(384d) Computational Fluid Dynamics Simulation of Fluid Catalytic Cracking in a Rotating Fluidized Bed in a Static Geometry

The application of a rotating fluidized bed in a static geometry (Figure 1) to fluid catalytic cracking is evaluated by means of computational fluid dynamics (CFD) simulations using an Eulerian-Eulerian model and the kinetic theory of granular flow. The reactions are described by a 10-lump model. First, the reaction kinetics is based on currently allowable cracking temperature and catalyst activity. Typical reactor dimensions required are presented, and an evaluation of the process intensification potential is made, based on a comparison with riser technology. Rotating fluidized beds in a static geometry have excellent particle bed mixing and heat transfer properties. Therefore, the additional process intensification potential of applying higher cracking temperatures or of using a more active catalyst was also evaluated.

The CFD simulations (Figures 2 and 3) confirm the potential of rotating fluidized beds in static geometry for the intensification of the fluid catalytic cracking process. Using the conventional catalyst and cracking temperature, a one order of magnitude process intensification can be easily achieved (Figure 3). The gasoline or light gases selectivity can also be optimized. Increasing the cracking temperature or catalyst activity increases the gas oil conversion in a similar, less than proportional way, but decreases the gasoline selectivity and increases the light gases selectivity. Allowing a higher cracking temperature or the use of more active catalyst, RFB-SGs may intensify the FCC process by up to a factor 70.

Figure 1. Rotating Fluidized Bed in a Static Geometry (RFB-SG).

(a)

(b)

Figure 2. (a) Typical contour plot of the solids volume fraction. (b) Corresponding profiles of the Gas Oil conversion and the conversions into gasoline and into Light Gases.

Figure 3. Process intensification potential of RFB-SG for the catalytic cracking of gas oil as a function of the gas oil conversion: comparison with riser technology. RFB-SG operated with conventional catalyst and cracking temperature of 775 K.