Fig. 1 Marine-type propeller. (From Ref. 8.) blending results. Depending on the depth of the vessel, a second propeller may be re-quired. Side-entry mixers normally provide good pumping action with a low initial cost. However, they are not currently in great demand in the pharmaceutical industry since they require an in-product seal mechanism that can be avoided with the top-entering designs. For blending applications in larger batches over 500 gal. marine propeller mix-ers are no longer the optimum choice. Turbine agitators that operate in the 20-120 rpm range are best for a good combination of low-shear mixing and lowest initial cost. These types of mixers should be installed on the centerline of tanks. To prevent vortexing and to optimize mixing, the vessel should be equipped with four vertical baffles that are 1/ 12 the diameter of the vessel. For miscible-liquid blending and also solids-suspension

doi:10.1201/9781420000955-36

Chapter

Fig. 1 Marine-type propeller. (From Ref. 8.) blending results. Depending on the depth of the vessel, a second propeller may be re-quired. Side-entry mixers normally provide good pumping action with a low initial cost. However, they are not currently in great demand in the pharmaceutical industry since they require an in-product seal mechanism that can be avoided with the top-entering designs. For blending applications in larger batches over 500 gal. marine propeller mix-ers are no longer the optimum choice. Turbine agitators that operate in the 20-120 rpm range are best for a good combination of low-shear mixing and lowest initial cost. These types of mixers should be installed on the centerline of tanks. To prevent vortexing and to optimize mixing, the vessel should be equipped with four vertical baffles that are 1/ 12 the diameter of the vessel. For miscible-liquid blending and also solids-suspension

Chapter

Fig. 1 Marine-type propeller. (From Ref. 8.) blending results. Depending on the depth of the vessel, a second propeller may be re-quired. Side-entry mixers normally provide good pumping action with a low initial cost. However, they are not currently in great demand in the pharmaceutical industry since they require an in-product seal mechanism that can be avoided with the top-entering designs. For blending applications in larger batches over 500 gal. marine propeller mix-ers are no longer the optimum choice. Turbine agitators that operate in the 20-120 rpm range are best for a good combination of low-shear mixing and lowest initial cost. These types of mixers should be installed on the centerline of tanks. To prevent vortexing and to optimize mixing, the vessel should be equipped with four vertical baffles that are 1/ 12 the diameter of the vessel. For miscible-liquid blending and also solids-suspension

ABSTRACT

When the viscosity of the process exceeds 50,000 centipoise, turbine and propeller mixers are rarely able to provide the pumping action necessary for good blending. It is at this point that a number of other mixing problems may arise, as for example, an excessively long residence time of the product near the heat transfer surfaces. If the product remains close to the heating jacket of the vessel, product degradation could occur. Consequently, for the higher viscosity type of products, even slower and wider blade devices, such as anchor agitators, are best employed. These operate as large paddling mixers that actually push the product around the blending tank.