2.1. Spouted bed
The experiments were carried out in a two-dimensional spouted bed with draft plates as shown in Fig. 1. The dryer has a vertical rectangular shape, withan inclined base (60angle) in order to avoid the dead zone (Passos, Mujumdar, & Raghavan, 1987). The inlet cross sectional area of 4·15 cm2, drying chamber with a dimension of 60·15·50 cm, spout width of 8 cm and entrance height of 12.5 cm were used. The selected values of spout width and entrance height could steadily maintain the transport of examined materials in the dryer. A 24 kW electric heater connected to a PID controller with an accuracy of ±1C was installed to heat the air up to the desired temperature. A 2.2 kW backward-curved blade centrifugal fan supplied the air and a variable speed unit controlled the air speed passing through the spouted bed. The entire drying system was insulated with the layers of glass wool to minimise heat loss of the system. The dryer front was made of heatresistant glass to visualise the flow of solid particles. Before starting the experiments, the system was heated until every part reached the desire temperature. To prevent the entrainment of particles, a deflector was fitted at a height of 142 cm from the dryer base. After the particles hit the deflector, they fell freely to downcomer region