is conveyed to the regenerator by transfer line 28 in the regenerator the coke is burned off and the catalyst is reactivated for recirculation to the riser reactor 10 because of their high momentum a relatively very small amount of catalyst particulates enters the primary cyclones 17 and even less passes to the secondary cyclones 20 the primary and secondary cyclones perform in the usual manner and deliver the separated particulates to the bottom of the vessel 11 through dip legs 30 from which point the particulates are free to slide into the stripper 12 in many cases secondary cyclones will not be necessary because effective separation can be effected in the first stage cyclones the spatial arrangement of the preferred embodiment of the apparatus makes the inclusion of secondary cyclones very convenient and their use can eliminate the need for decanting apparatus for the condensed effluent product the specific dimensions and structural arrangements set forth are intended to be illustrative of a preferred mode of carrying out the invention and they may be varied or adapted to specific situations which may be encountered for example in designing a revamp of an existing fluid catalytic cracker it was found that an external riser located outside of the separator vessel had to be utilized and that the telescoping relationship between the upper end of the riser and the flow reverser could not be used instead to accomplish the desired reversal to down flow the revamp design shown in fig4 of the drawings utilizes a downwardly extending flow reverse conduit.