Effect of Injection Zone Cracking on Fluid Catalytic Cracking

Fluid catalytic cracking (FCC) is a refining process for converting heavy oils to valuable products such as gasoline and olefins. Modeling of this process is quite challenging. A common assumption has been that vaporization is instantaneously fast and cracking is negligible in the injection zone. Relaxing this assumption, an approach for quantifying the effect of injection zone cracking on FCC performance is developed. The approach combines a Lagrangian description of the spray behavior with an Eulerian modeling of transport-cracking coupling in the FCC riser. Included in the model are droplet vaporization, a four-lump kinetic network, spray penetration trajectory, solid-fluid and solid-solid collisions, and multispray interactions. Parametric studies show that precracking in the injection zone plays an important role in steering the overall performance of an FCC riser. The model developed here can accommodate a large number of reactions, thus, allowing for composition-based modeling of the FCC process. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 1226-1235, 2013