of frustoconical baffles 74a 74b and 74c only three are designated over which the downflowing catalyst passes countercurrently to upflowing stripping gas hot flue gas is withdrawn from plenum section 58 of regenerator vessel 36 through conduit 60 control valve 90 positioned in line 80 sets the flowrate of hot flue gas flowing from the regenerator vessel 36 to the stripping section 73 hot regenerated catalyst is withdrawn from the regenerator vessel 36 through line 100 which is equipped with control valve 101 and flows into line 80 where it is fluidized in a stream of hot flue gas the fluidized mixture flows through line 80 into heat exchanger conduit 76 positioned inside the stripping section 73 while line 80 is illustrated as entering stripping section 73 near the top it is to be understood that the present invention encompasses both downflow and upflow embodiments consequently line 80 may alternatively be positioned near the bottom of stripper section 27 a compressor 85 may optionally be installed in line 80 to facilitate flow of flue gas and fluidized catalyst through line 81 into standpipe 6 once inside the stripper section 27 the conduit means may comprise a heat exchanger conduit 76 passing helically between the baffles or the conduit may comprise a plurality of vertical or horizontal tubes not shown the fluidized mixture of flue.