提升管与流化床耦合反应器内固含率的轴向分布

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，采用多点压力密度仪测定了提升管内轴向压力梯度及截面平均固含率沿轴向的分布规律。结果表明，提升管内固含率的轴向分布呈上下两端大、中间小的C型分布特征，颗粒在提升管内沿轴向的运动可分为颗粒加速区、充分发展区和颗粒约束返混区；提升管内截面平均固含率随颗粒循环强度的增大而增大，随表观气速的增大而减小，提升管出口的流化床内颗粒静床高度只对颗粒约束返混区固含率有影响，而对颗粒约束返混区长度及颗粒约束返混区以下区域固含率影响较小。利用实验数据回归出了提升管内截面平均固含率的轴向分布及颗粒约束返混区最大颗粒返混比的经验模型，其计算值与实验值吻合较好。

AXIAL DISTRIBUTIONS OF SOLIDS HOLDUP IN A RISER-FLUIDIZED BED COMPOUND REACTOR

A large scale cold model device of riser-fluidized bed compound reactor was set up based on the olefin reduction technology with auxiliary reactor for FCC naphtha upgrading. The axial distributions of pressure gradient and averaged cross-sectional solids holdup in the riser were measured using a multi-point pressure-density apparatus. The results show that the axial distributions of solids holdup in the riser are characterized by C type distributions with larger solids holdup value at the top and bottom sections, and smaller value in the middle section. The riser can be divided into three zones along the longitude according to the axial particles movement pattern, i. e. , accelerating zone, full developing zone and back-mixing zone. The averaged cross-sectional solids holdup in the riser increases with the increase of solids overall circulating flux and decreases with the increase of superficial gas velocity. The static bed height of particles in the fluidized bed located at the exit of the riser has influence on the solids holdup in the back-mixing zone,but has little effect on the length of the back-mixing zone and the solids holdup below the back-mixing zone. Furthermore, empirical model for estimating the axial distributions of averaged cross-sectional solids holdup and the maximum back-mixing ratio of particles in the backmixing zone was established based on the experimental data and theoretical analysis, respectively. The model predictions are in good agreement with the experimental data.