循环床提升管中粗重颗粒浓度的轴向分布

在10m高提升管中对空气-沙子体系的压力梯度进行系统测试，研究了粗重颗粒平均颗粒浓度云的轴向分布及操作条件对它的影响。结果表明，粗重颗粒的^εs在相同操作条件下显著低于FCC颗粒；随操作条件的不同，沙子颗粒表现出与FCC显著不同的轴向分布形态。高气速下粗重颗粒^εs的轴向分布与FCC相似表现为单调下降或直线形关系；但在表观气速Ug降低至某一临界值后，粗重颗粒^εs的轴向分布呈现出波动形式，表明沙子颗粒在提升管中的流动是一个加速-减速-再加速直至充分发展的过程。随Ug减小或Gs增大，提升管各截面上云升高；当^εs的轴向分布为波动形式时，提升管底部截面和中部颗粒聚集截面上^εs的变化较其它截面更为显著。

Axial Distributions of Averaged Solids Holdups for Coarse Particles in CFB Riser

The pressure gradients of air-sand two-phase flow in a CFB riser were systematically measured in a 10m high CFB riser to investigate the axial distributions of averaged solids holdups of coarse particles and the effects of operation conditions. The results show that the solids holdups of sand particles are much lower than those of FCC particles under the same operation conditions, and the axial distribution curves of the solids holdups for sand particles are significantly different from those for FCC particles, depending on the operation conditions. At high superficial gas velocity, the solids holdups for sand particles decrease exponentially along the riser height, similar to the variation trend of FCC particles; as gas velocity decreases to some extent, however, the axial distributions of solids holdups for sand particles become wave-shaped, indicating that the sand particles in CFB riser will experience a second acceleration process before reaching a fully developed flow at the top section of the riser. It is also found that with decreasing gas velocity or increasing solids circulating rate, the averaged solids holdups at all axial locations become increased, while for the wave-shaped distrbution, the variations of solids holdups are much more significant at the riser bottom and middle sections, where a larger amount of particles are concentrated.