School of Chemical Engineering, University of Birmingham, Edgbaston, UK.
Eur J Pharm Biopharm. 2012 Aug;81(3):666-73. doi: 10.1016/j.ejpb.2012.04.011. Epub 2012 Apr 26.
In this paper, Positron Emission Particle Tracking (PEPT) techniques are utilised to track the trajectory of single particles through the mixing and conveying zones of a Twin Screw Granulator (TSG). A TSG consisting of conveying zones and mixing zones is used in this study. The mixing zones are arranged with kneading discs at an angle of 30°, 60° or 90°. Experiments were carried out using different mixing configurations with various screw speed and total mass flow rate. The PEPT data obtained were then utilised to obtain the residence time distribution (RTD) and the Peclet number in an attempt to gain some insight into the mixing of the process. The fill level of the granulator was also estimated to study the mechanism of granulation. As might be expected, it was shown that the residence time of the granulation process increases with decreasing screw speed. It also increases with increasing angle of the arrangement of kneading blocks in the mixing zones, but will decreases when powder feed rate is increased. The fill level of the mixing zone in particular increases when the screw speed decreases or when powder feed rate increases. Furthermore, the fill level of the granulator will increase when the mixing zone configuration changes from 30° to 90°. It is shown that the granulator is never fully filled, even using 90° mixer elements implying limited compaction which may explain why the granules produced are porous compared with those from a high shear mixer. Interestingly, the RTD analysis reveals that the extent of axial mixing in the mixing zone of the granulator does not change significantly for different configurations and process conditions. There is evidence of a tail in the RTD which implies some material hold up and channelling.
在本文中，我们利用正电子湮没粒子跟踪（PEPT）技术来跟踪单颗粒在双螺杆造粒机（TSG）的混合区和输送区中的轨迹。在本研究中，使用了由输送区和混合区组成的 TSG。混合区采用 30°、60°或 90°夹角的捏合盘进行布置。实验采用不同的混合配置，螺杆速度和总质量流量不同。然后利用 PEPT 数据获得停留时间分布（RTD）和 Peclet 数，试图深入了解该过程的混合情况。还估计了造粒机的填充水平，以研究造粒的机理。正如预期的那样，造粒过程的停留时间随着螺杆速度的降低而增加。随着混合区中捏合块排列角度的增加而增加，但随着粉末进料速率的增加而减少。特别是在螺杆速度降低或粉末进料速率增加时，混合区的填充水平会增加。此外，当混合区配置从 30°变为 90°时，造粒机的填充水平将会增加。结果表明，即使使用 90°混合元件，造粒机也从未完全充满，这意味着压实程度有限，这可能解释了为什么与高剪切混合器相比，所生产的颗粒多孔。有趣的是，RTD 分析表明，不同配置和工艺条件下，造粒机混合区的轴向混合程度没有显著变化。RTD 中存在尾部，这意味着存在一些物料停留和通道。
