An Experimental Test of the Concept of the Characteristic Drying Curve Using the Thin-Layer Method

ABSTRACT The drying behaviour of paticles ( purolit and silica gel) was studied using the thin-layer method described by Langrish et al ( 1). The experiments covered inlet air temperatures between 100 and 150°C, inlet air humidities from 0.02 to 0.052 kgkg1 superficial air velocities between 3.8 and 10.8 ms-1, with layer thicknem of 2 – 10mm. No constant mle period war observed. Characteristic drying curves were found to fall within a narrow band fur these ranges of process variables, for material of uniform size and shape and with relative moisture content defined in terms of the end of the induction period. Small changes in panicle shape, particle size distribution and uniformity of particle layers had negligible infuence on the drying kinetics. However, reduction in particle size from 5.2mm diameter to 0.86mm had a marked effect: the normalised drying rate at a given relative moisture content became larger as the particle size became smaller. This phenomenon is attributed to an increase in available co...