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Container Design Meets Powder Handling Needs for Single-Use Mixing Systems
Increased availability has accelerated the use of single-use systems in the biopharmaceutical industry. Membrane adsorbers, bioreactors, and mixing systems are currently experiencing the fastest growth of all single-use systems (1). Single-use mixing systems are designed to efficiently mix media and buffer solutions and to produce bulk drug substances and vaccines. Single-use mixers can increase operational flexibility, decrease process and validation time, and decrease risk of contamination compared with traditional mixing systems, according to EMD Millipore’s research.
Mixing media and buffer solutions is a critical task in the biopharmaceutical industry. The use of concentrates, which have a high percentage of solids in the mixture, is expected to become more prevalent. As a result, powder delivery and mixing systems must be able to handle higher solids loading. In addition, powder delivery and mixing systems must be able to efficiently handle and properly dispense a wide range of solids from fine to coarse powders. A solid’s particle size, type, and physical properties (i.e., moisture content, electrostatic charges) will all impact how the solid flows. For example, a small particle may be electrostatically charged so it will not flow as easily as a larger, uncharged particle. Without the proper equipment, powders can be challenging to handle when balancing dosing accuracy with operational speed and rapid turnaround of the equipment from one batch or product to another. A powder container should be able to handle and to dispense solids at a consistent, controlled rate and be easily washed to remove residual powder.
Addressing powder flow concerns
Figure 1. Potential issues with powder flow from containers due to improper design include ratholing, arching, or erratic flow. All figures are courtesy of the authors.
Studies on powder properties conducted in Millipore’s laboratory compared symmetric container designs with a patented, asymmetric design (Mobius powder-delivery system, EMD Millipore). An asymmetric geometry, shown in Figure 2, optimizes flow performance of solids, eliminates potential bridging at the discharge outlet, and minimizes dead areas. The asymmetric design eliminates the uniform symmetry of forces that creates arching and encourages mass flow of both coarse and fine powders. Permeability tests defined the limiting rate of discharge that would prevent arching and erratic flow.
Figure 2. An asymmetric container design allows optimal mass flow behavior of both coarse and fine powders.
Controlling discharge rate
Figure 3. Contact surface of valve (A) and exterior of valve in closed position (B).
As single-use system options continue to be introduced into biomanufacturing operations, powder delivery and mixing systems must keep pace in order to support faster, more flexible processes.
Sue Walker is senior applications engineer at the Biomanufacturing Sciences Network of EMD Millipore and John Saragosa is product development engineer at EMD Millipore,