Technology optimization of drying wheat by spouted bed with draft tube

For spreading the use of spouted bed in China, which has good effect on heat and mass transfer ,a spouted bed grain dryer was designed and fabricated to study its effect on drying grains. The structural parameters were as follows: inner diameter was 180 mm, height of bed 700 mm, height of cone 100 mm, conic angle 90°, inner diameter of gas inlet tuber 25 mm , and its length 200 mm. A series of experiments of drying wet wheat were carried out with the spouted bed. A scheme of orthogonal test, which includes 3 factors and 3 levels, was designed. The factors were the air flow rate, the temperature of hot air and the load of wet wheat. The levels of the air flow rate were 42, 54, 71 m³/h(20℃，101.3 kPa)；the temperature of hot air were 60, 75, 90℃; the load of wet wheat were 2.0, 2.9, 3.8 kg. Taking the heat consumption per kilogram water as the appraising target, the technological parameters were optimized. The optimum conditions on the present apparatus were as follows: the air flow rate was 42 m³/h, the temperature of hot air was 75℃,and the load of wet wheat was 3.8 kg. The optimum heat consumption per kilogram water was 5 588 kJ. The temperature of hot air was the prominent factor. By the studies, the optimum result was obtained for drying wet wheat using the spouted bed dryer with a draft tube. Further research is necessary to enlarge spouted bed dryer to fit drying of grains in industrial scale.