Journal of Sustainable Development November, 2008 123 Drying Kinetics of Saw Dust in Tray Dryer C. SRINIVASA KANNAN Monash University Malaysia 2-Jalan University, Bandar Sunway, 46150 Petaling Jaya, Selangor, Malaysia N. BALA SUBRAMANIAN(Corresponding Author) Department of Chemical Engineering A.C. Tech. Campus, Anna University-Chennai Chennai-600 025, India E-mail: nbsbala@annauniv.edu Abstract Drying kinetics of palm wood saw in tray drying covering wide range in operating conditions have been investigated in the present study. The drying rate increased with an increase in the temperature and flow rate of the heating medium increased, and decreased with an increase in the bed height. A model has been developed based on Fick’s law of diffusion to explain the drying kinetics. Keywords: Drying kinetics, Palm wood sawdust, Tray dryer, Kinetic model 1. Introduction Malaysia contributes more than 50% of the world palm oil production. Palm tree based plywood’s are increasingly used due to its environmental friendliness. Nearly 100,000 hectares of replanting is carried out every year. Several saw mills ranging from small scale to large scale engaged in plywood production resulting generation of large amount of saw dust. The saw dust generated during plywood processing finds extensive applications in compressed powder boards, fuel pellets, mosquito coils, incense sticks, activated carbon etc. The mosquito coils prepared based on sawdust are reported to have less toxic compared to the coils prepared using coconut shells, resulting larger potential for utilization of saw dust for mosquito coil production (Akpinar et al., 2003; Crank, 1975) . Further the large scale saw mills can utilize the saw dust for cogeneration facility utilizing Integrated Gasification Combined Cycle (IGCC) technology. The high moisture content of saw dust deteriorates the quality of sawdust resulting restricted application. This forces the researchers to design a suitable drying unit to handle the saw dust for longer storage and cost reduction in transportation. Drying is fundamentally a simultaneous heat and mass transfer operation and used for various thermal energy applications. Several drying methods have been proposed in the literature for high quality products. Among the drying techniques, tray drying is one of the most frequently used methods in chemical process industries. A proper drier design requires knowledge on the characteristics of the material to be dried and the drying kinetics. Extensive work has been reported in literature on tray drying, with respect to kinetics, mechanism and modeling (Larson at al., 2001; Marcello and Osvaldir, 2007; Srinivasakannan et al., 1995). The present study attempts to study the drying kinetics of drying of palm sawdust covering wide range in operating conditions. 2. Experimental The sawdust collected from near by palm tree industry was 2 mm in size with 93% moisture. The samples moisture content were estimated by standard weight difference method and reported on dry basis (kg of moisture/kg of dry sawdust). The initial moisture content of the samples was estimated for each experimental run. Figure 1 shows the schematic representation of drying set-up. It consists of a fan, heating system, a drying chamber with tray and a weighing balance. The weighing balance had an accuracy of ± 0.01g. The drying chamber has the dimensions of 3m X 0.3mX 0.3m with a facility to load and unloading. The material depth in the tray can be varied with material loading. Experiments were conducted by varying material loading, temperature of heating medium and moisture content.