LevMixer™ single-use mixing system is a compact mixing system. The heart of this system is a mixing biocontainer incorporating a bottom-mounted levitating impeller designed for powder-liquid and liquid-liquid mixing applications. The impeller is frictionless and generates no particles.
Introduction
Powder-liquid mixing is a common requirement in biopharmaceutical processing. To maximize mixing efficiency for powder-liquid applications, we offer the LevMixer single-use mixing system with a 16.13 cm diameter impeller.
In this experiment, we tested the system’s ability to resist stalling when buried by compacted solids. We chose diatomaceous earth, a fine, inert, and insoluble powdered filter medium that is light and fluffy when dry yet forms a dense mud when mixed with water.
Materials and methods
We filled a 200 L LevMixer mixing biocontainer with 160 L of water and set the mixing speed to 180 rpm. We then added diatomaceous earth powder (density = 0.22 kg/L) to a total weight of 37 kg. The system provided sufficient agitation to maintain the diatomaceous earth powder in suspension. We then shut the mixer off and allowed the suspended powder to settle into a dense, compacted mud at the bottom of the mixing biocontainer. After the powder had settled, we restarted mixing, and we observed the impeller’s ability to resume mixing.
Results
The 37 kg powder load was sufficient to completely bury the system’s impeller in a dense sedimentary mud. Despite being less strongly coupled to the drive unit than our other mixing impellers (such as those on the magnetic mixer system), the levitated impeller was able to smoothly and immediately resume mixing without becoming decoupled or otherwise stalling.
Despite its ability to resist stalling, the upper speed limit of the levitated impeller (180 rpm) meant that the system’s mixing action was noticeably less vigorous than with our other mixers. Two hours after mixing had resumed, some residual powder (approximately 1% of the total powder load) was found adhered to the bottom of the mixing biocontainer.
Fig 1. LevMixer single-use mixing system at 0, 3, 6, and 9 min timepoints after adding the diatomaceous earth powder.
Conclusions
The LevMixer single-use mixing system is well suited to powder-liquid mixing applications, even when very high powder loads are anticipated. However, if resuspension of dense powder is a requirement, then we recommend alternative mixers such as the magnetic mixer as a more efficient choice.
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