An oxygen gas stream is distributed to a spent catalyst stream through an oxygen nozzle of an oxygen gas distributor and a fuel gas stream is distributed to the spent catalyst stream through a fuel nozzle of a fuel gas distributor. An oxygen gas jet generated from said oxygen nozzle and a fuel gas jet generated from said fuel gas nozzle have the same elevation in the regenerator. In a regenerator, an oxygen gas distributor and a fuel gas distributor may be located in a mixing chamber. A fuel outlet of a fuel nozzle of the fuel gas distributor may be within a fifth of the height of the mixing chamber from an oxygen outlet of an oxygen nozzle of the oxygen gas distributor. In addition, clear space is provided between a fuel gas nozzle on a fuel gas distributor and a closest oxygen nozzle on an oxygen gas distributor.