Liquid Mixer Design

Liquid-Liquid Mixer Design Many different types of impellers are used for liquid-liquid extraction, including flat-blade and pitched-blade turbines, marine-type propellers, and special pump-mix impellers. With pump-mix designs, the impeller serves not only to mix the fluids, but also to move the fluids through the extraction stages of a mixer-settler cascade. The agitated vessel should be baffled if the vessel is operated with a gas-liquid surface, to avoid forming a vortex. As noted earlier in reference to Eq. (15-172), baffles are not needed if the vessel is operated with the liquid full [Weinstein and Treybal, AIChEJ., 19(2), pp. 304-312 (1973)]. 

During liquid makeup produetion, eolor pigments (i.e., solid having identieal partiele size) are added to the produet via a mixer. In the pilot plant, this mixer runs at 6,700 rpm and has a diameter head of 0.035 m. Full-seale produetion is geometrieally similar and has a mixer head diameter of 0.12 m. Determine the speed of the full-seale produetion mixer head. What additional information is required for the motor to drive this mixer Assume that power eurves are available for this mixer design, and the seale-up basis is eonstant power/unit volume. 

The earliest agglomeration equipment consisted simply of solid-liquid mixers and, in common with newer designs, provided the mechanical means by which particles were brought into contact and densified into larger entities as the cohesive forces came into operation. Various other types of equip-... 

After the precise formulation of the liquid product constituents has been prepared, the constituents are manually added to a liquid mixer. This type of mixer is simpler in design than dry product mixers and more closely resembles a large drum with impeller blades. 

Control of Precipitate Formation. The problem with the character of the precipitated HML proved to be easily resolved with the particular lignin under study. When the addition of the glacial acetic acid was carried out at temperatures only as high as 50 °C, the reaction product was granular and did not retain large quantities of water in a semisolid mass. However, this condition required a redispersion of the solid after the oxalic acid catalyst had been added. This could be accomplished with mixers designed to homogenize and disperse materials in liquids. 

Fig. 7.7 Liquid requirements for obtaining the specific saturation levels S as defined by the energy consumption curve in Fig. 7.5 for different mixer designs [B.42, 7.4]. o Intensive, high energy mixer with vertical axis of rotation of the mixing tools (Mfg. DIOSNA). Intensive, high energy mixer with horizontal axis of rotation of the mixing tools (Mfg. LODIGE). Low shear planetary mixer (Mfg. LOEPTHIEN).

As indicated in section 1.1, mixing is carried out usually to reduce inhomogeneities, especially in the mixing of particulate solids, or to enhance a rate process, particularly in mechanically agitated vessels. An understanding of the way that the solids and liquids move to achieve these requirements is an essential prerequisite for a successful mixer design or selection. The different forms of movement constitute the mechanisms of mixing. 

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