Fermentation is a natural process which transforms matter through the use of bacteria (for example, transforming sugar into alcohol). This method is used to industrially produce substances such as vitamins.
Fermentation processes may occur anaerobically (without air) or aerobically (with air injection).
Anaerobic processes do not require specific agitation, due to the absence of contamination at the shaft sealing.
Aerobic processes require a particular form of agitation, as the bacteria must be fed with air and nutrients. They release waste to be neutralized and CO2, and produce heat for extraction.
The most important step in the process is the dispersion of air, creating fine bubbles that provide a large interfacial area of exchange with the liquid.
The bubbles coalesce at different rates depending upon the nature of the medium, and rise to the surface with a weak gas-liquid exchange.
Finally, the homogenization is disrupted by the presence of gas by modifying the apparent viscosity and density.
Agitation should allow for good dispersion of the gas mixture throughout the bulk.
Gas dispersion is created by a turbine with radial blades, assisted by a disk (in a design similar to the Rushton variety of turbines) for retaining the gas. Its sizing is not standardized as it is determined by the shear rate of the bubbles and excessive gas flooding of the turbine.
Homogenization is carried out by a methodical axial flow using propellers, as proper distribution of nutrients and correction of ammonia pH are essential to the process.
The tanks are normally tall in proportion to their width, and several propellers are needed to ensure a homogeneous distribution of additives and air.
Milton Roy Mixing has developed a series of turbines dedicated to dispersion of gas. If the Rushton form of turbine—one equipped with a disk—is used, the characteristics of blades (such as number or height) are not suitable for modern methods of fermentation, where oxygen demand is crucial.
Accurate sizing often requires assessment of oxygen transfer (Kla), power (kW/m3), and gas flow. Determining which turbine is most appropriate for the application requires more parameters than diameter and rotation speed.
Milton Roy Mixing offers the right turbine to meet the three parameters listed above, regardless of values. We have the ability to vary geometric parameters such as width and number of blades.
This flexible solution is not limited by the size of the bioreactor. Dozens of blades are an available option if circumstances require them, and scaling down to pilot fermenters is simple.
VDA mixers are direct driven mixers at 1500 rpmn.
VRH mixers are suitable for a lot of applications as: Water treatment: Homogenization, additive preparation, sludge suspension, flash mixing … ● And applications as Chemical Ind., consumable product (paint,ink,detergent...) and additive preparation in any Ind. For operations as: -dissolution -heat transfer -solid suspension -storage -...
Applications of VRP agitators include the blending of liquids as additives in water or oil, keeping solids such as lime in suspension, dissolving powders such as salts, heating liquids before reaction, cooling the bulk before conditioning, neutralization of waste, and additive makeup.
Applications of FRH agitators include flocculation process in water treatment for potable water (such as treatment of waste water), or any agitation operation requiring low rotation speed.