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.Fundação para a Ciência e a Tecnologia (FCT) - Programa Operacional “Ciência, Tecnologia, Inovação” (POCTI) - POCTI/EQU/37500/2001.União Europeia (UE). Fundo Europeu de Desenvolvimento Regional (FEDER)
