JP2019191177A - Method for cleaning radiation-contaminated soil and method for reducing volume - Google Patents
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本発明は、粘性土から構成される放射能汚染土壌と、粘土を多く含む放射能汚染土壌の洗浄処理、減容化処理に関する。 The present invention relates to a radioactively contaminated soil composed of cohesive soil and a cleaning treatment and a volume reducing treatment of the radioactively contaminated soil containing a large amount of clay.
東京電力福島第一原子力発電所事故により放出された放射性物質は、広い地域に拡散し、環境汚染を引き起こし、平成２４年には１６万人以上の市民が汚染地域からの避難を余儀なくされた。放射能汚染による環境被害を修復するために、これまで福島県内をはじめ多くの自治体で除染作業が行われてきた。福島県内の除染等で生じた除去土壌等については、中間貯蔵施設に一定期間保管した後、３０年以内に福島県外で最終処分を行うことが定められている。除染作業から発生した除染土等の量は、砂質土約９００万ｍ３、粘性土約１，１００万ｍ３からなると推定されている。除染土のうち砂質土は、主に住宅地、学校・公園等公共施設、商業施設等の除染から発生したものである。また、粘性土は、主に農地、森林から発生したもので、腐葉土など有機質を含み、団粒構造をもつ土壌が多くを占めている。今後、除染土壌を中間貯蔵施設に保管するために、除染土から放射性物質を分離処理して減容化する、経済性が高い処理技術が必要である。 Radioactive materials released by the accident at TEPCO's Fukushima Daiichi nuclear power plant diffused into a wide area and caused environmental pollution. In 2012, more than 160,000 citizens were forced to evacuate from the contaminated area. In order to repair the environmental damage caused by radioactive contamination, decontamination work has been carried out in many local governments including Fukushima Prefecture. It is stipulated that the removed soil, etc. generated by decontamination, etc. in Fukushima Prefecture will be stored in an intermediate storage facility for a certain period and then disposed of outside Fukushima Prefecture within 30 years. The amount of decontaminated soil generated from the decontamination work is estimated to be about 9 million m 3 of sandy soil and about 11 million m 3 of cohesive soil. Among the decontaminated soil, sandy soil is mainly generated from decontamination of residential areas, public facilities such as schools and parks, and commercial facilities. In addition, cohesive soil originates mainly from farmland and forests, and it contains organic matter such as humus and has a large aggregate structure. In the future, in order to store the decontaminated soil in the intermediate storage facility, it is necessary to have a highly economical treatment technology that separates and reduces the volume of radioactive material from the decontaminated soil.
近年の研究から、放射性セシウムは、土に含まれる雲母などの粘土の層間に固定され、溶出しないことが明らかとなっている。このため、放射性セシウムを土壌から分離除去するためには、放射性セシウムを固定している微細な粘土そのものを土壌から分離するか、または化学的処理、熱処理等により放射性セシウムを粘土鉱物から分離する処理方法が必要となる。 Recent studies have shown that radioactive cesium is fixed between clay layers such as mica contained in soil and does not elute. For this reason, in order to separate and remove radioactive cesium from the soil, the fine clay that fixes the radioactive cesium itself is separated from the soil, or treatment that separates the radioactive cesium from the clay mineral by chemical treatment, heat treatment, etc. A method is needed.
放射能汚染土の処理方法として、最初に、従来から重金属等の汚染土の処理に用いられてきたトロンメル等を洗浄分級装置とする土壌洗浄技術が挙げられる。この手法は、これまでの処理実績が豊富にあり、土の粒径分布の広い砂質土の処理には有効な経済的な処理法であり、今後、中間貯蔵のための減容化処理にも採用される計画となっている。しかしながら、既存の土壌洗浄技術は、微細な粒径をもつ粘性土の洗浄処理に適用することは困難である。このため、粘性土を主体とする放射性汚染土の経済的な処理技術の開発が大きな課題である。 As a method for treating radioactively contaminated soil, first, there is a soil washing technique using a trommel or the like conventionally used for treating contaminated soil such as heavy metals as a washing classifier. This method has abundant treatment results so far and is an effective economic treatment method for sandy soil with a wide soil particle size distribution. In the future, this method will be used for volume reduction treatment for intermediate storage. Is also planned to be adopted. However, existing soil washing techniques are difficult to apply to washing treatment of viscous soil having a fine particle size. For this reason, the development of economical treatment technology for radioactively contaminated soil mainly composed of cohesive soil is a major issue.
近年、除染事業が進められる中で、汚染土壌から放射性物質を効率よく分離する方法について研究開発が行われてきており、関連する先行文献として特許文献１〜５が挙げられる。 In recent years, research and development have been conducted on methods for efficiently separating radioactive substances from contaminated soil while decontamination projects are being carried out, and related prior art documents include Patent Documents 1 to 5.
文献１、２では、放射性セシウム汚染土をロータリーキルン等で７００℃以上の温度まで加熱し、放射性セシウムを含む排ガスと土壌を分離処理する処理方法について示されている。この方法では、ハロゲン物質、塩化物原料を混合することで効率よく放射性セシウムを分離することができるが、大きな熱エネルギーを必要とし、処理コストが高くなる問題点がある。また、この方法は、揮発分離できないストロンチウム等放射性物質を含む汚染土壌の処理には適用できない。 Documents 1 and 2 describe a treatment method in which radioactive cesium-contaminated soil is heated to a temperature of 700 ° C. or higher with a rotary kiln or the like to separate exhaust gas containing radioactive cesium from soil. In this method, radioactive cesium can be efficiently separated by mixing a halogen substance and a chloride raw material, but there is a problem that a large heat energy is required and the processing cost is increased. In addition, this method cannot be applied to the treatment of contaminated soil containing radioactive substances such as strontium that cannot be volatilized and separated.
文献３では、放射能汚染土を酸性溶液に混合して超音波処理を行うことで放射性セシウムを分離する方法について示されている。この方法では、処理のために大量の酸を要し、洗浄処理後の中和処理のために大量のアルカリ原料を要するため、処理コストが高くなる。また、最近の研究では原発事故後７年を経過した現在では、放射性セシウムは粘土鉱物内に事故直後より強く吸着されるよう変化しており、酸による抽出は困難となってきているといわれている。 Document 3 discloses a method for separating radioactive cesium by mixing radioactively contaminated soil with an acidic solution and performing ultrasonic treatment. In this method, a large amount of acid is required for the treatment, and a large amount of alkali raw material is required for the neutralization treatment after the washing treatment, so that the treatment cost becomes high. In recent research, seven years after the nuclear accident, radioactive cesium has changed to be strongly adsorbed in clay minerals immediately after the accident, and it is said that extraction with acid has become difficult. Yes.
文献４では、水、酸、金属塩、分散剤、場合によりフッ化物を含む放射能汚染物質洗浄剤と、放射性物質を含む土壌または飛灰とを接触させて、土壌又は飛灰に含有された放射性物質を該放射能汚染物質洗浄剤に移動させてこれを回収する方法等について記載されている。この方法は酸性環境下において、独自に配合された洗剤と汚染土を混合し放射性物質を回収するもので、酸や洗剤の添加を必須とするため処理コストが高くなる。 In Reference 4, the radioactive pollutant cleaning agent containing water, acid, metal salt, dispersant, and optionally fluoride was brought into contact with soil or fly ash containing radioactive material, and contained in soil or fly ash. It describes a method for transferring a radioactive substance to the radioactive pollutant cleaning agent and recovering it. This method is a method of collecting radioactive substances by mixing a detergent and a contaminated soil, which are uniquely formulated, in an acidic environment, and requires the addition of an acid or a detergent, which increases the processing cost.
文献５では、放射能汚染土に固化材とナノサイズの粒子を含む鉄粉、スラグ等の強磁性体粉末を混合し、磁力選別を施し放射性物質を含む土粒子を濃縮、分離する方法について示されている。この方法は、固化材と微細な鉄粉を混合することで土粒子表面にこれらを含む皮膜が形成され、粒子径の小さく、重量が軽い土粒子が磁石側に吸着される原理を用いたものである。この技術は、粒度分布の広い砂質系汚染土の処理には適するが、粘性土を主体とする土壌の処理には適用が難しい。 Reference 5 shows a method for concentrating and separating soil particles containing radioactive materials by mixing solidified material and iron powder containing nano-sized particles, ferromagnetic powder such as slag, etc., and magnetic separation. Has been. This method uses the principle that a film containing these is formed on the surface of the soil particles by mixing the solidified material and fine iron powder, and the soil particles having a small particle size and light weight are adsorbed on the magnet side. It is. This technique is suitable for the treatment of sandy contaminated soil having a wide particle size distribution, but is difficult to apply to the treatment of soil mainly composed of cohesive soil.
文献６では、高圧噴流による洗浄装置を用いて、放射能汚染土壌から土壌より比重の小さい木屑、根、葉等の植物系異物を除去する処理について記載されている。これは、汚染土壌の分級処理時の目詰まりを防止するための前処理に関するもので、放射能汚染土の洗浄処理、減容化処理を目的としたものではない。また、この文献では異物を分離するため塩化カルシウム等の選別液を使用して土壌洗浄を行うが、塩化カルシウムは凝集性があるため土壌の高い解砕、洗浄効果は得られない。また、高濃度の塩化カルシウム添加により洗浄装置、分級装置、脱水装置等の腐食が懸念される。 Document 6 describes a process for removing plant-based foreign matters such as wood chips, roots, leaves, and the like having a specific gravity smaller than the soil from radioactively contaminated soil using a cleaning device using a high-pressure jet. This is related to pretreatment for preventing clogging during classification of contaminated soil, and is not intended for cleaning treatment or volume reduction of radioactively contaminated soil. Further, in this document, soil washing is performed using a sorting solution such as calcium chloride in order to separate foreign substances. However, since calcium chloride is agglomerated, a high soil crushing and washing effect cannot be obtained. Moreover, there is a concern about the corrosion of the cleaning device, the classification device, the dehydrating device, etc. due to the addition of high concentration calcium chloride.
このように、これまでに放射性汚染土を減容化する技術が種々研究されてきた。しかしながら、これらは、酸、アルカリ、化学薬品を加えた抽出、焼成による揮発分離等によるもので、処理に大量の化学薬品を要したり、大きな熱エネルギーを消費するために経済性が低く、１，１００万ｍ３とも推計される大量の粘性土を含む汚染土壌の処理に適用することは難しいと思われる。 Thus, various techniques for reducing the volume of radioactively contaminated soil have been studied so far. However, these are based on extraction with addition of acid, alkali, chemicals, volatilization separation by firing, etc., and require a large amount of chemicals for processing or consume large heat energy, and are not economical. It is considered difficult to apply to the treatment of contaminated soil including a large amount of viscous soil estimated at 1 million m 3 .
本発明は、粘性土からなる放射能汚染土壌、粘土を多く含む放射能汚染土壌を、経済的かつ効率的に洗浄、減容化することのできる、新規の放射能汚染土の洗浄、減容化処理方法を提供することを目的とする。 The present invention is a novel radioactively contaminated soil that can be economically and efficiently cleaned and reduced in volume of soil contaminated with radioactive soil and radioactively contaminated soil containing a large amount of clay. An object of the present invention is to provide a processing method.
本発明者は、粘性土に分散剤を混合して高圧噴流を用いて洗浄を行うことで、団粒構造を解砕し、土壌中の微細な土粒子を分離除去することで、土壌に含有する放射性物質の含有量を大きく低下させることができることを見出し、本発明に想到した。粘性土の定義は、粒径７５μｍ未満の粘土分、シルト分を５０質量％以上含む土であるが、粘土分、シルト分が３０〜５０質量％の土においても、土壌は団粒化していることが多く経済的な処理が難しい。本発明は、このような粘土を多く含む放射能汚染土の処理にも好適に用いることができる。 The present inventor mixes a dispersant with viscous soil and performs washing using a high-pressure jet to break up the aggregate structure and separate and remove fine soil particles in the soil, so that it is contained in the soil. The present inventors have found that the content of radioactive materials to be reduced can be greatly reduced, and have arrived at the present invention. The definition of cohesive soil is soil that contains 50% by mass or more of clay and silt with a particle size of less than 75 μm, but the soil is aggregated even in soil with 30-50% by mass of clay and silt. It is often difficult to process economically. The present invention can be suitably used for the treatment of radioactively contaminated soil containing a large amount of such clay.
本発明の放射能汚染土の洗浄、減容化処理方法は、高圧噴流を導入した洗浄装置の中で高圧噴流により土壌と水と分散剤を混合して土壌を解砕する洗浄工程を有することを特徴とする。 The method for cleaning and reducing the volume of radioactively contaminated soil according to the present invention has a cleaning step of crushing the soil by mixing the soil, water and dispersant by the high-pressure jet in the cleaning device into which the high-pressure jet is introduced. It is characterized by.
また、前記洗浄装置が、高圧噴流を前記洗浄装置内に導入する導入部と、土壌と水と分散剤の混合物を前記洗浄装置内に投入する投入口と、高圧噴流により土壌と水と分散剤を混合して土壌を洗浄する洗浄部とを備えたことを特徴とする。 In addition, the cleaning device has an introduction portion for introducing a high-pressure jet into the cleaning device, an inlet for introducing a mixture of soil, water, and a dispersant into the cleaning device, and soil, water, and a dispersant by the high-pressure jet. And a washing section for washing the soil by mixing.
また、前記洗浄部が、内部に衝突板を有することを特徴とする。 Moreover, the said washing | cleaning part has a collision board inside, It is characterized by the above-mentioned.
また、前記洗浄工程において、さらにケイ砂、砂、鉄粉、活性炭のうち少なくとも１種を加えて洗浄することを特徴とする。 Moreover, in the said washing | cleaning process, it wash | cleans by adding at least 1 sort (s) further among quartz sand, sand, iron powder, and activated carbon.
また、前記洗浄工程の後に、湿式サイクロンにより、洗浄土を分級して微細土粒子を分離する分離工程を有することを特徴とする。 Moreover, after the said washing | cleaning process, it has the isolation | separation process which classifies washing | cleaning soil and isolate | separates a fine soil particle with a wet cyclone.
さらに、前記洗浄工程の後に、洗浄水に塩化カルシウム、塩化マグネシウム、硫酸マグネシウムのうち少なくとも１種を加えて、凝集処理した後に洗浄水を再利用することを特徴とする。 Furthermore, after the washing step, at least one of calcium chloride, magnesium chloride, and magnesium sulfate is added to the washing water, and after the aggregation treatment, the washing water is reused.
本発明の放射能汚染土壌の洗浄、減容化処理方法では、粘性土に分散剤を混合して高圧噴流により洗浄を行い、粘性土の団粒構造の主に表面部を解砕、剥離し、土壌に含有する放射性物質を大きく低下させる機能を有する。本発明の処理方法により、大量の化学薬品を要したり、大きなエネルギーを消費することなく、効率的かつ経済的に放射能汚染土の処理が可能である。本発明の粘土を多く含む放射能汚染土壌の洗浄、減容化処理方法は、放射性セシウムによる汚染土壌のほか、原子力発電所付近の放射性ストロンチウム、放射性プルトニウム等により汚染されている土壌の処理に用いることができる。 In the method for cleaning and reducing the volume of radioactively contaminated soil of the present invention, a dispersing agent is mixed with viscous soil and washed with a high-pressure jet, and the surface part of the aggregate structure of the viscous soil is mainly crushed and separated. , It has the function of greatly reducing radioactive materials contained in soil. By the treatment method of the present invention, radioactively contaminated soil can be treated efficiently and economically without requiring a large amount of chemicals or consuming large amounts of energy. The method for cleaning and reducing the volume of radioactively contaminated soil containing a large amount of clay of the present invention is used for treating soil contaminated with radioactive cesium, radioactive strontium, radioactive plutonium, etc. in the vicinity of a nuclear power plant. be able to.
粘土を多く含む放射能汚染土の処理では、汚染土が微細な土粒子から構成されるため、分級粒子径を７５μｍ以上とする従来の土壌洗浄技術を適用することは難しい。放射性セシウムは、土に含まれる雲母等の粘土の層間に固定され、容易に溶出しない性質があり、放射性セシウムを土壌から取り出すためには、放射性セシウムを固定している微細な粘土粒子そのものを土壌から分離するか、または化学的処理、熱処理等により放射性セシウムを粘土鉱物から分離する処理方法が必要となる。このため、これまで酸、アルカリ、化学薬品を加えた抽出、焼成による揮発分離等、様々な技術の提案がなされている。しかしながら、これらの処理では、大量の化学薬品を必要としたり、大きな熱エネルギーを消費し、経済的に放射能汚染土壌処理を行うことが難しい。 In the treatment of radioactively contaminated soil containing a large amount of clay, since the contaminated soil is composed of fine soil particles, it is difficult to apply a conventional soil cleaning technique in which the classification particle diameter is 75 μm or more. Radioactive cesium is fixed between clay layers such as mica contained in the soil and has the property of not easily eluting, and in order to extract radioactive cesium from the soil, the fine clay particles fixing the radioactive cesium itself are removed from the soil. Or a method of separating radioactive cesium from clay minerals by chemical treatment, heat treatment or the like. For this reason, various techniques have been proposed so far, such as extraction with addition of acid, alkali and chemicals, and volatilization separation by firing. However, these treatments require a large amount of chemicals, consume large heat energy, and are difficult to economically treat radioactively contaminated soil.
以下、本発明の放射能汚染土壌の洗浄、減容化処理方法について詳細に説明する。前記のとおり、対象の粘性土は、農地、森林から発生した除染土壌であり、団粒構造を有する土壌が多くを占めている。団粒土は、微細粘土粒子、アルミニウム、有機物等が結合して小粒の集合体となったもので、物理的強度をもち耐水性がある構造になっている。原子力発電所事故により放出された放射性物質は、先ず団粒土の表面部に存在する微細な粘土粒子に、優先的に吸着されたと考えられる。前記のとおり団粒土は強度、耐水性をもつ構造からなるため、放射性物質を吸着した粘土粒子の多くは、その後も内部に移動することなく、現在においても、主に団粒土の表面部に分布していると推測される。 Hereinafter, the method for cleaning and reducing the volume of radioactively contaminated soil of the present invention will be described in detail. As described above, the target clay soil is decontaminated soil generated from farmland and forest, and soil having a aggregate structure occupies most. Agglomerated soil is an aggregate of small particles formed by combining fine clay particles, aluminum, organic matter, and the like, and has a structure having physical strength and water resistance. It is considered that the radioactive material released by the nuclear power plant accident was preferentially adsorbed on the fine clay particles present on the surface of the aggregate soil. As described above, the aggregated soil has a structure having strength and water resistance, and therefore, most of the clay particles adsorbed with the radioactive substance do not move to the inside after that, and even today, mainly the surface part of the aggregated soil. It is presumed that they are distributed.
本発明は、団粒土から放射性物質を吸着している微細な粘土粒子を分離するために、分散剤を加えて高圧噴流により洗浄を行うことで表面部を効率的に解砕するものである。高圧噴流を用いた土壌洗浄は優れた機能を有するが、これだけでは団粒土を解砕するには不十分であり、分散剤を加えて団粒土に解膠作用を働かせて洗浄することで、大きな解砕効果が生まれる。また、土壌洗浄時に分散剤を加えなければ、後段で微細な土粒子は再凝集し、解砕効果は失われてしまう。なお、本発明を実施するにあたって、攪拌形式の洗浄装置の使用は好ましくない。その理由は攪拌形式の洗浄装置では、本発明の高圧洗浄処理のような高い解砕効果が得られないからである。 In the present invention, in order to separate fine clay particles adsorbing radioactive substances from the aggregate soil, the surface portion is efficiently crushed by adding a dispersant and washing with a high-pressure jet. . Soil washing using a high-pressure jet has an excellent function, but this alone is not sufficient to break up the aggregated soil, and it can be washed by adding a dispersing agent to the aggregated soil. A big crushing effect is born. Moreover, if a dispersing agent is not added at the time of soil washing | cleaning, a fine soil particle will re-aggregate at a latter stage and the crushing effect will be lost. In carrying out the present invention, it is not preferable to use a stirring type cleaning device. The reason is that the high-crushing effect as in the high-pressure washing treatment of the present invention cannot be obtained with a stirring type washing apparatus.
本発明は、汚染土に水と分散剤を加えて団粒土の凝集性を改質しながら、高圧噴流により洗浄を行うことで、団粒土の主に表面部の解砕と剥離を行う原理によっている。また、本発明の強い洗浄効果により、強度が小さい団粒土では全体が解砕されることもある。本発明により、放射性物質が吸着している微細な粘土粒子を団粒土から分離して、効率的な除染を行うことができる。また、分散剤の添加によって、洗浄後、微細な土粒子が再凝集して、解砕効果が失われることを防ぐ。本発明の除染原理の説明図を図１に示した。本発明の放射能汚染土壌の洗浄、減容化処理方法は、この処理原理により、放射性セシウムによる汚染土壌の外、原子力発電所付近の放射性ストロンチウム、放射性プルトニウム等により汚染されている土壌の処理に用いることができる。 In the present invention, the surface of the aggregated soil is mainly crushed and separated by washing with high-pressure jets while adding water and a dispersant to the contaminated soil to improve the cohesiveness of the aggregated soil. It depends on the principle. In addition, due to the strong cleaning effect of the present invention, the whole may be crushed in the aggregated soil with low strength. According to the present invention, fine clay particles adsorbed with a radioactive substance can be separated from the aggregate soil to perform efficient decontamination. Further, the addition of a dispersant prevents fine earth particles from reaggregating after washing and losing the crushing effect. An explanatory view of the decontamination principle of the present invention is shown in FIG. According to this treatment principle, the radioactively contaminated soil cleaning and volume reducing treatment method of the present invention is used to treat soil contaminated with radioactive cesium, radioactive strontium near the nuclear power plant, radioactive plutonium, and the like. Can be used.
本発明の放射能汚染土壌の洗浄、減容化処理方法では、高圧噴流を導入した洗浄装置の中で高圧噴流により土壌と水と分散剤を混合して土壌を解砕する洗浄工程を有することを特徴とする。 The method for cleaning and reducing the volume of radioactively contaminated soil according to the present invention has a cleaning step of crushing the soil by mixing the soil, water, and the dispersing agent by the high-pressure jet in the cleaning device into which the high-pressure jet is introduced. It is characterized by.
汚染土壌は、例えば、２〜３０倍質量の水、好ましくは５〜１０倍質量の水と、分散剤を添加した後、数十秒〜数時間、あるいは数日間撹拌を行った後に洗浄装置に投入される。また、汚染土壌に２〜２０倍質量の水を加えたスラリーと、分散剤溶液とを、別の経路により洗浄装置に投入することもできる。 Contaminated soil is, for example, added to 2 to 30 times the mass of water, preferably 5 to 10 times the mass of water, and the dispersant, and then stirred for several tens of seconds to several hours or several days, and then into the washing apparatus. It is thrown. Moreover, the slurry which added 2-20 times mass water to the contaminated soil, and a dispersing agent solution can also be thrown into a washing | cleaning apparatus by another path | route.
洗浄装置としては種々の構造を考えることができるが、連続的に処理を行うためには、図２に示すように、放射性汚染土壌と分散剤溶解液を混合したスラリー、すわなち、土壌と水と分散剤の混合物を洗浄装置内に投入するための投入口と、高圧噴流水が噴射される高圧噴流噴射口と吸気孔から構成され、高圧噴流を洗浄装置内に導入する導入部と、排出口を備えた略パイプ形状の洗浄部を有する構造とすることが合理的である。洗浄部では、高圧噴流により土壌と水と分散剤を混合して土壌を洗浄するようになっている。この構造の装置は、従来よりエジェクターと呼ばれ種々の産業で利用されており、粉体、液体、気体の輸送、混合、洗浄を行う機能をもっている。 Although various structures can be considered as a cleaning device, in order to perform continuous processing, as shown in FIG. 2, as shown in FIG. 2, slurry mixed with radioactively contaminated soil and dispersant solution, that is, soil and An inlet for introducing a mixture of water and a dispersant into the cleaning device, a high-pressure jet injection port through which high-pressure jet water is injected, and an intake hole, and an introduction unit for introducing the high-pressure jet into the cleaning device; It is reasonable to have a structure having a substantially pipe-shaped cleaning part with a discharge port. In the washing section, the soil is washed by mixing the soil, water, and a dispersing agent with a high-pressure jet. An apparatus having this structure is conventionally called an ejector and has been used in various industries, and has a function of transporting, mixing, and cleaning powder, liquid, and gas.
なお、この装置においては、高圧噴流噴射口から噴射された噴流水が吸気孔から供給された空気を巻き込んで、噴流水の周囲に空気層が形成された噴流を形成し、この噴流が、投入口から供給された土壌と水と分散剤を激しく混合して土壌の洗浄が行われるようになっている。 In this device, the jet water jetted from the high-pressure jet jet port entrains the air supplied from the intake hole to form a jet with an air layer formed around the jet water, and this jet is injected. The soil is washed by mixing vigorously the soil supplied from the mouth, water and a dispersant.
本発明において使用される洗浄装置は、例えば、汚染土の投入口、吸気孔、高圧噴流噴射口を備える部材と、これに接続した直径２０〜２００ｍｍ、長さ０．５〜２ｍの内部で洗浄を行うためのパイプ形状の部材と、排出口から構成される。洗浄装置の材質としては通常、鉄鋼またはステンレス製が使用される。また、セラミックス等の耐摩耗性に優れた材質を使用することもできる。土壌洗浄効果を高めるために、この洗浄部のパイプ内部に突起物を設置し、乱流を発生させ洗浄効果を高めることができる。 The cleaning apparatus used in the present invention is, for example, a member provided with a contaminated soil inlet, an intake hole, a high-pressure jet outlet, and an inside connected to this having a diameter of 20 to 200 mm and a length of 0.5 to 2 m. It consists of a pipe-shaped member and a discharge port. As the material of the cleaning device, steel or stainless steel is usually used. A material having excellent wear resistance such as ceramics can also be used. In order to increase the soil cleaning effect, a protrusion can be installed inside the pipe of the cleaning section to generate turbulent flow and increase the cleaning effect.
また、この洗浄装置の洗浄部の内部に衝突板を設置して、図３のような構造とすることができる。この構造では衝突板の設置により、排出口から衝突板付近に強い乱流が発生して非常に高い土壌の洗浄効果が得られるため、特に好適に用いられる。この洗浄装置は、例えば、汚染土の投入口、吸気孔、高圧噴流噴射口を備える部材と、これに接続した直径２０〜３００ｍｍ、長さ０．５〜３ｍの内部で洗浄を行うためのパイプ形状の部材と、排出口から構成される。洗浄装置の材質としては通常、鉄鋼またはステンレス製が使用される。また、セラミックス等の耐摩耗性に優れた材質を使用することもできる。 In addition, a collision plate can be installed inside the cleaning unit of the cleaning device to obtain a structure as shown in FIG. In this structure, the installation of the collision plate causes a strong turbulent flow from the discharge port to the vicinity of the collision plate, so that a very high soil cleaning effect can be obtained. This cleaning apparatus is, for example, a member having a contaminated soil inlet, an intake hole, and a high-pressure jet injection port, and a pipe for cleaning inside a diameter 20 to 300 mm and a length 0.5 to 3 m connected thereto. It consists of a shaped member and a discharge port. As the material of the cleaning device, steel or stainless steel is usually used. A material having excellent wear resistance such as ceramics can also be used.
本発明の放射能汚染土壌の洗浄、減容化処理方法では、汚染土の洗浄効果をさらに向上させるため、高圧噴流による洗浄装置を複数組み合わせて使用することができる。 In the method for cleaning and reducing the volume of radioactively contaminated soil according to the present invention, in order to further improve the cleaning effect of the contaminated soil, a plurality of cleaning devices using a high-pressure jet can be used in combination.
洗浄装置の諸元、高圧噴流の圧力、流量については、単位時間あたりの土壌の処理量により設計し、さらにべンチスケール試験を通じて最適化を行って仕様を決定する。例えば、洗浄装置内に導入される高圧噴流は、吐出口圧力２〜３０ＭＰａの高圧ポンプから供給することができ、ポンプ吐出口圧力２〜３０ＭＰａの高圧噴流を用いることにより、多くの場合において好適な洗浄効果が得られる。 The specifications of the specifications of the cleaning equipment, the pressure and flow rate of the high-pressure jet are determined based on the amount of soil treated per unit time, and further optimized through a bench scale test. For example, the high-pressure jet introduced into the cleaning device can be supplied from a high-pressure pump having a discharge port pressure of 2 to 30 MPa, and is suitable in many cases by using a high-pressure jet having a pump discharge port pressure of 2 to 30 MPa. A cleaning effect is obtained.
なお、洗浄装置内に導入される高圧噴流は、土壌表面部の解砕と剥離を行うことができるものであればよい。したがって、上記のように水と空気により形成されるものに限らず、水のみ、又は、空気のみからなる噴流であってもよい。 Note that the high-pressure jet introduced into the cleaning device may be any one that can crush and peel the soil surface portion. Therefore, it is not limited to the one formed by water and air as described above, and may be a jet of water only or air.
本発明では、粘土を多く含む放射能汚染土壌に分散剤を混合して高圧洗浄を行うことで、土壌表面部の解砕、洗浄を効率的に行うことができる。分散剤は、解膠剤と呼ばれることもあり、凝集した土粒子の解砕を促進する機能、土粒子を水中に均質に分散する機能を有する。本発明において使用される分散剤、解膠剤としては、公知のヘキサメタりん酸ナトリウム、ピロりん酸ナトリウム、テトラりん酸ナトリウム、トリポリりん酸ナトリウム等のりん酸ナトリウム塩、メタりん酸カリウム、ピロりん酸カリウム、トリポリりん酸カリウム、メタりん酸カリウム等のりん酸カリウム塩、ケイ酸ナトリウム、ケイ酸リチウム、炭酸ナトリウム、アルミン酸ナトリウム、シュウ酸ナトリウム、タンニン酸ナトリウム、水酸化ナトリウム、クエン酸ナトリウム、酒石酸ナトリウム、硫酸ナトリウム、酢酸ナトリウム、水酸化リチウム、アルミン酸リチウム、クエン酸リチウム等の無機分散剤の中から少なくとも１種を用いることができる。これらの中で、ヘキサメタりん酸ナトリウム、ピロりん酸ナトリウム等のりん酸ナトリウム塩、ピロりん酸カリウム等のりん酸ナトカリウム塩は、強力な分散効果を有し、本発明において特に好適に用いられる。また、ケイ酸ナトリウムは、古くから窯業で使用されている分散剤であり、処理効果も高く、本発明において特に好適に用いられる。なお、水酸化ナトリウム、水酸化リチウムを使用すると、スラリーのｐＨが大きく上がるため、後段の処理が難しくなる。このため、水酸化ナトリウム、水酸化リチウムの採用は好ましくない。 In the present invention, the surface of the soil can be efficiently crushed and washed by mixing the dispersant with the radioactively contaminated soil containing a large amount of clay and performing high-pressure washing. The dispersant is sometimes called a peptizer, and has a function of promoting the crushing of the aggregated soil particles and a function of uniformly dispersing the soil particles in water. Dispersants and peptizers used in the present invention include known sodium phosphates such as sodium hexametaphosphate, sodium pyrophosphate, sodium tetraphosphate, sodium tripolyphosphate, potassium metaphosphate, pyrophosphorus. Potassium phosphate such as potassium phosphate, potassium tripolyphosphate, potassium metaphosphate, sodium silicate, lithium silicate, sodium carbonate, sodium aluminate, sodium oxalate, sodium tannate, sodium hydroxide, sodium citrate, At least one of inorganic dispersants such as sodium tartrate, sodium sulfate, sodium acetate, lithium hydroxide, lithium aluminate, and lithium citrate can be used. Among these, sodium phosphates such as sodium hexametaphosphate and sodium pyrophosphate and sodium potassium phosphates such as potassium pyrophosphate have a strong dispersion effect and are particularly preferably used in the present invention. Sodium silicate is a dispersant that has been used in the ceramic industry for a long time, has a high treatment effect, and is particularly preferably used in the present invention. Note that when sodium hydroxide or lithium hydroxide is used, the pH of the slurry is greatly increased, which makes subsequent treatment difficult. For this reason, adoption of sodium hydroxide or lithium hydroxide is not preferable.
そのほか、本発明では、公知のカオリン、クレー用の有機系分散剤を用いることができる。有機系分散剤としては、ポリカルボン酸系ポリマー、ポリアクリル酸塩、ポリアクリル酸系ポリマー、ナフタレンスルホン酸系ポリマー等が挙げられ、これらのうち少なくとも１種、またはこれらのうち少なくとも１種を前記無機分散剤と併用して用いることができる。 In addition, in the present invention, known kaolin and organic dispersants for clay can be used. Examples of the organic dispersant include polycarboxylic acid polymers, polyacrylates, polyacrylic acid polymers, naphthalene sulfonic acid polymers, etc., and at least one of these, or at least one of these is the above-mentioned It can be used in combination with an inorganic dispersant.
分散剤の添加量は、粘性土の組成、陽イオン交換能力、使用する分散剤により異なるため一律に定めることは難しく、使用する薬品を用いてベンチスケール試験により試験評価を行い、決定する必要がある。粘性土の組成等にもよるものの、分散剤の添加量は、例えば、土壌の質量に対して５×１０−３ｍｏｌ／ｋｇ以上とすることができる。 The amount of dispersant added depends on the composition of the clay, cation exchange capacity, and the dispersant used, so it is difficult to determine uniformly, and it is necessary to determine by conducting a test evaluation with a bench scale test using the chemical used. is there. Although depending on the composition of the cohesive soil, the amount of the dispersant added can be, for example, 5 × 10 −3 mol / kg or more with respect to the mass of the soil.
本発明の放射能汚染土壌の洗浄、減容化処理方法では、高圧噴流による洗浄時にケイ砂、砂、鉄粉、活性炭からなる添加材のうち少なくとも１種を加えて処理を行うことができる。ケイ砂、砂、鉄粉は、研磨材に相当し、これを加えることで団粒土の解砕効果を向上させることができる。このほか、セラミックス粉、ステンレス等の金属粉など、硬質な粒状体を研磨剤として本発明に使用することができる。また、活性炭は比較的硬質な性状を持ち、土壌に含まれる有機物を洗浄水中で吸着除去して解砕効果を向上させる機能を有しており、本発明の洗浄処理の添加材として使用することができる。ケイ砂、砂、鉄粉等の研磨剤の粒径は、ふるいで容易に回収が可能な粒径５００μｍ以上のものが好ましい。活性炭については各種の粒径の製品を利用することができる。これらの添加材の添加量は、汚染土壌の質量に対して３〜２０質量％の範囲とするのが好ましい。 In the method for cleaning and reducing the volume of radioactively contaminated soil of the present invention, at least one of additive materials consisting of silica sand, sand, iron powder, and activated carbon can be added during the cleaning with a high-pressure jet. Silica sand, sand, and iron powder correspond to abrasives, and by adding this, the effect of crushing the aggregated soil can be improved. In addition, hard granular materials such as ceramic powder and metal powder such as stainless steel can be used as an abrasive in the present invention. Activated carbon has a relatively hard property and has the function of improving the pulverization effect by adsorbing and removing organic matter contained in the soil in the wash water, and should be used as an additive for the washing treatment of the present invention. Can do. The particle size of abrasives such as silica sand, sand and iron powder is preferably 500 μm or more, which can be easily recovered by sieving. About activated carbon, the product of various particle sizes can be utilized. The addition amount of these additives is preferably in the range of 3 to 20% by mass with respect to the mass of the contaminated soil.
本発明の放射能汚染土壌の洗浄、減容化処理方法では、分散剤を加え高圧噴流を用いて土壌を洗浄、解砕した後段に、放射性物質を除去した土壌と放射性物質を吸着している粘土を含む微細土、有機物質を分離して回収する設備、洗浄土を脱水する機能をもつ設備、分離された微細土を濃縮する設備を設置して、一連のシステムを構成することが好ましい。 In the method for cleaning and reducing the volume of radioactively contaminated soil of the present invention, the radioactive material and the soil from which radioactive material has been removed are adsorbed after washing and pulverizing the soil using a high-pressure jet after adding a dispersant. It is preferable to configure a series of systems by installing fine soil containing clay, equipment for separating and collecting organic substances, equipment having a function of dewatering washed soil, and equipment for concentrating the separated fine soil.
このシステムによって、汚染土に含まれる放射性物質を吸着した粘土粒子、有機物を土壌中から分離し、放射能汚染土壌の減容化、放射性物質濃度の低減を行うことができる。また、洗浄した土壌を脱水処理することにより、洗浄スラリーを減容化し、放射性物質を含み高含水の土壌の取扱いを容易にすることができる。 By this system, clay particles and organic substances adsorbed with radioactive substances contained in contaminated soil can be separated from the soil, and the volume of radioactively contaminated soil can be reduced and the concentration of radioactive substances can be reduced. In addition, by dehydrating the washed soil, the volume of the washed slurry can be reduced, and handling of soil containing a radioactive substance and high water content can be facilitated.
本発明の放射能汚染土壌の洗浄、減容化処理方法では、分散剤を導入した高圧洗浄装置の後段に、放射性物質を吸着している粘土、有機物質を分離して回収する設備として、公知の分級、分離装置を組合せて使用することができる。公知の分級装置としては、土粒子の粒径、比重による分級を原理とする振動ふるい、スクリューコンベア、湿式サイクロン、沈降分離、加圧浮上、遠心分離が挙げられる。また、親疎水性の差異による分離を原理とする浮遊選鉱処理を分離装置として用いることができる。浮遊選鉱処理によれば、汚染土中の土壌有機物を好適に分離することが可能である。 In the method for cleaning and reducing the volume of radioactively contaminated soil according to the present invention, as a facility for separating and recovering clay adsorbing radioactive substances and organic substances after the high-pressure washing apparatus into which the dispersant has been introduced. The classification and separation apparatus can be used in combination. Known classification devices include vibrating sieves based on the classification based on the particle size and specific gravity of soil particles, screw conveyors, wet cyclones, sedimentation separation, pressurized flotation, and centrifugal separation. Further, a flotation process based on the principle of separation based on differences in hydrophilicity and hydrophobicity can be used as a separation device. According to the flotation process, it is possible to suitably separate soil organic matter in the contaminated soil.
本発明の放射能汚染土壌の洗浄、減容化処理方法では、高圧洗浄装置の後段に、これらの分離装置のうち少なくとも１種を設置し、放射能汚染土中に含有する放射性物質を吸着している粘土、土壌有機物を効率的に分離除去することで、優れた放射性物質含有量の低減効果、減容化効果を生み出すことができる。本発明の処理法では、分散剤を導入した高圧洗浄により、土壌が効果的に解砕、分散されるため、これらの分級、分離装置の機能を有効に活用することができる。 In the method for cleaning and reducing the volume of radioactively contaminated soil according to the present invention, at least one of these separation devices is installed after the high-pressure washing device to adsorb the radioactive substances contained in the radioactively contaminated soil. Efficient separation and removal of clay and soil organic matter can produce excellent radioactive substance content reduction and volume reduction effects. In the treatment method of the present invention, the soil is effectively crushed and dispersed by high-pressure washing with a dispersing agent introduced, so that the functions of these classification and separation devices can be effectively utilized.
図４に本発明で用いられる粘性土の洗浄、減容化処理システムの一例を示した。このシステムの例では、まず、振動ふるいにより、洗浄後の土粒子のうち、例えば、粒径７５μｍ以上の土粒子を回収する。この粒径の土粒子は、放射性物質を含む微細粒子が分離されて低い放射線濃度に処理されており、例えば堤防建設用の盛土材等として有効利用に供することが可能である。 FIG. 4 shows an example of a viscous soil cleaning and volume reduction processing system used in the present invention. In the example of this system, first, soil particles having a particle size of 75 μm or more, for example, are collected from the washed soil particles by a vibration sieve. The soil particles having this particle diameter are processed to a low radiation concentration by separating fine particles containing a radioactive substance, and can be used effectively, for example, as a banking material for embankment construction.
振動ふるいを通過した土は、湿式サイクロンにより処理され、粒径２０〜７５μｍの土粒子が回収される。ここで、湿式サイクロンは処理流量が小さいため、複数組合せて処理を行うことができる。この粒径の土粒子についても、通常は低い放射線濃度に処理されており、有効利用に供することが可能である。 The soil that has passed through the vibrating screen is treated with a wet cyclone, and soil particles having a particle size of 20 to 75 μm are collected. Here, since the wet cyclone has a small processing flow rate, a plurality of combinations can be processed. The soil particles of this particle size are also usually processed at a low radiation concentration and can be used effectively.
なお、このシステムの例は、湿式サイクロンにより粒径２０μｍの粒度で処理を行うものであるが、現在の湿式サイクロンの技術では、２μｍ程度まで分離処理が可能である。処理粒度を小さくすると、分離された微細土の放射線濃度は極めて高くなる。湿式サイクロンによる処理粒度は、後段の処理を考慮して、有利な条件になるように設定を行えばよい。 In this example of the system, processing is performed with a particle size of 20 μm by a wet cyclone, but with the current wet cyclone technology, separation processing can be performed up to about 2 μm. When the treatment particle size is reduced, the radiation concentration of the separated fine soil becomes extremely high. The processing particle size by the wet cyclone may be set so as to be an advantageous condition in consideration of subsequent processing.
湿式サイクロンにより分離された粒径２０〜７５μｍの土粒子の脱水、回収方法としては、公知の種々のろ過・脱水技術を用いることができる。具体的には、フィルタープレス、膜式真空脱水、ベルトプレス、スクリュープレス、遠心脱水等が挙げられる。 As a method for dehydrating and recovering soil particles having a particle diameter of 20 to 75 μm separated by a wet cyclone, various known filtration / dehydration techniques can be used. Specific examples include filter press, membrane vacuum dehydration, belt press, screw press, and centrifugal dehydration.
湿式サイクロンにより分離された水中に含まれる粒径２０μｍ未満の微細土粒子の処理では、凝集剤を加えた後、濃縮してろ過・脱水処理後に容器に保管する、凝集濃縮後のスラリーを容器内に保管する、などの方法が考えられる。この凝集処理方法については、以降に詳細に示す。また、微細土粒子を含むスラリーの濃縮法として、蒸発濃縮を適用する方法等も考えられる。これらの作業はかなりの高線量環境で行う必要があるため、装置の無人化とともに、適切な処理法を決定する必要がある。 In the treatment of fine soil particles with a particle size of less than 20 μm contained in water separated by a wet cyclone, after adding a flocculant, it is concentrated and stored in a container after filtration and dehydration. A method such as storing in a storage is conceivable. This aggregation processing method will be described in detail later. Further, as a method for concentrating a slurry containing fine soil particles, a method of applying evaporation concentration may be considered. Since these operations need to be performed in a considerably high dose environment, it is necessary to determine an appropriate treatment method together with unmanned equipment.
さらに、近年の研究により、放射性物質を吸着している粘土鉱物は弱い磁性を有することが知られている。本発明の洗浄工程の後段で、高勾配磁気分離を適用し、磁力により水中に分離された微細な土粒子の回収を行う方法を適用することができる。 Furthermore, it is known from recent research that clay minerals adsorbing radioactive materials have weak magnetism. A method of applying high gradient magnetic separation and recovering fine soil particles separated in water by magnetic force can be applied after the washing step of the present invention.
本発明の放射能汚染土壌の洗浄、減容化処理方法においては、通常、汚染土質量の５〜１０倍質量の洗浄水を使用する。本処理方法の経済性を高めるためには、洗浄水中の懸濁物質を除去して清水をリサイクルする必要がある。本処理法から発生する洗浄水では、分散剤の添加によりゼータ電位が低下し、洗浄水中に微細な土粒子が多く懸濁した状態を保つ。例えば、洗浄水の中で最も細かい土粒子を含むサイクロンオーバー回収スラリーでは、分級した後、１日経過しても微細な土粒子は懸濁したまま沈降しない状態を示す。この洗浄水ではゼータ電位が低下し、微細な土粒子が高濃度で安定分散しているために、容易に凝集を行うことができず、この処理には通常の凝集剤の添加量の３〜１０倍量を添加する必要がある。この凝集処理を効率的に行うためには、マグネシウム、カルシウム等の多価電解質イオンを洗浄水に添加することが効果的である。具体的には、塩化マグネシウム、硫酸マグネシウム、塩化カルシウムを洗浄水に加え、撹拌することで洗浄水の凝集性を大きく改善することができる。 In the method for cleaning and reducing the volume of radioactively contaminated soil of the present invention, wash water having a mass of 5 to 10 times the mass of contaminated soil is usually used. In order to improve the economics of this treatment method, it is necessary to remove suspended substances in the wash water and recycle fresh water. In the washing water generated from this treatment method, the zeta potential is lowered by the addition of the dispersant, and a state in which many fine soil particles are suspended in the washing water is maintained. For example, a cyclone over recovered slurry containing the finest soil particles in the wash water shows a state where fine soil particles remain suspended and do not settle even after one day after classification. In this washing water, the zeta potential is lowered and the fine soil particles are stably dispersed at a high concentration, so that the agglomeration cannot be easily performed. It is necessary to add 10 times the amount. In order to efficiently perform this aggregation treatment, it is effective to add polyelectrolyte ions such as magnesium and calcium to the washing water. Specifically, the cohesiveness of the washing water can be greatly improved by adding magnesium chloride, magnesium sulfate, and calcium chloride to the washing water and stirring.
本発明の処理法から発生する洗浄水の処理では、塩化マグネシウム、硫酸マグネシウム、塩化カルシウムのうちの少なくとも１種と、公知の無機凝集剤、高分子凝集剤を組み合わせて凝集処理を行うことができる。多価電解質イオンをスラリーに添加することで、無機凝集剤、高分子凝集剤の処理効果を向上させることができる。公知の無機凝集剤としては、ＰＡＣ、硫酸アルミニウム等のアルミ系凝集剤、塩化第二鉄、ポリ硫酸鉄などの鉄系凝集剤が挙げられる。また、公知の高分子凝集剤としては、ポリアクリルアミド系凝集剤、ポリアクリ酸ナトリウム、ポリアクリル酸エステル系凝集剤等が挙げられる。本発明の処理法の洗浄水の処理では、これらにより効率的に凝集処理を行った後、公知のろ過、脱水技術により洗浄水を処理することにより、微細な懸濁土粒子と放射性物質を含んだ粘土粒子が除去されるため、洗浄水を好適にリサイクル利用することができる。 In the treatment of the washing water generated from the treatment method of the present invention, the coagulation treatment can be performed by combining at least one of magnesium chloride, magnesium sulfate and calcium chloride with a known inorganic coagulant and polymer coagulant. . By adding polyelectrolyte ions to the slurry, the treatment effect of the inorganic flocculant and polymer flocculant can be improved. Known inorganic flocculants include aluminum flocculants such as PAC and aluminum sulfate, and iron flocculants such as ferric chloride and polyiron sulfate. Examples of known polymer flocculants include polyacrylamide flocculants, sodium polyacrylate, polyacrylic ester flocculants, and the like. In the treatment of the washing water of the treatment method of the present invention, after performing the coagulation treatment efficiently by these, the washing water is treated by a known filtration and dehydration technique to contain fine suspended soil particles and radioactive substances. Since the clay particles are removed, the washing water can be suitably recycled.
以上に述べたように、本発明の放射能汚染土壌の洗浄、減容化処理方法では、粘性土に分散剤を混合して高圧噴流により洗浄を行うことで、粘性土の団粒構造の主に表面部を解砕、剥離し、振動ふるい、スクリューコンベア、湿式サイクロン、沈降分離、比重分離、遠心分離浮遊、選鉱分離により土粒子を回収処理することで、処理後の土壌に含有する放射性物質を大きく低下させ、汚染土の減容化処理をすることができる。 As described above, in the method for cleaning and reducing the volume of radioactively contaminated soil of the present invention, the dispersion structure is mixed with the viscous soil and washed with a high-pressure jet, so that the main structure of the aggregate structure of the viscous soil is obtained. The radioactive material contained in the treated soil by crushing, peeling off the surface part, collecting the soil particles by vibrating sieve, screw conveyor, wet cyclone, sedimentation separation, specific gravity separation, centrifugal floatation, and beneficiation separation Can be greatly reduced, and the volume of contaminated soil can be reduced.
本発明の処理方法により、大量の化学薬品を要したり、大きなエネルギーを消費することなく、効率的かつ経済的に放射能汚染土の経済的処理が可能である。本発明の粘土を多く含む放射能汚染土壌の洗浄、減容化処理方法は、その処理原理により、放射性セシウムによる汚染土壌のほか、原子力発電所付近の放射性ストロンチウム、放射性プルトニウム等、種々の核種により汚染されている土壌の処理にも用いることができる。 By the treatment method of the present invention, it is possible to economically and economically treat radioactively contaminated soil without requiring a large amount of chemicals or consuming a large amount of energy. According to the treatment principle, the method of cleaning and reducing the volume of radioactively contaminated soil containing a large amount of clay according to the present invention includes not only soil contaminated with radioactive cesium but also various nuclides such as radioactive strontium and radioactive plutonium near the nuclear power plant. It can also be used to treat contaminated soil.
神奈川県西部の農地から採取した団粒構造もつ粘性土を用いて、高圧洗浄による解砕効果を、下記の手順で評価した。 Using the cohesive soil with aggregate structure collected from farmland in western Kanagawa Prefecture, the crushing effect by high pressure washing was evaluated by the following procedure.
はじめに、対象の粘性土の粒度を、分散剤を加えて超音波分散による前処理をした後に、レーザー回折式粒度分布計により測定した。測定による粒径加積曲線を図５に示した。測定結果によれば、元の土壌の算術平均径は１７．９８μｍであり、１０μｍ以下の土粒子が４４％を占めていた。 First, the particle size of the target clay was measured by a laser diffraction particle size distribution analyzer after pretreatment by ultrasonic dispersion with the addition of a dispersant. The particle size accumulation curve by measurement is shown in FIG. According to the measurement results, the arithmetic average diameter of the original soil was 17.98 μm, and soil particles of 10 μm or less accounted for 44%.
次に、表１の試験条件に従って、下記の手順で高圧洗浄による粘性土の解砕効果を評価した。 Next, according to the test conditions of Table 1, the crushing effect of the viscous soil by high-pressure washing was evaluated according to the following procedure.
（１）粘性土５０ｇ、水１００ｇをＰＰ樹脂製ボトルに投入し、ボトルの蓋を閉めた後に軽く振とうした。実施例１ａでは、分散剤となるヘキサメタりん酸ナトリウム２０％溶液を所定量加えた後に、ボトルの蓋を閉めて軽く振とうした。実施例１ｂでは、分散剤となるピロりん酸カリウム２０％溶液を所定量加えた後に、ボトルの蓋を閉めて軽く振とうした。実施例１ｃでは、分散剤となるケイ酸ナトリウム粉末２０％溶液を所定量加えた後に、ボトルの蓋を閉めて軽く振とうした。 (1) 50 g of clay soil and 100 g of water were put into a PP resin bottle, and after shaking the bottle, it was shaken lightly. In Example 1a, a predetermined amount of a 20% sodium hexametaphosphate solution serving as a dispersant was added, and then the bottle was closed and shaken lightly. In Example 1b, a predetermined amount of potassium pyrophosphate 20% solution serving as a dispersant was added, and then the bottle lid was closed and lightly shaken. In Example 1c, a predetermined amount of a 20% sodium silicate powder solution as a dispersant was added, and then the bottle was closed and lightly shaken.
（２）スラリーを図３の構造をもつ高圧洗浄装置に投入し、圧力４．５ＭＰａ、高圧水流量７リットル／分の条件で洗浄を行った。 (2) The slurry was put into a high-pressure washing apparatus having the structure shown in FIG. 3 and washed under conditions of a pressure of 4.5 MPa and a high-pressure water flow rate of 7 liters / minute.
（３）洗浄後のスラリーを容器に受けて回収を行なった。比較例２では、回収容器に所定量の分散剤溶液を予め入れておき、この中に洗浄後の高圧洗浄装置から排出されるスラリーを注いだ。 (3) The washed slurry was received in a container and collected. In Comparative Example 2, a predetermined amount of the dispersant solution was put in a collection container in advance, and the slurry discharged from the high-pressure washing apparatus after washing was poured therein.
（４）回収したスラリーをビーカーに移して、ジャーテスターにより１分間攪拌を行い、均質に土粒子を分散した後に、スラリーをピペットで採取した。 (4) The recovered slurry was transferred to a beaker, stirred for 1 minute with a jar tester to uniformly disperse the soil particles, and the slurry was collected with a pipette.
（５）水を満たした内径４０ｍｍの塩ビ管に、採取したスラリーを静かに加え、沈降法により、粒径１０μｍ未満の土粒子と、これより粒径の大きい土粒子の分離を行った。 (5) The collected slurry was gently added to a polyvinyl chloride tube filled with water and having an inner diameter of 40 mm, and soil particles having a particle size of less than 10 μm and soil particles having a larger particle size were separated by a sedimentation method.
（６）沈降分離したスラリーに、硫酸アルミニウム、中アニオン高分子凝集剤から構成される凝集剤を０．１質量％添加して１分間攪拌を行った。 (6) 0.1% by mass of a flocculant composed of aluminum sulfate and a medium anionic polymer flocculant was added to the sedimented and separated slurry and stirred for 1 minute.
（７）凝集剤を加えたスラリー全量を孔径４．５μｍの定性ろ紙を用いてろ過し、スラリー中の土粒子を回収して電気炉で１２０℃、２４時間乾燥後に質量を測定した。質量の測定においては、添加した凝集剤の質量分を補正した。 (7) The whole amount of the slurry to which the flocculant was added was filtered using a qualitative filter paper having a pore size of 4.5 μm, and the soil particles in the slurry were collected and dried in an electric furnace at 120 ° C. for 24 hours, and the mass was measured. In measuring the mass, the mass of the added flocculant was corrected.
（８）試験条件毎に、乾燥土壌中の１０μｍ以下の土粒子の質量比を算定して、解砕効果を評価する指標とした。 (8) For each test condition, the mass ratio of soil particles of 10 μm or less in the dry soil was calculated and used as an index for evaluating the crushing effect.
（９）比較例１として、分散剤を添加せず、同条件で高圧洗浄のみを行い、回収した洗浄後スラリーを同様の沈降法により分離して、乾燥後の土壌中の１０μｍ以下の土粒子の質量比を算定した。 (9) As Comparative Example 1, only a high-pressure washing was performed under the same conditions without adding a dispersant, and the recovered washed slurry was separated by the same sedimentation method, and soil particles of 10 μm or less in the dried soil The mass ratio of was calculated.
（１０）比較例３として、等量の分散剤を添加して、粘性土を固液比（質量比）１：１００の条件でビーカーに加えて、ジャーテスターを用いて、強攪拌を１時間行って、スラリーを調製した。このスラリーを同様の沈降法により分離して、乾燥後の土壌中の１０μｍ以下の土粒子の質量比を算定した。 (10) As Comparative Example 3, an equivalent amount of a dispersant was added, and the viscous soil was added to the beaker at a solid-liquid ratio (mass ratio) of 1: 100, and strong stirring was performed for 1 hour using a jar tester. And a slurry was prepared. This slurry was separated by the same sedimentation method, and the mass ratio of soil particles of 10 μm or less in the soil after drying was calculated.
ここで、本試験では、分散剤として、関東化学（株）製、ヘキサメタりん酸ナトリウム試薬（純度６５〜７０％（Ｐ２Ｏ５として）、分子量６１１．７）、ピロりん酸カリウム試薬（純度９８％、分子量３３０．３）、純正化学（株）製、けい酸ナトリウム粉末試薬（ＳｉＯ２：５０〜５５％、Ｎａ２Ｏ：２３〜２７％、分子量１２２．１）を使用した。 Here, in this test, as a dispersant, manufactured by Kanto Chemical Co., Inc., sodium hexametaphosphate reagent (purity 65 to 70% (as P 2 O 5 ), molecular weight 611.7), potassium pyrophosphate reagent (purity) 98%, molecular weight 330.3), Junsei chemical Co., sodium silicate powder reagent (SiO 2: 50~55%, Na 2 O: 23~27%, were used molecular weight 122.1).
この試験結果を表２に示した。１０μｍ以下の土粒子の質量比により、粘性土の解砕効果を評価すると、土壌に水と分散剤を洗浄前に添加した実施例１ａにおける処理において、最も良好な結果となった。このケースでは、解砕された１０μｍ以下の土粒子の質量比は、元の土壌のおよそ１／２のレベルまで解砕されており、かなりの効果があることが分かる。別種の分散剤を加えた実施例１ｂ、実施例１ｃにおいても、ほぼ同等の解砕効果が認められた。 The test results are shown in Table 2. When the crushing effect of the viscous soil was evaluated by the mass ratio of the soil particles of 10 μm or less, the best result was obtained in the treatment in Example 1a in which water and a dispersant were added to the soil before washing. In this case, it can be seen that the mass ratio of the crushed soil particles of 10 μm or less is crushed to a level of about ½ of the original soil, which is quite effective. In Example 1b and Example 1c to which another type of dispersant was added, almost the same crushing effect was recognized.
比較例１の分散剤を添加せず高圧洗浄を行った場合には、解砕効果が殆ど得られなかった。また、洗浄後に分散剤を加えた比較例２では、予め分散剤を添加したケースの効果には及ばなかった。さらに、分散剤を加えて、希薄な固液比の条件で撹拌羽根により強撹拌を行った比較例３のケースでも、１０μｍ以下の土粒子の質量比は低く、解砕効果は実施例１ａ〜１ｃに及ばなかった。 When high-pressure washing was performed without adding the dispersant of Comparative Example 1, the crushing effect was hardly obtained. Further, in Comparative Example 2 in which the dispersant was added after washing, the effect of the case where the dispersant was added in advance was not reached. Furthermore, even in the case of Comparative Example 3 in which a dispersant was added and strong stirring was performed with a stirring blade under a dilute solid-liquid ratio, the mass ratio of soil particles of 10 μm or less was low, and the crushing effect was as in Example 1a to It did not reach 1c.
以上により、団粒構造をもつ粘性土に分散剤と水を添加した後、高圧噴流による洗浄を行えば、極めて高い解砕効果が得られることが分かった。この効果は、高圧噴流による洗浄のみでは得られず、また、分散剤を加えた撹拌処理では再現することができなかった。 From the above, it was found that if a dispersant and water are added to a viscous soil having a aggregate structure, then cleaning with a high-pressure jet is performed, an extremely high crushing effect can be obtained. This effect could not be obtained only by washing with a high-pressure jet, and could not be reproduced by stirring treatment with a dispersant added.
下記の手順で塩化セシウム試薬を用いて模擬汚染土を調製して、本発明の汚染土壌の洗浄、減容化効果を調べた。また、表３の試験条件に従って、下記の手順で高圧洗浄による粘性土の洗浄効果を調べた。 Simulated contaminated soil was prepared using a cesium chloride reagent by the following procedure, and the effects of washing and volume reduction of the contaminated soil of the present invention were examined. Moreover, according to the test conditions of Table 3, the washing | cleaning effect of the viscous soil by a high pressure washing | cleaning was investigated in the following procedures.
（１）濃度２５０ｍｇ／リットルの塩化セシウム溶液に、固液比１：４の条件で前記の粘性土を１日浸漬した後に、固液分離して室内で３日風乾し、セシウム含有量０．３６ｇ／ｋｇ、含水率１８％の模擬汚染土を調製した。 (1) After immersing the viscous soil in a cesium chloride solution having a concentration of 250 mg / liter for a solid-liquid ratio of 1: 4 for 1 day, the solid solution is separated and air-dried indoors for 3 days. A simulated contaminated soil having 36 g / kg and a water content of 18% was prepared.
（２）模擬汚染土１００ｇ、水２００ｇをＰＰ樹脂製ボトルに投入し、さらに所定量の分散剤を加えてボトルの蓋を閉め、軽く振とうした。 (2) 100 g of simulated contaminated soil and 200 g of water were put into a PP resin bottle, a predetermined amount of dispersant was added, the bottle lid was closed, and shaken lightly.
（３）上記の高圧洗浄装置で圧力４．５ＭＰａ、高圧水流量７リットル／分の条件で洗浄し、洗浄土を７５μｍのふるいで回収した。 (3) Washing was performed with the above-described high-pressure washing apparatus under conditions of a pressure of 4.5 MPa and a high-pressure water flow rate of 7 liters / minute, and the washing soil was recovered with a 75 μm sieve.
（４）回収した土壌を乾燥して、ふるいに残留した土壌の質量比を計算した。 (4) The collected soil was dried, and the mass ratio of the soil remaining on the sieve was calculated.
（５）乾燥した土壌をフッ酸１：硝酸３：塩酸１（容積比）の配合をもつ強酸に固液比（質量容積比）３：１００の条件で加えて、次に１５０℃で加熱しながらこれを溶解した。 (5) Dried soil was added to a strong acid having a composition of hydrofluoric acid 1: nitric acid 3: hydrochloric acid 1 (volume ratio) under the condition of a solid-liquid ratio (mass volume ratio) 3: 100, and then heated at 150 ° C. This was dissolved.
（６）上記溶解液をさらに分析用に調整した後、溶液中のセシウム濃度をＩＣＰ−ＭＳを用いて測定し、洗浄処理後の土壌含有量を調べた。 (6) After the said solution was further adjusted for analysis, the cesium concentration in the solution was measured using ICP-MS, and the soil content after the washing treatment was examined.
この結果を表４及び図６に示した。高圧洗浄のみを行った比較例４においても、高圧洗浄により汚染土表面部が解砕され、セシウムを吸着した微細な粒子が分離され、ふるいに残留しなくなるので、含有量が４０％低下している。さらに、分散剤を添加したケースでは、含有量がそれ以上に低下し、実施例２ｂでは、セシウム含有量が１／３まで低下しており、分散剤量を加えて高圧洗浄処理することで、Ｃｓを含む細粒粘土粒子が団粒土から分離除去され、セシウム含有量を大きく低下させる機能があることを確認された。 The results are shown in Table 4 and FIG. Also in Comparative Example 4 in which only high pressure cleaning was performed, the contaminated soil surface portion was crushed by high pressure cleaning, and fine particles adsorbing cesium were separated and remained on the sieve, so the content was reduced by 40%. Yes. Furthermore, in the case where the dispersant is added, the content is further reduced, and in Example 2b, the cesium content is reduced to 1/3, and by adding the dispersant amount, high-pressure washing treatment is performed. It was confirmed that fine clay particles containing Cs were separated and removed from the aggregate soil and had a function of greatly reducing the cesium content.
下記の手順により、実施例１と同一の粘性土に分散剤を加えて高圧洗浄を行い、振動ふるい（網目０．１５ｍｍ）を通過させた後の洗浄中の土粒子について、湿式サイクロンを用いて、２０μｍ分級試験を行なった。表５にこの試験における分散剤の添加条件を示した。 According to the following procedure, a dispersant is added to the same viscous soil as in Example 1 to perform high-pressure washing, and the soil particles being washed after passing through a vibrating sieve (mesh 0.15 mm) are used with a wet cyclone. A 20 μm classification test was conducted. Table 5 shows the conditions for adding the dispersant in this test.
（１）粘性土５ｋｇ、水３０ｋｇを、容量５０リットルの樹脂製容器に投入し、撹拌器で５分間撹拌を行った。次に実施例３では、分散剤であるヘキサメタりん酸ナトリウム試薬２０％溶液を所定量加えて、さらに３分間攪拌を行なった。比較例５ではヘキサメタりん酸ナトリウム試薬を添加しなかった。 (1) 5 kg of clay soil and 30 kg of water were put into a resin container having a capacity of 50 liters, and stirred with a stirrer for 5 minutes. Next, in Example 3, a predetermined amount of a 20% sodium hexametaphosphate reagent solution as a dispersant was added and further stirred for 3 minutes. In Comparative Example 5, no sodium hexametaphosphate reagent was added.
（２）このスラリーを図３の構造をもつ高圧洗浄装置に投入し、高圧水供給圧力４．５ＭＰａ、高圧水流量６０リットル／分の条件で洗浄を行い、網目０．１５ｍｍの振動ふるいにかけた。ふるいを通過した洗浄水を容器に受けて回収を行なった。 (2) This slurry was put into a high-pressure washing apparatus having the structure shown in FIG. 3 and washed under conditions of a high-pressure water supply pressure of 4.5 MPa and a high-pressure water flow rate of 60 liters / minute, and passed through a vibrating screen having a mesh size of 0.15 mm. . The washing water that passed through the sieve was received in a container and collected.
（３）ふるいを通過した洗浄水の固形分濃度を測定したところ４．３質量％であった。これについて、（株）ニクニ製、サイクロン（製品名：サイクロンキャッチャー）を用いて、粒径２０μｍの条件で分級を行なった。サイクロン分級の条件は、ポンプ供給圧力０．２ＭＰａ、流量７０リットル／分、サイクロンオーバーとサイクロンアンダー排出流量比を４０：１となるよう調整した。 (3) It was 4.3 mass% when solid content concentration of the washing water which passed the sieve was measured. This was classified using a cyclone (product name: cyclone catcher) manufactured by Nikuni Co., Ltd. under the condition of a particle size of 20 μm. The cyclone classification conditions were adjusted such that the pump supply pressure was 0.2 MPa, the flow rate was 70 liters / minute, and the cyclone over and cyclone under discharge flow rate ratio was 40: 1.
（４）サイクロンオーバー、サイクロンアンダーから回収した２種のスラリーに含まれる土粒子の粒度分布を堀場製作所（株）製、レーザー回折／散乱粒度分布測定装置ＬＡ９２０を用いて測定した。 (4) The particle size distribution of the soil particles contained in the two types of slurry recovered from the cyclone over and cyclone under was measured using a laser diffraction / scattering particle size distribution measuring apparatus LA920 manufactured by Horiba.
（５）実施例３のサイクロン分級スラリーから回収した粒度分布測定結果を図７に示した。また、比較例５のサイクロン分級スラリーから回収した粒度分布測定結果を図８に示した。 (5) The particle size distribution measurement results recovered from the cyclone classification slurry of Example 3 are shown in FIG. Moreover, the particle size distribution measurement result collect | recovered from the cyclone classification slurry of the comparative example 5 was shown in FIG.
図７に示されたサイクロンオーバー（サイクロン上）、サイクロンアンダー（サイクロン下）の粒度分布図より、分散剤を添加した実施例３では、サイクロンアンダーにおける２０μｍ未満の土粒子含有割合は２５％、サイクロンオーバーにおける２０μｍ未満の土粒子の含有割合は９８％となり、良好な分級ができている。次に、分散剤を加えない高圧洗浄である比較例５ではサイクロンオーバー、サイクロンアンダー回収土の粒度分布に有意な差は生じておらず、サイクロン分級は有効に機能しなかったと判断される。以上のとおり、本発明の処理方法では、粘性土を効果的に解砕、分散するため、湿式サイクロンによる２０μｍ分級が可能となる。この機能により放射性物質を吸着している粘土鉱物を分離回収することができ、これによって、放射能汚染土の放射性物質濃度の低減および減容化処理を行うことができる。 From the particle size distribution diagram of the cyclone over (on the cyclone) and the cyclone under (under the cyclone) shown in FIG. 7, in Example 3 in which the dispersant was added, the content of soil particles of less than 20 μm in the cyclone under was 25%, and the cyclone. The content ratio of soil particles of less than 20 μm in the over is 98%, and good classification is achieved. Next, in Comparative Example 5, which is high-pressure washing without adding a dispersant, there is no significant difference in the particle size distribution of the cyclone over and cyclone under recovered soil, and it is judged that the cyclone classification did not function effectively. As described above, in the treatment method of the present invention, the clay is effectively crushed and dispersed, so that 20 μm classification using a wet cyclone is possible. By this function, the clay mineral adsorbing the radioactive substance can be separated and recovered, whereby the radioactive substance concentration in the radioactively contaminated soil can be reduced and the volume can be reduced.
実施例３で得られたサイクロンオーバー回収スラリーは、分散剤の添加によりゼータ電位が低下しており、分級後１日経過しても微細な土粒子は懸濁したまま沈降しなかった。本発明の高圧洗浄処理方法では、粘土粒子が効果的に解砕、分散され、洗浄水中に微細な土粒子が安定分散した状態であり、凝集処理が難しい。また、当然のことながら土粒子の７０〜８０％が粒径１０μｍ未満の土粒子であるため、ろ過処理することは困難である。 In the cyclone over recovered slurry obtained in Example 3, the zeta potential was lowered by the addition of the dispersant, and even after 1 day after classification, fine earth particles were suspended and did not settle. In the high-pressure washing treatment method of the present invention, the clay particles are effectively crushed and dispersed, and the fine earth particles are stably dispersed in the washing water, and the aggregation treatment is difficult. Of course, since 70 to 80% of the soil particles are soil particles having a particle size of less than 10 μm, it is difficult to perform filtration.
下記により、多価電解質を添加してサイクロンオーバー回収スラリーの凝集試験を実施した。凝集試験における凝集剤の添加条件を表６に示した。なお、この試験に用いたスラリーの固形分濃度は３．８質量％であった。 In the following manner, a polyelectrolyte was added, and an agglomeration test of the cyclone over recovery slurry was performed. Table 6 shows the conditions for adding the flocculant in the coagulation test. The solid content concentration of the slurry used in this test was 3.8% by mass.
（１）サイクロンオーバー回収スラリーを容量５００ｍｌのビーカーに２００ｇ採取した。 (1) 200 g of cyclone over recovered slurry was collected in a 500 ml beaker.
（２）無機添加剤である塩化マグネシウム６水塩、塩化カルシウム、硫酸アルミニウム１６水塩については、それぞれを精製水に溶解して２０％溶液を調製した。高分子凝集剤は精製水に溶解して０．１％溶液を調製した。 (2) Regarding the magnesium chloride hexahydrate, calcium chloride, and aluminum sulfate 16 hydrate, which are inorganic additives, each was dissolved in purified water to prepare a 20% solution. The polymer flocculant was dissolved in purified water to prepare a 0.1% solution.
（３）塩化マグネシウム６水塩、塩化カルシウムを用いた凝集試験では、ビーカーをジャーテスターにセットし、表６に従ってスラリー重量に対して所定量の無機添加剤を加えて５分間攪拌した。続けて高分子凝集剤の溶解液を所定量添加して５分間撹拌を行なった。 (3) In the aggregation test using magnesium chloride hexahydrate and calcium chloride, a beaker was set on a jar tester, a predetermined amount of inorganic additive was added to the slurry weight according to Table 6, and the mixture was stirred for 5 minutes. Subsequently, a predetermined amount of the polymer flocculant solution was added and stirred for 5 minutes.
（３）硫酸アルミニウムを用いた凝集試験では、ビーカーをジャーテスターにセットし、表６に従って硫酸アルミニウム溶解液を添加し、次に水酸化ナトリウム溶液を添加して中和した後に５分間攪拌した。続けて高分子凝集剤の溶解液を所定量添加して５分間撹拌を行なった。 (3) In the agglomeration test using aluminum sulfate, a beaker was set on a jar tester, an aluminum sulfate solution was added according to Table 6, and then sodium hydroxide solution was added to neutralize, followed by stirring for 5 minutes. Subsequently, a predetermined amount of the polymer flocculant solution was added and stirred for 5 minutes.
（４）２０分間静置を行い、各試験条件における土粒子の凝集状況を観察した。試験結果を表７に示した。 (4) The mixture was allowed to stand for 20 minutes, and the state of aggregation of soil particles under each test condition was observed. The test results are shown in Table 7.
ここで、本試験の無機凝集剤として関東化学（株）製塩化マグネシウム６水和物（純度＞９９％）、塩化カルシウム（純度＞９５％）、硫酸アルミニウム１４−１８水和物（純度５１．０％〜５７．５％（Ａｌ２（ＳＯ４）３として）を使用した。また、高分子凝集剤としてＭＴアクアポリマー（株）製、ポリアクリ酸アミド系中アニオン高分子凝集剤Ａ?１１０を使用した。 Here, as an inorganic flocculant for this test, magnesium chloride hexahydrate (purity> 99%), calcium chloride (purity> 95%), aluminum sulfate 14-18 hydrate (purity 51. 0% to 57.5% (as Al 2 (SO 4 ) 3 ) was used, and as a polymer flocculant, an aquatic polymer flocculant A? used.
表７の凝集試験結果では、本発明の洗浄水のうち、最も微細な土粒子を含む、サイクロンオーバー回収スラリーに塩化カルシウム、塩化マグネシウムを加えて撹拌することで、少ない薬剤の添加量で、凝集処理することが可能であり、高分子凝集剤を加えることで凝集効果をさらに高めることができる。実施例に記載をしなかったが、塩化カルシウム０．０５質量％、塩化マグネシウム０．０５質量％の条件では、凝集効果は認められるが、効果は不十分であった。洗浄水の凝集処理では塩化マグネシウムより塩化カルシウム、硫酸マグネシウムの方が高い処理効果を得た。比較例６では実施例４ｂの４倍量の無機凝集剤を添加し、高分子凝集剤を加えたが、十分な凝集効果は得られなかった。 In the agglomeration test results in Table 7, by adding calcium chloride and magnesium chloride to the cyclone over recovery slurry containing the finest soil particles in the washing water of the present invention and stirring, the agglomeration can be achieved with a small amount of drug added. It can be processed, and the aggregation effect can be further enhanced by adding a polymer flocculant. Although not described in the examples, an aggregation effect was observed under the conditions of 0.05% by mass of calcium chloride and 0.05% by mass of magnesium chloride, but the effect was insufficient. In the agglomeration treatment of washing water, calcium chloride and magnesium sulfate were more effective than magnesium chloride. In Comparative Example 6, 4 times the amount of the inorganic flocculant as in Example 4b was added and the polymer flocculant was added, but a sufficient flocculant effect was not obtained.
以上に示したように、本発明の粘性土を多く含む放射能汚染土の洗浄、減容化処理方法は、汚染土壌に、分散剤を加えて高圧噴流による洗浄を行うことで、団粒土を解砕、剥離し、振動ふるい、スクリューコンベア、湿式サイクロン、沈降分離、比重分離、遠心分離浮遊選鉱分離により土粒子を回収処理することで、汚染土に含有するセシウム含有量を大きく低下させ、減容化処理を行う機能を有する。また、本発明の方法により、洗浄水のリサイクル利用も可能である。本発明の洗浄、減容化処理方法では、大量の化学薬品を要したり、大きなエネルギーを消費することなく、効率的かつ経済的に放射能汚染土壌を処理することが可能である。
As described above, the method for cleaning and reducing the volume of radioactively contaminated soil containing a large amount of viscous soil according to the present invention is performed by adding a dispersing agent to the contaminated soil and performing washing with a high-pressure jet to thereby remove the aggregated soil. By crushing, exfoliating, removing the soil particles by vibrating sieve, screw conveyor, wet cyclone, sedimentation separation, specific gravity separation, centrifugal separation by flotation, the content of cesium contained in the contaminated soil is greatly reduced, It has a function to perform volume reduction processing. In addition, the method of the present invention can be used to recycle cleaning water. According to the cleaning and volume reduction processing method of the present invention, it is possible to efficiently and economically treat radioactively contaminated soil without requiring a large amount of chemicals or consuming a large amount of energy.
Claims (6)
The washing water is reused after adding at least one of calcium chloride, magnesium chloride, and magnesium sulfate to the washing water after the washing step and coagulating the suspended soil particles. 5. The method for cleaning and reducing the volume of radioactively contaminated soil according to any one of 5 above.
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| JP2021154215A (en) * | 2020-03-27 | 2021-10-07 | 清水建設株式会社 | Washing/classification processing system for contaminated soil and washing/classification processing method for contaminated soil |
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| CN112629986A (en) * | 2020-11-25 | 2021-04-09 | 西安建筑科技大学 | Device and method for extracting clay particles |
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