快速流化床中颗粒团聚物尺寸的极值估算

EXTREME VALUE ESTIMATION OF CLUSTER SIZE IN A FAST FLUIDIZED BED

本工作采用微观显示技术及7mm 直径的光纤闪光摄象探头,获得了一组快速流化床中心处的颗粒团聚物的微观图象.随后,应用图象分析技术的极值统计理论研究了不同操作条件下团聚物长短轴尺寸和当量直径的极值分布。由此可以在极值图中估计一个已知范围之样本中团聚物的极值.本文对 A 类和 B 类颗粒快速流态化的重要特征—最大团聚物直径 D_(cm)与单颗粒平均直径 d_p 之比值进行了估计,对 A 类颗粒,若以10000个团聚物为统计标准,D_(cm)/d_p 约为140,而对于 B类颗粒,则 D_(cm)/d_p 约为20.

Micrographs of particle cluster at the centerline of a fast fluidized bed were obtained by micro-visualization through a 7-mm-diameter optical fiber probe.Both the image analysis technique and the statistical theory of extreme value were applied to investigate the extreme value distribution of the major and minor axes and the diameters of the clusters under different operating conddtions.Thus,it becomes possible to predict the extreme values of the maximum ckster sizes which are expected for particulate materials.Being the most important characterstics in the fast fluidization of Class A and Class B powders,the ratio of the maximum cluster diameter to the particle diameter is evaluated.For Class A and Class B powders,it turns to be about 140 and 20 respectively.