Abstract This study presents an evaluation of the predicted and experimentally observed flow behavior, i.e., flow pattern and critical outlet diameter, in a tablet press hopper. Three grades of a commonly used pharmaceutical additive, microcrystalline cellulose, were used for this purpose. The prediction of the flow behavior was made by first extrapolating shear and wall friction data and, subsequently, applying these extrapolation-based data as input variables to Jenike's hopper design method. Predictions were then compared with empirical discharge experiments from a tablet press hopper and a funnel with varying outlet diameters. By application of a mixed-effect 2nd order polynomial model for the extrapolation of the wall yield locus, accurate flow pattern predictions for the tablet press hopper was made. However, the observed flow patterns were very sensitive to the powders' moisture content. The comparison of the observed and predicted critical outlet diameters showed good agreement for the powder with the best flowability when linear extrapolation of the flow function was applied. In contrast, the predicted critical outlet diameter was slightly overestimated compared to the experimentally observed diameter for the two more cohesive powders. A likely reason for this overestimation is that the flow function probably has a non-linear convex upward shape for these two powders at very small consolidation stresses. These findings illustrate the relevance of measuring shear and wall shear stresses at very small consolidation stresses to improve the flow behavior predictions for small-scale process equipment typically used during production of solid state pharmaceuticals.

中文翻译：

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基于 Jenike 料斗设计方法的小型工艺设备中粉体流动预测的实验评估

摘要 本研究评估了压片机料斗中预测的和实验观察到的流动行为，即流动模式和临界出口直径。为此，使用了三个等级的常用药物添加剂微晶纤维素。流动行为的预测首先是通过外推剪切和壁面摩擦数据，然后将这些基于外推的数据作为输入变量应用于 Jenike 的料斗设计方法。然后将预测结果与来自不同出口直径的压片机料斗和漏斗的经验排放实验进行比较。通过应用混合效应二阶多项式模型外推壁屈服轨迹，对压片机料斗进行了准确的流型预测。然而，观察到的流动模式对粉末的水分含量非常敏感。当应用流动函数的线性外推法时，观察到的和预测的临界出口直径的比较表明具有最佳流动性的粉末具有良好的一致性。相比之下，与实验观察到的两种更具粘性的粉末的直径相比，预测的临界出口直径略有高估。这种高估的一个可能原因是，在非常小的固结应力下，这两种粉末的流动函数可能具有非线性向上凸出的形状。