循环流化床的流动特性

研究表明,循环流化床中粒子的循环速率决定了密相层和疏相层的空隙率。沿着粒子循环线的压力平衡控制了密相层的高度。在下降管中的粒子持有量和风力(?)的压力降决定了流化床的压力平衡。当风力阀的压降太大,或者在下降管中的粒子持有量不足,密相层消失。整个流化床成为疏相流动床。试验表明,当流速增至5m/s,没有产生从湍流流化床转化为其它形式的流化床。

Study on Flow Characteristic of Circulating Fluidized Bed

It is demonstrated that the voidages of the dense bed and its freeboard in the circulating fluidized bed are determined by the circulating rate of particle and the dense bed hight is controlled by the pressure balance around the particle circulating line affected by the hold-up of the particle in the downcommer and the pressure drop of the pneumatic valve.When the pressure drop of the pneumatic valve is too large or the hold-up of the particle in the downcommer is not enough, the dense bed disappears and whole bed is maintained dilute bed where the voidage has the same Value as that in the freeboard. Even when gas velocity is increased to 5m/s, definite trasition can not be observed from the turbulent flu-idization to other regimes of fluidization.