Thermodynamics analysis of in-container self-propagating high-temperature synthesis immobilization process using numerical simulation

doi:10.11949/j.issn.0438-1157.20171111

Abstract

Abstract:

Self-propagating high-temperature synthesis (SHS) is a high-efficiency and low-cost thermal technology that uses the energy released during exothermic oxidation-reduction reactions to immobilize solid radioactive wastes, such as high-level radioactive calcined ash and contaminated soil. It is effective to increase the product's density and control the diffusion of the hazardous aerosol by using SHS immobilization in a sealed container. By the analysis of the chemical reaction mechanism and process of the SHS immobilization, the numerical simulation model for the in-container treatment was established and the variation characteristics of the temperature and pressure during the immobilization were studied. By using the COMSOL finite element analysis software with the preset model size, unit type and boundary condition, the in-container temperature-time and pressure-time variation curves in 7200 s after SHS ignition were solved. The simulation is compared with the experiment data in the same in-container immobilization condition, and the results have strong consistency and show staged difference among ignition, burning, flameout and thermal insulation of the SHS immobilization process. The numerical simulation conclusion could act as the reference data for the container safety design.

Key words: self-propagating high-temperature synthesis immobilization, thermodynamics, numerical simulation, COMSOL, waste treatment, safety

摘要：

自蔓延高温合成固化是一种利用氧化还原反应放热处理高放废物煅烧灰、污染土壤等固体放射性废物的方法，在密封容器内对放射性废物采用自蔓延高温合成固化技术可有效提高产物的致密度并控制有害气溶胶的扩散。通过分析自蔓延化学反应机理和过程，建立容器内自蔓延高温合成固化数值模拟模型，对固化过程容器内温度-压力变化特征进行分析。利用COMSOL有限元分析软件，确定模型尺寸、单元类型和边界条件，计算得到点火后7200 s的容器内温度和压力随时间变化曲线。与相同条件的容器内SHS固化实验测量结果对比分析，数值模拟与实测情况一致性较强，能够较好反映SHS固化过程点火、燃烧、熄火、保温的四阶段性特征；模拟结果可作为容器安全性设计的参考数据。

关键词: 自蔓延高温合成固化, 热力学, 数值模拟, COMSOL, 废物处理, 安全

CLC Number:

TQ021.2

TAO Jun, ZHANG Jijun, MAO Xianhe, ZHAO Jianwei, ZHANG Dongliang, CAI Xinan. Thermodynamics analysis of in-container self-propagating high-temperature synthesis immobilization process using numerical simulation[J]. CIESC Journal, 2018, 69(5): 1846-1853.

陶钧, 张继军, 毛仙鹤, 赵建伟, 张东亮, 蔡溪南. 容器内自蔓延高温合成固化过程的热力学数值模拟[J]. 化工学报, 2018, 69(5): 1846-1853.

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