Control of fluid bed tea dryers: control in the context of design and operation conditions

A simulation model of a continuous fluid bed tea dryer, previously validated, was used to investigate the options for control of the dryer. Discharge weir height was not a suitable control parameter and should be maintained at 50 mm. The variation in heat available proved to limit the possibilities of compensation for variations in feed rate in practical dryers. If dryers operate under limited control power of the air temperatures it is recommended to control the feed rate into the continuous processing system as tightly as possible, and to correct this for other variations in the system such as feed moisture content.