Growth regime map for liquid-bound granules: further development and experimental validation
Growth regime map for liquid-bound granules: further development and experimental validation
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DOI：
10.1016/s0032-5910(01)00317-5
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发表时间：
2001-06-04
影响因子：
5.2
通讯作者：
Scarlett, B
中科院分区：
文献类型：
--
作者：
Iveson, SM;Wauters, PAL;Scarlett, B
尝试量化边界并验证Iveson和Litster最近提出的液体结合颗粒的颗粒生长状态图（AlChE J.44（1998）1510）。该状态图假定颗粒生长行为的类型是仅两个无量纲组的函数：碰撞期间颗粒变形的量（其特征在于斯托克斯变形数St（def））和最大颗粒孔隙饱和度s（max）。使用转鼓和高剪切混合制粒机对一系列材料（玻璃球、铁矿粉、黄铜矿铜粉末和硫酸钠与纤维素的混合物）进行实验的结果进行了检查。转鼓造粒结果与建议的状态图吻合良好。碎屑和稳定增长之间的边界发生在St（def）的顺序0.1和稳定和诱导增长之间的边界发生在St（def）的顺序0.001。仅成核边界出现在孔饱和度从70%增加到80%时，随着St（def）的降低。然而，高剪切混合器结果都具有太大的St（def）数。这很可能是因为切碎机叶尖速度是对颗粒经历的平均冲击速度的高估，也可能是由于材料的动态屈服强度显著大于在低应变速率下测量的屈服强度。因此，该图仅是用于比较同一设备中不同材料的造粒行为的有用工具。在我们更好地了解造粒机中的流动模式和冲击速度之前，它不能用于比较不同类型的设备。理论上的考虑还表明，几个政权的边界也没有明确包含在地图上的附加参数，如粘合剂粘度的功能。(C)2001爱思唯尔科技有限公司。保留所有权利。
An attempt was made to quantify the boundaries and validate the granule growth regime map for liquid-bound granules recently proposed by Iveson and Litster (AlChE J. 44 (1998) 1510). This regime map postulates that the type of granule growth behaviour is a function of only two dimensionless groups: the amount of granule deformation during collision (characterised by a Stokes deformation number, St(def)) and the maximum granule pore saturation, s(max). The results of experiments performed with a range of materials (glass ballotini, iron ore fines, copper chalcopyrite powder and a sodium sulphate and cellulose mixture) using both drum and high shear mixer granulators were examined. The drum granulation results gave good agreement with the proposed regime map. The boundary between crumb and steady growth occurs at St(def) of order 0.1 and the boundary between steady and induction growth occurs at St(def) of order 0.001. The nucleation only boundary occurs at pore saturations that increase from 70% to 80% with decreasing St(def).However, the high shear mixer results all had St(def) numbers which were too large. This is most likely to be because the chopper tip-speed is an over-estimate of the average impact velocity granules experience and possibly also due to the dynamic yield strength of the materials being significantly greater than the yield strengths measured at low strain rates. Hence, the map is only a useful tool for comparing the granulation behaviour of different materials in the same device. Until we have a better understanding of the flow patterns and impact velocities in granulators, it cannot be used to compare different types of equipment. Theoretical considerations also revealed that several of the regime boundaries are also functions of additional parameters not explicitly contained on the map, such as binder viscosity. (C) 2001 Elsevier Science B.V. All rights reserved.