Development of industrial scale fluidized bed paddy dryer

This research objective is to develop a fluidized bed paddy dryer with a capacity of 5-10 t/h. For the test on paddy drying machine with a capacity of 2.5-5 t/h, actual production capacity was 4.8 t/h. Drying conditions were: air flow rate 2.57 cubic m/s (2.30 kg/s), bed velocity about 2 m/s, fraction of air recycled 54 percent, bed height 10 cm and drying air temperature 150 deg C. Residence time of paddy was approximately 0.95 minutes. Moisture content of paddy was reduced from 27 percent dry-basis to 21 percent dry-basis. Electrical power consumed was 9,388 W. Average deisel consumption was 22.63 l/h. Primary energy consumption was 912.25 MJ/h, dividing into electrical energy in terms of primary energy 87.86 MJ/h and heat 824.40 MJ/h. Moisture evaported was 224 kg-water/h. Specific primary energy consumption was 4 MJ/kg-water. For 12-hour operation per day, paddy drying cost was 1.312 baht/kg-water. (Fixed cost 0.406 baht/kg-water and operating cost 0.906 baht/kg-water.) For the test on paddy drying machine with a capacity of 5-10 t/h, actual production capacity was 9.5 t/h. Drying conditions were: air flow rate 5.57 cubic m/s (5 kg/s), bed velocity about 2.23 m/s, drying air temperature 115-130 deg C, fraction of air recycled 69 percent and bed height 15 cm. Residence time of paddy was approximately 1.4 minutes. Moisture content of paddy was reduced from 29 percent dry-basis to 23 percent dry-basis. Electrical power consumed was 32,325 W. Average fuel oil consumption was 31.34 l/h. Primary energy consumption was 1,478.23 MJ/h, deviding in to electrical energy in terms of primary energy 302.56 MJ/h, and heat 1,175.67 MJ/h. Moisture evaporated was 420.29 kg-water/h. Specific primary energy consumption was 3.96 MJ/kg-water. For 12 hour operation/day, paddy drying cost was 0.095 baht/kg-water. (Fixed cost 0.361 baht/kg-water, and operating cost 0.543 baht/kg-water.) Comparing between simulated and experimental results (moisture content, energy consumption), at high moisture level, simulated final moisture content was 0.5-3 percent dry-basis higher than experimental one. But for low moisture level, simulated final moisture content was 0.5-1.5 percent dry-basis lower than experimental one. For energy consumption, simulated results were 0.5-2 MJ/kg-water higher than the experimental one for high moisture level and 1-3.5 MJ/kg-water lower than the experimental one for low moisture level, respectively.