Fig. 12 Radial (Rushton) type impeller. blade angle, it is best to work closely with the manufacturers of the mixer to specify an optimum design for the process. The preceding discussion of axial- and radial-flow turbines has been a very cur-sory survey of what can be a very involved and detailed study. As mentioned above, a large amount of research on these types of mixers is available [13,14]. A detailed dis-cussion of this subject would be beyond the scope of this work. If a blending or sus-pension problem occurs in large production batches, consultation of the references on mixing included at the end of this chapter or, even better, consulting the experts at the major manufacturers of this type of mixer, would be the best place to start. 3. Anchor Mixers An often overlooked mixing device, which is low speed and considered low capabil-ity, is the anchor agitator, so named for its anchorlike shape, as illustrated in Fig. 13. However, this slowly moving agitator makes it possible for many dispersion and emul-sification processes to be accomplished without overshear, aeration, and heat transfer problems. The anchor agitator is a slow (up to 50 rpm) device whose sole function is to rotate the contents of a batch in a radial direction without providing any significant shear. These are high-torque devices that must be designed sturdily to withstand the forces of the high viscosities. Anchor agitators are typically designed to be able to withstand a maximum viscosity beyond which they might actually bend or break. That is, the an-chor itself is built of materials strong enough to withstand the drag of the viscous liq-uid as it passes by the mixer. In addition, the motor has to supply the very high torque requirement that arises when the anchor is stirring viscous materials. When designing the mixer it is important not to understate the viscosity. This is especially important if there is a point in the process where the anchor must be stopped. If this happens, in the case of shear thinning materials, the agitator has to start up from rest in a viscosity much higher than that normally occurring during the process. Products exhibiting pseudoplastic or Bingham plastic behavior are very difficult to move when at rest.

DOI link for Fig. 12 Radial (Rushton) type impeller. blade angle, it is best to work closely with the manufacturers of the mixer to specify an optimum design for the process. The preceding discussion of axial- and radial-flow turbines has been a very cur-sory survey of what can be a very involved and detailed study. As mentioned above, a large amount of research on these types of mixers is available [13,14]. A detailed dis-cussion of this subject would be beyond the scope of this work. If a blending or sus-pension problem occurs in large production batches, consultation of the references on mixing included at the end of this chapter or, even better, consulting the experts at the major manufacturers of this type of mixer, would be the best place to start. 3. Anchor Mixers An often overlooked mixing device, which is low speed and considered low capabil-ity, is the anchor agitator, so named for its anchorlike shape, as illustrated in Fig. 13. However, this slowly moving agitator makes it possible for many dispersion and emul-sification processes to be accomplished without overshear, aeration, and heat transfer problems. The anchor agitator is a slow (up to 50 rpm) device whose sole function is to rotate the contents of a batch in a radial direction without providing any significant shear. These are high-torque devices that must be designed sturdily to withstand the forces of the high viscosities. Anchor agitators are typically designed to be able to withstand a maximum viscosity beyond which they might actually bend or break. That is, the an-chor itself is built of materials strong enough to withstand the drag of the viscous liq-uid as it passes by the mixer. In addition, the motor has to supply the very high torque requirement that arises when the anchor is stirring viscous materials. When designing the mixer it is important not to understate the viscosity. This is especially important if there is a point in the process where the anchor must be stopped. If this happens, in the case of shear thinning materials, the agitator has to start up from rest in a viscosity much higher than that normally occurring during the process. Products exhibiting pseudoplastic or Bingham plastic behavior are very difficult to move when at rest.

Fig. 12 Radial (Rushton) type impeller. blade angle, it is best to work closely with the manufacturers of the mixer to specify an optimum design for the process. The preceding discussion of axial- and radial-flow turbines has been a very cur-sory survey of what can be a very involved and detailed study. As mentioned above, a large amount of research on these types of mixers is available [13,14]. A detailed dis-cussion of this subject would be beyond the scope of this work. If a blending or sus-pension problem occurs in large production batches, consultation of the references on mixing included at the end of this chapter or, even better, consulting the experts at the major manufacturers of this type of mixer, would be the best place to start. 3. Anchor Mixers An often overlooked mixing device, which is low speed and considered low capabil-ity, is the anchor agitator, so named for its anchorlike shape, as illustrated in Fig. 13. However, this slowly moving agitator makes it possible for many dispersion and emul-sification processes to be accomplished without overshear, aeration, and heat transfer problems. The anchor agitator is a slow (up to 50 rpm) device whose sole function is to rotate the contents of a batch in a radial direction without providing any significant shear. These are high-torque devices that must be designed sturdily to withstand the forces of the high viscosities. Anchor agitators are typically designed to be able to withstand a maximum viscosity beyond which they might actually bend or break. That is, the an-chor itself is built of materials strong enough to withstand the drag of the viscous liq-uid as it passes by the mixer. In addition, the motor has to supply the very high torque requirement that arises when the anchor is stirring viscous materials. When designing the mixer it is important not to understate the viscosity. This is especially important if there is a point in the process where the anchor must be stopped. If this happens, in the case of shear thinning materials, the agitator has to start up from rest in a viscosity much higher than that normally occurring during the process. Products exhibiting pseudoplastic or Bingham plastic behavior are very difficult to move when at rest.