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EDITOR'S NOTE: The questioner offered additional information, to which our expert offered this additional advice:
This question and answer are quite different, once the objective of the mixing is clear. The need for a vortex, based on this description is still irrelevant. The amount of additional surface area provided by a vortex is inconsequential by comparison with the surface renewal provided by turbulent mixing. 1) The following are recommendations for the mixers: First container - Height 2.25 meters, Diameter 1.5 meters top and bottom, 2 meters center, barrel shaped, 4 baffles 0.15 meters wide, contoured to vessel shape, mounted about 0.01 meters off the wall.Impeller - pitched-blade turbine, 4 blades, 45 degree angle, pumping downward 0.6 meters in diameter, 0.12 meter wide blades, 0.1 meters off the bottom. Rotational speed 2.08 rps (125 rpm) with a 3.7 kW motor. Second container - Height 1 meter, Diameter 0.5 meters top and bottom, 0.6 meters center, barrel shaped, 4 baffles 0.04 meters wide, contoured to vessel shape, mounted about 0.005 meters off the wall.Impeller - pitched-blade turbine, 4 blades, 45 degree angle, pumping downward 0.25 meters in diameter, 0.05 meter wide blades, 0.04 meters off the bottom. Rotational speed 5.8 rps (350 rpm) with a 0.75 kW motor. 2) No known variable speed drive specifically programmed for liquid level feedback control. A programmed logic controller (PLC) with a liquid level sensor could be programmed to provide a form of feedback control. Control logic would have be developed to match surface motion and mixing intensity. Manual adjustment or incremental adjustment to liquid level could be more practical. 3) Baffle recommendation is included in the answer to question 1). Standard baffles are 4 at 90 degrees around the vessel, approximately 1/12 the tank diameter and spaced a small distance from the vessel wall.