Control of fluidized bed tea drying

Tea is a product made from the leaf of the tea bush by several processes, including drying. The drying stage is the most energy intensive, and has tight performance criteria. This project investigated the options for the control of a fluidized bed tea dryer. The work included establishing some of the basic drying properties of tea particles, which were not previously available. A mathematical model of the drying process was developed, from which methods of control were proposed and tested. The model was tested on commercial and experimental dryers. The work concluded that it is possible to use feedback control of the dryer. Instead of very expensive moisture sensors, it is possible to use cheap and readily available temperature sensors to predict the moisture content of the dry tea, so that the temperature based system could form a low cost controller suitable for use in a factory environment.