Kinetics of immersion nucleation driven by surface tension
Kinetics of immersion nucleation driven by surface tension
复制标题
表面张力驱动的浸入成核动力学
DOI：
10.1016/j.powtec.2018.05.001
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发表时间：
2018
影响因子：
5.2
通讯作者：
Pitt K
中科院分区：
文献类型：
--
作者：
Pitt K
浸没成核是湿法制粒系统的成核机制，其中液滴相对于初级颗粒较大。许多研究已经对浸没成核过程进行了检验，但是成核动力学还没有得到很好的理解，并且明显缺乏经过实验验证的模型。Hounslow 等人提出了一个动力学模型。 (2009)描述了表面张力驱动的浸没成核。本文介绍了测量浸入成核动力学的一系列实验的结果，并将这些结果与模型预测进行了比较。将模型液体滴（HPMC 水溶液和硅油）放置在沸石和乳糖的静态粉末床上。在不同时间仔细挖掘核颗粒，并测量颗粒质量随时间的变化。正如 Hounslow 等人的模型所预测的，颗粒质量随着时间的平方根增加，在初始调整期后的 timetmax 处达到最大颗粒尺寸。临界堆积因子被证明是粉末特性的函数，而不依赖于液体特性。该模型很好地捕捉了液体和粉末特性的测量影响。然而，成核过程的动力学比模型预测的要慢得多。据信这是由于在液滴完全浸入之后粉末床内的液体持续渗透所致。这种二次液体运动可能对颗粒生长动力学产生重要影响，并影响最终颗粒产品的特性。
Immersion nucleation is the nuclei formation mechanism for wet granulation systems where the liquid drops are large relative to the primary particles. The process of immersion nucleation has been examined in many studies, however the kinetics of nuclei formation are not well understood, and there is a distinct lack of experimentally validated models for this process.A kinetic model has been proposed by Hounslow et al. (2009) which describes surface tension driven immersion nucleation. This paper presents the results from a series of experiments measuring the kinetics of immersion nucleation, and these results are compared with the model predictions. Drops of model liquids (aqueous HPMC solution and silicone oil) are placed on static powder beds of zeolite and lactose. Nuclei granules are carefully excavated at different times and the change in granule mass with time is measured. As predicted by Hounslow et al.'s model, the granule mass increases with the square root of time to a maximum granule size at a timetmaxafter an initial adjustment period. The critical packing factor is shown to be a function of powder properties, and not dependent on the liquid properties. The model captures well the measured effects of liquid and powder properties. However, the kinetics of the nucleation process are much slower than predicted by the model. It is believed this is due to continued percolation of the liquid within the powder bed, after the liquid drop is fully immersed. This secondary liquid movement may have an important effect on granule growth kinetics, and influence final granule product properties.
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