EXPERIMENTAL AND 3D COMPUTATIONAL STUDY OF MULTIPHASE FLOW BEHAVIOUR IN A RISER OF A FCC PROCESS

摘要

This work deals with the experimental and computational study of the co-current gas-solid flow behaviour in a riser of a FCC process. The FCC particles belong to the group A of Geldart's classification and are inclined to form ephemeral agglomerates. Thus, such agglomeration process may constitute an important phenomenon in the fast fluidization of FCC particles because it modifies the structure of the flow and reduces the effectiveness of the gas-solid contact. As first approach for taking the phenomenon of agglomeration into account, we confronted experimental results and predictions of two series of unsteady three-dimensional calculations using the CFD code Saturne Polyphasique@Tlse. In the first series, the size and density of the particles are those of the FCC particles (70 μm and 1400 kg/m~3) whereas in the second ones, they correspond to an equivalent particle (350 μm and 950 kg/m~3). The computational results allow to obtain good predictions for the axial pressure gradients profiles for the FCC particles whereas the solid average mass flux profiles are not very well predicted for the two types of particles. The discrepancy between predictions for the two types of particles relies for the increase of inertia effect for the equivalent particles characterized by a larger value of the particle relaxation characteristic time. These results should enable us to direct our works for the understanding of the Group A particles behaviour.