Experimental study and CPFD simulation on circumferential flow heterogeneity in a disc-donut catalyst stripper

Abstract

Abstract Disc-donut strippers are widely equipped in fluid catalytic cracking (FCC) units of petroleum refineries. In this study, circumferential gas-solids flow heterogeneity in a disc-donut catalyst stripper was investigated using both experimental and CFD simulation approaches. A four-channel fiber optical densitometry was used to measure the radial gas-solids profiles synchronously from four different circumferential angles. Computational particle fluid dynamics (CPFD) model was used to simulate the experimental stripper section. It was found in experiment that the circumferential gas-solids distribution is highly heterogeneous throughout the disc-donut stripper. Local gas bypassing existed under all the experimental conditions. The CPFD model successfully predicted gas bypassing and circumferential flow heterogeneity in the disc-donut stripper. However, previous two-fluid model (TFM) simulations on disc-donut strippers using a single mean particle size can only predict axially symmetrical flow distribution. According to a series of sensitivity analyses, it is shown that the consideration of particle size distribution (PSD) is a possible key reason leading to the successful prediction of the circumferential flow heterogeneous by the CPFD model.