方形流化床内转变速度的研究

Research of Transition Velocity in Square Fluidized Bed

采用压差传感器在方形流化床中测试了多个床层截面的压力波动,研究了从鼓泡流态化到湍动流态化条件下气固方形床中截面平均压力梯度及其波动标准差的变化行为,获得了转变速度Uc,结合不同形式的圆形流化床关联式,采用当量直径方法对此流化床进行了转变速度的计算。比较分析的结果表明:通过当量直径的计算方法得出的转变速度与在相同操作条件下首先发生转变的床层上部的转变速度接近,说明用当量直径的方法是可行的。同时,发现床内流型的转变不是同时发生于整个床层的瞬时行为,而是由床层上部逐层向下扩展的递进行为,表明转变速度与床体尺寸及床层截面高度有关。

The pressure fluctuation at different axial locations were measured square fluidized bed with FCC particles by differential pressure transducers to investigate basic behaviors of pressure gradients and their standard deviation from bubbling to turbulent fluidization. The Ucs was gained and was calculated combing to different correlations of column fluidized bed by equivalent diameter. It is shown that, the transition velocity is close to transition velocity at upper bed in a square fluidized bed at same operation condition from bubbling to turbulent fluidization. The method is feasible of using equivalent diameter. The transition of turbulent is a process gradually happened from upper bed section to lower. The transition velocity is related to dimension and axial height of fluidized bed.