Application of magnetic bearing technology in high-speed centrifugation

• Magnetic drive and bearing technology was applied on a sedimentation type centrifuge.
• Separation experiments were performed on a technical scale for ultrafine particles.
• The outcome of the process is precisely adjustable via the operating parameters.

Centrifuges represent a well-established tool in separation technology to handle high throughputs of suspensions with micron-sized particles. However, extraordinarily high centrifugal accelerations are required for even smaller particles. For this purpose, we make use of magnetic bearing and drive technology. We report the first application of this contactless technique in separation experiments. The presented prototype is based on a semi-continuous principle, where sediment is built up within the rotor while the liquid (which contains the fine fraction in case of classification) is discharged at the overflow weir. The new centrifuge allows rotational speeds of more than 64k min−1. A broad variation of parameters with centrifugal accelerations of up to C=100,000 and flow rates of up to 0.4 l/min provides a sound experimental basis for this study. The cut size and the product loss of three particle systems between 10 nm and 1 µm (silver nanoparticles, silica nanoparticles, and polystyrene) are precisely adjustable via the mentioned parameters. Furthermore, a good comparability with a commercially available device was found regarding the specific efficiency. We consider our approach to be a promising contribution to nanoscale separation technology where scalable high-throughput methods are rare.