CRITICAL-ASSESSMENT OF THE STEADY-STATE NA2SO3 FEEDING METHOD FOR KLA MEASUREMENT IN FERMENTORS

Important aspects of kla measurement in agitated aerated vessels are briefly characterized from the standpoint of reliability of the measured data. It seems that most of the kla data, based on a number of variants of the steady‐state and dynamic methods in noncoalescent liquids, do not have a clear physical meaning, because they are affected by the differences between the actual driving force and the driving force assumed by the model used for its evaluation. A reliability test is given for the Na2SO3 feeding steady‐state method (FSM), by comparing the results of air and pure oxygen absorption in a noncoalescent liquid (0.5M Na2SO4 solution) with the results obtained by the independent pressure step dynamic method (RDM). The RDM is one of a few variants of the dynamic method which gives correct kla data unaffected by nonideal mixing of the gas phase in the reactor. It was found that the FSM yields correct kla values only when pure oxygen is used for absorption. When air is absorbed, the FSM gives kla values in the region of kla > 0.1 s−1 substantially (to 55%) lower than those for pure oxygen absorption. Copyright © 1990 John Wiley & Sons, Inc.