耦合流化床提升管内固含率径向分布及沿轴向的发展

针对催化汽油辅助反应器改质降烯烃工艺，结合提升管与流化床的特点，建立了一套提升管与流化床耦合反应器大型冷态实验装置. 在不同操作条件下，采用PV-4A型光纤密度仪测定了提升管内固含率沿径向的分布规律. 结果表明，固含率径向分布整体上呈现中心小、边壁大的环-核结构分布特征；沿轴向向上，各径向位置上的固含率在颗粒加速区逐渐降低，在充分发展区趋于稳定，在颗粒约束返混区又有所升高；各径向位置上的固含率随表观气速增大或颗粒循环强度减小而减小，且均匀性变好；提升管上部流化床内颗粒静床高度只对颗粒约束返混区内固含率径向分布有影响，而对颗粒加速区和充分发展区的固含率径向分布影响较小；当表观气速较低或颗粒循环强度较大时，颗粒约束返混区上部局部固含率最大值出现在无因次半径f=r/R=0.7附近，此时局部无因次固含率es*=es/ 沿轴向在H>5.33 m时不再具有相似性；通过比较径向不均匀指数，得到轴向各区固含率径向分布趋于均匀的程度依次为：充分发展区>颗粒约束返混区>颗粒加速区. 利用实验数据回归出了局部固含率径向分布关联式，其平均相对误差在6%以内.

Radial Distribution and Axial Development of Solids Hold-up in the Riser Coupled with Fluidized Bed

A large scale cold model experimental setup of a compound reactor mainly composed of riser and fluidized bed was established according to the olefin reduction technology with auxiliary reactor for FCC naphtha upgrading. The radial distribution of solids hold-up in the riser of the compound reactor was measured in different operating conditions by PV-4A optical fiber density apparatus. The experimental results show that the radial distribution of solids hold-up is the core-annular structure with lower solids hold-up in the center region and higher in the wall region. In the axial direction, the radial local solids hold-up gradually decreases in the particle accelerating region, tends to smooth in the fully-developed region, and then increases in the particle back-mixing region. The radial local solids hold-up decreases with increase of superficial gas velocity or decrease of solids flux. The static bed height of particles in the fluidized bed located atop the riser has effects on the radial distribution of solids hold-up in the back-mixing region, but has little effect on that of particle accelerating and fully-developed regions. The maximum solids hold-up in the particle back-mixing region appears to be close at the non-dimensional radial position f=r/R=0.7, and the axial distributions of radial local solids hold-up in different cross-sections in particle back-mixing region are not similar. According to the analysis of the radial non-uniformity index of local solids hold-up, the uniformity degree of radial distribution of local solids hold-up decreases in the following order: the fully developed region > the back-mixing region > the accelerating region. Furthermore, empirical model for estimating the radial distributions of local solids hold-up in the riser was established based on the experimental data and theoretical analysis. The error between the calculated data of the model and the experimental data is less than 6%.