Blender high shear

Convection blenders reorient groups of particles in relation to one another as the result of mechanical movement, for example, caused by a paddle or a plow. As a result, circulation patterns result in this type of blenders. Subclasses of convection blenders are typically defined by vessel shape and impeller geometry. Ribbon blenders (Fig. 30), planetary blenders (Figs. 31 and 32), orbiting screw blenders (Fig. 33) are examples of convection blenders. High shear mixers comprise another sub-class of convection blenders that will be discussed separately. 

Although there is no official ASTM test to measure the water handling properties of gasoline, there are a number of widely used industry tests. One uses a Waring Blender to simulate high shear (57), whereas another uses a wrist action shaker to simulate mild shear conditions (58). 

Figure 6. Effect of curing time on Marshall stability for mixes with sulfur-extended binders prepared in high-shear blender ana by aggregate shear...

A vertical helical ribbon blender can be combined with an axial screw of smaller diameter (Fig. 18-25). Such mixers are used in polymerization reactions in which uniform blending is required but in which high-shear dispersion is not a factor. Addition of the inner flight contributes little more turnover in mixing newtonian fluids but significantly shortens the mixing time in nonnewtonian systems and adds negligibly to the impeller power [Coyle etal.. Am. Inst Chem. Eng.J., 15, 903 (1970)]. 

To evaluate the impact of the blending conditions, a low-shear blender (Turbula) and a high-shear blender (Henschel-type) were used to blend toner particles with silica. Typical loading rates of silicas onto toner varied between 0.2 and 2.0 wt%. For our study the loading was 0.5 wt% silica. 

Alternately, instead of using shear in the blender, deagglomeration can be achieved outside the blender, such as milling and/or screening of the blend. Although this requires additional transfer steps and equipment, it may be the only option if blenders with high shear are not available. 

High shear blenders Horizontal high intensity mixers (side driven) Vertical high intensity mixers (top or bottom driven)... 

Tumble blenders also impart shear forces to the powders being blended as slip planes form between the walls of the blender and layers of the blend. The amount of shear force is often low for small-scale blenders, but can increase with increasing scale of the blending container. Because they tend to provide gentler blending and have less of an affect on the particle size of the materials being blended (compared to high shear mixers),... 

Despite their insubstantial nature, plant materials are also subject to contamination by sample containers and milling equipment. Paper sample bags may act as sources of contamination including boron (Standing Committee of Analysts 1986). Normally, vegetation is comminuted in high shear cyclone mills or blenders fitted with stainless steel or titanium-coated blades. As with other more resistant materials the amount of contamination from the mill can be related to the abrasiveness of the sample (Allan etal. 1999). 

Bottle shaking can be used to generate foam under conditions of relatively low shear (44), and a blender can be used (at about 8000 rpm) to generate foam under conditions of very high shear (45). 

Fig. 11.13 Photograph of different tumble/growth agglomeration work modules that are attached to the all purpose drive stand of Fig. 11.12. (a) disc or pan agglomerator (b) coating pan (c) bowl blender (d) planetary bowl blender (e) double cone blender (f) cube mixer (g) high shear mixer (h) pug mill/kneader (courtesy Erweka, Heusenstamm, Germany).

---