Mixing multiple impellers

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... 

Dohi N., Matsuda Y., Itano N., Shimizu K., Minekawa K., Kawase Y., Mixing in multiple-impeller stirred tank reactors with boiling liquids, Can. J. of Chem. Eng. Ottawa 77 (1999) 5,... 

Selection of a mixing configuration can be complex. The relationship between the open mixing impeller and its position in a mixing vessel is critical to process results. The proximity of the impeller or multiple impellers to the tank bottom, liquid surface, and tank wall can have a dramatic effect on the flow pattern and shear distribution in the tank. The placement of an inlet feed can affect the inlet dispersion and also greatly influence the yield. 

Montante, G., Micale, G., Brucato, A., and Magelli, F., CFD Simulation of Particle Distribution in a Multiple-Impeller High-Aspect-Ratio Stirred Vessel . Proceedings of the 10th European Conference on Mixing, Delft, Netherlands, 125-132 (2000). 

Y.Q. Cui, R.G.J.M. Van der Lans, HJ. Noorman, and K.C.A.M. Luyben. Compartment mixing model for stirred reactors with multiple impellers. Transactions of IChemE, 74 261-271,... 

Modern reactors are made of stainless steel and have capacities up to as much as 180 m (50,000 U.S. gal.). Designs vary, and include top and bottom entry stirrers and multiple impellers. Agitation of the reaction mixture must be given serious attention since many monomers are less dense than water while their polymers are more dense. The mixing systems must then pull monomer down from the surface of the charge and lift polymer olT the floor of the reaction vessel. 

Many types of multishaft mixers do not require planetary motion. Instead the mixers rely on an anchor-style impeller to move and shear material near the tank wall, while another mixer provides a different type of mixing. The second or third mixer shafts may have a pitched-blade turbine, hydrofoil impeller, high-shear blade, rotor-stator mixer, or other type of mixer. The combination of multiple impeller types adds to the flexibility of the total mixer. Many batch processes involve different types of mixing over a range of viscosities. Some mixer types provide the top-to-bottom motion that is missing from the anchor impeller alone. 

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