The proposed material of construction is either 304 or 316. These materials will seeing temperature as high as 300C but for no more than 72hrs (regeneratio process.
Where can I find corrosion rate information for short exposure time?
Treating the corrodent as if it were NaOH would be a conservative approach, NaOH being the most corrosive in the family. Using the CS<SS<Ni alloy hierarchy for increasing caustic resistance will probably result in the same alloy choice.