Department of Applied Chemistry, Chubu University , 1200 Matsumoto-Cho, Kasugai, Aichi 487-8501, Japan.
Institute of Technology, Shimizu Corporation , 3-4-17 Etchujima Koto-ku, Tokyo 135-8530, Japan.
Environ Sci Technol. 2016 Dec 20;50(24):13328-13334. doi: 10.1021/acs.est.6b03635. Epub 2016 Dec 6.
The vaporization mechanisms of water-insoluble Cs in raw ash and Cs-doped ash during thermal treatment with CaCl addition was systematically examined in a lab-scale electrical heating furnace over a temperature range of 500-1500 °C. The results indicate that the water-insoluble Cs in the ash was associated with aluminosilicate as pollucite. Addition of 10% CaCl caused the maximum vaporization ratio of Cs in the raw ash to reach approximately 80% at temperatures higher than 1200 °C, whereas approximately 95% of Cs was vaporized at temperatures higher than 1300 °C when 30% CaCl was added. The formation of an intermediate compound, CsCaCl, through the chemical reaction of Cs with CaCl was responsible for Cs vaporization by means of the subsequent decomposition of this intermediate upon the increase in temperature. The indirect chlorination of Cs by the gaseous chlorine released from the decomposition of CaCl was insignificant. A high CaCl content in the resulting annealed products with 30% CaCl addition delayed the decomposition of CsCaCl and thus lowered the Cs vaporization ratio compared to that with 10% CaCl addition at 900-1250 °C. Thermal treatment with CaCl addition is a proposed method to remove Cs from Cs-contaminated incineration ash.
在实验室规模的电加热炉中，系统地研究了在添加 CaCl 的情况下，原始灰分和 Cs 掺杂灰分中不溶于水的 Cs 在热处理过程中的蒸发机制，温度范围为 500-1500°C。结果表明，灰分中不溶于水的 Cs 与沸石（pollucite）形式的铝硅酸盐结合。当添加 10%CaCl 时，在高于 1200°C 的温度下，原始灰分中 Cs 的最大蒸发率达到约 80%，而当添加 30%CaCl 时，在高于 1300°C 的温度下，约 95%的 Cs 蒸发。Cs 与 CaCl 通过化学反应形成中间化合物 CsCaCl，通过随后在温度升高时分解这种中间化合物来实现 Cs 的蒸发。来自 CaCl 分解的气态氯气对 Cs 的间接氯化作用并不重要。在添加 30%CaCl 的情况下，由于退火产物中含有高含量的 CaCl，因此 CsCaCl 的分解延迟，与添加 10%CaCl 相比，在 900-1250°C 时 Cs 的蒸发率降低。添加 CaCl 的热处理是一种从 Cs 污染的焚烧灰中去除 Cs 的方法。
