Archimedian 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. 

Calcium bromide, currently quantitywise the most important inorganic bromide, is utilized in crude oil extraction as a so-called packing fluid or drilling fluid . Packing fluids surround the archimedian screw and equalize the pressure. Depending upon the pressure ratio solutions of sodium ehloride, of mixtures of sodium chloride with sodium carbonate or calcium chloride, of calcium chloride, of mixtures of ealcium chloride and calcium bromide or of mixtures of caleium bromide and zinc bromide (see below) are utilized. Solutions with 53% by weight of calcium bromides are used, which have a density of ca. 1.7 g/mL. 

Auger or Screw Method. This was the first mechanism used in industrial-scale machines, although the dosator and piston tamp mechanisms have now largely superseded it. The capsule body in its holder passes beneath the powder hopper on a turntable. The powder is fed into the capsule body by a revolving archimedian screw. The auger rotates at a constant rate so the fill weight is related to the duration of filling that is related to the speed of rotation of the turntable. 

The motion of the colunrn generates an Archimedian screw force. Independent of density, the contents of the column are driven towards one end called the head (the other end is referred to as the tail) [244]. The forces acting on the coiled column cause vigorous mixing of the two phases with formation of a succession of mixing and demixing zones in each successive turn of the coil. When hydrodynamic equilibrium is established, the phase ratio is constant, and only the mobile phase moves through the... 

Belford, A. J. R. (1965-66) Design of an Archimedian Screw, (DATA Publication Session). 

Figure 3.24 An example of an Archimedian Screw at the River Dart country park, Devon,Credit WRE Limited...

Figure 1.1 A Single Screw Extruder [Morton-Jones, 1989]. The machine consists mainly of an Archimedian screw fitting closely in a cylindrical barrel with just enough clearance to allow its rotation. Solid polymer is fed in at one end and the profiled molten extrudate emerges from the other. Inside, the polymer melts and homogenizes. Twin screw extruders are used where superior mixing or conveying is imponant.

The construction of a basic centrifuge with all its main components is shown in Figure 2.1. The heart of the decanter is the rotating assembly, which comprises a mainly cylindrical bowl housing an Archimedian screw conveyor, with a small clearance between it and the bowl. One end of the bowl is conical in shape, providing the means whereby solids can be removed from it. Affixed to one end of the bow l is usually a gearbox to effect a small differential speed between the conveyor and bowl. 

---