Band dryers

As the band dryer is a type zero system, and there are no integrators in the controller, steady-state errors must be expected. ITowever, the selection of the elements in the Q matrix, equation (9.90), focuses the control effort on control-... 

Conveyor dryers (continuous circulation band dryers) (Figure 10.26)... 

For both the band dryer and the rotary dryer with burner, there is sufficient heat available from the system to achieve all specified drying duties. For the rotary dryer without burner, th e is insufficient heat available where the initial moisture content is 100% and the desired moisture content is 20% or less. 

Conveyor Dryers (Continuous Circulation Band Dryers)... 

No agitation, e.g., tray and band dryers. This is desirable for friable materials. However, drying rates can be extremely low, particularly for cross-circulation and vacuum drying. 

FIG. 12-33 Gas passing through a bed of preformed solids, in through-circulation on a perforated-band dryer. 

FIG 12-35 Cross-flow of gas and solids in a fluid bed or band dryer. 

Incremental models track the local conditions of the gas and particles through the dryer, mainly in one dimension. They are especially suit le for cocurrent and countercurrent dryers, e.g., flash (pneumatic conveying) and rotary dryers. The air conditions are usually treated as uniform across the cross-section and dependent only on axial position. This method can also be used to determine local conditions (e.g., temperature) where a simpler model has been used to find the overall drying rate. A two- or three-dimensional grid can also be used, e.g., modeling vertical and horizontal variations in a band dryer or plug-flow fluidized bed. 

Belt-conveyor and screen-conveyor (band) dryers are truly continuous in operation, carrying a layer of solids on an endless conveyor. 

Continuous Through-Circulation Band Dryers Continuous... 

Vacuum band dryers utilize heating by conduction and are a continuous equivalent of vacuum tray (shelf) dryers, with the moving... 

Design Methods for Continuous Band Dryers In actual practice, design of a continuous through-circulation dryer is best based upon data taken in pilot-plant tests. Loading and distribution of solids on the screen are rarely as nearly uniform in commercial installations as in test dryers 50 to 100 percent may be added to the test drying time for commercial design. 

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