Spent catalyst distribution

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.