Granule nucleation and growth: Competing drop spreading and infiltration processes
Granule nucleation and growth: Competing drop spreading and infiltration processes
复制标题
颗粒成核和生长：竞争液滴扩散和渗透过程
DOI：
10.1016/j.powtec.2010.06.013
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发表时间：
2011
影响因子：
5.2
通讯作者：
A. Salman
中科院分区：
文献类型：
--
作者：
Heledd R. Charles;R. Wengeler;K. Flore;H. Feise;M. Hounslow;A. Salman
湿法制粒是形成由液体粘合剂粘合的粉末颗粒集合体。生产颗粒是为了防止混合物分离、改善流动特性并易于粉末处理。在此过程中，粉末在高剪切混合器或流化床内搅拌，并将液体粘合剂添加到粉末混合物中。然后粘合剂液滴渗透到粉末中并将它们粘合在一起。这种滴粉相互作用的动力学与所产生的颗粒的特性密切相关，如果形成的组件足够坚固，则较短的渗透时间通常会导致更理想的更窄的特性分布。虽然已经对液滴渗透到多孔粉末中的时间以及液滴在无孔表面上的扩散进行了几项单独的研究，但相对较少的工作集中在现实中可能发生的竞争性扩散渗透过程。为了研究这一点，在静态干燥和预湿粉末床中进行了单滴渗透实验。在这种情况下，预润湿是指之前已经被一滴相同的液滴润湿。粘性粘合剂已被证明在无孔表面上在较短的时间内表现出较小的铺展程度 [1,2]。然而，目前的工作发现，在多孔表面上，渗透速率与铺展速率相比，更大程度地依赖于粘度的变化。这意味着较高粘度的粘合剂将扩散得相对更远，但需要较小的“剩余液滴”体积减少，以毛细管诱导吸力来固定接触线。
Wet granulation is the formation of powder particle assemblies bound by a liquid binder. Granules are produced in order to prevent mixture segregation, improve flow characteristics and ease of powder handling. During this process powder is agitated inside a high shear mixer or fluidised bed and a liquid binder is added onto the powder mixture. The binder droplets then penetrate into the powder and bind them together. The kinetics of this drop-powder interaction is strongly linked to the properties of the granules produced, with shorter penetration times often leading to a more desirable narrower distribution of properties, providing the assembly formed is strong enough. Whilst there have been several separate studies into drop penetration times into porous powders and drop spreading on non-porous surfaces, relatively little work has focussed on the competitive spreading–infiltration process that would occur in reality. To investigate this, single drop penetration experiments were carried out into static dry and pre-wetted powder beds. Pre-wetted in this case means to have been previously wetted by one identical drop. Viscous binders have been shown to exhibit lesser degrees of spreading in shorter times on non-porous surfaces [1,2]. However, the current work has discovered that, on porous surfaces, the infiltration rate has a greater degree of dependence, to that of spreading, on changes in viscosity. This means that higher viscosity binders will spread comparably further but require a smaller reduction in ‘remaining drop’ volume for capillary induced suction to pin the contact line.