A new method for yeast recovery in batch ethanol fermentations: Filter aid filtration followed by separation of yeast from filter aid using hydrocyclones

Abstract

In the Melle-Boinot process for alcohol production, centrifuges are normally used for yeast recovery at the end of a batch fermentation. Centrifuges are expensive equipment and represent an impressive part of the equipment costs in alcohol industries. In the present work, an alternative method for yeast recovery using less expensive equipment was studied. Instead of using centrifuges, yeast was separated from the fermented broth by filter aid filtration, followed by separation of yeast from the filter aid using hydrocyclones. A stainless steel plate-and-frame filter of filtration area 1.14 m² and two 30 mm hydrocyclones, which followed the Bradley and Rietema recommended proportions, were used in this work. The filter aid was perlite. Tests of direct separation of yeast from the fermented broth using the Bradley hydrocyclone proved to be completely unfeasible, since the maximal reduced total efficiency obtained was only 1%. When the hydrocyclones were used to separate perlite from the resuspended filtration cake, the perlite total separation efficiency obtained in the underflow was as high as 95% when using the Bradley hydrocyclone with an underflow diameter of 3 mm. To show the feasibility of the proposed new method of yeast recovery, a complete cycle of experiments, which included fermentation, yeast separation, and new fermentation using the recycled cells, was performed with good results.