流化床提升管中脱油油砂颗粒固含率的轴向分布

Axial Distribution of Solids Holdup of Burned Oil Sand Particles in the Riser of a Fluidized Bed

针对油砂直接流化焦化工艺，建立了一套大型冷模提升管循环流化床装置．粒度测试结果表明，该脱油油砂颗粒属宽筛分混合颗粒，且细颗粒含量较多，粒度分布宽（1-〉2000μm）．在不同操作条件下，采用多点压力密度测量仪测定了提升管内压力梯度和截面平均固含率沿提升管轴向的分布．实验结果表明，脱油油砂颗粒在提升管内截面的平均固含率随表观气速增大而减小，随颗粒循环强度增大而增大；固含率沿提升管轴向的分布为C型，即上下两端较浓、中间较稀，且沿提升管自上而下分为3个区域：颗粒约束返混区（〉12m）、充分发展区（4-12m）和颗粒加速区（〈4m）；在相同操作条件下，脱油油砂颗粒在提升管内截面的平均固含率高于FCC颗粒，加速段与约束返混段长度大于FCC颗粒；确定了脱油油砂颗粒在提升管内截面平均固含率的影响参数为εp′，Fr及HГ／DГ。；通过实验数据回归得到提升管内截面平均固含率轴向分布的经验模型，计算与实验值吻合较好．

A large scale cold model apparatus of CFB riser reactor was established based on the method of directly fluidized coking oil sand. The measurement results of particle size indicate that the burned oil sand particles have wide size distribution （1-〉2 000 μm） with numerous fine particles. The axial distributions of pressure gradient and averaged cross-sectional solids holdup in the riser were measured by a multi-point pressure-fluctuation device. The results show that the latter increases with the increase of solid overall circulating flux and decreases with the increase of superficial gas velocity. The axial distribution of solids holdup in the riser is characterized by C type distribution with larger solid holdup values in the top and bottom sections, and smaller value in the middle section. The riser can be divided into three zones along the longitude based on the movement pattern of axial particles, i.e., accelerating zone （〈4 m）, full developing zone （4-12 m） and back-mixing zone （〉12 m）. Under the same operation conditions, the solids holdup of sand particles is much higher than that of FCC particles, the lengths of accelerating and back-mixing zones are both longer than that of FCC. Furthermore, an empirical model for estimating the axial distribution of averaged cross-sectional solids holdup was established based on the experimental data and theoretical analysis, respectively, which agreed with the experimental data.