GAS LIQUID MIXING

The dispersion of gasses in liquids is a standard operation in chemical and biological process technologies. The requirements of the process and equipment applied are complex and characterized by such limiting factors as high pressures and temperatures, aggressive media, or systems which require special hygienic standards. Simultaneously, extremely high aeration rates plus a homogeneous dispersion of reactants, and a high degree of efficiency must be realized.

Frings offers many years of experience in the field of gas-liquid-reactions, especially with regard to the food industry and in special sectors of the chemical industry. Success in these markets can be realized by the application of highly sophisticated processes and equipment.

An alternative technology to the traditional sparger aeration systems, is the dynamic Frings aeration system. It auto-aspirates the air or takes it up in a pre-compressed form. By continuous research and development work Frings has achieved high oxygen transfer rates and maximum yields with optimum mixing results and low energy and maintenance costs.

The Frings reactor technology is applied successfully in the most diverse fields of chemical and microbiological industries:

• Fermentation processes, e.g. production of vinegar or yeast
• Oxidation plants, e.g. desulfurization of highly contaminated waste water
• Tetraline-tetralone-oxidations
• Neutralizations with CO2 or flue gas
• Ozonation processes for drinking water disinfection
• Precipitation of calcium carbonate by CO2

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 fermenter. 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%.

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