GAS LIQUID MIXING

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Gas - Liquid Oxidative Reactions
Gas - Liquid Oxidative Transformations (with catalyst)
Precipitation of Calcium Carbonate

Scope of Supply:
High Performance Aerators
Defoamers
High Pressure Reactors
Laboratory Pilot Reactors
Process Control Systems

Aerobic fermentations proceed under ideal conditions only if the microorganisms are supplied with sufficient dissolved oxygen in each volume of the fermenter and if the substrate and nutrients are mixed into the fermenting liquid instantaneously and homogeneously. Both requirements are met by a fermentor equipped with a Frings Friborator or TRG system. Both systems utilized rotor-stator designs and are especially useful for fermentation using shear resistant microorganisms and relatively low viscosities.

Friborator
The friborator is a turbine aerator which is flange mounted to the bottom of a fermenter with the motor located underneath. It functions as a blower and a mixer at the same time. The star shaped rotor creates a vacuum behind it's leading edge into which atmospheric air flows from the outside of the fermentor. Multi-speed motors allow the turbine to aspirate at different volumes. Fermenting liquid flows into the open top of the turbine and is mixed with the air before being rapidly expelled through a stator surrounding the turbine. The gas-liquid jets cover the total cross section of the tank, as the air bubbles, with typical diameters of 0.1 - 1.0 mm, rise in the fermenting liquid and mix it well. The quality of the oxygen transfer is equivalent to 45% oxygen utilization in yeast propagation and as much as 75% in vinegar production.

The TRG system
This system is characterized by turbines which turn at 250-400 rpm. The turbines create a low vacuum and the air being mixed into the fermenting liquid may be pressurized slightly before entering the turbine. Using variable frequency drives, the blower speed can be controlled within a range of 50-100%. The TRG system is useful when air flows greater than 3000cbm/h are necessary or when efficient power consumption is important. Air bubble diameters are typically 0.3 - 2.0 mm and oxygen utilization peaks at 30%.