavy metals to the iron powder A stirring step;
In shield construction characterized by comprising a classification step of sending the concentrated mud mixed with iron powder to a magnetic sorter and classifying it into purified soil not mixed with iron powder and contaminated soil mixed with iron powder A method for treating heavy metal sludge water is provided.
上記請求項1記載の発明では、先ず泥水式又は泥水加圧式などのシールド工事で発生した余剰泥水を濃縮デカンタにより比重1.4±5%の濃縮泥水に調整する泥水濃縮工程を備える。通常、泥水式又は泥水加圧式などのシールド機に供給される泥水の比重は概ね1.15〜1.25、平均的には比重1.2程度に調整されている。この比重1.2の余剰泥水を比重1.4±5%まで濃縮することにより、処理する泥水量を約1/2に低減することが可能となる。また、後述する実験例で示すように、鉄粉を混入した比重1.2の泥水と比重1.4の泥水とについて磁気選別機による分級を行った結果、比重1.4の方が浄化土の割合が高くなるとの知見を得た。その結果、比重1.2の余剰泥水を比重1.4±5%まで濃縮することにより、重金属が混入していない浄化土の割合を高めることが可能となる。   In the first aspect of the present invention, a muddy water concentrating step is first provided in which surplus muddy water generated in a muddy water type or muddy water pressurizing type shield work is adjusted to a concentrated muddy water having a specific gravity of 1.4 ± 5% by a concentrated decanter. Usually, the specific gravity of muddy water supplied to a shield machine such as a muddy water type or a muddy water pressure type is adjusted to about 1.15 to 1.25, and on average, about 1.2. By concentrating the excess mud water having a specific gravity of 1.2 to a specific gravity of 1.4 ± 5%, the amount of muddy water to be treated can be reduced to about ½. Moreover, as shown in the experiment example mentioned later, as a result of classifying with a magnetic separator about the mud with specific gravity of 1.2 mixed with iron powder and the mud with specific gravity of 1.4, the specific gravity of 1.4 is more purified soil. We obtained the knowledge that the proportion of As a result, it is possible to increase the proportion of the purified soil in which heavy metals are not mixed by concentrating the excess mud water having a specific gravity of 1.2 to a specific gravity of 1.4 ± 5%.
次に、本発明では濃縮泥水中の土砂重量に対して重金属を吸着するための鉄粉を1〜5重量%の割合で混入し、10〜60分の撹拌を行い、前記鉄粉に重金属を吸着させる鉄粉混入撹拌工程を備える。後述の実験例で示すように、上記数値範囲で鉄粉の添加量と撹拌混合時間とを設定することにより、鉄粉の回収率98%以上を達成することができ、浄化土中に鉄粉が含有されないようにできる。   Next, in the present invention, iron powder for adsorbing heavy metals is mixed at a ratio of 1 to 5% by weight with respect to the weight of the earth and sand in the concentrated mud water, stirred for 10 to 60 minutes, and heavy metal is added to the iron powder. It is equipped with an iron powder mixing stirring process to adsorb. As shown in the experimental examples described later, by setting the addition amount of iron powder and the stirring and mixing time within the above numerical range, a recovery rate of iron powder of 98% or more can be achieved. Can be prevented from being contained.
更に、本発明では鉄粉を混入した濃縮泥水を磁気選別機に送り、鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する分級工程を備える。鉄粉の回収装置としては、遠心分離機と磁気選別機とが考えられるが、後述の実験例に示されるように、遠心分離機の場合は、遠心力の大きさによって多少のばらつきが生じるが、概ね浄化土の割合は95〜75%に留まるのに対して、磁気選別機の場合は、浄化土の割合は95〜98%とすることができ、磁気選別機を選択的に用いることによって浄化土の割合を高めることが可能となる。   Further, the present invention includes a classification process in which concentrated mud water mixed with iron powder is sent to a magnetic sorter and classified into purified soil not mixed with iron powder and contaminated soil mixed with iron powder. As iron powder recovery devices, centrifuges and magnetic separators are conceivable, but as shown in the experimental examples described later, in the case of a centrifuge, some variation occurs depending on the magnitude of the centrifugal force. In general, the ratio of the purified soil is 95 to 75%, whereas in the case of the magnetic sorter, the ratio of the purified soil can be 95 to 98%. By selectively using the magnetic sorter, It becomes possible to increase the proportion of the purified soil.
以上のように、本発明では泥水式又は泥水加圧式などのシールド工事で発生した余剰泥水を濃縮デカンタにより比重1.4±5%の濃縮泥水に調整する泥水濃縮工程と、鉄粉を混入した濃縮泥水を磁気選別機に送り、鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する分級工程とにより重金属が混入していない浄化土の割合を可及的に高めることが可能となる。   As described above, in the present invention, a muddy water concentration process for adjusting surplus muddy water generated in a shield work such as a muddy water type or a muddy water pressure type to a concentrated muddy water having a specific gravity of 1.4 ± 5% by a concentrated decanter, and iron powder are mixed. Send the concentrated mud water to the magnetic sorter and classify the purified soil that is not mixed with iron powder and the contaminated soil that is mixed with iron powder as much as possible. It becomes possible to raise.
請求項2に係る本発明として、前記分級工程において、前記磁気選別機に対する濃縮泥水の送泥量を決定するに当たり、
実機よりも小能力の実験用磁気選別機を用いた室内実験において、対象となる重金属含有汚泥水を比重1.4±5%の濃縮泥水に調整した濃縮泥水を用い、この濃縮泥水を前記実験用磁気選別機に送り、鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する作業を行い、送泥量と浄化土の割合との関係を示す相関図を得て、送泥量の最適範囲を決定し、
実施工において、前記送泥量の最適範囲を実機サイズにスケールアップするために下式(1)に示すスケールアップ係数αを乗じた送泥量によって前記磁気選別機の運転を行う請求項1記載のシールド工事における重金属汚泥水の処理方法が提供される。
As the present invention according to claim 2, in determining the amount of mud sent to the magnetic separator in the classification step,
In an indoor experiment using a magnetic separator for experiments with a smaller capacity than the actual machine, the concentrated mud was prepared by adjusting the concentrated heavy mud containing the target heavy metal to a concentrated mud with a specific gravity of 1.4 ± 5%. Sent to a magnetic separator, and classified into purified soil not containing iron powder and contaminated soil containing iron powder, and a correlation diagram showing the relationship between the amount of mud fed and the ratio of purified soil was obtained. Determine the optimum range of mud supply,
2. The magnetic sorter is operated by a mud feed amount multiplied by a scale-up factor α shown in the following formula (1) in order to scale up the optimum range of the mud feed amount to an actual machine size in an actual work. A method for treating heavy metal sludge water in shield construction is provided.
上記請求項2記載の発明では、請求項1の発明に加え、磁気選別機による分級工程に際して、濃縮泥水の送泥量を最適範囲に設定することにより重金属が混入していない浄化土の割合を可及的に高めるようにしたものである。   In the invention of claim 2, in addition to the invention of claim 1, in the classification process by the magnetic separator, the ratio of the purified soil not mixed with heavy metals is set by setting the amount of concentrated mud sent to the optimum range. It is intended to increase as much as possible.
具体的には、実機よりも小能力の実験用磁気選別機を用いた室内実験において、対象となる重金属含有汚泥水を比重1.4±5%の濃縮泥水に調整した濃縮泥水を用い、この濃縮泥水を前記実験用磁気選別機に送り、鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する作業を行い、送泥量と浄化土の割合との関係を示す相関図を得て、送泥量の最適範囲を決定する。なお、前記相関図は、送泥量を種々変化させた実験を行い、上側に凸となる曲線又は折れ線(凸側は浄化土の割合が高い)の相関関係が得られる範囲とするのが望ましい。この相関図に基づき、所定の数値範囲幅で送泥量の最適範囲を設定する。次に、前記送泥量の最適範囲は実験用磁気選別機による結果であるため、実機サイズにスケールアップするために上式(1)に示すスケールアップ係数αを乗じた送泥量によって前記磁気選別機の運転を行うようにする。これにより、重金属が混入していない浄化土の割合を可及的に高めることが可能となる。   Specifically, in a laboratory experiment using a magnetic separator for experiments having a smaller capacity than the actual machine, this was performed using concentrated mud water in which the target heavy metal-containing sludge water was adjusted to a concentrated mud water with a specific gravity of 1.4 ± 5%. Concentrated mud water is sent to the experimental magnetic sorter and classified into purified soil that is not mixed with iron powder and contaminated soil that is mixed with iron powder, and the relationship between the amount of mud fed and the ratio of purified soil is determined. The correlation diagram shown is obtained, and the optimum range of the amount of mud is determined. In addition, it is desirable that the correlation diagram be within a range in which a correlation with a curve or a broken line that protrudes upward (the ratio of the purified soil is high) is obtained by conducting experiments with various amounts of mud fed. . Based on this correlation diagram, the optimum range of the amount of mud is set within a predetermined numerical range. Next, since the optimum range of the amount of mud fed is a result of an experimental magnetic sorter, in order to scale up to the actual machine size, the magnetic mud amount multiplied by the scale-up factor α shown in the above equation (1) Operate the sorter. Thereby, it becomes possible to raise the ratio of the purification soil in which heavy metals are not mixed as much as possible.
請求項3に係る本発明として、前記鉄粉は、鉄分90%以上、かさ密度3.0(g/cm3)、平均粒径100μmの物性値のものを用いる請求項1、2いずれかに記載のシールド工事における重金属汚泥水の処理方法が提供される。 According to a third aspect of the present invention, the iron powder according to any one of the first and second aspects, wherein the iron powder has an iron content of 90% or more, a bulk density of 3.0 (g / cm 3 ), and an average particle size of 100 μm. A method for treating heavy metal sludge water in the described shield construction is provided.
上記請求項3記載の発明は、使用する鉄粉の物性値を具体的に特定したものである。上記鉄粉は例えばJFEミネラル社から容易に入手が可能である。この鉄粉は、重金属の吸着性能に優れた特殊鉄粉であり、砒素の他に鉛、セレンなどの重金属も吸着可能である。   The invention described in claim 3 specifically specifies the physical property values of the iron powder to be used. The iron powder can be easily obtained from, for example, JFE Minerals. This iron powder is a special iron powder excellent in heavy metal adsorption performance and can adsorb heavy metals such as lead and selenium in addition to arsenic.
請求項4に係る本発明として、泥水式又は泥水加圧式のシールド機から送られてくる泥水を振動脱水篩によって粒径0.075mmを境に礫・砂分とシルト・粘土分とに分級するとともに、前記シルト・粘土分を調整槽に送給し、この調整槽に貯留された泥水を再び前記シールド機に送る一次処理循環ラインと、前記濃縮デカンタで発生した低比重泥水を前記調整槽に送り比重調整のための希釈水として使用する二次処理循環ラインとを備える請求項1〜3いずれかに記載のシールド工事における重金属汚泥水の処理方法が提供される。   As the present invention according to claim 4, the muddy water sent from the muddy water type or muddy water pressure type shield machine is classified into gravel / sand and silt / clay with a particle size of 0.075 mm as a boundary by a vibrating dewatering sieve. The silt / clay is fed to the adjustment tank, and the muddy water stored in the adjustment tank is sent again to the shield machine, and the low specific gravity mud generated in the concentrated decanter is sent to the adjustment tank. The processing method of the heavy metal sludge water in the shield construction in any one of Claims 1-3 provided with the secondary treatment circulation line used as dilution water for specific gravity adjustment.
上記請求項4記載の発明は、泥水式又は泥水加圧式のシールド機における泥水の循環システム及び比重調整システムを具体的に述べたものである。本発明における一次処理循環ラインはごく一般的な構成であるが、本発明ではシールド工事で発生した余剰泥水を濃縮デカンタにより比重1.4±5%の濃縮泥水に調整する泥水濃縮工程を備えるため、前記濃縮デカンタで発生する低比重泥水を比重調整のための希釈水として使用する。   The invention described in claim 4 specifically describes a mud circulation system and a specific gravity adjustment system in a muddy water type or muddy water pressure type shield machine. Although the primary treatment circulation line in the present invention has a very general configuration, the present invention includes a muddy water concentrating step for adjusting surplus muddy water generated in shield construction to a concentrated muddy water having a specific gravity of 1.4 ± 5% by a concentrated decanter. The low specific gravity mud generated in the concentrated decanter is used as dilution water for adjusting the specific gravity.
請求項5に係る本発明として、前記振動脱水篩の前段に前処理機として、シールド機からの泥水を細かく解砕する泥水解砕装置を備える請求項4記載のシールド工事における重金属汚泥水の処理方法が提供される。   The present invention according to claim 5 is a treatment of heavy metal sludge water in shield construction according to claim 4, further comprising a muddy water crushing device that finely crushes muddy water from the shield machine as a pre-treatment device in front of the vibrating dewatering sieve. A method is provided.
上記請求項5記載の発明では、前記振動脱水篩の前段に前処理機として、シールド機からの泥水を細かく解砕する泥水解砕装置を備えるようにしたものである。振動脱水篩では、粒径0.075mmを境に礫・砂分とシルト・粘土分とに分級するようにしているが、泥水式シールド機による掘削土砂中に固結したシルト・粘土分の大きさが0.075mm以上である場合は、この一次処理機で一次処理土として分級されてしまうことになる。この一次処理土は、重金属が混入されているため管理型処分場で処分することになる。従って、管理型処分場での処分コストを低減するためには、掘削土砂を一次処理機による分級の前段に泥水を細かく解砕する泥水解砕装置を設けるようにして粒径0.075mm以下のシルト・粘土分を多くする処理を行うことで、管理型処分場で処分する土量を低減することが可能となる。   In the invention according to the fifth aspect, a muddy water crushing device for finely crushing muddy water from the shield machine is provided as a pre-treatment device in the previous stage of the vibrating dewatering sieve. Vibrating dewatering sieves are classified into gravel / sand and silt / clay with a particle size of 0.075mm as the boundary, but the size of silt / clay solidified in excavated soil using a muddy water shield machine. If it is 0.075 mm or more, it will be classified as primary treated soil by this primary processing machine. This primary treated soil will be disposed of in a managed disposal site because it contains heavy metals. Therefore, in order to reduce the disposal cost at the management-type disposal site, a silt with a particle size of 0.075 mm or less is provided by providing a mud crushing device that finely crushes mud before the classification by the primary treatment machine.・ By increasing the clay content, it will be possible to reduce the amount of soil to be disposed of at the managed disposal site.
以上詳説のとおり本発明によれば、シールド工事で発生した重金属を含む掘削土砂(余剰汚泥)の処理に関して、鉄粉が混入された濃縮泥水を鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する分級工程において、重金属が混入していない浄化土の割合を可及的に高めることが可能となる。   As described in detail above, according to the present invention, regarding the treatment of excavated earth and sand (excess sludge) containing heavy metals generated in shield construction, the concentrated mud mixed with iron powder is purified soil not containing iron powder, and iron powder. In the classification step of classifying the contaminated soil into which contaminated soil has been mixed, it becomes possible to increase the proportion of the purified soil in which heavy metals are not mixed as much as possible.
本発明に係るシールド工事における重金属汚泥水の処理方法を示す概略図である。It is the schematic which shows the processing method of the heavy metal sludge water in the shield construction which concerns on this invention. 磁気選別機9の分級原理を説明するための該略図である。6 is a schematic diagram for explaining the classification principle of the magnetic sorter 9. FIG. 実施例での重金属の吸着試験の手順を示すフロー図である。It is a flowchart which shows the procedure of the adsorption test of the heavy metal in an Example. 実施例での鉄粉分級試験の手順を示すフロー図である。It is a flowchart which shows the procedure of the iron powder classification test in an Example. 実施例での鉄粉分級試験における遠心分離機の浄化土の割合と鉄粉回収率を示すグラフである。It is a graph which shows the ratio of the purified soil of a centrifuge, and an iron powder collection | recovery rate in the iron powder classification test in an Example. 実施例での鉄粉分級試験における磁気選別機の浄化土の割合と鉄粉回収率を示すグラフである。It is a graph which shows the ratio of the purified soil of a magnetic sorter, and an iron powder collection | recovery rate in the iron powder classification test in an Example.
以下、本発明の実施の形態について図面を参照しながら詳述する。   Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
〔シールド工事における重金属汚泥水の処理〕
本発明に係るシールド工事における重金属汚泥水の処理方法は、図1に示されるように、シールド工事で発生した余剰泥水を濃縮デカンタ5により比重1.4±5%の濃縮泥水に調整する泥水濃縮工程Bと、前記濃縮泥水に対して重金属を吸着するための鉄粉を1〜5重量%の割合で混入し、10〜60分の撹拌を行い、前記鉄粉に重金属を吸着させる鉄粉混入撹拌工程Cと、前記鉄粉を混入した濃縮泥水を磁気選別機9に送り、鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する分級工程Dとを備えるものである。
[Treatment of heavy metal sludge water in shield construction]
As shown in FIG. 1, the method for treating heavy metal sludge water in shield construction according to the present invention adjusts the excess mud generated in the shield construction to concentrated mud with a specific gravity of 1.4 ± 5% by the concentrated decanter 5. Mixing iron powder for adsorbing heavy metals in the step B and the concentrated mud water at a ratio of 1 to 5% by weight, stirring for 10 to 60 minutes, and adsorbing heavy metals to the iron powder A stirring process C and a classification process D for sending the concentrated mud mixed with the iron powder to the magnetic separator 9 and classifying it into purified soil not containing iron powder and contaminated soil mixed with iron powder. It is.
以下、更に図1に基づいて、本発明のシールド工事における重金属汚泥水の処理方法について詳述する。   Hereinafter, based on FIG. 1, the processing method of the heavy metal sludge water in the shield construction of this invention is explained in full detail.
泥水式又は泥水加圧式シールド工法は、供給された泥水によって掘削面の安定を図りながら掘削を行うシールド工法であり、泥水式又は泥水加圧式のシールド機1によって掘削された土砂は、掘削面の安定と土砂の輸送を目的として一次処理設備Aから送られた泥水とともに、ポンプ圧送により再び一次処理設備Aに戻される。掘削された土砂の中には、礫、砂、塊状の粘性土、貝殻等の大粒径のものが含まれているため前記一次処理設備Aに振動脱水篩2が設けられている。前記振動脱水篩2は、サイクロンと振動ふるいを組み合わせ、汚泥の効率良い脱水処理を可能にした装置である。具体的には、礫用スクリーンを備え粒径2mm以上の礫が分級される。粒径2mm未満の固形物を含む泥水は、サイクロンに送られ粒径0.075mm以上の砂分が分級される。サイクロンをオーバーフローした0.075mm以下のシルト・粘土分は調整槽3に送られ、ここからポンプによりシールド機1に送られる。これが本発明における「一次処理循環ライン」である。   The muddy water type or muddy water pressure type shield method is a shield method in which excavation surface is stabilized by the supplied muddy water, and the earth and sand excavated by the muddy type or muddy water pressure type shield machine 1 Together with the muddy water sent from the primary treatment facility A for the purpose of stability and transport of earth and sand, it is returned to the primary treatment facility A again by pumping. Since the excavated earth and sand contain large-diameter particles such as gravel, sand, massive viscous earth, and shells, the primary treatment equipment A is provided with a vibrating dewatering sieve 2. The vibration dewatering sieve 2 is a device that combines a cyclone and a vibration sieve to enable efficient dewatering treatment of sludge. Specifically, gravel having a screen for gravel and having a particle diameter of 2 mm or more is classified. Mud containing solids with a particle size of less than 2 mm is sent to a cyclone to classify sand with a particle size of 0.075 mm or more. The silt / clay of 0.075 mm or less that has overflowed the cyclone is sent to the adjustment tank 3, from which it is sent to the shield machine 1 by a pump. This is the “primary processing circulation line” in the present invention.
泥水式又は泥水加圧式のシールド機に供給される泥水の比重は概ね1.15〜1.25、平均的には比重1.2程度に調整されている。この比重調整は、後述の濃縮デカンタ5で発生した低比重泥水を前記調整槽3に送り比重調整のための希釈水として使用することにより行われる。これが本発明における「二次処理循環ライン」である。   The specific gravity of the muddy water supplied to the muddy water type or muddy water pressure type shield machine is generally adjusted to 1.15 to 1.25, and the average density is adjusted to about 1.2. This specific gravity adjustment is performed by sending low specific gravity mud generated in a concentration decanter 5 described later to the adjustment tank 3 and using it as dilution water for adjusting specific gravity. This is the “secondary processing circulation line” in the present invention.
前記一次処理設備Aでは、掘削地山に含まれる水分と主として74μm以下の粒子は除去できないために、シールド掘削の進行に伴い、泥水の絶対量、比重及び粘性等が徐々に増加する。そのため、余剰泥水は、前記調整槽3からポンプにより余剰泥水槽4に送られる。   In the primary treatment facility A, since moisture and mainly particles of 74 μm or less contained in the excavated ground cannot be removed, the absolute amount, specific gravity, viscosity and the like of the muddy water gradually increase with the progress of shield excavation. Therefore, the excess muddy water is sent from the adjustment tank 3 to the excess muddy water tank 4 by a pump.
余剰泥水槽4に送られた余剰泥水は濃縮デカンタ5により比重1.4±5%の濃縮泥水に調整される。前記濃縮デカンタ5は、外胴内にスクリューコンベア付きの内胴を配設し、これら外胴及び内胴を電動機にて回転させて遠心力を生じさせるとともに、内胴を制動機にて制御して外胴と内胴とに回転差を生じさせ、この差速によって泥水を高比重泥水と低比重泥水とに分級するものである。本発明では、比重調整の目標値は1.4とするものであるが、誤差を±5%ほど見込んで比重範囲を比重1.4±5%としている。   The surplus muddy water sent to the surplus muddy water tank 4 is adjusted to a concentrated muddy water having a specific gravity of 1.4 ± 5% by the concentrated decanter 5. The concentrated decanter 5 is provided with an inner cylinder with a screw conveyor in the outer cylinder, the outer cylinder and the inner cylinder are rotated by an electric motor to generate centrifugal force, and the inner cylinder is controlled by a brake. Thus, a rotation difference is generated between the outer trunk and the inner trunk, and the mud is classified into high specific gravity mud and low specific gravity mud by this differential speed. In the present invention, the target value of the specific gravity adjustment is 1.4, but the specific gravity range is set to 1.4 ± 5% with an expectation of an error of ± 5%.
本発明では、約1,2の比重の泥水を比重1.4±5%の濃縮泥水に比重調整するものであるが、この制御方法としては、本出願人が先の特開2007−283269号公報にて開示した方法を採用することができる。詳細については同公報を参酌されたい。   In the present invention, the specific gravity of the mud having a specific gravity of about 1 or 2 is adjusted to the concentrated mud having a specific gravity of 1.4 ± 5%. As the control method, the applicant of the present invention has been disclosed in Japanese Patent Application Laid-Open No. 2007-283269. The method disclosed in the publication can be adopted. For details, please refer to this publication.
比重1.2の余剰泥水を比重1.4±5%まで濃縮することにより、処理する泥水量を約1/2に低減することが可能となる。また、後述する[実施例]の欄に示すように、鉄粉を混入した比重1.2の泥水と比重1.4の泥水とについて磁気選別機による分級を行った結果、比重1.4の方が浄化土の割合が高くなるとの知見に基づき、比重1.2の余剰泥水を比重1.4±5%まで濃縮することにより、重金属が混入していない浄化土の割合を可及的に高めるようにした。   By concentrating the excess mud water having a specific gravity of 1.2 to a specific gravity of 1.4 ± 5%, the amount of muddy water to be treated can be reduced to about ½. Moreover, as shown in the column of [Example] described later, as a result of performing classification by a magnetic sorter with respect to a mud having a specific gravity of 1.2 and a mud having a specific gravity of 1.4 mixed with iron powder, a specific gravity of 1.4 was obtained. Based on the knowledge that the ratio of purified soil is higher, excess mud water with a specific gravity of 1.2 is concentrated to a specific gravity of 1.4 ± 5%, so that the proportion of purified soil without heavy metals is as much as possible. I tried to increase it.
前記濃縮デカンタ5のアンダー泥水(高比重泥水)は、濃縮泥水槽6に貯留され、一方オーバー泥水(低比重泥水)については、前記調整槽3に送り比重調整のための希釈水として使用される。以上の工程が、本発明の「泥水濃縮工程B」である。   Under mud water (high specific gravity mud water) of the concentrated decanter 5 is stored in the concentrated mud water tank 6, while over mud water (low specific gravity mud water) is sent to the adjustment tank 3 and used as dilution water for adjusting specific gravity. . The above process is the “muddy water concentration process B” of the present invention.
前記濃縮泥水槽6に貯留された濃縮泥水は、次の鉄粉混入撹拌工程Cに送られる。この鉄粉混入撹拌工程Cでは、先ず鉄粉フィーダー7により前記濃縮泥水中の土砂重量に対して鉄粉が1〜5重量%の割合で混入される。鉄粉が混入された濃縮泥水は、その後、鉄粉混合槽8に送られ、ここで10〜60分の撹拌混合が行われる。この撹拌混合により、溶出した重金属が鉄粉に吸着される。   The concentrated muddy water stored in the concentrated muddy water tank 6 is sent to the next iron powder mixing and stirring step C. In this iron powder mixing stirring step C, first, iron powder is mixed by the iron powder feeder 7 at a ratio of 1 to 5% by weight with respect to the weight of earth and sand in the concentrated mud water. The concentrated mud water mixed with iron powder is then sent to the iron powder mixing tank 8, where stirring and mixing are performed for 10 to 60 minutes. By this stirring and mixing, the eluted heavy metal is adsorbed to the iron powder.
前記鉄粉としては、鉄分90%以上、かさ密度3.0(g/cm3)、平均粒径100μmの物性値のものを用いるのが望ましい。このような鉄粉は例えばJFEミネラル社から容易に入手が可能である。JFEミネラル(株)から品番「MSI-X3」で販売されている重金属専用の特殊鉄粉は、高い吸着能力を有するとともに、砒素の他に鉛、セレンなどの重金属も吸着可能である。また、前記鉄粉としては、神戸製鋼(株)から商品名「エコメル」として販売されている鉄粉も同様に使用することができる。 As the iron powder, it is desirable to use those having physical properties of iron content of 90% or more, bulk density of 3.0 (g / cm 3 ), and average particle size of 100 μm. Such iron powder can be easily obtained from, for example, JFE Minerals. The special iron powder for heavy metals sold under the product number “MSI-X3” from JFE Mineral Co., Ltd. has a high adsorption capacity and can adsorb heavy metals such as lead and selenium in addition to arsenic. Further, as the iron powder, iron powder sold under the trade name “Ecomel” from Kobe Steel can be used as well.
前記鉄粉の混入量と撹拌混合時間とは反比例の関係にあり、鉄粉の添加量が少ない場合は撹拌混合時間を長くし、鉄粉の添加量が多い場合は撹拌混合時間を短くできる。鉄粉の添加量と撹拌混合時間とは、室内実験により鉄粉の回収率が95%以上になるように設定するのが望ましい。   The mixing amount of the iron powder and the stirring and mixing time are in an inversely proportional relationship. When the addition amount of the iron powder is small, the stirring and mixing time can be lengthened, and when the adding amount of the iron powder is large, the stirring and mixing time can be shortened. The amount of iron powder added and the stirring and mixing time are preferably set so that the iron powder recovery rate is 95% or more by laboratory experiments.
撹拌混合を終えた鉄粉混入濃縮泥水は、次の分級工程Dに送られ、磁気選別機9によって鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級される。前記磁気選別機9の分級原理は、図2に示されるように、固定配置の永久磁石10と、その周囲を回転するドラムシェル11と、鉄粉を掻き取るスクレーパ12から主に構成されるもので、ドラムシェル11を囲むように設けられた泥水タンク13に対して鉄粉混入濃縮泥水が供給されると、濃縮泥水中の鉄粉は永久磁石により磁力によってドラムシェル11の外面に吸着し、そのままドラムシェル11の左回り回転(回転速度:2.5〜5.0rpmとするのが望ましい。)に伴って輸送される。鉄粉の輸送に際しては、ある程度の泥水も一緒にドラムシェル11の表面に付着して分級されることになる。そして、ほぼ半周した位置で、かつ永久磁石10による磁力が生じてない位置で、スクレーパ12によって鉄粉及び付着泥水はドラムシェル11の表面から掻き取られ回収される。ここで回収される泥水が「鉄粉が混入した汚染土」である。   The iron powder mixed concentrated mud water that has been stirred and mixed is sent to the next classification step D, and is classified by the magnetic sorter 9 into purified soil that is not mixed with iron powder and contaminated soil that is mixed with iron powder. As shown in FIG. 2, the classification principle of the magnetic sorter 9 is mainly composed of a fixedly arranged permanent magnet 10, a drum shell 11 that rotates around the permanent magnet 10, and a scraper 12 that scrapes off iron powder. Then, when the iron powder mixed concentrated muddy water is supplied to the muddy water tank 13 provided so as to surround the drum shell 11, the iron powder in the concentrated muddy water is adsorbed to the outer surface of the drum shell 11 by a magnetic force by a permanent magnet, The drum shell 11 is transported as it is rotated counterclockwise (rotation speed: preferably 2.5 to 5.0 rpm). When transporting the iron powder, a certain amount of muddy water is adhered to the surface of the drum shell 11 and classified. The iron powder and the adhering muddy water are scraped off and collected from the surface of the drum shell 11 by the scraper 12 at a position where the magnetic force is not generated by the permanent magnet 10 at a substantially half-circumferential position. The muddy water collected here is “contaminated soil mixed with iron powder”.
一方、鉄粉が取り除かれた濃縮泥水は、ドラムシェル11の下側と泥水タンク13のドラムシェル側に延びる底面との隙間bを流路15として浄化土タンク14に送られ、ここから回収される。こちら側が「鉄粉が混入していない浄化土」となる。   On the other hand, the concentrated muddy water from which the iron powder has been removed is sent to the purification soil tank 14 through the gap b between the lower side of the drum shell 11 and the bottom surface of the muddy water tank 13 extending to the drum shell side, and is collected from here. The This side is “Purified soil without iron powder”.
鉄粉の回収装置としては、遠心分離機と磁気選別機とが考えられるが、後述の実験例に示されるように、遠心分離機の場合は、遠心力によってばらつきが生じるが、概ね浄化土の割合は95〜75%に留まるのに対して、磁気選別機の場合は、浄化土の割合は95〜98%とすることができ、磁気選別機を選択的に用いることによって浄化土の割合を高めることが可能となる。   As iron powder recovery devices, centrifuges and magnetic separators can be considered, but as shown in the experimental examples described later, in the case of centrifuges, variations occur due to centrifugal force, The ratio stays at 95 to 75%, whereas in the case of a magnetic sorter, the ratio of the purified soil can be 95 to 98%. By selectively using the magnetic sorter, the ratio of the purified soil can be reduced. It becomes possible to raise.
また、本発明者等は、前記分級工程Dにおいて、前記磁気選別機9に対する濃縮泥水の送泥量の違いによって、浄化土の割合に変化があることを知見したため、実施工における前記磁気選別機9に対する濃縮泥水の送泥量を決定するに当たっては、下記の手順によって決定することが望ましい。   In addition, since the present inventors have found that in the classification step D, there is a change in the ratio of purified soil due to the difference in the amount of mud sent to the magnetic separator 9, the magnetic separator in the construction work In determining the amount of concentrated mud sent to 9, it is desirable to determine by the following procedure.
実機よりも小能力の実験用磁気選別機を用いた室内実験において、対象となる重金属含有汚泥水を比重1.4±5%の濃縮泥水に調整した濃縮泥水を用い、この濃縮泥水を前記実験用磁気選別機に送り、鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する作業を行い、送泥量と浄化土の割合との関係を示す相関図を得て、送泥量の最適範囲を決定し、
実施工における磁気選別機9への送泥量は、前記送泥量の最適範囲を実機サイズにスケールアップするために下式(1)に示すスケールアップ係数αを乗じた送泥量によって前記磁気選別機の運転を行うようにする。
In an indoor experiment using a magnetic separator for experiments with a smaller capacity than the actual machine, the concentrated mud was prepared by adjusting the concentrated heavy mud containing the target heavy metal to a concentrated mud with a specific gravity of 1.4 ± 5%. Sent to a magnetic separator, and classified into purified soil not containing iron powder and contaminated soil containing iron powder, and a correlation diagram showing the relationship between the amount of mud fed and the ratio of purified soil was obtained. Determine the optimum range of mud supply,
The amount of mud fed to the magnetic separator 9 in the construction work is determined by the amount of mud fed by multiplying the optimum range of the amount of mud sent by the scale-up factor α shown in the following equation (1) in order to scale up the optimum range of the amount of mud sent Operate the sorter.
前記スケールアップ係数αを決定する各因数に関して、第1因数β(ドラム幅の増加率)は、図2においてドラムシェル11の奥行き寸法の増加率であり、その増加率はそのまま処理効率の比となる。第2因数β(浄化土が流れる流路の高さ寸法の増加率)とは、図2において、ドラムシェル11の下側と泥水タンク13のドラムシェル側に延びる底面との隙間b(流路12の高さ寸法b)の増加率のことであり、その増加率はそのまま浄化土の処理効率の比となる。この増加率βは磁力の増加率に比例する。つまり、永久磁石の磁力が大きくなるとそれに応じて前記流路15の高さ寸法b(離隔幅)を大きくすることができ、この高さ寸法b(離隔幅)の増加率に正比例して浄化土の流水量が増大する。第3因数β(ドラム直径の増加率)は、ドラム周長の増加率と同じである。ドラムの回転角度θが仮に同じでもドラム直径が大きければそれに応じてドラム周長が長くなり、それに正比例して鉄粉の分級効率が増大するため、その増加率はそのまま鉄粉の処理効率の比となる。最後の第4因数β(ドラム回転速度の増加率)は、ドラムシェル11の回転数が上がればそれに正比例して鉄粉の分級効率が増加するため、その増加率はそのまま鉄粉の処理効率の比となる。 For each factor that determines the scale-up factor α, the first factor β 1 (drum width increasing rate) is the increasing rate of the depth dimension of the drum shell 11 in FIG. 2, and the increasing rate is the ratio of the processing efficiency as it is. It becomes. The second factor β 2 (increase rate of the height dimension of the flow path through which the purified soil flows) is a gap b (flow rate) between the lower side of the drum shell 11 and the bottom surface of the muddy water tank 13 on the drum shell side in FIG. It is the rate of increase of the height dimension b) of the path 12, and the rate of increase is directly the ratio of the processing efficiency of the purified soil. The increase rate beta 2 is proportional to the rate of increase in force. That is, when the magnetic force of the permanent magnet increases, the height dimension b (separation width) of the flow path 15 can be increased accordingly, and the purified soil is directly proportional to the increasing rate of the height dimension b (separation width). The amount of running water increases. The third factor β 3 (the increase rate of the drum diameter) is the same as the increase rate of the drum circumference. Even if the rotation angle θ of the drum is the same, if the drum diameter is large, the drum circumference will be correspondingly longer, and the iron powder classification efficiency will increase in direct proportion to it. It becomes. The final fourth factor β 4 (increase rate of the drum rotation speed) increases the iron powder classification efficiency in direct proportion to the increase in the rotation speed of the drum shell 11. Ratio.
なお、前記相関図は、送泥量を種々変化させた実験を行い、上側に凸となる曲線又は折れ線(凸の頂点側は浄化土の割合が高い)の相関関係が得られる範囲とするのが望ましい。この相関図に基づき、所定の数値範囲幅で送泥量の最適範囲を設定し、これに前記スケールアップ係数αを乗じた送泥量によって前記磁気選別機の運転を行うようにすれば、これにより、重金属が混入していない浄化土の割合を可及的に高めることが可能となる。   In addition, the correlation diagram is an experiment in which the amount of mud fed is changed in various ways, and a range in which a correlation of a curved line or a broken line that protrudes upward (the ratio of the purified soil is high on the convex vertex side) is obtained. Is desirable. Based on this correlation diagram, if the optimum range of the mud feed amount is set within a predetermined range of numerical values, and the mud feed amount obtained by multiplying this by the scale-up factor α, the magnetic separator is operated. As a result, it is possible to increase the proportion of the purified soil in which heavy metals are not mixed as much as possible.
ところで、前記振動脱水篩2の前段に前処理機として、シールド機からの泥水を細かく解砕する泥水解砕装置を備えるようにするのが望ましい。振動脱水篩2では、粒径0.075mmを境に礫・砂分とシルト・粘土分とに分級するようにしているが、泥水式又は泥水加圧式のシールド機1による掘削土砂中に固結したシルト・粘土分の大きさが0.075mm以上のものが多く含まれている場合は、この振動脱水篩2で一次処理土として分級されてしまうことになる。この一次処理土は、重金属が混入されているため管理型処分場で処分することになる。従って、管理型処分場での処分コストを低減するためには、掘削土砂を振動脱水篩2による分級の前段に泥水を細かく解砕する泥水解砕装置を設けるようにして粒径0.075mm以下のシルト・粘土分を多くする処理を行うことで、管理型処分場で処分する土量を低減することが可能となる。前記泥水解砕装置としては、古河産機システムズ株式会社製の商品名「ディスインテグレータ」と呼ばれる固形物破砕機や、新六精機株式会社製の商品名「ハリケーン」と呼ばれる固形物破砕機などを好適に用いることができる。   By the way, it is desirable to provide a muddy water crushing device for finely crushing muddy water from the shield machine as a pretreatment machine in the previous stage of the vibration dewatering sieve 2. Vibrating dewatering sieve 2 is classified into gravel / sand and silt / clay with a particle size of 0.075mm as a boundary, but it is consolidated in excavated sediment by mud or mud pressurizing shield machine 1. If there is a large amount of silt / clay of 0.075mm or more, it will be classified as primary treated soil by this vibrating dewatering sieve 2. This primary treated soil will be disposed of in a managed disposal site because it contains heavy metals. Therefore, in order to reduce the disposal cost at the management-type disposal site, a muddy water crushing device that finely crushes the muddy water before the classification of the excavated sediment by the vibrating dewatering sieve 2 is provided. It is possible to reduce the amount of soil to be disposed of at a managed disposal site by performing a treatment that increases the amount of silt and clay. As the muddy water crushing device, a solid material crusher called “Disintegrator” manufactured by Furukawa Industrial Systems Co., Ltd., a solid material crusher called “Hurricane” manufactured by Shinroku Seiki Co., Ltd., etc. It can be used suitably.
本実施例では、試験室において実汚染土を使用し、比重を調整した泥水中に特殊鉄粉を添加、撹拌して重金属として代表的な砒素を鉄粉に吸着、除去する重金属吸着実験を行い、汚染土を浄化するために必要な条件(鉄粉混入量と撹拌時間)を確認した(試験I)。また、濃縮泥水中から鉄粉を分級機(遠心分離機と磁気選別機)を使用して分級・回収する実験を行い、濃縮泥水中からの鉄粉分級に最適な分級機を確認した(試験II)。   In this example, actual contaminated soil was used in a test room, special iron powder was added to the muddy water with a specific gravity adjusted, and a heavy metal adsorption experiment was performed to adsorb and remove typical arsenic as a heavy metal on the iron powder. The conditions necessary for purifying the contaminated soil (iron powder mixing amount and stirring time) were confirmed (Test I). In addition, we conducted an experiment to classify and collect iron powder from concentrated mud using a classifier (centrifugal separator and magnetic separator), and confirmed the best classifier for classifying iron powder from concentrated mud (test). II).
〔試験I〕
(1)試験材料
A.鉄粉
本試験で用いた鉄粉(JFEミネラル社製)の特殊鉄粉の物性を下表1に示す。この鉄粉は重金属の吸着性能を有する特殊鉄粉であり、砒素のほかに鉛、セレンなど複数の重金属へ適用可能である。
[Test I]
(1) Test material Iron powder The physical properties of the special iron powder of iron powder (manufactured by JFE Mineral Co., Ltd.) used in this test are shown in Table 1 below. This iron powder is a special iron powder capable of adsorbing heavy metals, and can be applied to a plurality of heavy metals such as lead and selenium in addition to arsenic.
B.試料土
試料土として東京層の硬質シルトを使用した。この試料土を解砕し、乾式10mmで異物などを取り除いた後、湿式2mmで礫などを取り除き、篩を通過した2mmアンダーを「試験原土」として、試験において共通試料として取り扱うこととした。下表2に試験原土の砒素分析結果を示す。
B. Sample soil Hard silt from Tokyo layer was used as sample soil. This sample soil was crushed, foreign matter was removed with a dry type 10 mm, gravels were removed with a wet type 2 mm, and the 2 mm underpass that passed through the sieve was treated as a common sample in the test as “test soil”. Table 2 below shows the arsenic analysis results of the test soil.
(2)実験方法
下表3に実験条件、図3に実験フローを示す。試験原土に水を添加し、比重1.4に調整したスラリーにアルミナボールを添加して5分間のアトリッション(摩砕)を行った。アトリッションを行うのは土粒子の塊を解きほぐすことや、土粒子の表面に吸着している重金属を物理的に剥離させ、溶出を促進させるためである。比重1.1、1.2の場合は、水を加え比重調整した。各比重のスラリーに含まれる試験原土重量に対して設定量(1.0、2.0、5.0 wt%)の特殊鉄粉を添加し、2 Lのポリ容器に封入してロータリー式シェイカーにより10分間(および60分間)の混合を行った。この工程で水に溶出した砒素を鉄粉に吸着させる。混合後のスラリーから棒磁石と板磁石を用いて鉄粉のみを磁力選別回収した。鉄粉回収後の土壌スラリーを0.075 mmの篩にて湿式分級し、篩上の0.075〜2.0 mmを土壌分析試料とした。篩下の0.075 mm以下については卓上遠心分離機により固液分離し固形分を土壌分析試料とし液分を上澄液としての液体分析試料とした。
(2) Experimental method Table 3 below shows the experimental conditions, and Fig. 3 shows the experimental flow. Water was added to the test raw soil, and alumina balls were added to the slurry adjusted to a specific gravity of 1.4 to perform attrition (grinding) for 5 minutes. The attrition is performed to unravel the lump of soil particles or to physically separate heavy metals adsorbed on the surface of the soil particles to promote elution. In the case of specific gravity 1.1 and 1.2, the specific gravity was adjusted by adding water. Add the specified amount of special iron powder (1.0, 2.0, 5.0 wt%) to the weight of the test soil contained in the slurry of each specific gravity, enclose it in a 2 L plastic container and use a rotary shaker for 10 minutes (and 60 minutes). In this process, arsenic eluted in water is adsorbed to iron powder. Only iron powder was magnetically selected and collected from the mixed slurry using a bar magnet and a plate magnet. The soil slurry after the iron powder recovery was wet-classified with a 0.075 mm sieve, and 0.075 to 2.0 mm on the sieve was used as a soil analysis sample. With respect to 0.075 mm or less below the sieve, solid-liquid separation was performed using a desktop centrifuge, and the solid content was used as a soil analysis sample and the liquid content was used as a liquid analysis sample as a supernatant.
(3)実験結果及び考察
下表4に実験結果一覧を示す。砒素を対象とした鉄粉による吸着実験を行った結果、以下のことが明らかとなった。
(3) Experimental results and discussion Table 4 below lists the experimental results. As a result of an adsorption experiment using iron powder for arsenic, the following became clear.
(1) 水準1〜5の結果から、泥水比重1.1の場合、鉄粉添加量1 wt%、撹拌時間10分の条件では粗粒分、細粒分で溶出量が基準値を超過する結果となった。しかし、鉄粉添加量5 wt%、撹拌時間10分または鉄粉添加量1 wt%、撹拌時間60分の条件では、溶出量が基準値を満足する結果となった。したがって、鉄粉添加量を増加させるかまたは撹拌時間を増加させることで、溶出量を基準値以内にすることができる。 (1) From the results of levels 1 to 5, when the muddy water specific gravity is 1.1, the amount of iron powder added is 1 wt% and the stirring time is 10 minutes. became. However, when the iron powder addition amount was 5 wt% and the stirring time was 10 minutes or the iron powder addition amount was 1 wt% and the stirring time was 60 minutes, the dissolution amount satisfied the standard value. Therefore, by increasing the iron powder addition amount or increasing the stirring time, the elution amount can be within the reference value.
(2) 水準6、7の結果、泥水比重が1.2であっても撹拌時間60分、鉄粉添加量を1 wt%以上添加すれば、溶出量を基準値以内にすることができる。 (2) As a result of levels 6 and 7, even if the mud specific gravity is 1.2, the elution amount can be within the standard value by adding the iron powder addition amount of 1 wt% or more with a stirring time of 60 minutes.
(3) 水準8、9の結果、泥水比重1.4であっても撹拌時間60分、鉄粉添加量を1 wt%以上添加すれば、溶出量を基準値以内にすることができる。 (3) As a result of Levels 8 and 9, even if the specific gravity of mud water is 1.4, the amount of elution can be kept within the standard value by adding 60 wt.
以上の結果から、比重が1.4という高比重泥水であっても鉄粉添加量1 wt%以上であれば砒素溶出量・含有量ともに基準値を満足することができると判明した。   From the above results, it was found that even if high specific gravity mud with a specific gravity of 1.4 is satisfied, both the arsenic elution amount and the content can be satisfied if the iron powder addition amount is 1 wt% or more.
今回の実験では確実に砒素を鉄粉に吸着させるため撹拌時間を60分に設定したが、上記試験結果から、鉄粉の混入量と撹拌混合時間とは反比例の関係にあり、鉄粉の添加量が少ない場合は撹拌混合時間を長くし、鉄粉の添加量が多い場合は撹拌混合時間を短くしてよいことが知見された。従って、鉄粉の添加量と撹拌混合時間とは、室内実験により鉄粉の回収率が95%以上になるように設定するのが望ましい。

In this experiment, the stirring time was set to 60 minutes to ensure that arsenic was adsorbed to the iron powder. However, from the above test results, the mixing amount of iron powder and the mixing time are in inverse proportion, and the addition of iron powder It was found that when the amount is small, the stirring and mixing time may be lengthened, and when the amount of iron powder added is large, the stirring and mixing time may be shortened. Therefore, it is desirable to set the amount of iron powder added and the stirring and mixing time so that the iron powder recovery rate is 95% or more by laboratory experiments.

〔試験II〕
(1)試験材料
A.鉄粉
〔試験I〕で用いた鉄粉を用いる。
[Test II]
(1) Test material Iron powder The iron powder used in [Test I] is used.
B.試料土
試料土には、模擬汚染土として笠岡粘土を使用した。下表5に実験で使用した笠岡粘土の物性を示す。
B. Sample soil Kasaoka clay was used as the sample soil. Table 5 below shows the physical properties of Kasaoka clay used in the experiment.
C.分級機
分級機として遠心分離機、磁気選別機の2種類を使用した。
C. Classifier Two types of classifiers were used: a centrifugal separator and a magnetic separator.
(1) 遠心分離機
遠心分離機とは、固体と液体の混合液を固体と液体の比重差を利用し分離するもので、遠心力を利用しより効果的に固体と液体を分離することができる。今回の実験では、IHI社製のMW−4を使用した。下表6に遠心分離機の性能を示す。
(1) Centrifugal separator A centrifugal separator separates a mixed liquid of solid and liquid using the difference in specific gravity between the solid and liquid, and more effectively separates the solid and liquid using centrifugal force. it can. In this experiment, IHI MW-4 was used. Table 6 below shows the performance of the centrifuge.
(2) 磁気選別機
今回の実験では、日本エリーズマグネチックス社製のドラム回転式磁気選別機の実験機を使用した。下表7に磁気選別機の性能を示す。
(2) Magnetic sorter In this experiment, a drum rotating magnetic sorter experimental machine manufactured by Elise Magnetics Japan was used. Table 7 below shows the performance of the magnetic sorter.
(2)実験方法
図4に実験フロー、下表8、9に各実験条件を示す。粘土溶解槽に試料土、水を加え、比重1.2〜1.4の泥水に調整する。比重調整した泥水をポンプにて撹拌槽へ送り、ここで試料土重量に対して2 %の鉄粉を添加し、均一に撹拌する。次に鉄粉を含む泥水をポンプで圧送し、分級機にて鉄粉を含む重金属汚染土と浄化土に分級した。この時の送泥量は、分級機の処理能力に応じて、遠心分離機は2〜6 m3/h、磁気選別機は0.2〜0.6 m3/hとした。ポンプでの通水時間は3分間とし、開始2分後に各泥水をサンプリングし泥水比重、鉄粉量、土砂量等を計測した。
(2) Experimental method FIG. 4 shows the experimental flow, and Tables 8 and 9 below show the experimental conditions. Add sample soil and water to the clay dissolution tank and adjust to mud water with a specific gravity of 1.2-1.4. The specific gravity-adjusted mud is sent to the stirring tank by a pump, where 2% iron powder is added to the sample soil weight and stirred uniformly. Next, muddy water containing iron powder was pumped with a pump and classified into heavy metal contaminated soil and purified soil containing iron powder by a classifier. The amount of mud fed at this time was 2 to 6 m 3 / h for the centrifugal separator and 0.2 to 0.6 m 3 / h for the magnetic separator depending on the processing capacity of the classifier. The water flow time with the pump was 3 minutes, and 2 minutes after the start, each mud was sampled, and the specific gravity of mud, the amount of iron powder, the amount of earth and sand, etc. were measured.
(3)試験結果及び考察
今回の実験結果から得られるデータから考察するにあたり、「鉄粉回収率」と「浄化土の割合」に着目して実験を行った。鉄粉回収率と浄化土の割合は、下式(2)及び下式(3)より求める。
(3) Test results and discussion In considering from the data obtained from the results of this experiment, experiments were conducted focusing on the "iron powder recovery rate" and the "purified soil ratio". The iron powder recovery rate and the ratio of purified soil are obtained from the following formula (2) and the following formula (3).
鉄粉回収率は、分級前の泥水中の全鉄粉量に対する重金属汚染土中の鉄粉量の割合を示す。浄化土の割合は、分級前の全泥水量に対する浄化土の割合を示す。   The iron powder recovery rate indicates the ratio of the amount of iron powder in the heavy metal contaminated soil to the total amount of iron powder in the mud before classification. The ratio of the purified soil indicates the ratio of the purified soil to the total amount of mud before classification.
試験結果を、図5に泥水比重1.4での遠心分離機の鉄粉回収率と浄化土の割合を示し(表8のケース10〜18をグラフ化)、図6に泥水比重1.2及び1.4での磁気選別機の鉄粉回収率と浄化土の割合を示す(表9のケース1〜4、8、11、12をグラフ化)。   Fig. 5 shows the iron powder recovery rate of the centrifuge and the ratio of the purified soil at a muddy water specific gravity of 1.4 (graphed cases 10 to 18 in Table 8), and Fig. 6 shows the muddy water specific gravity of 1.2 and 1.4. The iron powder recovery rate of the magnetic sorter and the ratio of the purified soil are shown (graphs of cases 1 to 4, 8, 11, and 12 in Table 9).
(1) 鉄粉回収率
遠心分離機の鉄粉回収率をみると、遠心力を50 Gとすると最大でも86 %であり目標値である90 %を下回る結果となったが、遠心力を100 G以上とすると最大で99 %となりすべての送泥量で90 %以上を達成した。また、送泥量による変化をみると、各遠心力の場合において送泥量の増加に伴い鉄粉回収率も増加する傾向がみられた。一方、磁気選別機ではすべての送泥量において98 %以上を示した。また、送泥量の増加による鉄粉回収率の変化は見られなかった。
(1) Iron powder recovery rate Looking at the iron powder recovery rate of the centrifuge, when the centrifugal force was 50 G, the maximum was 86%, which was below the target value of 90%, but the centrifugal force was 100%. At G or higher, the maximum was 99%, and 90% or more was achieved for all mud feed rates. In addition, looking at changes due to the amount of mud fed, there was a tendency for the iron powder recovery rate to increase as the amount of mud fed increased for each centrifugal force. On the other hand, the magnetic sorter showed 98% or more in all mud feed. Moreover, the change of the iron powder recovery rate by the increase in the amount of mud was not seen.
(2) 浄化土の割合
浄化土の割合に着目すると、遠心分離機では、送泥量2 m3/h、遠心力50 Gの場合、95 %に達したが、遠心力を増加させ200 Gとすると75 %まで低下する結果となった。そのほかの送泥量でも遠心力の増加により浄化土の割合が低下する傾向があることが明らかとなった。磁気選別機で送泥量を0.2 m3/hとし、回転数を2.5 rpmから5.0 rpmに増加させても、浄化土の割合は95 %から93 %と低下幅は小さかった。したがって、鉄粉回収率が最も良い遠心力(200 G)もしくは回転数(2.5 rpm)で浄化土の割合を比較すると、遠心分離機より磁気選別機のほうが浄化土の割合が高い結果となった。
(2) Ratio of clarified soil Focusing on the ratio of clarified soil, the centrifugal separator reached 95% when the amount of mud was 2 m 3 / h and the centrifugal force was 50 G, but the centrifugal force was increased to 200 G. As a result, it decreased to 75%. It became clear that the percentage of purified soil tended to decrease due to the increase in centrifugal force at other mud feed rates. Even if the amount of mud was changed to 0.2 m 3 / h using a magnetic sorter and the rotation speed was increased from 2.5 rpm to 5.0 rpm, the percentage of the purified soil decreased from 95% to 93%. Therefore, when the ratio of the purified soil was compared at the centrifugal force (200 G) or the rotation speed (2.5 rpm) with the best iron powder recovery rate, the magnetic sorter showed a higher ratio of the purified soil than the centrifuge. .
今回の実験では、遠心分離機、磁気選別機のいずれでも投入した鉄粉の90%以上を回収できることが確認できた。しかし分級できる浄化土の割合を比較すると、遠心分離機では75%であったのに対し、磁気選別機では90%以上を回収できることから、濃縮泥水から鉄粉を回収するための分級機としては磁気選別機のほうが有効であることがわかった。   In this experiment, it was confirmed that more than 90% of the iron powder charged could be recovered using either a centrifugal separator or a magnetic separator. However, comparing the percentage of purified soil that can be classified, it was 75% in the centrifugal separator, but more than 90% can be recovered in the magnetic separator, so it is a classifier for recovering iron powder from concentrated mud water. We found that the magnetic sorter is more effective.
〔本発明への適用に関して〕
(1) 磁気選別機における比重差に関して
図6に示した試験結果を見ると分かるように、浄化土の割合に関して、比重1.2の泥水よりも比重1.4の泥水の方が浄化土の割合が高くなった。この理由は定かではないが下記のように推察できる。
[Regarding application to the present invention]
(1) Regarding the specific gravity difference in the magnetic sorter As can be seen from the test results shown in FIG. 6, the muddy water with a specific gravity of 1.4 is better than the muddy water with a specific gravity of 1.2 with respect to the ratio of the purified soil. The rate has increased. The reason for this is not clear, but can be inferred as follows.
(a)ドラム表面へ付着できる泥水量の違い
ドラム表面には、泥水が一定量付着する。比重1.2の泥水より比重1.4の泥水の方が鉄粉を多く含むため、ドラム表面には比重1.2の泥水に比べ多くの鉄粉が付着し、ドラム単位面積に占める鉄粉の割合が比重1.2に比べて多くなる。
(a) Difference in the amount of muddy water that can adhere to the drum surface A certain amount of muddy water adheres to the drum surface. Since muddy water with a specific gravity of 1.4 contains more iron powder than muddy water with a specific gravity of 1.2, more iron powder adheres to the drum surface than with muddy water with a specific gravity of 1.2, and the ratio of iron powder to the drum unit area is 1.2. More than that.
従って、ドラム表面に付着できる泥水の割合が比重1.2に比べて少なくなる。よって、ドラム表面に付着して汚染土側へ運ばれる泥水量が比重1.2に比べて少なくなることで、浄化土の割合が増加する。   Therefore, the ratio of muddy water that can adhere to the drum surface is smaller than the specific gravity of 1.2. Therefore, the amount of muddy water that adheres to the drum surface and is carried to the contaminated soil side is smaller than the specific gravity of 1.2, thereby increasing the proportion of the purified soil.
(b)ドラム表面から振り落とされる泥水量の違い
ドラム表面には、泥水が一定量付着するが、付着した泥水は比重により重量が異なる。軽い泥水であればドラム表面に付着して汚染土側に運ばれてしまうが、重い泥水であればドラム表面から落とされてしまうと考えられる。したがって、比重1.2の泥水は比重1.4と比較して軽い泥水であるため、比重1.4泥水に比べて多くの泥水が汚染土側に運ばれてしまったため、浄化土の割合が低下する。
(b) Difference in the amount of muddy water shaken off from the drum surface Although a certain amount of muddy water adheres to the drum surface, the adhering muddy water varies in weight due to its specific gravity. If it is light muddy water, it will adhere to the drum surface and will be carried to the contaminated soil side, but if it is heavy muddy water, it will be dropped from the drum surface. Accordingly, since the mud having a specific gravity of 1.2 is lighter than that of the specific gravity of 1.4, a larger amount of mud was carried to the contaminated soil than the mud of specific gravity of 1.4, and the ratio of the purified soil is reduced.
以上の知見に基づき、本発明では、比重1.2の余剰泥水を比重1.4±5%まで濃縮することにより、重金属が混入していない浄化土の割合を可及的に高めるようにした。   Based on the above knowledge, in the present invention, the excess mud water having a specific gravity of 1.2 is concentrated to a specific gravity of 1.4 ± 5%, so that the proportion of the purified soil not containing heavy metals is increased as much as possible. .
(2)実施工における磁気選別機への泥水供給量に関して
図6に示した試験結果を見ると分かるように、浄化土の割合に関して、比重1.4のケースで、上側に凸の折れ線となっており、送泥量0.4 m3/hの場合が浄化土の割合が最も高くなっている。従って、この図6の相関図に基づき、所定の数値範囲幅で送泥量の最適範囲を設定し、これに前記スケールアップ係数αを乗じた送泥量によって前記磁気選別機の運転を行うようにすれば、これにより、重金属が混入していない浄化土の割合を可及的に高めることが可能となると推察される。
(2) Concerning the amount of muddy water supplied to the magnetic separator in the construction work As can be seen from the test results shown in Fig. 6, the ratio of the purified soil is a convex line on the upper side in the case of specific gravity 1.4. When the amount of mud is 0.4 m 3 / h, the percentage of purified soil is the highest. Therefore, based on the correlation diagram of FIG. 6, the optimum range of the mud feed amount is set with a predetermined numerical range, and the magnetic sorter is operated by the mud feed amount multiplied by the scale-up coefficient α. In this case, it is presumed that this makes it possible to increase as much as possible the proportion of the purified soil in which heavy metals are not mixed.
以下に、具体例で示す。   Specific examples are shown below.
図6において送泥量の最適範囲を0.3〜0.5 m3/hと設定する。仮に実験用磁気選別機(ドラム径:380mm、ドラム幅:300mm)と、実施工用磁気選別機(ドラム径:1220mm、ドラム幅3050mm)との間で送泥量のスケールアップを行うものとする。なお、磁力の増加率は1.7倍(=浄化土が流れる流路の高さ寸法の増加率)とし、ドラムの回転速度の増加率は1.0(=回転速度は同じ)とする。 In FIG. 6, the optimum range of the amount of mud is set to 0.3 to 0.5 m 3 / h. Temporarily, the scale of mud feed shall be scaled up between a magnetic separator for experiments (drum diameter: 380 mm, drum width: 300 mm) and a magnetic separator for work (drum diameter: 1220 mm, drum width 3050 mm). . The increase rate of the magnetic force is 1.7 times (= the increase rate of the height dimension of the flow path through which the purification soil flows), and the increase rate of the drum rotation speed is 1.0 (= the rotation speed is the same).
実験用磁気選別機と実施工用磁気選別機とを比較すると、上式(1)の各因数は、β=10、β=1.7、β=3.2、β=1.0となるから、スケールアップ係数αは、α=10×1.7×3.2×1.0=54.4となる。 Comparing the magnetic separator for experiment with the magnetic separator for working construction, each factor of the above equation (1) becomes β 1 = 10, β 2 = 1.7, β 3 = 3.2, β 4 = 1.0. The scale-up coefficient α is α = 10 × 1.7 × 3.2 × 1.0 = 54.4.
従って、実施工における磁気選別機9への送泥量は、前記0.3〜0.5 m3/hの範囲を54.4倍することによって、16.3〜27.2m3/hと求めることができ、この送泥量で運転することにより、重金属が混入していない浄化土の割合を可及的に高めることが可能となる。 Therefore, Okudoro amount of the magnetic separator 9 in the real construction is the range of the 0.3 to 0.5 m 3 / h by multiplying 54.4, it can be determined as 16.3~27.2m 3 / h, the Okudoro amount It is possible to increase as much as possible the percentage of the purified soil not mixed with heavy metals.
〔他の形態例〕
(1)本形態例では、泥水式又は泥水加圧式シールド工法の例により説明を行ったが、泥土式のシールド工法であっても、掘削した土砂を解砕機により解砕し、水を加えて泥水とした後に、本発明を同様に適用して重金属が混入した土砂の処理を行うことが可能である。
[Other examples]
(1) In this example, explanation was given by using an example of a muddy water type or muddy water pressure type shield method, but even with a muddy type shield method, the excavated earth and sand were crushed with a crusher and water was added. After making muddy water, it is possible to treat the earth and sand mixed with heavy metals by applying the present invention in the same manner.
1…シールド機、2…振動脱水篩、3…調整槽、4…余剰汚泥槽、5…濃縮デカンタ、6…濃縮泥水槽、7…鉄粉フィーダー、8…鉄粉混合槽、9…磁気選別機、10…永久磁石、11…ドラムシェル、12…スクレーパ、13…泥水タンク、14…浄化土タンク、15…流路(浄化土)   DESCRIPTION OF SYMBOLS 1 ... Shield machine, 2 ... Vibration dehydration sieve, 3 ... Adjustment tank, 4 ... Excess sludge tank, 5 ... Concentrated decanter, 6 ... Concentrated mud tank, 7 ... Iron powder feeder, 8 ... Iron powder mixing tank, 9 ... Magnetic sorting 10 ... Permanent magnet, 11 ... Drum shell, 12 ... Scraper, 13 ... Muddy water tank, 14 ... Purified soil tank, 15 ... Flow path (purified soil)

Claims (5)

  1. シールド工事で発生した余剰泥水を濃縮デカンタにより比重1.4±5%の濃縮泥水に調整する泥水濃縮工程と、
    前記濃縮泥水中の土砂重量に対して重金属を吸着するための鉄粉を1〜5重量%の割合で混入し、10〜60分の撹拌を行い、前記鉄粉に重金属を吸着させる鉄粉混入撹拌工程と、
    前記鉄粉を混入した濃縮泥水を磁気選別機に送り、鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する分級工程とを備えることを特徴とするシールド工事における重金属汚泥水の処理方法。
    A muddy water concentration process for adjusting surplus muddy water generated by the shield construction to a concentrated muddy water with a specific gravity of 1.4 ± 5% by a concentrated decanter;
    Mixing iron powder for adsorbing heavy metals at a ratio of 1 to 5% by weight with respect to the weight of earth and sand in the concentrated mud water, stirring for 10 to 60 minutes, and mixing iron powder to adsorb heavy metals to the iron powder A stirring step;
    In shield construction characterized by comprising a classification step of sending the concentrated mud mixed with iron powder to a magnetic sorter and classifying it into purified soil not mixed with iron powder and contaminated soil mixed with iron powder Treatment method for heavy metal sludge water.
  2. 前記分級工程において、前記磁気選別機に対する濃縮泥水の送泥量を決定するに当たり、
    実機よりも小能力の実験用磁気選別機を用いた室内実験において、対象となる重金属含有汚泥水を比重1.4±5%の濃縮泥水に調整した濃縮泥水を用い、この濃縮泥水を前記実験用磁気選別機に送り、鉄粉が混入していない浄化土と、鉄粉が混入した汚染土とに分級する作業を行い、送泥量と浄化土の割合との関係を示す相関図を得て、送泥量の最適範囲を決定し、
    実施工において、前記送泥量の最適範囲を実機サイズにスケールアップするために下式(1)に示すスケールアップ係数αを乗じた送泥量によって前記磁気選別機の運転を行う請求項1記載のシールド工事における重金属汚泥水の処理方法。
    In the classification step, in determining the amount of concentrated mud sent to the magnetic separator,
    In an indoor experiment using a magnetic separator for experiments with a smaller capacity than the actual machine, the concentrated mud was prepared by adjusting the concentrated heavy mud containing the target heavy metal to a concentrated mud with a specific gravity of 1.4 ± 5%. Sent to a magnetic separator, and classified into purified soil not containing iron powder and contaminated soil containing iron powder, and a correlation diagram showing the relationship between the amount of mud fed and the ratio of purified soil was obtained. Determine the optimum range of mud supply,
    2. The magnetic sorter is operated by a mud feed amount multiplied by a scale-up factor α shown in the following formula (1) in order to scale up the optimum range of the mud feed amount to an actual machine size in an actual work. To treat heavy metal sludge water in shield construction in Japan.
  3. 前記鉄粉は、鉄分90%以上、かさ密度3.0(g/cm3)、平均粒径100μmの物性値のものを用いる請求項1、2いずれかに記載のシールド工事における重金属汚泥水の処理方法。 The heavy metal sludge water in shield construction according to any one of claims 1 and 2, wherein the iron powder is one having physical properties of iron content 90% or more, bulk density 3.0 (g / cm 3 ), and average particle size 100 µm. Processing method.
  4. 泥水式又は泥水加圧式のシールド機から送られてくる泥水を振動脱水篩によって粒径0.075mmを境に礫・砂分とシルト・粘土分とに分級するとともに、前記シルト・粘土分を調整槽に送給し、この調整槽に貯留された泥水を再び前記シールド機に送る一次処理循環ラインと、前記濃縮デカンタで発生した低比重泥水を前記調整槽に送り比重調整のための希釈水として使用する二次処理循環ラインとを備える請求項1〜3いずれかに記載のシールド工事における重金属汚泥水の処理方法。   The muddy water sent from the muddy water type or muddy water pressure type shield machine is classified into gravel, sand and silt / clay by a vibrating dewatering sieve with a particle size of 0.075mm as a boundary, and the silt / clay content is adjusted. The primary treatment circulation line that sends the muddy water stored in the adjustment tank to the shield machine again, and the low specific gravity muddy water generated in the concentrated decanter is sent to the adjustment tank and used as dilution water for adjusting the specific gravity. The processing method of the heavy metal sludge water in the shield construction in any one of Claims 1-3 provided with the secondary treatment circulation line which performs.
  5. 前記振動脱水篩の前段に前処理機として、シールド機からの泥水を細かく解砕する泥水解砕装置を備える請求項4記載のシールド工事における重金属汚泥水の処理方法。   The method for treating heavy metal sludge water in shield construction according to claim 4, further comprising a muddy water crushing device for finely crushing muddy water from the shield machine as a pre-treatment machine in the previous stage of the vibration dewatering sieve.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6358520B1 (en) * 2017-12-12 2018-07-18 公信 山▲崎▼ Soil purification system
JP6358519B1 (en) * 2017-12-12 2018-07-18 公信 山▲崎▼ Soil purification system
JP6399325B1 (en) * 2017-11-29 2018-10-03 公信 山▲崎▼ Soil purification system
JP6399326B1 (en) * 2017-11-29 2018-10-03 公信 山▲崎▼ Soil purification system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6399325B1 (en) * 2017-11-29 2018-10-03 公信 山▲崎▼ Soil purification system
JP6399326B1 (en) * 2017-11-29 2018-10-03 公信 山▲崎▼ Soil purification system
JP6358520B1 (en) * 2017-12-12 2018-07-18 公信 山▲崎▼ Soil purification system
JP6358519B1 (en) * 2017-12-12 2018-07-18 公信 山▲崎▼ Soil purification system

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