Drying of Sago Hampas in a Fluidized Bed Dryer
Sago hampas is one of the wastes produced in a high quantity in the manufacturing process of sago flour and causes serious environmental pollution. Once sago hampas is dried, it can be stored and used for further application to utilize its high content of starch. The original moisture content of sago hampas is at 90% wet basis, whereas the moisture content to be achieved after the drying process is 10% wet basis. In this study, the effect of bulk and tapped density on the moisture content of sago hampas is studied using the Compressibility Index and Hausner Ratio to characterize the flow of sago hampas in the fluidized bed dryer from 0% wet basis to 90% wet basis. Moisture content from 0% wet basis to 10% wet basis showed passable to excellent flow character which means fluidization is possible with this range of moisture content. The efficiency of temperature and velocity of air supplied into fluidized bed dryer is studied based on loss of moisture content, drying rate and fluidization profile of the drying process in the fluidized bed dryer. This study of temperature and air velocity are focused at air velocities of 1.50, 1.70, 1.90, and 2.10 m/s and air temperatures of 50°C, 60°C, 70°C and 80°C. From the experimental data, drying process takes lesser time and reaches higher drying rate with increasing temperature and velocity of air. Increasing air temperature will increase the heat transfer between sago hampas and dry air and quickens the moisture movement to the surface at a higher rate. The effect of air velocity on the drying is less significant compared to air temperature because air velocity plays a more important role in the fluidization of the sago hampas. Drying at maximum temperature 80°C and maximum air velocity 2.10 m/s takes 7-8 minutes to reach 10% wet basis, 9-10 minutes to reach 0% wet basis and a drying rate of 5.5 g/min. Data from fluidization profile shows fixed bed during early fluidization, then reaches bubbling fluidization state and lastly reaches turbulent fluidization. Increasing air temperature reduces the time taken to reach the turbulent fluidization state of sago hampas. Increasing air velocity increases the bubbling fluidization density and quickens the turbulent fluidization state. Other than that, particle size distribution and percentage of fines in sago hampas is obtained using dry sieve analysis. After sieving, the sago hampas is classified and is characterized visually according to each particle size range. From the analysis, sago hampas contains 12.67% gravel and 87.33% sand. 30.27% of the particles are classified in Group B and 69.73% are classified in Group D of the Geldart chart. Visual classification of sago hampas shows that sago hampas has 3 particle categories, which are sand, gravel and fibrous wood.
Keywords - Drying, Fluidized Bed Dryer, Sago Hampas