微型流化床内混合特性的数值模拟

Numerical simulation of mixing characteristics of trace sample and bed material in micro fluidized bed reaction analyzer

微型流化床反应分析仪是中国科学院过程工程研究所研制的具有等温微分反应特性,且适合于气固反应分析的新仪器。细微样品与高温流化介质的瞬间混合是该仪器实现等温微分的必要条件。针对如何满足该要求,基于欧拉多流体模型对连接不同进样器的微型反应器本体进行了三维数值模拟,得到了不同喷口结构和位置下的流动图景及混合区浓度的相对标准偏差曲线,定量表征了各种进样器的混合质量。同时采用高速摄像手段获得了冷态实验中颗粒流动的快照,验证了模拟计算结果的可靠性。模拟结果对脉冲射流微量进样器结构的优化提出了如下建议:进样细管应避免采用弯角喷口,弯角结构会导致脉冲进样载流气喷出方向与流化气流相逆,使得细微颗粒试样堆积滞留,影响混合效果。

The micro fluidized bed reaction analyzer （MFBRA） developed by Institute of Process Engineering, Chinese Academy of Sciences has isothermal differential characteristics and is suitable for gas-solids fast reaction analysis, including the measurement of reaction rate and kinetic parameters. The instantaneously intensive particle mixing between trace sample in milligrams and high-temperature fluidized material is the essential condition to keep isothermal differential characteristics of the micro fluidized bed reactor. Therefore a three-dimensional numerical simulation based on the Eulerian multi-fluid model was performed for the micro fluidized bed connected with different gas jet structures. The instantaneous flow structures and quantitative mixing characterizations for different injector structures and locations were obtained. Experiments were conducted through measurements using high speed camera to capture the instantaneous solids flow pictures in the bed. Comparison revealed good qualitative agreement between experiment and simulation. The simulation results suggested that the injector should avoid the bending angle that confronted the injected gas with the fluidizing gas or left the trace sample in the injector.