(707a) Blade Design Effect in Powder Phenomena and Residence Time Distribution Inside the Feed Frame

Daniel Mateo^a, Fernando J. Muzzio^b, Carlos Velázquez^a and Rafael Méndez^a.

^a Department of Chemical Engineering, University of Puerto Rico at Mayaguez, PO Box 9000 Mayaguez PR 00681, Puerto Rico

^bDepartment of Chemical and Biochemical Engineering, Rutgers University, 98 Brett Road, Piscataway, NJ 08854, United States

Tablet compression has great significance in the pharmaceutical industry since most of the drugs are in the tablet dosage form. The tablet press feed frame is used to fill powder into the empty dies. Die filling is one of the key steps to control final properties of tablets. The Discrete Element Method (DEM) is a computational method for simulating the dynamics of particle processes. Using DEM, a standard feed frame taken from a Manesty Betapress was simulated, which represents the tableting process without the compression step. This work examines how the blade design affects the performance of a feed frame system mainly to evaluate the effect on powder segregation and particle attrition. Three different blade designs were analyzed, rectangular, cylindrical and a 45° angle blades. The three simulations were done at the same feed frame operating conditions, blade speed 24 rpm and turret speed 29 rpm. Die weight variability, feed frame hold up and exit contributions to the die weights were analyzed but no significance difference were observed between each simulation. Results shows that die segregation can be reduced with the cylindrical or angle blades. Segregation reduction is due to normal forces that particles received. The results show a linear relationship between compressive forces versus particle volume. Bigger particles receive a greater compressive force and can be related to particle attrition. In the cylindrical and angle blade simulations the force applied to bigger particles is lower than in the rectangular blade simulation, therefore less particle attrition. Thus it demonstrated that blade deign is a significant factor in size segregation reduction and control of particle attrition. The residence time distribution (RTD) was also studied in order to evaluate the feed frame performance. RTD can be related to total shear applied, particle attrition and to the possibility of powder stratification in the die for granular material sensitive to total shear applied.