高放废液玻璃固化中配合料的玻璃化过程与建模

Feed-to-Glass Conversion and Modeling During High-Level Liquid Waste Vitrification

高放废液玻璃配合料在冷帽层向玻璃态的转化过程及模型构建是准确仿真模拟高放废液玻璃固化熔炉的重要依据。为澄清高放废液玻璃固化过程中配合料向玻璃态的转化过程,分析了配合料在冷帽层的物相转变与结构特征。结果表明:冷帽包括上部反应层(100~700℃)与下部泡沫层(700~1000℃),其中脱水及硝酸盐的分解集中在反应层,而连续熔体出现、中间物相生成与溶解发生在泡沫层。基于质量守恒方程和实验结果,将反应层简化为一维传质模型并建立了配合料向玻璃态转变的转化率方程,定量描述了配合料结晶水脱去(100~400℃)、硝酸盐熔融(200~300℃)和硝酸盐分解(400~700℃)3大主要反应随温度变化的反应速率,为后续熔炉仿真模型提供了数值依据。

The feed-to-glass conversion within the cold cap and the mathematical modeling of the process are of great concern for the accurate simulation of the melter for vitrification of high-level liquid waste(HLLW).To figure out the feed-to-glass conversion during the HLLW vitrification,the phase transitions and structural features within the cold cap were investigated.The results show that the cold cap consists of the upper reaction layer(at 100-700℃)and the lower foam layer(at 700-1000℃).The dehydration and nitrate decomposition occur in the reaction layer,while the continuous melt as well as the formation and dissolution of intermediate phases appear in the foam layer.The reaction layer can be simplified into a one-dimensional mass transfer model based on the mass conservation equation and experimental results.Subsequently,the kinetic equation of feed-to-glass conversion is proposed to quantitatively describe the three reaction rates of dehydration(at 100-400℃),and melting(at 200-300℃)and decomposition(at 400-700℃)of nitrates as functions of temperature in the reaction layer,providing some crucial parameters for melter simulation.