Acoustic Mixing, an Alternative Technology to High Shear Mixing
Traditional high shear mixers are used to impart high shear rates in fluids to create fluid mixing properties that result in very good mixing for many materials that cannot be achieved by conventional impeller mixers. However, high shear mixers, by design, create high shear stresses in the fluids as they normally require rotating parts (impellers, paddles, or screws) that drive materials against a mixing tank wall (that may include baffles or vanes). High shear mixers can also be configured use tightly spaced complex rotor/stator mixing assemblies, which are hard to maintain and may need maintenance (adjustment and/or replacement) due to wear that increases spacing between the rotor and stator. Cleaning of high shear mixer hardware can be both difficult and time consuming. Because of the work imparted by the rotating components in the mix, high shear mixing often results in rapid heating of the materials being mixed. In addition, the high shear caused by the rotating component can cause breakage of the mixed solid particle morphology. Because of the strong forces between the rotating mixer parts and the material being mixed, high shear mixers consume greater amounts of power than ordinary mixers.
Resodyn offers an alternative method to high shear mixers for “emulsifying, homogenizing, dispersing, grinding and /or dissolving immiscible mixtures with components of the same or different phases”.(1) See Figure 1. The Resodyn technology uniquely employees an acoustic field to efficiently mix materials. The acoustic field has been proven to be highly effective for a myriad of hard to mix and high viscosity materials that normally require high shear mixer technology to be mixed.
Rather than use impellers or rotating hardware of any type, the Resodyn technology imparts periodic sound waves from the vessel base and lid into the materials being mixed. These sound waves travel through the materials in the mix vessel at the speed of sound for each material encountered in the vessel. These sound waves impart strong body forces upon the materials in the mix vessel that induce motion between materials of different types that are proportional to the material interfacial properties and the various material densities. These intra-material disturbances result in body forces that cause relative motion between the various materials that enable efficient/effective mixing without the use of rotating parts. The sound field permeates that mix vessel contents rapidly and uniformly to create chaotic motion of the mix materials throughout the entire vessel contents.
The acoustic mixing process is energy efficient, is very rapid (10 to 100 times faster than conventional mixing), typically imparts little heat into the mix, is highly repeatable from mix-to-mix and has the capability to virtually mix any combination of materials. The Resodyn Acoustic mixing technology rapidly mixes materials ranging from 1 cPs to several millions of cPs without the adverse effects caused by high shear mixers.
The Acoustic mixing process scales from bench to commercial batch systems (See Figure 2.) and is also directly scalable to continuous operations (See Figure 3.), all of which can include clean in place capabilities, and having no rotating hardware to clean.
Resodyn Alternative To High Shear Mixing Figures
(1) Taken from the High Shear Mixer Power Page.