An apparatus for regenerating coke-contaminated fluid catalyst is disclosed which comprises a vertical combustion chamber, an inlet to said chamber for spent catalyst and regeneration gas, a fluid catalyst collecting means within the upper portion of said chamber, a first catalyst withdrawal conduit in communication with said collecting means, a heat removal chamber possessing heat removal means super adjacent said chamber, a second catalyst withdrawal conduit connected to said heat removal chamber and a mixing conduit connecting said first and second withdrawal conduits, wherein a control system senses the catalyst temperature in the first withdrawal conduit downstream of the mixer conduit, formulates an output signal via a temperature control means having an adjustable set point, and regulates the flow rate of regenerated catalyst through said mixing conduit via transmission of said output signal to a flow control means responsive thereto.