Turbine impeller configurations

Prochazka and Landau [19] developed a mixing time conelation for a single Rushton turbine impeller in a baffled tank in the standard configuration for > 10" ... 

Gas holdup studies in taU vessels including three impeller configurations were reported by Pinelli [51] for (a) three equally spaced Rushton turbines, (b) three A-315 turbines, and (c) one Rushton (bottom) and two A-315 turbines. Holdup was correlated using Equation (9.43), with constants shown in Table 9.12. The units for Pq/V are in W/m, V in m/s, and holdup in volume fraction gas. 

Moucha, T., Linek, V., and Prokopova, E. (2003), Gas hold-up, mixing time and gas-hquid volumetric mass transfer coefficient of various multiple-impeller configurations Rushton turbine, pitched blade and techmix impeller and their combinations, Chemical Engineering Science, 58(9) 1839-1846. 

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. 

Two impellers are included in the reactor configuration shown in Figure 2. A three-bladed turbine with 45° pitch and blades 1/8 in X 5/8 in is mounted on the impeller shaft at the top of the reactor. A three-bladed propeller with 45° pitch is mounted at the bottom of the impeller shaft at approximately two-thirds of the reactor depth. 

It is important to note that the small-scale agitator operations may be described in terms of impeller diameter and agitator speed, while manufacturing process equipment is more conveniently specified by horsepower and fluid velocity. For most standard turbine configurations, power number correlations are available to convert impeller diameter and agitator speed into a horsepower value for given fluid properties. Most laboratory bench equipment is designed to provide a torque measurement that can be readily converted to horsepower directly from the conditions of the pilot batches. 

For the case of equally spaced Rushton turbines in deionized water (fast coalescence), all constants are virtually the same. Power was additive, suggesting that the turbines functioned independently. While there is some variation in K for other configurations, values of a and p are nearly constant. The gas flow constant dominates over power. This is not the case for noncoalescing polyvinylpyrolidone (PVP) and salt-containing solutions. Experiments included one impeller with HIT = 1.0, two impellers with HIT = 2.0, and three impellers with HIT = 3. All impellers were equally spaced. 

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