Constant and intermittent drying characteristics of olive cake

The drying kinetics of olive cake, the solid by- product of the olive oil extraction process, has been experimentally investigated in a small- scale tray dryer using both constant and intermittent ( on/ off) heating schemes. The parameters investigated include inlet air temperature and intermittency of heat input. The drying kinetics was interpreted through two mathematical models, the Page equation and the Lewis equation. The Page equation was most appropriate in describing the drying behavior of olive cake. A diffusion model was used to describe the moisture transfer and the effective diffusion coefficient at each temperature was determined. The dependence of the effective diffusion coefficient on drying temperature can be adequately explained based on an Arrhenius- type relation. The effective diffusion coefficient varied between 7.6 x 10(-8) and 2.5 x 10(-7) m(2)/ min with an activation energy of 38.55 kJ/ mol. Comparison of time evolution of material moisture content due to intermittent and constant drying is also made.