Dryers agitated

Design, Scale-up, and Performance Like all batch dryers, agitated and rotating dryers are primarily sized to physically contain the required batch volume. Note that the nominal capacity of most dryers is significantly lower than their total internal volume, because of the headspace needed for mechanical drives, inlet ports, suction lines. 

Diyer Batch Dryer, dryer— agitated pan, blender, conical, freeze, fluid bed, horizontal paddle, rotary, spray, tray... 

Drying Tray dryer Agitated dryer (rotary tumble and conical) Filter dryer Huid bed dryer Cycle time and stability Particulate properties... 

Fig. 1. Fine chemicals plant design showing successive additions of processing equipment, where A represents the reaction vessel with agitator B, centrifuge C, dryer D, crystaUi2ation vessel E, raw material feed tanks F, centrifuge which may have an automatic discharge G, mother Hquor tank H,...

A 95% yield of pure anthraquinone was obtained. This is an almost quantitative yield based on the 100% content of the anthracene used. The cmde anthraquinone was then purified. To a jacketed steel kettie, provided with an agitator, was added cmde anthraquinone and nitrobenzene. Under agitation, the charge was heated at 130—140°C until a complete solution resulted. Under slow agitation, the solution was cooled to 30 °C and the resulting slurry of anthraquinone was filtered on a pressure filter. The cake was washed twice with nitrobenzene, then was reslurried on the filter with nitrobenzene, sucked dry, and transferred to a vacuum dryer where the nitrobenzene was distilled. The dried anthraquinone was discharged to suitable containers. A 99% yield of pure anthraquinone was obtained equal to a recovery of approximately 90% based on the cmde anthraquinone. 

Between 1 s and 1 min specific contact time, conduction heat-transfer performance decreases theoretically as the 0.29 power of contact time. This is consistent with empirical data from several forms of indirect-heat dryers which show performance variation as the 0.4 power of rotational speed (21). In agitator-stirred and rotating indirect-heat dryers, specific contact time can be related to rotational speed provided that speed does not affect the physical properties of the material. To describe the mixing efficiency of various devices, the concept of a mixing parameter is employed. An ideal mixer has a parameter of 1. 

N = agitator or dryer vessel rotational speed in units of 1/s. Values of reported for various dryers fie between 2 and 25. The principle appfies to... 

Fig. 22. Indirect-heat, paddle-type agitator dryer.

Fig. 23. Indirect-heat, high speed agitator dryer.

Radiative Heat Transfer Heat-transfer equipment using the radiative mechanism for divided solids is constructed as a table which is stationary, as with trays, or moving, as with a belt, and/or agitated, as with a vibrated pan, to distribute and expose the burden in a plane parallel to (but not in contacl with) the plane of the radiant-heat sources. Presence of air is not necessary (see Sec. 12 for vacuum-shelf dryers and Sec. 22 for resubhmation). In fact, if air in the intervening space has a high humidity or CO9 content, it acts as an energy absorber, thereby depressing the performance. 

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