Vacuum horizontal screw

Figure 5.24 Principle of a horizontal screw vacuum pump for industrial applications type c (Figure 5.24). (With permission from Oerlikon Leybold Vacuum, Cologne, Germany.)...

Fig. 6 Twin horizontal feed screw system with vacuum deaeration. (Courtesy of Alexanderwerk Inc.)...

Guigon and Simon, in 2001, showed a similar phenomenon using a horizontal single feed screw without vacuum deaeration when compacting sodium chloride. ... 

In several experiments, Miller studied the effects of using horizontal twin auger feed screws under partial vacuum (Alexanderwerk Inc., Horsham, Pennsylvania, model 50/75 compactor). The feed powder was vacuum deaerated just before roller compaction. The experimental design showed that the compactor s deaeration feed system significantly increased compaction output and minimized powder leakage when compacting very low density blends (<0.35 gcm ). ... 

The Fitzpatrick Co. roller compactor (Fig. 20) features two feed screws in series one horizontal and the second vertical. This system is designed to transfer powder bulk into a set of cantilevered rolls positioned in the horizontal mode one is fixed, the other floats. Operator interface allows for on-line monitoring and controlling feed screw speeds, roll pressure, and roll gap. Features such as on-line help and diagnostic functions, maintenance, and calibration screens are displayed. All functions are interfaced and adjustable by PLC for process control and report generating. The machines have vacuum deaeration and roll cooling capabilities. The sizing unit is separate from the compactor and is either a rotor bar or a hammer mill. 

Fig. 6.2-61 depicts two typical designs and arrangements of roller presses for pharmaceutical applications. As mentioned above, small presses in particular are sometimes equipped with rollers one-above-the-other (alternative a2). In this case, the force feeding screw is installed horizontally. It is often said that this design allows for better de-aeration as shown in Fig. 6.2-62. In this diagram, (1) is the raw blend, (2) is a special hopper equipped with a rotating flow stimulator, a separate de-aeration chamber, which is also used for feeding recycle (3) and additives (if applicable), and air removal port (4), (5) is a vacuum pad option for further direct de-aeration from the horizontal feed screw, and (6) is the recirculation of powder leakage [B.13b, B.48, B.97].

A gigantic combined de-airing extmsion machine with a barrel diameter as wide as 850 mm and the capacity for putting out 12 columns of brick at once has little in common with a tiny, 20 mm-diameter micro-extmder. Or, compare a vertical extmder for clay pipes with diameters up to 1.50 m with an intermittent-action piston extmder that can work vertically as well as horizontally. Or how about a twin-screw extruder or piston extmder sporting extmsion pressures up to 400 bar in contrast with a huge vacuum extmder for forming electrical porcelain slugs at relatively low pressure ... 

The newly designed equipment involved a compactor fitted with two horizontal feed screws, which featured vacuum deaeration. Specifically, the roller compactor was equipped with a conical storage hopper containing a variable speed agitator. Bulk powder was fed directly from the top of the hopper to the top of twin horizontal auger feed screws, which directly transported the powder to the nip roll area (13). Top and side views of the design features are shown in Figure 17. ... 

A novel stainless steel encasing that leads to the compactor rolls encloses the variable-speed auger screws. Just before the nip area, a pair of sintered stainless steel segments are assembled within the horizontal auger feed system, which can operate under partial vacuum. A small, self-contained vacuum pump draws negative pressure through a dry filter and a stainless steel line connected to the sintered assembly plates. The partial vacuum is adjustable from —0.1 to 0.8 bars. The compaction rolls... 

Evaporation and crystallization The thin juice is concentrated to 65-70% in multistep evaporators. The cooking is continued under stirring in vacuum until formation of a crystal suspension (90% d.s.). The mixture is transferred into horizontal crystallizers with screw stirrers in which crystallization is finished. The massecuits are separated by centrifugation into brownish raw sugar and syrup, which is further purified, concentrated, crystallized, and after dissolution, recycled into the thick juice. 

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