粗重颗粒在循环床提升管内的局部颗粒浓度分布

Investigation on Local Solid Concentration of Coarse Particles in Circulating Fluidized Bed Risers

为研究颗粒物性对循环床提升管中气固动力学行为的影响 ,以空气 -沙子为气 -固体系 ,采用光纤探头测试了Φ 10 0mm× 10m循环床提升管中的局部颗粒浓度 ,并与FCC颗粒进行了对比。结果表明 ,粗重颗粒 (沙子 )无因次浓度的径向分布及其沿轴向的发展与细颗粒 (FCC)有明显的不同 ,重颗粒无因次浓度的径向分布沿轴向没有明确的相似性 ,环核流动结构也发生变化 ,其环区缩小 ,核心区扩展到边壁处附近。采用间歇指数 (IntermittencyIn dex)对提升管内气 -固混合程度进行的定量描述表明 ,随着床层高度的增加 ,间歇指数逐渐减小 ,径向分布更加均匀 ;在相同Gs1.2 /Gg2 .0 条件下 ,确定截面上间歇指数的径向分布基本一致。

To investigate the flow behaviors of coarse particles in CFB, the local solid concentrations of sands in a Φ 100 mm×10 m CFB riser were systematically measured by an improved fiber-optic probe. The results show that compared with fine particles (FCC), the coarse particles (sands) have quite different distributions in both radial and axial directions due to the significant effect of gravity. For coarse particles, no clear similarities for the radial distributions of normalized solids holdup are found along the axial direction, and the core-annulus flow structures are also changed greatly, with the core region extending to the vicinity of the riser wall. The analyses of the flow behaviors of gas-solid indicate that the intermittency indexes decrease with increasing height of riser section and become more uniformly distributed in radial direction. It is also found that for various conditions with the same values of Gs1.2/Gg2.0, the radial distributions of intermittency index become similar on a given cross-section of riser.