Anchor impeller

Anchor impeller Anchors Anchovy Ancovemn [88201-41-6] Ancymidol... 

FIG. 18-43 Power numbers for anchor impellers typical two-arm impeller anchors 95 percent of tank diameter T and 90 percent of T three-arm impeller anchors 95 percent of T and three-arm impeller anchors 90 percent of T, similar to two-arm impeller that anchors 95 percent of T. 

It has to be mentionned that a two-dimensional flow model has been developped by Hirose and Murakami to calculate the power consumption in vessels equipped with paddle impeller, anchor, gate, helical ribbon or helical screw [5]. This approach is interesting because a single unified correlation is able to cover both straight and helical blades, but it suffers from an unavoidable complexity. 

Bertrand, J. and J.P. Couderc, Agitation of Pseudoplastic Fluids by Two-Blade Impellers, Anchors and Gate-Agitators , Can. J. Chem. Eng. 60, 738-744 (1982). 

Pig. 13. Blending quaHties with different impellers (A, turbines B, anchors C, heHcals) for different viscosity ranges. 

Close-Clearance Impellers There are two close-clearance impellers. They are the anchor impeller (Fig. 18-6) and the helical... 

Close-Clearance Stirrers For some pseiidoplastic fluid systems stagnant fluid may be found next to the -essel walls in parts remote from propeller or turbine impellers. In such cases, an anchor impeller maybe used (Fig, 18-6), The fluid flow is principally circular or helical (see Fig, 18-7) in the direction of rotation of the anchor. Whether substantial axial or radial fluid motion also occurs depends on the fluid iscosity and the design of the upper blade-supporting spokes. Anchor agitators are used particularly to obtain irnpro ed heat transfer in high-consistency fluids,... 

Suspensions of fine sohds may have pseudoplastic or plastic-flow properties. When they are in laminar flow in a stirred vessel, motion in remote parts of the vessel where shear rates are low may become negligible or cease completely. To compensate for this behavior of slurries, large-diameter impellers or paddles are used, with (D /Df) > 0.6, where Df is the tank diameter. In some cases, for example, with some anchors, > 0.95 Df. Two or more paddles may be used in deep tanks to avoid stagnant regions in slurries. 

Additional power data for other impeller types such as anchors, cui ved-blade turbines, and paddles in baffled and unbaffled vessels are available in the following references Holland and Chapman, op. 

A basic stirred tank design is shown in Fig. 23-30. Height to diameter ratio is H/D = 2 to 3. Heat transfer may be provided through a jacket or internal coils. Baffles prevent movement of the mass as a whole. A draft tube enhances vertical circulation. The vapor space is about 20 percent of the total volume. A hollow shaft and impeller increase gas circulation (as in Fig. 23-31). A splasher can be attached to the shaft at the hquid surface to improve entrainment of gas. A variety of impellers is in use. The pitched propeller moves the liquid axially, the flat blade moves it radially, and inclined blades move it both axially and radially. The anchor and some other designs are suited to viscous hquids. 

FIG. 23-30 Basic stirred tank design and selected lands of impellers, (h) Propeller, (c) Turbine, (d) Hollow, (e) Anchor,... 

Slow speed close-clearance impellers are used when mixing high viscosity materials. Helical or anchor type close-clearance impellers are used in this application at speeds from 5 to 20 rpm. Table 1 compares the pow er required and cost for conventional axial flow turbines and the helical type. 

Rakes, Gates Spirals, Anchors, Paddles Propellers Axial Flow Turbines Flat Blade Turbine Bar Turbine Bladeless Impeller Close Clearance Impeller and Stator... 

Figure 5-39. Close-clearance anchor and helical impellers. By permission, Oldshue, J. Y., Fluid Mixing Technology, 1983, Chemical Engineering McGraw-Hill Publications Co., Inc. [29].

Anchor impeller 22in. Diam. Tank and liquids like above 0.5 up to Nr, = 300 22... 

External jackets, 326-328 Helical coils, 312, 326, 327 Vertical coils, 326, 327 Mixing impellers, 290-297 Anchor, 290-329 Blending, 324, 326 Characteristic curves, 306 Chart to examine turbine applications, 296 Efficiency of propellers, 299 Flow of propellers. 298, 299 Flow patterns, 309-312 Gas-Liquid contacting, 324, 326 General list impellers, 291 Helical, 290, 329 Liquid-liquid dispersion, 326 Multiple, 297... 

This procedure can be repeated for different values of N. A compilation of the experimental values of ks for a variety of impellers, turbine, propeller, paddle, anchor, and so on, has been given by Skelland(16), and an examination of Table 7.1 suggesLs that for pseudo-plastic liquids, ks lies approximately in the range of 10-13 for most configurations of practical interest/22 231 SKELLAND l6) has also correlated much of the data on the agitation of purely viscous non-Newtonian fluids, and this is shown in Figure 7.8. 

Figure 7.20 shows some of the impellers which are frequently used. Propellers, turbines, paddles, anchors, helical ribbons and screws are usually mounted on a central vertical shaft in a cylindrical tank, and they are selected for a particular duty largely on the basis of liquid viscosity. By and large, it is necessary to move from a propeller to a turbine and then, in order, to a paddle, to an anchor and then to a helical ribbon and finally to a screw as the viscosity of the fluids to be mixed increases. In so doing the speed of agitation or rotation decreases. 

Figure 7,20. Commonly used impellers (a) Three-bladed propeller ( >) Six-bladed disc turbine (Rushton turbine) (c) Simple paddle (d) Anchor impeller (e) Helical ribbon (/) Helical screw with draft tubs...

The time required to pass through the high shear zone will be proportional to the volume of the vessel divided by the flow from the turbine. This will be porportional to 1/ND. With a turbine in turbulent flow, turnover is relatively rapid and all the fluid will pass through the impeller region in a relatively short period of time. The flow regime in an anchor or helically agitated vessel can be inferred from the flow studies by Smith and Peters (], 13j. These indicated... 

This formula also leads to good clustering of the results of the measurements for disc impellers (see Fig. 6) and for the other radial-flow impellers such as paddle and anchor impellers (see Fig. 7). Unsatisfactory correlation is found especially for axial-flow impellers, which show a systematic downward deviation in Fig. 7. 

For turbine agitators, impeller to tank diameter ratios of up to about 0.6 are used, with the depth of liquid equal to the tank diameter. Baffles are normally used, to improve the mixing and reduce problems from vortex formation. Anchor agitators are used with close clearance between the blades and vessel wall, anchor to tank diameter ratios of... 

The impeller is the part of the agitator that impacts force to the material being mixed. Propellers, turbines, gates, anchors, and paddles are all types of impellers. Typically, the impeller is a single propeller or turbine blade connected to a shaft that is driven by an electric motor at a fixed speed. There are two classes of impeller agitators axial-flow and radial-flow, and the mixing characteristics are shown in Figure 3.14. 

Some fermentation broths are highly viscous, and many are non-Newtonian liquids that follow Equation 2.6. For liquids with viscosities up to approximately 50 Pa s, impellers (Figure 7.7a-c) can be used, but for more viscous liquids special types of impeller, such as the helical ribbon-type and anchor-type, are often used. 

Gate and anchor impellers, long used advantageously for the mixing of vis-... 

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