Effect of a spiral on the performance in a conical bubbling fluidized bed paddy dryer

The present work is the comparative study of drying characteristics between two conical bubbling fluidized bed dryers having cone angles of 5° and 10° and a conventional one with a cone angle of 0°. A series of experiments were carried out with a spiral inside the dryers to investigate the drying characteristics of paddy. Hydrodynamic behaviour, drying characteristics and energy consumption of the blower were investigated for these three dryers and results were compared. The experiments were performed with three different inlet velocities (1, 1.6 and 2.1 m/s), three different inlet temperatures (55°C, 60°C and 65°C) with 1-3 kg batch sizes of paddy as a bed inventory. It was observed that the time taken to reduce the moisture content in the conical bubbling fluidized dryer having a cone angle of 10° was less than the other two dryers. The drying rate was also found to be faster with the use of a spiral inside the dryers than without the spiral. The effect of the spiral was to exhibit better drying characteristics in terms of nutritional value and milling quality. Conical fluidized bed dryer saved more energy than conventional fluidized bed dryers. Both thermal and blower energy consumption was found to be reduced with the use of a spiral inside the dryers.