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Extruder radial screw

The pressure exerted by the rotating extrusion heads on the screen as product is being pushed out in an A-R screw extruder (25) is shown in Figure 10. Each spike in the profile represents one revolution of the extrusion head while the frequency represents screw speed. Based on the shear stress developed during extrusion, wet mixtures of MCC-lactose had a lower yield stress in the radial screw extruder (130kN/m ) than in the ram... [Pg.342]

Among the formulation variables that control extrudability of a product, several studies (25,26,33-35) point to the fluid or moisture content of the wet feed material being more critical than others. The force or torque of extrusion and power consumption are often inversely proportional to moisture content of the extrudate as seen from Figures 11 and 12 (26,36-38), while the particle size of pellets increases linearly with water content when extruded with gravity feed basket and roll extruders (33). Using instrumented gravity feed and radial screw extruders, a three- to fourfold decrease in the force has been noted, with a 10% increase in water content of feed material (37). [Pg.343]

These studies point towards the need to optimize moisture content of the wet mass and extrudate by careful selection of formulation ingredients and type of extruder. A basket or gear/roll extruder is preferred for a very dense and moist wet mass, as it generates little shear and rise in temperature, while an axial or radial screw extruder which increases granule density and hardness is desirable for a wet mass which is less cohesive with poor binding. [Pg.345]

Screw-fed extruders have screws that rotate along the horizontal axis and hence transport the material horizontally they may be axial or radial screw extruders (Fig. 5). Axial extruders, which have a die plate that is positioned axially, consist of a feeding zone, a compression zone, and an extrusion zone. The product temperature is controlled during extrusion by jacketed... [Pg.2656]

Figure 312. Schematic representation of (a) axial and (b) radial screw extruders ... Figure 312. Schematic representation of (a) axial and (b) radial screw extruders ...
Unlike axial and dome extruders, radial extruders extrude the wet mass perpendicular to the plane of transport. Material is transported to the extrusion zone where it is wiped against the screen die by an extrusion blade. The mass is forced through the die by pressure generated at the nip. A screw feed radial extruder is shown in Figure 6(C). [Pg.341]

Tempered or nonconditioned maize grits, rice grits, and starches are introduced and transported into the barrel section of the stator, and the shear applied by the screw movement increases both the pressure and internal temperature (more than 120°C) so that the starch gelatinizes, melts, and plasticizes. The rotor fingers cut the extruding material, which is then immediately extruded radially between the two... [Pg.377]

In the A-R type, the feed screws end in blades that rotate along the horizontal axis but force the wet mass through a screen-placed radial or cylindrical around the blades (Fig. 5). The A-R extruders have somewhat conical extrusion heads resulting in an overflow, i.e., a certain amount of feed material is pushed axially between the screen and extrusion head at the front instead of radially through the screen area. A greater open area of screen results in a higher and faster throughput. However, the hardness... [Pg.331]

Figure 10 Schematic of a screen force profile from an instrumented radial screen screw extruder. Source From Ref 25. Figure 10 Schematic of a screen force profile from an instrumented radial screen screw extruder. Source From Ref 25.
The screw is placed within a barrel of diameter Df, Ds I 25f, where 6y is the radial flight clearance. This is shown schematically in Fig. 9.2. The figure shows a pelletizing extruder, but the discussion that follows is valid for any melt extruder equipped with any kind of die, and for the melt region in a plasticating extruder as well. [Pg.448]

Normal stress differences also have practical relevance for extrusion They assist in centering the shaft in the extruder when processing thermoplastics as the rotation of the screw generates radial forces (from the shaft to the wall). [Pg.43]

Ring mills consist of a power-driven rotating ring with radial holes, friction rolls to force the material holes and knives to cut the extrudate to the desired lengths. See Figure 12.16(a). The feed is charged with screw feeders into spaces between the rolls and feed... [Pg.382]

The twin-screw design and radial-die screen assembly of an extruder manufactured by the Fuji Paudal Company of Japan is shown in Fig. 9. Water... [Pg.1722]

Fig. 8 Screw extruder with (A) end-plate die and (B) radial-screen die. Fig. 8 Screw extruder with (A) end-plate die and (B) radial-screen die.
Fig. 9 Twin-screw extruder with radial-screen die. (Manufactured by Fuji Pauldal Company, Japan.)... Fig. 9 Twin-screw extruder with radial-screen die. (Manufactured by Fuji Pauldal Company, Japan.)...
Fig. 5 Schematic representation of screw-fed extruders (A) axial extruder and (B) radial extruder. Fig. 5 Schematic representation of screw-fed extruders (A) axial extruder and (B) radial extruder.
Basic types of extruders include both screw extruders such as axial endplate, radial screen, and basket designs, as well as pelletization equipment described above, such as rotary cylinder or gear and ram or piston extruders (Fig. 21-136). See Newton [Powder Technology ana Pharm. Processes, Chulia et al. (eds.), Elsevier, 1994, p. 391]> Pietsch (Size Enlargement by Ag omeraUon, Wiley, 1992), and Benbow and Bridgwater (Paste Flow and Extrusion, Oxford University Press, 1993). [Pg.2383]

The difference between a screen and a die plate extruder is quite substantial. While die plates are 2-30 mm thick, screens usually feature the same thickness as the hole diameter screens are rarely thicker than 1 mm. For extruders with the same barrel diameter, a radial discharge with a screen will have more than 6 times the open extrusion area than an axial discharge with a die plate.This has consequences for screw design but will also generally translate into higher specific capacity and cost advantages for the radial discharge extruder if the low density and small product diameter can be tolerated. [Pg.361]

In roller presses, radial angle defining the line on the roller surface at which the speed of the particulate mass is identical with that of the roller in extruders, the angle between the extrusion surface (e.g. die plate) and the pressure generating device (e.g. extrusion blade, screw, roller). Formation of nearly spherical lumps (a lomerates) from a wet mixture of particulate solids by either drying or chemical reaction during tumbling typically accomplished in dryers or rotary kilns. [Pg.22]

Screw feeder(s) and extrusion blades (radial, axial, and dome extruders)... [Pg.253]


See other pages where Extruder radial screw is mentioned: [Pg.326]    [Pg.474]    [Pg.590]    [Pg.336]    [Pg.2657]    [Pg.2658]    [Pg.50]    [Pg.8]    [Pg.421]    [Pg.421]    [Pg.422]    [Pg.556]    [Pg.360]    [Pg.1015]    [Pg.67]    [Pg.226]    [Pg.280]    [Pg.91]    [Pg.360]    [Pg.1722]    [Pg.360]    [Pg.360]    [Pg.1969]    [Pg.2350]    [Pg.358]    [Pg.438]    [Pg.317]    [Pg.499]    [Pg.34]    [Pg.419]   


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Screw extruders

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