Methodology for advanced measurement accuracy of the overall volumetric oxygen transfer coefficient with application to hydrocarbon–aqueous dispersions

Abstract

AbstractAccurate quantification of the overall volumetric oxygen transfer coefficient (KLa) is essential for the success of aerobic bioprocesses. In hydrocarbon‐based bioprocesses where KLa is depressed at higher viscosities, this is particularly critical. In this study an accessible methodology for KLa determination has been developed and validated for alkane‐based systems under a wide range of process conditions. Critical to measurement accuracy in around 90% of the KLa values was the incorporation of the response lag. Neglect of the response lag resulted in errors greater than 5% above KLa = 0.3Kp to KLa = 0.6Kp (where Kp is the inverse response lag or probe constant), at least 1.5‐fold to 3‐fold lower than the analogous KLa in water. Further, Kp varied significantly with both alkane concentration and chain length. A sensitivity analysis confirmed − 25% to 90% error in KLa with 30% over‐ and under‐estimation of Kp respectively. When incorporating Kp values specific to the process conditions, accurate KLa values were confirmed in 0 to 20% (v/v) C10–13 and C14–20 aqueous dispersions over 600 to 1200 rpm agitation. Copyright © 2012 Society of Chemical Industry