循环流化床提升管中团聚物的结构及发展过程

为了研究循环流化床提升管内颗粒团聚的形成与解体机理,采用高速摄像技术捕获了Geldart B类颗粒在循环流化床提升管内团聚物的形成、长大和解体的动态演化过程. 利用图像处理技术获得不同操作条件下团聚物的形状、尺寸及其从形成到解体的发展过程. 结果表明,在循环流化床复杂气流的作用下,不同空间位置上团聚物的形成情况不同,边壁区较中心区多,底部密相区较上部稀相区多; 床内团聚物形态各异,大致可分为U形、倒U形、中心带状、贴壁条状、彗星形、致密球形、双核形等,其中彗星形、致密球形、双核形团聚物在运动过程中会相互转变; 在提升管中心区多为向上运动的倒U形和彗星形团聚物,而在提升管边壁区多为向下运动的U形和贴壁条状团聚物,且团聚物存在横向迁移的现象.

Structure and Development of Clusters in the Circulating Fluidized Bed Riser

In order to study the formation and disintegration mechanism of particle clusters in a circulating fluidized bed riser,the dynamic evolution process of particle clusters,such as the cluster formation,development and dissipation in a circulating fluidized bed riser is reported by the high-speed video technology. The image processing technology is used to determine the cluster shape,size and record the clusters evolution from formation to breakup under various operating conditions. The results indicate that under the effect of the complex air flow in the circulating fluidized bed,the formation of clusters in different spatial positions is various. The clusters in side-wall regions are more than those in the center. Similarly,the clusters at the riser bottom are more than those in the upper part. In addition,clusters in the bed vary in the shape and can be divided into the U-shaped,the inverted U-shaped,the center-banded,the stick-wall strip,the comet-shaped,the dense-spherical and the double-core-shaped. The comet-shaped,the dense-spherical and the double-core-shaped clusters could change into each other in the movement process. The upward flowing inverted U-shaped and the comet-shaped clusters are majority in the center region of the riser,while the falling U-shaped and the stick-wall strip clusters are majority in the side-wall region. Furthermore,the clusters in the riser always lateral migrate.