Comparative study of hydrodynamic and mixing behaviors in different pre-lifting schemes for an FCC riser

Abstract

A comprehensive study of hydrodynamic behavior including the particle mass flow rate, solid volume fraction and particle velocity, as well as the mixing behavior, was conducted in the pre-lifting scheme with a central tube and the scheme without a central tube. Compared with the pre-lifting scheme without a central tube, higher mass flow rate, more uniform flow structure, and more vigorous gas-solid contact behaviors were obtained in the riser entrance region of the pre-lifting scheme with a central tube. The suggested installation height for the feedstock nozzles was lower in the pre-lifting scheme with a central tube as determined by analyzing the radial non-uniformity index of catalyst particles distributions. However, relatively complete and desirable mixing of cold and hot particles was presented in the pre-lifting scheme without a central tube by analysis of the distributions of heat exchange uniformity. Finally, the key hydrodynamic and mixing features were summarized, and some optimized structures over the pre-lifting scheme with a central tube were proposed to improve the mixing of cold and hot particles.