The steady-state performance of a bubble column combined with a membrane filter module for cell separation and recycle is investigated numerically in the case of vinegar fermentation. The one-dimensional dispersion model for describing the longitudinal mixing of the liquid phase is employed. Kinetic expressions and their parameter values are taken from the available literature. Several characteristics of this fermentor system namely the concentration profiles of cells, substrate and product, the viability of viable cells relative to total cells, the washout condition for cells and the productivity of acetic acid are discussed. The average cell viability in the whole column and the critical dilution rate for washout are presented as equations. Low levels of the axial mixing are found to enhance the vinegar productivity. The optimum dilution rate giving the maximum productivity is determined and both are shown as figures with the Peclet number, the recycle ratio and the bleed ratio as parameters.
List of symbols a parameter in Eq. (3) (h -1) b parameter in Eq. (3) B bleed ratio, (FL--Fc)/FL c parameter in Eq. (3
Fe volumetric flow rate of liquid through membrane (m3h -1) FG volumetric flow rate of gas (m3h i) FL volumetric flow rate of medium feed (m3h -1) kl parameter in Eq. (2) (h -1) k2 parameter in Eq. (2) (h) L working fermentor height (m) n parameter in Eq. (1) P acetic acid concentration (kgm -3) Pe