Abstract: A regenerator in a FCC unit, with the reactor elevated above the regenerator and a side entry spent catalyst introduction to the regenerator, is modified by installing a spent catalyst distribution apparatus along a central vertical axis of the regenerator to radially discharge the spent catalyst and 10-50 percent of the regeneration air into the dense phase of the catalyst. The existing compressor may be used to supply the regeneration air to the spent catalyst distributor. The remaining 50-90 percent of the regeneration air is supplied to the air distribution grid. The retrofit improves spent catalyst distribution and mixing in the regenerator to avoid dilute phase CO combustion or afterburning in the offgas.

Abstract: An improvement in a regenerator which incorporates an external plenum on the exterior of the regenerator apparatus for receiving and collecting the flue gases separated from regenerated catalyst by a plurality of cyclone separators or other separating apparatus is disclosed. The external plenum communicates by means of stand pipes through the wall of the regenerator. This supports the cyclone separators or other separating means mechanically and avoids certain thermal stresses which would otherwise occur in the plenum if it were placed on the interior of the regeneration chamber.