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Received April 27, 2009
Accepted June 20, 2009
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산소-공융염 기포탑에서 희토류염화물의 산화반응 특성
Characteristic of Oxidation Reaction of Lanthanide Chlorides in Oxygen-Eutectic Salt Bubble Column
한국원자력연구원 핵연료주기기술개발본부, 305-353 대전시 유성구 덕진동 150
Nuclear Fuel Cycle R&D Group, Korea Atomic Energy Research Institute, 150, Duckjin-dong, Yuseong-gu, Daejeon 305-353, Korea
Korean Chemical Engineering Research, August 2009, 47(4), 465-469(5), NONE Epub 25 August 2009
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Abstract
산소-공융염(LiCl-KCl) 기포탑에서 4종의 희토류염화물(Ce/Nd/Pr/EuCl3)의 산화반응 특성에 대한 연구를 수행하였다. HSC Chemistry software를 이용한 모델링 결과 산소 및 희토류염화물이 존재하는 계에서 가장 안정된 화합물은 옥시염화물(EuOCl, NdOCl, PrOCl)과 산화물(CeO2, PrO2)이었으며, 이러한 결과는 옥시염화물 및 산화물이 형성되는 반응의 Gibbs 자유에너지 경향성과도 일치하였다. 실험결과 공융염 내에서 산소와 희토류염화물과의 반응으로 산소분산 시간 및 공융염 온도와 상관없이 Eu, Nd, Pr은 옥시염화물로, Ce, Pr은 산화물형태의 침전물로 형성되었으며, 이러한 결과는 열역학적 데이터를 이용한 모델링 결과와 일치하였다. 4종의 복합희토류 침전물은 등방형태와 정방형태의 침전물로 구분되었는데 주사전자현미경(SEM-EDS) 분석결과 등방구조(cubic structure) 형태의 침전물은 산화물이었고, 정방형 구조(tetragonal structure)의 침전물은 옥시염화물이었다. 실험에 사용된 4종의 희토류염화물의 공융염에 불용성인 침전물로의 전환효율은 온도 및 분산시간이 증가하면 증가하였으며, Ce가 가장 빠른 반응특성을 나타내었다. 650 ℃의 공융염 온도 및 420분의 산소분산시간 조건에서 4종의 희토류염화물의 산화효율은 모두 99% 이상이었다.
Characteristics of oxidation reaction of four lanthanide chlorides(Ce, Nd, Pr and EuCl3) in a oxygen-eutectic(LiCl-KCl) salt bubble column was investigated. From the results obtained from the thermochemical calculations by HSC chemistry software, the most stable lanthanide compounds in the oxygen-used rare earth chlorides system were oxychlorides(EuOCl, NdOCl, PrOCl) and oxides(CeO2, PrO2), which coincide well with results of the Gibbs free energy of the reaction. In this study, similar to the thermochemical results, regardless of the sparging time and molten salt temperature, oxychlorides for Eu, Nd and Pr and oxides for Ce and Pr were formed as a precipitant by a reaction with oxygen. The structure of the rare earth precipitates was divided into two shapes : small cubic(oxide) and large tetragonal (oxychloride) structures. The conversion efficiencies of the lanthanide elements to their molten salt-insoluble precipitates(or compound) were increased with the sparging time and temperature, and Ce showed the best reactivity. In the conditions of 650 ℃ of the molten salt temperature and 420 min of the sparging time, the conversion efficiencies were over 99% for all the investigated lanthanide chlorides.
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Roine A, Outokumpu HSC Chemistry for windows, Pori, Finland (2002)
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