Abstract

Natural sun drying is one of the most common ways to preserve agricultural products. Many agricultural products are spread on the ground to be dried by sun and wind. This results to poor quality products due to contamination and high loss caused by uneven or incomplete dehydration. Parametric design of a drying system for processing cassava starch was carried out using Simprosys 2.0 Process simulation package specifically designed for drying systems. The units considered in this design includes; the air filter, blower, heater unit, solid dryer, input feeder, cyclone and product collector, a process flow diagram consisting of all the units was assembled. The drying system was designed on the basis of 20 kg/h of wet cassava starch with moisture content of 40%. From the results generated, the air particle loading for the air filter and filter area were found to be 0.038 kg/h and 0.267 m2 respectively, the blower suitable for the drying operation has a total discharge pressure of 3.296 kPa and power output of 0.505 kW. The heating unit has a total heating duty of 11.447 kW. Also from the process simulation results, for all range of temperature between 90oC to 120oC, an air flow rate of 450 kg/h has the highest values of drying efficiencies averaging 83.2%. Considering a circular transverse section, the suggested dryer diameter and length are 0.296 m and 2.366 m, respectively. Therefore, a total of 11 minute with an optimum temperature of 120oC can reduce the moisture content of cassava starch from 40 % wet basis to equilibrium moisture content of 10 % wet basis suitable for storage.