圆柱体重质大块物在鼓泡流化床中停留时间

Residence time of a large cylindrical heavy object in a bubbling fluidized bed

在带倾斜布风板和定向风帽的鼓泡流化床上,采用电容层析成像示踪法,研究了床内密相区内不同尺寸的单个等高圆柱体重质大块物在不同流化风速下的停留时间分布特性。通过对实验结果的统计学分析和大块物在流化床内的受力分析,探讨了流化风速、大块物尺寸对圆柱体大块物停留时间的影响。研究发现:圆柱体大块物在床内的平均停留时间随流化风速的升高先快速降低,后缓慢降低,最终趋于某一定值;受大块物下落状态、流场速度压力脉动等随机因素影响,大块物在床内停留时间分布曲线较宽;与尺寸较小的大块物相比,尺寸较大的大块物与布风板的摩擦系数较小,因而停留时间短。该研究成果可为流化床排渣设计提供参考。

The residence time distribution （RTD） of large heavy cy- lindrical objects of different sizes immersed in the dense phase of a fluidized bed equipped with an inclined air distributor was studied u- sing electrical capacitance tomography （ECT） tracing. The influ- ences of the superficial gas velocity and the object size were studied using probabilistic statistical analyses and mechanics analyses. The experimental results show that the residence time is reduced sharply at the beginning with increasing fluidization velocity and then the re- duction slows. Finally, the residence time tends to a minimum. The influence of random factors such as the stochastic positions of the fallen larger objects and stochastic pulsations of the pressures and velocities in the fluidized bed makes the RTD curves of the large cy- lindrical objects quite wide. The residence times of larger objects are shorter than smaller ones due to their lower drag coefficients. These results give a theoretical reference for the slag-off design of fluidized beds.