Thin-layer drying and thick-layer drying of crumb rubber
was carried out using a fixed-bed dryer with dimension
of 0.350.700.80m3 as shown in Fig. 3. The drying system
consisted of a 2.4-kW electrical heating unit (the 12-
vane axial heaters), a centrifugal fan driven by a 2.0-hp
motor, pipe, temperature controller unit, and a drying
chamber. Inlet air temperature was regulated by PID
temperature controller of DIGICON model MD-400N
(Thailand) with an accuracy of 1.0C. The inlet and outlet
air, ambient air, and the grain temperature in each rubber
bed depth were measured by a K-type thermocouple connected
to a Yogokawa data logger model FX100 (Japan)
while the change of the mass of the sample was weighed
during drying by four conventional load cells connected
to monitor with an accuracy of 0.05 kg. Air flow rate
was regulated by an electrical inverter of Frenic-Mini
model SCIS-7A (Japan). The moisture contents of rubber
were determined by ASAE method.