Impellers side-entering

Axial-tlow impellers rnav also be mounted near the bottom of the cylindrical wall of a cssel as shown in Fig, 18-10, Such side-entering agitators are used to blend low- iscositv fluids [<(), Pa-s (100 cP)] or to keep slowly settling sediment suspended in tanks as large as some 4000 rn (1(P gal). Mixing of paper pulp i.s often carried out by sideentering propellers. 

Side-Entering Impellers For vessels greater than 4 m (1000 gal), a side-entering propeller agitator (Fig. 18-9) mav be more economical than a top-mounted impeller on a centered vertical shaft. 

For turbine mixers that the width of a baffle should not exceed more than one-twelfth of the tank diameter and, for propeller mixers, no more than one-eighteenth the tank diameter. With side-entering, inclined or off-center propellers, as shown in Figure 13, baffles are not required. Instead, shrouded impellers and diffuser rings may be used to suppress vortex formation. These devices contribute to flow resistance and reduce circulation by creating intense shear and abnormal turbulence... 

Side-entering wide blade impeller (HE3-S or Mark II)... 

The top entering mixer units are better for producing flow at constant power than the side entering units [29]. The radial flow impellers require more horsepower when compared to the marine impellers. 

For side entering horizontal mixers not limited to blending operations, there are some differences in recommendations concerning the physical location of the impeller ... 

This type normally has a long cylindrical impeller having a relatively large number of shallow forward-curved blades. Due to the shape of the casing surrounding this impeller, air enters all along one side of the cylindrical surface of the impeller and leaves on another side. Static efficiency is typically 40-50 per cent. 

Side-entering wide blade impeller (HE3-S or Mark II) Oil storage. Paper pulp. Wastewater circulation. Flue gas desulphurisation... 

For vessels greater than 38 m (10,000 gal), the economic attractiveness of side-entering impellers increases. For vessels larger than 380 m (100,000 gal), units may be as large as 56 kW (75 hp), and two or even three may be installed in one tank. For the suspension of slow-settling particles or the maintenance of uniformity in a viscous slurry of small particles, the diameter and rotational speed of a sideentering agitator must be selected on the basis of model tests or experience with similar operations. 

Examples of axial impellers are marine propeller and pitched blade turbine, shown in Fig 7.2. A three bladed marine t3rpe propeller is similar to the propeller blade used in driving boats. The propeller can be a side entering type in a tank or be clamped on the side of an open vessel in an off-center position. Axial flow impellers are used in blending and mixing of miscible liquids. 

BLENDING OF MISCIBLE LIQUIDS. Miscible liquids are blended in relatively small process vessels by propellers or turbine impellers, usually centrally mounted, and in large storage and waste-treatment tanks by side-entering propellers or jet mixers. In a process vessel all the liquid is usually well agitated and blending is... 

Impellers usually enter the vessel from the top however, very large or novel vessels find it useful for the impeller to enter from the bottom or side (Hamby et al.. 

The power number of side-entering propellers depends on the impeller Reynolds number and the pitch. The propeller pitch is defined as the distance traversed by the propeller in one revolution divided by the diameter. For a square pitch (pitch = 1.0), this distance is equal to the diameter. As shown in Figure 6-19, Np is higher for higher-pitch propellers at all values of Re. 

Bakker, A., and J. B. Fasano (1993). A computational smdy of the flow pattern in an industrial paper pulp chest with a side entering impeller, in Process Mixing Chemical and Biochemical Applications, Part n, G. B. Tatterson, R. V. Calibrese, and W. R. Penny, eds., AIChE Symp. Ser., 293(89), 118-124. 

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