Mixer rotating-blade

High-Speed Mixers High-speed mixers include continuous-shaft mixers and batch high-speed mixers. Continuous-shaft mixers have blades or pins rotating at high speed on a central shaft. Both horizontal and vertical shaft designs are available. Examples include the vertical Schugi mixer (Fig. 20-84) and the horizontal pin or peg... 

Both PEPT and PET have been used extensively in studies of solids mixing, in devices ranging from rotating vessels, such as kilns and V-mixers, to bladed mixers with both horizontal and vertical axes. 

Intimate mixing is accomplished in change-can mixers in two ways. One method is to have the mixing-unit assembly revolve in a planetary motion so that the rotating blades sweep the entire circumference of the can (Fig. 18-39). The other is to mount the can on a rotating turntable so that all parts of the can wall pass fixed scraper blades or the agitator blades at a point of minimum clearance. 

The major droplet disruption occurs in the immediate vicinity of the rotating blades where shear forces are highest, e.g., due to the presence of Taylor vortexes. The effectiveness of droplet disruption depends on the geometry of the mixer and the rotational speed of the blades. Operational parameters include blade and vessel geometries and rotation speed of blades. 

Anchor Mixers Anchor mixers are the simplest and one of the more common types of high-viscosity mixers (Fig. 18-42). The diameter of the anchor D is typically 90 to 95 percent of the tank diameter T. The result is a small clearance C between the rotating impeller and the tank wall. Within this gap the fluid is sheared by the relative motion between the rotating blade and the stationary tank wall. The shear near the wall typically reduces the buildup of stagnant material and promotes heat transfer. To reduce buildups further, flexible or spring-loaded scrapers, typically made of polymeric material, can be mounted on the rotating blades to move material physically away from the wall. 

Anchor mixers may be used in combination with other types of mixers, such as turbine mixers, high-shear mixers, or rotor-stator mixers, which were described in the previous subsection. Such mixers can be placed on a vertical shaft midway between the anchor shaft and blade. A secondary mixer can promote top-to-bottom motion and also limit bulk rotation of the fluid. A stationary baffle is sometimes placed between the anchor shaft and rotating blade to limit fluid rotation and enhance shear. 

Pan mullers are the modern industrial equivalent of the traditional mortar and pestle. Typical mullers have two broad wheels (Ml and M2) on an axle (Fig. 18-54). The mixer rotates about the approximate midpoint of the axle, so that the wheels both rotate and skid over the bottom of the mixing chamber (A). Plow blades (PI and P2), which rotate with the mixer, push material from the center (T) and walls (C) of the mixing chamber into the path of the rollers. The mixing action combines both crushing and shearing to break lumps or agglomerates and evenly distribute moisture. 

In a 500 mL mixer with counter-rotating blades, sucrose (100 g), base, soap and 0-20 mL of water were mixed together at 75-100 °C for 1 h. The mixture was dried under vacuum for 30-60 min and then melted methyl palmitate was added. The mixture was allowed to react under vacuum at 125-135 °C, for 3-8 h. 

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