FLUIDIZED CATALYTIC CRACKING WITH REDUCED DILUTE-PHASE TEMPERATURE AND/OR COMPOSITION GRADIENTS IN THE REGENERATOR

摘要

The spent catalyst from a fluidized catalytic cracker (10) contaminated with coke and volatile hydrocarbons is circulated via a transfer line (22, 24) to a regenerator (26) wherein it is contacted in a dense phase fluidized bed with a regeneration gas (from 36). A minor proportion (e.g. from 2 to 20%) of the regeneration gas is employed to combust volatile hydrocarbons in the vicinity of the region where spent catalyst enters the dense phase bed (30) so that the regeneration in the dense bed is substantially uninfluenced by the presence of volatile hydrocarbons and gradients of temperature and/or composition in the dilute regenerator phase (34) are mitigated or eliminated thereby reducing or eliminating undesirable afterburning in the dilute phase (34). The minor proportion of regeneration gas is passed (from line 40) either into the transfer line (22,24) close to its end within the regenerator (26) or, in another embodiment, directly into a region of the dense bed (30) close to the end of the transfer line.