Abstract:

The fluidity characterization and hopper discharge experiments were carried out with glass beads, fluidized bed cracking catalyst particles, lignite and PVC particles as experimental materials. The study found that the fluidity of different powders is quite different, and the corresponding gravity discharging results are also different. The flow rate of the powder used in the experiment is much lower than that predicted by the traditional Brown and Richards model. The analysis shows that the cohesion and agglomeration caused by the interaction between particles is the main reason that hinders the flow of fine powders. Based on the above analysis, the tensile strength of the bed is obtained by shear test combined with the theory of molar stress circle. Meanwhile, with the help of the model between the interaction between particles and the bed stress of powder constructed by Rumpf equation, the interaction force between particles can be obtained. Finally, the Bond number is used to modify the voidage of the powder bed, and the influence of the interaction between particles on the structure of the powder bed is revealed. On the basis of that the prediction model of powder mass flow rate is established. The newly established powder flow rate model coupled with the force between particles has effectively improved the disadvantage of the traditional model for the high prediction value of the fine particle powder flow rate, and significantly reduced the flow rate prediction deviation.

Key words: powder, hopper discharge, interparticle interaction, bed voidage, mass flow rate prediction

摘要：

以玻璃微珠、流化床裂化催化剂颗粒、褐煤和聚氯乙烯颗粒为实验物料，开展粉体流动性表征与料仓下料实验。研究发现，不同粉体的流动性差异较大，相应的料仓重力下料结果也不同；实验所用粉体的下料流率远低于传统Brown and Richards模型的预测值。分析表明，颗粒间相互作用导致的粉体黏附团聚是阻碍细颗粒粉体下料流动的主要原因。基于上述分析，利用剪切测试结合摩尔应力圆理论获得床层拉伸应力，并借助Rumpf方程构建的颗粒间相互作用与粉体床层应力之间的模型来获得不同粉体的颗粒间作用力；继而采用Bond数对粉体床层空隙率进行修正，揭示了颗粒间相互作用对粉体床层结构的影响，并在此基础上建立了粉体下料流率预测模型。新建立的耦合颗粒间作用力的粉体流率模型，有效改善了传统模型对细颗粒粉体流率预测值偏高的弊端，显著降低了流率预测偏差。

关键词: 粉体, 料斗下料, 颗粒间作用, 床层空隙, 流率预测