Catalyst regenerators and methods for using same. The regenerator can include a regenerator housing containing a dense phase catalyst bed for receiving a catalyst to be regenerated. A heater can be disposed in the regenerator and can have a fuel nozzle configured to eject a mixture of fuel and an oxygen-lean gas for combustion to supplement the heat to satisfy the reactor heat demand when a light feedstock cracked that may not provide sufficient coke formation on the catalyst to fully satisfy the reactor heat demand.