Impactor-Assisted Atomization in Multi-Jet Twin-Fluid Injectors for FCC Risers

The Fluidized Bed Catalytic Cracking relies heavily on the atomization efficiency of the feed injection system, where vacuum gas oil is sprayed into the riser reactor for rapid vaporization and catalyst contact. This study experimentally investigates the spray behavior of a twin-fluid nozzle designed for FCC applications, focusing on the influence of air-to-liquid ratio (ALR) on droplet dynamics. Spatial measurements reveal that increasing ALR significantly reduces the section-averaged Sauter Mean Diameter (SMD) due to enhanced aerodynamic shear. The 3-hole injector consistently outperforms the 4-hole design, generating finer and more uniform droplets. Droplet size distributions exhibit lognormal behavior, with decreasing variance at higher ALRs, indicating improved spray uniformity. In contrast, axial velocity distributions deviate from normality, reflecting the influence of turbulent air–droplet interactions. The power-law correlation between SMD and ALR demonstrates that droplet breakup is primarily controlled by the air-to-liquid mass ratio and injector geometry.