气固循环床上行两相流颗粒曳力系数研究

Drag Coefficient in Gas-solid Two Phase Flow of CFB Riser

在高16 m气-固循环流化床提升管内,通过测定表观气速、颗粒质量流率和不同轴向高度的床层平均颗粒浓度,结合对单颗粒进行受力平衡分析,间接获得了不同轴向位置的颗粒曳力系数。同时通过分析雷诺数、阿基米德数、床层颗粒浓度对颗粒曳力系数的影响,结合实验中所获得的数据,提出颗粒曳力系数的关联式。该关联式考虑颗粒的物性参数、操作条件对曳力系数所造成的影响,其预测值与本文和文献实验值吻合良好,并且在一维轴向均相模型下较好预测了床层内轴向压力分布。

Systematic experiments were carried out in a 16 m high gas-solid CFB riser with FCC particles to investigate the drag force acted on solids by gas. Based on the measured data of the cross-sectional average solids holdups at different axial locations of riser under various operation conditions and through the dynamic balance analysis of single particle, drag coefficients were indirectly obtained. The results show that the solids holdups have great effect on drag coefficients, which obviously decrease with increasing solids holdups. Considering the effects of Reynolds number, Archimedes number and solids holdups, a new COiTelation for drag coefficients was developed. The predicted values of the new correlation for drag coefficients were compared with the experimental data of this work and some other authors, and a good agreement was observed for three different particles. Using the drag coefficient correlation, the axial pressure gradients of gas-solid flow in riser are successfully predicted.