COMPARATIVE DRYING CHARACTERISTICS OF AGRICULTURAL PRODUCT IN BUBBLING FLUIDIZED BED (BFB) AND ROTATING FLUIDIZED BED IN A STATIC GEOMETRY (RFB-SG) DRYER
Present work is focused towards performance analysis of a rotary fluidized bed with static geometry (RFB-SG). This dryer is developed based on the concept of injecting the fluidization gas tangentially into the fluidization chamber with the help of multi gas inlet slots. Upon contact with particles, the gas- phase motion quickly shifts from tangential to radial direction and gas leaves the vortex chamber through a chimney. Due to inertia, the particles follow a different gas flow path and form a rotating particles bed. The fluidizations of the particles are depending on the radial gas-solid drag force and the countering centrifugal force. Thus a very high acceleration in order of 7-8 times that of acceleration due to gravity is achieved which helps in quick removal of moisture even from the core of the particles to be dried.
In the present investigation, the performance of RFB-SG and conventional bubbling fluidized bed (BFB) dryer are analyzed for drying of wheat. The experiments were in batch drying. The drying vortex chamber (RFB-SG) diameter has 24 cm and length 5 cm. The experiments were conducted on drying of wheat particle whose length is 6.4 mm and diameter 3.5mm approximately with density 1020 kg/m3. The inlet drying air temperature was 50 to 65°C with air mass flow rate 400 to 700Nm3/h. The inventory of wheat for drying was 300 to 600g. The performance with respect to drying rate, inventory, air flow rate and process intensification were evaluated. The process intensification (PI) factor was 10 to 12 in RFB-SG dryer compare to BFB.