关键词: 锥形料腿, 超细粘附性颗粒, 循环流化床, 流态化

Abstract: Based on the fluidizing characteristics of cohesive powders, such as the formation of agglomerates with wide size distribution during fluidization, and partial defluidization due to disposition of large agglomerates, a novel design of CFB dipleg, the conical dipleg, was put forward for fluidizing ultrafine and cohesive powders. The conical dipleg consists of a conical dipleg and a V-valve with aeration of gas. Experiments on the conical dipleg showed that it can prevent the fluidized dipleg from disposition and defluidization of large agglomerates at the bottom of the bed and elutriation of smaller agglomerates at the top of the bed by providing variational superficial fluidizing gas velocity. The experiments also showed that the aeration gas is essential for V-valve to feed highly cohesive powders into riser smoothly. With the aid of the conical dipleg, stable circulation of highly cohesive ultrafine CaCO3 powder was achieved. Pictures taken from the inside of riser show that the ultrafine CaCO3 powders in the fluidized riser are in agglomerate form in spite of the high fluidizing gas velocity. The size of agglomerates is much smaller than that in conventional fluidized beds, and it has no significant variation along the riser height. Experiments also showed that the axial solids concentration in the riser is of S-shape distribution; and the lateral solids concentration displays a core-annulus structure. These phenomena are typical features of fast fluidization.

Key words: conical dipleg, ultrafine and cohesive powder, circulating fluidized bed(CFB), fluidization