Batch Discharge Centrifuge Capacity

In general, soHds-retaining batch and batch automatic machines are limited to low feed concentrations to minimize the time required to unload the soHds. Continuous disk centrifuges can have higher feed concentration. The limit is the underflow concentration. Conveyor discharge centrifuges can handle high feed concentration and are limited only by the volume of soHds displacement, or torque capacity. 

Table 18-15 summarizes the several types of commercial centrifuges, their manner of liquid and solids discharge, their unloading speed, and their relative volumetric capacity. When either the liquid or the solids discharge is not continuous, the operation is said to be cycHc. Cyclic or batch centrifuges are often used in continuous processes by providing appropriate upstream and downstream surge capacity. 

It is relatively easy to set and control the optimum drying conditions in cabinet dryers. For this reason, various heat-sensitive food materials can be dried in small batches. The heat source is usually steam batteries or steam coils. The air from a centrifugal fan is passed through the coils and then baffled across the trays loaded with the product. The trays may either be loaded onto trolleys in stacks of 10-12 or may be stacked individually into the slots of the cabinet. The movement of trays may be manual or mechanically assisted depending on the size and capacity of the dryer. The hot air in almost all cabinet dryers is introduced at the top, and provision is made to recycle the air so that its total drying potential is ntilized by the time it discharges to the atmosphere. A schematic illnstration of a cabinet dryer and its principle of operation are shown in Fignre 24.7. 

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