JP2021012115A - Desilting method and classification method for soil - Google Patents
Desilting method and classification method for soil Download PDFInfo
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Abstract
Description
本発明は、土壌の解泥方法及び分級方法に関する。 The present invention relates to a soil demudification method and a classification method.
従来、土壌をドラムウォッシャーやボールミルで粉砕することが行われている（例えば、特許文献１及び２参照）。粉砕及びその後の分級は、一般に所望の粒径を分級点として土壌を分離することを目的としている。 Conventionally, soil is crushed with a drum washer or a ball mill (see, for example, Patent Documents 1 and 2). Crushing and subsequent classification are generally aimed at separating the soil with the desired particle size as the classification point.
粉砕及び分級の対象とする土壌に有機物が含まれている場合は、土壌が団粒化している傾向があり、所望の解砕（解泥）・粉砕及び分級を達成することができない場合がある。また、上記特許文献１及び２の方法では、土壌を数μｍ程度にまで粉砕することは容易ではなく、数μｍ程度の粒径の土壌を得る要求に応えることが困難であった。 If the soil to be crushed and classified contains organic matter, the soil tends to be agglomerated, and the desired crushing (mud crushing), crushing and classification may not be achieved. .. Further, in the methods of Patent Documents 1 and 2, it is not easy to crush the soil to about several μm, and it is difficult to meet the demand for obtaining soil having a particle size of about several μm.
本発明は、土壌が有機物を含み団粒を形成している場合であってもこれを確実に解泥・粉砕でき、数μｍ程度の粒径の土粒子を含む土壌を得ることができる、土壌の解泥方法を提供することを目的とする。また、その解泥方法を使用した土壌の分級方法を提供することを目的とする。 According to the present invention, even when the soil contains organic matter and forms aggregates, it can be reliably demudged and crushed, and soil containing soil particles having a particle size of about several μm can be obtained. The purpose is to provide a method of demudification. Another object of the present invention is to provide a soil classification method using the demudification method.
本発明は、有機物を含む土壌を湿式ミルで粉砕し、湿式ミル内で用いる粉砕媒体は、粒径が２〜１８ｍｍである、土壌の解泥方法を提供する。 The present invention provides a method for demudging soil in which soil containing organic matter is pulverized with a wet mill and the pulverization medium used in the wet mill has a particle size of 2 to 18 mm.
有機物を含む土壌は団粒化している傾向があり、湿式ミル内にて粒径が数十ｍｍの粉砕媒体を用いた場合は、所定の粒径以下の団粒を粉砕することが困難である。ここで、粉砕媒体として粒径が２〜１８ｍｍであるものを用いることにより、これと同程度の大きさの団粒を粉砕することが容易となる。これによれば、土壌を数μｍ程度の粒子にまで粉砕することができる。 Soil containing organic matter tends to be agglomerated, and when a pulverizing medium having a particle size of several tens of millimeters is used in a wet mill, it is difficult to pulverize aggregates having a particle size of a predetermined size or less. .. Here, by using a pulverizing medium having a particle size of 2 to 18 mm, it becomes easy to pulverize aggregates having the same size as this. According to this, the soil can be crushed into particles of about several μm.
土壌は、放射性セシウムを含有しているものであってもよい。放射性セシウムは一般に、粒径が数μｍ〜２０μｍの粘土に付着している。従って、上記の粉砕を達成することができれば、放射性セシウムの濃度が高い数μｍ〜２０μｍの粘土粒子を粒径が大きな他の部分から分離することで、放射性被処理物の減容化に資する。 The soil may contain radioactive cesium. Radioactive cesium is generally attached to clay with a particle size of several μm to 20 μm. Therefore, if the above pulverization can be achieved, the clay particles having a high concentration of radioactive cesium of several μm to 20 μm can be separated from other portions having a large particle size, thereby contributing to the volume reduction of the radioactive object to be treated.
粉砕媒体は、砂又は礫であってもよい。 The crushing medium may be sand or gravel.
土壌は、農地由来の土壌であって腐植質を含有しているものであってもよい。農地由来の土壌は特に団粒化している傾向が強いので、本発明の適用対象として好適である。 The soil may be a soil derived from agricultural land and may contain humus. Agricultural land-derived soil has a particularly strong tendency to agglomerate, and is therefore suitable as an application target of the present invention.
本発明において、湿式ミルでの粉砕に際し、湿式ミル内の内容物のｐＨを９〜１３に調整することが好ましい。また、湿式ミルでの粉砕をする前に、土壌を水と混合し、これを所定の時間２５〜１００℃に保つことが好ましい。これらによれば、解泥速度が高まる。 In the present invention, it is preferable to adjust the pH of the contents in the wet mill to 9 to 13 when pulverizing in the wet mill. Further, it is preferable to mix the soil with water and keep it at 25 to 100 ° C. for a predetermined time before grinding with a wet mill. According to these, the demolition rate is increased.
また、本発明は、上記解泥方法によって解泥した後の泥水を、固液分離手段により固液分離する分級方法を提供する。これによれば、対象土壌から粒径が数μｍ程度の粘土を分級することができる。 The present invention also provides a classification method for solid-liquid separation of mud water after mud removal by the above-mentioned mud-removing method by solid-liquid separation means. According to this, clay having a particle size of about several μm can be classified from the target soil.
本発明によれば、土壌が有機物を含み団粒を形成している場合であってもこれを確実に解泥・粉砕でき、数μｍ程度の粒径の土粒子を含む土壌を得ることができる、土壌の解泥方法を提供することができる。また、その解泥方法を使用した土壌の分級方法を提供することができる。 According to the present invention, even when the soil contains organic matter and forms aggregates, it can be reliably demudged and crushed, and soil containing soil particles having a particle size of about several μm can be obtained. , Can provide a method of soil demudification. In addition, it is possible to provide a soil classification method using the demudification method.
以下、本発明の好適な実施形態について詳細に説明する。本実施形態の土壌の解泥方法及び分級方法では、有機物を含む土壌を湿式ミルで粉砕する。以下では、放射性セシウムを含有している農地由来の土壌を対象として説明する。 Hereinafter, preferred embodiments of the present invention will be described in detail. In the soil demudification method and classification method of the present embodiment, the soil containing organic matter is crushed with a wet mill. In the following, soil derived from agricultural land containing radioactive cesium will be described.
農地由来の土壌は、有機物を多く含む。ここで有機物とは、例えば腐植質、菌類、微生物、根毛、難腐植性セルロースが挙げられる。腐植質とは、植物や動物由来の有機物が分解して生じた物質であり、大きさとしては、数ｎｍ〜数ｃｍのものまで様々である。 Agricultural land-derived soil is rich in organic matter. Here, the organic matter includes, for example, humus, fungi, microorganisms, root hairs, and refractory cellulose. The humus is a substance produced by decomposing organic matter derived from plants and animals, and its size varies from several nm to several cm.
有機物を含む土壌は、有機物が土粒子同士を結合させて団粒化している傾向がある。団粒は、土壌を粉砕しようとする力に抵抗するので、任意の粉砕装置を用いた場合において、所望の粉砕を達成できない場合がある。従って、土壌を粉砕、更には分級する際には、団粒状態を解消すること（これを「解泥」と呼ぶ。）が望ましい。 In soil containing organic matter, the organic matter tends to bind soil particles to agglomerate. Since the aggregates resist the force of crushing the soil, the desired crushing may not be achieved when using any crushing device. Therefore, when crushing and further classifying the soil, it is desirable to eliminate the aggregated state (this is called "demudation").
本実施形態の解泥方法では、初めに対象土壌を水と混合して泥水とする。次に、この泥水を篩にかけて、粒径の大きな（例えば２ｍｍ以上）砂や礫を取り除く。篩を通過した泥水を湿式ミルに投入し、湿式ミルを稼働して土壌を粉砕する。 In the mud-removing method of the present embodiment, the target soil is first mixed with water to obtain muddy water. Next, this muddy water is sieved to remove sand and gravel having a large particle size (for example, 2 mm or more). The muddy water that has passed through the sieve is put into a wet mill, and the wet mill is operated to crush the soil.
ここで、湿式ミル内で用いる粉砕媒体は、金属球、合金球、金属酸化物球又は金属複合酸化物球等であってもよく、砂又は礫であってもよい。金属としては鉄、アルミニウム等、合金としてはステンレス等、金属酸化物及び金属複合酸化物としては鉄の酸化物やアルミニウム、ジルコン等の酸化物及び複合酸化物が挙げられる。砂又は礫としては、対象土壌とは別に用意した砂又は礫を用いてもよく、上記の篩で分離した砂又は礫を洗浄して用いてもよい。後者の場合は、同一の土壌に含まれていた粒子を再利用することとなるので経済的である。粉砕媒体の密度は、２．０〜８．０ｇ／ｃｍ３であることが好ましく、２．２〜６．０ｇ／ｃｍ３であることがより好ましく、２．４〜３．６ｇ／ｃｍ３であることが更に好ましい。 Here, the pulverizing medium used in the wet mill may be a metal sphere, an alloy sphere, a metal oxide sphere, a metal composite oxide sphere, or the like, or sand or gravel. Examples of the metal include iron and aluminum, the alloy includes stainless steel and the like, and examples of the metal oxide and the metal composite oxide include iron oxide and oxides and composite oxides such as aluminum and zircon. As the sand or gravel, sand or gravel prepared separately from the target soil may be used, or the sand or gravel separated by the above-mentioned sieve may be washed and used. In the latter case, it is economical because the particles contained in the same soil are reused. The density of the grinding media is preferably from 2.0~8.0g / cm 3, more preferably 2.2~6.0g / cm 3, in 2.4~3.6g / cm 3 It is more preferable to have.
湿式ミル内で用いる粉砕媒体は、粒径が２〜１８ｍｍである。当該粒径は、３〜１４ｍｍであることが好ましく、４〜１２ｍｍであることがより好ましい。土壌の団粒は大きさがこれらの範囲内である場合が多いので、粉砕媒体の粒径がこれらの範囲内であると、団粒を粉砕する効率が高い。なお、粉砕媒体として粒径が砂又は礫である場合の粒径の測定方法は、湿式振動篩い分け法、又は、水簸傾斜法による。 The pulverizing medium used in the wet mill has a particle size of 2 to 18 mm. The particle size is preferably 3 to 14 mm, more preferably 4 to 12 mm. Since the size of aggregates in soil is often within these ranges, the efficiency of crushing aggregates is high when the particle size of the crushing medium is within these ranges. When the particle size of the pulverizing medium is sand or gravel, the method of measuring the particle size is a wet vibration sieving method or an elutriation gradient method.
湿式ミルの外周移動距離（すなわち外周速度に解泥時間又は滞留時間を乗じた数値）は、解泥を十分なものとする観点から８０ｍ以上であることが好ましく、２４０ｍ以上であることがより好ましく、３９０ｍ以上であることが更に好ましい。 The outer peripheral movement distance of the wet mill (that is, a value obtained by multiplying the outer peripheral speed by the demudging time or the residence time) is preferably 80 m or more, and more preferably 240 m or more from the viewpoint of sufficient demudification. It is more preferably 390 m or more.
以上の方法で土壌を解泥すると、土壌の粒度分布が、粒径の小さなほうへ偏っていく。その後、湿式ミルから泥水を取り出し、これを篩にかけて所定の粒径以上（例えば７５μｍ以上）の土壌を取り除く。更に、例えばサイクロン等の分級機を用いて、粒径が３０μｍ以上又は２０μｍ以上又は１０μｍ以上の土壌を取り除く。 When the soil is demudified by the above method, the particle size distribution of the soil is biased toward the smaller particle size. Then, the muddy water is taken out from the wet mill and sieved to remove the soil having a predetermined particle size or more (for example, 75 μm or more). Further, a classifier such as a cyclone is used to remove soil having a particle size of 30 μm or more, 20 μm or more, or 10 μm or more.
そして、その分級後に残った泥水を固液分離手段によって固液分離する。固液分離手段としては、マイクロバブル浮選や凝集沈殿法を用いることができる。マイクロバブル浮選とは、μｍ程度の大きさの泡（マイクロバブル）を利用して懸濁液中の所定の微粒子を分離する方法である。マイクロバブルが所定の微粒子に付着して水面に浮上するので、これを回収することで粒径がμｍレベルの粘土粒子の分離が達成される。 Then, the muddy water remaining after the classification is solid-liquid separated by the solid-liquid separation means. As the solid-liquid separation means, microbubble flotation or coagulation precipitation method can be used. The microbubble flotation is a method of separating predetermined fine particles in a suspension by using bubbles (microbubbles) having a size of about μm. Since the microbubbles adhere to the predetermined fine particles and float on the water surface, the separation of clay particles having a particle size of μm level is achieved by collecting the microbubbles.
他方、凝集沈殿法は、凝集剤を添加して凝集物を生成して沈降速度を高める方法であり、粒子の表面電荷の中和、又は、表面の疎水性化がその原理となっている。凝集剤としては、表面電荷の中和を目的とする場合は特に多価金属イオンの塩が好ましく、ポリ塩化アルミニウム（ＰＡＣ）、硫酸アンモニウム、塩化鉄、硫酸鉄等が好ましい。表面の疎水性化を目的とする場合は、界面活性剤を用いることができる。 On the other hand, the coagulation-precipitation method is a method in which a coagulant is added to generate agglomerates to increase the sedimentation rate, and the principle is neutralization of the surface charge of particles or hydrophobization of the surface. As the flocculant, a salt of polyvalent metal ion is particularly preferable for the purpose of neutralizing the surface charge, and polyaluminum chloride (PAC), ammonium sulfate, iron chloride, iron sulfate and the like are preferable. A surfactant can be used for the purpose of making the surface hydrophobic.
以上に示した解泥方法及び分級方法によって、有機物を含む土壌から、粒径が数μｍ程度の粘土を分離することができる。 By the demudification method and the classification method shown above, clay having a particle size of about several μm can be separated from the soil containing organic matter.
本実施形態の解泥方法では、粉砕媒体の粒径が２〜１８ｍｍであるので、同程度の粒径に団粒化した土壌を粉砕するのに適している。粉砕媒体と団粒との粒径がこのような関係にあると、土壌粒子の表面を削り取るように粉砕すること（表面粉砕）、及び、土壌粒子を同程度の大きさの複数の小粒子に分割するように粉砕すること（体積粉砕）がバランスよく生じて、土壌中の有機団粒粒子が効率的に小さくなっていく。 In the demudification method of the present embodiment, since the particle size of the crushing medium is 2 to 18 mm, it is suitable for crushing soil aggregated to the same particle size. When the particle size of the crushing medium and the aggregates has such a relationship, the surface of the soil particles is crushed so as to be scraped off (surface crushing), and the soil particles are divided into a plurality of small particles of the same size. Grinding so as to divide (volume grind) occurs in a well-balanced manner, and the organic aggregate particles in the soil are efficiently reduced.
放射性セシウムは一般に、粒径が２０μｍ以下の粘土粒子、特に粒径が数百ｎｍ〜２０μｍの粘土粒子に多く付着している。従って、上記の解泥方法及び分級方法によれば、放射性セシウムの濃度が高い当該粘土粒子を粒径が大きな他の部分から分離することができる。これにより、当該他の部分（例えば粒径が２０μｍ以上の土壌）を資材として再利用することができるとともに、放射性セシウムを含有する部分を濃縮することができ、放射性被処理物の減容化に資することになる。 Radioactive cesium is generally adhered to a large amount of clay particles having a particle size of 20 μm or less, particularly clay particles having a particle size of several hundred nm to 20 μm. Therefore, according to the above-mentioned demudging method and classification method, the clay particles having a high concentration of radioactive cesium can be separated from other portions having a large particle size. As a result, the other part (for example, soil having a particle size of 20 μm or more) can be reused as a material, and the part containing radioactive cesium can be concentrated, thereby reducing the volume of the radioactive object to be treated. It will contribute.
以上、本発明の好適な実施形態について説明したが、本発明は上記実施形態に何ら限定されるものではない。例えば、上記実施形態では、粒径が比較的大きな（例えば２ｍｍ以上）砂や礫を取り除いた直後に当該泥水を湿式ミルに投入したが、当該分級をする前に泥水を湿式ミルに投入してもよく、反対に、更に目の小さな篩を用いて分級（例えば７５μｍ以上）した後に湿式ミルに投入してもよい。土壌が団粒化しているということは、本来であれば粒径が小さくて篩を通過する粒子であっても団粒化によって粒径が大きくなっており篩を通過しない場合がある。この場合、放射性セシウムを含有している粘土粒子が篩の上に残り得ることとなるため、これを避けるべく、湿式ミルによる解泥を分級工程全体における早い段階で行うことが好ましい。 Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the above embodiment, the muddy water is put into the wet mill immediately after removing sand and gravel having a relatively large particle size (for example, 2 mm or more), but the muddy water is put into the wet mill before the classification. On the contrary, it may be classified (for example, 75 μm or more) using a sieve having a smaller diameter and then put into a wet mill. The fact that the soil is agglomerated means that even particles that normally have a small particle size and pass through the sieve may not pass through the sieve because the particle size is increased due to agglomeration. In this case, clay particles containing radioactive cesium may remain on the sieve, and in order to avoid this, it is preferable to perform mud removal by a wet mill at an early stage in the entire classification step.
また、湿式ミルでの解泥に際し、解泥補助剤を添加してもよい。解泥補助剤としては、例えばｐＨ調整剤や分散剤が挙げられる。ｐＨ調整材としては、水酸化カルシウム（消石灰）、や水酸化ナトリウムのように、液性をアルカリ性にするものが挙げられる。対象土壌が酸性又は中性を示すものである場合、湿式ミルで解泥する泥水に対して、カルシウムイオンを添加して、泥水のｐＨを９〜１３、又は、１０〜１２、又は、１０．５〜１１．５程度に調整してもよい。これにより、解泥速度が高まる。カルシウムイオンの供給源としては水酸化カルシウム（消石灰）が好ましく、カルシウムイオンの供給源の添加量は、土壌（原土）１ｇに対して、カルシウムイオン（Ｃａ２＋）の量として、２．３×１０−６〜５．０×１０−３ｍｏｌとすることが好ましく、２．３×１０−５〜２．３×１０−３ｍｏｌとすることがより好ましく、５．０×１０−５〜１．０×１０−３ｍｏｌとすることが更に好ましく、１．０×１０−４〜８．０×１０−４ｍｏｌとすることが更により好ましく、２．３×１０−４〜３．０×１０−４ｍｏｌとすることが特に好ましい。 In addition, a mud removal aid may be added when demudging with a wet mill. Examples of the demudification auxiliary agent include a pH adjuster and a dispersant. Examples of the pH adjusting material include those that make the liquid alkaline, such as calcium hydroxide (slaked lime) and sodium hydroxide. When the target soil is acidic or neutral, calcium ions are added to the muddy water to be demudged with a wet mill to adjust the pH of the muddy water to 9 to 13, 10 to 12, or 10. It may be adjusted to about 5 to 11.5. This increases the rate of mud removal. Calcium hydroxide (sole lime) is preferable as the source of calcium ions, and the amount of the source of calcium ions added is 2.3 × as the amount of calcium ions (Ca 2+ ) with respect to 1 g of soil (raw soil). preferably to 10 -6 ~5.0 × 10 -3 mol, more preferably to 2.3 × 10 -5 ~2.3 × 10 -3 mol, 5.0 × 10 -5 ~1 It is more preferably 0.0 × 10 -3 mol, further preferably 1.0 × 10 -4 to 8.0 × 10 -4 mol, and 2.3 × 10 -4 to 3.0 ×. It is particularly preferably 10 -4 mol.
また、湿式ミルで粉砕をする前に、対象土壌を水と混合し、これを所定の時間２５〜１００℃に保ったあとで、湿式ミルで粉砕してもよい。この温度の下限は３０℃であってもよく、３５℃であってもよい。この温度の上限としては、８０℃であってもよく、６０℃であってもよい。排水の温度基準の観点から上限は４５℃であることが好ましい。温度を保つ時間は、５〜６０分であってもよく、１０分〜５０分であってもよい。この時間が経過する間に、温度は上記範囲内で変動してもよい。これらの条件を満たした処理を行ったうえで解泥をすると、解泥速度が一層高まり、解泥後の最終的な粒径として、より小さな粒径を有する土壌粒子の割合が一層高くなる。なお、この処理を行った場合、解泥時の温度は問わず、常温で解泥してもよい。 Further, before pulverizing with a wet mill, the target soil may be mixed with water, kept at 25 to 100 ° C. for a predetermined time, and then pulverized with a wet mill. The lower limit of this temperature may be 30 ° C. or 35 ° C. The upper limit of this temperature may be 80 ° C. or 60 ° C. From the viewpoint of the temperature standard of wastewater, the upper limit is preferably 45 ° C. The time for maintaining the temperature may be 5 to 60 minutes, or 10 to 50 minutes. During this time, the temperature may fluctuate within the above range. When the mud is demud after performing the treatment satisfying these conditions, the demud removal rate is further increased, and the proportion of soil particles having a smaller particle size is further increased as the final particle size after the demud. When this treatment is performed, the mud may be removed at room temperature regardless of the temperature at the time of mud removal.
また、上記実施形態では放射性セシウムを含有している農地由来の土壌を対象としたが、有機物を含む土壌であれば、農地由来のものに限らず他の土壌を対象としてもよい。 Further, in the above embodiment, the soil derived from the agricultural land containing radioactive cesium is targeted, but the soil containing organic matter may be targeted not only from the soil derived from the agricultural land but also from other soils.
以下、実施例を挙げて本発明の内容をより具体的に説明する。なお、本発明は下記実施例に限定されるものではない。実施例の記載において「粉砕」という場合、湿式ミルで行う行為を指しており、内部で実際に生じる「粉砕」と「解泥」の両方を指しているものとする。 Hereinafter, the contents of the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples. In the description of the examples, the term "crushing" refers to the act performed by a wet mill, and refers to both "crushing" and "demudation" that actually occur inside.
＜実施例１〜４＞
粉砕容器として市販の９００ｍＬ容器の磁性ポッドミル（外径１３０ｍｍ）、粉砕媒体として直径が６ｍｍ又は１０ｍｍのアルミナボール（比重３．６）、更にはマルチングストーン（比重２．５〜２．７；主成分は石灰石＝炭酸カルシウム）を用意した。腐植質を含む土壌として、鹿沼産黒ボク土（平均水分率３１％）１０７ｇ、水５００ｍＬ、及び、粉砕媒体３００ｍＬを磁性ポッドに投入し、これを下記条件にてそれぞれ市販の卓上ボールミル架台で粉砕を行った（表１も参照）。
・共通条件…回転速度：２４ｒｐｍ；ミル外周速度：１６．３ｃｍ／秒；室温（約２０℃）
・（原土）…粉砕時間：０分（つまり粉砕なし）
・実施例１…粉砕時間：１０分；粉砕媒体：１０ｍｍ径アルミナボール
・実施例２…粉砕時間：４０分；粉砕媒体：１０ｍｍ径アルミナボール
・実施例３…粉砕時間：４０分；粉砕媒体：６ｍｍ径アルミナボール
・実施例４…粉砕時間：４０分；粉砕媒体：５ｍｍ径マルチングストーン
<Examples 1 to 4>
A commercially available 900 mL magnetic pod mill (outer diameter 130 mm) as a crushing container, alumina balls with a diameter of 6 mm or 10 mm (specific gravity 3.6) as a crushing medium, and mulching stone (specific gravity 2.5 to 2.7; main component) Prepared limestone = calcium carbonate). As soil containing humus, 107 g of Andosols from Kanuma (average moisture content 31%), 500 mL of water, and 300 mL of crushing medium were put into a magnetic pod, and these were crushed with a commercially available tabletop ball mill stand under the following conditions. (See also Table 1).
-Common conditions: Rotation speed: 24 rpm; Mill outer circumference speed: 16.3 cm / sec; Room temperature (about 20 ° C)
・ (Original soil)… Crushing time: 0 minutes (that is, no crushing)
Example 1 ... Crushing time: 10 minutes; Crushing medium: 10 mm diameter alumina ball-Example 2 ... Crushing time: 40 minutes; Crushing medium: 10 mm diameter alumina ball-Example 3 ... Crushing time: 40 minutes; Crushing medium: 6 mm diameter alumina ball ・ Example 4 ... Crushing time: 40 minutes; Crushing medium: 5 mm diameter multing stone
磁性ポッドミルから粉砕産物を取り出し、湿式振動篩分けにより分級した。このとき、３８μｍ以上の篩はＪＩＳ規格のステンレス篩を用い、２０μｍ以下の篩は伊藤製作所製プラスチック篩を用いた。原土及び実施例１〜３の粒度分布（頻度分布）の結果を図１に示す。 The pulverized product was taken out from the magnetic pod mill and classified by wet vibration sieving. At this time, a JIS standard stainless steel sieve was used for the sieve of 38 μm or more, and a plastic sieve manufactured by Ito Seisakusho was used for the sieve of 20 μm or less. The results of the particle size distribution (frequency distribution) of the raw soil and Examples 1 to 3 are shown in FIG.
図１に示したグラフから、実施例１〜３では黒ボク土の解泥が進み、粒径が小さくなったことが分かる。粉砕時間（解泥時間）を長くするほど、又は、アルミナボールの径を１０ｍｍから６ｍｍへ小さくしたことにより、粗粒側の頻度のピークが細かい粒度のほうへシフトする傾向が認められた。 From the graph shown in FIG. 1, it can be seen that in Examples 1 to 3, the demudification of Andosols progressed and the particle size became smaller. As the crushing time (demudation time) was lengthened or the diameter of the alumina balls was reduced from 10 mm to 6 mm, the frequency peak on the coarse grain side tended to shift toward the finer particle size.
また、原土、及び実施例１〜４の粉砕産物における０〜２０μｍ、２０〜７５μｍ、７５μｍ〜の粒子の割合（ｗｔ％；回収乾土ベース）を表１に示す。これによれば、各実施例において粒径２０μｍ以下にまで選択的に解泥されていることが分かる。 Table 1 shows the proportions (wt%; recovered dry soil base) of particles from 0 to 20 μm, 20 to 75 μm, and 75 μm in the raw soil and the pulverized products of Examples 1 to 4. According to this, it can be seen that the mud is selectively demuded to a particle size of 20 μm or less in each example.
＜実施例５〜７＞
粉砕容器として市販の４８００ｍＬ容器の磁性ポッドミル（外径２１５ｍｍ）、粉砕媒体として径が５ｍｍの朝明砂（比重２．６）を用意した。腐植質を含む土壌として、茨城大子の田の土（平均水分率３６％）を用意し、表２に示した量で対象土、水、及び、朝明砂を磁性ポッドに投入し、これを下記条件にてそれぞれ市販の卓上ボールミル架台で粉砕を行った。
<Examples 5 to 7>
A commercially available magnetic pod mill (outer diameter 215 mm) of a 4800 mL container was prepared as the crushing container, and morning sand (specific gravity 2.6) having a diameter of 5 mm was prepared as the crushing medium. As soil containing humus, Ibaraki Daigo field soil (average moisture content 36%) was prepared, and the target soil, water, and morning sand were put into the magnetic pod in the amounts shown in Table 2, and this was added. The crushing was performed on a commercially available tabletop ball mill stand under the following conditions.
実施例６及び７では消石灰を添加し、ｐＨを１１．５とした。さらに実施例７では、対象土、水、朝明石、消石灰を混合した後、これを４５℃の恒温槽内で１０分間静置した後に、ミルで粉砕した。実施例５〜７における粉砕前と粉砕産物の粒子のアンダーサイズを表２に示す。このアンダーサイズは、粒度分布測定装置により測定した。 In Examples 6 and 7, slaked lime was added to adjust the pH to 11.5. Further, in Example 7, the target soil, water, morning Akashi, and slaked lime were mixed, and then the mixture was allowed to stand in a constant temperature bath at 45 ° C. for 10 minutes and then pulverized with a mill. Table 2 shows the undersize of the particles of the pulverized product before pulverization in Examples 5 to 7. This undersize was measured with a particle size distribution measuring device.
表２に示した結果から、茨城大子の田の土を対象とした場合でも粒径１０μｍ以下にまで有効に解泥することができたことが分かる（実施例５）。また、粉砕時（解泥時）に消石灰を添加してｐＨを１１．５に調整したことで、消石灰を添加しなかった場合と比べて粉砕後の粒子のサイズがより小さくなったことが分かる（実施例６）。また、粉砕前にｐＨ１１．５にして対象土を加温したことで、粉砕後の粒子のサイズが一層小さくなったことが分かる（実施例７）。 From the results shown in Table 2, it can be seen that even when the soil in the rice fields of Daigo Ibaraki was targeted, the mud could be effectively demuded to a particle size of 10 μm or less (Example 5). In addition, it can be seen that by adding slaked lime during crushing (during demudification) and adjusting the pH to 11.5, the size of the particles after crushing became smaller than when slaked lime was not added. (Example 6). Further, it can be seen that the size of the particles after pulverization was further reduced by heating the target soil at pH 11.5 before pulverization (Example 7).
＜実施例８〜１６＞
実施例１の黒ボク土に代えて、茨城の畑土（平均水分率２１％）を対象とした。粉砕時間、回転速度、ミル外周速度、アルミナボール（又は、朝明砂（花崗岩質。比重２．６）、マルチングストーン）径を表３に示したとおり変更して粉砕を行った。粉砕に際し、表３に示したとおりの量で、磁性ポッド内に消石灰を添加した。原土、及び、粉砕産物における粒径割合を表３に示す。
<Examples 8 to 16>
Instead of the Andosols of Example 1, the field soil of Ibaraki (average moisture content 21%) was targeted. The crushing time, rotation speed, mill outer circumference speed, and alumina ball (or morning sand (granite, specific gravity 2.6), multing stone) diameter were changed as shown in Table 3 for crushing. Upon pulverization, slaked lime was added into the magnetic pod in the amount as shown in Table 3. Table 3 shows the particle size ratios in the raw soil and the crushed product.
表３に示した結果から、茨城の畑土を対象とした場合でも粒径２０μｍ以下にまで有効に解泥することができたことが分かる。 From the results shown in Table 3, it can be seen that even when the field soil in Ibaraki was targeted, the mud could be effectively demuded to a particle size of 20 μm or less.
＜実施例１７〜１９＞
粉砕容器として市販の４８００ｍＬ容器の磁性ポッドミル（外径２１５ｍｍ）、粉砕媒体として径が５ｍｍの朝明砂（比重２．６）を用意した。腐植質を含む土壌として、実施例８〜１６と同一の茨城の畑土（平均水分率２１％）、又は、茨城大子の田の土（平均水分率３６％）を用意し、表４に示した量で対象土、水、及び、朝明砂を磁性ポッドに投入し、これを下記条件にてそれぞれ市販の卓上ボールミル架台で粉砕を行った。粉砕産物における粒径割合を表４に示す。
<Examples 17 to 19>
A commercially available magnetic pod mill (outer diameter 215 mm) of a 4800 mL container was prepared as the crushing container, and morning sand (specific gravity 2.6) having a diameter of 5 mm was prepared as the crushing medium. As soil containing humus, prepare the same Ibaraki field soil (average moisture content 21%) as in Examples 8 to 16 or Ibaraki Daigo rice field soil (average moisture content 36%), and Table 4 shows. The target soil, water, and Asahi sand were put into a magnetic pod in the indicated amounts, and the soil, water, and morning sand were crushed on a commercially available tabletop ball mill stand under the following conditions. Table 4 shows the particle size ratio in the pulverized product.
表４に示した結果から、茨城大子の田の土を対象とした場合でも有効に解泥することができたことが分かる。 From the results shown in Table 4, it can be seen that even when the soil in the rice fields of Daigo Ibaraki was targeted, the mud could be effectively removed.
本発明は、団粒化している土壌を解泥及び分級することに利用することができる。
The present invention can be used to demud and classify aggregated soil.
Claims (7)
前記湿式ミル内で用いる粉砕媒体は、粒径が２〜１８ｍｍである、土壌の解泥方法。 Soil containing organic matter is crushed with a wet mill and
The pulverization medium used in the wet mill is a soil demudification method having a particle size of 2 to 18 mm.
A method for classifying soil, wherein the muddy water after being dehumidified by the method for dehumidifying the soil according to any one of claims 1 to 6 is solid-liquid separated by a solid-liquid separating means.
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| JP2021181949A (en) * | 2020-05-20 | 2021-11-25 | 鹿島建設株式会社 | Mud loosening method for soil |
| JP7311863B2 (en) | 2020-05-20 | 2023-07-20 | 鹿島建設株式会社 | Soil thaw method |
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| JP7260114B2 (en) | 2023-04-18 |
| JP2023073351A (en) | 2023-05-25 |
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