An Investigation of Multicomponent Droplet Vaporization in Fluidized Catalytic Cracking Risers

Fluidized Catalytic Cracking (FCC) oil refining technology converts heavy feed oil into lighter, more valuable components using hot catalysts in a riser reactor. The interphase mixing, vaporization, and chemical reactions are the controlling processes inside the FCC riser. The interactions between the feed oil spray and the gas/solid flow determine the final products of the cracking process, and ultimately the profitability of the FCC unit. A three-phase reacting flow computational fluid dynamic (CFD) code, ICRKFLO, has been developed for the simulation of FCC riser flows. In this study, ICRKFLO is used to simulate a low profile FCC riser. A low profile riser has a shorter residence time than standard FCC risers, and the modeling of the droplet vaporization process is of great importance. Because feed oil is composed of many hydrocarbon components, each of which vaporize at a different temperature, a new vaporization model is developed to include multicomponent vaporization of a droplet. The model allows the boiling point temperature of the droplets to vary as the vaporizing droplet loses mass to the gaseous phase. Comparison between the existing and new models shows a significant change in gasoline yields at the riser exit.