摘要
用XRD谱图对比了煤系高岭土与高硅铝比高岭土煅烧酸浸前后的结晶分布特征 ,发现两者的煅烧活化过程完全相同 ,只有其中的高岭石经煅烧成为偏高岭石后才能进行酸浸反应 ,后者含有大量的硅铝化合物伴生矿使得最大浸取率很低。超声场的加入使颗粒细化 ,表面更新加快 ,导致浸出速率明显提高 ,但并未改变伴生矿结构与反应途径 ,故仍保持原有的最大浸取率。动力学分析表明 ,用液固缩芯反应模型能很好地模拟实验数据。与无超声下酸浸动力学相比 ,在较低的温度下 ,因超声空化效应造成颗粒细化与表面更新 ,加快了反应速率 ,使灰层扩散成为控制步骤。
A comparative investigation on the XRD spectra of coal series kaolin and high-SiO 2/Al 2O 3 kaolin before calcining and acid-leaching and after that, clearly shows that these two kinds of kaolins have the same calcining and acid-leaching mechanisms. Namely, only the real component-kaolinite in them can be transformed into sub-kaolinite in calcining process, and then the sub-kaolinite may take reaction with acid. However, the maximum leaching conversion for high-SiO 2/Al 2O 3 kaolin is much lower than that given by coal series kaolin due to large amount of inert silicate compounds containing in the former. Although ultrasound can makes the agglomerate particles of high-SiO 2/Al 2O 3 kaolin more dispersive and produce more fresh surfaces exposed to reaction, the maximum leaching conversion in this case still keeps the same value as the case without ultrasound. This demonstrates that ultrasound can not destroy any structure and enhance any activity of accompanied silicate compounds in the high-SiO 2/Al 2O 3 kaolin.The kinetic analysis of acid-leaching reaction indicates that the normal shrinkage core model agrees well with the experimental data. As compared with the kinetics without ultrasound, the internal diffusion of high-SiO 2/Al 2O 3 kaolin becomes the rate-limited step at lower temperatures in the presence of ultrasound. This change is attributable to the increase in reaction rate caused by the fractionization and surface renewal of kaolin particles by ultrasonic cavitation.
出处
《燃料化学学报》
EI
CAS
CSCD
北大核心
2001年第4期323-328,共6页
Journal of Fuel Chemistry and Technology
