Large scale fermenters are used to make such products as yeast, vitamin C, xantham-gum, citric acid, penicillin, and other products. Fermentations are usually carried out in tall vessels with multiple impeller systems.
Air is sparged in at the bottom, to provide the micro-organisms with oxygen.
It is important that the mixer disperse the gas into fine bubbles, to ensure good mass transfer from the air to the broth. The example here shows a drawing of a fermenter, the velocity magnitude around the cooling coils, and finally the results of a gas dispersion simulation, including mass transfer. The vessel has no baffles, but is equipped with twelve sets of eight cooling coils, that also act as swirl reducing baffles. This image shows the velocity magnitude in four cross sections. From top left to bottom right, at 0.8, 0.6, 0.4, and 0.2 fraction of the liquid level off the bottom.