The application of mini-hydrocyclones in the concentration of yeast suspensions

Abstract

Small diameter hydrocyclones have had an increasing use in performing difficult separations between phases, due to the large centrifugal forces generated in them. The potential use of hydrocyclones in the concentration of microbial suspensions is attractive as they are continuous, high capacity devices requiring low maintenance while having the additional benefit in that they can be readily sterilised. Results are reported on the de-watering of Bakers' yeast in a 10 mm diameter hydrocyclone to quantify the separation process. The form of the model equation for recovery has been derived based on the non-equilibrium residence time theory. This is shown to represent experimental data in that increasing pressure and temperature exhibit a positive effect on both the recovery and the concentrating effect while an increase in the feed concentration exhibits a negative effect on these. In addition, the influence of cyclone geometry on the recovery and concentration ratio has been illustrated. Increasing the vortex diameter results in an increasing concentration ratio and a decreasing recovery. Increasing the diameter of the spigot shows the opposing trends. Typical results from a single stage separation combine a recovery of 60% with a concentration ratio of 1.25 and a recovery of 30% with a concentration ratio of 2.0. Concomitant improvement of the recovery and concentration ratio will be attainable through the use of multi-stage hydrocyclone circuits.