it is depend how mush regenerated cat, slide valve how much passing if slightly passing and the valve are free not got stuck you can start normally during start up the reactor press. is higher than reg, so it will be passing steam only and while loading catalyst it will be stand pipe sealed then you can heat up the reactor via that passing and you can maintian temp. by torch oil flow rate remmber i told  if slightly passing  by my practice when temperature increase the slide valve may be you can close it i mean passing will stop may some coke around the slide valve guide or grove try to strok it when reg. temp.above 500c by opening and closing fast or try by handwheel
best regards
salam

The answer is it depends.
Catalyst slide-valves are not only used for control but are safety devices.
Restarting the FCCU/RFCCU with a by-passing/leaking slide-valve depends on if there
are other means of stopping catalyst circulation and sealing the catlyst transfer lines,
isolating the Reactor and Regenerator (such as slumping the catalyst).
IF there are no secondary means of stopping catalyst flow and isolating the Reactor
and Regenerator vessels; then the answer from a safety point of view is NO, one should
NOT restrat the FCCU/RFCCU!