导向管喷动床小麦干燥工艺优化研究

Technology optimization of drying wheat by spouted bed with draft tube

为在国内推广使用具有良好的传热和传质效果的喷动床 ,自行设计制造了喷动床粮食干燥机 ,以探索喷动床用于粮食干燥的实际效果和所存在问题的解决方法。喷动床的内径为 180mm ,高为 70 0mm ,锥体部分高为 10 0mm ,锥角为 90° ,气体入口管内径为 2 5mm ,所用导向管的内径为 2 5mm ,长 2 0 0mm ,距进气管口 5 4mm。以湿小麦为原料 ,进行喷动干燥试验。设计了三因素三水平正交试验方案。所考察的三个因素是空气流量、热空气温度和湿麦装料量。各因素的水平为 :空气流量取 42、5 4、71m3 /h( 2 0℃ ,10 1.3kPa) ;热空气温度取 60、75、90℃ ;湿麦装量取 2 .0、2 .9、3 .8kg。以单位质量水分热耗为指标进行评价 ,得到了优化工艺参数 :空气流量取 42m3 /h ,热空气温度取 75℃ ,湿麦装量为 3 .8kg。优化工艺的热耗为 55 88kJ/kg水。方差分析指出 ,热空气温度对指标有显著影响。研究表明 ,导向管喷动床用于小麦干燥试验取得了优化结果 ;可以进一步研究喷动床的放大问题 ,以使其真正用于粮食干燥。

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 m^3/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 m^3/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.