Wet particle dynamic equilibrium model based on coking in FCC cyclone separators and application status of particle deposition models

The carbonaceous deposition on the outer wall of the vortex finder in the cyclone separator within the disengager of fluid catalytic cracking (FCC) units severely restricts the long-term safe operation of the equipment. This paper systematically analyzes the particle deposition environment inside the disengager, the microscopic characteristics of coke samples, and the evolution patterns of the deposition layer. It also summarizes the current application status of particle contact theory, liquid bridge force models, restitution coefficients, and various critical deposition criteria. This paper proposes a dynamic equilibrium model for wet particle deposition on the outer wall of a cyclone separator vortex finder. The model uses a critical velocity criterion to determine whether particles initially deposit, and further introduces a critical shear detachment criterion: when the near-wall friction velocity exceeds the critical shear velocity, deposited particles undergo rolling detachment; otherwise, the coke layer continues to grow until a dynamic equilibrium is reached. The model fully accounts for the centrifugal force, Saffman force, Magnus force, drag force, and pressure gradient force in a strong swirling flow field, with the liquid bridge force and van der Waals force as the main adhesive forces. Based on critical moment theory, an analytical expression for the critical shear velocity is derived. Parameter sensitivity analysis and back-calculation verification demonstrate the rationality of the model. The model provides a new theoretical tool for the semi-quantitative prediction of coking on the vortex finder of FCC cyclone separators, and lays a foundation for subsequent cross-scale numerical simulation and anti-coking technology development.