Evaluating the role of intraparticle mass and heat transfers in a commercial FCC riser: A meso-scale study

摘要

The paper provides new insights into the fundamental mechanism of catalytic cracking from the meso-scale viewpoint. Intraparticle mass and heat transfers were studied under fluid catalytic cracking (FCC) reaction conditions. A comprehensive single particle model was developed to characterize detailed chemical and physical phenomena occurred within catalyst particles in a commercial FCC riser from an industrial-scale refinery. This model integrates the mass, energy, and momentum balances as well as the equations for gas-state, lumped-species reaction kinetics, the multicomponent diffusion and convective heat transfer. This model is capable of predicting temperature, pressure, species mass fraction distributions, as well as the reaction rate and the effective diffusivity coefficient within the particles as a function of catalyst position in the riser. A detailed study based on the validated model demonstrated that there are three typical particle phenomena along the axial direction in the FCC riser, which leads to different catalytic and reactive operating zones under simultaneous mass and heat transfers as well as reaction. The different operating zones can be named as the transport-controlled, the reaction-controlled and the intermediate transition zones, and they have been described in detailed in this work.