Search

The flow state has an important influence on the carbonaceous deposition for coking formation process. To study the flow of heavy oil droplets and catalyst particles in FCC process, we used the scanning-electron microscope (SEM) to analyze the microstructure of coke and simulated the flow by computational fluid dynamics (CFD) method. A new iso-vortex surface method according to swirling strength was used to analyze the fluid motion. The results showed that the dissolution of powdered coke sample in ethanol was more uniform than that in water. Swirling strength on the outer wall of vortex finder was large, and there was a depression in the flow layer at about 270°. Under the swirling strength of 654.59 s−1, the flow layer in the outer wall of vortex finder was thick in the range of 0–180°. A stable stagnant layer in the barotropic gradient boundary layer was easier to form a deposition layer of fine particles or droplets. When the fluid velocity outside the boundary layer increased, the shear force increased. The thickness of sedimentary layer and the size of sedimentary particles in the boundary layer tended to decrease. In addition, the backflow also affected the deposition of particles and droplets. [Display omitted] • Coking cases of catalytic cracking unit of China in recent years were summarized. • Mechanism of coking formation outside the vortex finder was systematically analyzed. • Flow with time series under different swirling strength was obtained by CFD method. • The interaction between droplets and catalyst particles has been deeply studied. [ABSTRACT FROM AUTHOR]