Fluid dryer

A few performance data of batch fluid dryers are in Table... 

A few performance data of batch fluid dryers are in Table 9.14(a). This process is faster and much less labor-intensive than tray drying and has largely replaced tray drying in the pharmaceutical industry which deals with small production rates. Drying rates of 2-101b/(hr)(cuft) are reported in this table, with drying times of a fraction of an hour to several hours. In the continuous operations of Table 9.15, the residence times are at most a few minutes. 

FIGURE 2.17 The contact-fluid dryer (see text for discussion). 

Rotary dryers, batch fluid dryers, continuous or batch tray dryers, hopper dryers, multispouted bed, and vacuum tumble dryers are typical long-residence units used in polymer drying. 

Usually, a premix of dry powders is loaded into the equipment and the liquid enzyme concentrate is injected and mixed. After a certain time, depending on the recipe and moisture content, granules are formed that are discharged and dried in a fluid dryer. After sieving the granules, over- and undersized materials are milled and recycled to the premix. 

Spray dryer, fluid dryer, pneumatic dryer... 

A number of papers published so far on safety aspects refer to the spray dryer [41-44] and the fluid dryer [45-47]. Few data refer to other types of dryer [48,49], like the contact dryer, which generally can be safeguarded easier than convective dryers. Table 56.10 provides a summary of the probable hazards associated with a few industrially common types of dryers and some hints on the recommended safety measures to be taken. Once again, it is noted that this tabulated information on measures and hazards is not exhaustive. The suggested measures may have to be changed or modified depending upon the specific application at hand. 

More details NA CSTR, possible addition of chemicals Separates water from slurry Flash dryer, fluid dryer Several layers of sieves CSTR NA NA... 

Minimum ignition temperature MIT T = MIT-50°C Spray dryer, fluid dryer, pneumatic dryer... 

Onset aerated exotherm temperature T = Ta-CSO-SO C) Fluid dryer, band dryer... 

Tables 7 and 8 compare conventional concepts of spouted bed dryers and vibrated bed dryers with some of the novel ideas not all of which have been tested yet. Table 9 shows the advantages of combining fluid bed dryers with fluid bed as well as other dryer types to improve the performance of the combined two-stage drying system. For some large scale drying applications although a single stage fluid dryer can perform the necessary drying, only the two-stage system is cost-effective. See Mujumdar and Suvachittanont (2000) and Mujumdar (2001) for further details.

Dry bead process Dry-cell batteries Dry chemistry Dry-cleaning Dry cleaning fastness Dry-cleaning fluid Dry-cleaning solvent Dryers... 

The ABS polymer is recovered through coagulation of the ABS latex. Coagulation is usually achieved by the addition of an agent to the latex which destabilizes the emulsion. The resulting slurry can then be filtered or centrifuged to recover the ABS resin. The wet resin is dried to a low moisture content. A variety of dryers can be used for ABS, including tray, fluid bed, and rotary kiln type dryers. 

Small, complex-shaped glass articles such as thread guides for the textile industry and television gun mounts for the electronics industry are made by the multiform process. The dry-milled powder is mixed with an inorganic binder and a fluid vehicle, and then atomi2ed by a spray dryer into small, dried agglomerates of glass powder and binder with good flow characteristics. They are subsequently pressed to the desired shape and fired. 

Process Va.ria.tlons. The conventional techniques for tea manufacture have been replaced in part by newer processing methods adopted for a greater degree of automation and control. These newer methods include withering modification (78), different types of maceration equipment (79), closed systems for fermentation (80), and fluid-bed dryers (81). A thermal process has been described which utilizes decreased time periods for enzymatic reactions but depends on heat treatment at 50—65°C to develop black tea character (82). It is claimed that tannin—protein complex formation is decreased and, therefore, greater tannin extractabiUty is achieved. Tea value is beheved to be increased through use of this process. 

Instant Active Dry Yeast. Instant ADY (lADY or HADY) production is similar to ADY production but requires a different strain of yeast. After pressing, the yeast is extmded into noodles 0.2—0.5 mm in diameter and 1—2 cm long and deposited on a metal screen or perforated plate in a fluid-bed air dryer. Drying time is shorter than with ADY, about 1—2 hours in practice, with a final moisture level of 4—6%. Instant active dry yeast does not require separate rehydration. It is always packaged in a protective atmosphere or under vacuum. On an equivalent soHds basis, the activity of lADY is greater than that of regular ADY, but stiU less than that of compressed yeast. 

Fig. 12. Material residence time profiles in A, a pneumatic conveyor, B, a spray, and C, a rotary or fluid-bed dryer.

Fig. 15. A two-stage fluid bed dryer (a) gas and material temperature profiles (b) bed arrangements.

The principal appHcations of pneumatic conveyors are for materials that are nonsticky and readily dispersible in the gas stream as drying must be entirely constant rate. Many are employed as predryers ahead of longer residence time fluid-bed and rotary dryers in polymer drying operations. 

Fig. 21. Iadirect-heat, two-stage, back mixed, and plug flow fluid-bed dryer.

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