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

Accurate quantification of the overall volumetric oxygen transfer coefficient (K _La) is essential for the success of aerobic bioprocesses. In hydrocarbon-based bioprocesses where K _La is depressed at higher viscosities, this is particularly critical. In this study an accessible methodology for K _La 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 K _La values was the incorporation of the response lag. Neglect of the response lag resulted in errors greater than 5% above K _La = 0.3K _p to K _La = 0.6K _p (where K _p is the inverse response lag or probe constant), at least 1.5-fold to 3-fold lower than the analogous K _La in water. Further, K _p varied significantly with both alkane concentration and chain length. A sensitivity analysis confirmed - 25% to 90% error in K _La with 30% over- and under-estimation of K _p respectively. When incorporating K _p values specific to the process conditions, accurate K _La values were confirmed in 0 to 20% (v/v) C _10-13 and C _14-20 aqueous dispersions over 600 to 1200 rpm agitation.