Mixer, dynamic

Dynamic mixers are a class of secondary mixers where part of the mixing device is aiiowed to move reiative to the barrei and screw surfaces or has an active channei positioned in the barrei waii. In generai, these mixers provide improved mixing over traditionai secondary mixers, but they are more compiicated and costiy to produce, require higher maintenance ieveis, and tend to have higher ieveis of wear. 

In these cases, mixing is preferably carried out by means of a stirrer. Since here, 

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A model of blending aqueous salt buffers for chromatography has been developed.1 The model assumed full miscibility, low mixing enthalpy and low volume change. It reproduced experimental S-curves of buffer strength produced by a Pharmacia P3500 dual piston system equipped with a model 24 V dynamic mixer with 0.6 mL internal volume as well as those produced by a BioSepra ProSys 4-piston system equipped with two dynamic mixers of 1.2 mL internal volume. 

Figure 8.30 Cross-sectional views [53] of the extrudate samples using a conventional screw with segmented tip for the testing of different types of dynamic mixers a) conventional screw with no mixer, b) Twente Mixing Ring, and c) Barr Fluxion ring mixer. The extruder was operated at a screw speed of 80 rpm and a letdown ratio of 220 1 of a white pigmented ABS resin to a black color concentrate...

High-intensity inline devices are often used to mix fluids in the process industries. Such devices include simple pipes, baffled pipes, tees, motionless mixers, dynamic mixers, centrifugal pumps, ejectors, and rotor/stator mixers. In addition to their traditional application in physical processes such as mixing and dispersion, such devices can provide very effective environments for mass transfer and chemical reaction to take place. Furthermore, combining effective inline mixing with heat transfer is the basis of combined heat exchanger reactors (HEX reactors). 

Fig. 2.15. Schematic automated isocratic and gradient elution nemo-liquid chromatograph/ capillary electrochromatograph according Alexander et al. (reproduced from Ref. [44] with permission of the publisher). 1, high-voltage power supply (negative polarity) 2, platinum electrode 3, outlet reservoir vial 4, UV detector with on-column flow cell 5, nanocolumn 6, two-position switching valve 7, jack stand 8, fused-silica make-up adapter (split device) 9, ground cable 10, internal loop micro-injection valve 11, plexiglas compartment 12, autosampler 13, dynamic mixer 14, micro-LC pumps.

Mixing operations can be performed in a number of static and dynamic devices, e. g., in static mixers, kneaders, or twin screw extruders [1]- Extruders belong to the group of continuous dynamic mixers. 

The synthesis of siloxane-urea block copolymers can be performed either in solution or in the melt at elevated temperatures up to 200 °C. We favor the use of dynamic mixers or extruders to ensure intensive mixing of the components. Surprisingly, adding aminosiloxane and isocyanate to get the block copolymers (2K process) is not the only possibility. We can also add the silanol fluid, the cyclic aminosilane, and the diiosocyanate consecutively to the extruder for a successful solventless preparation of siloxane-urea block copolymers (3K process). 

In low-pressure casting, static or dynamic mixers are employed and the pumping systems are set up to compensate for polymerization shrinkage by packing the mold with additional material. Thus, a solid part can be produced. 

In many instances, one wishes to produce solid parts so as to maximize the toughness of the product. In some cases, the economics of the busines will not permit the high cost and process sophistication of reaction injection molding equipment. Low-pressure casting is then the process of choice. Casting machine prices are usually 20 to 50% of those of RIM machines. They are typically smaller and simpler machines. They use static or dynamic mixers rather than impingement mix heads. 

Solvent Mixing. During gradient operation, the HPLC solvents that comprise the mobile phase must be mixed adequately, most commonly with either a static or dynamic mixer. Static mixers rely on laminar-flow dynamics, whereas dynamic mixers use magnetic stirrers. Solvent viscosity affects mixing characteristics inadequate mixing is detected by many UV detectors and may be expressed as an unstable baseline. 

Controlled Deformation Static or Dynamic MIxers/Reactors... 

Bourne, J.R. and J. Garcia-Rosas (1984). Rapid mixing and reaction in a Y-shape in-Une dynamic mixer. Paper 52c, presented at AIChE annual meeting, San Francisco, November. 

Their advantage compared with stirrers (the dynamic mixers) are utilization in a wide viscosity range, narrow residence time spectrum, easy insertion in the existing pipe system, often no extra space requirements, negligible maintenance and minimal wear, low investment and low operating costs [416],... 

In the continuous process, most mixing operations are achieved with static mixers only highly viscous or difficult materials are mixed with dynamic mixers. 

In industrial practice, commercial liquid detergent manufacturing processes may occur on a semicontinuous basis, through a combination of batch and inline static and/or dynamic mixers. This may be the result of special process requirements in the preparation of product intermediates, such as ... 

Dynamic mixer Mixer allowing the mixing of different matters by means of mechanical energy, usually by rotary motions. 

Apparatus. High performance liquid chromatographic separations were achieved on a binary gradient microbore HPLC systems primary pump (A) Model 305, secondary pump (B) Model 306, monomclric module Model 805, and a dynamic mixer Model 811C from Gilson Inc. (Middleton. Wl). Sample injections were achieved with a 20 pL loop on a Model EQ-36 injection valve from Valeo Instruments Co. Inc. (Houston, TX). A stainless steel Y-splitter also from Valeo was used in order to achieve a post-column split of the mobile phase Dow to the CLND. A Supelcosil LC-18S analytical HPLC column was purchased from SUPELCO Inc. (Bellefonte. PA). The Y-splitter was attached to the analytical column by a SLIPFREE connector, available from Keystone Scientific Inc. (Bellefonte, PA). Analyses of nor-dihydrocapsaicin, capsaicin and dihydrocapsaicin in spices as well... 

The effect of PP and PE ratios has been studied earlier (45 7) when itaconic acid (lA) was grafted to their blends containing L-101 peroxide as the initiator. Grafting was done in the extruder reactor assembled on the base of Brabender plastograph (Duisburg, Germany) equipped with the dynamic mixer (48,49). 

The results reported in this paper are characteristic not only of grafting of lA onto PP/PE blends carried out in the Brabender plastograph equipped with a dynamic mixer, but also of lA grafting performed in reactors of other types, particularly in a single-screw extruder. 

Only a selection of commercially available mixing equipment has been described here. Indeed, the devices described all exist in a variety of configurations. In a ition, there are many items of equipment based on altogether different principles typical examples include jet mixers, in-line dynamic mixers, mills, valve homogenisers, ultrasonic homogenisers, etc. These, as well as many other types, have been discussed by Harnby et alp-K Oldshue and Nagata ... 

Three different impingement or dynamic mixers were built to achieve homogeneous mixing. The devices are similar in concept, and the results to be presented show that the viscosities of the gels are not especially sensitive... 

Impellers 120 Jet mixers 125 In-line static mixers 126 In-line dynamic mixers 127 Mills 128... 

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