Experimental Study on Classification Performance of Multi-Arm Vortex Separator
The development of efficient catalyst classification technologies is crucial for optimizing fluid catalytic cracking (FCC) and catalytic pyrolysis coupling processes, where distinct particle size distributions are required for different reaction pathways. In this study, a large-scale cold-model experimental platform of a multi-arm vortex separator is established to explore the influence of operating conditions on classification behavior. Systematic experiments are conducted by changing ejection gas velocity (8~20 m/s), inlet particle concentration (30~70 g/m3), and bed linear velocity (0.15~0.25 m/s). The results demonstrate that ejection gas velocity governs classification sharpness by controlling the entrainment of fines within the coarse fraction. The increase in ejection gas velocity enlarges the upward axial gas velocity inside the device, thereby enhancing the entrainment effect on particles near the vortex arm outlets. Increasing the ejection gas velocity from 12 to 16 m/s reduces proportion of fine particles in coarse components from 14% to 12%. The inlet particle concentration imposes competing effects on classification performance: while higher concentrations promote agglomeration and modify turbulence distribution, excessive loading intensifies fine-particle entrainment, thereby diminishing classification selectivity. The system maintains stable pressure drop characteristics under different bed linear velocities, with the pressure drop increasing by maximum of about 15% when the bed linear velocity is raised from 0.15 m/s to 0.25 m/s. Analysis of grade efficiency curves reveals classical S-shaped profiles with cut sizes (dc50) shifting under different operating regimes. Higher particle concentrations reduces dc50, favoring fine-particle removal, while higher ejection gas velocities enlarge dc50, moving the classification boundary toward larger sizes. These findings confirm the synergistic effect of ejection gas velocity and inlet concentration, highlighting that rational parameter matching can simultaneously improve efficiency and selectivity. Beyond the experimental findings, this work emphasizes the broader applicability of multi-arm vortex separators in refining and petrochemical processes. By enabling precise adjustment of particle size distribution, the system offers a promising pathway for enhancing catalyst utilization, extending catalyst lifetime, and facilitating process intensification in coupled FCC-pyrolysis units.