I have been working on cell cultures in stirred tank reactors. I want to know how to calculate the kLa (oxygen mass transfer coefficient) in such cases where we are growing cells inside the reactor at different air flow rates and agitation rates. As far as air-water system is concerned it is very simple, because their is no consumption of oxygen inside the reactor. Can anybody let me know if anyone is working in this field.
Years ago, I have studied energetic optimization and adaptive control of dissolved oxygen concentration in aerobic fermenters. I was able to estimate the parameters of the usual KLa correlation (on-line and on real-time) through recursive least squares with forgetting factor.
Cf. C.M.G.A. Queirós, "Controlo do Oxigénio Dissolvido em Fermentadores para Minimização de Energia Consumida", MSc Thesis, Instituto Superior Técnico, Universidade Técnica de Lisboa (Lisbon), 1997 (in Portuguese).Thesis Controlo do Oxigénio Dissolvido em Fermentadores para Minimi...
Hi Carlos,
Thank you for your reply. I am sorry I can't understand this language in which the thesis is written. Do you have its English version.
Regards,
Sohail
I think you can do the same experiments on sulfite solution and determine KLa. In this case dissolved oxygen is zero.
Dear Sohail, we had some discussion on this subject before. The common dynamic approach is to stop oxygenation (stop aeration or shift oxygen content of injected gas to zero) for a short time. During that time there is only consumption, the rate of which can be deduced from the measurements. After starting again the 'standard' curve, close to exponential, results of which kla can be deduced. However, the dynamic method is not very accurate, even mire in this case.
Better is to use the stationary method, in which, besides liquid oxygen concentration, oxygen offgas concentration is measured. Next use also the gas phase balance. But it is a more expensive method...
Numerous people are working on the subject or at least use a descibed method in even more papers. What do you actually want to know?
Why is the dynamic method not very accurate? Why does it not give same result as the stationary method?
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