Batch Dryer

Through circulation dryers employ perforated or open screen bottom tray construction and have baffles that force the air through the bed. Superficial velocities of 150ft/min are usual. 

Hard Granular Fibrous Liquid Slurry Paste 

Classification of dryers based on physical form of feed 

Agitated batch Drum Spray Agitated batch Vacuum band Drum Spray Vacuum tray Agitated batch Convection tray Fluid bed Vacuum band Drum Spray Pneumatic Convection band Cont. tray Vacuum tray Convection tray Batch through-circulation Fluid bed Pneumatic Convection band Cont. tray Cont. through-circulation 

Vacuum tray Convection tray Indirect rotary Cont. tray 

Materials that require more than a few minutes drying time or are in small quantity are treated on a batch basis. If it is granular, the material is loaded on trays to a depth of 1-2 in. with spaces of approximately 3 in. between them. Perforated metal bottoms allow drying from both sides with improved heat transfer. Hot air is blown across or through the trays. Cross velocities of lOOOft/min are feasible if dusting is not a problem. Since the rate of 

Liquid Slurry Paste Preform Hard Granular Fibrous Sheet 

Small scale Medium scale Large scale 

Liquid Slurry Paste Reform Hard Granular Fibrous Sheet 

Agitated batch Vacuum band Indirect rotary 

Agitated batch Through-circulation Fluid bed Vacuum band Pneumatic 

Agitaiol batch Vacuum band Drum Spray 

Vacuum tray Agitated batch Convection tray Fluid bed Vacuum band Drum Spray Pneumatic Convection band Cont. tray 

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Batch dryer operation resulting in a high peak evaporation rate of flammable solvent causing buildup of flammables. Possibility of fire/explosion. 

Another example in the polymers industry is illustrated in Figure 17, which is a process aimed at the batch drying of waste residue with solvent recovery. In this application liquid or viscous waste solutions are pumped into a batch dryer where they are dried under vacuum to a solid granular residue. Vaporized water and solvent are recovered by condensation and then separated by gravity. The process scheme is flexible, offering a range of temperatures and vacuum levels for treating... 

Batch dryers are normally used for small-scale production and where the drying cycle is likely to be long. Continuous dryers require less labour, less floor space and produce a more uniform quality product. 

Batch dryers have high labour requirements, but close control can be maintained over the drying conditions and the product inventory, and they are suitable for drying valuable products. 

Batch crystallization, 8 130-134 Batch crystallizers, 23 464 Batch dechlorination, 21 672 Batch desilverizing, 14 751 Batch distillation, in hazardous waste management, 25 813-814 Batch dryer, 9 116 Batch dyeing fixation in, 9 213 machinery for, 9 205-211 Batch emulsion polymerization, of VDC, 25 722-724... 

Figure 9.4. Types of dryers cited in Tables 9.1 and 9.2. (a) Tray or compartment, (b) Vacuum tray, (c) Vertical agitated batch vacuum drier, (d) Continuous agitated tray vertical turbo, (e) Continuous through circulation, (f) Direct rotary, (g) Indirect rotary, (h) Agitated batch rotary (atmos or vacuum), (i) Horizontal agitated batch vacuum drier, (j) Tumble batch dryer, (k) Splash dryer. (I) Single drum, (m) Spray, (n) Fluidized bed dryer, (o) Pneumatic conveying (mostly after Nonhebel and Moss, 1971).

TABLE 9.7. Performance of Agitated Batch Dryers (See Fig. 9.7) (a) Double-Cone Tumbler ... 

TABLE 9.14. Performance Data of Fluidized Bed Dryers Batch and Multistage Equipment (a) Batch Dryers... 

Vacuum-Shelf Dryers Vacuum-shelf dryers are indirect-heated batch dryers consisting of a vacuumtight chamber usually constructed of cast iron or steel plate, heated, supporting shelves within the chamber, a vacuum source, and usually a condenser. One or two doors are provided, depending on the size of the chamber. The doors are sealed with resilient gaskets of rubber or similar material (Fig. 12-49). 

Vacuum Tray Batch Dryers (carbon steel)... 

Process Variable Batch Dryer, Bollman Type Continuous, Agitated-Film Evaporator... 

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