Multistage Dryer

Courtesy Calmic Engineering Co. Ltd. Williams-Gardner, 1971). (b) Multistage Dryers with Dual-flow Distributors [Equipment Sketch in Fig. 9.13(b)] ... 

Use of superheated steam in direct dryers Increased use of indirect (conduction) heating Use of combined (or integrated) heat transfer modes Use of volumetric heating (microwave [MW]/radio-frequency [RF] fields) in specialized situations Use of two-stage (or multistage) dryers Use of intermittent heat transfer Use of novel combnstion technologies (e.g., pulse combustion for flash drying)... 

Farm Fans, Indianapolis, Indiana, has a series of dryers of this type that they term continuous multistage dryers, ranging in capacity from about 5 to 27 tons/h (265-1220 bu/h) based on drying and cooling corn from 25% to 15% moisture. 

The advantage of the fluidized and vibrofluidized system is that it is isothermal due to intensive mixing of the solid state, which prevents local overheating of the particles. It is possible to build multistage dryers and apply independent temperature control in particular sections. Thus, the product can be dried uniformly and changes in material moistnre content can be controlled precisely in every zone of the dryer. This is particularly important for thermo- and xerolabile products. Advantageous also are high intensity of transfer processes, relatively simple dryer construction, and easy control of process parameters. 

Figure 11 Diagrams of multistage dryer with spiral flow plates. 1—spiral flow bed 2—spiral flow panel 3—first-stage cyclone 4—measure tank 5 storage tank 6—butterfly value 7—electric heater 8—flowmeter 9—second-stage cyclone 10—inlet.

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