Mixer conical-screw

SpiralTlevator Materials are moved upward by the centrally located spiral-type conveyor in a cylindrical or cone-shaped Nautamix vessel (Fig. 37c and d). Blending occurs by the downward movement at the outer walls of the vessel. The vessel serves the dual purposes of blending and storage. In these mixers the screw impeller actively agitates only a small portion of the mixture and natural circulation is used to ensure all the mixture passes through the impeller zone. In the case of Nautamix, an Archimedian screw lifts powder from the base of a conical hopper while progressing around the hopper wall. 

Screw mixer (rotating screw aligned along the inside of a cone hopper. Lifts solids from the bottom to the top. Progresses around the periphery of the cone.) Most effective when solids move along the conical hopper walls. Use for moderately cohesive fines different types of particles that have RAS differences < 3° and usually require moderate amounts of liquid addition. Not for moderately free flowing. 

Figure 5.2 Low-intensity mixer designs (a) double-cone blender (b) twin-shell ( V ) blender (c) conical screw mixer (d) conical screw mixer...

Conical screw mixers also contain a screw for conveying and mixing, but this is located inside an inverted conical-shaped mixing chamber. The screw is angled from the base of the mixer to the outside of the top. It may revolve on its own axis at about 60 rpm, whilst slowly orbiting the cone at around 3 rpm. Pelletised or powdered polymer, and additives are transferred from bottom to top by the rotating screw, from the walls to the centre of the chamber as the screw circulates, to fall on to material being carried upwards. 

Scale-up of Conical Screw Mixers (Nauta Mixers)... 

Entrop (1978) conducted a wide range of experiments in conical screw mixers. 

Hixon, L., and J. Ruschmann (1992). Using a conical screw mixer for more than mixing. 

Most of the compounds were extrusion compounded in a conical, partially intermeshing, counter rotating twin screw extruder (Haake Reomix TW-lOO). The extruder speed was set at 50 rpm and the barrel temperature profile was set to produce a melt temperature of 260°C at the die. Samples were injection molded in a 31.8 MT Battenfeld press with a 59 cc shot size. Where noted, samples were compounded in a 60 cc Brabender internal mixer and compression molded. 

Transfer 0.8 ml of the membrane suspension into two separate 15-ml plastic conical tubes with screw caps. Avoid polystyrene and any other types of plastics that are not compatible with this solvent. Add 3 ml of chlorofornnmethanol (1 2) to each tube. Cap and swirl each tube vigorously with a Vortex mixer for 30 sec. 

Conical Mixer Dryer The conical mixer dryer is a batch-wise operating unit commonly used in the pharmaceutical and specialty chemical industries for the drying of solvent or water wet, free-flowing powders. The process area is a vertically oriented conical vessel with an internally mounted screw. Figure 12-80 shows a schematic of the bottom drive conical mixer dryer. The dryer utilizes the heatable, internal rotating screw to provide agitation of the batch of material and thus improve the heat and mass transfer of the process. Because it rotates around the full circumference of the vessel, the screw provides a self-cleaning effect for the heated vessel walls. 

Conical mixers are also known as Nauta mixers (Fig. 18-53). Material placed in the conical bin is lifted by the rotation of the helical screw, which in turn is rotated around the wall of the cone. The lifting actions of the screw combined with motion around the cone provide bulk mixing for flowable dry powders, paste materials, and even viscous fluids. The specific energy input is relatively small, and the large volume of the mixers can even provide storage capacity The mixers may have multiple screws, tapered screws, and high-speed dispersers for different applications. At constant speed, both the mixing time and power scale up with the square root of volume. Sizes from 0.1 to 20 m3 (3.3 to 700 ft3) are available. 

Other batch or continuous mixers with an almost vertical axis of the mixing tool are the orbiting type screw blenders (Fig. 7.48) often also called Nauta mixers. The total contents of the conical silo is mixed by the orbiting screw which rotates such that it transports material from the depth of the bin to the surface. Although not often... 

Dispersion-type screw mixers are in an entirely separate class from the extruder designs described above. They are applicable to processing of either dry materials or moderately viscous pastes, creams, or lotions. These machines normally consist of a conical vessel equipped with a conical or inclined screw. There are either single- or twin-screw models that provide a gentle mixing action, and thus... 

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