JP6185100B2 - Treatment method for radioactive cesium contaminants - Google Patents
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Description
本発明は、特に福島第一原子力発電所事故により大量に発生している放射性セシウム汚染物の処理方法に関するものである。 The present invention particularly relates to a method for treating radioactive cesium contaminants generated in large quantities due to the accident at the Fukushima Daiichi nuclear power plant.
２０１１年３月１１日に発生した福島第一原子力発電所事故により、放射性セシウムに汚染した災害廃棄物（以下、放射性セシウム汚染物）が原子力発電所の敷地内外で大量に発生している。 Due to the accident at the Fukushima Daiichi Nuclear Power Station that occurred on March 11, 2011, a large amount of disaster waste contaminated with radioactive cesium (hereinafter referred to as radioactive cesium contaminants) was generated inside and outside the site of the nuclear power station.
現在、これらの放射性セシウム汚染物の処分に関する環境省の指針として、放射能濃度が８０００Ｂｑ/ｋｇ以下のものについては一般廃棄物最終処分場において埋立処分を行い、放射能濃度が８０００Ｂｑ/ｋｇ超のものについては、放射性セシウムの挙動を適切に把握し、国によって処分の安全性が確認されるまでの間、管理型最終処分場で一時保管することが示されている（非特許文献１）。 Currently, as a guideline of the Ministry of the Environment regarding the disposal of these radioactive cesium contaminants, those with a radioactivity concentration of 8000 Bq / kg or less are landfilled at the general waste final disposal site, and the radioactivity concentration exceeds 8000 Bq / kg. About thing, it is shown that the behavior of radioactive cesium is appropriately grasped and temporarily stored in a managed final disposal site until the safety of disposal is confirmed by the country (Non-patent Document 1).
廃棄物の減容化の観点から、可燃物については焼却処理して焼却灰とした後に、前記の埋立処分あるいは一時保管をすることが望ましい。 From the viewpoint of reducing the volume of waste, it is desirable to incinerate combustibles to incineration ash and then to landfill or temporarily store them.
従来から、通常の原子力発電所内で発生する可燃性雑固体廃棄物の処理技術に関しては、本願出願人らが各種技術を開示している。例えば、非特許文献２には、原子力施設での焼却処理では、廃棄物に含まれる放射性セシウムの６９％が焼却主灰中に残存することが示されている。今回処理対象としている放射性セシウム汚染物でも同様の挙動を示すことが予想される。この場合、例えば放射能濃度８０００Ｂｑ/ｋｇの放射性セシウム汚染物を焼却すると、焼却による減重比は概ね１／１０〜１／２０程度であるため、放射能濃度は１０〜２０倍に濃縮され８００００〜１６００００Bq／kgとなる。非特許文献２に記載のように、放射性セシウムの６９％が焼却主灰中に残存するとすると、焼却主灰の放射能濃度は、５５２００〜１１０４００Bq／kgとなる。前記のように、８０００Ｂｑ/ｋｇ超のものについては、放射性セシウムの挙動を適切に把握し、国によって処分の安全性が確認されるまでの間、一時保管する必要がある。 Conventionally, the applicants of the present application have disclosed various technologies regarding the processing technology of combustible miscellaneous solid waste generated in a normal nuclear power plant. For example, Non-Patent Document 2 shows that 69% of the radioactive cesium contained in the waste remains in the incineration main ash in the incineration process at the nuclear facility. It is expected that the radioactive cesium contamination that is treated this time will show the same behavior. In this case, for example, when radioactive cesium contaminants with a radioactive concentration of 8000 Bq / kg are incinerated, the weight loss ratio due to incineration is approximately 1/10 to 1/20, so the radioactive concentration is concentrated 10 to 20 times and 80000 ˜160000 Bq / kg. As described in Non-Patent Document 2, if 69% of the radioactive cesium remains in the incineration main ash, the radioactivity concentration of the incineration main ash becomes 55200 to 110400 Bq / kg. As described above, it is necessary to appropriately store the thing exceeding 8000 Bq / kg until the behavior of radioactive cesium is properly grasped and the safety of disposal is confirmed by the country.
なお、一時保管後の焼却灰に関し、最終処分の方法は、現在のところ未定であるが、セメント固化あるいは溶融固化による最終処分が行われるものと予想される。このうち、特に、溶融固化は、減容・安定化の観点より優れている方式である。 Regarding the incinerated ash after temporary storage, the final disposal method is not yet determined, but it is expected that final disposal will be performed by cement solidification or melt solidification. Among these, melt solidification is a method that is superior from the viewpoint of volume reduction and stabilization.
本願出願人らは、通常の原子力発電所内で発生する不燃性の固体状廃棄物を溶融固化する技術に関しても、従来から各種技術を開示している。例えば、非特許文献３には、高周波誘導加熱方式による溶融体作成時の核種挙動に関し、放射性セシウムを含んだ廃棄物を溶融すると、放射性セシウムの一部は排ガス系に飛散してセラミックフィルタやＨＥＰＡフィルタ等で捕集されるが、放射性セシウムの５０％以上は溶融固化体中に残存することが示されている。今回処理対象としている放射性セシウム汚染物でも同様の挙動を示すことが予想される。この場合、前記の焼却処理により放射能濃度が５５２００〜１１０４００Ｂｑ／ｋｇとなった焼却主灰を溶融処理すると、溶融による重量変化は殆どないため、溶融固化体の放射能濃度は２７６００〜５５２００Ｂｑ／ｋｇとなる。すなわち、溶融固化による減容・安定効果は得られるものの、一般廃棄物最終処分場への埋立処分は行うことができず、管理型最終処分場での処分が必要となる。管理型最終処分場には各種の規制が設けられており、処分コストが嵩む問題や、現在大量に発生している災害廃棄物の迅速処理の要請に十分対応できない問題がある。 The applicants of the present application have conventionally disclosed various techniques regarding techniques for melting and solidifying incombustible solid waste generated in a normal nuclear power plant. For example, Non-Patent Document 3 relates to the behavior of nuclides at the time of producing a melt by a high frequency induction heating method. When a waste containing radioactive cesium is melted, a part of the radioactive cesium is scattered in an exhaust gas system and a ceramic filter or HEPA is used. Although collected by a filter or the like, it is shown that 50% or more of the radioactive cesium remains in the molten solidified body. It is expected that the radioactive cesium contamination that is treated this time will show the same behavior. In this case, when the incineration main ash having a radioactivity concentration of 55200 to 110400 Bq / kg by the above incineration process is melted, there is almost no change in weight due to melting, so the radioactivity concentration of the molten solidified body is 27600 to 55200 Bq / kg. It becomes. That is, although the volume reduction and stability effect by melting and solidification can be obtained, landfill disposal to the general waste final disposal site cannot be performed, and disposal at the managed final disposal site is required. Various types of regulations are set up in the managed final disposal site, and there are problems that the disposal cost increases, and that there is a problem that it is not possible to sufficiently respond to the request for rapid disposal of disaster waste that is currently generated in large quantities.
本発明の目的は前記の問題を解決し、福島第一原子力発電所事故により大量に発生している放射性セシウム汚染物の内、可燃物を焼却処理により焼却灰とし、更に、該焼却灰を溶融固化処理して減容安定化を図りつつ、かつ、従来技術では、全て管理型最終処分場での処分が必要となっていた溶融固化体のうち、一部の放射能濃度を８０００Ｂｑ/ｋｇ以下として一般廃棄物最終処分場への埋立可能とする技術を提供することである。 The object of the present invention is to solve the above-mentioned problems, and among the radioactive cesium contaminants generated in large quantities due to the accident at the Fukushima Daiichi nuclear power plant, combustible materials are converted into incineration ash by incineration, and the incineration ash is further melted While solidifying to stabilize the volume reduction, and with the conventional technology, some of the radioactive concentration in the molten solidified material that had to be disposed of at the final disposal site is 8000 Bq / kg or less. It is to provide a technology that enables landfill to a general waste final disposal site.
上記課題を解決するためになされた本発明に係る放射性セシウム汚染物の処理方法は、放射性セシウムで汚染した可燃物の焼却により得られた焼却主灰に塩化ナトリウムを添加混合し、塩基度を０．３〜１．３の範囲に調整した状態で塩化セシウムの沸点以上で溶融し、塩化セシウムを溶融飛灰中に濃縮させて、溶融固化体中の放射性セシウム濃度を低減させることを特徴とするものである。 The method for treating radioactive cesium contaminants according to the present invention made to solve the above-mentioned problems is the addition of sodium chloride to the incinerated main ash obtained by incineration of combustible materials contaminated with radioactive cesium, and the basicity is reduced to 0. Melting above the boiling point of cesium chloride in a state adjusted to a range of 3 to 1.3, and concentrating cesium chloride in molten fly ash to reduce the concentration of radioactive cesium in the molten solidified product Is.
請求項２記載の発明は、請求項１記載の放射性セシウム汚染物の処理方法において、溶融固化体中の放射性セシウム濃度を８０００Ｂｑ/ｋｇ以下とすることを特徴とするものである。 The invention according to claim 2 is characterized in that in the method for treating radioactive cesium contaminants according to claim 1, the concentration of radioactive cesium in the molten solidified product is 8000 Bq / kg or less.
請求項３記載の発明は、請求項１記載の放射性セシウム汚染物の処理方法において、溶融温度が１４５０〜１６００℃であることを特徴とするものである。 The invention according to claim 3 is the method for treating radioactive cesium contaminants according to claim 1, wherein the melting temperature is 1450 to 1600 ° C.
請求項４記載の発明は、請求項１記載の放射性セシウム汚染物の処理方法において、溶融は、発熱性セラミックキャニスタを使用し、高周波誘導加熱によるインキャン方式で行うことを特徴とするものである。 According to a fourth aspect of the present invention, in the method for treating radioactive cesium contaminants according to the first aspect, the melting is performed using an exothermic ceramic canister by an in-can method using high frequency induction heating.
請求項５記載の発明は、請求項１記載の放射性セシウム汚染物の処理方法において、焼却主灰を塩化セシウムの沸点以上で溶融する際に発生する溶融飛灰に、溶融助剤を加え、塩化セシウムの沸点以下で再溶融することを特徴とするものである。 The invention according to claim 5 is the method for treating radioactive cesium contaminants according to claim 1, wherein a melting aid is added to the molten fly ash generated when the incinerated main ash is melted at the boiling point or higher of cesium chloride, It is characterized by remelting below the boiling point of cesium.
請求項６記載の発明は、請求項５記載の放射性セシウム汚染物の処理方法において、再溶融温度が１２００℃以下であることを特徴とするものである。 The invention according to claim 6 is the method for treating radioactive cesium contaminants according to claim 5, wherein the remelting temperature is 1200 ° C. or less.
請求項７記載の発明は、請求項１記載の放射性セシウム汚染物の処理方法において、焼却主灰を塩化セシウムの沸点以上で溶融する際に発生する溶融飛灰を、セメント固化することを特徴とするものである。
The invention according to
本発明に係る放射性セシウム汚染物の処理方法は、放射性セシウムで汚染した可燃物の焼却主灰に塩化ナトリウムを添加混合し、塩基度を０．３〜１．３の範囲に調整した状態で塩化セシウムの沸点以上で溶融させることにより、塩化セシウムを溶融飛灰中に濃縮させて、溶融固化体中の放射性セシウム濃度を低減させるものである。例えば、処理する放射性セシウム汚染物の放射能濃度が８０００Ｂｑ/ｋｇの場合、従来技術による焼却処理および溶融固化を行うと、溶融固化体の放射能濃度は２７６００〜５５２００Ｂｑ／ｋｇとなり、焼却処理および溶融固化により減容・安定効果は得られるものの、一般廃棄物最終処分場への埋立処分は行うことができず、管理型最終処分場での処分が必要となっていたが、本発明の方法によれば、溶融固化体の約９０%は、放射能濃度が原廃棄物と同等以下の８０００Ｂｑ/ｋｇ以下とすることができ、これらの部分に関しては一般廃棄物最終処分場への埋立を行うことができ、処分費用を大幅に低減することができる。 In the method for treating radioactive cesium contaminants according to the present invention, sodium chloride is added to and mixed with incinerated main ash of combustible materials contaminated with radioactive cesium, and the basicity is adjusted to a range of 0.3 to 1.3. By melting above the boiling point of cesium, cesium chloride is concentrated in the molten fly ash to reduce the concentration of radioactive cesium in the molten solidified body. For example, when the radioactive concentration of the radioactive cesium contaminant to be processed is 8000 Bq / kg, when the incineration process and the melt solidification are performed according to the conventional technique, the radioactive concentration of the molten solidified product is 27600 to 55200 Bq / kg. Although solidification can reduce volume and stabilize, landfill disposal at general waste final disposal sites was not possible, and disposal at managed final disposal sites was necessary. According to this, about 90% of the melted solids can have a radioactivity concentration of 8000 Bq / kg or less, which is equivalent to or less than that of the raw waste, and these parts should be landfilled at the general waste final disposal site. And disposal costs can be greatly reduced.
以下に本発明の好ましい実施形態を示す。 Preferred embodiments of the present invention are shown below.
従来知見によると、一般的な可燃物焼却時の主灰と飛灰の重量比率は、１０：１であり、更に、焼却灰を溶融処理する際の溶融固化体と飛灰の割合は１００：１程度である。 According to conventional knowledge, the weight ratio of main ash and fly ash during incineration of general combustibles is 10: 1, and the ratio of molten solidified product and fly ash when melting incineration ash is 100: 1 or so.
焼却、溶融により、放射性セシウムの主灰、あるいは溶融固化体への残存率を大幅に低減できれば、一般廃棄物最終処分場に埋立処分が可能となり、管理すべき廃棄物の量を大幅に低減することができる。 If the residual ratio of radioactive cesium to the main ash or melted solids can be significantly reduced by incineration and melting, landfill disposal at general waste final disposal sites will be possible, greatly reducing the amount of waste to be managed. be able to.
（放射性セシウムの挙動に関する検討）
福島第一原子力発電所事故により大量に発生している放射性セシウム汚染物を焼却および溶融する際の、放射性セシウムの挙動に関するデータは過去に蓄積されていないため、本発明にあたって、まず、放射性セシウムの挙動について検討を行った。
(Examination of behavior of radioactive cesium)
Since no data on the behavior of radioactive cesium when incinerating and melting radioactive cesium contaminants generated in large quantities due to the accident at the Fukushima Daiichi nuclear power plant has been accumulated in the past, in the present invention, first of all, The behavior was examined.
震災で発生した放射性セシウムは、事故直後には金属Ｃｓで存在するが、大気と接触後Ｃｓ２Ｏとなり、最終的にはＣｓ２ＣＯ３となった後、降雨等により水中に溶け込みＣｓ２ＣＯ３として地上に降り注いで樹木等に付着していると想定される。そこで、セシウムの形態を、Ｃｓ２ＣＯ３として、焼却主灰組成を模擬した試薬（ＳｉＯ２：ＣａＯ：Ａｌ２Ｏ３＝５：３：２）を調合し、焼却を模擬した温度（８００℃）及び溶融を模擬した温度（１５００℃）で各１時間加熱し、焼却主灰組成を模擬した試薬へのセシウム残存率を測定する試験を行った。 The radioactive cesium generated by the earthquake is present in the metal Cs immediately after the accident, but becomes Cs 2 O after contact with the atmosphere and finally becomes Cs 2 CO 3, and then dissolves in the water due to rain or the like Cs 2 It is assumed that CO 3 has fallen on the ground and is attached to trees. Therefore, the cesium form is Cs 2 CO 3 and a reagent (SiO 2 : CaO: Al 2 O 3 = 5: 3: 2) simulating the incineration main ash composition is prepared, and the temperature (800 ° C.) simulating incineration. ) And a temperature simulating melting (1500 ° C.) for 1 hour each, and a test was performed to measure the residual ratio of cesium to the reagent simulating the incinerated main ash composition.
その結果、８００℃では、残存率８０〜９０％、１５００℃では残存率４０〜８０%と、背景技術に記載の従来知見とほぼ同等の結果が得られ、通常の焼却処理および溶融処理では残存率を低減することは困難であることが確認された。 As a result, a residual rate of 80 to 90% at 800 ° C., a residual rate of 40 to 80% at 1500 ° C., which is almost the same as the conventional knowledge described in the background art, remains in ordinary incineration and melting treatments. It was confirmed that it was difficult to reduce the rate.
Ｃｓ２ＣＯ３は、６１０℃で溶融し、かつ、同時に分解するという化学的性質があり、分解により、Ｃｓ２Ｏ（４００℃で分解）またはＣｓ（沸点６７８℃）となるが、いずれも８００℃あるいは１５００℃では分解温度、沸点以上であり、理論上では焼却灰中および溶融固体中にセシウムは残存できないはずである。しかしながら、８００℃、１５００℃では上記の残存率を示している。本願発明者は、この現象を、Ｃｓ２ＣＯ３の分解により発生したＣｓが他の物質と化合物を作り安定化していることに起因するものと推測した。 Cs 2 CO 3 has a chemical property that it melts at 610 ° C. and decomposes at the same time, and becomes Cs 2 O (decomposes at 400 ° C.) or Cs (boiling point 678 ° C.) by decomposition. The decomposition temperature and boiling point are exceeded at ℃ or 1500 ℃, and theoretically, cesium should not remain in the incinerated ash and in the molten solid. However, at 800 ° C. and 1500 ° C., the above remaining rate is shown. The inventor of the present application speculated that this phenomenon is caused by the fact that Cs generated by the decomposition of Cs 2 CO 3 forms a compound with another substance and stabilizes it.
Ｃｓ２ＣＯ３の分解により発生したＣｓと結合した化合物の沸点が約８００℃以下であって、かつ、約８００℃の焼却温度において分解しない性質を有する場合、約８００℃の焼却処理により、Ｃｓと結合した化合物を焼却飛灰中へ分離することができ、焼却主灰中のセシウム残存率が大幅に低減される結果、焼却主灰を一般廃棄物最終処分場に埋立処分が可能となる可能性がある。あるいは、Ｃｓ２ＣＯ３の分解により発生したＣｓと結合した化合物の沸点が１４００〜１５００℃以下であって、かつ、約１４００〜１５００℃の溶融温度において分解しない性質を有する場合、約１４００〜１５００℃の溶融処理により、Ｃｓと結合した化合物を溶融飛灰中へ分離することができ、溶融固化体中のセシウム残存率が大幅に低減される結果、溶融固化体を一般廃棄物最終処分場に、埋立処分が可能となる可能性がある。なお、このような、化合物を合成するための添加材料としては、安価で安全であり、焼却灰に通常含まれるような物質が望ましい。 When the boiling point of the compound combined with Cs generated by the decomposition of Cs 2 CO 3 is about 800 ° C. or less and does not decompose at an incineration temperature of about 800 ° C., the incineration treatment at about 800 ° C. Can be separated into the incineration fly ash and the cesium residual rate in the incineration main ash can be greatly reduced, which makes it possible to land the incineration main ash in landfills for general waste. There is sex. Alternatively, when the boiling point of the compound bonded to Cs generated by the decomposition of Cs 2 CO 3 is 1400 to 1500 ° C. and does not decompose at a melting temperature of about 1400 to 1500 ° C., about 1400 to 1500 The compound combined with Cs can be separated into the molten fly ash by melting treatment at ℃, and the residual rate of cesium in the molten solidified material is greatly reduced. As a result, the molten solidified material becomes a general waste final disposal site. Landfill disposal may be possible. In addition, as such an additive material for synthesizing a compound, a material which is inexpensive and safe and is usually contained in incineration ash is desirable.
本願発明者は、上記観点から、硝酸セシウム、硫酸セシウム、塩化セシウムの各化合物について検討を行った。このうち、硝酸セシウムは４１４℃で分解し、セシウムは再度他の物質と化合物を作り焼却主灰に残存するため不可、硫酸セシウムは沸点が１９００℃と高く焼却主灰、溶融体に残存し易いため不可（但し、逆に固化体中に残そうとする場合効果あり）、塩化セシウムは、沸点が１２９５℃であり、焼却温度では残存し分離できないが、溶融温度では残存しないことが予想された。 The inventor of the present application examined each compound of cesium nitrate, cesium sulfate, and cesium chloride from the above viewpoint. Of these, cesium nitrate decomposes at 414 ° C, cesium is made again with other substances and remains in the incineration main ash, and cesium sulfate has a high boiling point of 1900 ° C and tends to remain in the incineration main ash and melt. Therefore, it is impossible (however, it is effective when trying to remain in the solidified body). Cesium chloride has a boiling point of 1295 ° C. and remains at the incineration temperature and cannot be separated, but it is expected not to remain at the melting temperature. .
（試験）
以上の検討より、前述の焼却灰試薬に塩化ナトリウムを１〜１０％添加して均一に混合し、８００℃、１５００℃で各１時間加熱した。その結果、８００℃では、残存率９０％で塩化ナトリウムを入れない場合と同等の値であったが、１５００℃では塩化ナトリウム５％添加では残存率１０％、塩化ナトリウム１０％添加では残存率５％となり、大幅に残存率を低減することができた。
(test)
From the above examination, 1-10% of sodium chloride was added to the above-mentioned incineration ash reagent, mixed uniformly, and heated at 800 ° C. and 1500 ° C. for 1 hour each. As a result, at 800 ° C., the residual rate was 90%, which was the same value as when sodium chloride was not added. At 1500 ° C., the residual rate was 10% when sodium chloride was added to 5%, and the residual rate was 5 when sodium chloride was added to 10%. %, And the residual rate could be greatly reduced.
塩基度（ＣａＯ／ＳｉＯ２）を１．０に調整した焼却主灰試薬（ＳｉＯ２：ＣａＯ：Ａｌ２Ｏ３＝４：４：２）について、同様に塩化ナトリウムを１０％添加し、８００℃、１５００℃で各1時間加熱した。その結果、残存率は、２％と大幅に低下した。 For the incineration main ash reagent (SiO 2 : CaO: Al 2 O 3 = 4: 4: 2 ) whose basicity (CaO / SiO 2 ) was adjusted to 1.0, 10% sodium chloride was added in the same manner, and 800 ° C. Each was heated at 1500 ° C. for 1 hour. As a result, the residual rate was significantly reduced to 2%.
試験の結果より、例えば８０００Bq/kgの廃棄物を焼却した場合を考えると、焼却による減重比は概ね１／１０〜１／２０程度であり、焼却により、放射能は、８００００〜１６００００Bq／kgとなるが、放射性セシウムは９０％が焼却灰中に残存するので、７２０００〜１４４０００Bq／kgとなる。これを溶融処理すると、残存率は５％であるので、３６００〜７２００ Bq／kgであり、一般廃棄物最終処分場に埋立処分が可能となる。 From the result of the test, for example, when considering the case where 8000 Bq / kg of waste is incinerated, the weight reduction ratio by incineration is about 1/10 to 1/20, and the radioactivity is 80000 to 160000 Bq / kg by incineration. However, since 90% of the radioactive cesium remains in the incineration ash, it becomes 72000-144000 Bq / kg. When this is melted, the residual rate is 5%, so it is 3600-7200 Bq / kg, and landfill disposal becomes possible at the general waste final disposal site.
一方、溶融飛灰は、放射能濃度が高くなるが、高温で溶融すると、再度飛散し、好ましくないため、これを処理するには、セシウムが飛散しにくい温度（１２００℃）以下で溶融が必要となる。焼却飛灰は、溶融飛灰と同等の低温溶融を実施することが望ましい。 On the other hand, molten fly ash has a high radioactivity concentration, but when melted at a high temperature, it is scattered again, which is not preferable. To treat this, melting is required at a temperature (1200 ° C.) or less at which cesium is difficult to fly. It becomes. The incinerated fly ash is desirably subjected to low temperature melting equivalent to molten fly ash.
尚、焼却飛灰は、焼却主灰に比べ、放射能濃度は同程度であるため（飛灰量を主灰の１０ｗｔ％、放射能移行率を１０％であれば同等）、高温溶融処理を実施すれば、溶融体は、一般廃棄物最終処分場に埋立処分が可能となる。しかし、再度飛灰が発生しやすいため、これについては、低温溶融が必要となる。 Incinerated fly ash has the same radioactivity concentration as incinerated main ash (the amount of fly ash is the same if the amount of fly ash is 10 wt% of the main ash and the radioactivity transfer rate is 10%). If implemented, the melt can be landfilled at a municipal waste final disposal site. However, since fly ash is likely to be generated again, this requires low-temperature melting.
上記検討に基づき下記の条件で本発明を実施した。図１には、本実施例のフロー図を示している。 Based on the above examination, the present invention was carried out under the following conditions. FIG. 1 shows a flowchart of the present embodiment.
ロータリーキルンを用いて、模擬廃棄物（木材、布、紙、ポリエチレン、ゴム）を８００℃で焼却処理した。セシウムの形態は、Ｃｓ２ＣＯ３として模擬廃棄物にふりかけて添加した。 Simulated waste (wood, cloth, paper, polyethylene, rubber) was incinerated at 800 ° C. using a rotary kiln. The form of cesium was added as sprinkled to the simulated waste as Cs 2 CO 3 .
ロータリーキルンでは、炉内温度コントロールのために水を噴霧することもあるが、本実施例では、この水に塩化ナトリウムを加え、１％濃度として炉内に連続的に噴霧供給した。この場合の塩素供給量は、模擬廃棄物量に対して、０．６７ｗｔ％である。ロータリーキルン式の焼却炉に、噴霧状態の塩化ナトリウム水溶液を廃棄物に吹き付けるとともに、投入される廃棄物は、炉の回転で撹拌され、塩化ナトリウムと十分に混合されるため、放射性セシウムを塩化セシウムの形態に変換するのに極めて好都合である。噴霧状態の塩化ナトリウムは、廃棄物の投入側から供給することが優先的に放射性セシウムと塩素を反応させる面より望ましい。従来原子力発電所で使用されている竪型、或いは横型の固定床式焼却炉では、このように塩化ナトリウムと廃棄物の混合ができないため、通常の廃棄物の性状では、例え、塩化ナトリウムを供給してもロータリーキルンのような効果は得られない。 In the rotary kiln, water may be sprayed to control the temperature in the furnace, but in this example, sodium chloride was added to this water and sprayed continuously into the furnace at a concentration of 1%. In this case, the chlorine supply amount is 0.67 wt% with respect to the simulated waste amount. Spraying sodium chloride aqueous solution in a rotary kiln type incinerator to waste, and the waste to be charged is stirred by the rotation of the furnace and mixed well with sodium chloride. Therefore, radioactive cesium is mixed with cesium chloride. Very convenient to convert to form. Sprayed sodium chloride is preferably supplied from the waste input side in terms of preferential reaction between radioactive cesium and chlorine. In vertical or horizontal fixed-bed incinerators used in conventional nuclear power plants, sodium chloride and waste cannot be mixed in this way. Therefore, for example, sodium chloride is supplied in normal waste properties. However, the effect like a rotary kiln cannot be obtained.
上記条件で焼却主灰を作成した。尚、比較評価のため、塩化ナトリウムを含まないで処理した焼却主灰も作成した。 Incinerated main ash was prepared under the above conditions. For comparison evaluation, an incinerated main ash treated without containing sodium chloride was also prepared.
焼却主灰中のＣｓ濃度を測定した結果、焼却灰中のセシウム残存率は、塩化ナトリウムを供給したものは９５％で、供給しないものは６０％であった。 As a result of measuring the Cs concentration in the incinerated main ash, the cesium residual rate in the incinerated ash was 95% when sodium chloride was supplied, and 60% when not supplied.
溶融は、非特許文献３に示す高周波誘導加熱式溶融炉のインキャン方式で、キャニスタは１６００℃に耐える自己発熱性のセラミックキャニスタを用いて行った。昇温前に６０kgをキャニスタに予投入し、約1時間かけて１５００℃に昇温した後、残りの１４０kgを２０kgずつ、合計７回バッチでキャニスタに投入した。最終投入が終了してから３０分１５００℃に保持した後、溶融炉を停止した。 Melting was performed using an in-can system of a high-frequency induction heating melting furnace shown in Non-Patent Document 3, and the canister was a self-heating ceramic canister that can withstand 1600 ° C. Before raising the temperature, 60 kg was pre-charged into the canister, and after raising the temperature to 1500 ° C. over about 1 hour, the remaining 140 kg was added to the canister in batches for a total of 7 times, 20 kg each. After the final charging was completed, the melting furnace was stopped after maintaining at 1500 ° C. for 30 minutes.
キャニスタの冷却後、溶融固化体よりサンプリングし、Ｃｓ濃度を測定し、溶融固化体中のセシウム残存率を求めた。その結果、塩化ナトリウムを供給していない溶融固化体の残存率は５５％であった。一方、塩化ナトリウムを供給した固化体は、溶融残存率５％であった。この場合の焼却灰の塩基度は０．６であった。 After cooling the canister, sampling was performed from the molten solidified body, the Cs concentration was measured, and the residual cesium ratio in the molten solidified body was determined. As a result, the residual rate of the melted solid without supply of sodium chloride was 55%. On the other hand, the solidified body supplied with sodium chloride had a residual melt rate of 5%. The basicity of the incinerated ash in this case was 0.6.
焼却灰の塩基度は通常０．５〜１．０であるが、塩基度が著しく小さい場合は、１５００℃での溶融が困難となることより、塩基度は０．３以上となるよう調整することが好ましく、残存率をより小さくするには塩基度を０．５〜１．３の範囲とし、１．０程度とするのが、溶融性の観点からより好ましい。 The basicity of the incinerated ash is usually 0.5 to 1.0, but if the basicity is extremely small, it is difficult to melt at 1500 ° C., so that the basicity is adjusted to 0.3 or more. In order to reduce the residual rate, the basicity is preferably set in the range of 0.5 to 1.3, more preferably about 1.0 from the viewpoint of meltability.
溶融飛灰は、１５００℃で溶融すると、再度飛散するため、溶融助剤を添加して、溶融温度を１１００℃まで、下げて溶融処理した。この場合のセシウム残存率は９０％であった。溶融飛灰のその他の処理技術としては、セメント固化があり、これを選択することもできる。 When the molten fly ash melts at 1500 ° C., the molten fly ash is scattered again. Therefore, a melting aid was added, and the melting temperature was lowered to 1100 ° C. to perform the melting treatment. In this case, the residual ratio of cesium was 90%. Another processing technique for molten fly ash is cement solidification, which can also be selected.
ここで、インキャン方式を用いるメリットは、以下の通りある。
（メリット１）都市ゴミで使用される溶湯のオーバフロー式の場合、保持時間の制御が難しいのに対し、バッチ式のインキャン方式では、Ｃｓ残存率を担保する保持時間を正確に確保することができる。
（メリット２）溶融飛灰にはセシウムが濃縮し、これらを溶融する場合、放射能濃度が高くなるが、インキャン式の場合、クロスコンタミの可能性がない。これに対し、耐火物式の場合（インキャン方式でない）、クラックなどにセシウムが濃縮し、コンタミする可能性があり、Ｃｓ濃度を管理するための操業が安定しない。
（メリット３）耐火物式の場合、耐火物の補修が必要になるが、インキャン式では、補修を必要としない。
Here, the merit of using the in-can method is as follows.
(Advantage 1) In the case of the overflow type of molten metal used in municipal waste, it is difficult to control the holding time, but in the batch type in-can method, it is possible to accurately secure the holding time that ensures the Cs remaining rate. .
(Merit 2) When cesium is concentrated in molten fly ash and these are melted, the radioactivity concentration becomes high, but in the incan type, there is no possibility of cross contamination. On the other hand, in the case of the refractory type (not the in-can type), cesium may be concentrated and contaminated in cracks, and the operation for managing the Cs concentration is not stable.
(Advantage 3) In the case of the refractory type, repair of the refractory is required, but in the in-can type, no repair is required.
なお、耐火物式の場合（インキャン方式でない）、１５００℃の溶融温度では、頻繁に耐火物の補修が必要であり、補修時の作業員の被曝の可能性が高まり、受け容れ難い。 In the case of the refractory type (not the in-can type), at a melting temperature of 1500 ° C., the refractory needs to be frequently repaired, which increases the possibility of exposure of workers during the repair and is unacceptable.
本実施例では、塩化ナトリウム水溶液を添加したが、ポリ塩化ビニールなど塩素を含む廃棄物を粉砕して相当量連続的に投入しても効果が得られるが、放射性セシウムとの接触性の問題より、塩化ナトリウムの水溶液の方が効率的であることは言うまでもない。また、震災で海水にさらされた廃棄物も効果が得られる。 In this example, an aqueous sodium chloride solution was added, but an effect can be obtained even if a considerable amount of waste containing chlorine such as polyvinyl chloride is pulverized and continuously added, but due to the problem of contact with radioactive cesium. Needless to say, an aqueous solution of sodium chloride is more efficient. In addition, waste exposed to seawater due to the earthquake can also be effective.
本実施例では、焼却の段階で塩化ナトリウムを添加しているが、焼却の段階で塩化ナトリウムを添加しなくて、一旦焼却灰とした後でも、焼却灰に５〜１０％の塩化ナトリウムを添加・混練して溶融しても同等の効果が得られる。 In this example, sodium chloride is added at the stage of incineration, but sodium chloride is not added at the stage of incineration, and 5-10% sodium chloride is added to the incineration ash even after it is once converted into incineration ash.・ Equivalent effects can be obtained even when kneaded and melted.
本実施例では溶融温度は１５００℃としたが、塩化セシウムの沸点１２９５℃以上であれば良い。より塩化セシウムを飛灰に移行させることと、処理速度が大きく取れることより１４５０〜１６００℃で処理することが望ましい。 In this embodiment, the melting temperature is 1500 ° C., but the boiling point of cesium chloride may be 1295 ° C. or higher. It is desirable to process at 1450 to 1600 ° C. because cesium chloride is transferred to fly ash and the processing speed can be increased.
最終投入が終了したのち、十分溶融するための保持時間として１４５０〜１６００℃で３０分以上保持することが望ましい。 After the final charging is completed, it is desirable to hold at 1450 to 1600 ° C. for 30 minutes or more as a holding time for sufficient melting.
塩素によるダイオキシン、塩化水素などの規制値対応については、既知の排ガス処理方法を採用することにより、十分対応が可能である。 With regard to compliance with regulation values such as dioxin and hydrogen chloride by chlorine, it is possible to sufficiently respond by adopting a known exhaust gas treatment method.
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| JPS6038079A (en) * | 1983-08-10 | 1985-02-27 | Kawasaki Heavy Ind Ltd | Method and equipment for high temperature melting treatment of waste material |
| JPS60142297A (en) * | 1983-12-28 | 1985-07-27 | 大同特殊鋼株式会社 | Method of treating radioactive waste |
| JPH0668557B2 (en) * | 1985-03-15 | 1994-08-31 | 日本碍子株式会社 | Continuous waste melting device |
| JP3764528B2 (en) * | 1996-07-11 | 2006-04-12 | 財団法人電力中央研究所 | Plasma melting treatment method for radioactive solid waste and plasma melting treatment equipment used therefor |
| JP3205273B2 (en) * | 1996-11-21 | 2001-09-04 | 日本碍子株式会社 | Waste incineration ash treatment method |
| US6241800B1 (en) * | 1999-09-02 | 2001-06-05 | Westinghouse Electric Company Llc | Acid fluxes for metal reclamation from contaminated solids |
| JP2004053093A (en) * | 2002-07-18 | 2004-02-19 | Ishikawajima Harima Heavy Ind Co Ltd | Flying ash melting treatment method |
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2016
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