title: A comparison of some methods of estimating volumetric mass-transfer coefficients in an external-loop airlift fermenter.
abstract: Volumetric mass-transfer coefficients were measured in an 11-L external-loop airlift fermenter with deionized water, a fermentation medium, and during a fermentation. Both a Mackareth oxygen electrode and a novel rapid-response probe were used. When the conventional step-change dynamic method was used for water, the long, nonlinear response time of the Mackareth electrode made correction of its readings difficult; this problem did not occur when the rapid-response probe was used. A comparison was made with a method of mass-transfer coefficient determination which does not involve any assumptions about the gas residence time distribution. However, this method requires that the liquid phase is well-mixed and this requirement was not met in the airlift fermenter. Comparison of the present results with other K(L) a determinations for airlift fermenters showed that K(L) a in water depends on the active gas holdup, the value of K(L) a/epsilon at 20 degrees C being ca. 0.37 s(-1). Although higher gas holdups were obtained with the fermentation medium than for water, the values of K(L) a/epsilon were lower, ca. 0.22 s(-1) at 20 degrees C.
authors.affiliation: University of Amsterdam, BCP Jansen Institute, University of Amsterdam, Plantage Muidergracht 12, 1018 TV Amsterdam, The Netherlands.
authors.forename: F
authors.initials: F
authors.lastname: Kamp
authors.forename: D A
authors.initials: DA
authors.lastname: Wase
authors.forename: W J
authors.initials: WJ
authors.lastname: McManamey
authors.forename: O
authors.initials: O
authors.lastname: Mendoza
authors.forename: K
authors.initials: K
authors.lastname: Thayanithy