Читать книгу Agitator Design for Gas-Liquid Fermenters and Bioreactors - Gregory T. Benz - Страница 18

It is possible to achieve the same mass transfer rate using a small amount of air and a lot of agitator power, or a lot of air with low agitator power, and an infinite number of steps between.

There are upper and lower airflow limits, however. The minimum airflow is where the OTR is stoichiometrically balanced; that is, the molar flow of oxygen in the incoming air stream exactly matches the molar rate of consumption. In other words, this would require 100% mass transfer. That would require an infinite amount of agitator power!

The upper bound would be when either the vessel or the agitator is flooded. We will define these conditions in Chapters 4 and 8. Suffice it to say for now that there is such a thing as too much airflow.

To keep calculation effort reasonable, the calculations should be performed incrementally: say, starting with 25% more than the minimum and stepping in about 5‐10% increments on that, up to the maximum.

Chapter 8 describes this procedure in detail.