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Korean Chemical Engineering Research,
Vol.42, No.1, 20-25, 2004
Vol.42, No.1, 20-25, 2004
고농도 질산 분해를 위한 연속식 화학-전해 조합 탈질 공정 (I)
A Continuous Denitration Process Combining Chemical and Electrolytic Systems for the Destruction of High Concentration of Nitric Acid (I)
본 논문에서는 고준위 폐액 중의 장수명 핵종을 분리하기 위한 군분리 공정에서 추출 공정의 산도조절 목적으로 사용되는 기존의 회분식 탈질 공정 개선이 시도되었다. 연속식 개미산 탈질과 잔여 산의 전해 분해 공정 조합 시의 질산 및 개미산의 분해 특성과 그때 분해 생성물의 변화 특성에 대한 연구가 수행되었다. 연속식 개미산 탈질에서는 약 30분 내에 정상상태에 도달하며 용액의 탈질 반응기 내의 체류시간은 최종 산도에 영향을 주고, 회분식처럼 개미산/질산의 몰 비가 1.5일 때 탈질에 의한 최저산도 값을 보여 주었다. Ti-IrO2 전해 반응기를 사용시 전류밀도에 따른 질산과 개미산의 분해 속도는 각각 9.33×10-3, 1.37×10-2 M/(hr·A/cm2)이었다. 질산은 Ti음극의 환원에 의해 개미산은 IrO2양극의 산화에 의해서만 분해 되었다. 본 연구에서 새롭게 제시된 연속식 개미산 탈질-잔여 산 전해 분해 공정의 조합은 2.0 M 질산 용액을 최종적으로 약 0.1 M 이하까지 연속 처리할 수 있었다.
This work has improved the conventional batch denitration by formic acid which has been used for controlling the acidity of solution for the solvent extractions to partition the long lived-radionuclides from the high level radioactive liquid waste. The characteristics of destructions of nitric acid and formic acid and their destructive products in a continuous denitration process combining a continuous denitration system by formic acid and an electrolytic residual acid-trimming system suggested in this work was evaluated. The continuous denitration by formic acid reached a steady state in 30 minutes and showed the dependence of the final acidity on the residence time of feeding solution into the reactor. Also the system had the lowest final acidity at a mole ratio of formic acid to nitric acid of 1.5 like the batch denitration. In a Ti-IrO2 electrolytic cell, the destructive rates of formic acid and nitric acid were 9.33×10-3 and 10-2 M/(hr·A/cm2), respectively. The nitric acid and the formic acid were destructed through the reduction at the Ti cathode and the oxidation at the IrO2 anode, respectively. The newly suggested continuous denitration process combining the denitation by formic acid and residual acid-electrolytic treatment could control continuously a feeding nitric acid of 2.0 M to below about 0.1 M.
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