C. Velazquez, D. Mateo, F.J. Muzzio, L. Obregon, R. Mendez
American Institute of Chemical Engineers
AIChE Conference -2011 Annual Meeting
Feed frame is used to fill powder into the tablet press dies. Die filling is one of the key steps to control final properties of tablets. Granular materials may segregate upon processing and handling based on differences in particle properties such as size, density, or shape. The Discrete Element Method (DEM) is a computational method for simulating the dynamics of particle processes. DEM was used to simulate the equipment used in the experimental partto understand powder phenomena inside the feed frame. Segregation behavior of a single material with a particle size distribution was investigated using this method. The computational setup was a fully 3D model of a Manesty Betapress feed frame with real boundaries, which represents die-filling process without the compression step. A cohesion model was used for some simulations. The DEM simulation component includes a 2 feed frame speed (24and 72 RPM) and 2 die disc speeds (29 and 57 RPM). It was found that the lower the die disc speed, the lower the relative standard deviation (RSD) of the die weight. Simulations with and without the cohesion linear model show basically the same hold-up and die weight variability. Results demonstrated size segregation. This effect was more noticeably for low feed frame speed. Velocity profile shows higher speed when powder enters to the feed frame and for powder closer to the paddles but separated to the center of the wheels. The most complicated flow pattern occurs between the two paddles and over the exit in the second stage. Particle velocity profile was lower at low feed frame speed and suggesting the posibility of a more significant particle rearrengement when going into the feed frame partially explaining a significant size segregation.The cumulative size distribution for 50 random dies demonstrate a more significant die size segregation at lower feed frame speed demonstrating size segregation inside the feed frame and dies.
die filling, feed frame, segregation