Twin screw dryer

A twin-screw extruder fitted with a stuffer box. The twin-screw extruder continues to blend the compound as it passes through although with the dryer. 

In other cases not the vessel is rotated, but revolving rotors are placed inside it. An example is the paddle dryer shown in Fig. 10.1-3. For sticky drying goods, a selfcleaning twin screw such as in Fig. 10. 1-4 can be employed, where the heat is supplied via the hollow screws as well as via the outer jacket. 

Fig. 29. TWin-screw extrusion compounding line for the preparation of mineral-filled thermoplastics showing pre-mixing, compounding and pelletizing stages [155] (a) Filler/poly-mer/additive feedstock, (b) high-speed pre-mixer, (e) dosing screw, (d) twin-screw compounder, (e) vacuum devolatilization, (f) water-cooled die-face cutter, (g) start-up diverter, (h) de-watering chute, (i) pellet dryer, (k) bagging...

Mixtures of PLA with Talc, and MMT were compounded on a Leistritz 34 mm co-rotating twin-screw extruder. PLA was dryed prior to extrusion at 65°C for 8 hr in a desiccant dryer. The minerals were dried in a vacuum oven at 100°C overnight. Produced pellets were injection molded into bars using a mold at 100°C, with and without thermal annealing in the mold. 

The measurements are done with an external mix twin-fluid nozzle in which inner diameter for the liquid is 0.7 mm and the annular outer diameter for the gas is 1.5 mm. The aspect ratio of the length and diameter of the inner liquid pipe is 4.5. This nozzle is made by Biichi GmbH and is an equipment of the laboratory spray dryer B191, which is also used for spray drying the polymer solutions. To avoid pulsation of the spray, the nozzle is fed with an eccentric screw pump. The gas flow is controlled with a mass flow controller by Bronkhorst B.V. 

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