Baker’s yeast filtration through mixed beds of filtration aids and large glass beads

Abstract

Filtration of baker´s yeast through a mixed particulate bed of filter aid and glass beads was investigated. Glass beads form the large size particle fraction in the mixture, whereas the small size particle fraction was made by the following filter aids: kieselgel, kieselguhr-G, and industrial kieselguhr of different grades. Investigated particle size ratio of beads and filter aids was in the range around 20 – 100. Obtained results show that the large size particles do not influence the cake filtration performance up to a volume fraction of large particles in the layer of 0.8 ÷ 0.85. Bench filtration through a composite layer was performed, being the mixed layer built by filtering a kieselguhr suspension through the glass beads packing formed on a support. Regeneration of the glass beads by fluidization allows its use as a non-disposal fraction of the filter bed. Obtained results clearly demonstrate that the amount of filter aid used is less than required in conventional processes, showing advantages in what concerns saving of filter aid and reduction of pollution levels. From the tested filter aids, the coarse grade kieselguhr proved to be the most adequate as it was the component that allowed for the higher initial filtration velocity in the large size particle volume fraction in the mixture of 0.82 – 0.85.