(147a) A Review of Spent Catalyst Feeders in FCC Regenerators

The fluidized bed regenerator is a key component of the fluid catalytic cracking (FCC) loop. Coke deposited on the spent catalyst particles in the regenerator is burnt off with air to restore the catalyst activity before it is reused in the riser reactor. Ideally, the spent catalyst returning from the stripper needs to be fed in the regenerator in such a way that provides a uniformly distributed catalyst and the incoming transport gas in the fluidized bed. Spreading the incoming spent catalyst uniformly in the regenerator improves solids mixing providing more efficient coke burning. Poor distribution In addition to the inefficient spent catalyst regeneration, there will be poorly fluidized regions of the bed that may lead to significant gas bypassing. Gas bypassing can cause “afterburn” in the freeboard which causes high temperatures in the freeboard which pose reliability concerns. A wide variety of solids distributor designs have been patented and many are in use in FCC regenerators. This paper presents a review of types of feed-solids distributors and their performance. Solids are introduced into fluidized beds as either dense streams via standpipes or as dilute feeds via risers. Although these solids distributors have been commercially used for decades, there is not much reported on the dispersion of the feed solids in the regenerator. To improve regenerator performance and meet the ever increasingly stricter environmental regulations there is need for more studies.