Abstract
In this paper, the authors introduced an analytical solution to obtain the drying rate on the fluidized bed drying of high moisture rough rice, particularly from the view point of pre-drying. Both observed and calculated values were compared. Consequently the propriety of analytical solution was found. The main results were as follows.
1) Analytical drying rate equations were developed based on the following assumptions. (Eqs. (16), (17)) (i) The relation between equilibrium moisture content of rough rice and relative humidity is approximated by a linear function. (ii) The moisture content of rough rice is uniform in the fluidized bed. (iii) The pattern of air flow in the fluidized bed is piston flow. (iv) The drying rate equation for the period of the first falling rate is applied in this analysis.
2) The large drying rate of early drying period was shown clearly in the drying curves. Therefore the drying process was devided in two periods. The coefficients of drying rate for each period were obtained based on the drying curves. (Eqs. (20), (21))
3) Close agreement between observed and calculated values was obtained after the consideration on the coefficient of drying rate.
4) The drying rate of rough rice was considerably affected by air temperature and independent of air rate. While the higher initial moisture content of rough rice was slightly larger drying rate.
5) This analytical solution could be calculated simply, giving only the values of air temperature, air rate and initial moisture content of rough rice as the drying conditions when atmospheric temperature and humidity are measured. Therefore the solution may be useful as the base of planning and operating the pre-drying apparatus of high moisture rough rice by fluidized bed.
