In bio-ethanol fermentation, the broth consists of mainly water and ethanol, together with particulate residues of unreacted feedstock and additives (mostly yeast). Prior to further processing (distillation), and to avoid fouling of heat exchangers and distillation columns, the solids residues of the broth need to be removed to as low a concentration as possible. The current mechanical separation (belt filter or centrifuge) can only remove +10 μm particles representing about 90% of the total solids content. The remaining 10% is usually recovered in the bottom stream of the first distillation column, and forms the stillage that is further treated. To avoid fouling and even eliminate the first distillation column where the ethanol fraction is only increased from 12% (feed) to 16% (top), a better particulate removal is required. Novel sintered metal fiber (SFM) fleeces are highly efficient for microfiltration, and the removal of suspended solids largely exceeds 99%. The paper (i) positions microfiltration in the overall bio ethanol process; (ii) describes the novel sintered metal fiber microfiltration application; (iii) experimentally determines the major operating characteristics of SFM and (iv) predicts the up-scaled operation by using a simplified filtration model. At an ambient feed temperature, the flux of permeate exceeds 5m3/m2h for a TMP of 1.5 bar and a yeast concentration of 15 g/l, as commonly encountered in the fermenter broth.

Bioethanol Microfiltration Sintered Metal Fleece Models

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