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JP4224631B2 - Method and apparatus for treating radioactive organic waste - Google Patents

Method and apparatus for treating radioactive organic waste Download PDF

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Publication number
JP4224631B2
JP4224631B2 JP23767598A JP23767598A JP4224631B2 JP 4224631 B2 JP4224631 B2 JP 4224631B2 JP 23767598 A JP23767598 A JP 23767598A JP 23767598 A JP23767598 A JP 23767598A JP 4224631 B2 JP4224631 B2 JP 4224631B2
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reaction
catalytic combustion
oxidative decomposition
combustion device
intermediate product
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JP2000065986A (en
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富美雄 岩本
昭 長谷川
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JGC Corp
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JGC Corp
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Description

【0001】
【発明の属する技術分野】
本発明は、放射性有機廃棄物の処理方法、とくに原子力発電所で行なう水処理に伴って発生する使用済イオン交換樹脂やフィルタースラッジ、あるいは除染作業の結果発生する除染廃液を酸化分解して処理する方法に関する。 本発明はまた、この酸化分解処理に使用する装置にも関する。
【0002】
【従来の技術】
原子力発電所において放射性核種を含有する排水の処理に使用したフィルタースラッジおよび使用済イオン交換樹脂の処理法として、出願人は、触媒としての鉄イオンの存在下に過酸化水素を作用させる湿式酸化法を提案した(特公昭61−9599)。 この種の湿式酸化法に関してはさまざまな技術が開発されており、触媒としての銅イオンの使用(特開昭59−44700、特開昭60−61697)、鉄触媒に対する助触媒としてのニッケルの使用(特開昭61−157539)、クエン酸の添加(特開昭63−158497)、酢酸塩の添加(特開平1−313799)、しゅう酸塩の添加(特開平1−313800)などが提案されている。
【0003】
過酸化水素を用いた湿式酸化分解は、核燃料再処理工場から出るリン酸トリブチル(TBP)を主成分とする廃溶媒の処理にも適用される(特開昭62−297792)が、ここではオゾンを併用する。
【0004】
湿式酸化分解の生成物を最終的にどう処理するかについて、出願人は、廃液を濃縮し中和して固化処理することを提案した(特開平2−63595)。 湿式酸化分解反応は、通常は常圧下に、ほぼ沸騰状態で実施するので、高分子有機物がまだ完全に酸化分解されていない段階、すなわちCO2やH2Oにまで分解される途上にある低分子量の有機酸、たとえばギ酸や酢酸が、反応液から揮発して来る。 フィルタースラッジの材料にアクリル繊維を用いた場合は、酸化分解によりシアン化合物が生成する。 酸化分解により生成したアミン類、アンモニアは、酸性の反応液中では固定されているが、反応の最終段階において、反応液を中和したとき放出される。 TBPの湿式酸化処理の場合は、n−ドデカンが生成する。
【0005】
揮発したこれらの中間生成物の一部は、発生する水蒸気とともにコンデンサーにおいて凝縮され、凝縮水のTOC(有機炭素含有量)やCODを高くする。 したがって、凝縮水を再利用したり放出したりするためには、二次的な処理が必要である。 非凝縮性の物質は排ガスの側に出るから、放出に先立って除去しなければならない。
【0006】
【発明が解決しようとする課題】
本発明の目的は、放射性核種が共存する有機物質を過酸化水素を用いた湿式酸化により処理する方法において、酸化分解反応の中間生成物が、プロセスの結果生じる凝縮水に入って来ることを防ぎ、二次処理の必要なく凝縮水の再利用または放出をすることができるようにした処理方法を提供することにある。 この方法の実施に使用する装置を提供することもまた、本発明の目的に含まれる。
【0007】
【課題を解決するための手段】
本発明の放射性有機廃棄物の処理方法は、原子力発電所で発生する使用済イオン交換樹脂、フィルタースラッジまたは除染廃液のいずれかである放射性有機廃棄物の処理方法であって、水性媒体中で、触媒としての鉄イオンおよび銅イオンの1種または2種の存在下に放射性有機廃棄物に過酸化水素を作用させて湿式酸化分解する処理方法において、
酸化分解反応の結果生成した、低分子量の有機酸、炭化水素、アンモニア、アミンおよびシアン化合物の少なくとも1種を含有する中間生成物と水蒸気との混合物を、酸化反応槽から取り出して加熱し、温度を高めてから、酸化触媒をそなえた触媒燃焼装置に導き、そこで酸素を供給して中間生成物を二次的に酸化分解したのち、燃焼装置からの分解生成物を含む排ガスを冷却し、TOCを実質上含まない凝縮水と無害無臭の排ガスとを得ることからなり、上記の中間生成物と水蒸気との混合物の加熱および上記の燃焼装置からの排ガスの冷却を、両者の熱交換によって行なうことからなる。
【0008】
本発明の放射性有機廃棄物の処理装置は、図1に全体の構成を示すように、放射性有機廃棄物に過酸化水素を作用させて湿式酸化分解するための、撹拌機をそなえた反応槽(2)、反応槽への過酸化水素、触媒溶液およびpH調整用の酸・アルカリの供給タンク(21〜25)、反応槽から揮発してくる酸化分解反応の中間生成物および水蒸気の混合物を受け入れて、中間生成物を二次的に酸化させるための、酸化触媒をそなえた触媒燃焼装置(3)、触媒燃焼装置への酸素供給手段(4)、触媒燃焼装置からの排ガスを冷却して凝縮水を得るためのコンデンサー(5)、ならびに、触媒燃焼装置からの排ガスの熱で混合ガスを加熱するための熱交換器(6)から本質的に構成される。 図1において、符号(1)は処理すべき放射性有機廃棄物のタンクを、また符号(7)は凝縮水を受けるタンクを、それぞれ示す。
【0009】
【発明の実施の形態】
本発明の方法で処理する放射性有機廃棄物は、原子力発電所で発生する使用済の粒状または粉末状のイオン交換樹脂がその代表であるが、濾過助材のフィルタースラッジも同様な処理の対象となる。フィルタースラッジは、セルロース系のものはもちろん、アクリル繊維系のものも処理できる。本発明の方法はまた、クエン酸、シュウ酸、EDTAを含む除染廃液の処理にも適用できる。
【0010】
触媒燃焼装置は、Ni−Cr系、SiO2−Al23−MgO系あるいはγ−Al23などの酸化触媒をそなえたものであって、スポンジ状、球状、ハニカム体など種々の形状のものがあり、任意に選択使用できる。 圧力損失を小さくするという観点からは、Ni−Cr系発泡金属触媒が好適である。 触媒燃焼装置は、塗装や印刷の業界で、有機溶剤を含有する雰囲気を浄化するために実用されている。 本発明においては、溶剤蒸気含有空気と違って、多量の水蒸気が共存する条件下の使用であるが、既存の装置を本発明の処理方法においても利用できることを確認してある。
【0011】
可燃性のガスを含有する気体を、上記のような酸化触媒に接触させてその表面で酸化を行なうとき、一般に、200℃以上、好ましくは300℃以上で酸化反応が盛んに起こり、触媒の温度が上昇する。 温度上昇の度合いは、もちろん供給される可燃物の濃度によって異なるが、しばしば100℃またはそれ以上に達する。 触媒床に入るガスの温度を300〜350℃に高めておけば、触媒床を出る排ガスの温度は400〜500℃に達する。
【0012】
二次的な酸化反応により、有機酸は完全に酸化されてCO2およびH2Oに変化し、アミン・アンモニアの類は、N2およびH2Oになる。 このようにして、TOCが実質上ゼロといってよい(1〜2ppm)凝縮水が得られる。
【0013】
酸化分解反応の中間生成物と水蒸気との混合物の加熱は、必要であれば、燃焼ガスの導入により実施することができる。 燃焼装置からの排ガスのもつ熱を、中間生成物と水蒸気との混合物と熱交換することが好ましい。
【0014】
湿式酸化分解は、連続式に行なってもバッチ式に行なってもよいが、後記する実施例にみるようなセミバッチ式が有利である。 すなわち、処理すべき放射性有機廃棄物の一部をあらかじめ反応槽に装入しておいて酸化分解反応を開始し、反応の進行に伴って廃棄物を補給して行き、所定の量を投入し終わったのちも過酸化水素の供給を続け、酸化分解をほぼ完全に進めてから停止するという手順に従う方式である。
【0015】
過酸化水素による湿式酸化は、水性媒体が酸性のときによく進行するから、反応の開始に当たって、硫酸などの酸を添加する。 すると、アンモニアやアミン類は、反応中は液中に固定されていて揮発せず、反応終了後、苛性ソーダなどのアルカリを加えて液を中和すると、放出される。 したがって、その段階で揮発してきた中間生成物を触媒燃焼装置に送って、二次酸化して完全に分解する。
【0016】
【実施例】
[実施例1]
図1に示す構成の、放射性有機廃棄物処理装置を組み立てた。 反応槽(2)は、容量250リットルで、ジャケットおよび撹拌機つきのものである。 使用済イオン交換樹脂を模擬したものとして、下記2種の粒状イオン交換樹脂
IR−120B:15.0kg
IRA−400:30.0kg
の混合物を、廃棄物の供給タンク(1)に入れ、10重量%水スラリーとした。
【0017】
イオン交換樹脂スラリーの75リットルを反応槽に移し、蒸留水を加えて容量を倍の150リットルとした。 酸供給タンク(24)から硫酸を添加してpHを1〜3に調節した。 ジャケットにスチームを通して加熱し、内容を沸騰状態にしたのち、触媒として、触媒溶液タンク(22、23)から、硫酸第一鉄および硫酸銅を濃厚溶液としてほぼ等量ずつ、あわせて3モルを添加した。 この状態で、模擬廃棄物スラリーを30リットル/時の供給速度で、また35%過酸化水素水を27リットル/時の供給速度で、反応槽に供給した。 反応槽内部は、スチーム加熱と反応熱により沸騰状態が継続し、液量がほぼ一定に保たれた。
【0018】
反応層から発生する水蒸気と酸化分解の中間生成物との混合物は、約90Nm3/時の速度で触媒燃焼装置(3)に通し、空気10Nm3/時を供給して、中間生成物を燃焼させた。 この燃焼装置は、Ni−Cr系の発泡金属からなる触媒床を備えている。 定常状態における触媒床の温度は、約320℃であった。 燃焼装置からの排ガスは、熱交換器(5)で熱交換の後、コンデンサー(6)で冷却し、非凝縮ガスと分離して、凝縮水を凝縮水タンク(7)に受けた。
【0019】
模擬廃棄物の供給を4時間で止め、その後は過酸化水素水のみを供給したまま反応を5時間継続し、その時点で反応を停止した。 定常状態の4時間のうち反応開始後1時間おき、および模擬廃棄物の供給を停止して1時間後の凝縮水について、TOCを測定した。 結果を図2の下段に示す。
【0020】
反応停止後、アルカリ供給タンク(25)から苛性ソーダ溶液を添加して、酸性の反応後の液を中和した。 すると、液中に固定されていたアミン類やアンモニアが分離揮発してきたので、このガスも触媒燃焼装置に送って酸化させ、ついでコンデンサーに導いた。 このとき、コンデンサーで分離された非凝縮性のガスの中には、アミン類もアンモニアも検出されなかった。
【0021】
[比較例1]
実施例1において、触媒燃焼装置による中間生成物の二次酸化分解を省略した工程を実施した。 凝縮水のTOCの時間変化は、図2の上段に示すとおりであって、620〜830ppm、平均688ppmであった。 有機炭素の成分を調べたところ、ギ酸、酢酸、プロピオン酸などであった。 反応後、アルカリによる中和を行なうと、コンデンサーの非凝縮ガス出口からアンモニアに似た臭気がしたので、ガスを採取してガスクロマトグラフで分析したところ、悪臭物質は主としてトリメチルアミンであることがわかった。
【0022】
[実施例2]
実施例1で用いた装置により、下記2種の粉末状イオン交換樹脂
PCH:7.5kg
PAO:7.5kg
の混合物を、実施例1と同様な条件で湿式酸化分解により処理した。
【0023】
凝縮水について、TOCを測定した結果を、図3の下段に示す。 コンデンサーで分離された非凝縮性のガスの中には、実施例1と同様、アミン類もアンモニアも検出されなかった。
【0024】
[比較例2]
比較例1と同じ装置を使用し、実施例2の工程を、触媒燃焼装置による中間生成物の二次酸化分解を省略して実施した。 凝縮水のTOCの時間変化は、図3の上段に示すとおり、420〜1350ppm、平均943ppmであった。 有機炭素成分は、比較例1と同様であった。 反応後、アルカリによる中和を行なったとき発生した非凝縮ガスも、比較例1と同様、悪臭物質は主としてトリメチルアミンであった。
【0025】
[実施例3]
実施例1で用いた装置において、セルロースを濃度10重量%のスラリーにして、実施例1と同様な条件で湿式酸化分解により処理した。 凝縮水についてTOCを測定したところ、4時間の反応時間とその後の1時間を通じて、1ppm 前後であった。
【0026】
[比較例3]
比較例1と同じ装置を使用し、実施例3の工程を、触媒燃焼装置による中間生成物の二次酸化分解を省略して実施した。 凝縮水のTOCは、4時間の反応時間とその後の1時間を通じて、26〜263ppm、平均125ppmであった。 有機炭素成分は、ギ酸および酢酸であった。
【0027】
[実施例4]
実施例1で用いた装置により、下記の濾過助材の混合物
DFK−10:3kg
DFA−10:6kg
L−10 :5kg
を濃度10重量%のスラリーにして、実施例1と同様な条件で湿式酸化分解により処理した。 凝縮水についてTOCを測定したところ、4時間の反応時間とその後の1時間を通じて、1ppm 前後であった。 非凝縮ガスの中に、有害な成分や悪臭をもつ成分は検出されなかった。
【0028】
[比較例4]
比較例1と同じ装置を使用し、実施例4の工程を、触媒燃焼装置による中間生成物の二次酸化分解を省略して実施した。 凝縮水中のTOCは、比較例2と同じような傾向を示した。 シアン化合物の生成が予測されたので、吸収液中に非凝縮ガスを通過させたところ、吸収液100ml中のシアン濃度は86.1ppm であった。 反応液の中にもシアンが残存しており、その濃度は0.36ppm と測定された。
【0029】
[実施例5]
実施例1で用いた装置により、下記の粒状イオン交換樹脂と濾過助材の混合物
IR−120B: 5kg
IRA−400:10kg
DFK−10: 6kg
DFA−10: 12kg
L−10 : 10kg
を濃度10重量%のスラリーにして、実施例1と同様な条件で湿式酸化分解により処理した。 凝縮水についてTOCを測定したところ、4時間の反応時間とその後の1時間を通じて、1ppm 前後であった。 非凝縮ガスの中に、有害な成分や悪臭をもつ成分は検出されなかった。
【0030】
【発明の効果】
本発明の方法によれば、放射性有機廃棄物を過酸化水素を用いた湿式酸化分解により処理したときに発生する酸化反応の中間生成物、すなわち低分子量の有機酸、アミン類、アンモニア、シアン化合物、炭化水素などを、コンデンサーに至る前に二次的に燃焼分解することによって、凝縮水や排気に混入することを防止できる。 その結果、TOCが実質上ゼロである凝縮水を得て、再利用したり放出したりすることができるし、排ガスは無臭かつ無害である。
【0031】
この処理方法に使用する装置は、在来の湿式酸化分解の装置に対し、溶剤蒸気を含む雰囲気の浄化に使用されている触媒燃焼装置と熱交換器を付加しただけで構成できるから、設備費の増大はさして問題ず、TOCの高い凝縮水の二次処理のための設備を設けるより、はるかに有利である。
【図面の簡単な説明】
【図1】 本発明の放射性有機廃棄物の処理装置の全体の構成を示すフローチャート。
【図2】 本発明の実施例1および比較例1の結果を示す図であって、コンデンサーからの凝縮水のTOCの時間変化を示す。 上段のグラフは比較例1のデータであり、下段のグラフは実施例1のデータである。
【図3】 本発明の実施例2および比較例2の結果を示す図であって、コンデンサーからの凝縮水のTOCの時間変化を示す。 上段のグラフは比較例2のデータであり、下段のグラフは実施例2のデータである。
【符号の説明】
1 放射性有機廃棄物のタンク
2 湿式酸化分解の反応槽
21 過酸化水素の供給タンク
22 触媒(硫酸第一鉄)溶液の供給タンク
23 触媒(硫酸銅)溶液の供給タンク
24 酸の供給タンク
25 アルカリの供給タンク
3 触媒燃焼装置
4 酸素供給手段
5 コンデンサー
6 熱交換器
7 凝縮水を受けるタンク
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating radioactive organic waste, in particular, oxidative decomposition of spent ion exchange resin and filter sludge generated with water treatment performed at a nuclear power plant, or decontamination waste liquid generated as a result of decontamination work. It relates to a method of processing. The present invention also relates to an apparatus used for this oxidative decomposition treatment.
[0002]
[Prior art]
As a method for treating filter sludge and spent ion exchange resin used to treat wastewater containing radionuclides in nuclear power plants, the applicant applied a wet oxidation method in which hydrogen peroxide acts in the presence of iron ions as a catalyst. Was proposed (Japanese Patent Publication No. 61-9599). Various techniques have been developed for this type of wet oxidation method, including the use of copper ions as a catalyst (JP 59-44700, JP 60-61697), and the use of nickel as a co-catalyst for iron catalysts. (JP 61-157539), addition of citric acid (JP 63-158497), addition of acetate (JP 1-331799), addition of oxalate (JP 1-313800), etc. have been proposed. ing.
[0003]
Wet oxidative decomposition using hydrogen peroxide is also applied to the treatment of waste solvent mainly composed of tributyl phosphate (TBP) from a nuclear fuel reprocessing plant (JP-A-62-297792). Use together.
[0004]
Regarding how to finally treat the product of the wet oxidative decomposition, the applicant has proposed that the waste liquid is concentrated, neutralized and solidified (Japanese Patent Laid-Open No. 2-63595). Since the wet oxidative decomposition reaction is usually carried out under normal pressure and almost in a boiling state, the high molecular organic substance is not yet completely oxidatively decomposed, that is, it is in the process of being decomposed to CO 2 or H 2 O. Molecular weight organic acids such as formic acid and acetic acid volatilize from the reaction solution. When acrylic fiber is used as the material of the filter sludge, a cyanide compound is generated by oxidative decomposition. Amines and ammonia generated by oxidative decomposition are fixed in the acidic reaction solution, but are released when the reaction solution is neutralized in the final stage of the reaction. In the case of wet oxidation treatment of TBP, n-dodecane is generated.
[0005]
Some of these volatilized intermediate products are condensed in the condenser together with the generated water vapor, increasing the TOC (organic carbon content) and COD of the condensed water. Therefore, in order to reuse or discharge the condensed water, a secondary process is necessary. Non-condensable material exits the exhaust gas and must be removed prior to release.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to prevent an intermediate product of an oxidative decomposition reaction from entering condensed water resulting from a process in a method of treating an organic substance coexisting with a radionuclide by wet oxidation using hydrogen peroxide. Another object of the present invention is to provide a treatment method that allows reuse or discharge of condensed water without the need for secondary treatment. It is also within the scope of the present invention to provide an apparatus for use in carrying out this method.
[0007]
[Means for Solving the Problems]
The method for treating radioactive organic waste according to the present invention is a method for treating radioactive organic waste that is one of used ion exchange resin, filter sludge, or decontamination waste liquid generated at a nuclear power plant, and is in an aqueous medium. In the treatment method in which hydrogen peroxide is allowed to act on radioactive organic waste in the presence of one or two of iron ion and copper ion as a catalyst,
A mixture of water vapor and an intermediate product containing at least one of low molecular weight organic acids, hydrocarbons, ammonia, amines, and cyanide, generated as a result of the oxidative decomposition reaction, is removed from the oxidation reaction tank, heated, and heated to a temperature. Is then introduced into a catalytic combustion device equipped with an oxidation catalyst, where oxygen is supplied to secondary oxidative decomposition of the intermediate product, and then the exhaust gas containing the decomposition product from the combustion device is cooled, and the TOC A mixture containing substantially no condensed water and harmless and odorless exhaust gas, and heating the mixture of the intermediate product and water vapor and cooling the exhaust gas from the combustion device by heat exchange between them. Consists of.
[0008]
As shown in FIG. 1, the radioactive organic waste treatment apparatus of the present invention is a reaction tank equipped with a stirrer for wet oxidation decomposition by causing hydrogen peroxide to act on the radioactive organic waste ( 2) Accepts hydrogen peroxide to the reaction tank, catalyst solution and acid / alkali supply tank for pH adjustment (21-25), intermediate product of oxidative decomposition reaction evaporating from reaction tank and steam mixture Then, the catalytic combustion device (3) having an oxidation catalyst for secondary oxidation of the intermediate product, the oxygen supply means (4) to the catalytic combustion device, and the exhaust gas from the catalytic combustion device is cooled and condensed. It consists essentially of a condenser (5) for obtaining water and a heat exchanger (6) for heating the mixed gas with the heat of the exhaust gas from the catalytic combustion device. In FIG. 1, reference numeral (1) indicates a tank of radioactive organic waste to be treated, and reference numeral (7) indicates a tank for receiving condensed water.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The radioactive organic waste to be treated by the method of the present invention is typified by used granular or powdered ion exchange resin generated at nuclear power plants, but filter sludge of filter aid is also subject to the same treatment. Become. The filter sludge can be treated not only with cellulose but also with acrylic fiber. The method of the present invention can also be applied to the treatment of decontamination waste liquid containing citric acid, oxalic acid and EDTA.
[0010]
The catalytic combustion apparatus is provided with an oxidation catalyst such as Ni—Cr, SiO 2 —Al 2 O 3 —MgO, or γ-Al 2 O 3 and has various shapes such as sponge, spherical, and honeycomb bodies. Can be selected and used arbitrarily. From the viewpoint of reducing the pressure loss, a Ni—Cr-based foamed metal catalyst is suitable. Catalytic combustion devices have been put to practical use in the coating and printing industries to purify atmospheres containing organic solvents. In the present invention, unlike solvent vapor-containing air, it is used under a condition where a large amount of water vapor coexists, but it has been confirmed that an existing apparatus can also be used in the treatment method of the present invention.
[0011]
When a gas containing a flammable gas is brought into contact with the oxidation catalyst as described above to oxidize the surface, generally, oxidation reaction occurs actively at 200 ° C. or higher, preferably 300 ° C. or higher, and the temperature of the catalyst. Rises. The degree of temperature rise will of course depend on the concentration of combustible material supplied, but often reaches 100 ° C. or higher. If the temperature of the gas entering the catalyst bed is increased to 300 to 350 ° C, the temperature of the exhaust gas exiting the catalyst bed reaches 400 to 500 ° C.
[0012]
By the secondary oxidation reaction, the organic acid is completely oxidized to CO 2 and H 2 O, and the amine / ammonia group becomes N 2 and H 2 O. In this way, condensed water that can be said to have substantially zero TOC (1-2 ppm) is obtained.
[0013]
If necessary, the mixture of the intermediate product of the oxidative decomposition reaction and water vapor can be heated by introducing combustion gas. It is preferable to exchange heat of the exhaust gas from the combustion apparatus with a mixture of the intermediate product and water vapor.
[0014]
The wet oxidative decomposition may be carried out continuously or batchwise, but the semibatch method as shown in the examples described later is advantageous. In other words, a part of the radioactive organic waste to be treated is charged in advance in the reaction tank, the oxidative decomposition reaction is started, the waste is replenished as the reaction proceeds, and a predetermined amount is charged. After the end, the hydrogen peroxide supply is continued, and the method follows a procedure in which the oxidative decomposition is almost completed and then stopped.
[0015]
Since wet oxidation with hydrogen peroxide proceeds well when the aqueous medium is acidic, an acid such as sulfuric acid is added at the start of the reaction. Then, ammonia and amines are fixed in the liquid during the reaction and do not volatilize, and are released when the liquid is neutralized by adding an alkali such as caustic soda after completion of the reaction. Therefore, the intermediate product that has volatilized at that stage is sent to the catalytic combustion apparatus, where it undergoes secondary oxidation and is completely decomposed.
[0016]
【Example】
[Example 1]
A radioactive organic waste treatment apparatus having the configuration shown in FIG. 1 was assembled. The reaction tank (2) has a capacity of 250 liters and is equipped with a jacket and a stirrer. As a simulated used ion exchange resin, the following two types of granular ion exchange resins IR-120B: 15.0 kg
IRA-400: 30.0kg
Was put into a waste supply tank (1) to form a 10 wt% water slurry.
[0017]
75 liters of the ion exchange resin slurry was transferred to the reaction vessel, and distilled water was added to double the volume to 150 liters. Sulfuric acid was added from the acid supply tank (24) to adjust the pH to 1-3. After heating the jacket through steam to bring the contents to a boiling state, from the catalyst solution tanks (22, 23), add approximately 3 moles of ferrous sulfate and copper sulfate as concentrated solutions. did. In this state, the simulated waste slurry was supplied to the reaction vessel at a supply rate of 30 liters / hour and 35% hydrogen peroxide was supplied at a supply rate of 27 liters / hour. The inside of the reaction vessel was kept boiling by steam heating and reaction heat, and the liquid volume was kept almost constant.
[0018]
The mixture of water vapor generated from the reaction layer and the intermediate product of oxidative decomposition is passed through the catalytic combustion device (3) at a rate of about 90 Nm 3 / hour, and air is supplied at 10 Nm 3 / hour to burn the intermediate product. I let you. This combustion apparatus is provided with a catalyst bed made of Ni-Cr-based foam metal. The temperature of the catalyst bed at steady state was about 320 ° C. The exhaust gas from the combustion device was heat-exchanged by the heat exchanger (5), cooled by the condenser (6), separated from non-condensed gas, and condensed water tank (7) was received.
[0019]
The supply of simulated waste was stopped in 4 hours, and then the reaction was continued for 5 hours while supplying only the hydrogen peroxide solution, and the reaction was stopped at that time. TOC was measured for condensed water 1 hour after the start of the reaction and 1 hour after stopping the supply of the simulated waste in 4 hours in the steady state. The results are shown in the lower part of FIG.
[0020]
After the reaction was stopped, a caustic soda solution was added from the alkali supply tank (25) to neutralize the acidic post-reaction solution. Then, amines and ammonia fixed in the liquid were separated and volatilized, and this gas was also sent to the catalytic combustion apparatus to be oxidized, and then led to the condenser. At this time, neither amines nor ammonia was detected in the non-condensable gas separated by the condenser.
[0021]
[Comparative Example 1]
In Example 1, the process which abbreviate | omitted the secondary oxidative decomposition of the intermediate product by a catalytic combustion apparatus was implemented. The time change of the TOC of the condensed water was as shown in the upper part of FIG. 2 and was 620 to 830 ppm, and the average was 688 ppm. When organic carbon components were examined, it was found to be formic acid, acetic acid, propionic acid, and the like. After the reaction, neutralization with alkali gave an odor similar to ammonia from the non-condensable gas outlet of the condenser. When the gas was collected and analyzed by gas chromatography, it was found that the malodorous substance was mainly trimethylamine. .
[0022]
[Example 2]
According to the apparatus used in Example 1, the following two kinds of powdered ion exchange resins PCH: 7.5 kg
PAO: 7.5kg
This mixture was treated by wet oxidative decomposition under the same conditions as in Example 1.
[0023]
The result of measuring the TOC for the condensed water is shown in the lower part of FIG. As in Example 1, neither amines nor ammonia was detected in the non-condensable gas separated by the condenser.
[0024]
[Comparative Example 2]
The same apparatus as in Comparative Example 1 was used, and the process of Example 2 was performed by omitting the secondary oxidative decomposition of the intermediate product by the catalytic combustion apparatus. The time change of the TOC of the condensed water was 420 to 1350 ppm and the average was 943 ppm as shown in the upper part of FIG. The organic carbon component was the same as in Comparative Example 1. After the reaction, the non-condensable gas generated when neutralization with alkali was performed was also mainly trimethylamine, as in Comparative Example 1.
[0025]
[Example 3]
In the apparatus used in Example 1, cellulose was made into a slurry having a concentration of 10% by weight and treated by wet oxidative decomposition under the same conditions as in Example 1. When the TOC of the condensed water was measured, it was around 1 ppm through the reaction time of 4 hours and the subsequent 1 hour.
[0026]
[Comparative Example 3]
The same apparatus as Comparative Example 1 was used, and the process of Example 3 was performed by omitting the secondary oxidative decomposition of the intermediate product by the catalytic combustion apparatus. The TOC of the condensed water was 26-263 ppm, average 125 ppm throughout the reaction time of 4 hours and the subsequent 1 hour. The organic carbon components were formic acid and acetic acid.
[0027]
[Example 4]
According to the apparatus used in Example 1, the following filter aid mixture DFK-10: 3 kg
DFA-10: 6kg
L-10: 5 kg
Was made into a slurry having a concentration of 10% by weight and treated by wet oxidative decomposition under the same conditions as in Example 1. When the TOC of the condensed water was measured, it was around 1 ppm through the reaction time of 4 hours and the subsequent 1 hour. No harmful components or odorous components were detected in the non-condensable gas.
[0028]
[Comparative Example 4]
The same apparatus as Comparative Example 1 was used, and the process of Example 4 was performed by omitting the secondary oxidative decomposition of the intermediate product by the catalytic combustion apparatus. The TOC in the condensed water showed the same tendency as in Comparative Example 2. Since generation of a cyanide compound was predicted, when a non-condensable gas was passed through the absorbing solution, the cyan concentration in 100 ml of the absorbing solution was 86.1 ppm. Cyanide also remained in the reaction solution, and its concentration was measured to be 0.36 ppm.
[0029]
[Example 5]
According to the apparatus used in Example 1, the following mixture of granular ion exchange resin and filter aid IR-120B: 5 kg
IRA-400: 10kg
DFK-10: 6kg
DFA-10: 12kg
L-10: 10 kg
Was made into a slurry having a concentration of 10% by weight and treated by wet oxidative decomposition under the same conditions as in Example 1. When the TOC of the condensed water was measured, it was around 1 ppm through the reaction time of 4 hours and the subsequent 1 hour. No harmful components or odorous components were detected in the non-condensable gas.
[0030]
【The invention's effect】
According to the method of the present invention, an intermediate product of an oxidation reaction generated when a radioactive organic waste is treated by wet oxidative decomposition using hydrogen peroxide, that is, a low molecular weight organic acid, an amine, ammonia, a cyanide compound It is possible to prevent hydrocarbons and the like from being mixed into condensed water and exhaust gas by secondary combustion and decomposition before reaching the condenser. As a result, condensed water having substantially zero TOC can be obtained and reused or discharged, and the exhaust gas is odorless and harmless.
[0031]
The equipment used in this treatment method can be configured by adding a catalytic combustion apparatus and a heat exchanger used for purification of an atmosphere containing solvent vapor to a conventional wet oxidative decomposition apparatus. This increase is much better than providing equipment for secondary treatment of condensed water with high TOC.
[Brief description of the drawings]
FIG. 1 is a flowchart showing the overall configuration of a radioactive organic waste treatment apparatus of the present invention.
FIG. 2 is a diagram showing the results of Example 1 of the present invention and Comparative Example 1, and shows the time change of TOC of condensed water from a condenser. The upper graph is the data of Comparative Example 1, and the lower graph is the data of Example 1.
FIG. 3 is a diagram showing the results of Example 2 and Comparative Example 2 of the present invention, and shows the time change of TOC of condensed water from a condenser. The upper graph is the data of Comparative Example 2, and the lower graph is the data of Example 2.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Radioactive organic waste tank 2 Wet oxidation decomposition reaction tank 21 Hydrogen peroxide supply tank 22 Catalyst (ferrous sulfate) solution supply tank 23 Catalyst (copper sulfate) solution supply tank 24 Acid supply tank 25 Alkali Supply tank 3 Catalytic combustion device 4 Oxygen supply means 5 Condenser 6 Heat exchanger 7 Tank for receiving condensed water

Claims (4)

原子力発電所で発生する使用済イオン交換樹脂、フィルタースラッジまたは除染廃液のいずれかである放射性有機廃棄物の処理方法であって、水性媒体中で、触媒としての鉄イオンおよび銅イオンの1種または2種の存在下に放射性有機廃棄物に過酸化水素を作用させて湿式酸化分解する処理方法において、
酸化分解反応の結果生成した、低分子量の有機酸、炭化水素、アンモニア、アミンおよびシアン化合物の少なくとも1種を含有する中間生成物と水蒸気との混合物を、酸化反応槽から取り出して加熱し、温度を高めてから、酸化触媒をそなえた触媒燃焼装置に導き、そこで酸素を供給して中間生成物を二次的に酸化分解したのち、燃焼装置からの分解生成物を含む排ガスを冷却し、TOCを実質上含まない凝縮水と無害無臭の排ガスとを得ることからなり、上記の中間生成物と水蒸気との混合物の加熱および上記の燃焼装置からの排ガスの冷却を、両者の熱交換によって行なう放射性有機廃棄物の処理方法。
Spent ion exchange resins generated in nuclear power plants, a method of processing the filter sludge or radioactive organic wastes is one of decontamination waste liquid in an aqueous medium, one of iron and copper ions as a catalyst Alternatively, in a treatment method in which hydrogen peroxide is allowed to act on radioactive organic waste in the presence of two kinds to perform wet oxidative decomposition,
A mixture of water vapor and an intermediate product containing at least one of low molecular weight organic acids, hydrocarbons, ammonia, amines, and cyanide, generated as a result of the oxidative decomposition reaction, is removed from the oxidation reaction tank, heated, and heated to a temperature. Is then introduced into a catalytic combustion device equipped with an oxidation catalyst, where oxygen is supplied to secondary oxidative decomposition of the intermediate product, and then the exhaust gas containing the decomposition product from the combustion device is cooled, and the TOC A condensed water that is substantially free of odor and an odorless and odorless exhaust gas, and the mixture of the intermediate product and the steam is heated and the exhaust gas from the combustion device is cooled by heat exchange between the two. Organic waste disposal methods.
湿式酸化分解をバッチ式ないしセミバッチ式に行ない、まず反応媒体に酸を加えて低いpHとして過酸化水素を作用させ、反応停止後、反応液にアルカリを加えてほぼ中性のpHとし、その結果放出されるアンモニアおよびアミン類の一方または両方を触媒燃焼装置で二次的に酸化分解する操業方式で実施する請求項1の処理方法。Wet oxidative decomposition is carried out in batch or semi-batch mode. First, acid is added to the reaction medium to cause hydrogen peroxide to act at a low pH, and after the reaction is stopped, alkali is added to the reaction solution to obtain an almost neutral pH. The processing method of Claim 1 implemented by the operation system which carries out the secondary oxidative decomposition of one or both of ammonia and amines discharge | released with a catalytic combustion apparatus. 原子力発電所で発生する使用済イオン交換樹脂、フィルタースラッジまたは除染廃液のいずれかである放射性有機廃棄物の処理装置であって、放射性有機廃棄物に過酸化水素を作用させて湿式酸化分解するための、撹拌機をそなえた反応槽(2)、反応槽への過酸化水素の供給タンク(21)、鉄イオンを含む触媒溶液の供給タンク(22)および銅イオンを含む触媒溶液の供給タンク(23)、ならびにpH調整用の酸の供給タンク(24)およびアルカリの供給タンク(25)、反応槽から揮発してくる酸化分解反応の中間生成物および水蒸気の混合物を受け入れて、中間生成物を二次的に酸化させるための、酸化触媒をそなえた触媒燃焼装置(3)、触媒燃焼装置への酸素供給手段(4)、触媒燃焼装置からの排ガスを冷却して凝縮水を得るためのコンデンサー(5)、ならびに、触媒燃焼装置からの排ガスの熱で前記混合を加熱するための熱交換器(6)から構成される処理装置。 It is a processing equipment for radioactive organic waste that is either used ion exchange resin, filter sludge or decontamination waste liquid generated at nuclear power plants, and it is wet oxidatively decomposed by applying hydrogen peroxide to the radioactive organic waste. for the reaction vessel provided with a stirrer (2), a supply tank of hydrogen peroxide to the reaction vessel (21), a supply tank of the catalyst solution containing the supply tank (22) and a copper ion catalyst solution containing iron ions (23), and an acid supply tank (24) and an alkali supply tank (25) for adjusting the pH , the intermediate product of the oxidation decomposition reaction volatilized from the reaction tank and the mixture of water vapor are received, and the intermediate product The catalytic combustion device (3) having an oxidation catalyst, the oxygen supply means (4) to the catalytic combustion device, the exhaust gas from the catalytic combustion device is cooled and condensed water Condenser for obtaining (5), and the processing device comprising a heat exchanger (6) for heating the mixture in the exhaust gas heat from the catalytic combustion device. 触媒燃焼装置(3)の酸化触媒として、Ni−Cr系金属触媒を使用した請求項の処理装置。The processing apparatus of Claim 3 which used the Ni-Cr type metal catalyst as an oxidation catalyst of a catalytic combustion apparatus (3).
JP23767598A 1998-08-24 1998-08-24 Method and apparatus for treating radioactive organic waste Expired - Lifetime JP4224631B2 (en)

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