(544b) Effects of Blade Shape and Angle On Solid Particle Mixing Using 2D and 3D Discrete Element Simulations

Among the various unit operations involved in the process and pharmaceutical industries, solid particle mixing is an important step, particularly for the pharmaceutical industry due to the strict requirement for quality control. Different types of industrial mixers are employed (including convective and tumbling mixers), among which convective mixers are the most important ones for cohesive materials and for continuous mixing operations. Although significant amount of research has been done, specific issues, such as impact of the blade shape and angle, have not been studied in detail, with a few exceptions [1].

In this work, a detailed study was performed using a simple geometry [2], i.e., a rectangular box with a single blade to allow for an understanding of mixing phenomena and the flow of the powder across the blade. Additionally, for the first time, three different blade-shapes i.e. concave, convex, and straight geometries were investigated by 2D and 3D simulations using the Discrete Element Method (DEM). The blade rake angles investigated covered a wide range from 40° to 150°. Particles of two sizes were used; 2 mm and 10 mm in diameter. Effects of wall friction were also investigated in this work. The results for all these cases were quantified using velocity profiles, inter-particle forces and mixing index, as well as experimental studies generated in our novel set up. Finally, results are presented of the optimal angle and shape as a function of the particle characteristics.

References

[1] Chandratilleke GR, Yu AB, Stewart RL and Bridgwater J, Effects of blade rake angle and gap on particle mixing in a cylindrical mixer. Powder Technol 193: 303-311 (2009).

[2] Siraj MS, Radl S, Khinast JG, Study of Effects of Blade Rake Angle and Particle Size on Mixing Performance using a Simple Rectangular Geometry. To be submitted (2010).