Tuesday January 15, 2013
Prediction of Scaling Effects
Pharmaceutical Fluidized Bed Processors
Effective operation of fluidized bed processors requires even gas distribution and effective gas-particle mixing. Scaling up a drying process from laboratory to production scale presents unique challenges, such as preventing granule attrition, fines loss, or segregation. Current methods make optimizing processor performance difficult without large-scale experimentation due to the scale-dependent parameters that affect fluidization. Fluidization behavior is also dependent on the particle size distribution and mechanical properties of the powder, so it is necessary for these to be considered in simulating a fluidized bed processor. To predict fluidized bed behavior, it was necessary to choose a numerical method capable of accounting not only for the particle-fluid effects (e.g., drag) but also for particle-wall impacts and particle-particle interactions.
Fluidized bed processors of approximate diameters 140mm, 300mm, and 900mm were simulated using a commercial CFD code with a unique model for particle-fluid simulation. For each processor, multiple flow rates were simulated at isothermal conditions for processor loadings between 0.15kg and 45 kg of a powder with a size distribution from 2 to 1500 microns diameter. The simulations modeled both start-up and steady operation of the processors on a full 3D, time-transient basis within a reasonable calculation time (1-2 days).
This study was performed as a “blind test,” with no results shared with the CFD analyst until the simulations were completed. Simulation results were compared with experimental data for dense phase bed height, elutriated particle trajectory, and patterns in the fluidization flow structure. Due to scale-dependent effects, the flow structure varied from a pattern approaching spouted flow to a homogeneously fluidized bed. Observations through the sight glasses were also compared to model predictions. The simulation results compared well with both the laboratory measurements and qualitative observations.
The numerical method and simulation approach were found to successfully predict flow behavior of several fluid bed scales, yielding qualitatively correlated information based solely on material properties, processor loading, inlet air flow rate and processor geometry. This implies that CFD of this kind may be used to assist in determining select operating parameters for pharmaceutical processors and in scaling processes to different sizes to meet production demands.
About the Speaker:
Wei Chen received his Ph.D from Clarkson University in Mechanical Engineering in 2006. Currently he holds the position of Senior Research Investigator at Bristol-Myers Squibb Co. and was honored with the Chemistry Leadership Award in 2010. His primary area of work is in modeling including mixing (liquid), dissolution (control release et. al. ), powder blending, fluidized bed and pan drying, reaction kinetics, and fermentation based on the CFD and DEM techniques all for pharmaceutical industry processes. Most notably, he developed an elegant mathematical model that predicts the relative deviation of tablet content uniformity for the pan coating process. The model was a key aspect of one of the first Quality by Design New Drug Applications and has been used in several related products which were also approved by the FDA and other health authorities around the globe.
Tuesday January 15, 2013
Registration 6:00 PM
Dinner 6:30 PM
Program 7:30 PM
Mountain and Park Avenues, Scotch Plains
Members and Guests …………………..………..$30
Unemployed/Retired Section members…. $15
Call Andy Soos at (908) 604-2670 or e-mail at email@example.com by Friday 1/11/13.
Executive Committee Meeting
The Executive Committee meeting for February will be held on the 5 th at Paisano’s Pizza at 6:30 pm. All members are welcome.
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