[learn_more caption=”Tom Baxter”]
Tom Baxter, Sr. Consultant, Jenike & Johanson, Inc., Tyngsboro, MA, USA (tbaxter@Jenike.com)
James Prescott, Director/Sr. Consultant, Jenike & Johanson, Inc.
Roger Barnum, Sr. Consultant, Jenike & Johanson, Inc.
THOMAS BAXTER is a Senior Consultant with Jenike & Johanson, Inc., of Tyngsboro, Massachusetts. Thomas joined Jenike & Johanson in 1997. Thomas has focused on pharmaceutical applications, including solving content uniformity problems, providing client support to address regulatory concerns and working with clients to develop more robust formulations and process designs, including the design and qualification of a continuous manufacturing process for oral solid dosages. Thomas has also worked on hundreds of projects working with clients to implement cost-effective and efficient material handling systems. He has published numerous papers, lectures frequently on the storage and flow of bulk solids and is a member of American Association of Pharmaceutical Scientists (AAPS) and American Institute of Chemical Engineers (AIChE). Tom received his Bachelor’s and Master’s degrees from Virginia Tech, both in engineering mechanics.
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Abstract:
Production rate limitations can develop when feeding fine powders to a press, granulator or mill. These powder feed rate limitations arise when the powder interacts with entrained air, resulting in adverse “two-phase” (powder-air) flow effects. Two-phase flow problems can result in out-of-specification tablets, requiring operating at below target production rates. A critical step in developing a robust process, including conducting Quality by Design (QbD) studies, is modeling two-phase flow behavior in the press feed system.
Two-phase flow risks can be accounted for during process design by:
- Measuring key flow properties to use as inputs in the two-phase flow model;
- Computational modeling the two-phase flow effects based upon first principle models;
- Evaluating potential corrective actions through two-phase modeling.
The two-phase modeling software uses key powder flow properties, including:
- Permeability
- Compressibility
- Specific gravity of a particle
- Wall friction angles (phi-prime, f’)
- Effective angle of internal friction (delta, d) measured via a cohesive strength test.
The two-phase model as includes the press feed system geometry and process parameters as inputs. The model outputs include parameters that dictate two-phase flow behavior, such as vertical solids stress, interstitial gas pressure, bulk density and normalized gas pressure gradient. These modeling outputs are used to predict whether flow problems will occur and analyze potential corrective actions, including modifying the geometry of the press feed system, increasing the permeability of the powder and adding venting.