Cross-flow ceramic microfiltration of ethanol fermentation broths
Saglam, Naci
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https://hdl.handle.net/2142/21374
Description
Title
Cross-flow ceramic microfiltration of ethanol fermentation broths
Author(s)
Saglam, Naci
Issue Date
1995
Department of Study
Food Science and Human Nutrition
Discipline
Food Science and Human Nutrition
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Biology, Microbiology
Language
eng
Abstract
The overall objective of this research was to optimize the ceramic cross-flow microfiltration of ethanol fermentation broths. The ceramic membranes from three different manufacturers were made of $\alpha$-alumina with pore sizes of 0.05 $\mu$m-1.4 $\mu$m. Water permeabilities for the 0.2 $\mu$m Ceraver, Ceraflo and CeraMem membranes were 903, 625 and 308 Lm$\sp{-2}$h$\sp{-1}$bar$\sp{-1}$ (LMH) respectively at 30$\sp\circ$C. Water flux increased with increasing pore size, transmembrane pressure and temperature.
Flux of yeast suspensions (0-50 gL$\sp{-1}$) in water and in the model fermentation medium declined dramatically in the first 3 hours and then reached a steady state value. Smaller pore membranes (0.05 $\mu$m) gave slightly higher flux than 0.2 $\mu$m membranes. However, the 1.4 $\mu$m membrane of Ceraver gave the highest flux. Even though higher cell concentrations resulted in lower flux, contribution of fermentation medium ingredients to membrane fouling was greater than yeast cells. In addition, there was little effect of cross-flow velocity on flux of the fermentation medium without yeast cells.
Flux increased at low transmembrane pressures but became asymptotic at higher pressures. Higher cross-flow velocity gave higher flux. Periodic backwashing did not give much improvement especially for smaller pore-sized membranes (i.e., 0.05 $\mu$m). However, co-current permeate flow resulted in substantial improvement over the conventional mode. The performance data of the model fermentation medium was confirmed with real ethanol fermentation broth (10.3% v/v ethanol, 19 gL$\sp{-1}$ total solids). However, the steady-state flux was lower for real fermentation broth than that of model fermentation medium (i.e., 51.7 LMH and 64. 5 LMH).
A semi-empirical mathematical model based on the resistance model was developed to predict flux from the operating parameters. Resistance due to internal fouling was much greater than the intrinsic resistance of the membrane itself. The intrinsic resistance of the polarized cake layer on the membrane surface was expressed in terms of cross-flow velocity and cell concentration in the form of a polynomial equation. Due to complexity of the feeds, each feed-membrane combination required its own set of parameters to predict the flux with a reasonable degree of accuracy.
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